Asymmetric Organocatalyzed Cascade Reactions─Merging the -Halogen and Halogen Effect with Dienamine Catalysis

The combination of asymmetric organocatalysis with the ()-halogen effect enables the formation of chiral norcarane scaffolds in high yields and selectivities (up to 92% yield, >99% ee, and >95:5 d.r.). This was achieved by reacting ()-halogenated 3-vinyl chromones with generated chiral dienamines in an inverse electron demand [4 + 2] cycloaddition followed by an intramolecular S2 reaction. These scaffolds could easily undergo photoinduced rearrangements or lactonization to form intricate chiral ring structures.