Organocatalytic enantioselective direct vinylogous Michael addition of γ-substituted deconjugate butenolides to azadienes

Abstract

The diastereoselective and enantioselective direct vinylogous Michael addition of γ-substituted β,γ-unsaturated γ-lactones to 2-arylidene-N-tosylbenzofuran-3(2H)-imines has been achieved with the aid of a quinine-derived squaramide. The protocol features a low catalyst loading, mild reaction conditions, and enables the formation of butenolides bearing both benzofurans and adjacent quaternary and tertiary stereocenters in high to excellent yields with generally high enantioselectivities and perfect diastereoselectivities.