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991.
Multisite Organic–Inorganic Hybrid Catalysts for the Direct Sustainable Synthesis of GABAergic Drugs 下载免费PDF全文
Dr. Antonio Leyva‐Pérez Dr. Pilar García‐García Prof. Dr. Avelino Corma 《Angewandte Chemie (International ed. in English)》2014,53(33):8687-8690
Multisite organic–inorganic hybrid catalysts have been prepared and applied in a new general, practical, and sustainable synthetic procedure toward industrially relevant GABA derivatives. The domino sequence is composed of seven chemical transformations which are performed in two one‐pot reactions. The method produces both enantiomeric forms of the product in high enantiopurity as well as the racemate in good yields after a single column purification step. This protocol highlights major process intensification, catalyst recyclability, and low waste generation. 相似文献
992.
Palladium‐Catalyzed Decarboxylative Cycloaddition of Vinylethylene Carbonates with Formaldehyde: Enantioselective Construction of Tertiary Vinylglycols 下载免费PDF全文
Ajmal Khan Dr. Renfeng Zheng Prof. Dr. Yuhe Kan Jiang Ye Juxiang Xing Prof. Dr. Yong Jian Zhang 《Angewandte Chemie (International ed. in English)》2014,53(25):6439-6442
An efficient method for the enantioselective construction of tertiary vinylglycols through a palladium‐catalyzed asymmetric decarboxylative cycloaddition of vinylethylene carbonates with formaldehyde was developed. By using a palladium complex generated in situ from [Pd2(dba)3]?CHCl3 and a phosphoramidite ligand as a catalyst under mild reaction conditions, the process allows conversion of racemic 4‐substituted 4‐vinyl‐1,3‐dioxolan‐2‐ones into the corresponding 1,3‐dioxolanes, as methylene acetal protected tertiary vinylglycols, in high yields with good to excellent enantioselectivities. 相似文献
993.
Platinum‐Promoted Ga/Al2O3 as Highly Active,Selective, and Stable Catalyst for the Dehydrogenation of Propane 下载免费PDF全文
Jesper J. H. B. Sattler Dr. Ines D. Gonzalez‐Jimenez Dr. Lin Luo Brien A. Stears Dr. Andrzej Malek Dr. David G. Barton Dr. Beata A. Kilos Dr. Mark P. Kaminsky Tiny W. G. M. Verhoeven Eline J. Koers Prof. Dr. Marc Baldus Prof. Dr. Bert M. Weckhuysen 《Angewandte Chemie (International ed. in English)》2014,53(35):9251-9256
A novel catalyst material for the selective dehydrogenation of propane is presented. The catalyst consists of 1000 ppm Pt, 3 wt % Ga, and 0.25 wt % K supported on alumina. We observed a synergy between Ga and Pt, resulting in a highly active and stable catalyst. Additionally, we propose a bifunctional active phase, in which coordinately unsaturated Ga3+ species are the active species and where Pt functions as a promoter. 相似文献
994.
Trinuclear Gold Clusters Supported by Cyclic (alkyl)(amino)carbene Ligands: Mimics for Gold Heterogeneous Catalysts 下载免费PDF全文
Dr. Liqun Jin David S. Weinberger Dr. Mohand Melaimi Dr. Curtis E. Moore Prof. Arnold L. Rheingold Prof. Guy Bertrand 《Angewandte Chemie (International ed. in English)》2014,53(34):9059-9063
The synthesis of air‐ and moisture‐stable trinuclear mixed‐valence gold(I)/gold(0) clusters is described. They promote the catalytic carbonylation of amines under relatively mild conditions. The synthetic route leading to the trinuclear clusters involves a simple ligand exchange from the readily available μ3‐oxo‐[(Ph3PAu)3O]+ complex. This synthetic method paves the way for the preparation of a variety of mixed‐valence gold(I)/gold(0) polynuclear clusters. Moreover, the well‐defined nature of the complexes demonstrates that the catalytic process involves a rare example of a definite change of oxidation state of gold from Au02AuI to AuI3. 相似文献
995.
A Molecular Approach to Self‐Supported Cobalt‐Substituted ZnO Materials as Remarkably Stable Electrocatalysts for Water Oxidation 下载免费PDF全文
Johannes Pfrommer Dr. Michael Lublow Anahita Azarpira Dr. Caren Göbel Marcel Lücke Dr. Alexander Steigert Martin Pogrzeba Dr. Prashanth W. Menezes Dr. Anna Fischer Dr. Thomas Schedel‐Niedrig Prof. Dr. Matthias Driess 《Angewandte Chemie (International ed. in English)》2014,53(20):5183-5187
In regard to earth‐abundant cobalt water oxidation catalysts, very recent findings show the reorganization of the materials to amorphous active phases under catalytic conditions. To further understand this concept, a unique cobalt‐substituted crystalline zinc oxide (Co:ZnO) precatalyst has been synthesized by low‐temperature solvolysis of molecular heterobimetallic Co4?xZnxO4 (x=1–3) precursors in benzylamine. Its electrophoretic deposition onto fluorinated tin oxide electrodes leads after oxidative conditioning to an amorphous self‐supported water‐oxidation electrocatalyst, which was observed by HR‐TEM on FIB lamellas of the EPD layers. The Co‐rich hydroxide‐oxidic electrocatalyst performs at very low overpotentials (512 mV at pH 7; 330 mV at pH 12), while chronoamperometry shows a stable catalytic current over several hours. 相似文献
996.
