The hydroxylation of cyclohexane by t-butyl hydroperoxide using [Fe2O(TPA)2(H2O)2]4+ (1, TPA=tris(2-pyridylmethyl)amine) as the catalyst has been investigated with the use of a syringe pump to control the concentration of the alkyl hydroperoxide. Unlike an alkoxy radical-based radical chain autoxidation mechanism, the reaction observed produces only alcohol (no ketone) with a deuterium kinetic isotope effect of 10, similar to heme catalyzed hydroxylations. An alkylperoxoiron(III) intermediate can be trapped at -40°C and characterized by a number of spectroscopic methods. A mechanistic scheme is proposed involving this intermediate which either serves as the precursor to the metal-based oxidant or oxidizes the substrate directly.
Bibliographical noteFunding Information:
This work was supported by funds from the National Institutes of Health (Grant No. GM-38767).
- Alkylperoxide intermediates
- Nonheme iron complexes
- Oxygen activation