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1.
A metal-free approach for the synthesis of seven-membered N-heterocycles has been developed by the I2-promoted intramolecular cross-coupling/annulation of butenyl anilines. This cyclization reaction involves C−H activation and C−C bond formation and exhibits good functional group tolerance. A series of benzo[b]azepine derivatives are obtained in moderate to good yields. 相似文献
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L. Bonhomme-Coury N. Lequeux S. Mussotte P. Boch 《Journal of Sol-Gel Science and Technology》1994,2(1-3):371-375
Sol-gel routes in the ternary system Al2O3-TiO5-ZrO2 were investigated to prepare Al2TiO5-ZrO2 mixed powders. The preparation of ZrTiO4 and Al2TiO5 was studied before going on with the ternary system. Zirconium titanate precursor gels were prepared from Ti(OPri)4 and Zr(OPrn)4 mixtures. The crystallization of ZrTiO4 develops at T<700°C. Al2TiO5 was prepared by different ways, using mixtures of Al(OBus)2(C6H9O3) with Ti(OPr
i
)4 (i), or with acetic acid addition (ii). Route (i) leads to a separate crystallization of TiO2 and -Al2O3, with subsequent formation of -Al2TiO5 at T1360°C. Although the pseudobrookite -Al2TiO5 is thermodynamically unstable below 1280°C, route (ii) leads to the crystallization of metastable -Al2TiO5 at T800°C. At increasing temperature, -Al2TiO5 decomposes into TiO2 and -Al2O3, then the two compounds react to form stable -Al2TiO5. For the ternary system, all the preparation routes which were studied lead to ZrTiO4 and -Al2O3 with subsequent reaction (at T1500°C) to give -Al2TiO5 and ZrO2. 相似文献
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Aeysha Sultan 《合成通讯》2014,44(3):417-423
An efficient free radical–mediated intramolecular cyclization strategy has been developed for the synthesis of 3-aryl-5-chloroindan-1-ones. Variously substituted 2,4-dichloroenones afforded 3-aryl-5-chloroindan-1-ones in quantitative yields upon intramolecular cyclization under free radical conditions. 相似文献
5.
Preparation and characterization of porous TiO_2/ZnO composite nanofibers via electrospinning 总被引:1,自引:0,他引:1
<正>Porous TiO_2/ZnO composite nanofibers have been successfully prepared by electrospinning technique for the first time.It was generated by calcining TiO_2/ZnCl_2/PVP[PVP:polyvinyl pyrrolidone)]nanofibers,which were electrospun from a mixture solution of TiO_2,ZnCl_2 and PVP.Transmission electron microscopy(TEM) and X-ray diffraction(XRD) analyses were used to identify the morphology of the TiO_2/ZnO nanofibers and a formation of inorganic TiO_2/ZnO fibers.The porous structure of the TiO_2/ZnO fibers was characterized by N_2 adsoption/desorption isotherm.Surface photovoltage spectroscopy(SPS) and photocatalytic activity measurements revealed advance properties of the porous TiO_2/ZnO composite nanofibers and the results were compared with pure TiO_2 nanofibers,pure ZnO nanofibers and TiO_2/ZnO nanoparticles. 相似文献
6.
Jae Du Ha Sun Young Kim Su Jung Lee Seung Kyu Kang Jin Hee Ahn Sung Soo Kim Joong-Kwon Choi 《Tetrahedron letters》2004,45(31):5969-5972
The regio- and stereoselective ring opening of vinyl epoxides has been achieved by the use of Lewis acid, MgBr2, affording bromohydrins in excellent yield, which are readily transformed to azidoalcohol, a key intermediate of several classes of pyrrolizidine and indolizidine alkaloids. The scope and limitations of the reaction are discussed. 相似文献
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2-oxazolines are common moieties in numerous natural products, pharmaceuticals, and functional copolymers. Current methods for synthesizing 2-oxazolines mainly rely on stoichiometric dehydration agents or catalytic dehydration promoted by specific catalysts. These conditions either generate stoichiometric amounts of waste or require forcing azeotropic reflux conditions. As such, a practical and robust method that promotes dehydrative cyclization while generating no byproducts would be attractive to oxazoline production. Herein, we report a triflic acid (TfOH)-promoted dehydrative cyclization of N-(2-hydroxyethyl)amides for synthesizing 2-oxazolines. This reaction tolerates various functional groups and generates water as the only byproduct. This method affords oxazoline with inversion of α-hydroxyl stereochemistry, suggesting that alcohol is activated as a leaving group under these conditions. Furthermore, the one-pot synthesis protocol of 2-oxazolines directly from carboxylic acids and amino alcohols is also provided. 相似文献
9.
