The Two-step Synthesis and Crystal and Molecular Structure of Tetracyclo[6.4.0.02,11.04,9]dodec-6-ene-3,10-dione

1975 ◽  
Vol 53 (14) ◽  
pp. 2068-2075 ◽  
Author(s):  
Yuen-Mui Ngan ◽  
Steven J. Rettig ◽  
John R. Scheffer ◽  
James Trotter
Keyword(s):  
Crystal And Molecular Structure ◽  
Direct Methods ◽  
Membered Ring ◽  
Diels Alder ◽  
High Yield ◽  
Side Chain ◽  
X Ray ◽  
Long Wavelength ◽  
Vinyl Group ◽  
Alder Adduct

The photochemistry of the trans-1,3,5-hexatriene-p-benzoquinone Diels–Alder adduct has been investigated. Irradiation of this material in its long wavelength n → π* absorption band leads to a single photoproduct in high yield. A single crystal X-ray structure determination shows this product to be tetracyclo[6.4.0.02,11.04,9]dodec-6-ene-3,10-dione, the result of a novel regiospecific intramolecular 2 + 2 photoaddition between the side chain vinyl group and the enedione double bond. Crystals of tetracyclo[6.4.0.02,11.04,9]dodec-6-ene-3,10-dione are monoclinic, a = 7.5290(7), b = 19.072(1), c = 6.7237(4) Å, β = 107.918(6) °, Z = 4, space group P21/n. The structure was solved by direct methods and was refined by full-matrix least-squares procedures to a final R of 0.041 for 1603 reflections with I ≥ 3σ(I). The structure consists of well-separated molecular units. Bond distances are: C=O, 1.216 and 1.219(2), C=C, 1.318(2), mean C(sp3)—C(sp2), 1.508, mean C(sp3)—C(sp3), 1.560 in the four-membered ring and 1.544 elsewhere, mean C(sp3)—H, 0.99, and mean C(sp2)—H, 0.95 Å. Bond distances between nonhy drogen atoms have been corrected for thermal motion. A possible rationalization for the observed photoprocess is discussed in terms of conformational and radical stability effects.

The crystal and molecular structure of 5-(propyn-1-yl)-1-(β-D-arabinofuranosyl)uracil. A very short C≡C triple bond

1984 ◽  
Vol 62 (1) ◽  
pp. 147-152 ◽  
Author(s):  
Mlroslaw Cygler ◽  
Wayne F. Anderson ◽  
Jerzy Giziewicz ◽  
Morris J. Robins
Keyword(s):  
Triple Bond ◽  
Crystal And Molecular Structure ◽  
Direct Methods ◽  
Pyrimidine Ring ◽  
Side Chain ◽  
X Ray Diffraction ◽  
X Ray ◽  
Anti Conformation ◽  
Sugar Ring ◽  
Glycosidic Torsion Angle

The crystal structure of 5-(propyn-1-yl)-1-(β-D-arabinofuranosyl)uracil, an analog of the active antiherpes nucleoside 1-(β-D-arabinofuranosyl)thymine, was determined by X-ray diffraction. The compound crystallizes in the space group P212121 with a = 4.925(1), b = 14.326(2), c = 17.454 Å. Reflections were measured on a diffractometer and the structure was solved by direct methods. Least-squares refinement converged at R = 0.032 for 1159 observed reflections. The sugar ring exhibits an 3E or a C(3′)endo conformation with a pseudorotation angle P = 28.3° and puckering amplitude τm = 31.7°. The orientation of the —CH2OH side chain is g+. The base is in an anti conformation with respect to the sugar ring, with a glycosidic torsion angle χ = 33.7°. Changes in the C(5)—C(6) and C(6)—N(1) bond lengths suggest some interaction of the propynyl group with the pyrimidine ring. The C≡C bond length of 1.121 Å is very short. Its shortening could result from intermolecular interactions with the neighboring pyrimidine ring and nearby oxygen atoms.

