To a solution of 2-bromo-4-chloro-1-fluorobenzene (5 g, 0.0238 mol) in anhydrous ether (30 ) at -70C under nitrogen atmosphere was added a 2M solution of n-BuLi in hexane (13 mL, 0.0262 mol).
mL) in anhydrous ether (30 ) was added to a 2 M solution of n-BuLi in hexane (13 mL, 0.0262 mol). The solution was stirred at the same temperature for 30 min and then triisopropyl borate (4.93 g,0.0262 mol) was added dropwise to the solution. The white slurry formed was stirred at -70 C for 30 min and then warmed to room temperature and stirred for 1 h. The reaction was monitored by TLC and H
NMR to monitor the reaction. After the reaction was completed, the reaction mixture was hydrolyzed with 6N
NaOH and stirred for 1 h. The reaction mixture was extracted with EtOAc. The organic layer was washed with brine and concentrated under reduced pressure to obtain a viscous compound, which was ground with n-pentane and dried to obtain 5-chloro-2-fluorophenylboronic acid as an off-white solid.
