N-Alkyl lmidazoles as Effective Axial Ligands in the Aerobic Asymmetric Epoxidation of Unfunctionalized Olefins Catalyzed by Optically Active Manganese(III)-salen-type Complex

Abstract

Abstract 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.