General procedure for the synthesis of benzo[d][1,3]dioxol-5-ylboronic acid from 4-bromo-1,2-methylenedioxybenzene and triisopropyl borate: In a 100 mL three-necked round-bottomed flask under nitrogen protection, 5-bromobenzo[d][1,3]dioxolene (2 g, 9.95 mmol, 1.00 eq.) and THF (20 mL) were added, and the flask was cooled to -78 °C. Butyl lithium (BuLi, 5.6 mL, 1.40 eq.) was slowly added dropwise, followed by triisopropyl borate (1.96 g, 14.00 mmol). The reaction mixture was stirred at -78 °C for 1 hour and then slowly warmed to room temperature and continued stirring for 4 hours. Upon completion of the reaction, the reaction was quenched with 10 mL of water and acidified with sulfuric acid (4.9 g, 50.00 mmol, 5.00 equiv). The mixture was heated to reflux overnight. After cooling, it was extracted with ethyl acetate (3 x 50 mL), the organic layers were combined, dried over anhydrous sodium sulfate and concentrated under reduced pressure. The resulting solid was washed with ethyl acetate (3 x 3 mL) to give 0.5 g (30% yield) of benzo[d][1,3]dioxol-5-ylboronic acid as a white solid.