利用吸附法原位制备CuO/SiO2、CuO-Ag/SiO2纳米复合物,研究了不同吸附质体系中预负载的纳米Ag粒子对CuO的影响。结果表明:Ag粒子对CuO的影响因吸附质的不同而不同。以Cu(Ac)2为吸附质,纳米Ag几乎没有影响;以NaOH为吸附质,纳米Ag使得CuO的晶粒粒径增大。这一结果与铜物种对Ag晶粒粒径的影响规律完全不同。通过比较不同吸附质的吸附行为,Cu(OH)2与硅胶表面的相互作用被认为是导致这一现象的原因。 相似文献
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Prof. Dr. Daniel Solé Dr. Israel Fernández Prof. Dr. Miguel A. Sierra 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(22):6950-6958
The factors that control the chemoselectivity of palladium‐catalyzed cyclization reactions of (2‐iodoanilino)carbonyl compounds have been explored by an extensive experimental computational (DFT) study. It was found that the selectivity of the process, that is, the formation of fused six‐ versus five‐membered rings, can be controlled by the proper selection of the initial reactant, reaction conditions, and additives. Thus, esters or amides produce ketones by a nucleophilic addition process, whereas the addition of PhO? ions leads to the formation of indolines by an α‐arylation reaction. In contrast, the corresponding ketone reactants yield a mixture of both reaction products, the ratio of which depends on the base used, in the presence of phenol. The outcome of the processes can be explained by the formation of a common four‐membered palladacycle intermediate from which the competitive nucleophilic addition and α‐arylation reactions occur. The remarkable effect of phenol in the process, which makes the α‐arylation reaction easier, favored the formation of enol complexes, which are stabilized by an intramolecular hydrogen bond between the hydroxy group of the enol moiety and the oxygen atom of the phenoxy ligand. Moreover, the chemoselectivy of the process can be also controlled by the addition of bidendate ligands that lead to the almost exclusive formation of indoles at expenses of the corresponding alcohols. 相似文献
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以氯化亚铜,硝酸锌,氯化锡和硫脲作为反应前驱体,聚乙二醇作为模板,利用溶剂热方法合成Cu2ZnSnS4中空球。其中,聚乙二醇对于产物的最终形成起到关键作用。文章讨论了Cu2ZnSnS4中空球的生长机制,并通过X射线衍射(XRD)、拉曼光谱、场发射电子显微镜(FESEM)、透射电子显微镜(TEM)、X射线能量色散谱(EDX)、X射线光电子谱(XPS)、选区电子衍射谱(SAED)和紫外-可见光分光光度计(UV-Vis)等技术对样品的微结构以及光学性质进行了表征和分析。结果显示Cu2ZnSnS4中空球为四方晶体,尺寸为600 nm。其禁带宽度为1.52 eV,适用于制作光伏器件。 相似文献
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以氯化亚铜,硝酸锌,氯化锡和硫脲作为反应前驱体,聚乙二醇作为模板,利用溶剂热方法合成Cu2ZnSnS4中空球。其中,聚乙二醇对于产物的最终形成起到关键作用。文章讨论了Cu2ZnSnS4中空球的生长机制,并通过X射线衍射(XRD)、拉曼光谱、场发射电子显微镜(FESEM)、透射电子显微镜(TEM)、X射线能量色散谱(EDX)、X射线光电子谱(XPS)、选区电子衍射谱(SAED)和紫外-可见光分光光度计(UV-Vis)等技术对样品的微结构以及光学性质进行了表征和分析。结果显示Cu2ZnSnS4中空球为四方晶体,尺寸为600 nm。其禁带宽度为1.52 eV,适用于制作光伏器件。 相似文献
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Sunil Sharma 《Tetrahedron letters》2008,49(49):7062-7065
A mild, efficient, and one-pot protocol for the intramolecular cyclization of 2-substituted nitroarenes via C-N bond formation using SnCl2·2H2O is described. The versatility of the method has been demonstrated by synthesizing two sets of polycyclic structures based on privileged structures of indole and pyrrole, and of the alkaloid cryptotackieine associated with antimalarial activity. Our new approach provides a powerful entry into polycyclic structures related to an alkaloid. 相似文献
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A simple, efficient, and diastereoselective synthesis of 5-methylene-dihydropyran-2,6-diones and 3-methylene-3,4-dihydropyran-2-ones from substrates afforded by the SN2 reaction between the acetyl derivatives of the Baylis–Hillman adducts and methylacetoacetate or acetylacetone or benzoyl acetone via saponification followed by P2O5-mediated cyclization is described. 相似文献
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M. Iwasaki A. Yasumori S. Shibata M. Yamane 《Journal of Sol-Gel Science and Technology》1994,2(1-3):387-391
