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Dissertations / Theses on the topic 'Organic synthesis ; organometallic chemistry ; transition metal catalysis'
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Benedetto, Elena. "Synthesis and reactivity of allylic fluorides under transition metal catalysis." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:8c9965ef-2694-4792-a0ef-932e4eff6c7b.
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In this thesis, C-F bond activation and C-F bond construction under platinum and iridium catalysis is described. Chapter 1 provides a general introduction on the use of transition metal catalysis for the formation and activation of Csp³-F bonds in organofluorine compounds. In Chapter 2, an investigation on the reactivity of allylic fluorides, under platinum and palladium catalysed alkylation conditions, is presented. The relative reactivity of fluoride versus other commonly used leaving groups was compared via internal competition experiments. Fluoride showed a different reactivity profile, when subjected to Pt and Pd catalytic systems. Based on the observed reactivity trend, a Pd-catalysed fluorination reaction of allylic alcohol derivatives was successfully developed, within the group. In Chapter 3, a new iridium catalysed fluorination using branched, E- or Z-linear allylic carbonates is described. The catalyst [Ir(COD)Cl]₂ leads to an unexpected regio- and stereoretentive selectivity, affording fluorinated products not accessible via palladium catalysis. The effect of a fluoride additive on the selectivity of the Ir-catalysed alkylation reaction is also presented. A highly efficient <sup>18</sup>F-fluorination variant for this new catalytic transformation is reported. Chapter 4 gives full experimental procedures and characterisation data for all compounds.
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Hopkinson, Matthew Neil. "Transition metal catalysis in the presence of fluorinating reagents." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:4f29607a-7aad-473b-aabc-af320ea2b1e5.
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In this thesis, the effect of fluorinating reagents on a selection of transition metal-mediated organic transformations was investigated. The first four chapters are focused on gold-catalysed nucleophilic addition processes performed in the presence of “F⁺” sources. Chapter 1 provides a general introduction to homogeneous gold catalysis and summarises the aims and objectives of the project. The effect of the electrophilic fluorinating reagent Selectfluor (82) on the gold-catalysed rearrangement of propargyl acetates 85 is discussed in Chapter 2. α-Fluoroenones 92 resulting from fluorodeacetylation of an allenyl acetate intermediate were delivered as the major products of these reactions (Scheme i). [Scheme i Gold-Catalysed Rearrangement-Fluorodeacetylation of Propargyl Acetates 85.] By contrast, performing the gold(I)-catalysed cyclisation of allenoates 102 in the presence of Selectfluor (82) led to products of oxidative coupling. The “F⁺” source in these processes most likely acts as an external oxidant in an Au<sup>I</sup</Au<sup>III</sup> redox cycle. In Chapter 3, the cascade cyclisation-intramolecular arylation of benzyl-substituted substrates is discussed whilst the extension of the methodology towards intermolecular homocoupling and intermolecular alkynylation is presented in Chapter 4 (Scheme ii). [Scheme ii Gold-Catalysed Cyclisation-Oxidative Coupling of tert-Butyl Allenoates 102.] In Chapter 5, the feasibility of palladium-catalysed allylic [<sup>18</sup>F]radiofluorination was investigated using high-specific-activity [<sup>18</sup>F]fluoride. This study led to the development of the first transition metal-mediated C-<sup>18</sup>F bond-forming process of relevance for the preparation of radiotracers for PET imaging (Scheme iii). [Scheme iii Palladium-Catalysed Allylic [18F]Radiofluorination of Allylic Methyl Carbonate 227b.] Chapter 6 gives full experimental procedures and characterisation data for all compounds.
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Deeming, Alex. "Applications of DABSO for the delivery of sulfur dioxide in organic synthesis." Thesis, University of Oxford, 2015. http://ora.ox.ac.uk/objects/uuid:ae0a6c5c-57a1-48bc-b219-ad22678d51ca.
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This thesis documents the development of novel synthetic methodologies for the incorporation of sulfur dioxide into organic molecules employing the amine-sulfur dioxide complex DABSO (vide infra). These developed processes serve to access a range of sulfonyl-containing (-SO<sub>2</sub>-) compounds including sulfones and sulfonamides, via sulfinic acid precursors. <b>Chapter 1</b> provides an overview of the synthesis and applications of sulfonyl-containing compounds and the organic chemistry of sulfur dioxide. A comprehensive introduction to the developed uses of sulfur dioxide surrogates in organic chemistry is given. The synthetic utility of metal sulfinates towards accessing sulfonyl-containing compounds is also discussed. <b>Chapter 2</b> details the development of a one-pot sulfone synthesis via metal sulfinates generated from organometallic reagents and DABSO. Alkyl, alkenyl and (hetero)aryl sulfinates prepared from organolithium and Grignard reagents can be efficiently coupled with a range of electrophiles to access a range of products including diaryl, aryl-heteroaryl and β-hydroxy sulfones. <b>Chapter 3</b> describes an array-compatible, one-pot sulfonamide synthesis employing metal sulfinates and N-chloroamines as in situ-generated intermediates. This employs DABSO and sodium hypochlorite (bleach) as simple reagents and organolithium, organozinc and Grignard reagents along with amines as readily-accessible building blocks. The robust nature of this methodology and its potential application in discovery chemistry is demonstrated with a 65-compound array synthesis. <b>Chapter 4</b> documents the development of a palladium-catalysed sulfination reaction of boronic acids to access a range of sulfonyl-containing compounds. This involved the establishment of a one-pot/one step synthesis of sulfones leading to the discovery of a redox-neutral, ligand-free sulfination procedure using DABSO and palladium(II) catalysis. Sulfinic acid derivatives can be generated and subsequently trapped in situ with a variety of electrophiles to furnish sulfones and sulfonamides. <b>Chapter 5</b> summarises the research and the potential future work. <b>Chapter 6</b> provides experimental details and data.
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Perego, Luca Alessandro. "Transition metal-catalyzed reactions : mechanistic studies and methodology developments." Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLEE003/document.
