Copper‐Catalyzed C(sp3)−H Amidation: Sterically Driven Primary and Secondary C−H Site‐Selectivity

Undirected C(sp³)?H functionalization reactions often follow site‐selectivity patterns that mirror the corresponding C?H bond dissociation energies (BDEs). This often results in the functionalization of weaker tertiary C?H bonds in the presence of stronger secondary and primary bonds. An important, contemporary challenge is the development of catalyst systems capable of selectively functionalizing stronger primary and secondary C?H bonds over tertiary and benzylic C?H sites. Herein, we report a Cu catalyst that exhibits a high degree of primary and secondary over tertiary C?H bond selectivity in the amidation of linear and cyclic hydrocarbons with aroyl azides ArC(O)N₃. Mechanistic and DFT studies indicate that C?H amidation involves H‐atom abstraction from R‐H substrates by nitrene intermediates Cu](κ²‐N,O‐NC(O)Ar) to provide carbon‐based radicals R^. and copper(II)amide intermediates Cu^II]‐NHC(O)Ar that subsequently capture radicals R^. to form products R‐NHC(O)Ar. These studies reveal important catalyst features required to achieve primary and secondary C?H amidation selectivity in the absence of directing groups.