Acid catalysis,one of the most important industrial processes,suffers from the toxicity,corrosion and recyclability problems of conventional homogeneous acid catalysts.Thus,the development of green heterogeneous acid ...Acid catalysis,one of the most important industrial processes,suffers from the toxicity,corrosion and recyclability problems of conventional homogeneous acid catalysts.Thus,the development of green heterogeneous acid catalysts becomes the focus of fundamental research and industrial catalysis.As a class of discrete anionic metal-oxygen clusters with tunable structure at the molecular and atomic scales,polyoxometalates(POMs)benefit from their super strong Br?nsted acidity,high proton mobility,and thermal stability.POMs-based heterogeneous catalysts have been used as the potential green alternatives to conventional homogeneous acid catalysts.In this review,we summarize recent progress on the design strategies of the POMs-based heterogeneous catalysts and their catalytic properties in acid-catalyzed reactions,where they are combined with functionalized cations,modified through covalent interactions,supported onto the non-precious metal support,and introduced into the framework of porous polymers.The design,functional strategies and catalytic performance of these POMs-based heterogeneous catalysts in specific acid-catalyzed reactions are emphasized.展开更多
INTRODUCTIONThough potassium salts of rare earth substituted silicotungsticacids were synthesized early in 1971 by R.D.Peacock etc.,sofar the reports about the application of the corresponding acidshave not been found...INTRODUCTIONThough potassium salts of rare earth substituted silicotungsticacids were synthesized early in 1971 by R.D.Peacock etc.,sofar the reports about the application of the corresponding acidshave not been found.We prepared fourteen rare earth substitutedsilicotungstic acids and determined their thermal stability,IRabsorption Spectra and x-ray diffraction spectra.Furthermore,thecatalytic activities of the fourteen heteropoly acids in acid cata-lytic reaction were investigated.Our experimental results demonstrated rare earth substituted silico-tungstic acids have very high catalytic activity in the reaction展开更多
In this paper,sulfonic groups functionalized annealed bio-based carbon microspheres loaded polytetrafluoroethylene(A-BCMSs-SO_(3)H@PTFE)fibers with high activity,high stability,and easy regeneration were successfully ...In this paper,sulfonic groups functionalized annealed bio-based carbon microspheres loaded polytetrafluoroethylene(A-BCMSs-SO_(3)H@PTFE)fibers with high activity,high stability,and easy regeneration were successfully fabricated by a simple method using low-cost raw materials.The characterization results showed that the annealed biomass carbon microspheres derived from waste Camellia oleifera shells were evenly distributed on the polytetrafluoroethylene fibers and the sulfonic groups can be successfully loaded on the surface of annealed biomass carbon microspheres by room temperature sulfonation.Subsequently,the as-prepared A-BCMSs-SO_(3)H@PTFE fibers were applied to the acidcatalyzed synthesis of liquid biofuel 5-ethoxymethylfurfural.The catalytic experiment results indicated that the annealing temperature and time during catalyst preparation have a significant effect on the activity and selectivity of A-BCMSs-SO_(3)H@PTFE fibers.The results of catalytic reaction kinetics showed that the yield of 5-ethoxymethylfurfural can reach more than 60%after 72 h of acid-catalyzed reaction.The stability test showed that the as-prepared A-BCMSs-SO_(3)H@PTFE fibers still maintained a stable acid catalytic activity after four recycles.展开更多
In this study, African crude palm olein (CPO) was used to synthesize biodiesel. The objective was to determine the optimal reaction conditions for the methanolysis of olein. The used CPO had a 5.72% concentration of f...In this study, African crude palm olein (CPO) was used to synthesize biodiesel. The objective was to determine the optimal reaction conditions for the methanolysis of olein. The used CPO had a 5.72% concentration of free fatty acids (FFA);thus, the production of biodiesel was carried out in two stages: 1) esterification using sulfuric acid and 2) transesterification using sodium methoxide. In order to optimize the yield of biodiesel during the transesterification process, a central rotatable design and the response surface methodology were used. The studied variables were: catalyst loading, reaction time and reaction temperature. The analysis of variance showed that the variables with significant effect were the catalyst loading, reaction temperature and reaction time;as well as the catalyst loading*reaction temperature and catalyst loading*reaction time. Results indicate that the optimal reaction conditions during transesterification are: 0.65% catalyst loading (wt/wt<sub>aceite</sub>), reaction time of 135 min and a reaction temperature of 56°C. The optimal reaction conditions during esterification are: 2.5% weight of catalyst, reaction time of 150 min and a reaction temperature of 64.5°C. Under these conditions, a 90% yield of biodiesel was obtained.展开更多
