Showing papers on "Heck reaction published in 2004"

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.

High‐Turnover Palladium Catalysts in Cross‐Coupling and Heck Chemistry: A Critical Overview

Abstract: This review discusses the problems associated with developing high-turnover catalysts for the cross-coupling and Heck reactions. New developments in the area, principally constituted by palladacycles and coordinatively unsaturated Pd catalysts featuring bulky phosphanes of high donicity, are reviewed from a mechanistic and synthetic standpoint, and compared with more traditional catalysts obtained from conventional mono- and polydentate N- and P-based ligands, as well as Pd catalysts without strong ligands, such as Pd colloids or heterogeneous catalysts. Carbene ligands are also briefly presented. Whereas a single, most promising approach to high-turnover Pd catalysis cannot presently be defined, it is clear that the new “PdL1” catalysts (where L1 is a monodentate bulky P ligand of high donicity) represent the latest, most important development in Pd research, certainly from the standpoint of scope and probably also from the standpoint of efficiency. High turnovers with these catalysts have been described and their use will certainly increase in the next few years. The review ends with a brief discussion containing practical considerations on how to choose a high TON catalyst for a given Heck or cross-coupling reaction of interest.

Nitrile-functionalized pyridinium ionic liquids: Synthesis, characterization, and their application in carbon-carbon coupling reactions

Abstract: A series of relatively low-cost ionic liquids, based on the N-butyronitrile pyridinium cation [C(3)CNpy](+), designed to improve catalyst retention, have been prepared and evaluated in Suzuki and Stille coupling reactions. Depending on the nature of the anion, these salts react with palladium chloride to form [C(3)CNpy](2)[PdCl(4)] when the anion is Cl(-) and complexes of the formula [PdCl(2)(C(3)CNpy)(2)][anion](2) when the anion is PF(6)(-), BF(4)(-), or N(SO(2)CF(3))(2)(-). The solid-state structures of [C(3)CNpy]Cl and [C(3)CNpy](2)[PdCl(4)] have been established by single-crystal X-ray diffraction. The catalytic activity of these palladium complexes following immobilization in both N-butylpyridinium and nitrile-functionalized ionic liquids has been evaluated in Suzuki and Stille coupling reactions. All of the palladium complexes show good catalytic activity, but recycling and reuse is considerably superior in the nitrile-functionalized ionic liquid. Inductive coupled plasma spectroscopy reveals that the presence of the coordinating nitrile moiety in the ionic liquid leads to a significant decrease in palladium leaching relative to simple N-alkylpyridinium ionic liquids. Palladium nanoparticles have been identified as the active catalyst in the Stille reaction and were characterized using transmission electron microscopy.

Asymmetric Heck Reaction

Abstract: The asymmetric Heck reaction is a powerful method for the synthesis of both tertiary and quaternary chiral carbon centers, with an enantiomeric excess often greater than 80%, and in some cases much higher (up to 99% ee). A variety of carbocyclic and heterocyclic systems can be constructed, including spirocyclic systems. The scope of the reaction with respect to the product alkene isomerization is somewhat limited by problems of regioselectivity, however, these problems are surmountable, and a new generation of ligands that dissociate more rapidly from the products, might improve both enantio- and regiocontrol. A variety of chiral compounds prepared by the asymmetric Heck reaction were successfully utilized in the enantioselective syntheses of complex natural products.

Aqueous-phase, palladium-catalyzed cross-coupling of aryl bromides under mild conditions, using water-soluble, sterically demanding alkylphosphines.

Abstract: Sterically demanding, water-soluble alkylphosphines have been used in combination with various palladium salts in Suzuki, Sonogashira, and Heck couplings of aryl bromides under mild conditions in aqueous solvents. The tert-butyl-substituted ligands 2-(di-tert-butylphosphino)ethyltrimethylammonium chloride (t-Bu-Amphos) and 4-(di-tert-butylphosphino)-N,N-dimethylpiperidinium chloride (t-Bu-Pip-phos) in combination with palladium(II) salts were found to give catalysts that were significantly more active than catalysts derived from tri(3-sulfonatophenyl)phosphine trisodium (TPPTS). Suzuki couplings of unactivated aryl bromides occurred efficiently at room temperature in water/acetonitrile and water/toluene biphasic mixtures or in neat water. Notably, Suzuki couplings of hydrophilic aryl bromides gave high yields without using organic solvents for the reaction or purification. This methodology has been applied to a highly efficient synthesis of diflunisal. The catalyst derived from t-Bu-Amphos was recycled th...

