B.-R. Chang et al. / Tetrahedron Letters 43 (2002) 3233–3235
3235
References
solution (1 mL) and extracted with AcOEt (3×20 mL). The
organic layers were washed with brine (2×10 mL), dried
with anhydrous MgSO4, filtered and evaporated. Without
purification, crude 5a was treated with boron trifluoride
(cat.) in 20 mL of CH2Cl2 for 1 day, water (20 mL) was
then added. After extraction with CH2Cl2 (2×20 mL), the
organic layers were washed with brine (2×10 mL), dried
with anhydrous MgSO4, filtered and evaporated. The
crude product was purified by flash chromatography (hex-
ane/AcOEt=4/1) to afford dehydration product 6a (293
mg, 86%).
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1
8. Selected spectral data of 6a: H NMR (500 MHz, CDCl3):
l 7.72 (d, J=8.5 Hz, 2H), 7.35–7.26 (m, 7H), 5.95 (dd,
J=8.0, 3.0 Hz, 1H), 5.15–5.12 (m, 1H), 4.70 (d, J=15.0
Hz, 1H), 4.61 (d, J=15.0 Hz, 1H), 4.05 (dd, J=8.0, 3.0
Hz, 1H), 3.21 (ddd, J=19.0, 5.0, 3.0 Hz, 1H), 2.88–2.81
1
(m, 1H), 2.42 (s, 3H); 6b: H NMR (500 MHz, CDCl3): l
7.73 (d, J=8.0 Hz, 2H), 7.35–7.26 (m, 7H), 5.66 (s, 1H),
4.65 (d, J=15.0 Hz, 1H), 4.57 (d, J=15.0 Hz, 1H), 4.05
(dd, J=8.0, 3.0 Hz, 1H), 3.01 (dd, J=18.5, 3.0 Hz, 1H),
2.83 (dd, J=18.5, 8.0 Hz, 1H), 2.43 (s, 3H), 1.72 (s, 3H);
6e: 1H NMR (500 MHz, CDCl3): l 7.71 (d, J=8.0 Hz,
2H), 7.37–7.23 (m, 12H), 6.21 (d, J=2.5 Hz, 1H), 4.72 (s,
2H), 4.20 (dd, J=8.0, 3.5 Hz, 1H), 3.59 (dd, J=18.0, 3.5
Hz, 1H), 3.25 (ddd, J=18.0, 8.0, 2.5 Hz, 1H), 2.42 (s, 3H);
6f: 1H NMR (500 MHz, CDCl3): l 7.67 (d, J=8.5 Hz,
2H), 7.35–7.23 (m, 10H), 7.134 (d, J=7.0 Hz, 2H), 5.75 (d,
J=1.0 Hz, 1H), 4.69 (d, J=15.0 Hz, 1H), 4.59 (d, J=15.0
Hz, 1H), 4.00 (dd, J=8.5, 3.5 Hz, 1H), 3.34 (S, 2H), 2.96
(dd, J=18.5, 3.5 Hz, 1H), 2.70 (dd, J=18.5, 1.0 Hz, 1H),
5. Chang, M. Y.; Chang, B. R.; Tai, H. M.; Chang, N. C.
Tetrahedron Lett. 2000, 41, 10273.
6. Koomen, G. J.; Wanner, M. J. J. Org. Chem. 1994, 59,
7479.
7. Standard procedure: A solution of 1a (357 mg, 1.0 mmol)
in THF (10 mL) was added to a rapidly stirred suspension
of sodium hydride (60% dispersion in mineral oil, 1.2
mmol). After the reaction mixture was stirred at room
temperature for 5 min, 2.0 mmol of LiAlH4 was then
added and the resulting reaction mixture was stirred for
1.0 h, quenched with a saturated ammonium chloride
1
2.42 (s, 3H); 6j: H NMR (500 MHz, CDCl3): l 7.72 (d,
J=8.0 Hz, 2H), 7.39–7.30 (m, 7H), 7.00–6.97 (m, 2H),
6.92–6.88 (m, 2H), 6.21 (d, J=7.5 Hz, 1H), 5.31 (dd,
J=7.5, 6.5 Hz, 1H), 4.88 (d, J=14.5 Hz, 1H), 4.57 (d,
J=6.5 Hz, 1H), 4.54 (d, J=14.5 Hz, 1H), 4.00 (s, 1H),
1
2.44 (s, 3H); 8b: H NMR (500 MHz, CDCl3): l 7.31–7.21
(m, 5H), 5.74 (s, 1H), 4.63 (s, 2H), 2.56 (t, J=8.0 Hz, 2H),
2.22 (t, J=8.0 Hz, 2H), 1.65 (s, 3H).