Remarkably Selective Iridium Catalysts for the Elaboration of Aromatic C-H Bonds
11 Jan 2002-Science (American Association for the Advancement of Science)-Vol. 295, Iss: 5553, pp 305-308
TL;DR: A family of Ir catalysts now enables the direct synthesis of arylboron compounds from aromatic hydrocarbons and boranes under “solventless” conditions because they are highly selective for C–H activation and do not interfere with subsequent in situ transformations, including Pd-mediated cross-couplings with aryL halides.
Abstract: Arylboron compounds have intriguing properties and are important building blocks for chemical synthesis. A family of Ir catalysts now enables the direct synthesis of arylboron compounds from aromatic hydrocarbons and boranes under "solventless" conditions. The Ir catalysts are highly selective for C-H activation and do not interfere with subsequent in situ transformations, including Pd-mediated cross-couplings with aryl halides. By virtue of their favorable activities and exceptional selectivities, these Ir catalysts impart the synthetic versatility of arylboron reagents to C-H bonds in aromatic and heteroaromatic hydrocarbons.
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TL;DR: A review of palladium-catalyzed coupling of CH bonds with organometallic reagents through a PdII/Pd0 catalytic cycle can be found in this paper.
Abstract: Pick your Pd partners: A number of catalytic systems have been developed for palladium-catalyzed CH activation/CC bond formation. Recent studies concerning the palladium(II)-catalyzed coupling of CH bonds with organometallic reagents through a PdII/Pd0 catalytic cycle are discussed (see scheme), and the versatility and practicality of this new mode of catalysis are presented. Unaddressed questions and the potential for development in the field are also addressed.
In the past decade, palladium-catalyzed CH activation/CC bond-forming reactions have emerged as promising new catalytic transformations; however, development in this field is still at an early stage compared to the state of the art in cross-coupling reactions using aryl and alkyl halides. This Review begins with a brief introduction of four extensively investigated modes of catalysis for forming CC bonds from CH bonds: PdII/Pd0, PdII/PdIV, Pd0/PdII/PdIV, and Pd0/PdII catalysis. A more detailed discussion is then directed towards the recent development of palladium(II)-catalyzed coupling of CH bonds with organometallic reagents through a PdII/Pd0 catalytic cycle. Despite the progress made to date, improving the versatility and practicality of this new reaction remains a tremendous challenge.
3,533 citations
TL;DR: This Review provides an overview of C-H bond functionalization strategies for the rapid synthesis of biologically active compounds such as natural products and pharmaceutical targets.
Abstract: The direct functionalization of C-H bonds in organic compounds has recently emerged as a powerful and ideal method for the formation of carbon-carbon and carbon-heteroatom bonds. This Review provides an overview of C-H bond functionalization strategies for the rapid synthesis of biologically active compounds such as natural products and pharmaceutical targets.
2,391 citations
TL;DR: Investigations revealed that the conversion of C-H bonds to C-B bonds was both thermodynamically and kinetically favorable and highlighted the accessible barriers for C- H bond cleavage and B-C bond formation during the borylation of alkanes and arenes.
Abstract: A number of studies were conducted to demonstrate C-H activation for the construction of C-B bonds. Investigations revealed that the conversion of C-H bonds to C-B bonds was both thermodynamically and kinetically favorable. The reaction at a primary C-H bond of methane or a higher alkene B 2(OR)4 formed an alkylboronate ester R' -B(OR)2 and the accompanying borane H-B(OR2. The ester and the borane were formed on the basis of calculated bond energies for methylboronates and dioaborolanes. The rates of key steps along the reaction pathway for the conversion of a C-H bond in an alkane or arene to the C-B bond in an alkyl or arylboronate ester were favorable. These studies also highlighted the accessible barriers for C-H bond cleavage and B-C bond formation during the borylation of alkanes and arenes.
2,108 citations
TL;DR: In this paper, the functionalization of C-H bonds in complex organic substrates catalyzed by transition metal catalysts is studied and the key concepts and approaches aimed at achieving selectivity in complex settings are discussed.
