Download or read book Development of Novel Cyclopentadienone Based Transition Metal Complexes for Catalytic and Electrocatalytic Transfer Hydrogenation of Polar Bonds written by Weiwei Wu and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Development of Novel Transition Metal Catalysts and Electrochemical Methods for the Formation of Carbon carbon and Carbon heteroatom Bonds written by Mikhaila D.. Ritz and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Transition metal catalysis has revolutionized modern synthetic methodology by enabling the facile activation and generation of sp2 and sp3 (hetero)carbon bonds. Thus, organometallic complexes are ubiquitous in the production of commodity chemicals, synthetic building blocks, and polymers. Although transition metal catalysis has been broadly used, there is still room for improvement in its efficiency, sustainability, and applicability. To this extent this dissertation will focus on employing different strategies to address these challenges. Chapter 2 will discuss the implementation of an electrocatalytic system for the metal catalyzed oxidation of alcohols and amines using benzoquinones as regenerable hydrogen acceptors. Chapter 3 will illustrate the design and development of a novel bisoxazoline-pincer ligated cobalt complex and its catalytic ability to hydrogenate alkenes, followed by discussion of exploratory work of this scaffold's early transition metal analogs and potential further catalytic reactivity. Lastly, chapter 4 will examine a set of trispyrazoylborate metal complexes for their capacity to perform direct arene borylation and compare the resulting reactivity to their heavily studied isoelectronic cyclopentamethyldienyl iridium counterparts. Analysis of the reaction reveals formation of nanoparticles leading to further characterization via XRD and TEM imaging."--Page x.
Download or read book N4 Macrocyclic Metal Complexes written by J.H. Zagal and published by Springer Science & Business Media. This book was released on 2007-07-16 with total page 828 pages. Available in PDF, EPUB and Kindle. Book excerpt: In response to significant developments in sensor science and technology, this book offers insight into the various extended applications and developments of N4 macrocycle complexes in biomimetic electrocatalysis. Chapters are devoted to the chemistry, electronic and electrochemical properties of porphyrin- based polymetallated supramolecular redox catalysts and their applications in analytical and photoelectrochemical molecular devices; the use of porphyrins, phthalocyanines and related complexes as electrocatalysts for the detection of a wide variety of environmentally polluting and biologically relevant molecules; and the use of electropolymerized metalloporphyrin and metallophthalocyanine films as powerful materials for analytical tools, especially for sensing biologically relevant species.
Download or read book Investigations of Homogeneous Ruthenium and Cobalt Complexes for Electrocatalytic Transformations written by Kate M. Waldie and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Transition metal hydrides are key intermediates implicated in a wide range of chemical and electrochemical transformations. Herein, select examples of molecular transition metal hydride complexes and their applications in critical hydrogen transfer reactions, specifically transfer hydrogenation, electrocatalytic alcohol oxidation, and electrocatalytic hydrogen evolution, are presented. An octahedral Ru-hydride complex reacts rapidly and irreversibly with CO2 under ambient conditions to yield the Ru-formate. The analogous insertion of various ketones yields an equilibrium mixture of the hydride and alkoxide complexes, for which the equilibrium constants are measured by 1H NMR. Density functional theory is used to compare the mechanism of acetone and CO2 insertion. Investigations on the kinetic profile of transfer hydrogenation with the Ru-hydride complex reveal some key aspects of the mechanism. The Ru-hydride undergoes an irreversible oxidation at low potential by cyclic voltammetry. In the presence of alcohol and alkoxide base, large current enhancement is observed at this potential, consistent with electrocatalytic alcohol oxidation. The synthesis and characterization of a family of dicationic Co(III) complexes with bidentate nitrogen ligands are presented. Upon addition of protonated N, N-dimethylformamide buffer, electrocatalytic hydrogen evolution is observed at onset potentials near -1.1 V. Further studies demonstrate that these complexes decompose under acidic reducing conditions to form an active species at the electrode surface. A Co(III)-azopyridine complex exhibits a reversible 2e- reduction at very mild potentials. Chemical reduction with cobaltocene yields a neutral complex as an air stable, diamagnetic solid. Spectroscopic and crystallographic studies illuminate key structural and electronic changes that occur upon reduction, indicating that the neutral complex is best described as a highly delocalized system. Protonation of the neutral species yields a monocationic hydrazino complex. All three cleavage modes (i.e. proton, hydride, and hydrogen atom) for this ligand N-H bond are demonstrated. Studies on the stoichiometric reactivity of this complex with the triphenylcarbenium cation and TEMPO radical are explored.
