Dissertations / Theses: 'Acid catalyzed reactions'

1

Knol, Jochem. "Chiral Lewis acid catalyzed Diels-Alder reactions." [S.l. : [Groningen : s.n.] ; University of Groningen] [Host], 2008. http://irs.ub.rug.nl/ppn/.

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晏意隆 and Yi-long Yan. "Lewis acid-catalyzed atom transfer radical cyclization reactions." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2003. http://hub.hku.hk/bib/B31245018.

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Sanders, Shanina Devondia Brookhart Maurice S. "Lewis acid-catalyzed cycloaddition reactions of donor-acceptor cyclopropanes." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2009. http://dc.lib.unc.edu/u?/etd,2534.

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Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2009.
Title from electronic title page (viewed Oct. 5, 2009). "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Chemistry." Discipline: Chemistry; Department/School: Chemistry.

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4

Payard, Pierre-Adrien. "Mechanistic studies of metal-catalyzed reactions : predicting tools for reaction optimization." Thesis, Paris Sciences et Lettres (ComUE), 2019. http://www.theses.fr/2019PSLEE009/document.

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Cette thèse est consacrée à l’étude de mécanismes de réactions catalysées par des métaux ainsi qu’au développement de nouveaux outils pour la rationalisation et la prévision du comportement catalytique. L’étape de transmétallation entre le bore et le nickel a été étudiée en détail à l’aide de méthodes expérimentales variées (electrochimie, RMN, cinétiques) et par DFT, permettant d’expliquer certaines limitations rencontrées par les experimentateurs. La seconde partie de cette thèse est dédiée à la rationalisation du comportement d’une famille d’acides de Lewis : les sels de triflate et de triflimidate. Leur comportement a été étudié sur des réactions modèles d’amination et d’oxidation et une nouvelle échelle théorique d’acidité de Lewis basée sur l’estimation du transfert de charge vers l’acide à permis de reproduire et prévoir l’activité catalytique
In this thesis mechanistic studies of metal-catalyzed reactions as well as development of new tools to predict and rationalize the catalytic properties are presented. The boron-tonickel transmetalation step was thoroughly studied by experimental technics (electrochemistry, NMR, kinetics) and DFT calculations, allowing us to solve some of the limitation encountered by the synthetic chemists. In the second part of this thesis the behavior of a family of Lewis acids (triflates and triflimides) is rationalize. Two model reactions (SN and redox) were studied and a new theoretical scale of Lewis acidity was developed based on the charge transferred to the acid allowing us to reproduce and predict the catalytic activity of these salts

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Kaplan, Matthew Jon. "Chiral Phosphoric Acid-Catalyzed Acetalization and Iso-Pictet-Spengler Reactions." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4515.

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The development of novel asymmetric reaction methodologies has been invaluable in both the academic and industrial world. In just 15 years, organocatalysis has provided a new means of developing asymmetric reaction methodologies using catalysts that are environmentally benign, relatively inexpensive, bench stable, and non-toxic. One development in organocatalysis that is important to our group in particular is chiral phosphoric acid-catalysis. BINOL-derived and VAPOL-derived phosphoric acids have proven to be excellent catalysts for a number of reactions. The two projects I will discuss my efforts on are acetalization and iso-Pictet-Spengler reactions. These were projects that I performed during my first two years as a graduate student. The acetalization was particularly fascinating as only one literature report existed for the catalytic asymmetric variant of a reaction that makes such important compounds--O,O-acetals. The acetalization reaction proved to be a formidable opponent, and to this date no research report has been published documenting the intra-, or intermolecular catalytic asymmetric acetalization of vinyl ethers or the intermolecular catalytic asymmetric transacetalization. The iso-Pictet-Spengler reaction is one that is interesting because exhaustive research has been conducted into the development of catalytic asymmetric Pictet-Spengler reactions, but at the time of my research, not a single catalytic asymmetric method existed to synthesize tetrahydro-γ-carbolines, the product of the iso-Pictet-Spengler reaction. Structurally, the tetrahydro-γ-carboline is isomeric to the tetrahydro-β-carboline, the product of the Pictet-Spengler reaction. They differ only in the position of nitrogen in the annulated product. This reaction seemed attractive to investigate, since independent elegant reports by Professors Benjamin List, Henk Hiemstra, and Darren Dixon documented the excellent control over enantioselectivity that chiral phosphoric acid have in the Pictet-Spengler reaction. Concurrent with the beginning stages of this project, Professor Eric Jacobsen reported the enantioselective thiourea-catalyzed iso-Pictet-Spengler reaction. The results were very good but not as great as the Pictet-Spengler work he pioneered. Around the time this report came out I commenced my reaction studies, and this thesis is the sum of just two projects I worked on. There were many more including halolactonization, VAPOL synthesis, chiral phosphoric acid synthesis, catalytic asymmetric hydroamination, and others.

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Zheng, Baofu. "Lewis acid-catalyzed asymmetric atom and group transfer radical cyclization reactions." Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B3625812X.

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Zheng, Baofu, and 鄭保富. "Lewis acid-catalyzed asymmetric atom and group transfer radical cyclization reactions." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B3625812X.

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Sandrin, Franco. "Lewis acid catalyzed reactions of 1-benzyl-2, 5-bis (trimethylsiloxy) pyrrole." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66047.

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9

Rendina, Victor L. "Development of Lewis Acid Catalyzed Asymmetric Ring Expansion Reactions and Catalysis of Etherification Reactions with sp3 Electrophiles." Thesis, Boston College, 2013. http://hdl.handle.net/2345/3041.

