A. General procedure for the synthesis of 2-(4-(difluoromethoxy)phenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane:
Under nitrogen protection, 1-bromo-4-(difluoromethoxy)benzene (1 g, 4.48 mmol), pinacol ester of bis(boronic acid) (1.2 g, 4.71 mmol), potassium acetate (1.3 g, 13.4 mmol), and PdCl2(dppf)-CH2Cl2 adduct (0.18 g, 0.22 mmol) were dissolved in DMF (15 mL) at 90 °C for 1 h. The reaction was stirred. After completion of the reaction, the reaction mixture was diluted with dichloromethane, washed sequentially with water, saturated NaHCO3 solution and brine, and the organic phase was dried with anhydrous MgSO4 and concentrated. The crude product was purified by ISCO fast chromatography (silica gel column, eluent 100:0 to 50:50 hexane/ethyl acetate gradient) to afford the target product 2-(4-(difluoromethoxy)phenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (1.12 g, 3.32 mmol, yield 74.0%) as a brown oil.
