Creating a Vision for Photochromic and Chiral Helicenoid Diarylethenes

已知螺旋烯表现出大的比旋光度。为了引起旋光度的大变化，应发生非对映选择性光致变色反应。我们选择用连接到闭环己三烯部分的简单手性助剂来诱导非对映选择性光致变色反应。然后，我们合成了六种手性螺烯二芳基乙烯，其芳族基团在C-3或C-2处连接到全氟环戊烯。我们研究了这六个分子的光化学行为，特别是光致变色中的非对映选择性。在这些研究过程中，我们可以对二芳基乙烯中的非对映选择性和取代基（甲氧基和甲氧基甲氧基）之间的关系进行有用的检查，以获得光致变色的大旋光度变化。也就是说，我们发现这些分子中两个取代基之间的空间和电子排斥以及甲氧基和苯并噻吩部分之间的电子排斥很重要。

Helicenes are known to show large specific optical rotation. In order to induce a large change in optical rotation, a diastereoselective photochromic reaction should take place. We chose to induce a diastereoselective photochromic reaction with a simple chiral auxiliary attached to the ring-closing hexatriene moiety. Then, we synthesized six chiral helicenoid diarylethenes having the aromatic group connected to perfluorocyclipentene at C-3 or C-2. We examined the photochemical behaviors of these six molecules, especially about the diastereoselectivity in photochromism. In the course of these investigations, we could gain the useful inspection about the relation between the diastereoselectivity and the substitution groups (methoxyl group and methoxymethoxyl group) in diarylethenes to obtain large optical rotation changes in photochromism. That is, we found the steric and electronic repulsion between two substitution groups and the electronic repulsion between the methoxyl group and benzothiophen moiety in these molecules were important.