Thioesters of the formula RCOSR are produced from a mercaptan of the formula RSH wherein R is a benzylic, aromatic or aliphatic moiety by reacting the mercaptan with carbon monoxide in the presence of a polyunsaturated olefinic hydrocarbon and as catalyst a metal component selected from iron, cobalt, nickel, molybdenum, ruthenium, rhodium and iridium, the metal component being in free or combined form.
