ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Life and Medical Sciences  (1,825)
  • Cell & Developmental Biology  (1,408)
  • FLUID MECHANICS AND HEAT TRANSFER  (731)
  • Inorganic Chemistry  (727)
  • Aircraft Propulsion and Power
  • 2005-2009  (49)
  • 1990-1994  (3,285)
  • 1950-1954
  • 2008  (49)
  • 1993  (3,285)
Collection
Keywords
Publisher
Years
  • 2005-2009  (49)
  • 1990-1994  (3,285)
  • 1950-1954
Year
  • 1
    facet.materialart.
    Unknown
    High Temperature Investigations into an Active Turbine Blade Tip Clearance Control Concept (2008)
    In:  Other Sources
    Details
    Publication Date: 2018-06-06
    Description: System studies have shown the benefits of reducing blade tip clearances in modern turbine engines. Minimizing blade tip clearances throughout the engine will contribute materially to meeting NASA s Ultra-Efficient Engine Technology (UEET) turbine engine project goals. NASA GRC is examining two candidate approaches including rub-avoidance and regeneration which are explained in subsequent slides.
    Keywords: Aircraft Propulsion and Power
    Type: 2007 NASA Seal/Secondary Air System Workshop; 101-123; NASA/CP-2008-215263/VOL1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 2
    facet.materialart.
    Unknown
    A Theoretical Solid Oxide Fuel Cell Model for Systems Controls and Stability Design (2008)
    In:  Other Sources
    Details
    Publication Date: 2018-06-06
    Description: As the aviation industry moves toward higher efficiency electrical power generation, all electric aircraft, or zero emissions and more quiet aircraft, fuel cells are sought as the technology that can deliver on these high expectations. The hybrid solid oxide fuel cell system combines the fuel cell with a micro-turbine to obtain up to 70% cycle efficiency, and then distributes the electrical power to the loads via a power distribution system. The challenge is to understand the dynamics of this complex multidiscipline system and the design distributed controls that take the system through its operating conditions in a stable and safe manner while maintaining the system performance. This particular system is a power generation and a distribution system, and the fuel cell and micro-turbine model fidelity should be compatible with the dynamics of the power distribution system in order to allow proper stability and distributed controls design. The novelty in this paper is that, first, the case is made why a high fidelity fuel cell mode is needed for systems control and stability designs. Second, a novel modeling approach is proposed for the fuel cell that will allow the fuel cell and the power system to be integrated and designed for stability, distributed controls, and other interface specifications. This investigation shows that for the fuel cell, the voltage characteristic should be modeled but in addition, conservation equation dynamics, ion diffusion, charge transfer kinetics, and the electron flow inherent impedance should also be included.
    Keywords: Aircraft Propulsion and Power
    Type: Journal of Fuel Cell Science and Technology; Volume 5
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 3
    facet.materialart.
    Unknown
    NASA C-17 Usage Overview (2008)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: The usage and integrated vehicle health management of the NASA C-17. Propulsion health management flight objectives for the aircraft include mapping of the High Pressure Compressor in order to calibrate a Pratt and Whitney engine model and the fusion of data collected from existing sensors and signals to develop models, analysis methods and information fusion algorithms. An additional health manage flight objective is to demonstrate that the Commercial Modular Aero-Propulsion Systems Simulation engine model can successfully execute in real time onboard the C-17 T-1 aircraft using engine and aircraft flight data as inputs. Future work will address aircraft durability and aging, airframe health management, and propulsion health management research in the areas of gas path and engine vibration.
    Keywords: Aircraft Propulsion and Power
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 4
    facet.materialart.
    Unknown
    Ceramic matrix composite turbine engine vane (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: A vane has an airfoil shell and a spar within the shell. The vane has an outboard shroud at an outboard end of the shell and an inboard platform at an inboard end of the shell. The spar has a first chamber essentially along the suction side and a second chamber along the pressure side opposite the first chamber.
    Keywords: Aircraft Propulsion and Power
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 5
    facet.materialart.
    Unknown
    Seal Technology Development for Advanced Component for Airbreathing Engines (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: Key aspects of the design of sealing systems for On Rotor Combustion/Wave Rotor (ORC/WR) systems were addressed. ORC/WR systems generally fit within a broad class of pressure gain Constant Volume Combustors (CVCs) or Pulse Detonation Combustors (PDCs) which are currently being considered for use in many classes of turbine engines for dramatic efficiency improvement. Technology readiness level of this ORC/WR approaches are presently at 2.0. The results of detailed modeling of an ORC/WR system as applied to a regional jet engine application were shown to capture a high degree of pressure gain capabilities. The results of engine cycle analysis indicated the level of specific fuel consumption (SFC) benefits to be 17 percent. The potential losses in pressure gain due to leakage were found to be closely coupled to the wave processes at the rotor endpoints of the ORC/WR system. Extensive investigation into the sealing approaches is reported. Sensitivity studies show that SFC gains of 10 percent remain available even when pressure gain levels are highly penalized. This indicates ORC/WR systems to have a high degree of tolerance to rotor leakage effects but also emphasizes their importance. An engine demonstration of an ORC/WR system is seen as key to progressing the TRL of this technology. An industrial engine was judged to be a highly advantageous platform for demonstration of a first generation ORC/WR system. Prior to such a demonstration, the existing NASA pressure exchanger wave rotor rig was identified as an opportunity to apply both expanded analytical modeling capabilities developed within this program and to identify and fix identified leakage issues existing within this rig. Extensive leakage analysis of the rig was performed and a detailed design of additional sealing strategies for this rig was generated.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/CR-2008-215479 , E-16656
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 6
    facet.materialart.
    Unknown
    Analysis of Plume Effects on Sonic Boom Signature for Isolated Nozzle Configurations (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: Computational fluid dynamics (CFD) analysis has been performed to study the plume effects on sonic boom signature for isolated nozzle configurations. The objectives of these analyses were to provide comparison to past work using modern CFD analysis tools, to investigate the differences of high aspect ratio nozzles to circular (axisymmetric) nozzles, and to report the effects of underexpanded nozzle operation on boom signature. CFD analysis was used to address the plume effects on sonic boom signature from a baseline exhaust nozzle. Near-field pressure signatures were collected for nozzle pressure ratios (NPRs) between 6 and 10. A computer code was used to extrapolate these signatures to a ground-observed sonic boom N-wave. Trends show that there is a reduction in sonic boom N-wave signature as NPR is increased from 6 to 10. The performance curve for this supersonic nozzle is flat, so there is not a significant loss in thrust coefficient as the NPR is increased. As a result, this benefit could be realized without significant loss of performance. Analyses were also collected for a high aspect ratio nozzle based on the baseline design for comparison. Pressure signatures were collected for nozzle pressure ratios from 8 to 12. Signatures were nearly twice as strong for the two-dimensional case, and trends also show a reduction in sonic boom signature as NPR is increased from 8 to 12. As low boom designs are developed and improved, there will be a need for understanding the interaction between the aircraft boat tail shocks and the exhaust nozzle plume. These CFD analyses will provide a baseline study for future analysis efforts.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2008-215414 , AIAA Paper 2008-3729 , E-16535-1
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 7
    facet.materialart.
    Unknown
    Signal Detection Theory Applied to Helicopter Transmission Diagnostic Thresholds (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: Helicopter Health Usage Monitoring Systems (HUMS) have potential for providing data to support increasing the service life of a dynamic mechanical component in the transmission of a helicopter. Data collected can demonstrate the HUMS condition indicator responds to a specific component fault with appropriate alert limits and minimal false alarms. Defining thresholds for specific faults requires a tradeoff between the sensitivity of the condition indicator (CI) limit to indicate damage and the number of false alarms. A method using Receiver Operating Characteristic (ROC) curves to assess CI performance was demonstrated using CI data collected from accelerometers installed on several UH60 Black Hawk and AH64 Apache helicopters and an AH64 helicopter component test stand. Results of the analysis indicate ROC curves can be used to reliably assess the performance of commercial HUMS condition indicators to detect damaged gears and bearings in a helicopter transmission.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2008-215262 , E-16530
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 8
    facet.materialart.
    Unknown
    An Investigation of Noise Reduction for the 3BB Nozzle with a Pylon Using External Flaps (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: Flaps (or half wedges) attached to the sides of a pylon are shown to result in a small but clear noise benefit. Noise radiated towards the ground is reduced apparently through a deflection and thickening of the fan stream underneath. Based on results from the current as well as concurrent investigations at the University of California at Irvine, it is recommended that further tests in a larger facility simulating realistic engine conditions be considered.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2008-215288 , E-16562
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 9
    facet.materialart.
    Unknown
    Intelligent Engine Systems: Thermal Management and Advanced Cooling (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: The objective is to provide turbine-cooling technologies to meet Propulsion 21 goals related to engine fuel burn, emissions, safety, and reliability. Specifically, the GE Aviation (GEA) Advanced Turbine Cooling and Thermal Management program seeks to develop advanced cooling and flow distribution methods for HP turbines, while achieving a substantial reduction in total cooling flow and assuring acceptable turbine component safety and reliability. Enhanced cooling techniques, such as fluidic devices, controlled-vortex cooling, and directed impingement jets, offer the opportunity to incorporate both active and passive schemes. Coolant heat transfer enhancement also can be achieved from advanced designs that incorporate multi-disciplinary optimization of external film and internal cooling passage geometry.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/CR-2008-215236 , E-16495
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 10
    facet.materialart.
    Unknown
    Intelligent Engine Systems: Thermal Management and Advanced Cooling (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: The objective of the Advanced Turbine Cooling and Thermal Management program is to develop intelligent control and distribution methods for turbine cooling, while achieving a reduction in total cooling flow and assuring acceptable turbine component safety and reliability. The program also will develop embedded sensor technologies and cooling system models for real-time engine diagnostics and health management. Both active and passive control strategies will be investigated that include the capability of intelligent modulation of flow quantities, pressures, and temperatures both within the supply system and at the turbine component level. Thermal management system concepts were studied, with a goal of reducing HPT blade cooling air supply temperature. An assessment will be made of the use of this air by the active clearance control system as well. Turbine component cooling designs incorporating advanced, high-effectiveness cooling features, will be evaluated. Turbine cooling flow control concepts will be studied at the cooling system level and the component level. Specific cooling features or sub-elements of an advanced HPT blade cooling design will be downselected for core fabrication and casting demonstrations.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/CR-2008-215238 , E-16497
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 11
    facet.materialart.
    Unknown
    System Study: Technology Assessment and Prioritizing Update (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: For the Intelligent Engine System (Propulsion 21) study, each technology was evaluated to determine the impact to fuel burn, acoustics, and NOx emissions. The optimum combination of technologies and their overall benefits to the system were also evaluated, resulting in noise improvement potential of 1.89 EPNdB cumulative margin,-1.34 percent fuel burn, and 50 percent NOx reduction from the 2015 UEET-QAT baseline. All the technology evaluations, except T18-20D, were based on newengines, where the engine was resized to obtain the maximum system benefit while maintaining the same cycle parameters as the 2015 UEET-QAT baseline. The impact of turbine clearance control on deteriorated engines, T18-20D, was also evaluated. Recommendations for future system study work include, but were not limited to, validation of a university-developed engine deterioration model and customer value analysis as figures of merit beside fuel burn, emissions, and acoustics.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/CR-2008-215224 , E-16492
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 12
    facet.materialart.
    Unknown
    An Adaptive Instability Suppression Controls Method for Aircraft Gas Turbine Engine Combustors (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: An adaptive controls method for instability suppression in gas turbine engine combustors has been developed and successfully tested with a realistic aircraft engine combustor rig. This testing was part of a program that demonstrated, for the first time, successful active combustor instability control in an aircraft gas turbine engine-like environment. The controls method is called Adaptive Sliding Phasor Averaged Control. Testing of the control method has been conducted in an experimental rig with different configurations designed to simulate combustors with instabilities of about 530 and 315 Hz. Results demonstrate the effectiveness of this method in suppressing combustor instabilities. In addition, a dramatic improvement in suppression of the instability was achieved by focusing control on the second harmonic of the instability. This is believed to be due to a phenomena discovered and reported earlier, the so called Intra-Harmonic Coupling. These results may have implications for future research in combustor instability control.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2008-215202 , E-16414-1
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 13
    facet.materialart.
    Unknown
    Low-noise fan exit guide vanes (2008)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: Low-noise fan exit guide vanes are disclosed. According to the present invention a fan exit guide vane has an outer shell substantially shaped as an airfoil and defining an interior cavity. A porous portion of the outer shell allows communication between the fluctuations in the air passing over the guide vane and the interior cavity. At least one acoustically resonant chamber is located within the interior cavity. The resonant chamber is in communication with the porous portion of the outer perimeter. The resonant chamber is configured to reduce the noise generated at a predetermined frequency. In various preferred embodiments, there is a plurality of acoustically resonant chambers located within the interior cavity. The resonant chambers can be separated by one or more partitions within the interior cavity. In these embodiments, the resonant chambers can be configured to reduce the noise generated over a range of predetermined frequencies.
    Keywords: Aircraft Propulsion and Power
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 14
    facet.materialart.
    Unknown
    Comparison Between Numerically Simulated and Experimentally Measured Flowfield Quantities Behind a Pulsejet (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Pulsed combustion is receiving renewed interest as a potential route to higher performance in air breathing propulsion systems. Pulsejets offer a simple experimental device with which to study unsteady combustion phenomena and validate simulations. Previous computational fluid dynamic (CFD) simulation work focused primarily on the pulsejet combustion and exhaust processes. This paper describes a new inlet sub-model which simulates the fluidic and mechanical operation of a valved pulsejet head. The governing equations for this sub-model are described. Sub-model validation is provided through comparisons of simulated and experimentally measured reed valve motion, and time averaged inlet mass flow rate. The updated pulsejet simulation, with the inlet sub-model implemented, is validated through comparison with experimentally measured combustion chamber pressure, inlet mass flow rate, operational frequency, and thrust. Additionally, the simulated pulsejet exhaust flowfield, which is dominated by a starting vortex ring, is compared with particle imaging velocimetry (PIV) measurements on the bases of velocity, vorticity, and vortex location. The results show good agreement between simulated and experimental data. The inlet sub-model is shown to be critical for the successful modeling of pulsejet operation. This sub-model correctly predicts both the inlet mass flow rate and its phase relationship with the combustion chamber pressure. As a result, the predicted pulsejet thrust agrees very well with experimental data.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2008-215432 , AIAA-2008-5046 , E-16597 , 44th Joint Propulsion Conference and Exhibit; Jul 21, 2008 - Jul 23, 2008; Hartford, CT; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 15
    facet.materialart.
    Unknown
    Data Turbine Activities at NASA (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Mission Support Features: a) Shirtsleeve environment, . 18 scientists; b) worldwide deployment experience; c) Extensive modifications to support in-situ and remote sensing instruments 1) zenith and nadir viewports; 2) modified power systems; 3) 19 inch rack mounting; 4) on-board data acquisition network.
    Keywords: Aircraft Propulsion and Power
    Type: 1st Workshop of the Open Source Data Turbine Initiative; Oct 07, 2008; La Jolla, CA; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 16
    facet.materialart.
