Methods for selective benzylic $\mathrm{C}$–$\mathrm{H}$ oxofunctionalization of organic compounds

The development of methods for the selective oxidation of $\mathrm{C}$–$\mathrm{H}$ groups of organic compounds resulting in the formation of $\mathrm{C}$–$\mathrm{O}$ bonds is a challenging problem in modern synthetic organic chemistry. Versatile methods for oxofunctionalization of these groups are currently lacking. Approaches for the oxidation of benzylic $\mathrm{C}$–$\mathrm{H}$ groups having a relatively weak $\mathrm{C}$–$\mathrm{H}$ bond (the homolytic dissociation energy is $\sim80$–$90$ kcal/mol) differ from the methods used for the oxidation of aliphatic and aromatic $\mathrm{C}$–$\mathrm{H}$ groups with stronger $\mathrm{C}$–$\mathrm{H}$ bonds. The review summarizes homogeneous catalytic and non-catalytic methods for the selective oxofunctionalization of benzylic groups of organic compounds developed in the past $40$ years. Reactions involving various oxidizing agents in the presence or in the absence of transition metal compounds are considered. Putative mechanisms of selected transformations are discussed, with a particular focus on selective oxidation of various substrates. The bibliography includes 278 references.