5-Bromo-2-chlorobenzoic acid (5 g, 21.23 mmol) was dissolved in tetrahydrofuran (THF, 10 mL) at 0 °C and 10 M borane-methyl sulfide complex (2.123 mL, 21.23 mmol) was added slowly. The reaction system was gradually warmed to 23 °C with continuous stirring for 14 hours. Upon completion of the reaction, the reaction mixture was cooled and an additional 10 M borane-methyl sulfide complex (1.062 mL, 10.62 mmol) was added. Subsequently, the reaction mixture was cooled in an ice water bath and methanol (2.00 mL) was added slowly and dropwise to quench the reaction. After the production of bubbles essentially ceased, the volatile solvent was removed by distillation under reduced pressure. The residue was dissolved in ethyl acetate (EtOAc, 1 mL) and washed with saturated aqueous sodium bicarbonate. The aqueous phase was back-extracted with ethyl acetate (50 mL) and the combined organic phases were washed sequentially with water (5 mL) and saturated aqueous sodium chloride. The organic layer was dried over anhydrous sodium sulfate and concentrated under reduced pressure to afford the target product 2-chloro-5-bromobenzyl alcohol (4.62 g, 98% yield). The product was characterized by 1H NMR (400 MHz, methanol-d4): δ 7.70 (s, 1H), 7.40 (d, J = 8.28Hz, 1H), 7.28 (d, J = 8.53Hz, 1H), 4.66 (s, 2H).
