Copper catalyzed asymmetric formal [3＋2] cycloaddition of propargylic esters toβ‐keto phospho‐nates for the synthesis of chiral phosphonylated 2,3‐dihydrofurans was developed. By using a bulky and structurally ri...Copper catalyzed asymmetric formal [3＋2] cycloaddition of propargylic esters toβ‐keto phospho‐nates for the synthesis of chiral phosphonylated 2,3‐dihydrofurans was developed. By using a bulky and structurally rigid tridentate ketimine P,N,N ligand, a series of optically active phosphonylated 2,3‐dihydrofurans were prepared in high yield and up to 92%ee.展开更多
Recyclable CuO nanoparticles were successfully employed to catalyze the microwave‐assisted(3+2)cycloaddition reaction between nitriles and NaN3to efficiently synthesize5‐substituted1H‐tetrazoles.The salient feature...Recyclable CuO nanoparticles were successfully employed to catalyze the microwave‐assisted(3+2)cycloaddition reaction between nitriles and NaN3to efficiently synthesize5‐substituted1H‐tetrazoles.The salient features associated with this protocol are its cost effectiveness,rapid synthesis,stability,reusability,mild reaction conditions without any additives,high tolerance to various functional groups,and excellent yields under microwave irradiation.This environmentally friendly,microwave‐assisted,nanoparticle‐catalyzed synthetic methodology is seen as an alternative to conventional procedures that involve Lewis acid catalysts and a simple operation to the privileged scaffold.展开更多
The development of catalytic asymmetric radical reactions is an attractive but formidable task.The high reactivity of radicals enables the use of readily accessible feedstocks and mild reaction conditions,but it leads...The development of catalytic asymmetric radical reactions is an attractive but formidable task.The high reactivity of radicals enables the use of readily accessible feedstocks and mild reaction conditions,but it leads to substantial difficulty for chiral catalysts to provide sufficient enantiocontrol.Moreover,a racemic background process is often inevitable,further deteriorating enantioselectivity.In this regard,an effective protocol has been established for enantioselective intermolecular[2+2]photocycloadditions to overcome the challenges,which is capitalising on the ground-state preassociations of chiral catalysts with photoactivated substrates.Here,we report the viability of substrate-differentiating synergistic catalysis for this important reaction.In this new platform,energy transfer occurs between DPZ as a photosensitizer and enones or(E)-2-substituted vinylazaarenes for producing triplet-state species,and chiral phosphoric acid interacts with ground-state 2-vinylazaarenes via hydrogen bonding for subsequent enantiofacial cycloaddition.Although all active species are dispersed in the reaction system,valuable enantioenriched mono-and di-azaarene-functionalized cyclobutanes are obtained efficiently and selectively.In addition to constructing all-carbon quaternary stereocentres,flexible modulation of azaaryl groups and other substituents on the cyclobutane ring is also operative.展开更多
The hydrogenation of CO_(2) into methanol has attracted much attention and In_(2)O_(3) is a promising catalyst.Introducing metal elements into In_(2)O_(3)(M/In_(2)O_(3))is one of the main strategies to improve its per...The hydrogenation of CO_(2) into methanol has attracted much attention and In_(2)O_(3) is a promising catalyst.Introducing metal elements into In_(2)O_(3)(M/In_(2)O_(3))is one of the main strategies to improve its performance.However,its mechanism and active sites remain unclear and need to be further elucidated.Here,the noble‐metal‐free In_(x)‐Co_(y) oxides catalysts were prepared.Much‐improved performance and obvious product selectivity shift were observed.The optimized catalyst(In_(1)‐Co_(4))(9.7 mmol g_(cat)^(–1) h^(–1))showed five times methanol yields than