Download or read book Rhodium Catalysed Asymmetric Ring Opening of Oxabicyclic Alkenes and Diastereoselective Ring Opening of Epoxides with Heteroatom Nucleophiles written by and published by . This book was released on 2000 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Rhodium Catalysed Asymmetric Ring Opening of Oxabicyclic Alkenes and Diastereoselective Ring Opening of Epoxides with Heteroatom Nucleophiles written by Keith Fagnou and published by . This book was released on 2000 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Oxabenzonorbornadienes were shown to undergo asymmetric ring opening with a variety of alcohol, phenol and activated amine nucleophiles in the presence of catalytic amounts of [Rh(COD)Cl]2 and chiral diphosphine ligands. The product dihydronaphthalenols were produced in 73-99%ee. Extension of this methodology to 'o'-halophenols required changing the rhodium source to [Rh(CO)2Cl]2. These products were applied to the synthesis of benzodihydrofurans. In order for carboxylates and unactivated amines to induce ring opening, the addition of a proton source was required. Enantioselectivities of up to 74% and 81% were observed for the amine and the carboxylate ring opened products respectively. These products were applied towards the synthesis of 1,4-dihydronaphthalenols. Vinyl Epoxides were shown to undergo diastereoselective ring opening reaction with alcohols and aromatic amine nucleophiles in the presence of catalytic amounts of [Rh(CO)2Cl]2. The 'trans '-1,2-alkoxyalcohols and aminoalcohols were produced in >80% yield and >20:1 diastereoselectivity.
Download or read book Organic Reaction Mechanisms 2003 written by A. C. Knipe and published by John Wiley & Sons. This book was released on 2007-03-13 with total page 644 pages. Available in PDF, EPUB and Kindle. Book excerpt: The only book series to summarize the latest progress on organic reaction mechanisms, Organic Reaction Mechanisms, 2003 surveys the development in understanding of the main classes of organic reaction mechanisms reported in the primary scientific literature in 2003. The 39th annual volume in this highly successful series highlights mechanisms of stereo-specific reactions. Reviews are compiled by a team of experienced editors and authors, allowing advanced undergraduates, graduate students, postdocs, and chemists to rely on the volume's continuing quality of selection and presentation.
Download or read book Rhodium Catalyzed Asymmetric Ring Opening of Oxabicyclic Alkenes and Palladium Catalyzed Carbon Halogen Bond Forming Reactions written by Christine Le and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Atom-economical addition reactions to unsaturated carbonâ carbon bonds represent a powerful class of transformations in organic chemistry, since a great deal of molecular complexity can be generated from simple starting materials. Highly regio- and stereoselective processes have been made possible through the use of transition metal catalysts, alongside specialized ancillary ligands and in combination with rational substrate design. One area of research in the Lautens group involves the transition metal catalyzed asymmetric ring opening (ARO) of strained alkenes, which provides access to enantioenriched carbocyclic frameworks. Although a variety of coupling partners have been applied in this transformation, the use of soft carbon nucleophiles remains limited in scope. The first chapter describes a rhodium(I)-catalyzed ARO of meso-oxabicyclic alkenes using silyl enol ethers and ketene acetals. In analogy to the Mukaiyama aldol reaction, a novel silyl migration occurs, enabling an in situ protection of the chiral alcohols obtained. Developing new reactivity from Heck-type carbopalladation processes represents another research interest in the Lautens group. Oxidative addition into a carbonâ halogen bond constitutes the first step of nearly all palladium(0)-catalyzed cross-couplings. Conversely, reductive elimination from palladium(II) to yield an organohalide product represents a rare and often thermodynamically unfavoured process. The next two chapters address challenges in the synthesis of vinyl halides using palladium(0) catalysis via the intramolecular carbohalogenation and chlorocarbamoylation of alkynes. During our investigations, we discovered that the steric bulk of both the substrate and the phosphine ligand play an important role in promoting the desired reactivity. Mechanistic insight has been gained through combined experimental and computational studies, which implicate a palladium-catalyzed stereoisomerization in both of these transformations. Under certain conditions, we demonstrate that highly stereoselective trans-additions to alkynes can be achieved, which illustrates that specific substrate/catalyst combinations can override the inherent cis-selectivity in carbometallations. In the fourth chapter, a formal palladium(II)-catalyzed alkyne chlorocarbamoylation reaction is presented, which provides access to medicinally relevant methylene oxindole scaffolds. In contrast to the analogous protocol using palladium(0) catalysts, the reaction is initiated by an alkyne chloropalladation step, followed by intramolecular cross-coupling with a carbamoyl chloride. Experimental and computational studies provide insight into the mechanism of this reaction.
