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

Abstract

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 Me₃SiOSO₂CF₃(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.