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Author: Eva J. Meeus
Publisher:
ISBN: 9789464733488
Category :
Languages : en
Pages : 0
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Book Description
"Transition metal catalysis proves a powerful tool to achieve otherwise synthetically challenging, or even impossible, transformations with (high) selectivity and is therefore employed in various areas of chemistry. Recently, transition metal-catalysed reactions have been successfully performed in cells (in vitro) and living systems (in vivo). The achievements made thus far reveal the potential of transition metal catalysis and its applications in such biological settings. Interestingly, the scope is limited compared to the breadth of transition metal-catalysed reactions that have been unlocked for synthetic applications. Translating transition metal-catalysed reactions from flasks to cells is non-trivial as the conditions in cells are fairly different compared to the highly controlled and adaptable conditions achieved in a flask. The development of catalytic systems for future applications in vivo therefore proceeds through many steps, starting with evaluating their reactivity, selectivity, and stability in water and under biologically relevant and biomimetic conditions. By exploring transition metal-catalysed reactions in water for in vivo applications, this dissertation has contributed to the subfield of bioorthogonal chemistry devoted to complementing Nature’s repertoire of reactions. Our studies have revealed the challenges associated with the performance of transition metal catalysis in aqueous media and how a detailed understanding of a catalytic system can address them. Apart from these fundamental studies, we have performed explorative studies under biologically relevant and biomimetic conditions in the context of intracellular drug synthesis. Moreover, we have developed a new and compatible protocol that enables detailed kinetic studies in complex reaction media, comparable to the cellular environment, to facilitate the translation of transition metal catalysis from flasks to cells."--
Author: Eva J. Meeus
Publisher:
ISBN: 9789464733488
Category :
Languages : en
Pages : 0
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Book Description
"Transition metal catalysis proves a powerful tool to achieve otherwise synthetically challenging, or even impossible, transformations with (high) selectivity and is therefore employed in various areas of chemistry. Recently, transition metal-catalysed reactions have been successfully performed in cells (in vitro) and living systems (in vivo). The achievements made thus far reveal the potential of transition metal catalysis and its applications in such biological settings. Interestingly, the scope is limited compared to the breadth of transition metal-catalysed reactions that have been unlocked for synthetic applications. Translating transition metal-catalysed reactions from flasks to cells is non-trivial as the conditions in cells are fairly different compared to the highly controlled and adaptable conditions achieved in a flask. The development of catalytic systems for future applications in vivo therefore proceeds through many steps, starting with evaluating their reactivity, selectivity, and stability in water and under biologically relevant and biomimetic conditions. By exploring transition metal-catalysed reactions in water for in vivo applications, this dissertation has contributed to the subfield of bioorthogonal chemistry devoted to complementing Nature’s repertoire of reactions. Our studies have revealed the challenges associated with the performance of transition metal catalysis in aqueous media and how a detailed understanding of a catalytic system can address them. Apart from these fundamental studies, we have performed explorative studies under biologically relevant and biomimetic conditions in the context of intracellular drug synthesis. Moreover, we have developed a new and compatible protocol that enables detailed kinetic studies in complex reaction media, comparable to the cellular environment, to facilitate the translation of transition metal catalysis from flasks to cells."--
Author: Sweta Shrestha
Publisher:
ISBN:
Category : Chemistry
Languages : en
Pages : 307
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Book Description
The goal of this dissertation is to explore the application of transition metals in two energy-intensive processes, photochemical water oxidation and olefin/paraffin separation. Photochemical water splitting is widely studied and involves the exploitation of renewable resources solar energy and water to produce clean hydrogen along with oxygen. Water oxidation process to make oxygen is not thermodynamically and kinetically feasible, thus catalysts which can promote this reaction are needed. With efficient water oxidizing catalysts, the entire water splitting process is promoted. We are focusing on birnessite as catalysts for photochemical water oxidation. Birnessite are layered manganese oxides with intercalated cations and water molecules in the interlayer space. They are known as moderate water oxidizing catalysts. We have developed two strategies to enhance water oxidizing catalytic activity of birnessite. Our first strategy was the deposition of birnessite on zeolite surfaces. The synthesis method involves ion-exchanging Mn2+ cations along with alkaline earth metal co-cations (M2+: Mg2+, Ca2+, Sr2+, Ba2+) into zeolite followed by the precipitation of manganese oxides on zeolite surfaces. M2+ cations control the loading of Mn2+ cations into zeolite, such that the larger cationic size of M2+, the lower the loading of Mn. These samples are amorphous manganese oxides and referred to as M2+MnOx-Y. After treating with high concentration of K+ cations, there was improvement in crystallinity in manganese oxides forming birnessite, and we refer to them as KMnOx-Y(M2+).
