Tetracyclic coumarins are a class of important compounds with diverse and superior pharmacolog‐ical activities.However,a direct stereoselective method from simple and readily‐made coumarins derivatives remains chall...Tetracyclic coumarins are a class of important compounds with diverse and superior pharmacolog‐ical activities.However,a direct stereoselective method from simple and readily‐made coumarins derivatives remains challenging due to the inertness of coumarins as dienophiles.Herein,we de‐velop a decarboxylative asymmetric[4+2]cycloaddition of 3‐cyanocoumarins with vinyl benzoxa‐zinones,affording the coumarin‐derived condensed rings bearing three continuous stereocenters in high yields with excellent diastereoselectivities(>20/1 d.r.)and enantioselectivities(up to 99%ee).This direct enantioselective reaction was achieved by a Pd(0)/Cu(I)bimetallic catalytic system.The mechanism studies indicated that the synergistic activation effect,in which chiral Cu(I)as an availa‐ble Lewis acid catalyst activates 3‐cyanocoumarin and chiral Pd(0)complex activates benzoxazi‐none by the formation ofπ‐allyl‐palladium intermediate,plays an important role on the stereoselec‐tive control.The current work provides a new activation modes of Cu catalyst in the Pd/Cu bimetal‐lic catalytic system.展开更多
Cu-x-Fe-y/SiO2 catalysts were prepared using urea-assisted sol-gel method. The structure and physicochemical properties of the catalysts were characterized using N-2 adsorption-desorption, transmission electron micros...Cu-x-Fe-y/SiO2 catalysts were prepared using urea-assisted sol-gel method. The structure and physicochemical properties of the catalysts were characterized using N-2 adsorption-desorption, transmission electron microscopy, H-2-temperature-programmed reduction, powder X-ray diffraction, and X-ray photoelectron spectroscopy. Compared with monometallic Cu or Fe catalysts, the bimetallic Cu-x-Fe-y/SiO2 catalysts exhibited enhanced catalytic performance for the selective hydrogenation of diethyl malonate to 1,3-propanediol. The bimetallic catalyst with an optimal Cu/Fe atomic ratio of 2 exhibited the highest activity, which yielded 96.3% conversion to diethyl malonate and 93.3% selectivity to 1,3-propanediol under the optimal reaction conditions. Characterization results revealed that interactions between Cu and Fe contributed to the improvement of diethyl malonate conversion and selectivity to 1,3-propanediol. The X-ray photoelectron spectroscopy results revealed that the addition of appropriate amount of Fe species enhanced the reduction of Cu2+ species, thereby increasing the Cu-0 species on the surface of bimetallic catalyst. It led to a better chemisorption capacity of hydrogen and further promoted of the activation of hydrogen molecule. The ethyl acetate temperature-programmed desorption results indicated that the FeOx species provided the additional adsorption sites for substrate molecules, and they activated the C=O bond. The improved catalytic performance of bimetallic Cu-x-Fe-y/SiO2 catalyst was mainly attributed to the synergistic effect between Cu-0 and FeOx species. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.展开更多
