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Keywords:

  • Diels[BOND]Alder reaction;
  • Bis(dihydrooxazole) ligands;
  • Fluorous reversed-phase silica gel;
  • Immobilization;
  • Enantioselective synthesis;
  • Fluorine compounds;
  • Catalysis;
  • Copper complexes

Abstract

The three different perfluoroalkyl-tagged bis(dihydrooxazole)copper complexes 1921 were synthesized and immobilized noncovalently on fluorous reversed-phase silica gel (FRPSG) by fluorous[BOND]fluorous interactions (Schemes 2 and 3). These supported catalysts were successfully applied to asymmetric Diels[BOND]Alder reactions in H2O and in CH2Cl2 (Scheme 4). Besides high conversion of the dienophile, we observed enantiomer excesses of up to 88% in H2O and 97% in CH2Cl2, and we were able to recover and re-use these catalytic systems several times. Despite the relatively high catalyst loading, the leaching of copper was remarkably low ranging from 2.4 to 5.9 ppm.