The first efficiently N-heterocyclic carbene-catalyzed[4+2]cycloaddition of salicylaldehydes and pyrazole-4,5-diones to directly synthesis of spiro-ketal-pyrazolones bearing both oxygens of the ketal unit in the same ...The first efficiently N-heterocyclic carbene-catalyzed[4+2]cycloaddition of salicylaldehydes and pyrazole-4,5-diones to directly synthesis of spiro-ketal-pyrazolones bearing both oxygens of the ketal unit in the same ring was disclosed.This reaction was qualified with broad substrate scope,achieving moderate to excellent yield(up to 98%).This method has mild reaction conditions and simple operation,providing a new attractive strategy for the practical syntheses of multifunctionalized spiroketals including pyrazolone structures with mild reaction condition and operational simplicity.Furthermore,the gram scale and derivative transformations have also been achieved.展开更多
A blue light-induced formal insertion reaction ofα-siloxy carbene into the C—H bond of 1,3-diketones has been reported.Under the irradiation of blue light,acylsilane converts toα-siloxy carbene,which then undergoes...A blue light-induced formal insertion reaction ofα-siloxy carbene into the C—H bond of 1,3-diketones has been reported.Under the irradiation of blue light,acylsilane converts toα-siloxy carbene,which then undergoes formal C—H bond insertion reaction with the enol form of 1,3-diketone.This method uses readily available and relative stable acylsilane as car-bene precursor,which features a simple and metal-free approach under mild conditions.Moreover,the synthetic potential of this protocol has been demonstrated by performing the reaction on a gram scale with comparable high yield.展开更多
The switchable cross-coupling of indoles and pyridotriazoles through carbene insertion at C_(2)-or C_(3)-positon has been developed in this paper.This highly site-selective C-H carbenoid functionalization is determine...The switchable cross-coupling of indoles and pyridotriazoles through carbene insertion at C_(2)-or C_(3)-positon has been developed in this paper.This highly site-selective C-H carbenoid functionalization is determined by both the Rh-catalyst species and auxiliary groups.[Cp∗RhCl_(2)]_(2) and coordinating pyrimidyl group direct the C-H carbenoid functionalization to occur at the C_(2)-position,while Rh2OAc4 and noncoordinating benzyl group lead the reaction to occur at the C_(3)-position of the indoles.This regioselective C−H functionalization strategy is of significant importance for the discovery of indole drugs.展开更多
The precise control over the hierarchical self-assembly of sophisticated structures with comparable complexities and functions relying on the modulation of basic building blocks is elusive and highly desirable.Here,we...The precise control over the hierarchical self-assembly of sophisticated structures with comparable complexities and functions relying on the modulation of basic building blocks is elusive and highly desirable.Here,we report a fluorinated N-heterocyclic carbene(NHC)–based pillarplex with a tunable quaternary structure,employed as an efficient building block for constructing hierarchical superstructures.Initially,multiple noncovalent interactions in the NHC-based pillarplex,particularly those between the fluorinated pillarplex and PF_(6)-anions,induce the formation of a supramolecular gel at high concentrations.Additionally,this hierarchical self-assembled structure can be regulated by adjusting anion types,facilitating the controlled transformation from a supramolecular gel into a supramolecular channel upon the introduction of four monocarboxylic acids as anions.The study provides insight into the construction and controlled regulation of superstructures based on NHC-based pillarplexes.展开更多
Biocatalysis,which involves using enzymes to address synthetic challenges of significance to humans,has rapidly developed into a pivotal technology for chemical innovation.Over the past decade,there has been a notable...Biocatalysis,which involves using enzymes to address synthetic challenges of significance to humans,has rapidly developed into a pivotal technology for chemical innovation.Over the past decade,there has been a notable increase in the use of metalloproteins as catalysts for abiotic,synthetically valuable carbene and nitrene transfer reactions.This trend highlights the adaptability of protein-based catalysts and our growing ability to harness this potential for novel enzyme chemistry.This review focuses on the most recent advancements in metalloenzyme-catalyzed carbene and nitrene transfer reactions,including cyclopropanation,carbene Y–H and C–H insertions,Doyle-Kirmse reactions,aldehyde olefinations,nitrene azide-to-aldehyde conversions,and nitrene C–H insertion.A variety of protein scaffolds have been engineered to offer varied levels of reactivity and selectivity towards pharmaceutically relevant compounds.The application of these new catalysts in preparative-scale synthesis underscores their emerging biotechnological significance.Furthermore,insights into key intermediate and determining factors in stereochemistry are offering valuable guidance for engineering metalloproteins,thereby expanding the scope and utility of these non-natural activities.展开更多
An unprecedented 2,3-arylacylation reaction of allenes with aryl iodides and aldehydes was developed by resorting to Pd/NHC synergetic catalysis.It is the first time that allene was introduced into transition metal an...An unprecedented 2,3-arylacylation reaction of allenes with aryl iodides and aldehydes was developed by resorting to Pd/NHC synergetic catalysis.It is the first time that allene was introduced into transition metal and NHC synergetic catalysis,which demonstrated a versatile three-component reaction pattern,thus enabling two C-C bonds forged regioselectively in the reaction.The important reaction intermediates were successfully captured and characterized by HRMS analysis,and the migrative insertion of allene to the Ph-Pd species was identified as the reaction rate-limiting step by kinetic experiments.展开更多
