Organocatalytic Enantioselective Cross-Vinylogous Rauhut-Currier Reaction of Methyl Coumalate with Enals.

The organocatalytic enantioselective intermolecular cross-vinylogous Rauhut-Currier (RC) reaction of methyl coumalate with α,β-unsaturated aldehydes is reported, and the enals are activated by iminium catalysis to serve as the Michael acceptors and methyl coumalate is used as an activated diene to generate a latent enolate. The excellent selectivity is driven by the aromaticity of methyl coumalate, and the post transformation of this heterocyclic structure into other electron-deficient arenes and heterocycles have addressed, in part, the challenging selectivity issues of the intermolecular cross-RC reactions and the limited scope of iminium catalysis.