Formation of CC-type palladacycles with assistance from an apparently innocent NH(CO) functional group.

A novel cyclometalation pathway to form CC-type palladacycles is reported. Unlike common donor-assisted cyclometalation, the NH(CO) auxiliary group undergoes a deprotonation step to form a palladalactam intermediate. The coordinating nitrogen atom functions as an intramolecular base promoting selective C-H bond cleavage. Without the NH proton, the ortho-N-phenyl C-H is activated instead.