The Synthesis and Reactivity of Novel Donor-Acceptor Cyclopropanes and Progress Towards Pyrrolidine Alkaloids PDF Download
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Author: Michael R. Emmett
Publisher:
ISBN:
Category :
Languages : en
Pages : 510
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Book Description
The first chapter of this thesis focuses on the synthesis and reactivity of cyclopropane hemimalonates. The cyclopropane hemimalonates can easily be synthesized from 1,1-cyclopropanediesters. The reactivity of cyclopropane hemimalonates with indole under ultra-high pressure conditions leads to ring opened adducts that are complementary to previous research in the Kerr group. The tandem ring opening decarboxylation reaction of cyclopropane hemimalonates led to the synthesis of -aminobutyric acid analogues. When an external nucleophile was not present, the cyclopropane hemimalonates could rearrange to form butyrolactones in good to excellent yields. The stereochemical integrity of the cyclopropane hemimalonate is retained through this process, which is not usually seen in cyclopropane reactivity. The second chapter describes the progress towards the synthesis of Kainic acid. While the progress towards this natural product appeared to be going well, after closer analysis of the products, a new reactivity of diazo species and cyclopentadiene was realized. In the third chapter, the progress towards the synthesis of Actinophyllic acid is provided. Synthesis of advanced intermediates was completed, however the key formation of a 1,4-dicarbonyl species of the pyrrolidine ring eluded this study.
Author: Michael R. Emmett
Publisher:
ISBN:
Category :
Languages : en
Pages : 510
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Book Description
The first chapter of this thesis focuses on the synthesis and reactivity of cyclopropane hemimalonates. The cyclopropane hemimalonates can easily be synthesized from 1,1-cyclopropanediesters. The reactivity of cyclopropane hemimalonates with indole under ultra-high pressure conditions leads to ring opened adducts that are complementary to previous research in the Kerr group. The tandem ring opening decarboxylation reaction of cyclopropane hemimalonates led to the synthesis of -aminobutyric acid analogues. When an external nucleophile was not present, the cyclopropane hemimalonates could rearrange to form butyrolactones in good to excellent yields. The stereochemical integrity of the cyclopropane hemimalonate is retained through this process, which is not usually seen in cyclopropane reactivity. The second chapter describes the progress towards the synthesis of Kainic acid. While the progress towards this natural product appeared to be going well, after closer analysis of the products, a new reactivity of diazo species and cyclopentadiene was realized. In the third chapter, the progress towards the synthesis of Actinophyllic acid is provided. Synthesis of advanced intermediates was completed, however the key formation of a 1,4-dicarbonyl species of the pyrrolidine ring eluded this study.
Author: Florian de Nanteuil
Publisher: Springer
ISBN: 3319230069
Category : Science
Languages : en
Pages : 329
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Book Description
This thesis presents a general approach to accessing nitrogen-substituted hetero- and carbocycles. In short, the annulation reactions developed in the thesis make it possible to access nitrogen-substituted four-, five- and six-membered rings, all essential building blocks for the synthesis of bioactive molecules. Many natural products display a saturated polycyclic core allowing a well-defined arrangement of functional groups in space. As such, they can interact with biological targets with a high degree of affinity and selectivity, surpassing many synthetic drugs. Nevertheless, the efficient synthesis of such complex ring systems poses a challenge for organic chemistry. Through careful tuning of the electronic properties of a nitrogen donor group and a diester acceptor group, the first [3+2] annulation reaction between aminocyclopropanes and enol ethers or carbonyl compounds is now possible. The reaction proceeded under mild catalytic conditions, and the building blocks obtained can be found at the core of bioactive alkaloids, drugs such as Ramipril and biomolecules such as DNA and RNA. Thanks to the dynamic kinetic asymmetric annulation of aminocyclopropanes with enol ethers and aldehydes, access to enantioenriched compounds is also now possible. Lastly, a synthesis of donor-acceptor aminocyclobutanes via [2+2] cycloaddition using a cheap iron catalyst was developed, allowing them to be used in [4+2] annulations to access cyclohexylamines.
Author: Prabal Banerjee
Publisher: John Wiley & Sons
ISBN: 3527349871
Category : Science
Languages : en
Pages : 469
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Book Description
Facilitate milder, simpler reactions in organic synthesis with this cutting-edge family of building blocks Donor-Accepted Cyclopropanes, or DACs, have attracted a resurgence of interest from organic chemists in recent decades for their role in facilitating various reactions such as cycloadditions, annulations, ring-opening and enantioselective transformations. The structural arrangement of DACs leads to milder, simpler reaction conditions, which have made them indispensable for a range of fundamentally and industrially important processes. Donor-Acceptor Cyclopropanes in Organic Synthesis covers comprehensively the chemistry and applications of this compound class. The result is an invaluable guide for any researcher looking to bring DACs to bear in their own areas of research or development. Readers will also find: A brief introduction of the history and reactivity of DACs Detailed discussion of reactions including Lewis acid-catalyzed cycloadditions, metal-free activation, asymmetric transformations, organocatalysis, and many more Application of DACs in natural product synthesis and pharmaceutical/agrochemical research Donor-Acceptor Cyclopropanes in Organic Synthesis is ideal for organic chemists, experts in catalysis, pharmaceutical researchers, and any other scientists interested in facilitating milder, simpler reactions.
Author: Nareddy Radhika Reddy
Publisher:
ISBN:
Category :
Languages : en
Pages : 97
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Book Description
Natural products serve as a major resource for many pharmacologically-active drugs found in the market today. Using natural products as medicines, however, is associated with many limitations such as availability and isolation. An alternative to this is the synthesis of these compounds, which can be done using two different approaches: (1) Total synthesis of the molecule, and (2) A semi-synthetic approach. Total synthesis generally involves synthesis of the target molecule by assembling the ring systems or the core skeletal framework of the natural product. There are numerous methods reported in the literature for the synthesis of these ring systems. Despite this, there is always a quest for new methods; methods with improved efficiency in terms of chemo-, regio- and stereoselectivities. As a result, new synthetic tools are needed to address these issues. These new tools can be the development of new catalysts, new techniques, or innovative methodologies, which will allow new transformations and aid in the synthesis of complex natural products. In recent years small, strained molecules such as cyclopropanes, cyclobutanes and cyclopropenes, have been successfully employed for the synthesis of complex ring systems. In this dissertation a new method to access certain carbocyclic and heterocyclic ring systems using cyclopropanes as building blocks will be presented. This involves synthesis of novel cyclopropanes by intermolecular reaction between substituted styrenes and different alpha-arylmethyl-alpha-diazo compounds in the presence of Rhodium catalysts. The challenge in the synthesis of these cyclopropanes is that these diazo compounds are notorious for undergoing beta-hydride elimination reactions, thus limiting their use for intermolecular reactions. In this study, we aim to synthesize the proposed cyclopropanes in good yields while minimizing, if not completely eliminating, the betahydride elimination reaction. The first half of the thesis discusses the different approaches taken to synthesize the desired cyclopropanes with limited success. However using Rh2 (S-PTTL)3 TPA as the catalyst and optimizing the reaction conditions allowed us to synthesize these cyclopropanes in moderate to good yields. The second part of the thesis focuses on the study of ring opening reactions of the cyclopropanes synthesized using various Lewis acids.
Author: Huck K. Grover
Publisher:
ISBN:
Category :
Languages : en
Pages : 556
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Book Description
The development and utility of cyclopropanes is an ever-growing field within organic chemistry. In particular, donor-acceptor cyclopropanes have been used in a vast array of methods to access a variety of different hetero and carbocyclic molecular scaffolds. Recently, we have developed a Zn(NTf2)2 catalyzed tandem reaction consisting of a nucleophilic ringopening of 1,1-cyclopropanediesters by 2-alkynyl indoles followed by a Conia-ene ring closure, resulting in the efficient one-step synthesis of tetrahydrocarbazoles. These adducts may be further elaborated to carbazoles. The scope and limitations of this method were determined along with a mechanistic study into the function of the zinc catalyst. In an expansion of our work with 1,1-cyclopropanediesters, we have explored the reactivity and utilization of hemimalonate cyclopropanes. To this end, we have developed two unique methods exploring the self-activating nature of these cyclopropanes under catalyst free conditions. Cyclopropane hemimalonates, when treated with sodium azide, undergo a tandem ring-opening decarboxylation to produce?-azidobutyric acids in good yields. These adducts were hydrogenated to form?-aminobutyric acid (GABA) methyl esters. Additionally, cyclopropane hemimalonates have led to the facile synthesis of?-substituted butanolides. Under microwave irradiation, cyclopropane hemimalonates undergo rapid conversion to butanolides in the presence of inorganic salts with an unprecedented retention of stereochemistry. This unique process, in conjunction with a newly developed crossmetathesis method, has been applied to the total synthesis of the naturally occurring, (R)- dodecan-4-olide. Finally, recent efforts to develop a unified approach to piperidine-containing indole natural products have shown great promise. A preliminary investigation into the prospect of a common synthetic intermediate for the synthesis of a variety of indole alkaloids has led to a synthesis of substituted piperidinones and the corresponding piperidines. These common natural product cores are accessed via a reductive amination/lactamization sequence of dimethyl 3-ethyl-3-formylpimelate. The synthetic utility of this initial study has been displayed in the formal synthesis of (+/- )-quebrachamine.
