Boron tribromide → 6-Bromo-2-fluoro-3-hydroxybenzaldehyde

A solution of 6-bromo-2-fluoro-3-methoxybenzaldehyde (2.0 g, 8.6 mmol) in dichloromethane (43 mL) under a nitrogen balloon was cooled to −78° C. in an acetone dry ice bath. Boron tribromide (1 M in dichloromethane, 9.5 mL) was added dropwise under nitrogen atmosphere. The reaction was stirred at room temperature overnight. The flask was then put on an ice water bath and the excess boron tribromide was quenched with ice chips. Water was added and the solution was extracted with dichloromethane. The aqueous layer was extracted twice with dichloromethane. The organic layers were combined, washed with brine, dried over anhydrous sodium sulfate, and filtered. The solvent was removed under reduced pressure to give 6-bromo-2-fluoro-3-hydroxybenzaldehyde (1.61 g, 86%).