3,5-Difluorophenylboronic acid

121-43-7

461-96-1

156545-07-2

(1) A solution was prepared by dissolving 100 g of 3,5-difluorobromobenzene in 150 mL of tetrahydrofuran (THF) under nitrogen protection. The solution was slowly added dropwise to a mixture containing 13.85 g of magnesium shavings and 55 mL of THF at a controlled titration rate to keep the reaction system at mild reflux. (2) After the dropwise addition was completed, the reaction mixture was stirred at 40°C for 1 hour and subsequently cooled in an ice bath. (3) A solution prepared from 64.59 g of trimethyl borate dissolved in 130 mL of THF was slowly added dropwise under ice bath cooling. After completion of the dropwise addition, the ice bath was removed and the reaction mixture was continued to be stirred at room temperature for 1 hour. (4) 10% hydrochloric acid solution was added dropwise to the reaction system until the system became acidic, followed by stirring at room temperature for 30 minutes. (5) The organic layer was separated and the aqueous layer was extracted with hexane. The organic layer and hexane extract were combined and washed with saturated saline. (6) The washed organic layer was dried by adding anhydrous sodium sulfate, filtered and distilled under reduced pressure to remove the solvent to obtain 71.65 g of 3,5-difluorophenylboronic acid.