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  • 1
    Electronic Resource
    Electronic Resource
    Intramolekulare Cycloadditionen mit Nitriloxiden: Untersuchungen zur Synthese von Heterophanen (1989)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 2147-2157 
    Details
    ISSN: 0009-2940
    Keywords: 1,3-Dipolar cycloadditions, intramolecular ; Nitrile oxides ; Regioselectivity ; Furanophanes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Intramolecular Cycloadditions with Nitrile Oxides: Investigtions towards the Synthesis of HeterophanesThe intramolecular cycloaddition reactions of the nitrile oxides 30a-d, 35, 36, and 47, obtained in situ from the 2,5-difunctional furan hydroximoyl chlorides 12a, b, 18 and the nitro compounds 9c, d, 21, 29, are described. With 30c the expected isoxazolofuranophane of type 31 is formed in acceptable yield; the additionally formed regioisomer 32c and the dimer 34c are very minor products in this case. Whereas the highest homologue 30d gives a complex product mixture with small amounts of 31 d and the macrocycle 34d as the only identified compounds, the derivatives bearing a shorter side chain (30a, b; n = 1, 2) give rise to the exclusive reaction of the dipole with a double bond of the furan system (to give 33a, b). The same behavior is observed in the case of the electronically and sterically modified dipole systems 35/36 and 47, resp.; in spite of the much more favorable conditions for the formation of cyclophanes the cycloadditions result in the exclusive formation of the heterotricycles 41, 42 and 49. Possible preparative applications of the isomeric cycloaddition compounds are discussed.
    Notes: Die intramolekularen Cycloadditionsreaktionen der aus 2,5-difunktionellen Furan-Hydroximsäurechloriden (12a, b und 18) bzw. den Nitroverbindungen 9c, d, 21 und 29 in situ hergestellten Nitriloxide 30a-d, 35, 36 und 47 werden beschrieben. Eine Reaktion zu den angestrebten Isoxazolo-furanophanen des Typs 31 verläuft für 30c in brauchbarer Ausbeute; das Regioisomere 32c sowie das Dimere 34c treten hierbei nur in geringem Maße auf. Während das höchste Homologe 30d neben 31d und dem Makrocyclus 34d hauptsächlich Zersetzungsprodukte bildet, reagieren die Derivate mit kürzerer Seitenkette (30a, b; n = 1, 2) ausschließlich unter dipolarer Addition an eine Furandoppelbindung zu 33a, b. Für n = 1 entsprechen diesem Verhalten auch die elektronisch bzw. sterisch modifizierten Dipolsysteme 35/36 und 47, die trotz günstigerer Voraussetzungen für die Cyclophanbildung nur zu den Tricyclen 41, 42 bzw. 49 reagieren. Die präparativen Anwendungsmöglichkeiten der isomeren Cycloadditionsverbindungen als Synthesezwischenprodukte werden diskutiert.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19891221116
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  • 2
    Electronic Resource
    Electronic Resource
    Intramolekulare Cycloadditionen Mit Azomethin-Yliden: Synthese und NMR-Untersuchungen einiger Paracyclophan-Derivate vom Makrolid-Typ (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 404-418 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Intramolecular Cycloaddition Reactions with Azomethine Ylides: Synthesis and NMR Investigations of Some Macrolide-Type ParacyclophanesSeveral aziridine derivatives bearing a para-substituted phenyl group have been prepared as precursors of azomethine ylides for intramolecular 1,3-dipolar cycloadditions. Upon heating in refluxing toluene, the expected reactions take place resulting in the regioselective formations of the pairs of diastereoisomers 14/15 and 16/17, respectively. As indicated by the sharply decreasing yield in the a-series (〈 5%), a useful application of this method for preparing paracyclophane compounds is restricted to derivatives with more than 11 bridging atoms. The results of detailed 1H- and 13C-NMR investigations with the pyrrolidino-annulated cyclophanes are discussed with respect to the configuration at the five-membered heterocycles and to the conformational flexibility of the bridges.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710214
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  • 3
    Electronic Resource
    Electronic Resource
    2,4,6,8-Tetraphenylbarbaralan - ein orangeroter, thermochromer Kohlenwasserstoff ohne Chromophor[1,2] (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 1047-1060 
    Details
    ISSN: 0009-2940
