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A comparative study on kinetics and dynamics of two dump truck lifting mechanisms using MATLAB simscape
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作者 Thong Duc Hong Minh Quang Pham +2 位作者 Son Cong Tran Lam Quang Tran Truong Thanh Nguyen 《Theoretical & Applied Mechanics Letters》 CAS CSCD 2024年第2期146-156,共11页
In this paper,two lifting mechanism models with opposing placements,which use the same hydraulic hoist model and have the same angle of 50°,have been developed.The mechanical and hydraulic simulation models are e... In this paper,two lifting mechanism models with opposing placements,which use the same hydraulic hoist model and have the same angle of 50°,have been developed.The mechanical and hydraulic simulation models are established using MATLAB Simscape to analyze their kinetics and dynamics in the lifting and holding stages.The simulation findings are compared to the analytical calculation results in the steady state,and both methods show good agreement.In the early lifting stage,Model 1 produces greater force and discharges goods in the container faster than Model 2.Meanwhile,Model 2 reaches a higher force and ejects goods from the container cleaner than its counterpart at the end lifting stage.The established simulation models can consider the effects of dynamic loads due to inertial moments and forces generated during the system operation.It is crucial in studying,designing,and optimizing the structure of hydraulic-mechanical systems. 展开更多
关键词 Dump truck Lifting mechanism HYDRAULIC MATLAB Simscape Kinetic dynamic analysis
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Atomistic simulations of graphene origami:Dynamics and kinetics
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作者 张盼盼 贾海洪 +1 位作者 张艳芳 杜世萱 《Chinese Physics B》 SCIE EI CAS CSCD 2023年第8期79-85,共7页
Origami offers two-dimensional(2D)materials with great potential for applications in flexible electronics,sensors,and smart devices.However,the dynamic process,which is crucial to construct origami,is too fast to be c... Origami offers two-dimensional(2D)materials with great potential for applications in flexible electronics,sensors,and smart devices.However,the dynamic process,which is crucial to construct origami,is too fast to be characterized by using state-of-the-art experimental techniques.Here,to understand the dynamics and kinetics at the atomic level,we explore the edge effects,structural and energy evolution during the origami process of an elliptical graphene nano-island(GNI)on a highly ordered pyrolytic graphite(HOPG)substrate by employing steered molecular dynamics simulations.The results reveal that a sharper armchair edge is much easier to be lifted up and realize origami than a blunt zigzag edge.The potential energy of the GNI increases at the lifting-up stage,reaches the maximum at the beginning of the bending stage,decreases with the formation of van der Waals overlap,and finally reaches an energy minimum at a half-folded configuration.The unfolding barriers of elliptical GNIs with different lengths of major axis show that the major axis should be larger than 242 A to achieve a stable single-folded structure at room temperature.These findings pave the way for pursuing other 2D material origami and preparing origami-based nanodevices. 展开更多
关键词 origami process dynamics and kinetics structure and energy evolution stability of single-folded structure
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Hot-deformation kinetics analysis and extrusion parameter optimization of a dilute rare-earth free magnesium alloy
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作者 Qinghang Wang Haowei Zhai +5 位作者 Zhaoyang Jin Junjie He Qin Yang Wenjun Liu Yulong Li Daolun Chen 《Journal of Magnesium and Alloys》 SCIE EI CAS CSCD 2023年第9期3302-3322,共21页
