Regioselectivity Umpolung in Asymmetric Diels-Alder Reaction of ortho-Formyl-Substituted Cinnamates and Dienals via Double Aminocatalysis.

The cinnamates having an ortho-formyl group can potentially form vinylogous iminium ion species under the catalysis of chiral amines, which facilitates the Diels-Alder cycloaddition reaction with the concurrently generated trienamines between dienals and amine catalysts in a regioselectivity umpolung manner. A cascade intramolecular aldol reaction was followed, finally furnishing polyhydrophenanthrene frameworks with excellent diastereo- and enantioselectivity.