The aminoarylation reaction of N-allylureas under oxidative palladium catalysis, in the absence of ligands and by using inexpensive H2O2 as the sole oxidant, occurs in a chemo- and regioselective fashion. This intramolecular process takes place via a 5-exo-trig cyclization, and represents an easy approach to 4-arylmethyl imidazolidinones.