Catalytic Signal Amplification Using a Heck Reaction. An Example in the Fluorescence Sensing of Cu(II)

Abstract: Catalytic signal enhancement using an organometallic reaction is demonstrated. The reactivity of a Heck cross-coupling reaction that creates a fluorophore is modulated by the addition of a polyazacyclam inhibitor. The inhibitor will complex with Cu(II), which restores the activity of the Pd(II). The addition of Cu(II) therefore leads to the generation of fluorescence, thereby creating a very sensitive assay for Cu(II). The rate of the Heck reaction is followed by monitoring emission as a function of time. The rate is proportional to the Cu(II) concentration and correlates to the affinity of the inhibitor to various metals. This strategy represents a general technique that can be exploited with other catalytic organometallic reactions.

Homogeneous Catalysis: Understanding the Art

Abstract: Preface- Acknowledgements- 1: Introduction- 11 Catalysis 12 Homogeneous catalysis 13 Historical notes on homogeneous catalysis 14 Characterization of the catalyst 15 Ligand effects 16 Ligands according to donor atoms 2: Elementary Steps- 21 Creation of a 'vacant' site and co-ordination of the substrate 22 Insertion versus migration 23 beta-Elimination and de-insertion 24 Oxidative addition 25 Reductive elimination 26 alpha-Elimination reactions 27 Cycloaddition reactions involving a metal 28 Activation of a substrate toward nucleophilic attack 29 sigma-Bond metathesis 210 Dihydrogen activation 211 Activation by Lewis acids 212 Carbon-to-phosphorus bond breaking 213 Carbon-to-sulfur bond breaking 214 Radical reactions 3: Kinetics- 31 Introduction 32 Two-step reaction scheme 33 Simplifications of the rate equation and the rete-determining step 34 Determining the selectivity 35 Collection of rate data 36 Irregularities in catalysis 4: Hydrogenation- 41 Wilkinson's catalyst 42 Asymmetric hydrogenation 43 Overview of chiral bidentate ligands 44 Monodentate ligands 45 Non-linear effects 46 Hydrogen transfer 5: Isomerisation- 51 Hydrogen shifts 52 Asymmetric isomerisation 53 Oxygen shifts 6: Carbonylation of Methanol and Methyl Acetate- 61 Acetic acid 62 Process scheme Monsanto process 63 Acetic anhydride 64 Other systems 7: Cobalt Catalysed Hydroformylation- 71 Introduction 72 Thermodynamics 73 Cobalt catalysed processes 74 Cobalt catalysed processes for higher alkenes 75 Kuhlmann cobalt hydroformylation process 76 Phosphine modified cobalt catalysts: the shell process 77 Cobalt carbonyl phosphine complexes 8: Rhodium Catalysed Hydroformylation- 81 Introduction 82 Triphenylphosphine asthe ligand 83 Diphosphines as ligands 84 Phosphites as ligands 85 Diphosphites 86 Asymmetric hydroformylation 9: Alkene Oligomerisation- 91 Introduction 92 Shell-higher-olefins-process 93 Ethene trimerisation 94 Other alkene oligomerisation reactions 10: Propene Polymerisation- 101 Introduction to polymer chemistry 102 Mechanistic investigations 103 Analysis by 13CNMR spectroscopy 104 The development of metallocene catalysts 105 Agostic interactions 106 The effect of dihydrogen 107 Further work using propene and other alkenes 108 Non-metallocene ETM catalysts 109 Late transition metal catalysts 11: Hydrocyanation of Alkenes- 111 The adiponitrile process 112 Ligand effects 12: Palladium Catalysed Carbonylations of Alkenes- 121 Introduction 122 Polyketone 123 Ligand effects on chain length 124 Ethene/propene/CO terpolymers 125 Stereoselective styrene/CO terpolymers 13: Palladium Catalysed Cross-Coupling Reactions- 131 Introduction 132 Allylic reaction 133 Heck reaction 134 Cross-coupling reaction 135 Heteroatom-carbon bond formation 136 Suzuki reaction 14: Epoxidation- 141 Ethene and propene oxide 142 Asymmetric epoxidation 143 Asymmetric hydroxilation of alkenes with osmium tetroxide 144 Jacobsen asymmetric ring-opening of epoxides 145 Epoxidations with dioxygen 15: Oxydation with Dioxygen- 151 Introduction 152 The Wacker reaction 153 Wacker type reactions 154 Terephthalic acid 155 PPO 16: Alkene Metathesis- 161 Introduction 162 The mechanism 163 Reaction overview 164 Well-characterised tungsten and molybdenum catalysts 165 Ruthenium catalysts 166 Stereochemistry 167 Catalyst decomposition 168 Alkynes 169 Industrial applications 17: Enantioselective Cyclopropanation-

Pd-catalyzed alkyl to aryl migration and cyclization: an efficient synthesis of fused polycycles via multiple C-H activation.

