Helvetica Chimica Acta – Vol. 91 (2008)
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(S)-3-{[(tert-Butyl)dimethylsilyloxy]methyl}-3,7-dimethylocta-1,6-diene (6). To a stirred suspension
of (methyl)(triphenyl)phosphonium iodide powder (1.53g, 3.8 mmol) in 20 ml of dry THF at 0 8 was
added BuLi (1.6 ml, 3.7 mmol; 2.3m in hexane) over 15 min, and the mixture was stirred 20 min at 08. A
soln. of 5 (0.6 g, 2.1 mmol) in 5.0 ml of THF was added dropwise over 15 min, and the resulting mixture
was stirred at r.t. for 2 h. Acetone (1 ml) was added to the mixture to consume the excess Wittig reagent.
The mixture was poured into sat. aq. NaCl soln. and extracted with AcOEt (2 ꢁ 50 ml). The combined
extracts were dried (Na2SO4), and then concentrated under reduced pressure. The crude product was
purified by CC (silica gel; cyclohexane) to afford 6 (0.54 g, 90.6%). Colorless liquid. [a]2D0 ¼ ꢀ0.5 (c ¼
1
t
1.25, CHCl3). H-NMR (CDCl3, 300 MHz): 0.01 (s, Me2Si); 0.87 (s, BuSi); 0.95 (s, MeꢀC(3)); 1.33 (t,
J ¼ 8.4, 2 HꢀC(4)); 1.57 (s, 3 HꢀC(8)); 1.66 (s, MeꢀC(7)); 1.86 (q, J ¼ 7.3, 2 H ꢀC(5)); 3.30 (d, J ¼ 9.5,
1 H, CH2O); 3.35 (d, J ¼ 9.3, 1 H, CH2O); 4.95 (d, J ¼ 17.6, 1 HꢀC(1)); 5.00 (d, J ¼ 10.7, 1 HꢀC(1));
5.07 (t, J ¼ 7.3, H ꢀC(6)); 5.76 (dd, J ¼ 10.9, 17.7, HꢀC(2)). 13C-NMR (CDCl3, 100 MHz): ꢀ 5.5, 18.3,
25.9 (tBuMe2Si); 17.6, 20.3, 25.7 (3 Me); 22.7 (C(5)); 37.0 (C(4)); 41.8 (C(3)); 70.3 (CH2O); 125.2 (C(6));
130.9 (C(7)); 112.4, 144.8 (C(1), C(2)). EI-MS: 282 (2, Mþ), 267 (1), 225 (63), 183 (5), 169 (6), 149 (25),
141 (6), 121 (7), 107 (12), 89 (34), 75 (100), 69 (29), 55 (6).
(S)-2-Ethenyl-2,6-dimethylhept-5-en-1-ol (7). To a soln. of 6 (0.77 g, 2.73mmol) in 25 ml of dry THF
was added 4- M.S. (3.0 g) and Bu4NF · 3H 2O (0.95 g, 3.0 mmol) in one portion. The mixture was stirred
at r.t. for 3h. After the completion of the reaction, the org. phase was poured out carefully, and then M.S.
was washed with AcOEt (2 ꢁ 40 ml). The combined org. phase was washed with sat. aq. NaCl soln. and
dried (Na2SO4). The solvent was removed under reduced pressure, and the crude product was purified by
CC (silica gel; AcOEt/cyclohexane 1:15) to afford 7 (1.37 g, 91.8%). Colorless oil. [a]2D0 ¼ ꢀ16.9 (c ¼
1.23, CHCl3). 1H-NMR (CDCl3, 300 MHz): 1.03 (s, MeꢀC(2)); 1.33 (t, J ¼ 8.6, 2 HꢀC(3)); 1.59 (s,
3 HꢀC(7)); 1.67 (s, MeꢀC(6)); 1.91 (q, J ¼ 7.0, 2 HꢀC(4)); 3.33 (d, J ¼ 10.8, HꢀC(1)); 3.40 (d, J ¼ 10.8,
HꢀC(1)); 5.06 (d, J ¼ 17.8, 1 H, CH2¼CH); 5.10 (t, J ¼ 7.2, HꢀC(5)); 5.18 (d, J ¼ 10.9, 1 H, CH2¼CH);
5.72 (dd, J ¼ 10.8, 17.5, CH2¼CH). 13C-NMR (CDCl3, 100 MHz): 17.9, 19.8, 26.0 (3Me); 22.8 (C(4));
37.5 (C(3)); 42.7 (C(2)); 70.4 (C(1)); 115.0, 144.3 (CH2¼CH); 124.9 (C(5)); 131.8 (C(6)). EI-MS: 167 (6,
[M ꢀ H]þ), 151 (11), 125 (22), 111 (32), 109 (33), 97 (43), 83 (50), 69 (100), 55 (65).
