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 - 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 - Kirpichenko, Svetlana V. A1 - Chipanina, Nina N. A1 - Oznobikhina, Larisa P. A1 - Kleinpeter, Erich A1 - Shlykov, Sergey A. A1 - Osadchiy, Dmitriy Yu. T1 - Synthesis and Conformational Analysis of 3-Methyl-3-silatetrahydropyran by GED, FTIR, NMR, and Theoretical Calculations: Comparative Analysis of 1-Hetero-3-methyl-3-silacyclohexanes JF - The journal of organic chemistry N2 - 3-Methyl-3-silatetrahydropyran 1 was synthesized and its molecular structure and conformational behavior was studied by gas-phase electron diffraction (GED), FTIR, low temperature H-1 and C-13 NMR spectroscopy, and by theoretical calculations (DFT, MP2). Two conformers; 1-ax and 1-eq; were located on the potential energy Surface. In the gas phase; a slight predominance of the axial conformer was determined, with the ratio 1-ax:1-eq = 54(9):46(9) (from GED) or 53:47 or 61;39 (from IR). In solution, LT NMR spectroscopy at 103 K gives the ratio 1-ax:1-eq = 35:65 (-Delta G(103)degrees = 0.13 kcal/mol). Simulation of solvent effects using the PCM continuum model or by calculation of the corresponding solvent-solute complexes allowed us to rationalize the experimentally observed opposite conformational predominance of the conformers of 3-methyl-3-silatettahydropyran in the gas phase and in solution. Comparative analysis of the effect of heteroatom in 1-hetero-3-methyl-3-silacyclohexanes on the structure, stereoelectronic interactions, and relative energies of the conformers is done. Y1 - 2015 U6 - https://doi.org/10.1021/acs.joc.5b02355 SN - 0022-3263 VL - 80 IS - 24 SP - 12492 EP - 12500 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Shainyan, Bagrat A. A1 - Kirpichenko, Svetlana V. A1 - Kleinpeter, Erich A1 - Shlykov, Sergey A. A1 - Osadchiy, Dmitriy Yu. T1 - Molecular structure and conformational analysis of 3-methyl-3-phenyl-3-silatetrahydropyran. Gas-phase electron diffraction, low temperature NMR and quantum chemical calculations JF - Tetrahedron N2 - The molecular structure and conformational behavior of 3-methyl-3-phenyl-3-silatetrahydropyran 1 was studied by gas-phase electron diffraction (GED-MS), low temperature C-13 NMR spectroscopy (LT NMR) and theoretical calculations. The 1-Ph-eq and 1-Ph-ax conformers were located on the potential energy surface. Rotation about the Si-C-ph bond revealed the phenyl ring orthogonal to the averaged plane of the silatetrahydropyran ring for 1-Ph-eq and a twisted orientation for 1-Ph-ax. Theoretical calculations and GED analysis indicate the predominance of 1-Ph-ax in the gas phase with the ratio of conformers (GED) 1-Ph-eq:1-Ph-ax=38:62 (Delta G degrees(307)=-0.29 kcal/mol). In solution, LT NMR spectroscopy gives almost the opposite ratio Ph-eq:1-Ph-ax=68:32 (Delta G degrees(103)=0.16 kcal/mol). Simulation of solvent effects using the PCM continuum model or by calculation of the solvent-solute complexes allowed us to rationalize the experimentally observed opposite conformational predominance of the conformers of compound 1 in the gas phase and in solution. (C) 2015 Elsevier Ltd. All rights reserved. KW - 3-Silatetrahydropyrans KW - Conformational analysis KW - Low temperature NMR spectroscopy KW - Gas-phase electron diffraction KW - Quantum chemical calculations Y1 - 2015 U6 - https://doi.org/10.1016/j.tet.2015.03.117 SN - 0040-4020 VL - 71 IS - 23 SP - 3810 EP - 3818 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 - TY - JOUR A1 - Shainyan, Bagrat A. A1 - Kirpichenko, Svetlana V. A1 - Kleinpeter, Erich A1 - Shlykov, Sergey A. A1 - Osadchiy, Dmitriy Yu A1 - Chipanina, Nina N. A1 - Oznobikhina, Larisa P. T1 - 1,3-Dimethy1-3-silapiperidine - synthesis, molecular structure, and conformational analysis by gas-phase electron diffraction, low temperature NMR, IR and Raman Spectroscopy, and quantum chemical calculations JF - The journal of organic chemistry N2 - The first Si-H-containing azasilaheterocycle, 1,3-dimethyl-3-silapiperidine 1, was synthesized, and its molecular structure and conformational properties were studied by gas-phase electron diffraction (GED), low temperature NMR, IR and Raman spectroscopy and quantum chemical calculations. The compound exists as a mixture of two conformers possessing the chair conformation with the equatorial NMe group and differing by axial or equatorial position of the SiMe group. In the gas phase, the SiMeax conformer predominates (GED: ax/eq = 65(7):35(7)%,Delta G = 0.36(18) kcal/mol; IR: ax/eq = 62(5):38(5)%,Delta G = 0.16(7) kcal/mol). In solution, at 143 k the SiMeeq conformer predominates' in the frozen equilibrium (NMR: ax/eq = 31.5(1.5):68.5(1.5)%, Delta G = -0.22(2) kcal/mol). Thermodynamic parameters of the ring inversion are determined (Delta G(double dagger) = 8.9-9.0 kcal/mol, Delta H-double dagger = 9.6 kcal/mol, Delta S-double dagger = 2.1 eu). High-level quantum chemical calculations :(MP2, G2, CCSD(T)) nicely reproduce the experimental geometry and the predominance of the axial conformer in the gas phase. Y1 - 2013 U6 - https://doi.org/10.1021/jo400289g SN - 0022-3263 VL - 78 IS - 8 SP - 3939 EP - 3947 PB - American Chemical Society CY - Washington ER -