Internal-Edge-Substituted Coumarin-Fused [6]Helicenes: Asymmetric Synthesis, Structural Features, and Control of Self-Assembly.

Research paper by Kazuteru K Usui, Kosuke K Yamamoto, Yuhei Y Ueno, Kazunobu K Igawa, Ryusuke R Hagihara, Toshinobu T Masuda, Akio A Ojida, Satoru S Karasawa, Katsuhiko K Tomooka, Go G Hirai, Hiroshi H Suemune

Indexed on: 01 Aug '18Published on: 01 Aug '18Published in: Chemistry - A European Journal


π-Conjugated helicenes containing heteroatoms have attracted significant attention due to their diverse chemical and electronic structures, as well as tunable physical properties. We rationally anticipated that the self-assembly of coumarin-fused helicenes would be controlled by the effects of a substituent on the internal edge of the helix. Here, we report the efficient syntheses of coumarin-fused helicenes 1a,b (R = Ph, Me), and the enantioselective synthesis of 1a (R = Ph) by chiral Au(I)-catalyzed hydroarylation. The helical structure of 1 was unambiguously determined by X-ray crystallography. Of particular note, the enantiomerically pure crystal of 1a adopted a one-dimensional columnar structure based on π-π stacking interactions, as expected. Furthermore, a significant difference between the fluorescence quantum yields of the enantiomerically pure form and racemate of 1a was observed. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.