Potassium acetate (KOAc, 1.07 g, 10.92 mmol) was added to a solution of 4-bromo-1-(tetrahydrofuran-3-yl)-1H-pyrazole (0.79 g, 3.64 mmol) and pinacol ester of bis(boronic acid) (1.11 g, 4.37 mmol) in N,N-dimethylformamide (DMF, 20 mL). The reaction mixture was degassed with nitrogen (N2) and stirred for 10 min, followed by the addition of [1,1'-bis(diphenylphosphino)ferrocene]palladium dichloride (Pd(dppf)Cl2, 89 mg, 0.109 mmol). After degassing again with nitrogen, the reaction mixture was stirred at 80 °C overnight. After completion of the reaction, DMF was removed by rotary evaporation and the residue was purified by column chromatography (eluent ratio: ethyl acetate:petroleum ether = 1:10) to afford 1-(tetrahydrofuran-3-yl)-1H-pyrazole-4-boronic acid pinacol ester (0.63 g, 65.6% yield).
