Ring Transformation of 7-Nitro-1-(4-nitrophenyl)-4,5-dihydro-1H-imidazo- and -[1,2,3]triazolo[4,5-c]pyridin-4-ones

Nitration of 1-phenyl-4,5-dihydroimidazo- and -1,2,3-triazolo4,5-c]pyridin-4-ones initially occurs at the para position of the phenyl ring, and the subsequent nitration yields the corresponding 7-nitro-1-(4-nitrophenyl) derivatives. Treatment of the latter with hydrazine hydrate leads to formation of 1-(4-aminophenyl)-7-methyl-4,5-dihydroimidazo- and -1,2,3-triazolo4,5-d]pyridazin-4-ones.