Author: Oleg G. Kulinkovich
Publisher: John Wiley & Sons
ISBN: 1118978404
Category : Science
Languages : en
Pages : 431
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Book Description
This is a practical guidebook about cyclopropanes that thoroughly surveys derivatives and transformations, synthetic methods, and experimental efficiency as a gateway for further research and development in the field. • Provides comprehensive lists and synthetically-oriented synopses of cyclopropane chemistry review references along with publication data on applications in the syntheses of natural and related biologically active compounds • Acts as a resource to help readers better understand cyclopropane applications for the efficient realization of synthetically important organic transformations and popular experimental procedures • Includes new developments and up-to-date information that will lead to original methodologies for complex organic synthesis • Stresses universality, flexibility, and experimental efficiency of a strategy based on preparing cyclopropane derivatives and performing ring cleavage reactions with inexpensive reagents • Focuses on the synthetic potential of cyclopropane applications, for example the synthesis of natural compounds and other target-oriented syntheses via cyclopropane intermediaries, as well on their planning by retrosynthetic analysis
Author: Takahiko Akiyama
Publisher: John Wiley & Sons
ISBN: 1119736412
Category : Science
Languages : en
Pages : 798
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Book Description
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.
Author: Florencio Zaragoza Dörwald
Publisher: John Wiley & Sons
ISBN: 3527604987
Category : Science
Languages : en
Pages : 389
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Book Description
Most syntheses in the chemical research laboratory fail and usually require several attempts before proceeding satisfactorily. Failed syntheses are not only discouraging and frustrating, but also cost a lot of time and money. Many failures may, however, be avoided by understanding the structure-reactivity relationship of organic compounds. This textbook highlights the competing processes and limitations of the most important reactions used in organic synthesis. By allowing chemists to quickly recognize potential problems this book will help to improve their efficiency and success-rate. A must for every graduate student but also for every chemist in industry and academia. Contents: 1 Organic Synthesis: General Remarks 2 Stereoelectronic Effects and Reactivity 3 The Stability of Organic Compounds 4 Aliphatic Nucleophilic Substitutions: Problematic Electrophiles 5 The Alkylation of Carbanions 6 The Alkylation of Heteroatoms 7 The Acylation of Heteroatoms 8 Palladium-Catalyzed C-C Bond Formation 9 Cyclizations 10 Monofunctionalization of Symmetric Difunctional Substrates
Author: Ernesto Fattorusso
Publisher: John Wiley & Sons
ISBN: 3527621083
Category : Science
Languages : en
Pages : 689
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Book Description
This book presents all important aspects of modern alkaloid chemistry, making it the only work of its kind to offer up-to-date and comprehensive coverage. While the first part concentrates on the structure and biology of bioactive alkaloids, the second one analyzes new trends in alkaloid isolation and structure elucidation, as well as in alkaloid synthesis and biosynthesis. A must for biochemists, organic, natural products, and medicinal chemists, as well as pharmacologists, pharmaceutists, and those working in the pharmaceutical industry.
Author: Ronald Michael Painter
Publisher: Stanford University
ISBN:
Category :
Languages : en
Pages : 110
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Book Description
The chemoselective oxidation of vicinal diols to α-hydroxyketones is a challenge in organic syntheses because not only does the diol need to be oxidized selectively to a monocarbonyl compound, but diols are also prone to overoxidation and oxidative cleavage. Employing a cationic palladium complex, [(neocuproine)Pd(OAc)]2(OTf)2, we were able to demonstrate the selective oxidation of glycerol to dihydroxyacetone mediated by either benzoquinone or O2 as the terminal oxidant, an accomplishment that has little precedent in homogeneous catalysis. Mechanistic studies were undertaken to uncover the nature of this remarkable chemoselectivity. Kinetic and deuterium-labeling studies implicate reversible β-hydride elimination from isomeric Pd alkoxides and turnover-limiting displacement of the dihydroxyacetone product by benzoquinone. We successfully extended this methodology to other terminal 1,2-diols and symmetric vicinal 1,2-diols and have carried out aerobic oxidation of these substrates catalyzed by 1. Examination of the reactivity of 1 with conformationally-restricted 1,2-cyclohexanediols suggests that the diol must chelate to the Pd center for effective oxidation to the hydroxyketone product. In a separate project, we have also investigated the electrocatalytic reduction of dioxygen by several dinuclear copper complexes, an important reaction for fuel cell applications.
