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1.
Site‐Selective Remote Radical C−H Functionalization of Unactivated C−H Bonds in Amides Using Sulfone Reagents 下载免费PDF全文
Dr. Yong Xia Lin Wang Prof. Dr. Armido Studer 《Angewandte Chemie (International ed. in English)》2018,57(39):12940-12944
A general and practical strategy for remote site‐selective functionalization of unactivated aliphatic C?H bonds in various amides by radical chemistry is introduced. C?H bond functionalization is achieved by using the readily installed N‐allylsulfonyl moiety as an N‐radical precursor. The in situ generated N‐radical engages in intramolecular 1,5‐hydrogen atom transfer to generate a translocated C radical which is subsequently trapped with various sulfone reagents to afford the corresponding C?H functionalized amides. The generality of the approach is documented by the successful remote C?N3, C?Cl, C?Br, C?SCF3, C?SPh, and C?C bond formation. Unactivated tertiary and secondary C?H bonds, as well as activated primary C?H bonds, can be readily functionalized by this method. 相似文献
2.
The N‐centered radical directed remote C?H bond functionalization via hydrogen‐atom‐transfer at distant sites has developed as an enormous potential tool for the organic synthetic chemists. Unactivated and remote secondary and tertiary, as well as selected primary C?H bonds, can be utilized for functionalization by following these methodologies. The synthesis of the heterocyclic scaffolds provides them extra attention for the modern days′ developments in this field of unactivated remote C?H bonds functionalizations. 相似文献
3.
1,4‐Iron Migration for Expedient Allene Annulations through Iron‐Catalyzed C−H/N−H/C−O/C−H Functionalizations 下载免费PDF全文
Jiayu Mo Thomas Müller Dr. João C. A. Oliveira Prof. Dr. Lutz Ackermann 《Angewandte Chemie (International ed. in English)》2018,57(26):7719-7723
C?H activation bears great potential for enabling sustainable molecular syntheses in a step‐ and atom‐economical manner, with major advances having been realized with precious 4d and 5d transition metals. In contrast, we employed earth abundant, nontoxic iron catalysts for versatile allene annulations through a unique C?H/N?H/C?O/C?H functionalization sequence. The powerful iron catalysis occurred under external‐oxidant‐free conditions even at room temperature, while detailed mechanistic studies revealed an unprecedented 1,4‐iron migration regime for facile C?H activations. 相似文献
4.
Chase A. Salazar Joseph J. Gair Kaylin N. Flesch Ilia A. Guzei Jared C. Lewis Shannon S. Stahl 《Angewandte Chemie (International ed. in English)》2020,59(27):10873-10877
Mono‐N‐protected amino acids (MPAAs) are increasingly common ligands in Pd‐catalyzed C?H functionalization reactions. Previous studies have shown how these ligands accelerate catalytic turnover by facilitating the C?H activation step. Here, it is shown that MPAA ligands exhibit a second property commonly associated with ligand‐accelerated catalysis: the ability to support catalytic turnover at substoichiometric ligand‐to‐metal ratios. This catalytic role of the MPAA ligand is characterized in stoichiometric C?H activation and catalytic C?H functionalization reactions. Palladacycle formation with substrates bearing carboxylate and pyridine directing groups exhibit a 50–100‐fold increase in rate when only 0.05 equivalents of MPAA are present relative to PdII. These and other mechanistic data indicate that facile exchange between MPAAs and anionic ligands coordinated to PdII enables a single MPAA to support C?H activation at multiple PdII centers. 相似文献
5.
