Topochemical transketalization reaction driven by hydrogen bonding.
An unusual thermal isomerization of 1,2;3,4-di-O-isopropylidene-myo-inositol to 1,2;5,6-di-O-isopropylidene-myo-inositol was observed in the solid state. A detailed study revealed that this ketal migration is a topochemically driven one. X-ray structure revealed that strong intermolecular hydrogen bonding in the crystal preorganizes the hydroxyl and ketal carbon in a transition-state-like arrangement favorable for the reaction. The 5-OH of each molecule faces the trans ketal carbon of a neighboring molecule at a close distance and an angle of approach near to linearity, making a trigonal-bipyramidal-like arrangement in the crystal, which could facilitate the reaction. This is the first report of a topochemical transketalization reaction.
Department of Applied Chemistry, Faculty of Engineering, Ehime University, Matsuyama 790-0607, Japan. sureshankm@yahoo.co.in
Kana M
KM
Sureshan
Tomohiro
T
Murakami
Tomomi
T
Miyasou
Yutaka
Y
Watanabe