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Dans cette thèse les mécanismes de trois réactions catalysées par des complexes de palladium et de cuivre ont été étudiés en utilisant des méthodes expérimentales et théoriques. La première réaction est la synthèse d’amides à partir d’halogénoarènes, d’isonitriles et d’eau, qui est un exemple de couplage catalysé par le palladium impliquant l’insertion d’un isonitrile. Cette dernière molécule sert à la fois de ligand et de substrat, et son influence sur chaque étape du cycle catalytique a été mise en évidence. La deuxième réaction est l’ouverture des benzofuranes conduisant à des dérivés indoliques catalysée par des sels de palladium. Les conditions opératoires ont été optimisées et les étapes clés du mécanisme ont été élucidées.La dernière réaction étudiée, qui est le sujet principal de cette thèse, est l’addition d’amines sur des allènes catalysée par des sels de cuivre (hydroamination). La caractérisation des espèces catalytiques de cuivre(I) et l’étude théorique du mécanisme ont permis d’étendre cette réaction à différents substrats (allénamides, N-allénylazoles, N-allénylsulfamides) dans des conditions particulièrement douces et efficaces<br>In this thesis, the mechanism of three organic reactions catalyzed by palladium and copper complexes has been elucidated by the use of both experimental and theoretical methods. The first reaction is the synthesis of amides from haloarenes, isocyanides and water as an example of the broad family of palladium-catalyzed imidoylative couplings. Multiple roles of the isocyanide as both a ligand and a substrate in the different steps of the catalytic cycle have been disclosed. The second transformation is the palladium-catalyzed ring opening of benzofurans leading to indoles. Optimal conditions for this transformation have been found and the key aspects of its mechanism clarified. The last reaction, which is the main topic of this thesis, is the addition of amines to allenes catalyzed by copper salts (hydroamination). A characterization of the catalytically active copper(I) species and insight from theoretical calculations suggested how to extend this reaction to other substrates (allenamides, N-allenylazoles, N-allenylsulfonamides) under mild and efficient conditions
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Truscott, Fiona Rosemary. "Transition metal catalysed C-C bond formation via C-H functionalisation." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:6a1ef296-8d63-470d-96bd-3e01a887c81f.
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The functionalisation of C-H bonds has been widely studied in organic synthesis. This work presents the results of investigation into two areas of current research, copper-catalysed aromatic C-H functionalisation and rhodium-catalysed hydroacylation. Chapter 1 presents the development of palladium- and copper-catalysed aromatic C-H functionalisation with particular attention paid to regiocontrol. Chapter 2 describes the development of copper-catalysed cross-coupling of perfluorinated arenes and alkenyl halides along with efforts to expand this methodology to a more general reaction. In Chapter 3 the development of chelation-controlled rhodium-catalysed hydroacylation is discussed. Chapter 4 outlines the utilisation of amino acid derived N-methylthiomethyl aldehydes in rhodium-catalysed hydroacylation methodology.
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Elliott, Mark Christopher. "Transition metal catalysis : application to the synthesis of novel heterocycles." Thesis, Loughborough University, 1994. https://dspace.lboro.ac.uk/2134/13422.
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Larabi, Cherif. "Surface organometallic chemistry on Metal Organic Frameworks (MOF) : synthesis, characterization and their application in catalysis." Thesis, Lyon 1, 2011. http://www.theses.fr/2011LYO10008/document.
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Les structures organométalliques poreuses (Metal Organic Framework, MOF) sont une nouvelle classe de matériaux, composées d'ions métalliques ou de clusters liés à des ligands organiques ou des complexes organométalliques dans des réseaux cristallins 1D, 2D ou 3D. Au cours de cette thèse la possibilité de construire de nouveaux MOF a été illustrée par le développement de matériaux MOF à base d’imidazolium, précurseur important pour la synthèse de catalyseurs. En outre, ce travail démontre l’utilité de la modification post-synthèse des MOFs par chimie organométallique de surface à visée catalytique : i) un MOF connu, UiO-66, avec des pores relativement petits a été fonctionnalisé avec un groupement amino et ses capacités d'adsorption de gaz ont été étudiées. ii) la synthèse de MOF a structure poreuse, CPO-27, MOF a été optimisée et utilisée comme précurseur pour produire un catalyseur d'hydrodésulfuration après l'introduction d'espèces actives, via la chimie organométallique de surface, dont les performances catalytiques ont été évaluées<br>Metal organic frameworks (MOF) are a new class of material, which consist of metal ions or clusters coordinated to organic ligands or metal-organic complexes and result in 1D, 2D or 3D crystalline networks. The possibility of constructing new MOF has been exemplified in this thesis by development of imidazolium based MOF, a highly important ligand system in catalysis. Moreover, this work has performed post synthesis modification via surface organometallic chemistry on existing MOF: i) a known MOF, UiO-66, with relatively small pores has been functionalized with amino group and its gas adsorption capacity has been investigated, ii) the syntheses of a 3D open structure MOF, CPO-27, MOFs have been optimized and used as a precursor to produce a hydrodesulfurization catalyst after introducing active species via surface organometallic chemistry approach, whose catalytic performances have been measured
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Shen, Di. "Transition metal catalyzed alkylation and synthesis of biotin derivatives." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:1467ba98-846c-46e6-9620-e4639ed07e43.
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<b>Transition Metal Catalyzed Alkylation</b> We have reported methodology for the use of methanol as an alkylation reagent using catalytic rhodium or iridium species for the formation of branched products from methyl ketones. The synthetic utility of the dialkylated products was enhanced by performing a regioselective Baeyer-Villiger oxidation which allowed access to ester products. A range of different phosphine ligands were screened, and sterically hindered and electron rich phosphine ligands were found to favour the formation of enone and methoxy adducts under an O2 atmosphere. This interrupted hydrogen borrowing reaction enabled the in situ addition of a nucleophile to give more complex products. A range of tetrasubsitituted pyridines were then synthesized from 1, 5-dicarbonyl compounds formed in the methylenation/conjugate addition sequence. Finally, deuteration experiments suggest that the reaction proceeds via a monohydride mechanism, and the possibilities for the beneficial effect of O2 were discussed. <b>Synthesis of biotin derivatives</b> The streptavidin-biotin system was chosen for the studies of protein/ligand interactions at molecular level. A series of modified biotin ligands were designed and synthesized to introduce repulsive interations with streptavidin. The protein/ligand complexes were analyzed at high resolution by X-ray crystallography.
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Brookings, Daniel Christopher. "The design, synthesis and application to asymmetric catalysis of chiral transition metal cyclopentadienyl complexes." Thesis, University of Southampton, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.273849.
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Leon, Robert. "Stereoselective Transition-Metal-Free Diboration of Alkenes." Thesis, Boston College, 2016. http://hdl.handle.net/2345/bc-ir:106845.
