General procedure for the synthesis of 3-trifluoromethyl-4-aminobenzoic acid from 4-nitro-3-(trifluoromethyl)benzoic acid: 4-nitro-3-(trifluoromethyl)benzoic acid (1 g, 4.25 mmol) was dissolved in methanol at room temperature, 10% Pd/C catalyst was added, and the hydrogenation reaction was carried out overnight under hydrogen atmosphere (balloon pressure). Upon completion of the reaction, the catalyst was removed by filtration and the solvent was evaporated to give the colorless solid product 3-trifluoromethyl-4-aminobenzoic acid (870 mg, quantitative yield).
