Borylation of 1,3-enynes with bis(boronate)compounds often ends up with the formation of hydroborylated products,leaving the diborylation of 1,3-enynes for the formation of 1,4-diborylated allenes to be challenging.He...Borylation of 1,3-enynes with bis(boronate)compounds often ends up with the formation of hydroborylated products,leaving the diborylation of 1,3-enynes for the formation of 1,4-diborylated allenes to be challenging.Herein,a copper-catalyzed chemo-,regio-,and stereo-selective diborylation of 1,3-enynes for the efficient construction of 1,4-diborylated allenes under base-free conditions was reported.A wide range of 1,3-enynes bearing various functional groups can participant in the reaction and afforded the corresponding 1,4-diborylated allenes in good to excellent yields,which was enabled by the protocol of Bpin to BF3K conversion.the borylcopper species was supposed to selectively attack the C-C triple bond of the 1,3-enynes.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
By developing gem-difluoromethylene allenes as viable partners,regiocontrolled Rh(Ⅲ)-catalyzed redoxneutral C-C coupling/C-N cyclization has been realized to build the pyridin-2(1H)-one motifs with the embedment of a...By developing gem-difluoromethylene allenes as viable partners,regiocontrolled Rh(Ⅲ)-catalyzed redoxneutral C-C coupling/C-N cyclization has been realized to build the pyridin-2(1H)-one motifs with the embedment of a Z-configured monofluoroalkene functionality,in which either(hetero)aromatic or vinylic amides were found to be compatible.Integrated experimental and computational mechanistic studies revealed that a tandem regioselective allene 1,2-insertion/β-H elimination/hydrogen transfer/oxidative addition/cyclization/cis-β-F elimination involving an unconventional Rh(Ⅲ)-Rh(I)-Rh(Ⅲ)catalytic cycle accounts for the established transformation.Through further FMO analysis and IGMH maps,a non-covalent weak interaction network between the gem-difluoromethylene part and the OPiv moiety was rationally defined for the unconventional and specific regioselectivity control.展开更多
A three-component reaction of 1,3-enynes and cyclobutanone oxime esters in the presence of aryl boronic acids or organozinc reagents via the photoredox/copper or photoredox/nickel catalysis has been established.This r...A three-component reaction of 1,3-enynes and cyclobutanone oxime esters in the presence of aryl boronic acids or organozinc reagents via the photoredox/copper or photoredox/nickel catalysis has been established.This redox-neutral 1,4-cyanoalkylarylation reaction has demonstrated mild condition,high catalytic reactivity and wide functional group compatibility,allowing access to a variety of functionalized tetra-substituted allene derivatives with high chemo-and regioselectivity.Moreover,using photocatalytic continuous flow technique to promote this process would result in increased yields(70%in flow vs.61%in batch),reduced reaction times(7 min in flow vs.6 h in batch),and easy scale-up(upgrade to gram scale),showcasing its potential as a synthetic platform.展开更多
Main observation and conclusion A facile synthetic method for the construction of 3-azabicyclo[3.1.0]hexane in the presence of copper catalyst system was developed.The reaction proceeds through Michael addition of all...Main observation and conclusion A facile synthetic method for the construction of 3-azabicyclo[3.1.0]hexane in the presence of copper catalyst system was developed.The reaction proceeds through Michael addition of allylamines with allenes followed by copper-mediated intramolecular oxidative carbanion 5-exo-trig radical cyclization,affording potential biologically active 3-azabicyclo[3.1.O]hexane derivatives in moderate to high yields(42%-85%).展开更多
A straightforward protocol for the synthesis of mono-fluorinated allenes via catalytic defluorinative silylation of the readily availableα,α-difluoroalkylalkynes with commercially available copper catalyst and phosp...A straightforward protocol for the synthesis of mono-fluorinated allenes via catalytic defluorinative silylation of the readily availableα,α-difluoroalkylalkynes with commercially available copper catalyst and phosphine ligand is described.A broad scope ofα,α-difluoroalkylalkynes were well accommodated and a gram-scale synthesis demonstrated the synthetic utility of this methodoglogy.展开更多
