A Halide-for-Anion Swap Using an Anion-Exchange Resin (A- Form) Method: Revisiting Imidazolium-Based Anion Receptors and Sensors

• Published in: European Journal of Organic Chemistry 2012-01, Vol.2012 (2), p.298-304
• Main Authors: Alcalde, Ermitas, Mesquida, Neus, Ibáñez, Anna, Dinarès, Immaculada
• Format: Article
• Language: English
• Subjects: Alicyclic compounds; Alicyclic compounds, terpenoids, prostaglandins, steroids; Anion recognition; Anions; Chemistry; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Heterocyclic compounds; Heterocyclic compounds with several n hetero atoms in the same ring, in separated rings or in fused rings; Ion exchange; Materials science; Methods of nanofabrication; Organic chemistry; Physics; Preparations and properties; Receptors; Sensors; Supramolecular and biochemical assembly; Supramolecular chemistry
• ISSN: 1434-193X; 1099-0690
• DOI: 10.1002/ejoc.201101355

Faced with an extensive pool of imidazolium‐based systems, the present study was based on selected examples of bis(imidazolium) models for anion recognition to broaden the applicability of counteranion exchange by using the anion‐exchange resin (AER) (A– form) method in nonaqueous media. Relying on the hydrophobicity of the quaternary imidazolium salt for counteranion exchange, the AER (A– form) method was performed in organic solvents of different polarity, such as CH3OH and CH3CN. Anion exchange proceeded in excellent to quantitative yields, simultaneously removing halide impurities―often a troublesome purification task. The results of electrospray mass spectrometry [ESI(+)‐MS] analysis focused on the gas‐phase behavior of the dicationic cyclophane prototype 5·2Cl and the open‐chain compound pairs 4·2Br and 15·2Br are briefly described. The anion‐exchange resin (A– form) method was applied to the counteranion exchange of quaternary heteroaromatic salts in organic solvents. Anion exchange proceeded in excellent to quantitative yields, simultaneously removing halide impurities.