Synthesis and reactions of some new heterocyclic compounds containing thieno[2,3-c] pyridazine moiety

Saponification of ethyl 3-amino-4,5-diphenylthieno[2,3-c]pyridazine-2-carboxyate (1) with alcoholic sodium hydroxide, followed by acidification, afforded the corresponding acid 2. Also, reaction of 1 with ethanolamine and formamide, respectively, gave compounds 5 and 6. Compound 2 reacts with orthophosphoric acid under different conditions to give some new thieno[2,3-c] pyridazine derivatives 3 and 4, which were subjected to reactions to produce compounds 7-18. Furtheremore, compounds 5 and 6 were used to synthesize some substituted pyrimido[4′,5′:4,5)-thieno[2,3-c]pyridazine derivatives 21-30.