Stereoselective synthesis of (E)-alpha,beta-unsaturated esters via carbene-catalyzed redox esterification.

[reaction: see text] Stereoselective, carbene-mediated redox esterification of alkynyl aldehydes provides mild and atom economical access to (E)-configurated, alpha,beta-unsaturated carboxylic esters. The organocatalytic method relies on the generation of activated carboxylates via extended/conjugated umpolung in the presence of catalytic amounts of carbene precursor and base.