Nitrogen hydrides organoaluminums

Because organoaluminum compounds react readily with all types of Brpnsted acids and with atmospheric oxygen or peroxides, hydroalumination reactions must be conducted anhydrous in an atmosphere of pure nitrogen, and in deoxygenated solvents. Detailed experimental directions for the manipulation and transfer of aluminum alkyls and hydrides are available. °... 

In the presence of the organoaluminum, the substituent (R) on the chiral center adjacent to nitrogen in (67) is forced to occupy an axial position to relieve the strain created by the steric interaction with aluminum. This would favor approach by hydride from the top face of (67), whereas in the absence of aluminum the favored approach of hydride is from the bottom foce of transition state structure (66). 

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