Millions of people in poor areas are still under the threat of fluoride contamination.How to effectively separate fluorine in water is an important step to reduce the ecological risk.In this paper,we performed a syste...Millions of people in poor areas are still under the threat of fluoride contamination.How to effectively separate fluorine in water is an important step to reduce the ecological risk.In this paper,we performed a systematic DFT calculation focused on the defluorination behavior between the LiAl-and MgAl-LDHs.The results indicated that the LiAl-LDHs exhibited high chemical activity before the defluorination,because of the better electronic structure.After the defluorination,the LiAl-LDHs with adsorbed-F–were also more stable than the MgAl-LDHs.In addition,the existence of coordination covalent bond for the adsorbed-F–attached to the LiAl-LDHs was confirmed.This is an important reason for the high defluorination efficiency by the LiAl-LDHs.In addition,a series of weak interaction,including hydrogen bond and van der Waals interaction were also observed.Finally,a LiAl-LDHs with excellent fluoride removal properties were synthesized well by simple hydrothermal method.The results showed that our synthesized LiAl-LDHs with the capacity of 156.09 mg/g,could be effectively defluorinated in water.Notably,it surpasses most materials and has potential applications.展开更多
The bastnaesite was defluorinated by steam roasting process,and fluorine was removed in the form of hydrogen fluoride to realize the separation from rare earth.The effects of particle size of raw material,roasting tem...The bastnaesite was defluorinated by steam roasting process,and fluorine was removed in the form of hydrogen fluoride to realize the separation from rare earth.The effects of particle size of raw material,roasting temperature and time on defluorination rate of bastnaesite were studied.The suitable conditions of steam roasting process are that the particle size of raw material is less than 74μm,the roasting temperature is 1000℃and the roasting time is 4 h.The defluorination rate of bastnaesite is close to 100%under above these conditions.When the temperature rises to 1000℃,the voids on the surface of the particles increase obviously,and there is a developed network of voids,which indicates that the fluorine oxides in bastnaesite react fully with the saturated water vapor at this stage,and a large amount of fluorine escapes in the form of hydrogen fluoride from the surface and inside of the mineral.X-ray diffraction results show that there are only rare-earth oxides in the form of Ce_(0.33)La_(0.33)Ca_(0.33)O_(1.5)and Ce_(7)O_(12)in the slag.The results of energy spectra and chemical analysis show that the fluorine in the baking sand was basically completely removed.展开更多
Defluorination roasting of lepidolite ore in a fluidized bed reactor has been proposed for improving the extraction efficiency of lithium.In this paper,a vacuum was introduced to the fluidized bed reactor,which signif...Defluorination roasting of lepidolite ore in a fluidized bed reactor has been proposed for improving the extraction efficiency of lithium.In this paper,a vacuum was introduced to the fluidized bed reactor,which significantly improved the defluorination efficiency of lepidolite particles.This improvement could be attributed to an increase in the H2O/HF ratio.The highest defluorination rate for the lepidolite particles was obtained in the fluidized bed reactor under vacuum.The rate in the vacuum reactor was 1.5-2 times that in a fixed bed reactor or conventional fluidized bed reactor.The defluorination efficiency of the lepidolite particles also improved and the consumption of steam was greatly reduced by addition of coal char.This enhancement was mainly attributed to changes in the structures of the reduced lepidolite particles.This defluorination roasting method for high lithium extraction with low water steam consumption is a promising method for lithium ore treatment.展开更多
A novel defluorinative ring-opening of gem-difluorocyclopropenes is presented,providing a concise and efficient method for accessing 2-fluoropropenals and 2-fluorobuta-1,3-dienes in moderate to good yields with excell...A novel defluorinative ring-opening of gem-difluorocyclopropenes is presented,providing a concise and efficient method for accessing 2-fluoropropenals and 2-fluorobuta-1,3-dienes in moderate to good yields with excellent regio-and stereoselectivities.The reaction is performed under mild conditions with no need of using an excess amount of nucleophilic reagents.Water plays a crucial role in this transformation.展开更多
