TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Heydenreich, Matthias
A1  - Koch, Andreas
A1  - Linker, Torsten
T1  - Synthesis and NMR spectroscopic conformational analysis of esters of 4-hydroxy-cyclohexanone-the more polar the molecule the more stable the axial conformer
JF  - Tetrahedron
N2  - The esters of 4-hydroxy-cyclohexanone and a series of carboxylic acids R-COOH with R of different electronic and steric influence (R=Me, Et, n-Pr, i-Pr, n-Bu, i-Bu, sec-Bu, t-Bu, CF3, CH2Cl, CHCl2, CCl3, CH2Br, CHBr2, and CBr3) were synthesized and the conformational equilibria studied by H-1 and C-13 NMR spectroscopy at 103 K and at 295 K, respectively. The geometry of optimized structures of the axial 'equatorial chair conformers was computed at the ab initio MO and DFT levels of theory. Only one preferred conformation was obtained for the axial and the equatorial conformer as well. When comparing the conformational equilibria of the cyclohexanone esters with those of the corresponding cyclohexyl esters a certain polarity contribution of the cyclohexanone framework was revealed, which is independent of the substituent effects and increases the stability of the axial conformers by a constant amount.
KW  - 4-Substituted cyclohexanones
KW  - Conformational analysis
KW  - Dynamic NMR
KW  - Simulation of H-1 NMR spectra
KW  - Quantum chemical calculations
KW  - ALTONA equation
Y1  - 2012
U6  - https://doi.org/10.1016/j.tet.2012.01.022
SN  - 0040-4020
VL  - 68
IS  - 10
SP  - 2363
EP  - 2373
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Lazareva, Nataliya F.
A1  - Albanov, Alexander I.
A1  - Shainyan, Bagrat A.
A1  - Kleinpeter, Erich
T1  - Synthesis and conformational properties of substituted 1,4,2-oxazasilinanes low temperature NMR study and quantum chemical calculations
JF  - Tetrahedron
N2  - A number of N-substituted 2,2-dimethyl-1,4,2-oxazasilinanes 1 were synthesized and studied by variable temperature dynamic H-1 and C-13 NMR spectroscopy, room temperature N-15 NMR spectroscopy and theoretical calculations at the DFT and MP2 levels of theory. Both the preferred conformers were assigned and the barrier to the ring inversion of the saturated six-membered ring determined. From 1 the corresponding methyl iodide salts were produced, their structure studied by X-ray analysis and found to be in excellent agreement with the results of the theoretical calculations.
KW  - 1,4,2-Oxazasilinanes
KW  - Conformational analysis
KW  - Dynamic NMR
KW  - X-ray analysis
KW  - Quantum chemical calculations
Y1  - 2012
U6  - https://doi.org/10.1016/j.tet.2011.11.077
SN  - 0040-4020
VL  - 68
IS  - 4
SP  - 1097
EP  - 1104
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  -