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Thesis advisor: James Morken<br>Boronates are extremely useful in synthesis due to the ability of carbon-boron bonds to be transformed into carbon-oxygen, carbon-nitrogen, or carbon-carbon bonds stereospecifically. This makes the stereoselective construction of carbon-boron bonds especially useful. The development of transition-metal catalyzed diboration of alkenes gave synthetic organic chemists a way to quickly make not one, but two carbon-boron bonds in a stereoselective fashion. However, there are many drawbacks to transition-metal catalysis, such as high cost of catalysts and chiral ligands, and air and moisture sensitivity of catalysts. These issues, in addition to difficulties in removing trace amounts of metal contaminants from reaction products have prevented transition-metal-catalysis from being used on the industrial scale. Discussed in this thesis are two different methods for stereoselective, transition-metal-free diboration of alkenes developed by the Morken group. Also discussed is the pioneering work in the area of transition-metal-free diboration done by the Fernández group, which inspired these methodologies<br>Thesis (BS) — Boston College, 2016<br>Submitted to: Boston College. College of Arts and Sciences<br>Discipline: Departmental Honors<br>Discipline: Chemistry
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Nama, Devendra Babu. "Synthesis, PGSE diffusion and multidimensional NMR studies on transition metal organometallic species : applications in coordination chemistry and homogeneous catalysis /." Zürich : ETH, 2007. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17177.
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Carson, Cantwell G. "Noble and transition metal aromatic frameworks synthesis, properties, and stability /." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29657.
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Thesis (Ph. D.)--Materials Science and Engineering, Georgia Institute of Technology, 2009.<br>Committee Chair: Rina Tannenbaum; Committee Co-Chair: Rosario A. Gerhardt; Committee Member: E. Kent Barefield; Committee Member: Karl I. Jacob; Committee Member: Preet Singh; Committee Member: R. Bruce King. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Hedberg, Christian. "Design, Synthesis, Mechanistic Rationalization and Application of Asymmetric Transition-Metal Catalysts." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-5740.
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Williams-Benjamin, Dilys. "New directions in early transition metal organometallic chemistry : the development of new high valent complexes for organic synthesis." Thesis, University of Newcastle Upon Tyne, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327246.
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Gonzalez-Santiago, Berenice. "Synthesis and properties of scandium carboxylate metal-organic frameworks." Thesis, University of St Andrews, 2015. http://hdl.handle.net/10023/6904.
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This work investigated the synthesis, characterisation and properties of known and novel scandium carboxylate Metal-organic Frameworks (MOFs). The first part reports the performance of these Sc-MOFs as Lewis acid catalysts. The porous MOF scandium trimesate MIL-100(Sc) and the scandium terephthalates such as MIL-101(Sc), MIL-88B(Sc) and MIL-68(Sc) (prepared as the Sc-analogue for the first time), and scandium biphenyldicarboxylate MIL-88D(Sc) were prepared and tested as Lewis acid catalysts. Chromium MIL-101 and MIL-100 and scandium-exchanged zeolites were prepared for comparison. Moreover, successful encapsulation of the phosphotungstate polyoxometalates (POMs) in the cavities of MIL-101(Sc) enhanced the stability of this material. These scandium and chromium MOFs, POM-MOF composites and scandium-exchanged zeolite were tested as heterogeneous catalysts in the carbonyl ene reaction between α-methyl styrene and ethyl trifluoropyruvate. This showed that MIL-100(Sc) was the best catalyst for this reaction, achieving a conversion of 99% to the desired product. The stabilized MIL-101(Sc) was also very active, but less selective for this reaction. Acetalisation of acetaldehyde was also studied, and in this reaction the isoreticular MOFs MIL-88(B) and MIL-88D(Sc) were the most active and selective catalysts. For this reaction, the activity of MIL-100(Sc) was low, which was attributed to reduce pore size and blockage. Functionalisation of the range of scandium terephthalates such as MIL-101(Sc), MIL-88B(Sc), MIL-68(Sc), Sc₂BDC₃,and MIL-53(Sc) particularly with –NH₂ groups, made up the second main part of this research. Solvothermal synthesis were performed at lower temperatures and using mixed solvents to synthesize these amino-terephthalate MOFs, often for the first time, and their adsorption properties were studied, particularly for the adsorption of CO₂. The synthesis of pure Sc₂(NH₂-BDC)₃ and Sc₂(Br-BDC)₃ was achieved for first time by a solvothermal route, lower temperatures, and mixed solvents. This approach yielded large crystals suitable for single crystal diffraction and microcrystal IR spectroscopy. Post-synthetic modification (PSM) of Sc₂(NH₂-BDC)₃ was explored by incorporation of NO₂-groups into the framework by solvent-assisted ligand exchange. The adsorption properties of functionalised and post-modified materials were compared with those of Sc₂BDC₃ and Sc₂(NO₂-BDC)₃ for methanol and hydrocarbons This study demonstrated that Sc₂BDC₃ and Sc₂(NH₂-BDC)₃ give the higher uptakes while the –Br and –NO₂ forms display shape selectivity for n-alkanes over iso-alkanes. Amino-functionalised MIL-53(Sc) was prepared for the first time using a mixed ligand approach, so that 10-20% of a second functionalised terephthalate ligand (NO₂, Br, -(OH)₂) was required for successful single phase synthesis in addition to amino-terephthalic acid. The materials were characterised using PXRD, TGA and gas adsorption, which confirms the samples show a range of behaviour for CO₂ adsorption. Notably, the `breathing´ behaviour is strongly dependent on the type of functionalisation. Finally, the exploratory synthesis of novel scandium MOFs, using isophthalic acid (IA) and its amino and nitro- derivatives, 2,5-furandicarboxylate (FDA) and the porphyrin tetra(carboxyphenyl)porphyrin (TCPP) as linkers was carried out and six novel materials were synthesized, three of which gave crystals large enough for their structure to be determined by single crystal diffraction. Further characterisation was carried out by PXRD, TGA and solid-state NMR. Some of these materials have been shown to be porous to CO₂ and N₂.
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Poole, Darren L. "Studies towards the nucleophilic dearomatisation of electron-deficient heteroaromatics and hydrogen borrowing reactions of methanol." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:d9b862ca-1680-42eb-b93b-a1a7d44e1a75.
