Synthesis of 3-fluoro-3-methyl-3-silatetrahydropyran and its conformational preferences in gas and solution by GED, NMR and theoretical calculations
| Autor: | Erich Kleinpeter, Svetlana V. Kirpichenko, Sergey A. Shlykov, Bagrat A. Shainyan, Alexander I. Albanov, Tran Dinh Phien |
|---|---|
| Rok vydání: | 2018 |
| Předmět: |
Silicon
010405 organic chemistry Organic Chemistry Substituent chemistry.chemical_element Fluorine-19 NMR Nuclear magnetic resonance spectroscopy 010402 general chemistry 01 natural sciences Biochemistry Spectral line 0104 chemical sciences Crystallography chemistry.chemical_compound chemistry Electron diffraction ddc:540 Drug Discovery Institut für Chemie Molecule Conformational isomerism |
| Zdroj: | Tetrahedron. 74:1859-1867 |
| ISSN: | 0040-4020 |
| DOI: | 10.1016/j.tet.2018.02.055 |
| Popis: | The 3,3-disubstitued 3-silaheterocyclohexane with an electronegative substituent at silicon, 3-fluoro-3-methyl-3-silatetrahydropyran 1, was synthesized, and its molecular structure and conformational properties studied by gas-phase electron diffraction (GED) and low temperature C-13 and F-19 NMR spectroscopy. Quantum-chemical calculations were carried out both for the isolated species and Hcomplexes in gas and in polar medium. The predominance of the 1-FeqMeax conformer (1-F-eq:1-F-ax ratio of 65:35, Delta G degrees = 0.37 kcal/mol) determined from GED is close to the theoretically estimated conformational equilibrium, especially at the DFT level. In solution, low temperature NMR spectroscopy showed no decoalescence of the signals in C-13 (down to 95 K) and F-19 NMR spectra (down to 123 K). However, the calculated F-19 chemical shift of -173.6 ppm for the 1-FeqMeax conformer practically coincides with the experimentally observed value (-173 to -175 ppm) as distinct from that for the 1-FaxMeeq conformer (-188.8 ppm), suggesting compound 1 to be anancomeric in solution, in compliance with its theoretical and experimental preference in the gas phase. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|
Full Text from ScienceDirect