Ag_(2)CO_(3)-promoted dehydroxymethylative fluorination of aliphatic alcohols has been achieved with Selectfluor as both oxidant and fluorine source.The reaction involvesβ-fragmentation of primary alkoxy radicals,fol...Ag_(2)CO_(3)-promoted dehydroxymethylative fluorination of aliphatic alcohols has been achieved with Selectfluor as both oxidant and fluorine source.The reaction involvesβ-fragmentation of primary alkoxy radicals,followed by the fluorination of the resulting C-centered radical intermediates.The transformation proceeds under mild reaction conditions and exhibits a broad substrate scope,thus opening up a new entrance to the synthesis of fluorinated constructs includingα-fluoroimides and 1-fluoroalkyl benzoates as well as secondary and tertiary alkyl fluorides like versatile 2-fluoro-2-alkyl 1,3-propandiol derivatives.The divergent functionalization of the obtainedα-fluoroimides enables an efficient access to amine derivatives through C-F bond activation under the action of BF_(3)·OEt_(2).展开更多
The carbon-carbon bond is the one of the most fundamental and abundant bonds that exist in organic molecules,and the challenge of functionalization of carbon-carbon bond has always been a critical pursuit in organic s...The carbon-carbon bond is the one of the most fundamental and abundant bonds that exist in organic molecules,and the challenge of functionalization of carbon-carbon bond has always been a critical pursuit in organic synthesis.In recent years,there have been a growing number of studies on the C-C bond activation.Nevertheless,the metal-catalyzed cleavage of the C-C(O)bond in unstrained ketones has remained relatively underexplored due to the strong affinity of carbonyl groups for metals.In this study,we report a nickel-catalyzed strategy for the reductive alkynylation of ketoimines viaβ-carbon elimination.This method involves the conversion of aryl ketones into aryl ketoimines,thus expanding the toolbox of aryl electrophiles.The use of a N-heterocyclic carbene(NHC)ligand is crucial for this catalytic transformation.This discovery leads to a cross electrophile coupling reaction characterized by its operational simplicity,unique chemo-selectivity and excellent functional group tolerance.In addition,the approach has been effectively applied to the late-stage alkynylation of diverse pharmaceuticals.Ultimately,a series of comprehensive experiments and theoretical studies were conducted to provide insights into the reaction pathway,which supports the proposedβ-carbon elimination process.展开更多
The divergent behavior of C-H bond oxidations of aliphatic substrates compared to those of aromatic substrates shown in Gupta’s experiment was mechanistically studied herein by means of density functional theory calc...The divergent behavior of C-H bond oxidations of aliphatic substrates compared to those of aromatic substrates shown in Gupta’s experiment was mechanistically studied herein by means of density functional theory calculations.Our calculations reveal that such difference is caused by different reaction mechanisms between two kinds of substrates(the aliphatic cyclohexane,2,3-dimethylbutane and the aromatic toluene,ethylbenzene and cumene).For the aliphatic substrates,C-H oxidation by the oxidant Fe^(V)(O)(TAML)is a hydrogen atom transfer process;whereas for the aromatic substrates,C-H oxidation is a proton-coupled electron transfer(PCET)process with a proton transfer character on the transition state,that is,a proton-coupled electron transfer process holding a proton transfer-like transition state(PCET(PT)).This difference is caused by the strongπ-πinteractions between the tetra-anionic TAML ring and the phenyl ring of the aromatic substrates,which has a“pull”effect to make the electron transfer from substrates to the Fe=O moiety inefficient.展开更多
Metal halide perovskite(MHP)quantum dots(QDs)offer immense potentialfor several areas of photonics research due to their easy and low-costfabrication and excellent optoelectronic properties.However,practicalapplicatio...Metal halide perovskite(MHP)quantum dots(QDs)offer immense potentialfor several areas of photonics research due to their easy and low-costfabrication and excellent optoelectronic properties.However,practicalapplications of MHP QDs are limited by their poor stability and,in particular,their tendency to aggregate.Here,we develop a two-step double-solventstrategy to grow and confine CsPbBr_(3)QDs within the three-dimensional(3D)cavities of a mesoporous SBA-16 silica scaffold(CsPbBr_(3)@SBA-16).Strongconfinement and separation of the MHP QDs lead to a relatively uniform sizedistribution,narrow luminescence,and good ambient stability over 2 months.In addition,the CsPbBr_(3)@SBA-16 presents a high activity and stability forvisible-light-driven photocatalytic toluene C(sp^(3))-H bond activation toproduce benzaldehyde with~730 umolg^(-1)h^(-l) yield rate and near-unityselectivity.Similarly,the structural stability of CsPbBr_(3)@SBA-16QDs issuperior to that of both pure CsPbBr3 QDs and those confined in MCM-41with 1D channels.展开更多
The potential energy surface and reaction mechanism corresponding to the reaction of ytterbium monocation with fluoromethane, which represents a prototype of the activation of C-F bond in fluorohydrocarbons by bare la...The potential energy surface and reaction mechanism corresponding to the reaction of ytterbium monocation with fluoromethane, which represents a prototype of the activation of C-F bond in fluorohydrocarbons by bare lanthanide cations, have been investigated for the first time by using density functional theory. A direct fluorine abstraction mechanism was revealed, and the related thermochemistry data were determined. The electron-transfer reactivity of the reaction was analyzed using the two-state model, and a strongly avoided crossing behavior on the transition state region was shown. The present results support the reaction mechanism inferred from early experimental data and the related thermochemistry data can provide a guide for further experimental researches.展开更多
