3526 J. Agric. Food Chem., Vol. 52, No. 11, 2004
Robert et al.
3
then the reaction mixture was refluxed for 1 h. After cooling to room
temperature, the organic layer was separated and distilled without further
treatment under reduced pressure using a fractionating column (17 ×
2 cm). The yields were between 40 and 70%. In each case, one of the
stereoisomers was formed in high excess: except for (E)-2-methylpent-
2-enal (2a), the Z-isomer was preponderant. The GC and MS data for
the E/Z isomers are given below. The NMR data refer to the major
isomer.
1.66 (m, 18H, 9 CH2), 2.28 (t, 2H, CH2, J ) 7.1 Hz), 2.35 (q, 2H,
CH2, 3J ) 7.3 Hz), 6.46 (t, 1H, CH, 3J ) 7.3 Hz), 9.37 (s,1H,
CHdO); 13C NMR (90 MHz, C2HCl3) δ 14.46 (CH3), 14.48 (CH3),
22.99 (CH2), 23.02 (CH2), 23.05 (CH2), 24.40 (CH2), 29.10 (CH2), 29.30
(CH2), 29.47 (CH2), 29.74 (CH2), 32.04 (CH2), 32.12 (CH2), 32.23
(CH2), 144.21 (Cq), 155.83 (CH), 195.70 (CdO).
Synthesis of 3-(Acetylthio)-2-alkyl Alkanals. Piperidine (100 µL) was
added to alkenals 2a-e (34 mmol) under nitrogen at 10 °C in separated
cylinders of the Quest 205 apparatus. Thioacetic acid (3.68 mL, 51.6
mmol) was then added dropwise at 10 °C. Thereafter, the reaction
mixture was stirred for another 18 h at room temperature. The mixture
was diluted with Et2O (10 mL), washed first with HCl (10 mL, 1 N)
and then twice with a saturated NaHCO3 solution (10 mL). The organic
phases were dried over Na2SO4. All of these steps were carried out at
the same time in the Quest 205 device. Then, the solvent was evaporated
for each sample. The GC purity of the crude products was 50-90%,
depending on the starting alkenal. In each case, a mixture of the two
diastereomers was obtained. In general, only small differences were
found for the NMR data of the two diastereomers (A/B), which are
explicitly reported below. The GC and MS data for the two diastere-
omers (A/B) are given below.
(E)-2-Methylpent-2-enal (2a): distillation, 110 °C, 1 bar; purity,
>95% by NMR, >99% by GC; GC ratio for E/Z (%), 99.2/0.8; GC,
RI(PONA) ) 810/810, RI(DB-Wax) ) 1175/1172; MS (EI, m/z, rel
%) 98 (M+, 48/62), 83 (17/24), 69 (32/32), 55 (31/35), 53 (14/22), 43
(15/20), 41 (100/100), 39 (52/53); 1H NMR (360 MHz, C2HCl3) δ
3
4
1.07 (t, 3H, CH3, J ) 7.6 Hz), 1.69 (d, 3H, CH3, J ) 1.3 Hz), 2.33
3
3
3
(dq, 2H, CH2, J ) 7.4 Hz, J ) 7.6 Hz), 6.44 (tq, 1H, CH, J ) 7.4
Hz, J ) 1.3 Hz), 9.30 (s, 1H, CHdO); 13C NMR (90 MHz, C2HCl3)
4
δ 9.3 (CH3), 13.1 (CH3), 22.6 (CH2), 139.1 (Cq), 156.6 (CH), 195.7
(CdO).