    Unknown
    Model-Based Fault Tolerant Control (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The Model Based Fault Tolerant Control (MBFTC) task was conducted under the NASA Aviation Safety and Security Program. The goal of MBFTC is to develop and demonstrate real-time strategies to diagnose and accommodate anomalous aircraft engine events such as sensor faults, actuator faults, or turbine gas-path component damage that can lead to in-flight shutdowns, aborted take offs, asymmetric thrust/loss of thrust control, or engine surge/stall events. A suite of model-based fault detection algorithms were developed and evaluated. Based on the performance and maturity of the developed algorithms two approaches were selected for further analysis: (i) multiple-hypothesis testing, and (ii) neural networks; both used residuals from an Extended Kalman Filter to detect the occurrence of the selected faults. A simple fusion algorithm was implemented to combine the results from each algorithm to obtain an overall estimate of the identified fault type and magnitude. The identification of the fault type and magnitude enabled the use of an online fault accommodation strategy to correct for the adverse impact of these faults on engine operability thereby enabling continued engine operation in the presence of these faults. The performance of the fault detection and accommodation algorithm was extensively tested in a simulation environment.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/CR-2008-215273 , E-16555
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 17
    facet.materialart.
    Unknown
    Assessment of Current Jet Noise Prediction Capabilities (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An assessment was made of the capability of jet noise prediction codes over a broad range of jet flows, with the objective of quantifying current capabilities and identifying areas requiring future research investment. Three separate codes in NASA s possession, representative of two classes of jet noise prediction codes, were evaluated, one empirical and two statistical. The empirical code is the Stone Jet Noise Module (ST2JET) contained within the ANOPP aircraft noise prediction code. It is well documented, and represents the state of the art in semi-empirical acoustic prediction codes where virtual sources are attributed to various aspects of noise generation in each jet. These sources, in combination, predict the spectral directivity of a jet plume. A total of 258 jet noise cases were examined on the ST2JET code, each run requiring only fractions of a second to complete. Two statistical jet noise prediction codes were also evaluated, JeNo v1, and Jet3D. Fewer cases were run for the statistical prediction methods because they require substantially more resources, typically a Reynolds-Averaged Navier-Stokes solution of the jet, volume integration of the source statistical models over the entire plume, and a numerical solution of the governing propagation equation within the jet. In the evaluation process, substantial justification of experimental datasets used in the evaluations was made. In the end, none of the current codes can predict jet noise within experimental uncertainty. The empirical code came within 2dB on a 1/3 octave spectral basis for a wide range of flows. The statistical code Jet3D was within experimental uncertainty at broadside angles for hot supersonic jets, but errors in peak frequency and amplitude put it out of experimental uncertainty at cooler, lower speed conditions. Jet3D did not predict changes in directivity in the downstream angles. The statistical code JeNo,v1 was within experimental uncertainty predicting noise from cold subsonic jets at all angles, but did not predict changes with heating of the jet and did not account for directivity changes at supersonic conditions. Shortcomings addressed here give direction for future work relevant to the statistical-based prediction methods. A full report will be released as a chapter in a NASA publication assessing the state of the art in aircraft noise prediction.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2008-215275 , AIAA Paper 2008-2933 , E-16545 , 14th Aeroacoustics Conference; May 05, 2008 - May 07, 2008; Vancouver; Canada
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 18
    facet.materialart.
    Unknown
    A Numerical Study of Anti-Vortex Film Cooling Designs at High Blowing Ratio (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A concept for mitigating the adverse effects of jet vorticity and liftoff at high blowing ratios for turbine film cooling flows has been developed and studied at NASA Glenn Research Center. This "anti-vortex" film cooling concept proposes the addition of two branched holes from each primary hole in order to produce a vorticity counter to the detrimental kidney vortices from the main jet. These vortices typically entrain hot freestream gas and are associated with jet separation from the turbine blade surface. The anti-vortex design is unique in that it requires only easily machinable round holes, unlike shaped film cooling holes and other advanced concepts. The anti-vortex film cooling hole concept has been modeled computationally for a single row of 30deg angled holes on a flat surface using the 3D Navier-Stokes solver Glenn-HT. A modification of the anti-vortex concept whereby the branched holes exit adjacent to the main hole has been studied computationally for blowing ratios of 1.0 and 2.0 and at density ratios of 1.0 and 2.0. This modified concept was selected because it has shown the most promise in recent experimental studies. The computational results show that the modified design improves the film cooling effectiveness relative to the round hole baseline and previous anti-vortex cases, in confirmation of the experimental studies.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2008-215209 , GT2008-50845 , E-16482 , ASME Turbo Expo 2008 Gas Turbine Technical Congress and Exposition; Jun 09, 2008 - Jun 13, 2008; Berlin; Germany
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 19
    facet.materialart.
    Unknown
    Benchmarking Gas Path Diagnostic Methods: A Public Approach (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Recent technology reviews have identified the need for objective assessments of engine health management (EHM) technology. The need is two-fold: technology developers require relevant data and problems to design and validate new algorithms and techniques while engine system integrators and operators need practical tools to direct development and then evaluate the effectiveness of proposed solutions. This paper presents a publicly available gas path diagnostic benchmark problem that has been developed by the Propulsion and Power Systems Panel of The Technical Cooperation Program (TTCP) to help address these needs. The problem is coded in MATLAB (The MathWorks, Inc.) and coupled with a non-linear turbofan engine simulation to produce "snap-shot" measurements, with relevant noise levels, as if collected from a fleet of engines over their lifetime of use. Each engine within the fleet will experience unique operating and deterioration profiles, and may encounter randomly occurring relevant gas path faults including sensor, actuator and component faults. The challenge to the EHM community is to develop gas path diagnostic algorithms to reliably perform fault detection and isolation. An example solution to the benchmark problem is provided along with associated evaluation metrics. A plan is presented to disseminate this benchmark problem to the engine health management technical community and invite technology solutions.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2008-215271 , GT2008-51360 , E-16542 , Turbo Expo 2008 Gas Turbine Technical Congress and Exposition; Jun 09, 2008 - Jun 13, 2008; Berlin; Germany
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 20
    facet.materialart.
    Unknown
    Automated Power Assessment for Helicopter Turboshaft Engines (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An accurate indication of available power is required for helicopter mission planning purposes. Available power is currently estimated on U.S. Army Blackhawk helicopters by performing a Maximum Power Check (MPC), a manual procedure performed by maintenance pilots on a periodic basis. The MPC establishes Engine Torque Factor (ETF), an indication of available power. It is desirable to replace the current manual MPC procedure with an automated approach that will enable continuous real-time assessment of available power utilizing normal mission data. This report presents an automated power assessment approach which processes data currently collected within helicopter Health and Usage Monitoring System (HUMS) units. The overall approach consists of: 1) a steady-state data filter which identifies and extracts steady-state operating points within HUMS data sets; 2) engine performance curve trend monitoring and updating; and 3) automated ETF calculation. The algorithm is coded in MATLAB (The MathWorks, Inc.) and currently runs on a PC. Results from the application of this technique to HUMS mission data collected from UH-60L aircraft equipped with T700-GE-701C engines are presented and compared to manually calculated ETF values. Potential future enhancements are discussed.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2008-215270 , E-16541 , 64th Annual Forum and Technology Display (AHS Forum 64); Apr 29, 2008 - May 01, 2008; Montreal; Canada
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 21
    facet.materialart.
    Unknown
    Aircraft Engine On-Line Diagnostics Through Dual-Channel Sensor Measurements: Development of a Baseline System (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: In this paper, a baseline system which utilizes dual-channel sensor measurements for aircraft engine on-line diagnostics is developed. This system is composed of a linear on-board engine model (LOBEM) and fault detection and isolation (FDI) logic. The LOBEM provides the analytical third channel against which the dual-channel measurements are compared. When the discrepancy among the triplex channels exceeds a tolerance level, the FDI logic determines the cause of the discrepancy. Through this approach, the baseline system achieves the following objectives: (1) anomaly detection, (2) component fault detection, and (3) sensor fault detection and isolation. The performance of the baseline system is evaluated in a simulation environment using faults in sensors and components.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2008-215228 , GT2008-50345 , E-16515 , ASME Turbo Expo 2008 Gas Turbine Congress and Exposition; Jun 09, 2008 - Jun 13, 2008; Berlin; Germany
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 22
    facet.materialart.
    Unknown
    Preliminary Analysis for an Optimized Oil-Free Rotorcraft Engine Concept (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Recent developments in gas foil bearing technology have led to numerous advanced high-speed rotating system concepts, many of which have become either commercial products or experimental test articles. Examples include Oil-Free microturbines, motors, generators and turbochargers. The driving forces for integrating gas foil bearings into these high-speed systems are the benefits promised by removing the oil lubrication system. Elimination of the oil system leads to reduced emissions, increased reliability, and decreased maintenance costs. Another benefit is reduced power plant weight. For rotorcraft applications, this would be a major advantage, as every pound removed from the propulsion system results in a payload benefit. Implementing foil gas bearings throughout a rotorcraft gas turbine engine is an important long-term goal that requires overcoming numerous technological hurdles. Adequate thrust bearing load capacity and potentially large gearbox applied radial loads are among them. However, by replacing the turbine end, or hot section, rolling element bearing with a gas foil bearing many of the above benefits can be realized. To this end, engine manufacturers are beginning to explore the possibilities of hot section gas foil bearings in propulsion engines. This paper presents a logical follow-on activity by analyzing a conceptual rotorcraft engine to determine the feasibility of a foil bearing supported core. Using a combination of rotordynamic analyses and a load capacity model, it is shown to be reasonable to consider a gas foil bearing core section.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2008-215064 , ARL-TR-4398 , E-16290 , American Helicopter Society 63rd Annual Forum and Technology Display; May 01, 2007 - May 03, 2007; Virginia Beach, VA; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 23
    facet.materialart.
    Unknown
    Design, Fabrication, and Performance of Foil Gas Thrust Bearings for Microturbomachinery Applications (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A methodology for the design and construction of simple foil thrust bearings intended for parametric performance testing and low marginal costs is presented. Features drawn from a review of the open literature are discussed as they relate to bearing performance. The design of fixtures and tooling required to fabricate foil thrust bearings is presented, using conventional machining processes where possible. A prototype bearing with dimensions drawn from the literature is constructed, with all fabrication steps described. A load-deflection curve for the bearing is presented to illustrate structural stiffness characteristics. Start-top cycles are performed on the bearing at a temperature of 425 C to demonstrate early-life wear patterns. A test of bearing load capacity demonstrates useful performance when compared with data obtained from the open literature.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2008-215062 , GT2008-50377 , E-16284 , Turbo Expo 2008 Gas Turbine Technical Congress and Exposition; Jun 09, 2008 - Jun 13, 2008; Berlin; Germany
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 24
    facet.materialart.
    Unknown
    Pre-Stall Behavior of a Transonic Axial Compressor Stage via Time-Accurate Numerical Simulation (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: CFD calculations using high-performance parallel computing were conducted to simulate the pre-stall flow of a transonic compressor stage, NASA compressor Stage 35. The simulations were run with a full-annulus grid that models the 3D, viscous, unsteady blade row interaction without the need for an artificial inlet distortion to induce stall. The simulation demonstrates the development of the rotating stall from the growth of instabilities. Pressure-rise performance and pressure traces are compared with published experimental data before the study of flow evolution prior to the rotating stall. Spatial FFT analysis of the flow indicates a rotating long-length disturbance of one rotor circumference, which is followed by a spike-type breakdown. The analysis also links the long-length wave disturbance with the initiation of the spike inception. The spike instabilities occur when the trajectory of the tip clearance flow becomes perpendicular to the axial direction. When approaching stall, the passage shock changes from a single oblique shock to a dual-shock, which distorts the perpendicular trajectory of the tip clearance vortex but shows no evidence of flow separation that may contribute to stall.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2008-215163 , ARL-TR-4085 , E-16405 , ASME Turbo Expo 2007; May 14, 2007 - May 17, 2007; Montreal; Canada
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 25
    facet.materialart.
    Unknown
    Modeling of Fixed-Exit Porous Bleed Systems (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A model has been developed to simulate a fixed-exit porous bleed system for supersonic inlets. The fixed-exit model allows the amount of bleed flow to vary according to local flow conditions and fixed-exit characteristics of the bleed system. This variation is important for the control of shock-wave/boundary-layer interactions within the inlet. The model computes the bleed plenum static pressure rather than requiring its specification. The model was implemented in the Wind-US computational fluid dynamics code. The model was then verified and validated against experimental data for bleed on a flat plate with and without an impinging oblique shock and for bleed in a Mach 3.0 axisymmetric, mixed-compression inlet. The model was able to accurately correlate the plenum pressures with bleed rates and simulate the effect of the bleed on the downstream boundary layer. Further, the model provided a realistic simulation of the initiation of inlet unstart. The results provide the most in-depth examination to date of bleed models for use in the simulation of supersonic inlets. The results also highlight the limitations of the models and aspects that require further research.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2008-215178 , AIAA Paper 2008-0094 , E-16423 , 46th AIAA Aerospace Sciences Meeting and Exhibit; Jan 07, 2008 - Jan 10, 2008; Reno, NV; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 26
    facet.materialart.
    Unknown
    Distributed Turboelectric Propulsion for Hybrid Wing Body Aircraft (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Meeting future goals for aircraft and air traffic system performance will require new airframes with more highly integrated propulsion. Previous studies have evaluated hybrid wing body (HWB) configurations with various numbers of engines and with increasing degrees of propulsion-airframe integration. A recently published configuration with 12 small engines partially embedded in a HWB aircraft, reviewed herein, serves as the airframe baseline for the new concept aircraft that is the subject of this paper. To achieve high cruise efficiency, a high lift-to-drag ratio HWB was adopted as the baseline airframe along with boundary layer ingestion inlets and distributed thrust nozzles to fill in the wakes generated by the vehicle. The distributed powered-lift propulsion concept for the baseline vehicle used a simple, high-lift-capable internally blown flap or jet flap system with a number of small high bypass ratio turbofan engines in the airframe. In that concept, the engine flow path from the inlet to the nozzle is direct and does not involve complicated internal ducts through the airframe to redistribute the engine flow. In addition, partially embedded engines, distributed along the upper surface of the HWB airframe, provide noise reduction through airframe shielding and promote jet flow mixing with the ambient airflow. To improve performance and to reduce noise and environmental impact even further, a drastic change in the propulsion system is proposed in this paper. The new concept adopts the previous baseline cruise-efficient short take-off and landing (CESTOL) airframe but employs a number of superconducting motors to drive the distributed fans rather than using many small conventional engines. The power to drive these electric fans is generated by two remotely located gas-turbine-driven superconducting generators. This arrangement allows many small partially embedded fans while retaining the superior efficiency of large core engines, which are physically separated but connected through electric power lines to the fans. This paper presents a brief description of the earlier CESTOL vehicle concept and the newly proposed electrically driven fan concept vehicle, using the previous CESTOL vehicle as a baseline.
    Keywords: Aircraft Propulsion and Power
    Type: 2008 International Powered Lift Conference Royal Aeronautical Society; Jul 22, 2008 - Jul 24, 2008; London; United Kingdom
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 27
    facet.materialart.
    Unknown
    Intelligent Propulsion System Foundation Technology: Summary of Research (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The purpose of this cooperative agreement was to develop a foundation of intelligent propulsion technologies for NASA and industry that will have an impact on safety, noise, emissions, and cost. These intelligent engine technologies included sensors, electronics, communications, control logic, actuators, smart materials and structures, and system studies. Furthermore, this cooperative agreement helped prepare future graduates to develop the revolutionary intelligent propulsion technologies that will be needed to ensure pre-eminence of the U.S. aerospace industry. This Propulsion 21 - Phase 11 program consisted of four primary research areas and associated work elements at Ohio universities: 1.0 Turbine Engine Prognostics, 2.0 Active Controls for Emissions and Noise Reduction, 3.0 Active Structural Controls and Performance, and 4.0 System Studies and Integration. Phase l, which was conducted during the period August 1, 2003, through September 30, 2004, has been reported separately.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/CR-2008-215226 , E-16509
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 28
    facet.materialart.
