(2H, q, J 7.3, CH CH ), 5.35 (1H, t, J 6.1, CH᎐C), 6.63 (1H, d,
4.4 mmol)) in anhydrous diethyl ether (2 cm3) was added to a
᎐
2
3
J 10.4, CH᎐C). (E)-11c: Colorless oil (Found: C, 64.89; H,
solution of aluminium trichloride (0.23 g, 1.7 mmol) in
anhydrous diethyl ether (3 cm3) and the mixture was stirred at
0 ЊC for 1 h under argon. After dropwise addition of a solution
of the ester 12 (0.26 g, 1 mmol) in anhydrous diethyl ether
(1.5 cm3), stirring was continued at 0 ЊC for 3 h. The reaction
mixture was then diluted with diethyl ether (5 cm3), acidified
with 10% hydrochloric acid, and extracted with diethyl ether
(4 × 10 cm3). The combined organic layers were washed succes-
sively with saturated aq. sodium hydrogen carbonate and then
with brine, dried (MgSO4), filtered, and concentrated. The
residue was purified by column chromatography to give
tetraene alcohol 13 (0.20 g, 90%) as a colorless oil (Found: C,
81.56; H, 11.15. C15H24O requires C, 81.76; H, 10.98%);
νmax(neat)/cmϪ1 3350, 1040, 990 and 900; δH (270 MHz; CDCl3;
Me4Si) 1.2–1.3 (1H, br s, OH), 1.61 (3H, s, 6-Me), 1.67 (3H, s,
2-Me), 2.0–2.7 (8H, m, 4 × CH2), 3.99 (2H, s, CH2O), 5.0–5.1
᎐
10.72; N, 3.69. C20H39NO3Si requires C, 64.99; H, 10.63; N,
3.79%); νmax(neat)/cmϪ1 2950, 1710, 1465, 1250, 1100, 1060, 840
and 790; δH (270 MHz; CDCl3; Me4Si) 0.06 (6H, s, 2 × Me),
0.89 (9H, s, 3 × Me), 1.26 (3H, t, J 7.3, CH2CH3), 1.62 (3H, s,
6-Me), 1.82 (3H, s, 2-Me), 2.28 (6H, s, 2 × NMe), 2.0–2.3 (2H,
m, CH2), 3.2–3.4 (1H, m, CHN), 3.9–4.2 (2H, m, CH2O), 4.12
(2H, q, J 7.3, CH CH ), 5.31 (1H, t, J 6.3, CH᎐C), 6.67 (1H, d,
᎐
2
3
J 10.2, CH᎐C).
᎐
Methyl (2E,6E )-2,6-dimethyl-4-dimethylamino-10-methylene-
dodeca-2,6,11-trienoate ((E )-11d)
To a solution of ammonium salt 9d (0.39 g, 1 mmol) in a
mixture of THF (36 cm3) and 1,3-dimethyl-3,4,5,6-tetrahydro-
pyrimidin-2(1H )-one (DMPU) (9 cm3) was added potassium
tert-butoxide (0.224 g, 2 mmol) at Ϫ70 ЊC. After stirring of the
mixture for 2 h at the same temperature, water (5 cm3) was
added to the reaction mixture, which was extracted with diethyl
ether. The combined organic layers were washed with brine,
dried (MgSO4), filtered, and evaporated. The residual material
was purified by column chromatography to give the desired
rearrangement product (E)-11d (142.6 mg, 49%) and (Z)-11d
(58 mg, 20%) as colorless oils. (E)-11d (Found: C, 74.02; H,
10.26; N, 4.71. C18H29NO2 requires C, 74.18; H, 10.03; N,
4.81%); νmax(neat)/cmϪ1 1740, 1450, 1160, 1040, 900, 800 and
770; δH (270 MHz; CDCl3; Me4Si) 1.60 (3H, s, 6-Me), 1.82 (3H,
s, 2-Me), 2.0–2.4 (6H, m, 3 × CH2), 2.29 (6H, s, 2 × NMe),
3.3–3.4 (1H, m, CHN), 3.73 (3H, s, OMe), 4.9–5.0 (2H, m,
(2H, m, CH ᎐C), 5.06 (1H, d, J 10.9, CHH᎐CH), 5.1–5.3 (1H,
᎐
᎐
2
m, CH᎐C), 5.24 (1H, d, J 17.8, CHH᎐CH), 5.40 (1H, t, J 8,
᎐
᎐
CH᎐C), 6.38 (1H, dd, J 10.9 and 17.8, CH᎐CH ).
