A novel method for synthesis of quinazoline through the hydrogen transfer/annulation reaction using 2-nitrobenzyl alcohol and benzylamine as starting materials is presented.The reaction is catalyzed by a ruthenium(II)...A novel method for synthesis of quinazoline through the hydrogen transfer/annulation reaction using 2-nitrobenzyl alcohol and benzylamine as starting materials is presented.The reaction is catalyzed by a ruthenium(II)complex bearing a N-heterocyclic carbene nitrogen phosphine(CNP)ligand.The pronouncedα-donating capacity of the carbene within the CNP ligand of the catalyst plays a crucial role in stabilizing the catalytically active species.Additionally,the hemilability of the nitrogen facilitates the creation of coordination vacancies,which are essential for the activation of reaction substrate molecules.The synergistic interplay between these two functionalities markedly enhances catalytic efficiency.This catalytic system shows the significant catalytic activity and selectivity,along with a broad substrate adaptability.All substrates yield the target product in good to excellent yields with the maximum yield reaching 95%.Control experiments have substantiated that benzaldehyde and phenylmethanimine may serve as intermediates in the reaction,thereby reinforcing the role of benzylamine as both a hydrogen donor and a nitrogen source in the process.展开更多
A[3+4]annulation of α-substituted allenes and Schiff bases is reported.This methodology serves as a conduit for the construction of a series of biologically important benzazepine derivatives in good to excellent yiel...A[3+4]annulation of α-substituted allenes and Schiff bases is reported.This methodology serves as a conduit for the construction of a series of biologically important benzazepine derivatives in good to excellent yields under mild conditions by an unprecedented mode involving β’-carbon of α-substituted allenes and the proposed mechanism is supported by capturing the intermediate.Moreover,this class of benzazepine derivatives exhibited potential ability of cytotoxicity toward cancer cells.展开更多
Designing efficient,recyclable,and low-cost catalysts is crucial for the synthesis of quinoxaline derivatives.In this context,a novel N-stable Co_(2)P nano-catalyst(CoP@N–C-1.5)was developed using a templatesacrifici...Designing efficient,recyclable,and low-cost catalysts is crucial for the synthesis of quinoxaline derivatives.In this context,a novel N-stable Co_(2)P nano-catalyst(CoP@N–C-1.5)was developed using a templatesacrificial approach.The catalyst demonstrated a broad substrate scope and good functional group tolerance,achieving yields of up to 84%.Additionally,the catalyst exhibited reusability and can be recycled up to three times.The CoP@N–C-1.5 was characterized using X-ray powder diffraction(XRD),scanning electron microscopy(SEM),and transmission electron microscopy(TEM).The results indicated that the catalyst contained Co2P nanoparticles.The X-ray photoelectron spectroscopy(XPS)further confirms the presence of Co-P.Analysis of the characterization data and experimental results revealed that the active site of the catalyst comprises N-stable Co_(2)P nanoparticles.展开更多
Chromones serve as versatile heterocyclic scaffolds and are common core structural units in a variety of natural products and bioactive organic molecules.This area of research,at the forefront of organic synthesis,has...Chromones serve as versatile heterocyclic scaffolds and are common core structural units in a variety of natural products and bioactive organic molecules.This area of research,at the forefront of organic synthesis,has seen remarkable progress in recent years.Among the various synthetic methodologies for accessing chromone scaffolds,the tandem annulation of o-hydroxyaryl enaminones has emerged as a robust and practical strategy.This approach,through direct vinyl C-H bond functionalization of o-hydroxyaryl enaminones,enables the construction of structurally diverse chromones(including 3-substituted chromones,2-substituted chromones,and 2,3-disubstituted chromones)and their derivatives since mid-2019.In this review,we highlight recent advances in the synthesis of various types of chromones and their derivatives,achieved through tandem direct vinyl C-H activation and chromone annulation of o-hydroxyaryl enaminones.展开更多
Polycyclic compounds are widely found in natural products and drug molecules with important biological activities,which attracted the attention of many chemists.Phosphine-catalyzed nucleophilic addition is one of the ...Polycyclic compounds are widely found in natural products and drug molecules with important biological activities,which attracted the attention of many chemists.Phosphine-catalyzed nucleophilic addition is one of the most powerful tools for the construction of various cyclic compounds with the advantages of atom economy,mild reaction conditions and simplicity of operation.Allenolates,Morita−Baylis−Hillman(MBH)alcohols and their derivatives(MBHADs),electron-deficient olefins and alkynes are very efficient substrates in phosphine mediated annulations,which formed many phosphonium species such asβ-phosphonium enolates,β-phosphonium dienolates and vinyl phosphonium ylides as intermediates.This review describes the reactivities of these phosphonium zwitterions and summarizes the synthesis of polycycle compounds through phosphine-mediated intramolecular and intermolecular sequential annulations.Thus,a systematic summary of the research process based on the phosphine-mediated sequential annulations of allenolates,MBH alcohols and MBHADs,electron-deficient olefins and alkynes are presented in Chapters 2-6,respectively.展开更多
A new oxidative N-heterocyclic carbene(NHC)-catalyzed high-order[7+3]annulation reaction ofγ-indolyl phenols as 1,7-dinucleophiles andα,β-alkynals with the aid of Sc(OTf)_(3)is reported,enabling the highly regiosel...A new oxidative N-heterocyclic carbene(NHC)-catalyzed high-order[7+3]annulation reaction ofγ-indolyl phenols as 1,7-dinucleophiles andα,β-alkynals with the aid of Sc(OTf)_(3)is reported,enabling the highly regioselective access to unprecedented polyarene-fused ten-membered lactams bearing a bridged aryl-aryl-indole scaffold in moderate to good yields.This protocol demonstrates a broad substrate scope,good compatibility with substituents and complete regioselectivity,providing an organocatalytic modular synthetic strategy for creating medium-sized lactams.展开更多
