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  • 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.
221

Accessing Chemically Differentiated 1,5-dienes Through Palladium Catalyzed Allyl-Allyl Cross-Coupling with Internal Allyl Electrophiles

Batten, Amanda Lynn January 2015 (has links)
Thesis advisor: James P. Morken / Internal allyl electrophiles were successfully implemented in a catalytic cross-coupling to allylB(pin) with high regiocontrol to afford multisubstituted 1,5-dienes bearing chemically differentiated olefins. Construction of alkenyl compounds with all carbon quaternary centers and high enantiomeric excess can be achieved in one step without the use of enantiomerically enriched chiral ligands. / Thesis (MS) — Boston College, 2015. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.
222

Nonracemic Organoboronates by Transition Metal-Catalyzed C-C and C-Si Bond Forming Reactions

Szymaniak, Adam Anthony January 2018 (has links)
Thesis advisor: James P. Morken / This dissertation will describe the development of three transition metal-catalyzed syntheses of nonracemic organoboronates. The first chapter explains the development of a palladium-catalyzed enantiotopic-group-selective cross-coupling of geminal bis(boronates) with alkenyl electrophiles. This process enables the synthesis of highly valuable nonracemic disubstituted allylic boronates. Chapter two describes a palladium-induced 1,2-metallate rearrangement of vinylboron “ate” complexes. The newly developed process incorporates an alternative route for the transmetallation step of Suzuki-Miyaura cross-couplings. Lastly, an enantioselective platinum-catalyzed hydrosilylation of alkenyl boronates is disclosed. This reaction enables the synthesis of nonracemic geminal silylboronates for the divergent synthesis of functionalized / Thesis (PhD) — Boston College, 2018. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.
223

Do screening ao mecanismo de ação, uma contribuição para a descoberta de ciclopaladados bioativos : a atividade leishmanicida de CP2 e seu efeito inibitório frente à DNA topoisomerase 1B de Leishmania /

Velásquez, Angela Maria Arenas. January 2017 (has links)
Orientadora: Marcia Aparecida Silva Graminha / Banca: Adelino Vieira de Godoy Netto / Banca: Luiz Ricardo Orsini Tosi / Banca: Pio Colepicolo Neto / Banca: Silvia Reni Bortolin Uliana / Resumo: As leishmanioses são doenças mundialmente distribuídas, encontradas nas áreas tropicais e subtropicais do mundo e que são caudas por protozoários parasitos do gênero Leishmania spp. A pesar dos inúmeros problemas associados aos tratamentos disponíveis (como alta toxicidade dos fármacos, limitada eficácia e casos de resistência haverem surgido), ainda estás doenças são negligenciadas pelas industrias farmacêuticas e pelos governos. Na procura por novos fármacos com amplo espectro de ação e baixa toxicidade, há evidências que sugerem que complexos de metais de transição podem atuar em diversos compartimentos ou organelas dos protozoários, além de apresentar baixa toxicidade no hospedeiro mamífero. No presente trabalho, realizou-se a avaliação leishmanicida in vitro de seis compostos ciclopaladados, [Pd(dmba)(µ-Cl)]2 (CP1), [Pd(dmba)(µ-N3)]2 (CP2), [Pd(dmba)(µ-NCO)]2 (CP3), [Pd(dmba)Cl(isn)] (CP4), [Pd(dmba)(N3)(isn)] (CP5) e [Pd(dmba)(NCO)(isn)] (CP6) e seus correspondentes ligantes livres, Hdmba: N,N-dimetilbenzilamina e isn: isonicotinamida. O composto CP2 inibiou o crescimento das formas promastigotas de Leishmania amazonensis (IC50 = 13,2 ± 0,7 µM), reduz a proliferação das formas amastigotas intracelulares (IC50 = 10,2 ± 2,2 µM) e apresentou um baixo efeito citotóxico frente a macrófagos peritoneais (CC50 = 506,0 ± 10,7 µM). Dados in vitro da atividade anti-T. cruzi e anti-T. brucei, parasitos causadores das doenças de Chagas e do sono, respectivamente, também demonstraram que os compostos ciclopaladados apresentam amplo espectro de ação constituindo-se em excelentes candidatos para o tratamento das doenças negligenciadas em estudo. O composto CP2 apresentou-se para as formas amastigotas intracelulares de L. amazonensis pelo menos 50 vezes mais seletivo e 200 vezes mais seletivo para as amastigotas de T. cruzi vs. células de mamífero... / Abstract: Leishmaniasis are diseases globally distributed in tropical and subtropical areas of the world and Leishmania spp. are the etiological agents of the diseases. Numerous problems associated with available treatments of the disease are still unsatisfactory because currently available drugs are highly toxic, little effectiveness and drug resistance cases have emerged. Furthermore, leishmaniasis are a neglected disease by pharmaceutical industries and governments. In the search for new drugs with a broad spectrum of action and low toxicity, there is evidence to suggest that transition metal complexes can act in several compartments or organelles of protozoa, as well as to present low toxicity in the mammalian host. In this work, we evaluated the leishmanicidal and trypanocidal in vitro activity of six cyclopalladated compounds: [Pd(dmba)(µ-Cl)]2 (CP1), [Pd(dmba)(µ-N3)]2 (CP2), [Pd(dmba)(µ-NCO)]2 (CP3), [Pd(dmba)Cl(isn)] (CP4), [Pd(dmba)(N3)(isn)] (CP5), [Pd(dmba)(NCO)(isn)] (CP6) and the free ligands, Hdmba: N,N- dimethylbenzylamine e isn: isonicotinamide. The cyclopalladated complexes CP2 inhibited the growth of the promastigote forms of Leishmania amazonensis (IC50 = 13,2 ± 0,7 µM), reduced the proliferation of intracellular amastigote forms (IC50 = 10,2 ± 2,2 µM) and showed a low cytotoxic effect against peritoneal macrophages (CC50 = 506,0 ± 10,7 µM). In vitro assays against T. cruzi and T. brucei, parasites that cause Chagas disease and sleeping sickness, respectively, demons... (Resumo completo, clicar acesso eletrônico abaixo) / Doutor
224

