Mechanistic Insights into Fe Catalyzed α-C-H Oxidations of Tertiary Amines

29 July 2019, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


We report detailed mechanistic investigations of an iron-based catalyst system, which allows the α-C-H oxidation of a wide variety of amines, including acyclic tertiary aliphatic amines, to afford dealkylated or amide products. In contrast to other catalysts that affect α-C-H oxidations of tertiary amines, the system under investigation employs exclusively peroxy esters as oxidants. More common oxidants (e.g. tBuOOH) previously reported to affect amine oxidations via free radical pathways do not provide amine α-C-H oxidation products in combination with the herein described catalyst system. Motivated by this difference in reactivity to more common free radical systems, the investigations described herein employ initial rate kinetics, kinetic profiling, Eyring studies, kinetic isotope effect studies, Hammett studies, ligand coordination studies, and EPR studies to shed light on the Fe catalyst system. The obtained data suggest that the catalytic mechanism proceeds through C-H abstraction at a coordinated substrate molecule. This rate-determining step occurs either at an Fe(IV) oxo pathway or a 2-electron pathway at a Fe(II) intermediate with bound oxidant. We further show via kinetic profiling and EPR studies that catalyst activation follows a radical pathway, which is initiated by hydrolysis of PhCO3 tBu to tBuOOH in the reaction mixture. Overall, the obtained mechanistic data support a non-classical, Fe catalyzed pathway that requires substrate binding, thus inducing selectivity for α-C-H functionalization.


C-H bond activation
amine group
iron oxo compound
Kinetic Characterization
Reaction profile analysis
EPR spectroscopic data
Eyring analyses
Ligand coordination
peroxo derivatives
Initial rate studies
Kinetic Isotope Effect Analysis
Hammett studies
heterolytic bond dissociation
initiation time reduction
Base Metal Catalysis

Supplementary materials

Supporting Information 072419


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