• Title/Summary/Keyword: tautomeric forms

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Synthesis of its Tautomeric Forms and New 6-Substituted Pyridazin-3(2H)-one Analogs (새로운 6-Substituted Pyridazin-3(2H)-one 유도체 및 토토머형의 합성)

  • Kim, Chaewon;Park, Myung-Sook
    • YAKHAK HOEJI
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    • v.57 no.5
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    • pp.316-322
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    • 2013
  • The new pyridazinone analogs were synthesized for development of candidates to retain anticancer activity. Various 6-substituted pyridazin-3(2H)-ones were prepared from the pyridazinyl chloride 3a~d via endothermic nucleophilic substitution with hydroxide ion as nucleophile for 2~48 h. Pyridazinyl chloride 3a~d could be converted to hydroxypyridazines (or pyridazin-3(2H)ones) using 1~5 equivalents of water (or 1 equivalent of sodium hydroxide) at reflux in DMF. The tautomerism of lactim form to lactam form was also accomplished in pyridazine derivatives. Formation of pyridazinones 10 was undertaken with stirring using sodium hydroxide at reflux in DMF for 2 h. Synthetic compounds were identified using NMR spectrum.

Proton Transfer in Biomolecules Facilitated by Water: Quantum Chemical Investigations

  • Lee, Sung-Yul
    • Bulletin of the Korean Chemical Society
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    • v.32 no.4
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    • pp.1117-1124
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    • 2011
  • We present a brief review for theoretical/computational studies of proton transfer processes of some simple biomolecules promoted by microsolvating water molecules. Focus is given on the relative stability of the canonical vs. zwitterionic forms of amino acids, tautomeric forms of the DNA base adenine, and the biologically active vs. inactive forms of nicotine. The biochemical implications of these findings are also discussed.

MO Theoretical Studies on 1,5-Sigmatropic Hydrogen Shifts in Systems with Terminal Heteroatoms, O and S (말단 헤테로원자가 산소(O)와 황(S)인계의 1,5-수소원자 이동반응에 관한 MO 이론적 연구)

  • Ho Soon Kim;Ikchoon Lee
    • Journal of the Korean Chemical Society
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    • v.30 no.2
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    • pp.195-200
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    • 1986
  • MO studies have been carried out on 1,5-hydrogen shifts between tautomeric forms (6${\pi}$ system) of ${\beta}$-diketones, ${\beta}$-thioxoketones and ${\beta}$-dithioketones by determining transition state and analyzing structural stability effects on the activation barriers using MNDO method. The barrier was found to increase with the stability of the ground state having greater charge separation and with the increase (less stabilization) in the one electron energy ${\Delta}(2\sum\limits^{occ}{\varepsilon}i)^{\neq}$ in the activation process.

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Synthesis of Core-Modified Porphyins and Studies of Their Temperature-dependent Tautomerism

  • 이창희;김한재;윤대위
    • Bulletin of the Korean Chemical Society
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    • v.20 no.3
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    • pp.276-280
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    • 1999
  • The different core-modified porphyrins 21-thia-23-carba-12-aza-5,10-dimesityl-15,20-diphenylporphyrin (6), and their N(12)-methyl derivatives (8) were synthesized by acid-catalyzed [3+1] condensation of the corresponding 16-thia-5,10-dimesityltripyrromethanes and 2,4-bis[(α-hydroxy-α-phenyl)methyl]pyrrole. Spectroscopic evidence indicates the existence of two different tautomeric forms at room temperature in porphyrin (6). A third form of tautomer was observed when the temperature was lowered to 223 K. The most stable tautomer is one in which the nitrogenic proton resides outside the core of the macrocycle. The ratio of the three different tautomers (outer N-H/ two inner N-H, i.e. 6/12/13) was 1/l/0.5 in the case of (6) while the ratio of 1/l/0.3 was observed in the case of (10). In the case of 21-oxa-23-carba-12-aza-5,10,15,20-tetraphenylporphyrin (7), the only stable tautomeric form observed by 1H NMR was the one that nitrogenic proton resides inside the core on

Tautomeric Fluxional Process in Metal Complexes. Insight into Cobalt(Ⅲ) and Pentamethylcyclopentadienylrhodium(Ⅲ) Complexes of 2-Mercaptopyrimidine Ligand

  • 정옥상;김용태;김윤주;전정균;Cha, Hee K.
    • Bulletin of the Korean Chemical Society
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    • v.20 no.6
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    • pp.648-652
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    • 1999
  • Studies have been carried out on the unusual molecular nonrigidity of CoⅢ(PymS)3 and Cp* RhⅢ(PymS)2(PymS:2-mercaptopyrimidine). The crystal structure of CoⅢ(PymS)3 approximates to an octahedral mer isomer with 4-membered N-Schelating fashion. For Cp*RhⅢ(PymS)2, one PymS ligand bonds to the rhodium ion in an S-monodentate mode (Rh-S(2) = 2.366(1)Å) while the other ligand chelates to the metal ion in an N,S-bidentae mode (Rh-S(1)=2.414(1);Rh-N(1)=2.103(3)Å). Even though the conformations and configurations of both complexes are still retained in solution, an unusual nonrigidity for the protons of the PymS region is obsered in the solution. The broad proton signals of CoⅢ(PymS)3 exhibit a temperature-dependence in the range of -40∼40℃ with a free energy of activation ΔG=64.49kJ/mol(40℃). For Cp*RhⅢ(PymS)₂,such a fluxionality has been markedly observed in solution. This fluxional behavior can be explained in terms of "ligand tautomerism" in metal complexes containing potential tautomeric forms.

Synthesis of Novel 1,2,4-Triazole Derivative (새로운 1,2,4-Triazole 유도체의 합성에 관한 연구)

  • Kim, Ho Sik;Park Tae Joo;Doh Yi Hyang;Lee Man Kil;Kurasawa Yoshihisa
    • Journal of the Korean Chemical Society
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    • v.36 no.5
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    • pp.738-743
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    • 1992
  • ${\alpha}-Arylhydrazonoacylazide(7) was synthesized starting from {\circo}-phenylenediamine(3) in four steps. The tautomeric behavior of {\alpha}-arylhydrazonoacylazide(7) between the hydrazone imine and diazenyl enamine forms in the dimethyl sulfoxide solution was investigated on the basis of the tautomer ratio determined by the ^1H-NMR spectral data. The 1-aryl-3-quinoxalinyl-1,2,4-triazol(8) was synthesized from {\alpha}-arylhydrazonoacylazide(7) by refluxing in benzene.$

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