3,4-Dihydroisoquinoline(DHIQ)is an important precursor used in the production of drugs for treating cancer,HIV,Alzheimer's disease,etc.Major studies on DHIQ synthesis show low catalytic selectivity due to the susc...3,4-Dihydroisoquinoline(DHIQ)is an important precursor used in the production of drugs for treating cancer,HIV,Alzheimer's disease,etc.Major studies on DHIQ synthesis show low catalytic selectivity due to the susceptible over-oxidation feedstock of1,2,3,4-tetrahydroisoquinoline(THIQ),which often requires alkali co-catalysts.Therefore,it is desirable yet challenging to explore a highly selective and efficient oxydehydrogenation capacity for DHIQ synthesis under eco-friendly reaction conditions.Herein,a novel framework 1 was synthesized,exhibiting 1D channels with the size of 4.6 A×9.6 A and high solvent/p H/thermal stability.A stable framework allows it to encapsulate Cu nanoparticles(NPs)to form Cu NPs@1-x(x=1,2,3,and 4)with varying loading amounts of Cu NPs at 2.0 wt%,3.0 wt%,4.0 wt%,and 6.0 wt%,respectively.Cu NPs@1-3 could selectively catalyze the reaction from THIQ to DHIQ with a high selectivity of 98%and a recorded turnover frequency(TOF)of 22.1 h-1under eco-friendly mild conditions.The corresponding catalytic activity can maintain at least five recyclings and can be further applied to gram-scale experiments.Additionally,the efficient preparation of DHIQ catalyzed by Cu NPs@1-3 could be realized even under air conditions.Importantly,the anticancer molecule precursor synthesis of 6,7-dimethoxy-3,4-dihydroisoquinoline was also selectively catalyzed by Cu NPs@1-3.Mechanism investigations revealed that high catalytic performance can be attributed to the stable framework and the synergistic catalytic effect of the loaded Cu NPs and Co metal centers.More importantly,this work represents the first example of MOF catalysts for selectively thermo-catalytic DHIQ synthesis and demonstrates a simple approach to obtain efficient catalysts for selective oxydehydrogenation in the production of unsaturated compounds.展开更多
FeO_x/HZSM-5 catalyst with 8 wt.%Fe-loading（8-FeZ） exhibited significantly higher reactivity in the benzylation of benzene with benzyl chloride than FeO_x/HZSM-5 catalyst with 2.5 wt.%Fe-loading（2.5-FeZ） because t...FeO_x/HZSM-5 catalyst with 8 wt.%Fe-loading（8-FeZ） exhibited significantly higher reactivity in the benzylation of benzene with benzyl chloride than FeO_x/HZSM-5 catalyst with 2.5 wt.%Fe-loading（2.5-FeZ） because the synergistic catalysis between isolated Fe^（3＋） and superfine Fe_2O_3 occurred on 8-FeZ in the reaction.展开更多
In this work. phenol and oxalic acid （OA） degradation in an ozone and photocatalysis integrated process was intensively conducted with Fe3 ＋/TiO2 catalyst. The ferrioxalate complex formed between Fe3＋ and oxalate ...In this work. phenol and oxalic acid （OA） degradation in an ozone and photocatalysis integrated process was intensively conducted with Fe3 ＋/TiO2 catalyst. The ferrioxalate complex formed between Fe3＋ and oxalate accelerated the removal of OA in the ozonation, photolysis and photocatalytic ozonation process, for its high reactivity with ozone and UV. Phenol was degraded in ozonation and photolysis with limited TOC removal rates, but much higher TOC removal was achieved in photocatalytic ozonation due to the generation of-OH. The sequence of UV light and ozone in the sequential process also influences the TOC removal, and ozone is very powerful to oxidize intermediates catechol and hydroquinone to maleic acid. Fenton or photo-Fenton reactions only played a small part in Fe3＋/TiO2 catalyzed processes, because Fe＋ was greatly reduced but not regenerated in many cases. The synergetic effect was found to be highly related with the property of the target pollutants. Fe3 ＋/TiO2 catalyzed system showed the highest ability to destroy organics, but the TiO2 catalyzed system showed little higher synergy.展开更多
