N-Heterocyclic Carbene-Catalyzed Oxidations.
N-Heterocyclic 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, including protected carboxylates. The oxidation proceeds under mild conditions, with low loadings of a simple 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.
Maki
Brooks E
BE
Department of Chemistry, Northwestern University, 2145 Sheridan Rd., Evanston, Illinois, 60208.
Chan
Audrey
A
Phillips
Eric M
EM
Scheidt
Karl A
KA