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Dissertations / Theses on the topic 'Quaternary carbon'

Author: Grafiati

Published: 4 June 2021

Last updated: 27 April 2022

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1

Frimpong, Kwame. "Synthesis of Quaternary Carbon Centers via Hydroformylation." Thesis, Boston College, 2011. http://hdl.handle.net/2345/2413.

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Thesis advisor: Kian L. Tan<br>Utilization of directing groups in a general and efficient manner for highly regioselective hydroformylation of 1,1-disubstituted olefins<br>Thesis (MS) — Boston College, 2011<br>Submitted to: Boston College. Graduate School of Arts and Sciences<br>Discipline: Chemistry

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2

Xue, Sijing. "Dual Transition Metal/Photoredox Catalysis for the Synthesis of Quaternary Carbon Stereocenters." Doctoral thesis, Universitat Rovira i Virgili, 2021. http://hdl.handle.net/10803/673186.

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Els estereocentres de carboni quaternaris són omnipresents en molècules bioactives i farmacèuticament rellevants. No obstant això, la construcció d'enllaços C-C que condueixen a carbonis quaternaris quirals segueix sent poc desenvolupada. El nostre grup ha explorat reaccions de substitució al·lílica mitjançant l'ús de carbonats cíclics de vinil (VCC) com a motius de substrat privilegiats, permetent així la formació versàtil de blocs de construcció estereodefinits. Tanmateix, en el moment de l'inici d'aquest treball de tesi, l'enfocament s'havia centrat només en mètodes preparatius que don

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3

Jones, Dyfyr Heulyn. "Approaches to quaternary carbon centres using organoboron chemistry." Thesis, Cardiff University, 2013. http://orca.cf.ac.uk/50197/.

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The main focus of the work contained within this thesis was to explore the possible use of novel organoboron chemistry in generating quaternary carbon centres, with the ultimate aim of developing new routes for the asymmetric synthesis of chiral quaternary carbon centres. Chapter 1 contains a general introduction to the literature of organoboron chemistry, focusing particularly on organoboron reactions that contain 1, 2 - boron to carbon migrations. Chapters 2 and 3 contain attempts at generating tertiary alkyl groups bonded to boron in an asymmetric fashion. Chapter 2 specifically deals with

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4

Minicone, Fabrizio. "Stereoselective synthesis of cyclopropanes with quaternary carbon centres." Thesis, Queen Mary, University of London, 2014. http://qmro.qmul.ac.uk/xmlui/handle/123456789/8766.

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Multi-substituted optically pure cyclopropanes are important motifs present in many agrochemicals, pharmaceuticals and materials employed in manifold applications. Their synthesis is challenging due to both the strained conformation and the need to control both the relative and absolute stereochemistry. This thesis describes an investigation of the scope of the Wadsworth-Emmons cyclopropanation, highlighting it as a potential efficient methodology for diastereoselective and enantiospecific synthesis of these valuable ring systems. Chapter 1 is an introduction to the cyclopropanation protocols

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5

Oliveira, Marllon Nascimento de. "Palladium-catalyzed asymmetric allylic alkylations : control of all-carbon quaternary centers." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066612/document.

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Dans le cadre de nos travaux, nous avons développé une méthode extrêmement douce et particulièrement efficace d’accès à des γ-butyrolactones possédant un centre stéréogène quaternaire en α à partir d’énols carbonates d’allyle cycliques et exocycliques en utilisant la réaction d’alkylation allylique asymétrique décarboxylante pallado-catalysée (Pd-DAAA). Remarquablement, cette méthode a permis d’étendre l’utilisation de l’allylation asymétrique décarboxylante à des substrats sans précèdent dans la littérature, tels que les énols carbonates allyliques exocycliques. Cette réaction a été utilisée

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6

Doda, Kanae. "Development of Asymmetric Carbon-Carbon Bond-Forming Reactions Using Novel Catalysis of Chiral Quaternary Ammonium Fluorides." 京都大学 (Kyoto University), 2004. http://hdl.handle.net/2433/147843.

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7

Fornace, Kyrstin L. "Late Quaternary climate variability and terrestrial carbon cycling in tropical South America." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/103257.