Theσ-bond activation by main group element has received enormous attention from theoretical and experimental chemists.Here,the reaction of C-X(X=Cl,Br,I)bonds in benzyl and allyl halides with a pincer-type phosphorus...Theσ-bond activation by main group element has received enormous attention from theoretical and experimental chemists.Here,the reaction of C-X(X=Cl,Br,I)bonds in benzyl and allyl halides with a pincer-type phosphorus(Ⅲ)species was reported.A series of structurally robust phosphorus(Ⅴ)compounds were formed via the formal oxidative addition reactions of C-X bonds to the phosphorus(Ⅲ)center.Density functional theory calculations show that the nucleophilic addition process is more favorable than the direct oxidative addition mechanism.Isomerization of bent structures of phosphorus(Ⅲ)compound to poorly nucleophilic compounds to undergo further C-X bond activation can be rationalized by frontier molecule orbital analysis.This study not only provides a deep understanding of the reactivity of phosphorus(Ⅲ)species but also demonstrates a potential of main group elements for the small-molecule activation.展开更多
Propane dehydrogenation(PDH)on Ga/H-ZSM-5 catalysts is a promising reaction for propylene production,while the detail mechanism remains debatable.Ga_(2)O_(2)^(2+) stabilized by framework Al pairs have been identified ...Propane dehydrogenation(PDH)on Ga/H-ZSM-5 catalysts is a promising reaction for propylene production,while the detail mechanism remains debatable.Ga_(2)O_(2)^(2+) stabilized by framework Al pairs have been identified as the most active species in Ga/H-ZSM-5 for PDH in our recent work.Here we demonstrate a strong correlation between the PDH activity and a fraction of Ga_(2)O_(2)^(2+) species corresponding to the infrared GaH band of higher wavenumber(GaHHW)in reduced Ga/H-ZSM-5,instead of the overall Ga_(2)O_(2)^(2+) species,by employing five H-ZSM-5 supports sourced differently with comparable Si/Al ratio.This disparity in Ga_(2)O_(2)^(2+) species stems from their differing capacity in completing the catalytic cycle.Spectroscopic results suggest that PDH proceeds via a two-step mechanism:(1)C-H bond activation of propane on H-Ga_(2)O_(2)^(2+) species(rate determining step);(2)β-hydride elimination of adsorbed propyl group,which only occurs on active Ga_(2)O_(2)^(2+) species corresponding to GaHHW.展开更多
Developing method for strong Si–F σ bond activation is a very important tool in organosilicon transformation chemistry, only few examples of Si–F bond activation are precedent in the literature. Herein, we develope...Developing method for strong Si–F σ bond activation is a very important tool in organosilicon transformation chemistry, only few examples of Si–F bond activation are precedent in the literature. Herein, we developed a new and efficient method to activate strong Si–F bond by transition-metal-free Si–F/Si–H cross coupling reaction catalyzed with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) catalytic system under mild conditions. Various disiloxanes bearing tolerated functional groups were successfully synthesized in moderate to excellent yields from fluorosilanes and hydrosilanes. Moreover, H_(2)O was found to be the oxygen donor in this catalytic system. Density functional theory calculations were performed to verify the mechanism of DBU promoted Si–F/Si–H cross-coupling reactions.展开更多
Poly-substituted olefins,one of the most important aggregation-induced emission luminogens(AIEgens),have garnered significant attention due to their various applications in chemical-and bio-sensing,bio-imaging,and opt...Poly-substituted olefins,one of the most important aggregation-induced emission luminogens(AIEgens),have garnered significant attention due to their various applications in chemical-and bio-sensing,bio-imaging,and opto-electronics.However,the synthetic methods for these olefins remain limited,impeding the progress of AIEgens.This study introduces an unprecedented cross-coupling reaction between aryl sulfonium triflates and tosylhydrazones from naturally abundant thioethers and ketones.The generality of this method is exemplified by the facile synthesis of over forty poly-substituted olefins.Importantly,the luminescent properties of these AIEgens(e.g.,quantum yield and emission color)can be easily tuned by adjusting the substituents of the electrophile and nucleophile substrates,exhibiting excellent performance in bio-imaging.Notably,the mechanistic studies reveal the critical role ofβ-H elimination in the formation of the double bond.This contribution provides an efficient method to synthesize poly-substituted olefins,pushing forward the development of AIEgens.展开更多
The activation of the N≡N triple bond in N_(2) is a fascinating topic in nitrogen chemistry.The transition metals have been demonstrated to effectively modulate the reactivity of N_(2) molecules under high pressure,l...The activation of the N≡N triple bond in N_(2) is a fascinating topic in nitrogen chemistry.The transition metals have been demonstrated to effectively modulate the reactivity of N_(2) molecules under high pressure,leading to nitrogen-rich compounds.However,their use often results in a significant reduction in energy density.In this work,we propose a series of low-enthalpy nitrogen-rich phases in CN_(x)(x=3,...,7)compounds using a first-principles crystal structure search method.The results of calculations reveal that all these CN compounds are assembled from both CN_(4) tetrahedra and N_(x)(x=1,2,or 5)species.Strikingly,we find that the CN_(4) tetrahedron can effectively activate the N≡N bond through weakening of the π orbital of N_(2) under a pressure of 40 GPa,leading to stable CN polynitrides.The robust structural framework of CN polynitrides containing C-N and N-N bonds plays a crucial role in enhancing their structural stability,energy density,and hardness.Among these polynitrides,CN_(6) possesses not only a very high mass density of 3.19 g/cm^(3),but also an ultrahigh energy density of 28.94 kJ/cm^(3),which represents a significant advance in the development of energetic materials using high-pressure methods.This work provides new insights into the mechanism of N_(2) activation under high pressure,and offers a promising pathway to realize high-performance energetic materials.展开更多
