The general procedure for the synthesis of 5-bromo-1H-indazole-3-carbonitrile from 2-(2-amino-5-bromophenyl)acetonitrile is as follows: to a cooled solution of 2-(2-amino-5-bromophenyl)acetonitrile (11 g, 52 mmol) in concentrated hydrochloric acid (110 mL) was slowly added a solution of sodium nitrite (3.9 g, 57 mmol) in water (20 mL) at -50 °C. . After addition, the reaction mixture was stirred continuously at -50°C for 2 hours. Subsequently, the temperature of the mixture was raised to 0 °C, neutralized with 33% ammonium hydroxide solution and extracted with ethyl acetate (3 x 100 mL). The organic phases were combined, washed with saturated sodium chloride solution (100 mL), dried over anhydrous sodium sulfate and concentrated under reduced pressure. The resulting crude product was purified by column chromatography (100-200 mesh silica gel) with the eluent being a petroleum ether solution of 10% ethyl acetate. The eluate was collected to give the target product 5-bromo-3-cyanoindazole (7 g, 60% yield) as a solid. Its 1HNMR (CDCl3) data were as follows: δ 10.7 (br, 1H), 8.1 (s, 1H), 7.64 (d, 1H), 7.5 (d, 1H).