Structure and conformation of hydroxylubimin, a sesquiterpenoid phytoalexin

1977 ◽  
Vol 55 (10) ◽  
pp. 1619-1623 ◽  
Author(s):  
George I. Birnbaum
Keyword(s):  
Structure Analysis ◽  
Direct Methods ◽  
Membered Ring ◽  
Side Chain ◽  
Equatorial Position ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
X Ray ◽  
Independent Molecules ◽  
Chiral Centers

In order to determine the orientation of the isopropenyl group and confirm the stereochemistry at other chiral centers in lubimin (1) and hydroxylubimin (2), two antifungal sesquiterpenes, an X-ray structure analysis of 2 was carried out. Crystals of 2 are orthorhombic, space group P212121, a = 6.190, b = 7.210, c = 63.082 Å, Z = 8. The structure was solved by direct methods and refined to R = 0.045. In both independent molecules the six-membered ring is chair-shaped with all four substituents equatorially oriented. The five-membered ring, attached by a spiro junction, is a half-chair with the isopropenyl substituent in an equatorial position. This side-chain is trans to the methyl-bearing carbon in the six-membered ring.

The preparation and the crystal and molecular structure of S3N2NH2+BF4−; a molecular orbital study of the protonation of the trisulphur trinitride anion

1984 ◽  
Vol 62 (9) ◽  
pp. 1822-1827 ◽  
Author(s):  
Clifford G. Marcellus ◽  
Richard T. Oakley ◽  
A. Wallace Cordes ◽  
William T. Pennington
Keyword(s):  
Molecular Structure ◽  
Molecular Orbital ◽  
Crystal And Molecular Structure ◽  
Direct Methods ◽  
Membered Ring ◽  
Molecular Orbital Calculations ◽  
X Ray Diffraction ◽  
Triclinic Space Group ◽  
X Ray ◽  
Molecular Orbital Study

Protonation of the trisulphur trinitride ion, S3N3−, with tetrafluoroboric acid yields the ring-contracted S-amino thiodithiazyl salt, S3N2NH2+BF4−. The crystal and molecular structure of this salt has been determined by X-ray diffraction. The crystals are triclinic, space group P1, with a = 5.445(2), b = 7.346(3), c = 9.473(5) Å, α = 85.89(4), β = 83.92(3), γ = 82.13(3)°, V = 372.6(4) Å3, Dc = 2.02 g cm−3, and Z = 2. The structure was solved by direct methods and refined by full-matrix least-squares procedures to give a final R = 0.060. The structure of the five-membered ring with a single exocyclic NH2 group bonded to sulphur is discussed in relation to other S3N2NR derivatives. The reasons for the instability of six-membered rings of the type S3N3R are discussed in the light of MNDO molecular orbital calculations on an S3N3H model.

Structural Study of an Unusual Diels-Alder Adduct

1992 ◽  
Vol 45 (12) ◽  
pp. 2089 ◽  
Author(s):  
EL Ghisalberti ◽  
BW Skelton ◽  
AH White
Keyword(s):  
Single Crystal ◽  
Diffraction Study ◽  
Structural Study ◽  
Spectroscopic Studies ◽  
Diels Alder ◽  
X Ray Diffraction ◽  
X Ray ◽  
Naturally Occurring ◽  
Chemical Evidence ◽  
Alder Adduct

The structure of the compound obtained on heating the naturally occurring clerodane furanoditerpene (1) had been formulated as (2) on the basis of spectroscopic studies. A single-crystal X-ray diffraction study on the dihydro derivative of (2) has confirmed this and provides support for the stereochemistry previously assigned to (1) on the basis of chemical evidence.

Crystal and molecular structure of trans-[RhCl(CO)(PtBu2Ph)2]

2018 ◽  
Vol 73 (12) ◽  
pp. 1029-1032
Author(s):  
Peter Mayer ◽  
Hans-Christian Böttcher
Keyword(s):  
Molecular Structure ◽  
Ir Spectroscopy ◽  
Crystal And Molecular Structure ◽  
Title Complex ◽  
High Yield ◽  
X Ray ◽  
Carbonyl Ligands ◽  
Pale Yellow ◽  
X Ray Crystallography ◽  
Type Complex

AbstractTreatment of THF solutions containing the rhodium(II) complex trans-[RhCl2(PtBu2Ph)2] (1) with [Fe2(CO)9] in the same solvent resulted in the formation of the Vaska-type complex trans-[RhCl(CO)(PtBu2Ph)2] (2) in high yield. The title complex 2 was obtained as pale yellow crystals, characterized by NMR and IR spectroscopy, as well as by microanalyses. Additionally, the molecular structure of 2 has been established by X-ray crystallography. As often reported for similar constituted compounds, the chlorido and carbonyl ligands in crystals of 2 are strongly disordered.

