Laser spectroscopic imaging techniques have received tremendous attention in the-eld of cancer diagnosis due to their high sensitivity,high temporal resolution,and short acquisition time.However,the limited tissue pen...Laser spectroscopic imaging techniques have received tremendous attention in the-eld of cancer diagnosis due to their high sensitivity,high temporal resolution,and short acquisition time.However,the limited tissue penetration of the laser is still a challenge for the in vivo diagnosis of deep-seated lesions.Nanomaterials have been universally integrated with spectroscopic imaging techniques for deeper cancer diagnosis in vivo.The components,morphology,and sizes of nanomaterials are delicately designed,which could realize cancer diagnosis in vivo or in situ.Considering the enhanced signal emitting from the nanomaterials,we emphasized their combination with spectroscopic imaging techniques for cancer diagnosis,like the surface-enhanced Raman scattering(SERS),photoacoustic,fluorescence,and laser-induced breakdown spectroscopy(LIBS).Applications ofthe above spectroscopic techniques offer new prospectsfor cancer diagnosis.展开更多
With the increasing awareness of sustainable chemistry and green chemistry,catalytic conversion of carbon dioxide(CO_(2))into high value‐added and bulk chemicals is a promising tech‐nology that can utilize CO_(2) as...With the increasing awareness of sustainable chemistry and green chemistry,catalytic conversion of carbon dioxide(CO_(2))into high value‐added and bulk chemicals is a promising tech‐nology that can utilize CO_(2) as an ideal C1 source while simulta‐neously storing renewable energy.Despite being frustrated with its thermodynamic stability and kinetic inertness,CO_(2) has been tamed for triggering catalytic constructions of highly‐valued entities like important hydrocarbon fuels and fine chemicals,mainly aiding by two scenarios:CO_(2) reduction and CO_(2)‐involved organic synthesis.Accordingly,science,industry and govern‐ment agencies have been devoted to leverage these synthetic tools in targeting the catalytic conversion of CO_(2).Therefore,it motivates us to organize the special column of“Catalytic Con‐version of CO_(2)”.The column contains 14 papers,including 4 reviews,4 communications and 6 articles,which cover the frontiers and most of the research aspects of catalytic con‐version of CO_(2).展开更多
Poly(Imino Ketone) (PIK) is a group of novel high performance polymer material with excellent thermal properties and dissolubility. Aiming at the requirements of inertial confined fusion (ICF) studies on low den...Poly(Imino Ketone) (PIK) is a group of novel high performance polymer material with excellent thermal properties and dissolubility. Aiming at the requirements of inertial confined fusion (ICF) studies on low density polymer foams, we firstly synthesized poly(imino imino ketone) (PIIK) by palladium catalyzed C-N cross-coupling reaction, and successfully prepared the PIIK foam material with a density of 80-300 mg/cm3 by using PIIK as the raw material with thermal-induced phase separation and lyophilization technique. Mercury injection method was used to determine the structure of PIIK foams, and the results indicated that the mean pore diameter was lower than 5 ~tm and it had relatively high voidage and specific surface area.展开更多
A highly efficient asymmetric allylic alkylation of cyclic and acyclic carbon nucleophiles with vinyl epoxides has been developed,which exhibits good functional group compatibility,high atomic and step economy.This pr...A highly efficient asymmetric allylic alkylation of cyclic and acyclic carbon nucleophiles with vinyl epoxides has been developed,which exhibits good functional group compatibility,high atomic and step economy.This protocol utilizes a strategy of synergistic catalysis with a chiral N,N'-dioxide/Ni~Ⅱ complex and an achiral Pd~0 catalyst,generating a series of multisubstituted allylic alcohols with a quaternary carbon stereocenter in high yield and excellent regio-,Z/E-and enantioselectivity under mild conditions.Further transformations of the product demonstrate the potential utility of this protocol in the synthesis of allyl alcohol derivatives and natural product analogues.Experimental studies revealed that the N,N′-dioxide/metal complexes play an important role in controlling the Z/E-and enantioselectivity.The density functional theory(DFT) calculations further demonstrated that multiple C–H···π interactions between the aromatic rings of the two substrates and the amide moiety in the ligand stabilized the dominant transition state.展开更多
Dicarboxylic acids have a wide range of applications in the polymer industry to construct valuable materials.Photocatalysis has recently emerged as an efficient and sustainable strategy to generate dicarboxylic acids....Dicarboxylic acids have a wide range of applications in the polymer industry to construct valuable materials.Photocatalysis has recently emerged as an efficient and sustainable strategy to generate dicarboxylic acids.However,photocatalytic dicarboxylation with CO_(2) is mainly limited to unsaturated bonds,and the dicarboxylation of C-C single bonds still remains a challenge.Herein,we report a photocatalytic dicarboxylation of C-C single bonds in strained rings with CO_(2) units via consecutive photo-induced electron transfer(ConPET).It is also the first photocatalytic reductive ring-opening reaction of cyclobutanes.Notably,this transition-metal-free protocol exhibits good functional group tolerance,broad substrate scope,facile scalability,and easy product derivatizations.Moreover,diacids can easily be derivatized to mainchain liquid crystalline polyesters.展开更多
