A Novel Method for the Preparation of Acid-Sensitive Epoxides from Olefins with the Combined Use of Molecular Oxygen and Aldoacetal Catalyzed by a Cobalt(II) Complex
An efficient synthesis of acid-sensitive epoxides, such as chromene oxide or epoxide of γ,δ-unsaturated alcohol, was successfully achieved by the oxygenation of corresponding olefins with the combined use of an atmospheric pressure of molecular oxygen and aldoacetal catalyzed by a cobalt(II) complex coordinated with the 1,3-diketone ligand. The reactions proceeded under mild and neutral conditions
<i>N</i>-Alkyl lmidazoles as Effective Axial Ligands in the Aerobic Asymmetric Epoxidation of Unfunctionalized Olefins Catalyzed by Optically Active Manganese(III)-salen-type Complex
are effective axial ligands to achieve highly enantioselectiveepoxidation of unfunctionalizedolefins by combined use of molecular oxygen and pivalaldehyde with opticallyactive Mn(III)-salen-type complexcatalysts. In the presence of N-alkyl imidazole, the epoxidation of 2,2-dimethylchromene proceeded smoothly to afford the corresponding opticallyactive epoxide in 92% enantiomeric excess.