Asymmetric synthesis of primary amines via the spiroborate-catalyzed borane reduction of oxime ethers.

The enantioselective borane reduction of O-benzyloxime ethers to primary amines was studied under catalytic conditions using the spiroborate esters 5 – 10 derived from non-racemic 1,2-amino alcohols and ethylene glycol. Effective catalytic conditions were achieved using only 10% of catalyst 5 derived from diphenylvalinol in dioxane at 0 °C resulting in complete conversion to the corresponding primary amine in up to 99% ee.