Favoring alkene insertion over beta-hydride elimination: Aqueous media and ligands enable a double Heck reaction on a substrate for which beta-hydride elimination is possible

Under Pd-0 catalysis, the (iodoaryl)diene N-methyl-N-(1,5-hexadiene-3-yl)-2-iodobe acid amide (6) would normally be expected to give monocyclized product from initial oxidative addition of the C-I bond, followed by insertion of one alkene function and beta-hydride elimination. Conditions were sought to favor insertion of the second alkene unit over beta-hydride elimination, so as to increase the yield of polycyclic products. In fact, the use of phenanthroline ligand and aqueous media in reactions of 6 increased the total yield of expected tricyclic products (11-13) to 52%. Three other products (14-16) appear to be derived from an unusual rearrangement. By a process of elimination, control experiments point to the possibility of a chelation-assisted Pd-catalyzed Cope rearrangement in the formation of these unexpected products.