Asymmetric Synthesis of Primary Amines via the Spiroborate-Catalyzed Borane Reduction of Oxime Ethers

Abstract
The enantioselective borane reduction of O-benzyloxime ethers to primary amines was studied under catalytic conditions using the spiroborate esters 5−10 derived from nonracemic 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.