An N-heterocyclic carbene(NHC)catalyzed enantioselective cyclisation and trifluoromethylation of olefins with cinnamaldehydes via radical relay cross-coupling in the presence of Togni reagent is reported andδ-lactone...An N-heterocyclic carbene(NHC)catalyzed enantioselective cyclisation and trifluoromethylation of olefins with cinnamaldehydes via radical relay cross-coupling in the presence of Togni reagent is reported andδ-lactones tolerated with stereogenic centers atβ-andγ-positions are obtained in moderate to high yields and with high enantioselectivities.Further computational studies explain that the radical crosscoupling step is the key to determining the enantioselectivity.Energy analysis of key transition states and intermediates also provides a reasonable explanation for the difficulty of diastereoselective control.DFT calculations also reveal that the hydrogen-bonding interaction plays a vital role in the promotion of this chemistry.展开更多
Enones are widely explored in synthetic chemistry as fundamental building blocks for a wide range of reactions and exhibit intriguing biological activities that are pivotal for drug discovery.The development of synthe...Enones are widely explored in synthetic chemistry as fundamental building blocks for a wide range of reactions and exhibit intriguing biological activities that are pivotal for drug discovery.The development of synthetic strategies for highly efficient preparation of enones thereby receives intense attention,in particular through the transition metal-catalyzed coupling reactions.Here,we describe a carbene-catalyzed cross dehydrogenative coupling(CDC)reaction that enables effective assembly of simple aldehydes and alkenes to afford a diverse set of enone derivatives.Mechanistically,the in situ generated aryl radical is pivotal to“activate”the alkene by forming an allyl radical through intermolecular hydrogen atom transfer(HAT)pathway and thus forging the carbon-carbon bond formation with aldehyde as the acyl synthon.Notably,our method represents the first example on the enone synthesis through coupling of“non-functionalized”aldehydes and alkenes as coupling partners,and offers a distinct organocatalytic pathway to the transition metal-catalyzed coupling transformations.展开更多
Kinetic resolution is one of the most commonly used methods allowing access to enantioenriched compounds.The last two decades have seen the rapid development of kinetic resolutions enabled by N-heterocyclic carbene ca...Kinetic resolution is one of the most commonly used methods allowing access to enantioenriched compounds.The last two decades have seen the rapid development of kinetic resolutions enabled by N-heterocyclic carbene catalysis,and part of the achievements have been summarized in our previous review paper published in 2017.Since then,a series of new advances have been realized,and this review will provide an update of this field covering reports from mid-2017 to 2023.展开更多
While nickel(II)complexes have been widely used as catalysts for carbon-carbon coupling reactions,the exploration of their photophysical and photochemical properties is still in the infancy.Here,a series of square-pla...While nickel(II)complexes have been widely used as catalysts for carbon-carbon coupling reactions,the exploration of their photophysical and photochemical properties is still in the infancy.Here,a series of square-planar Ni(II)complexes[(diNHC)NiX2]bearing chelating benzimidazole-based bis(N-heterocyclic carbene)ligands and varying anionic coligands(1,X=Cl;2,X=Br;3,X=I)are synthesized and structurally characterized.In solid state,both 1 and 2 exhibit orange-red photoluminescence under ambient conditions.The photophysical and electrochemical measurements along with density functional theory(DFT)calculations reveal that the low-energy emissions can be attributed to singlet excited states with ligand-to-ligand charge-transfer(LLCT)character.This work suggests that strong-field N-heterocyclic carbene ligands play a crucial role to achieve the luminescence of Ni(II)complexes.展开更多
The highly efficient method has been developed for the synthesis of NHC·VOCl_(3) containing symmetrical or unsymmetrical Nheterocyclic carbene(NHC) ligands by the transmetallation reaction of NHC·AgCl with V...The highly efficient method has been developed for the synthesis of NHC·VOCl_(3) containing symmetrical or unsymmetrical Nheterocyclic carbene(NHC) ligands by the transmetallation reaction of NHC·AgCl with VOCl_(3).The total isolated yield of VOCl_(3)[1,3-(2,4,6-Me_(3)C_(6)H_(2))_(2)(NCH=)_(2)C:](V4') reached 86% by transmetallation reaction,which is much higher than that(48%) by direct coordination method.This methodology has also been used to synthesize the novel vanadium complexes containing unsymmetrical NHC ligands of VOCl_(3)[PhCH_(2)NCH=CHNR)C:](V5',R=2,4,6-Me_(3)C_(6)H_(2);V6',R=2,4-Me_(2)-6-Ph-C_(6)H_(2);V7',R=2,6-^(i)Pr_(2)-C_(6)H_(3)) with high yield,which could not be obtained by direct coordination method.The catalytic activity and copolymerization ability would be improved by introducing unsymmetrical NHC ligands due to their less steric bulky effect.The vanadium complex V5' containing unsymmetrical NHC ligand exhibits higher catalytic activity(3.7×10^(5)g_(copolymer)·mol^(-1) of V·h^(-1)) than that of V4' containing symmetrical NHC ligand.Moreover,the higher propylene incorporation ratio(45.6 mol%) in the copolymers of ethylene with propylene could be obtained by using V5' than that(39.9%) by using V4'.The results would provide a highly efficient strategy for the synthesis of early transition metal complexes containing versitile NHC ligands,affording the catalyst with both high catalytic activity and copolymerization ability for the synthesis of high performance polyolefin elastomers.展开更多
