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⋅(SO2 )2 , and potassium halide in the presence of copper(I) chloride (10 mol %) gives rise to β-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.