Stereoselective Synthesis of Atropisomeric Acridinium Salts by the Catalyst‐Controlled Cyclization of <i>ortho</i> ‐Quinone Methide Iminiums

Quinone methides are fundamental intermediates for a wide range of reactions in which catalyst stereocontrol is often achieved by hydrogen bonding. Herein, we describe the feasibility an intramolecular Friedel–Crafts 6π electrocyclization through ortho-quinone methide iminiums stereocontrolled contact ion pair. A disulfonimide activates racemic trichloroacetimidate substrates and imparts cyclization step, providing new avenue selective iminium functionalization. highly stereospecific oxidation readily transforms enantioenriched acridanes into rotationally restricted acridiniums. Upon exchange, method selectively affords atropisomeric acridinium tetrafluoroborate salts high yields enantioenrichment up to 93 : 7 e.r. We envision that ion-pairing catalysis over enables synthesis diversity heterocycles aniline derivatives with distinct stereogenic units.