1H and 13C NMR study of the pyrazolo[1,5-a]pyrimidine system

1992 ◽  
Vol 70 (4) ◽  
pp. 1093-1097 ◽  
Author(s):  
Stefano Chimichi ◽  
Barbara Cosimelli ◽  
Fabrizio Bruni ◽  
Silvia Selleri
Keyword(s):  
Coupling Constants ◽  
Pyrimidine Derivatives ◽  
Simple Method ◽  
Nmr Spectrum ◽  
1H And 13C Nmr ◽  
Methyl Group ◽  
H Nmr ◽  
Nmr Study ◽  
Methyl Derivatives ◽  
Carbon Chemical Shift

The 13C and 1H NMR spectra of some pyrazolo[1,5-a]pyrimidine derivatives are discussed. All 13C resonances were unambiguously assigned by means of both 2D experiments and gated decoupled spectra from which one-bond and long-range 13C–1H coupling constants were determined. The literature assignments for H-5 and H-7 in the parent system have been revised and a simple method for distinguishing between 5-methyl and 7-methyl compounds is suggested, based on the carbon chemical shift of the methyl group or on its fine structure in the 1H NMR spectrum. Regioselective syntheses for all the reported methyl derivatives are also described.

1H and 13C NMR study of some substituted 2-furyl- and 2-thienylethylene derivatives

1986 ◽  
Vol 51 (4) ◽  
pp. 889-898 ◽  
Author(s):  
Miloslava Dandárová ◽  
Daniel Végh ◽  
Jaroslav Kováč ◽  
Igor Goljer ◽  
Nadežda Prónayová ◽  
...  
Keyword(s):  
Double Bond ◽  
Heterocyclic Ring ◽  
Coupling Constants ◽  
Side Chain ◽  
1H And 13C Nmr ◽  
H Nmr ◽  
Nmr Data ◽  
Nmr Study ◽  
Thiophene Derivatives ◽  
C Nmr

The 1H and 13C NMR spectral data of 1-(5-nitro-2-furyl)-2-X-2-Y-ethylenes and some their thienyl analogues are presented. Geometrical arrangement of the trisubstituted ethylenes was adduced from vicinal coupling constants 3J(C, H) for the carbon atom at the functional group attached to the double bond and the ethylene proton. The orientation of the heterocyclic ring towards the double bond of the side chain was determined from the 1H NMR data. The preferred s-cis or s-trans conformations of 5-nitro-2-furylethylene derivatives is substituent at the double bond dependent; all thiophene derivatives under study were found in the s-trans conformation.

21,22-Disubstituted 18α,19βH-Ursane Derivatives with Oxabicyclooctane System in Ring E

1993 ◽  
Vol 58 (1) ◽  
pp. 173-190 ◽  
Author(s):  
Eva Klinotová ◽  
Jiří Klinot ◽  
Václav Křeček ◽  
Miloš Buděšínský ◽  
Bohumil Máca
Keyword(s):  
Spectral Data ◽  
Spin Systems ◽  
Coupling Constants ◽  
Complete Analysis ◽  
Nmr Spectrum ◽  
Proton Proton ◽  
H Nmr ◽  
Proton Coupling ◽  
C Nmr

Reaction of 3β-acetoxy-21,22-dioxo-18α,19βH-ursan-28,20β-olide (IIIa) and 20β,28-epoxy-21,22-dioxo-19α,19βH-ursan-3β-yl acetate (IIIb) with diazomethane afforded derivatives XII-XIV with spiroepoxide group in position 21 or 22, which were further converted into hydroxy derivatives XV and XVII. Ethylene ketals VIII-X were also prepared. In connection with the determination of position and configuration of the functional groups at C(21) and C(22), the 1H and 13C NMR spectral data of the prepared compounds are discussed. Complete analysis of two four-spin systems in the 1H NMR spectrum of bisethylenedioxy derivative Xb led to the proton-proton coupling constants from which the structure with two 1,4-dioxane rings condensed with ring E, and their conformation, was derived.