Combining the advantages of high efficiency,low-pressure drop,and large throughput,the pore arrayenhanced tube-in-tube microchannel(PA-TMC) is a promising microreactor for industrial applications.However,most of the m...Combining the advantages of high efficiency,low-pressure drop,and large throughput,the pore arrayenhanced tube-in-tube microchannel(PA-TMC) is a promising microreactor for industrial applications.However,most of the mass transfer takes place in the upstream pore region,while the contribution of the downstream annulus is limited.In this work,helical wires were introduced into the annulus by adhering to the outer surface of the inner tube.Mixing behavior and mass transfer of liquid-liquid twophase flow in PA-TMC with different helical wires have been systematically studied by a combination of experiments and volume of fluid(VOF) method.The introduction of helical wires improves the overall volumetric mass transfer coefficient KLa by up to 133% and the mass transfer efficiency E by up to 117%.The simulation results show that the helical wire brings extra phase mixing regions and increases the specific interface area,while accelerating the fluid flow and expanding the area of enhanced turbulent dissipation rate.Influences of helical wires in various configurations are compared by the comprehensive index I concerning the pressure drop and mass transfer performance simultaneously and a new correlation between KLa and specific energy consumption φ is proposed.This research deepens the understanding of the mixing behavior and mass transfer in the PA-TMCs and provides practical experience for the process intensification of microchannel reactors.展开更多
Catalytic C–H activation-initiated annulation reactions have emerged as a versatile strategy for the efficient construction of diverse ring structural units and complex cyclic molecules in synthetic chemistry.Herein,...Catalytic C–H activation-initiated annulation reactions have emerged as a versatile strategy for the efficient construction of diverse ring structural units and complex cyclic molecules in synthetic chemistry.Herein,we describe a new Rh(Ⅲ)-catalyzed C–H activation-initiated transdiannulation reaction of N,Ndimethyl enaminones with gem-difluorocyclopropenes in the presence of H_(2)O,enabling a facile and oxygen transfer access to ring-fluorinated tricyclicγ-lactones with a 6-5 ring-junction tetrasubstituted stereocenter.This approach features bond-forming/annulation efficiency,good functional group tolerance and complete regioselectivity,which may include a complex process consisting of Rh(Ⅲ)-catalyzed C(sp2)–H activation,cyclic alkene insertion,defluorinated ring-opening of gem-difluorocyclopropane,intramolecular oxygen transfer,intramolecular cyclization and oxidative hydration.展开更多
Rhodium-catalyzed C4aryl-H activation and ring-retentive annulation of 2H-imidazoles with internal alkynes to build imidazo[5,1-a]isoquinolinium salts with high yields and broad scope has been disclosed.These novel sa...Rhodium-catalyzed C4aryl-H activation and ring-retentive annulation of 2H-imidazoles with internal alkynes to build imidazo[5,1-a]isoquinolinium salts with high yields and broad scope has been disclosed.These novel salts serve as new full-color emissive fluorophores(433-633 nm),just by simply modifying the substituents on C3 and C4 positions of isoquinoline ring.Furthermore,these salts can undergo ring-opening C5_(aryl)-H activation/annulation with a different alkyne to form non-symmetric and AIE-active1,1-biisoquinolines,where NH_(4)OAc plays an indispensable role that accounts for Hofmann elimination and imine formation,leading to an unprecedented imine dance:cyclic imine→N-alkenyl imine→NH imine.The15N labelling experiments indicate that the 2ndannulation includes two pathways:N-exchange(major)and N-retention(minor).展开更多
A[4+4]annulation reaction for the construction of medium-sized N-heterocycles is reported.This process involves the generation of all-carbon 1,4-dipoles containing aπ-allylpalladium complex from Morita-Baylis-Hillman...A[4+4]annulation reaction for the construction of medium-sized N-heterocycles is reported.This process involves the generation of all-carbon 1,4-dipoles containing aπ-allylpalladium complex from Morita-Baylis-Hillman(MBH)carbonates under the catalysis of Pd/Synphos,which then undergo Michael addition/N-allylic alkylation with 1-azadienes.A spectrum of eight-membered N-heterocycles featuring a trisubstituted exo-cyclic double bond is furnished efficiently with moderate to good E/Z selectivity and moderate atroposelectivity.In addition,moderate enantioselectivity can be realized by using a chiral ligand or with the assistant of a chiral quaternary ammonium salt.展开更多
A new photocatalytic annulative acylative difunctionalization of 1,6-enynes is reported,enabling stereoselective access to acylated 1-indanones with cyclic quaternary centers in moderate to good yields.This photocatal...A new photocatalytic annulative acylative difunctionalization of 1,6-enynes is reported,enabling stereoselective access to acylated 1-indanones with cyclic quaternary centers in moderate to good yields.This photocatalysis enables two types of acylation of unsaturated hydrocarbons by adjusting the categories of acyl radical precursors.Aroyl chlorides as bifunctional reagents react with 1,6-enynes to realize annulative chloroacylation,while acyl oxime esters are used as acyl radical precursors,which undergo a three-component annulative alkoxyacylation by treatment with 1,6-enynes and alcohols.The current method demonstrates good functional group compatibility,a broad substrate scope and mild reaction conditions.展开更多
The Rh(III)-catalyzed C—H functionalization of sulfoxonium ylides and successively annulation with two classes of cyclic diazo compounds has been realized,affording structurally diverse fused-ring or spirocyclic comp...The Rh(III)-catalyzed C—H functionalization of sulfoxonium ylides and successively annulation with two classes of cyclic diazo compounds has been realized,affording structurally diverse fused-ring or spirocyclic compounds under redoxneutral conditions.The reaction proceeds via successive chelation-assisted C—H activation,carbene insertion,and intramolecular[3+3]/[4+1]annulation processes.展开更多
