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Computational Studies Of Iridium Catalyzed Borylation Reactions And Defying Torquoselectivity In Cyclobutene Ring Opening Via Strain Induced Thermal Selectivity
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Book Synopsis Computational Studies of Iridium-catalyzed Borylation Reactions and Defying Torquoselectivity in Cyclobutene Ring-opening Via Strain-induced Thermal Selectivity by : Aaron Gabriel Green
Download or read book Computational Studies of Iridium-catalyzed Borylation Reactions and Defying Torquoselectivity in Cyclobutene Ring-opening Via Strain-induced Thermal Selectivity written by Aaron Gabriel Green and published by . This book was released on 2013 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt: The studies reported in this dissertation illustrate a few selected examples of using density functional theory (DFT) calculations to investigate various aspects of iridium-catalyzed reactions and ring-opening of bicyclic cyclobutene rings. These computational predictions not only reproduce and explain experimental results and offer insights to reaction mechanisms, but also provide theoretical models to predict reactivity, regio- and stereoselectivities. Chapter 1 is a review surveying the literature of iridium-catalyzed borylation reactions. Emphasis is placed on iridium-catalyzed borylation of alkenes and arenes. In particular, I discuss the history leading up to the current catalyst systems for iridium-catalyzed borylation reactions, and regioselectivity of borylation for a number of different substrates. Despite the large amount of work on iridium-catalyzed borylation reactions, this review shows that there is still much to be understood regarding the origins of observed regioselectivities. Chapters 2 and 3 describe theoretical investigations of Ir(III)-catalyzed borylation reactions. The origins of regioselectivities observed in the borylation of pyridine are discussed in Chapter 2. The high selectivity for borylation at the 3- and 4- position of pyridine is attributed to the formation of a Lewis acid-base complex between pyridine and either boron species or iridium species in solution. The origins of regioselectivities for the iridium-catalyzed borylation of substituted arenes and 5-membered heterocycles are discussed in Chapter 3. The distortion/interaction model was employed to understand the origins of the selectivities in these reactions. Computations revealed that regioselectivity is mainly controlled by differences in the interaction energies between the iridium catalyst and arene carbon. Chapter 4 illustrates a theoretical study of ring-opening in strained, trans-substituted cyclobutenes. The torquoselectively preferred outward ring-opening products are unable to form due to ring strain inherent in 9- and 10-membered macrocyclic (E, E)-1,3-dienes. As a result of this study, I propose a general methodology for stereoselective synthesis of macrocyclic (Z, Z)-1,3-dienes termed strain-induced thermal selectivity (SITS).
Book Synopsis Advancing Frontiers in Reactive and Selective Iridium C-h Borylation Catalysis and Targeted Silsesquioxane Synthesis by : Jonathan E. Dannatt
Download or read book Advancing Frontiers in Reactive and Selective Iridium C-h Borylation Catalysis and Targeted Silsesquioxane Synthesis written by Jonathan E. Dannatt and published by . This book was released on 2019 with total page 521 pages. Available in PDF, EPUB and Kindle. Book excerpt: The studies in this dissertation are aimed at uncovering reactive and selective Ir-catalyzed C-H borylation (CHB) catalysts. Due to the high versatility of organoboron species, green methodology to produce the C-B bond is poised to support a myriad of subsequent transformations. These transformations include Suzuki couplings, aminations, oxidations, halogenations, cyanations, and trifluoromethylations.Typical iridium catalyzed CHBs proceed through an iridium trisboryl with a bidentate ligand such as bipyridine or 1,10-phenanthroline. The selectivity of these standard catalysts is generally driven by sterics; however, many methods of overcoming the steric bias have been developed in the two decades since the first thermal catalytic C-H activation borylation. These methods include both inner- and outer-sphere directed mechanisms. Outer-sphere directed borylations have been accomplished by leveraging hydrogen bonding, Lewis acid-base, and ion-pairing as directing elements. In general this reactivity is activated by precise design of the bidentate ligand framework.Herein is reported a subtle electrostatic interaction to direct ortho-borylation of phenols by simply switching boron source from the common B2pin2 (pin = pinacolate) to B2eg2 (eg = ethyleneglycolate). This electrostatic interaction was revealed by a careful computational analysis of key C-H activation transition states. Understanding gained by the computational studies led to the redesign of the boron source which enabled by selectivities of > 99% ortho borylation. This methodology was extended to the highly selective ortho-borylation of anilines, and the underlying mechanism has been interrogated.Currently, iridium based catalysts have been generated to borylate ortho, meta, and even para to a variety of classes of substrates; however, control of selectivity can breakdown in many fluorinated arenes without a directing group. These substrates are challenging because the fluoro moiety being similar in size to a hydrogen offers little in the way of steric bias. While working to overcome these challenges, a serendipitously discovered hydrazone based ligand was discovered. Exploration of the catalysts generated by this ligand revealed not only impressive activity rivaling dtbpy but also incredible selectivity for meta to a fluoro group.In general iridium CHB catalysts selectively activate sp2 C-H bonds leaving all sp3 C-H bonds intact; however, a method to turn on sp3 C-H activation would be desirable. It was reasoned that a directing group able to increase the effective concentration of the iridium catalyst near a C(sp3)-H bond may enable this transformation. Indeed, it was discovered that catalysts able to accept amide directing groups were able to selectively borylate compounds with amide N-methyl substituents.
