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941.
Dr. Sreekumar Vellalath Prof. Dr. Daniel Romo 《Angewandte Chemie (International ed. in English)》2016,55(45):13934-13943
Although acylammonium salts are well‐studied, chiral α,β‐unsaturated acylammonium salts have received much less attention. While these intermediates are convenient synthons, which are readily available from several commodity unsaturated acids and acid chlorides, and possess three reactive sites, their application in organic synthesis has been limited because of the lack of appropriate chiral Lewis bases for their generation. In recent years, the utility of chiral, unsaturated acylammonium salts has expanded considerably, thus demonstrating the unique reactivity of this intermediate leading to the development of a diverse array of catalytic, asymmetric transformations including organocascade processes. This Minireview highlights the recent and growing interest in these intermediates which might spark further research into their untapped potential for asymmetric organocascade catalysis. A cursory comparison is made to related unsaturated iminium and acylazolium intermediates. 相似文献
942.
Dry Reforming of Methane on a Highly‐Active Ni‐CeO2 Catalyst: Effects of Metal‐Support Interactions on C−H Bond Breaking 下载免费PDF全文
B. Sc. Zongyuan Liu Dr. David C. Grinter Dr. Pablo G. Lustemberg Dr. Thuy‐Duong Nguyen‐Phan Dr. Yinghui Zhou B. Sc. Si Luo Dr. Iradwikanari Waluyo Dr. Ethan J. Crumlin Dr. Dario J. Stacchiola Prof. Jing Zhou Dr. Javier Carrasco Prof. H. Fabio Busnengo Dr. M. Verónica Ganduglia‐Pirovano Dr. Sanjaya D. Senanayake Prof. José A. Rodriguez 《Angewandte Chemie (International ed. in English)》2016,55(26):7455-7459
Ni‐CeO2 is a highly efficient, stable and non‐expensive catalyst for methane dry reforming at relative low temperatures (700 K). The active phase of the catalyst consists of small nanoparticles of nickel dispersed on partially reduced ceria. Experiments of ambient pressure XPS indicate that methane dissociates on Ni/CeO2 at temperatures as low as 300 K, generating CHx and COx species on the surface of the catalyst. Strong metal–support interactions activate Ni for the dissociation of methane. The results of density‐functional calculations show a drop in the effective barrier for methane activation from 0.9 eV on Ni(111) to only 0.15 eV on Ni/CeO2?x(111). At 700 K, under methane dry reforming conditions, no signals for adsorbed CHx or C species are detected in the C 1s XPS region. The reforming of methane proceeds in a clean and efficient way. 相似文献
943.
Zongyang Qiu Prof. Li Song Prof. Jin Zhao Prof. Zhenyu Li Prof. Jinlong Yang 《Angewandte Chemie (International ed. in English)》2016,55(34):9918-9921
Metal‐nanoparticle‐catalyzed cutting is a promising way to produce graphene nanostructures with smooth and well‐aligned edges. Using a multiscale simulation approach, we unambiguously identified a “Pac‐Man” cutting mechanism, characterized by the metal nanoparticle “biting off” edge carbon atoms through a synergetic effect of multiple metal atoms. By comparing the reaction rates at different types of edge sites, we found that etching of an entire edge carbon row could be triggered by a single zigzag‐site etching event, which explains the puzzling linear dependence of the overall carbon‐atom etching rate on the nanoparticle surface area observed experimentally. With incorporation of the nanoparticle size effect, the mechanisms revealed herein open a new avenue to improve controllability in graphene cutting. 相似文献
944.
Isolating Reactions at the Picoliter Scale: Parallel Control of Reaction Kinetics at the Liquid–Liquid Interface 下载免费PDF全文
Gia Chuong Phan‐Quang Hiang Kwee Lee Prof. Xing Yi Ling 《Angewandte Chemie (International ed. in English)》2016,55(29):8304-8308
Miniaturized liquid–liquid interfacial reactors offer enhanced surface area and rapid confinement of compounds of opposite solubility, yet they are unable to provide in situ reaction monitoring at a molecular level at the interface. A picoreactor operative at the liquid–liquid interface is described, comprising plasmonic colloidosomes containing Ag octahedra strategically assembled at the water‐in‐decane emulsion interface. The plasmonic colloidosomes isolate ultrasmall amounts of solutions (<200 pL), allowing parallel monitoring of multiple reactions simultaneously. Using the surface‐enhanced Raman spectroscopy (SERS) technique, in situ monitoring of the interfacial protonation of dimethyl yellow (p‐dimethylaminoazobenzene (DY)) is performed, revealing an apparent rate constant of 0.09 min?1 for the first‐order reaction. The presence of isomeric products with similar physical properties is resolved, which would otherwise be indiscernible by other analytical methods. 相似文献
945.
Yang Jiao Wan‐Lu Li Dr. Jiang‐Fei Xu Dr. Guangtong Wang Prof. Jun Li Prof. Zhiqiang Wang Prof. Xi Zhang 《Angewandte Chemie (International ed. in English)》2016,55(31):8933-8937
Tuning the activity of radicals is crucial for radical reactions and radical‐based materials. Herein, we report a supramolecular strategy to accelerate the Fenton reaction through the construction of supramolecularly activated radical cations. As a proof of the concept, cucurbit[7]uril (CB[7]) was introduced, through host–guest interactions, onto each side of a derivative of 1,4‐diketopyrrolo[3,4‐c]pyrrole (DPP), a model dye for Fenton oxidation. The DPP radical cation, the key intermediate in the oxidation process, was activated by the electrostatically negative carbonyl groups of CB[7]. The activation induced a drastic decrease in the apparent activation energy and greatly increased the reaction rate. This facile supramolecular strategy is a promising method for promoting radical reactions. It may also open up a new route for the catalytic oxidation of organic pollutants for water purification and widen the realm of supramolecular catalysis. 相似文献
946.
