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Catalytic Enantioselective Desymmetrization of meso-Epoxides
Malatinec, Štefan ; Kotora, Martin (advisor) ; Baszczyňski, Ondřej (referee)
Catalytic enantioselective desymmetrization of meso-epoxides is widely used in many areas of chemistry. Such process is usually catalyzed by a transition metal complex with a chiral ligand. Recently, a synthesis of an analogue of Bolm's 2,2'-bipyridine ligand was developed and its combination with metal salts were tested in various reactions. In this master's thesis, a catalytic system composed of Sc(OTf)3/Bolm's ligand analogue was studied in alcoholysis and aminolysis of the meso- epoxides. The reaction has been extended to a broad range of alcohols providing 1,2-diol monoethers in excellent enantioselectivity up to 99% ee. The aminolysis of meso-epoxides has been optimized, as well. The catalyst loading could be lowered to 1 mol% with only marginal effects on the enantioselectivity. Key words: epoxides, enantioselective catalysis, chiral ligands.
Catalytic annulation reactions of N-heterocycles with alkynes
Hrubý, Samuel ; Kotora, Martin (advisor) ; Matoušová, Eliška (referee)
The aim of the bachelor thesis was to use C-C and C-H bond cleavage for the synthesis of cationic N-heterocycle compounds. Within the thesis was the aim to study various catalytic systems, reactions considering structural variations of reactants along with the effect of structure of reactants on their reactivity. The synthesis consists of rhodium-catalysed C-C bond cleavage in biphenylene followed C-H activation. Key words: C-C bond activation, C-H bond activation, heterocycles, catalysis
Synthesis of azaindenofluorenes
Zelina, Ondřej ; Kotora, Martin (advisor) ; Rýček, Lukáš (referee)
Azafluorene derivates are naturally occurring compounds that possess multiple types of biological activity with the potential of being used as pharmaceuticals. Azaindenofluorenes are studied as potential candidates to be used as organic light-emitting diodes because of their photophysical properties. In this work, compounds belonging to these groups were synthesized using cyclotrimerization. Keywords: cyclotrimerization, catalysis, azafluorene, azafluorenone, azaindenofluorene, azaindenofluorenone, natural compound, OLED
Synthesis of selaginpulvilins
Beytlerová, Nela ; Kotora, Martin (advisor) ; Hájíček, Josef (referee)
This bachelor thesis is focused on the application of [2+2+2] cyclotrimerization in the total synthesis of natural fluorene derivate, selaginpulvilin D, which was isolated from the plant Selaginella pulvinata. The plant is used in the traditional Chinese medicine for treatment of asthma and traumatic injuries. The study is focused on development of the catalytic cyclotrimerization reaction that is used to prepare the key intermediate. The integral part of the project is a study how various catalysts and catalytic systems, solvents and reaction temperatures affect the course of the reaction. Synthesis of the suitable cyclotrimerization precursor was achieved from benzaldehyde and the formal synthesis of selaginpulvilin D was completed by conversion of cyclotrimerization product to the known intermediate of the selaginpulvilin D synthesis. Key words: [2+2+2] cyclotrimerization, selaginpulvilin D, natural compound, fluorene core
Application of enantioselective allylation for synthesis of compounds isolated from Streptomyces gramineus
Morávková, Terézia ; Kotora, Martin (advisor) ; Matoušová, Eliška (referee)
E-492, actinofuranone A, and JBIR-108 are natural compounds isolated from actinobacteria Streptomyces genus and can lead to the development of new pharmaceuticals as they have some biological interesting activities. Although the synthesis of these actinofuranones has been already published, this work brings new methods for the preparation of their fragments. The key step of the synthesis is enantioselective crotylboration of an aldehyde catalyzed by a chiral Brønsted acid and by which two centres of chirality are introduced in one step. The other crucial steps of the synthesis are composed of Ru-catalyzed alkene-alkene cross-metathesis and Pd- catalyzed Suzuki cross-coupling. Keywords: natural compound, enantioselective syntheses, crotylation, catalysis, actinofuranone fragment
Catalytic Cycloaddition Reactions of Tribenzocyclyne
Jacko, Jaroslav ; Kotora, Martin (advisor) ; Schulz, Jiří (referee)
