66 results on '"Zhenjie Lu"'
Search Results
2. S/N-codoped carbon nanotubes and reduced graphene oxide aerogel based supercapacitors working in a wide temperature range
- Author
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Zhenjie Lu, Xuanli Liu, Tao Wang, Xinning Huang, Jinxiao Dou, Dongling Wu, Jianglong Yu, Shiyong Wu, and Xingxing Chen
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Biomaterials ,Colloid and Surface Chemistry ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials - Published
- 2023
3. Co-Ni Bimetallic Zeolitic Imidazolate Frameworks Supported on Carbon Cloth as Free-Standing Electrode for Highly Efficient Oxygen Evolution.
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Wuxin Bai, Qianqian Zhou, Zhenjie Lu, Ye Song, and Yongsheng Fu
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- 2024
- Full Text
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4. Modulation of Photogenerated Carrier Transport by Integration of Sb2O3 with Fe2O3 for Improved Photoelectrochemical Water Oxidation
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Fukun Chen, Haoran Pan, Zhenjie Lu, Xinning Huang, Zhenyu Sun, and Xingxing Chen
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Materials Chemistry ,Electrochemistry ,Energy Engineering and Power Technology ,Chemical Engineering (miscellaneous) ,Electrical and Electronic Engineering - Published
- 2022
5. Free-standing Co/Zn sulfide supported on Cu-foam for efficient overall water splitting
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Haoran Pan, Yue Wang, Zhenjie Lu, Xinning Huang, and Xingxing Chen
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Materials Chemistry ,General Chemistry ,Catalysis - Abstract
A bifunctional self-supported electrode is prepared for both electrochemical water oxidation and reduction.
- Published
- 2022
6. The Effect of Organizational Trust on Turnover Intention of Rural Kindergarten Teachers: The Mediating Role of Teaching Efficacy and Job Satisfaction
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Yan Zhao, Zhenjie Lu, Xiulan Cheng, and Jiaqi Li
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Health, Toxicology and Mutagenesis ,Public Health, Environmental and Occupational Health ,mental health ,rural kindergarten teachers ,organizational trust ,teaching efficacy ,job satisfaction ,turnover intention ,COVID-19 ,Humans ,Intention ,Trust ,Pandemics ,Job Satisfaction - Abstract
Recent studies have focused on turnover among rural kindergarten teachers. However, none of these studies have shown a clear connection between turnover intention and organizational trust, although there are studies in other areas showing that organizational trust can affect turnover intention. Drawing on a sample of 330 kindergarten teachers in rural areas, this study explores the mechanism of influence between organizational trust and turnover intention with teaching efficacy and job satisfaction as mediators. We found that organizational trust negatively impacted teachers’ turnover intention, and this relationship was mediated by a significant chain mediating effect of teaching efficacy and job satisfaction. The findings enrich knowledge about turnover among rural kindergarten teachers and inspire us to create a more supportive organizational environment against the backdrop of the COVID-19 pandemic to improve job satisfaction and alleviate turnover among rural kindergarten teachers.
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- 2022
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7. Praziquantel promotes protection against Schistosoma japonicum infection in mice
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Bing Shao, Xiang Gui, Zhenjie Lu, Rongxue Lv, Hao Li, Ke Lu, Yang Hong, Zhiqiang Fu, Yamei Jin, Jiaojiao Lin, Chenzhong Fei, and Jinming Liu
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Infectious Diseases ,Insect Science ,Veterinary (miscellaneous) ,Parasitology - Published
- 2023
8. Earth-abundant coal-derived carbon nanotube/carbon composites as efficient bifunctional oxygen electrocatalysts for rechargeable zinc-air batteries
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Zhenjie Lu, Zhenyu Sun, Dongling Wu, Tao Wang, Xingxing Chen, Haoran Pan, Songdong Yao, Xinning Huang, and Dong Yanzeng
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Battery (electricity) ,Materials science ,business.industry ,Heteroatom ,Oxygen evolution ,Energy Engineering and Power Technology ,02 engineering and technology ,Carbon nanotube ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Anode ,law.invention ,Catalysis ,Fuel Technology ,Chemical engineering ,law ,Electrochemistry ,Water splitting ,Coal ,0210 nano-technology ,business ,Energy (miscellaneous) - Abstract
The exploration of active and robust electrocatalysts for both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is the bottleneck to realize the commercialization of rechargeable metal-air batteries and regenerative fuel cells. Here we report facile synthesis of three-dimensional (3D) carbon nanotube (CNT)/carbon composites using earth-abundant coal as the carbon source, hydrogen reductant and heteroatom dopant to grow CNTs. The prepared composite featuring 3D structural merits and multiple active sites can efficiently catalyze both ORR and OER, affording high activity, fast kinetics, and long-term stability. With the additional incorporation of manganese, the developed catalyst afforded a potential difference of 0.80 V between ORR at the half wave potential and OER at a current density of 10 mA cm−2. The optimized sample has presented excellent OER performance within a constructed solar-powered water splitting system with continuously generating oxygen bubbles at anode. Notably, it can be further used as a durable air-electrode catalyst in constructed Zn-air battery, delivering an initial discharge/charge voltage gap of 0.73 V, a remained voltaic efficiency of 61.2% after 160 cycles and capability to power LED light for at least 80 h. This study provides an efficient approach for converting traditional energy resource i.e. coal to value-added alternative oxygen electrocatalysts in renewable energy conversion systems.
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- 2021
9. Insulation board-derived N/O self-doped porous carbon as an electrode material for high-performance symmetric supercapacitors
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Yingjie Su, Zhenjie Lu, Lijuan Gao, Junxia Cheng, Xuefei Zhao, and Xingxing Chen
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Supercapacitor ,Chemical engineering ,Chemistry ,Carbonization ,Specific surface area ,Doping ,Heteroatom ,Materials Chemistry ,General Chemistry ,Capacitance ,Catalysis ,Faraday efficiency ,Power density - Abstract
The development of highly-efficient and low-cost heteroatom-doped porous carbon materials is vitally important for high-performance supercapacitors. Herein, waste phenolic resin-based insulation boards, which naturally contain N and O elements, were deliberately chosen as an absolute “zero”-cost green raw material for the preparation of heteroatom self-doped porous carbon. Through carbonization and activation steps, N/O self-doped porous carbon with a high surface area has been successfully prepared. The constructed symmetrical supercapacitor based on the best sample thermally activated at 600 °C had a specific capacitance of 262.2 F g−1 at 0.5 A g−1. Furthermore, the output energy density was 17.4 W h kg−1 at a power density of 500 W kg−1. Impressively, a significantly stable cycling duration with almost 100% capacitance retention and coulombic efficiency were retained after running 20 000 cycles. Moreover, it took 150 h to self-discharge to half of its maximum voltage. The prominent performance of the constructed symmetrical supercapacitor was attributed to the large specific surface area, hierarchical pore size distribution, and optimal doped heteroatoms in the carbon matrix. This work uncovers a promising strategy of converting waste construction materials into high-value electrode materials for green energy storage applications, such as supercapacitors.
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- 2021
10. Electrochemical performance of porous carbons derived from needle coke with different textures for supercapacitor electrode materials
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Xingxing Chen, Xuefei Zhao, Junxia Cheng, Zhenjie Lu, Yaming Zhu, and Hongyu Chu
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Supercapacitor ,Materials science ,Renewable Energy, Sustainability and the Environment ,Process Chemistry and Technology ,Organic Chemistry ,Petroleum coke ,Energy Engineering and Power Technology ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Microstructure ,01 natural sciences ,0104 chemical sciences ,Amorphous solid ,Inorganic Chemistry ,Microcrystalline ,Chemical engineering ,chemistry ,Specific surface area ,Materials Chemistry ,Ceramics and Composites ,0210 nano-technology ,Carbon ,Faraday efficiency - Abstract
The porous carbons with high specific surface area and excellent electrochemical properties were prepared using three types of green needle coke as raw materials. Electrochemical performances of the porous carbons derived from different microstructure green needle coke were investigated. The XRD and Raman spectra demonstrated that the content of the ordered carbon microcrystals were decreased and the content of amorphous and cross-linked structure were increased in the porous carbons with comparison to the raw materials. The results of N2 adsorption–desorption analysis verified that the content of ordered microcrystalline structure in the raw materials evidently influence the specific surface area and pore size distribution of the porous carbons. The porous carbon with 1665 m2 g−1 specific surface area and 2.89 nm average pore size has shown that the specific capacitance was 288 F g−1 at the current density 1 A g−1. Furthermore, the capacity retention was 94.93% and the Coulombic efficiency was 92.87% after 5000 charge/discharge cycles.
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- 2020
11. Catalytic Asymmetric Aziridination of Benzhydryl Imines and Diazoacetate Esters with BOROX Catalysts from 3,3′-Disubstituted VANOL Ligands
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Aliakbar Mohammadlou, Richard J. Staples, Zhenjie Lu, Xiaopeng Yin, William D. Wulff, and Yong Guan
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010405 organic chemistry ,Chemistry ,Ligand ,Organic Chemistry ,Enantioselective synthesis ,Substituent ,010402 general chemistry ,01 natural sciences ,Asymmetric induction ,Combinatorial chemistry ,Catalysis ,0104 chemical sciences ,Benzaldehyde ,chemistry.chemical_compound ,Ethyl diazoacetate - Abstract
This work details the synthesis of 22 new chiral VANOL ligands that differ by the nature of the substituent in the 3- and 3′-positions of the ligand. These ligands were incorporated into boroxinate catalysts that were used to screen the catalytic asymmetric aziridination of benzhydryl imines with ethyl diazoacetate. Each catalyst was screened in the reaction of imines generated from benzaldehyde and cyclohexanecarboxaldehyde and some with 4-nitro- and 4-methoxybenzaldehyde. In addition, the first report of the effect of the ester substituent of the diazoacetate ester on the asymmetric induction in these aziridination reactions is presented. The first X-ray structure of a boroxinate catalyst generated from a VANOL-derived ligand is also reported.
