α-Trifluoromethyl ketones are a class of useful compounds with versatile applications.Their synthetic application via the transformation of the C—F bonds is of particular interest by allowing the synthesis of organi...α-Trifluoromethyl ketones are a class of useful compounds with versatile applications.Their synthetic application via the transformation of the C—F bonds is of particular interest by allowing the synthesis of organic compounds with diverse structures.Herein,the advances in the research areas ofα-trifluoromethyl ketone synthesis and their defluorination reactions are reviewed.Discussion on the mechanisms of the typical reactions has also been provided,in hope of affording some guides to the chemistry ofα-trifluoromethyl ketones in the synthetic methods toward themselves and their derivatives.展开更多
The C—F bond transformation of gem-difluorinated cyclopropanes without cleavage of the highly strained C—C bond is an intractable challenge. The synthesis of cyclopropanone ketals via double defluorination of gem-di...The C—F bond transformation of gem-difluorinated cyclopropanes without cleavage of the highly strained C—C bond is an intractable challenge. The synthesis of cyclopropanone ketals via double defluorination of gem-difluorinated cyclo-propanesunder transition-metal free and basic conditions has been developed. A broad range of gem-difluorinated cyclopro-panesand alcohols are amenable in present reaction to permit the synthesis of corresponding products in high yields. The reaction is elucidated to proceed via elimination and addition other than direct substitution based on the mechanistic studies. This transformation not only provides a new strategy for the construction of cyclopropanone ketals, but also reveals a new paradigm on C—F bond transformation without ring-opening of gem-difluorinated cyclopropanes.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
A catalyst-free and additive-free ring-opening reaction of polyfluoroalkyl peroxides,triethylenediamine(DABCO),and 1,2-dichloroethane(DCE)has been developed for the defluorinative synthesis of structurally diverse pip...A catalyst-free and additive-free ring-opening reaction of polyfluoroalkyl peroxides,triethylenediamine(DABCO),and 1,2-dichloroethane(DCE)has been developed for the defluorinative synthesis of structurally diverse piperazines featuring a fluoroenone framework and a N-chloroethyl-substituent with high Z-stereoselectivity.The success of this three-component reaction is attributed to the in situ generation of an active 1-(2-chloroethyl)-1,4-diazabicyclo[2.2.2]octan-1-ium(DABCO·DCE)salt,which judiciously acts as a formal N-(2-chloroethyl)piperazine equivalent in the defluorinative coupling with less-studied aliphatic fluorinated substances.Impressively,this reaction accomplishes multi-activation of robust C(sp^(3))-F,C(sp^(3))-Cl,C(sp^(3))-O,and C(sp^(3))-N bonds in a one-pot process,offering a practical platform for the late-stage functionalization of complex molecules.Furthermore,the resulting products can not only serve as versatile building blocks for the synthesis of fluorinated heterocycles,but also undergo C—Cl bond displacement transformations with N-,O-,and S-nucleophiles.展开更多
We herein describe an enantio-and diastereoselective rhodium(I)-catalyzed defluorinative arylation of pentafluoroethyl alkenes with arylboronic acids.A new class of previously inaccessible functionalized fluoroalkenes...We herein describe an enantio-and diastereoselective rhodium(I)-catalyzed defluorinative arylation of pentafluoroethyl alkenes with arylboronic acids.A new class of previously inaccessible functionalized fluoroalkenes featuring a sp^(2)-carbon connected to F and CF_(3) can be synthesized.Using both 1,1-and 1,2-disubstituted alkene substrates,tetra-and trisubstituted fluoroalkene products are obtained in excellent Z/E selectivities with well-defined alkene geometry.These fluoroalkenes are potential synthons for accessing chiral compounds containing a stereogenic centre with F and CF_(3) group.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
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
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
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
Organic fluorine compounds are ubiquitous and pivotally important organic molecules,yet their activation and transformation have long been a formidable challenge due to the high energy and low reactivity of C-F bonds....Organic fluorine compounds are ubiquitous and pivotally important organic molecules,yet their activation and transformation have long been a formidable challenge due to the high energy and low reactivity of C-F bonds.Organic electrosynthesis,an environmentally benign synthetic method in organic chemistry,enables a myriad of chemical transformations without the need for external redox reagents.In recent years,organic electrochemistry has emerged as a powerful tool for achieving the activation and transformation of C-F bonds in fluorine-containing compounds.This review aims to succinctly recapitulate the latest advancements in the electrochemical defluorinative transformations of C-F bonds and to delve into the reaction design,mechanistic insights,and developmental prospects ofthese methods.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