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Thesis advisor: Marc L. Snapper
Chapter 1: Over the past 100 years, ring expansion chemistry with non-stabilized diazoalkanes has grown slowly. While the intrinsic hazards and stigma associated with the use of diazoalkanes has been a serious impediment to more widespread development, a number of groups have made significant advances over the years. This chapter aims to provide a brief historical account of the most significant developments related to diazoalkane- based ring expansion methods. Chapter 2: The construction of stereogenic centers adjacent to ketones remains a challenging synthetic problem for chemists. Deficiencies with regard to reaction scope, efficiency, and generality remain. In contrast to the majority of other methods in the literature, stereoselective insertion of diazoalkanes provides a pathway to directly access enantiomerically enriched α-substituted cycloalkanones. In this chapter, an account of how we developed the first catalytic asymmetric diazoalkane-based ring expansion reactions is presented. Ring expansion of unfunctionalized cycloalkanones with diazoalkanes efficiently affords α-aryl substituted cycloalkanones with high enantiopurity. Additionally, this work led to the synthesis of new chiral bis(oxazoline) ligands and the discovery of a rapid method to assay the concentration of diazoalkane solutions. Chapter 3: Single-carbon ring expansion is a powerful synthetic disconnection, allowing chemists to construct or purchase the lower homologue of a ring system before expanding to the target ring size. Starting from a smaller ring size can often allow access to a broader array of transformations that proceed with greater stereoselection. In our approach to a class of natural products bearing a cis-decalin core, we successfully implemented a catalytic regioselective single-carbon ring expansion reaction in the context of an advanced synthetic intermediate. This chapter describes the experimental details behind the first catalytic single carbon cyclopentanone homologations and how we extended the method to more complex substrates. Chapter 4: Catalytic activation of sp2 hybridized electrophiles by nucleophilic catalysts has been studied extensively and proceeds through a well-defined mechanistic pathway. In constrast, activation of sp3 hybridized electrophiles in a similar fashion with small-molecule organocatalysts remains an elusive endeavor for chemists. This chapter describes prelimi- nary studies towards this lofty goal and how we discovered a new class of imidazole-based catalysts. Thorough mechanistic studies with the newly discovered catalysts ultimately proved that the reactions proceeded through a pathway that does not involve electrophile activation. However, inexpensive and commercially available imidazolium salts were found to catalyze Williamson etherification reactions under mild conditions through a mechanism that involves an unusual imidazolium alkoxide ion-pair
Thesis (PhD) — Boston College, 2013
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Chemistry

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Abaee, Mohammad Saeed. "Lewis acid catalyzed and self-assembled Diels-Alder reactions (LACASA-DA), a new strategy to control Diels-Alder reactions." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0026/NQ37867.pdf.

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11

Dolliver, Debra D. "Mechanisms of Methoxide Ion Substitution and Acid- Catalyzed Z/E Isomerization of N-Methoxyimines." Thesis, University of North Texas, 2001. https://digital.library.unt.edu/ark:/67531/metadc3017/.

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The second order rate constants for nucleophilic substitution by methoxide of (Z)- and (E)-O-methylbenzohydroximoyl fluorides [C6H4C(F)=NOCH3] with various substituents on the phenyl ring [p-OCH3 (1h, 2h), p-CH3 (1g, 2g), p-Cl (1f, 2f), p-H (1e, 2e), (3,5)-bis-CF3 (1i, 2i)] in 90:10 DMSO:MeOH have been measured. A Hammett plot of these rate constants vs σ values gave positive ρ values of 2.95 (Z isomer) and 3.29 (E isomer). Comparison of these rates with methoxide substitution rates for Omethylbenzohydroximoyl bromide [C6H4C(Br)=NOCH3] and Omethylbenzohydroximoyl chloride [C6H4C(Cl)=NOCH3] reveal an element effect for the Z isomers of Br:Cl:F(1e) = 2.21:1.00:79.7 and for the E isomers of Cl:F(2e) = 1.00:18.3. With the p-OCH3-imidoyl halides the following element effects are found: Br:Cl:F(1h) = 2.78:1.00:73.1 for the Z isomer and Br:Cl:F(2h) = 1.97:1.00:12.1 for the E isomer. Measurement of activation parameters revealed ∆S≠ = -17 eu for 1e and ∆S≠ = -9.9 eu for 2e. Ab initio calculations (HF/6-31+G*, MP2/6-31+G*//HF/6-31+G*, B3LYP/6- 31+G*//HF/6-31+G*, HF-SCIPCM/6-31+G*//HF/6-31+G*) were performed to define the reaction surface. These calculations demonstrate a relatively large barrier for nucleophilic attack in relation to halogen loss and support the experimental findings that this reaction proceeds by an addition-elimination mechanism (AN# + DN). The imidoyl fluorides have been used to synthesize highly functionalized O-methyloximes by reaction with enolate anions derived from malononitrile, ethyl cyanoacetate, and diethyl malonate. Acid-catalyzed isomerization of compounds containing the O-methyloxime moiety have been investigated with ab initio calculations (HF/6-31+G*, MP2/6- 31+G*//HF/6-31+G*, B3LYP/6-31+G*//HF/6-31+G*). Barriers for rotation around the C-N bond following protonation have been calculated. The calculated barriers are discussed in relation to an isomerization mechanism of protonation-rotation versus a nucleophilic catalysis.

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12

Koyuncu, Hasan. "Fam-zinc Catalyzed Asymmetric 1,3-dipolar Cycloaddition Reactions Of Azomethine Ylides And Fam-titanium Catalyzed Enantioselective Alkynylation Of Aldehydes." Phd thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/2/12608783/index.pdf.

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In the first part of this study, four new chiral ligands (FAM) were synthesized and used in catalytic amounts in asymmetric 1,3-dipolar cycloaddition reactions of azomethine ylides. This method leads to the synthesis of chiral pyrrolidines, which are found in the structure of many biologically active natural compounds and drugs. It was found that using 10 mol% of one of these chiral ligands with different dipolarophiles (dimethyl maleate, dimethyl fumarate, methyl acrylate, tert-butyl acrylate, and Nmethylmaleimide), pyrrolidine derivatives could be synthesized in up to 94% yield and 95% ee. In the second part of the study, the catalytic activity of these chiral ligands were tested with titanium in asymmetric alkynylzinc addition reactions to aldehydes. By this method, chiral propargylic alcohols, which are important precursors for the natural products and pharmaceuticals can be synthesized. Using our catalyst, chiral propargylic alcohols were obtained in up to 96% yield and 98% ee. Although, most of the catalyst systems in the literature worked only with aromatic or aliphatic aldehydes and phenylacetylene, the catalyst system developed in this study worked with four different types of aldehydes (aromatic, aliphatic, heteroaromatic and a,b-unsaturated) and two different aliphatic acetylenes very successfully. Additionally, chiral ligand can be recovered in more than 90% yield and reused without losing its activity.

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13

Ou, Jun, and 欧军. "Asymmetric reactions induced by phase-tagged phosphoric acid organocatalysts and copper hydride-catalyzed reductions of unsaturatedthioesters." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B47849708.

