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Synthesis of helical aromatics for applications in enantioselective catalysis and nanoscience
Klívar, Jiří ; Stará, Irena (advisor) ; Hrdina, Radim (referee) ; Církva, Vladimír (referee)
The aim of this work was to explore the scope and limitations of [2+2+2] co- cyclotrimerization of cyanodiynes in the preparation of conformationally stable and optionally optically pure azahelicenes, helically chiral bipyridines and helicenes laterally extended by a pyridine unit. As a key reaction for the construction of a helical skeleton, crucial [2+2+2] (co-)cyclotrimerization mediated by various transition metal complexes was chosen for the preparation of racemic azahelicenes. Oligoynes as key intermediates were prepared by a sequence of Sonogashira and Suzuki-Miyaura coupling. For optically pure azahelicenes and bispyridohelicenes, a sequence of Sonogashira and Suzuki-Miyaura coupling and Mitsunobu reaction was used. Importantly, the Mitsunobu reaction was used for its extraordinary ability to transfer chirality from the starting chiral alcohol to the early helicene precursor without configurational scrambling. It is worth noting that optical purity of the key oligoynes have crucial role in the chirality transfer to final azahelicenes or bispyridohelicenes. An in situ generated Ni(0) catalyst was used for bispyridohelicenes with a connection in the 2,2'-position, which enabled both [2+2+2] cyclotrimerization and Ullmann-type coupling. The conformationally stable racemic aza[6]- and...
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The synthesis of azahelicenes and the study of their properties
Klívar, Jiří ; Starý, Ivo (advisor) ; Číhalová, Sylva (referee)
The objective of this Thesis was to find out whether it is possible to use [2+2+2] cyclotrimerization of aromatic nitriles for the synthesis of azahelicenes. This work deals with the preparation of tetrahydro-7-aza[5]helicene 76, 7-aza[5]helicene 23 and 7,8-diaza[5]helicene 77. The Theoretical Introduction mainly outlines the key methods for preparation of helicenes and azahelicenes, it also deals with the mechanism of [2+2+2] cyclotrimerization and the most common catalysts for this transformation are discussed. In the Results and Discussion and Experimental Part the synthesis of tetrahydro-7-aza[5]helicene 76, 7-aza[5]helicene 23 and 7,8-diaza[5]helicene 77 from the corresponding triynes is discussed.
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Cyclotrimerization of alkynes and nitriles in the synthesis of helically chiral compounds
Klívar, Jiří ; Stará, Irena (advisor) ; Tobrman, Tomáš (referee)
The objective of this Thesis was to prepare dialkynenitriles 156 and 168 for the synthesis of aza[6]helicene 146 and 147 via intramolecular [2+2+2] co-cyclotrimerization. It was found that it is possible to use co-cycloisomerization of alkynedinitriles 182, 187, 192 and 195, a reaction so far not described in the literature, for the preparation of dibenzodiazahelicenes 148 and 149 and dioxadiazahelicenes 150 and 151 possessing a pyridazine subunit. Moreover, alkynedinitriles 152, 153, 154 and 155 were synthesized to further study of this co-cycloisomerization reaction. The Theoretical Part outlines some representative examples of methods for the preparation of azahelicenes and azoniumhelicenes, current development of [2+2+2] cocyclotrimerization in the synthesis of pyridine derivatives and methods of pyridazine synthesis. The syntheses of dialkynenitriles 156 a 168, diazahelicenes 148, 149, 150, 151 and alkynedinitriles 152, 153, 154 and 155 are described in the section Results and Discussion and Experimental Part.
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The synthesis of azahelicenes and the study of their properties
Klívar, Jiří ; Starý, Ivo (advisor) ; Číhalová, Sylva (referee)
The objective of this Thesis was to find out whether it is possible to use [2+2+2] cyclotrimerization of aromatic nitriles for the synthesis of azahelicenes. This work deals with the preparation of tetrahydro-7-aza[5]helicene 76, 7-aza[5]helicene 23 and 7,8-diaza[5]helicene 77. The Theoretical Introduction mainly outlines the key methods for preparation of helicenes and azahelicenes, it also deals with the mechanism of [2+2+2] cyclotrimerization and the most common catalysts for this transformation are discussed. In the Results and Discussion and Experimental Part the synthesis of tetrahydro-7-aza[5]helicene 76, 7-aza[5]helicene 23 and 7,8-diaza[5]helicene 77 from the corresponding triynes is discussed.
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Investigation of acid-based properties of mono- and diaza[5]helicenes by non-aqueous capillary electrophoresis and quantum chemical calculations
Šolínová, Veronika ; Štěpánová, Sille ; Jančařík, Andrej ; Klívar, Jiří ; Šámal, Michal ; Stará, Irena G. ; Vacek Chocholoušová, Jana ; Vacek, Jaroslav ; Starý, Ivo ; Kašička, Václav
Non-aqueous capillary electrophoresis (NACE) using methanol (MeOH) as a solvent of the background electrolytes was used to determine the thermodynamic acidity (ionization) constants (pKa) of a series of monoaza[5]helicenes and diaza[5]helicenes protonated to the first degree in MeOH and water. Depending on the number and position of the nitrogen atoms in their molecules, the analyzed aza[5]helicenes were found to be weak to moderate bases with methanolic pKa,MeOH in the range 3.90-8.75 and with aqueous pKa,H2O in the range 3.53-8.28.
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