TY  - JOUR
A1  - Kirpichenko, Svetlana
A1  - Shainyan, Bagrat A.
A1  - Kleinpeter, Erich
A1  - Shlykov, Sergey A.
A1  - Tran Dinh Phien, 
A1  - Albanov, Alexander
T1  - Synthesis of 3-fluoro-3-methyl-3-silatetrahydropyran and its conformational preferences in gas and solution by GED, NMR and theoretical calculations
JF  - Tetrahedron
N2  - 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.
KW  - 3-Fluoro-3-methyl-3-silatetrahydropyran
KW  - Conformational analysis
KW  - Gas phase electron diffraction
KW  - Low-temperature NMR
KW  - DFT
KW  - MP2 and CCSD(T) calculations
Y1  - 2018
U6  - https://doi.org/10.1016/j.tet.2018.02.055
SN  - 0040-4020
VL  - 74
IS  - 15
SP  - 1859
EP  - 1867
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Shainyan, Bagrat A.
A1  - Suslova, Elena N.
A1  - Tran Dinh Phien, 
A1  - Shlykov, Sergey A.
A1  - Kleinpeter, Erich
T1  - Synthesis, conformational preferences in gas and solution, and molecular gear rotation in 1-(dimethylamino)-1-phenyl-1-silacyclohexane by gas phase electron diffraction (GED), LT NMR and theoretical calculations
JF  - Tetrahedron
N2  - 1-(Dimethylamino)-1-phenyl-1-silacyclohexane 1, was synthesized, and its molecular structure and conformational properties studied by gas-phase electron diffraction (GED), low temperature C-13 NMR spectroscopy and quantum-chemical calculations. The predominance of the 1-Ph-ax conformer (1-Ph-eq:1-Ph-ax ratio of 20:80%, Delta G degrees (317 K) = -0.87 kcal/mol) in the gas phase is close to the theoretically estimated conformational equilibrium. In solution, low temperature NMR spectroscopy showed analyzable decoalescence of C-ipso and C(1,5) carbon signals in C-13 NMR spectra at 103 K. Opposite to the gas state in the freon solution employed (CD2Cl2/CHFCl2/CHFCl2 = 1:1:3), which is still liquid at 100 K, the 1-Ph-eq conformer was found to be the preferred one [(1-Ph-eq: 1-Ph-ax = 77%: 23%, K = 77/23 = 2.8; -Delta G degrees = -RT In K (at 103 K) = 0.44 +/- 0.1 kcal/mol]. When comparing 1 with 1-phenyl-1-(X)silacylohexanes (X = H, Me, OMe, F, Cl), studied so far, the trend of predominance of the Ph-ax conformer in the gas phase and of the Ph-eq conformer in solution is confirmed.
KW  - 1-(Dimethylamino)-1-phenyl-1-silacyclohexane
KW  - Conformational analysis
KW  - Gas phase electron diffraction
KW  - Low-temperature d-NMR
KW  - DFT
KW  - MP2
KW  - M062X/6-311G** calculations
Y1  - 2018
U6  - https://doi.org/10.1016/j.tet.2018.06.023
SN  - 0040-4020
VL  - 74
IS  - 32
SP  - 4299
EP  - 4307
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Shainyan, Bagrat A.
A1  - Suslova, Elena N.
A1  - Tran Dinh Phien, 
A1  - Shlykov, Sergey A.
A1  - Heydenreich, Matthias
A1  - Kleinpeter, Erich
T1  - 1-Methylthio-1-phenyl-1-silacyclohexane: Synthesis, conformational preferences in gas and solution by GED, NMR and theoretical calculations
JF  - Tetrahedron
N2  - 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 C-13 and Si-29 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-MeSaxPheq conformer in gas phase (1-Ph-eq :1-Ph-ax = 55:45, Delta G degrees = 0.13 kcal/mol) determined from GED is consistent with that measured in the freon solution by LT NMR (1-Ph-eq:1-Ph-ax = 65:35, Delta G degrees = 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. (C) 2019 Elsevier Ltd. All rights reserved.
KW  - 1-Methylthio-1-phenyl-1-silacyclohexane
KW  - Conformational analysis
KW  - Gas phase electron diffraction
KW  - Low-temperature C-13 and Si-29 NMR
KW  - DFT and MP2 calculations
Y1  - 2019
U6  - https://doi.org/10.1016/j.tet.2019.130677
SN  - 0040-4020
VL  - 75
IS  - 46
PB  - Elsevier
CY  - Oxford
ER  -