N-Heterocyclic carbene-catalyzed oxidations

N-Hererocyclic carbenes catalyze the oxidation of allylic and benzylic alcohols as well as saturated aldehydes to esters with manganese(IV) oxide in excellent yields. A variety of esters can be synthesized,, protected carboxylates. The oxidation proceeds Under mild conditions, with low loadings of including a simple triazolium salt pre-catalyst in the presence of base. Substrates containing potentially epimerizable triazolium salt pre-catalyst in the presence of base. Substrates containing potentially epimerizable centers are oxidized while preserving stereochemical integrity. The acyl triazolium intermediate generated under catalytic conditions can be employed as a chiral acylating agent in the desymmetrization of meso-diols.