Download or read book Development of Bifunctional Phosphines Metal Complexes and Catalysts for Various Organic Transformations written by and published by . This book was released on 2011 with total page 424 pages. Available in PDF, EPUB and Kindle. Book excerpt: A series of phosphines with different heterocycles (pyridine and imidazole) possessing different substituents (alkyl and aryl) were synthesized. The phosphine ligands were reacted with different metal precursors to from organometallic complexes which were applied to catalysis. This dissertation describes, part of the discovery process of a uniquely active and selective catalyst for alkene isomerization and the importance of heterocyclic ring in the ligand, enhancing the acceleration of the reaction to almost 11,000 times faster than a non-heterocyclic analog. Further investigation of the isomerization catalyst, as a catalyst for cycloisomerization of alkynols led to discovery of the fact that a related alkyne hydration catalyst, reported by Dan Lev in 2004, was broadly useful in cycloisomerization reactions leading to synthesis of both indoles and benzofurans. A series of allylpalladium(II) chloride bifunctional phosphine complexes were also synthesized and characterized and eventually applied as catalysts for aryl amination reactions. Finally, two mechanistically distinct approaches to anti-Markovnikov alkene hydration using bifunctional ligands are described, which show promise for further development.

Download or read book Metal Complexes with Bifunctional Imidazolyl Phosphines for Catalytic Organic Transformations written by and published by . This book was released on 2012 with total page 242 pages. Available in PDF, EPUB and Kindle. Book excerpt: The research covered in this thesis involves studying and understanding the behavior of bifunctional ligands, specifically imidazolylphoshines. The major field of study is reaction of cyclopentadienyl ruthenium complexes with olefins, namely alkene isomerization. In these complexes, the basic nitrogen of the imidazolylphosphine is thought to deprotonate coordinated alkene intermediates reversibly, facilitating isomerization of terminal alkenes to yield internal alkenes selectively. The CpRu alkene isomerization catalyst is capable of moving double bonds as far as 30 positions; further mechanistic studies in presence of deuterium labeling as a tool, has led to development of hydrogen deuterium exchange of olefins at allylic positions. This finding supports the proposed mechanism and provides and outstanding deuteration at positions accessible by isomerization. The alkene isomerization catalyst can be used in a two-phase setting where the catalyst is dissolved in the organic layer and the non-toxic, non-flammable isotopic source (D2O) is immiscible with the organic layer. Using biphasic settings one can literally wash out reactive protons on the substrate without using organic solvents. In order to control high activity of alkene isomerization catalyst in absence of steric bulk provided by the substrate, bulkier phosphine ligands were synthesized and the activity of their metal complexes toward linear olefins was investigated. As a result, a family of catalysts that is capable of isomerizing unsubstituted linear alkenes to various mixtures have been established, where one can choose a complex to fit the needs of the process at hand. Further investigation with terminal alkenes bearing functional groups can be carried out to investigate whether mono-isomerization will still be the major transformation taking place, which is expected to give access to high-value 2-alkenes. To provide easy product-catalyst separation and potential wider application, the first syntheses of polymer-supported imidazolylphophines were developed, and the alkene isomerization catalyst was thus immobilized on polystyrene-based Merrifield resin. Compared to the homogeneous catalyst, the immobilized catalysts give the same high (E)-selectivity and conversion in isomerizations of terminal olefins to internal olefins with very low metal leaching from the insoluble support. Furthermore, use of organic solvents can be excluded and isomerization can be carried out in neat liquid organic substrates.