Abstract: A novel palladium migration methodology for the synthesis of complex fused polycycles has been developed. This process involves 1,4-palladium alkyl to aryl migrations via through-space C−H activation, followed by intramolecular arylation or an intermolecular Heck reaction providing a very efficient way to synthesize fused ring systems.

A New Tridentate Pincer Phosphine/N-Heterocyclic Carbene Ligand: Palladium Complexes, Their Structures, and Catalytic Activities

Abstract: A new imidazolium salt, 1,3-bis(2-diphenylphosphanylethyl)-3H-imidazol-1-ium chloride (2), for the phosphine/N-heterocyclic carbene-based pincer ligand, PC(NHC)P, and its palladium complexes were reported. The complex, [Pd(PC(NHC)P)Cl]Cl (4), was prepared by the common route of silver carbene transfer reaction and a novel direct reaction between the ligand precursor, PC(NHC)P.HCl and PdCl(2) without the need of a base. Metathesis reactions of 4 with AgBF(4) in acetonitrile produced [Pd(PC(NHC)P)(CH(3)CN)](BF(4))(2) (5). The same reaction in the presence of excess pyridine gave [Pd(PC(NHC)P)(py)](BF(4))(2) (6). The X-ray structure determination on 4-6 revealed the chiral twisting of the central imidazole rings from the metal coordination plane. In solution, fast interconversion between left- and right-twisted forms occurs. The twisting reflects the weak pi-accepting property of the central NHC in PC(NHC)P. The uneven extent of twisting among the three complexes further implies the low rotational barrier about the Pd-NHC bond. Related theoretical computations confirm the small rotational energy barrier about the Pd-NHC bond (ca. 4 kcal/mol). Catalytic applications of 4 and 5 have shown that the complexes are modest catalysts in Suzuki coupling. The complexes were active catalysts in Heck coupling reactions with the dicationic complex 5 being more effective than the monocationic complex 4.

