Transition-metal-catalyzed C–H activation represents one of most attractive research fields in modern organic chemistry while theoretical studies have become a popular and effective tool for elucidating mechanism now...Transition-metal-catalyzed C–H activation represents one of most attractive research fields in modern organic chemistry while theoretical studies have become a popular and effective tool for elucidating mechanism nowadays. The recent achievements in the cross field of the two orientations are reviewed in this article. The first part introduced the advances in theoretical study on transition-metal-catalyzed C–H activation. The elegant work reported mainly in and after 2013, classified according to the mechanisms of C–H activation, were covered. The second part provided an analysis on the distribution of quantum-chemical methods, solvation models and basis sets in the collected theoretical studies.展开更多
The rhodium-catalyzed formal C（sp^3）-H activation/spiroannulation of α-arylidene pyrazolones with alkynes was investigated by means of density functional theory calculations. The calculations indicate that the spir...The rhodium-catalyzed formal C（sp^3）-H activation/spiroannulation of α-arylidene pyrazolones with alkynes was investigated by means of density functional theory calculations. The calculations indicate that the spiroannulation through the proposed C-C reductive elimination is kinetically unfeasible, Instead, the C-C coupling from the eight-membered rhodacycle was proposed to account for the experimental results. The overall catalytic cycle consists of six steps： （1） the keto-enol isomerization; （2） the O-H deprotonation, （3） the C（sp^2）-H bond cleavage; （4） the migratory insertion of alkyne into the Rh-C bond; （5） the C-C coupling and （6） the regeneration of the active catalyst.展开更多
Intramolecular ortho-C-H activation and C-N/C-O cyclizations of phenyl amidines and amides have recently been achieved under Cu catalysis. These reactions provide important examples of Cu-catalyzed functionalization o...Intramolecular ortho-C-H activation and C-N/C-O cyclizations of phenyl amidines and amides have recently been achieved under Cu catalysis. These reactions provide important examples of Cu-catalyzed functionalization of inert C-H bonds, but their mechanisms remain poorly understood. In the present study the several possible mechanisms including electrophilic aromatic substitution, concerted metalation-deprotonation (CMD), Friedel-Crafts mechanism, radical mechanism, and protoncoupled electron transfer have been theoretically examined. Cu(Ⅱ)-assisted CMD mechanism is found to be the most feasible for both C-O and C-N cyclizations. This mechanism includes three steps, i.e. CMD with Cu(Ⅱ), oxidation of the Cu(Ⅱ) intermediate, and reductive elimination from Cu(Ⅲ). Our calculations show that Cu(Ⅱ) mediates the C-H activation through an six-membered ring CMD transition state similar to that proposed for many Pd-catalyzed C-H activation reactions. It is also interesting to find that the rate-limiting steps are different for C-N and C-O cyclizations: for the former it is concerted metalation-deprotonation with Cu(Ⅱ), whereas for the latter it is reductive elimination from Cu(Ⅲ). The above conclusions are consistent with the experimental kinetic isotope effects (1.0 and 2.1 for C-O and C-N cyclizations, respectively), substituent effects, and the reactions under O2 -free conditions.展开更多
The transition metal-mediated C–H bond activation has emerged as a powerful and ideal method for the total syntheses of natural products and pharmaceuticals, and has had a significant impact on synthetic planning and...The transition metal-mediated C–H bond activation has emerged as a powerful and ideal method for the total syntheses of natural products and pharmaceuticals, and has had a significant impact on synthetic planning and strategy in complex natural products.In this review, we describe selected recent examples of the transition metal-mediated C–H bond activation strategies for the rapid syntheses of natural products.展开更多