We herein report an effective hydrosilylation of 1,1-disubstituted allenes with a palladium catalyst modified by a monophosphorus ligand,leading to a series ofα-tertiary allylsilanes in high yields and exceptional re...We herein report an effective hydrosilylation of 1,1-disubstituted allenes with a palladium catalyst modified by a monophosphorus ligand,leading to a series ofα-tertiary allylsilanes in high yields and exceptional regiose-lectivities.The employment of BI-DIME is essential for the high reactivities and selectivities.A chiralα-tertiary allylsilane is formed in excellent ee for the first time by employing a chiral monophosphorus ligand.展开更多
A palladium-catalyzed regioselective three-component cascade reaction of carbon dioxide,amines and allenes has been developed,providing an expedient and practical method for the construction of a range of functionaliz...A palladium-catalyzed regioselective three-component cascade reaction of carbon dioxide,amines and allenes has been developed,providing an expedient and practical method for the construction of a range of functionalized carbamates containing dihydrobenzofuran or indole moiety in moderate to excellent yields.The broad substrate scope,good functional group tolerance and excellent chemo-and regioselectivity are the features of the transformation.展开更多
The indene moiety is an important unit because of its presence in many chemical catalysts, functional materials and biologically relevant molecules. Herein, we report a facile reaction of arylallenes with benzylic or ...The indene moiety is an important unit because of its presence in many chemical catalysts, functional materials and biologically relevant molecules. Herein, we report a facile reaction of arylallenes with benzylic or allylic alcohols through TfOH/Fe(OTf)3 cocatalyzed cleavage of sp3 carbon-oxygen. In the presence of 5 mol% TfOH and 5 mol% Fe(OTf)3, a range of arylallenes undergo carbocation initiated cyclization reaction with alkyl alcohols to give structurally diverse polysubstituted indenes in good to excellent yields. H2O is the sole byproduct that makes this transformation highly atom-economic and environmentally benign.展开更多
Using fewer catalysts to promote the chemical conversion of more substrates is the dream synthesis pursued by synthetic chemists.Achieving highly selective reactions using trace amounts(<1 ppm)of catalysts is rare ...Using fewer catalysts to promote the chemical conversion of more substrates is the dream synthesis pursued by synthetic chemists.Achieving highly selective reactions using trace amounts(<1 ppm)of catalysts is rare and has undoubted practical value.Herein,we designed and synthesized a single-atom Pd-metalated porous organic ligand polymer,denoted as Pd1@POL,and used the polymer to realize the regioselective hydrosilylation of allenes(Pd loading was as low as 0.98 ppm).The synergistic effect of the dispersed catalytic active sites in the catalyst and supports with ligand regulation function can directionally realize the formation of specifically configured hydrosilylation products.The as-fabricated single-atom catalyst(SAC;i.e.,Pd1@POL-5)showed an amazing catalytic efficiency and selectivity for hydrosilylation of allene(turnover number was up to 772,358,which was 200 times higher than previously recorded,and regioselectivity>100:1).The catalyst could be recycled numerous times in a continuous flow system without reductions in activity and selectivity.This work demonstrated the application prospect of the SAC in the synthesis of complex organic compounds and trace amount catalysis,which can lay the foundation for its large-scale and industrialized application in drug synthesis and other fields.展开更多
Functionalized bisboryl compounds have recently emerged as a new class of synthetically useful building blocks in organic synthesis.Herein,we report an efficient strategy to synthesizeβ-geminal-diboryl ketones enable...Functionalized bisboryl compounds have recently emerged as a new class of synthetically useful building blocks in organic synthesis.Herein,we report an efficient strategy to synthesizeβ-geminal-diboryl ketones enabled by a Cu/Pd-catalyzed borocarbonylative trifunctionalization of readily available alkynes and allenes.This reaction promises to be a useful method for the synthesis of functionalizedβ-geminal-diboryl ketones with broad functional group tolerance.Mechanistic studies suggest that the reaction proceeds through borocarbonylation/hydroboration cascade of both alkynes and allenes.展开更多
A novel protocol for palladium-catalyzed fluoroarylation of 1,1-difluoroallenes was described here.The reaction proceeded smoothly under mild condition and various trifluoromethylated alkenes were obtained in moderate...A novel protocol for palladium-catalyzed fluoroarylation of 1,1-difluoroallenes was described here.The reaction proceeded smoothly under mild condition and various trifluoromethylated alkenes were obtained in moderate yields with excellent E selectivity.The mechanism involving a vital trifluoromethylated vinyl silver intermediate,which generated through the F-nucleophilic addition to 1,1-difluoroallenes,has been proposed.展开更多