The fundamental research on thermo-mechanical conditions provides an experimental basis for high-performance Mg-Al-Ca-Mn alloys.However, there is a lack of systematical investigation for this series alloys on the hot-... The fundamental research on thermo-mechanical conditions provides an experimental basis for high-performance Mg-Al-Ca-Mn alloys.However, there is a lack of systematical investigation for this series alloys on the hot-deformation kinetics and extrusion parameter optimization. Here, the flow behavior, constitutive model, dynamic recrystallization(DRX) kinetic model and processing map of a dilute rare-earth free Mg-1.3Al-0.4Ca-0.4Mn(AXM100, wt.%) alloy were studied under different hot-compressive conditions. In addition, the extrusion parameter optimization of this alloy was performed based on the hot-processing map. The results showed that the conventional Arrhenius-type strain-related constitutive model only worked well for the flow curves at high temperatures and low strain rates. In comparison, using the machine learning assisted model(support vector regression, SVR) could effectively improve the accuracy between the predicted and experimental values. The DRX kinetic model was established, and a typical necklace-shaped structure preferentially occurred at the original grain boundaries and the second phases. The DRX nucleation weakened the texture intensity, and the further growth caused the more scattered basal texture. The hot-processing maps at different strains were also measured and the optimal hot-processing range could be confirmed at the deformation temperatures of 600~723 K and the strain rates of 0.018~0.563 s^(-1). Based on the optimum hot-processing range, a suitable extrusion parameter was considered as 603 K and 0.1 mm/s and the as-extruded alloy in this parameter exhibited a good strength-ductility synergy(yield strength of ~ 232.1 MPa, ultimate strength of ~ 278.2 MPa and elongation-to-failure of ~ 20.1%). Finally, the strengthening-plasticizing mechanisms and the relationships between the DRXed grain size, yield strength and extrusion parameters were analyzed. 展开更多
关键词 Mg-Al-Ca-Mn alloy Constitutive model Dynamic recrystallization kinetic model Extrusion parameter optimization Strengthening-plasticizing mechanisms
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Hot deformation behavior and dynamic recrystallization kinetics of AZ61 and AZ61+Sr magnesium alloys 被引量:8
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作者 S.Aliakbari Sani G.R.Ebrahimi A.R.Kiani Rashid 《Journal of Magnesium and Alloys》 SCIE EI CAS 2016年第2期104-114,共11页
In this study,the effect of strontium addition on hot deformation of AZ61 alloy was investigated by hot compression tests.A reference alloy(AZ61)and an Sr-containing alloy(AZ61+Sr)was cast while their average initial ... In this study,the effect of strontium addition on hot deformation of AZ61 alloy was investigated by hot compression tests.A reference alloy(AZ61)and an Sr-containing alloy(AZ61+Sr)was cast while their average initial grain size were supposed to be about 140 and 40μm,respectively.In AZ61+Sr alloy,the Sr-containing precipitations were stable at homogenization temperature.Analysing the hot compression curves,it was revealed that dynamic recrystallization phenomenon had occurred and controlled the thermomechanical behaviour of the alloys.The derived constitutive equations showed that the hot deformation parameters(n and Q)in AZ61+Sr alloy is smaller than those of AZ61 alloy;this can be related to the small initial grain size and the lower amounts of solute aluminium atoms.The analysis of DRX kinetics along with the micrographs of the deformed microstructures showed that at the same condition the development of DRXed microstructure in AZ61+Sr alloy was faster than AZ61 alloy.The increased recrystallized microstructure was interpretated to be attributed to(1)the more grain boundaries present and(2)the existance of the Al-Mg-Sr precipitations assisted the PSN mechanism.Also,the attenuated intensity of the basal texture of AZ61+Sr was related to the DRX fraction of microstructure. 展开更多
关键词 AZ61 alloy STRONTIUM DRX Grain size PSN Dynamic recrystallization kinetics
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Dynamic recrystallization behavior and kinetics of high strength steel 被引量:1
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作者 吴光亮 周超洋 刘新彬 《Journal of Central South University》 SCIE EI CAS CSCD 2016年第5期1007-1014,共8页
