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Published on: May 21, 2019
Photoracemization of Blestriarene C and Its Analogs
Koichi Natori1, Taizo Iwayama1, Osamu Yamabe1
1Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai, Japan.
Abstract:
Two analogs of blestriarene C (4,4'-dimethoxy-1,1'-biphenanthrene-2,2',7,7'-tetraol) bearing no 7,7'-dihydroxy (3) and 4,4'-dimethoxy groups were prepared. Unlike blestriarene C (1), compounds and , as well as 1,1'-biphenanthrene-2,2'-diol (5), do not racemize under fluorescent lamp illumination. Cyclic voltammetry analysis reveals that compound has a lower half-wave potential (E(1/2)) than compounds , suggesting that a redox cycle is involved in the racemization. Compound racemizes by absorbing UV light corresponding to the (1) L(b) band. During the reaction, no side products are observed. The racemization is significantly inhibited under nitrogen. Based on these observations, we propose a feasible mechanism for the easy racemization of compound , which is mediated by a cation radical generated in situ by a reversible photo-induced oxygen oxidation.
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