Chiral molecules, which may contain one or more different type(s) of stereocentres, such as central, axial, planar, and helical chiralities, etc., are indispensable in chemistry, pharmaceutical industry, and life sc...Chiral molecules, which may contain one or more different type(s) of stereocentres, such as central, axial, planar, and helical chiralities, etc., are indispensable in chemistry, pharmaceutical industry, and life science. Despite many advances for the preparation of chiral molecules usually with a single type of chirality have been realized, simultaneous construction of different types of chiralities is still a significant challenge. Here, we wish to report a protocol for preparation of chiral allenes with both central and axial chiralities via a catalytic asymmetric allenylation of different biologically or syn- thetically useful fluorinated or non-fluorinated nucleophiles with readily available racemic allenes by using a single chiral ligand. An echoing between the central chirality and axial chirality for the enantioselectivity was observed. This strategy provides a general and practical approach to functionalized optically active allenes bearing both central and axial chiralities with an excellent enantioselectivity under mild conditions.展开更多
A highly regio-, diastereo- and enantioselective addition of 2-acyl imidazoles or 2-acyl pyridines with allenes promoted by Rh/Lewis acid synergistically catalytic system is described. This atom economic approach lead...A highly regio-, diastereo- and enantioselective addition of 2-acyl imidazoles or 2-acyl pyridines with allenes promoted by Rh/Lewis acid synergistically catalytic system is described. This atom economic approach leads to the formation of the branched allylic alkylated products including acyclic quaternary all-carbon stereogenic centres in good yields with good to excellent diastereo- and enantioselectivities. Kinetic studies reveal that the rate-determining step in this process is the oxidative addition of Rh(I) with C H bond.展开更多
Transition-metal-catalyzed C–H activation reaction has proven to be a powerful and efficient tool for the formation of diverse C-C and C–X bond and construction of functional complex molecules.From the viewpoint of ...Transition-metal-catalyzed C–H activation reaction has proven to be a powerful and efficient tool for the formation of diverse C-C and C–X bond and construction of functional complex molecules.From the viewpoint of sustainable chemistry,the first-row transition metals,such as Mn,Fe,Co,Ni and Cu,have been recognized as cheap,environmentally friendly and reactively effective catalysts for a number of C-H functionalization reactions.However,compared with the commonly used alkenes and alkynes in the first-row transition-metal-catalyzed C–H activations,considerable achievements have just been made by the use of structurally unique and reactively rich allenes as coupling partners in recent years.This review summarizes the recent progress of the first-row transition-metal-catalyzed C–H activations with allenes.展开更多
A cascade carbonylative ring expansion and [2+2]/[4+2] cycloaddition of strained 1-iminylphosphirane complexes with aryl allenes were reported.The carbonylative ring expansion of 1-iminylphosphirane complexes provides...A cascade carbonylative ring expansion and [2+2]/[4+2] cycloaddition of strained 1-iminylphosphirane complexes with aryl allenes were reported.The carbonylative ring expansion of 1-iminylphosphirane complexes provides an azaphosphacyclohexone complex intermediate with a C=P double bond.The following [2+2] or dearomatic [4+2] cycloaddition of this intermediate with allenes is modulated by the aryl substituents on the imino carbon.The regioselective [2+2] cycloaddition with 1,1-diarylallene provides an entry to bicyclo[4.2.0]octan-4-one skeletons featuring a four-membered phosphacyclobutane moiety.While dearomatic [4+2] cycloaddition was preferred with less aromatic naphthalene and yielded octahydrochrysene skeleton containing heteroatoms.展开更多