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Thesis: Ph. D., Joint Program in Chemical Oceanography (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2016.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references.<br>Characterizing global and regional climate variability and climate-carbon cycle interactions in the past provides critical context for evaluating present and future climate trends. In this thesis, I use stable isotope and radiocarbon analysis of vascular plant biomarkers in lacustrine and marine sediment core

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8

Subramanian, Hariharaputhiran. "Achiral Templates in Asymmetric Catalysis: Applications in Construction of All Carbon Quaternary Centers." Diss., North Dakota State University, 2018. https://hdl.handle.net/10365/29015.

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Conjugated olefins are readily available and inexpensive starting materials and their functionalization offers a rapid access to many important building blocks for organic synthesis. The functionalization of these olefins by asymmetric catalytic methods for the formation of C-C and C-X bonds is an active area of research. Major advances in this field are not only triggered by the development of new catalysts but also by engineering of new acceptor olefins. In our lab we have successfully developed acceptor olefins appended to alkoxyimidazoles as a novel template. Using these templated acceptor

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9

Sakata, Mazuki. "Phase-transfer Catalyzed Asymmetric Synthesis of All-carbon Quaternary Centers and Tetrasubstituted Allenes." 京都大学 (Kyoto University), 2013. http://hdl.handle.net/2433/175139.

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10

Wei, Lai. "Asymmetric organocatalysis in the Michael reaction of cyclic α-alkyl ketones : enantioselective synthesis of suberosanes and succinimides". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS325.

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La découverte des activités cytotoxiques impressionnantes des subérosanes, des sesquiterpènes d’origine marine isolées dès 1996 de la gorgone Subergorgia suberosa, ainsi que leurs structures tricycliques complexes possédant jusqu’à cinq centre stéréogènes contigus dont un centre quaternaire central, ont fait de ces molécules des cibles de choix tant pour les acteurs de la chimie médicinale que pour ceux travaillant dans le domaine de la synthèse totale. Enfin, une molécule d’origine synthétique « simplifiée » de cette famille, la nor-subérosénone, a également montré des activités cytotoxiques

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11

Wang, Ning, and 王宁. "Organic carbon signatures of the middle-late quaternary lacustrine history of tropical South China." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/208631.

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In order to reconstruct a long-time tropical terrestrial record of Asian monsoon in South China, the organic carbon in a 120 m lacustrine sediments from Maar Lake Tianyang was analyzed. Results in TOC, C/N and δ13C value show two lines of variations: (1) from a deep lake environment below 42 m to a shallow lake environment of the upper 42 m, (2) environmental changes between glacial and interglacial conditions throughout the lacustrine sediment sequence. In the shallow lake stage, δ13C values change according to glacial and interglacial periods, comparable with other proxies such as pollen, TO

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12

Dommain, Rene [Verfasser]. "Late Quaternary evolution and carbon cycling of tropical peatlands in equatorial Southeast Asia / Rene Dommain." Greifswald : Universitätsbibliothek Greifswald, 2015. http://d-nb.info/1068494689/34.

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13

Taylor, Donald Fulton. "Measurement of binary phase equilibria and ternary/quaternary gas antisolvent (GAS) system measurement and analysis." Thesis, Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-07112004-194307/unrestricted/taylor%5Fonald%5Ff%5F200407%5FMS.pdf.

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Thesis (M.S.)--School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, 2005. Directed by Charles Eckert.<br>Charles Eckert, Committee Chair ; Amyn Teja, Committee Member ; Pete Ludovice, Committee Member. Includes bibliographical references.

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14

May, Tricia Lee. "Copper-Based N-Heterocyclic Carbene Complexes for Catalytic Enantioselective Conjugate Additions of Alkyl-, Aryl- and Vinyl-Based Nucleophiles to Form All-Carbon Quaternary Stereogenic Centers." Thesis, Boston College, 2011. http://hdl.handle.net/2345/2650.