Polyoxometalates(POMs)have conducive properties such as controlled Bronsted and Lewis acidity,high thermal stability,nontoxic nature,tunable solubility,and less corrosiveness.POMs have been extensively applied in cata...Polyoxometalates(POMs)have conducive properties such as controlled Bronsted and Lewis acidity,high thermal stability,nontoxic nature,tunable solubility,and less corrosiveness.POMs have been extensively applied in catalytic organic reactions and have an exciting prospect for industrial applications.This review summarized recent progress in the application of POMs as acid catalysts for various organic reactions including C-C bond formation,C-N bond formation,C-O bond formation,heterocyclic synthesis reactions,cyanosilylation and hydrolysis reactions.Various POMs catalysts including heteropoly acids(HPAs)and cationic functionalized HPAs with Bronsted acidity,HPAs supported on non-precious metal support with Bronsted acidity(or both Bronsted and Lewis acidity),transition metal substituted POMs with Lewis acidity were applied in above reactions.This review attempts to provide up-to-date information about POMs acid-catalyzed organic reactions and propose future prospects.展开更多
Catalytic asymmetric dearomatization of indoles and alkynes has received much attention in the past decade because this strategy offers an attractive and alternative way for the efficient synthesis of valuable chiral ...Catalytic asymmetric dearomatization of indoles and alkynes has received much attention in the past decade because this strategy offers an attractive and alternative way for the efficient synthesis of valuable chiral polycyclic indolines. However, these reactions have been mostly limited to transition-metal catalysts, and the related chiral Br■nsted acid catalysis has been scarcely reported. Herein, we disclose a chiral phosphoric acid-catalyzed asymmetric dearomatization of indolyl ynamides by direct activation of alkynes. This metal-free method enables the practical and atom-economical construction of an array of valuable chiral polycyclic indolines in moderate to good yields with high enantioselectivities.展开更多
Acid-catalyzed tandem reactions were established by employing a novel class of 2-arylglycerol derivative,5-aryl-1,3-dioxan-5-ol,as versatile 1,3-biselectrophile.In the reactions,5-aryl-1,3-dioxan-5-ol works like atrop...Acid-catalyzed tandem reactions were established by employing a novel class of 2-arylglycerol derivative,5-aryl-1,3-dioxan-5-ol,as versatile 1,3-biselectrophile.In the reactions,5-aryl-1,3-dioxan-5-ol works like atropaldehydes or 2-aryl malondialdehydes,and can react with 2-naphthols andβ-keto amides,allowing the synthesis of 4H-chromenes and 5-aryl-2-pyridinones.High yields,good functional group tolerance,broad substrate scope and simple reaction operation make this protocol attractive.展开更多
A facile Tf OH-catalyzed oxidative cyclization of allyl compounds and isocyanide has been developed with the assistance of DDQ, where isocyanide is used as the crucial "N" and "CN" sources. Highly ...A facile Tf OH-catalyzed oxidative cyclization of allyl compounds and isocyanide has been developed with the assistance of DDQ, where isocyanide is used as the crucial "N" and "CN" sources. Highly functionalized 2-cyanopyrroles are constructed efficiently through a new formal [3 + 2] mode, demonstrating diverse reactivity and synthetic utility in organic chemistry. 2-Cyanopyrrole is converted into a nucleobase analogue of Remdesivir and 5H-pyrrolo[2,1-a]isoindole through a three-step or a two-step sequence, respectively. This protocol features broad substrate scope, operational simplicity and good functional group tolerance.展开更多
Solid acid catalysts are widely used in the production of various high-value added and industrially important chemicals.Although the use of organosilicon compounds to modify the vacancy site has been extensively studi...Solid acid catalysts are widely used in the production of various high-value added and industrially important chemicals.Although the use of organosilicon compounds to modify the vacancy site has been extensively studied,the covalent tethering-SO_(3)H functionalized organosilicon modified polyoxometalates(POMs)has been rarely reported.In this work,two catalysts(TBA_(4)[SiW_(11)O_(39)(O(SiC_(3)H_(6)SO_(3)H)_(2))](compound 2)and TBA_(4)[SiW_(11)O_(39)(O(SiC_(8)H_(8)SO_(3)H)_(2))](compound 3))were synthesized successfully through covalently grafting different sulfonic acid(-SO_(3)H)groups onto[SiW_(11)O_(39)]^(8−)cluster,respectively.Compound 2 was achieved by surface grafting and in situ oxidation(3-mercaptopropyl)-trimethoxysilane,while compound 3 was achieved by surface grafting of 2-(4-chlorosulfonylphenyl)ethyltrimethoxysilane.Strong Brønsted acid strength of compounds 2 and 3 can be demonstrated by different methods including potentiometric titration,pyridine adsorption studies,and the ^(31)P trimethylphosphine oxides(TMPO)nuclear magnetic resonance(NMR).The systematic investigation of the relationship among POM structures,acid strength,and electron density was carried out based on density functional theory(DFT)calculation and experimental results,which revealed that covalent modification of compounds 2 and 3 decreased the electron density of the O-H bond,and promoted the release of H^(+).When applied in hydroxyalkylation/alkylation(HAA)reaction of 2-methylfuran(2-MF)with cyclohexanone,compound 2 exhibited better catalytic performance with conversion of ~93%,monocyclic fuel precursors(1a)yield of 79.9% and selectivity of 85.7% than compound 3,which can be attributed to strong Brønsted acid and the intramolecular hydrogen-bonding interactions between the neighboring -SO_(3)H moieties in compound 2.Finally,compound 2 also showed excellent catalytic activity in the HAA reaction of 2-MF with several different aldehydes and ketones(e.g.,furfuraldehyde,5-methylfurfuraldehyde,acetone,butyraldehyde and 4-methoxybenzaldehyde).This result opens a new pathway for design and fabrication of novel solid acid catalysts.展开更多
