preparation | preparation of 2, 5-dibromotrifluorobenzene benzene trifluoride was prepared by bromination reaction using benzene trifluoride as starting material, the synthesis reaction formula is shown in the figure below: Fig. 1 2, the commonly used bromination reagents in the synthesis reaction formula of 5-dibromotrifluorobenzene mainly include: elemental bromine, organic bromination reagent, perbromo type quaternary ammonium salt and Quaternary phosphorus salt, tetrabromocyclic ketone, perbrominated pyridinium hydrobromide, N-bromosuccinimide, dibromohydantoin, etc. This time a new synthetic brominating agent is used, which is a 2: 1: 1 type complex of N,N-dimethylacetamide, hydrobromic acid, Pure bromine. The brominating agent is a mild and highly selective brominating agent, and when it is reacted with aryl acetone, bromine can selectively replace the hydrogen atom in the alpha position, and the reaction can stay in the mono-bromination stage. The process conditions of bromination reaction were studied. Experimental operation N,N-dimethylacetamide and 40% hydrobromic acid solution were added to the reaction flask, and the mixture was stirred. Bromine was added dropwise at room temperature, and the mixture was further stirred and filtered to obtain a solid bis (dimethylacetamido) trihydrogen bromide. A predetermined amount of BIS (dimethylacetamido) hydrogen tribromide, benzene trifluoride and 60ml of methanol were added to a 250ml three-necked flask equipped with a thermometer and a condenser tube, and the mixture was stirred and reacted at room temperature for 2 hours. The residue was dissolved by adding chloroform, washed with water, and the organic layer was dried overnight by adding anhydrous sodium sulfate. The solvent was removed under reduced pressure and purified by silica gel column chromatography to obtain 2, 5-dibromotrifluorobenzene. |