In the paper entitled"Efficient adsorption of Mn(Ⅱ)by layered double hydroxides intercalated with di ethylenetriaminepentaacetic acid and the mechanistic study"in Journal of Environmental Sciences,volume 85...In the paper entitled"Efficient adsorption of Mn(Ⅱ)by layered double hydroxides intercalated with di ethylenetriaminepentaacetic acid and the mechanistic study"in Journal of Environmental Sciences,volume 85,page 56-65,there were problems with mathematical notation and dimensional errors in the calculation for Giibbs free energy.In Section 2.5:Adsorption isotherms and thermodynamics studies,authors calculated the Gibbs free energy change(△G°)展开更多
Objective To observe the effects of low expressed Angiotensin-converting enzyme 2(Ace2) gene on senescence related signals of alveolar typeⅡepithelial cells in silicotic mice.Methods In March 2022,20 8-12W SPF male w...Objective To observe the effects of low expressed Angiotensin-converting enzyme 2(Ace2) gene on senescence related signals of alveolar typeⅡepithelial cells in silicotic mice.Methods In March 2022,20 8-12W SPF male wild-type C57BL/6 mice and 20 Ace2 gene knockdown mice(Ace2^(+/-),C57BL/6 background) were randomly divided into wild-type control group Ace2 low expression group,wild-type silicosis group,Ace2 low expression silicosis group,with 10 mice in each group.展开更多
Mechanistic studies of the cleavage and transformation of unactivated C_(sp3)-H bonds are a significant field of chemistry.Overcoming the inherent low acidity of C-H bonds to activate the inert substrates is challenge...Mechanistic studies of the cleavage and transformation of unactivated C_(sp3)-H bonds are a significant field of chemistry.Overcoming the inherent low acidity of C-H bonds to activate the inert substrates is challenge under mild conditions.And their complex multi-step transformations may also hinder mechanistic understanding.Herein,we perform theoretical calculations and experimental studies to explore the C_(sp3)-H bonds activation and acylation mechanisms of toluene/thioether using the relatively weak base LDA.A synergistic"main and auxiliary"model was revealed involving dual lithium metal by LDA dimers,and the aryl dilithium species as an intermediate base can facilitate C_(sp3)-H activation.This model not only aids in understanding the acidity of unactivated C_(sp3)-H bonds and the nucleophilicity of their conjugate bases for their kinetic control through cooperative interactions,but also predicts unusual kinetic isotope effects(KIE)for newly designed 2-(methylthio)naphthalene that are experimentally validated.This research is expected to provide a crucial scenario for the cleavage and transformation of unactivated C_(sp3)-H bonds and the development of new functionalities for alkali metal reagents.展开更多
Photolysis of benzyl phenylacetate (ACO_2A), benzyl p-methylphenylacetate (BCO_2A) and 1-naphthyl phenylacetate (ACO_2Np) in homogeneous and micellar solutions results in products typical of radical coupling reactions...Photolysis of benzyl phenylacetate (ACO_2A), benzyl p-methylphenylacetate (BCO_2A) and 1-naphthyl phenylacetate (ACO_2Np) in homogeneous and micellar solutions results in products typical of radical coupling reactions and loss of carbon dioxide. The cage effects upon direct photolysis of these esters in acetonitrile are significantly greater than zero and those in SDS or HDTBr micellar solutions are even greater. In the triplet sensitization reaction of ACO_2 Np in micellar solutions the cage effects are smaller than those obtained upon direct irradiation. However, the application of a 0.05 or 0.2 T external magnetic field in the photolysis in micellar solutions decreases the cage effects dramatically. All these results suggest that the photoextrusions of carbon dioxide from these esters proceed via radical intermediates, and upon direct photolysis the reactive states for the cleavage re- action involve both singlet and triplet excited states.展开更多
The synthesis of phosphine compounds through the addition reaction of H-[P(O)]species to olefins and alkynes has been extensively studied.Two different mechanisms of the addition of H-[P(O)]species to non-activated al...The synthesis of phosphine compounds through the addition reaction of H-[P(O)]species to olefins and alkynes has been extensively studied.Two different mechanisms of the addition of H-[P(O)]species to non-activated alkyne are mainly summarized.One is the oxidative addition-migration insertion-reductive elimination mechanism,namely the Chalk-Harrod type mechanism,and the other is the proton transfer-reductive elimination mechanism.This review elaborates on the specific steps of each mechanism,and discusses experimental and computational evidence supporting these steps.Additionally,a few other types of mechanisms are briefly mentioned.The mechanism of H-[P(O)]reaction with relevant conjugated dienes was also involved when closely related.展开更多
Hymoins A–C(1–3),three unusual polycyclic polyprenylated acylphloroglucinols(PPAPs)were isolated from the flowers of Hypericum monogynum.Hymoin A features the first intriguing 6/5/5/5/7 pentacyclic caged PPAP.Hymoin...Hymoins A–C(1–3),three unusual polycyclic polyprenylated acylphloroglucinols(PPAPs)were isolated from the flowers of Hypericum monogynum.Hymoin A features the first intriguing 6/5/5/5/7 pentacyclic caged PPAP.Hymoin B is characterized by an unprecedented rearranged 5/6/8 tricyclic ring system,while hymoin C represents the first rearranged PPAP with a fantastic spirocyclic 5/6/7 ring system.Their structures were established by extensive spectroscopic analysis,X-ray crystallography,and computational methods.The plausible biosynthetic routes for the compounds were also proposed.In oleic acid(OA)-induced HepG2 cells,all compounds exhibited significant lipid-lowering activity at the concentrations of 2–8μmol/L.Further mechanistic study implied that compound 1 exhibited excellent lipid-lowering activity in OA-induced HepG2 cells through inhibiting the proteins of free fatty acids synthesis and improving lipidolysis.展开更多
