A compact 15.0-MeV, 1.5-kW electron linear accelerator(LINAC) was successfully constructed to provide an electron beam for the first photoneutron source at the Shanghai Institute of Applied Physics, Shanghai,China. Th...A compact 15.0-MeV, 1.5-kW electron linear accelerator(LINAC) was successfully constructed to provide an electron beam for the first photoneutron source at the Shanghai Institute of Applied Physics, Shanghai,China. This LINAC consists of five main parts: a thermal cathode grid-controlled electron gun, a pre-buncher, a variable-phase-velocity buncher, a light-speed accelerating structure, and a high-power transportation beamline. A digital feedforward radio frequency compensator is adopted to reduce the energy spread caused by the transient beam loading effect. Furthermore, a real-time electron gun emission feedback algorithm is used to keep the beam stable. After months of efforts, all the beam parameters successfully met the requirements of the facility. In this paper, the beam commissioning process and performance of the LINAC are presented.展开更多
In recent years,the synthesis and application of alkenes have attracted increased attention.Triphenylethenes(TriPEs)have lower molecular torsion than tetraphenylethenes(TPEs),which helps to balance the degree of conju...In recent years,the synthesis and application of alkenes have attracted increased attention.Triphenylethenes(TriPEs)have lower molecular torsion than tetraphenylethenes(TPEs),which helps to balance the degree of conjugation and the aggregation-induced emission(AIE)effect.The geometry of double bonds has a significant impact on luminescence.Therefore,it is essential to provide a comprehensive summary of the stereoselective synthetic strategies for trisubstituted alkenes.In this review,common strategies for the stereoselective synthesis of alkenes are described,with an emphasis on the origin of stereoselectivity and the types of substrates.In addition,the AIE properties of TriPE and its applications in optoelectronic devices,stimuli-responsive materials,sensors,and therapies were discussed.展开更多
Significant advancements have been achieved in the field of C,C-palladacycles functionalization in recent decades,which have greatly contributed to the synthesis of intricate drug molecules,natural products,innovative...Significant advancements have been achieved in the field of C,C-palladacycles functionalization in recent decades,which have greatly contributed to the synthesis of intricate drug molecules,natural products,innovative materials,and chiral ligands.Additionally,these advancements have led to the establishment of highly efficient and atom-economic synthetic processes.Based on the differences in the C–Pd bonds,C,C-palladacycles can be further classified into several main types:C(aryl),C(alkyl)-,C(aryl),C(aryl)-,C(aryl),C(vinyl)-,and C(alkyl),C(carbonyl)-palladacycles.This minireview will highlight the recent advances in the synthesis of functional molecules through the functionalization of different C,C-palladacycles,and we hope this survey will inspire future strategic developments for C,C-palladacycle catalysts and their synthetic application.展开更多
Molecular aggregation affects the electronic interactions between molecules and has emerged as a powerful tool in material science.Aggregate effect finds wide applications in the research of new physical phenomena;how...Molecular aggregation affects the electronic interactions between molecules and has emerged as a powerful tool in material science.Aggregate effect finds wide applications in the research of new physical phenomena;however,its value for chemical reaction development has been far less explored.Herein,we report the development of aggregation-enabled alkene insertion into carbon–halogen bonds.The spontaneous cleavage of C–X(X=Cl,Br,or I)bonds generates an intimate ion pair,which can be quickly captured by alkenes in an aggregated state.Additional catalysts or promoters are not necessary under such circumstances,and solvent quenching experiments indicate that the aggregated state is critical for achieving such sequences.The ionic insertion mode is supported by mechanistic studies,density functional theory calculations,and symmetry-adapted perturbation theory analysis.Results also show that the non-aggregated state may quench the transition state and terminate the insertion process.展开更多
