N,N′-Dioxide-Scandium(III)-Catalyzed Asymmetric Michael Addition of β,γ-Unsaturated Butenolides to α,β-Unsaturated γ-Keto Esters

A highly efficient N,N-dioxide-scandium(III) complex catalytic system has been developed for the asymmetric vinylogous Michael reaction of -angelica lactone and its derivatives to ,-unsaturated -keto esters, affording the corresponding ,-disubstituted butenolide products in moderate to good yields (up to 93%) with high dr (up to >19:1) and ee values (up to 97%) under mild reaction conditions.