Cobalt-Catalyzed Thiolative Lactonization of Alkynes with Double CO Incorporation

When the Co-2(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 alpha,beta-unsaturated gamma-thio-gamma-lactones with excellent regioselectivity.