ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

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
  • Chemistry  (5)
  • General Chemistry  (4)
  • 2000-2004  (5)
  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 217-224 
    ISSN: 1434-1948
    Keywords: Reaction mechanisms ; Cyclopalladation ; Acetic acid ; Pd-C bond stability ; Polynuclear species ; Palladium ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The processes operating during the synthetic cyclopalladation reactions of imines in acetic acid have been studied from a kinetico-mechanistic point of view. These reactions include a fast initial coordination to the palladium through the N-donor atom of the imine, followed by the proper C-H bond activation to produce the acetato bridged dimeric species. At this point, the lability of the bridging acetato groups, the hydrolysis of the C-Pd bonds, and/or the hydrolysis of C=N exo bonds contribute to the generation of dark red polynuclear compounds. The processes occurring after the C-H activation have been followed kinetically, both from palladium acetate plus imine, and the synthetically pure isolated acetato dimers as starting materials. The kinetic and activation parameters have been found identical within experimental error whatever the starting material was (k323 = 1.5 × 10-4 s-1; ΔH# = 51 kJ mol-1; ΔS# = -163 JK-1 mol-1 ΔV# = +19 cm3 mol-1 for the 4-ClC6H4-CH=N-CH2-C6H5 imine derivative 1a). Acidolysis of C-Pd bonds has been found to occur in these polynuclear species. When alternative monomeric Cbenzylic-Pd bond-containing complexes are possible follow ups of the reactions produce them as final dead-end complexes (k323 = 2.2 × 10-5 s-1; ΔH# = 61 kJ mol-1; ΔS# = JK-1 mol-1 ΔV# ≈ 0 cm3 cm-1 for the [2,4,6-(CH3)3]C6H2-CH=N-CH2-[2-(CH3]C6[H4] imine derivative 3d). The same study has been carried out with primary amines in order to check the validity of the data if C=N bond hydrolysis is taking place in the imine derivatives with exo C=N bonds. For complexes with similar type of metallacycles, the results agree reasonably well with the proposed mechanism [k323 = 1.2·10-4 s-1, ΔH# = 46 kJ·mol-1, ΔS# = -180 J·K-1mol-1, ΔV# = -16 cm3·mol-1 for the polynuclear formation of the C6H5-CH2-NH2 derivative 4e; k323 = 3.0·10-4 s-1, ΔH# = 55 kJ·mol-1, ΔS
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 23 (2000), S. 373-378 
    ISSN: 0935-6304
    Keywords: Open tubular columns ; capillary electrochromatography ; column efficiency ; injected volume ; applied voltage ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of some instrumental parameters on column efficiency in open tubular capillary electrochromatography (OTCEC) has been evaluated. First, it was investigated whether band broadening due to the sample injection process is within a tolerable range when an open tubular column (OTC) of about 10 μm i. d. is used. As a result of the small injection profile factor (K2 = 1.3), injected volumes must be sufficiently small (less than 10 pL) to avoid a significant efficiency loss (〉5%) when hydrodynamic injection by siphoning is employed. Secondly, the kinetic performance of OTCs in a CEC system was estimated from the variation of the reduced plate height (h) with the reduced linear velocity (ν) which was controlled by the voltage applied. Reasonable agreement was obtained between the theoretical h versus ν curve and the experimental values for a group of polycyclic aromatic hydrocarbons used as test compounds. Values of 0.25 for minimum h at an optimum ν of 16 are estimated, which permit separations with around 400,000 plates per meter to be obtained in less than 5 min. Finally, the possibility of estimating the diffusion coefficients of the solutes in the mobile phase from the plot of the height of a theoretical plate versus electroosmotic flow velocity is shown.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1434-193X
    Keywords: Amino acids ; coupling ; N-Substituted amide ; Cyclizations ; Cyclic dipeptides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A short synthesis of new, functionalized seven-membered ring cyclic dipeptides is described. After the coupling of N-protected β-amino acids to N-substituted α-amino tert-butyl esters, the protective groups of the terminal functions were removed and the cyclization took place diastereoselectively in the presence of the coupling agent BOP. Amide substitution was found to be effective in promoting the cyclization of linear dipeptides.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 807-811 
    ISSN: 1434-193X
    Keywords: Proline analogues ; Asymmetric synthesis ; Schöllkopf's method ; Silicon ; Amino acids ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The asymmetric synthesis of a new proline surrogate, incorporating the dimethylsilyl group at position 4 of proline using Schöllkopf's bis-lactim ether method, is described.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 1434-193X
    Keywords: Thiadiazolidinones ; Spiro compounds ; Thiazoles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The design, synthesis and evaluation of a series of 1,2,4-thiadiazolidinones with potential muscarinic receptor binding properties has been performed. During the synthesis of the target compounds, we observed an interesting reductive cleavage of the thiadiazolidinone system which leads to the formation of the novel piperidine spiro triazine heterocycle. The synthesis, structural elucidation (NMR spectroscopy and X-ray diffraction) and biological evaluation of the new compounds are described. With the structures unequivocally established, a mechanism for the formation of the spiro compound is proposed.Supporting information for this article is available on the WWW under //http://www.wiley-vch.de/contents/jc_2046/2000/099462_s.pdf or from the author.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...