Abstract: Direct and selective replacement of carbon-hydrogen bonds with new bonds (such as C-C, C-O, and C-N) represents an important and long-standing goal in chemistry. These transformations have broad potential in synthesis because C-H bonds are ubiquitous in organic substances. At the same time, achieving selectivity among many different C-H bonds remains a challenge. Here, we focus on the functionalization of C-H bonds in complex organic substrates catalyzed by transition metal catalysts. We outline the key concepts and approaches aimed at achieving selectivity in complex settings and discuss the impact these reactions have on synthetic planning and strategy in organic synthesis.
1,812 citations
TL;DR: A general method for directing-group-containing arene arylation by aryl iodides is developed and palladium acetate as the catalyst, which arylated anilides, benzamides, benzoic acids, benzylamines, and 2-substituted pyridine derivatives under nearly identical conditions.
Abstract: The transition-metal-catalyzed functionalization of C-H bonds is a powerful method for generating carbon-carbon bonds. Although significant advances to this field have been reported during the past decade, many challenges remain. First, most of the methods are substrate-specific and thus cannot be generalized. Second, conversions of unactivated (i.e., not benzylic or alpha to heteroatom) sp(3) C-H bonds to C-C bonds are rare, with most examples limited to t-butyl groups, a conversion that is inherently simple because there are no beta-hydrogens that can be eliminated. Finally, the palladium, rhodium, and ruthenium catalysts routinely used for the conversion of C-H bonds to C-C bonds are expensive. Catalytically active metals that are cheaper and less exotic (e.g., copper, iron, and manganese) are rarely used. This Account describes our attempts to provide solutions to these three problems. We have developed a general method for directing-group-containing arene arylation by aryl iodides. Using palladium acetate as the catalyst, we arylated anilides, benzamides, benzoic acids, benzylamines, and 2-substituted pyridine derivatives under nearly identical conditions. We have also developed a method for the palladium-catalyzed auxiliary-assisted arylation of unactivated sp(3) C-H bonds. This procedure allows for the beta-arylation of carboxylic acid derivatives and the gamma-arylation of amine derivatives. Furthermore, copper catalysis can be used to mediate the arylation of acidic arene C-H bonds (i.e., those with pK(a) values <35 in DMSO). Using a copper iodide catalyst in combination with a base and a phenanthroline ligand, we successfully arylated electron-rich and electron-deficient heterocycles and electron-poor arenes possessing at least two electron-withdrawing groups. The reaction exhibits unusual regioselectivity: arylation occurs at the most hindered position. This copper-catalyzed method supplements the well-known C-H activation/borylation methodology, in which functionalization usually occurs at the least hindered position. We also describe preliminary investigations to determine the mechanisms of these transformations. We anticipate that other transition metals, including iron, nickel, cobalt, and silver, will also be able to facilitate deprotonation/arylation reaction sequences.
1,747 citations
References
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25 Aug 2004
TL;DR: In this paper, the authors present an approach to the formation of C-X (X = N, O, S) bonds in metal-catalyzed cross-coupling reactions.
