1H-Indazole-5-boronic acid pinacol ester

53857-57-1

73183-34-3

862723-42-0

5-Bromoindazole (9.45 g, 48 mmol), bis(pinacolato)diboron (15.5 g, 61 mmol), potassium acetate (16.7 g, 170 mmol), and anhydrous DMF (160 mL) were added to the reaction flask under argon protection. Pd(dppf)Cl2-CH2Cl2 (985 mg, 1.2 mmol) was subsequently added as a catalyst. The reaction mixture was stirred at 90 °C for 24 hours. After completion of the reaction, it was cooled to room temperature, diluted with ethyl acetate (250 mL) and washed with water (2 x 50 mL). The organic phase was concentrated under reduced pressure and purified by silica gel column chromatography (eluent: hexane/ethyl acetate, 10:1, v/v, Rf = 0.6) to afford 1H-indazole-5-boronic acid pinacol ester (9.8 g, 84% yield). The product was confirmed by 1H NMR (300 MHz, CD3OD) and mass spectrometry (DCI/NH3).1H NMR data: δ 1.36 (s, 12H), 7.51 (dt, J = 8.5, 1.0 Hz, 1H), 7.73 (dd, J = 8.5, 1.0 Hz, 1H), 8.08 (d, J = 1.0 Hz, 1H), 8.23 ( t, J = 1.0 Hz, 1H). Mass spectral data: m/z 245 (M + 1)+.