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1
Cambridge, James R. A. "Lewis acid catalysed rearrangement of epoxides :a mechanistic study." Thesis, University of Canterbury. Chemistry, 2004. http://hdl.handle.net/10092/5646.
Full textAbstract:
The Lewis acid catalysed rearrangement of optically active, deuterium labelled styrene oxide derivatives to aldehydes is studied experimentally and the mechanism is further elucidated by ab initio molecular orbital and density functional calculations. The Lewis acid catalysed rearrangement of styrene oxide derivatives is shown to occur via a carbocation intermediate. Opening of the epoxide ring occurs with rotation of the Lewis acid coordinated oxygen either towards or away from the aryl group to form either the cis or trans carbocation. Calculations indicate that conversion between the cis and trans cations will only occur via ring closure back to the epoxide. The selectivity for hydride migration is controlled by the preferred geometry of thc carbocation intemediate, specifically whether the C-O bond prefers to adopt an eclipsed confonnation relative to the adjacent cation substituent or whether the stabilisation of the cation is obtained from hyperconjugation of a terminal hydrogen to the cation centre.
Chapter One contains a review of the relevant literature and the results of previous mechanistic studies into the Lewis acid catalysed rearrangement of epoxides are discussed.
In Chapter Two, a methodology is developed to measure the relative amounts of hydrogen or deuterium in each position of the aldehyde produced by hydride or deuteride migration in the rearrangement of a styrene oxide derivative. The aldehyde product is reduced to an alcohol and reacted with a chiral acid chloride. The resulting ester can be analysed by III NMR in the presence of Yb(hfC)3 or Eu(hfc)3 chiral shift reagents so that the full stereochemical course of the hydride migration can be determined.
Chapter Three describes the BF3.OEt2 and LiC104 catalysed rearrangement of deuterated analogues of optically active p-methylstyrene oxide. It is shown that the rearrangement reaction must proceed at least in part via a carbocation intermediate. The results are analysed by the method of Fujimoto and show that for both the BF3.OEt2 and LiC104 catalysed reactions, the majority of the reaction occurs by epoxide opening with rotation of the Lewis acid coordinated oxygen towards the aromatic group (66% : 34% and 57% : 43% respectively). This is in contrast to previous studies where it was assumed that this reaction pathway would not occur. In the LiC104 catalysed reaction, where epoxide opening occurs with rotation of the oxygen away from the aromatic group, hydride/deuteride migration occurs almost exclusively with inversion of configuration; while in the other reactions hydride migrates to an equal extent with inversion or retention of configuration.
In Chapter Four, deuterated fluorohydrin is synthesised from deuterated p-methylstyrene oxide and converted to aldehyde with an excess of BF3.OEh in order to determine whether fluorohydrin is an undetected intermediate in the BF3.OEt2 catalysed rearrangement of p-methyl styrene oxide. It is shown the conversion of fluorohydrin to aldehyde occurs by a nearly concerted mechanism, in contrast to the rearrangement of p-methylstyrene oxide to aldehyde which occurs via a carbocation. The rates of the two reactions are also not compatible and fluorohydrin is shown not to be an intem1ediate in the reaction.
Chapter Five describes the LiC104 and BF3.OEt2 catalysed rearrangement of deuterated optically active m-methoxystyrene oxide. The selectivity for hydride migration observed is consistent with the mechanism developed for the rearrangement of p-methylstyrene oxide in chapter 3. More of the reaction goes by epoxide opening with rotation towards the aryl group for the destabilised m-methoxy compared to the p-methyl substituted epoxide.
Chapter Six describes a computational investigation into the BF3 and Li+ catalysed rearrangement of various styrene oxide derivatives. Stationary points are calculated on the potential energy surfaces for the reactions and the stationary points are characterised by vibrational frequency calculations. Two confom1ations of carbocation are found on the Li+ catalysed reaction surface. One structure has the C-O bond eclipsed with the adjacent C- aryl bond and both terminal hydrogens equally aligned for migration. The other cation minimum shows one terminal hydrogen already in hyperconjugation with the carbocation p-orbital, making it more likely to migrate. It is also shown that rotation of the oxygen
towards and away from the aryl group can be considered separately when analysing the reaction.
Chapter Seven describes a computational study into the BF3 catalysed rearrangement of 2,3,3-trimethyl-1-butene oxide. The results are combined with a previous computational and experimental studies and it is shown that the reaction fits with the mechanism developed to explain the results of the rearrangement of styrene oxide derivatives. The synthesis of chiral deuterated, 1-octene oxide and 2,3,3-trimethyl-1-butene oxide and the attempted synthesis of p-methoxystyrene oxide is described in Chapter Eight. Chapter Nine describes an investigation into acetate participation in epoxide rearrangement reactions. In this study epoxide rearranged to ketone and no participation of acetate in a cyclisation reaction was observed. The final chapter details the experimental procedures used in the preceding chapters.
2
Nam, Shayne G. C. "The mechanism of Lewis acid catalysed epoxide rearrangement to aldehyde." Thesis, University of Canterbury. Chemistry, 2005. http://hdl.handle.net/10092/6091.
Full textAbstract:
This thesis describes investigations centred on the mechanistic pathway of the Lewis acid-promoted conversion of epoxides into aldehydes. Such studies were directed to gain new information about this important, fundamental rearrangement which contributes to our knowledge and understanding of how and why chemical reactions occur. The research undertaken involved the use of deuterium labelling studies working with enantio-enriched epoxides.
Chapter One reviews previous literature and the results of previous mechanistic studies into the Lewis acid catalysed rearrangements of epoxides.
Chapter Two describes the development of new methodology for the measurement of the relative amounts of hydrogen and deuterium in each position of the aldehyde produced by hydride or deuteride migration in the rearrangement of styrene oxide. The method consisted of reduction of the aldehyde to an alcohol and subsequent reaction of the alcohol with a chiral acid chloride in the presence of a chiral shift reagent [Yb(hfc)3 or Eu(hfc)3] to measure the diastereomeric/enantiomeric excess in the aldehyde product mixture. The diastereomeric/enantiomeric excess thus determined, can be correlated back to determine the full stereochemical course of the initial epoxide rearrangement. De-convolution of overlapping peaks by mathematical modelling was sometimes necessary.
Chapter Three describes the enantiose1ective synthesis of several undeuterated and deuterated styrene oxides that were then used as substrates to study their BF3.OEt2 and LiClO4 rearrangement to give aldehydes.
In Chapter Four the BF3.OEt2 catalysed rearrangement of enantioenriched deuterated analogues of styrene oxide are investigated.
Chapter Five describes the difficulties encountered when attempting to rearrange both racemic and optically active styrene oxides with LiClO4 in refluxing benzene. Dr D.Q. McDonald's reactions are reproduced to substantiate the claim that his previously reported results were compromised by traces of acid present in the samples of epoxide starting material.
The LiClO4/ether catalysed rearrangement of enantio-enriched deuterated analogues of styrene oxide are investigated in Chapter Six with evidence of some racemisation occurring during the rearrangement process.
An overall discussion is presented in Chapter Seven with results of the rearrangements of styrene oxide. The results are interpreted using both the Blackett and Fujimoto models and comparisons are made with previous mechanistic studies. Explanations and final conclusions are drawn with future studies outlined. The experimental details that substantiate the claims made in the previous chapters are included in Chapter Eight.
3
Owston, Nathan Ashley. "Novel transition metal-catalysed syntheses of carboxylic acid derivatives." Thesis, University of Bath, 2008. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.512253.
Full textAbstract:
This thesis describes the chemistry developed during a study of novel transition metalcatalysed reactions for the synthesis of carboxylic acid derivatives. Chapter 2 describes a novel protocol for the synthesis of primary amides from alcohols in one-pot where a metal complex mediates two fundamentally different catalytic processes. An iridium catalyst has been shown to be effective for the selective rearrangement of aldoximes into primary amides. In addition, an iridium-catalysed oxidation of activated alcohols via hydrogen transfer has been developed using an alkene as formal oxidant. These reactions have been combined in a sequential process affording good yields for a range of benzylic alcohols. An improved system for the rearrangement of aldoximes into amides using a new ruthenium catalyst is described in Chapter 3. Through a systematic program of optimisation excellent selectivity was achieved for a wide range of substrates at markedly reduced catalyst loading. Chapter 4 describes the development of a ruthenium-catalysed elimination reaction for the conversion of oxime ethers into nitriles. The application of this reaction to tandem and sequential reactions has been explored, albeit with limited success. Also, a method for the ruthenium-catalysed oxidation of alcohols using an electron-deficient alkene as hydrogen acceptor is described, and its application to a tandem oxidation process with a nitrogen nucleophile demonstrated. As an extension of the concept presented in Chapter 4, tandem oxidation processes with oxygen nucleophiles are the subject of Chapter 5. This strategy has been used for the oxidation of primary alcohols to their corresponding methyl esters in one-pot, with good yields obtained for a range of substrates. The use of water as a nucleophile in such a process has also been examined.
4
Lukamto, Daniel Hartoyo. "Applications of hypervalent iodine reagents : from enantioselective copper-catalysed arylation-semipinacol cascade to methionine functionalisation for peptide macrocyclisation." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/283560.
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The unifying theme of this thesis is the exploitation of the reactivity of aryliodonium salts as electrophile transfer reagents. In the first part of the thesis, diaryliodonium salts are employed as arylation reagents for the enantioselective copper-catalysed arylative semipinacol rearrangement (SPR) of various tertiary allylic alcohols. This cascade reaction is a rare example of asymmetrically activating SPR using carbon electrophiles. Different substrate classes - including dihydropyran, indene and dihydronaphthalene moieties - are converted to enantioenriched beta-aryl spirocyclic ketones in excellent yields and enantioselectivities, and often as a single diastereomer. These are in turn useful functional handles for transformations into other moieties, including further rearrangements via Baeyer-Villiger oxidation. In the second part of this thesis, a two-step process for the macrocyclisation of native peptides via a non-natural linkage is developed. This study exploits previous work conducted in the group on the use of aryliodonium salts as methionine-selective diazoacetate transfer reagents. The functionalised methionine is in turn used for an intramolecular rhodium-catalysed insertion into tryptophan. Eventual translation onto solid-phase enables facile access into various macrocyclic peptides.
5
Albers, Lena Verfasser], Thomas [Akademischer Betreuer] [Müller, and Rüdiger [Akademischer Betreuer] Beckhaus. "Mechanistic investigations on Lewis acid-catalysed skeletal rearrangement reactions of polysilanes and germapolysilanes : subtle capture of intermediates / Lena Albers. Betreuer: Thomas Müller ; Rüdiger Beckhaus." Oldenburg : BIS der Universität Oldenburg, 2015. http://d-nb.info/1084187159/34.
