113713-60-3

75-15-0

28020-38-4

113713-60-3

2-Mercapto-5-methoxyimidazo[4,5-b]pyridine (Compound 9c) was synthesized in five steps, methoxylation, nitration, amination, reduction and cyclization, using 2,6-dichloropyridine as starting material in 45.7% overall yield. The structure of the product was confirmed by 1H NMR, mass spectrometry (MS) and infrared spectroscopy (IR). The procedure was as follows: 6-methoxy-3-nitropyridin-2-amine (0.5 g, 3 mmol) was dissolved in a mixed solvent of methanol (100 mL) and water (2 mL), 10% Pd/C catalyst (0.1 g) was added, and the reaction was carried out in a hydrogenation unit under hydrogen (3 bar) atmosphere with shaking until the pressure was constant. After completion of the reaction, the catalyst was removed by filtration and carbon disulfide (1 mL) and potassium hydroxide (0.225 g) were added to the filtrate and refluxed under heat. The progress of the reaction was monitored by thin layer chromatography (TLC), and after completion of the reaction the solvent was removed by concentration under reduced pressure. The resulting solid was recrystallized from ethanol to afford the target product 2-mercapto-5-methoxyimidazo[4,5-b]pyridine (0.187 g, 1.1 mmol) in 35% yield with a melting point of 223-225 °C. IR (cm-1 ): 3262, 3051. 1H NMR (200 MHz, DMSO-d6) δ (ppm): 12.99 (s, 1H , NH), 12.54 (s, 1H, NH), 7.43-7.47 (d, 1H, J = 8.5 Hz, Harom.), 6.55-6.60 (d, 1H, J = 8.5 Hz, Harom.), 3.83 (s, 3H, CH3).13C NMR (50 MHz, DMSO-d6) δ (ppm): 167.60, 160.12, 143.62, 120.17, 119.65, 103.90, 53.49.