Nickel-Catalyzed Asymmetric Propargylation for the Synthesis of Axially Chiral 1,3-Disubstituted Allenes.

Abstract

The general enantioselective catalytic synthesis of axially chiral 1,3-disubstituted allenes from readily available racemic propargylic alcohol derivatives remains a long-standing challenge in organic synthesis. Here we report an efficient nickel-catalyzed asymmetric propargylic substitution reaction/Myers rearrangement of racemic propargylic carbonates that furnishes a series of enantioenriched 1,3-disubstituted allenes using newly designed N-sulfonylhydrazone reagents as efficient diazo surrogates. This reaction proved to be remarkably general with regard to substrate scope, affording a diverse range of 1,3-disubstituted allenic compounds in good yields with excellent enantioselectivities. Additionally, applications of this powerful strategy for the enantioselective synthesis of methyl (S)-8-hydroxyocta-5,6-dienoate, (S)-laballenic acid, (S)-phlomic acid, and (S)-Δ9,10-pentacosadiene are described, further highlighting the broad potential of these new reagents for the discovery of novel reactions.