᎐
᎐
2
ꢀ-Sinensal (6)
To a solution of alcohol 13 (0.20 g, 0.9 mmol) in hexane
(120 cm3) was added manganese() oxide (2.6 g, 29.9 mmol)
and the mixture was stirred for 3 h at 0 ЊC. After filtration, the
solution was evaporated to give an oil, which was purified by
column chromatography to give β-sinensal (6) (0.14 g, 72%) as a
colorless oil, νmax(neat)/cmϪ1 1690, 1650 and 900; δH (270 MHz;
CDCl3; Me4Si) 1.63 (3H, s, 6-Me), 1.75 (3H, s, 2-Me), 2.1–2.6
CH ᎐C), 5.04 (1H, d, J 10.9, CHH᎐CH), 5.1–5.3 (1H, m,
᎐
᎐
2
(8H, m, 4 × CH ), 5.00 (2H, m, CH ᎐C), 5.06 (1H, d, J 10.9,
᎐
2 2
CH᎐C), 5.20 (1H, d, J 17.8, CHH᎐CH), 6.36 (1H, dd, J 10.9
᎐
᎐
CHH᎐CH), 5.1–5.3 (1H, m, CH᎐C), 5.24 (1H, d, J 17.8,
᎐
᎐
and 17.8, CH᎐CH ), 6.67 (1H, d, J 10.2, CH᎐C). (Z)-11d
᎐
᎐
2
CHH᎐CH), 6.38 (1H, dd, J 10.9 and 17.8, CH᎐CH ), 6.48 (1H,
᎐ ᎐
2
(Found: C, 74.12; H, 10.14; N, 4.75. C18H29NO2 requires C,
74.18; H, 10.03; N, 4.81%); νmax(neat)/cmϪ1 1740, 1450, 1160,
1040, 900, 800 and 770; δH (270 MHz; CDCl3; Me4Si) 1.70 (3H,
s, 6-Me), 1.82 (3H, s, 2-Me), 2.0–2.4 (6H, m, 3 × CH2), 2.28
(6H, s, 2 × NMe), 3.3–3.4 (1H, m, CHN), 3.74 (3H, s, OMe),
t, J 8.9, CH᎐C), 9.39 (1H, s, CHO).
᎐
Ethyl (2E,4E,6Z )-8-tert-butyldimethylsiloxy-2,6-dimethylocta-
2,4,6-trienoate (15)
To a suspension of the allylamine (Z)-11c (0.99 g, 2.68 mmol)
and sodium carbonate (0.31 g, 2.92 mmol) in dichloromethane
(30 cm3) was added dropwise 40% peracetic acid (0.56 g,
2.94 mmol) at Ϫ60 ЊC. After stirring for 30 min at Ϫ60 ЊC, the
reaction mixture was allowed to warm to 0 ЊC over a period
of 30 min. Saturated aqueous sodium hydrogen carbonate
(10 cm3) was poured into the reaction mixture. After stirring for
10 min at room temperature, the layers were separated and
the aqueous layer was extracted with ethyl acetate (4 × 10 cm3).
The combined organic layers were washed with brine, dried
(MgSO4), filtered, and evaporated under reduced pressure. The
residue was purified by column chromatography to give 15 (0.60
g, 69%), 16 (0.11g, 11%) and 17 (0.07g, 7%). 15: Colorless oil
(Found: C, 66.44; H, 10.16. C18H32O3Si requires C, 66.62; H,
9.94%); νmax(neat)/cmϪ1 1710, 1620, 1245, 1100 and 1070;
δH (270 MHz; CDCl3; Me4Si) 0.09 (6H, s, 2 × Me), 0.91 (9H, s,
3 × Me), 1.32 (3H, t, J 7, CH2CH3), 1.92 (3H, s, 6-Me), 1.99
(3H, s, 2-Me), 4.22 (2H, q, J 7, CH2CH3), 4.39 (2H, d, J 6.3,
4.9–5.0 (2H, m, CH ᎐C), 5.03 (1H, d, J 10.9, CHH᎐CH),
᎐
᎐
2
5.1–5.3 (1H, m, CH᎐C), 5.20 (1H, d, J 17.8, CHH᎐CH), 6.36
᎐
᎐
(1H, dd, J 10.9 and 17.8, CH᎐CH ), 6.67 (1H, d, J 10.3, CH᎐C).
