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Li et al.
oil (1.92 g, 98%), which was dissolved in pyridine ꢁ(3 mL) and added to a
catalytic amount of DMAP and Ac2O (2 mL ) at 0C. After being stirred
vigorously for 0.5 h at that temperature, the reaction mixture was diluted
with H2O (10 mL) and extracted with Et2O (3 ꢂ 30 mL), the combined
organic layer was washed 10% aqueous HCl, H2O, brine, then dried and
concentrated, purified by chromatography to give acetate 3 (2.28 g,
100%) as a colorless oil. IR ꢀmax: 2927, 2925, 1773, 1447, 1375, 1249,
912, 734; ꢁH (200 MHz, CDCl3): 5.08 (2H, m, 2HC¼), 4.89 (1H, m,
CHOAc), 2.04 (3H, s, CH3CO–), 2.03–2.00 (6H, m, 3CH2), 1.68 (3H, s,
CH3), 1.60 (3H, s, CH3), 1.59 (3H, s, CH3), 1.56 (2H, m, CH2), 1.22
(3H, d, J ¼ 6.4 Hz). m/z: 238 (1), 195 (3), 178 (8), 163 (6), 135 (17), 109
(84), 69 (100), 43 (92).
6,10-Dimethyl-11-hydroxy-5(E ),
9(E )-undecadien-2-ol Acetyl Acetate (4)
t
To a clear solution of SeO2 (111 mg, 1 mmol) and BuOOH (70%,
1.71 mL, 12.5 mmol) in CH2Cl2 (30 mL) at 0ꢁC was added compound 3
(1.19 g, 5 mmol) in CH2Cl2 (100 mL). After being stirred at 0ꢁC for 2 h,
the reaction mixture was diluted with Et2O (100 mL) and washed
sequentially with 10% aqueous KOH, H2O, and brine, then dried and
concentrated. The resulting oil was purified by flash column chromato-
graphy on silica gel to yield the terminal alcohol 4 (0.64 g, 50%) as
a colorless oil. IR ꢀmax: 3412, 3385, 2927, 1734, 1247, 1023. ꢁH
(200 MHz, CDCl3): 5.40 (1H, t, HC¼), 5.12 (1H, t, HC¼), 4.89
(1H, m, CHOAc), 4.00 (2H, s, CH2O), 2.04 (3H, s, CH3CO–),
2.00–2.08 (6H, m, 3CH2), 1.70 (3H, s, CH3), 1.68 (3H, s, CH3), 1.56
(2H, m, CH2), 1.22 (3H, d, J ¼ 6.4 Hz). m/z: 236 (M À 18) (1), 194 (1),
161 (18), 109 (77), 67 (62), 43 (100).
3-Methyl-2-butenal (7)
To the suspension of PCC (646.5 mg, 3 mmol) in CH2Cl2 (15 mL) was
added 3-methyl-2-buten-1-ol 6 (172 mg, 2 mmol) in CH2Cl2 (5 mL) with
stirring at room temperature for 3 h, the reaction mixture was Et2O
(100 mL) diluted and filtered through a short column on silica gel to
remove the black solid, then the resulting filtrate was concentrated and
purified to give enal 7 (135 mg, 80%) as a clear oil.
ꢁH (200 MHz, CDCl3): 9.89 (1H, d, J ¼ 5.6 Hz, CHO), 5.93 (1H, d,
J ¼ 8.2 Hz, HC¼), 2.25 (3H, s, CH3), 2.05 (3H, s, CH3).