Conventionally,organic radicals adhere to the Aufbau principle,the energy level of the singly occupied molecular orbital(SOMO)is not below the highest occupied molecular orbital(HOMO),but somewhat abnormal phenomena h...Conventionally,organic radicals adhere to the Aufbau principle,the energy level of the singly occupied molecular orbital(SOMO)is not below the highest occupied molecular orbital(HOMO),but somewhat abnormal phenomena have appeared recently.In this study,we introduce a novel strategy by incorporating unique NHC-Au-X units into a tris(2,4,6-trichlorophenyl)methyl(TTM)system to create metal-involved open-shell complexes,denoted as TTM-NHC-Au-X(X=I,Br,or Cl).Density-functional theory calculations were used to predict an inversion in the energy of the SOMO and highest doubly occupied molecular orbital(HOMO)of TTM-NHC-Au-I,which is supported by experimental results.Organometallic radicals TTM-NHC-Au-X demonstrated distinct properties with different coordinated halides.The radical behaviors have been investigated by EPR,UV-vis spectroscopy and cyclic voltammetry,additional structural information provided by structurally comparing related the precursor complexes given by X-ray crystallography.TTM-NHC-Au-I with SOMO-HOMO conversion(SHC)features a highly thermal decomposition temperature up to 305℃.Furthermore,the photostability of TTM-NHC-Au-I was found to be 75and 23 times greater than that of TTM-NHC-Au-Br and TTM-NHC-Au-Cl,respectively.These findings provide valuable insights into the structural and electronic design principles governing the occurrence of SOMO-HOMO conversion in open-shell systems.展开更多
The mechanism of the oxide extraction reaction between singlet germylene carbene and its derivatives X2Ge=C： （X=H, F, Cl, CH3） and ethylene oxide has been investigated with B3LYP/6-311G（d,p） method. The results s...The mechanism of the oxide extraction reaction between singlet germylene carbene and its derivatives X2Ge=C： （X=H, F, Cl, CH3） and ethylene oxide has been investigated with B3LYP/6-311G（d,p） method. The results show that this kind of reaction has similar mechanism, the shift of 2p lone electron pair of O in ethylene oxide to the 2p unoccupied orbital of C in X2Ge=C： gives a p→p donor-acceptor bond, thereby leading to the formation of intermediate. As the p→p donor-acceptor bond continues to strengthen, that is the C-O bond continues to shorten, the intermediate generates product （P＋C2H4） via transition state. It is the substituent electronegativity that mainly affect the extraction reactions. When the substituent electronegativity is greater, the energy barrier is lower, and the reaction rate is greater.展开更多
The mechanism of the cycloaddition reaction of forming germanic bis-heterocyclic compound between singlet dichloro-germylene carbene and formaldehyde has been investigated with CCSD（T）//MP2/6-31G^＊ method, from the...The mechanism of the cycloaddition reaction of forming germanic bis-heterocyclic compound between singlet dichloro-germylene carbene and formaldehyde has been investigated with CCSD（T）//MP2/6-31G^＊ method, from the potential energy profile, we predict that the reaction has two competitive dominant reaction pathways. The presented rule of this reaction： the 2p unoccupied orbital of the C atom in dichloro-germylene carbene insert the π orbital of formaldehyde from oxygen side, resulting in the formation of intermediate. In the intermediate and between two reactants, because of the two bonding π orbital in dichloro-germylene carbene and formaldehyde have occurred [2＋2] cycloaddition reaction, forming two four- membered ring compounds in which Ge and O are in the opposite orientation and in the syn-position, respectively. Because of the unsaturated property of C atom from carbene in the two four-membered ring compounds, they further reacts with formaldehyde, resulting in the generation of two germanic bis-heterocyclic compounds.展开更多
The mechanism of the cycloaddition reaction between singlet dimethyl-silylene carbene and acetone has been investigated with density functional theory, From the potential energy profile, it can be predicted that the r...The mechanism of the cycloaddition reaction between singlet dimethyl-silylene carbene and acetone has been investigated with density functional theory, From the potential energy profile, it can be predicted that the reaction has two competitive dominant reaction pathways. The presented rule of this reaction： the [2＋2] cycloaddition effect between the πorbital of dimethyl-silylene carbene and the π orbital of π-bonded compounds leads to the formation of a twisty four-membered ring intermediate and a planar four-membered ring product; The unsaturated property of C atom from carbene in the planar four-membered ring product,resulting in the generation of CH3-transfer product and silicic bis-heterocyclic compound.展开更多
The N-heterocyclic carbene(NHC)-catalyzed reactions involving two-electron reaction pathway have been well-established.However,the development of NHC-catalyzed radical reactions is still in its infancy in terms of rea...The N-heterocyclic carbene(NHC)-catalyzed reactions involving two-electron reaction pathway have been well-established.However,the development of NHC-catalyzed radical reactions is still in its infancy in terms of reaction types and enantioselectivity.In the past decade,several elegant NHC-catalyzed radical reactions have been developed,including NHC-catalyzed oxidation of aldehydes to esters,reductive coupling reactions using Breslow intermediate as SET reductant and NHC-catalyzed reactions via radical homoenolates,dienoaltes and trienolates.This review summarizes the recent advances in NHC-catalyzed reactions involving radical intermediates.展开更多
