The first asymmetric epoxidation using a combination of achiral (salen)manganese(III) complex and chiral amine

A new catalyst system for asymmetric epoxidation was developed by using an achiral (salen)manganese(III) complex with chiral amine. Commercially available (-)-sparteine showed the highest asymmetric induction over the other chiral amines examined and addition of water to the reaction medium improved the induction up to 73% ee in the epoxidation of chromene derivative. Application of the system to the asymmetric oxidation of methyl phenyl sulfide to its sulfoxide was a so examined (at most 25% ee). These results support our proposal that a non-planar and chiral structure of the salen ligand plays an important role in the enantioface selection of olefins by (salen)manganese(III) complex.