Lanthanide complexes combined with chiral salen ligands: application in the enantioselective epoxidation reaction of α,β-unsaturated ketones

Readily available lanthanide amides Ln[N(SiMe(3))(2)](3) (Ln = Nd (1), Sm (2), Eu (3), Yb (4), La (5)), combined with chiral salen ligands H(2)L(a) ((S,S)-N,N′-di-(3,5-disubstituted-salicylidene)-1,2-cyclohexanediamine) and H(2)L(b) ((S,S)-N,N′-di-(3,5-disubstituted-salicylidene)-1,2-diphenyl-1,2-ethanediamine) were employed in the enantioselective epoxidation of α,β-unsaturated ketones. It was found that the salen–La complex shows the highest efficiency and enantioselectivity. A relatively broad scope of α,β-unsaturated ketones was investigated, and excellent yields (up to 99%) and moderate to good enantioselectivities (37–87%) of the target molecules were achieved.