Step (f): n-BuLi (2.5 M, n-hexane solution, 2.5 mL, 1.2 eq., 6.3 mmol) was slowly added dropwise under nitrogen protection to a solvent mixture of toluene and THF (4: 1, 10 mL, 10 mL) containing 2-bromo chlorobenzene (I) (1 g, 0.6 mL, 5.2 mmol) and triisopropyl borate (1.44 mL, 1.2 eq., 6.27 mmol). 1, 10 mL) in a reaction temperature of -70°C and a dropwise addition time of 1 hour. After the dropwise addition, the reaction mixture was continued to be stirred at -70°C for 0.5 hr. Subsequently, the reaction system was slowly warmed to -20 °C and the reaction was quenched by the addition of 2N HCl solution (5 mL). After the reaction mixture was brought to room temperature, it was extracted with dichloromethane. The organic phases were combined, dried and concentrated to give a white solid. The solid was purified by recrystallization from acetonitrile to give the target product 2-chlorophenylboronic acid in 98% yield (800 mg).
