• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 8
  • 3
  • 1
  • 1
  • Tagged with
  • 21
  • 14
  • 11
  • 8
  • 8
  • 5
  • 5
  • 5
  • 5
  • 4
  • 4
  • 3
  • 3
  • 3
  • 3
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Rhodium-catalyzed Intermolecular Ketone Hydroacylation: Towards an Enantioselective and Diastereoselective Protocol

Longobardi, Lauren Elizabeth 15 November 2013 (has links)
The addition of an aldehyde C−H bond across a ketone functionality, formally a hydroacylation, has emerged as an atom-economical approach to the synthesis of esters. While this is an efficient strategy for producing biologically-relevant materials, the field of transition metal-catalyzed ketone hydroacylation is currently limited to intramolecular systems. The development of a new rhodium catalyst will be presented, and its application to intermolecular ketone hydroacylation will be discussed. Ester products were synthesized from unfunctionalized, aliphatic aldehydes and chelating ketones in excellent yields under relatively mild reaction conditions. Efforts towards an asymmetric intermolecular ketone hydroacylation will be described, including the application of known chiral catalysts and the development of novel chiral phosphine ligands for asymmetric catalysis. Ester products were obtained in as high as 78% enantiomeric excess.
2

Rhodium-catalyzed Intermolecular Ketone Hydroacylation: Towards an Enantioselective and Diastereoselective Protocol

Longobardi, Lauren Elizabeth 15 November 2013 (has links)
The addition of an aldehyde C−H bond across a ketone functionality, formally a hydroacylation, has emerged as an atom-economical approach to the synthesis of esters. While this is an efficient strategy for producing biologically-relevant materials, the field of transition metal-catalyzed ketone hydroacylation is currently limited to intramolecular systems. The development of a new rhodium catalyst will be presented, and its application to intermolecular ketone hydroacylation will be discussed. Ester products were synthesized from unfunctionalized, aliphatic aldehydes and chelating ketones in excellent yields under relatively mild reaction conditions. Efforts towards an asymmetric intermolecular ketone hydroacylation will be described, including the application of known chiral catalysts and the development of novel chiral phosphine ligands for asymmetric catalysis. Ester products were obtained in as high as 78% enantiomeric excess.
3

Enantioselective Rhodium-catalyzed Hydroacylation of Alkenes and Ketones & Silver-catalyzed Hydroamination of Cyclopropenes

Phan, Diem 31 August 2012 (has links)
Due to the scarcity of energy resources that we are facing today, there is an increasing need for new methodology developments that are green and sustainable while minimizing unnecessary substrate pre-functionalization, by-product formation and waste generation. In this context, asymmetric rhodium-catalyzed hydroacylation is an atom-economical method for the preparation of chiral ketone derivatives from aldehyde and olefin precursors. This transformation is also applicable to keto-aldehyde precursors en route to chiral lactones. This dissertation describes the development of three specific methodologies, namely: 1) the synthesis of enantioenriched cyclopropyl ketones by enantio- and diastereoselective intermolecular rhodium-catalyzed hydroacylation of cyclopropenes, 2) the synthesis of enantioenriched phthalides by enantioselective rhodium-catalyzed intramolecular hydroacylation of ketones, and 3) the synthesis of tertiary branched allylic amines by silver-catalyzed ring-opening hydroamination of cyclopropenes.
4

Enantioselective Rhodium-catalyzed Hydroacylation of Alkenes and Ketones & Silver-catalyzed Hydroamination of Cyclopropenes

Phan, Diem 31 August 2012 (has links)
Due to the scarcity of energy resources that we are facing today, there is an increasing need for new methodology developments that are green and sustainable while minimizing unnecessary substrate pre-functionalization, by-product formation and waste generation. In this context, asymmetric rhodium-catalyzed hydroacylation is an atom-economical method for the preparation of chiral ketone derivatives from aldehyde and olefin precursors. This transformation is also applicable to keto-aldehyde precursors en route to chiral lactones. This dissertation describes the development of three specific methodologies, namely: 1) the synthesis of enantioenriched cyclopropyl ketones by enantio- and diastereoselective intermolecular rhodium-catalyzed hydroacylation of cyclopropenes, 2) the synthesis of enantioenriched phthalides by enantioselective rhodium-catalyzed intramolecular hydroacylation of ketones, and 3) the synthesis of tertiary branched allylic amines by silver-catalyzed ring-opening hydroamination of cyclopropenes.
5

