A Computational Study of C-CN Bond Activation Through Nickel Catalysis Using the Random Phase Approximation PDF Download

Author: Craig Waitt
Publisher:
ISBN:
Category : Chemical bonds
Languages : en
Pages : 0

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Author: Ting Li
Publisher:
ISBN:
Category :
Languages : en
Pages : 892

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"[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.

Author: Guangbin Dong
Publisher: Springer
ISBN: 364255055X
Category : Science
Languages : en
Pages : 265

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The series Topics in Current Chemistry presents critical reviews of the present and future trends in modern chemical research. 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. Review articles for the individual volumes are invited by the volume editors. Readership: research chemists at universities or in industry, graduate students

Author: Sensuke Ogoshi
Publisher: John Wiley & Sons
ISBN: 3527344071
Category : Science
Languages : en
Pages : 348

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A comprehensive reference to nickel chemistry for every scientist working with organometallic catalysts Written by one of the world?s leading reseachers in the field, Nickel Catalysis in Organic Synthesis presents a comprehensive review of the high potential of modern nickel catalysis and its application in synthesis. Structured in a clear and assessible manner, the book offers a collection of various reaction types, such as cross-coupling reactions, reactions for the activation of unreactive bonds, carbon dioxide fixation, and many more. Nickel has been recognized as one of the most interesting transition metals for homogeneous catalysis. This book offers an overview to the recently developed new ligands, new reaction conditions, and new apparatus to control the reactivity of nickel catalysts, allowing scientists to apply nickel catalysts to a variety of bond-forming reactions. A must-read for anyone working with organometallic compounds and their application in organic synthesis, this important guide: -Reviews the numerous applications of nickel catalysis in synthesis -Explores the use of nickel as a relatively cheap and earth-abundant metal -Examines the versatility of nickel catalysis in reactions like cross-coupling reactions and CH activations -Offers a resource for academics and industry professionals Written for catalytic chemists, organic chemists, inorganic chemists, structural chemists, and chemists in industry, Nickel Catalysis in Organic Synthesis provides a much-needed overview of the most recent developments in modern nickel catalysis and its application in synthesis.

Author: Olivia Bercher
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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This dissertation is focused on developing methods through activation of C-N bonds to form new C(sp3)-C(sp3) bonds as well as understanding the mechanism behind these transformations. In addition to gaining understanding of the mechanism via C-N bond activation, it also focuses on gaining insight on the mechanism of a Suzuki arylation via C-O bond activation.

Author: Jacob Edward Dander
Publisher:
ISBN:
Category :
Languages : en
Pages : 419

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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.

Author: Kishore Sinnu
Publisher: Self Employed
ISBN:
Category : Business & Economics
Languages : en
Pages : 0

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In the field of organic chemistry, the use of alcohols as catalysts for C-N bond activation and alkylation reactions has garnered significant attention in recent years. Jagannath Rana, a renowned chemist, has contributed greatly to this area of research through his groundbreaking studies. Alcohols, a widely available and environmentally friendly resource, have proven to be effective catalysts for a variety of chemical reactions, including C-N bond activation and alkylation. This type of catalysis can be achieved with either homogeneous or heterogeneous catalysis. Homogeneous catalysis, in which the alcohol is completely dissolved in the reaction mixture, is widely used in laboratory-scale reactions. Heterogeneous catalysis, on the other hand, involves the use of a solid-supported alcohol catalyst, which can be recycled and reused. The activation of C-N bonds using alcohols as catalysts is a highly efficient and selective process. The reaction occurs by nucleophilic attack of the amide or other nitrogen-containing compound on the activated alcohol. The resulting intermediate can undergo alkylation by a variety of electrophiles, including alkyl halides, alkenes, and alkynes. The use of alcohols as catalysts for C-N bond activation and alkylation reactions has several advantages over traditional methods. First, alcohols are abundant and inexpensive, making them an attractive alternative to more costly catalysts. Additionally, alcohols are non-toxic and can be used in environmentally friendly, sustainable chemistry practices. Rana's research has focused on the use of metal catalysis for C-N bond activation and alkylation reactions using alcohols as catalysts. In particular, he has studied the use of palladium catalysts in these reactions, as palladium is a widely available and inexpensive metal with excellent catalytic activity. Rana's work has demonstrated that palladium-catalyzed C-N bond activation and alkylation using alcohols as catalysts can be highly selective, producing the desired products with high yields and minimal waste. Overall, the use of alcohols as catalysts for C-N bond activation and alkylation reactions is a promising area of research in the field of organic chemistry. Rana's contributions have advanced our understanding of this process and opened up new avenues for the development of sustainable, environmentally friendly chemical processes.

