40.0 g (322.2 mmol) of 3-methoxyphenol was dissolved in 1 L of acetonitrile and cooled to 0 °C under nitrogen protection. A solution of 57.35 g (322.2 mmol) of N-bromosuccinimide in 500 mL of acetonitrile was added slowly dropwise, with the rate of dropwise acceleration being controlled to maintain the temperature of the reaction mixture at 0 °C (for about 2 hours). After titration was completed, the reaction mixture was continued to be stirred at 0 °C for 1 hour. After completion of the reaction, the reaction mixture was concentrated under reduced pressure. The residue was treated with carbon tetrachloride and filtered to remove the resulting solid. The filtrate was concentrated under reduced pressure to give a mixture of brominated isomers in the form of a red oil. The mixture was separated by silica gel column chromatography using a hexane gradient elution system containing 0-30% ethyl acetate. The first eluted fractions were collected and concentrated under reduced pressure to give 18.1 g (28% yield) of 2-bromo-5-methoxyphenol as a clear liquid.1H-NMR (CDCl3): δ 7.31 (d, 1H), 6.6 (d, 1H), 6.41 (dd, 1H), 5.5 (s, 1H), 3.77 (s, 3H). Subsequently, the post-eluted fractions were combined and concentrated under reduced pressure. The residue was further purified by silica gel column chromatography using dichloromethane as eluent. The fraction containing high purity 4-bromo-3-methoxyphenol was collected and concentrated under reduced pressure to give 24.1 g (37% yield) of white crystalline solid (melting point 68-69 °C).1H-NMR (CDCl3): δ 7.34 (d, 1H), 6.45 (d, 1H), 6.33 (dd, 1H), 4.9 (br s, 1H), 3.85 (s, 3H).
