Selective fluorination of substituted trichloromethyl benzenes by HF in liquid phase Preparation of fluorinated building blocks

The selective fluorination by successive Cl/F exchanges of alpha alpha alpha-trichlorotoluene substituted or not by a chlorine atom was studied in the presence of HF as the fluorin long agent The influence of the presence of a catalyst or a basic solvent (such as dioxane pyridine tributylphosphate) in order to control the fluorination was also investigated In mild conditions (50 C and after 1 h of reaction) HF in excess was required in order to obtained the trifluoromethylation by Cl/F exchanges The presence of SbCl5 in small amount activated the Cl/F exchanges and only a stoichiometric amount of HF was required whatever the chlorinated molecules Selective mono and difluorination could be obtained by using basic solvents (C) 2010 Elsevier B V All rights reserved