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Albers, Lena [Verfasser], Thomas [Akademischer Betreuer] Müller, and Rüdiger [Akademischer Betreuer] Beckhaus. "Mechanistic investigations on Lewis acid-catalysed skeletal rearrangement reactions of polysilanes and germapolysilanes : subtle capture of intermediates / Lena Albers. Betreuer: Thomas Müller ; Rüdiger Beckhaus." Oldenburg : BIS der Universität Oldenburg, 2015. http://d-nb.info/1084187159/34.
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7
Nomura, Hiroshi. "An Investigation into the Allylic Imidate Rearrangement of Trichloroacetimidates Catalysed by Cobalt Oxazoline Palladacycles. The Use of Chiral Allylic Amides for the synthesis of Mono- and Bicyclic Nitrogen Heterocycles." Thesis, University of East Anglia, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.520457.
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8
Cadu, Alban. "Noble Metal Catalysed Reductions and Rearrangements." Doctoral thesis, Uppsala universitet, Syntetisk organisk kemi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-272383.
Full textAbstract:
The focus of this thesis has been organometallic catalysis applied to compounds containing heteroatoms which are usually poisonous to metal catalysts, by channelling their innate reactivity advantageously. The studies described in this thesis concentrate, in the first part, on iridium catalysed asymmetric hydrogenation (papers I and II) and in the second part, on gold catalysed internal rearrangements (papers III and IV). In each case, two classes of compounds are studied: pyridinium salts or sulphurous compounds. The asymmetric hydrogenation of pyridinium compounds was performed with 2% loading of N,P-ligated Ir catalyst with I2 additive (paper I) to achieve moderate to good enantiomeric excess (up to 98%). In paper II, olefinic sulphones were hydrogenated with an efficient 0.5% catalytic loading. In most cases full conversion was obtained and with good to excellent ees (up to 99%). The products of these reductions are chiral compounds, which could constitute further chemical building blocks. Palladium and gold were used sequentially in paper III, in order to perform a “Click” thiol-yne reaction followed by a semi-Pinacol rearrangement, leading to isolated yields of up to 98%. In paper IV The gold catalysed rearrangement of alkyl-pyridinium diynes was conducted, with a number of substrates providing >90% NMR yield. A highly selective hydrogenation was performed with a heterogeneous palladium catalyst to yield single diastereomer products. This methodology consists of up to three steps, with two catalysts in one pot.
9
Kasten, Kevin. "Lewis base-catalysed enantioselective formal cycloadditions and rearrangements." Thesis, University of St Andrews, 2017. http://hdl.handle.net/10023/11365.
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This thesis describes the use of chiral nitrogen-based Lewis base catalysts in transformations such as cycloadditions and rearrangements. Cinchona alkaloids were employed as catalysts within a formal [4+2]-cycloaddition of trifluoromethyl- substituted α,β-unsaturated ketones and allenoates. Either 1,1,1-trifluorobut-3-en-2- ones or 4,4,4-trifluorobut-2-en-1-ones were used to selectively introduce a trifluoromethyl moiety in the 4- or 6-position within a dihydropyran scaffold. The reaction proceed successfully to give a range of dihydropyran products with (hetero)aryl- and alkyl-substituted trifluoromethyl ketones in up to 81% yield and 98% e.e. The dihydropyran products can be derivatised using selective hydrogenation methods to give tetrahydropyrans in high yield and diastereoselectivity without loss of stereointegrity. Furthermore, isothioureas were applied in the [2,3]-sigmatropic rearrangement of 3- fluorocinnamyl substituted quaternary ammonium salts. A broad range of substituents at either the nitrogen or the cinnamyl group has been evaluated showing the generality of this process. Enantioenriched amino acid derivatives containing a tertiary flourinated carbon centre were produced in high yield and good enantio- and diastereoselectivity (up to 76%, 94:6 d.r., 96% e.e.). It was attempted to extend the scope of this reaction to the [2,3]-Sommelet-Hauser rearrangement of benzylic ammonium salts, which proved to be difficult. A range of conditions as well as variety of substituted benzyl substrates were investigated but no rearrangement product could be isolated. The further extension of the scope of the [2,3]-rearrangement using allylic ammonium salts with 3-methylcinnamyl substitution was investigated. Mixtures of enantioenriched products derived from [2,3]- and [1,2]-rearrangement were observed. The fomation of the [1,2]-product led to the further investigation of this rearrangement. Applying ammonium salts bearing bulky 3,3-disubstituted allyl groups a selective [1,2]-rearrangement has been observed. The optimisation of this process is discussed and products were obtained in up to 68% yield and 58% e.e. This represents the first catalytic enantioselective [1,2]-rearrangement of ammonium salts.
10
Renny, Joseph S. "The Newman-Kwart Rearrangement : Molecularity and Catalysis." Thesis, University of Bristol, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.525440.
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11
Yoon, Tehshik Peter MacMillan David W. C. "The acyl-Claisen rearrangement development of a novel metal-catalyzed Claisen rearrangement and enantioselective variants of the acyl-Claisen rearrangement /." Diss., Pasadena, Calif. : California Institute of Technology, 2002. http://resolver.caltech.edu/CaltechTHESIS:01282010-153053761.
Full textAbstract:
Thesis (Ph. D.)--California Institute of Technology, 2002. PQ #3052855.Advisor names found in the Acknowledgments pages of the thesis. Title from home page. Viewed 02/11/2010. Includes bibliographical references.
12
Yang, Yanbo. "Pd0-Catalyzed Formal 1,3-Diaza-Claisen Rearrangement. Design And Development Of Cationic 1,3-Diaza-Claisen Rearrangement." ScholarWorks @ UVM, 2014. http://scholarworks.uvm.edu/graddis/261.
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The dissertation describes Pd0-catalyzed formal 1,3-diaza-Claisen rearrangement and the design and development of cationic 1,3-diaza-Claisen rearrangement.
Our previous work has shown that isocyanates react with azanorbornenes and azabicyclo[2.2.2]octenes under thermal conditions to afford zwitterionic intermediates that undergo a thermal 1,3-diaza-Claisen rearrangement to give both ureas and isoureas. However, some azanorbornenes and azabicyclooctenes failed to rearrange or proceeded in low yields. To address these challenging substrates for the thermal 1,3-diaza-Claisen rearrangement, we have developed a Pd0-catalyzed formal 1,3-diaza-Claisen rearrangement. Interestingly, under Pd0-catalyzed condition, both isocyanates with electron-withdrawing groups and isocyanates without electron-withdrawing groups react with azanorbornenes and azabicyclo[2.2.2]octenes to provide ureas as the only products in high yields. More importantly, the reactions that failed under thermal conditions were all successful under Pd0-catalysis. In addition to azanorbornenes and azabicyclo[2.2.2]octenes, other ring systems were also investigated. Pd0 catalysis has broadened the scope of tertiary allylic amines that react with isocyanates to afford 1,3-diaza-Claisen rearrangement products.
In the presence of p-TsCl and NEt3, allylaminopropyl benzyl ureas were initially dehydrated to form protonated carbodiimides whose presence was confirmed by the infrared absorption frequency at 2100 cm-1 which is the characteristic band of -N=C=N-; then the in situ generated protonated carbodiimides were poised for further cationic 1,3-diaza-Claisen rearrangement to afford synthetically challenging guanidines. The effect of acid on the rearrangement was ascertained by the fact that no rearrangement product was observed by simply heating free base carbodiimide 3.10 in benzene at reflux. Other dehydration reagents, such as Tf2O, Ts2O, MsCl were also investigated, and none of them provide satisfactory results. A selection of allyamino benzyl ureas with different tether length, substituents, or in varied ring systems, were synthesized to explore the scope of this methodology. This methodology works best at allylaminopropyl benzyl ureas, and the substituents on the benzyl group does not seem to affect the reaction rate in a significant way.
13
Huang, Chaofeng Harmata Michael. "Studies of 2,1-benzothiazine, silver-catalyzed rearrangement and 1,5-hydride shift." Diss., Columbia, Mo. : University of Missouri--Columbia, 2009. http://hdl.handle.net/10355/6971.
Full textAbstract:
Title from PDF of title page (University of Missouri--Columbia, viewed on Feb 26, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Thesis advisor: Dr. Michael Harmata. Vita. Includes bibliographical references.
14
Barker, Thomas A. "Palladium-catalyzed [1,3] O→C rearrangement of pyrans towards functionalized cyclohexanones." Thesis, University of Sheffield, 2012. http://etheses.whiterose.ac.uk/2594/.
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Waddington, C. R. "The Fries rearrangement : added-ion effects and spectroscopic investigations." Thesis, University of Bristol, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355092.
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Cristiano, Maria de Lurdes dos Santos. "Thermal and photochemical rearrangements in heteroaromatic and aromatic compounds." Thesis, University of Liverpool, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384994.
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17
Heusser, Carolyn Andrea. "Efforts Towards the Cross Coupling of Acylsilanes and Electrophiles via a Metal-Catalyzed Brook Rearrangement." Thesis, Boston College, 2013. http://hdl.handle.net/2345/3402.
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Thesis advisor: Jeffrey A. ByersChapter 1: There are a limited number of examples of metal-catalyzed Brook rearrangements in the literature, none of which involve ruthenium, rhodium, or iridium which are common ketone hydrogenation catalysts. The content of this chapter introduces the traditional Brook rearrangement and its advantages and disadvantages in chemical synthesis. Furthermore, the few examples of metal-catalyzed Brook rearrangements of acylsilanes and structurally similar moieties are discussed. Chapter 2: Utilizing a Brook rearrangement under hydrogenation or transfer hydrogenation conditions opens up a new area of catalytic reactivity that has not been fully explored. To our knowledge, metal complexes based on ruthenium and rhodium have never been shown to catalyze a Brook rearrangement of acylsilanes. This chapter describes the mechanistic implications of a Brook rearrangement under hydrogenation or transfer hydrogenation conditions as well as the first example of a ruthenium-catalyzed Brook rearrangement of aryl acylsilanes. Chapter 3: Pioneering work performed by Jeffrey Johnson and co-workers in the area of catalytic coupling of acylsilanes and various electrophiles showed that formation of new C-C bonds through a Brook rearrangement can be a powerful synthetic tool. In this chapter, we investigate an intermolecular coupling of aryl acylsilanes and aldehydes through a metal-catalyzed Brook rearrangement under transfer hydrogenation conditions to yield two synthetically useful motifs, specifically oxygenated bicyclic compounds. A reaction screen was performed on the coupling capabilities of these two species with various ruthenium and rhodium catalysts. The result of the screen was synthesis of a silyl ether acetal through employing the starting material as the reducing equivalent. Additionally, mechanistic insight was gained to further develop the proposed methodology. Chapter 4: An intramolecular approach to achieving coupling of acylsilanes and many different types of electrophiles was envisioned as a way of furnishing synthetically useful bicyclic compounds in one step. The focus of this chapter is the synthesis of a novel acylsilane that we proposed could undergo an intramolecular cross coupling reaction under transfer hydrogenation conditions. The conclusion of this chapter outlines the future direction of the project, which entails a new route to an intermolecular cross coupling of acylsilanes and various electrophiles. Published work from Michael Krische's laboratory helped us envision a different type of acylsilane, specifically an α,β-unsaturated acylsilane, in which binding to a metal center would proceed through a π-allyl intermediate. Ongoing efforts in the coupling of α,β-unsaturated acylsilanes with electrophiles are currently underway
Thesis (MS) — Boston College, 2013
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Chemistry
18
Pillai, SK, O. Gheevarghese, and S. Sugunan. "Catalytic properties of V2O5/SnO2 towards vapour-phase Beckmann rearrangement of cyclohexanone oxime." Elsevier, 2008. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1001694.