Download or read book Homogeneous Catalysis with Metal Phosphine Complexes written by Louis M. Pignolet and published by Springer Science & Business Media. This book was released on 2013-11-21 with total page 494 pages. Available in PDF, EPUB and Kindle. Book excerpt: The field of transition metal catalysis has experienced incredible growth during the past decade. The reasons for this are obvious when one considers the world's energy problems and the need for new and less energy demanding syntheses of important chemicals. Heterogeneous catalysis has played a major industrial role; however, such reactions are generally not selective and are exceedingly difficult to study. Homogeneous catalysis suffers from on-site engineering difficulties; however, such reactions usually provide the desired selectivity. For example, Monsanto's synthesis of optically-active amino acids employs a chiral homogeneous rhodium diphosphine catalyst. Industrial uses of homogeneous catalyst systems are increasing. It is not by accident that many homogeneous catalysts contain tertiary phosphine ligands. These ligands possess the correct steric and electronic properties that are necessary for catalytic reactivity and selectivity. This point will be emphasized throughout the book. Thus the stage is set for a comprehensive be treatment of the many ways in which phosphine catalyst systems can designed, synthesized, and studied.

Download or read book Design Synthesis and Performance of Novel Bifunctional Transition Metal Complexes for Organic Reactions written by Braden Eric Silva and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: CHAPTER 1. This chapter introduces the field of study and motivations steering the direction of development. The topics of catalysis and bifunctional catalysis are discussed. CHAPTER 2. This chapter describes the development of biaryl phosphines containing functionalization with a pendent base for use in gold catalyzed organic reactions. This chapter starts with development of synthetic methods for high efficiency in the synthesis of new iterations on the chemical structure. The use of high throughput screening for reaction discovery is discussed and the result from our trials is discussed. Evaluation of the different ligand candidates is done through NMR spectroscopic studies on two reactions. The first reaction studied is carboxylic acid addition to terminal alkynes. The second reaction studied is isomerization of alkynes. CHAPTER 3. This chapter describes the synthesis of hydrogen-bond-donor-functionalized ferrocenyl bisphosphines, and studies on the coordination chemistry of the novel bisphosphines with platinum and nickel. Development of the synthetic route to yielding the target compounds was necessary, and the major points of concern are discussed. Studies on the coordination chemistry of the ferrocenyl bisphosphines with platinum and nickel are discussed

Download or read book Cooperative Catalysis written by René Peters and published by John Wiley & Sons. This book was released on 2015-01-30 with total page 456 pages. Available in PDF, EPUB and Kindle. Book excerpt: Written by experts in the field, this is a much-needed overview of the rapidly emerging field of cooperative catalysis. The authors focus on the design and development of novel high-performance catalysts for applications in organic synthesis (particularly asymmetric synthesis), covering a broad range of topics, from the latest progress in Lewis acid / Brønsted base catalysis to e.g. metal-assisted organo catalysis, cooperative metal/enzyme catalysis, and cooperative catalysis in polymerization reactions and on solid surfaces. The chapters are classified according to the type of cooperating activating groups, and describe in detail the different strategies of cooperative activation, highlighting their respective advantages and pitfalls. As a result, readers will learn about the different concepts of cooperative catalysis, their corresponding modes of operation and their applications, thus helping to find a solution to a specific synthetic catalysis problem.

Download or read book Phosphines as Reagents and Catalysts in Organic Synthesis written by Hongchao Guo and published by Elsevier. This book was released on 2019-01-15 with total page 500 pages. Available in PDF, EPUB and Kindle. Book excerpt: Phosphines as Reagents and Catalysts in Organic Synthesis provides comprehensive coverage of metal-free organic reactions with phosphines as reagents or catalysts as well as their synthetic uses. The work begins with a short historical overview of the use of phosphines in metal-free organic reactions, followed by details of their physical properties, as well as the source and preparation methods for representative phosphines and chiral variants. The applications of phosphines as reagents and catalysts in organic synthesis are discussed, along with case studies organized according to reaction type. These reactions include halogenation under Appel conditions, Wittig reaction, Staudinger reaction, Mitsunobu reaction, alcohol acylation and kinetic resolution, Rauhut-Currier reaction, Morita-Baylis-Hillman reaction, conjugate addition, umpolung additions, annulation reactions, allylic substitution, allylic amination, and isomerization reactions. For each reaction an overview of the state of art is presented along with the reaction data, enantioselective version using chiral phosphine, and its application in the synthesis of biologically active compounds and total synthesis of natural products. The work concludes with a summary that highlights the most promising reactions for future development in this field of research. Researchers, graduate students and undergraduates working in organic synthesis will find this work to be an invaluable resource. Covers the application of organic reactions involving phosphine as reagents and catalysts in organic synthesis and biological chemistry Features synthetic methods for creating heterocyclic compounds Includes comprehensive coverage of organic reactions and reaction mechanisms involving phosphine as reagents and catalysts

