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. Both supramolecular host and L-proline are required for the reaction to occur, implying that encapsulation of the substrates and co-catalyst are necessary for the reaction to occur. We explore the substrate scope for a variety of E-cinnamaldehydes and dienes. Finally, we probe the supramolecular assembly processes responsible for the observed catalysis using NMR spectroscopic methods.