Iron Catalysis of C(sp³)–H Azidation Using a Heteroarene Radical Cation Strategy

The Fe^III(phen)₃ catalysis of the benzylic C(sp³)–H azidation of indoles has been investigated. The Fe(III) complex can selectively oxidize indoles to form arene radical cations, which are transformed into benzylic C(sp³) radical intermediates. This strategy exhibits a difference in reactivity between N-heteroarenes and benzene, which is difficult to achieve via direct hydrogen abstraction approaches. Various biorelevant azide precursors were constructed, highlighting the utility of this mild first-row transition-metal catalyst system.