(Z)-2-Ethylhex-2-enal (2b): distillation, 35 °C, 130 mbar; purity,
>95% by NMR, 98.5% by GC; GC ratio for E/Z (%), 1.8/98.2; GC,
RI(PONA) ) 989/982, RI(DB-Wax) ) 1322/1318; MS (EI, m/z, rel
%) 126 (M+, 36/36), 111 (27/23), 97 (72/53), 93 (27/19), 69 (32/24),
67 (30/24), 55 (100/100), 43 (36/25), 41 (89/73), 39 (61/53); 1H NMR
3-(Acetylthio)-2-methylpentanal (3a): conversion yield, > 98% by
GC; boiling point, 120 °C (1.5 mbar); purity, 95% by NMR, 96.5%
by GC; A/B ratio (GC, %), 49.5/50.5; GC, RI(PONA) ) 1209/1213,
RI(DB-Wax) ) 1812/1825; MS (EI, m/z, rel %) 174 (M+, <1/<1),
131 (15/9), 103 (13/11), 77 (9/12), 70 (34/30), 61 (12/9), 55 (21/19),
3
(360 MHz, C2HCl3) δ 0.88-0.96 (2t, 6H, 2 CH3, J ) 7.1 Hz), 1.45
3
3
3
(tq, 2H, CH2, J ) 7.4 Hz, J ) 7.1 Hz), 2.18 (dt, 2H, CH2, J ) 7.4
Hz, 3J ) 7.4 Hz), 2.26 (q, 2H, CH2, 3J ) 7.1 Hz), 6.35 (t, 1H, CH, 3J
) 7.4 Hz), 9.28 (s, 1H, CHdO); 13C NMR (90 MHz, C2HCl3) δ 13.2
(CH3), 13.8 (CH3), 17.2 (CH2), 21.9 (CH2), 30.6 (CH2), 145.3 (Cq),
154.5 (CH), 195.0 (CdO).
1
43 (100/100); MS data are close to those reported in ref 10; H NMR
(360 MHz, C2HCl3) δ 0.92/0.96 (t, 3H, CH3, J ) 7.2 Hz), 1.06/1.10
3
(d, 3H, CH3, 3J ) 7.0 Hz), 1.47-1.74 (m, 2H, CH2), 2.29/2.31 (s, 3H,
CH3), 2.60-2.70 (m, 1H, CH), 3.76/3.94 (dt, 1H, S-CH, 3J ) 4.8/4.1
(Z)-2-Propylhept-2-enal (2c): distillation, 35 °C, 25 mbar; purity,
>95% by NMR, 98.2% by GC; GC ratio for E/Z (%), 0.3/99.7; GC,
RI(PONA) ) 1177/1168, RI(DB-Wax) ) 1503/1496; MS (EI, m/z, rel
%) 154 (M+, 50/49), 125 (72/51), 111(27/26), 107 (32/23), 97 (22/
25), 83 (68/51), 79 (43/35), 69 (33/37), 67 (34/29), 55 (100/86), 41
Hz, 3J ) 4.6/4.4 Hz), 9.56/9.57 (d, 1H, CHdO, 3J ) 0.9/1.7 Hz); 13
C
NMR (90 MHz, C2HCl3) δ 10.2/11.3 (CH3), 11.9/12.1 (CH3), 25.3/
26.5 (CH2), 31.0/31.1 (CH3), 46.1/46.3 (CH), 50.2/50.7 (S-CH), 195.3/
195.7 (S-CdO), 202.9/203.1 (CdO).
1
3
(98/100); H NMR (360 MHz, C2HCl3) δ 0.85 (t, 3H, CH3, J ) 7.2
3-(Acetylthio)-2-ethylhexanal (3b): conversion yield (GC), 90%;
boiling point, 85 °C (0.3 mbar); purity, 95% by NMR; A/B ratio (GC,
%), 69/31; GC, RI(PONA) ) 1373/1368, RI(DB-Wax) ) 1942/1932;
MS (EI, m/z, rel %) 202 (M+, <1/<1), 159 (4/10), 131 (10/11), 98
3
Hz), 0.90 (t, 3H, CH3, J ) 7.2 Hz), 1.29-1.49 (m, 6H, 3 CH2), 2.18
(t, 2H, CH2, 3J ) 7.4 Hz), 2.32 (q, 2H, CH2, 3J ) 7.4 Hz), 6.42 (t, 1H,
CH, 3J ) 7.4 Hz), 9.32 (s, 1H, CHdO); 13C NMR (90 MHz, C2HCl3)
δ 13.8 (CH3), 14.0 (CH3), 21.9 (CH2), 22.4 (CH2), 25.9 (CH2), 28.6
(CH2), 30.8 (CH2), 143.5 (Cq), 155.5 (CH), 195.3 (CdO).
