Dissertations / Theses: 'Chiral Lewis acid'

1

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

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2

Cao, Min. "Enantioselective Transformations Promoted by Cooperative Functions of an Achiral Lewis Acid and a Chiral Lewis Acid:." Thesis, Boston College, 2021. http://hdl.handle.net/2345/bc-ir:109203.

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Thesis advisor: Masayuki Wasa
Thesis advisor: Amir H. Hoveyda
This dissertation describes the development of cooperative catalyst systems that contain an achiral Lewis acid and a chiral Lewis acid that may have overlapping functions but play their independent roles to promote enantioselective C–C bond formations. Chapter 1 provides a summary of recent advances made in the field of enantioselective cooperative catalysis that served as intellectual foundations for this dissertation research. As it will be discussed in the first chapter, key limitations of cooperative catalysis are: (1) undesirable catalyst deactivation which occurs due to acid/base complexation, (2) requirement for base sensitive pronucleophiles and acid sensitive electrophiles, and (3) poor reaction efficiency. In an effort to overcome these fundamental limitations, we have developed “frustrated” Lewis pair (FLP)-based catalyst systems that consist of potent and sterically encumbered Lewis acids used in pair with bulky N-containing Lewis bases. To demonstrate the potential of the novel FLP catalyst system, we describe our work involving the enantioselective Conia-ene-type cyclization (Chapter 2). In the subsequent chapter (Chapter 3), we discuss the application of the FLP catalysts for enantioselective β-amino C–H functionalization reactions
Thesis (PhD) — Boston College, 2021
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Chemistry

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3

Mahal, R. S. "Preparation and use of chiral borane lewis acids." Thesis, University of Salford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381853.

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4

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

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5

Mellberg, Annika. "Chiral Carbocations as Lewis Acid Catalysts in Diels-Alder Reactions." Thesis, KTH, Skolan för kemivetenskap (CHE), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-156209.

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Lewis acids can be used as catalysts in different reactions, but the term Lewis acid catalysts often refers to metal salts. Metal complexes have been widely used for asymmetric catalysis. Asymmetric synthesis can however be performed in a metal-free way by using organocatalysis. New Lewis acid catalysts that are more effective, enantioselective and environmental friendly is of interest. This new type of Lewis acid catalysts could for example be of carbocation based character. The aim of this project was to synthesize chiral carbocations with different degree of sterical hindrance and investigate their catalytic ability in Diels-Alder reactions. It was presumed that the Diels-Alder reactions were going to be performed in an asymmetric way since the carbocation catalysts were achiral. Two chiral carbocations were synthesized successfully. The first synthesized carbocation, the less sterical hindered compound 8, was formed as a racemic mixture. The second carbocation, compound 16, could be formed as an enatiomeric pure compound. Both carbocations showed catalytic ability in Diels-Alder reactions and compound 8 was comparable with some common Lewis acid catalysts. In general, when using compound 8 as catalyst, higher catalyst amount gave higher conversions. Higher concentrations also gave higher conversions, but up to a certain level. No trend between polarity of different solvents and conversions could be seen. However, an increased temperature leads to faster reactions. The more rigid and sterical hindered compound 16 catalyzed the reactions slower than compound 8. The longer reaction time may indicate that the reaction occurs with higher selectivity, but no method to measure the ee of the product was found. An attempt to synthesize a third even more sterical hindered chiral carbocation, compound 19, resulted in a product contaminated by impurities that showed a catalytic ability lower than compound 8 and compound 16 in Diels-Alder reactions. The synthesis and the use of carbocations as Lewis acid catalysts in Diels-Alder reactions seem promising as a new type of catalysts even though there are questions that are still unanswered, e.g. counter ions effects, possible side reactions, selectivity etc.

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6

Risberg, Erik. "Lewis acid Mediated Aza-Diels-Alder Reactions and Asymmetric Alkylations of 2H-azirines." Doctoral thesis, KTH, Chemistry, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3822.

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This thesis describes the use of 2H-azirines, three-membered unsaturatednitrogen-containing heterocycles, as reactive intermediates ina number of Lewis acid promoted alkylations and Diels-Alderreactions providing synthetically useful aziridines.

In order to carry out this investigation a new generalprocedure for the ring closure of vinyl azides, forming theresultant 3-substituted-2H-azirines, was developed applying low boiling solventsin closed reaction vessels at elevated temperatures.

The addition of organolithium reagents in the presence ofcommercially available chiral ligands, to the 3-(2-naphthyl)-2H-azirine was studied, which gave the correspondingaziridines.

