Polycyclic pyridines: Synthesis of pyridothienopyrimidines pyridothienotriazines and pyridothienotriazepines

Thienopyridines 3a-c were acetylated with Ac2O to afford the pyridothienopy rimidines 4a-c. Also 3a-c were treated with carbon disulfide in dioxan solu tion to give 5a-c. Diazotization of 3a-c gave the triazine derivatives 6a-c . Treatment of 3a-c with triethyl orthoformate in acetic acid gave 7a-c in good yield. Chlorination of 7a by POCl3 afforded the chlorine derivatives 8 . Similarly diazotization of the ortho-aminohydrazide 3d give the correspon ding azide 9 which was subjected to Curtius rearrangement in boiling xylene to give the imidazothienopyridine 10. Compound 12 was obtained by the reac tion of 3d with either formic acid or triethyl orthoformate. Compound 14 wa s also obtained by the reaction of 3d with ethyl chloroformate. Refluxing o f 3d with methyl isothiocyanate gave 15. The interaction of 3d with acetyla cetone furnished the pyrazolyl derivative 16. The ortho-aminonitrile 3e rea cts with mixture of formic acid and formamide (1:1) to give 7a, whereas 3e reacts with formamide alone give 17. Treatment of 3e with carbon disulfide in boiling pyridine afforded 18, Also, acetylation of 3e with acetic anhydr ide afforded 4a.