Palladium reagents and catalysts : new perspectives for the 21st century

Abstract: Preface Abbreviations 1 The Basic Chemistry of Organopalladium Compounds 11 Characteristic Features of Pd Promoted or Catalyzed Reactions 12 Palladium Compounds, Complexes, and Ligands Widely Used in Organic Synthesis 13 Fundamental Reactions of Pd Compounds 131 'Oxidative' Addition 132 Insertion 133 Transmetallation 134 Reductive Elimination 135 beta H Elimination (beta Elimination, Dehydropalladation) 136 Elimination of Heteroatom Groups and beta Carbon 137 Electrophilic Attack by Organopalladium Species 138 Termination of Pd Catalyzed or Promoted Reactions and a Catalytic Cycle 139 Reactions Involving Pd(II) Compounds and Pd(0) Complexes References 2 Oxidative Reactions with Pd(II) Compounds 21 Introduction 22 Reactions of Alkenes 221 Introducti on 22 2 Reaction with Water 223 Reactions with Alcohols and Phenols 224 Reactions with Carboxylic Acids 225 Reactions with Amines 226 Reactions with Carbon Nucleophiles 227 Oxidative Carbonylation 228 Reactions with Aromatic Compounds 229 Coupling of Alkenes with Organometallic Compounds 23 Stoichiometric Reactions of pi Allyl Complexes 24 Reactions of Conjugated Dienes 25 Reactions of Allenes 26 Reaction of Alkynes 27 Homocoupling and Oxidative Substitution Reactions of Aromatic Compounds 28 Regioselective Reactions Based on Chelation and Participation of Heteroatoms 29 Oxidative Carbonylation of Alcohols and Amines 210 Oxidation of Alcohols 211 Enone Formation from Ketones and Cycloalkenylation References 3 Pd(0) Catalyzed Reactions of sp2Organic Halides and Pseudohalides 31 Introduction 32 Reactions with Alkenes (Mizoroki Heck Reaction) 321 Introduction 322 Catalysts and Ligands 323 Reaction Conditions (Bases, Solvents, and Additives) 324 Halides and Pseudohalides 325 Alkenes 326 Formation of Neopentylpalladium and its Termination by Anion Capture 327 Intramolecular Reactions 328 Asymmetric Reactions 329 Reactions with 1,2 , 1,3 , and 1,4 Dienes 3210 Amino Heck Reactions of Oximes References 33 Reactions of Aromatics and Heteroaromatics 331 Arylation of Heterocycles 332 Intermolecular Arylation of Phenols 333 Intermolecular Polyarylation of Ketones 334 Intramolecular Arylation of Aromatics References 34 Reactions with Alkynes 341 Introduction 342 Reactions of Terminal Alkynes to Form Aryl and Alkenylalkynes (Sonogashira Coupling) References 343 Reactions of Internal and Terminal Alkynes with Aryl and Alkenyl Halides via Insertion References 35 Carbonylation and Reactions of Acyl Chlorides 351 Introduction 352 Formation of Carboxylic Acids, Esters, and Amides 353 Formation of Aldehydes and Ketones 354 Reactions of Acyl Halides and Related Compounds 355 Miscellaneous Reactions References 36 Cross Coupling Reactions with Organometallic Compounds of the Main Group Metals via Transmetallation 361 Introduction 362 Organoboron Compounds (Suzuki Miyaura Coupling) References 363 Organostannanes (Kosugi Migita Stille Coupling) 364 Organozinc Compounds (Negishi Coupling) 365 Organomagnesium Compounds 366 Organosilicon Compounds (Hiyama Coupling) References 37 Arylation and Alkenylation of C, N, O, S, and P Nucleophiles 371 alpha Arylation and alpha Alkenylation of Carbon Nucleophiles 372 Intramolecular Attack of Aryl Halides on Carbonyl Groups References 373 Arylation of Nitrogen Nucleophiles References 374 Arylation of Phenols, Alcohols, and Thiols References 375 Arylation of Phosphines, Phosphonates, and Phosphinates References 38 Miscellaneous Reactions of Aryl Halides 381 The Catellani Reactions using Norbornene as a Template for ortho Substitution References 382 Reactions of Alcohols with Aryl Halides Involving beta Carbon Elimination References 383 Hydrogenolysis with Various Hydrides 384 Homocoupling of Organic Halides (Reductive Coupling) References 4 Pd(0) Catalyzed Reactions of Allylic Compounds via PI Allylpalladium Complexes 41 Introduction and Range of Leaving Groups 42 Allylation 421 Stereo and Regiochemistry of Allylation 422 Asymmetric Allylation 423 Allylation of Stabilized Carbon Nucleophiles 424 Allylation of Oxygen and Nitrogen Nucleophiles 425 Allylation with Bis Allylic Compounds and Cycloadditions 43 Reactions with Main Group Organometallic Compounds via Transmetallation 431 Cross Coupling with Main Group Organometallic Compounds 432 Formation of Allylic Metal Compounds 433 Allylation Involving Umpolung 434 Reactions of Amphiphilic Bis pi Allylpalladium Compounds 44 Carbonylation Reactions 45 Intramolecular Reactions with Alkenes and Alkynes 46 Hydrogenolysis of Allylic Compounds 461 Preparation of 1 Alkenes by Hydrogenolysis with Formates 462 Hydrogenolysis of Internal and Cyclic Allylic Compounds 47 Allyl Group as a Protecting Group 48 1,4 Elimination 49 Reactions via pi Allylpalladium Enolates 491 Generation of pi Allylpalladium Enolates from Silyl and Tin Enolates 492 Reactions of Allyl beta Keto Carboxylates and Related Compounds 410 Pd(0) and Pd(II) Catalyzed Allylic Rearrangement 411 Reactions of 2,3 Alkadienyl Derivatives via Methylene pi allylpalladiums References 5 Pd(0) Catalyzed Reactions of 1,3 Dienes, 1,2 Dienes (Allenes), and Methylenecyclopropanes 51 Reactions of Conjugated Dienes 52 Reactions of Allenes 521 Introduction 522 Reactions with Pronucleophiles 523 Carbonylation 524 Hydrometallation and Dimetallation 525 Miscellaneous Reactions 53 Reactions of Methylenecyclopropanes 531 Introduction 532 Hydrostannation and Dimetallation 533 Hydrocarbonation and Hydroamination References 6 Pd(0) Catalyzed Reactions of Propargyl Compounds 61 Introduction and Classification of Reactions 62 Reactions via Insertion of Alkenes and Alkynes 63 Carbonylations 64 Reactions of Main Group Metal Compounds 65 Reactions of Terminal Alkynes Formation of 1,2 Alkadien 4 ynes 66 Reactions of Nucleophiles on Central sp Carbon of Allenylpalladium Intermediates 67 Hydrogenolysis and Elimination of Propargyl Compounds References 7 Pd(0) and Pd(II) Catalyzed Reactions of Alkynes and Benzynes 71 Reactions of Alkynes 711 Carbonylation 712 Hydroarylation 713 Hydroamination, Hydrocarbonation, and Related Reactions 714 Hydrometallation and Hydro Heteroatom Addition 715 Dimetallation and Related Reactions 716 Cyclization of 1,6 Enynes and 1,7 Diynes 717 Benzannulation 718 Homo and Cross Coupling of Alkynes 719 Miscellaneous Reactions 72 Reactions of Benzynes 721 Cyclotrimerization and Cocyclization 722 Addition Reactions of Arynes 595 References 8 Pd(0) Catalyzed Reactions of Alkenes 81 Carbonylation 82 Hydroamination 83 Hydrometallation 84 Miscellaneous Reactions References 9 Pd(0) Catalyzed Miscellaneous Reactions of Carbon Monoxide References 10 Miscellaneous Reactions Catalyzed by Chiral and Achiral Pd(II) Complexes References Tables 11 to 118 Index

