To a solution of the 2-bromo-5-trifluoromethyl-benzonitrile (2.6 g, 10.4 mmol) in toluene (20 mL) at -78° C. was added diisobutylaluminium hydride (21 mL, 21 mmol, 1.0 M in toluene) cooled to -78° C. by cannula. The solution was stirred at -78 to -50° C. for 2 hours. Water (5 mL) was added slowly to the reaction and the reaction was allowed to warm up to room temperature. The mixture was adjusted to pH 10 with NaOH. The product was extracted with dichloromethane, washed with saturated sodium bicarbonate and brine, dried over sodium sulfate and concentrated. The residue was purified by flash chromatography (hexanes/ether 90:10) to give 2-Bromo-5-(trifluoromethyl)benzaldehyde (2.0 g, 76 %) as a dark solid.
