Catalyst-free cascade reaction of heterocyclic ketene aminals with N-substituted maleimide to synthesise bicyclic pyrrolidinone derivatives

Abstract

An efficient synthesis of highly substituted bicyclic pyrrolidinone derivatives via a cascade reaction of heterocyclic ketene aminals (HKAs) and N-substituted maleimide in an environmentally friendly medium under catalyst-free conditions is described. This protocol uses group-assisted purification (GAP) chemistry in which purification via chromatography and recrystallization can be avoided, and the pure products were obtained simply by washing the crude products with 95% ethanol. The library of bicyclic pyrrolidinone derivatives has been constructed with moderate to excellent yields.