Synthesis of Pyrazolo [4,5]pyridazine and Isoxazolo [3,4d]pyridazine Derivatives

Arylhydrazones of diethylacetondicarboxylate 3 was treated with formaldehyde to give 1 aryl-4, 5, 6-trihydropyridaine derivatives 4a-f Cyclization of compound 4a-f by hydroxylamine afforded [3, 4d] 1, 3, 4, 5-tetrahydropyridazine derivatives 5a-f. Also cyclization of compound 4c with semicarbazide gave 1-amidopyrazolo-5-one-1-aryl-3-carboxypyridazine 6. On the other hand compounds 3 reacted with ethylorthoformate to give diethyl-1, 4-dihydro-1-arylpyridazine-4one-2.5 dicarboxylate 7, which on treatment with hydrazine. Semicarbazide and thiosemicarbazide gave pyridazine, amido and thioamido derivatives. The spectral and antimicrobial data of these compounds 1-8 were studied.