Download or read book Diastereoselective Synthesis of Seven membered Ring Trans alkenes and Development of Stereospecific Nickel catalyzed Cross coupling Reactions written by Margaret A. Greene and published by . This book was released on 2013 with total page 297 pages. Available in PDF, EPUB and Kindle. Book excerpt: The understanding of the reactivity of strained silacyclopropanes has been expanded to include the reactivity of vinylsilacyclopropanes, formed by silylene transfer to a 1,3-diene. The reactivity of vinylsilacyclopropane with carbonyl compounds has been explored and is shown to yield trans-oxasilacycloheptenes. Trans-Oxasilacycloheptenes are formed stereoselectively as a result of carbonyl insertion through allylic transposition. Trans-Oxasilacycloheptene is a highly strained compound that exhibits elevated reactivity. Trans-Oxasilacycloheptene rearranges at room temperature to vinyloxasilacyclopentane by a 1,3-silyl migration. Trans-Oxasilacycloheptene has been trapped by a variety of methods. Adapting conditions established in the Jarvo laboratory for stereospecific nickel-catalyzed cross-coupling of naphthylic ethers with methyl Grignard reagent, work is presented which expands the scope of these reactions to include benzylic ethers. A traceless directing group is employed to facilitate the coupling of this challenging class of substrates. This method is shown to increase the reactivity of benzylic ethers, which is proposed to occur by magnesium salt coordination to the directing group. The reaction proceeds with excellent transfer of stereochemical information. The mechanism of nickel-catalyzed Kumada cross-coupling of naphthylic ethers with methyl Grignard reagent has been studied. The reaction is first order in electrophile, catalyst, and magnesium iodide. The rate of the reaction shows no dependence on methyl magnesium iodide. Competition experiments demonstrate the importance of the traceless directing group for the coupling of benzylic ethers. A method has been developed for the stereospecific nickel-catalyzed cross-coupling of naphthylic carbamates with aryl boronic esters. Products with retention or inversion can be formed from the same enantiomer of starting material with proper choice of an achiral catalyst. Phosphine ligand provides product with retention and N-heterocyclic carbene ligand provides products with inversion at the electrophilic carbon.
Download or read book Stereoselective Alkene Synthesis written by Jianbo Wang and published by Springer. This book was released on 2012-08-13 with total page 283 pages. Available in PDF, EPUB and Kindle. Book excerpt: Stereoselective Synthesis of Tetrasubstituted Alkenes via Torquoselectivity-Controlled Olefination of Carbonyl Compounds with Ynolates, by Mitsuru Shindo and Kenji Matsumoto.- Stereoselective Synthesis of Z-Alkenes, by Woon-Yew Siau, Yao Zhang and Yu Zhao.- Stereoselective Synthesis of Mono-fluoroalkenes, by Shoji Hara.- Recent Advances in Stereoselective Synthesis of 1,3-Dienes, by Michael De Paolis, Isabelle Chataigner and Jacques Maddaluno.- Selective Olefination of Carbonyl Compounds via Metal-Catalyzed Carbene Transfer from Diazo Reagents, by Yang Hu and X. Peter Zhang.- Selective Alkene Metathesis in the Total Synthesis of Complex Natural Product, by Xiaoguang Lei and Houhua Li.- Olefination Reactions of Phosphorus-Stabilized Carbon Nucleophiles, by Yonghong Gu and Shi-Kai Tian.- Alkene Synthesis Through Transition Metal-Catalyzed Cross-Coupling of N-Tosylhydrazones, by Yan Zhang and Jianbo Wang.
Download or read book Development of Stereospecific Nickel Catalyzed Cross Coupling Reactions written by Emily Jean Tollefson and published by . This book was released on 2016 with total page 575 pages. Available in PDF, EPUB and Kindle. Book excerpt: The development of asymmetric transition-metal-catalyzed reactions has emerged as an important area of research in the past decade. Advances in the field are transforming the way chemists approach the construction of target compounds. This dissertation focuses on the expansion of stereospecific nickel-catalyzed reactions to synthesize small unnatural polyketide analogs, chiral long chain carboxylic acids, and highly substituted cyclopropanes. In the presence of an achiral nickel catalyst, a bidentate phosphine ligand, and a Grignard reagent, aryl-substituted tetrahydropyrans and tetrahydrofurans undergo a stereospecific ring-opening to afford acyclic polyketide analogs with complex stereoarrays and promising anti-cancer activity. Reactions proceed with inversion of stereochemistry at the benzylic position and are substrate controlled. Similarly, enantioenriched aryl-substituted lactones undergo a Negishi-type cross-coupling with dimethylzinc to afford enantioenriched carboxylic acids. The utility of this reaction was demonstrated in a two-step synthesis of an anti-dyslipidemia agent.The nickel catalyst system was employed to develop the first stereospecific reductive cross-coupling reaction. 2-Aryl-4-chlorotetrahydropyrans undergo an intramolecular ring contraction to afford highly substituted cyclopropanes. The reactions proceed with retention at the benzylic center and inversion at the alkyl halide position. Vinyl-substituted tetrahydropyrans are also amenable substrates for this transformation and afford vinylcyclopropane products with excellent control of stereochemistry. This is the first reported reductive coupling between alkyl ethers and alkyl halides and provides a new, mild synthetic route to both aryl- and vinyl-substituted cyclopropanes.
