Hydrocarboxylation of 1-(4-isobutylphenyl) ethanol catalyzed by heterogeneous palladium catalysts

Heterogeneous palladium catalysts were employed for the synthesis of 2-(4-isobutylphenyl) propionic acid (ibuprofen) by carbonylating 1-(4-isobutylphenyl) ethanol (IBPE) with carbon monoxide and water, Among the supported palladium catalysts tested, palladium anchored on montmorillonite showed good activity for the carbonylation and good selectivity to ibuprofen. For the palladium/montmorillonite catalyst, the presence of triphenylphosphine and hydrogen chloride in the reaction solution was essential for its catalytic activity even if triphenylphosphine and chloride ion had already been coordinated to the palladium precursor. The effects of reaction variables on the heterogeneous carbonylation have been investigated for the regiospecific synthesis of ibuprofen, and it was revealed that the palladium/montmorillonite showed better selectivity to ibuprofen than the homogeneous counterpart. This heterogeneous catalyst recovered by filtration after a batch of the reaction showed activity similar to that of the fresh catalyst for a new batch of reaction. Furthermore, the filtrate without the solid catalyst did not show any carbonylation activity. These implied that dissolution of palladium component from the solid catalyst had not been serious. (C) 1999 Elsevier Science B.V. All rights reserved.