    Unknown
    Intelligent Engine Systems: HPT Clearance Control (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The Advanced Thermally Actuated Clearance Control System underwent several studies. Improved flow path isolation quantified what can be gained by making the HPT case nearly adiabatic. The best method of heat transfer was established, and finally two different borrowed air cooling circuits were evaluated to be used for the HPT Active Clearance Control System.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/CR-2008-215234 , E-16493
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 29
    facet.materialart.
    Unknown
    Progress in NASA Rotorcraft Propulsion (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This presentation reviews recent progress made under NASA s Subsonic Rotary Wing (SRW) propulsion research activities. Advances in engines, drive systems and optimized propulsion systems are discussed. Progress in wide operability compressors, modeling of variable geometry turbine performance, foil gas bearings and multi-speed transmissions are presented.
    Keywords: Aircraft Propulsion and Power
    Type: E-16832 , Fundamental Aeronautics Meeting 2008; Oct 07, 2008 - Oct 09, 2008; Atlanta, GA; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 30
    facet.materialart.
    Unknown
    Comparison of Far-field Noise for Three Significantly Different Model Turbofans (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Far-field noise sound power level (PWL) spectra and overall sound pressure level (OASPL) directivities were compared for three significantly different model fan stages which were tested in the NASA Glenn 9 15 Low Speed Wind Tunnel. The test fans included the Advanced Ducted Propulsor (ADP) Fan1, the baseline Source Diagnostic Test (SDT) fan, and the Quiet High Speed Fan2 (QHSF2). These fans had design rotor tangential tip speeds from 840 to 1474 ft/s and stage pressure ratios from 1.29 to 1.82. Additional parameters included rotor-stator spacing, stator sweep, and downstream support struts. Acoustic comparison points were selected on the basis of stage thrust. Acoustic results for the low tip speed/low pressure ratio fan (ADP Fan1) were thrust-adjusted to show how a geometrically-scaled version of this fan might compare at the higher design thrust levels of the other two fans. Lowest noise levels were typically observed for ADP Fan1 (which had a radial stator) and for the intermediate tip speed fan (Source Diagnostics Test, SDT, R4 rotor) with a swept stator. Projected noise levels for the ADP fan to the SDT swept stator configuration at design point conditions showed the fans to have similar noise levels. However, it is possible that the ADP fan could be 2 to 3 dB quieter with incorporation of a swept stator. Benefits of a scaled ADP fan include avoidance of multiple pure tones associated with transonic and higher blade tip speeds. Penalties of a larger size ADP fan would include increased nacelle size and drag.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM--2008-215136 , AIAA-2008-0049 , E-16299-1 , 46th Aerospace Sciences Meeting and Exhibit; Jan 07, 2008 - Jan 10, 2008; Reno, NV; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 31
    facet.materialart.
    Unknown
    Testing of SMA-enabled Active Chevron Prototypes under Representative Flow Conditions (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Control of jet noise continues to be an important research topic. Exhaust-nozzle chevrons have been shown to reduce jet noise, but parametric effects are not well understood. Additionally, thrust loss due to chevrons at cruise suggests significant benefit from active chevrons. The focus of this study is development of an active chevron concept for the primary purpose of parametric studies for jet noise reduction in the laboratory and secondarily for technology development to leverage for full scale systems. The active chevron concept employed in this work consists of a laminated composite structure with embedded shape memory alloy (SMA) actuators, termed a SMA hybrid composite (SMAHC). SMA actuators are embedded on one side of the neutral axis of the structure such that thermal excitation, via joule heating, generates a moment and deflects the structure. The performance of two active chevron concepts is demonstrated in the presence of representative flow conditions. One of the concepts is shown to possess significant advantages for the proposed application and is selected for further development. Fabrication and design changes are described and shown to produce a chevron prototype that meets the performance objectives.
    Keywords: Aircraft Propulsion and Power
    Type: Paper-6928-36 , LAR-17332 , ASCE 11th Earth and Space Conference; Mar 09, 2008 - Mar 13, 2008; San Diego, cA; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 32
    facet.materialart.
    Unknown
    Damping of High-temperature Shape Memory Alloys (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Researchers at NASA Glenn Research Center have been investigating high temperature shape memory alloys as potential damping materials for turbomachinery rotor blades. Analysis shows that a thin layer of SMA with a loss factor of 0.04 or more would be effective at reducing the resonant response of a titanium alloy beam. Two NiTiHf shape memory alloy compositions were tested to determine their loss factors at frequencies from 0.1 to 100 Hz, at temperatures from room temperature to 300 C, and at alternating strain levels of 34-35x10(exp -6). Elevated damping was demonstrated between the M(sub s) and M(sub f) phase transformation temperatures and between the A(sub s) and A(sub f) temperatures. The highest damping occurred at the lowest frequencies, with a loss factor of 0.2-0.26 at 0.1 Hz. However, the peak damping decreased with increasing frequency, and showed significant temperature hysteresis in heating and cooling. Keywords: High-temperature, shape memory alloy, damping, aircraft engine blades, NiTiHf
    Keywords: Aircraft Propulsion and Power
    Type: SPIE Smart Materials and Structures Conference; Mar 09, 2008 - Mar 13, 2008; San Diego, CA; United States|Nondestructive Evaluation and Health Monitoring; Mar 09, 2008 - Mar 13, 2008; San Diego, CA; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 33
    facet.materialart.
    Unknown
    Thermal and Environmental Barrier Coating Development for Advanced Propulsion Engine Systems (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Ceramic thermal and environmental barrier coatings (TEBCs) are used in gas turbine engines to protect engine hot-section components in the harsh combustion environments, and extend component lifetimes. Advanced TEBCs that have significantly lower thermal conductivity, better thermal stability and higher toughness than current coatings will be beneficial for future low emission and high performance propulsion engine systems. In this paper, ceramic coating design and testing considerations will be described for turbine engine high temperature and high-heat-flux applications. Thermal barrier coatings for metallic turbine airfoils and thermal/environmental barrier coatings for SiC/SiC ceramic matrix composite (CMC) components for future supersonic aircraft propulsion engines will be emphasized. Further coating capability and durability improvements for the engine hot-section component applications can be expected by utilizing advanced modeling and design tools.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2008-215040 , ARL-TR-4368 , AIAA Paper 2007-2130 , E-16206 , 48th Structures, Structural Dynamics, and Materials Conference; Apr 23, 2008 - Apr 26, 2008; Waikiki, HI; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 34
    facet.materialart.
    Unknown
    Operability of an Ejector Enhanced Pulse Combustor in a Gas Turbine Environment (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A pressure-gain combustor comprised of a mechanically valved, liquid fueled pulsejet, an ejector, and an enclosing shroud, was coupled to a small automotive turbocharger to form a self-aspirating, thrust producing gas turbine engine. The system was constructed in order to investigate issues associated with the interaction of pulsed combustion devices and turbomachinery. Installed instrumentation allowed for sensing of distributed low frequency pressure and temperature, high frequency pressure in the shroud, fuel flow rate, rotational speed, thrust, and laboratory noise. The engine ran successfully and reliably, achieving a sustained thrust of 5 to 6 lbf, and maintaining a rotor speed of approximately 90,000 rpm, with a combustor pressure gain of approximately 4 percent. Numerical simulations of the system without pressure-gain combustion indicated that the turbocharger would not operate. Thus, the new combustor represented a substantial improvement in system performance. Acoustic measurements in the shroud and laboratory indicated turbine stage sound pressure level attenuation of 20 dB. This is consistent with published results from detonative combustion experiments. As expected, the mechanical reed valves suffered considerable damage under the higher pressure and thermal loading characteristics of this system. This result underscores the need for development of more robust valve systems for this application. The efficiency of the turbomachinery components did not appear to be significantly affected by unsteadiness associated with pulsed combustion, though the steady component efficiencies were already low, and thus not expected to be particularly sensitive.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2008-215169 , AIAA Paper 2008-0119 , E-16410 , 46th Aerospace Sciences Meeting and Exhibit; Jan 07, 2008 - Jan 10, 2008; Reno, NV; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 35
    facet.materialart.
    Unknown
    An Object-oriented Computer Code for Aircraft Engine Weight Estimation (2008)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Reliable engine-weight estimation at the conceptual design stage is critical to the development of new aircraft engines. It helps to identify the best engine concept amongst several candidates. At NASA Glenn (GRC), the Weight Analysis of Turbine Engines (WATE) computer code, originally developed by Boeing Aircraft, has been used to estimate the engine weight of various conceptual engine designs. The code, written in FORTRAN, was originally developed for NASA in 1979. Since then, substantial improvements have been made to the code to improve the weight calculations for most of the engine components. Most recently, to improve the maintainability and extensibility of WATE, the FORTRAN code has been converted into an object-oriented version. The conversion was done within the NASA s NPSS (Numerical Propulsion System Simulation) framework. This enables WATE to interact seamlessly with the thermodynamic cycle model which provides component flow data such as airflows, temperatures, and pressures, etc. that are required for sizing the components and weight calculations. The tighter integration between the NPSS and WATE would greatly enhance system-level analysis and optimization capabilities. It also would facilitate the enhancement of the WATE code for next-generation aircraft and space propulsion systems. In this paper, the architecture of the object-oriented WATE code (or WATE++) is described. Both the FORTRAN and object-oriented versions of the code are employed to compute the dimensions and weight of a 300- passenger aircraft engine (GE90 class). Both versions of the code produce essentially identical results as should be the case. Keywords: NASA, aircraft engine, weight, object-oriented
    Keywords: Aircraft Propulsion and Power
    Type: GT2008-50062 , Proceedings of ASME Turbo Expo 2008: Power for Land, Sea and Air; Jun 09, 2008 - Jun 13, 2008; Berlin; Germany
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 36
    facet.materialart.
    Unknown
    A Cryogenic High-Power-Density Bearingless Motor for Future Electric Propulsion (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The NASA Glenn Research Center (GRC) is developing a high-power-density switched-reluctance cryogenic motor for all-electric and pollution-free flight. However, cryogenic operation at higher rotational speeds markedly shortens the life of mechanical rolling element bearings. Thus, to demonstrate the practical feasibility of using this motor for future flights, a non-contact rotor-bearing system is a crucial technology to circumvent poor bearing life that ordinarily accompanies cryogenic operation. In this paper, a bearingless motor control technology for a 12-8 (12 poles in the stator and 8 poles in the rotor) switched-reluctance motor operating in liquid nitrogen (boiling point, 77 K (-196 C or -321 F)) was presented. We pushed previous disciplinary limits of electromagnetic controller technique by extending the state-of-the-art bearingless motor operating at liquid nitrogen for high-specific-power applications. The motor was levitated even in its nonlinear region of magnetic saturation, which is believed to be a world first for the motor type. Also we used only motoring coils to generate motoring torque and levitation force, which is an important feature for developing a high specific power motor.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2008-215211 , E-16485 , Paper no. 3114 , 2008 Propulsion-Safety and Affordable Readiness (P-SAR) Conference; Mar 19, 2008 - Mar 20, 2008; Myrtle Beach, SC; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 37
    facet.materialart.
    Unknown
    The General Aviation Propulsion (GAP) Program (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: The General Aviation Propulsion (GAP) Program Turbine Engine Element focused on the development of an advanced small turbofan engine. Goals were good fuel consumption and thrust-to-weight ratio, and very low production cost. The resulting FJX-2 turbofan engine showed the potential to meet all of these goals. The development of the engine was carried through to proof of concept testing of a complete engine system. The proof of concept engine was ground tested at sea level and in altitude test chambers. A turboprop derivative was also sea-level tested.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/CR-2008-215266 , E-16536
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 38
    facet.materialart.
    Unknown
    Aerodynamic Design of a Dual-Flow Mach 7 Hypersonic Inlet System for a Turbine-Based Combined-Cycle Hypersonic Propulsion System (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: A new hypersonic inlet for a turbine-based combined-cycle (TBCC) engine has been designed. This split-flow inlet is designed to provide flow to an over-under propulsion system with turbofan and dual-mode scramjet engines for flight from takeoff to Mach 7. It utilizes a variable-geometry ramp, high-speed cowl lip rotation, and a rotating low-speed cowl that serves as a splitter to divide the flow between the low-speed turbofan and the high-speed scramjet and to isolate the turbofan at high Mach numbers. The low-speed inlet was designed for Mach 4, the maximum mode transition Mach number. Integration of the Mach 4 inlet into the Mach 7 inlet imposed significant constraints on the low-speed inlet design, including a large amount of internal compression. The inlet design was used to develop mechanical designs for two inlet mode transition test models: small-scale (IMX) and large-scale (LIMX) research models. The large-scale model is designed to facilitate multi-phase testing including inlet mode transition and inlet performance assessment, controls development, and integrated systems testing with turbofan and scramjet engines.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/CR-2008-215214 , E-16505 , TRR-121507
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 39
    facet.materialart.
    Unknown
    Demonstration of Active Combustion Control (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: The primary objective of this effort was to demonstrate active control of combustion instabilities in a direct-injection gas turbine combustor that accurately simulates engine operating conditions and reproduces an engine-type instability. This report documents the second phase of a two-phase effort. The first phase involved the analysis of an instability observed in a developmental aeroengine and the design of a single-nozzle test rig to replicate that phenomenon. This was successfully completed in 2001 and is documented in the Phase I report. This second phase was directed toward demonstration of active control strategies to mitigate this instability and thereby demonstrate the viability of active control for aircraft engine combustors. This involved development of high-speed actuator technology, testing and analysis of how the actuation system was integrated with the combustion system, control algorithm development, and demonstration testing in the single-nozzle test rig. A 30 percent reduction in the amplitude of the high-frequency (570 Hz) instability was achieved using actuation systems and control algorithms developed within this effort. Even larger reductions were shown with a low-frequency (270 Hz) instability. This represents a unique achievement in the development and practical demonstration of active combustion control systems for gas turbine applications.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/CR-2008-215491 , E-16813
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 40
    facet.materialart.
    Unknown
    Post Test Evaluation of HSCT Nozzle Acoustic Liner Subcomponents Subjected to a Hot Acoustic Durability Test (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: The acoustic liner system designed for use in the High Speed Civil Transport (HSCT) was tested in a thermal-acoustic environment. Five ceramic matrix composite (CMC) acoustic tile configurations, five bulk acoustic absorbers, and one thermal protection system design were tested. The CMC acoustic tiles were subjected to two 2 3/4 hr ambient temperature acoustic exposures to measure their dynamic response. One exposure was conducted on the tiles alone and the second exposure included the tiles and the T-foam bulk absorber. The measured tile RMS strains were small. With or without the T-foam absorber, the dynamic strains were below strain levels that would cause damage during fatigue loading. After the ambient exposure, a 75-hr durability test of the entire acoustic liner system was conducted using a thermal-acoustic cycle that approximated the anticipated service cycle. Acoustic loads up to 139 dB/Hz and temperatures up to 1670 F (910 C) were employed during this 60 cycle test. During the durability test, the CMC tiles were exposed to temperatures up to 1780 F and a transient through thickness gradient up to 490 F. The TPS peak temperatures on the hot side of the panels ranged from 750 to 1000 F during the 60 cycles. The through thickness delta T ranged from 450 to 650 F, varying with TPS location and cycle number. No damage, such as cracks or chipping, was observed in the CMC tiles after completion of the testing. However, on tile warped during the durability test and was replaced after 43 or 60 cycles. No externally observed damage was found in this tile. No failure of the CMC fasteners occurred, but damage was observed. Cracks and missing material occurred, only in the fastener head region. No indication of damage was observed in the T-foam acoustic absorbers. The SiC foam acoustic absorber experienced damage after about 43 cycles. Cracking in the TPS occurred around the attachment holes and under a vent. In spite of the development of damage, the TPS maintained its insulative capability throughout the durability test. The durability test results demonstrate damage-tolerant CMC tile, CMC fastener, TPS, and T-foam absorber designs for the combined thermal and acoustic engine nozzle environment.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM--2008-215015 , E-16184 , HSR075
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 41
    facet.materialart.