Download or read book Rhodium Catalyzed Enantioselective Desymmetrizations of Oxabicyclic Alkenes and Alkene Difunctionalization Via Nickel Catalyzed Arylcyanation written by Andy Wei Jen Yen and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The synthesis of heterocycles using transition metal catalysis is a topic of broad interest in the field of organic chemistry. Transition metal catalysts allow many diverse bond disconnections to be realized, allowing for many ways to assemble heterocycles. Many of the transformations developed in the Lautens group are aimed at atom economical bond construction processes that streamline synthesis and minimize waste. The arylcyanation reaction and the asymmetric ring opening (ARO) reaction are two examples of methods developed in our group that embody this design principle. Chapter 1 of this thesis describes the development of a nickel-catalyzed arylcyanation reaction for the synthesis of 3,3-disubstituted oxindoles. This method was inspired by our work on the palladium-catalyzed arylcyanation reaction, originally developed to address challenges in the formal synthesis of (+)-corynoline. This nickel-catalyzed reaction uses an air-stable catalyst precursor to achieve a highly practical synthesis of a nitrile-containing oxindole via a domino Heck-cyanide capture cascade. Derivatizations of the nitrile group affords a series of novel heterocyclic scaffolds. Chapter 2 details the discovery and development of a novel enantioselective cycloisomerization reaction of oxabicyclic alkenes. Our work on developing the intramolecular asymmetric ring opening reaction led to the discovery of a novel epoxide synthesis. Specifically, when bridgehead substituted oxabicyclic alkenes with non-nucleophilic side chains are reacted with the [Rh(cod)2]OTf/PPF-PtBu2 catalyst in the absence of an external nucleophile, chiral epoxides are obtained. The synthesis of epoxides through cycloisomerization reactions possesses 100% atom economy and avoids the use of external oxidant. Chapter 3 describes an asymmetric ring opening reaction, specifically to address gaps in the methodology concerning amine nucleophiles. We were inspired by our group's previous attempts to use amino acid derived nucleophiles in the ARO reaction. We developed a way to incorporate amino acids into the ARO reaction by employing their 2-nitrobenzenesulfonamide (nosyl) derivatives as pronucleophiles. Intriguingly, we observed a divergence in reactivity between the diastereomeric hydroxyester products, in that one diastereomer was capable of lactonization and the other was not. This led to the enantioselective synthesis of chiral oxazinones, which are similar to the naphthoxazine class of compounds which possess dopaminergic activity.
Download or read book Iridium catalyzed asymmetric ring opening reactions of oxabicyclic alkenes with secondary amine nucleophiles written by 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 Mechanistic and Synthetic Studies of Asymmetric Catalytic Epoxide Ring opening Reactions written by Karl B. Hansen and published by . This book was released on 1998 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Rhodium catalyzed Ring Opening of Vinyl Epoxides and Vinyl Aziridines with Aniline Nucleophiles microform written by Jasmine Almas and published by National Library of Canada = Bibliothèque nationale du Canada. This book was released on 2002 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Inter and Intramolecular Ring Opening Reactions of Oxabicyclic Substrates written by Christopher Wicks and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Oxabenzonorbornadiene (OBD) and derivatives thereof have become key substrates of interest within synthetic organic chemistry and natural product synthesis as they enable the formation of multiple stereocenters in a single transformation. The present work expands on previous studies to investigate various intramolecular transformations, and regiochemical implications regarding ring-opening reactions of asymmetric oxabicyclic alkenes. Acid-catalyzed intramolecular ring-opening reactions of cyclopropanated oxabenzonorbornadiene (CPOBD) derivatives were investigated to afford novel medium-sized ring systems in moderate to good yields and good to excellent regioselectivity. Similarly, a Ni catalyzed intramolecular ring-opening reaction of alkyl halide tethered OBD compounds was optimized, thus generating a naphthalene derivative in excellent yields. Lastly, iridium-catalyzed ring-opening reactions of unsymmetrical C1-substituted OBD derivatives is presented using alcohols and water as nucleophiles which allows for the selective synthesis of previously inaccessible substrates.
Download or read book Nickel Catalyzed Asymmetric Reductive Ring Opening of written by TOMISLAV. ROVIS and published by . This book was released on 1998 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Catalytic Asymmetric Ring opening Reactions of Epoxides Mechanistic Investigation and Theoretical Studies written by Lars Peter Christian Nielsen and published by . This book was released on 2006 with total page 277 pages. Available in PDF, EPUB and Kindle. Book excerpt: A review of nonenzymatic, catalytic methods in the context of asymmetric ring-opening reactions of epoxides is presented. Nucleophilic-addition reactions are discussed according to the identity of the reactive nucleophilic center and are followed by a section on enantioselective rearrangements of both meso and chiral epoxides. The criteria for practicality is outlined in each case as are limitations, applications to synthesis, and mechanistic details of interest.
