Download or read book Investigation of the Scope and Mechanism of the Palladium catalyzed Synthesis of Enantioenriched Allylic Esters from Prochiral Z allylic Alcohols and Progress Toward the Total Synthesis of massadine written by Jeffrey Scott Cannon and published by . This book was released on 2012 with total page 523 pages. Available in PDF, EPUB and Kindle. Book excerpt: In Chapter 1, a review of the development and applications of enantioselective palladium(II) catalysts for the reactions of allylic imidates is provided. Planar chiral catalysts containing a metallocene unit were found to be the optimal catalysts for palladium(II)-catalyzed reactions. Cobalt oxazoline palladacycles (COP) are the most effective catalysts known for the enantioselective rearrangement of allylic imidates as well as a number of allylic displacement reactions. In Chapter 2, the scope and mechanism of the COP-catalyzed reaction of prochiral (Z)-allylic trichloroacetimidates to form enantioenriched 3-carboxy-1-alkenes is investigated. The scope of this reaction was determined to be broad, tolerating a wide variety of organic functionality. Experimental and computational mechanistic analysis established that anti oxypalladation is the rate- and enantiodetermining step. DFT computational studies further established a model for enantioselectivity. In Chapter 3, a review of recent synthetic approaches to the oxidized dimeric pyrrole imidazole alkaloids is provided. The first total syntheses of massadine, axinellamines, and palau'amine are described. Reports of progress toward the total synthesis of these natural products are also summarized. In Chapter 4, progress toward the total synthesis of ( - )-massadine is reported. The synthetic route features two key steps. The first is an Ireland-Claisen rearrangement of a trianionic allylic acetate that occurs with high stereospecificity. The second is an unprecedented intramolecular nitrone dipolar cycloaddition which stereoselectively constructs a fully substituted cyclopentane. Elaboration of cyclopentane intermediates to incorporate the bisguanidine functionality is described.
Download or read book Palladium Catalyzed Asymmetric Allylic Alkylation AAA of Prochiral Nucleophiles written by Gretchen Marie Schroeder and published by . This book was released on 2002 with total page 734 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Palladium catalyzed Allylic arylation written by Krupa H. Shukla and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Transition Metal Catalyzed Enantioselective Allylic Substitution in Organic Synthesis written by Uli Kazmaier and published by Springer. This book was released on 2011-10-28 with total page 354 pages. Available in PDF, EPUB and Kindle. Book excerpt: Giovanni Poli, Guillaume Prestat, Frédéric Liron, Claire Kammerer-Pentier: Selectivity in Palladium Catalyzed Allylic Substitution.- Jonatan Kleimark and Per-Ola Norrby: Computational Insights into Palladium-mediated Allylic Substitution Reactions.- Ludovic Milhau, Patrick J. Guiry: Palladium-catalyzed enantioselective allylic substitution.- Wen-Bo Liu, Ji-Bao Xia, Shu-Li You: Iridium-Catalyzed Asymmetric Allylic Substitutions.- Christina Moberg: Molybdenum- and Tungsten-Catalyzed Enantioselective Allylic Substitutions.- Jean-Baptiste Langlois, Alexandre Alexakis: Copper-catalyzed enantioselective allylic substitution.- Jeanne-Marie Begouin, Johannes E. M. N. Klein, Daniel Weickmann, B. Plietker: Allylic Substitutions Catalyzed by Miscellaneous Metals.- Barry M. Trost, Matthew L. Crawley: Enantioselective Allylic Substitutions in Natural Product Synthesis.
Download or read book Applications of Enantioselective Palladium Catalyzed Allylic Aminations Toward the Synthesis of physostigmine written by Elbert Chin and published by . This book was released on 1997 with total page 234 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Stereocontrolled Palladium 0 Catalyzed Allylic Alkylations in the Total Synthesis of valienamine written by Louis S. Chupak and published by . This book was released on 1997 with total page 610 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Catalytic Asymmetric Synthesis of Allylic Aryl Ethers and Progress Toward the Total Synthesis of Palau amine Axinellamines A D and Massadine written by Nicole Suzanne White and published by . This book was released on 2009 with total page 574 pages. Available in PDF, EPUB and Kindle. Book excerpt: In chapter 2, the isolation, characterization, and biological activity of the pyrrole-imidazole alkaloids palau'amine, axinellamines A--D and massadine are reviewed. The proposed biosynthesis of these alkaloids is described and several synthetic approaches toward these alkaloids are discussed.
