3-Fluoro-4-methoxyphenylboronic acid was synthesized as follows: using 4-bromo-2-fluoroanisole (10 g, 0.049 mol) as starting material, n-butyllithium (23.4 mL of 2.5 M hexane solution, 0.059 mol) was added dropwise under anhydrous and oxygen-free conditions at -78°C and the reaction was stirred for 1 hour. Subsequently, triisopropyl borate (45.2 mL, 36.9 g, 0.196 mol) was slowly added and the reaction mixture was gradually warmed to room temperature and stirring was continued for 12 hours. Upon completion of the reaction, the reaction was quenched by the addition of dilute hydrochloric acid, extracted with ethyl acetate and the organic phase was dried over anhydrous sodium sulfate and concentrated. The crude product was purified by column chromatography to afford 7.1 g of 3-fluoro-4-methoxyphenylboronic acid as white solid in 85.2% yield. The product was confirmed by mass spectrometry (ESI), m/z 169 (MH)-; 1H NMR (DMSO-d6) data were as follows: δ 3.84 (3H, s), 7.10-7.16 (1H, m), 7.51-7.60 (2H, m).
