共查询到20条相似文献,搜索用时 0 毫秒
1.
Dr. Alexander G. O'Brien Dr. Akinobu Maruyama Dr. Yasuhide Inokuma Prof. Makoto Fujita Prof. Phil S. Baran Prof. Donna G. Blackmond 《Angewandte Chemie (International ed. in English)》2014,53(44):11868-11871
Electrochemical reactions are shown to be effective for the C? H functionalization of a number of heterocyclic substrates that are recalcitrant to conventional peroxide radical initiation conditions. Monitoring reaction progress under electrochemical conditions provides mechanistic insight into the C? H functionalization of a series of heterocycles of interest in medicinal chemistry. 相似文献
2.
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
3.
Exceedingly Fast Copper(II)‐Promoted ortho CH Trifluoromethylation of Arenes using TMSCF3 下载免费PDF全文
Ming Shang Shang‐Zheng Sun Dr. Hong‐Li Wang Dr. Brian N. Laforteza Prof. Dr. Hui‐Xiong Dai Prof. Dr. Jin‐Quan Yu 《Angewandte Chemie (International ed. in English)》2014,53(39):10439-10442
The direct ortho‐trifluoromethylation of arenes, including heteroarenes, with TMSCF3 has been accomplished by a copper(II)‐promoted C? H activation reaction which completes within 30 minutes. Mechanistic investigations are consistent with the involvement of C? H activation, rather than a simple electrophilic aromatic substitution (SEAr), as the key step. 相似文献
4.
5.
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
6.
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
7.
Unexpected Cyclization of Tritylamines Promoted by Copper Salt through CH and CN Bond Cleavages to Produce Acridine Derivatives 下载免费PDF全文
Ryosuke Morioka Dr. Koji Hirano Prof. Dr. Tetsuya Satoh Prof. Dr. Masahiro Miura 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(40):12720-12724
Herein, we demonstrate that tritylamines undergo an unprecedented copper‐mediated cyclization involving the cleavages of two C?H bonds and one C?N bond to give 9‐arylacridine derivatives. This kind of acridines is of interest due to their biological properties and their unique optical and electro‐ and photochemical properties. Some of obtained acridine derivatives exhibit intense fluorescence in the solid state. 相似文献
8.
Shira D. Halperin Hope Fan Stanley Chang Dr. Rainer E. Martin Prof. Robert Britton 《Angewandte Chemie (International ed. in English)》2014,53(18):4690-4693
Fluorination reactions are essential to modern medicinal chemistry, thus providing a means to block site‐selective metabolic degradation of drugs and access radiotracers for positron emission tomography imaging. Despite current sophistication in fluorination reagents and processes, the fluorination of unactivated C? H bonds remains a significant challenge. Reported herein is a convenient and economic process for direct fluorination of unactivated C? H bonds that exploits the hydrogen abstracting ability of a decatungstate photocatalyst in combination with the mild fluorine atom transfer reagent N‐fluorobenzenesulfonimide. This operationally straightforward reaction provides direct access to a wide range of fluorinated organic molecules, including structurally complex natural products, acyl fluorides, and fluorinated amino acid derivatives. 相似文献
9.
Copper(I)‐Catalyzed Alkylation of Polyfluoroarenes through Direct CH Bond Functionalization 下载免费PDF全文
Shuai Xu Guojiao Wu Fei Ye Xi Wang Huan Li Xia Zhao Dr. Yan Zhang Prof. Dr. Jianbo Wang 《Angewandte Chemie (International ed. in English)》2015,54(15):4669-4672
The copper(I)‐catalyzed alkylation of electron‐deficient polyfluoroarenes with N‐tosylhydrazones and diazo compounds has been developed. This reaction uses readily available starting materials and is operationally simple, thus representing a practical method for the construction of C(sp2)? C(sp3) bonds with polyfluoroarenes through direct C? H bond functionalization. Mechanistically, copper(I) carbene formation and subsequent migratory insertion are proposed as the key steps in the reaction pathway. 相似文献
10.
