Asymmetric intramolecular cyclopropanation of allylic diazoacetate was investigated using a chiral (β-diketone)-copper complex as catalyst, excellent yield and enantioselectivity were achieved. Some factors influenci...Asymmetric intramolecular cyclopropanation of allylic diazoacetate was investigated using a chiral (β-diketone)-copper complex as catalyst, excellent yield and enantioselectivity were achieved. Some factors influencing enantioselectivity were discussed.展开更多
The reactions of halocarbenes with pre-aromatic ketones 1, 2 resulted in cyclopropanation and deoxygenation products. The varying product ratio could be accounted for by a mechanism involving the carbonyl ylide interm...The reactions of halocarbenes with pre-aromatic ketones 1, 2 resulted in cyclopropanation and deoxygenation products. The varying product ratio could be accounted for by a mechanism involving the carbonyl ylide intermediate.展开更多
An efficient synthesis of β-alkoxycarbonyl vinylsulfonium salts had been developed. Their reaction with indene-1,3-diones and other active methylene compounds provided cyclopropane carboxylates in good yields. A tent...An efficient synthesis of β-alkoxycarbonyl vinylsulfonium salts had been developed. Their reaction with indene-1,3-diones and other active methylene compounds provided cyclopropane carboxylates in good yields. A tentative reaction mechanism was proposed.展开更多
A straightforward and efficient protocol for dearomatizing indoles is described.The reaction,catalyzed by an inexpensive Co(III)/Zn(II)catalyst,starts from easily accessible N‐pyrimidinyl indoles and ene‐yne ketones...A straightforward and efficient protocol for dearomatizing indoles is described.The reaction,catalyzed by an inexpensive Co(III)/Zn(II)catalyst,starts from easily accessible N‐pyrimidinyl indoles and ene‐yne ketones.Mild reaction conditions,high diastereoselectivity,a broad substrate scope,effective functional group tolerance,and reasonable to remarkable yields were observed.展开更多
Four chiral 1,1?bis(oxazolinyl)ferrocenes(1a-1d) have been prepared and used as ligands in the copper catalyzed asymmetric cyclopropanation of styrene with ethyl diazoacetate (EDA) and the magnesium catalyzed Diels-Al...Four chiral 1,1?bis(oxazolinyl)ferrocenes(1a-1d) have been prepared and used as ligands in the copper catalyzed asymmetric cyclopropanation of styrene with ethyl diazoacetate (EDA) and the magnesium catalyzed Diels-Alder reaction between 3-acryloyl-2-oxazolidinone and cyclopentadiene. Enantioselectivities up to 24% and 41%, respectively, for cyclopropanation and Diels-Alder reaction were observed.展开更多
In order to have efficient and highly stereoselective cyclopropanating reagents, the cyclopropabation reaction of ethylene promoted with Samarium（Ⅱ） carbenoid [Simmons-Smith（SS）reagent] were studied by means of B...In order to have efficient and highly stereoselective cyclopropanating reagents, the cyclopropabation reaction of ethylene promoted with Samarium（Ⅱ） carbenoid [Simmons-Smith（SS）reagent] were studied by means of B3LYP hybrid density functional method. The geometries for reactants, transition states and products are completely optimized. All transition states were verified by the vibrational analysis and the intrinsic reaction coordinate （IRC） calculations. The results showed that, identical with the lithium carbenoid, CH3SmCH2X（X=Cl, Br and Ⅰ） can fairly react with ethylene via both methylene transfer pathway （pathway A） and carbometalation pathway （pathway B）. And the cyclopropanation reaction via methylene transfer pathway proceeds with a lower barrier and at lower temperatures.展开更多
Four stereoisomers of a copper-(Schiff-base) complex with double chiral centers were applied to catalyze the asymmetric cyclopropanation. Two of the stereoisomers were also efficient catalysts affording high enantiom...Four stereoisomers of a copper-(Schiff-base) complex with double chiral centers were applied to catalyze the asymmetric cyclopropanation. Two of the stereoisomers were also efficient catalysts affording high enantiomeric excess of up to 91.8%. A mechanism that predicts the observed results accurately was proposed.展开更多
Several cyclopropanation catalysts for the synthesis of 3(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylates have been studied in this paper. Owing to electron deficiency of 1,1-dichloro-4-methyl-1,3-pentadiene, ...Several cyclopropanation catalysts for the synthesis of 3(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylates have been studied in this paper. Owing to electron deficiency of 1,1-dichloro-4-methyl-1,3-pentadiene, yield of this reaction is rather law compared with that of 2,5-dimethyl-2,4-pentadiene, Of all catalysts concerned. yield ranged from 25.1% to 47.2%.展开更多