Electrocatalytic nitrogen reduction reaction(NRR)at ambient conditions holds great promise for sustainably synthesizing ammonia(NH3),while developing highly-efficient,long-term stable,and inexpensive catalysts to acti...Electrocatalytic nitrogen reduction reaction(NRR)at ambient conditions holds great promise for sustainably synthesizing ammonia(NH3),while developing highly-efficient,long-term stable,and inexpensive catalysts to activate the inert N≡N bond is a key scientific issue.In this work,on the basis of the concept"N-heterocyclic carbenes(NHCs)",we propose a carbon decorated graphitic-carbon nitride(C/g-C3N4)as novel metal-free NRR electrocatalyst by means of density functional theory(DFT)computations.Our results reveal that the introduced C atom in g-C3N4 surface can be regarded as NHCs and catalytic sites for activating N≡N bond,and are stabilized by the g-C3N4 substrate due to sterically disfavored dimerization.Especially,this NHCs-based heterogeneous catalysis can efficiently reduce the activated N2 molecule to NH3 with a low overpotential of 0.05 V via an enzymatic mechanism.Our work is the first report of NHCs-based electrocatalyst for N2 fixation,thus opening an alternative avenue for advancing sustainable NH3 production.展开更多
The title complex [Ag（carbene）2]2[Ag2Br4] has been synthesized by the reaction of Ag2O with 1-ethyl-3-benyl-imidazolium bromide in DMSO at room temperature, and characterized by elemental analysis, 1H NMR and single...The title complex [Ag（carbene）2]2[Ag2Br4] has been synthesized by the reaction of Ag2O with 1-ethyl-3-benyl-imidazolium bromide in DMSO at room temperature, and characterized by elemental analysis, 1H NMR and single-crystal X-ray diffraction analysis. It crystallizes in triclinic, space group P with a = 10.1597（10）, b =11.0646（11）, c = 13.0245（14） , α = 102.230（2）, β = 90.606, γ = 113.9250（10）o, V = 1300.3（2） 3, Mr = 748.06, Z = 2, Dc = 1.911 g/cm3, μ（MoKα） = 4.60 mm-1 and F（000） = 728. The structure was refined to R = 0.0316 and wR = 0.0835 for 3744 observed reflections with I 〉 2σ（I）. The title compound crystallizes as a centrosymmetric tetranuclear compound. One half of the molecule comprises the asymmetric unit of the structure. The Ag（1） atom is nearly linear or T-shaped when the Ag（1）-Ag（2） interaction is taken into consideration, which is bi-coordinated by two carbene carbon atoms. The Ag（2） atom adopts tetrahedral geometry. The catalytic behavior of the title complex has been investigated, and the results indicate it has a highly catalytic activation for L-lactide polymerization.展开更多
Neodymium complexes containing N heterocyclic carbene(NHC)ligands,NdCl5[1,3,R(NCH=)2C]-THF,(Nd1:R=2,6-Pr2C6H3,x=0;Nd2:R=2,6-Et2C6H3,x=1;Nd3:R=2.4,6-Me3C6H2,x=1)were synthesized and employed as precatalysts for the coo...Neodymium complexes containing N heterocyclic carbene(NHC)ligands,NdCl5[1,3,R(NCH=)2C]-THF,(Nd1:R=2,6-Pr2C6H3,x=0;Nd2:R=2,6-Et2C6H3,x=1;Nd3:R=2.4,6-Me3C6H2,x=1)were synthesized and employed as precatalysts for the coordination polymerization of conjugated dienes(butadiene and isoprene).In combination with trisobutylaluminium(TIBA),Nd1 promoted butadiene polymerization to produce extremely high cis-1,4(up to 99.0%)polybutadienes with high molecular weight(Mw=250-780 kg·mol 1).The Nd1/TIBA catalytic system also exhibited both high catalytic activity and cis-1,4 selectivity(up to 97.8%)for isoprene polymerization.The catalytic activity,molecular weight and molecular weight distribution of resulting polydienes were directly influenced by Al/Nd molar ratio,aging method,and polymerization temperature.Very interestingly,the high cis-1,4 selectivity of the catalyst towards butadiene and isoprene kept almost unchanged under different reaction conditions.The cis-1,4 polyisoprenes with high molecular weight(Mw=210-530 kg·mol 1)and narrow molecular weight distribution (Mw/Mn=1.9-2.7)as well as high cis-1.4 selectivity(-~97%)could be synthesized by using the aged Nd1/TIBA catalytic system in the presence of isoprene(100 equivalent to Nd)at low AlNd molar ratios of 6-10.Polyisoprenes with low molecular weights(Mw=12-76 kg·mol-7)and narrow molecular weight distributions (Mw/Mn=1.7-2.6)were obtained by using Nd2 and Nd3 as precatalysts,indicating that the molecular weight of resulting polyisoprenes can be adjusted by changing the substitutes of ligand in Nd complex.展开更多
Despite the extraordinary success has been achieved in metal catalyst-promoted stereoselective ring-opening polymerization（ROP） of rac-lactide（rac-LA）, well-controlled stereoselective rac-LA ROP by organic catalys...Despite the extraordinary success has been achieved in metal catalyst-promoted stereoselective ring-opening polymerization（ROP） of rac-lactide（rac-LA）, well-controlled stereoselective rac-LA ROP by organic catalyst still remains a scientific challenge. Here we report our investigations into organocatalytic stereoselective ROP of rac-LA by utilizing novel bulky chiral and achiral N-heterocyclic carbenes（NHC）, 1,3-bis-（1′-naphthylethyl）imidazolin-2-ylidene. The effect of polymerization conditions（e.g. solvent, temperature, alcohol initiator） on ROP behavior by these bulky NHCs has been fully studied, leading to the formation of isotactic-rich stereoblock polylactide（Pi = 0.81） under optimized conditions with high activity（Conv. = 98% in 30 min） and narrow molecular weight dispersity（D = 1.05）.展开更多
文摘The first efficiently N-heterocyclic carbene-catalyzed[4+2]cycloaddition of salicylaldehydes and pyrazole-4,5-diones to directly synthesis of spiro-ketal-pyrazolones bearing both oxygens of the ketal unit in the same ring was disclosed.This reaction was qualified with broad substrate scope,achieving moderate to excellent yield(up to 98%).This method has mild reaction conditions and simple operation,providing a new attractive strategy for the practical syntheses of multifunctionalized spiroketals including pyrazolone structures with mild reaction condition and operational simplicity.Furthermore,the gram scale and derivative transformations have also been achieved.