Electrocatalytic CO_(2) reduction(ECR)is a promising approach to converting CO_(2) into chemicals and fuels.Among the ECR products,C_(2) products such as ethylene,ethanol,and acetate have been extensively studied due ...Electrocatalytic CO_(2) reduction(ECR)is a promising approach to converting CO_(2) into chemicals and fuels.Among the ECR products,C_(2) products such as ethylene,ethanol,and acetate have been extensively studied due to their high industrial demands.However,the mechanistic understanding of C_(2) product formation remains unclear due to the lack of in situ or operando measurements that can observe the complex and instantaneous atomic evolutions of adsorbates at the electrode/electrolyte interface.Moreover,the sensitivity of ECR reactions to variations at the interface further widens the gap between mechanistic understanding and performance enhancement.To bridge this gap,first-principle studies provide insights into how the interface influences ECR.In this study,we present a review of mechanistic studies investigating the effects of various factors at the interface,with an emphasis on the C_(2) product formation.We begin by introducing ECR and the essential metrics.Next,we discuss the factors classified by their components at the interface,namely,electrocatalyst,electrolyte,and adsorbates,respectively,and their effects on the C_(2) product formation.Due to the interplay among these factors,we aim to deconvolute the influence of each factor and clearly demonstrate their impacts.Finally,we outline the promising directions for mechanistic studies of C_(2) products.展开更多
The development of new catalytic techniques for wastewater treatment has long attracted much attention from industrial and academic communities.However,because of catalyst leaching during degradation,catalysts can be ...The development of new catalytic techniques for wastewater treatment has long attracted much attention from industrial and academic communities.However,because of catalyst leaching during degradation,catalysts can be short lived,and therefore expensive,and unsuitable for use in wastewater treatment.In this work,we developed a bimetallic CuO-Co3O4@γ-Al2O3 catalyst for phenol degradation with bicarbonate-activated H2O2.The weakly basic environment provided by the bicarbonate buffer greatly suppresses leaching of active Cu and Co metal ions from the catalyst.X-ray diffraction and X-ray photoelectron spectroscopy results showed interactions between Cu and Co ions in the CuO-Co3O4@γ-Al2O3 catalyst,and these improve the catalytic activity in phenol degradation.Mechanistic studies using different radical scavengers showed that superoxide and hydroxyl radicals both played significant roles in phenol degradation,whereas singlet oxygen was less important.展开更多
MCRs for preparation of chromenopyridines under reflux conditions and chromenes at room temperature conditions from different salicylaldehydes,malononitrile and different thiols（mol ratio- 1：2：1） were established....MCRs for preparation of chromenopyridines under reflux conditions and chromenes at room temperature conditions from different salicylaldehydes,malononitrile and different thiols（mol ratio- 1：2：1） were established.Mechanistic investigation suggests that the MCRs undergo different pathways at different temperatures and catalyzed by different organic bases.The structure of chromenopyridine and chromene are confirmed by crystal X-ray crystallography.展开更多
High valent iron complexes Fe-X have been known to transfer their X group toward carbon radical species to form R–X bond.To utilize this capability of iron catalyst,novel photo-induced iron catalysis system had been ...High valent iron complexes Fe-X have been known to transfer their X group toward carbon radical species to form R–X bond.To utilize this capability of iron catalyst,novel photo-induced iron catalysis system had been developed in the difunctionalization of alkenes in the presence of radical initiator.However,the details of the reaction mechanism are still unclear,especially the transformations of the photocatalyst and the iron catalyst during the catalytic turnover.Herein,we expanded the photo-driven non-heme iron complex catalyzed thiocyanation of styrene substrate.This protocol exhibited broad substrate scope and high efficiency.Detailed mechanistic studies using various spectroscopies,such as UV-vis,mass spectrometry,transient absorption spectroscopy and X-ray absorption spectroscopy,revealed the transformations of photocatalyst[Ir^(Ⅲ)(ppy)_(3)]and group transfer catalyst[Fe^(Ⅱ)(bpmen)]^(2+).Real-time spectroscopies combined with mechanistic experiments demonstrated that[Ir^(Ⅳ)(ppy)_(3)]^(+)and[Fe^(Ⅲ)(bpmen)]^(3+)were the key intermediates involved in the reaction cycle.展开更多
Objective: To investigate the effective compounds, potential targets and molecular mechanism of Kanglaite injection (KLTi) in the treatment of Non-Small Cell Lung Cancer (NSCLC) based on network pharmacology. Methods:...Objective: To investigate the effective compounds, potential targets and molecular mechanism of Kanglaite injection (KLTi) in the treatment of Non-Small Cell Lung Cancer (NSCLC) based on network pharmacology. Methods: The active compounds and targets of KLTi which extracted and isolated from Coix Seed were screened by Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform (TCMSP). The related genes of NSCLC were obtained by searching the Human Gene Database (GeneCards) and Online Mendelian Inheritance in Man (OMIM). The candidate targets of KLTi in the treatment of NSCLC were obtained after extracting the intersection network. The "drug-component-target-disease" network was constructed with the help of Cytoscape 3.7.2. The Protein- Protein Interaction networks were constructed on the STRING platform and core network modules were screened. The Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis of candidate genes were performed using Metascape platform, and a "pathway-target- compounds" network was constructed to further screen key genes and active compounds. Results: A total of 11 compounds, 22 candidate targets, 206 GO functions and 12 KEGG pathways were obtained. Conclusion: The active compounds of KLTi in the treatment of NSCLC are stigmasterol, stigmasterol α1 and ergosterol. The key targets are PGR, NCOA2, PTGS2, NR3C2, and PTGS1. The core GO functions included receptor activity and binding, neuronal signal transmission and hormone stimulation;KEGG mainly involves cancer pathways, neuroactive ligand-receptor interactions and calcium signaling pathways. This study reveals the molecular biological mechanism of KLTi in the treatment of NSCLC, which is speculated to be related to neuroendocrine, providing a new basis and therapeutic direction for subsequent clinical application and experimental research.展开更多
