Unexpected high oxidation of cyclohexane by Fe salts and dihydrogen peroxide in acetonitrile

The reaction of cyclohexane (CyH) with 1.5 equivalent of dihydrogen peroxide (30% aqueous solution) in the presence of 1 mol% of an iron(II) or iron(III) salt (without added ligand), at 50 °C in acetonitrile, produces cyclohexanol (CyOH) and cyclohexanone (CyO) in high yields (up to 87% of CyH is converted to CyOH + CyO). Remarkably, CyH is totally converted within 2 h in the presence of Fe(ClO4)2 as catalyst under argon, producing 45% of CyOH and 42% of CyO. The addition of a tridentate Schiff-base ligand, namely 2,6-bis-[1-(benzylimino)ethyl]pyridine (dapb), leads to a clear increase of the selectivity towards CyOH + CyO, which are obtained with an overall yield of 93% (and even 100% selectivity to CyOH and CyO) in the case of the [Fe(ClO4)3/dapb] catalytic system.

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