[Synthesis]
General procedure for the synthesis of 5-nitro-3-(trifluoromethyl)pyridin-2-amine from 2-amino-3-(trifluoromethyl)pyridine: 2-amino-3-(trifluoromethyl)pyridine (2 g, 12.34 mmol) was dissolved in concentrated sulfuric acid (10 mL) at 0 °C, and fuming nitric acid (0.56 mL, 12.34 mmol) was slowly added dropwise. After the dropwise addition, the reaction mixture was kept stirred at 0°C for 15 minutes, then brought to room temperature and continued to stir for 1 hour. After that, the reaction system was heated to 50 °C and maintained for 2 hours. Upon completion of the reaction, the mixture was cooled to room temperature and quenched by slowly pouring into ice water (200 mL). The precipitated solid product was collected by filtration and dried under high vacuum to afford 5-nitro-3-(trifluoromethyl)pyridin-2-amine (1.92 g, 75% yield). The structure of the product was confirmed by 1H NMR (d6-DMSO, 300 MHz) δ 8.02 (brs, 2H), 8.38 (d, 1H, J = 2.6 Hz), 9.04 (d, 1H, J = 2.6 Hz) and mass spectrum (ESI) m/z = 208 (MH+). |