᎐
᎐
2
Methyl (2E,6E )-2,6-dimethyl-10-methylenedodeca-2,6,11-
trienoate (12)
A solution of amine (E)-11d (0.31 g, 1 mmol) in anhydrous
diethyl ether (30 cm3) and MeI (0.21 g, 1.5 mmol) was stirred
for 2 d at room temperature. The solvent was evaporated off to
give a solid, which was purified by washing with anhydrous
diethyl ether several times. The residual material was dried
under reduced pressure to give 0.45 g of the crude desired
ammonium salt quantitatively. To a solution of the ammonium
salt (0.45 g, 1 mmol) and potassium dihydrogen phosphate (2.2
g, 16.2 mmol) in methanol (10 cm3) was added 5% sodium
amalgam (2.2 g, 4.8 mmol) and the mixture was stirred for
30 min at room temperature. Water (5 cm3) was added to the
reaction mixture, which was extracted with diethyl ether. The
combined organic layers were washed with brine, dried
(MgSO4), filtered, and evaporated. The residual material was
purified by column chromatography to give 12 (0.18 g, 68%) as
a colorless oil (Found: C, 77.25; H, 9.94. C16H24O2 requires C,
77.38; H, 9.74%); νmax(neat)/cmϪ1 1720, 1600, 1260, 1160 and
900; δH (270 MHz; CDCl3; Me4Si) 1.62 (3H, s, 6-Me), 1.84 (3H,
s, 2-Me), 2.0–2.7 (8H, m, 4 × CH2), 3.73 (3H, s, OMe), 5.0–5.1
CH O), 5.63 (1H, t, J 6.3, CH᎐C), 6.50 (1H, dd, J 11 and 15,
᎐
2
CH᎐CH), 6.85 (1H, d, J 15, CH᎐CH), 7.26 (1H, d, J 11,
᎐
᎐
CH᎐C). 16: Colorless oil (Found: C, 62.17; H, 10.47; N, 3.57.
᎐
C20H39NO4Si requires C, 62.29; H, 10.19; N, 3.63%); νmax(neat)/
cmϪ1 1740, 1245, 1100 and 1070; δH (270 MHz; CDCl3; Me4Si)
0.06 (6H, s, 2 × Me), 0.90 (9H, s, 3 × Me), 1.28 (3H, t, J 7.3,
CH2CH3), 1.54 (3H, s, 2-Me), 1.67 (3H, s, 6-Me), 2.5–2.6 (2H,
m, CH2), 2.61 (6H, s, 2 × NMe), 4.16 (2H, d, J 6.6, CH2O), 4.20
(2H, m, CH ᎐C), 5.06 (1H, d, J 10.9, CHH᎐CH), 5.1–5.3 (1H,
᎐
᎐
2
(2H, q, J 7.3, CH CH ), 5.39 (1H, t, J 6.6, CH᎐C), 5.5–5.7 (2H,
᎐
2
3
m, CH᎐C), 5.24 (1H, d, J 17.8, CHH᎐CH), 6.38 (1H, dd, J 10.9
᎐
᎐
m, CH᎐CH). 17: Colorless oil (Found: C, 61.91; H, 10.44; N,
᎐
and 17.8, CH᎐CH ), 6.75 (1H, t, J 10, CH᎐C).
᎐
᎐
2
3.46. C20H39NO4Si requires C, 62.29; H, 10.19; N, 3.63%);
νmax(neat)/cmϪ1 1716, 1472, 1255, 1065, 836 and 777; δH (270
MHz; CDCl3; Me4Si) 0.06 (6H, s, 2 × Me), 0.90 (9H, s,
3 × Me), 1.29 (3H, t, J 7.3, CH2CH3), 1.77 (3H, s, 6-Me), 1.87
(3H, s, 2-Me), 2.0–2.5 (2H, m, CH2), 2.54 (6H, s, 2 × NMe),
(2E,6E )-2,6-Dimethyl-10-methylenedodeca-2,6,11-trien-1-ol
(13)
A suspension of lithium aluminium hydride (LAH) (0.17 g,
J. Chem. Soc., Perkin Trans. 1, 2002, 1387–1396
1393