Ligands can definitely influence C−H activation at the metal center.A ligand not directly participating in the reaction is called a spectator ligand.We attempt to quantitatively characterize the effects of diverse spe...Ligands can definitely influence C−H activation at the metal center.A ligand not directly participating in the reaction is called a spectator ligand.We attempt to quantitatively characterize the effects of diverse spectator ligands on C−H activation at palladium.We designed a model palladium catalyst and selected an array of spectator ligands,such as methoxyl,amide,methyl,phenyl,cyanide,fluorine,chlorine,and several neutral ligands,and performed density functional theory calculations on the mechanism and energetics of C−H activation reactions of benzene with different catalysts.Univalent ligands have substantially larger effects than neutral ligands,and stronglyσ-donating ligands(e.g.,methyl and phenyl)severely hinder the C−H activation in progress.A ligand trans to the reaction site influences C−H activation more than that cis to the reaction site,indicating electronic effects to be at work.For example,the existence of a methyl ligand raises the barrier height of C−H activation by 6.4 or 14.4 kcal/mol when it is placed at the position cis or trans to the C−H activation site.The effects of poorlyσ-donating ligands are not significant and similar to those of theκ1-acetate ligand.Someσ-donating andπ-accepting ligands,such as cyanide and isonitrile,hinder the C−H activation trans to them but appear to facilitate the C−H activation cis to them.On the basis of molecular orbital analyses,a chemical model is proposed to understand the observed ligand effects.Lastly,the conclusions are applied to explain the plausible mechanism of the dehydrogenative Heck coupling.展开更多
In this paper, we used density functional theory(DFT) computations to study the mechanisms of the hydroacylation reaction of an aldehyde with an alkene catalyzed by Wilkinson's catalyst and an organic catalyst 2-a...In this paper, we used density functional theory(DFT) computations to study the mechanisms of the hydroacylation reaction of an aldehyde with an alkene catalyzed by Wilkinson's catalyst and an organic catalyst 2-amino-3-picoline in cationic and neutral systems. An aldehyde's hydroacylation includes three stages: the C–H activation to form rhodium hydride(stage I), the alkene insertion into the Rh–H bond to give the Rh-alkyl complex(stage II), and the C–C bond formation(stage III). Possible pathways for the hydroacylation originated from the trans and cis isomers of the catalytic cycle. In this paper, we discussed the neutral and cationic pathways. The rate-determining step is the C–H activation step in neutral system but the reductive elimination step in the cationic system. Meanwhile, the alkyl group migration-phosphine ligand coordination pathway is more favorable than the phosphine ligand coordination-alkyl group migration pathway in the C–C formation stage. Furthermore, the calculated results imply that an electron-withdrawing group may decrease the energy barrier of the C–H activation in the benzaldehyde hydroacylation.展开更多
基金supported by the National Natural Science Foundation of China (21473100, 21403123)the Project of Shandong Province Higher Educational Science and Technology Program (J14LC17)+1 种基金the Opening Foundation of Shandong Provincial Key Laboratory of Detection Technology for Tumor Makers (KLDTTM2015-9)the Doctoral Start-Up Scientific Research Foundation of Qufu Normal University (BSQD2012018)
文摘Transition-metal-catalyzed C–H activation represents one of most attractive research fields in modern organic chemistry while theoretical studies have become a popular and effective tool for elucidating mechanism nowadays. The recent achievements in the cross field of the two orientations are reviewed in this article. The first part introduced the advances in theoretical study on transition-metal-catalyzed C–H activation. The elegant work reported mainly in and after 2013, classified according to the mechanisms of C–H activation, were covered. The second part provided an analysis on the distribution of quantum-chemical methods, solvation models and basis sets in the collected theoretical studies.
基金supported by the National Natural Science Foundation of China(No.21503143)the Tianjin Natural Science Foundation(Nos.16JCQNJC05600 and 16JCYBJC43600)+1 种基金the Talent Research Start-up Fund of Tianjin Normal University(No.5RL139)support from the Shenzhen Peacock Plan(No.1208040050847074)
文摘The rhodium-catalyzed formal C（sp^3）-H activation/spiroannulation of α-arylidene pyrazolones with alkynes was investigated by means of density functional theory calculations. The calculations indicate that the spiroannulation through the proposed C-C reductive elimination is kinetically unfeasible, Instead, the C-C coupling from the eight-membered rhodacycle was proposed to account for the experimental results. The overall catalytic cycle consists of six steps： （1） the keto-enol isomerization; （2） the O-H deprotonation, （3） the C（sp^2）-H bond cleavage; （4） the migratory insertion of alkyne into the Rh-C bond; （5） the C-C coupling and （6） the regeneration of the active catalyst.