Download or read book New Frontiers in Palladium catalyzed Asymmetric Allylic Alkylations written by David Andrew Thaisrivongs and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The research described in this dissertation defines two endeavors into the field of palladium-catalyzed allylic alkylation chemistry: the employment of unstabilized nitrogen-containing aromatic heterocycles as nucleophiles and the use of C--H activation to access [pi]-allyl-palladium electrophiles. With regard to the former program, we demonstrate that 2-methylpyridines, substrates whose corresponding anions are too unstabilized to react productively in palladium-catalyzed asymmetric allylic alkylation (AAA) reactions, form complexes when exposed to boron trifluoride diethyl etherate that can be deprotonated with lithium hexamethyldisilazide to afford competent nucleophiles for AAA processes. Investigations into the reaction mechanism establish that the configuration of the allylic stereocenter of the electrophile is retained, a finding that is consistent with the canonical outer sphere mechanism invoked for palladium-catalyzed allylic substitution processes of stabilized anions. We also show that under modified conditions, this protocol is applicable to the highly regio-, diastereo-, and enantioselective allylic alkylation of 2-substituted pyridines, reactions that form homoallylic stereocenters containing alkyl, aryl, heteroaryl, and nitrogen substituents. When the reaction is correspondingly performed with unsymmetric acyclic electrophiles, both linear and branched products may be obtained regio- and enantioselectively by choosing the appropriate regioisomeric starting material and ligand. We further report that this strategy extends to reactions of a variety of nitrogen-containing aromatic heterocycles, including pyrazines, pyrimidines, pyridazines, quinoxalines, benzoimidazoles, and tetrazoles. The mesityl ester, whose steric bulk prevents competitive deacylation of the electrophile from these nucleophiles, is introduced as a new leaving group in allylic alkylation chemistry. We describe the first general palladium-catalyzed allylic alkylation of 1,4-dienes that proceeds via C--H activation. A broad range of nucleophiles undergo reaction with variously substituted 1,4-dienes under relatively mild conditions, providing direct access to the corresponding 1,3-diene-containing products with high regio- and stereocontrol. This is the first catalytic allylic alkylation that proceeds via C--H activation in the absence of sulfoxide ligands, a discovery that provides for further developments in this chemistry enabled by phosphorus-based ligands. This finding is applied to a new assisted tandem catalytic process that effects sequential palladium(0)-catalyzed allylic alkylations via leaving group ionization and palladium(II)-catalyzed allylic alkylations via C--H activation. By employing an oxidative trigger to convert the initial palladium(0) species to a palladium(II) one, both transformations can be conducted in a single reaction vessel using the same precatalyst. This strategy allows for the introduction of otherwise indistinguishable allyl groups by exploiting complementary catalytic redox cycles. Finally, we detail the discovery and development of the first catalytic enantioselective palladium-catalyzed allylic C--H alkylations, an achievement made possible by a novel class of pyroglutamic-based phosphoramidite ligands. A wide array of sterically and electronically diverse allylarenes undergo allylic substitution by 2-acetyl-1-tetralones to form quaternary carbon stereocenters. Control experiments verify that this palladium-catalyzed process involves direct allylic alkylation, rather than initial allylic C--H acetoxylation. This conceptually and mechanistically distinct strategy averts many of the chemoselectivity issues inherent to traditional methods for the synthesis of enantioenriched allylic substitution products, providing the groundwork for the next generation of palladium-catalyzed allylic alkylation methods.
Download or read book Handbook of Organopalladium Chemistry for Organic Synthesis written by Ei-ichi Negishi and published by John Wiley & Sons. This book was released on 2003-11-24 with total page 1657 pages. Available in PDF, EPUB and Kindle. Book excerpt: Organized to provide maximum utility to the bench synthetic chemist. The editor is well-known for his work in exploring, developing, and applying organopalladium chemistry. Contributors include over 24 world authorities in the field.
Download or read book Ruthenium and Palladium Catalysis written by Hanbiao Yang and published by . This book was released on 2006 with total page 560 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Palladium catalyzed Asymmetric Allylic Alkylation written by Nathan Bruce Bennett and published by . This book was released on 2013 with total page 1828 pages. Available in PDF, EPUB and Kindle. Book excerpt: The asymmetric construction of quaternary stereocenters is a topic of great interest in the organic chemistry community given their prevalence in natural products and biologically active molecules. Over the last decade, the Stoltz group has pursued the synthesis of this challenging motif via a palladium-catalyzed allylic alkylation using chiral phosphinooxazoline (PHOX) ligands. Recent results indicate that the alkylation of lactams and imides consistently proceeds with enantioselectivities substantially higher than any other substrate class previously examined in this system. This observation prompted exploration of the characteristics that distinguish these molecules as superior alkylation substrates, resulting in newfound insights and marked improvements in the allylic alkylation of carbocyclic compounds.