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- 2020
12. Heterojunctional Sb2o3/Fe2o3 Photoanode for Improved Photoelectrochemical Water Oxidation
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Fukun Chen, Haoran Pan, Zhenjie Lu, Xinning Huang, and Xingxing Chen
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- 2022
13. Porous Carbon Coated Fe-Zn Oxide Prepared Under Solvent-Free Hypersaline Environment as Efficient Catalyst for High Performance Zinc-Air Battery
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Xiaofeng Han, Tao Wang, Dongling Wu, Zhenjie Lu, and Xingxing Chen
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- 2022
14. Probing Catalyst Function – Electronic Modulation of Chiral Polyborate Anionic Catalysts
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Emily C. Matthews, Wynter E. G. Osminski, Jennifer S. Hirschi, Aliakbar Mohammadlou, Zhenjie Lu, William D. Wulff, Connor J. Allen, Virginia M. Canestraight, Richard J. Staples, Xiaopeng Yin, and Wenjun Zhao
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Steric effects ,Anions ,Organic Chemistry ,Imine ,Aziridines ,Enantioselective synthesis ,Protonation ,Stereoisomerism ,Combinatorial chemistry ,Asymmetric induction ,Article ,Catalysis ,chemistry.chemical_compound ,chemistry ,Covalent bond ,Lewis acids and bases ,Electronics - Abstract
Boroxinate complexes of VAPOL and VANOL are a chiral anionic platform that can serve as a versatile staging arena for asymmetric catalysis. The structural underpinning of the platform is a chiral polyborate core that covalently links together alcohols (or phenols) and vaulted biaryl ligands. The polyborate platform is assembled in situ by the substrate of the reaction, and thus a multiplex of chiral catalysts can be rapidly assembled from various alcohols (or phenols) and bis-phenol ligands for screening of catalyst activity. In the present study, variations in the steric and electronic properties of the phenol/alcohol component of the boroxinate catalyst are probed to reveal their effects on the asymmetric induction in the catalytic asymmetric aziridination reaction. A Hammett study is consistent with a mechanism in which the two substrates are hydrogen-bonded to the boroxinate core in the enantiogenic step. The results of the Hammett study are supported by a computational study in which it is found that the H-O distance of the protonated imine hydrogen bonded to the anionic boroxinate core decreases with an increase in the electron releasing ability of the phenol unit incorporated into the boroxinate. The results are not consistent with a mechanism in which the boroxinate catalyst functions as a Lewis acid and activates the imine by a Lewis acid/Lewis base interaction.
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- 2021
15. Preparation of ultrahigh surface area carbon microspheres under solvent-free hypersaline environment for zinc-air batteries with high power density
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Xiaofeng Han, Tao Wang, Jia Guo, Zhenjie Lu, Xingxing Chen, and Dongling Wu
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General Materials Science ,Condensed Matter Physics - Published
- 2022
16. Highly-stable cobalt metal organic framework with sheet-like structure for ultra-efficient water oxidation at high current density
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Zhenjie Lu, Wenzhi Luo, Xinning Huang, Huixuan Yu, Zhiwei Li, Guocheng Liu, Jianwen Liu, and Xingxing Chen
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Biomaterials ,Colloid and Surface Chemistry ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials - Abstract
The development of efficient and robust non-precious electrocatalysts for water oxidation at a mild condition is extremely desirable for industrial water splitting. Herein we developed a facile solvothermal strategy to synthesize cobalt metal organic frameworks (Co-MOFs) with sheet-like structure, which showed highly promising performance for electrocatalytic oxygen evolution. The best Co-MOF sample afforded an ultra-high oxygen evolution current density of 63.4 mA cm
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- 2021
17. Investigation of functionalization effect of carbon nanotubes as supercapacitor electrode material on hydrogen evolution side-reaction by scanning electrochemical microscopy
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Xuanli Liu, Zhenjie Lu, Haoran Pan, Junxia Cheng, Jinxiao Dou, Xinning Huang, and Xingxing Chen
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General Chemical Engineering ,Electrochemistry - Published
- 2022
18. Metal-induced various properties and structures of complexes based on methylene-derived diamide and S2-bridged carboxylate
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Zhenjie Lu, Xiang Wang, Yan Li, Xiu-Li Wang, Xingxing Chen, and Guo-Cheng Liu
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010405 organic chemistry ,Dimethyl sulfoxide ,Metal ions in aqueous solution ,010402 general chemistry ,Bromate ,01 natural sciences ,0104 chemical sciences ,Ion ,Inorganic Chemistry ,Metal ,chemistry.chemical_compound ,Crystallography ,chemistry ,visual_art ,Materials Chemistry ,visual_art.visual_art_medium ,Carboxylate ,Physical and Theoretical Chemistry ,Methylene ,Luminescence - Abstract
By introducing different metal ions, six new coordination polymers (CPs) [Zn(L)0.5(DTSA)]·H2O (CP1), [Cd(L)0.5(DTSA)(H2O)] (CP2), [Mn(L)0.5(DTSA)(H2O)] (CP3), [Co(L)0.5(DTSA)(H2O)] (CP4), [Ni(L)0.5(DTSA)(H2O)] (CP5), [Pb2(L)0.5(DTSA)2] (CP6), [N,N′-bis(4-methylenepyridin-4-yl)-1,4-benzenedicarboxamide (L), 2,2′-dithiodibenzoic acid (H2DTSA)] have been synthesized under hydrothermal conditions. CP1 is a unified node (4,4)-connected network derived from Zn2 nodes, pairs of DTSA anions and μ2-L linkers. CP2–CP5 display similar binode (4,4)-connected layers based on single metal centers, μ2-DTSA anions and μ4-L linkers. CP6 show a novel 3D (3,4,4,5)-connected Pb-based framework, which is constructed form Pb-DTSA layers and μ4-L linkers. The effect of metal ions on the architectures of the title complexes is investigated. The experimental results indicate that CP1, CP2 and CP6 are efficient luminescent sensors for the detection of Fe3+ ions (CP1 and CP2) and dimethyl sulfoxide (DMSO) (CP1 and CP6). In addition, CP3–CP5 show different electrochemical response to nitrite and bromate in water solution.
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- 2019
19. Significant enhancement of the oxygen reduction activity of self-heteroatom doped coal derived carbon through oxidative pretreatment
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Tao Wang, Zhenjie Lu, Huimin Liu, Xinning Huang, Xingxing Chen, Junxia Cheng, Justus Masa, Xuefei Zhao, and Yaming Zhu
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Tafel equation ,Chemistry ,business.industry ,General Chemical Engineering ,Heteroatom ,chemistry.chemical_element ,02 engineering and technology ,Thermal treatment ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Catalysis ,chemistry.chemical_compound ,Amorphous carbon ,Chemical engineering ,Electrochemistry ,Coal ,Methanol ,0210 nano-technology ,business ,Carbon - Abstract
Functional low-cost catalysts derived from earth abundant materials are vitally important for enabling mass implementation of renewable energy conversion systems, such as fuel cells and metal-air batteries. Herein, we report the activation of earth-abundant coal to realize very active and stable catalysts for the oxygen reduction reaction (ORR) through oxidative pretreatment followed by thermal treatment under ammonia forming self-doped heteroatoms and defects. The coal thermally pretreated in air at 350 °C for 30 min followed by treatment in ammonia for 2 h presented very good electrocatalytic ORR activity with onset potential of 0.978 V, half-wave potential of 0.871 V, Tafel slope of 57 mV dec−1, and predominant 4-electron reduction of O2 to OH−. The influence of the preoxidation step prior to ammonia treatment on the properties of the coal-derived carbon and hence the ORR has been specifically studied. The optimized catalyst also displayed stable performance during the ORR in 0.1 M NaOH for a test period of 35 h and exhibited excellent tolerance to methanol. The preoxidation step facilitates elimination of aliphatic and amorphous carbon, condensation of aromatic structures and the formation of initial pore structures, and subsequent removal of unstable heteroatoms from aromatic carbon rings to form surface and edge defects as potential active sites for promoting the ORR. Using pristine coal as raw material to produce functional ORR catalysts will be of great importance for real applications.
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- 2019
20. Microwave-Assisted Synthesis of Co/CoOx Supported on Earth-Abundant Coal-Derived Carbon for Electrocatalysis of Oxygen Evolution
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Justus Masa, Xuefei Zhao, Zhenjie Lu, Xingxing Chen, Haoran Pan, Junxia Cheng, Kunpeng Xie, Xinning Huang, Dongling Wu, Bingcai He, and Penggao Liu
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Materials science ,Hydrogen ,Renewable Energy, Sustainability and the Environment ,business.industry ,020209 energy ,Heteroatom ,Oxygen evolution ,chemistry.chemical_element ,02 engineering and technology ,Condensed Matter Physics ,Electrocatalyst ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Catalysis ,chemistry ,Chemical engineering ,0202 electrical engineering, electronic engineering, information engineering ,Materials Chemistry ,Electrochemistry ,Water splitting ,Coal ,business ,Cobalt - Abstract
The evident demand for hydrogen as the ultimate energy fuel for posterity calls for the development of low-cost, efficient and stable electrocatalysts for water splitting. Herein, we report the synthesis of Co/CoOx supported on coal-derived N-doped carbon via a simple microwave-assisted method and demonstrate its application as an efficient catalyst for the oxygen evolution reaction (OER). With the optimal amount of cobalt introduced into the N-doped coal-derived, the developed catalyst achieved overpotentials of 0.370 and 0.429 V during water oxidation at current densities of 1 mA cm(-2) and 10 mA cm(-2), respectively. There was no noticeable loss in the activity of the catalyst during continuous galvanostatic polarization at a current density of 10 mA cm(-2) for a test period of 66 h. The synergistic interaction of the Co/CoOx moieties with the pyridinic and pyrollic nitrogen functional groups in the N-doped carbon, as well with the other heteroatoms species in the pristine coal favored enhancement of the OER electrocatalytic performance. (C) The Author(s) 2019. Published by ECS.