Download or read book Pincer Compounds written by David Morales-Morales and published by Elsevier. This book was released on 2018-04-11 with total page 756 pages. Available in PDF, EPUB and Kindle. Book excerpt: Pincer Compounds: Chemistry and Applications offers valuable state-of-the-art coverage highlighting highly active areas of research—from mechanistic work to synthesis and characterization. The book focuses on small molecule activation chemistry (particularly H2 and hydrogenation), earth abundant metals (such as Fe), actinides, carbene-pincers, chiral catalysis, and alternative solvent usage. The book covers the current state of the field, featuring chapters from renowned contributors, covering four continents and ranging from still-active pioneers to new names emerging as creative strong contributors to this fascinating and promising area. Over a decade since the publication of Morales-Morales and Jensen’s The Chemistry of Pincer Compounds (Elsevier 2007), research in this unique area has flourished, finding a plethora of applications in almost every single branch of chemistry—from their traditional application as very robust and active catalysts all the way to potential biological and pharmaceutical applications. Describes the chemistry and applications of this important class of organometallic and coordination compounds Includes contributions from global leaders in the field, featuring pioneers in the area as well as emerging experts conducting exciting research on pincer complexes Highlights areas of promising and active research, including small molecule activation, earth abundant metals, and actinide chemistry

Download or read book C2 and C3 Symmetric Chiral Bis and Tris phosphines in Asymmetric Catalysis written by Zhiming Xu and published by . This book was released on 2017 with total page 332 pages. Available in PDF, EPUB and Kindle. Book excerpt: Chapter 1. Effect of linker length on selectivity and cooperative reactivity in platinum-catalyzed asymmetric alkylation of bis(phenylphosphino)alkanes. The selectivity of catalytic asymmetric transformations of bifunctional symmetrical substrates often depends on the linker between the two reactive sites. If the catalyst controls the selectivity of reactions at both sites, the rac product will be formed in high enantiomeric ratio (er) via asymmetric amplification. Substrate control may augment this selectivity (positive cooperativity) or detract from it (negative cooperativity). We investigated the effect of linker length on the selectivity of catalytic asymmetric alkylation of the bis(secondary phosphines) PhHP-(CH2)[subscript n]PHPh (n = 2-6, 1a-e) with benzyl bromide using the base NaOSiMe3 and the catalyst precursor Pt((R,R)-Me-DuPhos)(Ph)(Cl). The two alkylations of bis(secondary phosphines) 1b-e with longer linker lengths (n = 3-6) showed identical selectivity, within experimental error. This catalyst control resulted in asymmetric amplification of rac-2. In contrast, the selectivity of the first alkylation of ethano-bridged 1a was lower than that in 1b-e (negative cooperativity), but the selectivity of the second alkylation increased due to positive cooperativity. I developed an efficient synthesis of the intermediate PhHP(CH2)2PPh(CH2Ph) (3a), which was required for determination of the selectivity of both steps in Pt-catalyzed alkylation of 1a. Possible mechanistic explanations for the observed dependence of selectivity on linker length are discussed in this chapter. Chapter 2. Selective formation of a C3-symmetric P-stereogenic tris(phosphine) via platinum-catalyzed asymmetric alkylation of a tris(secondary phosphine). C2-symmetric bis(phosphines) are the most common and successful ligands for metal-catalyzed reactions. Considering the great success of C2-symmetric ligands in asymmetric catalysis, C3-symmetric chiral tris(phosphines) were proposed to be useful in octahedral complexes, creating three homotopic sites. However, very little is known about C3-symmetric tris(phosphines) and their applications, mostly because of the lack of synthetic routes. We used Pt-catalyzed asymmetric alkylation to prepare enantiomerically enriched C3-symmetric, P-stereogenic