Composite supports Zr0.5Al0.5O1.75 modified by metal oxides, such as La2O3, ZnO, Y2O3 or BaO, were prepared by co-precipitation method, and palladium catalysts supported on the modified composite supports were prepare...Composite supports Zr0.5Al0.5O1.75 modified by metal oxides, such as La2O3, ZnO, Y2O3 or BaO, were prepared by co-precipitation method, and palladium catalysts supported on the modified composite supports were prepared by impregnation method. Their properties were characterized by X-ray diffraction (XRD), NH3 temperature-programmed desorption (NH3-TPD), He temperature-programmed reduction (He-TPR), N2 adsorption/desorption, and CO-chemisorption. The catalytic activity and the resistance to water poisoning of the prepared Pd catalysts were tested in a simulated exhaust gas from lean-burn natural gas vehicles with and without water vapor. The results demonstrated that the modified supports had an apparent effect on the performance of Pd catalysts, compared with the Pd catalyst supported on the unmodified ZrA1. The addition of ZnO or Y203 promoted the conversion of CH4. In the absence of water vapor, Pd/ZnZrA1 exhibited the best activity for CH4 conversion with the light-off temperature (Tso) of 275 ℃ and the complete conversion temperature (T90) of 314 ℃, respectively. However, in the presence of water vapor, Pd/YZrA1 was the best one over which the light-off temperature (Tso) of methane was 339 ℃ and the complete conversion temperature (T90) was 371 ℃. These results indicated that Pd catalyst supported on the modified composite ZrA1 support showed excellent catalytic activity at low temperature and high resistance to H20 poisoning for the exhaust purification of lean-burn natural gas vehicles.展开更多
An array of rare-earth bis(aminobenzyl)complexes supported by imidazolin-2-iminato ligands were synthesized and structurally characterized.These complexes showed high activity towards ortho-Csp^(2)–H alkylation of 2-...An array of rare-earth bis(aminobenzyl)complexes supported by imidazolin-2-iminato ligands were synthesized and structurally characterized.These complexes showed high activity towards ortho-Csp^(2)–H alkylation of 2-alkylpyridines and benzylic Csp^(3)–H alkylation of 2,6-dialkylpyridines with alkenes.A wide range of alkyl or aryl substituted olefin substrates are compatible,providing an atom-economical route to linear or branched alkylated pyridine derivatives in moderate to high yields(45 examples,up to 99%yield).The primary study suggested that the asymmetric version of Csp^(3)–H alkylation of 2,4,6-collidine with allylbenzene was feasible with chiral imidazolin-2-iminato-ligated scandium(III)complexes,and good yield with moderate enantioselectivity was obtained(84%yield,84:16 er).Mechanistic investigations including kinetic isotope effect(KIE)experiments and density functional theory(DFT)calculations shed light on the catalytic cycle and the origin of enantiocontrol.展开更多
Photo-induced electron transfer (PET) of silyl enol ethers has been employed to synthesize several fused ring systems. However, the method has limited applicability due to its narrow substrate scope, low product yield...Photo-induced electron transfer (PET) of silyl enol ethers has been employed to synthesize several fused ring systems. However, the method has limited applicability due to its narrow substrate scope, low product yields, unsatisfactory stereo- and regioselectivity. Herein, we report a PET-triggered cascade reaction of silyl enolates that leads to the formation of angularly fused tricyclic scaffolds. The reaction exhibits broad substrate scope and excellent stereoselectivity. The regio- and stereoselectivity of this cascade reaction is elucidated via DFT calculation and conformational analysis.展开更多
A highly efficient asymmetric(3 + 2) cycloaddition of α-diazo pyrazoleamides with silyl enol ethers was realized by employing a chiral N,N’-dioxide-Ni(II) complex catalyst. The process includes the formation of chir...A highly efficient asymmetric(3 + 2) cycloaddition of α-diazo pyrazoleamides with silyl enol ethers was realized by employing a chiral N,N’-dioxide-Ni(II) complex catalyst. The process includes the formation of chiral nickel carbenoid intermediate and the following enantioselective cycloaddition reaction. The desired dihydrofuran O,O-acetal derivatives were obtained in good yields(up to 90%) with high enantioselectivity(up to 99% ee) under mild reaction conditions within short reaction time. On the basis of the determination of the catalyst structure, a possible transition state mode was proposed.展开更多
The diastereo-and enantioselective tandem cycloisomerization/[4+2]-cycloaddition reaction of cyclopropyl tethered allenyl ketones withα,β-unsaturated carbonyl compounds was realized firstly under mild reaction condi...The diastereo-and enantioselective tandem cycloisomerization/[4+2]-cycloaddition reaction of cyclopropyl tethered allenyl ketones withα,β-unsaturated carbonyl compounds was realized firstly under mild reaction conditions by using bimetallic silver(I)/chiral metal-N,N′-dioxide catalysts,providing a facile and atom-economic route to enantioenriched polysubstituted furopyran derivatives with good results.Possible transition state models were proposed to explain the stereoinduction.展开更多
