Asymmetric reduction of ketoxime O-alkyl ethers with chirally modified NaBH4–ZrCl4
Abstract
Reducing agents prepared from sodium borohydride (NaBH4), zirconium tetrachloride (ZrCl4), and chiral amino alcohols have been successfully applied to the enantioselective reduction of oxime ethers. Optically active primary amines were obtained in high enantiomeric excess (⩽95% e.e.) with good chemical yield. The extent of asymmetric synthesis was dependent on the solvent, the temperature, the structure of chiral amino alcohol, and the proportions [NaBH4] : [ZrCl4] : [chiral amino alcohol] : [oxime ether].