Chiral bioinspired non-heme iron complexes for enantioselective epoxidation of α,β-unsaturated ketones

Chiral bioinspired iron complexes of N₄ ligands based on the ethylenediamine backbone display remarkable levels of enantioselectivity for the first time in the asymmetric epoxidation of α,β-unsaturated ketones using hydrogen peroxide (up to 87% ee) or peracetic acid as oxidant, respectively. Notablely, isotopic labeling with H₂¹⁸O strongly demonstrated that there is a reversible water binding step prior to generation of the significant intermediate. Besides, the complex [L ₂Fe(III)₂(μ-O)(μ-CH₃CO₂)] ³⁺ usually derived from the decay of the LFe(IV)=O species or thermodynamic sinks for a number of iron complexes was identified by HR-MS. In addition, the possible mechanisms were proposed and LFe(V)=O species may be the main active intermediate in the catalytic system.