Aluminumoxyhydride: improved synthesis and application as a selective reducing agent

Aluminumoxyhydride (HAlO) has been obtained by the reaction of aluminum hydride with the siloxane (Me2HSi)2O or the stannoxane (Bu3Sn)2O as an amorphous colorless insoluble powder. The highest-purity product resulted from the reaction of H3Al.NMe3 with (Me2HSi)2O. However, HAlO suspensions in tetrahydrofuran (THF) of sufficient quality for synthetic applications can be prepared from commercially available reagents with only minor precautions. A LiAlH4 solution in THF was treated successively with Me3SiCl and (Me2HSi)2O, followed by heating at 60 degrees C for 20 h. The resulting suspensions are 0.4-0.5 M in active hydride content and selectively reduce aldehydes and ketones to the respective alcohols in the presence of any other common nonprotic functional group.