Transition Metal-catalyzed Bond Formations [microform] : an Expansion of the Utility of Organotrifluoroborate Salts and Organoboronic Acids

Transition Metal-catalyzed Bond Formations [microform] : an Expansion of the Utility of Organotrifluoroborate Salts and Organoboronic Acids
Author: Tan Dai Quach
Publisher: Library and Archives Canada = Bibliothèque et Archives Canada
Total Pages: 620
Release: 2004
Genre:
ISBN: 9780612942615

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This thesis is a summary of the research conducted since September 1999 at the University of Toronto in the laboratory of Dr. Robert A. Batey. This manuscript is divided into four chapters. Chapter one provides a general introduction to the nature and reactivity of organo trifluoroborate salts. Their preparation from organoboron or organohalide precursors, as well as their use in a variety of synthetic transformations is reviewed. The preparation of novel tetra- n-butylammonium organotrifluoroborate salts within our own laboratory is also described. Chapter two provides an overview of the classical copper-mediated Ullmann Reaction for carbon-carbon bond formation between aryl halides, as well as modern variations of the Ullmann-Goldberg Condensation for carbon-oxygen bond formation. Our contributions to this area of synthetic chemistry are described, including the copper-catalyzed cross-coupling of potassium aryl- and alkenyltrifluoroborates with unactivated alcohols and phenols, which were achieved in good to excellent yields by utilizing copper acetate monohydrate as catalyst under an atmosphere of oxygen in the presence of 4A molecular sieves. Recent work into the copper-mediated/catalyzed cross-coupling of potassium organotrifluoroborate salts with activated carboxylate salts is also described. Chapter four describes our efforts in the investigation of the mechanism of the cross-coupling. The various stages of the catalytic cycle are examined with particular focus upon the oxidation state of the copper species involved. The role of molecular sieves in the transformation is also explored, as experimental observations have suggested that they play a greater part than just as desiccant in the reaction. Finally, the result of a short study on the phenomenon of the deactivation of the catalytic transformation by the presence of quaternary ammonium species is also presented. Chapter three describes modern approaches to carbon-nitrogen bond formation through the Ullmann-Goldberg Condensation of organometalloid species with nitrogen-based nucleophiles. The result of an investigation into the stoichiometric copper-mediated cross-coupling of potassium organotrifluoroborate salts and anilines is presented. In addition a novel reaction protocol for the ligandless and base free copper-catalyzed arylation of aliphatic amines is presented. The cross-coupling was found to work equally well with both potassium organotrifluoroborate salts and organoboronic acids.

Developments and Applications of Methods for Palladium- and Copper-catalyzed Carbon-nitrogen Bond Formation

Developments and Applications of Methods for Palladium- and Copper-catalyzed Carbon-nitrogen Bond Formation
Author: Jeffrey Chih-Yeh Yang
Publisher:
Total Pages: 467
Release: 2018
Genre:
ISBN:

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The studies presented in this dissertation are aimed at the development and application of methodologies that enable carbon-nitrogen (C-N) bond formation catalyzed by late transition metals such as palladium and copper. The first part of this thesis focuses on the use of palladium catalysis for the construction of a carbon(sp2)-nitrogen bond in the context of a biphasic continuous-flow system (Chapter 1). The second part of this thesis describes the recent developments of copper-hydride (CuH) catalyzed asymmetric hydroamination for the formation of a-chiral carbon(sp3)-nitrogen bonds from olefins. This work includes the application of CuH catalysis to the synthesis of chiral N-alkyl aziridines (Chapter 2), and the discovery and development of novel electrophilic amines to enable CuH-catalyzed asymmetric hydroamination to directly access primary amines (Chapter 3). Part I. Chapter 1. Use of a "Catalytic" Cosolvent, N,N-Dimethyl Octanamide, Allows the Flow Synthesis of Imatinib with no Solvent Switch A general, efficient method for C-N cross-coupling has been developed using N,N-dimethyloctanamide as a cosolvent for biphasic continuous-flow applications. In addition to utilizing a proper co-solvent, the described method harnesses the superior mixing abilities of a stainless-steel powder packed tube reactor to efficiently couple a wide range of aryl/heteroaryl halides and aryl/heteroaryl/alkyl amines in a short period of time (

Catalytic Methods for Carbon-carbon and Carbon-nitrogen Bond Formation

Catalytic Methods for Carbon-carbon and Carbon-nitrogen Bond Formation
Author: Stephen David Ramgren
Publisher:
Total Pages: 511
Release: 2014
Genre:
ISBN:

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This dissertation describes the study of metal-catalyzed cross-coupling reactions to construct carbon-carbon and carbon-heteroatom bonds. The key feature of much of this work is the use of inexpensive Ni and Fe catalysts to enable the coupling of unconventional electrophilic substrates, specifically aryl O-sulfamates and O-carbamates. The ability to use O-sulfamates and O-carbamates in catalytic processes is notable, as these substrates are readily derived from phenols and can be used for directed arene functionalization. Chapter one provides a summary of the efforts towards using alcohol-based solvents for the Suzuki-Miyaura cross-coupling reaction. Emphasis is placed on the cross-coupling of heterocycles, which are commonly encountered in natural product synthesis and in the pharmaceutical sector. Chapters two, three, and four describe carbon-nitrogen bond forming reactions. Chapter two pertains to the nickel-catalyzed amination of sulfamates, which culminated in the synthesis of the antibacterial drug, linezolid. Chapter three covers the amination of aryl O-carbamates and their use in sequential functionalization/site-selective cross-couplings. Chapter four describes a more user-friendly variant of the amination reaction, which relies on a bench-stable Ni(II) precatalyst, rather than a more commonly used Ni(0) precatalyst. Chapters five, six, and seven focus on carbon-carbon bond formation via Fe-, Ni- and Pd-mediated processes. Chapter five pertains to iron-catalyzed couplings of sulfamates and carbamates to generate sp2-sp3 carbon-carbon bonds. This method can be used to assemble sterically-congested frameworks. Chapter six describes the nickel-catalyzed Suzuki-Miyaura reactions of halides and phenol derivatives in `green' solvents, which was applied to the preparative scale assembly of bis(heterocycles) using low nickel catalyst loadings. Chapter seven pertains to the acetylation of arenes using palladium catalysis, which provides a simple and efficient means for the construction of a variety of aryl methyl ketones.

Advances in Palladium-catalyzed Carbon-nitrogen Bond Forming Processes

Advances in Palladium-catalyzed Carbon-nitrogen Bond Forming Processes
Author: Rachel Elizabeth Tundel
Publisher:
Total Pages: 136
Release: 2006
Genre:
ISBN:

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Chapter 1. Microwave-assisted, palladium-catalyzed C-N bond-forming reactions with aryl/heteroaryl nonaflates/halides and amines using the soluble amine bases DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) or MTBD (7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene) and a catalyst system consisting of Pd2dba3 and ligands (XantPhos, 2-dicylcohexylphosphino-2',4',6'-triisopropyl-1,1 '-biphenyl (XPhos) and 2-di-tert-butylphosphino-2',4',6'-triisopropyl-1, '-biphenyl) resulted in good to excellent yields of arylamines in short reaction times. Chapter 2. Using a catalyst comprised of the bulky, electron-rich monophosphine ligand di-tert-Butyl XPhos (2-di-tert-butylphosphino-2',4',6'-triisopropyl-1,1'-biphenyl) and Pd2dba3 with sodium tert-butoxide as the base, amino heterocycles were coupled successfully with aryl/heteroaryl halides in moderate to excellent yields.

The Development of Palladium- and Copper-catalyzed Transformations for the Asymmetric Synthesis of Biologically Active Small Molecules

The Development of Palladium- and Copper-catalyzed Transformations for the Asymmetric Synthesis of Biologically Active Small Molecules
Author: James Thomas Masters
Publisher:
Total Pages:
Release: 2016
Genre:
ISBN:

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The continued demand for efficient chemo-, regio-, and stereoselective organic transformations motivates the development of new chemical reactions. Transition metal catalysis represents a powerful method for the construction of carbon-carbon, carbon-hydrogen, and carbon-heteroatom bonds in a highly selective fashion. This dissertation describes the development of several new transition metal-catalyzed organic reactions useful in the preparation of various chiral small molecules, including both fundamental organic "building block" compounds and structurally complex natural products and pharmaceutical agents. We report a new strategy for the synthesis of chiral beta-alkynyl esters, ketones, and sulfones via sequential palladium-catalyzed carbon-carbon bond formation and copper-catalyzed carbon-hydrogen bond formation. The process is operationally straightforward, compatible with a broad range of substrates, and delivers the targets in high yields with excellent levels of enantioselectivity. It is compatible with both oxygen and nitrogen functionality, and this enabled the rapid elaboration of the products into a diverse set of chiral heterocycles. The sequential catalysis protocol was employed in a concise, enantioselective synthesis of AMG 837, a potent agonist of G-protein coupled receptor 40. Recognizing both the biological relevance of chiral alkaloids and the synthetic challenges associated with the construction of quaternary, all-carbon stereocenters, we pursued a palladium-catalyzed asymmetric allylic alkylation that effected carbon-carbon bond formation on prochiral oxindole nucleophiles. Although prior research has demonstrated that allylic alkylation reactions of geminal dicarboxylate electrophiles typically yield branched products as the result of ipso-addition, we identify conditions wherein oxindoles react with a dipivaloyl electrophile to afford linear enol pivalate compounds. A mild hydrolysis reaction converts these products into the aldehyde that formally results from asymmetric conjugate addition to acrolein, a challenging transformation with limited literature precedent. These adducts are established precursors to tricyclic alkaloid scaffolds of pharmaceutical interest. Chiral gamma-heteroatom-substituted cycloalkenones are well-established organic "building blocks" that are widely used in the synthesis of complex molecules. The exposure of meso-1,4-allylic dibenzoates to chiral phosphine-ligated palladium salts in the presence of a potassium nitronate nucleophile promotes a unique oxidative desymmetrization reaction. This process yields enantiopure gamma-benzoyloxy cyclopentenones, cyclohexenones, and cycloheptenones. We describe the elaboration of these products into diverse, enantioenriched oxygen- and nitrogen-substituted cycloalkenones via subsequent palladium-catalyzed allylic alkylation reactions involving heteroatom nucleophiles. Separately, we employ enantiopure gamma-benzoyloxy cyclohexenones in short, asymmetric syntheses of enantio- and diastereomerically diverse epoxyquinoid natural products. We further highlight the utility of palladium catalysis in complex molecule synthesis through the development of a unique, intramolecular carbon-carbon bond-forming reaction that generates a strained enyne and through an asymmetric formal synthesis of aliskiren, a renin inhibitor used in the treatment of hypertension.

Recent Advances in Copper- and Palladium-catalyzed Carbon-heteroatom and Carbon-carbon Bond-formation

Recent Advances in Copper- and Palladium-catalyzed Carbon-heteroatom and Carbon-carbon Bond-formation
Author: Ryan Alan Altman
Publisher:
Total Pages: 752
Release: 2008
Genre:
ISBN:

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Metal-catalyzed nucleophilic substitution reactions of aryl halides have become one of the most valuable and useful classes of reactions developed in the last 30 years. Foremost among these processes are the classes of palladium- and copper-catalyzed reactions, which employ heteroatom-based nucleophiles. Herein, newly designed catalyst systems are presented for the palladium- and/or copper-catalyzed nucleophilic substitution reactions of aryl halides with a variety of nucleophiles, including (benz)imidazoles, oxindoles, 2-, 3- and 4-hydroxypyridines, anilines, and aliphatic, benzylic, allylic and propargylic alcohols. In many cases, catalyst optimization and ligand structure are discussed and evaluated. Where applicable, the palladiumand copper-based catalyst systems are contrasted to demonstrate the complementary relationships between the employment of these two metals. Chapter One Chapter Two Chapter Three Chapter Four Chapter Five. Palladium- and Copper-catalyzed Reactions of Imidazoles and Benzimidazoles with Aryl Halides. Orthogonal Selectivity in Copper- and Palladium-catalyzed Reactions of Aryl Halides with Oxindoles. Copper-catalyzed Reactions of Hydroxypyridines and Related Compounds with Aryl Halides. Pyrrole-2-carboxylic Acid as a Ligand for the Copper-catalyzed Reactions of Primary Anilines with Aryl Halides. An Improved Copper-based Catalyst System for the Reactions of Aryl Halides with Aliphatic Alcohols.

