Step 1: Indazole-3-carboxylic acid (CXXXI) (1.0 g, 6.16 mmol) was suspended in glacial acetic acid (60 mL) and heated to 120 °C until a clear solution was formed. The solution was then cooled to 90 °C. A solution of bromine (0.633 mL, 12.33 mmol) in glacial acetic acid (2 mL) was slowly added dropwise to the solution at 90 °C. After addition, the reaction continued to be heated at 90 °C for 16 hours. After completion of the reaction, the solution was cooled to room temperature and poured into ice water and stirred at room temperature for 15 minutes. The precipitated solid was filtered, washed with cold water and dried under vacuum at room temperature to afford 5-bromo-1H-indazole-3-carboxylic acid (CXXXII) as a white solid (1.30 g, 5.39 mmol, 87.5% yield). The product was characterized by 1H NMR (DMSO-d6): δ 13.95 (s, 1H), 13.18 (br s, 1H), 8.21 (d, J = 1.2 Hz, 1H), 7.65 (d, J = 7.0 Hz, 1H), 7.56 (dd, J = 7.0, 1.2 Hz, 1H); ESIMS m/z 242.0 ([M + H]+. (calculated value C8H4BrN2O2).
