Asymmetric epoxidation using aqueous hydrogen peroxide as oxidant: bio-inspired construction of pentacoordinated Mn-salen complexes and their catalysis

Pentacoordinated Mn-salen complexes 1 and 5 possessing an internal pyridine or N-methylimidazole ligand, respectively, were found to be efficient catalysts for asymmetric epoxidation of conjugated Z-olefins using aqueous hydrogen peroxide, in particular, the epoxidation of chromene derivatives proceeded with high enantioselectivity greater than or equal to 97% ee.