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Two syntheses of non-cross-linked polystyrene-supported TADDOL-based phosphoric acid organocatalyst have been developed. The optimal polymer-supported catalyst 2.29d exhibited comparable catalytic activity to its small molecule counterpart in asymmetric Mannich-type reactions, and the syntheses of several chiral β-amino esters were demonstrated using 2.29d as catalyst. However, when this TADDOL-based phosphoric acid was immobilized on a polystyrene cross-linked with 1,4-bis(4-vinylphenoxy)butane, ie. JandaJelTM, the catalytic activity diminished in the first recycling and reuse of the catalyst. Building on the success of the immobilization of chiral phosphoric acid, a more robust phase-tagged BINOL-based phosphoric acid organocatalyst was developed. By taking advantage of a tetraarylphosphonium salt as a solubility-controlling group, a widely-used BINOL-based phosphoric acid, TRIP (3.1), was introduced onto a tetraphenylphosphonium salt to produce a phosphonium salt-tagged phosphoric acid catalyst 3.3e. After systematic optimizations of reaction conditions, it was found that the catalyst 3.3e with PF6 as counteranion exhibited the best performance in terms of enantioselectivity. Catalyst 3.3e was proved to be highly effective in asymmetric Friedel-Crafts reaction of indoles because it was shown to be recyclable and reusable after six cycles without loss of catalytic activity. Based on our previous studies on the reduction of unsaturated thioesters catalyzed by (BDP)CuH, further investigation of ligand effects revealed that in addition to BDP, dppf was also an effective ligand for the simple reduction of 5.8. In the stoichiometric reduction of unsaturated thioester 5.8, dppe and dppf were both efficient ligands for copper hydride that could convert 5.8 to aldehyde 5.18 in the presence of TMSCl, without the formation of the undesired enol ester 5.17, which was a major product when stoichiometric amounts of Stryker’s reagent was employed. When 5.30 bearing both a saturated and unsaturated thioester was reduced under these conditions, only the enethioate functional group underwent reaction to yield the mono-reduced product 5.31 while the saturated thioester functional group remained inert. The desymmetrizing reductive aldol reactions of symmetrical keto-enethioates 6.19, 6.22, 6.24 and 6.26 catalyzed by in situ generated chiral copper hydride were investigated. After a screening of the reaction conditions, TaniaPhos L8 was found to be the most effective chiral ligand to achieve high ee and yields. Under the optimum reaction condition (5 mol% Cu(OAc)-H2O and L8 with 2.0 eq. PhSiH3), a range of keto-enethioates smoothly underwent desymmetrizing reductive aldol cyclizations, offering bicyclic or polycyclic β-hydroxythioesters (6.28a-6.32a, 6.37a-6.47a) in 35- 84% yield and 30-97% ee with high diastereoselectivity. The addition of 5 mol% of bipyridine as additive resulted in an accelerated reaction rate in all of the reductions of keto-enethioates. The crystal structure of the L8-copper bromide complex allowed the rationalization of the major enantiomer (eg. 6.48a), in which all of the substituents are cis, to be a result of a reductively generated (Z)-thioester enolate reacting through a Zimmerman-Traxler transition state. This stereochemical outcome is in contrast to the reduction of the analogous oxoesters, which yield trans β-hydroxyesters, (eg. 6.54b), as the major products. Several proposals to explain the divergent stereochemistry, including the predominance of a Zimmerman-Traxler transition state of (E)-enolates or subsequent retroaldol rearrangements, were discussed. The retroaldol rearrangement has been observed in the conversion of 6.48a to 6.57c, in which there was retention of the configuration at C5 and a perfect conservation of enantiomeric purity.
published_or_final_version
Chemistry
Doctoral
Doctor of Philosophy

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14

Felipe-Blanco, Diego. "Salicylic Acid-Catalyzed Radical Arylations from In-situ Formed Arenediazonium Salts." Doctoral thesis, Universidad de Alicante, 2020. http://hdl.handle.net/10045/112757.

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In this thesis, it has been studied the deamination of aromatic amines, through in situ formed diazonium salts as reaction intermediates, catalyzed by salicylic acid, a nontoxic, eco-friendly and economic catalyst. In the early part of the thesis (Chapter I) it has studied the deamination process using THF as solvent as hydrogen donor and anilines as radical source, to carry the hydrodeamination reaction, as well as the process in its deuterodeamination manner using deuterated solvent. Following with this study in Chapter II and Chapter III, it has been studied the addition of the aromatic radicals, generated with the methodology employed in the first chapter, to different types of double bond, to form α-arylketones (Chapter II) and γ-aryl lactones, throw a following intramolecular cyclization (Chapter III). Finally, in Chapter IV was studied the construction of arylphosphonates, starting from anilines as radical source, and triphenylphosphite, and in this case specially, mechanism was hard explored. In every work, the methodologies could be scaled-up above 1 g, reaction mechanisms were proposed and studied through control and mechanistical experiments, and follow reactions were carried out.

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Nugent, Benjamin M. "Regio- and stereoselective additions to azomethines free radical cyclizations and chiral Bronsted acid catalyzed reactions of imines /." [Bloomington, Ind.] : Indiana University, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:3206873.

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Thesis (Ph. D.)--Indiana University, Dept. of Chemistry, 2006.
Source: Dissertation Abstracts International, Volume: 67-01, Section: B, page: 0275. Adviser: Jeffrey N. Johnston. "Title from dissertation home page (viewed Feb. 22, 2007)."

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Orecchia, Patrizio [Verfasser], Martin [Akademischer Betreuer] Oestreich, Martin [Gutachter] Oestreich, and Philipp [Gutachter] Heretsch. "Boron Lewis acid-catalyzed transfer reactions towards alkenes / Patrizio Orecchia ; Gutachter: Martin Oestreich, Philipp Heretsch ; Betreuer: Martin Oestreich." Berlin : Technische Universität Berlin, 2020. http://d-nb.info/1211392333/34.

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Engqvist, Magnus. "Direct Amino Acid-Catalyzed Enantioselective α-Oxidation Reactions and Asymmetric de novo Synthesis of Carbohydrates." Doctoral thesis, Stockholms universitet, Institutionen för organisk kemi, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-449.

