Non-Heme Perferryl Intermediates: Effect of Spin State on the Epoxidation Enantioselectivity Full article
| Journal |
Molecular Catalysis
ISSN: 2468-8231 |
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| Output data | Year: 2021, Volume: 502, Article number : 111403, Pages count : 6 DOI: 10.1016/j.mcat.2021.111403 | ||
| Tags | Asymmetric; Biomimetics; Epoxidation; Iron; Mechanism | ||
| Authors |
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| Affiliations |
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Funding (1)
| 1 | Russian Science Foundation | 17-13-01117 |
Abstract:
The catalyst systems Fe2(PDPNR1R2)2/H2O2/RCOOH (PDP = N,N′-bis(pyridyl-2-methyl)-(S,S)-2,2′-bipyrrolidine, NR1R2 = NMe2, NEt2, NMeiPr or N(CH2)4 at the para-position in the pyridine rings, RCOOH = acetic or 2-ethylhexanoic acid) generate the high-spin (S = 3/2) oxoiron(V) oxidizing intermediates with proposed structure [(PDPNR1R2)FeV=O(OC(O)R)]2+ and the EPR spectrum g1, = 4.30, g2 = 3.69, g3 = 1.96. In contrast, the catalyst systems Fe2(PDPMe2OMe)2/H2O2/RCOOH and Fe2(PDPMeOCH2CF3)2/H2O2/RCOOH, based on similar iron complexes, containing 3,5-Me2-4-OMe and 3-Me-4-OCH2CF3 substituents at the pyridine rings, generate the low-spin (S = 1/2) oxoiron(V) intermediates with characteristic EPR spectrum g1 = 2.07, g2 = 2.01, g3 = 1.96. Both high and low-spin intermediates directly epoxidize cyclohexene, with the low-spin species being much more reactive than the high-spin congeners; the corresponding second-order rate constants have been evaluated. Crucially, the catalyst systems exhibiting the high-spin oxidizing intermediates demonstrate higher enantioselectivity in the epoxidation of prochiral olefinic substrates, compared with the catalyst systems featuring the low-spin intermediates. This enhanced enantioselectivity is explained in terms of attenuated reactivity of the high-spin intermediates, leading to more product-like transition state with tighter substrate-catalyst interactions.
Cite:
Zima A.M.
, Lyakin O.Y.
, Bushmin D.S.
, Soshnikov I.E.
, Bryliakov K.P.
, Talsi E.P.
Non-Heme Perferryl Intermediates: Effect of Spin State on the Epoxidation Enantioselectivity
Molecular Catalysis. 2021. V.502. 111403 :1-6. DOI: 10.1016/j.mcat.2021.111403 WOS Scopus РИНЦ AN OpenAlex
Non-Heme Perferryl Intermediates: Effect of Spin State on the Epoxidation Enantioselectivity
Molecular Catalysis. 2021. V.502. 111403 :1-6. DOI: 10.1016/j.mcat.2021.111403 WOS Scopus РИНЦ AN OpenAlex
Dates:
| Submitted: | Oct 15, 2020 |
| Accepted: | Jan 6, 2021 |
| Published online: | Jan 25, 2021 |
| Published print: | Feb 1, 2021 |
Identifiers:
| Web of science: | WOS:000649342100026 |
| Scopus: | 2-s2.0-85099803226 |
| Elibrary: | 44990690 |
| Chemical Abstracts: | 2021:344414 |
| OpenAlex: | W3121701064 |