1999
DOI: 10.1002/(sici)1097-458x(199904)37:4<259::aid-mrc442>3.0.co;2-6
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NMR of enaminones. part 6—17O and13C NMR study of tautomerization in Schiff bases

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Cited by 50 publications
(19 citation statements)
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“…The proton transfer equilibrium (Scheme 6) in Schiff bases has been investigated by NMR spectroscopy. [114][115][116][117][118][119][120][121][122][123][124][125][126][127][128][129][130] The description of the NH tautomer by only a keto structure is not adequate, and therefore the procedure for description of the NH form needs the application of at least two resonance structures (keto and zwitterionic). To Table 2.…”
Section: Nmr and Uv Investigations Of Tautomeric Equilibriummentioning
confidence: 99%
“…The proton transfer equilibrium (Scheme 6) in Schiff bases has been investigated by NMR spectroscopy. [114][115][116][117][118][119][120][121][122][123][124][125][126][127][128][129][130] The description of the NH tautomer by only a keto structure is not adequate, and therefore the procedure for description of the NH form needs the application of at least two resonance structures (keto and zwitterionic). To Table 2.…”
Section: Nmr and Uv Investigations Of Tautomeric Equilibriummentioning
confidence: 99%
“…Benzoannulation at positions 5,6 favors N ‐salicylideneamine (solutions in chloroform and acetonitrile) over its NH tautomer [i.e., aminomethylene‐1 H ‐naphthalene‐2‐one (2‐oxo‐1,2‐dihydro‐naphthylidene‐1‐amine)] 9. These compounds and some tautomers of 2‐acylmethylpyridines contain structurally similar fragments.…”
Section: Introductionmentioning
confidence: 99%
“…15 N chemical shifts can easily distinguish benzohydroxamic acid (δ = −200 to −220 ppm) and the corresponding hydroximic acid derivatives (δ = −110 to −150 ppm) as well [73]. Also, the 17 [74]. The tautomerism of 15 N-labeled isocytosine was reinvestigated in solution and in the solid state (Scheme 5.28) [75].…”
Section: Scheme 523mentioning
confidence: 99%
“…Both δ( 15 N) and 1 J N-H in the two tautomers are characteristically different and can be employed to study the equilibria [-N(1)=N-(δ N-1 = 119.4 ppm) -N(1)H-N= (δ N-1 = −42.6 ppm); δ N-2 = 219.8 ppm; 1 J N-1,NH = 96 Hz] [6] but model values are needed of the certain tautomers 66a,b (therefore reference compounds have to be included that exhibit no temperature dependence of the implemented NMR parameters [6,129], or the pure tautomers are computed theoretically) [130,131]. In addition, δ( 13 C) of a characteristically different aromatic ring carbon atom was used [74], the β-isotope effect [132] was employed, and the chemical exchange of the N-H protons was followed by nuclear Overhauser effect spectroscopy by NOESY experiments adopting various mixing times [133]. …”
Section: Azo-hydrazone Tautomerismmentioning
confidence: 99%