Cobalt-Catalyzed Thiolative Lactonization of Alkynes with Double CO Incorporation

When the Co₂(CO)₈-catalyzed reaction of alkynes with thiols is conducted under the pressure of carbon monoxide, a novel thiolative lactonization with simultaneous introduction of two carbon monoxide molecules into the carbon–carbon triple bonds takes place successfully to afford α,β-unsaturated γ-thio-γ-lactones with excellent regioselectivity.