86
Papers
SYNTHESIS
Dienes 4, 9, 12, and 14 by Palladium-Catalyzed Elimination;
2-[2-(Methoxycarbonyloxy)but-3-enyl]pyridine (11a):
Yield: 3.55 g (86%); purified by distillation, bp 67 °C (0.07 mbar).
Anal. calc. for C11H13O3N: C, 63.74; H, 6.33. Found: C, 63.86;
H, 6.58.
General Procedure D:
A 5 mL two-necked flask was equipped with a magnetic stirrer and
charged with either purified or crude carbonate 3, 7, 8, 11, or 13
(5.0 mmol). Pd(PPh3)4 (0.058–0.289 g; 0.05–0.25 mmol) was added,
and the mixture was stirred under N2 at 25 to 35 °C until the evolution
of CO2 ceased. The crude product was purified by distillation or
column chromatography.
(E)-2-[2-(Methoxycarbonyloxy)pent-3-enyl]pyridine (11b):
Yield: 3.08 g (70%); purified by distillation, bp 84°C (0.05 mbar).
Anal. calc. for C12H15O3N: C, 65.14; H, 6.83. Found: C, 65.29;
H, 6.97.
(E)-Penta-2,4-dienoic Acid 1¢,1¢-Dimethylethyl Ester (4a):
Yield: 0.71 g (93%); purified by distillation, bp 44°C (13 mbar). The
physical and spectroscopic data are in accordance with those describ-
ed in the literature.18
3-(Methoxycarbonyloxy)pent-4-enenitrile (13):
Under N2 atmosphere, a 1.6 M solution of BuLi in hexane (6.6 mL,
10.5 mmol) was stirred in a 50 mL two-necked flask, equipped with
a magnetic stirrer, a septum, and a thermocouple. After cooling to
–20°C, anhyd THF (8 mL) was added, and the mixture was cooled to
–78°C. In a second flask, a solution of MeCN (0.52 mL, 10 mmol) in
anhyd THF (2 mL) was prepared under N2 and also cooled to –78°C.
The solution of MeCN was transferred by a cannula into the slightly
evacuated flask containing the solution of BuLi. The temperature was
allowed to reach –50°C, and a white precipitate formed gradually. The
mixture was cooled to –78°C, and aldehyde 1a (0.8 mL, 12 mmol) was
injected in one portion whereby the temperature reached –50°C. The
cooling bath was removed, so that the mixture warmed up to –20°C.
Methyl chloroformate (0.92 mL, 12 mmol) was injected rapidly, and
the temperature rose to 15°C within 1 min. After stirring for 18 h at r.t.,
the mixture was worked up according to Procedure C. Yield: 1.30 g
(84%) after column chromatography; Rf 0.6 (CHCl3). The product was
submitted to Procedure D without further purification.
(2E,4E)-Hexa-2,4-dienoic Acid 1¢,1¢-Dimethylethyl Ester (4b):
Yield: 0.76 g (91%); purification by distillation, bp 45 °C (4 mbar).
The physical and spectroscopic data are in accordance with those de-
scribed in the literature.19
(2E,4E)-5-Phenylpenta-2,4-dienoic Acid 1¢,1¢-Dimethylethyl Ester
(4c):
Yield: 1.03 g (90%); purified by column chromatography; Rf 0.8
(CHCl3). The physical and spectroscopic data are in accordance with
those described in the literature.20
(2E,4E)-2-Methylpenta-2,4-dienoic Acid [2¢,6¢-Bis(1¢¢,1¢¢-dimethyl-
ethyl)-4¢-methyl]phenyl Ester (9a):
Yield: 1.37 g (87%); purified by distillation, bp 60°C (2 mbar).
Anal. calc. for C21H30O2: C, 80.20; H, 9.62. Found: C, 80.06; H, 9.70.