A straightforward protocol using readily available aromatic amines,N,N,N',N'-tetramethyl-p-phenylenediamine or N,N,N',N'-tetramethylbenzidine,as photocatalysts was developed for theefficient hydrodehal...A straightforward protocol using readily available aromatic amines,N,N,N',N'-tetramethyl-p-phenylenediamine or N,N,N',N'-tetramethylbenzidine,as photocatalysts was developed for theefficient hydrodehalogenation of organic halides,such as 4'-bromoacetophenone,polyfluoroarenes,cholorobenzene,and 2,2',4,4'-tetrabromodiphenyl ether(a resistant and persistent organic pollu-tant).The strongly reducing singlet excited states of the amines enabled diffusion-controlled disso-ciative electron transfer to effectively cleave carbon-halogen bonds,followed by radical hydrogena-tion.Diisopropylethylamine served as the terminal electron/proton donor and regenerated theamine sensitizers.展开更多
We report a palladium-catalyzed formal intermolecular [4＋2] cycloaddition of benzoic and acrylic acids with 1,3-dienes including the stock chemicals 1,3-butadiene and isoprene leading to synthetically useful 3,4-dihy...We report a palladium-catalyzed formal intermolecular [4＋2] cycloaddition of benzoic and acrylic acids with 1,3-dienes including the stock chemicals 1,3-butadiene and isoprene leading to synthetically useful 3,4-dihydroisocoumarins and 5,6-dihydrocoumalins. Stepwise C-H bond cleavage and annulation are likely involved in the reaction pathway. The synthetic potential of the methodology was demonstrated by two short derivatizations and total synthesis of natural product Clausamine B.展开更多
A new palladium-catalyzed selective aminomethylation of conjugated 1,3-dienes with aminais via double C-N bond activation is described. This simple method provides an effective and rapid approach for the synthesis of ...A new palladium-catalyzed selective aminomethylation of conjugated 1,3-dienes with aminais via double C-N bond activation is described. This simple method provides an effective and rapid approach for the synthesis of linear a,13-unsaturated allylic amines with perfect regioselectivity. Mechanistic studies disclosed that one palladium catalyst cleaved two distinct C-N bond to furnish a cascade double C-N bond activation, in which an allylic 1,3-diamine and allylic 1,2-diamine were initially formed as key intermediates through the palladium-catalyzed C-N bond activation of aminal and the α,β-unsaturated allylic amine was subsequently produced via palladium-catalyzed C-N bond activation of the allylic diamines.展开更多
Main observation and conclusion A new strategy for the generation of the active Pd-alkyl species from aminal via C-N bond activation has been established,in which the formation of zwitterionic intermediate through aza...Main observation and conclusion A new strategy for the generation of the active Pd-alkyl species from aminal via C-N bond activation has been established,in which the formation of zwitterionic intermediate through aza-Michael addition of aminal to nitrodienes or dienones is identified as a key step for the activation of the C-N bond.The efficient strategy has enabled a new palladium-catalyzed a-aminomethylation of nitro-dienes and dienones via double C-N bond activation.The scope and versatility of the reaction were demonstrated and a broad range of substrates bearing electron-donating and-withdrawing groups on the aromatic rings were all compatible with this reaction to furnish the desired a-aminomethylated products in moderate to good yields with excellent regioselectivities and E/Z selectivities.展开更多
Main observation and conclusion In this work,a novel mode for the activation of N-heterocyclic carbene boranes(NHC-boranes)was developed by generating the highly reactive zwitterion species through hydride abstraction...Main observation and conclusion In this work,a novel mode for the activation of N-heterocyclic carbene boranes(NHC-boranes)was developed by generating the highly reactive zwitterion species through hydride abstraction with Lewis acid B(C_(6)F_(5))_(3) in an frustrated Lewis pairs manner.A broad range of alkenes including stilbenes,β-methylstyrenes,styrenes,and alkyl-alkenes were suitable substrates for the B(C_(6)F_(5))_(3)-catalyzed hydroboration to furnish the desired products in good to high yields.Significantly,excellent regioselectivities were obtained in some cases.Mechanistic studies indicate that the B-H bond cleavage is likely involved in the rate-determining step.In addition,an electrophilic addition of NHC-borenium cation to alkenes and the subsequent formation of carbocation are also postulated.The current work provides a promising method for the activation of stable borane adducts,which might lead to some interesting transformations in the future.展开更多
Herein, we report that a series of novel palladium（II）-NHC complexes （NHC=N-heterocyclic carbene） were synthesized. The structures of all novel complexes were characterized by ^1H NMR, ^13C NMR, FT-IR spectroscopy...Herein, we report that a series of novel palladium（II）-NHC complexes （NHC=N-heterocyclic carbene） were synthesized. The structures of all novel complexes were characterized by ^1H NMR, ^13C NMR, FT-IR spectroscopy and elemental analysis techniques. These palladium（ll）-NHC complexes were tested as efficient catalysts in the direct C-H bond activation of benzoxazole and benzothiazole with aryl bromides in the presence of 1 mol% catalyst loading at 150 ℃ for 4 h. Under the given conditions, various aryl bromides were successfully applied as the arylating reagents to achieve the 2-arylbenzoxazoles and 2-arylbenzothiazoles in acceptable to high yields.展开更多