tripodal tris(phosphines) from the tris(secondary phosphine) MeC(CH2PHPh)3 (5 a racemic mixture of C1- and C3-symmetric diastereomers) and a benzl bromide, utilizing the Pt((R,R)-Me-Duphos)(Ph)(Cl) catalyst precursor and a base. Pt-catalyzed alkylation of MeC(CH2PHPh)3 (5) with 2-cyanobenzyl bromide gave a mixture of tris(phosphines) MeC(CH2PPh(CH2Ar))3 (6) enriched in C3-6; oxidation of 6 by sulfur or H2O2 formed phosphine sulfide S-6 and oxide O-6. Hydrogen bonding between O-6 and the chiral amino acid (S)-Fmoc-Trip(BOC)-OH leads to the formation of new diastereomers. By integrating the 31P NMR spectra, I measured the dr and er values. Tris(phosphine) 6 was formed with a disatereomeric ratio (dr - C3/C1) of 2.1(2) and enantiomeric ratios of 54(10) and 3.8(7) for C3-3 and C1-3 respectively, which showed that the selectivity of the triple alkylation was not the same at each site (substrate control). Chapter 3. Screening racemic catalysts provides information on selectivity and mechanism in platinum-mediated asymmetric alkylation of bis- and tris(secondary phosphines). Screening racemic catalysts for transformations of symmetrical bifunctional substrates can provide information on the selectivity of an enantiopure catalyst. This idea was extended to Pt-catalyzed asymmetric alkylation of the bis(secondary phosphines) PhHP(CH2)3PHPh and PhHPCH2CMe2CH2PHPh and the tris(phosphine) MeC(CH2PHPh)3 with benzyl bromides using the catalyst precursors Pt(Me-DuPhos)(Ph)(CI) and Pt(BenzP*)(Ph)(CI). Depending on the catalyst and the substrate, these reactions occured under catalyst control without dissociation of the substrate, or under substrate control with or without substrate dissociation. The resulting structure-selectivity relationships provided mechanistic information. Chapter 4. Synthesis of new chiral bis(phospholane) metal-pincer complexes. Metal pincer complexes have received great attention in recent years as robust catalyst precursors. However, chiral metal pincer complexes for application in asymmetric catalysis are rare. Dialkylphospholane groups have an outstanding track record in asymmetric catalysis (commercial DuPhos and BPE ligands) and their steric properties can be easily controlled by tuning the alkyl substituents on the phospholane ring. These donors have similar steric and electronic properties to the common used bulky dialkylphosphine groups (P(t-Bu)2, P(i-Pr)2, etc.). Optimization of the synthesis of chiral PCP ligands bearing such phospholane groups and investigation of their coordination chemistry are discussed in this chapter.

Download or read book Asymmetric Organocatalysis Combined with Metal Catalysis written by Bruce A. Arndtsen and published by Springer Nature. This book was released on 2020-04-24 with total page 211 pages. Available in PDF, EPUB and Kindle. Book excerpt: The series Topics in Current Chemistry Collections presents critical reviews from the journal Topics in Current Chemistry organized in topical volumes. The scope of coverage is all areas of chemical science including the interfaces with related disciplines such as biology, medicine and materials science. The goal of each thematic volume is to give the non-specialist reader, whether in academia or industry, a comprehensive insight into an area where new research is emerging which is of interest to a larger scientific audience.Each review within the volume critically surveys one aspect of that topic and places it within the context of the volume as a whole. The most significant developments of the last 5 to 10 years are presented using selected examples to illustrate the principles discussed. The coverage is not intended to be an exhaustive summary of the field or include large quantities of data, but should rather be conceptual, concentrating on the methodological thinking that will allow the non-specialist reader to understand the information presented. Contributions also offer an outlook on potential future developments in the field.The chapter "Enamine/Transition Metal Combined Catalysis: Catalytic Transformations Involving Organometallic Electrophilic Intermediates" is available open access under a CC BY 4.0 License via link.springer.com.