- Published
- 2019
21. Versatile carboxylate-directed structures of ten 1D → 3D Ni(<scp>ii</scp>) coordination polymers: fluorescence behaviors and electrochemical activities
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Xingxing Chen, Xiao-Wu Li, Xiu-Li Wang, Zhenjie Lu, Yan Li, Xiang Wang, and Guo-Cheng Liu
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chemistry.chemical_classification ,Ligand ,Chemistry ,02 engineering and technology ,General Chemistry ,Polymer ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Electrochemistry ,01 natural sciences ,Fluorescence ,0104 chemical sciences ,chemistry.chemical_compound ,Crystallography ,General Materials Science ,Carboxylate ,0210 nano-technology ,Luminescence ,Powder diffraction ,Benzoic acid - Abstract
To study the effects of carboxylates on the assembly and structures of Ni(II) coordination polymers (CPs) based on a phenyl/methylene-mixed-bridged bis-pyridyl-bis-amide [N,N′-bis(4-methylenepyridin-4-yl)-1,4-benzenedicarboxamide] (L) ligand, ten 1D → 3D Ni(II) CPs, namely [Ni(L)(2-NB)2(H2O)2] (1), [Ni(L)(4-NB)2(H2O)2] (2), [Ni(L)2(2-MOB)2] (3), [Ni(L)2(3-CB)2] (4), [Ni(L)(2-CP)(H2O)] (5), [Ni(L)(5-NIP)(H2O)2]·2H2O (6), [Ni(L)(3-NP)(H2O)2] (7), [Ni(L)(4,4′-OBA)]·H2O (8), [Ni(L)(1,4-BDC)(H2O)2]·2H2O (9) and [Ni(L)(1,4-CHDA)(H2O)2]·4H2O (10) [2-nitrobenzoic acid (2-HNB), 4-nitrobenzoic acid (4-HNB), 2-methoxybenzoic acid (2-HMOB), 3-chlorobenzoic acid (3-HCB), 2-carboxyphenylacetic acid (2-H2CP), 5-nitroisophthalic acid (5-H2NIP), 3-nitrophthalic acid (3-H2NP), 4,4′-oxybis(benzoic acid) (4,4′-H2OBA), 1,4-benzenedicarboxylic acid (1,4-H2BDC) and trans-1,4-cyclohexanedicarboxylic acid (1,4-H2CHDA)], have been hydrothermally synthesized with various carboxylates and structurally characterized by IR, PXRD and X-ray single-crystal diffraction. 1 and 2 are similar 1D coordination polymers. 3 and 4 feature similar 2D coplanar 4,4-connected networks extended by single L linkers. 5 displays a 2D wave-like 4,4-connected network based on L and 2-CP mixed linkers. 6 shows a 2D 4,4-connected structure derived from L and 5-NIP mixed spacers. 7 is a CdSO4 type 4-connected 3D framework. 8 displays a 2D → 3D parallel polycatenation array based on 2D (4,4)-connected wave-like coordinated layers. 9 and 10 feature similar 2D → 3D inclined polycatenation arrays based on 2D (4,4)-connected coplanar networks. The effects of the carboxylates on the structures of the title complexes are discussed in detail. The solid-state luminescent and fluorescent sensing properties of 1–10 for Fe3+ ions were investigated. Moreover, the effects of 1, 5 and 7 on the fluorescence properties of bovine serum albumin (BSA) and the electrocatalytic activities of carbon paste electrodes (CPEs) bulk-modified with 1, 3, 5, 7 and 9 for the reduction of hydrogen peroxide, bromate and nitrite were studied.
- Published
- 2019
22. Blockchain-based engine data trustworthy swarm learning management method
- Author
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Zhenjie Luo and Hui Zhang
- Subjects
Engine ,Data integrity ,Data management ,Blockchain ,Swarm learning ,Information technology ,T58.5-58.64 - Abstract
Engine data management is of great significance for ensuring data security and sharing, as well as facilitating multi-party collaborative learning. Traditional data management approaches often involve decentralized data storage that is vulnerable to tampering, making it challenging to conduct multi-party collaborative learning under privacy protection conditions and fully leverage the value of data. Moreover, data with compromised integrity can lead to incorrect results if used for model training. Therefore, this paper aims to break down data sharing barriers and fully utilize decentralized data for multi-party collaborative learning under privacy protection conditions. We propose a trustworthy engine data management method based on blockchain technology to ensure data immutability and non-repudiation. To address the issue of limited data samples for some users resulting in poor model performance, we introduce swarm learning techniques based on centralized machine learning and design a trustworthy data management method for swarm learning, achieving trustworthy regulation of the entire process. We conduct research on engine models under swarm learning based on the NASA open dataset, effectively organizing decentralized data samples for collaborative training while ensuring data privacy and fully leveraging the value of data.
- Published
- 2024
- Full Text
- View/download PDF
23. Trace metals dramatically boost oxygen electrocatalysis of N-doped coal-derived carbon for zinc–air batteries
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Zhenjie Lu, Xinning Huang, Alex W. Robertson, Huimin Liu, Tao Wang, Junxia Cheng, Zhenyu Sun, Xingxing Chen, Yue Wang, Yaming Zhu, and Dongling Wu
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Materials science ,business.industry ,Heteroatom ,Oxygen evolution ,Oxide ,Carbon nanotube ,Electrocatalyst ,law.invention ,Catalysis ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,law ,General Materials Science ,Coal ,Bifunctional ,business - Abstract
The commercialization of metal-air batteries requires efficient, low-cost, and stable bifunctional electrocatalysts for reversible electrocatalysis of the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). The modification of natural coal by heteroatoms such as N and S, or metal oxide species, has been demonstrated to form very promising electrocatalysts for the ORR and OER. However, it remains elusive and underexplored as to how the impurity elements in coal may impact the electrocatalytic properties of coal-derived catalysts. Herein, we explore the influence of the presence of various trace metals that are notable impurities in coal, including Al, Si, Ca, K, Fe, Mg, Co, Mn, Ni, and Cu, on the electrochemical performance of the prepared catalysts. The constructed Zn-air batteries are further shown to be able to power green LED lights for more than 80 h. The charge-discharge polarization curves exhibited excellent and durable rechargeability over 500 (ca. 84 h) continuous cycles. The promotional effect of the trace elements is believed to accrue from a combination of electronic structure modification of the active sites, enhancement of the active site density, and formation of a conductive 3-dimensional hierarchical network of carbon nanotubes.
- Published
- 2020
24. Co-Mn Hybrid Oxides Supported on N-Doped Graphene as Efficient Electrocatalysts for Reversible Oxygen Electrodes
- Author
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Zhigang Fang, Xingxing Chen, Justus Masa, Xinning Huang, Songdong Yao, Jiong Wei, Zhong Ren, Penggao Liu, Zhenjie Lu, and Tao Wang
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Materials science ,Renewable Energy, Sustainability and the Environment ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Oxygen ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry ,Chemical engineering ,Electrode ,Materials Chemistry ,Electrochemistry ,Doped graphene ,0210 nano-technology - Published
- 2018
25. Self-assembled S,N co-doped reduced graphene oxide/MXene aerogel for both symmetric liquid- and all-solid-state supercapacitors
- Author
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Chao Li, Chuanjun Tu, Xinning Huang, Jinfeng Bai, Xingxing Chen, Zhenjie Lu, and Xuanli Liu
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Supercapacitor ,Materials science ,Renewable Energy, Sustainability and the Environment ,Graphene ,Oxide ,Energy Engineering and Power Technology ,Aerogel ,Electrochemistry ,Capacitance ,law.invention ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,law ,Electrical and Electronic Engineering ,Physical and Theoretical Chemistry ,Current density ,Faraday efficiency - Abstract
Two-dimensional (2D) transition metal carbon/nitrogen compound (MXene) and graphene are popular energy storage materials. Still, the electrochemical performance and application of those 2D materials are severely limited due to their easy self-stacking. In this article, three-dimensional (3D) hybrid porous aerogel made of sulfur and nitrogen doped reduced graphene oxide and MXene (S,N-rGO@MXene) is successfully self-assembled via a simple hydrothermal method. The reductive nature of MXene positively tune the hydrophilicity of rGO, thus leading to a controllable formation of 3D mutual cross-linking rGO/MXene. The involvement of elemental S and N additionally promotes electrochemical performance. The specific capacitances of 85.4 and 88.9 F g−1 in symmetric liquid- and all-solid-state supercapacitors assembled with S,N-rGO@MXene are achieved at the current density of 1 A g−1, respectively. Notably, the capacitance retention and Coulombic efficiency remain almost unchanged after 20,000 and 10,000 charge/discharge cycles in the respective systems. In particular, the all-solid-state supercapacitor achieves a high energy density of 24.2 Wh kg−1 at the power density of 1400.6 W kg−1, outperforming most of the MXene-based all-solid-state supercapacitors reported so far. Practically, the constructed supercapacitor is applicable to light up LED lamps. Our self-assembled 3D aerogel provides a valuable reference for the fabrication of efficient symmetric supercapacitors.
- Published
- 2021
26. Dual oxidation and sulfurization enabling hybrid Co/Co3O4@CoS in S/N-doped carbon matrix for bifunctional oxygen electrocatalysis and rechargeable Zn-air batteries
- Author
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Haoran Pan, Tao Wang, Dongling Wu, Xinning Huang, Zhiqiang Zhang, Zhenjie Lu, Fangyi Cheng, Baigang An, and Xingxing Chen
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Battery (electricity) ,Materials science ,Carbonization ,General Chemical Engineering ,Oxygen evolution ,chemistry.chemical_element ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrocatalyst ,01 natural sciences ,Oxygen ,Industrial and Manufacturing Engineering ,0104 chemical sciences ,Catalysis ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Environmental Chemistry ,0210 nano-technology ,Bifunctional ,Carbon - Abstract
The development of high-performance non-precious bifunctional electrocatalysts for both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) is urgently needed to realize the commercialization of rechargeable metal-air battery. Herein, we report a ZIF-67 derived hybrid Co-based carbon composite as bifunctional ORR/OER electrocatalyst exhibiting excellent performance and stability in a custom-built Zn-air battery. The catalyst was formed by pyrolytic carbonization of ZIF-67 followed by mild oxidation and sulfurization to a hybrid composite (Co/Co3O4@CoS-SNC) comprised of multiple active sites including Co-N4, Co-N/S-C, C-N/S-C, Co3O4 and CoS, as well as the surface and edge defects in the carbon matrix, that act concertedly yielding a highly efficient bifunctional ORR/OER catalyst for reversible oxygen electrodes. The catalyst affords remarkably low reversible overpotentials and stability not only in a 3-electrode system, but also in a custom-constructed Zn-air battery, exhibiting competitive performance against state-of-the-art bifunctional ORR/OER electrocatalysts reported to date and thus placing it among the best non-precious metal catalysts for reversible oxygen reactions.
- Published
- 2021
27. Green needle coke-derived porous carbon for high-performance symmetric supercapacitor
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Zhenjie Lu, Xingxing Chen, Xuefei Zhao, Junxia Cheng, and Yuhong Liu
- Subjects
Supercapacitor ,Materials science ,Renewable Energy, Sustainability and the Environment ,Capacitive sensing ,Petroleum coke ,Energy Engineering and Power Technology ,02 engineering and technology ,Electrolyte ,Thermal treatment ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Capacitance ,0104 chemical sciences ,Electrode ,Electrical and Electronic Engineering ,Physical and Theoretical Chemistry ,Composite material ,0210 nano-technology ,Faraday efficiency - Abstract
The synthesis of low-cost and high-performance electrode material is one of the key challenges in the supercapacitor development. Herein, we report to prepare the porous carbon materials by thermal treatment using coal-based green needle coke. The as-synthesized porous carbon thermally treated at 750 °C achieves the best ideal electric double-layer capacitive performance, which is superior to the ones treated at other temperatures. Because of the high conductivity and free ion diffusion pathway possessed in porous carbon, high specific capacitance (274.9 F/g at 1A/g), and ideal coulomb efficiency (98.9% after 1000 circles at 5 A/g) of the sample observes in 3-electrode testing systems. The operational voltage window can be expanded to 0–1.8 V in 1 M Na2SO4 electrolyte for the 2-electrode system. Moreover, a symmetric button-type supercapacitor has assembled using the as-synthesized porous carbon supported on Ni-foam as both the positive and negative electrodes. The device delivers a high capacitance of 147.7 F/g, capacitive retention rate of 75.8% at 12 A/g, and a prominent energy density of 20.51 Wh/kg at power density of 1031.42 W/kg. Notably, the constructed supercapacitor shows outstanding cycling stability with capacity retention of 95.6% and coulombic efficiency of 98.5% after running 5000 cycles at 1 A/g.
- Published
- 2021
28. Atomic Cu dispersed ZIF-8 derived N-doped carbon for high-performance oxygen electrocatalysis in Zn-air battery
- Author
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Weihua Jin, Qichao Wang, Zhigang Fang, Xingxing Chen, Haoran Pan, Songdong Yao, Zhenjie Lu, Xinning Huang, and Yaming Zhu
- Subjects
Battery (electricity) ,Materials science ,chemistry ,Chemical engineering ,Transition metal ,Doped carbon ,chemistry.chemical_element ,General Materials Science ,Condensed Matter Physics ,Electrocatalyst ,Oxygen ,Atomic and Molecular Physics, and Optics - Abstract
Single-atom catalysts have attracted widespread attention in recent years due to their high atom utilization and excellent catalytic performance, particularly, in oxygen electrocatalysis. Herein, we report to use ZIF-8 as precursor, which was annealed and subsequently mixed with melamine and transition metal salt to finally synthesize Cu-atoms modified N-doped carbon (NC) catalysts, which exhibited excellent oxygen reduction reaction activity and kinetic performance in alkaline solution. The constructed rechargeable Zn-air battery using Cu-NC and benchmark Pt/C catalyst supported on carbon fiber paper as the cathode and anode, respectively, exhibited super good long-term stability with remaining voltaic efficiency of 56% at a charge/discharge current density of 5 mA cm−2 after running 250 cycles (ca. 42 h). Moreover, the power density was as high as 104.5 mW cm−2 at 0.65 V, and such three Zn-air batteries connected in series could light up 34 LED bulbs (2 V and 1.5 W for each) used for constructing a figure of ‘USTL’ for at least 12 h. This research provides a facile method on the synthesis of efficient and cost-effective ORR electrocatalysts in renewable energy storage and conversion systems.
- Published
- 2021
29. Free-standing hierarchical Co@CoO/CNFs/Cu-foam composite based on electrochemical deposition as high-performance supercapacitor electrode
- Author
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Dongling Wu, Liwei Zhang, Qing Yang, Yun Gao, Zhenjie Lu, Xingxing Chen, Xinning Huang, Tao Wang, Haoran Pan, and Junxia Cheng
- Subjects
Supercapacitor ,Materials science ,Carbon nanofiber ,Mechanical Engineering ,Composite number ,Metals and Alloys ,Nanoparticle ,02 engineering and technology ,Electrolyte ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Capacitance ,0104 chemical sciences ,Chemical engineering ,Mechanics of Materials ,Electrode ,Materials Chemistry ,0210 nano-technology ,Current density - Abstract
Three-dimensional structural materials with sufficient reactive contact surface to the electrolyte can significantly improve the capacitance performance of supercapacitors. Herein, we report a facile method to fabricate a hierarchical carbon nanofibers (CNFs) modified Cu-foam supported Co@CoO hybrid as a free-standing and binder-free electrode for supercapacitor application. The optimized Co@CoO/CNFs/Cu-foam shows a high specific capacitance of 19.2 F cm−3 at the current density of 50 mA cm−3 and a remarkable capacitance retention of 97.5% after 5000 cycles in a 3-electrode system. A button-type asymmetric supercapacitor was additionally constructed by using Co@CoO/CNFs/Cu foam as the positive electrode and activated carbon electrode as negative electrode to examine its practical application. The stored energy density reached to 180.5 mWh cm−2 with the corresponding power density of 6000 mW cm−2 at a discharging current density of 4 mA cm−2. An excellent cycling life of retention 100% was maintained after 5000 cycles. The high-surface area and conductivity of the CNFs played a positive role as support to highly-dispersed Co@CoO nanoparticles. The pulsed electrodeposition additionally favored the controllable fabrication of Co@CoO nanoparticles with homogeneously distribution and uniform sizes. The hierarchical hybrid electrode with porous architecture eventually allowed good access of electrolyte and efficient charge storage and transfer, which concomitantly improved its overall electrochemical performance.
- Published
- 2021
30. β-Amino Esters from the Reductive Ring Opening of Aziridine-2-carboxylates
- Author
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Zhenjie Lu, William D. Wulff, and Wenjun Zhao
- Subjects
Trimethylsilyl Compounds ,Amino esters ,Stereochemistry ,Aryl ,Organic Chemistry ,Aziridines ,Benzenesulfonates ,Substituent ,Esters ,Stereoisomerism ,Aziridine ,Cleavage (embryo) ,Article ,3. Good health ,chemistry.chemical_compound ,Sulfonate ,chemistry ,Carboxylate ,Bond cleavage ,Palladium - Abstract
A general study is undertaken to examine the scope of the reductive ring opening of aziridine-2-carboxylates with samarium diiodide. The competition between C-C and C-N bond cleavage is examined as a function of the nature of the N-substituent of the aziridine, the nature of the substituent in the 3-position of the aziridine, and whether the substituent in the 3-position is in a cis or trans relationship with the carboxylate in the 2-position. The desired C-N bond cleavage leads to β-amino esters that are the predominant products for most aziridines with an N-activating group. However, C-C cleavage products are observed with an aryl group in the 3-position; this can be particularly pronounced with cis-aziridines where a nearly equal mixture of the two is observed. Exclusive formation of the C-N cleavage product is observed for all aziridines with the strongly N-activating p-toluene sulfonate group. Similarly high selectivity is observed for the 2-trimethylsilylethyl sulfonate group (SES), which is easier to remove. The utility of these methods is illustrated in the synthesis of protected forms of (R)-β(3)-DOPA and L-DOPA from the same aziridine, the former by SmI2-mediated reductive opening at C-2 and the latter by palladium-mediated reductive opening at C-3.
- Published
- 2014
31. Catalytic Asymmetric Synthesis of Alkynyl Aziridines: Both Enantiomers of cis ‐Aziridines from One Enantiomer of the Catalyst
- Author
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Mathew J. Vetticatt, Yijing Dai, William D. Wulff, Zhenjie Lu, Aman A. Desai, Aniruddha P. Patwardhan, Yong Guan, Maria P. Lopez‐Alberca, and Yu Zhang
- Subjects
Models, Molecular ,Chemistry ,Stereochemistry ,Aryl ,Aziridines ,Organic Chemistry ,Imine ,Enantioselective synthesis ,Stereoisomerism ,General Chemistry ,Aziridine ,Medicinal chemistry ,Catalysis ,Transition state ,chemistry.chemical_compound ,Alkynes ,Diazo ,Imines ,Enantiomer ,Azo Compounds - Abstract
Alkynyl aziridines can be obtained from the catalytic asymmetric aziridination (AZ reaction) of alkynyl imines with diazo compounds in high yields and high asymmetric inductions mediated by a chiral boroxinate or BOROX catalyst. In contrast to the AZ reaction with aryl- and alkyl-substituted imines, alkynyl imines react to give cis-substituted aziridines with both diazo esters and diazo acetamides. Remarkably, however, the two diazo compounds give different enantiomers of the cis-aziridine from the same enantiomer of the catalyst. Theoretical considerations of the possible transition states for the enantiogenic step reveal that the switch in enantiomers results from a switch from Si-face to Re-face addition to the imine, which in turn is related to a switch from reaction with an E-imine in the former and a Z-isomer of the imine in the latter.
- Published
- 2014
32. Ynamides: a modern functional group for the new millennium
- Author
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DeKorver, Kyle A., Hongyan Li, Lohse, Andrew G., Hayashi, Ryuji, Zhenjie Lu, Yu Zhang, and Hsung, Richard P.
- Subjects
Amides -- Chemical properties ,Ring formation (Chemistry) -- Analysis ,Elimination reactions -- Analysis ,Chemistry - Published
- 2010
33. Wild-type microglia arrest pathology in a mouse model of Rett syndrome
- Author
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Eric Xu, Stephen B. G. Abbott, Zhenjie Lu, Noël C. Derecki, James C. Cronk, Patrice G. Guyenet, and Jonathan Kipnis
- Subjects
Male ,Pathology ,medicine.medical_specialty ,Methyl-CpG-Binding Protein 2 ,Apoptosis ,Rett syndrome ,Phosphatidylserines ,Biology ,Article ,Rotarod performance test ,MECP2 ,Mice ,Phagocytosis ,Rett Syndrome ,medicine ,Animals ,Annexin A5 ,Insulin-Like Growth Factor I ,Bone Marrow Transplantation ,Multidisciplinary ,Microglia ,Respiration ,Body Weight ,Wild type ,Brain ,medicine.disease ,Mice, Inbred C57BL ,Transplantation ,Disease Models, Animal ,medicine.anatomical_structure ,Rotarod Performance Test ,Immunology ,Disease Progression ,Female ,Bone marrow ,Locomotion - Abstract
Rett syndrome is an X-linked autism spectrum disorder. The disease is characterized in most cases by mutation of the MECP2 gene, which encodes a methyl-CpG-binding protein. Although MECP2 is expressed in many tissues, the disease is generally attributed to a primary neuronal dysfunction. However, as shown recently, glia, specifically astrocytes, also contribute to Rett pathophysiology. Here we examine the role of another form of glia, microglia, in a murine model of Rett syndrome. Transplantation of wild-type bone marrow into irradiation-conditioned Mecp2-null hosts resulted in engraftment of brain parenchyma by bone-marrow-derived myeloid cells of microglial phenotype, and arrest of disease development. However, when cranial irradiation was blocked by lead shield, and microglial engraftment was prevented, disease was not arrested. Similarly, targeted expression of MECP2 in myeloid cells, driven by Lysm(cre) on an Mecp2-null background, markedly attenuated disease symptoms. Thus, through multiple approaches, wild-type Mecp2-expressing microglia within the context of an Mecp2-null male mouse arrested numerous facets of disease pathology: lifespan was increased, breathing patterns were normalized, apnoeas were reduced, body weight was increased to near that of wild type, and locomotor activity was improved. Mecp2(+/-) females also showed significant improvements as a result of wild-type microglial engraftment. These benefits mediated by wild-type microglia, however, were diminished when phagocytic activity was inhibited pharmacologically by using annexin V to block phosphatydilserine residues on apoptotic targets, thus preventing recognition and engulfment by tissue-resident phagocytes. These results suggest the importance of microglial phagocytic activity in Rett syndrome. Our data implicate microglia as major players in the pathophysiology of this devastating disorder, and suggest that bone marrow transplantation might offer a feasible therapeutic approach for it.