N-heterocyclic olefins(NHOs)possess an electron-rich and highly polarized C=C double bond due to the donating property of nitrogen atoms.This feature imparts exocyclic carbon atom of NHOs with strong basicity and high...N-heterocyclic olefins(NHOs)possess an electron-rich and highly polarized C=C double bond due to the donating property of nitrogen atoms.This feature imparts exocyclic carbon atom of NHOs with strong basicity and high nucleophilicity.Although NHOs have been emerging as a new type of organocatalyst and ligand for metal complexes in organic synthesis,chiral NHOmediated highly enantioselective organic transformations were still elusive.Herein,we developed a new type of chiral aminederived C_(2)-symmetric NHOs and employed them as efficient chiral bifunctional organocatalysts for asymmetricα-functionalization ofβ-ketoesters.With as low as 0.1 mol%catalyst loading,the desired amination and trifluoromethylthiolation products were afforded in good yields with high enantioselectivities(up to 99%yield and 99%ee).Experimental studies and theoretical calculation disclosed that hydrogen-bonding interaction upon protonation and other weak interaction between substrate and catalyst were crucial for the enantiocontrol.展开更多
A highly chemo-and enantioselective alkylation of vinyl azides with 3-bromo-3-substituted oxindoles was achieved through a chiral N,N′-dioxide/Ni(OTf)2-mediated conjugate addition/water addition/elimination tandem pr...A highly chemo-and enantioselective alkylation of vinyl azides with 3-bromo-3-substituted oxindoles was achieved through a chiral N,N′-dioxide/Ni(OTf)2-mediated conjugate addition/water addition/elimination tandem process. Water was critical to the chemo-and enantioselectivity. The hydrated Na3PO4 acted as both a base and a reservoir to regulate the amount of water in solution. A wide range of enantioenriched oxindoles having α-carbonyl-substituted all-carbon quaternary stereocenters were achieved in good yields and good ee values(51 examples, up to 90% yield, 97% ee). Easy transformations of products to analogues of(+)-physovenine and(+)-desoxyeseroline enhanced the synthetic value. Mechanistic studies including control experiments, kinetic studies, and density functional theory(DFT) calculations, enabled a proposition of a possible catalytic cycle along with transition states to elucidate the reaction process and chiral induction.展开更多
We report the development of a new class of multifunctional chiral guanidine/Pd(0)catalyst system for 1,4-addition/arylation tandem reaction.A variety of tetra-substituted allenes were readily accessible from three-co...We report the development of a new class of multifunctional chiral guanidine/Pd(0)catalyst system for 1,4-addition/arylation tandem reaction.A variety of tetra-substituted allenes were readily accessible from three-component“one-pot”transformations of acyclic or cyclic 2-activated 1,3-enynes,malonates and halobenzenes under mild reaction conditions.High levels of yield and enantioselectivity were achieved in the construction of stereogenic center and axis using readily available acyclic guanidineamides.The mechanistic studies suggest that the guanidine/Pd(0)collaboration has obvious synergism to both base-dominated conjugate addition,and Pd(0)-dominated Heck-type reaction.展开更多
Reversal of regioselectivity in the catalytic asymmetric conjugate additions of 3-substituted oxindoles toβ-nitroenones orβ-nitroacrylates was established with chiral scandium catalysts.It enabled the construction o...Reversal of regioselectivity in the catalytic asymmetric conjugate additions of 3-substituted oxindoles toβ-nitroenones orβ-nitroacrylates was established with chiral scandium catalysts.It enabled the construction of functionalized 3,3-disubstituted oxindoles,including terminal and internal vinyl groups in excellent yields and ee values.展开更多
The nanostructures and redox properties of CeO_(2)-ZrO_(2)materials can be tuned via optimized thermal treatments.In this study,the CeO_(2)-ZrO_(2)-Y_(2)O_(3)-La_(2)O_(3)(CZ) materials were prepared by co-precipitatio...The nanostructures and redox properties of CeO_(2)-ZrO_(2)materials can be tuned via optimized thermal treatments.In this study,the CeO_(2)-ZrO_(2)-Y_(2)O_(3)-La_(2)O_(3)(CZ) materials were prepared by co-precipitation method and submitted to different thermal treatment conditions(atmosphere:nitrogen(N) and air(A);temperature(x):700,800 and 900℃).Due to the protective effects of the "in-situ-formed" carbon powder,treating the surfactants assisted-CZ precursors under N2atmosphere can keep the pore structures and then the CZ-N700 and CZ-N800 can achieve larger surface area than CZ-A700 and CZ-A800,respectively.In comparison,with high treatment temperature(900℃),the effects of thermal atmosphere on surface area can be ignored.However,the redox properties of CZ materials correlate closely with thermal treatment atmosphere and temperature simultaneously.As demonstrated by X-ray diffraction(XRD) and X-ray photoelectron spectroscopy(XPS) characterizations,the N_(2)atmosphere facilitates the formation of Ce^(3+)without disturbing the mixing degree of Ce and Zr.Thereby the CZ-Nx materials exhibit superior reducibility than corresponding CZ-Ax materials.In additio n,the XRD and XPS results also demonstrate the formation of a more homogeneous CZ solid solution by Zr atoms rearrangement with temperature ignoring the atmosphere.As a result,the reducibility of CZ materials increases with the treatment temperature increasing and is not affected by the worsening of the textural properties.Specially,due to the synergistic effects of N_(2)atmosphere and high treatment temperature,the CZ-N900 shows the best reducibility.This improvement also emphasizes the important role of structural properties of CZ in explaining the temperature-dependent reducibility.展开更多
