A nickel-catalyzed C(sp^(2))–H alkynylation of unprotected α-substituted benzylamines is achieved by utilizing a transient directing group. The combination of a TDG with a nickel catalyst significantly improves the ...A nickel-catalyzed C(sp^(2))–H alkynylation of unprotected α-substituted benzylamines is achieved by utilizing a transient directing group. The combination of a TDG with a nickel catalyst significantly improves the reaction step and atom economy. It has been investigated that the 2,4,6-trimethylpyridine ligand was critical to achieve the optimized reactivity. This protocol provides a straightforward route for synthesizing the alkynylated free benzylamines, featuring good substrate compatibility and monoselectivity.展开更多
The transition metal-catalyzed C–H activation have been considered as increasingly useful approach for installing new functional groups onto organic small molecules due to their high step-and atom-economy,the abundan...The transition metal-catalyzed C–H activation have been considered as increasingly useful approach for installing new functional groups onto organic small molecules due to their high step-and atom-economy,the abundance of hydrocarbon compounds,and the potential for late-stage functionalization of complex organic molecules.The ortho-and meta-C-H activation and functionalization of aromatic compounds have been widely explored in recent years,however the distal para-C-H activation and functionalization has remained a significant challenge because of the difficulty in forming energetically favorable metallacyclic transition states.The utilization of appropriate directing groups or templates as well as the meticulous design of catalysts and ligands has proven to be effective in transition-metal-catalyzed remote para-C-H bonds activation and functionalization of aromatic compounds.This review aims to summarize the strategies for controlling para-selective C–H functionalization using the directing group,template engineering,and catalyst/ligand design under transition metals catalysis in recent years.展开更多
Fluoroalkoxylated heterocycles,such as indoles,holds significant importance in pharmaceuticals and biology.Herein,we report a copper-mediated C4-H fluoroalkoxylation reaction of indoles via a transient directing group...Fluoroalkoxylated heterocycles,such as indoles,holds significant importance in pharmaceuticals and biology.Herein,we report a copper-mediated C4-H fluoroalkoxylation reaction of indoles via a transient directing group(TDG)strategy.This reaction exhibits excellent regioselectivity and broad functional group compatibility,offering a new approach for the synthesis of fluoroalkoxylated indoles.The reaction also represents an unprecedented example of 3d-transition metal-catalyzed C-H fluoroalkoxylation via a TDG strategy.展开更多
A nickel-catalyzed cascade C(sp^(2))–H alkynylation/hydroamination of unprotectedα-substituted benzylamines is achieved using a transient directing group(TDG).The combination of a TDG with a nickel catalyst signific...A nickel-catalyzed cascade C(sp^(2))–H alkynylation/hydroamination of unprotectedα-substituted benzylamines is achieved using a transient directing group(TDG).The combination of a TDG with a nickel catalyst significantly improves the overall step-and atom-economy.Studies have shown that the p-trifluoromethylbenzoic acid ligand is critical for achieving C(sp^(2))–H alkynylation and subsequent intramolecular hydroamination.This protocol provides a straightforward and efficient route for synthesizing substituted 1H-isoindoles,featuring good substrate compatibility.展开更多
Transition-metal catalyzed C--H functionalization of benzaldehydes is of great interest in organic synthesis. Herein, we developed a transient directing group assisted amidation of benzaldehydes catalyzed by rhodium c...Transition-metal catalyzed C--H functionalization of benzaldehydes is of great interest in organic synthesis. Herein, we developed a transient directing group assisted amidation of benzaldehydes catalyzed by rhodium catalyst. With the employment of 10 mol% of 4-trifluoromethyl aniline, the in situ generated imine groups as the directing group efficiently enable this transformation. By using this protocol, a wide range of benzaldehydes were efficiently converted into the corresponding N-（2-formylphenyl）benzamides utilizing dioxazolones as the nitrogen source.展开更多
