Michael additions to metallocene analogues of chalcones

1987 ◽  
Vol 52 (1) ◽  
pp. 174-181 ◽  
Author(s):  
Jozef Federič ◽  
Štefan Toma
Keyword(s):  
Double Bond ◽  
Chemical Shift ◽  
Aryl Group ◽  
Chemical Shift Difference ◽  
Michael Additions ◽  
Methyl Malonate

Eleven analogues of chalcones were synthesized; the variously substituted ferrocenyl, ruthenocenyl or η5-cyclopentadienyltricarbonylmanganese are attached to the β-carbon of the chalcone double bond. Methyl malonate was added to eight selected chalcones. The effect of an aryl group on the chemical shift difference of diastereotopic -COOCH3 groups is discussed. The Vilsmeier-Haack formylation was employed to prepare 1'-chloro and 1'-bromoferrocenecarbaldehydes. The synthesis of 2-chloroferrocenecarbaldehyde from 2-chloroferrocenylmethyldimethylamine is also described.

Circular dichroism spectra of tetraamminecobalt(III) complexes of amino alcohols

1978 ◽  
Vol 31 (11) ◽  
pp. 2399 ◽  
Author(s):  
CJ Hawkins ◽  
GA Lawrance ◽  
JA Palmer
Keyword(s):  
Circular Dichroism ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Amino Alcohols ◽  
Circular Dichroism Spectra ◽  
Chemical Shift Difference ◽  
Solvent Dependence ◽  
Cotton Effects ◽  
Circular Dichroïsm ◽  
Chiral Amino Alcohols

The circular dichroism spectra are reported for tetraamminecobalt(III) complexes with the chiral amino alcohols 2-aminopropan-1-ol, 2- aminobutan-1-ol, 1-aminopropan-2-ol, 2-amino-1-phenyl-ethanol, ψ- ephedrine and ephedrine with the alcohol groups protonated (OH) and deprotonated (O-). The solvent dependence of the chemical shifts of the NH protons was investigated to determine the effects of stereoselective solvation on the circular dichroism, but, in contrast to some other related systems, the chemical shift difference between the two NH2 protons was relatively insensitive to solvent. Consistent with this, the circular dichroism spectra of the tetraphenylborate salts of the deprotonated complexes were found not to be markedly dependent on solvent. Tetraammine-{(-)-ψ-ephedrine)cobalt(III) and tetraammine{(-)- ephedrine}cobalt(III) were found to have the same signs of Cotton effects for the various d-d transitions, whereas bis{(-)-ψ- ephedrine}copper(II) and bis{(-)-ephedrine}copper(II) had opposite signs. This has been explained in terms of different conformer populations in the cobalt(III) and copper(II) systems.

17O nuclear magnetic resonance:mutual effect between two β oxygen atoms and α,β double bond effect on 17O chemical shift

Tetrahedron ◽  
1980 ◽  
Vol 36 (23) ◽  
pp. 3431-3435 ◽  
Author(s):  
Jean-Pirre Kintzinger ◽  
Claude Delseth ◽  
T.Thanh-tâm nguyên
Keyword(s):  
Double Bond ◽  
Chemical Shift ◽  
Bond Effect ◽  
Nuclear Magnetic ◽  
Oxygen Atoms

13C NMR spectroscopy of heterocycles: 3,5-diaryl-4-bromoisoxazoles

2015 ◽  
Vol 21 (5) ◽  
pp. 279-283 ◽  
Author(s):  
Jiayo Yu ◽  
Beatrice Edjah ◽  
Hector Argueta-Gonzalez ◽  
Stephanie Ross ◽  
Patrick Gaulden ◽  
...  
Keyword(s):  
Chemical Shift ◽  
Substituent Effects ◽  
13C Nmr Spectroscopy ◽  
Ring System ◽  
Aryl Group ◽  
Torsion Angles ◽  
Chemical Shift Data ◽  
Molecular Modeling Studies ◽  
Torsional Angles ◽  
Moderate Yield

