Stereo- and Regiospecific Syntheses of α- and β-Substituted Vinyl and Dienyl Triflones via the Stille Reaction¹

Acetylenic anions undergo efficient sulfonylation with trifluoromethanesulfonic anhydride to provide acetylenic triflones. These materials are stereospecifically converted to (Z)-β-iodovinyl triflones in one step via the addition of hydrogen iodide. Access to (Z)-α-iodovinyl triflones is also possible via a two-step process involving tributyltin hydride addition to the acetylenic triflones to generate (Z)-α-(tributylstannyl)vinyl triflones followed by an iododestannylation reaction. Both classes of iodovinyl triflones smoothly undergo palladium (0)-mediated Stille reactions with vinyl, aryl, heteroaryl, and acetylenic stannanes to stereospecifically provide trisubstituted vinyl and dienyl triflones.