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841.
Caleb J. Hiller Dr. Chi Chung Lee Dr. Martin T. Stiebritz Lee A. Rettberg Prof. Dr. Yilin Hu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(10):2389-2395
Nitrogenase utilizes an ATP-dependent reductase to deliver electrons to its catalytic component to enable two important reactions: the reduction of N2 to NH4+, and the reduction of CO to hydrocarbons. The two nitrogenase-based reactions parallel the industrial Haber–Bosch and Fischer–Tropsch processes, yet they occur under ambient conditions. As such, understanding the enzymatic mechanism of nitrogenase is crucial for the future development of biomimetic strategies for energy-efficient production of valuable chemical commodities. Mechanistic investigations of nitrogenase has long been hampered by the difficulty to trap substrates and intermediates relevant to the nitrogenase reactions. Recently, we have successfully captured CO on the Azotobacter vinelandii V-nitrogenase via two approaches that alter the electron fluxes in a controlled manner: one approach utilizes an artificial electron donor to trap CO on the catalytic component of V-nitrogenase in the resting state; whereas the other employs a mismatched reductase component to reduce the electron flux through the system and consequently accumulate CO on the catalytic component of V-nitrogenase. Here we summarize the major outcome of these recent studies, which not only clarified the catalytic relevance of the one-CO (lo-CO) and multi-CO (hi-CO) bound states of nitrogenase, but also pointed to a potential competition between N2 and CO for binding to the same pair of reactive Fe sites across the sulfur belt of the cofactor. Together, these results highlight the utility of these strategies in poising the cofactor at a well-defined state for substrate- or intermediate-trapping via controlled alteration of electron fluxes, which could prove beneficial for further elucidation of the mechanistic details of nitrogenase-catalyzed reactions. 相似文献
842.
Copper‐Catalyzed Reaction Cascade of Thiophenol Hydroxylation and S‐Arylation through Disulfide‐Directed C−H Activation
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Prof. Dr. Dawei Wang Xin Yu Wei Yao Wenkang Hu Chenyang Ge Prof. Dr. Xiaodong Shi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(16):5543-5546
Copper‐catalyzed thiophenol C?H activation is described. Through an initial attempt to conduct C‐arylation with arylboronic acid, a rather surprising sequential C?H activation and S‐arylation was discovered. Mechanistic investigation revealed the disulfide intermediate as the key component in directing C?H oxidation. The overall reaction proceeded under mild conditions with molecular oxygen as the oxidant. Discovery of disulfide as the directing group provides a potential new direction for catalytic C?H functionalization under mild conditions. 相似文献
843.
An Unprecedented Two‐Fold Nested Super‐Polyrotaxane: Sulfate‐Directed Hierarchical Polythreading Assembly of Uranyl Polyrotaxane Moieties
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Dr. Lei Mei Dr. Qun‐yan Wu Dr. Li‐yong Yuan Dr. Lin Wang Shu‐wen An Zhen‐ni Xie Dr. Kong‐qiu Hu Prof. Zhi‐fang Chai Prof. Peter C. Burns Prof. Wei‐qun Shi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(32):11329-11338
The hierarchical assembly of well‐organized submoieties could lead to more complicated superstructures with intriguing properties. We describe herein an unprecedented polyrotaxane polythreading framework containing a two‐fold nested super‐polyrotaxane substructure, which was synthesized through a uranyl‐directed hierarchical polythreading assembly of one‐dimensional polyrotaxane chains and two‐dimensional polyrotaxane networks. This special assembly mode actually affords a new way of supramolecular chemistry instead of covalently linked bulky stoppers to construct stable interlocked rotaxane moieties. An investigation of the synthesis condition shows that sulfate can assume a vital role in mediating the formation of different uranyl species, especially the unique trinuclear uranyl moiety [(UO2)3O(OH)2]2+, involving a notable bent [O=U=O] bond with a bond angle of 172.0(9)°. Detailed analysis of the coordination features, the thermal stability as well as a fluorescence, and electrochemical characterization demonstrate that the uniqueness of this super‐polyrotaxane structure is mainly closely related to the trinuclear uranyl moiety, which is confirmed by quantum chemical calculations. 相似文献
844.