    Unknown
    Mixing of Multiple Jets with a Confined Subsonic Crossflow: Part III--The Effects of Air Preheat and Number of Orifices on Flow and Emissions in an RQL Mixing Section (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: This study was motivated by a goal to understand the mixing and emissions in the Rich-burn/Quick-mix/Lean-burn (RQL) combustor scheme that has been proposed to minimize the formation of oxides of nitrogen (NOx) in gas turbine combustors. The study reported herein was a reacting jet-in-crossflow experiment at atmospheric pressure. The jets were injected from the perimeter of a cylindrical duct through round-hole orifices into a fuel-rich mainstream flow. The number of orifices investigated in this study gave over- to optimum to underpenetrating jets at a jet-to-mainstream momentum-flux ratio of J = 57. The size of individual orifices was decreased as the number of orifices increased to maintain a constant total area; the jet-to-mainstream mass-flow ratio was constant at MR = 2.5. The experiments focused on the effects of the number of orifices and inlet air preheat and were conducted in a facility that provided the capability for independent variation of jet and main inlet air preheat temperature. The number of orifices was found to have a significant effect on mixing and the distributions of species, but very little effect on overall NOx emissions, suggesting that an aerodynamically optimum mixer might not minimize NOx emissions. Air preheat was found to have very little effect on mixing and the distributions of major species, but preheating both main and jet air did increase NOx emissions significantly. Although the air jets injected in the quick-mix section of an RQL combustor may comprise over 70 percent of the total air flow, the overall NOx emission levels were found to be more sensitive to main stream air preheat than to jet stream air preheat.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2008-215151 , E-16378
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 42
    facet.materialart.
    Unknown
    Halbach Magnetic Rotor Development (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: The NASA John H. Glenn Research Center has a wealth of experience in Halbach array technology through the Fundamental Aeronautics Program. The goals of the program include improving aircraft efficiency, reliability, and safety. The concept of a Halbach magnetically levitated electric aircraft motor will help reduce harmful emissions, reduce the Nation s dependence on fossil fuels, increase efficiency and reliability, reduce maintenance and decrease operating noise levels. Experimental hardware systems were developed in the GRC Engineering Development Division to validate the basic principles described herein and the theoretical work that was performed. A number of Halbach Magnetic rotors have been developed and tested under this program. A separate test hardware setup was developed to characterize each of the rotors. A second hardware setup was developed to test the levitation characteristics of the rotors. Each system focused around a unique Halbach array rotor. Each rotor required original design and fabrication techniques. A 4 in. diameter rotor was developed to test the radial levitation effects for use as a magnetic bearing. To show scalability from the 4 in. rotor, a 1 in. rotor was developed to also test radial levitation effects. The next rotor to be developed was 20 in. in diameter again to show scalability from the 4 in. rotor. An axial rotor was developed to determine the force that could be generated to position the rotor axially while it is rotating. With both radial and axial magnetic bearings, the rotor would be completely suspended magnetically. The purpose of this report is to document the development of a series of Halbach magnetic rotors to be used in testing. The design, fabrication and assembly of the rotors will be discussed as well as the hardware developed to test the rotors.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2008-215056 , E-16281
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 43
    facet.materialart.
    Unknown
    Enhanced Self Tuning On-Board Real-Time Model (eSTORM) for Aircraft Engine Performance Health Tracking (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: A key technological concept for producing reliable engine diagnostics and prognostics exploits the benefits of fusing sensor data, information, and/or processing algorithms. This report describes the development of a hybrid engine model for a propulsion gas turbine engine, which is the result of fusing two diverse modeling methodologies: a physics-based model approach and an empirical model approach. The report describes the process and methods involved in deriving and implementing a hybrid model configuration for a commercial turbofan engine. Among the intended uses for such a model is to enable real-time, on-board tracking of engine module performance changes and engine parameter synthesis for fault detection and accommodation.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/CR-2008-215272 , FR-26751 , E-16543
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 44
    facet.materialart.
    Unknown
    System Study for Axial Vane Engine Technology (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: The purpose of this engine feasibility study was to determine the benefits that can be achieved by incorporating positive displacement axial vane compression and expansion stages into high bypass turbofan engines. These positive-displacement stages would replace some or all of the conventional compressor and turbine stages in the turbine engine, but not the fan. The study considered combustion occurring internal to an axial vane component (i.e., Diesel engine replacing the standard turbine engine combustor, burner, and turbine); and external continuous flow combustion with an axial vane compressor and an axial vane turbine replacing conventional compressor and turbine systems.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/CR-2008-215175 , E-16418
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 45
    facet.materialart.
    Unknown
    Assessment of Microphysical Models in the National Combustion Code (NCC) for Aircraft Particulate Emissions: Particle Loss in Sampling Lines (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This paper at first describes the fluid network approach recently implemented into the National Combustion Code (NCC) for the simulation of transport of aerosols (volatile particles and soot) in the particulate sampling systems. This network-based approach complements the other two approaches already in the NCC, namely, the lower-order temporal approach and the CFD-based approach. The accuracy and the computational costs of these three approaches are then investigated in terms of their application to the prediction of particle losses through sample transmission and distribution lines. Their predictive capabilities are assessed by comparing the computed results with the experimental data. The present work will help establish standard methodologies for measuring the size and concentration of particles in high-temperature, high-velocity jet engine exhaust. Furthermore, the present work also represents the first step of a long term effort of validating physics-based tools for the prediction of aircraft particulate emissions.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2008-215304 , AIAA Paper-2009-0257 , E-16575 , 47th AIAA Aerpspace Sciences Meeting (ASM); Jan 05, 2009 - Jan 08, 2009; Florida; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 46
    facet.materialart.
    Unknown
    Multiplexed Predictive Control of a Large Commercial Turbofan Engine (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Model predictive control is a strategy well-suited to handle the highly complex, nonlinear, uncertain, and constrained dynamics involved in aircraft engine control problems. However, it has thus far been infeasible to implement model predictive control in engine control applications, because of the combination of model complexity and the time allotted for the control update calculation. In this paper, a multiplexed implementation is proposed that dramatically reduces the computational burden of the quadratic programming optimization that must be solved online as part of the model-predictive-control algorithm. Actuator updates are calculated sequentially and cyclically in a multiplexed implementation, as opposed to the simultaneous optimization taking place in conventional model predictive control. Theoretical aspects are discussed based on a nominal model, and actual computational savings are demonstrated using a realistic commercial engine model.
    Keywords: Aircraft Propulsion and Power
    Type: E-16761 , AIAA Journal of Guidance, Control, and Dynamics (ISSN 0731-5090); 31; 2; 273-281
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 47
    facet.materialart.
    Unknown
    Concepts for Variable/Multi-Speed Rotorcraft Drive System (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: In several recent studies and on-going developments for advanced rotorcraft, the need for variable or multi-speed capable rotors has been raised. A speed change of up to 50 percent has been proposed for future rotorcraft to improve overall vehicle performance. Accomplishing rotor speed changes during operation requires both a rotor that can perform effectively over the operation speed/load range, and a propulsion system that can enable these speed changes. A study has been completed to investigate possible drive system arrangements that can accommodate up to the 50 percent speed change. Several concepts will be presented and evaluated. The most promising configurations will be identified and developed for future testing in a sub-scaled test facility to validate operational capability.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2008-215276 , ARL-TR-4564 , AHS 080273 , 64th Annual Forum and Technology Display (American Helicopter Society Forum); Apr 29, 2008 - May 01, 2008; Montreal; Canada
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 48
    facet.materialart.
    Unknown
    NASA / Pratt and Whitney Collaborative Partnership Research in Ultra High Bypass Cycle Propulsion Concepts (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Current collaborative research with Pratt & Whitney on Ultra High Bypass Engine Cycle noise, performance and emissions improvements as part of the Subsonic Fixed Wing Project Ultra High Bypass Engine Partnership Element is discussed. The Subsonic Fixed Wing Project goals are reviewed, as well as their relative technology level compared to previous NASA noise program goals. Progress toward achieving the Subsonic Fixed Wing Project goals over the 2008 fiscal year by the UHB Partnership in this area of research are reviewed. The current research activity in Ultra High Bypass Engine Cycle technology, specifically the Pratt & Whitney Geared Turbofan, at NASA and Pratt & Whitney are discussed including the contributions each entity bring toward the research project, and technical plans and objectives. Pratt & Whitney Geared Turbofan current and future technology and business plans are also discussed, including the role the NASA SFW UHB partnership plays toward achieving those goals.
    Keywords: Aircraft Propulsion and Power
    Type: E-16905 , Fundamental Aeronautics Program - 2nd Annual Meeting; Oct 07, 2008 - Oct 09, 2008; Georgia; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 49
    facet.materialart.
    Unknown
    NASA / GE Aviation Collaborative Partnership Research in Ultra High Bypass Cycle Propulsion Concepts (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Current collaborative research with General Electric Aviation on Open Rotor propulsion as part of the Subsonic Fixed Wing Project Ultra High Bypass Engine Partnership Element is discussed. The Subsonic Fixed Wing Project goals are reviewed, as well as their relative technology level compared to previous NASA noise program goals. The current Open Rotor propulsion research activity at NASA and GE are discussed including the contributions each entity bring toward the research project, and technical plans and objectives. GE Open Rotor propulsion technology and business plans currently and toward the future are also discussed, including the role the NASA SFW UHB partnership plays toward achieving those goals.
    Keywords: Aircraft Propulsion and Power
    Type: E-16903 , FA Annual Meeting; Oct 07, 2008 - Oct 09, 2008; Georgia; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 50
    Electronic Resource
    Electronic Resource
    Synthese, Struktur und Umlagerung von Chlorbis(2,4,6-tri-tert-butylphenyl)gallan (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2255-2257 
    Details
    ISSN: 0009-2940
    Keywords: Gallane, chlorobis(supermesityl) ; Rearrangement ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis, Structure, and Rearrangement of Chlorobis(2,4,6-tri-tert-butylphenyl)gallaneThe title compound 1 is easily obtained from GaCl3 and 2 equvialents of supermesityllithium. According to an X-ray structure analysis one of the supermesityl rings shows a large deviation from planarity. Heating of 1 in vacuo gives mainly two products: an isomer of 1 in which one of the supermesityl groups is bound to Ga by one of its tert-butyl groups (2) and a benzo[b]gallolane (3) formed by elimination of HCl, X-ray structure analyses and full NMR (1H, 13C) data are provided for 1 and 2, MS and characteristic NMR (1H, 13C) data for 3.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931261014
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 51
    Electronic Resource
    Electronic Resource
    Masthead (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993) 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260101
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 52
    Electronic Resource
    Electronic Resource
    Darstellung und Eigenschaften von und Reaktionen mit metallhaltigen Heterocyclen, LXXX. Insertions- und Additions-Reaktionen an Diphosphamanganacyclopropanen mit aktivierten Alkinen (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 23-29 
    Details
    ISSN: 0009-2940
    Keywords: Diphosphamanganacyclopropanes ; Alkyne insertion ; Alkyne addition ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Metal-;Containing Heterocycles: Preparation, Properties, Reactions, LXXX.  -  Insertion and Addition Reactions on Diphosphamanganacyclopropanes with Activated AlkynesThe thermally and kinetically stable diphosphamanganabicyclooctadienones 3a  -  e [R2 = tBu: R1 = iPr (a), nPr (b), Ph (c); R2 = Cy: R1 = nPr (d), Ph (e)] are obtained by the reaction of the alkyne (CCO2Me)2 with the diphosphamanganacyclopropanes (OC)4Mn-PR12=PR2 (2a  -  e). Depending on steric factors the formation of 3a  -  e occurs in two different ways. In a first step the alkyne is inserted into the P  -  P bond of 2a  -  e to give the kinetically labile five-membered rings 1a  -  e. Subsequently another alkyne is added to the PR2 and a CO group of 1a  -  e to give 3a  -  e. In an alternative way the alkyne is added first to the PR2 and a CO group of 2a with formation of the diphosphamanganabicyclohexenone 4a. Insertion of a second alkyne into the P  -  P bond of 4a affords the bicyclooctadienone 3a. Compound 2a, 3c, and 4a have been characterized by X-ray structural analyses.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260105
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 53
    Electronic Resource
    Electronic Resource
    Mehrfachbindungen zwischen Hauptgruppenelementen und Übergangsmetallen, CXIV. Organorhenium(VII)-oxide (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 45-50 
    Details
    ISSN: 0009-2940
    Keywords: Rhenium compounds ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Multiple Bonds between Main Group Elements and Transition Metals, CXIV.  -  Organorhenium(VII) OxidesAlkylrhenium(VII) oxides of formulae RReO3 and RReO3 · L (L = quinuclidine) result from dirhenium heptaoxide and dialkylzinc compounds at low temperatures in THF solution. Unbranched, noncyclic organorhenium oxides prove to be less thermolabile than branched-chain derivatives, with the thermal stability decreasing with increasing chain length. Complexes with branched carbon chains normally can be isolated as 1:1 adducts of a nitrogen base, e.g. quinuclidine. A first chiral alkylmetal oxide and base-stabilized cyclopropyltrioxorhenium(VII) are also described.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260108
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 54
    Electronic Resource
    Electronic Resource