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<strong>Introduction – Dearomatisation of Heteroaromatic Compounds</strong> The introduction provides a survey of dearomatisation reaction of heteroaromatics, with a particular focus on pyridines/pyridinium salts and furans. The mechanism, scope, and limitations of various approaches are covered, along with the goals of this project. <strong>Results and Discussion – Dearomatisation of Electron-Deficient Heteroaromatics</strong> This chapter initially explores the asymmetric addition of organometallic nucleophiles to pyridinium salts bearing a chiral counterion. Unfortunately, this approach ultimately proved unsuccessful, due to low observed enantioselectivities, and the low solubility of such salts. The second part of this chapter concerns the attempted asymmetric addition of dicarbonyl nucleophiles to electron-deficient furans, under conditions of chiral phase-transfer catalysts, affording bicyclic products in moderate enantioselectivity. Various alternative routes were also explored for the dearomatisation of furans and benzenoid systems. <strong>Introduction – Hydrogen Borrowing Alkylation Reactions with Alcohols</strong> The introduction surveys the range of methods available for the alkylation of various nucleophiles with alcohols under transition metal-catalysed conditions. Related methodologies are also explored, along with methods for the dehydrogenation of methanol. <strong>Results and Discussion - Rhodium-catalysed Methylation of Ketones Using Methanol</strong> This chapter describes the development of a novel ketone α-methylation using methanol. The development of reaction conditions is explored, followed by expansion of the substrate scope, including limitations of the methylation reaction. Mechanistic investigations support a methanol oxidation, aldol reaction/elimination, conjugate reduction pathway. Investigations into the role of O2 in the methylation reaction proved inconclusive. The utility of the reaction was also expanded via one-pot dialkylation reactions (work by Di Shen), Baeyer-Villiger oxidation of the products, and an attempted asymmetric transfer-hydrogenation. <strong>Results and Discussion - Interrupted Hydrogen Borrowing Reactions of Methanol</strong> This chapter looks to intercept intermediates from the α-methylation reaction. The selective methylenation of ketones is described, and a range of nucleophiles are screened for further functionalisation of ketones. Finally, a number of nucleophiles, including nitroalkanes, amines, peroxides and boronic acids are applied to one pot methylenation/conjugate addition protocols, affording complex products after two steps in one reaction vessel. <strong>Experimental</strong> Full experimental procedures and spectroscopic characterisation of compounds are provided.
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Kim, Jiyeon [Verfasser], Roland A. [Gutachter] Fischer, and Anjana [Gutachter] Devi. "Organometallic chemistry of transition metal-group 13 complexes and metal-organic precursor synthesis for ALD cobalt oxide thin films / Jiyeon Kim ; Gutachter: Roland A. Fischer, Anjana Devi." Bochum : Ruhr-Universität Bochum, 2017. http://d-nb.info/1144613949/34.
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Gallen, Ortiz Albert. "P-Stereogenic ligands with the tert-butylmethylphosphine fragment. Coordination chemistry and catalysis of their organometallic complexes." Doctoral thesis, Universitat de Barcelona, 2019. http://hdl.handle.net/10803/666577.
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The Thesis deals with the preparation, coordination chemistry and use in asymmetric homogeneous catalysis of several optically pure P-stereogenic ligands containing a tert-butylmethylphosphino fragment.
In the first part a highly stereoselective synthesis of the Secondary Phosphine Oxide (SPO) tert-butylmethylphosphine oxide is presented. Despite its simplicity, the stereoselective synthesis of this SPO had not been described in the literature. It is known that SPOs present a tautomeric equilibrium between the air-stable pentavalent form (phosphine oxide) and the trivalent form (phosphinous acid), usually completely shifted towards the pentavalent form but that can be displaced towards the phosphinous acid form by metal complexation. In the Thesis the complexation of the mentioned oxide towards Ru, Rh, Ir, Ni, Pd and Au has been explored, yielding a variety of coordination and organometallic compounds, with several coordination modes of the ligand. Some asymmetric catalytic applications of these species have also been studied, giving good conversions but low enantioselectivities.
In the second part of the Thesis, the C1-symmetric P-stereogenic ligand MaxPhos has been coordinated to [MCp*Cl] (M = Rh and Ir) and [Ru(p-cymene)Cl] fragments, yielding cationic M-stereogenic organometallic compounds as tetrafluoroborate or hexafluorophosphate salts. Interestingly, in all cases a single stereoisomer has been formed, as confirmed by NMR and X-ray crystallography. This has been rationalised by steric grounds. For Ir, the abstraction of the remaining chloride ligand by silver salts produced a diastereoselective C–H activation of a tert-butyl group of the ligand. The complexes have been used in transfer hydrogenation giving good activities but no enantioselectivities.
Finally the third part of the Thesis is devoted to the cyclometallation of [Ir(MaxPHOX)COD]BArF complexes (MaxPHOX stands for a type of P,N phosphinooxazoline ligand recently described by our group having three stereogenic centres) by several ligands under hydrogen atmosphere. It has been found that cyclometallated Ir(III)-hydrido complexes are formed, which are very stable and have been characterised thoroughly. They have been used in asymmetric hydrogenation of N-alkylimines, giving in general complete conversions and very high enantioselectivities (up to 96% ee) for these substrates, which rank among the best described to date. The mechanism of the reaction has been studied and the stereochemical outcome rationalised by means of DFT-based computational methods.<br>La Tesi presenta la preparació, coordinació i ús en catàlisi homogènia asimètrica d’una varietat de lligands P-estereogènics òpticament purs que contenen el grup tert- butimetilfosfina.
A la primera part es presenta la síntesi, altament estereoselectiva, de l’òxid de fosfina secundari (SPO) òxid de tert-butilmetilfosfina. Malgrat la simplicitat d’aquest compost, no se n’havia descrit la síntesi de forma estereoselectiva a la bibliografia. Se sap que els SPOs presenten un equilibri tautomèric entre la forma pentavalent estable a l’aire (òxid de fosfina) i la forma trivalent (àcid fosfinós). Habitualment aquest equilibri es troba totalment desplaçat envers la forma pentavalent però es pot desplaçar cap a l’àcid fosfinós per complexació amb un metall. A la Tesi, s’ha estudiat la complexació de l’òxid esmentat a Ru, Rh, Ir, Ni, Pd i Au i ha donat una gran varietat de compostos de coordinació i organometàl·lics, en els quals el lligand presenta una varietat de modes coordinació. També s’han explorat algunes aplicacions catalítiques d’aquestes espècies i s’han trobat bones conversions però baixes enantioselectivitats.
A la segona part de la Tesi el lligand P-estereogènic de simetria C1 MaxPhos s’ha coordinat a fragments [MCp*Cl] (M = Rh o Ir) i [Ru(p-cimè)Cl] i ha donat compostos organometàl·lics catiònics M-estereogènics en forma de sals de tretrafluoroborat o hexafluorofosfat. És interessant destacar que estudis de RMN i cristal·lografia de raigs X han demostrat que en tots els casos s’ha format un sol estereoisòmer, fet que s’ha racionalitzat per arguments estèrics. En el cas del Ir, la abstracció del lligand cloruro amb sals de plata ha provocat l’activació de l’enllaç C–H d’un grup tert-butil de lligand en forma diastereoselectiva. Tots els compostos preparats s’han utilitzat en transferència d’hidrogen asimètrica i han donat bones activitats però enantioselectivitats baixes.