In this paper the C--F bond activation of polyfluoroaryl imines is explored at cobalt（0） center with an imine-N atom as an anchoring group. The reaction of F5C6-CH=N-（2＇-ClC6H4） （2） and FsC6-CH=N-C6H5 （3） wit...In this paper the C--F bond activation of polyfluoroaryl imines is explored at cobalt（0） center with an imine-N atom as an anchoring group. The reaction of F5C6-CH=N-（2＇-ClC6H4） （2） and FsC6-CH=N-C6H5 （3） with Co（PMe3h afforded the C-F bond activation products （ortho-F4C6-CH=N-（2＇-CIC6H4））Co（I）（PMe3）3 （5） and （ortho-F4C6-CH=N-C6Hs）Co（II）（F）（PMe3）2 （6）, while only n-（C=N） coordinated cobalt（0） complex （2,4,5- F3C6H2-CH=N-（4＇-ClC6H4））Co（0）（PMe3）3 （4） was obtained from 2,4,5-F3C6H2-CH=N-（4＇-C1C6H4） （1） without C--F bond activation. Complexes 4--6 were characterized through X-ray single crystal diffraction. It was also found that dialkylation of N-（perfluorobenzylidene）benzenamine with organozinc reagents could be catalyzed by Co（PMe3）4 via C,C-coupling reaction under mild conditions.展开更多
We report herein a practical approach for regio-selective B—H/C—H bond activation at azo-substituted carboranes. The reaction proceeded through Iridium(III)-induced selective B—H/C—H bond activations based on an a...We report herein a practical approach for regio-selective B—H/C—H bond activation at azo-substituted carboranes. The reaction proceeded through Iridium(III)-induced selective B—H/C—H bond activations based on an azo directing group. Through this strategy, a series of mononuclear, trinuclear and tetranuclear cyclometalated iridium complexes containing Cp*Ir—B or Cp*Ir—C bonds were successfully isolated in a high yield. In this work, efficient routes are developed through one-pot reactions to prepare polynuclear organometallic complexes.展开更多
Semiconductor photocatalysis holds great promise for breaking the inert chemical bonds under mild condition;however,the photoexcitation-induced modulation mechanism has not been well understood at the atomic level.Her...Semiconductor photocatalysis holds great promise for breaking the inert chemical bonds under mild condition;however,the photoexcitation-induced modulation mechanism has not been well understood at the atomic level.Herein,by performing the DFT+U calculations,we quantitatively compare H_(2) activation on rutile TiO_(2)(110)under thermo-versus photo-catalytic condition.It is found that H2 dissociation prefers to occur via the heterolytic cleavage mode in thermocatalysis,but changes to the homolytic cleavage mode and gets evidently promoted in the presence of photoexcited hole(h^(+)).The origin can be ascribed to the generation of highly oxidative lattice O-radical(O_(br)^(·−))with a localized unoccupied O-2p state.More importantly,we identify that this photo-induced promotion effect can be practicable to another kind of important chemical bond,i.e.,C-H bond in light hydrocarbons including alkane,alkene and aromatics;an exception is the C(sp^(1))-H in alkyne(HC≡CH),which encounters inhibition effect from photoexcitation.By quantitative analysis,the origins behind these results are attributed to the interplay between two factors:C-H bond energy(E_(bond))and the acidity.Owing to the relatively high E_(bond) and acidity,it favors the C(sp^(1))-H bond to proceed with the heterolytic cleavage mode in both thermo-and photo-catalysis,and the photoexcited O_(br)^(·−)is adverse to receiving the transferred proton.By contrast,for the other hydrocarbons with moderate/low E_(bond),the O_(br)^(·−)would enable to change their activation mode to a more favored homolytic one and evidently decrease the C-H activation barrier.This work may provide a general picture for understanding the photocatalytic R-H(R=H,C)bond activation over the semiconductor catalyst.展开更多
Indanones are ubiquitous in biologically active compounds.Intramolecular hydroacylation of aldehydes and alkenes is an efficient and atomeconomic route to indane rings.However,these reactions are limited to the transf...Indanones are ubiquitous in biologically active compounds.Intramolecular hydroacylation of aldehydes and alkenes is an efficient and atomeconomic route to indane rings.However,these reactions are limited to the transfer of a hydride to the alkene.The transfer of aryl groups enabling the formation of C–C bonds during the cyclization would be a new method for the synthesis of substituted indanones.This report describes the regiodivergent carboacylation of alkenes with ketones to furnish both 2-and 3-substituted indanones in a regiocontrolled manner.展开更多
基金financial support from the Marine S&T Fund of Shandong Province for Pilot National Laboratory for Marine Science and Technology(Qingdao)(No.2022QNLM030003-2)the National Natural Science Foundation of China(No.21977088)the National Natural Science Foundation of China-Shandong Joint Fund(No.U1906213)。
文摘Ag_(2)CO_(3)-promoted dehydroxymethylative fluorination of aliphatic alcohols has been achieved with Selectfluor as both oxidant and fluorine source.The reaction involvesβ-fragmentation of primary alkoxy radicals,followed by the fluorination of the resulting C-centered radical intermediates.The transformation proceeds under mild reaction conditions and exhibits a broad substrate scope,thus opening up a new entrance to the synthesis of fluorinated constructs includingα-fluoroimides and 1-fluoroalkyl benzoates as well as secondary and tertiary alkyl fluorides like versatile 2-fluoro-2-alkyl 1,3-propandiol derivatives.The divergent functionalization of the obtainedα-fluoroimides enables an efficient access to amine derivatives through C-F bond activation under the action of BF_(3)·OEt_(2).
