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
Depositing User: Pure Connector
Date Deposited: 25 Jul 2014 15:20
Last Modified: 21 Jul 2020 23:58
URI: https://ueaeprints.uea.ac.uk/id/eprint/49743
DOI: 10.1002/chem.201302922

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