Thioester

Thioesters are compounds with the functional group C-S-CO-C. They are the product of esterification between a carboxylic acid and a thiol. Thioesters are widespread in biochemistry, the best-known derivative being acetyl-CoA.

Synthesis

Thioesters have been prepared in many ways, but the main route involves condensation of thiols and carboxylic acids in the presence of dehydrating agents:

A typical dehydration agent is DCC or related reagents.Acid anhydrides and some lactones also react with thiols in the presence of base.

Thioesters can be conveniently prepared from alcohols by the Mitsunobu reaction, using thioacetic acid.

They also arise via carbonylation of alkynes and alkenes in the presence of thiols.

Reactions

The carbonyl center in thioesters is reactive toward nucleophiles, the reactivity being reminiscent of, but milder than, acid chlorides. Thus, thioesters and amines combine to give amides:

A reaction unique to thioesters is the Fukuyama coupling, in which the thioester is coupled with an organozinc halide by a palladium catalyst to give a ketone.