Visible‐Light‐Promoted Aliphatic C−H Chlorination and Bromination Using Haloform as the Halogen Donor and Azidobenziodoxole as the Mediator

Abstract An azidobenziodoxole (BIN 3 )‐mediated tunable radical reaction system for selective chlorination and bromination of tertiary and secondary C( sp 3 )−H bonds of alkyl substrates using haloform as the halogen donor was developed. Reactions of various substrates with BIN 3 under visible light irradiation without any photo or metal catalysts gave C−H chlorinated or brominated products. These reactions are selective, and compatible with many functional groups. Mechanistic studies suggest that haloform serves as the halogen atom donor and HN 3 generated in situ from the reaction of BIN 3 and water relays the radical chain reaction as the hydrogen atom donor. HN 3 reacts with CHX 2 ⋅ to form CH 2 X 2 and N 3 ⋅, which propagates a radical chain by abstracting a hydrogen atom of the alkane substrate.