Stereochemistry of Epoxidation of Some Caryophyllenols

Epoxidation of the caryophyllene allylic alcohols 3−5 by tert-butyl hydroperoxide/vanadyl acetylacetonate afforded the epoxides 6a, 7, and 8, respectively. The tetracyanoethylene-catalyzed solvolysis shed some light on the stereochemistry of epoxidation. Formation of trans epoxides by syn epoxidation is a consequence of the conformational flexibility of the nine-membered ring, which places the alcohol at C-5 close to the α-face of the endo-alkene in 4 and close to the β-face in 3 and 5.