3-Nitro-5-(trifluoromethyl)benzoic acid (1 g, 4.25 mmol) was dissolved in methanol (15 mL) and concentrated sulfuric acid (5 drops) was added as a catalyst. The reaction mixture was heated to reflux for 48 hours. After completion of the reaction, methanol was removed by distillation under reduced pressure. The residue was dissolved in ethyl acetate (20 mL) and washed sequentially with 5% sodium carbonate solution (3 x 20 mL) and saturated saline (20 mL). The organic layer was dried over anhydrous sodium sulfate and concentrated under reduced pressure to afford methyl 3-nitro-5-trifluoromethylbenzoate without further purification. The yield was 87% and the product was a colorless oil.1H NMR (500 MHz, CDCl3) δ 9.05 (t, J = 1.8 Hz, 1H), 8.68 (t, J = 1.8 Hz, 1H), 8.63 (s, 1H), 4.05 (s, 3H). 13C NMR (126 MHz, CDCl3) δ 163.62, 148.47, 133.16, 132.83 (q, J = 34.7 Hz), 131.87 (q, J = 3.5 Hz), 127.50, 124.42 (q, J = 3.8 Hz), 122.37 (q, J = 273.2 Hz), 53.26.
