52548-00-2

443-82-3

52548-00-2

General procedure for the synthesis of 3-bromo-6-fluoro-o xylene from 2,3-dimethylfluorobenzene: 400 g of dichloromethane, 124 g of 2,3-dimethylfluorobenzene, and 5 g of aluminum trichloride were sequentially added to 1 L of a three-necked reaction flask, and stirred at 20 °C. The reaction solution was slowly added 16-32 g of bromine from a constant-pressure dropping funnel containing 160 g of bromine to a three-necked reaction flask. From a constant-pressure dropping funnel containing 160 g of bromine, 16-32 g of bromine was slowly added dropwise to the three-necked reaction flask, followed by warming to 30 °C with stirring to initiate the reaction, which showed a red color and was accompanied by the formation of a large amount of hydrogen bromide gas. The remaining bromine in the constant-pressure dropping funnel was added slowly to the reaction system, and after completion of the addition, the reaction was continued at 20 °C with stirring for 0.5 h. The reaction was completed by adding 16-32 g of bromine to a three-necked reaction flask. After the reaction was completed, 50 mL of saturated sodium sulfite aqueous solution was added dropwise to the reaction solution to quench the unreacted bromine, and the reaction solution gradually changed from red to colorless, indicating that the bromine treatment was completed. The reaction solution was allowed to stand, the aqueous and organic phases were separated, and the aqueous phase was retained. The organic phase was dried with anhydrous sodium sulfate and filtered, the filtrate was collected and the cake was washed with a small amount of dichloromethane. The washings and filtrate were combined to obtain the organic phase. The organic phase was concentrated under reduced pressure at 50-55 °C until no liquid was distilled out, yielding 189 g of product. Hydrogen bromide gas generated during the reaction was introduced into the exhaust gas absorption treatment system through a pipe connected to a three-neck reaction flask and absorbed with aqueous sodium hydroxide. By GC analysis, the retention time of the product 3-bromo-6-fluoro-o xylene was 3.8 min, that of the feedstock 2,3-dimethylfluorobenzene was 6.8 min, and that of the by-product was 8.9 min. The purity of the product was 88.4%, the content of the by-product was about 3.3% and the rest was unreacted feedstock, the calculated yield was 87%.