Difunctionalizing carboxylation of alkynes with CO_(2)is a sustainable and important strategy to generate valuable acrylate derivatives from both readily available starting materials.Such protocols,however,always suff...Difunctionalizing carboxylation of alkynes with CO_(2)is a sustainable and important strategy to generate valuable acrylate derivatives from both readily available starting materials.Such protocols,however,always suffer from the use of excess metallic reagents and transition metal residue.Herein,we report the first thio-carboxylation of alkynes with thiophenols and CO_(2),which is a visible-light-driven and transition metal-free process.In contrast to previous carboxylations of alkynes via two-electron activation of CO_(2),mechanistic and computational investigations suggest that the single-electron activation of CO_(2)is involved in the thio-carboxylation,rendering uniqueβ-carboxylation.The following cyclizing acylation affords important thiochromones efficiently.Moreover,the one-pot method features mild reaction conditions(room temperature,1 atmosphere of CO_(2)),high chemo-and regio-selectivity,easy scalability and facile derivatization of products to bioactive compounds.展开更多
A series of Mn-Cu mixed oxide catalysts were prepared by precipitation method. The catalysts were characterized by N2 adsorp- tion-desorption, H2-TPR and XPS. When the loading ratio of manganese oxides to copper oxide...A series of Mn-Cu mixed oxide catalysts were prepared by precipitation method. The catalysts were characterized by N2 adsorp- tion-desorption, H2-TPR and XPS. When the loading ratio of manganese oxides to copper oxides was 8:2 or 7:3, the catalysts possessed better catalytic activity, and benzene was converted completely at 558 K. Results of H2-TPR showed that the loading of a small amount of copper oxides decreased the reduction temperature of catalysts. Results of XPS showed that the loading of a small amount of copper oxides increased the proportion of manganese and defective oxygen on the surface of catalysts, and stabilized manganese at higher oxidation state. And the catalyst with the loading ratio 7:3 was a little worse than 8:2, since the interaction between manganese oxides and copper oxides is too strong, copper oxides migrate to the surface of catalysts and manganese oxides in excess are immerged.展开更多
Ce-Zr-Al-Nd2O3 (CZAN) support materials were prepared by co-precipitation and impregnation methods, respectively. They were characterized by X-ray diffTaction (XRD), low temperature nitrogen adsorption-desorption,...Ce-Zr-Al-Nd2O3 (CZAN) support materials were prepared by co-precipitation and impregnation methods, respectively. They were characterized by X-ray diffTaction (XRD), low temperature nitrogen adsorption-desorption, oxygen pulsing technique, H2-temperamre programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS). The Pd-only three-way catalysts (Pd-TWC) supported on these materials were prepared by incipient wetness method and studied by activity tests. The results demonstrated that the CZAN supports obtained by the two methods showed better structural, textural and redox properties than the CZA without Nd2O3, and the addition of Nd203 improved the catalytic activity of TWC. Especially, the CZAN-i support prepared by impregnation method had better thermal stability and redox property. Meanwhile, the Pd/CZAN-i catalyst exhibited the best catalytic performance. XPS measurements indicated that the Nd-modified samples possessed more Ce3+ and oxygen vacancies on the surface of samples, which led to a better redox property. The excellent redox property of support materials helped to improve the catalytic activity of TWC.展开更多
Herein we report a novel visible-light-mediated external reductant-free reductive cross coupling for the construction of C sp2–C sp3 bonds.A variety of benzylammonium salts underwent selective coupling with(hetero)ar...Herein we report a novel visible-light-mediated external reductant-free reductive cross coupling for the construction of C sp2–C sp3 bonds.A variety of benzylammonium salts underwent selective coupling with(hetero)aryl nitriles to deliver important diarylmethanes under mild reaction conditions.Importantly,photocatalysts can be omitted for many cases,which might involve the electron donor acceptor(EDA)complex.Mechanistic studies indicated benzylic radicals might be involved as the key intermediates.Moreover,the in situ generated NMe3 via cleavage of C–N bond in ammonium salts acts as the electron donor,thus avoiding the use of external-reductant.展开更多
Prediction of reaction yields using machine learning(ML)can help chemists select high-yielding reactions and provide prior experience before wet-lab experimenting to improve efficiency.However,the exploration of a mul...Prediction of reaction yields using machine learning(ML)can help chemists select high-yielding reactions and provide prior experience before wet-lab experimenting to improve efficiency.However,the exploration of a multicomponent organic reaction features many complex variables and limited number of experimental data,which are challenging for the application of ML.Herein,we perform yield prediction for the synthesis of 2-oxazolidones via Cu-catalyzed radical-type oxy-alkylation of allylamines and herteroaryl-methylamines with CO_(2),which is a three-component reaction.Using physicochemical descriptors as features to launch ML modelling,we find that XGBoost shows significantly improved performance over linear models and these features are effective for the yield prediction.Moreover,out-of-sample prediction indicates the application potential of the model.This study demonstrates great potential of regression-modelling-based ML in organic synthesis even with complex factors and a general small size of reaction data,which are generated from the classical research pattern of method for the inquiry of multicomponent reactions.展开更多
基金support from the Sichuan Science and Technology Program(2019ZDZX0036)the support from the Analytical&Testing Center of Sichuan University.