The dynamic recrystallization behavior of high strength steel during hot deformation was investigated.The hot compression test was conducted in the temperature range of 950-1150 °C under strain rates of 0.1,1 and... The dynamic recrystallization behavior of high strength steel during hot deformation was investigated.The hot compression test was conducted in the temperature range of 950-1150 °C under strain rates of 0.1,1 and 5 s-1.It is observed that dynamic recrystallization(DRX) is the main flow softening mechanism and the flow stress increases with decreasing temperature and increasing strain rate.The relationship between material constants(Q,n,α and ln A) and strain is identified by the sixth order polynomial fit.The constitutive model is developed to predict the flow stress of the material incorporating the strain softening effect and verified.Moreover,the critical characteristics of DRX are extracted from the stress-strain curves under different deformation conditions by linear regression.The dynamic recrystallization volume fraction decreases with increasing strain rate at a constant temperature or decreasing deformation temperature under a constant strain rate.The kinetics of DRX increases with increasing deformation temperature or strain rate. 展开更多
关键词 flow stress dynamic recrystallization kinetics high strength steel constitutive model material constants
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Dynamic Kinetics of Methanol Synthesis over a Commercial Copper-Based Catalyst
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作者 陈晓春 李成岳 饶国瑛 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2000年第4期315-320,共6页
Adsorption, surface reaction and process dynamics on the surface of a commercial copper-based catalyst for methanol synthesis from CO/CO2/H2 were systematically studied by means of temperature programmed desorption (T... Adsorption, surface reaction and process dynamics on the surface of a commercial copper-based catalyst for methanol synthesis from CO/CO2/H2 were systematically studied by means of temperature programmed desorption (TPD), temperature programmed surface reaction (TPSR), in-situ Fourier transform-inferred spec-troscopy(FTIR) and stimulus-response techniques. As a part of results, an elementary step sequence was suggested and a group of ordinary differential equations (ODEs) for describing transient conversations relevant to all species on the catalyst surface and in the gas phase in a micro-fixed-bed reactor was derived. The values of the parameters referred to dynamic kinetics were estimated by fitting the solution of the ODEs with the transient response data obtained by the stimulus-response technique with a FTIR analyzer as an on-line detector. 展开更多
关键词 methanol synthesis copper-based catalyst dynamic kinetics elementary step sequence parameter estimation
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Molecular dynamics study of anisotropic growth of silicon
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作者 周耐根 刘博 +2 位作者 张弛 李克 周浪 《Chinese Physics B》 SCIE EI CAS CSCD 2016年第7期515-519,共5页
Based on the Tersoff potential, molecular dynamics simulations have been performed to investigate the kinetic coefficients and growth velocities of Si(100),(110),(111), and(112) planes. The sequences of the ki... Based on the Tersoff potential, molecular dynamics simulations have been performed to investigate the kinetic coefficients and growth velocities of Si(100),(110),(111), and(112) planes. The sequences of the kinetic coefficients and growth velocities are μ((100))〉 μ((110))〉 μ((112))〉 μ((111))and v((100))〉 v((110))〉 v((112))〉 v((111)), respectively, which are not consistent with the sequences of the interface energies, interplanar spacings, and melting points of the four planes. However,they agree well with the sequences of the distributions and diffusion coefficients of the melting atoms near the solid–liquid interfaces. It indicates that the atomic distributions and diffusion coefficients affected by the crystal orientations determine the anisotropic growth of silicon. The formation of stacking fault structure will further decrease the growth velocity of the Si(111) plane. 展开更多
关键词 anisotropy growth kinetic coefficient silicon molecular dynamics
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Recent advance of chemoenzymatic catalysis for the synthesis of chemicals: Scope and challenge 被引量:2
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作者 Mengjiao Xu Zhuotao Tan +3 位作者 Chenjie Zhu Wei Zhuang Hanjie Ying Pingkai Ouyang 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2021年第2期146-167,共22页