Several Lewis acids were shown to catalyze the normalelectron-demand Diels-Alder reaction between 3-alkyl-,3-aromatic-, and 3-ester-substituted 2H-azirines and various dienes. These reactions gave theexpected cycloadducts in moderate yields.

Using a chiral auxiliary high diastereoselectivity wasobtained in the addition of alkyl radicals to a8-phenylmenthyl-substituted 2H-azirine-3-carboxylate. The alkyl radicals weregenerated from the corresponding trialkyl borane and molecularoxygen. Hydroborations and transmetallations were used toprepare these trialkylboranes. Catalytic amounts of CuClincreased the diastereoselectivity in the radical additionreactions.

Attempts were made to explain how the coordination of aLewis acid to the azirine nitrogen atom affects thereactivity/stability of the azirine. DFT calculations and NMRexperiments involving Lewis acid-azirine complexes wereperformed.

Keywords:Enantioselective, diastereoselective, vinylazide, 2H-azirines, aziridines, Lewis acid, chiral ligand,chiral auxiliary, organolithiums, Diels-Alder reaction, alkylradicals, triethylborane.

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7

Lundgren, Stina. "Efficient Synthesis and Analysis of Chiral Cyanohydrins." Doctoral thesis, Stockholm : Kungliga Tekniska högskolan (KTH), 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4315.

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8

Risberg, Erik. "Lewis Acid Mediated Alkylation and Diels-Alder Reactions of 2H-Azirines." Licentiate thesis, KTH, Chemistry, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1489.

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This thesis describes the use of 2H-azirines as reactivesubstrates in Lewis acid catalysed nucleophilic additions andin the Diels-Alder reaction.A number of carbon nucleophiles have been added to aseries of 2H-azirines in the presence and absence ofBF3·Et2O. 3-(2-Naphthyl)-2H-azirine has been used as amodel substrate in the enantioselective addition oforganolithium reagents to an 2H-azirine.A selection of Lewis acids has been screened for theirpossible use in the normal electron demand Diels-Alder reactionbetween 3-alkyl-, 3-aryl-, and 3- carboxyl-2H-azirines and avariety of dienes. Lewis acid activation was found to shortenreaction times and facilitate lower reaction temperatures.These cycloadditions proceeded with endo selectivity providinga single diastereoisomeric product.DFT calculations of Lewis acid activated 2H-azirineshave been carried out.

Keywords:2H-azirines, Lewis acid activation, chiralligands, organolithium reagents, Diels-Alder reactions,DFT-calculations

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9

Wingstrand, Erica. "New Methods for Chiral Cyanohydrin Synthesis." Doctoral thesis, KTH, Kemi, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10205.

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This thesis deals with method development in asymmetric catalysis and specifically syntheses of enantioenriched O-functionalized cyanohydrins. The first part describes the development of a method for the synthesis of O‑alkoxycarbonylated and O-acylated cyanohydrins. Ethyl cyanoformate and acyl cyanides were added to aldehydes in a reaction catalyzed by a chiral dimeric Ti-salen complex together with a tertiary amine. High yields and enantioselectivities were in most cases obtained. Mechanistic studies were performed and a reaction mechanism was proposed. The second part describes a method in which the undesired minor enantiomer in a Lewis acid–Lewis base-catalyzed acylcyanation is continuously recycled into prochiral starting material. Close to enantiopure O‑acylated cyanohydrins were obtained in high yields. The third part deals with asymmetric acylcyanations of ketones. Acetyl cyanide was found to add to α‑ketoesters in a reaction catalyzed by a chiral Lewis base. Yields up to 77% and 82% ee were obtained. The final part describes an enzymatic method for high-throughput analysis of O‑acylated cyanohydrins. The enantiomeric excess and conversion were determined for products obtained from a number of aromatic and aliphatic aldehydes.
QC 20100818

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10

Chang, Yejin. "Enantioselective Transformations of α- and β-Amino C-H Bonds Promoted by Cooperative Actions of Achiral and Chiral Lewis Acid Catalysts:." Thesis, Boston College, 2021. http://hdl.handle.net/2345/bc-ir:109179.

