Catalytic Enantioselective Cycloaddition Transformation of Tricyclic Arenes Enabled by a Dual-Role Chiral Cage-Reactor

An enzyme mimic catalytic system was established by employing a chiral metal–organic cage as the supramolecular reactor, and asymmetric dearomative Diels–Alder (D–A) cycloaddition with polyaromatic rings as diene precursors was realized with up to 96% enantiomeric excess (ee). The high positive-charges (+28) on the cage sphere induced partial deprotonation of 24 imidazole-NH amine units to result in microheterogeneity of the cage solution with outer-cage environment turned acidic while the cage-confined inner-spaces turned basic, which enabled facile conversion of both acid-favored anthracene and base-favored 9-anthrone derivatives into value-added chiral tricyclic [4 + 2] cycloadducts under mild conditions. The stereochemical outcome of the transformation was dictated by the adequate host–guest interactions, of which the noncovalent π–π stacking and electrostatic interactions act as the dominant control forces. This dual-role catalytic system with amphoteric properties provides an unconventional platform for the asymmetric D–A reactions of polyaromatic compounds, showing the promise of the cage-reactor for supramolecular catalysis in multitasking organic transformations.