Author: Matthew L. Crawley
Publisher: John Wiley & Sons
ISBN: 1118309839
Category : Science
Languages : en
Pages : 386
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Book Description
This book focuses on the drug discovery and development applications of transition metal catalyzed processes, which can efficiently create preclinical and clinical drug candidates as well as marketed drugs. The authors pay particular attention to the challenges of transitioning academically-developed reactions into scalable industrial processes. Additionally, the book lays the groundwork for how continued development of transition metal catalyzed processes can deliver new drug candidates. This work provides a unique perspective on the applications of transition metal catalysis in drug discovery and development – it is a guide, a historical prospective, a practical compendium, and a source of future direction for the field.
Author: Pierre Dixneuf
Publisher: John Wiley & Sons
ISBN: 3527656812
Category : Technology & Engineering
Languages : en
Pages : 438
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Book Description
Water is abundant in nature, non-toxic, non-flammable and renewable and could therefore be safer and economical for the chemical industry wherever it is used as a solvent. This book provides a comprehensive overview of developments in the use of water as a solvent for metal catalysis, illustrating the enormous potential of water in developing new catalytic transformations for fi ne chemicals and molecular materials synthesis. A group of international experts cover the most important metalcatalyzed reactions in water and bring together cutting-edge results from recent literature with the first-hand knowledge gained by the chapter authors. This is a must-have book for scientists in academia and industry involved in the fi eld of catalysis, greener organic synthetic methods, water soluble ligands and catalyst design, as well as for teachers and students interested in innovative and sustainable chemistry.
Author: Kelly E. Aldrich
Publisher:
ISBN: 9781392071069
Category : Electronic dissertations
Languages : en
Pages : 824
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Book Description
The valency or oxidation state of a transition metal in a complex plays a large role in determining the reactivity of the complex. With transition metal chemistry, historically accessible chemistry has often focused on metals in a low oxidation state. However, transformations involving transition metals in high oxidation states are of equal importance in providing complex products for use in consumer products. Expanding the applications and understanding of transition metal complexes in high oxidation states is the focus of the research presented in this dissertation. Fundamental studies of how ligands interact with high valent metals is presented in chapters 2 and 3, where a chromium(VI) model complex has been used to study bonding interactions between this d0 transition metal and phosphine ligands. Practical application of high valent titanium(IV) catalysts to C--N bond forming reactions is presented in chapters 4--6. Finally, chapters 7 and 8 focus on the changes in the character of M--N double bonds, with M=Fe and Ru, as the metal is forced to higher oxidation states. Collectively, these studies demonstrate different approaches to the same general problems and questions of how chemists can better understand and utilize high valent transitions metals to do catalytically-target desired transformations.
Author: L. Brandsma
Publisher:
ISBN: 9783642603297
Category :
Languages : en
Pages : 360
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Book Description
Author: Xi-Jie Dai
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
"This thesis advances the knowledge in two fundamentally important organic chemical transformations: (1) cleavage of carbon-oxygen bonds and (2) formation of carbon-carbon bonds. Such advancement consists of four late transition metal-catalyzed reactions based on the oxygenated chemical feedstock, which will be discussed on a chapter-by-chapter basis. Chapter 2 introduces our initial attempts to address a 40-year-old scientific challenge in the field of alcohol deoxygenation: how to selectively and efficiently remove hydroxyl groups in organic molecules without affecting other existing functional groups. We hypothesize a single-step, redox process to solve this problem, whereby the dehydrogenative oxidation of alcohols and the Wolff-Kishner reduction are combined. As a proof-of-concept discovery, the early development of this reaction is catalyzed by iridium complexes and mediated by hydrazine under forcing reaction conditions. This deoxygenation protocol proves effective for many simple activated substrates such as benzylic and allylic alcohols. The major limitation, however, is the poor reactivity and selectivity seen in aliphatic alcohol substrates. Chapter 3 describes the adaptation of ruthenium(II) catalysis for the direct deoxygenation of primary aliphatic alcohols in a completely chemo- and regio-selective manner. Such a robust catalytic system, comprising [Ru(p-cymene)Cl2]2 and 1,2-bis(dimethylphosphino)ethane, is vital to lower the activation energy barriers to the dehydrogenative oxidation of aliphatic alcohols, and makes this step more kinetically favorable. Equally important is the combination of KOt-Bu, DMSO and t-BuOH, which promotes the subsequent Wolff-Kishner reduction at low temperature. This method is thus more practical compared with the iridium-based protocol, proceeding under milder thermal conditions. Its synthetic utility is demonstrated by the selective cleavage of carbon-oxygen bonds in both simple and complex organic molecules such as steroids and alkaloids. Chapter 4 presents a synthetic approach to utilize naturally occurring carbonyl compounds (i.e. aldehydes and ketones) as more sustainable alkyl carbanion equivalents for formation of carbon-carbon bonds via carbonyl addition reactions. Traditionally, such transformations depend on organometallic reagents which are made from petroleum-derived chemical feedstocks and a stoichiometric quantity of metal. Accessing this