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Thesis advisor: Amir H. Hoveyda<br>Chapter 1 Enantioselective Conjugate Additions of Carbon Nucleophiles to Activated Olefins: Preparation of Enantioenriched Compounds Containing All-Carbon Quaternary Stereogenic Centers. Methods for enantioselective conjugate addition of nucleophiles to activated olefins generating products containing all-carbon quaternary stereogenic centers are critically reviewed. Enantioselective conjugate addition has been shown to be a powerful and concise approach to construct carbon-carbon bonds to prepare compounds containing sterically hindered stereogenic centers a

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15

Arpin, Azélie. "Development of a practical method for the asymmetric synthesis of quaternary carbon centers : a second generation auxiliary." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=97894.

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Despite significant progress in the field of organic chemistry, the asymmetric formation of all-carbon quaternary centers still represents a considerable challenge. Our group previously reported the stereocontrolled generation and alkylation of alpha,alpha-disubstituted amide enolates to form quaternary centers. This reaction takes place via the reduction of bicyclic alpha,alpha-dialkylated alpha-thioglycolate lactams using one-electron transfer reagents.<br>This method suffered from several limitations to practicality, thus this research project has focused on the development of a second-gene

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16

Oliver, Samuel. "Rhodium-catalysed allylic substitution with an acyl anion equivalent : asymmetric construction of acyclic quaternary carbon stereogenic centres." Thesis, University of Liverpool, 2012. http://livrepository.liverpool.ac.uk/8433/.

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The asymmetric construction of substituted carbonyl compounds, particularly those containing α-quaternary carbon stereogenic centres, remains a significant area of interest in organic chemistry. This can largely be attributed to the ubiquity and versatility of these compounds as synthetic intermediates, and the presence of such motifs in a range of biologically active pharmaceutical agents and natural products. In this context, the transition metal-catalysed allylic substitution provides an extremely powerful tool for the asymmetric construction of a range of C-C, C-N and C-O bonds, and has fo

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17

Miki, Takashi. "Studies on asymmetric construction of quaternary carbon centers on β-keto esters by phase-transfer-catalyzed alkylation". 京都大学 (Kyoto University), 2006. http://hdl.handle.net/2433/136712.

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18

Burke, Elizabeth Diane. "Stereoselective carbon-carbon bond forming reactions : improving the stereoselectivity of a catalytic homoaldol reaction and the development of a general method to access the [alpha]-quaternary carbon [beta]-hydroxy carbonyl motif." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=85054.

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The following thesis describes two stereoselective carbon-carbon bond forming processes---the aldol reaction and its one-carbon homologue, the homoaldol reaction. The first chapter describes our efforts to increase the stereoselectivity of a catalytic homoaldol reaction. This methodology features a second generation Binol titanium (IV) fluoride catalyst capable of opening a silyloxycyclopropane ring to form discrete homoenolates. These homoenolates react with a variety of aldehydes to form 1,4-hydroxy carbonyl compounds. The catalyst was prepared by a literature method and has improved

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19

Dabrowski, Jennifer A. "Development of Selective Methods to Form C-C Bonds. Enantioselective Formation of Tertiary and Quaternary Stereogenic Centers." Thesis, Boston College, 2013. http://hdl.handle.net/2345/3771.

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Thesis advisor: Amir H. Hoveyda<br>Formation of C-C bonds is an invaluable tool for the construction of materials, pharmaceuticals, natural products, and the building blocks of life. Although great strides in this area have been made, there remain several limitations in regio-, site-, and enantioselective additions of carbon-based nucleophiles. Solving these challenges by expanding the scope, efficiency, and selectivity of alkyl, aryl, heteroaryl, vinyl, and alkynyl additions to carbon-based electrophiles is the topic of this dissertation<br>Thesis (PhD) — Boston College, 2013<br>Submitted to:

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20

Darabi, Hamed. "Altering the configuration of the secondary alcohol and quaternary carbon in pantothenate derivatives: synthesis of novel N-Pentylpantothenamides." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=119530.

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The synthesis of pantothenamides with various but defined stereoconfigurations is promising for medicinal chemistry studies. N-pentylpantothenamides are antibacterial agents. Previous SAR studies reported an MIC of 3.6 µM against S. aureus for the allyl derivative with anti stereoconfiguration with respect to the secondary alcohol and the quaternary carbon. With the goal of improving the MIC, it was envisaged that compounds with the syn stereoconfiguration might have different activity. Thus a synthetic approach was developed which set the anti stereochemistry at the di alkyl germinal carbon v

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21

Kane, Deborah M. "Evaluation of a sanitizing system using isopropyl alcohol quaternary ammonium formula and carbon dioxide for dry-processing environments." Thesis, Kansas State University, 2012. http://hdl.handle.net/2097/14175.

