Use of 1H NMR chemical shifts to determine the absolute configuration and enantiomeric purity for enantiomers of 3,3′-disubstituted-MeO-BIPHEP derivatives

2006 ◽  
Vol 84 (2) ◽  
pp. 93-98 ◽  
Author(s):  
Evgueni Gorobets ◽  
Masood Parvez ◽  
Bronwen MM Wheatley ◽  
Brian A Keay
Keyword(s):  
Chemical Shift ◽  
Absolute Configuration ◽  
Chemical Shifts ◽  
Enantiomeric Purity ◽  
Methoxyl Group ◽  
Nmr Spectrum ◽  
Nmr Chemical Shifts ◽  
H Nmr ◽  
Asymmetric Heck Reaction ◽  
The Absolute

The absolute configuration of a series of 3,3′-disubstituted-MeO-BIPHEP derivatives can be determined by the 1H NMR chemical shift of the methoxyl group when the 3,3′-disubsituted-MeO-BIPHEP derivative is mixed with (–)-(2R,3R)-dibenzoyltartaric acid ((–)-DBTA) (1:2) and its NMR spectrum is run in CDCl3. The chemical shift of the methoxyl group in the Sax enantiomer always occurred at higher field than the corresponding Rax enantiomer. Integration of the corresponding methoxyl signals provides the enantiomeric purity of any mixtures.Key words: assignment of absolute configuration, 2,2′-bis(diphenylphosphino)-1,1′-biaryls, MeO-BIPHEP derivatives, asymmetric Heck reaction, 1H NMR chemical shifts.

scholarly journals NMR spectroscopic properties of furo[2′,3′:4,5]pyrrolo[1,2-d][1,2,4]triazine derivatives

2017 ◽  
Vol 16 (2) ◽  
pp. 147-151 ◽  
Author(s):  
Ivana Zemanová ◽  
Renata Gašparová
Keyword(s):  
Chemical Shift ◽  
Carbonyl Group ◽  
Chemical Shifts ◽  
Spectroscopic Properties ◽  
Chloromethyl Group ◽  
Nmr Chemical Shifts ◽  
H Nmr ◽  
Triazine Derivatives ◽  
C Nmr ◽  
Electron Withdrawing Substituents

Abstract The 1H and 13C NMR spectroscopic properties of a series of furo[2′,3′:4,5]pyrrolo[1,2-d][1,2,4]triazin-8(7H)-ones and -thiones were investigated. The influence of various electron donating as well as electron withdrawing substituents at C-5 or N-7 on 1H NMR chemical shifts as well as 13C chemical shifts at C8 were observed. The 5-chloromethyl group had a little influence on the chemical shift of H-7 proton and the 8-thione group causes deshielding of H-7 as well as H-5 protons in comparison with the C-8 carbonyl group.

scholarly journals Spektroskopische Untersuchungen an Cyclopentadienyl-dinitrosylvanadium-Komplexen CpV(NO)2L (L = Lewis-Base) / Spectroscopic Studies with Cyclopentadienyl Dinitrosylvanadium Complexes CpV(NO)2L (L = Lewis Base)

1982 ◽  
Vol 37 (5) ◽  
pp. 614-619 ◽  
Author(s):  
Max Herberhold ◽  
Herbert Trampisch
Keyword(s):  
Chemical Shift ◽  
Chemical Shifts ◽  
Spectroscopic Studies ◽  
Lewis Base ◽  
Nmr Chemical Shift ◽  
Nmr Chemical Shifts ◽  
Lewis Bases ◽  
H Nmr ◽  
Ligand Atom

Displacement of the CO ligand in CpV(NO)2CO (Cp = η5-cyclopentadienyl) by various Lewis bases (L) in solution leads to a series of (28) complexes CpV(NO)2L which were characterised by the 51V NMR chemical shift, the 13C and 1H NMR chemical shifts of the cyclopentadienyl ring, and by the NO stretching frequencies of the two nitrosyl ligands. The chemical shift δ(51V) varies over the range of ca. -1300 and -500 ppm depending on the nature of L, whereas δ(13C) of the cyclopentadienyl ring varies only between 98 and 102 ppm. The shielding of the 51V and 13C nuclei decreases as the electronegativity of the ligand atom bound to the metal increases in the order P <S <N <O

Assignment techniques for 29Si NMR chemical shifts in pertrimethylsilylated products. Tests of empirical assignment rules by a modified 29Si indor

1985 ◽  
Vol 50 (2) ◽  
pp. 343-347 ◽  
Author(s):  
Jan Schraml ◽  
Michail Fedorovich Larin ◽  
Vadim Aleksandrovich Pestunovich
Keyword(s):  
Chemical Shifts ◽  
29Si Nmr ◽  
Additivity Rule ◽  
Nmr Spectrum ◽  
Nmr Chemical Shifts ◽  
H Nmr ◽  
Modified Method ◽  
Nmr Methods

