The introduction of chlorine atoms into organic molecules is fundamental to the manufacture of industrial chemicals, the elaboration of advanced synthetic intermediates and also the fine-tuning of physicochemical and biological properties of drugs, agrochemicals and polymers. We report here a general and practical photochemical strategy enabling the site-selective chlorination of sp3 C-H bonds. This process exploits the ability of protonated N-chloroamines to serve as aminium radical precursors and also radical chlorinating agents. Upon photochemical initiation, an efficient radical-chain propagation is established allowing the functionalization of a broad range of substrates due to the large number of compatible functionalities. The ability to synergistically maximize both polar and steric effects in the H-atom transfer transition state through appropriate selection of the aminium radical has provided the highest known selectivity in radical sp3 C-H chlorination.
Keywords: C−H functionalization; H-atom transfer; aminium radical; chlorination; late-stage functionalization.
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