Heterogeneous photocatalysis has gained substantial research interest in treating per-and polyfluoroalkyl substances(PFAS)-contaminated water.However,sluggish degradation kinetics and low defluorination efficiency com...Heterogeneous photocatalysis has gained substantial research interest in treating per-and polyfluoroalkyl substances(PFAS)-contaminated water.However,sluggish degradation kinetics and low defluorination efficiency compromise their practical applications.Here,we report a superior photocatalyst,defected Bi_(3)O(OH)(PO_(4))_(2),which could effectively degrade typical PFAS,perfluorooctanoic acid(PFOA),with high defluorination efficiency.The UV light irradiation could in situ generate oxygen vacancies on Bi_(3)O(OH)(PO_(4))_(2) through oxidation of the lattice hydroxyls,which further promotes the formation of Lewis acidic coordinately unsaturated bismuth sites.Then,the Lewis acidic sites couple with the proximal surface hydroxyls to constitute the surface frustrated Lewis pairs(SFLPs).With the in-depth spectroscopic analysis,we revealed that the photo-induced SFLPs act as collection centers to effectively adsorb PFOA and endow accessible pathways to transfer photogenerated holes to PFOA rapidly.Consequently,activation of the terminal carboxyl,a ratelimiting step for PFOA decomposition,could be easily achieved over the defected Bi_(3)O(OH)(PO_(4))_(2) photocatalyst.These results suggest that SFLPs exhibit great potential in developing highly efficient photocatalysts to degrade persistent organic pollutants.展开更多
An efficient decarboxylative/defluorinative alkylation for synthesizing gem-difluoroalkenes is described,providing a general method for installation of the challenging alkyl fragments containing a-electron-withdrawing...An efficient decarboxylative/defluorinative alkylation for synthesizing gem-difluoroalkenes is described,providing a general method for installation of the challenging alkyl fragments containing a-electron-withdrawing groups into a-trifluoromethyl alkenes.Mechanistic studies suggest that this process involves an SN2,-type synthetic route in the absence of transition-metal catalysts or photocatalysis.Moreover,this protocol can easily be scaled up,and successfully applied to the modification of biologically active molecules,thus complementing methodologies that give access to structurally versatile gem-difluoroalkenes.展开更多
Nanophotocatalysts have shown great potential for degrading poly-and perfluorinated substances(PFAS).In light of the fact that most of these catalysts were studied in pure water,this study was designed to elucidate ef...Nanophotocatalysts have shown great potential for degrading poly-and perfluorinated substances(PFAS).In light of the fact that most of these catalysts were studied in pure water,this study was designed to elucidate effects from common environmental factors on decomposing and defluorinating perfluorooctanoic acid(PFOA)by In2O3 nanoparticles.Results from this work demonstrated that among the seven parameters,pH,sulfate,chloride,H2O2,In2O3 dose,NOM and O2,the first four had statistically significant negative effects on PFOA degradation.Since PFOA is a strong acid,the best condition leading to the highest PFOA removal was identified for two pH ranges.When pH was between 4 and 8,the optimal condition was:pH=4.2;sulfate=5.00 mg/L;chloride=20.43 mg/L;H2O2=0 mmol/L.Under this condition,PFOA decomposition and defluorination were 55.22 and 23.56%,respectively.When pH was between 2 and 6,the optimal condition was:pH=2;sulfate=5.00 mg/L;chloride=27.31 mg/L;H2O2=0 mmol/L.With this condition,the modeled PFOA decomposition was 97.59%with a defluorination of approximately 100%.These predicted results were all confirmed by experimental data.Thus,In2O3 nanoparticles can be used for degrading PFOA in aqueous solutions.This approach works best when the target contaminated water contains low concentrations of NOM,sulfate and chloride and at a low pH.展开更多
