TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Laemmermann, Anica
A1  - Kühn, Heiner
T1  - Synthesis and NMR spectra of the syn and anti isomers of substituted cyclobutanes-evidence for steric and spatial hyperconjugative interactions
JF  - Tetrahedron
N2  - The syn and anti isomers of cis,cis-tricyclo[5.3.0.0(2.6)]dec-3-ene derivatives have been synthesized and their (1)H and (13)C NMR spectra unequivocally analyzed. Both their structures and their (1)H and (13)C NMR chemical shifts were calculated by DFT, the latter two calculations employing the GIAO perturbation method. Additionally, calculated NMR shielding values were partitioned into Lewis and non-Lewis contributions from the bonds and lone pairs involved in the molecules by accompanying NBO and NCS analyses. The differences between the syn and anti isomers were evaluated with respect to steric and spatial hyperconjugation interactions.
KW  - Conformational analysis
KW  - cis,cis-Tricyclo[5.3.0.0(2,6)]dec-3-enes
KW  - NMR
KW  - DFT calculation
KW  - NBO/NCS analysis
Y1  - 2011
U6  - https://doi.org/10.1016/j.tet.2011.02.012
SN  - 0040-4020
VL  - 67
IS  - 14
SP  - 2596
EP  - 2604
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Laemmermann, Anica
A1  - Kühn, Heiner
T1  - The anisotropic effect of functional groups in H-1 NMR spectra is the molecular response property of spatial nucleus independent chemical shifts (NICS)-Conformational equilibria of exo/endo tetrahydrodicyclopentadiene derivatives
JF  - Organic & biomolecular chemistry : an international journal of synthetic, physical and biomolecular organic chemistry
N2  - The inversion of the flexible five-membered ring in tetrahydrodicyclopentadiene (TH-DCPD) derivatives remains fast on the NMR timescale even at 103 K. Since the intramolecular exchange process could not be sufficiently slowed for spectroscopic evaluation, the conformational equilibrium is thus inaccessible by dynamic NMR. Fortunately, the spatial magnetic properties of the aryl and carbonyl groups attached to the DCPD skeleton can be employed in order to evaluate the conformational state of the system. In this context, the anisotropic effects of the functional groups in the H-1 NMR spectra prove to be the molecular response property of spatial nucleus independent chemical shifts (NICS).
Y1  - 2011
U6  - https://doi.org/10.1039/c0ob00356e
SN  - 1477-0520
VL  - 9
IS  - 4
SP  - 1098
EP  - 1111
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  -