The general procedure for the synthesis of 4-chloro-3-methoxyphenylboronic acid from 5-bromo-2-chloroanisole was as follows: n-butyllithium (8.7 mL, 1.6 M hexane solution, 14 mmol) was added slowly and dropwise to a mixture of toluene/THF (16/6 mL) of 4-bromo-1-chloro-2-methoxybenzene (2.2 g, 9.9 mmol) at -78 °C. After the reaction mixture was stirred at -78 °C for 30 min, trimethyl borate (2.2 mL, 19.8 mmol) was added. Subsequently, the reaction system was slowly warmed to room temperature and stirring was continued overnight. Upon completion of the reaction, the reaction was quenched with 1 M HCl (15 mL). The organic layer was separated and dried with anhydrous sodium sulfate. After removing the solvent under reduced pressure, the crude product was purified by fast column chromatography to afford the target compound 4-chloro-3-methoxyphenylboronic acid (1.2 g, 65% yield) as a white solid.1H NMR (400 MHz, CD3OD) δ ppm: 3.87 (s, 3H), 7.11 (d, J=7.83 Hz, 1H), 7.20 (s, 1H), 7.29 ( d, J=7.83Hz, 1H).
