To a stirring solution of methyl 1H-pyrazolo[3,4-c]pyridine-5-carboxylate (0.628 g, 3.545 mmol) in DMF (15 mL) was added 4-fluorobenzyl bromide (0.442 mL, 3.545 mmol) followed by potassium carbonate (0.490 g, 3.545 mmol), and the mixture was stirred overnight at room temperature. Saturated sodium bicarbonate was added and the mixture was extracted with ethyl acetate (3×50 mL). The combined organic extracts were dried over sodium sulfate, filtered and concentrated. The crude solid was purified by flash column chromatography (silica gel, 0-20% acetonitrile:chloroform v/v) to provide pure desired methyl 1-(4-fluorobenzyl)-1H-pyrazolo[3,4-c]pyridine-5-carboxylate (0.66 g, 30% yield over three steps) and the undesired methyl 2-(4-fluoro-benzyl)-2H-pyrazolo[3,4-c]pyridine-5-carboxylate (0.73 g, 33% yield) as white solids. Methyl 1-(4-fluorobenzyl)-1H-pyrazolo[3,4-c]pyridine-5-carboxylate: 1HNMR (CDCl3, 300 MHz) δ ppm 8.91 (s, 1H), 8.59 (s, 1H), 8.22 (s, 1H), 7.26 (m, 2H), 7.02 (m, 2H), 5.69 (s, 2H), 4.03 (s, 3H). LCMS (API-ES M+H+) 286. Methyl 2-(4-fluoro-benzyl)-2H-pyrazolo[3,4-c]pyridine-5-carboxylate: 1HNMR (CDCl3, 300 MHz): 6 ppm 9.32 (s, 1H), 8.51 (s, 1H), 8.10 (s, 1H), 7.36 (m, 2H), 7.09 (m, 2H), 5.65 (2H, s), 4.02 (s, 3H). LCMS (API-ES M+H+) 286.