Organic nanophotocatalysts are promising candidates for solar fuels production,but they still face the challenge of unfavorable geminate recombination due to the limited exciton diffusion lengths.Here,we introduce a b...Organic nanophotocatalysts are promising candidates for solar fuels production,but they still face the challenge of unfavorable geminate recombination due to the limited exciton diffusion lengths.Here,we introduce a binary nanophotocatalyst fabricated by blending two polymers,PS-PEG5(PS)and PBT-PEG5(PBT),with matched absorption and emission spectra,enabling a Forster resonance energy transfer(FRET)process for enhanced photocatalysis.These heterostructure nanophotocatalysts are processed using a facile and scalable flash nanoprecipitation(FNP)technique with precious kinetic control over binary nanoparticle formation.The resulting nanoparticles exhibit an exceptional photocatalytic hydrogen evolution rate up to 65 mmol g^(-1) h^(-1),2.5 times higher than that single component nanoparticles.Characterizations through fluorescence spectra and transient absorption spectra confirm the hetero-energy transfer within the binary nanoparticles,which prolongs the excited-state lifetime and extends the namely“effective exciton diffusion length”.Our finding opens new avenues for designing efficient organic photocatalysts by improving exciton migration.展开更多
In scenarios such as vehicle radiation monitoring and unmanned aerial vehicle radiation detection,rapid measurements using a NaI(Tl)detector often result in low photon counts,weak characteristic peaks,and significant ...In scenarios such as vehicle radiation monitoring and unmanned aerial vehicle radiation detection,rapid measurements using a NaI(Tl)detector often result in low photon counts,weak characteristic peaks,and significant statistical fluctuations.These issues can lead to potential failures in peak-searching-based identification methods.To address the low precision associated with short-duration measurements of radionuclides,this paper proposes an identification algorithm that leverages heterogeneous spectral transfer to develop a low-count energy spectral identification model.Comparative experiments demonstrated that transferring samples from 26 classes of simulated heterogeneous gamma spectra aids in creating a reliable model for measured gamma spectra.With only 10%of target domain samples used for training,the accuracy on real low-count spectral samples was 95.56%.This performance shows a significant improvement over widely employed full-spectrum analysis methods trained on target domain samples.The proposed method also exhibits strong generalization capabilities,effectively mitigating overfitting issues in low-count energy spectral classification under short-duration measurements.展开更多
Catalytic oxidation of organic pollutants is a well-known and effective technique for pollutant abatement.Unfortunately,this method is significantly hindered in practical applications by the lowefficiency and difficul...Catalytic oxidation of organic pollutants is a well-known and effective technique for pollutant abatement.Unfortunately,this method is significantly hindered in practical applications by the lowefficiency and difficult recovery of the catalysts in a powdery form.Herein,a three-dimensional(3D)framework of Fe-incorporated Ni_(3)S_(2)nanosheets in-situ grown on Ni foam(Fe-Ni_(3)S_(2)@NF)was fabricated by a facile two-step hydrothermal process and applied to trigger peroxymonosulfate(PMS)oxidation of organic compounds inwater.A homogeneous growth environment enabled the uniform and scalable growth of Fe-Ni_(3)S_(2)nanosheets on the Ni foam.Fe-Ni_(3)S_(2)@NF possessed outstanding activity and durability in activating PMS,as it effectively facilitated electron transfer from organic pollutants to PMS.Fe-Ni_(3)S_(2)@NF initially supplied electrons to PMS,causing the catalyst to undergo oxidation,and subsequently accepted electrons from organic compounds,returning to its initial state.The introduction of Fe into the Ni_(3)S_(2)lattice enhanced electrical conductivity,promoting mediated electron transfer between PMS and organic compounds.The 3D conductive Ni foam provided an ideal platform for the nucleation and growth of Fe-Ni_(3)S_(2),accelerating pollutant abatement due to its porous structure and high conductivity.Furthermore,its monolithic nature simplified the catalyst recycling process.A continuous flow packed-bed reactor by encapsulating Fe-Ni_(3)S_(2)@NF catalyst achieved complete pollutant abatement with continuous operation for 240 h,highlighting its immense potential for practical environmental remediation.This study presents a facile synthesis method for creating a novel type of monolithic catalyst with high activity and durability for decontamination through Fenton-like processes.展开更多
Layered double hydroxide(LDH)based heterogonous peroxymonosulfate(PMS)activation degradation of pollutants has attracted extensive attention.The challenge is to selectively regulate the traditional free radical domina...Layered double hydroxide(LDH)based heterogonous peroxymonosulfate(PMS)activation degradation of pollutants has attracted extensive attention.The challenge is to selectively regulate the traditional free radical dominant degradation pathway into a nonradical degradation pathway.Herein,an interface ar-chitecture of Ti_(3) C_(2) T_(x)-MXene(MXene)loading on the Fe-Al LDH scaffold was developed,which showed excellent stability and robust resistance against harsh conditions.Significantly,the rate constant for tetra-cycline hydrochloride(TC)degradation in the MXene-LDH/PMS process was 0.421 min^(-1),which was ten times faster than the rate constant for pure Fe-Al LDH(0.042 min^(-1)).Specifically,more reactive Fe with the closer d-band center to the Fermi level results in higher electron transfer efficiency.The occupa-tions of Fe-3d orbitals in Mxene/Fe-Al LDH are pushed above the Fermi level to generate,which results in higher PMS adsorption and inhibition of the release of oxygen-containing active species intermedi-ates,leading to the enhanced^(1)O_(2) generation.Additionally,the built-in electric field in the heterojunc-tion was driven by the charge redistribution between MXene and Fe-Al LDH,resulting in a mediated-electron transfer mechanism,differentiating it from the Fe-Al LDH/PMS system.It was fascinating that MXene/Fe-Al LDH achieved satisfactory treatment efficiency in continuous column reactor and real landfill leachate.展开更多
The current deep learning models for braced excavation cannot predict deformation from the beginning of excavation due to the need for a substantial corpus of sufficient historical data for training purposes.To addres...The current deep learning models for braced excavation cannot predict deformation from the beginning of excavation due to the need for a substantial corpus of sufficient historical data for training purposes.To address this issue,this study proposes a transfer learning model based on a sequence-to-sequence twodimensional(2D)convolutional long short-term memory neural network(S2SCL2D).The model can use the existing data from other adjacent similar excavations to achieve wall deflection prediction once a limited amount of monitoring data from the target excavation has been recorded.In the absence of adjacent excavation data,numerical simulation data from the target project can be employed instead.A weight update strategy is proposed to improve the prediction accuracy by integrating the stochastic gradient masking with an early stopping mechanism.To illustrate the proposed methodology,an excavation project in Hangzhou,China is adopted.The proposed deep transfer learning model,which uses either adjacent excavation data or numerical simulation data as the source domain,shows a significant improvement in performance when compared to the non-transfer learning model.Using the simulation data from the target project even leads to better prediction performance than using the actual monitoring data from other adjacent excavations.The results demonstrate that the proposed model can reasonably predict the deformation with limited data from the target project.展开更多
