Structure and nuclear magnetic resonance spectra of 6-bromo-3,3′,4′,5,7-penta-O-methylcatechin

1985 ◽  
Vol 63 (8) ◽  
pp. 2176-2180 ◽  
Author(s):  
F. W. B. Einstein ◽  
E. Kiehlmann ◽  
E. K. Wolowidnyk
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Title Compound ◽  
Bromine Atom ◽  
Heterocyclic Ring ◽  
Equatorial Orientation ◽  
X Ray ◽  
X Ray Crystallography ◽  
Nuclear Magnetic Resonance Spectra ◽  
Ring Conformations

The title compound has been synthesized by selective debromination of 6,8-dibromocatechin and indirect methylation of the resulting 6-bromocatechin via its pentaacetate. The structure of C20H23BrO6 has been determined by X-ray crystallography. The compound crystallizes in the space group P1 with a = 9.589(3) Å, b = 11.576(3) Å, c = 11.326(3) Å, α = 118.80(3)°, β = 93.23(3)°, γ = 111.44(3)°, ρc = 1.481 g cm−3, and Z = 2. Intensities were measured for 2584 independent reflections (2θ < 45°) of which 2213 were observed (I > 3.0σ(I)) and used in subsequent refinement (final R values were R = 0.0268 and Rw = 0.0344). Crystallographic and pmr data confirm the position of the bromine atom at C-6, the trans-diaxial arrangement of H-2/H-3 and the quasi-equatorial orientation of the 3,4-dimethoxyphenyl group (ring B). The two heterocyclic ring conformations are consistent with the expected flexibility of the molecule.

Étude structurale de l'amino-5 dibenzyl-4,4 one-3 2H-thiadiazine-1,2,6 dioxyde-1,1

1988 ◽  
Vol 66 (10) ◽  
pp. 2477-2482 ◽  
Author(s):  
Pierre Brouant ◽  
Jacques Barbe ◽  
Pilar Goya ◽  
Carmen Ochoa
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Dipole Moment ◽  
Solid State ◽  
Magnetic Resonance ◽  
Title Compound ◽  
Heterocyclic Ring ◽  
X Ray Diffraction ◽  
X Ray ◽  
Present Structure ◽  
Related Compounds

5-Amino-4,4-dibenzyl-3-one-2H-1,2,6-thiadiazine-1,1-dioxide was structurally characterized in the solid state by X-ray diffraction. The structure shows that the title compound exists in the solid in a sheet-packed form and as the amino tautomer. The unconjugated heterocyclic ring, which in the structures of related compounds is usually folded, is planar in the present structure. 1H nuclear magnetic resonance and dipole moment data indicate that the title compound has the same structure in the solid state and in solution.

Synthesis, 1H, 13C, and 29Si nuclear magnetic resonance spectra and crystal structure of trans-1,4-diphenyldecamethylcyclohexasilane

1987 ◽  
Vol 65 (2) ◽  
pp. 437-440 ◽  
Author(s):  
Kanta Kumar ◽  
Morton H. Litt ◽  
Raj K. Chadha ◽  
John E. Drake
Keyword(s):  
Crystal Structure ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Coupling Reaction ◽  
Chair Conformation ◽  
Site Symmetry ◽  
X Ray ◽  
X Ray Crystallography ◽  
Nuclear Magnetic Resonance Spectra ◽  
Phenyl Rings

The coupling reaction between PhMeSiCl2 and Me2SiCl2 in the presence of Na/K alloy resulted in a variety of phenylated permethylcyclohexasilanes of which only trans-1,4-Ph2Me10Si6 could be obtained in pure form by repeated recrystallizations. It was studied by means of nmr (1H, 13C, and 29Si) and X-ray crystallography. The crystals are monoclinic, P21/c with a = 10.105(6), b = 14.77(1), c = 9.973(6) Å, β = 94.08(5)°, V = 1485(2) Å3, and Z = 2 for 1922 unique "observed" reflections and the structure refined to an R index of 0.036. The molecule has site symmetry [Formula: see text] and the chair conformation of cyclohexane, with the two phenyl rings occupying the equatorial positions.