Book Synopsis Frontiers in Iridium-Catalyzed C-H Borylation by : Matthew Alan Larsen
Download or read book Frontiers in Iridium-Catalyzed C-H Borylation written by Matthew Alan Larsen and published by . This book was released on 2016 with total page 246 pages. Available in PDF, EPUB and Kindle. Book excerpt: The following dissertation discusses the development of novel methodology for the catalytic borylation of C-H bonds and includes in-depth studies on the mechanism and selectivity of these synthetic transformations. These methods include the borylation of heteroaryl C-H bonds, the selective borylation of benzylic C-H bonds, and the directed and undirected borylation of unactivated alkyl C-H bonds. Chapter 1 contains a comprehensive review of C-H borylation methodology. This review focuses on the initial development of catalytic C-H borylation and on the state-of- the-art of methodology for the undirected and directed borylation of aryl, benzylic, and alkyl C-H bonds. Additionally, this review highlights knowledge gaps and unsolved challenges. Furthermore, this review provides the author's opinion on future directions for research on the borylation of C-H bonds. Chapter 2 describes the study of the iridium-catalyzed borylation of heteroaryl C- H bonds. Contained is an examination of the scope of the borylation of heterocycles containing more than one heteroatom and rules for predicting the site-selectivity of this reaction. Also included are experimental and computational studies that reveal the mechanism of this reaction and the origins of the observed regioselectivity. Chapter 3 discusses the development of the selective borylation of the primary benzylic C-H bonds of methylarenes. Key to this development was the discovery that the combination of a novel iridium catalyst and a silylborane allows for the selective borylation of benzylic C-H bonds over aryl C-H bonds. Experimental and computational studies that investigate the origins of this selectivity are also discussed. Chapter 4 discusses the development of the iridium-catalyzed, hydrosilyl-directed borylation of alkyl C-H bonds. This methodology allows for the diastereoselective borylation of secondary alkyl C-H bonds under relatively mild conditions. Chapter 5 explores the effect of ligand structure on the rates of alkyl C-H borylation catalyzed by Ir-phenanthroline complexes. Experimental and computational studies reveal that in addition to the relative electron-donating ability of phenanthrolines, weak interactions involving the phenanthroline in the transition state of the turnover- limiting step for the borylation of alkyl C-H bonds can have a large impact on the relative rates of alkyl C-H borylation catalyzed by various Ir-phenanthroline complexes.
Book Synopsis Iridium Catalyzed C-H Borylation by : Behnaz Ghaffari
Download or read book Iridium Catalyzed C-H Borylation written by Behnaz Ghaffari and published by . This book was released on 2016 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Overcoming Regioselectivity Challenges in Iridium Catalyzed C-h Borylation Via Noncovalent Interactions and Advances on Cross Coupling Reactions of Aryl Imidazolylsulfonates by : Jose Raul Montero Bastidas
Download or read book Overcoming Regioselectivity Challenges in Iridium Catalyzed C-h Borylation Via Noncovalent Interactions and Advances on Cross Coupling Reactions of Aryl Imidazolylsulfonates written by Jose Raul Montero Bastidas and published by . This book was released on 2021 with total page 879 pages. Available in PDF, EPUB and Kindle. Book excerpt: Direct functionalization of C0́2H bonds reduces the number of synthetic steps for a target molecule enhancing efficiency and avoiding undesired waste material. Iridium catalyzed C-H activation-borylation (CHB) is an established method to access aryl boronic esters. Regioselectivity challenges can arise when multiple hydrogens are present in the molecule. This thesis describes the design of novel strategies to selective direct the CHB to one specific position.Ortho selective CHB has the challenge to go against the traditional CHB selectivity dictated by steric effects. Previously, our group reported a strategy for highly ortho-selective CHB of anilines by using a small B2eg2 (eg = ethanediol) as the borylating reagent. However, the products were unstable and transesterification with pinacol was needed. Chapter 2 builds upon this issue and presents a solution based on the modulation of the size of the boron partner. Small diboron partners retain the high ortho regioselectivity for CHB of aniline but larger borylating reagents generate more stable products. In our estimation, B2bg2 (bg = 1,2-butanediol) represents the best balance of reactivity, regioselectivity and stability.Remote functionalization including para selective reactions are difficult because a potential directing group would be far from the desired reactive site. Chapter 3 details how para CHB of tetraalkylammonium sulfates and sulfamates have been achieved using bipyridine-ligated Ir boryl catalysts. Selectivities can be modulated by both the length of the alkyl groups in the tetraalkylammonium cations and the substituents on the bipyridine ligands. Ion pairing, where the alkyl groups of the cation shield the meta C8́2H bonds in the counteranions, is proposed to account for para selectivity. The 4,4'-dimethoxy-2,2'-bipyridine ligand