In radiology,magnetic resonance imaging(MRI)is an essential diagnostic tool that provides detailed images of a patient’s anatomical and physiological structures.MRI is particularly effective for detecting soft tissue...In radiology,magnetic resonance imaging(MRI)is an essential diagnostic tool that provides detailed images of a patient’s anatomical and physiological structures.MRI is particularly effective for detecting soft tissue anomalies.Traditionally,radiologists manually interpret these images,which can be labor-intensive and time-consuming due to the vast amount of data.To address this challenge,machine learning,and deep learning approaches can be utilized to improve the accuracy and efficiency of anomaly detection in MRI scans.This manuscript presents the use of the Deep AlexNet50 model for MRI classification with discriminative learning methods.There are three stages for learning;in the first stage,the whole dataset is used to learn the features.In the second stage,some layers of AlexNet50 are frozen with an augmented dataset,and in the third stage,AlexNet50 with an augmented dataset with the augmented dataset.This method used three publicly available MRI classification datasets:Harvard whole brain atlas(HWBA-dataset),the School of Biomedical Engineering of Southern Medical University(SMU-dataset),and The National Institute of Neuroscience and Hospitals brain MRI dataset(NINS-dataset)for analysis.Various hyperparameter optimizers like Adam,stochastic gradient descent(SGD),Root mean square propagation(RMS prop),Adamax,and AdamW have been used to compare the performance of the learning process.HWBA-dataset registers maximum classification performance.We evaluated the performance of the proposed classification model using several quantitative metrics,achieving an average accuracy of 98%.展开更多
Thermally activated delayed fluorescence(TADF)materials driven by a through-space charge transfer(TSCT)mechanism have garnered wide interest.However,access of TSCT-TADF molecules with longwavelength emission remains a...Thermally activated delayed fluorescence(TADF)materials driven by a through-space charge transfer(TSCT)mechanism have garnered wide interest.However,access of TSCT-TADF molecules with longwavelength emission remains a formidable challenge.In this study,we introduce a novel V-type DA-D-A’emitter,Trz-mCzCbCz,by using a carborane scaffold.This design strategically incorporates carbazole(Cz)and 2,4,6-triphenyl-1,3,5-triazine(Trz)as donor and acceptor moieties,respectively.Theoretical calculations alongside experimental validations affirm the typical TSCT-TADF characteristics of this luminogen.Owing to the unique structural and electronic attributes of carboranes,Trz-mCzCbCz exhibits an orange-red emission,markedly diverging from the traditional blue-to-green emissions observed in classical Cz and Trz-based TADF molecules.Moreover,bright emission in aggregates was observed for Trz-mCzCbCz with absolute photoluminescence quantum yield(PLQY)of up to 88.8%.As such,we have successfully fabricated five organic light-emitting diodes(OLEDs)by utilizing Trz-mCzCbCz as the emitting layer.It is important to note that both the reverse intersystem crossing process and the TADF properties are profoundly influenced by host materials.The fabricated OLED devices reached a maximum external quantum efficiency(EQE)of 12.7%,with an emission peak at 592 nm.This represents the highest recorded efficiency for TSCT-TADF OLEDs employing carborane derivatives as emitting layers.展开更多
The overall heat transfer coefficient(OHTC)of rock fractures is a fundamental parameter for characterizing the heat transfer behavior of rock fractures in hot dry rock(HDR)geothermal mining.Although a number of practi...The overall heat transfer coefficient(OHTC)of rock fractures is a fundamental parameter for characterizing the heat transfer behavior of rock fractures in hot dry rock(HDR)geothermal mining.Although a number of practical formulae for heat transfer coefficients have been developed in the literature,there is still no widely accepted analytical solution.This paper constructs highly accurate analytical solutions for the temperatures of the inner fracture wall and the fluid.Then they are employed to develop new definition-based formulae(formula A and its simplification formula B)of the OHTC,which are well validated by the experimental and numerical simulation results.An empirical correlation formula of heat transfer coefficient is proposed based on the definition-based formulae which can be directly used in the numerical simulations of heat transfer in rock fractures.A site-scale application example of numerical simulation also demonstrates the effectiveness of the empirical correlation formula.展开更多
文摘A novel method for synthesis of quinazoline through the hydrogen transfer/annulation reaction using 2-nitrobenzyl alcohol and benzylamine as starting materials is presented.The reaction is catalyzed by a ruthenium(II)complex bearing a N-heterocyclic carbene nitrogen phosphine(CNP)ligand.The pronouncedα-donating capacity of the carbene within the CNP ligand of the catalyst plays a crucial role in stabilizing the catalytically active species.Additionally,the hemilability of the nitrogen facilitates the creation of coordination vacancies,which are essential for the activation of reaction substrate molecules.The synergistic interplay between these two functionalities markedly enhances catalytic efficiency.This catalytic system shows the significant catalytic activity and selectivity,along with a broad substrate adaptability.All substrates yield the target product in good to excellent yields with the maximum yield reaching 95%.Control experiments have substantiated that benzaldehyde and phenylmethanimine may serve as intermediates in the reaction,thereby reinforcing the role of benzylamine as both a hydrogen donor and a nitrogen source in the process.
