Enantioselective Synthesis and Application to the Allylic Imidate Rearrangement of Amine-Coordinated Palladacycle Catalysts of Cobalt Sandwich Complexes

Cassar, Doyle J., Ilyashenko, Gennadiy, Ismail, Muhammad, Woods, James, Hughes, David L. and Richards, Christopher J. (2013) Enantioselective Synthesis and Application to the Allylic Imidate Rearrangement of Amine-Coordinated Palladacycle Catalysts of Cobalt Sandwich Complexes. Chemistry - A European Journal, 19 (52). pp. 17951-17962. ISSN 0947-6539

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    Abstract

    The reaction of (η5-(N,N-dimethylaminomethyl)cyclopentadien-yl)(η4-tetraphenylcyclobutadiene)cobalt with sodium tetrachloropalladate and (R)-N-acetylphenylalanine gave planar chiral palladacycle di-μ-chloridebis[(η5-(Sp)-2-(N,N-dimethylaminomethyl)cyclopentadienyl,1-C,3′-N)(η4-tetraphenylcyclobutadiene)cobalt]dipalladium [(Sp)-Me2-CAP-Cl] in 92 % ee and 64 % yield. Enantiopurity (>98 % ee) was achieved by purification of the monomeric (R)-proline adducts and conversion back to the chloride dimer. Treatment with AgOAc gave (Sp)-Me2-CAP-OAc which was applied to asymmetric transcyclopalladation (up to 78 % ee). The (R)-N-acetylphenylalanine mediated palladation methodology was applicable also to the corresponding N,N-diethyl (82 % ee, 39 % yield) and pyrrolidinyl (>98 % ee, 43 % yield) cobalt sandwich complexes. A combination of 5 mol % of the latter [(Sp)-Pyrr-CAP-Cl] and AgNO3 (3.8 equiv) is a catalyst for the allylic imidate rearrangement of an (E)-N-aryltrifluoroacetimidate (up to 83 % ee), and this catalyst system is also applicable to the rearrangement of a range of (E)-trichloroacetimidates (up to 99 % ee). This asymmetric efficiency combined with the simplicity of catalyst synthesis provides accessible solutions to the generation of non-racemic allylic amine derivatives.

    Item Type: Article
    Uncontrolled Keywords: asymmetric synthesis,catalysis,metallacycles,palladium,sandwich complexes
    Faculty \ School: Faculty of Science > School of Chemistry
    Faculty of Science > School of Chemical Sciences and Pharmacy
    Faculty of Science
    University of East Anglia > Faculty of Science > Research Groups > Synthetic Chemistry
    Depositing User: Pure Connector
    Date Deposited: 25 Jul 2014 16:20
    Last Modified: 25 Jul 2018 09:56
    URI: https://ueaeprints.uea.ac.uk/id/eprint/49743
    DOI: 10.1002/chem.201302922

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