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  - Kirpichenko, Svetlana V.
A1  - Kleinpeter, Erich
T1  - Synthesis and conformational analysis of 1,3-azasilinanes
JF  - Tetrahedron
N2  - 1-Isopropyl-3-methyl-3-phenyl-1,3-azasilinane 1 and 1-isopropyl-3,3-dimethyl-1,3-azasilinane 2 were synthesized and a detailed analysis of their NMR spectra, conformational equilibria and ring inversion processes is presented. Low temperature H-1/C-13 NMR spectroscopy, iteration of the H-1 NMR spectra and quantum chemical calculations showed slight predominance of the PheqMeax over the PhaxMeeq conformer of 1 at low temperature. The barrier for the chair to chair interconversion of both compounds was measured to be 8.25 kcal/mol.
KW  - 1,3-Azasilinanes
KW  - Conformational analysis
KW  - Dynamic NMR spectroscopy
KW  - Quantum chemical calculations
KW  - Ring current effect
Y1  - 2012
U6  - https://doi.org/10.1016/j.tet.2012.05.106
SN  - 0040-4020
VL  - 68
IS  - 36
SP  - 7494
EP  - 7501
PB  - Elsevier
CY  - Oxford
ER  -