Recent Progress in Asymmetric Ion‐Pairing Catalysis with Ammonium Salts

Abstract Quaternary ammonium salts play an important role in asymmetric catalysis. In this Minireview, how asymmetric ion‐pairing catalysis with ammonium ions has been utilized in organic synthesis is explained, particularly in the design of novel catalytic cycles. This includes the use of chiral ammonium‐based catalysts for the construction of challenging stereogenic centers. Ammonium‐derived electrophilic reagents, typically formed in situ and in the context of phase‐transfer catalysis (PTC), have also been utilized in asymmetric bond‐forming reactions. Furthermore, ammonium salts have been employed as substrates in several stereocontrolled C−N bond cleavage processes, leading to enantioenriched products by using novel asymmetric induction modes. In addition, merging ammonium ion‐pairing catalysis with other catalytic approaches has also emerged as a new platform for achieving previously less straightforward reactions, thereby allowing new synthetic applications.