1-Methylthio-1-phenyl-1-silacyclohexane: Synthesis, conformational preferences in gas and solution by GED, NMR and theoretical calculations. Issue 46 (15th November 2019)

• Record Type: Journal Article
• Authors: Shainyan, Bagrat A.; Suslova, Elena N.; Phien, Tran Dinh; Shlykov, Sergey A.; Heydenreich, Matthias; Kleinpeter, Erich
• Is Part Of: Tetrahedron. Volume 75:Issue 46(2019)
• Publication Date: 2019-11-15
• Subjects: 1-Methylthio-1-phenyl-1-silacyclohexane -- Conformational analysis -- Gas phase electron diffraction -- Low-temperature 13C and 29Si NMR -- DFT and MP2 calculations; Chemistry, Organic -- Periodicals; 547.005
• DOI: 10.1016/j.tet.2019.130677
• Languages: English
• ISSNs: 0040-4020

Abstract

Abstract: 1-Methylthio-1-phenyl-1-silacyclohexane 1, the first silacyclohexane with the sulfur atom at silicon, was synthesized and its molecular structure and conformational preferences studied by gas-phase electron diffraction (GED) and low temperature 13 C and 29 Si NMR spectroscopy (LT NMR). Quantum-chemical calculations were carried out both for the isolated species and solvate complexes in gas and in polar medium. The predominance of the 1 -MeSax Pheq conformer in gas phase (1 -Pheq :1 -Phax = 55:45, Δ G ° = 0.13 kcal/mol) determined from GED is consistent with that measured in the freon solution by LT NMR (1 -Pheq :1 -Phax = 65:35, Δ G ° = 0.12 kcal/mol), the experimentally measured ratios being close to that estimated by quantum chemical calculations at both the DFT and MP2 levels of theory. Graphical abstract: Image 1 Highlights: 1-Methylthio-1-phenylsilacyclohexane 1, the first silacyclohexane with the sulfur atom at silicon was synthesized. Conformational analysis of 1 done by GED, low-temperature NMR spectroscopy and theoretical calculations. In gas phase, the most stable conformers are 1 -Pheq and 1 -Phax in the ratio of 55:45% [∆ G °(333K) = 0.13 kcal/mol]. In a freon solution, the conformational equilibrium is 1 -Pheq : 1 -Phax = 65 : 35% [∆ G °(98K) = 0.12 kcal/mol]. The barrier to ring interconversion was determined to be Δ G ≠ = 5.8 kcal/mol.