1H and 13C NMR Study of Proton Transfer in Azoles. Mechanism of Proton Transfer in Pyrazole in Solutions Containing bis-(Acetylacetonato) Nickel (II)

1976 ◽  
Vol 31 (7-8) ◽  
pp. 353-360 ◽  
Author(s):  
V. N. Babin ◽  
E. B. Zavelovidi ◽  
E. I. Fedin
Keyword(s):  
Proton Transfer ◽  
Ligand Exchange ◽  
Hyperfine Coupling ◽  
Outer Sphere ◽  
Coupling Constants ◽  
1H And 13C Nmr ◽  
Nmr Study ◽  
Nmr Techniques ◽  
Kinetics Of ◽  
C Nmr

Abstract Proton Transfer, Pyrazole, Outer-Sphere Coordination Proton transfer in pyrazole systems involving interaction with a paramagnetic transition metal complex has been studied with 1H and 13C NMR techniques. Kinetics of the ligand exchange in the pyrazole complex of bis-(acetylacetonato) nickel (II) has been investigated, and hyperfine coupling constants for the interaction of the nickel unpaired electron with the ligand nuclei in the complex have been determined. Catalytic admixtures of bis-(acetylacetonato) nickel (II) are shown to modify the mechanism of the proton transfer in pyrazole. The spectral data are discussed in terms of outer-sphere coordination and cooperative proton transfer effects.

Conformational analysis of acyclic compounds with oxygen–sulphur interactions. Part VI. Some 1-thioderivatives of 2-propanol and its acetates

1979 ◽  
Vol 57 (18) ◽  
pp. 2426-2433 ◽  
Author(s):  
Felipe Alcudia ◽  
José L. García Ruano ◽  
Jesús Rodríguez ◽  
Félix Sánchez
Keyword(s):  
Conformational Analysis ◽  
Nmr Spectra ◽  
Coupling Constants ◽  
Conformational Study ◽  
Conformational Preference ◽  
Methyl Group ◽  
Opposite Charge ◽  
H Nmr ◽  
Vicinal Coupling Constants

A conformational study of 1-X-2-propanol (X = SH, SMe, SOMe, SO2Me, +SMe2) and their O-acetyl derivatives (X = SMe, SOMe, SO2Me, and +SMe2) is reported. From the relative values of the vicinal coupling constants in 1H nmr spectra it has been possible to establish the conformational preference. When a density of opposite charge is supported by heteratoms, polar factors determined a great predominance of that conformation in which the sulphur function has an anti-relationship with respect to the methyl group. In thiol and thioethers the conformational preference is not so marked.

The probable planarity of 1,2-dimethoxybenzene in solution

1983 ◽  
Vol 61 (2) ◽  
pp. 224-229 ◽  
Author(s):  
Ted Schaefer ◽  
Reino Laatikainen
Keyword(s):  
Benzene Solution ◽  
Theoretical Data ◽  
Spin Coupling ◽  
Coupling Constant ◽  
Nmr Spectrum ◽  
Methyl Group ◽  
H Nmr ◽  
Planar Conformation ◽  
Precise Analysis ◽  
Spin Spin Coupling

A precise analysis of the 1H nmr spectrum of 1,2-dimethoxybenzene in benzene solution yields an accurate value for the proximate spin–spin coupling constant, [Formula: see text], between the ortho ring proton and the methyl protons. The latter also couple to other ring protons and these couplings are assessed. Comparison with some values in other anisole derivatives and with a variety of INDO MO FPT calculations of [Formula: see text] strongly implies the predominance of a planar conformation in solution. This implication disagrees with the interpretation of some other experimental and theoretical data. The mechanism of this proximate coupling is examined by the procedure of Barfield. It seems that the magnitude of the coupling is dominated by interactions involving the orbitals on the carbon atom of the methyl group.