Monofluoroalkenes are important and versatile privileged components in pharmacologically relevant molecules.Here,we report a method for the selective construction of these compounds in a diversity-oriented fashion thr...Monofluoroalkenes are important and versatile privileged components in pharmacologically relevant molecules.Here,we report a method for the selective construction of these compounds in a diversity-oriented fashion through regiodivergent cross-coupling of gem-difluorocyclopropanes with allylboronates by employing a palladium catalyst with two different ligands,in which gem-difluorocyclopropanes were used as allyl electrophiles by C—C and C—F bond activation.In the presence of 2-biphenylyl(diphenyl)phosphine as ligand,the linear-selective allyl–allyl bond formation is highly obtained,while utilizing the sterically hindered BrettPhos(dicyclohexyl[3,6-dimethoxy-2',4',6'-tris(1-methylethyl)[1,1'-biphenyl]-2-yl]phosphine)as the ligand favors the generation of the branched-selective product.Experimental and computational studies investigated the key steps of the cross-coupling reactions,revealing the origin of the ligand-controlled regiodivergence.展开更多
A straightforward protocol for the synthesis of mono-fluorinated allenes via catalytic defluorinative silylation of the readily availableα,α-difluoroalkylalkynes with commercially available copper catalyst and phosp...A straightforward protocol for the synthesis of mono-fluorinated allenes via catalytic defluorinative silylation of the readily availableα,α-difluoroalkylalkynes with commercially available copper catalyst and phosphine ligand is described.A broad scope ofα,α-difluoroalkylalkynes were well accommodated and a gram-scale synthesis demonstrated the synthetic utility of this methodoglogy.展开更多
A selective monodefluorinative alkylation of 3,3-difluorooxindoles is achieved.The reaction starts by the attack of a 4-dimethylaminopyrine-boryl radical to the carbonyl oxygen atom of 3,3-difluorooxindoles,followed b...A selective monodefluorinative alkylation of 3,3-difluorooxindoles is achieved.The reaction starts by the attack of a 4-dimethylaminopyrine-boryl radical to the carbonyl oxygen atom of 3,3-difluorooxindoles,followed by a spin-center shift to generate radical intermediates with the elimination of a fluoride anion.The subsequent radical addition to alkenes affords a range of 3-alkyl-fluorooxindoles products.The strategy offers access to C-3 functionalized oxindoles with wide substrate scope and tolerates a wide range of functional groups.展开更多
A method for stereoselective construction of Z-monofluoroalkenes by nickel-catalyzed defluorinative coupling of gem‑difluoroalkenes in mild conditions was described.The combination of lithium organoborate and ZnBr_(2)...A method for stereoselective construction of Z-monofluoroalkenes by nickel-catalyzed defluorinative coupling of gem‑difluoroalkenes in mild conditions was described.The combination of lithium organoborate and ZnBr_(2) generated in situ lithium aryl zincates,which facilitates the transmetalation step of the nickel-catalyzed cross coupling reaction.展开更多
gem-Difluoroalkenes are considered ideal isosteres for metabolically susceptible carbonyl groups in modern drug discovery and medicinal chemistry.In addition,gem-difluoroalkenes are used as versatile precursors for th...gem-Difluoroalkenes are considered ideal isosteres for metabolically susceptible carbonyl groups in modern drug discovery and medicinal chemistry.In addition,gem-difluoroalkenes are used as versatile precursors for the synthesis of difluoroalkylated compounds and monofluoroalkenes.Therefore,a great deal of effort has been devoted to developing efficient methods for their preparation.The catalytic defluorinative functionalization of trifluoromethyl alkenes represents a useful strategy for the preparation of chiral gem-difluoroalkenes.However,most of these catalytic processes are still essentially limited to two-component defluorinative cross-couplings to form single C—C bonds.Due to the challenge of controlling chemoselectivity in the carbon-carbon bond forming events,three-component defluorinative cross-coupling involving multiple C—C bond formations has rarely been studied.We report a nickel-catalyzed three-component defluorinative reductive cross-coupling of organohalides,alkenes and trifluoromethyl alkenes.A variety of electron-rich and electron-deficient alkenes,as well as aryl and alkyl halides can efficiently participate in the formation of three-component cross-coupling products.This reaction proceeds under mild conditions and exhibits excellent functional group compatibility without requiring a pendant chelating group,providing a variety of functionalized gem-difluoroalkenes in good yields with excellent chemoselectivity.展开更多
