Mechanistic Studies On Metal Catalyzed Carbon Nitrogen Bond Forming Reactions
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Mechanistic Studies On Metal Catalyzed Carbon Nitrogen Bond Forming Reactions
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Author : Eric R. Strieter
language : en
Publisher:
Release Date : 2005
Mechanistic Studies On Metal Catalyzed Carbon Nitrogen Bond Forming Reactions written by Eric R. Strieter and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2005 with categories.
(Cont.) A systematic mechanistic analysis of Pd(OAc)2/ monophosphino- biaryl-catalyzed C-N bond forming reactions with aryl chlorides has been performed. The results provide insights into the relationship between the steady-state concentration of active Pd and the size and substitution pattern of the monophosphinobiaryl ligands. These insights into the nature of catalyst activation help highlight the importance of establishing a high concentration of active catalyst. The catalyst derived from the bulkiest ligand in the series, the tri-i-propyl ligand 13, exhibits both accelerated rate and the increased stability required for practical application of this reaction.
Synthetic And Mechanistic Studies Of Transition Metal Mediated Carbon Nitrogen Bond Forming Reactions
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Author : Alexandra Eve Strom
language : en
Publisher:
Release Date : 2015
Synthetic And Mechanistic Studies Of Transition Metal Mediated Carbon Nitrogen Bond Forming Reactions written by Alexandra Eve Strom and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with categories.
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.
New Reactivity And Selectivity In Transition Metal Catalyzed C C And C N Bond Forming Processes
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Author :
language : en
Publisher:
Release Date : 2015
New Reactivity And Selectivity In Transition Metal Catalyzed C C And C N Bond Forming Processes written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with categories.
Part I. Palladium-Catalyzed Carbon-Carbon Bond Forming Cross-Couplings Chapter 1. Ligand-Controlled Palladium-Catalyzed Regiodivergent Suzuki-Miyaura Cross-Coupling of Allylboronates and Aryl Halides An orthogonal set of catalyst systems based on the use of two biarylphosphine ligands has been developed for the Suzuki-Miyaura coupling of 3,3-disubstituted and 3-monosubstituted allylboronates with (hetero)aryl halides. These methods allow for the regiodivergent preparation of either the ct- or the [gamma]-isomeric coupling product with high levels of site selectivity using a common allylboron building block. Preliminary investigations have demonstrated the feasibility of an enantioselective variant for the [gamma]-selective cross-coupling using chiral monodentate biarylphosphine ligands. Chapter 2. Palladium-Catalyzed Completely Linear-Selective Negishi Coupling of 3,3-Disubstituted Organozinc Reagents with Aryl and Vinyl Electrophiles A palladium-catalyzed general and completely linear-selective Negishi coupling of 3,3- disubstituted allyl organozinc reagents with (hetero)aryl and vinyl electrophiles has been developed. This method provided an effective means for accessing highly functionalized aromatic and heteroaromatic compounds bearing prenyl-type side chains. The utility of the current protocol was further illustrated in the concise synthesis of the anti-HIV natural product siamenol. Chapter 3. Palladium-Catalyzed Highly Selective Negishi Cross-Coupling of Secondary Alkylzinc Reagents with Aryl and Heteroaryl Halides The palladium-catalyzed Negishi cross-coupling of secondary alkylzinc reagents and heteroaryl halides with high levels of regioisomeric retention has been described. The development of a series of biarylphosphine ligands has led to the identification of an improved catalyst for the coupling of electron-deficient heterocyclic substrates. Preparation and characterization of oxidative addition complex (L)Pd(Ar)(Br) provided insight into the unique reactivity of palladium catalysts based on CPhos-type biarylphosphine ligands in facilitating challenging reductive elimination processes. Chapter 4. Mechanistic Studies on the Aryl-Trifluoromethyl Reductive Elimination from Pd(II) Complexes Based on Biarylphosphine Ligands A series of monoligated (L)Pd(Ar)(CF3) (L = dialkyl biarylphosphine) have been prepared and studied in an effort to shed light on the mechanism of the aryl-trifluoromethyl reductive elimination from these systems. Combined experimental and computational investigations revealed unique reactivity and binding modes of (L)Pd(Ar)(CF3) complexes derived from BrettPhos-type biarylphosphines. In contrast to a variety of C-C and C-heteroatom bond forming reductive eliminations, kinetic measurements showed this Ar-CF3 reductive elimination is largely insensitive to the electronic nature of the to-be-eliminated aryl substituent. Furthermore, the aryl group serves as the nucleophilic coupling partner in this reductive elimination process. The structure-reactivity relationship of biarylphosphine ligands was also investigated, uncovering distinct roles of the ipso-arene and alkoxy interactions in affecting these reductive elimination reactions. Part II. Copper-Catalyzed Carbon-Carbon and Carbon-Nitrogen