基金financial support from the National Natural Science Foundation of China(Nos.22001147,22371171)Taishan Scholars Project of Shandong Province(No.tsqn202103027)+1 种基金Distinguished Young Scholars of Shandong Province(Overseas)(No.2022HWYQ-001)Qilu Youth Scholar Funding of Shandong University。
文摘The carbon-carbon bond is the one of the most fundamental and abundant bonds that exist in organic molecules,and the challenge of functionalization of carbon-carbon bond has always been a critical pursuit in organic synthesis.In recent years,there have been a growing number of studies on the C-C bond activation.Nevertheless,the metal-catalyzed cleavage of the C-C(O)bond in unstrained ketones has remained relatively underexplored due to the strong affinity of carbonyl groups for metals.In this study,we report a nickel-catalyzed strategy for the reductive alkynylation of ketoimines viaβ-carbon elimination.This method involves the conversion of aryl ketones into aryl ketoimines,thus expanding the toolbox of aryl electrophiles.The use of a N-heterocyclic carbene(NHC)ligand is crucial for this catalytic transformation.This discovery leads to a cross electrophile coupling reaction characterized by its operational simplicity,unique chemo-selectivity and excellent functional group tolerance.In addition,the approach has been effectively applied to the late-stage alkynylation of diverse pharmaceuticals.Ultimately,a series of comprehensive experiments and theoretical studies were conducted to provide insights into the reaction pathway,which supports the proposedβ-carbon elimination process.
基金supported by the National Natural Science Foundation of China(No.21806018 and No.21873052)the Fundamental Research Funds for the Central Universities(DUT20RC(4)002)+1 种基金Scientific Research Grant of Ningbo University(No.215-432000282)Ningbo Top Talent Project(No.215-432094250)。
文摘The divergent behavior of C-H bond oxidations of aliphatic substrates compared to those of aromatic substrates shown in Gupta’s experiment was mechanistically studied herein by means of density functional theory calculations.Our calculations reveal that such difference is caused by different reaction mechanisms between two kinds of substrates(the aliphatic cyclohexane,2,3-dimethylbutane and the aromatic toluene,ethylbenzene and cumene).For the aliphatic substrates,C-H oxidation by the oxidant Fe^(V)(O)(TAML)is a hydrogen atom transfer process;whereas for the aromatic substrates,C-H oxidation is a proton-coupled electron transfer(PCET)process with a proton transfer character on the transition state,that is,a proton-coupled electron transfer process holding a proton transfer-like transition state(PCET(PT)).This difference is caused by the strongπ-πinteractions between the tetra-anionic TAML ring and the phenyl ring of the aromatic substrates,which has a“pull”effect to make the electron transfer from substrates to the Fe=O moiety inefficient.
基金Research Foundation—Flanders,Grant/Award Numbers:1242922N,1280021N,12Y7221N,V400622NFlemishgovernment for iBOF funding,Grant/Award Number:PERsist:iBOF-21-085+2 种基金KU Leuven Research Fund,Grant/A ward Number:C14/23/090China Scholarship Council(CSC),Grant/Award Number:201806650002Australian Research Council,Grant/Award Number:DE230100173。
文摘Metal halide perovskite(MHP)quantum dots(QDs)offer immense potentialfor several areas of photonics research due to their easy and low-costfabrication and excellent optoelectronic properties.However,practicalapplications of MHP QDs are limited by their poor stability and,in particular,their tendency to aggregate.Here,we develop a two-step double-solventstrategy to grow and confine CsPbBr_(3)QDs within the three-dimensional(3D)cavities of a mesoporous SBA-16 silica scaffold(CsPbBr_(3)@SBA-16).Strongconfinement and separation of the MHP QDs lead to a relatively uniform sizedistribution,narrow luminescence,and good ambient stability over 2 months.In addition,the CsPbBr_(3)@SBA-16 presents a high activity and stability forvisible-light-driven photocatalytic toluene C(sp^(3))-H bond activation toproduce benzaldehyde with~730 umolg^(-1)h^(-l) yield rate and near-unityselectivity.Similarly,the structural stability of CsPbBr_(3)@SBA-16QDs issuperior to that of both pure CsPbBr3 QDs and those confined in MCM-41with 1D channels.
基金supported by the National Science Foundation of Shandong Province(No.Z2000B02).
