Ionic `Diels-Alder' reactions of hexa-3,5-dienyl trimethylsilyl ether and enones: X-ray structural determination of adduct stereostructure, and a stereoselective approach to trans-fused octalin systems

The trimethylsilyl (TMS) and tert-butyldimethylsilyl (TBDMS) ethers of hexa-3,5-dien-1-ol react with cyclohexenones and an acyclic enone, methyl vinyl ketone (MVK), in the presence of 5-10 mol\% of Me(3)SiOSO(2)CF(3) (TMSOTf) in MeCN to provide trans-fused adducts arising via ionic (Gassman-type) Diels-Alder reactions; structural confirmation for adduct stereochemistry for this type of reaction is provided by an X-ray structural determination