Bifunctional Iminophosphorane Superbases Enable the Highly Enantioselective Sulfa-Michael Addition to Fully
Kang Yuan1, Alberto I Ristache1, Szymon M Kosc1
1Department of Chemistry, Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, U.K.
Abstract:
The metal-free catalytic enantioselective intermolecular conjugate addition of alkyl thiols to unactivated β-substituted cyclopropene carboxylic acid derivatives has been developed. High enantiomeric excesses and yields were consistently achieved across a broad range of thiol pronucleophiles and fully substituted cyclopropene electrophiles under mild reaction conditions, enabled by a novel tert-leucine-derived amide-containing bifunctional iminophosphorane (BIMP) catalyst. Additionally, lowering the catalyst loading to 5.0 mol % was possible and allowed the reaction to be carried out on a gram scale.
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