Recent Advances in Photoinduced Amidyl Radical-Mediated Remote C(sp3)–H Activation via 1,5-Hydrogen Atom Transfer

C-H bonds are widely present in organic molecules and play a crucial role in chemical diversification. Among them, the functionalization of unactivated C(sp3)-H bonds is highly challenging. The 1,5-hydrogen atom transfer (1,5-HAT) strategy offers an avenue for the functionalization of remote inert C-H bonds with excellent regioselectivity and chemoselectivity. This review looks back at the history and mechanism of the Hofmann-Löffler-Freytag (HLF) reaction and highlights the recent advances in the functionalization of remote inert C(sp3)-H bonds triggered by nitrogen-centered radicals (NCRs) via photoinduced 1,5-hydrogen atom transfer processes.