(1) Lithiation reaction: Add 50 g of 1,3-dichlorobenzene to a 1000 mL three-necked flask under nitrogen atmosphere and cool to -80 to -60°C. Slowly add 176 mL of n-butyl lithium (n-BuLi) dropwise. Slowly add 176 mL of n-Butyl lithium (n-BuLi) dropwise and keep the reaction temperature between -80 and -50℃. After the dropwise addition, the reaction was continued for 2 hours. (2) Lithium-hydrogen exchange reaction: 117 g of tributyl borate (B(OBu)3) was added dropwise to the phenyl lithium solution prepared above, and the reaction temperature was maintained at a holding temperature after the dropwise addition was completed. At the end of the reaction, 10% hydrochloric acid solution was added to the system for acidification, stirred and left to stratify. The organic layers were separated, combined and the solvent was removed, and treated with hydrated succinamide to obtain 51.7 g of crude 2,6-dichlorophenylboronic acid in 80% yield. (3) Purification step: 51.7 g of crude 2,6-dichlorophenylboronic acid was placed in a 1 L three-necked flask and dissolved by adding 200 mL of methyl tert-butyl ether (MTBE). After removing the solvent, cooled and crystallized, centrifuged to obtain 48.4 g of pure 2,6-dichlorophenylboronic acid in 75% yield.
