FeBr3-cyclodextrin complexes as efficient and chemoselective catalysts for sulfoxidation reactions

Complexes of FeBr3 with alpha-cyclodextrin (alpha-CD-Fe), hydroxypropyl-beta-cyclodextrin (HPCD-Fe) and gamma-cyclodextrin (gamma-CD-Fe) were prepared from the interaction of the salt dissolved in CH2O2 and solid cyclodextrins, and analyzed by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), infrared spectroscopy (IR) and elemental analysis. These complexes were used as catalysts in the oxidation reactions of sulfides to sulfoxides giving good yields and a high chemoselectivity. The solid complexes can be used several times and in the case of the gamma-CD-Fe complex after five cycles the yield decreased only 5% (from 85 to 80%). (C) 2004 Elsevier B.V. All rights reserved.