Download or read book Metallocenes in Regio and Stereoselective Synthesis written by Marko Hapke and published by Springer. This book was released on 2024-06-20 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents the latest synthetic protocols for the assembly of functionalized Cp ligands and their transition metal complexes. Cyclopentadienyl (Cp) complexes of transition metals belong to the most important classes of transition metal complexes with tightly bound ligands in the coordination sphere since their discovery in the middle of the last century. Even though they have been known for a long time, this field constantly evolves to deliver novel modified Cp ligands and complexes and to blossom into new fields of application. Beside the synthesis of ligands and metal complexes this book concentrates on novel and prospering fields of their application in organic synthesis. In this respect the Cp complexes have been applied to induce and catalyze various significant chemical transformations such as new C-C bond formation involving unsaturated substrates (e.g. cyclotrimerizations, cycloadditions, carbometallations, etc.), C-H bond and C-C bond activations followed by subsequent reactions (e.g. arylation, alkenylations, annulations, etc.), as well as many other processes. This volume also covers the recent development and application of chiral Cp complexes in enantioselective synthesis.
Download or read book Design and Development of Novel Organoselenide based Transition Metal Catalysts and Their Utility in Carbon carbon and Carbon heteroatom Bond Formation Reactions written by Elizabeth Pearl Kinney and published by . This book was released on 2005 with total page 272 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Transition Metal catalyzed Reductive C C Bond Formation Under Hydrogenation and Transfer Hydrogenation Conditions written by Ming-yu Ngai and published by . This book was released on 2008 with total page 652 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbon-carbon bond forming reactions are vital to the synthesis of natural products and pharmaceuticals. In 2003, the 200 best selling prescription drugs reported in Med Ad News are all organic compounds. Synthesizing these compounds involves many carbon-carbon bond forming processes, which are not trivial and typically generate large amounts of waste byproducts. Thus, development of an atom economical and environmentally benign carbon-carbon bond forming methodology is highly desirable. Hydrogenation is one of the most powerful catalytic reactions and has been utilized extensively in industry. Although carbon-carbon bond forming reactions under hydrogenation conditions, such as, alkene hydroformylation and the Fischer-Tropsch reaction are known, they are limited to the coupling of unsaturated hydrocarbons to carbon monoxide. Recently, a breakthrough was made by the Krische group, who demonstrated that catalytic hydrogenative C-C bond forming reactions can be extended to the coupling partners other than carbon monoxide. This discovery has led to the development of a new class of carbon-carbon bond forming reactions. Herein, an overview of transition metal-catalyzed reductive couplings of [pi]-unsaturated systems employing various external reductants is summarized in Chapter 1. Chapters 2-4 describe a series of rhodium- and iridium-catalyzed asymmetric hydrogenative couplings of various alkynes to a wide range of imines and carbonyl compounds. These byproduct-free transformations provide a variety of optically enriched allylic amines and allylic alcohols, which are found in numerous natural products, and are used as versatile precursors for the synthesis of many biologically active compounds. Transfer hydrogenation represents another important class of reactions in organic chemistry. This process employs hydrogen sources other than gaseous dihydrogen, such as isopropanol. The Krische group succeeded in developing a new family of transfer hydrogenative carbon-carbon bond formation reactions. Chapter 5 presents two novel ruthenium- and iridium-catalyzed transfer hydrogenative carbonyl allylation reactions. The catalytic system employing iridium complexes enables highly enantioselective carbonyl allylation from both the alcohol and aldehyde oxidation level. These systems define a departure from the use of preformed organometallic reagents in carbonyl additions that transcends the boundaries of oxidation level.