The main aim of the bachelor thesis was to investigate the reactivity of tribenzocyclyne, a triangular molecule, undergoing reactions with antiaromatic biphenylenes and their heteroanalogues. Those reactions consist of C-C activations of strained bond mediated by the complexes of the group 9 elements, followed by migratory insertion of present alkyne which leads to the formation of a substituted aromatic ring. Presented method facilitated the setting of a experiment as well as cutting down on reaction steps. These investigations will subsequently serve for further progress in the chemistry of cyclic hexa- ortho-phenylenes. Key words: catalysis, cycloaddition, tribenzocyclyne, the C-C bond cleavage
Preparation of catalysts derived from cyclopentadiene and their use in organic synthesis
Reiberger, Róbert ; Veselý, Jan (advisor) ; Kotora, Martin (referee)
Chiral acidic catalysts are extremely useful for the synthesis of enantioenriched small molecules, however, these catalysts require challenging preparation. This work is focused on the preparation of readily affordable chiral Brønsted acid catalysts containing of 1,2,3,4,5-pentamethylcarboxycyclopentadiene (PCCP) or carboxytetracyanocyclopentadiene (CTCCP) scaffolds. Aromatic stabilization of conjugated PCCP or CTCCP anion is key factor of potent acidity of these compounds. A set of catalyst was prepared via transesterification or amidation of PCCP or via alkylation/desulfurylation reaction of tetracyanodithiine with chiral tosylacetates. Effectiveness of these catalysts has been shown on direct aminalization of aldehydes leading to a stereoselective formation of tetrahydroquinazolinones in excellent yields, even 99 % and with enantioselectivity of reaction up to 84 % e.e. Key words Organocatalysis, Brønsted acids, cyclopentadiene, PCCP, CTCCP, aminalization, aminals, tetrahydroquinazolinones, asymmetic synthesis.
Synthesis and application of new bipyridine ligands
Bednářová, Eva ; Kotora, Martin (advisor) ; Cibulka, Radek (referee) ; Michelet, Véronique (referee)
2,2'-Bipyridines and their appropriate N,N'-dioxides form a significant class of heteroaromatic compounds, which has found application in various fields of chemistry and predominantly in asymmetric catalysis. One of the most powerful methods for their synthesis is cocyclotrimerization of alkynes with nitriles. A new variant of cyclotrimerization reaction - cocyclotrimerization of halodiynes with nitriles, which results in the formation of 2- and 3-halopyridines, has been developed. The reaction was studied on a wide range of substrates providing the pyridine products in good isolated yields. Formation of an unexpected product of halogen exchange reaction was observed during the course of the study and its origin was elucidated by experimental studies. The prepared 2-halopyridines were used as starting materials for syntheses of new chiral 2,2'-bipyridine ligands. The crucial step of their synthesis turned out to be the reductive dimerization of 2-halopyridines to the corresponding 2,2'-bipyridines. Application of the formed bipyridine ligands was then tested in various metal-catalyzed asymmetric reactions, namely Mukaiyama aldol reaction, hydroxymethylation, conjugate addition, C-H activation of indole and desymmetrization of meso-epoxides, in which one of the bipyridine ligands showed...
Application of a Bolm ligand analog in catalysis
Malatinec, Štefan ; Kotora, Martin (advisor) ; Matoušová, Eliška (referee)
Bolm`s ligand belongs to the group of 2,2'-bipyridines, which represents a class of C2 symmetric ligands. These ligands form complexes with Lewis acids, which could be used in asymmetric catalysis, for example in the ring-opening of epoxides. Bolm`s ligand analogue was prepared and the enantioselectivity of the ring-opening reaction of cis-stilben oxide with aniline and variety of substituted benzyl alcohols catalyzed by scandium(III) triflate was studied as a part of this bachelor thesis. The enantioselectivity of the reaction using Bolm's ligand analogue was compared to that of Bolm`s ligand. Key words: synthesis, catalysis, bipyridines
Enantioselective allylation of dienals and their application in tiacumicin synthesis
Koukal, Petr ; Kotora, Martin (advisor) ; Cibulka, Radek (referee) ; Pour, Milan (referee)
The current methodologies of catalytic enantioselective allylation of aldehydes were studied on conjugated dienals and later on haloacrylaldehydes as the substrates. The resulting enantioenriched homoallylalcohols were prepared by reactions promoted either by commercial Brønsted acid catalysts or by Lewis base catalysts developed by our group, often with high enantio- and diastereoselectivities. Subsequently, the methodology was expanded on catalytic enantioselective crotylation and pentenylation reactions, practically unknown not only with these substrates. The applicability of this synthetic approach was demonstrated on preparation of several natural products or their intermediates.

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