    Notizen / Notes [Li2(THF)4DAD] und [DAD  -  H][ZrCl5(THF)]: Neue Strukturvarianten phenylsubstituierter 1,4-Diaza-1,3-dien-Liganden (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 57-61 
    Details
    ISSN: 0009-2940
    Keywords: Lithium compounds ; Enediamide structure ; 1,4-Diaza-1,3-diene, protonated ; Hydrogen bond ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: [Li2(THF)4DAD] and [DAD  -  H][ZrCl5(THF)]: New Types of Phenyl-;Substituted 1,4-Diaza-1,3-diene LigandsTwo extreme situations in 1,4-diaza-1,3-diene (DAD) chemistry are described. Reaction of phenyl-substituted DAD 1a  -  c with lithium in the molecular ratio of 1:2 affords in high yield the extremely air-sensitive complexes [Li2(THF)4DAD] (2a  -  c). The structure of 2b has been determined by X-ray diffraction. Each of the Li+ ions is coordinated by the two terminal N atoms of the s-cis-configurated DAD dianion and by two molecules of THF. Protonation of ZrCl4 · DAD (3a) by HCl in THF gives the ionic complex [ZrCl5(THF)][DAD  -  H] (4), which contains a protonated [DAD  -  H]+ cation. The structure of the sterically crowded N = C  -  C = N skeleton of the [DAD  -  H]+ cation is not influenced by the positive charge and adopts the unusual Z-gauche-Z conformation.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260110
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 55
    Electronic Resource
    Electronic Resource
    Reaktive E = C(p-p)π-Systeme, XXXIII. Side-on-Koordination des Phosphaalkins P ≡ C  -  N(iPr)2 im 16e-Nickel(0)-Komplex Ni(CO)PCy3[PCN(iPr)2] (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 63-65 
    Details
    ISSN: 0009-2940
    Keywords: Phosphaalkyne, amino- ; Nickel carbonyl phosphane complex ; π Coordination ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactive E = C(p-p)π Systems, XXXIII.  -  Side-on Coordination of the Phosphaalkyne P ≡ C  -  N(iPr)2 in the 16e Nickel(0) Complex Ni(CO)PCy3[PCN(iPr)2]The reaction of (diisopropylamino)phosphaethyne P ≡ C  -  N(iPr)2 with the nickel complex [Ni(CO)3PCy3] - in contrast to the analogous reactions with Ni(CO)4 or Ni(CO)3PR3 (R = Me, Ph) - leads to the novel 16e nickel(0) system [Ni{η2-P ≡ C  -  N(iPr2)}(CO)PCy3] with a planar geometry of all skeleton atoms besides the methyl and cyclohexyl groups. Side-on coordination of the P ≡ C triple bond results in an increase of the PC distance to 1.665 Ȧ typical for phosphaalkenes.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260111
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 56
    Electronic Resource
    Electronic Resource
    Zur Tautomerie von 5,5-Diphenyldihydro-4H-1,2,3-triazol-4-on und 5-Amino-4,4-diphenyl-4H-1,2,3-triazolen (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 103-108 
    Details
    ISSN: 0009-2940
    Keywords: 1,2,3-Triazol-4-ones, 3,5-dihydro-4H- ; 1,2,3-Triazoles, 5-amino-4H- ; Tautomerism ; 15N-NMR Spectroscopy ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tautomerism of 5,5-Diphenyldihydro-4H-1,2,3-triazol-4-one and 5-Amino-4,4-diphenyl-4H-1,2,3-triazolesMethylation of the 5-amino-4H-1,2,3-triazole 5 affords the N-methyl- (12) and the N,N-dimethylaminotriazole 13. X-ray diffraction analyses show that the tautomer 5b exists in the crystal and that 5b and 13 possess similar structures and atomic distances. Both compounds exhibit restricted rotation of the amino groups in solution. The comparison of UV, carbon-13 and nitrogen-15 spectra of the tautomeric triazoles 2 and 5 with those of the N-methyl compounds 3 and 13 demonstrates that the tautomers 2a and 5b are strongly favoured also in solution.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260117
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 57
    Electronic Resource
    Electronic Resource
    3a,6-Dihydro-3H-imidazo[1,2-d]tetrazole aus 1- und 4-Phenacyl-1H-tetrazolium-Salzen und Ammoniak (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 129-132 
    Details
    ISSN: 0009-2940
    Keywords: 3H-Imidazo[1,2-d]tetrazoles, 3a,6-dihydro- ; Tetrazolium salts, 1,5-dialkyl(aryl)-4-phenacyl- ; reaction with ammonia ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 3a,6-Dihydro-3H-imidazo[1,2-d]tetrazoles from 1- and 4-Phenacyl-1H-tetrazolium Salts and AmmoniaTreatment of the tetrazolium salts 1 with aqueous ammonia affords the novel ring system 2 (in certain cases along with the ylides 3). The structure of 2 has been confirmed by an X-ray analysis of 2a.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260120
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 58
    Electronic Resource
    Electronic Resource
    Crystal Structure of the Explosive Parent Benzyne Precursor: 2-Diazoniobenzenecarboxylate Hydrate (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 243-249 
    Details
    ISSN: 0009-2940
    Keywords: Benzyne precursor ; Neighboring group interactions ; Incipient nucleophilic attack ; 2-Diazoniobenzenecarboxylate ; Calculations, ab initio, MO ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The structure of the highly unstable benzyne precursor 2-diazoniobenzenecarboxylate (3) has been determined by single-crystal X-ray diffraction. The structure is discussed in comparison to ab initio results for several conformers of 3, related aromatic diazonium ions, and phenyl cation and also to crystal structures of simple diazonium ion salts and of benzoates. Structural features and characteristic distortions are related to the electron density distributions and to intra- and intermolecular interactions between the neighboring functional groups.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260133
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 59
    Electronic Resource
    Electronic Resource
    Darstellung und Charakterisierung von Anthrylenmagnesium-Innerkomplexen (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 225-237 
    Details
    ISSN: 0009-2940
    Keywords: Anthracene derivatives ; Magnesium anthracene inner complexes ; 13C CP/MAS NMR spectra ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Preparation and Characterization of Inner Complexes of AnthrylenemagnesiumAnthracene derivatives containing ether or amino groups in 9- or 9,10-position (1 - 10) react with magnesium to form new magnesium anthracene inner complexes (11 - 20). These complexes as well as their organic starting materials have been extensively characterized by spectroscopy and chemical means. It was found that solvent ligands which are present in all magnesium anthracene complexes known to date can be partially or totally replaced by inner complexation. For some of the new magnesium anthracene inner complexes the complex formation rates have been determined.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260131
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 60
    Electronic Resource
    Electronic Resource
    Reversibility of the [2 + 2] Cycloaddition of Isocyanates to Glycals (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 265-267 
    Details
    ISSN: 0009-2940
    Keywords: [2 + 2] Cycloaddition, reversible ; Glycals ; Isocyanates ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: [2 + 2] Cycloadducts obtained by the addition of tosyl isocyanate to glycals (10 - 13) undergo retro-addition upon heating or even at room temperature. The rate of retro-addition increases with rising temperature and polarity of the solvent.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260136
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 61
    Electronic Resource
    Electronic Resource
    Synthesis and Aggregation Properties in Solution of a New Octasubstituted Copper Phthalocyanine: {2,3,9,10,16,17,23,24-Octakis-[(dioctylaminocarbonyl)methoxy]phthalocyaninato}copper(II) (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 269-271 
    Details
    ISSN: 0009-2940
    Keywords: Phthalocyanine, soluble ; Cation-induced phthalocyanine aggregates ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of the octasubstituted phthalocyanine 1, highly soluble in organic solvents, is described. Its aggregation properties in different solvents and in the presence of alkaline, alkaline earth, and ammonium salts are studied.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260137
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 62
    Electronic Resource
    Electronic Resource
    Organometall-Oxide  -  Höhervalente Derivate der d-Metall-Säuren, 6. Tris(3,5-dimethyl-1-pyrazolyl)boranato-substituierte Alkyl(dioxo)1-, Methylenphosphoranyl(dioxo)1- und s̰1-Allyl(dioxo)1-Komplexe des Molybdäns und Wolframs (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 289-296 
    Details
    ISSN: 0009-2940
    Keywords: Oxo complexes, organometallic ; Borato, hydrotris(3,5-dimethyl-1-pyrazolyl)1-, complexes ; Molybdenum complexes ; Tungsten complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Organometallic Oxo Complexes  -  Highervalent Derivatives of the d-Metal Acids, 6.  -  Hydrotris(3,5-dimethyl-1-pyrazolyl)borato-Substituted Alkyl(dioxo)1-, Methylenephosphoranyl(dioxo)1-, and s̰1-Allyl(dioxo) Complexes of Molybdenum and TungstenTp*MoO2Cl (1) and Tp*WO2Cl (2) [Tp* = κ31-HB(3,5-Me2pz)3] react with trimethyl aluminium to form the corresponding dioxo(methyl) complexes Tp*MO2(CH3), M=Mo (3), W (4). An X-ray crystal structure analysis of 3 is performed. The less oxidizing tungsten complex 2 is alkylated by Grignard reagents to yield alkyl complexes of the type Tp*WO2R 5-7 [R=CH2SiMe3, CH2tBu and CH2C(Me)Ph2] and the s̰1-2-methallyl complex Tp*WO2(CH2CMe=CH2) 8. Reactions of 2 with methylenephorphoranes R3P=CH2 (R=iPr, Ph) give transylidation products Tp*WO2(CHPiPr3) (9) and Tp*WO2(CH-PPh3) (10). Hydrolysis of 10 leads to a trioxotungstate [Tp*WO3]- (11), stabilized by a hydroxyphosphonium cation.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260204
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 63
    Electronic Resource
    Electronic Resource
    all-Homocalixarene: Carbocyclische Wirtverbindungen mit intra- und extraannularen Ligandarmen (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2483-2491 
    Details
    ISSN: 0009-2940
    Keywords: Carbocycles ; Homocalixarenes ; Calixarenes, Homo- ; Large rings ; Macrocycles ; [2n]Metacyclophanes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: all-Homocalixarenes: Carbocyclic Host Compounds with Intra- and Extraannular Ligand ArmsMethoxy-substituted [2n]metacyclophanes 1-10, obtained by Müller-Röscheisen cyclization, are converted into all-homocalixarenes 11-20 with free phenolic hydroxy functions. The well-soluble cyclic pentamer 11 and octamer 14 with endo-acidic host properties are investigated with regard to guest binding. They exhibit selectivity towards alkaline earth metal ions (Ba2+) in liquid/liquid extraction studies. Some of the macrocyclic oligophenols are transformed into homocalixarenes 21-25 with intra- or extraannular oxapropionate groups. The diester 22 and the tetraester 23 are converted into carbocycles 26 and 27 with two and four free oxapropionic acid groups. Complexation properties of the oligoesters in extraction studies and log K values in water are reported. X-ray structural analyses were performed of the [6]-, [8]- and [4]- homocalixarenes 9 and 21, 14 and 23; the inclusion of solvent molecules is proven.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931261123
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 64
    Electronic Resource
    Electronic Resource
    Preparation and Conformational Studies of Ethylene-Bridged Calixarene-Analogous Macrocyclic Metacyclophanes (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2501-2504 
    Details
    ISSN: 0009-2940
    Keywords: [(2.1)n]Metacyclophanes, hydroxy- ; Calixarenes ; Trans-tert-butylation ; Conformation ; Hydrogen bonding, intramolecular ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The novel macrocyclic compounds hexahydroxy[2.1.2.1.2.1]- (7b) and octahydroxy[2.1.2.1.2.1.2.1]metacyclophane (7c) have been prepared from anisole in six steps by using the tert-butyl function as a positional protective group on the aromatic ring. Base-catalyzed condensation of 1,2-bis(5-tert-butyl-2-hydroxy-phenyl)ethane (5) with formaldehyde in refluxing xylene does not afford the dimeric product, tetrahydroxy[2.1.2.1]metacyclophane 6a, but furnishes the larger macrocycles 6b and 6c in 70-90% yield. AlCl3/MeNO2-catalyzed trans-tert-butylation of 6b and 6c in toluene gives the desired metacyclophanes 7b and 7c in 60 and 80% yields, respectively, along with tert-butyltoluene 8b. The conformations of the systems such as trimer 6b and tetramers 6c, 7c have been evaluated from their dynamic 1H-NMR spectra. The tetramer 6c is fixed to form a “pleated-loop” conformation like the calix[8]arenes due to the much more stronger intramolecular hydrogen bonding among the hydroxyl groups than in the trimer 6b.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931261125
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 65
    Electronic Resource
    Electronic Resource
    Stereoselectivity of the Thermally Initiated Free-Radical Chain Addition of Cyclohexane to 1-Alkynes (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2493-2499 
    Details
    ISSN: 0009-2940
    Keywords: Radicals ; Addition ; Stereoselectivity ; Alkynes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Alkanes can be added to alkynes in a thermally initiated free-radical chain reaction (“ane reaction”). The addition of cyclohexane to 1-alkynes 1a-1 yields a mixture of (Z)- and (E)-2-cyclohexyl-1-alkenes 3a-1. An essential step in this reaction is the addition of cyclohexyl radicals to the alkynes to give 2-cyclohexyl-1-alkenyl radicals 2a-1 which abstract hydrogen from cyclohexane to yield the products 3a-1. The stereoselectivity of the addition has been measured in the temperature range of 160-260°C. It strongly depends on the substituent X of the radical center and varies over a range of almost four orders of magnitude from [(Z)-3a]:[(E)-3a] = 33 (X = OMe) at 160°C to [(Z)-31]:[(E)-31] = 0.012 (X = tBu) at 260°C. The stereoselectivity is further influenced by the temperature and in most cases by the concentration of the hydrogen donor cyclohexane. The reaction is discussed in terms of the stereoselectivity of the addition of cyclohexyl radicals to the alkyne, of the structure of the 1-alkenyl radical (σ and π radical, respectively), the rate of inversion in the case of σ alkenyl radicals, and the relative rates of syn and anti hydrogen transfer.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931261124
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 66
    Electronic Resource
    Electronic Resource
    Medium-Sized Cyclophanes, 29. Synthesis and Desulfurization of 2,11-Dithia[3]metacyclo- and 2,11-Dithia[3]paracyclo[3](4,9)pyrenophanes (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2505-2511 
    Details
    ISSN: 0009-2940
    Keywords: Cyclophanes ; Benzenopyrenophane, 4,9-bridged ; Sulfones, pyrolysis of ; Photodesulfurization ; [2]Naphthaleno[2]paracyclophane, 1,5-bridged ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2,11-Dithia[3]metacyclo- (14b) and 2,11-dithia[3]paracyclo[3]-(4,9)pyrenophane (14c) were obtained by the coupling reactions of 4,9-bis(chloromethyl)pyrene (12) with the corresponding bis(mercaptomethyl)benzenes (13b, c). Attempted pyrolysis of the disulfones 18b, 18c to afford [2]metacyclo- (19b) and [2]paracyclo[2](4,9)pyrenophane (19c) failed. Only the ring cleavage products 16 and 20 were obtained. The sulfur dioxide extrusion by vapor-phase pyrolysis of the corresponding disulfone 18 to the highly strained 19 clearly demonstrates the limits of these preparative ring contraction method. The photolytic desulfurization of 14c afforded the [2](1,5)naphthal-eno[2]paracyclophane analogue 21 instead of [2]paracyclo[1]-(4,9)pyrenophane 21′. The mechanism of the pyrolysis and photolysis reactions is discussed.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931261126
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 67
    Electronic Resource
    Electronic Resource
    Flow-Vacuum Pyrolysis of Polycyclic Compounds, 6. Pyrolysis of Dibenzo [CH]8 Hydrocarbons (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2513-2517 
    Details
    ISSN: 0009-2940
    Keywords: Dibenzo [CH]8 hydrocarbons ; Flow-vacuum pyrolysis ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The flow-vacuum pyrolysis of dibenzo [CH]8 hydrocarbons 2,3,4, and 5 are studied at 1 Torr and in the temperature range between 400 and 650°C. The following new transformations have been observed: 2⇆4, 2→5, 3→5, 3⇆4, 3→2, 5→11, the last three presenting analogies in the [CH]8 and/or benzo [CH]8 series. A reaction mechanism is suggested.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931261127
