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Synthesis and Characterization of Helicene-Based Imidazolium Salt
Žádný, Jaroslav ; Vacek, J. ; Večerková, R. ; Kubala, M. ; Sýkora, Jan ; Církva, Vladimír ; Storch, Jan
Helicenes are functional molecules with broad spectrum of applications in physical and (bio)chemical research and development. Today, we are focused on synthetic approaches for preparation of helicene derivatives and conjugates leading to novel compounds with unique properties. A helicene-based imidazolium salt was synthesized starting from 2-methyl[6]helicene which undergoes radical bromination providing 2-(bromomethyl)[6]helicene. The subsequent treatment with 1-butylimidazole leads to corresponding bromide salt. The product prepared was consequently fully characterized from chemico-physical point of view using NMR and X-ray analysis, various spectrometric approaches, especially fluorescence spectroscopy, and electrochemical tools as chronopotentiometry and voltammetry. Here we present the first evidence of ionic fluid (molten salt) based on helicene substitution.
Fulltext: content.csg -  PDF
Plný tet: 20140210184348 - PDF
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Exploration of 9-Bromo[7]helicene Reactivity
Žádný, Jaroslav ; Jakubec, Martin ; Velíšek, Petr ; Sýkora, Jan ; Storch, Jan
Our new microwave assisted photodehydrocyclisation and completely reviewed synthetic approach for a multi-gram scale production of 9-bromo-[7]helicene led us to explore the reactivity of this compound mainly in Pd-catalysed reactions and to the further functionalization of this molecule. Next to other transformations, palladium catalysed carbon – heteroatom coupling reactions provide a large portfolio of racemic helicenes bearing different functional groups in good to excellent yields. Many of the reactions are performed in the microwave initiator saving reaction time to a minimum comparing with conventional and known synthetic methods. Such prepared compounds can undergo further synthetic reactions or can be used on a field of molecular electronics, surface chemistry or in other applications. The separation of racemic mixtures is under running in our lab. Optically pure compounds of such a type can open new possibilities in their use.
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Design and Synthesis of Helicene like Molecules
Bernard, Martin ; Sýkora, Jan ; Storch, Jan
Azahelicenes are unique inherently chiral three-dimensional aromatic compounds with high potential in homogenous assymetric catalysis. Their synthesis has many drawbacks and cannot be done in multigram scale so far. Recently, we have developed a route to new type of helicene-like molecules II. Multigram-scale synthesis of model compound where two benzene rings in [6]helicene skeleton are replaced by cyclopentadiene rings was accomplished in three steps. Such molecules have helical structure similar to helicenes, however, lower racemization barrier. Appropriately modified aza-analogues could be suitable catalysts for asymmetric reactions. Therefore, our synthetic approach leading to these compounds will be discussed.
Fulltext: content.csg - PDF
Plný tet: 20120415230504 - PDF
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