A strategy for Pd-catalyzed ortho-C–H silylation of biaryl aldehydes enabled by a transient auxiliary is presented. This protocol provides a broad range of ortho-silylated biaryl aldehydes in good yields. The silyl m...A strategy for Pd-catalyzed ortho-C–H silylation of biaryl aldehydes enabled by a transient auxiliary is presented. This protocol provides a broad range of ortho-silylated biaryl aldehydes in good yields. The silyl moiety can be further functionalized under mild conditions, rendering the silylated products useful building blocks. Notably, this protocol also offers an opportunity to establish a platform for expeditious synthesis of structurally diverse axially chiral biaryl aldehydes via sequential atroposelective interannular C–H functionalization/intraanular C–H silylation.展开更多
Transition-metal-catalyzed C–H bond functionalization has attracted tremendous attention as an increasingly important protocol for the construction of C–C and C–X bonds.In particular,C–H bond functionalization ass...Transition-metal-catalyzed C–H bond functionalization has attracted tremendous attention as an increasingly important protocol for the construction of C–C and C–X bonds.In particular,C–H bond functionalization assisted by the phosphorus-containing directing groups has made significant progress in the past few years.A series of valuable phosphorous compounds,especially phosphine ligands have been provided conveniently.This review comprehensively describes recent advances in transition-metal-catalyzed C–H bond functionalization assisted by the phosphorus-containing directing groups,highlights its potential applications in organic synthesis,and gives some insights into future advances.展开更多
Reported herein is the first example of heterogeneous palladium catalyzed C(sp^(3))-H bonds arylation by a transient-ligand-directed strategy.Using supported palladium(metallic state) na nopariticles as catalyst,a wid...Reported herein is the first example of heterogeneous palladium catalyzed C(sp^(3))-H bonds arylation by a transient-ligand-directed strategy.Using supported palladium(metallic state) na nopariticles as catalyst,a wide range of aryl iodides undergo the coupling with various o-methylbenzaldehyde derivatives to assemble a library of highly selective and functionalized o-benzylbenzaldehydes.The stability of the catalyst was easily recovered four runs without significant loss of activity.The XPS analysis of the catalyst before and after reaction indicated that the reaction might be carried out by a catalytic cycle starting with Pd~0.展开更多
Remote ether groups could be used as directing groups to prepare fully substituted 5-ether-1,2,3-triazoles with exclusive 1,5-regioselectivities and excellent chemoselectivities. Ether group could coordinate with irid...Remote ether groups could be used as directing groups to prepare fully substituted 5-ether-1,2,3-triazoles with exclusive 1,5-regioselectivities and excellent chemoselectivities. Ether group could coordinate with iridium catalyst by lone-pair electron at a distance(up to four σ bonds) away from alkyne to control the regioselectivity by weak coordination effect. The cycloaddition reaction chemoselectively occurred at the propargyl ether moiety of diyne to give unique fully substituted 4-alkynyl-triazole.展开更多
A rhodium-catalyzed directing group promoted selective C-H olefination reaction of indolizines at the 8-position is re ported.Di-olefination at 2,8-positions also achieved with silver hexafluoroantimonate as an additi...A rhodium-catalyzed directing group promoted selective C-H olefination reaction of indolizines at the 8-position is re ported.Di-olefination at 2,8-positions also achieved with silver hexafluoroantimonate as an additive under similar reaction conditions.Weakly coordinating groups,such as ketone,alde hyde,amide and ester,were used as directing groups.The ester group can be removed under acid conditions and therefore is used as a traceless directing group.展开更多
A.M.W. Glass and S.H.McCleary have given the 2 transitive representation of the countable free l group F η(1<η≤ω 0 ).In this paper we shall give the highly ordered transitive representation of count...A.M.W. Glass and S.H.McCleary have given the 2 transitive representation of the countable free l group F η(1<η≤ω 0 ).In this paper we shall give the highly ordered transitive representation of countable free groups on the rational line Q, which generalizes their results. As applications,we obtain the highly ordered transitive representation for the direct product of countable free groups,and the inverse limit of countable free groups must be an action on the set Q.展开更多
