Sulfur dioxide-mediated syntheses of polyfunctional alkenes and (E,Z)- and (E,E)-2,4-dien-1-ones

Efficient methods for the stereoselective synthesis of polyfunctional (E)- and (2)-alkenes and conjugated (EE)- and (E,2)-dienones are presented. They rely upon one-pot, four-component processes that condense 1-oxy-1,3-dienes, silyl enol ethers, SO2, and carbon electrophiles.