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A B S T R A C T
V2O5/SnO2 solid acid catalysts have been employed for the vapour-phase Beckmann rearrangement of
cyclohexanone oxime to e-caprolactam. Catalysts with different vanadia loading (3–15 wt%) were
prepared by impregnation method and characterized by XRD, BET surface area, FTIR and 51V NMR
techniques. The surface acidic properties were determined by temperature programmed desorption and
cumene cracking reaction. Under optimized reaction conditions, catalyst with 9 wt% V2O5 gives the
maximum amount of desired product (yield 78.8%). However, the catalysts are susceptible for
deactivation due to the basic nature of the reaction products (50% deactivation in 5 h). A good correlation
was obtained among the rearrangement activities of V2O5/SnO2 catalysts, their weak plus medium
acidities (usually of the Bro¨ nsted type) and structural properties.
19
Lamb, Alan David. "Asymmetric synthesis of heterocycles via cation-directed cyclizations and rearrangements." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:4c0cf06c-d461-42a4-b4d8-a2a2bd961435.
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The aim of this project was to utilize chiral cation-directed catalysis in the asymmetric synthesis of novel hererocycles. This goal was initially realized by the synthesis of azaindolines in high yields and enantioselectivities (Chapter 2). Extension of this methodology to substrates bearing two stereogenic centres was successful, although control over both diastereoselectivity and enantioselectivity in this process was modest. Finally the synthesis of heterocycles utilizing cation-directed rearrangement processes was examined, with proof of concept obtained for a novel asymmetric cyclization to form xanthenes.
20
Zirimwabagabo, Jean-Olivier. "Kinetic resolution of cyclic enol ethers by Pd-catalyzed [1,3] O-C rearrangement." Thesis, University of Sheffield, 2014. http://etheses.whiterose.ac.uk/7105/.
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This thesis concerns the development of kinetic resolution of cyclic enol ethers utilizing a Pd-catalyzed [1,3] O-C rearrangement reaction. The required enol ethers were prepared from commercially available starting materials in good to excellent yields. The Pd-catalyzed [1,3] O-C rearrangement of these enol ethers in the presence of a chiral ligand proceeds smoothly via a kinetic resolution process returning remaining starting material with low to excellent levels of enantioselectivity. Enantiomerically enriched enol ethers were further transformed to a series of carbo- and heterocyclic products in good yield and with excellent levels of stereocontrol. Synthesis of (R)-goniothalamin was successfully accomplished via stereoselective transformations from an enantioenriched enol ether starting material. Aspects of the reaction mechanism are described, which resulted in the development of a model that explains the observed selectivities in the kinetic resolution. DFT studies aimed at providing a better understanding of the underpinning reasons for these selectivities are also described.
21
Ohmatsu, Kohsuke. "Development of aluminum-catalyzed 1,2-rearrangement of α,α-disubstituted α-siloxy aldehydes." 京都大学 (Kyoto University), 2008. http://hdl.handle.net/2433/136906.
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Le, Bideau Franck. "Rearrangements de vinyloxiranes silyles chiraux catalyses par les complexes du palladium zerovalent." Paris 6, 1995. http://www.theses.fr/1995PA066646.
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La reaction de vinyloxiranes silyles en presence de quantites catalytiques de palladium zerovalent a conduit, d'une maniere simple, aux aldehydes alpha-silyles-beta, gamma-ethyleniques presentant un caractere ambident interessant en synthese organique. Cette nouvelle reaction s'effectue dans des conditions douces et se fait avec un transfert total de la chiralite. Ces aldehydes conduisent, en presence de nucleophiles lithies, a basse temperature, aux alcools homoallyliques correspondants avec de bons exces diastereomeriques et d'excellents rendements. Une etude de l'influence des substituants du silicium et des ligands associes au metal sur la distribution en produits de cette reaction a ete realisee. Une nouvelle approche de synthese enantioselective de l'acide shikimique a ete commencee. Elle est basee sur la mise au point de conditions permettant la cyclisation intramoleculaire d'un vinyloxirane silyle catalyse par les complexes du palladium zerovalent, selon un processus de type 6-endo-trig
23
Fretwell, Mark. "Asymmetric synthesis of cyclic ethers via a tandem carbenoid insertion and ylide rearrangement strategy." Thesis, University of Nottingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324477.
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Joannesse, Caroline. "Isothiourea-promoted O- to C-carboxyl transfer reactions." Thesis, University of St Andrews, 2011. http://hdl.handle.net/10023/3109.
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This thesis describes an extensive investigation of the O- to C-carboxyl transfer of oxazolyl carbonates using isothioureas as Lewis base catalysts. The structural requirements of simple bicyclic amidines and isothioureas to promote this transformation have been investigated, showing that the catalytic efficiency and product distribution of these reactions are markedly affected by the catalyst structure. The optimal isothiourea catalyst was efficiently applied to the rearrangement of a wide range of oxazolyl, benzofuranyl and indolyl carbonates. The structural motif of tetrahydropyrimidine-based isothioureas has then been evaluated in order to develop an asymmetric variant of the O- to C-carboxyl transfer of oxazolyl carbonates. A number of chiral isothioureas bearing stereodirecting groups in C(2) and/or C(3) have been synthesised and used in this rearrangement, showing that a C(2)-stereodirecting unit is essential for high enantioselectivity, with an additional C(3)-substituent increasing the reactivity. The optimal chiral C(2)-substituted isothioureas identified are general and efficient asymmetric catalysts for O- to C-carboxyl transfer of oxazolyl carbonates, generating a quaternary stereocentre with high enantioselectivity (up to 94% ee). The origin of the enantioselectivity of this process has been probed mechanistically and rationalised computationally. Having gained an insight into the structural motifs of isothioureas required to impart good catalytic activity and asymmetric induction in the O- to C-carboxyl transfer of oxazolyl carbonates, the mechanism of this reaction was probed using kinetic and mechanistic experiments. ¹⁹F NMR spectroscopic analysis allowed the evolution of product, by-product and intermediate throughout the reaction to be monitored while a number of crossover and stability experiments gave additional information about the catalytic cycle. Extension to a related system has been demonstrated with the O- to C-carboxyl transfer of furanyl carbonates, producing a mixture of α- and γ-butenolides depending on the nature of the Lewis base employed. DMAP gives a mixture of both regioisomers with a preference for the α-regioisomer, while NHCs lead predominantly to the γ-regioisomer. Chiral isothioureas have been used to promote this rearrangement, giving the major α-regioisomer with good enantioselectivity (up to 83% ee). To quantify the different reactivities observed with these isothioureas, their nucleophilicities and Lewis basicities using the stopped-flow technique have been determined. Finally, model studies toward the synthesis of the natural product calcaridine A, using the methodology developed herein, have been investigated.
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Wang, Ming De. "Metal catalyzed ring expansion carbonylation, rearrangement, cyclization and oxidation reactions of nitrogen containing heterocyclic compounds." Thesis, University of Ottawa (Canada), 1993. http://hdl.handle.net/10393/6851.
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An important class of carbonylation reactions to construct lactams are those that involve the direct "stitching" of carbon monoxide into a nitrogen heterocycle resulting in ring expansion. Cobalt carbonyl catalyzed the carbonylation of a series of 2-substituted pyrrolidines to form piperidinones. The reaction is regiospecific in most cases and the yield of product is increased when ruthenium carbonyl is present as a second catalyst. Chapter 2 of this thesis describes this piece of work. During the investigation of the ring expansion carbonylation reactions of pyrrolidines, a new rearrangement process was discovered which occurred with nitrogen heterocyclic ketones $\rm\lbrack (CH\sb2)\sb{n}NCH\sb2COR,$ n = 4-7) to give lactams in 72-93% yields, catalyzed by the dual metallic $\rm\lbrack Co\sb2(CO)\sb8/Ru\sb3(CO)\sb \rbrack$ system. Studies, including several labelling experiments, indicated a hydrogen-oxygen positional exchanging path. After rearrangement, Ru$\sb3$(CO)$\sb $ could be recovered, and no Ru-Co clusters was detected. The most probable explanation for this finding may be that some of the steps in the reaction pathway are catalyzed by ruthenium while others are more effectively catalyzed by cobalt complexes. This work is discussed in detail in Chapter 3. A novel cyclization reaction was also observed during mechanistic studies giving information on the rearrangement reaction. That is, when ketones in which only one of the hydrogen atoms at an $\alpha$-carbon atom of a nitrogen-containing heterocycle is replaced by an alkyl group (e.g. 2-methyl (or 2,6-dimethyl)piperidinyl ketones), the reaction afforded the bicyclic 5,6,7,8-tetrahydroindolizines in 72-94% yields. In contrast to the rearrangement process which requires both Co$\sb2$(CO)$\sb8$ and Ru$\sb3$(CO)$\sb $ as catalysts, Co$\sb2$(CO)$\sb8$ or Ru$\sb3$(CO)$\sb $ only could catalyze the cyclization reaction in high yields. These bicyclic products are well known precursors of many alkaloids. Reaction of 2-aryl-5,6,7,8-tetrahydroindolizines with singlet oxygen, whether generated under sensitized photoreaction conditions or by cobalt catalyzed oxidation under mild conditions, gave 2-aryl-8a-hydroxy-6,7,8,8a-tetrahydro-3(5H)indolizinones in 63-71% yield. Chapter 4 deals with these transformations. Under phase transfer catalysis conditions some five and six-membered nitrogen-containing heteroaromatics reacted with acetylcobalt tetracarbonyl, generated in situ from CO, CH$\sb3$I and dicobalt octacarbonyl. Isoxazoles or isothiazoles gave N-acylated 1-amino-2-alken-3-ones or thiones, i.e. ring-cleavage reductive acylation products. The highest stereoselectivity (Z/E: 10/1) of the acylation reaction was found in the case of 5-methylisoxazole. Under the same conditions phthalazine, quinoline and isoquinoline gave N-acylated dimers in low to moderate yields. The reactivity of several other nitrogen-containing heterocycles such as pyrazoles was also investigated and the results are summarized in Chapter 5.
