An unusual stereoretentive 13-quaternary carbon shift resulting in an enantioselective RhII-catalyzed formal 4+1-cycloaddition between diazo compounds and vinyl ketenes

摘要

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.