A novel catalyst system of Pd (OAc) 2–HFIP induces double-bond migration of allylbenzenes under mild conditions with low catalytic loading to afford 1-propenylbenzenes. The reaction shows a unique substituent effect that is highly dependent on the distance of substituents from the allylic moiety. Thus, the reactivity of substrates bearing a methyl group is ordered in para> meta> ortho, whereas it is entirely reversed as ortho> meta> para for methoxy and ...