Shape-Selective Recognition of Quaternary Ammonium Chloride Ion Pairs
Synthetic receptors that recognize ion pairs are potentially useful for many technical applications, but to date there has been little work on selective recognition of quaternary ammonium (Q+) ion pairs. This study measured the affinity of a tetralactam macrocycle for 11 different Q+·Cl- salts in chloroform solution. In each case, NMR spectroscopy was used to determine the association constant (Ka) and the structure of the associated complex. Ka was found to depend strongly on the molecular shape of Q+ and was enhanced when Q+ could penetrate the macrocycle cavity and engage in attractive noncovalent interactions with the macrocycle's NH residues and aromatic sidewalls. The highest measured Ka of 7.9 × 103 M-1 was obtained when Q+ was a p-CN-substituted benzylic trimethylammonium. This high-affinity Q+·Cl- ion pair was used as a template to enhance the synthetic yield of macrocyclization reactions that produce the tetralactam receptor or structurally related derivatives. In addition, a permanently interlocked rotaxane was prepared by capping the end of a noncovalent complex composed of the tetralactam macrocycle threaded by a reactive benzylic cation. The synthetic method provides access to a new family of rotaxanated ion pairs that can likely act as anion sensors, molecular shuttles, or transport molecules.
Li, Dong-Hao,Smith, Bradley D.
p. 2808 - 2816
(2019/03/26)
Palladium-Catalysed Cross-Coupling of Benzylammonium Salts with Boronic Acids under Mild Conditions
Herein, we give a full account of the development of the palladium-catalysed cross-coupling of benzylammonium salts with boronic acids. A range of benzylamine-derived quaternary ammonium salts can be coupled with boronic acids under relatively mild conditions. Our optimization has identified ligands that can be used to chemoselectively cross-couple at the ammonium in the presence of chlorides. We demonstrate that intramolecular palladium-catalysed C-H activation is also a viable pathway for the putative benzyl-Pd(II) intermediate obtained upon oxidative addition and have optimised this to obtain fluorene in good yield.
Türtscher, Paul L.,Davis, Holly J.,Phipps, Robert J.
p. 793 - 803
(2017/10/07)
Towards an efficient microsystem for the Real-Time detection and quantification of mercury in water based on a specifically designed fluorogenic binary Task-Specific ionic liquid
Chemical Equation Presented Quick test for quicksilver: A microdevice for liquid-liquid extraction and sensing of mercury ions in water uses an ionic liquid containing a task-specific ionic fluorogenic salt (L1) as the extracting liquid phase. The off-on sensing response decreases the likelihood of false positives and allows detection of Hg2+ in aqueous solution down to 50 ppb.
Faidjiba, Loe-Mie,Marchand, Gilles,Berthier, Jean,Sarrut, Nicolas,Pucheault, Mathieu,Mireille, Blanchard-Desce,Vinet, Francoise,Vaultier, Michel
supporting information; experimental part
p. 424 - 427
(2010/04/02)
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