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Thesis advisor: Masayuki Wasa
Thesis advisor: Amir H. Hoveyda
This dissertation describes the development of cooperative catalyst systems for the regio- and enantio-selective α- and β-amino C-H functionalization of N-alkylamines, inspired by the concepts of frustrated Lewis pairs (FLPs). Prior to this dissertation research, the development of effective and broadly applicable catalytic protocol to transform amino C-H bonds with high enantioselectivity remained as a formidable problem. In Chapter 1, the recent advances in the field of amino C-H functionalization through hydride transfer process that served as intellectual foundations for this dissertation research is presented. As highlighted in the first chapter, key challenges of amino C-H functionalization are: (1) unreactive nature of α, β- and/or γ-amino C-H bonds, (2) requirement for the use of precious metal-based catalysts and external oxidants under acidic/basic and harsh conditions, (3) use of directing groups for regioselectivity, and (4) poor functional group tolerance. Inspired by the unique capability of FLPs to activate otherwise unreactive molecules while disfavoring undesirable acid-base complexation, we have developed a protocol for enantioselective α-amino C-H functionalization of N-alkylamines, where chiral and achiral Lewis acid catalysts work cooperatively (Chapter 2). The application of the cooperative catalyst system comprising of B(C6F5)3, a chiral Lewis acid, and a Brønsted base to the enantioselective β-amino C-H functionalization is described in Chapter 3
Thesis (PhD) — Boston College, 2021
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Chemistry

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11

Jay, David Alexander. "A generic parallel combinatorial approach to Chiral Lewis acid catalyst discovery : application to the aza-Diels-Alder reaction." Thesis, Durham University, 2003. http://etheses.dur.ac.uk/4066/.

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A generic parallel combinatorial method was used in order to attempt to develop new asymmetric processes for the aza-Diels-Alder reaction. Initially, an N-para-methoxyphenyl glyoxylate derived imine and its reactions with a variety of dienes was examined. Several new adducts were obtained, which included both "normal" "inverse" electron-demand aza-Diels-Alder products, and an acyclic product. These results strongly suggested the intervention of a stepwise addition-cyclisation mode of the reaction of diene with the imine. Later, new W-phosphorus imines were examined as dienophile substrates for aza-Diels-Alder reactions. The results of the reactions between these imines and a variety of dienes showed a reduced level of imine reactivity when compared to the N-para-methoxyphenyl C-carboxylate-derived system. Several new products were obtained and the results indicated a stepwise reaction process was in operation, due to the formation of other di-dehydro-piperidinone or acyclic ketone or aldehyde derivatives, hi this study, the first apparent N-phosphonyl imino-Diels-Alder reaction on such systems has been recorded. Screening reactions with different Lewis acids and chiral ligands produced no asymmetric induction, however, this system proved to be unreliable for monitoring by HPLC due to the presence of both cyclic and acyclic products.

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12

Belda, de Lama Oscar. "Bispyridylamides as ligands in asymmetric catalysis." Doctoral thesis, KTH, Chemistry, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3764.

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This thesis deals with the preparation and use of chiralbispyridylamides as ligands in metal-catalyzed asymmetricreactions.

The compounds were prepared by amide formation usingdifferent coupling reagents. Bispyridylamides havingsubstituents in the 4- or 6- positions of the pyridine ringswere prepared by functional group interconversion of the 4- or6- halopyridine derivatives. These synthetic approaches provedto be useful for various types of chiral backbones. Pseudo C₂-symmetric bispyridylamides were also synthesizedby means of stepwise amide formation.

The compounds were used as ligands in themicrowave-accelerated Mocatalyzed asymmetric allylic alkylationreaction. Ligands having ð-donating substituents in the4-positions of the pyridine rings gave rise to products withhigher branched to linear ratio. The catalytic reaction, whichproved to be rather general for allylic carbonates with anaromatic substituent, was used as the key step in thepreparation of (R)-baclofen. The Mo-bispyridylamide catalystprecursor was studied by NMR spectroscopy.

Bispyridylamide complexes of metal alkoxides were alsoevaluated in the asymmetric addition of cyanide to aldehydesand the metal complexes involved were studied by NMRspectroscopy and X-ray crystallography. Chiral diamines wereused as additives to study the ring opening of cyclohexeneoxide with azide, catalyzed by Zr(IV)-bispyridylamidecomplexes.

Various bispyridylamides were attached to solid supports oforganic or inorganic nature. The solid-supported ligands wereused in Mo-catalyzed asymmetric allylic alkylation reactionsand in the asymmetric addition of cyanide to benzaldehyde.

Keywords:asymmetric catalysis, chiral ligand, pyridine,amide, allylic alkylation, enantioselective, cyanation,ring-opening, chiral Lewis acid.

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13

Beck, Daniel Antony Speedie, and beckautomatic@gmail com. "Stereoselective intramolecular Michael addition reactions of pyrrole and their application to natural product syntheses." The Australian National University. Research School of Chemistry, 2006. http://thesis.anu.edu.au./public/adt-ANU20070130.130009.

