A reaction mixture was prepared from 4-bromo-1-(tetrahydro-2H-pyran-4-yl)-1H-pyrazole (1.0 g, 4.33 mmol) and pinacol ester of bis(boronic acid) (1.32 g, 5.19 mmol) in 10 mL DMF. Potassium acetate (1.27 g, 12.98 mmol) and 1,1'-bis(diphenylphosphino)ferrocene-palladium(II) dichloride dichloromethane complex (177 mg, 0.22 mmol) were added sequentially and the reaction was carried out under argon protection. The reaction mixture was stirred at 80 °C for 10 hours. After completion of the reaction, the reaction solution was diluted with 40 mL of water and subsequently extracted with ethyl acetate (30 mL x 3). The organic phases were combined, washed sequentially with water (30 mL x 3) and brine, dried over anhydrous Na2SO4 and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography (ethyl acetate/petroleum ether, 1/4) to afford 1-(tetrahydropyran-4-yl)-1H-pyrazole-4-boronic acid pinacol ester (39) as a white solid in 68% yield. The product was characterized by NMR (300 MHz, CDCl3): δ 7.80 (s, 1H), 7.75 (s, 1H), 4.42-4.31 (m, 1H), 4.12-4.07 (m, 2H), 3.57-3.49 (m, 2H), 2.13-1.99 (m, 4H), 1.32 (s, 12H).
