Efficient Synthesis of Pyrrolo[1, 2-a]indole-3-ones through Radical-Initiated Cascade Cyclization Reaction

Abstract

A radical cascade cyanoisopropylation/cyclization reaction of 2,2'-azobis(2-methylpropionitrile) (AIBN) with 1-methacryloyl-3-phenyl-1H-indole-2-carbonitrile has been realized, providing an efficient strategy to access various pyrrolo[1, 2-a]indol-3-one in good to excellent yields with good functional group compatibility. The notable features of these protocols include avoiding the use of photocatalyst and transition metal, scalability, and ethanol as the green solvent. Moreover, mechanistic studies have been conducted and a plausible mechanism has been proposed.