New synthesis of polyfunctionally substituted pyridazine, pyridazinone, pyridazino[1,6-a]-quinazoline, pyrido[2,3-c]pyridazine, azafluoreno [3,4-c]pyridazine and benzimidazo[1,2-a]pyridine derivatives

An efficient synthesis of pyridazines and fused pyridazine ring derivatives starting from the appropriate aryl methyll ketones is described. The latter were converted in two steps to 3-oxo-3-aryl-2-arylhydrazonopropanals, which upon treatment with cyanomethyl derivatives gave the corresponding pyridazine, pyridazino[1,6-a]-quinazoline, pyrido[2,3-c]pyridazine, azafluoreno[3,4-c]pyridazine and benzimidazo[1,2-a]pyridine derivatives.