The addition of difluorocarbene generated from phenyl(trifluoromethyl)mercury and anhydrous sodium iodide,with trimethylsilyl enol ethers derived from cyclohexanone,cycloheptanone, 3-pentanone and acetophenone was des...The addition of difluorocarbene generated from phenyl(trifluoromethyl)mercury and anhydrous sodium iodide,with trimethylsilyl enol ethers derived from cyclohexanone,cycloheptanone, 3-pentanone and acetophenone was described.The corresponding 2,2-difluoro-1-trimethylsilyloxy- cyclopropanes were obtained in good yields.The thermal stability of these cyclopropyl derivatives was affected by the molecular strain and the nature of their substituents.Thus,1-trimethylsilyloxy- cyclopentene reacted with difluorocarbene to give only 2-fluoro-2-cyclohexen-1-one instead of the expected 1-trimethylsilyloxy-6,6-difluorobicyclo[3.1.0]hexane,and a mechanism for its formation was proposed.展开更多
Dendronized polymers(DenPols)with tunable shape and surface property have been recognized as a type of promising unimolecular nanomaterials.However,it still has lacked a rapid and efficient approach to the facile synt...Dendronized polymers(DenPols)with tunable shape and surface property have been recognized as a type of promising unimolecular nanomaterials.However,it still has lacked a rapid and efficient approach to the facile synthesis of DenPols with high-generation and well-defined structures.Herein,we report a“m+n”grafting-onto strategy combined with the copper-catalyzed azide-alkyne cycloaddition(CuAAC)reaction with reaction-enhanced reactivity of intermediates(RERI)mechanism for synthesizing DenPols G_(m+n) by attaching n-generation dendrons(G_(n))onto the m-generation DenPols G_(m).In this“m+n”grafting-onto strategy,the DenPols G_(m)(m=1,2)bearing 1,3-triazido branches on the repeating unit were capable of RERI effect that guaranteed the CuAAC reaction in an extremely efficient way with ultrafast kinetics to synthesize third-,fourth-and fifth-generation DenPols(G_(1+2),G_(1+3),G_(1+4),G_(2+2),and G_(2+3))with near quantitative grafting density and narrow distribution.Moreover,these resultant DenPols G_(m+n) had more terminal groups per repeating unit due to the three branches of 1,3-triazido structure,exhibiting valuable potential opportunities for molecular surface engineering.The development of this“m+n”grafting-onto strategy with RERI mechanism not only presents a new avenue for ultrafast preparing DenPols but also holds great promise for preparing unimolecular materials with more functional terminal groups.展开更多
The complexation of Cr^3＋ with F^- undergoes a muhistep reversible process. An approach to research the involved equilibria and kinetics using suitable chemometrics methods to the online measured UV-Vis spectra is pr...The complexation of Cr^3＋ with F^- undergoes a muhistep reversible process. An approach to research the involved equilibria and kinetics using suitable chemometrics methods to the online measured UV-Vis spectra is proposed. By investigating the equilibrium spectra of the complexes at different molar ratios of M to L（ metal to ligand） and 50 ℃, the result of Principal Component Analysis（PCA） shows that three complexes, ML, ML2 and ML3, can be formed under the research conditions. The spectrum of each complex was then analyzed and the accumulated equilibrium constants were calculated by applying Target Testing Factor Analysis（TITA）. Meanwhile, a reactive intermediate was observed before the formation of MLx during the specific kinetic study at 15℃. The equilibrium constant and spectrum of the intermediate as well as the rate constants were all resolved by using TTFA.展开更多
The methanol-to-olefins(MTO)reaction offers an alternative pathway for the production of low-carbon olefins from non-oil feedstocks.Fundamental research has been impeded by a lack of comprehensive understanding of its...The methanol-to-olefins(MTO)reaction offers an alternative pathway for the production of low-carbon olefins from non-oil feedstocks.Fundamental research has been impeded by a lack of comprehensive understanding of its underlying mechanism,despite the significant progress made in industry.In-situ solid-state nuclear magnetic resonance(ss NMR)spectroscopy has emerged as a pivotal tool,offering crucial insights into key species under real-time operando conditions.Furthermore,the host–vip interaction between zeolites or surface species residing on zeolites and the reactant/active intermediates is revealed by the combination of in-situ^(13)C MAS NMR and 2D correlation spectroscopy.Moreover,recent technological advancements in hyperpolarization(HP)methods,including HP^(129)Xe NMR and dynamic nuclear polarization(DNP),have significantly improved the sensitivity of ssNMR,enabling detailed structural and kinetic analysis as well as the detection of trace species.In this feature article,we summarized recent advancements in(in-situ)ssNMR spectroscopy applied to MTO reaction processes,encompassing mechanistic investigations at various stages and the intricate host–vip interactions.These theoretical insights into the dynamic evolution of MTO reactions lay a solid foundation for the optimization of catalytic processes and the development of efficient catalysts,thereby advancing the techniques towards more sustainable and economical production route for olefins.展开更多