文摘The potential energy surface and reaction mechanism corresponding to the reaction of ytterbium monocation with fluoromethane, which represents a prototype of the activation of C-F bond in fluorohydrocarbons by bare lanthanide cations, have been investigated for the first time by using density functional theory. A direct fluorine abstraction mechanism was revealed, and the related thermochemistry data were determined. The electron-transfer reactivity of the reaction was analyzed using the two-state model, and a strongly avoided crossing behavior on the transition state region was shown. The present results support the reaction mechanism inferred from early experimental data and the related thermochemistry data can provide a guide for further experimental researches.
基金supported by the National Natural Science Foundation of China(Nos.21772088 and 21573179)the Natural Science Foundation of Jiangsu Province(No.BK20170635)the Young Elite Scientist Sponsorship Program of China Association of Science and Technology,the program of Jiangsu SpeciallyAppointed Professor and Shuangchuang Talent Plan of Jiangsu Province。
文摘Theσ-bond activation by main group element has received enormous attention from theoretical and experimental chemists.Here,the reaction of C-X(X=Cl,Br,I)bonds in benzyl and allyl halides with a pincer-type phosphorus(Ⅲ)species was reported.A series of structurally robust phosphorus(Ⅴ)compounds were formed via the formal oxidative addition reactions of C-X bonds to the phosphorus(Ⅲ)center.Density functional theory calculations show that the nucleophilic addition process is more favorable than the direct oxidative addition mechanism.Isomerization of bent structures of phosphorus(Ⅲ)compound to poorly nucleophilic compounds to undergo further C-X bond activation can be rationalized by frontier molecule orbital analysis.This study not only provides a deep understanding of the reactivity of phosphorus(Ⅲ)species but also demonstrates a potential of main group elements for the small-molecule activation.
文摘Propane dehydrogenation(PDH)on Ga/H-ZSM-5 catalysts is a promising reaction for propylene production,while the detail mechanism remains debatable.Ga_(2)O_(2)^(2+) stabilized by framework Al pairs have been identified as the most active species in Ga/H-ZSM-5 for PDH in our recent work.Here we demonstrate a strong correlation between the PDH activity and a fraction of Ga_(2)O_(2)^(2+) species corresponding to the infrared GaH band of higher wavenumber(GaHHW)in reduced Ga/H-ZSM-5,instead of the overall Ga_(2)O_(2)^(2+) species,by employing five H-ZSM-5 supports sourced differently with comparable Si/Al ratio.This disparity in Ga_(2)O_(2)^(2+) species stems from their differing capacity in completing the catalytic cycle.Spectroscopic results suggest that PDH proceeds via a two-step mechanism:(1)C-H bond activation of propane on H-Ga_(2)O_(2)^(2+) species(rate determining step);(2)β-hydride elimination of adsorbed propyl group,which only occurs on active Ga_(2)O_(2)^(2+) species corresponding to GaHHW.
基金the support of the Foundation of Department of Education of Guangdong Province(Nos.2021ZDZX2045,2024KTSCX040)the Wuyi University Innovation and Entrepreneurship Project(2023CX07,S202411349118)+1 种基金the National Natural Science Foundation of China(22163007)Guizhou Provincial Key Technology R&D Program(ZZSG[2024]002).
文摘Developing method for strong Si–F σ bond activation is a very important tool in organosilicon transformation chemistry, only few examples of Si–F bond activation are precedent in the literature. Herein, we developed a new and efficient method to activate strong Si–F bond by transition-metal-free Si–F/Si–H cross coupling reaction catalyzed with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) catalytic system under mild conditions. Various disiloxanes bearing tolerated functional groups were successfully synthesized in moderate to excellent yields from fluorosilanes and hydrosilanes. Moreover, H_(2)O was found to be the oxygen donor in this catalytic system. Density functional theory calculations were performed to verify the mechanism of DBU promoted Si–F/Si–H cross-coupling reactions.
基金support from the National Natural Science Foundation of China(51925306,52120105006,52222309,52173187,and 52303221)the Strategic Priority Research Program of Chinese Academy of Sciences(XDB 0520103)+3 种基金Beijing Natural Science Foundation(Z210017)the Science and Technology Innovation Commission of Shenzhen(JCYJ20220530150604009)Project of International Cooperation of Chinese Academy of Sciences(124GJHZ2023079MI)Xiaomi Young Talents Program,and Fundamental Research Funds for the Central University.
文摘Poly-substituted olefins,one of the most important aggregation-induced emission luminogens(AIEgens),have garnered significant attention due to their various applications in chemical-and bio-sensing,bio-imaging,and opto-electronics.However,the synthetic methods for these olefins remain limited,impeding the progress of AIEgens.This study introduces an unprecedented cross-coupling reaction between aryl sulfonium triflates and tosylhydrazones from naturally abundant thioethers and ketones.The generality of this method is exemplified by the facile synthesis of over forty poly-substituted olefins.Importantly,the luminescent properties of these AIEgens(e.g.,quantum yield and emission color)can be easily tuned by adjusting the substituents of the electrophile and nucleophile substrates,exhibiting excellent performance in bio-imaging.Notably,the mechanistic studies reveal the critical role ofβ-H elimination in the formation of the double bond.This contribution provides an efficient method to synthesize poly-substituted olefins,pushing forward the development of AIEgens.
基金supported by the Higher Educational Youth Innovation Science and Technology Program Shandong Province(Grant Nos.2022KJ183 and 2022KJ175)the Natural Science Foundation of Shandong Province(Grant Nos.ZR2023MA016 and ZR2023JQ001)+1 种基金the National Natural Science Foundation of China(Grant Nos.11974208 and 12374012)financial support from the award of Taishan Scholar(Grant No.tsqn202211128).
