Advances and developments in transition metal-free benzylic C(sp3)–H activation/functionalization reactions

Abstract

Transition metal-free C(sp³)–H activation of toluene derivatives is known as a green and sustainable methodology for constructing carbon–carbon and carbon–heteroatom bonds. Benzylic C(sp³)–H activation/functionalization bond formation can be carried out in the presence of organic/inorganic peroxides, bases, acids, and other radical initiators. These radical transformations also occur under photochemical and electrochemical conditions. In this review, we highlight the C–H activation/annulation or C–H activation/functionalization reactions of benzylic carbon atoms in the presence of non-metal catalysts or promoters or without any catalyst.