1H-IMidazo[4,5-b]pyridine-6-carboxylic acid, Methyl ester

64-18-6

104685-76-9

77862-95-4

Step 2: A mixed solution of methyl 5,6-diaminonicotinate (1.69 g, 10.12 mmol), formic acid (0.5 mL) and triethyl orthoformate (25 mL) prepared in Step 1 was stirred and reacted at 90 °C for 2.5 hours. After completion of the reaction, the mixture was cooled to room temperature, and the precipitated solid was collected by filtration and dried to afford methyl 3H-imidazo[4,5-b]pyridine-6-carboxylate (588 mg, 33% yield) as a milky white solid, which did not require further purification. The filtrate was concentrated under reduced pressure and the residue was purified by fast column chromatography on silica gel with gradient elution from dichloromethane to dichloromethane solution containing 10% methanol as eluent to afford additional methyl 3H-imidazo[4,5-b]pyridine-6-carboxylate (550 mg, 31% yield) as a cream colored solid. The structure of the product was confirmed by 1H NMR (300 MHz, DMSO-d6) δ 13.33 (br s, 1H), 8.95 (d, J = 1.5 Hz, 1H), 8.64 (s, 1H), 8.50 (d, J = 1.5 Hz, 1H), 3.91 (s, 3H) and LCMS (ESI) m/z 178 (M + H)+.