TY  - JOUR
A1  - Shainyan, Bagrat A.
A1  - Suslova, Elena N.
A1  - Kleinpeter, Erich
T1  - Conformational analysis of N-phenyl- and N-trifyl-4,4-dimethyl-4-silathiane 1-sulfimides
JF  - Journal of physical organic chemistry
N2  - N-Substituted 4,4-dimethyl-4-silathiane 1-sulfimides Me2Si(sic)S=NSO2R [R- Ph (1), CF3 (2)] were studied experimentally by variable temperature dynamic NMR spectroscopy. Low temperature 13 C NMR spectra of the two compounds revealed the frozen ring inversion process and approximately equal content of the axial and equatorial conformers. Calculations of the 4-silathiane derivatives 1, 2 and the model compound [R Me (3)] as well as their carbon analogs, the similarly N-substituted (sic)S=NSO2R thiane 1-sulfimides [R = Ph (4), CF3 (5), Me (6)] at the DFT/B3LYP/6-311G(d, p) level in the gas phase and in chloroform solution using the PCM model at the same level of theory showed a strong dependence of the relative stability of the conformer on the solvent. The electronegative trifluoromethyl group increases the relative stability of the axial conformer.
KW  - 4-silathianes
KW  - conformational analysis
KW  - dynamic NMR
KW  - quantum chemical calculations
KW  - sulfimides
Y1  - 2011
U6  - https://doi.org/10.1002/poc.1811
SN  - 0894-3230
VL  - 24
IS  - 8
SP  - 698
EP  - 704
PB  - Wiley-Blackwell
CY  - Malden
ER  - 
TY  - JOUR
A1  - Pihlaja, Kalevi
A1  - Sinkkonen, Jari
A1  - Stajer, Geza
A1  - Koch, Andreas
A1  - Kleinpeter, Erich
T1  - 1-Oxo-1,3-dithiolanes - synthesis and stereochemistry
JF  - Magnetic resonance in chemistry
N2  - 1-Oxo-1,3-dithiolane (4) and its cis- and trans-2-methyl (5,6), -4-methyl (7,8) and -5-methyl (9,10) derivatives were prepared by oxidizing the corresponding 1,3-dithiolanes (1-3) with NaIO(4) in water. The oxides were purified and their isomers separated using thin layer chromatography. The structural characterization was carried out with (1)H and (13)C NMR spectroscopy and molecular modelling. The sulfoxides 4-6 and 8-10 attain two S(1) type envelopes (sometimes slightly distorted) the S=O(ax) envelope greatly dominating. Cis-4-methyl-1-oxo-1,3-dithiolane is a special case exhibiting both two closely related S=O(ax) (30 and 27%) as well as S=O(eq) (21 and 22%) forms [S(1) and C(4) envelopes, respectively]. The relative energies of these conformations, the values of (1)H-(1)H coupling constants and (1)H and (13)C chemical shifts were estimated by computational methods and they support well the conclusions based on the experimental data.
KW  - NMR
KW  - (1)H NMR
KW  - (13)C NMR
KW  - sulfur heterocycles
KW  - conformational analysis
KW  - computational chemistry
Y1  - 2011
U6  - https://doi.org/10.1002/mrc.2764
SN  - 0749-1581
VL  - 49
IS  - 7
SP  - 443
EP  - 449
PB  - Wiley-Blackwell
CY  - Malden
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  - https://doi.org/10.1002/poc.1758
SN  - 0894-3230
VL  - 24
IS  - 4
SP  - 320
EP  - 326
PB  - Wiley-Blackwell
CY  - Hoboken
ER  -