gave superior selectivities.The next chapter describes how intramolecular hydrogen bonding (IMHB) can lead to steric shielding effects that can direct CHB regiochemistry. Bpin/arene IMHB can promote remote borylations of N-borylated anilines, 2-amino-N-alkylpyridine, tetrahydroquinolines, indoles and 1-borylated naphthalenes. Our studies support molecular geometries with the Bpin orientation controlled by a C-H0́Ø0́Ø0́ØO IMHB. Calculated rotation barriers to displace the Bpin group are above 4 kcal/mol, suggesting that the planar ground conformation of the borylated arenes is retained during CHB. This study informs researchers to evaluate not only inter- but also intramolecular noncovalent interactions as potential drivers of remote CHB regioselectivity.The borylated products from CHB can be further manipulated in Suzuki-Miyaura cross-coupling (SMC) with aryl halides as the typical electrophilic partner. Aryl imidazolylsulfonates are nongenotoxic electrophiles that can be used in palladium catalyzed SMC to avoid halogenated materials. Chapter 5 shows the efforts towards a nickel-catalyzed SMC of aryl imidazolyl-sulfonates. Results show considerable amounts of the corresponding diarylsulfate formed during the reaction. Interestingly, the diaryl sulfa byproducts were found to be competent electrophilic partners for both palladium and nickel-catalyzed SMC.In summary, this thesis presents novel methodologies to access challenging transformations as the para borylations of phenols, anilines and benzyl alcohols. This was possible by the analysis of the different components of the catalytic system: design of ligands, diboron partners and substrate directing groups and how they interact during the reaction. Finally, the potential of aryl imidazolylsulfonates as nongenotoxic pseudohalides in nickel-catalyzed SMC was evaluated.
Book Synopsis Modern Acetylene Chemistry by : Peter J. Stang
Download or read book Modern Acetylene Chemistry written by Peter J. Stang and published by John Wiley & Sons. This book was released on 2008-09-26 with total page 527 pages. Available in PDF, EPUB and Kindle. Book excerpt: This comprehensive handbook presents the full potential of modern acetylene chemistry, from organic synthesis through materials science to bioorganic chemistry. K. Houk, H. Hopf, P. Stang, K. M. Nicholas, N. Schore, M. Regitz, K. C. Nicolaou, R. Gleiter, L. Scott, R. Grubbs, H. Iwamura, J. Moore, and F. Diederich - internationally renowned authors introduce the reader, in a didactically skilful manner, to the state-of-the-art in alkyne chemistry. Emphasis is placed on presenting carefully selected and instructive examples as well as essential references to the original literature. Special benefits: Each chapter is rounded off by useful experimental procedures.
Book Synopsis Acetylene Chemistry by : François Diederich
Download or read book Acetylene Chemistry written by François Diederich and published by John Wiley & Sons. This book was released on 2006-03-06 with total page 528 pages. Available in PDF, EPUB and Kindle. Book excerpt: Acetylenes are an important and valuable class of compounds in organic synthesis. This book expands on this historically well-established concept, while incorporating the many new developments that have widened the number of applications in this field. It remains the only handbook available that embodies all the important facets of acetylene chemistry. Following the first section on synthesis, the leading authors deal with advanced materials before turning to the properties and theory of acetylenes, while a final section looks at the biological aspects. With its range of experimental procedures, this book is a practical aid for both organic and organometallic chemists, as well as for materials scientists, biochemists, and industrial chemists.
Book Synopsis Frontiers of Free Radical Chemistry by : William Pryor
Download or read book Frontiers of Free Radical Chemistry written by William Pryor and published by Elsevier. This book was released on 2012-12-02 with total page 400 pages. Available in PDF, EPUB and Kindle. Book excerpt: Frontiers of Free Radical Chemistry covers the proceedings of the 1979 symposium on Frontiers of Free Radical Chemistry, held in Louisiana State University Chemistry Department, supported by the Exxon Education Foundation. The contributors discuss the mechanisms of hydrocarbon cracking; oxidation processes; inhibition; and the theory of organic radical reactions, halogenations, and organic peroxide chemistry. This book is organized into three parts encompassing 15 chapters. Part I deals with the understanding of molecular and free radical mechanisms in predicting thermochemical data for radicals and molecules. This part also describes the relationship between distortions of organic molecules and the reactions of pericyclic, ionic, and radical molecules. Part II presents quantitative evaluations of gas phase reactions or carbynes and hydrocarbon pyrolysis and cracking. Discussions on the reactions of free atoms and radicals in the chemistry of the stratosphere and natural troposphere, with an emphasis on the ozone layer and its potential depletion by artificial pollutants, are included in this part. Part III explores the pertinent free radical reactions related to fuel research. Petroleum chemists, researchers, and engineers will find this book invaluable.
