Synthesis, Alkylation and Reduction of 4‐Aryl‐2 H ‐1,2,3‐benzothiadiazine 1,1‐dioxides

Abstract ortho ‐(2‐Aryl‐1,3‐dioxolan‐2‐yl)benzenesulfonyl chlorides obtained from benzophenone ketals by directed ortho ‐lithiation chemistry were cyclized either with hydrazine monohydrate or with acetohydrazide to furnish variously substituted 4‐aryl‐2 H ‐1,2,3‐benzothiadiazine 1,1‐dioxides. Alkylation of benzothiadiazine dioxides with alkyl iodides under basic conditions was elaborated, revealing significant differences compared to the reactivity of 4‐unsubstituted ones. Hydrogenation of the C=N double bond in the presence of platinum(IV) oxide is also described. Detailed NMR studies and DFT calculations supported the structure elucidation of the compounds.