Manganese(I)‐Catalyzed C−H Activation: The Key Role of a 7‐Membered Manganacycle in H‐Transfer and Reductive Elimination 下载免费PDF全文
Dr. Nasiru P. Yahaya Kate M. Appleby Magdalene Teh Conrad Wagner Erik Troschke Joshua T. W. Bray Prof. Simon B. Duckett L. Anders Hammarback Dr. Jonathan S. Ward Jessica Milani Dr. Natalie E. Pridmore Dr. Adrian C. Whitwood Dr. Jason M. Lynam Prof. Ian J. S. Fairlamb 《Angewandte Chemie (International ed. in English)》2016,55(40):12455-12459
Manganese‐catalyzed C?H bond activation chemistry is emerging as a powerful and complementary method for molecular functionalization. A highly reactive seven‐membered MnI intermediate is detected and characterized that is effective for H‐transfer or reductive elimination to deliver alkenylated or pyridinium products, respectively. The two pathways are determined at MnI by judicious choice of an electron‐deficient 2‐pyrone substrate containing a 2‐pyridyl directing group, which undergoes regioselective C?H bond activation, serving as a valuable system for probing the mechanistic features of Mn C?H bond activation chemistry. 相似文献
6.
M. Lakshmi Kantam Chandrakanth Gadipelly Gunjan Deshmukh K. Rajender Reddy Suresh Bhargava 《Chemical record (New York, N.Y.)》2019,19(7):1302-1318
Activation of C?H bonds and their application in cross coupling chemistry has received a wider interest in recent years. The conventional strategy in cross coupling reaction involves the pre‐functionalization step of coupling reactants such as organic halides, pseudo‐halides and organometallic reagents. The C?H activation facilitates a simple and straight forward approach devoid of pre‐functionalization step. This approach also addresses the environmental and economical issues involved in several chemical reactions. In this account, we have reported C?H bond activation of small organic molecules, for example, formamide C?H bond can be activated and coupled with β‐dicarbonyl or 2‐carbonyl substituted phenols under oxidative conditions to yield carbamates using inexpensive copper catalysts. Phenyl carbamates were successfully synthesized in moderate to good yields by cross dehydrogenative coupling (CDC) of phenols with formamides using copper catalysts in presence of a ligand. We have also prepared unsymmetrical urea derivatives by oxidative cross coupling of formamides with amines using copper catalysts. Synthesis of N,N‐dimethyl substituted amides, 5‐substituted‐γ‐lactams and α‐acyloxy ethers was carried out from carboxylic acids using recyclable CuO nanoparticles. Copper nanoparticles afforded N‐aryl‐γ‐amino‐γ‐lactams by oxidative coupling of aromatic amines with 2‐pyrrolidinone. Reusable transition metal HT‐derived oxide catalyst was used for the synthesis of N,N‐dimethyl substituted amides by the oxidative cross‐coupling of carboxylic acids and substituted benzaldehydes. Overview of our work in this area is summarized. 相似文献
7.
Jeffrey A. Boerth Joshua R. Hummel Prof. Dr. Jonathan A. Ellman 《Angewandte Chemie (International ed. in English)》2016,55(41):12650-12654
A highly stereoselective three‐component C(sp2)?H bond addition across alkene and polarized π‐bonds is reported for which CoIII catalysis was shown to be much more effective than RhIII. The reaction proceeds at ambient temperature with both aryl and alkyl enones employed as efficient coupling partners. Moreover, the reaction exhibits extremely broad scope with respect to the aldehyde input; electron rich and poor aromatic, alkenyl, and branched and unbranched alkyl aldehydes all couple in good yield and with high diastereoselectivity. Multiple directing groups participate in this transformation, including pyrazole, pyridine, and imine functional groups. Both aromatic and alkenyl C(sp2)?H bonds undergo the three‐component addition cascade, and the alkenyl addition product can readily be converted into diastereomerically pure five‐membered lactones. Additionally, the first asymmetric reactions with CoIII‐catalyzed C?H functionalization are demonstrated with three‐component C?H bond addition cascades employing N‐tert‐butanesulfinyl imines. These examples represent the first transition metal catalyzed C?H bond additions to N‐tert‐butanesulfinyl imines, which are versatile and extensively used intermediates for the asymmetric synthesis of amines. 相似文献
8.
