Backbone-Enabled and Ester Groups Switched δ‑C(sp2)–H Amination/Fluorination: Cyclic Dipeptides Synthesis

An efficient and concise strategy for the synthesis of cyclic dipeptides via Pd-catalyzed site-selective δ-C­(sp2)–H amination/fluorination and N-to-C cyclization is disclosed. The backbone amides within the dipeptides serves as endogenous directing groups, while the desired products were switched by the C-terminal ester group. This chemistry presents a novel and robust alternative to construct cyclodipeptide fragments.