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Chapter one; (-)-Rhazinilam and (-)-Rhazinal: Alkaloids with Anti-mitotic Properties Derived from Kopsia teoi, provides the background information behind the motives that initiated this research project. The plant alkaloid (-)-rhazinilam [(-)-1] and its naturally-occurring derivative (-)-rhazinal [(-)-13] both exhibit potent anti-mitotic activities and, as such, are interesting targets for total synthesis. Chapter one is a review of the literature regarding these two compounds and discusses the occurrence, proposed biosynthetic origins, structural elucidation and biological activites of compound (-)-1 and that of its analogues including alkaloid (-)-13. Previous total syntheses of these two compounds are then examined, concluding with the only reported total synthesis of compound (-)-13. Developed within the Banwell research group, this total synthesis produced the racemic modification of alkaloid (-)-13 due to a lack of any stereocontrol in the key intramolecular Michael addition step. This unprecedented key step, involving cyclisation of the C2 of pyrrole onto an N-tethered and ?,?-disubstituted acrylate to produce a quaternary-carbon stereogenic centre, would be of greatly enhanced utility if it could be achieved in a catalytic-enantioselective fashion. The realisation of this goal is the central aim of the research conducted within this thesis. ¶ Chapter two; Investigating Asymmetric Induction in the Intramolecular Michael Addition of pyrrole to N-Tethered Acrylates and Related Species, introduces the model study used to direct research towards achieving the goal of asymmetric induction in the title process. The model is a somewhat simplified version of the original process used in the total synthesis of compound (-)-13 involving cyclisation of the C2 of pyrrole onto an N-tethered and ?-monosubstituted Michael acceptor, to produce a tertiary-carbon stereogenic centre. This simplification allows the rapid synthesis of a broad range of potential substrates for use in the title process, thus enabling the investigation of various different approaches to inducing asymmetry therein. High levels of asymmetric induction are observed with the use of chiral substrates or catalysts, facilitating the synthesis of both 6- and 7-membered rings annulated to pyrrole with construction of the relevant tertiary-carbon stereogenic centre in enantio-enriched form. For the reactions producing a 6-membered ring annulated to pyrrole, unambiguous proof of the absolute sense of asymmetric induction observed in the intramolecular Michael addition event is established using a chemical correlation study involving elaboration of a key indolizine-type cyclisation product, to the plant alkaloid of known absolute stereochemistry, (-)-tashiromine [(-)-75]. For the reaction producing a 7-membered ring annulated to pyrrole, the same information is obtained via X-ray crystallographic analyses of a dibrominated derivative of a key pyrroloazepine-type cyclisation product. ¶ Chapter three An Enantioselective Total Synthesis of the Alkaloid (-)-Rhazinal: An Anti-mitotic Agent Isolated from Kopsia teoi., focuses on the application of methodology developed in the previous chapter, to the original goal of inducing asymmetry in the intramolecular Michael addition reaction, involving cyclisation of the C2 of pyrrole onto an N-tethered and ?,?-disubstituted acrylate to produce a quaternary-carbon stereogenic centre. This is ultimately achieved in a catalytic-enantioselective fashion, resulting in the first such total synthesis of the anti-mitotic alkaloid (-)-rhazinal [(-)-13]. ¶ Chapter four Extending the Reaction Manifold to the Syntheses of Related Natural Products: A Formal Total Synthesis of (+)-Aspidospermidine and Syntheses of (-)-Rhazinilam and (-)-Leuconolam from (-)-Rhazinal, describes three extensions to the reaction manifold used in the enantioselective total synthesis of alkaloid (-)-13: The acquisition in an enantioselective manner, of an intermediate previously obtained in racemic form, en route to the racemic modification of the natural product (±)-aspidospermidine [(±)-134], constitutes a formal and enantioselective total synthesis of (+)-aspidospermidine [(+)-134]. The direct deformylation of (-)-rhazinal [(-)-13], is carried out, to produce the parent alkaloid (-)-rhazinilam [(-)-1]. The pyrrole ring present in (-)-rhazinilam [(-)-1] is oxidised, to produce the related natural product (-)-Leuconolam [(-)-12] which has not, hitherto, been prepared by total synthesis. ¶Chapter five contains the experimental procedures and characterisation data associated with compounds described in chapters two to four.

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14

Zuo, Wei [Verfasser], and Eric [Akademischer Betreuer] Meggers. "Chiral-at-Metal Iridium(III) and Rhodium(III) Lewis Acid Catalysts for the α-Functionalization of 2-Acyl Imidazoles / Wei Zuo ; Betreuer: Eric Meggers." Marburg : Philipps-Universität Marburg, 2018. http://d-nb.info/1156461731/34.

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15

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

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

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16

Frölander, Anders. "Impact of Secondary Interactions in Asymmetric Catalysis." Doctoral thesis, KTH, Organisk kemi, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4380.

