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Author: Dawei Yue Publisher: ISBN: Category : Languages : en Pages : 452
Book Description
In this dissertation the scope and limitations of several electrophilic cyclization processes have been presented. In particular, electrophilic cyclization has been used for the synthesis of a variety of heterocycles, including benzo[b]furans, isochromenes, dihydroisoquinolines, isobenzofurans and coumestans. An unusual palladium migration has also been explored and applied to the synthesis of fluoren-9-ones. Chapter 1 describes the synthesis of 2,3-disubstituted benzo[b]furans by the palladium-catalyzed coupling and electrophilic cyclization of terminal alkynes. A highly chemoselective electrophilic cyclization has been achieved by carefully choosing the protecting group on the oxygen functionality. Various electrophiles, such as I2, Br2, PhSeCl and p-O2NC6H4SCl, can be used to introduce different functionalities into the desired cyclization products. Chapter 2 presents the synthesis of heterocycles by electrophilic cyclization reactions of acetylenic aldehydes, ketones and imines. The overall synthetic process involves the coupling of a terminal acetylene with o-iodoarenecarboxaldehydes or ketones by a palladium-catalyzed coupling reaction, followed by electrophilic cyclization with various electrophiles in the presence of proper nucleophiles. Oxygen- and nitrogen-containing heterocycles can be quickly assembled by this three component process in good to excellent yields. Chaper 3 describes the synthesis of coumestan and coumestrol by selective electrophilic cyclization, followed by palladium-catalyzed intramolecular carbonylation and lactonization. The biologically interesting coumestan system can be quickly constructed by this very efficient approach from common starting materials. The palladium-catalyzed reaction effects as both carbonylation and lactonization in one step. Chapter 4 examines the scope and synthetic utility of a 1,4-Pd through space migration. The synthesis of various fluoren-9-ones has been accomplished by the Pd-catalyzed intramolecular C-H activation of imines derived from 2-iodoaniline and biarylcarboxaldehydes. This methodology makes use of a novel 1,4-palladium migration from an aryl position to an imidoyl position to generate the key imidoyl palladium intermediate, which undergoes intramolecular arylation to produce imines of complex polycyclic compounds containing the fluoren-9-one core structure. Both electronic effects and steric effects have been investigated.
Author: Dawei Yue Publisher: ISBN: Category : Languages : en Pages : 452
Book Description
In this dissertation the scope and limitations of several electrophilic cyclization processes have been presented. In particular, electrophilic cyclization has been used for the synthesis of a variety of heterocycles, including benzo[b]furans, isochromenes, dihydroisoquinolines, isobenzofurans and coumestans. An unusual palladium migration has also been explored and applied to the synthesis of fluoren-9-ones. Chapter 1 describes the synthesis of 2,3-disubstituted benzo[b]furans by the palladium-catalyzed coupling and electrophilic cyclization of terminal alkynes. A highly chemoselective electrophilic cyclization has been achieved by carefully choosing the protecting group on the oxygen functionality. Various electrophiles, such as I2, Br2, PhSeCl and p-O2NC6H4SCl, can be used to introduce different functionalities into the desired cyclization products. Chapter 2 presents the synthesis of heterocycles by electrophilic cyclization reactions of acetylenic aldehydes, ketones and imines. The overall synthetic process involves the coupling of a terminal acetylene with o-iodoarenecarboxaldehydes or ketones by a palladium-catalyzed coupling reaction, followed by electrophilic cyclization with various electrophiles in the presence of proper nucleophiles. Oxygen- and nitrogen-containing heterocycles can be quickly assembled by this three component process in good to excellent yields. Chaper 3 describes the synthesis of coumestan and coumestrol by selective electrophilic cyclization, followed by palladium-catalyzed intramolecular carbonylation and lactonization. The biologically interesting coumestan system can be quickly constructed by this very efficient approach from common starting materials. The palladium-catalyzed reaction effects as both carbonylation and lactonization in one step. Chapter 4 examines the scope and synthetic utility of a 1,4-Pd through space migration. The synthesis of various fluoren-9-ones has been accomplished by the Pd-catalyzed intramolecular C-H activation of imines derived from 2-iodoaniline and biarylcarboxaldehydes. This methodology makes use of a novel 1,4-palladium migration from an aryl position to an imidoyl position to generate the key imidoyl palladium intermediate, which undergoes intramolecular arylation to produce imines of complex polycyclic compounds containing the fluoren-9-one core structure. Both electronic effects and steric effects have been investigated.
