Cyclodextrin host as a supramolecular catalyst in nonpolar solvents: stereoselective synthesis of (E)-3-alkylideneoxindoles

Heptakis(6-O-triisopropylsilyl)-β-cyclodextrin (TIPS-β-CD) effectively formed inclusion complexes with oxindole and its derivatives as guests in nonpolar solvents. Their inclusion complex formation was remarkably affected by the position and size of substituents on the oxindole ring of the guest. The Knoevenagel condensation reaction of these oxindoles with cinnamaldehyde to give 3-alkylideneoxindoles was accelerated with enhanced E/Z selectivities in the presence of catalytic amounts of TIPS-β-CD.