Intramolecular epoxidation in unsaturated ketones and oxaziridines

Abstract

The possibility of intramolecular epoxidation in acyclic unsaturated ketones (via dioxiranes) and oxaziridines (via oxaziridinium species) has been investigated. Treatment of several acyclic unsaturated ketones with Oxone^® led to low levels of regio- and stereocontrol, suggesting that background epoxidation by Oxone^® dominates. However, treatment of unsaturated oxaziridines with methyl trifluoromethanesulfonate led to intramolecular epoxidation. This process allowed regioselective epoxidation of a non-conjugated diene. It also proceeded with a high degree of stereocontrol consistent with a stereoelectronic preference for a spiro-transition state.