The Rearrangement of Aryl Thiohydrazonates

Abstract

Rearrangement and cyclization of a series of p-nitrophenyl and heteroaryl thiohydrazonates ArSCAr′ = NNHC6H3XY(2,4), where the displaced substituent X is Br or F and the remaining substituent Y is Br or NO2, occurs under suitable basic conditions to the corresponding 7-substituted 2-aryl-4-p-nitrophenyl- and -4-heteroaryl-4H-1,3,4-benzothiadiazines, e.g. 13 → 19. Under these or suitable acidic conditions, the 4,6-dimethyl-2-pyrimidinyl thiohydrazonate rearranges to the thiohydrazide Ar′CSNHNArC6H3XY(2,4), apparently the first case of thiohydrazonate thiohydrazide rearrangement; such acidic treatment produces cleavage of some other heteroaryl thiohydrazonates.Independent syntheses of two of the 4-heteroaryl-substituted benzothiadiazines are reported.