Synthesis
General procedure for the synthesis of 2-ethyl-5-nitroaniline from 2-ethylaniline: 2-ethylaniline (24.2 g, 0.2 mol) was slowly added to concentrated sulfuric acid (100 mL), keeping the temperature of the reaction system lower than 0°C. The reaction was carried out at a controlled temperature. Fuming nitric acid (18.6 g, 0.3 mol) was slowly added dropwise under strictly controlled temperature conditions. After the dropwise addition, the reaction mixture was kept stirring at room temperature. Upon completion of the reaction, the reaction solution was carefully poured into ice water (1000 mL) and stirred while adding. Subsequently, the pH of the mixture was adjusted slowly by adding 50% sodium hydroxide solution to about 8. The precipitate was collected by filtration and the filter cake was recrystallized with petroleum ether to give 2-ethyl-5-nitroaniline (26.6 g, 80.1% yield) as a yellow needle-like solid.
References
[1] Patent: CN103373989, 2016, B. Location in patent: Paragraph 0031; 0032
[2] Patent: CN103739550, 2016, B. Location in patent: Paragraph 0125-0129
[3] Tetrahedron, 1990, vol. 46, # 17, p. 6085 - 6112
[4] Journal of Medicinal Chemistry, 2008, vol. 51, # 15, p. 4632 - 4640
[5] Patent: WO2009/62658, 2009, A1. Location in patent: Page/Page column 33; 1/10