文摘The activation of the N≡N triple bond in N_(2) is a fascinating topic in nitrogen chemistry.The transition metals have been demonstrated to effectively modulate the reactivity of N_(2) molecules under high pressure,leading to nitrogen-rich compounds.However,their use often results in a significant reduction in energy density.In this work,we propose a series of low-enthalpy nitrogen-rich phases in CN_(x)(x=3,...,7)compounds using a first-principles crystal structure search method.The results of calculations reveal that all these CN compounds are assembled from both CN_(4) tetrahedra and N_(x)(x=1,2,or 5)species.Strikingly,we find that the CN_(4) tetrahedron can effectively activate the N≡N bond through weakening of the π orbital of N_(2) under a pressure of 40 GPa,leading to stable CN polynitrides.The robust structural framework of CN polynitrides containing C-N and N-N bonds plays a crucial role in enhancing their structural stability,energy density,and hardness.Among these polynitrides,CN_(6) possesses not only a very high mass density of 3.19 g/cm^(3),but also an ultrahigh energy density of 28.94 kJ/cm^(3),which represents a significant advance in the development of energetic materials using high-pressure methods.This work provides new insights into the mechanism of N_(2) activation under high pressure,and offers a promising pathway to realize high-performance energetic materials.
文摘A straightforward protocol using readily available aromatic amines,N,N,N',N'-tetramethyl-p-phenylenediamine or N,N,N',N'-tetramethylbenzidine,as photocatalysts was developed for theefficient hydrodehalogenation of organic halides,such as 4'-bromoacetophenone,polyfluoroarenes,cholorobenzene,and 2,2',4,4'-tetrabromodiphenyl ether(a resistant and persistent organic pollu-tant).The strongly reducing singlet excited states of the amines enabled diffusion-controlled disso-ciative electron transfer to effectively cleave carbon-halogen bonds,followed by radical hydrogena-tion.Diisopropylethylamine served as the terminal electron/proton donor and regenerated theamine sensitizers.
基金We are grateful to the National Natural Science Foundation of China （Nos. 21772218, 21421091, XDB20000000）, the ＂Thousand Plan＂ Youth program, State Key Laboratory of Organome-tallic Chemistry, Shanghai Institute of Organic Chemistry and the Chinese Academy of Sciences.
文摘We report a palladium-catalyzed formal intermolecular [4＋2] cycloaddition of benzoic and acrylic acids with 1,3-dienes including the stock chemicals 1,3-butadiene and isoprene leading to synthetically useful 3,4-dihydroisocoumarins and 5,6-dihydrocoumalins. Stepwise C-H bond cleavage and annulation are likely involved in the reaction pathway. The synthetic potential of the methodology was demonstrated by two short derivatizations and total synthesis of natural product Clausamine B.
基金This research was supported by the National Natural Science Foundation of China （Nos. 21672199 and 21790333） and CAS Interdisciplinary Innovation Team.
文摘A new palladium-catalyzed selective aminomethylation of conjugated 1,3-dienes with aminais via double C-N bond activation is described. This simple method provides an effective and rapid approach for the synthesis of linear a,13-unsaturated allylic amines with perfect regioselectivity. Mechanistic studies disclosed that one palladium catalyst cleaved two distinct C-N bond to furnish a cascade double C-N bond activation, in which an allylic 1,3-diamine and allylic 1,2-diamine were initially formed as key intermediates through the palladium-catalyzed C-N bond activation of aminal and the α,β-unsaturated allylic amine was subsequently produced via palladium-catalyzed C-N bond activation of the allylic diamines.
基金the National Natural Science Foundation of China(Nos.21672199,21790333,21925111 and 21702197)the Fundamental Research Funds for the Central Universities(No.WK2060190086).
文摘Main observation and conclusion A new strategy for the generation of the active Pd-alkyl species from aminal via C-N bond activation has been established,in which the formation of zwitterionic intermediate through aza-Michael addition of aminal to nitrodienes or dienones is identified as a key step for the activation of the C-N bond.The efficient strategy has enabled a new palladium-catalyzed a-aminomethylation of nitro-dienes and dienones via double C-N bond activation.The scope and versatility of the reaction were demonstrated and a broad range of substrates bearing electron-donating and-withdrawing groups on the aromatic rings were all compatible with this reaction to furnish the desired a-aminomethylated products in moderate to good yields with excellent regioselectivities and E/Z selectivities.
基金the financial support from the National Natural Science Foundation of China(Nos.21871269 and 21521002).
文摘Main observation and conclusion In this work,a novel mode for the activation of N-heterocyclic carbene boranes(NHC-boranes)was developed by generating the highly reactive zwitterion species through hydride abstraction with Lewis acid B(C_(6)F_(5))_(3) in an frustrated Lewis pairs manner.A broad range of alkenes including stilbenes,β-methylstyrenes,styrenes,and alkyl-alkenes were suitable substrates for the B(C_(6)F_(5))_(3)-catalyzed hydroboration to furnish the desired products in good to high yields.Significantly,excellent regioselectivities were obtained in some cases.Mechanistic studies indicate that the B-H bond cleavage is likely involved in the rate-determining step.In addition,an electrophilic addition of NHC-borenium cation to alkenes and the subsequent formation of carbocation are also postulated.The current work provides a promising method for the activation of stable borane adducts,which might lead to some interesting transformations in the future.