文摘Laser spectroscopic imaging techniques have received tremendous attention in the-eld of cancer diagnosis due to their high sensitivity,high temporal resolution,and short acquisition time.However,the limited tissue penetration of the laser is still a challenge for the in vivo diagnosis of deep-seated lesions.Nanomaterials have been universally integrated with spectroscopic imaging techniques for deeper cancer diagnosis in vivo.The components,morphology,and sizes of nanomaterials are delicately designed,which could realize cancer diagnosis in vivo or in situ.Considering the enhanced signal emitting from the nanomaterials,we emphasized their combination with spectroscopic imaging techniques for cancer diagnosis,like the surface-enhanced Raman scattering(SERS),photoacoustic,fluorescence,and laser-induced breakdown spectroscopy(LIBS).Applications ofthe above spectroscopic techniques offer new prospectsfor cancer diagnosis.
文摘With the increasing awareness of sustainable chemistry and green chemistry,catalytic conversion of carbon dioxide(CO_(2))into high value‐added and bulk chemicals is a promising tech‐nology that can utilize CO_(2) as an ideal C1 source while simulta‐neously storing renewable energy.Despite being frustrated with its thermodynamic stability and kinetic inertness,CO_(2) has been tamed for triggering catalytic constructions of highly‐valued entities like important hydrocarbon fuels and fine chemicals,mainly aiding by two scenarios:CO_(2) reduction and CO_(2)‐involved organic synthesis.Accordingly,science,industry and govern‐ment agencies have been devoted to leverage these synthetic tools in targeting the catalytic conversion of CO_(2).Therefore,it motivates us to organize the special column of“Catalytic Con‐version of CO_(2)”.The column contains 14 papers,including 4 reviews,4 communications and 6 articles,which cover the frontiers and most of the research aspects of catalytic con‐version of CO_(2).
基金Funded by the National Natural Science Foundation of China(No.11447215)Scientific Research Project of Mianyang Normal University(No.2013A02)Research Fund of Education Department of Sichuan Province(No.13ZB0118)
文摘Poly(Imino Ketone) (PIK) is a group of novel high performance polymer material with excellent thermal properties and dissolubility. Aiming at the requirements of inertial confined fusion (ICF) studies on low density polymer foams, we firstly synthesized poly(imino imino ketone) (PIIK) by palladium catalyzed C-N cross-coupling reaction, and successfully prepared the PIIK foam material with a density of 80-300 mg/cm3 by using PIIK as the raw material with thermal-induced phase separation and lyophilization technique. Mercury injection method was used to determine the structure of PIIK foams, and the results indicated that the mean pore diameter was lower than 5 ~tm and it had relatively high voidage and specific surface area.
基金supported by the National Natural Science Foundation of China (U19A2014)Sichuan University(2020SCUNL204)。
文摘A highly efficient asymmetric allylic alkylation of cyclic and acyclic carbon nucleophiles with vinyl epoxides has been developed,which exhibits good functional group compatibility,high atomic and step economy.This protocol utilizes a strategy of synergistic catalysis with a chiral N,N'-dioxide/Ni~Ⅱ complex and an achiral Pd~0 catalyst,generating a series of multisubstituted allylic alcohols with a quaternary carbon stereocenter in high yield and excellent regio-,Z/E-and enantioselectivity under mild conditions.Further transformations of the product demonstrate the potential utility of this protocol in the synthesis of allyl alcohol derivatives and natural product analogues.Experimental studies revealed that the N,N′-dioxide/metal complexes play an important role in controlling the Z/E-and enantioselectivity.The density functional theory(DFT) calculations further demonstrated that multiple C–H···π interactions between the aromatic rings of the two substrates and the amide moiety in the ligand stabilized the dominant transition state.
基金Financial support is provided by the National Natural Science Foundation of China(No.22225106)Fundamental Research Funds from Sichuan University(No.2020SCUNL102)the Fundamental Research Funds for the Central Universities。
文摘Dicarboxylic acids have a wide range of applications in the polymer industry to construct valuable materials.Photocatalysis has recently emerged as an efficient and sustainable strategy to generate dicarboxylic acids.However,photocatalytic dicarboxylation with CO_(2) is mainly limited to unsaturated bonds,and the dicarboxylation of C-C single bonds still remains a challenge.Herein,we report a photocatalytic dicarboxylation of C-C single bonds in strained rings with CO_(2) units via consecutive photo-induced electron transfer(ConPET).It is also the first photocatalytic reductive ring-opening reaction of cyclobutanes.Notably,this transition-metal-free protocol exhibits good functional group tolerance,broad substrate scope,facile scalability,and easy product derivatizations.Moreover,diacids can easily be derivatized to mainchain liquid crystalline polyesters.
