Dissertations / Theses on the topic 'Aldol Reaction'
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1
Tan, Duygu. "Silicon Tetrachloride Mediated Asymmetric Aldol Addition Reaction." Master's thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615396/index.pdf.
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Aldol addition reaction is one of the most important and most studied carbon-carbon bond
forming reactions in organic chemistry. Recent studies focused on the catalytic version of
this chemistry. Different from the classical Mukaiyama-type aldol reactions, chiral lewis
bases have been used as promoters. In the presence of SiCl4, these reactions proceed
through a cyclic transition state leading to anti aldol product as a major product with
moderate-to-good diastereo and enantioselectivities. Phosphoramide derivatives, BINAPO,
BINAPO derivatives, N,N-dioxides and N-oxides have been extensively used for this
purpose.
Recently, our group has designed new phosphine oxy aziridinyl phosphonates (POAP) as
chiral Lewis bases. These promoters were used for the asymmetric aldol addition reaction
between cyclohexanone and different aldehydes in the presence of SiCl4. Moreover, our
previously designed phosphine oxy ferrocenyl substituted aziridinyl methanol (POFAM)
ligands were also tested as Lewis bases. Among these 6 potential promoters, POAP-A gave
the best results, and the aldol product were obtained in moderate to good yields up to 80%,
and with moderate enantioselectivities (the highest, 66%) after standard optimization studies.
Aldehyde screening experiments provided the highest enantioselectivity (68%) with 2-
naphthaldehyde.
2
Goodman, J. M. "Studies on the boron-mediated aldol reaction." Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316774.
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Tokuda, Osamu. "Studies on organocatalytic direct asymmetric aldol reaction." 京都大学 (Kyoto University), 2007. http://hdl.handle.net/2433/136966.
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Nixon, Tracy Dawn. "Catalyst design for the asymmetric phospho-aldol reaction." Thesis, University of Leeds, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.424504.
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Lou, Samuel. "Stereochemical Control of Polyketides through Asymmetric Aldol Reaction." Master's thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/37095.
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Polyketides are a group of complex natural products that can inhibit the growth of
bacteria, viruses, fungi, and tumor cells. Most polyketides are very difficult to extract from
bacteria. Therefore, numerous syntheses of polyketide-related synthons have been
attempted.
However, controlling the stereochemistry of the polyketide poses the most
challenging task for researchers. The aim of this report is to discuss control of the
stereochemistry of the polyketide-related synthons in asymmetric aldol reactions. Several
important methodologies for stereochemical control in the aldol reaction exist. The first
approach is to control the enolate geometry and the aldehyde (or ketone) geometry. The second approach is to use a chiral auxiliary and chiral ligands. The third approach is to use
a chiral catalyst, which is the most efficient method if the catalyst operates with complete
efficiency. Proposed transition states are also described to explain the resulting
stereochemistry of the aldol adduct.
Master of Science
6
Freiria, Marta. "Novel rhodium (I) catalysed tandem hydrosilylation - intramolecular aldol reaction." Thesis, University College London (University of London), 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.409927.
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Kephart, Susan E. "Synthetic and mechanistic studies on a silicon-mediated aldol reaction." Diss., Pasadena, Calif. : California Institute of Technology, 1995. http://resolver.caltech.edu/CaltechETD:etd-10312007-082516.
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Tempkin, Orin 1967. "New chiral catalyts for the asymmetric Mukaiyama-type aldol reaction." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/17349.
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9
Tang, Gongkun [Verfasser]. "Novel Organocatalysts with Pyrrolidine and Brönsted Acids for Aldol Reaction and other Reactions / Gongkun Tang." Wuppertal : Universitätsbibliothek Wuppertal, 2013. http://d-nb.info/1038029023/34.
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10
Taylor, Anthony Philip. "Regio- and diastereo-selectivity in directed aldol reactions of cyclopent-2-enone and but-2-en-4-olide." Thesis, University of Bath, 1988. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380865.
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Sakamoto, Ryu. "Development of Amine-catalyzed Asymmetric Reactions Using Hetero-functionalized Acetaldehydes as Nucleophiles." 京都大学 (Kyoto University), 2014. http://hdl.handle.net/2433/188503.
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12
Georgiou, Irene. "Organocatalysis using bifunctional aminoboronic acids : application to the asymmetric aldol reaction." Thesis, Durham University, 2012. http://etheses.dur.ac.uk/3540/.
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The organocatalytic iminium activation strategy acting cooperatively with a Lewis acidic group has been applied to the development of a novel generation of proline-based aminoboronic acid catalysts. Key steps for their synthesis included (-)-sparteine mediated asymmetric deprotonation of N-Boc-pyrrolidine, copper(I) catalysed borylation of alkylhalides and catalysed hydroboration of alkenes. The evaluation of the first proline-based aminoboronic acids is described in the context of organocatalysed aldol reactions between p-nitrobenzaldehyde and acetone. Enhanced reactivity and enantioselectivity observed in the presence of a boronate ester analogue of the catalyst resulted in further examination regarding the role of the esterification diol in these organocatalytic reactions. Notably, 11B NMR studies have been assessed, allowing the evaluation of different diols in terms of stability and Lewis acid tuning, and plausible identification of the catalytic species present. The feasibility of the catalyst under optimised reaction conditions was demonstrated in the aldol reaction of different substrates. Extended mechanistic studies lead to the proposal of a catalytic cycle in which a highly organised transition state plays a key role for both the reactivity and enantioselectivity observed. Finally, strategies employed to further examine both reactivity and asymmetric induction of the free boronic acid catalyst are discussed, examing the carbon length chain between the secondary amine moiety and the boronic acid group of the catalyst.
13
Gledhill, Alexandra Cathleen. "Designing new metallo-organic catalysts for the asymmetric phospho-aldol reaction." Thesis, University of Leeds, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.507721.
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Yeste, Sonia Lozano. "Boron-BINOL catalysed asymmetric Mannich and aldol type reaction : novel boronate esters." Thesis, University of Bath, 2007. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.516904.
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15
Seifert, Andrea. "Säurekatalysierte Tandem-Aldol- Meerwein-Ponndorf-Verley-Reaktionen." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2010. http://dx.doi.org/10.18452/16242.
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Im Rahmen dieser Dissertation wurde die säurekatalysierte Tandem-Aldol-MPV-Reaktion zur Darstellung von 1,3-Diolethern als Eintopfverfahren entwickelt. Dabei konnte ein Syntheseprotokoll entwickelt werden, das durch geschickte Wahl der Reaktionspartner, eines Katalysatorsystems aus LiClO4/ Trifluoressigsäure und geeigneter Reaktionsbedingungen ermöglichte, die klassische dreistufige Synthese von 1,3-Diolethern auf ein effizientes Eintopfverfahren zu reduzieren. Die Kombination mit umfangreichen mechanistischen Untersuchungen ermöglichte erstmals die Entwicklung einer asymmetrischen Variante der Tandem-Aldol-MPV-Reaktion. Dabei hat sich eine Kombination von chiralem Menthol und Methanol bewährt, wodurch die Reaktion mit hoher Chemoselektivität und ohne Konkurrenzreaktionen abläuft. Mit Hilfe dieser neuen Reaktionsbedingungen der asymmetrischen Tandem-Aldol-MPV-Reaktion gelang erstmals die Synthese von chiralen 1,3-Diolethern mit sehr guter Regio- und guter bis sehr guter Diastereo- und Enantioselektivität. Bemerkenswert ist die Möglichkeit der Steuerung der asymmetrischen Synthese und damit des selektiven Zugangs zu jeweils einem Enantiomer durch Variation zwischen (-)- bzw. (+)-Menthol. Als Erweiterung gelang erstmals eine intramolekulare Tandem-Aldol-MPV-Reaktion mit der Synthese verschieden substituierter pentacyclischer 1,3-Diolether. Auch hier gelang die Synthese ausgehend von zuvor synthetisierten Dialdehyden in einer Eintopfreaktion mit sehr hoher Diastereoselektivität. Auf dem zweiten großen Gebiet der Dissertation konnte eine neue innovative Syntheseroute zu Verbindungen in der Thiochromanreihe mit völlig neuartigem Substitutionsmuster entwickelt werden. Es gelang die Entwicklung einer milden Eintopfsynthese, die die Synthese hochsubstituierter anti-konfigurierter Thiochromane ermöglicht. Dabei gelang die Synthese eines Thiochromans ausgehend von racemischen Edukten, in dem stereoselektiv drei benachbarte Stereozentren aufgebaut wurden.In this thesis, the acid-catalyzed tandem-aldol-Meerwein-Ponndorf-Verley-reaction for the preparation of 1,3-diolethers was developed. By handy choice of the reactants, the LiClO4/ trifluoroacetic acid catalyst system and appropriate reaction conditions an efficient one-pot-reaction protocol has been established. The development of an asymmetric execution was enabled by employing extensive mechanistic examinations. Consequently, a combination of chiral menthol and methanol leads to products with high chemoselectivities and without occurrence of competitive reactions. For the first time, by employing the novel optimized synthetic scheme for the asymmetric tandem-aldol-MPV reaction, chiral 1,3-diolethers have been prepared with very high regio- and moderate to very high diastereo- as well as enantioselectivity. Moreover, an opportunity for controlling asymmetric synthesis by variation of (-)- and (+)-menthol was developed. Hence, a selective access to the desired enantiomer is given. In continuative work an intramolecular tandem-aldol-MPV-reaction for the preparation of highly substituted penta-cyclic 1,3-diolethers was developed. Also in this case, the reaction was realized as an one-pot reaction with high anti-diastereoselectivity. The second chapter of this thesis describes a new innovative synthesis of thiochromans with completely unknown substitution pattern. We were able to establish a mild one-pot synthesis of highly substituted anti-configured thiochromans. As a special highlight we suceeded in the steroeselective synthesis of a thiochroman with three adjacent stereogenic centers starting from racemic educts.
