Synthesis of novel pyrido[3′,2′:4,5]thieno[3,2-d]pyrimidines, pyrido[3″,2″:4′,5′]thieno[3′,2′:4,5]pyrimido[l,6-a]benzimidazoles and related fused systems

3-Amino-4-aryl-5-ethoxycarbonyl-6-methylthieno[2,3-b]pyridine-2-carboxamides 3a-c were prepared from ethyl 4-aryl-3-cyano-6-methyl-2-thioxo-1,2-dihydropyridine-5-carbonylates 1a-c and reacted with some carbonyl compounds to give tetrahydropyridothienopyrimidine derivatives 6a-c, 7a-c and 8a-c, respectively. Treatment of compound 3c with chloroacetyl chloride led to the formation of a next key compound, ethyl 2-chloromethyl-4-oxo-3,4-dihydropyrido[3′,2′:4,5]thieno[3,2-d]pyrimidine-8-carboxylate 9. Also, 3-amino-2-benzimidazolylthieno[2,3-b]pyridine-5-carboxylate 5 and 2-(3′-aminothieno [2,3-b]pyridin-2′-yl)-4-oxo-3,4-dihydropyrido[3′,2′:4,5]thieno[3,2-d]pyrimidine-8-carboxylate 17 were prepared from 1c. The compounds 5, 9 and 17 were used as good synthons for other pyridothienopyrimidines and pyridothienopyrimidobenzimidazoles as well as for related fused polyheterocyclic systems.