S-Methyl thioates
(CH2), 43.9 (CH2) and 200.0 (CO); m/z (EI) 159 (12%), 127 (57),
109 (7), 75 (14), 57 (100) and 41 (44).
A mixture of Me3Al (20 mL, 2 M in toluene, 40 mmol) and
elemental sulfur (1.34 g, 42 mmol) was heated to reflux for 2 h
resulting in complete consumption of the sulfur and the formation
of a translucent pale yellow solution. After cooling to 0 ◦C
the methyl ester (38 mmol) or dimethyl carbonate (19 mmol)
dissolved in dry CH2Cl2 (20 mL) was added. The mixture was
stirred for 1 h at 0 ◦C and for 1 h at room temperature.
Cautious hydrolysis of the remaining organometallic reactant was
performed at 0 ◦C by the dropwise addition of water, saturated
NH4Cl, and 2 N HCl (Caution! The hydrolysis reaction was slow in
the beginning, but became very violent after an initiation period.)
The aqueous phase was separated and extracted with diethyl ether
(3 ¥ 50 mL). The combined organic layers were dried (MgSO4)
and concentrated. The pure S-methyl thioates were obtained by
column chromatography on silica gel with pentane–diethyl ether
(20 : 1) as a colourless oils.
S-Methyl benzothioate 15. Yield: 5.54 g (96%); TLC (pentane–
diethyl ether = 20 : 1): RF 0.29; GC: I 1317; nmax(film)/cm-1 3062,
2928, 1659, 1580, 1447, 1312, 1204, 1174, 967, 906, 771, 684 and
645; lmax(CH2Cl2)/nm 222 (e/dm3 mol-1 cm-1 7850), 238 (10300)
1
and 268 (7380); dH(400 MHz; CDCl3; Me4Si) 2.47 (3 H, s, JC,H
141.9, CH3), 7.41–7.47 (2 H, m, 2 ¥ CH), 7.56 (1 H, tt, J 7.4, 4JH,H
1.5, CH) and 7.95–7.98 (2 H, m, 2 ¥ CH); dC(100 MHz; CDCl3;
Me4Si) 11.7 (CH3), 127.1 (2 ¥ CH), 128.6 (2 ¥ CH), 133.2 (CH),
137.1 (Cquart.) and 192.4 (CO); m/z (EI) 152 (7%), 105 (100), 77
(69) and 51 (30).
S-Methyl 2-phenylethanethioate 16. Yield: 5.92 g (94%);
TLC (pentane–diethyl ether = 20 : 1): RF 0.41; GC: I 1389;
n
max(film)/cm-1 3063, 3030, 2928, 1682, 1495, 1453, 1420,
1309, 1182, 1074, 1018, 998, 912, 774, 723, 699 and 596;
l
max(CH2Cl2)/nm 234 (e/dm3 mol-1 cm-1 4580); dH(400 MHz;
1
1
CDCl3; Me4Si) 2.27 (3 H, s, JC,H 141.7, CH3), 3.82 (2 H, s, JC,H
130.2, CH2) and 7.26–7.35 (5 H, m, 5 ¥ CH); dC(100 MHz; CDCl3;
Me4Si) 11.9 (CH3), 50.3 (CH2), 127.4 (CH), 128.6 (2 ¥ CH), 129.5
(2 ¥ CH), 133.7 (Cquart.) and 197.7 (CO); m/z (EI) 166 (17%), 138
(1), 119 (16), 91 (100), 75 (5), 65 (22) and 39 (10).
S-Methyl butanethioate 11. Yield: 1.96
(pentane–diethyl ether 20 : 1): RF 0.48; GC:
max(film)/cm-1 2965, 2932, 2876, 1688, 1458, 1417, 1261,
1114, 996, 885, 800, 761, 695 and 598; lmax(CH2Cl2)/nm 232
(e/dm3 mol-1 cm-1 3810); dH(400 MHz; CDCl3; Me4Si) 0.96 (3
H, t, J 7.4, 1JC,H 125.7, CH3), 1.70 (2 H, sextet, J 7.4, 1JC,H 128.8,
CH2), 2.29 (3 H, s, 1JC,H 141.4, CH3) and 2.54 (2 H, t, J 7.4, 1JC,H
128.4, CH2); dC(100 MHz; CDCl3; Me4Si) 11.5 (CH3), 13.5 (CH3),
19.2 (CH2), 45.7 (CH2) and 199.9 (CO); m/z (EI) 118 (7%), 103
(11), 75 (10), 71 (45) and 43 (100).
g
(44%); TLC
=
I
897;
n
S,S¢-Dimethyl carbonodithioate 17. Yield: 4.50 g (97%);
TLC (pentane–diethyl ether = 10 : 1): RF 0.62; GC: I 981;
n
max(film)/cm-1 2929, 1745, 1642 (CO), 1422, 1310, 1043, 966,
856 and 573; lmax(CH2Cl2)/nm 227 (e/dm3 mol-1 cm-1 3270) and
249 (5230); dH(400 MHz; CDCl3; Me4Si) 2.44 (6 H, s, 1JC,H 142.4,
2 ¥ CH3); dC(100 MHz; CDCl3; Me4Si) 13.0 (2 ¥ CH3) and 190.3
(CO); m/z (EI) 122 (50%), 94 (61), 75 (100) and 45 (73).
