3-Bromoindazole

271-44-3

40598-94-5

General procedure for the synthesis of 3-bromoindazole from indazole: 1H-indazole (3.00 g, 25.4 mmol) was suspended in 2.0 M sodium hydroxide solution (70 mL) at ambient temperature and a solution of bromine (3.00 g, 18.8 mmol) was slowly added. Subsequently, 2.0 M sodium hydroxide solution (30 mL) was added dropwise. The reaction mixture was stirred for 3 h. Sodium bisulfite (0.1 g) was added to quench the reaction, followed by acidification with the addition of 2.0 N hydrochloric acid solution (80 mL). The precipitate was collected by filtration and washed with water to give the final 3-bromoindazole (3.98 g, 80% yield). The product characterization data were as follows: melting point 136 °C; 1H NMR (CDCl3) δ 13.4 (broad single peak, 1H), 7.57 (multiple peaks, 2H), 7.45 (triple peak, 1H), 7.22 (triple peak, 1H); EI-MS (m/z) 198 [M+2]+, 196 [M]+.