Pyrazolidinones,as significant analogs ofβ-lactam antibiotics,have garnered substantial interest for their enantioselective synthesis.Azomethine imines,recognized as valuable building blocks for the construction of t...Pyrazolidinones,as significant analogs ofβ-lactam antibiotics,have garnered substantial interest for their enantioselective synthesis.Azomethine imines,recognized as valuable building blocks for the construction of these nitrogen-containing compounds,underscore the continuous pursuit of novel building blocks and reaction methodologies within the chemical community.In this paper,we present a cascade cyclization between alkenyl azomethine imines and furan-2(5H)-one to generate chiral coronal polyheterocyclic compounds with high yields and enantioselectivities,catalyzed by dipeptide-derived phosphonium salts.In-vitro biological activity assays highlight the potential of these chiral compounds in drug discovery.Additionally,density functional theory(DFT)calculations elucidate the pivotal role of phosphonium salts,demonstrating their cooperative activations via hydrogen bonding and ion-pairing interactions.展开更多
Chiral N-substituted amino amides and esters are ubiquitous scaffolds in pesticides and pharmaceutical chemicals,but their asymmetric synthesis remains challenging especially for those with multiple chiral centers.In ...Chiral N-substituted amino amides and esters are ubiquitous scaffolds in pesticides and pharmaceutical chemicals,but their asymmetric synthesis remains challenging especially for those with multiple chiral centers.In this study,IR104 from Streptomyces aureocirculatus was identified from 157 wild-type imine reductases for the synthesis of(S)-2-((R)-2-oxo-4-propylpyrrolidin-1-yl)butanamide(antiepileptic drug Brivaracetam)via dynamic kinetic resolution reductive amination from ethyl 3-formylhexanoate and(S)-2-aminobutylamide with high diastereoselectivity.To further improve the catalytic efficiency of IR104,its mutant D191E/L195I/E253S/M258A(M3)was identified by saturation mutagenesis and iterative combinatorial mutagenesis,which exhibited a 102-fold increase in the catalytic efficiency relative to that of wild-type enzyme and high diastereoselectivity(98:2 d.r.).Crystal structural analysis and molecular dynamics simulations provided some insights into the molecular basis for the improved activity of the mutant enzyme.The imine reductase identified in this study could accept chiral amino amides/esters as amino donors for the dynamic kinetic resolution reductive amination of racemicα-substituted aldehydo-esters,expanding the substrate scope of imine reductases in the dynamic kinetic resolution-reductive amination.Finally,IR104-M3 was successfully used for the preparation of Brivaracetam at gram scale.Using this mutant,various N-substituted amino amides/esters with two chiral centers were also synthesized with up to 99:1 d.r.and 96%yields and subsequently converted intoγ-andδ-lactams,providing an efficient protocol for the synthesis of these important compounds via enzymatic dynamic kinetic resolution-reductive amination from simple building blocks.展开更多
N-substituted furfurylamines(FAs)are valuable precursors for producing pharmacologically active compounds and polymers.However,enzymatic synthesis of the type of chemicals is still in its infancy.Here we report an imi...N-substituted furfurylamines(FAs)are valuable precursors for producing pharmacologically active compounds and polymers.However,enzymatic synthesis of the type of chemicals is still in its infancy.Here we report an imine reductase from Streptomyces albidoflavus(SaIRED)for the reductive amination of biobased furans.A simple,fast and interference-resistant high-throughput screening(HTS)method was developed,based on the coloration reaction of carbonyl compounds with 2,4-dinitrophenylhydrazine.The reductive amination activity of IREDs can be directly indicated by a colorimetric assay.With the reductive amination of furfural with allylamine as the model reaction,SaIRED with the activity of 4.8 U mg^(-1) was subjected to three rounds of protein engineering and screening by this HTS method,affording a high-activity tri-variant I127V/D241A/A242T(named M3,20.2 U mg^(-1)).The variant M3 showed broad substrate scope,and enabled efficient reductive amination of biobased furans with a variety of amines including small aliphatic amines and sterically hindered amines,giving the target FAs in yields up to>99%.In addition,other variants were identified for preparative-scale synthesis of commercially interesting amines such as N-2-(methylsulfonyl)ethyl-FA by the screen method,with isolated yields up to 87%and turnover numbers up to 9700 for enzyme.Gram-scale synthesis of N-allyl-FA,a valuable building block and potential polymer monomer,was implemented at 0.25 mol L^(-1) substrate loading by a whole-cell catalyst incorporating variant M3,with 4.7 g L^(-1) h^(-1) space-time yield and 91%isolated yield.展开更多
Polyimides are a family of high-tech plastics that have irreplaceable applications in the fields of aerospace,defense,and opto-electronics,but polyimides are difficult to be reprocessed and recycled at the end of thei...Polyimides are a family of high-tech plastics that have irreplaceable applications in the fields of aerospace,defense,and opto-electronics,but polyimides are difficult to be reprocessed and recycled at the end of their service life,resulting in a significant waste of resources.Hence,it is of great significance to develop recyclable polyimides with comparable properties to the commercial products.Herein,we report a novel polymer-to-monomers chemically recyclable poly(imide-imine)(PtM-CR-PII)plastic,synthesized by cross-linking the amine-terminated aromatic bisimide monomer and the hexa-vanillin terminated cyclophosphazene monomer via dynamic imine bonds.The PtM-CR-PII plastic exhibits comparable mechanical and thermal properties as well as chemical stability to the commercial polyimides.The PtM-CR-PII plastic possesses a high Young’s modulus of≈3.2 GPa and a tensile strength as high as≈108 MPa,which also exhibits high thermal stability with a glass transition temperature of≈220℃.Moreover,the PtM-CR-PII plastic exhibits outstanding waterproofness,acid/alkali-resistance,and solvent-resistance,its appearance and mechanical properties can be well maintained after long-term soaking in water,highly concentrated acid and base,and various organic solvents.Furthermore,the cyclophosphazene moieties endow the PtM-CR-PII plastic with excellent flame retardancy.The PtM-CR-PII plastic exhibits the highest UL-94 flame-retarding rating of V-0 and a limiting oxygen index(LOI)value of 45.5%.Importantly,the PtM-CR-PII plastic can be depolymerized in an organic solvents-acid mixture medium at room temperature,allowing easy separation and recovery of both monomers in high purity.The recovered pure monomers can be used to regenerate new PtM-CR-PII plastics,enabling sustainable polymer-monomers-polymer circulation.展开更多
