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Showing 1 to 16 of 16 for “"Organokatalyse"”.
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Asymmetrische Organokatalyse zu Alpha-Fluorierung von Aldehyden und Ketonen und zur Synthese von Cyclohexencarbaldehyden via Dominoreaktionen
Chiral secondary amines play a crucial role in the fast growing field of organocatalysis. Due to their two activation modes of several carbonyl compounds, namely enamine catalysis (HOMO-raising) and iminiumion catalysis (LUMO-lowering), they are capable to catalyze a broad variety of different …
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Asymmetrische Synthese von Thiadecalinen : Organokatalytische Dominoreaktionen kombiniert mit intramolekularen Michael-Reaktionen
An efficient asymmetric synthesis of highly substituted thiadecalins using organocatalytic domino-reactions and intramolecular Michael-additions is presented. The combination of organocatalytic domino-reactions and intramolecular Michael-reactions leads to the formation of four new bonds and allows …
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Novel sulfur containing electrophiles in asymmetric organocatalysis
Three different kinds of sulfur containing electrophiles in organo- and metal catalyzed reactions have been evaluated. We demonstrated the first diastereoselective reaction of beta-keto esters with 1-chloroethylphenyl sulfide catalyzed by cinchona alkaloids. At the same time, we could confirm the …
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Synthese neuartiger Sulfonimidamide zur Anwendung in der asymmetrischen Katalyse
In the context of this research the synthesis of novel sulfonimidamides and their modification was envisaged with regard to their application in asymmetric catalysis. The first part of this work was dedicated to the synthesis of these highly oxidized sulfur compounds. Starting from sulfinic acid …
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Zur asymmetrischen Synthese von Myriocin- und Mycestericin-Analoga
Myriocin and mycestericins were first isolated from the fermentation broths of different fungal sources in 1972 and 1992, respectively. These substances are structurally related to the class of sphingoids, which are present in mammalian tissues. Owing to the structural similarity myriocin and …
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Neue Heterazoliumsalze aus Prolin und Pyroglutaminsäure und Anwendungen in Carben-katalysierten asymmetrischen nucleophilen Acylierungen
The coenzyme thiamine (vitamin B1), a natural thiazolium salt, is involved in many enzymatic catalyses in vivo. It has been proposed that the catalytically active species of these reactions is a nucleophilic carbene. Consequently, enzyme mimetic asymmetric catalytic processes that are mediated by …
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Organokatalytische Synthesen biologisch aktiver Naturstoffe : Totalsynthesen von Amaminol A und B und (+)-Mitsugashiwalacton sowie Synthesen 2,6-disubstituierter Tetrahydropyranen
Amaminol A and B are two diastereomeric 1,2-aminoalcohols of marine origin with a basic structure of a trans-fused bicyclononane. This work, for the first time, developed a complete synthesis of amaminol B, which, starting from 2E,4E-hepta-2,4-dien-1-ol and in a process of only eleven steps …
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Versuche zur asymmetrischen organokatalytischen de novo Synthese von Amino-, Desoxy- und Thiozuckern
Due to the versatile biological importance of carbohydrates, the field of asymmetric synthesis of monosaccharides is gaining more and more attention. Rare and unnatural carbohydrates, as well as those with an uncommon pattern of substitution are of particular interest. Within the framework of this …
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Bifunctional organocatalysis in the asymmetric Aza-Baylis-Hillman reaction
In this doctoral thesis, the mechanism of the Lewis base-mediated aza-Baylis-Hillman reaction was examined. Intermediates of the reaction were intercepted and structurally characterized, an extensive kinetic study was performed and the effects of Brønsted acidic co-catalysts on the reaction …
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Methoden zur asymmetrischen nucleophilen Glyoxylierung
Chiral alpha-ketoacids and their derivatives play an important role in organic synthesis and are widely used as inhibitors of both proteolytic enzymes as well as inhibitors of leukotriene A4 hydrolase. Furthermore they are an integral part of important biologically active ulosonic- and sialic …
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Entwicklung von Carben-katalysierten asymmetrischen intermolekularen Stetter-Reaktionen und direkt gekreuzter intermolekularer Benzoin-Reaktionen
A new chiral triazolium based carbene precatalyst was synthesized and successfully employed in the asymmetric intermolecular Stetter reaction. The resulting 1,4-diketones were obtained in moderate to excellent yields (49-98%) and good enantioselectivities (56-78% ee). For several Stetter products …
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Entwicklung und Erweiterung von organokatalytischen Domino-Reaktionen
An organocatalytic quadruple-cascade-reaction between Acetaldehyde and aromatic Nitrostyrenes has been developed. This reaction was conducted in a microwave oven with THF as solvent. The additive was water. With diphenylprolinol-TMS-ether as catalyst, several examples of trisubstituted …
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Neue chirale Triazoliumsalze in der Carben-katalysierten intramolekularen gekreuzten Benzoin-Reaktion
In nature many metal free catalytic reactions are accomplished in enzymes. The broad facilities of organocatalysis as a selective and environment-friendly synthetic method has only been recognized recently by chemists. This thesis deals with the synthesis of novel chiral polycylic triazolim salts …
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Entwicklung anion-chiraler ionischer Flüssigkeiten und ihre Anwendung in der Katalyse
The aim of this dissertation was the investigation of anion-chiral ionic liquids (ILs) in catalytic reactions in order to investigate a potential chirality transfer. Thus chirality has been incorporated into the anion of the molten salt. There are several examples of catalytic reactions known in …
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Chirale ionische Flüssigkeiten in der homogenen Katalyse
The aim of asymmetric synthesis is to produce enantiomerically enriched compounds, which are for example important for pharmaceutical or agrochemical commodities. Different methods can be applied to achieve this: the separation of racemic compounds, the use of chiral substrates or the application …