General procedure for the synthesis of 4-chloro-2-methoxyphenylboronic acid: preparation of intermediate I-1. 22.1 g (100 mmol) of 2-bromo-5-chloroanisole was dissolved in 500 mL of tetrahydrofuran (THF) and stirred for 10 min at -78 °C and protected by nitrogen (N2). Subsequently, 44 mL of a 2.5 M solution of n-butyllithium (n-BuLi) was slowly added through a dropping funnel and stirring was continued for 30 minutes. Next, 10.4 g (110 mmol) of trimethyl borate was slowly added dropwise, and after completion of the dropwise addition, the reaction mixture was warmed to room temperature and stirred for 3 hours. After completion of the reaction, the reaction was quenched with 300 mL of 1 M hydrochloric acid (HCl) and the organic layer was extracted three times with diethyl ether and washed with water. The organic layers were combined, dried with anhydrous magnesium sulfate and concentrated under reduced pressure to remove the solvent. The residue was purified by silica gel column chromatography to afford 13.61 g of Intermediate I-1 (73 mmol, 73% yield). The resulting compound was characterized by mass spectrometry (MS/FAB): theoretical value of [M+H]+ (C7H8BClO3) 186.40, measured value 186.47.