Synthetic and Mechanistic Studies of Transition Metal-Mediated Carbon-Nitrogen Bond Forming Reactions

Synthetic and Mechanistic Studies of Transition Metal-Mediated Carbon-Nitrogen Bond Forming Reactions
Author: Alexandra Eve Strom
Publisher:
Total Pages: 323
Release: 2015
Genre:
ISBN:

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The following dissertation discusses reactions for the formation of carbon-nitrogen bonds mediated by organotransition metal reagents and catalysts. Chapter 1 presents a synthetic method for the formal hydroamination of unactivated alkenes to form anti-Markovnikov primary and secondary amine products. This transformation is accomplished through the hydrozirconation and subsequent amination of alkenes. The method is then applied to the reaction of complex molecules to emphasize the functional group tolerance of these reactions. Chapter 2 of this thesis comprises the synthesis and evaluation of a series of rhodium-phosphine hydroamination catalysts. These complexes are evaluated in a series of catalytic intramolecular Markovnikov hydroamination reactions. The mechanism of hydroamination catalyzed by the rhodium(I) complexes in this study was examined computationally, and the turnover-limiting step was elucidated. The difference in reactivity of electron-rich and electron-poor catalysts was compared to the computational results of a computational ligand screen, and it was found that the computational analysis of reaction intermediates overestimated the reactivity of electron-poor catalysts. The analysis of the catalysts in this study was expanded to include the binding preference of each ligand, compared to the unsubstituted ligand, which corrects for the disparity between observed reactivity and the calculated overall reaction barrier for electron-poor ligands. The ligand-binding preferences for new ligand structures were calculated, and it was found that ligands that were predicted to bind strongly to rhodium had improved reactivity in catalytic reactions. Chapter 3 discusses the mechanistic study of the palladium-catalyzed aminocarbonylation of aryl halides with ammonia and CO to form primary benzamides. Conditions for reactions of aryl bromides, chlorides, and iodides are described, and the mechanism of reactions of aryl bromides was studied. The kinetic order in the concentration of aryl bromide was found to be first order, and the order in the pressure of CO was found to be inverse first order. These studies were complemented by DFT calculations on the mechanism of oxidative addition of aryl bromides. The products of oxidative addition, aroyl bromide palladium intermediates, were reacted with ammonia in the presence of additives to gain insight into the mechanism of release of product. The overall dependence on the rate of the catalytic reaction was found to be insensitive to excess ammonia, indicating that the overall turnover-limiting step of the reaction is during the oxidative addition step.

Development of New Transition Metal-catalyzed Carbon-fluorine, Carbon-nitrogen, and Carbon-carbon Bond Forming Processes

Development of New Transition Metal-catalyzed Carbon-fluorine, Carbon-nitrogen, and Carbon-carbon Bond Forming Processes
Author: Yuxuan Ye (Ph. D.)
Publisher:
Total Pages: 226
Release: 2018
Genre:
ISBN:

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Chapter 1. Palladium-Catalyzed Fluorination of Cyclic Vinyl Triflates: Dramatic Effect of TESCF3 as an Additive A method for the synthesis of cyclic vinyl fluorides with high levels of regiochemical fidelity has been achieved by Pd-catalysis employing a new biarylphosphine ligand and TESCF3 as a crucial additive. Five, six, and seven-membered vinyl triflate substrates, as well as a few acyclic substrates undergo the transformation successfully. The intriguing "TESCF3 effect" provided a new tool for addressing the problem of the formation of regioisomers in Pd-catalyzed fluorination reactions. Chapter 2. Mechanistic Studies on Pd-Catalyzed Fluorination of Cyclic Vinyl Triflates: Evidence for in situ Ligand Modification by TESC3 as an additive. A detailed mechanistic hypothesis for the Pd-catalyzed fluorination of cyclic vinyl triflates, and the unusual effect of TESCF3 as an additive has been developed by combined experimental and computational studies. The preference of conducting [beta]-hydrogen elimination rather than reductive elimination from the trans-LPd(vinyl)F complex, which is generated predominantly due to the trans-effect, caused the poor regioselectivity of the fluorination reaction under TESCF3-free conditions. An in situ ligand modification by trifluoromethyl anion, leading to the generation of the cis-LPd(vinyl)F complex which prefers reductive elimination rather than Phydrogen elimination, is proposed to be responsible for the improved regioselectivity of the fluorination reaction when TESCF3 was used as an additive. Chapter 3. CuH-Catalyzed Enantioselective Alkylation of Indoles with Ligand-Controlled Regiodivergence A method for the enantioselective synthesis of either NI- and C3-chiral indoles by CuH-catalysis, depending on the choice of ligand, was developed. In contrast to conventional indole functionalization in which indoles are used as nucleophiles, hydroxyindole derivatives are employed as electrophiles in this method. DFT calculations indicated that the extent to which the Cu-P bonds of the alkylcopper intermediate distort, determines the regioselectivity of the reaction.