Finalment, la tercera part de la Tesi està dedicada a la ciclometal·lació de complexos [Ir(MaxPHOX)COD)BArF amb diferents lligands auxiliars sota atmosfera d’hidrogen, on MaxPHOX és un lligand P,N de tipus fosfinooxazolina que el nostre grup de recerca ha descrit recentment i que conté tres centres estereogènics. S’ha observat la formació de complexos ciclometal·lats Ir(III)-hidrur molt estables, que s’han caracteritzat exhaustivament. Aquests complexos s’han usat com a catalitzadors per la reacció d’hidrogenació asimètrica d’imines alquíliques i ha donat conversions completes i enantioselectivitats de fins el 96% d’ee, que es troben entre els millors que s’han descrit mai per a aquests tipus de substrats. S’ha estudiat el mecanisme de la reacció i el curs estereoquímic, que s’ha racionalitzat mitjançant mètodes computacionals de tipus DFT.
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Huang, Yan. "Synthesis, Kinetic and Photocatalytic Studies of Porphyrin-Ruthenium-Oxo Complexes." TopSCHOLAR®, 2010. http://digitalcommons.wku.edu/theses/182.
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Macrocyclic ligand-complexed transition metal-oxo intermediates are the active oxidizing species in a variety of important biological and catalytic oxidation reactions. Many transition metal catalysts have been designed to mimic the predominant oxidation catalysts in Nature, namely the cytochrome P450 enzymes. Ruthenium porphyrin complexes have been the center of the research and have successfully been utilized, as catalysts, in major oxidation reactions such as the hydroxylation of alkanes. This study focuses on kinetic and photocatalytic studies of oxidation reactions with wellcharacterized high-valent ruthenium-oxo porphyrin complexes. The trans-dioxoruthenium(VI) porphyrins have been among the best characterized metal-oxo intermediates and their involvement as the active oxidant in the hydrocarbon oxidation have been extensively studied. Following the literature known methods, a series of trans-dioxoruthenium(VI) porphyrin complexes (3a-b) were synthesized and spectroscopically characterized by UV-vis, IR and lH-NMR. In addition to the well-known chemical methods, we developed a novel photochemical approach for generation of trans-dioxoruthenium(VI) porphyrins with visible light. The fast kinetic study of two-electron oxidations of para-substituted phenyl methyl sulfides by these dioxoruthenium(VI) species was conducted by using stopped-flow spectroscopy. Results showed that the decay of trans--dioxoruthenium(VI) porphyrins in the presence of reactive sulfides follows a biexponential process. The reactivity order in the series of dioxoruthenium complexes follows TPFPP> TPP> TMP, consistent with expectations based on the electrophilic nature of high-valent metal-oxo species. Moreover, the sulfoxidation reactions are 3 to 4 orders of magnitude faster than the well-known epoxidation reactions. In addition, several ruthenium porphyrins were used as the catalysts in the competitive oxidation reactions to identify the kinetically competent oxidants during catalytic turnover conditions. The photocatalytic studies of aerobic oxidation reactions of hydrocarbons catalyzed by a bis-porphyrin-ruthenium(lV) fl-OXO dimer using atmospheric oxygen as oxygen source in the absence of co-reductants were investigated as well. The ruthenium(lV) fl-OXO bisporphyrin (6a) was found to catalyze aerobic oxidation of a variety of organic substrates efficiently. By comparison, 6a was found to be more efficient photocatalyst than the well-known 3a under identical conditions. A KIE at 298K was found to be larger than those observed in autoxidation processes, suggesting a nonradical mechanism that involved the intermediacy of ruthenium(V)-oxo species as postulated.
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Pearce, Gordon M. "Synthesis, adsorption and catalysis of large pore metal phosphonates." Thesis, University of St Andrews, 2010. http://hdl.handle.net/10023/823.
Full textAbstract:
The synthesis and properties of metal phosphonates prepared using piperazine-based bisphosphonic acids have been investigated. The ligands N,N’-piperazinebis(methylenephosphonic acid) (H₄L), and the 2-methyl (H₄L-Me) and 2,5-dimethyl (H₄L 2,5-diMe) derivatives have been prepared using a modified Mannich reaction. Hydrothermal reaction of gels prepared from metal (II) acetates and the bisphosphonic acids results in the synthesis of four structures: STA-12, Ni VSB-5, Co H₂L.H₂O and Mg H₂L. STA-12, synthesised by reaction of Mn, Fe, Co or Ni acetate with H₄L or H₄L-Me, has been investigated further. STA-12 crystallises in the space group R⁻₃, and Ni STA-12 is the most crystalline version. Its structure was solved from synchrotron data (a = b = 27.8342(1) Å, c = 6.2421(3) Å, α = β = 90°, γ = 120°), and it has large 10 Å hexagonal shaped pores. Helical chains of Ni octahedra are coordinated by the ligands, resulting in phosphonate tetrahedra pointing towards the pore space. Water is present, both coordinated to the Ni²⁺ cations and physically adsorbed in the pores. Mixed metal structures based on Ni STA-12, where some Ni is replaced in the gel by another divalent metal (Mg, Mn, Fe or Co) can also be synthesised. Dehydration of STA-12 results in two types of behaviour, depending on the metal present. Rhombohedral symmetry is retained on dehydration of Mn and Fe STA-12, the a cell parameter decreasing compared to the as-prepared structures by 2.42 Å and 1.64 Å respectively. Structure solution of dehydrated Mn STA-12 indicates changes in the torsion angles of the piperazine ring bring the inorganic chains closer together. Fe and Mn STA-12 do not adsorb N₂, which is thought to be due to the formation of an amorphous surface layer. Dehydration of Ni and Co STA-12 causes crystallographic distortion. Three phases were isolated for Ni STA-12: removal of physically adsorbed water results in retention