Using the modified CK＇s direct method, we derive a symmetry group theorem of （2＋1）-dimensional dispersive long-wave equations. Based upon the theorem, Lie point symmetry groups and new exact solutions of （2＋1）-...Using the modified CK＇s direct method, we derive a symmetry group theorem of （2＋1）-dimensional dispersive long-wave equations. Based upon the theorem, Lie point symmetry groups and new exact solutions of （2＋1）- dimensional dispersive long-wave equations are obtained.展开更多
A palladium-catalyzed multi-acetoxylation of 1,3-disubstituted 1H-pyrazole-5-carboxylate derivatives containing multiple potential reactive sites is described. Therein, the sequence of this process has been appropriat...A palladium-catalyzed multi-acetoxylation of 1,3-disubstituted 1H-pyrazole-5-carboxylate derivatives containing multiple potential reactive sites is described. Therein, the sequence of this process has been appropriately investigated. The protocol mainly provides the di- and tri-acetoxylated products for 1,3- diarylpyrazoles. Besides, it is found that the acetoxylation of C（sp3）-H bond is prior to that of C（sp2）-H bond under structurally competitive conditions.展开更多
A convenient rhodium catalyzed oxidative arene homologation of aniline derivatives with symmetrical or unsymmetrical alkynes using Cu（OAc）2 as oxidant is described. Urea group is shown to be effective as a directing...A convenient rhodium catalyzed oxidative arene homologation of aniline derivatives with symmetrical or unsymmetrical alkynes using Cu（OAc）2 as oxidant is described. Urea group is shown to be effective as a directing group for initial ortho C–H activation. Two migratory insertion events of alkyne into Rh–C bond occur successively, both with complete regioselectivity. This method is particularly useful for synthesis of polyarenes with different substituents, which has not been reported with conventional protocol. A mechanism has been proposed to explain the observed data.展开更多
A rhodium-catalyzed[4+3]cycloaddition reaction between N-methoxybenzamides and gem–difluorocyclopropenes is described.The reaction offers a mild and efficient approach towards the synthesis of fluorinated 2 H-azepin-...A rhodium-catalyzed[4+3]cycloaddition reaction between N-methoxybenzamides and gem–difluorocyclopropenes is described.The reaction offers a mild and efficient approach towards the synthesis of fluorinated 2 H-azepin-2-ones with broad substrate scope.A consecutive HOAc-assisted C–N bond formation and fluorine elimination are involved as key steps for success as illustrated by detailed DFT studies.展开更多
The direct Pd-catalyzed β-C（sp3）--H activation and cyclization of aliphatic amides bearing a removable 2-pyridylmethyl directing group with gem-dibromoolefins is described for the first time to construct a variety ...The direct Pd-catalyzed β-C（sp3）--H activation and cyclization of aliphatic amides bearing a removable 2-pyridylmethyl directing group with gem-dibromoolefins is described for the first time to construct a variety of γ-lactams, The resulting products with Z- and E-configurations can be easily separated and purified after the reaction, demonstrating the effectiveness and applicability of the method herein developed.展开更多
Let ARDkCS（v） denote an almost resolvable directed k-cycle system of order v. It is clear that a necessary condition for the existence of an ARDkCS（v） is v=1（mod k）. For k：3,4,5 and 6, the existence of an ARDk...Let ARDkCS（v） denote an almost resolvable directed k-cycle system of order v. It is clear that a necessary condition for the existence of an ARDkCS（v） is v=1（mod k）. For k：3,4,5 and 6, the existence of an ARDkCS （v） had been completely solved. This paper shows that there exists an ARD7CS（v） if and only if v≡1 （rood 7） and v≥8.展开更多
In the past decade,transition-metal-catalyzed C–H functionalization by weak coordination has emerged as a practical and powerful tool to access many valuable chemicals.Two classes of weakly coordinating directing gro...In the past decade,transition-metal-catalyzed C–H functionalization by weak coordination has emerged as a practical and powerful tool to access many valuable chemicals.Two classes of weakly coordinating directing groups,commonly occurring functional groups,and easily removable auxiliaries,have been found to be efficient and practical for C–H activation reactions.This mini-review contains examples of recent research advances on transition-metal-catalyzed SP2 C–H functionalization via weak coordination,using Ru,Rh,and Pd.A number of weakly coordinating functional groups(e.g.,ketone,ester,carbamate,tertiary amide,ether,thioether,alcohol,and some others)are covered.As the field of transition-metal-catalyzed C–H functionalization continues to develop and more synthetically useful chemo-,regio-,and enantioselective reactions catalyzed by transition metal via weak coordination are discovered,this promising and attractive strategy will play a more important role in modern organic synthesis.展开更多