1
(28/28), 97 (13/16), 69 (15/19), 55 (38/47), 43 (100/100); H NMR
3
(360 MHz, C2HCl3) δ 0.87 (t, 3H, CH3, J ) 7.0 Hz), 0.89 (t, 3H,
CH3, 3J ) 7.4 Hz), 1.30-1.79 (m, 6H, 3 CH2), 2.34/2.36 (s, 3H, CH3),
2.40-2.45 (m, 1H, CH), 3.92/3.88 (dt, 1H, S-CH, 3J ) 4.6 Hz, 3J )
5.0 Hz), 9.62/9.57 (s, 1H, CHdO); 13C NMR (90 MHz, C2HCl3) δ
12.4 (CH3), 14.0 (CH3), 19.7/20.5 (CH2), 20.6/20.5 (CH2), 31.0/30.9
(CH2), 34.8/35.5 (CH3), 43.6/43.3 (CH), 57.8/58.0 (S-CH), 195.4/195.7
(S-CdO), 203.4/203.3 (CdO).
(Z)-2-Butyloct-2-enal (2d): distillation, 110 °C, 70 mbar; purity,
>95% by NMR, 97.7% by GC; GC ratio for E/Z (%), 5/95; GC,
RI(PONA) ) 1371/1361, RI(DB-Wax) ) 1697/1688; MS (EI, m/z, rel
%) 182 (M+, 48/54), 139 (41/56), 125 (25/37), 111 (38/75), 97 (26/
40), 95 (58/48), 83 (67/58), 79 (39/40), 69 (43/41), 67 (36/44), 55 (87/
99), 41 (100/100); 1H NMR (360 MHz, C2HCl3) δ 0.85 (t, 3H, CH3, 3J
) 7.2 Hz), 0.90 (t, 3H, CH3, 3J ) 7.2 Hz), 1.25-1.40 (m, 8H, 4 CH2),
1.55 (m, 2H, CH2), 2.22 (t, 2H, CH2, 3J ) 7.4 Hz), 2.35 (q, 2H, CH2,
3-(Acetylthio)-2-propylheptanal (3c): conversion yield (GC), 80%;
boiling point, 109 °C (0.3 mbar); purity, 95% by NMR; A/B ratio
(GC, %), 66/34; GC, RI(PONA) ) 1543/1536, RI(DB-Wax) )
2087/2074; MS (EI, m/z, rel %) 230 (M+, <1/<1), 187 (3/6), 159
(10/11), 155 (5/3), 126 (27/22), 97 (10/12), 83 (15/19), 69 (32/38),
3J ) 7.4 Hz), 6.42 (t, 1H, CH, 3J ) 7.4 Hz), 9.34 (s, 1H, CHdO); 13
C
NMR (90 MHz, C2HCl3) δ 13.8 (CH3), 14.0 (CH3), 22.4 (CH2), 22.7
(CH2), 23.7 (CH2), 28.3 (CH2), 28.8 (CH2), 30.9 (CH2), 31.5 (CH2),
143.8 (Cq), 155.3 (CH), 195.3 (CdO).
