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Abstract
Diethyl acetylenedicarboxylate 2 reacted with benzilmonohydrazone 1 to form 3,4-dicarboxycarbony 1-5,6-diphenylpyridazine 3, which upon alkaline hydrolysis gave the corresponding dicarboxylic acid 4. Decarboxylation of 4 gave 3,4-diphenyl-pyridazine 7. On treatment of 4 with acetyl chloride or thionyl chloride, 3,4-diphenyl-5,7-dioxofuro[3,4-c]pyridazine 8 was formed. Friedel-Crafts acylation on 8 gave 4-benzoyl-3-carboxy-5,6-diphenylpyridazine 9, 3-benzoyl-4-carboxy-5,6-diphenyl-pyridazine 10 and 4-benzoyl-5,6-diphenylpyridazine 11. Hydrazinolyis of 9 and 10 produced the isomeric pyridazino[4,5-]pyridazines 15 and 16, respectively. Reaction of 5,7-di-oxofuro[3.4-c]pyridazine 8 with distilled aniline gave the unexpected product 3,4-diphenyl-5-(N-phenyl) formamidopyridazine 17.