Catalytic Asymmetric Phase-Transfer Hydroxylation of Oxindoles

Significance

An asymmetric hydroxylation of oxindoles catalyzed by a phase-transfer catalyst is presented. Several different phase-transfer catalysts were tested. High chemical yields and good enantioselectivities were obtained using the cinchonidine-derived PTC-1. It was found that alkyl-, alkenyl- and alkynyl-substituted oxindoles gave high yields and high enantioselectivities. Remarkably, ester groups do not undergo hydrolysis under these conditions and are suitable compounds for this method.