Aluminumoxyhydride: improved synthesis and application as a selective reducing agent.

Aluminumoxyhydride (HAIO) has been obtained by the reaction of aluminum hydride with the siloxane (Me 2 HSi) 2 O or the stannoxane (Bu 3 Sn) 2 O as an amorphous colorless insoluble powder. The highest-purity product resulted from the reaction of H 3 Al·NMe 3 with (Me 2 HSi) 2 O. However, HAIO suspensions in tetrahydrofuran (THF) of sufficient quality for synthetic applications can be prepared from commercially available reagents with only minor precautions. A LiAlH 4 solution in THF was treated successively with Me 3 SiCl and (Me 2 HSi) 2 O, followed by heating at 60 °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.