[en] There have been only limited methods for the synthesis of cyclopenta[d][1,2]oxazines and their derivatives. Linn and Sharkey reported the first practical synthesis of cyclopenta[d][1,2]oxazine by use of benzoylated cyclopentadiene. Lloyd and co-workers also reported the synthesis of cyclopenta[d][1,2]oxazine by reaction of diaroylcyclopentadi-enes with hydroxylamine. The reaction of benzonitrile oxide with fulvene was known to yield both 1 : 1 and 2 : 1 adducts. Herein, we report the first example of a facile and convenient synthesis of various cyclopenta[d][1,2]oxazines starting from chlorooxime and fulvene through [6+4] cycloaddition. In an effort to pursue of PTP1B inhibitors, a convenient synthesis of functionalized cyclopenta[d][1,2]-oxazine derivatives was required. Fulvenes were obtained from the reaction of dimethyl sulfate salt of dimethylamides and cyclopentadienyl sodium as cited

[en] New data on the synthesis and properties of cyclopentadienyltricarbonylmanganese (cymantrene) derivatives are considered.

No abstract available

[en] Long sought structural data on an f-element tuck-in complex have been obtained for the title compound that contains the first example of both tuck-in and tuck-over bonding in a ligand derived from C_5Me_5"- by metalation. (Abstract Copyright [2008], Wiley Periodicals, Inc.)

[en] The uranium(III) iodide complex UI₃(THF)₄ reacts cleanly at ambient temperature with 1 equiv of sodium and potassium pentamethylcyclopentadienide salts in tetrahydrofuran to form the mono-ring uranium(III) complex (η-C₅Me₅)UI₂(THF)₃(1). Additionally, reaction of UI₃(THF)₄ with 2 equiv or more of K(C₅Me₅) in THF solution leads to the formation of the bis-ring adduct (η-C₅Me₅)₂UI(THF) (2) in high yield. In the solid state 1 exhibits a pseudo-octahedral mer,trans ligand geometry with the C₅Me₅ ligand occupying one axial position. U-I bond lengths range from 3.161(1) to 3.179(1)angstrom, while U-O distances to the THF ligands lie in the range 2.496(8)-2.594(10)angstrom. 1 also provides a convenient entry into a variety of other mono-ring complexes of uranium(III). In the presence of excess pyridine, the coordinated THF ligands of 1 are readily displaced for form the tris(tyridine) adduct (η-C₅Me₅)UI₂(py)₃(3), which exhibits a mer,trans ligand geometry in the solid state similar to that of 1. Methathesis of the iodide ligands in 1 with 2 equiv of KN(SiMe₃)₂ affords the bis(amido) complex (η-C₅Me₅)U[N(SiMe₃)₂]₂(4). An X-ray diffraction study of this molecule reveals that methyl groups from both amido ligands are involved in agostic interactions with the uranium-(III) center

[en] The crystal of 1,5-diphenyl-1,4-pentadien-3-one shows disappearance of reflections during UV/Vis irradiation without changes in its external appearance. The behaviour of molecules and changes in the crystal structure were monitored at initial stages of this process by the use of the X-ray diffraction and the structure analysis. The studies revealed that the photo-induced rearrangement in the crystal proceeds in a smooth way with a constant rate and it is accompanied by (a) the reduction of a percentage of the translationally related molecules; (b) the change of the existing molecular disorder; (c) the increase of intermolecular distances and (d) the change of the cell constants and the increase of the unit cell volume. The presented work is the first example of such studies in the scientific literature

[en] The potential barriers for the internal rotation of silole dimers are studied theoretically using the ab initio molecular orbital method at the RHF/6-31G** level of calculations. In 2,2'-bisilole, it is found that the anti-conformation is the most stable structure in the ground state and that the potential barrier height for rotation over the perpendicular conformation is 3.3 kcal/mol. 21 refs., 4 figs., 2 tabs

[en] The compound 1,4-pentadien-3-one,(1E,4E)-1,5-diphenyl-2-(2,4-dinitrophenyl)hydrazone presents the molecular formula C₂₃H₁₈N₄O₄ and was prepared in an undergraduate laboratory. The hydrazone was synthesized from the condensation between dibenzalacetone and 2,4-dinitrophenylhydrazine (DNPH) and crystallized employing water/acetone liquid-liquid diffusion. The structure presents three aromatic rings connected by an unsaturated Y-shaped system. Dinitro substituted and one of the other aromatic rings are 15° out of a coplanarity, while the other phenyl group is almost orthogonal to the first (89°). The only observed classical hydrogen bonding is an intramolecular N-H···O. The supramolecular structure was analyzed employing the Hirshfeld surface and that is organized through C-H···O hydrogen bond and C-H···π, polar-π, and π-stacking. An interaction involving NO₂···NO₂ was also observed. (author)

[en] A new technique for the determination of the concentration of active centers of polymerization and propagation rate constants for processes of cationic polymerization of conjugated dienes was proposed. The method consists of the quantitative calculation from the ¹³C NMR spectra of the concentration of the initial units of the polymer chain polydienes synthesized at different monomer conversions and the subsequent extrapolation of the obtained values to the zero monomer conversion. Using the proposed procedure, the chain propagation rate constants were determined for the cationic polymerization of isoprene and 1,3-pentadiene in the presence of a titanium tetrachloride–tert-butyl chloride catalytic system.

No abstract available