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 <i>in situ</i> generation of the arylsulfonyl radical from the reaction of anilines, ^<i>t</i>BuONO, 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 ^<i>t</i>BuONO 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.