TY - JOUR
A1 - Shainyan, Bagrat A.
A1 - Kirpichenko, Svetlana V.
A1 - Shlykov, Sergei A.
A1 - Keinpeter, Erich
T1 - Structure and conformational properties of 1,3,3-Trimethyl-1,3-Azasilinane gas electron diffraction, dynamic NMR, and theoretical study
JF - The journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment & general theory
N2 - Structure and the conformational properties of 1,3,3-trimethyl-1,3-azasilinane have been studied. According to gas electron diffraction (GED), the molecule exists in a slightly distorted chair conformation with the N-Me group in equatorial position. High-level quantum chemical calculations excellently, reproduce the experimental geometry. Employing variable temperature H-1 and C-13 NMR spectroscopy down to 103 K, the conformational equilibrium could be frozen and the barrier to ring inversion determined.
Y1 - 2012
U6 - http://dx.doi.org/10.1021/jp2110852
SN - 1089-5639 (print)
VL - 116
IS - 1
SP - 784
EP - 789
PB - American Chemical Society
CY - Washington
ER -
TY - JOUR
A1 - Shainyan, Bagrat A.
A1 - Kirpichenko, Svetlana V.
A1 - Kleinpeter, Erich
T1 - Synthesis and conformational properties of 1,3-dimethyl-3-phenyl-1,3-azasilinane low temperature dynamic NMR and computational study
JF - Arkivoc : free online journal of organic chemistry
N2 - 1,3-Dimethyl-3-phenyl-1,3-azasilinane was synthesized and its conformational behavior was studied by the low temperature NMR spectroscopy and quantum chemical calculations. The compound was shown to exist as an equilibrium mixture of the PhaxMeeq and PheqMeax chair conformers with the N-methyl substituent in equatorial position. The barrier to ring inversion was also determined.
KW - 1,3-Dimethyl-3-phenyl-1,3-azasilinane
KW - conformational analysis
KW - low temperature NMR spectroscopy
KW - quantum chemical calculations
Y1 - 2012
SN - 1551-7004 (print)
IS - 24
SP - 175
EP - 185
PB - ARKAT
CY - Gainesville
ER -
TY - JOUR
A1 - Kirpichenko, Svetlana V.
A1 - Shainyan, Bagrat A.
A1 - Kleinpeter, Erich
T1 - Unusual conformational preferences of 1,3-dimethyl-3-isopropoxy-3-silapiperidine
JF - Journal of physical organic chemistry
N2 - The conformational analysis of the first representative of the Si-alkoxy substituted six-membered Si,N-heterocycles, 1,3-dimethyl-3-isopropoxy-3-silapiperidine, was performed by low-temperature 1H and 13C NMR spectroscopy and DFT theoretical calculations. In contrast to the expectations from the conformational energies of methyl and alkoxy substituents, the Meaxi-PrOeq conformer was found to predominate in the conformational equilibrium in the ratio Meaxi-PrOeq : Meeqi-PrOax of ca. 2 : 1 as from the 1H and 13C NMR study. The thermodynamic parameters obtained by the complete line shape analysis showed that the main contribution to the barrier to ring inversion originates from the entropy term of the free energy of activation.
KW - barrier to ring inversion
KW - conformational equilibrium
KW - DFT theoretical calculations
KW - dynamic NMR
KW - silapiperidines
Y1 - 2012
U6 - http://dx.doi.org/10.1002/poc.3028
SN - 0894-3230 (print)
VL - 25
IS - 12
SP - 1321
EP - 1327
PB - Wiley-Blackwell
CY - Hoboken
ER -
TY - JOUR
A1 - Kirpichenko, Svetlana V.
A1 - Kleinpeter, Erich
A1 - Ushakov, Igor A.
A1 - Shainyan, Bagrat A.
T1 - Conformational Analysis of 3-Methyl-3-Silathiane and 3-Fluoro-3-Methyl-3-Silathiane
JF - Journal of physical organic chemistry
N2 - The conformational equilibria of 3-methyl-3-silathiane 5, 3-fluoro-3-methyl-3-silathiane 6 and 1-fluoro-1-methyl-1- silacyclohexane 7 have been studied using low temperature C-13 NMR spectroscopy and theoretical calculations. The conformer ratio at 103 K was measured to be about 5(ax):5(eq) - 15:85, 6(ax):6(eq)-50:50 and 7(ax):7(eq)-25:75. The equatorial preference of the methyl group in 5 (0.35 kcal mol(-1)) is much less than in 3-methylthiane 9 (1.40 kcal mol(-1)) but somewhat greater than in 1-methyl-1-silacyclohexane 1 (0.23 kcal mol(-1)). Compounds 5-7 have low barriers to ring inversion: 5.65 (ax -> eq) and 6.0 kcal mol(-1) (eq -> ax) (5), 4.6 kcal mol(-1) (6), 5.1 kcal mol(-1) (Me-ax -> Me-eq), and 5.4 kcal mol(-1) (Me-eq -> Me-ax) (7). Steric effects cannot explain the observed conformational preferences, like equal population of the two conformers of 6, or different conformer ratio for 5 and 7. Actually, by employing the NBO analysis, in particular, considering the second order perturbation energies, vicinal stereoelectronic interactions between the Si-X and adjacent C-H, C-S, and C-C bonds proved responsible.