Download or read book Rhodium catalyzed Asymmetric Carbon Carbon Bond Formation Leading to the Development of Rhodium Palladium Multi metal Catalysis written by Lei Zhang and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis describes the development of rhodium-catalyzed asymmetric ring opening of strained alkenes and the subsequent use of rhodium and palladium catalysis in the development of domino reactions. The contents are divided into 4 chapters. Chapter 1 describes the rhodium-catalyzed asymmetric ring opening (ARO) of strained bicyclic alkenes using silyl enolates. The development of this method achieved a highly enantioselective addition of alkyl fragments onto bicyclic alkenes, affording broad scope, mild reaction conditions, and high functional group tolerance. The synthetic utility of the method was demonstrated through functionalization of the ARO products to a number of core scaffolds of natural products. Chapter 2 describes the development of a domino rhodium/palladium-catalyzed synthesis of dihydroquinolines. The use of two different ligands in the reaction led to a mechanistic investigation that revealed metal-ligand interactions that were crucial to the success of this domino reaction. The mechanistic insights facilitated reaction optimization, leading to an expansion of the reaction scope, including the synthesis of chromenes. Chapter 3 describes the importance of time resolution and ligand interference in the development of enantioselective domino rhodium/palladium catalysis employing chiral and achiral ligands. The development of this method provided access to chiral C4-substituted dihydroquinolinones in a direct manner, affording high yields and enantioselectivities. Current work on developing multicomponent enantioselective rhodium/palladium catalysis is also disclosed. Chapter 4 describes the development of multi-metal-catalyzed multicomponent reactions (MC)2R. The development of a highly compatible rhodium/palladium catalyst system allowed the incorporation of a third catalyst, copper, achieving a three-component one-pot reaction. Current work on the development of the use of other metal combinations to achieve (MC)2R is also disclosed.
Download or read book Investigations Into the Ruthenium Catalyzed Ring Opening and Dimerization Reactions of Oxabicyclic Alkenes written by Kelsey Jack and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Modern Rhodium Catalyzed Organic Reactions written by P. Andrew Evans and published by John Wiley & Sons. This book was released on 2006-03-06 with total page 496 pages. Available in PDF, EPUB and Kindle. Book excerpt: Rhodium has proven to be an extremely useful metal due to its ability to catalyze an array of synthetic transformations, with quite often-unique selectivity. Hydrogenation, C-H activation, allylic substitution, and numerous other reactions are catalyzed by this metal, which presumably accounts for the dramatic increase in the number of articles that have recently emerged on the topic. P. Andrew Evans, the editor of this much-needed book, has assembled an internationally renowned team to present the first comprehensive coverage of this important area. The book features contributions from leaders in the field of rhodium-catalyzed reactions, and thereby provides a detailed account of the most current developments, including: Rhodium-Catalyzed Asymmetric Hydrogenation (Zhang) Rhodium-Catalyzed Hydroborations and Related Reactions (Brown) Rhodium-Catalyzed Asymmetric Addition of Organometallic Reagents to Electron Deficient Olefins (Hayashi) Recent Advances in Rhodium(I)-Catalyzed Asymmetric Olefin Isomerization and Hydroacylation Reactions (Fu) Stereoselective Rhodium(I)-Catalyzed Hydroformylation and Silylformylation Reactions and Their Application to Organic Synthesis (Leighton) Carbon-Carbon Bond-Forming Reactions Starting from Rh-H or Rh-Si Species (Matsuda) Rhodium(I)-Catalyzed Cycloisomerization and Cyclotrimerization Reactions (Ojima) The Rhodium(I)-Catalyzed Alder-ene Reaction (Brummond) Rhodium-Catalyzed Nucleophilic Ring Cleaving Reactions of Allylic Ethers and Amines (Fagnou) Rhodium(I)-Catalyzed Allylic Substitution Reactions and their Applications to Target Directed Synthesis (Evans) Rhodium(I)-Catalyzed [2+2+1] and [4+1] Carbocyclization Reactions (Jeong) Rhodium(I)-Catalyzed [4+2] and [4+2+2] Carbocyclizations (Robinson) Rhodium(I)-Catalyzed [5+2], [6+2], and [5+2+1] Cycloadditions: New Reactions for Organic Synthesis (Wender) Rhodium(II)-Stabilized Carbenoids Containing both Donor and Acceptor Substituents (Davies) Chiral Dirhodium(II)Carboxamidates for Asymmetric Cyclopropanation and Carbon-Hydrogen Insertion Reactions (Doyle) Cyclopentane Construction by Rhodium(II)-Mediated Intramolecular C-H Insertion (Taber) Rhodium(II)-Catalyzed Oxidative Amination (DuBois) Rearrangement Processes of Oxonium and Ammonium Ylides Formed by Rhodium(II)-Catalyzed Carbene-Transfer (West) Rhodium(II)-Catalyzed 1,3-Dipolar Cycloaddition Reactions (Austin) "Modern Rhodium-Catalyzed Organic Reactions" is an essential reference text for researchers at all levels in the general area of organic chemistry. This book provides an invaluable overview of the most significant developments in this important area of research, and will no doubt be an essential text for researchers at academic institutions and professionals at pharmaceutical/agrochemical companies.
Download or read book Transition Metal Catalyzed Ring opening Reactions of Unsymmetrical Oxabicyclic Alkenes written by Raheem Mohammed Abdul and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Development of Asymmetric Catalytic Reactions written by Bridget Debora Brandes and published by . This book was released on 1998 with total page 314 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Asymmetric Catalytic Epoxide Ring opening Reactions written by Sang Kyun Kim and published by . This book was released on 2005 with total page 204 pages. Available in PDF, EPUB and Kindle. Book excerpt:
