检索结果-南通市图书馆

Chiral N-triflylphosphoramide-catalyzed asymmetric hydroamination of unactivated alkenes: a hetero-ene reaction mechanism

在线全文

学校读者我要写书评

暂无评论

Organic Chemistry Frontiers 2022年第6期9卷 1649-1661页

作者： Na Wang Li-Wen Fan Jin Zhang qiang-Shuai gu Jin-Shun Lin guo-qiang Chen Xin-Yuan Liu Peiyuan Yu College of Chemistry and Environmental Engineering Shenzhen UniversityShenzhen 518071China College of Physics and Optoelectronic Engineering Shenzhen UniversityShenzhen 518060China Department of Chemistry and Shenzhen Grubbs Institute Guangdong Provincial Key Laboratory of CatalysisSouthern University of Science and TechnologyShenzhen 518055China Academy for Advanced Interdisciplinary Studies and Department of Chemistry Southern University of Science and TechnologyShenzhen 518055China

A highly enantioselective intramolecular hydroamination reaction catalyzed by chiralN-triflylphosphoramide (NTPA) that features an exceptionally broad substrate scope of isolated unactivated alkenes was recently reported by some of us. Herein we report a detailed density functional theory(DFT) study that unveil an uncommon hetero-ene reaction mechanism for this transformation. The reaction changes from a stepwise mechanism involving discrete tertiary carbocation formation to a concertedmechanism to avoid the generation of energetically unfavorable secondary carbocation species for distinctly substituted alkene substrates. The reactivity of this reaction is primarily affected by the substituentson the internal carbon of the alkene, with the carbocation-stabilizing ones promoting the reaction. Inaddition, the reaction is also influenced by the substituents on the terminal alkene carbons: those diminishing the innate alkene polarization of the starting alkenes retard the reaction by disfavoring the formation of related transition states featuring highly polarized alkene residues. The steric effect of all thesealkene substituents was found to be largely unimportant due to the unique arrangement of the heteroene reaction complex that keeps the reacting alkene away from the sterically congested core region ofthe catalyst pocket. The lower acidity of chiral phosphoric acids than that of chiral NTPAs renders the protonated precomplex along the hetero-ene reaction pathway greatly thermodynamically disfavored. Thisindirectly results in a greater relative distortion in the corresponding transition state, which in turn causesreaction retardation. Our results demonstrate the use of intramolecular pericyclic reactions as an alternative strategy for alkene activation by chiral Brønsted acid catalysis and provide insights into the furtherdevelopment of asymmetric hydrofunctionalization of unactivated alkenes.

关键词： mechanism substituent asymmetric

Phase-Modulated 2D Topological Physics in a One-Dimensional Ultracold System

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Physics Letters 2021年第4期38卷 7-11页

作者： Gang-Feng guo Xi-Xi Bao Lei Tan Huai-qiang gu Institute of Theoretical Physics Lanzhou UniversityLanzhou 730000China School of Nuclear Science and Technology Lanzhou UniversityLanzhou 730000China

We propose a one-dimensional optical lattice model to simulate and explore two-dimensional topological phases with ultracold atoms,considering the phases of the hopping strengths as an extra *** is shown that the model exhibits nontrivial phases,and corresponding two chiral-edge ***,we demonstrate the connections between changes in the topological invariants and the Dirac ***,the topological order detected by the particle pumping approach in cold atoms is also *** results obtained here provide a feasible and flexible method of simulating and exploring high-dimensional topological phases in lowdimension systems via the controllable phase of the hopping strength.

关键词： dimension. strength. topological

Preparation of high-efficiency ceramic planar membrane and its application for water desalination

在线全文

学校读者我要写书评

暂无评论

Journal of Advanced Ceramics 2018年第2期7卷 117-123页

作者： Shan TAO Yan-Dong XU Jian-qiang gu Hamidreza ABADIKHAH Jun-Wei WANG Xin XU Sinopec Northwest Oilfield Branch Research Institute of Petroleum Engineering CAS Key Laboratory of Materials for Energy Conversion Department of Materials Science and EngineeringUniversity of Science and Technology of China

Highly efficient Si3N4 ceramic planar membrane for water desalination process using membrane distillation was prepared by the dual-layer phase inversion tape casting and sintering method. In comparison with typical phase inversion tape casting method, the green tape was formed using Si3N4 slurry on the top and graphite slurry on the bottom. After consuming away the graphite structure, a ceramic membrane consisting of a two-layered structure （skin and finger-like layers） was obtained. The skin layer was relatively tight, and thus could act as a functional layer for separation, while the finger-like layer contained straight open pores with a diameter of 100 gm, acting as a support with low transport resistance. For comparison, typical Si3N4 ceramic membrane was fabricated by phase inversion technique without graphite substrate, resulting in a three-layered structure （skin, finger-like, and sponge layers）. After membrane modification from hydrophilic to hydrophobic with polymer derived nanoparticle method, the water desalination performance of the membranes was tested using the sweeping gas membrane distillation （SGMD） with different NaC1 feed solutions. With the increase of salt content from 4 to 12 wt%, the water flux decreased slightly while rejection rate maintained over 99.99%. Comparing with typical three-layered Si3N4 membrane, an excellent water flux enhancement of over 83% was resulted and the rejection rate remained over 99.99%.

关键词： dual-layer phase inversion tape casting graphite full-inorganic hydrophobic membrane membrane distillation

Microwave-assisted Catalyzed Synthesis and In vitro Bioactivity Evaluation of Benzimidazoles Bearing Phenolic Hydroxyl

在线全文

学校读者我要写书评

暂无评论

Chemical Research in Chinese Universities 2021年第3期37卷 639-646页

作者： YAN Liuqing FU Jiaxu LI Shuang ZHANG Jinlong WANG Shuang gu qiang ZHANG Yumin LIN Feng College of Chemistry Jilin UniversityChangchun130012P.R.China School of life Sciences Jilin UniversityChangchun130012P.R.China

An efficient and facile method was introduced for the synthesis of benzimidazoles in this *** optimum reaction conditions were determined.A series of benzimidazoles bearing phenolic hydroxyl(2a—2t)were synthesized in moderate to excellent yields starting from differently substituted hydroxyl benzaldehyde and 4-position substituted o-phenylenediamine via nu-cleophilic addition in the presence of catalyst Na2S2O5 under microwave irradiation ***,effects of the catalyst,molar ratio of reactants,reaction temperature and solvent were *** optimal reaction condition was *** effect of DMF and EtOH solvent on the reaction was *** synthesized compounds were characterized by FTIR,HRMS,1H NMR and 13C NMR ***,the bacteriostatic activities of the synthesized compounds were evaluated with ciprofloxacin and itraconazole as a positive control,*** 2b,2n,2q and 2r exhibited some antibacterial *** lowest MIC of antibacterial activity of compound 2b was 32µg/***,the luminescence property of compound 2b was *** antibacterial activity of compound 2b,along with their good fluorescence performance highlighted the potential of these compounds as lead structures and owned fluorescence trace for further study towards the development of novel drugs and functional mechanisms in living organisms.

关键词： Benzimidazole Microwave irradiation Solvent effect Antimicrobial activity Luminescence property

Design of a 162.5 MHz continuous-wave normal-conducting radiofrequency electron gun

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Nuclear Science and Techniques 2020年第11期31卷 50-59页

作者： Cheng Wang Zi-Han Zhu Zeng-Gong Jiang Qi-Sheng Tang Zhen-Tang Zhao qiang gu Shanghai Institute of Applied Physics Chinese Academy of SciencesShanghai 201800China University of Chinese Academy of Sciences Beijing 100049China Shanghai Advanced Research Institute Chinese Academy of SciencesShanghai 201210China

A high-gradient radiofrequency(RF)gun operated in continuous-wave(CW)mode is required in various accelerating *** to the high RF power loss,a traditional normal-conducting(NC)RF electron gun has difficulty meeting the requirement of generating a high-repetition-rate electron *** development of a scheme for a CW NC-RF gun is urgently *** as a photoinjector of a high-repetition-rate free-electron laser(FEL),an electron gun operated in CW mode and the VHF band is *** analysis of the reentrant gun cavity is presented in this paper to increase the gradient and decrease the power density and power *** to the analysis results,the design of a162.5 MHz gun cavity is optimized by a multi-objective evolutionary algorithm to achieve better performance in CW *** and thermal analyses are also deliberated in the design to coordinate with RF and mechanical *** optimized 162.5 MHz gun cavity can be operated in CW mode to generate a high-repetition-rate beam with voltage up to 1 MV and gradient up to 32.75 MV/m at the cathode.