- Published
- 2012
34. Phagocytic activity of neuronal progenitors regulates adult neurogenesis
- Author
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Yubo Chen, Michael R. Elliott, Kodi S. Ravichandran, Zhenjie Lu, James T. Walsh, Jonathan Kipnis, and Alexander L. Klibanov
- Subjects
Doublecortin Domain Proteins ,Male ,Doublecortin Protein ,Time Factors ,Neurogenesis ,Cellular differentiation ,Phagocytosis ,Population ,Apoptosis ,Biology ,Article ,Mice ,Neural Stem Cells ,Cell Movement ,Animals ,Progenitor cell ,education ,Cells, Cultured ,Adaptor Proteins, Signal Transducing ,Cell Proliferation ,Mice, Knockout ,Neurons ,Phagocytes ,education.field_of_study ,Microscopy, Confocal ,Neuropeptides ,Brain ,Cell Differentiation ,Cell Biology ,Immunohistochemistry ,Cell biology ,Doublecortin ,Mice, Inbred C57BL ,ELMO1 ,biology.protein ,Female ,Microtubule-Associated Proteins ,Ex vivo - Abstract
Whereas thousands of new neurons are generated daily during adult life, only a fraction of them survive and become part of neural circuits; the rest die, and their corpses are presumably cleared by resident phagocytes. How the dying neurons are removed and how such clearance influences neurogenesis are not well understood. Here, we identify an unexpected phagocytic role for the doublecortin (DCX)-positive neuronal progenitor cells during adult neurogenesis. Our in vivo and ex vivo studies demonstrate that DCX(+) cells comprise a significant phagocytic population within the neurogenic zones. Intracellular engulfment protein ELMO1, which promotes Rac activation downstream of phagocytic receptors, was required for phagocytosis by DCX(+) cells. Disruption of engulfment in vivo genetically (in Elmo1-null mice) or pharmacologically (in wild-type mice) led to reduced uptake by DCX(+) cells, accumulation of apoptotic nuclei in the neurogenic niches and impaired neurogenesis. Collectively, these findings indicate a paradigm wherein DCX(+) neuronal precursors also serve as phagocytes, and that their phagocytic activity critically contributes to neurogenesis in the adult brain.
- Published
- 2011
35. Seeking Passe-Partout in the Catalytic Asymmetric Aziridination of Imines: Evolving Toward Substrate Generality for a Single Chemzyme
- Author
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Yu Zhang, Anil K. Gupta, Munmun Mukherjee, Zhenjie Lu, and William D. Wulff
- Subjects
chemistry.chemical_classification ,Aldehydes ,Molecular Structure ,Aryl ,Aziridines ,Organic Chemistry ,Imine ,Enantioselective synthesis ,Stereoisomerism ,Diazonium Compounds ,Aldehyde ,Asymmetric induction ,Catalysis ,chemistry.chemical_compound ,Boric Acids ,chemistry ,Organic chemistry ,Imines ,Amines ,Enantiomeric excess ,Aliphatic compound - Abstract
The asymmetric catalytic aziridination reaction (AZ reaction) of imines derived from dianisylmethyl (DAM) amine and tetra-methyldianisylmethyl (MEDAM) amine were examined with boroxinate catalysts prepared from both the VANOL and VAPOL ligands. This included an evaluation of different protocols for the preparation of the catalyst. The AZ reaction of DAM and MEDAM imines prepared from nine different aryl and aliphatic aldehydes were examined. The MEDAM imines were superior to the DAM imines in the AZ reaction, giving much higher asymmetric inductions and higher overall yields of aziridines. The MEDAM imines were found to also be superior to the previously studied diphenylmethyl (benzhydryl or Bh) and tetra-tert-butyldianisylmethyl (BUDAM) imines especially for imines derived from aliphatic aldehydes. The average asymmetric induction over the nine different MEDAM imines studied was 97% ee with the VAPOL catalyst and 96% ee with the VANOL catalyst. The MEDAM imines can be deprotected to give N-H aziridines in all cases except for some electron-rich aryl aldehydes. The MEDAM imines are much more reactive than benzhydryl imines, and this was most evident when a diazoacetate ester is replaced by a diazoacetamide. The less reactive diazoacetamides give very low yields in their reactions with benzhydryl imines but high yields with MEDAM imines.
- Published
- 2010
36. Ynamides: A Modern Functional Group for the New Millennium
- Author
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Hongyan Li, Zhenjie Lu, Kyle A. DeKorver, Andrew G. Lohse, Yu Zhang, Richard P. Hsung, and Ryuji Hayashi
- Subjects
Biological Products ,Intramolecular reaction ,Regioselectivity ,General Chemistry ,Amides ,Combinatorial chemistry ,Catalysis ,Article ,chemistry.chemical_compound ,Isomerism ,chemistry ,Cyclization ,Metals ,Alkynes ,Intramolecular force ,Functional group ,Organic chemistry ,Ynol ,Organic synthesis ,Amines ,Carbene ,Organometallic chemistry - Abstract
An Overview on Ynamines Alkynes represent one of the most important and versatile building blocks in organic synthesis. Heteroatom-substituted alkynes, which can be considered as subgroups of alkynes, have also been vastly utilized in developing synthetic methods. In particular, ynamines [1-amino-alkynes or N-alkynyl amines] became the most valuable subgroup of alkynes after the establishment of their practical synthesis in the 1960's. The first attempt at preparation of an ynamine was reported by Bode1,2 in 1892. While well-characterized ynamines were reported in 19583 and 1960,4 a practical synthesis was not achieved until the effort led by Viehe5 in 1963 in addition to other subsequent works. In the ensuing twenty years, the synthetic significance of ynamines in organic and organometallic chemistry was firmly established by the work of many creative synthetic chemists. These elegant pioneer works have been informatively and carefully reviewed by Viehe in 19676 and 1969;7 Ficini in 1976;8 Pitacco and Valentin9 in 1979; Collard-Motte and Janousek10 in 1986; Himbert11 in 1993; and most recently by us12,13 and Katritzky14. Open in a separate window The synthetic eminence of ynamines is well merited because of the predicable regioselectivity in their transformations as shown by the generalization in Scheme i, and more importantly, because they are inherently highly reactive. However, this latter attribute is also the source of the limitation that has seriously hampered the development of ynamine chemistry, thereby shortening the period of its prominence in synthesis. Ynamines are very sensitive toward hydrolysis, as protonation of the electron-rich alkynyl motif affords reactive keteniminium intermediates, which upon trapping with water leads to simple amides in a rather expensive manner (Scheme i). This hydrolytic instability has caused much difficulty in the experimental preparation and general handling of ynamines, and more detrimentally, rendered ynamine chemistry inaccessible. Open in a separate window Scheme i Consequently, the synthetic utility of ynamines has suffered a dramatic decline during the last thirty years.15 The most glaring limitations have been in the development of intramolecular and stereoselective reactions.7–14 The only reported intramolecular reaction of ynamines was Genet and Kahn's acid catalyzed addition of a hydroxyl group to an ynamine [i→ii in Scheme ii] in 1980,16 and although clever, it constitutes a hydrolytic process. Open in a separate window Scheme ii Besides Reinhoudt's17 sole account in 1987 reporting hetero-[4 + 2] cycloadditions of chiral ynamine iii with nitroalkenes that led to cycloadducts iv in modest de, the only other notable studies were reported ten years later by Fischer18 showcasing [2 + 2] cycloadditions of chiral ynamides v and vi with vinylidene chromium carbene complexes, and another three years later by Pericas19 in their Pauson-Khand cycloadditions using chiral ynamines vii.
- Published
- 2010
37. Catalytic Asymmetric Aziridination with Catalysts Derived from VAPOL and VANOL
- Author
-
William D. Wulff, Yu Zhang, and Zhenjie Lu
- Subjects
chemistry.chemical_compound ,Ethyl diazoacetate ,chemistry ,Organic Chemistry ,Enantioselective synthesis ,VANOL ligand ,Substituent ,Organic chemistry ,Diazo ,Lewis acids and bases ,Catalysis - Abstract
This Account describes the discovery and development of the catalytic asymmetric aziridination reaction (AZ reaction) that has been the subject of efforts in our laboratory over the last 12 years. The optimized catalyst system involves catalysts generated from either the VAPOL or VANOL ligand and triphenyl borate. These catalysts are effective for formation of aziridines from the reaction of imines that bear a N-benzhydryl substituent with stabi- lized diazo compounds including the commercially available ethyl diazoacetate (EDA). The reaction is general for N-benzhydryl im- ines prepared from electron-rich and electron-poor aromatic alde- hydes, as well as from primary, secondary and tertiary aliphatic aldehydes. This reaction is highly enantioselective and diastereo- selective giving cis-3-substituted aziridine-2-carboxylates in excel- lent yields. This Account presents the scope of the AZ reaction as defined by the work that has been done in our laboratory up to the present time, as well as applications of the resulting aziridines that have been demonstrated to date.
