General Features
The degree of enantioselectivity depends on numerous factors, namely the structure of the olefin, the nature of the axial donor ligand on the active oxomanganese species and the reaction temperature. Cyclic and acyclic (Z)-1,2-disubstituted olefins are epoxidized with almost 100% enantioselectivity whereas (E)-1,2-disubstituted olefins are poor substrates for Jacobsen's catalysts but yet give higher enantioselectivities when Katsuki's catalysts are used. Furthermore, the enantioselective epoxidation of conjugated dienes is much higher than that of the nonconjugated dienes.
The enantioselectivity is explained by either a "top-on" approach (Jacobsen) or by a "side-on" approach (Katsuki) of the olefin.
Read more about this topic: Jacobsen Epoxidation
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