AEROBIC ENANTIOSELECTIVE EPOXIDATION OF UNFUNCTIONALIZED OLEFINS CATALYZED BY OPTICALLY-ACTIVE SALEN MANGANESE (III) COMPLEXES

Enantioselective epoxidation of unfunctionalized olefins is achieved by the combined use of molecular oxygen and pivalaldehyde in the presence of a catalytic amount of optically active Mn(III)-salen complexes. N-Alkylimidazoles are effective axial ligands to produce optically active epoxides with high enantioselectivities in the present procedure; that is, 1,2-dihydronaphthalene derivatives and 2,2-dialkyl-2H-chromene derivatives are converted into the corresponding optically active epoxides with 60-92% enantiomeric excess. The key intermediates in the present aerobic epoxidation are also discussed.