AbstractA series of 3,5-diarylisoxazoles (1–9) underwent reaction with N-bromosuccinimide in acetic acid to yield the corresponding 3.5-diaryl-4-bromoisoxazoles (1Br–9Br) in low to moderate yield. The X-ray structure of 3-(4-chlorophenyl)-5-phenyl-4-bromoisoxazole showed torsion angles of ~40° and ~36° between the 3- and 5-aryl groups and the central ring system, respectively. Molecular modeling studies predicted the 3,5-phenylisoxazole ring system to be essentially coplanar and the 3,5-diphenyl groups of the 4-bromoisoxazole derivative to be twisted with torsional angles of 50° and 37°, respectively. Carbon-13 nuclear magnetic resonance (13C NMR) data of the 3,5-diaryl-4-bromoisoxazoles were obtained in dimethyl sulfoxide-d6 (DMSO-d6) at 50°C. Plots of the C4 chemical shift data for isoxazoles (1–9) vs. those for 4-bromoisoxazoles (1Br–9Br) showed a good linear correlation (r2 = 0.974) with a slope of 0.96. Substitution on the 3-aryl group had essentially no effect on the chemical shift for C4 of the 4-bromoisoxazole, whereas that on the 5-aryl group showed an excellent correlation with σ+ values. Despite the predicted torsion angle differences, distal transmission of substituent effects in the 4-bromo ring system was essentially analogous to that in the planar 3,5-diarylisoxazoles.

Correlations of NHN hydrogen bond energy with geometry and1H NMR chemical shift difference of NH protons for aniline complexes

2019 ◽  
Vol 150 (11) ◽  
pp. 114305 ◽  
Author(s):  
E. Yu. Tupikina ◽  
M. Sigalov ◽  
I. G. Shenderovich ◽  
V. V. Mulloyarova ◽  
G. S. Denisov ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Chemical Shift ◽  
Bond Energy ◽  
Nmr Chemical Shift ◽  
Hydrogen Bond Energy ◽  
Chemical Shift Difference

A concise approach for determining the relative configuration of H-7 and H-8 in 8,4′-oxyneolignans by 1H NMR spectroscopy

2019 ◽  
Vol 6 (7) ◽  
pp. 886-891 ◽  
Author(s):  
Ya-Nan Yang ◽  
Bing Han ◽  
Peng-Fei Yang ◽  
Zi-Ming Feng ◽  
Jian-Shuang Jiang ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Chemical Shift ◽  
1H Nmr ◽  
1H Nmr Spectroscopy ◽  
Relative Configuration ◽  
Chemical Shift Difference

The chemical shift difference between H-9a and H-9b can be used to accurately and rapidly determine the relative configuration of H-7 and H-8 in three types of 8,4′-oxyneolignan glucosides.

Determination of the Chemical-Shift Difference between the Lactate Multiplets and Its pH Dependence

1996 ◽  
Vol 112 (3) ◽  
pp. 236-239 ◽  
Author(s):  
Michael Bunse ◽  
Wulf-Ingo Jung ◽  
Günther Dietze ◽  
Otto Lutz
Keyword(s):  
Chemical Shift ◽  
Ph Dependence ◽  
Chemical Shift Difference

An investigation into the origins of polar substituent effects upon 19F chemical shifts, using 4-substituted β,β-difluorostyrenes

1980 ◽  
Vol 58 (8) ◽  
pp. 839-845 ◽  
Author(s):  
William F. Reynolds ◽  
Victoria G. Gibb ◽  
Nick Plavac
Keyword(s):  
Chemical Shift ◽  
Electron Density ◽  
Molecular Orbital ◽  
Excellent Agreement ◽  
Field Effect ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Molecular Orbital Calculations ◽  
Chemical Shift Difference ◽  
Polar Substituent

19F, 13C, and 1H chemical shifts have been determined for β,β-difluorostyrene and eight 4-substituted derivatives. The β-fluorine chemical shift difference, ΔδF, is used to evaluate the constant in the Buckingham equation. A = 3.0 × 10−11 esu for C—F bonds which is in excellent agreement with the value derived by Adcock and Khor. This allows accurate estimates of direct field effect contributions to 19F chemical shifts in aryl fluorides. Substituent parameter correlations demonstrate that the primary polar effect on 19F chemical shifts is field-induced π polarization. Abinitio molecular orbital calculations confirm that the substituent-induced 19F chemical shifts reflect changes in fluorine π electron density.

Sign in / Sign up

Export Citation Format

Share Document