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The ability of amino acids to form nucleophilic enamines with aldehydes and ketones has been used in the development of asymmetric α-oxidation reactions with electrophilic oxidizing agents. Singlet molecular oxygen has for the first time been asymmetrically incorporated into aldehydes and ketones, and the products were isolated as their corresponding diols in good yields and ee’s. Organocatalytic α-oxidations of cyclic ketones with iodosobenzene and N-sulfonyloxaziridine were also possible and furnished after reduction the product diols in generally low yields and in low to good ee’s. Amino acids have also been shown to catalyze the formation of carbohydrates by sequential aldol reactions. For example, proline and hydroxy proline mediate a highly selective trimerisation of α-benzyloxyacetaldehyde into allose, which was obtained in >99 % ee. Non linear effect studies of this reaction revealed the largest permanent nonlinear effect observed in a proline-catalyzed reaction to date. Moreover, polyketides were also assembled in a similar fashion by an amino acid-catalyzed one-pot reaction, and was successful for the trimerisation of propionaldehyde, however the sequential cross aldol reactions suffered from lower selectivities. This problem was overcome by the development of a two-step synthesis that enabled the formation of a range of polyketides with excellent selectivities from a variety of aldehydes. The method furnishes the polyketides via the shortest route reported and in comparable product yields to most multi-step synthesis. All polyketides were isolated as single diastereomers with >99 % ee. Based on the observed amino acid-catalysis, amino acids are thought to have taken part in the prebiotic formation of tetroses and hexoses.

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18

Ho, David Gai. "Adventures in Lewis acid catalyzed highly hindered Diels-Alder reactions; Novel non-Diels-Alder Diels-Alder reaction and its utility for the synthesis of haterumaimide E." Diss., Restricted to subscribing institutions, 2007. http://proquest.umi.com/pqdweb?did=1495960681&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.

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Liu, Yuanshuai [Verfasser], Johannes A. [Akademischer Betreuer] [Gutachter] Lercher, and Richard W. [Gutachter] Fischer. "Acid catalyzed reactions of cyclohexanol in liquid phase / Yuanshuai Liu ; Gutachter: Johannes A. Lercher, Richard W. Fischer ; Betreuer: Johannes A. Lercher." München : Universitätsbibliothek der TU München, 2017. http://d-nb.info/1128819430/34.

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20

Crosman-Modrogan, Elena. "New heterogeneous catalysts based on ionic liquids for acid catalyzed organic reactions on the example of cyclohexane oxidation and phenol alkylation." Aachen Shaker, 2007. http://d-nb.info/991821165/04.

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Husmann, Ralph [Verfasser]. "Synthesis and application of silylated pyrrolidines enantioselective organocatalytic synthesis of a-trifluoromethyl a-amino acid derivatives and copper-catalyzed multicomponent reactions / Ralph Husmann." Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2011. http://d-nb.info/1018190465/34.

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Crosman-Modrogan, Elena [Verfasser]. "New heterogeneous catalysts based on ionic liquids for acid catalyzed organic reactions on the example of cyclohexane oxidation and phenol alkylation / Elena Crosman-Modrogan." Aachen : Shaker, 2008. http://d-nb.info/1161309209/34.

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Llewelyn, Peter William. "Supported heteropoly acids for acid catalysed reactions." Thesis, Cardiff University, 2011. http://orca.cf.ac.uk/54120/.

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Carpenter, Alexis Anne. "The chemistry of silyl enol ethers : titanium (IV) catalyzed reactions of 1, 3-bis (trimethylsiloxy)-4-chloro-1-methoxybuta-1, 3-diene and its application in the synthesis of Nonactic acid." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66027.

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Bissett, James S. "Lanthanide Lewis acid catalysed allylation reactions." Thesis, University of Liverpool, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367709.

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Teoh, Euneace Ching Mei. "Synthesis of amino acids by metal-catalysed reactions." Monash University, School of Chemistry, 2004. http://arrow.monash.edu.au/hdl/1959.1/9633.

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Penrose, Stephen David. "Recent advances in rhodium-catalysed conjugate addition reactions." Thesis, University of Bath, 2008. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.492243.

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The research presented herein is concerned with the exploration of rhodium-catalysed addition reactions with organoboranes encompassing the 1,4-addition enolate protonation to benzyl acrylate esters, and the synthesis of chiral organoboranes for use in the synthesis of natural products Hermitamides A and B. Chapter 1 introduces the area of rhodium-catalysed conjugate addition as a tool for asymmetric synthesis. An extensive discussion of this methodology is included and recent advances in the area will be highlighted. In addition to this some recently published alternatives to organoboranes are outlined and their use in rhodium-catalysed chemistry documented. Chapter 2 discusses the tandem process of rhodium-catalysed conjugate addition enolate protonation, a recently observed asymmetric development. By using a novel route to benzyl acrylic esters the synthesis of α,α′-dibenzyl esters is achieved in excellent yields and selectivity. This study highlights the fact that when dealing with 1,1-disubstituted activated alkenes it is more difficult to produce enantioselective results as the chirality is determined in the protonation step and not during insertion. Some insights into the mechanism are proposed based on the outcomes observed. Chapter 3 describes the total synthesis of Lyngbic Acid and related structures Hermitamides A and B. Synthesis of these natural products are achieved by synthesis of an enantiopure organoborane species and its subsequent coupling via rhodium catalysis. Some interesting insights into the addition of alkenyl organoborane species to unsubstituted 1,1-activated alkenes are detailed. Chapter 4 describes the synthesis and characterisation for the compounds discussed in the previous chapters.

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Lamminpää, K. (Kaisa). "Formic acid catalysed xylose dehydration into furfural." Doctoral thesis, Oulun yliopisto, 2015. http://urn.fi/urn:isbn:9789526209142.

