@article{KarrasHolecBednarovaetal.2018,
  author    = {Karras, Manfred and Holec, Jan and Bednarova, Lucie and Pohl, Radek and Schmidt, Bernd and Stara, Irena G. and Stary, Ivo},
  title     = {Asymmetric Synthesis of Nonracemic 2-Amino[6]helicenes and Their Self-Assembly into Langmuir Films},
  series = {The journal of organic chemistry},
  volume    = {83},
  journal   = {The journal of organic chemistry},
  number    = {10},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {0022-3263},
  doi       = {10.1021/acs.joc.8b00538},
  pages     = {5523 -- 5538},
  year      = {2018},
  abstract  = {Alternative ways of preparing nonracemic 2-amino[6]helicene derivatives were explored. The enantioselective [2 + 2 + 2] cycloisomerization of a nonchiral triyne under Ni(cod)(2)/(R)-QUINAP catalysis delivered the enantioenriched (+)-(P)-2-aminodibenzo[6]helicene derivative in 67\% ee. An ultimate "point-to-helical" chirality transfer was observed in the cyclization of enantiopure triynes mediated by Ni(CO)(2)(PPh3)(2) affording (-)-(M)- or (+)-(P)-7,8-bis(p-tolyl)hexahelicen-2-amine in >99\% ee as well as its benzoderivative in >99\% ee. The latter mode of stereocontrol was inefficient for a 2-aminobenzo[6]helicene congener with an embedded five-membered ring. The rac-, (-)-(M)-, and (+)-(P)-7,8-bis(p-tolyl)hexahelicen-2-amines formed Langmuir monolayers at the air water interface featuring practically identical surface pressure vs mean molecular area isotherms. The corresponding Langmuir-Blodgett films on quartz or silicon substrates were characterized by UV vis/ECD spectroscopy and AFM microscopy, respectively.},
  language  = {en}
}
@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}
}