Synthesis and x-ray structure of a Diels-Alder adduct of fullerene C60

1993 ◽  
Vol 115 (1) ◽  
pp. 344-345 ◽  
Author(s):  
Yves Rubin ◽  
Saeed Khan ◽  
Daron I. Freedberg ◽  
Chahan Yeretzian
Keyword(s):  
Diels Alder ◽  
Fullerene C60 ◽  
X Ray ◽  
Alder Adduct

The crystal and molecular structure of 1,4-diphenyl-2,2′,3,3′,5,5′,6,6′-octamethylcyclo-1,4-diphospha-2,3,5,6-tetrasilahexane, a phosphorus–silicon heterocycle

1979 ◽  
Vol 57 (2) ◽  
pp. 174-179 ◽  
Author(s):  
A. Wallace Cordes ◽  
Paul F. Schubert ◽  
Richard T. Oakley
Keyword(s):  
Molecular Structure ◽  
Crystal And Molecular Structure ◽  
Direct Methods ◽  
Chair Conformation ◽  
Monoclinic Space Group ◽  
Single Bond ◽  
X Ray Diffraction ◽  
Full Matrix ◽  
X Ray ◽  
Bond Lengths

The crystal structure of 1,4-diphenyl-2,2′,3,3′,5,5′,6,6′-octamethylcyclo-1,4-diphospha-2,3,5,6-tetrasilahexane, (PhPSi2Me4)2, has been determined by single crystal X-ray diffraction. The crystals are monoclinic, space group P21/c, with a = 9.866(1), b = 11.921(1), and c = 11.324(2) Å, β = 104.31(1)°, Z = 2, and ρcalcd = 1.15 g/cm3. The structure was solved by direct methods and was refined by full-matrix least-squares procedures to a final R of 0.060 and Rw of 0.078, for 1173 reflections with intensities greater than 3σ. The (PhPSi2Me4)2 molecule lies on a crystallographic centre of symmetry, and the six-membered P2Si4 ring has a chair conformation with equatorial phenyl groups. The endocyclic angles at P (104.4(1)°) and Si (104.9(2)°) are intermediate between those found in cyclic hexaphosphine and hexasilane molecules, and the Si—Si and P—Si distances of 2.345(3) and 2.252(4) Å, respectively, correspond to single bond lengths, with no appreciable evidence for secondary pπ → dπ bonding between phosphorus and silicon. The Si—C (1.867(8) Å) and P—C (1.828(7) Å) bond lengths are also normal. The variations in the Si—P—C (101.6(2)°, 108.6(2)°), P—Si—C (range 106.2(3)–120.0(3)°), and Si—Si—C (range 105.8(3)–113.7(3)°) angles indicate that the positions of the exocyclic methyl and phenyl groups are influenced by both intra- and intermolecular steric forces.

The methylgallium-2-carboxylatobenzimidazolato hexamer, [MeGa·C8H4N2O2]6·C6H6·(Me2C6H4)2; synthesis and X-ray crystal structure

1999 ◽  
Vol 77 (4) ◽  
pp. 434-438 ◽  
Author(s):  
Steven J Rettig ◽  
Alan Storr ◽  
James Trotter
Keyword(s):  
Crystal Structure ◽  
Carboxylic Acid ◽  
Room Temperature ◽  
Direct Methods ◽  
Membered Ring ◽  
Coordination Geometry ◽  
Temperature Reaction ◽  
Full Matrix ◽  
X Ray ◽  
Solvent Molecules

