TY  - JOUR
A1  - Karras, Manfred
A1  - Holec, Jan
A1  - Bednarova, Lucie
A1  - Pohl, Radek
A1  - Schmidt, Bernd
A1  - Stara, Irena G.
A1  - Stary, Ivo
T1  - Asymmetric Synthesis of Nonracemic 2-Amino[6]helicenes and Their Self-Assembly into Langmuir Films
T2  - The journal of organic chemistry
N2  - 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.
Y1  - 2018
UR  - https://publishup.uni-potsdam.de/frontdoor/index/index/docId/52886
SN  - 0022-3263
SN  - 1520-6904
VL  - 83
IS  - 10
SP  - 5523
EP  - 5538
PB  - American Chemical Society
CY  - Washington
ER  -