Synthesis of new polyfunctionally substituted pyridazines, phthalazines, cinnolines and thieno[3,4-c]pyridazines

The reaction of ethyl 2-arylhydrazono-3-oxobutyrates (Ia, Ib) with active methylene ketones afforded pyridazin-5-carbonitrile derivatives. The methyl function in the ethyl pyridazin-3-carboxylate derivatives IIa, IIb reacted with arylidenemalononitrile to yield the phthalazine derivatives Va-Vf and with elemental sulfur to yield the thienopyridazines XIXa, XIXb. The cinnolines are producted from reaction of IIa, IIb with diethyl acetonedicarboxylate.