Author: Jie Jack Li Publisher: Elsevier ISBN: 0080465846 Category : Science Languages : en Pages : 662
Book Description
Palladium chemistry, despite its immaturity, has rapidly become an indispensable tool for synthetic organic chemists. Heterocycles are of paramount importance in the pharmaceutical industry and palladium chemistry is one of the most novel and efficient ways of making heterocycles. Today, palladium-catalyzed coupling is the method of choice for the synthesis of a wide range of biaryls and heterobiaryls. The number of applications of palladium chemistry to the syntheses of heterocycles has grown exponentially. These developments highlight the need for a monograph dedicated solely to the palladium chemistry in heterocycles and this book provides a comprehensive explanation of the subject. The principal aim of the book is to highlight important palladium-mediated reactions of heterocycles with emphasis on the unique characteristics of individual heterocycles. 1. Palladium chemistry of heterocycles has its “idiosyncrasies stemming from their different structural properties from the corresponding carbocyclic aryl compounds. Even activated chloroheterocycles are sufficiently reactive to undergo Pd-catalyzed reactions. As a consequence of &agr and &bgr activation of heteroaryl halides, Pd-catalyzed chemistry may take place regioselectively at the activated positions, a phenomenon rarely seen in carbocyclic aryl halides. In addition, another salient peculiarity in palladium chemistry of heterocycles is the so-called "heteroaryl Heck reaction". For instance, while intermolecular palladium-catalyzed arylations of carbocyclic arenes are rare, palladium-catalyzed arylations of azoles and many other heterocycles readily take place. Therefore, the principal aim of this book is to highlight important palladium-mediated reactions of heterocycles with emphasis on the unique characteristics of individual heterocycles. 2. A myriad of heterocycles are biologically active and therefore of paramount importance to medicinal and agricultural chemists. Many heterocycle-containing natural products (they are highlighted in boxes throughout the text) have elicited great interest from both academic and industrial research groups. Recognizing the similarities between the palladium chemistry of arenes and heteroarenes, a critical survey of the accomplishments in heterocyclic chemistry will keep readers abreast of such a fast-growing field. We also hope this book will spur more interest and inspire ideas in such an extremely useful area. This book comprises a compilation of important preparations of heteroaryl halides, boranes and stannanes for each heterocycle. The large body of data regarding palladium-mediated polymerization of heterocycles in material chemistry is not focused here; neither is coordination chemistry involving palladium and heterocycles. Many heterocycle-containing natural products (highlighted throughout the text) have elicited great interest from both academic and industrial research groups. Recognizing the similarities between the palladium chemistry of arenes and heteroarenes, a critical survey of the accomplishments in heterocyclic chemistry keeps readers abreast of this fast-growing field. It is also hoped that this book will stimulate more interest and inspire new ideas in this exciting area. Contains the most up-to-date developments in this fast-moving field Includes 3 new chapters Incorporates material from selected well-respected authors on heterocyclic chemistry
Author: Tuanli Yao Publisher: ISBN: Category : Languages : en Pages : 342
Book Description
