Atropisomerism in Boron-Nitrogen Heterocycles/Atropisomerism in Boron-Nitrogen Heterocycles

1987 ◽  
Vol 42 (2) ◽  
pp. 191-194 ◽  
Author(s):  
Roland Köster ◽  
Günther Seidel ◽  
Susanna Kerschl ◽  
Bernd Wrackmeyer
Keyword(s):  
Elemental Analysis ◽  
Mass Spectra ◽  
Nitrogen Heterocycles ◽  
Spin Coupling ◽  
Trifluoromethyl Group ◽  
Hindered Rotation ◽  
First Derivative ◽  
Spin Spin Coupling ◽  
Spectroscopic Probe ◽  
Boron Nitrogen

Abstract Atropisomerism owing to hindered rotation about the N-aryl bond is observed in 4,5-diethyl-2,2,3-trimethyl-1-(o-trifluormethyl)phenyl-2,5-dihydro-1H-1,2,5-azasila-(2) and -azastanna-boroles (5). The compounds 2 and 5 are characterized by elemental analysis, mass spectra and 1H, 11B, 13 C, 29Si and119Sn NMR. The ortho-trifluoromethyl group serves as an additional NMR spectroscopic probe because of “through space” 19F-1H and 19F-13C spin spin coupling. Compound 5 is the first derivative of a 2,5-dihydro-1H-1,2,5-azastannaborol.

scholarly journals Spin-Spin Coupling Constants 1J(15N,11B) in Boron-Nitrogen Compounds. Experimental Data and DFT Calculations

2007 ◽  
Vol 62 (2) ◽  
pp. 220-224 ◽  
Author(s):  
Bernd Wrackmeyer ◽  
Oleg L. Tok
Keyword(s):  
Experimental Data ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Positive Sign ◽  
Nitrogen Compounds ◽  
Dft Methods ◽  
Spin Coupling Constants ◽  
Fermi Contact ◽  
Spin Spin Coupling ◽  
Boron Nitrogen

Boron-nitrogen compounds were studied with respect to indirect nuclear 15N-11B spin-spin coupling (1J(15N,11B)). Some new experimental data were determined for aminoboranes and tetra-Npyrrolylborate, and a variety of compounds with B-N single, double and triple bonds were examined using DFT methods for the calculation of 1J(15N,11B) at the B3LYP/6-311+G(d,p) level of theory. The calculations predict magnitude and sign of 1J(15N,11B) reasonably well, and the Fermi contact term was found to be dominant. A positive sign of 1J(15N,11B) was calculated in the case of 1-azacloso- dodecaborane(12), in contrast to all other compounds studied.

Signs of long-range proton–fluorine spin–spin coupling constants in 2-amino-5-bromobenzotrifluoride

1968 ◽  
Vol 46 (4) ◽  
pp. 652-654 ◽  
Author(s):  
D. J. Blears ◽  
S. S. Danyluk ◽  
T. Schaefer
Keyword(s):  
Long Range ◽  
Bond Order ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Trifluoromethyl Group ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling

The signs of the spin–spin coupling constants between the fluorine nuclei in the trifluoromethyl group and the ring protons in 2-amino-5-bromobenzotrifluoride are reported. [Formula: see text] and [Formula: see text] are negative while [Formula: see text] is positive. These signs are in agreement with fluorine contact shifts in certain Ni(II) chelates and therefore provide evidence for hyperconjugation of the CF3 group with the ring. The magnitude of [Formula: see text] is rather larger than expected on the basis of a relationship between the square of the bond order between the relevant ring carbons and the size of the coupling.

Long-range proton–19F spin–spin coupling interactions in phenyltrifluorosilane

1977 ◽  
Vol 55 (18) ◽  
pp. 3243-3247 ◽  
Author(s):  
William J. E. Parr ◽  
T. Schaefer ◽  
K. Marat
Keyword(s):  
Long Range ◽  
Resonance Spectrum ◽  
Base Point ◽  
Proton Magnetic Resonance Spectrum ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Hindered Rotation ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling ◽  
Coupling Mechanisms

Analysis of the proton magnetic resonance spectrum of phenyltrifluorosilane yields the spin–spin coupling constants between the fluorine nuclei and the protons. These are compared with the analogous long-range coupling constants in benzotrifluoride, toluene, and phenylsilane and are rationalized in terms of coupling mechanisms. The coupling over six bonds is assessed as a base point for the estimation of hindered rotation about the carbon–silicon bond.