A new method for post-assembly modification of peptides via the Pd-catalyzed endogenous group-directed sp^(3) C—H arylation with aryl iodides is developed.The sulfide side chain of methionine(Met)residue can facilita...A new method for post-assembly modification of peptides via the Pd-catalyzed endogenous group-directed sp^(3) C—H arylation with aryl iodides is developed.The sulfide side chain of methionine(Met)residue can facilitate the arylation of bothβandγmethyl C—H bonds of N-terminal aliphatic amino acids of peptides via formation of 5 or 6-membered palladacycle intermediates.The reactions can proceed in moderate to good yield and with excellent diastereoselectivity.展开更多
Highly stereoselective synthesis of 2-azido-2-deoxyglucosides and 2-azido-2-deoxygalactosides is achieved via a gold-catalyzed S_(N)2 glycosylation.The glycosyl donors feature a designed 1-naphthoate leaving group con...Highly stereoselective synthesis of 2-azido-2-deoxyglucosides and 2-azido-2-deoxygalactosides is achieved via a gold-catalyzed S_(N)2 glycosylation.The glycosyl donors feature a designed 1-naphthoate leaving group containing an amide group.Upon gold activation of the leaving group,the amide group is optimally positioned to direct an S_(N)2 attack by an acceptor via H-bonding interaction.Both 2-azido-2-deoxyglucosyl/galactosyl donor anomers can undergo stereoinversion at the anomeric position,affording the opposite anomeric glycoside products with excellent levels of stereoselectivity or stereospecificity and in mostly excellent yields.This S_(N)2 glycosylation accommodates a broad range of acceptors.The utility of this chemistry is demonstrated in the synthesis of a trisaccharide featuring three 1,2-cis-2-azido-2-deoxyglycosidic linkages.展开更多
基金supported financially by the Excellent Going Abroad Expert's Training Program in Hebei Province (No. 201940)the Hebei Natural Science Foundation of China (No. H2020208030)the S & T Program of Hebei (No. 22567607H) for financial support。
文摘A nickel-catalyzed C(sp^(2))–H alkynylation of unprotected α-substituted benzylamines is achieved by utilizing a transient directing group. The combination of a TDG with a nickel catalyst significantly improves the reaction step and atom economy. It has been investigated that the 2,4,6-trimethylpyridine ligand was critical to achieve the optimized reactivity. This protocol provides a straightforward route for synthesizing the alkynylated free benzylamines, featuring good substrate compatibility and monoselectivity.
基金support from the National Natural Science Foundation of China(No.21901206)Postdoctoral Science Foundation of China(No.2022M712589)+2 种基金General Key R&D Projects in Shaanxi Province(No.2023-YBGY-321)Natural Science Foundation of Chongqing(No.CSTB2022NSCQ-MSX0826)National&Local Joint Engineering Research Center for mineral Salt Deep Utilization,Huaiyin Institute of Technology(No.SF202407)for financial support。
文摘The transition metal-catalyzed C–H activation have been considered as increasingly useful approach for installing new functional groups onto organic small molecules due to their high step-and atom-economy,the abundance of hydrocarbon compounds,and the potential for late-stage functionalization of complex organic molecules.The ortho-and meta-C-H activation and functionalization of aromatic compounds have been widely explored in recent years,however the distal para-C-H activation and functionalization has remained a significant challenge because of the difficulty in forming energetically favorable metallacyclic transition states.The utilization of appropriate directing groups or templates as well as the meticulous design of catalysts and ligands has proven to be effective in transition-metal-catalyzed remote para-C-H bonds activation and functionalization of aromatic compounds.This review aims to summarize the strategies for controlling para-selective C–H functionalization using the directing group,template engineering,and catalyst/ligand design under transition metals catalysis in recent years.
基金supported by Natural Science Foundation of Shanghai(No.23ZR1468700)the National Natural Science Foundation of China(No.22371211).
