Potassium thiocyanate → 2-Oxo-2-[3-(trifluoromethyl)phenyl]ethyl thiocyanate

A solution of 2-bromo-1-[3-(trifluoromethyl)phenyl]ethanone (20 g) in ethanol (100 mL) was heated to 60-70° C., and aqueous solution (10 mL) of potassium thiocyanate (8 g) was added dropwise. The reaction mixture was heated at 80° C. for 10 min, and the mixture was stirred at room temperature for 4 hr and diluted with water. The precipitate was collected by filtration, dissolved in ethyl acetate and dried over anhydrous sodium sulfate. The solvent was evaporated to give 2-oxo-2-[3-(trifluoromethyl)phenyl]ethyl thiocyanate (14 g) as a solid. This solid (10 g) was dissolved in acetic acid (50 mL), and 48% hydrogen bromide-acetic acid solution (10 mL) was added. The reaction mixture was heated at 70-80° C. for 3 hr, and the solvent was evaporated under reduced pressure. The residue was dissolved in ethyl acetate and water, sodium bicarbonate was added, and the mixture was adjusted to pH 7. The ethyl acetate layer was separated, washed with saturated brine and dried over sodium sulfate, and the solvent was evaporated. The residue was purified by column chromatography (carrier: silica gel, eluent: hexane-ethyl acetate) to give the title compound (4.2 g) as a colorless solid.