pure In_(2)O_(3)(2.2 mmol g_(cat)^(–1) h^(–1))(P=4.0 MPa,T=300°C,GHSV=24000 cm^(3)_(STP) g_(cat)^(–1) h^(–1),H_(2):CO_(2)=3).And the cobalt‐catalyzed CO_(2) methanation activity was suppressed,although cobalt was most of the metal element.To unravel this selectivity shift,detailed catalysts performance evaluation,together with several in‐situ and ex‐situ characterizations,were employed on cobalt and In‐Co for comparative study.The results indicated CO_(2) hydrogenation on cobalt and In‐Co catalyst both followed the formate pathway,and In‐Co reconstructed and generated a surface In_(2)O_(3)‐enriched core‐shell‐like structure under a reductive atmosphere.The enriched In_(2)O_(3) at the surface significantly enhanced CO_(2) adsorption capacity and well stabilized the intermediates of CO_(2) hydrogenation.CO_(2) and carbon‐containing intermediates adsorbed much stronger on In‐Co than cobalt led to a feasible surface C/H ratio,thus allowing the*CH_(3)O to desorb to produce CH_(3)OH instead of being over‐hydrogenated to CH_(4).展开更多
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
The widespread utilization of fossil fuels has caused an associated increase in CO_(2) emissions over the past few decades,which has resulted in global warming and ocean acidification.CO hydrogenation(Fischer‐Tropsch...The widespread utilization of fossil fuels has caused an associated increase in CO_(2) emissions over the past few decades,which has resulted in global warming and ocean acidification.CO hydrogenation(Fischer‐Tropsch synthesis,FTS)is considered a significant route for the production of liquid fuels and chemicals from nonpetroleum sources to meet worldwide demand.Conversion of CO_(2) with renewable H_(2) into valuable hydrocarbons is beneficial for reducing dependence on fossil fuels and mitigating the negative effects of high CO_(2) concentrations in the atmosphere.Iron‐based catalysts exhibit superior catalytic performance in both FTS and CO_(2) hydrogenation to value‐added hydrocarbons.The abundance and low cost of iron‐based catalysts also promote their wide application in CO_(x) hydrogenation.This paper provides a comprehensive overview of the significant developments in the application of iron‐based catalysts in these two fields.The active phases,promoter effect,and support of iron‐based catalysts are discussed in the present paper.Based on understanding of these three essential aspects,we also cover recent advances in the design and preparation of novel iron‐based catalysts for FTS and CO_(2) hydrogenation.Current challenges and future catalytic applications are also outlined.展开更多
基金supported by the National Natural Science Foundation of China (21403022,21572226)the Natural Science Foundation of Liaoning Province of China (2015020194)~~
文摘Copper catalyzed asymmetric formal [3＋2] cycloaddition of propargylic esters toβ‐keto phospho‐nates for the synthesis of chiral phosphonylated 2,3‐dihydrofurans was developed. By using a bulky and structurally rigid tridentate ketimine P,N,N ligand, a series of optically active phosphonylated 2,3‐dihydrofurans were prepared in high yield and up to 92%ee.
基金CSIR-Govt of India for funding through Grant No. 01(2913)/17/EMR-II
文摘Recyclable CuO nanoparticles were successfully employed to catalyze the microwave‐assisted(3+2)cycloaddition reaction between nitriles and NaN3to efficiently synthesize5‐substituted1H‐tetrazoles.The salient features associated with this protocol are its cost effectiveness,rapid synthesis,stability,reusability,mild reaction conditions without any additives,high tolerance to various functional groups,and excellent yields under microwave irradiation.This environmentally friendly,microwave‐assisted,nanoparticle‐catalyzed synthetic methodology is seen as an alternative to conventional procedures that involve Lewis acid catalysts and a simple operation to the privileged scaffold.
