An efficient vicinal double allylation of activated alkenes by allyl acetates and allylstannanes catalyzed by palladium nanoparticles, generated in situ from palladium(II) chloride, has been demonstrated. Several activated alkenes produce functionalized 1,7-octadiene derivatives in one pot. The additions of substituted allyl acetates are highly regioselective. The Grubbs cyclization of octadiene derivatives gives an easy access to stereodefined substituted cyclohexene derivatives.