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This thesis deals with secondary interactions in asymmetric catalysis and their impact on the outcome of catalytic reactions. The first part revolves around the metal-catalyzed asymmetric allylic alkylation reaction and how interactions within the catalyst affect the stereochemistry. An OH–Pd hydrogen bond in Pd(0)–π-olefin complexes of hydroxy-containing oxazoline ligands was identified by density functional theory computations and helped to rationalize the contrasting results obtained employing hydroxy- and methoxy-containing ligands in the catalytic reaction. This type of hydrogen bond was further studied in phenanthroline metal complexes. As expected for a hydrogen bond, the strength of the bond was found to increase with increased electron density at the metal and with increased acidity of the hydroxy protons. The second part deals with the use of hydroxy- and methoxy-containing phosphinooxazoline ligands in the rhodium- and iridium-catalyzed asymmetric hydrosilylation reaction. The enantioselectivities obtained were profoundly enhanced upon the addition of silver salts. This phenomenon was explained by an oxygen–metal coordination in the catalytic complexes, which was confirmed by NMR studies of an iridium complex. Interestingly, the rhodium and iridium catalysts nearly serve as pseudo-enantiomers giving products with different absolute configurations. The final part deals with ditopic pyridinobisoxazoline ligands and the application of their metal complexes in asymmetric cyanation reactions. Upon complexation, these ligands provide catalysts with both Lewis acidic and Lewis basic sites, capable of activating both the substrate and the cyanation reagent. Lanthanide and aluminum complexes of these ligands were found to catalyze the addition of the fairly unreactive cyanation reagents ethyl cyanoformate and acetyl cyanide to benzaldehyde, whereas complexes of ligands lacking the Lewis basic coordination sites failed to do so.
QC 20100709

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17

Scotney, Christopher C. J. "Investigations using chiral scandium (III) Lewis acids." Thesis, University of Nottingham, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.555431.

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Lewis acidic chiral scandium(III) catalysts have been developed and tested with a range of bidentate substrates in both Diels-Alder and aza-Michael reactions. Scandium(III) complexes incorporating bipybox, phenbox (a new class oftetradentate chiral ligand) and pybox ligands, have been found to give significant enantioselectivity in reactions involving 3-acyloxazolidinones and 3-formylpyrone- containing substrates. Molecular modelling has been used to understand more about the action of these catalysts and to design new ligands which can lead to higher levels of enantioselectivity in these reactions. For acyloxazolidinone-containing substrates it was found that scandium(III)/pybox catalysts gave the same sense of stereocontrol in both Diels-Alder and aza-Michael reactions. It was observed that the sense of enantiocontrol with a particular class of ligand was determined by the stereochemistry of the R -substituent on the ligand and the degree of this stereocontrol was influenced by its size. These observations have lead to a proposal of how the substrates bind to the chiral scandium(III) catalysts for each ligand type and how the enantioselectivity of the products is derived. The chiral scandium(III) Lewis acid catalysts were also used to promote an endo- selective intramolecular Diels-Alder reaction of a 3-formylpyrone-containing substrate, the key step in a synthesis of solanapyrone D. This natural product was prepared in up to 77 % ee with all four contiguous formed in this final step of the synthesis. The highest levels of enantioselectivity for this reaction were given by scandium(III)-pybox catalysts. A greater understanding of chiral scandium(III) catalysts, particularly the substrate- catalyst interactions, has been gained in this thesis and can hopefully be used in the future to aid further development of asymmetric catalysis with scandium(III). 11.

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Armitage, Mark Alan. "Studies in asymmetric synthesis : attempted asymmetric Reformantsky reactions and approaches towards the alkaloid fastigiatine." Thesis, University of East Anglia, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357935.

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Clot, Almenara Lidia. "Immobilization of Chiral Brønsted Acids and Lewis Bases for Batch and Flow Enantioselective Catalysis." Doctoral thesis, Universitat Rovira i Virgili, 2018. http://hdl.handle.net/10803/552409.

