Asymmetric Epoxidations with H2O2 on Fe and Mn Aminopyridine Catalysts: Probing the Nature of Active Species by Combined Electron Paramagnetic Resonance and Enantioselectivity Study

作者：Lyakin Oleg Y; Ottenbacher Roman V; Bryliakov Konstantin P^*; Talsi Evgenii P

来源：ACS Catalysis, 2012, 2(6): 1196-1202.

DOI：10.1021/cs300205n

• asymmetric catalysis
• epoxidation
• hydrogen peroxide
• intermediate
• iron
• manganese

Chiral bipyrrolidine based iron and manganese complexes R((S,S)-pdp)M-II(OTf)(2)] catalyze the asymmetric epoxidation of various olefins with H2O2 in the presence of carboxylic acid additives with high efficiency (up to 1000 turnover number (TON)) and selectivity (up to 100%), and with good to high enantioselectivity (up to 93% enantiomeric excess (ee)). The enantioselectivity increases with growing steric demand of the acid. On the basis of the electron paramagnetic resonance (EPR) spectroscopy and enantioselectivity studies, the active oxygen-transferring species of the above systems can be identified as structurally similar oxometal(V) species of the type R((S,S)-pdp)M-v=O(OCOR)](2+) (M = Fe, Mn; R = alkyl).

• 出版日期2012-6