文摘Fluoroalkoxylated heterocycles,such as indoles,holds significant importance in pharmaceuticals and biology.Herein,we report a copper-mediated C4-H fluoroalkoxylation reaction of indoles via a transient directing group(TDG)strategy.This reaction exhibits excellent regioselectivity and broad functional group compatibility,offering a new approach for the synthesis of fluoroalkoxylated indoles.The reaction also represents an unprecedented example of 3d-transition metal-catalyzed C-H fluoroalkoxylation via a TDG strategy.
基金supported by the Excellent Going Abroad Expert's Training Program in Hebei Province(No.201940)S.L.was supported by the S&T Program of Hebei(No.22567607H)+3 种基金D.J.C.was supported by a National Health and Medical Research Council(Australia)Leadership Fellowship(2009564)ARC Centre of Excellence for Innovations in Peptide and Protein Science(CE200100012)L.Y.C.was supported by the CIPPS Parental Leave Momentum Initiative Grant(CE200100012)Advance Queensland Women's AcademicFoundation(WAF-6884942288).
文摘A nickel-catalyzed cascade C(sp^(2))–H alkynylation/hydroamination of unprotectedα-substituted benzylamines is achieved using a transient directing group(TDG).The combination of a TDG with a nickel catalyst significantly improves the overall step-and atom-economy.Studies have shown that the p-trifluoromethylbenzoic acid ligand is critical for achieving C(sp^(2))–H alkynylation and subsequent intramolecular hydroamination.This protocol provides a straightforward and efficient route for synthesizing substituted 1H-isoindoles,featuring good substrate compatibility.
基金Acknowledgement We thank National Basic Research Program of China （973 Program） （No. 2015CB856600）, the National Natural Science Foundation of China （Nos. 21632001, 21772002）, National Young Topnotch Talent Support Program, and Peking University Health Science Center （No. BMU20160541） for financial support of this work. We thank Bencong Zhu in this group for reproducing the results of 3b and 4f.
文摘Transition-metal catalyzed C--H functionalization of benzaldehydes is of great interest in organic synthesis. Herein, we developed a transient directing group assisted amidation of benzaldehydes catalyzed by rhodium catalyst. With the employment of 10 mol% of 4-trifluoromethyl aniline, the in situ generated imine groups as the directing group efficiently enable this transformation. By using this protocol, a wide range of benzaldehydes were efficiently converted into the corresponding N-（2-formylphenyl）benzamides utilizing dioxazolones as the nitrogen source.
基金supported by the National Natural Science Foundation of China (21925109, 21772170)the Outstanding Young Talents of Zhejiang Province High-level Personnel of Special Support (ZJWR0108)+1 种基金the Fundamental Research Funds for the Central Universities (2018XZZX001-02)Zhejiang Provincial Natural Science Foundation (LR17B020001)。
文摘A strategy for Pd-catalyzed ortho-C–H silylation of biaryl aldehydes enabled by a transient auxiliary is presented. This protocol provides a broad range of ortho-silylated biaryl aldehydes in good yields. The silyl moiety can be further functionalized under mild conditions, rendering the silylated products useful building blocks. Notably, this protocol also offers an opportunity to establish a platform for expeditious synthesis of structurally diverse axially chiral biaryl aldehydes via sequential atroposelective interannular C–H functionalization/intraanular C–H silylation.
基金supported by the Leading Innovative and Entrepreneur Team Introduction Program of Zhejiang(No.2022R01007)the National Natural Science Foundation of China(Nos.21971062 and 22171082.)the Start-up Research Grant from Zhejiang Normal University.
文摘Transition-metal-catalyzed C–H bond functionalization has attracted tremendous attention as an increasingly important protocol for the construction of C–C and C–X bonds.In particular,C–H bond functionalization assisted by the phosphorus-containing directing groups has made significant progress in the past few years.A series of valuable phosphorous compounds,especially phosphine ligands have been provided conveniently.This review comprehensively describes recent advances in transition-metal-catalyzed C–H bond functionalization assisted by the phosphorus-containing directing groups,highlights its potential applications in organic synthesis,and gives some insights into future advances.