Developments in palladium catalyzed reactions: Strategies to synthesize asymmetric 1,5-dienes and 1,4-dicarbonyls

Le, Hai January 2014 (has links)
Thesis advisor: James P. Morken / This dissertation details recent developments in palladium catalyzed carbon-carbon bond formation reactions with two areas of focus: the palladium catalyzed branched and enantioselective allyl-allyl cross-coupling, and the palladium catalyzed carbonylative conjugate addition. Allyl-allyl cross-coupling presents an opportunity to synthesize 1,5-dienes, a scaffold that resembles subunits of terpenes, a critical building block in nature. Chapter I provides an overview of the developments in the allyl-allyl cross-coupling area. Chapter II, III, and IV detail strategies to construct complex substituted asymmetric 1,5-dienes through branched selective and enantioselective allyl-allyl cross-coupling. In chapter V, the palladium catalyzed carbonylative conjugate addition is discussed. This method enables the synthesis of 1,4-dicarbonyl compounds in an atom economical and environmentally friendly fashion, and provides a direct access to five membered heterocycles, a valuable class of chemicals in medicine. / Thesis (PhD) — Boston College, 2014. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.
225

Enantioselective synthesis and stereospecific transformations of organoboronic esters

Edelstein, Emma Kate January 2018 (has links)
Thesis advisor: James P. Morken / This dissertation details the development of several enantioselective or stereospecific transformations involving organoboronic esters. Chapter one will introduce electrophile-induced boronate rearrangements which underpins much of the reactivity that will be discussed in subsequent chapters. In chapter two the conjunctive cross-coupling reaction is presented. Its development and application to the synthesis of non-racemic boronic esters, along with its application to the synthesis of enantioenriched allylic boronic esters, will be discussed. In chapter three the cross-coupling of geminal bis(boronic) esters is introduced and the development of a method to employ them in cross-coupling with alkenyl bromides, affording enantioenriched substituted allylic boronic esters is outlined. In chapter four we highlight the utility of allylic boronic esters, and detail the development of a cross-coupling reaction that involves the use of these substrates and halide electrophiles to furnish enantiomerically enriched products containing all carbon quaternary stereocenters. Finally, in chapter five we describe the development of a metalfree amination reaction of organoboron compounds, which is able to deliver otherwise difficult-to-access enantiomerically enriched α-tertiary amines. / Thesis (PhD) — Boston College, 2018. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.
226

Biocompatible palladium catalysts for biological applications

Indrigo, Eugenio January 2016 (has links)
Transition metals have been used to mediate bioorthogonal reactions within a biological environment. In particular, applications of biocompatible palladium catalysis currently range from biomolecules modification to the in cellulo synthesis or activation of drugs. Here, the scope of palladium-mediated chemistry in living systems has been further extended with the development of a new homogenous palladium catalyst. This water-soluble, biocompatible, and traceable catalysts is based on a palladium-carbene complex coupled to a fluorescent labelled homing peptide for targeted delivery inside cells. This “SMART” catalyst is designed to activate both caged fluorophores and drugs through the cleavage of protecting groups or cross-coupling reactions. A second strategy for targeted delivery of a biocompatible palladium catalysis involves metal nanoparticles loaded onto a heterogeneous solid support. This “modular” catalyst can be implanted in vivo at the desired site of action, e.g. a tumour, and locally activate biomolecules. These two catalytic systems will allow us to selectively activate pro-drugs in vivo, with spatial control, thus minimising the side effects of the treatment on the whole body.
227

Trimetallic N-heterocyclic carbene complexes

Ellul, Charles January 2011 (has links)
No description available.
228

A user-friendly synthesis of aryl arsines and phosphines.