Solid-state 2H NMR study of methyl-d3-cobalamin

1998 ◽  
Vol 76 (2-3) ◽  
pp. 423-428 ◽  
Author(s):  
Jennifer R Garbutt ◽  
Gillian R Goward ◽  
Christopher W Kirby ◽  
William P Power
Keyword(s):  
Solid State ◽  
Rotational Diffusion ◽  
Group Analysis ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Methyl Group ◽  
Spin Lattice ◽  
H Nmr ◽  
Nmr Study

A solid-state 2H NMR study of methyl-d3-cobalamin has been performed as a function of temperature to provide information concerning the character and energetics of the motion performed by this unique bioorganometallic methyl group. Analysis of the 2H NMR line shape indicates that the methyl group undergoes rapid three-fold rotation, and that the Co-C-2H angle lies between 105.9 and 109.5°. Determination of the spin-lattice relaxation times T1 shows that the relaxation is anisotropic, consistent with a "jumping" motion of the methyl group rather than rotational diffusion. This also provides the activation energy to methyl jumps as 8.3 ± 1.3 kJ/mol. It is proposed that this energetic barrier may be a useful probe of changes in the electronic character of the Co-C bond that accompany the biological role of this molecule in such enzymes as methionine synthase.Key words: cobalamin, solid-state NMR, deuterium NMR, molecular dynamics.

Spectroscopic conformational study of PMS 952, a specific imidazoline ligand. Experimental results

1999 ◽  
Vol 77 (12) ◽  
pp. 2015-2024 ◽  
Author(s):  
Marie-Hélène Baron ◽  
Sabine Halut-Desportes ◽  
Hai-Fen Ye ◽  
Jack Huet ◽  
Edith Favre
Keyword(s):  
Hydrogen Bonds ◽  
Tautomeric Form ◽  
Proton Donor ◽  
Coupling Constants ◽  
X Ray ◽  
H Nmr ◽  
Ftir Studies ◽  
Nmr Study ◽  
Imidazoline Ring ◽  
Imidazoline Derivative

X-ray analysis of PMS 952 displays two kinds of very strong hydrogen bonds, an intramolecular one stabilizing the conformer A and an intermolecular one that associates conformers A to form two infinite chains. The 1H NMR study of vicinal coupling constants based on dihedral angle values, evidences that PMS 952 takes up an eclipsed conformation, in CCl4 and CDCl3 solutions, closely related to the conformation in solid state. Deuterium exchange in methanol-d4 points out the presence of a tautomeric form. However, as there is spectral evidence neither from NMR nor from FTIR studies for such a tautomer, this specie cannot be taken into account to explain the complexity of the FTIR spectra. NMR data also reveal that the imidazoline ring freely rotates while FTIR analysis allows characterizing two conformers (A and B), with lifetime shorter than NMR time scale. These two conformers are stabilized by two different intramolecular H-bonds. Taking into account that conformer A could exist in two states (monomer A and (A)n-chains), an equilibrium between A, (A)n, and B entities allowed the assignment of all main bands of the IR spectra, assigned to vNH, vOH, vCH, and vCN modes. The strength of hydrogen bonds is solvent dependent. Polar solvents, either proton donor or acceptor stabilized the conformer A, while CCl4 favors the conformer B.Key words: hydrogen bonds, X-ray, NMR, FTIR, imidazoline derivative.

scholarly journals Lineare Oligophosphaalkane, XX [1]: Alkalimetall-und Trimethylsilylderivate PH-funktioneller Methylenbisphosphane / Linear Oligophosphaalkanes, XX [1]: Alkali Metal and Trimethylsilyl Derivatives of PH-Functional Methylenebisphosphanes

1988 ◽  
Vol 43 (1) ◽  
pp. 31-44 ◽  
Author(s):  
Franjo Gol ◽  
Gerd Hasselkuß ◽  
Peter C. Knüppel ◽  
Othmar Stelzer
Keyword(s):  
Conformational Changes ◽  
Coupling Constants ◽  
Protecting Groups ◽  
Temperature Dependent ◽  
Nmr Spectrum ◽  
H Nmr ◽  
Trimethylsilyl Derivatives ◽  
First Time ◽  
Derivatives Of ◽  
Association Equilibrium