The silver(1)-catalyzed synthesis picture of axially chiral allenes based on propargylamines has been outlined using density functional theory (DFT) method for the first time. Our calculations find that, the coord...The silver(1)-catalyzed synthesis picture of axially chiral allenes based on propargylamines has been outlined using density functional theory (DFT) method for the first time. Our calculations find that, the coordination of sil- ver(I) into triple bond of propargylamines at anti-position of nitrogen shows a stronger activation on the triple bond than that at cis-position, which is favorable for the subsequent hydrogen transfer. The NBO charge analysis for the hydrogen transfer affirms the experimental speculation that this step is a hydride transfer process. The energy bar- rier of the anti-periplanar elimination of vinyl-silver is 26.9 kJomol l lower than that of the syn-periplanar elimina- tion, supporting that (--)-allene is the main product of this reaction. In a word, the most possible route for this reac- tion is that the silver(I) coordinates into the triple bond of propargylamines at anti-position of nitrogen, then the formed silver(I) complex undergoes a hydride transfer to give a vinyl-silver, finally the vinyl-silver goes through an anti-periplanar elimination to give (--)-allene. The hydride transfer with the energy barrier of 44.8 kJ.mol-1 is the rate-limiting step in whole catalytic process. This work provides insight into why this reaction has a very high enan- tioselectivity.展开更多
Polyketides,a large class of secondary metabolites,have been of long-standing interest to the synthetic community due to their intriguing biological activities and structural versatility and complexity.A typical struc...Polyketides,a large class of secondary metabolites,have been of long-standing interest to the synthetic community due to their intriguing biological activities and structural versatility and complexity.A typical structural unit of various natural products,polypropionate,has prompted enormous efforts in the development of novel synthetic methods and strategies in the past five decades.In this study,a non-aldol-type approach based on double hydroboration of allenes has been developed to provide a powerful method for the stereodivergent construction of various polyol stereotriads and stereotetrads that are amenable for synthesizing polypropionates.The stereochemical control is possibly attributable to the boronate complex that aligned itself as a rigid conformation for the second stereoselective hydroboration reaction by suppressing the barotropic rearrangement of allylborane intermediates.The feasibility of preparing the key polypropionate motif facilitates the efficient synthesis of(-)-pironetin,a potentα-tubulin inhibitor halting the cell cycle at M phase.展开更多
基金supported by the National Natural Science Foundation of China(NSFC,Nos.22001251,21922112,and 22225107)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB20000000)+1 种基金National Key R&D Program of China(No.2017YFA0700103)the Guizhou Provincial S&T Project(No.2018[4007]).
文摘Borylation of 1,3-enynes with bis(boronate)compounds often ends up with the formation of hydroborylated products,leaving the diborylation of 1,3-enynes for the formation of 1,4-diborylated allenes to be challenging.Herein,a copper-catalyzed chemo-,regio-,and stereo-selective diborylation of 1,3-enynes for the efficient construction of 1,4-diborylated allenes under base-free conditions was reported.A wide range of 1,3-enynes bearing various functional groups can participant in the reaction and afforded the corresponding 1,4-diborylated allenes in good to excellent yields,which was enabled by the protocol of Bpin to BF3K conversion.the borylcopper species was supposed to selectively attack the C-C triple bond of the 1,3-enynes.
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the National Natural Science Foundation of China(NSFC,Nos.21877020,22007020)Natural Science Foundation of Guangdong Province(No.2019A1515010935)Science and Technology Program of Guangzhou(No.202102020615)for financial support on this study。
文摘By developing gem-difluoromethylene allenes as viable partners,regiocontrolled Rh(Ⅲ)-catalyzed redoxneutral C-C coupling/C-N cyclization has been realized to build the pyridin-2(1H)-one motifs with the embedment of a Z-configured monofluoroalkene functionality,in which either(hetero)aromatic or vinylic amides were found to be compatible.Integrated experimental and computational mechanistic studies revealed that a tandem regioselective allene 1,2-insertion/β-H elimination/hydrogen transfer/oxidative addition/cyclization/cis-β-F elimination involving an unconventional Rh(Ⅲ)-Rh(I)-Rh(Ⅲ)catalytic cycle accounts for the established transformation.Through further FMO analysis and IGMH maps,a non-covalent weak interaction network between the gem-difluoromethylene part and the OPiv moiety was rationally defined for the unconventional and specific regioselectivity control.
