Subsequently, we investigated the possibility of cascade radical 1,2-N-shift/bromination, chlorination, and selenation in the presence of radical sources, including BrCCl3, TsCl, and (PhSe)2 (Table ). These results show that bromination, chlorination, and selenation proceeded smoothly over the afore-mentioned C-H cyclization. Notably, the variation from L1 to 4,4'-dimethoxy-2,2'-bipyridine (L6) was observed to be beneficial for the cascade 1,2-N migration/substitution reaction. In the presence of BrCCl3, a series of α-amino-β-bromocarboxylic acid esters smoothly underwent a radical 1,2-N-shift/bromination sequence under the optimal conditions, which effectively realized the N/Br-exchange to yield various β-amino-α-bromocarboxylic acid esters in moderate yields with trans-stereoselectivity (3a-3h). Moreover, the configuration of product 3a was unambiguously confirmed by X-ray crystallography. Additionally, the resulting α-bromocarboxylic acid esters can function as cross-coupling electrophiles to construct complex and valuable β-amino acid motifs. As expected, TsCl proved to be an efficient XAT (halogen atom transfer) reagent to terminate radical cascades, thereby affording the corresponding chlorinated β-amino acid ester (3i). In addition, (PhSe)2 can also function as a viable radical terminator in this reaction, thereby yielding selenated β-amino acids (3j and 3k).