On The Design And Further Applications Of Iridium I Complexes In Hydrogen Isotope Exchange Processes
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On The Design And Further Applications Of Iridium I Complexes In Hydrogen Isotope Exchange Processes
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Author : Marc Reid
language : en
Publisher:
Release Date : 2015
On The Design And Further Applications Of Iridium I Complexes In Hydrogen Isotope Exchange Processes written by Marc Reid and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with categories.
A new synthetic procedure for isolation of three established Kerr group catalysts has been successfully developed. The final yield of these catalysts has now been improved beyond those published in the literature, and has allowed for the commercialisation of such catalysts for the first time. The synthesis of a series of iridium(I) complexes of the type [(COD)Ir(IMes)(PPh3)]X (X = BF4, OTf, and BArF) has been established. Application of these species in hydrogen isotope exchange (HIE) processes revealed more efficient catalysis and a wider solvent scope when X = BArF. Additionally, these findings have allowed for the development of a novel method for ortho-HIE in unprotected tetrazoles under basic conditions, revealing a rare account of N-H tetrazole C-H activation and a new mode of reactivity for Kerr group HIE catalysts. Towards predictive catalyst design, a combined experimental and theoretical model has been developed to describe the impact of ligand combinations on catalyst performance. Experimentally, this has resulted in a further broad range of novel NHC/phosphine iridium carbonyl complexes, as well as a catalyst 'quick screen' method based on in-situ formation of Ir dihydride complexes. Computationally, novel parameters have been assessed, culminating in a combined ligand map derived from Principal Component Analysis (PCA) of 140 DFT-optimised iridium complexes. Ligand mapping methods have been employed to assess the use of natural product Lepidiline A as a NHC ligand precursor in novel HIE catalysts, revealing the almost purely electronic influence of 4,5-dimethyl substitution on the imidaz-2-ylidene ring. The PCA model has also highlighted complexes of the type [(COD)Ir(NHC)Cl] to be promising in delivering orthogonal reactivity to the now traditional NHC/phosphine pairing. This analysis has led to the realisation of the first regio- and chemoselective catalytic labelling methods for primary sulfonamides and aldehydes. Finally, a novel, one-parameter approach has been developed to describe chelating and monodentate ligand spheres on the same comparable and quantifiable footing. Chelating NHC/phosphine-ligated iridium catalysts have been designed, synthesised, and successfully applied to ortho-labelling of previously inaccessible sulfones, secondary sulfonamides, and bulky tertiary amides.
Computationally Guided Rational Ligand Design Of Novel Iridium I Complexes For Elevated Substrate Applicability In Hydrogen Isotope Exchange Processes
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Author : Gary J. Knox
language : en
Publisher:
Release Date : 2018
Computationally Guided Rational Ligand Design Of Novel Iridium I Complexes For Elevated Substrate Applicability In Hydrogen Isotope Exchange Processes written by Gary J. Knox and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018 with categories.
Using a computationally guided rational ligand design approach, a novel chelated NHC-P iridium(I) catalyst system has been identified for the directed hydrogen isotope exchange (HIE) of aryl sulfones. The catalyst design process was aided primarily through DFT binding energy calculations. The solvent scope of the reaction was studied, and the optimised conditions applied to the successful deuterium labelling of a broad range of 20 aryl sulfones. The catalyst system was also shown to be highly active in the HIE of aryl sulfones at sub-atmospheric pressures of deuterium. Additionally, the catalyst system was applied in the tritiation of aryl sulfones, affording tritiated samples of methylphenyl sulfone, as well as a GPR119 agonist, in high levels of specific activity.This chelated catalyst system was then further refined for the labelling of highly substituted sulfonamides. A more focussed approach to the catalyst design process was taken at this stage, with a combination of binding energy calculations and binding mode analysis being used to guide the modification of the ligand. This resulted in a novel, chelated NHC-Py system, which proved to be highly active in the HIE of a broad range of highly substituted sulfonamides. A total of 22 sulfonamide substrates were synthesised, and labelled using this novel catalyst system. Additionally, this complex was shown to be highly effective in the deuteration of sulfoximines, for which the means of labelling are severely under met.Finally, our studies in the labelling of aryl sulfones led us to the serendipitous discovery of ether-directed HIE. This process was investigated with our novel NHC-P catalyst system, and a substrate scope established. Additionally, a potential application in form of labelling natural products, and natural product-like molecules has been proposed, with a series of three natural product-like molecules having been synthesised for attempts towards labelling.