With the development of the economy and the increasing demand for environmental protection,the efficient and selective recovery of Gd(Ⅲ)from actual wastewater is of critical importance.In this work,lanthanum-based me...With the development of the economy and the increasing demand for environmental protection,the efficient and selective recovery of Gd(Ⅲ)from actual wastewater is of critical importance.In this work,lanthanum-based metal-organic framework(LaBDC)materials were prepared by a hydrothermal method,and then polyethyleneimine(PEI)and LaBDC were combined by an impregnation method to form a novel LaBDC@xPEI composite.The prepared materials were characterized using Fourier transfo rm infrared spectroscopy(FTIR),X-ray diffraction(XRD),scanning electron microscopy(SEM),energy dispersive X-ray spectroscopy(EDX),B runauer-Emmett-Teller(BET),thermogravimetric analysis(TGA)and X-ray photoelectron spectroscopy(XPS).Experiments show that LaBDC@50%PEI has the highest adsorption capacity(181.77 mg/g)among lanthanum-based MOFs with different PEI loadings at pH=5.5,which is about 5.1 times that of bare LaBDC.The adsorption isotherm analysis shows that LaBDC@50%PEI follows the Langmuir model.In addition,the adsorption kinetics of LaBDC@50%PEI follows a pseudo-second-order kinetic model,indicating that the adsorption process is chemical adsorption.It is worth noting that LaBDC@50%PEI maintains good adsorption performance and stability after three recycling tests,and exhibits excellent selectivity in cation interference experiments.Overall,the LaBDC@50%PEI composites possess good stability and hold great promises in rapid recovery of Gd(Ⅲ)from practical aqueous environments.展开更多
Organic-inorganic MoO_(3)/PI(MoPI)composites were prepared using a simple one-pot thermal copolymerization method.The resulting composites exhibited enhanced photocatalytic activity for the selective oxidation of benz...Organic-inorganic MoO_(3)/PI(MoPI)composites were prepared using a simple one-pot thermal copolymerization method.The resulting composites exhibited enhanced photocatalytic activity for the selective oxidation of benzylamine to N-benzylidene benzylamine(N-BDBA)in ambient air under simulated solar light irradiation compared to pristine MoO_(3) or polyimide(PI).In particular,the MoPI composite with a 0.3:1 molar ratio of Mo to melamine,referred to as MoPI-0.3,demonstrated the best performance in the photo-oxidation of benzylamine,achieving a benzylamine conversion of 95%with a N-BDBA selectivity exceeding 99%after 3 h irradiation.The enhanced photocatalytic activity of the MoPI-0.3 catalyst was attributed to the formation of a direct Z-scheme heterojunction between MoO_(3) and PI,facilitating more efficient separation of the photoinduced electrons and holes.Additionally,the MoPI-0.3 composite maintained considerably high activity over four consecutive cycles,highlighting its good stability and recyclability.Furthermore,the MoPI-0.3 composite could photo-oxidize benzylamine derivatives and heterocyclic amines to their corresponding imines,demonstrating the universal applicability of this composite catalyst.展开更多
Imine bonds are among the most explored building motifs in dynamic chemistry,polymers,and materials,and yet,their acid-resistance remains a longstanding issue.Herein we demonstrate a concept of internal protecting gro...Imine bonds are among the most explored building motifs in dynamic chemistry,polymers,and materials,and yet,their acid-resistance remains a longstanding issue.Herein we demonstrate a concept of internal protecting groups for improving the kinetic stability of dynamic imine bonds and polymers.Systematic examination of structure-reactivity relationship of a series of aldehydes/imines bearing a neighboring carboxyl allowed uncovering of required structural features for dynamically masking imine bonds with cyclic structures.Mechanistic studies indicated that noncovalent interactions along with sterics control the ringchain equilibrium and the stability of imine bonds.The incorporation of internal protecting groups into imine polymers further enabled their controlled stability in acidic media.Moreover,a combination of dynamic covalent network and coordination supramolecular network provided a facile means for the modulation of luminescent and mechanical properties of polymers.The strategies and results reported should be beneficial to molecular assemblies,dynamic polymers,biological delivery,and intelligent materials.展开更多
