Tungsten-catalyzed continuous-flow oxidation of sulfides to sulfones with hydrogen peroxide.

Continuous-flow oxidation of sulfides to sulfones was achieved with hydrogen peroxide (H2O2) using a catalyst column, which was simply packed with a mixture of oxodiperoxotungstate-2,2'-bipyridine and commercially available activated carbon. Sulfones were continuously produced in more than 90% yield for up to 160 h by passing an acetonitrile solution of sulfides and H2O2 through the catalyst column. Activated carbon played a key role in immobilizing the tungsten catalyst while the other supports, Celite or silica gel did not have such an ability to catch the catalyst. Selective oxidation to sulfone took place under continuous-flow conditions even though the sulfide substrates contained other oxidizable functional groups, such as olefinic double bond, hydroxy, pyridyl and amino functional groups.