R. Dumeunier et al. / Tetrahedron Letters 43 (2002) 2307–2311
2311
chemoselective involvement of the enol silane system in
electrophilically-induced cyclisations.
in 15 mL of THF was added Bu4NF in THF (2.44 mL of
1 M, 2.44 mmol). A yellow colour appeared immediately.
The mixture was stirred for 5 min at 25°C, diluted with 20
mL of diethyl ether and washed with 20 mL of brine. The
aqueous layer was extracted twice with 20 mL of diethyl
ether. The combined extracts were dried (MgSO4) and
concentrated in vacuo. Chromatography of the residue
over silica gel (eluted with EtOAc–hexane, 1:3) gave 125
mg of the corresponding aldehyde 8 (73%) as a thick oil.
This sensitive material was directly used in the oxidation
step. Thus, to a cold solution (0°C) of aldehyde 8 (0.33 g,
2.30 mmol) in 20 mL of acetonitrile were added succes-
sively, MnO2 (4 g, 46 mmol) and KCN (15 mg, 0.23
mmol). The mixture was stirred for 25 min at 0°C and
filtered over silica-gel. The filtrate was concentrated under
reduced pressure and the resulting oil purified by silica-gel
column chromatography (with EtOAc–hexane, 1:13), giv-
ing 275 mg (84%) of pure a-methylene-g-butyrolactone 5.
1H NMR (300 MHz, CDCl3) lH (ppm): 6.20 (1H, t,
J=2.8 Hz), 5.61 (1H, t, J=2.7 Hz), 4.56–4.47 (1H, m),
3.00 (1H, ddt, J=17, 7.6, 2.5 Hz), 2.56 (1H, ddt, J=17,
5.9, 2.8 Hz), 1.48–1.33 (4H, m), 0.95 (3H, t, J=7.2
Hz).13C NMR (50 MHz, CDCl3) lC (ppm): 170.20,
134.86, 121.67, 77.23, 38.36, 33.60, 18.18, 13.72. MS (EI)
7. (a) Bartlett, P. A.; Myerson, J. J. Am. Chem. Soc. 1978,
100, 3950; (b) Bedford, S. B.; Bell, K. E.; Bennett, F.;
Hayes, C. J.; Knight, D. W.; Shaw, D. E. J. Chem. Soc.,
Perkin Trans. 1 1999, 15, 2143; (c) Jung, M. E.; Karama,
U.; Marquez, R. J. Org. Chem. 1999, 64, 663; (d) For
mechanistic studies, see: Barks, J. M.; Knight, D. W.;
Seaman, C. J.; Weingarten, G. G. Tetrahedron Lett. 1994,
35, 7259.
8. See for example: Galatsis, P.; Manwell, J. J. Tetrahedron
Lett. 1995, 36, 8179 and references cited therein.
9. (a) Morton, D. R.; Lee-Ruff, E.; Southam, R. M.; Turro,
N. J. J. Am. Chem. Soc. 1970, 92, 4349; (b) Wood, W. W.;
Watson, G. M. J. Chem. Soc., Chem. Commun. 1986, 21,
1599.
10. Corey, E. J.; Gilman, N. W.; Ganem, B. E. J. Am. Chem.
Soc. 1968, 90, 5616.
11. Typical experimental procedure: To a solution of 0.40 g of
ene adduct 3 [Table 1, entry 1, 1.22 mmol] in 10 mL of
THF was added 0.22 g of N-bromosuccinimide (1.22
mmol). The mixture was stirred at 25°C for 5 min.
Volatiles were then removed under reduced pressure. The
residue, a white solid, was stirred with pentane (10 mL)
for 1 min and filtered. The resulting solution was concen-
trated in vacuo, giving 0.51 g of pure bromoacetal 7
(>99%). To a solution of 7 [Table 2, entry 1, 1.22 mmol]
+
+
+
m/z: 141 (M +H , 80), 140 (M , 36). IR (film): 2961–
2874, 1765, 1666, 1466, 1399, 1273, 1187, 1001, 940, 813
cm−1. RN: [58557-51-3].