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Lovchik, Martin Alan. "TRANSITION METAL CATALYZED REARRANGEMENT OF DIMETHYL VINYLCYCLOBUTENE DICARBOXYLATES DERIVATIVES TO DIMETHYL CYCLOHEXADIENE DICARBOXYLATES AND PHTHALATES." University of Cincinnati / OhioLINK, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1000127850.
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Yazicioglu, Emre Yusuf. "Development Of Novel Asymmetric Catalysts For Various Transformations And Investigation Of A Rearrangement Reaction." Phd thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612536/index.pdf.
Full textAbstract:
A new class of pyridine and sulfur containing chiral compounds are synthesized. Camphor sulfonyl chloride is chosen as a valuable chiral starting compound. In our synthetic strategy, sulfonylchloride moiety is first reduced to corresponding thiol compound by using triphenylphosphine and then the resultant thiol will be converted to various alkyl, aryl substituted derivatives. The second part of our strategy includes the pyridine ring construction on the carbonyl side of camphor with the formation of &beta-hydroxymethylene moiety followed by further reaction with various enamines. The resultant chiral ligands are characterized and used as a chiral ligand in asymmetric transfer of hydrogenation. Also novel class of organocatalysts synthesized from C2-symmetrical chiral diamine backbones and halopyridine derivatives are also synthesized and tested for their performance in kinetic resolution of racemic secondary alcohols. Also, a base mediated aromatization reaction is investigated in terms of both scope and mechanism.
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Hoffmann, Marie. "Catalyse à l'or (I/III) : de la réactivité au catalyseur, en passant par l'analyse structurale." Thesis, Strasbourg, 2015. http://www.theses.fr/2015STRAF020/document.
Full textAbstract:
La catalyse organométallique est l’un des outils les plus puissants de la synthèse chimique, car elle permet de réaliser des transformations sélectives et spécifiques selon le catalyseur employé. Dans ce contexte, les sels et complexes d’or ont émergé il y a une quinzaine d’années et se sont révélés très utiles et attractifs pour la synthèse organique, faisant preuve de propriétés particulières de type acide de Lewis à la fois π (alcyno- alcènophilie) et σ (oxo- azaphile). L’objectif initial de cette thèse a été d'approfondir l’étude de la réactivité de l’or au travers la mise au point de nouvelles réactions catalysées par l’or(I/III). Si la majorité des réactions développées en catalyse à l’or concerne des processus de type π, nous avons dans un premier temps, souhaité évaluer son potentiel dans une réaction qui repose sur une activation purement σ, la cyclisation de Nazarov. Cette réaction a ensuite été étendue à un processus de type cascade, combinant activations π et σ. De plus, la formation d’un sous-produit inattendu au cours de cette étude a orienté nos recherches vers un nouveau processus catalytique, le réarrangement de γ–acyloxy alcynylcétones en furanes. Par la suite, nous nous sommes aussi intéressés au potentiel de l’or dans les réactions asymétriques, ce qui a conduit au développement d’un nouveau type de complexes d’or chiraux basés sur des ligands de type NHC-oxazoline. Enfin, nous nous sommes proposés d’utiliser la spectroscopie RMN J-résolue hétéronucléaire (une méthode simple mais peu exploitée), pour répondre à des problèmes d’attribution structuraleOrganometallic catalysis is one of the most powerful tools in chemical synthesis, because, depending on the catalyst, it allows for selective and specific transformations. Thus, the reactivity of gold salts and complexes was revamped around fifteen years ago. Nowadays, they are considered as powerful and very attractive for organic synthesis, showing both π (alcyno- alcènophilie) and σ (oxo- azaphile) Lewis acid properties.The first objective of this thesis was to study the reactivity of gold catalysts by the development of new reactions catalyzed by gold(I/III). If most of the developed reactions in gold catalysis is related to π activation, we proved its potential in a reaction dealing with σ activation, the Nazarov cyclization. This reaction was then extended to a cascade process, combining both π and σ Lewis acidities. Moreover, the obtainment of an unexpected by-product during the study directed our research towards a new gold catalytic reaction, the formation of furans from γ-acyloxyalkynyl ketones. Subsequently, we were also interested in the potential of gold in asymmetric reactions, which led to the development of new chiral gold complexs, based on NHC-oxazoline type ligands. Finally, we proposed to use the heteronuclear J-resolved NMR spectroscopy (a simple but scarce method), to answer some structural assignment problems
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Tugny, Coralie. "Application of the metal-catalyzed rearrangement of propargyl acetates to the total synthesis of natural products of the neomerane family : application in catalysis of new secondary phosphine oxide- and NHC-capped cyclodextrin-gold(I) complexes." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066607.
Full textAbstract:
L'étude des petites molécules naturelles apporte continuellement de nouvelles connaissances en chimie organique et a un impact certain sur la recherche biomédicale. Les réactions catalysées par des métaux de transition ont fréquemment été utilisées dans des étapes clés vers la synthèse de produits naturels. En particulier au cours de la dernière décennie, l'or a été de plus en plus utilisé en catalyse homogène pour effectuer ces transformations. Le présent travail a pour objectif la valorisation en synthèse totale du réarrangement des acétates propargyliques catalysé par l'or. La (±)-Valénéomérine B et le (±)-Néoméranol sont deux produits naturels de la famille des Néoméranes dont nous avons envisagé la synthèse via la préparation d'un intermédiaire commun issu du réarrangement d'un acétate propargylique catalysé à l'or. Parallèlement, le comportement de nouveaux complexes d'or(I) à base d'oxides de phosphines secondaires et de cyclodextrines a été étudié dans le but de mieux contrôler la sélectivité des réactions catalysées à l'orThe study of small molecule natural products provides some knowledge about organic chemistry and has an impact on biomedical research. Transition metal-catalyzed reactions have been frequently used to affect key transformations. Especially, there has been a noticeable trend during the past decade towards the use of homogeneous gold-catalyzed transformations. This work aims at the valorization of the gold-catalyzed rearrangement of propargyl acetates in the total syntheses of (±)-Valeneomerin B and (±)-Neomeranol. These compounds are sequiterpenoid natural products, the synthesis of which has been envisioned from the preparation of a common intermediate resulting from the gold-catalyzed rearrangement of a propargyl acetate precursor. At the same time, the behaviour of new secondary phosphine oxide- and CNHC-capped cyclodextrin-gold(I) complexes has been studied, to try and achieve better control on the course of gold-catalyzed transformations
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Biggs, Robyn A. "5-and 6-Membered Hydrazides as Potential Catalysts for Diels-Alder Cycloadditions." Thesis, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/30723.
Full textAbstract:
Part A: Synthesis of 5- and 6-Membered Camphor-Based Hydrazides as Organocatalysts for Cycloaddition Reactions
The favorable environmental and reactivity qualities of organocatalysts are contributing to the popularization of this method for the acceleration of enantioselective reactions. Research in our group has been focused on the synthesis of camphor-derived hydrazide based organocatalysts for enantioselective cycloaddition processes. Recent results suggest that the presence of an exocyclic electron withdrawing group on the hydrazide moiety, as well as the incorporation of the hydrazide moiety into a 6-membered ring, may have a beneficial effect on the kinetics of the catalysts. A variety of camphor-based cyclic hydrazides have been synthesized and tested in Diels-Alder reactions, varying both the ring size and placement of the electron withdrawing group.
Part B: Synthesis of Isocampholenic Acids by the Rearrangement of Camphor Derivatives
A variety of substituted isocampholenic acid derivatives have been prepared by rearrangement of the camphor skeleton of a variety of tertiary alcohols derived from ketopinic acid. The reaction is highly reliable and retains the stereochemical information from the camphor scaffold. This rearrangement represents an efficient way to prepare synthetically useful isocampholenic acids. Mechanistic experiments show that the rearrangement does not involve exogenous water and that a short-lived carbocation is implicated in the reaction.
Part C: Diastereoselective Formation of Quaternary Centers from Stereodefined Trisubstituted Alkenes
Previous work in our laboratory has focused on the preparation of single-isomer tri- and tetra-substituted olefins. This methodology has been used in the construction of a variety of alkenyl esters in good to excellent yields. These alkenyl esters could then be transformed into the corresponding 3,3-disubstituted allyl boronates in a stereocontrolled fashion. There are a limited number of methods available to prepare single isomer 3,3-disubstituted allyl boronates, which can be important precursors in the stereoselective preparation of all-carbon quaternary centers. Our methodology has therefore been applied to the construction of single isomer 3,3-disubstituted allyl boronates and subsequently used in the stereoselective generation of all-carbon quaternary centers by the reaction of these allyl boronates with aldehydes.
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Phillips, Janice Paige. "Rearrangements of Radical Anions Generated from Cyclopropyl Ketones." Diss., Virginia Tech, 1998. http://hdl.handle.net/10919/40178.
Full textAbstract:
Cyclopropyl-containing substrates have been
frequently utilized as "probes" for the detection
of SET pathways in organic and biorganic systems.
These reactions are based on the
cyclorpropylcarbinyl - homoallyl rearrangement,
which is fast and essentially irreversible.
The implicit assumption in such studies is that if
a "radical" species is produced, it will undergo
ring opening. We have found that there are two
important factors to consider in the design of
SET probes: 1) ring strain, the thermodynamic
driving force for the rearrangement, and
2) resonance energy, which may help or hinder
rearrangement, depending on the specific system.
Delocalization of spin and charge were found to
be important factors pertaining to substituent
effects on the rates of radical anion
rearrangements.
Previous studies from our lab have
centered on highly conjugated phenyl
cyclopropyl ketones. This work considers a series
of compounds varying in their conjugative
components from a highly conjugated
spiro[2.5]octa-4,7-dien-6-one and derivatives to
simple aliphatic ketones. Utilizing cyclic,
linear sweep voltammetry, and preparative
electrolysis techniques, it was discovered that
all substrates yielded ring opened products with
rates and selectivities that will prove useful
and informative in the design of mechanistic
probes based on the cyclorpropylcarbinyl -
homoallyl rearrangement. Rates of homogeneous
electron transfer from a series of hydrocarbon
mediators to substrates were measured using
homogeneous catalysis techniques. Standard
reduction potentials and reorganization energies
of substrates were derived using Marcus theory.
Conjugative interactions with the cyclopropyl
group are discussed.Ph. D.
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Romeo, Michelangelo. "Proprietes des catalyseurs intermetalliques platine-uranium, platine sur oxyde d'uranium et platine-cobalt-oxyde d'uranium sur alumine pour les reactions de rearrangement de squelette des hydrocarbures." Université Louis Pasteur (Strasbourg) (1971-2008), 1987. http://www.theses.fr/1987STR13098.
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PETIT, KLEIN CORINNE. "Etudes esca et caracterisations physiques de systemes supportes : mecanismes de reactions de rearrangement de squelette des alcanes sur catalyseurs bimetalliques pt-mo." Université Louis Pasteur (Strasbourg) (1971-2008), 1988. http://www.theses.fr/1988STR13024.
