Multinuclear 1H, 13C and 15N NMR study of some substituted 2-amino-4-nitropyridines and their N-oxides

Laihia, Katri; Kolehmainen, Erkki; Kauppinen, Reijo; Lorenc, J.; Puszko, Aniela

doi:10.1016/s1386-1425(01)00583-2

Cited by 27 publications

(13 citation statements)

References 25 publications

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“…The structures of substituted pyridine N-oxides (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18) and pyridines (19)(20)(21)(22)(23)(24)(25)(26)(27) are presented in Fig. 1.…”

Section: Resultsmentioning

confidence: 99%

“…In 2-nitramino-4-nitropyridine N-oxides and related pyridines, the tautomeric equilibria were again manifested by the 15 N NMR chemical shifts. 2 However, it was thought worthwhile to reinvestigate the tautomeric properties for a large and diverse set of novel nitramino-and 4-nitro-2-nitraminopyridine N-oxides and 2-nitramino-and 4-nitro-2-nitraminopyridines using their 1 H, 13 C and 15 N chemical shifts, ab initio/HF calculations and x-ray diffraction methods.…”

Section: Introductionmentioning

confidence: 99%

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¹H, ¹³C and ¹⁵N NMR spectroscopic, x‐ray structural and ab initio/HF studies on nitramino and N‐alkylamino‐4‐nitro derivatives of pyridine N‐oxides and pyridines

Laihia

Kolehmainen

Virtanen

et al. 2003

Magnetic Reson in Chemistry

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“…The structures of substituted pyridine N-oxides (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18) and pyridines (19)(20)(21)(22)(23)(24)(25)(26)(27) are presented in Fig. 1.…”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

¹H, ¹³C and ¹⁵N NMR spectroscopic, x‐ray structural and ab initio/HF studies on nitramino and N‐alkylamino‐4‐nitro derivatives of pyridine N‐oxides and pyridines

Laihia

Kolehmainen

Virtanen

et al. 2003

Magnetic Reson in Chemistry

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“…The assignments of 13 C NMR chemical shifts (Table 2) are based on literature data and substituent induced chemical shifts [6,[23][24][25] as well as homo-and heteronuclear 2D chemical shift correlation measurements. When C-2 in pyridine N-oxide is substituted with an amino group the ipso carbon chemical shift changes from 138.2 ppm [25] (6), the 2-ipso carbon is 1.11 (5) and 2.18 ppm (6) shielded from that of 1.…”

Section: Nmr Shiftsmentioning

confidence: 99%

“…It means that these compounds exist mainly as amino tautomers [6,23,24]. In neat pyridine N-oxide, the corresponding d( 15 N) is -86.8 ppm [25].…”

Section: N Nmr Shiftsmentioning

confidence: 99%

“…When the molar ratio of the imino form in the tautomer balance is increasing, the d( 15 N) of ring nitrogen becomes more shielded varying from -124.1 to -168.7. In 4-nitro derivatives with secondary 2-amino substituent, d( 15 N) of ring varies from -112.8 to -120.9 ppm [22] and in 5-nitro derivatives with secondary 2-amino substituent from -128.4 to -129.5 [24]. d( 15 N) of ring in pyridine N-oxide and 2-aminopyridine N-oxide are -86.6 ppm [6] and -126.1 ppm, respectively.…”

Section: N Nmr Shiftsmentioning

confidence: 99%

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Specificity of 15N NMR chemical shifts to the nature of substituents and tautomerism in substituted pyridine N-oxides

et al. 2012

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1 H, 13 C, and 15 N NMR chemical shifts have been measured for 2-aminopyridine N-oxide (1), its eleven derivatives (2-10, 13, 14), and 3-Cl and 3-Br substituted 4-nitropyridine N-oxides (11, 12). d( 15 N) of pyridine ring nitrogen in 2-acetylaminopyridine N-oxides are 5.9-11.5 ppm deshielded from those in 2-aminopyridine N-oxides. When amino and acetylamino substituents are in 4-position, d( 15 N) of ring nitrogen is 21.3 ppm deshielded in the acetylated derivative. The strong resonance interaction between 2-amino and 5-nitro groups reflects in the decrease of amino nitrogen shielding about 5.3-17.9 ppm. Also, 1 H and 13 C NMR spectral data are in agreement with 15 N NMR results reflected as deshielded amino protons and carbons C-2 and C-5. The pyridine nitrogen chemical shift in all amino-and acetylamino derivatives vary between -101.2 and -126.7 ppm, which has been connected with the tautomeric balance in our earlier studies.