Iridium Complexes As Highly Active Catalysts For Hydrogen Isotope Exchange And Hydrogen Borrowing Processes
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Author : Philippa Kate Owens
language : en
Publisher:
Release Date : 2018
Iridium Complexes As Highly Active Catalysts For Hydrogen Isotope Exchange And Hydrogen Borrowing Processes written by Philippa Kate Owens and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018 with categories.
Over the last several decades, the organic chemistry community has become increasingly reliant upon iridium catalysis, with applications reported across a number of research areas. In recent years, the Kerr group has developed a series of iridium complexes, which were found to be excellent catalysts for hydrogen isotope exchange and olefin hydrogenation processes. The work described within this thesis centres upon the expansion of these catalysts' reactivity in hydrogen isotope exchange, as well as the synthesis and application of a series of novel iridium complexes, designed for use in hydrogen borrowing catalysis. Chapter one focuses on the development of three efficient and selective methods for hydrogen isotope exchange. Iridium(I) catalysts previously developed within the group have been employed in the successful deuteration of N-heterocycles, which represent an important and relatively underexplored class of labelling substrates. The labelling of a large range of indole, pyrrole, and quinoline derivatives is reported, in which the regioselectivity can be controlled through careful choice of N-protecting group. Extensive practical and computational mechanistic investigations offered insight into the mechanism of indole C3 labelling, which is believed to proceed via an iridium-indoline intermediate. In chapter two, the design and synthesis of a series of novel unsymmetrical NHC ligands, functionalised with electron donating substituents, is described. The corresponding neutral iridium NHC/halide complexes were prepared, and the steric and electronic properties of the ligands were investigated using a number of techniques. These novel complexes were then tested in the catalysis of hydrogen borrowing processes. Extensive optimisation led to the development of an efficient method for the room-temperature N-alkylation of anilines. This methodology was also expanded to include the synthesis of N-heterocycles viaintramolecular C-N bond formation, albeit using more forcing conditions. Lastly, a small series of chiral NHC ligands was designed, and their corresponding iridium complexes prepared and used in a preliminary screening of asymmetric hydrogen borrowing.
Advances In The Synthesis And Application Of Iridium I Complexes For Use In Hydrogen Isotope Exchange
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Author : Alison R. Cochrane
language : en
Publisher:
Release Date : 2012
Advances In The Synthesis And Application Of Iridium I Complexes For Use In Hydrogen Isotope Exchange written by Alison R. Cochrane and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with categories.
Investigations into the application of catalysts of the type [Ir(COD)(PR3)(IMes)]PF6 in the field of hydrogen isotope exchange have been undertaken. In particular, the use of alternative solvents has been examined, resulting in the identification of reaction media considered more industrially acceptable than those currently utilised in isotopic labelling processes. Following a series of optimisation studies, the newly developed conditions for H-D exchange were applied to a range of substrates containing a variety of functional groups. In the majority of instances, high levels of deuteration were achieved in reactions employing low catalyst loadings and short reaction times. With regards to the iridium complexes themselves, focus has centred on the introduction of alternative NHC ligands, leading to the synthesis of six novel Ir(I) catalysts. These complexes have been employed in hydrogen isotope exchange reactions, demonstrating high activity in the isotopic labelling of numerous substrates. As a result of such explorations, increased levels of selectivity have been achieved in compounds offering multiple sites of labelling, with catalysts displaying a greater preference for exchange via a 5-mmi over the less energetically favourable 6-mmi. In addition, a catalyst capable of facilitating higher levels of isotope incorporation adjacent to a sulfonamide moiety has been accomplished. A series of DFT studies have also been undertaken. The calculation of solvent binding energies to the iridium complex has revealed a broad correlation between the strength with which solvent molecules coordinate to the metal centre, and the degree of isotope incorporation observed. Further theoretical investigations were performed regarding our novel Ir(I) complexes bearing alternative NHC ligands. More specifically, computational experiments have identified the relative energies of the key processes which occur within the catalytic cycle.
Iridium I Complexes For The Functionalisation Of Carbon Hydrogen Bonds
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Author : Renan Zorzatto
language : en
Publisher:
Release Date : 2018
Iridium I Complexes For The Functionalisation Of Carbon Hydrogen Bonds written by Renan Zorzatto and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018 with categories.
