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Copper-Free Asymmetric Allylic Alkylation with a Grignard Reagent: Design of the Ligand and Mechanistic Studies

Authors

  • David Grassi,

    1. Département de Chimie Organique, Université de Genève, 30 quai Ernest-Ansermet, CH-1211 Genève-4 (Switzerland), Fax: (+41) 223796522
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  • Dr. Chrysanthi Dolka,

    1. Département de Chimie Organique, Université de Genève, 30 quai Ernest-Ansermet, CH-1211 Genève-4 (Switzerland), Fax: (+41) 223796522
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  • Dr. Olivier Jackowski,

    1. Département de Chimie Organique, Université de Genève, 30 quai Ernest-Ansermet, CH-1211 Genève-4 (Switzerland), Fax: (+41) 223796522
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  • Prof. Alexandre Alexakis

    Corresponding author
    1. Département de Chimie Organique, Université de Genève, 30 quai Ernest-Ansermet, CH-1211 Genève-4 (Switzerland), Fax: (+41) 223796522
    • Département de Chimie Organique, Université de Genève, 30 quai Ernest-Ansermet, CH-1211 Genève-4 (Switzerland), Fax: (+41) 223796522
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Abstract

The Cu-free asymmetric allylic alkylation, catalysed by NHC, with Grignard reagents is reported on allyl bromide derivatives with good results. The enantioselectivity was quite homogeneous (around 85 % ee) on large and various substrates, regardless of the nature of the Grignard reagent. The formation of stereogenic quaternary centres was highly regioselective for both aliphatic and aromatic derivatives with good enantiomeric excess (up to 92 % ee). The methodology developed was found to be complementary with the Cu-catalysed version. Several new NHCs were tested with improved efficiency. In addition, mechanistic studies, using NMR spectroscopy, led to the discovery of the catalytically active species.

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