Organocatalytic sulfoxidation

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