This paper discloses the reaction mechanism of two consecutive but different visible light photo-induced chain processes for the rapid construction of spirobi[indene]skeletons.The first process is triggered by a photo...This paper discloses the reaction mechanism of two consecutive but different visible light photo-induced chain processes for the rapid construction of spirobi[indene]skeletons.The first process is triggered by a photo-induced single-electron-transfer(SET)of an electron donor-accepter(EDA)complex.The second process is initiated by a direct SET process between aryldiazonium salt and the excited allenic intermediate.In these two processes,another SET took place respectively on the in situ formed radical intermediate to realize a redox-neutral outcome.The mechanistic studies have been carried out by control experiments,kinetic and spectroscopic analyses,deuterium labeling experiments to support these two chain processes.展开更多
An aerobic oxidation of aldehydes towards carboxylic acids in MeCN using 1 atm of pure oxygen or oxygen in air as the oxidant and a catalytic amount of single component catalyst, Fe（NO3）3.9H20, has been developed. C...An aerobic oxidation of aldehydes towards carboxylic acids in MeCN using 1 atm of pure oxygen or oxygen in air as the oxidant and a catalytic amount of single component catalyst, Fe（NO3）3.9H20, has been developed. Carboxylic acids with different synthetically useful functional groups were obtained at room temperature. Two mechanistic pathways have been proposed based on isotopic labeling, NMR monitoring, and control experiments. The practicality of this reaction has been demonstrated by conducting several 50 mmol-scale reactions using pure oxygen or an air-flow of -30 mL/min.展开更多
Acceptorless dehydrogenation (AD) that uses non-toxic reagents and produces no waste is a type of catalytic reactions toward green chemistry. Acceptorless alcohol dehydrogenation (AAD) can serve as a key step in const...Acceptorless dehydrogenation (AD) that uses non-toxic reagents and produces no waste is a type of catalytic reactions toward green chemistry. Acceptorless alcohol dehydrogenation (AAD) can serve as a key step in constructing new bonds such as C-C and C-N bonds in which alcohols need to be activated into more reactive ketones or aldehydes. AD reactions also can be utilized for hydrogen production from biomass or its fermentation products (mainly alcohols). Reversible hydrogenation/ dehy-drogenation with hydrogen uptake/release is crucial to realization of the potential organic hydride hydrogen storage. In this article, we review the recent computational mechanistic studies of the AD reactions catalyzed by various transition metal complexes as well as the experimental developments. These reactions include acceptorless alcohol dehydrogenations, reversible dehydrogenation/hydrogenation of nitrogen heterocycles, dehydrogenative coupling reactions of alcohols and amines to construct C-N bonds, and dehydrogenative coupling reactions of alcohols and unsaturated substrates to form C-C bonds. For the catalysts possessing metal-ligand bifunctional active sites (such as 28, 45, 86, 87, and 106 in the paper), the dehydrogenations prefer the "bifunctional double hydrogen transfer" mechanism rather than the generally accepted-H elimination mechanism. However, methanol dehydrogenation involved in the C-C coupling reaction of methanol and allene, catalyzed by the iridium complex 121, takes place via the-H elimination mechanism, because the Lewis basicity of either the-allyl moiety or the carboxyl group of the ligand is too weak to exert high Lewis basic reactivity. Unveiling the catalytic mechanisms of AD reactions could help to develop new catalysts.展开更多
Carbon-supported single-atom catalysts were found to suffer reversible deactivation in catalytic hydrogenation,but the mechanism is still unclear.Herein,nitro compounds hydrogenation catalyzed by N-doped carbon-suppor...Carbon-supported single-atom catalysts were found to suffer reversible deactivation in catalytic hydrogenation,but the mechanism is still unclear.Herein,nitro compounds hydrogenation catalyzed by N-doped carbon-supported Co single atom(Co1/NC)was taken as a model to uncover the mechanism of the reversible deactivation phenomenon.Co1/NC exhibited moderate adsorption towards the substrate molecules(i.e.,nitro compounds or related intermediates),which could be strengthened by the confinement effect from the porous structure.Consequently,substrate molecules tend to accumulate within the pore channel,especially micropores that host Co1,making it difficult for the reactants to access the active sites and finally leading to their deactivation.The situation could be even worse when the substrate molecules possess a large size.Nevertheless,the catalytic activity of Co1/NC could be restored via a simple thermal treatment,which could remove the adsorbates within the pore channel,hence releasing active sites that were originally inaccessible to reactants.展开更多
The Reformatsky reagent derived from ethyl bromoacetate circumvents the challenge associated with the direct regio-and enantioselective iridium-catalyzed allylic alkylation with an unstabilized aliphatic ester enolate...The Reformatsky reagent derived from ethyl bromoacetate circumvents the challenge associated with the direct regio-and enantioselective iridium-catalyzed allylic alkylation with an unstabilized aliphatic ester enolate. Notably, this work represents the first example of using a Reformatsky reagent in a metal-allyl reaction, which permits the direct construction of enantioenriched β-stereogenic homoallylic esters without preactivation of the pronucleophile or post-reaction modification of the product(e.g., thermal decarboxylation of a 1,3-dicarbonyl). Moreover, the process allows the coupling of a broad range of sterically and electronically diverse electrophiles bearing aryl, heteroaryl and alkenyl derivatives, including the significantly more challenging alkyl-substituted allylic carbonates. The versatility of the ester product is exemplified by a series of functional group manipulations and the development of a concise and efficient enantioselective total synthesis of the natural product,(+)-descurainolide A. Finally, mechanistic studies indicate that the zinc enolate behaves as a soft nucleophile that undergoes outer-sphere alkylation.展开更多
