Nitropyrazoles

A method of preparation of 5-amino-3,4-dinitropyrazole (1) from 3(5)-methyl-5(3)-nitro- and 3(5)-methyl-4,5(3)-dinitropyrazoles was developed, the key step of which was the Hofmann rearrengement of nitro- and dinitropyrazolecarboxamides. The protonation of 5-amino- 3,4-dinitropyrazole was studied by spectral methods (UV spectroscopy, NMR spectroscopy). In spite of low basicity of the amino group, compound 1 undergoes N-arylation, N-nitration, and annulation reactions with formation of dinitropyrazolo5,1-a]pyrimidine derivatives and hitherto unknown dinitroimidazo1,2-b]pyrazole derivatives. Diazotization of 1 leads to 5-diazo-3,4-dinitropyrazole (19), which exists in the form of the internal salt. Some reactions of this compound were studied and the formation of the corresponding 5-halogeno(azido)- 3,4-dinitropyrazoles under the action of the halide and azide ion was shown. Dinitropyrazolo- 5,1-c]1,2,4]triazine and 7-hydroxydinitro-4,7-dihydropyrazolo5,1-c]1,2,4]triazine deriva- tives were obtained by the action of active methylene compounds on the betaine 19.