H. Hiemstra et al.
FULL PAPER
(0.98 g, 78%); m.p. 50–52 °C. H NMR: δ = 5.45 (s, 1 H), 4.66 (d,
J = 2.4 Hz, 2 H), 2.57 (t, J = 2.4 Hz, 1 H), 2.30 (s, 2 H), 2.22 (s, 2
H), 1.07 (s, 6 H) ppm. 13C NMR: δ = 199.1, 174.3, 102.2, 76.3,
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2 H), 1.49 (s, 9 H), 1.46–1.40 (m, 2 H), 1.37–1.32 (m, 2 H), 1.06 (s,
6 H), 0.90 (t, J = 7.3 Hz, 3 H) 13C NMR ppm. δ = 204.4, 199.6,
161.0, 152.4, 114.2, 100.9, 82.0, 78.9, 50.7, 50.4, 43.9, 33.9, 29.3,
55.8, 50.4, 42.3, 32.4, 28.0 ppm. IR: ν = 3243, 2960, 1655, 1011
29.0, 27.9, 22.2, 13.7. IR: ν = 1961, 1711, 1640, 1593 cm–1.
˜
˜
cm–1.
General Procedure for the Formation of Allenes: To a solution of
the acetylene in 1,4-dioxane (0.05 ) was added paraformaldehyde
(2.5 equiv.), copper iodide (0.5 equiv.) and diisopropylamine
(2 equiv.). The resulting mixture was heated to reflux and stirred
overnight. Then the reaction mixture was cooled to room tempera-
ture and quenched with saturated NaHSO4 (30 mL). The reaction
mixture was diluted with water (30 mL) and extracted with CH2Cl2
(4 ϫ 25 mL). The combined organic layers were washed with brine
(2 ϫ 25 mL), dried with MgSO4 and concentrated in vacuo.
5,5-Dimethyl-3-(2-vinylidenehexylamino)cyclohex-2-enone (25): To a
suspension
of
5,5-dimethyl-1,3-cyclohexanedione
(56 mg,
0.4 mmol) in 5 mL of benzene was added crude allene 24[13] (50 mg,
0.4 mmol). The resulting mixture was heated to reflux and stirred
for 1 h. The solvent was removed and the residue was purified by
chromatography (PE/EtOAc, 1:1 + 10% Et3N) to afford 25 as a
yellow oil (66 mg, 67%), Rf = 0.27. 1H NMR: δ = 5.08 (s, 1 H),
4.99 (br. s, 1 H), 4.88–4.85 (m. 2 H), 3.56 (d, J = 4.2 Hz, 2 H), 2.18
(s, 2 H), 2.15 (s, 2 H), 1.96–1.92 (m, 2 H), 1.42–1.36 (m, 2 H), 1.34–
1.28 (m, 2 H), 1.04 (s, 6 H), 0.89 (t, J = 7.3 Hz, 3 H) ppm. 13C
NMR: δ = 204.2, 196.7, 162.3, 100.6, 96.1, 79.3, 60.3, 50.3, 43.7,
tert-Butyl N-(Buta-2,3-dienyl)-N-(3-oxocyclohex-1-enyl)carbamate
(15): Prepared according to the general procedure from 12 (0.5 g,
2.0 mmol). The residue was purified by chromatography (PE/
EtOAc, 1:2) to give 15 as a colorless oil (0.44 g, 82%); Rf = 0.41.
1H NMR: δ = 5.76 (s, 1 H), 5.19–5.13 (m, 1 H), 4.84–4.80 (m, 2
H), 4.16–4.13 (m, 2 H), 2.73 (t, J = 5.9 Hz, 2 H), 2.36 (t, J =
6.9 Hz, 2 H), 2.01–1.94 (m, 2 H), 1.49 (s, 9 H) ppm. 13C NMR: δ
= 208, 198.5, 162.5, 151.7, 114.7, 86.7, 81.7, 77.2, 47.1, 36.4, 29.9,
32.7, 29.4, 29.4, 28.2, 22.2, 13.8 ppm. IR: ν = 3407, 1959, 1584,
˜
1518 cm–1.
