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1.
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
2.
Lewis Acid Mediated Tandem Reaction of Propargylic Alcohols to Tetrazoles Involving CO‐ and CC‐Bond Cleavage Reactions and a CN‐Bond Formation
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Dr. Xian‐Rong Song Ya‐Ping Han Yi‐Feng Qiu Zi‐Hang Qiu Xue‐Yuan Liu Prof. Dr. Peng‐Fei Xu Prof. Dr. Yong‐Min Liang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(38):12046-12050
A novel and direct synthesis of 1‐aryl‐5‐arylvinyl‐tetrazoles from easily prepared propargylic alcohols and TMSN3 is developed in the presence of TMSCl under mild conditions (TMS=trimethylsilyl). The process involves an allenylazide intermediate, followed by a C?C‐bond cleavage and C?N‐bond formation to afford the desired products. Moreover, this method offers a good functional‐group applicability and can be scaled‐up to grams (yield up to 85 %). 相似文献
3.
Dr. Limin She Xiaoli Li Jason Lee Prof. Dr. Dao‐Xin Yao Dr. Haiming Zhang Prof. Dr. Lifeng Chi Prof. Dr. Harald Fuchs Prof. Dr. Dingyong Zhong 《Chemphyschem》2015,16(7):1356-1360
Linear alkanes undergo different C?C bond chemistry (coupling or dissociation) thermally activated on anisotropic metal surfaces depending on the choice of the substrate material. Owing to the one‐dimensional geometrical constraint, selective dehydrogenation and C?C coupling (polymerization) of linear alkanes take place on Au(110) surfaces with missing‐row reconstruction. However, the case is dramatically different on Pt(110) surfaces, which exhibit similar reconstruction as Au(110). Instead of dehydrogenative polymerization, alkanes tend to dehydrogenative pyrolysis, resulting in hydrocarbon fragments. Density functional theory calculations reveal that dehydrogenation of alkanes on Au(110) surfaces is an endothermic process, but further C?C coupling between alkyl intermediates is exothermic. On the contrary, due to the much stronger C?Pt bonds, dehydrogenation on Pt(110) surfaces is energetically favorable, resulting in multiple hydrogen loss followed by C?C bond dissociation. 相似文献
4.
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
5.
Mechanistic Study on Rh‐Catalyzed Stereoselective CC/CH Activation of tert‐Cyclobutanols
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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.
Manganese‐Catalyzed Oxidative Azidation of Cyclobutanols: Regiospecific Synthesis of Alkyl Azides by CC Bond Cleavage
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Rongguo Ren Huijun Zhao Leitao Huan Prof. Dr. Chen Zhu 《Angewandte Chemie (International ed. in English)》2015,54(43):12692-12696
A novel, manganese‐catalyzed oxidative azidation of cyclobutanols is described. A wide range of primary, secondary, and tertiary alkyl azides were generated in synthetically useful yields and exclusive regioselectivity. Aside from linear alkyl azides, otherwise elusive medium‐sized cyclic azides were also readily prepared. Preliminary mechanistic studies reveal that the reaction likely proceeds by a radical‐mediated C? C bond cleavage/C? N3 bond formation pathway. 相似文献
7.
Palladium‐Catalyzed Construction of Heteroatom‐Containing π‐Conjugated Systems by Intramolecular Oxidative CH/CH Coupling Reaction
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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
8.
Rhodium(III)‐Catalyzed CC and CO Coupling of Quinoline N‐Oxides with Alkynes: Combination of CH Activation with O‐Atom Transfer
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Xueyun Zhang Zisong Qi Prof. Xingwei Li 《Angewandte Chemie (International ed. in English)》2014,53(40):10794-10798
[Cp*RhIII]‐catalyzed C? H activation of arenes assisted by an oxidizing N? O or N? N directing group has allowed the construction of a number of hetercycles. In contrast, a polar N? O bond is well‐known to undergo O‐atom transfer (OAT) to alkynes. Despite the liability of N? O bonds in both C? H activation and OAT, these two important areas evolved separately. In this report, [Cp*RhIII] catalysts integrate both areas in an efficient redox‐neutral coupling of quinoline N‐oxides with alkynes to afford α‐(8‐quinolyl)acetophenones. In this process the N? O bond acts as both a directing group for C? H activation and as an O‐atom donor. 相似文献
9.
Stereoselective CH Borylations of Cyclopropanes and Cyclobutanes with Silica‐Supported Monophosphane–Ir Catalysts
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Ryo Murakami Kiyoshi Tsunoda Dr. Tomohiro Iwai Prof. Dr. Masaya Sawamura 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(41):13127-13131
Heteroatom‐directed C?H borylation of cyclopropanes and cyclobutanes was achieved with silica‐supported monophosphane–Ir catalysts. Borylation occurred at the C?H bonds located γ to the directing N or O atoms with exceptional cis stereoselectivity relative to the directing groups. This protocol was applied to the borylation of a tertiary C?H bond of a ring‐fused cyclopropane. 相似文献
10.
