An unusual stereoretentive 1,3-quaternary carbon shift resulting in an enantioselective RhII-catalyzed formal [4+1]-cycloaddition between diazo compounds and vinyl ketenes

Abstract

Enantioselective quaternary carbon construction in the assembly of cyclopentenones employing a Rh^II-catalyzed, formal [4+1]-cycloaddition is described. A Rh₂(S-TCPTTL)₄-catalyzed cyclopropanation of a vinyl ketene with a disubstituted diazo compound initiates a stereoretentive, accelerated ring expansion to provide the cycloadduct in good to excellent yields and enantioselectivity.