N-Heterocyclic carbene-catalyzed cyclotetramerization of acrylates.

N-Heterocyclic carbenes (NHCs) were found to catalyze the unprecedented cyclotetramerization of acrylates, producing the trisubstituted cyclopentenones in moderate yields. The proton or deuterium adducts of the deoxy-Breslow intermediate derived from NHC and two molecules of methyl acrylate were obtained. A reaction mechanism involving the new umpolung/cyclization sequence is proposed.