Download or read book Palladium Catalyzed Transformations of Allenes and Progress Towards the Total Synthesis of Nogalamycin written by Logan Vine (Ph.D.) and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Transition metal-catalyzed transformations of allenes are underexplored compared to other unsaturated functional groups. However, the consecutive, orthogonal double bonds of allenes represent an extremely valuable functional handle that can be manipulated to rapidly build molecular complexity. The first section of this work (Chapter 2) describes how targeted changes to the reaction conditions enable control over the mechanism of Pd-catalyzed allene cross-coupling/cyclization and cycloisomerization, irrespective of the allene substitution pattern. Both enantioenriched cyclopropanes and cyclopentenes can be obtained through axis-to-center chirality transfer from the allene precursor at room temperature. The next section (Chapter 4) demonstrates a highly stereoselective Pd-catalyzed Heck-type reaction of allenes to form 1,3-dienes in which the stereochemistry of both olefins is set simultaneously. The stereodetermining factors and a plausible mechanism for this work are proposed and both inter- and intramolecular trapping of the Ï0-allyl intermediate with an oxygen nucleophile are demonstrated. The final portion of this work will be focused on progress towards the total synthesis of Nogalamycin (NOG) (Chapter 6). NOG is a member of the glycosidic anthracyclines and shows a unique dumbbell type binding to DNA. Toxicity and relatively low antineoplastic activity have prevented NOG from clinical use, but semisynthetically accessed derivatives have shown great potential, leading to the need for a highly modular synthetic approach to access new analogs and further probe SARs. A complex bicyclic aminosugar motif creates a significant challenge for the synthesis of NOG, as there are no reliable synthetic methods to install the C℗Ơaryl-Cglycoside bond late stage. In this section, we propose a late-stage chemoenzymatic installation of the C℗Ơaryl-Cglycoside bond inspired by the biosynthetic pathway. The synthesis of the tetracyclic anthracycline core includes a key boron-directed cycloaddition, a novel SmI2 mediated ring opening of an oxanorbornadiene, and a proposed Ni-catalyzed cross electrophile coupling.
Download or read book Palladium Catalyzed Decarboxylative Asymmetric Allylic Alkylation of Unstabilized Enolates written by Jiayi Xu and published by . This book was released on 2008 with total page 1042 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Palladium Catalysis Directed Towards the Synthesis of Natural Products written by Lara Schwartz Kallander and published by . This book was released on 1998 with total page 508 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Palladium catalyzed Decarboxylative and Decarbonylative Transformations in the Synthesis of Fine and Commodity Chemicals written by Yiyang Liu and published by . This book was released on 2015 with total page 1012 pages. Available in PDF, EPUB and Kindle. Book excerpt: Decarboxylation and decarbonylation are important reactions in synthetic organic chemistry, transforming readily available carboxylic acids and their derivatives into various products through loss of carbon dioxide or carbon monoxide. In the past few decades, palladium-catalyzed decarboxylative and decarbonylative reactions experienced tremendous growth due to the excellent catalytic activity of palladium. Development of new reactions in this category for fine and commodity chemical synthesis continues to draw attention from the chemistry community. The Stoltz laboratory has established a palladium-catalyzed enantioselective decarboxylative allylic alkylation of beta-keto esters for the synthesis of alpha-quaternary ketones since 2005. Recently, we extended this chemistry to lactams due to the ubiquity and importance of nitrogen-containing heterocycles. A wide variety of alpha-quaternary and tetrasubstituted alpha-tertiary lactams were obtained in excellent yields and exceptional enantioselectivities using our palladium-catalyzed decarboxylative allylic alkylation chemistry. Enantioenriched alpha-quaternary carbonyl compounds are versatile building blocks that can be further elaborated to intercept synthetic intermediates en route to many classical natural products. Thus our chemistry enables catalytic asymmetric formal synthesis of these complex molecules. In addition to fine chemicals, we became interested in commodity chemical synthesis using renewable feedstocks. In collaboration with the Grubbs group, we developed a palladium-catalyzed decarbonylative dehydration reaction that converts abundant and inexpensive fatty acids into value-added linear alpha olefins. The chemistry proceeds under relatively mild conditions, requires very low catalyst loading, tolerates a variety of functional groups, and is easily performed on a large scale. An additional advantage of this chemistry is that it provides access to expensive odd-numbered alpha olefins. Finally, combining features of both projects, we applied a small-scale decarbonylative dehydration reaction to the synthesis of alpha-vinyl carbonyl compounds. Direct alpha-vinylation is challenging, and asymmetric vinylations are rare. Taking advantage of our decarbonylative dehydration chemistry, we were able to transform enantioenriched delta-oxocarboxylic acids into quaternary alpha-vinyl carbonyl compounds in good yields with complete retention of stereochemistry. Our explorations culminated in the catalytic enantioselective total synthesis of (-)-aspewentin B, a terpenoid natural product featuring a quaternary alpha-vinyl ketone. Both decarboxylative and decarbonylative chemistries found application in the late stage of the total synthesis.
