Epoxidation of allylic amidocycloalkenes of five to seven membered rings consistently showed qualified syn-stereoselectivity. However, the cis-selectivity of homoallylic amido cyclopentene was related to the specific amido group. Epoxidation of 4-acetamidocyclopentene furnished good diastereoselectivity comparable to that of allylic ones. But 4-benzamidocyclopentene was epoxidized to obtain a relatively poor cis-selectivity. As to the homoallylic cyclohexene series, epoxidation of 4-acetamidocyclohexene afforded the corresponding cis-epoxide, whereas 4-benzamidocyclohexene gave, besides the cis-epoxide, an unexpected product: exo-2-oxa-3-phenyl-4-azabicyclo[3.3.1]non-3-en-8-ol that might be formed from an intramolecular cyclization of the virtual trans-epoxide. The quantum calculations and the results of the epoxidation of the derivatives supported this mechanism. The highly cis-stereoselective epoxidation of the ami-docycloalkenes could be used to the synthesis of the stereodefined analogues.

Key words: diastereoselectivity, epoxidation, intramolecular cyclization