General Procedure for the Preparation of Vinylogous Carbamates:
To a suspension of vinylogous amide was added Boc2O (2 equiv.)
and DMAP (10 mol-%) in CH2Cl2 (0.4 ). The resulting mixture
was stirred at room temperature until complete conversion was ob-
served with TLC. Then imidazole was added (1 equiv.) and the mix-
ture was stirred for 1 h.[24] The mixture was washed with 1 HCl
(2 ϫ 25 mL), saturated NaHCO3 (2 ϫ 25 mL), dried with MgSO4
and concentrated in vacuo.
27.6, 22.8 ppm. IR: ν = 1958, 1714, 1647 cm–1.
˜
tert-Butyl N-(Buta-2,3-dienyl)-N-(5,5-dimethyl-3-oxocyclohex-1-en-
yl)carbamate (16): Prepared according to the general procedure
from of 13 (0.5 g, 1.8 mmol). The residue was purified by
chromatography (PE/EtOAc, 1:1) to afford 16 as a colorless oil
tert-Butyl N-(3-Oxocyclohex-1-enyl)-N-(prop-2-ynyl)carbamate (12): (0.45 g, 85%); Rf = 0.47. 1H NMR: δ = 5.77 (s, 1 H), 4.82–5.19 (m,
Prepared according to the general procedure from 8 (1.0 g,
6.7 mmol) and isolated as a light brown oil, which crystallized on
standing. Recrystallization from n-hexane afforded 12 as colorless
1 H) 4.82–4.79 (m, 2 H), 4.16–4.13 (m, 2 H), 2.59 (s, 2 H), 2.21 (s,
2 H), 1.48 (s, 9 H), 1.04 (s, 6 H) ppm. 13C NMR: δ = 208.1, 199.0,
160.5, 152.0, 114.3, 86.8, 82.1, 77.4, 50.2, 47.5, 43.8, 33.7, 27.8 ppm.
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crystals (1.1 g, 66%); m.p. 71–72 °C. H NMR: δ = 5.94 (s, 1 H),
IR: ν = 1957, 1723, 1652 cm–1.
˜
4.30 (d, J = 2.4 Hz, 2 H), 2.74 (t, J = 5.9 Hz, 2 H), 2.39 (t, J =
6.3 Hz, 2 H), 2.26 (t, J = 2.4 Hz, 1 H), 2.00 (m, 2 H), 1.52 (s, 9 H)
ppm. 13C NMR: δ = 198.9, 162.0, 151.5, 115.2, 82.8, 78.2, 72.4,
tert-Butyl N-(Buta-2,3-dienyl)-N-(3-oxo-5-phenylcyclohex-1-enyl)-
carbamate (17): Was prepared according to the general procedure
from 14 (0.5 g, 1.5 mmol). The residue was purified by chromatog-
raphy (PE/EtOAc, 2:1) to give a colorless oil, which crystallized on
standing. Recrystallization from n-hexane afforded 17 as colorless
crystals (0.43 g, 83%); Rf = 0.43; m.p. 68–69 °C. 1H NMR: δ =
7.34 (t, J = 6.1 Hz, 2 H), 7.32–7.24 (m, 3 H), 5.86 (s, 1 H), 5.22–
5.16 (m, 1 H), 4.87–4.83 (m, 2 H), 4.38–432 (m, 1 H), 4.09–4.03
(m, 1 H), 3.33–3.25 (m, 1 H), 3.07–2.91 (m, 2 H), 2.69–2.56 (m, 2
H), 1.47 (s, 9 H) ppm. 13C NMR: δ = 208.0, 198.3, 161.8, 151.9,
142.9, 128.5, 126.8, 126.5, 114.4, 86.9, 82.3, 77.7, 47.3, 43.7, 41.3,
38.6, 36.6, 29.9, 27.8, 22.8 ppm. IR: ν = 3307, 1715, 1650 cm–1.
˜
tert-Butyl N-(5,5-Dimethyl-3-oxocyclohex-1-enyl)-N-(prop-2-ynyl)-
carbamate (13): Prepared according to the general procedure from
9 (1.0 g, 5.6 mmol) and isolated as a light brown oil, which crys-
tallized on standing. Recrystallization from n-hexane afforded 13
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as colorless crystals (1.2 g, 77%); m.p. 106–107 °C. H NMR: δ =
5.95 (s, 1 H), 4.31 (d, J = 2.4 Hz, 2 H), 2.62 (s, 2 H), 2.27 (t, J =
2.4 Hz, 1 H), 2.24 (s, 2 H), 1.52 (s, 9 H), 1.07 (s, 6 H) ppm. 13C
NMR: δ = 199.2, 159.9, 151.7, 114.9, 82.9, 78.2, 77.2, 72.4, 50.3,
37.9, 27.8 ppm. IR: ν = 3007, 1957, 1715, 1647, 1592 cm–1.
