Chiral Bioinspired Non‐Heme Iron Complexes for Enantioselective Epoxidation of α,β‐Unsaturated Ketones

Abstract

Chiral bioinspired iron complexes of N 4 ligands based on the ethylenediamine backbone display remarkable levels of enantioselectivity for the first time in the asymmetric epoxidation of a,b-unsaturated ketones using hydrogen peroxide (up to 87% ee) or peracetic acid as oxidant, respectively. Notablely, isotopic labeling with H 2 18O strongly demonstrated that there is a reversible water binding step prior to generation of the significant intermediate.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.

Identification of a low-spin acylperoxoiron(III) intermediate in bio-inspired non-heme iron-catalysed oxidations

“…Their catalytic activity and selectivity are further enhanced by the addition of acetic acid to the reaction mixture, leading to predictable regio-and stereoselectivity in the oxidation of particular aliphatic C-H bonds in complex organic molecules, as demonstrated by White for ( þ )-artemisinin and ( À )-dihydropleuromutilone 7,8 . Highly enantioselective olefin epoxidation reactions can also be achieved [9][10][11][12] .…”

Non-heme manganese complexes of C1-symmetric N4 ligands: Synthesis, characterization and asymmetric epoxidations of α,β-enones

“…With 1 mol % of manganese catalyst loading, the enantioselecive epoxidation of olefins proceeds to nearly complete conversion and enantiometic excess values of up to 89%. The respective iron(II) complexes also show good performance in the same reaction with up to 87% ee [35]. Recently, Talsi and co-workers (S,S-BPBP) [36] and Costas et al (S,S,ReBPBPP or R,R,ReBPBPP) ( Fig.…”

“…As a part of our research on oxidation catalyzed by non-heme metal complex of N 4 ligands [28,35,38], we report on the synthesis of a series of C 1 esymmetric N 4 ligands derived from proline and various pyridine donors. Further, catalytic efficiency of the corresponding manganese complexes of N 4 ligands has been investigated in the asymmetric epoxidation of a,b-enones with peracetic acid as oxidant.…”

Biomimetic Iron‐Catalyzed Asymmetric Epoxidations: Fundamental Concepts, Challenges and Opportunities

“…[246] Excess (5 equivalents) acetic acid is needed for the success of the reaction in acetonitrile solvent. [246] Excess (5 equivalents) acetic acid is needed for the success of the reaction in acetonitrile solvent.…”