Synthesis
The general procedure for the synthesis of 2,4-dimethyl-5-nitroaniline from 2,4-dimethylaniline is as follows: nitric acid (33 g) was added slowly and dropwise to a stirring solution of 2,4-dimethylaniline (40 g, 0.33 mmol) in concentrated hydrochloric acid over a period of 3 h, keeping the reaction temperature below 15 °C. The reaction temperature was kept below 15 °C for the first time. Subsequently, sulfuric acid (400 g) was added. After addition, the reaction mixture was continued to be stirred at 15 °C for 1 h. The reaction was then poured into ice (600 mL), stirred for 30 min and filtered. The resulting yellow filter cake was neutralized with saturated aqueous sodium bicarbonate (500 mL) and subsequently extracted with ethyl acetate (3 x 200 mL). The organic extracts were combined, dried with magnesium sulfate, filtered and the solvent was removed in vacuum to give the crude product. The crude product was recrystallized by ethanol-water mixed solvent to give a final orange solid product (39 g, 71% yield, containing 20% dinitro by-product). The product was analyzed by IR showing characteristic absorption peaks (Nujol, cm-1): 3469, 3386, 3239, 2956, 2925, 2855, 1719, 1636, 1514, 1461, 1377, 1339, 1297, 1273, 1222, 1170, 1034, 992, 885, 870, 849. 805, 758, 745, 723, 640, 607 and 571; 1H NMR (400 MHz, CDCl3) δ: 7.15 (1H, s), 6.87 (1H, s), 4.99 (2H, br.s), 2.21 (3H, s), 1.97 (3H, s).
References
[1] European Journal of Organic Chemistry, 2009, # 5, p. 687 - 698
[2] Bioorganic and Medicinal Chemistry, 2016, vol. 24, # 3, p. 403 - 427
[3] Patent: EP1147110, 2003, B1
[4] Chemische Berichte, 1884, vol. 17, p. 265
[5] Journal of the Chemical Society, 1921, vol. 119, p. 718
