N-ALKYL IMIDAZOLES AS EFFECTIVE AXIAL LIGANDS IN THE AEROBIC ASYMMETRIC EPOXIDATION OF UNFUNCTIONALIZED OLEFINS CATALYZED BY OPTICALLY-ACTIVE MANGANESE(III)-SALEN-TYPE COMPLEX

N-Alkyl imidazoles are effective axial ligands to achieve highly enantioselective epoxidation of unfunctionalized olefins by combined use of molecular oxygen and pivalaldehyde with optically active Mn(III)-salen-type complex catalysts. In the presence of N-alkyl imidazole, the epoxidation of 2,2-dimethylchromene proceeded smoothly to afford the corresponding optically active epoxide in 92% enantiomeric excess.