Use of "Homeopathic" Ligand-Free Palladium as Catalyst for Aryl-Aryl Coupling Reactions

Abstract: We have previously shown that the use of ligand-free palladium employing Pd(OAc)2 as catalyst precursor in the Heck reaction of aryl bromides is possible if low catalyst loadings, typically between 0.01 – 0.1 mol % are used. We have now tested this phenomenon, which we have dubbed “homeopathic” palladium, in biaryl formation using the Suzuki, the Negishi and the Kumada cross-coupling reactions. The Suzuki reaction of aryl bromides, both activated and deactivated, is possible using 0.02–0.05 mol % of Pd(OAc)2. In this reaction turnover frequencies up to 30,000 have been reached with activated substrates. Even aryl chlorides could be reacted if strongly electron-withdrawing substituents were present. The Negishi coupling with a variety of arylzinc halides was possible on aryl bromides containing electron-withdrawing substituents. The Kumada reaction only gave low yields of products under “homeopathic' conditions.

A copper- and amine-free sonogashira reaction employing aminophosphines as ligands.

Abstract: An efficient Pd-catalyzed Sonogashira coupling reaction was achieved in the absence of a copper salt or amine with an inorganic base and easily prepared, air-stable aminophosphine ligands in commonly used organic solvents; good to excellent yields were obtained. Under optimized reaction conditions, the Sonogashira coupling reaction occurred selectively when an enyne substrate was employed and no Heck reaction product was detected; acetone-masked acetylene and trimethylsilylacetylene can also be efficiently coupled, providing a method to make terminal alkynes.

Elucidating reactivity differences in palladium-catalyzed coupling processes: the chemistry of palladium hydrides.

Abstract: This communication describes a series of studies directed at obtaining a better understanding of the Heck reaction. For the first time, the postulated palladium-hydride intermediate (L2PdHX) in the catalytic cycle of the Heck arylation has been identified. In addition, this study establishes that the base-mediated Pd(0)-regeneration step (L2PdHX --> PdL2) of the cycle can be kinetically slow and thermodynamically unfavorable and that the process is remarkably sensitive to the structure of L (PCy3 vs P(t-Bu)3). Finally, this investigation demonstrates that, for certain catalyst systems, slow rates of Heck arylation can be correlated with reluctant reductive elimination of L2PdHX, furnishing a possible rationalization for Bronsted-base (Cs2CO3 vs Cy2NMe) and ligand (PCy3 vs P(t-Bu)3) effects that have been observed.

Dioxygen-promoted regioselective oxidative heck arylations of electron-rich olefins with arylboronic acids.

Abstract: Arylations of electron-rich heteroatom-substituted olefins were performed with arylboronic acids. This appears to constitute the first example of palladium(II)-catalyzed internal Heck arylations. The novel protocol exploits oxygen gas for environmentally benign reoxidation and a stable 1,10-phenanthroline bidentate ligand to promote the palladium(II) regeneration and to control the regioselectivity. Internal arylation is strongly favored with electron-rich arylboronic acids. DFT calculations support a charge-driven selectivity rationale, where phenyls substituted with electron-donating groups prefer the electron-poor α-carbon of the olefin. Experiments, verified by calculations, confirm the cationic nature of the catalytic route. This Heck methodology provides a facile and mild access to functionalized enamides. Controlled microwave heating and increased oxygen pressure were used to further reduce the reaction time to 1 h.