A. R. M. Oliveira et al. / Tetrahedron Letters 48 (2007) 1507–1509
1509
argon, was cooled in a dry ice/acetone bath (À78 ꢁC) and
n-BuLi (4.2 mmol) was added dropwise. After stirring for
30 min at À78 ꢁC, a solution of ZnCl2 (4.2 mL of 0.5 mol/
L in THF) was added to the oxazoline anion and the
resulting solution was stirred at À78 ꢁC for 15 min and
transferred to an ice bath at 0 ꢁC for 30 min. After this
period, the solution was cooled at À78 ꢁC and a solution
of appropriate 2-nitrovinyl benzene (2 mmol) in dry THF
(4 mL) was added. The reaction was slowly warmed to
room temperature, then quenched with saturated aqueous
NH4Cl solution. The mixture was extracted with ethyl
acetate (3 · 20 mL) and dried over anhydrous Na2SO4.
The product was isolated by filtration, followed by solvent
removal under vacuum and then purified by flash chro-
matography (ethyl acetate/hexane 2:1). Spectral data of
O
HO
, K CO , 90%
Br
O
NO
2
2
3
1)
H
(24)
2) MeNO , NH OAc, 91%
MeO
2
4
MeO
(23)
O
THF
N
Zn
2
-78ºC
rt
80%
(3)
N
O
O
N
H
O
1) H SO , EtOH, 5% H O
O
NO
2
4
2
2
1
72% crude yield
(9): H NMR (200 MHz, CDCl3) d: 1.10 (s, 3H); 1.18 (s,
MeO
,
2) NiCl NaBH , EtOH
3H); 2.67 (d, J = 7.8 Hz, 2H); 3.79–3.97 (m, 3H); 4.79 (dd,
J1 = 12.72 Hz, J2 = 8.02 Hz, 1H); 4.73 (dd, J1 = 12.72 Hz,
J2 = 7.05 Hz, 1H); 7.20–7.33 (m, 5H). 13C NMR (50 MHz,
CDCl3) d: 28.18; 32.13; 41.10; 67.18; 79.11; 79.46; 127.40;
127.93; 129.00; 138.38; 162.40.
MeO
2
4
(26)
(25)
80%
Scheme 3.
12. Rimkus, A.; Sewald, N. Org. Lett. 2002, 4, 3289–
3291.
13. When the THF solution was cooled to À78 ꢁC most of
compound (8) precipitates and is recovered at the end of
the reaction.
to the corresponding amino ester to form lactam (26)24
in an 80% yield (Scheme 3).
´
14. Fustero, S.; Dıaz, D.; Barluenga, J.; Aguilar, E. Tetra-
Acknowledgements
hedron Lett. 1992, 33, 3801–3804.
´
15. (a) Fustero, S.; Dıaz, M. D.; Asensio, A.; Navarro, A.;
The authors gratefully acknowledge the financial sup-
Kong, J.-S.; Aguilar, E. Tetrahedron 1999, 55, 2695–2712;
(b) Lee, A. S. Y.; Cheng, R.-Y. Tetrahedron Lett. 1997, 38,
443–446.
´
port of CNPq, CAPES and Fundac¸ao Araucaria and
˜
the fellowship from CAPES to J.A.F.P.V. and R.A.G.
16. Knochel, P.; Rozema, M. J.; Tucker, C. E. In Organo-
copper Reagents: A Practical Approach; Taylor, R. J. K.,
Ed.; Oxford University Press: Oxford, UK, 1994.
17. Demnitz, J.; LaVecchia, L.; Bacher, E.; Keller, T. H.;
References and notes
Muller, T.; Schurch, F.; Weber, H.; Pombo-Villar, E.
Molecules 1998, 3, 107–119.
¨
¨
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21. Spectral data of (25): 1H NMR (200 MHz, CDCl3) d: 1.07
(s, 3H); 1.13 (s, 3H); 1.40–1.60 (m, 2H); 1.40–1.90 (m, 6H);
2.59 (d, J = 7.81 Hz, 2H); 3.70–3.90 (m, 6H); 4.53 (dd,
J1 = 12.45 Hz, J2 = 8.05 Hz, 1H); 4.66 (m, 3H); 6.60–6.80
(m, 3H). 13C NMR (50 MHz, CDCl3) d: 149.88; 147.98;
130.85; 125.63; 119.52; 114.70; 112.37; 80.73; 79.98; 56.22;
40.89; 32.96; 32.34; 28.44; 28.36; 24.21.
22. Meyers, A. I.; Temple, D. L.; Haidukewych, D.; Mihelich,
E. D. J. Org. Chem. 1974, 39, 2787–2793.
23. Corey, E. J.; Zhang, F. Org. Lett. 2000, 2, 4257–4259.
24. Spectral data of (26): H NMR (200 MHz, CDCl3): 1.50–
10. The 2-nitrovinyl benzenes (4) and (5): (a) Vogel, A. I.
Vogel’s Textbook of Practical Organic Chemistry 5th ed.;
(rev. by Furniss, B. S.; Hannaford, A. J.; Smith, P. W. G.;
Tatchell, A. R.), Longman Scientific and Technical, 1989;
p-chloro and p-metoxy-2-nitrovinyl benzene (6–8): (b)
Ford, P. W.; Narbut, M. R.; Belli, J.; Davidson, B. S.
J. Org. Chem. 1994, 59, 5955–5960.
1
2.00 ppm (m, 8H); 2.48 (dd, J2 = 8.8 Hz, J2 = 17.22 Hz,
1H); 2.73 (dd, J1 = 8.8 Hz, J2 = 16.82 Hz, 1H); 3.39 (dd,
J1 = 7.05 Hz, J1 = 8.8 Hz); 3.50–3.85 (m, 2H); 3.84 (s,
3H); 4.70–4.83 (m, 1H); 6.43 (s, 1H); 6.75–6.87 (m, 3H).
13C NMR (50 MHz, CDCl3): 24.22; 33.02; 38.31; 40.19;
49.98; 56.35; 80.81; 112.43; 114.06; 119.02; 134.74; 148.13;
177.97.
11. General procedure: A flask containing 2,4,4-trimethyl-2-
oxazoline (0.535 mL, 4.2 mmol) and 9 mL of THF under