The first transition metal-free highly stereoselective positional isomerization of various α-alkyl styrenes through a carbocation mech-anism triggered strategy is developed by using AI(OTf)_(3) as a hidden Br0nsted a...The first transition metal-free highly stereoselective positional isomerization of various α-alkyl styrenes through a carbocation mech-anism triggered strategy is developed by using AI(OTf)_(3) as a hidden Br0nsted acid catalyst,which provides facile access to value-added acyclic tri-and tetra-substituted alkenes in good yields with high stereoselectivity under mild conditions.展开更多
A Lewis acid-catalyzed[4+2]cycloaddition of 3-alkyl-2-vinylindoles withβ,γ-unsaturatedα-ketoesters has been established in the presence of Sc(OTf)3,which afforded a series of indole-containing pyran derivatives in ...A Lewis acid-catalyzed[4+2]cycloaddition of 3-alkyl-2-vinylindoles withβ,γ-unsaturatedα-ketoesters has been established in the presence of Sc(OTf)3,which afforded a series of indole-containing pyran derivatives in generally good yields(up to 90%yield)with excellent diastereoselectivities(up to >95:5 dr)under mild conditions.This approach not only enriches the chemistry of 3-alkyl-2-vinylindoles,but also has provided an atom-economic method for the synthesis of indole-containing pyran derivatives with potential bioactivity.展开更多
Chiral silyl ethers and silanols are important synthetic intermediates and bioactive compounds.In this work,we developed a onepot remote desymmetrization/Peterson-olefination of silacyclopentene oxides with benzoic ac...Chiral silyl ethers and silanols are important synthetic intermediates and bioactive compounds.In this work,we developed a onepot remote desymmetrization/Peterson-olefination of silacyclopentene oxides with benzoic acids in the presence of Martin’s sulfurane.This new methodology not only realizes the atom-economy of Peterson olefination,but also represents a catalytic method for synthesis of silicon-stereogenic silyl ethers.Using a bulky chiral phosphoric acid 4i as organocatalyst,the reactions proceeded efficiently to afford various olefin-functionalized organosilyl ethers in excellent diastereoelectivities(up to 25/1 d.r.)and high enantioselectivities(up to 94%ee).展开更多
The tacticity of vinyl polymers is a key factor affecting the properties of materials.Recently,organic Brønsted acids have been demonstrated as effective catalysts for the development of highly stereoselective ca...The tacticity of vinyl polymers is a key factor affecting the properties of materials.Recently,organic Brønsted acids have been demonstrated as effective catalysts for the development of highly stereoselective cationic reversible addition-fragmentation chain transfer(RAFT)polymerizations of vinyl ethers,in which the use of RAFT agents could allow the control the molecular weight and tacticity of polymer products simultaneously.However,the effect of RAFT agents on the tacticity-regulation remains elusive and lacks of investigation.In this study,we synthesized four types of RAFT agents and evaluated their influence in the stereoselective cationic polymerization of isobutyl vinyl ether in the presence of PADI as a Brønsted acid catalyst,which unveils that the Z group of RAFT agents could not only affect the polydispersity of the products,but also exert a profound effect on the stereoselectivity.After extensive screening of the RAFT agents,high stereoregularity(isotacticity,90%m)was obtained when using dithiocarbonate ester-type RAFT agents with a benzyloxy Z group.展开更多
A versatile heteropoly acid(H_(3)PMo_(12)O_(40))-catalyzed coupling of diarylmethanols with epoxides was established for the synthesis of polyaryl-substituted aldehydes.Furthermore,the catalytic system was also suitab...A versatile heteropoly acid(H_(3)PMo_(12)O_(40))-catalyzed coupling of diarylmethanols with epoxides was established for the synthesis of polyaryl-substituted aldehydes.Furthermore,the catalytic system was also suitable for the reaction of diarylmethanols and diols/aldehydes.The application of such an earthabundant,readily accessible,and nontoxic catalyst provides a green approach for the construction of polyaryl-substituted aldehydes.展开更多
Asymmetric electrochemical synthesis has emerged as an attractive and sustainable alternative for the distinctive activation of bond connections in the preparation of diverse enantiomerically enriched targets,includin...Asymmetric electrochemical synthesis has emerged as an attractive and sustainable alternative for the distinctive activation of bond connections in the preparation of diverse enantiomerically enriched targets,including natural products and pharmaceutical agents.Herein,we describe the chiral Lewis acid-catalyzed enantioselective electrochemical anodic coupling reaction as a key step in the presented formal synthesis of isopavine alkaloids.展开更多
The synthesis of diverse 1,4-dihydropyridines have been achieved via the multicomponent reactions of aldehydes,enaminones and amines.The reactions have been smoothly performed in water to provide all products with mod...The synthesis of diverse 1,4-dihydropyridines have been achieved via the multicomponent reactions of aldehydes,enaminones and amines.The reactions have been smoothly performed in water to provide all products with moderate to excellent yields by using lactic acid as a green catalyst.展开更多
