The sulfur-containing esters can be divided into two classes; one in which the sulfur atom belongs
to the organic acid, such as CH3SCH2CH2COOCH3, and the other in which the sulfur atom is from an
alcohol or mercaptan (AOM), such as CH3COOCH2CH2SCH3 or CH3COSCH2CH2CH3. The first
sulfur-containing ester class can be synthesized by the thia-Michael addition reaction, which is facile
and efficient [1-3]. The second ester class can be synthesized by several methods. One method is the
preparation of the ester from AOM and an organic acid in the presence of a catalyst, which can be
basic, like triethylamine [4] or acidic [5,6] like solid superacids or p-toluenesulfonic acid. A second
method is treatment of AOM with an anhydride yielding the corresponding ester [6-9]; mercaptans can
be used directly as the starting reagent or can be obtained by reducing an alkyl disulfide with tributyl
phophine [9]. A third method is the preparation of the esters by reaction of an acyl chloride with AOM
[10-15]; however, the hydrogen chloride side product must sometimes be eliminated by pyridine
addition. The fourth method is the synthesis of esters by reaction of a haloalkane with the salt of a thioorganic
acid in THF [16]; these starting materials are not readily available, so this method is mainly
used in the synthesis of esters from thioacetic acid.