Oxoiron(IV) porphyrin π-cation radical complexes with a chameleon behavior in cytochrome P450 model reactions

Ju Song Woon, Ok Ryu Yon, Rita Song, Wonwoo Nam

Research output: Contribution to journalArticlepeer-review

146 Scopus citations

Abstract

There is an intriguing, current controversy on the involvement of multiple oxidizing species in oxygen transfer reactions by cytochromes P450 and iron porphyrin complexes. The primary evidence for the "multiple oxidants" theory was that products and/or product distributions obtained in the catalytic oxygenations were different depending on reaction conditions such as catalysts, oxidants, and solvents. In the present work, we carried out detailed mechanistic studies on competitive olefin epoxidation, alkane hydroxylation, and C=C epoxidation versus allylic C-H hydroxylation in olefin oxygenation with in situ generated oxoiron(IV) porphyrin π-cation radicals (1) under various reaction conditions. We found that the products and product distributions were markedly different depending on the reaction conditions. For example, 1 bearing different axial ligands showed different product selectivities in competitive epoxidations of cis-olefins and trans-olefins and of styrene and para-substituted styrenes. The hydroxylation of ethylbenzene by 1 afforded different products, such as 1-phenylethanol and ethylbenzoquinone, depending on the axial ligands of 1 and substrates. Moreover, the regioselectivity of C=C epoxidation versus C-H hydroxylation in the oxygenation of cyclohexene by 1 changed dramatically depending on the reaction temperatures, the electronic nature of the iron porphyrins, and substrates. These results demonstrate that 1 can exhibit diverse reactivity patterns under different reaction conditions, leading us to propose that the different products and/or product distributions observed in the catalytic oxygenation reactions by iron porphyrin models might not arise from the involvement of multiple oxidizing species but from 1 under different circumstances. This study provides strong evidence that 1 can behave like a "chameleon oxidant" that changes its reactivity and selectivity under the influence of environmental changes.

Original languageEnglish
Pages (from-to)294-304
Number of pages11
JournalJournal of Biological Inorganic Chemistry
Volume10
Issue number3
DOIs
StatePublished - May 2005

Keywords

  • Compound I
  • Cytochrome P450
  • Iron porphyrin
  • Multiple oxidants
  • Oxygenation

Fingerprint

Dive into the research topics of 'Oxoiron(IV) porphyrin π-cation radical complexes with a chameleon behavior in cytochrome P450 model reactions'. Together they form a unique fingerprint.

Cite this