Selective defluorinative functionalization of trifluoromethylarenes(ArCF3)to obtain the pharmaceutically commonα,α-difluorobenzylic motif is an attractive and elegant synthetic route.Over the past decade,although C(...Selective defluorinative functionalization of trifluoromethylarenes(ArCF3)to obtain the pharmaceutically commonα,α-difluorobenzylic motif is an attractive and elegant synthetic route.Over the past decade,although C(sp^(3))-F bonds functionalization have been greatly developed,catalytic cross-coupling of trifluoromethylarenes with C-H of terminal alkynes remains a challenge.Here,we report an approach to achieve Sonogashira-type cross-coupling of trifluoromethylarenes with terminal alkynes C(sp)-H bonds via photoredox and Cu/L dual catalysis.Tridentate anionic ligand is pivotal to realize this C-H sp-sp^(3) cross-coupling.Moreover,this unique catalytic system is also suitable for cross-coupling of C(sp^(3))-F bonds with azoles C(sp^(2))-H bonds.A series of trifluoromethylarenes,terminal alkynes and azoles with various functional groups are compatible with this protocol affording a variety of defluoroalkynylation or defluoroazolation products.Preliminary mechanistic studies indicated that deprotonated BINOL involved as a photocatalyst to activate ArCF3 rather than a ligand to the metal.展开更多
This study investigates the removal of fluorine(F)impurities from phosphogypsum(PG)using steam as the reaction medium.The effects of the reaction atmosphere,temperature,time,and steam velocity on F impurities removal ...This study investigates the removal of fluorine(F)impurities from phosphogypsum(PG)using steam as the reaction medium.The effects of the reaction atmosphere,temperature,time,and steam velocity on F impurities removal were systematically examined.The results showed that with a steam velocity of 0.0184 m·s^(-1),a reaction temperature of 700℃,and a reaction time of 60 min,the F removal rate reached 95.87%.Further investigations into the defluorination mechanism revealed that steam and SiO_(2) synergistically enhance fluoride removal,playing a crucial role in improving the defluorination efficiency.Kinetic analysis of the defluorination process,based on the shrinking core model(SCM),indicated that internal diffusion is the rate-controlling step,with the activation energy of 30.12 kJ·mol^(-1).This study identifies optimal conditions for PG defluorination and proposes a defluorination mechanism,contributing to the theoretical understanding of impurity removal through the thermal treatment of PG.展开更多
Perfluoroalkyl substances(PFASs)are typical persistent organic pollutants,and their removal is urgently required but challenging.Photocatalysis has shown potential in PFASs degradation due to the redox capabilities of...Perfluoroalkyl substances(PFASs)are typical persistent organic pollutants,and their removal is urgently required but challenging.Photocatalysis has shown potential in PFASs degradation due to the redox capabilities of photoinduced charge carriers in photocatalysts.Herein,hexagonal ZnIn_(2)S_(4)(ZIS)nanosheets were synthesized by a one-pot oil bath method and were well characterized by a series of techniques.In the degradation of sodium p-perfluorous nonenoxybenzenesulfonate(OBS),one kind of representative PFASs,the assynthesized ZIS showed activity superior to P25 TiO_(2) under both simulated sunlight and visible-light irradiation.The good photocatalytic performance was attributed to the enhanced light absorption and facilitated charge separation.The pH conditions were found crucial in the photocatalytic process by influencing the OBS adsorption on the ZIS surface.Photogenerated e−and h+were the main active species involved in OBS degradation in the ZIS system.This work confirmed the feasibility and could provide mechanistic insights into the degradation and defluorination of PFASs by visible-light photocatalysis.展开更多