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Abstract Lignocellulosic biomass, such as wood or agricultural residues, is a resource widely available for use in chemical production. In a lignocellulosic feedstock biorefinery, the major parts of biomass, cellulose, hemicellulose and lignin, are converted to valuable chemicals, materials and energy. Furfural production is one option for the use of the pentose sugars available in hemicellulose, and the process could be integrated with the pulp or cellulosic ethanol industry. In the past, furfural production catalysed by organic acids has been in industrial use, but no detailed studies about the kinetics exist. However, the use of organic acid would prevent the waste problems linked to the mineral acids widely used in the furfural industry. In this thesis, furfural formation in formic acid media was studied. The major part of this work concerns the kinetics of xylose dehydration into furfural and further furfural degradation. Based on the results of this thesis and a literature review, adequate prediction of furfural yield in the conditions used can be achieved using a simple kinetic model, including three reactions: 1) Xylose dehydration into furfural, 2) Furfural degradation, and 3) Xylose degradation to products other than furfural. Moreover, it was shown that the overall order of the furfural degradation reaction, usually modelled as a first order reaction, changes with acidity (H+-concentration). Suggestions for a possible reaction mechanism have been made based on the results. In the last part of this thesis, furfural formation in the presence of kraft lignin (Indulin AT) was considered. Sulphuric acid was used as a baseline for formic acid. It was shown that the lignin has an acid-neutralising capacity, but the higher pH did not explain all the changes in the xylose conversion and the furfural yield. Thus, it is highly likely the lignin inhibits the formation of furfural. Altogether, the effects were smaller in formic acid than in sulphuric acid. This thesis confirms the fact that formic acid is an effective catalyst for furfural production. The focus of the thesis was on the reaction kinetics, and the results can be used in conceptual process design. Moreover, the results emphasise the importance of including acidity explicitly in the kinetic model and monitoring acidity changes when real process streams are used
Tiivistelmä Lignoselluloosaa, kuten puita tai maanviljelyn jäännösmateriaaleja, on laajasti saatavilla kemiallisen tuotannon raaka-aineeksi. Biojalostamossa lignoselluloosan pääjakeet, selluloosa, hemiselluloosa ja ligniini, muutetaan arvokkaiksi kemikaaleiksi, materiaaleiksi ja energiaksi. Furfuraalin tuotanto on yksi vaihtoehto hemiselluloosan sisältämien pentoosien hyödyntämiseksi. Furfuraaliprosessi voidaan yhdistää sellun tai bioetanolin tuotantoon, ja orgaanisia happoja käyttämällä voitaisiin välttää mineraalihappoihin liittyvät jäteongelmat furfuraalin tuotannossa. Tämän väitöskirjan aiheena on muurahaishappokatalysoitu furfuraalin muodostuminen ksyloosista. Pääpaino on reaktiokinetiikassa, ja työssä on kehitetty kineettinen malli ksyloosin dehydraatiolle furfuraaliksi ja sitä seuraaville furfuraalin sivureaktioille. Tehdyn tutkimuksen ja kirjallisuusselvityksen perusteella yksinkertainen kolmen reaktion malli antaa riittävän tarkan ennustuksen furfuraalisaannoista käytetyissä olosuhteissa. Reaktiot ovat 1) ksyloosin dehydraatio sekä 2) furfuraalin ja 3) ksyloosin reaktiot sivutuotteiksi. Lisäksi huomattiin, että reaktion, jossa syntyy furfuraalin häviämistuotteita, reaktioaste on riippuvainen happamuudesta (H+-konsentraatio). Työssä onkin ehdotettu mahdollisia reaktiomekanismeja furfuraalin sivureaktioille. Työn viimeisessä osassa tutkittiin ligniinin vaikutusta furfuraalin muodos¬tu¬miseen. Vertailukohtana muurahaishapolle käytettiin rikkihappoa. Tutkimuksessa selvisi, että käytetty ligniini, Indulin AT, huononsi furfuraalisaantoa. Suurin osa vaikutuksesta johtui ligniinin neutralointikapasiteetista, jolloin reaktioliuoksen happamuus laski, mutta mahdollisia sivureaktioita ei voitu sulkea pois. Kaiken kaikkiaan vaikutukset olivat pienempiä muurahaishapolla kuin rikkihapolla. Tämä väitöskirjatutkimus osoitti, että muurahaishappo katalysoi furfuraalin tuotantoa tehokkaasti. Tutkimuksessa muodostettiin reaktiokineettinen malli, jota voidaan käyttää käsitteellisessä prosessisuunnittelussa. Tulosten perusteella on tärkeää huomioida reaktioliuoksen happamuus kinetiikassa ja tarkkailla happamuuden muutoksia käytettäessä prosessisivuvirtoja

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McIver, Edward G. "Lewis acid-catalysed allylation and Diels-Alder reactions using novel earth complexes." Thesis, University of Liverpool, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367082.

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30

Nakatsu, Hiroki. "Studies on Chiral Bronsted Acid-Catalyzed Activation of Imino Functionalities." 京都大学 (Kyoto University), 2014. http://hdl.handle.net/2433/188505.

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31

Clapham, Gary. "New Lewis acid promoted Diels-Alder reaction and transition catalysed hydrocarbons." Thesis, University of Exeter, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284618.

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32

Rowland, Emily Bretherick. "Enantioselective Brønsted Acid-Catalyzed Reaction Methodology Part A: Enantioselective Mannich Reaction Part B: Enantioselective Desymmetrization of meso-Aziridines." [Tampa, Fla] : University of South Florida, 2008. http://purl.fcla.edu/usf/dc/et/SFE0002613.

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33

喜教, 鈴間. "Asymmetric addition reaction of organoboronic acid catalyzed by palladium with ferrocene-based phosphine ligand." Thesis, https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB10352112/?lang=0, 2010. https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB10352112/?lang=0.

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34

Skillinghaug, Bobo. "Palladium(II)-Catalysed Heck and Addition Reactions : Exploring Decarboxylative and Desulfitative Processes." Doctoral thesis, Uppsala universitet, Avdelningen för organisk farmaceutisk kemi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-304746.

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Palladium complexes have the ability to catalyse cross-coupling of two organic moieties through the formation of transient metal-carbon bonds, thus bringing them closer to each other to facilitate the formation of a new bond. Palladium-catalysed coupling reactions are one of the most important carbon-carbon forming reactions available to organic chemists and many of these reactions rely on the reactivity of aryl-palladium complexes. The investigation of new aryl-palladium precursors is thus of great interest, especially as more sustainable and economic methods can be developed. This thesis describes the use of carboxylic acids and sodium arylsulfinates as such new arylating agents. Protocols for microwave-assisted palladium(II)-catalysed decarboxylative synthesis of electron-rich styrenes and 1,1-diarylethenes were developed. However, these transformations had very limited substrate scopes which prompted the investigation of sodium arylsulfinates as alternative arylating agents. These substrates were employed in the microwave-assisted palladium(II)-catalysed desulfitative addition to nitriles, and the substrate scope was demonstrated by combining a wide array of sodium arylsulfinates and nitriles to yield the corresponding aryl ketones. The application of the desulfitative reaction in a continuous flow setup was demonstrated, and aluminium oxide was identified as safe alternative to borosilicate glass as a reactor material. The mechanisms of the decarboxylative and desulfitative transformations were investigated by density functional theory (DFT) calculations. The desulfitative reaction was also investigated by direct electrospray ionization mass spectrometry (ESI-MS), providing further mechanistic insight. Finally, a protocol for the safe and convenient synthesis of a wide range of sodium arylsulfinates was developed.

