“Ene” Reactions of Singlet Oxygen at the Air–Water Interface

• Published in: Journal of organic chemistry Vol. 81; no. 15; pp. 6395 - 6401
• Main Authors: Malek, Belaid, Fang, William, Abramova, Inna, Walalawela, Niluksha, Ghogare, Ashwini A., Greer, Alexander
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 05.08.2016; Amer Chemical Soc
• Subjects: Chemistry; Chemistry, Organic; Physical Sciences; Science & Technology; MICELLAR SYSTEMS; ORGANIC-SYNTHESIS; ALUMINUM; GEMINAL SELECTIVITY; CHEMISTRY; PHOTOCHEMISTRY; PHOTOOXYGENATIONS; SOLVENT; MOLECULAR-OXYGEN; PHOTOOXIDATION
• ISSN: 0022-3263; 1520-6904
• DOI: 10.1021/acs.joc.6b01030

Prenylsurfactants [(CH3)2CCH­(CH2) n SO3 – Na+ (n = 4, 6, or 8)] were designed to probe the “ene” reaction mechanism of singlet oxygen at the air–water interface. Increasing the number of carbon atoms in the hydrophobic chain caused an increase in the regioselectivity for a secondary rather than tertiary surfactant hydroperoxide, arguing for an orthogonal alkene on water. The use of water, deuterium oxide, and H2O/D2O mixtures helped to distinguish mechanistic alternatives to homogeneous solution conditions that include dewetting of the π bond and an unsymmetrical perepoxide transition state in the hydroperoxide-forming step. The prenylsurfactants and a photoreactor technique allowed a certain degree of interfacial control of the hydroperoxidation reaction on a liquid support, where the oxidant (airborne 1O2) is delivered as a gas.