Step 1: 4-Ethylaniline (10.3 mL, 82.5 mmol) was slowly added dropwise to 96% sulfuric acid (63 mL), and the reaction system was cooled to 8°C and ensured that the temperature was maintained below 10°C. After the dropwise addition was completed, the reaction mixture was further cooled to -5 °C, followed by the slow addition of a mixed acid consisting of 100% nitric acid (4 mL) and 96% sulfuric acid (10 mL), controlling the reaction temperature below 0 °C. The reaction mixture was stirred continuously at -5°C for 1 hour. Upon completion of the reaction, the mixture was slowly poured into ice water (200 mL), precipitated, filtered and washed with water. The resulting solid was resuspended in water (100 mL) and neutralized to neutral with 35% ammonium hydroxide solution. The precipitate was collected by filtration and dried in an oven to give the light brown solid product 4-ethyl-3-nitroaniline (10 g, 73% yield). The product was characterized by 1H NMR (400 MHz, DMSO-d6): δ 1.11 (t, J = 7.45 Hz, 3H), 2.63 (q, J = 7.45 Hz, 2H), 5.53 (s, 2H), 6.81 (dd, J = 8.30, 2.44 Hz, 1H), 7.04 (d, J = 2.44 Hz, 1H), 7.11 ( d, J = 8.30 Hz, 1H).