Download or read book Ion tagged Phosphines for Catalytic Reactions in Ionic Liquids written by Adam J. Keith and published by . This book was released on 2014 with total page 197 pages. Available in PDF, EPUB and Kindle. Book excerpt: Development of methods to reduce energy consumption and which use non-renewable resources more efficiently is of great importance to the chemical industry. This is especially true for the production of fine chemicals and pharmaceuticals where the ratio of waste generated per quantity of product is large. Major contributions to waste stem from employing organic solvents and syntheses requiring a large number of chemical transformations. Waste can be minimized by using atom-economical reactions that promote high selectivity. Consumption of expensive transition metal catalysts is a drawback common to many catalytic reactions; therefore, development of systems that can minimize catalyst loadings and improve recyclability are of great importance. Carbon-carbon coupling reactions are an example of catalysis in need of such improvement. Suzuki-Miyaura coupling is among the most common reactions for the generation of new C-C bonds. Although well explored, the reaction still suffers from the expense of the required palladium catalyst as well as low activity in the coupling of aryl chlorides. Ionic liquids have a number of properties which make them attractive to the field of green chemistry. When used as a reaction medium, ionic liquids help prevent catalyst degradation pathways which leads to greater activity and reduction of the quantity of catalyst required. Ionic liquids can be tailored to obtain properties, such as solubility or high thermal stability, needed for a given process. Because of their unique solubility properties ionic liquids are good candidates for alleviating the high energy requirement found in solvent removal and separation of product from catalyst. This often allows for facile recycling of the expensive metal catalyst. Herein is presented research on the synthesis of an easily tunable set of ion-tagged phosphinogramine ligands for improved catalyst utility in ionic liquids. A range of steric and electronic properties was accessible by varying the substituents on phosphorus and the position of the phosphine on the indole moiety. Synthesis of metal complexes was conducted to help elucidate the electronic and steric properties of the ligands. Performance in palladium-catalyzed C-C coupling reactions was tested in ionic liquids and compared to traditional organic solvents. The results show modest catalytic activity, but are competitive with other known ionic liquid systems for difficult substrates such as aryl chlorides and electron-rich arenes. Preliminary research was also conducted on catalytic systems for asymmetric hydroformylation of styrene in ionic liquids.

Download or read book Phosphorus III Ligands in Homogeneous Catalysis written by Paul C. J. Kamer and published by Wiley. This book was released on 2012-06-25 with total page 566 pages. Available in PDF, EPUB and Kindle. Book excerpt: Over the last 60 years the increasing knowledge of transition metal chemistry has resulted in an enormous advance of homogeneous catalysis as an essential tool in both academic and industrial fields. Remarkably, phosphorus(III) donor ligands have played an important role in several of the acknowledged catalytic reactions. The positive effects of phosphine ligands in transition metal homogeneous catalysis have contributed largely to the evolution of the field into an indispensable tool in organic synthesis and the industrial production of chemicals. This book aims to address the design and synthesis of a comprehensive compilation of P(III) ligands for homogeneous catalysis. It not only focuses on the well-known traditional ligands that have been explored by catalysis researchers, but also includes promising ligand types that have traditionally been ignored mainly because of their challenging synthesis. Topics covered include ligand effects in homogeneous catalysis and rational catalyst design, P-stereogenic ligands, calixarenes, supramolecular approaches, solid phase synthesis, biological approaches, and solubility and separation. Ligand families covered in this book include phosphine, diphosphine, phosphite, diphosphite, phosphoramidite, phosphonite, phosphinite, phosphole, phosphinine, phosphinidenene, phosphaalkenes, phosphaalkynes, P-chiral ligands, and cage ligands. Each ligand class is accompanied by detailed and reliable synthetic procedures. Often the rate limiting step in the application of ligands in catalysis is the synthesis of the ligands themselves, which can often be very challenging and time consuming. This book will provide helpful advice as to the accessibility of ligands as well as their synthesis, thereby allowing researchers to make a more informed choice. Phosphorus(III) Ligands in Homogeneous Catalysis: Design and Synthesis is an essential overview of this important class of catalysts for academic and industrial researchers working in catalyst development, organometallic and synthetic chemistry.

