Regioselective C2-Sulfonylation of Indoles and Pyrroles via SO ₂ Insertions

A molecular iodine-catalyzed three-component cascade reaction of indoles/pyrroles, anilines, and DABSO has been developed, providing C2-sulfonylated indoles/pyrroles in good to excellent yields. The transformation proceeds via the in situ generation of the arylsulfonyl radical from the reaction of anilines, tBuONO, and DABSO, followed by controlled formation of a carbon-centered radical intermediate. In this radical-mediated cascade reaction, DABSO acts as the sulfone (SO₂) source while tBuONO facilitates the generation of reactive species. Moreover, this one-pot transformation proceeds under mild conditions, exhibits a broad substrate scope, and offers an efficient and sustainable strategy for the construction of C2-sulfonated indoles and pyrroles.