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Catalytic and photochemical cycloadditions of alkynes
Fadeev, Aleksandr ; Kotora, Martin (advisor) ; Pour, Milan (referee) ; Parkan, Kamil (referee)
Novel approaches to utilizing alkynes in transition metal-catalyzed [2+2+2] cycloadditions and photochemical [2+2] cycloadditions were investigated with respect to the potential applications of these transformations. First, a chemo- and regioselective fully intermolecular cocyclotrimerization of internal alkynes with a commercially available ethynyl boronate was developed using Ru-catalysis and its mechanism was examined using DFT calculations. The established method allows for a straightforward preparation of various 1,4-diborylated benzenes, which can serve as multifunctional building blocks in organic synthesis. In particular, the products can be used in cross-coupling, carbonylation and oxidation reactions to access a broad variety of contiguously substituted arenes, such as natural products mirandamycin and violaceoid C. Second, a comparative study of catalytic and uncatalyzed photocycloadditions between alkynes and quinones was undertaken. Contrary to the recent reports, irradiation with visible light alone is sufficient to obtain not only the [2+2] cycloaddition products, but also several products of cascade transformations. Thus, depending on the structure of the quinone used, either carbo- or heterocycloaddition pathway is mainly realized, giving rise either to annulated cyclobutenes or...
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Development of New Syntheses of Azaaromatic Compounds with Extended π-System
Ulč, Jan ; Kotora, Martin (advisor) ; Hrdina, Radim (referee) ; Tobrman, Tomáš (referee)
Azapolyaromatic compound are a class of heterocyclic compounds, which contains at least one nitrogen atom. A subclass of these compounds are quinolizinium salts, which contains nitrogen atom in bridgehead position. These salts usually have interesting photophysical properties. Naphthoquinolizinium salts are a group of quinolizinium salts, but their synthesis as well as their photophysical properties haven't been studied in detail yet. This work is about development of a new modular method for preparation of naphthoquinoliziniu salts. This method is based on catalytic C-C and C-H bond activations by transition metal catalysts. 1-Azabiphenylene was used as a starting material, which reacted in catalytic C-C bond cleavage followed by insertion of various alkyne to form benzo[h]quinolines. These benzo[h]quinolines then reacted in catalytic C-H bond activation reaction followed by insertion of another alkyne to form final tetrasubstituted naphthoquinolizinium salts. Photophysical properties of the prepared salts was studied. The developed method was used on a more complex starting material such as linear 1- 1-aza-[3]triphenylene, which was converted to phenanthroquinolines and eventually to the corresponding azonia salts. Key words: azapolyaromatic compounds, catalysis by transition metal complexes, C-C...
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Cycloaddition of 3-(deoxyribos-1-yl)propynoate with alkynes
Kulhavá, Lucie ; Kotora, Martin (advisor) ; Machara, Aleš (referee)
The object of this work is development of method for a syntesis of Dewar benzenes bearing the deoxyriboside group. The synthesis was based on ethynylation of halogenose resulting in the formation of a mixture of anomeric ethynyldeoxiriboses, which was followed by silylation and separation of individiual anomers. After removal of the silyl group the isomerically pure ethynyldeoxyriboses were transformed into corresponding propynoates that were the key substance for the formation od Dewar benzenes. The reaction of the propynoates with the tetramethylcyclobutadiene-aluminium trichloride complex provided the desired Dewar benzenes bearing the deoxyribose group. Finally, rearrangement of the formed Dewar benzenes to 1-aryldeoxyriboses was studied under thermal and photochemical conditions. Keywords: cycloaddition, arenes, Dewar benzene
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Azidoperfluoroalkanes: Synthesis and Application
Blastik, Zsófia Eszter ; Beier, Petr (advisor) ; Církva, Vladimír (referee) ; Kvíčala, Jaroslav (referee)
The incorporation of the trifluoromethyl and perfluoroalkyl motifs into organic compounds has been a hot topic in synthetic organofluorine chemistry. There is a plethora of methods for the introduction of the CF3 moiety at carbon, oxygen and sulfur centers. In sharp contrast, methods for synthesizing N-trifluoromethyl and N-perfluoroalkyl compounds are very limited and new approaches are highly sought-after. The scarcity of these compounds prompted us to develop reagents capable of transferring the perfluoroalkyl unit to nitrogen atom. To fulfil this purpose, we have regarded azidoperfluoroalkanes as ideal reagents, therefore, this thesis is concerned with the synthesis and applications of these azides. The first part describes the preparation of azidoperfluoroalkanes. Upon activation by cesium fluoride, TMSCF3 transfers the trifluoromethyl group to an electrophilic azide to produce the desired azidotrifluoromethane. Longer carbon chain azidoperfluoroalkanes were prepared in a similar way, starting from the corresponding organosilane. A different synthetic strategy was applied for the preparation of azidopentafluoroethane where the perfluoroalkyl anion was generated from pentafluoroethane with n BuLi, followed by the addition of tosyl azide. The isolation of these fluorinated azides was...
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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
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Cycloaddition of 3-(deoxyribos-1-yl)propynoate with alkynes
Kulhavá, Lucie ; Kotora, Martin (advisor) ; Machara, Aleš (referee)
The object of this work is development of method for a syntesis of Dewar benzenes bearing the deoxyriboside group. The synthesis was based on ethynylation of halogenose resulting in the formation of a mixture of anomeric ethynyldeoxiriboses, which was followed by silylation and separation of individiual anomers. After removal of the silyl group the isomerically pure ethynyldeoxyriboses were transformed into corresponding propynoates that were the key substance for the formation od Dewar benzenes. The reaction of the propynoates with the tetramethylcyclobutadiene-aluminium trichloride complex provided the desired Dewar benzenes bearing the deoxyribose group. Finally, rearrangement of the formed Dewar benzenes to 1-aryldeoxyriboses was studied under thermal and photochemical conditions. Keywords: cycloaddition, arenes, Dewar benzene
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