General procedure for the synthesis of 3-iodo-5-(1H)indazolecarboxylic acid from indazole-5-carboxylic acid hydrochloride: 1H-indazole-5-carboxylic acid (200 mg, 1.23 mmol), N,N-dimethylformamide (3 mL), potassium hydroxide (138 mg, 2.46 mmol), and iodine (470 mg, 1.85 mmol) were added to a 25 mL round bottomed flask. The reaction mixture was stirred at 25°C for 3 hours. After the reaction was completed, the reaction was quenched by adding 10 mL of Na2S2O3 solution. The pH of the reaction solution was adjusted with 10% hydrochloric acid solution to 6. The resulting solid was collected by filtration. Finally 300 mg (84% yield) of 3-iodo-1H-indazole-5-carboxylic acid was obtained as a white solid.