Poly(butylene succinate)(PBS)exhibits many advantages,such as renewability,biodegradability,and impressive thermal and mechanical properties,but is limited by the low melt viscosity and strength resulted from the line...Poly(butylene succinate)(PBS)exhibits many advantages,such as renewability,biodegradability,and impressive thermal and mechanical properties,but is limited by the low melt viscosity and strength resulted from the linear structure.To address this,vitrimeric network was introduced to synthesize PBS vitrimers(PBSVs)based on dynamic imine bonds through melt polymerization of hydroxyl-terminated PBS with vanillin derived imine containing compound and hexamethylene diisocyanate using trimethylolpropane as a crosslinking monomer.PBSVs with different crosslinking degrees were synthesized through changing the content of the crosslinking monomer.The effect of crosslinking degree on the thermal,theological,mechanical properties,and stress relaxation behavior of the PBSVs was studied in detail.The results demonstrated that the melt viscosity,melt strength,and heat resistance were enhanced substantially without obvious depression in crystallizability,thermal stability,and mechanical properties through increasing crosslinking degree.In addition,the PBSVs exhibit thermal reprocessability with mechanical properties recovered by more than 90%even after processing for three times.Furthermore,PBSV with improved melt properties shows significantly improved foamability compared to commercial PBS.This research contributes to the advancement of polymer technology by successfully developing PBS vitrimers with improved properties,showcasing their potential applications in sustainable and biodegradable materials.展开更多
Photocatalytic reductive amination of biomass-derived aldehydes is a desirable way to selectively upgrade biomass into value-added nitrogen-containing chemicals under mild conditions.However,it is challenging to produ...Photocatalytic reductive amination of biomass-derived aldehydes is a desirable way to selectively upgrade biomass into value-added nitrogen-containing chemicals under mild conditions.However,it is challenging to produce imines in high selectivity because of the undesirable side reactions caused by the activity of functional groups.Here,we demonstrate the highly reactive and selective production of imines from biomass derived aldehydes via the photocatalytic reductive amination,using a defective TiO_(2)supported nickel catalyst.The employment of methanol as the hydrogen donor and ammonia solution as the nitrogen source avoids the use of high-pressure H_(2)and expensive amines,rendering the current catalytic process safe,economical,and environmentally friendly.In depth investigations attribute the improved separation and transfer of photogenerated charge carriers to the presence of oxygen vacancies and decorated Ni nanoparticles,thereby accelerating the production of imines from benzaldehyde amination(conversion,95.8%;seleetivity,95.2%).Furthermore,the developed system could be easily translated to the photocatalytic conversions of various biomass derived aldehydes,which provided an example of a cost-effective and sustainable approach for the valorization of biomass derived feedstocks.展开更多
This study presents the synthesis of three dinuclear cobalt complexes based on three imine derivatives:bis-[4-(2-pyridylmethyleneamino)-phenyl]thioether(L1),bis-[4-(2-pyridylmethyleneamino)-phenyl]ether(L2),and bis-[4...This study presents the synthesis of three dinuclear cobalt complexes based on three imine derivatives:bis-[4-(2-pyridylmethyleneamino)-phenyl]thioether(L1),bis-[4-(2-pyridylmethyleneamino)-phenyl]ether(L2),and bis-[4-(2-pyridylmethyleneamino)-phenyl]methane(L3).Single-crystal X-ray diffraction analysis reveals that the complexes[Co_(2)(L1)3](ClO_(4))4·2CH_(3)CN(1),[Co_(2)(L2)3](ClO_(4))4·2CH_(3)OH(2),and[Co_(2)(L3)3](ClO_(4))4·2CH_(3)OH(3)all exhibit a dinuclear structure.Magnetic test results show that complex 3 exhibited irreversible SCO behavior induced by loss of solvent at 300 K,with the average Co-N bond length increasing from 0.2139(3)to 0.2153(3)nm.Meanwhile,the desolvated complex 3 exhibited paramagnetic behavior similar to that of complexes 1 and 2.Variable-temperature UV-Vis spectroscopic studies also indicate that complex 3 undergoes a solvent-loss-induced spin-state transition.CCDC:2347354,1(120 K);2347355,2(120 K);2347356,3(120 K);2347357,3(400 K).展开更多
The Ni(Ⅱ)-chiral(4S,4'S)-2,2'-(4,6-dibenzofurandiyl)bis[4,5-dihydro-4-phenyloxazole](DBFOX/Ph)-catalyzed asymmetric 1,3-dipolar cycloadditions of nitrile imines to N-α,β-unsaturated acylpyrazoles was presen...The Ni(Ⅱ)-chiral(4S,4'S)-2,2'-(4,6-dibenzofurandiyl)bis[4,5-dihydro-4-phenyloxazole](DBFOX/Ph)-catalyzed asymmetric 1,3-dipolar cycloadditions of nitrile imines to N-α,β-unsaturated acylpyrazoles was presented.This tactic rendered a facile and feasible route to prepare the optically active tetrasubstituted 5-3,5-dimethylpyrazole acyl dihydropyrazole cy-cloadducts bearing one or two contiguous stereocenters in good yields(up to 97%yield)with high regioselectivities(100%)and enantioselectivities(up to 97.5%ee).Following that,chiral cycloadducts could be obtained consistently in good chemical yields with excellent enantioselectivities within the gram scale process,additionally,toward five kinds of derivatization reac-tions like nucleophilic and reduction for further conversion of chiral cycloadducts to related chiral dihydropyrazole derivatives encompassing different substituents.展开更多
1-Phenyl-1,3-butandione benzidine diketoimine 2a （C32H28N2O2, Mr = 472.56） was synthesized in high yield by the reaction of 1-phenyl-1,3-butandione with benzidine in absolute ethanol, and determined by X-ray structu...1-Phenyl-1,3-butandione benzidine diketoimine 2a （C32H28N2O2, Mr = 472.56） was synthesized in high yield by the reaction of 1-phenyl-1,3-butandione with benzidine in absolute ethanol, and determined by X-ray structure analysis. It crystallizes in the orthorhombic system, space group P21/c with a = 7.9839（16）, b = 12.910（3）, c = 12.358（3）A, α = 90.00, β= 93.71（3）,γ = 90.00°, V = 1271.1（4） A3, Z = 2, Dc = 1.235 g/cm^3,/1 = 0.077 mm^-1, F（000） = 500, the final R = 0.0717 and wR = 0.1187. It presents a linear centrosymmetric framework constituted by a linkage of benzidine as a bridge and two terminal 1-phenyl-1,3-butanedione moieties.展开更多
Eleven new imine derivatives 6 containing 1H-1,2,4-triazole and thiazole rings were synthesized by the condensation of 5-((1H- 1,2,4-triazol-1-yl)methyl)-4-tert-butylthiazol-2-amine with various substituted benzaldehy...Eleven new imine derivatives 6 containing 1H-1,2,4-triazole and thiazole rings were synthesized by the condensation of 5-((1H- 1,2,4-triazol-1-yl)methyl)-4-tert-butylthiazol-2-amine with various substituted benzaldehydes.The structures of the title compounds were characterized by ~1H NMR,MS and elemental analysis.The plant-growth regulatory activities of these compounds were evaluated.The primary bioassay results indicated that these target compounds exhibited promising plant-growth regulatory activities.展开更多