    Keywords: Bicyclo[3.3.1]nonane, derivatives of ; 2-Oxatwistane, derivative of ; 2-Oxatricyclo[4.4.0.03,8]decane, derivative of ; Phenyllithium-cerium(III) chloride reagent ; 1,2-Addition to carbonyl groups ; Transannular reaction ; Dipotassium tetraphenylbicyclo[3.3.1]nonadienediide by deprotonation with butylpotassium ; Barbaralane, 2,4,6,8-tetraphenyl-, by oxidation of dipotassium tetraphenylbicyclo[3.3.1]nonadienediide with 1,2-dibromo-ethane ; Thermochromism ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2,4,6,8-Tetraphenylbarbaralane - an Orange-Red, Thermochromic Hydrocarbon Devoid of a Chromophore[1,2]The diphenylbicyclo[3.3.1]nonanedione 6 adds phenylcerium-(III) dichloride to afford a high yield of the triphenyl-2-oxa-twistanol 8. In contrast, phenyllithium yields a mixture of tri-phenylhydroxyketone exo-7, tetraphenylbicyclo[3.3.1]nona-nediol 9, and 8. The latter is dehydrated by sulfuric acid in acetic acid to produce the triphenylbicyclo[3.3.1]nonenone 10 in almost quantitative yield. Addition of phenylcerium(III) dichloride to 10 affords a 3:2 mixture of the tetraphenylbicy-clo[3.3.1]nonenols exo- and endo-11 which may be separated by chromatography. Dehydration of the mixture yields quantitatively the tetraphenyldiene 12. On treatment with an excess of butylpotassium in pentane, 12 is converted to the deep violet, crystalline dipotassium salt 17 which may be purified by reprecipitation from its tetrahydrofuran solution with pentane. When the solution of 17 in tetrahydrofuran is slowly added to an excess of 1,2-dibromoethane at -60°C, the dianion is immediately oxidized to produce the tetraphenylbarbara-lane 4 which is isolated in 30% yield as orange-red crystals after chromatography. - The structures of the new compounds are based on spectroscopic evidence and X-ray diffraction analyses of 4, 8, exo-11, and 12. The conformations in solution are inferred on the basis of vicinal proton coupling constants and a comparison with coupling constants calculated with the aid of the Karplus equation from torsional angles obtained by X-ray diffraction analyses. The conformation of exo-11 in solution closely resembles that present in the crystal. - While the barbaralane 4 exists as a pair of very rapidly rearranging degenerate valence tautomers in solution, the degeneracy is lifted in the crystal lattice. As a result, the crystal consists of two rapidly rearranging but non-equivalent valence tautomers in a ratio of 9:1 as estimated from the apparent atomic distance C2-C8 of 4 and the C2-C8 bond length of the model barbaralane 18. - The orange-red colour of 4 in the crystal and in solution results from a pronounced shoulder in the UV/Vis spectrum at 430 nm, the intensity of which strongly depends on the temperature. Thus, 4 is the first barbaralane which exhibits colour though it is lacking a classical long-wavelength chromophore.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260427
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  • 4
    Electronic Resource
    Electronic Resource
    2,6-Dicyan-4,8-diphenylbarbaralan (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 1465-1475 
    Details
    ISSN: 0009-2940
    Keywords: Bicyclo[3.3.1]nonane, derivatives of ; Barbaralane, 2,6-dicyano-4,8-diphenyl- ; Cyanohydrins, O-(trimethylsilyl)- ; Hydrogen fluoride - phosphorus oxychloride - pyridine, elimination of trimethylsilanol by ; Phenylcuprate reagent, conjugate addition of ; Cyclization of debromination with the zinc-copper couple ; Phase-transfer catalysis ; Chlorination by hexachloroethane ; Cyclization by dehydrochlorination ; Thermochromism ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2,6-Dicyano-4,8-diphenylbarbaralane[1]Conjugate addition of the phenylcuprate reagent, obtained from phenyllithium, copper(I) cyanide, and boron trifluoride-diethylether, to the bicyclo[3.3.1]nonadienedione 3 affords the diphenylbicyclo[3.3.1]nonanedione 4 in high yield. Catalyzed by the potassium cyanide/18-crown-6 complex, addition of trimethylsilyl cyanide produces a mixture of the diastereomeric bis[O-(trimethylsilyl)cyanohydrins] exo,exo-, exo,endo- and endo,endo-5. The hydrogen fluoride - pyridine complex in phosphorus oxychloride as solvent and, subsequently, an excess of pyridine convert the diastereomers 5 into the unsaturated γ,γ′1-diphenyldinirile 6. This is brominated by N1-bromosuccinimide to yield the γ,γ′1-dibromodinitriles exo- and endo- 7 (6:1). The predominant diastereomer exo-7 is debrominated by the zinc-copper couple to afford the orange-red title compound 2 in 78% yield. More conveniently, the unsaturated dinitrile 6 is converted to 2 in a single step by treatment with hexachloroethane and concentrated aqueous sodium hydroxide in the presence of tetrabutylammonium hydroxide as phase-transfer catalyst. Surprisingly, low yields of 2 are also obtained when the bis[O-(trimethylsilyl)cyanohydrins] 5 or the unsaturated dinitrile 6 are treated with phosphorus oxychloride in boiling pyridine. - The structures of the new compounds are based on spectroscopic evidence and X-ray diffraction analyses of 2, 4, and endo,endo-5. The conformations of 4 and endo,endo-5 in solution are inferred on the basis of vicinal proton coupling constants and a comparison with coupling constants calculated with the aid of the Karplus equation and torsional angles obtained by X-ray diffraction