Pyridazine derivatives and related compounds Part 19: The synthesis of different heterocycles from ethyl 5-amino-3,4-diphenylthieno{[}2,3-c]pyridazine-6-carboxylate

7-substituted pyrido{[}2',3':4,5] thieno{[}2,3-c]pyridazines and 6-substituted pyrimido{[}4',5':4,5]thieno{[}2,3-c]pyridazines were synthesized starting from ethyl 5-aminothieno{[}2,3-c]pyridazino-6-carboxylate 1. The reaction of amino ester 1 with benzoyl isothiocyanate affords thiourea derivative 8, which undergoes further transformation to the related fused heterocyclic systems.