Methods for selective benzylic C-H oxofunctionalization of organic compounds

The development of methods for the selective oxidation of C-H groups of organic compounds resulting in the formation of C-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 C-H groups having a relatively weak C-H bond (the homolytic dissociation energy is ≈80-90 kcal/mol) differ from the methods used for the oxidation of aliphatic and aromatic C-H groups with stronger C-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.