Download or read book N Heterocyclic Bisphosphine Ligands For Use In Nickel Catalyzed C sp2 N Cross Coupling written by Alexandre Gatien and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Notwithstanding the utility of Buchwald-Hartwig Amination (BHA) technology, the cost and scarcity of palladium has prompted a move to base metal catalysis in recent years. Nickel has emerged as a prime candidate in this chemistry to compete with palladium, being both cheap and abundant. Amination chemistry with nickel is relatively unexplored, and the distinct electronic properties of nickel offer reactivity benefits over palladium when employing challenging phenol derived electrophiles. While ligand design requirements for BHA chemistry are well-understood, structure-reactivity trends for nickel counterparts are ill-defined, with few ligands capable of promoting these nickel-catalyzed cross-couplings. Following the establishment of PAd-DalPhos as the state-of-the-art ligand in challenging nickel-catalyzed amination reactions, we sought to build on this ortho phenylene bridged motif and explore new architectures encompassing a bulky, modestly electron-donating bisphosphine framework which would favour reductive elimination, the presumed rate-limiting step in the catalytic cycle.

Download or read book Investigating the Design of Bisphosphine Ligands for Use in Nickel catalyzed C sp2 N Cross Coupling written by Jillian Clark and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Notwithstanding the matured protocol of palladium-catalyzed C(sp2)-N cross-coupling (Buchwald Hartwig Amination, BHA), the development of nickel-based catalysts that carry out analogous transformations is motivated both by the benefits of employing Earth-abundant, cost-effective first-row transition-metals, and the potential for nickel catalysts to unveil new modes of reactivity. Over the past five years, significant advances in nickel-catalyzed amination chemistry have led to a widespread interest and expansion of this methodology. Although nickel catalysts are highly effective in the cross-coupling of ammonia, alkylamine, indole, and primary amide nucleophiles with (hetero)aryl electrophiles, these catalytic systems have yet to contend with palladium analogs in terms of exceedingly low catalyst loadings and the turnover of increasingly challenging substrate classes. Whereas BHA benefits from an unambiguous set of criteria that defines optimal ancillary ligand properties for this palladium-catalyzed transformation, structure-reactivity trends for nickel counterparts are ill-defined. Additionally, complex mechanistic details exist for nickel-catalyzed C(sp2)-N cross-coupling, which may be responsible for the vague guidelines for optimizing ancillary ligands, and the need for higher catalyst loadings. My thesis work explores ancillary ligand design criteria for nickel-catalyzed C(sp2)-N cross-coupling by cross-examining top-tier bisphosphine ligand classes with aims of clarifying the apparently divergent properties that exist among state-of-the-art ancillary ligands. Information gathered from the systematic comparisons of these ligand classes results in the development of the new bisphosphine ligand, PAd2-DalPhos, which enables the hitherto unknown nickel-catalyzed C(sp2)-N cross-coupling of primary heteroarylamines with (hetero)aryl chlorides. This chemical transformation is highly sought-after by pharmaceutical chemists for the synthesis of heteroatom-dense molecular structures, and reveals a new mode of reactivity involving challenging substrates in the context of nickel catalysis.

Download or read book A Systematic Investigation Into Bisphosphine Ligands for Nickel Catalyzed C sp2 N Cross Coupling written by Nicole Martinek and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Research into transition metal-catalyzed C-N cross-coupling reactions has been driven by a need for robust and facile synthetic routes towards bioactive molecules which are rich in C-N linkages. The use of Pd-based catalysts in Buchwald-Hartwig Amination (BHA) protocols are the most well studied and utilized within industry. The choice of Pd source, ancillary ligand, base, solvent, and the use of additives have been thoroughly investigated aiding in the selection and optimization of reaction conditions. However, research has refocused towards finding more Earth-abundant and cost-effective transition metals capable of comparable reactivity. Ni has proven to be a competitor with the development of new ancillary ligands after efforts to repurpose well-known ligands in Pd-catalysis had limited success. In particular, bisphosphines within the DalPhos ligand family have enabled the Ni-catalyzed N-arylation of challenging substrates including ammonia, alkylamines, heteroarylamines, indole, and amides with (hetero)aryl electrophiles prompting the commercialization of several ligand variants. The effects of varying experimental parameters within these ligand/Ni systems are less established and prompt further investigation in order to determine trends in reactivity and limitations. A systematic evaluation of selected bases and solvents on the effectiveness of leading DalPhos ligand variants in the C-N cross-coupling of structurally varied (hetero)aryl electrophiles with primary and secondary amines is reported herein.

