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Preparation method of 2-bromo-3-fluoronitrobenzene: Add 21.6g (0.1mol) 2-bromo-3-nitroaniline, 12.5ml (0.15mol) concentrated hydrochloric acid, and 12.5ml water into a reaction bottle, and reduce the temperature to 15°C; dissolve 8.3g (0.12mol) sodium nitrite in 14.5ml water and slowly add dropwise to the above system, then add 11.4g (0.13mol) fluoroboric acid, keep warm at 15°C and stir for 2 hours, track the reaction by HPLC until the reaction of 2-bromo-3-nitroaniline is complete; filter, rinse the filter cake with methanol, and dry to obtain 25.8g of intermediate IV. Add 30 ml of toluene to the reaction flask, heat to 100 ° C, slowly add 10 g (31.7 mmol) of intermediate IV, keep warm and stir for 1 hour, track the reaction by HPLC until the intermediate IV reacts completely: concentrate, recrystallize from ethyl acetate and n-hexane to obtain 5.7 g of 2-Bromo-3-fluoronitrobenzene, with a molar yield of 83%.