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Master of Science<br>Food Science<br>Kelly J. K. Getty<br>Dry-processing environments are particularly challenging to clean and sanitize because water introduced into systems not designed for wet cleaning can favor growth and establishment of pathogenic microorganisms such as Salmonella. The objective was to determine the efficacy of isopropyl alcohol quaternary ammonium (IPAQuat) formula and carbon dioxide (CO[subscript]2) sanitizer system for eliminating Enterococcus faecium and Salmonella on food contact surfaces. Coupons of stainless steel and conveyor belting material used in dry-proces

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22

Hernández, Hernández Armand. "Ultra-high resolution environmental and climatic reconstruction using oxygen and carbon isotopes of diatom frustules." Doctoral thesis, Universitat de Barcelona, 2010. http://hdl.handle.net/10803/670535.

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Calcareous microfossils are not always present in marine or lacustrine sediments owing to unfavourable ecological or post-depositional conditions. These non-carbonated sediments sometimes contain abundant biogenic silica, rendering them suitable for studies of stable isotopes. For this reason, considerable progress has been made in the study of biogenic silica using isotopes in recent years. Diatom isotopes are increasingly being used for palaeoenvironmental reconstructions in lacustrine sedimentary records. Tropical proxy records offer valuable insights into past climate and environmental

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23

Biggs, Robyn A. "5-and 6-Membered Hydrazides as Potential Catalysts for Diels-Alder Cycloadditions." Thesis, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/30723.

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Part A: Synthesis of 5- and 6-Membered Camphor-Based Hydrazides as Organocatalysts for Cycloaddition Reactions The favorable environmental and reactivity qualities of organocatalysts are contributing to the popularization of this method for the acceleration of enantioselective reactions. Research in our group has been focused on the synthesis of camphor-derived hydrazide based organocatalysts for enantioselective cycloaddition processes. Recent results suggest that the presence of an exocyclic electron withdrawing group on the hydrazide moiety, as well as the incorporation of the hydrazide m

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24

Li, Xiaoyun, and 李瀟云. "Late quaternary climate and sedimentary history derived from N-alkanes, alkenones and bulk organic carbon analyses in Fujian coast, China." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/207998.

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Late Quaternary is an important period for paleoclimate study due to the boom of human civilization and thus its influence on climate conditions of the present interglacial period. In this study, a 52 m long borehole was drilled in a coastal embayment of Fujian, China, within which a thick marine layer from 16.05 to 32.60 m is found. Bulk organic geochemical analyses, containing total organic carbon content (TOC), carbon isotope ratio (δ13C), alkenones and n-alkanes, were analyzed for the whole core. Organic carbon isotope ratios (δ13C) of the sediment layers vary between -22.1‰ and -32.9‰, wi

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Callinan, Andrew J. "Exploratory methods for the preparation of quaternary carbon centers and their potential application to the synthesis of tazettine and pretazettine /." The Ohio State University, 1992. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487777901659153.

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Isaksson, Rebecka. "Synthetic Approach to Dehaloperophoramidine via a Samarium Mediated Reductive Dialkylation." Thesis, KTH, Skolan för kemivetenskap (CHE), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-156317.

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Marine ascidian metabolite perophoramidine has since its isolation in 2002 attracted the interest of several research groups. The complex polycyclic structure with vicinal quaternary carbon stereocenters and two amidine functionalities constitutes a formidable synthetic challenge. In this project a new synthetic approach to dehalogenated perophoramidine has been investigated. The vicinal quaternary carbon stereocenters were introduced via a samarium mediated reductive dialkylation, in which the stereochemistry was determined by the metal chelate that formed, as outlined below. Several of the s

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27

Creighbaum, Adam J. "Examination and reconstitution of the glycine betaine-dependent methanogenesis pathway from the obligate methylotrophic methanogen Methanolobus vulcani B1d." Miami University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=miami158754951585964.

