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Author: Gang Greg Chen
Publisher:
ISBN: 9780494393925
Category :
Languages : en
Pages : 514
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Book Description
This thesis contains three parts of research, all of which are focused on utilizing aziridines as the intermediates to synthesize valuable building blocks or bioactive structures. The aziridine functionality, a three-membered ring structure containing a nitrogen atom, is widely used in synthesis for chemical bond elaborations and functional group transformations. The most important synthetic application of aziridines is their ring opening reactions which take advantage of strain in the three-membered ring. Other special properties such as oxidative stability or weak basicity have seldom been considered as the rationale for synthetic methodology development or utilized in synthetic route design. In the first part of this thesis, the oxidative stability of aziridines was utilized to carry out a sequence of cyclization and aziridine-opening transformations. The process provides straightforward synthetic entries into a range of larger heterocyclic structures (such as five-membered ring pyrrolidine or six-membered ring piperidine) which are often found in the bioactive natural products or pharmaceuticals. This methodology is of significance in term of generating libraries of the nitrogen heterocycles. The broad scope of substrates used in this research demonstrates the potential value of this methodology. The second part of this thesis deals with an application of the above methodology towards the natural product ficellomycin. Ficellomycin is a naturally occurring antibiotic which shows in vivo antibacterial activity. Due to its rare chemical structure, no successful total synthesis has been reported. We noticed that our aziridine cyclization methodology can be applied to the synthesis of ficellomycin. In this thesis, two synthetic approaches were developed to construct the core structure of ficellomycin. The control of the relative stereochemistry provides an opportunity to synthesize the diastereomeric analogs of ficellomycin. In the third part of the thesis, synthesis of allyl amines from 2-ketoaziridines has been studied. Allyl amine structures are often found in natural products and pharmaceuticals. The hydrazinolysis of 2-ketoaziridines were found to afford allyl amines and pyrazoles. The reaction condition was optimized. The electronic and steric effects from the substituents were studied. A variety of 2-ketoaziridines were transformed into diversely substituted linear or cyclic allyl amines in good yields using this methodology.
Author: Gang Greg Chen
Publisher:
ISBN: 9780494393925
Category :
Languages : en
Pages : 514
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Book Description
This thesis contains three parts of research, all of which are focused on utilizing aziridines as the intermediates to synthesize valuable building blocks or bioactive structures. The aziridine functionality, a three-membered ring structure containing a nitrogen atom, is widely used in synthesis for chemical bond elaborations and functional group transformations. The most important synthetic application of aziridines is their ring opening reactions which take advantage of strain in the three-membered ring. Other special properties such as oxidative stability or weak basicity have seldom been considered as the rationale for synthetic methodology development or utilized in synthetic route design. In the first part of this thesis, the oxidative stability of aziridines was utilized to carry out a sequence of cyclization and aziridine-opening transformations. The process provides straightforward synthetic entries into a range of larger heterocyclic structures (such as five-membered ring pyrrolidine or six-membered ring piperidine) which are often found in the bioactive natural products or pharmaceuticals. This methodology is of significance in term of generating libraries of the nitrogen heterocycles. The broad scope of substrates used in this research demonstrates the potential value of this methodology. The second part of this thesis deals with an application of the above methodology towards the natural product ficellomycin. Ficellomycin is a naturally occurring antibiotic which shows in vivo antibacterial activity. Due to its rare chemical structure, no successful total synthesis has been reported. We noticed that our aziridine cyclization methodology can be applied to the synthesis of ficellomycin. In this thesis, two synthetic approaches were developed to construct the core structure of ficellomycin. The control of the relative stereochemistry provides an opportunity to synthesize the diastereomeric analogs of ficellomycin. In the third part of the thesis, synthesis of allyl amines from 2-ketoaziridines has been studied. Allyl amine structures are often found in natural products and pharmaceuticals. The hydrazinolysis of 2-ketoaziridines were found to afford allyl amines and pyrazoles. The reaction condition was optimized. The electronic and steric effects from the substituents were studied. A variety of 2-ketoaziridines were transformed into diversely substituted linear or cyclic allyl amines in good yields using this methodology.
