Organocatalytic Tail-to-Tail Dimerization of Olefin: Umpolung of Methyl Methacrylate Mediated by N-Heterocyclic Carbene

Highly selective tail-to-tall dimerization of methyl methacrylate has been realized by an N-heterocyclic carbene catalyst, giving dimethyl 2,5-dimethyl-2-hexenedioate with an E/Z ratio of 95:5 in 86% isolated yield. The umpolung mechanism Is proposed on the basis of Interception of the intermediates using ESI-MS analyses and deuterium-labeling experiments.