Useful Ligands for Asymmetric Oxidation

Chiral bishydroxamic acids (CBHA) 1 and 2 are ligands used for asymmetric oxidation developed by Yamamoto and his group. For example, a complex with vanadium is used to catalyze the asymmetric epoxidation of allylic alcohols and homoallylic alcohols,^1a-c) while a complex with molybdenum is used to catalyze the asymmetric epoxidation of olefins^1d) and asymmetric oxidation of sulfides.^1e) Asymmetric oxidation reactions using ligands 1 and 2 proceed with high stereoselectivity and can be applied to a wide range of substrates. Application to an industrial-scale synthesis would be expected because the reaction has the following benefits: (1) no dehydration agents are required; (2) the work-up procedure is simple; (3) and the reaction proceeds at 0 dgreeC to room temperature.