Download or read book Organocatalytic Asymmetric Domino Reactions Via N heterocyclic Carbene and Bifunctional Hydrogen bonding Donor Catalysts written by Long Zhao and published by . This book was released on 2018* with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Hydrogen Bonding in Organic Synthesis written by Petri M. Pihko and published by John Wiley & Sons. This book was released on 2009-09-09 with total page 395 pages. Available in PDF, EPUB and Kindle. Book excerpt: This first comprehensive overview of the rapidly growing field emphasizes the use of hydrogen bonding as a tool for organic synthesis, especially catalysis. As such, it covers such topics as enzyme chemistry, organocatalysis and total synthesis, all unified by the unique advantages of hydrogen bonding in the construction of complex molecules from simple precursors. Providing everything you need to know, this is a definite must for every synthetic chemist in academia and industry.
Download or read book Planar Chiral Hydrogen Bond Donor Catalysts written by Jakob Schneider and published by Cuvillier Verlag. This book was released on 2010-11-02 with total page 276 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis focuses on the first synthesis and application of planar-chiral [2.2]paracyclophane- derived hydrogen-bond donor catalysts, thereby inducing a unique chiral motif into the emerging field of thiourea organocatalysis. Reaction acceleration through hydrogen-bond catalysis has made a significant impact on the field, rendering the development of potent catalyst structures extremely valuable. Based on the [2.2]paracyclophane scaffold, mono- and bi-functional thiourea catalysts were prepared. The rigidity of the [2.2]paracyclophane structure leads to a unique setup of the substituents. In pseudo-geminal position to the thiourea moiety, a hydroxy group was selected and introduced as the second functionality. In a 12-step synthesis, the enantiopure hydroxy- substituted [2.2]paracyclophanylene thiourea was obtained. Furthermore, efficient access to enantiopure pseudo-geminally substituted 13-amino-4- bromo[2.2]paracyclophane was developed. The aminobromide was employed in cross- coupling reactions to yield arylated amino[2.2]paracyclophanes, exhibiting a broad range of electronic and steric features useful for organocatalytic applications. The developed catalysts were applied in asymmetric organic transformations and proved most useful in the transfer hydrogenation reaction. The hydroxy-substituted thiourea catalyst particularly exhibited catalytic activity and stereoselectivity. To shed light on the mode of action of this class of hydrogen-bond catalysts, various analytic methods were conducted. Through extensive crystallographic and NMR complexation experiments, the binding properties of the catalysts were investigated in terms of their interaction with hydrogen-bond- accepting functional groups. Furthermore, quantum chemical DFT and ab initio calculations were undertaken to explore the favored conformations of [2.2]paracyclophane-derived thioureas. The combined findings revealed substrate-dependent activation via single or double hydrogen bonding between the NH groups of the thiourea and the respective substrate. Furthermore, a class of readily accessible hydrogen-bond thiourea catalysts was developed, derived from amino acids. Their steric and electronic features were modulated by their degree of substitution at the carbinol carbon center. All catalysts were applied in the asymmetric transfer hydrogenation of nitroolefins, furnishing the products in up to 99% yield and 87% enantiomeric excess.
