LETTER
S. D.; Lee, W. S.; Yoon, Y. J. Bull. Korean Chem. Soc. 2004,
Selective Halogenation of Bithiophenes
493
5-Bromo-5¢-chloro-2,2¢-bithiophene (4c)
Colorless crystals; mp 123 °C; Rf = 0.64 (n-hexane). IR
25, 501. (e) Park, Y. D.; Kim, H. K.; Kim, J. J.; Cho, S. D.;
Kim, S. K.; Shiro, M.; Yoon, Y. J. J. Org. Chem. 2003, 68,
9113. (f) Park, Y. D.; Kim, J. J.; Chung, H. A.; Kweon,
D. H.; Cho, S. D.; Lee, S. G.; Yoon, Y. J. Synthesis 2003,
560. (g) Kim, J. J.; Park, Y. D.; Lee, W. S.; Cho, S. D.; Yoon,
Y. J. Synthesis 2003, 1517. (h) Kang, Y. J.; Chung, H. A.;
Kim, J. J.; Yoon, Y. J. Synthesis 2002, 733. (i) Kweon, D.
H.; Kim, H. K.; Kim, J. J.; Chung, H. A.; Lee, W. S.; Kim,
S. K.; Yoon, Y. J. J. Heterocycl. Chem. 2002, 39, 203.
(8) Kim, J. J.; Kweon, D. H.; Cho, S. D.; Kim, H. K.; Lee, S. G.;
Yoon, Y. J. Synlett 2006, 194.
(KBr): 3069, 3040, 1730, 1578, 1541, 1504, 1418, 1342,
1279, 1196, 1065, 999, 966, 868, 791, 633, 457 cm–1. 1H
NMR (300 MHz, CDCl3): d = 6.98 (d, 1 H, J = 3.8 Hz), 6.88
(d, 1 H, J = 3.9 Hz), 6.85 (d, 1 H, J = 4.0 Hz), 6.84 (d, 1 H,
J = 4.0 Hz) ppm. 13C NMR (75 MHz, CDCl3): d = 137.90,
134.94, 130.65, 129.28, 126.95, 124.04, 123.18, 111.43
ppm. HRMS (EI): m/z calcd for C8H4BrClS2: 277.8626;
found: 277.8626. Anal. Calcd for C8H4BrClS2: C, 34.36; H,
1.44. Found: C, 34.39; H, 1.50.
3,5,5¢-Trichloro-2,2¢-bithiophene (5a)
(9) General Procedure
Colorless crystals; mp 99 °C (recrystallization from CHCl3;
lit.3c mp 102–103 °C), Rf = 0.69 (n-hexane). IR (KBr): 3097,
2925, 1499, 1402, 1305, 1136, 1012, 812 cm–1. 1H NMR
(300 MHz, CDCl3): d = 7.02 (d, 1 H, J = 4.0 Hz), 6.87 (d,
1 H, J = 4.0 Hz), 6.79 (s, 1 H) ppm. 13C NMR(75 MHz,
CDCl3): d = 131.35, 131.19, 128.56, 128.28, 127.86, 127.05,
126.24, 125.48, 120.06 ppm. HRMS (EI): m/z calcd for
C8H3Cl3S2: 267.8742; found: 267.8742. Anal. Calcd for
C8H3Cl3S2: C, 35.64; H, 1.12. Found: C, 35.68; H, 1.17.
3,5,5¢-Tribromo-2,2¢-bithiophene (5b)
To a solution of zinc halide (1 mol%), 2-halo-4,5-dichloro-
pyridazin-3 (2H)-one 2 (1–5 equiv), and CH2Cl2 (50 mL),
bithiophenes (1 equiv) were added with stirring at r.t. Then,
the reaction mixture was stirred until the 2 disappeared by
TLC monitoring. The reaction mixture was filtered using
Celite-545 pad, and washed with EtOAc (10–20 mL). The
combined filtrate was evaporated under reduced pressure.
The resulting residue was applied to the top of open-bed
silica gel column (3 × 20 cm), and the column was eluted
with n-hexane. Fractions containing the product were
combined and evaporated under reduced pressure to give
product.
