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Author: Owen Scadeng
Publisher:
ISBN:
Category : Azides
Languages : en
Pages : 259
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Book Description
The five-membered carbocycle is a structural motif found in a plethora of natural products and bioactive compounds. The Nazarov reaction has emerged as an effective method to synthesize cyclopentenones and acts as a tool for adding structural complexity to molecular frameworks. This dissertation will discuss several projects involving the Nazarov cyclization and its use to build functionality to the cyclopentanoid framework. Chapter 1 provides a detailed recount of recent advances in Nazarov chemistry. Focus on methods to induce enantioselectivity, the use of alternative substrates as Nazarov reaction precursors, and the use of the Nazarov reaction in total synthesis is presented. Chapter 2 describes the formation of bridged bicyclic compounds via a [3+3]-cycloaddition between organoazides and the Nazarov intermediate. These cycloadducts were also found to thermally decompose to produce ring-enlarged dihydropyridones and 6-methylenepiperidinones. In Chapter 3, details the attempted development of a domino Nazarov cyclization/Baeyer-Villiger oxidation are provided. While the desired 3,4-dihydropyra-2-one was formed with the use of bis(trimethylsilyl)peroxide as the oxidant, optimization of the transformation failed to produce synthetically useful yields. Chapter 4 divulges the findings of Nazarov cyclizations of 2-hydroxyalkyl-1,4-diene-3-ones. Originally proposed as substrates that could undergo domino Nazarov cyclization/semipinacol rearrangements, these compounds were found to readily produce alkylidene cyclopentenones under Lewis acid conditions. These substrates provided insight into the effect that 2-hydroxyalkyl substituents have on the charge density of the oxyallyl cation intermediate of the Nazarov reaction and subsequent alkene formation.
Author: Owen Scadeng
Publisher:
ISBN:
Category : Azides
Languages : en
Pages : 259
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Book Description
The five-membered carbocycle is a structural motif found in a plethora of natural products and bioactive compounds. The Nazarov reaction has emerged as an effective method to synthesize cyclopentenones and acts as a tool for adding structural complexity to molecular frameworks. This dissertation will discuss several projects involving the Nazarov cyclization and its use to build functionality to the cyclopentanoid framework. Chapter 1 provides a detailed recount of recent advances in Nazarov chemistry. Focus on methods to induce enantioselectivity, the use of alternative substrates as Nazarov reaction precursors, and the use of the Nazarov reaction in total synthesis is presented. Chapter 2 describes the formation of bridged bicyclic compounds via a [3+3]-cycloaddition between organoazides and the Nazarov intermediate. These cycloadducts were also found to thermally decompose to produce ring-enlarged dihydropyridones and 6-methylenepiperidinones. In Chapter 3, details the attempted development of a domino Nazarov cyclization/Baeyer-Villiger oxidation are provided. While the desired 3,4-dihydropyra-2-one was formed with the use of bis(trimethylsilyl)peroxide as the oxidant, optimization of the transformation failed to produce synthetically useful yields. Chapter 4 divulges the findings of Nazarov cyclizations of 2-hydroxyalkyl-1,4-diene-3-ones. Originally proposed as substrates that could undergo domino Nazarov cyclization/semipinacol rearrangements, these compounds were found to readily produce alkylidene cyclopentenones under Lewis acid conditions. These substrates provided insight into the effect that 2-hydroxyalkyl substituents have on the charge density of the oxyallyl cation intermediate of the Nazarov reaction and subsequent alkene formation.