Download or read book Rationalization and Innovative Design of Asymmetric Organocatalysts Through Computational Investigation written by Ryne Connell Johnston and published by . This book was released on 2015 with total page 392 pages. Available in PDF, EPUB and Kindle. Book excerpt: My work on computing complex catalyzed organic transformations reveals that only a few subtle chemical factors, e.g. non-classical hydrogen bonding, (hyper)conjugation and steric effects, common across different catalyst manifolds are critical for catalysis and selectivity. Rational manipulation and exploitation of these factors has led to improved catalyst designs, which has previously been an oft-promised but rarely delivered endeavor. Hydrogen bonding is critical to stabilizing structures in both the ground and transition state across many branches of chemistry and life. C-H bonds polarized through either hybridization or proximity to a developing or full positive charge can provide stabilization through interaction with negatively charged atoms in a C-H···O non-classical hydrogen bond (NCHB). In the transition state, where a molecule experiences temporarily amplified polarization, these hydrogen bonds can serve to stabilize the structures and differentiate between diastereomeric TSs A joint experimental and computational investigation on a diaryl prolinol silyl ether-catalyzed Michael cascade reaction to complex furanyl/pyranyl products uncovered the synergistic relationship between catalyst and substrate beyond the basic enamine activation and steric control. NCHBs were discovered to stabilize the transiently polar transition state. The kinetic resolution of addition products was afforded by virtue of the conformation of the substrate preventing or allowing hyperconjugation. An N-heterocyclic carbene-catalyzed dynamic kinetic resolution of [beta]-ketoesters was discovered to display an unusual resolution mechanism. Rapid substrate epimerization early in the aldol mechanism allowed routing through the lowest energy diastereomeric pathway, which also differs in mechanism from the other diastereomeric TSs. Facial control arises from the presence or absence of a single chiral NCHB donor stabilizing the developing alkoxide. Diastereocontrol is afforded by the configuration of the epimerizable [beta]-stereocenter hydrogen affecting the conjugative ability of the keto aryl group. This same control arises in the rapid and enantioselective retro-[2+2] decarboxylations of the product bicyclic [beta]-lactones to cyclopentenes. A study on the origins of enantioselectivity of an NHC-catalyzed homoaldol with acylphosphonates uncovered stereodifferentiating pockets of NCHB akin to an oxyanion hole between the catalyst aryl groups and the phosphonyl (P=O) oxygen. Computations predicted an increase of selectivity by blocking the sites stabilizing the minor transition state. Synthesis and test of the catalyst verified computational predictions. A chiral bifunctional aminothiourea has been developed for the Michael addition of acrylates to [alpha]-ketones to generate asymmetric all-carbon quaternary centers. This catalyst both activates the nucleophile via enamine catalysis and employs hydrogen bonding catalysis to activate the carbonyl-bearing electrophile. A joint experimental and computational study reveals the mechanism of this process and seeks to uncover the origins of selectivity. Computations predict that deletion of the catalyst [beta]-phenyl group would increase selectivity; however, experimental synthesis and test led to unforeseen catalyst decomposition.
Download or read book Development of Novel Hydrogen Bond Donor Catalysts written by Tsubasa Inokuma and published by Springer. This book was released on 2015-07-01 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work describes novel, effective hydrogen-bond (HB) donor catalysts based on a known bifunctional tertiary amine-thiourea, a privileged structure, which has been proven to be one of the most widely used organocatalysts. These HB donor catalysts derived from quinazoline and benzothiadiazine were initially synthesized as novel HB donors with their HB-donating abilities being measured by analytical methods. They were found to be effective for a variety of asymmetric transformations including Michael reactions of a, b-unsaturated imides and hydrazination reactions of 1,3-dicarbonyl compounds. Thiourea catalysts that have an additional functional group are also described. Specifically, thioureas that bear a hydroxyl group were synthesized and subsequently used as novel bifunctional organocatalysts for catalytic, asymmetric Petasis-type reactions involving organoboronic acids as nucleophiles. These addition reactions were difficult to achieve using existing organocatalysts. One of the developed catalytic methods can be applied to the synthesis of biologically interesting peptide-derived compounds possessing unnatural vinyl glycine moieties. These findings introduce new criteria required for the development of organocatalysts for asymmetric reactions, thus making a significant contribution to the field of organocatalysis.
Download or read book N Heterocyclic Carbenes in Organocatalysis written by Akkattu T. Biju and published by John Wiley & Sons. This book was released on 2019-01-07 with total page 407 pages. Available in PDF, EPUB and Kindle. Book excerpt: Summarizing the emerging field of N-heterocyclic carbenes used in organocatalysis, this is an excellent overview of the synthesis and applications of NHCs focusing on carbon-carbon and carbon-heteroatom bond formation. Alongside comprehensive coverage of the synthesis, characteristics and applications, this handbook and ready reference also includes chapters on NHCs for polymerization reactions and natural product synthesis.