文摘Herein, we report that a series of novel palladium（II）-NHC complexes （NHC=N-heterocyclic carbene） were synthesized. The structures of all novel complexes were characterized by ^1H NMR, ^13C NMR, FT-IR spectroscopy and elemental analysis techniques. These palladium（ll）-NHC complexes were tested as efficient catalysts in the direct C-H bond activation of benzoxazole and benzothiazole with aryl bromides in the presence of 1 mol% catalyst loading at 150 ℃ for 4 h. Under the given conditions, various aryl bromides were successfully applied as the arylating reagents to achieve the 2-arylbenzoxazoles and 2-arylbenzothiazoles in acceptable to high yields.
基金Acknowledgement We gratefully acknowledge the support by National Natural Science Foundation of China （No. 21172132）. We also thank the kind assistance from Prof. Dieter Fenske and Dr. Olaf Fuhr （Karlsruhe Nano-Micro Facility, KNMF） for the X-ray diffraction analysis.
文摘In this paper the C--F bond activation of polyfluoroaryl imines is explored at cobalt（0） center with an imine-N atom as an anchoring group. The reaction of F5C6-CH=N-（2＇-ClC6H4） （2） and FsC6-CH=N-C6H5 （3） with Co（PMe3h afforded the C-F bond activation products （ortho-F4C6-CH=N-（2＇-CIC6H4））Co（I）（PMe3）3 （5） and （ortho-F4C6-CH=N-C6Hs）Co（II）（F）（PMe3）2 （6）, while only n-（C=N） coordinated cobalt（0） complex （2,4,5- F3C6H2-CH=N-（4＇-ClC6H4））Co（0）（PMe3）3 （4） was obtained from 2,4,5-F3C6H2-CH=N-（4＇-C1C6H4） （1） without C--F bond activation. Complexes 4--6 were characterized through X-ray single crystal diffraction. It was also found that dialkylation of N-（perfluorobenzylidene）benzenamine with organozinc reagents could be catalyzed by Co（PMe3）4 via C,C-coupling reaction under mild conditions.
基金This work was supported by the National Natural Science Foun-dation of China(Nos.21531002,21720102004,22031003)the Shanghai Science Technology Committee(No.13JC1400600).
文摘We report herein a practical approach for regio-selective B—H/C—H bond activation at azo-substituted carboranes. The reaction proceeded through Iridium(III)-induced selective B—H/C—H bond activations based on an azo directing group. Through this strategy, a series of mononuclear, trinuclear and tetranuclear cyclometalated iridium complexes containing Cp*Ir—B or Cp*Ir—C bonds were successfully isolated in a high yield. In this work, efficient routes are developed through one-pot reactions to prepare polynuclear organometallic complexes.
基金supported by National Nature Science Foundation of China(Nos.21873028.91945302)National Ten Thousand Talent Program for Young Top-notch Talents in China,Shanghai Shu-Guang project(No.17SG30)the Fundamental Research Fundsfor the Central Universities.
文摘Semiconductor photocatalysis holds great promise for breaking the inert chemical bonds under mild condition;however,the photoexcitation-induced modulation mechanism has not been well understood at the atomic level.Herein,by performing the DFT+U calculations,we quantitatively compare H_(2) activation on rutile TiO_(2)(110)under thermo-versus photo-catalytic condition.It is found that H2 dissociation prefers to occur via the heterolytic cleavage mode in thermocatalysis,but changes to the homolytic cleavage mode and gets evidently promoted in the presence of photoexcited hole(h^(+)).The origin can be ascribed to the generation of highly oxidative lattice O-radical(O_(br)^(·−))with a localized unoccupied O-2p state.More importantly,we identify that this photo-induced promotion effect can be practicable to another kind of important chemical bond,i.e.,C-H bond in light hydrocarbons including alkane,alkene and aromatics;an exception is the C(sp^(1))-H in alkyne(HC≡CH),which encounters inhibition effect from photoexcitation.By quantitative analysis,the origins behind these results are attributed to the interplay between two factors:C-H bond energy(E_(bond))and the acidity.Owing to the relatively high E_(bond) and acidity,it favors the C(sp^(1))-H bond to proceed with the heterolytic cleavage mode in both thermo-and photo-catalysis,and the photoexcited O_(br)^(·−)is adverse to receiving the transferred proton.By contrast,for the other hydrocarbons with moderate/low E_(bond),the O_(br)^(·−)would enable to change their activation mode to a more favored homolytic one and evidently decrease the C-H activation barrier.This work may provide a general picture for understanding the photocatalytic R-H(R=H,C)bond activation over the semiconductor catalyst.
基金support for this study was provided by the National Natural Science Foundation of China(nos.21632003,21901202,and 21971205)the Natural Science Basic Research Program of Shaanxi(no.2020JQ-576).
文摘Indanones are ubiquitous in biologically active compounds.Intramolecular hydroacylation of aldehydes and alkenes is an efficient and atomeconomic route to indane rings.However,these reactions are limited to the transfer of a hydride to the alkene.The transfer of aryl groups enabling the formation of C–C bonds during the cyclization would be a new method for the synthesis of substituted indanones.This report describes the regiodivergent carboacylation of alkenes with ketones to furnish both 2-and 3-substituted indanones in a regiocontrolled manner.