Photooxidation provides a promising strategy for removing the dominant indoor pollutant of HCHO,while the underlying photooxidation mechanism is still unclear,especially the exact role of H2O molecules.Herein,we utili...Photooxidation provides a promising strategy for removing the dominant indoor pollutant of HCHO,while the underlying photooxidation mechanism is still unclear,especially the exact role of H2O molecules.Herein,we utilize in-situ spectral techniques to unveil the H2O-mediated HCHO photooxidation mechanism.As an example,the synthetic defective Bi2WO6 ultrathin sheets realize high-rate HCHO photooxidation with the assistance of H2O at room temperature.In-situ electron paramagnetic resonance spectroscopy demonstrates the existence of•OH radicals,possibly stemmed from H2O oxidation by the photoexcited holes.Synchrotron-radiation vacuum ultraviolet photoionization mass spectroscopy and H218O isotope-labeling experiment directly evidence the formed•OH radicals as the source of oxygen atoms,trigger HCHO photooxidation to produce CO2,while in-situ Fourier transform infrared spectroscopy discloses the HCOO*radical is the main photooxidation intermediate.Density-functional-theory calculations further reveal the•OH formation process is the rate-limiting step,strongly verifying the critical role of H2O in promoting HCHO photooxidation.This work first clearly uncovers the H2O-mediated HCHO photooxidation mechanism,holding promise for high-efficiency indoor HCHO removal at ambient conditions.展开更多
The asymmetric hydroxylation of inactive carbon atoms in organic compounds remains an important reaction in the industrial synthesis of valuable chiral compounds.Fe(II)and 2-ketoglutarate-dependent dioxygenases(Fe/2-k...The asymmetric hydroxylation of inactive carbon atoms in organic compounds remains an important reaction in the industrial synthesis of valuable chiral compounds.Fe(II)and 2-ketoglutarate-dependent dioxygenases(Fe/2-kg DOs)are the largest known subgroups of mononuclear nonheme-Fe(II)-dependent oxygenases,catalyzing various oxidation reactions of C-H bonds.Recent developments in Fe/2-kg DO-related researches have coupled concepts from bioinformatics,synthetic biology,and computational biology to establish effective biotransformation systems.The most well-studied and characterized activ-ity of the Fe/2-kg DOs is substrate hydroxylation,with regard to which mechanistic studies involving the Fe center assist in engineering the protein frameworks of these enzymes to obtain the desired catalytic enhancements.Amino acids are typical substrates of Fe/2-kg DOs and are usually converted into hydroxyl amino acids,which are widely used as intermediates in pharmaceutical and fine chemical industries.Herein,we have reviewed prior structural and mechanistic studies on Fe/2-kg DOs,as well as studies on the Fe/2-kg DO-mediated selective C-H oxidation process for selective hydroxyl amino acid synthesis,which will further our journey along the promising path of building complexity via C-H bond oxidation.Further,new bioinformatics techniques should be adopted with structure-based protein rational design to mine sequence databases and shrink mutant libraries to produce a diverse panel of functional Fe/2-kg DOs capable of catalyzing targeted reactions.展开更多
Objective:The objective of this study was to investigate the potential mechanisms of ephedra-gypsum in the treatment ofrespiratory diseases(RDs)using network pharmacology and molecular docking techniques.Materials and...Objective:The objective of this study was to investigate the potential mechanisms of ephedra-gypsum in the treatment ofrespiratory diseases(RDs)using network pharmacology and molecular docking techniques.Materials and Methods:The TCMSP and UniProt databases were used to mine the active components and targets of ephedra-gypsum,and the targets of RD were screened using the Online Mendelian Inheritance in Man(OMIM)and GeneCards databases.The protein-protein interaction network graph was created using the drug-disease intersection targets in the STRING database.The network diagram was analyzed using Cytoscape 3.9.1's topology function.The gene ontology(GO)and KEGG enrichment analyses were performed using the DAVID platform.Molecular docking bioactivity validation of the main active components and core targets was performed using AutoDock and PyMOL software.Results:Twenty-four compounds were screened,and 113 drug-disease targets overlapped.In total,358 biological processes,67 molecular functions,38 cellular components of GO,and 139 pathways were identified.Molecular docking analysis demonstrated the strong binding ability of tumor protein 53(TP53)-luteolin.Conclusion:The core components of ephedra-gypsum,such as quercetin,luteolin,kaempferol,and CaSO_(4)·2H_(2)O,act on key targets,such as tumor necrosis factor(TNF),interleukin-6(IL-6),TP53,and IL-1β through cytokine-mediated signaling pathways,infiammatory responses,cell proliferation,and apoptosis.This could be useful for the treatment of RD.展开更多
基金funded by the National Natural Science Foundation of China(Nos.31971551,31470573 and 31070478)the Tianjin Key Projects of Scientific and Technological Support(Nos.17YFZCNC00220 and 18YFZCNC01270)
文摘In the paper entitled"Efficient adsorption of Mn(Ⅱ)by layered double hydroxides intercalated with di ethylenetriaminepentaacetic acid and the mechanistic study"in Journal of Environmental Sciences,volume 85,page 56-65,there were problems with mathematical notation and dimensional errors in the calculation for Giibbs free energy.In Section 2.5:Adsorption isotherms and thermodynamics studies,authors calculated the Gibbs free energy change(△G°)
文摘Objective To observe the effects of low expressed Angiotensin-converting enzyme 2(Ace2) gene on senescence related signals of alveolar typeⅡepithelial cells in silicotic mice.Methods In March 2022,20 8-12W SPF male wild-type C57BL/6 mice and 20 Ace2 gene knockdown mice(Ace2^(+/-),C57BL/6 background) were randomly divided into wild-type control group Ace2 low expression group,wild-type silicosis group,Ace2 low expression silicosis group,with 10 mice in each group.
