Optically Active N,N'-Bis(3-oxobutylidene)diaminato-manganese(III) Complexes as Novel and Efficient Catalysts for Aerobic Enantioselective Epoxidation of Simple Olefins.

A novel manganese(III) complex having an optically active N,N′-bis(3-oxobutylidene)diamine ligand with bulky substituents was prepared and characterized crystallographically. In the presence of a catalytic amount of the manganese(III) complex, unfunctionalized olefins were oxygenated to give optically active epoxides with molecular oxygen by the combined use of several aliphatic aldehydes. Cyclic and acyclic cis-β-substituted styrene derivatives, conjugated dienes, and enynes were converted into the corresponding epoxides with moderate-to-good enantioselectivities. The present aerobic and enantioselective epoxidation proceeded with the opposite enantioface selection from those obtained by using terminal oxidants, such as sodium hypochlorite and iodosylbenzene. The key intermediate of the aerobic asymmetric epoxidation is also discussed.