Back, Thomas GeorgeSands, Kai NMendoza Rengifo, EmeritaGeorge, Graham NPickering, Ingrid JGelfand, Benjamin S2020-01-022020-01-022019-12-24http://hdl.handle.net/1880/111401https://doi.org/10.11575/PRISM/46092Benzeneperoxyseleninic acid has been proposed as the key intermediate in the widely used epoxidation of alkenes with benzeneseleninic acid and hydrogen peroxide. However, it reacts sluggishly with cyclooctene and instead rapidly decomposes in solution to a mixed selenonium-selenonate salt that was identified by x-ray absorption, 77 Se NMR spectroscopy, and by single crystal x-ray diffraction. This process includes a selenoxide elimination of the peroxyseleninic acid with liberation of oxygen and additional redox steps. The salt is relatively stable in the solid state, but generates the corresponding selenonic acid in the presence of hydrogen peroxide. The selenonic acid is inert towards cyclooctene on its own; however, rapid epoxidation occurs when hydrogen peroxide is added. This shows that the selenonic acid must first be activated through further oxidation, presumably to the heretofore unknown benzeneperoxyselenonic acid. The latter is the principal oxidant in this epoxidation.engUnless otherwise indicated, this material is protected by copyright and has been made available with authorization from the copyright owner. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.benzeneperoxyseleninic acidbenzeneperoxyselenonic acidepoxidationoxidationperoxidesjournal articlehttp://dx.doi.org/10.1002/anie.201913566