Asymmetric Synthesis of 3-Lactone-Substituted 2-Oxindoles with Vicinal Quaternary Carbon Centers through Vinylogous Conjugate Addition

Abstract

AbstractA new method has been developed for constructing vicinal quaternary stereocenters with an oxindole–butanolide hybrid framework through asymmetric vinylogous addition of a siloxyfuran to an indol-2-one in the presence of a readily available N,N′-dioxide–Ni(OTf)2 complex catalyst. Various oxindole–lactones were obtained in up to 98% yield with >19:1 dr and 97% ee under mild reaction conditions. A possible transition-state model is proposed to explain the origin of the asymmetric induction.