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 sp 3 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, SbCl 6 - , was involved in the radical chlorination process, which provides a new way to understand the role of the counterions.