of rhombohedral symmetry, while dehydration at 323 K removes some coordinated water forming a triclinic structure. A fully dehydrated structure (dehydrated at 423 K) was solved from synchrotron data (a = 6.03475(5) Å, b = 14.9156(2) Å, c = 16.1572(7) Å, α = 112.5721(7)°, β = 95.7025(11)°, γ = 96.4950(11)°). The dehydration mechanism, followed by UV-vis and Infra-red spectroscopy, involves removal of water from the Ni²⁺ cations and full coordination of two out of three of the phosphonate tetrahedra forming three crystallographically distinct Ni and P atoms. No structural distortion takes place on dehydration of Ni and Co STA-12 prepared using the methylated bisphosphonate, and the solids give a higher N₂ uptake as a result. Dehydrated Ni and Co STA-12 were tested for adsorption performance for fuel related gases and probe molecules. Investigations were undertaken at low temperature with H₂, CO and CO₂, and ambient temperature with CO₂, CH₄, CH₃CN, CH₃OH and large hydrocarbons. Due to the presence of lower crystallinity, Co STA-12 has an inferior adsorption performance to Ni STA-12, although it has similar adsorption enthalpies for CO₂ at ambient temperature (-30 to -35 kJ mol⁻¹). Ni STA-12 adsorbs similar amounts of CO₂ and N₂ at low temperature, indicating the adsorption mechanisms are similar. Also, it adsorbs 10 × more CO₂ than CH₄ at low pressure, meaning it could be used for separation applications. Ni STA-12 adsorbs 2 mmol g⁻¹ H₂ with an enthalpy of -7.5 kJ mol⁻¹, the uptake being due to adsorption on only one-third of the Ni²⁺ cations. The uptake for CO is 6 mmol g⁻¹, with adsorption enthalpies ranging from -24 to -14 kJ mol⁻¹. This uptake is due to adsorption on all the Ni²⁺, meaning the adsorption enthalpies are high enough to allow the structure to relax. This is also observed for adsorption of CH₃CN and CH₃OH, where there is a return to rhombohedral symmetry after uptake. The adsorption sites in dehydrated Ni and Co STA-12 were investigated via Infra-red spectroscopic analysis of adsorbed probe molecules (H₂, CO, CO₂, CH₃CN and CH₃OH). The results indicate the adsorption sites at both low and ambient temperature are the metal cations and the P=O groups. The metal cation sites are also characterised as Lewis acids with reasonable strength. STA-12 was shown to have acidic activity for the liquid phase selective oxidations of 1-hexene and cyclohexene, although there is evidence active sites are coordinated by products and/or solvents during the reaction. STA-12 also demonstrates basic activity for the Knoevenagel condensation of ethyl cyanoacetate and benzaldehyde. Modification of STA-12 by adsorption of diamine molecules causes a slight increase in the basicity, and the highest conversions are where water and diamine molecules are both present.
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González, Miera Greco. "Homogeneous and heterogeneous Cp*Ir(III) catalytic systems : Mechanistic studies of redox processes catalyzed by bifunctional iridium complexes, and synthesis of iridium-functionalized MOFs." Doctoral thesis, Stockholms universitet, Institutionen för organisk kemi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-143343.
Full textAbstract:
The purpose of this doctoral thesis is to investigate and develop catalytic processes mediated by iridium(III) complexes. By understanding the mechanisms, the weaknesses of the designed catalysts can be identified and be overcome in the following generation. The thesis is composed of two general sections dedicated to the synthesis and applications of homogeneous catalysts and to the preparation of heterogeneous catalysts based on metal-organic frameworks (MOFs). After a general introduction (Chapter 1), the first part of the thesis (Chapters 2-4, and Appendix 1) covers the use of several homogeneous bifunctional [Cp*Ir(III)] catalysts in a variety of chemical transformations, as well as mechanistic studies. Chapter 2 summarizes the studies on the N-alkylation of anilines with benzyl alcohols catalyzed by bifunctional Ir(III) complexes. Mechanistic investigations when the reactions were catalyzed by Ir(III) complexes with a hydroxy-functionalized N-heterocyclic carbene (NHC) ligand are discussed, followed by the design of a new generation of catalysts. The chapter finishes presenting the improved catalytic performance of these new complexes. A family of these NHC-iridium complexes was evaluated in the acceptorless dehydrogenation of alcohols, as shown in Chapter 3. The beneficial effect of a co-solvent was investigated too. Under these base-free conditions, a wide scope of alcohols was efficiently dehydrogenated in excellent yields. The unexpected higher activity of the hydroxy-containing bifunctional NHC-Ir(III) catalysts, in comparison to that of the amino-functionalized one, was investigated experimentally. In the fourth chapter, the catalytic process presented in Chapter 3 was further explored on 1,4- and 1,5-diols, which were transformed into their corresponding tetrahydrofurans and dihydropyrans, respectively. Mechanistic investigations are also discussed. In the second part of the thesis (Chapter 5), a Cp*Ir(III) complex was immobilized into a MOF. The heterogenization of the metal complex was achieved efficiently, reaching high ratios of functionalization. However, a change in the topology of the MOF was observed. In this chapter, the use of advanced characterization techniques such as X-ray absorption spectroscopy (XAS) and pair distribution function (PDF) analyses enabled to study a phase transformation in these materials.<br><p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Submitted.</p>
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Binding, Samantha Carys. "Synthesis and characterisation of permethylpentalene complexes and permethylpentalene derivatives." Thesis, University of Oxford, 2015. http://ora.ox.ac.uk/objects/uuid:7855e90d-7ce9-42eb-b962-b68606ade746.