- Published
- 2009
38. Catalytic Asymmetric Aziridination with Borate Catalysts Derived from VANOL and VAPOL Ligands: Scope and Mechanistic Studies
- Author
-
Yu Zhang, Aman A. Desai, William D. Wulff, Gang Hu, Zhenjie Lu, and Zhensheng Ding
- Subjects
Molecular Structure ,Ligand ,Aziridines ,Organic Chemistry ,Enantioselective synthesis ,Stereoisomerism ,General Chemistry ,Nuclear magnetic resonance spectroscopy ,Naphthalenes ,Phenanthrenes ,Aziridine ,Ligands ,Combinatorial chemistry ,Catalysis ,chemistry.chemical_compound ,Ethyl diazoacetate ,chemistry ,Borates ,Organic chemistry ,Enantiomeric excess ,Acids - Abstract
An extended study of the scope and mechanism of the catalytic asymmetric aziridination of imines with ethyl diazoacetate mediated by catalysts prepared from the VANOL and VAPOL ligands and triphenylborate is described. Nonlinear studies with scalemic VANOL and VAPOL reveal an essentially linear relationship between the optical purity of the ligand and the product suggesting that the catalyst incorporates a single molecule of the ligand. Two species are present in the catalyst prepared from B(OPh)(3) and either VANOL or VAPOL as revealed by (1)H NMR studies. Mass spectral analysis of the catalyst mixture suggests that one of the species involves one ligand molecule and one boron atom (B1) and the other involves one ligand and two boron atoms (B2). The latter can be formulated as either a linear or cyclic pyroborate and the (11)B NMR spectrum is most consistent with the linear pyroborate structure. Several new protocols for catalyst preparation are developed which allow for the generation of mixtures of the B1 and B2 catalysts in ratios that range from 10:1 to 1:20. Studies with catalysts enriched in the B1 and B2 species reveal that the B2 catalyst is the active catalyst in the VAPOL catalyzed asymmetric aziridination reaction giving significantly higher asymmetric inductions and rates than the B1 catalyst. The difference is not as pronounced in the VANOL series. A series of 12 different imines were surveyed with the optimal catalyst preparation procedure with the finding that the asymmetric inductions are in the low to mid 90s for aromatic imines and in the mid 80s to low 90s for aliphatic imines for both VANOL and VAPOL catalysts. Nonetheless, the crystallinity of the N-benzhydryl aziridines is such that nearly all of the 12 aziridine products screened can be brought to >99 % ee with a single recrystallization.
- Published
- 2008
39. The influence of glycogen synthase kinase 3 in limiting cell addition in the mammalian ear
- Author
-
Jeffrey T. Corwin and Zhenjie Lu
- Subjects
medicine.medical_specialty ,Indoles ,Cell ,Fluorescent Antibody Technique ,Transfection ,Maleimides ,Glycogen Synthase Kinase 3 ,Mice ,Cellular and Molecular Neuroscience ,Developmental Neuroscience ,GSK-3 ,Internal medicine ,medicine ,Animals ,Glycogen synthase ,Cells, Cultured ,beta Catenin ,Cell Proliferation ,Glycogen Synthase Kinase 3 beta ,Hair Cells, Auditory, Inner ,biology ,Cell growth ,Regeneration (biology) ,Age Factors ,Epithelial Cells ,Cadherins ,Epithelium ,Electroporation ,medicine.anatomical_structure ,Endocrinology ,Animals, Newborn ,biology.protein ,Hair cell ,Lithium Chloride - Abstract
In the vestibular organs of the inner ear, an early postnatal decline in the capacity for cell proliferation appears to be responsible for limits to hair cell regeneration that are unique to mammals. We have investigated the time course of that decline in cell proliferation and its potential regulation by glycogen synthase kinase-3 (GSK3). Our immunoblots have revealed that inactive GSK3β decreases postnatally in the murine utricular epithelium, as E-cadherin and the active forms of GSK3α and GSK3β each increase. In cultured utricular epithelia, pharmacological inhibition of GSK3 by LiCl and SB-216763 increased cell proliferation across a range of postnatal ages. LiCl treatments also led to increased levels of β-catenin and Snail and decreased expression of E-cadherin. Transfection with a dominant-negative GSK3β enhanced proliferation in these epithelia in a cell-autonomous manner, while overexpression of wild-type GSK3β markedly reduced it. The evidence from these measurements and experimental manipulations indicates that the balance of active and inactive forms of GSK3 helps to determine whether mammalian vestibular supporting cells will proliferate; permitting proliferation during early development when inactive GSK3 predominates and progressively inhibiting proliferation, and thereby limiting the capacity for hair cell regeneration as more GSK3 becomes active during the first week of postnatal maturation. © 2008 Wiley Periodicals, Inc. Develop Neurobiol, 2008.
- Published
- 2008
40. Direct Access to N-H-Aziridines from Asymmetric Catalytic Aziridination with Borate Catalysts Derived from Vaulted Binaphthol and Vaulted Biphenanthrol Ligands
- Author
-
Zhenjie Lu, William D. Wulff, and Yu Zhang
- Subjects
Chemistry ,Ligand ,Aziridines ,Imine ,General Medicine ,Naphthols ,General Chemistry ,Aziridine ,Ligands ,Biochemistry ,Asymmetric induction ,Medicinal chemistry ,Catalysis ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,Ethyl diazoacetate ,Yield (chemistry) ,Borates ,Organic chemistry ,Enantiomeric excess - Abstract
The asymmetric catalytic aziridination reaction (AZ reaction) of N-dianisylmethylimines (N-DAM-imines) with ethyl diazoacetate is developed with chiral catalysts prepared from triphenylborate and both the vaulted binaphthol (VANOL) and vaulted biphenanthrol (VAPOL) ligands. Catalysts derived from both ligands were equally effective in terms of asymmetric induction, but the VANOL catalyst was slightly faster. Up to 400 turnovers could be achieved with the VANOL catalyst while still maintainingor=90% ee in the aziridine product. The ligand could be recovered in 95% yield with no loss in optical purity. Excellent asymmetric inductions were observed with arylimines, and although slightly lower inductions were observed for alkyl-substituted imines, the optical purity of the aziridines from all of the imine substrates could be enhanced toor=99% ee with a single crystallization. Methods were developed for deprotection of the N-DAM-aziridines under acidic conditions without causing an acid-promoted opening of the ring. Excellent yields of the N-H-aziridines could be obtained with both alkyl- and aryl-substituted aziridines. Finally, activation of the N-H-aziridines was achieved with Boc, tosyl, and Fmoc groups. The activated aziridines can be converted to beta3-amino esters, and unexpectedly, the N-Boc-protected aziridine-2-carboxylate 16b with a phenyl substituent in the 3-position cis to the ester group was found to undergo ring expansion to a mixture of cis- and trans-oxazolidinones.
- Published
- 2007
41. ChemInform Abstract: Catalytic Asymmetric Synthesis of Alkynyl Aziridines: Both Enantiomers of cis-Aziridines from One Enantiomer of the Catalyst
- Author
-
Maria P. Lopez‐Alberca, Yijing Dai, William D. Wulff, Zhenjie Lu, Aniruddha P. Patwardhan, Mathew J. Vetticatt, Aman A. Desai, Yong Guan, and Yu Zhang
- Subjects
chemistry.chemical_compound ,chemistry ,Organocatalysis ,Aryl ,Imine ,Enantioselective synthesis ,Diazo ,General Medicine ,Enantiomer ,Medicinal chemistry ,Transition state ,Catalysis - Abstract
Alkynyl aziridines can be obtained from the catalytic asymmetric aziridination (AZ reaction) of alkynyl imines with diazo compounds in high yields and high asymmetric inductions mediated by a chiral boroxinate or BOROX catalyst. In contrast to the AZ reaction with aryl- and alkyl-substituted imines, alkynyl imines react to give cis-substituted aziridines with both diazo esters and diazo acetamides. Remarkably, however, the two diazo compounds give different enantiomers of the cis-aziridine from the same enantiomer of the catalyst. Theoretical considerations of the possible transition states for the enantiogenic step reveal that the switch in enantiomers results from a switch from Si-face to Re-face addition to the imine, which in turn is related to a switch from reaction with an E-imine in the former and a Z-isomer of the imine in the latter.
- Published
- 2015
42. Microwave-Assisted Synthesis of Co/CoOx Supported on Earth-Abundant Coal-Derived Carbon for Electrocatalysis of Oxygen Evolution.
