Oxidation of sulfides to sulfones with hydrogen peroxide in the presence of acetic acid and Amberlyst 15

Abstract

The oxidation of thioanisole to its sulfone with hydrogen peroxide (H2O2) in the presence of acetic acid and Amberlyst 15 was investigated and found to be a simple and effective method. Oxidation experiments in the absence of acetic acid or Amberlyst 15 confirmed the essentiality of these components for the complete oxidation of thioanisole to its sulfone with H2O2. In the two-step oxidation process of sulfide, in the oxidation of sulfide to sulfoxide, H2O2 plays a major role, whereas in the oxidation of sulfoxide to sulfone, peracetic acid formed with H2O2 in the presence of acetic acid and Amberlyst 15 plays a major role. Sulfone formation increased with an increase in H2O2, temperature and Amberlyst 15 and decreased with acetic acid. However, with a very low amount of acetic acid, sulfone formation decreased due to water in H2O2 and released in the reaction. Reutilization of Amberlyst 15 for six cycles resulted in a 6.8 % decrease in sulfone yield and 3.4 % decrease in oxygenation. Dialkyl, dibenzyl, diphenyl, alkylaryl, arylbenzyl, alkylbenzyl sulfides are completely oxidized with this oxidation system to their corresponding sulfones. The reactivity of sulfides is in the order dialkyl > dibenzyl > diphenyl sulfides, which is in line with their order of nucleophilicity.