Flavin Based Catalysis
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Flavin Based Catalysis
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Author : Radek Cibulka
language : en
Publisher: John Wiley & Sons
Release Date : 2021-06-10
Flavin Based Catalysis written by Radek Cibulka and has been published by John Wiley & Sons this book supported file pdf, txt, epub, kindle and other format this book has been release on 2021-06-10 with Technology & Engineering categories.
The book gives a unique overview of this rapidly developing research field, presenting structures and properties of flavin derivatives as well as their proven application as bioinspired catalysts in various organocatalytic, biocatalytic, and photocatalytic reactions.
Synthesis And Application Of Flavin Based Oxidation Catalysts
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Author : Christian Smit
language : en
Publisher:
Release Date : 2010
Synthesis And Application Of Flavin Based Oxidation Catalysts written by Christian Smit and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.
New And Future Developments In Catalysis
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Author : Ram Singh
language : en
Publisher: Elsevier Inc. Chapters
Release Date : 2013-07-17
New And Future Developments In Catalysis written by Ram Singh and has been published by Elsevier Inc. Chapters this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013-07-17 with Science categories.
New Approaches For Flavin Catalysis
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Author :
language : en
Publisher: Academic Press
Release Date : 2019-05-07
New Approaches For Flavin Catalysis 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 2019-05-07 with Science categories.
New Approaches for Flavin Catalysis, Volume 620, a new volume in the Methods in Enzymology series, continues the legacy of this premier serial with quality chapters authored by leaders in the field. Topics covered in this update include Anaerobiosis and Methods for Reduction, Reduction Potentials, Anaerobic Stopped-Flow, No Glove-Box, Anaerobic Stopped-Flow, in a Glove-Box, Chemical Quenching, Oxygen Reactions, Double-mixing Stopped-Flow, Kinetic Isotope Effects and Viscosity Effects, Heavy Enzymes Synthetic Flavins & Linear Free Energy Relationships, Vibrational Spectroscopy, Stark Spectroscopy, EPR and Related Methods, Molecular Dynamics, Phylogenetic Relationships/Superfamilies, O2 and Superoxide Analogs, and more. Provides the authority and expertise of leading contributors from an international board of authors Presents the latest release in the Methods in Enzymology series Updated release includes the latest information on New Approaches for Flavin Catalysis
Natural And Artificial Flavin Based Catalysis
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Author : Ekaterina Viktorovna Mirzakulova
language : en
Publisher:
Release Date : 2013
Natural And Artificial Flavin Based Catalysis written by Ekaterina Viktorovna Mirzakulova and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with Bioluminescence categories.
Artificial water splitting becomes an essential element for solar energy conversion, since the obtained energy can be stored in the form of hydrogen and oxygen gas. There are numerous studies on the development of efficient water oxidation catalysts based on transition metal complexes. One of the obstacles in using them in real large-scale applications is their high cost. Hence, the development of efficient, cheap and made from earth-abundant elements is critical for successful implementation of the solar fuel cells. Nature controls a tremendous amount of oxidation reactions that are catalyzed by fully organic compounds. For example, in the bioluminescence reaction the oxygen transfer process is catalyzed by a flavin derivative. In particular, our group is attempting to study the reverse of the bioluminescence reaction, which is the oxidation of water to oxygen using the oxidized form of flavin. Inspired by organocatalysts present in biological systems we designed and study a fully organic catalyst N(5)-ethylflavinium ion (Et-Fl+) and its pseudobase Et-FlOH as the potential water oxidation catalysts. Initially our studies have been focused on Et-FlOH as a possible water oxidation catalyst using the electrochemical and chemical oxidation experiments. Two previously published reports suggested the two-electron oxidation of Et-FlOH leads to the formation of Et-Fl+ which release the hydroxyl cation. Based on our results we conclude that this is not the case and Et-FlOH is not capable of oxidizing water itself. However, the cyclic voltammogram of Et-Fl+ showed interesting catalytic properties, which triggered us to further investigate. It was shown that Et-Fl+ performs catalytic water oxidation at a high overpotential ~ +1.9V vs NHE selectively on carbon and platinum electrodes. We carried out several different experiments such as bulk electrolysis coupled with oxygen sensing, rotating disk electrode experiments, spectroelectrochemistry to study electrochemical and catalytic performance of Et-Fl+ along with identifying the key intermediates in the catalytic cycle. We found that Et-Fl+ exhibits a modest TON=13. Density function theory (DFT) calculations revealed the mechanistic insights and the role of the working electrode in the catalysis. The essential O-O bond-forming step is proposed to occur by the coupling of two oxygen-centered radicals, one of which is attached to the flavin moiety and the other one which is attached to the electrode surface. Another interesting side of the bioluminescence reaction is the light production reaction. It is believed that hydroxyflavin is the emitter in the bioluminescence reaction and is responsible for the light production. However, outside of the protein this compound no longer emits light. Such a behavior triggered us to study the mechanism of the fast excited state deactivation. As a model compound we chose Et-FlOH. Using pump-probe spectroscopy we found that Et-FlOH exhibits a short-lived excited state. Several possible mechanisms for the fast excited deactivation have been considered and explored. The DFT calculations suggested that the existence of conical intersection. Ab initio calculations were performed on a reduced model of Et-FlOH to identify the nuclear coordinates responsible for the fast excited state deactivation. Based on our findings we concluded that there are three main nuclear modes involved, where the main one is associated with the distortion of the ring.