Reported here is a precise electro-reduction strategy for radical defluorinative alkylation towards the synthesis of gem-difluoroalkenes from α-trifluoromethylstyrenes. According to the redox-potential difference of ...Reported here is a precise electro-reduction strategy for radical defluorinative alkylation towards the synthesis of gem-difluoroalkenes from α-trifluoromethylstyrenes. According to the redox-potential difference of the radical precursors, direct or indirect electrolysis is respectively adopted to realize the precise reduction. An easy-to-handle, catalyst-and metal-free condition is developed for the reduction of alkyl radical precursors that are generally easier to be reduced than α-trifluoromethylstyrenes,while a novel electro-Ni-catalytic system is established for the electro-reduction of alkyl bromides or chlorides towards the electrochemical synthesis of gem-difluoroalkenes. The merit of this protocol is exhibited by its mild conditions, wide substrate scope, and scalable preparation. Mechanistic studies and DFT calculations proved that the coordination of α-trifluoromethylstyrenes to Ni-catalyst prevents the direct reduction of the alkene and, in turn, promotes the activation of alkyl bromide through halogen atom transfer mechanism.展开更多
基金supported by the National Science Fund for Distinguished Young Scholars (No.52022111)the Natural Science Foundation of China (No.51974379)the Scientific and Technological Innovation Program of Hunan Province,Huxiang Youth Talent Project (No.2020RC_(3)012)。
文摘Millions of people in poor areas are still under the threat of fluoride contamination.How to effectively separate fluorine in water is an important step to reduce the ecological risk.In this paper,we performed a systematic DFT calculation focused on the defluorination behavior between the LiAl-and MgAl-LDHs.The results indicated that the LiAl-LDHs exhibited high chemical activity before the defluorination,because of the better electronic structure.After the defluorination,the LiAl-LDHs with adsorbed-F–were also more stable than the MgAl-LDHs.In addition,the existence of coordination covalent bond for the adsorbed-F–attached to the LiAl-LDHs was confirmed.This is an important reason for the high defluorination efficiency by the LiAl-LDHs.In addition,a series of weak interaction,including hydrogen bond and van der Waals interaction were also observed.Finally,a LiAl-LDHs with excellent fluoride removal properties were synthesized well by simple hydrothermal method.The results showed that our synthesized LiAl-LDHs with the capacity of 156.09 mg/g,could be effectively defluorinated in water.Notably,it surpasses most materials and has potential applications.
基金Project supported by the National Key Research and Development Program of China(2020YFC1907500)the Fundamental Research Funds of the Ministry of Education of China(N2125033)。
文摘The bastnaesite was defluorinated by steam roasting process,and fluorine was removed in the form of hydrogen fluoride to realize the separation from rare earth.The effects of particle size of raw material,roasting temperature and time on defluorination rate of bastnaesite were studied.The suitable conditions of steam roasting process are that the particle size of raw material is less than 74μm,the roasting temperature is 1000℃and the roasting time is 4 h.The defluorination rate of bastnaesite is close to 100%under above these conditions.When the temperature rises to 1000℃,the voids on the surface of the particles increase obviously,and there is a developed network of voids,which indicates that the fluorine oxides in bastnaesite react fully with the saturated water vapor at this stage,and a large amount of fluorine escapes in the form of hydrogen fluoride from the surface and inside of the mineral.X-ray diffraction results show that there are only rare-earth oxides in the form of Ce_(0.33)La_(0.33)Ca_(0.33)O_(1.5)and Ce_(7)O_(12)in the slag.The results of energy spectra and chemical analysis show that the fluorine in the baking sand was basically completely removed.
