6750
F. Palacios et al. / Tetrahedron Letters 48 (2007) 6747–6750
4. (a) Kitahara, Y.; Tamura, F.; Kubo, A. Chem. Pharm.
17. Gibson, M. S. In The Chemistry of Amino Group; Patai, S.,
Ed.; John Wiley: London, 1968; p 61.
18. For the synthesis of a,b-unsaturated sulfinylimine 2, a
Bull. 1994, 42, 1363–1364; (b) Kitahara, Y.; Kubo, A.
Heterocycles 1992, 34, 1089–1092; (c) Bracker, F. Liebigs
Ann. Chem. 1989, 87–88.
solution of (E)-4-p-nitrophenyl-2-oxo-3-butenoate
1
5. (a) Boger, D. L.; Kasper, A. M. J. Am. Chem. Soc. 1989,
111, 1517–1519; (b) Boger, D. L.; Corbett, W. L.; Wiggins,
J. M. J. Org. Chem. 1990, 55, 2999–3000; (c) Boger, D. L.;
Curran, T. T. J. Org. Chem. 1990, 55, 5439–5442.
6. Clark, R. C.; Pfeiffer, S. S.; Boger, D. L. J. Am. Chem.
Soc. 2006, 128, 2587–2593.
(1.25 g, 5 mmol) (5 mmol), (S)-p-toluensufinynimide
(0.78 g, 5 mmol) and Ti(OEt)4 (2.10 mL, 10 mmol) in
THF (20 mL) was stirred and refluxed for 2 h. The
reaction was allowed to warm to room temperature and
a solution of aqueous saturated NH4Cl (20 mL) was then
added. The mixture was filtered through celite, washed
with H2O (50 mL) and extracted with CH2Cl2 (3 · 25 mL).
The organic layer was dried over MgSO4 and concentrated
under reduced pressure and the crude residue was purified
by chromatography (SiO2, AcOEt/hexanes 1:4), affording
1.30 g (78%) of 2 as a pale yellow oil. Rf = 0.89 (AcOEt).
´
7. (a) Palacios, F.; Herran, E.; Rubiales, G.; Alonso, C.
Tetrahedron 2007, 63, 5669–5676; (b) Palacios, F.; Alonso,
C.; Rubiales, G.; Villegas, M. Tetrahedron 2005, 61, 2779–
´
2794; (c) Palacios, F.; Herran, E.; Rubiales, G. J. Org.
Chem. 2002, 67, 2131–2135; (d) Palacios, F.; Alonso, C.;
Amezua, P.; Rubiales, G. J. Org. Chem. 2002, 67, 1941–
1946.
20
½aꢀD +121.2 (c 1.04, CH2Cl2). 1H NMR (300 MHz,
3
CDCl3): d = 8.23 (d, JHH = 7.0 Hz, 2H), 7.69 (d,
3
8. For recent contributions, see: (a) Palacios, F.; Alonso, C.;
Legido, M.; Rubiales, G.; Villegas, M. Tetrahedron Lett.
3JHH = 7.0 Hz, 2H), 7.65 (d, JHH = 8.0 Hz, 2H), 7.34
(d, 3JHH = 8.0 Hz, 2H), 7.23 (d, 3JHH = 16.6 Hz, 1H), 6.99
(d, 3JHH = 16.6 Hz, 1H), 4.51 (q, 3JHH = 6.9 Hz, 2H), 2.41
´
2006, 47, 7815–7818; (b) Palacios, F.; Herran, E.; Alonso,
3
C.; Rubiales, G. Tetrahedron 2006, 62, 7661–7666; (c)
Palacios, F.; Ochoa de Retana, A. M.; Alonso, J. M. J.
(s, 3H), 1.47 (t, JHH = 6.9 Hz, 3H) ppm. 13C NMR
(75 MHz, CDCl3): d = 164.1, 161.2, 148.2, 142.0, 141.1,
140.3, 139.4, 129.7, 128.4, 127.7, 124.8, 123.8, 62.6, 21.2,
13.8 ppm. IR (film): mmax = 1725 (C@O st), 1607 (C@N st)
cmꢁ1. EIMS m/z = 385 ([M+], 81), 312 ([M+]–CO2Et,
100), 246 ([M+] – SOTol, 33) amu. Elem. Anal. Calcd for
C19H18N2O5S: C, 59.06; H, 4.70; N, 7.25. Found: C, 59.27;
H, 4.66; N, 7.31.
