Diastereospecific photocyclization of a isopropylbenzophenone derivative in crystals and the morphological changes.
Reaction of crystals of 2,4,6-triisopropylbenzophenone derivative with the (S)-phenylethylamide group caused diastereospecific Norrish type II photocyclization by UV irradiation to give (R,S)-cyclobutenol as a sole product. In contrast, the solution photolysis gave an almost 1:1 mixture of (R,S)- and (S,S)-cyclobutenol. The specific diastereodifferentiation in the crystalline state is attributed to the smooth transformation with minimum molecular motion due to the very similar molecular shapes as well as the 2-fold helical arrangements between the reactant crystal and the product (R,S)-cyclobutenol crystal. UV irradiation of the bulk crystals led to cracking and breaking into small fragments. In contrast, the microcrystals maintained the single-crystalline morphology in the course of photocyclization, suggesting the single-crystal-to-single-crystal transformation.
Koshima
Hideko
H
Department of Materials Science and Biotechnology, Ehime University, Matsuyama 790-8577, Japan. koshima@eng.ehime-u.ac.jp
Fukano
Michitaro
M
Uekusa
Hidehiro
H