High selectivity toward cyclohexanol in oxidation of cyclohexane using manganese aminophenylporphyrins as catalysts

This work reports that the cyclohexane oxidation by iodosylbenzene and iodobenzene diacetate yields cyclohexanol as the sole product if catalyzed by the simple Mn(III) aminophenylporphyrins 5,10,15,20-tetrakis(2-aminophenyl)porphyrinatomanganese(III) chloride (Mn(III)(T2APP)Cl) and 5,10,15,20-tetrakis(4-aminophenyl)porphyrinatomanganese(III) chloride (Mn(III)(T4APP)Cl). This high selectivity was unmatched by other simple phenyl-substituted Mn(III) meso-tetraphenylporphyin-based catalysts (Mn(III)(T-X-PP)Cl, where X = H, 4-OMe, 4-Me, 4-CO2Me, 2-Me), which led to a mixture of both cyclohexanol and cyclohexanone. The absence of cyclohexanone in the Mn(III)(T2APP)Cl and Mn(III)(T4APP)Cl as well as the possibility of re-use of the catalysts was investigated. An intermolecular coordination of the amino moieties in Mn(III)(T2APP)Cl and Mn(III)(T4APP)Cl is suggested to play a role in the high selectivity of these systems.

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► Mn(III) aminophenylporphyrins catalyze selectively the cyclohexane oxidation.
► There is an exclusive formation of Cy-ol in these aminophenylporphyrin systems.
► It has been proposed that the porphyrin –NH2 moieties may act as axial ligands.