Abstract
γ,ß'-Dicarbonylphosphonates and phosphineoxides 1 and 2 react with hydrazines to give 4-phosphopyridazine and pyridazin-3-one derivatives 3, 4 and 5. 4-Phosphodihydro-pyridazin-3-ones 5were dehydrogenated by the action of bromine in acetic acid to give phosphopyridazinones 6. The structure of all obtained products is confirmed by NMR and IR spectroscopy.