文摘The development of catalytic asymmetric radical reactions is an attractive but formidable task.The high reactivity of radicals enables the use of readily accessible feedstocks and mild reaction conditions,but it leads to substantial difficulty for chiral catalysts to provide sufficient enantiocontrol.Moreover,a racemic background process is often inevitable,further deteriorating enantioselectivity.In this regard,an effective protocol has been established for enantioselective intermolecular[2+2]photocycloadditions to overcome the challenges,which is capitalising on the ground-state preassociations of chiral catalysts with photoactivated substrates.Here,we report the viability of substrate-differentiating synergistic catalysis for this important reaction.In this new platform,energy transfer occurs between DPZ as a photosensitizer and enones or(E)-2-substituted vinylazaarenes for producing triplet-state species,and chiral phosphoric acid interacts with ground-state 2-vinylazaarenes via hydrogen bonding for subsequent enantiofacial cycloaddition.Although all active species are dispersed in the reaction system,valuable enantioenriched mono-and di-azaarene-functionalized cyclobutanes are obtained efficiently and selectively.In addition to constructing all-carbon quaternary stereocentres,flexible modulation of azaaryl groups and other substituents on the cyclobutane ring is also operative.
文摘The hydrogenation of CO_(2) into methanol has attracted much attention and In_(2)O_(3) is a promising catalyst.Introducing metal elements into In_(2)O_(3)(M/In_(2)O_(3))is one of the main strategies to improve its performance.However,its mechanism and active sites remain unclear and need to be further elucidated.Here,the noble‐metal‐free In_(x)‐Co_(y) oxides catalysts were prepared.Much‐improved performance and obvious product selectivity shift were observed.The optimized catalyst(In_(1)‐Co_(4))(9.7 mmol g_(cat)^(–1) h^(–1))showed five times methanol yields than pure In_(2)O_(3)(2.2 mmol g_(cat)^(–1) h^(–1))(P=4.0 MPa,T=300°C,GHSV=24000 cm^(3)_(STP) g_(cat)^(–1) h^(–1),H_(2):CO_(2)=3).And the cobalt‐catalyzed CO_(2) methanation activity was suppressed,although cobalt was most of the metal element.To unravel this selectivity shift,detailed catalysts performance evaluation,together with several in‐situ and ex‐situ characterizations,were employed on cobalt and In‐Co for comparative study.The results indicated CO_(2) hydrogenation on cobalt and In‐Co catalyst both followed the formate pathway,and In‐Co reconstructed and generated a surface In_(2)O_(3)‐enriched core‐shell‐like structure under a reductive atmosphere.The enriched In_(2)O_(3) at the surface significantly enhanced CO_(2) adsorption capacity and well stabilized the intermediates of CO_(2) hydrogenation.CO_(2) and carbon‐containing intermediates adsorbed much stronger on In‐Co than cobalt led to a feasible surface C/H ratio,thus allowing the*CH_(3)O to desorb to produce CH_(3)OH instead of being over‐hydrogenated to CH_(4).
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.
文摘The widespread utilization of fossil fuels has caused an associated increase in CO_(2) emissions over the past few decades,which has resulted in global warming and ocean acidification.CO hydrogenation(Fischer‐Tropsch synthesis,FTS)is considered a significant route for the production of liquid fuels and chemicals from nonpetroleum sources to meet worldwide demand.Conversion of CO_(2) with renewable H_(2) into valuable hydrocarbons is beneficial for reducing dependence on fossil fuels and mitigating the negative effects of high CO_(2) concentrations in the atmosphere.Iron‐based catalysts exhibit superior catalytic performance in both FTS and CO_(2) hydrogenation to value‐added hydrocarbons.The abundance and low cost of iron‐based catalysts also promote their wide application in CO_(x) hydrogenation.This paper provides a comprehensive overview of the significant developments in the application of iron‐based catalysts in these two fields.The active phases,promoter effect,and support of iron‐based catalysts are discussed in the present paper.Based on understanding of these three essential aspects,we also cover recent advances in the design and preparation of novel iron‐based catalysts for FTS and CO_(2) hydrogenation.Current challenges and future catalytic applications are also outlined.
