Using 2,4-difluorophenyl ethyl carbonate (3.1 g, 16 mmol) as raw material, nitric acid (0.78 ml, 19 mmol) was slowly added to a solution of sulfuric acid (10 mL) at 0 °C, keeping the reaction temperature at about 0 °C. After 15 min of reaction, the reaction was terminated by adding ice-cold water (70 mL), and the product was extracted with ethyl acetate (2 × 50 mL). The organic layers were combined, washed with brine, dried over anhydrous sodium sulfate, and concentrated to give the nitro product as a thick syrup. The nitro product was dissolved in methanol (20 mL), solid sodium bicarbonate (4.0 g, 47 mmol) was added and stirred for 16 hours at room temperature. After completion of the reaction, the mixture was filtered and the filtrate was concentrated. The resulting solid was dissolved in water (20 ml) and acidified with 3M HCl solution to pH~5. The product was extracted with dichloromethane (3 x 25 mL), the organic layers were combined, washed with brine, dried over anhydrous sodium sulfate, and concentrated to give 2,4-difluoro-5-nitrophenol (2.34 g, 84% yield). The product was confirmed by 1H NMR (400 MHz, acetone-d6): δ 9.59 (s, 1H), 7.78 (t, J=7.2 Hz, 1H), 7.45 (t, J=10.4 Hz, 1H); mass spectrometry (ESI) m/z: 176.0 (M+H+).
