Example 9A Step 1: 4-Fluoro-3-methoxyaniline (2.0 g, 14.2 mmol) was dissolved in dichloromethane (20 mL) at 0 °C and a dichloromethane solution of 1.0 M boron tribromide (40 mL) was slowly added dropwise. The reaction mixture was stirred at 0 °C, followed by gradual warming to room temperature and continued stirring overnight. Upon completion of the reaction, the reaction was quenched by the addition of methanol, followed by removal of the solvent under reduced pressure. Water was added to the residue, which was alkalized with saturated sodium bicarbonate solution to pH neutral and then extracted with ethyl acetate. The organic phase was washed with saturated brine, dried over anhydrous magnesium sulfate and concentrated under reduced pressure to give 5-amino-2-fluorophenol as a white solid (1.3 g, 73% yield). The product was characterized by 1H NMR (300 MHz, DMSO-d6): δ 9.26 (s, 1H), 6.81 (dd, 1H), 6.34 (dd, 1H), 6.04 (dd, 1H), 4.63 (br, 2H).
