Diastereoselective formation of 18-membered ring BINOL-hydrogen phosphonate dimers - Quasi-covalent hydrogen bonds?

2007 ◽  
Vol 85 (7-8) ◽  
pp. 466-474 ◽  
Author(s):  
Hossein A Dabbagh ◽  
Nader Noroozi-Pesyan ◽  
Ali R Najafi-Chermahini ◽  
Brian O Patrick ◽  
Brian R James
Keyword(s):  
Hydrogen Bonds ◽  
Computational Analysis ◽  
Ring Structure ◽  
Membered Ring ◽  
Hydrogen Atoms ◽  
Constrained Geometry ◽  
Decomposition Point ◽  
Point Data ◽  
Hydrolysis Of ◽  
Hydroxyl Hydrogen

Diastereoselective syntheses of the unusual dimers, 4-heptyl-2-(2′-hydroxy-binaphthyl)hydrogen phosphonate (5) and the cyclohexyl analogue (7), are achieved by hydrolysis of 4-(3,5-dioxa-4-phosphacyclohepta[2,1-α;3,4-α′]-dinaphthalene-4-yloxy)heptane (4) and the cyclohexane analogue (6), respectively. Two out of eight possible pairs of monomers units are involved in the stereoselective formation of the dimer 5a of configuration BINOLR-PS:BINOLR-PS; this is determined by X-ray crystallographic data, which reveal a centrosymmetric, 18-membered ring structure with Ci symmetry, consisting of two monomers strongly hydrogen-bonded between the oxygen of P=O units and hydroxyl hydrogen atoms. Mass spectrometric, melting point, and thermal decomposition point data, as well as NMR data, support the presence of strong, quasi-covalent hydrogen bonds. Computational analysis suggests that the diastereoselectivity is controlled by molecularly constrained geometry of the monomer. Compound 7, although not characterized crystallographically, appears to be analogous to 5.Key words: 18-membered ring, phosphonate dimer, diastereoselectivity, hydrogen-bonds, computational analysis.

scholarly journals Crystal structure of 6,6,12,12-tetrachlorotricyclo[8.2.0.04,7]dodecane-5,11-dione

2015 ◽  
Vol 71 (9) ◽  
pp. 1000-1002
Author(s):  
Esra Turan Akın ◽  
Tuncer Hökelek
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Membered Ring ◽  
Two Dimensional ◽  
Asymmetric Unit ◽  
Hydrogen Atoms ◽  
Compound C ◽  
Dimensional Network ◽  
Independent Molecules

The asymmetric unit of the title compound, C12H12Cl4O2, contains two crystallographically independent molecules with almost identical conformations (r.m.s. overlay fit for the non-hydrogen atoms = 0.059 Å). In each molecule, the central eight-membered ring has a distorted boat configuration, and two non-planar four-membered rings are fused on either side of the eight-membered ring. A weak C—H...O hydrogen bond links the two independent molecules. In the crystal, weak C—H...O hydrogen bonds link the molecules into a two-dimensional network parallel to (001).

scholarly journals 4-Aminobenzoic acid 4-methylpyridine/4-methylpyridinium 4-aminobenzoate 0.58/0.42: a redetermination from the original data

2017 ◽  
Vol 73 (10) ◽  
pp. 1508-1512
Author(s):  
Jan Fábry
Keyword(s):  
Hydrogen Bonds ◽  
Original Data ◽  
Amine Group ◽  
Aminobenzoic Acid ◽  
Hydrogen Atoms ◽  
Acta Cryst ◽  
Methyl Group ◽  
Hydrogen Bond Pattern ◽  
Hydroxyl Hydrogen Atom ◽  
Hydroxyl Hydrogen

