Unusual conformational preferences of 1,3‐dimethyl‐3‐isopropoxy‐3‐silapiperidine |
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| Authors: | Svetlana V. Kirpichenko Bagrat A. Shainyan Erich Kleinpeter |
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| Affiliation: | 1. A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Division of the Russian Academy of Science, , 664033 Irkutsk, Russian Federation;2. Chemisches Institut der Universitat Potsdam, , D‐14476 Potsdam (Golm), Germany |
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| Abstract: | The conformational analysis of the first representative of the Si‐alkoxy substituted six‐membered Si,N‐heterocycles, 1,3‐dimethyl‐3‐isopropoxy‐3‐silapiperidine, was performed by low‐temperature 1H and 13C NMR spectroscopy and DFT theoretical calculations. In contrast to the expectations from the conformational energies of methyl and alkoxy substituents, the Meaxi‐PrOeq conformer was found to predominate in the conformational equilibrium in the ratio Meaxi‐PrOeq : Meeqi‐PrOax of ca. 2 : 1 as from the 1H and 13C NMR study. The thermodynamic parameters obtained by the complete line shape analysis showed that the main contribution to the barrier to ring inversion originates from the entropy term of the free energy of activation. Copyright © 2012 John Wiley & Sons, Ltd. |
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| Keywords: | barrier to ring inversion conformational equilibrium DFT theoretical calculations dynamic NMR silapiperidines |
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