Chiral–achiral ligand synergy: activation of a zirconium–BINOL Lewis acid complex by the addition of 4-tert-butylcalix[4]arene

Abstract

4-tert-Butylcalix[4]arene activates the enantioselective allylation of aldehydes catalyzed by a new zirconium–BINOL Lewis acid system allowing the use of less than 2% of the catalyst.

References

1. A. L. Costa, M. G. Piazza, E. Tagliavini, C. Trombini and A. Umani-Ronchi, J. Am. Chem. Soc., 1993, 115, 7001; G. E. Keck, K. H. Tabert and L. S. Geraci, J. Am. Chem. Soc., 1993, 115, 8467; G. E. Keck, D. Krishnamurthy and M. C. Grier, J. Org. Chem., 1993, 58, 6543; G. E. Keck, D. Krishnamurthy and X. Chen, Tetrahedron Lett., 1993, 35, 8323; S. Weigand and R. Brukner, Chem. Eur. J., 1996, 2, 1072; J. W. Faller, O. W. I. Sams and X. Liu, J. Am. Chem. Soc., 1996, 118, 1217; P. G. Cozzi, E. Tagliavini and A. Umani-Ronchi, Gazz. Chim. It., in the press.
2. C.-M. Yu, H.-S. Choi, W.-H. Jung, H.-J. Kim and J. Shin, Chem. Commun., 1997, 761 Although high enantiomeric excesses were obtained using only 2% of a titanium–BINOL Lewis acid complex, the additive is used in stoichiometric amount and is not commercially available.
3. D. R. Gauthier and E. M. Carreira, Angew. Chem., Int. Ed. Engl., 1996, 35, 2363; R. O. Duthaler and A. Hafner, Angew. Chem., Int. Ed. Engl., 1997, 36, 43.
4. L. E. Manzer, Inorg. Synth., 1982, 21, 136.
5. P. Bedeschi, S. Casolari, A. L. Costa, E. Tagliavini and A. Umani-Ronchi, Tetrahedron Lett., 1995, 36, 7897.
6. K. Mikami and S. Matsukawa, Nature, 1997, 385, 613.
7. S. Matsukawa and K. Mikami, Tetrahedron: Asymmetry, 1997, 8, 815.
8. V. Böhmer, Angew. Chem., Int. Ed. Engl., 1995, 34, 713.