Asymmetric Reduction of Acetophenone O-Methyloxime with Reagents Prepared from L-Proline and Borane

Asymmetric reduction of acetophenone O-methyloxime with reagents in situ prepared from L-pronne and borane has been investigated. A series of conditions opfimiTation were made, including an examination of the effect of the temperature of ratalyst pretreatment, the temperature of reduction, the amount of borane, the additive, the solvent, the reducing agent and various chiral anxiHaries on the enanfioselecfivlty. Under the opti-mal condition, (S)-a-phenylethylamlne was obtained in 53% yield with 83.1% ee in the presence of 25 mol% L-proline.