Photochemical Synthesis of S,N,O-Containing Polyheterocycles via an α-C(sp)-H Functionalization/Radical Cyclization Cascade.

A highly effective approach based on an organophotocatalytic α-C(sp)-H functionalization/radical cyclization cascade has been developed. This method enables the synthesis of various tricyclic heterocycles containing S, O, and N atoms with excellent site selectivity and diastereoselectivity. Mechanistic investigations have confirmed that the reaction involves photoredox-triggered C(sp)-H cleavage followed by a radical cyclization and aromatization process. These findings are expected to pave the way for developing cost-effective tandem radical reactions and synthesizing heterocyclic drugs.