基金supported by the National Natural Scientific Foundation of China(Grant Nos.21978300,U1462128,and 91334108)the State Key Development Program for Basic Research of China(973 Program,Grant No.2015CB251402).
文摘Defluorination roasting of lepidolite ore in a fluidized bed reactor has been proposed for improving the extraction efficiency of lithium.In this paper,a vacuum was introduced to the fluidized bed reactor,which significantly improved the defluorination efficiency of lepidolite particles.This improvement could be attributed to an increase in the H2O/HF ratio.The highest defluorination rate for the lepidolite particles was obtained in the fluidized bed reactor under vacuum.The rate in the vacuum reactor was 1.5-2 times that in a fixed bed reactor or conventional fluidized bed reactor.The defluorination efficiency of the lepidolite particles also improved and the consumption of steam was greatly reduced by addition of coal char.This enhancement was mainly attributed to changes in the structures of the reduced lepidolite particles.This defluorination roasting method for high lithium extraction with low water steam consumption is a promising method for lithium ore treatment.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.21861007 and 21702034)Natural Science Foundation of Guangxi Province(Nos.2021GXNSFAA075024 and 2022GXNSFAA035468)+2 种基金the Guangdong Basic and Applied Basic Research Foundation(No.2020A1515010624)Natural Science Foundation of Jiangxi Province of China(No.20212BAB213024)“BAGUI Scholar”Program of Guangxi Province of China.
文摘A novel defluorinative ring-opening of gem-difluorocyclopropenes is presented,providing a concise and efficient method for accessing 2-fluoropropenals and 2-fluorobuta-1,3-dienes in moderate to good yields with excellent regio-and stereoselectivities.The reaction is performed under mild conditions with no need of using an excess amount of nucleophilic reagents.Water plays a crucial role in this transformation.
基金financially supported by the National Natural Science Foundation of China(Nos.22006088 and 42077293)the Natural Science Foundation of Guangdong Province(China)(No.2019QN01L797)+1 种基金the Shenzhen Municipal Science and Technology Innovation Committee(China)(Nos.WDZC20200817103015002 and RCYX20210609104448111)the Tsinghua Shenzhen International Graduate School(China)(Nos.HW2020002 and QD2021010N).
文摘Heterogeneous photocatalysis has gained substantial research interest in treating per-and polyfluoroalkyl substances(PFAS)-contaminated water.However,sluggish degradation kinetics and low defluorination efficiency compromise their practical applications.Here,we report a superior photocatalyst,defected Bi_(3)O(OH)(PO_(4))_(2),which could effectively degrade typical PFAS,perfluorooctanoic acid(PFOA),with high defluorination efficiency.The UV light irradiation could in situ generate oxygen vacancies on Bi_(3)O(OH)(PO_(4))_(2) through oxidation of the lattice hydroxyls,which further promotes the formation of Lewis acidic coordinately unsaturated bismuth sites.Then,the Lewis acidic sites couple with the proximal surface hydroxyls to constitute the surface frustrated Lewis pairs(SFLPs).With the in-depth spectroscopic analysis,we revealed that the photo-induced SFLPs act as collection centers to effectively adsorb PFOA and endow accessible pathways to transfer photogenerated holes to PFOA rapidly.Consequently,activation of the terminal carboxyl,a ratelimiting step for PFOA decomposition,could be easily achieved over the defected Bi_(3)O(OH)(PO_(4))_(2) photocatalyst.These results suggest that SFLPs exhibit great potential in developing highly efficient photocatalysts to degrade persistent organic pollutants.