Author: Georgios Alachouzos
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
"Access to biologically relevant small molecule libraries is a top priority for pharmaceutical chemists. Methods towards previously unattainable carbon frameworks to increase the structural and chiral richness of these libraries rely primarily on new ways to form carbon-carbon bonds and new ways to introduce stereochemical complexity. However, the diastereoselective installation of multiple stereogenic centers in polycyclic systems, especially quaternary all-carbon stereogenic centers (QASCs), remains an outstanding challenge. To address this challenge, outlined herein are a series of studies towards the previously unexplored interrupted halo-Nazarov cyclization. Chapter 1 establishes the existing state-of-the-art cyclization methods that install multiple QASCs from the last decade. A theoretical basis for developing new methods within this challenging scientific field is also established based on computational chemistry predictions that suggest highly favorable energetics for the unexplored halo-Nazarov reaction. Chapter 2 highlights the development of interrupted halo-Nazarov methodologies. Two interruption methods for the cyclization were successfully developed that are capable of installing one or more QASCs . A third study from Chapter 2 resulted in the discovery of an entirely different reaction that ended up not proceeding through a halo-Nazarov cyclization and instead furnishes unusual fused oxa-/azacycles. Thereafter, Chapter 3 shows the evolution of computational studies involving the disclosed halo- Nazarov methodology. Density functional theory was used as a computational method to gain deeper understanding of the halo-Nazarov thermochemistry and stereochemistry. Finally, Chapter 4 shows the efforts towards the total synthesis of natural products tubingensin A and B, indole alkaloids with interesting biological and structural properties. Significant progress towards a new total synthesis of tubingensin A that is significantly shorter than the current published route is shown. The final step of the synthesis was reached, but the study was cut short prematurely due to the COVID-19 pandemic that is transpiring at the time of writing. In summary, the development of novel synthetic methods, strongly supported by computational chemistry calculations are disclosed, as well as a direct application of these new methods towards the synthesis of a complex natural product. Future studies and research directions for each discipline are proposed in each chapter"--Pages xvii-xviii.
Author: Michael Harmata
Publisher: John Wiley & Sons
ISBN: 1118057864
Category : Science
Languages : en
Pages : 395
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Book Description
The first authoritative book on using silver cations in organic chemistry—for catalysis and more! With more sophisticated catalytic methodologies fueling a resurgence in the study of cation-based chemistry, gold and platinum have stepped to the fore as the unique agents used to create new chemical reactions. Although these metals have become a primary focus of researchers in the field, another coinage metal that is often overlooked—but is as powerful as the others—is silver, a far less costly alternative to gold and platinum in aiding the development of new reactions. Making a strong case for the use of silver as a catalyst and structural element in organometal constructs, this authoritative book is the first to explore the benefits of using silver in organic chemistry by taking a close look at silver’s unique reactivity and structural characteristics for the development of new methods and materials. Silver in Organic Chemistry is: The first book to address catalysis using silver, whose use in organic chemistry is on the verge of exploding A resource for researchers wishing to do chemistry with silver cations, an area that stands in the shadow of gold chemistry, but still glistens, demonstrating that all that glitters is not gold—sometimes it’s silver! A guide for “first attempts” in working with silver cations Edited by a very well-respected, highly visible authority in this field Silver in Organic Chemistry promotes further scientific discussion by offering important new ways to examine the future possibilities of an emerging field. By elevating the importance of silver chemistry, this thought-provoking guide illustrates how this versatile metal can become an increasingly significant player in opening the door to new catalytic organic reactions and new organometal materials.
Author: A. C. Knipe
Publisher: John Wiley & Sons
ISBN: 0470022043
Category : Science
Languages : en
Pages : 664
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Book Description
This volume is the 38th in this classical series. In every volume the content is divided in the different classes of organic reaction mechanisms: Reaction of Aldehydes and Ketones and their Derivatives Reactions of Carboxylic, Phosphoric, and Sulfonic Acids and their Derivatives Oxidation and Reduction Carbenes and Nitrenes Nucleophilic Aromatic Substitution Electrophilic Aromatic Substitution Carbocations Nucleophilic Aliphatic Substitution Carbanions and Electrophilic Aliphatic Substitution Elimination Reactions Radical Reactions Addition Reactions: Polar Addition Addition Reactions: Cycloadditions Molecular Rearrangements An experienced team of authors is compiling these reviews every year, so that the reader can rely on a continuing quality of selection and presentation. As a new service to the reader all reaction mechanisms leading to stereospecific products are highlighted. This reflects the needs of the organic synthetic community with leads to chiral reactions. Detailed author and subject indexes help the reader to find the information they are looking for.