KW - conformational analysis
KW - low-temperature NMR spectroscopy
KW - NBO analysis
KW - quantum chemical calculations
KW - 3-silathianes
Y1 - 2011
U6 - http://dx.doi.org/10.1002/poc.1758
SN - 0894-3230 (print)
VL - 24
IS - 4
SP - 320
EP - 326
PB - Wiley-Blackwell
CY - Hoboken
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 - http://dx.doi.org/10.1021/jo400289g
SN - 0022-3263 (print)
VL - 78
IS - 8
SP - 3939
EP - 3947
PB - American Chemical Society
CY - Washington
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 - http://dx.doi.org/10.1016/j.tet.2012.05.106
SN - 0040-4020 (print)
VL - 68
IS - 36
SP - 7494
EP - 7501
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 - http://dx.doi.org/10.1021/acs.joc.5b02355
SN - 0022-3263 (print)
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 - http://dx.doi.org/10.1016/j.tet.2015.03.117
SN - 0040-4020 (print)
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 - Stereochemistry of 3-isopropoxy-3-methyl-1,3-oxasilinane-the first 3-silatetrahydropyran with an exo-cyclic RO-Si bond
JF - Tetrahedron
N2 - Molecular structure and conformational behavior of 3-isopropoxy-3-methyl-3-oxasilinane is studied by low temperature C-13 NMR spectroscopy and theoretical calculations (DFT, MP2). Two conformers, 1-ROax and 1-ROeq, were found experimentally and located on the potential energy surface. LT C-13 NMR spectroscopy gives almost equal population of the two conformers at 98 K with Delta G(98K)degrees=0.02 kcal/mol in favor of 1-ROax and Delta G(98K)(#)=4.5 kcal/mol. The corresponding DFT calculated values (Delta G(98K)degrees=0.03 kcal/mol, Delta G(98K)(#)=5.1 kcal/mol) are in excellent agreement with the experiment. Detailed DFT and MP2 calculations of the solvent effect on the conformational equilibrium were performed and highlighted the leveling out of the two conformers when transferred from gas to solution. (C) 2015 Published by Elsevier Ltd.
KW - 1,3-Oxasilinanes
KW - Conformational equilibrium
KW - Barrier to ring inversion
KW - Solvent effects
KW - Assignment of stereochemistry
Y1 - 2015
U6 - http://dx.doi.org/10.1016/j.tet.2015.07.047
SN - 0040-4020 (print)
VL - 71
IS - 38
SP - 6720
EP - 6726
PB - Elsevier
CY - Oxford
ER -
TY - JOUR
A1 - Kirpichenko, Svetlana V.
A1 - Kleinpeter, Erich
A1 - Shainyan, Bagrat A.
T1 - Conformational analysis of 3,3-dimethyl-3-silathiane, 2,3,3-trimethyl-3-silathiane and 2-trimethylsilyl-3,3- dimethyl-3-silathianeùpreferred conformers, barriers to ring inversion and substituent effec
N2 - The first conformational analysis of 3-silathiane and its C-substituted derivatives, namely, 3,3-dimethyl-3- silathiane 1, 2,3,3-trimethyl-3-silathiane 2, and 2-trimethylsilyl-3,3-dimethyl-3-silathiane 3 was performed by using dynamic NMR spectroscopy and B3LYP/6-311G(d,p) quantum chemical calculations. From coalescence temperatures, ring inversion barriers ;G; for 1 and 2 were estimated to be 6.3 and 6.8;kcal/mol, respectively. These values are considerably lower than that of thiacyclohexane (9.4;kcal/mol) but slightly higher than the one of 1,1- dimethylsilacyclohexane (5.5;kcal/mol). The conformational free energy for the methyl group in 2 (;;G°;=;0.35;kcal/mol) derived from low-temperature 13C NMR data is fairly consistent with the calculated value. For compound 2, theoretical calculations give ;E value close to zero for the equilibrium between the 2-Meax and 2-Meeq conformers. The calculated equatorial preference of the trimethylsilyl group in 3 is much more pronounced (;;G°;=;1.8;kcal/mol) and the predominance of the 3-SiMe3 eq conformer at room temperature was confirmed by the simulated 1H NMR and 2D NOESY spectra. The effect of the 2-substituent on the structural parameters of 2 and 3 is discussed.
Y1 - 2010
SN - 0894-3230
ER -