A. Bayer, O. R. Gautun / Tetrahedron: Asymmetry 12 (2001) 2937–2939
2939
been performed in the presence of stoichiometric
amounts of Cu(II)- and Zn(II)-chiral bis(oxazoline)
complexes. Attempts with catalytic amounts of Lewis
acid were most promising for the Zn(II) complex. Fur-
ther efforts to find catalysts offering an increased
turnover and high enantioselectivities, as well as studies
of the scope and limitation of these reactions in general
are now in progress.
4. Bayer, A.; Gautun, O. R. Tetrahedron Lett. 2000, 41,
3743.
5. For reviews of C2-bisoxazoline–Lewis acid complexes as
catalysts for HDA reactions, see e.g.: (a) Ghosh, A. K.;
Mathivanan, P.; Cappiello, J. Tetrahedron: Asymmetry
1998, 9, 1; (b) Jørgensen, K. A.; Johannsen, M.; Yao, S.;
Audrain, H.; Thorhauge, J. Acc. Chem. Res. 1999, 32,
605; For a recent review about Zn(II)-catalysts, see: (c)
Motoyama, Y.; Nishiyama, H. In Lewis Acids in Organic
Synthesis; Yamamoto, H., Ed.; Wiley-VCH: Weinheim,
2000; Vol. I, p. 59; For recent reviews about Cu(II)-cata-
lysts, see: (d) Johnson, J. S.; Evans, D. A. Acc. Chem.
Res. 2000, 33, 325; (e) Sibi, M. P.; Cook, G. R. In Lewis
Acids in Organic Synthesis; Yamamoto, H., Ed.; Wiley-
VCH: Weinheim, 2000; Vol. II, p. 543.
Acknowledgements
We are grateful to the Norwegian Research Council
(Grant 122792/432 to A.B.) for financial support.
6. Garigipati, R. S.; Freyer, A. J.; Whittle, R. R.; Weinreb,
S. M. J. Am. Chem. Soc. 1984, 106, 7861.
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