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  • 1
    Electronic Resource
    Electronic Resource
    Assessment of the negative factors responsible for the decrease in the enantioselectivity for the ring opening of epoxides catalyzed by chiral supported Cr(III)-salen complexes (2000)
    Springer
    Catalysis letters 68 (2000), S. 113-119 
    Details
    ISSN: 1572-879X
    Keywords: chromium ; salen ; zeolite ; clay ; epoxide ; azidotrimethylsilyl ether
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In order to determine the influence of the inorganic support on the asymmetric induction, different chiral chromium(III)-salen complexes have been incorporated within the cavities of zeolites Y, EMT and into the interlamellar region of K-10 montmorillonite. These heterogeneous catalysts are able to promote the asymmetric ring opening of epoxides with trimethylsilylazide to afford chiral azido trimethylsilyl ethers and azido alcohols with modest enantiomeric excess that varies depending on the inorganic support. The factors that have been found to play a negative influence diminishing the enantioselectivity of the supported Cr(III)-salen catalyst compared to the unsupported complexes are the following: (i) the presence of adventitious acid sites, (ii) the encapsulation of no sufficiently stereogenic ligands and (iii) the change in the reaction mechanism from bimetallic to a single metal reaction mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019046411998
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  • 2
    Electronic Resource
    Electronic Resource
    13C and 1H NMR assignments for a series of dehydroabietic acid derivatives (1995)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 33 (1995), S. 318-321 
    Details
    ISSN: 0749-1581
    Keywords: NMR ; 1H NMR ; 13C NMR ; INEPT ; HMBC ; nitro ; amine ; dehydroabietic acid derivatives ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reliable assignments were made for a series of nitro and amine C ring-substituted dehydroabietic acid derivatives, the main resin acid present in disproportionated rosin and an important intermediate in the chemical industry. A combination of 1D and 2D NMR techniques, including HETCORR, COSY and DEPT experiments, was used. Quaternary carbon atoms, mainly aromatic substituted, require care owing to assignment difficulties that are based on calculated data and are confirmed by long-range 1H, 13C NMR correlation with selective INEPT and the proton-detected HMBC experiment.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260330416
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    Paper (German National Licenses)
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