文摘A blue light-induced formal insertion reaction ofα-siloxy carbene into the C—H bond of 1,3-diketones has been reported.Under the irradiation of blue light,acylsilane converts toα-siloxy carbene,which then undergoes formal C—H bond insertion reaction with the enol form of 1,3-diketone.This method uses readily available and relative stable acylsilane as car-bene precursor,which features a simple and metal-free approach under mild conditions.Moreover,the synthetic potential of this protocol has been demonstrated by performing the reaction on a gram scale with comparable high yield.
基金CAMS Innovation Fund for Medical Sciences(CIFMS)(Nos.2022-I2M-1-013,2022-I2M-1-014,2022-I2M-2-002).
文摘The switchable cross-coupling of indoles and pyridotriazoles through carbene insertion at C_(2)-or C_(3)-positon has been developed in this paper.This highly site-selective C-H carbenoid functionalization is determined by both the Rh-catalyst species and auxiliary groups.[Cp∗RhCl_(2)]_(2) and coordinating pyrimidyl group direct the C-H carbenoid functionalization to occur at the C_(2)-position,while Rh2OAc4 and noncoordinating benzyl group lead the reaction to occur at the C_(3)-position of the indoles.This regioselective C−H functionalization strategy is of significant importance for the discovery of indole drugs.
基金financial support from the National Natural Science Fund for Distinguished Young Scholars of China(No.22025107)Shaanxi Fundamental Science Research Project for Chemistry&Biology(No.22JHZ003)+2 种基金the Key International Scientific and Technological Cooperation and Exchange Project of Shaanxi Province(No.2023-GHZD-15)the National Youth Top-notch Talent Support Program of Chinathe FM&EM International Joint Laboratory of Northwest University。
文摘The precise control over the hierarchical self-assembly of sophisticated structures with comparable complexities and functions relying on the modulation of basic building blocks is elusive and highly desirable.Here,we report a fluorinated N-heterocyclic carbene(NHC)–based pillarplex with a tunable quaternary structure,employed as an efficient building block for constructing hierarchical superstructures.Initially,multiple noncovalent interactions in the NHC-based pillarplex,particularly those between the fluorinated pillarplex and PF_(6)-anions,induce the formation of a supramolecular gel at high concentrations.Additionally,this hierarchical self-assembled structure can be regulated by adjusting anion types,facilitating the controlled transformation from a supramolecular gel into a supramolecular channel upon the introduction of four monocarboxylic acids as anions.The study provides insight into the construction and controlled regulation of superstructures based on NHC-based pillarplexes.
文摘Biocatalysis,which involves using enzymes to address synthetic challenges of significance to humans,has rapidly developed into a pivotal technology for chemical innovation.Over the past decade,there has been a notable increase in the use of metalloproteins as catalysts for abiotic,synthetically valuable carbene and nitrene transfer reactions.This trend highlights the adaptability of protein-based catalysts and our growing ability to harness this potential for novel enzyme chemistry.This review focuses on the most recent advancements in metalloenzyme-catalyzed carbene and nitrene transfer reactions,including cyclopropanation,carbene Y–H and C–H insertions,Doyle-Kirmse reactions,aldehyde olefinations,nitrene azide-to-aldehyde conversions,and nitrene C–H insertion.A variety of protein scaffolds have been engineered to offer varied levels of reactivity and selectivity towards pharmaceutically relevant compounds.The application of these new catalysts in preparative-scale synthesis underscores their emerging biotechnological significance.Furthermore,insights into key intermediate and determining factors in stereochemistry are offering valuable guidance for engineering metalloproteins,thereby expanding the scope and utility of these non-natural activities.
基金the National Natural Science Foundation of China(Nos.21831008,22025109,22101286)CAS Project for Young Scientists in Basic Research(No.YSBR-050)+1 种基金Beijing National Laboratory for Molecular Sciences(No.BNLMS-CXXM-201901)the State Key Laboratory of Fine Chemicals,Dalian University of Technology(No.KF2102)are gratefully acknowledged.
文摘An unprecedented 2,3-arylacylation reaction of allenes with aryl iodides and aldehydes was developed by resorting to Pd/NHC synergetic catalysis.It is the first time that allene was introduced into transition metal and NHC synergetic catalysis,which demonstrated a versatile three-component reaction pattern,thus enabling two C-C bonds forged regioselectively in the reaction.The important reaction intermediates were successfully captured and characterized by HRMS analysis,and the migrative insertion of allene to the Ph-Pd species was identified as the reaction rate-limiting step by kinetic experiments.
