Greener Oxidation Reactions Using Catalysis with Organic Ligands from Renewble Sources

LAURA I. ROSSI*

Venecia, Italia

Congreso; 10th Summer School on Green Chemistry; 2008

Consorzio Interuniversitario " La Chimica per l´Ambiente " (INCA)

Greener oxidation reactions using catalysts with organic ligands from renewable sources Laura Isabel Rossi Instituto de Investigaciones en Físico Química de Córdoba (INFIQC), Departamento de Química Orgánica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria. 5000 Córdoba, Argentina. e-mail: lauraros@dqo.fcq.unc.edu.ar. The physical and chemical properties of FeBr3 such as high hygroscopicity and thermal instability are well known.1 On the other hand, ferric salts and other transition metals form complexes with DMSO.2 For instance, it is known that a complex such as [(FeBr3)2(DMSO)3] is not only more stable and easier to handle than FeBr3, but also has properties similar to a catalyst in oxidation reactions.3 The complex also was shown to be more effective in aromatic brominations.4 The preparation of complexes of FeBr3 with chiral ligands is of interest because they could be used to induce enantioselectivity in the reactions catalyzed by FeBr3. The affinity of Fe3+ for oxygen ligands such as poly-alcohols5 led us to think about the possibility of forming complexes of this salt with cyclodextrins, which have been shown to form complexes with several transition metals.6 Cyclodextrins are cyclic oligomers of a-d-Glucose, which are produced from enzymatic degradation of starch. They have a structure similar to a truncated cone with a cavity formed by the glycosidic oxygens and two rings of the CH groups. Outside the cavity are the primary and secondary OH groups located at the narrower and wider rims respectively. They form complexes with a great variety of organic7 and inorganic molecules8 and also are known to induce enantioselectivity in several reactions.9 Complexes of FeBr3 with a-cyclodextrin, b-cyclodextrin, hydroxipropyl-b- cyclodextrin and g-cyclodextrin were prepared from the interaction of the salt dissolved in organic solvent and solid cyclodextrins, and analysed by DSC, TGA , IR and elemental analysis. The selective oxidation of organic sulfides to sulfoxides without any overoxidation to sulfones is a challenging issue in synthetic organic chemistry, partly because of the importance of sulfoxides as intermediates for biologically active compounds.10 Of the many classical oxidants, H2O2-based systems are considered to be relatively clean and free of pollution.11 Nevertheless, under catalytic conditions, the choice of reaction conditions and the stoichiometry of H2O2 with respect to the catalyst are critical to the selectivity of the reaction. For these reasons new catalysts,12 micelles13 or enzymes are being explored.14 These synthetized complexes were used as catalysts in the sulfoxidation reactions with good yields. Generally, the sulfoxide was obtained with 80% yields using 5% complex. On the order hands, Green Chemistry was introduced with the aim to overcome health and environmental problems at the source by developing cleaner chemical processes for chemical industry through the design of innovative and environmentally benign chemical reactions.15 We have analyzed the results in terms of reported green metric parameters and we demonstrate that the methodology proposed for the oxidation of sulfides fulfil several of the green chemistry principles since the oxidant is oxygen from the air, the reactions are highly selective producing a minimum amount waste and the catalyst is a non-contaminating metal. References 1. Mellor, J. W. A Comprehensive Treatise on Inorganic and Theoretical Chemistry. Longmans, Green and Co.: London, 1957, Vol. 14 (Part 3), Chapter 66. 2. Selbin, J.; Bull, W. E.; Straup, D. K. J. Inorg. Nucl. Chem. 1961, 16, 219. 3. (a) Suarez, A. R.; Rossi, L. I.; Martın, S. E. Tetrahedron Lett. 1995, 36, 1201. (b) Suarez, A. R.; Baruzzi, A. M.; Rossi, L. I. J. Org. Chem. 1998, 63, 5689. (c) Suarez, A. R.; Rossi, L. I. Sulfur Lett. 1999, 23, 89. (d) Suarez, A. R.; Rossi, L. I. Sulfur Lett. 2000, 21, 73. 4. Cotton, F. A.; Wilkinson, G. Quımica Inorganica Avanzada. Limusa S.A.; Mexico, 1993, Chapter 21. 5. (a) Shortreed, M. E.; Wylie, R. S.; Macartney, D. H. Inorg. Chem. 1993, 32, 1824. (b) Cromwell, W. C.; Bystrom, K.; Eftink, M. R. J. Phys. Chem. 1994, 89, 326. 6. Connors, K. A. Chem. Rev. 1997, 97, 1325. 7. Yashiro, M.; Miyama, S.; Takarada, T.; Komiyama, M. J. Inclusion Phenom. Mol. Recogn. 1994, 17, 393. 8. Kano, K. J. Phys. Org. Chem. 1997, 10, 286. 9. Albert, M. R.; Yates, J. T. Jr., The Surface Scientist‘s Guide to Organometallic Chemistry. American Chemical Society, Washington, DC, 1987, Chapter 3. 10. (a) M. Hudlický, Oxidations in Organic Chemistry, ACS Monograph 186, American Chemical Society, Washington, DC, 1980. (b) M.C. Carreño, Chem. Rev. 95 (1995) 1717. 11. (a) J. Brinksma, R.L. Crois, B.L. Feringa, M.I. Donnoli, C. Rosini, Tetrahedron Lett. 42 (2001) 4049. (b) S. Choi, J.-D. Yang, M. Ji, H. Choi, M. Kee, K.-H. Ahn, S.-H. Byeon, W. Baik, S. Koo, J. Org. Chem. 66 (2001) 8192. 12. (a) J.-M. Zen, S.-L. Liou, A.S. Kumar, M.-S. Hsia, Angew. Chem. Int. Ed. 42 (2003) 577. (b) S.A. Blum, R.G. Bergman, J.A. Ellman, J. Org. Chem. 68 (2003) 150. 14. E.N. Kadnikova, N.M. Kostic, J. Org. Chem. 68 (2003) 2600. 15. (a) P. Tundo, A. Perosa, F. Zecchini. Methods and Reagents for Green Chemistry: An Introduction. Wiley. 2007. (b) P. T. Anastas, M. M. Kirchhoff and T. C. Williamson. Appl. Catal. A: Gen., 2001, 221, 3. (c) G. Centi and S. Perathoner. Catal. Today, 2003, 77, 287.