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The Influence on De-NOx of Metal-Oxidation Catalysts with acidic modificationHuang, Ling-Hsuan 12 September 2001 (has links)
Abstract
The objective of this study is to compare the performance over copper oxide catalyst under nonselective catalytic reduction of nitric oxide with methane and selective catalytic reduction of nitric oxide with propane. The copper catalysts was prepared by impregnating the support Al2O3 with copper nitrate. In order to find the favorable kind and concentration of acid solution¡Awe conducted the modification of three acid solutions on the support Al2O3 in the same normal concentration in the first¡Aand followed by the test of various concentration of the most-favoured acid. The experiment operated condition was as follow¡G
reaction temperature 623K-1023K¡AF/W¡×108000ml/hr.g¡Aoxygen concentration 2¢M¡ANOx inlet concentration 1000ppm.
In view of the result of NSCR reactions with methane over Cu/£^-Al2O3 catalyst¡Athe conversion of De-NOx increased with the increasing loading of copper on Cu/£^-Al2O3¡Aand achieved a max. value when copper loading was 8¢Mwt.. The performance of De-NOx over the modified copper catalysts three different acid with the same normal concentraion¡Ashowed that the best reduction efficiency was with nitric acid modified¡Athen with¡Aand followed with acetic acid¡Aphosphoric acids. Through compared the conversion of De-NOx between non-modified Cu/£^-Al2O3 with modified Cu/£^-Al2O3¡Athere had the best efficiency in treating for NO conversion. It showed that the best efficiency in raising the conversion of NO over copper catalyst is modified with nitric acid¡Athere is not helpful on reduction efficiency of NO by modification with acetic and phosphatic acids. Nevertheless¡Athe higher concentration¡]N¡^ of nitric acid is¡Athe higher efficiency of De-NO is¡F
For the SCR reactions with propane, when the inlet concentraion NO/C3H8 was 1¡Athere has better reductive activity. The trends for the NO conversion versus reaction temperature were similar for the same catalysts used. In general, the NO conversion was an increasing function of copper loading for these copper catalysts. The 8¢Mwt. Cu/£^-Al2O3 was found to enhance the NO conversion. The activity of acid-treated catalysts in nitric acid with 2¢MO2 present had the best NO conversion, while the same order was in NSCR reaction. Treating the supports with a higher concentration of acid would result in a higher activity for the copper catalyst, implying that acid treatment not only duces surface area to decrease on catalyst and enhance the reactivity, but also the presence of Cu+ and Cu2+ might be responsible for the reaction efficiency. no matter what the reactant is propane or methan , propane is better reactant to catalyst NO to N2.
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Copper-Catalyzed Amination of Indoles via C-H Bond ActivationPan, Ming-kai 07 September 2012 (has links)
A new protocol for direct amination of N-Methyl-2-phenylindole catalyzed by copper(II) trifluoromethanesulfonate was presented. Both of (E)-N-(1,1'-Dimethyl-2,2'
-diphenyl-2,3'-biindolin-3-ylidene)-4-methylbenzenesulfonamide¡]4¡^and 4-methyl
-N-(1-methyl-2-phenyl-1H-indol-3-yl)benzenesulfonamide¡]2¡^were obtained under the optimal reaction conditions (2.5 mol% Cu(OTf)2, 1.2 equiv PhI=O, 0.7 equiv PhI=NTs heated at 25 ¢J in acetonitrile for 1 hour) in 78 % and 11 % yields, respectively. In addition, (E)-N-(2-hydroxy-1-methyl-2-phenylindolin-3-ylidene)-4-methylbenzene
sulfonamide ¡]6¡^and (E)-N-(1,1'-dimethyl-2,2'-diphenyl-2,3'-biindolin-3-ylidene)
-4-methylbenzenesulfonamide ¡]4¡^were synthesized in 47 % and 24 % yields, respectively, by using 5 mol% Cu(OTf)2, 2 equiv PhI=O, 1.2 equiv PhI=NTs at ambient temperature in acetonitrile for 1 hour. Finally, 4-methyl-N-(1-methyl-2-oxo-3-phenyl
indolin-3-yl)benzenesulfonamide ¡]3¡^and 1,1'-dimethyl-2,2'-diphenyl-2,3'-biindolin
-3-one ¡]7¡^can be formed under the following reaction condition, 5 mol% Cu(OTf)2, 2 equiv PhI=O, 1.2 equiv PhI=NTs and 3 equiv Ag2CO3 heated at 100 ¢J in acetonitrile for 1 hour, in 41% and 22% yields, respectively.