Electrochemical mass spectrometry(EC-MS)is a powerful tool to capture and analyze the intermediates and products during elec-trochemical reactions.This hyphenated technique combines electrochemistry with mass spectrom...Electrochemical mass spectrometry(EC-MS)is a powerful tool to capture and analyze the intermediates and products during elec-trochemical reactions.This hyphenated technique combines electrochemistry with mass spectrometry using specific apparatuses,which helps researchers study mechanisms of redox reactions by in situ detecting chemical composition changes.Recently,various EC-MS methods have been applied in a series of electrochemical reactions to reveal the mechanisms,mainly in the areas of electro-chemical sensors,organic electrochemistry,and electrocatalysis.In this review,we intend to summarize the recent advances in re-al-time analysis of different types of electrochemical reactions by EC-MS and offer an outlook on the perspectives in these areas.展开更多
Knowledge of asymmetric catalytic reaction mechanism is very important for rational design and synthesis of new chiral catalysts or catalytic systems with high catalytic activity and stereoselectivity.The studies of n...Knowledge of asymmetric catalytic reaction mechanism is very important for rational design and synthesis of new chiral catalysts or catalytic systems with high catalytic activity and stereoselectivity.The studies of nonlinear effect have attracted wide attentions as a simple and practical mechanistic tool to probe complex asymmetric catalytic reactions.展开更多
The discovery of Kahne glycosylation forwards a big step in the carbohydrate chemistry.Despite an extensive series of studies,the precise mechanism of this powerful glycosylation is still not fully understood.To addre...The discovery of Kahne glycosylation forwards a big step in the carbohydrate chemistry.Despite an extensive series of studies,the precise mechanism of this powerful glycosylation is still not fully understood.To address these 30-year puzzles,the far side of Kahne glycosylation is explored in this study.After a series of control and tracking experiments,a number of important intermediates including glycosyl oxo-sulfonium ion and sulfenic anhydride(Crich's intermediate)are suggested to be responsible for the complex reaction pathway.It also reveals that in addition to the conventional ionic glycosylation pathway,a novel free radical pathway is very likely to contribute to the various side-and co-products.This study provides further understanding of Kahne glycosylation,and it also sheds light on how to improve the efficiency of sulfoxide-based glycosylation reactions.展开更多
This review reports our recent work on developing polymer synthesis methods based on a self-accelerating double-strain-promoted 1,3-dipole-alkyne cycloaddition(DSPDAC)click reaction.In DSPDAC,the cycloaddition of 1,3-...This review reports our recent work on developing polymer synthesis methods based on a self-accelerating double-strain-promoted 1,3-dipole-alkyne cycloaddition(DSPDAC)click reaction.In DSPDAC,the cycloaddition of 1,3-dipole with the first alkyne of sym-dibenzo-1,5-cyclooctadiene-3,7-diyne(DIBOD)activates the second unreacted alkyne,which reacts with 1,3-dipole much faster than the original alkyne of DIBOD.When using DIBOD and bis-dipole compounds as monomer pairs,the self-accelerating property of DSPDAC allows us to develop a stoichiometric imbalance-promoted step-growth polymerization method.It could produce polymers with ultrahigh molecular weight in the presence of excess DIBOD monomers.When using DIBOD to ring-close linear polymers with 1,3-dipole end groups,the self-accelerating property of DSPDAC facilitates us to develop a unique bimolecular ring-closure method.It could efficiently prepare pure cyclic polymers in the presence of excess DIBOD small linkers to linear polymer precursors.展开更多
文摘The addition of difluorocarbene generated from phenyl(trifluoromethyl)mercury and anhydrous sodium iodide,with trimethylsilyl enol ethers derived from cyclohexanone,cycloheptanone, 3-pentanone and acetophenone was described.The corresponding 2,2-difluoro-1-trimethylsilyloxy- cyclopropanes were obtained in good yields.The thermal stability of these cyclopropyl derivatives was affected by the molecular strain and the nature of their substituents.Thus,1-trimethylsilyloxy- cyclopentene reacted with difluorocarbene to give only 2-fluoro-2-cyclohexen-1-one instead of the expected 1-trimethylsilyloxy-6,6-difluorobicyclo[3.1.0]hexane,and a mechanism for its formation was proposed.