Magnetic assembly at the nanoscale level brings potential possibilities in obtaining novel delicate nanostructures with unique physical, photonic or electronic properties. Interface surfactant micelle-directed assembl...Magnetic assembly at the nanoscale level brings potential possibilities in obtaining novel delicate nanostructures with unique physical, photonic or electronic properties. Interface surfactant micelle-directed assembly strategy holds great promising in fabricating ordered mesoporous materials with multifunctionality and pore parameter tunability. Combing these, herein, one-dimensional (1D) nanochains with well-aligned silica-coated magnetic particles as core and mesoporous aluminosilicate as shell are rational fabricated for the first time through magnetic field induced interface coassembly in biliquid system followed by the incorporation of Al species via in-situ chemical modification and transformation strategy. The obtained magnetic mesoporous aluminosilicate nanochains (MMAS-NCs) possess well-defined core-shell-shell sandwich nanostructure, tunable perpendicular mesopore channels in the shell (2.7–7.6 nm), high surface area (359 m^(2)·g^(-1)), abundant acidic sites, and superparamagnetism with a magnetization saturation of 13.8 emu·g^(-1). Thanks to the unique properties, the MMAS-NCs exhibit excellent performance in acting as magnetically recyclable superior solid acid catalysts and nanostirrers with high conversion of over 96.8%, selectivity of 95.0% in the deprotection reaction of benzaldehyde dimethylacetal to benzaldehyde. Moreover, MMAS-NCs exhibit an interesting pore size effect on the catalytic activity, namely, in the pore size range of 2–8 nm, the catalysts with larger pores show significantly enhanced catalytic activity due to the balanced mass transport and density of surface active sites.展开更多
The Lewis acid-catalyzed addition of tri-methylsilyl cyanide to p-chlorobenzaldehyde in a micro-channel reactor was investigated.The microchannel was integrated to promote both reaction and separation of the biphase s...The Lewis acid-catalyzed addition of tri-methylsilyl cyanide to p-chlorobenzaldehyde in a micro-channel reactor was investigated.The microchannel was integrated to promote both reaction and separation of the biphase system.FeF3 and Cu(triflate)2 were used as water-stable Lewis acid catalysts.Sodium dodecyl sulfate was incorporated in the organic-aqueous system to enhance the reactivity and to manipulate the multiphaseflow inside the microchannel.It was found that the dynamics and the kinetics of the multiphase reaction were affected by the new micellar system.Parallel multiphaseflow inside the microchannel was obtained,allowing for continuous and acceptable phase separation.Enhanced selectivity was achieved by operating at lower conversion values.展开更多
Although simultaneous saccharification and fermentation(SSF)has been investigated extensively,the optimum condition for SSF of wheat straw has not yet been determined.Dilute sulfuric acid impregnated and steam explosi...Although simultaneous saccharification and fermentation(SSF)has been investigated extensively,the optimum condition for SSF of wheat straw has not yet been determined.Dilute sulfuric acid impregnated and steam explosion pretreated wheat straw was used as a substrate for the production of ethanol by SSF through orthogonal experiment design in this study.Cellulase mixture(Celluclast 1.5 1 and β-glucosidase Novozym 188)were adopted in combination with the yeast Saccharomyces cerevisiae AS2.1.The effects of reaction temperature,substrate concentration,initial fermentation liquid pH value and enzyme loading were evaluated and the SSF conditions were optimized.The ranking,from high to low,of influential extent of the SSF affecting factors to ethanol concentration and yield was substrate concentration,enzyme loading,initial fermentation liquid pH value and reaction temperature,respectively.The optimal SSF conditions were:reaction temperature,35℃;substrate concentration,100 g·L^(-1);initial fermentation liquid pH,5.0;enzyme loading,30 FPU·g21.Under these conditions,the ethanol concentration increased with reaction time,and after 72 h,ethanol was obtained in 65.8%yield with a concentration of 22.7 g·L^(-1).展开更多
Processes for the isomerization of light alkanes have been commercialized;however,the isomerization of paraffins(C_(n)H_(2n+2),n≥7)remains a challenge.On mesoporous tungsten-zirconia catalyst supported Pt catalysts(P...Processes for the isomerization of light alkanes have been commercialized;however,the isomerization of paraffins(C_(n)H_(2n+2),n≥7)remains a challenge.On mesoporous tungsten-zirconia catalyst supported Pt catalysts(Pt/WZrOx),initial isomerization productivity of 5249 moli-C7/molPt/h was obtained for n-heptane reforming at 275°C and 5 bar of hydrogen.展开更多
基金supported by the National Natural Nature Science Foundation of China(U1707603,21625101,21521005,21808011,U1507102)the National Key Research and Development Program of China(2017YFB0307303)+1 种基金Beijing Natural Science Foundation(2182047,2202039)the Fundamental Research Funds for the Central Universities(XK1802-6,XK1803-05,XK1902,12060093063)。
文摘Acid catalysis,one of the most important industrial processes,suffers from the toxicity,corrosion and recyclability problems of conventional homogeneous acid catalysts.Thus,the development of green heterogeneous acid catalysts becomes the focus of fundamental research and industrial catalysis.As a class of discrete anionic metal-oxygen clusters with tunable structure at the molecular and atomic scales,polyoxometalates(POMs)benefit from their super strong Br?nsted acidity,high proton mobility,and thermal stability.POMs-based heterogeneous catalysts have been used as the potential green alternatives to conventional homogeneous acid catalysts.In this review,we summarize recent progress on the design strategies of the POMs-based heterogeneous catalysts and their catalytic properties in acid-catalyzed reactions,where they are combined with functionalized cations,modified through covalent interactions,supported onto the non-precious metal support,and introduced into the framework of porous polymers.The design,functional strategies and catalytic performance of these POMs-based heterogeneous catalysts in specific acid-catalyzed reactions are emphasized.
