Three-component systems containing Pd(OAc)(2), Al2O3, and an IL (IL= ionic liquid) were applied in the Heck arylation of cyclohexene. The highest productivity and selectivity to 4-phenylcyclohexene was noted in reaction catalyzed by Pd/Al2O3 in the presence of a small amount of an IL, dimethyldidode-cylammonium lactate (C). The addition of Al2O3 alone to the reaction catalyzed by soluble precursors, PdCl2(PhCN)(2) or Pd(OAc)(2) and IL, remarkably increased conversion to 4-phenylcyclohexene. Hg(0) inhibited the reaction catalyzed by Pd/Al2O3 by formation of Pd-Hg amalgam immobilized on Al2O3. SEM/EDX studies of Pd/Al2O3 performed after treatment with Hg(0) showed that the IL modified the surface properties of Pd/Al2O3. (C) 2015 Elsevier B.V. All rights reserved.