Download or read book Heterocycles from Transition Metal Catalysis written by András Kotschy and published by Springer Science & Business Media. This book was released on 2005-12-28 with total page 209 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Heterocycles from Transition Metal Catalysis: Formation and Functionalization" provides a concise summary of the prominent role of late transition metal (palladium, nickel, copper) catalysed processes in the synthesis and functionalization of heterocyclic systems. It gives an introduction to catalytic transformations, an overview of the most important reaction types, and presents synthetically useful catalytic processes classified by the target system and the type of transformation. The book provides a representative selection of transition metal catalysed reactions transformations that are relevant in heterocyclic chemistry. In this way, the authors present a useful resource for members of the academic community looking for a textbook as well as industrial chemists in search of a reference book. This book will be an invaluable resource for synthetic chemists, medicinal chemists, and those more generally interested in applied catalysis.
Download or read book Cleavage of Carbon Carbon Single Bonds by Transition Metals written by Masahiro Murakami and published by John Wiley & Sons. This book was released on 2015-09-21 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt: Edited by leading experts and pioneers in the field, this is the first up-to-date book on this hot topic. The authors provide synthetic chemists with different methods to activate carbon-carbon sigma bonds in organic molecules promoted by transition metal complexes. They explain the basic principles and strategies for carbon-carbon bond cleavage and highlight recently developed synthetic protocols based on this methodology. In so doing, they cover cleavage of C-C bonds in strained molecules, reactions involving elimination of carbon dioxide and ketones, reactions via retroallylation, and cleavage of C-C bonds of ketones and nitriles. The result is an excellent information source for researchers in academia and industry working in the field of synthetic organic chemistry, while equally serving as supplementary reading for advanced courses in organometallic chemistry and catalysis.
Download or read book Activation of Saturated Hydrocarbons by Transition Metal Complexes written by A.E. Shilov and published by Springer Science & Business Media. This book was released on 1984-06-30 with total page 226 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book First row Transition Metal Coordination Compounds for the Electrocatalytic Generation of Hydrogen from Organic and Aqueous Solutions written by Patrick M. Crossland and published by . This book was released on 2015 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt: The development of stable proton reduction catalysts is imperative due to their importance as a source of a carbon-neutral fuel. A cobalt-salen complex with electron withdrawing groups was synthesized. This complex generated protons from organic solutions at a 190 mV overpotential with a kobs of 42000 M-2s-1, and a corresponding turnover frequency of 420 s-1. This is one of the lowest overpotentials reported for a cobalt proton reduction catalyst. While insoluble in water, an experiment where water was added to an electrochemical cell showed a 20% increase in catalytic activity. This indicates that cobalt-salen complexes could be highly active in aqueous solutions. Developing first row transition metal complexes for electro- and photocatalytic hydrogen evolution is of great interest. A photocatalyst for proton reduction could be incorporated into an artificial photosynthesis device to generate hydrogen gas as a solar fuel. Nickel was complexed with the H3ttfasbz ligand, which is known to be redox active.35 In order to assess its catalytic ability electrochemical tests, including proton concentration experiments, and catalyst concentration experiments were performed. These tests showed the nickel complex to be highly active for hydrogen reduction at a cathodic potential (-1.37 V vs. SCE). Due to the high overpotential of this complex, it was integrated into a photocatalytic system with fluorescein as a chromophore.