Download or read book Phosphorus iii Ligands in Homogeneous Catalysis written by Paul Kamer and published by John Wiley & Sons. This book was released on 2012-07-01 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Over the last 60 years the increasing knowledge of transition metal chemistry has resulted in an enormous advance of homogeneous catalysis as an essential tool in both academic and industrial fields. Remarkably, phosphorus(III) donor ligands have played an important role in several of the acknowledged catalytic reactions. The positive effects of phosphine ligands in transition metal homogeneous catalysis have contributed largely to the evolution of the field into an indispensable tool in organic synthesis and the industrial production of chemicals. This book aims to address the design and synthesis of a comprehensive compilation of P(III) ligands for homogeneous catalysis. It not only focuses on the well-known traditional ligands that have been explored by catalysis researchers, but also includes promising ligand types that have traditionally been ignored mainly because of their challenging synthesis. Topics covered include ligand effects in homogeneous catalysis and rational catalyst design, P-stereogenic ligands, calixarenes, supramolecular approaches, solid phase synthesis, biological approaches, and solubility and separation. Ligand families covered in this book include phosphine, diphosphine, phosphite, diphosphite, phosphoramidite, phosphonite, phosphinite, phosphole, phosphinine, phosphinidenene, phosphaalkenes, phosphaalkynes, P-chiral ligands, and cage ligands. Each ligand class is accompanied by detailed and reliable synthetic procedures. Often the rate limiting step in the application of ligands in catalysis is the synthesis of the ligands themselves, which can often be very challenging and time consuming. This book will provide helpful advice as to the accessibility of ligands as well as their synthesis, thereby allowing researchers to make a more informed choice. "Phosphorus(III) Ligands in Homogeneous Catalysis: Design and Synthesis" is an essential overview of this important class of catalysts for academic and industrial researchers working in catalyst development, organometallic and synthetic chemistry.

Download or read book Development of Transitional Metal catalyzed Reactions for Organic Synthesis written by Matthew Paul Rainka and published by . This book was released on 2005 with total page 260 pages. Available in PDF, EPUB and Kindle. Book excerpt: Chapter 1. A general catalyst system for the synthesis of tetra-ortho-substituted biaryls via the Suzuki-Miyaura cross-coupling reaction is described. It was found that the most efficient catalyst system is based on a phenanthrene-substituted biaryl phosphine ligand. Utilizing this ligand, a number of tetra-ortho-substituted biaryls were synthesized in good to excellent yields. Chapter 2. A procedure for the arylation of methyl and cyclic ketone enolates with o-halonitroarenes was developed. An unusual additive effect of phenols on the outcome of the reaction was observed and explored. This process has provided for the regioselective synthesis of a wide variety of substituted indoles from commercially available materials. Chapter 3. The first method for the asymmetric copper-catalyzed conjugate reduction of [alpha], [beta] unsaturated esters containing [beta]-heteroatoms was developed. We found that this system tolerated the presence of both lactams as well as azaheterocycles in the [beta]-position of various enoates. This has led to the asymmetric synthesis of a number of interesting [5- amino acid derivatives. Chapter 4. A copper-catalyzed conjugate reduction reaction that allows for a variety of [gamma]-aryl containing [alpha], [beta]-unsaturated butenolides to be reduced in both high enantiomeric and diastereomeric excess was developed. While a number of catalysts based on chiral bisphosphines were found to successfully perform this transformation, optimal enantioselectivity was obtained when employing the commercially SYNPHOS ligand.

Download or read book Copper I Chemistry of Phosphines Functionalized Phosphines and Phosphorus Heterocycles written by Maravanji S. Balakrishna and published by Elsevier. This book was released on 2019-04-26 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Copper(I) Complexes of Phosphines, Functionalized Phosphines and Phosphorus Heterocycles is a comprehensive guide to one of the most widely used and extensively studied metals: copper. The numerous practical applications of copper compounds are discussed, including homogeneous and heterogeneous catalysis and their use as fungicides, pesticides, pigments for paints, resins and glasses, and in high-temperature superconductors. The remarkable structural flexibility of simple copper(I) complexes, such as cuprous halides is covered, including numerous structural motifs that, when combined with different ligand systems, exhibit linear, trigonal planar or tetrahedral geometries. This work is an essential reference for inorganic and coordination chemists, as well as researchers working on catalysis, anticancer reagents, luminescence, fluorescence and photophysical aspects.