Chemoenzymatic catalysis can give full play to the advantages of versatile reactivity of chemocatalysis and excellent chemo-,regio-,and stereoselectivities of biocatalysis.These chemoenzymatic methods can not only sav... Chemoenzymatic catalysis can give full play to the advantages of versatile reactivity of chemocatalysis and excellent chemo-,regio-,and stereoselectivities of biocatalysis.These chemoenzymatic methods can not only save resource,cost,and operating time but also reduce the number of reaction steps,and avoid separating unstable intermediates,leading to the generation of more products under greener circumstances and thereby playing an indispensable role in the fields of medicine,materials and fine chemicals.Although incompatible challenges between chemocatalyst and biocatalyst remain,strategies such as biphasic system,artificial metalloenzymes,immobilization or supramolecular host,and protein engineering have been designed to overcome these issues.In this review,chemoenzymatic catalysis according to different chemocatalysis types was classifiably described,and in particular,the classic dynamic kinetic resolutions(DKR)and cofactor regeneration were summarized.Finally,the bottlenecks and development of chemoenzymatic catalysis were summarized,and future development was prospected. 展开更多
关键词 CHEMOENZYMATIC Dynamic kinetic resolution Cofactor regeneration BIOCATALYSIS Chemocatalysis
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A new approach to quantifying vehicle induced turbulence for complex traffic scenarios 被引量:3
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作者 Yesul Kim Li Huang +1 位作者 Sunling Gong Charles Q.Jia 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2016年第1期71-78,共8页
Traffic-related pollutants adversely affect air quality, especially in regions near major roadways. The vehicleinduced turbulence(VIT) is a significant factor that controls the initial dilution, dispersion, and ultima... Traffic-related pollutants adversely affect air quality, especially in regions near major roadways. The vehicleinduced turbulence(VIT) is a significant factor that controls the initial dilution, dispersion, and ultimately the chemical and physical fate of pollutants by altering the conditions in the microenvironment. This study used a computational fluid dynamics(CFD) software FLUENT to model the vehicle-induced turbulence(VIT) generated on roadways, with a focus on impact of vehicle-vehicle interactions, traffic density and vehicle composition on turbulent kinetic energy(TKE). We show, for the first time, that the overall TKE from multiple vehicles traveling in series can be estimated by superimposing the TKE of each vehicle, without considering the distance between them while the distance is greater than one vehicle length. This finding is particularly significant since it enables a new approach to VIT simulations where the overall TKE is calculated as a function of number of vehicles. We found that the interactions between vehicles traveling next to each other in adjacent lanes are insignificant,regardless the directions of the traffic flow. Consequently, simulations of different traffic scenarios can be substantially simplified by treating two-way traffic as one-way traffic, with less than 5% difference in the overall volume-averaged TKE. We also developed equations that allow the estimation of the overall volume-averaged TKE as a function of the number and the type of vehicles. 展开更多
关键词 Computational fluid dynamics Turbulent kinetic energy Vehicle-induced turbulence Road-induced turbulence Mixed traffic
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Regional Characteristics of Typhoon-Induced Ocean Eddies in the East China Sea 被引量:3
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作者 Jianhong WANG Meiqi LI +4 位作者 X.San LIANG Xing WANG Feng XUE Mo PENG Chunsheng MIAO 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2018年第7期826-838,共13页