Sulfur and Nitrogen Codoped Carbon Tubes as Bifunctional Metal‐Free Electrocatalysts for Oxygen Reduction and Hydrogen Evolution in Acidic Media
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Tao Sun Prof. Qiang Wu Yufei Jiang Zhiqi Zhang Lingyu Du Prof. Lijun Yang Prof. Xizhang Wang Prof. Zheng Hu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(30):10261-10261
Invited for the cover of this issue is the group of Qiang Wu and Zheng Hu at Nanjing University. The image depicts sulfur and nitrogen codoped carbon tubes as bifunctional metal‐free electrocatalysts for oxygen reduction and hydrogen evolution in acidic media. Read the full text of the article at 10.1002/chem.201601535 . 相似文献
845.
Jianhua Hu Yinjun Xie Hanmin Huang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(28):7400-7404
A new and atom‐economic palladium‐catalyzed aminomethylamination of allenes with aminals by C N bond activation is described. This direct and operationally simple method provides a fundamentally novel approach for the synthesis of 1,3‐diamines. Mechanistic studies suggest that a unique cationic π‐allylpalladium complex containing an aminomethyl moiety is generated as a key intermediate through the carbopalladation of the allene with a cyclometalated palladium–alkyl species. 相似文献
846.
Shu‐Ting Wu Zhen‐Wen Cai Qiao‐Yan Ye Chen‐Hao Weng Xi‐He Huang Xiao‐Lin Hu Chang‐Cang Huang Nai‐Feng Zhuang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(47):13074-13078
Circular dichroism is known to be the feature of a chiral agent which has inspired scientist to study the interesting phenomena of circularly polarized light (CPL) modulated molecular chirality. Although several organic molecules or assemblies have been found to be CPL‐responsive, the influence of CPL on the assembly of chiral coordination compounds remains unknown. Herein, a chiral coordination polymer, which is constructed from achiral agents, was used to study the CPL‐induced enantioselective synthesis. By irradiation with either left‐handed or right‐handed CPL during the reaction and crystallization, enantiomeric excesses of the crystalline product were obtained. Left‐handed CPL resulted in crystals with a left‐handed helical structure, and right‐handed CPL led to crystals with a right‐handed helical structure. It is exciting that the absolute asymmetric synthesis of a chiral coordination polymer could be enantioselective when using CPL, and provides a strategy for the control of the chirality of chiral coordination polymers. 相似文献
847.
848.
849.
Guo Qiang Hu Xiao Kui Wu Guo Qiang Wang Nan Nan Duan Xiao Yi Wen Tie Yao Cao Yin Jun Wang Wei Song Qiang Xie Wen Long Huang 《中国化学快报》2012,23(5):515-517
To further explore an efficient modified route for the shift from an antibacterial fluoroquinolone to an antitumor one,mono-Schiff bases 6a-6h related to ciprofloxacin C3 carbonylhydrazone and bis-Schiff bases 4a-4h corresponding to C3/C7 carbonylhydrazone/hydrazone attached on a skeleton of ciprofloquinolone were designed and synthesized,and their in vitro antitumor activity against CHO,HL60,L1210 cells and antibacterial activity against Staphylococcus aureus and Escherichia coli were also reported. 相似文献
850.
3-Carboxy-2-pyrazinehydroxamic acid was prepared by a one pot reaction starting from pyrazine-2,3-dicarboxylic anhydride with a high yield, and characterized by IR, Mass spectrum, 1H NMR and 13C NMR spectra and single-crystal X-ray diffraction. It crystallizes in triclinic, space group Pī with a=4.8659(10), b=7.4233(15), c=11.602(2), α=96.904(2), β=92.422(3), γ=107.454(2)°, V=395.51(14)3 , Z=2, Dc=1.689g/cm3 , F(000)=208, μ(MoKα)=0.149 mm-1 , the final R=0.0473 and wR=0.1306 for 2853 observed reflections (I>2σ (I)). A three-dimensional framework was assembled through intermolecular hydrogen bonding between water and 3-carboxy-2-pyrazine-carbohydroxamic acid molecules. 相似文献