The first highly diastereo- and enantioselective polymeric catalyst for the 1,3-cycloaddition reaction of nitrones with alkenes

Abstract

A highly diastereo- and enantioselective 1,3-dipolar cycloaddition reaction of nitrones with alkenes catalyzed by chiral polybinaphthyl Lewis acids has been developed giving isoxazolidines with up to 99% ee; the chiral polymer ligand shows almost identical stereoselectivity to its monomeric version but has the advantage of easy recovery and reuse, and this work further demonstrates that a rigid and sterically regular polymer chain can be used to preserve the catalytic properties of monomeric catalysts.

References

1. (a) S. Itsuno, Polymeric Materials Encyclopedia; Synthesis, Properties and Applications, ed. J. C. Salamone, CRC Press, Boca Raton FL, 1996, vol 10, p 8078; (b) E. C. Blossey and W. T. Ford, Comprehensive Polymer Science. The Synthesis, Characterization, Reactions and Applications of Polymers, ed. G. Allen and J. C. Bevington, Pergamon, New York, 1989, vol. 6, p. 81; (c) L. Pu, Chem. Rev., 1998, 98, 2405.
2. Q.-S. Hu, X.-F. Zheng and L. Pu, J. Org. Chem., 1996, 61, 5200; Q.-S. Hu, D. Vitharana, X.-F. Zheng, C. Wu, C. M. S. Kwan and L. Pu, J. Org. Chem., 1996, 61, 8370.
3. See e.g.: W.-S. Huang, Q.-S. Hu, X.-F. Zheng, J. Anderson and L. Pu, J. Am. Chem. Soc., 1997, 119, 4313; Q.-S. Hu, W.-S. Huang, D. Vitharana, X.-F. Zheng and L. Pu, J. Am. Chem. Soc., 1997, 119, 12454; Q.-S. Hu, W.-S. Huang and L. Pu, J. Org. Chem., 1998, 63, 2798.
4. M. Johannsen, K. A. Jørgensen, X.-F. Zheng, Q.-S. Hu and L. Pu, J. Org. Chem., 1999, 64, 299.
5. For reviews see: K. V. Gothelf and K. A. Jørgensen, Chem. Rev., 1998, 98, 863; M. Frederickson, Tetrahedron, 1997, 53, 403.
6. See e.g.: K. V. Gothelf and K. A. Jørgensen, J. Org. Chem., 1994, 59, 5687; K. V. Gothelf, I. Thomsen and K. A. Jørgensen, J. Am. Chem. Soc., 1996, 118, 59; K. V. Gothelf, R. G. Hazell and K. A. Jørgensen, J. Org. Chem., 1996, 61, 346; K. B. Jensen, K. V. Gothelf, R. G. Hazell and K. A. Jørgensen, J. Org. Chem., 1997, 62, 2471; K. B. Jensen, K. V. Gothelf and K. A. Jørgensen, Helv. Chim. Acta, 1997, 80, 2039; S. Murahashi, Y. Imada, M. Kohno and T. Kawakami, Synlett, 1993, 395; S. Kobayashi and M. Kawamura, J. Am. Chem. Soc., 1998, 120, 5840; S. Kanemasa, T. Tsuruoka and H. Yamamoto, Tetrahedron Lett., 1995, 36, 5019; S. Kanemasa, Y. Oderaotoshi, J. Tanaka and E. Wada, J. Am. Chem. Soc., 1998, 120, 12355.
7. See e.g.: (a) J.-P. G. Seerden, A. W. A. Scholte op Reimer and H. W. Scheeren, Tetrahedron Lett., 1994, 35, 4419; (b) J.-P. G. Seerden, M. M. M. Boeren and H. W. Scheeren, Tetrahedron, 1997, 53, 11843; (c) K. B. Simonsen, P. Bayón, R. G. Hazell, K. V. Gothelf and K. A. Jørgensen, J. Am. Chem. Soc., 1999, in the press.
8. D. Seebach, R. E. Marti and T. Hintermann, Helv. Chim. Acta, 1996, 79, 1710.
9. Experimental procedure. The appropriate ligand (0.02 mmol) was placed in a 5 mL Schlenk flask flushed three times with N₂, and CH₂Cl₂(1 mL) was added with a syringe. To this solution was added a 2 M solution of AlMe₃ in heptane (10 mL, 0.02 mmol). The solution was stirred for 1 h and the nitrone (0.2 mmol) and vinyl ether (0.5 mmol) were added. After the appropriate reaction time, the reaction was quenched with MeOH (1 mL) and the ligand was isolated by centrifugation. The clear solution was evaporated to give the single diasteromer of exo-3 as a pure product (TLC, ¹H and ¹³C NMR).