Author: Nicholas A. Afagh
Publisher:
ISBN: 9780494675199
Category :
Languages : en
Pages : 0
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Book Description
N-alkenyl aziridines are a unique class of molecules that do not behave as typical enamines as a result of the inability of the nitrogen atom lone-pair of electrons to delocalize. The attenuated nucleophilicity of these enamines presents opportunities for the selective functionalization and reactivity not available to classical enamines. An operationally simple and mild copper-mediated coupling has been developed that facilitates the preparation of a broad range of N-alkenyl aziridines not available through existing methods. The preparation and reactivity of highly-functionalized N-alkenyl aziridines are reported. Also reported is the application of the chemoselective amine/aldehyde/alkyne (A3) multicomponent coupling involving amphoteric aziridine aldehydes as the aldehyde component. This coupling allows access to propargyl amines with pendent aziridine functionality.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Many biologically active molecules contain three or more contiguous heteroatom stereocenters (`triads'), but rapid installation of these motifs can be a strategic challenge when one must consider the abundance of possible patterns and stereochemical configurations. In order to accomplish the synthesis of these motifs, we have focused our efforts to develop methods that allow rapid construction of heteroatom stereotriads from allenes. This was accomplished with bicylic methylene aziridine intermediates that are synthesized by an intramolecular metal catalyzed nitrene transfer reaction on an allene. In the first portion of this dissertation, the methylene aziridine's fate will follow an `electrophile then nucleophile' approach. In chapter 2, this strategy yields N,N,X spiroaminals from intermediate diazaspiro[2.2]pentane intermediates. Chapter 3 will focus on a unique rearrangement of these spiroaminals to yield N,O,N stereotriads. Chapter 4 will center on the synthesis of O,O,N stereotriads via dihydroxylation of the methylene aziridine. In our efforts to synthesize methylene aziridines, we found it increasingly difficult to control the outcome of nitrene transfer reactions. In the second portion of this thesis, Chapter 6, 7, and 8 will detail our efforts to control the selectivity of amination. Chapter 6 examines a method to control for C-H aminated allenes through substrate dependence by Rh catalyzed C-H amination of propargyl C-H bonds which can then be transformed into the desired allene. Chapter 7 will introduce a Ag nitrene transfer catalyst system that is capable of selective allene aziridination. The work in Chapter 8 then evolves this system by demonstrating that this Ag catalyst can be modified by adjustments in ligand stoichiometry. This simple alteration to the system reveals a catalyst that is capable of favoring the C-H insertion products over aziridine products. The consequence of these results gave rise to we now refer to as "dynamic catalysis". The last chapter of this thesis will delve into our attempts to synthesize the natural product jogyamycin with our allene fuctionalization protocols. These attempts demonstrate that our allene functionalization methods are viable for generating rapid and densely functionalized aminocyclopentitols, which will provide useful synthetically diversified variants of the jogyamycin core for biological evaluation.
Author: Andrei K. Yudin
Publisher: John Wiley & Sons
ISBN: 9783527312139
Category : Science
Languages : en
Pages : 532
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Book Description
Aziridines and epoxides are among the most widely used intermediates in organic synthesis, acting as precursors to complex molecules due to the strains incorporated in their skeletons. Besides their importance as reactive intermediates, many biologically active compounds also contain these three-membered rings. Filling a gap in the literature, this clearly structured book presents the much needed information in a compact and concise way. The renowned editor has succeeded in gathering together excellent authors to cover synthesis, applications, and the biological aspects in equal depth. Divided roughly equally between aziridines and epoxides, the twelve chapters discuss: * Synthesis of aziridines * Nucleophilic ring-opening of aziridines and epoxides * Organic synthesis with aziridine building blocks * Vinyl aziridines in organic synthesis * Diastereoselective aziridination reagents * Synthetic aspects of aziridinomitocene chemistry * Biosynthesis of biologically important aziridines * Organic catalysis of epoxide and aziridine ring formation * Metal-mediated synthesis of epoxides * Asymmetric epoxide ring opening chemistry * Epoxides in complex molecule synthesis * Biological activity of epoxide-containing molecules A high-quality reference manual for academic and industrial chemists alike.
