Synthesis conditions and activity of various Lewis acids for the fluorination of trichloromethoxy-benzene by HF in liquid phase

Abstract

The experimental conditions (temperature, reaction time, amount of hydrogen fluoride (HF)) for the comparison of the performances of various Lewis acids in the liquid phase fluorination by HF of the trichloromethoxy-benzene were determined by using SbCl 5 as the reference catalyst. After 1 h reaction at 50 °C, C 6H 5OCCl 3 was totally converted into C 6H 5OCF 3 requiring only 2 mol% of SbCl 5 and a stoichiometric amount of HF. The most efficient catalysts were found to be chlorinated Lewis acids in which the metal is at the state of oxidation +V (SbCl 5, MoCl 5, TaCl 5 and NbCl 5). The appropriate catalyst has to be able to form a nucleophilic complex with HF, which constitutes the actual fluorinating agent and is more efficient than HF alone.