Download or read book Development of Nickel catalyzed Stereospecific Cross coupling Reactions written by Buck L. H. Taylor and published by . This book was released on 2012 with total page 171 pages. Available in PDF, EPUB and Kindle. Book excerpt: Transition-metal catalyzed cross-coupling reactions are powerful methods for the synthesis of natural products and medicinal compounds. Cross-coupling reactions of secondary alkyl electrophiles are currently more challenging than those of aryl or vinyl halides, but these reactions enable the construction of tertiary stereogenic centers with control of configuration. Several methods have been reported for the stereoconvergent cross-coupling of alkyl halides using chiral nickel catalysts. Herein, we report the development of a stereospecific cross-coupling reaction of enantioenriched benzylic ethers using achiral nickel catalysts. We initially performed mechanistic studies to determine the stereochemical course of established nickel-catalyzed cross-coupling reactions. A deuterium-labeled alkylborane reagent was used to establish that transmetalation from boron to nickel occurs with retention of configuration. In addition, these studies establish that alkylnickel intermediates are stereochemically stable under these cross-coupling conditions. A stereospecific cross-coupling reaction of benzylic ethers with alkyl Grignard reagents has been developed. Enantioenriched benzylic ethers, derivatives of easily synthesized chiral secondary alcohols, undergo cross-coupling with high enantiospecificity using an achiral nickel catalyst. The method was applied to the asymmetric synthesis of a biologically active diarylethane, a common structural motif in medicinally relevant compounds. Initial mechanistic studies are consistent with a rate-limiting oxidative addition that is facilitated by a magnesium Lewis-acid. The cross-coupling method has been extended to include aryl Grignard reagents for the asymmetric synthesis of triarylmethanes. The reaction proceeds in high enantiospecificity and employs an ether leaving group capable of chelating to magnesium ions. The method was applied to the asymmetric synthesis of an anti-breast-cancer agent.
Download or read book Development of Stereospecific Nickel catalyzed Transformations of Benzylic Alcohol Derivatives written by Michael R. Harris and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Transition metal catalyzed reactions are indispensable tools for the asymmetric construction of carbon–carbon bonds. Traditionally, cross-coupling reactions have relied on the use of aryl, vinyl or 1° alkyl electrophiles. Advances in asymmetric catalysis have permitted the use of 2° alkyl electrophiles in cross-coupling reactions allowing for the development of several stereoconvergent transformations. Herein, we report a complementary approach to asymmetric cross-coupling reactions by means of the development of stereospecific, nickel-catalyzed transformations of benzylic alcohol derivatives. Our initial efforts were directed toward expanding upon a Kumada cross-coupling reaction of secondary benzylic ethers with methylmagnesium iodide previously reported by the Jarvo laboratory. We extended the scope of this reaction by developing conditions to enable the use of aryl Grignard reagents for the construction of enantioenriched triarylmethanes by stereospecific nickel-catalyzed cross-coupling of diaryl methanol derivatives. The reaction proceeds in high enantiospecificity and overall inversion. This methodology is used to prepare a single enantiomer of an anti-breast-cancer agent. Further advances in our cross-coupling methodology are demonstrated in the development of a stereospecific Suzuki–Miyaura coupling of benzylic carbamates and pivolates with aryl- and heteroarylboronic esters. The reaction proceeds with selective inversion or retention at the electrophilic carbon depending on the nature of the ligand. Tricyclohexylphosphine ligand provides product with retention, while an NHC ligand provides product with inversion. The reaction proceeds in high enantiospecificity to afford either enantiomer of a variety of triarylmethanes.Taking advantage of our growing expertise in nickel catalyzed reactions of secondary alkyl electrophiles, we designed the first alkyl Heck reaction with control of stereochemistry at the electrophilic carbon. Enantioenriched methylenecyclopentanes are synthesized by stereospecific, nickel-catalyzed Heck cyclizations of secondary benzylic ethers. The reaction proceeds in high yield and enantiospecificity for benzylic ethers of both [pi]-extended and simple arenes. Ethers with pendant 1,2-disubstituted olefins form trisubstituted olefins with control of both absolute configuration and alkene geometry. The diastereoselective synthesis of a polycyclic furan is demonstrated. In the final chapter of this work, we demonstrate a nickel-catalyzed generation of secondary benzylzinc reagents from 2-pyridyl carbinols that are phosphorylated in situ. A variety of benzylzinc reagents are formed in high yield, allowing for facile hydrogenolysis of 2-pyridyl carbinols. The utility of this transformation is highlighted in a high-yielding intramolecular addition of a secondary benzylzinc reagent to an [alpha],[beta]-unsaturated ester.
