Catalytic Reaction Mechanism for Hydroxylation of Benzene to Phenol with H2O2/O2 as Oxidants

Activation of C-H bond is one of the most important scientific topics in organic synthesis area. Hydroxylation of benzene to phenol with environmentally friendly oxidants like H2O2 and O-2 is a challenge in this filed for tens of years, since it involves not only the fundamental issue of the C-sp2-H bond activation for benzene, but also other issues such as the activation of H2O2/O-2, decomposition of H2O2, and deep oxidation of phenol product. More importantly, in the context of green chemical industry , this green process becomes more attractive due to the promising alternative to replace the current cumene route. In this review, recent researches on metal-based catalysts and newly emerging non-metal catalysts are summarized, clued by the catalytic reaction mechanism of hydroxylation of benzene to phenol. The structure-activity relationship between catalysts' composition and structure with their reactive activity and selectivity is analyzed in detail based on radical and non-radical mechanisms. Outlook and suggestions on the further development of rational design of catalysts and deeper insights into reaction mechanism in this field are proposed. This review is hopefully to benefit the exploring of novel catalysts with higher activity and better stability for hydroxylation of benzene to phenol.