CrN films were deposited on the high-speed-steel substrates by arc ion plating. The effect of an axial magnetic field on the microstructure and mechanical properties was investigated. The chemical composition, microst...CrN films were deposited on the high-speed-steel substrates by arc ion plating. The effect of an axial magnetic field on the microstructure and mechanical properties was investigated. The chemical composition, microstructure, surface morphology, surface roughness, hardness and film/substrate adhesion of the film were characterized by X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscope(SEM), surface morphology analyzer, Vickers microhardness test and scratch test. The results showed that the magnetic field puts much effect on the microstructure,chemical composition, hardness and film/substrate adhesion of the Cr N films. The N content increases and Cr content decreases when the magnetic flux density increases from 0 to 30 m T. All of the Cr N films were found to be substoichiometric. With an increase in the magnetic flux density, the film structures change in such way: Cr_2N →Cr_(2-N)+CrN→CrN+Cr_2N→CrN.The SEM results showed that the number of macroparticles(MPs) on the film surface is significantly reduced when the magnetic flux density increases to 10 mT or higher. The surface roughness decreases with the magnetic field, which is attributed to the fewer MPs and sputtered craters on the film surface. The hardness value increases from 2074 HV_(0.025) at 0 mT(without magnetic field) and reaches a maximum value of 2509 HV_(0.025) at 10 m T.The further increase in the magnetic flux density leads to a decrease in the film hardness. The critical load of film/substrate adhesion shows a monotonous increase with the increase in magnetic flux density.展开更多
Transition metal catalyzed C-H Functionalization is one of the most important and challenging research fields in organic chemistry and has rapidly evolved in recent decades.Some recent achievements in the field includ...Transition metal catalyzed C-H Functionalization is one of the most important and challenging research fields in organic chemistry and has rapidly evolved in recent decades.Some recent achievements in the field include i)minimizing the pre-activation procedures of substrates,ii)reducing waste production,and iii)shortening synthetic steps by developing direct activations and straightforward transfor-展开更多
To study the influence of the nitrogen vacancy(V_N)on mechanical and electrical properties of zirconium nitride deeply,Zr N_x films with different V_N concentrations were synthesized on the Si(111)substrates by enhanc...To study the influence of the nitrogen vacancy(V_N)on mechanical and electrical properties of zirconium nitride deeply,Zr N_x films with different V_N concentrations were synthesized on the Si(111)substrates by enhanced magnetic filtering arc ion plating.The morphologies,microstructures,residual stresses,compositions,chemical states,mechanical and electrical properties of the as-deposited films were characterized by field-emission scanning electron microscopy,X-ray diffraction,X-ray photoelectron spectrometry,Nanoindenter and Hall effect measurements.The results showed that Zr N_x films exhibited rocksalt single-phase structure within a V_N concentration ranging from 26 to 5%.The preferred orientation,thickness,grain size and residual stress of the Zr N_x films kept constant at different V_N concentrations.Both the nanohardness and elastic modulus first increased and then decreased with the decrease in V_N concentration,reaching the peaks around 16%.And the electric conductivity of the Zr N_x films showed a similar tendency with nanohardness.The underlying atomic-scale mechanisms of V_N concentration-dependent hardness and electric conductivity enhancements were discussed and attributed to the different electronic band structures,rather than conventional meso-scale factors,such as preferred orientation,grain size and residual stress.展开更多
Different from the established trans-endo-selective cyclization of alkyne-tethered electrophiles that involve an E/Z isomerization process,herein,the authors present a novel strategy to allow trans-exo-selective aryla...Different from the established trans-endo-selective cyclization of alkyne-tethered electrophiles that involve an E/Z isomerization process,herein,the authors present a novel strategy to allow trans-exo-selective arylative cyclization of 1,6-enynes.Through initiation of rhodium(III)-catalyzed C-H activation,a diverse range of N-heterocyclic directing groups,including pyridine,pyrazole,imidazo[1,2-a]pyridine,benzoxazole,benzothiazole,and purine,was feasible for the cascade transformation,exhibiting high efficiency(up to 92%yield),broad substrate scope,and excellent functional group compatibility.Moreover,the modification of natural products and pharmaceutical compounds was also demonstrated to showcase its synthetic utility.Based on density functional theory(DFT)calculations,a key three-membered ring intermediate through the insertion relay,rather than the direct E/Z isomerization of alkenyl rhodium species,controlled the stereochemical outcome for this trans-exo-selective cyclization.The subsequent ring-opening protonation of the more favored rotamer led to exclusive trans-exo-selectivity.展开更多