基金financially supported by the National Natural Science Foundation of China(No.21572271).
文摘A[3+4]annulation of α-substituted allenes and Schiff bases is reported.This methodology serves as a conduit for the construction of a series of biologically important benzazepine derivatives in good to excellent yields under mild conditions by an unprecedented mode involving β’-carbon of α-substituted allenes and the proposed mechanism is supported by capturing the intermediate.Moreover,this class of benzazepine derivatives exhibited potential ability of cytotoxicity toward cancer cells.
基金support from the National Natural Science Foundation of China(Nos.22061017 and21862006)the Science and Technology program of Gansu Province(Nos.22YF7GG127 and 23JRRG0002)+1 种基金National innovative training program for college students(No.202310740015)the Open Project Funding of Hubei Key Laboratory of Processing and Application of Catalytic materials(No.202306004)。
文摘Designing efficient,recyclable,and low-cost catalysts is crucial for the synthesis of quinoxaline derivatives.In this context,a novel N-stable Co_(2)P nano-catalyst(CoP@N–C-1.5)was developed using a templatesacrificial approach.The catalyst demonstrated a broad substrate scope and good functional group tolerance,achieving yields of up to 84%.Additionally,the catalyst exhibited reusability and can be recycled up to three times.The CoP@N–C-1.5 was characterized using X-ray powder diffraction(XRD),scanning electron microscopy(SEM),and transmission electron microscopy(TEM).The results indicated that the catalyst contained Co2P nanoparticles.The X-ray photoelectron spectroscopy(XPS)further confirms the presence of Co-P.Analysis of the characterization data and experimental results revealed that the active site of the catalyst comprises N-stable Co_(2)P nanoparticles.
基金financially supported by National Natural Science Foundation of China(No.22161022).
文摘Chromones serve as versatile heterocyclic scaffolds and are common core structural units in a variety of natural products and bioactive organic molecules.This area of research,at the forefront of organic synthesis,has seen remarkable progress in recent years.Among the various synthetic methodologies for accessing chromone scaffolds,the tandem annulation of o-hydroxyaryl enaminones has emerged as a robust and practical strategy.This approach,through direct vinyl C-H bond functionalization of o-hydroxyaryl enaminones,enables the construction of structurally diverse chromones(including 3-substituted chromones,2-substituted chromones,and 2,3-disubstituted chromones)and their derivatives since mid-2019.In this review,we highlight recent advances in the synthesis of various types of chromones and their derivatives,achieved through tandem direct vinyl C-H activation and chromone annulation of o-hydroxyaryl enaminones.
基金the National Natural Science Foundation of China(Nos.22171147 and 21871148)for the financial support。
文摘Polycyclic compounds are widely found in natural products and drug molecules with important biological activities,which attracted the attention of many chemists.Phosphine-catalyzed nucleophilic addition is one of the most powerful tools for the construction of various cyclic compounds with the advantages of atom economy,mild reaction conditions and simplicity of operation.Allenolates,Morita−Baylis−Hillman(MBH)alcohols and their derivatives(MBHADs),electron-deficient olefins and alkynes are very efficient substrates in phosphine mediated annulations,which formed many phosphonium species such asβ-phosphonium enolates,β-phosphonium dienolates and vinyl phosphonium ylides as intermediates.This review describes the reactivities of these phosphonium zwitterions and summarizes the synthesis of polycycle compounds through phosphine-mediated intramolecular and intermolecular sequential annulations.Thus,a systematic summary of the research process based on the phosphine-mediated sequential annulations of allenolates,MBH alcohols and MBHADs,electron-deficient olefins and alkynes are presented in Chapters 2-6,respectively.
基金National Natural Science Foundation of China(Nos.21971090 and 22271123)the NSF of Jiangsu Province(No.BK20230201)+1 种基金the Natural Science Foundation of Jiangsu Education Committee(No.22KJB150024)the Natural Science Foundation of Jiangsu Normal University(No.21XSRX010)。
文摘A new oxidative N-heterocyclic carbene(NHC)-catalyzed high-order[7+3]annulation reaction ofγ-indolyl phenols as 1,7-dinucleophiles andα,β-alkynals with the aid of Sc(OTf)_(3)is reported,enabling the highly regioselective access to unprecedented polyarene-fused ten-membered lactams bearing a bridged aryl-aryl-indole scaffold in moderate to good yields.This protocol demonstrates a broad substrate scope,good compatibility with substituents and complete regioselectivity,providing an organocatalytic modular synthetic strategy for creating medium-sized lactams.
