Synthesis and reactions of 1H-4,1,2-benzothiadiazines, and observations on the structure of hydrazonoyl sulphides

Abstract

Syntheses of 1-acetyl-7- and -8-bromo- and -6,8-dibromo-3-phenyl-4,1,2-benzothiadiazines establish, in conjunction with previous data, the generality of 1H-4,1,2-benzothiadiazine synthesis from appropriately substituted N′-acetyl-N′-arylbenzothiohydrazides. The corresponding 6-nitrobenzothiadiazine is also available by this route, and such cyclizations can proceed by expulsion of a nitro-group, presumably as nitrite ion. These 1H-4,1,2-benzothiadiazines undergo electrophilic substitution at positions 6 and 8, are nucleophilic at position 1, and are oxidizable at position 4 to the corresponding sulphone. X-Ray crystallographic studies of bis-[α-(2,6-dibromophenylhydrazono)benzyl] sulphide confirm the symmetrical structure of hydrazonoyl sulphides.