Full textAbstract:
This thesis expands the scope for using the permethylpentalene ligand and its precursors in the synthesis of organometallic complexes. <strong>Chapter one</strong> begins with a brief review of linked metallocenes, with which multimetallic compounds bridged by pentalene ligands have often been compared, followed by a comprehensive review of the routes used to make pentalenes and substituted pentalenes. Organometallic compounds of pentalenes are introduced, with a focus on bimetallic systems. <strong>Chapter two</strong> explores the diversification of substituents added to the permethylpentalene (Pn*) precursor WeissH<sub>4</sub>, to include ethyl and isopropyl groups. Low-symmetry mono-, di-, tri- and tetraalkylated products are formed, eight such organic molecules have been identified by NMR spectroscopy, and two characterised crystallographically. It has been demonstrated that subsequent hydrolysis and decarboxylation of two of these products produces low-symmetry alkylpentalene precursors. The chapter concludes with discussions on the selectivity exhibited in these reactions, and the assignment of stereochemistry. <strong>Chapter three</strong> describes the synthesis of the first homoleptic double metallocene complex of iron. Fe<sub>2</sub>Pn*<sub>2</sub> has been characterised by X ray diffraction, and cyclic voltammetry studies demonstrate four accessible oxidation states (-1, 0, +1, +2). Magnetic measurements in the solid and solution state reveal an unusual triplet configuration, and DFT calculations indicate the origin of a high magnetic moment likely resides in unquenched orbital angular momentum contributions from SOMOs which have metal d character. Fe<sub>2</sub>Pn*<sub>2</sub> is EPR silent at 5, 40, and 300 K both in solution and the solid state, suggesting a large zero-field splitting parameter. The reaction of the di-iron complex with carbon monoxide, ethylene and H2 is reported; the bimetallic CO adduct, Fe<sub>2</sub>(μ η<sup>5</sup>,η<sup>3</sup> Pn*)(μ η<sup>5</sup>,η<sup>1</sup> Pn*)(CO)<sub>2</sub>, has been crystallographically characterised, and contains a highly distorted allylic bonding motif, which to the author’s knowledge is believed to be unique among iron complexes. <strong>Chapter four</strong> discusses the interaction of the bidentate Pn* ligand in anti bimetallic fused metallocenes. A new ligand exchange route has been developed to access the complexes (MCp)<sub>2</sub>Pn* (M = Co, Ni), and the isostructural complexes (MCp*)<sub>2</sub>Pn* have been made for M = Fe, Co, Ni by salt metathesis reactions. All five complexes have been characterised by single crystal X-ray crystallography, and have diamagnetic ground states in solution in common with their Pn bridged analogues. Variable temperature NMR studies reveal a spin-equilibrium between S = 0 and S = 1 in the dinickel complexes. DFT calculations reproduce the spin states found, and suggest the distortion towards η<sup>3</sup> coordination observed on crossing from Fe, to Co, to Ni, results from population of orbitals with M―bridgehead antibonding character. The electronic structures show it is important to draw comparisons between isoelectronic linked metallocenes. Electrochemical studies on the diiron, dicobalt, and (NiCp)<sub>2</sub>Pn* complexes reveal at least three redox events for each. <strong>Chapter five</strong> documents the successful synthesis and characterisation of monometallic complexes of iron and manganese with Pn*H ligands. The isostructural complexes Fe(Pn*H)<sub>2</sub> and Mn(Pn*H)<sub>2</sub> can have been characterised crystallographically, and are potential precursors for accessing heterometallic, and multimetallic complexes. Mn(Pn*H)<sub>2</sub> is a rare example of a manganese sandwich compound and magnetic studies on a single isomer in the solution and solid states suggest it adopts intermediate spin states of S = 2 in solution, and S = 3/2 in the solid state. <strong>Chapter six</strong> gives experimental details for all syntheses and studies described in the preceding chapters. <strong>Chapter seven</strong> provides characterising data for all new compounds. Fitting data for VT NMR and SQUID studies are provided in the <strong>appendix</strong> at the end of this thesis. Crystallographic data in the form of .cif files, DFT output files, and raw SQUID data, can be found in the <strong>electronic appendix</strong>.
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Spinella, Stephen. "Transition metal catalysis for organic synthesis." 2009. http://hdl.rutgers.edu/1782.2/rucore10001600001.ETD.000051912.
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(6847970), Jacob J. Werth. "TRANSITION METAL CATALYZED SIMMONS–SMITH TYPE CYCLOPROPANATIONS." Thesis, 2019.
Find full textAbstract:
<div>Cyclopropanes are commonly found throughout synthetic and natural biologically active compounds. The Simmons–Smith cyclopropanation reaction is one of the most useful methods for converting an alkene into a cyclopropane. Zinc carbenoids are the active intermediate in the reaction, capable of delivering the methylene unit to a broad variety of substrates. Significant advances have been made in the field to increase overall efficiency of the reaction including the use of diethyl zinc as a precursor and allylic alcohols as directing groups.</div><div>Despite the many notable contributions in zinc carbenoid chemistry, persistent limitations of the Simmons–Smith reaction still exist. Zinc carbenoids exhibit poor steric discrimination in the presence of a polyolefin with minimal electronic bias. Additionally, due to the electrophilic nature of zinc carbenoid intermediates, the reaction performs inefficiently with electron-deficient olefins. Finally, alkyl-substituted zinc carbenoids are known to be quite unstable, limiting the potential for substituted cyclopropanation reactions.</div><div>In this work, we demonstrate that cobalt catalysis can be utilized to access novel cyclopropane products through the activation of dihaloalkanes. The content of this thesis will focus on the limitations of Zn carbenoid chemistry and addressing them with cobalt catalyzed, reductive cyclopropanations. In addition to this reactivity, we also demonstrate the dimethylcyclopropanation of activated alkenes to furnish valuable products applicable to natural product synthesis and pharmaceutically relevant compounds. Finally, we will show the unique character of the cobalt catalyzed cyclopropanation reaction through mechanistic experiments and characterization of reaction intermediates. In whole, these studies offer a complementary method to zinc carbenoid chemistry in producing novel and diverse cyclopropane products.</div>
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Holtz-Mulholland, Michael. "Synthesis of transition metal N-heterocyclic carbene complexes and applications in catalysis." Thèse, 2014. http://hdl.handle.net/1866/11407.
Full textAbstract:
Les ligands de carbènes N-hétérocycliques (NHC) qui possèdent une symétrie C1 attirent beaucoup l’attention dans la littérature. Le présent projet de recherche propose de synthétiser une nouvelle série de ligands NHC C1-symétriques avec deux groupements N-alkyles qui exploitent un relais chiral. Un protocole modulaire et efficace pour la synthèse des sels d’imidazolium chiraux qui servent comme préligands pour les NHC a été développé. Quelques-uns de ces nouveaux ligands ont été installés sur le cuivre et de l’or, créant de nouveaux complexes chiraux.
Les nouveaux complexes à base de cuivre ont été évalués comme catalyseurs pour le couplage oxydatif de 2-naphthols. Les ligands C1-symmétriques ont fourni des meilleurs rendements que les ligands C2-symmétriques. Au cours de l’optimisation, des additifs ont été évalués; les additifs à base de pyridine ont fourni des énantiosélectivités modérées tandis que les additifs à base de malonate ont donné des meilleurs rendements de la réaction de couplage oxydatif.
Ultérieurement, les additifs à base de malonate ont été appliqués envers l’hétérocouplage de 2-naphthols. Le partenaire de couplage qui est riche en électrons est normalement en grand excès à cause de sa tendance à dégrader. Avec le bénéfice de l’additif, les deux partenaires de couplage peuvent être utilisés dans des quantités équivalentes. La découverte de l’effet des additifs a permis le développement d’un protocole général pour l’hétérocouplage de 2-naphthols.<br>A new class of C1-symmetric N-heterocyclic carbene (NHC) ligands has been developed. The new ligands exploit a biaryl methyne as a chiral relay, and an N-methyl group as a reactivity controlling element. The precursors for the new ligands were synthesized via a modular scheme that allows for facile diversification. Several of the new ligands were installed onto both copper and gold, generating mono N-heterocyclic carbene transition metal complexes.