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GISIE, HERVE. "Etudes mecanistiques du rearrangement des alcools allyliques catalyse par des complexes oxo du molybdene (6) et du rhenium (7)." Université Louis Pasteur (Strasbourg) (1971-2008), 1995. http://www.theses.fr/1995STR13159.
Full textAbstract:
L'isomerisation des alcools allyliques peut etre catalysee en phase homogene par des especes metal-oxo a haut degre d'oxydation (metal = v, w, mo, re). Ce type de procede a un interet industriel considerable en chimie appliquee (pharmacie, agrochimie, parfumerie, saveurs). Bien que le mecanisme le plus communement admis pour ce procede est de type pericyclique, il n'est aujourd'hui pas encore connu de facon precise et reste toujours sujet a controverses. Les travaux exposes dans cet ouvrage tentent de clarifier ce mecanisme. La synthese et l'etude par rmn #1#7o du rearrangement allylique de complexes du mo(6) de type mo#1#7o#2(ocr#1r#2ch=cr#3r#4)#2l#2(r#1, r#2, r#3, r#4 = ch#3, h ; l = ch#3cn), dont les ligands oxo ont prealablement ete enrichis en #1#7o, ont montre que les ligand oxo sont directement impliques dans les reactions. De plus, lorsque c'est le cas, l'incorporation des noyaux #1#7o dans les ligands -ocr#1r#2ch=cr#3r#4 a pu etre demontree sans ambiguite. La cinetique et la stereochimie du rearrangement du 1-hexenee-3-ol, du trans-2-hexene-1-ol et du cis-2-hexene-1-ol catalyse a temperature ambiante par des complexes oxo du mo(6) et du re(7) ont permis de montrer que ces reactions sont stereoselectives. Finalement, des complexes bis-oxo chiraux du mo(6) susceptibles de catalyser l'isomerisation enantioselective d'alcools allyliques prochiraux ont ete synthetises mais aucun exces enantiomerique n'a ete observe. Certains d'entre eux catalysent des reactions de transfert d'oxygene. Au terme de ce travail, l'ensemble des resultats obtenus soutiennent l'hypothese d'un mecanisme pericyclique similaire a un rearrangement de claisen
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GANDOLFI, ISABELLE. "Rearrangements acido-catalyses de systemes 2-oxa-bicyclo(4. 2. 0) octanes. Contribution a la synthese d'analogues des trichothecenes." Paris 11, 1993. http://www.theses.fr/1993PA112027.
Full textAbstract:
Ce travail decrit les rearrangements acido-catalyses des systemes 2-oxa-bicyclo(4. 2. 0) octanes: contribution a la synthese des cycles pontes b/c des mycotoxines de type trichothecene telles que l'anguidine: 1) voie lactone: l'addition photochimique de l'acetylene sur la lactone 15 n'est pas stereospecifique. De ce fait, aucun rearrangement n'a ete tente sur le cyclobutenyl carbinol b; 2) voie enone: differents alcools tertiaires 48 et 49, possedant le systeme 2-oxa-bicyclo(4. 2. 0)octane ont ete synthetises. Leur stabilite en presence de bf#3-et#2o ou d'acide formique ne conduit pas, dans les conditions douces etudiees, a la formation du systeme ponte (3. 2. 1) octane cible; 3) la stabilite de ces unites 2-oxa-bicyclo(4. 2. 0)octanes a ete confirmee dans le cas du compose 69 en presence de bf#3-et#2o. La formation de l'isomere 73 a partir de 69 implique la rupture de la liaison centrale par un mecanisme de type retroaldolisation; 4) l'etude des effets conformationnels des differents composes synthetises en r. M. N. #1#3c montre que ce squelette 2-oxa-bicyclo(4. 2. 0) octene est flexible. A l'inverse, la stabilite du systeme sature correspondant est a associer aux plus faibles variations relevees des deplacements chimiques
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末次, 聖. "Pd触媒による分子内アリル位アミノ化および分子内Ｃ－Ｈ官能基化反応の開発." 京都大学 (Kyoto University), 2017. http://hdl.handle.net/2433/225305.
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Joncour, Roxan. "Nouvelles voies de synthèses du paracétamol et de son précurseur." Thesis, Lyon 1, 2014. http://www.theses.fr/2014LYO10295/document.
Full textAbstract:
Le paracétamol est un analgésique parmi les plus consommés dans le monde. Les synthèses actuelles de cette molécule induisent la formation de quantités non-négligeables de sels ou de produits secondaires non valorisables. En plus d'induire de faibles économies d'atomes, la présence de ces déchets engendre des surcoûts importants pour la synthèse du paracétamol dus aux lourds traitements des réactions. Les objectifs de la thèse étaient à la fois de proposer une synthèse plus respectueuse de l'environnement mais également économiquement viable. En ce sens, deux synthèses du paracétamol ont été étudiées. La première synthèse étudiée concerne la réduction sélective du nitrobenzène en p-aminophénol, l'intermédiaire clé du paracétamol. Cette synthèse nécessite typiquement une quantité importante d'acide sulfurique qui est corrosif et engendre la formation de sels (sulfate d'ammonium) importante. Un catalyseur acide recyclable à base d'oxyde de niobium a été utilisé et associé à l'acide sulfurique. Ainsi les sélectivités en aminophénol de 74 % sans catalyseur de niobium ont été améliorées à 82 % en présence de ce catalyseur. En outre, la quantité d'acide sulfurique a été réduite au minimum sans pertes significatives de sélectivité. La deuxième synthèse est la substitution de l'hydroquinone par l'acétate d'ammonium en milieu acide acétique. Cette synthèse innovante s'est révélée être particulièrement performante car elle induit la formation du paracétamol en une étape en partant d'un produit disponible en grande quantité, avec de très bons rendements et sélectivités. De plus, un test à large échelle a permis de montrer que le paracétamol produit est facilement récupérable par précipitation et l'acide acétique récupérable par distillation. Enfin, la réaction a été testée avec succès à d'autres polyhydroxybenzènes et aux naphtolsParacetamol is an analgesic among the most consumed in the world. Currents syntheses of paracetamol induce a quantity of salts and non-reusable by-products. These wastes lead to both a low atom economy and a high process cost due to the work-ups. The main objectives of this thesis were to propose eco-friendly and competitive synthesis of paracetamol. Two syntheses have been studied. The first one was the selective reduction of nitrobenzene to p-aminophenol, the key intermediate of paracetamol. This synthesis requires a large amount of sulphuric acid which is corrosive and induces salts formation. A reusable niobium oxide-based catalyst has been associated with sulphuric acid. This association gave better selectivities to aminophenol (82%) compare to sulphuric acid alone (74%). Moreover, the quantity of sulphuric acid has been minimized without significant loss of selectivities. The second synthesis study was the hydroquinone substitution to paracetamol with ammonium acetate in acid acetic. This new synthesis is very powerful due to the one-step synthesis of paracetamol from bulk quantity available products, with very good conversion and selectivity. Moreover, a large scale synthesis has been tested which demonstrates that paracetamol and acetic acid were easily recovered by precipitation and distillation, respectively. The reaction has been successfully extended to other polyhydroxybenzenes and naphtols
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Bellavance, Gabriel. "Part A: Development of a Modular Synthetic Approach to Polycyclic Polyprenylated Acylphlorogluginols: Total Synthesis of Papuaforin A, B, C, Hyperforin and Formal Synthesis of Nemorosone. Part B: Studies Toward the Synthesis of Ginkgolides." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34630.
Full textAbstract:
Polycyclic Polyprenylated Acylphloroglucinols (PPAPs) are a vast family of natural products, which includes more than 200 members. They contain a stunningly complex molecular architecture which in most cases includes a bicyclo[3.3.1]nonane core. PPAPs have been of interest to the scientific community for their intricate structure, their powerful aid in treating many ailments and large portfolio of biological activities. More particularly, they have been of synthetic interest since 1999 with the first report of an approach to these complicated cores by Nicolaou. Herein, we present the first total synthesis of papuaforin A, papuaforin B, papuaforin C, hyperforin and the formal synthesis of nemorosone following a report by Simpkins and co-workers. We relied on a gold(I)-catalyzed carbocyclization for the construction of the core of this family of natural products. Ginkgolides are isolated from the ginko tree, Ginkgo biloba, a living fossil with records of its existence dating back 280 million years. For centuries, the plant and its extracts have been used extensively for their beneficial properties, especially in China, Japan and India. For example, extract Egb761, one of the most potent fraction, generates over $500 million a year alone. The ginkgolides possess a truly unique compact diterpene framework of six 5-membered rings with a high content oxygen. Eleven oxygens can be found in ginkgolide C for a core containing only 23 carbons. The ginkgolides also include a very unique feature: a tert-butyl group located on the most convoluted ring system: the B ring. Few groups have found success in limning a synthetic route to ginkgolides. Corey’s group was the first to achieve the total synthesis of ginkgolide B in 1987. He was also able to complete ginkgolide A a year later. Crimmins and co-workers also achieved the total synthesis of ginkgolide B a decade later in 1999. Herein, we present our new approach toward ginkgolides through a newly developed methodology for the α-allylation of ketones and the creation of highly hindered contiguous quaternary centers. The synthesis is still at an early stage but a synthetic pathway giving access to the ring B with all the key moieties has been extensively investigated.
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Khan, Rana Kashif. "New Concepts, Catalysts, and Methods in Stereoselective Olefin Metathesis." Thesis, Boston College, 2014. http://hdl.handle.net/2345/bc-ir:104359.
