Conformational properties of propargyloxy-calix[4]arene tricarboxamides: NMR and DFT studies on the O-through-the-annulus rotation |
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| Authors: | János B Czirok Ákos Tarcsay Pál D Mezei András Simon László Balázs |
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| Institution: | 1. Department of Organic Chemistry and Technology, Budapest University of Technology and Economics, Budafoki út 8, Budapest 1521, Hungary;2. Gedeon Richter Plc., Gy?mr?i út 19-21., Budapest 1103, Hungary;3. Institute of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics, Gellért tér 5., Budapest 1521, Hungary;4. Chinoin Co.Ltd.,Tó u. 1-5., Budapest 1045, Hungary |
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| Abstract: | The size limit of substituents allowing O-through-the-annulus rotation of substituted calix4]arenes was further extended to the propargyloxy group in 24-propargyloxy-25,26,27-tris(N,N-dimethylcarbamoylmethoxy)-p-tert-butylcalix4]arene by demonstrating its free but slow motion affording equilibrium between the partial cone and 1,2-alternate conformers. The effect of solvent and upper rim substituents R1 on the conformational inversion was investigated by means of 1H NMR. The rotational isomerisation of the parent (R1 = H) analogue could not unambiguously be detected. The experimental results were supported by comprehensive density functional theory studies. |
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| Keywords: | calix[4]arene propargyloxy group rotation partial cone 1 2-alternate conformational equilibrium |
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