Iron Catalysed Oxidation Reactions. Moftah Darwish and Martin Wills * * Department of Chemistry, University of Warwic

1. Iron Catalysed Oxidation Reactions. Moftah Darwish and Martin Wills* * Department of Chemistry, University of Warwick, Coventry, CV4 7AL, UK. Introduction: Iron-catalyzed asymmetric epoxidation of aromatic alkenes using iron complexes of TsDPEN derivatives, first disclosed by Beller,1 has been studied. Epoxidation of aromatic alkenes with hydrogen peroxide is possible using catalyst consisting of ferric chloride hexahydrate (FeCl3.6H2O), pyridine-2,6-dicarboxylic acid (H2pydic), and an organic base (Figure 1). Results: Epoxidation of trans-stilbene under different conditions and a comparison of the efficiency of additives used in the epoxidation are summarized in Table 1 and Table 2. The combination of RR and SS configuration ligands indicated no second order effect (Graph 1). Several additives and different conditions were examined in order to establish which groups were essential for promotion of the reaction. Different bidentate and tetradentateligands, were next investigated (Figure 2). The results of these studies, and the synthesis and applications of new ligands, is described and comparisons drawn with related asymmetric epoxidation processes.2-4 Table 1: Epoxidation of trans-stilbene under different conditions Table 2: Comparison of the efficiency of additives used in the (Figure 1) * H2O2 added in one portion Conclusion: Bidentateligands were tested in an asymmetric epoxidation, which requires 2:1 Ligand : FeCl3.6H2O and one equivalent of pyridine-2,6-dicarboxylic acid .The pyridine and carboxylic group are reqired for high ee. Given the possible involvement of two equivalents of ligand in the reaction, a test for second order effects were completed by using a series of ligands with varying ee. In addition, a series of tetradentateligands were synthesized and evaluated in the reaction. References: 1. Gelalcha, F. G.; Bitterlich, B.; Anilkumar, G.; Tse M. K.; Beller, M. Angew. Chem. Int. Ed. 2007, 46, 7293-7296. 2. a) Jorgensen, K. A.in Transition Metals for Organic Synthesis, vol. 2 (Ed. Beller, M.; Bolm, C.), Wiley-VCH, 1998, p. 157; b) Sundermeier, U.; Dobler, C. in Modern Oxidation Methods (Ed. Backvall, J. E.), Wiley-VCH, Weinheim, 2004, p. 1. 3. a) Tokunaga, M.; Larraw, J.; Kakiuchi, F.; Jacobsen, E. N. Science, 1997, 277, 936-938; b) Gayet, A.; Bertilsson, S.; Andersson, P. G. Org. Lett. 2002, 4, 3777-3779. 4. a) Katsuki, K. in Comprehensive Asymmetric Catalysis, Vol. 2 (Eds.: Jacobsen, E. N.; Pfaltz, A.; Yamamoto, H.), Springer, Berlin, 1999, pp. 621-648; b) Johnson, R. A.; Sharpless, K. B. in catalytic asymmetric synthesis (Ed.: Ojima, I.), Wiley-VCH, New York, 1993, pp. 103-158. Acknowledgement: I would like to thank my supervisor Prof. Martin wills and the Libyan Government for funding of this research project.