基金supported by the National Natural Science Foundation of China (21173153)Science and Technology Department of Science and Technology Support Project of Sichuan Povince,China (2011GZ0035)
文摘Composite supports Zr0.5Al0.5O1.75 modified by metal oxides, such as La2O3, ZnO, Y2O3 or BaO, were prepared by co-precipitation method, and palladium catalysts supported on the modified composite supports were prepared by impregnation method. Their properties were characterized by X-ray diffraction (XRD), NH3 temperature-programmed desorption (NH3-TPD), He temperature-programmed reduction (He-TPR), N2 adsorption/desorption, and CO-chemisorption. The catalytic activity and the resistance to water poisoning of the prepared Pd catalysts were tested in a simulated exhaust gas from lean-burn natural gas vehicles with and without water vapor. The results demonstrated that the modified supports had an apparent effect on the performance of Pd catalysts, compared with the Pd catalyst supported on the unmodified ZrA1. The addition of ZnO or Y203 promoted the conversion of CH4. In the absence of water vapor, Pd/ZnZrA1 exhibited the best activity for CH4 conversion with the light-off temperature (Tso) of 275 ℃ and the complete conversion temperature (T90) of 314 ℃, respectively. However, in the presence of water vapor, Pd/YZrA1 was the best one over which the light-off temperature (Tso) of methane was 339 ℃ and the complete conversion temperature (T90) was 371 ℃. These results indicated that Pd catalyst supported on the modified composite ZrA1 support showed excellent catalytic activity at low temperature and high resistance to H20 poisoning for the exhaust purification of lean-burn natural gas vehicles.
基金supported by the National Key R&D Program of China(2022YFA1504301)the National Natural Science Foundation of China(92056107,22271199,92256303,21890723)Sichuan University(2020SCUNL204)。
文摘An array of rare-earth bis(aminobenzyl)complexes supported by imidazolin-2-iminato ligands were synthesized and structurally characterized.These complexes showed high activity towards ortho-Csp^(2)–H alkylation of 2-alkylpyridines and benzylic Csp^(3)–H alkylation of 2,6-dialkylpyridines with alkenes.A wide range of alkyl or aryl substituted olefin substrates are compatible,providing an atom-economical route to linear or branched alkylated pyridine derivatives in moderate to high yields(45 examples,up to 99%yield).The primary study suggested that the asymmetric version of Csp^(3)–H alkylation of 2,4,6-collidine with allylbenzene was feasible with chiral imidazolin-2-iminato-ligated scandium(III)complexes,and good yield with moderate enantioselectivity was obtained(84%yield,84:16 er).Mechanistic investigations including kinetic isotope effect(KIE)experiments and density functional theory(DFT)calculations shed light on the catalytic cycle and the origin of enantiocontrol.
基金supported by NSFC(21925106,U19A2014)Si-chuan University(2020SCUNL204)Department of Science and Technology of Sichuan Province(2023NSFSC0105).
文摘Photo-induced electron transfer (PET) of silyl enol ethers has been employed to synthesize several fused ring systems. However, the method has limited applicability due to its narrow substrate scope, low product yields, unsatisfactory stereo- and regioselectivity. Herein, we report a PET-triggered cascade reaction of silyl enolates that leads to the formation of angularly fused tricyclic scaffolds. The reaction exhibits broad substrate scope and excellent stereoselectivity. The regio- and stereoselectivity of this cascade reaction is elucidated via DFT calculation and conformational analysis.
基金the National Natural Science Foundation of China(No. 22188101)Sichuan Science and Technology Program (No.2021YJ0561)Sichuan University (No. 2020SCUNL204)for financial support。
文摘A highly efficient asymmetric(3 + 2) cycloaddition of α-diazo pyrazoleamides with silyl enol ethers was realized by employing a chiral N,N’-dioxide-Ni(II) complex catalyst. The process includes the formation of chiral nickel carbenoid intermediate and the following enantioselective cycloaddition reaction. The desired dihydrofuran O,O-acetal derivatives were obtained in good yields(up to 90%) with high enantioselectivity(up to 99% ee) under mild reaction conditions within short reaction time. On the basis of the determination of the catalyst structure, a possible transition state mode was proposed.
基金supported by the National Natural Science Foundation of China(21890723,22171189)the Fundamental Research Funds for the Central Universities(YJ201819)。
文摘The diastereo-and enantioselective tandem cycloisomerization/[4+2]-cycloaddition reaction of cyclopropyl tethered allenyl ketones withα,β-unsaturated carbonyl compounds was realized firstly under mild reaction conditions by using bimetallic silver(I)/chiral metal-N,N′-dioxide catalysts,providing a facile and atom-economic route to enantioenriched polysubstituted furopyran derivatives with good results.Possible transition state models were proposed to explain the stereoinduction.
