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排序方式: 共有159条查询结果,搜索用时 15 毫秒
101.
Dr. Youai Qiu Prof.Dr. Jan‐E. Bäckvall 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(9):2939-2943
An olefin‐directed palladium‐catalyzed regio‐ and stereoselective hydroboration of allenes has been developed to afford fully substituted alkenylboron compounds. The reaction showed a broad substrate scope: a number of functionalized allenes, including 2,3‐dienoate, 3,4‐dienoate, 3,4‐dienol, 1,2‐allenylphosphonate, and alkyl‐substituted allenes, could be used in this olefin‐directed allene hydroboration. The olefin unit was proven to be an indispensable element for this transformation. 相似文献
102.
103.
Inside Back Cover: Synthesis of Silicate Zeolite Analogues Using Organic Sulfonium Compounds as Structure‐Directing Agents (Angew. Chem. Int. Ed. 43/2015) 下载免费PDF全文
104.
Lin‐Bao Zhang Dr. Xin‐Qi Hao Shou‐Kun Zhang Zhan‐Jiang Liu Xin‐Xiang Zheng Dr. Jun‐Fang Gong Dr. Jun‐Long Niu Prof. Mao‐Ping Song 《Angewandte Chemie (International ed. in English)》2015,54(1):272-275
The cobalt‐catalyzed alkoxylation of C(sp2)? H bonds in aromatic and olefinic carboxamides has been developed. The reaction proceeded under mild conditions in the presence of Co(OAc)2?4H2O as the catalyst and tolerates a wide range of both alcohols and benzamide substrates, including even olefinic carboxamides. In addition, this reaction is the first example of the direct alkoxylation of alkenes through C? H bond activation. 相似文献
105.
Vicente J. Margarit Marta E. Martínez‐Armero Dr. M. Teresa Navarro Dr. Cristina Martínez Prof. Avelino Corma 《Angewandte Chemie (International ed. in English)》2015,54(46):13724-13728
A two‐dimensional zeolite with the topology of MWW sheets has been obtained by direct synthesis with a combination of two organic structure‐directing agents. The resultant material consists of approximately 70 % single and double layers and displays a well‐structured external surface area of about 300 m2 g?1. The delaminated zeolite prepared by means of this single‐step synthetic route has a high delamination degree, and the structural integrity of the MWW layers is well preserved. The new zeolite material displayed excellent activity, selectivity, and stability when used as a catalyst for the alkylation of benzene with propylene and found to be superior to the catalysts that are currently used for producing cumene. 相似文献
106.
Clément Jacob Prof. Bert U. W. Maes Prof. Gwilherm Evano 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(56):13899-13952
The direct functionalization of C−H bonds is among the most fundamental chemical transformations in organic synthesis. However, when the innate reactivity of the substrate cannot be utilized for the functionalization of a given single C−H bond, this selective C−H bond functionalization mostly relies on the use of directing groups that allow bringing the catalyst in close proximity to the C−H bond to be activated and these directing groups need to be installed before and cleaved after the transformation, which involves two additional undesired synthetic operations. These additional steps dramatically reduce the overall impact and the attractiveness of C−H bond functionalization techniques since classical approaches based on substrate pre-functionalization are sometimes still more straightforward and appealing. During the past decade, a different approach involving both the in situ installation and removal of the directing group, which can then often be used in a catalytic manner, has emerged: the transient directing group strategy. In addition to its innovative character, this strategy has brought C−H bond functionalization to an unprecedented level of usefulness and has enabled the development of remarkably efficient processes for the direct and selective introduction of functional groups onto both aromatic and aliphatic substrates. The processes unlocked by the development of these transient directing groups will be comprehensively overviewed in this review article. 相似文献
107.
以非离子表面活性剂P123为结构导向剂,采用溶胶-凝胶与溶解热相结合方法,制备了两类介孔材料H3PW12O40/TiO2和H4SiW12O40/TiO2,并对其进行了表征.?X射线粉末衍射和拉曼光谱分析表明,所制催化剂为锐钛矿晶型,体系中H3PW12O40和H4SiW12O40的Keggin结构经400?℃焙烧后仍保持完整.?H3PW12O40/TiO2和H4SiW12O40/TiO2的平均粒径分别为15.49和7.75?nm.?N2吸附-脱附和扫描电镜结果表明,P123的加入使催化剂的粒径减小,比表面积和孔体积明显增大,其中H3PW12O40/TiO2和H4SiW12O40/TiO2的比表面积分别高达252.2和250.0?m2/g.?紫外漫反射吸收光谱表明,与纯TiO2相比,复合催化剂的吸收光谱发生了明显的红移,且吸收强度明显增大.?催化剂对DNT降解实验表明,在最佳操作条件下降解率可高达95%.? 相似文献
108.
S. Volden W. R. Glomm H. Magnusson G. Øye J. Sjöblom 《Journal of Dispersion Science and Technology》2013,34(6):893-897
Anionic dendritic macromolecules (hyperbranched polyesters and polyamidoamine (PAMAM) dendrimers) and amine‐functionalized PAMAM dendrimers have been used as structure‐directing agents in the synthesis of nanoporous silica structures. When utilizing carboxylates as structure‐directing agents the incorporation of the negatively charged species into a SiO2 framework was achieved via a sol‐gel synthesis route using a quaternized aminosilane as co‐structure‐directing agent to yield silica materials of various morphologies and high surface areas. Amine dendrimers as porogens gave materials with high surface areas, revealing increasing pore sizes corresponding to the increasing size of the porogen. The resulting materials have been characterized by X‐ray diffraction (XRD), N2 adsorption/desorption (BET), scanning electron microscopy (SEM), infrared spectroscopy (IR), and thermogravimetric analysis (TGA). 相似文献
109.
110.
在干凝胶法制备ZSM-5 分子筛的体系中添加晶种导向剂, 控制分子筛的生长, 制备了纳米沸石组装的无粘结剂成型多级孔ZSM-5 分子筛, 一步完成纳米分子筛的制备及组装成型, 即克服了传统纳米粒子难以过滤分离的问题, 同时组装所形成的多级孔有助于改善分子在催化剂内的扩散, 从而提高催化反应效率. 以硅胶、薄水铝石为原料, 四丙基氢氧化铵(TPAOH)和ZSM-5 晶种导向胶作为粘结剂, 通过混捏、挤条得到直径2 mm的条状前驱物, 随后通过干凝胶转换法制备成型分子筛. 所用晶种导向剂组成为0.35TPAOH:1SiO2:20H2O:4C2H5OH. 通过X射线衍射(XRD), 热重(TG)分析和傅里叶变换红外(FTIR)光谱等方法对分子筛晶化过程进行了表征, 结果表明晶种导向剂加入量对分子筛生长速度及多级孔结构均有影响. 当所加晶种导向剂中TPAOH与SiO2的摩尔比为0.025时, 经过3 h晶化, 分子筛相对结晶度达到100%. 扫描电镜(SEM)结果表明, 合成的分子筛尺寸约为200 nm, 组装形成的多级孔分子筛的介孔体积为0.28 cm3·g-1. 通过NH3 程序升温脱附(NH3-TPD)考察了所得成型分子筛的酸性, 发现该分子筛酸性与市售的粉末H-ZSM-5分子筛类似. 相似文献