In BaO-TiO2-SiO2 system, crystallization from various gel by heating depended on the sol-gel processes and gel homogeneity. Through the condensation reaction of Si(OAc)4 and TiAcAc(O
i
Pr)3 in tetrahydrofuran solvent, homogeneous TiO2-SiO2 sol with oligomers of relatively large molecular weight was obtained. The gel prepared by mixing the binary sol, Ba(OAc)2, and Si(OMe)4 was the most homogeneous in term of suppression of crystallization. By heating the above gel, only Ba2TiSi2O8 crystal appeared, which was observed in a melt quenched glass. In the case of the gels made by other sol-gel processes, TiO2 or BaTiO3 crystal was first observed from the heated gels prior to the precipitation of Ba2TiSi2O8. 相似文献
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为了满足低温制备可见光光催化材料的需要,采用溶胶-凝胶法制备TiO2纳米晶溶胶,再与聚乙烯基吡咯烷酮(PVP)直接反应制备N掺杂TiO2可见光光催化剂。通过XPS分析,说明N取代了部分晶格中的O,UV-Vis漫反射吸收光谱显示,光催化剂具有明显的可见光响应,这是由于N原子的2p轨道位于O原子的2p轨道之上,从而使得价带和导带间的能量带隙变窄,引起吸收带红移,产生明显的可见光吸收。依靠亚甲基兰(MB)的可见光降解实验证明,N掺杂光催化剂具有良好的可见光光催化活性,16 h MB降解率接近25%。 相似文献
17.
TiO2,ZrO2-TiO2,andZrO2-TiO2-CeO2 were prepared by co-precipitation method and characterized by X-ray diffraction (XRD), specific surface area measurements (BET), temperature programmed desorption (NH3-TPD), oxygen storage capacity (OSC), and temperature programmed reduction (H2-TPR). The results showed that ZrO2-TiO2-CeO2 exhibited large number of surface strong acid, possessed some oxygen storage capacity, and strong redox property. The three materials were used as supports and the monolith catalysts were prepared with 1% (w) V2O5 and 9% (w)WO3 for selective catalytic reduction (SCR) of NO with ammonia in the presence of excessive O2, and the results of catalytic activity showed that the catalyst used ZrO2-TiO2-CeO2 as support yielded nearly 100% NO conversion at 275 °C at a gas hourly space velocity (GHSV) of 10000 h−1, and it had the best catalytic activity and showed great potential for practical application. 相似文献
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等离子体技术在材料制备和改性方面的优势得到众多研究者的认可。Ti O2具有化学稳定性高、氧化活性强、生产成本低等优势,被广泛应用于太阳能电池和光催化领域。本文综述了近年来介质阻挡放电等离子体在强化制备Ti O2光催化材料方面的研究成果,包括等离子体辅助制备Ti O2光催化薄膜和Ti O2的等离子体法掺杂两个方面,并分析了其作用机理。从目前的研究成果来看,等离子体技术制得的Ti O2光催化材料具有更好的均匀性和催化活性,这主要得益于等离子体中的高能电子,一方面,Ti O2粒子吸附电子,彼此之间产生静电场的斥力作用,可以抑制颗粒的团聚,另一方面,电子的强还原能力,能够打断Ti-O键,形成氧空位,从而提高其催化性能。 相似文献
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Sb2S3/Bi2S3 doped TiO2 were prepared with the coordination compounds [M(S2CNEt)3] (M=Sb, Bi; S2CNEt=pyrrolidinedithiocarbamate) as precursors via gel-hydrothermal techniques. The doped TiO2 were characterized by XRD, SEM, XPS and UV-vis diffuse reflectance means. The photocatalyst based on doped TiO2 for photodecolorization of 4-nitrophenol (4-NP) was examined. The optimal Bi2S3/Sb2S3 content, pH and different doped techniques have been investigated. Photocatalytic tests reveal that M2S3 doped TiO2 via the gel-hydrothermal route performs better photocatalytic activity for photodegradation reaction of 4-nitrophenol (4-NP). 相似文献
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ZrO2/SiO2 particles, which were prepared by a layer-by-layer self-assemble technique and consist of micrometer-sized silica spheres
as cores and nanometer-sized zirconia particles as surface coatings, have a higher surface area and pore volume than other
zirconia supports have. Further more it is more stable than silica is. In this paper we made a reversed-phase support by bonding
octadecyltrichlorosilane on ZrO2/SiO2 particles, it had a comparable high carbon amount of 9.62% and good chemical stability being stable up to pH 11. The chromatographic
behavior showed that the support acted as a true reversed chromatographic stationary phase and had a hydrophobic selectivity.
Basic and aromatic compounds are well separated and the peaks are symmetrical. 相似文献