Download or read book Advances in Nickel Catalyzed C N Cross Coupling Enabled by Tailored Ancillary Ligand Design written by Christopher Lavoie and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The nickel-catalyzed Csp2-N cross-coupling of NH substrates and (hetero)aryl (pseudo)halides for the synthesis of (hetero)anilines is in the midst of a resurgence. Reactivity breakthroughs that have been achieved in this field within the past five years have served to establish Ni catalysis as being competitive with, and in some cases superior to, more well-established Pd- or Cu-based protocols. Whereas the repurposing of useful ancillary ligands from the Pd domain has been the most frequently employed approach in the quest to develop effective Ni-based catalysts for such transformations, considerable progress has been made as of late in the design of ancillary ligands tailored specifically for use with Ni. Bisphosphine ancillary ligands have proven to be well-suited for such an approach, given their modular and facile syntheses. As part of this thesis research, several new bidentate phosphine ancillary ligands were developed that are particularly effective in enabling a range of otherwise challenging Nicatalyzed Csp2-N cross-couplings. Presented herein is a comprehensive summary of my contributions to the field of Ni-catalyzed Csp2-N cross-coupling, achieved by the application of a newly developed PAd-DalPhos ancillary ligand class. It is anticipated that the discussion of key ancillary ligand design concepts and mechanistic considerations presented herein will provide a useful platform for researchers to initiate ancillary ligand design efforts for the continued development of high-performing Ni cross-coupling catalysts.

Download or read book Ligand Design in Metal Chemistry written by Mark Stradiotto and published by John Wiley & Sons. This book was released on 2016-09-01 with total page 448 pages. Available in PDF, EPUB and Kindle. Book excerpt: The design of ancillary ligands used to modify the structural and reactivity properties of metal complexes has evolved into a rapidly expanding sub-discipline in inorganic and organometallic chemistry. Ancillary ligand design has figured directly in the discovery of new bonding motifs and stoichiometric reactivity, as well as in the development of new catalytic protocols that have had widespread positive impact on chemical synthesis on benchtop and industrial scales. Ligand Design in Metal Chemistry presents a collection of cutting-edge contributions from leaders in the field of ligand design, encompassing a broad spectrum of ancillary ligand classes and reactivity applications. Topics covered include: Key concepts in ligand design Redox non-innocent ligands Ligands for selective alkene metathesis Ligands in cross-coupling Ligand design in polymerization Ligand design in modern lanthanide chemistry Cooperative metal-ligand reactivity P,N Ligands for enantioselective hydrogenation Spiro-cyclic ligands in asymmetric catalysis This book will be a valuable reference for academic researchers and industry practitioners working in the field of ligand design, as well as those who work in the many areas in which the impact of ancillary ligand design has proven significant, for example synthetic organic chemistry, catalysis, medicinal chemistry, polymer science and materials chemistry.

Download or read book Challenging Nickel Catalyzed Cross Couplings Enabled by Ligand Design written by Ryan McGuire and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbon-nitrogen linkages are highly prevalent in bioactive molecules, and as such, the development of sustainable methodologies for their formation is of immense importance to both the pharmaceutical and agricultural industries. Within this realm, the advent of homogeneous transition metal catalysis has allowed significant progress to be made in the development of routes toward the formation of these linkages, encompassing a wide range of different carbon and nitrogen-containing organic reagents. Specifically, the development of Pd-catalyzed C(sp2)-N (herein, C-N) cross-coupling (i.e. Buchwald-Hartwig-Amination, BHA) has transformed the way chemists approach solving synthetic problems. Indeed, research efforts in BHA over the past 25 years have allowed for the development of several catalytic systems, encompassing a large array of both (hetero)aryl (pseudo)halide and NH-bearing substrates. Successes in BHA can be largely attributed to the rational design of ancillary ligands, which are able to dramatically influence the reactive properties of Pd through a combination of steric and electronic effects. Despite the utility of BHA, researchers have now turned to more Earth-abundant sources for effecting these transformations, including the implementation of Cu for improved versions of well-known Ullmann-coupling, and the implementation of Ni, both as alternatives to precious Pd. In this thesis, my contributions toward the rational design, syntheses and use of appropriate ancillary ligands for enabling Ni-catalyzed C-N cross-coupling are described. Included are the development of new phosphonite/phosphine ligands such as Phen-DalPhos and related variants, along with the application of Ni-based pre-catalysts for the cross-coupling of ammonia, (hetero)anilines, indoles, sulfonamides, fluoroalkylamines and amides with (hetero)aryl (pseudo)halides under unprecedently mild conditions in Ni-based catalysis.

