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961.
Peng Lv Zhong-min Wang Ying Peng Wen-ping Liu Muhammad-Sadeeq Balogun Huai-ying Zhou 《Journal of Solid State Electrochemistry》2014,18(9):2563-2572
The effect of Cu content on structure, hydrogen storage, and electrochemical properties of LaNi4.1-x Co0.6Mn0.3Cu x alloys has been investigated. For sample, A, B, C, and D are used to represent alloys (x?=?0, 0.15, 0.3, and 0.45), respectively. The results indicate that the four alloys are all single-phase alloy with LaNi5 phase of CaCu5 hexagonal structure, the hydrogen storage capacities of the alloy are about 1.49 wt% (A), 1.48 wt% (B), 1.43 wt% (C), and 1.25 wt% (D) at 303 K. With the increase of Cu content (x) from A to D, hydrogen desorption plateau pressure and pressure hysteresis decrease. Alloy electrode A shows better activation property and higher capacity (334.44 mAh/g). The addition of Cu improves the cyclic stability of the alloy electrodes when x?=?0?~?0.45. However, their self-discharge properties and high-rate dischargeability (HRD) decrease with the increase of x. Further, electrochemical kinetics and electrochemical impedance spectroscopy (EIS) analysis show that the reaction of alloy electrode is controlled by charge transfer step, and the adding of Cu benefits the electrode properties in alkaline solution. 相似文献
962.
Divergent Syntheses of Fused β‐Naphthol and Indene Scaffolds by Rhodium‐Catalyzed Direct and Decarbonylative Alkyne–Benzocyclobutenone Couplings
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Peng‐hao Chen Dr. Tao Xu Prof. Dr. Guangbin Dong 《Angewandte Chemie (International ed. in English)》2014,53(6):1674-1678
A tunable rhodium‐catalyzed intramolecular alkyne insertion reaction proceeding through the C? C cleavage of benzocyclobutenones is described. Selective formation of either the direct or decarbonylative insertion product can be controlled by using different catalytic systems. A variety of fused β‐naphthol and indene scaffolds were obtained in good yields with high functional group tolerance. This work illustrates a divergent approach to synthesize fused‐ring systems by C? C activation/functionalization. 相似文献
963.
Facile Synthesis of Chiral Spirooxindole‐Based Isotetronic Acids and 5‐1H‐Pyrrol‐2‐ones through Cascade Reactions with Bifunctional Organocatalysts
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Wengang Guo Xu Wang Dr. Boyu Zhang Shuai Shen Dr. Xin Zhou Peng Wang Prof. Yan Liu Prof. Can Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(28):8545-8550
Unprecedented organocatalyzed asymmetric cascade reactions have been developed for the facile synthesis of chiral spirooxindole‐based isotetronic acids and 5‐1H‐pyrrol‐2‐ones.The asymmetric 1,2‐addition reactions of α‐ketoesters to isatins and imines by using an acid–base bifunctional 6′‐OH cinchona alkaloid catalyst, followed by cyclization and enolization of the resulting adducts, gave chiral spiroisotetronic acids and 5‐1H‐pyrrol‐2‐ones, respectively, in excellent optical purities (up to 98 % ee). FT‐IR analysis supported the existence of hydrogen‐bonding interaction between the 6′‐OH group of the cinchona catalyst and an isatin carbonyl group, an interaction that might be crucial for catalyst activity and stereocontrol. 相似文献
964.
Mixed‐Ligand Catalysts: A Powerful Tool in Transition‐Metal‐Catalyzed Cross‐Coupling Reactions
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Yuting Fan Mei Cong Ling Peng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(10):2698-2702
Transition‐metal‐catalyzed cross‐coupling reactions have fundamentally revolutionized organic synthesis, empowering the otherwise difficult to achieve products with rapid and convenient accesses alongside excellent yields. Within these reactions, ligands often play a critical role in specifically and effectively advocating the corresponding catalysis. Consequently, a myriad of ligands have been created and applied to make a fine tuning of electronic and steric effect of catalysts, remarkably promoting catalytic efficiency and applicability. The “mixed‐ligand” concept has recently emerged; by combining and capitalizing on the superiority of each individual ligand already available, an expedient way can be achieved to reach a larger extent of catalytic diversity and efficacy. Given the availability of a wealth of ligands, it is reasonable to have great expectations for the original application of mixed‐ligand catalytic systems and their important value in organic synthesis. 相似文献
965.
