A convenient synthesis of new phosphonomethyl-containing 4,5-dihydropyridazin-3(2H)-ones

An expedient access to novel 4-phosphonomethyl-containing 2,6-disubstituted 4,5-dihydropyridazin-3(2H)-ones involves the reaction of β-phosphono γ'-keto ester intermediates with hydrazines. The construction of the pyridazinone ring allows the installation of various substituents at the positions 2 and 6 as well as a valuable 4-positioned phosphonomethyl fragment.