Unusual formation of 4-diazo-3-nitriminopyrazoles upon acid nitration of pyrazolo[3,4-d][1,2,3]triazoles

Nitration of 6-R-4-phenylpyrazolo[3,4-d][1,2,3]triazoles at the phenyl substituent is accompanied by the triazole ring opening to give new 3-R-4-diazo-1-(di)nitrophenylpyrazole- 5-nitrimines. Chemical and physicochemical properties of the prepared compounds are reported.