Free Energy Barrier to Rotation of the Amino Group in 2-Aminoacetophenone

1971 ◽  
Vol 49 (21) ◽  
pp. 3575-3576 ◽  
Author(s):  
R. Wasylishen ◽  
T. Schaefer
Keyword(s):  
Free Energy ◽  
Accurate Determination ◽  
Activation Parameters ◽  
Spin Coupling ◽  
Molecular Orbital Calculations ◽  
Free Energy Barrier ◽  
Amino Group ◽  
Hindered Rotation ◽  
Free Energy Of Activation ◽  
Spin Spin Coupling

The free energy of activation for hindered rotation of the amino group about the N-aryl bond in 2-aminoacetophenone is found to be 10.6 ± 0.5 kcal/mol in toluene solution at 233 ± 10 °K. Separate amino p.m.r. peaks are observed at low temperatures and these are strongly broadened by incompletely relaxed spin–spin coupling to the quadrupolar 14N nucleus, making a more accurate determination of activation parameters impractical. Some INDO molecular orbital calculations are performed in an attempt to rationalize the barrier magnitude.

Vibrational and thermal averaging of the indirect nuclear spin-spin coupling constants of CH4, SiH4, GeH4 and SnH4

1997 ◽  
Vol 91 (5) ◽  
pp. 897-907 ◽  
Author(s):  
SHEELA KIRPEKAR ◽  
THOMAS ENEVOLDSEN ◽  
JENS ODDERSHEDE ◽  
WILLIAM RAYNES
Keyword(s):  
Nuclear Spin ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling

Synthesis and Anticonvulsant Activity of 3-(alkylamino, alkoxy)-1,3,4,5- Tetrahydro-2H-benzo [b] azepine-2-one Derivatives

2018 ◽  
Vol 17 (6) ◽  
pp. 448-457 ◽  
Author(s):  
Xia Huang ◽  
Tie Chen ◽  
Rong-Bi Han ◽  
Feng-Yu Piao
Keyword(s):  
1H Nmr ◽  
Elemental Analysis ◽  
13C Nmr ◽  
Anticonvulsant Activity ◽  
Mass Spectra ◽  
Maximal Electroshock ◽  
Test Compound ◽  
Maximal Electroshock Test ◽  
Mes Test ◽  
Structure Activity

Background & Objective: A series of novel 3-Substituted-1,3,4,5-Tetrahydro-2H-benzo [b] azepine-2-one Derivatives (4, 5, 7, 10, 12, 5a-j, 8a-e) were synthesized from 1,2,3,4-Tetrahydro-1- naphthalenone. The structures of these compounds were confirmed by IR, 1H NMR, 13C NMR, MASS spectra and elemental analysis. Their anticonvulsant activity was evaluated by the maximal electroshock (MES) test, subcutaneous pentylenetetrazol (scPTZ) test, and their neurotoxicity was evaluated by the rotarod neurotoxicity test. Compound 4 showed the maximum anticonvulsant activity against the maximal electroshock test (ED50=26.4, PI =3.2) and against the subcutaneous pentylenetetrazol test (ED50=40.2, PI =2.1). Conclusion: Possible structure-activity relationship was discussed.

Structural Characterization of Natural Products By Means of Quantum Chemical Calculations of NMR Parameters: New insights

2021 ◽  
Author(s):  
Fabio Luiz Paranhos Costa ◽  
Ana Carolina Ferreira de Albuquerque ◽  
Rodolfo Goetze Fiorot ◽  
Luciano Morais Lião ◽  
Lucas Haidar Martorano ◽  
...  
Keyword(s):  
Natural Products ◽  
Structural Characterization ◽  
Quantum Chemical ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Nmr Parameters ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling

The calculation of NMR parameters for natural products was pioneered by Bifulco and coworkers in 2002. Since then, modelling 1H and 13C chemical shifts and spin-spin coupling constants for this...

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