Download or read book Development of Cobalt and Nickel N Heterocyclic Carbene Complexes for Cross Coupling Reactions written by Michael Evan Lazarus and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Cross-coupling, which relies on the use of transition metals, is among the most utilized chemical means of establishing carbon-carbon or carbon-heteteroatom bonds between appropriately functionalized sp, sp2, or sp3 centres. However, most cross-coupling reactions rely on the use of palladium to synthesize valuable synthetic targets. This is problematic for the chemical industry as palladium is limited in supply and expensive. Chemists have therefore sought to replace palladium with first-row transition metals (e.g., iron, cobalt and nickel) and recent reports on cobalt and nickel catalyzed cross-coupling reactions indicate that these metals can be used in this capacity. Unfortunately, protocols developed (so far) for these metals are unsuitable for the synthesis of targets with base-sensitive functional groups as they involve strongly basic reaction conditions. Research in this thesis aims to develop both cobalt and nickel pre-formed catalysts that will display high catalytic activity in mildly basic reaction conditions. Current methodologies for cobalt and nickel cross-coupling reactions use either phosphine ligands or NHC ligands of moderate steric bulk (IMes or IPr). Recent advancements in the development of Pd-PEPPSI catalysts have demonstrated that both pre-forming the catalyst and using larger NHC ligands (IPent, IPentCl, or IHept) are required for high catalytic activity in weakly basic conditions. Thus, it was hypothesized that the development of pre-formed cobalt and nickel NHC complexes analogous to their Pd counterparts would improve reactivity in Negishi, Suzuki-Miyaura, and Buchwald-Hartwig amination cross-coupling reactions. Co(IPent)Cl2(Pyr), Co(IPentCl)Cl2(Pyr), and Co2IPr2(OAc)4 were prepared, identified by X-ray crystallography, and evaluated in preliminary Negishi cross-coupling reactions. These complexes were found to be ineffective, but Co2IPr2(OAc)4 was found to be effective for Suzuki-Miyaura cross-coupling. A base screen was performed to enable the use of weak bases, however, the reaction only worked by pre-forming the boronate with n-BuLi, rendering the reaction conditions intolerant of base-sensitive functional groups. [Ni(IPr)]2(μ-Cl)2 , Ni(IPr)Cl(allyl), and Ni(IPent)Cl(allyl) complexes were synthesized and evaluated in Buchwald-Hartwig aminations. Several bases were examined for these reactions but only sodium tert-butoxide was found to be effective. The presence of TEMPO and BHT in these transformations proved deleterious suggesting the involvement of radical intermediates. Finally, stoichiometric reactions were performed to isolate intermediates in the catalytic cycle, supporting the formation of nickel(0).

Download or read book Exploring Ligand Enabled Nickel Catalyzed Cross Coupling of Sulfur Based Nucleophiles written by Connor Simon and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The catalytic synthesis of C(sp2)-N linkages is of utmost significance in modern synthetic chemistry, predominantly due to their prevalence in active pharmaceutical ingredients and natural products. Pd-catalyzed cross-couplings of this type, known colloquially as Buchwald-Hartwig amination (BHA), represent a tremendously important class of reactions in research and industrial settings. The success achieved by BHA can largely be attributed to the rational design of ancillary ligands specifically configured to exploit the natural electronic characteristics of the Pd metal centre. Research efforts surrounding the BHA reaction have enabled the scope of suitable coupling partners to grow rapidly, encompassing a vast array of (hetero)aryl (pseudo)halides and NH couplings partners. Notwithstanding the value of the BHA reaction, concerns over the rising costs of Pd and subsequent sustainability issues have prompted researchers to seek economical methods for accessing these linkages. One of the most promising alternatives to Pd-catalysis is the developing field of its 3d congener, Ni. However, given the relatively underdeveloped nature of Ni-catalyzed C-N bond formation, many questions regarding the mechanistic underpinnings and scope limitations remain unanswered. In this thesis, my contributions include experimental investigations into the elementary steps of a successful Ni-catalyzed cross-coupling. The successful synthesis and characterization of primary Ni-NHR catalytic intermediates reveal previously undocumented C-N bond-forming pathways, and the implementation of the mechanistic lessons learned from these studies allow for the discovery of new ligand-enabled Ni-catalyzed C-N cross-couplings.