The asymmetrical structure of typhoon-induced ocean eddies(TIOEs) in the East China Sea(including the Yellow Sea)and the accompanying air–sea interaction are studied using reanalysis products. Thirteen TIOEs are ... The asymmetrical structure of typhoon-induced ocean eddies(TIOEs) in the East China Sea(including the Yellow Sea)and the accompanying air–sea interaction are studied using reanalysis products. Thirteen TIOEs are analyzed and divided into three groups with the k-prototype method: Group A with typhoons passing through the central Yellow Sea; Group B with typhoons re-entering the sea from the western Yellow Sea after landing on continental China; and Group C with typhoons occurring across the eastern Yellow Sea near to the Korean Peninsula. The study region is divided into three zones(Zones Ⅰ, Ⅱ and Ⅲ) according to water depth and the Kuroshio position. The TIOEs in Group A are the strongest and could reverse part of the Kuroshio stream, while TIOEs in the other two groups are easily deformed by topography. The strong currents of the TIOEs impact on the latent heat flux distribution and upward transport, which facilitates the typhoon development. The strong divergence within the TIOEs favors an upwelling-induced cooling. A typical TIOE analysis shows that the intensity of the upwelling of TIOEs is proportional to the water depth, but its magnitude is weaker than the upwelling induced by the topography. In Zones Ⅰ and Ⅱ, the vertical dimensions of TIOEs and their strong currents are much less than the water depths.In shallow water Zone Ⅲ, a reversed circulation appears in the lower layer. The strong currents can lead to a greater, faster,and deeper energy transfer downwards than at the center of TIOEs. 展开更多
关键词 typhoon-induced ocean eddies East China Sea asymmetrical dynamic structure kinetic energy transfer and evolution
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Effects of a flexible net barrier on the dynamic behaviours and interception of debris flows in mountainous areas 被引量:4
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作者 HUO Miao ZHOU Jia-wen +1 位作者 YANG Xing-guo ZHOU Hong-wei 《Journal of Mountain Science》 SCIE CSCD 2017年第10期1903-1918,共16页
Flexible net barriers are a new type of effective mitigation measure against debris flows in valleys and can affect the kinematic energy and mass of debris flows. Here, ten flume tests were performed to study the dyna... Flexible net barriers are a new type of effective mitigation measure against debris flows in valleys and can affect the kinematic energy and mass of debris flows. Here, ten flume tests were performed to study the dynamic behaviours of debris flows with differences in volumes, concentrations(solid volume fraction), and travel distances after interception by a uniform flexible net barrier. A high-speed camera was used to monitor the whole test process, and their dynamic behaviours were recorded. A preliminary computational framework on energy conversion is proposed according to the deposition mechanisms and outflow of debris flow under the effects of the flexible net barrier. The experimental results show that the dynamic interaction process between a debris flow and the flexible net barrier can be divided into two stages:(a) the two-phase impact of the leading edge of the debris flow with the net and(b) collision and friction between the body of the debris flow and intercepted debris material. The approach velocity of a debris flow decreases sharply(a maximum of 63%) after the interception by the net barrier, and the mass ratio of the debris material being intercepted and the kinetic energy ratio of the debris material being absorbed by the net barrier are close due to the limited interception efficiency of the flexible net barrier, which is believed to be related to the flexibility. The energy ratio of outflow is relative small despite the large permeability of the flexible net barrier. 展开更多
关键词 Debris flow Flexible net barrier Dynamic behaviours Interception efficiency Kinetic energy absorption High speed photography
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Microstructural evolution of a superaustenitic stainless steel during a two-step deformation process 被引量:3
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作者 N.Bayat G.R.Ebrahimi +1 位作者 A.Momeni H.R.Ezatpour 《International Journal of Minerals,Metallurgy and Materials》 SCIE EI CAS CSCD 2018年第2期181-189,共9页
