New Developments in Chiral Cooperative Ion Pairing Organocatalysis by Means of Ammonium Oxyanions and Fluorides: From Protonation to Deprotonation Reactions.

Abstract

This personal account summarizes our contribution to the ion pairing organocatalysis mainly by use of chiral quaternary or tertiary ammonium fluorides, aryloxides and carboxylates. Starting from an experimental observation, we were able to develop several approaches for the enantioselective protonation of silyl enolates and enol esters giving rise to chiral carbonyl compounds bearing a stereogenic center at the α-position. Moving from protonation to deprotonation reactions, chiral ammonium ion pair catalysts were successfully applied to several asymmetric transformations such as an Henry reaction or a direct vinylogous aldol reaction to cite a few. An outlook of further possible developments in this field of research will also be discussed.

An Integrated Smart Sensor Dressing for Real-Time Wound Microenvironment Monitoring and Promoting Angiogenesis and Wound Healing

“…With the increase of external pH value, the degree of protonation of hydrogels increases, which enhances their hydrophilicity and swelling capacity. In a neutral environment, protonation and deprotonation reach a balance, so the hydrogel can remain stable in a simulated human environment (Legros et al, 2017;Ehtesabi et al, 2020). In addition, an acidic environment may be more conducive to hydrogels degradation.…”

Enantioselective “organocatalysis in disguise” by the ligand sphere of chiral metal-templated complexes

“…66,67 Although, recently highly efficient asymmetric organocatalysts have been developed (with requirement of o1 mol% (ppm levels) of catalyst loadings) [67][68][69][70] there is still need to develop more active and alternative catalysts and related catalytic reactions. The underlying reasons for this observation can be attributed to the relatively weak noncovalent interactions of the substrate and catalyst (e.g., hydrogen bonding, [71][72][73][74][75][76] ion-pairing, [77][78][79] etc.). [80][81][82][83] On the other hand, non-covalent interactions play a key role in catalysis by lowering the kinetic barriers to reactions through transition state stabilization.…”

Organocatalysis: A Tool of Choice for the Enantioselective Nucleophilic Dearomatization of Electron-Deficient Six-Membered Ring Azaarenium Salts

“…Whereas enantioselective hydride addition requires the use of pre-functionalized azaarenes (introduction of Nu prior to the addition of the hydride) and leads to tetrahydro products (and therefore will not be discussed herein) [7][8][9], nucleophilic dearomatization (Nu = H) offers the advantage of introducing chemical diversity Taking into account the above-mentioned challenges, enantioselective nucleophilic dearomatization of azaarenium salts has attracted a great deal of attention mostly by using metal catalysts with chiral ligands [11][12][13][14][15][16][17][18][19][20]. Nevertheless, in the last fifteen years and due to the advent of organocatalysis [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36], which was recently highlighted through the Taking into account the above-mentioned challenges, enantioselective nucleophilic dearomatization of azaarenium salts has attracted a great deal of attention mostly by using metal catalysts with chiral ligands [11][12][13][14][15][16][17][18][19][20]. Nevertheless, in the last fifteen years and due to the advent of organocatalysis [21][22]…”

“…Nevertheless, in the last fifteen years and due to the advent of organocatalysis [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36], which was recently highlighted through the Taking into account the above-mentioned challenges, enantioselective nucleophilic dearomatization of azaarenium salts has attracted a great deal of attention mostly by using metal catalysts with chiral ligands [11][12][13][14][15][16][17][18][19][20]. Nevertheless, in the last fifteen years and due to the advent of organocatalysis [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36], which was recently highlighted through the Nobel Prize of Prof. B. List and Prof. D. MacMillan, several enantioselective organocatalytic dearomatization reactions of azaarenium salts have been reported [11,[13][14]…”