文摘INTRODUCTIONThough potassium salts of rare earth substituted silicotungsticacids were synthesized early in 1971 by R.D.Peacock etc.,sofar the reports about the application of the corresponding acidshave not been found.We prepared fourteen rare earth substitutedsilicotungstic acids and determined their thermal stability,IRabsorption Spectra and x-ray diffraction spectra.Furthermore,thecatalytic activities of the fourteen heteropoly acids in acid cata-lytic reaction were investigated.Our experimental results demonstrated rare earth substituted silico-tungstic acids have very high catalytic activity in the reaction
基金financially supported by the National Natural Science Foundation of China(21966023,21665018)the Natural Science Foundation of Jiangxi Province,China(20171ACB21035)
文摘In this paper,sulfonic groups functionalized annealed bio-based carbon microspheres loaded polytetrafluoroethylene(A-BCMSs-SO_(3)H@PTFE)fibers with high activity,high stability,and easy regeneration were successfully fabricated by a simple method using low-cost raw materials.The characterization results showed that the annealed biomass carbon microspheres derived from waste Camellia oleifera shells were evenly distributed on the polytetrafluoroethylene fibers and the sulfonic groups can be successfully loaded on the surface of annealed biomass carbon microspheres by room temperature sulfonation.Subsequently,the as-prepared A-BCMSs-SO_(3)H@PTFE fibers were applied to the acidcatalyzed synthesis of liquid biofuel 5-ethoxymethylfurfural.The catalytic experiment results indicated that the annealing temperature and time during catalyst preparation have a significant effect on the activity and selectivity of A-BCMSs-SO_(3)H@PTFE fibers.The results of catalytic reaction kinetics showed that the yield of 5-ethoxymethylfurfural can reach more than 60%after 72 h of acid-catalyzed reaction.The stability test showed that the as-prepared A-BCMSs-SO_(3)H@PTFE fibers still maintained a stable acid catalytic activity after four recycles.
文摘In this study, African crude palm olein (CPO) was used to synthesize biodiesel. The objective was to determine the optimal reaction conditions for the methanolysis of olein. The used CPO had a 5.72% concentration of free fatty acids (FFA);thus, the production of biodiesel was carried out in two stages: 1) esterification using sulfuric acid and 2) transesterification using sodium methoxide. In order to optimize the yield of biodiesel during the transesterification process, a central rotatable design and the response surface methodology were used. The studied variables were: catalyst loading, reaction time and reaction temperature. The analysis of variance showed that the variables with significant effect were the catalyst loading, reaction temperature and reaction time;as well as the catalyst loading*reaction temperature and catalyst loading*reaction time. Results indicate that the optimal reaction conditions during transesterification are: 0.65% catalyst loading (wt/wt<sub>aceite</sub>), reaction time of 135 min and a reaction temperature of 56°C. The optimal reaction conditions during esterification are: 2.5% weight of catalyst, reaction time of 150 min and a reaction temperature of 64.5°C. Under these conditions, a 90% yield of biodiesel was obtained.
基金supported by the National Natural Science Foundation of China(No.22001034)Jiangxi Provincial Natural Science Foundation(No.20212BAB213001)the Open Fund of the Jiangxi Province Key Laboratory of Synthetic Chemistry(No.JXSC202008)。
文摘Polyoxometalates(POMs)have conducive properties such as controlled Bronsted and Lewis acidity,high thermal stability,nontoxic nature,tunable solubility,and less corrosiveness.POMs have been extensively applied in catalytic organic reactions and have an exciting prospect for industrial applications.This review summarized recent progress in the application of POMs as acid catalysts for various organic reactions including C-C bond formation,C-N bond formation,C-O bond formation,heterocyclic synthesis reactions,cyanosilylation and hydrolysis reactions.Various POMs catalysts including heteropoly acids(HPAs)and cationic functionalized HPAs with Bronsted acidity,HPAs supported on non-precious metal support with Bronsted acidity(or both Bronsted and Lewis acidity),transition metal substituted POMs with Lewis acidity were applied in above reactions.This review attempts to provide up-to-date information about POMs acid-catalyzed organic reactions and propose future prospects.