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El següent treball, titulat “Immobilització d’àcids de Brønsted i bases de Lewis quirals per catàlisi asimètrica en batch i flux”, esta basat en el disseny de nous materials organocatalítics suportats i en la seva aplicació en reaccions asimètriques. La tesi presenta una discussió detallada de diverses rutes sintètiques per a la immobilització en poliestirè d’àcids de Brønsted i bases de Lewis. En particular, s’ha aconseguit optimitzar una ruta directa i efectiva per a la preparació d’àcids fosfòrics quirals (CPA) i N,N’-diòxids suportats en poliestirè (PS). Per a realitzar la immobilització s’ha dut a terme un estudi exhaustiu amb la finalitat d’escollir la manera més efectiva de modificar el catalitzador homogeni i emprar el linker més adequat. Les característiques d’aquests nous catalitzadors permeten la seva aplicació en sistemes de flux continu, contribuint d’aquesta manera a millorar la sostenibilitat dels processos catalítics. L’efectivitat dels catalitzadors d’àcids fosfòrics quirals immobilitzats, en termes d’activitat catalítica, selectivitat i reciclatge, s’ha comprovat en reaccions d’alilació d’aldehids i en la desimetrització de meso-1,3-diones. Els bons resultats obtinguts ens han incentivat per la implementació de sistemes de flux continu, on aquests catalitzadors han demostrat la seva estabilitat.
El siguiente trabajo, titulado “Inmovilización de ácidos de Brønsted y bases de Lewis quirales para catálisis asimétrica en batch y flujo”, está basado en el diseño de nuevos materiales organocatalíticos soportados y en su aplicación en reacciones asimétricas. La tesis presenta una discusión detallada de varias rutas sintéticas para la inmovilización en poliestireno de ácidos de Brønsted y bases de Lewis. En particular, se ha conseguido optimizar una ruta directa y efectiva para la preparación de ácidos fosfóricos quirales (CPA) y N,N'-dióxidos soportados en poliestireno (PS). Para realizar la inmovilización se ha llevado a cabo un estudio exhaustivo con el fin de elegir la manera más efectiva de modificar el catalizador homogéneo y emplear el linker más adecuado. Las características de estos nuevos catalizadores permiten su aplicación en sistemas de flujo continuo, contribuyendo de esta manera a mejorar la sostenibilidad de los procesos catalíticos. La efectividad de los catalizadores de ácidos fosfóricos quirales inmovilizados, en términos de actividad catalítica, selectividad y reciclaje, se ha comprobado en reacciones de alilación de aldehídos y en la desimetrización de meso-1,3-dionas. Los buenos resultados obtenidos nos han incentivado a implementar de sistemas de flujo continuo, donde estos catalizadores han demostrado su estabilidad.
The following work, entitled “Immobilization of chiral Brønsted acids and Lewis bases for batch and flow enantioselective catalysis”, deals with the design of new supported organocatalytic materials and their application in asymmetric reactions. The thesis presents a detailed discussion of several synthetic routes for polystyrene immobilization of Brønsted acids and Lewis bases. In particular, it has been possible to optimize a direct and effective route for the preparation of chiral phosphoric acids (CPA) and N,N'-dioxides supported on polystyrene (PS). To carry out the immobilization, an exhaustive study has been carried out in order to choose the most effective way to modify the homogeneous catalyst, employing the most suitable linker. The characteristics of these new catalysts allow their application in continuous flow systems, contributing in this way to improve the sustainability of the catalytic processes. The effectiveness of immobilized chiral phosphoric acid catalysts, in terms of catalytic activity, selectivity and recycling, has been proven in allylation reactions of aldehydes and in the desymetrization of meso-1,3-diones. The good results obtained have motivated us to study the implementation of continuous flow systems, where these catalysts have demonstrated their robustness.

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20

Xuan, Wenjing. "Hybrids derived from intrinsically chiral Dawson polyoxometalate : preparation and applications in enantioselective catalysis." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066070.

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Cette thèse traite de dédoublement cinétique, de fonctionnalisation et d’utilisation de composés chiraux dérivés de polyoxométalates lacunaires de structure Dawson [α1-P2W17O61]10¬-. La première partie traite de l’utilisation de complexes organosolubles TBA5K[α1-Hf-P2W17O61] pour catalyser l’addition de nucléophiles comme des ethers d’énol ou des acétals de cétènes silylés mais également des pronucléophiles sur des hémiaminals. La seconde partie détaille l’étude sur la préparation et l’utilisation de trichlorostannanes énantiopures en vue du dédoublement cinétique des composés chiraux lacunaires [α1-P2W17O61]10-¬. La fonctionalisation diastéréosélective de derive chiraux organosoluble TBA7[α2-RSnP2W17O61] est également présentée. Le dernier chapitre décrit des hybrides chiraux POM-imidazolidinones dont la chiralité est uniquement apportée par le polyanion. Utilisé avec succès pour catalyser de manière énantiosélective des réactions de Diels Alder, ces composés sont les premiers POM de structure chirale a transféré la chiralité de manière aussi efficace vers des composés organiques
This manuscript deals with the kinetic resolution, the functionalization and the use of chiral lacunary Dawson α1-POM [α1-P2W17O61]10-¬. The first part deals with the racemic organo-soluble TBA5K[α1-Hf-P2W17O61] complex used to catalyze the nucleophilic addition of silyl enol ethers, ketene-acetals and activated methylene C-nucleophiles onto hemiaminals. The second part describes the synthesis of enantiopure trichlorostannane complexes as resolving agents for the kinetic resolution of chiral [α1-P2W17O61]10-¬. The diastereoselective functionalization of organosoluble chiral TBA7[α2-RSnP2W17O61] is also reported. The final chapter describes chiral POM imidazolidinones hybrids based on the known chiral α1-Dawson POM. Successfully applied as asymmetric catalysts in Diels-Alder reactions, these compounds are the first intrinsically chiral POM to efficiently transfer chirality to organic products