A series of new ligands L_1-L_7 were readily prepared in one step.Friedel-Crafts alkylation of indoles with nitroalkenes catalyzed by a novel Cu（Ⅱ）-L complex has been developed.The remarkable advantages of this rea...A series of new ligands L_1-L_7 were readily prepared in one step.Friedel-Crafts alkylation of indoles with nitroalkenes catalyzed by a novel Cu（Ⅱ）-L complex has been developed.The remarkable advantages of this reaction are mild reaction conditions,simple workup procedure,high yields of products and the use of ethanol as a green solvent.展开更多
A series of Mg‐Al mixed oxide catalysts are prepared and introduced as efficient irreducible catalysts for the oxidative coupling of alcohols and amines to imine.The structure and surface properties of Mg‐Al oxides ...A series of Mg‐Al mixed oxide catalysts are prepared and introduced as efficient irreducible catalysts for the oxidative coupling of alcohols and amines to imine.The structure and surface properties of Mg‐Al oxides are modulated by changing the Mg/Al ratios,calcination temperature and treatment with probe molecules.Detailed characterization,including X‐ray diffraction,27Al magic angle spinning nuclear magnetic resonance spectroscopy,N2‐adsorption,NH3‐temperature‐programmed desorption,CO2‐temperature‐programmed desorption and X‐ray photoelectron spectroscopy are carried out to determine the physicochemical properties of these catalysts.The Mg‐Al oxides with Mg/Al=3exhibit the highest activity in the reaction,which possess a large number of surface weak basic sites and a relatively small number of weak acidic sites.The role of the acidic and basic sites in the reaction process is systematically investigated,and are shown to serve as adsorption and activation sites for amines and alcohols,respectively.Under the synergistic effect of these acid‐base centers,the oxidative coupling process successfully occurs on the surface of Mg‐Al mixed oxides.Compared with the acidic sites,the weak basic sites play a more important role in the catalytic process.The acidic sites are the catalytic centers for the benzyl alcohol activation,which control the reaction rate of the oxidative coupling reaction.展开更多
Manganese-catalyzed hydrogenation of unsaturated molecules has made tremendous progresses recently benefiting from non-innocent pincer or bidentate ligands for manganese.Herein,we describe the hydrogenation of quinoli...Manganese-catalyzed hydrogenation of unsaturated molecules has made tremendous progresses recently benefiting from non-innocent pincer or bidentate ligands for manganese.Herein,we describe the hydrogenation of quinolines and imines catalyzed by simple manganese carbonyls,Mn2(CO)10 or MnBr(CO)5,thus eliminating the prerequisite pincer-type or bidentate ligands.展开更多
Nanomaterials are considered as suitable heterogeneous catalysts for many organic reactions.Herein nano-tube TiO_2 has been reported as a heterogeneous catalyst,for synthesis of imines in sunlight at room temperature ...Nanomaterials are considered as suitable heterogeneous catalysts for many organic reactions.Herein nano-tube TiO_2 has been reported as a heterogeneous catalyst,for synthesis of imines in sunlight at room temperature under solvent-free conditions.The condensation of less electrophilic carbonyl compounds with poorly nucleophilic amines was afforded imines in excellent yields.展开更多
Direct oxidative coupling of an alcohol and amine,with air or molecular oxygen as the oxygen source,is an environmentally friendly method for imine synthesis.We developed an Fe catalyst supported on mesoporous carbon...Direct oxidative coupling of an alcohol and amine,with air or molecular oxygen as the oxygen source,is an environmentally friendly method for imine synthesis.We developed an Fe catalyst supported on mesoporous carbon（denoted by FeOx/HCMK-3） for this reaction with excellent activity and recyclability.FeOx/HCMK-3 was prepared by impregnating HNO3-treated mesoporous carbon（CMK-3） with iron nitrate solution.The highly dispersed FeOx species give FeOx/HCMK-3 high reducibility and are responsible for the high catalytic performance.Imine synthesis over FeOx/HCMK-3 follows a redox mechanism.The oxygen species in FeOx/HCMK-3 participate in the reaction and are then regenerated by oxidation with molecular O2.The reaction involves two consecutive steps：oxidative dehydrogenation of an alcohol to an aldehyde and coupling of the aldehyde with an amine to give an imine.Oxidative dehydrogenation of the alcohol is the rate-determining step in the reaction.展开更多
Covalent organic frameworks (COFs) are promising crystalline materials for the light-driven hydrogen evolution reaction (HER) due to their tunable chemical structures and energy band gaps.However,deeply understanding ...Covalent organic frameworks (COFs) are promising crystalline materials for the light-driven hydrogen evolution reaction (HER) due to their tunable chemical structures and energy band gaps.However,deeply understanding corresponding mechanism is still challenging due to the multiple components and complicated electron transfer and reduction paths involved in photocatalytic HER.Here,the photocatalytic HER investigation has been reported based on three COFs catalysts,1–3,which are prepared by benzo[1,2-b:3,4-b’:5,6-b’]trithiophene-2,5,8-trialdehyde to react with C3symmetric triamines including tris(4-aminophenyl)amine,1,3,5-tris(4-aminophenyl)benzene,and (1,3,5-tris-(4-aminophenyl)triazine,respectively.As the isostructural hexagonal honeycomb-type COF of 2 and 3 reported previously,the crystal structure of 1 has been carefully correlated through the powder X-ray diffraction study with the help of theoretical simulations.1 shows highly porous framework with Brunauer-Emmett-Teller surface area of1249 m^(2)/g.Moreover,the introduction of ascorbic acid into the photocatalytic system of COFs achieves the hydrogen evolution rate of 3.75,12.16 and 20.2 mmol g^(–1)h^(–1) for 1–3,respectively.The important role of ascorbic acid in photocatalysis of HER is disclosed to protonate the imine linkages of these COFs,leading to the obvious absorbance red-shift and the improved charge separation efficiency together with reduced resistance in contrast to pristine materials according to the spectroscopic and electronic characterizations.These innovations of chemical and physical properties for these COFs are responsible for their excellent photocatalytic performance.These results elucidate that tiny modifications of COFs structures is able to greatly tune their band structures as well as catalytic properties,therefore providing an available approach for optimizing COFs functionalities.展开更多