基金financial supports for this work are provided by the National Natural Science Foundation of China(Nos.21871160,21672121,22071130)。
文摘An N-heterocyclic carbene(NHC)catalyzed enantioselective cyclisation and trifluoromethylation of olefins with cinnamaldehydes via radical relay cross-coupling in the presence of Togni reagent is reported andδ-lactones tolerated with stereogenic centers atβ-andγ-positions are obtained in moderate to high yields and with high enantioselectivities.Further computational studies explain that the radical crosscoupling step is the key to determining the enantioselectivity.Energy analysis of key transition states and intermediates also provides a reasonable explanation for the difficulty of diastereoselective control.DFT calculations also reveal that the hydrogen-bonding interaction plays a vital role in the promotion of this chemistry.
基金funding supports from the National Natural Science Foundation of China(Nos.21732002,22061007,22071036,and 22207022)Frontiers Science Center for Asymmetric Synthesis and Medicinal Molecules,National Natural Science Fund for Excellent Young Scientists Fund Program(Overseas),the starting grant of Guizhou University[No.(2022)47)]+10 种基金Department of Education,Guizhou Province[Qianjiaohe KY No.(2020)004]The 10 Talent Plan(Shicengci)of Guizhou Province(No.[2016]5649)Science and Technology Department of Guizhou Province(Nos.[Qiankehe-jichu-ZK[2022]zhongdian024],[2018]2802,[2019]1020,QKHJC-ZK[2022]-455)Department of Education of Guizhou Province(No.QJJ(2022)205)Program of Introducing Talents of Discipline to Universities of China(111 Program,No.D20023)at Guizhou UniversitySingapore National Research Foundation under its NRF Investigatorship(No.NRF-NRFI2016–06)Competitive Research Program(No.NRF-CRP22–2019–0002)Ministry of Education,Singapore,under its MOE Ac RF Tier 1 Award(Nos.RG7/20,RG70/21)MOE AcRF Tier 2(No.MOE2019-T2–2–117)MOE AcRF Tier 3 Award(No.MOE2018-T3–1–003)a Chair Professorship Grant,and Nanyang Technological University。
文摘Enones are widely explored in synthetic chemistry as fundamental building blocks for a wide range of reactions and exhibit intriguing biological activities that are pivotal for drug discovery.The development of synthetic strategies for highly efficient preparation of enones thereby receives intense attention,in particular through the transition metal-catalyzed coupling reactions.Here,we describe a carbene-catalyzed cross dehydrogenative coupling(CDC)reaction that enables effective assembly of simple aldehydes and alkenes to afford a diverse set of enone derivatives.Mechanistically,the in situ generated aryl radical is pivotal to“activate”the alkene by forming an allyl radical through intermolecular hydrogen atom transfer(HAT)pathway and thus forging the carbon-carbon bond formation with aldehyde as the acyl synthon.Notably,our method represents the first example on the enone synthesis through coupling of“non-functionalized”aldehydes and alkenes as coupling partners,and offers a distinct organocatalytic pathway to the transition metal-catalyzed coupling transformations.
文摘Kinetic resolution is one of the most commonly used methods allowing access to enantioenriched compounds.The last two decades have seen the rapid development of kinetic resolutions enabled by N-heterocyclic carbene catalysis,and part of the achievements have been summarized in our previous review paper published in 2017.Since then,a series of new advances have been realized,and this review will provide an update of this field covering reports from mid-2017 to 2023.
基金the Natural Science Foundation of China(No.22175191)Y.C.thanks the financial support from CAS-Croucher Funding Scheme for Joint Laboratories and Beijing Municipal Science&Technology Commission(No.Z211100007921020).
文摘While nickel(II)complexes have been widely used as catalysts for carbon-carbon coupling reactions,the exploration of their photophysical and photochemical properties is still in the infancy.Here,a series of square-planar Ni(II)complexes[(diNHC)NiX2]bearing chelating benzimidazole-based bis(N-heterocyclic carbene)ligands and varying anionic coligands(1,X=Cl;2,X=Br;3,X=I)are synthesized and structurally characterized.In solid state,both 1 and 2 exhibit orange-red photoluminescence under ambient conditions.The photophysical and electrochemical measurements along with density functional theory(DFT)calculations reveal that the low-energy emissions can be attributed to singlet excited states with ligand-to-ligand charge-transfer(LLCT)character.This work suggests that strong-field N-heterocyclic carbene ligands play a crucial role to achieve the luminescence of Ni(II)complexes.
基金financially supported by the National Natural Science Foundation of China (Nos.21774006 and 21634002)。
文摘The highly efficient method has been developed for the synthesis of NHC·VOCl_(3) containing symmetrical or unsymmetrical Nheterocyclic carbene(NHC) ligands by the transmetallation reaction of NHC·AgCl with VOCl_(3).The total isolated yield of VOCl_(3)[1,3-(2,4,6-Me_(3)C_(6)H_(2))_(2)(NCH=)_(2)C:](V4') reached 86% by transmetallation reaction,which is much higher than that(48%) by direct coordination method.This methodology has also been used to synthesize the novel vanadium complexes containing unsymmetrical NHC ligands of VOCl_(3)[PhCH_(2)NCH=CHNR)C:](V5',R=2,4,6-Me_(3)C_(6)H_(2);V6',R=2,4-Me_(2)-6-Ph-C_(6)H_(2);V7',R=2,6-^(i)Pr_(2)-C_(6)H_(3)) with high yield,which could not be obtained by direct coordination method.The catalytic activity and copolymerization ability would be improved by introducing unsymmetrical NHC ligands due to their less steric bulky effect.The vanadium complex V5' containing unsymmetrical NHC ligand exhibits higher catalytic activity(3.7×10^(5)g_(copolymer)·mol^(-1) of V·h^(-1)) than that of V4' containing symmetrical NHC ligand.Moreover,the higher propylene incorporation ratio(45.6 mol%) in the copolymers of ethylene with propylene could be obtained by using V5' than that(39.9%) by using V4'.The results would provide a highly efficient strategy for the synthesis of early transition metal complexes containing versitile NHC ligands,affording the catalyst with both high catalytic activity and copolymerization ability for the synthesis of high performance polyolefin elastomers.