Hydroacylation carbonylante d'alcynes : nouvelle voie d'accès à des cétones alpha, béta-insaturées / Carbonylative hydroacylation on alkynes : a new access to alpha, beta-unsatured ketones

Dheur, Julien 12 November 2008 (has links)
Du fait de leur difonctionnalités et, donc, de par leur réactivité particulière, les cétones alpha,beta-insaturées interviennent dans de nombreux schémas de synthèse de molécules complexes et le développement de nouvelles voies pour leur préparation est donc d'une grande importance. Ce travail consiste à développer la réaction d'hydroacylation carbonylante d'alcynes pour la synthèse d'énones. L'optimisation et le développement de ce système en utilisant les alcynes tenninaux simples a permis d'obtenir divers énones avec de bons résultats. De plus, l'application de la réaction à des alcynes particuliers, notmmnent les alcools propargyliques, a permis l'accès à des furanes. L'étude du mécanisme de la réaction a aussi été entrepris avec l'utilisation d'outils analytiques et, plus particulièrement, la RMN sous pression de monoxyde de carbone. Cette étude a permis de recueillir des informations quant au cycle catalytique engagé dans cette transformation. / By their difonctionnality and, then, by their special reactivity, alpha,beta-unsaturated ketones are involved in numerous synthesis to access complexe molecules. The development of new pathways for their fonnation is a major field of research interest. This work deals with the application of carbonyaltive hydroacylation reaction on terminal akynes for enones synthesis. After an optimisation step and the development of this system, we were able to obtain different enones in good yield and selectivities. ln addition, the use of propargyl alcohols as substrate leads to the fonnation of furane derivatives. A mecanistic investigation upon this reaction has been done with the help of analytical tools, especially NMR under high pressure of carbon monoxide. This study has brought several informations concerning the catalytic cycle of this transformation.
6

Heteroatom-directed Olefin Hydroacylation

Coulter, Matthew 05 January 2012 (has links)
Rhodium-catalyzed hydroacylation is a powerful and atom-economical method for synthesizing ketones from aldehydes and olefins. Despite this, a narrow scope of reactive substrates has limited the utility and broad application of this transformation. Efforts towards the development of new classes of reactive substrates have focused on the use of oxygen- and sulfur-containing olefins, which have enabled various modes of reactivity and thus allowed access to novel types of hydroacylation products. In addition to reactivity, a key to the success of these transformations is the control of regio-, stereo-, and chemoselectivity. In combination with substrate structure, strategies in enantioselective catalysis and metal-organic cooperative catalysis have been applied to achieve requisite reactivity and selectivity when required. A variety of products, such as medium-sized heterocycles, branched sulfur-containing and β-hydroxy ketones, and ketones bearing quaternary carbon centres have been synthesized via hydroacylation using these strategies. A method for preparing polyelectrolyte-stabilized palladium nanoparticles and their use in Suzuki coupling reactions have also been developed.
7

Rhodium-catalyzed Intermolecular Hydroacylation of Unactivated Alkenes and Application to the Total Synthesis of Octaketide Natural Products

Le, Christine 20 November 2012 (has links)
Transition metal-catalyzed olefin hydroacylation represents an atom-economical approach for the synthesis of valuable ketone products. To date, the intermolecular variant of this reaction suffers from several drawbacks, which include limited substrate scope, poor reactivity and/or regioselectivity for non-activated, non-chelating alkene substrates, and competitive reductive decarbonylation pathways that lead to catalyst decomposition. Herein, we report the linear-selective intermolecular hydroacylation of a wide range of electronically diverse olefins with salicylaldehydes employing catalyst loadings as low as 2 mol%. A unique reactivity profile is observed for the chiral C2-symmetric phosphoramidite ligand employed in our catalyst system, and thus, we outline progress made towards the synthesis of new phosphoramidite ligands. We have applied our methodology in the total synthesis of nine octaketide natural products belonging to the dothiorelone, cytosporone, and phomopsin families. Due to recent reports demonstrating the anticancer activity of cytosporone B (Csn-B), we will also discuss progress towards the synthesis of Csn-B analogues.
8

