The effect of Al2O3 and ionic liquids in palladium catalyzed arylation of cyclohexene. Interaction of Hg(0) with immobilized palladium

• Pd/Al2O3, modified with ionic liquid, efficiently catalyzes formation of 4-phenylcyclohexene.
• The addition of Al2O3 to the homogeneous catalytic system remarkably increased the yield of product.
• Hg(0) added to the Heck reaction mixture forms Pd-Hg amalgam immobilized on Al2O3.
• Ionic liquids changed the surface properties of Pd/Al2O3.

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, dimethyldidodecylammonium 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.

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