Various addition-elimination approaches have been explored for diastereoselective construction of 1-amino- 1-cyclopropane-carboxylic acid (ACPC) derivatives, and the desired product was obtained from a reaction of cyc...Various addition-elimination approaches have been explored for diastereoselective construction of 1-amino- 1-cyclopropane-carboxylic acid (ACPC) derivatives, and the desired product was obtained from a reaction of cyclo(NAc-L-Val-NAc-Gly) and methyl α-bro-moacrylate under protonic solvent.展开更多
A new chiral β-diketone Cu (Ⅱ) catalyst was synthesized and used for the asymmetric cyclopropanation of styrene with diazoester. A high optical yield (~90%) was achieved. The effect of the structure of substrate on ...A new chiral β-diketone Cu (Ⅱ) catalyst was synthesized and used for the asymmetric cyclopropanation of styrene with diazoester. A high optical yield (~90%) was achieved. The effect of the structure of substrate on the enantioselectivity was studied. Both chendcal yield and optical yield being reduced when the steric bulky substrate was employed. The reaction mechanism and the chiral model of the transition state are under fufther investigation.展开更多
Nine copper compounds are used for catalyzing the cyclopropanation of 1-hexene/TME with alkyl diazoacetate.Cu(Salad)2 shows the highest yield for the reaction of TME at high temperature such as 100℃.The reaction of c...Nine copper compounds are used for catalyzing the cyclopropanation of 1-hexene/TME with alkyl diazoacetate.Cu(Salad)2 shows the highest yield for the reaction of TME at high temperature such as 100℃.The reaction of crude RDA with TME in 73.7% yield under the optimal condition is obtained.展开更多
Chiral[2.2]paracyclophane(PCP)is an intriguing prevalent scaffold widely utilized inπ-stacked polymers,luminescent materials,and asymmetric catalysis.However,current synthetic methods to access chiral PCP derivatives...Chiral[2.2]paracyclophane(PCP)is an intriguing prevalent scaffold widely utilized inπ-stacked polymers,luminescent materials,and asymmetric catalysis.However,current synthetic methods to access chiral PCP derivatives are still limited to physical separation and chemical or kinetic resolution.The direct desymmetric functionalization of nonsubstituted PCP has been a challenge since its discovery 70 years ago.Herein,we present a catalytic desymmetric dearomatization cyclopropanation reaction of PCP,providing rapid access to enantioenriched PCP cyclopropyl carboxylates with continuous tertiary/quaternary/quaternary chiral centers.The application of the chiral PCPs obtained has also been demonstrated by transformation to structurally novel C_(2) symmetric dirhodium catalysts.Of equal importance,detailed density functional theory calculations have been carried out to reveal the mechanism of this reaction.The key to this success is a structurally symmetric bulky C_(4) dirhodium catalyst:noncovalent interactions exist between substrates and catalysts,which form a cavity to host substrates,and mainly affect the regio-and enantioselectivity.展开更多
We report a novel cyano migration-mediated radical-polar crossover process,whereby both the sulfonylcyanation of aliphatic alkenes and the formation of cyclopropanes are concurrently achieved.This transformation yield...We report a novel cyano migration-mediated radical-polar crossover process,whereby both the sulfonylcyanation of aliphatic alkenes and the formation of cyclopropanes are concurrently achieved.This transformation yields a diverse array of multisubstituted cyclopropanes under mild photocatalytic conditions.Mechanistic studies elucidate that the reaction proceeds via intramolecular nucleophilic substitution,leading to the formation of the cyclopropane derivatives.展开更多
G-quadruplex DNA(G4)can function as a kind of nucleic acid apoenzyme for constructing G4/hemin biocatalyst to mimic the catalytic function of hemoprotein.However,achieving stereoselective control with G4/hemin remains...G-quadruplex DNA(G4)can function as a kind of nucleic acid apoenzyme for constructing G4/hemin biocatalyst to mimic the catalytic function of hemoprotein.However,achieving stereoselective control with G4/hemin remains a persistent challenge.Here,we report that a PW17/hemin(PW17:5’-GGGTAGGGCGGGTTGGG-3’),adopting the 5’-5’stacked dimeric parallel G4 topology,can realize the enantioselective induction in intramolecular cyclopropanation of allyl diazoacetates with enantioselectivity up to 87%ee.Spectroscopic characterization and catalytic results demonstrate that the relatively open G-quartet of the 3’terminal in dimeric PW17 contributes a catalytic pocket for hemin accommodation and plays a pivotal role in enantioselective control.This finding expands the unique repertoire of heme enzyme using biological scaffolds from proteins to nucleic acids and resolves the long-standing challenge of stereochemical control in G4/hemin catalysis.展开更多