基金the support from the National Natural Science Foundation of China(Nos.21732006,51821006 and 51961135104)the Natural Science Foundation of Anhui(No.2008085MB40)+1 种基金the USTC Research Funds of the Double First Class Initiative(No.YD2060002003)The authors thank Xi Lu(University of Science and Technology of China)for insightful discussion during the preparation of the manuscript.
文摘An efficient decarboxylative/defluorinative alkylation for synthesizing gem-difluoroalkenes is described,providing a general method for installation of the challenging alkyl fragments containing a-electron-withdrawing groups into a-trifluoromethyl alkenes.Mechanistic studies suggest that this process involves an SN2,-type synthetic route in the absence of transition-metal catalysts or photocatalysis.Moreover,this protocol can easily be scaled up,and successfully applied to the modification of biologically active molecules,thus complementing methodologies that give access to structurally versatile gem-difluoroalkenes.
基金funding provided by University at Albany,State University of New York。
文摘Nanophotocatalysts have shown great potential for degrading poly-and perfluorinated substances(PFAS).In light of the fact that most of these catalysts were studied in pure water,this study was designed to elucidate effects from common environmental factors on decomposing and defluorinating perfluorooctanoic acid(PFOA)by In2O3 nanoparticles.Results from this work demonstrated that among the seven parameters,pH,sulfate,chloride,H2O2,In2O3 dose,NOM and O2,the first four had statistically significant negative effects on PFOA degradation.Since PFOA is a strong acid,the best condition leading to the highest PFOA removal was identified for two pH ranges.When pH was between 4 and 8,the optimal condition was:pH=4.2;sulfate=5.00 mg/L;chloride=20.43 mg/L;H2O2=0 mmol/L.Under this condition,PFOA decomposition and defluorination were 55.22 and 23.56%,respectively.When pH was between 2 and 6,the optimal condition was:pH=2;sulfate=5.00 mg/L;chloride=27.31 mg/L;H2O2=0 mmol/L.With this condition,the modeled PFOA decomposition was 97.59%with a defluorination of approximately 100%.These predicted results were all confirmed by experimental data.Thus,In2O3 nanoparticles can be used for degrading PFOA in aqueous solutions.This approach works best when the target contaminated water contains low concentrations of NOM,sulfate and chloride and at a low pH.
基金the National Natural Science Foundation of China(Grants 22025104,21972064 and 21901111)the Fundamental Research Funds for the Central Universities for their financial support(Grant 020514380254)The project was also supported by Open Research Fund of School of Chemistry and Chemical Engineering,Henan Normal University.
文摘Monofluoroalkenes are important and versatile privileged components in pharmacologically relevant molecules.Here,we report a method for the selective construction of these compounds in a diversity-oriented fashion through regiodivergent cross-coupling of gem-difluorocyclopropanes with allylboronates by employing a palladium catalyst with two different ligands,in which gem-difluorocyclopropanes were used as allyl electrophiles by C—C and C—F bond activation.In the presence of 2-biphenylyl(diphenyl)phosphine as ligand,the linear-selective allyl–allyl bond formation is highly obtained,while utilizing the sterically hindered BrettPhos(dicyclohexyl[3,6-dimethoxy-2',4',6'-tris(1-methylethyl)[1,1'-biphenyl]-2-yl]phosphine)as the ligand favors the generation of the branched-selective product.Experimental and computational studies investigated the key steps of the cross-coupling reactions,revealing the origin of the ligand-controlled regiodivergence.
基金support of the National Natural Science Foundation of China(No.21871138)Distinguished Youth Foundation of Jiangsu province.
文摘A straightforward protocol for the synthesis of mono-fluorinated allenes via catalytic defluorinative silylation of the readily availableα,α-difluoroalkylalkynes with commercially available copper catalyst and phosphine ligand is described.A broad scope ofα,α-difluoroalkylalkynes were well accommodated and a gram-scale synthesis demonstrated the synthetic utility of this methodoglogy.