Mechanisms Of Catalysis
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Author :
language : en
Publisher: Academic Press
Release Date : 1991-01-28
Mechanisms Of Catalysis 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 1991-01-28 with Technology & Engineering categories.
The remarkable expansion of information leading to a deeper understanding of enzymes on the molecular level necessitated the development of this volume which not only introduces new topics to The Enzymes series but presents new information on some covered in Volume I and II of this edition.
Design And Synthesis Of Flavin Based Organocatalysts For Biomimetic Aerobic Oxidation Reactions
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Author : Shuai Chen
language : en
Publisher:
Release Date : 2014
Design And Synthesis Of Flavin Based Organocatalysts For Biomimetic Aerobic Oxidation Reactions written by Shuai Chen and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with Catalysis categories.
Oxidation reactions are among the most costly and least selective transformations in synthetic chemistry. Catalytic methods that utilize O2 as a terminal oxidant strive to reduce the inefficiency in this large area of synthesis. Recent efforts have been aimed primarily at metal-/organometallic- or enzyme-catalyzed transformations. The goal of the research described in this dissertation was to develop organocatalytic systems based on natural biosynthetic catalysts in order to develop selective metal-free aerobic oxidations that function at room temperature. Prior to our work, riboflavin mimics were previously investigated to understand flavoenzyme function and to perform catalytic oxidations of primarily heteroatom systems. We set out to extend this relatively limited area of organocatalysis to the oxidation of more valuable carbon centers in a mild, chemoselective and stereoselective manner. In Chapter 1, a description of the development and application of biomimetic flavin organocatalysts thus far reported in the literature are summarized. In Chapter 2, the flavin-catalyzed Dakin oxidation is discussed. A range of riboflavin derivatives is used as catalysts to accelerate the transformation of o- or p- hydroxyl benzaldehydes into dihydroxybenzenes using H2O2 as the terminal oxidant. An aerobic version of this transformation is developed using the flavin catalysts and NAD(P)H mimics. In Chapter 3, an aerobic asymmetric Weitz-Scheffer epoxidation of enals using flavin and chiral, non-racemic pyrrolidines in a dual catalysis strategy is discussed. High enantioselectivity and diastereoselectivity are observed in the epoxides obtained using this method. A mechanical study is conducted to elucidate the characteristics of the reaction pathway. In Chapter 4, the flavin catalyzed aerobic aromatization of heterocycles is discussed. Riboflavin derivatives are used to convert substituted dihydropyridines and benzothiazolines to pyridines and benzothiazoles with molecular oxygen as terminal oxidant under mild reaction conditions.
Design Synthesis And Applications Of Biomimetic Flavin Based Organocatalysts
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Author : Mohammad Shawkat Hossain
language : en
Publisher:
Release Date : 2019
Design Synthesis And Applications Of Biomimetic Flavin Based Organocatalysts written by Mohammad Shawkat Hossain and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019 with Catalysis categories.
Oxidation reactions are one of the most important transformations in synthetic chemistry. Most commonly used oxidants are metal oxides, which are neither green nor selective towards multi-functional molecules. The efficiency of the reactions can be improved by the introduction of a catalyst by lowering the activation energy. In nature, oxidation reactions are highly specific and are controlled by enzymes, co-enzymes, and availability of a renewable terminal oxidant, molecular oxygen. Among the various enzymatic oxidative transformations, our research was inspired by the oxidations controlled by co-enzymes FMN or FAD in the presence of flavoproteins and molecular oxygen. Flavin mimics were often studied/used to oxidize heteroatoms; however, the goal of this research was initialy focused on mimicking other chemoselective oxidations of flavins, primarily at carbon centers. In chapter one, the function of natural flavins in nature and different approaches to perform nucleophilic and electrophilic oxidation using artificial flavin is described. In chapter two, flavin reactivity was extended to the Dakin oxidation of electron-rich benzaldehydes. This conversion of aryl aldehyde to phenol worked efficiently under mild conditions with either hydrogen peroxide or molecular oxygen as terminal oxidant. The mechanism was understood by various reaction rates studies. Substituent effects of catalysts and substrates aided in the identification of the rate determining step. The order of reagents and extensive pH studies reveal the various way flavin catalysts enable oxo-transfer under mild, more neutral conditions, by altering both the pKa of the active nucleophilic oxygen source, and by lowering the energy of the oxide leaving group, as previously hypothesized by Briuce and coworkers. In chapter three, pre-heteroaromatic compounds (initially investigated as possible reducing agents for flavin mimics) were transformed to their aromatic form aerobically using flavin catalyst in arguably the most mild methods described to date. Chapters four through six describe the preparation and function of various classes of flavins. Chapter four discussed the bioactivity of new flavin species against cancerous and normal breast cells. Chapter five details the preparation of water-soluble classes of flavins and their photochemical properties (O2 activation and Methyl Orange degredation). And Chapter six discusses the preparation of redox active flavins that were prepared for tethering to metal oxide photocatalyst and various electrode surfaces. Chapter seven describes a new preparation of 5-deazaflavin cofactors - deazariboflavin, 8-hydroxydeazariboflavin (an F420-precursor), and 10-methyl deazaflavin. An improved route to these species is described, and their redox activity were investigated in F420-dependent enzymes. Finally, chapter eight shows a new, concise and high yielding synthetic route explored for the synthesis of flavin catalysts, which includes the synthesis of different o-phenylenediamine derivatives and alloxan derivatives.
