共查询到20条相似文献,搜索用时 15 毫秒
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Dr. Rishikesh Narayan Dr. Kiran Matcha Dr. Andrey P. Antonchick 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(42):14678-14693
The formation of C?C bonds embodies the core of organic chemistry because of its fundamental application in generation of molecular diversity and complexity. C?C bond‐forming reactions are well‐known challenges. To achieve this goal through direct functionalization of C?H bonds in both of the coupling partners represents the state‐of‐the‐art in organic synthesis. Oxidative C?C bond formation obviates the need for prefunctionalization of both substrates. This Minireview is dedicated to the field of C?C bond‐forming reactions through direct C?H bond functionalization under completely metal‐free oxidative conditions. Selected important developments in this area have been summarized with representative examples and discussions on their reaction mechanisms. 相似文献
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Michael C. Haibach Nicholas Lease Prof. Alan S. Goldman 《Angewandte Chemie (International ed. in English)》2014,53(38):10160-10163
The development of efficient catalytic methods to cleave the relatively unreactive C? O bonds of ethers remains an important challenge in catalysis. Building on our group’s recent work, we report the dehydroaryloxylation of aryl alkyl ethers using pincer iridium catalysts. This method represents a rare fully atom‐economical method for ether C? O bond cleavage. 相似文献
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Mechanistic Study on Rh‐Catalyzed Stereoselective CC/CH Activation of tert‐Cyclobutanols 下载免费PDF全文
Dr. Haizhu Yu Dr. Chen Wang Yimeng Yang Prof. Zhi‐Min Dang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(13):3839-3848
A mechanistic study was performed on the Rh‐catalyzed stereoselective C?C/C?H activation of tert‐cyclobutanols. The present study corroborated the previous proposal that the reaction occurs by metalation, β‐C elimination, 1,4‐Rh transfer, C?O insertion, and a final catalyst‐regeneration step. The rate‐determining step was found to be the 1,4‐Rh transfer step, whereas the stereoselectivity‐determining step did not correspond to any of the aforementioned steps. It was found that both the thermodynamic stability of the product of the β‐C elimination and the kinetic feasibility of the 1,4‐Rh transfer and C?O insertion steps made important contributions. In other words, three steps (i.e., β‐C elimination, 1,4‐Rh transfer, and C?O insertion) were found to be important in determining the configurations of the two quaternary stereocenters. 相似文献
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Palladium‐Catalyzed Construction of Heteroatom‐Containing π‐Conjugated Systems by Intramolecular Oxidative CH/CH Coupling Reaction 下载免费PDF全文
Kenta Saito Dr. Prasanna Kumara Chikkade Prof. Dr. Motomu Kanai Prof. Dr. Yoichiro Kuninobu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(23):8365-8368
Synthesis of heteroatom‐containing ladder‐type π‐conjugated molecules was successfully achieved via a palladium‐catalyzed intramolecular oxidative C?H/C?H cross‐coupling reaction. This reaction provides a variety of π‐conjugated molecules bearing heteroatoms, such as nitrogen, oxygen, phosphorus, and sulfur atoms, and a carbonyl group. The π‐conjugated molecules were synthesized efficiently, even in gram scale, and larger π‐conjugated molecules were also obtained by a double C?H/C?H cross‐coupling reaction and successive oxidative cycloaromatization. 相似文献
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Palladium‐Catalyzed Synthesis of Phenanthridine/Benzoxazine‐Fused Quinazolinones by Intramolecular CH Bond Activation 下载免费PDF全文
Puneet K. Gupta Nisha Yadav Subodh Jaiswal Mohd. Asad Dr. Ruchir Kant Dr. Kanchan Hajela 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(38):13210-13215
A highly efficient synthesis of phenanthridine/benzoxazine‐fused quinazolinones by ligand‐free palladium‐catalyzed intramolecular C?H bond activation under mild conditions has been developed. The C?C coupling provides the corresponding N‐fused polycyclic heterocycles in good to excellent yields and with wide functional group tolerance. 相似文献
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Dr. Brian N. Laforteza Kelvin S. L. Chan Prof. Dr. Jin‐Quan Yu 《Angewandte Chemie (International ed. in English)》2015,54(38):11143-11146
The commonly used para‐nitrobenzenesulfonyl (nosyl) protecting group is employed to direct the C? H activation of amines for the first time. An enantioselective ortho‐C? H cross‐coupling between nosyl‐protected diarylmethylamines and arylboronic acid pinacol esters has been achieved utilizing chiral mono‐N‐protected amino acid (MPAA) ligands as a promoter. 相似文献
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Dr. Margaret L. Scheuermann David W. Boyce Prof. Kyle A. Grice Prof. Werner Kaminsky Prof. Stefan Stoll Prof. William B. Tolman Prof. Ole Swang Prof. Karen I. Goldberg 《Angewandte Chemie (International ed. in English)》2014,53(25):6492-6495
