EPOXIDATION REACTIONS CATALYZED BY IRON PORPHYRINS. OXYGEN TRANSFER FROM IODOSYLBENZENE.

Article abstract of DOI:10.1021/ja00356a015

The epoxidation of olefins by iodosylbenzene is catalyzed by synthetic iron porphyrins. With (chloro-5, 10, 15, 20 -tetraphenylporphyrinato) iron(III) (FeTPPCl), cyclohexadiene oxide was produced in 93% yield and with (chloro-5, 10, 15, 20-tetra-o-tolyporphyrinato) iron (III) (FeTTPCl), cycloctene oxide was produced in 84% yield. Cis olefins were found to be more reactive than trans olefins. Thus, whereas cis-stilbene was epoxidized by FeTPPCl/iodosylbenzene in 77% yield, trans-stilbene was unreactive under these conditions. The degree of cis/trans selectivity was a sensitive function of substitution of the porphyrin periphery. With (chloro-5, 10, 15, 20-tetramesitylporphyrinato)iron(III), the relative reactivity of cis-and trans-cyclododecene was 8. 92:1. Similarly, the less reactive cis double bond of trans, trans, cis-cyclododecatriene could be selectively epoxidized by this catalyst. Trans 1,2-disubstituted double bonds showed similar reactivities. These results suggest an approach of the double bond from the side of iron-bound oxygen and parallel to the prophyrin plane. A mechanism involving formation of an oxygen transfer from a reactive iron-oxo intermediate is proposed for this reaction.