General procedure for the synthesis of 2,3-difluoro-4-bromophenyl ethyl ether and trimethyl borate as raw materials for the synthesis of 2,3-difluoro-4-ethoxyphenylboronic acid: intermediate compound T-2 (129.5 g) obtained in Example 1 was dissolved in dry tetrahydrofuran (Dry THF, 500 ml) and the resulting solution was cooled to -70 °C. Under nitrogen protection, n-butyllithium (n-BuLi, 500 ml) was slowly added dropwise and the reaction was stirred at -70 °C for 2 hours. Subsequently, a dry tetrahydrofuran (Dry THF) solution of trimethyl borate (129.5 g) was added slowly dropwise at the same temperature. Upon completion of the reaction, the reaction solution was warmed to room temperature and stirring was continued for 16 hours. The reaction mixture was acidified by adding 2N hydrochloric acid (200 ml) to the reaction mixture and subsequently extracted with toluene. The organic layer was washed sequentially with water and saturated aqueous sodium chloride solution and then dried with anhydrous magnesium sulfate. The solvent was removed by concentration under reduced pressure to give a light brown solid. Purification by recrystallization (heptane: toluene = 4:1, v/v) resulted in colorless crystals T-20 (117.2 g, yield: 71%).