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Liu, Shih-Yuan 1975. "Applications of novel boron-nitrogen containing heterocycles : design and synthesis o planar-chiral Lewis acids for stereoselective organic synthesis." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/30063.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, February 2004.
Vita.
Includes bibliographical references.
Because Lewis acids are very versatile mediators of a variety of stereoselective organic transformations, a great deal of effort has been devoted toward the development of chiral Lewis acids. This thesis describes the design, synthesis, and applications of 1,2-azaborolyl complexes as a novel family of planar-chiral Lewis acids that can perform a wide range of stereoselective transformations. The 1,2-azaborolyl ligand is a five-membered B-N bearing heterocycle that is isoelectronic and isostructural with the ubiquitous cyclopentadienyl ligand. In Part I of this dissertation, the feasibility of using boron-substituted 1,2-azaborolyls as tunable cyclopentadienyl surrogates is established. Thus, X-ray structural and spectroscopic studies demonstrate that 1,2-azaborolyls can serve as six-electron [pi]-ligands to a variety of transition metals and that the electronic nature of the boron substituent can modulate the properties of the resulting complexes. Building on the foundations of 1,2-azaborolyl ligand chemistry described in Part I, we establish in Part II that 1,2-azaborolyl complexes bearing good leaving groups on boron can serve indeed as planar-chiral Lewis acids. As a result, we have successfully synthesized a number of enantiomerically pure planar-chiral Lewis acids, and we show through structural and stereochemical correlation studies that these Lewis acids can activate substrates such as aldehydes and imines toward stereoselective nucleophilic attack in a predictable fashion. Specifically, we have investigated planar-chiral Lewis acid mediated nucleophilic attack of Grignard reagents to imines and Lewis acid mediated Mukaiyama aldol reaction of aldehydes with silyl ketene acetals.
(cont.) Our studies indicate that unfavorable peri-interactions between the imine substrate and the Lewis acid may be the conformation-controlling element for nucleophilic additions to imines. On the other hand, detailed mechanistic studies of the Mukaiyama aldol reaction suggest a reaction pathway involving an intermediate with a coplanar aldehyde-Lewis acid conformation. These studies demonstrate the broad scope and the high efficiency with which the chiral information is transferred from the planar-chiral Lewis acid to its substrates. Consequently, the turnover step (regeneration of the active Lewis acid) represents the last hurdle to be addressed for achieving asymmetric Lewis acid catalysis. Part III of this thesis describes miscellaneous applications that have been discovered during the course of the development of 1,2-azaborolyl-based planar-chiral Lewis acids. In Chapter 7, we present a surprisingly mild and versatile method for palladium-catalyzed Suzuki cross-couplings of aryl chlorides in the presence of a triarylphosphine. With this catalytic system, both sterically demanding and electronically deactivated aryl chlorides can be efficiently coupled with a range of boronic acids in good yields, and coupling of activated aryl chlorides can be accomplished at room temperature. In Chapter 8, we report the synthesis and characterization of novel 1,2-azaborines and their potential as benzene surrogates.
by Shih-Yuan Liu.
Ph.D.

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Colonne, Mathilde. "Préparation et caractérisation de matrices minérales porteuses de greffons chiraux. Evaluation de leur potentiel catalytique dans l'addition énantiosélective de nucléophiles silylés." Rouen, 2000. http://www.theses.fr/2000ROUES042.

