Cleavage of water-insoluble alkylallylcarbonates catalysed by a palladium/TPPTS/cyclodextrin system: effect of phosphine/cyclodextrin interactions on the reaction rate

An astonishing aspect of the aqueous organometallic catalysis assisted by randomly methylated p-cyclodextrin (RAME-beta-CD) has been elucidated. Actually, it has been shown that the molecular recognition ability of RAME-beta-CD towards the TPPTS ligand was responsible for a decrease in the rate of a palladium catalysed cleavage reaction of the water-insoluble allylundecylcarbonate. Indeed, when the TPPTS/RAME-beta-CD ratio is too high, the cyclodextrin is poisoned by the ligand and the substrate transfer is diminished. Thus, the use of RAME-beta-CD as an inverse phase transfer catalyst in palladium/TPPTS catalytic system has to be accurately controlled. On the contrary, randomly methylated alpha-cyclodextrin (RAME-alpha-CD) which is not able to associate to TPPTS led to better performances since no decrease in the activity was observed with this cyclodextrin. NMR experiments have been performed throughout this study to substantiate the catalytic results. (C) 2004 Elsevier B.V. All rights reserved.