Bidentate Urea Derivatives of p-tert-Butyldihomooxacalix[4]arene: Neutral Receptors for Anion Complexation

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• 作者：Paula M. Marcos ; Filipa A. Teixeira ; Manuel A. P. Segurado ; José R. Ascenso ; Raul J. Bernardino ; Sylvia Michel ; Véronique Hubscher-Bruder
• 刊名：Journal of Organic Chemistry
• 出版年：2014
• 出版时间：January 17, 2014
• 年：2014
• 卷：79
• 期：2
• 页码：742-751
• 全文大小：516K
• ISSN：1520-6904

文摘

Three new bidentate ureidodihomooxacalix[4]arene derivatives (phenyl 5a, n-propyl 5b, and tert-butyl 5c) were synthesized in four steps from the parent compound p-tert-butyldihomooxacalix[4]arene and obtained in the cone conformation, as shown by NMR studies. The binding ability of these neutral receptors toward spherical, linear, trigonal planar, and tetrahedrical anions was assessed by ¹H NMR and UV鈥搗is titrations. The structures and complexation energies of some complexes were also studied by DFT methods. The data showed that the association constants are strongly dependent on the nature of the substituent (aryl/alkyl) at the urea moiety. In general, for all the receptors, the association constants decrease with decrease of anion basicity. Ph-urea 5a is the best anion receptor, showing the strongest complexation for F^{鈥?/sup> (log K_assoc = 3.10 in CDCl₃) and also high binding affinity for the carboxylates AcO鈥?/sup> and BzO鈥?/sup>. Similar results were obtained by UV鈥搗is studies and were also corroborated by DFT calculations.}