Chemical shift non-equivalence of methylene protons adjacent to an asymmetric nitrogen atom

1971 ◽  
Vol 3 (2) ◽  
pp. 249-253 ◽  
Author(s):  
A. Vigevani ◽  
B. Gioia ◽  
B. Cavalleri ◽  
G. G. Gallo
Keyword(s):  
Chemical Shift ◽  
Nitrogen Atom ◽  
Asymmetric Nitrogen

ChemInform Abstract: Asymmetric Nitrogen. Part 52. Nucleophilic Substitution at the Nitrogen Atom of N-Chloro-N-alkoxyamides.

ChemInform ◽  
1987 ◽  
Vol 18 (15) ◽  
Author(s):  
V. F. RUDCHENKO ◽  
S. M. UGNOTOV ◽  
V. S. NOSOVA ◽  
I. I. CHERVIN ◽  
R. G. KOSTYANOVSKII
Keyword(s):  
Nitrogen Atom ◽  
Nucleophilic Substitution ◽  
Asymmetric Nitrogen

ChemInform Abstract: Asymmetric Nitrogen. Part 68. Geminal Systems. Part 42. A Diastereomeric NH-Dialkoxyamine with an Asymmetric Nitrogen Atom in an Open Chain.

ChemInform ◽  
1989 ◽  
Vol 20 (31) ◽  
Author(s):  
V. F. RUDCHENKO ◽  
I. I. CHERVIN ◽  
V. N. VOZNESENSKII ◽  
V. S. NOSOVA ◽  
R. G. KOSTYANOVSKII
Keyword(s):  
Nitrogen Atom ◽  
Open Chain ◽  
Asymmetric Nitrogen

Asymmetric nitrogen. 68. Geminal systems. 42. Diastereomeric NH-dialkoxyamines with an asymmetric nitrogen atom in an open chain

1988 ◽  
Vol 37 (12) ◽  
pp. 2513-2516
Author(s):  
V. F. Rudchenko ◽  
I. I. Cher'vin ◽  
V. N. Voznesenskii ◽  
V. S. Nosova ◽  
R. G. Kostyanovskii
Keyword(s):  
Nitrogen Atom ◽  
Open Chain ◽  
Asymmetric Nitrogen

14N nuclear magnetic resonance: amines and ammonium ions

1969 ◽  
Vol 47 (8) ◽  
pp. 1321-1325 ◽  
Author(s):  
M. Witanowski ◽  
H. Januszewski
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Nitrogen Atom ◽  
Excited States ◽  
Ammonium Ion ◽  
Ammonium Ions ◽  
Alkyl Groups ◽  
Phenyl Vinyl ◽  
Nuclear Magnetic

The 14N nuclear magnetic resonance (n.m.r.) signals of alkylamines and ammonium ions are shifted to lower magnetic fields with the increasing number of alkyl groups at the carbon atom directly bonded to the nitrogen atom, and at the nitrogen atom itself. The resonance of an ammonium ion always occurs at a field lower than that for the corresponding amine. It seems that high-lying excited states, not only those corresponding to lowest-wavelength transitions, are important for an explanation of the observed resonance shifts. A downfield shift of the 14N resonance and a substantial increase in signal width, as compared with the spectra of neat amines, are observed for aqueous solutions of amines. There is a very characteristic chemical shift for the R—CH2—NH2 molecules (R = alkyl, phenyl, vinyl) in the 14N n.m.r. spectra.

Sulfur-free penicillin derivatives. VII. Multiple functionalization of 2-azetidinyl-3-methyl-2-butenoates

1982 ◽  
Vol 60 (2) ◽  
pp. 144-153 ◽  
Author(s):  
Saul Wolfe ◽  
Chia-Cheng Shaw
Keyword(s):  
Magnetic Resonance ◽  
Chemical Shift ◽  
Nitrogen Atom ◽  
Proton Magnetic Resonance ◽  
Methylene Chloride ◽  
Methyl Groups ◽  
Reliable Criterion ◽  
Geometrical Isomers ◽  
Methoxycarbonyl Group ◽  
Magnetic Resonance Spectra

The title compounds, substituted with chlorine in the 4′-position and with phthalimido, 2,2,2-trichloroethoxycarbonylamino, or phenoxycarbonylamino in the 3′-position of the azetidinone ring, have been converted to bis-allylic formates via bromination of both methyl groups with excess N-bromosuccinimide, and displacement of both bromines by formate ions in methylene chloride solvent. The diformates react smoothly with a deficit of a boron halide to form E/Z mixtures of halogeno-formates, in which the E-isomer predominates. Depending on the 3′-azetidinyl substituent, these halogeno-formates undergo a second displacement with acetate either with retention of olefinic geometry or inversion of olefinic geometry. The mechanisms of these reactions are discussed, along with further transformations leading to hydroxylactones, halogenolactones, halogenohydrins, and other compounds. Examination of the proton magnetic resonance spectra of twenty-one compounds reveals that methylene protons cis to the β-lactam nitrogen atom of a methyl 2-azetidinyl-2-butenoate are found at higher field than methylene protons cis to the methoxycarbonyl group. This observation appears to provide a more reliable criterion for the assignment of configuration to geometrical isomers than one based on the magnitude of the chemical shift nonequivalence of the E and Z methylene protons.

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