Download or read book The Development of Palladium and Copper catalyzed Transformations for the Asymmetric Synthesis of Biologically Active Small Molecules written by James Thomas Masters and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The continued demand for efficient chemo-, regio-, and stereoselective organic transformations motivates the development of new chemical reactions. Transition metal catalysis represents a powerful method for the construction of carbon-carbon, carbon-hydrogen, and carbon-heteroatom bonds in a highly selective fashion. This dissertation describes the development of several new transition metal-catalyzed organic reactions useful in the preparation of various chiral small molecules, including both fundamental organic "building block" compounds and structurally complex natural products and pharmaceutical agents. We report a new strategy for the synthesis of chiral beta-alkynyl esters, ketones, and sulfones via sequential palladium-catalyzed carbon-carbon bond formation and copper-catalyzed carbon-hydrogen bond formation. The process is operationally straightforward, compatible with a broad range of substrates, and delivers the targets in high yields with excellent levels of enantioselectivity. It is compatible with both oxygen and nitrogen functionality, and this enabled the rapid elaboration of the products into a diverse set of chiral heterocycles. The sequential catalysis protocol was employed in a concise, enantioselective synthesis of AMG 837, a potent agonist of G-protein coupled receptor 40. Recognizing both the biological relevance of chiral alkaloids and the synthetic challenges associated with the construction of quaternary, all-carbon stereocenters, we pursued a palladium-catalyzed asymmetric allylic alkylation that effected carbon-carbon bond formation on prochiral oxindole nucleophiles. Although prior research has demonstrated that allylic alkylation reactions of geminal dicarboxylate electrophiles typically yield branched products as the result of ipso-addition, we identify conditions wherein oxindoles react with a dipivaloyl electrophile to afford linear enol pivalate compounds. A mild hydrolysis reaction converts these products into the aldehyde that formally results from asymmetric conjugate addition to acrolein, a challenging transformation with limited literature precedent. These adducts are established precursors to tricyclic alkaloid scaffolds of pharmaceutical interest. Chiral gamma-heteroatom-substituted cycloalkenones are well-established organic "building blocks" that are widely used in the synthesis of complex molecules. The exposure of meso-1,4-allylic dibenzoates to chiral phosphine-ligated palladium salts in the presence of a potassium nitronate nucleophile promotes a unique oxidative desymmetrization reaction. This process yields enantiopure gamma-benzoyloxy cyclopentenones, cyclohexenones, and cycloheptenones. We describe the elaboration of these products into diverse, enantioenriched oxygen- and nitrogen-substituted cycloalkenones via subsequent palladium-catalyzed allylic alkylation reactions involving heteroatom nucleophiles. Separately, we employ enantiopure gamma-benzoyloxy cyclohexenones in short, asymmetric syntheses of enantio- and diastereomerically diverse epoxyquinoid natural products. We further highlight the utility of palladium catalysis in complex molecule synthesis through the development of a unique, intramolecular carbon-carbon bond-forming reaction that generates a strained enyne and through an asymmetric formal synthesis of aliskiren, a renin inhibitor used in the treatment of hypertension.
Download or read book Palladium Reagents and Catalysts written by Jiro Tsuji and published by Wiley. This book was released on 2004-06-07 with total page 670 pages. Available in PDF, EPUB and Kindle. Book excerpt: Jiro Tsuji, one of the pioneers in this field of organic synthesis, provides synthetic organic chemists with a remarkable overview of the many applications of organopalladium chemistry. Tsuji discusses the recent developments in the field as well as the explosive growth over the last five years. Highlighting the most recent discoveries in this rapidly expanding field, the book; Focuses on new aspects of organopalladium chemistry, putting emphasis on synthetic applications Investigates the new perspectives on the synthetic uses of contemporary organopalladium chemistry This volume, together with Innovations in Organic Synthesis, Tsuji's previous title, provides complete coverage of over 40 years of organopalladium chemistry. Palladium Reagents and Catalysts: New Perspectives for the 21st Century is an essential reference source and companion for students, and both industrial and academic research chemists working in organic synthesis, particularly on synthesis of natural products and medicinal compounds. Those studying development of new synthetic methodology and organometallic chemistry will also find this book valuable.
