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Application of amines for the preparation of chiral cyclic compounds
Formánek, Bedřich ; Veselý, Jan (advisor) ; Kočovský, Pavel (referee) ; Soural, Miroslav (referee)
Organocatalysis, along with catalysis by metal complexes or enzymes, has become one of the very useful tools of asymmetric synthesis. Different activation modes or their combinations into sequences (domino reactions) enable effective access to enantiomerically enriched complex substances. The objective of this work was the preparation of chiral molecules from simple precursors activated by amine-based organocatalysts. In particular, we were focused on a study of asymmetric allyl substitution of Morita-Baylis-Hillman carbonates and two-component domino reactions on sulfur-containing heterocycles. The thesis deals with the organocatalytic allyl amination of Morita-Baylis-Hillman carbonates with aromatic amines catalyzed by β-isocupreidine. The corresponding allylic amines were obtained in high yields (90-96%) with moderate enantiomeric excess. It was possible to get substances of high optical purity (ee 82-99%) by recrystallization of selected products. Furthermore, the developed method was applied in the preparation of enantiomerically enriched β-lactams, which represent valuable precursors, for example, in the synthesis of the drug Ezetimibe. The second part of the work is focused on stereoselective cyclization reactions comprising selected sulfur heterocycles. Although the cyclization reaction of...
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N-heterocyclic carbene catalysis in enantioselective cycloadditions
Krejčířová, Kateřina ; Veselý, Jan (advisor) ; Baszczyňski, Ondřej (referee)
This diploma thesis deals with selected enantioselective cycloaddition reactions catalyzed by N-heterocyclic carbenes. First, we focused on studying the [4+3] cycloaddition reaction. Non-commercial ketimines were prepared as starting materials for the model reaction. Subsequently, the reaction between ketimines and salicylaldehyde was studied, where, despite all efforts, preparing the desired product was impossible. Furthermore, the [3+3] cyclization reaction was studied. Aminopyrazole and substituted α-bromenals were prepared for these purposes. However, while optimizing this reaction, the same concept was published. Finally, our attention was focused on the [3+2] cycloaddition reaction between α-bromenals and hydrazides derived from oxalic acid esters. Here, the reaction conditions were optimized, and the substrate scope was subsequently studied.
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Preparation of chiral amides and their use as organocatalysts
Brandejsová, Aneta ; Veselý, Jan (advisor) ; Hrdina, Radim (referee)
This bachelor thesis is focused on preparation of C-9 amino derivatives of Cinchona alkaloids and derived bifunctional squaramide catalysts, which are used as organocatalysts in a wide variety of chemical transformations leading to enantiomerically pure compounds. The first part deals with choosing the most efficient method for the preparation of C-9 amino derivates of Cinchona alkaloids and the synthesis of four selected examples. In the second part, the prepared derivates are used for the synthesis of bifunctional squaramide catalysts, which are further tested in newly designed cyclization reactions.
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The synthesis of π-electron systems suitable for transfer and retention of charges
Nejedlý, Jindřich ; Starý, Ivo (advisor) ; Tobrman, Tomáš (referee) ; Storch, Jan (referee)
The aim of my Thesis was to develop a general synthetic methodology for the preparation of long helicenes equipped with suitable functional groups that control their solubility or serve as anchoring groups for attachment to metallic surfaces, especially gold. The well-established transition metal catalyzed [2+2+2] cyclotrimerization of triynes was selected as the key scaffold-forming transformation in the synthesis of long helicenes because of its high regioselectivity, atom efficiency, functional group tolerance and general robustness. A modular approach was used for the preparation of the starting oligoynes, thus enabling a high level of their structural diversity. Individual resorcinol- based aromatic building blocks were interconnected by Sonogashira cross-coupling reactions, providing complex cyclization precursors encompassing up to twelve alkyne units pre-arranged for the multiple [2+2+2] cycloisomerization to produce three six- membered rings from each set of three neighboring alkyne units. Thus, a small series of long helicenes with up to 19 rings constituting the helical scaffold was synthesized. The quadruple cyclization leading to the longest oxahelicene prepared to date was performed in a high-temperature-high-pressure flow reactor at 250 řC in the presence of CpCo(CO)2. The set of...
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Organocatalytic asymmetric synthesis of various organic compounds from α,β-unsaturated aledyhes
Kamlar, Martin ; Veselý, Jan (advisor) ; Trnka, Tomáš (referee)
With regard to a fast development in the field of fluoroorganic chemisty, the intention of this diploma thesis is focused to utilize of organocatalysis by secondary amines as catalysts for preparation enantiomerically pure compounds containing fluorine atom in its structure. The preparation of these subsances is realized by way of nucleofilic addition to α,β- unsaturated aldehydes using suitable fluorine containing nuclephilic agent 1-(fluoronitromethylsulphonyl)benzene, to get appropriate 1,4-adduct.
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Organocatalytic reactions leading to functionalized cyclic compounds
Formánek, Bedřich ; Veselý, Jan (advisor) ; Jindřich, Jindřich (referee)
First part is focused on finding suitable reaction conditions for organocatalytic domino Michael/Michael reaction of ethyl (E)-3-(2-thiophenyl)acrylate with α,β-unsaturated aldehydes. Second part deals with the preparation of pyrazolone derivatives from commercially available compounds and describes effects of various substituents in α-position on chemical efficiency and stereoselectivity of amination with azodicarboxylate catalyzed by quinine.
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The use of BH carbonates in organocatalytic transformations
Tichá, Iveta ; Veselý, Jan (advisor) ; Jindřich, Jindřich (referee)
This diploma thesis is focused on the preparation of enantiomerically pure compounds based on organocatalytic allylic substitution using Baylis-Hillman carbonates. As selected substrates for the allylic substitution were chosen α-azidoketones such as azidoacetophenone, 2-azido-1-indanone and then heterocyclic compounds (N-phenylrhodanine and its derivate) belonging to the pharmaceutical privileged compounds. Other substrate for allylic substitution was allylmalononitrile. In addition, this thesis includes with synthesis of cyclic compounds based on the reaction of products of allylmalononitrile with B-H carbonates using olefin metathesis.
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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...
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Preparation of enantiomerically pure cyclic compounds via organocatalytic concept
Remeš, Marek
Since 2000 the organocatalytic synthesis has developed massively in a third pillar of asymmetric synthesis standing next to catalysis with metal complexes and enzymatic catalysis. Organocatalysts, due to their various activation modes which could be combined in domino reactions, offer a way for a synthesis of complex molecules from a simple starting material. This thesis deals with investigation of usage of chiral secondary amines as catalysts for asymmetric synthesis of cyclic compounds. The main part of research was devoted to development of organocatalytic method leading to synthesis of enantiomerically pure cyclopentanecarbaldehydes and nitrocyclopentanecarbaldehydes. We focused also on the organocatalytic preparation of cyclohexanecarbaldehydes. During this work we developed an asymmetric domino Michael addition/α- substitution reaction of 2-(2-bromoethyl)malonates resp. 1-bromo-3-nitropropane with various enals catalyzed by chiral secondary amine. In the first case cyclopentanecarbaldehydes were formed where two chiral centres were created. In second case nitrocyclopentanecarbaldehydes were formed where three chiral centres were created. Yields of such developed reaction protocol reach up to 74 % and the reaction proceeds with excellent diastereo- and enantioselectivity (up to 19:1 d.r. and...
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