The title structure, 4-aminobenzoic acid 4-methylpyridine/4-methylpyridinium 4-aminobenzoate 0.58/0.42, 0.58(C6H7N·C7H7NO2)·0.42(C6H8N+·C7H6NO2−), has been redetermined from the data published by Kumaret al.(2015).Acta Cryst.E71, o125-o126. The improvement of the present redetermination consists in the introduction of disorder of the methyl group over two positions as well as in the correction of the positional parameters of the hydrogen atoms that are involved in the O—H...N or N—H...O hydrogen bonds. After the correction, the hydroxyl hydrogen atom turned out to be disordered over two positions about the centre of the O...N bond, which is relatively long [2.642 (2) Å], while the H atoms of the primary amine group account more realistically for the hydrogen-bond pattern after the removal of the positional constraints. All the O—H...N or N—H...O hydrogen bonds which are present in the title structure are of moderate strength.

The Crystal and Molecular Structure of sym-fac-(1,4,7-Triazaheptane)-(S)-aspartatocobalt(III) Diperchlorate Dihydrate

1994 ◽  
Vol 59 (5) ◽  
pp. 1052-1058 ◽  
Author(s):  
Jan Ondráček ◽  
Jana Ondráčková ◽  
Jaroslav Maixner ◽  
František Jursík
Keyword(s):  
Molecular Structure ◽  
Aspartic Acid ◽  
Crystal And Molecular Structure ◽  
Heavy Atom ◽  
Membered Ring ◽  
Boat Conformation ◽  
Hydrogen Atoms ◽  
Orthorhombic System ◽  
Anisotropic Temperature ◽  
Heavy Atom Method

The crystal and molecular structure of s-fac-[Co((S)-Asp)(dien)]ClO4 . HClO4 .2 H2O (dien = 1,4,7-triazaheptane) was solved by the heavy atom method. The position parameters of the non-hydrogen atoms and their anisotropic temperature parameters were refined based on 1 726 observed reflections with a final value of R = 0.073. The substance crystallizes in the orthorhombic system in the space group P212121, Z = 4, a = 8.506(1), b = 17.171(2), c = 13.277(1) Å. The structure involves hydrogen bonds between the O2, O4 and HN2 atoms of aspartic acid and the two molecules of water. The five-membered dien chelate rings take the asymmetric envelope conformations. The five-membered ring of (S)-aspartic acid possesses the symmetric envelope conformation whereas the six-membered ring exhibits the skew boat conformation.

Crystal structure of pomalidomide Form I, C13H11N3O4

2021 ◽  
pp. 1-6
Author(s):  
James A. Kaduk ◽  
Amy M. Gindhart ◽  
Thomas N. Blanton
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Powder Diffraction ◽  
Density Functional ◽  
Double Layers ◽  
Carbonyl Groups ◽  
Hydrogen Atoms ◽  
Powder Diffraction File ◽  
Functional Theory ◽  
Amine Hydrogen

The crystal structure of pomalidomide Form I has been solved and refined using synchrotron X-ray powder diffraction data and optimized using density functional theory techniques. Pomalidomide Form I crystallizes in the space group P-1 (#2) with a = 7.04742(9), b = 7.89103(27), c = 11.3106(6) Å, α = 73.2499(13), β = 80.9198(9), γ = 88.5969(6)°, V = 594.618(8) Å3, and Z = 2. The crystal structure is characterized by the parallel stacking of planes parallel to the bc-plane. Hydrogen bonds link the molecules into double layers also parallel to the bc-plane. Each of the amine hydrogen atoms acts as a donor to a carbonyl group in an N–H⋯O hydrogen bond, but only two of the four carbonyl groups act as acceptors in such hydrogen bonds. Other carbonyl groups participate in C–H⋯O hydrogen bonds. The powder pattern has been submitted to ICDD® for inclusion in the Powder Diffraction File™ (PDF®).