基金the financial support from the National Basic Research Program of China (973 program, 2012CB215306)the National Natural Science Foundation of China (NSFC, 20832004, 20972148)CAS(KJCX2-EW-J02)
文摘Intramolecular ortho-C-H activation and C-N/C-O cyclizations of phenyl amidines and amides have recently been achieved under Cu catalysis. These reactions provide important examples of Cu-catalyzed functionalization of inert C-H bonds, but their mechanisms remain poorly understood. In the present study the several possible mechanisms including electrophilic aromatic substitution, concerted metalation-deprotonation (CMD), Friedel-Crafts mechanism, radical mechanism, and protoncoupled electron transfer have been theoretically examined. Cu(Ⅱ)-assisted CMD mechanism is found to be the most feasible for both C-O and C-N cyclizations. This mechanism includes three steps, i.e. CMD with Cu(Ⅱ), oxidation of the Cu(Ⅱ) intermediate, and reductive elimination from Cu(Ⅲ). Our calculations show that Cu(Ⅱ) mediates the C-H activation through an six-membered ring CMD transition state similar to that proposed for many Pd-catalyzed C-H activation reactions. It is also interesting to find that the rate-limiting steps are different for C-N and C-O cyclizations: for the former it is concerted metalation-deprotonation with Cu(Ⅱ), whereas for the latter it is reductive elimination from Cu(Ⅲ). The above conclusions are consistent with the experimental kinetic isotope effects (1.0 and 2.1 for C-O and C-N cyclizations, respectively), substituent effects, and the reactions under O2 -free conditions.
基金supported by the National Natural Science Foundation of China (21290183, 21572008, 21372017)the State Key Laboratory of Bioorganic and Natural Products Chemistry
文摘The transition metal-mediated C–H bond activation has emerged as a powerful and ideal method for the total syntheses of natural products and pharmaceuticals, and has had a significant impact on synthetic planning and strategy in complex natural products.In this review, we describe selected recent examples of the transition metal-mediated C–H bond activation strategies for the rapid syntheses of natural products.
基金supported by the National Natural Science Foundation of China (22003045, 21808156)the Fundamental Research Funds for Tianjin Colleges (2018KJ171, 2017KJ064)the High-performance Computing Platform of Tianjin Chengjian University
文摘Ligands can definitely influence C−H activation at the metal center.A ligand not directly participating in the reaction is called a spectator ligand.We attempt to quantitatively characterize the effects of diverse spectator ligands on C−H activation at palladium.We designed a model palladium catalyst and selected an array of spectator ligands,such as methoxyl,amide,methyl,phenyl,cyanide,fluorine,chlorine,and several neutral ligands,and performed density functional theory calculations on the mechanism and energetics of C−H activation reactions of benzene with different catalysts.Univalent ligands have substantially larger effects than neutral ligands,and stronglyσ-donating ligands(e.g.,methyl and phenyl)severely hinder the C−H activation in progress.A ligand trans to the reaction site influences C−H activation more than that cis to the reaction site,indicating electronic effects to be at work.For example,the existence of a methyl ligand raises the barrier height of C−H activation by 6.4 or 14.4 kcal/mol when it is placed at the position cis or trans to the C−H activation site.The effects of poorlyσ-donating ligands are not significant and similar to those of theκ1-acetate ligand.Someσ-donating andπ-accepting ligands,such as cyanide and isonitrile,hinder the C−H activation trans to them but appear to facilitate the C−H activation cis to them.On the basis of molecular orbital analyses,a chemical model is proposed to understand the observed ligand effects.Lastly,the conclusions are applied to explain the plausible mechanism of the dehydrogenative Heck coupling.
基金supported by the National Natural Science Foundation of China(21373023,21203006,21072018)
文摘In this paper, we used density functional theory(DFT) computations to study the mechanisms of the hydroacylation reaction of an aldehyde with an alkene catalyzed by Wilkinson's catalyst and an organic catalyst 2-amino-3-picoline in cationic and neutral systems. An aldehyde's hydroacylation includes three stages: the C–H activation to form rhodium hydride(stage I), the alkene insertion into the Rh–H bond to give the Rh-alkyl complex(stage II), and the C–C bond formation(stage III). Possible pathways for the hydroacylation originated from the trans and cis isomers of the catalytic cycle. In this paper, we discussed the neutral and cationic pathways. The rate-determining step is the C–H activation step in neutral system but the reductive elimination step in the cationic system. Meanwhile, the alkyl group migration-phosphine ligand coordination pathway is more favorable than the phosphine ligand coordination-alkyl group migration pathway in the C–C formation stage. Furthermore, the calculated results imply that an electron-withdrawing group may decrease the energy barrier of the C–H activation in the benzaldehyde hydroacylation.