Polyketides,a large class of secondary metabolites,have been of long-standing interest to the synthetic community due to their intriguing biological activities and structural versatility and complexity.A typical struc...Polyketides,a large class of secondary metabolites,have been of long-standing interest to the synthetic community due to their intriguing biological activities and structural versatility and complexity.A typical structural unit of various natural products,polypropionate,has prompted enormous efforts in the development of novel synthetic methods and strategies in the past five decades.In this study,a non-aldol-type approach based on double hydroboration of allenes has been developed to provide a powerful method for the stereodivergent construction of various polyol stereotriads and stereotetrads that are amenable for synthesizing polypropionates.The stereochemical control is possibly attributable to the boronate complex that aligned itself as a rigid conformation for the second stereoselective hydroboration reaction by suppressing the barotropic rearrangement of allylborane intermediates.The feasibility of preparing the key polypropionate motif facilitates the efficient synthesis of(-)-pironetin,a potentα-tubulin inhibitor halting the cell cycle at M phase.展开更多
As the chemical industry grapples with the need for more eco-friendly practices,the use of water as a reaction medium is gaining attraction in organic transformations.This mini-review delves into Pd-catalyzed reaction...As the chemical industry grapples with the need for more eco-friendly practices,the use of water as a reaction medium is gaining attraction in organic transformations.This mini-review delves into Pd-catalyzed reactions that utilize the "on-water" mechanism,spanning from 2019 to late 2023.These reactions are neatly categorized into several types: (A) Catalytic C—H activations,(B) Mizoroki- Heck-type reactions,(C) Suzuki-Miyaura reactions,and (D) Cyclization reactions.By showcasing the potential of water as a sustainable reaction medium for organic transformations,these reactions leave no doubt about the importance of embracing eco-friendly practices in the chemical industry.Key Scientists In 1980,a seminal work by Breslow et al.showed an acceleration of reaction rate in the Diels-Alder reaction.Sharpless and co-workers noted a significant increase in the rate of the [2σ+2σ+2π] cycloaddition of quadricyclane and dimethyl azodicarboxylate (DMAD) when the reaction was conducted in water,as opposed to when it was carried out in organic solvents.The term "on-water" was then coined to describe this phenomenon.This strategy was further expanded to transition-metal catalyzed transformations by Ackermann in 2011.Later,Varma and Leazer disclosed a Pd-catalyzed Mizoroki-Heck type arylation of alkenes with diaryliodonium salts “on-water”.The enantioselective version of "on-water" process was not realized until 2014 by the Zhou group.Later on,the Schaub group described a Pd-catalyzed Suzuki–Miyaura coupling reaction of electron-poor aryl chlorides with water,using only 50 ppm of catalyst loading.Very recently,Liu and Lin extended the "on-water" strategy to Pd-catalyzed double Mizoroki-Heck reactions.This mini-review has focused on Pd-catalyzed reactions involving the “on-water” mechanism.展开更多
基金supported by the Youth Innovation Promotion Association CAS(No.2018300)
文摘A compact 15.0-MeV, 1.5-kW electron linear accelerator(LINAC) was successfully constructed to provide an electron beam for the first photoneutron source at the Shanghai Institute of Applied Physics, Shanghai,China. This LINAC consists of five main parts: a thermal cathode grid-controlled electron gun, a pre-buncher, a variable-phase-velocity buncher, a light-speed accelerating structure, and a high-power transportation beamline. A digital feedforward radio frequency compensator is adopted to reduce the energy spread caused by the transient beam loading effect. Furthermore, a real-time electron gun emission feedback algorithm is used to keep the beam stable. After months of efforts, all the beam parameters successfully met the requirements of the facility. In this paper, the beam commissioning process and performance of the LINAC are presented.