The electrophilic cyclization of functionally-substituted alkynes is a very promising route to an extraordinary range of medicinally interesting, functionally-substituted heterocycles and carbocycles. For instance, a variety of substituted isocoumarins and [alpha]-pyrones are readily prepared in excellent yields under very mild reaction conditions by the reaction of o-(l-alkynyl)benzoates and (Z)-2-alken-4-ynoates with IC1,I2, PhSeCl, p-O2NC6H4SCl, and HI. This methodology accommodates various alkynyl esters and has been successfully extended to the synthesis of polycyclic aromatic and biaryl compounds. Electrophilic cyclization of o-(l-alkynyl)benzamides with IC1, I2, and NBS, affords a variety of substituted isoindolin-1-ones in good to excellent yields. In a few cases, substituted isoquinolin-1-ones were obtained as the major product instead. This methodology accommodates various alkynyl amides and functional groups, and has been successfully extended to heterocyclic starting materials. This chemistry has been successfully applied to the formal synthesis of a biologically interesting alkaloid cepharanone B.A variety of substituted polycyclic aromatics are readily prepared in good to excellent yields under very mild reaction conditions by the reaction of 2-(1-alkynyl)biphenyls with IC1, I2, NBS, and p-O2NC6H4SCl. This methodology readily accommodates various functional groups and has been successfully extended to systems containing a variety of polycyclic and heterocyclic rings. The coupling of 2-(1-alkynyl)-2-alken-1-ones with nucleophiles, either catalyzed by AuCl3 or induced by an electrophile, provides highly substituted furans in good to excellent yields under very mild reaction conditions. Various nucleophiles, including functionalized alcohols, H2O, carboxylic acids, 1,3-diketones and electron-rich arenes, and a range of cyclic and acyclic 2-(1-alkynyl)-2-alken-1-ones readily participate in these cyclizations. Iodine, NIS, and PhSeCl have proven successful as electrophiles in this process. The resulting iodine-containing furans can be readily elaborated to more complex products using known organopalladium chemistry.
Author: Qinhua Huang Publisher: ISBN: Category : Languages : en Pages : 629
Book Description
The tert-butylimines of o-(1-alkynyl)benzaldehydes and analogous pyridinecarbaldehydes have been cyclized under very mild reaction conditions in the presence of I2, ICl, PhSeCl, and p-O2NC6H4SCl to give the corresponding halogen-, selenium-, and sulfur containing disubstituted isoquinolines and naphthyridines, respectively. Monosubstituted isoquinolines and naphthyridines have been synthesized by the metal-catalyzed ring closure of these same iminoalkynes. The Pd(II)-catalyzed cyclization of 2-(1-alkynyl)arylaldimines in the presence of various alkenes provides an efficient way to synthesize a variety of 4-(1-alkenyl)-3-arylisoquinolines in moderate to excellent yields. The introduction of an ortho-methoxy group on the arylaldimine promotes the Pd-catalyzed cyclization and stabilizes the resulting Pd(II) intermediate, improving the yields of the isoquinoline products. Highly substituted naphthalenes have been synthesized by the palladium-catalyzed annulation of a variety of internal alkynes, in which two new carbon-carbon bonds are formed in a single step under relatively mild reaction conditions. This method has also been used to synthesize carbazoles, although a higher reaction temperature is necessary. This method accommodates a variety of functional groups and affords the anticipated highly substituted naphthalenes and carbazoles in good to excellent yields. Novel palladium migration/arylation methodology for the synthesis of complex fused polycycles has been developed, in which one or more sequential Pd-catalyzed intramolecular migration processes involving C-H activation are employed. The chemistry works best with electron-rich aromatics, which is in agreement with the idea that these palladium-catalyzed C-H activation reactions parallel electrophilic aromatic substitution. A relatively efficient synthesis of cyclopropanes has been developed using palladium-catalyzed C-H activation chemistry, in which two new carbon-carbon bonds are formed in a single step. This method involves the palladium-catalyzed activation of relatively unreactive C-H bonds, and provides a very efficient way to synthesize cyclopropapyrrolo[1,2-a]indoles, analogues of the mitomycin antibiotics.