Colorless crystals; mp 84 °C; Rf = 0.63 (n-hexane). IR
(KBr): 3090, 2953, 2922, 2851, 1732, 1680, 1535, 1493,
1464, 1450, 1410, 1371, 1283, 1240, 1219, 1130, 1063,
1018, 974, 866, 814, 785, 638, 453 cm–1. 1H NMR (300
MHz, CDCl3): d = 7.05 (d, 1 H, J = 3.9 Hz), 7.02 (d, 1 H,
J = 3.9 Hz), 6.98 (s, 1 H) ppm. 13C NMR (75 MHz, CDCl3):
d = 134.78, 133.80, 133.14, 130.03, 127.08, 113.79, 111.57,
107.32 ppm. HRMS (EI): m/z calcd for C8H3Br3S2:
399.7226; found: 399.7215. Anal. Calcd for C8H3Br3S2: C,
23.85; H, 0.75. Found: C, 23.87; H, 0.80.
5-Chloro-2,2¢-bithiophene (3a)
Liquid; Rf = 0.56 (n-hexane). IR (KBr): 3070, 3043, 1507,
1421, 1065, 1001, 869, 789 cm–1. 1H NMR (300 MHz,
CDCl3): d = 7.21 (dd, 1 H, J = 1.2, 5.1 Hz), 7.09 (dd, 1 H,
J = 1.2, 3.6 Hz), 6.99 (dd, 1 H, J = 3.6, 5.1 Hz), 6.92 (d, 1 H,
J = 3.9 Hz), 6.82 (d, 1 H, J = 3.9 Hz) ppm. 13C NMR (75
MHz, CDCl3): d = 136.50, 136.03, 128.65, 127.86, 126.86,
124.76, 123.93, 122.86 ppm. HRMS (EI): m/z calcd for
C8H5ClS2: 199.9521; found: 199.9519. Anal. Calcd for
C8H5ClS2: C, 47.87; H, 2.51. Found: C, 47.90; H, 2.55.
5-Bromo-2,2¢-bithiophene (3b)
3,3¢,5,5¢-Tetrachloro-2,2¢-bithiophene (6a)
Colorless crystals; mp 113–114 °C (recrystallization from
CHCl3; lit.3c mp 120–121); Rf = 0.73 (n-hexane). IR (KBr):
3095, 2932, 1509, 1418, 1301, 1125, 1007, 811 cm–1. 1H
NMR (300 MHz, CDCl3): d = 6.88 (s, 2 H) ppm. 13C NMR
(75 MHz, CDCl3): d = 131.09, 127.05, 124.33, 123.63 ppm.
HRMS (EI): m/z calcd for C8H2Cl4S2: 301.8352; found:
301.8352. Anal. Calcd for C8H2Cl4S2: C, 31.60; H, 0.66.
Found: C, 31.63; H, 0.69.
Colorless crystals; mp 33 °C (recrystallization from CHCl3;
lit.10 mp 32–33 °C), Rf = 0.51 (n-hexane). IR (KBr): 3099,
3082, 3066, 1501, 1439, 1414, 1350, 1198, 1074, 1051, 966,
879, 835, 820, 787, 690, 644, 611, 455 cm–1. 1H NMR (300
MHz, CDCl3): d = 7.20 (dd, 1 H, J = 1.2, 5.1 Hz), 7.09 (dd,
1 H, J = 1.2, 3.6 Hz), 6.99 (dd, 1 H, J = 3.6, 5.1 Hz), 6.95 (d,
1 H, J = 3.8 Hz), 6.89 (d, 1 H, J = 3.8 Hz) ppm. 13C NMR (75
MHz, CDCl3): d = 138.93,136.42, 130.58, 127.85, 124.82,
124.06, 123.85, 110.93 ppm. HRMS (EI): m/z calcd for
C8H5BrS2: 243.9016; found: 243.9012. Anal. Calcd for
C8H5BrS2: C, 39.19; H, 2.06. Found: C, 39.21; H, 2.10.