Download or read book Nickel Catalyzed Cross Coupling Reactions written by Luke Edward Hanna and published by . This book was released on 2016 with total page 333 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cross-coupling technology has become an indispensable tool for the rapid and efficient synthesis of complex molecules. Over the past few decades a foundational understanding of organometallic chemistry has been laid using palladium and other precious metals. Recent research on first row base metal catalysts such as nickel, cobalt and iron has uncovered new and complementary modes of reactivity compared to their more well-studied precious metal counterparts. While nickel sits one row above palladium on the periodic table, ongoing research has illustrated that nickel possesses a unique reactivity profile. Thus, while nickel is commonly thought of as a cheaper alternative to palladium, research in the field of nickel catalysis has demonstrated far more potential than this. The unique propensity of nickel to undergo single electron chemistry as well as its ability to break strong carbon oxygen bonds make research into nickel reactivity an immensely beneficial endeavor to the fields of inorganic, organometallic and synthetic organic chemistry.Chapter 1 describes the development of a stereospecific Suzuki coupling of benzylic carbamates and pivalates with aryl- and heteroarylboronic esters. The reaction proceeds with selective inversion or retention at the electrophilic carbon, depending on the identity of the ligand used. Tricyclohexylphosphine ligand provides products with retention of configuration at the electrophilic carbon, while an N-heterocyclic carbene ligand SIMes provides products with inversion.Chapter 2 discusses the development of a regio- and stereoselective nickel-catalyzed hydroarylation of alkynes using propargylic carbamates as directing groups. The reaction proceeds under mild reaction conditions using arylboronic acids in the absence of base. A range of heterocycles and functional groups are tolerated under the reaction conditions. Additionally, the method is applied to the synthesis of tamoxifen.Chapter 3 details a nickel-catalyzed cross-electrophile coupling reaction of benzylic esters and aryl halides. Both inter- and intramolecular variants proceed under mild reaction conditions. A range of heterocycles and functional groups are tolerated under the reaction conditions. Additionally, the first example of a stereospecific cross-electrophile coupling of a secondary benzylic ester is described.Chapter 4 presents secondary benzylzinc reagents generated from 2-pyridylcarbinols using a nickel catalyst and diethylzinc. Substrates are activated in situ using a chlorophosphate reagent. Quenching the organozinc reagents allows for facile deoxygenation of 2-pyridylcarbinols in a one-pot reaction with straightforward incorporation of a deuterium label from deuteromethanol. An intramolecular conjugate addition of a secondary benzylzinc reagent with an alpha,beta-unsaturated ester is also demonstrated.

Download or read book Olefin Polymerization written by Walter Kaminsky and published by Wiley-VCH. This book was released on 2006-08-18 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: With an enormous velocity, olefin polymerization has expanded to one of the most significant fields in polymers since the first industrial use about 50 years ago. In 2005, 100 million tons of polyolefins were produced - the biggest part was catalyzed by metallorganic compounds. The Hamburg Macromolecular Symposium 2005 with the title "Olefin Polymerization" involved topics such as new catalysts and cocatalysts, kinetics, mechanism and polymer reaction engineering, synthesis of special polymers, and characterization of polyolefins. The conference combined scientists from different disciplines to discuss latest research results of polymers and to offer each other the possibility of cooperation. This is reflected in this volume, which contains invited lectures and selected posters presented at the symposium.

