We report here on the interaction of a-cyclodextrin, b-cyclodextrin, g-cyclodextrin and hydroxipropyl-b-cyclodextrin with FeBr3, which led to a stable and very easy to handle complex. These complexes catalyze the oxidation of sulfides very efficiently.
It can be concluded that complexes of FeBr3 with Cyclodextrins can be prepared by a novel two-phase system. To the best of our knowledge, there are not previous reports of formation of complexes from solid cyclodextrin and the guest dissolved in an organic solvent were the cyclodextrin is non soluble. They are very stable to oxygen and humidity so they can be stored and handled without any special care.
The complexes can be used as catalyst in the oxidation reaction of sulfides in the same way as FeBr3, with the possibility to induce enantiselectivity
In the presence of cyclodextrin, when the molar ratio of b-CD/FeBr3 was higher than 3, no precipitation was observed after 96 hours. This is evidence that even in water cyclodextrin can compete with OH to coordinate the metal and that it stabilizes the metal in water solution.