Structure in the solid state and conformational analysis in solution of 1,4-diacetyl-1,4-dihydro-2,3-diphenylpyrazine, a potential antiaromatic heterocyclic compound

1982 ◽  
Vol 60 (3) ◽  
pp. 349-354 ◽  
Author(s):  
Joseph Armand ◽  
Claudette Bois ◽  
Michèle Philoche-Levisalles ◽  
Marie-José Pouet ◽  
Marie-Paule Simonnin
Keyword(s):  
Solid State ◽  
Nitrogen Atom ◽  
Conformational Analysis ◽  
Nmr Spectra ◽  
Equilibrium Mixture ◽  
X Ray ◽  
X Ray Crystallography ◽  
Nitrogen Bonds ◽  
Unambiguous Assignment ◽  
C Nmr

It is shown by X-ray crystallography that the 1,4-dihydropyrazine skeleton of 1,4-diacetyl-1,4-dihydro-2,3-diphenylpyrazine 2 has a boat shape. The C(2)–C(3) and C(5)–C(6) double bonds are localized; therefore 2 does not exist as an azahomoaromatic entity with 6 electrons delocalized on the ring and two electrons localized on one nitrogen atom. In the solid state 2 is in a Z, Z conformation. The 1H and 13C nmr spectra indicate that 2 exists as an equilibrium mixture of Z,E, E,E, and Z,Z conformers in CD2Cl2 at −80 °C. An unambiguous assignment of the different sets of signals has been obtained by nOe experiments performed at −80 °C. The conformer distribution is the following: 65% (Z,E), 22% (E,E), and 13% (Z,Z). The relatively low barrier to rotation about the carbonyl nitrogen bonds of the two amide groups [Formula: see text] is in line with a rather large C—N bond length (~1.375 Å) in the crystal.

The relative stabilities of PhE(NH-t-Bu)2 and PhE(μ-N-t-Bu)2EPh (E = As, Sb, and Bi): X-ray structures of {Li2[PhAs(N-t-Bu)2]}2 and PhE(μ-N-t-Bu)2EPh (E = Sb, Bi)

2003 ◽  
Vol 81 (2) ◽  
pp. 169-174 ◽  
Author(s):  
Glen G Briand ◽  
Tristram Chivers ◽  
Masood Parvez
Keyword(s):  
Solid State ◽  
Nmr Spectra ◽  
Phenyl Group ◽  
Synthetic Approach ◽  
Relative Stabilities ◽  
X Ray ◽  
X Ray Crystallography ◽  
In Trans ◽  
C Nmr

The reaction of PhECl2 with 2 equiv of LiHN-t-Bu has been studied for the series E = As, Sb, and Bi to determine the effect of the phenyl group on subsequent amine condensation processes. For PhAsCl2, the metathesis product PhAs(NH-t-Bu)2 4 was obtained as a colourless oil. Similar reactions involving PhECl2, where E = Sb or Bi, yielded the cyclodipnict(III)azanes PhE(μ-N-t-Bu)2EPh 5 (E = Sb) and 6 (E = Bi), respectively. Treatment of 4 with 2 equiv of n-BuLi produced the dilithium salt Li2[PhAs(N-t-Bu)2] 7a. Products 4, 5, 6, and 7a were characterized by 1H, 7Li (7a), and 13C NMR spectra, while 5, 6, and 7a were also structurally characterized by X-ray crystallography. Compound 7a is dimeric in the solid state via intermolecular Li···N and η6-Li···Ph interactions. The cyclodipnict(III)azanes 5 and 6 have similar structures, with the exocyclic phenyl groups in trans positions relative to the E2N2 ring. This synthetic approach provides a new route to the four-membered rings RE(μ-N-t-Bu)2ER (E = Sb, Bi) and the first example of a bis(organyl)cyclodibism(III)azane.Key words: arsenic, antimony, bismuth, amides, imides.