The new C1-symmetric copper complexes were tested as catalysts for the synthesis of binaphthols via the oxidative coupling of electron poor 2-naphthols. The new C1-symmetric ligands afforded higher yields than their C2-symmetric counterparts. During the course of the optimization, small molecule additives were found to modulate the reactivity of the copper catalyst. Pyridine additives, such as 2-picoline, were found to induce low to moderate enantioselectivity in the oxidative coupling reaction, while diethylmalonate was found to improve the reaction yield without affecting the selectivity.
The malonate additive was employed in the catalytic oxidative heterocoupling of electronically dissimilar 2-naphthols. The electron-rich coupling partner is normally added in a large excess due to its tendency to degrade. When the malonate additive is used, the coupling partners can be used in equimolar quantities. The discovery resulted in the development of a general protocol for the additive assisted aerobic oxidative heterocoupling of electronically dissimilar 2-naphthols.
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Tsui, Chit. "New Synthetic Applications of Rhodium-Catalyzed Carbon-Carbon and Carbon-Heteroatom Bond Forming Reactions." Thesis, 2013. http://hdl.handle.net/1807/36019.
Full textAbstract:
This thesis is divided into four chapters that describe the new development in rhodium-catalyzed addition reactions and asymmetric ring opening (ARO) reactions of strained alkenes.
Chapter 1 describes a regioselective Rh(I)-catalyzed addition reaction of arylboronic acids to unactivated alkenes - protected allylic amines and allyl sulfones. These formal hydroarylation processes have significantly advanced the substrate scope. Comprehensive studies were carried out to optimize the reaction conditions and a wide range of arylboronic acids were employed. The reaction was found to be linear-selective and a mechanism based on functional group- directing effects has been proposed.
Chapter 2 discloses the discovery of Rh(I)-catalyzed addition of arylboronic acids to (benzyl- /arylsulfonyl)acetonitriles. Novel β-sulfonylvinylamine products were formed in a stereoselective fashion (Z-alkene). Upon hydrolysis, β-keto sulfones were obtained with a broad scope of aryl and sulfonyl substituents. These (Z)-β-sulfonylvinylamines were useful synthons in the synthesis of unsymmetrical polysubstituted pyridines via 1-aza-allyl anion intermediates as well as 1,4- benzothiazine derivatives via intramolecular cyclization. Chapter 3 reports the use of two new nucleophiles in Rh(I)-catalyzed ARO of oxabicyclic alkenes - water and triethylamine trihydrofluoride. In the water-induced ARO, an unprecedented domino ARO/isomerization process was discovered which led to the formation of 2-hydroxy-1- tetralones. By modifying the reaction conditions, trans-1,2-diols can be obtained in excellent enantioselectivity. Using triethylamine trihydrofluoride as a nucleophile, an aliphatic C-F bond was constructed enantioselectively in the ring-opening process which provided fluorinated building blocks containing both allylic fluoride and fluorohydrin units.
Finally, Chapter 4 details the development of a one-pot synthesis of a chiral dihydrobenzofuran framework using Rh-catalyzed asymmetric ring opening and Pd-catalyzed C-O coupling. The product can be obtained in excellent enantioselectivity without isolation of intermediates. Systematic metal-ligand studies were carried out to investigate the compatibility of each catalytic system using product enantiopurity as an indicator.
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Yeung, Charles See Ho. "Transition Metal Catalysis: Activation of CO2, C–H, and C–O Bonds En Route to Carboxylic Acids, Biaryls, and N-containing Heterocycles." Thesis, 2011. http://hdl.handle.net/1807/31986.
Full textAbstract:
Transition metal catalysis is a powerful tool for the construction of biologically active and pharmaceutically relevant architectures. With the challenge of continually depleting resources that this generation of scientists faces, it is becoming increasingly important to develop sustainable technologies for organic synthesis that utilize abundant and renewable feedstocks while minimizing byproduct formation and shortening the length of synthetic sequences by removing unnecessary protecting group manipulations and functionalizations. To this end, we have developed four new methods that transform inexpensive starting materials to valuable products. This dissertation covers the following key areas: 1) activation of CO2 for a mild and functional group tolerant synthesis of carboxylic acids, 2) oxidative twofold C–H bond activations as a strategy toward biaryls, 3) migratory O- to N-rearrangements in pyridines and related heterocycles for the preparation of N-alkylated heterocycles, and 4) asymmetric hydrogenations of cyclic imines and enamines en route to chiral 1,2- and 1,3-diamines and macrocyclic peptides.
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(11197530), Matthew C. Hewitt. "Redox Active Ligands To Facilitate Reactivity From Redox Restricted Metals." Thesis, 2021.
Find full textAbstract:
The synthesis of
metal-redox active ligand complexes is described, along with reactivity studies
aimed at facilitating novel C-N bond forming reactions. A copper
bis(iminosemiquinone) structure is characterized, analyzed and its reduction
series are characterized and the reactivity of the Cu(II) bis(amidophenolate)
analog is investigated with tosyl azide. The identification of the major
reaction product and its characterization is detailed, with reaction
sensitivities and heavily distorted x-ray diffraction single crystal structure
generating a complex data set. The characterization of the isolated product is
ongoing, with EPR studies aimed at identifying the radical nature of the
complex. Unusual solvent effects and solubility issues have been noted with
these initial EPR studies and more data is necessary before analysis can be
properly attempted. An ytterbium bis(amidophenolate) complex was synthesized
and its reactivity studied with aryl azides. Initial reactivities generate the
first documented lanthanide tetrazenes in-lieu of the targeted ytterbium imido.
Reactivities and characterization of these complexes support a stable, heavily
ionic tetrazene-metal complex with no observed redox nature, UV light
sensitivities, or imido azide-tetrazene equilibrium observed in various
tetrazene transition metal complexes. Synthesis of a sterically blocked ytterbium
imido was attempted, utilizing DMAP. Initial isolation was achieved with
characterization and reactivity studies supporting the imido nature of the
complex. The weak coordinating of the DMAP provided instability that proved in
opposition to crystallization, however, so the imido could not be confirmed.
Initial reactions using alternative steric hinderance from triphenylphosphine
oxide and pyridine N-oxide prove promising to increasing the stability of the
presumed ytterbium imido. Organic synthesis was performed generating a
potential antibacterial agent. The synthesis of cyclopropenes was initiated as
antagonists for ETR proteins in fruits and plants. The intermediates proved
highly sensitive to harsh chemical conditions, which was overcome utilizing a
tin-mediated Barbier allylation. The cyclopropene alcohol synthon was
synthesized, though protecting group optimization is necessary.