基金support from the National Natural Science Fund for Distinguished Young Scholars of China(No.22025107)Shaanxi Fundamental Science Research Project for Chemistry&Biology(No.22JHZ003)the National Youth Top-notch Talent Support Program of China,Xi’an Key Laboratory of Functional Supramolecular Structure and Materials,and the FM&EM International Joint Laboratory of Northwest University。
文摘Conventionally,organic radicals adhere to the Aufbau principle,the energy level of the singly occupied molecular orbital(SOMO)is not below the highest occupied molecular orbital(HOMO),but somewhat abnormal phenomena have appeared recently.In this study,we introduce a novel strategy by incorporating unique NHC-Au-X units into a tris(2,4,6-trichlorophenyl)methyl(TTM)system to create metal-involved open-shell complexes,denoted as TTM-NHC-Au-X(X=I,Br,or Cl).Density-functional theory calculations were used to predict an inversion in the energy of the SOMO and highest doubly occupied molecular orbital(HOMO)of TTM-NHC-Au-I,which is supported by experimental results.Organometallic radicals TTM-NHC-Au-X demonstrated distinct properties with different coordinated halides.The radical behaviors have been investigated by EPR,UV-vis spectroscopy and cyclic voltammetry,additional structural information provided by structurally comparing related the precursor complexes given by X-ray crystallography.TTM-NHC-Au-I with SOMO-HOMO conversion(SHC)features a highly thermal decomposition temperature up to 305℃.Furthermore,the photostability of TTM-NHC-Au-I was found to be 75and 23 times greater than that of TTM-NHC-Au-Br and TTM-NHC-Au-Cl,respectively.These findings provide valuable insights into the structural and electronic design principles governing the occurrence of SOMO-HOMO conversion in open-shell systems.
文摘The mechanism of the oxide extraction reaction between singlet germylene carbene and its derivatives X2Ge=C： （X=H, F, Cl, CH3） and ethylene oxide has been investigated with B3LYP/6-311G（d,p） method. The results show that this kind of reaction has similar mechanism, the shift of 2p lone electron pair of O in ethylene oxide to the 2p unoccupied orbital of C in X2Ge=C： gives a p→p donor-acceptor bond, thereby leading to the formation of intermediate. As the p→p donor-acceptor bond continues to strengthen, that is the C-O bond continues to shorten, the intermediate generates product （P＋C2H4） via transition state. It is the substituent electronegativity that mainly affect the extraction reactions. When the substituent electronegativity is greater, the energy barrier is lower, and the reaction rate is greater.
基金ACKNOWLEDGMENT This work was supported by the National Natural Science Foundation of China （No.20273066）.
文摘The mechanism of the cycloaddition reaction of forming germanic bis-heterocyclic compound between singlet dichloro-germylene carbene and formaldehyde has been investigated with CCSD（T）//MP2/6-31G^＊ method, from the potential energy profile, we predict that the reaction has two competitive dominant reaction pathways. The presented rule of this reaction： the 2p unoccupied orbital of the C atom in dichloro-germylene carbene insert the π orbital of formaldehyde from oxygen side, resulting in the formation of intermediate. In the intermediate and between two reactants, because of the two bonding π orbital in dichloro-germylene carbene and formaldehyde have occurred [2＋2] cycloaddition reaction, forming two four- membered ring compounds in which Ge and O are in the opposite orientation and in the syn-position, respectively. Because of the unsaturated property of C atom from carbene in the two four-membered ring compounds, they further reacts with formaldehyde, resulting in the generation of two germanic bis-heterocyclic compounds.
文摘The mechanism of the cycloaddition reaction between singlet dimethyl-silylene carbene and acetone has been investigated with density functional theory, From the potential energy profile, it can be predicted that the reaction has two competitive dominant reaction pathways. The presented rule of this reaction： the [2＋2] cycloaddition effect between the πorbital of dimethyl-silylene carbene and the π orbital of π-bonded compounds leads to the formation of a twisty four-membered ring intermediate and a planar four-membered ring product; The unsaturated property of C atom from carbene in the planar four-membered ring product,resulting in the generation of CH3-transfer product and silicic bis-heterocyclic compound.
基金the financial support from the National Natural Science Foundation of China (Nos.21672216,21831008)the Beijing National Laboratory for Molecular Sciences (No. BNLMS-CXXM-202003)。
文摘The N-heterocyclic carbene(NHC)-catalyzed reactions involving two-electron reaction pathway have been well-established.However,the development of NHC-catalyzed radical reactions is still in its infancy in terms of reaction types and enantioselectivity.In the past decade,several elegant NHC-catalyzed radical reactions have been developed,including NHC-catalyzed oxidation of aldehydes to esters,reductive coupling reactions using Breslow intermediate as SET reductant and NHC-catalyzed reactions via radical homoenolates,dienoaltes and trienolates.This review summarizes the recent advances in NHC-catalyzed reactions involving radical intermediates.