[Pd(P(Ar)(tBu)2)2] ( 1 , Ar=naphthyl) reacts with molecular oxygen to form PdII hydroxide dimers in which the naphthyl ring is cyclometalated and one equivalent of phosphine per palladium atom is released. This reaction involves the cleavage of both C? H and O? O bonds, two transformations central to catalytic aerobic oxidizations of hydrocarbons. Observations at low temperature suggest the initial formation of a superoxo complex, which then generates a peroxo complex prior to the C? H activation step. A transition state for energetically viable C? H activation across a Pd? peroxo bond was located computationally. 相似文献
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The Cross‐Dehydrogenative Coupling of CH Bonds: A Versatile Strategy for CC Bond Formations 下载免费PDF全文
Simon A. Girard Dr. Thomas Knauber Prof. Dr. Chao‐Jun Li 《Angewandte Chemie (International ed. in English)》2014,53(1):74-100
Over the last decade, substantial research has led to the introduction of an impressive number of efficient procedures which allow the selective construction of C? C bonds by directly connecting two different C? H bonds under oxidative conditions. Common to these methodologies is the generation of the reactive intermediates in situ by activation of both C? H bonds. This strategy was introduced by the group of Li as cross‐dehydrogenative coupling (CDC) and discloses waste‐minimized synthetic alternatives to classic coupling procedures which rely on the use of prefunctionalized starting materials. This Review highlights the recent progress in the field of cross‐dehydrogenative C? C formations and provides a comprehensive overview on existing procedures and employed methodologies. 相似文献
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The Mechanism of NO Bond Cleavage in Rhodium‐Catalyzed CH Bond Functionalization of Quinoline N‐oxides with Alkynes: A Computational Study 下载免费PDF全文
Yingzi Li Song Liu Zisong Qi Xiaotian Qi Prof. Dr. Xingwei Li Prof. Dr. Yu Lan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(28):10131-10137
Metal‐catalyzed C?H activation not only offers important strategies to construct new bonds, it also allows the merge of important research areas. When quinoline N‐oxide is used as an arene source in C?H activation studies, the N?O bond can act as a directing group as well as an O‐atom donor. The newly reported density functional theory method, M11L, has been used to elucidate the mechanistic details of the coupling between quinoline N?O bond and alkynes, which results in C?H activation and O‐atom transfer. The computational results indicated that the most favorable pathway involves an electrophilic deprotonation, an insertion of an acetylene group into a Rh?C bond, a reductive elimination to form an oxazinoquinolinium‐coordinated RhI intermediate, an oxidative addition to break the N?O bond, and a protonation reaction to regenerate the active catalyst. The regioselectivity of the reaction has also been studied by using prop‐1‐yn‐1‐ylbenzene as a model unsymmetrical substrate. Theoretical calculations suggested that 1‐phenyl‐2‐quinolinylpropanone would be the major product because of better conjugation between the phenyl group and enolate moiety in the corresponding transition state of the regioselectivity‐determining step. These calculated data are consistent with the experimental observations. 相似文献
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Dr. Dajian Zhu Dr. Guoqiang Yang Jian He Ling Chu Dr. Gang Chen Dr. Wei Gong Dr. Ke Chen Dr. Martin D. Eastgate Prof. Dr. Jin‐Quan Yu 《Angewandte Chemie (International ed. in English)》2015,54(8):2497-2500
2,4,6‐Trimethoxypyridine is identified as an efficient ligand for promoting a Pd‐catalyzed ortho‐C? H amination of both benzamides and triflyl‐protected benzylamines. This finding provides guidance for the development of ligands that can improve or enable PdII‐catalyzed C? H activation reactions directed by weakly coordinating functional groups. 相似文献
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Dr. Shao‐Jie Lou Prof. Dan‐Qian Xu Prof. Zhen‐Yuan Xu 《Angewandte Chemie (International ed. in English)》2014,53(39):10330-10335
A novel and facile C? H bond fluorination proceeds under remarkably mild conditions (close to room temperature in most cases). Both aromatic and olefinic C(sp2)? H bonds with a wide range of electronic properties are selectively fluorinated in the presence of a catalytic amount of simple, cheap, and nontoxic nitrate as the promoter. A PdII/PdIV catalytic cycle that is initiated by an in situ generated cationic [Pd(NO3)]+ species was proposed based on preliminary mechanistic studies. 相似文献
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M. Sc. Fanzhi Yang Karsten Rauch M. Sc. Katharina Kettelhoit Prof. Dr. Lutz Ackermann 《Angewandte Chemie (International ed. in English)》2014,53(42):11285-11288
Versatile ruthenium(II) complexes allow for site‐selective C? H oxygenations with weakly‐coordinating aldehydes. The challenging C? H functionalizations proceed with high chemoselectivity by rate‐determining C? H metalation. The new method features an ample substrate scope, which sets the stage for the step‐economical preparation of various bioactive heterocycles. 相似文献
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Copper‐Catalyzed Aerobic Oxidative Inert CC and CN Bond Cleavage: A New Strategy for the Synthesis of Tertiary Amides 下载免费PDF全文