55 (30/35), 43 (100/100); H NMR (360 MHz, C2HCl3) δ 0.78-0.84
1
3
(Z)-2-Pentylnon-2-enal (2e): distillation, 72 °C, 20 mbar; purity,
>95% by NMR, 97.0% by GC; GC ratio for E/Z (%), 5/95; GC,
RI(PONA) ) 1570/1555, RI(DB-Wax) ) 1900/1884; MS (EI, m/z,
rel %) 210 (M+, 21/19), 153 (32/24), 139 (24/21), 125 (12/35), 111
(17/19), 109 (20/19), 97 (29/34), 95 (31/29), 83 (47/45), 69 (34/37),
(2t, 6H, 2 CH3, J ) 7.0 Hz), 1.14-1.39 (m, 10H, 5 CH2), 2.24/2.25
(s, 3H, CH3), 2.39-2.47 (m, 1H, CH), 3.78/3.72 (dt, 1H, S-CH, 3J )
4.8 Hz, J ) 5.0 Hz), 9.53/9.55 (s, 1H, CHdO); 13C NMR (90 MHz,
3
C2HCl3) δ 14.3 (CH3), 14.4 (CH3), 21.2/21.1 (CH2), 22.6/22.7 (CH2),
28.6/29.3 (CH2), 29.6/29.5 (CH2), 31.1 (CH2), 32.4/33.1 (CH3),
44.1/43.7 (CH), 55.9/56.1 (S-CH), 195.5/195.7 (S-CdO), 203.5/203.3
(CdO).
1
67 (43/40), 55 (69/75), 41 (100/100); H NMR (360 MHz, C2HCl3) δ
0.83 (t, 3H, CH3, 3J ) 7.2 Hz), 0.86 (t, 3H, CH3, 3J ) 7.2 Hz), 1.21-
3
1.50 (m, 14H, 7 CH2), 2.18 (t, 2H, CH2, J ) 7.1 Hz), 2.31 (q, 2H,
3-(Acetylthio)-2-butyloctanal (3d): conversion yield (GC), 72%;
boiling point, 130 °C (0.3 mbar); purity, 95% by NMR; A/B ratio (GC,
%), 70/30; GC, RI(PONA) ) 1726/1720, RI(DB-Wax) ) 2260/2247;
MS (EI, m/z, rel %) 258 (M+, <1/<1), 215 (2/5), 187 (12/14), 183
(5/4), 154 (26/21), 117 (10/9), 115 (8/13), 111 (9/10), 97 (18/23), 83
CH2, 3J ) 7.4 Hz), 6.40 (t, 1H, CH, 3J ) 7.4 Hz), 9.31 (s, 1H,
CHdO); 13C NMR (90 MHz, C2HCl3) δ 13.9 (CH3), 14.0 (CH3), 22.4
(CH2), 22.5 (CH2), 23.9 (CH2), 24.8 (CH2), 28.4 (CH2), 28.6 (CH2),
28.9 (CH2), 30.9 (CH2), 31.5 (CH2), 143.8 (Cq), 155.3 (CH), 195.3
(CdO).
1
(22/25), 69 (22/28), 55 (42/49), 43 (100/100); H NMR (360 MHz,
3
(Z)-2-Hexyldec-2-enal (2f): purity, >90% by NMR, 93.6% by GC;
GC ratio for E/Z (%), 4.5/95.5; GC, RI(PONA) ) 1769/1752, RI(DB-
Wax) ) 2101/2086; MS (EI, m/z, rel %) 238 (M+, 14/16), 167 (20/
19), 153 (16/19), 139 (10/32), 97 (26/32), 95 (29/43), 83 (41/44), 69
C2HCl3) δ 0.83-0.88 (2t, 6H, 2 CH3, J ) 7.0 Hz), 1.17-1.76 (m,
14H, 7 CH2), 2.32/2.31 (s, 3H, CH3), 2.44-2.52 (m, 1H, CH), 3.80/
3
3
3.85 (dt, 1H, S-CH, J ) 4.8 Hz, J ) 5.0 Hz), 9.52/9.58 (d, 1H,
CHdO, 3J ) 2.8/2.2 Hz); 13C NMR (90 MHz, C2HCl3) δ 14.2 (CH3),
14.3 (CH3), 22.8 (CH2), 23.1/23.0 (CH2), 26.3/26.9 (CH2), 27.1/27.0
(CH2), 30.1/30.0 (CH2), 31.1 (CH2), 31.7/31.8 (CH2), 32.6/323.3 (CH3),
1
(37/41), 67 (35/39), 55 (72/74), 43 (80/79), 41 (100/100); H NMR
(360 MHz, C2HCl3) δ 0.87-0.92 (2t, 6H, 2 CH3, 3J ) 7.2 Hz), 1.24-