´
Org. Chem. 2006, 71, 6141–6148; (d) Palacios, F.; Herran,
E.; Alonso, C.; Rubiales, G.; Lecea, B.; Ayerbe, M.;
´
Cossıo, F. P. J. Org. Chem. 2006, 71, 6020–6030; (e)
Palacios, F.; Ochoa de Retana, A. M.; Gil, J. I.; Alonso, J.
M. Tetrahedron 2004, 60, 8937–8947.
´
9. (a) Palacios, F.; Aparicio, D.; Lopez, Y.; de los Santos, J.
M. Tetrahedron 2006, 62, 1095–1101; (b) Palacios, F.;
19. Representative example for the cycloaddition reaction of
1-azadiene 2 and electron rich dienophiles is described for
the synthesis of pyridine 4a. A solution of ethyl 2-(S)-p-
tolylsulfinimido-4-p-nitrophenyl-(E)-3-butenoate 2 (0.39 g,
1 mmol) and 1-cyclohex-1-enyl-pyrrolidine 3a (0.15 g,
1 mmol) in CH2Cl2 (3 mL) was stirred and refluxed
overnight. The resulting solution was concentrated under
reduced pressure and the crude residue was purified by
chromatography (SiO2, AcOEt/hexanes 1:3) to afford
0.23 g (71%) of pyridine 4a as a white solid. Mp 132–
133 ꢁC. 1H NMR (300 MHz, CDCl3): d = 8.26 (d,
´
Aparicio, D.; Lopez, Y.; de los Santos, J. M. Heterocycles
2006, 67, 815–822.
´
´
10. (a) Palacios, F.; Aparicio, D.; Garcıa, J.; Rodrıguez, E.;
´
Fernandez, A. Tetrahedron 2001, 57, 3131–3141; (b)
´
Palacios, F.; Aparicio, D.; de los Santos, J. M.; Rodrıguez,
E. Tetrahedron 1998, 54, 599–614; (c) Palacios, F.;
Aparicio, D.; de los Santos, J. M. Tetrahedron 1994, 50,
12727–12742.
11. For a recent review of aza-Wittig reaction, see: Palacios,
F.; Alonso, C.; Aparicio, D.; Rubiales, G.; de los Santos,
J. M. Tetrahedron 2007, 63, 523–575.
12. (a) Palacios, F.; Vicario, J.; Maliszewska, A.; Aparicio, D.
J. Org. Chem. 2007, 72, 2682–2685; (b) Palacios, F.;
Vicario, J.; Aparicio, D. J. Org. Chem. 2006, 71, 7690–
7696.
13. Palacios, F.; Vicario, J. Org. Lett. 2007, 8, 5405–
5408.
14. Palacios, F.; Vicario, J.; Aparicio, D. Eur. J. Org. Chem.
2006, 2843–2850.
3
3JHH = 8.9 Hz, 2H), 7.71 (s, 1H), 7.41 (d, JHH = 8.9 Hz,
3
3
2H), 4.41 (q, JHH = 7.0 Hz, 2H), 3.07 (t, JHH = 6.4 Hz,
3
2H), 2.57 (t, JHH = 6.4 Hz, 2H), 1.87 (m, 2H), 1.70 (m,
2H), 1.18 (t, JHH = 7.0 Hz, 3H) ppm. 13C NMR
3
(75 MHz, CDCl3): d = 165.3, 159.1, 148.0, 145.6, 145.3,
133.6, 129.6, 123.8, 122.8, 62.0, 33.2, 27.7, 22.6, 22.5,
14.3 ppm. IR (KBr): mmax = 1718 (C@O st) cmꢁ1. EIMS
m/z = 326 ([M+], 100), 253 ([M+]–CO2Et, 61) amu. Elem.
Anal. Calcd for C18H18N2O4: C, 66.25; H, 5.56; N, 8.58.
Found: C, 66.39; H, 5.65; N, 8.65.
´
´
15. Esquivias, J.; Gomez Arrayas, R.; Carretero, J. C. J. Am.
Chem. Soc. 2007, 129, 1480–1481.
20. For reviews, see: (a) Schneider, M. J. In Alkaloids:
Chemical and Biological Perspectives; Pelletier, S. W.,
Ed.; Pergamon: Oxford, 1996; Vol. 10, p 155; (b) Shipman,
M. Contemp. Org. Synth. 1995, 2, 1.
16. (a) Pearson, W. H.; Jacobs, V. A. Tetrahedron Lett. 1994,
35, 7001–7004; (b) Brady, W. T.; Shieh, C. H. J. Org.
Chem. 1983, 48, 2499–2502.