(Chemical Equation Presented) The reaction of piperdin-2-ones with a 2-bromobenzyl substituent in the 5-position in the presence of a palladium catalyst leads to biaryl compounds. Their formation can be explained via initial C-H insertion of the aryl palladium species into the allylic C-H bond of the piperidinone. This eventually leads to a metallacycle containing Pd(II) that inserts another aryl bromide, promoting the formation of the biaryl bond. © 2008 American Chemical Society.