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.

Remote Friedel-Crafts Reaction with α-Heteroaryl-Substituted Cyclic Ketones via HOMO Activation of Lewis Bases.

Under the catalysis of Lewis bases, cyclic enones bearing an α-(2-furyl) motif can undergo remote Friedel-Crafts reaction with electrophilic reagents via a HOMO-activation strategy, proceeding in a formal vinylogous Rauhut-Currier or Morita-Baylis-Hillman-type reaction pattern. Moreover, even less reactive α-(2-benzofuranyl)-substituted cyclopeten-2-ones can be similarly HOMO-raised and furnish [4 + 2] products with alkylidenemalononitriles in a cascade Friedel-Crafts/Michael addition process.