Author: Huifeng Yue
Publisher:
ISBN:
Category :
Languages : en
Pages : 128

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Author: Yahya Albkuri
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Different metals and metal complexes have been used as catalysts in many industries such as commodity petrochemicals, fine and specialty chemicals, polymers, environmental services, agrochemicals and pharmaceuticals. Although these catalysts allow for increased reaction rates and selectivity, they can also be toxic, expensive and of limited supply (cf. Pt group metals). This has led researchers to the intensive study of first row metal catalysts, with nickel standing out as the most widely studied to date. As found for other first row metal catalysts, nickel's easy access to oxidation states 0-3 allows for a number of different one- and two-electron mechanisms and novel transformations. In Chapter 2 we use a phosphine-free, tridentate N,N,N ligand to generate an active catalyst for the C-N cross-coupling reaction of aryl halides with amines. The catalyst demonstrated excellent turnover numbers (up to 484) for the amination reactions that are proposed to proceed through a Ni(I)-Ni(III) cycle. In Chapter 3 we investigate the Ni coordination chemistry of a biomimetic SNS thiolate ligand. Protonation of the Ni bis(thiolate) complex, Ni(-SNS)2, removes one SNS ligand, affording crystals of a thiolate-bridged dimer dication, {[Ni(--SNS)]2}2+ that exhibits unique anionic tridentate ligand dynamics. Dissolving these crystals, even in weakly-coordinating solvents such as dichloromethane, gives a mixture of 'naked' Ni2+ and paramagnetic, trinuclear {[Ni(--SNS)2]2Ni}2+. Although this equilibrium lies far to the right (no diamagnetic dication visible in NMR), addition of ancillary ligands proceeds smoothly to provide several mono- and dinuclear Ni thiolate products, [Ni-SNS)L]n - potential bifunctional catalysts for further studies. In Chapter 4 we demonstrate using chemical and electrochemical techniques that one-electron reduction of Ni(-SNS)2 triggers quantitative imine C-C bond coupling, forming [Ni(S2N2)]- with a redox-active ligand. Spectroelectrochemical studies indicated reversible oxidation and reduction steps give three stable redox states, ([Ni(S2N2)]0/-/2-), that were characterized by NMR, EPR and UV-Vis spectroscopy, X-ray diffraction and computational chemistry. While the Ni(0) dianion (and not the Ni(I) anion) reacted reversibly with phenol and carbon dioxide, results from Chapter 5 showed that reactions with strong electron-acceptor fluoroalkenes proceeded more cleanly with the Ni(I) anion. The latter reactions afforded a mixture of fluoroalkenyl and fluoroalkyl products resulting from C-F bond activation and electron transfer/H atom abstraction, respectively. In Chapter 6 we discuss our results in the context of the current state of the art and suggest some avenues for future development.

Author: Marc Taillefer
Publisher: Springer
ISBN: 9783662505663
Category : Science
Languages : en
Pages : 0

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Palladium-Catalyzed sp2C–N Bond Forming Reactions: Recent Developments and Applications. Metal-catalyzed C(sp2)-N bond formation.- Recent Developments in Recyclable Copper Catalyst Systems for C−N Bond Forming Cross-Coupling Reactions Using Aryl Halides and Arylboronic Acids. Assembly of N-containing heterocycles via Pd and Cu-catalyzed C-N bond formation reactions. Copper-Catalyzed C(aryl)-N Bond Formation.