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 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)