Selective Heck Arylation of Cyclohexene with Homogeneous and Heterogeneous Palladium Catalysts

Palladium catalysts containing Pd(II) supported on Al(2)O(3) and alumina-based mixed oxides, Al(2)O(3)-ZrO(2), Al(2)O(3)-CeO(2), and Al(2)O(3)-Fe(2)O(3), are very effective in the Heck coupling of iodobenzene with cyclohexene in DMF solution. The best results, up to 81% of monoarylated products with a selectivity to 4-phenylcyclohexene (3) close to 90% were obtained with KOH as a base. The catalytic activity of palladium supported on alumina-based oxides was compared with that of homogeneous precursors, such as Pd(OAc)(2) and PdCl(2)(PhCN)(2), used in [Bu(4)N]Br as the reaction medium. Under such conditions homogeneous systems were more selective and produced up to 60% of monoarylated products with a selectivity to 3 close to 60%.