Download or read book Diastereoselective Nickel catalyzed Reductive Coupling of Alkynes and Aldehydes and Application Towards the B type Amphidinolides written by Chudi O. Ndubaku and published by . This book was released on 2006 with total page 482 pages. Available in PDF, EPUB and Kindle. Book excerpt: The application of recently developed stereoselective nickel-catalyzed reductive coupling reactions of alkynes and aldehydes to the synthesis of complex natural product targets was explored. The "B-Type" amphidinolides were selected as ideal targets owing to their molecular complexity and the paucity of synthetically viable means for their total construction. The diastereoselective nickel-catalyzed reductive coupling of simple aryl-substituted alkynes and a-oxyaldehydes was developed and applied to the construction of the C15-C26 region of amphidinolide H3. ... Alternatively, the nickel-catalyzed reductive coupling reaction of 1,3-enynes and aldehydes was found to be a very effective way of installing the congested 1,3-diene moiety common to all members of this class of natural products. This methodology was further examined as a fragment coupling strategy for the syntheses of amphidinolides G3 and H4. This allowed for a highly convergent and functional group tolerant assembly of these ... molecules and, to date, stands as the most complicated setting for the application of the catalytic reductive coupling reaction.
Download or read book Stereoselective Synthesis of Seven membered Rings Using Intramolecular 4 3 Cycloaddition Reactions written by Rawshan Ara Ripa and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Heterocyclic molecules containing seven-membered rings have importance in organic synthesis owing to their presence in some natural products and biologically active molecules. Furthermore, these scaffolds act as important tools for developing new drugs and biological probes. A stereoselective, intramolecular (4+3) cycloaddition of an oxidopyridinium ion has been developed. N-Alkylation of a nicotinate derivative followed by reaction under basic condition in acetonitrile afforded (4+3) cycloaddition products in excellent yield and high stereoselectivity. Substitution at the 3, 2-TMS, and 1, 3 positions of the diene resulted in 100 [percent] stereoselectivity.
Download or read book Development of Nickel Catalyzed Coupling Reactions written by Mikhail Olegovich Konev and published by . This book was released on 2017 with total page 503 pages. Available in PDF, EPUB and Kindle. Book excerpt: Transition metal catalyzed reactions are ubiquitous in the realm of synthetic chemistry, allowing for the strategic construction of complex molecular frameworks of pharmaceuticals, natural products, and synthetic materials. Palladium-catalyzed cross-coupling reactions are part of the foundation of these transformations, insofar as they were recognized with the 2010 Nobel Prize in chemistry. Traditionally, these reactions have relied on aryl and vinyl electrophiles, whereas the alkyl counterparts have only recently begun to emerge in the literature. Nickel has been on the forefront of enantioconvergent alkyl cross--coupling reactions due to its propensity to undergo single electron chemistry. However, under special conditions, it has a unique ability to break strong carbon--oxygen bonds in a stereospecific manner, making research into its reactivity a valuable endeavor to the field of organometallic chemistry.Chapter 1 describes the development of a stereospecific intramolecular alkyl-Heck cyclization of benzylic ethers. The reaction proceeds with inversion at the electrophilic carbon, for the synthesis of methylenecyclopentanes of both extended pi-electron and simple aromatic systems. The enantioenriched products can be effectively derivatized to cyclic alpha-aryl ketones in good yields with good transfer of chirality. Avenues to expand the utility of this reaction have been identified and further studies are ongoing.Chapter 2 discusses the development of nickel-catalyzed cross-electrophile coupling reactions of benzylic esters and aryl halides. An intermolecular reaction proceeds in high yields for primary benzylic esters for the synthesis of pharmacologically relevant diarylmethanes. The corresponding intramolecular cyclization proceeds under mild conditions, demonstrating the first example of a stereospecific cross-electrophile coupling of secondary benzylic esters. A variety of heterocyclic and functionalized substrates are tolerated under the reaction conditions.Chapter 3 examines the development a regio- and stereoselective nickel-catalyzed hydroarylation of alkynes with arylboronic acids. The reaction is facilitated by propargyl carbamates as directing groups. The reaction is tolerant of a range of functional groups and heterocycles. Mechanistic studies reveal that the acidic protons of the arylboronic acid coupling partner serve as the origin of hydrogen. Furthermore, the synthesis of tamoxifen can be completed in two steps from a simple hydroarylation product.