Download or read book Methodologies in Amine Synthesis written by Alfredo Ricci and published by John Wiley & Sons. This book was released on 2021-04-26 with total page 480 pages. Available in PDF, EPUB and Kindle. Book excerpt: Discover a comprehensive overview of efficient synthetic routes to an important compound class in organic and pharmaceutical chemistry Methodologies in Amine Synthesis: Challenges and Applications delivers powerful and state-of-the-art methods for the efficient preparation of amines. The text summarizes recent advances in the electrophilic amination reaction, hydroamination, C-H amination and newly developed photocatalytic approaches. The distinguished editor has included resources that discuss organocatalytic and enzymatic routes to the generation of amines under mild and environmentally friendly conditions. The book also highlights the relevance of the amino function in bioactive molecules, drugs, and smart materials, as well as the palladium-catalyzed aromatic amination reaction. It presents efficient and practical synthetic methods, highlights the opportunities and challenges associated with each, and discusses their possible applications in pharmaceutical chemistry and materials science. Edited by the expert who wrote Modern Amination Methods and Amino Group Chemistry, the book includes a breadth and depth of material essential to the practice of academic and industrial chemists working in organic synthesis and catalysis. Readers will also benefit from the inclusion of: A thorough introduction to new openings and perspectives in the electrophilic amination Discussions of asymmetric catalysed hydroaminomethylation and amino organocatalysis A treatment of the synthetic application of transaminase or MAO biocatalysis to the synthesis of amines An exploration of recent developments in C-H amination, as well as photocatalytic approaches to the synthesis of amines An examination of primary amines from renewable bio-based resources Perfect for organic, natural product, catalytic, medicinal, and polymer chemists, Methodologies in Amine Synthesis: Challenges and Applications will also earn a place in the libraries of materials scientists and chemists working with organometallics who desire a one-stop reference edited by a well-known expert in the field.

Download or read book Cross coupling Reactions written by Joffrey Vrijdag and published by . This book was released on 2020 with total page 268 pages. Available in PDF, EPUB and Kindle. Book excerpt: "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"--

Download or read book Nickel and Palladium Catalyzed Cross Coupling Reactions written by Rebecca Green and published by . This book was released on 2016 with total page 183 pages. Available in PDF, EPUB and Kindle. Book excerpt: The following dissertation discusses the development of a nickel catalyst for the synthesis of Csp2-Csp bonds in addition to the development and mechanistic studies of nickel and palladium catalysts for the synthesis of Csp2-N bonds. The first chapter is a review of the cross-coupling reactions discussed in this dissertation. Nickel and palladium will be compared with respect to physical properties and reactivity differences. The challenges associated with nickel-catalyzed cross coupling will be illustrated, while drawing analogies to analogous palladium-catalyzed reactions. The literature background for the synthesis of Csp2-Csp bonds, catalyzed by palladium and palladium/copper catalytic systems, will be reviewed, while highlighting the challenges and limitations of the field. The field of Csp2-N bond-forming reactions will be examined, as the differences in reactivity between nickel and palladium will be emphasized. Chapter 2 discusses our efforts towards the development of a nickel catalyst for the development of a Csp2-Csp bond forming reaction, performed in the absence of a copper co-catalyst. Chapter 3 describes the development of a single-component nickel complex that catalyzes the coupling of aryl chlorides with primary alkylamines. A series of mechanistic experiments, including synthesis of catalytic intermediates and kinetic experiments, were performed to elucidate the mechanism of the reaction. Chapter 4 discusses our report the palladium-catalyzed coupling of aryl halides withammonia and gaseous amines as their ammonium salts. A difference in selectivity between reactions of aryl chlorides and aryl bromides was discovered and investigated. Chapter 5 describes the development of a single-component nickel catalyst for the coupling of aryl chlorides with ammonia and ammonium sulfate to form the corresponding primary arylamines. The application of ammonium salts was extended to the coupling of gaseous amines, such as methylamine and ethylamine, which were subjected to the reaction conditions as their hydrochloride salt.