基金This work was supported by the National Natural Science Foundation of China(Nos.21702103,21522604)the Jiangsu Synergetic Innovation Center for Advanced Bio-Manufacture(No.XTD2203)the Natural Science Research Projects of Jiangsu Higher Education(No.19KJB150027).
文摘A three-component reaction of 1,3-enynes and cyclobutanone oxime esters in the presence of aryl boronic acids or organozinc reagents via the photoredox/copper or photoredox/nickel catalysis has been established.This redox-neutral 1,4-cyanoalkylarylation reaction has demonstrated mild condition,high catalytic reactivity and wide functional group compatibility,allowing access to a variety of functionalized tetra-substituted allene derivatives with high chemo-and regioselectivity.Moreover,using photocatalytic continuous flow technique to promote this process would result in increased yields(70%in flow vs.61%in batch),reduced reaction times(7 min in flow vs.6 h in batch),and easy scale-up(upgrade to gram scale),showcasing its potential as a synthetic platform.
基金the Shanghai Comittee of Science and Technology(No.17ZR1407600)。
文摘Main observation and conclusion A facile synthetic method for the construction of 3-azabicyclo[3.1.0]hexane in the presence of copper catalyst system was developed.The reaction proceeds through Michael addition of allylamines with allenes followed by copper-mediated intramolecular oxidative carbanion 5-exo-trig radical cyclization,affording potential biologically active 3-azabicyclo[3.1.O]hexane derivatives in moderate to high yields(42%-85%).
基金support of the National Natural Science Foundation of China(No.21871138)Distinguished Youth Foundation of Jiangsu province.
文摘A straightforward protocol for the synthesis of mono-fluorinated allenes via catalytic defluorinative silylation of the readily availableα,α-difluoroalkylalkynes with commercially available copper catalyst and phosphine ligand is described.A broad scope ofα,α-difluoroalkylalkynes were well accommodated and a gram-scale synthesis demonstrated the synthetic utility of this methodoglogy.
基金We are grateful for financial support from the Strategic Priority Research Program of the Chinese Academy of Sciences(Nos.XDB20000000)Chinese Academy of Sciences(No.QYZDY-SSWSLH029)+1 种基金National Natural Science Foundation of China(Nos.21725205,21432007,21572246 and 21702223)the K.C.Wong Education Foundation.
文摘We herein report an effective hydrosilylation of 1,1-disubstituted allenes with a palladium catalyst modified by a monophosphorus ligand,leading to a series ofα-tertiary allylsilanes in high yields and exceptional regiose-lectivities.The employment of BI-DIME is essential for the high reactivities and selectivities.A chiralα-tertiary allylsilane is formed in excellent ee for the first time by employing a chiral monophosphorus ligand.
基金supported by the Ministry of Science and Technology of China(2016YFA0602900)the National Natural Science Foundation of China(21971073,21572071)+2 种基金the Guangdong Natural Science Foundation(2019A1515011468,2017A030313054)China Postdoctoral Science Foundation(2018M640774)the Fundamental Research Funds for the Central Universities(D2191970).
文摘A palladium-catalyzed regioselective three-component cascade reaction of carbon dioxide,amines and allenes has been developed,providing an expedient and practical method for the construction of a range of functionalized carbamates containing dihydrobenzofuran or indole moiety in moderate to excellent yields.The broad substrate scope,good functional group tolerance and excellent chemo-and regioselectivity are the features of the transformation.
基金We are grateful for the financial support from the National Natural Science Foundation of China (No. 21202154), the Natural Science Foundation of The Jiangsu Higher Education Institutes of China (15KJB150007), the Nanjing Institute of Technology Scientific Research Foundation for Introducing Talents (No. ZKJ201614), and Nanjing Institute of Technology.
文摘The indene moiety is an important unit because of its presence in many chemical catalysts, functional materials and biologically relevant molecules. Herein, we report a facile reaction of arylallenes with benzylic or allylic alcohols through TfOH/Fe(OTf)3 cocatalyzed cleavage of sp3 carbon-oxygen. In the presence of 5 mol% TfOH and 5 mol% Fe(OTf)3, a range of arylallenes undergo carbocation initiated cyclization reaction with alkyl alcohols to give structurally diverse polysubstituted indenes in good to excellent yields. H2O is the sole byproduct that makes this transformation highly atom-economic and environmentally benign.