Single-and two-step hot compression experiments were carried out on 16Cr25Ni6Mo superaustenitic stainless steel in the temperature range from 950 to 1150°C and at a strain rate of 0.1 s^(-1). In the two-step te... Single-and two-step hot compression experiments were carried out on 16Cr25Ni6Mo superaustenitic stainless steel in the temperature range from 950 to 1150°C and at a strain rate of 0.1 s^(-1). In the two-step tests, the first pass was interrupted at a strain of 0.2; after an interpass time of 5, 20, 40, 60, or 80 s, the test was resumed. The progress of dynamic recrystallization at the interruption strain was less than 10%. The static softening in the interpass period increased with increasing deformation temperature and increasing interpass time. The static recrystallization was found to be responsible for fast static softening in the temperature range from 950 to 1050°C. However, the gentle static softening at 1100 and 1150°C was attributed to the combination of static and metadynamic recrystallizations. The correlation between calculated fractional softening and microstructural observations showed that approximately 30% of interpass softening could be attributed to the static recovery. The microstructural observations illustrated the formation of fine recrystallized grains at the grain boundaries at longer interpass time. The Avrami kinetics equation was used to establish a relationship between the fractional softening and the interpass period. The activation energy for static softening was determined as 276 kJ/mol. 展开更多
关键词 superaustenitic stainless steel dynamic recrystallization static softening metadynamic recrystallization microstructural evolution Avrami kinetics equation
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N-Heterocyclic carbene-catalyzed enantioselective(dynamic) kinetic resolutions and desymmetrizations 被引量:2
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作者 Yi Zhang Hui Cai +1 位作者 Xiuhai Gan Zhichao Jin 《Science China Chemistry》 SCIE EI CAS CSCD 2024年第2期482-511,共30页
N-heterocyclic carbene-catalyzed enantioselective kinetic resolutions,dynamic kinetic resolutions,and desymmetrization reactions are systematically reviewed.The content is organized according to the activation modes i... N-heterocyclic carbene-catalyzed enantioselective kinetic resolutions,dynamic kinetic resolutions,and desymmetrization reactions are systematically reviewed.The content is organized according to the activation modes involved in these transformations.Future advances within this highly active research field are discussed from our perspectives on the topic. 展开更多
关键词 N-heterocyclic carbene kinetic resolution dynamic kinetic resolution DESYMMETRIZATION ORGANOCATALYSIS
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Chiral Isothiourea-Catalyzed Acylative Dynamic Kinetic Resolution of 3-Hydroxyphthalides for Enantioselective Synthesis of Phthalidyl Esters
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作者 Zeyang Hao Wei Lin +2 位作者 Zi-Qi Yuan Wei Zhang Xin Li 《Chinese Journal of Chemistry》 SCIE CAS CSCD 2024年第19期2341-2345,共5页
Comprehensive Summary Phthalides serve as core structures pervasive in a wide array of natural products and drug molecules,which display a diverse array of biological activities.We report herein a highly efficient dyn... Comprehensive Summary Phthalides serve as core structures pervasive in a wide array of natural products and drug molecules,which display a diverse array of biological activities.We report herein a highly efficient dynamic kinetic resolution of 3-hydroxyphthalides by chiral isothioureas(ITUs)catalyzed asymmetric acylation,facilitating the effective synthesis of a variety of chiral phthalidyl esters with good yields and enantioselectivities.Notably,this reaction features mild reaction conditions,expansive substrate scope as well as good functional group compatibility.In addition,the practicality of this method is underscored by the large-scale synthesis,reduced catalyst loading experiment and the synthesis of the chiral phthalidyl ester prodrug. 展开更多
关键词 Asymmetric catalysis Phthalidyl ester Dynamic kinetic resolution Chiral isothiourea ACYLATION Methodology and reactions Syntheticmethods
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Stereochemical editing:Catalytic racemization of secondary alcohols and amines
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作者 Jun Zhang Zhiyao Zheng Can Zhu 《Chinese Chemical Letters》 SCIE CAS CSCD 2024年第5期17-31,共15页