Biochar,as an efficient,effective,and potential soil improver,has broad application prospects in the field of defluoridation.This study aimed to evaluate the defluoridation potential of iron(Fe)and manganese(Mn)co-mod...Biochar,as an efficient,effective,and potential soil improver,has broad application prospects in the field of defluoridation.This study aimed to evaluate the defluoridation potential of iron(Fe)and manganese(Mn)co-modified biochar from groundwater.The varied Fe/Mn molar ratio(2∶1 and 1∶2)modified biochar was prepared by corncob with the pyrolysis temperature of 300℃,400℃,and 500℃.Batch experiments for fluoride(F^(-))removal were performed by corncob biochar before and after Fe-Mn modified.Their composition,structure,and performance were analyzed by multiple characterization techniques to clarify F‒removal mechanisms.Our results indicated that unmodified corncob biochar produced at 400℃(BC400)exhibited the highest F‒adsorption efficiency(87.3%)among three unmodified samples,attributable to its largest specific surface area(2.55 m^(2)/g).Notably,F‒removal amounts by Fe-Mn modified BC400 were 2 times higher than BC400.The enhanced F⁻removal performance of Fe-Mn modified biochar can be attributed to several mechanisms:(1)the modification produced rougher surface textures,resulting in an increased specific surface area(about 3.50 m^(2)/g);(2)newly formed Fe-O and Mn-O bonds on the biochar surface facilitated the formation of complexes with F^(-);and(3)the adsorption results fitted well with pseudo-second-order and Freundlich models(R^(2)>0.98),indicating that the removal process involved physicochemical adsorption.These findings demonstrate that Fe-Mn modified biochar is a highly efficient and cost-effective material for F^(-)remediation and holds significant potential for application in contaminated groundwater and soil systems.展开更多
A systematic and green low-temperature sulfation roasting−water leaching strategy was put forward to achieve a very high fluorine removal rate of 97.82%for spent carbon cathode(SCC),which was believed as a hazardous s...A systematic and green low-temperature sulfation roasting−water leaching strategy was put forward to achieve a very high fluorine removal rate of 97.82%for spent carbon cathode(SCC),which was believed as a hazardous solid waste.And the carbon could be recycled with a purity of 90.29 wt.%in the flaky microstructure.Thermodynamic analysis and the results of SEM,XRD and EDS indicate that most of the fluoride could convert into water-soluble sulfate at low temperature.And the highest fluorine removal rate could be obtained when<0.15 mm SCC particles were mixed with sulfuric acid at a liquid-to-solid ratio of 1:1,and then roasted at 300℃ for 0.5 h.The sulfate was removed to purify the carbon via water-leaching process.Avrami exponents and corresponding activation energy for the roasting and leaching process demonstrated that both processes are controlled by diffusion.展开更多
Perfluorooctanoic acid （PFOA） is a new-found hazardous persistent organic pollutant, and it is resistant to decomposition by hydroxyl radical （HO.） due to its stable chemical structure and the high electronegativi...Perfluorooctanoic acid （PFOA） is a new-found hazardous persistent organic pollutant, and it is resistant to decomposition by hydroxyl radical （HO.） due to its stable chemical structure and the high electronegativity of fluorine. Photocatalytic reduction of PFOA with β-Ga2O3 in anoxic aqueous solution was investigated for the first time, and the results showed that the photoinduced electron （ecb） coming from the β-Ga2O3 conduction band was the major degradation substance for PFOA, and shorter-chain perfluorinated carboxylic acids （PFCAs, CnF2n＋1COOH, 1 ≤ n ≤ 6） were the dominant products. Furthermore, the concentration of F- was measured by the IC technique and defluorination efficiency was calculated. After 3 hr, the photocatalytic degradation efficiency was 98.8% and defluorination efficiency was 31.6% in the presence of thiosulfate and bubbling N2. The degradation reaction followed first-order kinetics （k = 0.0239 min-1, t1/2 = 0.48 hr）. PFCAs （CnF2n＋xCOOH, 1 ≤ n≤ 7） were detected and measured by LC-MS and LC-MS/MS methods. It was deduced that the probable photocatalytic degradation mechanism involves ec-b attacking the carboxyl of CnF2n＋1COOH, resulting in decarboxylation and the generation of CnFzn＋1. The produced CnF2n＋1 reacted with H2O, forming CnF2n＋1OH, then CnF2n＋1OH underwent HF loss and hydrolysis to form CnF2,＋1COOH.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
文摘α-Trifluoromethyl ketones are a class of useful compounds with versatile applications.Their synthetic application via the transformation of the C—F bonds is of particular interest by allowing the synthesis of organic compounds with diverse structures.Herein,the advances in the research areas ofα-trifluoromethyl ketone synthesis and their defluorination reactions are reviewed.Discussion on the mechanisms of the typical reactions has also been provided,in hope of affording some guides to the chemistry ofα-trifluoromethyl ketones in the synthetic methods toward themselves and their derivatives.