基金the Guangxi Natural Science Foundation of China(No.2021GXNSFFA220005)the central government guides local science and technology development fund projects(No.guike ZY21195014)+1 种基金the National Natural Science Foundation of China(Nos.22061003 and 22161008)the Opening Project of Hunan Engineering Laboratory for Analyse and Drugs Development of Ethnomedicine in Wuling Mountain(No.hgxy2101)for financial support.
文摘Using fewer catalysts to promote the chemical conversion of more substrates is the dream synthesis pursued by synthetic chemists.Achieving highly selective reactions using trace amounts(<1 ppm)of catalysts is rare and has undoubted practical value.Herein,we designed and synthesized a single-atom Pd-metalated porous organic ligand polymer,denoted as Pd1@POL,and used the polymer to realize the regioselective hydrosilylation of allenes(Pd loading was as low as 0.98 ppm).The synergistic effect of the dispersed catalytic active sites in the catalyst and supports with ligand regulation function can directionally realize the formation of specifically configured hydrosilylation products.The as-fabricated single-atom catalyst(SAC;i.e.,Pd1@POL-5)showed an amazing catalytic efficiency and selectivity for hydrosilylation of allene(turnover number was up to 772,358,which was 200 times higher than previously recorded,and regioselectivity>100:1).The catalyst could be recycled numerous times in a continuous flow system without reductions in activity and selectivity.This work demonstrated the application prospect of the SAC in the synthesis of complex organic compounds and trace amount catalysis,which can lay the foundation for its large-scale and industrialized application in drug synthesis and other fields.
基金This work was supported by the Chinese Scholarship Council(CSC).
文摘Functionalized bisboryl compounds have recently emerged as a new class of synthetically useful building blocks in organic synthesis.Herein,we report an efficient strategy to synthesizeβ-geminal-diboryl ketones enabled by a Cu/Pd-catalyzed borocarbonylative trifunctionalization of readily available alkynes and allenes.This reaction promises to be a useful method for the synthesis of functionalizedβ-geminal-diboryl ketones with broad functional group tolerance.Mechanistic studies suggest that the reaction proceeds through borocarbonylation/hydroboration cascade of both alkynes and allenes.
基金We thank the National Natural Science Foundation of China(Nos.21672097,21901111)the National Natural Science Foundation of Jiangsu Province(No.BK20170632)for their financial support.
文摘A novel protocol for palladium-catalyzed fluoroarylation of 1,1-difluoroallenes was described here.The reaction proceeded smoothly under mild condition and various trifluoromethylated alkenes were obtained in moderate yields with excellent E selectivity.The mechanism involving a vital trifluoromethylated vinyl silver intermediate,which generated through the F-nucleophilic addition to 1,1-difluoroallenes,has been proposed.
文摘Chiral molecules, which may contain one or more different type(s) of stereocentres, such as central, axial, planar, and helical chiralities, etc., are indispensable in chemistry, pharmaceutical industry, and life science. Despite many advances for the preparation of chiral molecules usually with a single type of chirality have been realized, simultaneous construction of different types of chiralities is still a significant challenge. Here, we wish to report a protocol for preparation of chiral allenes with both central and axial chiralities via a catalytic asymmetric allenylation of different biologically or syn- thetically useful fluorinated or non-fluorinated nucleophiles with readily available racemic allenes by using a single chiral ligand. An echoing between the central chirality and axial chirality for the enantioselectivity was observed. This strategy provides a general and practical approach to functionalized optically active allenes bearing both central and axial chiralities with an excellent enantioselectivity under mild conditions.
文摘A highly regio-, diastereo- and enantioselective addition of 2-acyl imidazoles or 2-acyl pyridines with allenes promoted by Rh/Lewis acid synergistically catalytic system is described. This atom economic approach leads to the formation of the branched allylic alkylated products including acyclic quaternary all-carbon stereogenic centres in good yields with good to excellent diastereo- and enantioselectivities. Kinetic studies reveal that the rate-determining step in this process is the oxidative addition of Rh(I) with C H bond.
