The dual function of the N À Fb ond as an effective oxidant and subsequent nitrogen source in intramolecular aliphatic C À Hfunctionalization reactions is explored. Copper catalysis is demonstrated to exercise full regio-and chemoselectivity control, whicho pens new synthetic avenues to nitrogenated heterocycles with predictable ring sizes.F or the first time,auniform catalysis manifold has been identified for the construction of both pyrrolidine and piperidine cores.The individual steps of this new copper oxidation catalysis were elucidated by control experiments and computational studies, clarifying the singularity of the NÀFf unction and characterizing the catalytic cycle to be based on acopper(I/II) manifold.