Synthesis and Reactions of Some Pyridazine Derivatives

3, 4-Diphenyl-5-cyanopyridazin-6-one 3 was prepared from the reaction of cyano acetamide 2 with benzihydrazone in dry pyridine. A series of its derivatives was prepard. Tolyl and benene sulphonyl derivatives 6a and 6b are also prepared. 3, 4-Diphenyl-5-cyanopyridazin-6-thione 5 was obtained from 3 by the action of $P_2S_5$ while 3, 4 diphenyl-5-cyano 6-chloropyridazine 4 was obtained from 3 by the action POCl$_3$. The reaction of 4 with hydrazine hydrate directly afforded the pyrazolopyridazine derivative 7. Compound 4 also reacted with phenylhydrazine, aniline, thiophenol and anthranilic acid to yield pyridazine derivatives 8, 9, 10 and 11, respectively. On treatment of compound 11 with acetic anhydride it cyclised to afford pyridazino pyrimidine derivatives 12.