Photoracemization of Blestriarene C and Its Analogs
Photoracemization of Blestriarene C and Its Analogs
复制标题
Blestrirene C 及其类似物的光外消旋化
作者：
Natori;K.; Iwayama;T.; Yamabe;O.; Kitamoto;Y.; Ikeda;H.; Sakamoto;K.; Hattori;T.; Miyano;S.
制备了两种不含7，7 '-二羟基（3）和4，4'-二甲氧基4的泡三芳烃C（4，4 '-二甲氧基-1，1'-联菲-2，2 '，7，7'-四醇）类似物。与blestriarene C（1）不同，化合物3和4以及1，1 '-联菲-2，2'-二醇（5）在荧光灯照射下不发生外消旋。循环伏安法分析表明化合物1的半波电位（E1/2）比化合物3、4、5低，表明外消旋化过程中涉及氧化还原循环。化合物1通过吸收对应于1 Lb带的UV光而外消旋化。在反应过程中，没有观察到副产物。在氮的作用下，外消旋作用受到明显抑制。基于这些观察结果，我们提出了化合物1易于外消旋化的可行机制，其由可逆光诱导氧氧化原位产生的阳离子自由基介导。Chirality 27：479- 486，2015。© 2015 Wiley Periodicals，Inc.
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 groups4were prepared. Unlike blestriarene C (1), compounds3and4, as well as 1,1'‐biphenanthrene‐2,2'‐diol (5), do not racemize under fluorescent lamp illumination. Cyclic voltammetry analysis reveals that compound1has a lower half‐wave potential (E1/2) than compounds3,4,5, suggesting that a redox cycle is involved in the racemization. Compound1racemizes by absorbing UV light corresponding to the1Lbband. 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 compound1, which is mediated by a cation radical generated in situ by a reversible photo‐induced oxygen oxidation.Chirality 27:479–486,2015. © 2015 Wiley Periodicals, Inc.