Arylamines constitute the core structure of many therapeutic agents, agrochemicals and organic materials. The development of methodologies for the efficient and selective construction of these structural motifs from simple building blocks is desirable but still challenging. Here, we demonstrate that protonated electron poor O-aryl hydroxylamines lead, in the presence of Ru(bpy)3Cl2, to the formation of aminium radicals. These highly electrophilic species undergo polarized radical addition to aromatics in high yield and selectivity. We have successfully applied this methodology to the late-stage modification of chiral catalyst templates, therapeutic agents and natural products.