Origin of the oxygen atom in metalloporphyrin-catalyzed epoxidations with LiOCl as oxidant |
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| Affiliation: | 1. Department of Chemical Sciences University of Padova and Institute on Membrane Technology, Unit of Padova, via F. Marzolo 1, Padova, 35131, Italy;2. Institut Lavoisier de Versailles, UMR 8180, Université Paris-Saclay, Université de Versailles Saint-Quentin en Yvelines, 45 Avenue des Etats-Unis Versailles cedex, 78035, France;3. Department of Chemical and Pharmaceutical Sciences, University of Ferrara, Via Fossato di Mortara 17-19, Ferrara, 44121, Italy;1. Department of Studies in Chemistry, University of Mysore, Mysuru, Karnataka, 570006, India;2. Department of Chemistry, Sri Jayachamarajendra College of Engineering, Mysuru, Karnataka, 570006, India;1. Laboratório de Bioinorgânica e Catálise, Departamento de Química – Centro Politécnico, Curitiba – PR, Universidade Federal do Paraná (UFPR), Brazil;2. Centro de Estudos do Mar, Pontal do Paraná - PR, Universidade Federal do Paraná (UFPR), Brazil;3. Universidade Federal de Minas Gerais, Departamento de Química, Belo Horizonte - MG, Brazil;1. School of Chemistry and Chemical Engineering, Central South University, Changsha, 410083 China;2. Key Laboratory of Hunan Province for Metallurgy and Material Processing of Rare Metals, Changsha, 410083, China;3. College of Resources and Environment, Hunan Agricultural University, Changsha, 410128, China;4. Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, UK |
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| Abstract: | Abstract – The origin of the oxygen atom incorporated into epoxides during the oxidation of olefins with the catalytic system Mn(TPP)Cl/LiOCl in the presence of 18O-labelled water has been investigated. One molar equivalent of H218O with respect to Li16OCl led to a 53 % 18O-incorporation within the epoxide formed, and near complete incorporation of 18O from water was achieved when no limiting amount of water was used. These results clearly indicate that the epoxidic oxygen atom arose from the high-valent metal-oxo species generated by LiOCl, but the exchange of the oxygen atom of hypochlorite with bulk water is fast, compared to the oxidation of the manganese(III) porphyrin by LiOCl. Therefore hypochlorite is not a suitable oxidant for mechanistic studies of metal-catalyzed oxygenation reactions involving high-valent metal-oxo species. Potassium monopersulfate is the adequate oxidant for such studies, because of its slow oxygen atom exchange with bulk water. |
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