In the presence of a catalytic amount of Lewis acid, various carboxylic esters or S-phenyl carbothioates are prepared in excellent yields by the respective reactions of equimolar amounts of silyl carboxylates and alkyl silyl ethers or phenyl silyl sulfides with 4-trifluoromethylbenzoic anhydride.
Intermolecular reaction of an organo-radical with thioester gives the sulphide, which is formed by the sulphur centred substitution of acyl groups with a nucleophilic organo-radical, but no displacement of S-alkyl groups with the organo-radical takes place.