Novel synthesis of pyridopyridazine, pyrrolopyridazine and some pyridazine derivatives

Ethyl-1-aryl-5-cyano-1,6-dihydro-4-methyl-6-oxopyridazine-3-carboxylate (1) reacts with hydrazine hydrate in ethanol to give the corresponding hydrazide 2. Compound 2 gave the carboazide 3 upon treatment with nitrous acid. The carboazide 3 reacts with different alcohols, hydrazine hydrate, and different amines to give the corresponding carbamate, semicarbazide and urea derivatives 4-6. respectively, also compound 3 when refluxed in xylene gave pyrrolopyridazine 7. Compound 1 reacts with aromatic aldehydes to give styryl derivative 8 which upon refluxing with hydrazine hydrate gave the corresponding hydrazide 9 which undergoes cyclization to pyridopyridazine 10 upon treatment with Cu2Cl2.