Cyclopropanation of styrene with ethyl diazoacetate catalyzed by Pd(II) inionic liquid [omim][BF_4] was investigated. Palladium catalysts can be effectively immobilized inionic liquid. The catalysts PdCl_2 and cyclopa...Cyclopropanation of styrene with ethyl diazoacetate catalyzed by Pd(II) inionic liquid [omim][BF_4] was investigated. Palladium catalysts can be effectively immobilized inionic liquid. The catalysts PdCl_2 and cyclopalladated complex 2 contained in ionic liquid could berecycled for 6 and 7 times, respectively, without losing the efficiency.展开更多
A copper-catalyzed highly stereoselective cyclopropanation of 1,2-disubstituted olefins with α-nitrodiazo acetates has been developed, giving the desired products in up to 97 % yields, up to 〉99/1 dr and up to 98 % ...A copper-catalyzed highly stereoselective cyclopropanation of 1,2-disubstituted olefins with α-nitrodiazo acetates has been developed, giving the desired products in up to 97 % yields, up to 〉99/1 dr and up to 98 % ee, which provides an efficient access to the synthesis of optical active cyclopropane α-amino acids and unnatural α-amino acid derivatives.展开更多
A novel palladium-catalyzed oxidative cyclopropanation of enamides and norbornenes has been developed. The reaction proceeded through palladium-catalyzed vinyl C–H bond activation of enamides followed by two migrator...A novel palladium-catalyzed oxidative cyclopropanation of enamides and norbornenes has been developed. The reaction proceeded through palladium-catalyzed vinyl C–H bond activation of enamides followed by two migratory insertions, β-(N)H elimination and hydrolyzation cascade steps. The reaction tolerates a range of functional groups and provides an effective method for the synthesis of cyclopropane-fused norbornanes in good yields under mild conditions.展开更多
A highly efficient asymmetric cyclopropanation of trisubstituted olefins with methyl diazoacetate has been developed in terms of an elaborate modified chiral bisoxazoline/copper complex as a catalyst. A broad scope of...A highly efficient asymmetric cyclopropanation of trisubstituted olefins with methyl diazoacetate has been developed in terms of an elaborate modified chiral bisoxazoline/copper complex as a catalyst. A broad scope of substrates is compatible with this catalyst system, including various trisubstituted olefins bearing different aryl-, fused aryl-and alkyl-substituents, providing an easy access to optically active 1,1-dimethyl cyclopropanes in good yields with excellent diastereo-and enantio-selectivity.展开更多
The C—F bond transformation of gem-difluorinated cyclopropanes without cleavage of the highly strained C—C bond is an intractable challenge. The synthesis of cyclopropanone ketals via double defluorination of gem-di...The C—F bond transformation of gem-difluorinated cyclopropanes without cleavage of the highly strained C—C bond is an intractable challenge. The synthesis of cyclopropanone ketals via double defluorination of gem-difluorinated cyclo-propanesunder transition-metal free and basic conditions has been developed. A broad range of gem-difluorinated cyclopro-panesand alcohols are amenable in present reaction to permit the synthesis of corresponding products in high yields. The reaction is elucidated to proceed via elimination and addition other than direct substitution based on the mechanistic studies. This transformation not only provides a new strategy for the construction of cyclopropanone ketals, but also reveals a new paradigm on C—F bond transformation without ring-opening of gem-difluorinated cyclopropanes.展开更多
文摘Asymmetric intramolecular cyclopropanation of allylic diazoacetate was investigated using a chiral (β-diketone)-copper complex as catalyst, excellent yield and enantioselectivity were achieved. Some factors influencing enantioselectivity were discussed.
文摘The reactions of halocarbenes with pre-aromatic ketones 1, 2 resulted in cyclopropanation and deoxygenation products. The varying product ratio could be accounted for by a mechanism involving the carbonyl ylide intermediate.
基金the National Natural Science Foundation of China (Nos. 21772240, 21472248)National Science and Technology Major Project of the Ministry of Science and Technology of China (No. 2017ZX09305010)+2 种基金Guangzhou Science Technology and Innovation Commission(No. 201707010210)Department of Science and Technology of Guangdong Province(Nos. 2017A020211011,2017A020211027)China Scholarship Council (No. 201608440090)
文摘An efficient synthesis of β-alkoxycarbonyl vinylsulfonium salts had been developed. Their reaction with indene-1,3-diones and other active methylene compounds provided cyclopropane carboxylates in good yields. A tentative reaction mechanism was proposed.
