Nucleophilic carbene-catalyzed redox-esterification reaction of α-halo-α,β-unsaturated aldehyde

A nucleophilic carbene catalyzed redox esterification between α-halo-α,β-unsaturated aldehydes and various alcohols has been developed. Interestingly, the reaction provided α,β-unsaturated esters instead of the saturated α-halo substituted esters as the only product in good to high yield with excellent trans-selectivity, presumably via the umpolung-halo-elimination pathway.

N-Heterocyclic carbenes can catalyze redox esterification of α-halo-α,β-unsaturated aldehydes with various alcohols to provide α,β-unsaturated esters in high yield with excellent trans-stereoselectivity.