16
Balnaves, Andrew Stuart. "Scope and limitations of the aldol reaction for the synthesis of difluorinated polyols." Thesis, University of Birmingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.396231.
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Cosgrove, Nichola Elizabeth. "Studies on the phospho-aldol reaction catalysed by aluminium salcyan and related complexes." Thesis, University of Leeds, 2011. http://etheses.whiterose.ac.uk/1737/.
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The phospho-aldol (PA) reaction is one of the most versatile reactions for the formation of phosphorus-carbon [P-C] bonds. The reaction is a base-catalysed addition reaction between a hydrogen-phosphonate ester and a carbonyl substrate, affording alpha-functionalised phosphonate esters. These PA products have found a wide-spread application in biomedical science. Since the PA reaction is capable of affording products with new stereocentres, considerable effort has been devoted over the last few decades to developing asymmetric catalytic variants of the PA reaction. Through the manipulation of the substituent groups of the salcyan ligands there is the possibility of controlling the enantioselectivity and stereochemical outcome of the reaction. This thesis describes previous work that has been carried out with regards to the PA reaction, how it works, Schiff base complexes and how aluminium can be incorporated in a Schiff base complex, ultimately resulting in the catalysis of the PA reaction. Discussed are the studies carried out towards the construction of chiral aluminium complexes based on the (R,R)- N4-salcyan framework for application as catalyst precursors for the asymmetric phospho-aldol reaction. A computational study focusing on the complex {[(R,R)-salcyan(tBu)2]Al(μ-OH)}2 as part of a validation study carried out on Gaussian 03 is outlined. The results were used to validate the original molecular modelling studies that used semi-empirical methods. In addition, geometry optimisation calculations were carried out on a selection of single crystal X-ray structures as a means of identifying the most basic site of the complex and therefore determine where deprotonation of DMHP could take place. To conclude this thesis two relatively new areas for PA catalysis are discussed. One such area focuses on the incorporation of cyclams into the salcyen backbone, which could serve as a versatile framework for PA catalysts with the inclusion of a secondary basic functionality. The second area introduces phosphine oxide and phosphine substituted N2O2 salcyan compounds, which can provide a basic complex construction with the added advantage of being able to introduce suitable co-factors, tuneable to a specific substrate. This approach would open up the chance of parallel processing and analysis.
18
Belletti, Giada. "Organocatalytic Enantioselective Vinylogous Aldol-Lactonization Cascade Reaction of 3-Alkylidene Oxindoles to Trifluoromethyl Ketones." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/14463/.
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In this work, an highly enantioselective vinylogous aldol-lactonization cascade reaction of 3-alkylidene oxindole to α,β-unsaturated trifluoromethyl ketone, promoted by bifunctional organocatalysts, is presented. The reaction proceed through 1,2-addition followed by cascade lactonization to afford an unsaturated lactone bearing a chiral trifluoromethylated tetrasubstituted carbon stereocenter with high enantioselectivity and moderate yield. Nevertheless, also the two E/Z isomers of the correspondent 1,2-addition product are obtained.
19
Bañón, Caballero Abraham. "Recoverable binam derivatives as organocatalysts in asymmetric synthesis." Doctoral thesis, Universidad de Alicante, 2014. http://hdl.handle.net/10045/42322.
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D'Elia, Valerio. "Synthesis, characterization and application of alpha-beta-oligopeptides as bifunctional organocatalysts for the aldol reaction." kostenfrei, 2009. http://www.opus-bayern.de/uni-regensburg/volltexte/2010/1166/.
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Wade, Charles. "Studies towards the total synthesis of isoavenaciolide and the development of the amino tartrate aldol reaction." Thesis, University of Sheffield, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341816.
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Abramite, Joseph A. "The intramolecular Yamamoto vinylogous aldol reaction and its application in the total synthesis of (+)-peloruside A." Connect to online resource, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3337042.
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Karak, Milandip. "A stereoselective vinylogous aldol reaction of tetronamides and the synthesis of rubrolides and beta- substituted butenolides." Universidade Federal de Viçosa, 2017. http://www.locus.ufv.br/handle/123456789/13425.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Os butenolídeos, que apresentam em sua estrutura o núcleo lactona α, -insaturada, são encontrados em produtos naturais e não naturais com diversas propriedades biológicas. Devido à prevalência dos butenolídeos substituídos, muitos esforços têm sido direcionados para explorar metodologias eficientes para suas sínteses e transformações. Entre elas, o acesso estereosseletivo dos derivados de butenolídeos -substituídos utilizando o conceito de vinilogia, o qual envolve a formação de ligação carbono-carbono com um eletrófilo apropriado na posição do butenolídeo, tem provocado um interesse crescente. Portanto, esta tese apresenta uma reação aldólica viníloga estereosseleva (VAR) eficiente, simples, escalável e diretamente estereosseletiva de butenolídeos -amino-substituídos (tetronamidas) com aldeídos. Esta tese também descreve as sínteses totais de butenolídeos contendo metabólitos naturais marinhos rubrolídeos pela bromação altamente regiosseletiva de fase tardia a partir de intermediários apropriados. Além disso, a tese inclui uma desalogenação redutiva de butenolídeos α-halo- -substituídos sob condições suaves com rendimentos elevados e regiosseletivos. Uma introdução ao contexto geral, incluindo estratégias sintéticas versáteis, sínteses totais e propriedades biológicas dos butenolídeos substituídos estão documentadas na seção: Capítulo 1. Sendo seguida por uma ilustração dos métodos selecionados para a construção do núcleo de butenolídeos. São também discutidos os vários métodos para a preparação de alguns produtos naturais selecionados que possuem o núcleo de butenolídeo ou sintetizados a partir de butenolídeos que atuam como “building blocks”. Finalmente, foram descritos alguns butenolídeos sintéticos que são comercializados como medicamentos ou agroquimicos recentemente. Os resultados da VAR estereosseletiva de tetronamidas estão apresentatos no Capítulo 2. O procedimento descrito, simples e escalável, funciona bem com aldeídos aromáticos e alifáticos, proporcionando principalmente os adutos correspondentes de syn-aldol. Em muitos casos, estes últimos são obtidos isentos dos seus isômeros anti com rendimentos elevados. Foi também realizado um estudo computacional detalhado. Os estudos experimentais e computacionais sugerem que a diastereosseletividade observada surge através da interconversão do isômero anti-syn, através da reação reversível retro-aldólica. No Capítulo 3, as estruturas cristalinas de alguns produtos aldólicos de tetronamida com dois estereocentros foram descritos. Os compostos relacionados revelaram tendências conformacionais e supramoleculares com padrões de substituição do anel aromático/heteroaromático. Tais tendências foram racionalizadas com base nos perfis energéticos dos principais confôrmeros. A principal contribuição deste estudo refere-se ao controle sobre a conformação molecular de tetronamidas que apresentam várias ligações que permitem giros, além da elevada liberdade conformacional através do padrão de substituição de um único anel. As primeiras sínteses totais de produtos naturais marinhos, os rubrolídeos I e O e alguns de seus derivados não naturais são relatadas no Capítulo 4. Uma versátil estratégia de bromação na última etapa permitiu a funcionalização dos anéis aromáticos de maneira altamente regiosseletiva, permitindo o acesso rápido aos alvos, rubrolídeos, a partir de precursores comuns. Posteriormente, a cloração regiosselectiva foi também aplicada à preparação de análogos sintéticos biologicamente importantes a partir de precursores facilmente acessíveis. No Capítulo 5, foi relatado a desalogenação redutiva catalisada por paládio binário de butenolídeos α-halo- -substituídos. O procedimento sintético permitiu o acesso rápido aos butenolídeos substituídos sob condições suaves, com rendimentos elevados e excelente regiosseletividade. Além disso, uma nova proposta para a síntese dos rubrolídeos E, F e composto com a estrutura correspondente à descrita para 3"-bromorubrolídeo F de ocorrência natural utilizando este mesmo protocolo.
