Cyclotransformation in the series of fused 5-nitropyridin-2(1<Emphasis Type="Italic">H</Emphasis>)-ones

Reactions with excess hydrazine hydrate of 5-nitropyridin-2(1H)-ones fused with benzene, pyridine, and 1,2,3-triazole rings led to a cyclotransformation of the 5-nitro-2-oxopyridine fragment into the 6-methyl-3-oxopyridazine structure. This cyclotransformation is of general character; a probable mechanism of the process is suggested. Details of the assumed mechanism were experimentally confirmed on model compounds.