Generation of β-Halo Vinylsulfones through a Multicomponent Reaction with Insertion of Sulfur Dioxide

A four-component reaction of terminal alkynes, aryldiazonium tetrafluoroborates, sulfur dioxide surrogate of DABCO center dot(SO2)(2), and potassium halide in the presence of copper(I) chloride (10 mol %) gives rise to beta-halo vinylsulfones with good stereoselectivity. The vicinal difunctionalization of alkynes through sulfonylation and halogenation with the insertion of sulfur dioxide works efficiently. A plausible mechanism is proposed, which includes a radical process.