title: Photoracemization of Blestriarene C and Its Analogs.
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.
authors.affiliation: Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Natori
authors.affiliation: Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai, Japan.
authors.forename: Taizo
authors.initials: T
authors.lastname: Iwayama
authors.affiliation: Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Yamabe
authors.affiliation: Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai, Japan.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Kitamoto
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, Osaka, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ikeda
authors.affiliation: Department of Chemistry, Faculty of Science, Shizuoka University, Shizuoka, Japan.
authors.forename: Kenkichi
authors.initials: K
authors.lastname: Sakamoto
authors.affiliation: Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai, Japan.
authors.forename: Tetsutaro
authors.initials: T
authors.lastname: Hattori
authors.affiliation: Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai, Japan.
authors.forename: Sotaro
authors.initials: S
authors.lastname: Miyano
mesh_terms: D010616:Phenanthrenes / Q000737:chemistry*; D055668:Photochemical Processes; D013237:Stereoisomerism; D013267:Stilbenes / Q000737:chemistry*; D014466:Ultraviolet Rays
chemical_list: D010616:Phenanthrenes; D013267:Stilbenes; C468328:blestriarene C
keywords: atropisomerism; biaryl synthesis; photooxidation; photoreaction; racemization