analyses. - While the barbaralane 2 exists as a pair of very rapidly rearranging degenerate valence tautomers in solution, the degeneracy is lifted in the crystal lattice. As a result, the crystal consists of two rapidly rearranging but non-equivalent valence tautomers in a ratio of 9:1 as estimated from the apparent atomic distance C2-C8 of 2 and the C2-C8 bond length of non-rearranging barbaralanes. - The colour of 2 in the crystal and in solution results from a maximum at 436 nm which increases on heating of the solution to 450 K. Cooling to 77 K results in reversible fading and the disappearance of the maximum. Thus, 2 is a barbaralane like 1 which exhibits colour though it is lacking a classical long-wavelength chromophore.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260630
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  • 5
    Electronic Resource
    Electronic Resource
    Konformation und Bromierung von Bicyclo[3.3.1]nonan-2,6-dion sowie Dehydrobromierung der Bromketone. - Verbesserte Synthese von Bicyclo[3.3.1]nona-3,7-dien-2,6-dion (1994)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1994 (1994), S. 109-120 
    Details
    ISSN: 0170-2041
    Keywords: Bicyclo[3.3.1]nonane-2,6-dione, brominated derivatives of ; Bromination of ketones by copper(II) bromide ; Dehydrobromination, 1,2- and transannular ; Noradamantane, derivative of ; Conformation of bicyclo[3.3.1]-nonane-2,6-dione and derivatives ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conformation and Bromination of Bicyclo[3.3.1]nonane-2,6-dione and Dehydrobromination of the Bromo Ketones. - Improved Synthesis of Bicyclo[3.3.1]nona-3,7-diene-2,6-dioneBromination by copper(II) bromide of bicyclo[3.3.1]nonane-2,6-dione (1) affords the epimeric α-bromo diketones exo-and endo-5 and, eventually, the α, α′-dibromo diketones exo- and endo-7 (3:7) in high yield. Dehydrobromination of the mixtures of bromo diketones by calcium carbonate in dimethylacetamide yields the unsaturated diketones 6 (30%) and 2 (72%), respectively. Bromination of 1 by molecular bromine is less selective and furnishes mixtures of brominated diketones consisting of exo- and endo-7, 8 and the tetrabromo diketone 10. An excess of bromine yields pure 10. - The ethylene acetal 12 is brominated by pyridinium perbromide to produce the α,α′-dibromo acetal 13 which is very reluctant towards 1,2-dehydrobromination by potassium tert-butoxide. Thus, with an excess of potassium tert-butoxide in tetrahydrofuran, 1,2-dehydrobromination is achieved only on one side to afford 14. In contrast, potassium tert-butoxide in dimethyl sulphoxide induces a transannular dehydrobromination leading to the diacetal 15 of 3-bromonoradamantane-2,6-dione. - The conformations of 1,10, and 13 in the solid state are determined by X-ray diffraction analyses. From torsional angles, vicinal proton coupling constants are calculated with the aid of the Karplus equation and compared to those determined from solutions by high-field NMR spectroscopy. The reasonable agreement provides the basis for the assessment of the configuration and conformation for exo- and endo-7.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199419940203
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  • 6
    Electronic Resource
    Electronic Resource
    Synthese und Struktur Phenyl-substituierter Bicyclo[3.3.1]nonene (1993)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1993 (1993), S. 777-784 
    Details
    ISSN: 0170-2041
    Keywords: Bicyclo[3.3.1]non-2-ene, phenyl-substituted derivatives of ; Conformation of bicyclo[3.3.1]non-2-enes ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and Structure of Phenyl-Substituted Bicyclo[3.3.1]nonenesAddition of one mole of phenyllithium to bicyclo[3.3.1]nonane-2,6-dione (5) affords the hydroxy ketone 6 besides small amounts of the known diol 7. Dehydration of this mixture by sulfuric acid in acetic acid yields the unsaturated ketone 8 and the diene 1 which are separated by chromatography. Wolff-Kishner reduction of 8 furnished the hydrocarbon 2. In the same way, the known ketones exo- and endo-10 are converted into 4. The preferential formation of the less stable endo-10 is interpreted in terms of the relative stability of the conformations required in the intramolecular aldol reaction of diketone 9. The conformations of 4, 8, exo- and endo-10 are determined by X-ray diffraction analyses. Vicinal proton coupling constants are calculated from torsional angles and compared to those determined in solutions by high-field NMR spectroscopy.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1993199301123
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  • 7
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    Ammonite habitat revealed via isotopic composition and comparisons with co-occurring benthic and planktonic organisms (2015)
    National Academy of Sciences