基金the National Key Research and Development Program of China(No.2021YFA1500100)the National Natural Science Foundation of China(Nos.92156017 and 21890722)+1 种基金“Frontiers Science Center for New Organic Matter”,Nankai University(No.63181206)Haihe Laboratory of Sustainable Chemical Transformation of Tianjin(No.24HHWCSS00019)for generous financial support。
文摘Mechanistic studies of the cleavage and transformation of unactivated C_(sp3)-H bonds are a significant field of chemistry.Overcoming the inherent low acidity of C-H bonds to activate the inert substrates is challenge under mild conditions.And their complex multi-step transformations may also hinder mechanistic understanding.Herein,we perform theoretical calculations and experimental studies to explore the C_(sp3)-H bonds activation and acylation mechanisms of toluene/thioether using the relatively weak base LDA.A synergistic"main and auxiliary"model was revealed involving dual lithium metal by LDA dimers,and the aryl dilithium species as an intermediate base can facilitate C_(sp3)-H activation.This model not only aids in understanding the acidity of unactivated C_(sp3)-H bonds and the nucleophilicity of their conjugate bases for their kinetic control through cooperative interactions,but also predicts unusual kinetic isotope effects(KIE)for newly designed 2-(methylthio)naphthalene that are experimentally validated.This research is expected to provide a crucial scenario for the cleavage and transformation of unactivated C_(sp3)-H bonds and the development of new functionalities for alkali metal reagents.
基金This work was supported by the National Science Foundation of China and the National Laboratory for Structure Chemistry of Unstable and Stable Species
文摘Photolysis of benzyl phenylacetate (ACO_2A), benzyl p-methylphenylacetate (BCO_2A) and 1-naphthyl phenylacetate (ACO_2Np) in homogeneous and micellar solutions results in products typical of radical coupling reactions and loss of carbon dioxide. The cage effects upon direct photolysis of these esters in acetonitrile are significantly greater than zero and those in SDS or HDTBr micellar solutions are even greater. In the triplet sensitization reaction of ACO_2 Np in micellar solutions the cage effects are smaller than those obtained upon direct irradiation. However, the application of a 0.05 or 0.2 T external magnetic field in the photolysis in micellar solutions decreases the cage effects dramatically. All these results suggest that the photoextrusions of carbon dioxide from these esters proceed via radical intermediates, and upon direct photolysis the reactive states for the cleavage re- action involve both singlet and triplet excited states.
文摘The synthesis of phosphine compounds through the addition reaction of H-[P(O)]species to olefins and alkynes has been extensively studied.Two different mechanisms of the addition of H-[P(O)]species to non-activated alkyne are mainly summarized.One is the oxidative addition-migration insertion-reductive elimination mechanism,namely the Chalk-Harrod type mechanism,and the other is the proton transfer-reductive elimination mechanism.This review elaborates on the specific steps of each mechanism,and discusses experimental and computational evidence supporting these steps.Additionally,a few other types of mechanisms are briefly mentioned.The mechanism of H-[P(O)]reaction with relevant conjugated dienes was also involved when closely related.
基金financially supported by the National Natural Science Foundation of China(Nos.32270413,82060631,82160808,and 82360035)the Science and Technology Department of Guizhou Province(Nos.QKHJC 2020–1Z076,QKHJC-ZK[2023]YB156,QKHJC-ZK[2021]YB569,and QKHPTRC[2020]5008)+4 种基金Excellent Young Talents Plan of Guizhou Medical University(2023,No.106)the 13thbatch of outstanding young scientific and technological talents in Guizhou Province(No.QKHPTRC[2021]5633)Guizhou Science and Technology Innovation Talent Team(No.QKHPTRC–CXTD[2022]007)High-level Innovative Talents in Guizhou Province(Thousand Levels of Talent for Chunmao Yuan in 2018)the project of State Key Laboratory of Functions and Applications of Medicinal Plants,Guizhou Medical University(Nos.FAMP202102K and QJJ[2023]113)。
文摘Hymoins A–C(1–3),three unusual polycyclic polyprenylated acylphloroglucinols(PPAPs)were isolated from the flowers of Hypericum monogynum.Hymoin A features the first intriguing 6/5/5/5/7 pentacyclic caged PPAP.Hymoin B is characterized by an unprecedented rearranged 5/6/8 tricyclic ring system,while hymoin C represents the first rearranged PPAP with a fantastic spirocyclic 5/6/7 ring system.Their structures were established by extensive spectroscopic analysis,X-ray crystallography,and computational methods.The plausible biosynthetic routes for the compounds were also proposed.In oleic acid(OA)-induced HepG2 cells,all compounds exhibited significant lipid-lowering activity at the concentrations of 2–8μmol/L.Further mechanistic study implied that compound 1 exhibited excellent lipid-lowering activity in OA-induced HepG2 cells through inhibiting the proteins of free fatty acids synthesis and improving lipidolysis.
基金supported by the National Research Foundation Singapore Investigatorship Program(Grant No.NRF-NRFI08-2022-0009)A*STAR(Agency for Science,Technology and Research)LCER FI program(Award No.U2102d2002)the E-CO2RR CREATE Program.