This study demonstrated that as-synthesized nano Fe/Cu bimetals could achieve significant enhancement in the degradation of diclofenac(DCF),as compared to much slow removal of DCF by Cu(Ⅱ) or zero valent iron nanopar...This study demonstrated that as-synthesized nano Fe/Cu bimetals could achieve significant enhancement in the degradation of diclofenac(DCF),as compared to much slow removal of DCF by Cu(Ⅱ) or zero valent iron nanoparticles(nZVI),respectively.Further observations on the evolution of O_(2) activation process by nano Fe/Cu bimetals was conducted stretching to the preparation phase(started by nZVI/Cu2+).Interesting breakpoints we re observed with obvious sudden increase in the DCF degradation efficiency and decrease in solution pH,as the original nZVI just consumed up to Fe(Ⅱ) and Cu(II) appeared again.It suggested that the four-electrons reaction of O_(2) and Cu-deposited nZVI would occur to generate water prior to the breakpoints,while Cu(0) and Fe(Ⅱ) would play most important role in activation of O_(2) afterwards.Through the electron spin resonance(ESR) analysis and quenching experiments.·OH was identified as the responsible reactive species.Further time-dependent quantifications in the cases of Cu(0)/Fe(Ⅱ) systems we re carried out.It was found that the ’OH accumulation was positively and linearly correlated with nCu dose,Fe(Ⅱ) consumption,and Fe(II) dose,respectively.Since either Cu(O) or Fe(Ⅱ)would be inefficient in activating oxygen to produce ·OH,a stage-evolution mechanism of O_(2) activated by nano Fe/Cu bimetals was proposed involving:(a) Rapid consumption of Fe(0) and release of Fe(Ⅱ) based on the Cu-Fe galvanic corrosion,(b) adsorption and transformation of O_(2) to O_(2)2 at the nCu surface,and(c) Fe(Ⅱ)-catalyzed activation of the adsorbed O_(2)2 to ·OH.展开更多
Main observation and conclusion A highly enantioselective 2,3-allenylation of acyclic and cyclicα-imino carboxylates via a synergistic bimetallic Pd/Cu catalysis with the same commercially available(R,Rp)-iPr-FOXAP(a...Main observation and conclusion A highly enantioselective 2,3-allenylation of acyclic and cyclicα-imino carboxylates via a synergistic bimetallic Pd/Cu catalysis with the same commercially available(R,Rp)-iPr-FOXAP(also as Phosferrox,(R,R)-[2-(4’-i-propyloxazolin-2’-yl)ferrocenyl]diphenyl phosphine)ligand for both metals affording optically active 2,3-butadienylα-amino acid derivatives in high to excellent yields with excellent enantioselectivities has been developed.展开更多
文摘Tetracyclic coumarins are a class of important compounds with diverse and superior pharmacolog‐ical activities.However,a direct stereoselective method from simple and readily‐made coumarins derivatives remains challenging due to the inertness of coumarins as dienophiles.Herein,we de‐velop a decarboxylative asymmetric[4+2]cycloaddition of 3‐cyanocoumarins with vinyl benzoxa‐zinones,affording the coumarin‐derived condensed rings bearing three continuous stereocenters in high yields with excellent diastereoselectivities(>20/1 d.r.)and enantioselectivities(up to 99%ee).This direct enantioselective reaction was achieved by a Pd(0)/Cu(I)bimetallic catalytic system.The mechanism studies indicated that the synergistic activation effect,in which chiral Cu(I)as an availa‐ble Lewis acid catalyst activates 3‐cyanocoumarin and chiral Pd(0)complex activates benzoxazi‐none by the formation ofπ‐allyl‐palladium intermediate,plays an important role on the stereoselec‐tive control.The current work provides a new activation modes of Cu catalyst in the Pd/Cu bimetal‐lic catalytic system.