基金supported by the National Natural Science Foundation of China(92056107,22271199,21801175)the Sichuan University(2020SCUNL204)。
文摘N-heterocyclic olefins(NHOs)possess an electron-rich and highly polarized C=C double bond due to the donating property of nitrogen atoms.This feature imparts exocyclic carbon atom of NHOs with strong basicity and high nucleophilicity.Although NHOs have been emerging as a new type of organocatalyst and ligand for metal complexes in organic synthesis,chiral NHOmediated highly enantioselective organic transformations were still elusive.Herein,we developed a new type of chiral aminederived C_(2)-symmetric NHOs and employed them as efficient chiral bifunctional organocatalysts for asymmetricα-functionalization ofβ-ketoesters.With as low as 0.1 mol%catalyst loading,the desired amination and trifluoromethylthiolation products were afforded in good yields with high enantioselectivities(up to 99%yield and 99%ee).Experimental studies and theoretical calculation disclosed that hydrogen-bonding interaction upon protonation and other weak interaction between substrate and catalyst were crucial for the enantiocontrol.
基金supported by the National Natural Science Foundation of China(21871188,21921002)the Sichuan Science and Technology Program(2021YJ0561)the Sichuan University(2020SCUNL204)。
文摘A highly chemo-and enantioselective alkylation of vinyl azides with 3-bromo-3-substituted oxindoles was achieved through a chiral N,N′-dioxide/Ni(OTf)2-mediated conjugate addition/water addition/elimination tandem process. Water was critical to the chemo-and enantioselectivity. The hydrated Na3PO4 acted as both a base and a reservoir to regulate the amount of water in solution. A wide range of enantioenriched oxindoles having α-carbonyl-substituted all-carbon quaternary stereocenters were achieved in good yields and good ee values(51 examples, up to 90% yield, 97% ee). Easy transformations of products to analogues of(+)-physovenine and(+)-desoxyeseroline enhanced the synthetic value. Mechanistic studies including control experiments, kinetic studies, and density functional theory(DFT) calculations, enabled a proposition of a possible catalytic cycle along with transition states to elucidate the reaction process and chiral induction.
基金supported by the National Natural Science Foundation of China(21625205)the Sichuan University(2020SCUNL204)。
文摘We report the development of a new class of multifunctional chiral guanidine/Pd(0)catalyst system for 1,4-addition/arylation tandem reaction.A variety of tetra-substituted allenes were readily accessible from three-component“one-pot”transformations of acyclic or cyclic 2-activated 1,3-enynes,malonates and halobenzenes under mild reaction conditions.High levels of yield and enantioselectivity were achieved in the construction of stereogenic center and axis using readily available acyclic guanidineamides.The mechanistic studies suggest that the guanidine/Pd(0)collaboration has obvious synergism to both base-dominated conjugate addition,and Pd(0)-dominated Heck-type reaction.
基金financial support from the National Natural Science Foundation of China(No.21890723)。
文摘Reversal of regioselectivity in the catalytic asymmetric conjugate additions of 3-substituted oxindoles toβ-nitroenones orβ-nitroacrylates was established with chiral scandium catalysts.It enabled the construction of functionalized 3,3-disubstituted oxindoles,including terminal and internal vinyl groups in excellent yields and ee values.
基金Project supported by the National Natural Science Foundation of China (21972097)the National Engineering Laboratory for Mobile Source Emission Control Technology (NELMS2020A04)。
文摘The nanostructures and redox properties of CeO_(2)-ZrO_(2)materials can be tuned via optimized thermal treatments.In this study,the CeO_(2)-ZrO_(2)-Y_(2)O_(3)-La_(2)O_(3)(CZ) materials were prepared by co-precipitation method and submitted to different thermal treatment conditions(atmosphere:nitrogen(N) and air(A);temperature(x):700,800 and 900℃).Due to the protective effects of the "in-situ-formed" carbon powder,treating the surfactants assisted-CZ precursors under N2atmosphere can keep the pore structures and then the CZ-N700 and CZ-N800 can achieve larger surface area than CZ-A700 and CZ-A800,respectively.In comparison,with high treatment temperature(900℃),the effects of thermal atmosphere on surface area can be ignored.However,the redox properties of CZ materials correlate closely with thermal treatment atmosphere and temperature simultaneously.As demonstrated by X-ray diffraction(XRD) and X-ray photoelectron spectroscopy(XPS) characterizations,the N_(2)atmosphere facilitates the formation of Ce^(3+)without disturbing the mixing degree of Ce and Zr.Thereby the CZ-Nx materials exhibit superior reducibility than corresponding CZ-Ax materials.In additio n,the XRD and XPS results also demonstrate the formation of a more homogeneous CZ solid solution by Zr atoms rearrangement with temperature ignoring the atmosphere.As a result,the reducibility of CZ materials increases with the treatment temperature increasing and is not affected by the worsening of the textural properties.Specially,due to the synergistic effects of N_(2)atmosphere and high treatment temperature,the CZ-N900 shows the best reducibility.This improvement also emphasizes the important role of structural properties of CZ in explaining the temperature-dependent reducibility.
