(Step 1) Synthesis of 2-methyl-2H-indazole-3-carboxylic acid: 2-methyl-2H-indazole-3-carboxylic acid methyl ester (1.59 g, 8.36 mmol) was dissolved in tetrahydrofuran (85 mL), followed by addition of 0.25 N sodium hydroxide solution (50 mL, 12.5 mmol). The reaction mixture was stirred at room temperature for 24 hours. Upon completion of the reaction, the solvent was removed by distillation under reduced pressure. Water (appropriate amount) was added to the residue, which was then acidified with 1 N hydrochloric acid (50 mL). The precipitate precipitated was collected by filtration under reduced pressure, washed with water and dried under reduced pressure to give 2-methyl-2H-indazole-3-carboxylic acid (1.34 g, 91% yield) as a colorless solid.1H-NMR (DMSO-d6) δ: 4.43 (s, 3H), 7.29 (m, 1H), 7.35 (m, 1H), 7.74 (dd, J = 8.1, 1.0 Hz, 1H), 7.98 (d, J = 8.5 Hz, 1H), 13.59 (broad s, 1H).MS (ESI) m/z 177 (M++1).