Table 2. Spectroscopic Properties of Carbonates 3, 7, 8, 11, 13 and Dienes 9 Prepared
Product
IR (cm–1) 1H NMR (CDCl3/TMS)
13C NMR (CDCl3/TMS)
MS m/z
d, J (Hz)
d
(%)
3a
1760
1745
1.44 (s, 9H, CCH3), 2.50–2.72 (m, 2H,
28.11, 40.58, 54.78, 75.07, 81.27, 174 (12), 157 (15), 128 (19), 99
CH2), 3.79 (s, 3H, OCH3), 5.23–5.90 (m,
4H, CH2=CHCH)
118.15, 134.64, 154.85, 168.71
(21), 81 (53), 57 (100)
3b
3c
1752
1733
1.43 (s, 9H, CCH3), 1.69 (d, J=1.3, CH3),
2.45–2.71 (m, 2H, CH2), 3.76 (s, 3H,
OCH3), 5.40–5.90 (m, 3H, CH=CHCH)
17.72, 28.01, 40.94, 54.63, 75.36, 188 (15), 171 (6), 142 (19), 130
81.05, 127.66, 130.98, 154.89, (34), 57 (100)
168.86
28.00, 40.97, 54.78, 75.26, 81.30, 306 (M+, 3), 250 (12), 204 (83),
125.36, 126.75, 128.28, 128.61, 174 (24), 157 (53), 130 (100)
133.90, 135.85, 154.85, 168.65
1760
1735
1.44 (s, 9H, CCH3), 2.63 (dd, J=6, 15.5,
1H, CH2CO), 2.79 (dd, J=8, 15.5, 1H,
CH2CO), 3.78 (s, 3H, OCH3), 5.62–5.65
(m, 1H, CH), 6.17 (dd, J=7.5, 16, 1H,
CH), 6,73 (d, J=16, 1H, CHPh), 7.25–7.40
(m, 5H, Harom
)
7b/8b
1725
1750
1.11; 1.18 (d, J=7, 3H, CH3), 1.444; 1.436
(s, 9H, CCH3), 2.62–2.70 (m, 1H, CH),
3.768; 3.783 (s, 3H, OCH3), 5.22–5.44 (m,
3H, CH2=CCH), 5.69–5.83 (m, 1H, CH)
12.82, 29.97, 44.52, 54.70, 80.00, 188 (4), 171 (9), 142 (18), 112
80.92, 120.08, 133.72, 154.79, (10), 95 (26), 57 (100)
172.33, 12.32, 27.97, 44.61, 54.77,
79.29, 80.98, 118.70, 132.99,
155.07, 172.04
15.61, 26.13, 43.89, 44.89, 54.80, 228 (M+, 0.5), 171 (19), 152 (6), 95
80.79, 119.01, 134.05, 155.07, (100)
216.00
7c
1710
1760
1.13 (s, 9H, CCH3), 1.15 (d, J=7, 3H,
CH3), 3.32–3.37 (m, 1H, CH), 3.79 (s, 3H,
OCH3), 5.16–5.32 (m, 3H, CH2=CCH),
5.72–5.83 (m, 1H, CH)
11.02, 19.63, 21.03, 50.72, 54.76, 290 (M+, 3), 214 (6), 147 (100)
77.83, 118.02, 128.82, 133.51,
134.26, 137.70, 138.74, 154.88,
209.60
7d
1700
1760
1.20 (d, J=7.3, 3H, CH3), 2.19 (s, 6H,
CH3), 2.27 (s, 3H, CH3), 3.11–3.15 (m,
1H, CH), 3.75 (s, 3H, OCH3), 5.26–5.38
(m, 2H, CH2), 5.55–5.59 (m, 1H, CH),
6.83 (s, 2H, Harom
)
8a
1751
1.30 (s, 9H, CCH3), 1.32 (s, 9H, CCH3),
1.45 (d, J=3, 3H, CH3), 2.31 (s, 3H, CH3),
3.12–3.22 (m, 1H, CH), 3.77 (s, 3H,
OCH3), 5.32–5.48 (m, 2H, CH2), 5.57–
5.62 (m, 1H, CH), 5.82–5.95 (m, 1H, CH),
12.15, 21.45, 31.33, 31.47, 35.17, 276 (2), 220 (93), 204 (77), 95
35.21, 43.93, 54.71, 78.10, 120.00, (15), 57 (100)
126.94, 127.26, 132.35, 134.66,
142.00, 142.04, 146.02, 154.65,
172.64
7.09–7.13 (m, 2H, Harom
)