˜
43.8, 38.7, 33.8, 27.9 ppm. IR: ν = 3307, 1716, 1650 cm–1.
˜
3-(Buta-2,3-dienyloxy)-5,5-dimethylcyclohex-2-enone (18): Prepared
according to the general procedure from 11 (2.4 g, 15.8 mmol). The
residue was purified by chromatography (PE/EtOAc, 2:1) to afford
tert-Butyl N-(3-Oxo-5-phenylcyclohex-1-enyl)-N-(prop-2-ynyl)car-
bamate (14): Prepared according to the general procedure from 10
(0.5 g, 2.2 mmol) and purified by chromatography (PE/EtOAc, 1:2)
to afford 14 as a colorless oil, which crystallized on standing (1.2 g,
77%); Rf = 0.50; m.p. 62–63 °C. 1H NMR: δ = 7.35 (t, J = 7.4 Hz,
2 H), 7.28–7.24 (m, 3 H), 6.03 (s, 1 H), 4.47 (dd, J = 17.9, 2.4 Hz,
1 H), 4.18 (dd, J = 17.9, 2.4 Hz, 1 H), 3.35–3.29 (m, 1 H), 3.07–
2.95 (m, 2 H), 2.70–2.58 (m, 2 H), 2.29 (t, J = 2.4 Hz, 1 H), 1.50
(s, 9 H) ppm. 13C NMR: δ = 198.9, 161.5, 152.0, 143.2, 129.1,
127.3, 127.0, 115.4, 83.7, 78.6, 73.0, 44.2, 41.7, 39.3, 38.3, 28.3 ppm.
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18 as a yellow oil (1.26 g, 42%); Rf = 0.28. H NMR: δ = 5.32 (s,
1 H), 5.27 (m, 1 H), 4.88 (dt, J = 6.8, 2.4 Hz, 2 H), 4.40 (dt, J =
6.8, 2.4 Hz, 2 H), 2.27 (s, 2 H), 2.20 (s, 2 H), 1.06 (s, 6 H), 13C
NMR ppm. δ = 209.4, 199.2, 175.3, 101.9, 85.5, 76.9, 65.9, 60.1,
50.5, 42.6, 32.2. IR: ν = 2975, 1957, 1703, 1680, 1650, 1591 cm–1.
˜
2-Vinylidenehexan-1-ol (21): LiBr (5.63 g, 64.8 mmol) and CuBr
(9.3 g, 64.8 mmol) were dried under vacuum (2 Torr) at 150 °C for
2 h. THF (130 mL) was added and the mixture was stirred for
15 min and then allowed to cool to –78 °C. To this mixture was
IR: ν = 3307, 1717, 1651 cm–1.
˜
tert-Butyl N-(5,5-Dimethyl-3-oxocyclohex-1-enyl)-N-(2-vinylidene- added n-butylmagnesium chloride (2 solution in THF, 35 mL).
hexyl)carbamate (26): Prepared according to the general procedure
from 25 (60 mg, 0.24 mmol). Purification of the crude product by
chromatography (PE/EtOAc, 4:1) gave 26 as a colorless oil (30 mg,
48%); Rf = 0.30. H NMR: δ = 5.71 (s, 1 H), 4.79–4.76 (m, 2 H),
4.06 (t, J = 3.7 Hz, 2 H), 2.62 (s, 2 H), 2.22 (s, 2 H), 1.93–1.88 (m,
After being stirred for 15 min HMPA (32 mL) was added followed
by a solution of 19[11] (12.2 g, 59 mmol) in THF (10 mL). The re-
sulting mixture was slowly warmed up to room temperature for
20 min and stirred for an additional 30 min. Saturated NH4Cl
(100 mL) was added and the mixture was filtered through celite.
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Eur. J. Org. Chem. 2008, 925–933