基金financially supported by the National Natural Science Foundation of China(No.21861030)the Program for Young Talents of Science and Technology in Universities of Inner Mongolia Autonomous Region(No.NJYT-17-A22)。
文摘Reported herein is the first example of heterogeneous palladium catalyzed C(sp^(3))-H bonds arylation by a transient-ligand-directed strategy.Using supported palladium(metallic state) na nopariticles as catalyst,a wide range of aryl iodides undergo the coupling with various o-methylbenzaldehyde derivatives to assemble a library of highly selective and functionalized o-benzylbenzaldehydes.The stability of the catalyst was easily recovered four runs without significant loss of activity.The XPS analysis of the catalyst before and after reaction indicated that the reaction might be carried out by a catalytic cycle starting with Pd~0.
基金supported by grants from the National Natural Science Foundation of China (No. 21978039)Special Funds of the Central Government Leading Local Government for the Technology Development (Nos. 2021JH6/10500146, 2021JH6/10500148)the Fundamental Research Funds for the Central Universities (Nos. DUT20YG120, DUT19LK60)。
文摘Remote ether groups could be used as directing groups to prepare fully substituted 5-ether-1,2,3-triazoles with exclusive 1,5-regioselectivities and excellent chemoselectivities. Ether group could coordinate with iridium catalyst by lone-pair electron at a distance(up to four σ bonds) away from alkyne to control the regioselectivity by weak coordination effect. The cycloaddition reaction chemoselectively occurred at the propargyl ether moiety of diyne to give unique fully substituted 4-alkynyl-triazole.
基金Jiangsu Province(No.BK20161307 and“333”Talents Project for H.Hu)Huaiyin Normal University(No.JSKC18014)for their financial support。
文摘A rhodium-catalyzed directing group promoted selective C-H olefination reaction of indolizines at the 8-position is re ported.Di-olefination at 2,8-positions also achieved with silver hexafluoroantimonate as an additive under similar reaction conditions.Weakly coordinating groups,such as ketone,alde hyde,amide and ester,were used as directing groups.The ester group can be removed under acid conditions and therefore is used as a traceless directing group.
文摘A.M.W. Glass and S.H.McCleary have given the 2 transitive representation of the countable free l group F η(1<η≤ω 0 ).In this paper we shall give the highly ordered transitive representation of countable free groups on the rational line Q, which generalizes their results. As applications,we obtain the highly ordered transitive representation for the direct product of countable free groups,and the inverse limit of countable free groups must be an action on the set Q.
基金supported by the Natural Science Foundation of Shandong Province of China under Grant Nos.Q2005A01
文摘Using the modified CK＇s direct method, we derive a symmetry group theorem of （2＋1）-dimensional dispersive long-wave equations. Based upon the theorem, Lie point symmetry groups and new exact solutions of （2＋1）- dimensional dispersive long-wave equations are obtained.
基金the National Natural Science Foundation of China(Nos.21176074 and 21476074)the Research Fund for the Doctoral Program of Higher Education of China(No.20130074110009)for financial support
文摘A palladium-catalyzed multi-acetoxylation of 1,3-disubstituted 1H-pyrazole-5-carboxylate derivatives containing multiple potential reactive sites is described. Therein, the sequence of this process has been appropriately investigated. The protocol mainly provides the di- and tri-acetoxylated products for 1,3- diarylpyrazoles. Besides, it is found that the acetoxylation of C（sp3）-H bond is prior to that of C（sp2）-H bond under structurally competitive conditions.
基金the National Natural Science Foundation of China (No. 21272077)the Natural Science Foundation of Jiangsu Province (No. BK20131143)Jiangsu Key Laboratory of Advanced Catalytic Materials & Technology and the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)
文摘A convenient rhodium catalyzed oxidative arene homologation of aniline derivatives with symmetrical or unsymmetrical alkynes using Cu（OAc）2 as oxidant is described. Urea group is shown to be effective as a directing group for initial ortho C–H activation. Two migratory insertion events of alkyne into Rh–C bond occur successively, both with complete regioselectivity. This method is particularly useful for synthesis of polyarenes with different substituents, which has not been reported with conventional protocol. A mechanism has been proposed to explain the observed data.
