4-Bromo-2-fluorobenzonitrile (4.0 g, 20 mmol), pinacol ester of bisboronic acid (3.8 g, 30 mmol), and potassium acetate (6.1 g, 60 mmol) were suspended in dimethyl sulfoxide (DMSO, 50 mL) under nitrogen protection. Subsequently, [1,1'-bis(diphenylphosphino)ferrocene]palladium dichloride (Pd(dppf)Cl2, 1.5 g, 0.2 mmol) was added. The reaction mixture was stirred at 80 °C for 4 hours. After completion of the reaction, the mixture was diluted with water (100 mL) and extracted with ethyl acetate (100 mL × 3). The organic layers were combined and washed sequentially with water (50 mL × 3) and saturated saline (50 mL), then dried with anhydrous sodium sulfate. After drying, the filtrate was filtered and the filtrate was concentrated under reduced pressure. The residue was purified by silica gel column chromatography (eluent ratio: petroleum ether/ethyl acetate = 50:1 to 10:1) to afford the target product 4-cyano-3-fluorophenylboronic acid pinacol ester (56-a, 3.6 g, 73% yield). The product was characterized by 1H-NMR (400 MHz, CD3OD): δ 7.62 (m, 3H), 1.35 (s, 12H) ppm.