Download or read book Development of Nickel catalyzed Cross electrophile Coupling of Aryl Chlorides and Triflates with Alkyl Halides written by Seoyoung Kim and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cross-coupling is one of the most commonly used reactions in synthetic chemistry. While palladium-catalyzed cross-coupling is well-developed and established, cross-electrophile coupling is significantly younger field of study. In this approach two carbon electrophiles are directly coupled under reductive conditions, avoiding the need to prepare organometallic reagents. This is an attractive strategy because these reactions proceed through mild conditions, have high functional group tolerance, and employ readily available coupling partners. Nickel-catalyzed cross-electrophile couplings have seen considerable success in the past decade, initially in the coupling of organic iodides and later organic bromides. Despite these advances, the cross-coupling with the more abundant and inexpensive organic chlorides remain elusive due to their low reactivity. Furthermore the nickel-catalyzed cross-coupling of aryl triflates presents analogous challenges due to their differential reactivity. This thesis presents our studies to address these limitations. Through a combination of: (1) new ligand application, (2) fine tuning of alkyl electrophile reactivity through in situ halide exchange, (3) detailed mechanistic investigation of elementary steps, we demonstrate the nickel-catalyzed cross-electrophile coupling of these traditionally inert organic coupling partner. This dissertation is presented as follows: Chapter 1 is an introduction to cross-coupling strategies. Common palladium-catalyzed cross-coupling methods are discussed and their origin of cross-selectivity is highlighted. This is contrasted to cross-electrophile approaches of which mechanism is less well-understood. Early reports on nickel-catalyzed cross-electrophile coupling are presented and how mechanistic studies have elucidated the origin of cross-selectivity in these processes. Finally, the challenges of applying aryl chlorides in these first generation approaches are briefly discussed. Chapter 2 describes the development of nickel-catalyzed cross-electrophile coupling of aryl chlorides with primary alkyl chlorides to form C(sp2)-C(sp3) bonds. Investigation of ligands on selectivity and in situ halide exchange on the activation of C(sp3)-Cl bonds are detailed. Chapter 3 discusses a strategy for nickel-catalyzed cross-electrophile coupling of aryl triflates with alkyl halides. The development of reaction conditions for differing aryl electronics and mechanistic insights are described in detail. Mechanistically driven optimization and the extent of halide exchange to modulate alkyl halide reactivity are also discussed.

Download or read book Expansion of Reductive Cross couplings written by Brett Daniel Akana-Schneider and published by . This book was released on 2024 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation will discuss the expansion of cross-electophile coupling reactions to allow for the formation of C-N bonds and the improvement of existing C(sp2)-C(sp3) bond-forming reactions by the development of improved catalysts. Chapter 1 will introduce the concepts of cross-electrophile coupling, compare and contrast them with redox-neutral cross-couplings, and identify key areas for improvement. Chapter 2 describes the development of the reductive arylation of nitroarenes with aryl halides and the investigation into the mechanism of this transformation. Chapter 3 translates computational and statistical methods to nickel-catalyzed cross-electophile coupling, allowing for the devleopment of improved 2,2'-bipyridine ligands, and describes their application to a variety of cross-electrophile coupling reactions. Chapter 4 discusses the identification and initial survey of reactivity of 2,2'- bipyridine-6-carbonitrile ligands, and describes their similar yet distinct reactivity relative to their non-cyanated bpy analogues.

Download or read book C sp2 C sp3 Cross coupling of Aryl Halides and Active C sp3 H Bonds Via Dual Catalysis written by Nicholas Armada and published by . This book was released on 2019 with total page 51 pages. Available in PDF, EPUB and Kindle. Book excerpt: Convenient catalytic methodologies that can facilitate the formation of C-C bonds are undoubtedly of great interest in synthetic organic chemistry. Recent reports in literature have showcased hybrid catalytic methods that couple Ni-redox catalysis and photocatalysis to enable C-H activation of tetrahydrofuran (THF) and subsequent cross-coupling with aryl halides in appreciable yields and under relatively mild reaction conditions.1-2 However, these studies used expensive, heavy metal-containing photocatalysts and both report difficulty obtaining low-specificity across their scopes of aryl-halides. The following report will shed light on a class of photo-excitable small organic molecules that – in conjunction with a catalytic Ni-redox cycle – can be used to catalyze C-C cross-coupling reactions between THF and aryl chlorides, bromides, and iodides with yields comparable to the aforementioned reports. After screening several organic molecules with suspected photoactivity and optimization of the reaction conditions, several benzophenone derivatives were found to catalyze the cross-coupling reaction in yields up to 97%. Mechanistic investigations suggest that this reaction proceeds through a tandem catalytic pathway that involves a photocatalyzed hydrogen atom transfer/proton-coupled electron transfer (HAT/PCET) process and a Ni-mediated oxidative addition/reductive elimination cross-coupling process.

Download or read book N Heterocyclic Carbenes in Synthesis written by Steven P. Nolan and published by John Wiley & Sons. This book was released on 2006-10-27 with total page 330 pages. Available in PDF, EPUB and Kindle. Book excerpt: This first handbook to focus solely on the application of N-heterocyclic carbenes in synthesis covers metathesis, organocatalysis, oxidation and asymmetric reactions, along with experimental procedures. Written by leading international experts this is a valuable and practical source for every organic chemist.