Dr. Martin Pichette Drapeau Prof. Dr. Lukas J. Gooßen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(52):18654-18677
The selective transformation of C?H bonds is one of the most desirable approaches to creating complexity from simple building blocks. Several directing groups are efficient in controlling the regioselectivity of catalytic C?H bond functionalizations. Among them, carboxylic acids are particularly advantageous, since they are widely available in great structural diversity and at low cost. The carboxylate directing groups can be tracelessly cleaved or may serve as the anchor point for further functionalization through decarboxylative couplings. This Minireview summarizes the substantial progress made in the last few years in the development of reactions in which carboxylate groups direct C?H bond functionalizations with formation of C?C, C?O, C?N, or C?halogen bonds at specific positions. It is divided into sections on C?C, C?O, C?N, and C?halogen bond formation, each of which is subdivided by reactions and product classes. Particular emphasis is placed on methods that enable multiple derivatizations by combining carboxylate‐directed C?H functionalization with decarboxylative couplings. 相似文献
9.
Jompol Thongpaen Romane Manguin Olivier Basl 《Angewandte Chemie (International ed. in English)》2020,59(26):10242-10251
The asymmetric functionalization of C?H bond is a particularly valuable approach for the production of enantioenriched chiral organic compounds. Chiral N‐heterocyclic carbene (NHC) ligands have become ubiquitous in enantioselective transition‐metal catalysis. Conversely, the use of chiral NHC ligands in metal‐catalyzed asymmetric C?H bond functionalization is still at an early stage. This minireview highlights all the developments and the new advances in this rapidly evolving research area. 相似文献
10.
Dr. Youai Qiu Cong Tian Leonardo Massignan Torben Rogge Prof. Dr. Lutz Ackermann 《Angewandte Chemie (International ed. in English)》2018,57(20):5818-5822
Electrocatalysis has been identified as a powerful strategy for organometallic catalysis, and yet electrocatalytic C?H activation is restricted to strongly N‐coordinating directing groups. The first example of electrocatalytic C?H activation by weak O‐coordination is presented, in which a versatile ruthenium(II) carboxylate catalyst enables electrooxidative C?H/O?H functionalization for alkyne annulations in the absence of metal oxidants; thereby exploiting sustainable electricity as the sole oxidant. Mechanistic insights provide strong support for a facile organometallic C?H ruthenation and an effective electrochemical reoxidation of the key ruthenium(0) intermediate. 相似文献
11.
Iron(II)‐Catalyzed Site‐Selective Functionalization of Unactivated C(sp3)−H Bonds Guided by Alkoxyl Radicals 下载免费PDF全文
Honghao Guan Shutao Sun Ying Mao Lei Chen Ran Lu Jiancheng Huang Prof. Dr. Lei Liu 《Angewandte Chemie (International ed. in English)》2018,57(35):11413-11417
An alkoxyl radical guided strategy for site‐selective functionalization of unactivated methylene and methine C?H bonds enabled by an FeII‐catalyzed redox process is described. The mild, expeditious, and modular protocol allows efficient remote aliphatic fluorination, chlorination, amination, and alkynylation of structurally and electronically varied primary, secondary, and tertiary hydroperoxides with excellent functional‐group tolerance. The application for one‐pot 1,4‐hydroxyl functionalization of non‐oxygenated alkane substrates initiated by aerobic C?H oxygenation is also demonstrated. 相似文献
12.
Complementary Strategies for Directed C(sp3)−H Functionalization: A Comparison of Transition‐Metal‐Catalyzed Activation,Hydrogen Atom Transfer,and Carbene/Nitrene Transfer 下载免费PDF全文
John C. K. Chu Prof. Tomislav Rovis 《Angewandte Chemie (International ed. in English)》2018,57(1):62-101
The functionalization of C(sp3)?H bonds streamlines chemical synthesis by allowing the use of simple molecules and providing novel synthetic disconnections. Intensive recent efforts in the development of new reactions based on C?H functionalization have led to its wider adoption across a range of research areas. This Review discusses the strengths and weaknesses of three main approaches: transition‐metal‐catalyzed C?H activation, 1,n‐hydrogen atom transfer, and transition‐metal‐catalyzed carbene/nitrene transfer, for the directed functionalization of unactivated C(sp3)?H bonds. For each strategy, the scope, the reactivity of different C?H bonds, the position of the reacting C?H bonds relative to the directing group, and stereochemical outcomes are illustrated with examples in the literature. The aim of this Review is to provide guidance for the use of C?H functionalization reactions and inspire future research in this area. 相似文献
13.