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Utilizing Long-Range¹H-¹⁵N 2-D NMR Spectroscopy for Chemical Structure Elucidation and Confirmation

Martin

Williams²

2010

Encyclopedia of Magnetic Resonance

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H detection for an equal number of nuclei, the relative sensitivity of 15 N is 0.00194; relative to 13 C at natural isotopic abundance, the relative sensitivity is 0.0214. 8 These attributes conspire to make measuring times long and sample requirements rather high, with larger diameter tubes preferable. When we consider X-nucleus excitation and detection, and compare 1 H/ 13 C correlation experiments to 1 H/ 15 N the time to attain equal s/n ratios is ~100 times longer for 1 H/ 15 N than for 1 H/ 13 C. Consequently, there is a relatively rich body of literature involving 1 H/ 13 C heteronuclear correlation with 13 C detection while there is virtually none for the 1 H/ 15 N heteronuclide pair. When we consider 1 H excitation and X-nucleus detection, the disadvantage for 1 H/ 15 N relative to 1 H/ 13 C drops to a factor of 15.6. When we compare these methods to contemporary 1 H excitation and detection, the disadvantage is erased. 17 Consequently, there is a rich and growing body of applications of both direct and long-range 1 H-15 N heteronuclear shift correlation in chemical structure elucidation. [1][2][3][4] Spectrometer and Probe ConsiderationsIf an investigator has a choice of instruments on which to acquire 1 H-15 N heteronuclear shift correlation data, it is usually beneficial to use higher field instruments up to a point. 15 N has a very wide spectral range comprising more than 900 ppm from one extreme to the other. More practically, the spectral range for a given compound is usually <500 ppm and in most cases is in the range of 300-350 ppm or less for natural products containing both aromatic and aliphatic 15 N resonances. Going from 400-500 MHz instruments to higher field instruments, perhaps 700-800 MHz, affords higher sensitivity but as the spectral width to be excited increases with observation frequency, so

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Multinuclear 1H, 13C and 15N NMR study of some substituted 2-amino-4-nitropyridines and their N-oxides

Cited by 27 publications

References 25 publications

¹H, ¹³C and ¹⁵N NMR spectroscopic, x‐ray structural and ab initio/HF studies on nitramino and N‐alkylamino‐4‐nitro derivatives of pyridine N‐oxides and pyridines

¹H, ¹³C and ¹⁵N NMR spectroscopic, x‐ray structural and ab initio/HF studies on nitramino and N‐alkylamino‐4‐nitro derivatives of pyridine N‐oxides and pyridines

Specificity of 15N NMR chemical shifts to the nature of substituents and tautomerism in substituted pyridine N-oxides

Utilizing Long-Range¹H-¹⁵N 2-D NMR Spectroscopy for Chemical Structure Elucidation and Confirmation

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Multinuclear 1H, 13C and 15N NMR study of some substituted 2-amino-4-nitropyridines and their N-oxides

Cited by 27 publications

References 25 publications

1H, 13C and 15N NMR spectroscopic, x‐ray structural and ab initio/HF studies on nitramino and N‐alkylamino‐4‐nitro derivatives of pyridine N‐oxides and pyridines

1H, 13C and 15N NMR spectroscopic, x‐ray structural and ab initio/HF studies on nitramino and N‐alkylamino‐4‐nitro derivatives of pyridine N‐oxides and pyridines

Specificity of 15N NMR chemical shifts to the nature of substituents and tautomerism in substituted pyridine N-oxides

Utilizing Long-Range1H-15N 2-D NMR Spectroscopy for Chemical Structure Elucidation and Confirmation

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¹H, ¹³C and ¹⁵N NMR spectroscopic, x‐ray structural and ab initio/HF studies on nitramino and N‐alkylamino‐4‐nitro derivatives of pyridine N‐oxides and pyridines

¹H, ¹³C and ¹⁵N NMR spectroscopic, x‐ray structural and ab initio/HF studies on nitramino and N‐alkylamino‐4‐nitro derivatives of pyridine N‐oxides and pyridines

Utilizing Long-Range¹H-¹⁵N 2-D NMR Spectroscopy for Chemical Structure Elucidation and Confirmation