Asymmetric epoxidation of olefins with homogeneous chiral (salen) manganese (III) complex

Optically active epoxides are known as versatile chiral building blocks in organic synthesis, and many efforts have been directed toward developing asymmetric epoxidation (AE) reaction of olefins. The first major breakthrough in AE using synthetic catalysts was realized by Katsuki and Sharpless in 1980, they achieved enantiomeric excesses (ee's) greater than 90% in the titanium tartrate-based epoxidation of a variety of allylic alcohols. However, the substrates must bear specific functional groups to achieve the precoordination required for high enantioselectivity. In 1990 Jacobsen et al. and Katsuki et al. announced their independently developed systems for the catalytic AE of unfunctionalized olefins using chiral manganese (III) salen complexes. Since that time, the area of chiral manganese (III)-catalyzed AE has expanded greatly. In this review we will focus on the ligand development and the application of homogeneous chiral (salen) manganese (III)-promoted AE of olefins in recent years.