基金supported by the National Natural Science Foundation of China(81874181,21871284)the Major Scientific and Technological Special Project for“Significant New Drugs Creation”(2019ZX09301158)+2 种基金the Emerging Frontier Program of Hospital Development Centre(SHDC12018107)the Science&Technology Department of Shanghai(18401933500)the State Key Laboratory of Bioorganic and Natural Products Chemistry。
文摘In recent years,the synthesis and application of alkenes have attracted increased attention.Triphenylethenes(TriPEs)have lower molecular torsion than tetraphenylethenes(TPEs),which helps to balance the degree of conjugation and the aggregation-induced emission(AIE)effect.The geometry of double bonds has a significant impact on luminescence.Therefore,it is essential to provide a comprehensive summary of the stereoselective synthetic strategies for trisubstituted alkenes.In this review,common strategies for the stereoselective synthesis of alkenes are described,with an emphasis on the origin of stereoselectivity and the types of substrates.In addition,the AIE properties of TriPE and its applications in optoelectronic devices,stimuli-responsive materials,sensors,and therapies were discussed.
基金This work was supported by the National Natural Science Foundation of China(22101296)the State Key Laboratory of Systems Medicine for Cancer(SB23-09,KF2130-93).
文摘Significant advancements have been achieved in the field of C,C-palladacycles functionalization in recent decades,which have greatly contributed to the synthesis of intricate drug molecules,natural products,innovative materials,and chiral ligands.Additionally,these advancements have led to the establishment of highly efficient and atom-economic synthetic processes.Based on the differences in the C–Pd bonds,C,C-palladacycles can be further classified into several main types:C(aryl),C(alkyl)-,C(aryl),C(aryl)-,C(aryl),C(vinyl)-,and C(alkyl),C(carbonyl)-palladacycles.This minireview will highlight the recent advances in the synthesis of functional molecules through the functionalization of different C,C-palladacycles,and we hope this survey will inspire future strategic developments for C,C-palladacycle catalysts and their synthetic application.
基金National Natural Science Foundation of China,Grant/Award Numbers:91940305,21933009,81874181,22271195,21871284Natural Science Foundation of Fujian Province,Grant/Award Number:2021J01525+3 种基金Major Scientific and Technological Special Project for“Significant New Drugs Creation”,Grant/Award Number:2019ZX09301158The Emerging Frontier Program of Hospital Development Centre,Grant/Award Number:SHDC12018107Shanghai Science and Technology Development Fund from Central Leading Local Government,Grant/Award Number:YDZX20223100001004Shanghai Municipal Health Commission/Shanghai Municipal Administration of Traditional Chinese Medicine,Grant/Award Number:ZY(2021-2023)−0501。
文摘Molecular aggregation affects the electronic interactions between molecules and has emerged as a powerful tool in material science.Aggregate effect finds wide applications in the research of new physical phenomena;however,its value for chemical reaction development has been far less explored.Herein,we report the development of aggregation-enabled alkene insertion into carbon–halogen bonds.The spontaneous cleavage of C–X(X=Cl,Br,or I)bonds generates an intimate ion pair,which can be quickly captured by alkenes in an aggregated state.Additional catalysts or promoters are not necessary under such circumstances,and solvent quenching experiments indicate that the aggregated state is critical for achieving such sequences.The ionic insertion mode is supported by mechanistic studies,density functional theory calculations,and symmetry-adapted perturbation theory analysis.Results also show that the non-aggregated state may quench the transition state and terminate the insertion process.