scholarly journals Simple Methylcadmium Alkoxides

2007 ◽  
Vol 62 (10) ◽  
pp. 1339-1342 ◽  
Author(s):  
Surajit Jana ◽  
Tania Pape ◽  
Norbert W. Mitzel
Keyword(s):  
Mass Spectrometry ◽  
Solid State ◽  
Molecular Formula ◽  
Equimolar Ratio ◽  
X Ray ◽  
X Ray Crystallography ◽  
Elemental Analyses ◽  
Solid State Structures ◽  
Structural Aspects ◽  
C Nmr

The reaction of dimethylcadmium with alcohols R-OH in equimolar ratio leads to the formation of tetrameric methylcadmium alkoxides with molecular formula [(MeCd)4 (OR)4] [R = Me (1), Et (2) and iPr (3)]. These compounds have been characterised by 1H, 13C NMR and IR spectroscopy, by mass spectrometry, elemental analyses and by X-ray crystallography (for 2 and 3). The solid state structures show distorted cubane-type aggregates with Cd4O4 cores. The structural aspects and the spectroscopic characterisations of these compounds are discussed.

scholarly journals Solid-state tautomeric structure and invariom refinement of a novel and potent HIV integrase inhibitor

2013 ◽  
Vol 69 (3) ◽  
pp. 285-288 ◽  
Author(s):  
John Bacsa ◽  
Maurice Okello ◽  
Pankaj Singh ◽  
Vasu Nair
Keyword(s):  
Solid State ◽  
Integrase Inhibitor ◽  
Correlation Spectroscopy ◽  
Hiv Integrase ◽  
Acta Cryst ◽  
X Ray ◽  
X Ray Crystallography ◽  
Molecular Charge ◽  
Intramolecular Hydrogen ◽  
C Nmr

The conformation and tautomeric structure of (Z)-4-[5-(2,6-difluorobenzyl)-1-(2-fluorobenzyl)-2-oxo-1,2-dihydropyridin-3-yl]-4-hydroxy-2-oxo-N-(2-oxopyrrolidin-1-yl)but-3-enamide, C27H22F3N3O5, in the solid state has been resolved by single-crystal X-ray crystallography. The electron distribution in the molecule was evaluated by refinements with invarioms, aspherical scattering factors by the method of Dittrichet al.[Acta Cryst.(2005), A61, 314–320] that are based on the Hansen–Coppens multipole model [Hansen & Coppens (1978).Acta Cryst.A34, 909–921]. The β-diketo portion of the molecule exists in the enol form. The enol –OH hydrogen forms a strong asymmetric hydrogen bond with the carbonyl O atom on the β-C atom of the chain. Weak intramolecular hydrogen bonds exist between the weakly acidic α-CH hydrogen of the keto–enol group and the pyridinone carbonyl O atom, and also between the hydrazine N—H group and the carbonyl group in the β-position from the hydrazine N—H group. The electrostatic properties of the molecule were derived from the molecular charge density. The molecule is in a lengthened conformation and the rings of the two benzyl groups are nearly orthogonal. Results from a high-field1H and13C NMR correlation spectroscopy study confirm that the same tautomer exists in solution as in the solid state.

Two-bond 13C–13C spin-coupling constants in saccharides: dependencies on exocyclic hydroxyl group conformation

2021 ◽  
Author(s):  
Jieye Lin ◽  
Reagan J. Meredith ◽  
Allen G. Oliver ◽  
Ian Carmichael ◽  
Anthony S. Serianni
Keyword(s):  
Solid State ◽  
Torsion Angle ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Hydroxyl Group ◽  
X Ray ◽  
X Ray Crystallography ◽  
Spin Coupling Constants ◽  
C Nmr

13C-Labeled mono- and disaccharides were studied by X-ray crystallography and solid-state 13C NMR to determine the dependence of 2JC1,C3 in aldopyranosyl rings on the C1–C2–O2–H torsion angle, θ2, involving C2 of the C1–C2–C3 coupling pathway.