The crystal structure of ethyl-Z-3-amino-2-benzoyl-2-butenoate and measurement of the barrier to E,Z-isomerization

1980 ◽  
Vol 58 (17) ◽  
pp. 1821-1828 ◽  
Author(s):  
Gary D. Fallon ◽  
Bryan M. Gatehouse ◽  
Allan Pring ◽  
Ian D. Rae ◽  
Josephine A. Weigold
Keyword(s):  
Crystal Structure ◽  
Nuclear Magnetic Resonance ◽  
Hydrogen Bond ◽  
Free Energy ◽  
Magnetic Resonance ◽  
Energy Of Activation ◽  
X Ray ◽  
X Ray Crystallography ◽  
Free Energy Of Activation ◽  
Nuclear Magnetic

Ethyl-3-amino-2-benzoyl-2-butenoate crystallizes from pentane as either the E (mp 82–84 °C) or the Z-isomer (mp 95.5–96.5 °C). The E isomer is less stable, and changes spontaneously into the Z, which bas been identified by X-ray crystallography. The structure is characterised by an N–H/ester CO hydrogen bond and a very long C2—C3 bond (1.39 Å). Nuclear magnetic resonance methods have been used to measure the rate of [Formula: see text] isomerization at several temperatures, leading to the estimate that the free energy of activation at 268 K is 56 ± 8 kJ.

Synthesis and conformation studies by x-ray crystallography and nuclear magnetic resonance of cyclo(L-Phe-L-Pro-D-Ala)2

1984 ◽  
Vol 106 (13) ◽  
pp. 3844-3850 ◽  
Author(s):  
Gopinath Kartha ◽  
K. Krishna Bhandary ◽  
Kenneth D. Kopple ◽  
Anita Go ◽  
Peng Peng Zhu
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
X Ray ◽  
X Ray Crystallography ◽  
Nuclear Magnetic

scholarly journals Supersize Cp! Tetrabenzo[a,c,g,i]fluorenyl complexes of yttrium

2017 ◽  
Vol 95 (4) ◽  
pp. 363-370 ◽  
Author(s):  
Jianlong Sun ◽  
David J. Berg ◽  
Brendan Twamley
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Ethylene Polymerization ◽  
Nmr Studies ◽  
X Ray ◽  
X Ray Crystallography ◽  
Trinuclear Cluster ◽  
Polymerization Catalyst ◽  
Dynamic Nuclear Magnetic Resonance ◽  
Trimethylsilyl Isocyanate

The synthesis of tetrabenzo[a,c,g,i]fluorenyl (Tbf) yttrium dialkyl complexes, (Tbf)Y(CH2SiMe3)2(L) (L = tetrahydrofuran (THF), 1; L = bipy, 2), by direct protonolysis of the tris(alkyl) complex, Y(CH2SiMe3)3(THF)2, are reported. The X-ray crystal structures of 1 and 2 display the helical twisting typically observed for the Tbf ligand. Dynamic nuclear magnetic resonance (NMR) studies on 1 show a barrier to Tbf helical inversion (epimerization or “wagging”) of 38.1 ± 0.5 kJ mol−1. The reaction of 1 with acidic hydrocarbons such as 1,3-bis(trimethylsilyl)cyclopentadiene or trimethylsilylacetylene results in protonolysis to form the mixed Cp derivative [(Tbf){C5H3(SiMe3)2}Y(CH2SiMe3)(THF)] (3) or [(Tbf)Y(CCSiMe3)2(THF)]n (4), respectively. In the case of 4, a small amount of the trinuclear cluster (Tbf)Y3(μ3-CCSiMe3)2(μ2-CCSiMe3)3(CCSiMe3)3(THF)2 (5) was isolated and characterized by X-ray crystallography. Dialkyl 1 undergoes smooth insertion of trimethylsilyl isocyanate to afford [(Tbf)Y{κ2-(N,O)-Me3SiN(Me3SiCH2)CO}2(THF)] (6) but it does not react with alkenes. Treating 1 with [Ph3C]+[B(C6F5)4]− in bromobenzene generates a moderately active ethylene polymerization catalyst (36 kg mol−1 h−1 bar−1).

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