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La montmorillonite K10 et la silice ont été activées par des acides de Lewis, et nous y avons incorporé ensuite des greffons chiraux (diéthyltartrate, diisopropyltartrate, phénylalaninol, éphédrine, et salen). Des silices ont également été greffées avec des esters d'allyles et ont été activées ensuite avec des acides de Lewis. Ces catalyseurs ont été caractérisés par absorption atomique, analyse élémentaire, et infrarouge. Ils ont été utilisés dans trois réactions types : la formation de phosphonates - fonctionnels, la réaction d'aldolisation et la réaction de cyanosilylation. La première réaction se fait par addition d'un aldéhyde ou d'une imine à un phosphite (silylé ou non) ; les rendements obtenus sont dans l'ensemble satisfaisants, et mettent en évidence l'influence de la présence d'un motif chiral sur le pouvoir catalytique de nos supports. La réaction d'aldolisation a été étudié par addition d'un énoxysilane à un aldéhyde, voie qui ne fournit pas de résultats satisfaisants ; le remplacement de l'énoxysilane par un acétal de cétène silylé permet d'obtenir de bons rendements, mais pas d'énantiosélectivité. La réaction de cyanosilylation a été étudiée par addition de cyanotriméthylsilane au benzaldéhyde, et permet d'obtenir le mandélonitrile avec un rendement quantitatif et jusqu'à 40% d'excès énantiomérique ; le catalyseur peut être recyclé sans perte de rendement et avec une légère baisse d'énantiosélectivité. L'ensemble de ce travail montre que les catalyseurs supportés sur montmorillonite et silice sont efficaces, sont compatibles avec des réactifs très sensibles à l'hydrolyse et qu'ils produisent dans certains cas une énantiosélectivité tout en permettant de limiter les quantités de solvants utilisés.

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Nguyen, Truc Minh. "The generation of chiral borenium cations : evaluation of the [alpha]-metallations of Lewis acid-complexed heterocycles /." 2000. http://www.library.wisc.edu/databases/connect/dissertations.html.

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Hung, Hsiu-Yin, and 洪秀銀. "Michael Addition Studies of b-amino, a,b-unsaturated-g-thiolactone under Lewis acid condition and Chiral Anti-Aldol Reaction with Synthetic applications of Chiral Vinylogous Urethanes." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/05634826383446734589.

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碩士
朝陽大學
應用化學系碩士班
88
Abstract 一. Michael Addition Reaction of b-amino, a,b-unsaturated-g-thiolactone under Lewis acid conditions. 4-(1-pyrrolidinyl)-2(5H)thiophenon 1, which developed in our laboratory was used to study it''s Michael reaction under Lewis acid conditions. Their reaction products were analyzed using HPLC techniques to determine diastereoselectivity. 二.Chiral Anti-Aldol Reaction Studies of Chiral Vinylogous Urethane and their Application in Natural Product Synthesis. 1. Camphor derived chiral vinylogous urethane 3 was deprotonated and reacted with aldehyde to from anti-aldol product, the product selectivity was analyzed using chiral column to determine their enantioselectivity. 2. Product 5 was used to synthesize Bafilomycin A1 fragment prelactone B.

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Perreault, Christian. "Cycloaddition dipolaire [3+2] à partir d'hétérocycles aromatiques N-aminés." Thèse, 2008. http://hdl.handle.net/1866/7834.

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Dubland, Joshua. "Studies towards Developing Diastereoselective SN1 Reactions of α-Keto Carbocations." Thesis, 2010. http://hdl.handle.net/1807/24246.

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Although α-keto carbocations have been demonstrated to be viable intermediates in solvolysis reactions, their applications in synthesis are scarce. These species can be considered to be equivalent to “reversed polarity” enolates and, as such, could be useful for the asymmetric formation of carbon-carbon and carbon-heteroatom bonds. In principle, facial selectivity in additions to α-keto carbocations may be induced using easily removed ester, amide, or imide chiral auxiliaries. Efforts to achieve such diastereoselective SN1 reactions of α-keto carbocations are described herein.

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Simelane, Sandile Bongani. "Aluminium triflate-mediated reactions of glycals: towards chiral multicyclic products." Thesis, 2015. http://hdl.handle.net/10210/13698.

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Ph.D. (Chemistry)
The bridged chiral benzopyrans were strategically ring opened via acetolysis to yield either galactose based chromenes or chromans, depending on the reaction conditions. A proposal relating to the mechanism of this selective ring opening acetolysis is discussed. The benzopyrans (chromenes, chromans and bridged chiral benzopyrans) were de-acetylated via triethyl amine catalysed transesterification. Interestingly, the chromenes did not yield the anticipated hydrolysis product (triol) but a new class of bridged chiral benzopyrans which were a result of intramolecular oxa-Michael addition. A chromene that formed during the selective ring opening of the bridged chiral benzopyrans was employed to develop a method for the synthesis of a carbohydrate derived oxepane. The oxepane synthesis was achieved, albeit in the face of numerous challenges from side reactions. The difficulties encountered in the synthesis are discussed...

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Nguyen, Maud. "Synthèse de motifs propionate optiquement purs via une aldolisation énantiosélective de Mukaiyama suivie d'une réduction radicalaire diastéréosélective contrôlées à l'aide d'acides de Lewis." Thèse, 2005. http://hdl.handle.net/1866/16784.

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Dissertations / Theses on the topic 'Chiral Lewis acid'

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