Abstract: Preface.List of Contributors.1 Mechanistic Aspects of Metal-Catalyzed C,C- and C,X-Bond-Forming Reactions (Antonio M. Echavarren and Diego J. Cardenas).1.1 Mechanisms of Cross-Coupling Reactions.1.2 Formation of C,C-Bonds in the Palladium-Catalyzed alpha-Arylation of Carbonyl Compounds and Nitriles.1.3 Key Intermediates in the Formation of C-X (X = N, O, S) bonds in Metal-Catalyzed Reactions 251.3.1 Reductive Elimination of C-N, C-O, and C-S Bonds From Organopalladium(II) Complexes.1.4 Summary and Outlook.Abbreviations.References.2 Metal-Catalyzed Cross-Coupling Reactions of Organoboron Compounds with Organic Halides (Norio Miyaura).2.1 Introduction.2.2 Advances in the Synthesis of Organoboron Compounds.2.3 Reaction Mechanism.2.4 Reaction Conditions.2.5 Side Reactions.2.6 Reactions of B-Alkyl Compounds.2.7 Reactions of B-Alkenyl Compounds.2.8 Reactions of B-Aryl Compounds.2.9 Reactions of B-Allyl and B-Alkynyl Compounds.2.10 Reactions Giving Ketones.2.11 Dimerization of Arylboronic Acids.2.12 N-, O-, and S-Arylation.Abbreviations.References.3 Organotin Reagents in Cross-Coupling Reactions (Terence N. Mitchell).3.1 Introduction.3.2 Mechanism and Methodology.3.3 Natural Product Synthesis.3.4 Organic Synthesis.3.5 Polymer Chemistry.3.6 Inorganic Synthesis.3.7 Conclusions.3.8 Experimental Procedures.Abbreviations.References.4 Organosilicon Compounds in Cross-Coupling Reactions (Scott E. Denmark and Ramzi F. Sweis).4.1 Introduction.4.2 Modern Organosilicon-Cross-Coupling.4.3 Mechanistic Studies in Silicon-Cross-Coupling.4.4 Applications to Total Synthesis.4.5 Summary and Outlook.4.6 Experimental Procedures.Abbreviations.References.5 Cross-Coupling of Organyl Halides with Alkenes: The Heck Reaction (Stefan Brase and Armin de Meijere).5.1 Introduction.5.2 Principles.5.3 Cascade Reactions and Multiple Couplings.5.4 Related Palladium-Catalyzed Reactions.5.5 Enantioselective Heck-Type Reactions.5.6 Syntheses of Heterocycles, Natural Products and Other Biologically Active Compounds Applying Heck Reactions.5.7 Carbopalladation Reactions in Solid-Phase Syntheses.5.8 The Heck Reaction in Fine Chemicals Syntheses.5.9 Conclusions.5.10 Experimental Procedures.Acknowledgments.Abbreviations and Acronyms.References.6 Cross-Coupling Reactions to sp Carbon Atoms (Jeremiah A. Marsden and Michael M. Haley).6.1 Introduction.6.2 Alkynylcopper Reagents.6.3 Alkynyltin Reagents.6.4 Alkynylzinc Reagents.6.5 Alkynylboron Reagents.6.6 Alkynylsilicon Reagents.6.7 Alkynylmagnesium Reagents.6.8 Other Alkynylmetals.6.9 Concluding Remarks.6.10 Experimental Procedures.Acknowledgments.Abbreviations and Acronyms.References.7 Carbometallation Reactions (Ilan Marek, Nicka Chinkov, and Daniella Banon-Tenne).7.1 Introduction.7.2 Carbometallation Reactions of Alkynes.7.3 Carbometallation Reactions of Alkenes.7.4 Zinc-Enolate Carbometallation Reactions.7.5 Carbometallation Reactions of Dienes and Enynes.7.6 Carbometallation Reactions of Allenes.7.7 Conclusions.7.8 Experimental Procedures.Acknowledgments.References.8 Palladium-Catalyzed 1,4-Additions to Conjugated Dienes (Jan-E. Backvall).8.1 Introduction.8.2 Palladium(0)-Catalyzed Reactions.8.3 Palladium(II)-Catalyzed Reactions.References.9 Cross-Coupling Reactions via PI-Allylmetal Intermediates (Uli Kazmaier and Matthias Pohlman)9.1 Introduction.9.2 Palladium-Catalyzed Allylic Alkylations.9.3 Allylic Alkylations with Other Transition Metals.9.4 Experimental Procedures.Abbreviations.References.10 Palladium-Catalyzed Coupling Reactions of Propargyl Compounds (Jiro Tsuji and Tadakatsu Mandai).10.1 Introduction.10.2 Classification of Pd-Catalyzed Coupling Reactions of Propargyl Compounds.10.3 Reactions with Insertion into the sp2 Carbon Bond of Allenylpalladium Intermediates (Type I).10.4 Transformations via Transmetallation of Allenylpalladium Intermediates and Related Reactions (Type II).10.5 Reactions with Attack of Soft Carbon and Oxo Nucleophiles on the sp-Carbon of Allenylpalladium Intermediates (Type III).10.6 Experimental Procedures.Abbreviations.References.11 Carbon-Carbon Bond-Forming Reactions Mediated by Organozinc Reagents (Paul Knochel, M. Isabel Calaza, and Eike Hupe).11.1 Introduction.11.2 Methods of Preparation of Zinc Organometallics.11.3 Uncatalyzed Cross-Coupling Reactions.11.4 Copper-Catalyzed Cross-Coupling Reactions.11.5 Transition Metal-Catalyzed Cross-Coupling Reactions.11.6 Conclusions.11.7 Experimental