Comparison of the Reactivities and Selectivities of Group 9 [Cp*MIII] Catalysts in C−H Functionalization Reactions 下载免费PDF全文
Pentamethylcyclopentadienyl (Cp*)‐based Group 9 metal (Co, Rh, or Ir) catalysts have emerged as powerful tools for C?H functionalization reactions. Whilst a diverse range of organic transformations have been developed by using [Cp*MIII] catalysts, they have often exhibited orthogonal reactivities and varied selectivities that depended on the choice of the central metal atom. An understanding of the physicochemical properties of the metals, as well as of their reaction mechanisms, has led to significant expansion of the synthetic scope of C?H functionalization reactions. This Focus Review summarizes and discusses the comparative catalytic reactivities and selectivities of the [Cp*MIII] catalysts, with an emphasis on metal‐dependent pathway‐switching by considering the mechanistic rationale. 相似文献
14.
In recent years, transition‐metal‐catalyzed C?H activation has become a key strategy in the field of organic synthesis. Rhodium complexes are widely used as catalysts in a variety of C?H functionalization reactions because of their high reactivity and selectivity. The availability of a number of rhodium complexes in various oxidation states enables diverse reaction patterns to be obtained. Regioselectivity, an important issue in C?H activation chemistry, can be accomplished by using a directing group to assist the reaction. However, to obtain the target functionalized compounds, it is also necessary to use a directing group that can be easily removed. A wide range of directed C?H functionalization reactions catalyzed by rhodium complexes have been reported to date. In this Review, we discuss Rh‐catalyzed C?H functionalization reactions that are aided by the use of a removable directing group such as phenol, amine, aldehyde, ketones, ester, acid, sulfonic acid, and N‐heteroaromatic derivatives. 相似文献
15.
A General Approach to Site‐Specific,Intramolecular C−H Functionalization Using Dithiocarbamates 下载免费PDF全文
Christina G. Na Prof. Erik J. Alexanian 《Angewandte Chemie (International ed. in English)》2018,57(40):13106-13109
Intramolecular hydrogen atom transfer is an established approach for the site‐specific functionalization of unactivated, aliphatic C?H bonds. Transformations using this strategy typically require unstable intermediates formed using strong oxidants and have mainly targeted C?H halogenations or intramolecular aminations. Herein, we report a site‐specific C?H functionalization that significantly increases the synthetic scope and convergency of reactions proceeding via intramolecular hydrogen atom transfer. Stable, isolable N‐dithiocarbamates are used as precursors to amidyl radicals formed via either light or radical initiation to efficiently deliver highly versatile alkyl dithiocarbamates across a wide range of complex structures. 相似文献
16.
Dr. Jun Xu Dr. Chao Shen Dr. Xiaolei Zhu Prof. Pengfei Zhang Dr. Manjaly J. Ajitha Prof. Kuo‐Wei Huang Dr. Zhongfu An Prof. Xiaogang Liu 《化学:亚洲杂志》2016,11(6):882-892
Achieving site selectivity in carbon–hydrogen (C?H) functionalization reactions is a formidable challenge in organic chemistry. Herein, we report a novel approach to activating remote C?H bonds at the C5 position of 8‐aminoquinoline through copper‐catalyzed sulfonylation under mild conditions. Our strategy shows high conversion efficiency, a broad substrate scope, and good toleration with different functional groups. Furthermore, our mechanistic investigations suggest that a single‐electron‐transfer process plays a vital role in generating sulfonyl radicals and subsequently initiating C?S cross‐coupling. Importantly, our copper‐catalyzed remote functionalization protocol can be expanded for the construction of a variety of chemical bonds, including C?O, C?Br, C?N, C?C, and C?I. These findings provide a fundamental insight into the activation of remote C?H bonds, while offering new possibilities for rational design of drug molecules and optoelectronic materials requiring specific modification of functional groups. 相似文献
17.