Simon Wübbolt Prof. Dr. Martin Oestreich 《Angewandte Chemie (International ed. in English)》2015,54(52):15876-15879
A C? H silylation of pyridines that seemingly proceeds through electrophilic aromatic substitution (SEAr) is reported. Reactions of 2‐ and 3‐substituted pyridines with hydrosilanes in the presence of a catalyst that splits the Si? H bond into a hydride and a silicon electrophile yield the corresponding 5‐silylated pyridines. This formal silylation of an aromatic C? H bond is the result of a three‐step sequence, consisting of a pyridine hydrosilylation, a dehydrogenative C? H silylation of the intermediate enamine, and a 1,4‐dihydropyridine retro‐hydrosilylation. The key intermediates were detected by 1H NMR spectroscopy and prepared through the individual steps. This complex interplay of electrophilic silylation, hydride transfer, and proton abstraction is promoted by a single catalyst. 相似文献
11.
Palladium‐Catalyzed Synthesis of Phenanthridine/Benzoxazine‐Fused Quinazolinones by Intramolecular CH Bond Activation
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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
12.
Unexpected Cyclization of Tritylamines Promoted by Copper Salt through CH and CN Bond Cleavages to Produce Acridine Derivatives
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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
13.
The Cross‐Dehydrogenative Coupling of CH Bonds: A Versatile Strategy for CC Bond Formations
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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
14.
Thorsten vom Stein Dr. Tim den Hartog Dr. Julien Buendia Dr. Spas Stoychev Jakob Mottweiler Prof. Dr. Carsten Bolm Prof. Dr. Jürgen Klankermayer Prof. Dr. Walter Leitner 《Angewandte Chemie (International ed. in English)》2015,54(20):5859-5863
Ruthenium–triphos complexes exhibited unprecedented catalytic activity and selectivity in the redox‐neutral C? C bond cleavage of the β‐O‐4 lignin linkage of 1,3‐dilignol model compounds. A mechanistic pathway involving a dehydrogenation‐initiated retro‐aldol reaction for the C? C bond cleavage was proposed in line with experimental data and DFT calculations. 相似文献
15.
CH Functionalization/Asymmetric Michael Addition Cascade Enabled by Relay Catalysis: Metal Carbenoid Used for CC Bond Formation
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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
16.
Highly Efficient CH Hydroxylation of Carbonyl Compounds with Oxygen under Mild Conditions
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A transition‐metal‐free Cs2CO3‐catalyzed α‐hydroxylation of carbonyl compounds with O2 as the oxygen source is described. This reaction provides an efficient approach to tertiary α‐hydroxycarbonyl compounds, which are highly valued chemicals and widely used in the chemical and pharmaceutical industry. The simple conditions and the use of molecular oxygen as both the oxidant and the oxygen source make this protocol very environmentally friendly and practical. This transformation is highly efficient and highly selective for tertiary C(sp3)? H bond cleavage. 相似文献
17.
Iridium‐Catalyzed Synthesis of Diaryl Ethers by Means of Chemoselective CF Bond Activation and the Formation of BF Bonds
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Jianping Chen Keyan Zhao Bingyang Ge Chongying Xu Dr. Dawei Wang Prof. Yuqiang Ding 《化学:亚洲杂志》2015,10(2):468-473
Transition‐metal‐catalyzed C? F activation, in comparison with C? H activation, is more difficult to achieve and therefore less fully understood, mainly because carbon–fluorine bonds are the strongest known single bonds to carbon and have been very difficult to cleave. Transition‐metal complexes are often more effective at cleaving stronger bonds, such as C(sp2)? X versus C(sp3)? X. Here, the iridium‐catalyzed C? F activation of fluorarenes was achieved through the use of bis(pinacolato)diboron with the formation of the B? F bond and self‐coupling. This strategy provides a convenient method with which to convert fluoride aromatic compounds into symmetrical diaryl ether compounds. Moreover, the chemoselective products of the C? F bond cleavage were obtained at high yields with the C? Br and C? Cl bonds remaining. 相似文献
18.
Christopher J. Teskey Andrew Y. W. Lui Prof. Michael F. Greaney 《Angewandte Chemie (International ed. in English)》2015,54(40):11677-11680
The first example of a transition‐metal‐catalyzed, meta‐selective C? H bromination procedure is reported. In the presence of catalytic [{Ru(p‐cymene)Cl2}2], tetrabutylammonium tribromide can be used to functionalize the meta C? H bond of 2‐phenylpyridine derivatives, thus affording difficult to access products which are highly predisposed to further derivatization. We demonstrate this utility with one‐pot bromination/arylation and bromination/alkenylation procedures to deliver meta‐arylated and meta‐alkenylated products, respectively, in a single step. 相似文献
19.
Hui Yu Guoying Zhang Prof. Dr. Hanmin Huang 《Angewandte Chemie (International ed. in English)》2015,54(37):10912-10916
A fundamentally novel approach to bioactive quinolizinones is based on the palladium‐catalyzed intramolecular cyclocarbonylation of allylamines. [Pd(Xantphos)I2], which features a very large bite angle, has been found to facilitate the rapid carbonylation of azaarene‐substituted allylamines into bioactive quinolizinones in good to excellent yields. This transformation represents the first dearomative carbonylation and is proposed to proceed by palladium‐catalyzed C? N bond activation, dearomatization, CO insertion, and a Heck reaction. 相似文献
20.
This Focus Review presents recent developments in the cleavage of C? C bonds in organic molecules. Significant progress in C? C activation, including the development of a variety of new synthetic strategies, has contributed to the development of this field over the past few decades. Transition‐metal‐mediated C? C bond cleavage has been shown to be a quite efficient process and several elegant metal‐free methods have also recently been developed. Strained rings have been widely used in C? C cleavage transformations; however, unstrained C? C activation has increasingly caught the attention of organic researchers, which inspired us to clarify the developments in this field. 相似文献