341-23-1

518990-32-4

Step 1: Preparation of 4-fluoro-3-iodo-1H-indazole (B-2). Iodine (I2) (18.64 g, 73.46 mmol) and potassium hydroxide (KOH) (7.73 g, 137.7 mmol) were sequentially added to a stirring solution of 4-fluoro-1H-indazole (B-i) (5.00 g, 36.73 mmol) in DMF (80 mL) at room temperature. After 2 hours of reaction, thin layer chromatography (TLC) monitoring showed completion of the reaction. The reaction mixture was slowly poured into 10% aqueous sodium bisulfite (NaHSO3) (200 mL) and extracted with ethyl acetate (EA) (3 x 200 mL). The organic layers were combined, washed sequentially with water (100 mL) and saturated saline (2×200 mL), dried over anhydrous sodium sulfate (Na2SO4), filtered and concentrated. The crude product was washed with petroleum ether (PE) to give a yellow solid B-2 (8.33 g) in 86.5% yield.The physical characterization data of B-2 were as follows: liquid chromatography-mass spectrometry (LCMS) (electrospray ionization, ESI): calculated value of C7H4FIN2, 261.9; measured value of [M + H]+ = 262.9.