Enantiomer Separation and Molecular Recognition with New Chiral Stationary Phases on 4‐Chloro‐3,5‐dinitrobenzoic Acid Amides of α,β‐Aminoalcohols and α‐Arylethylamines

Abstract

Abstract Amides of 4‐chloro‐3,5‐dinitrobenzoic acid (1) (CDNB) with enantiomerically pure α,β‐aminoalcohols (2–5) and α‐substituted ethylamines,6–9 Welch, C. J. 1994. “Design, synthesis and evaluation of a brush‐type chiral stationary phase with broad generality”. In Book of Abstract, Chiral '94 33–37. USA Pirkle, W. H. and Liu, Y. 1996. On the relevance of face‐to‐edge‐ π‐π interactions to chiral recognition. J. Chromatogr. A, 749: 19–24. Kontrec, D., Vinkovic, V. and Šunjic, V. 2000. Preparation and evaluation of chiral stationary phases based on N,N‐2,4‐(or 4,6)‐disubstituted 4,5‐(or 2,5)‐dichloro‐1,3‐dicyanobenzene. Chirality, 12: 63–70. Kontrec, D., Vinkovic, V., Lesac, A., Šunjic, V. and Aced, A. 2000. Novel chiral stationary phases comprising 2,4‐(or 2,6)‐diamino‐5,6‐(or 2,5)‐dichlorobenzene‐1,3‐dicarbonitrile and 1‐acyl (1R,2R)‐diaminocyclohexane. Enantiomer, 5: 333–344. have been prepared as chiral selectors 10–17 and bound to aminopropyl silica gel affording chiral stationary phases CSPs 1–8. Comparative tests of their separation efficacy for 32 racemic analytes, representative of racemates with selected functionalities, has revealed important contribution of the π‐acidic branching unit, the amide of 3,5‐dinitro‐4‐alkylaminobenzoic acid, but limited contribution of both, hydrophilic hydroxy groups in the CSPs 1–4 and π‐basic aromatic units in the CSPs 6–8. Contribution to enantioselection efficacy of the γ‐aminopropyl groups on the silica surface, in the vicinity to the chiral selector, is documented comparing the efficacy of CSP 8 and CSP 8′.