A catalytic system is discovered for the intramolecular C–H amidation of N-phenoxy acetamide derivatives. Herein, a cobalt catalyst has been employed for the olefin-mediated ortho C–H functionalization. Moreover, a monocyclic olefin, maleimide, has been used as a transient mediator instead of well-established bicyclic norbornenes. Maleimide promotes a Co(III) intermediate to undergo oxidative addition into the O–N bond to form a Co(V) nitrene species and subsequently directs nitrene addition to the ortho position. Mechanistic study and density functional theory (DFT) study support the proposed mechanism. The products derived from this methodology have been demonstrated as a ligand in the C–H olefination reaction. Furthermore, the synthetic utility of this methodology was demonstrated via the ortho-amidation of estrone.