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Synthesis of Boron-Containing Carbon Nanotubes Catalyzed by Cu/£^- Al2O3Chen, Yun-chu 07 September 2011 (has links)
Boron-doped carbon nanotubes are predicted to behave as semiconductors over a large range of diameters and chiralities and might thus constitute a suitable class of material for nanoelectronics technology. Boron-doped CNTs were reported as by-products when BC2N nanotubes were prepared by an arc-discharge method. The potential doping of CNTs with different kinds of atoms might provide a mechanism for controlling their electronic properties. We have synthesized boron-doped carbon nanotubes (CNTs) directly on copper catalyst by decomposition of B(OCH3)3 in chemical vapor deposition method. The results were characterized and analyzed by scanning electron microscopy (SEM), Raman, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), solid-state NMR and TGA.
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The Study of Catalytic Oxidation of Ammonia over Copper Catalysts Supported on Slag PowderHuang, Pei-Hsuan 23 June 2003 (has links)
This study was to investigate the effect on the conversion, long-term test, product selectivity and kinetics in oxidation of ammonia over copper catalyst supported on slag powder. The operation parameters in heterogeneous reactor were performed as follows: 1000 ppm initial concentration of ammonia, temperature of reaction in ranging from 100 ¢J to 500 ¢J, 10 % of oxygen concentration, and 80000hr-1 of space velocity.
In the experiments of catalyst selection, we decided to use 15% Cu catalyst for its high conversion and selectivity in oxidation of ammonia. The conversion of ammonia in catalytic reaction increased with the increasing both of reaction temperature and influent concentration of oxygen but decreased with the going up of initial concentration of ammonia and of space velocity.
In the long-term test of catalyst stability, Cu catalyst had a good stability after 48 hours reaction in heterogeneous reactor. The tests such as XRD, SEM and EA were also determined. The kinetics of heterogeneous reactor over Cu catalyst supported on slag powder in oxidation of ammonia was found that a pseudo-first order could be described by Mars-Van Krevelend model. The apparent reaction order and activated energy were obtained.
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Earth-Abundant Metal-Catalyzed and Transition Metal-Free Borylation of Aryl Halides / Borylierung von Arylhalogeniden basierend auf kostengünstigen Übergangsmetallkatalysatoren sowie einer übergangsmetallfreien AlternativeKuehn, Laura January 2022 (has links) (PDF)
The present work focusses on the borylation of aryl halides. The first chapter presents a detailed review about previously reported nickel-catalyzed borylation reactions. The second chapter of the thesis describes, the borylation reaction of C–Cl bonds in aryl chlorides mediated by an NHC-stabilized nickel catalyst. The cyclohexyl substituted NHC Cy2Im was used to synthesize novel Cy2Im-stabilized nickel complexes [Ni2(Cy2Im)4(μ-(η2:η2)-COD)] 1, [Ni(Cy2Im)2(η2-C2H4)] 2, and [Ni(Cy2Im)2(η2-COE)] 3. An optimized procedure was developed using 5 mol% of the Ni-catalyst, 1.5 equivalents of the boron reagent B2pin2, and 1.5 equivalents of NaOAc as the base in methylcyclohexane at 100 °C. With these optimized conditions, it was shown that a variety of aryl chlorides, containing either electron-withdrawing or -donating groups, were converted to the corresponding aryl boronic esters in yields up to 99% (88% isolated) yield. Mechanistic investigations revealed that the C–Cl oxidative addition product [Ni(Cy2Im)2(Cl)(4-F3C-C6H4)] 11, which has been synthesized and isolated separately, also catalyzes the reaction. Thus, rapid oxidative addition of the C–Cl bond of the aryl chloride to [Ni2(Cy2Im)4(μ-(η2:η2)-COD)] 1 to yield trans-[Ni(Cy2Im)2(Cl)(Ar)] represents the first step in the catalytic cycle. The rate limiting step in this catalytic cycle is the transmetalation of boron to nickel forming trans-[Ni(Cy2Im)2(Bpin)(Ar)], which was not possible to isolate. The boryl transfer reagent is assumed to be the anionic adduct Na[B2pin2(OAc)]. A final reductive elimination step gives the desired borylated product Ar–Bpin and regenerates [Ni(Cy2Im)2].