文摘Electrocatalytic CO_(2) reduction(ECR)is a promising approach to converting CO_(2) into chemicals and fuels.Among the ECR products,C_(2) products such as ethylene,ethanol,and acetate have been extensively studied due to their high industrial demands.However,the mechanistic understanding of C_(2) product formation remains unclear due to the lack of in situ or operando measurements that can observe the complex and instantaneous atomic evolutions of adsorbates at the electrode/electrolyte interface.Moreover,the sensitivity of ECR reactions to variations at the interface further widens the gap between mechanistic understanding and performance enhancement.To bridge this gap,first-principle studies provide insights into how the interface influences ECR.In this study,we present a review of mechanistic studies investigating the effects of various factors at the interface,with an emphasis on the C_(2) product formation.We begin by introducing ECR and the essential metrics.Next,we discuss the factors classified by their components at the interface,namely,electrocatalyst,electrolyte,and adsorbates,respectively,and their effects on the C_(2) product formation.Due to the interplay among these factors,we aim to deconvolute the influence of each factor and clearly demonstrate their impacts.Finally,we outline the promising directions for mechanistic studies of C_(2) products.
基金supported by the National Natural Science Foundation of China(21273086)Chutian Scholar Foundation from Hubei Province,China~~
文摘The development of new catalytic techniques for wastewater treatment has long attracted much attention from industrial and academic communities.However,because of catalyst leaching during degradation,catalysts can be short lived,and therefore expensive,and unsuitable for use in wastewater treatment.In this work,we developed a bimetallic CuO-Co3O4@γ-Al2O3 catalyst for phenol degradation with bicarbonate-activated H2O2.The weakly basic environment provided by the bicarbonate buffer greatly suppresses leaching of active Cu and Co metal ions from the catalyst.X-ray diffraction and X-ray photoelectron spectroscopy results showed interactions between Cu and Co ions in the CuO-Co3O4@γ-Al2O3 catalyst,and these improve the catalytic activity in phenol degradation.Mechanistic studies using different radical scavengers showed that superoxide and hydroxyl radicals both played significant roles in phenol degradation,whereas singlet oxygen was less important.
基金supported by the National High Technology Research and Development Program of China(863 Program,No.2012AA02A701)the National High Technology Research and Development Program of China(863 Program,No. 2013AA031901)Program for Changjiang Scholars and Innovative Research Team in University(No.IRT1066)
文摘MCRs for preparation of chromenopyridines under reflux conditions and chromenes at room temperature conditions from different salicylaldehydes,malononitrile and different thiols（mol ratio- 1：2：1） were established.Mechanistic investigation suggests that the MCRs undergo different pathways at different temperatures and catalyzed by different organic bases.The structure of chromenopyridine and chromene are confirmed by crystal X-ray crystallography.
基金supported by the National Natural Science Foundation of China(22171216)the National Key R&D Program of China(2021YFA1500100).
文摘High valent iron complexes Fe-X have been known to transfer their X group toward carbon radical species to form R–X bond.To utilize this capability of iron catalyst,novel photo-induced iron catalysis system had been developed in the difunctionalization of alkenes in the presence of radical initiator.However,the details of the reaction mechanism are still unclear,especially the transformations of the photocatalyst and the iron catalyst during the catalytic turnover.Herein,we expanded the photo-driven non-heme iron complex catalyzed thiocyanation of styrene substrate.This protocol exhibited broad substrate scope and high efficiency.Detailed mechanistic studies using various spectroscopies,such as UV-vis,mass spectrometry,transient absorption spectroscopy and X-ray absorption spectroscopy,revealed the transformations of photocatalyst[Ir^(Ⅲ)(ppy)_(3)]and group transfer catalyst[Fe^(Ⅱ)(bpmen)]^(2+).Real-time spectroscopies combined with mechanistic experiments demonstrated that[Ir^(Ⅳ)(ppy)_(3)]^(+)and[Fe^(Ⅲ)(bpmen)]^(3+)were the key intermediates involved in the reaction cycle.
基金2018 National Key RESEARCH and Development Plan"Research on Modernization of Traditional Chinese Medicine"(No.2018YFC1707405)NSFC(No.81273946,81473463,81774289)+2 种基金Beijing Science and Technology Plan Major Fund supported projects(No.D161100005116004)Beijing Science and Technology Nova Crossover Project(NO.Z171100001117128)Independent topic selection of Chinese Academy of TCM(No.ZZ11-028)
文摘Objective: To investigate the effective compounds, potential targets and molecular mechanism of Kanglaite injection (KLTi) in the treatment of Non-Small Cell Lung Cancer (NSCLC) based on network pharmacology. Methods: The active compounds and targets of KLTi which extracted and isolated from Coix Seed were screened by Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform (TCMSP). The related genes of NSCLC were obtained by searching the Human Gene Database (GeneCards) and Online Mendelian Inheritance in Man (OMIM). The candidate targets of KLTi in the treatment of NSCLC were obtained after extracting the intersection network. The "drug-component-target-disease" network was constructed with the help of Cytoscape 3.7.2. The Protein- Protein Interaction networks were constructed on the STRING platform and core network modules were screened. The Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis of candidate genes were performed using Metascape platform, and a "pathway-target- compounds" network was constructed to further screen key genes and active compounds. Results: A total of 11 compounds, 22 candidate targets, 206 GO functions and 12 KEGG pathways were obtained. Conclusion: The active compounds of KLTi in the treatment of NSCLC are stigmasterol, stigmasterol α1 and ergosterol. The key targets are PGR, NCOA2, PTGS2, NR3C2, and PTGS1. The core GO functions included receptor activity and binding, neuronal signal transmission and hormone stimulation;KEGG mainly involves cancer pathways, neuroactive ligand-receptor interactions and calcium signaling pathways. This study reveals the molecular biological mechanism of KLTi in the treatment of NSCLC, which is speculated to be related to neuroendocrine, providing a new basis and therapeutic direction for subsequent clinical application and experimental research.
