Photochemical Reactions 127th CommunicationPhotochemistry of Epoxy-enones: Intramolecular Trapping of a Carbonyl Ylide

On ¹n, π* -excitation 5, 6-epoxy-2-hydroxy-5, 6-dihydro-β-ionone ((E)-4) shows the typical behaviour of a, β-unsaturated γ, δ-epoxy ketones undergoing primarily C(γ), O-cleavage of the oxiran. However, ¹π, π*-excitation of (E)? 4 leads to enol ether 10 which is formed by intramolecular insertion of the hydroxyl group of the ylide c .