基金the National Natural Science Foundation of China(Nos.22071271,22371313)Natural Science Foundation of Guangdong Province(2024A1515011133 and 2021A1515110853)the Fundamental Research Funds for the Central Universities(23yxqntd002).
文摘Dendronized polymers(DenPols)with tunable shape and surface property have been recognized as a type of promising unimolecular nanomaterials.However,it still has lacked a rapid and efficient approach to the facile synthesis of DenPols with high-generation and well-defined structures.Herein,we report a“m+n”grafting-onto strategy combined with the copper-catalyzed azide-alkyne cycloaddition(CuAAC)reaction with reaction-enhanced reactivity of intermediates(RERI)mechanism for synthesizing DenPols G_(m+n) by attaching n-generation dendrons(G_(n))onto the m-generation DenPols G_(m).In this“m+n”grafting-onto strategy,the DenPols G_(m)(m=1,2)bearing 1,3-triazido branches on the repeating unit were capable of RERI effect that guaranteed the CuAAC reaction in an extremely efficient way with ultrafast kinetics to synthesize third-,fourth-and fifth-generation DenPols(G_(1+2),G_(1+3),G_(1+4),G_(2+2),and G_(2+3))with near quantitative grafting density and narrow distribution.Moreover,these resultant DenPols G_(m+n) had more terminal groups per repeating unit due to the three branches of 1,3-triazido structure,exhibiting valuable potential opportunities for molecular surface engineering.The development of this“m+n”grafting-onto strategy with RERI mechanism not only presents a new avenue for ultrafast preparing DenPols but also holds great promise for preparing unimolecular materials with more functional terminal groups.
基金Supported by the National Natural Science Foundation of China(No. 50478106)
文摘The complexation of Cr^3＋ with F^- undergoes a muhistep reversible process. An approach to research the involved equilibria and kinetics using suitable chemometrics methods to the online measured UV-Vis spectra is proposed. By investigating the equilibrium spectra of the complexes at different molar ratios of M to L（ metal to ligand） and 50 ℃, the result of Principal Component Analysis（PCA） shows that three complexes, ML, ML2 and ML3, can be formed under the research conditions. The spectrum of each complex was then analyzed and the accumulated equilibrium constants were calculated by applying Target Testing Factor Analysis（TITA）. Meanwhile, a reactive intermediate was observed before the formation of MLx during the specific kinetic study at 15℃. The equilibrium constant and spectrum of the intermediate as well as the rate constants were all resolved by using TTFA.
基金the financial support provided by the National Key Research and Development Program of China(2022YFE0116000)the National Natural Science Foundation of China(22241801,22022202,22032005,22288101,21972142,21991090,21991092,and 21991093)Dalian Outstanding Young Scientist Foundation(2021RJ01)。
文摘The methanol-to-olefins(MTO)reaction offers an alternative pathway for the production of low-carbon olefins from non-oil feedstocks.Fundamental research has been impeded by a lack of comprehensive understanding of its underlying mechanism,despite the significant progress made in industry.In-situ solid-state nuclear magnetic resonance(ss NMR)spectroscopy has emerged as a pivotal tool,offering crucial insights into key species under real-time operando conditions.Furthermore,the host–vip interaction between zeolites or surface species residing on zeolites and the reactant/active intermediates is revealed by the combination of in-situ^(13)C MAS NMR and 2D correlation spectroscopy.Moreover,recent technological advancements in hyperpolarization(HP)methods,including HP^(129)Xe NMR and dynamic nuclear polarization(DNP),have significantly improved the sensitivity of ssNMR,enabling detailed structural and kinetic analysis as well as the detection of trace species.In this feature article,we summarized recent advancements in(in-situ)ssNMR spectroscopy applied to MTO reaction processes,encompassing mechanistic investigations at various stages and the intricate host–vip interactions.These theoretical insights into the dynamic evolution of MTO reactions lay a solid foundation for the optimization of catalytic processes and the development of efficient catalysts,thereby advancing the techniques towards more sustainable and economical production route for olefins.