Download or read book Modern Organonickel Chemistry written by Yoshinao Tamaru and published by John Wiley & Sons. This book was released on 2006-03-06 with total page 346 pages. Available in PDF, EPUB and Kindle. Book excerpt: Organonickel chemistry plays an increasingly important role in organic chemistry, and interest in this topic is now just as keen as in organopalladium chemistry. While there are numerous, very successful books on the latter, a book specializing in organonickel chemistry is long overdue. Edited by one of the leading experts in the field, this volume covers the many discoveries made over the past 30 years, and previously scattered throughout the literature. Active researchers working at the forefront of organonickel chemistry provide a comprehensive review of the topic, including cross-coupling reactions, asymmetric synthesis and heterogeneous catalysis reaction types. A must-have for both organometallic chemists and synthetic organic chemists.
Download or read book Science of Synthesis Stereoselective Synthesis Vol 3 written by P. Andrew Evans and published by Thieme. This book was released on 2014-05-14 with total page 1172 pages. Available in PDF, EPUB and Kindle. Book excerpt: The major emphasis here is on enantioselective reactions using asymmetric catalysts. Examples from the total synthesis of various natural and unnatural targets validates the utility of the synthetic methods. Specific topics discussed: cycloaddition, cycloisomerization and sigmatropic rearrangement reactions, allylic and carbonyl functionalization reactions, metal-catalyzed cross-coupling reactions, desymmetrization, fluorination, polymerization and sulfide oxidation reactions. This volume is part of a 3-volume set: Science of Synthesis Stereoselective Synthesis Workbench Edition Further information about Stereoselective Synthesis (including sample pages and the table of contents)
Download or read book Enantioselective Nickel catalysed Transformations written by Hélène Pellissier and published by Royal Society of Chemistry. This book was released on 2016 with total page 404 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presenting the impressive range of uses that have been found for nickel chiral catalysts, for researchers and industrialists in organic chemistry, synthesis and medicinal chemistry.
Download or read book Classics in Stereoselective Synthesis written by Erick M. Carreira and published by John Wiley & Sons. This book was released on 2009-02-09 with total page 664 pages. Available in PDF, EPUB and Kindle. Book excerpt: Die wichtigsten und nützlichsten Methoden der modernen stereoselektiven Synthese sind in diesem Band zusammengefasst. Viele anschauliche Beispiele für die Darstellung von Wirkstoffen und Naturstoffen regen zur gezielten Abwandlung und Integration in eigene Synthesewege an. Dabei geht es den Autoren weniger darum, das Gebiet in seiner Gesamtheit darzustellen; vielmehr versuchen sie, die wirklich grundlegenden Ansätze auszuwählen, die jeder organische Synthesechemiker kennen und anwenden sollte.