Full textAbstract:
Thesis advisor: Amir H. HoveydaChapter 1. Mechanistic Insights and Factors Influencing Polytopal Rearrangements in Stereogenic-at-Ru Carbenes. Herein, the mechanistic elucidation of the stereochemical inversion in stereogenic-at-Ru carbene complexes through olefin metathesis (OM) and non-olefin metathesis (non-OM) based polytopal rearrangements is provided. Our investigations involve the isolation and characterization of previously hypothesized higher-energy (e.g., endo-anti) and lower-energy (e.g., exo-anti) diastereomers, and their interconversion under thermal and/or acid-catalyzed conditions is demonstrated. Furthermore, our computational efforts highlighting the importance of the anionic ligands, due to their critical role in trans influence, dipolar interactions, and e-e repulsions, in polytopal rearrangements are reported. Finally, the positive influence of H-bonding in OM and non-OM processes is also rationalized. (a) Khan, R. K. M.; Zhugralin, A. R.; Torker, S.; O'Brien, R. V.; Lombardi, P. J. and Hoveyda, A. H. "Synthesis, Isolation, Characterization, and Reactivity of High-Energy Stereogenic-at-Ru Carbenes: Stereochemical Inversion Through Olefin Metathesis and Other Pathways," J. Am. Chem. Soc. 2012, 134, 12438-12441. (b) Torker, S.; Khan, R. K. M. and Hoveyda, A. H. "The Influence of Anionic Ligands on Stereoisomerism of Ru Carbenes and Their Importance to Efficiency and Selectivity of Catalytic Olefin Metathesis Reactions," J. Am. Chem. Soc. 2014, 136, 3439-3455. Chapter 2. Highly Z- and Enantioselective Ring-Opening/Cross-Metathesis of Enol Ethers Through Curtin-Hammett Kinetics. The first instances of Z- and enantioselective Ru-catalyzed olefin metathesis are presented. Ring-opening/cross-metathesis (ROCM) reactions of oxabicyclic alkenes and enol ethers and a phenyl vinyl sulfide are promoted by 0.5-5.0 mol % of enantiomerically pure stereogenic-at-Ru complexes with an aryloxy chelate tethered to the N-heterocyclic carbene. Products are formed efficiently and with exceptional enantioselectivity (up to >98:2 enantiomer ratio). Surprisingly, the enantioselective ROCM reactions proceed with high Z selectivity (up to >98% Z). Moreover, reactions proceed with the opposite sense of enantioselectivity versus aryl olefins, which afford E- isomers exclusively. DFT calculations and deuterium-scrambling experiments, indicating fast interconversion between endo- and exo-Fischer carbene diastereomers, support a Curtin-Hammett situation. On this basis, models accounting for the stereoselectivity levels and trends are provided. Furthermore, the correlation of Fischer carbene character to the observed chemoselectivity in ROCM with enol ethers is also disclosed. Finally, a general proposal for the substrate-controlled Z selectivity in OM is also discussed. (a) Khan, R. K. M.; O'Brien, R. V.; Torker, S.; Li, B. and Hoveyda, A. H. "Z- and Enantioselective Ring-Opening Cross-Metathesis with Enol Ethers Catalyzed by Stereogenic-at-Ru Carbenes: Reactivity, Selectivity, and Curtin-Hammett Kinetics," J. Am. Chem. Soc. 2012, 134, 12774-12779. (b) Torker, S.; Koh, M. J.; Khan, R. K. M. and Hoveyda, A. H. "Origin of Z selectivity in Olefin Metathesis Reactions of Certain Terminal Alkenes Catalyzed by Typically E-Selective Ru Carbenes," manuscript submitted. Chapter 3. A New Class of Highly Efficient Ru Catalysts for Z-Selective Olefin Metathesis. Herein, we outline a general design for Z-selective OM, which led to the development of a new class of stereogenic-at-Ru carbene complexes (Ru4-9). Furthermore, we demonstrate that the newly developed dithiolate complexes Ru4b and Ru5 efficiently promote high activity and selectivity in ROMP reactions of norbornene and cyclooctene. Notably, the catechothiolate Ru4b catalyzes Z-selective ROCM with a broad scope of alkenes involving various functional groups (e.g., alcohols, enol ethers, vinyl sulfides, amides, heterocycles, and conjugated 1,3-dienes). More importantly, we disclose that the catecholate complex Ru4a is kinetically non-selective in OM and readily decomposes in the presence of mildly acidic moieties (e.g., alcohols and CDCl3). Subsequently, Ru9 is developed to efficiently promote highly Z-selective CM of a diol cross-partner with a wide range of alkene substrates. Most remarkably, the aforementioned protocol is employed in two natural product syntheses and the OM-based Z-selective cracking of oleic acid, which is unprecedented with existing Ru-carbenes and Mo/W-alkylidenes. (a) Khan, R. K. M.; Torker, S. and Hoveyda, A. H. "Readily Accessible and Easily Modifiable Ru-Based Catalysts for Efficient and Z-Selective Ring-Opening Metathesis Polymerization and Ring-Opening Cross-Metathesis," J. Am. Chem. Soc. 2013, 135, 10258-10261. (b) Koh, M. J.; Khan, R. K. M.; Torker, S. and Hoveyda, A. H. "Broadly Applicable Z- and Diastereoselective Ring-Opening/Cross-Metathesis Catalyzed By a Dithiolate Ru Complex," Angew. Chem., Int. Ed. 2014, 53, 1968-1972. (c) Khan, R. K. M. ; Torker, S. and Hoveyda, A. H. "Reactivity and Selectivity Differences Between Catecholate and Catechothiolate Ru Complexes. Implications Regarding Design of Stereoselective Olefin Metathesis Catalysts," J. Am. Chem. Soc. 2014, 136, 14337-14340. (d) Koh, M. J.; Khan, R. K. M.; Torker, S.; Yu, M.; Mikus, M. S. and Hoveyda, A. H. "Synthesis of High-Value Alcohols, Aldehydes and Acids by Catalytic Z-Selective Cross-Metathesis" manuscript submitted
Thesis (PhD) — Boston College, 2014
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Chemistry
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Bellemin-Laponnaz, Stéphane. "Etudes mecanistiques et theoriques du rearrangement des alcools allyliques et de leurs derives catalyse par des complexes oxo de metaux de transition." Université Louis Pasteur (Strasbourg) (1971-2008), 1998. http://www.theses.fr/1998STR13181.
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La migration d'une double liaison sur une olefine est une reaction catalytique tres etudiee. De nombreux procedes industriels necessitant des catalyseurs sont utilises pour isomeriser des olefines. L'isomerisation des alcools allyliques fait partie de ce type de reaction et constitue le sujet principal du manuscrit. De nouveaux systemes catalytiques a partir de complexes oxo du rhenium au degre d'oxydation (vii) ont ete testes pour cette reaction et se sont averes etre les systemes les plus actifs connus a ce jour. Nous avons etudie de plus pres cette reaction afin de mieux comprendre les mecanismes. Des etudes cinetiques, thermodynamiques ainsi que de marquages isotopiques par rmn #1#7o ont permis de clarifier cette reaction. Nous avons egalement effectue des etudes en chimie theorique. Les geometries des etats de transition des complexes allyliques ont ete determinees. Des modeles ont permis de montrer la forte influence du solvant sur la geometrie des etats de transition obtenus. Dans une autre partie, nous avons developpe la reaction d'isomerisation d'ethers allyliques silyles. Cette reaction catalytique est nouvelle et peut offrir des applications synthetiques. Les equilibres obtenus entre les isomeres allyliques proteges sont differents de ceux obtenus avec les alcools allyliques. Nous avons etudie le mecanisme de cette reaction catalytique par des etudes cinetiques. La reactivite de ces complexes du rhenium a egalement ete testee avec les silicones. Enfin la derniere partie rassemble les resultats obtenus dans la synthese de deux ligands chiraux qui peuvent avoir des potentiels en catalyse enantioselective. Des complexes oxo du vanadium (iv et v) ainsi que du molybdene (vi) ont ete prepares. Les structures ont pu etre determinees par diffraction x.
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Campbell, Craig D. "Lewis base-promoted organocatalysis : O- to C-carboxyl transfer reactions." Thesis, University of St Andrews, 2010. http://hdl.handle.net/10023/2609.
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This work describes the application of a variety of Lewis bases, encompassing predominantly N-heterocyclic carbenes (NHCs), but also the use of imidazoles, aminopyridines, amidines and isothioureas, as effective catalysts in the dearomatisation of heterocyclic carbonates, predominantly the rearrangement of oxazolyl carbonates to their C-carboxyazlactone isomers by means of the Steglich rearrangement. This rearrangement reaction has been investigated extensively, with the development of simplified reaction procedures and the invention of domino cascade protocols incorporating this transformation. In an attempt to understand the mechanism of this O- to C-carboxylation process, a number of interesting observations have been made. Firstly, the class of NHC has an important factor in promoting the rearrangement, with triazolinylidenes being the most effective. Secondly, an interesting chemoselectivity has been delineated using triazolium-derived NHCs, prepared using weak bases (typically Et₃N) or strong metallated bases; both alkyl and aryl oxazolyl carbonates undergo smooth rearrangement with triazolinylidenes derived from strong metallated bases such as KHMDS, while only aryl oxazolyl carbonates undergo rearrangement using Et₃N. Extensive effort has focused towards the development of asymmetric variants of these protocols, primarily towards the design, synthesis and evaluation of chiral NHC precatalysts. To this end, a number of chiral azolium salts have been prepared, encompassing a number of different NHC classes, including C₁- and C₂-imidazolinium salts, C₂-imidazolium salts and a range of triazolium salts. Efforts towards the asymmetric catalysis of the Steglich rearrangement of oxazolyl carbonate substrates have given an optimal 66% ee. Similar rearrangements have been demonstrated with the related furanyl heterocyclic substrate class, producing a mixture of α- and γ-carboxybutenolides. In contrast to the analogous oxazolyl carbonates, the regioselectivity of this rearrangement is dependent upon the nature of the Lewis base employed. Amidines and aminopyridines give a mixture of the α- and γ- regioisomers with generally the α-regioisomer being preferred, while a triazolium-derived NHC gives rise to predominantly the thermodynamically more stable γ-carboxybutenolide. Using amidines or aminopyridines, this rearrangement has been shown to proceed via an irreversible C-C bond-forming process, but in contrast, the rearrangement using the NHC proceeds via an equilibrium process with an optimised regioselectivity of >98:2 for the γ-carboxybutenolide regioisomer over the α-regioisomer. Whilst the asymmetric variant using chiral NHCs has proven unfruitful, rearrangements using a chiral isothiourea have given high levels of regioselectivity towards the α- regioisomer and with excellent levels of enantiodiscrimination (77–95% ee).
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Gayet, Arnaud. "Development of New Chiral Bicyclic Ligands : Applications in Catalytic Asymmetric Transfer Hydrogenation, Epoxidations, and Epoxide Rearrangements." Doctoral thesis, Uppsala University, Organic Chemistry, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4753.
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This thesis describes the synthesis and application of new chiral bicyclic ligands and their application in asymmetric catalysis. The studies involved: [i] The development of novel chiral bicyclic amino sulfur ligands and their use in transfer hydrogenation. [ii] The development of the kinetic resolution of racemic epoxide through the use of chiral lithium amides. [iii] The synthesis and application of chiral bicyclic amine in the organocatalysed epoxidation of alkenes. [iv] Development and application of new chiral diamine ligands in the rearrangement of epoxides into allylic alcohols.
[i] The preparation of two-series of amino thiol ligands based on the structure of camphor is described, together with their application in the iridium-catalysed asymmetric transfer hydrogenation of acetophenone using isopropanol as the hydrogen source. Excellent activity and good enantioselectivity have been achieved using 2 mol% of chiral ligand in combination with [IrCl(COD)]2.
[ii] The chiral diamines (1S,3R,4R)-3-(pyrrolidine-1-ylmethyl)-2-aza-bicyclo[2.2.1]heptane and its (2R,5R)-dimethylpyrrolidine derivative were applied to the kinetic resolution of a variety of racemic 5-7 membered cycloalkene oxides with lithium diisopropylamide (LDA) as the bulk base. Using 5 mol% of the chiral diamines, both unreacted epoxides and allylic alcohols could be produced in enantiomeric excess up to 99%.
