Chlorination of Heterocyclic and Acyclic Sulfonhydrazones

Chlorination of 2H-1,2,3-benzothiadiazine 1,1-dioxide(1) in wet methylene chloride gives o-formylbenzenesulfonyl chloride (4), but in dry methylene chloride at 0° yields the chlorosultine 3-chloro-3H-2,1-benzoxathiole 1-oxide (2); the latter is readily hydrolyzed to the "pseudo-acid" 3H-2,1-benzoxathiol-3-ol 1-oxide (3) which on further chlorination forms 4. In 1,2-dichloroethane at −20° chlorination of 1 gave the "coupled product" 14, whereas in dimethylformamide at room temperature the cyclic acyl chloride hydrazone 4-chloro-2H-1,2,3-benzothiadiazine was isolated in poor yield. The acyl chloride hydrazones (16) were the products obtained following chlorination of some representative aromatic acyclic tosylhydrazones (15). 3H-2,3,4-Benzothiadiazepine2,2-dioxide (19), a previously unknown heterocyclic system, was synthesized in two steps from 1,3-dihydrobenzo[c]thiophene (17). Chlorinolysis of 19 gave o-chloromethylbenzal chloride (21). These reactions are believed to involve formation of the α-chloroazo compound (e.g. 22) as the first step. The formation of 2 from 1 is discussed in terms of three possible routes, two which involve the sulfene 23.