Organocatalytic sulfoxidation

Davidson, Stuart C. and dos Passos Gomes, Gabriel and Kuhn, Leah R. and Alabugin, Igor V. and Kennedy, Alan and Tomkinson, Nick C.O. (2021) Organocatalytic sulfoxidation. Tetrahedron, 78. 131784. ISSN 0040-4020 (https://doi.org/10.1016/j.tet.2020.131784)

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Abstract

Treatment of a sulfide with a catalytic amount of a 1,3 diketone in the presence of silica sulfuric acid as a co-catalyst and hydrogen peroxide (50% aq) as the stoichiometric oxidant leads to the corresponding sulfoxide product. The reaction is effective for diaryl, aryl-alkyl and dialkyl sulfides and is tolerant of oxidisable and acid sensitive functional groups. Investigations have shown that the tris-peroxide 2, formed on reaction of pentane-2,4-dione with hydrogen peroxide under acidic reaction conditions, can oxidise two equivalents of sulfide using the exocyclic peroxide groups whereas the endocyclic peroxide remains intact. Calculations provide a mechanism consistent with experimental observations and suggest the reaction proceeds via an initial acid catalysed ring opening of a protonated tris-peroxide prior to oxygen transfer to a sulfur nucleophile.