Triferrocenylborane – Molecular Structure in Solution and in the Solid State

1995 ◽  
Vol 50 (2) ◽  
pp. 201-204 ◽  
Author(s):  
Bernd Wrackmeyer ◽  
Udo Dörfler ◽  
Wolfgang Milius ◽  
Max Herberhold
Keyword(s):  
Molecular Structure ◽  
Solid State ◽  
Low Temperature ◽  
Single Crystal ◽  
Nmr Spectra ◽  
The Other ◽  
X Ray ◽  
Single Diastereomer ◽  
Structure In Solution ◽  
C Nmr

According to a single crystal X-ray structure determination all three ferrocenyl substituents of triferrocenylborane (1) adopt the same orientation with respect to the BC3-plane [P21/c monoclinic; Z = 4; a = 1353.5(3), b = 1695.6(3), c = 1056.4(2) pm, β = 109.27(3)°]. The simulated X-ray powder pattern of the single crystal is identical with the powder diagram of a macroscopic sample, indicating the presence of a single diastereomer (1a) in the solid state. However, at low temperature (< - 95 °C) in solution, the 13C NMR spectra suggest the presence of the second diastereomer (1b) in which one ferrocenyl group is oriented opposite to the other two with respect to the central BC3-plane.

Preparation and X-ray crystal structures of the arsenic pentafluoride adducts of benzo-2,1,3-thiadiazole and benzo-1,2,3-thiadiazole

1986 ◽  
Vol 64 (5) ◽  
pp. 849-853 ◽  
Author(s):  
Allen Apblett ◽  
Tristram Chivers ◽  
John F. Richardson
Keyword(s):  
Nitrogen Atom ◽  
Crystal Structures ◽  
Benzene Ring ◽  
Heterocyclic Ring ◽  
Monoclinic Space Group ◽  
Crystal Data ◽  
Space Group ◽  
X Ray ◽  
X Ray Crystallography ◽  
C Nmr

The reaction of arsenic pentafluoride with benzo-2,1,3-thiadiazole, 1, or benzo-1,2,3-thiadiazole, 2, in liquid SO2 gave 1:1 adducts that were characterized spectroscopically (infrared and 13C nmr) and by X-ray crystallography. Crystal data: for 1•AsF5, monoclinic, space group P21/n, a = 6.932(1), b = 9.113(1), c = 15.136(2) Å, β = 98.035(7)°, V = 946.8(2) Å3, Z = 4; for 2•AsF5, monoclinic, space group P21/a, a = 7.573(2), b = 13.101(2), c = 9.514(3) Å, β = 90.95(2)°, V = 943.9(4) Å3, Z = 4. The coordination of AsF5 to one of the nitrogen atoms in 1 introduces asymmetry in the heterocyclic ring, with the longer bond lengths being associated with the coordinated nitrogen atom, d(S—N) = 1.633(5) and 1.577(6) Å, d(C—N) = 1.364(7) and 1.339(8) Å. The quinonoid character of the benzene ring is still apparent in the adduct. In 2•AsF5, the AsF5 molecule is coordinated to the nitrogen atom that is bonded to carbon.

Structural studies on 6-ethoxytetrahydropyrylium cations; stereoelectronic control in the reactions of lactonium salts

1991 ◽  
Vol 69 (12) ◽  
pp. 2024-2032 ◽  
Author(s):  
Ronald F. Childs ◽  
Marianne D. Kostyk ◽  
Colin J. L. Lock ◽  
Mailivaganam Mahendran
Keyword(s):  
Nmr Spectra ◽  
Positive Charge ◽  
Nucleophilic Attack ◽  
Structural Studies ◽  
Narrow Line ◽  
Crystal Lattices ◽  
X Ray ◽  
X Ray Crystallography ◽  
Stereoelectronic Control ◽  
C Nmr

