Synthesis of pyrido[1,2-a]indol-6(7H)-ones via a visible light-photocatalyzed formal (4 + 2) cycloaddition of indole-derived bromides and alkenes or alkynes

Abstract

We successfully developed an unprecedented synthesis route to pyrido[1,2-a]indol-6(7H)-ones through a visible light-photocatalyzed formal (4 + 2) cycloaddition of indole-derived bromides and alkenes or alkynes in a microchannel reactor. This novel protocol features extremely mild conditions, a broad substrate scope and high reaction efficiency. In addition, a reasonable reaction mechanism based on controlled experiments was proposed.