o‐Benzoylbenzenesulfonyl chlorides (I) were prepared conveniently from aminobenzophenones by diazotization followed by reaction with sulphur dioxide in the presence of Cu+, according to the general method of Meerwein.
Reaction of the sulfonyl chlorides with hydrazine led to 4‐phenyl‐2H‐1,2,3‐benzothiadiazine‐1,1‐dioxides (II). The latter compounds could be methylated and acetylated readily in the 2‐position. The 2‐methyl derivative (III) could be prepared also by reaction of the sulfonyl chloride (Ia) with methylhydrazine. Catalytic hydrogenation of 6‐chloro‐4‐phenyl‐2H‐1,2,3‐benzothiadiazine‐1,1‐dioxide (IIa) gave the 3,4‐dihydro derivative (V). Reaction of the sulfonyl chlorides (I) with o‐phenylenediamine followed by cyclodehydration led to 11H‐11,11a‐dihydrobenzimidazo[1,2‐b] [1,2]benzisothiazole‐5,5‐dioxides (VII). One of the latter compounds (VIIa) in sodium hydroxide solution in the presence of methyl iodide or benzyl chloride was transformed into 6‐methyl‐ and 6‐benzyl‐5H‐dibenzo[c,g] [1,2,6]thiadiazocine‐5,5‐dioxides (VIII), respectively.
5H‐Dibenzo[c,g] [1,2,6] thiadiazocine‐6,6‐dioxides (XIV) were prepared also by cyclodehydration of 2‐amino‐2′‐benzoylbenzenesulfonanilides (XIII).