基金supported by the Natural Science Foundation of China (91545115,21473145,and 21403178)the Postgraduate Basic Innovative Research Program of Xiamen University (201412G001)the Program for Innovative Research Team in Chinese Universities (no.IRT_14R31)
文摘Cu-x-Fe-y/SiO2 catalysts were prepared using urea-assisted sol-gel method. The structure and physicochemical properties of the catalysts were characterized using N-2 adsorption-desorption, transmission electron microscopy, H-2-temperature-programmed reduction, powder X-ray diffraction, and X-ray photoelectron spectroscopy. Compared with monometallic Cu or Fe catalysts, the bimetallic Cu-x-Fe-y/SiO2 catalysts exhibited enhanced catalytic performance for the selective hydrogenation of diethyl malonate to 1,3-propanediol. The bimetallic catalyst with an optimal Cu/Fe atomic ratio of 2 exhibited the highest activity, which yielded 96.3% conversion to diethyl malonate and 93.3% selectivity to 1,3-propanediol under the optimal reaction conditions. Characterization results revealed that interactions between Cu and Fe contributed to the improvement of diethyl malonate conversion and selectivity to 1,3-propanediol. The X-ray photoelectron spectroscopy results revealed that the addition of appropriate amount of Fe species enhanced the reduction of Cu2+ species, thereby increasing the Cu-0 species on the surface of bimetallic catalyst. It led to a better chemisorption capacity of hydrogen and further promoted of the activation of hydrogen molecule. The ethyl acetate temperature-programmed desorption results indicated that the FeOx species provided the additional adsorption sites for substrate molecules, and they activated the C=O bond. The improved catalytic performance of bimetallic Cu-x-Fe-y/SiO2 catalyst was mainly attributed to the synergistic effect between Cu-0 and FeOx species. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.
基金supported by the National Natural Science Foundation of China(92161202,22271159,22121005,21971125)。
文摘3,4-Dihydroisoquinoline(DHIQ)is an important precursor used in the production of drugs for treating cancer,HIV,Alzheimer's disease,etc.Major studies on DHIQ synthesis show low catalytic selectivity due to the susceptible over-oxidation feedstock of1,2,3,4-tetrahydroisoquinoline(THIQ),which often requires alkali co-catalysts.Therefore,it is desirable yet challenging to explore a highly selective and efficient oxydehydrogenation capacity for DHIQ synthesis under eco-friendly reaction conditions.Herein,a novel framework 1 was synthesized,exhibiting 1D channels with the size of 4.6 A×9.6 A and high solvent/p H/thermal stability.A stable framework allows it to encapsulate Cu nanoparticles(NPs)to form Cu NPs@1-x(x=1,2,3,and 4)with varying loading amounts of Cu NPs at 2.0 wt%,3.0 wt%,4.0 wt%,and 6.0 wt%,respectively.Cu NPs@1-3 could selectively catalyze the reaction from THIQ to DHIQ with a high selectivity of 98%and a recorded turnover frequency(TOF)of 22.1 h-1under eco-friendly mild conditions.The corresponding catalytic activity can maintain at least five recyclings and can be further applied to gram-scale experiments.Additionally,the efficient preparation of DHIQ catalyzed by Cu NPs@1-3 could be realized even under air conditions.Importantly,the anticancer molecule precursor synthesis of 6,7-dimethoxy-3,4-dihydroisoquinoline was also selectively catalyzed by Cu NPs@1-3.Mechanism investigations revealed that high catalytic performance can be attributed to the stable framework and the synergistic catalytic effect of the loaded Cu NPs and Co metal centers.More importantly,this work represents the first example of MOF catalysts for selectively thermo-catalytic DHIQ synthesis and demonstrates a simple approach to obtain efficient catalysts for selective oxydehydrogenation in the production of unsaturated compounds.
基金financially supported by Ministry of Education(No.NCET-10-878,20096101120018,2009-37th of SRFROCS)Shaanxi Province(No.2009ZDKG-70,09JK793)+1 种基金Northwest University(No.PR200905)State Key Lab for SSPC(2009)
文摘FeO_x/HZSM-5 catalyst with 8 wt.%Fe-loading（8-FeZ） exhibited significantly higher reactivity in the benzylation of benzene with benzyl chloride than FeO_x/HZSM-5 catalyst with 2.5 wt.%Fe-loading（2.5-FeZ） because the synergistic catalysis between isolated Fe^（3＋） and superfine Fe_2O_3 occurred on 8-FeZ in the reaction.
