Combining Iminium and Supramolecular Catalysis for the [4 + 2] Cycloaddition of E-Cinnamaldehydes

Herein we describe a method for combining supramolecular catalysis with imininum-based organocatalysis in the Diels–Alder cycloaddition reaction. Notably, both cage and L-proline are required for the reaction to occur, implying that encap-sulation of the substrates and co-catalyst are necessary for the reaction to occur. We explore the substrate scope for a va-riety of E-cinnamaldehydes and dienes. Finally, we probe the supramolecular assembly processes responsible for the observed catalysis using NMR spectroscopic methods, determining that the reaction is negative order in the cinnamalde-hyde substrate and experiences product inhibition.