基金financially supported in China by the National Natural Science Foundation of China(21103224 and 21878227)Natural Science Funds for Distinguished Young Scholar of Heilongjiang Province(No.JC2018004)+2 种基金Natural Science Foundation of Hebei Province of China(B2019202210)in USA by NSF-CREST Center for Innovation,Research and Education in Environmental Nanotechnology(CIRE2N)(Grant Number HRD-1736093)supported by the Supercomputing Center in Harbin Normal University and Lvliang。
文摘Electrocatalytic nitrogen reduction reaction(NRR)at ambient conditions holds great promise for sustainably synthesizing ammonia(NH3),while developing highly-efficient,long-term stable,and inexpensive catalysts to activate the inert N≡N bond is a key scientific issue.In this work,on the basis of the concept"N-heterocyclic carbenes(NHCs)",we propose a carbon decorated graphitic-carbon nitride(C/g-C3N4)as novel metal-free NRR electrocatalyst by means of density functional theory(DFT)computations.Our results reveal that the introduced C atom in g-C3N4 surface can be regarded as NHCs and catalytic sites for activating N≡N bond,and are stabilized by the g-C3N4 substrate due to sterically disfavored dimerization.Especially,this NHCs-based heterogeneous catalysis can efficiently reduce the activated N2 molecule to NH3 with a low overpotential of 0.05 V via an enzymatic mechanism.Our work is the first report of NHCs-based electrocatalyst for N2 fixation,thus opening an alternative avenue for advancing sustainable NH3 production.
基金Sichuan Application Basic Foundation (2009JY0075)
文摘The title complex [Ag（carbene）2]2[Ag2Br4] has been synthesized by the reaction of Ag2O with 1-ethyl-3-benyl-imidazolium bromide in DMSO at room temperature, and characterized by elemental analysis, 1H NMR and single-crystal X-ray diffraction analysis. It crystallizes in triclinic, space group P with a = 10.1597（10）, b =11.0646（11）, c = 13.0245（14） , α = 102.230（2）, β = 90.606, γ = 113.9250（10）o, V = 1300.3（2） 3, Mr = 748.06, Z = 2, Dc = 1.911 g/cm3, μ（MoKα） = 4.60 mm-1 and F（000） = 728. The structure was refined to R = 0.0316 and wR = 0.0835 for 3744 observed reflections with I 〉 2σ（I）. The title compound crystallizes as a centrosymmetric tetranuclear compound. One half of the molecule comprises the asymmetric unit of the structure. The Ag（1） atom is nearly linear or T-shaped when the Ag（1）-Ag（2） interaction is taken into consideration, which is bi-coordinated by two carbene carbon atoms. The Ag（2） atom adopts tetrahedral geometry. The catalytic behavior of the title complex has been investigated, and the results indicate it has a highly catalytic activation for L-lactide polymerization.
基金supported by the National Natural Science Foundation of China(No.21634002)the Fundamental Research Funds for the Central Universities(Nos.XK1802-2 and XK1802-1).
文摘Neodymium complexes containing N heterocyclic carbene(NHC)ligands,NdCl5[1,3,R(NCH=)2C]-THF,(Nd1:R=2,6-Pr2C6H3,x=0;Nd2:R=2,6-Et2C6H3,x=1;Nd3:R=2.4,6-Me3C6H2,x=1)were synthesized and employed as precatalysts for the coordination polymerization of conjugated dienes(butadiene and isoprene).In combination with trisobutylaluminium(TIBA),Nd1 promoted butadiene polymerization to produce extremely high cis-1,4(up to 99.0%)polybutadienes with high molecular weight(Mw=250-780 kg·mol 1).The Nd1/TIBA catalytic system also exhibited both high catalytic activity and cis-1,4 selectivity(up to 97.8%)for isoprene polymerization.The catalytic activity,molecular weight and molecular weight distribution of resulting polydienes were directly influenced by Al/Nd molar ratio,aging method,and polymerization temperature.Very interestingly,the high cis-1,4 selectivity of the catalyst towards butadiene and isoprene kept almost unchanged under different reaction conditions.The cis-1,4 polyisoprenes with high molecular weight(Mw=210-530 kg·mol 1)and narrow molecular weight distribution (Mw/Mn=1.9-2.7)as well as high cis-1.4 selectivity(-~97%)could be synthesized by using the aged Nd1/TIBA catalytic system in the presence of isoprene(100 equivalent to Nd)at low AlNd molar ratios of 6-10.Polyisoprenes with low molecular weights(Mw=12-76 kg·mol-7)and narrow molecular weight distributions (Mw/Mn=1.7-2.6)were obtained by using Nd2 and Nd3 as precatalysts,indicating that the molecular weight of resulting polyisoprenes can be adjusted by changing the substitutes of ligand in Nd complex.
基金financially supported by the Science and Technology Commission of Shanghai Municipality(No.17JC1401200)
文摘Despite the extraordinary success has been achieved in metal catalyst-promoted stereoselective ring-opening polymerization（ROP） of rac-lactide（rac-LA）, well-controlled stereoselective rac-LA ROP by organic catalyst still remains a scientific challenge. Here we report our investigations into organocatalytic stereoselective ROP of rac-LA by utilizing novel bulky chiral and achiral N-heterocyclic carbenes（NHC）, 1,3-bis-（1′-naphthylethyl）imidazolin-2-ylidene. The effect of polymerization conditions（e.g. solvent, temperature, alcohol initiator） on ROP behavior by these bulky NHCs has been fully studied, leading to the formation of isotactic-rich stereoblock polylactide（Pi = 0.81） under optimized conditions with high activity（Conv. = 98% in 30 min） and narrow molecular weight dispersity（D = 1.05）.
