4
964
S.-M. T. Toguem et al. / Tetrahedron Letters 50 (2009) 4962–4964
4
.
.
Reviews: (a) Iddon, B.; Scrowston, R. M. Adv. Heterocycl. Chem. 1970, 11, 177;
b) Scrowston, R. M. Adv. Heterocycl. Chem. 1981, 29, 171.
Iddon, B. In New Trends in Heterocyclic Chemistry; Mitra, R. B., Ed.; Elsevier:
Amsterdam, 1979; p 250.
Review: Schröter, S.; Stock, C.; Bach, T. Tetrahedron 2005, 61, 2245.
(a) Dang, T. Tung.; Rasool, N.; Dang, T. Tuan.; Reinke, H.; Langer, P. Tetrahedron
Lett. 2007, 48, 845; (b) Dang, T. Tung.; Dang, T. Tuan; Villinger, A.; Langer, P.
Adv. Synth. Catal., in press.
and the acrylate (2.5 equiv per Br). The reaction mixture was stirred at 120 °C
for 48 h. The solution was cooled to 20 °C, poured into H O and CH Cl (25 mL
each), and the organic and the aqueous layer were separated. The latter was
extracted with CH Cl
(3 ꢀ 25 mL). The combined organic layers were washed
with H SO ), and concentrated in vacuo. The residue
O (3 ꢀ 20 mL), dried (Na
(
2
2
2
5
2
2
6
7
.
.
2
2
4
was purified by chromatography (flash silica gel, heptanes/EtOAc).
19. Billingsley, K.; Buchwald, S. L. J. Am. Chem. Soc. 2007, 129, 3358. and references
cited therein.
8
.
.
Dang, T. Tung.; Dang, T. Tuan.; Ahmad, R.; Reinke, H.; Langer, P. Tetrahedron
Lett. 2008, 49, 1698.
Dang, T. T.; Villinger, A.; Langer, P. Adv. Synth. Catal. 2008, 350, 2109.
20. General procedure B for the synthesis of benzothiophenes 4a–e and 4h–l. A xylene
solution (3 mL) of 3a–e, h–l was stirred at 200 °C for 24 h in a pressure tube.
The solution was allowed to cool to 20 °C and Pd/C (30 mg, 10 mol %) was
added. The solution was stirred at 200 °C for 48 h under argon atmosphere. The
reaction mixture was filtered and the filtrate was concentrated in vacuo. The
residue was purified by chromatography (flash silica gel, heptanes/EtOAc).
Diisobutyl benzo[b]thiophene-5,6-dicarboxylate (4c). Compound 4c was
prepared starting with 2,3-dibromothiophene (1) (242 mg, 1.0 mmol),
following the general procedures A and B, as a light yellow highly viscous oil
9
1
1
1
0. Pereira, R.; Iglesias, B.; de Lera, A. R. Tetrahedron 2001, 57, 7871.
1. Carpita, A.; Rossi, R. Gazz. Chim. Ital. 1985, 115, 575.
2. (a) Gronowitz, S.; Hörnfeld, A.-B.; Yang, Y. Croat. Chem. Acta 1986, 59, 313; (b)
Raju, B.; Wu, C.; Kois, A.; Vermer, E.; Okun, I.; Stavros, F.; Chan, M. F. Bioorg.
Med. Chem. Lett. 1996, 6, 2651.
1
3. Yamamura, K.; Kusuhara, N.; Kondou, A.; Hashimoto, M. Tetrahedron 2002, 58,
7
653.
(287 mg, 86%). 1H NMR (300 MHz, CDCl
0.94 (d, 6H, J = 6.7 Hz, 2CH ), 1.91–2.06 (m, 2H, CH), 4.05 (d, J = 6.8 Hz, 2CH
7.35 (dd, 1H, J = 0.7, 5.6 Hz, ArH), 7.58 (d, 1H, J = 5.5 Hz, ArH), 8.10 (s, 1H, ArH),
8.20 (s, 1H, ArH). 13C NMR (62 MHz, CDCl
): d = 19.1, 19.2 (CH ), 27.7, 27.8
(CH), 71.8, 71.9 (CH O), 123.8, 124.0, 124.4 (CH), 127.8, 128.9 (C), 130.6 (CH),
140.8, 141.5 (C), 167.6, 168.3 (CO). IR (KBr): = 3106, 2958, 2873 (w), 1716 (s),
3
): d = 0.93 (d, 6H, J = 6.7 Hz, 2CH
3
),
1
1
1
4. Hussain, M.; Nguyen, T. H.; Langer, P. Tetrahedron Lett. 2009, 50, 3929.
5. Hussain, M.; Dang, T. T. Synlett, in press.
6. De Meijere and co-workers reported twofold Heck reactions of 1,2-
3
2
O),
3
3
dibromocycloalk-1-enes and related substrates and subsequent
6
p-
2
electrocyclization: Voigt, K.; von Zezschwitz, P.; Rosauer, K.; Lansky, A.;
Adams, A.; Reiser, O.; de Meijere, A. Eur. J. Org. Chem. 1998, 1521. and
references cited therein.
m
1626, 1601, 1545, 1490, 1468 (w), 1448, 1452, 1405, 1392, 1392, 1375, 1341
(m), 1314, 1271, 1239, 1190, 1167, 1119, 1097, 1073 (s), 1005, 982, 945, 904,
ꢁ
1
1
7. For reviews of domino reactions, see: (a) Tietze, L. F.; Beifuss, U. Angew. Chem.
785, 775, 754, 702 (m), 682, 653, 626 (w) cm . GC–MS (EI, 70 eV): m/z
+
1
993, 105, 137; . Angew. Chem. Int. Ed. Engl. 1993, 32, 131; (b) Tietze, L. F. Chem.
(%) = 334 ([M] , 8), 222 (57), 206 (17), 205 (100), 178 (15), 160 (06). HR-MS (EI,
+
Rev. 1996, 96, 115.
70 eV): calcd for C18
H
22
O
4
S [M] : 334.12388; found: 334.12360.
1
8. General procedure A for the synthesis of 3a–l: In a pressure tube (glass bomb) a
ordered from the following address: Cambridge Crystallographic Data Centre,
suspension of Pd(OAc)
.10 mmol, 10 mol %) in DMF (5 mL) was purged with Ar and stirred at 20 °C
to give a yellowish or brownish clear solution. To the stirred solution were
added 2,3-dibromothiophene (1) (242 mg, 1.0 mmol), NEt (1.1 mL, 8.0 mmol)
2
(12 mg, 0.05 mmol, 5 mol %) and XPhos (47 mg,
0
3