Under nitrogen protection, copper bromide (3.568 g, 16 mmol, 1.5 eq.) was dissolved with tert-butyl nitrite (3.399 g, 33 mmol, 3 eq.) in acetonitrile (250 mL), heated to 50 °C and stirred. Subsequently, a solution of 4-fluoro-2-methoxy-5-nitroaniline (2 g, 11 mmol, 1 eq.) dissolved in acetonitrile (20 mL) was slowly added dropwise to the reaction system, and the reaction was continued with stirring for 2.5 hours. After completion of the reaction, the reaction mixture was cooled to room temperature and separated by extraction with ethyl acetate and water. The organic phase was washed with water and saturated saline in turn, dried over anhydrous sodium sulfate, and concentrated under reduced pressure to obtain a brown oily crude product. The crude product was purified by silica gel column chromatography (eluent: petroleum ether/ethyl acetate=10/1) to afford the target compound 1-bromo-4-fluoro-2-methoxy-5-nitrobenzene as yellow solid (1.87 g, yield 69.57%).
