Synthesis and antimicrobial activity of pyrazolo[3',4':4,3]pyrido[6,5-c]pyridazine and thieno[2,3-c]pyridazine derivatives.

4-Acetyl-5,6-diphenyl-2(H)pyridazine-3-one (1) was allowed to react with phenyl hydrazine to afford the corresponding hydrazone 2. Hydrazone 2 upon treatment with Vilsmeier's reagent gave pyrazolylpyridazine derivative 3, which was allowed to react with thiosemicarbazide and hydroxyl amine to give the corresponding thiosemicarbazone and oxime 4 and 5, respectively. Treatment of oxime 5 with Ac2O gave the pyrazolylpyridazine carbonitrile derivative 6. Compound 5 reacts with POCl3 to give the corresponding chloro compound 7. The chloro compound 7 was reacted with hydrazine hydrate or aniline to afford pyrazolopyridazodiazepine 9 or pyrazolopyridazopyridazine 10. When compound 1 was allowed to react with POCl3 the chloro derivative 11 resulted. This compound reacts with thiourea, piperidine or hydrazine hydrate to give compounds 12, 14 and 15, respectively. Compound 12 reacted with alpha-haloester or alpha-haloketone to give the thienopyridazines 13a and b, respectively. Most of the newly synthesized compounds were screened for fungicidal and bactericidal activity.