Heteroatom-directed Olefin Hydroacylation

Coulter, Matthew 05 January 2012 (has links)
Rhodium-catalyzed hydroacylation is a powerful and atom-economical method for synthesizing ketones from aldehydes and olefins. Despite this, a narrow scope of reactive substrates has limited the utility and broad application of this transformation. Efforts towards the development of new classes of reactive substrates have focused on the use of oxygen- and sulfur-containing olefins, which have enabled various modes of reactivity and thus allowed access to novel types of hydroacylation products. In addition to reactivity, a key to the success of these transformations is the control of regio-, stereo-, and chemoselectivity. In combination with substrate structure, strategies in enantioselective catalysis and metal-organic cooperative catalysis have been applied to achieve requisite reactivity and selectivity when required. A variety of products, such as medium-sized heterocycles, branched sulfur-containing and β-hydroxy ketones, and ketones bearing quaternary carbon centres have been synthesized via hydroacylation using these strategies. A method for preparing polyelectrolyte-stabilized palladium nanoparticles and their use in Suzuki coupling reactions have also been developed.
9

Rhodium-catalyzed Intermolecular Hydroacylation of Unactivated Alkenes and Application to the Total Synthesis of Octaketide Natural Products

Le, Christine 20 November 2012 (has links)
Transition metal-catalyzed olefin hydroacylation represents an atom-economical approach for the synthesis of valuable ketone products. To date, the intermolecular variant of this reaction suffers from several drawbacks, which include limited substrate scope, poor reactivity and/or regioselectivity for non-activated, non-chelating alkene substrates, and competitive reductive decarbonylation pathways that lead to catalyst decomposition. Herein, we report the linear-selective intermolecular hydroacylation of a wide range of electronically diverse olefins with salicylaldehydes employing catalyst loadings as low as 2 mol%. A unique reactivity profile is observed for the chiral C2-symmetric phosphoramidite ligand employed in our catalyst system, and thus, we outline progress made towards the synthesis of new phosphoramidite ligands. We have applied our methodology in the total synthesis of nine octaketide natural products belonging to the dothiorelone, cytosporone, and phomopsin families. Due to recent reports demonstrating the anticancer activity of cytosporone B (Csn-B), we will also discuss progress towards the synthesis of Csn-B analogues.
10

Investigating rhodium-catalysed hydroacylation and carbon-carbon bond activation

Coxon, Thomas January 2017 (has links)
The work described in this thesis documents the development of new rhodium(I)-catalysed methodologies within two areas of research. The first examines the use of carbonyls as chelating groups in hydroacylation to produce synthetically valuable ketones and enones. The second area explores new carbon-carbon bond activation methodologies. Chapter 1 presents a literature review of the historical development of rhodium-catalysed hydroacylation, with a focus on chelating groups that can currently be used to suppress decarbonylation. A brief review of methodologies that avoid the requirement for a tether is also included. Chapter 2 describes the development of a novel hydroacylation methodology employing carbonyl-based functional groups as tethers on aldehyde substrates. The chapter begins with the optimisation studies for the hydroacylation of β-formyl amides with terminal and internal alkynes, allenes and terminal alkenes, and subsequently explores the substrate scope for each case. The chapter then outlines the investigations undertaken with 1,4-dicarbonyl and 1,5-dicarbonyl systems, N-formyl amides, β-formyl esters and finally β-formyl ketones. A detailed description of the routes undertaken to synthesise each starting material is also presented. Chapter 3 presents a short review surveying the key milestones in the development of carbon-carbon activation methodologies. The chapter begins with a theoretical comparison to carbon-hydrogen activation and a discussion of the unique challenges that are faced. An overview of the major strategies employed to enact these processes is subsequently presented for both strained and unstrained substrates. Chapter 4 outlines the attempts undertaken to develop a novel carbon-carbon bond activation methodology. The work evaluates sulfur-, nitrogen- and alkene-based chelating groups, known to be successful in hydroacylation, in analogous ketone substrates. Chapter 5 discusses the conclusions from this work and the potential for further work. Chapter 6 presents the experimental procedures and data.

Page generated in 0.0965 seconds