Author: Iain David Glean Watson
Publisher:
ISBN: 9780494217894
Category :
Languages : en
Pages : 334
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Book Description
The reactivity of the synthesized non-activated aziridines was examined. Non-activated aziridines were found to be reactive to a number of different nucleophiles. In particular, the ring opening reactions of non-activated aziridines with amine nucleophiles was efficiently catalyzed by tris-(pentafluorophenyl)borane leading to derivatives of trans-1,2-diamines in high yields. A mechanistic investigation of the reaction suggests that in situ formed [(C 6F5)3B(OH2)]·H2O catalyses the opening through a Brensted acid manifold. Conversion of allyl aziridines into alpha-aziridino aldehydes creates reactive intermediates that react with nucleophiles without destruction of the aziridine ring. The conversion from allyl aziridines takes advantage of the high enantioselectivities and unique regioselectivities achieved by the palladium catalyzed process. Finally, the application of non-activated aziridines towards the synthesis of a number of radiolabelled beta-adrenergic agonists and antagonists was undertaken, providing a concrete example of the usefulness of aziridines as reactive intermediates in organic synthesis.*Investigations into the synthesis and reactivity of non-activated aziridines were undertaken. 1 New synthetic methodologies for the synthesis of non-activated aziridines were developed by the N-functionalization of NH-aziridines. In particular, the palladium-catalyzed allylic amination of N-unsubstituted aziridines has been carried out. The use of NH aziridines as nucleophiles favors formation of branched products in the case of aliphatic allyl acetates. The regioselectivity of this reaction is opposite to that observed when other amines are used as nucleophiles. These studies provide evidence for the palladium-catalyzed isomerization of the branched (kinetic) product formed with common secondary amines into the thermodynamic (linear) product. On the contrary, the branched allyl products obtained from N-unsubstituted aziridines do not undergo the isomerization process. The methodology addresses the important issue of forming quaternary carbon centers next to nitrogen. The new insights into the mechanism of palladium-catalyzed allylic amination obtained will facilitate the synthesis of complex heterocycles and the design of new ligands to control branched/linear ratio as well as absolute stereochemistry of allyl amines. 1 (a) Watson, I.D.G.; Yu, L.; Yudin, A.K. Advances in nitrogen transfer reactions involving aziridines. Acc. Chem. Res. 2006, 39, 194-206. (b) Watson, I.D.G.; Yudin, A.K. New insights into the mechanism of palladium-catalyzed allylic amination. J. Am. Chem. Soc. 2005, 127, 17516 - 17529. (c) Watson, I.D.G.; Styler, S.A.; Yudin, A.K. Unusual selectivity of unprotected aziridines in palladium-catalyzed allylic amination enables facile preparation of branched aziridines. J. Am. Chem. Soc. 2004, 126, 5086-5087. (d) Watson, I.D.G.; Yudin, A.K. Ring-opening reactions of nonactivated aziridines catalyzed by tris(pentafluorophenyl)borane. J. Org. Chem. 2003, 68, 5160-5167. (e) Watson, I.D.G.; Yudin, A.K. Selective functionalization of small organic molecules using electrophilic nitrogen sources. Curr. Opin. Drug Discovery Dev. 2002, 5, 906-917. *Please refer to dissertation for diagrams.
