Diastereoselective photochromism of a bisbenzothienylethene governed by steric as well as electronic interactions.
Introduction of an asymmetric center to C-2 of one of the benzothiophene rings of bisbenzothienylperfluorocyclopentene results in a highly diastereoselective photochromic system. The stereogenic center bears a hydrogen atom, a methyl group, and a methoxymethoxy group. The steric as well as the electronic repulsions gave an 87-88% diastereomer excess in various solvents at room temperature with 80-85% conversion to the colored form. The enantioselective synthesis was also carried out. Upon photoirradiation in hexane, a change in optical rotation at 820 nm, where neither the open form nor the colored form absorbs light, was observed repeatedly.
Yokoyama
Yasushi
Y
Department of Advanced Materials Chemistry, Graduate School of Engineering, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501 Japan. yyokoyam@ynu.ac.jp
Shiraishi
Hidenori
H
Tani
Yutaka
Y
Yokoyama
Yayoi
Y
Yamaguchi
Yoshitaka
Y