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Facile Synthesis and Chiral Resolution of Expanded Helicenes with up to 35 cata-Fused Benzene Rings** |
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| Authors: | Dr Gui-Fei Huo Dr Toshiya M Fukunaga Dr Xudong Hou Dr Yi Han Dr Wei Fan Dr Shaofei Wu Prof Hiroyuki Isobe Prof Jishan Wu |
| Institution: | 1. Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore, 117543 Singapore
These authors contributed equally to this work.;2. Department of Chemistry, The University of Tokyo Hongo, Bunkyo-ku, Tokyo, 113-0033 Japan These authors contributed equally to this work.;3. Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore, 117543 Singapore;4. Department of Chemistry, The University of Tokyo Hongo, Bunkyo-ku, Tokyo, 113-0033 Japan |
| Abstract: | Expanded helicenes are expected to show enhanced chiroptical properties as compared to the classical helicenes but the synthesis is very challenging. Herein, we report the facile synthesis of a series of expanded helicenes Hn (n=1–4) containing 11, 19, 27 and 35 cata-fused benzene rings through Suzuki coupling-based oligomerization followed by Bi(OTf)3-mediated regioselective cyclization of vinyl ethers. Their structures were determined by X-ray crystallographic analysis. Enantiopure H2 , H3 , and H4 can be isolated by chiral HPLC and they all exhibit strong chiroptical responses with high absorption dissymmetry factor (|gabs|) values (0.020 for H2 , 0.021 for H3 , and 0.021–0.024 for H4 ). |
| Keywords: | Benzannulation Chiral Molecules Circular Dichroism Expanded Helicenes Polyarenes |