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 68
    Electronic Resource
    Electronic Resource
    On the Reaction of 1-Aza-2-azoniaallene Salts with Carbodiimides (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2519-2524 
    Details
    ISSN: 0009-2940
    Keywords: 1-Aza-2-azoniaallene cations ; Carbodiimides ; 1H-1,2,4-Triazolium salts ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1-Aza-2-azoniaallene cations 3, prepared in situ from geminal (chloroalkyl)azo compounds 2, react with carbodiimides 4 to give 4,5-dihydro-5-imino-1H-1,2,4-triazolium salts 7. An X-ray structural analysis was carried out for 71. According to AM1 calculations the cycloaddition of carbodiimides to 1-aza-2-azoniaallene cations occurs in a nonconcerted manner via cyanamidium cations 5 as intermediates. Hetero-Wagner-Meerwein rearrangements of the primary cycloadducts 6 provide the final products 7.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931261128
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 69
    Electronic Resource
    Electronic Resource
    Organophosphorverbindungen, 73. Der Tri-tert-butyl-2-cyclopropen-1-yl-Rest als kinetisch stabilisierende Gruppe für 1-Aza-3-phosphaallene (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2525-2530 
    Details
    ISSN: 0009-2940
    Keywords: Phosphanes, cyclopropenyl- ; Phosphaalkenes, cyclopropenyl ; Shifts, [1,3]-silyl and [1,3]-H ; 1-Aza-3-phosphaallenes ; Cyclopropenyl substituents ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Organophosphorus Compounds, 73[1]. - The Tri-tert-butyl-2-cyclopropen-1-yl Substituent as Kinetically Stabilizing Group for 1-Aza-3-phosphaallenes[2]The cyclopropenylphosphane 5 reacts with the isocyanates 6a-g to form the phosphaalkenes 7a-g. An analogous transformation occurs with the same phosphane and the bifunctional isocyanates 8a, b (→ 9a, b). In contrast, the reaction 5 + 6h ends at the stage of the tautomers 11h ⇆ 12h. Methanolysis of 7b and of 11h ⇆ 12h leads to the carbamoyl-cyclopropenylphosphanes 14a and b, respectively. Sodium hydroxide-catalyzed elimination of hexamethyldisiloxane from 7b, g and the tautomer mixture 11h ⇆ 12h yields the target 1-aza-3-phosphaallenes 16a-c.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931261129
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 70
    Electronic Resource
    Electronic Resource
    4,5,12,13-Tetrabromo[2.2]paracyclophane - A New Bis(aryne) Equivalent (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2531-2534 
    Details
    ISSN: 0009-2940
    Keywords: [2.2]Paracyclophanes ; 1,2-Dibromoarenes ; anti-[2.2]Paracyclophanes ; Aryne generation ; Diels-Alder reactions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of 2 with nBuLi at -78°C generates aryne intermediates within the aromatic rings of [2.2]paracyclophane which are trapped in Diels-Alder reactions with dienes like furan, 1,9-diphenylisobenzofuran, or cyclopentadiene. Reductive deoxygenation with low-valent titanium reagents or TMSI converts the adducts of furan and isobenzofuran into anti-[2.2]paracyclophanes 4 and 5, respectively. The reaction of two aryne intermediates with [2.2](2,5)furanophane (7) yields 8 with three [2.2]paracyclophane units arranged in a stair-like fashion; yet, in this compound the highly shielded oxygen atoms cannot be removed anymore by reduction.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931261130
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 71
    Electronic Resource
    Electronic Resource
    Coordinated 1-Aza-1,3-butadienes: Stable Intermediates in the Formation of Pyridines from [(β-Aminoethenyl)carbene]chromium Complexes (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2535-2541 
    Details
    ISSN: 0009-2940
    Keywords: Chromium, (β-aminoethenyl)carbene complexes ; 1-Aza-1,3-butadienes, coordinated ; Pyridines, cycloaddition with alkynes ; Chelated chromium complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: [(β-Aminoethenyl)carbene]chromium complexes 3a-c rearrange to coordinated 1-aza-1,3-butadienes 6a-c, which undergo cycloadditions with alkynes 7a, c to pyridines 9a, 10a-c.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931261131
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 72
    Electronic Resource
    Electronic Resource
    A Soluble Benzodifluoranthene Derivative by Dehydration of an Oxygen-Bridged Precursor (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2543-2546 
    Details
    ISSN: 0009-2940
    Keywords: Multicyclic aromatic hydrocarbons, dehydration to ; Multicyclic aromatic hydrocarbons, solubility of ; Benzodifluoranthene derivative ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and characterization of the alkyl chain-substituted benzodifluoranthene 6 are described. The final synthetic step involves an acid-promoted dehydration whose conversion is determined to be quantitative. The solubilities of compounds 4e, 5, and 6 are qualitatively correlated with structural features. The molecular structure of 6 in the crystal is elucidated by an X-ray structure analysis.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931261132
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 73
    Electronic Resource
    Electronic Resource
    Synthese mittlerer und großer Ringe, XXXIV. Stereoselektive Synthese überbrückter und verzweigter Methyl-desoxyfuranoside aus 3,6-Hexanooxepin-4,5-dicarbonsäure-dimethylester (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2547-2551 
    Details
    ISSN: 0009-2940
    Keywords: Furanosides, methyl ; Photochemistry ; Stereoselective reactions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Syntheses of Medium and Large Rings, XXXIV[1,2]. - Stereoselective Synthesis of Bridged and Branched Methyl Deoxyfuranosides from Dimethyl 3,6-Hexanooxepine-4,5-dicarboxylateThe stereoselective synthesis of the bridged methyl furanosides 4-8 with four, five, and six stereogenic centers is described. The reaction sequence starts with the addition of methanol to the oxepine 1. The photochemical electrocyclic ring closure of 2 gives the cyclobutene 3. Ruthenium tetraoxide oxidation of 3 leads to the title compound 4 that is further converted to 5-8 by stereoselective reductions.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931261133
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 74
    Electronic Resource
    Electronic Resource
    Synthese, Struktur und Reaktivität von Diphosphiranen (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 645-648 
    Details
    ISSN: 0009-2940
    Keywords: Diphosphiranes, molecular structure of ; 1,2-Diphospha-2-propene ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis, Structure, and Reactivity of DiphosphiranesThe 1,1-diamino-1,2-diphospha-2-propen (2,6-Me2C5H8N)2P - P=C(SiMe3)2 (3) is obtained by treatment of bis(2,6-dimethyl-piperidino)(trimethylsilyl)phosphane (1) with [bis(trimethylsilyl)methylene]chlorophosphane (2). Compound 3 readily undergoes thermally isomerization to the diphosphirane 2,6- Nucleophilic substitution of the P1-chloro function of 1-chloro-2-(diisopropylamino)1-3,3-bis(trimethylsilyl)diphosphirane (6) leads to alkyl, amino, phosphanyl, and arsanyl derivatives 7a - d. The corresponding hydrogen derivative 7e is formed by reduction of 6 with tri-n1-butylstannane. The molecular structure of 7c as well as the NMR data of the diphosphiranes are discussed.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260314
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 75
    Electronic Resource
    Electronic Resource
    Übergangsmetall-Stannyl-Komplexe, 7. Darstellung von Carben-Komplexen (π1-Aromat)(CO)2CrCR2 durch Umsetzung der anionischen Stannyl-Komplexe [(π1-Aromat)(CO)2CrSnPh3]- mit R2CX2 oder [R2CX]Y (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 657-664 
    Details
    ISSN: 0009-2940
    Keywords: Carbene complexes ; Stannyl complexes ; Chromium complexes ; Anionic complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Transition Metal Stannyl Complexes, 7[1]. - Preparation of Carbene Complexes (π1-Arene)(CO)2CrCR2 by the Reaction of the Anionic Stannyl Complexes [(π1-Arene)(CO)2CrSnPh3]- with R2CX2 or [R2CX]YCarbene complexes (π1-arene)(CO)2Cr=CR2 are formed in substitution/elimination reactions from the anionic stannyl complexes K[(π1-arene)(CO)2CrSnPh3] [π1-arene=C6H6 (1a), 1,3,5-Me3C6H3 (1b), 1,2,4,5-Me4C6H2 (1c)] C6Me6 (1d) and organic dihalides R2CX2 containing activated C - X bonds or ionic halides [R2CX]Y. Bis(stannyl) complexes (π1-arene)(CO)2Cr(SnPh3)2 (3) and hydrido(stannyl)complexes (π1-arene)(CO)2Cr(H)SnPh3 are formed as byproducts due to the reaction of the eliminated Ph3SnCl with the anionic starting complexes or electron transfer reactions, respectively. The portion and ratio of the byproducts is largely influenced by the steric properties of both the (π1-arene)(CO)2Cr fragment and the organic halide. Pyridinylidene complexes 2) are only obtained from 2-chloro-N1-methylpyridinium tetrafluoroborat with 1a - c, but not with 1d. With the sterically less demanding halides [R2N=C(H)Cl]Cl [NR2=NMe2, (n=3, 4)] or 3,3-dichloro-1,2-diphenylcyclopropene the carbene complexes (π1-arene)(CO)2Cr=C(H)NR2 or are obtained with all employed π1-arene ligands.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260316
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 76
    Electronic Resource
    Electronic Resource
    Vinyliden-Übergangsmetallkomplexe, XXII. Alkin-, Alkinyl(hydrido)1-, Vinyliden-und Vinylvinyliden-Komplexe des Rhodiums aus OH-, NH2- und Cl-funktionalisierten Alkinen (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 669-678 
    Details
    ISSN: 0009-2940
    Keywords: Vinylidenerhodium complexes, γ1-functionalized, generation from alkynols and their derivatives ; (Vinylvinylidene)1- and allenylidenerhodium complexes, formation by HX elimination ; Alkynyl(hydrido)1- rhodium(III) complexes, preparation from alkyne or vinylidene precursors ; Rhodium complexes, cyclopentadienyl, with vinylvinylidene ligands ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Vinylidene Transition Metal Complexes, XXII[1]. - Alkyne, Alkynyl(hydrido)1-, Vinylidene-, and Vinylvinylidene Complexes of Rhodium from OH-, NH2-, and Cl-Functionalized Alkynes
    Notes: The reaction of [RhCl(PiPr3)2]n with γ1-functionalized 1-alkynes HC≡C-CRR′X (X=OH, OMe, Cl, NH2) at room temperature leads to the formation of either alkyne-, alkynyl(hydrido)1-, or vinylidenerhodium complexes. The alkyne and alkynyl-(hydrido) derivatives rearrange thermally or in the presence of deactivated Al2O3 to the isomeric vinylidenerhodium compounds in almost quantitative yield. On treatment of the γ1-functionalized vinylidenerhodium complexes trans-[RhCl(=C=CH-CRR′X)(PiPr3)2] with Al2O3 or traces of acids, elimination of HX occurs and (for R=H, CH3; R′=CH3; X=OH, Cl, NH2) the (vinylvinylidene)rhodium compounds trans-[RhCl(=C=CH-CR=CH2)(PiPr3)2] are formed. In contrast, the reaction of trans-[RhCl(=C=CHCPh2OH)(PiPr3)2] with either Al2O3 or acid gives the allenylidene complex trans-[RhCl(=C=C=CPh2)(PiPr3)2]. The 1-hexyne derivatives HC≡C[CH2]3CH2X (X=OH, Cl) react with [RhCl(PiPr3)2]n to give alkyne-, alkynyl(hydrido)1-, and vinylidenerhodium compounds; attempts to form the cyclic vinylidene complex trans- by HX elimination from trans-[RhCl(=C=C=CH[CH2]3CH2X)(PiPr3)2] (X=OH, Cl) failed. The half-sandwich-type (vinylvinylidene)rhodium compounds [C5H5Rh(=C=CH-CR=CH2)(PiPr3)] (R=H, Me) are obtained from [RhH(C≡C-CR=CH2)Cl(py)(PiPr3)2] and NaC5H5.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260318
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 77
    Electronic Resource
    Electronic Resource
    (Bicyclo[3.2.0]hepta-1,3-dienyl)cobalt(I) Complexes (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 713-724 
    Details
    ISSN: 0009-2940
    Keywords: Bicyclo[3.2.0]hepta-1,3-dienyl complexes ; Calculations, semiempirical ; Alkyne trimerization ; Cobalt complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three isomeric bicyclo[3.2.0]heptadienes 1 - 3 are compared by semiempirical calculations. Experimental attempts directed to the synthesis of derivatives of 1 are described. The synthesis, properties and some reactions of (η51-bicyclo[3.2.0]hepta-1,3-dienyl)(η41-cycloocta-1,5-diene)cobalt(I) (22), including an X-ray crystal structure determination of the reaction product with diphenylethyne, the tetraphenylcyclobutadiene complex 30, are presented.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260323
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 78
    Electronic Resource
    Electronic Resource
    Synthese und Struktur von Phosphiren-Iminen und Iminophosphaspiro[2.2]pentanen (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 649-655 
    Details
    ISSN: 0009-2940
    Keywords: λ51-Phosphirenes, imino- ; λ51-Phosphaspiro[2.2]pentanes, imino ; Imines ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and Structure of Phosphirene Imines and Iminophosphaspiro[2.2]pentanesThe reaction of the iminophosphanes R1P=NR2=[1, R2=2,4,6-tBu3C6H2;R1=Me (a) Et (b), PhCH=CH (c), Cl (d); R2=tBu, R1=Et3C (e)] with the alkynes R3C ≡ CR4 [2, R3=R4=Ph (a), CO2Me (b)] affords the corresponding phosphirene imines 3a - g. A [2 + 1] cycloadduct 3h is also formed in the reaction of the alkyne 2c (R3=H, R4=Ph) with 1d, while in the case of 1b the 1,2-addition product 4 is obtained. As demonstrated by the [2 + 1] cycloaddition reaction of the P1-alkylated iminophosphanes 1a, b with methylene-cyclopropanes 5a, b, the formation of the iminophosphaspiro[2.2]pentanes 6a, b is observed. The structures of the P/C heterocycles 3a, b and 6b have been determined by NMR spectroscopy and X-ray analysis.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260315
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 79
    Electronic Resource
    Electronic Resource
    Schwefel(IV)1-Verbindungen als Liganden, 19. Kationische Ruthenium-Sulfen-Komplexe: Synthese und Reaktionen. Kristallstrukturanalyse von [Cp*(Me3P)2Ru(CH2=SO2)]PF6 (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 679-684 
    Details
    ISSN: 0009-2940
    Keywords: Ruthenium complexes ; Sulfur dioxide complexes ; Sulfene complexes ; Nucleophilic addition ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Sulfur(IV) Compounds as Ligands, 19[1]. - Cationic Ruthenium-Sulfene Complexes: Synthesis and Reactions. Crystal Structure Analysis of [Cp*(Me3P)2Ru(CH2=SO2)]PF6Methylene addition to coordinated sulfur dioxide yields the novel η2(C, S) sulfene complexes [Cp(dppm)Ru(CHR=SO2)]PF6 (R=H:3, Me: 4) and [Cp*(Me3P)2Ru(CH2=SO2)]PF6 (5). An X-ray structure determination of 5 reveals a relatively short C - S bond (167.5 pm). The sulfene complexes are powerful carbon electrophiles as shown by the rapid addition of halides, pseudohalides, amines, including „nonnucleophiles“ such as ethyldiisopropylamine and DBU, and phosphanes to 3. The regioselectivity of the reaction of 3 with enamines is opposite to that of free sulfene, i.e. coordination of the sulfene to ruthenium effects umpolung.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260319
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 80
    Electronic Resource
    Electronic Resource
    Monofunktionelle tetraedrische Zink-Komplexe L3ZnX [L3=Tris(pyrazolyl)borat] (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 685-694 
    Details
    ISSN: 0009-2940
    Keywords: Zinc complexes ; Tris(pyrazolyl)borat ligands ; Reactivity ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Monofunctional Tetrahedral Zinc Complexes L3ZnX [L3=Tris(pyrazolyl)borate]The pyrazolyl borates K[HBpz3*] (abbreviated KL3, pz*=3-phenyl-, 3-tolyl-, 3-anisyl-3,5-diphenyl pyrazolyl) react with zinc salts ZnX2 (X=Cl, Br, I, NO3) to form the mononuclear neutral tetrahedral zinc complexes L3ZnX (1 - 4). The corresponding alkylzinc complexes L3ZnR (5 - 8; R=Me, Et, tBu, Ph) result either from L3ZnCl and LiR or from ZnEt2 and KL3. These alkylzinc compounds are remarkably stable towards oxidation and hydrolysis. For specific cases the reaction of L3ZnR with carboxylic acids is found to yield the carboxylates L3ZnOCOR (9, 10), and likewise with thioacetic acid to yield the thioacetates L3ZnSCOMe (11). Facile cleavage of L3ZnR with thiols and selenophenol produces the thiolates L3ZnSR (12, 13) and the selenolates L3ZnSePh (14). The complexes L3ZntBu which are the most reactive of the alkylzinc compounds are cleaved by H2O, H2S, NH3 and various OH and NH compounds with formation of the bis(ligand) complexes Zn(L3)2 (15). Crystal structure determinations of one L3ZnX complex each for X=NO3 (4a), CH3 (5a), SCOMe (11a), and SEt (12a) confirm the nature of the compounds and the relation of 4a and 12a to the active centers of zinc-containing enzymes.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260320
