Stereoselective synthesis of 6-oxabicyclo[3.2.1]octene via (3,5)-oxonium-ene reaction

Oxabicyclo[3.2.1]octene can efficiently be synthesized by the reaction of (−)-terpinen-4-ol and aldehyde or epoxide catalyzed by indium triflate (In(OTf)3) in good yields. The reaction is stereoselective and proceeds via (3,5)-oxonium-ene-type reaction.