文摘A straightforward and efficient protocol for dearomatizing indoles is described.The reaction,catalyzed by an inexpensive Co(III)/Zn(II)catalyst,starts from easily accessible N‐pyrimidinyl indoles and ene‐yne ketones.Mild reaction conditions,high diastereoselectivity,a broad substrate scope,effective functional group tolerance,and reasonable to remarkable yields were observed.
文摘Four chiral 1,1?bis(oxazolinyl)ferrocenes(1a-1d) have been prepared and used as ligands in the copper catalyzed asymmetric cyclopropanation of styrene with ethyl diazoacetate (EDA) and the magnesium catalyzed Diels-Alder reaction between 3-acryloyl-2-oxazolidinone and cyclopentadiene. Enantioselectivities up to 24% and 41%, respectively, for cyclopropanation and Diels-Alder reaction were observed.
基金This work was supported by the Northwest Normal University Science Foundation of Gansu Province （No. NWNU-QN-2001-08）.
文摘In order to have efficient and highly stereoselective cyclopropanating reagents, the cyclopropabation reaction of ethylene promoted with Samarium（Ⅱ） carbenoid [Simmons-Smith（SS）reagent] were studied by means of B3LYP hybrid density functional method. The geometries for reactants, transition states and products are completely optimized. All transition states were verified by the vibrational analysis and the intrinsic reaction coordinate （IRC） calculations. The results showed that, identical with the lithium carbenoid, CH3SmCH2X（X=Cl, Br and Ⅰ） can fairly react with ethylene via both methylene transfer pathway （pathway A） and carbometalation pathway （pathway B）. And the cyclopropanation reaction via methylene transfer pathway proceeds with a lower barrier and at lower temperatures.
文摘Four stereoisomers of a copper-(Schiff-base) complex with double chiral centers were applied to catalyze the asymmetric cyclopropanation. Two of the stereoisomers were also efficient catalysts affording high enantiomeric excess of up to 91.8%. A mechanism that predicts the observed results accurately was proposed.
文摘Several cyclopropanation catalysts for the synthesis of 3(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylates have been studied in this paper. Owing to electron deficiency of 1,1-dichloro-4-methyl-1,3-pentadiene, yield of this reaction is rather law compared with that of 2,5-dimethyl-2,4-pentadiene, Of all catalysts concerned. yield ranged from 25.1% to 47.2%.
文摘Various addition-elimination approaches have been explored for diastereoselective construction of 1-amino- 1-cyclopropane-carboxylic acid (ACPC) derivatives, and the desired product was obtained from a reaction of cyclo(NAc-L-Val-NAc-Gly) and methyl α-bro-moacrylate under protonic solvent.
文摘A new chiral β-diketone Cu (Ⅱ) catalyst was synthesized and used for the asymmetric cyclopropanation of styrene with diazoester. A high optical yield (~90%) was achieved. The effect of the structure of substrate on the enantioselectivity was studied. Both chendcal yield and optical yield being reduced when the steric bulky substrate was employed. The reaction mechanism and the chiral model of the transition state are under fufther investigation.
文摘Nine copper compounds are used for catalyzing the cyclopropanation of 1-hexene/TME with alkyl diazoacetate.Cu(Salad)2 shows the highest yield for the reaction of TME at high temperature such as 100℃.The reaction of crude RDA with TME in 73.7% yield under the optimal condition is obtained.
基金support of the Natural Science Foundation of China and Shandong Province(grant nos.21971149,92156007,21933003,ZR2019ZD45,and ZR2020KB005).
文摘Chiral[2.2]paracyclophane(PCP)is an intriguing prevalent scaffold widely utilized inπ-stacked polymers,luminescent materials,and asymmetric catalysis.However,current synthetic methods to access chiral PCP derivatives are still limited to physical separation and chemical or kinetic resolution.The direct desymmetric functionalization of nonsubstituted PCP has been a challenge since its discovery 70 years ago.Herein,we present a catalytic desymmetric dearomatization cyclopropanation reaction of PCP,providing rapid access to enantioenriched PCP cyclopropyl carboxylates with continuous tertiary/quaternary/quaternary chiral centers.The application of the chiral PCPs obtained has also been demonstrated by transformation to structurally novel C_(2) symmetric dirhodium catalysts.Of equal importance,detailed density functional theory calculations have been carried out to reveal the mechanism of this reaction.The key to this success is a structurally symmetric bulky C_(4) dirhodium catalyst:noncovalent interactions exist between substrates and catalysts,which form a cavity to host substrates,and mainly affect the regio-and enantioselectivity.
