D. Dakternieks et al. / Tetrahedron: Asymmetry 14 (2003) 3057–3068
3067
3.7. Reduction of 2-bromonaproxen ethyl ester 16 (X=
Br)
9. Renaud, P.; Gerster, M. Angew. Chem., Int. Ed. Engl.
1998, 37, 2563.
10. Murakata, M.; Tsutsui, H.; Hoshino, O. J. Chem. Soc.,
Following the standard procedure, (S)-naproxen ethyl
ester 16 (X=H) was obtained as colourless oil (74%)
and with identical properties to that prepared from an
authentic sample of (S)-naproxen. 1H (NMR) CDCl3: l
7.0–7.5 (6H, m), 4.1 (2H, m), 3.9 (3H, s), 3.8 (1H, q, J
9 Hz), 1.5 (3H, m), 1.2 (3H, m), [h]1D0=+32.6 (c 0.12,
CHCl3) 99%ee (GC).
Chem. Commun. 1995, 481.
11. Part of this work has been published in preliminary form:
Dakternieks, D.; Dunn, K.; Perchyonok, V. T.; Schiesser,
C. H. Chem. Commun. 1999, 1665.
12. Dakternieks, D.; Dunn, K.; Henry, D. J.; Schiesser, C.
H.; Tiekink, E. R. T. Organometallics 1999, 18, 3342.
13. Lucas, C.; Santini, C.; Prinz, M.; Cordinnier, M.; Basset,
J.; Connil, M.; Jousseaume, B. J. Organomet. Chem.
1996, 520, 102.
3.8. Reduction of 2-bromoibuprofen ethyl ester 15 (X=
Br)
14. Perchyonok, V. T.; Schiesser, C. H. Tetrahedron Lett.
1998, 39, 5437.
Following the standard procedure, (S)-ibuprofen ethyl
ester (15, X=H) was obtained as colourless oil (55%)
and with identical properties to that prepared from an
15. Miura, K.; Ichinose, Y.; Nozaki, K.; Fugami, K.;
Oshima, K.; Utimoto, K. Bull. Chem. Soc. Jpn. 1989, 62,
143.
16. (a) Campbell, A.; Kenyon, S. J. Chem. Soc. 1946, 25; (b)
Aaron, C.; Dull, D.; Schmiegel, S. L.; Jaeger, D.; Ohashi,
J.; Mosher, H. S. J. Org. Chem. 1967, 32, 2797; (c)
Elhafez, F. A. A.; Cram, D. J. J. Am. Chem. Soc. 1952,
74, 5846.
1
authentic sample of (S)-ibuprofen. H (NMR) CDCl3:
l 7.1–7.6 (4H, m), 4.2 (2H, m), 3.6 (1H, m), 2.6 (2H, d,
J 8 Hz), 2.4 (1H, m), 1.5 (3H, m), 1.1 (3H, m), 0.9 (6H,
m), [h]1D0=+38.0 (c 0.8, CHCl3) 99% ee (GC).
3.9. Reduction of ethyl 2-bromo-2-cyclopentyl-2-phenyl
acetate 7 (R=cyclo-Pen, X=Br)
17. Jacobson’s catalyst: Jacobsen, E. N.; Zhang, W.; Muci,
A. R.; Ecker, J. R.; Deng, L. J. Am. Chem. Soc. 1991,
113, 7063.
Following the standard procedure, ethyl (S)-2-
cyclopentyl-2-phenyl acetate 7 (R=cyclo-Pen, X=H)
was obtained as colourless oil (55%) and with identical
properties to an authentic sample.31 1H (NMR) CDCl3:
l 7.2 (5H, m), 4.1 (2H, m), 3.2 (1H, d, J 7.5 Hz), 2.6
(1H, m), 1.0–2.0 (11H, m), a2D6=+26.4 (c 1.0, CHCl3)
96%ee (GC).
18. (a) Dakternieks, D.; Dunn, K.; Schiesser, C. H.; Tiekink,
E. R. T. J. Organomet. Chem. 2000, 605, 209; (b)
Schiesser, C. H.; Skidmore, M. A.; White, J. M. Aust. J.
Chem. 2001, 54, 199.
19. While use of more than one equivalent of fresh Lewis
acid provided no increase in observed enantioselectivity,
often two equivalents were added when older stocks of
Lewis acid were employed. This excess was routinely
applied with the magnesium based additives in this study.
20. (a) Gue´rin, B.; Ogilvie, W. W.; Guindon, Y. In Radicals
in Organic Synthesis; Renaud, P.; Sibi, M. P., Eds.;
Wiley-VCH: Weinheim, 2001 and references cited therein;
(b) Sibi, M. P.; Rheault, T. R. In Radicals in Organic
Synthesis; Renaud, P.; Sibi, M. P., Eds.; Wiley-VCH:
Weinheim, 2001 and references cited therein.
21. Dakternieks, D.; Duthie, A.; Schiesser, C. H., unpub-
lished results.
Acknowledgements
We thank the Australian Research Council and Chiro-
gen Pty. Ltd. for financial support.
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