基金the National Natural Science Foundation of China(22208320)the Science and Technology Program of Henan Province(212102210044)The Henan Association for Science and Technology Youth Talent Support Program(2022HYTP026).
文摘Combining the advantages of high efficiency,low-pressure drop,and large throughput,the pore arrayenhanced tube-in-tube microchannel(PA-TMC) is a promising microreactor for industrial applications.However,most of the mass transfer takes place in the upstream pore region,while the contribution of the downstream annulus is limited.In this work,helical wires were introduced into the annulus by adhering to the outer surface of the inner tube.Mixing behavior and mass transfer of liquid-liquid twophase flow in PA-TMC with different helical wires have been systematically studied by a combination of experiments and volume of fluid(VOF) method.The introduction of helical wires improves the overall volumetric mass transfer coefficient KLa by up to 133% and the mass transfer efficiency E by up to 117%.The simulation results show that the helical wire brings extra phase mixing regions and increases the specific interface area,while accelerating the fluid flow and expanding the area of enhanced turbulent dissipation rate.Influences of helical wires in various configurations are compared by the comprehensive index I concerning the pressure drop and mass transfer performance simultaneously and a new correlation between KLa and specific energy consumption φ is proposed.This research deepens the understanding of the mixing behavior and mass transfer in the PA-TMCs and provides practical experience for the process intensification of microchannel reactors.
基金financial support from the schoollevel research projects of Yancheng Institute of Technology(No.xjr2020044)the National Natural Science Foundation of China(Nos.22101152,22271123 and 21971090)。
文摘Catalytic C–H activation-initiated annulation reactions have emerged as a versatile strategy for the efficient construction of diverse ring structural units and complex cyclic molecules in synthetic chemistry.Herein,we describe a new Rh(Ⅲ)-catalyzed C–H activation-initiated transdiannulation reaction of N,Ndimethyl enaminones with gem-difluorocyclopropenes in the presence of H_(2)O,enabling a facile and oxygen transfer access to ring-fluorinated tricyclicγ-lactones with a 6-5 ring-junction tetrasubstituted stereocenter.This approach features bond-forming/annulation efficiency,good functional group tolerance and complete regioselectivity,which may include a complex process consisting of Rh(Ⅲ)-catalyzed C(sp2)–H activation,cyclic alkene insertion,defluorinated ring-opening of gem-difluorocyclopropane,intramolecular oxygen transfer,intramolecular cyclization and oxidative hydration.
基金financial support from the National Natural Science Foundation of China(Nos.22261013 and 22001049)Guangxi Natural Science Foundation(No.2020GXNSFBA297003)Magneto-Chemical Functional Materials(No.EMFM20221102)。
文摘Rhodium-catalyzed C4aryl-H activation and ring-retentive annulation of 2H-imidazoles with internal alkynes to build imidazo[5,1-a]isoquinolinium salts with high yields and broad scope has been disclosed.These novel salts serve as new full-color emissive fluorophores(433-633 nm),just by simply modifying the substituents on C3 and C4 positions of isoquinoline ring.Furthermore,these salts can undergo ring-opening C5_(aryl)-H activation/annulation with a different alkyne to form non-symmetric and AIE-active1,1-biisoquinolines,where NH_(4)OAc plays an indispensable role that accounts for Hofmann elimination and imine formation,leading to an unprecedented imine dance:cyclic imine→N-alkenyl imine→NH imine.The15N labelling experiments indicate that the 2ndannulation includes two pathways:N-exchange(major)and N-retention(minor).
文摘A[4+4]annulation reaction for the construction of medium-sized N-heterocycles is reported.This process involves the generation of all-carbon 1,4-dipoles containing aπ-allylpalladium complex from Morita-Baylis-Hillman(MBH)carbonates under the catalysis of Pd/Synphos,which then undergo Michael addition/N-allylic alkylation with 1-azadienes.A spectrum of eight-membered N-heterocycles featuring a trisubstituted exo-cyclic double bond is furnished efficiently with moderate to good E/Z selectivity and moderate atroposelectivity.In addition,moderate enantioselectivity can be realized by using a chiral ligand or with the assistant of a chiral quaternary ammonium salt.
文摘A new photocatalytic annulative acylative difunctionalization of 1,6-enynes is reported,enabling stereoselective access to acylated 1-indanones with cyclic quaternary centers in moderate to good yields.This photocatalysis enables two types of acylation of unsaturated hydrocarbons by adjusting the categories of acyl radical precursors.Aroyl chlorides as bifunctional reagents react with 1,6-enynes to realize annulative chloroacylation,while acyl oxime esters are used as acyl radical precursors,which undergo a three-component annulative alkoxyacylation by treatment with 1,6-enynes and alcohols.The current method demonstrates good functional group compatibility,a broad substrate scope and mild reaction conditions.
文摘The Rh(III)-catalyzed C—H functionalization of sulfoxonium ylides and successively annulation with two classes of cyclic diazo compounds has been realized,affording structurally diverse fused-ring or spirocyclic compounds under redoxneutral conditions.The reaction proceeds via successive chelation-assisted C—H activation,carbene insertion,and intramolecular[3+3]/[4+1]annulation processes.
基金supported by National Natural Science Foundation of China(NSFC,22338006,92356301,9235630033 and 22375062)Shanghai Municipal Science and Technology Major Project(21JC1401700)+4 种基金Shanghai Pilot Program for Basic Research(22TQ1400100-10)Fundamental Research Funds for the Central UniversitiesShanghai Pujiang Program(22PJ1402400)“Chenguang Program”supported by Shanghai Education Development Foundation and Shanghai Municipal Education Commission(22CGA32)the Young Elite Scientists Sponsorship Program by CAST(2023QNRC001).