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Lima, Claudia Moré de. "Dinâmica da vegetação e inferências climáticas no Quaternário Tardio na região da Ilha de Marajó (PA), empregando os isótopos do carbono (12C, 13C, 14C) da matéria orgânica de solos e sedimentos." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/64/64134/tde-15042009-104930/.

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Considerada a maior ilha flúvio-marítima do mundo, com aproximadamente 48.000 km2, a Ilha de Marajó situa-se na zona equatorial brasileira, no litoral do Estado do Pará. Apresenta dois domínios distintos relacionados a geologia e vegetação. No setor oeste dominam solos desenvolvidos sobre os sedimentos Pós Barreiras (plio-pleistocênicos) recobertos pela Floresta Amazônica, enquanto no setor leste dominam sedimentos holocênicos derivados de ambiente fluvial/estuarino atualmente desativado. Neste setor encontram-se os extensos campos naturais marajoaras. O objetivo deste trabalho consistiu em ap

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Kouns, Carolina, and Yael Margulis. "Rock-magnetic and Soil Organic Carbon Proxies of Climate Change from Loess – Aeolian Sediments of Brittany, France." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-445688.

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The aeolian sediment loess, which consists of mineral dust, is one of the most detailed terrestrial record of both global and regional climate changes. As climate changes in the past cover a much wider range of climate variability than humans have directly recorded, the soil memory of loess is vital for understanding the Earth’s climate system. By examining past climate records and analyzing past climate changes and factors that have instigated changes, inferences regarding future climate can be made. Therefore, the aim of this research was to define the specific depositional and post-depositi

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Ticak, Tomislav. "Anoxic quaternary amine utilization by archaea and bacteria through a non-L-pyrrolysine methyltransferase; insights into global ecology, human health, and evolution of anaerobic systems." Miami University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=miami1429897518.

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Yu, Qing. "The rhodium(II)-catalyzed intramolecular tertiary C-H insertion of diazoacetates, application in the total synthesis of alkaloids possessing a chiral quaternary carbon center." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/NQ65793.pdf.

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Tiong, Erica. "Stereoselective formation of all carbon quaternary centers: synthesis of alpha,alpha-disubstituted beta-amino carbonyl compounds via the Mannich reaction and total synthesis of (-)-puraquinonic acid." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=104585.

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A bicyclic thioglycolate lactam chiral auxiliary was previously developed in our group for the asymmetric formation of quaternary carbon stereocenters via enolate alkylation. This method is notable for the stereocontrolled generation of alpha, alpha-disubstituted amide enolates, without reliance on the steric differences of the alpha-substituents. Coupled with excellent facial discrimination in electrophilic approach, this led to a general and practical method for enantioselective preparation of quaternary carbon centers via alkylation reactions. This thesis describes the extension of this met

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Kristen, Iris. "Investigations on rainfall variability during the late Quaternary based on geochemical analyses of lake sediments from tropical and subtropical southern Africa." Phd thesis, Universität Potsdam, 2009. http://opus.kobv.de/ubp/volltexte/2009/3254/.

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This thesis presents investigations on sediments from two African lakes which have been recording changes in their surrounding environmental and climate conditions since more than 200,000 years. Focus of this work is the time of the last Glacial and the Holocene (the last ~100,000 years before present [in the following 100 kyr BP]). One important precondition for this kind of research is a good understanding of the present ecosystems in and around the lakes and of the sediment formation under modern climate conditions. Both studies therefore include investigations on the modern environment (in

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Bell, Benjamin. "Advancing the application of analytical techniques in the biological chemistry of sporopollenin : towards novel plant physiological tracers in Quaternary palynology." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/advancing-the-application-of-analytical-techniques-in-the-biological-chemistry-of-sporopollenin-towards-novel-plant-physiological-tracers-in-quaternary-palynology(59605f2b-642a-4ea9-8921-4c926217e6f2).html.

