An improved process for the trimethylsilylation of organic compounds with at least one active hydrogen atom with hexamethyldisilazane, the improvement comprising effecting the reaction in the presence of 0.001 to 10 mole percent of a catalyst of the formula X--NH--Y I wherein X and Y are individually an electron-withdrawing group or when X is an electron-withdrawing group, Y is selected from the group consisting of hydrogen and trialkylsilyl of 1 to 6 carbon atoms or X and Y together with the nitrogen atom to which they are attached form a cyclic electron-withdrawing group and novel trimethylsilylated thiols of the formula ##STR1## wherein R is a 5-or 6-membered heterocycle having at least one nitrogen or sulfur heteroatom and optionally substituted with at least one member of the group consisting of alkyl of 1 to 6 carbon atoms, phenyl, trimethylsilyl, trimethylsilyloxycarbonylmethyl and alkylamino of 1 to 6 carbon atoms, and novel trimethylsilylated 3'-substituted cephalosporanic acid derivatives.
A novel process for the preparation of thioethers comprising reacting a silylated thiol of the formula R--S--SiR.sub.1 R.sub.2 R.sub.3 I wherein R is an organic group and R.sub.1, R.sub.2 and R.sub.3 are individually selected from the group consisting of alkyl of 1 to 4 carbon atoms with an organic halide, sulfate or sulfonate in the presence of hexamethylphosphoric triamide as a solvent or co-solvent preferably under neutral conditions in aprotic solvents at a temperature between 0.degree. and 150.degree. C.