Download or read book Organocatalytic Enantioselective Conjugate Addition Reactions written by Jose L Vicario and published by Royal Society of Chemistry. This book was released on 2010-10-18 with total page 365 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book, unique in its field, is a comprehensive description of all the methodologies reported for carrying out conjugate addition reactions in a stereoselective way, using small chiral organic molecules as catalysts (organocatalysts). In the last 3-4 years, this has been a rapidly growing field in organic chemistry, and many papers have appeared reporting excellent protocols for carrying out these highly efficient transformations that compete well with other classical approaches using transition metal catalysts. A particularly attractive feature of this transformation relies upon the fact that the conjugate addition (Michael and Hetero-Michael reactions) is an extraordinarily effective means to initiate cascade processes which result in the formation of complex molecules from very small and simple starting blocks. The book, written by noted experts, covers all recent advances in this hot topic, and provides a good state-of-the-art review for organic chemists working in this field and all those who wish to start projects in this area.
Download or read book Non Covalent Catalysis and Hydrogen Bonding written by and published by GRIN Verlag. This book was released on 2019-08-08 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt: Research Paper (undergraduate) from the year 2019 in the subject Chemistry - Bio-chemistry, grade: 1,0, University of Cologne, language: English, abstract: This work is about the non-covalent catalysis and concentrates on the hydrogen-bond catalysis. Nowadays it is common to use catalysis in organic synthesis. It can help in orienting the substrates, lowering barriers to reaction and accelerating the rates of reaction. In addition to metal-ligand systems and biocatalysts, there is another class of catalysts, the organocatalysts which are free of any metals, like many enzymes. The organocatalysts often consist of chiral compounds. The output materials are easy to find in the nature. How these catalysts accelerate the reaction rates is a central question in organic synthesis. It is important to distinguish the interactions with the organic substrates between covalent and non-covalent bonds. The activation of a carbonyl compound by conversion into an enamine or into an iminium ion belongs to the covalent catalysis, while to increase the electrophilicity of a carbonyl group by formation of hydrogen bondings is a typical example for non-covalent organocatalysis. Thus, the acceleration and the control of the reaction rates depend on formation of hydrogen bonds for non-covalent organocatalysis. It is possible to catalyse two hydrogen bonds which occur in dual hydrogen bonding donors.
Download or read book Asymmetric Domino Reactions written by Helene Pellissier and published by Royal Society of Chemistry. This book was released on 2013-03-13 with total page 519 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book covers the latest developments in asymmetric domino reactions, focussing on those published in the last 6 years. These fascinating reactions have rapidly become one of the most current fields in organic chemistry, since they allow reaching easily high molecular complexity in an economically favourable way with advantages of savings in solvent, time, energy, and costs. Unsurprisingly, the high levels of efficiency and enantioselectivity generally reached in these reactions have been exploited for the production of a wide number of complex chiral molecules with dense stereochemistry and functionality, which are motifs present in biologically active compounds and natural products. The book is divided into three principal sections, dealing successively with asymmetric domino reactions based on the use of chiral auxiliaries, asymmetric domino reactions based on the use of chiral metal catalysts, and asymmetric domino reactions based on the use of chiral organocatalysts, covering the literature since the beginning of 2006.
Download or read book Spiro Compounds written by Ramon Rios Torres and published by John Wiley & Sons. This book was released on 2022-02-15 with total page 468 pages. Available in PDF, EPUB and Kindle. Book excerpt: SPIRO COMPOUNDS A comprehensive treatment of the latest research in, and applications of, spiro compounds Spiro Compounds: Synthesis and Applications combines discussions of the latest advances in spiro compound research with the most cutting-edge, real-world applications of that knowledge. This book provides in-depth coverage of the history, significance, properties, synthetic methods, and applications of spiro compounds. As interest in spiro compounds grows due to their unique conformational features and their structural implications on biological systems, Spiro Compounds delivers fulsome treatments of advances in spiro compound synthesis (including stereoselective synthesis) methodologies. With a special focus on the mechanisms of the reactions that lead to the synthesis of spiro compounds, chapters in the book cover topics such as: The history, significance, and unique properties of spiro compounds The most important methodologies for their synthesis The applications of spiro compounds in organic chemistry, biology, drug discovery The most important syntheses of natural products bearing a spiro ring Perfect for academic and industrial chemists, this comprehensive discussion of spirocycles is an indispensable resource for those practicing in the field.