CH Functionalization/Asymmetric Michael Addition Cascade Enabled by Relay Catalysis: Metal Carbenoid Used for CC Bond Formation 下载免费PDF全文
Dr. Dian‐Feng Chen Feng Zhao Yue Hu Prof. Dr. Liu‐Zhu Gong 《Angewandte Chemie (International ed. in English)》2014,53(40):10763-10767
A combination of either ruthenium(II) or rhodium(II) complexes and quinine‐derived squaramide enables 3‐diazooxindoles, indoles, and nitroalkenes to undergo highly efficient asymmetric three‐component reactions, thus affording optically active 3,3′‐bis(indole)s through a consecutive C? C bond‐forming sequence, which turned out to be applicable to the facile total synthesis of (?)‐folicanthine. 相似文献
11.
Transition Metal‐Catalyzed Carbonylative CH Bond Functionalization of Arenes and C(sp3)H Bond of Alkanes 下载免费PDF全文
Sandip T. Gadge Prashant Gautam Bhalchandra M. Bhanage 《Chemical record (New York, N.Y.)》2016,16(2):835-856
In this article, we present the progress made in the area of carbonylative C? H functionalization, with special emphasis on arenes and alkanes. The importance of directing group assistance and C? H functionalization using CO surrogates is also included. The budding development in the area of transition metal‐catalyzed C(sp3)? H activation makes us feel it necessary to file a summary on the past, as well as current, contributions and a prospective outlook on the transition metal‐catalyzed carbonylative transformation of C? H bonds, which is the focus of this review. 相似文献
12.
13.
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
14.
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
15.
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
16.
Iridium‐Catalyzed Enantioselective CH Alkylation of Ferrocenes with Alkenes Using Chiral Diene Ligands 下载免费PDF全文
Prof. Dr. Takanori Shibata Tsubasa Shizuno 《Angewandte Chemie (International ed. in English)》2014,53(21):5410-5413
The first catalytic and enantioselective C? H alkylation of ferrocene derivatives with various alkenes was achieved. A cationic iridium complex, having a chiral diene ligand, and an isoquinolyl moiety as a directing group are essential for regioselective and enantioselective C? H bond activation. 相似文献
17.
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
18.
Rhodium‐Catalyzed CS and CN Functionalization of Arenes: Combination of CH Activation and Hypervalent Iodine Chemistry 下载免费PDF全文
Fen Wang Xinzhang Yu Zisong Qi Prof. Dr. Xingwei Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(2):511-516
Rhodium‐catalyzed sulfonylation, thioetherification, thiocyanation, and other heterofunctionalizations of arenes bearing a heterocyclic directing group have been realized. The reaction proceeds by initial RhIII‐catalyzed C?H hyperiodination of arene at room temperature followed by uncatalyzed nucleophilic functionalization. A diaryliodonium salt is isolated as an intermediate, which represents umpolung of the arene substrate, in contrast to previous studies that suggested umpolung of the coupling partner. 相似文献
19.
Copper‐Catalyzed Trifluoromethylation of Internal Olefinic CH Bonds: Efficient Routes to Trifluoromethylated Tetrasubstituted Olefins and N‐Heterocycles 下载免费PDF全文
Zhifeng Mao Fei Huang Dr. Haifeng Yu Prof. Dr. Jiping Chen Prof. Dr. Zhengkun Yu Prof. Dr. Zhaoqing Xu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(12):3439-3445
The functionalization of internal olefins has been a challenging task in organic synthesis. Efficient CuII‐catalyzed trifluoromethylation of internal olefins, that is, α‐oxoketene dithioacetals, has been achieved by using Cu(OH)2 as a catalyst and TMSCF3 as a trifluoromethylating reagent. The push–pull effect from the polarized olefin substrates facilitates the internal olefinic C?H trifluoromethylation. Cyclic and acyclic dithioalkyl α‐oxoketene acetals were used as the substrates and various substituents were tolerated. The internal olefinic C?H bond cleavage was not involved in the rate‐determining step, and a mechanism that involves radicals is proposed based on a TEMPO‐quenching experiment of the trifluoromethylation reaction. Further derivatization of the resultant CF3 olefins led to multifunctionalized tetrasubstituted CF3 olefins and trifluoromethylated N‐heterocycles. 相似文献
20.
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