The mechanism of the ene reaction of singlet oxygen with olefins

MCSCF study of singlet oxygen addition to ethenol?a model of photooxidation reactions of unsaturated and aromatic compounds bearing hydroxy groups

“…attached to the carbon᎐carbon double C C bond. 1,13,14 Some of the oxygen-addition reactions are schematically depicted in Figure 1.…”

“…Based on the results of generalized valence bond Ž . GVB calculations, orbital-symmetry, and bondenergy analysis, as well as the regio-and stereoselectivity of the formation of dioxethanes and allylic peroxides, Harding and Goddard 14 concluded that the reaction most probably proceeds through the peralcoxyl intermediate; they predicted its character to be largely biradicaloid in the gas phase or weakly polar solvents, and gradually more zwitterionic with increasing the polarity of the solvent. Ž .…”

“…However, their calculations were carried out with a closed-shell scheme and, therefore, the conclusions are valid only as long as the intermediates in the reaction can be considered single-configuration states; this may be incorrect in view of the results of the multiconfigurational studies of Tonachini et al 22 and preceding workers. 14,18 In the aforementioned study, 14 Harding and Goddard suggested that allylic hydroperoxides can be formed from the 1,4-biradical intermediates by hydrogen-atom transfer from the neighboring carbon to the attached oxygen molecule Ž . Fig.…”

Repeatable and adjustable on-demand sciatic nerve block with phototriggerable liposomes

“…In particular, irradiation of photosensitizers within liposomes can produce singlet oxygen, which will cause peroxidation of unsaturated lipids (21). The formation of a new α-bond and a 1,5 hydrogen shift (22) will render the lipid hydrophilic, destabilizing the hydrophobic interactions that maintain liposome integrity (23,24) and allowing the release of encapsulated drugs. For example, irradiation with visible light of photosensitizerloaded liposomes containing unsaturated egg phosphocholine (EggPC) lipids induced the release of an encapsulated dye (25,26).…”

Reactions of singlet oxygen with enol esters

“…Some experiments have been interpreted in favor of a concerted reaction, 2 while others are believed to support a stepwise processes involving perepoxide, 3 * zwitterion,4 biradical, 5 or reversibly formed exciplex 6 intermediates. To some extent, these differences of opinion may reflect the diversity of the olefinic systems studied.…”