Download or read book Development of Phosphorus Mediated Reactions in Organic Synthesis Y Xia Xuanshu B SC Sun Yat Sen U written by Xuanshu Xia and published by Open Dissertation Press. This book was released on 2017-01-27 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Development of phosphorus-mediated reactions in organic synthesis / y Xia Xuanshu, B. Sc., Sun Yat-sen U" by Xuanshu, Xia, 夏轩庶, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Polymer-supported catalysts and reagents have been widely used in organic chemistry because they could facilitate the purification procedures and usually be recycled. Much research has been directed to polymer-supported catalysts and reagents, mainly focusing on these aspects, such as new polymer support, new application in organic chemistry, different modifications and so on. Many polymer-supported phosphine reagents have been developed for Wittig reaction. However, most of them suffer from swelling issue or low loading. A new polyethlyeneimine-supported triphenylphosphine has been synthesized and used as a highly loaded bifunctional homogeneous reagent in a range of one-pot Wittig reactions. All the substrates afforded desired products in high yields after only simple purification procedures. Furthermore, it also served efficiently in reaction cascades involving a one-pot Wittig reaction followed by conjugate reduction of alkene products. In these transformations the phosphine oxide generated in Wittig reaction served as the catalyst for activating trichlorosilane in the subsequent reduction reaction. Triphenylphosphine oxide is always considered as a byproduct of Wittig and Mitsunobu reactions which complicates the purification procedures. One option to utilize it is its application in halogenation reaction with oxalyl halide. Heterogeneous polymer-supported triphenylphosphine oxides based on the rasta resin architecture have been synthesized, and applied as reagent precursors in a wide range of halogenation reactions. The rasta resin-triphenylphosphine oxides reacted with either oxalyl chloride or oxalyl bromide to form the corresponding halophosphonium salts, and these in turn reacted with alcohols, aldehydes, aziridines and epoxides to form halogenated products in high yields after simple purification. The polymer-supported triphenylphosphine oxides formed as a byproduct during these reactions could be recovered and reused numerous times with no appreciable decrease in reactivity. Another option is to use triphenylphosphine oxide as catalyst in organic synthesis. A highly regioselective 1,4-reduction of conjugated polyunsaturated ketones catalyzed by triphenylphosphine oxide is described. In the presence of triphenylphosphine oxide, conjugated di-, tri-, and tetraenones were selectively α,β-reduced using trichlorosilane without over reduction or isomerization, and all the substrates rendered desired products in high yields. Furthermore, 1,4-reduction products were successfully obtained in sequential one-pot Wittig/conjugate reduction reaction, triphenylphosphine oxide generated in Wittig reaction served as the catalyst for reduction reaction. In addition, natural moth pheromones and their analogues were synthesized in high yields using this method. Finally, the synthesis of γ-sanshool and hydroxy-γ-sanshool is depicted. The synthetic route started from simple and commercially available building blocks using an alkyne for E, E-2,4-diene group of the key synthetic intermediate 2E,4E,8Z,10E,12E-tetradecapentaenoic acid, which in turn was converted into both γ-sanshool and hydroxy-γ-sanshool by reaction with the appropriate amines. DOI: 10.5353/th_b5435655 Subjects: Supported reagents Polymers

Download or read book Zinc Catalysis written by Stephan Enthaler and published by John Wiley & Sons. This book was released on 2015-04-27 with total page 326 pages. Available in PDF, EPUB and Kindle. Book excerpt: Filling the gap in the market for comprehensive coverage of this hot topic, this timely book covers a wide range of organic transformations, e. g. reductions of unsaturated compounds, oxidation reactions, Friedel-Crafts reactions, hydroamination reactions, depolymerizations, transformations of carbon dioxide, oxidative coupling reactions, as well as C-C, C-N, and C-O bond formation reactions. A chapter on the application of zinc catalysts in total synthesis is also included. With its aim of stimulating further research and discussion in the field, this is a valuable reference for professionals in academia and industry wishing to learn about the latest developments.

