Catalytic asymmetric epoxidation of unfunctionalized olefins using chiral (salen)manganese(III) complexes

Article abstract of DOI:10.1016/S0957-4166(00)86102-9

Several kinds of chiral (salen)manganese(III) complexes (2 and 3) having chiral salicylaldehyde and chiral ethylenediamine moieties were prepared and used for catalytic asymmetric epoxidation of unfunctionalized olefins with iodosobenzene as a terminal oxidant. Catalysts 2 and 3 were found to show the characteristic substrate specificity for the enantiofacial selection of olefins, respectively. Furthermore, the addition of donor ligands such as pyridine N-oxide or 2-methylimidazole to the epoxidation reaction system was found to alter the enantioselectivity. As a result, the highest enantioselectivity for nonenzaymatic catalytic epoxidation was achieved for (E)-1-phenylpropene (56% ee, with 2c in the presence of 2-methylimidazole), (E)-stilbene (48% ee, with 3a), and dihydronaphthalene (83% ee, with 3a in the presence of pyridine N-oxide)