Low-temperature rapid-scan detection of reactive intermediates in epoxidation reactions catalyzed by a new enzyme mimic of cytochrome p450

The use of synthetic iron(III) porphyrins as models for heme-type catalysts in biomimetic cytochrome P 450 research has provided valuable information on the nature and reactivity of intermediates produced in the "peroxide shunt" pathway.  This article reports spectroscopic detection of reactive intermediates formed in the epoxidn. reaction of cis-stilbene with m-chloroperoxybenzoic acid catalyzed by a new mimic of cytochrome P 450 with a substituted RSO3- group (1).  The application of low-temp. rapid-scan stopped-flow techniques enabled the detn. of equil. and rate consts. for the formation and decay of all intermediates in the catalytic cycle of 1, including the rate const. for the formation (1.bul.+)FeIV:O and for oxygen transfer to the substrate.  Noteworthy, the reaction of (1.bul.+)FeIV:O with cis-stilbene leads to an almost complete re-formation (95%) of the starting complex 1.  The results show that complex 1 is a valuable catalyst with promising properties for further applications in a biomimetic approach toward mimicking oxygenation reactions of cytochrome P 450.