The mesomorphie properties of title complexes are investigated by means of DSC and polarizing microscopy. The mesophase temperature ranges of complexes are wider than that of corresponding organic ligands. The bridgin...The mesomorphie properties of title complexes are investigated by means of DSC and polarizing microscopy. The mesophase temperature ranges of complexes are wider than that of corresponding organic ligands. The bridging groups of the complexes have profoand effects on the mesomorphic behavior, When the bridging groups are opticallhy active. the compleve show chiral smectic展开更多
基金Financial support from National Natural Science Foundation of China(Nos.21871282,22377113,22301309)Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB0590000)+6 种基金National Key Research and Development Program of China(No.2023YFA0914502)Taishan Scholar Program of Shandong Province(No.tsqn202306103,tsqn202306026)Postdoctoral Fellowship Program of CPSF(No.GZC20232509)Distinguished Young Scholars of Shandong Province(Overseas)(No.2022HWYQ-004)Shandong Postdoctoral Science Foundation(No.SDBX2023044)Qingdao Postdoctoral Science Foundation(No.QDBSH20230202048)the Fundamental Research Funds for the Central Universities(Ocean University of China)。
文摘Pyrazolidinones,as significant analogs ofβ-lactam antibiotics,have garnered substantial interest for their enantioselective synthesis.Azomethine imines,recognized as valuable building blocks for the construction of these nitrogen-containing compounds,underscore the continuous pursuit of novel building blocks and reaction methodologies within the chemical community.In this paper,we present a cascade cyclization between alkenyl azomethine imines and furan-2(5H)-one to generate chiral coronal polyheterocyclic compounds with high yields and enantioselectivities,catalyzed by dipeptide-derived phosphonium salts.In-vitro biological activity assays highlight the potential of these chiral compounds in drug discovery.Additionally,density functional theory(DFT)calculations elucidate the pivotal role of phosphonium salts,demonstrating their cooperative activations via hydrogen bonding and ion-pairing interactions.
文摘Chiral N-substituted amino amides and esters are ubiquitous scaffolds in pesticides and pharmaceutical chemicals,but their asymmetric synthesis remains challenging especially for those with multiple chiral centers.In this study,IR104 from Streptomyces aureocirculatus was identified from 157 wild-type imine reductases for the synthesis of(S)-2-((R)-2-oxo-4-propylpyrrolidin-1-yl)butanamide(antiepileptic drug Brivaracetam)via dynamic kinetic resolution reductive amination from ethyl 3-formylhexanoate and(S)-2-aminobutylamide with high diastereoselectivity.To further improve the catalytic efficiency of IR104,its mutant D191E/L195I/E253S/M258A(M3)was identified by saturation mutagenesis and iterative combinatorial mutagenesis,which exhibited a 102-fold increase in the catalytic efficiency relative to that of wild-type enzyme and high diastereoselectivity(98:2 d.r.).Crystal structural analysis and molecular dynamics simulations provided some insights into the molecular basis for the improved activity of the mutant enzyme.The imine reductase identified in this study could accept chiral amino amides/esters as amino donors for the dynamic kinetic resolution reductive amination of racemicα-substituted aldehydo-esters,expanding the substrate scope of imine reductases in the dynamic kinetic resolution-reductive amination.Finally,IR104-M3 was successfully used for the preparation of Brivaracetam at gram scale.Using this mutant,various N-substituted amino amides/esters with two chiral centers were also synthesized with up to 99:1 d.r.and 96%yields and subsequently converted intoγ-andδ-lactams,providing an efficient protocol for the synthesis of these important compounds via enzymatic dynamic kinetic resolution-reductive amination from simple building blocks.
文摘N-substituted furfurylamines(FAs)are valuable precursors for producing pharmacologically active compounds and polymers.However,enzymatic synthesis of the type of chemicals is still in its infancy.Here we report an imine reductase from Streptomyces albidoflavus(SaIRED)for the reductive amination of biobased furans.A simple,fast and interference-resistant high-throughput screening(HTS)method was developed,based on the coloration reaction of carbonyl compounds with 2,4-dinitrophenylhydrazine.The reductive amination activity of IREDs can be directly indicated by a colorimetric assay.With the reductive amination of furfural with allylamine as the model reaction,SaIRED with the activity of 4.8 U mg^(-1) was subjected to three rounds of protein engineering and screening by this HTS method,affording a high-activity tri-variant I127V/D241A/A242T(named M3,20.2 U mg^(-1)).The variant M3 showed broad substrate scope,and enabled efficient reductive amination of biobased furans with a variety of amines including small aliphatic amines and sterically hindered amines,giving the target FAs in yields up to>99%.In addition,other variants were identified for preparative-scale synthesis of commercially interesting amines such as N-2-(methylsulfonyl)ethyl-FA by the screen method,with isolated yields up to 87%and turnover numbers up to 9700 for enzyme.Gram-scale synthesis of N-allyl-FA,a valuable building block and potential polymer monomer,was implemented at 0.25 mol L^(-1) substrate loading by a whole-cell catalyst incorporating variant M3,with 4.7 g L^(-1) h^(-1) space-time yield and 91%isolated yield.
