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991.
Sabbasani Rajasekhara Reddy 《Tetrahedron letters》2004,45(18):3561-3564
Polyaniline supported vanadium complex 1 catalyzes efficiently the oxidation of alcohols to aldehydes and ketones in high yields under molecular oxygen in toluene at ca. 100 °C. The catalyst 1 can be recycled without loss of activity. 相似文献
992.
Synthesis of the structure claimed for puetuberosanol 1 (using the Juliá-Colonna oxidation in a key step) showed that the natural product was a different material. The isomeric epoxy alcohols 16-18 can be discounted from the alternatives. An analogue 19 of marshrin 2 was prepared but the synthesis of the natural product was thwarted by failure of a Juliá-Colonna oxidation in the key step. The epoxy ketone 29 was prepared by Darzens condensation and was converted into (±)-phebalosin 3. 相似文献
993.
Subbarayan VelusamyT Punniyamurthy 《Tetrahedron letters》2003,44(50):8955-8957
Copper(II) complex 1 efficiently catalyses the oxidation of alkylbenzenes and cyclohexane into the corresponding ketones in moderate to high yields in the presence of 30% H2O2. This protocol is simple, clean and generates water as the only by-product. 相似文献
994.
Traversa Enrico Di Vona Maria Luisa Licoccia Silvia Sacerdoti Michele Carotta Maria Cristina Gallana Massimiliano Martinelli Giuliano 《Journal of Sol-Gel Science and Technology》2000,19(1-3):193-196
Pure, 5 at%, and 10 at% Ta- or Nb-doped TiO2 nanosized powders were prepared by the sol-gel method. The powders heated to 400°C have the crystalline anatase structure. While the pure TiO2 powder heated to 850°C has the rutile structure, the addition of Ta and Nb inhibited the anatase-to-rutile phase transformation at this temperature. Ta was soluble in the titania lattice up to the concentration of 10 at%, while the solubility of Nb was 5 at%. Thick films were fabricated with these powders by screen printing technology and then fired at 650°C and 850°C for 1 h. SEM observations showed that the anatase-to-rutile phase transformation induces a grain growth of about one order of magnitude for pure TiO2. The addition of Ta and Nb is effective to keep the TiO2 grain size at the nanometric level even at 850°C. Conductance measurements showed that a good gas response is observed only for the nanostructured titania-based films. The CO response of these materials is only slightly affected by humidity. 相似文献
995.
Ming Wen Kejia E Haiquan Qi Lujiang Li Juan Chen Ying Chen Qingsheng Wu Tao Zhang 《Journal of nanoparticle research》2007,9(5):909-917
Dispersed-well FePt nanoparticles with particle size ~5 nm have been prepared by hydrazine hydrate reduction of H2PtCl6·6H2O and FeCl2·4H2O in ethanol–water system. By employing as-synthesized FePt nanoparticles, the monolayer can be formed by LB Technique. The
structural, magnetic properties and electrochemical properties of FePt monolayer were respectively studied by XRD, TEM, VSM
and CHI 820 electrochemical workstation. The as-synthesized particle has a chemically disordered fcc structure and can be
transformed into chemically ordered fct structure after annealing treatment above 400°C. The coercivity of ordered fct FePt
phase can be up to 2515Oe. CVs of 0.5 M H2SO4/0.5M CH3OH on GCE modified with FePt nanoparticles monolayer films illustrate that the as-synthesized FePt is a kind of active electrochemical
catalyst. 相似文献
996.
997.
Small bimetallic Pd-Fe particles supported on a well ordered alumina film grown on NiAl (1 1 0) were studied focusing on the geometric, electronic, adsorption, as well as magnetic properties. The morphology, growth mode and surface composition were investigated by combining scanning tunneling microscopy (STM), temperature-programmed desorption (TPD) and infrared spectroscopy (IRAS) using CO as a probe molecule. Information on the electronic properties of the bimetallic systems was obtained by means of X-ray photoelectron spectroscopy (XPS). These measurements were amended by in situ ferromagnetic resonance spectroscopy to address the magnetic properties of the bimetallic particles. The subsequent deposition of the metals at 300 K varying the order of metal deposition resulted in two distinct bimetallic systems. Pd deposited on existing Fe particles forms a shell, however, FMR and XPS suggest that intermixing of Pd and Fe occurs to some extent. For the reverse order, a larger amount of Fe is required to coat Pd particles, due to the strong tendency of Pd to segregate to the surface of the particles. 相似文献
998.
This review focuses mainly on recent endeavors in the field of cyclizations triggered by the catalytic hydroamination (formal or direct) of alkynes. The new strategies developed offer an efficient and convenient entry to several heterocycles of biological importance. 相似文献
999.
Hongwei Lu Yusheng Qin Xianhong Wang Xiangguang Yang Suobo Zhang Fosong Wang 《Journal of polymer science. Part A, Polymer chemistry》2011,49(17):3797-3804
Recently, rare earth ternary coordination catalyst represented as Y(CCl3OO)3‐Glycerin‐ZnEt2 has been used for producing poly(propylene carbonate) (PPC, an alternating copolymer of carbon dioxide and propylene oxide) in industry scale, but its catalytic activity needs further improvement. One reason for the relatively low catalytic activity lied in that only 11.7% of active center was efficient due to possible embedding of active center in the heterogeneous catalyst. In this report, supporting strategy was developed, where Y(CCl3OO)3‐Glycerin‐ZnEt2 was supported on various inorganic oxides. Two supporting methods were carried out. One way was to mix Y(CCl3OO)3‐Glycerin with inorganic oxide first and then ZnEt2 was dropped to form the supported catalyst, and the other was to make Y(CCl3OO)3‐Glycerin‐ZnEt2 at first and then mixing with inorganic oxides. The former showed decreasing catalytic activity compared with corresponding unsupported rare earth ternary catalyst, while an improvement of 16–36% in catalytic activity was realized in the latter. PPC with an average number molecular weight (Mn) of over 100 kg/mol and carbonate unit (CU) content of higher than 96% was prepared by both supported catalysts. The catalytic activity of the supported catalyst depended significantly on the supports, which increased in the following order: α‐Al2O3 < MgO < ZnO ≈ SiO2 <γ‐Al2O3. γ‐Al2O3 was the best support for rare earth ternary catalyst, which showed a remarkable 36% increase in catalytic activity, corresponding to the utilization of 17% of active center. Although MgO supported catalyst gave only an 8% increase in catalytic activity, the Mn and CU content of PPC were raised to about 143 kg/mol and 99%, whereas the PPC from common rare earth ternary catalyst was about 108 kg/mol and 97%, respectively. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
1000.
Dan He Seok Kyun Noh Won Seok Lyoo 《Journal of polymer science. Part A, Polymer chemistry》2011,49(21):4594-4602
Past research has examined the atom transfer radical polymerization (ATRP) with high oxidation state metal complexes and without the need for any additives such as reducing agent or free radical initiator. To extend this research, half‐metallocene ruthenium(III) (Ru(III)) catalysts were used for the polymerization of methyl methacrylate (MMA) for the first time. These catalysts were generated in situ simply by mixing phosphorus‐containing ligand and pentamethylcyclopentadienyl (Cp*) Ru(III) polymer ((Cp*RuCl2)n). The complexes in their higher oxidation state such as Cp*RuCl2(PPh3) were air‐stable, highly active, and removable catalysts for the ATRPs of MMA with both precision control of molecular weight and narrow polydispersity index. The addition of ppm amount of metal catalyst contributed to the formation of very well‐defined homopolymers and copolymers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献