The room-temperature reaction of Me3Ga with benzimidazole 2-carboxylic acid in xylene solvent has yielded a novel crystalline hexameric gallium compound with "MeGa" moieties bridged by the doubly depronotated ligand precursor. Crystals of [MeGa(4,5-benzimidazolato-2-carboxylato)]6·(C6H6)·(m-Me2C6H4)2 are monoclinic, a = 18.091(2), b = 17.094(2), c = 13.2215(5) Å, Z = 2, space group C2/m. The structure was solved by direct methods and refined by full-matrix least-squares procedures to R (F, I [Formula: see text] 3σ(I)) = 0.064 (Rw (F2, all data) = 0.134). The hexameric Ga complex contains a six-membered ring of Ga atoms, bridged by the benzimidazolate ligands with the benzo rings projecting alternately above and below the Ga plane, thus forming a ball-shaped molecule. The complex could have ideal D3d symmetry, but it contains an encapsulated molecule of benzene, which distorts the regularity of the Ga6 hexagon, and reduces the symmetry of the complex to the crystallographically observed C2h. The coordination geometry at each of the two independent GaO2N2C centres approximates a trigonal bipyramid, with a N2C trigonal plane, and the O atoms above and below; average dimensions are Ga-O = 2.176(2), Ga-N = 1.973(3), Ga-C = 1.927(5) Å, O-Ga-O = 165°. The unit cell also contains four m-xylene solvent molecules (outside the molecular cage).Key words: gallium, crystal structure, benzene intercalate, benzimidazolecarboxylic acid.

Synthese und Molekülgeometrie von Dichloro[η2-bis(di-r-butylphosphino)methan]pIatin(II), Pt(dtbpm)Cl2. Die Elektronenstruktur von 1,3-Diphosphaplatinacyclobutan-Fragmenten / Synthesis and Molecular Structure of Dichloro[η2-bis(di-t-butylphosphino)methane]platinum(II), Pt(dtbpm)Cl2. The Electronic Structure of 1,3-Diphosphaplatinacyclobutane Fragments

1987 ◽  
Vol 42 (4) ◽  
pp. 395-409 ◽  
Author(s):  
Peter Hofmann ◽  
Helmut Heiß ◽  
Gerhard Müller
Keyword(s):  
Molecular Structure ◽  
Electronic Structure ◽  
Crystal And Molecular Structure ◽  
Cone Angle ◽  
Membered Ring ◽  
Experimental Investigations ◽  
Molecular Orbital Calculations ◽  
X Ray Diffraction ◽  
X Ray ◽  
Potential Precursor

Based upon the experimentally known but yet unexplained very different reactivities of the two isoelectronic and isolobal intermediates Pt(PMe3)2 and Pt(PEt3)2, the electronic structure and bonding capability of such 14 electron fragments as a function of their geometry (P-Pt-P angle α, determined by the phosphane cone angle) are investigated using molecular orbital calculations. A decrease of the P-Pt -P angle leads to an exceptionally pronounced energy ascent of the b2-HOMO of Pt(PR3)2 species, which, as a consequence, might lead to unusual reactivity patterns and bonding capabilities of 1,3-diphosphaplatinacyclobutane fragments, for which an extreme electronic situation is enforced by steric constraints. Dichloro[η2-bis(di-r-butylphosphino) methane]platinum(II), Pt(dtbpm)Cl2, is synthesized as a potential precursor of Pt(dtbpm), in order to allow experimental investigations of this taylor made four-membered ring chelate complex of Pt(0). The crystal and molecular structure of Pt(dtbpm)Cl2 · 2 CHCl3 has been determined by X-ray diffraction.

The crystal and molecular structure of tetrabenzocyclodecan-1,6-dione

1980 ◽  
Vol 58 (8) ◽  
pp. 777-779 ◽  
Author(s):  
T. Stanley Cameron ◽  
Christine Chan ◽  
David G. Morris ◽  
Alistair G. Shepherd
Keyword(s):  
Molecular Structure ◽  
Diffraction Analysis ◽  
Title Compound ◽  
Crystal And Molecular Structure ◽  
Membered Ring ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
Nmr Spectrum ◽  
X Ray ◽  
C Nmr

The crystals belong to the orthorhombic space group C222, with a = 9.226, b = 12.092, c = 16.513 Å, Z = 4. A single crystal X-ray diffraction analysis has shown that the title compound, in which all carbon atoms are sp2 hybridized, exists with the ten membered ring in a slightly twisted tub conformation. The 13C nmr spectrum is also reported.

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