Xiuling Chen Dr. Tieqiao Chen Qiang Li Dr. Yongbo Zhou Prof. Li‐Biao Han Prof. Shuang‐Feng Yin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(38):12234-12238
A copper‐catalyzed aerobic oxidative amidation reaction of inert C?C bonds with tertiary amines has been developed for the synthesis of tertiary amides, which are significant units in many natural products, pharmaceuticals, and fine chemicals. This method combines C?C bond activation, C?N bond cleavage, and C?H bond oxygenation in a one‐pot protocol, using molecular oxygen as the sole oxidant without any additional ligands. 相似文献
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Electrochemical Intramolecular CH Amination: Synthesis of Benzoxazoles and Benzothiazoles 下载免费PDF全文
Tatsuya Morofuji Dr. Akihiro Shimizu Prof. Dr. Jun‐ichi Yoshida 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(8):3211-3214
A new method for metal‐free intramolecular C?H amination has been developed. Electrochemical oxidation of 2‐pyrimidyloxybenzenes and 2‐pyrimidylthiobenzenes, which can be easily prepared from phenols and thiophenols, respectively, followed by the treatment of the resulting pyrimidinium ions with piperidine gives 2‐aminobenzoxazoles and 2‐aminobenzothiazoles, respectively. 相似文献
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Michael C. Haibach Prof. Dr. Daniel Seidel 《Angewandte Chemie (International ed. in English)》2014,53(20):5010-5036
Known for over a century, reactions that involve intramolecular hydride‐transfer events have experienced a recent resurgence. Undoubtedly responsible for the increased interest in this research area is the realization that hydride shifts represent an attractive avenue for C? H bond functionalization. The redox‐neutral nature of these complexity‐enhancing transformations makes them ideal for sustainable reaction development. This Review summarizes recent progress in this field while highlighting key historical contributions. 相似文献
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Ruthenium‐Catalyzed Oxidative Coupling of Primary Amines with Internal Alkynes through CH Bond Activation: Scope and Mechanistic Studies 下载免费PDF全文
Sara Ruiz Dr. Pedro Villuendas Dr. Manuel A. Ortuño Prof. Dr. Agustí Lledós Dr. Esteban P. Urriolabeitia 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(23):8626-8636
The oxidative coupling of primary amines with internal alkynes catalyzed by Ru complexes is presented as a general atom‐economy methodology with a broad scope of applications in the synthesis of N‐heterocycles. Reactions proceed through regioselective C?H bond activation in 15 minutes under microwave irradiation or in 24 hours with conventional heating. The synthesis of 2,3,5‐substituted pyridines, benzo[h]isoquinolines, benzo[g]isoquinolines, 8,9‐dihydro‐benzo[de]quinoline, 5,6,7,8‐tetrahydroisoquinolines, pyrido[3,4g]isoquinolines, and pyrido[4,3g]isoquinolines is achievable depending on the starting primary amine used. DFT calculations on a benzylamine substrate support a reaction mechanism that consists of acetate‐assisted C?H bond activation, migratory‐insertion, and C?N bond formation steps that involve 28–30 kcal mol?1. The computational study is extended to additional substrates, namely, 1‐naphthylmethyl‐, 2‐methylallyl‐, and 2‐thiophenemethylamines. 相似文献
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Zi‐Yu Li Lianrui Hu Qing‐Yu Liu Prof. Dr. Chuan‐Gang Ning Prof. Dr. Hui Chen Prof. Dr. Sheng‐Gui He Prof. Dr. Jiannian Yao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(49):17748-17756
Although early transition metal (ETM) carbides can activate C?H bonds in condensed‐phase systems, the electronic‐level mechanism is unclear. Atomic clusters are ideal model systems for understanding the mechanisms of bond activation. For the first time, C?H activation of a simple alkane (ethane) by an ETM carbide cluster anion (MoC3?) under thermal‐collision conditions has been identified by using high‐resolution mass spectrometry, photoelectron imaging spectroscopy, and high‐level quantum chemical calculations. Dehydrogenation and ethene elimination were observed in the reaction of MoC3? with C2H6. The C?H activation follows a mechanism of oxidative addition that is much more favorable in the carbon‐stabilized low‐spin ground electronic state than in the high‐spin excited state. The reaction efficiency between the MoC3? anion and C2H6 is low (0.23±0.05) %. A comparison between the anionic and a highly efficient cationic reaction system (Pt++C2H6) was made. It turned out that the potential‐energy surfaces for the entrance channels of the anionic and cationic reaction systems can be very different. 相似文献
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RhIII‐Catalyzed CH Activation with Pyridotriazoles: Direct Access to Fluorophores for Metal‐Ion Detection 下载免费PDF全文
Dr. Ju Hyun Kim Tobias Gensch Dr. Dongbing Zhao Linda Stegemann Priv.‐Doz. Dr. Cristian A. Strassert Prof. Dr. Frank Glorius 《Angewandte Chemie (International ed. in English)》2015,54(37):10975-10979
The first C? H bond activation with pyridotriazoles as coupling partners is presented using a RhIII catalyst. The pyridotriazoles can be used as new carbene precursors in C? H activation for direct access to novel fluorescent scaffolds. These tunable fluorophores can be applied for the detection of metal ions. 相似文献