Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 12
Book Description
Carbon-hydrogen Bond Activation, C-N Bond Coupling, and Cycloaddition Reactivity of a Three-coordinate Nickel Complex Featuring a Terminal Imido Ligand
Author: Experimental and Theoretical Investigations of Carbon-carbon, Carbon-hydrogen and Carbon-sulfur Bond Activations of Nitriles Using Zerovalent Nickel
Author: Ting LiPublisher:
ISBN:
Category :
Languages : en
Pages : 892
Book Description
"[Ni(dippe)H]2 complex has been reacted with a variety of carbon nitriles. Upon mixing with substrates, it releases H2 to generate the 14-electron fragment [Ni(dippe)], which is proposed to be the active species in bond activations. In the reaction with acetonitrile, initially the [...characters removed]-nitrile complex was observed, which upon heating or photolysis leads to the C-CN bond activation product Ni(dippe)(CH3)(CN). No product from C-H bond cleavage was seen and the independently synthesized Ni(dippe)(H)(CH2CN) complex was very unstable and can only exist at low temperature. Computational studies using DFT calculation methods showed that the C-CN bond activation is favored exclusively over the C-H bond activation due to the strong thermodynamic driving force and slightly lower kinetic barrier. In reactions with aromatic nitriles, the [Ni(dippe)] fragment first coordinates [...characters removed] to the nitrile C=̲N and/or C=C moiety. Rearrangement then occurs to give the C-CN oxidative addition product Ni(dippe)(Aryl)(CN). Both experimental and DFT calculation results have shown that an [...characters removed]-arene complex with nickel coordinated to the C=C double bond next to the cyano substituent is the crucial intermediate leading to C-CN bond activation. Furthermore, the fluxional processes of the [...characters removed]-arene species were investigated by low-temperature experiments as well as computational methods. In the cases of benzonitrile and dicyanobenzenes, a mechanism was found with the Ni(dippe) fragment rotating as it migrates around the phenyl ring through a series of [...characters removed]-allyl-like transition states. For polycyclic aromatic nitriles, only certain [...characters removed]-arenes were stable enough to contribute to the fluxional process, and nickel migrates via an [...characters removed]-coordinated transition state. The transition states connecting the [...characters removed]-nitrile complex to the [...characters removed]-arene intermediate and the [...characters removed]-arene intermediate to the C-CN bond activation products are at much higher energies compared to those for migration around the ring. In the reaction of 9-cyanoanthracene, the instability of the [...characters removed]-arene precursor and the high energy activation barrier resulted in the absence of the C-CN oxidative addition product. The complex with 9-cyanophenanthrene only undergoes C-CN cleavage upon photolysis. The Lewis acid BEt3 disfavors the C-CN bond activation in acetonitrile, but can facilitate C-CN cleavage in aromatic nitriles. The isomerization of 2-methyl-3-butenenitrile (2M3BN) carried out by [Ni(dippe)H]2 can follow either a C-CN activation pathway to form the linear product 3-pentenenitrile (3PN), or a C-H activation pathway to give the branched olefin product 2-methyl-2-butenenitrile (2M2BN). Both pathways have been studied by DFT calculation methods and the results matched well with those observed in stoichiometric experiments. A detailed mechanism has been proposed and tested on several other model bisphosphine ligands to investigate bite angle and electronic effects on the selectivity of nickel bisphosphine catalysts. In the reaction of [Ni(dippe)H]2 with 2-cyanothiophene, the processes of C-C and C-S bond cleavage have been studied. At room temperature, cleavage of the nitrile-substituted C-S bond occurs, forming the Ni-metallacycle complex (dippe)Ni(K2-S,C-SCH=CHCH=C(CN)), which was converted to the C-CN cleavage product (dippe)Ni(CN)(2-thiophenyl) when heated in solution. A kinetic product (dippe)Ni(K2-S,C-SC(CN)=CHCH=CH) was formed from cleavage of the non-substituted C-S bond, as well as a [...characters removed], and a dinuclear mixed Ni(0)-Ni(II) product. A complete DFT analysis of this system has been carried out to reveal comparative details about the two bond cleavage transition states."--Leaves vii-ix.
Olefin Polymerization
Author: Walter KaminskyPublisher: Wiley-VCH
ISBN: 9783527317424
Category : Technology & Engineering
Languages : en
Pages : 0
Book Description
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.
New Carbon–Carbon Coupling Reactions Based on Decarboxylation and Iron-Catalyzed C–H Activation
Author: Rui ShangPublisher: Springer
ISBN: 9811031932
Category : Science
Languages : en
Pages : 225
Book Description
This thesis presents the latest developments in new catalytic C–C bond formation methods using easily accessible carboxylate salts through catalytic decarboxylation with good atom economy, and employing the sustainable element iron as the catalyst to directly activate C–H bonds with high step efficiency. In this regard, it explores a mechanistic understanding of the newly discovered decarboxylative couplings and the catalytic reactivity of the iron catalyst with the help of density functional theory calculation. The thesis is divided into two parts, the first of which focuses on the development of a series of previously unexplored, inexpensive carboxylate salts as useful building blocks for the formation of various C–C bonds to access valuable chemicals. In turn, the second part is devoted to several new C–C bond formation methodologies using the most ubiquitous transition metal, iron, as a catalyst, and using the ubiquitous C–H bond as the coupling partner.
