Zirconium cation coordination in the borohydride-mediated synthesis of β-hydroxy-N-alkoxylamines

Hydride reductions of oxime ethers to hydroxylamine derivatives are facilitated by the participation of neighboring hydroxyl groups. Precomplexation with zirconium cation in ether–methylene chloride solutions is effective for selective CN bond reduction. The course for stereochemical control is dictated by Lewis acid coordination complexes of E- and Z-oximino ethers which lead to the preferred diastereofacial delivery of external hydride.