The general procedure for the synthesis of 3-fluoro-4-hydroxybenzonitrile using 3-fluoro-4-methoxybenzonitrile as starting material was as follows: to a solution of 3-fluoro-4-methoxybenzonitrile (15.6 g, 0.103 mol) in dichloromethane (100 mL) was slowly added boron tribromide (BBr3, 20 mL, 0.211 mol) at 0 °C. The reaction mixture was refluxed under nitrogen protection for 3 days. Upon completion of the reaction, the reaction was quenched with ice water and extracted with dichloromethane. The organic layers were combined, washed sequentially with water and saturated brine and dried over anhydrous sodium sulfate. The solvent was removed by concentration under reduced pressure to give 13.3 g of gray solid product in 94% yield. The product was characterized by 1H NMR (400 MHz, CDCl3): δ 7.38-7.42 (m, 2H), 7.09 (dd, J = 8.8 Hz, 8.4 Hz, 1H), 5.68 (s, 1H).
