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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.
Plný tet: 20120415230504 -  PDF
Plný text: content.csg - PDF
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LC-NMR Analysis of Phenylsilane Polymers
Pinkas, Jiří ; Merna, J. ; Sýkora, Jan
We report the analysis of dehydrocoupling polymerization reactions of phenylsilane via on-flow LC-NMR experiment. The successful separation was achieved by isocratic elution of acetonitrile and aceton (80:20). The separation was solely monitored by 1H NMR detection. The properties of the polymeric product depend on the catalytical system. The products can differ in the molar weight distribution, degree of branching and amount of cyclic and rearranged products. In our particular cases, the weight average molar mass (Mw) varies from several silane units up to 4100 g.mol-1. The branching of polysilanes is monitored by 29Si{1H} INEPT experiment with the polarization transfer from the ortho hydrogen (J~7 Hz). The connectivity within branched unit was established via 1H à 29Si-29Si INEPT-INADEQUATE experiment.
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