Catalytic enantioselective aryl transfer: asymmetric addition of diphenylzinc to aldehydes

Abstract

The asymmetric addition of diphenylzinc to aldehydes in the presence of catalytic amounts of a planar chiral ferrocene-based hydroxy oxazoline affords products with enantiomeric excesses of up to 96%.

References

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2. (a) For a pioneering report on an asymmetric phenylation in the presence of stoichiometric amounts of a chiral titanium–BINOL complex, see: D. Seebach, A. K. Beck, S. Roggo and A. Wonnacott, Chem. Ber., 1985, 118, 3673; (b) For a later catalytic version employing Ti–TADDOLates, see: B. Weber and D. Seebach, Tetrahedron, 1994, 50, 7473.
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6. M. Sakai, M. Ueda and N. Miyaura, Angew. Chem. Int. Ed., 1998, 37, 3475.
7. (a) C. Bolm, K. Muñiz Fernández, A. Seger and G. Raabe, Synlett, 1997, 1051; (b) C. Bolm, K. Muñiz Fernández, A. Seger, G. Raabe and K. Günther, J. Org. Chem., 1998, 63, 7860.
8. K. Muñiz Fernández, PhD thesis, RWTH Aachen, 1999.
9. C. Bolm, K. Muñiz and J. P. Hilderbrand, Org. Lett., in press.
10. Diphenylzinc was perchased from Strem (ref. 3) and stored as a 2.0 M solution in toluene. Under these conditions ZnPH₂ proved to be stable over a long period of time.
11. Recent examples of asymmetric autocatalyses: T. Shibata, S. Yonekubo and K. Soai, Angew. Chem., Int. Ed., 1999, 38, 659; T. Shibata, J. Yamamoto, N. Matsumoto, S. Yonekubo, S. Osanai and K. Soai, J. Am. Chem. Soc., 1998, 120, 12 157; C. Bolm, A. Seger and F. Bienewald, Organic Synthesis Highlights III, ed. J. Mulzer and H. Waldmann, Wiley-VCH, Weinheim, 1998, p. 79.
12. For a structurally related pyridyl alcohol in asymmetric ZnEt₂ additions, see: C. Bolm, M. Zehnder and D. Bur, Angew. Chem., Int. Ed. Engl., 1990, 29, 205; C. Bolm, G. Schlingloff and K. Harms, Chem. Ber., 1992, 125, 1191.
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14. To date, there is only one report on a non-linear effect (NLE) for a ferrocene ligand in an asymmetric diethylzinc addition: G. Nicolosi, A. Patti, R. Morrone and M. Piattelli, Tetrahedron: Asymmetry, 1994, 5, 1639.