基金financial support from the National Natural Science Foundation of China(Nos.22125108,22101238,92056104 and 21772161)the China Postdoctoral Science Foundation(No.2020M680087)+3 种基金the Natural Science Foundation of Fujian Province of China(No.2019J02001)the President Research Funds from Xiamen University(No.20720210002)the Fundamental Research Funds for the Central Universities(No.20720202008)NFFTBS(No.J1310024)。
文摘Catalytic asymmetric dearomatization of indoles and alkynes has received much attention in the past decade because this strategy offers an attractive and alternative way for the efficient synthesis of valuable chiral polycyclic indolines. However, these reactions have been mostly limited to transition-metal catalysts, and the related chiral Br■nsted acid catalysis has been scarcely reported. Herein, we disclose a chiral phosphoric acid-catalyzed asymmetric dearomatization of indolyl ynamides by direct activation of alkynes. This metal-free method enables the practical and atom-economical construction of an array of valuable chiral polycyclic indolines in moderate to good yields with high enantioselectivities.
基金The National Key Research and Development Project(No.2022YFE0124100)Ordos Key Research and Development Project(No.2022EEDSKJZDZX003)+3 种基金National Natural Science Foundation of China(Nos.21872060,21902054,21761132014,and 22072049)the Open Research Fund(No.2022JYBKF01)of Key Laboratory of Material Chemistry for Energy Conversion and Storage(HUST),Ministry of Education,are acknowledged for the financial supportProgram for HUST Academic Frontier Youth Team(No.2019QYTD06)is also acknowledgedsupported by The Innovation and Talent Recruitment Base of New Energy Chemistry and Device。
文摘Acid-catalyzed tandem reactions were established by employing a novel class of 2-arylglycerol derivative,5-aryl-1,3-dioxan-5-ol,as versatile 1,3-biselectrophile.In the reactions,5-aryl-1,3-dioxan-5-ol works like atropaldehydes or 2-aryl malondialdehydes,and can react with 2-naphthols andβ-keto amides,allowing the synthesis of 4H-chromenes and 5-aryl-2-pyridinones.High yields,good functional group tolerance,broad substrate scope and simple reaction operation make this protocol attractive.
基金the National Natural Science Foundation of China(Nos.22171178, 21871174, 22071143)Innovation Program of Shanghai Municipal Education Commission (No.2019–01–07–00–09-E00008) for financial support。
文摘A facile Tf OH-catalyzed oxidative cyclization of allyl compounds and isocyanide has been developed with the assistance of DDQ, where isocyanide is used as the crucial "N" and "CN" sources. Highly functionalized 2-cyanopyrroles are constructed efficiently through a new formal [3 + 2] mode, demonstrating diverse reactivity and synthetic utility in organic chemistry. 2-Cyanopyrrole is converted into a nucleobase analogue of Remdesivir and 5H-pyrrolo[2,1-a]isoindole through a three-step or a two-step sequence, respectively. This protocol features broad substrate scope, operational simplicity and good functional group tolerance.
基金supported by the National Key Research and Development Program of China(2017YFB0307303)the National Nature Science Foundation of China(21625101,21521005)the Fundamental Research Funds for the Central Universities(XK1802-6,XK1803-05,XK1902,12060093063)。
文摘Solid acid catalysts are widely used in the production of various high-value added and industrially important chemicals.Although the use of organosilicon compounds to modify the vacancy site has been extensively studied,the covalent tethering-SO_(3)H functionalized organosilicon modified polyoxometalates(POMs)has been rarely reported.In this work,two catalysts(TBA_(4)[SiW_(11)O_(39)(O(SiC_(3)H_(6)SO_(3)H)_(2))](compound 2)and TBA_(4)[SiW_(11)O_(39)(O(SiC_(8)H_(8)SO_(3)H)_(2))](compound 3))were synthesized successfully through covalently grafting different sulfonic acid(-SO_(3)H)groups onto[SiW_(11)O_(39)]^(8−)cluster,respectively.Compound 2 was achieved by surface grafting and in situ oxidation(3-mercaptopropyl)-trimethoxysilane,while compound 3 was achieved by surface grafting of 2-(4-chlorosulfonylphenyl)ethyltrimethoxysilane.Strong Brønsted acid strength of compounds 2 and 3 can be demonstrated by different methods including potentiometric titration,pyridine adsorption studies,and the ^(31)P trimethylphosphine oxides(TMPO)nuclear magnetic resonance(NMR).The systematic investigation of the relationship among POM structures,acid strength,and electron density was carried out based on density functional theory(DFT)calculation and experimental results,which revealed that covalent modification of compounds 2 and 3 decreased the electron density of the O-H bond,and promoted the release of H^(+).When applied in hydroxyalkylation/alkylation(HAA)reaction of 2-methylfuran(2-MF)with cyclohexanone,compound 2 exhibited better catalytic performance with conversion of ~93%,monocyclic fuel precursors(1a)yield of 79.9% and selectivity of 85.7% than compound 3,which can be attributed to strong Brønsted acid and the intramolecular hydrogen-bonding interactions between the neighboring -SO_(3)H moieties in compound 2.Finally,compound 2 also showed excellent catalytic activity in the HAA reaction of 2-MF with several different aldehydes and ketones(e.g.,furfuraldehyde,5-methylfurfuraldehyde,acetone,butyraldehyde and 4-methoxybenzaldehyde).This result opens a new pathway for design and fabrication of novel solid acid catalysts.
