C−H Bond Activation Relay (CHAR) of Proline Ester Derivatives Promoted by In Situ Triarylamine Radical Cation: Selective Synthesis of 4‐Bromopyrrole Derivatives

Abstract

Using the in situ generated triarylamine radical cation as an initiator, the sp 3 CÀ H bond of proline esters was smoothly oxidized and brominated through CÀ H activation relay (CHAR), giving a series of 4-bromopyrroles in good yields with high regioselectivity. The mechanistic study revealed that the oxidation of the active CÀ H bond initiated the followed 1,5-HAT and bromination, which provides a new method to realize the functionalization of the remote CÀ H bond.