基金support from the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XD2000000)the National Natural Science Foundation of China(21421091,21372250,21121062,21302203,20732008,21772037,21772226,21861132014 and 91956115).
文摘This paper discloses the reaction mechanism of two consecutive but different visible light photo-induced chain processes for the rapid construction of spirobi[indene]skeletons.The first process is triggered by a photo-induced single-electron-transfer(SET)of an electron donor-accepter(EDA)complex.The second process is initiated by a direct SET process between aryldiazonium salt and the excited allenic intermediate.In these two processes,another SET took place respectively on the in situ formed radical intermediate to realize a redox-neutral outcome.The mechanistic studies have been carried out by control experiments,kinetic and spectroscopic analyses,deuterium labeling experiments to support these two chain processes.
文摘An aerobic oxidation of aldehydes towards carboxylic acids in MeCN using 1 atm of pure oxygen or oxygen in air as the oxidant and a catalytic amount of single component catalyst, Fe（NO3）3.9H20, has been developed. Carboxylic acids with different synthetically useful functional groups were obtained at room temperature. Two mechanistic pathways have been proposed based on isotopic labeling, NMR monitoring, and control experiments. The practicality of this reaction has been demonstrated by conducting several 50 mmol-scale reactions using pure oxygen or an air-flow of -30 mL/min.
基金supported by the Chinese Academy of Sciencesthe National Natural Science Foundation of China (20973197 and 21173263)
文摘Acceptorless dehydrogenation (AD) that uses non-toxic reagents and produces no waste is a type of catalytic reactions toward green chemistry. Acceptorless alcohol dehydrogenation (AAD) can serve as a key step in constructing new bonds such as C-C and C-N bonds in which alcohols need to be activated into more reactive ketones or aldehydes. AD reactions also can be utilized for hydrogen production from biomass or its fermentation products (mainly alcohols). Reversible hydrogenation/ dehy-drogenation with hydrogen uptake/release is crucial to realization of the potential organic hydride hydrogen storage. In this article, we review the recent computational mechanistic studies of the AD reactions catalyzed by various transition metal complexes as well as the experimental developments. These reactions include acceptorless alcohol dehydrogenations, reversible dehydrogenation/hydrogenation of nitrogen heterocycles, dehydrogenative coupling reactions of alcohols and amines to construct C-N bonds, and dehydrogenative coupling reactions of alcohols and unsaturated substrates to form C-C bonds. For the catalysts possessing metal-ligand bifunctional active sites (such as 28, 45, 86, 87, and 106 in the paper), the dehydrogenations prefer the "bifunctional double hydrogen transfer" mechanism rather than the generally accepted-H elimination mechanism. However, methanol dehydrogenation involved in the C-C coupling reaction of methanol and allene, catalyzed by the iridium complex 121, takes place via the-H elimination mechanism, because the Lewis basicity of either the-allyl moiety or the carboxyl group of the ligand is too weak to exert high Lewis basic reactivity. Unveiling the catalytic mechanisms of AD reactions could help to develop new catalysts.
基金the National Natural Science Foundation of China(Nos.22008221 and 22238013)the Foundation of State Key Laboratory of Biobased Material and Green Papermaking,Qilu University of Technology,Shandong Academy of Sciences(No.GZKF202010).
文摘Carbon-supported single-atom catalysts were found to suffer reversible deactivation in catalytic hydrogenation,but the mechanism is still unclear.Herein,nitro compounds hydrogenation catalyzed by N-doped carbon-supported Co single atom(Co1/NC)was taken as a model to uncover the mechanism of the reversible deactivation phenomenon.Co1/NC exhibited moderate adsorption towards the substrate molecules(i.e.,nitro compounds or related intermediates),which could be strengthened by the confinement effect from the porous structure.Consequently,substrate molecules tend to accumulate within the pore channel,especially micropores that host Co1,making it difficult for the reactants to access the active sites and finally leading to their deactivation.The situation could be even worse when the substrate molecules possess a large size.Nevertheless,the catalytic activity of Co1/NC could be restored via a simple thermal treatment,which could remove the adsorbates within the pore channel,hence releasing active sites that were originally inaccessible to reactants.
基金the National Sciences and Engineering Research Council (NSERC) for a Discovery Grantsupporting a Tier 1 Canada Research Chair (P.A.E)the Huxiang High-Level Talent Gathering Project from the Science and Technology Department of Hunan Province (Grant No. 2020RC5001)。
文摘The Reformatsky reagent derived from ethyl bromoacetate circumvents the challenge associated with the direct regio-and enantioselective iridium-catalyzed allylic alkylation with an unstabilized aliphatic ester enolate. Notably, this work represents the first example of using a Reformatsky reagent in a metal-allyl reaction, which permits the direct construction of enantioenriched β-stereogenic homoallylic esters without preactivation of the pronucleophile or post-reaction modification of the product(e.g., thermal decarboxylation of a 1,3-dicarbonyl). Moreover, the process allows the coupling of a broad range of sterically and electronically diverse electrophiles bearing aryl, heteroaryl and alkenyl derivatives, including the significantly more challenging alkyl-substituted allylic carbonates. The versatility of the ester product is exemplified by a series of functional group manipulations and the development of a concise and efficient enantioselective total synthesis of the natural product,(+)-descurainolide A. Finally, mechanistic studies indicate that the zinc enolate behaves as a soft nucleophile that undergoes outer-sphere alkylation.
