9
98
Helvetica Chimica Acta – Vol. 89 (2006)
1
13
7
40vs, 683s. H-NMR: 1.89 (br. s, 6 H); 6.31 (s, 1 H); 7.18–7.51 (m, 5 H). C-NMR (CDCl ): 31.8 (Me);
3
6
5.6 (C); 112.7 (CH); 126.7 (arom. C); 127.9 (arom. C); 128.8 (arom. C); 134.6 (C); 134.7 (C). MS: 208
+
(
27, M ), 194 (10), 193 (100), 134 (10). Anal. calc. for C H S (208.35): C 63.41, H 5.81, S 30.78; found: C
11
12 2
6
3.38, H 5.84, S 30.41.
,2-Dimethyl-2,3-dihydro-4H-1,3-benzothiazine-4-thione (21). CC (hexane/CH Cl 1:1) and recrys-
2
2
2
tallization from hexane/CH Cl gave 1005 mg (96%) of 21. Yellow solid. M.p. 191–1928 (hexane/
2
2
CH Cl ). IR (KBr): 3148m (NH), 3069m, 2984m, 2960w, 2937w, 1584w, 1567s, 1521vs, 1453m, 1425s,
2
2
1
1
387m, 1367m, 1225vs, 1160w, 1148w, 1000m, 768vs, 753w, 722m. H-NMR: 1.70 (s, 6 H); 7.10–7.45
(
m, 3 H); 8.48–8.65 (m, 1 H); 8.95 (br. s, 1 H). Anal. calc. for C H NS (209.33): C 57.38, H 5.30, N
10
11
2
6
.69, S 30.49; found: C 57.35, H 5.29, N 6.60, S 30.24.
. Thermolysis of Thiones: General Procedure. The flash vacuum thermolysis was carried out in a
4
2
ꢀ3
3
0·2.5 cm electrically heated horizontal quartz tube packed with quartz rings at 1.5 · 10 Torr. The start-
ing compounds (2 mmol) were slowly sublimed from a flask held at 40–508 (for 6a,b, 15a,b, and 19) or 808
for 21) into the thermolysis tube preheated to 8508. The products were collected in a CO /aceton trap.
(
2
After thermolysis, the system was brought to atmospheric pressure allowing a slow warming up to r.t., and
the products were dissolved in MeOH or CHCl . The solvent was evaporated and the products were puri-
3
fied by CC (SiO ), recrystallization, distillation, or prep. TLC.
2
Thermolysis of 6a. The product of the thermolysis was rinsed from the cold finger with cold MeOH.
After warming to r.t., excess MeOH was evaporated: 316 mg (94%) of methyl 2-mercaptobenzoate (7).
Thermolysis of 6b. The product of the thermolysis was rinsed from the cold finger with CHCl . Evap-
3
oration and recrystallization from hexane gave 342 mg (89%) of 2-methyl-4H-1-benzothiopyran-4-thione
(
8). M.p.107–1088 ([10]: 107–1088). Spectral data: identical with those of an authentic sample [10].
Thermolysis of 15a,b. The products of the thermolysis were rinsed from the cold finger with CHCl
Evaporation, CC (SiO , hexane/AcOEt 99 :1), and recrystallization from petroleum ether gave 291 mg
3
.
2
(
97%) of benzo[c]thiophen-1(3H)-one (16a) or 338 mg (95%) of 3,3-dimethyl-benzo[c]thiophen-1(3H)-
one (16b).
1
1
6a: M.p. 60–618 ([19]: 58–608). Spectral data: identical with those in [19].
6b: M.p. 47–488 ([20]: 46–488). Spectral data: identical with those in [14].
Thermolysis of 19. The products of the thermolysis were rinsed from the cold finger with CHCl .
3
ꢀ
2
Evaporation and CC (SiO , hexane/AcOEt 99 :1) followed by bulb-to-bulb distillation at 508/5 · 10
2
Torr gave 224 mg (54%) of 3-benzylidene-4-methyl-3H-1,2-dithiole (20). Colorless oil. IR (neat):
3
1
082w, 3060m, 2970w, 2947w, 2921m, 2863w, 1598m, 1497s, 1452m, 1430w, 1380w, 1333w, 1203m,
1
073m, 1032w, 922w, 916w, 855m, 838m, 759s, 690m. H-NMR: 2.28 (br. s, 3 H); 6.84 (br. s, 1 H); 7.12
13
(
br. s, 1 H); 7.17–7.40 (m, 3 H); 7.53–7.63 (m, 2 H). C-NMR: major isomer: 144.2, 138.7, 134.7 (3 C);
1
1
1
6
28.9, 127.4, 125.8, 125.6, 120.3 (5 CH); 16.0 (Me); minor isomer: 143.3, 137.2, 136.3 (3 C); 128.7,
28.4, 127.1, 123.1, 122.1 (5 CH); 15.7 (Me). MS (isomer mixture): 206 (11, M ), 205 (20), 204 (100),
+
90 (23), 174 (41), 173 (29), 128 (11), 115 (17), 1021 (13), 89 (13). Anal. calc. for C H S (206.32): C
11
10 2
4.03, H 4.89, S 31.08; found: C 64.00, H 4.81, S 30.88.
Thermolysis of 21. The products of the thermolysis were rinsed from the cold finger with CHCl3.
Evaporation and CC (silica gel, hexane/AcOEt) gave 84 mg (70%) of 22, after recrystallization from hex-
ane/CHCl , 77 mg (42%) of 23, after recrystallization from hexane/CH Cl , and 40 mg (9%) of 24, after
3
2
2
further purification by TLC (SiO , hexane/AcOEt 9 :1).
2
Phenanthro[9,10-c]-1,2-dithiete (22): Orange solid. M.p. 213–2158 (hexane/CH Cl ). IR (KBr):
2
2
1
3
7
070w, 3051w, 1456w, 1437s, 1336s, 1297m, 1254m, 1127w, 1059w, 1015w, 952w, 742vs, 723s. H-NMR:
13
.10–7.50 (m, 3 H); 7.70–7.80 (m, 1 H). C-NMR: 142.3, 133.4, 133.1 (3 C); 125.0, 124.9, 124.0, 121.6
+
(
4 CH). MS: 240 (100, M ). Anal. calc. for C H S (240.35): C 69.96, H 3.35, S 26.68; found: C 69.99,
14 8 2
H 3.28, S 26.51.
3
H-1,2-Benzodithiole-3-thione (23): Yellow solid. M.p. 95–978 ([21]: 988). Spectral data: identical
with those in [21].
N-(3H-1,2-Benzodithiol-3-ylidene)prop-1-en-2-amine (24): Oil. IR (neat): 3091w, 3062w, 2976w,
2
1
953w, 2921w, 2850w, 1632m (C=N), 1589m, 1469s, 1456s, 1447m, 1362m, 1322m, 1221s, 1165m,
076m, 908m, 809m, 783m, 742vs. H-NMR: 2.25–2.32 (m, 3 H); 5.53–5.68 (m, 2 H); 7.33–7.55 (m, 2
1