Download or read book Dienamine Catalysis for Organic Synthesis written by Kengadarane Anebouselvy and published by Royal Society of Chemistry. This book was released on 2018-03-02 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the last decade a new era in asymmetric catalysis has been realised by the discovery of L-proline induced chiral enamines from carbonyls. Inspired by this, researchers have developed many other primary catalytic species in situ, more recently secondary catalytic species such as aminals have been identified for use in asymmetric synthesis. High-yielding asymmetric synthesis of bioactive and natural products through mild catalysis is an efficient approach in reaction engineering. In the early days, synthetic chemists mainly focused on the synthesis of complex molecules, with less attention on the reaction efficiency and eco-friendly conditions. Recent investigations have been directed towards the development of atom economy, eco-friendly and enantioselective synthesis for more targeted and efficient synthesis. Building on the momentum of this rapidly expanding research area, Dienamine catalysis for organic synthesis will provide a comprehensive introduction, from the preformed species, in situ generation and onto their applications in the synthesis of bioactive molecules and natural products.
Download or read book Development and Applications of N Sulfinyl Organocatalysts written by MaryAnn Theresa Robak and published by . This book was released on 2010 with total page 122 pages. Available in PDF, EPUB and Kindle. Book excerpt: The development of new catalysts for asymmetric organic transformations is a broad and important research goal in modern synthetic organic chemistry. The use of chiral ligands as a source of asymmetric induction in metal-catalyzed reactions has been a traditional focus of this field. One class of chiral ligands is those which incorporate enantiomerically pure sulfinamides. Chapter 1 provides an overview of this area of research. Also included are examples of sulfinamide-based ligands for reactions involving stoichiometric metals, as well as a few examples of sulfinamide-based organocatalysts that have been reported in the literature. The literature reviewed serves as an important foundation for the research described in Chapters 2 and 3. Asymmetric organocatalysis, the use of chiral small molecules as metal-free catalysts, has developed into an area of intense research in the past decade. One mode of substrate activation by organocatalysts is hydrogen bonding. The urea/thiourea scaffold is one of the most effective and well developed types of hydrogen bonding organocatalysts. The acidity (and corresponding strength of the hydrogen bonding interaction) of the hydrogen bond donor is an important consideration for the development of efficient catalysts. Chapter 2 details the development of organocatalysts that incorporate an N-sulfinyl urea as a hydrogen bond donor. In these catalysts, the sulfinyl substituent serves both to acidify the urea N-H bond and to act as a source of asymmetric induction by virtue of the sulfur-based chirality that is presented proximal to the hydrogen bond donor. The application of these catalysts to two different nucleophilic addition reactions is described. Organocatalysts that incorporate a nucleophilic amine have also been developed extensively in recent years. One of the earliest reported examples of this type of catalysis was the use of proline as a catalyst for the enantioselective intermolecular aldol reaction via a nucleophilic enamine intermediate. While the amine may be considered the primary catalytic site, the carboxylic acid has also been implicated in the catalytic cycle, and is proposed to provide a key hydrogen bonding interaction in the enantiodetermining step of the reaction. Chapter 3 describes the development of an N-sulfinyl proline amide as a novel and superior catalyst for the aldol reaction, again demonstrating the utility a sulfinyl N-H as a chiral hydrogen bond donor.