基金This work was financially supported by National Key R&D Program of China(Nos.2019YFA0210004 and 2017YFA0207301)the National Natural Science Foundation of China(Nos.21975242 and 21890754)+5 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB36000000)Youth Innovation Promotion Association of CAS(No.CX2340007003)Major Program of Development Foundation of Hefei Center for Physical Science and Technology(No.2020HSC-CIP003)Key Research Program of Frontier Sciences of CAS(No.QYZDYSSW-SLH011)the Fok Ying-Tong Education Foundation(No.161012)Supercomputing USTC and National Supercomputing Center in Shenzhen are acknowledged for computational support.
文摘Photooxidation provides a promising strategy for removing the dominant indoor pollutant of HCHO,while the underlying photooxidation mechanism is still unclear,especially the exact role of H2O molecules.Herein,we utilize in-situ spectral techniques to unveil the H2O-mediated HCHO photooxidation mechanism.As an example,the synthetic defective Bi2WO6 ultrathin sheets realize high-rate HCHO photooxidation with the assistance of H2O at room temperature.In-situ electron paramagnetic resonance spectroscopy demonstrates the existence of•OH radicals,possibly stemmed from H2O oxidation by the photoexcited holes.Synchrotron-radiation vacuum ultraviolet photoionization mass spectroscopy and H218O isotope-labeling experiment directly evidence the formed•OH radicals as the source of oxygen atoms,trigger HCHO photooxidation to produce CO2,while in-situ Fourier transform infrared spectroscopy discloses the HCOO*radical is the main photooxidation intermediate.Density-functional-theory calculations further reveal the•OH formation process is the rate-limiting step,strongly verifying the critical role of H2O in promoting HCHO photooxidation.This work first clearly uncovers the H2O-mediated HCHO photooxidation mechanism,holding promise for high-efficiency indoor HCHO removal at ambient conditions.
基金Financial supports from the National Natural Science Foundation of China(NSFC)(No.21676120)the 111 Project(No.111-2-06)+5 种基金the High-End Foreign Experts Recruitment Program(No.G20190010083)the Program for Advanced Talents within Six Industries of Jiangsu Province(No.2015-NY-007)the National Program for Support of Top-Notch Young Professionals,the Fundamental Research Funds for the Central Universities(No.JUSRP51504)the Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions,Top-Notch Academic Programs Project of Jiangsu Higher Education Institutions,the Jiangsu Province“Collaborative Innovation Center for Advanced Industrial Fermentation”Industry Development Program,the Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX19_1833)the Program for the Key Laboratory of Enzymes of Suqian(No.M201803)the National First-Class Discipline Program of Light Industry Technology and Engineering(No.LITE2018-09)are greatly appreciated。
文摘The asymmetric hydroxylation of inactive carbon atoms in organic compounds remains an important reaction in the industrial synthesis of valuable chiral compounds.Fe(II)and 2-ketoglutarate-dependent dioxygenases(Fe/2-kg DOs)are the largest known subgroups of mononuclear nonheme-Fe(II)-dependent oxygenases,catalyzing various oxidation reactions of C-H bonds.Recent developments in Fe/2-kg DO-related researches have coupled concepts from bioinformatics,synthetic biology,and computational biology to establish effective biotransformation systems.The most well-studied and characterized activ-ity of the Fe/2-kg DOs is substrate hydroxylation,with regard to which mechanistic studies involving the Fe center assist in engineering the protein frameworks of these enzymes to obtain the desired catalytic enhancements.Amino acids are typical substrates of Fe/2-kg DOs and are usually converted into hydroxyl amino acids,which are widely used as intermediates in pharmaceutical and fine chemical industries.Herein,we have reviewed prior structural and mechanistic studies on Fe/2-kg DOs,as well as studies on the Fe/2-kg DO-mediated selective C-H oxidation process for selective hydroxyl amino acid synthesis,which will further our journey along the promising path of building complexity via C-H bond oxidation.Further,new bioinformatics techniques should be adopted with structure-based protein rational design to mine sequence databases and shrink mutant libraries to produce a diverse panel of functional Fe/2-kg DOs capable of catalyzing targeted reactions.
基金supported by Grants from the National Natural Science Foundation of China(grant no.U20A20404)National College Students'Innovation and Entrepreneurship Training Program(202210752014).
文摘Objective:The objective of this study was to investigate the potential mechanisms of ephedra-gypsum in the treatment ofrespiratory diseases(RDs)using network pharmacology and molecular docking techniques.Materials and Methods:The TCMSP and UniProt databases were used to mine the active components and targets of ephedra-gypsum,and the targets of RD were screened using the Online Mendelian Inheritance in Man(OMIM)and GeneCards databases.The protein-protein interaction network graph was created using the drug-disease intersection targets in the STRING database.The network diagram was analyzed using Cytoscape 3.9.1's topology function.The gene ontology(GO)and KEGG enrichment analyses were performed using the DAVID platform.Molecular docking bioactivity validation of the main active components and core targets was performed using AutoDock and PyMOL software.Results:Twenty-four compounds were screened,and 113 drug-disease targets overlapped.In total,358 biological processes,67 molecular functions,38 cellular components of GO,and 139 pathways were identified.Molecular docking analysis demonstrated the strong binding ability of tumor protein 53(TP53)-luteolin.Conclusion:The core components of ephedra-gypsum,such as quercetin,luteolin,kaempferol,and CaSO_(4)·2H_(2)O,act on key targets,such as tumor necrosis factor(TNF),interleukin-6(IL-6),TP53,and IL-1β through cytokine-mediated signaling pathways,infiammatory responses,cell proliferation,and apoptosis.This could be useful for the treatment of RD.
