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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 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 (
Late-metal catalyzed cross-couplings have emerged as efficient and selective methodologies for the formation of C-C and C-N bonds. The ability to synthesize complex heterocycles from cheap and abundant starting materials is an invaluable asset to the pharmaceutical industry, given that many pharmaceuticals contain at least one heterocyclic component. This reactivity can be achieved by tuning the steric and electronic properties of ancillary ligands to support metal catalysts in the reaction steps leading to the target substrate. The Stradiotto group has developed several state-of-the-art methodologies involving ligands for palladium catalysis, for both C-C and C-N bond-forming reactions. These methodologies can be amalgamated into a multicomponent reaction platform to synthesize more complex products from simple materials. Chapter 1 outlines this concept with the application of a Mor-DalPhos/Pd catalyst in the one-pot synthesis of indoles from acetone and simple amines involving C-C and C-N bond formation. The robust nature of this method can be extended to include benchtop reaction conditions in a one-step, one-pot synthesis of indoles, thus representing a useful synthetic protocol. While palladium provides a powerful tool for C-C and C-N bond formation, the general trend in catalysis has shifted away from the precious metals toward first row metals as economic alternatives. Nickel complexes have recently emerged as excellent catalysts for a number of amination reactions. The ability to utilize ammonia also represents a sought after reaction, due to the widespread availability and synthetic utility of amino-functionalized products. In this regard, Chapter 2 will focus on the development and application of both commercially available and strategically designed ligand classes for the monoarylation of ammonia with substituted heterocycles. Hydrazine represents an important synthon in synthetic chemistry. It is synthesized on multi-ton scale every year and represents an important building block in many industrial processes. Many synthetic challenges arise from using free hydrazine as reactant, which has led to lethargic growth of its application in the field of late-metal catalyzed C-N bond-formation. However, gold-catalyzed methodologies have been developed utilizing NHC ligands to allow for the hydrohydrazination of alkynes with parent hydrazine. Chapter 4 examines the development and application of a series of (PR3)AuCl complexes for use in such transformations, leading to the identification of the first effective phosphine-bound gold complex for use in the hydrohydrazination of alkynes at room temperature.
"Cross-Coupling Reactions: An Overview opens with an overview of the fundamentals and applications of the young and fast developing area of transition metal catalyzed/mediated oxidative (dehydrogenative) C-H/C-H coupling reactions between two (hetero)arenes. Continuing, the authors highlight the recent advances regarding the ligand supported transition metal-catalyzed domino (cascade) or one-pot syntheses of various heterocycles involving cross-coupling reactions. The recent advances in Cu catalyzed tandem reactions for heterocycle synthesis are also addressed. Cu metal chemistry has garnered attention as a potential alternative to precious transition metals, being cheaper, more sustainable and more easily available. A comprehensive account of research on green chemical routes is provided, involving various palladium metal-based catalysts utilized in facilitating cross-coupling reaction in aqueous media. Reported decarboxylative cross-coupling reactions are discussed along with suitable examples, focusing on their mechanism of action"--
Organized to provide maximum utility to the bench synthetic chemist. The editor is well-known for his work in exploring, developing, and applying organopalladium chemistry. Contributors include over 24 world authorities in the field.
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.
(Cont.) This system allows for the conversion of aryl and heteroaryl iodides, bromides and several chlorides, containing a variety of functional groups, to the corresponding pinacol boronate esters. In addition to the increase in substrate scope, this is the first general method where relatively low quantities of catalyst and short reaction times can be employed.
"This thesis describes the design and development of reductive amination methodologies of unactivated carbon-oxygen bonds using palladium on charcoal as a heterogeneous catalyst. The underlying premise is the transformation of starting materials that can be obtained from bio-renewable resources into commodity chemicals. Specifically, 2-cyclohexen-1-one and phenol were used as lignin building-block surrogates for C-N bond formation. The first chapter places the work developed in this thesis both in a global and a scientific context. Its objective is to provide an overview of our societal needs while describing the latest scientific developments related to this thesis topic. Thus, it begins by exploring the United Nation's Sustainable Goals, followed by an overview of petroleum and lignin chemistry, and finishes with a review on amino acid N-modification. In chapter two, the development of a novel methodology for the N-arylation of [alpha]-amino acids using 2-cyclohexen-1-one is described. Palladium on carbon was chosen as the catalyst, and several reaction conditions were explored to obtain optimal yields. This methodology's attractiveness lies in the absence of an aryl halide or protecting group on the 2-cyclohexen-1-one for the N-arylation to proceed. The reaction requires substoichiometric amounts of base and oxygen as the terminal oxidant. Aliphatic amino acids were ideal substrates for the reaction, and cyclohexanone provided the N-biarylated amino acids in good yields (up to 74%). Chapter three describes efforts to improve the harsh conditions required for the N-arylation of [alpha]-amino acids, resulting in the development of a novel methodology for their N-cyclohexylation in water, at room temperature, using phenol as a coupling partner. The reaction successfully achieves N-cyclohexylation for 17 out of the 20 naturally occurring amino acids without racemization with up to quantitative yields. Furthermore, small peptides were also successful substrates for the reaction. The fourth chapter explores the possibility of applying the latter methodology for the formation of one- and two-component peptide staples using tyrosine as a handle. The one component staple was investigated using acetyl-lysine and acetyl-tyrosine, while the two-component staple was investigated using acetylated-tyrosine 2,2'-(ethylenedioxy)bis(ethylamine). While model substrates proved to couple successfully under previously optimized conditions, concentration and characterization proved to be challenging for working with larger peptides. Additional experiments exploring the possibility of using tyrosine amination as a pH responding hydrogel are also described in this chapter. Finally, chapter five explores the possibility of synthesizing diphenylamines from phenol and ammonia formate as a convenient ammonia surrogate. Seventeen different diarylamines were synthesized with palladium on charcoal as the catalyst, with yields ranging from good to excellent. Notably, water and CO2 were the only byproducts generated from this transformation. Triphenylamine was also obtained in combination with the methodology described in Chapter 1"--
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.