From C-H to C-C Bonds
Author: Chao-Jun LiPublisher: Royal Society of Chemistry
ISBN: 1849737975
Category : Science
Languages : en
Pages : 330
Book Description
This book examines the first ten years of this rapidly-expanding field, providing the reader with the knowledge to develop new syntheses in keeping with the principles of Green Chemistry.
Cleavage of Carbon-Carbon Single Bonds by Transition Metals
Author: Masahiro MurakamiPublisher: John Wiley & Sons
ISBN: 352768011X
Category : Technology & Engineering
Languages : en
Pages : 292
Book Description
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.
Electronically Unsaturated Tri-coordinate Nickel Complexes and Their Reactivity, Including Activation of CO2
Author: Benjamin C. FullmerNi- and Fe-Based Cross-Coupling Reactions
Author: Arkaitz CorreaPublisher: Springer
ISBN: 3319497847
Category : Science
Languages : en
Pages : 342
Book Description
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.
Nickel-Catalyzed Amide Carbon-Nitrogen Bond Activation Methodologies and Progress Toward the Total Synthesis of Dodecahedrane
Author: Jacob Edward DanderPublisher:
ISBN:
Category :
Languages : en
Pages : 419
Book Description
This dissertation describes efforts in the field of nickel-catalyzed amide C-N bond activations and studies toward the total synthesis of dodecahedrane. Although amide C-N bonds are generally considered inert, recent progress in the activation of these bonds has allowed for their use as synthetic building blocks. Herein, several nickel-catalyzed transformations of amides and strategies to improve the practicality of these reactions are outlined. Each of these studies highlights the utility of nickel catalysis and amides in the context of organic synthesis. Furthermore, a synthetic strategy for and experimental progress toward the synthesis of dodecahedrane are reported. The realization of this total synthesis is expected to push our understanding of molecular reactivity and represent a milestone in the field of total synthesis. Chapters one, two, and three describe the development of transformations and experimental techniques that improve the scope and practicality of nickel-catalyzed activations of aryl amide C-N bonds. More specifically, chapter one describes a nickel-catalyzed alkylation of amides to access aryl-alkyl ketone products. This catalytic methodology represents a mild approach to synthesizing these products that is complementary to the Weinreb ketone synthesis. Chapter two details a strategy for the benchtop delivery of Ni(cod)2. The air- and moisture-sensitivity of this important nickel precatalyst limits its general utility. By utilizing paraffin-Ni(cod)2 capsules, a variety of nickel-catalyzed transformations, including aryl amide cross-couplings, can be performed outside of a glovebox. Chapter three outlines efforts to deploy paraffin-Ni(cod)2 capsules in an undergraduate organic chemistry laboratory. Through the use of these reagents in an esterification of an aryl amide, students gain meaningful insights into frontiers in cross-coupling research, nickel catalysis, and the use of amides in synthetic organic chemistry. Chapters four and five are concerned with the development of nickel-catalyzed transformations of aliphatic amides. Chapter four specifically details efforts to develop a nickel-catalyzed transamidation of aliphatic secondary amides. Through the use of a two-step activation-cross-coupling approach, we have achieved a mild and general solution to this long-standing problem in organic chemistry. Chapter five describes a method for performing arylations of aliphatic amides on the benchtop. By employing paraffin-Ni(cod)2/Benz-ICy[TM]HCl capsules, Suzuki-Miyaura cross-couplings of aliphatic amides to generate aryl-alkyl ketones can be achieved without the need for glovebox manipulations. Both of these studies expand the field of nickel-catalyzed amide C-N bond activations and promote amides as useful synthetic building blocks. Chapter six illustrates a chemoenzymatic approach to enantioselective transformations of amides. The development of a one-pot Suzuki-Miyaura cross-coupling and ketoreductase-mediated reduction allows for rapid, selective access to enantioenriched alcohol products from amides. This methodology represents the first enantioselective transformation of amides that relies on amide C-N bond activation and is expected to guide the development of other asymmetric transformations of amides. Finally, chapter seven details a strategy for the total synthesis of the complex hydrocarbon dodecahedrane. Our proposed symmetry-based approach to this fascinating icosahedral molecule relies on an ambitious [2+2+2+2+2] cyclization to assemble five key C-C bonds in a single synthetic operation. Current efforts to synthesize the necessary substrate for the [2+2+2+2+2] cyclization are detailed. If successful, these studies should provide efficient access to dodecahedrane and are expected to lead to insights into new modes of reactivity.
Oxidative Cross-Coupling Reactions
Author: Aiwen LeiPublisher: John Wiley & Sons
ISBN: 3527681000
Category : Technology & Engineering
Languages : en
Pages : 240
Book Description
The first handbook on this emerging field provides a comprehensive overview of transition metal-catalyzed coupling reactions in the presence of an oxidant. Following an introduction to the general concept and mechanism of this reaction class, the team of authors presents chapters on C-C cross-coupling reactions using organometallic partners, C-Heteroatom bond forming reactions via oxidative couplings, and C-H couplings via C-H activation. The text also covers such groundbreaking topics as recent achievements in the fields of C-C and C-X bond formation reactions as well as C-H activation involving oxidative couplings. With its novel and concise approach towards important building blocks in organic chemistry and its focus on synthetic applications, this handbook is of great interest to all synthetic chemists in academia and industry alike.