文摘Organic nanophotocatalysts are promising candidates for solar fuels production,but they still face the challenge of unfavorable geminate recombination due to the limited exciton diffusion lengths.Here,we introduce a binary nanophotocatalyst fabricated by blending two polymers,PS-PEG5(PS)and PBT-PEG5(PBT),with matched absorption and emission spectra,enabling a Forster resonance energy transfer(FRET)process for enhanced photocatalysis.These heterostructure nanophotocatalysts are processed using a facile and scalable flash nanoprecipitation(FNP)technique with precious kinetic control over binary nanoparticle formation.The resulting nanoparticles exhibit an exceptional photocatalytic hydrogen evolution rate up to 65 mmol g^(-1) h^(-1),2.5 times higher than that single component nanoparticles.Characterizations through fluorescence spectra and transient absorption spectra confirm the hetero-energy transfer within the binary nanoparticles,which prolongs the excited-state lifetime and extends the namely“effective exciton diffusion length”.Our finding opens new avenues for designing efficient organic photocatalysts by improving exciton migration.
基金supported by the National Defense Fundamental Research Project(No.JCKY2022404C005)the Nuclear Energy Development Project(No.23ZG6106)+1 种基金the Sichuan Scientific and Technological Achievements Transfer and Transformation Demonstration Project(No.2023ZHCG0026)the Mianyang Applied Technology Research and Development Project(No.2021ZYZF1005)。
文摘In scenarios such as vehicle radiation monitoring and unmanned aerial vehicle radiation detection,rapid measurements using a NaI(Tl)detector often result in low photon counts,weak characteristic peaks,and significant statistical fluctuations.These issues can lead to potential failures in peak-searching-based identification methods.To address the low precision associated with short-duration measurements of radionuclides,this paper proposes an identification algorithm that leverages heterogeneous spectral transfer to develop a low-count energy spectral identification model.Comparative experiments demonstrated that transferring samples from 26 classes of simulated heterogeneous gamma spectra aids in creating a reliable model for measured gamma spectra.With only 10%of target domain samples used for training,the accuracy on real low-count spectral samples was 95.56%.This performance shows a significant improvement over widely employed full-spectrum analysis methods trained on target domain samples.The proposed method also exhibits strong generalization capabilities,effectively mitigating overfitting issues in low-count energy spectral classification under short-duration measurements.
基金supported by the National Natural Science Foundation of China(No.21876039)Y.Yao acknowledges the scholarship support from the China Scholarship Council(No.202106695010)Partial support from the Australian Research Council for DP230102406 is also acknowledged.
文摘Catalytic oxidation of organic pollutants is a well-known and effective technique for pollutant abatement.Unfortunately,this method is significantly hindered in practical applications by the lowefficiency and difficult recovery of the catalysts in a powdery form.Herein,a three-dimensional(3D)framework of Fe-incorporated Ni_(3)S_(2)nanosheets in-situ grown on Ni foam(Fe-Ni_(3)S_(2)@NF)was fabricated by a facile two-step hydrothermal process and applied to trigger peroxymonosulfate(PMS)oxidation of organic compounds inwater.A homogeneous growth environment enabled the uniform and scalable growth of Fe-Ni_(3)S_(2)nanosheets on the Ni foam.Fe-Ni_(3)S_(2)@NF possessed outstanding activity and durability in activating PMS,as it effectively facilitated electron transfer from organic pollutants to PMS.Fe-Ni_(3)S_(2)@NF initially supplied electrons to PMS,causing the catalyst to undergo oxidation,and subsequently accepted electrons from organic compounds,returning to its initial state.The introduction of Fe into the Ni_(3)S_(2)lattice enhanced electrical conductivity,promoting mediated electron transfer between PMS and organic compounds.The 3D conductive Ni foam provided an ideal platform for the nucleation and growth of Fe-Ni_(3)S_(2),accelerating pollutant abatement due to its porous structure and high conductivity.Furthermore,its monolithic nature simplified the catalyst recycling process.A continuous flow packed-bed reactor by encapsulating Fe-Ni_(3)S_(2)@NF catalyst achieved complete pollutant abatement with continuous operation for 240 h,highlighting its immense potential for practical environmental remediation.This study presents a facile synthesis method for creating a novel type of monolithic catalyst with high activity and durability for decontamination through Fenton-like processes.
基金financially supported by the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(No.2019QZKK1003)the Science and Technology Innovation Pro-gram of Hunan Province(No.2022RC1122)。
文摘Layered double hydroxide(LDH)based heterogonous peroxymonosulfate(PMS)activation degradation of pollutants has attracted extensive attention.The challenge is to selectively regulate the traditional free radical dominant degradation pathway into a nonradical degradation pathway.Herein,an interface ar-chitecture of Ti_(3) C_(2) T_(x)-MXene(MXene)loading on the Fe-Al LDH scaffold was developed,which showed excellent stability and robust resistance against harsh conditions.Significantly,the rate constant for tetra-cycline hydrochloride(TC)degradation in the MXene-LDH/PMS process was 0.421 min^(-1),which was ten times faster than the rate constant for pure Fe-Al LDH(0.042 min^(-1)).Specifically,more reactive Fe with the closer d-band center to the Fermi level results in higher electron transfer efficiency.The occupa-tions of Fe-3d orbitals in Mxene/Fe-Al LDH are pushed above the Fermi level to generate,which results in higher PMS adsorption and inhibition of the release of oxygen-containing active species intermedi-ates,leading to the enhanced^(1)O_(2) generation.Additionally,the built-in electric field in the heterojunc-tion was driven by the charge redistribution between MXene and Fe-Al LDH,resulting in a mediated-electron transfer mechanism,differentiating it from the Fe-Al LDH/PMS system.It was fascinating that MXene/Fe-Al LDH achieved satisfactory treatment efficiency in continuous column reactor and real landfill leachate.
