Anion‐(π)_n‐π Catalytic Micelles

Abstract

Anion‐π catalysis operates by stabilizing anionic transition states on π‐acidic aromatic surfaces. In anion‐(π)n‐π catalysis, π stacks add polarizability to strengthen interactions. In search of synthetic methods to extend π stacks beyond the limits of foldamers, the self‐assembly of micelles from amphiphilic naphthalenediimides (NDIs) is introduced. To interface substrates and catalysts, chargetransfer complexes with dialkoxynaphthalenes (DANs), a classic in supramolecular chemistry, are installed. In π‐stacked micelles, the rates of bioinspired ether cyclizations exceed rates on monomers in organic solvents by far. This is particularly impressive considering that anion‐π catalysis in water has been elusive so far. Increasing rates with increasing π acidity of the micelles evince operational anion‐(π)n‐π catalysis. At maximal π acidity, autocatalytic behavior emerges. Dependence on position and order in confined micellar space promises access to emergent properties. Anion‐(π)n‐π catalytic micelles in water thus expand supramolecular systems catalysis accessible with anion‐π interactions with an inspiring topic of general interest and great perspectives.

Anion–π catalysis on carbon allotropes

“…This result was consistent with pyrene as best interfacers for MWCNTs. For anion–π catalysis on NDI stacks, the reversed order was obtained, consistent with the preferred formation of DAN-NDI charge transfer complexes [ 8 , 100 – 106 ].…”

“…This suggested that induced rather than intrinsic anion-π interactions should provide access to really strong catalysts [3]. They have been predicted theoretically to occur on π-stacks [6], and confirmed recently to exist and apply to anion-π catalysis on π-stacked foldamers (Figure 1B) [7] and micelles [8]. However, due to their unique polarizability [9][10][11], the dream scaffolds for induced anion-π interactions are carbon allotropes.…”

“…The strength of anion–π interactions increases with face-to-face π stacking because the delocalized π electrons move within the stack away from the charge, which induces a macrodipole along the stack that supports the binding of the anion ( Figure 1B ) [ 61 ]. What works for anion–(π) n –π catalysis on π-stacked foldamers [ 61 ] and micelles [ 8 ] should apply to fullerenes as well. The unique polarizability of fullerene monomers like 1 is thought to induce strong anion–π interactions and thus account for the observed catalytic activity ( Figure 7A ) [ 12 ].…”

A Fluorogenic Substrate for Quinoline Reduction: Pnictogen‐Bonding Catalysis in Aqueous Systems

“…This stability in water was already essential for the use of Sb(III) 1 in lipid bilayer membranes to catalyze cascade cyclizations of biomimetic polyether cation transporters in situ [54] . However, in aqueous systems without micelles [55] or membranes [54] to shield the catalyst, water should compete for pnictogen bonding, forming the catalyst‐inhibitor complex CI‐1 ( Figure 1 a ). For this reason, pnictogen‐bonding catalysis as in TS‐1 , and σ ‐hole catalysis in general are often not considered realistic in water.…”