Visible-Light-Mediated Aerobic Oxidative Cyclization of 2-Aminobenzenesulfonamides and Alcohols for the Synthesis of Benzothiadiazine-1,1-Dioxides under Ambient Conditions.

A straightforward visible light-driven synthetic strategy has been established for the construction of benzothiadiazine-1,1-dioxide scaffolds. This protocol employs readily accessible alcohols and 2-aminobenzenesulfonamides as starting materials with 9-fluorenone acting as a metal-free organic photocatalyst under an oxygen atmosphere at room temperature. A variety of functionalized benzothiadiazine-1,1-dioxide derivatives were successfully obtained in good to excellent yields. Notably, gram-scale synthesis of compound 3a was achieved, demonstrating the favorable scalability and promising industrial applicability of this catalytic system. Furthermore, mechanistic investigations suggest that the product formation proceeds via a radical pathway.