Counting of Oxygen Defects versus Metal Surface Sites in Methanol Synthesis Catalysts by Different Probe Molecules 下载免费PDF全文
Matthias B. Fichtl Julia Schumann Igor Kasatkin Nikolas Jacobsen Malte Behrens Robert Schlögl Martin Muhler Olaf Hinrichsen 《Angewandte Chemie (International ed. in English)》2014,53(27):7043-7047
Different surface sites of solid catalysts are usually quantified by dedicated chemisorption techniques from the adsorption capacity of probe molecules, assuming they specifically react with unique sites. In case of methanol synthesis catalysts, the Cu surface area is one of the crucial parameters in catalyst design and was for over 25 years commonly determined using diluted N2O. To disentangle the influence of the catalyst components, different model catalysts were prepared and characterized using N2O, temperature programmed desorption of H2, and kinetic experiments. The presence of ZnO dramatically influences the N2O measurements. This effect can be explained by the presence of oxygen defect sites that are generated at the Cu‐ZnO interface and can be used to easily quantify the intensity of Cu‐Zn interaction. N2O in fact probes the Cu surface plus the oxygen vacancies, whereas the exposed Cu surface area can be accurately determined by H2. 相似文献
997.
The Origin of Shape Sensitivity in Palladium‐Catalyzed Suzuki–Miyaura Cross Coupling Reactions 下载免费PDF全文
Dr. Gillian Collins Michael Schmidt Dr. Colm O'Dwyer Prof. Justin D. Holmes Dr. Gerard P. McGlacken 《Angewandte Chemie (International ed. in English)》2014,53(16):4142-4145
The shape sensitivity of Pd catalysts in Suzuki–Miyaura coupling reactions is studied using nanocrystals enclosed by well‐defined surface facets. The catalytic performance of Pd nanocrystals with cubic, cuboctahedral and octahedral morphologies are compared. Superior catalytic reactivity is observed for Pd NCs with {100} surface facets compared to {111} facets. The origin of the enhanced reactivity associated with a cubic morphology is related to the leaching susceptibility of the nanocrystals. Molecular oxygen plays a key role in facilitating the leaching of Pd atoms from the surface of the nanocrystals. The interaction of O2 with Pd is itself facet‐dependent, which in turn gives rise to more efficient leaching from {100} facets, compared to {111} facets under the reaction conditions. 相似文献
998.
M. Sc. Moritz C. Baier Dr. Martin A. Zuideveld Prof. Dr. Stefan Mecking 《Angewandte Chemie (International ed. in English)》2014,53(37):9722-9744
Research on “post‐metallocene” polymerization catalysis ranges methodologically from fundamental mechanistic studies of polymerization reactions over catalyst design to material properties of the polyolefins prepared. A common goal of these studies is the creation of practically useful new polyolefin materials or polymerization processes. This Review gives a comprehensive overview of post‐metallocene polymerization catalysts that have been put into practice. The decisive properties for this success of a given catalyst structure are delineated. 相似文献
999.
Caitlin M. McMahon Prof. Erik J. Alexanian 《Angewandte Chemie (International ed. in English)》2014,53(23):5974-5977
A palladium‐catalyzed, intermolecular Heck‐type coupling of alkyl iodides and alkenes is described. This process is successful with a variety of primary and secondary unactivated alkyl iodides as reaction partners, including those with hydrogen atoms in the β position. The mild catalytic conditions enable intermolecular C? C bond formations with a diverse set of alkyl iodides and alkenes, including substrates containing base‐ or nucleophile‐sensitive functionality. 相似文献
1000.
Dr. Jae‐Il Jung Dr. Hu Young Jeong Jang‐Soo Lee Dr. Min Gyu Kim Prof. Dr. Jaephil Cho 《Angewandte Chemie (International ed. in English)》2014,53(18):4582-4586
La0.3(Ba0.5Sr0.5)0.7Co0.8Fe0.2O3?δ is a promising bifunctional perovskite catalyst for the oxygen reduction reaction and the oxygen evolution reaction. This catalyst has circa 10 nm‐scale rhombohedral LaCoO3 cobaltite particles distributed on the surface. The dynamic microstructure phenomena are attributed to the charge imbalance from the replacement of A‐site cations with La3+ and local stress on Co‐site sub‐lattice with the cubic perovskite structure. 相似文献