共查询到20条相似文献,搜索用时 15 毫秒
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S Wesselbaum U Hintermair W Leitner 《Angewandte Chemie (International ed. in English)》2012,51(34):8585-8588
Dual role for CO(2) : Pure formic acid can be obtained continuously by hydrogenation of CO(2) in a single processing unit. An immobilized ruthenium organometallic catalyst and a nonvolatile base in an ionic liquid (IL) are combined with supercritical CO(2) as both reactant and extractive phase. 相似文献
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Dipl.‐Chem. Thomas Dröge Prof. Dr. Frank Glorius 《Angewandte Chemie (International ed. in English)》2010,49(39):6940-6952
Quantification and variation of characteristic properties of different ligand classes is an exciting and rewarding research field. N‐Heterocyclic carbenes (NHCs) are of special interest since their electron richness and structure provide a unique class of ligands and organocatalysts. Consequently, they have found widespread application as ligands in transition‐metal catalysis and organometallic chemistry, and as organocatalysts in their own right. Herein we provide an overview on physicochemical data (electronics, sterics, bond strength) of NHCs that are essential for the design, application, and mechanistic understanding of NHCs in catalysis. 相似文献
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《Angewandte Chemie (International ed. in English)》2017,56(52):16464-16483
Despite the large number of disparate approaches for the direct selective partial oxidation of methane, none of them has translated into an industrial process. The oxidation of methane to methanol is a difficult, but intriguing and rewarding, task as it has the potential to eliminate the prevalent natural gas flaring by providing novel routes to its valorization. This Review considers the synthesis of methanol and methanol derivatives from methane by homogeneous and heterogeneous pathways. By establishing the severe limitations related to the direct catalytic synthesis of methanol from methane, we highlight the vastly superior performance of systems which produce methanol derivatives or incorporate specific measures, such as the use of multicomponent catalysts to stabilize methanol. We thereby identify methanol protection as being indispensable for future research on homogeneous and heterogeneous catalysis. 相似文献
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A General Strategy for Site‐Directed Enzyme Immobilization by Using NiO Nanoparticle Decorated Mesoporous Silica 下载免费PDF全文
Dr. Daishun Ling Dr. Liqian Gao Dr. Jianpeng Wang Mohammadreza Shokouhimehr Jiahui Liu Yongsheng Yu Dr. Michael J. Hackett Dr. Pui‐Kin So Dr. Bo Zheng Prof. Zhongping Yao Prof. Jiang Xia Prof. Taeghwan Hyeon 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(26):7916-7921
Mesoporous materials have recently gained much attention owing to their large surface area, narrow pore size distribution, and superior pore structure. These materials have been demonstrated as excellent solid supports for immobilization of a variety of proteins and enzymes for their potential applications as biocatalysts in the chemical and pharmaceutical industries. However, the lack of efficient and reproducible methods for immobilization has limited the activity and recyclability of these biocatalysts. Furthermore, the biocatalysts are usually not robust owing to their rapid denaturation in bulk solvents. To solve these problems, we designed a novel hybrid material system, mesoporous silica immobilized with NiO nanoparticles (SBA‐NiO), wherein enzyme immobilization is directed to specific sites on the pore surface of the material. This yielded the biocatalytic species with higher activity than free enzyme in solution. These biocatalytic species are recyclable with minimal loss of activity after several cycles, demonstrating an advantage over free enzymes. 相似文献
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Christian Ohde Christian Limberg Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(23):6892-6899
Silsesquioxane dioxovanadate(V) complexes were investigated with respect to their potential as a catalyst for the oxidative dehydrogenation of alcohols with O2 as an oxidant. The turnover frequencies determined were comparatively low, but during the oxidation of cinnamic alcohol an increase in activity was observed in the course of the process, which was inspected more closely. It turned out that during the oxidation of cinnamic alcohol, not only was the aldehyde formed but also cinnamic acid, which in turn reacts with the silsesquioxane complex employed to give NBu4[O2V(O2CC2H2Ph)2], which can also be obtained from NBu4VO3 and cinnamic acid and represents a far more active catalyst, not only for cinnamic alcohol but also for other activated alcohols and hydrocarbons. The rate‐determining step of the conversion corresponds to an hydrogen‐atom abstraction from the C? H units, as shown by the determination of the kinetic isotope effect in case of 9‐hydroxyfluorene, and the reoxidation of the reduced catalyst proceeds via a peroxo intermediate, which is also capable of oxidizing one alcohol equivalent. Furthermore the influence of the organic residues at the carboxylate ligands on the catalyst performance was investigated, which showed that the activity increases with decreasing pKs value. Moreover, it was found that during the oxidation the catalyst slowly decomposes, but can be regenerated by addition of excessive carboxylic acid. 相似文献
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Prof. Dr. Scott E. Denmark William E. Kuester Dr. Matthew T. Burk 《Angewandte Chemie (International ed. in English)》2012,51(44):10938-10953
Despite the fact that halogenation of alkenes has been known for centuries, enantioselective variants of this reaction have only recently been developed. In the past three years, catalytic enantioselective versions of halofunctionalizations with the four common halogens have appeared and although important breakthroughs, they represent just the very beginnings of a nascent field. This Minireview provides a critical analysis of the challenges that accompany the development of general and highly enantioselective halofunctionalization reactions. Moreover, the focus herein, diverges from previous reviews of the field by identifying the various modes of catalysis and the different strategies implemented for asymmetric induction. 相似文献
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Dr. Sylvain Antoniotti Prof. Dr. Vincent Dalla Dr. Elisabet Duñach 《Angewandte Chemie (International ed. in English)》2010,49(43):7860-7888
The continuously increasing need for novel and selective methods in organic synthesis to aid drug discovery and to address environmental concerns is a constant source of stimulation to develop novel and more efficient reaction systems. This has often resulted in a focus on transition metals, ligands, and additives, with much less attention paid to the counterion(s) of the metal cation. Recently, metal salts with one or more triflimidate counterion(s) have appeared as a unique class of catalysts that display outstanding σ‐ and π‐Lewis acid character. The highly delocalized nature of the triflimidate counterion, combined with its high steric hindrance results in virtually no nucleophilic behavior and an extremely high positive charge density on the metal cation, thus enhancing its Lewis acid character. Consequently, these metal triflimidates often outperform their metal halide or triflate analogues. This Review describes general methods for the preparation of metal triflimidate salts and their use as catalysts. 相似文献