Acetic Acid → 3-Bromo-4-(trifluoromethyl)benzoic acid

5.0 g of 3-amino-4-trifluoromethyl-benzoic acid were dissolved using 50 ml of acetic acid. Then, 50 g of ice and 50 ml of a saturated aqueous HBr-solution were added and a solution of 2.0 g NaNO2 in 10 ml of water was added dropwise at 0° C. The reaction mixture was then stirred at room temperature for 10 minutes. Then, the reaction mixture was added dropwise to a suspension of 7.0 g CuBr and 10.9 g CuBr2 in 100 ml of a half-concentrated aqueous solution of HBr. The resulting mixture was then stirred for 2 h at room temperature, then diluted using 21 of water, stirred for 1 h and finally the precipitate was isolated by filtration. The precipitate was dried in vacuo to yield 5.2 g of the title compound that was used without further purification.