Selective heck arylation of cyclohexene with homogeneous and heterogeneous palladium catalysts

Abstract

Palladium catalysts containing Pd(II) supported on Al2O 3 and alumina-based mixed oxides, Al2O3- ZrO2, Al2O3-CeO2, and Al 2O3-Fe2O3, 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 aluminabased oxides was compared with that of homogeneous precursors, such as Pd(OAc)2 and PdCl 2(PhCN)2, used in [Bu4N]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%. Copyright © 2010 by the authors.