Catalytic fluorination of dichloromethylbenzene by HF in liquid phase. Preparation of fluorinated building blocks

The selective fluorination by successive Cl/F exchanges of the dichloromethylbenzene, was studied in the presence of HF as the fluorinating agent. The influence of the presence of a catalyst or a basic solvent (such as dioxane, pyridine, tributylphosphate) in order to favour the fluorination was investigated. In mild conditions, (50 °C and after 1 h of reaction), the fluorination of the dichloromethylbenzene was observed and the polymerization reaction inhibited. The best results were obtained in the presence of the HF-dioxane system and antimony trifluoride as catalyst.