title: Diastereoselective photochromism of a bisbenzothienylethene governed by steric as well as electronic interactions.
abstract: 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.
authors.affiliation: 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
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Yokoyama
authors.forename: Hidenori
authors.initials: H
authors.lastname: Shiraishi
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Tani
authors.forename: Yayoi
authors.initials: Y
authors.lastname: Yokoyama
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Yamaguchi