基金We gratefully acknowledge the financial support from the National Natural Science Foundation of China(Grant No.21901074)"Zijiang Scholar Program"of East China Normal University。
文摘The first transition metal-free highly stereoselective positional isomerization of various α-alkyl styrenes through a carbocation mech-anism triggered strategy is developed by using AI(OTf)_(3) as a hidden Br0nsted acid catalyst,which provides facile access to value-added acyclic tri-and tetra-substituted alkenes in good yields with high stereoselectivity under mild conditions.
基金This work was supported by National Natural Science Foundation of China(No.21772069)Natural Science Foundation of Jiangsu Province(No.BK20201018)+1 种基金Undergraduate Students Project of Jiangsu Province(No.202010320050Z)High-level Innovative and Entrepreneurial Talents Introduction Plan of Jiangsu Province,and Natural Science Foundation of JSNU(No.19XSRX010).
文摘A Lewis acid-catalyzed[4+2]cycloaddition of 3-alkyl-2-vinylindoles withβ,γ-unsaturatedα-ketoesters has been established in the presence of Sc(OTf)3,which afforded a series of indole-containing pyran derivatives in generally good yields(up to 90%yield)with excellent diastereoselectivities(up to >95:5 dr)under mild conditions.This approach not only enriches the chemistry of 3-alkyl-2-vinylindoles,but also has provided an atom-economic method for the synthesis of indole-containing pyran derivatives with potential bioactivity.
基金supported by the National Natural Science Foundation of China(22271276,21871254,21702203)the National Key Research and Development Program of China(2022YFC2105900)。
文摘Chiral silyl ethers and silanols are important synthetic intermediates and bioactive compounds.In this work,we developed a onepot remote desymmetrization/Peterson-olefination of silacyclopentene oxides with benzoic acids in the presence of Martin’s sulfurane.This new methodology not only realizes the atom-economy of Peterson olefination,but also represents a catalytic method for synthesis of silicon-stereogenic silyl ethers.Using a bulky chiral phosphoric acid 4i as organocatalyst,the reactions proceeded efficiently to afford various olefin-functionalized organosilyl ethers in excellent diastereoelectivities(up to 25/1 d.r.)and high enantioselectivities(up to 94%ee).
基金supported by the Recruitment Program of Global Experts of China,the National Natural Science Foundation of China(Nos.21602028 and 22371240)Beijing National Laboratory for Molecular Sciences(No.BNLMS201913)100-Talent program of Fujian,Fuzhou University and Xiamen University.
文摘The tacticity of vinyl polymers is a key factor affecting the properties of materials.Recently,organic Brønsted acids have been demonstrated as effective catalysts for the development of highly stereoselective cationic reversible addition-fragmentation chain transfer(RAFT)polymerizations of vinyl ethers,in which the use of RAFT agents could allow the control the molecular weight and tacticity of polymer products simultaneously.However,the effect of RAFT agents on the tacticity-regulation remains elusive and lacks of investigation.In this study,we synthesized four types of RAFT agents and evaluated their influence in the stereoselective cationic polymerization of isobutyl vinyl ether in the presence of PADI as a Brønsted acid catalyst,which unveils that the Z group of RAFT agents could not only affect the polydispersity of the products,but also exert a profound effect on the stereoselectivity.After extensive screening of the RAFT agents,high stereoregularity(isotacticity,90%m)was obtained when using dithiocarbonate ester-type RAFT agents with a benzyloxy Z group.
基金the financial support from the National Natural Science Foundation of China(Nos.21871026,21971224)Research Found of East China University of Technology(Nos.DHBK2019265,DHBK2019267,DHBK2019264)。
文摘A versatile heteropoly acid(H_(3)PMo_(12)O_(40))-catalyzed coupling of diarylmethanols with epoxides was established for the synthesis of polyaryl-substituted aldehydes.Furthermore,the catalytic system was also suitable for the reaction of diarylmethanols and diols/aldehydes.The application of such an earthabundant,readily accessible,and nontoxic catalyst provides a green approach for the construction of polyaryl-substituted aldehydes.
基金The authors acknowledge financial support from the National Natural Science Foundation of China(grant nos.21702198 and 21971227)the Anhui Provincial Natural Science Foundation(grant no.1808085MB30)the Fundamental Research Funds for the Central Universities(no.WK2340000090).
文摘Asymmetric electrochemical synthesis has emerged as an attractive and sustainable alternative for the distinctive activation of bond connections in the preparation of diverse enantiomerically enriched targets,including natural products and pharmaceutical agents.Herein,we describe the chiral Lewis acid-catalyzed enantioselective electrochemical anodic coupling reaction as a key step in the presented formal synthesis of isopavine alkaloids.
基金the Department of Education of Jiangxi Province(No.GJJ13245)the Open Research Project from College of Basic Medical Sciences,Zhejiang Chinese Medical University and a Innovative Program of Graduate Students of Jiangxi Province(No.YC2014-S158).