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35

Tanji, Yutaka. "Steric Effect of Carboxylate Ligands on Pd-Catalyzed C-H Bond Arylation Reactions." Kyoto University, 2020. http://hdl.handle.net/2433/253293.

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36

Ahmed, Awais. "[4+2] and [4+3] cycloaddition reactions and Lewis acid catalysed cycloisomerisation of malonyl epoxides." Thesis, Loughborough University, 2003. https://dspace.lboro.ac.uk/2134/12572.

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Donor-acceptor cyclopropanes have been extensively used in synthetic chemistry in [3+2] and [3+3] cycloaddition reactions for the preparation of highly substituted carbo- and heterocyclic products. This methodology is further extended to donor-acceptor cyclobutane in [4+2] and [4+3] cycloaddition reactions for the synthesis of highly substituted carbo- and heterocyclic products. Initial work carried out makes use of cyclobutanes substituted with a metal-alkyne complex towards the synthesis of tetrahydropyrans in good yields and with acceptable diastereoselectivity. The initial aim of the project was to improve and expand the scope of the previous work carried out within the group on [4+2] cycloaddition reaction. For example, [4+2] and [4+3] cycloaddition reaction were carried out by using diester cyclobutanes having an alkene and phenyl π-donors. The [4+3] cycloaddition reaction of cyclobutane with nitrone did not work but [4+2] cycloaddition was successful when aldehydes were used as trapping reagents. Lower yields of the cycloadducts were observed due to formation of (±)-dimethyl-2-methyl-6-phenylcyclohex-3-ene-1,1-dicarboxylate and 2,6-diphenyl-4,8-dipropenylcyclooctane-1,1,5,5-tetracarboxylic acid tetramethyl ester. During the synthesis of a precursor cyclobutane a novel cycloisomerisation of malonyl epoxide under Lewis acidic conditions to 6,8-dioxabicyclo[3.2.1]octane derivatives was developed. This reaction has opened a new pathway for the synthesis of 6,8-dioxabicyclo[3.2.1]octanes in a diastereoselective fashion using malonyl epoxides as precursors. A wide range of malonyl epoxides were cycloisomerised under Lewis acidic conditions and the cycloisomerisation of syn and anti malonyl epoxides were stereospecific. The diastereoselectivity of the process was proven by nOe and X-ray analysis. The cycloisomerisation of malonyl diepoxide has also been investigated towards the formation of 5,5-dimethoxy-6,6,8,8-tetraoxa4,4-spirobi[bicyclo[3.2.1]octane].

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37

Paredes, Cecilia Glenys. "Acid-catalysed Nicholas reactions of hexacarbonyldicobalt-coordinated propargyl ligands with sulfur- and carbon-based nucleophiles." Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615125.

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38

Tobaldi, Elisabetta. "Acid catalysed abiotic reactions in biological system : from design to in Vivo proof of concept." Thesis, Strasbourg, 2019. http://www.theses.fr/2019STRAF004/document.

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Cette thèse porte sur les réactions abiotiques catalysées par un acide dans les systèmes biologiques. Elles sont définis comme des systèmes réactionnels composés d'un substrat xénobiotique - un acétal cyclique dans ce travail - stable dans des conditions biologiques et clivable à un pH bas et d'un catalyseur acide hétérogène correspondant biocompatible. Le défi de cette approche est de maintenir le catalyseur actif dans un milieu biologique tamponné et toujours capable d'hydrolyser le substrat xénobiotique d'acétal et de maintenir le pH tamponné du système vivant dans son état d'origine. Dans la première partie de ce travail, nous nous concentrons sur le réglage précis des acétals cycliques. Nous identifions 4 structures acétales et montrons que les changements structurels conduisent à une réactivité différente dans différentes gammes de pH, chacune correspondant à des applications possibles in vivo, notamment des lieurs stables pour les conjugués anticorps-médicaments et des lieurs clivables dans des conditions physiologiques pour la bioconjugaison.La deuxième partie est axée sur le catalyseur biocompatible. Ici, nous identifions deux catalyseurs biocompatibles solides, ayant différents degrés d'hydrophobie et de propriétés d’adsorption : le copolymère Nafion NR-50 et le copolymère PEG-AASA. Nous démontrons qu’avec un traitement approprié, ils peuvent maintenir un pH interne inférieur à 4, hydrolyser le substrat et ne pas affecter le biofluide hautement tamponné utilisé comme solvant
This thesis object is acid-catalysed abiotic reactions in biological systems. They are defined as reaction systems composed by a xenobiotic substrate – a cyclic acetal in this work - stable in biological conditions and cleavable at low pH and a corresponding biocompatible heterogeneous acid catalyst. The challenge of this approach is to keep the catalyst active in a buffered biological media and still capable of hydrolysing the xenobiotic acetal substrate and to maintain the buffered pH of the living system in its original state. In the first part of this work we focus on the fine-tuning of cyclic acetals. We identify 4 acetal structures and we show that structural changes lead to a different reactivity in different pH ranges, each corresponding to possible applications in vivo, including stable linkers for antibody drug conjugates and linkers cleavable in physiological conditions for bioconjugation.The second part is focused on the biocompatible catalyst. Herein we identify two solid biocompatible catalysts, with different degree of hydrophobicity and adsorbance properties: Nafion NR-50 and PEG-AASA co-polymer. We demonstrate that, upon proper treatment, they can maintain an inner pH < 4, hydrolyse the substrate and do not affect the highly buffered biofluid used as solvent

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Geogheghan, Katherine Jayne. "Boronic acid speciation in Suzuki-Miyaura cross-coupling." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/33092.