- Author
-
Haoran Pan, Dongling Wu, Xinning Huang, Kunpeng Xie, Bingcai He, Zhenjie Lu, Penggao Liu, Junxia Cheng, Xuefei Zhao, Justus Masa, and Xingxing Chen
- Subjects
ELECTROCATALYSIS ,NITROGEN ,HYDROGEN evolution reactions ,HYDROGEN as fuel ,OXYGEN evolution reactions ,WATER currents ,DENSITY currents ,CARBON - Abstract
The evident demand for hydrogen as the ultimate energy fuel for posterity calls for the development of low-cost, efficient and stable electrocatalysts for water splitting. Herein, we report the synthesis of Co/CoO
x supported on coal-derived N-doped carbon via a simple microwave-assisted method and demonstrate its application as an efficient catalyst for the oxygen evolution reaction (OER). With the optimal amount of cobalt introduced into the N-doped coal-derived, the developed catalyst achieved overpotentials of 0.370 and 0.429 V during water oxidation at current densities of 1 mA cm-2 and 10 mA cm-2 , respectively. There was no noticeable loss in the activity of the catalyst during continuous galvanostatic polarization at a current density of 10 mA cm-2 for a test period of 66 h. The synergistic interaction of the Co/CoOx moieties with the pyridinic and pyrollic nitrogen functional groups in the N-doped carbon, as well with the other heteroatoms species in the pristine coal favored enhancement of the OER electrocatalytic performance. [ABSTRACT FROM AUTHOR]- Published
- 2019
- Full Text
- View/download PDF
43. ChemInform Abstract: Allenamides: A Powerful and Versatile Building Block in Organic Synthesis
- Author
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Zhenjie Lu, Zhi-Xiong Ma, Richard P. Hsung, Ting Lu, and Yu Zhang
- Subjects
Flexibility (engineering) ,chemistry.chemical_compound ,Intramolecular reaction ,Nucleophile ,chemistry ,Cyclopropanation ,Propargyl ,Electrophile ,Regioselectivity ,Organic synthesis ,General Medicine ,Combinatorial chemistry - Abstract
In the past four decades, allenes have progressively risen from an unenviable status of being a structural curiosity to becoming one of the most powerful and versatile synthetic building blocks in organic synthesis.1–3 Although the focal theme of this review is centered on chemistry of allenamides, a proper introduction would need to commence with allenamines. Allenamides are functionally derived from allenamines,4 which along with structurally related systems such as allenol ethers5 and allenyl sulfides,6 can be classified as heteroatom-substituted allenes. Allenamines have been known for more than forty years since the first documentation of their preparations and characterizations in 1968 by Viehe.7 It is noteworthy that Viehe was at the time developing a based-catalyzed isomerization of propargyl amines as a useful protocol for synthesizing ynamines (Scheme 1), which had just come onto the scene as a useful synthetic building block.8–10 Allenamines were postulated as an intermediate en route to ynamines in this prototropic isomerization that follows essentially the zipper-type mechanism. Open in a separate window Scheme 1 The π-donating ability of nitrogen atom renders allenamines more electron-rich than simple allenes, thereby predisposing them to electrophilic activations. An electronic bias can be exerted through delocalization of the nitrogen lone pair toward the allenic moiety as demonstrated in the resonance form of allenamines. Accordingly, highly regioselective transformations can be achieved with consecutive addition of electrophiles and nucleophiles (Scheme 2). In addition to aforementioned regiochemical control, allenamines also offer a number of other advantages over simple allenes. The trivalent nature of the nitrogen atom allows: (1) Tethering of a chirality-inducing unit for providing stereochemical induction; concomitantly with the inclusion of a coordinating unit to provide conformational rigidity; (2) a much greater flexibility in designing intramolecular reactions or tandem processes than with oxygen- or sulfur-substituted allenes; and last but not the least, (3) a novel entry to alkaloids if the nitrogen atom can be preserved throughout the entire transformative sequence. Moreover, intramolecular reaction manifolds as shown with a possible diastereoselective cyclopropanation reaction (Scheme 2) can greatly manifest these remarkable features, particularly the latter two. Therefore, while the chemistry of other heteroatom-substituted allenes is of high impact and value to organic synthesis, allenamines should prove to be more attractive for developing stereoselective methodologies as well as rapid assembly of structural complexity.1,2 Open in a separate window Scheme 2 Without illustrating any specifics here on allenamine chemistry given all the comprehensive reviews,1,2 elegant precedents adopting allenamines in a range of transformations have indeed been documented to further support their synthetic potential and provoke interest from the synthetic community. Unfortunately, further developments had been severely thwarted because allenamines are also highly sensitive toward hydrolysis with a tendency to polymerize even at low temperatures (Scheme 3), thereby creating serious difficulties in their preparation and experimental handling.1,2 Consequently, the great potential of chemistry of nitrogen-substituted allenes could only be partially realized. Therefore, efforts to identify an allenamine-equivalent should be of high significance if it can strike the right balance between stability and reactivity. Open in a separate window Scheme 3 Toward this end, allenamides should represent ideal candidates as a stable allenamine-equivalent. Delocalization of the nitrogen lone-pair into the electron-withdrawing amido group should diminish its donating ability toward the allenic moiety, thereby leading to improved stability (Scheme 4). In short, the very simple fact that allenamides can champion an extra resonance form speaks volume of its superior stability over allenamines. It could be a great story if allenamides were a result of some clever design in search for a stable allenamine-equivalent. However, this is not true and the story is much less dramatic. Allenamides have co-existed along side of allenamines for all of the last four plus decades after Dickinson's first preparation and concise characterizations of 1,2-propadienyl-2-pyrrolidinone in 1967 (Scheme 5).11 Open in a separate window Scheme 4 Open in a separate window Scheme 5 In fact, Dickinson coined the term “allenamide” to describe 1,2-propadienyl-2-pyrrolidinone based the analogy of using enamides17 for Stork’s N-acylated enamines. To clarify reports by Cho12 and others,13 Dickinson concisely demonstrated that treatment of 2-pyrrolidinone with NaH and propargyl bromide had indeed led to the allenamide as the major and stable product also via the same prototropic isomerization pathway. Intriguingly, unlike Viehe’s work, allenamide did not undergo further isomerization to the respective ynamide, although with further treatment of NaOMe and pyrrolidine, ynamide was postulated as an intermediate en route to the N-acyl-pyrrolidine product. Nevertheless, this documentation of ynamide actually predated Viehe’s 1972 account,14 and chemistry of ynamides has indeed generated an immense amount of interest from the synthetic community in the last 15 years.15,16 To align with the history, our foray into this field coincides with both of Viehe and Dickinson’s work. In search of a useful synthetic method to construct chiral ynamides 16 years ago,10 we found that based-catalyzed prototropic isomerization of propargyl amides reliably arrested at the allenic stage and gave none of the desired ynamides10 (Scheme 6) regardless of nature of the base used, temperature, and solvents (also see Schemes 24 and and2525 vide infra). More importantly, to properly acknowledge a critical person in our entire endeavor in allenamide chemistry, I owe everything to the very first postdoctoral research fellow in my group, Dr. Lin-Li Wei [Ph.D. with Professor Teck-Peng Loh at National University of Singapore]. Dr. Wei, who was working on these isomerizations, pointed out that these allenamides that she had obtained could prove to be an excellent allenamine-equivalent, and evolve into highly versatile synthetic building blocks in organic synthesis. Open in a separate window Scheme 6 Open in a separate window Scheme 24 Open in a separate window Scheme 25 Given the precedent, the ease of preparation, and stability, the most critical question would be whether these allenamides could possess sufficient reactivity. A survey of the literature indicates that although it was far from a blank page, allenamides have been much less explored relative to allenamines.4,18–20 Precise reasons are not very clear, but there were very few citations on synthesis and applications of allenamides before 1989. While few more reports appeared from late 1980’s to mid-1990’s, the real outburst in chemistry of allenamides came 16 years ago, just as we also became deeply involved in the development of allenamide chemistry. Such sustained emergence strongly suggests that allenamides have set the gold standard for balancing reactivity and stability. They are becoming proven allenamine-equivalents that can be employed in a diverse array of stereoselective and intramolecular reactions that were not possible with traditional allenamines. They represent the ideal platform for pushing the limit of synthetic potential of nitrogen-substituted allenes. It is the purpose of this review to provide proper illustrations of the elegant chemistry involving allenamides that has come to pass, thereby eliciting a greater amount of interests from the synthetic community to create new allenamide chemistry. Lastly, this perspective that advancement of any field requires collective creativity and innovation from many people and not just a few individuals rings hollow here. On that note, although we are trying our very best to be comprehensive, it is likely that we have inadvertently missed some beautiful work for which we express our regret here in advance.
- Published
- 2013
44. Allenamides: a powerful and versatile building block in organic synthesis
- Author
-
Ting Lu, Zhenjie Lu, Zhi-Xiong Ma, Yu Zhang, and Richard P. Hsung
- Subjects
Flexibility (engineering) ,Intramolecular reaction ,Alkylation ,Cycloaddition Reaction ,Chemistry ,Cyclopropanation ,Stereochemistry ,Regioselectivity ,General Chemistry ,Combinatorial chemistry ,Amides ,Catalysis ,Article ,Alkadienes ,chemistry.chemical_compound ,Nucleophile ,Cyclization ,Metals ,Electrophile ,Propargyl ,Organic synthesis ,Amination - Abstract
In the past four decades, allenes have progressively risen from an unenviable status of being a structural curiosity to becoming one of the most powerful and versatile synthetic building blocks in organic synthesis.1–3 Although the focal theme of this review is centered on chemistry of allenamides, a proper introduction would need to commence with allenamines. Allenamides are functionally derived from allenamines,4 which along with structurally related systems such as allenol ethers5 and allenyl sulfides,6 can be classified as heteroatom-substituted allenes. Allenamines have been known for more than forty years since the first documentation of their preparations and characterizations in 1968 by Viehe.7 It is noteworthy that Viehe was at the time developing a based-catalyzed isomerization of propargyl amines as a useful protocol for synthesizing ynamines (Scheme 1), which had just come onto the scene as a useful synthetic building block.8–10 Allenamines were postulated as an intermediate en route to ynamines in this prototropic isomerization that follows essentially the zipper-type mechanism. Open in a separate window Scheme 1 The π-donating ability of nitrogen atom renders allenamines more electron-rich than simple allenes, thereby predisposing them to electrophilic activations. An electronic bias can be exerted through delocalization of the nitrogen lone pair toward the allenic moiety as demonstrated in the resonance form of allenamines. Accordingly, highly regioselective transformations can be achieved with consecutive addition of electrophiles and nucleophiles (Scheme 2). In addition to aforementioned regiochemical control, allenamines also offer a number of other advantages over simple allenes. The trivalent nature of the nitrogen atom allows: (1) Tethering of a chirality-inducing unit for providing stereochemical induction; concomitantly with the inclusion of a coordinating unit to provide conformational rigidity; (2) a much