Oxidation of Sulfides with a Silica-Supported Peracid in Supercritical Carbon Dioxide under Flow Conditions: Tuning Chemoselectivity with Pressure

Supercritical carbon dioxide is a convenient medium for performing the selective oxidation of sulfides 1 to either sulfoxides 2 or sulfones 3 with [2‐percarboxyethyl]‐functionalized silica (4) under flow conditions. The chemoselectivity of the reaction, which results from the different diffusion rates of sulfide and sulfoxide over the reagent bed, can be controlled by adjusting the pressure and the hydration of the silica surface as both the solvating power of the mobile phase and the surface activity of the stationary phase determine the migration rates of sulfide 1 and sulfoxide 2 over the supported peroxide. The results elucidate the impact of surface phenomena on the course of chemical reactions carried out under flow conditions. The oxidation of sulfides 1 with hydrated [2‐percarboxyethyl]‐functionalized silica (4) in scCO2 under flow conditions can be tuned to give either sulfoxides 2 or sulfones 3 by adjusting the pressure.