General procedure for the synthesis of 2-fluoro-3-hydroxyphenylboronic acid from 2-fluoro-3-methoxyphenylboronic acid: 2-fluoro-3-methoxyphenylboronic acid (1.1 g, 6.5 mmol) was dissolved in 30 mL of dichloromethane and cooled to 5 °C under nitrogen protection. Under stirring conditions, 32 mL of a dichloromethane solution of boron tribromide (1 M, 32 mmol) was slowly added dropwise. After the dropwise addition, the reaction mixture was stirred at room temperature for 1 hour. Subsequently, the reaction mixture was slowly added dropwise to 50 mL of pre-cooled ethanol. An excess of solid sodium bicarbonate was added in batches to neutralize the reaction mixture under cooled conditions. After completion of neutralization, stirring was continued for 15 minutes, followed by filtration and the filtrate was evaporated and concentrated. The residue was dissolved in tetrahydrofuran, filtered again and the solvent evaporated to give 0.96 g (96% yield) of 2-fluoro-3-hydroxyphenylboronic acid. The product was characterized by 1H NMR (200 MHz, DMSO-d6): δ 9.53 (1H, s), 8.13 (2H, m), 6.91 (3H, m).