greater flexibility in designing intramolecular reactions or tandem processes than with oxygen- or sulfur-substituted allenes; and last but not the least, (3) a novel entry to alkaloids if the nitrogen atom can be preserved throughout the entire transformative sequence. Moreover, intramolecular reaction manifolds as shown with a possible diastereoselective cyclopropanation reaction (Scheme 2) can greatly manifest these remarkable features, particularly the latter two. Therefore, while the chemistry of other heteroatom-substituted allenes is of high impact and value to organic synthesis, allenamines should prove to be more attractive for developing stereoselective methodologies as well as rapid assembly of structural complexity.1,2 Open in a separate window Scheme 2 Without illustrating any specifics here on allenamine chemistry given all the comprehensive reviews,1,2 elegant precedents adopting allenamines in a range of transformations have indeed been documented to further support their synthetic potential and provoke interest from the synthetic community. Unfortunately, further developments had been severely thwarted because allenamines are also highly sensitive toward hydrolysis with a tendency to polymerize even at low temperatures (Scheme 3), thereby creating serious difficulties in their preparation and experimental handling.1,2 Consequently, the great potential of chemistry of nitrogen-substituted allenes could only be partially realized. Therefore, efforts to identify an allenamine-equivalent should be of high significance if it can strike the right balance between stability and reactivity. Open in a separate window Scheme 3 Toward this end, allenamides should represent ideal candidates as a stable allenamine-equivalent. Delocalization of the nitrogen lone-pair into the electron-withdrawing amido group should diminish its donating ability toward the allenic moiety, thereby leading to improved stability (Scheme 4). In short, the very simple fact that allenamides can champion an extra resonance form speaks volume of its superior stability over allenamines. It could be a great story if allenamides were a result of some clever design in search for a stable allenamine-equivalent. However, this is not true and the story is much less dramatic. Allenamides have co-existed along side of allenamines for all of the last four plus decades after Dickinson's first preparation and concise characterizations of 1,2-propadienyl-2-pyrrolidinone in 1967 (Scheme 5).11 Open in a separate window Scheme 4 Open in a separate window Scheme 5 In fact, Dickinson coined the term “allenamide” to describe 1,2-propadienyl-2-pyrrolidinone based the analogy of using enamides17 for Stork’s N-acylated enamines. To clarify reports by Cho12 and others,13 Dickinson concisely demonstrated that treatment of 2-pyrrolidinone with NaH and propargyl bromide had indeed led to the allenamide as the major and stable product also via the same prototropic isomerization pathway. Intriguingly, unlike Viehe’s work, allenamide did not undergo further isomerization to the respective ynamide, although with further treatment of NaOMe and pyrrolidine, ynamide was postulated as an intermediate en route to the N-acyl-pyrrolidine product. Nevertheless, this documentation of ynamide actually predated Viehe’s 1972 account,14 and chemistry of ynamides has indeed generated an immense amount of interest from the synthetic community in the last 15 years.15,16 To align with the history, our foray into this field coincides with both of Viehe and Dickinson’s work. In search of a useful synthetic method to construct chiral ynamides 16 years ago,10 we found that based-catalyzed prototropic isomerization of propargyl amides reliably arrested at the allenic stage and gave none of the desired ynamides10 (Scheme 6) regardless of nature of the base used, temperature, and solvents (also see Schemes 24 and and2525 vide infra). More importantly, to properly acknowledge a critical person in our entire endeavor in allenamide chemistry, I owe everything to the very first postdoctoral research fellow in my group, Dr. Lin-Li Wei [Ph.D. with Professor Teck-Peng Loh at National University of Singapore]. Dr. Wei, who was working on these isomerizations, pointed out that these allenamides that she had obtained could prove to be an excellent allenamine-equivalent, and evolve into highly versatile synthetic building blocks in organic synthesis. Open in a separate window Scheme 6 Open in a separate window Scheme 24 Open in a separate window Scheme 25 Given the precedent, the ease of preparation, and stability, the most critical question would be whether these allenamides could possess sufficient reactivity. A survey of the literature indicates that although it was far from a blank page, allenamides have been much less explored relative to allenamines.4,18–20 Precise reasons are not very clear, but there were very few citations on synthesis and applications of allenamides before 1989. While few more reports appeared from late 1980’s to mid-1990’s, the real outburst in chemistry of allenamides came 16 years ago, just as we also became deeply involved in the development of allenamide chemistry. Such sustained emergence strongly suggests that allenamides have set the gold standard for balancing reactivity and stability. They are becoming proven allenamine-equivalents that can be employed in a diverse array of stereoselective and intramolecular reactions that were not possible with traditional allenamines. They represent the ideal platform for pushing the limit of synthetic potential of nitrogen-substituted allenes. It is the purpose of this review to provide proper illustrations of the elegant chemistry involving allenamides that has come to pass, thereby eliciting a greater amount of interests from the synthetic community to create new allenamide chemistry. Lastly, this perspective that advancement of any field requires collective creativity and innovation from many people and not just a few individuals rings hollow here. On that note, although we are trying our very best to be comprehensive, it is likely that we have inadvertently missed some beautiful work for which we express our regret here in advance.
- Published
- 2013
45. Co-Mn Hybrid Oxides Supported on N-Doped Graphene as ad Efficient Electrocatalysts for Reversible Oxygen Electrodes.
- Author
-
Zhenjie Lu, Xingxing Chen, Penggao Liu, Xinning Huang, Jiong Wei, Zhong Ren, Songdong Yao, Zhigang Fanga, Tao Wanga, and Justus Masas
- Subjects
GRAPHENE ,ELECTROCATALYSTS ,ELECTRODES - Abstract
Despite metal-air batteries possessing very high theoretical energy densities, inefficient reversibility of the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) at the oxygen electrode undermines their rechargeability, which has slowed their market entry. Herein, we demonstrate a simple procedure for synthesis of a hybrid of MnO and metallic Co supported on N-doped graphene that exhibits activity and stability as a bifunctional ORR/OER catalyst, with a round trip ORR/OER overvoltage of 0.85 V, which remained constant for at least 70 h when cycling alternately, between oxygen evolution at a current density of 10 mA cm
-2 and oxygen reduction at-1 mA cm-2 . Insights into the key properties of the catalyst that influence its performance are proposed based on structural characterization by TEM, SEM, Raman spectroscopy, XRD and XPS. Besides MnO and metallic Co as the predominant crystalline species in the Co-Mn hybrid oxide, XPS revealed Mn3 O4 and CoO rich surfaces, ascribed to oxidation of MnO and metallic Co due to atmospheric exposure. The synergetic interaction between the Co-Mn hybrid oxides and N-doped graphene, as well as Co-Mn interaction, favor improved ORR, OER and bifunctional ORR/OER performance of the catalyst. [ABSTRACT FROM AUTHOR]- Published
- 2018
- Full Text
- View/download PDF
46. ChemInform Abstract: Seeking Passe-Partout in the Catalytic Asymmetric Aziridination of Imines: Evolving Toward Substrate Generality for a Single Chemzyme
- Author
-
Munmun Mukherjee, Anil K. Gupta, Zhenjie Lu, William D. Wulff, and Yu Zhang
- Subjects
Generality ,Chemistry ,Stereochemistry ,Yield (chemistry) ,Substrate (chemistry) ,General Medicine ,Catalysis - Abstract
Best results (yield and enantioselectivity) are obtained with imines bearing a tetramethyldianisylmethyl group (MAM).
- Published
- 2010
47. ChemInform Abstract: Ynamides: A Modern Functional Group for the New Millennium
- Author
-
Ryuji Hayashi, Andrew G. Lohse, Yu Zhang, Hongyan Li, Richard P. Hsung, Zhenjie Lu, and Kyle A. De Korver
- Subjects
Cognitive science ,chemistry.chemical_compound ,Chemistry ,Functional group ,General Medicine - Published
- 2010
48. Thrombospondin 1—a key astrocyte-derived neurogenic factor
- Author
-
Jonathan Kipnis and Zhenjie Lu
- Subjects
Cellular differentiation ,Neurogenesis ,Blotting, Western ,Synaptogenesis ,Fluorescent Antibody Technique ,Biology ,Biochemistry ,Research Communications ,Immunoenzyme Techniques ,Thrombospondin 1 ,Mice ,Genetics ,medicine ,Animals ,RNA, Messenger ,Thrombospondins ,Molecular Biology ,Cells, Cultured ,Cell Proliferation ,Mice, Knockout ,Neurons ,Reverse Transcriptase Polymerase Chain Reaction ,Stem Cells ,Cell Differentiation ,Anatomy ,Flow Cytometry ,Neural stem cell ,Cell biology ,Mice, Inbred C57BL ,medicine.anatomical_structure ,Bromodeoxyuridine ,Astrocytes ,Culture Media, Conditioned ,Stem cell ,Biotechnology ,Astrocyte - Abstract
Thrombospondin 1 (TSP1), an oligomeric matrix protein, is known for its antiangiogenic activity. Recently, TSP1 has been shown to regulate synaptogenesis in the developing brain. In this study, we examine another role of TSP1 in the CNS, namely, in proliferation and differentiation of neural progenitor cells (NPCs). We found that adult mice deficient in TSP1 exhibit reduced proliferation of NPCs in vivo [13,330±826 vs. 4914±455 (mean±se wt vs. TSP1−/−); P
- Published
- 2010
49. ChemInform Abstract: Catalytic Asymmetric Aziridination with Catalysts Derived from VAPOL and VANOL
- Author
-
Yu Zhang, Zhenjie Lu, and William D. Wulff
- Subjects
chemistry.chemical_compound ,chemistry ,Ethyl diazoacetate ,VANOL ligand ,Enantioselective synthesis ,Substituent ,Diazo ,General Medicine ,Combinatorial chemistry ,Catalysis - Abstract
This Account describes the discovery and development of the catalytic asymmetric aziridination reaction (AZ reaction) that has been the subject of efforts in our laboratory over the last 12 years. The optimized catalyst system involves catalysts generated from either the VAPOL or VANOL ligand and triphenyl borate. These catalysts are effective for formation of aziridines from the reaction of imines that bear a N-benzhydryl substituent with stabi- lized diazo compounds including the commercially available ethyl diazoacetate (EDA). The reaction is general for N-benzhydryl im- ines prepared from electron-rich and electron-poor aromatic alde- hydes, as well as from primary, secondary and tertiary aliphatic aldehydes. This reaction is highly enantioselective and diastereo- selective giving cis-3-substituted aziridine-2-carboxylates in excel- lent yields. This Account presents the scope of the AZ reaction as defined by the work that has been done in our laboratory up to the present time, as well as applications of the resulting aziridines that have been demonstrated to date.
- Published
- 2010
50. Mapping the active site in a chemzyme: diversity in the N-substituent in the catalytic asymmetric aziridination of imines
- Author
-
Zhenjie Lu, William D. Wulff, Aman A. Desai, and Yu Zhang
- Subjects
chemistry.chemical_classification ,biology ,Stereochemistry ,VAPOL ligand ,Nitrogen ,Aryl ,Organic Chemistry ,Imine ,Aziridines ,Substituent ,Molecular Conformation ,Active site ,Electrons ,Naphthalenes ,Biochemistry ,Catalysis ,Article ,chemistry.chemical_compound ,chemistry ,Catalytic Domain ,biology.protein ,Imines ,Physical and Theoretical Chemistry ,Alkyl - Abstract
The active site of the aziridination catalyst derived from either the VANOL or VAPOL ligand and B(OPh)(3) is larger than expected and can accommodate not only significant substitution on the diarylmethyl unit of the imine but also that alkyl (but not perfluorylalkyl) substituents on the aryl groups lead to enhanced rates and enantioselection. The screen of diarylmethyl N-substituents on the imine revealed that the 3,5-di-tert-butyldianisylmethyl group (BUDAM) gave exceptionally high asymmetric inductions for imines of aryl aldehydes.
- Published
- 2008
Catalog
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