Butenolides are α, -unsaturated lactone and are found in many natural and unnatural products with diverse biological properties. Owing to the prevalence of the substituted butenolides, much effort has been directed towards developing efficient methodologies for their synthesis and transformations. Among them, stereoselective access of the -substituted butenolide derivatives by utilizing the concept of vinylogy, which usually involves the carbon– carbon formation with an appropriate electrophile at the -position of butenolides, has triggered increasing interest. This thesis presents an efficient, simple, scalable and direct stereoselective vinylogous aldol reaction (VAR) of -aminosubstituted butenolides (tetronamides) with aldehydes. In addition, this thesis also describes the total syntheses of butenolide core bearing marine natural metabolites, rubrolides by using a highly regioselective late-stage bromination from appropriate intermediates, and apprises a facile reductive dehalogenation of α-halo- -substituted butenolides. An introduction to the general background, including versatile synthetic strategies, total syntheses, and biological properties of substituted butenolides is documented in Chapter 1. It is followed by an illustration of selected methods for construction of the butenolide core. Also discussed are the various methods for preparation of some selected natural products which either possess a butenolide core or synthesized from butenolide building blocks. Finally, some synthetic butenolide derivatives are described which are recently marketed as either medicines or agrochemicals. The results of the stereoselective VAR of tetronamides are compiled in Chapter 2. The described procedure, is simple and scalable, works well with both aromatic and aliphatic aldehydes, and affords mainly the corresponding syn-aldol adducts. In many cases, the latter are obtained essentially free of their anti-isomers in high yields. A detailed computational study was also carried out to establish the reaction mechanism. The experimental and computational studies suggest that the observed diastereoselectivity arises through anti–syn isomer interconversion, enabled by an iterative retro-aldol/aldol reaction. In Chapter 3, the crystal structures of several tetronamide aldol products with two stereocenters are described. Those compounds revealed conformational and supramolecular trends with the substitution pattern of a side aromatic/ heteroaromatic ring. The major contribution of this study concerns the control over the molecular conformation of tetronamide aldolates bearing several rotatable bonds and the high conformational freedom through the substitution pattern of a single ring. The first total syntheses of the marine natural products rubrolides I and O and some of their unnatural congeners are reported in Chapter 4. A versatile late-stage bromination strategy allowed functionalization of the aromatic rings in a highly regioselective fashion, enabling rapid access to the target rubrolides from common precursors. Next, the regioselective chlorination was also applied to the preparation of biologically important synthetic analogous of rubrolides from easily accessible precursors. In Chapter 5, a binary palladium catalyzed reductive dehalogenation of α-halo- -substituted butenolides is documented. The synthetic procedure allowed rapid access to the -substituted butenolides under mild conditions with high yields and excellent regioselectivity. In addition, a protecting group free step-economical synthesis of rubrolides E, F and γ”-bromorubrolide F has been reported by employing this protocol.
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Liu, Jing. "Synthesis of resveratrol and its analogs, phase-transfer catalyzed asymmetric glycolate aldol reactions, and total synthesis of 8,9-methylamido-geldanamycin /." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd1998.pdf.
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Issa, Issa. "Synthesis of monoterpenoid derivatives and evaluation for biocatalytic transformations." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/synthesis-of-monoterpenoid-derivatives-and-evaluation-for-biocatalytic-transformations(c06f8f06-e42c-48f0-bf29-d5bb92fd1353).html.
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Monoterpenoid derivatives are some of the most effective asymmetric controllers used in organic synthesis. They are also precursors in target syntheses, especially in synthesis of natural products with useful biological properties. However, there are still significant opportunities to develop new structural synthetic modifications. This project target focuses on employing commercially available chiral pool cyclic ketones, such as R-(-)-carvone, (+)-isomenthone, and (-)-isopinocamphone to create new potential substrates for biocatalytic modifications, via terpenone enolate alkylations, aldol additions, and formation of alkylidenes. Evaluation of these substrates has been carried out using isolated enzymes as biocatalysts to reduce the double bond and/or carbonyl group, as well expansion of six membered rings by Baeyer-Villiger monooxygenase to generate lactone derivatives, consequently resulting in new high-value terpenone, terpenol and lactone derivatives. Bioreduction of R-(-)-carvone substituted (with Me or OH) at C6 and/or C3 via OYEs afforded with highly diastereoselectivity in most cases with varied yields; and there was no activity observed toward substrates with substituents bigger than Me. Biooxidation of dihydrocarvone substituted (Me) at C6 or C3 via cyclohexanone monooxygenase (CHMO_Phi1) was selective, and oxidised only one diastereomer. For instance, (2R,3R,6R)-methyldihydrocarvone was completely converted to lactone with high regio- and enantioselectivity, while for the (2S,3R,6R)-diastereomer no lactone was produced, and starting material was recovered. (+)-Isomenthone, R-(-)-carvone, (-)-isopinocamphone and their derivatives were treated with carbonyl reductase, and only (+)-isomenthone, R-(-)-carvone and anti (5S,6S)-hydroxycarvone showed reaction, with varied yields and selectivities. The bioreduction and oxidation of substrates were scaled up to 50-100 mg as part of chemo-enzymatic reactions. The simulation of substrates with PETNR enzyme was studied, and docking was modelled.
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Perez, Carla Cristina 1979. "Síntese formal dos policetídeos bicíclicos salinecetais A e B." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/248357.
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Orientador: Luiz Carlos DiasTese (doutorado) - Universidade Estadual de Campinas, Instituto de Química
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Resumo: Os salinecetais A e B foram isolados em 2007 por Fenical e colaboradores a partir da actinobactéria marinha Salinispora arenicola, e mostraram ser importantes alvos na quimioprevenção do câncer como inibidores da ornitina descarboxilase. Concluímos a síntese do fragmento avançado C-4/C-17 (19) envolvendo 19 etapas em 5,5% de rendimento global a partir do éster de Roche (rota linear mais longa). No decorrer deste trabalho algumas mudanças de estratégia se fizeram necessárias, estando sempre voltadas à procura da rota sintética mais criativa e eficiente. Foram utilizadas como etapas chave na rota sintética principal, reações aldólicas do tipo syn seletivas para a preparação do aduto 139, bem como reação aldólica de dupla diastereodiferenciação na preparação de 134b. Uma reação de Grignard estereocontrolada pelo substrato foi determinante na preparação de 169, seguido de uma ciclização intramolecular do tipo Wacker para formação do biciclo espirocetal presente em 29. A reação de homologação de Seyferth-Gilbert foi usada na preparação do alcino 187 e uma syn-hidroestanilação converteu o mesmo na estanana vinílica 19. Esse resultado permitiu a determinação inequívoca da estereoquímica dos centros formados por comparação com os dados obtidos nesse trabalho com os da literatura, além dessa rota permitir, a princípio, a obtenção dos mesmos fragmentos em escalas maiores
Abstract: The saliniketals A (1) and B (2) were isolated in 2007 by Fenical and coworkers from Salinispora arenicola and showed to be important inhibitors of ornithine decarboxylase. We concluded the synthesis of C-4/C-17 fragment (19) after 19 steps in 5.5% overall yield from Roche ester (longest linear sequence). This work was always focused on the search for the more creative and efficient synthetic route. The key steps involved an efficient syn-aldol reaction for the preparation of adducts 139 and a double diastereo-differentiating aldol reaction for the preparation of 134b. Substrate controlled Grignard reaction provide 169, and an intramolecular Wacker-type cyclization established the bicyclic spiroketal in 29. The Seyferth-Gilbert homologation was used in the preparation of alkyne 187 and a syn-hydrostannation provided the vinyl stannane 19. This result allowed the unequivocal determination of the stereochemistry for all stereocenters formed by comparison with data obtained from the literature. We are able to conclude a formal total synthesis of saliniketals A and B and the synthetic route is, in principle, amenable to a large scale synthesis
Doutorado
Quimica Organica
Doutora em Ciências
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Hansch, Markus. "Die Zirconiumalkoxid-katalysierte Aldol-Tishchenko-Reaktion von Keton-Aldolen." Doctoral thesis, [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=975299727.
