Enantioselective epoxidation of trans-disubstituted alkenes by D₂-symmetric chiral dioxoruthenium(VI) porphyrins

Abstract

A series of D₂-symmetric chiral trans-dioxoruthenium(VI) porphyrins can effect enantioselective epoxidation of trans-β-methylstyrene in up to 70% ee, and 76% ee is attained for the oxidation of cinnamyl chloride; the facial selection for the trans-alkenes epoxidation is explained by a ‘head-on approach’ model.

References

1. E. N. Jacobsen, in Comprehensive Organometallic Chemistry II, ed. G. Wilkinson, F. G. A. Stone, E. W. Abel and L. S. Hegedus, Pergamon, New York, 1995, vol. 12, ch. 11.1For chiral ruthenium complexes catalyzed asymmetric epoxidation of trans-alkenes, see: N. End and A. Pfaltz, Chem. Commun., 1998, 589.
2. Z. Gross, S. Ini, M. Kapon and S. Cohen, Tetrahedron Lett., 1996, 37, 7325.
3. J. P. Collman, V. J. Lee, C. J. Kellen-Yuen, X. Zhang, J. A. Ibers and J. I. Brauman, J. Am. Chem. Soc., 1995, 117, 692.
4. C.-J. Liu, W.-Y. Yu, S.-M. Peng, T. C.-W. Mak and C.-M. Che, J. Chem. Soc., Dalton Trans., 1998, 1805.
5. J. T. Groves, K. T. Ahn and R. Quinn, J. Am. Chem. Soc., 1988, 110, 4217.
6. The best reported ee is 83% for the oxidation of trans-β-methylstyrene using chiral Cr–salen catalysts, see: C. Bousquet and D. C. Gilheany, Tetrahedron Lett., 1995, 36, 7739.
7. T.-S. Lai, R. Zhang, K.-K. Cheung, H.-L. Kwong and C.-M. Che, Chem. Commun., 1998, 1583; T.-S. Lai, H.-L. Kwong, R. Zhang and C.-M. Che, J. Chem. Soc., Dalton Trans., 1998, 3559.
8. Z. Gross and S. Ini, J. Org. Chem., 1997, 62, 5514.
9. W. Zhang, N. H. Lee and E. N. Jacobson, J. Am. Chem. Soc., 1994, 116, 425; W.-H. Fung, W.-Y. Yu and C.-M. Che, J. Org. Chem., 1998, 63, 7715.
10. J. T. Groves and R. S. Myers, J. Am. Chem. Soc., 1983, 105, 5791.
11. D. Ostovic and T. C. Bruice, Acc. Chem. Res., 1992, 25, 314.