S-Methyl 3-methylbutanethioate 12. Yield: 3.08 g (61%);
TLC (pentane–diethyl ether = 20 : 1): RF 0.57; GC: I 951;
n
max(film)/cm-1 2959, 2931, 2872, 1688, 1466, 1134, 1018, 940 and
Tropone hydrate 42b
757; lmax(CH2Cl2)/nm 232 (e/dm3 mol-1 cm-1 3190); dH(400 MHz;
CDCl3; Me4Si) 0.96 (6 H, d, J 6.7, 1JC,H 125.3, 2 ¥ CH3), 2.17 (1
H, septet, J 6.8, CH), 2.30 (3 H, s, CH3) and 2.44 (2 H, d, J 7.1,
CH2); dC(100 MHz; CDCl3; Me4Si) 11.5 (CH3), 22.3 (2 ¥ CH3),
26.4 (CH), 52.7 (CH2) and 199.4 (CO); m/z (EI) 132 (4%), 117 (6),
85 (55), 75 (20), 57 (100) and 41 (74).
The diol 41 was prepared according to the method of Celestini
et al.26 This diol (0.1 g, 0.78 mmol) was dissolved in a mixture
of diethyl ether (15 mL) and dichloromethane (5 mL), and Celite
(0.31 g) was added. The mixture was cooled to 0 ◦C, and CrO3
(0.31 g, 3.1 mmol) was added in small portions.27 After stirring
for 30 min, the reaction mixture was diluted with diethyl ether
and then filtered through a Celite pad. Drying over MgSO4
and removal of the solvent gave the desired product in 2 : 1
mixture with the starting material. Purification was not possible
because it started to decompose directly after synthesis. GC: I
1171; nmax/cm-1 1012, 1131, 1244, 1405, 1539, 1730, 2990, 3045;
dH(300 MHz, CDCl3, Me4Si) 3.29 (4 H, dd, 3JH,H 3.5, 4JH,H 1.1, 2 ¥
CH2CH), 3.77 (2 H, s, CH2(CO)), 5.93 (2 H, tt, 3JH,H 3.5, 4JH,H 1.2,
2 ¥ CH), dC(75 MHz, CDCl3, Me4Si) 43.9 (2 ¥ CH2), 59.4 (CH2),
128.2 (2 ¥ CH), 200.8 (2 ¥ CO);; m/z (EI) 124 (33%), 96 (12), 82
(43), 54 (100), 42 (13) and 39 (41).
S-Methyl hexanethioate 13. Yield: 5.18
(pentane–diethyl ether 20 : 1): RF 0.68; GC:
max(film)/cm-1 2957, 2929, 2861, 1690, 1462, 1121, 1032, 922,
g
(93%); TLC
=
I
1105;
n
736, 696 and 599; lmax(CH2Cl2)/nm 232 (e/dm3 mol-1 cm-1 4060);
dH(400 MHz; CDCl3; Me4Si) 0.89 (3 H, t, J 7.0, 1JC,H 124.7, CH3),
1.26–1.37 (4 H, m, 2 ¥ CH2), 1.63–1.71 (2 H, m, CH2), 2.29 (3
H, s, 1JC,H 141.4, CH3) and 2.55 (2 H, t, J 7.5, 1JC,H 128.2, CH2);
dC(100 MHz; CDCl3; Me4Si) 11.5 (CH3), 13.8 (CH3), 22.3 (CH2),
25.4 (CH2), 31.1 (CH2), 43.9 (CH2) and 200.0 (CO); m/z (EI) 131
(17%), 99 (52), 75 (16), 71 (48), 55 (18) and 43 (100).
S-Methyl octanethioate 14. Yield: 5.56
(pentane–diethyl ether 20 : 1): RF 0.79; GC:
max(film)/cm-1 2954, 2926, 2856, 1691, 1462, 1416, 1124,
g
(84%); TLC
[ring-2H5]Benzyl alcohol 44
=
I
1312;
n
A solution of the Grignard reagent [2H5]phenylmagnesium bro-
mide in diethyl ether (40 mL) was prepared from 43 (5 g,
30.9 mmol) and magnesium (0.75 g, 30.9 mmol). Paraformalde-
hyde (1.11 g, 37 mmol) was added, the mixture was heated to
reflux for 3 h, and quenched by the addition of a saturated
NH4Cl solution. The aqueous layer was extracted with diethyl
ether (3 ¥ 50 mL). The combined extracts were dried (MgSO4)
1041, 999, 760, 726, 696 and 599; lmax(CH2Cl2)/nm 232
(e/dm3 mol-1 cm-1 4190); dH(400 MHz; CDCl3; Me4Si) 0.88 (3
1
H, t, J 6.9, JC,H 124.5, CH3), 1.22–1.33 (8 H, m, 4 ¥ CH2), 1.66
1
(2 H, quintet, J 7.4, CH2), 2.29 (3 H, s, JC,H 141.4, CH3) and
2.55 (2 H, t, J 7.5, 1JC,H 128.3, CH2); dC(100 MHz; CDCl3; Me4Si)
11.5 (CH3), 14.0 (CH3), 22.6 (CH2), 25.7 (CH2), 28.9 (CH2), 31.6
244 | Org. Biomol. Chem., 2010, 8, 234–246
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