Abstract The synthesis of the trimethylsilyl derivatives of the PH-functional methylenebisphosphanes, R2-n(Me3 Si)nP-CH2 -PR(SiMe3) (R = Me, iPr, tBu, Ph, 2.4.6-Me3C6H2 ; n = 0.1) is reported. In the Li-phosphides R2-nLinP - CH2 - PLiR used as reactive intermediates, a monomer-oligomer association equilibrium causes a rapid Li-exchange as indicated by the solvent and temperature dependent 31P{1H} and 7Li NMR spectrum of (iPr)2 P-CH2 -P(iPr)Li in various solvents (Et2O, THF and MTHF) in the temperature range from 30 to -110 °C. For the syntheses of the Me-and Ph-substituted PH-functional methylenebisphosphanes R2P-CH2 -PRH and RHP-CH2 -PRH (R = Me, Ph) the chlorophosphane CKP -CH2 -PCl2 is used as a starting material. Bifunctional substituents (Ph -N̍-N̍ -Ph and Me -N̍-CO-N̍-Me) are employed for the first time as protecting groups to block one or two PCl-functions in Cl2P-CH2-PCI2,. Cleavage of the PN-bonds in the five membered ring systems (R = Me, Ph) with HCl affords the P-substituted methylenebis-chlorophosphanes RClP-CH2 - PClR in satisfactory yields. The compounds have been characterized by 1H, 13 C{1H} and 31P{1H} NMR spectroscopy. With-in homologous substitution series of methylenebisphosphanes, e.g. R2P-CH2-PR2-nHnthe coupling constants 2J(PP) seem to reflect conformational changes at the PCP-skeleton.

(MePNMe)4S3, ein Cyclotetra(λ3,λ5,λ5,λ5-phosphazan) / (MePNMe)4S3, a Cyclotetra(λ3,λ5,λ5,λ5-phosphazan)

1980 ◽  
Vol 35 (8) ◽  
pp. 959-963 ◽  
Author(s):  
Werner Zeiß ◽  
Wolfgang Schwarz ◽  
Heinz Hess
Keyword(s):  
Crystal Structure ◽  
Spin System ◽  
Structure Determination ◽  
Coupling Constants ◽  
Crystal Structure Determination ◽  
Ring Inversion ◽  
Nmr Spectrum ◽  
H Nmr

Abstract Octamethylcyclotetra(λ3-phosphazane) (1) reacts with three mole equivalents of sulfur, added either in excess or in deficite, to give 2, the first cyclotetra(λ3,λ5,λ5,λ5-phosphazane). Its crystal structure determination shows a completely unsymmetrical molecule, which does not undergo ring inversion in solution. Thus an ABMX spin system with remarkably different AM and BM coupling constants is observed in the 31P{1H} NMR spectrum. By means of selective {31P} decoupling, all CH3 proton signals could be assigned in the 1H NMR spectrum.

Conformation of the A ring in 1-oxo and 3-oxotriterpenoids. Vicinal interproton coupling constants

1986 ◽  
Vol 51 (3) ◽  
pp. 593-610 ◽  
Author(s):  
Jiří Klinot ◽  
Miloš Buděšínský ◽  
Eva Klinotová ◽  
Alois Vystrčil
Keyword(s):  
Nmr Spectra ◽  
Chair Conformation ◽  
Spin Systems ◽  
Coupling Constants ◽  
Boat Conformation ◽  
H Nmr ◽  
Vicinal Coupling Constants ◽  
Full Analysis ◽  
Solvent Shifts ◽  
Methyl Derivatives

The coupling constants of the protons on the A ring were determined by full analysis of the spin systems in the 1H NMR spectra of 4,4-dimethyl-5α-cholestan-3-one (XIX) and 1-oxo and 3-oxo triterpenoids I, XIV-XVI, XX and their 2-methyl derivatives V, VI, XVII, XVIII, XXIII and XXIV. from the values of vicinal coupling constants it was inferred that in 2α-methyl-1-oxo and 3-oxo derivatives V, XVII and XXIII the A ring assumes a chair conformation, while in 2β-methyl derivatives VI, XVIII and XXIV a boat conformation. The chair form greatly predominates in 4,4-dimethyl-5α-cholestan-3-one (XIX) and in 1-oxotriterpenoid XX, while in triterpenoid 3-oxo derivatives I, XIV-XVI a significant amount of boat conformation is present at equilibrium (up to 40%). The solvent shifts and the lanthanide induced shifts of the protons on C(2) lead to the same conclusion.

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