UV light-driven asymmetric vinylogous aldol reaction of isatins with 2-alkylbenzophenones and enantioselective synthesis of 3-hydroxyoxindoles

Abstract

Chiral 3-hydroxyoxindoles are biologically important molecular motifs which are frequently present in natural products and artificial compounds. Herein, we report an ultraviolet light-driven asymmetric vinylogous aldol reaction between versatile isatins and 2-alkylbenzophenones. Under mild conditions, this reaction is catalysed by a chiral amine-derived thiourea, producing chiral 3-hydroxyoxindoles with up to 95% yields and up to 96 : 4 er enantioselectivities with a good substrate scope. Thus, it provides a new and facile method to prepare chiral 3-hydroxyoxindoles. A plausible mechanism is also proposed to rationalize product formation and enantioselectivity.