Facile Synthesis and Chiral Resolution of Expanded Helicenes with up to 35 cata-Fused Benzene Rings

Gui-Fei Huo; Toshiya M Fukunaga; Xudong Hou; Yi Han; Wei Fan; Shaofei Wu; Hiroyuki Isobe; Jishan Wu

doi:10.1002/anie.202218090

Facile Synthesis and Chiral Resolution of Expanded Helicenes with up to 35 cata-Fused Benzene Rings

Angew Chem Int Ed Engl. 2023 Apr 24;62(18):e202218090. doi: 10.1002/anie.202218090. Epub 2023 Mar 22.

Authors

Gui-Fei Huo¹, Toshiya M Fukunaga², Xudong Hou¹, Yi Han¹, Wei Fan¹, Shaofei Wu¹, Hiroyuki Isobe², Jishan Wu¹

Affiliations

¹ Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore, 117543, Singapore.
² Department of Chemistry, The University of Tokyo Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.

PMID: 36826385
DOI: 10.1002/anie.202218090

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 (|g_abs |) 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.

Abstract

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