Download or read book Transition metal catalyzed C C Bonds Formation Via Transfer Hydrogenation written by Gang Wang (Ph. D.) and published by . This book was released on 2017 with total page 684 pages. Available in PDF, EPUB and Kindle. Book excerpt: Redox-triggered carbonyl addition via transfer hydrogenation, which enables direct primary alcohol C-H functionalization to form C-C bond, avoids usage of premetalated reagents or discrete alcohol to aldehyde redox reactions. Moreover, step-economy could be greatly improved by site-selective transformations of polyfunctional molecules due to bypassing the need to install and remove protecting groups. However, the redox site-selective transformations still pose a significant challenge in the area of synthetic organic chemistry. Efforts have been focused on the development of iridium catalyzed transfer hydrogenative coupling reactions of primary alcohols with different allyl donors through carbonyl addition in a site-selective manner as well as ruthenium catalyzed regioselective hydrohydroxyalkylation of primary alcohols with a basic feedstock-styrene. Additionally, studies towards the total synthesis of type I polyketide natural product (+)-SCH 351448 in the most concise route is presented.
Download or read book Transition Metal catalyzed Reductive C C Bond Forming Hydrogenation transfer Hydrogenation and Applications in the Total Synthesis of roxaticin written by Soo Bong Han and published by . This book was released on 2010 with total page 860 pages. Available in PDF, EPUB and Kindle. Book excerpt: By simply hydrogenating enones in the presence of aldehydes at ambient temperature and pressure, aldol adducts are generated under neutral conditions in the absence of any stoichiometric byproducts. Using cationic rhodium complexes modified by tri(2-furyl)phosphine, highly syn-diastereoselective reductive aldol additions of vinyl ketones are achieved. Finally, using novel monodentate TADDOL-like phosphonite ligands, the first highly diastereo- and enantioselective reductive aldol couplings of vinyl ketones were devised. These studies, along with other works from our laboratory, demonstrate that organometallics arising transiently in the course of catalytic hydrogenation offer byproduct-free alternatives to preformed organometallic reagents employed in classical carbonyl addition processes. Existing methods for enantioselective carbonyl allylation, crotylation and tert-prenylation require stoichiometric generation of pre-metallated nucleophiles, and often employ stoichiometric chiral modifiers. Under the conditions of transfer hydrogenation employing an ortho-cyclometallated iridium C, O-benzoate catalyst, enantioselective carbonyl allylations, crotylations and tert-prenylations are achieved in the absence of stoichiometric metallic reagents or stoichiometric chiral modifiers. Moreover, under transfer hydrogenation conditions, primary alcohols function dually as hydrogen donors and aldehyde precursors, enabling enantioselective carbonyl addition directly from the alcohol oxidation level.
Download or read book Synthesis Electrochemical and Electrocatalytic Properties of Transition Metal Complexes Based on Cyclohexane supported Bis imino Pyridines written by Simon Child and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Late Transition Metal Complexes Bearing Functionalized N Heterocyclic Carbenes and the Catalytic Hydrogenation of Polar Double Bonds written by Wylie Wing Nien O and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Synthesis and Reactivity of Transition Metal and Main Group Hydrogenation Catalysts written by Eliar Mosaferi and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since its discovery by Paul Sabatier, catalytic hydrogenation of unsaturated substrates has become the single largest industrial process to date and encompasses the production of many products, such as foods, agrochemicals, pharmaceuticals, and materials. Over the last century research in the area has predominantly focused on the use of transition metals such as palladium, platinum, rhodium, and ruthenium to develop heterogeneous and homogeneous hydrogenation catalysts. The research presented herein focuses on the use of ruthenium complexes bearing electron-rich phosphorylated N-heterocyclic carbene ligands as well as the development of main-group compounds