Recent Advances in Selective C-H Bonds Functionalization through Aryl Radical Mediated Hydrogen Atom Transfer Strategy

Selective C-H bond functionalization of organic molecules has developed as an increasingly versatile platform that found wide applications in the synthesis of naturally occurring compounds, functional group modification, material sciences, and chemical and pharmaceutical industries. Apart from transition metal catalysis, which traditionally underwent a two-electron mechanism, a recent renascence of radical chemistry based on the hydrogen atom transfer (HAT) strategy has resulted in the rapid development of C-H bond functionalization. While many methodologies involving heteroatom-based HAT have been widely studied during the last decade, areas employing their carbon analogs were still challenging for chemists and remained less explored. Recent progress has been made to generate aryl radical species under relatively mild conditions, which can be utilized in the HAT step conveniently, and as a result, motivated the advancements of remote C(sp³)-H functionalization of various organic compounds, including amines, alcohols, amides and so on. This review will discuss the recent progresses in the functionalization of C-H bonds characterized by a key aryl HAT process, and, at the same time, some emphases have been laid on selective C-H functionalization catalyzed by photoredox chemistry.