Understanding the microcrystal tests of three related phenethylamines: theortho-metallated (±)-amphetamine formed with gold(III) chloride, and the tetrachloridoaurate(III) salts of (+)-methamphetamine and (±)-ephedrine

2013 ◽  
Vol 69 (4) ◽  
pp. 388-393 ◽  
Author(s):  
Matthew R. Wood ◽  
Roger A. Lalancette
Keyword(s):  
Drug Use ◽  
Illicit Drug ◽  
Illicit Drug Use ◽  
Ring Structure ◽  
Membered Ring ◽  
Asymmetric Unit ◽  
Organic Components ◽  
Bidentate Complex

Theortho-metallation product of the reaction of (±)-amphetamine with gold(III) chloride, [D,L-2-(2-aminopropyl)phenyl-κ2N,C1]dichloridogold(III), [Au(C9H12N)Cl2], and the two salts resulting from crystallization of (+)-methamphetamine with gold(III) chloride, D-methyl(1-phenylpropan-2-yl)azanium tetrachloridoaurate(III), (C10H16N)[AuCl4], and of (±)-ephedrine with gold(III) chloride, D,L-(1-hydroxy-1-phenylpropan-2-yl)(methyl)azanium tetrachloridoaurate(III), (C10H16NO)[AuCl4], have different structures. The first makes a bidentate complex directly with a dichloridogold(III) group, forming a six-membered ring structure; the second and third each form a salt with [AuCl4]−(each has two formula units in the asymmetric unit). The organic components are all members of the same class of stimulants that are prevalent in illicit drug use. These structures are important contributions to the understanding of the microcrystal tests for these drugs that have been employed for well over 100 years.

Bestimmung von innermolekularen Torsionswinkeln aus Hyperfeinstruktur-Aufspaltungen und g-Faktoren

1965 ◽  
Vol 20 (9) ◽  
pp. 1117-1121 ◽  
Author(s):  
K. Möbius
Keyword(s):  
Electron Diffraction ◽  
Aromatic Hydrocarbon ◽  
Aromatic Hydrocarbons ◽  
Small Amplitude ◽  
Membered Ring ◽  
Radical Ions ◽  
Hydrogen Atoms ◽  
Stereochemical Structure ◽  
X Ray ◽  
Phenyl Rings

The stereochemical structure of aromatic hydrocarbons in solution being overcrowded with hydrogen atoms is not known with certainty, because the conventional X-ray and electron diffraction methods are suitable only for samples in the crystalline and vapor phase. Using EPR spectroscopy for the aromatic hydrocarbon radicals biphenyl (—), phenanthrene (—) and pentaphenylcyclopentadienyl (PPCPD) innermolecular twist and bond angles could be determined by means of hfssplittings and g-factors. Stably solvated biphenyl radical ions are found to have twist angles of 38 ±2°; phenanthrene ions turn out to be planar but change their angles of hybridization at particular positions; in the PPCPD radical the phenyl rings oscillate with small amplitude around planes orthogonal to the five-membered ring.

scholarly journals 14,15-Didehydrohellebrigenin

2012 ◽  
Vol 68 (6) ◽  
pp. o1614-o1615
Author(s):  
Tong Yu ◽  
Hai-Yan Tian ◽  
Xiao-Feng Yuan ◽  
Shu-Zhi Hu ◽  
Ren-Wang Jiang
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Title Compound ◽  
Lactone Ring ◽  
Three Dimensional ◽  
Membered Ring ◽  
Envelope Conformation ◽  
Compound C ◽  
Dimensional Network ◽  
Hydroxy Groups

The title compound, C24H30O5, is the didehydro product of the steroid hellebrigenin (systematic name: 3β,5,14-trihydroxy-19-oxo-5β-bufa-20,22-dienolide). It consists of three cyclohexane rings (A, B and C), a five-membered ring (D) and a six-membered lactone ring (E). The stereochemistry of the ring junctions are A/B cis, B/C trans and C/D cis. Cyclohexane rings A, B and C have normal chair conformations. The five-membered ring D with the C=C bond adopts an envelope conformation. Lactone ring E is essentially planar with a mean derivation of 0.006 (4) Å and is β-oriented at the C atom of ring D to which it is attached. There is an O—H...O hydrogen bond in the molecule involving the hydroxy groups. In the crystal, O—H...O hydrogen bonds link the molecules into chains propagating along [010]. The chains are linked by C—H...O contacts into a three-dimensional network.