Bond Formation via Olefin Functionalization Chapter 5. Copper-Catalyzed ortho C-H Cyanation of Vinylarenes A copper-catalyzed regioselective ortho C-H cyanation of vinylarenes has been developed. This method provides an effective means for the selective functionalization of vinylarene derivatives. A copper-catalyzed cyanative dearomatization mechanism is proposed to account for the regiochemical course of this reaction. This mechanism has been validated through density functional theory calculations. Computational studies revealed that the high level of ortho selectivity in the electrophilic cyanation event originates from a unique six-membered transition state that minimizes unfavorable steric repulsions. Chapter 6. Regio- and Stereospecific 1,3-Allyl Group Transfer Triggered by a Copper-Catalyzed Borylation/ortho-Cyanation Cascade A copper-catalyzed borylation/cyanation/allyl group transfer cascade has been developed. This process features an unconventional copper-catalyzed electrophilic dearomatization followed by the subsequent regio- and stereospecific 1,3-transposition of the allyl fragment enabled by the aromatization-driven Cope rearrangement. This method provides an effective means for the construction of adjacent tertiary and quaternary stereocenters with high levels of stereochemical purity. Chapter 7. Copper-Catalyzed Asymmetric Hydroamination of Unactivated Internal Olefins: an Effective Means to Access Highly Enantioenriched Aliphatic Amines Catalytic assembly of enantiopure aliphatic amines from abundant and readily available precursors has long been recognized as a paramount challenge in synthetic chemistry. We describe a mild and general copper-catalyzed hydroamination that effectively converts unactivated internal olefins-an important yet unexploited class of abundant feedstock chemicals-into highly enantioenriched [alpha]-branched amines (>/= 96% ee) featuring two minimally differentiated aliphatic substituents. This method provides a powerful means to access a broad range of advanced, highly functionalized enantioenriched amines of interest in pharmaceutical research and other areas.
Development Of New Transition Metal Catalyzed Carbon Fluorine Carbon Nitrogen And Carbon Carbon Bond Forming Processes
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Author : Yuxuan Ye (Ph. D.)
language : en
Publisher:
Release Date : 2018
Development Of New Transition Metal Catalyzed Carbon Fluorine Carbon Nitrogen And Carbon Carbon Bond Forming Processes written by Yuxuan Ye (Ph. D.) and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018 with categories.
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.
Cross Coupling Reactions
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Author : Joffrey Vrijdag
language : en
Publisher:
Release Date : 2020
Cross Coupling Reactions written by Joffrey Vrijdag and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2020 with Science categories.
"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"--
Homogeneous Catalysis
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Author : Sumit Bhaduri
language : en
Publisher: John Wiley & Sons
Release Date : 2014-09-08
Homogeneous Catalysis written by Sumit Bhaduri and has been published by John Wiley & Sons this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014-09-08 with Science categories.
Over the last decade, the area of homogeneous catalysis with transition metal has grown in great scientific interest and technological promise, with research in this area earning three Nobel Prizes and filing thousands of patents relating to metallocene and non-metallocene single site catalysts, asymmetric catalysis, carbon-carbon bond forming metathesis and cross coupling reactions. This text explains these new developments in a unified, cogent, and comprehensible manner while also detailing earlier discoveries and the fundamentals of homogeneous catalysis. Serving as a self-study guide for students and all chemists seeking to gain entry into this field, it can also be used by experienced researchers from both academia and industry for referring to leading state of the art review articles and patents, and also as a quick self-study manual in an area that is outside their immediate expertise. The book features: • Topics including renewable feed stocks (biofuel, glycerol), carbon dioxide based processes (polycarbonates), fluorous solvents, ionic liquid, hydroformylation, polymerization, oxidation, asymmetric catalysis, and more • Basic principles of organometallic chemistry, homogeneous catalysis, and relevant technological issues • Problems and answers, industrial applications (case studies), and examples from proven industrial processes with clear discussions on environmental and techno-commercial issues • Extensive references to cutting edge research with application potential and leading patents • Tables and illustrations to help explain difficult concepts
Hypervalent Iodine Chemistry
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Author : Viktor V. Zhdankin
language : en
Publisher: John Wiley & Sons
Release Date : 2013-10-01
Hypervalent Iodine Chemistry written by Viktor V. Zhdankin and has been published by John Wiley & Sons this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013-10-01 with Science categories.
