Theoretical study on the reactivity and regioselectivity of the ene reaction of 1Δg O2 with α,β-unsaturated carbonyl compounds

The ene reaction of singlet dioxygen with α,β-unsaturated carbonyl compounds gives unsaturated hydroperoxides and displays interesting features: different reactivities of the s-cis and s-trans reactants and a marked regioselectivity, influenced to some extent by solvent polarity. All of these traits are accounted for by a polar diradical mechanism. A perepoxide intermediate is not a critical point on the reaction's potential energy surface. Also, a trioxene intermediate is located too high in energy to be significantly populated. An alternative pathway leading to dioxetane is not as effective as the ene pathway giving the hydroperoxide.