General procedure for the synthesis of 7-methyl-1H-indazole-5-carboxylic acid from carbon dioxide and 5-bromo-7H-methyl-1H-indazole: To a solution of 5-bromo-7-methylindazole (2.00 g, 9.47 mmol) in anhydrous THF (50 mL) was added NaH (570 mg, 14.25 mmol; 60% suspension in mineral oil) at room temperature. after 20 min. After 20 min, the reaction mixture was cooled to -78 °C, sec-butyllithium (1.4 M in cyclohexane, 17 mL; 23.8 mmol) was added dropwise, and the resulting mixture was stirred at -78 °C for 4 h. The reaction mixture was then purged with a dry CO2 gas (1.4 M in cyclohexane, 17 mL; 23.8 mmol). Subsequently, a dry CO2 gas was bubbled through the reaction mixture for 1 hour while slowly warming to room temperature. The reaction mixture was continued to be stirred overnight at room temperature. After completion of the reaction, the reaction was acidified by adding 1N HCl solution and extracted with EtOAc. The organic layer was washed with saturated aqueous NaCl solution, dried over anhydrous MgSO4, filtered and concentrated. The residue was redissolved in MeOH, filtered and concentrated to give 7-methyl-1H-indazole-5-carboxylic acid as a brown solid (1.445 g, 86.6% yield). The product was confirmed by 1H NMR (DMSO-d6) and LC/MS analysis: 1H NMR (DMSO-d6) δ 8.23 (s, 1H), 8.17 (s, 1H), 7.65 (s, 1H), 2.46 (s, 3H); LC/MS ES+ m/z 177 (MH+).