Author: Steve Vencil Gagnier Publisher: ISBN: Category : Languages : en Pages : 530
Book Description
In order to achieve quinoline product, this annulation process needs to proceed through a 6-endo ring closure. However, this process is in competition with the more favorable 5-exo ring closure, which leads to an isoindole system. While the yields and generality for the synthesis of quinolines are only moderate, the optimization results have proven to be interesting from a mechanistic point of view. Chapter 4 concerns the synthesis of [alpha], [beta]-unsaturated ketones from the corresponding enol silyl ethers using a catalytic palladium(II) strategy. This palladium(II) procedure is performed using catalytic amounts of Pd(OAC)2 in DMSO at room temperature and uses 02 as an efficient reoxidant.
Author: Navjeet Kaur Publisher: CRC Press ISBN: 1351242601 Category : Medical Languages : en Pages : 432
Book Description
This book is a compilation of the recent applications of palladium catalysts in organic synthesis. The book demonstrates that it is a highly dynamic research field. This methodology has emerged as a powerful tool for the efficient and chemoselective synthesis of heterocyclic molecules. In the past few years, several strategies have been pointed out to pursue more efficient, sustainable, and environment friendly chemical processes. Among those strategies, catalysis and the design of new processes that avoid the use of toxic reagents have been the focus of intense research.
Author: Guangxiu Dai Publisher: ISBN: Category : Languages : en Pages : 714
Book Description
A wide variety of 3,4-disubstituted isoquinolines containing an aryl, allylic, benzylic, alkynyl and vinylic group at the 4 position have been prepared via cross-coupling of 2-(1-alkynyl)benzaldimines with organic halides in the presence of a palladium catalyst. The best results are obtained by employing 5 mol % Pd(PPh3)4, 5 equiv of K2CO3 in DMF at 100°C. The electronic effect of the imine substrates and organic halides on the yields has been discussed. 3-Substituted 4-aroylisoquinolines have been prepared in high yields via carbonylative cross-coupling of 2-(1-alkynyl)benzaldimines with aromatic iodides or aroyl chlorides in the presence of a palladium catalyst under 1 atm of CO pressure. Imine substrates having an aryl, vinylic or alkyl substituent on the distal end of the triple bond all undergo this palladium-catalyzed carbonylative cross-coupling cyclization in high yields. The palladium(II)-catalyzed oxidative carbonylation of 2-(1-alkynyl)benzaldimines for synthesis of the corresponding isoquinoline-4-carboxylates has been studied and the optimal reaction conditions have been investigated. Although this methodology study has not provided an efficient route to synthesize methyl 3-substituted isoquinoline-4-carboxylates in synthetically useful yields, it provides an insight into the nature of the palladium-catalyzed cyclization reactions promoted by organopalladium intermediates. A novel intramolecular alkyl-to-aryl palladium rearrangement has been observed by trapping the arylpalladium intermediate with an olefin by a Heck reaction. The reaction conditions have been optimized and the reaction scope has been extensively studied. In all of the successful examples, migration products were isolated exclusively. In addition, this alkyl-to-aryl palladium migration can be controlled by simply modifying the reaction conditions.
Author: Marco Bandini Publisher: Springer ISBN: 3319351443 Category : Science Languages : en Pages : 294
Book Description
The series Topics in Heterocyclic Chemistry presents critical reviews on present and future trends in the research of heterocyclic compounds. Overall the scope is to cover topics dealing with all areas within heterocyclic chemistry, both experimental and theoretical, of interest to the general heterocyclic chemistry community. The series consists of topic related volumes edited by renowned editors with contributions of experts in the field. All chapters from Topics in Heterocyclic Chemistry are published Online First with an individual DOI. In references, Topics in Heterocyclic Chemistry is abbreviated as Top Heterocycl Chem and cited as a journal
Author: Dawei Yue
Author: Dawei Yue
Author: Saurabh Mehta
Author: Shilpa Arvind Worlikar
Author: Jie Jack Li
Author: Tuanli Yao
Author: Qinhua Huang
Author: Steve Vencil Gagnier
Author: Navjeet Kaur
Author: Guangxiu Dai
Author: Marco Bandini