Tris(4-bromophenyl)aminium Hexachloroantimonate as a “Waste-Utilized”-Type Initiator-Promoted C–H Chlorination via C–H Activation Relay: Synthesis of Chlorinated Pyrroles

Using tris­(4-bromophenyl)­aminium hexachloroantimonate as a “waste-utilized”-type initiator, the aerobic oxidation of the sp3 C–H bond of proline esters was realized via C–H activation relay, giving a series of halogenated pyrroles in high yields. The mechanistic study revealed that the counterion, SbCl6 –, was involved in the radical chlorination process, which provides a new way to understand the role of the counterions.