基金Supported by the Natural Science Foundation of Beijing City(8172043)the National Science Fund for Distinguished Young Scholars(51425405)National Natural Science Foundation of China(51378487)
文摘In this work. phenol and oxalic acid （OA） degradation in an ozone and photocatalysis integrated process was intensively conducted with Fe3 ＋/TiO2 catalyst. The ferrioxalate complex formed between Fe3＋ and oxalate accelerated the removal of OA in the ozonation, photolysis and photocatalytic ozonation process, for its high reactivity with ozone and UV. Phenol was degraded in ozonation and photolysis with limited TOC removal rates, but much higher TOC removal was achieved in photocatalytic ozonation due to the generation of-OH. The sequence of UV light and ozone in the sequential process also influences the TOC removal, and ozone is very powerful to oxidize intermediates catechol and hydroquinone to maleic acid. Fenton or photo-Fenton reactions only played a small part in Fe3＋/TiO2 catalyzed processes, because Fe＋ was greatly reduced but not regenerated in many cases. The synergetic effect was found to be highly related with the property of the target pollutants. Fe3 ＋/TiO2 catalyzed system showed the highest ability to destroy organics, but the TiO2 catalyzed system showed little higher synergy.
基金the National Natural Science Foundation of China(Nos.21677055 and 21407052)National Key Research and Development Program of China(No.2019YFC1805204)+1 种基金Project of Three Gorges Corporation(No.JDZC-FW-20-001)the Fundamental Research Funds for the Central Universities,HUST(No.2017KFXKJC004)。
文摘This study demonstrated that as-synthesized nano Fe/Cu bimetals could achieve significant enhancement in the degradation of diclofenac(DCF),as compared to much slow removal of DCF by Cu(Ⅱ) or zero valent iron nanoparticles(nZVI),respectively.Further observations on the evolution of O_(2) activation process by nano Fe/Cu bimetals was conducted stretching to the preparation phase(started by nZVI/Cu2+).Interesting breakpoints we re observed with obvious sudden increase in the DCF degradation efficiency and decrease in solution pH,as the original nZVI just consumed up to Fe(Ⅱ) and Cu(II) appeared again.It suggested that the four-electrons reaction of O_(2) and Cu-deposited nZVI would occur to generate water prior to the breakpoints,while Cu(0) and Fe(Ⅱ) would play most important role in activation of O_(2) afterwards.Through the electron spin resonance(ESR) analysis and quenching experiments.·OH was identified as the responsible reactive species.Further time-dependent quantifications in the cases of Cu(0)/Fe(Ⅱ) systems we re carried out.It was found that the ’OH accumulation was positively and linearly correlated with nCu dose,Fe(Ⅱ) consumption,and Fe(II) dose,respectively.Since either Cu(O) or Fe(Ⅱ)would be inefficient in activating oxygen to produce ·OH,a stage-evolution mechanism of O_(2) activated by nano Fe/Cu bimetals was proposed involving:(a) Rapid consumption of Fe(0) and release of Fe(Ⅱ) based on the Cu-Fe galvanic corrosion,(b) adsorption and transformation of O_(2) to O_(2)2 at the nCu surface,and(c) Fe(Ⅱ)-catalyzed activation of the adsorbed O_(2)2 to ·OH.
基金Financial support from the National Natural Science Foundation of China(Grant No.21690063 to S.M.,and Grant No.21901158 to X.H.)is greatly appreciated.We thank Mr.Huanan Wang in this group for reproducing the results of(R)-3'd,(Rm-3and(R)-17k,presented in Tables 2,3,and 4,respectively.
文摘Main observation and conclusion A highly enantioselective 2,3-allenylation of acyclic and cyclicα-imino carboxylates via a synergistic bimetallic Pd/Cu catalysis with the same commercially available(R,Rp)-iPr-FOXAP(also as Phosferrox,(R,R)-[2-(4’-i-propyloxazolin-2’-yl)ferrocenyl]diphenyl phosphine)ligand for both metals affording optically active 2,3-butadienylα-amino acid derivatives in high to excellent yields with excellent enantioselectivities has been developed.