The development of catalytic systems for the functionalisation of carbon-hydrogen bonds has been an intensive area of research for the last 5 decades. In this context, transition metal complexes play a crucial role in reaction discovery, mechanistic evaluation and synthetic applications. In the Kerr group, this technology has been explored in the context of hydrogen isotope exchange, resulting in the development of highly active iridium(I) complexes bearing phosphines and NHC ligands. Despite their broad functional group compatibility, existing methods for isotope exchange are ineffective in the labelling of sterically encumbered directing groups. Hence, in the first chapter we investigate the synthesis of three new iridium(I) complexes bearing chelating phosphine-functionalised NHC ligands, and their application in the isotope exchange of sterically hindered carbamates. Our initial studies revealed high catalytic efficiency and tolerance for steric encumbrance, prompting us to perform a combined theoretical and experimental investigation of the reaction mechanism.Therefore, by conducting DFT calculations and kinetic experiments, we were able to identify a rich dynamic behaviour in solution and ultimately propose a reaction mechanism. Additionally, our interest in the activation of carbon-hydrogen bonds resulted in the exploration of a theoretical model for the prediction of enthalpies of activation, resulting in the identification of relevant electronic and steric descriptors.From the knowledge gathered in our initial studies, the second chapter describes the application of our novel iridium catalysts in the functionalisation of carbon-hydrogen bonds in the context of hydroarylation of olefins. Thus, we identified carboxylic acids as suitable directing groups for this transformation and employed Design of Experiments to optimise the reaction conditions. Synthetic studies were focused on the preparation of 14 substrates, enabling quick assessment of the capabilities and limitations of this reaction. These investigations resulted in a synthetic method suitable for the synthesis of bi- and tricycles featuring tertiary and quaternary benzylic stereocentres in a racemic fashion.Finally, we investigated the mechanism of this process by DFT calculations, which led us to identify a plausible reaction pathway which should guide future kinetic evaluations.
Highly Active Iridium I Complexes For Catalytic Hydrogen Isotope Exchange And Selective Hydrogenation
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Author : Stephanie Irvine
language : en
Publisher:
Release Date : 2009
Highly Active Iridium I Complexes For Catalytic Hydrogen Isotope Exchange And Selective Hydrogenation written by Stephanie Irvine and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2009 with categories.
New Iridium Catalysed Methods For The Hydrogen Isotope Exchange Of Pharmaceutically Relevant Compounds
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Author : Nathan Knight
language : en
Publisher:
Release Date : 2022
New Iridium Catalysed Methods For The Hydrogen Isotope Exchange Of Pharmaceutically Relevant Compounds written by Nathan Knight and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2022 with categories.
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Encyclopedia Of Spectroscopy And Spectrometry
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Author :
language : en
Publisher: Academic Press
Release Date : 2016-09-22
Encyclopedia Of Spectroscopy And Spectrometry written by and has been published by Academic Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016-09-22 with Science categories.
This third edition of the Encyclopedia of Spectroscopy and Spectrometry, Three Volume Set provides authoritative and comprehensive coverage of all aspects of spectroscopy and closely related subjects that use the same fundamental principles, including mass spectrometry, imaging techniques and applications. It includes the history, theoretical background, details of instrumentation and technology, and current applications of the key areas of spectroscopy. The new edition will include over 80 new articles across the field. These will complement those from the previous edition, which have been brought up-to-date to reflect the latest trends in the field. Coverage in the third edition includes: Atomic spectroscopy Electronic spectroscopy Fundamentals in spectroscopy High-Energy spectroscopy Magnetic resonance Mass spectrometry Spatially-resolved spectroscopic analysis Vibrational, rotational and Raman spectroscopies The new edition is aimed at professional scientists seeking to familiarize themselves with particular topics quickly and easily. This major reference work continues to be clear and accessible and focus on the fundamental principles, techniques and applications of spectroscopy and spectrometry. Incorporates more than 150 color figures, 5,000 references, and 300 articles for a thorough examination of the field Highlights new research and promotes innovation in applied areas ranging from food science and forensics to biomedicine and health Presents a one-stop resource for quick access to answers and an in-depth examination of topics in the spectroscopy and spectrometry arenas
Novel Methods To Access Tracelessly Labelled Molecules Via Iridium Catalysed Hydrogen Isotope Exchange
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Author : J. Conor Townsley
language : en
Publisher:
Release Date : 2022
Novel Methods To Access Tracelessly Labelled Molecules Via Iridium Catalysed Hydrogen Isotope Exchange written by J. Conor Townsley and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2022 with categories.
Nuclear Science Abstracts
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Author :
language : en
Publisher:
Release Date : 1972
Nuclear Science Abstracts written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1972 with Nuclear energy categories.