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司徒振邦 and Chun-pong Szeto. "Studies on the use of (triphenylphosphine)copper(I) hydride hexamer inthe tandem reduction-intramolecular aldol cyclisation reaction." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B31223412.
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Curati, Federico. "Synthesis of a chiral, water soluble porphyrin containing a pyrrolidine unit and initial study of its catalytic activity." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/16731/.
Full textAbstract:
Asymmetric organocatalysis have taken hold in the last decades due to affordability and lack of toxicity of their catalysts. Unfortunately, organocatalytic enantioselective reactions in an environmentally friendly and safe solvent as water are still scarce. During the training internship our aim has been to find an effective water soluble organocatalyst able to drive in an enantioselective fashion a reaction, to maximize the diasteromeric and the enantiomeric excess. Pursuing this objective we synthesized a meso 3-sulfonatophenyl porphyrin with a chiral aminoaldehyde substituent, with the sulfonate-groups allowing its solubilization in water and the chiral group which should improve the enantioselectivity.
The chiral aldehyde has been prepared starting from L-proline, a widely used organocatalyst, and finally tried in an aldol reaction, giving excellent yield, moderate diastereoselectivity and very low enantiomeric excess.
The reaction products can be easily removed washing in organic solvent and the catalyst can be recovered by aggregation in acidic medium.
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Szeto, Chun-pong. "Studies on the use of (triphenylphosphine)copper(I) hydride hexamer in the tandem reduction-intramolecular aldol cyclisation reaction /." Hong Kong : University of Hong Kong, 2000. http://sunzi.lib.hku.hk/hkuto/record.jsp?B21827369.
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Agrahari, Aditya. "Synthesis and Characterization of Di- Aryl Pentanes and Mechanistic Study of Aldol Reaction of 9-Acetylanthracene with Paraformaldehyde." Cleveland State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=csu1440082002.
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Atkinson, Duncan. "Novel methods for allylic amination by an intramolecular nitroso ene reaction." Thesis, Loughborough University, 2013. https://dspace.lboro.ac.uk/2134/14069.
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C-H functionalisation reactions aim for the selective cleavage of C-H bonds, and formation of a new carbon or heteroatom bond, often with the use of a transition metal catalyst. These reactions offer potential for functionalisation of hydrocarbons in fewer steps than conventional methods, and with high atom efficiency. They are therefore a subject of intense research in organic synthesis. Carbon-heteroatom bond forming reactions are particularly sought after, and useful in the efficient synthesis of many biologically significant groups such as oxazolidinone rings, 1,2 or 1,3 amino alcohols and amino acid analogues. An efficient, cheap and robust method for C-H amination would also be adaptable to varied syntheses of important large molecules. The necessity for complex and efficient transformations with a minimal number of steps means that heteroatom ring closures are also attractive and widely used reactions in such large molecule syntheses. The nitroso group is a highly reactive species which is normally generated in situ by oxidation of a hydroxylamine, for carbon-nitrogen bond forming reactions including the nitroso Heteroatomic Diels Alder reaction, nitroso ene reaction, and nitroso aldol reaction. Nitroso group reactions often show high stereo- and regioselectivity, and have formed key components of the syntheses of important biological molecules. Enantioselectivive protocols for the nitroso-ene reaction and, to a lesser extent, the nitroso HDA reaction, are poorly developed, however, and the range of available intramolecular nitroso reactions is limited. We aimed to establish efficient single-step intermolecular C-H amination reactions, to give 1,2 and 1,3 heteroatom functionalised molecules, and to develop the capacity for enantioselective induction in this reaction, if possible. Having synthesised a model set of unsaturated hydroxycarbamates, we identified a suitable system for nitroso generation, using a catalytic metal and stoichiometric oxidant. This resulted in in situ generation of cyclised product, with the olefin functionality intact. This cyclisation was then optimised and used to obtain a range of new heterocycles. The possibility of enantioselective induction via chiral catalysts was explored, as well as catalytic systems to increase the stereoselectivity of the reaction. In summary, a cheap, novel and reliable method was developed for formation of oxazolidinone rings from unsaturated hydroxycarbamates using an original intramolecular nitroso ene reaction, and a range of unsaturated heterocycles were synthesised in fairly good yields. Distereoselectivity of the nitroso ene cyclisations was optimised. However, to-date, we were unable to develop an enantioselective varient of the reaction. Several related aminations, as well as transformations of N-hydroxyoxazolidinone products, were also attempted during the project.
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Crossman, Julia Stephanie, and julia crossman@flinders edu au. "Biomimetic Approaches to the Synthesis of Polyketide Derived Marine Natural Products; (-)-Maurenone and the Spiculoic Acids." Flinders University. SoCPES, 2007. http://catalogue.flinders.edu.au./local/adt/public/adt-SFU20080212.134949.
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This thesis describes the total synthesis of the polyketide derived marine natural product (-)-maurenone (14) and synthetic studies of a model system for the marine polyketides, the spiculoic acids (20, 22-24). A biomimetic approach involving cyclisation of linear polyketide precursors to install the complex chemical frameworks was employed.
Maurenone is a polypropionate derived metabolite isolated from pulmonate molluscs collected off the coast of Costa Rica. While structural assignment following isolation revealed a relatively uncommon tetra-substituted dihydropyrone moiety the only stereochemical information deduced was the trans-relative relationship between the C8 and C9 protons. The total synthesis of a series of eight stereoisomeric putative structures was achieved in order to assign the stereochemistry of (-)-maurenone (14), as that depicted above. A time and cost efficient strategy was developed utilising common intermediates providing access to the eight stereoisomeric structures in a convergent manner. Six key fragments, four aldehydes (109) and two ketones (110), were synthesised using highly diastereoselective syn- and anti-boron aldol reactions and were coupled using a lithium-mediated aldol reaction. Trifluoroacetic acid-promoted cyclisation/dehydration enabled installation the ×-dihydropyrone ring. All eight isomers of one enantiomeric series were synthesised by coupling two ketones with each of four aldehydes. By comparison of the NMR data for the eight isomers with that reported for the natural product, the relative stereochemistry was established as shown. The (-)-enantiomer of maurenone was synthesised in nine linear steps (13 % overall yield) from (R)-2-benzylpentan-3-one ((R)-40) and (R)-2-benzoyloxypentan-3-one ((R)-39).
The spiculoic acid family of polyketide derived natural products, isolated from plakortis sponges, possess a unique [4.3.0]-bicyclic core which is proposed to be formed via an enzyme catalysed Intramolecular Diels-Alder (IMDA) cycloaddition reaction of linear polyene precursors 25. Model linear precursors (114), possessing various olefin geometries at C2 and both stereochemical orientations of the C5 stereocentre, were synthesised in order to examine stereoselectivity of the thermally induced IMDA cycloaddition reaction.
The two alternative C4-C6 stereotriads of the linear precursors 114 were achieved by employing highly diastereoselective substrate-controlled aldol reactions; an anti-boron aldol reaction, controlled by the facial preference of (R)-2-benzoyloxypentan-3-one ((R)-39), and a syn-titanium aldol reaction, under the control of chiral N-acylthiazolidinethione ((R)-43a). The diene and dienophile moieties were installed using either standard Wittig, H.W.E. or ¡§modified¡¨ Julia olefination reactions.
A thorough stereochemical assignment of the cycloadducts of the thermally induced IMDA reaction of each linear precursor was accomplished employing 2D NMR techniques. Comparison of the stereochemistry of each of the cycloadducts with the spiculoic acids revealed that the linear precursor (2E,5S)-114 produced a cycloadduct 232 with stereochemistry analogous to the natural products in 94 % diastereoselectivity. Thus, a synthetic approach to the spiculoic acids via synthesis of a linear precursor 285 possessing a TBS ether at C5 in the S configuration was proposed. Unfortunately, problems encountered in the synthesis of the proposed linear precursors to the spiculoic acids ultimately prevented the total synthesis from being achieved.
