Scheme 3

While the proline-based C₁ -symmetric Ti-(salan) from 4 and Ti(OⁱPr)₄ has been found to be excellent catalyst for the epoxidation of styrene derivatives (Scheme 4).

Scheme 4

5.4.4 Lanthanoid-Catalyzed Epoxidation

Nucleophilic epoxidation methods represent a viable alternative to electrophilic methods, many of which do not epoxidize electron-poor double bonds. The lanthanide based catalysts derived from chiral ligands 5-7 have been found to be effective in the epoxidation of α,β-unsaturated ketones (Scheme 5). It is mainly nucleophilic epoxidation of electron-deficient double bonds through the action of nucleophilic oxidants.

Scheme 5