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A Two-Step Protocol for Umpolung Functionalization of Ketones Via Enolonium Species
Published on: August 16, 2018
Copper(I)-Catalyzed Enantioselective Addition of Enynes to Ketones
Xiao-Feng Wei1, Xiao-Wei Xie1, Yohei Shimizu1
1Graduate School of Pharmaceutical Sciences, The University of Tokyo , Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Abstract:
A copper(I)-catalyzed enantioselective addition of enynes to ketones was developed. The method allows facile construction of enantiomerically enriched tertiary alcohols using skipped enynes as stable hydrocarbon pronucleophiles. The combination of a soft copper(I)-conjugated Brønsted base catalyst with a chiral diphosphine ligand, (S,S)-Ph-BPE, enabled chemoselective deprotonation of the skipped enynes in the presence of ketones bearing intrinsically more acidic α-protons. The catalytically generated chiral allylcopper species enantio-, diastereo-, regio-, and chemoselectively reacted with ketones, thereby demonstrating excellent substrate generality with functional group tolerance. The skipped enyne moieties of the pronucleophiles were exclusively converted to cis-conjugated enynes, which will eventually allow for further versatile transformations.
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