Examples of catalytic and selective routes for fluorinated building blocks

Article abstract of DOI:10.1021/op500182w

Examples are presented for the catalytic fluorination of chlorinated starting materials in order to produce building blocks or HFCs. The fluorination of CF₃CH₂Cl, of CCl₂=CCl₂, of trichloromethoxylbenzenes and trichloromethoxybenzene involving nucleophilic substitution are reported. In all cases, HF was the fluorinating agent. Depending on the chlorinated substrate and the degree of fluorination required, liquid- or gas-phase processes were involved. Usually, catalysts were SbCl ₅ in liquid phase and chromium oxide in gas phase. In the presence of SbCl₅, at 90 °C under an initial pressure of 10 bar, the fluorination of CCl₂=CCl₂ leads mainly to the formation of CClF₂CHCl₂, and the active catalyst is an antimony mixed halide (SbCl₃F₂). In the same way, the presence of SbCl₅ favored the formation of 1-trifluoromethyl-3- trichloromethylbenzene from bis-1,3-trichloromethylbenzene at low temperature (50 °C) and in the presence of a low amount of HF. Moreover, trichloromethoxybenzene was totally transformed into trifluoromethoxybenzene. At 380 °C and at atmospheric pressure, the transformation of CF ₃CH₂Cl into CF₃CH₂F was favored over chromium oxide-based catalyst modified by zinc (corresponding to a (Zn/Zn + Cr) molar ratio of 0.22).