Photoracemization of Blestriarene C and Its Analogs

Koichi Natori; Taizo Iwayama; Osamu Yamabe; Yuichi Kitamoto; Hiroshi Ikeda; Kenkichi Sakamoto; Tetsutaro Hattori; Sotaro Miyano

doi:10.1002/chir.22447

Photoracemization of Blestriarene C and Its Analogs

Koichi Natori, Taizo Iwayama, Osamu Yamabe, Yuichi Kitamoto, Hiroshi Ikeda, Kenkichi Sakamoto, Tetsutaro Hattori, Sotaro Miyano

ENG - Biomolecular Engineering

Research output: Contribution to journal › Article › peer-review

4 Citations (Scopus)

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 4 were prepared. Unlike blestriarene C (1), compounds 3 and 4, as well as 1,1'-biphenanthrene-2,2'-diol (5), do not racemize under fluorescent lamp illumination. Cyclic voltammetry analysis reveals that compound 1 has a lower half-wave potential (E_1/2) than compounds 3, 4, 5, suggesting that a redox cycle is involved in the racemization. Compound 1 racemizes by absorbing UV light corresponding to the ¹L_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 1, which is mediated by a cation radical generated in situ by a reversible photo-induced oxygen oxidation. Chirality 27:479-486, 2015.

Original language	English
Pages (from-to)	479-486
Number of pages	8
Journal	Chirality
Volume	27
Issue number	8
DOIs	https://doi.org/10.1002/chir.22447
Publication status	Published - 2015 Aug 1

Keywords

atropisomerism
biaryl synthesis
photooxidation
photoreaction
racemization

ASJC Scopus subject areas

Analytical Chemistry
Catalysis
Pharmacology
Drug Discovery
Spectroscopy
Organic Chemistry

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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 4 were prepared. Unlike blestriarene C (1), compounds 3 and 4, as well as 1,1'-biphenanthrene-2,2'-diol (5), do not racemize under fluorescent lamp illumination. Cyclic voltammetry analysis reveals that compound 1 has a lower half-wave potential (E1/2) than compounds 3, 4, 5, suggesting that a redox cycle is involved in the racemization. Compound 1 racemizes by absorbing UV light corresponding to the 1Lb 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 1, which is mediated by a cation radical generated in situ by a reversible photo-induced oxygen oxidation. Chirality 27:479-486, 2015.",

keywords = "atropisomerism, biaryl synthesis, photooxidation, photoreaction, racemization",

author = "Koichi Natori and Taizo Iwayama and Osamu Yamabe and Yuichi Kitamoto and Hiroshi Ikeda and Kenkichi Sakamoto and Tetsutaro Hattori and Sotaro Miyano",

year = "2015",

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doi = "10.1002/chir.22447",

language = "English",

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T1 - Photoracemization of Blestriarene C and Its Analogs

AU - Natori, Koichi

AU - Iwayama, Taizo

AU - Yamabe, Osamu

AU - Kitamoto, Yuichi

AU - Ikeda, Hiroshi

AU - Sakamoto, Kenkichi

AU - Hattori, Tetsutaro

AU - Miyano, Sotaro

PY - 2015/8/1

Y1 - 2015/8/1

N2 - 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 4 were prepared. Unlike blestriarene C (1), compounds 3 and 4, as well as 1,1'-biphenanthrene-2,2'-diol (5), do not racemize under fluorescent lamp illumination. Cyclic voltammetry analysis reveals that compound 1 has a lower half-wave potential (E1/2) than compounds 3, 4, 5, suggesting that a redox cycle is involved in the racemization. Compound 1 racemizes by absorbing UV light corresponding to the 1Lb 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 1, which is mediated by a cation radical generated in situ by a reversible photo-induced oxygen oxidation. Chirality 27:479-486, 2015.

AB - 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 4 were prepared. Unlike blestriarene C (1), compounds 3 and 4, as well as 1,1'-biphenanthrene-2,2'-diol (5), do not racemize under fluorescent lamp illumination. Cyclic voltammetry analysis reveals that compound 1 has a lower half-wave potential (E1/2) than compounds 3, 4, 5, suggesting that a redox cycle is involved in the racemization. Compound 1 racemizes by absorbing UV light corresponding to the 1Lb 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 1, which is mediated by a cation radical generated in situ by a reversible photo-induced oxygen oxidation. Chirality 27:479-486, 2015.

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KW - biaryl synthesis

KW - photooxidation

KW - photoreaction

KW - racemization

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