基金We thank the National Natural Science Foundation of China(Nos.21971226 and 22171253)the Anhui Provincial Natural Science Foundation(No.2108085MB59)the Fundamental Research Funds for the Central Universities(No.WK2060000017)for financial support.
文摘A selective monodefluorinative alkylation of 3,3-difluorooxindoles is achieved.The reaction starts by the attack of a 4-dimethylaminopyrine-boryl radical to the carbonyl oxygen atom of 3,3-difluorooxindoles,followed by a spin-center shift to generate radical intermediates with the elimination of a fluoride anion.The subsequent radical addition to alkenes affords a range of 3-alkyl-fluorooxindoles products.The strategy offers access to C-3 functionalized oxindoles with wide substrate scope and tolerates a wide range of functional groups.
基金the National Natural Science Foundation of China(Nos.21625206.21632009,21421002,22061160465)for financial support.
文摘A method for stereoselective construction of Z-monofluoroalkenes by nickel-catalyzed defluorinative coupling of gem‑difluoroalkenes in mild conditions was described.The combination of lithium organoborate and ZnBr_(2) generated in situ lithium aryl zincates,which facilitates the transmetalation step of the nickel-catalyzed cross coupling reaction.
基金support from NSFC(22171215)Guangdong Basic and Applied Basic Research Foundation(2022A1515010246)+2 种基金Y.P.thanks the Fundamental Research Funds for the Central Universities(2042021kf0032)the 68th China Postdoctoral Science Foundation(2020M680108)the Postdoctoral Foundation of Hubei Province(211000012).
文摘gem-Difluoroalkenes are considered ideal isosteres for metabolically susceptible carbonyl groups in modern drug discovery and medicinal chemistry.In addition,gem-difluoroalkenes are used as versatile precursors for the synthesis of difluoroalkylated compounds and monofluoroalkenes.Therefore,a great deal of effort has been devoted to developing efficient methods for their preparation.The catalytic defluorinative functionalization of trifluoromethyl alkenes represents a useful strategy for the preparation of chiral gem-difluoroalkenes.However,most of these catalytic processes are still essentially limited to two-component defluorinative cross-couplings to form single C—C bonds.Due to the challenge of controlling chemoselectivity in the carbon-carbon bond forming events,three-component defluorinative cross-coupling involving multiple C—C bond formations has rarely been studied.We report a nickel-catalyzed three-component defluorinative reductive cross-coupling of organohalides,alkenes and trifluoromethyl alkenes.A variety of electron-rich and electron-deficient alkenes,as well as aryl and alkyl halides can efficiently participate in the formation of three-component cross-coupling products.This reaction proceeds under mild conditions and exhibits excellent functional group compatibility without requiring a pendant chelating group,providing a variety of functionalized gem-difluoroalkenes in good yields with excellent chemoselectivity.
基金supported by the National Key Research and Development Program of China(2021YFA1500100)the National Natural Science Foundation of China(22031008)the Science Foundation of Wuhan(2020010601012192)。
文摘Reported here is a precise electro-reduction strategy for radical defluorinative alkylation towards the synthesis of gem-difluoroalkenes from α-trifluoromethylstyrenes. According to the redox-potential difference of the radical precursors, direct or indirect electrolysis is respectively adopted to realize the precise reduction. An easy-to-handle, catalyst-and metal-free condition is developed for the reduction of alkyl radical precursors that are generally easier to be reduced than α-trifluoromethylstyrenes,while a novel electro-Ni-catalytic system is established for the electro-reduction of alkyl bromides or chlorides towards the electrochemical synthesis of gem-difluoroalkenes. The merit of this protocol is exhibited by its mild conditions, wide substrate scope, and scalable preparation. Mechanistic studies and DFT calculations proved that the coordination of α-trifluoromethylstyrenes to Ni-catalyst prevents the direct reduction of the alkene and, in turn, promotes the activation of alkyl bromide through halogen atom transfer mechanism.
