Catalytic asymmetric construction of C2-symmetric contiguous quaternary carbon centers enabled a concise synthesis of (−)-chimonanthidine and (−)-folicanthine

Abstract

Herein, we disclose a catalytic asymmetric conjugated addition of 3-substutited oxindoles to indol-2-one in situ generated from 3-bromooxindoles promoted by Ni(BF4)2·6H2O/chiral N,N′-chiral dioxide. This protocol enables forging C2-symmetric CQCCs in excellent enantioselectivities as single diastereoisomer via directly fusing two congested 3-substituted oxindoles. The asymmetric synthesis of (−)-chimonanthidine and (−)-folicanthine is concisely achieved respectively in four and five steps by taking advantage of this protocol.