文摘The C—F bond transformation of gem-difluorinated cyclopropanes without cleavage of the highly strained C—C bond is an intractable challenge. The synthesis of cyclopropanone ketals via double defluorination of gem-difluorinated cyclo-propanesunder transition-metal free and basic conditions has been developed. A broad range of gem-difluorinated cyclopro-panesand alcohols are amenable in present reaction to permit the synthesis of corresponding products in high yields. The reaction is elucidated to proceed via elimination and addition other than direct substitution based on the mechanistic studies. This transformation not only provides a new strategy for the construction of cyclopropanone ketals, but also reveals a new paradigm on C—F bond transformation without ring-opening of gem-difluorinated cyclopropanes.
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the financial support from the National Natural Science Foundation of China(22001121)Nanjing Tech University。
文摘A catalyst-free and additive-free ring-opening reaction of polyfluoroalkyl peroxides,triethylenediamine(DABCO),and 1,2-dichloroethane(DCE)has been developed for the defluorinative synthesis of structurally diverse piperazines featuring a fluoroenone framework and a N-chloroethyl-substituent with high Z-stereoselectivity.The success of this three-component reaction is attributed to the in situ generation of an active 1-(2-chloroethyl)-1,4-diazabicyclo[2.2.2]octan-1-ium(DABCO·DCE)salt,which judiciously acts as a formal N-(2-chloroethyl)piperazine equivalent in the defluorinative coupling with less-studied aliphatic fluorinated substances.Impressively,this reaction accomplishes multi-activation of robust C(sp^(3))-F,C(sp^(3))-Cl,C(sp^(3))-O,and C(sp^(3))-N bonds in a one-pot process,offering a practical platform for the late-stage functionalization of complex molecules.Furthermore,the resulting products can not only serve as versatile building blocks for the synthesis of fluorinated heterocycles,but also undergo C—Cl bond displacement transformations with N-,O-,and S-nucleophiles.
基金supported by the Research Grants Council of Hong Kong(CUHK 14301324 and JLFS/P-404/24)The Chinese University of Hong Kong(Strategic Seed Funding for Collaborative Research Scheme SSFCRS 2024-25).
文摘We herein describe an enantio-and diastereoselective rhodium(I)-catalyzed defluorinative arylation of pentafluoroethyl alkenes with arylboronic acids.A new class of previously inaccessible functionalized fluoroalkenes featuring a sp^(2)-carbon connected to F and CF_(3) can be synthesized.Using both 1,1-and 1,2-disubstituted alkene substrates,tetra-and trisubstituted fluoroalkene products are obtained in excellent Z/E selectivities with well-defined alkene geometry.These fluoroalkenes are potential synthons for accessing chiral compounds containing a stereogenic centre with F and CF_(3) group.
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.
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 Natural Science Foundation of Zhejiang Province(LQ22B020005,LZ22B020003)the National Natural Science Foundation of China(22101201,22071171)for financial support of this work.
文摘Organic fluorine compounds are ubiquitous and pivotally important organic molecules,yet their activation and transformation have long been a formidable challenge due to the high energy and low reactivity of C-F bonds.Organic electrosynthesis,an environmentally benign synthetic method in organic chemistry,enables a myriad of chemical transformations without the need for external redox reagents.In recent years,organic electrochemistry has emerged as a powerful tool for achieving the activation and transformation of C-F bonds in fluorine-containing compounds.This review aims to succinctly recapitulate the latest advancements in the electrochemical defluorinative transformations of C-F bonds and to delve into the reaction design,mechanistic insights,and developmental prospects ofthese methods.