Author: Peter Metz
Publisher: Springer
ISBN: 3540447261
Category : Science
Languages : en
Pages : 210
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Book Description
Keeping up with the advances in modern heterocyclic chemistry is essential for many of our colleagues in academia and industry. It is the aim of this series on "Stereoselective Heterocyclic Synthesis" to assist the chemical community in this respect by presenting a selection of exciting recent developments. As it was for the first two volumes (1997), the stereoselective synthesis of - or with the aid of - heterocycles is the common motif for all the chapters in this third volume. I am very glad that again leading researchers in this area have contrib- ed highly stimulating accounts with up-to-date coverage. "Stereoselective Heterocyclic Synthesis 111" features chapters on "Stereoselective Intramolecular J,3-Dipolar Cycloadditions" by I.N.N. Nambothiiri and A. Hassner giving an in depth survey of the generation and synthetic application of valuable 1,3-dipoles, "4-Acetoxy- and 4-Cyano-12-dioxanes in Synthesis" by C.J. Sinz and S.D. Rychnovsky presenting a comprehensive summary of the utility of the versatile title compounds in natural products synthesis, "The Synthetic Potential of Three-Membered Ring Aza-Heterocycles" by B. Zwanenburg and l? ten Holte highlighting the fascinating chemistry of aziridine and azirine carboxylic esters, and '(Synthesis of Medium-Sized Ring Lactams" by U. Nubbemeyer discussing a wide range of modern strategies for the stereoselective preparation of these important heterocycles
Author: David S. Soriano
Publisher:
ISBN:
Category :
Languages : en
Pages : 428
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Book Description
Author: Navjeet Kaur
Publisher: Elsevier
ISBN: 0443220603
Category : Science
Languages : en
Pages : 354
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Book Description
The smallest possible saturated azaheterocycle, aziridine, is well-known to organic chemists for its tremendous potential in pharmaceutical chemistry and organic synthesis. The general biological importance of aziridines is proven by the fact that they found several uses as subunits in pharmacologically active compounds such as antitumor agents, enzyme inhibitors, and antibiotics. Although aziridines are highly reactive, this framework occurs in many synthetic compounds and the natural products of biological interest also contain aziridine skeleton in their structures. The synthetic community is captivated with prospects of selective synthesis and conversions of aziridines. Several important advances in this area have been witnessed in recent years and discovering efficient novel methods for the synthesis of aziridines has been very active field of research. Its powerful synthetic utility has been described by an overpowering amount of documentation on the approaches for the formation of aziridine. Synthesis of Aziridines and Oxaziridines from Imines describes the new and old methods for the synthesis of aziridines from imines and covers an important and rapidly growing branch of heterocyclic chemistry. Readers will have access to different methods and information allowing them to evaluate which method is most suitable for particular cases. - Focuses on the biological importance of different heterocycles - Describes traditional and innovative methods for the synthesis of aziridines from imines - Includes comparison amongst different methods, reagents, reaction conditions in tabulated forms, advantages, disadvantages, and critical analysis of different methodologies with respect to their comparison with green technique
Author: Ikuo Funaki
Publisher:
ISBN:
Category :
Languages : en
Pages : 95
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Book Description
Zsfassung in niederländ. Sprache.
Author: Kazuaki Ishihara
Publisher: John Wiley & Sons
ISBN: 3527348298
Category : Technology & Engineering
Languages : en
Pages : 452
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Book Description
Iodine Catalysis in Organic Synthesis The first book of its kind to highlight iodine as a sustainable alternative to conventional transition metal catalysis Iodine Catalysis in Organic Synthesis provides detailed coverage of recent advances in iodine chemistry and catalysis, focusing on the utilization of various iodine-containing compounds as oxidative catalysts. Featuring contributions by an international panel of leading research chemists, this authoritative volume explores the development of environmentally benign organic reactions and summarizes catalytic transformations of molecular iodine and iodine compounds such as hypervalent organoiodine and inorganic iodine salts. Readers are first introduced to the history of iodine chemistry, the conceptual background of homogeneous catalysis, and the benefits of iodine catalysis in comparison with transition metals. Next, chapters organized by reaction type examine enantioselective transformations, catalytic reactions involving iodine, catalyst states, oxidation in iodine and iodine catalyses, and catalytic reactions based on halogen bonding. Practical case studies and real-world examples of different applications in organic synthesis and industry are incorporated throughout the text. An invaluable guide for synthetic chemists in both academic and industrial laboratories, Iodine Catalysis in Organic Synthesis: Provides a thorough overview of typical iodine-catalyzed reactions, catalyst systems, structures, and reactivity Explores promising industrial applications of iodine-based reagents for organic synthesis Highlights the advantages iodine catalysis has over classical metal-catalyzed reactions Discusses sustainable and eco-friendly methods in hypervalent iodine chemistry Edited by two world authorities on the catalytic applications of organoiodine compounds, Iodine Catalysis in Organic Synthesis is required reading for catalytic, organic, and organometallic chemists, medicinal and pharmaceutical chemists, industrial chemists, and academic researchers and advanced students in relevant fields.
