In a 500 mL three-neck flask, methyl 4-bromobenzoate (20.2 g, 77.2 mmol) was dissolved in anhydrous THF (200.0 mL) and triisopropyl borate (18.9 g, 100.3 mmol) was added. The reaction mixture was cooled to -78 °C, N-butyllithium (6.8 g, 96.5 mmol) was slowly added dropwise and the reaction was kept at this temperature for 0.5 h. The reaction was completed with the addition of saturated chloride (1.2 mmol). Upon completion of the reaction, the reaction was quenched with saturated aqueous ammonium chloride solution, followed by adjusting the pH with 1 mol/L hydrochloric acid to 1. The aqueous phase was extracted with ethyl acetate (100.0 mL x 3), the organic phases were combined, washed with saturated brine (60 mL x 1) and dried over anhydrous sodium sulfate. The solvent was removed by distillation under reduced pressure, the residue was pulped with hexane, and 13.3 g of 4-methoxycarbonylphenylboronic acid was obtained after filtration in 95.5% yield.