Author: Judy Szeto
Publisher:
ISBN:
Category :
Languages : en
Pages : 189
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Book Description
General base-catalyzed double-Michael reactions of allenes with various dinucleophiles are described. The reactions are facilitated most efficiently by a catalytic amount of trimethylphosphine, affording six different types of benzannulated five-membered heterocycles: benzimidazolines, benzoxazolines, benzothiazolines, 1,3-benzodioxoles, 1,3-benzoxathioles, and 1,3-benzodithioles. This atom-economical reaction is operationally simple and provides the product heterocycles in good to excellent yields. Careful mechanistic studies unveiled the phosphine-triggered general base catalysis pathway. Furthermore, the double-Michael reaction can serve as an alternative method for the selective mono-ketalization of beta-diketones. We have employed a novel acid-mediated nitro-Nazarov reaction of conjugated nitrodienes to synthesize a variety of five-membered cyclic nitronates via a proposed nitro-allyl cation intermediate. An array of nitronates with varying alkyl and aryl substituents was isolated in good to excellent yields. To verify the existence of the nitro-allyl cation intermediate, we synthesized nitrodienes tethered to an aromatic ring in hopes of trapping the cationic nitro-Nazarov reaction intermediate by electrophilic aromatic substitution. We were pleased that tetracyclic nitronates were constructed through an interrupted nitro-Nazarov cyclization reaction, which generated two new rings and an all carbon quaternary center. A five-membered cyclic nitronate was then subjected to a [3+2] dipolar cycloaddition with acrylates to obtain highly functionalized nitroso acetals. Reduction conditions were also performed on the cyclic nitronate to obtain a dihydroisoxazole and a four-membered cyclic nitrone. Progress toward synthesizing alpha-aryl vinylboronic acids was fruitless. Transmetalation with trimethyl borate and aryl vinylaluminum intermediates did not transpire as hoped. The substrates that were successful based on thin layer chromatography (TLC) proved difficult to purify due to boronic acids being highly soluble in water. As of now, the condition in synthesizing and purifying alpha-aryl vinylboronic acids is still pending.
Author: Pierre Vogel
Publisher: John Wiley & Sons
ISBN: 3527819258
Category : Science
Languages : en
Pages : 1382
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Book Description
The know-how about reactivity, reaction mechanisms, thermodynamics and other basics in physical organic chemistry is the key for successful organic reactions. This textbook presents comprehensively this knowledge to the student and to the researcher, too. Includes Q&As.
Author: Laszlo Kurti
Publisher: Elsevier
ISBN: 0080575412
Category : Science
Languages : en
Pages : 808
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Book Description
Kurti and Czako have produced an indispensable tool for specialists and non-specialists in organic chemistry. This innovative reference work includes 250 organic reactions and their strategic use in the synthesis of complex natural and unnatural products. Reactions are thoroughly discussed in a convenient, two-page layout--using full color. Its comprehensive coverage, superb organization, quality of presentation, and wealth of references, make this a necessity for every organic chemist. - The first reference work on named reactions to present colored schemes for easier understanding - 250 frequently used named reactions are presented in a convenient two-page layout with numerous examples - An opening list of abbreviations includes both structures and chemical names - Contains more than 10,000 references grouped by seminal papers, reviews, modifications, and theoretical works - Appendices list reactions in order of discovery, group by contemporary usage, and provide additional study tools - Extensive index quickly locates information using words found in text and drawings
Author: Luc LeBlanc
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Author:
Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 682
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Book Description
Author: A. C. Knipe
Publisher: John Wiley & Sons
ISBN: 1118707869
Category : Science
Languages : en
Pages : 728
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Book Description
Organic Reaction Mechanisms 2013, the 49th annual volume in this highly successful and unique series, surveys research on organic reaction mechanisms described in the available literature dated 2013. The following classes of organic reaction mechanisms are comprehensively reviewed: Reaction of Aldehydes and Ketones and their Derivatives Reactions of Carboxylic, Phosphoric, and Sulfonic Acids and their Derivatives Oxidation and Reduction Carbenes and Nitrenes Nucleophilic Aromatic Substitution Electrophilic Aromatic Substitution Carbocations Nucleophilic Aliphatic Substitution Carbanions and Electrophilic Aliphatic Substitution Elimination Reactions Polar Addition Reactions Cycloaddition Reactions Molecular Rearrangements An experienced team of authors compile these reviews every year, so that the reader can rely on a continuing quality of selection and presentation.
