TY - JOUR
A1 - Shainyan, Bagrat A.
A1 - Moskalik, Mikhail Yu
A1 - Heydenreich, Matthias
A1 - Kleinpeter, Erich
T1 - Conformational equilibrium and dynamic behavior of bis-N-triflyl substituted 3,8-diazabicyclo[3.2.1]octane
JF - Magnetic resonance in chemistry
N2 - Restricted rotation about the N-S partial double bonds in a bis-N-triflyl substituted 3,8-diazabicyclo[3.2.1]octane derivative 1 has been frozen at low temperature (Delta G* = 11.6 kcal mol(-1)), and the existence of all four rotamers about the two N-S bonds, 3-in, 8-in, 3-in, 8-out, 3-out, 8-in, and 3-out, 8-out, respectively, proved experimentally by NMR spectroscopy and theoretically by DFT and MP2 calculations. Copyright (C) 2014 John Wiley & Sons, Ltd.
KW - NMR
KW - H-1
KW - C-13
KW - F-19
KW - Dynamic NMR
KW - Conformational equilibrium
KW - restricted N-S rotation
Y1 - 2014
U6 - http://dx.doi.org/10.1002/mrc.4086
SN - 0749-1581 (print)
SN - 1097-458X (online)
VL - 52
IS - 8
SP - 448
EP - 452
PB - Wiley-Blackwell
CY - Hoboken
ER -
TY - JOUR
A1 - Wessig, Pablo
A1 - Pick, Charlotte
T1 - Photochemical synthesis and properties of axially chiral naphthylpyridines
JF - Journal of photochemistry and photobiology : A, Chemistry
N2 - Five alkynyl pyridines were prepared and cyclized to naphthylpyridines as the main products in the course of a Photo-Dehydro-Diels-Alder reaction. Four of the final products are axially chiral and the determination of the rotational barrier by DFT calculations, dynamic NMR and H PLC experiments is demonstrated. (C) 2011 Elsevier B.V. All rights reserved.
KW - Photochemistry
KW - Axial chirality
KW - Photo-Dehydro-Diels-Alder reaction
KW - Dynamic NMR
KW - Dynamic HPLC
KW - Molecular modeling
Y1 - 2011
U6 - http://dx.doi.org/10.1016/j.jphotochem.2011.06.006
SN - 1010-6030 (print)
VL - 222
IS - 1
SP - 263
EP - 265
PB - Elsevier
CY - Lausanne
ER -
TY - JOUR
A1 - Shainyan, Bagrat A.
A1 - Kleinpeter, Erich
T1 - Conformational preferences of Si-Ph,H and Si-Ph,Me silacyclohexanes and 1,3-thiasilacyclohexanes. Additivity of conformational energies in 1,1-disubstituted heterocyclohexanes
JF - Tetrahedron
N2 - The conformational equilibria of 1-phenyl-1-silacyclohexane 1, 3-phenyl-1,3-thiasilacyclohexane 2, 1-methyl-1-phenyl-1-silacyclohexane 3, and 3-methyl-3-phenyl-1,3-thiasilacyclohexane 4 have been studied for the first time by low temperature C-13 NMR spectroscopy at 103 K. Predominance of the equatorial conformer of compound 1 (Ph-eq/Ph-ax=78%:22%) is much less than in its carbon analog, phenylcyclohexane (nearly 100% of Ph-eq). And in contrast to 1-methyl-1-phenylcyclohexane, the conformers with the equatorial Ph group are predominant for compounds 3 and 4: at 103 K, Ph-eq/Ph-ax ratios are 63%:37% (3) and 68%:32% (4). As the Si-C bonds are elongated with respect to C-C bonds, the barriers to ring inversion are only between 5.2-6.0 (ax -> eq) and 5.4-6.0 (eq -> ax) kcal mol(-1). Parallel calculations at the DFT and MP2 level of theory (as well as the G2 calculations for compound 1) show qualitative agreement with the experiment. The additivity/nonadditivity of conformational energies of substituents on cyclohexane and silacyclohexane derivatives is analyzed. The geminally disubstituted cyclohexanes containing a phenyl group show large deviations from additivity, whereas in 1-methyl-1-phenyl-1-silacyclohexane and 3-methyl-3-phenyl-1,3-thiasilacyclohexane the effects of the methyl and phenyl groups are almost additive. The reasons for the different conformational preferences in carbocyclic and heterocyclic compounds are analyzed using the homodesmotic reactions approach.
KW - Conformational analysis
KW - Heterocycles
KW - Dynamic NMR
KW - Theoretical calculations
KW - Additivity of conformational energies
Y1 - 2012
U6 - http://dx.doi.org/10.1016/j.tet.2011.10.082
SN - 0040-4020 (print)
VL - 68
IS - 1
SP - 114
EP - 125
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 - http://dx.doi.org/10.1016/j.tet.2011.11.077
SN - 0040-4020 (print)
VL - 68
IS - 4
SP - 1097
EP - 1104
PB - Elsevier
CY - Oxford
ER -
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 - http://dx.doi.org/10.1016/j.tet.2012.01.022
SN - 0040-4020 (print)
VL - 68
IS - 10
SP - 2363
EP - 2373
PB - Elsevier
CY - Oxford
ER -