new chemical reactivity of carbonyl compounds attributes to the ruthenium(II) catalytic system discovered in the early deoxygenation chemistry. By controlling the basicity, preformed carbonyl-derived hydrazones can intercept another carbonyl compounds to form new carbon-carbon bonds via a Zimmerman-Traxler chair-like transition state. This chemical transformation delivers a wide range of synthetically valuable secondary and tertiary alcohols. Additional highlights include excellent functional group compatibility and good stereochemical control governed by chiral amido and phosphine ligands. Chapter 5 focuses on the further exploration of such unique 'umpolung' reactivity for formation of carbon-carbon bonds via conjugate addition reactions. Inspired by the softness of ruthenium(II) pre-catalyst, which bears a resemblance to that of 'soft' transition metals in the classical 1,4-conjugate addition, we presume that this ruthenium(II)-based catalytic system may be more effective for conducting nucleophilic conjugate additions. Indeed, a variety of highly functionalized aromatic carbonyl compounds are used as latent benzyl carbanions, to couple with electron-deficient [alpha],[beta]-unsaturated compounds including esters, ketones, sulfones, phosphonates, and amides. Two bidentate phosphine ligands (dppp and dmpe) are found to facilitate this process in a complementary manner, largely depending on electronic profiles of the carbonyl compounds. Chapter 6 summarizes all research present in this thesis and contributions to knowledge advancement. " --
Author: Luca Gonsalvi
Publisher:
ISBN: 9783038975854
Category : Electronic books
Languages : en
Pages : 1
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Book Description
In recent years, water phase chemistry and catalysis has witnessed a renewed interest, also in view of increasing environmental and economical concerns. Novel approaches, materials, and catalysts have been designed, for example, to convey the properties of known transition metal catalysts to their water-soluble analogs, reaching high activities and selectivities. This was possible thanks to new synthetic pathways to molecular catalysts, new mechanistic insights into the role of water as a non-innocent solvent, the use of theoretical methods and advanced engineering techniques, and the application of novel concepts for phase transfer agents in biphasic catalysis. The book contains three review articles and six research articles, addressing topics related to water phase chemistry and catalysis, ranging from the use of cyclodextrins as mass transfer agents in biphasic catalysis, to water-soluble catalyst design for targeted chemical transformation, to the application of ultrasonic monitoring of biocatalysis in water, covering aspects such as chemical synthesis, various aspects of catalysis, and engineering solutions. The range of topics addressed in this book will stimulate the reader's interest and provide a valuable source of information for researchers in academia and industry.
Author: T. R. Cundari
Publisher:
ISBN:
Category :
Languages : en
Pages : 13
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Book Description
There is considerable impetus for identification of aqueous OM catalysts as water is the ultimate ''green'' solvent. In collaboration with researchers at Ames Lab, we investigated effective fragment and Monte Carlo techniques for aqueous-phase hydroformylation (HyF). The Rh of the HyF catalyst is weakly aquated, in contrast to the hydride of the Rh-H bond. As the insertion of the olefin C=C into Rh-H determines the linear-to-branched aldehyde ratio, it is reasonable to infer that solvent plays an important role in regiochemistry. Studies on aqueous-phase organometallic catalysis were complemented in studies of the gas-phase reaction. A Rh-carbonyl-phosphine catalyst was investigated. Two of the most important implications of this research include (a) pseudorotation among five-coordinate intermediates is significant in HyF, and (b) CO insertion is the rate-determining step. The latter is in contrast to experimental deductions, highlighting the need for more accurate modeling. To this end, we undertook studies of (a) experimentally relevant PR{sub 3} co-ligands (PMe{sub 3}, PPh{sub 3}, P(p-PhSO{sub 3{sup -}}){sub 3}, etc.), and (b) HyF of propene. For the propylene research, simulations indicated that the linear: branched aldehyde ratio (linear is more desirable) is determined by thermodynamic discrimination of two distinct pathways. Other projects include a theory-experiment study of C-H activation by early transition metal systems, which establishes that weakly-bound adducts play a key role in activity selectivity. By extension, more selective catalysts for functionalization of methane (major component of natural gas) will require better understanding of these adducts, which are greatly affected by steric interactions with the ligands. In the de novo design of Tc complexes, we constructed (and are now testing) a coupled quantum mechanics-molecular mechanics protocol. Initial research shows it to be capable of accurately predicting structure ''from scratch.'' Challenges include conformational, geometric, coordination, spin, and particularly linkage (e.g., Tc-SCN versus Tc-NCS) isomerism. In general, our protocol can rapidly (
Author: Stephan Enthaler
Publisher: John Wiley & Sons
ISBN: 3527335986
Category : Technology & Engineering
Languages : en
Pages : 326
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Book Description
Filling the gap in the market for comprehensive coverage of this hot topic, this timely book covers a wide range of organic transformations, e. g. reductions of unsaturated compounds, oxidation reactions, Friedel-Crafts reactions, hydroamination reactions, depolymerizations, transformations of carbon dioxide, oxidative coupling reactions, as well as C-C, C-N, and C-O bond formation reactions. A chapter on the application of zinc catalysts in total synthesis is also included. With its aim of stimulating further research and discussion in the field, this is a valuable reference for professionals in academia and industry wishing to learn about the latest developments.
