Oxidation of halohydroxybenzo-2,1,3-thiadiazoles with nitric acid

4,5-Dioxobenzo-2,1,3-thiadiazole has been synthesized. Its structure was proven by conversion to the known 4,5-dioximinobenzo-2,1,3-thiadiazole and to 2,1,3-thiadiazolo4,5-a]phenazine, and by reduction to 4,5-dihydroxybenzo-2,1,3-thiadiazole. Oxidation of 5,6-dichloro-4,7-dihydroxy- and 5,7-dichloro-4-hydroxy-benzo-2,1,3-thiadiazoles forms 5,6-dichloro-4,7-dihydroxybenzo-2,1,3-thiadiazole, of known structure, and 7-chloro-4,5-dioxobenzo-2,1,3-thiadiazole; the latter by reaction with ortho-phenylene diamine is converted to 4-chloro-2,1,3-thiadiazolo4,5-a]phenazine.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 850–852, June, 1987.