Aromatic Nitrogen Mustard‐Based Prodrugs: Activity,Selectivity, and the Mechanism of DNA Cross‐Linking
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Dr. Wenbing Chen Dr. Yanyan Han Prof. Xiaohua Peng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(24):7410-7418
Three novel H2O2‐activated aromatic nitrogen mustard prodrugs ( 6 – 8 ) are reported. These compounds contain a DNA alkylating agent connected to a H2O2‐responsive trigger by different electron‐withdrawing linkers so that they are inactive towards DNA but can be triggered by H2O2 to release active species. The activity and selectivity of these compounds towards DNA were investigated by measuring DNA interstrand cross‐link (ICL) formation in the presence or absence of H2O2. An electron‐withdrawing linker unit, such as a quaternary ammonia salt ( 6 ), a carboxyamide ( 7 ), and a carbonate group ( 8 ), is sufficient to deactivate the aromatic nitrogen mustard resulting in less than 1.5 % cross‐linking formation. However, H2O2 can restore the activity of the effectors by converting a withdrawing group to a donating group, therefore increasing the cross‐linking efficiency (>20 %). The stability and reaction sites of the ICL products were determined, which revealed that alkylation induced by 7 and 8 not only occurred at the purine sites but also at the pyrimidine site. For the first time, we isolated and characterized the monomer adducts formed between the canonical nucleosides and the aromatic nitrogen mustard ( 15 ) which supported that nitrogen mustards reacted with dG, dA, and dC. The activation mechanism was studied by NMR spectroscopic analysis. An in vitro cytotoxicity assay demonstrated that compound 7 with a carboxyamide linker dramatically inhibited the growth of various cancer cells with a GI50 of less than 1 μM , whereas compound 6 with a charged linker did not show any obvious toxicity in all cell lines tested. These data indicated that a neutral carboxyamide linker is preferable for developing nitrogen mustard prodrugs. Our results showed that 7 is a potent anticancer prodrug that can serve as a model compound for further development. We believe these novel aromatic nitrogen mustards will inspire further and effective applications. 相似文献
966.
Dr. Valentine K. Johns Dr. Ping Peng Joseph DeJesus Zhuozhi Wang Dr. Yi Liao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(3):689-692
A new photoacid that reversibly changes from a weak to a strong acid under visible light was designed and synthesized. Irradiation generated a metastable state with high C?H acidity due to high stability of a trifluoromethyl‐phenyl‐tricyano‐furan (CF3PhTCF) carbanion. This long‐lived metastable state allows a large proton concentration to be reversibly produced with moderate light intensity. Reversible pH change of about one unit was demonstrated by using a 0.1 mM solution of the photoacid in 95 % ethanol. The quantum yield was calculated to be as high as 0.24. Kinetics of the reverse process can be fitted well to a second‐order‐rate equation with k=9.78×102 M ?1 s?1. Response to visible light, high quantum yield, good reversibility, large photoinduced proton concentration under moderate light intensity, and good compatibility with organic media make this photoacid a promising material for macroscopic control of proton‐transfer processes in organic systems. 相似文献
967.
Dr. Guo Peng Dr. Valeriu Mereacre Dr. George E. Kostakis Dr. Juliusz A. Wolny Prof.Dr. Volker Schünemann Prof. Dr. Annie K. Powell 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(39):12381-12384
Two [FeLn2Fe(μ3‐OH)2(teg)2(N3)2(C6H5COO)4] compounds (where Ln=YIII and DyIII; teg=triethylene glycol anion) have been synthesized and studied using SQUID and Mössbauer spectroscopy. The magnetic measurements on both compounds indicate dominant antiferromagnetic interactions between the metal centers. Analysis of the 57Fe Mössbauer spectra complement the ac magnetic susceptibility measurements, which show how a static magnetic field can quench the slow relaxation of magnetization generated by the anisotropic DyIII ions. 相似文献
968.
