General procedure for the synthesis of 3-chloro-2-methoxyphenylboronic acid from 1-bromo-3-chloro-2-methoxybenzene and triisopropyl borate: 1-bromo-3-chloro-2-methoxybenzene (113.2 g, 426.4 mmol) was dissolved in tetrahydrofuran (1000 mL), and cooled to -78°C. At the same temperature 1.7 M tertiary-butyllithium (t-BuLi) was added slowly to a tert-butyl lithium (t-BuLi) ) to a hexane solution (251.7 mL, 426.4 mmol). The reaction mixture was stirred at -78°C for 1 h. Triisopropyl borate (B(OiPr)3) (113.2 mL, 852.4 mmol) was added, followed by gradual warming of the reaction mixture to room temperature and continued stirring for 3 hours. Upon completion of the reaction, 2 N aqueous hydrochloric acid (800 mL) was added to the mixture and stirred at room temperature for 1.5 hours. The resulting precipitate was collected by filtration, washed sequentially with water and ether and dried under vacuum. The crude product was recrystallized by a solvent mixture of chloroform and ethyl acetate and dried to give 3-chloro-2-methoxyphenylboronic acid as a white solid (89.6 g, 91% yield; Mass Spectrometry (MS): [M + H]+ = 230.
