Thiery et al.
JOCNote
SCHEME 1. Proposed Mechanism
9.1, 27.5, 64.1, 74.0, 124.7, 126.3, 127.7, 128.5, 136.2, 142.6,
174.4; IR (film) 3445, 2982, 2942, 1738, 1454, 1382, 1349, 1276,
1186, 1083, 1009, 974, 759, 701. Anal. Calcd for C13H16O3: C,
70.89; H, 7.32. Found: C, 70.63; H, 7.45.
(E)-4-Hydroxy-4-phenylbut-2-enyl pivalate (5f): colorless oil,
78%, L/B and E/Z > 99.9; 1H NMR (250 MHz, CDCl3) δ 1.11
(s, 9H), 2.72 (br s, 1H), 4.46 (d, 2H, J = 4.6 Hz), 5.10 (d, 1H, J =
4.9 Hz), 5.80 (m, 2H), 7.21 (m, 5H); 13C NMR (63 MHz, CDCl3)
δ 27.6, 39.2, 64.5, 74.6, 125.5, 126.8, 128.2, 129.0, 136.2, 143.0,
178.8; IR (film) 3455, 2975, 1728, 1480, 1373, 1283, 1156, 1045,
971, 701; ESHRMS calcd for C15H20O3Na 271.1310, found
271.1304.
(E)-4-(4-Chlorophenyl)-4-hydroxybut-2-enyl propionate (3h):
pale yellow oil, 78%, L/B and E/Z > 99.9; 1H NMR (250 MHz,
CDCl3) δ 1.09 (t, 3H, J = 7.3 Hz), 2.30 (q, 2H, J = 7.3 Hz), 3.19
(br s, 1H), 4.53 (d, 2H, J = 4.0 Hz), 5.12 (d, 1H, J = 4.1 Hz),
5.84 (m, 2H), 7.25 (m, 4H); 13C NMR (63 MHz, CDCl3) δ 8.9,
27.3, 63.8, 73.2, 125.0, 127.6, 128.5, 133.2, 135.6, 140.8, 174.2;
IR (film) 3417, 2979, 1731, 1491, 1383, 1187, 1090, 1014, 911,
735; ESHRMS calcd for C13H15O3NaCl 277.0607, found
277.0614.
(E)-4-(2-Bromophenyl)-4-hydroxybut-2-enyl propionate (3j):
pale yellow oil, 74%, L/B and E/Z > 99.9; 1H NMR (250
MHz, CDCl3) δ 0.88 (t, 3H, J = 7.6 Hz), 2.08 (q, 2H, J = 7.5
Hz), 3.11 (br, 1H), 4.31 (m, 2H), 5.35 (s, 1H), 5.66 (m, 2H), 6.89
(dt, 1H, J = 1.5 Hz, J = 7.9 Hz), 7.08 (dd, 1H, J = 4.6 Hz, J =
9.6 Hz), 7.28 (m, 2H); 13C NMR (63 MHz, CDCl3) δ 8.9, 27.3,
64.0, 72.1, 122.1, 125.0, 127.6, 127.7, 128.9, 132.5, 134.0, 141.3,
174.2; IR (film) 3436, 2980, 1729, 1465, 1349, 1190, 1084, 1016,
910, 733; ESHRMS calcd for C13H15O3NaBr 321.0102, found
321.0095.
(E)-4-Hydroxy-4-p-tolylbut-2-enyl pivalate (5k): colorless oil,
80%, L/B and E/Z > 99.9; 1H NMR (250 MHz, CDCl3) δ 1.08
(s, 9H), 2.21 (s, 3H), 3.23 (br s, 1H), 4.41 (d, 2H, J = 4.8 Hz),
5.00 (d, 1H, J = 4.4 Hz), 5.71 (td, 1H, J = 4.9 Hz, J = 15.6 Hz),
5.79 (dd, 1H, J = 5.2 Hz, J = 15.7 Hz), 7.01 (d, 2H, J = 7.6 Hz),
7.10 (d, 2H, J = 7.8 Hz); 13C NMR (63 MHz, CDCl3) δ 20.8,
27.0, 38.5, 64.0, 73.5, 124.3, 126.0, 128.9, 135.8, 137.0, 139.5,
178.1; IR (film) 3439, 2973, 1728, 1480, 1397, 1283, 1156, 1088,
970, 819; ESHRMS calcd for C16H22O3Na 285.1467, found
285.1457.