Download or read book Catalytic Asymmetric Synthesis written by Takahiko Akiyama and published by John Wiley & Sons. This book was released on 2022-05-27 with total page 798 pages. Available in PDF, EPUB and Kindle. Book excerpt: Catalytic Asymmetric Synthesis Seminal text presenting detailed accounts of the most important catalytic asymmetric reactions known today This book covers the preparation of enantiomerically pure or enriched chemical compounds by use of chiral catalyst molecules. While reviewing the most important catalytic methods for asymmetric organic synthesis, this book highlights the most important and recent developments in catalytic asymmetric synthesis. Edited by two well-qualified experts, sample topics covered in the work include: Metal catalysis, organocatalysis, photoredox catalysis, enzyme catalysis C–H bond functionalization reactions Carbon–carbon bond formation reactions, carbon–halogen bond formation reactions, hydrogenations, polymerizations, flow reactions Axially chiral compounds Retaining the best of its predecessors but now thoroughly up to date with the important and recent developments in catalytic asymmetric synthesis, the 4th edition of Catalytic Asymmetric Synthesis serves as an excellent desktop reference and text for researchers and students, from upper-level undergraduates all the way to experienced professionals in industry or academia.
Download or read book Cooperative Catalysis written by René Peters and published by John Wiley & Sons. This book was released on 2015-04-27 with total page 452 pages. Available in PDF, EPUB and Kindle. Book excerpt: Written by experts in the field, this is a much-needed overview of the rapidly emerging field of cooperative catalysis. The authors focus on the design and development of novel high-performance catalysts for applications in organic synthesis (particularly asymmetric synthesis), covering a broad range of topics, from the latest progress in Lewis acid / Br?nsted base catalysis to e.g. metal-assisted organo catalysis, cooperative metal/enzyme catalysis, and cooperative catalysis in polymerization reactions and on solid surfaces. The chapters are classified according to the type of cooperating activating groups, and describe in detail the different strategies of cooperative activation, highlighting their respective advantages and pitfalls. As a result, readers will learn about the different concepts of cooperative catalysis, their corresponding modes of operation and their applications, thus helping to find a solution to a specific synthetic catalysis problem.
Download or read book Multi component Reactions in Molecular Diversity written by Jean-Philippe Goddard and published by John Wiley & Sons. This book was released on 2020-04-28 with total page 198 pages. Available in PDF, EPUB and Kindle. Book excerpt: While very useful for studying syntheses of molecular diversity, multi-component reactions also offer rapid access to a variety of complex molecules that are relevant for biological applications. Multi-component Reactions in Molecular Diversity analyzes these reactions, whether they are realized by organometallic, ionic or even radical processes. It highlights popular methods based on monotype reactions (cascade, tandem, domino) and their efficiency and academic industrial domain are illustrated. This book also investigates the most efficient ways to prepare complex molecules. Multi-component reactions are in tune with the concepts of atom and steps economy, which are of prior importance in all the reported processes ? from the laboratory to the pilot scale. The essential criteria for green chemistry are also examined in the book in detail.
Download or read book Fluorinated Heterocycles written by American Chemical Society. Meeting and published by . This book was released on 2009 with total page 390 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the first ACS symposium series book solely devoted to fluorinated heterocyclic compounds. Its contents encompasses all aspects of chemistry and applications of fluoroheterocycles including synthesis, biological activity, computational and medicinal research covering all major classes of heterocycles as well as popular fluorine-containing fragments.
Download or read book Hydrogen Transfer Reactions written by Gabriela Guillena and published by Springer. This book was released on 2016-09-27 with total page 393 pages. Available in PDF, EPUB and Kindle. Book excerpt: The series Topics in Current Chemistry Collections presents critical reviews from the journal Topics in Current Chemistry organized in topical volumes. The scope of coverage is all areas of chemical science including the interfaces with related disciplines such as biology, medicine and materials science. The goal of each thematic volume is to give the non-specialist reader, whether in academia or industry, a comprehensive insight into an area where new research is emerging which is of interest to a larger scientific audience. Each review within the volume critically surveys one aspect of that topic and places it within the context of the volume as a whole. The most significant developments of the last 5 to 10 years are presented using selected examples to illustrate the principles discussed. The coverage is not intended to be an exhaustive summary of the field or include large quantities of data, but should rather be conceptual, concentrating on the methodological thinking that will allow the non-specialist reader to understand the information presented. Contributions also offer an outlook on potential future developments in the field.