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 81
    Electronic Resource
    Electronic Resource
    Nucleophile Singulett-Carbene in der [4 + 1]1-Cycloaddition mit 1,2,4,5-Tetrazinen: Eine neue Isopyrazol-Synthese (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 733-738 
    Details
    ISSN: 0009-2940
    Keywords: Singlet carbenes ; [4 + 1] Cycloadditions ; Isopyrazoles ; Diels-Alder reactions ; [4 + 2] Cycloreversion ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nucleophilic Singlet Carbenes in the [4 + 1] Cycloaddition with 1,2,4,5-Tetrazines: a New Synthesis of IsopyrazolesA series of 3,6-disubstituted 1,2,4,5-tetrazines 6, including C6H5, SCH3, SO2CH3, N(CH3)2, CF3, CO2CH3 groups, has been submitted to [4 + 1] cycloaddition with the nucleophilic singlet carbenes 4, 15, and 20, which are generated from the precursors 1, 11 and 19, resp. In all cases isopyrazoles (4H1-pyrazoles) 9, 10, 18, and 21 are isolated in good yields. They are formed in a two-step reaction sequence with the [4 + 1] cycloadducts of type 8 as intermediates which eliminate nitrogen by subsequent [4 + 2] cycloreversion. The acceptor-substituted isopyrazole 9e is characterized as an electron-deficient diene by some Diels-Alder reactions with inverse electron demand leading to the expected azo-bridged cycloadducts 23, 25, 27, 29, and 31 without acid catalysis or application of higher pressure. With cyclooctyne (32), the [4 + 2] cycloaddition is followed by a [4 + 2] cycloreversion with formation of the cyclopentacyclooctene 34.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260325
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 82
    Electronic Resource
    Electronic Resource
    Metall-π1-Komplexe von Benzolderivaten, XLI. Bis(η61-anilin)chrom: Synthese, Redoxverhalten und Brønsted-Basizität (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 399-404 
    Details
    ISSN: 0009-2940
    Keywords: Chromium complexes ; Aniline as an η61-ligand ; Voltammetry, cyclic ; Nerst-Clark plots ; Acid dissociation constants ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Metal π Complexes of Benzene Derivatives, XLI[1].  -  Bis(η61-aniline)chromium: Synthesis, Redox Properties and Brønsted BasicityBis(η61-aniline)chromium (6) has been prepared by protodesilylation of its N,N,N′,N′1-tetrakis(trimethylsilyl) derivative 5, which is accessible by metal-atom ligand-vapor cocondensation (cc). Bis(η61-dimethylaniline)chromium (3) is obtained directly from cc. The couples 3+/0 and 6+/0 feature the most negative redox potentials E1/2 ever reported for bis(arene)1-metal complexes. According to EPR spectroscopy, applied to the radical cations 3+· and 6+· the site of oxidation is largely localized on the metal. The pH dependence of E1/2 is cast in Nerst-Clark plots, whose breaks supply the pKs values of the mono-and diprotonated forms of 3 and 6. η61-Coordination to CrI increases the basicity of aniline by three pK units, whereas η61-coordination to Cr1 effects a decrease by more than seven pK units. The first and second dissociation constants of the organometallic bis(ammonium) ions 3(H+)2 and 6(H+)2 differ by 2.7 pK units. This interval reflects the interaction of the two basic centers in 3 and 6 which approaches that of p1-phenylenediamine. Thus, conjugation across the bis(η61-arene)chromium unit is virtually uninhibited.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260216
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 83
    Electronic Resource
    Electronic Resource
    Bis(pentamethylcyclopentadienyl)keton und -thioketon: Kohlenstoff-Verbindungen mit präformierter Diels-Alder-Geometrie (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 415-420 
    Details
    ISSN: 0009-2940
    Keywords: 1,3-Cyclopentadiene-5-carbonyl chloride, 1,2,3,4,5-pentamethyl- ; 1,3-Cyclopentadiene-5-carbothioyl chloride, 1,2,3,4,5-pentamethyl- ; Ketone, bis(1,2,3,4,5-pentamethyl-1,3-cyclopentadien-5-yl) ; Thioketone, bis(1,2,3,4,5-pentamethyl-1,3-cyclopentadien-5-yl) ; Diels-Alder preformation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Bis(pentamethylcyclopentadienyl) Ketone and Thioketone: Carbon Compounds with Performed Diels-Alder Geometry1,2,3,4,5-Pentamethyl-1,3-cyclopentadien-5-carbonyl chloride (2) is formed in good yields by the reaction of pentamethylcyclopentadienyllithium (1) with phosgene. The corresponding carbothioyl chloride 3 is synthesized by treatment of 1 with thiophosgene. Both acyl chlorides are stable against air and moisture and difficult to attack in SN2-type reactions. Treatment of 2 and 3 with trimethyl(pentamethylcyclopentadienyl)stannane in the presence of boron trifluoride  -  ether leads to bis(1,2,3,4,5-pentamethyl-1,3-cyclopentadien-5-yl) ketone (5) and thioketone (6), respectively. Even at room temperature, 5 and 6 tend to intramolecular [4 + 2] cycloaddition reactions. X-ray crystal structure investigations of 2, 5, and 6 show the steric demand of the pentamethylcyclopentadienyl ligand and explain the untypical chemical behavior of 2 and the easy [2 + 4] cycloaddition reactions of 5 and 6.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260219
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 84
    Electronic Resource
    Electronic Resource
    Multistep Redoxsystems, LX. 1,4,5,8-Tetraoxo-1,4,5,8-tetrahydrothianthrene: Synthesis, Structure, and Spectroelectrochemical Properties (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 465-471 
    Details
    ISSN: 0009-2940
    Keywords: Thianthrene derivatives ; X-ray analysis ; MO calculation ; Cyclovoltammetry ; UV-Vis spectroelectrochemistry ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis, structure, cyclovoltammetric and spectroelectrochemical data of 1,4,5,8-tetraoxo-1,4,5,8-tetrahydrothianthrene (2a) are presented. A relation between the positive partial charge at the sulfur atom and the dihedral angle at the S—S axis is discussed on the basis of semiempirical MO calculations.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260226
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 85
    Electronic Resource
    Electronic Resource
    Neue Beobachtungen zur Stereoselektivität von Monoiodcarben-Additionen (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 499-502 
    Details
    ISSN: 0009-2940
    Keywords: Iodocarbene, addition to alkenes ; endo1-Selectivity ; Cyclooctadiene ; Cyclooctatetraene ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New Observations Concerning the Stereoselectivity of Monoiodocarbene AdditionsContrary to our earlier claim, CHI gives endo/exo isomer mixtures with cyclooctene. However, only endo1-iodo compounds 7, 8, 10-12 are obtained from COD and COT. Tricyclic compound 7 rearranges partially to bicyclic 9, X-ray structure determinations of 7 and 9 were performed.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260229
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 86
    Electronic Resource
    Electronic Resource
    Reaktivität s̰1-bishomoaromatischer Heterocyclen: Elektrocyclische Reaktionen und Cycloadditionen von syn- und anti1-Bishomofuran und -BishomothiophenProfessor William von E. Doering zum 75. Geburtstag gewidmet. (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 485-498 
    Details
    ISSN: 0009-2940
    Keywords: Carbonyl ylides, generation from syn1-bishomofuran ; Thiocarbonyl ylides, generation from syn1-bishomothiophene ; Ylides, carbonyl and thiocarbonyl, 1,3-dipolar cycloaddition, electrocyclization, sigmatropic 1,4-hydrogen shift of ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactivity of s̰1-Bishomoaromatic Heterocyles: Electrocyclic Reactions and Cycloadditions of syn- and anti1-Bishomofuran and -BishomothiopheneProfessor William von E. Doering zum 75. Geburtstag gewidmet.The title compounds syn-4a, b and anti-4a, b, synthesized by the CuCl-catalyzed reaction of homofuran 1a or homothiophene 1b with diazomethane, are very different in their thermal stability. syn-4a isomerizes to 2,3-dihydrooxepine (7a) readily at 130°C whereas the rearrangement anti-4a → 7a requires a temperature of about 370°C. A similar difference in thermal reactivity is observed between syn-4b and anti-4b. But syn-4b undergoes in addition to the rearrangement to 2,3-dihydrothiepine (7b) a dimerization (to 12?) on thermolysis in [D6]benzene solution at 140°C, whereas mainly isomerization to 9b, cis-10b, and 11 (product of the elimination of sulfur from cis-10b) occurs on thermolysis in the gas phase. The formation of 7a and 7b, respectively, is explained by the electrocyclic ring opening of syn-4a or syn-4b leading to the carbonyl ylide 5a or the thiocarbonyl ylide 5b followed by a sigmatropic 1,4 hydrogen shift. To rationalize the additional products in the thermolysis of syn-4b an electrocyclic conrotatory ring closure in 5b leading to the highly strained episulfide trans-10b is assumed to complete with the hydrogen shift. Under the reaction conditions trans-10b is unstable and either dimerizes in solution or isomerizes in the gas phase. The formation of 9b in the thermolysis of syn-4b indicates that a two-step pathway may compete with the concerted process. syn-4a, b react with various π acceptor-substituted olefins to form cycloadducts of the general type 6a, b. The cycloaddition occurs stereospecifically cis with respect to the configuration of the starting olefin and non-stereoselectively with respect to the endo/exo ratio. The kinetic analysis of the reaction of syn-4a with fumaronitrile (FN), N1-phenylmaleinimide (NPMI) or dimethyl dicyanofumarate (DCFM) shows unambiguously, that the adducts are formed by a 1,3-dipolar cycloaddition of the intermediate carbonyl ylide 5a rather than a homo-Diels-Alder reaction of syn-4a (in contrast to the cycloaddition of homofuran 1a). A comparison between the enthalpies of reactions syn-4a → 5a (ΔHR ≤ 22.4 kcal/mol) and syn-4d → 5d (ΔHR ≥ 47.5 kcal/mol) shows the carbonyl ylide to be a 1,3-diradical, highly resonance-stabilized by the heteroatom (resonance energy R.E. ≍ -25 kcal/mol).
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260228
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 87
    Electronic Resource
    Electronic Resource
    1-Sila-3-alumina-4-aluminatacyclopentan mit Al-Al-Bindung und C2Al2Si-Heterocyclus (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2637-2641 
    Details
    ISSN: 0009-2940
    Keywords: Aluminium-aluminium bond ; C2Al2Si heterocycle ; Aluminium, three- and fourfold coordinated ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1-Sila-3-alumina-4-aluminatacyclopentane with an Al-Al Bond and a C2Al2Si HeterocycleTetrakis[bis(trimethylsilyl)methyl]dialuminium(4) (1) with an aluminium-aluminium bond reacts in the presence of tetramethylethylenediamine (TMEDA) with the sterically highly shielded bases bis(trimethylsilyl)methyllithium or bis(dimethylphosphanyl)methyllithium to yield under deprotonation of a methyl group a carbanionic species, which is stabilized by an interaction with one of the coordinatively unsaturated Al atoms. The five-membered heterocycle 5 is formed containing two Al, one Si and two C atoms. The Al-Al bond remains uncleaved. Interestingly, 5 crystallizes in different crystals with and without crystal ether, which were both characterized by crystal-structure determinations. The Al-Al bond length in 5 [264.1(2) and 266.5(3) pm, respectively] is only slightly changed in comparison to the neutral starting compound 1 (266.0 pm). Under similar conditions the sterically less demanding ethyllithium leads to a β-elimination and addition of the thereby formed LiH to one of the two Al atoms to give the recently published hydridodialuminate(5) Li(TMEDA)2+ [R2Al-AlHR2]- (2).
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931261211
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 88
    Electronic Resource
    Electronic Resource
    Homo- und Hetero-Metall-Amide des Tris(tert-butylamino)methylsilans - Polycyclen und Cluster mit Li, Na, Mg, Al und Tl (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2625-2635 
    Details
    ISSN: 0009-2940
    Keywords: Amides, hetero metal ; Polycycles ; Metal clusters of thallium ; Metal nitrogen bonding ; Carbanion, stabilized by metal complexation ; Silane, tris(tert-butylamino) ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Homo and Hetero Metal Amides of Tris(tert-butylamino)methylsilane - Polycycles and Clusters with Li, Na, Mg, Al and TlThe hydrogen atoms attached to nitrogen in tris(tert-butyl-amino)methylsilane (1) can be substituted by metallic main-group elements in a quite general way. If 1 is treated with trimethylaluminium apart from the monosubstituted product MeSi(tBuNH)2(tBuNAlMe2) (2) the trisamide MeSi(tBuNAlMe2)3 (3) is obtained. In similar ways complete substitution of the amino hydrogen atoms in 1 yields the compounds MeSi[tBuNMgN(SiMe3)2]3 (6), [MeSi(tBuNLi)3]2 (10), and [MeSi(tBuNTl)3]2 (11), the later two being dimeric. If methyl-magnesium iodide is allowed to react with 1 the intermediate MeSi(tBuNMgI)3 (4) in some instances can be isolated as the THF adduct or may react with a further equivalent of the Grignard compound to generate the complex [MgI-(THF)5]+ [MeSi(tBuNMgI)3CH3 · THF]- (5). The aluminium compound 2 has been used to access to heterometallic amides combining aluminium and sodium as in MeSi(tBuNAlMe2)(tBuNNa)(tBuNH) (7) or magnesium and aluminium as in the dimeric compounds [MeSi(tBuNAlMe2)(tBuNH)(tBuNMgI)]2 (8) and [MeSi(tBuNAlMe2)(tBuNH)(tBuNMgMe)]2 (9). X-ray structure analyses reveal 3 (tricyclic SiN3Al3 skeleton with Al - N distances from 2.014 to 2.025 Å), 6 (tricyclic Si-N3Mg3 skeleton), and 7 [bicyclic SiN3AlNa skeleton with Na - N distances of 2.47(1) and 2.52(1) Å] to be monomeric even in the solid state. The compounds 8 and 9 (both pentacyclic with spiro magnesium atoms) form centrosymmetric dimers by Mg - I - Mg and Mg - (CH3) - Mg bridges, respectively. The dimers 10 and 11 are completely different in terms of chemical bonding: while in the lithium compound 10 a centrosymmetric polycycle is formed by principly ionic interactions of the lithium atoms with corresponding nitrogen atoms, the centrosymmetric dimer in 11 is held together by Tl - Tl bonds. The X-ray structure analysis of 5 reveals the anion containing a Mg-coordinated CH3-.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931261210
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 89
    Electronic Resource
    Electronic Resource
    Tetraindeno-Fused Cyclooctatetraene and Oligomeric Biindenyls by Oxidative Coupling of 2,2′1-Biindenyl (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 969-973 
    Details
    ISSN: 0009-2940
    Keywords: 1,1′1-Bi(2,2′1-biindenylyls) ; Carbanions ; Oxidative coupling ; Cyclooctatetraindenes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Lithiated biindenyls 2 and 4, prepared by deprotonation of 2,2′1-biindenyl (1) and 10,11-dihydrodiindeno[1,2-b:2′,1′-d]thiophene (3) with n1-butyllithium, are oxidatively coupled to give oligomeric biindenyls (17) as well as tetraindeno-fused eight-membered rings (16, 19, 24).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260418
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 90
    Electronic Resource
    Electronic Resource
    Zinkkomplexe von Aminosäuren und Peptiden, 2[1]. Koordination einfacher Histidin-Derivate an Zink (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2643-2648 
    Details
    ISSN: 0009-2940
    Keywords: Histidine derivatives ; Zinc complexes ; Solution equilibria ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Zinc Complexes of Amino Acids and Peptides, 2[1]. - Coordination of Simple Histidine Derivatives to ZincThe bis(L-histidine)ZnCl2 complex 1 is likely to have tetrahedral ZnN2Cl2 coordination. For the compound (L-histidine)-ZnCl2 · HCl (2) a structure determination has revealed a tetrahedral ZnOCl3 coordination. Of the C-protected histidine derivatives His-OMe and His-NH2 and zinc salts of non-coordinating anions the complexes (His-OMe)2ZnX2 (3) and (His-NH2)2Zn(ClO4)2 (4) were obtained. A structure determination of (His-OMe)2Zn(BPh4)2 · H2O has revealed a ZnN4 coordination with chelating histidine units. Of the N-protected histidine derivative Nα-acetylhistidine the complexes (Ac-His)ZnX · H2O (5, X = ClO4, BF4) have been isolated which are coordination polymers in the solid state. From pH-dependent 13C-NMR studies it is concluced that in solution the imidazole N and carboxyl O are coordinated to zinc in (Ac-His)Zn and (Ac-His)2Zn units. The doubly protected histidine derivative Bz-His-OMe acts as a monodentate ligand forming the tetrahedral complexes (Bz-His-OMe)4Zn(ClO4)2 (6) and [(Bz-His-OMe)2Zn(2,9-dimethyl-o-phenanthroline)](ClO4)2 (7).
