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General procedure for the synthesis of 5-bromo-1H-pyrazolo[3,4-c]pyridine from 2-bromo-4-methyl-5-aminopyridine: to a solution of 2-bromo-4-methyl-5-aminopyridine (4.00 g, 21.4 mmol) in acetic acid (300 ml) was added sodium nitrite (1.48 g, 21.4 mmol) and the reaction mixture was stirred at room temperature overnight. After completion of the reaction, the mixture was concentrated under vacuum. The residue was diluted with ethyl acetate and washed sequentially with saturated aqueous sodium bicarbonate solution and brine. The organic layer was dried over anhydrous magnesium sulfate and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (eluent: 0-50% hexane solution of ethyl acetate) to afford 5-bromo-1H-pyrazolo[3,4-c]pyridine as a yellow solid (2.48 g, 59% yield).1H NMR (300 MHz, CDCl3): δ 7.86-7.90 (m,1H), 8.09-8.14 (m,1H) 8.83-8.88 (m, 1H). ms ESI/APCI Dual m/z: 198 [M + H].

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