基金supported by the National Key Research and Development Program of China(Grant No.2023YFC3009400)the National Natural Science Foundation of China(Grant Nos.42307218 and U2239251).
文摘The current deep learning models for braced excavation cannot predict deformation from the beginning of excavation due to the need for a substantial corpus of sufficient historical data for training purposes.To address this issue,this study proposes a transfer learning model based on a sequence-to-sequence twodimensional(2D)convolutional long short-term memory neural network(S2SCL2D).The model can use the existing data from other adjacent similar excavations to achieve wall deflection prediction once a limited amount of monitoring data from the target excavation has been recorded.In the absence of adjacent excavation data,numerical simulation data from the target project can be employed instead.A weight update strategy is proposed to improve the prediction accuracy by integrating the stochastic gradient masking with an early stopping mechanism.To illustrate the proposed methodology,an excavation project in Hangzhou,China is adopted.The proposed deep transfer learning model,which uses either adjacent excavation data or numerical simulation data as the source domain,shows a significant improvement in performance when compared to the non-transfer learning model.Using the simulation data from the target project even leads to better prediction performance than using the actual monitoring data from other adjacent excavations.The results demonstrate that the proposed model can reasonably predict the deformation with limited data from the target project.
文摘In radiology,magnetic resonance imaging(MRI)is an essential diagnostic tool that provides detailed images of a patient’s anatomical and physiological structures.MRI is particularly effective for detecting soft tissue anomalies.Traditionally,radiologists manually interpret these images,which can be labor-intensive and time-consuming due to the vast amount of data.To address this challenge,machine learning,and deep learning approaches can be utilized to improve the accuracy and efficiency of anomaly detection in MRI scans.This manuscript presents the use of the Deep AlexNet50 model for MRI classification with discriminative learning methods.There are three stages for learning;in the first stage,the whole dataset is used to learn the features.In the second stage,some layers of AlexNet50 are frozen with an augmented dataset,and in the third stage,AlexNet50 with an augmented dataset with the augmented dataset.This method used three publicly available MRI classification datasets:Harvard whole brain atlas(HWBA-dataset),the School of Biomedical Engineering of Southern Medical University(SMU-dataset),and The National Institute of Neuroscience and Hospitals brain MRI dataset(NINS-dataset)for analysis.Various hyperparameter optimizers like Adam,stochastic gradient descent(SGD),Root mean square propagation(RMS prop),Adamax,and AdamW have been used to compare the performance of the learning process.HWBA-dataset registers maximum classification performance.We evaluated the performance of the proposed classification model using several quantitative metrics,achieving an average accuracy of 98%.
基金supported by the Natural Science Foundation of Jiangsu Province(No.BZ2022007)the National Natural Science Foundation of China(No.92261202)+1 种基金the Ministry of Science and Technology of the People’s Republic of China(No.2021YFE0114800)the Ministry of Science and Higher Education of the Russian Federation(No.075-15-2021-1027).
文摘Thermally activated delayed fluorescence(TADF)materials driven by a through-space charge transfer(TSCT)mechanism have garnered wide interest.However,access of TSCT-TADF molecules with longwavelength emission remains a formidable challenge.In this study,we introduce a novel V-type DA-D-A’emitter,Trz-mCzCbCz,by using a carborane scaffold.This design strategically incorporates carbazole(Cz)and 2,4,6-triphenyl-1,3,5-triazine(Trz)as donor and acceptor moieties,respectively.Theoretical calculations alongside experimental validations affirm the typical TSCT-TADF characteristics of this luminogen.Owing to the unique structural and electronic attributes of carboranes,Trz-mCzCbCz exhibits an orange-red emission,markedly diverging from the traditional blue-to-green emissions observed in classical Cz and Trz-based TADF molecules.Moreover,bright emission in aggregates was observed for Trz-mCzCbCz with absolute photoluminescence quantum yield(PLQY)of up to 88.8%.As such,we have successfully fabricated five organic light-emitting diodes(OLEDs)by utilizing Trz-mCzCbCz as the emitting layer.It is important to note that both the reverse intersystem crossing process and the TADF properties are profoundly influenced by host materials.The fabricated OLED devices reached a maximum external quantum efficiency(EQE)of 12.7%,with an emission peak at 592 nm.This represents the highest recorded efficiency for TSCT-TADF OLEDs employing carborane derivatives as emitting layers.
基金support of this work by the National Natural Science Foundation of China (Grant Nos.41972316 and 41672252).
文摘The overall heat transfer coefficient(OHTC)of rock fractures is a fundamental parameter for characterizing the heat transfer behavior of rock fractures in hot dry rock(HDR)geothermal mining.Although a number of practical formulae for heat transfer coefficients have been developed in the literature,there is still no widely accepted analytical solution.This paper constructs highly accurate analytical solutions for the temperatures of the inner fracture wall and the fluid.Then they are employed to develop new definition-based formulae(formula A and its simplification formula B)of the OHTC,which are well validated by the experimental and numerical simulation results.An empirical correlation formula of heat transfer coefficient is proposed based on the definition-based formulae which can be directly used in the numerical simulations of heat transfer in rock fractures.A site-scale application example of numerical simulation also demonstrates the effectiveness of the empirical correlation formula.
