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Ephedrinium‐based protic chiral ionic liquids for enantiomeric recognition
Author(s) -
De Rooy Sergio L.,
Li Min,
Bwambok David K.,
ElZahab Bilal,
Challa Santhosh,
Warner Isiah M.
Publication year - 2011
Publication title -
chirality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.43
H-Index - 77
eISSN - 1520-636X
pISSN - 0899-0042
DOI - 10.1002/chir.20920
Subject(s) - chemistry , ionic liquid , enantiopure drug , enantiomer , chirality (physics) , circular dichroism , imide , differential scanning calorimetry , chiral derivatizing agent , pyrrolidine , proton nmr , organic chemistry , crystallography , chiral column chromatography , enantioselective synthesis , catalysis , chiral symmetry breaking , physics , quantum mechanics , quark , nambu–jona lasinio model , thermodynamics
We report the synthesis of a series of novel structurally related protic chiral ionic liquids (PCILs) derived from ephedrines. Enantiopure norephedrine, ephedrine, and methylephedrine were neutralized by use of fluorinated acids, bis(trifluoromethanesulfonyl)imide, and bis(pentafluoroethanesulfonyl)imide to afford six PCILs with protonated primary, secondary, and tertiary amines. The goal of this study is to investigate the influence of structure on both chiral recognition abilities and physicochemical properties of these closely related PCILs. The newly synthesized PCILs were characterized by use of nuclear magnetic resonance (NMR), thermal gravimetric analysis, differential scanning calorimetry, circular dichroism (CD), mass spectrometry, and elemental analysis. The PCILs were thermally stable up to 220°C and had glass transition temperatures between −60 and −30°C. Both enantiomers of the PCILs retained chirality throughout the synthesis as demonstrated by use of CD measurements. More interestingly, these ephedrinium PCILs displayed strong chiral recognition capabilities as evidenced by peak splitting of the chemical shift of the trifluoro group of potassium Mosher's salt by use of 19 F‐NMR. In addition , these PCILs demonstrated enantiomeric recognition capabilities toward a range of structurally diverse analytes using steady‐state fluorescence spectroscopy. Chirality, 2011. © 2010 Wiley‐Liss, Inc.