Novel Synthesis of Some New Pyridazine and Pyridazino[4,5-d]pyridazine Derivatives

[image omitted] Phenacyl-malononitrile derivatives 1a and b react with dimethylformamide dimethylacetal (DMFDMA) in refluxing toluene to afford the enaminones 2a and b respectively. Compounds 2a and 2b react with the hydrazine hydrate 3a and phenyl hydrazine 3b in refluxing ethanol to afford the pyridazine derivatives 5a-d, presumably via the intermediates 4. Compounds 5a-d, react with hydrazine hydrate 3a to afford the pyridazino[4,5-d]pyridazines 6a-d respectively. The pyridazines 5a and b and the pyridazino[4,5-d] pyridazines 6a and b could be oxidized into the full aromatic systems 7a and b and 8a and b respectively. Compounds 7a and b react also with hydrazine hydrate 3a to afford 8a and b respectively.