Pyridazine derivatives and related compounds, part 20: Synthesis of different heterocycles from 5-aminothieno{[}2,3-c]pyridazine-6-carbohydrazide

7-substituted 3,4-diphenylpyrimido{[}4',5':4,5]thieno{[}2,3-c]pyridazines were synthesized starting from 5-amino-3,4-diphenylthieno{[}2,3-c]pyridazine-6-carbohydrazide (1). Reaction of carbohydrazide 1 with phthalic anhydride afforded 12,13-diphenyl-6H-pyridazino-{[}3{''},4{''}:5',4']thieno{[}3',2':4,5]pyr imido-{[}2,1-a]phthalazine-5,6-dione, (6) which underwent further transformation to the related compounds.