N-Heterocyclic Carbene-Mediated Oxidative Esterification of Aldehydes: Ester Formation and Mechanistic Studies

An unexpected N-heterocyclic carbene-catalyzed esterification of α,β-unsaturated aldehydes including aromatic aldeHydes with reactive cinnamyl bromides in the presence of air oxygen or MnO(2) as an oxidant is described.

Abstract

An unexpected N-heterocyclic carbene-catalyzed esterification of α,β-unsaturated aldehydes including aromatic aldehydes with reactive cinnamyl bromides in the presence of air oxygen or MnO(2) as an oxidant is described. In the presence of oxygen, halogenated and electron-deficient aldehydes react smoothly to furnish esters in good yields. Great efforts have been made on mechanistic studies to deduce a plausible mechanism, based on the experimental results and isotopic labeling experiment.