Procedures.Abbreviations.References.12 Carbon-Carbon Bond-Forming Reactions Mediated by Organomagnesium Reagents (Paul Knochel, Ioannis Sapountzis, and Nina Gommermann).12.1 Introduction.12.2 Preparation of Polyfunctionalized Organomagnesium Reagents via a Halogen-Magnesium Exchange.12.3 Conclusions.12.4 Experimental Procedures.References.13 Palladium-Catalyzed Aromatic Carbon-Nitrogen Bond Formation (Lei Jiang and Stephen L. Buchwald).13.1 Introduction.13.2 Mechanistic Studies.13.3 General Features.13.4 Palladium-Catalyzed C-N Bond Formation.13.5 Vinylation.13.6 Amination On Solid Support.13.7 Conclusion.13.8 Representative Experimental Procedures.References.14 The Directed ortho-Metallation (DoM) Cross-Coupling Nexus. Synthetic Methodology for the Formation of Aryl-Aryl and Aryl-Heteroatom-Aryl Bonds (Eric J.-G. Anctil and Victor Snieckus).14.1 Introduction.14.2 The Aim of this Chapter.14.3 Synthetic Methodology derived from the DoM-Cross-Coupling Nexus.14.4 Applications of DoM in Synthesis.14.5 Conclusions and Prognosis.14.6 Selected Experimental Procedures.Abbreviations.References and Notes.15 Palladium- or Nickel-Catalyzed Cross-Coupling with Organometals Containing Zinc, Aluminum, and Zirconium: The Negishi Coupling (Ei-ichi Negishi, Xingzhong Zeng, Ze Tan, Mingxing Qian, Qian Hu, and Zhihong Huang).15.1 Introduction and General Discussion of Changeable Parameters.15.2 Recent Developments in the Negishi Coupling and Related Pd- or Ni-Catalyzed Cross-Coupling Reactions.15.3 Summary and Conclusions.15.4 Representative Experimental Procedures.References.Index.
4,387 citations
TL;DR: The palladium-catalyzed cross-coupling reaction between organoboron compounds and organic halides or triflates provides a powerful and general methodology for the formation of carbon-carbon bonds as discussed by the authors.
2,712 citations
TL;DR: The transition metal-catalyzed reactions of organometallics with organic halides have been extensively studied to prove a new approach to selective formation of carbon-carbon bonds as mentioned in this paper.
1,703 citations
TL;DR: The rhodium complex Cp*Rh(eta(4)-C(6)Me(6)) (Cp*, C(5)Me (5); Me, methyl) catalyzes the high-yield formation of linear alkylboranes from commercially available borane reagents under thermal conditions.
Abstract: The formation of a single product from terminal functionalization of linear alkanes from a transition metal-catalyzed reaction is reported. The rhodium complex Cp*Rh(eta(4)-C(6)Me(6)) (Cp*, C(5)Me(5); Me, methyl) catalyzes the high-yield formation of linear alkylboranes from commercially available borane reagents under thermal conditions. These reactions now allow catalytic, regiospecific functionalization of alkanes under thermal conditions. The organoborane products are among the most versatile synthetic intermediates in chemistry and serve as convenient precursors to alcohols, amines, and other common classes of functionalized molecules.
745 citations
TL;DR: In this paper, a comparative evaluation of the relative equilibrium constants and rates of reaction for both alkane and arene hydrocarbon activation has been provided for the first time, based on a series of homogeneous rhodium organometallic complexes.
Abstract: Alkanes are among the most abundant and unreactive of all organic compounds. Industrial use of these resources often relies upon free-radical activation of carbon-hydrogen bonds, often at high temperatures, thereby limiting the selectivities that can be achieved in any functionalization reaction. Consequently, the selective activation of C-H bonds by homogeneous transition-metal compounds has been a topic that has been of great interest to the organometallic community for many years. In this Account, mechanistic studies with a series of homogeneous rhodium organometallic complexes are summarized that provide for the first time a comparative evaluation of the relative equilibrium constants and rates of reaction for both alkane and arene hydrocarbon activation.
407 citations