In the next chapter the first effective C–Cl bond borylation of aryl chlorides using NHC-stabilized Cu(I)-complexes of the type [Cu(NHC)(Cl)] was developed. The known complexes [Cu(iPr2Im)(Cl)] 15, [Cu(Me2ImMe)(Cl)] 16, and [Cu(Cy2Im)(Cl)] 17, bearing the small alkyl substituted NHCs, were synthesized in good yields by the reaction of copper(I) chloride with the corresponding free NHC at low temperature (-78 °C) in THF. A range of catalysts, bases, solvents, and boron sources were screened to determine the scope and limitations of this reaction. [Cu(Cy2Im)(Cl)] 17 revealed a significantly higher catalytic activity than [Cu(iPr2Im)(Cl)] 15. KOtBu turned out to be the only efficient base for this borylation reaction. Besides methylcyclohexane, toluene was the only solvent that gave the borylated product in moderate yields of 53%. It was shown that a variety of electron-rich and electron-poor aryl chlorides can be converted to the corresponding aryl boronic esters in isolated yields of up to 80%. A mechanism was proposed, in which a Cu-boryl complex [Cu(L)(Bpin)] is formed in the initial step. This is followed by C–B bond formation via σ-bond metathesis with the aryl chloride forming the aryl boronic ester and [Cu(L)(Cl)]. The latter reacts with KOtBu to give [Cu(L)(OtBu)], which regenerates the copper boryl complex by reaction with B2pin2.
Chapter 4 describes studies directed towards the transition metal-free borylation of aryl halides using Lewis base adducts of diborane(4) compounds. A variety of novel pyridine and NHC adducts of boron compounds were synthesized. Adducts of the type pyridine·B2cat2 18-19 and NHC·B2(OR)4 20-23 were examined for their ability to transfer a boryl moiety to an aryl iodide. However, only Me2ImMe∙B2pin2 20 was found to be effective. The stoichiometric reaction of 20 with different substituted aryl iodides and bromides in benzene, at elevated temperatures, gave the desired aryl boronic esters in good yields. Interestingly, depending on the reaction temperature, C–C coupling between the aryl halide and the solvent (benzene), was detected leading to a side product which, together with observed hydrodehalogenation of the aryl halide, provided indications that the reaction might be radical in nature.