基金support of this work by the National Natural Science Foundation of China (No. 21502242)the State Key Laboratory of Natural and Biomimetic Drugs (No. K20150215)
文摘Transition-metal-catalyzed C–H activation reaction has proven to be a powerful and efficient tool for the formation of diverse C-C and C–X bond and construction of functional complex molecules.From the viewpoint of sustainable chemistry,the first-row transition metals,such as Mn,Fe,Co,Ni and Cu,have been recognized as cheap,environmentally friendly and reactively effective catalysts for a number of C-H functionalization reactions.However,compared with the commonly used alkenes and alkynes in the first-row transition-metal-catalyzed C–H activations,considerable achievements have just been made by the use of structurally unique and reactively rich allenes as coupling partners in recent years.This review summarizes the recent progress of the first-row transition-metal-catalyzed C–H activations with allenes.
基金supported by the National Natural Science Foundation of China(Nos.21302174,21672193 and 21272218)China Post-doctoral Science Foundation(No.2017M622362)+1 种基金Ministry of Industry and Information Technology of the People's Republic of China(No.Z135060009002)Key Research Projects of Universities in Henan Province(No.20A150040)。
文摘A cascade carbonylative ring expansion and [2+2]/[4+2] cycloaddition of strained 1-iminylphosphirane complexes with aryl allenes were reported.The carbonylative ring expansion of 1-iminylphosphirane complexes provides an azaphosphacyclohexone complex intermediate with a C=P double bond.The following [2+2] or dearomatic [4+2] cycloaddition of this intermediate with allenes is modulated by the aryl substituents on the imino carbon.The regioselective [2+2] cycloaddition with 1,1-diarylallene provides an entry to bicyclo[4.2.0]octan-4-one skeletons featuring a four-membered phosphacyclobutane moiety.While dearomatic [4+2] cycloaddition was preferred with less aromatic naphthalene and yielded octahydrochrysene skeleton containing heteroatoms.
文摘The silver(1)-catalyzed synthesis picture of axially chiral allenes based on propargylamines has been outlined using density functional theory (DFT) method for the first time. Our calculations find that, the coordination of sil- ver(I) into triple bond of propargylamines at anti-position of nitrogen shows a stronger activation on the triple bond than that at cis-position, which is favorable for the subsequent hydrogen transfer. The NBO charge analysis for the hydrogen transfer affirms the experimental speculation that this step is a hydride transfer process. The energy bar- rier of the anti-periplanar elimination of vinyl-silver is 26.9 kJomol l lower than that of the syn-periplanar elimina- tion, supporting that (--)-allene is the main product of this reaction. In a word, the most possible route for this reac- tion is that the silver(I) coordinates into the triple bond of propargylamines at anti-position of nitrogen, then the formed silver(I) complex undergoes a hydride transfer to give a vinyl-silver, finally the vinyl-silver goes through an anti-periplanar elimination to give (--)-allene. The hydride transfer with the energy barrier of 44.8 kJ.mol-1 is the rate-limiting step in whole catalytic process. This work provides insight into why this reaction has a very high enan- tioselectivity.
基金support obtained from the Chinese Academy of Sciences(QYZDY-SSWSLH026 and XDB20020000)and the Drug Innovation Major Project(2018ZX09711001-005)is highly appreciated.The authors thank Zuming Lin for assisting with the experiments and Dr.Xiaoli Bao(SJTU)and Jie Sun(SIOC)for performing the X-ray analysis.
文摘Polyketides,a large class of secondary metabolites,have been of long-standing interest to the synthetic community due to their intriguing biological activities and structural versatility and complexity.A typical structural unit of various natural products,polypropionate,has prompted enormous efforts in the development of novel synthetic methods and strategies in the past five decades.In this study,a non-aldol-type approach based on double hydroboration of allenes has been developed to provide a powerful method for the stereodivergent construction of various polyol stereotriads and stereotetrads that are amenable for synthesizing polypropionates.The stereochemical control is possibly attributable to the boronate complex that aligned itself as a rigid conformation for the second stereoselective hydroboration reaction by suppressing the barotropic rearrangement of allylborane intermediates.The feasibility of preparing the key polypropionate motif facilitates the efficient synthesis of(-)-pironetin,a potentα-tubulin inhibitor halting the cell cycle at M phase.