Model systems for cytochrome P450 dependent mono-oxygenases. Part 1. Oxidation of alkenes and aromatic compounds by tetraphenylporphinatoiron(III) chloride and lodosylbenzene

Abstract

A selection of aliphatic alkenes, substituted styrenes, and cis- and trans-stilbene have been epoxidised with tetraphenylporphinatoiron(III) chloride and iodosylbenzene, a model system for the cytochrome P450 dependent mono-oxygenases. The epoxidations are stereospecifically syn and the reactivities of the alkenes show that cis-alkenes are more reactive than their trans-isomers and that electron-releasing substituents favour the reaction. A Hammett ρ value of –0.93 is obtained from the epoxidation of the substituted styrenes. Three polycyclic hydrocarbons, phenanthrene, acenaphthylene, and pyrene, are epoxidised in low yield. The model system hydroxylates anisole and naphthalene but is insufficiently reactive to oxidise benzene; with toluene, side-chain oxidation but no ring hydroxylation occurs. The mechanisms of these oxidations and the nature of the reactive species are discussed.