基金supported by the National Natural Science Foundation of China(22225106,21822108,21822303)the Sichuan Science and Technology Program(20CXTD0112)+2 种基金the Central Government Funds of Guiding Local Scientific and Technological Development for Sichuan Province(2021ZYD0063)the Fundamental Research Funds from Sichuan University(2020SCUNL102)the Fundamental Research Funds for the Central Universities。
文摘Difunctionalizing carboxylation of alkynes with CO_(2)is a sustainable and important strategy to generate valuable acrylate derivatives from both readily available starting materials.Such protocols,however,always suffer from the use of excess metallic reagents and transition metal residue.Herein,we report the first thio-carboxylation of alkynes with thiophenols and CO_(2),which is a visible-light-driven and transition metal-free process.In contrast to previous carboxylations of alkynes via two-electron activation of CO_(2),mechanistic and computational investigations suggest that the single-electron activation of CO_(2)is involved in the thio-carboxylation,rendering uniqueβ-carboxylation.The following cyclizing acylation affords important thiochromones efficiently.Moreover,the one-pot method features mild reaction conditions(room temperature,1 atmosphere of CO_(2)),high chemo-and regio-selectivity,easy scalability and facile derivatization of products to bioactive compounds.
基金Project supported by National Natural Science Foundation of China (20773090)the National High Technology Research and Development Program of China (863 Program, 2006AA06Z347)the Youth Fund of Sichuan University (2008119)
文摘A series of Mn-Cu mixed oxide catalysts were prepared by precipitation method. The catalysts were characterized by N2 adsorp- tion-desorption, H2-TPR and XPS. When the loading ratio of manganese oxides to copper oxides was 8:2 or 7:3, the catalysts possessed better catalytic activity, and benzene was converted completely at 558 K. Results of H2-TPR showed that the loading of a small amount of copper oxides decreased the reduction temperature of catalysts. Results of XPS showed that the loading of a small amount of copper oxides increased the proportion of manganese and defective oxygen on the surface of catalysts, and stabilized manganese at higher oxidation state. And the catalyst with the loading ratio 7:3 was a little worse than 8:2, since the interaction between manganese oxides and copper oxides is too strong, copper oxides migrate to the surface of catalysts and manganese oxides in excess are immerged.
基金Project supported by National Natural Science Foundation of China (20773090, 20803049)the Specialized Research Fund for the Doctoral Program of Higher Education (20070610026, 200806100009)
文摘Ce-Zr-Al-Nd2O3 (CZAN) support materials were prepared by co-precipitation and impregnation methods, respectively. They were characterized by X-ray diffTaction (XRD), low temperature nitrogen adsorption-desorption, oxygen pulsing technique, H2-temperamre programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS). The Pd-only three-way catalysts (Pd-TWC) supported on these materials were prepared by incipient wetness method and studied by activity tests. The results demonstrated that the CZAN supports obtained by the two methods showed better structural, textural and redox properties than the CZA without Nd2O3, and the addition of Nd203 improved the catalytic activity of TWC. Especially, the CZAN-i support prepared by impregnation method had better thermal stability and redox property. Meanwhile, the Pd/CZAN-i catalyst exhibited the best catalytic performance. XPS measurements indicated that the Nd-modified samples possessed more Ce3+ and oxygen vacancies on the surface of samples, which led to a better redox property. The excellent redox property of support materials helped to improve the catalytic activity of TWC.
基金supported by the National Natural Science Foundation of China(21772129,21801176)the The National Basic Research Program of China from the Minstry of Science and Technology of China(2015CB856600)+2 种基金Sichuan Science and Technology Program(2019YJ0379)Neijiang Normal University(KF10076)the Fundamental Research Funds for the Central Universities(YJ201516)
文摘Herein we report a novel visible-light-mediated external reductant-free reductive cross coupling for the construction of C sp2–C sp3 bonds.A variety of benzylammonium salts underwent selective coupling with(hetero)aryl nitriles to deliver important diarylmethanes under mild reaction conditions.Importantly,photocatalysts can be omitted for many cases,which might involve the electron donor acceptor(EDA)complex.Mechanistic studies indicated benzylic radicals might be involved as the key intermediates.Moreover,the in situ generated NMe3 via cleavage of C–N bond in ammonium salts acts as the electron donor,thus avoiding the use of external-reductant.
基金We thank the financial support from the National Natural Science Foundation of China(Nos.21775107,21822108)the Sichuan Science and Technology Program(20CXTD0112)the Fundamental Research Funds for the Central Universities.
文摘Prediction of reaction yields using machine learning(ML)can help chemists select high-yielding reactions and provide prior experience before wet-lab experimenting to improve efficiency.However,the exploration of a multicomponent organic reaction features many complex variables and limited number of experimental data,which are challenging for the application of ML.Herein,we perform yield prediction for the synthesis of 2-oxazolidones via Cu-catalyzed radical-type oxy-alkylation of allylamines and herteroaryl-methylamines with CO_(2),which is a three-component reaction.Using physicochemical descriptors as features to launch ML modelling,we find that XGBoost shows significantly improved performance over linear models and these features are effective for the yield prediction.Moreover,out-of-sample prediction indicates the application potential of the model.This study demonstrates great potential of regression-modelling-based ML in organic synthesis even with complex factors and a general small size of reaction data,which are generated from the classical research pattern of method for the inquiry of multicomponent reactions.