基金supported by Natural Science Foundation of Jilin Province(No.***202302003)the National Natural Science Foundation of China(No.22275069)National Key R&D Program of China(No.2023YFA1008804)。
文摘Polyimides are a family of high-tech plastics that have irreplaceable applications in the fields of aerospace,defense,and opto-electronics,but polyimides are difficult to be reprocessed and recycled at the end of their service life,resulting in a significant waste of resources.Hence,it is of great significance to develop recyclable polyimides with comparable properties to the commercial products.Herein,we report a novel polymer-to-monomers chemically recyclable poly(imide-imine)(PtM-CR-PII)plastic,synthesized by cross-linking the amine-terminated aromatic bisimide monomer and the hexa-vanillin terminated cyclophosphazene monomer via dynamic imine bonds.The PtM-CR-PII plastic exhibits comparable mechanical and thermal properties as well as chemical stability to the commercial polyimides.The PtM-CR-PII plastic possesses a high Young’s modulus of≈3.2 GPa and a tensile strength as high as≈108 MPa,which also exhibits high thermal stability with a glass transition temperature of≈220℃.Moreover,the PtM-CR-PII plastic exhibits outstanding waterproofness,acid/alkali-resistance,and solvent-resistance,its appearance and mechanical properties can be well maintained after long-term soaking in water,highly concentrated acid and base,and various organic solvents.Furthermore,the cyclophosphazene moieties endow the PtM-CR-PII plastic with excellent flame retardancy.The PtM-CR-PII plastic exhibits the highest UL-94 flame-retarding rating of V-0 and a limiting oxygen index(LOI)value of 45.5%.Importantly,the PtM-CR-PII plastic can be depolymerized in an organic solvents-acid mixture medium at room temperature,allowing easy separation and recovery of both monomers in high purity.The recovered pure monomers can be used to regenerate new PtM-CR-PII plastics,enabling sustainable polymer-monomers-polymer circulation.
基金Project supported by the National Natural Science Foundation of China(41662004)。
文摘With the development of the economy and the increasing demand for environmental protection,the efficient and selective recovery of Gd(Ⅲ)from actual wastewater is of critical importance.In this work,lanthanum-based metal-organic framework(LaBDC)materials were prepared by a hydrothermal method,and then polyethyleneimine(PEI)and LaBDC were combined by an impregnation method to form a novel LaBDC@xPEI composite.The prepared materials were characterized using Fourier transfo rm infrared spectroscopy(FTIR),X-ray diffraction(XRD),scanning electron microscopy(SEM),energy dispersive X-ray spectroscopy(EDX),B runauer-Emmett-Teller(BET),thermogravimetric analysis(TGA)and X-ray photoelectron spectroscopy(XPS).Experiments show that LaBDC@50%PEI has the highest adsorption capacity(181.77 mg/g)among lanthanum-based MOFs with different PEI loadings at pH=5.5,which is about 5.1 times that of bare LaBDC.The adsorption isotherm analysis shows that LaBDC@50%PEI follows the Langmuir model.In addition,the adsorption kinetics of LaBDC@50%PEI follows a pseudo-second-order kinetic model,indicating that the adsorption process is chemical adsorption.It is worth noting that LaBDC@50%PEI maintains good adsorption performance and stability after three recycling tests,and exhibits excellent selectivity in cation interference experiments.Overall,the LaBDC@50%PEI composites possess good stability and hold great promises in rapid recovery of Gd(Ⅲ)from practical aqueous environments.
基金supported by the Opening Project of Key Laboratory of Green Catalysis of Higher Education Institutes of Sichuan (LZJ2101)the Fundamental Research Funds of China West Normal University (19D038)
文摘Organic-inorganic MoO_(3)/PI(MoPI)composites were prepared using a simple one-pot thermal copolymerization method.The resulting composites exhibited enhanced photocatalytic activity for the selective oxidation of benzylamine to N-benzylidene benzylamine(N-BDBA)in ambient air under simulated solar light irradiation compared to pristine MoO_(3) or polyimide(PI).In particular,the MoPI composite with a 0.3:1 molar ratio of Mo to melamine,referred to as MoPI-0.3,demonstrated the best performance in the photo-oxidation of benzylamine,achieving a benzylamine conversion of 95%with a N-BDBA selectivity exceeding 99%after 3 h irradiation.The enhanced photocatalytic activity of the MoPI-0.3 catalyst was attributed to the formation of a direct Z-scheme heterojunction between MoO_(3) and PI,facilitating more efficient separation of the photoinduced electrons and holes.Additionally,the MoPI-0.3 composite maintained considerably high activity over four consecutive cycles,highlighting its good stability and recyclability.Furthermore,the MoPI-0.3 composite could photo-oxidize benzylamine derivatives and heterocyclic amines to their corresponding imines,demonstrating the universal applicability of this composite catalyst.
基金the National Natural Science Foundation of China(NSFC,Nos.22071247,92156010,22101283,and 22101284)the Key Research Program of Frontier Sciences(No.QYZDBSSW-SLH030)of the CAS+1 种基金Natural Science Foundation of Fujian Province(Nos.2020J06035 and 2022J05085)Fujian Science&Technology Innovation Laboratory for Optoelectronic Information of China(No.2021ZR112)for support.
文摘Imine bonds are among the most explored building motifs in dynamic chemistry,polymers,and materials,and yet,their acid-resistance remains a longstanding issue.Herein we demonstrate a concept of internal protecting groups for improving the kinetic stability of dynamic imine bonds and polymers.Systematic examination of structure-reactivity relationship of a series of aldehydes/imines bearing a neighboring carboxyl allowed uncovering of required structural features for dynamically masking imine bonds with cyclic structures.Mechanistic studies indicated that noncovalent interactions along with sterics control the ringchain equilibrium and the stability of imine bonds.The incorporation of internal protecting groups into imine polymers further enabled their controlled stability in acidic media.Moreover,a combination of dynamic covalent network and coordination supramolecular network provided a facile means for the modulation of luminescent and mechanical properties of polymers.The strategies and results reported should be beneficial to molecular assemblies,dynamic polymers,biological delivery,and intelligent materials.
基金financially supported by the National Natural Science Foundation of China(No.51973176)the Chongqing Talent Plan for Young Top-Notch Talents(No.CQYC2021059217)the Fundamental Research Funds for the Central Universities(No.SWUXDJH202314)。
文摘Poly(butylene succinate)(PBS)exhibits many advantages,such as renewability,biodegradability,and impressive thermal and mechanical properties,but is limited by the low melt viscosity and strength resulted from the linear structure.To address this,vitrimeric network was introduced to synthesize PBS vitrimers(PBSVs)based on dynamic imine bonds through melt polymerization of hydroxyl-terminated PBS with vanillin derived imine containing compound and hexamethylene diisocyanate using trimethylolpropane as a crosslinking monomer.PBSVs with different crosslinking degrees were synthesized through changing the content of the crosslinking monomer.The effect of crosslinking degree on the thermal,theological,mechanical properties,and stress relaxation behavior of the PBSVs was studied in detail.The results demonstrated that the melt viscosity,melt strength,and heat resistance were enhanced substantially without obvious depression in crystallizability,thermal stability,and mechanical properties through increasing crosslinking degree.In addition,the PBSVs exhibit thermal reprocessability with mechanical properties recovered by more than 90%even after processing for three times.Furthermore,PBSV with improved melt properties shows significantly improved foamability compared to commercial PBS.This research contributes to the advancement of polymer technology by successfully developing PBS vitrimers with improved properties,showcasing their potential applications in sustainable and biodegradable materials.