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support of this work by the National Natural Science Foundation of China(Nos.22371307,21971267)the program for Guangdong Introducing Innovative and Entrepreneurial Teams(No.2017ZT07C069).
文摘Selective defluorinative functionalization of trifluoromethylarenes(ArCF3)to obtain the pharmaceutically commonα,α-difluorobenzylic motif is an attractive and elegant synthetic route.Over the past decade,although C(sp^(3))-F bonds functionalization have been greatly developed,catalytic cross-coupling of trifluoromethylarenes with C-H of terminal alkynes remains a challenge.Here,we report an approach to achieve Sonogashira-type cross-coupling of trifluoromethylarenes with terminal alkynes C(sp)-H bonds via photoredox and Cu/L dual catalysis.Tridentate anionic ligand is pivotal to realize this C-H sp-sp^(3) cross-coupling.Moreover,this unique catalytic system is also suitable for cross-coupling of C(sp^(3))-F bonds with azoles C(sp^(2))-H bonds.A series of trifluoromethylarenes,terminal alkynes and azoles with various functional groups are compatible with this protocol affording a variety of defluoroalkynylation or defluoroazolation products.Preliminary mechanistic studies indicated that deprotonated BINOL involved as a photocatalyst to activate ArCF3 rather than a ligand to the metal.
基金funded by the National Key Research and Development Program of China(2018YFC1903500)the National Key Research and Development Program of China(2019YFC1905800)+1 种基金Hebei Provincial Key Research Projects(22373101D)the commercial project by Beijing Zhong Dian Hua Yuan Environment Protection Technology Co.,Ltd.(E01211200005)。
文摘This study investigates the removal of fluorine(F)impurities from phosphogypsum(PG)using steam as the reaction medium.The effects of the reaction atmosphere,temperature,time,and steam velocity on F impurities removal were systematically examined.The results showed that with a steam velocity of 0.0184 m·s^(-1),a reaction temperature of 700℃,and a reaction time of 60 min,the F removal rate reached 95.87%.Further investigations into the defluorination mechanism revealed that steam and SiO_(2) synergistically enhance fluoride removal,playing a crucial role in improving the defluorination efficiency.Kinetic analysis of the defluorination process,based on the shrinking core model(SCM),indicated that internal diffusion is the rate-controlling step,with the activation energy of 30.12 kJ·mol^(-1).This study identifies optimal conditions for PG defluorination and proposes a defluorination mechanism,contributing to the theoretical understanding of impurity removal through the thermal treatment of PG.
基金supported by the National Natural Science Foundation of China (Nos.22206113 and 22376124)the Outstanding Youth Science Fund (Overseas)of Shandong Provincial Natural Science Foundation (No.2022HWYQ-015)+2 种基金the Taishan Scholars Project Special Fund (No.tsqn202211039)the Guangdong Basic and Applied Basic Research Foundation (No.2021A1515111137)Qilu Youth Talent Program of Shandong University (No.61440082163171).
文摘Perfluoroalkyl substances(PFASs)are typical persistent organic pollutants,and their removal is urgently required but challenging.Photocatalysis has shown potential in PFASs degradation due to the redox capabilities of photoinduced charge carriers in photocatalysts.Herein,hexagonal ZnIn_(2)S_(4)(ZIS)nanosheets were synthesized by a one-pot oil bath method and were well characterized by a series of techniques.In the degradation of sodium p-perfluorous nonenoxybenzenesulfonate(OBS),one kind of representative PFASs,the assynthesized ZIS showed activity superior to P25 TiO_(2) under both simulated sunlight and visible-light irradiation.The good photocatalytic performance was attributed to the enhanced light absorption and facilitated charge separation.The pH conditions were found crucial in the photocatalytic process by influencing the OBS adsorption on the ZIS surface.Photogenerated e−and h+were the main active species involved in OBS degradation in the ZIS system.This work confirmed the feasibility and could provide mechanistic insights into the degradation and defluorination of PFASs by visible-light photocatalysis.
基金financially supported by the National Natural Science Foundation of China(42007181)Chinese Academy of Geological Sciences Basal Research Fund(CSJ-2024-03)National Key Research and Development Program of China(2023YFC3709104).