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De, Raffele Daria. "Computational studies of the Retro-Aldol reaction catalyzed by different protein scaffolds. Towards the redesign of an improved enzyme." Doctoral thesis, Universitat Jaume I, 2022. http://dx.doi.org/10.6035/14122.2022.709183.
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The main objective of this dissertation was to investigate the structure-function relationship in different designed Retro-Aldolases, to understand not only their catalytic efficiency but to provide information to design a new more efficient enzyme. In particular, the first step of the project was to investigate and analyze the reaction mechanism of two previously published de novo Retro-Aldolases (RA95.5-5 and RA95.5-8F) and one catalytic antibody (33F12). The free-energy landscape of the whole chemical process was explored through statistical methods with multiscale quantum mechanics / molecular mechanics (QM/MM) potentials, in terms of the PMF. The agreement between the theoretical predictions and the experimental data allowed to carry out deeper analysis, exploring the structural function and the interaction with the residues. The comparative analysis of the data generated from the computational simulations on the three protein scaffolds allowed to suggest a new variant of de novo Retro-Aldolase with a predicted higher catalytic efficiency.Programa de Doctorat en Química Teòrica i Modelització Computacional
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Fischer, Gerd. "Quantenchemische Berechnungen zur enantioselektiv katalysierten Aldolreaktion." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2004. http://nbn-resolving.de/urn:nbn:de:swb:14-1089129893015-50097.
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Die Mukaiyama-Aldolreaktion ist die Umsetzung eines Silylenolethers mit einer Carbonylverbindung in Gegenwart einer Lewis-Säure. Diese Reaktion ist eine wichtige Methode zur Knüpfung einer Kohlenstoff-Kohlenstoff-Bindung in der Organischen Chemie. In der vorliegenden Arbeit wird mittels quantenchemischer Methoden ein Einblick in den Mechanismus der Reaktion und die Ursachen der Enantioselektivität gegeben. Ausgehend von der unkatalysierten Reaktion wurde der Mechanismus der von kleineren achiralen Lewis-Säuren wie BF3 und TiCl4 katalysierten bzw. vermittelten Reaktion bearbeitet. Mit dem NEB-Verfahren zur Berechnung des Reaktionsmechanismus der enantioselektiv katalysierten Reaktion kam eine neuartige Möglichkeit zur Optimierung von Reaktionswegen zum Einsatz. Es konnte gezeigt werden, dass die Optimierung auch sehr komplexer Reaktionswege möglich ist. So wurde der gesamte katalytische Cyclus der Ti-BINOL katalysierten Reaktion berechnet, wobei sich der Einsatz der DFTB-Methode (density-functional based tight-binding method) zur Berechnung des Systems als sehr gut geeignet erwies. Die Leistungsfähigkeit der DFTB Methode konnte im Vergleich mit den geometrischen Daten aus Röntgenkristallstrukturanalysen nachgewiesen werden. Die Richtung der stereochemischen Differenzierung konnte in Übereinstimmung mit den experimentellen Ergebnissen bestimmt werden. Aus diesem Ergebnis war es möglich, ein schematisches Modell zu entwickeln, das die Ursache der Selektivität veranschaulicht.
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Yunis, Ruhamah. "Synthesis and characterization of amino acid ionic liquids and low symmetry ionic liquids based on the triaminocyclopropenium cation." Thesis, University of Canterbury. Chemistry, 2015. http://hdl.handle.net/10092/10207.
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This thesis involves the synthesis of two main classes of triaminocyclopropenium (tac) Ionic
Liquids (ILs) (i) Amino Acid Ionic Liquids (AAILs) and (ii) reduced-symmetry cations.
[C₃(NEt₂)₂(NRR’)]X (X = TFSA and MeSO₄) were prepared, whereby NHR is derived from amino acids. Optically pure AAILs, [E₄AminoAcid]X (X = TFSA and MeSO₄) were obtained as a mixture of the IL and its zwitterion. The ratios of these mixtures were determined by pH titration and microanalysis. The AAILs specific rotations and pKa values were determined. AAILs can be used for chiral discrimination and form diasterreomeric salts with the entioenriched sodium salt of Mosher’s acid. The AAILs were also successfully used as a solvent and/or catalyst in an aldol reaction and a Diels-Alder reaction.
The low-molecular weight series, [C₃(NMe₂)₂(NRR’)]X and [C₃(NMe₂)₂(NR’2)]X was synthesized and characterized: protic ILs NRR’, where R = ethyl, propyl, allyl, butyl, - CH2CH2OCH₃ and pentyl, R’ = H and X = TFSA: and aprotic ILs NRR’, where R = Me, R’ = ethyl, allyl, propyl, butyl, -CH2CH2OCH₃ and hexyl and X = TFSA and DCA.
ILs with C2v symmetry [C₃(NEt₂)₂(NH2)]X (X = TFSA and MeSO₄), [C₃(NEt₂)₂(NBu2)]I, [C₃(NEt₂)₂(NHex₂)]I and [C₃(NEt₂)₂(NHex₂)]OTf were also synthesized and characterized. The C₃h cations, [C₃(NMeR)₃]X (R = ethyl, allyl, -CH2CH2OCH₃ and phenyl, X = TFSA and DCA) were successfully prepared as well.
The D₃h cation salts [C₃(NEt₂)₃]X (X = MeC6H4SO₃, OTf, I and F5C6O) and [C₃(NBu2)₃]X (X = B(CN)4 and FAP) were also prepared.
The tac-based ILs [C₃(NEt₂)₃]+ and [C₃(NBu2)₃]+ were also complexed with metal halides
- - 2- 2-
forming salts with FeCl₄ , SnCl₃ , CuCl₄
and ZnCl₄ .
Reaction of pentachlorocyclopropane (C₃Cl5H) with BuNH2 gave the open ring allylium product [H2C₃(NBuH)4]2+. This was characterized as Cl- and TFSA- salt. During the synthesis of [C₃(NMe₂)₃]Cl, the open ring cation [HC₃(NMe₂)4]+ was also isolated and was characterized as
the TFSA- salt.
XX
Abstract
The TGA, DSC, density, viscosity, conductivity, and molar conductivity properties for the ILs were measured where possible. The viscosity and conductivity data was fitted for the Arrhenius and Vogel-Fulcher Tamman equations. The entire tac-based ILs lie below the KCl ideal line in Walden plot. A fragility plot was obtained by fitting the viscosity data and all the tac-based ILs were fragile.
The crystal structures of [C₃(NPhH)₃]TFSA, [C₃(NEt₂)₃]FeCl₄ and [HC₃(NMe₂)4]Cl.2CH₃Cl were determined.
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Liu, Jing. "Synthesis of Resveratrol and Its Analogs, Phase-Transfer Catalyzed Asymmetric Glycolate Aldol Reaction, and Total Synthesis of 8,9-Methylamido-Geldanamycin." BYU ScholarsArchive, 2007. https://scholarsarchive.byu.edu/etd/1415.
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The phytoalexin resveratrol and its acetyl analogs have been made using a decarbonylative Heck reaction. The acid chloride derived from 3,5-dihydroxybenzoic acid was coupled with suitable protected 4-hydroxystyrene in the presence of palladium acetate and N,N-bis-(2,6-diisopropylphenyl)-4,5-dihydro imidazolium chloride to give the substituted stilbene in good yield as the key step. Human HL-60 cell assays showed the 4'-acetyl resveratrol variant improved activity (ED50 17 μM) relative to resveratrol (24 μM). Cinchona phase-transfer catalysts (PTC) were developed for glycolate aldol reactions to give differentially protected 1,2-diol products. Silyl enol ether of diphenylmethoxy-2,5-dimethoxyacetophenone reacted to generate benzhydryl-protected products. O-Allyl trifluorobenzyl cinchonium hydrodifluoride (20 mol %) catalyzed the addition of the silyl enol ether to benzaldehyde to give aldol product as a single syn-product in 76% yield and 80% ee. Recrystallization enriched the product to 95% ee, and a Baeyer-Villiger reaction transformed the product into useful ester intermediates. A novel unnatural product, 8,9-Methylamido-Geldanamycin, has been designed and synthesized. Using a convergent route, the total synthesis of the molecule involved only 27 longest linear steps. New synthesis methodologies, including auxiliary controlled asymmetric anti-glycolate aldol, syn-norephedrine aldol, and selective p-quinone formation, were used.
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Polo, Ellen Christine 1985. "Controle da estereoquímica remota 1,5 em adições de enolatos de boro de metilcetonas a aldeídos." [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/248454.