When the boryl transfer reaction based on Me2ImMe∙B2pin2 20 was followed by EPR spectroscopy, a signal (though very weak and ill-defined) was detected, which is suggestive of a mechanism involving a boron-based radical. In addition, the boronium cation [(Me2ImMe)2∙Bpin]+ 37 with iodide as the counterion was isolated from the reaction residue, indicating the fate of the second boryl moiety. A preliminary mechanism for the boryl transfer from 20 to aryl iodides was proposed, which involves an NHC–Bpin˙ radical as the key intermediate. Me2ImMe–Bpin˙ is formed by homolytic B–B bond cleavage of the bis-NHC adduct (Me2ImMe)2∙B2pin2, which is formed in situ in small amounts under the reaction conditions. Me2ImMe–Bpin˙ reacts with the aryl iodide to give the aryl boronic ester with recovery of aromaticity. In the same step, from the second equivalent of NHC–Bpin˙, an NHC-stabilized iodo-Bpin adduct is formed as an intermediate, which is further coordinated by another NHC, yielding [(Me2ImMe)2∙Bpin]+I- 37. / Das erste Kapitel gibt zunächst einen detaillierten Überblick über die Nickel-katalysierte Borylierung. Das zweite Kapitel dieser Arbeit beschreibt die Borylierung von Arylchloriden mithilfe NHC-stabilisierter Nickelkatalysatoren. Dafür wurden zunächst die Nickelkomplexe [Ni2(Cy2Im)4(μ-(η2:η2)-COD)] 1, [Ni(Cy2Im)2(η2-C2H4)] 2 und [Ni(Cy2Im)2(η2-COE)] 3 dargestellt. Als optimale Bedingungen für die Borylierung haben sich 5 Mol-% des Ni-Katalysators, 1.5 Äquivalente des Borylierungsreagenzes B2pin2 und 1.5 Äquivalente NaOAc als Base in Methylcyclohexan bei 100 °C erwiesen. Unter diesen optimierten Bedingungen lassen sich eine Vielzahl unterschiedlicher Arylchloride in die jeweiligen Arylboronsäureester in Ausbeuten von bis zu 99% (88% für die isolierte Verbindung) überführen. Der Komplex [Ni(Cy2Im)2(Cl)(4-F3C-C6H4)] 11, das Produkt der oxidativen Addition von 4-F3C-C6H4-Cl an [Ni2(Cy2Im)4(μ-(η2:η2)-COD)] 1, katalysiert ebenfalls die Reaktion. Mechanistischen Untersuchungen zufolge, stellt die rasche oxidative Addition der C–Cl-Bindung des Arylchlorids an [Ni2(Cy2Im)4(μ-(η2:η2)-COD)] 1 unter der Ausbildung von trans-[Ni(Cy2Im)2(Cl)(Ar)], den ersten Schritt des Katalysezykluses dar. Der geschwindigkeitsbestimmende Schritt in diesem Katalysezyklus ist die Transmetallierung von Bor zu Nickel unter Bildung von trans-[Ni(Cy2Im)2(Bpin)(Ar)]. Es wird angenommen, dass es sich bei dem Boryltransferreagenz um das anionische Addukt Na[B2pin2(OAc)] handelt. Ein letzter reduktiver Eliminierungsschritt ergibt das gewünschte borylierte Produkt Ar–Bpin unter Rückgewinnung von [Ni(Cy2Im)2].
Im nächsten Kapitel der Arbeit wurde die erste effiziente C–Cl-Borylierung von Arylchloriden entwickelt. Eine Reihe verschiedener Katalysatoren des Typs [Cu(NHC)(Cl)], Basen, Lösungsmitteln und Borylierungsreagenzien wurden untersucht, um die Anwendungsmöglichkeiten und Grenzen dieser Reaktion zu bestimmen. Der Komplex [Cu(Cy2Im)(Cl)] 17 zeigte dabei eine signifikant höhere katalytische Aktivität als [Cu(iPr2Im)(Cl)] 15. Des Weiteren erwies sich KOtBu als einzige geeignete Base für diese Reaktion und Methylcyclohexan stellte sich als optimales Lösungsmittel heraus. Unter diesen optimierten Bedingungen lassen sich eine Vielzahl, sowohl elektronenreicher als auch elektronenarmer Arylchloride in die entsprechenden Arylboronsäureester in Ausbeuten von bis zu 80% überführen. Ein Mechanismus der Reaktion wurde postuliert, wonach zunächst ein Kupfer-Boryl-Komplex [Cu(L)(Bpin)] gebildet wird. Darauf folgt die Knüpfung einer C–B-Bindung durch eine σ-Bindungsmetathese mit dem Arylchlorid, wobei der gewünschte Arylboronsäureester und [Cu(L)(Cl)] gebildet wird. Im Folgenden reagiert [Cu(L)(Cl)] mit KOtBu zu [Cu(L)(OtBu)], wodurch durch Reaktion mit B2pin2 der Kupfer-Boryl-Komplex regeneriert wird.