关键词： High-repetition-rate beam Radiofrequency gun Continuous-wave mode Multi-objective evolutionary algorithm

Research Progress in Enantioselective Radical Desymmetrization Reactions

在线全文

学校读者我要写书评

暂无评论

CCS Chemistry 2024年第7期6卷 1612-1627页

作者： Chang-Jiang Yang Lin Liu qiang-Shuai gu Xin-Yuan Liu Department of Chemistry and Dongguan Key Laboratory for Data Science and Intelligent Medicine Great Bay UniversityDongguan 523000 Shenzhen Grubbs Institute Department of Chemistryand Guangming Advanced Research InstituteSouthern University of Science and TechnologyShenzhen 518055 Academy for Advanced Interdisciplinary Studies and Department of Chemistry Southern University of Science and TechnologyShenzhen 518055

Enantioselective radical desymmetrization is a highly effective approach for rapidly creating enantioenriched molecules,introducing dramatically increased structural complexity from readily available prochiral or meso compound *** strategic modes have been developed for these reactions,which differ in the nature of the stereo-determining *** first category deals primarily with the stereoselective desymmetrization of closed-shell radical precursors or functional reagents,whereas the second category achieves desymmetrization by stereoselectively functionalizing open-shell radical *** mini-review explores the research progress in this growing field,aiming to elucidate mechanistic scenarios related to stereochemical ***,it offers insights into the challenges and opportunities that lie ahead for further development.

关键词： radical desymmetrization enantioselective desymmetrization radical functionalization transition metal catalysis asymmetric catalysis

Anti-deSitter时空内柱黑洞的量子熵

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

物理学报 2006年第2期55卷 995-998页

作者：李固强湛江师范学院信息科技学院广东湛江524048

利用brick-wall方法计算了Anti-de Sitter时空内起源于Dirac场的柱黑洞的量子熵.结果表明,忽略远离围绕系统的真空的贡献时,量子熵包含了线性发散项和对数发散项,整个表达式的形式与标量场的不一样.无论整个对数项还是与自旋联系的子对... 详细信息

利用brick-wall方法计算了Anti-de Sitter时空内起源于Dirac场的柱黑洞的量子熵.结果表明,忽略远离围绕系统的真空的贡献时,量子熵包含了线性发散项和对数发散项,整个表达式的形式与标量场的不一样.无论整个对数项还是与自旋联系的子对数项都总是正的.

关键词： brick-wall方法量子熵柱黑洞 Dimc场

Kerr-Newman-de Sitter黑洞的统计熵

在线全文

学校读者我要写书评

暂无评论

物理学报 2005年第7期54卷 3005-3008页

作者：李固强湛江师范学院信息科技学院广东湛江524048

避开求解波动方程的困难,利用量子统计的方法,直接计算Kerr Newman deSitter黑洞背景下玻色场和费米场的配分函数.然后利用砖墙膜模型计算和讨论黑洞背景下的玻色场和费米场的熵.

关键词：黑洞统计熵波动方程量子统计直接计算模型计算配分函数费米场玻色场

Synthesis of Highly Sensitive Fluorescent Probe Based on Tetrasubstituted Imidazole and Its Application for Selective Detection of Ag^＋ Ion in Aqueous Media

在线全文

学校读者我要写书评

暂无评论

Chemical Research in Chinese Universities 2018年第3期34卷 369-374页

作者： MI Zhiming CHEN Yao CHEN Xiaodong YAN Liuqing gu qiang ZHANG Hanqi CHEN Chunhai ZHANG Yumin College of Chemistry Jilin University Changchun 130012 P. R. China

A small molecule fluorescent probe, 4-[2-（4-chlorophenyl）-4,5-diphenyl- 1H-imidazol- 1-yl]aniline（L） for detecting Ag^＋ ion was gently synthesized via one-pot multi-component reaction catalyzed by H3[PW12O40] under solvent-free microwave irradiation. When the concentration of Ag＋ ion changed from 0 to 8.0 × 10^-6 mol/L in the solution of H2O/CH3OH（19：1, volume ratio）, the fluorescence emission spectrum was blue-shifted and accompanied by a gradual increase in fluorescence intensity with a low detection limit of 3.0× 10^-11 mol/L. Moreover, UV-Vis absorption titration experiment demonstrated a 1：1 stoichiometric ratio and an association constant of （9.95±0.44）×10^5 L/mol between probe L and Ag^＋ ion, and thus their complexation mechanism was also proposed and verified. More importantly, this fluorescent probe was remarkably specific for Ag^＋ ion under the interference of other metal ions and exhibited a wide pH application range of 4.0-8.0. Additionally, preliminary application of this probe was also carried out and satisfactory results were shown.

关键词： Fluorescent probe Imidazole Ag^+ ion Microwave irradiation