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Orientador: Luiz Carlos DiasDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química
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Resumo: As reações aldólicas com o enolato de boro da metilcetona 44, com protetor cíclico de acetonídeo e relação trans entre os centros quirais, levaram à obtenção de adutos de aldol com níveis de seletividade variando de moderados a bons, em favor do isômero 1,5-anti. Reações aldólicas envolvendo enolatos de boro da metilcetona 45, com protetor cíclico de acetonídeo e relação cis entre os centros quirais, levaram à formação de adutos de aldol com excelentes níveis de seletividade em favor do isômero 1,5-anti. As reações aldólicas entre o enolato de boro da metilcetona 46, com protetor cíclico de silício e relação trans entre os centros quirais, levaram a obtenção de adutos de aldol com níveis de seletividade variando de moderados a bons em favor do isômero 1,5-anti. A reação aldólica entre o enolato de boro da metilcetona 47, com protetor cíclico de silício e relação cis entre os centros quirais, e pivalaldeído levou à formação do aduto de aldol em bom nível de seletividade em favor do isômero 1,5-anti
Abstract: The aldol reactions of the boron enolate generated from methylketone 44 (containing a trans-acetonide), led to aldol adducts with moderate to good levels of diastereoselectivity, favoring the 1,5-anti adduct. The aldol reactions involving the boron enolate of methylketone 45 (containing a cis-acetonide) gave the corresponding aldol adducts with excellent levels of diastereoselectivity, favoring the 1,5-anti adduct. The aldol reactions of the boron enolate generated from methylketone 46 (containing a cyclic silicon protecting group and trans relationship between the chiral centers), led to the formation of aldol adducts with moderate to good levels of diastereoselectivity favoring the 1,5-anti isomer. The aldol reaction between the boron enolate prepared from methylketone 47 (containing a cyclic silicon protecting group and cis relationship between the chiral centers), led to the formation of aldol adduct with good level of diastereoselectivity favoring the 1,5-anti isomer
Mestrado
Quimica Organica
Mestre em Química
39
Lucca, Júnior Emilio Carlos de 1986. "Estudo do efeito do substituinte em ß nas reações aldólicas envolvendo enolatos de boro de metilcetonas." [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/248453.
Full textAbstract:
Orientador: Luiz Carlos DiasDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química
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Resumo: As reações aldólicas envolvendo os enolatos de boro 71 (P = TBS, R = t-Bu), 72 (P = PMB, R = t-Bu) e 96 (P = TPS, R = t-Bu) levaram à formação de adutos de aldol com seletividades de moderadas a boas em favor do isômero 1,5-syn. As reações aldólicas envolvendo os enolatos de boro 90 (P = Tr, R = t-Bu), 91 (P = Tr, R = Me) e 97 (P = TPS, R = Me) levaram à formação de adutos de aldol em uma proporção equimolar de 1,5-anti e 1,5-syn. A reação aldólica envolvendo o enolato de boro 131 (P = TBS, R = Ph3C) levou à obtenção de excelentes níveis de seletividade em favor do aduto de aldol 1,5-syn
Abstract: The aldol reactions involving boron enolates 71 (P = TBS, R = t-Bu), 72 (P = PMB, R = t-Bu) and 96 (P = TPS, R = t-Bu) led to the formation of aldol adducts with moderate to good levels of diastereoselectivity, favouring the 1,5-syn isomer. The aldol reactions involving boron enolates 90 (P = Tr, R = t-Bu), 91 (P = Tr, R = Me) and 97 (P = TPS, R = Me) led to the formation of aldol in a 50:50 mixture. The aldol reactions of boron enolate 131 (P = TBS, R = Ph3C) led to excellent levels of diastereoselectivity, favouring the 1,5-syn adduct
Mestrado
Quimica Organica
Mestre em Química
40
Keskin, Eda. "Synthesis Of Heterocyclic Amine Substituted Novel 1,4-aminoalcohols And Applications In Various Asymmetric Transformations." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608317/index.pdf.
Full textAbstract:
Aminoalcohols are very important compounds used in various asymmetric transformations as chiral ligands or chiral auxiliaries. In this thesis, four novel heterocyclic amine substituted chiral 1,4-aminoalcohols were synthesized.
In the synthetic strategy, amide esters were synthesized from (2S, 3R)-3-methoxycarbonylbicyclo[2.2.1]hept-5-ene-2-carboxylic acid by DCC coupling method. Subsequent reduction of these amide esters lead to target 1,4-aminoalcohols.
The activities of these novel chiral 1,4-aminoalcohols were tested in enantioselective diethylzinc addition, Mukaiyama aldol and Diels-Alder reactions. The enantioselectivities were measured by HPLC.
All the products were identified by H NMR and C NMR spectroscopy
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Blaquiere, Nicole. "Part I The development and mechanistic study of a biomimetic decarboxylative aldol reaction Part II Ruthenium-catalyzed dehydrogenation of ammonia-boranes." Thesis, University of Ottawa (Canada), 2009. http://hdl.handle.net/10393/28048.
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Part I. The development and mechanistic study of a biomimetic decarboxylative aldol reaction. A reaction has been developed in which malonic acid half thioesters (MAHTs) and malonic acid half oxyesters (MAHOs) are shown to undergo decarboxylative nucleophilic addition reactions with ketone and aldehyde electrophiles under exceptionally mild conditions. In the presence of Et3N at room temperature in THF, various nucleophile and electrophile analogues form beta3-hydroxyester and thioester products in moderate to good yields.
It is also demonstrated spectroscopically that these decarboxylative aldol reactions proceed through a post-addition, pre-decarboxylation intermediate. The formation of this intermediate is shown to be reversible using both experimental and kinetic means of analysis. The rate constants for intermediate formation and decomposition to product in various solvents have been calculated using two different models and calculation methods.
Part II. Ruthenium-catalyzed dehydrogenation of ammonia-boranes. The dehydrogenation of ammonia-borane (AB) and methylammonia-borane (MeAB) is shown to be catalyzed by several Ru-amido complexes. Up to one equivalent H2 (1.0 system wt %) is released from AB by as little as 0.03 mol % Ru within 5 minutes, and up to two equivalents H2 (3.0 system wt %) are released from MeAB with 0.5 mol % Ru in under 10 minutes at room temperature, the first equivalent emerging within 10 seconds. Also, a mixture of AB/MeAB yields up to 3.6 system wt % H2 within 1 hour with 0.1 mol % Ru. Several catalytic analogues were synthesized to evaluate the active species the catalytic cycle, and computational studies were performed to elucidate the mechanism of dehydrogenation of AB. Finally, it was shown that alkylamine-boranes can serve as a source of H2 in the Ru-catalyzed reduction of ketones and imines.
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Wang, Zheng. "Preparation and Characterization of Rare Earth Elements Modified Hydrotalcites and Their Catalytic Performances for Aldol Condensation Reactions." Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10091.
Full textAbstract:
Résumé anglais uniquementNowadays there is an urgent need to develop green chemical processes, where the use and generation of toxic substances can be avoided. Indeed, the lignocellulose feedstock destructuration will produce aqueous solutions of ketones or aldehydes and it would be an important breakthrough to develop solid base catalysts capable to promote the aldol condensation. In this thesis, the main results are shown as follows: Magnesium and rare earth mixed oxides (MgReOx), rare earth modified MgAl-HT catalyst were prepared and were evaluated in liquid phase acetone self-aldolization. Rare earth modified MgAl catalysts show enhanced catalystic activity than MgReOx catalysts. Rehydrated MgAl-HT modified with Y and La, also present a higher water tolerance for aldol reaction. The same catalysts were also applied to acetone gas phase self-condensation reaction. At low temperature, the mesityl oxide is the main product for all the catalysts. At high temperatures, deactivation rate is lowered over MgAlCe(Y)O catalysts, and the presence of trimers (selectivity of IP over 50%) is much more noticeable for the MgAlY(Ce)O catalysts. A good balance between basicity and acidity is proposed to increase the selectivity of IP. In the cross condensation of citral and acetone, the citral conversion and pseudoionone yield were significantly enhanced over Mg3AlaY1-aOx catalysts. A general mechanism of reaction was proposed that the Y modified MgAl mixed oxides undergoes the rehydration by the water formed during the reaction, and the rehydrated catalysts with active Brønsted basic sites are responsible for the significantly improvement of catalytic activity
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Beiger, Jason James. "Total Synthesis of Aflastatin A." Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:11040.