Kapitel 4 beschreibt Untersuchungen zur übergangsmetallfreien Borylierung von Arylhalogeniden unter Verwendung von Lewis-Basen-Addukten von Diboran(4)-Verbindungen. Die Addukte des Typs Pyridin·B2cat2 18-19 und NHC·B2(OR)4 20-23 wurden weiter auf ihre Fähigkeiten hin untersucht, eine Boryleinheit auf ein Aryliodid zu übertragen. Ausschließlich Me2ImMe∙B2pin2 20 stellte sich hierbei als wirksam heraus. Die stöchiometrische Reaktion von 20 mit verschiedenartig substituierten Aryliodiden und -bromiden in Benzol bei erhöhten Temperaturen lieferte die gewünschten Arylboronsäureester in guten Ausbeuten. Interessanterweise wurde als Nebenreaktion eine von der Reaktionstemperatur abhängige C–C-Kupplung zwischen dem Arylhalogenid und dem Lösungsmittel (Benzol) beobachtet. Sowohl das C–C-Kupplungsnebenprodukt, als auch eine beobachtete Hydrodehalogenierung des Arylhalogenids deuten darauf hin, dass die Reaktion von radikalischer Natur sein könnte. Die Verfolgung der von Me2ImMe∙B2pin2 20 ausgehenden Boryltransferreaktion mittels ESR-Spektroskopie zeigte ein Signal, was auf einen Mechanismus mit Beteiligung eines Borradikals hinweist. Weitere Untersuchungen ergaben experimentelle Beweise für die Anwesenheit von Radikalen im Verlauf der Reaktion. Des Weiteren wurde das Boroniumkation [(Me2ImMe)2∙Bpin]+ 37 mit Iodid als Gegenion aus dem Reaktionsrückstand isoliert, was den Verbleib der zweiten Boryleinheit erklärt. Ein vorläufiger Mechanismus für den Boryltransfer von Me2ImMe∙B2pin2 20 auf Aryliodide wurde vorgeschlagen, wobei ein NHC–Bpin˙-Radikal als Schlüsselintermediat fungiert. Me2ImMe–Bpin˙ wird durch homolytische Spaltung der B–B-Bindung des Bis-NHC-Addukts (Me2ImMe)2∙B2pin2 gebildet, welches unter den gegebenen Reaktionsbedingungen in geringen Mengen in situ gebildet wird. Me2ImMe–Bpin˙ reagiert mit dem Aryliodid unter Rückgewinnung der Aromatizität zum gewünschten Arylboronsäureester. Im gleichen Schritt wird aus dem zweiten Äquivalent NHC–Bpin˙ ein NHC-stabilisiertes Iod-Bpin-Addukt als Zwischenprodukt gebildet. Dieses wird von einem weiteren NHC unter Bildung von [(Me2ImMe)2∙Bpin]+I- 37 koordiniert.
