Substrate-Dependent Asymmetric Allylic Alkylation of Morita–Baylis–Hillman Carbonates with 3-Alkylidene Oxindoles

Abstract

A substrate-dependent, regio- and stereo-controlled asymmetric allylic alkylation of 3-alkylidene oxindoles and racemic Morita–Baylis–Hillman carbonates has been achieved using chiral cinchona alkaloid-derived catalysts. This present methodology enables the divergent synthesis of chiral γ-substituted alkylidene oxindoles and 3,3-disubstituted oxindoles in a highly selective manner. Plausible catalytic pathways for the formation of these biologically interesting compounds are proposed. Density functional theory calculations have clarified the high diastereoselectivity of allylic alkylation of 1a with 2a and have confirmed that the chiral 3,3-disubstituted oxindoles 6 are from an asymmetric allylic alkylation/Cope rearrangement sequence.