ALLYLIC OXIDATION AND EPOXIDATION OF CYCLOALKENES BY IODOSYLBENZENE CATALYZED BY IRON(III) AND MANGANESE(III) TETRA(DICHLOROPHENYL)PORPHYRIN - THE MARKED INFLUENCE OF RING SIZE ON THE RATE OF ALLYLIC OXIDATION

Five cis-cycloalkenes, with ring sizes 5, 6, 7, 8 and 10, and a cis-tr ans mixture of cyclododecene have been oxidised by iodosylbenzene usin g iron(III) or manganese(III) tetra(2,6-dichlorophenyl)porphyrin as ca talysts, Both catalysts give very similar product distributions, altho ugh the reactions with the manganese porphyrin are sensitive to the pr esence of dioxygen whilst those with the iron porphyrin. are not. With all the substrates the dominant or sole reaction is epoxidation. Howe ver, with cyclopentene, cyclohexene and cyclododecene a significant am ount of allylic oxidation also occurs. The dependence of the product d istribution on the structure of the cycloalkene is discussed and attri buted to the sensitivity of allylic oxidation rather than epoxidation to changes in ring size.