[iii] The synthesis of chiral bicyclic amines and their use in the organocatalysed epoxidation of alkene has been described. Using a substoichiometric amount of the chiral amines and aldehydes as ligands precursors, with Oxone® as oxidant, a good activity but moderate enantioselectivity was observed for the epoxidation of trans-stilbene.
[iv] The preparation of 6-substituted-7-bromo-aza-bicyclo[2.2.1]heptanes via nucleophilic addition of organocopper reagents to 3-bromo-1-azoniatricyclo[2.2.1.0]heptyle bromide has been described. These compounds have been utilised as chiral building blocks in the preparation of novel chiral diamine ligands, which have been successfully applied to the catalysed asymmetric rearrangement of epoxide into the corresponding allylic alcohol.
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Tomakinian, Terry. "Nouvelles méthodes de synthèse de benzofuroindolines. Vers la synthèse de la phalarine." Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLS031.
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Les benzofuroindolines forment une famille de composés qui se retrouvent sous deux formes : les benzofuro[2,3-b]indolines ou les benzofuro[3,2-b]indolines. Ce motif se retrouve dans de nombreuses molécules naturelles comme la bipleiophylline, la voacalgine A, le diazonamide A et la phalarine ce qui a mené à de nombreuses recherches pour leur synthèse. La biogénèse postulée est le couplage oxydant d'un indole et d'un phénol. Nous avons développé plusieurs voies d'accès à ces motifs en utilisant le noyau indolique. La première étude a consisté en un couplage oxydant direct entre un N-acétylindole et un phénol en présence de FeCl₃ et de DDQ. La méthodologie a montré sa généralité sur des dérivés d'indoles N-acétylés pour former en une seule étape des benzofuro[3,2-b]indolines. Dans certains cas, la benzofuro[2,3-b]indoline est obtenue si les groupements fonctionnels en position 2 et 3 sur l'indole sont identiques. Dans un but de synthétiser la phalarine, unique molécule naturelle contenant un motif benzofuro[3,2-b]indoline, nous avons réalisé une étape de C2-arylation d'un indole par un phénol à l'aide d'un couplage pallado-catalysé. La cyclisation à l'aide de NIS permet d'obtenir la benzofuro[3,2-b]indoline. L'ajout du carbone manquant de l'un des cycles est en cours d'étude par ajout d'un nucléophile monocarboné possédant un groupement partant. Par ailleurs, une dernière voie d'accès aux benzofuro[3,2-b]indolines a pu été mise au point par une réaction de Fischer interrompue. La réaction entre des benzofuran-3-ones et des arylhydrazines dans des conditions acides conduit aux benzofuroindolines souhaitées sous forme d'hémiacétals. La méthode a montré sa généralité et sa robustesse. Finalement, réaliser l'Umpolung de l'indole est un défi intéressant pour additionner des nucléophiles en position 3 de l'indole. Pour cela, des N-hydroxyindoles ont été synthétisés et l'utilisation de sels de biaryliodonium triflate a permis de réaliser une O-arylation. Le produit formé étant instable, il subit un réarrangement sigmatropique [3,3] pour conduire aux benzofuro[2,3-b]indolines désiréesBenzofuroindolines are a family of compounds which can be found in two regioisomeric forms: benzofuro[2,3-b]indolines or benzofuro[3,2-b]indolines. This core is present in several natural products such as bipleiophylline, voacalgine A, diazonamide A or phalarine which have been the subject of intensive efforts towards their syntheses. The postulated biogenesis is the oxidative coupling of an indole and a phenol. We developed four pathways to access these structures using the indole nucleus.The first part consisted in a direct oxidative coupling between a N-acetylindole and a phenol in presence of FeCl₃ and DDQ. This strategy showed its generality on N-acetylindoles derivatives to form in only one step the benzofuro[3,2-b]indoline core. In some cases, the benzofuro[2,3-b]indoline is obtained if the substitution in the C-2 and C-3 position is the same. In order to synthesize the phalarine, the unique natural product to possess a benzofuro[3,2-b]indoline core, we designed a C-2 arylation of an indole with a phenol using a palladium-catalyzed coupling. The cyclization steps using NIS led to the benzofuro[3,2-b]indoline core. The insertion of the missing carbon of one of the rings is under study by adding a nucleophile which contains only one carbon and a leaving group. The last strategy to access to benzofuro[3,2-b]indolines has been focused on an interrupted Fischer indolization. The reaction between benzofuran-3-ones and arylhydrazines in acidic conditions led to the desired benzofuro[3,2-b]indolines. This methodology is general and robust. Another part of the project was to achieve the Umpolung of the indole to add nucleophiles in C-3 position of the indole nucleus. N-hydroxyindoles were synthesized and the use of biaryliodonium triflate salts allowed an O-arylation reaction. The product being unstable, a [3,3] sigmatropic rearrangement can take place to afford the desired benzofuro[2,3-b]indolines
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Dauscher, Anne. "Etudes des reactions de rearrangement de squelette des hexanes sur des catalyseurs a base de platine en presence ou non d'interactions metal-support." Université Louis Pasteur (Strasbourg) (1971-2008), 1987. http://www.theses.fr/1987STR13032.
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Marrot, Sébastien. "Carbènes N-Hétérocycliques : Des catalyseurs en chimie des silicones. Carbodiphosphoranes cycliques : Synthèse, coordination et réactivité." Phd thesis, Toulouse 3, 2007. http://www.theses.fr/2007TOU30037.
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Dans un premier chapitre, nous nous intéressons à l'utilisation des Carbènes N-Hétérocycliques comme catalyseurs organiques nucléophiles pour la polymérisation par ouverture de cycle de l'octamethylcyclosiloxane et pour des réactions de polycondensation. Dans un deuxième chapitre, nous effectuons une revue bibliographique sur des composés phosphorés présentant deux fonctions ylures cumulées : les carbodiphosphoranes. Dans un troisième chapitre, nous présentons la synthèse et la coordination de nouveaux carbodiphosphoranes cycliques. Nous montrons que ces ligands ont un caractère fortement s-donneur. Dans un quatrième chapitre, nous étudions la thermolyse d'un de ces composés qui conduit par réarrangement à la formation d'un 1,2l5-azaphosphète. Une étude théorique met en évidence une inter-conversion entre les carbodiphosphoranes et les disphosphinocarbènesIn a first chapter, we are interested in the use of N-Heterocyclic Carbenes like nucleophilic organic catalysts for ring opening polymerization of octamethylcyclosiloxane and for reactions of polycondensation. In a second chapter, we carry out a bibliographical review on compounds presenting two cumulated ylides functions : carbodiphosphoranes. In a third chapter, we present the synthesis and the coordination of new cyclic carbodiphosphoranes. They are recognized to be strong s-donor ligands for transition metals. In a fourth chapter, we study the thermolysis of one of these compounds which leads by rearrangement to the formation of a 1,2l5-azaphosphète. A theoretical study highlights an inter-conversion between carbodiphosphoranes and disphosphinocarbenes
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Liang, Tao. "Chiral Phosphoric Acids and Alkaline Earth Metal Phosphates Chemistry." Thesis, University of South Florida, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3632228.
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Asymmetric synthesis and catalysis is one of the leading research areas in chemistry society, for its versatility and efficiency in obtaining chiral molecules that found the vast majority in natural active compounds and synthetic drugs. Developing asymmetric catalytic methodology is at the frontier in both industrial and academic research laboratories. Enantioselective organocatalysis has emerged as a powerful synthetic tool that is complementary to metal-catalyzed transformations. The development of chiral phosphoric acid and metal phosphate as catalysts has been a breakthrough in recent years. Chiral phosphoric acids have been shown to be powerful catalysts in many organic transformations. Moreover, chiral metal phosphates, which formed by simply replacing the proton in phosphoric acid with metals, have introduced new catalytic activations and broaden the scope of phosphoric acids. This thesis details new highly enantioselective chiral phosphoric acid-catalyzed Pinacol rearrangement and robust alkaline phosphates catalytic system, which utilizes novel carbonyl activation.
The Pinacol rearrangement has long been known to be difficult to control in terms of regioselectivity and stereoselectivity. The initial studies found that indolyl-diol compounds can be treated with chiral phosphoric acids to afford the Pinacol rearrangement with high regio- and enantioselectivity. Over 16 chiral phosphoric acids were screened, and it was found an H8-BINOL-phosphoric acid variant with 1-naphthyl groups at 3 and 3' position was the excellent catalyst. This asymmetric transformation is tolerant toward variety of substituents both on the indole ring and migrating groups.
During the study, it was found that different ways to generate the catalyst had critical effect on this catalytic transformation. Only those phosphoric acids washed with HCl after column chromatography afforded the rearrangement products with high enantioselectivity. And those without treating with HCl were found contaminated by alkaline metals. These "contamination" catalysts were also found active with carbonyl activations.
A highly enantioselective catalytic hetero-Diels-Alder reaction of alpha-keto esters has been developed with chiral alkaline metal phosphates. A calcium 1-naphthyl-BINOL phosphate was found to be the optimum catalyst. A large range of alpha-keto esters as well as isatins can be applied in this alkaline phosphates catalytic system with high efficiency and selectivity. The structure of the catalyst is detailed for the first time by X-ray crystal structure analysis. A proposed Transition state model is provided based on the catalyst crystal structure and Raman spectroscopy analysis.
This methodology was further developed with an asymmetric Mukaiyama-Michael addition of beta,gamma-unsaturated alpha-keto ester. The best catalyst was found to be a magnesium chiral phosphate. And the transformation was found capable of tolerating a wide variety of beta,gamma-unsaturated alpha-keto esters.
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Vu, Huy-Dinh. "Accès à des hétérocycles azotés énantiopurs par cyclisation d’amino-ynones." Thesis, Rennes 1, 2014. http://www.theses.fr/2014REN1S098/document.