A. A. A. Emara Jeanette A. Krause Bauer A. Galal 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(5):515-517
The title compound crystallizes as the monohydrate, [Co(SeO3)(NH3)4]NO3·H2O. The crystallographic mirror symmetry coincides with the molecular symmetry; the mirror plane passes through the cation, anion and water molecule. The CoN4O2 octahedron is distorted, with the selenito group acting as a bidentate ligand through two bridging O atoms to the cobalt. The coordinated Se—O distance is 1.742 (2) Å, whereas the uncoordinated Se—O distance is 1.646 (3) Å. A three‐dimensional hydrogen‐bonded network exists between [Co(SeO3)(NH3)4]NO3 and the water molecule. The nitrate anion and water molecule form open pores in the structure when hydrogen bonded to two neighboring [Co(SeO3)(NH3)4]+ cations. Selenium participates in two types of relatively close intermolecular interactions with neighboring charged species (Se?N1 and Se?O3), but does not participate in an interaction with a neighboring O2 atom, the nearest contact distance being 4.638 (3) Å. 相似文献
947.
Fructosamine-3-kinase (FN3K) mediates the regeneration of lysine from fructosamines formed on proteins as a result of the
‘early’ Maillard reaction. As fructosamines and advanced glycation endproducts derived therefrom are supposed to play an adverse
role in the development of diabetic complications, FN3K is discussed as a protein-repairing enzyme. In this study, a method
for the determination of FN3K activity in erythrocyte lysate is described which overcomes the complexity of currently known
assays. The assay is based on the FN3K-dependent conversion of the synthetic UV-active fructosamine N
α-hippuryl-N
ε-(1-deoxy-D-fructosyl)lysine (BzGFruK) to N
α-hippuryl-N
ε-(phosphofructosyl)lysine (BzGpFruK). The FN3K activity was quantified by measuring the formation of BzGpFruK using RP-HPLC
with UV detection. Identification of the metabolite BzGpFruK was achieved by means of UV and mass spectroscopy. The results
are related to the content of haemoglobin for standardisation. First activity measurements with a chosen number of normoglycaemic
subjects confirmed the convenient applicability of the method and showed distinctly different individual activities, as already
discovered recently. The new established assay needs only the equipment of a routine laboratory with HPLC instrumentation.
This should facilitate further studies about a possible relationship between the FN3K activity and the development of diabetic
complications. 相似文献
948.
Solvothermal reaction of [MnCl2(terpy)] with elemental As and Se at a 1:1:2 molar ratio in H2O/trien (10:1) at 150 °C affords the linear trimanganese(II) complex [{Mn(terpy)}3(μ‐AsSe4)2] ( 1 ). The tridentate [AsSe2(Se2)]3? anions of 1 chelate the terminal {Mn(terpy)}2+ fragments and bridge these through their remaining Se atom to the central {Mn(terpy)}2+ moiety. Weak interactions of Mn1···Se and Mn3···Se bonds with length 2.914(7) and 3.000(7) Å link the molecules of 1 into infinite chains. Treatment of [MnCl2(cyclam)]Cl with As and Se at a 1:1:2 molar ratio in superheated H2O/CH3OH (1:1) at 150 °C yields the dinuclear complex [{Mn(cyclam)}2 (μ‐As2Se6)] ( 2 ), whose novel [(AsSe2)2(μ‐Se2)]4? ligands bridge the MnII atoms in a μ‐1κ2Se1, Se2: 2κ2Se5,Se6 manner. 相似文献
949.
Two novel coordination polymers, [Cd(BIM)Cl2]n ( 1 ) and [Pb(BIM)Cl2]n ( 2 ) [wherein BIM = bis(imidazol‐1‐yl)methane], were synthesized by the reactions of the BIM ligand with CdCl2 and PbCl2, respectively. They were characterized by elemental analyses, IR, TGA and X‐ray single‐crystal diffraction techniques. Single‐crystal X‐ray structure analyses showed there is a pseudooctahedral arrangement around the cadmium atom in the complex 1 . It has a three‐dimensional network which contains one‐dimensional inorganic‐organic hybrid chains and μ2‐bridging chloride ligands. A rare pentacoordinate square‐pyramidal arrangement was adopted for the lead(II) atom in the complex 2 , which has an unusual two‐dimensional layer structure of macrometallacycles crosslinked with the bridging Pb2Cl2 units. The metal atoms in both complexes were coordinated with two BIM ligands in cis arrangement and bridged by μ2‐bridging chloride ligands. 相似文献
950.
Sonja Herres‐Pawlis Dr. Tarimala Seshadri Ulrich Flörke Gerald Henkel Prof. Dr. 《无机化学与普通化学杂志》2009,635(8):1209-1214
The reaction of 2,2′‐Bis(2N‐(1,1′,3,3′‐tetramethyl‐guanidino))diphenylene‐amine (TMG2PA) ( 1 ) with CuI in MeCN results in the formation of [CuII(TMG2PAamid)I] ( 2 ) indicatingthat CuI is the target of an oxidative attack of the N‐H proton of the ligand which itself is converted to molecular hydrogen. In contrast, if [Cu(MeCN)4][PF6] is used as the CuI source, [CuI2(TMGbenz)2][PF6]2 ( 3 ) is obtained instead. The use of the non‐coordinating counterion [PF6]– apparently prevents CuI from oxidation but induces itself a cyclisation reaction within the ligand which results in the formation of a benzimidazole‐guanidine ligand. 相似文献