Under argon protection, 3-methoxyphenylboronic acid (9.12 g, 60.0 mmol) was dissolved in dichloromethane (200 mL) with triphenylphosphine sulfide (932 mg, 6.00 mmol) in a 300 mL aubergine flask, and stirred until completely dissolved. Subsequently, N-bromosuccinimide (13.0 g, 72.0 mmol) was added to the solution and stirred continuously for 48 hours at room temperature. Upon completion of the reaction, saturated aqueous sodium thiosulfate solution was added to quench the reaction. Extraction was carried out with dichloromethane (100 mL × 3) and the organic phases were combined, washed with saturated brine and dried over anhydrous sodium sulfate. After filtration, the crude product was concentrated under reduced pressure. The target product 2-bromo-5-methoxyphenylboronic acid (8.45 g, 36.6 mmol, 61.0% yield) was purified by silica gel column chromatography (silica gel 290 g, eluent hexane/acetone = 1/1).
