Theoretical Study on the Reactivity and Regioselectivity of the Ene Reaction of1Δg O2 with α,β-Unsaturated Carbonyl Compounds

The ene reaction of singlet oxygen 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. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)