Cyclization/acylation reactions by nickel-catalyzed reactions of 1,6-ynal and 1,6-enyne derivatives with acylzirconocene chloride

NiCl₂(PPh₃)₂-catalyzed reactions of 1,6-ynal or 1,6-enyne compounds with n-nonanoylzirconocene chloride afforded stereoselectively cyclopentane derivatives or bicyclo[3.1.0] compounds by catalytic cyclization/acylation reactions, which would involve (i) the primary formation of a metallacycle followed by (ii) the transfer of an acyl group from the acylzirconocene complex (transmetalation).     

Thermoanalytical study on the oxidation of uranium dioxides derived from uranyl nitrate,uranyl acetate and ammonium diuranate

The oxidation of UO₂ was investigated by TG, DSC and X-ray diffraction . UO₂ samples were prepared by the reduction of UO₃ at P_H2 + P_N2 = 100 + 50 mm Hg and 5°C min^?1 up to 800°C. In order to obtain six UO₂ samples with different preparative histories, UNH, UAH and ADU were used as starting materials and their thermal decomposition was carried out at 450–625°C for 0–9 h at an air flow rate of 100 ml min^?1. α-UO₃, γ-UO₃, UO₃ - 2 H₂O, and their mixtures were obtained. The reduction of UO₃ gave β-UO_2+x with different x values from 0.030 to 0.055. The oxidation carried out at P_O2 = 150 mm Hg was found to consist of oxygen uptake at room temperature. UO₂ - U₃O₇ (Step I) and U₃O₇ → U₃O₈ (Step II). TG and DSC curves of the oxidation showed two plateaus and two exothermic peaks corresponding to Steps I and II. In the case of two of the samples, the DSC peak of Step II split into two substeps, which were assumed to be due to the different reactivities of U₃O- formed from α-CO₃ and that from other types of UO₃. The increase in O/U ratio due to the oxygen uptake at room temperature changed from 0.010 to 0.042 except for a sample prepared from ADU which showed an extraordinarily large value of 0.445. TG curves showed an increase in O/U from room temperature to near 250°C for Step I and the plateau at 250–350°C where O/U was about 2.42, and showed a sharp increase in O/U above 350°C for Step II and the plateau above 100°C where O/U was 2.72–2.75. It is thought that the prepared UO₂ had a defective structure with a large interstitial volume to accommodate the excess oxygen.     

Reaction of alkenes and dienes with t-butylmagnesium halides and zirconocene dihalides. A convenient procedure for hydrozirconation and a novel t-butylzirconation of conjugated alkenes

The reaction of nonconjugated monosubstituted alkenes with t-BuMgCl and Cl₂ZrCp₂ at room temperature produces the corresponding monoalkylzirconium derivatives in high yields, while conjugated alkenes undergo either a novel t-butylzirconation or hydrozirconation depending on the reaction conditions.     

A novel photochemical cycloaddition of 2-alkoxy-3-cyanopyridines to 2-cyanofuran

Irradiation of a benzene solution of 2-alkoxy-3-cyanopyridines in the presence of 2-cyanofuran gave 4+4 photoadducts in good yields, and the structure was established by X-ray single crystal analysis.     

Radiation-induced oxidation of polyethylene,ethylene–butene copolymer,and ethylene–propylene copolymer

Oxygen consumption and yield of oxidation products during γ-irradiation were studied on five types of polyethylene (PE), ethylene–butene copolymer (EB), and ethylene–propylene copolymer (EPR) using gas chromatography, mass spectrography, and high-resolution NMR. Samples were irradiated in oxygen under pressure from 0 to 500 torr by ⁶⁰Co γ-rays up to 20 Mrad at 22–25°C. In enough oxygen, oxygen consumption and yield of oxidation products are independent of oxygen pressure for low-density PE, EB, and EPR. The G values of oxygen consumption were 14–18.4 for PE, 11.6 for EB at 1 × 10⁶ rad/h, and 8.3 for EPR at 2 × 10⁵ rad/h. The oxidation products determined were carboxylic acid (? CH₂? CO? OH), H₂O, CO₂, and CO. The oxygen consumption and oxidation products for PE were found to increase with increasing crystallinity.     

Temperature effects on radiation induced phenomena in polytetrafluoroetylene (PTFE)-Change of G-value

Temperature dependencies on the radiation induced phenomena and G-value of polytetrafluoroethylene (PTFE) have been studied in a temperature range 77–653 K. It is well known that main chain scission occurs very effectively below the melting temperature of PTFE (600 K). We have found in our experiments that G-value of chain scission increases significantly with increasing irradiation temperature, until 600 K. In addition to that, we have realized that crosslinking occurs by irradiation in the molten state at 613 K (Tabata, 1992; Oshima et al., 1995; Tabata et al., 1996). In the molten state, G-value of crosslinking was found to be 0.35 (number of crosslinking/100 eV absorption), as a lower limit, and the apparent G-value of chain scission is drastically reduced. Above 633 K, radiation induced crosslinking mainly occurs, however parallel thermal depolymerization or decomposition takes place to some extent.     

Study of the parameters controlling the enantio-differentiating ability of asymmetrically modified solid catalysts for the hydrogenation of γ-ketoesters

The enantio-differentiating hydrogenation of γ-ketoesters was carried out over asymmetrically modified solid catalysts. The parameters affecting the enantiomer excess (ee) were investigated and the results were compared with those of the hydrogenation of methyl acetoacetate and 2-octanone reported in the literature. The highest value of enantiomer excess of 51% was attained for the hydrogenation of methyl 4-oxopentanoate over a tartaric acid (TA)-NaBr-modified reduced nickel catalyst prepared from nickel oxide. The amount of NaBr in the modification solution needed to be optimized according to the manufacturers of the nickel oxides. The addition of an appropriate amount of carboxylic acid to the reaction media increased the enantiomer excess of the hydrogenated products.     

ESR study on free radicals trapped in crosslinked polytetrafluoroethylene (PTFE)

Free radicals in crosslinked PTFE which formed by ⁶⁰Co γ-rays irradiaion at 77 K and at room temperature were studied by electron spin resonance (ESR) spectroscopy. The crosslinked PTFE specimens with different crosslinking density were prepared by electron beam irradiation in the molten state. The ESR spectra observed in the irradiated crosslinked PTFE are much different from those in non-crosslinked PTFE (virgin); a broad singlet component increases with increasing the crosslinking density, G-value of radicals is much higher in crosslinked PTFE than in non-crosslinked one. Free radicals related to the broad component are trapped in the non-crystalline region of crosslinked PTFE and rather stable at room temperature, whereas radicals trapped in amorphous non-crosslinked PTFE are unstable at room temperature. It is thought that most of free radicals trapped in the crosslinked PTFE are formed in the crosslinked amorphous region. The trapped radicals decays around 383 K (110°C) due to the molecular motion of -relaxation.     

Thermotropic liquid crystalline poly(L-glutamate) esters with long alkyl chain containing aromatic segment at terminal position

Poly(L -glutamate) esters ( 3a – 3d ) with long alkyl side chains containing a mesogenic aromatic segment at the terminal position were synthesized. The superstructure of these polypeptides in solution and film were found to hold a α-helical conformation which was confirmed by CD, IR, and dichroic IR spectroscopy. The thermotropic liquid crystalline behavior was investigated by DSC, x-ray diffraction, and polarizing microscopy with hot stage. Polymers 3a and 3b , having transesterification over 60%, were assumed at least to have two liquid crystalline states. Polymer 3c-H-95 exhibited one crystalline state and two liquid crystalline states; however, 3d-H-97 did not show distinct liquid crystalline states.