The structures of 6-ethoxy-2,3,4,5-tetrahydropyrylium, 1, 6-ethoxy-2-methyl-2,3,4,5-tetrahydropyrylium, 2, and 2-ethoxy-3,4,4a,5,6,7,8,8a-octahydro-1-benzopyrylium, 3, hexachloroantimonates have been determined by X-ray crystallography. In each case the tetrahydropyrylium rings exist in shallow half-chair conformations with the cationic centers C(6), C(5), O(1), and O(6) having a planar arrangement. The cations all have a Z conformation about the O(6)—C(7) bonds and it is shown that this conformation is also preferred in solution by comparison of narrow-line 13C NMR spectra in the solid state and solution. The O(1)—C(2) and O(6)—C(7) bond distances in 1–3 are significantly longer than those of comparable bonds in neutral esters. The length of the O(1)—C(2) bond is very dependent on substitution at C(2) suggesting a considerable fraction of the positive charge resides on this carbon as well as C(7). The closest cation/anion interactions present in the crystal lattices of these salts are between the chlorine atoms of the anion and the cationic center, C(6). These interactions provide information on the origin of the stereoselectivity observed in nucleophilic attack on these cations. The conformations, details of the C—O bonding, and closest contacts between cation and anion are discussed in terms of the concept of stereoelectronic control. Key words: 6-ethoxytetrahydropyrylium cations, lactonium salts, structure, X-ray, stereoelectronic control.

cis-Cyclohexano-9-crown-3 ether. Solid state and low-temperature solution stereochemistry as determined by X-ray crystallography and nuclear magnetic resonance spectroscopy

1993 ◽  
Vol 71 (7) ◽  
pp. 951-959 ◽  
Author(s):  
G.W. Buchanan ◽  
A.B. Driega ◽  
A. Moghimi ◽  
C. Bensimon ◽  
K. Bourque
Keyword(s):  
Low Temperature ◽  
Nmr Spectra ◽  
Solid Phase ◽  
Resonance Spectroscopy ◽  
Ring Inversion ◽  
X Ray ◽  
Common Features ◽  
X Ray Crystallography ◽  
Temperature Solution ◽  
C Nmr

The X-ray crystal structure of the title material has been determined at −130 °C. Low-temperature 1H1H COSY, 13C1H HETCOR, and DEPT 13C NMR spectra have been recorded, which permit unambiguous assignments of all carbon resonances when ring inversion is slow on the NMR timescale. The limiting low-temperature solution phase 13C spectrum has many common features with the solid phase 13C CPMAS spectrum recorded at 300 K. Spectra for the 7,10-tetra-deuterio derivative have also been obtained and substituent influences on 13C shieldings are discussed in detail.

Metal complexes of an amine bisphenol with a thiophene side-arm

2010 ◽  
Vol 75 (10) ◽  
pp. 1051-1060 ◽  
Author(s):  
Eero Salminen ◽  
Reijo Sillanpää ◽  
Ari Lehtonen
Keyword(s):  
Solid State ◽  
Nitrogen Atom ◽  
Dimeric Complex ◽  
State Structure ◽  
Molybdenum Complex ◽  
Reaction Conditions ◽  
One Pot ◽  
X Ray ◽  
X Ray Crystallography ◽  
Phenolic Oxygen

Dioxomolybdenum(VI) and oxotungsten(VI) complexes with a new amine bisphenol ligand (H2L) are reported. The ligand which carries a neutral nitrogen atom, two phenolic oxygen atoms and a thiophene side-arm was synthesized by a simple one-pot Mannich reaction. Further reaction with [MoO2(acac)2] yielded a monomeric molybdenum complex [MoO2(L)(MeOH)] (2a) or a dimeric complex [Mo2O2(μ-O)2(L)2] (2b), depending on the reaction conditions. The reaction with a tungsten trisglycolate [W(eg)3] led to the formation of a monomeric compound [WO(eg)(L)] (3). In these complexes, the potentially tetradentate amine bisphenolate dianion coordinates as a tridentate O,N,O donor while the sulfur side-arm donor remains intact. The solid-state structure of 2a was investigated by X-ray crystallography.

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