Polyether Natural Product Inspired Cascade Cyclizations: Autocatalysis on π‐Acidic Aromatic Surfaces

Abstract

Anion‐π catalysis functions by stabilizing anionic transition states on aromatic π surfaces, thus providing a new approach to molecular transformation. The delocalized nature of anion–π interactions suggests that they serve best in stabilizing long‐distance charge displacements. Aiming therefore for an anionic cascade reaction that is as charismatic as the steroid cyclization is for conventional cation‐π biocatalysis, reported here is the anion‐π‐catalyzed epoxide‐opening ether cyclizations of oligomers. Only on π‐acidic aromatic surfaces having a positive quadrupole moment, such as hexafluorobenzene to naphthalenediimides, do these polyether cascade cyclizations proceed with exceptionally high autocatalysis (rate enhancements kauto/kcat >104 m−1). This distinctive characteristic adds complexity to reaction mechanisms (Goldilocks‐type substrate concentration dependence, entropy‐centered substrate destabilization) and opens intriguing perspectives for future developments.

A Water‐ and Base‐Stable Iminopyridine‐Based Cage That Can Bind Larger Organic Anions

“…Only a few examples of catalysis of reactions with anionic transition states in supramolecular cages are known [50–56] . Additionally, Matile and co‐workers have demonstrated the application of anion‐π interactions in the context of catalysis using aromatic naphthalenediimide (NDI) moieties in open, non‐capsular systems [57–60] . Although supramolecular cages bearing such NDI structures have been reported, [61–65] anion‐π catalysis has not yet been investigated within them to our knowledge.…”