Enantioselective N-heterocyclic carbene-catalyzed ß-hydroxylation of enals using nitroarenes: an atom transfer reaction that proceeds via single electron transfer.

ABSTRACT

A novel oxidative N-heterocyclic carbene-catalyzed reaction pathway has been discovered. Alkyl and aryl enals undergo ß-hydroxylation via oxygen atom transfer from electron-deficient nitrobenzenes, followed by trapping of the resultant acyl azolium by the solvent. The proposed mechanism involves a single electron transfer event to initiate the reaction followed by radical recombination. This represents a profound mechanistic departure from the established two-electron disconnects in NHC catalysis.