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Palynology, the study of organic microfossils, is an important tool for improving our understanding of past environments and landscapes. Palynology provides a wealth of information from which climatic and environmental conditions can be inferred. However, inferred climatic and environmental conditions are often open to interpretation. Assumptions made about past climate conditions from pollen assemblages often rely on qualitative understanding of modern-day vegetation distributions, rather than empirical relationships. Historic anthropogenic impact on the environment must also be inferred, and

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Song, Tao. "Alkylation allylique asymétrique pallado-catalysée : contrôle de centres quaternaires au sein d'hétérocycles azotés." Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLET012.

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Le développement d’outils synthétiques permettant le contrôle de centres stéréogènes quaternaires reste un défi important en synthèse organique. Dans ce contexte, l’alkylation allylique asymétrique pallado-catalysée est apparue comme une méthode particulièrement efficace. Le premier chapitre de cette thèse est consacré à l’application de cette réaction d’alkylation allylique asymétrique à des dérivés de type succinimides. Cette méthode, convergente, nous a permis d’accéder à un grand nombre de composés de type succinimide comportant un centre stéréogène quaternaire en position alpha avec de bo

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Francisquini, Mariah Izar. "Reconstitution of Atlantic Rainforest vegetation dynamics since the Late Pleistocene at southeastern (Espirito Santo state coast and Minas Gerais eastern) and northeastern (Bahia southern) Brazil." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/64/64134/tde-30112017-083827/.

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This research is associated to the FAPESP 2011/0095-7 thematic project, \"Interdisciplinary palaeoenviromental studies at Espirito Santo coast\" and to the FAPESP Research Program about Climate Global Change (PFPMCG-FAPESP). The objectives were: (1) to characterize the late Pleistocene connection between Atlantic and Amazon rainforest and possible routes of interaction (coast, continent or both); (2) to identify environmental characteristics that indicates the Northeastern Espírito Santo and Southern Bahia as a stable forest since the late Pleistocene; (3) reconstitute the vegetation dynamics

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Wieland, Laura Caroline. "Catalytic enantioselective synthesis of O- and N-substituted quaternary carbon stereogenic centers : 1. AL-catalyzed alkylations of α-ketoesters with dialkylzinc reagents. 2. AG-catalyzed vinylogous Mannich-type reactions of α-ketoimine esters with siloxyfurans". Thesis, Boston College, 2008. http://hdl.handle.net/2345/356.

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Thesis advisor: Amir H. Hoveyda<br>Chapter 1: We disclose an Al-catalyzed enantioselective method for additions of Me2Zn and Et2Zn to α-ketoesters bearing aromatic alkenyl, and alkyl substituents. These transformations are promoted in the presence of a readily available amino acid-based ligand, and afforded the desired products in excellent yields and in up to 95% ee. In addition, we discovered a remarkable enhancement of efficiency and selectivity in the presence of an achiral phosphoramidate additive. Chapter 2: An efficient diastereo- and enantioselective Ag-catalyzed method for additions o

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Petersen, Jade Oriane. "Traçage isotopique (36CI, 4He, 234U) et modélisation hydrogéologique du Système Aquifère du Sahara Septentrional. Application à la recharge Quaternaire du Continental Intercalaire." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4325/document.

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L'exploitation des réserves d'eau douce, principalement contenues dans les aquifères est une préoccupation croissante dans les zones où elle se traduit par une baisse des niveaux piézométriques.Ce travail de thèse propose de caractériser l'évolution du Système Aquifère du Saharan Septentrional (SASS), et plus particulièrement le Continental Intercalaire (CI) à l'aide d'un couplage entre des outils de modélisation hydrogéologique et de traceurs géochimiques (36Cl, 234U/238U). Situé dans une région semi-aride à aride et s'étendant sur plus d'un million de km2, le CI présente un potentiel d'enreg

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Afewerki, Samson. "Development of catalytic enantioselective C-C bond-forming and cascade transformations by merging homogeneous or heterogeneous transition metal catalysis with asymmetric aminocatalysis." Doctoral thesis, Mittuniversitetet, Avdelningen för naturvetenskap, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-23605.

