Unexpected Keto-enol Tautomerism in the Cyclopyridinophane Class Direct and indirect proofs

2008 ◽  
Vol 59 (10) ◽  
Author(s):  
Paul Ionut Dron ◽  
Neculai Doru Miron ◽  
Gheorghe Surpateanu
Keyword(s):  
Nmr Spectroscopy ◽  
1H Nmr ◽  
Stable Conformer ◽  
Ph Measurements ◽  
Theoretical Methods ◽  
Nmr Data ◽  
Tautomeric Forms ◽  
New Compounds

The paper presents the synthesis of cyclo (bis-paraquat p-phenylene p-phenylene-carbonyl) tetrakis (hexafluorophosphate), named �CETOBOX�, and the closely related structural determinations. This compound exists in three tautomeric forms. These forms were evidentiated by NMR-data (1H-NMR, TOCSY, COSY, NOESY), UV-Vis spectra coupled with pH measurements and by synthesis. As the �CETOBOX� gives �in situ� only the corresponding monoylide, the synthesis of a new fluorescent indolizine cyclophane has been performed by a 3+2 cycloaddition. All structures of the new compounds presented herein have been established by NMR spectroscopy. Also, theoretical methods (MM3, AM1, AM1-COSMO and B88LYPDFT) have been used to determine the most stable conformer structures.

scholarly journals New 1H-1-alkyl-6-methyl-3-phenyl-7-phenylazo-pyrazolo[5,1-c][1,2,4]triazoles through regioselective alkylation of 1H-6-methyl-3-phenyl-7-phenylazopyrazolo[5,1-c][1,2,4]triazoles

2012 ◽  
Vol 10 (2) ◽  
pp. 373-379 ◽  
Author(s):  
Vasile-Nicolae Bercean ◽  
Valentin Badea ◽  
Călin Deleanu ◽  
Alina Nicolescu
Keyword(s):  
Nmr Spectroscopy ◽  
1H Nmr ◽  
13C Nmr ◽  
15N Nmr ◽  
Tautomeric Forms ◽  
Regioselective Alkylation ◽  
15N Nmr Spectroscopy ◽  
New Compounds

Abstract1H-1-Alkyl-6-methyl-3-phenyl-7-phenylazopyrazolo[5,1-c][1,2,4]triazoles (2aa-ad) were obtained by regioselective alkylation of 1H-6-methyl-3-phenyl-7-phenylazopyrazolo[5,1-c][1,2,4]triazoles (2a). 1H-1-Alkyl-6-methyl-3-phenyl-7-phenylazopyrazolo[5,1-c][1,2,4]triazoles 2aa and 2ab were also prepared by coupling phenyldiazonium chloride with 1H-1-alkyl-6-methyl-3-phenyl-pyrazolo[5,1-c][1,2,4]triazoles 1aa and 1ab. The new compounds were characterized by IR, UV-VIS, 1H-NMR, 13C-NMR, and 15N-NMR spectroscopy and their structures and actual tautomeric forms were established unequivocally.

The Origin of Molecular Mobility During Biomass Pyrolysis as Revealed by In situ 1H NMR Spectroscopy

ChemSusChem ◽  
2012 ◽  
Vol 5 (7) ◽  
pp. 1258-1265 ◽  
Author(s):  
Anthony Dufour ◽  
Miguel Castro-Diaz ◽  
Nicolas Brosse ◽  
Mohamed Bouroukba ◽  
Colin Snape
Keyword(s):  
Nmr Spectroscopy ◽  
1H Nmr ◽  
Molecular Mobility ◽  
1H Nmr Spectroscopy ◽  
Biomass Pyrolysis

Tautomerism in 3{5}-(dimethoxyphenyl)pyrazoles

1996 ◽  
Vol 52 (4) ◽  
pp. 746-752 ◽  
Author(s):  
M. A. Halcrow ◽  
H. R. Powell ◽  
M. J. Duer
Keyword(s):  
Hydrogen Bond ◽  
Nmr Spectroscopy ◽  
Solvate Water Molecule ◽  
X Ray ◽  
Nmr Data ◽  
Tautomeric Forms ◽  
Oxygen Donor ◽  
Intramolecular Hydrogen ◽  
Pyridinic N ◽  
C Nmr

