Cyclodextrin/Amphiphilic Phosphane Mixed Systems and their Applications in Aqueous Organometallic Catalysis

When mixed with a water-soluble phosphane capable of self-assembling into micelles, native or modified β-cyclodextrins (β-CDs) show very contrasting behavior depending on their neutral or ionic nature. In the post-micellar region, neutral β-CDs led to a micelle destructuring. Conversely, micelles remained stable over a well-defined range of ionic β-CD concentrations. In that case, the micelle destruction was only observed when using a large excess of ionic β-CDs. The catalytic performances of these micellar systems have been evaluated in a rhodium-catalyzed hydroformylation reaction of 1-decene. We showed that, using ionic β-CDs, the catalytic activity could be improved without a detrimental impact upon the regioselectivity. A linear/branched aldehyde ratio as high as 8.6 could be achieved. The best results were obtained with stoichiometric quantities of ionic randomly methylated β-CDs with respect to the phosphane with a beneficial effect on the decantation at the end of the reaction.