An Unusual Triphenylphosphine Oxide Catalyzed Stereoselective 1,3‐Dichlorination of Unsaturated Ketoesters
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Tian‐Yang Yu Yao Wang Peng‐Fei Xu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(1):98-101
An unusual Ph3PO‐catalyzed stereoselective 1,3‐dicholorination of an unsaturated ketoester has been developed. The novel activation mode involved in this cascade reaction can promote consecutively elusive transformations. The products were obtained with good yields and excellent stereoselectivities. This reaction makes important complementation to the limitations associated with the field of dichlorination. 相似文献
969.
Hetero‐tri‐spin [2p‐3d‐4f] Chain Compounds Based on Nitronyl Nitroxide Lanthanide Metallo‐Ligands: Synthesis,Structure, and Magnetic Properties
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Mei Zhu Peng Hu Yungai Li Xiufeng Wang Prof. Licun Li Prof. Daizheng Liao V. M. L. Durga Prasad Goli Prof. S. Ramasesha Dr. Jean‐Pascal Sutter 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(41):13356-13365
Employing nitronyl nitroxide lanthanide(III) complexes as metallo‐ligands allowed the efficient and highly selective preparation of three series of unprecedented hetero‐tri‐spin (Cu?Ln‐radical) one‐dimensional compounds. These 2p–3d–4f spin systems, namely [Ln3Cu(hfac)11(NitPhOAll)4] (LnIII=Gd 1Gd , Tb 1Tb , Dy 1Dy ; NitPhOAll=2‐(4′‐allyloxyphenyl)‐4,4,5,5‐tetramethylimidazoline‐1‐oxyl‐3‐oxide), [Ln3Cu(hfac)11(NitPhOPr)4] (LnIII=Gd 2Gd , Tb 2Tb , Dy 2Dy , Ho 2Ho , Yb 2Yb ; NitPhOPr=2‐(4′‐propoxyphenyl)‐4,4,5,5‐tetramethyl‐imidazoline‐1‐oxyl‐3‐oxide) and [Ln3Cu(hfac)11(NitPhOBz)4] (LnIII=Gd 3Gd , Tb 3Tb , Dy 3Dy ; NitPhOBz=2‐(4′‐benzyloxyphenyl)‐4,4,5,5‐tetramethyl‐imidazoline‐1‐oxyl‐3‐oxide) involve O‐bound nitronyl nitroxide radicals as bridging ligands in chain structures with a [Cu‐Nit‐Ln‐Nit‐Ln‐Nit‐Ln‐Nit] repeating unit. The dc magnetic studies show that ferromagnetic metal–radical interactions take place in these hetero‐tri‐spin chain complexes, these and the next‐neighbor interactions have been quantified for the Gd derivatives. Complexes 1Tb and 2Tb exhibit frequency dependence of ac magnetic susceptibilities, indicating single‐chain magnet behavior. 相似文献
970.
Wei Chen Linxin Zhong Xinwen Peng Jiehua Lin Runcang Sun 《Cellulose (London, England)》2014,21(1):125-137
Xylan-type hemicelluloses supported terpyridine–palladium(II) as a novel biomass-supported catalyst was synthesized and characterized in terms of morphology, composition, and thermal stability. The nano-Pd catalyst was further explored for Suzuki–Miyaura reaction between arylboronic acid and aryl halide under aerobic condition, with a yield up to 98 %. In particular, the catalyst exhibited both high catalytic activity and stability for Suzuki–Miyaura reaction. Furthermore, the catalyst could be easily recovered by simple filtration and reused at least six times without significant loss of its catalytic activity. This work provides a novel and effective supported catalyst, and broadens the applications of polysaccharides in green catalysis. 相似文献