The general procedure for the synthesis of 2,3-methylenedioxyphenylboronic acid from 4-bromo-1,3-benzodioxazole and triisopropyl borate was as follows: under argon protection, nBuLi (2.5 M hexane solution, 2.38 mL, 5.97 mmol) was slowly added dropwise to a 50 mL anhydrous tetrahydrofuran solution containing 4-bromo-1,3-benzodioxazole (1 g, 4.97 mmol) and triisopropyl borate (1.49 mL, 6.47 mmol) in 50 mL of anhydrous tetrahydrofuran solution at a reaction temperature of -78°C. The reaction temperature was maintained at this temperature for 3 hours. After maintaining this temperature for 3 hours, the reaction was gradually warmed up to room temperature and then immediately cooled down to 0°C. The reaction solution was then washed with 2N HCl. The reaction solution was acidified with 2N HCl to pH=2 and then neutralized with 2N NaOH to pH=7. The reaction mixture was extracted with ethyl acetate (3 x 25 mL), and the organic phases were combined, washed with saturated brine and dried over anhydrous sodium sulfate. The solvent was removed by concentration under reduced pressure to give 2,3-methylenedioxyphenylboronic acid (570 mg, 69% yield) as a white solid. The product was characterized by 1H-NMR (CD3OD): δ 5.92 (s, 2H), 6.80-6.86 (m, 3H).
