Mechanism of Hemin-Catalyzed Epoxidations: Electron Transfer from Alkenes

Article abstract of DOI:10.1021/ja00243a033

Two rearrangements of alkenes, known to proceed through the intermediacy of the alkene cation radical, have been observed to accompany the hemin-catalyzed epoxidations of these alkenes.Hexamethyl(Dewar benzene) partially rearranged to hexamethylbenzene during its epoxidation using (tetraphenylporphyrinato)iron(III) chloride and m-chloroperbenzoic acid, but not with either of the reagents separately.In a similar manner the diene, 1,4,4a,5,8,8a-hexahydro-1,4,5,8-endo,endo-dimethanonaphthalene, closed to the known "birdcage hydrocarbon" under these conditions.This diene also brought about some N-alkylation of the catalyst during the reaction.These observations are interpreted in terms of an electron transfer from alkene to the high-valent iron intermediate, leading to both rearrangement and epoxidation.