Rhodium(III)‐Catalyzed Alkenylation–Annulation of closo‐Dodecaborate Anions through Double B−H Activation at Room Temperature 下载免费PDF全文
Yuanbin Zhang Yuji Sun Furong Lin Jiyong Liu Dr. Simon Duttwyler 《Angewandte Chemie (International ed. in English)》2016,55(50):15609-15614
1,2,3‐Trisubstituted closo‐dodecaborates with B?O, B?N, and B?C bonds as well as a fused borane oxazole ring have been synthesized by rhodium‐catalyzed direct cage B?H alkenylation and annulation of ureido boranes in the first reported example of regioselective B?H bond functionalization of the [B12H12]2? cage by transition‐metal catalysis. This reaction proceeded at room temperature under ambient conditions and exhibited excellent selectivity for efficient monoalkenylation with good functional‐group tolerance. The urea moiety enabled B?H activation by acting as a directing group, was incorporated in the oxazole ring in situ, and also avoided multiple alkenylation. A possible mechanism is proposed on the basis of the isolation of a rhodium agostic intermediate and control experiments. 相似文献
18.
Parthasarathy Gandeepan Julian Koeller Korkit Korvorapun Jens Mohr Lutz Ackermann 《Angewandte Chemie (International ed. in English)》2019,58(29):9820-9825
Visible‐light‐induced ruthenium catalysis has enabled remote C?H alkylations with excellent levels of position control under exceedingly mild conditions at room temperature. The metallaphotocatalysis occurred under exogenous‐photosensitizer‐free conditions and features an ample substrate scope. The robust nature of the photo‐induced mild meta‐C?H functionalization is reflected by the broad functional group tolerance, and the reaction can be carried out in an operationally simple manner, setting the stage for challenging secondary and tertiary meta‐C?H alkylations by ruthenaphotoredox catalysis. 相似文献
19.
Iron and Manganese Catalysts for the Selective Functionalization of Arene C(sp2)−H Bonds by Carbene Insertion 下载免费PDF全文
Dr. Ana Conde Gerard Sabenya Mònica Rodríguez Verònica Postils Dr. Josep M. Luis Dr. M. Mar Díaz‐Requejo Dr. Miquel Costas Prof. Dr. Pedro J. Pérez 《Angewandte Chemie (International ed. in English)》2016,55(22):6530-6534
The first examples of the direct functionalization of non‐activated aryl sp2 C?H bonds with ethyl diazoacetate (N2CHCO2Et) catalyzed by Mn‐ or Fe‐based complexes in a completely selective manner are reported, with no formation of the frequently observed cycloheptatriene derivatives through competing Buchner reaction. The best catalysts are FeII or MnII complexes bearing the tetradentate pytacn ligand (pytacn= 1‐(2‐pyridylmethyl)‐4,7‐dimethyl‐1,4,7‐triazacyclononane). When using alkylbenzenes, the alkylic C(sp3)?H bonds of the substituents remained unmodified, thus the reaction being also selective toward functionalization of sp2 C?H bonds. 相似文献
20.
Recent Trends in Copper‐Catalyzed C−H Amination Routes to Biologically Important Nitrogen Scaffolds 下载免费PDF全文
Parthasarathi Subramanian Dr. Georg C. Rudolf Prof. Dr. Krishna P. Kaliappan 《化学:亚洲杂志》2016,11(2):168-192
Nitrogen‐containing heterocycles have found remarkable applications in natural product research, material sciences, and pharmaceuticals. Although the synthesis of this interesting class of compounds attracted the interest of generations of organic chemists, simple and straightforward assembly methods based on transition‐metal catalysis have regularly been elusive. The recent advancements in the development of C?H functionalization have helped in accomplishing the synthesis of a variety of complex heterocycles from simple precursors. This Focus Review summarizes the recent advances in one particular field: the copper‐catalyzed C?N bond formation reactions via C?H bond functionalization to furnish a comprehensive range of nitrogen heterocycles. Applicability and synthetic feasibility of a particular reaction represent major requirements for the inclusion in this review. 相似文献