Redox And Non Redox Reactions Catalyzed By Biomimetric Flavin Based Organocatalysts And The Discovery Of Selective Oxidation Methods For The Preparation Of N Heterocycles
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Author : Pawan Thapa
language : en
Publisher:
Release Date : 2019
Redox And Non Redox Reactions Catalyzed By Biomimetric Flavin Based Organocatalysts And The Discovery Of Selective Oxidation Methods For The Preparation Of N Heterocycles written by Pawan Thapa and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019 with Chemical bonds categories.
In nature, flavoproteins (FMN and FAD) are known to catalyze several chemical transformations which play a vital role in the growth, development, and survival of organisms. They are involved in one-electron and two-electron transfer reactions, photo-induced electron transfer reactions, dehydrogenase reactions, oxidative atom transfer reactions and also rare non-redox reactions. Their enhanced stability and ability to turn over in presence of dioxygen has inspired synthetic chemists, including our group, to perform biomimetic transformations within a range of function of natural flavoproteins. In chapter 1, both intramolecular and intermolecular dehydrogenative coupling between the alpha carbon of tertiary amines and various nitrogen, phosphorus, and carbon-based nucleophilesare reported. This study signifies the flavin dependent oxidase type chemistry promoted by synthetic flavins, rendering the catalytic construction of some sophisticated heterocycles through an atom economical and aerobic approach. Mechanistic studies with different radical probes suggest the involvement of radical intermediates in the reaction cycle. Moreover, intramolecular kinetic isotope studies performed reveal possibility of Hydrogen atom abstraction being rate determining step. In chapter 2, a non-redox type of chemistry is disclosed. A subclass of riboflavin mimics was found to catalyze C-C bond formation by activating small molecules in a new manner. This approach was successfully applied to synthesize various industrially important dyes and chemical reagents. Additionally, the relationship discovered between molecular structure and catalytic function of riboflavin mimics in these new chemical reactions revealed a plausible explanation for the function of natural riboflavin-dependent hydroxynitrilase enzymes in biological system. Mechanistic studies using nuclear magnetic resonance (NMR) spectroscopy, UV-vis spectroscopy and electron paramagnetic resonance (EPR) spectroscopy showed a possible frustrated lewis-pair (FLP) type of interaction between aldehydes and flavin mimics. In chapter 3, studies on benzimidazole synthesis by iron catalysts will be discussed. 1,2-disubstituted benzimidazoles serve as important class of molecules in several area of chemistry including drug discovery, catalysis, etc. Our investigation in this area with redox active iron catalysts revealed N,N'-disubstituted-ortho-phenylenediamine substrates being superior to N,N disubstituted-ortho-phenylenediamines in generating 1,2-disubstituted benzimidazoles. Extensive UV-vis spectroscopy studies and kinetic studies have been performed in addition to EPR spectroscopy to understand the nature of mechanism. Both Lewis acid property and redox active property of iron trichloride are thought to play a significant role in catalysis. Smooth complex formation between N,N'-disubstituted-ortho-phenylenediamine substrates and iron catalyst provides the driving force for the electron transfer process to form productive iminiumintermediate.A simple method for chemo-selective oxidation of isoindolines to isoindolinones was also studied in chapter 4. This method utilizes no catalyst, no additive, mild condition and is highlighted as just solvent mediated transformation. Mechanistic investigation shows hydrogen atom abstraction process leading to isoindole intermediates which further binds to oxygen to give desired isoindolinones products.
Catalysis In Chemistry And Biochemistry Theory And Experiment
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Author : A. Pullman
language : en
Publisher: Springer Science & Business Media
Release Date : 2012-12-06
Catalysis In Chemistry And Biochemistry Theory And Experiment written by A. Pullman and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012-12-06 with Science categories.
Proceedings of the Twelfth Jerusalem Symposium on Quantum Chemistry and Biochemistry held in Jerusalem, Israel, April 2-4, 1979