Download or read book Stereoselective Synthesis written by Mihály Nógrádi and published by John Wiley & Sons. This book was released on 1994-12-05 with total page 407 pages. Available in PDF, EPUB and Kindle. Book excerpt: The state-of-the-art in stereoselective synthesis! Thoroughly revised and updated, this enlarged second edition offers a plethora of valuable information on methods and reagents in stereoselective synthesis. Methods have been selected for high efficiency and selectivity; mechanistic aspects are treated succinctly, with a strong emphasis on practical applications. For this new edition, material has been added on * homogeneous diastereoselective hydrogenations * enantioselective oxidations * novel, efficient chiral auxiliaries Much of the information given is presented in figures and tables, which makes the book a valuable reference work for the practically minded organic chemist. From reviews of the first edition: 'The extensive material in the volume should prove particularly useful to anyone involved in synthetic chemistry or teaching a course in organic chemistry.' Journal of Medicinal Chemistry 'With nearly 1400 references cited, the book contains a wealth of information and should be a useful addition to the chemist's library.' The American Scientist
Download or read book Stereospecific Nickel catalyzed Cross couplings of Amine and Alcohol Derived Substrates written by Kelsey M. Cobb and published by . This book was released on 2017 with total page 615 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation focuses on nickel-catalyzed cross-couplings of amine and alcohol derivatives to set stereogenic centers. Chapter 1 focuses on the cross-coupling of benzylic ammonium triflates with aryl, heteroaryl, and vinyl boronic acids. This method expands the scope of previous methods from our group, utilizing Ni(cod)2 without any additional phosphine or N-heterocyclic carbene (NHC) ligands. This reaction allows for cross-coupling of both naphthyl and phenyl substituted ammonium salts. The mild conditions of this reaction displays excellent functional group tolerance. ☐ Chapter 2 focuses on the cross-coupling of benzylic ammonium triflates with bis(pinacolato)diboron to afford secondary benzylic boronates with excellent chirality transfer, This reaction utilizes Ni(cod)2 as a catalyst with either phosphine or NHC ligands. The reaction proceeds with mild reaction conditions and excellent functional group tolerance. It allows for the cross-coupling of both naphthyl and phenyl substituted ammonium salts. This is the first example of a Miyaura borylation of a non-allylic electrophile to deliver products in highly enantioenriched form. ☐ Chapter 3 describes the development of the cross-coupling of tertiary benzylic acetates to form all-carbon quaternary stereocenters. This reaction prioritizes the use of an air-stable nickel(II) catalyst and environmentally friendly 2-Me-THF. The mild reaction conditions allow for excellent functional group tolerance. The reaction provides an efficient route to both di-aryl and tri-aryl quaternary stereocenters in high stereochemical fidelity. This method shows an expansion in transition metal catalysis to go beyond electrophiles adjacent to functional groups such as carbonyls and alkenes, and displays the possibility for tertiary benzylic electrophiles to under go transition metal catalysis. ☐ Chapter 4 focuses on the cross-coupling of enantioenriched allylic pivalates with aryl and heteroaryl borxines to form allylic, all-carbon quaternary stereocenters. This utilizes an air-stable nickel (II) catalyst, and functional group tolerant boroxine coupling partners to afford these quaternary stereocenters with high stereochemical fidelity. This reaction provides a powerful way to readily access allylic quaternary stereocenters with substituted internal alkenes and a variety of functional groups and heteroatoms in high yield and enantioenrichment
Download or read book Applied Cross Coupling Reactions written by Yasushi Nishihara and published by Springer Science & Business Media. This book was released on 2012-12-14 with total page 247 pages. Available in PDF, EPUB and Kindle. Book excerpt: “Applied Cross-Coupling Reactions” provides students and teachers of advanced organic chemistry with an overview of the history, mechanisms and applications of cross-coupling reactions. Since the discovery of the transition-metal-catalyzed cross-coupling reactions in 1972, numerous synthetic uses and industrial applications have been developed. The mechanistic studies of the cross-coupling reactions have disclosed that three fundamental reactions: oxidative addition, transmetalation, and reductive elimination, are involved in a catalytic cycle. Cross-coupling reactions have allowed us to produce a variety of compounds for industrial purposes, such as natural products, pharmaceuticals, liquid crystals and conjugate polymers for use in electronic devices. Indeed, the Nobel Prize for Chemistry in 2010 was awarded for work on cross-coupling reactions. In this book, the recent trends in cross-coupling reactions are also introduced from the point of view of synthesis design and catalytic activities of transition-metal catalysts.
Download or read book Stereoselective Heterocycle Synthesis via Alkene Difunctionalization written by David A. Petrone and published by Springer. This book was released on 2019-01-05 with total page 365 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book investigates the use of palladium modified by bulky ligands as catalysts for new chemical transformations that rapidly assemble several classes of complex heterocyles. It documents the development of new chemical reactions involving carbon–carbon (C‒C) and carbon–halogen (C‒X) bond formation in the context of alkene difunctionalization and dearomatization reactions. Due to the ubiquity of heterocycles in bioactive natural products and life-improving pharmaceutical treatments, a long-term goal for synthetic organic chemists has been to develop novel and creative heterocycle syntheses that illicit a high degree of product diversity and are characterized by mild reaction conditions and limited waste production. A considerable fraction of leading pharmaceutical drugs contain at least one heterocycle within their chemical structure, and their prevalence in these technologies is strong evidence that the fundamental curiosities of organic chemistry lead to real-world solutions for the health and wellness of the global population.
Download or read book Catalysis with Earth abundant Elements written by Uwe Schneider and published by Royal Society of Chemistry. This book was released on 2020-10-30 with total page 431 pages. Available in PDF, EPUB and Kindle. Book excerpt: Considering the limited resources of our planet, earth-abundant elements will have to be explored increasingly in the future. This book highlights the uses of the most earth-abundant elements in catalysis and will be of interest to graduates, academic researchers and practitioners in catalysis.