Chiral alcohols and amines are important structural units widely existing in pharmaceuticals,agrochemicals,and food additives.Dynamic kinetic resolution(DKR)is an efficient strategy to deliver optically active alcohol... Chiral alcohols and amines are important structural units widely existing in pharmaceuticals,agrochemicals,and food additives.Dynamic kinetic resolution(DKR)is an efficient strategy to deliver optically active alcohols and amines from their racemates.For the development of DKR method,racemization catalyst plays as a crucial element with the requirement of compatibility with the kinetic resolution(KR)system.In this paper,recent advance in the catalytic racemization of secondary alcohols and amines is summarized based on different types of racemizing intermediates,which are redox racemization via ketone/imine intermediates,racemization via radical intermediates,and racemization via carbocation intermediates.Enzymatic racemization of secondary alcohols and amines is also enclosed. 展开更多
关键词 RACEMIZATION Secondary alcohols AMINES Kinetic resolution Dynamic kinetic resolution
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Magnetic wrinkled organosilica-based metal-enzyme integrated catalysts for enhanced chemoenzymatic catalysis
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作者 Yunting Liu Na Guo +5 位作者 Weixi Kong Shiqi Gao Guanhua Liu Liya Zhou Jing Gaoa Yanjun Jiang 《Green Synthesis and Catalysis》 2024年第2期122-125,共4页
Core-shell structured magnetic wrinkled organosilica-based metal-enzyme integrated catalysts were synthesized,and their catalytic performances were studied in the chemoenzymatic dynamic kinetic resolution of chiral am... Core-shell structured magnetic wrinkled organosilica-based metal-enzyme integrated catalysts were synthesized,and their catalytic performances were studied in the chemoenzymatic dynamic kinetic resolution of chiral amines in an organic solvent,as well as in the chemoenzymatic synthesis of chiral alcohols in water.Structureperformance studies revealed the important influence of their tunable structure and composition on the optimization of activity,stability,and recyclability in chemoenzymatic catalysis. 展开更多
关键词 Magnetic wrinkled organosilica Chemoenzymatic catalysis CO-IMMOBILIZATION Asymmetric synthesis Chiral amines/alcohols Dynamic kinetic resolution Nanomaterials
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Asymmetric synthesis of syn-aryl-(2S,3R)-2-chloro-3-hydroxy esters via an engineered ketoreductase-catalyzed dynamic reductive kinetic resolution
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作者 Xiaoping Yue Yitong Li +3 位作者 Di Sang Yuan Tao Zedu Huang Fener Chen 《Chinese Chemical Letters》 SCIE CAS CSCD 2023年第9期156-159,共4页
We report here a generic,green synthesis of 17 valuable syn-aryl-(2S,3R)-2–chloro-3–hydroxy esters(syn-(2S,3R)-1)in 73%-99%isolated yields along with 6.1:1–83:1 dr and 31%~>99%ee,through dynamic reductive kineti... We report here a generic,green synthesis of 17 valuable syn-aryl-(2S,3R)-2–chloro-3–hydroxy esters(syn-(2S,3R)-1)in 73%-99%isolated yields along with 6.1:1–83:1 dr and 31%~>99%ee,through dynamic reductive kinetic resolution of racemic arylα–chloroβ-keto esters(2)catalyzed by an engineered ketoreductase which was obtained via ep PCR-based directed evolution.The hectogram scale synthesis of syn-(2S,3R)-1b at a substrate concentration of 120 g/L showcased the application potential of the biocatalytic method developed presently. 展开更多
关键词 (2S 3R)-2-Chloro-3-hydroxy esters Dynamic reductive kinetic resolution KETOREDUCTASE Directed evolution Asymmetric synthesis
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Carbene-catalyzed activation of cyclopropylcarbaldehydes for mannich reaction andδ-lactam formation:remote enantioselecitvity control and dynamic kinetic asymmetric transformation 被引量:1
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作者 Jie Lv Jun Xu +2 位作者 Xuling Pan Zhichao Jin Yonggui Robin Chi 《Science China Chemistry》 SCIE EI CSCD 2021年第6期985-990,共6页
An N-heterocyclic carbene(NHC)-catalyzed enantioselective Mannich reaction of the remoteγ-carbon of cyclopropylcarbaldehydes is disclosed for the first time.Diastereo-and enantiomerically enriched multicyclicδ-lacta... An N-heterocyclic carbene(NHC)-catalyzed enantioselective Mannich reaction of the remoteγ-carbon of cyclopropylcarbaldehydes is disclosed for the first time.Diastereo-and enantiomerically enriched multicyclicδ-lactam compound is afforded as the main product from 8 possible stereo-specific isomers through dynamic kinetic asymmetric transformation(DYKAT)processes.Multiple chiral functional molecules can be afforded from the lactam products through simple protocols with retentions of the optical purities. 展开更多
