The preparation of (Methylthio)- and (Methylseleno)-tri(alkyl or aryl)phosphonium salts and their reactions with carboxylic acids and alcohols

A series of (methylthio)- and (methylseleno)-triphenylphosphonium salts and the analogous tributylphosphonium salts have been prepared by methylation of the corresponding tertiary phosphine sulfides and selenides. Details of their 1H, 13C and 31P n.m.r. spectra are given. Whereas the (methylthio)- and (methylseleno)-triphenylphosphonium salts undergo rapid decomposition in the presence of tertiary ammonium carboxylates or tertiary amines, the (methy1thio)- and (methylseleno)-tributylphosphonium salts convert such carboxylates into methanethiol and methaneselenol esters in acceptable yields. A tris(dimethylamino)(methylthio)phosphonium salt, on the other hand, converts benzoate into methyl benzoate in quantitative yield. Inferior yields of (methy1thio)- and (methylseleno)-alkanes are obtained from two primary alcohols and the tributylphosphonium salts.