Download or read book Design of Precatalysts and Phosphine Ligands for Pd catalyzed Transformations written by Bryan Taylor Ingoglia and published by . This book was released on 2019 with total page 373 pages. Available in PDF, EPUB and Kindle. Book excerpt: The work described in this thesis pertains to the formation of carbon-heteroatom bonds facilitated by palladium catalysts supported by bulky phosphine ligands. The first chapter is a summary of how biaryl monophosphine ligands have been used for carbon-heteroatom bond formations, including a ligand selection guide. The second chapter demonstrates how phosphinesupported Pd(II) oxidative addition complexes can be used as precatalysts in a variety of cross-coupling reactions. The third chapter presents a systematic study of the ligand architecture in an effort to rationally design new ligands capable of facilitating the challenging C-F reductive elimination from Pd(II). The fourth chapter highlights a structurally interesting side-product that resulted during ligand synthesis. Chapter 1: Biaryl Monophosphine Ligands in Palladium-Catalyzed C-N Coupling: An Updated User's Guide Over the past three decades, Pd-catalyzed cross-coupling reactions have become a mainstay of organic synthesis. In particular, catalysts derived from biaryl monophosphines have shown wide utility in forming C-N bonds under mild reaction conditions. This work summarizes a variety of C-N cross-coupling reactions using biaryl monophosphines as supporting ligands, with the goal of directing synthetic chemists toward the ligands and conditions best suited for a particular coupling. Chapter 2. Oxidative Addition Complexes as Precatalysts for Cross-Coupling Reactions Requiring Extremely Bulky Biarylphosphine Ligands. Palladium-based oxidative addition complexes were found to be effective precatalysts for C-N, C-O, and C-F cross-coupling reactions with a variety of aromatic electrophiles. These Pd(II) complexes are easily prepared and offer a convenient alternative to previously developed classes of precatalysts as they can be formed even with extremely large phosphine ligands, for which palladacycle-based precatalysts do not readily form. The complexes were found to be stable to long-term storage under ambient conditions. Chapter 3. Structure-Activity Relationship of Phosphine Ligands for the Fluorination of Five-membered Heteroaromatic Compounds Palladium catalysts supported by bulky dialkyl triaryl monophosphine ligands have been shown to promote the coupling of metal fluorides with (hetero)aryl bromides and triflates in good yield. A limitation of this methodology is the use of five-membered heteroaryl bromides, as the reductive elimination is more challenging due to the smaller size and electron-rich nature of the aryl electrophiles. In order to understand which structural features of the ancillary ligand are critical to facilitating the desired transformation, the ligand backbone was systematically varied and the initial rate of fluorination was monitored. These studies revealed that substitution at the 2" and 6" positions of the ligand scaffold has a dramatic impact on the reaction rate. As a result of these studies, new ligands were proposed which may be better able to accelerate the fluorination reaction. Chapter 4: Discovery of a Sterically Encumbered Hexasubstituted Arene through the Pdmediated Dearomative Rearrangement of Biaryl Monophosphine Ligands A key feature of the Pd-catalyzed aromatic fluorination reaction is the presence of the aryl group at the 3' position of the ligand backbone. It has been shown that supporting ligands lacking substitution at this position can be modified through a dearomative rearrangement, which incorporates one catalytic equivalent of the aryl electrophile into the ligand backbone when very bulky biarylphosphines are used. In Chapter 3, it was demonstrated that this rearrangement reaction is useful for rapidly accessing a variety of dialkyl triaryl monophosphine derivatives. During these studies, it was noted that for electron-rich aryl groups, this arylation occurred twice to form an unusual sterically congested hexasubstituted arene. X-ray crystallographic data indicates that the fully substituted aromatic ring is not planar.