Base/Acid-Controlled Oxidative Ring Opening of Sulfonium Salts for Divergent Access to Arylthiobutyraldehydes, Arylthiobutanols, and Sulfur-Containing Pyrrolo[1,2- <i>a</i> ]quinoxalines

We report a base/acid-controlled oxidative ring opening of sulfonium salts that delivers, in a switchable and selective manner, two distinct classes of <i>S</i>-containing linear products, arylthiobutyraldehydes and arylthiobutanols. The transformation proceeds under operationally simple conditions and exhibits a broad substrate scope and high functional group tolerance. In addition, sulfonium salts can be directly engaged in one-pot coupling/annulation with 2-(1<i>H</i>-pyrrol-1-yl)anilines to furnish sulfur-containing pyrrolo[1,2-<i>a</i>]quinoxaline derivatives. The resulting products are readily diversified to sulfoxides, sulfones, sulfoximines, and additional heterocyclic scaffolds, demonstrating the synthetic utility of this platform.