Nmr spectral characteristics of N‐H protons in purine derivatives

Twanmoh, Li-Ming; Wood, Harry B.; Driscoll, John S.

doi:10.1002/jhet.5570100210

Cited by 50 publications

(16 citation statements)

References 12 publications

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“…The corresponding signal to (N7-H) has been not observed. The assignments of these signals are in accordance with the bibliographic data for other methylxanthine derivatives (7,8).…”

Section: Preparatiorl Of the M(tm)?(nh)? Compoundssupporting

confidence: 82%

1,3,8-Trimethylxanthine complexes of Cu(II), Zn(II), Cd(II), and Hg(II)

1983

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New 1,3,8-trimethylxanthine complexes of Cu(II), Zn(II), Cd(II), and Hg(II) were prepared and studied by ir, H-nmr, magnetic measurements, TG, and DSC techniques. In the Cu(II), Zn(II), and Cd(II) complexes, the 1,3,8-trimethylxanthine is present in anionic form and the coordination to metal ion occurs probably through N7 atom. In the mercury complex, coordination to metal ion is realized via the N9 atom of neutral TMH.

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“…The corresponding signal to (N7-H) has been not observed. The assignments of these signals are in accordance with the bibliographic data for other methylxanthine derivatives (7,8).…”

Section: Preparatiorl Of the M(tm)?(nh)? Compoundssupporting

confidence: 82%

1,3,8-Trimethylxanthine complexes of Cu(II), Zn(II), Cd(II), and Hg(II)

1983

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“…Furthermore, from Table 2 the energy difference between DTP(1,3,9)W1 and DTP (1,3,7)W1 is 38.1 kJ•mol -1 , which is less by 6.0 kJ•mol -1 than that in the gas. This shows that in the gas phase environment DTP (1,3,7) and DTP (1,3,9) clusters with water molecules are observed.…”

Section: Proton Transfer Reaction With One Water Catalysismentioning

confidence: 82%

“…Figure 1 gives the structure of the most stable N7(H) and N9(H) tautomers [that is named as DTP (1,3,7) and DTP (1,3,9), and the numbers of 1,3,7 and 1,3,9 stand for the number of the nitrogen atoms to which the hydrogens are attached]. Table 1 show that DTP (1,3,9) is higher than DTP (1,3,7) in energy by 44.1 kJ•mol -1 at B3LYP/6-311＋G(d,p). We focus on the tautomerization reaction between DTP (1,3,7) and DTP (1,3,9).…”

Section: Resultsmentioning

confidence: 99%

“…The results indicated that the dithiol DTP (9,10,11) exists in the gas phase and the dithione DTP (1,3,9) is in the aqueous phase predominantly. For DTP (1,3,7) and DTP (1,3,9) tautomers, it is much closer in energies in the aqueous than in the gas phase. Hanna et al 11 have investigated the tautomerism of 2,6-dithiopurine by the infrared spectroscopies and quantum-mechanical calculations [B3LYP/6-31G(d,p)].…”

Section: Introductionmentioning

confidence: 94%

“…[7][8][9][10][11] Twanmoh et al 7 have reported the NMR spectra of the compound, showing that the predominant tautomer is dithione form with the imidazole proton on N(7) in dimethyl sulphoxide-d 6 solution. This result differs from UV spectroscopy, 8 indicating that the predominant tautomer exists in the dithione DTP (1,3,9), with the imidazole proton on N(9).…”

Section: Introductionmentioning

confidence: 99%

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A Theoretical Investigation on N7(H)→N9(H) Tautomerization of Isolated and Monohydrated 2,6‐Dithiopurine Combined with IPCM Solvent Model

Ren

Wang²,

Wang

et al. 2010

Chin. J. Chem.

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The tautomerization reaction mechanism has been reported between N7(H) and N9(H) of isolated and monohydrated 2,6-dithiopurine using B3LYP/6-311＋G(d,p). The isodensity polarized continuum model (IPCM) in the self-consistent reaction field (SCRF) method is employed to account for the solvent effect of water on the tautomerization reaction activation energies. The results show that the two pathways P(1) (via the carbene intermediate I1) and P(2) (via the sp 3 -hybrid intermediate I2) are found in intramolecular proton transfer, and each pathway is composed by two primary steps. The calculated activation energy barriers of the rate-determining steps in isolated 2,6-dithiopurine N7(H)→N9(H) tautomerism are 308.2 and 220.0 kJ•mol -1 in the two pathways, respectively. Interestingly, in one-water molecule catalyst, it dramatically lowers the N7(H)→N9(H) energy barriers by the concerted double proton transfer mechanism in P(1), favoring the formation of 2,6-dithiopurine N9(H). However, the single proton transfer mechanism assisted with out-of-plane water in the first step of P(2) increases the activation energy barrier from 220.0 to 232.3 kJ•mol -1 , while the second step is the out-of-plane concerted double proton transfer mechanism, indicating that they will be less preferable for proton transfer. Additionally, the results also show that all the pathways are put into the aqueous solution, and the activation energy barriers have no significant changes. Therefore, the long-range electrostatic effect of bulk solvent has no significant impact on proton transfer reactions and the interaction with explicit water molecules will significantly influence proton transfer reactions.

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Azaindolizine Systems Having More Than One Nitrogen Atom in the 6‐Membered Ring

Mauey

1977

Chemistry of Heterocyclic Compounds: A Series of Monographs

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Nmr spectral characteristics of N‐H protons in purine derivatives

Cited by 50 publications

References 12 publications

1,3,8-Trimethylxanthine complexes of Cu(II), Zn(II), Cd(II), and Hg(II)

1,3,8-Trimethylxanthine complexes of Cu(II), Zn(II), Cd(II), and Hg(II)

A Theoretical Investigation on N7(H)→N9(H) Tautomerization of Isolated and Monohydrated 2,6‐Dithiopurine Combined with IPCM Solvent Model

Azaindolizine Systems Having More Than One Nitrogen Atom in the 6‐Membered Ring

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