Pyridazines, 1,6-dihydro-, 6-imino

Reaction of l-aryl-3-carbethoxy-6-phenyl-l,4,5,6-tetrahydropyridazin-4-ones 718 with activated olefins such as benzalacetophenone, benzalacetone, 3-benzylideneacetylacetone, diethyl 2-benzylidenemalonate, and a-cyano-/3-phenylacrylic acid in the presence of an organic base like pyrrolidine, morpholine, piperidine, or triethylamine gave the corresponding 2,8-dihydro-l//-pyrano[2,3-t7 pyridazines 719-723, respectively. The 1-oxo- and 1-imino derivatives of the pyrano[2,3-r/ pyridazine ring system were also prepared from the respective 6-oxo or 6-imino derivative of the starting pyridazine 718 under the same conditions (Equation 60) <1989IJB733>. 

H-Purin 6-Imino-l-methyl-9-(l-propenyi)-l, 6-dihydro- E9b/2, 422 (1-Methylier.) Pyrido[2,3-c]pyridazin 4-Amino-7-... 

Ninhydrin 2-phenylhydrazone refluxed 40 min. with malononitrile and piperidine in ethanol 2-phenyl-4-cyano-9-dicyanomethylene-3-imino-2,3-dihydro-9H-in-deno[2,l-c]pyridazine. Y 90%. F. e. s. G. Zacharias and H. Junek, Z. Naturf. 31b, 371 (1976). 

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