基金National Natural Science Foundation of China(Nos.21861007,21702034)Natural Science Foundation of Guangxi Province(No.2021GXNSFAA075024)+1 种基金“BAGUI Scholar”Program of Guangxi Province of ChinaHigh-Level Innovation Team and Distinguished Scholar Program in Guangxi Colleges and Universities。
文摘A rhodium-catalyzed[4+3]cycloaddition reaction between N-methoxybenzamides and gem–difluorocyclopropenes is described.The reaction offers a mild and efficient approach towards the synthesis of fluorinated 2 H-azepin-2-ones with broad substrate scope.A consecutive HOAc-assisted C–N bond formation and fluorine elimination are involved as key steps for success as illustrated by detailed DFT studies.
基金the financial supports from the National Natural Science Foundation of China(Nos. 21672154 and 21372164)
文摘The direct Pd-catalyzed β-C（sp3）--H activation and cyclization of aliphatic amides bearing a removable 2-pyridylmethyl directing group with gem-dibromoolefins is described for the first time to construct a variety of γ-lactams, The resulting products with Z- and E-configurations can be easily separated and purified after the reaction, demonstrating the effectiveness and applicability of the method herein developed.
基金Natural Science Research Leading Item ofJiangsu (No.04 DJ110144) Natural Out-standing Younger Science Foundation(No.60225007)and Postdoctoral ScienceFoundation of China(No.20020248024)
文摘Let ARDkCS（v） denote an almost resolvable directed k-cycle system of order v. It is clear that a necessary condition for the existence of an ARDkCS（v） is v=1（mod k）. For k：3,4,5 and 6, the existence of an ARDkCS （v） had been completely solved. This paper shows that there exists an ARD7CS（v） if and only if v≡1 （rood 7） and v≥8.
基金supported by the National Basic Research Program of China(2011CB965300)the National Natural Science Foundation of China(21142008,21302106)Tsinghua University 985 Phase II Funds,and the Tsinghua University Initiative Scientific Research Program
文摘In the past decade,transition-metal-catalyzed C–H functionalization by weak coordination has emerged as a practical and powerful tool to access many valuable chemicals.Two classes of weakly coordinating directing groups,commonly occurring functional groups,and easily removable auxiliaries,have been found to be efficient and practical for C–H activation reactions.This mini-review contains examples of recent research advances on transition-metal-catalyzed SP2 C–H functionalization via weak coordination,using Ru,Rh,and Pd.A number of weakly coordinating functional groups(e.g.,ketone,ester,carbamate,tertiary amide,ether,thioether,alcohol,and some others)are covered.As the field of transition-metal-catalyzed C–H functionalization continues to develop and more synthetically useful chemo-,regio-,and enantioselective reactions catalyzed by transition metal via weak coordination are discovered,this promising and attractive strategy will play a more important role in modern organic synthesis.
基金supported by the National Natural Science Foundation of China(21725204)Frontiers Science Center for New Organic Matter(63181206)Haihe Laboratory of Sustainable Chemical Transformations,and NCC2020FH02。
文摘A new method for post-assembly modification of peptides via the Pd-catalyzed endogenous group-directed sp^(3) C—H arylation with aryl iodides is developed.The sulfide side chain of methionine(Met)residue can facilitate the arylation of bothβandγmethyl C—H bonds of N-terminal aliphatic amino acids of peptides via formation of 5 or 6-membered palladacycle intermediates.The reactions can proceed in moderate to good yield and with excellent diastereoselectivity.
基金the National Institutes of Health(grant nos.U01GM125289 and R35GM139640)for financial supportthe National Science Foundation(grant no.MRI-1920299)for the acquisition of two Bruker NMR instruments.
文摘Highly stereoselective synthesis of 2-azido-2-deoxyglucosides and 2-azido-2-deoxygalactosides is achieved via a gold-catalyzed S_(N)2 glycosylation.The glycosyl donors feature a designed 1-naphthoate leaving group containing an amide group.Upon gold activation of the leaving group,the amide group is optimally positioned to direct an S_(N)2 attack by an acceptor via H-bonding interaction.Both 2-azido-2-deoxyglucosyl/galactosyl donor anomers can undergo stereoinversion at the anomeric position,affording the opposite anomeric glycoside products with excellent levels of stereoselectivity or stereospecificity and in mostly excellent yields.This S_(N)2 glycosylation accommodates a broad range of acceptors.The utility of this chemistry is demonstrated in the synthesis of a trisaccharide featuring three 1,2-cis-2-azido-2-deoxyglycosidic linkages.