基金supported by the National Natural Science Foundation of China(22171201,22371185)the Fundamental Research Funds for the Central Universities(22X010201631)the Program of Shanghai Academic/Technology Research Leader(23XD1421900)。
文摘We report a novel cyano migration-mediated radical-polar crossover process,whereby both the sulfonylcyanation of aliphatic alkenes and the formation of cyclopropanes are concurrently achieved.This transformation yields a diverse array of multisubstituted cyclopropanes under mild photocatalytic conditions.Mechanistic studies elucidate that the reaction proceeds via intramolecular nucleophilic substitution,leading to the formation of the cyclopropane derivatives.
文摘G-quadruplex DNA(G4)can function as a kind of nucleic acid apoenzyme for constructing G4/hemin biocatalyst to mimic the catalytic function of hemoprotein.However,achieving stereoselective control with G4/hemin remains a persistent challenge.Here,we report that a PW17/hemin(PW17:5’-GGGTAGGGCGGGTTGGG-3’),adopting the 5’-5’stacked dimeric parallel G4 topology,can realize the enantioselective induction in intramolecular cyclopropanation of allyl diazoacetates with enantioselectivity up to 87%ee.Spectroscopic characterization and catalytic results demonstrate that the relatively open G-quartet of the 3’terminal in dimeric PW17 contributes a catalytic pocket for hemin accommodation and plays a pivotal role in enantioselective control.This finding expands the unique repertoire of heme enzyme using biological scaffolds from proteins to nucleic acids and resolves the long-standing challenge of stereochemical control in G4/hemin catalysis.
基金theFoundationofShanghaiScienceandTechnologyDevelopment (No .0 1JC140 0 2 )
文摘Cyclopropanation of styrene with ethyl diazoacetate catalyzed by Pd(II) inionic liquid [omim][BF_4] was investigated. Palladium catalysts can be effectively immobilized inionic liquid. The catalysts PdCl_2 and cyclopalladated complex 2 contained in ionic liquid could berecycled for 6 and 7 times, respectively, without losing the efficiency.
基金supported by the National Natural Science Foundation of China(21421091,21432011 and21272250)the Chinese Academy of Sciences
文摘A copper-catalyzed highly stereoselective cyclopropanation of 1,2-disubstituted olefins with α-nitrodiazo acetates has been developed, giving the desired products in up to 97 % yields, up to 〉99/1 dr and up to 98 % ee, which provides an efficient access to the synthesis of optical active cyclopropane α-amino acids and unnatural α-amino acid derivatives.
基金supported by the National Natural Science Foundation of China (NSFC-21622203, 21472147, 21702161)the China Postdoctoral Science Foundation Funded Project (2017M610644)Fund of Northwest University (334100036)
文摘A novel palladium-catalyzed oxidative cyclopropanation of enamides and norbornenes has been developed. The reaction proceeded through palladium-catalyzed vinyl C–H bond activation of enamides followed by two migratory insertions, β-(N)H elimination and hydrolyzation cascade steps. The reaction tolerates a range of functional groups and provides an effective method for the synthesis of cyclopropane-fused norbornanes in good yields under mild conditions.
基金supported by the National Natural Science Foundation of China(21432011,21772224)Key Research Program of Frontier Sciences of Chinese Academy of Sciences(QYZDY-SSWSLH016)+2 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB20000000)the Youth Innovation Promotion Association CAS(2017301)the National Basic Research Program of China(2015CB856600)
文摘A highly efficient asymmetric cyclopropanation of trisubstituted olefins with methyl diazoacetate has been developed in terms of an elaborate modified chiral bisoxazoline/copper complex as a catalyst. A broad scope of substrates is compatible with this catalyst system, including various trisubstituted olefins bearing different aryl-, fused aryl-and alkyl-substituents, providing an easy access to optically active 1,1-dimethyl cyclopropanes in good yields with excellent diastereo-and enantio-selectivity.
文摘The C—F bond transformation of gem-difluorinated cyclopropanes without cleavage of the highly strained C—C bond is an intractable challenge. The synthesis of cyclopropanone ketals via double defluorination of gem-difluorinated cyclo-propanesunder transition-metal free and basic conditions has been developed. A broad range of gem-difluorinated cyclopro-panesand alcohols are amenable in present reaction to permit the synthesis of corresponding products in high yields. The reaction is elucidated to proceed via elimination and addition other than direct substitution based on the mechanistic studies. This transformation not only provides a new strategy for the construction of cyclopropanone ketals, but also reveals a new paradigm on C—F bond transformation without ring-opening of gem-difluorinated cyclopropanes.