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Since its discovery in 1979, the Suzuki-Miyaura (SM) reaction has become one of the most widely utilised tools for carbon-carbon bond formation. The palladium catalysed coupling of an organoboron and organohalide compounds proceeds through a three-stage mechanism of oxidative addition, transmetalation and reductive elimination. The transmetalation of boronic acids to a palladium(II) complex has been widely studied. However, very little is known about the transmetalation of boronic esters, which are commonly used as an alternative to unstable boronic acids. Whether these species undergo direct transmetalation or prior hydrolysis to the boronic acid under SM conditions remains unknown. This research aimed to elucidate the mechanism of this cross-coupling process. Initial results under typical SM conditions created a biphasic reaction, promoted by the inorganic base and solvent composition, and showed that the boronic esters and corresponding boronic acid couple at the same absolute rate. This is thought to be a consequence of the formation of a biphasic mixture, rendering phase transfer the turnover-limiting step. The conditions were thus adapted to maintain a monophasic system using an organic soluble base, 2-tert-butyl-1,1,3,3-tetramethylguanidine, enabling the focus to be transmetalation as the turnover-limiting step. These new conditions show a significant difference in both reaction rate and induction period when using a boronic ester compared to the corresponding boronic acid. The use of guanidine was also shown to have an interesting effect on the boronic acid/ester species by 19F and 11B NMR. Further studies found the use of guanidine to create a boronate species, with this species being an aryl trihydroxyboronate or the hydroxyl"ate"-complex of the boronic ester, depending on the presence of diol in the system. Formation of a boronate species was found to be crucial for efficient cross-coupling. When testing weaker bases, unable to form a boronate species, poor SM cross-coupling conversion was found using the newly developed phosphine-free guanidine conditions, showing the importance of the boronate species under these conditions. The results suggest that depending on the strength of base used, the pathway of transmetalation pathway can be switched, between the boronate pathway and the oxo-palladium pathway, under the specific conditions developed.

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40

Larson, Shawn E. "Enantioselective Brønsted and Lewis Acid-Catalyzed Reaction Methodology: Aziridines as Building Blocks for Catalytic Asymmetric Induction." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4357.

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Chiral molecules as with biological activity are plentiful in nature and the chemical literature; however they represent a smaller portion of the pharmaceutical drug market. As asymmetric methodologies grow more powerful, the tools are becoming available to synthesize chiral molecules in an enantioselective and efficient manner. Recent breakthroughs in our understanding of phosphoric acid now allow for Lewis acid catalysis via pairing with alkaline earth metals. Using alkaline earth metals with chiral phosphates is an emerging approach to asymmetric methodology, but already has an influential record. The development of new conditions for the phosphoric acid-catalyzed highly enantioselective ring-opening of meso-aziridines with a series of functionalized aromatic thiol nucleophiles is described in this thesis. This methodology utilizes commercially available aromatic thiols, a series of meso-aziridines, and a catalytic amount of VAPOL calcium phosphate to explore the substrate scope of this highly enantioselective reaction. Additionally, the development of new conditions for a catalytic asymmetric aza-Darzens aziridine synthesis mediated by a vaulted biphenanthrol (VAPOL) magnesium phosphate salt is described in this thesis. Using simple substrates, this methodology explores the scope and reactivity of a new magnesium catalyst for an aziridination reaction capable of building chirality and complexity simultaneously.

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41

Sun, Lele. "Peptidyltransfer Reaction Catalyzed by the Ribosome and the Ribozyme: a Dissertation." eScholarship@UMMS, 2003. https://escholarship.umassmed.edu/gsbs_diss/115.

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The "RNA world" hypothesis makes two predictions that RNA should have been able both to catalyze RNA replication and to direct protein synthesis. The evolution of RNA-catalyzed protein synthesis should be critical in the transition from the RNA world to the modem biological systems. Peptide bond formation is a fundamental step in modem protein biosynthesis. Although many evidence suggests that the ribosome is a ribozyme, peptide bond formation has not been achieved with ribosomal RNAs only. The goal of this thesis is to investigate whether RNA could catalyze peptide bond formation and how RNA catalyzes peptide bond formation. Two systems have been employed to approach these questions, the ribozyme system and the ribosome system. Ribozymes have been isolated by in vitro selection that can catalyze peptide bond formation using the aminoacyl-adenylate as the substrate. The isolation of such peptide-synthesizing ribozymes suggests that RNA of antiquity might have directed protein synthesis and bolsters the "RNA world" hypothesis. In the other approach, a novel assay has been established to probe the ribosomal peptidyltransferase reaction in the presence of intact ribosome, ribosomal subunit, or ribosomal RNA alone. Several aspects of the peptidyltransfer reaction have been examined in both systems including metal ion requirement, pH dependence and substrate specificity. The coherence between the two systems is discussed and their potential applications are explored. Although the ribozyme system might not be a reminiscence of the ribosome catalysis, it is still unique in other studies. The newly established assay for ribosomal peptidyltransferase reaction provides a good system to investigate the mechanism of ribosomal reaction and may have potential application in drug screening to search for the specific peptidyltransferase inhibitors.

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42

Pih, Steven Michael. "The Lewis acid catalysed nitro-mannich reaction : steps towards an enantioselective synthesis of vicinal diamines." Thesis, University of Nottingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275957.

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43

Morcillo, Gómez María. "Use of cyclic and acyclic carbonates as solvents for amino acids and quinine catalysed asymmetric reactions." Thesis, University of Newcastle upon Tyne, 2015. http://hdl.handle.net/10443/2829.

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44

DANINOS, GUILLOTTE SANDRA. "Inversion de chiralite d'un -amino acide par couplage d'une catalyse enzymatique et de reactions electrochimiques." Paris 7, 1998. http://www.theses.fr/1998PA077198.

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L'inversion de chiralite d'un -amino acide peut etre obtenue par mise en oeuvre simultanee de la selectivite enantiomerique de la l- amino acide deshydrogenase, de la regeneration electrochimique tres efficace du coenzyme nad + a une anode de feutre de carbone et de la reduction electrochimique aminative de l'-ceto acide en tampon ammoniac/ammonium (1. 28 m/1. 28 m) a une cathode mercure. L'enzyme deshydrogenase presente une activite et une stabilite etonnantes dans ces conditions extremes de ph et de force ionique. Le principal inconvenient du systeme est sa lenteur. Au mieux, la complete inversion d'une solution 10 mm l-alanine demande 140 heures. Une analyse quantitative approfondie et detaillee de chacune des etapes cles mises en jeu montre que l'oxydation catalysee par la deshydrogenase est thermodynamiquement difficile. Pour obtenir une complete inversion, il faut que la regeneration du coenzyme nad + et la reduction de l'imine du pyruvate soient efficaces. La premiere condition est facilement atteinte. Dans les meilleures conditions, c'est la vitesse de formation de l'imine qui controle cinetiquement le procede.

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45

Smith, Craig R. "Metal-Catalyzed Reactions of Ethene: Asymmetric Hydrovinylation and Palladacycle-Mediated Low Pressure Vinylation of Aryl and Vinyl Halides." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1274734379.

