N. S. Camilo, R. A. Pilli / Tetrahedron Letters 45 (2004) 2821–2823
2823
2. (a) Li, C.-J. Chem. Rev. 1993, 93, 2023; (b) Lindstrom, M.
U. Chem. Rev. 2002, 102, 2751; (c) Kobayashi, S.;
Manabe, K. Acc. Chem. Res. 2002, 35, 209.
3. (a) Kobayashi, S.; Wakabayashi, T.; Nagayama, S.;
Oyamada, H. Tetrahedron Lett. 1997, 38, 4559; (b)
Kobayashi, S.; Busujima, T.; Nagayama, S. Chem. Com-
mun. 1998, 19; (c) Kobayashi, S.; Busujima, T.; Naga-
yama, S. Synlett 1999, 545.
4. (a) Kobayashi, S.; Wakabayashi, T. Tetrahedron Lett.
1998, 39, 5389; (b) Manabe, K.; Kobayashi, S. Synlett
1999, 547; (c) Manabe, K.; Mori, Y.; Kobayashi, S.
Tetrahedron 1999, 55, 11203; (d) Manabe, K.; Mori, Y.;
Wakabayashi, T.; Nagayama, S.; Kobayashi, S. J. Am.
Chem. Soc. 2000, 122, 7202.
5. (a) Kobayashi, S.; Nagayama, S.; Busujima, T. Tetrahe-
dron 1999, 55, 8739; (b) Kobayashi, S.; Mori, Y.;
Nagayama, S.; Manabe, K. Green Chem. 1999, 1, 175;
(c) Kobayashi, S.; Hamada, T.; Nagayama, S.; Manabe, K.
J. Braz. Chem. Soc. 2001, 12, 627.
10. For clarity, only the structure of the major diastereoiso-
mer erythro-3a is depicted in Table 1.
11. A representative procedure follows: To a mixture of SDS
(0.011 g, 0.038 mmol) in water (1.0 mL) was added
2-methoxypyrrolidine 1a (0.076 g, 0.38 mmol), silyl enol
ether 2 (0.156 g, 0.76 mmol), and 0.2 M aqueous HCl
(0.056 mL, 0.011 mmol). The mixture was stirred 2 h at rt
and worked-up with brine (1.0 mL). The aqueous layer
was extracted with ethyl acetate (3 · 1.0 mL) and the
combined organic extracts were dried over anhydrous
MgSO4. After filtration, the solvent was evaporated under
reduced pressure and the residue was chromatographed on
silica gel (10% ethyl acetate/hexanes) to yield a 5:1 mixture
of erythro-3a and threo-3a (0.082 g, 0.28 mmol) as a
1
colorless oil in 74% yield. Data for erythro-3a: H NMR
(CD3CN, 298 K): d 1.14 (d, J ¼ 6:6 Hz, 3H), 1.43 (s, 9H),
1.65 (m, 2H), 1.85 (m, 2H), 2.73 (m, 1H), 3.27 (m, 1H),
4.09 (m, 2H), 7.30–7.70 (m, 3H), 7.90 (d, J ¼ 8:0 Hz, 2H);
13C NMR (CD3CN, 298 K): d 15.4, 22.4, 24.1, 28.9, 43.7,
47.3, 61.9, 79.8, 127.3, 129.5, 129.6, 133.8, 155.2, 204.9. IR
6. Akiyama, T.; Itoh, J.; Fuchibe, K. Synlett 2002, 1269.
7. (a) Loh, T.-P.; Liung, S. B. K. W.; Tan, K.-L.; Wei, L.-L.
Tetrahedron 2000, 56, 3227; (b) Manabe, K.; Mori, Y.;
Kobayashi, S. Tetrahedron 2001, 57, 2537.
8. (a) Schuch, C. M.; Pilli, R. A. Tetrahedron: Asymmetry
2002, 13, 1973; (b) Tomazela, D. M.; Moraes, L. A. B.;
Pilli, R. A.; Eberlin, M. N.; DꢀOca, M. G. M. J. Org.
(KBr, film): 2074, 2979, 2940, 2861, 1693, 1682, 1597 cmÀ1
.
Elemental analysis calcd for C18H25NO3: C-71.26; H-8.31,
N-4.62. Found: C-71.55; H-8.56; N-4.78. Although a 13:1
mixture (70% yield) of erythro-3a and threo-3a was formed
in CH2Cl2 at )78 ꢁC and BF3ÆOEt2 (1.0 equiv) as Lewis
acid, this ratio dropped significantly (3.5:1) when the
reaction was carried out in CH2Cl2 at rt.
€
Chem. 2002, 67, 4652; (c) Pilli, R. A.; Bockelmann, M. A.;
Alves, C. F. J. Braz. Chem. Soc. 2001, 12, 634; (d) DꢀOca,
M. G. M.; Moraes, L. A. B.; Pilli, R. A.; Eberlin, M. N. J.
Org. Chem. 2001, 66, 3854; (e) de Oliveira, M. C. F.;
Santos, L. S.; Pilli, R. A. Tetrahedron Lett. 2001, 42, 6995;
(f) Santos, L. S.; Pilli, R. A. Tetrahedron Lett. 2001, 42,
6999.
12. The remarkable effect of SDS may be due to the
confinement of the reactants in the surface of the SDS
micelle and to the association of the sulfate groups with
Hþ or In3þ ions. The increase in the local concentration of
the reactants, the availability of acid sites in the micelle
surface and the stabilization of reaction intermediates and
transition state may lead to the increase of the reaction
rate when compared with the results in water without SDS.
9. Russowsky, D.; Petersen, R. Z.; Godoi, M. N.; Pilli, R. A.
Tetrahedron Lett. 2000, 41, 9939.