Electrophilic ene-type reactions of phenyl vinyl sulfoxide with alkenes
Abstract
Phenyl vinyl sulfoxide 1 can be made to react as an α,β-dicarbocation with alkenes by formation of one, or two new C–C bonds. These reactions take place at or below room temperature, under the conditions of the Pummerer reaction, i.e. trifluoroacetic acid and its anhydride. The key step is an electrophilic ene-type reaction between a thionium ion and the alkene. The primary β-trifluoroacetoxy sulfides thus formed then undergo rearrangement via an episulfonium ion to the more stable, secondary isomer.