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Efficient syntheses of π-electron deficient macrocycles

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journal contribution
posted on 2020-01-08, 04:57 authored by Cheng Peng, Chi Zhang, Jiwei Zhang, Hao Li

Cyclobis(paraquat-p-phenylene) (CBPQT4+) cyclophane represents an ideal π-electron deficient macrocycles, which demonstrates the extraordinary ability of hosting a variety of π-electron-rich guests in its rigid, preorganised cavity. However, this macrocycle undergoes large ring strain and therefore its preparation is often low yielding. In order to increase its yields, high-dilution conditions and template-directed synthesis are employed, which are rather time-consuming, i.e. a few weeks including template removal. Herein, we attempt to solve these problems by either using click reaction, or decreasing the ring strain by using a flexible linker. Three analogues of CBPQT4+ ring were synthesised without the need of guest template, each of which contains two bipyridinium units. Two of these three macrocycles are able to recognise π-electron rich guests within their cavities. However, the one obtained via click reaction demonstrates low guest recognition ability.

Funding

Support from the Chinese “Thousand Youth Talents Plan”, the National Natural Science Foundation of China [No. 21772173, 91856116 and 21922108], and the Natural Science Foundation of Zhejiang Province of China [No. LR18B020001], as well as “the Fundamental Research Funds for the Central Universities” [No. 2019FZA3007] are gratefully acknowledged.

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