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G. Chelucci, A. Saba / Tetrahedron: Asymmetry 9 (1998) 2575–2578
1H, J=8.1, 1.8), 7.71 (s, 2H), 7.68 (s, 1H), 7.56 (dd, 1H, J=8.1, 4.2), 3.66 (m, 1H), 3.02 (t, 1H, J=5.4), 2.68 (m, 1H),
2.27 (m, 1H), 1.64 (d, 3H, J=6.9), 1.48 (s, 3H), 1.45 (d, 1H, J=10.2), 0.68 (s, 3H). Compound 6b: was isolated in 43%
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yield after chromatographic purification on Al2O3 (petroleum ether:ethyl acetate=1:1): mp 65–66°C; [α]D −33.9 (c 1.3,
CHCl3); 1H-NMR (CDCl3): δ 9.18 (dd, 1H, J=4.2, 1.5), 8.17 (dd, 1H, J=8.1, 1.8), 7.67 (s, 2H), 7.65 (s, 1H), 7.53 (dd, 1H,
J=8.1, 4.5), 3.60 (m, 1H), 2.99 (t, 1H, J=5.7), 2.19 (m, 1H), 2.52–2.40 (m, 2H), 1.80 (m, 1H), 1.66 (m, 1H), 1.48 (s, 3H),
1.44 (d, 1H, J=9.6), 1.09 (d, 3H, J=6.6), 1.00 (d, 3H, J=6.6), 0.65 (s, 3H). Compound 6c: was isolated in 35% yield after
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chromatographic purification on Al2O3 (petroleum ether:ethyl acetate=1:1): mp 72–73°C; [α]D −49.1 (c 0.9 CHCl3);
1H-NMR (CDCl3): δ 9.19 (dd, 1H, J=4.2, 1.5), 8.20 (dd, 1H, J=8.1, 1.8), 7.71 (s, 2H), 7.68 (s, 1H), 7.56 (dd, 1H, J=8.1,
4.2), 3.66 (m, 1H), 3.02 (t, 1H, J=5.4), 2.62 (m, 1H), 2.27 (m, 1H), 1.64 (d, 3H, J=6.9), 1.48 (s, 3H), 1.45 (d, 1H, J=10.2),
0.68 (s, 3H). Compound 6d: was isolated in 55% yield after chromatographic purification on Al2O3 (petroleum ether:ethyl
25
1
acetate=1:1): mp 70–71°C; [α]D +56.1 (c 1.1 CHCl3); H-NMR (CDCl3): δ 9.20 (dd, 1H, J=4.5, 1.8), 8.18 (dd, 1H,
J=8.1, 1.8), 7.70 (s, 1H), 7.69 (s, 2H), 7.54 (dd, 1H, J=8.1, 4.2), 7.40–7.18 (m, 5H), 4.22 (dd, 1H, J=13.5, 4.23), 3.86 (m,
1H), 3.00 (t, 1H, J=5.7), 2.83 (dd, 1H, J=13.5, 11.7), 2.60 (m, 1H), 2.14 (m, 1H), 1.54 (d, 1H, J=9.9), 1.36 (s, 3H), 0.64 (s,
3H).
7. Trost, B. M.; Van Vranken, D. L. Chem. Rev., 1996, 96, 395. Reiser, O. Angew. Chem., 1993, 105, 576; Angew. Chem., Int.
Ed. Engl., 1993, 32, 547. Hayashi, T. In Catalytic Asymmetric Synthesis, Ojima, I., Ed.; VCH: Weinheim, 1993. Frost, C.
G.; Howarth, J.; Williams, J. M. J. Tetrahedron: Asymmetry, 1992, 3, 1089.
8. Trost, B. M.; Murphy, D. J. Organometallics, 1985, 34, 2015.
9. For a leading reference, see: Chelucci, G. Gazz. Chim. Ital., 1992, 122, 89. For more recent applications in asymmetric
catalysis, see: Chelucci, G.; Cabras, M. A.; Saba, A. J. Mol. Catal. A., 1995, 95, L7–L10 and Ref. 2.
10. After the submission of this paper, two important references have come to our attention: Riesgo, E. C.; Credi, A.; De Cola,
L.; Thummel, R. P. Inorg. Chem., 1998, 37, 2145. Poña-Cabrera, E.; Norby, P. O.; Sjógren, M.; Vitagliano, A.; De Felice,
V.; Oslob, I.; Ishii, S.; O’Neill, D.; Åkermark, B.; Helquist, P. J. Am. Chem. Soc., 1996, 118, 4299.