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46

Tredgett, David Gordon. "Studies on the scope of acid-catalysed cyclisation reactions of ortho-substituted nitroaromatic derivatives to N-hydroxy heterocycles and related compounds." Thesis, University of Edinburgh, 2000. http://hdl.handle.net/1842/14572.

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The subject matter of this thesis is concerned with investigations on the novel acid-catalyst cyclisation reactions of ortho- substituted nitroaromatic derivatives to N-oxygenated quinolinones and related heterocycles. The description of the results obtained in these studies is preceded in Chapter 1 by a survey of the known acid-catalysed cyclisation reactions of ortho-substituted nitroaromatic derivatives to N-oxygenated heterocycles and the potential biological properties of such N-oxygenated heterocyclic derivatives. Chapter 2 describes investigations on the synthesis of N-hydroxyquinolinone derivatives by the acid-catalysed cyclisation reactions of ortho- substituted nitrobenzene derivatives. In particular these studies were concerned with substituent effects para to the ortho- side- chain in the nitrobenzene derivatives in respect of the efficiency of their cyclisation to N-hydroxyquinolinone derivatives in the presence of hydrogen chloride. Subsequent studies on the reactivity of the N-hydroxyquinolinone derivatives obtained are also reported in this Chapter. Investigations were also carried out on the Lewis acid catalysed cyclisation reactions of trans 2-benzoyl-3-(2-nitrophenyl)oxirane derivatives to novel 2,1-benzisoxazolone derivatives. Chapter 3 describes the efficient synthesis of novel N-hydroxybenzoquinolinone derivatives by the hydrogen chloride catalysed cyclisation reactions of 2-nitronaphthylidene derivatives as well as investigations of the reactivity of the N-hydroxy heterocycles so produced. Studies seeking to extend this work to the synthesis of N-hydroxythienopyridinones and N-hydroxyimidazopyridinones by the acid-catalysed cyclisation reactions of the corresponding nitrothienylidene and nitroimidazolylidene derivatives are also reported. Also described in this Chapter are studies on the hydrogen chloride and Lewis acid catalysed cyclisation reactions of 2-nitronaphthyloxirane, 2-nitrothienyloxirane and 5-nitroimidazolyloxirane derivatives, in the case of the Lewis acid promoted processes to afford naphthisoxazolone, thienoisoxazolone and imidazoisoxazolone derivatives.

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47

Iwadate, Noriyuki. "New Synthesis of Organoboronic Acids via Transition-Metal-Catalyzed Reactions of New Boron Reagents Bearing 1,8-Diaminonaphthalene-Masked Boronyl Groups." 京都大学 (Kyoto University), 2010. http://hdl.handle.net/2433/120899.

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48

Othman, Mazin A. "Palladium-catalysed aerobic oxidative homocoupling reaction of arylboronic acids in aqueous micellar medium : kinetic and mechanistic studies." Thesis, Cardiff University, 2011. http://orca.cf.ac.uk/55140/.

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This thesis is divided into five Chapters. The first Chapter introduces water and micellar solutions as reaction medium, catalysis, palladium catalysts, the Suzuki cross-coupling and the oxidative homocoupling of arylboronic acids. The second Chapter describes studies of the aerobic oxidative homocoupling reaction of arylboronic acids in aqueous micellar media using Pd(bimsulfide)Cl₂ as a (pre) catalyst. Our results, in particular a bell-shaped pH-rate profile, favour a reaction mechanism where the rate-determining step is transmetalation involving a palladium-hydroxo complex and the acidic form of the arylboronic acid, although an alternative mechanism involving a palladium- aqua complex reacting with the arylboronate cannot be excluded. The third Chapter presents the synthesis of Pd-CTAB nanoparticles and their use as catalysts for the aerobic oxidative homocoupling of phenylboronic acid in aqueous micellar solutions. Again, a bell-shaped pH dependence of observed rate constant (&0bs) was observed which, together with our other results, suggests that the reaction again involves pH-dependent Pd-hydroxo and Pd-aqua species. We cannot confirm whether catalysis occurs on the surface of the nanoparticles or through leached Pd atoms/ions. The fourth Chapter embraces bimetallic core-shell Au-Pd nanoparticles encapsulated in a shell of poly(7V-isopropylacrylamide) (pNIPAM) of different sizes and morphologies, as well as Pd-pNIPAM nanocomposites. Both systems were used to catalyse the aerobic oxidative homocoupling reaction of PBA in aqueous micellar medium. Our kinetic studies gave similar results as observed for the Pd-complex described in Chapter 2 and the nanoparticles described in Chapter 3. Hence, an analogous mechanism was proposed. The observed rate constant showed non-Eyring-like behaviour, highlighting the dependence of Abs on the state (swollen or collapsed) of the pNIPAM shell surrounding the nanoparticles. Finally, the fifth Chapter describes preliminary studies exploring aerobic oxidative cross-coupling reactions of arylboronic acids and their derivatives in aqueous micellar solutions. Conclusions, future outlooks, remarks and suggestions finish Chapter 5 and the thesis.

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49

Broan, Christopher John. "A mechanistic study of the acid and base catalysed reactions of thiourea, 1-substituted thioureas and 1,3 -disubstituted thioureas with 1,2-diketones." Thesis, University of St Andrews, 1989. http://hdl.handle.net/10023/14978.

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Thiourea, 1-substituted thioureas and 1,3-disubstituted thioureas react under acidic or basic catalysis with 1,2-diketones to give a wide variety of products. The nature of the product or products depends on the conditions used, the degree of substitution of the thiourea and on the nature of the aromatic or aliphatic groups attached to the dicarbonyl unit of the diketone. The mechanisms of formation of the various products have been investigated by a variety of techniques, including the determination of rate equations by ultraviolet spectroscopy, the influence of side group substituents on the rate and course of the reactions and the synthesis of putative Intermediates on the reaction pathway. The single most informative technique used was, without a doubt, the detection of low concentrations of transient intermediates and side products by the application of carbon-13 nmr spectroscopy to the reaction as it progressed using carbon-13 labelled di ketones to enhance the detection of low level intermediates. It has been shown convincingly that some organic reactions proceed via a small number of irreversible processes amongst a very complex set of more rapid equilibrium processes.

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Carpenter, Russell Ellis Holly R. "Functional roles of conserved active site amino acids in the desulfonation reaction catalyzed by the alkanesulfonate monooxygenase from Escheria coli." Auburn, Ala, 2008. http://hdl.handle.net/10415/1426.

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Dissertations / Theses on the topic 'Acid catalyzed reactions'

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