The single-crystal X-ray structures of 3{5}-(2′,5′-dimethoxyphenyl)pyrazole (HI) and the hemihydrate of 3 {5}-(3/,4′-dimethoxyphenyl)pyrazole (IV) have been determined. Compound (HI) exists purely as the 5-substituted prototropomer in the crystal; the pyrazole pyrollic N—H proton is involved in a three-way hydrogen bond, involving an intramolecular contact with a methoxy oxygen donor and an intermolecular interaction to the pyridinic N atom of a neighbouring molecule, forming discrete hydrogen-bonded dimers. There is no evidence of degenerate proton transfer within the dimeric units from CPMAS 13C NMR spectroscopy, in contrast to other known pyrazoles that associate in this manner. In (IV).1/2H2O, however, the pyrrolic proton is disordered over both N(1) and N(2) via hydrogen bonding to the solvate water molecule. CPMAS 13C NMR spectroscopy shows that the prototropic disorder in (IV).1/2H2O is static at temperatures up to 370 K. Solution 1H and 13C NMR data in DMSO-d 6 show that for both (HI) and (IV) the 3- and 5-substituted tautomeric forms are similarly populated in this solvent, suggesting both that the intramolecular hydrogen bond in (HI) has been disrupted and that the two tautomers of (HI) and (IV) are close in energy.

Application of progress curve analysis to in situ enzyme kinetics using 1H NMR spectroscopy

1986 ◽  
Vol 155 (1) ◽  
pp. 38-44 ◽  
Author(s):  
Jamie I. Vandenberg ◽  
Philip W. Kuchel ◽  
Glenn K. King
Keyword(s):  
Nmr Spectroscopy ◽  
Enzyme Kinetics ◽  
1H Nmr ◽  
1H Nmr Spectroscopy ◽  
Curve Analysis ◽  
Progress Curve

Synthesis and Characterization of Indolylfulgide Photochromic Colorants

2013 ◽  
Vol 821-822 ◽  
pp. 522-526
Author(s):  
Ning Ning Lv ◽  
An Guo Sang ◽  
Yan Zhang
Keyword(s):  
Nmr Spectroscopy ◽  
1H Nmr Spectroscopy ◽  
Room Temperature ◽  
Uv Light ◽  
Synthesis And Characterization ◽  
Indole Derivatives ◽  
Thermal Stabilities ◽  
Nmr Data ◽  
New Compounds

This paper describes the synthesis of two photochromic 2-indolyl-fulgides by stobbe condensation of the corresponding 2-acyl-1,3-dimethyl-indole derivatives with diethyl isopropylidene succinate in the presence of hexamethyldisilazane potassium. The overall yields was up to 41% for 3 steps. Both prepared compounds are sensitive to UV light and change colors upon irradiation. And the two fulgides can be switched back and forth 100 times without obvious degradation. Thermal stabilities of the fulgides in acetonitrile at room temperature for 30 days and at 80 °C for 12 h were measured using UV-vis and 1H NMR spectroscopy. The absorption spectra of both forms did not exhibit any sign of degradation. The NMR data indicated that no new compounds were detected. The utilization of these materials for use in photochromic textiles were discussed.

Synthesis of 4-Aryl-3(5)-(2-hydroxyphenyl)pyrazoles by Reaction of Isoflavones and their 4-Thio Analogues with Hydrazine Derivatives

2007 ◽  
Vol 60 (12) ◽  
pp. 905 ◽  
Author(s):  
Albert Lévai ◽  
Artur M. S. Silva ◽  
José A. S. Cavaleiro ◽  
José Elguero ◽  
Ibon Alkorta ◽  
...  
Keyword(s):  
Reaction Mechanism ◽  
Nmr Spectroscopy ◽  
Hydrogen Bonds ◽  
Hydrazine Hydrate ◽  
1H Nmr ◽  
Theoretical Calculations ◽  
Intramolecular Hydrogen Bonds ◽  
Nmr Study ◽  
Intramolecular Hydrogen ◽  
New Compounds

4-Aryl-3(5)-2-(hydroxyphenyl)pyrazoles have been prepared by the reaction of isoflavones and their 4-thio analogues with hydrazine hydrate and phenylhydrazine in hot pyridine. The reaction mechanism for the formation of these pyrazoles is discussed. All the new compounds have been fully characterized by NMR spectroscopy. In [D6]DMSO, a 1H NMR study allows observation of the presence of both pyrazole annular tautomers, due to the presence of intramolecular hydrogen bonds in each tautomer (OH···N and NH···O). Theoretical calculations have been carried out on tautomers and conformers of compounds 20 (3(5)-(2-hydroxy-4-methoxyphenyl)-5(3)-methyl-4-phenylpyrazole) and 21 (3(5)-(2-hydroxy-4-methoxyphenyl)-4-(2-methoxyphenyl)-5(3)-methylpyrazole), including the absolute shieldings (GIAO/B3 LYP/6–311++G**) of 21.