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Chiral molecules play a central role in our daily life and in nature, for instance the different enantiomers or diastereomers of a chiral molecule may show completely different biological activity. For this reason, it is a vital goal for synthetic chemists to design selective and efficient methodologies that allow the synthesis of the desired enantiomer. In this context, it is highly important that the concept of green chemistry is considered while designing new approaches that eventually will provide more environmental and sustainable chemical synthesis.The aim of this thesis is to develop th

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Guillot, Marie. "Analyse rétrospective des relations nappe-végétation de sous-bassins versants forestiers de la rivière Leyre." Thesis, Bordeaux 1, 2011. http://www.theses.fr/2011BOR14427/document.

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Dans les Landes de Gascogne, le fonctionnement de la nappe phréatique superficielle plio-quaternaire est très liée au fonctionnement de la végétation subjacente. Pour comprendre la variabilité à l'échelle du paysage de la productivité de ces forêts, il est important de passer de l'échelle de la parcelle à celle du bassin versant. La mise en place d'un dispositif de suivi de type bassins versants jumelés à l'échelle de petits bassins versants forestiers situés dans le Massif Landais : les bassins versants du Tagon (Biganos) et du Bouron (Belin-Beliet) a permis le suivi hydrologique et piézométr

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Campos, Marília de Carvalho. "Variabilidade milenar da Corrente do Brasil e do clima da América do Sul durante o último período glacial." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/100/100136/tde-27072016-113954/.

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A Corrente do Brasil (CB) representa o ramo sul da bifurcação da Corrente Sul Equatorial que interage com a margem continental sudeste do Brasil. A temperatura da superfície do mar na região da CB exerce um importante papel no controle da intensidade e posição da Zona de Convergência do Atlântico Sul, um dos principais componentes do Sistema de Monção da América do Sul (SMAS). Tal sistema atmosférico é responsável pela precipitação de verão em grande parte do continente sul-americano, sendo, portanto, uma feição natural de grande importância para o contexto político-econômico nacional e intern

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Chen, Li. "New developments in green asymmetric catalysis : Application to Michael reaction and ring opening polymerisation." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS162.

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La synthèse asymétrique organo-catalysée est un domaine de recherche en pleine expansion visant une chimie plus verte. Nous nous sommes intéressés au développement d’une réaction de Michael asymétrique organocatalysée en mettant à profit la catalyse par liaison hydrogène et l’activation énamine afin de contrôler en une seule étape la formation d’adduits portant un centre carboné quaternaire à partir de cétones non activées. Ainsi, nous avons développé des organocatalyseurs bifonctionnels de type squaramide qui ont permis d’obtenir les adduits de Michael attendu à partir de cycloalcanones alpha

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43

Biggs, Thomas. "Fire Frequency, Nutrient Concentrations and Distributions, and δ13C of Soil Organic Matter and Plants in Southeastern Arizona Grassland". Diss., The University of Arizona, 1997. http://hdl.handle.net/10150/244085.

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Over the past century, woody plants and shrubs have increased in abundance at the expense of grasslands in many semiarid regions. The availability and concentrations of nutrients influence the relative success of plants, but the effects of fire frequency on soil nutrients is unknown for semiarid grasslands. On the gunnery ranges of Fort Huachuca in southeastern Arizona, study sites were established to examine the effects of fire frequency on soil biogeochemistry, plant biochemistry, and δ¹³C values in soil organic matter (SOM). The sites were on homogeneous granitic alluvium where wildfire fre

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Millot, Nicolas. "Syntheses et reactivites de nouveaux complexes (cyclohexadiene) fer carbonyle." Paris 11, 1998. http://www.theses.fr/1998PA114801.

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Junior, Jaime Rissi Passarini. "Estudo interdisciplinar em sedimentos lacustres da região sul do estado de São Paulo. Reconstrução da vegetação e do clima no Quaternário tardio." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/64/64134/tde-16122009-102402/.

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O estudo de um testemunho coletado às margens de uma lagoa situada em meio a vegetação de Mata Atlântica no Parque Estadual Turístico do Alto Ribeira, sul do estado de São Paulo, permitiu a reconstituição da história da vegetação local ao longo dos últimos 2500 anos. Para isso, foram realizadas análises elementares, isotópicas e palinológicas. Também a partir de material retirado deste testemunho procedeu-se a comparação entre dois protocolos de tratamento químico para análises palinológicas do Quaternário. Os protocolos utilizados seguiram as metodologias propostas por Faegri e Iversen, 1989

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Bouttes, Nathaëlle. "L’évolution du cycle du carbone au cours du Quaternaire." Paris 6, 2010. http://www.theses.fr/2010PA066376.