基金supported by Key Laboratory of Materials Modification by Laser, Ion, and Electron Beams (Dalian University of Technology)Ministry of Education (Grant No. LABKF1405)
文摘CrN films were deposited on the high-speed-steel substrates by arc ion plating. The effect of an axial magnetic field on the microstructure and mechanical properties was investigated. The chemical composition, microstructure, surface morphology, surface roughness, hardness and film/substrate adhesion of the film were characterized by X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscope(SEM), surface morphology analyzer, Vickers microhardness test and scratch test. The results showed that the magnetic field puts much effect on the microstructure,chemical composition, hardness and film/substrate adhesion of the Cr N films. The N content increases and Cr content decreases when the magnetic flux density increases from 0 to 30 m T. All of the Cr N films were found to be substoichiometric. With an increase in the magnetic flux density, the film structures change in such way: Cr_2N →Cr_(2-N)+CrN→CrN+Cr_2N→CrN.The SEM results showed that the number of macroparticles(MPs) on the film surface is significantly reduced when the magnetic flux density increases to 10 mT or higher. The surface roughness decreases with the magnetic field, which is attributed to the fewer MPs and sputtered craters on the film surface. The hardness value increases from 2074 HV_(0.025) at 0 mT(without magnetic field) and reaches a maximum value of 2509 HV_(0.025) at 10 m T.The further increase in the magnetic flux density leads to a decrease in the film hardness. The critical load of film/substrate adhesion shows a monotonous increase with the increase in magnetic flux density.
基金Financial support from the National Natural Science Foundation of China (Nos. 21472212, 21572253, 21772216), the Strategic Priority Research Program of the Chinese Academy of Sciences (No. XDB 20020100) and the Key Research Program of Frontier Science (No.QYZDY-SSW-SLH026) is acknowledged.
文摘Transition metal catalyzed C-H Functionalization is one of the most important and challenging research fields in organic chemistry and has rapidly evolved in recent decades.Some recent achievements in the field include i)minimizing the pre-activation procedures of substrates,ii)reducing waste production,and iii)shortening synthetic steps by developing direct activations and straightforward transfor-
基金supported financially by the National Natural Science Foundation of China(No.51271047)
文摘To study the influence of the nitrogen vacancy(V_N)on mechanical and electrical properties of zirconium nitride deeply,Zr N_x films with different V_N concentrations were synthesized on the Si(111)substrates by enhanced magnetic filtering arc ion plating.The morphologies,microstructures,residual stresses,compositions,chemical states,mechanical and electrical properties of the as-deposited films were characterized by field-emission scanning electron microscopy,X-ray diffraction,X-ray photoelectron spectrometry,Nanoindenter and Hall effect measurements.The results showed that Zr N_x films exhibited rocksalt single-phase structure within a V_N concentration ranging from 26 to 5%.The preferred orientation,thickness,grain size and residual stress of the Zr N_x films kept constant at different V_N concentrations.Both the nanohardness and elastic modulus first increased and then decreased with the decrease in V_N concentration,reaching the peaks around 16%.And the electric conductivity of the Zr N_x films showed a similar tendency with nanohardness.The underlying atomic-scale mechanisms of V_N concentration-dependent hardness and electric conductivity enhancements were discussed and attributed to the different electronic band structures,rather than conventional meso-scale factors,such as preferred orientation,grain size and residual stress.
基金Financial support was generously provided by the National Natural Science Foundation of China(nos.21871184,21871284,21702182,and 21873081),the Shanghai Municipal Education Commission(no.2019-01-07-00-10-E00072),the Science and Technology Commission of Shanghai Municipality(no.18401933500),the Strategic Priority Research Program of the Chinese Academy of Sciences(no.XDB 20020100),the Key Research Program of Frontier Science(no.QYZDYSSW-SLH026),the Fundamental Research Funds for the Central Universities(no.2019QNA3009),and the China Postdoctoral Science Foundation(no.2018M640546).Calculations were performed on the high-performance computing system at the Department of Chemistry,Zhejiang University.The authors thank Jie Sun(Shanghai Institute of Organic Chemistry)for X-ray crystallographic analysis.
