Cycloadducts from highly functionalized nitrones and oximes as ligands in the enantioselective addition of diethylzinc to benzaldehyde

Abstract

Highly diastereoselective intramolecular cycloaddition of nitrones 5–7 and 16, as well as oximes 11–13 that are easily accessible from diethyl (R,R)-tartrate, affords bicyclic compounds 8–10 and 17. The tetracyclic compound 14 is formed as the main product by an intramolecular domino reaction of dioxime 11. Some of the bicyclic compounds and the tetracyclic compound 14 are tested as chiral ligands in the enantioselective addition of diethylzinc to benzaldehyde. An ee of 93% was achieved in the presence of the best ligand.

References

1. (a) See for instance R. E. Gawley and J. Aube, Principles of Asymmetric Synthesis, ed. J. E. Baldwin and P. D. Magnus, Tetrahedron Organic Chemistry Series, vol. 14, Pergamon, Oxford, 1996, pp. 4–7; (b) G. Procter, Asymmetric Synthesis, Oxford University Press, 1996, pp. 7–8; (c) D. J. Berrisford, C. Bolm and K. B. Sharpless, Angew. Chem., Int. Ed. Engl., 1995, 34, 1059.
2. A collection of enantioselective catalysts derived from the chiral pool is given by H.-U. Blaser, Chem. Rev., 1992, 92, 935.
3. See for instance (a) K. Soai and S. Niwa, Chem. Rev., 1992, 92, 833; (b) R. Noyori and M. Kitamura, Angew. Chem., Int. Ed. Engl., 1991, 30, 49; (c) R. M. Devant and H.-E. Radunz, in Methods of Org. Chem., Houben-Weyl, 4th Edn.; Stereoselective Synthesis, eds. G. Helmchen, R. W. Hoffmann, J Mulzer and E. Schaumann, 1995, vol. 21b, pp. 1314–1334.
4. H. G. Aurich, F. Biesemeier, M. Geiger and K. Harms, Liebigs Ann./Recl., 1997, 423.
5. See ref. (4) and references cited therein.
6. H. G. Aurich and F. Biesemeier, Synthesis, 1995, 1171 Preparation of compounds 8a and 8b were described therein.
7. (a) For preparation of the N-alkylhydroxylamines see ref. 4; (b) It is obvious that for the conversion of compound 4 to the corresponding cycloadducts 8, the yield should be relatively low, since every step of the reaction sequence must take place twice.
8. S. Baskaran and H. G. Aurich, Synlett, 1998, 277.
9. See for example (a) W. Oppolzer and K. Keller, Tetrahedron Lett., 1970, 1117; (b) A. Hassner, R. Maurya and E. Mesko, Tetrahedron Lett., 1988, 29, 5313; (c) A. Hassner, R. Maurya, A. Padwa and W. H. Bullock, J. Org. Chem., 1991, 56, 2775; (d) R. Grigg, J. Markandu, T. Perrior, S. Surendrakumar and W. J. Warnock, Tetrahedron, 1992, 48, 6929.
10. (a) L. F. Tietze and U. Beifuss, Angew. Chem., Int. Ed. Engl., 1993, 32, 131; (b) L. F. Tietze, Chem. Rev., 1996, 96, 115.
11. (a) H. G. Aurich, M. Boutahar, H. Köster, K.-D. Möbus and L. Ruiz, Chem. Ber., 1990, 123, 1999; (b) most characteristic for compound 17 are the ¹³C NMR signals for 5-C and 4-C and the ¹H NMR signal for 5-H. For a direct comparison of analogous compounds of type 17 and 19 see for example, ref. 11(a), in which the data of compounds 12Ba and Ca should be compared with those of 21Ba and Ca, respectively.
12. H. G. Aurich, C. Gentes and K. Harms, Tetrahedron, 1995, 51, 10497.
13. M. Hesse, H. Meier and B. Zeeh, in Spektroskopische Methoden in der Organischen Chemie, Georg Thieme Verlag, Stuttgart, 1991, p. 105. The agreement between J_found and J_calc is good, even though the Karplus equation was established for carbocyclic rather than heterocyclic compounds.
14. α-H's are those which are cis-orientated to 1-H, β-H's are those which are trans-orientated.
15. D. Parker, J. Chem. Soc., Perkin Trans. 2, 1983, 83.
16. H. G. Aurich and M. Geiger, unpublished results; M. Geiger, Dissertation, University of Marburg, Germany, 1997.
17. G. M. Sheldrick, SHELXS-97 Program for the solution of crystal structures, Göttingen, 1997.
18. G. M. Sheldrick, SHELXL-97 Program for the Refinement of Crystal Structures, Göttingen, 1997.