A modification of the 29Si INDOR technique is described that monitors instead of the usual Si(CH3)3 proton line the line of CHnXSi (n = 1, 2; X = O, S, NH) protons while the 29Si NMR spectrum is being scanned. Though less sensitive and accurate than the routine INDOR, the modified method permits assignment of 29Si chemical shifts providing that the CHn proton lines in 1H NMR spectrum are well separated and assigned. The modified INDOR is used here to assign the 29Si chemical shifts in pertrimethylsilylated 1,6-anhydro-β-D-glucopyranose (1) and methyl β-D-xylopyranoside (2). The values of chemical shifts determined by this technique agree with those determined by standard 29Si NMR methods but the assignment suggested for 1 on empirical grounds previously must be partially revised, the empirical assignment in the spectrum of 2 (based on additivity rule) is fully confirmed.

THE RELATION OF 15N NMR, 1H NMR CHEMICAL SHIFTS WITH THE ATOMIC NET CHARGE AND MOLECULAR STRUCTURES

1987 ◽  
Vol 3 (06) ◽  
pp. 632-637
Author(s):  
Chen Yuehua ◽  
◽  
Guo Guolin ◽  
Shen Qifeng ◽  
Zhao Yufen ◽  
...  
Keyword(s):  
Chemical Shifts ◽  
Molecular Structures ◽  
Net Charge ◽  
Nmr Chemical Shifts ◽  
H Nmr

scholarly journals A New Bisabolene from Stevia tomentosa

2011 ◽  
Vol 6 (9) ◽  
pp. 1934578X1100600
Author(s):  
Alejandro Valdez-Calderón ◽  
J. Martín Torres-Valencia ◽  
J. Jesús Manríquez-Torres ◽  
René Velázquez-Jiménez ◽  
Mario A. Gómez-Hurtado ◽  
...  
Keyword(s):  
Absolute Configuration ◽  
Coupling Constants ◽  
Spectral Studies ◽  
Dihedral Angles ◽  
Model Compounds ◽  
H Nmr ◽  
Aerial Parts ◽  
The Absolute

The new sesquiterpene (1 R,2 R,3 R,6 R,7 S)-1-acetoxy-2,3-dmydroxy-2,3-dihydrobisabolene (3) together with ten known terpenes and three known flavonoids were isolated from the aerial parts and from the roots of Stevia tomentosa. The structure of 3 follows from spectral studies, the relative chirality at C-3 follows from 1H NMR coupling constants comparison with the corresponding calculated values obtained by applying a generalized Karplus-type relationship to the dihedral angles of model compounds, and the absolute configuration is assumed in analogy to known (2 R,3 R,6 R,7 S)-2,3-epoxy-2,3-dihydrobisabolen-1-one (2).

Origin of the 29Si NMR chemical shift in R3Si–X and relationship to the formation of silylium (R3Si+) ions

2020 ◽  
Vol 49 (45) ◽  
pp. 16453-16463 ◽  
Author(s):  
Winn Huynh ◽  
Matthew P. Conley
Keyword(s):  
Chemical Shift ◽  
Chemical Shifts ◽  
29Si Nmr ◽  
Surface Oxygen ◽  
Nmr Chemical Shift ◽  
Dft Methods ◽  
Nmr Chemical Shifts

The origin in deshielding of 29Si NMR chemical shifts in R3Si–X, where X = H, OMe, Cl, OTf, [CH6B11X6], toluene, and OX (OX = surface oxygen), as well as iPr3Si+ and Mes3Si+ were studied using DFT methods.

scholarly journals Determination of the Absolute Configuration of 19-OH-(-)-Eburnamonine Using a Combination of Residual Dipolar Couplings, DFT Chemical Shift Predictions, and Chiroptics

2012 ◽  
Vol 7 (6) ◽  
pp. 1934578X1200700 ◽  
Author(s):  
Pablo Trigo-Mouriño ◽  
Roxana Sifuentes ◽  
Armando Navarro-Vázquez ◽  
Chakicherla Gayathri ◽  
Helena Maruenda ◽  
...  
Keyword(s):  
Chemical Shift ◽  
Absolute Configuration ◽  
Residual Dipolar Couplings ◽  
Indole Alkaloid ◽  
Dipolar Couplings ◽  
The Absolute ◽  
Natural Derivative ◽  
High Level ◽  
Configuration And Conformation

19-OH-(-)-eburnamonine 1 is a new indole alkaloid isolated from Bonafusia macrocalyx. A natural derivative from (-)-eburnamonine for which absolute configuration and conformation has been determined by making use of residual dipolar couplings enhanced NMR, circular dichroism spectra and high-level computations.

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