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The syntheses of aflastatin A and its C3-C48 degradation fragment are described. The syntheses feature several complex diastereoselective fragment couplings, including a C35-C36 anti-Felkin-selective boron-mediated oxygenated aldol reaction, a C15-C16 Felkin-selective trityl-catalyzed Mukaiyama aldol reaction, and a C26-C27 chelate-controlled aldol reaction involving soft enolization with magnesium. Careful comparison of the spectroscopic data for the synthetic aflastatin A C3–C48 degradation fragment (2) to that reported by the isolation group revealed a structural misassignment in the lactol region of the naturally derived degradation product. The cause of the mismatch was initially believed to be stereochemical in origin. Ultimately, the data reported for the naturally derived aflastatin A C3–C48 degradation lactol (2, R = H) was attributed to its derivative lactol trideuteriomethyl ether \((R = CD_3)\). Further, the absolute configurations of six stereogenic centers (C8, C9 and C28–C31) in aflastatin A (1) were formally revised by the isolation group prior to completion of its total synthesis. The synthesis of the aflastatin A C3–C48 lactol trideuteriomethyl ether and its spectroscopic match to the naturally derived C3–C48 degradation fragment confirm the stereochemical revision. The synthesis of a degradation product containing the tetramic acid and two overlapping stereocenters (C4 and C6) was also achieved. Its spectroscopic match to the corresponding naturally derived degradation fragment verified the absolute configuration of the aflastatin A C5' stereocenter. When combined with previous degradation fragment syntheses, and eventually the total synthesis of aflastatin A, the revised stereochemical assignment of aflastatin A was fully affirmed.Chemistry and Chemical Biology
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Kuroishi, Paula Kishi 1989. "Síntese total do (-)-criptocariol A." [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/248484.
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Orientador: Luiz Carlos DiasDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química
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Resumo: Os criptocarióis A-H foram isolados em 2011 por Gustafson e colaboradores. Esses compostos apresentaram uma promissora atividade contra o câncer por serem capazes de estabilizar Pdcd4, uma proteína supressora de tumor. Neste trabalho, foi concluída a síntese total do enantiômero do criptocariol A em 17 etapas e 0,1% de rendimento (rota linear mais longa) a partir do (R)-penten-2-ol. As etapas chave dessa rota foram reações aldólicas mediadas por boro, assim como reduções estereosseletivas que permitiram a instalação de todos os seis estereocentros presentes na molécula. Além disso, realizamos a reação de Horner-Wadsworth-Emmons utilizando o protocolo de Ando para obter a olefina Z presente no anel a-pirona. Nas etapas finais da síntese, foram observados baixos rendimentos. Sendo assim, foram realizados estudos de modo a tentar otimizar essas condições reacionais utilizando substratos modelo. Embora as condições otimizadas tivessem sido apropriadas para os compostos modelos, elas não se mostraram efetivas para o substrato real
Abstract: Cryptocaryols A-H were isolated in 2011 by Gustafson and coworkers. These compounds have notable anticancer activity because of their ability to stabilize tumor suppressor protein Pdcd4. In this work, the total synthesis of the enantiomer of cryptocaryol A was completed in 17 steps and 0.1% yield (longest linear sequence) starting from (R)-penten-2-ol. The key steps are comprised of boron-mediated aldol reactions and stereoselective reductions allowing the installation of all six stereocenters present in the molecule. In addition, we performed a Horner-Wadsworth-Emmons reaction using Ando's protocol to obtain the Z-alkene present in the a-pyrone ring. The final steps of the synthesis were low yielding; thus, we attempted to optimize the reaction conditions with model substrates. Although the optimized conditions worked well for the model compounds, they were ineffective for the actual substrate.
Mestrado
Quimica Organica
Mestra em Química
45
Polo, Ellen Christine 1985. "Síntese total da estrutura proposta para a nhatrangina A e análogos." [s.n.], 2015. http://repositorio.unicamp.br/jspui/handle/REPOSIP/248473.
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Orientador: Luiz Carlos DiasTese (doutorado) - Universidade Estadual de Campinas, Instituto de Química
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Resumo: A nhatrangina A foi isolada em 2010, por Orjala e colaboradores, a partir de uma coleção vietnamita da cianobactéria marinha Lyngbya majuscula. Este policetídeo apresenta seis centros estereogênicos e sua determinação estrutural foi realizada através da análise conjunta dos espectros de RMN 1D e 2D. O objetivo principal deste trabalho foi investigar uma rota sintética convergente e flexível para a obtenção deste produto natural e checar o assinalamento estrutural proposto pelos autores do isolamento. A estrutura proposta para a nhatrangina A foi sintetizada em 19 etapas, considerando a rota linear mais longa, e rendimento global de 6,7%. As etapas chave envolveram reação aldólica, reação de Corey-Fuchs, acoplamento entre alcino e amida de Weinreb mediado por lítio, redução estereosseltiva de Noyori e reação de esterificação de Yamaguchi. Além disso, sintetizamos seis diastereoisômeros da estrutura proposta para o produto natural, utilizando a mesma estratégia sintética empregada na síntese da estrutura proposta para a nhatrangina A, no entanto nenhum destes isômeros corresponderam ao produto natural
Abstract: The nhatrangin A was isolated in 2010 by Orjala and co-workers, from a Vietnamese collection of marine cyanobacterium Lyngbya majuscula. This polyketide containing six stereogenic centers and its structure was assigned based on spectrometric and spectroscopic methods including 1D and 2D NMR experiments. The aim of this work was to investigate the convergent and flexible synthetic route for obtaining this natural product and check the structural assignment proposed by the authors of isolation. The proposed structure of nhatrangin A was synthesized in 19 steps, considering the longest linear route, and overall yield of 6.7%. The key steps involved aldol reaction, Corey-Fuchs reaction, lithium-mediated coupling between alkyne and Weinreb amide, Noyori stereoselective reduction and Yamaguchi esterification. In addition, we synthesized six diastereoisomers of the proposed structure for the natural product, using the same synthetic strategy employed in the synthesis of the proposed structure of nhatrangin A, however none of these isomers correspond to the natural product
Doutorado
Quimica Organica
Doutora em Química
46
Ma, Bing. "Novel Cinchona Alkoloid Derived Ammonium Salts as Phase-Transfer Catalysts for the Asymmetric Synthesis of Beta-Hydroxy Alpha-Amino Acids Via Aldol Reactions and Total Synthesis of Celogentin C." BYU ScholarsArchive, 2009. https://scholarsarchive.byu.edu/etd/2195.
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Project I. Cinchona alkaloid-derived quaternary ammonium salts have been successfully used as phase-transfer catalysts, particularly in asymmetric alkylations. Our group applied this type of catalyst in the synthesis of β-hydroxy α-amino acids via aldol reactions and discovered that the Park-Jew catalyst afforded good yields and good enantiomeric excess of the syn diasteromers, but negligible diastereoselectivity. This project was therefore focused on the synthesis of novel cinchonidine-derived catalysts with the Park-Jew catalyst as the lead structure. The C3 position of cinchonidine nucleus was modified to achieve dimers and catalysts possessing electron-deficient alkyne and alkene moieties. Synthesized catalysts were tested in the asymmetric aldol reactions, with some of them yielding improvements relative to the Park-Jew catalyst.
Project II. Celogentin C is a natural product that was isolated from the seeds of Celosia argentea by Kobayashi in 2001. It is the most potent inhibitor of the polymerization of tubulin from among the celogentin family. The novel bicyclic octapeptide structure contains unusual linkages between leucine β-carbon and indole C-6 of tryptophan and between tryptophan indole C-2 and imidazole N-1 of histidine. The project culminated in the first total synthesis of celogentin C. Reaction conditions were developed by synthesizing the left-hand ring and the right-hand ring separately, and the total synthesis was accomplished via a left to right strategy. Key transformations in the construction included intermolecular Knoevenagel condensation, radical conjugate addition, macrolactamization, and oxidative coupling.
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Ferreira, Bruno Ricardo Vilachã. "Estudos visando a uma nova abordagem para a sintese total da (+)-Napalilactona, um sesquiterpeno halogenado isolado de fonte marinha." [s.n.], 2005. http://repositorio.unicamp.br/jspui/handle/REPOSIP/250228.