Hypervalent Iodine Chemistry is the first comprehensive text covering all of the main aspects of the chemistry of organic and inorganic polyvalent iodine compounds, including applications in chemical research, medicine, and industry. Providing a comprehensive overview of the preparation, properties, and synthetic applications of this important class of reagents, the text is presented in the following way: The introductory chapter provides a historical background and describes the general classification of iodine compounds, nomenclature, hypervalent bonding, structural features, and the principles of reactivity of polyvalent iodine compounds. Chapter 2 gives a detailed description of the preparative methods and structural features of all known classes of organic and inorganic derivatives of polyvalent iodine. Chapter 3, the key chapter of the book, deals with the many applications of hypervalent iodine reagents in organic synthesis. Chapter 4 describes the most recent achievements in hypervalent iodine catalysis. Chapter 5 deals with recyclable polymer-supported and nonpolymeric hypervalent iodine reagents. Chapter 6 covers the "green" reactions of hypervalent iodine reagents under solvent-free conditions or in aqueous solutions. The final chapter provides an overview of the important practical applications of polyvalent iodine compounds in medicine and industry. This book is aimed at all chemists interested in iodine compounds, including academic and industrial researchers in inorganic, organic, physical, medicinal, and biological chemistry. It will be particularly useful to synthetic organic and inorganic chemists, including graduate and advanced undergraduate students. It comprehensively covers the green chemistry aspects of hypervalent iodine chemistry, making it especially useful for industrial chemists.
Advances In Late Metal Carbon Nitrogen Bond Formation For The Synthesis Of Substituted Heterocycles
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Author : Nicolas Rotta-Loria
language : en
Publisher:
Release Date : 2017
Advances In Late Metal Carbon Nitrogen Bond Formation For The Synthesis Of Substituted Heterocycles written by Nicolas Rotta-Loria and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with categories.
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.
Catalyzed Carbon Heteroatom Bond Formation
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Author : Andrei K. Yudin
language : en
Publisher: John Wiley & Sons
Release Date : 2010-12-01
Catalyzed Carbon Heteroatom Bond Formation written by Andrei K. Yudin and has been published by John Wiley & Sons this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010-12-01 with Science categories.
Written by an experienced editor widely acclaimed within the scientific community, this book covers everything fromo9xygen to nitrogen functionalities. From the contents: Palladium-Catalyzed Syntheses of Five-Member Saturated Heterocyclic and of Aromatic Heterodynes Palladium-Catalysis for Oxidative 1, 2-Difunctionalization of Alkenes Rhodium-Catalyzed Amination of C-H-Bonds Carbon-Heteroatom Bond Formation by RH(I)-Catalyzed Ring-Opening Reactions Transition Metal-Catalyzed Synthesis of Lactones and of Monocyclic and Fused Five-Membered Aromatic heterocycles the Formation of Carbon-Sulfur and Carbon-Selenium bonds by Substitution and Addition reactions catalyzed by Transition Metal Complexes New Reactions of Copper Acetylides Gold Catalyzed Addition of Nitrogen, Sulfur and Oxygen Nucleophiles to C-C Multiple Bonds. The result is an indispensable source of information for the Strategic Planning of the Synthetic routes for organic, catalytic and medicinal chemists, as well as chemists in industry.
Catalytic Methods For Carbon Carbon And Carbon Nitrogen Bond Formation
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Author : Stephen David Ramgren
language : en
Publisher:
Release Date : 2014
Catalytic Methods For Carbon Carbon And Carbon Nitrogen Bond Formation written by Stephen David Ramgren and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with categories.
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.
