Iminium Catalysis inside a Self-Assembled Supramolecular Capsule: Modulation of Enantiomeric Excess

The noncovalent combination of a supramolecular host with iminium organocatalysis is described. Due to cation–π interactions the reactive iminium species is held inside the host and reacts in this confined environment. The products formed differ up to 92 % ee from the control experiments without added host. A model rationalizing the observed difference is presented. An accommodating host: The iminium‐catalyzed 1,4‐reduction of unsaturated aldehydes can be performed inside a supramolecular host. Only catalytic amounts of the supramolecular capsule are required. The intermolecular, noncovalent interactions inside the host system dramatically improve enantioselectivity for several amine catalysts.