基金financially supported by the National Natural Science Foundation of China(Nos.22202105,22002043 and 22205113)the Natural Science Foundation of Jiangsu Province(Nos.BK20210608 and BK20210626)+1 种基金the Natural Science Foundation of Jiangsu Higher Education Institutions of China(Nos.21KJA150003 and 21KJB150027)the China Postdoctoral Science Foundation(No.2022M711645)。
文摘Photocatalytic reductive amination of biomass-derived aldehydes is a desirable way to selectively upgrade biomass into value-added nitrogen-containing chemicals under mild conditions.However,it is challenging to produce imines in high selectivity because of the undesirable side reactions caused by the activity of functional groups.Here,we demonstrate the highly reactive and selective production of imines from biomass derived aldehydes via the photocatalytic reductive amination,using a defective TiO_(2)supported nickel catalyst.The employment of methanol as the hydrogen donor and ammonia solution as the nitrogen source avoids the use of high-pressure H_(2)and expensive amines,rendering the current catalytic process safe,economical,and environmentally friendly.In depth investigations attribute the improved separation and transfer of photogenerated charge carriers to the presence of oxygen vacancies and decorated Ni nanoparticles,thereby accelerating the production of imines from benzaldehyde amination(conversion,95.8%;seleetivity,95.2%).Furthermore,the developed system could be easily translated to the photocatalytic conversions of various biomass derived aldehydes,which provided an example of a cost-effective and sustainable approach for the valorization of biomass derived feedstocks.
文摘This study presents the synthesis of three dinuclear cobalt complexes based on three imine derivatives:bis-[4-(2-pyridylmethyleneamino)-phenyl]thioether(L1),bis-[4-(2-pyridylmethyleneamino)-phenyl]ether(L2),and bis-[4-(2-pyridylmethyleneamino)-phenyl]methane(L3).Single-crystal X-ray diffraction analysis reveals that the complexes[Co_(2)(L1)3](ClO_(4))4·2CH_(3)CN(1),[Co_(2)(L2)3](ClO_(4))4·2CH_(3)OH(2),and[Co_(2)(L3)3](ClO_(4))4·2CH_(3)OH(3)all exhibit a dinuclear structure.Magnetic test results show that complex 3 exhibited irreversible SCO behavior induced by loss of solvent at 300 K,with the average Co-N bond length increasing from 0.2139(3)to 0.2153(3)nm.Meanwhile,the desolvated complex 3 exhibited paramagnetic behavior similar to that of complexes 1 and 2.Variable-temperature UV-Vis spectroscopic studies also indicate that complex 3 undergoes a solvent-loss-induced spin-state transition.CCDC:2347354,1(120 K);2347355,2(120 K);2347356,3(120 K);2347357,3(400 K).
基金Project supported by the National Natural Science Foundation of China(Nos.22278098,21908034,22008045)the Natural Science Foundation of Heilongjiang Province(Nos.LH2021H001,LH2023B013)。
文摘The Ni(Ⅱ)-chiral(4S,4'S)-2,2'-(4,6-dibenzofurandiyl)bis[4,5-dihydro-4-phenyloxazole](DBFOX/Ph)-catalyzed asymmetric 1,3-dipolar cycloadditions of nitrile imines to N-α,β-unsaturated acylpyrazoles was presented.This tactic rendered a facile and feasible route to prepare the optically active tetrasubstituted 5-3,5-dimethylpyrazole acyl dihydropyrazole cy-cloadducts bearing one or two contiguous stereocenters in good yields(up to 97%yield)with high regioselectivities(100%)and enantioselectivities(up to 97.5%ee).Following that,chiral cycloadducts could be obtained consistently in good chemical yields with excellent enantioselectivities within the gram scale process,additionally,toward five kinds of derivatization reac-tions like nucleophilic and reduction for further conversion of chiral cycloadducts to related chiral dihydropyrazole derivatives encompassing different substituents.
文摘1-Phenyl-1,3-butandione benzidine diketoimine 2a （C32H28N2O2, Mr = 472.56） was synthesized in high yield by the reaction of 1-phenyl-1,3-butandione with benzidine in absolute ethanol, and determined by X-ray structure analysis. It crystallizes in the orthorhombic system, space group P21/c with a = 7.9839（16）, b = 12.910（3）, c = 12.358（3）A, α = 90.00, β= 93.71（3）,γ = 90.00°, V = 1271.1（4） A3, Z = 2, Dc = 1.235 g/cm^3,/1 = 0.077 mm^-1, F（000） = 500, the final R = 0.0717 and wR = 0.1187. It presents a linear centrosymmetric framework constituted by a linkage of benzidine as a bridge and two terminal 1-phenyl-1,3-butanedione moieties.
基金the National Natural Science Foundation of China(No.20772068)the National Key Project of Scientific and Technical Supporting Programs of China(No.2006BAE01A01-5) for financial support
文摘Eleven new imine derivatives 6 containing 1H-1,2,4-triazole and thiazole rings were synthesized by the condensation of 5-((1H- 1,2,4-triazol-1-yl)methyl)-4-tert-butylthiazol-2-amine with various substituted benzaldehydes.The structures of the title compounds were characterized by ~1H NMR,MS and elemental analysis.The plant-growth regulatory activities of these compounds were evaluated.The primary bioassay results indicated that these target compounds exhibited promising plant-growth regulatory activities.
