Sulfobutyl ether-β-cyclodextrins:: Promising supramolecular carriers for aqueous organometallic catalysis

The potentialities of sulfobutyl ether-beta-CDs derivatives as supramolecular carrier in a biphasic Tsuji-Trost reaction catalyzed by a water-soluble palladium complex of trisulfonated triphenylphosphine have been investigated. The efficiency of these cyclodextrins (CDs) strongly depends on the average molar substitution degree of cyclodextrin and the highest rate enhancements were obtained with cyclodextrins containing about 7 sulfobutyl ether groups. This result was attributed to the absence of a strong interaction between this cyclodextrin and the trisulfonated triphenylphosphine used to dissolve the catalyst in the aqueous phase and to the presence of an extended hydrophobic cavity allowing a better molecular recognition between the substrate and the cyclodextrin. This constitutes the first example of a non-interacting beta-cyclodextrin/phosphine couple with high catalytic activities.