Book Synopsis Transition State Modeling for Catalysis by : Donald G. Truhlar
Download or read book Transition State Modeling for Catalysis written by Donald G. Truhlar and published by . This book was released on 1999 with total page 556 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains the latest research on the applications of computational chemistry, computational biochemistry, and computational physics to the new field of direct modeling of transition states for catalytic reactions. It includes all types of catalysts: organometals, metals and metalloids, metal oxides and zeolites, and enzymes.
Book Synopsis Acidity and Basicity of Solids by : J. Fraissard
Download or read book Acidity and Basicity of Solids written by J. Fraissard and published by Springer. This book was released on 2012-10-25 with total page 513 pages. Available in PDF, EPUB and Kindle. Book excerpt: The subject of acidity and basicity has enormous economic and technological value while it continues to present significant scientific challenges with prospects for further important technological developments. Historically, technological developments in acidity/basicity have often preceded the scientific understanding of the phenomena involved, certainly in the petroleum industry, a key beneficiarry and user of the concepts of acidity. This process, however, is very expensive and less efficient than developments based on a fundamental understanding of the scientific phenomena involved. This has been recognized over the years and it explains why university, government and industrial laboratories have in the last 50 years devoted large efforts to understanding acidity (and basicity to a lesser extent) so they can gain the technological advantage. The scientific and technological literature on the subject is truly enormous. There have been some very important articles and books on the subject that have attempted to critically review many individual contributions. During the last few years there have been three developments that led us to organize the Advanced Study Institute on which this volume is based: a) Significant developments in the theory of acids and bases; b) Developments in instrumentation that allow the detailed characterization of materials including in-situ conditions relevant to industrial processes; c) The realization that closer coupling of scientific and technological pursuits can lead to greater scientific understanding and better technology. The structure of the ASI reflected the coming-together of these three factors.
Book Synopsis AB INITIO Molecular Orbital Theory by : Warren J. Hehre
Download or read book AB INITIO Molecular Orbital Theory written by Warren J. Hehre and published by Wiley-Interscience. This book was released on 1986-03-24 with total page 572 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book addresses the formulation of theoretical molecular orbital models starting from quantum mechanics, and compares them to experimental results. It draws on a series of models that have already received widespread application and are available for new applications.
Book Synopsis Stereochemistry of Organic and Bioorganic Transformations by : Wilhelm Bartmann
Download or read book Stereochemistry of Organic and Bioorganic Transformations written by Wilhelm Bartmann and published by VCH Publishers. This book was released on 1987 with total page 354 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Organometallic Reactions by : Ernest I. Becker
Download or read book Organometallic Reactions written by Ernest I. Becker and published by . This book was released on 1970 with total page 470 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Three-Membered Rings by : A. Davison
Download or read book Three-Membered Rings written by A. Davison and published by Springer. This book was released on 1973-08-24 with total page 151 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Catalytic Antibodies by : Ehud Keinan
Download or read book Catalytic Antibodies written by Ehud Keinan and published by John Wiley & Sons. This book was released on 2006-03-06 with total page 616 pages. Available in PDF, EPUB and Kindle. Book excerpt: Exploiting the inherent combinatorial mechanism in the biosynthesis of antibodies, an almost limitless variety of biocatalysts may be generated. Catalytic antibodies are capable of performing almost any type of reaction with high selectivity and stereospecificity. Here, the pioneers in the use of catalytic antibodies review the entire scope of this interdisciplinary field, covering such topics as: * theoretical aspects of structure, mechanism and kinetics * practical considerations, from immunization techniques to screening methods * in vitro evolution and other modern approaches * applications from organic synthesis to medical uses. Backed by the leading authorities in antibody catalysis, this is the first book to provide such comprehensive coverage and constitutes a prime reference for biochemists, organic chemists, biotechnologists and biomedical researchers.
Book Synopsis Sulfur Ylides: Emerging Synthetic Intermediates by : Barry M. Trost
Download or read book Sulfur Ylides: Emerging Synthetic Intermediates written by Barry M. Trost and published by . This book was released on 1975 with total page 368 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Orotidine Monophosphate Decarboxylase by : Jeehiun K. Lee
Download or read book Orotidine Monophosphate Decarboxylase written by Jeehiun K. Lee and published by Springer. This book was released on 2010-12-01 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
