5,6,7,8-Tetrahydrobenzo[b]thieno[2,3-d]pyrimidine-4(3H)one as a synthon of heterocyclic systems

Reaction of 5,6,7,8-tetrahydrobenzo[b]thieno[2,3-d]pyrimidine-4(3H)-one with ethyl chloroacetate afforded an ester, which upon treatment with p-chlorobenzaldehyde under various conditions and with benzylamine gave new compounds. Chlorothienopyrimidine reacted with thiourea, benzoylhydrazine, thiosemicarbazide, semicarbazide, sodium azide and glycine, to give pyrimidinethione, 1,2,4-triazole, thioxo-1,2,4-triazole, oxo-1,2,4-triazole, tetrazole, and imidazole, respectively. The reaction of pyrimidinthione with beta-aroylacrylic acid produced gamma-ketoacid, which reacted with acetic anhydride and hydrazine hydrate to afford furanone and pyridazinone, respectively. Ethyl 2-amino-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxylate was utilized to synthesize the 3-aminothienopyrimidinone derivative via reaction with benzoyl chloride followed by hydrazine hydrate. An interesting condensation product was obtained by reaction of ethyl 2-amino-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxylate with ethyl cyanoacetate in DMF.