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Catalytic Enantioselective Formations of C–B, C–C and C–Si Bonds by Organic Molecules or Transition-Metal ComplexesWu, Hao January 2015 (has links)
Thesis advisor: Amir H. Hoveyda / Catalytic enantioselective reactions are of great importance in synthetic organic chemistry. Thus, development of efficient, selective and easily accessible catalyst for various bond formations is the main task in our laboratories. First, we have developed the first broadly applicable enantioselective boryl conjugate addition reactions to a variety of α,β-unsaturated carbonyls, promoted by a chiral Lewis basic N-heterocyclic carbene. The valuable β-boryl carbonyls were further used in complex molecule syntheses. The mechanism of these C–B bond formations was studied in details. We have also developed a practical method for enantioselective addition of an allene unit to aryl-, heteroaryl- and alkyl-substituted Boc-aldimines. These efficient C–C bond formations, catalyzed by an aminophenol-derived boron-based catalyst, were further utilized in succinct syntheses of anisomycin and epi-cytoxazone. Finally, chiral NHC–Cu complexes were employed for site-, diastereo- and enantioselective silyl conjugate additions to acyclic and cyclic dienones and dienoates. The precious enantiomerically enriched allylsilane obtained can be converted into a ketone-aldol type product, which is difficult to access through alternative methods. / Thesis (PhD) — Boston College, 2015. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.
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New Design of Bipyridine Ligands for Copper-Catalyzed Asymmetric Molecular Transformations / ビピリジン配位子の精密設計に基づいた銅触媒不斉分子変換法の開発Yoshinaga, Yukako 25 May 2020 (has links)
京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22662号 / 工博第4746号 / 新制||工||1742(附属図書館) / 京都大学大学院工学研究科合成・生物化学専攻 / (主査)教授 杉野目 道紀, 教授 村上 正浩, 教授 中尾 佳亮 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM
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Copper-Catalyzed Asymmetric Allylic Substitution with Organo- and Silylboronates / 銅触媒による有機およびシリルボロン酸エステルを用いた不斉アリル位置換反応Takeda, Momotaro 24 March 2014 (has links)
京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18093号 / 理博第3971号 / 新制||理||1572(附属図書館) / 30951 / 京都大学大学院理学研究科化学専攻 / (主査)教授 大須賀 篤弘, 教授 丸岡 啓二, 教授 時任 宣博 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM
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Formação de acetato de etila a partir do etanol sobre catalisadores de Cu/ZrO2: efeito da carga de cobre nas propriedades físicas e catalíticasFreitas, Isabel Cristina de 10 March 2010 (has links)
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Previous issue date: 2010-03-10 / Financiadora de Estudos e Projetos / The ethanol dehydrocoupling in ethyl acetate distinguishes among the reactions of alcohol transformation in products with higher added value. Due to the possibility of obtaining ethanol from biomass in Brazil, the production of ethyl acetate is of great interest, being their production very economical. The ethanol dehydrocoupling in ethyl acetate was studied over Cu/ZrO2 catalysts prepared by impregnation method followed by calcinations in air. The samples with different Cu loadings were characterized by thermal analyze, X-Ray powder diffraction, determination of the specific surface area, temperature-programmed reduction (TPR), decomposition of N2O and X-Ray photoelectron spectroscopy (XPS). TPR results showed the formation of low temperature reduction Cu species (peaks α1, α2 e β) predominant at low loadings of supported Cu in ZrO2, these species are attributed to CuO highly dispersed on support. The increase of Cu loading caused the formation of CuO bulk species with high temperature reduction (peaks γ1 e γ2). XPS results for Cu/ZrO2 reduced catalysts showed that an increase in the Cu loading caused a shift in the Cu 2p3/2 peak to regions of lower biding energy. The spectra of Cu Auger region suggest that a decrease in the Cu loading increases the ratio of Cu+/Cuo species. Catalytic tests for dehydrocoupling reaction of ethanol were carried out at atmospheric pressure and showed an increasing activity per Cu site for ethyl acetate formation with the increase in the dispersion of supported Cu. Furthermore, the by-products formation due the acetaldehyde via aldol condensation occurs on the ZrO2 support surface. Also, it could be seen that catalysts with Cu loading up to 20% showed an increase in the ethyl acetate selectivity with an increase in the Cu loading. This