文摘Different from the established trans-endo-selective cyclization of alkyne-tethered electrophiles that involve an E/Z isomerization process,herein,the authors present a novel strategy to allow trans-exo-selective arylative cyclization of 1,6-enynes.Through initiation of rhodium(III)-catalyzed C-H activation,a diverse range of N-heterocyclic directing groups,including pyridine,pyrazole,imidazo[1,2-a]pyridine,benzoxazole,benzothiazole,and purine,was feasible for the cascade transformation,exhibiting high efficiency(up to 92%yield),broad substrate scope,and excellent functional group compatibility.Moreover,the modification of natural products and pharmaceutical compounds was also demonstrated to showcase its synthetic utility.Based on density functional theory(DFT)calculations,a key three-membered ring intermediate through the insertion relay,rather than the direct E/Z isomerization of alkenyl rhodium species,controlled the stereochemical outcome for this trans-exo-selective cyclization.The subsequent ring-opening protonation of the more favored rotamer led to exclusive trans-exo-selectivity.
基金support obtained from the Chinese Academy of Sciences(QYZDY-SSWSLH026 and XDB20020000)and the Drug Innovation Major Project(2018ZX09711001-005)is highly appreciated.The authors thank Zuming Lin for assisting with the experiments and Dr.Xiaoli Bao(SJTU)and Jie Sun(SIOC)for performing the X-ray analysis.
文摘Polyketides,a large class of secondary metabolites,have been of long-standing interest to the synthetic community due to their intriguing biological activities and structural versatility and complexity.A typical structural unit of various natural products,polypropionate,has prompted enormous efforts in the development of novel synthetic methods and strategies in the past five decades.In this study,a non-aldol-type approach based on double hydroboration of allenes has been developed to provide a powerful method for the stereodivergent construction of various polyol stereotriads and stereotetrads that are amenable for synthesizing polypropionates.The stereochemical control is possibly attributable to the boronate complex that aligned itself as a rigid conformation for the second stereoselective hydroboration reaction by suppressing the barotropic rearrangement of allylborane intermediates.The feasibility of preparing the key polypropionate motif facilitates the efficient synthesis of(-)-pironetin,a potentα-tubulin inhibitor halting the cell cycle at M phase.
基金support from the National Natural Science Foundation of China(22101296)the State Key Laboratory of Systems Medicine for Cancer(SB23-09,KF2130-93).
文摘As the chemical industry grapples with the need for more eco-friendly practices,the use of water as a reaction medium is gaining attraction in organic transformations.This mini-review delves into Pd-catalyzed reactions that utilize the "on-water" mechanism,spanning from 2019 to late 2023.These reactions are neatly categorized into several types: (A) Catalytic C—H activations,(B) Mizoroki- Heck-type reactions,(C) Suzuki-Miyaura reactions,and (D) Cyclization reactions.By showcasing the potential of water as a sustainable reaction medium for organic transformations,these reactions leave no doubt about the importance of embracing eco-friendly practices in the chemical industry.Key Scientists In 1980,a seminal work by Breslow et al.showed an acceleration of reaction rate in the Diels-Alder reaction.Sharpless and co-workers noted a significant increase in the rate of the [2σ+2σ+2π] cycloaddition of quadricyclane and dimethyl azodicarboxylate (DMAD) when the reaction was conducted in water,as opposed to when it was carried out in organic solvents.The term "on-water" was then coined to describe this phenomenon.This strategy was further expanded to transition-metal catalyzed transformations by Ackermann in 2011.Later,Varma and Leazer disclosed a Pd-catalyzed Mizoroki-Heck type arylation of alkenes with diaryliodonium salts “on-water”.The enantioselective version of "on-water" process was not realized until 2014 by the Zhou group.Later on,the Schaub group described a Pd-catalyzed Suzuki–Miyaura coupling reaction of electron-poor aryl chlorides with water,using only 50 ppm of catalyst loading.Very recently,Liu and Lin extended the "on-water" strategy to Pd-catalyzed double Mizoroki-Heck reactions.This mini-review has focused on Pd-catalyzed reactions involving the “on-water” mechanism.