(S)-2-Ethenyl-2,6-dimethylhept-5-enal (8). To a stirred soln. of pyridine (1.62 ml, 20 mmol) in 24 ml
of CH2Cl2 was added CrO3 (1.0 g, 10 mmol) in one portion at 08. After 1 h, a soln. of 7 (0.34 g, 2 mmol) in
8 ml of CH2Cl2 was added dropwise over 5 min at r.t. The mixture was stirred for 13min, and then filtered
through silica gel (200 – 300 mesh) under reduced pressure. The org. phase was washed with sat. aq. NaCl
soln. and dried (Na2SO4). The solvent was removed under reduced pressure to give 8 (0.3g, 91.0%).
Colorless liquid. [a]2D0 ¼ þ9.7 (c ¼ 1.05, CHCl3). 1H-NMR (CDCl3, 300 MHz): 1.17 (s, MeꢀC(2)); 1.57 (s,
3 HꢀC(7)); 1.60 (t, J ¼ 7.8, 2 HꢀC(3)); 1.66 (s, MeꢀC(6)); 1.91 (q, J ¼ 7.7, 2 H ꢀC(4)); 5.07 (t, J ¼ 7.2,
HꢀC(5)); 5.12 (d, J ¼ 17.7, 1 H, CH2¼CH); 5.26 (d, J ¼ 10.8, 1 H, CH2¼CH); 5.80 (dd, J ¼ 10.8, 17.4,
CH2¼CH); 9.38 (s, HꢀC(1)). 13C-NMR (CDCl3, 100 MHz): 17.6, 25.6 (3Me); 22.6 (C(4)); 35.6 (C(3));
52.7 (C(2)); 116.5, 138.6 (CH2¼CH); 123.6 (C(5)); 132.3 (C(6)); 202.7 (C(1)). EI-MS: 166 (Mþ), 165 (9),
151 (13), 137 (18), 109 (27), 95 (40), 84 (47), 69 (100), 55 (41).
(2S,3S)/(2R,3S)-3-Ethenyl-1-(4-methoxyphenyl)-3,7-dimethyloct-6-en-2-ol (9). To a soln. of
8
(0.17 g, 1 mmol) in 10 ml of THF was added (4-methoxybenzyl)magnesium chloride (4.5 ml, 2.0 mmol,
0.45m in THF) at 08 over 15 min. The mixture was stirred at r.t. for 2 h, and then the reaction was
quenched with 5 ml of sat. aq. NH4Cl soln. The resulting mixture was extracted with AcOEt (3 ꢁ 3 0 ml).
The combined org. phase was washed with sat. aq. NaCl soln. and dried (Na2SO4). The solvent was
removed under reduced pressure, and the crude product was purified by CC (silica gel; AcOEt/
cyclohexane 1:10) to afford 9 (0.27 g, 96.0%). Colorless oil. 1H-NMR (CDCl3, 300 MHz): 1.06 – 1.10 (m,
MeꢀC(3)); 1.45 – 1.60 (m, 2 HꢀC(4)); 1.59 (s, 3 HꢀC(8)); 1.68 (s, MeꢀC(7)); 1.87 – 1.98 (m,
2 HꢀC(5)); 2.35 – 2.47 (m, HꢀC(1)); 2.78 – 2.88 (m, HꢀC(1)); 3.45 – 3.54 (m, HꢀC(2)); 3.79 (s,
MeO); 5.04 – 5.14 (m, 1 H, CH2¼CH); 5.07 – 5.16 (m, HꢀC(6)); 5.17 – 5.26 (m, 1 H, CH2¼CH); 5.78 –
5.91 (m, CH2¼CH); 6.85 (d, J ¼ 7.4, HꢀC(3’), HꢀC(5’)); 7.09 – 7.17 (m, HꢀC(2’), HꢀC(6’)). 13C-NMR
(CDCl3, 100 MHz): 17.2, 17.4, 17.6, 25.7 (3 Me); 22.6, 22.7 (C(5)); 36.8, 37.4 (C(1)); 37.5 (C(4)); 44.4, 44.7
(C(3)); 55.2 (MeO); 78.3, 78.9 (C(2)); 113.9 (C(3’)); 114.3, 114.8, and 143.6, 143.8 (CH2¼CH); 124.7,
124.8 (C(6)); 130.2 (C(2’)); 131.3, 131.4 (C(1’)); 131.7 (C(7)); 158.1 (C(4’)). EI-MS: 288 (14, Mþ), 270 (4),
255 (1), 227 (2), 150 (38), 121 (100), 109 (7), 95 (16), 69 (29), 55(7).