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Durant les 2,6 derniers millions d'années (le Quaternaire), le climat de la Terre n'a cessé d'osciller entre un climat plus froid (période glaciaire) et un climat plus chaud (période interglaciaire). Pendant ces variations, appelées cycles glaciaires-interglaciaires, les carottes de glace venant d'Antarctique indiquent que les concentrations en CO2 dans l'atmosphère passent de valeurs faibles en période froide à des valeurs élevées en périodes chaudes. Cette évolution n'avait pour l'instant pas trouvé d'explication satisfaisante malgré de nombreuses hypothèses. Or comprendre les mécanismes à l

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Freire, Brântuas Pedro. "Captage du dioxyde de carbone par des semiclathrate hydrates : Modélisation, expérimentation et dimensionnement d’une unité pilote." Thesis, Saint-Etienne, EMSE, 2013. http://www.theses.fr/2013EMSE0691/document.

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Les hydrates de gaz sont une façon non conventionnelle de piéger et de stocker des molécules de gaz par cristallisation d’eau à haute pression et à basse température. Les sels d'ammonium quaternaire forment des semiclathrates hydrates à pression atmosphérique et des hydrates mixtes en présence de gaz. Il est important de connaître leurs propriétés thermodynamiques, afin d'évaluer leurs applications potentielles : une des ces-ci est la capture du dioxyde de carbone à partir des gaz de combustion. Dans nos expériences, les semiclathrates ont été fabriqués à partir de sels de peralkylammonium (TB

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Brandon, Margaux. "Les changements majeurs de la productivité biologique au cours du Quaternaire et leurs impacts sur les cycles du carbone et de l’oxygène." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASJ010.

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A l’échelle des cycles glaciaires-interglaciaires (G/IG) du Quaternaire, la concentration atmosphérique en CO₂ (p CO₂) est associée à d’importantes variations, notamment pendant les transitions entre périodes glaciaires et interglaciaires, aussi appelées terminaisons, qui enregistrent des augmentations de pCO₂ de l’ordre de 100 ppm en quelques milliers d’années. Alors que les rôles de la circulation océanique et de l’étendue de la couverture de glace sur le pCO₂ sont étudiés depuis plusieurs années, peu de travaux s’intéressent à l’impact de la productivité biologique. L’objectif de cette thès

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Carvalho, Rocha Catarina. "Towards a catalytic system allowing the "one-pot" conversion of alkenes into cyclic carbonates in the presence of dioxygen/carbon dioxide mixtures." Paris 6, 2013. http://www.theses.fr/2013PA066758.

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This work aims to develop a heterogeneous catalyst for the direct conversion of an alkene to the corresponding cyclic carbonate in the presence of O2 and CO2. A MnIII salen complex and quaternary ammonium salts (QAS) bearing a -(CH2)2OH function were considered as active phases for the epoxidation and epoxide cyclocarbonatation, respectively. The activity of several QAS was measured to study the influence of the ammonium structure, as well as that of counter-ions. The C16H33N(CH3)2(CH2CH2OH)+Br- salt (HEA16Br) turned out to be more active than choline chloride (HEA1Cl). DFT calculations were u

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Manthorpe, Jeffrey Michael. "A general method for the asymmetric synthesis of quaternary carbons : reductive formation and alkylation of [alpha],[alpha]-disubstituted enolates." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=82927.

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A new, general method for the asymmetric synthesis of quaternary carbons is described. This technique involves stereocontrolled generation of alpha,alpha-disubstituted amide enolates via reduction of bicyclic alpha,alpha-disubstituted alpha-thioglycolate lactams using one-electron transfer reagents. A model of the geometric constraints necessary to reductively prepare alpha,alpha-disubstituted amide enolates with control of enolate E/Z stereochemistry is described and several chiral auxiliaries were prepared to test this design.<br>Successful preparation, trapping, isolation and charact

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