文摘Biochar,as an efficient,effective,and potential soil improver,has broad application prospects in the field of defluoridation.This study aimed to evaluate the defluoridation potential of iron(Fe)and manganese(Mn)co-modified biochar from groundwater.The varied Fe/Mn molar ratio(2∶1 and 1∶2)modified biochar was prepared by corncob with the pyrolysis temperature of 300℃,400℃,and 500℃.Batch experiments for fluoride(F^(-))removal were performed by corncob biochar before and after Fe-Mn modified.Their composition,structure,and performance were analyzed by multiple characterization techniques to clarify F‒removal mechanisms.Our results indicated that unmodified corncob biochar produced at 400℃(BC400)exhibited the highest F‒adsorption efficiency(87.3%)among three unmodified samples,attributable to its largest specific surface area(2.55 m^(2)/g).Notably,F‒removal amounts by Fe-Mn modified BC400 were 2 times higher than BC400.The enhanced F⁻removal performance of Fe-Mn modified biochar can be attributed to several mechanisms:(1)the modification produced rougher surface textures,resulting in an increased specific surface area(about 3.50 m^(2)/g);(2)newly formed Fe-O and Mn-O bonds on the biochar surface facilitated the formation of complexes with F^(-);and(3)the adsorption results fitted well with pseudo-second-order and Freundlich models(R^(2)>0.98),indicating that the removal process involved physicochemical adsorption.These findings demonstrate that Fe-Mn modified biochar is a highly efficient and cost-effective material for F^(-)remediation and holds significant potential for application in contaminated groundwater and soil systems.
基金the Natural Science Foundation of Hunan Province,China(No.2020JJ1007).
文摘A systematic and green low-temperature sulfation roasting−water leaching strategy was put forward to achieve a very high fluorine removal rate of 97.82%for spent carbon cathode(SCC),which was believed as a hazardous solid waste.And the carbon could be recycled with a purity of 90.29 wt.%in the flaky microstructure.Thermodynamic analysis and the results of SEM,XRD and EDS indicate that most of the fluoride could convert into water-soluble sulfate at low temperature.And the highest fluorine removal rate could be obtained when<0.15 mm SCC particles were mixed with sulfuric acid at a liquid-to-solid ratio of 1:1,and then roasted at 300℃ for 0.5 h.The sulfate was removed to purify the carbon via water-leaching process.Avrami exponents and corresponding activation energy for the roasting and leaching process demonstrated that both processes are controlled by diffusion.
基金supported by the National Natural Science Foundation of China (No. 20907026)the High Level Talent Research Foundation of Qindao Technological University (No:C-10-210)
文摘Perfluorooctanoic acid （PFOA） is a new-found hazardous persistent organic pollutant, and it is resistant to decomposition by hydroxyl radical （HO.） due to its stable chemical structure and the high electronegativity of fluorine. Photocatalytic reduction of PFOA with β-Ga2O3 in anoxic aqueous solution was investigated for the first time, and the results showed that the photoinduced electron （ecb） coming from the β-Ga2O3 conduction band was the major degradation substance for PFOA, and shorter-chain perfluorinated carboxylic acids （PFCAs, CnF2n＋1COOH, 1 ≤ n ≤ 6） were the dominant products. Furthermore, the concentration of F- was measured by the IC technique and defluorination efficiency was calculated. After 3 hr, the photocatalytic degradation efficiency was 98.8% and defluorination efficiency was 31.6% in the presence of thiosulfate and bubbling N2. The degradation reaction followed first-order kinetics （k = 0.0239 min-1, t1/2 = 0.48 hr）. PFCAs （CnF2n＋xCOOH, 1 ≤ n≤ 7） were detected and measured by LC-MS and LC-MS/MS methods. It was deduced that the probable photocatalytic degradation mechanism involves ec-b attacking the carboxyl of CnF2n＋1COOH, resulting in decarboxylation and the generation of CnFzn＋1. The produced CnF2n＋1 reacted with H2O, forming CnF2n＋1OH, then CnF2n＋1OH underwent HF loss and hydrolysis to form CnF2,＋1COOH.
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.
