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3,4-Diphenyl-5-cyanopyridazin-6-one 3 was prepared from the reaction of cyanoacetamide 2 with benzilhydrazone in dry pyridine. A series of its derivatives was prepared. Tolyl and benzene sulphonyl derivatives 6a and 6b are also prepared. 3,4-Diphenyl-5-cyanopyridazin-6-thione 5 was obtained from 3 by the action of P2S5 while 3,4-diphenyl-5-cyano-6-chloropyridazine 4 was obtained from 3 by the action of POCl3. 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.
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