can be attributed to the higher ZrO2 coating by active phase providing the suppression of by-products that are formed via aldol condensation. / O desidroacoplamento do etanol em acetato de etila destaca-se dentre as reacoes de transformacao de alcoois em produtos de maior valor agregado. Devido a abundancia de etanol no Brasil e a possibilidade de sua obtencao a partir da biomassa, a producao de acetato de etila desperta grande interesse, sendo a sua producao muito economica. O desidroacoplamento do etanol em acetato de etila foi estudado sobre catalisadores de Cu/ZrO2 preparados pelo metodo de impregnacao, seguidos de calcinacao em ar. As amostras com diferentes cargas de Cu foram caracterizadas por analise termica, difracao de Raios X, determinacao da area superficial especifica, reducao a temperatura programada (TPR), decomposicao do N2O e espectroscopia de fotoeletrons excitados por Raios X (XPS). Resultados de TPR mostraram a formacao de especies de cobre de baixa temperatura de reducao (picos α1, α2 e β) predominantes em baixas cargas de Cu suportados em ZrO2, estas especies sao atribuidas ao CuO altamente disperso no suporte. Com o aumento da carga de Cu obteve-se a formacao de especies de CuO massico de alta temperatura de reducao (picos γ1 e γ2). Resultados de XPS para catalisadores de Cu/ZrO2 reduzidos revelaram que com o aumento da carga de cobre suportado houve o deslocamento do pico da regiao Cu 2p3/2 para regioes de menor energia de ligacao. Os espectros da regiao Auger do Cu sugerem que com a diminuicao da carga de Cu tem-se o aumento da razao das especies Cu+/Cuo. Ensaios cataliticos para a reacao de desidroacoplamento do etanol foram realizados a pressao atmosferica e mostraram o aumento da atividade por sitio de Cu para a formacao de acetato de etila com o aumento da dispersao do cobre no suporte. Sobre a superficie do suporte ZrO2 ocorre a formacao de subprodutos devido a condensacao do acetaldeido via condensacao aldolica. Para catalisadores com carga de Cu de ate 20% verifica-se o aumento da seletividade a acetato de etila com o aumento da carga de cobre, em decorrencia do aumento do grau de recobrimento da ZrO2 pela a fase ativa proporcionando a supressao de subprodutos formados via condensacao aldolica.
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Transition-metal catalyzed cyclization reactionsPedro De Andrade Horn (14094015) 11 November 2022 (has links)
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<p>A historically important reaction, the Ueno-Stork reaction promotes, through the use of toxic organotin species, the cyclization of a haloacetal onto an alkene generating bicyclic acetals. This reaction has been used over the years in several total syntheses of biologically relevant natural products, especially the prostaglandin class of natural products. Herein, will be described the development of a novel nickel-catalyzed Ueno-Stork cyclization reaction, which no toxic organotin and radical promoters are used, and instead a greener, operationally friendly, and non-toxic earth abundant nickel catalyst is applied. Optimization studies, substrate scope, scalability, relative stereochemistry of the bicyclic acetals, as well as derivatization of the products were studied. Furthermore, the newly developed reaction was applied on the total synthesis of tricyclic-PGDM Methyl ester, a prostaglandin D2 metabolite of important clinical relevance that currently suffers from material supply issues.</p>
<p>Cyclopropanol ring opening reactions have different reactivity modes. Either a metal homoenolate species or a b-keto radical species can be formed after ring opening depending on the reaction conditions applied. More specifically, hydroxycyclopropanols have been studied to access several important motifs present in an array of natural products and medicinally important molecules. The Dai group has used this strategy to access several motifs through intramolecular trapping of the homoenolate species with and without the presence of carbon monoxide to generate oxaspirolactones, THF/THP-fused bicyclic lactones, and disubstituted THF/THP heterocycles. Herein, it will be discussed the application of similar concepts to access new classes of heterocycles 4-ketovalerolactones and 3-furanones. The optimization of two reaction conditions to selectively synthesize each product starting from the same starting material was studied. Furthermore, the substrate scope, scale-up, and derivatization studies of each motif will be disclosed. </p>
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