On the Reaction of Lithium Aluminum Hydride with Alcohols

Article abstract of DOI:10.1021/jo00155a004

Infrared spectra of the reaction products of lithium aluminum hydride (LiAlH4) with 3 molar equiv of isobutyl alcohol, 2-propanol, and the more sterically hindered 2,4-dimethyl-3-pentanol, 4, in diethyl ether were examined.Alcohol 4 reacts with LiAlH4 in diethyl ether, giving a clear solution that is highly stereoselective in the reduction of 3,3,5-trimethylcyclohexanone, 1.The reaction of LiAlH4 with 4 does not lead to tricoordinate aluminum species.On the basis of infrared spectra and the stereochemistry of reduction of 1, it is concluded that LiAlH4 is presentin solution after its reaction with 3 molar equiv of isobutyl alcohol.LiAlH4 is also the initial reducing species in solution after reaction with 2-propanol.On the other hand, LiAlH4 reacts with methanol, ethanol, and 4, giving lithium alkoxyaluminum hydride species.Possible pathways for the reaction of LiAlH4 with alcohols are discussed.