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931261212
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 91
    Electronic Resource
    Electronic Resource
    Synthese und Röntgenstrukturanalyse einer neuartigen gemischtvalenten zwitterionischen Diphosphor-Fluor-Verbindung (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2653-2655 
    Details
    ISSN: 0009-2940
    Keywords: Diphosphorus zwitterion ; Phosphorus, hexacoordinated ; Phosphorus, tetracoordinated ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and X-Ray Crystal Structure Analysis of a Novel Mixed-Valent Zwitterionic Diphosphorus Fluoro CompoundThe cyclic zwitterionic λ6P,λ4P-diphosphorus compound F5P-N(Me)P+ [N(Me)C(=O)]2NMe (3), which contains a biuret system, was synthesized by the reaction of (MeNPF3)2 (1) with MeNCO (2). Compound 3 was characterized by means of 1H-, 13C-, 19F- and 31P-NMR spectroscopy, IR spectroscopy, and mass spectrometry. A single-crystal X-ray structure determination revealed the presence of two independent formula units, in which the -N(Me)PF5 side chains display widely differing conformations.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931261214
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 92
    Electronic Resource
    Electronic Resource
    Metallorganische Verbindungen der Lanthanoide, 82[1]. (2,5-Di-tert-butylpyrrolyl)-Komplexe von Neodym(III), Samarium(II) und Ytterbium(II): Synthese und Röntgenstrukturanalyse von dimerem Natrium-dichlorobis(2,5-di-tert-butylpyrrolyl)(tetrahydrofuran)neodymat(III) (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2657-2659 
    Details
    ISSN: 0009-2940
    Keywords: Azacyclopentadienyl complexes ; Neodymium compounds ; Samarium compounds ; Ytterbium compounds ; Lanthanoides, organo-, chlorides ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Organometallic Compounds of the Lanthanoids, 82[1]. - [2,5-Di-tert-butylpyrrolyl) Complexes of Neodymium(III), Samarium(II), and Ytterbium(II): Synthesis and X-Ray Structural Analysis of Dimeric Sodium Dichlorobis(2,5-di-tert-butylpyrrolyl)(tetrahydrofuran)neodymiate(III)NdCl3(THF)1,8 reacts with Na[pyr*
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931261215
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 93
    Electronic Resource
    Electronic Resource
    Ephedrine-Derived Imidazolidin-2-ones. Broad Utility Chiral Auxiliaries in Asymmetric Synthesis (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2663-2673 
    Details
    ISSN: 0009-2940
    Keywords: Imidazolidin-2-one, (4R,5S)-1,5-dimethyl-5-phenyl- or cyclohexyl- ; (-)-Ephedrine ; Stereoselective aldol ; alkylation, acylation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The scope of the readily available (4R,5S)-1,5-dimethyl-4-phenylimidazolidin-2-one (4) and its 4-cyclohexyl analogue 6 as practical, efficient chiral auxiliaries has been demonstrated. The enolate chemistry of their N-acyl derivatives exhibits features which recommend their use in asymmetric synthesis. The stereoselective boron-mediated aldol as well as alkylation and acylation results are presented. The steric control benefit derived by conversion of phenyl to cyclohexyl is highlighted.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931261216
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 94
    Electronic Resource
    Electronic Resource
    Gas-Phase Thermolysis of Pyrazolines, 2[1]. Electronic Structure and Gas-Phase Thermolysis of 4,5-Dihydro-3H-pyrazoles Studied by Photoelectron Spectroscopy, Semiempirical Quantum-Chemical Calculations, and Flash Vacuum Pyrolysis (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2675-2681 
    Details
    ISSN: 0009-2940
    Keywords: Electronic structure ; PE spectroscopy ; Gas-phase thermolysis ; 3H-Pyrazoles, 4,5-dihydro- ; 1,3,4-Oxadiazole, 2,5-dihydro- ; 1,3,4-Thiadiazole, 2,5-dihydro- ; Cyclopropanol, 2,2,3,3-tetramethyl- ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The PE spectra of the 4,5-dihydro-3H-pyrazoles 1, 2, of 2,5-dihydro-1,3,4-oxadiazole 3, and 2,5-dihydro-1,3,4-thiadiazole 4 have been recorded. Based on HAM/3, MNDO, AM1, and PM3 calculations, the ionization potentials have been assigned to molecular orbitals. The gas-phase thermolyses of 1-4 have been studied by PE-controlled gas analysis. Extrusion of molecular nitrogen leads to reactive species which cyclize to three-membered rings of different stability. At higher temperatures and in flash vacuum pyrolysis, consecutive reactions may lead to smaller acyclic molecules. The cyclo-propanol 7, obtained by denitrogenation of 2, is thermally rather stable. Its PE spectrum has been recorded and analyzed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931261217
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 95
    Electronic Resource
    Electronic Resource
    Photochemical and Thermal Rearrangement of Acyl-Substituted Quinone Methides, Accessible by Dimethyldioxirane Oxidation of Benzofurans and Subsequent Valence Isomerization of the Resulting Epoxides (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2697-2699 
    Details
    ISSN: 0009-2940
    Keywords: Epoxidation ; Dioxirane, dimethyl- ; Benzofurans, 2-methyl-3-phenyl ; Benzofuran epoxides ; Quinone methides ; (Z/E) Photoisomerization ; Norcaradiene ; Benzocycloheptafuran ; Thermal rearrangement ; Xanthenes, 9-acetyl- ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The photoisomerization of quinone methides 3 to benzocycloheptafuran 4 and the thermolysis of the latter to xanthenes 5 are reported. The quinone methides 3 are accessible by dimethyldioxirane oxidation and subsequent valence isomerization of the resulting benzofuran epoxides 2. On irradiation (λ 〉 400 nm), the quinone methides 3 rearrange by cyclization to the corresponding norcaradiene, and ring enlargement affords the benzocycloheptafurans 4. Thermolysis of the cycloheptatrienes 4 leads to the xanthenes 5, first by cycloreversion to the norcaradienes, followed by electrocyclization to the chromenes and tautomerization of the latter. The new cycloheptatrienes 4 and xanthenes 5 were fully characterized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931261220
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 96
    Electronic Resource
    Electronic Resource
    Oxidative Spaltung von Poly(o1-phenylendiselenid) (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 1071-1076 
    Details
    ISSN: 0009-2940
    Keywords: Selenium halogen compounds ; Poly(o1-phenylenediselenide), cleavage of ; Oxidative cleavage ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Oxidative Cleavage of Poly(o1-phenylenediselenide)Poly(o1-phenylenediselenide) is cleaved at the Se-Se bond by treatment with SOCl2 to give benzene-1,2-bis(selenenyl chloride) (2) and benzene-1,2-bis(selenium trichloride) (3), respectively. In the solid state 2 is dimerized by Se…Se bonds whereas 3 is monomeric having terminal as well as intramolecular bridging Cl atoms. Treatment of 2 with SbCl5 gives an ionic compound (4) with a dimeric cation exhibiting a weak Se—Se bond and SbCl6- as a counterion 3 reacts with W(CO)6 to give trigonal prismatic dicarbonyl bis(o1-phenylenediselenolato)tungsten (5).
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260502
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 97
    Electronic Resource
    Electronic Resource
    Enantioselektive Katalyse, IX. Neue optisch reine 3,4-Bis(phosphanyl)pyrrolidine mit Phenyl-und Anisylgruppen sowie deren Palladium-und Rhodiumkomplexe (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 1091-1100 
    Details
    ISSN: 0009-2940
    Keywords: 3,4-Bis(phosphanyl)pyrrolidines ; Palladium complexes ; Rhodium complexes ; Asymmetric hydrogenation ; Phosphanes, chiral ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enantioselective Catalysis, IX[1]. - New Optically Pure 3,4-Bis(phosphanyl)pyrrolidines with Phenyl and Anisyl Groups Including Their Palladium and Rhodium ComplexesMethods for the synthesis of the diastereomeric mixture of the [P(R,S),3R,4R,P′(R,S)]1-1-(tert1-butoxycarbonyl)1-3,4-bis[(2-methoxyphenyl)phenylphosphanyl]pyrrolidines (2a, b, c) are described. For the chromatographic separation and purification of the ligand diastereomers we transformed them into the PdI21-complexes (10a, b, c). The structure of (PR,3R,4R,P′R)1-1-(tert1-butoxycarbonyl)1-3,4-bis[(2-methoxyphenyl)phenylphosphanyl]pyrrolidine-P,P′}diiodopalladium (10 b) was determined by X-ray diffraction. Treatment of the palladium complexes with KCN yielded the pure phosphanes. The rhodium complexes (11a, 11b, 11c), which can be used as catalysts in enantioselective hydrogenations, were obtained by reaction of [Rh(COD)2]BF4 with compound 2a, 2b, or 2c.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260505
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 98
    Electronic Resource
    Electronic Resource
    Organo-substituierte Silole durch zweifache Organoborierung von Di-1-alkinylsilanen (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 1107-1114 
    Details
    ISSN: 0009-2940
    Keywords: Dialkynylsilanes, intermolecular 1,1-ethyloboration of ; 1,1-Vinyloboration, intramolecular ; 3-Borylsiloles, protodeborylation of ; (Ligand)transition metal, η4 complexes of ; Sandwich complex, cyclodiastereomers of ; Siloles, boryl-organo-substituted ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Organo-Substituted Siloles by Twofold Organoboration of Di-1-alkynylsilanesMe2Si(C≡CR)2 [R=Me (A), Bu (B), tBu (C), iPent (D), Ph (E), Me3Si (F)], prepared from Me2SiCl2 and MC≡CR (M=Li, Na, K), react with Et3B by 1,1-ethyloboration to form the organo-substituted siloles Me2 (1a - f) in high yields with different reaction rates: F 〉 B ≍ D 〉 A 〉 C 〉 E. Me2Si(C ≡CiPent)(C ≡ CPh) (H) and Et3B give a 5 : 1 mixture of the two regioisomeric substituted siloles 2 and 2′. - 1a and e are deborylated with H2NCH2CH2OH or MeCO2H to 3a and e, respectively. 1a reacts with maleic anhydride to yield the [4 + 2] addition compound 4a. With (OC)5Fe, Cp-Co(C2H4)2, and (CDT)Ni the cycloracemic (ligand)transition metal η41-complexes [(OC)3Fe-1a (5a), (OC)3Fe-3a (6a), CpCo-3a (7a)] and the cyclodiastereomeric η4,η41-complexes Ni-(3a)2 (8a/8a′) are formed. All products were characterized by multinuclear NMR, including measurements of J(29Si13C) and J(13C13C).
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260507
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 99
    Electronic Resource
    Electronic Resource
    Beiträge zur Chemie des Bors, 217. [2 + 2]1-Cycloadditionsreaktionen von 9-Fluorenyliden-(tetramethylpiperidino)boran mit Carbonyl-und Thiocarbonyl-Verbindungen (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 1119-1125 
    Details
    ISSN: 0009-2940
    Keywords: Cycloaddition reactions ; 1,2-Oxaboretanes ; 1,2-Thiaboretanes ; 1,2-Azaboretidines ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Contributions to the Chemistry of Boron, 217[1]. - [2 + 2] Cycloaddition Reactions of 9-Fluorenylidene(tetramethylpiperidino)borane with Carbonyl and Thiocarbonyl CompoundsAmino-9-fluorenylidene-borane 1 reacts with acetone or benzophenone in a [2 + 2] cycloaddition manner to give stable 1,2-oxaboretane derivatives 2. Aldehydes behave similarly but the oxaboretanes formed decompose readily. The esters MeCO2Et and MeC≡C - CO2Me as well as Cp(CO)2Fe - COCH3 also provide access to novel oxaboretane derivatives (2e, f, h). In contrast, no oxaboretane is obtained from 1 and MeC(O)NMe2 and only (tmpBO)n (n=2, 3) was isolated as a decomposition product. The amides MeC(O)NHMe and MeC(O)NH2 also provide no access to cycloaddition since their NH bonds insert into the BC double bond of 1. Thioketones react with 1 to yield 1,2-thiaboretanes 5. Tetramethyl-cyclobutan-1-one-3-thione 8 adds 1 at its carbonyl function regiospecifically to form 9. No reaction between 1 and CO2 was observed, but COS produces an 1,2-oxaboretane-4-thione 7, and CS2 in the form of [CpFe(CO)2]2CS2 the corresponding 1,2-thiaboretane-4-thione 10. Analogously, the ketimine Ph2C=NMe adds to 1 producing the 1,2-azaboretidine 11. X-ray structure determination of the 1,2-oxaboretane 2h reveals a butterfly structure (folding anlge: 159.9°) of the four-membered ring in contrast to the 1,2-thiaboretane 5a whose four-membered ring is almost planar, the folding angle being 176.9°.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260509
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 100
    Electronic Resource
    Electronic Resource
    Repetitive-Synthesis of Bulky Dendrimers - A Reversibly Photoactive Dendrimer with Six Azobenzene Side Chains (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 1161-1169 
    Details
    ISSN: 0009-2940
    Keywords: Azobenzene units ; Dendrimer ; Divergent synthesis ; Solvent inclusion ; Supramolecular chemistry ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dendrimers with bulky repeating units containing up to 43 benzene rings (in 9) have been obtained by using a repetitive divergent synthetic strategy (three generations). The new functional dendrimer 13 containing six azobenzene units at the periphery was synthesized allowing a reversible switching of the shape and size of the molecule upon irradiation. An X-ray structure analysis of the dendritic molecule 3a shows the inclusion of acetonitrile.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260516
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...