文摘The synthesis of diverse 1,4-dihydropyridines have been achieved via the multicomponent reactions of aldehydes,enaminones and amines.The reactions have been smoothly performed in water to provide all products with moderate to excellent yields by using lactic acid as a green catalyst.
基金This work was supported by the National Natural Science Foundation of China(Nos.21701153,21875044,52073064,22005058,and 22005057)the National Key R&D Program of China(No.2020YFB2008600)+4 种基金Program of Shanghai Academic Research Leader(No.19XD1420300)the State Key Laboratory of Transducer Technology of China(No.SKT1904)China Postdoctoral Science Foundation(Nos.2020M670973 and BX20200085)Sichuan Science and Technology Program(No.2020YJ0243)The authors extend their appreciation to the International Scientific Partnership Program ISPP at King Saud University for funding this research work through ISPP-17-94(2).
文摘Magnetic assembly at the nanoscale level brings potential possibilities in obtaining novel delicate nanostructures with unique physical, photonic or electronic properties. Interface surfactant micelle-directed assembly strategy holds great promising in fabricating ordered mesoporous materials with multifunctionality and pore parameter tunability. Combing these, herein, one-dimensional (1D) nanochains with well-aligned silica-coated magnetic particles as core and mesoporous aluminosilicate as shell are rational fabricated for the first time through magnetic field induced interface coassembly in biliquid system followed by the incorporation of Al species via in-situ chemical modification and transformation strategy. The obtained magnetic mesoporous aluminosilicate nanochains (MMAS-NCs) possess well-defined core-shell-shell sandwich nanostructure, tunable perpendicular mesopore channels in the shell (2.7–7.6 nm), high surface area (359 m^(2)·g^(-1)), abundant acidic sites, and superparamagnetism with a magnetization saturation of 13.8 emu·g^(-1). Thanks to the unique properties, the MMAS-NCs exhibit excellent performance in acting as magnetically recyclable superior solid acid catalysts and nanostirrers with high conversion of over 96.8%, selectivity of 95.0% in the deprotection reaction of benzaldehyde dimethylacetal to benzaldehyde. Moreover, MMAS-NCs exhibit an interesting pore size effect on the catalytic activity, namely, in the pore size range of 2–8 nm, the catalysts with larger pores show significantly enhanced catalytic activity due to the balanced mass transport and density of surface active sites.
文摘The Lewis acid-catalyzed addition of tri-methylsilyl cyanide to p-chlorobenzaldehyde in a micro-channel reactor was investigated.The microchannel was integrated to promote both reaction and separation of the biphase system.FeF3 and Cu(triflate)2 were used as water-stable Lewis acid catalysts.Sodium dodecyl sulfate was incorporated in the organic-aqueous system to enhance the reactivity and to manipulate the multiphaseflow inside the microchannel.It was found that the dynamics and the kinetics of the multiphase reaction were affected by the new micellar system.Parallel multiphaseflow inside the microchannel was obtained,allowing for continuous and acceptable phase separation.Enhanced selectivity was achieved by operating at lower conversion values.
文摘Although simultaneous saccharification and fermentation(SSF)has been investigated extensively,the optimum condition for SSF of wheat straw has not yet been determined.Dilute sulfuric acid impregnated and steam explosion pretreated wheat straw was used as a substrate for the production of ethanol by SSF through orthogonal experiment design in this study.Cellulase mixture(Celluclast 1.5 1 and β-glucosidase Novozym 188)were adopted in combination with the yeast Saccharomyces cerevisiae AS2.1.The effects of reaction temperature,substrate concentration,initial fermentation liquid pH value and enzyme loading were evaluated and the SSF conditions were optimized.The ranking,from high to low,of influential extent of the SSF affecting factors to ethanol concentration and yield was substrate concentration,enzyme loading,initial fermentation liquid pH value and reaction temperature,respectively.The optimal SSF conditions were:reaction temperature,35℃;substrate concentration,100 g·L^(-1);initial fermentation liquid pH,5.0;enzyme loading,30 FPU·g21.Under these conditions,the ethanol concentration increased with reaction time,and after 72 h,ethanol was obtained in 65.8%yield with a concentration of 22.7 g·L^(-1).
基金support from the Natural Science Foundation of China(nos.21725301,21932002,22005007,and 21821004)the National Key R&DProgram of China(no.2017YFB0602200)and the Chinese Postdoctoral Science Foundation(no.8206300246).B.Z.gratefully acknowledges the support of the Boya Postdoctoral Fellowship of Peking University(2019–2020)and the Junior Fellowship of Beijing National Laboratory of Molecular Science(BMS Junior Fellow,2020–2023).D.M.acknowledges support from the Tencent Foundation through the XPLORER PRIZE and the support from OSSO state key lab。
文摘Processes for the isomerization of light alkanes have been commercialized;however,the isomerization of paraffins(C_(n)H_(2n+2),n≥7)remains a challenge.On mesoporous tungsten-zirconia catalyst supported Pt catalysts(Pt/WZrOx),initial isomerization productivity of 5249 moli-C7/molPt/h was obtained for n-heptane reforming at 275°C and 5 bar of hydrogen.