Asymmetric Synthesis of Nonracemic 2-Amino[6]helicenes and Their Self-Assembly into Langmuir Films

0490755 - ÚOCHB 2019 RIV US eng J - Journal Article
Karras, Manfred - Holec, Jan - Bednárová, Lucie - Pohl, Radek - Schmidt, B. - Stará, Irena G. - Starý, Ivo
Asymmetric Synthesis of Nonracemic 2-Amino[6]helicenes and Their Self-Assembly into Langmuir Films.
Journal of Organic Chemistry. Roč. 83, č. 10 (2018), s. 5523-5538. ISSN 0022-3263. E-ISSN 1520-6904
R&D Projects: GA ČR(CZ) GA16-08294S
Institutional support: RVO:61388963
Keywords : aminohelicene * asymmetric synthesis * self-assembly
OECD category: Organic chemistry
Impact factor: 4.745, year: 2018

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.
Permanent Link: http://hdl.handle.net/11104/0284905