Osmium-Catalyzed Dihydroxylation of Olefins in Acidic Media: Old Process, New Tricks

A screen of over 500 diversely functionalized additives in osmium-catalyzed dihydroxylation has uncovered that electron-deficient olefins are converted into the corresponding diols much more efficiently when the pH of the reaction medium is maintained on the acidic side. Further studies have identified citric acid as the additive of choice, for it allows preparation of very pure diols in yields generally exceeding 90%. As described here, a much wider range of olefin classes can now be successfully dihydroxylated. The process is experimentally simple, in most cases involving little more than dissolving the reactants in water or a water/tert-butyl alcohol mixture, stirring them, and filtering off the pure diol product.