In a 500 mL three-necked flask, 1-bromo-4-fluoronaphthalene (27.9 g, 0.124 mol) was dissolved in anhydrous tetrahydrofuran (200.0 mL), followed by the addition of triisopropyl borate (26.8 g, 0.142 mol), and the reaction mixture was cooled to -78°C. At -78°C, a solution of n-butyllithium (9.5 g, 0.149 mol) was slowly added dropwise. ) to the solution, and the dropwise addition lasted for 0.5 hours. After the dropwise addition was completed, the reaction mixture was allowed to gradually warm up to room temperature. Upon completion of the reaction, the reaction was quenched by addition of saturated aqueous ammonium chloride solution. After adjusting the pH of the reaction mixture to strongly acidic, it was extracted with ethyl acetate (200.0 mL x 3). The organic phases were combined, washed with saturated brine and dried over anhydrous sodium sulfate. Subsequently, the solvent was removed by distillation under reduced pressure. The residue was pulped with hexane and filtered to give 21.2 g of 4-fluoronaphthalene-1-boronic acid solid in 90.2% yield.