关键词 N-heterocyclic carbene ORGANOCATALYSIS dynamic kinetic asymmetric transformation 1-cyclopropylcarbaldehydes asymmetric reactions
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Organocatalytic dynamic kinetic resolution of N-arylindole lactams:atroposelective construction of axially chiral amino acids bearing a C–N chiral axis 被引量:1
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作者 Xianfang Hong Jingcheng Guo +5 位作者 Jinhua Liu Wei Cao Chenlong Wei Ye Zhang Xiaoxiang Zhang Zhenqian Fu 《Science China Chemistry》 SCIE EI CSCD 2022年第5期905-911,共7页
Organocatalytic dynamic kinetic resolution of configurationally labile cyclic molecules represents one of the most efficient methods for the atroposelective construction of axially chiral molecules bearing a tetra-ort... Organocatalytic dynamic kinetic resolution of configurationally labile cyclic molecules represents one of the most efficient methods for the atroposelective construction of axially chiral molecules bearing a tetra-ortho-substituted chiral axis.Notably,this privileged strategy is limited to constructing a C–C chiral axis.Herein,organocatalytic dynamic kinetic resolution of configurationally labile N-arylindole lactams has been successfully achieved at the first time,allowing for access to a structurally diverse set of axially chiral N-arylindole amino esters with a tetra-ortho-substituted C–N chiral axis in excellent yields and atroposelectivities.In addition to the N-arylindole skeleton,N-aryl thieno[3,2-b]pyrrole,furo[3,2-b]pyrrole,and pyrrolo[2,3-b]pyridine skeletons are also compatible with this transformation.This transition-metal-free facile strategy features a broad substrate scope,mild reaction conditions,easy scale-up and excellent atom economy.Several potentially valuable molecules,such as axially chiral peptides,were efficiently generated from the resulting configurationally stable axially-chiral N-arylindole amino esters,demonstrating the power of this strategy. 展开更多
关键词 axially chiral amino acids C–N chiral axis dynamic kinetic resolution N-arylindole lactams organocatalysis
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Spin polarization strategy to deploy proton resource over atomic-level metal sites for highly selective CO_(2) electrolysis 被引量:2
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作者 Yingjie Zhao Xinyue Wang +5 位作者 Xiahan Sang Sixing Zheng Bin Yang Lecheng Lei Yang Hou Zhongjian Li 《Frontiers of Chemical Science and Engineering》 SCIE EI CSCD 2022年第12期1772-1781,共10页
Unlocking of the extremely inert C=O bond during electrochemical CO_(2) reduction demands subtle regulation on a key“resource”,protons,necessary for intermediate conversion but also readily trapped in water splittin... Unlocking of the extremely inert C=O bond during electrochemical CO_(2) reduction demands subtle regulation on a key“resource”,protons,necessary for intermediate conversion but also readily trapped in water splitting,which is still challenging for developing efficient single-atom catalysts limited by their structural simplicity usually incompetent to handle this task.Incorporation of extra functional units should be viable.Herein,a proton deployment strategy is demonstrated via“atomic and nanostructured iron(A/N-Fe)pairs”,comprising atomically dispersed iron active centers spin-polarized by nanostructured iron carbide ferromagnets,to boost the critical protonation steps.The as-designed catalyst displays a broad window(300 mV)for CO selectivity>90%(98%maximum),even outperforming numerous cutting-edge M–N–C systems.The well-placed control of proton dynamics by A/N-Fe can promote*COOH/*CO formation and simultaneously suppress H2 evolution,benefiting from the magnetic-proximity-induced exchange splitting(spin polarization)that properly adjusts energy levels of the Fe sites’d-shells,and further those of the adsorbed intermediates’antibonding molecular orbitals. 展开更多
关键词 CO_(2)electrolysis/single-atom catalysts/spin polarization/proton dynamics/in situ IR spectroscopy/kinetic isotope effect
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