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.