Visible-light-promoted synthesis of imidazo[1,5-a]indole-3-ones via cascade carbene N–H insertion and oxidative cyclization

Abstract

A visible-light-induced, transition-metal-free cascade reaction of indole-1-carboxamides with aryl diazoacetates has been developed, providing efficient access to imidazo[1,5-a]indole-3-ones. The transformation proceeds via sequential carbene N–H insertion, base-promoted intramolecular cyclization, and oxygen-mediated oxidative aromatization, in a concise one-pot, two-step process. This protocol features mild conditions and good functional group tolerance, enabling late-stage diversification of bioactive fragments.