    Details
    Publication Date: 2015-11-16
    Description: Ammonites are among the best-known fossils of the Phanerozoic, yet their habitat is poorly understood. Three common ammonite families (Baculitidae, Scaphitidae, and Sphenodiscidae) co-occur with well-preserved planktonic and benthic organisms at the type locality of the upper Maastrichtian Owl Creek Formation, offering an excellent opportunity to constrain their depth habitats through isotopic comparisons among taxa. Based on sedimentary evidence and the micro- and macrofauna at this site, we infer that the 9-m-thick sequence was deposited at a paleodepth of 70–150 m. Taxa present throughout the sequence include a diverse assemblage of ammonites, bivalves, and gastropods, abundant benthic foraminifera, and rare planktonic foraminifera. No stratigraphic trends are observed in the isotopic data of any taxon, and thus all of the data from each taxon are considered as replicates. Oxygen isotope-based temperature estimates from the baculites and scaphites overlap with those of the benthos and are distinct from those of the plankton. In contrast, sphenodiscid temperature estimates span a range that includes estimates of the planktonic foraminifera and of the warmer half of the benthic values. These results suggest baculites and scaphites lived close to the seafloor, whereas sphenodiscids sometimes inhabited the upper water column and/or lived closer to shore. In fact, the rarity and poorer preservation of the sphenodiscids relative to the baculites and scaphites suggests that the sphenodiscid shells may have only reached the Owl Creek locality by drifting seaward after death.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 8
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    Escape Burrowing of Modern Freshwater Bivalves as a Paradigm for Escape Behavior in the Devonian Bivalve Archanodon catskillensis (2017)
    Molecular Diversity Preservation International
    Details
    Publication Date: 2017-10-09
    Electronic ISSN: 2076-3263
    Topics: Geosciences
    Published by Molecular Diversity Preservation International
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  • 9
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    Intramolekulare Cycloadditionen Mit Azomethin-Yliden: Synthese und NMR-Untersuchungen einiger Paracyclophan-Derivate vom Makrolid-Typ (1988)
    Wiley
    Details
    Publication Date: 1988-03-16
    Print ISSN: 0018-019X
    Electronic ISSN: 1522-2675
    Topics: Chemistry and Pharmacology
    Published by Wiley
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  • 10
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    Geology and taphonomy of a unique tyrannosaurid bonebed from the upper Campanian Kaiparowits Formation of southern Utah: implications for tyrannosaurid gregariousness (2021)
    PeerJ
    Details
    Publication Date: 2021-04-19
    Description: Tyrannosaurids are hypothesized to be gregarious, possibly parasocial carnivores engaging in cooperative hunting and extended parental care. A tyrannosaurid (cf. Teratophoneus curriei) bonebed in the late Campanian age Kaiparowits Formation of southern Utah, nicknamed the Rainbows and Unicorns Quarry (RUQ), provides the first opportunity to investigate possible tyrannosaurid gregariousness in a taxon unique to southern Laramidia. Analyses of the site’s sedimentology, fauna, flora, stable isotopes, rare earth elements (REE), charcoal content and taphonomy suggest a complex history starting with the deaths and transport of tyrannosaurids into a peri-fluvial, low-energy lacustrine setting. Isotopic and REE analyses of the fossil material yields a relatively homogeneous signature indicating the assemblage was derived from the same source and represents a fauna living in a single ecospace. Subsequent drying of the lake and fluctuating water tables simultaneously overprinted the bones with pedogenic carbonate and structurally weakened them through wet-dry cycling. Abundant charcoal recovered from the primary bone layer indicate a low temperature fire played a role in the site history, possibly triggering an avulsion that exhumed and reburied skeletal material on the margin of a new channel with minimal transport. Possible causes of mortality and concentration of the tyrannosaurids include cyanobacterial toxicosis, fire, and flooding, the latter being the preferred hypothesis. Comparisons of the RUQ site with other North American tyrannosaur bonebeds (Dry Island-Alberta; Daspletosaurus horneri-Montana) suggest all formed through similar processes. Combined with ichnological evidence, these tyrannosaur mass-burial sites could be part of an emerging pattern throughout Laramidia reflecting innate tyrannosaurid behavior such as habitual gregariousness.
    Electronic ISSN: 2167-8359
    Topics: Biology , Medicine
    Published by PeerJ
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