Chiral Bioinspired Non-Heme Iron Complexes for Enantioselective Epoxidation of a,ß-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 a,beta-unsaturated ketones using hydrogen peroxide (up to 87 parts per thousand 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 [L2Fe(III)2(mu-O)(mu-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.