REEXAMINATION OF DIISOBUTYLALUMINUM HYDRIDE AS A STEREOSELECTIVE REDUCING AGENT FOR REDUCTION OF CYCLIC-KETONES TO THERMODYNAMICALLY MORE STABLE ALCOHOLS

The reducing property of diisobutylaluminum hydride (DIBAH) has been r eexamined as a stereoselective reducing agent for reduction of represe ntative cyclic ketones. When the reduction of excess cyclic ketone wit h DIBAH was carried put at 0 degrees C in ethyl ether, only 1 equiv of the free hydride was involved to show a low stereoselectivity. Howeve r, when performed at 25 degrees C or under reflux in ethyl ether, one isobutyl group as well as the free hydride was also involved in this r eduction: the first equiv of ketone was reduced rapidly and the second one reduced, in a relatively slow rate. In addition, the stereoselect ivity increases consistently with increase of reaction time to afford the thermodynamically more stable isomer alcohols exclusively.