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Orientador: Fernando Antonio Santos CoelhoDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica
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Resumo: Napalilactona e Patilactona A são dois sesquiterpenóides espirolactônicos isolados de fontes marinhas. Esses sesquiterpenos, biogeneticamente derivados de um esqueleto carbônico do tipo aristoleno, apresentam em suas estruturas quatro centros estereogênicos contínuos e diferem apenas na substituição do heteroátomo (Cl versus OH) vizinho à unidade espiro g-butirolactônica. Como parte de um programa de pesquisa direcionado à síntese de alguns produtos naturais, descrevemos, nesse trabalho, um estudo focado no desenvolvimento de um método direto, que permitiria a preparação de um alceno funcionalizado, opticamente ativo. Esse intermediário pode ser usado para a síntese assimétrica dos dois sesquiterpenos. Devido ao elevado custo da (S)-(-)-pulegona, iniciamos esse trabalho com a (R)-(+)-pulegona, como um sistema modelo. O nosso objetivo principal era estabelecer uma estratégia sintética que mais tarde pudesse ser extrapolada para a síntese dos sesquiterpenos citados. Baseado nos dados anteriormente descritos pelo nosso laboratório para a síntese racêmica da Patilactona A, realizamos uma seqüência de reações na tentativa de se formar esse alceno funcionalizado. De acordo com a rota sintética partindo da (R)-(+)-pulegona, o intermediário seleneto foi preparado em 9 etapas com um rendimento global de 12%. Em vista do sucesso na síntese de intermediários avançados a partir da (R)-(+)-pulegona, esta mesma sequência sintética pôde ser usada na síntese assimétrica da (+)-Napalilactona, usando como material de partida a (S)-(-)-pulegona
Abstract: Napalilactone and Pathylactone A are two sesquiterpenoids spirolactones isolated from marine corals. These sesquiterpenes, biogenetically derivable from an aristolene carbon skeleton, show in their structures four contiguous stereocenters and differ only in the nature of heteroatom substituent (Cl versus OH) adjacent to the spirolactone ring junction. As part of a research program directed toward the total synthesis of some marine natural products, we describe in this work a study focused on the development of a straightforward method, which would allow the preparation of an optically active functionalized alkene. This key intermediate could be used for the asymmetric synthesis of both sesquiterpenes. Owing to the high cost of (S)-pulegone, we began this work using (R)-pulegone as a model system. Our aim was to establish a synthetic strategy that later could be surpassed for the synthesis of the sesquiterpenes cited. Based on data previously described from our laboratory for the racemic synthesis of Pathylactone-A, we carried out a sequence of reactions in an attempt to form the functionalized alkene. According to the synthetic route from (R)-(+)-pulegone, the intermediate selenide was prepared in 9 steps with overall yield of 13%. In view of the success in the synthesis of advanced intermediates from (R)-pulegone, this same synthetic sequence could be used for the asymmetric synthesis of (+)-Napalilactone, using as starting material the (S)-(-)-pulegone
Mestrado
Quimica Organica
Mestre em Química
48
Finelli, Fernanda Gadini. "Sintese da macrolactona da migrastatina e analogo : sinteses e aplicações de novos substratos em reações de RCAM catalisadas por [Mo]." [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/248483.
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Orientador: Luiz Carlos DiasTese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica
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Resumo: O capítulo 1 relata as sínteses da macrolactona da migrastatina 11 e da macrolactona análoga 62a. A macrolactona da migrastatina é o composto que apresenta a maior atividade de inibição de migração de células tumorais in vitro dentre os compostos da família da migrastatina até hoje sintetizados. A macrolactona 62a, ainda inédita na literatura, é epímero em C8 da macrolactona 62b sintetizada pelo grupo do Professor Danishefsky em 2004 e apresenta atividade de inibição semelhante à macrolactona 11. Além disso, foram realizados estudos visando à síntese da macrolactona 124, epímero da macrolactona 11. Paralelamente, em colaboração com a Farmoquímica Cristália e o grupo do Professor Adriano Andricopulo, do IF/USP de São Carlos, foram realizados testes de avaliação biológica de diversos compostos sintetizados neste trabalho com o intuito de gerar novas substâncias químicas bioativas candidatas a novos fármacos no tratamento do câncer de mama. O capítulo 2 relata a síntese e aplicação de alguns substratos contendo grupos funcionais que ainda não haviam sido testados frente à reação de metátese de alcinos utilizando um novo catalisador de molibdênio. Este projeto foi desenvolvido no laboratório do Professor Alois Fürstner, no Instituto Max-Planck, em Mülheim an der Ruhr ¿ Alemanha. Além disso, um precursor do fragmento B das Latrunculinas A e B foi sintetizado em grande escala, fornecendo material para subsequentes estudos químicos e biológicos
Abstract: Chapter 1 describes the syntheses of macrolactones 11 and 62a. Macrolactone 11 presents the best tumor cell migration inhibitory effect among the compounds of the migrastatin family synthesized so far. Macrolactone 62a, not described in the literature, is the C8-epimer of macrolactone 62b, which was synthesized by Professor Danishefsky¿s group in 2004 and shows similar antitumor activities when compared to macrolactone 11. Studies aiming at the synthesis of macrolactone 124, epimer of macrolactone 11, were also performed. Besides, in collaboration with Farmoquímica Cristália and Professor Andricopulo¿s group (IF/USP, São Carlos), biological assays of several compounds synthesized in this work were carried out, with the purpose of developing new bioactive chemical substances which may soon be employed in the manufacturing of novel drugs in the treatment of breast cancer.Chapter 2 describes the syntheses of new substrates for applications in Mo-catalyzed RCAM. This project was carried out in Professor Fürstner¿s laboratory, at Max-Planck Institute, in Mülheim an der Ruhr ¿ Germany. In this part of the work, a Latrunculin A and B fragment precursor was also synthesized in large scale to provide further material for new biological and chemical studies
Doutorado
Quimica Organica
Doutor em Ciências
49
Hiault, Florence. "Biocatalyse : aldolisation, acylation et oxydation - Applications synthétiques." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066515.
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Les travaux présentés dans ce manuscrit s’inscrivent dans le contexte général de l’essor de la biocatalyse et de son utilisation en synthèse organique. Le thème principal porte sur l’étude et le développement de différentes voies d’accès stéréosélectives à des acides alpha-aminés bêta-hydroxylés substitués. L’utilisation d’un biocatalyseur permettant d’accéder à des acides alpha-aminés bêta-hydroxylés par une aldolisation entre la glycine et divers aldéhydes, en présence de phosphate de pyridoxal, a été étudiée. Des aldéhydes aliphatiques, aromatiques et hétéroaromatiques ont pu être impliqués avec succès comme partenaires électrophiles dans ces réactions qui permettent un excellent contrôle de la configuration du carbone asymétrique créé en alpha du groupe carbonyle mais s’effectuent généralement avec des diastéréosélectivités plus modestes. Par ailleurs, un dédoublement cinétique enzymatique d’esters alpha,bêta-dihydroxylés, précurseurs d’acides alpha-aminés bêta-hydroxylés substitués en alpha, a été étudié. La méthode développée repose sur la monoacylation d’esters alpha,bêta-dihydroxylés, acycliques ou cycliques, en présence d’une lipase et d’un donneur d’acyle. De façon indépendante, la mise au point de séquences réactionnelles monotopes faisant intervenir une étape d’oxydation biocatalytique a été étudiée pour accéder à des composés aminés hautement fonctionnalisésThe research work presented in this manuscript pertains to the field of biocatalysis and some applications in organic synthesis. The main subject is the development of stereoselective synthetic methods allowing access to substituted alpha-amino beta-hydroxy acids. The use of a biocatalyst enabling the preparation of optically enriched alpha-amino beta-hydroxy acids in a single step from glycine by an aldol reaction, in the presence of pyridoxal phosphate, was investigated. Aliphatic, aromatic and heteroaromatic aldehydes could be successfully used as electrophilic partners in such reactions that allow an excellent control of the stereocenter created at the alpha position of the carbonyl group whereas moderate levels of diastereoselectivity were generally observed. The enzymatic kinetic resolution of acyclic or cyclic alpha,beta-dihydroxy esters, which are precursors of alpha-substituted alpha-amino beta-hydroxy acids, was also achieved by monoacylation in the presence of a lipase and an acyl donor. Independently, a one-pot sequence involving a biocatalytic oxidation was developed to access highly functionalized nitrogen containing compounds
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Naini, Arun [Verfasser]. "Synthesis of desepoxyisotedanolide : a proposed biosynthetic precursor of the marine polyketide tedanolide and application of Kiyooka aldol reaction to generate tertiary alcohols stereoselectively / Arun Naini." Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover (TIB), 2015. http://d-nb.info/1070283274/34.
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