New Heterocyclic Compounds from 1,2,4-triazoles Class with Potential Cytotoxic Activity

2017 ◽  
Vol 68 (11) ◽  
pp. 2503-2508 ◽  
Author(s):  
Laura Ileana Socea ◽  
Stefania Felicia Barbuceanu ◽  
Bogdan Socea ◽  
Constantin Draghici ◽  
Theodora Venera Apostol ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Cytotoxic Activity ◽  
Spectral Data ◽  
1H Nmr ◽  
Elemental Analysis ◽  
13C Nmr ◽  
Heterocyclic Compounds ◽  
Cytotoxic Effect ◽  
13C Nmr Spectroscopy ◽  
New Compounds

Acylhydrazinecarbothioamides (2a,b) were synthesized by addition of 2-(5H-dibenzo[a,d][7]annulen-5-yl)acetohydrazide to different isothiocyanates. The new 1,2,4-triazol-3-thioles (3a,b) were synthesized by cyclization of new 2- acylhydrazinecarbothioamides (3a,b) in basic media. Alkylation of 1,2,4-triazole-3-thiols (3a-c) with ethyl bromide gave only S-substituted derivatives (4a-c). The structures of the synthesized compounds have been established on spectral data (IR, 1H-NMR and 13C-NMR spectroscopy) and elemental analysis. The cytotoxic effect of new compounds was evaluated using two alternative models on plant and invertebrate organisms.

1,3-Distanna-2-phospha-[3]ferrocenophanes - Synthesis, Reactivity and NMR Spectroscopic Properties

1999 ◽  
Vol 54 (1) ◽  
pp. 57-62 ◽  
Author(s):  
Max Herberhold ◽  
Udo Steffl ◽  
Bernd Wrackmeyer
Keyword(s):  
Nmr Spectroscopy ◽  
Dynamic Process ◽  
Phosphorus Atom ◽  
Spectroscopic Properties ◽  
Coupling Constants ◽  
Nmr Data ◽  
Fast Movement ◽  
New Compounds

1,1,3,3-Tetramethyl-2-organo(R)-1,3-distanna-2-phospha-[3]ferrocenophanes [R = Me (2a), tBu (2b), C6H11 (2c), Ph (2d)] and one arsa-analogue 2d(As) were obtained from the reaction of 1,1′-bis(chlorodimethylstannyl)ferrocene 1 with either bis(trimethylsilyl)methylphosphane or the dilithio derivatives, Li2PR and Li2AsPh, respectively. All compounds 2 react with chalcogens (oxygen, sulfur, selenium) by cleavage of the Sn-P bonds and formation of the known 1,3-distanna-2-chalcogena-[3]ferrocenophanes. In contrast, 2d traps pentacarbonylmetal fragments [M(CO)5] to give the stable phosphane complexes [M = Cr (4d), Mo (5d), W (6d)]. The 1,1′-bis(diorganophosphanostannyl)ferrocenes [R = tBu (3b), Ph (3d)] were prepared for comparison of NMR data. The ferrocenophanes 2 are fluxional with respect to fast movement of the cyclopentadienyl rings which induces inversion at the pyramidal phosphorus atom. This dynamic process is slow in the cases of 2d(As) and of the pentacarbonyl complexes 4d - 6d. All new compounds were characterised by 1H, 13C, 31P and 119Sn NMR spectroscopy. Various 2D heteronuclear shift correlations (e.g. 31P/1H and 119Sn/1H ) were carried out for the compounds 2 and also for non-cyclic derivatives such as bis(trimethylstannyl)phenvlphosphane and -arsane in order to determine absolute signs of coupling constants [e.g. 1J(119Sn,31P) > 0 and 2J(119Sn,117Sn) < 0]. The NMR data suggest that the molecular frameworks of the ferrocenophanes 2 are not particularly strained.

scholarly journals Detection of thymosin beta 4 in situ in a guinea pig cerebral cortex preparation using 1H NMR spectroscopy.

1992 ◽  
Vol 267 (14) ◽  
pp. 9905-9910
Author(s):  
R.A. Kauppinen ◽  
T Nissinen ◽  
A.M. Kärkkäinen ◽  
T.R. Pirttilä ◽  
J Palvimo ◽  
...  
Keyword(s):  
Cerebral Cortex ◽  
Nmr Spectroscopy ◽  
Guinea Pig ◽  
1H Nmr ◽  
1H Nmr Spectroscopy ◽  
Thymosin Beta 4
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