基金This work was supported by the Beijing National Laboratory for Molecular Sciences(BNLMS-CXXM-202008)the National Science Foundation of China(22034001)the National Key Research and Development Program of China(2016YFA0201300).
文摘Electrochemical mass spectrometry(EC-MS)is a powerful tool to capture and analyze the intermediates and products during elec-trochemical reactions.This hyphenated technique combines electrochemistry with mass spectrometry using specific apparatuses,which helps researchers study mechanisms of redox reactions by in situ detecting chemical composition changes.Recently,various EC-MS methods have been applied in a series of electrochemical reactions to reveal the mechanisms,mainly in the areas of electro-chemical sensors,organic electrochemistry,and electrocatalysis.In this review,we intend to summarize the recent advances in re-al-time analysis of different types of electrochemical reactions by EC-MS and offer an outlook on the perspectives in these areas.
基金the National Key R&D Program of China(Grant No.2017YFA0700103)the NSFC(Grant Nos.22225107,21922112,21871258)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB20000000).
文摘Knowledge of asymmetric catalytic reaction mechanism is very important for rational design and synthesis of new chiral catalysts or catalytic systems with high catalytic activity and stereoselectivity.The studies of nonlinear effect have attracted wide attentions as a simple and practical mechanistic tool to probe complex asymmetric catalytic reactions.
基金The National Natural Science Foundation of China(22025102,22077039,21877043)the Open Projects Fund of Shandong Key Laboratory of Carbohydrate Chemistry and Glycobiology,Shandong University(2021CCG02)the Fundamental Research Funds fortheCentralUniversities,HUST(2019kfyXKJC080,2019JYCXJJ046,2019kfyRCPY034)were appreciated.
文摘The discovery of Kahne glycosylation forwards a big step in the carbohydrate chemistry.Despite an extensive series of studies,the precise mechanism of this powerful glycosylation is still not fully understood.To address these 30-year puzzles,the far side of Kahne glycosylation is explored in this study.After a series of control and tracking experiments,a number of important intermediates including glycosyl oxo-sulfonium ion and sulfenic anhydride(Crich's intermediate)are suggested to be responsible for the complex reaction pathway.It also reveals that in addition to the conventional ionic glycosylation pathway,a novel free radical pathway is very likely to contribute to the various side-and co-products.This study provides further understanding of Kahne glycosylation,and it also sheds light on how to improve the efficiency of sulfoxide-based glycosylation reactions.
基金Generous support was primarily provided by the National National Science Foundation of China(Nos.21871273,21622406 and 22001199).
文摘This review reports our recent work on developing polymer synthesis methods based on a self-accelerating double-strain-promoted 1,3-dipole-alkyne cycloaddition(DSPDAC)click reaction.In DSPDAC,the cycloaddition of 1,3-dipole with the first alkyne of sym-dibenzo-1,5-cyclooctadiene-3,7-diyne(DIBOD)activates the second unreacted alkyne,which reacts with 1,3-dipole much faster than the original alkyne of DIBOD.When using DIBOD and bis-dipole compounds as monomer pairs,the self-accelerating property of DSPDAC allows us to develop a stoichiometric imbalance-promoted step-growth polymerization method.It could produce polymers with ultrahigh molecular weight in the presence of excess DIBOD monomers.When using DIBOD to ring-close linear polymers with 1,3-dipole end groups,the self-accelerating property of DSPDAC facilitates us to develop a unique bimolecular ring-closure method.It could efficiently prepare pure cyclic polymers in the presence of excess DIBOD small linkers to linear polymer precursors.
