Fine tuning of sulfoalkylated cyclodextrin structures to improve their mass-transfer properties in an aqueous biphasic hydroformylation reaction

The structure of sulfoalkylated cyclodextrins (CDs) have been varied and optimised to improve their performances as mass-transfer promoters in an aqueous biphasic hydroformylation reaction. Their surface tensions have been measured using the Wilhelmy plate technique and compared. Their behaviour towards two hydrosoluble derivatives of triphenylphosphine has been evaluated by 31P{1H} and 1H NMR measurements and their catalytic activity has been assessed in a rhodium-catalyzed hydroformylation reaction of 1-decene. The best result was obtained using a β-CD sulfobutylated on the primary face and methylated on the secondary face. Indeed, this CD increased the reaction rate by a factor of 250 without inducing selectivity decrease. The accessibility to the secondary face of the CD appears to be determining in the catalytic process as it governs the approach between the CD-included substrate and the water-soluble catalyst. The impact of the nature of the CD substituents on the chemo- and regioselectivity of the reaction is also discussed.

A β-cyclodextrin sulfobutylated on its primary face and methylated on its secondary face was found to be the best cyclodextrin ever used as mass-transfer promoter in a biphasic rhodium-catalyzed hydroformylation reaction. The surface-active properties and the accessibility to the CD cavity appear to be the key parameters to explain the efficiency of this cyclodextrin. Figure optionsDownload as PowerPoint slide