Synthesis And Application Of Flavin Based Oxidation Catalysts
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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.
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.
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.
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.
Synthesis And Application Of Supramolecular Catalysts In The Oxidation Of Unactivated C Sp H Bonds
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Author : Melina Knezevic
language : en
Publisher:
Release Date : 2023
Synthesis And Application Of Supramolecular Catalysts In The Oxidation Of Unactivated C Sp H Bonds written by Melina Knezevic and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2023 with categories.
Synthesis And Optimization Of Tempo Based Polymeric Oxidation Catalysts
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Author : Ayşegül Tosun
language : en
Publisher:
Release Date : 2002
Synthesis And Optimization Of Tempo Based Polymeric Oxidation Catalysts written by Ayşegül Tosun and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2002 with categories.
Polyoxomolybdates As Green Catalysts For Aerobic Oxidation
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Author : Anjali Patel
language : en
Publisher: Springer
Release Date : 2014-11-22
Polyoxomolybdates As Green Catalysts For Aerobic Oxidation written by Anjali Patel and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014-11-22 with Science categories.
Heterogeneously catalyzed selective oxidations of alcohols is a highly topical field. The first chapter of this brief describes the importance of the selective oxidation of alcohols and advantages of heterogeneous catalysts over conventional catalysts, use of environmentally benign oxidants, and the design of selective catalysts by tailoring of polyoxometalates at the molecular level. Chapter 2 describes synthesis, characterization 11-molybdophosphate based supported materials and their use as heterogeneous catalysts for oxidation of alcohols with molecular oxygen under solvent free mild reaction condition. ZrO2, Al2O3, MCM-41 and zeolite Hβ were used as supports. Chapter 3 describes synthesis, characterization of transition metals (Mn, Co, Ni, Cu)- substituted phosphomolybdates and their use as heterogeneous catalysts for oxidation of alcohols with molecular oxygen under solvent free mild reaction condition. Chapter 4 describes conclusive remarks for present catalytic systems.
Biocatalytic Synthesis Of Bioactive Compounds
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Author : Josefina Aleu
language : en
Publisher: MDPI
Release Date : 2020-12-02
Biocatalytic Synthesis Of Bioactive Compounds written by Josefina Aleu and has been published by MDPI this book supported file pdf, txt, epub, kindle and other format this book has been release on 2020-12-02 with Science categories.
Biocatalysis, the application of enzymes as catalysts for chemical synthesis, has become an increasingly valuable tool for the synthetic chemist. Enzymatic transformations carried out by enzymes or whole-cell catalysts are used for the production of a wide variety of compounds ranging from bulk to fine chemicals. The primary consideration for the incorporation of biotransformation in a synthetic sequence is regio- and stereocontrol that can be achieved with enzyme-catalyzed reactions. Biotransformations are thus becoming accepted as a method for generating optically pure compounds as well as for developing efficient routes to target compounds. This Special Issue aims to address the main applications of biocatalysts, isolated enzymes, and whole microorganisms in the synthesis of bioactive compounds and their precursors.
Chemical Photocatalysis
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Author : Burkhard König
language : en
Publisher: Walter de Gruyter GmbH & Co KG
Release Date : 2020-04-06
Chemical Photocatalysis written by Burkhard König and has been published by Walter de Gruyter GmbH & Co KG this book supported file pdf, txt, epub, kindle and other format this book has been release on 2020-04-06 with Science categories.
Visible light is an abundant source of energy. While the conversion of light energy into electrical energy (photovoltaics) is highly developed and commercialized, the use of visible light in chemical synthesis is far less explored. Chemical photocatalysts that mimic principles of biological photosynthesis utilize visible light to drive endothermic or kinetically hindered reactions.
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.