Vinyl ether hydrolysis. XVII. Oxacyclonon-2,8-diene and the question of the unorthodox reaction mechanism for 9-methoxyoxacyclonon-2-ene

1984 ◽  
Vol 62 (1) ◽  
pp. 74-76 ◽  
Author(s):  
R. A. Burt ◽  
Y. Chiang ◽  
A. J. Kresge ◽  
S. Szilagyi
Keyword(s):  
Reaction Mechanism ◽  
Vinyl Ether ◽  
Membered Ring ◽  
Specific Rate ◽  
Ether Group ◽  
Reaction Proceeds ◽  
Great Reactivity ◽  
Rate Of Hydrolysis ◽  
Acid Catalyzed ◽  
Hydrolysis Of

The acid-catalyzed hydrolysis of the nine-membered ring cyclic vinyl ether, oxacyclonon-2,8-diene, occurs with a normal isotope effect, [Formula: see text], which indicates that this reaction proceeds by the conventional vinyl ether hydrolysis mechanism involving rate-determining proton transfer to carbon. The specific rate of this reaction, [Formula: see text], may then be used to show that there is no significant ring-size effect on the rate of hydrolysis of a vinyl ether group in a nine-membered ring. The previously noted unusually great reactivity of the vinyl ether group in 9-methoxyoxacyclonon-2-ene, for which an unorthodox reaction mechanism has been claimed, must therefore be due to some other cause.

Distinguishment of Weak Interactions of Hydrogen Atoms Bound to Carbon Atoms: X-Ray Crystal Structural and Hirshfeld Surface Analyses of 2-Hydroxy-7-methoxy-3-(2,4,6-trimethylbenzoyl)naphthalene with the 2-Methoxylated Homologue

2021 ◽  
Vol 19 ◽  
Author(s):  
Kikuko Iida ◽  
Toyokazu Muto ◽  
Miyuki Kobayashi ◽  
Hiroaki Iitsuka ◽  
Kun Li ◽  
...  
Keyword(s):  
Hydrogen Bonds ◽  
Title Compound ◽  
Molecular Conformation ◽  
Weak Interactions ◽  
Carbonyl Oxygen ◽  
Hirshfeld Surface ◽  
Molecular Surface ◽  
Hydrogen Atoms ◽  
X Ray ◽  
Classical Hydrogen Bond

Abstract: X-ray crystal and Hirshfeld surface analyses of 2-hydroxy-7-methoxy-3-(2,4,6-trimethylbenzoyl)naphthalene and its 2-methoxylated homologue show quantitatively and visually distinct molecular contacts in crystals and minute differences in the weak intermolecular interactions. The title compound has a helical tubular packing, where molecules are piled in a two-folded head-to-tail fashion. The homologue has a tight zigzag molecular string lined up behind each other via nonclassical intermolecular hydrogen bonds between the carbonyl oxygen atom and the hydrogen atom of the naphthalene ring. The dnorm index obtained from the Hirshfeld surface analysis quantitatively demonstrates stronger molecular contacts in the homologue, an ethereal compound, than in the title compound, an alcohol, which is consistent with the higher melting temperature of the former than the latter. Stabilization through the significantly weak intermolecular nonclassical hydrogen bonding interactions in the homologue surpasses the stability imparted by the intramolecular C=O…H–O classical hydrogen bonds in the title compound. The classical hydrogen bond places the six-membered ring in the concave of the title molecule. The hydroxy group opposingly disturbs the molecular aggregation of the title compound, as demonstrated by the distorted H…H interactions covering the molecular surface, owing to the rigid molecular conformation. The position of effective interactions predominate over the strength of the classical/nonclassical hydrogen bonds in the two compounds.

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