January 2001 (has links)
by Lai Chi Wai. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (leaves 63-68). / Abstracts in English and Chinese. / Table of Contents --- p.i / Acknowledgments --- p.iii / Abbreviations --- p.iv / Abstract --- p.v / Chapter Chapter 1 --- General introduction / Chapter 1.1 --- Background of phosphines and arsines ligands in metal catalysis --- p.1 / Chapter 1.2 --- Electronic effect of phosphines and arsines ligands in metal catalysis --- p.2 / Chapter 1.3 --- Synthesis of Aryl Phosphines --- p.7 / Chapter 1.4 --- Synthesis of Aryl Arsines --- p.9 / Chapter 1.5 --- The objective of this work --- p.11 / Chapter Chapter 2 --- Palladium catalyzed phosphination of aryl triflates / Chapter 2.1 --- Synthesis of aryl triflates --- p.12 / Chapter 2.2 --- Palladium catalyzed phosphination of aryl triflates --- p.15 / Chapter 2.3 --- Mechanistic studies of phosphination --- p.19 / Chapter Chapter 3 --- Palladium catalyzed arsination of aryl triflates --- p.22 / Chapter 3.1 --- Solvent and catalyst screening in palladium catalyzed arsination --- p.23 / Chapter 3 2 --- Stoichiometry of triphenylarsine --- p.24 / Chapter 3.3 --- Temperature effect of arsination --- p.25 / Chapter 3.4 --- Results of palladium catalyzed arsination --- p.26 / Chapter 3.5 --- Mechanistic studies of arsination --- p.28 / Chapter Chapter 4 --- Green chemistry approach 一 solventless phosphination and arsination / Chapter 4.1 --- Introduction to green chemistry --- p.30 / Chapter 4.2 --- Results of solventless phosphination --- p.31 / Chapter 4.3 --- Results of solventless arsination --- p.33 / Conclusion --- p.36 / Experimental --- p.37 / Reference --- p.63
229

Electrolysis of Palladium in Heavy Water

Zaczek, Christoph 03 July 1995 (has links)
Following several reports in the past few years about compositional changes on palladium used as a cathode in heavy water electrolysis, the purpose of this research project was to reproduce this results. Two experiments were performed using two cells connected in series, an experimental cell and a control cell. Both experiments used platinum anodes, the experimental cell had a palladium cathode and the control cell had a platinum cathode. The electrolyte was D20 with H2S04. Radiation was monitored during both experiments. Also temperature and voltage were recorded for both experiments, to allow statements about excess heat of the experimental cell in comparison to the control cell. Both experiments had problems with unequal electrolyte loss, so that no statements about excess heat could be made. No significant radiation was detected in either experiment. Also no compositional changes on the palladium cathodes after electrolysis in both experiments could be detected. Impurities in grain-shaped defects on the palladium cathode before the experiment were found in either experiment. These impurities were Si, Ca, 0, and sometimes also Mg, Na and Fe. Localized findings of Au and Pt, in a distance of 1-2μm to each other, were made on the palladium cathode from the second experiment before electrolysis. Spot, grain-shaped and longitudinal defects were found on the original palladium foil used for the cathodes in either experiment No evidence for fusion, or any other nuclear reaction in the crystal lattice of palladium, used as cathode in heavy water electrolysis, was observed.
230

Soil Remediation using Solvent Extraction with Hydrodehalogenation and Hydrogenation in a Semicontinuous System

Panczer, Robert John 20 March 2014 (has links)
The objective of this thesis is to aid in the development of Remedial Extraction And Catalytic Hydrodehalogenation (REACH), a green remediation technology used to remove and destroy halogenated hydrophobic organic compounds from soil. REACH has no secondary waste streams, uses an environmentally benign solvent, and aims to catalytically destroy rather than transfer the organic contaminants into a different phase. In this thesis, a bench-top semicontinuous model of the proposed remediation technology was constructed and used to extract the model contaminant, 1,2,4,5-tetrachlorobenzene, from soil and to convert it to an acceptable end product, cyclohexane. Palladium was used as a catalyst for hydrodehalogenation, which converted the tetrachlorobenzene to benzene. Rhodium was used to catalyze the hydrogenation of benzene to cyclohexane. A novel method, ultraviolet solvent treatment, was proposed to mitigate catalyst deactivation that occurs because of extracted chemicals contained in the contaminated soil. The goal of this treatment is to degrade organic matter that is suspected of causing catalyst deactivation. The REACH process was found to successfully extract TeCB from the soil, but only partial conversion from TeCB to cyclohexane occurred. Catalyst deactivation was the suspectedcause of the low amount of conversion observed. Hydrogen limitation was also tested as a cause of limited conversion, but was not found to be a contributor. Ultraviolet solvent treatment was tested as a means of mitigating catalyst deactivation. However, the treatment was not effective in making a profound difference in stopping the catalyst from deactivating. The experiments conducted in this research show that REACH has the potential to become a viable technology for cleaning soil contaminated with halogenated organic compounds. However, future research needs to be done to greatly reduce the severity of catalyst deactivation and to determine with which other halogenated organic compounds the technology works well.

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