Synthesis of 4-Benzo[1,3]Dioxol-5-Ylthieno-[2,3-b]Pyridines

4,7-Dihydrothieno[2,3-b]pyridine 4 and thieno[2,3-b]pyridine 6 were obtained by Thorpe–Ziegler cyclization. Mn(OAc)3/acetic acid system had been used for oxidation of 1,4-dihydropyridine 3 to pyridine derivative 5. 6-Carbamoylmethylsulfanyl-1,4-dihydropyridine 3 was prepared by alkylation of piperidinium 1,4-dihydropyridine-2-thiolate 1 with iodoacetamide.