5,5¢-Dichloro-2,2¢-bithiophene (4a)
Colorless crystals; mp 109 °C (recrystallization from CHCl3;
lit.11 mp 109–110 °C); Rf = 0.64 (n-hexane). IR (KBr): 3095,
1504, 1418, 1137, 1075, 1012, 857, 816, 785 cm–1. 1H NMR
(300 MHz, CDCl3) d = 6.85 (d, 2 H, J = 3.9 Hz), 6.81 (d, 2
H, J = 3.9 Hz) ppm. 13C NMR (75 MHz, CDCl3): d = 135.03,
129.18, 126.91, 123.06 ppm. HRMS (EI): m/z calcd for
C8H4Cl2S2: 233.9131; found: 233.9130. Anal. Calcd for
C8H4Cl2S2: C, 40.86; H, 1.71. Found: C, 40.90; H, 1.74.
5,5¢-Dibromo-2,2¢-bithiophene (4b)
Colorless crystals; mp 141 °C (recrystallization from CHCl3;
lit.1a mp 147 °C, mp 146 °C,12 mp 142 °C13); Rf = 0.59 (n-
hexane). IR (KBr): 3090, 3067, 3036, 2922, 1732, 1535,
1497, 1454, 1412, 1317, 1196, 1057, 966, 864, 814, 789,
623, 604, 455 cm–1. 1H NMR (300 MHz, CDCl3): d = 6.98
(d, 2 H, J = 3.9 Hz), 6.87 (d, 2 H, J = 3.9 Hz) ppm. 13C NMR
(75 MHz, CDCl3): d = 137.81, 130.66, 124.16, 111.55 ppm.
HRMS (EI): m/z calcd for C8H4Br2S2: 321.8121; found:
321.8126. Anal. Calcd for C8H5 Br2S2: C, 29.65; H, 1.24.
Found: C, 29.68; H, 1.29.
3,3¢,5,5¢-Tetrabromo-2,2¢-bithiophene (6b)
Colorless crystals; mp 140 °C (recrystallization from CHCl3;
lit.5 mp 138–140 °C); Rf = 0.66 (n-hexane). IR (KBr): 3097,
2920, 2851, 1537, 1479, 1447, 1393, 1288, 1126, 980, 920,
872, 827, 800, 739, 669, 584, 503, 469 cm–1. 1H NMR (300
MHz, CDCl3): d = 7.07 (s, 2 H) ppm. 13C NMR (75 MHz,
CDCl3): d = 133.01, 129.59, 114.82, 112.13 ppm. HRMS
(EI): m/z calcd for C8H2Br4S2: 477.6331; found: 477.6335.
Anal. Calcd for C8H2Br4S2: C, 19.94; H, 0.42. Found: C,
20.00; H, 0.48.
3,3¢,5-Tribromo-5¢-chloro-2,2¢-bithiophene (6c)
Colorless crystals; mp 125 °C;, Rf = 0.69 (n-hexane). IR
(KBr): 3099, 1539, 1485, 1452, 1396, 1315, 1292, 1230,
1198, 1128, 1011, 978, 874, 831, 798, 675, 586, 474 cm–1.
1H NMR (300 MHz, CDCl3): d = 7.04 (s, 1 H), 6.92 (s, 1 H)
ppm. 13C NMR (75 MHz, CDCl3): d = 132.98, 132.55,
129.56, 126.69, 114.80, 112.17, 111.47, 111.41 ppm. HRMS
(EI): m/z calcd for C8H2Br3ClS2: 433.6837; found:
433.6841. Anal. Calcd for C8H2Br3ClS2: C, 21.97; H, 0.46.
Found: C, 22.01; H, 0.49.
5-Bromo-3,3¢,5¢-trichloro-2,2¢-bithiophene (6d)
Colorless crystals; mp 125 °C; Rf = 0.71 (n-hexane). IR
(KBr): 3094, 2920, 2851, 1742, 1717, 1701, 1634, 1495,
1456, 1398, 1373, 1302, 1215, 1136, 1014, 982, 812, 685,
590, 465 cm–1. 1H NMR (300 MHz, CDCl3): d = 6.98 (s,
1 H), 6.86 (s, 1 H) ppm. 13C NMR (75 MHz, CDCl3): d =
Synlett 2009, No. 3, 490–494 © Thieme Stuttgart · New York