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La synthèse d’hétérocycles azotés énantiopurs est un enjeu important dans la chimie du vivant et représente l’un des axes de notre laboratoire depuis quelques années. L’ensemble du travail a bénéficié pour cela du « pool chiral » constitué par les acides aminés naturels. Dans la première partie de notre travail, nous avons utilisé l’acide aspartique à partir duquel des exemples variés de β-amino-ynones ont été construits. Leur cyclisation par catalyse à l’or a donné accès à des pyridones, précurseurs de dérivés pipécoliques énantiopurs. Un travail analogue a été entrepris sur des γ-amino-ynones et a donné un résultat moins prévisible : cyclisation à cinq sommets suivie du réarrangement de Meyer-Schuster. Cette synthèse s’est montrée plus efficace en milieu acide méthane sulfonique qu’en présence d’or et représente un nouveau mode d’accès aux vinylogues d’amides de la pyrrolidine, intermédiaires-clé en synthèse totale. Enfin, l’utilisation d’un acide de Lewis, ZnCl₂, sur des γ- et δ-amino-ynones a fourni des imines cycliques, à cinq ou six sommets et portant un alcyne, que nous avons isolées sous forme libre ou complexée par l’acide de LewisThe synthesis of enantiopure nitrogen heterocycles is an important issue in chemistry and has been part our laboratory work for several years. The entire work took advantage of the chiral pool consisting of natural amino acids. In the first part of our work, we used aspartic acid from which various examples of β-amino-ynones were built. Their catalytic cyclization gave access to pyridones that were used as enantiopure pipecolic acid precursors. A similar work was undertaken on γ-amino-ynones and gave a less predictable result: cyclization to a five members ring followed by Meyer-Schuster rearrangement. This synthesis was more effective in a methane sulfonic acid medium than in the presence of gold and represents a new mode of access to pyrrolidine vinylogous amides that are key-intermediate in total synthesis. Finally, the use of a Lewis acid -ZnCl₂- on γ- and δ-amino-ynones provided five and six members cyclic imines, carrying an alkyne, which we isolated in the free form or complexed with the Lewis acid
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Martinand-Lurin, Élodie. "Hétérocycles et réactions pallado-catalysées : développements méthodologiques, études mécanistiques et application en synthèse totale." Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112018/document.
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Le développement de nouvelles méthodologies de synthèse toujours plus efficaces, sélectives et éco-compatibles apparaît comme un défi permanent tant l’intérêt suscité pour les composés hétérocycliques est important. Ce projet de thèse s’articule autour de plusieurs axes dans ce domaine.Tout d’abord, nous avons exploité la réactivité des N-(sulfonyl) et N-(sulfamoyl)aziridines en tant que précurseurs de dipôles 1,3 en vue de préparer divers 1-azaspiro[5.n]alcanes. L’étude mécanistique de cette réaction de cycloaddition [3+2] réalisée par calculs DFT permet de montrer que l’étape cinétiquement déterminante de la réaction est la formation du dipôle 1,3 ; la force motrice étant la fermeture du cycle à cinq chaînons.Nous nous sommes également attachés à valoriser le savoir-faire du laboratoire dans le domaine des transferts catalytiques de nitrènes (aziridination et amination C-H) dans le cadre du projet de synthèse totale de la pactamycine, aminocyclopentitol hautement fonctionnalisé.Par ailleurs, la mise au point d’une cascade Passerini-Smiles/Réduction/Cyclisation et d’une séquence monotope Passerini-Double-Smiles/SNAr permet un accès rapide et efficace à des motifs hétérocycliques de type 1,4-benzoxazin-3-ones. Conduisant à des familles régioisomères de produits, ces deux voies de synthèse se sont avérées complémentaires.Parallèlement, une nouvelle méthodologie basée sur l’ouverture pallado-catalysée de thiocyclopropanes a permis d’obtenir de nouveaux hétérocycles de type thiochromènes. Compte tenu des nombreuses fonctionnalisations envisageables, ces composés semblent très prometteurs dans le domaine de la chimie hétérocyclique.Enfin, des études électrochimiques et RMN couplées à des calculs DFT ont été entreprises afin d’élucider le mécanisme mis en jeu lors des couplages pallado-catalysés entre un halogénure d’aryle, un isonitrile et un nucléophileThe development of new and more efficient synthetic methodologies, selective and eco-friendly seems to be an ongoing challenge as the interest in the heterocyclic compounds is important. All the studies performed during the last three years are divided in several axes in this field.First, the reactivity of N-(sulfonyl) and N-(sulfamoyl) aziridines as precursors of 1,3-zwitterionic species was explorated in order to obtain various 1-azaspiro[5.n]alkanes. The mechanism of the reaction has been studied by DFT calculations. The initial formation of the zwitterionic 1,3-dipole has been found to be the rate-determining step whereas the five-membered ring closure appeared to be the driving force.We tried to apply our expertise in the field of catalytic nitrene transfers (aziridination and C-H amination) to the total synthesis of pactamycin, highly functionalized aminocyclopentitol compound.Furthermore, the developments of a Passerini-Smiles/reduction/cyclization cascade and of a one-pot Passerini-Double-Smiles/SNAr sequence provide straightforward and efficient accesses to 1,4-benzoxazin-3-ones. These paths are complementary as they lead to regioisomers.Meanwhile, a new methodology based on Pd-catalyzed thiocyclopropanes ring opening gave thiochromenes. Due to their high synthetic potential, these compounds appear to be very promising scaffolds in heterocyclic chemistry.Finally, electrochemical and NMR studies coupled with DFT calculations have been done in order to elucidate the mechanism involved in the Pd-catalyzed couplings between an aryl halide, an isocyanide and a nucleophile
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Grimster, Neil Patrick. "New strategies for chemical synthesis : 1) Development of a palladium-catalyzed direct C-H alkenylation of indoles by solvent-controlled regioselective C-H bond functionalisation; 2) Studies towards the development of a catalytic diastereoselective [3,3] sigmatropic rearrangement at ambient temperature." Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612869.
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Kirsten, Martin. "Organokatalyse: Theoretische Untersuchungen zur Claisen-Umlagerung und zum Einfluss von Azolen auf die Morita-Baylis-Hillman-Reaktion sowie neuartige Bis(carben)metallkomplexe auf der Basis von Triazolen." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-71134.
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Ziel der Arbeit war es, Katalysatoren zu entwickeln, in Modellsystemen zu testen und Rückschlüsse auf deren Aktivität und Verbesserungspotential zu ziehen. Dabei standen sowohl theoretische Betrachtungen mittels quantenmechanischer Berechnungen, aber auch experimentelle Arbeiten im Mittelpunkt. Die Untersuchungen wurden an ausgewählten Beispielen der Claisen-Umlagerung und der Morita-Baylis-Hillmann-Reaktion sowie verbrückter Bis(NHC)metallkomplexe auf der Basis von Triazolen in der Mizoroki-Heck-Reaktion durchgeführt.
Claisen-Umlagerung. Die Wechselwirkung zwischen Substrat und dem Katalysator sollte hierbei auf eine bidendate Ausbildung von Wasserstoffbrücken zum Substrat entsprechend dem Design nach Jørgensen[1-4] abzielen. Die Auswahl der „Organokatalysatoren“ erstreckte sich von den Thioharnstoffen, über L-Milchsäure, einem Phosphorsäure-Derivat bis hin zu 2,2,2-Trifluorethanol (TFE).
Mit dem Allyl Vinyl Ether (AVE) 83 wurden die theoretischen Betrachtungen der Wechselwirkung und der sich daraus ergebende Einfluss auf die Umlagerungs-geschwindigkeit durchgeführt. Der Thioharnstoff 1 und dessen Wechselwirkung mit 83 standen dabei im Mittelpunkt der Betrachtungen. Es wurden zwei mögliche entscheidende Übergangszustände postuliert. Im Vergleich zum konkurrierenden Übergangszustand [s-cis-83b•1A]# war [s-trans-83b•1A]# in Summe bevorzugt. Gegenüber der thermischen Claisen-Umlagerung von 83 war [s-trans-83b•1A]# für ΔG#[3,3] um +3,1 Kcal mol-1 erniedrigt, was einer leichten Erhöhung der Umlagerungsgeschwindigkeit entsprach. Dies konnte durch experimentelle Untersuchungen bestätigt werden. Das Phosphorsäure-Derivat 94 war im Vergleich zur L-Milchsäure 91 besser in der Lage, die Barriere des sigmatropen Umlagerungsschrittes abzusenken. Es zeigte sich, dass die Kombination von 91 mit einem Wassermolekül 8 zu dem Komplex 92 zu einer verbesserten Stabilisierung des Übergangszustandes führte. Bei beiden Systemen wurde jedoch beobachtet, dass die Barrieren über den Gesamtverlauf der Reaktion nicht ausreichend stark abgesenkt werden konnten. Für die Berechnungen mit dem Lösungsmittel TFE wurde gezeigt, dass die Betrachtung der Wechselwirkung einzelner TFE-Moleküle mit dem Substrat 83 nicht ausreichte.
Morita-Baylis-Hillman-Reaktion. Mit der Morita-Baylis-Hillman-Reaktion[5, 6] (MBH) kann im Sinne einer C-C-Verknüpfungs-reaktion neben der atomökonomischen Durchführung zusätzlich ein Stereozentrum erzeugt werden. Basierend auf den Ergebnissen von Cheng et al.[7] wurde ein systematischer Zusammenhang zwischen dem eingesetzen Vermittler/Katalysator und Ausbeute/Umsatz hergestellt. Die aus der Literatur bekannte pH-Wert-Abhängigkeit der Reaktion konnte auf einen Bereich zwischen 8 und 9 eingegrenzt werden. Unter Verwendung verschiedener Substitutionsmuster am Imidazol konnte gezeigt werden, dass 1H-substituierte Imidazole die Reaktion wesentlich langsamer als die in 1-Position unsubstituierten Imidazole vermittelten, was durch DFT-Rechnungen unterstrichen werden konnte.
Im weiteren Verlauf der experimentellen Untersuchungen stellte sich heraus, dass TFE als Lösungsmittel ohne Zusatz einer weiteren Base für die Vermittlung der Reaktion gut geeignet ist.
Verbrückte Bis(NHC)metallkomplexe auf der Basis von Triazolen. Die Synthese der Bis(NHC)metallkomplexe und deren Einsatz in der Katalyse wurde von Straßner et al.[8-15] sehr intensiv studiert. Teil dieser Arbeit war es, die Bandbreite der Katalysatoren zu erweitern und den Einfluss von einem Stickstoffatom im (NHC)-Rückgrat zu untersuchen. Die synthetische Zugänglichkeit der Konstitutionsisomere wurde bereits bei der Darstellung der aromatischen Triazole gewährleistet. Die sich anschließende Darstellung der entsprechenden Salze konnte für die Methoxy-Gruppe am Aromaten erfolgreich durchgeführt werden. Die Unterscheidung von Konstitutionsisomeren eines Komplexes wurde am Beispiel von 126 und 128 durchgeführt. Hierbei zeigten sich bereits im 1H-NMR-Spektrum feine Unterschiede in den Kopplungskonstanten und auch in den Signalen für die Methylenbrücke. Der tatsächliche Beweis wurde mit der 2D-Methode, der sogenannten „Heteronuclear Multiple Bond Correlation“ – HMBC, erbracht. Der Einsatz der dargestellten Palladium(II)komplexe zeigte für p-Bromacetophenon analoge Ergebnisse zu den Imidazol-Derivaten bei „gleicher“ Konzentration. Für die Komplexe, ausgehend von den asymmetrischen Triazolen (zum Beispiel 128), wurde eine erhöhte Reaktivität beobachtet. Weiterhin wurde ein signifikanter Unterschied in der Ausbeute bei Reaktionen mit p-Chloracetophenon beobachtet.
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