(E)-4-(4-Chlorophenyl)-4-methoxybut-2-enyl pivalate (5q):
colorless oil, 64%, L/B and E/Z > 99.9; 1H NMR (250 MHz,
CDCl3) δ 1.13 (s, 9H), 3.23 (s, 3H), 4.53 (m, 3H), 5.74 (m, 2H),
7.21 (m, 4H); 13C NMR (63 MHz, CDCl3) δ 27.0, 38.5, 56.2,
63.6, 82.5, 126.6, 128.0, 128.5, 133.2, 133.5, 139.0, 177.8; IR
(film) 2976, 1729, 1482, 1462, 1282, 1152, 1090, 1015, 968, 824;
ESHRMS calcd for C16H21O3NaCl 319.1077, found 319.1082.
improved the efficiency and the selectivity of the process. The
methodology is particularly convenient for the oxidation of
homoallylic alcohols, corresponding E-acyloxylated pro-
ducts being obtained in fair to good yields.
Experimental Section
Method A for the Oxidation of 1. A round-bottomed flask was
charged with LiOH H2O (2.0 mmol, 84 mg) and EtCO2H
3
(1 mL) and the mixture was heated (oil bath, 40 °C) for 10 min.
BQ (2.0 mmol, 216 mg), Pd(OAc)2 (0.1 mmol, 22.4 mg), and
EtCO2H (1 mL) were added, and the mixture was stirred at rt for
15 min. 1 (1.0 mmol) was added, and the mixture was heated (oil
bath, 40 °C) for 24 h. After cooling to rt, the mixture
was filtered through a SiO2 pad, which was washed with Et2O
(50 mL). NaOH (2 M, 25 mL) was added, and the mixture was
stirred for 15 min. The organic phase was washed with H2O
(25 mL). The aqueous combined phases were extracted with
Et2O (25 mL). The combined organic phases were dried over
MgSO4, and then evaporated to dryness. Flash chromatography
(petroleum ether/EtOAc, 95:5-60:40) led to 3.
Method B for the Oxidation of 1. A round-bottomed flask was
charged with LiOH.H2O (2.0 mmol, 84 mg) and t-BuCO2H
(2 g), and the mixture was heated (oil bath, 40 °C) for 10 min. BQ
(0.05 mmol, 5.5 mg), MnO2 (2.0 mmol, 174 mg), Pd(OAc)2
(0.1 mmol, 22.4 mg), and CH3CN (1 mL) were added, and the
mixture was stirred at rt for 15 min. 1 (1.0 mmol) was added, and
the mixture was heated (oil bath, 40 °C) for 72 h. After cooling to
rt, the mixture was filtered through a SiO2 pad, which was
washed with Et2O (50 mL). NaOH (2 M, 25 mL) was added, and
the mixture was stirred for 15 min. The organic phase was
washed with H2O (25 mL). The aqueous combined phases were
extracted with Et2O (25 mL). The combined organic phases were
dried over MgSO4, and then evaporated to dryness. Flash
chromatography (petroleum ether/EtOAc, 95:52-60:40) led
to 5.
Acknowledgment. We are indebted to “Ville de Reims” for
a Ph.D. studentship to E.T. and to the CNRS for financial
support through the program “CPDD, Chimie et
ꢀ
Developpement Durables”.
Supporting Information Available: General information,
analytical data of compounds 3a-3e, 3g, 3i, 3m-3p, 5a, 5c, 5e,
5g, 5l, and 5r-5v, ESI/MS(þ) spectra (Figures S1-S6), and the
copies of 1H NMR and 13C NMR. This material is available free
(E)-4-Hydroxy-4-phenylbut-2-enyl propionate (3f): pale yel-
low oil, 64%, L/B and E/Z > 99.9; 1H NMR (250 MHz, CDCl3)
δ 1.00 (t, 3H, J = 7.6 Hz), 2.20 (q, 2H, J = 7.5 Hz), 3.05 (br s,
1H), 4.43 (d, 2H, J = 5.0 Hz), 5.05 (d, 1H, J = 5.2 Hz),
5.65-5.85 (m, 2H), 7.21 (m, 5H); 13C NMR (63 MHz, CDCl3) δ
1774 J. Org. Chem. Vol. 75, No. 5, 2010