SYNTHETIC APPLICATION OF LITHIATED TRIS(METHYLTHIO)METHANE - PREPARATION OF ALIPHATIC METHYL THIOLCARBOXYLATES FROM THE CORRESPONDING HALIDES - CONVENIENT SYNTHESIS OF TRIS(METHYLTHIO)METHANE

A thorough study directed towards the synthesis of methyl thiolcarboxylates was made on the basis of the following steps: (i) conversion of alkyl halides into the corresponding trimethyl trithioortho-carboxylates by using tris(methylthio) methyllithium in THF at -78-degrees-C; (ii) selective hydrolysis of the intermediates to methyl thiolcarboxylates by using 35% aq. HBF4 in DMSO or, in some cases, in THF. The overall yields of the two stages are, usually, between 70 and 88%. By this procedure it is also possible to incorporate O-18 in the carbonyl group of thiol esters (approximately 98% isotopic purity). Furthermore, a new, convenient method for the preparation of tris(methylthio)methane as the precursor of tris(methylthio)methyllithium was developed.