@article{KarrasDabrowskiPohletal.2018, author = {Karras, Manfred and Dabrowski, Michal and Pohl, Radek and Rybacek, Jiri and Vacek, Jaroslav and Bednarova, Lucie and Grela, Karol and Stary, Ivo and Stara, Irena G. and Schmidt, Bernd}, title = {Helicenes as Chirality-Inducing Groups in Transition-Metal Catalysis}, series = {Chemistry - a European journal}, volume = {24}, journal = {Chemistry - a European journal}, number = {43}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {0947-6539}, doi = {10.1002/chem.201802786}, pages = {10994 -- 10998}, year = {2018}, abstract = {Helical chirality is a novel enantioselectivity-inducing property in transition-metal-catalyzed transformations. The principle is illustrated herein for the example of asymmetric olefin metathesis. This work reports the synthesis of the first helically chiral Ru-NHC alkylidene complex from an aminohelicene-derived imidazolium salt, which was ligated to the first generation Hoveyda-Grubbs catalyst. Kinetic data were acquired for benchmark test reactions and compared to an achiral catalyst. The helically chiral Ru-catalyst was evaluated in asymmetric ring-closing metathesis (RCM) and ring-opening metathesis-cross-metathesis (ROM/CM) reactions, which proceeded with promising levels of enantioselectivity. Extensive NMR-spectroscopic investigations and a DFT geometry optimization were performed. These results led to a topographic steric map and calculation of percent-buried-volume values for each quadrant around the metal center.}, language = {en} } @article{HolecRybačekVaceketal.2019, author = {Holec, Jan and Ryb{\´a}ček, Jiř{\´i} and Vacek, Jaroslav and Karras, Manfred and Bedn{\´a}rov{\´a}, Lucie and Budesinsky, Milos and Slusna, Michaela and Holy, Petr and Schmidt, Bernd and Star{\´a}, Irena G. and Star{\´y}, Ivo}, title = {Chirality-Controlled Self-Assembly of Amphiphilic Dibenzo[6]helicenes into Langmuir-Blodgett Thin Films}, series = {Chemistry - a European journal}, volume = {25}, journal = {Chemistry - a European journal}, number = {49}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {0947-6539}, doi = {10.1002/chem.201901695}, pages = {11494 -- 11502}, year = {2019}, abstract = {Racemic and highly enantioenriched 3-methoxycarbonyl, 3-carboxy, and 3-hydroxymethyl derivatives of dibenzo[6]helicene were prepared. The Langmuir layers of these helicenes were formed at the air-water interface and transferred onto solid substrates to afford Langmuir-Blodgett films, which were then studied by ambient atomic force microscopy and (chir)optical spectroscopy. Significant differences were found in the behaviour of the Langmuir layers as well as in the morphology, UV/Vis, electronic circular dichroism (ECD), and fluorescence spectra of the Langmuir-Blodgett thin films depending on the molecular chirality and nature of the polar group. The experimental results were supported by molecular dynamics simulations.}, language = {en} }