for frustrated Lewis pair catalysis. Complexes [Ru(0)LL'2(CO)] and [RuHL2(CO)][Cl], where L = N-phosphorylated N-heterocyclic carbene (NHCP), and L' = triphenylphosphine, were prepared as a mixture by treatment of RuHCl(CO)(PPh3)3 with excess NHCP carbene and separated by crystallization. The zero-valent complex [Ru(0)LL'2(CO)] was shown to undergo rapid oxidative addition to the corresponding Ru(II) species when treated with small molecules to afford complexes of the general type [RuHXLL'(CO)], where L = N-phosphorylated N-heterocyclic carbene, L = triphenylphosphine, and X = H, SiPh3, or Si(H)Ph2. The reaction of NHCP carbene with [RuCl2(p-cymene)]2 resulted in the isolation of the piano-stool half-sandwich complex [RuCl2(p-cymene)(NHCP)] as well as an unusual arene-activated species. The half-sandwich complex was treated with a halide-abstracting agent to afford the cationic compound [RuCl(p-cymene)(NHCP)]+, which was shown to rapidly undergo dihydrogen activation via an outer-sphere mechanism involving the phosphine appended to the carbene ligand. To demonstrate the utility of main-group catalysts, trityl cations of the form [(4-MeO-C6H4)xCPh3-x][BR4] were synthesized, where x = 1 and 3, and R = F, or C6F5. Treatment of equimolar solutions of [(4-MeO-C6H4)CPh2][BF4] and sterically encumbered phosphines with dihydrogen resulted in activation of dihydrogen but no catalytic activity was observed. The air- and moisture-stable [(4-MeO-C6H4)CPh2][BF4] was shown to be a potent Lewis acid catalyst in the hydrothiolation of olefins.
Download or read book Development of New Transition Metal Catalyzed C C Bond Forming Reactions and Their Application Toward Natural Product Synthesis written by Abbas Hassan and published by . This book was released on 2011 with total page 670 pages. Available in PDF, EPUB and Kindle. Book excerpt: In Michael J. Krische research group we are developing new transition metal catalyzed Carbon-Carbon (C-C) forming reactions focusing on atom economy and byproduct free, environmental friendly approaches. We have developed a broad family of C-C bond forming hydrogenations with relative and absolute stereocontrol which provide an alternative to stoichiometric organometallic reagents in certain carbonyl and imine additions. Inspiring from the group work my goal was to develop new reactions, extend the scope of our group chemistry and their application towards synthesis of biologically active natural products. I have been part of enantioselective Rh catalyzed Aldol reaction of vinyl ketones to different aldehydes. Also, we have found that iridium catalyzed transfer hydrogenation of allylic acetates in the presence of aldehydes or alcohols results in highly enantioselective carbonyl allylation under the conditions of transfer hydrogenative. Based on this reactivity a concise enantio- and diastereoselective synthesis of 1,3-polyols was achieved via iterative chain elongation and bidirectional iterative asymmetric allylation was performed, which enables the rapid assembly of 1,3-polyol substructures with exceptional levels of stereocontrol. The utility of this approach stems from the ability to avoid the use of chirally modified allylmetal reagents, which require multistep preparation, and the ability to perform chain elongation directly from the alcohol oxidation level. This approach was utilized for the total synthesis of (+)-Roxaticin from 1,3-propanediol in 20 longest linear steps and a total number of 29 manipulations. Further, advancements were made in iridium catalyzed C-C bond formation under transfer hydrogenation. While methallyl acetate does not serve as an efficient allyl donor, the use of more reactive leaving group in methallyl chloride compensate for the shorter lifetime of the more highly substituted olefin [pi]-complex. Based on this insight into the requirements of the catalytic process, highly enantioselective Grignard-Nozaki-Hiyama methallylation is achieved from the alcohol or aldehyde oxidation levels. Also, a catalytic method for enantioselective vinylogous Reformatsky- type aldol addition was developed in which asymmetric carbonyl addition occurs with equal facility from the alcohol or aldehyde oxidation level. Good to excellent levels of regioselectivity and uniformly high levels of enantioselectivity were observed across a range of alcohols and aldehydes.
