General procedure for the synthesis of 1,2-dibromo-4,5-difluorobenzene from 1,2-difluorobenzene: First, 84 mg (1.5 mmol) of iron powder was homogeneously dispersed in 7.53 g (50 mmol) of 1,2-difluorobenzene and the temperature of the reaction system was adjusted to 20 °C. Subsequently, 18.4 g (115 mmol) of bromine was slowly added dropwise over a period of 50 min, during which the reaction temperature was maintained at about 20 °C. Upon completion of the dropwise addition, the reaction temperature was raised to 40 °C for 2 hours, followed by further raising the temperature to 50 °C to continue the reaction for 2 hours. Upon completion of the reaction, the mixture was cooled to room temperature and poured into an aqueous solution prepared from 25.2 g of sodium bicarbonate and 12.6 g of sodium sulfite dissolved in 100 mL of water. The reaction product was extracted with ethyl acetate and the organic phase was washed sequentially with water and saturated brine solution, followed by drying with magnesium sulfate. After filtration to remove the desiccant, the reaction was quantified by HPLC, which showed 94% yield of 1,2-dibromo-4,5-difluorobenzene.