基金the financial support from the National Natural Science Foundation of China(Nos.20962018, 20862015,20762009 and 20562011)
文摘A series of new ligands L_1-L_7 were readily prepared in one step.Friedel-Crafts alkylation of indoles with nitroalkenes catalyzed by a novel Cu（Ⅱ）-L complex has been developed.The remarkable advantages of this reaction are mild reaction conditions,simple workup procedure,high yields of products and the use of ethanol as a green solvent.
文摘A series of Mg‐Al mixed oxide catalysts are prepared and introduced as efficient irreducible catalysts for the oxidative coupling of alcohols and amines to imine.The structure and surface properties of Mg‐Al oxides are modulated by changing the Mg/Al ratios,calcination temperature and treatment with probe molecules.Detailed characterization,including X‐ray diffraction,27Al magic angle spinning nuclear magnetic resonance spectroscopy,N2‐adsorption,NH3‐temperature‐programmed desorption,CO2‐temperature‐programmed desorption and X‐ray photoelectron spectroscopy are carried out to determine the physicochemical properties of these catalysts.The Mg‐Al oxides with Mg/Al=3exhibit the highest activity in the reaction,which possess a large number of surface weak basic sites and a relatively small number of weak acidic sites.The role of the acidic and basic sites in the reaction process is systematically investigated,and are shown to serve as adsorption and activation sites for amines and alcohols,respectively.Under the synergistic effect of these acid‐base centers,the oxidative coupling process successfully occurs on the surface of Mg‐Al mixed oxides.Compared with the acidic sites,the weak basic sites play a more important role in the catalytic process.The acidic sites are the catalytic centers for the benzyl alcohol activation,which control the reaction rate of the oxidative coupling reaction.
基金the National Natural Science Foundation of China(No.21772202,21831008)Beijing Municipal Science&Technology Commission(No.Z191100007219009)Beijing National Laboratory for Molecular Sciences(No.BNLMS-CXXM201901)。
文摘Manganese-catalyzed hydrogenation of unsaturated molecules has made tremendous progresses recently benefiting from non-innocent pincer or bidentate ligands for manganese.Herein,we describe the hydrogenation of quinolines and imines catalyzed by simple manganese carbonyls,Mn2(CO)10 or MnBr(CO)5,thus eliminating the prerequisite pincer-type or bidentate ligands.
基金the lran National Science Foundation(No.87040564) for financial support
文摘Nanomaterials are considered as suitable heterogeneous catalysts for many organic reactions.Herein nano-tube TiO_2 has been reported as a heterogeneous catalyst,for synthesis of imines in sunlight at room temperature under solvent-free conditions.The condensation of less electrophilic carbonyl compounds with poorly nucleophilic amines was afforded imines in excellent yields.
基金supported by the National Natural Science Foundation of China(21473073,21473074)the "13th Five-Year" Science and Technology Research of the Education Department of Jilin Province(2016403)~~
文摘Direct oxidative coupling of an alcohol and amine,with air or molecular oxygen as the oxygen source,is an environmentally friendly method for imine synthesis.We developed an Fe catalyst supported on mesoporous carbon（denoted by FeOx/HCMK-3） for this reaction with excellent activity and recyclability.FeOx/HCMK-3 was prepared by impregnating HNO3-treated mesoporous carbon（CMK-3） with iron nitrate solution.The highly dispersed FeOx species give FeOx/HCMK-3 high reducibility and are responsible for the high catalytic performance.Imine synthesis over FeOx/HCMK-3 follows a redox mechanism.The oxygen species in FeOx/HCMK-3 participate in the reaction and are then regenerated by oxidation with molecular O2.The reaction involves two consecutive steps：oxidative dehydrogenation of an alcohol to an aldehyde and coupling of the aldehyde with an amine to give an imine.Oxidative dehydrogenation of the alcohol is the rate-determining step in the reaction.
基金financially supported by the Natural Science Foundation of China(Nos.22235001,22175020,22131005 and 21631003)Xiaomi Young Scholars Program+2 种基金the Fundamental Research Funds for the Central UniversitiesUniversity of Science and Technology Beijing。
文摘Covalent organic frameworks (COFs) are promising crystalline materials for the light-driven hydrogen evolution reaction (HER) due to their tunable chemical structures and energy band gaps.However,deeply understanding corresponding mechanism is still challenging due to the multiple components and complicated electron transfer and reduction paths involved in photocatalytic HER.Here,the photocatalytic HER investigation has been reported based on three COFs catalysts,1–3,which are prepared by benzo[1,2-b:3,4-b’:5,6-b’]trithiophene-2,5,8-trialdehyde to react with C3symmetric triamines including tris(4-aminophenyl)amine,1,3,5-tris(4-aminophenyl)benzene,and (1,3,5-tris-(4-aminophenyl)triazine,respectively.As the isostructural hexagonal honeycomb-type COF of 2 and 3 reported previously,the crystal structure of 1 has been carefully correlated through the powder X-ray diffraction study with the help of theoretical simulations.1 shows highly porous framework with Brunauer-Emmett-Teller surface area of1249 m^(2)/g.Moreover,the introduction of ascorbic acid into the photocatalytic system of COFs achieves the hydrogen evolution rate of 3.75,12.16 and 20.2 mmol g^(–1)h^(–1) for 1–3,respectively.The important role of ascorbic acid in photocatalysis of HER is disclosed to protonate the imine linkages of these COFs,leading to the obvious absorbance red-shift and the improved charge separation efficiency together with reduced resistance in contrast to pristine materials according to the spectroscopic and electronic characterizations.These innovations of chemical and physical properties for these COFs are responsible for their excellent photocatalytic performance.These results elucidate that tiny modifications of COFs structures is able to greatly tune their band structures as well as catalytic properties,therefore providing an available approach for optimizing COFs functionalities.
文摘The mesomorphie properties of title complexes are investigated by means of DSC and polarizing microscopy. The mesophase temperature ranges of complexes are wider than that of corresponding organic ligands. The bridging groups of the complexes have profoand effects on the mesomorphic behavior, When the bridging groups are opticallhy active. the compleve show chiral smectic
