Definition of the Problem and First Attempts

The direct oxidation of benzene to phenol is usually affected by a poor selectivity due to the lack of kinetic control. Indeed, phenol is more reactive towards oxidation than benzene itself and consecutive reactions occur, with substantial formation of overoxidized products like catechol, hydroquinone, benzoquinones and tars. This is the usual output of the oxidation of aromatic hydrocarbons by the classical Fenton system, a mixture of hydrogen peroxide and an iron(II) salt, usually ferrous sulfate, most often used in stoichiometric amounts [8]. 

to obtain a selective synthesis of phenol via direct oxidation of benzene, suitable strategies have to be envisaged to slow dovm the undesired consecutive reactions and to allow phenol to accumulate. The first step in this direction was made by George Olah, who used extremely concentrated (98%) hydrogen peroxide in a 

A few years later, Hubert Mimoun discovered the rather selective oxidation of benzene by a few vanadium(V) peroxo complexes [10], Using an excess of hydrogen peroxide under phase-transfer conditions transformed this stoichiometric reaction into a true catalytic process, but the turnover numbers remained very low [11]. 

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