Indole and Pyrrole Derivatives as Pre-photocatalysts and Substrates in the Sulfonyl Radical-Triggered Relay Cyclization Leading to Sulfonylated Heterocycles.

A visible-light-induced method for the construction of heterocyclic scaffolds such as pyrido[1,2- a ]indoles and indolizines via sulfonyl radical-triggered relay cyclization without employing any external photocatalyst has been developed. Preliminary mechanistic investigation indicated that indole and pyrrole derivatives could serve as pre-photocatalysts to promote the sulfonylation/cyclization, thereby providing a facile method to synthesize valuable sulfonylated heterocycles.