1. A solution was prepared by dissolving 1-bromo-2,3-dichlorobenzene (20 g, 0.088 mol, Aldrich) in anhydrous tetrahydrofuran (44.24 ml) under the protection of dry inert gas. 2. The above solution was slowly added dropwise to anhydrous tetrahydrofuran (16 ml) of n-butyllithium (1.6 M in hexane, 66.36 ml, 0.11 mol) solution, with the reaction temperature strictly controlled below -65°C. 3. After the dropwise addition, the light yellow suspension formed was stirred continuously at -78°C for 75 min. 4. Trimethyl borate (13.28 ml, 12.16 g, 0.12 mol) was slowly added while keeping the temperature below -55°C. 5. The reaction mixture was gradually warmed up to room temperature and stirred overnight. 6. Excess n-butyllithium was quenched with water (30 ml) and the reaction mixture was subsequently concentrated under reduced pressure.7. The concentrated residue was suspended in water and acidified with 2M hydrochloric acid (10 ml).8. The insoluble solid was collected by filtration, washed well with water and then dried.9. The dried solid was suspended in petroleum ether at 60-80°C, stirred at room temperature for 10 min, filtered and dried under vacuum.10. Finally, 8.42 g of 2,3-dichlorophenylboronic acid was obtained in 50% yield with a melting point of 235-238 °C.
