Sep-Oct 2001
Preparation of Variously Substituted Thieno[2,3-b]thiophene
1169
Melting points were determined on a Kofler hot stage apparatus
and are uncorrected. Elemental analyses were performed on a
Carlo Erba elemental analyzer. Infra red (ir) were measured on a
Perkin-Elmer 881 spectrometer (KBr pellets) and uv spectra were
recorded on a Shimadzu 1205 apparatus (solution in ethanol).
form): δ 1.33 (m, 6H, CH ), 4.29 (m, 4H, CH ), 7.61 (m, 5H,
3 2
13
C H ), 7.91 ppm (s, 1H, 4-H); C nmr: δ 14.1 (CH ), 14.3
6
5
3
(CH ), 61.6 (CH ), 62.2 (CH ), 128.6 (2 CAr), 129.1 (2 CAr),
3
2
2
132.4 (CAr), 132.8 (CAr), 135.6 (CAr), 137.1 (CAr), 138.1
(CAr), 143.8 (CAr), 145.1 (CAr), 148.7 (CAr), 169.8 ppm (CO ),
2
171.1 ppm (CO ).
Anal. Calcd. for C H O S : C, 60.00; H, 4.17. Found: C,
59.84; H, 4.28.
2
General Procedure for the Preparation of Thieno[2,3-b]thiophene
1a-f.
18 16
4 2
To 0.3 mol (41.5 g) oven dried potassium carbonate in 30 to 40
mL DMF, 0.1 mol of the 1,3-dicarbonyl derivatives dissolved in
10 to 20 mL DMF followed by 0.15 mol (9.0 mL) carbon disul-
fide were added dropwise under vigorous stirring. After 30 min-
utes, the mixture was cooled to 0 °C and 0.2 mol of the activated
alkylating agents (ethyl bromacetate, chloroacetone or chloroace-
tonitrile) in 10 mL of DMF was added in 20 minutes. The reac-
tion mixture was then stirred for 3 to 7 hours at room temperature
and poured into 200 mL of cold water. The precipitate was col-
lected and washed 3 times with 100 mL of water. The crude
thieno[2,3-b]thiophenes obtained were purified by crystallization
to give 1a to 1k in 92 ([15]: 93), 72 ([8]: 35), 86 ([18]: 67), 91
([7]: 52), 70, 65, 61, 78, 83 ([14]: 88), 87 ([14]: 81) and 66 ([14]:
63) % yield, respectively.
Diethyl 3-Methyl-4-phenylthieno[2,3-b]thiophene-2,5-dicar-
boxylate (1e).
This compound was obtained as colorless crystals (ethanol), mp
128 °C; ir (potassium bromide): CH 2986, 2938, CO 1712, 1686,
3
-1
1
CHAr 717 cm ; uv: λ max 271 nm (ε 11,900); H nmr (deuteri-
ochloroform): δ 1.13 (t, 3H, CH , J = 7.1 Hz), 1.37 (t, 3H, CH ,
3
3
J = 7.1 Hz), 2.11 (s, 3H, CH ), 4.13 (q, 2H, CH , J = 7.1 Hz), 4.32
3
2
(q, 2H, CH , J = 7.1 Hz), 7.29 (m, 2H, C H ), 7.43 ppm (m, 3H,
2
6 5
13
C H ); C nmr: δ 13.7 (CH ), 13.9 (CH ), 14.1 (CH ), 60.9 (2
6
5
3
3
3
CH ), 127.2 (2 CAr), 128.1 (CAr), 129.1 (2 CAr), 130.1 (CAr),
2
131.9 (CAr), 136.8 (CAr), 139.7 (CAr), 142.6 (CAr), 146.6 (CAr),
148.9 (CAr), 161.4 (CO ), 162.1 ppm (CO ).
2
2
Anal. Calcd. for C H O S : C, 60.96; H, 4.81. Found: C,
19 18
4 2
61.01; H, 4.80.
Diethyl 3,4-Dimethylthieno[2,3-b]thiophene-2,5-dicarboxylate
(1a).
Diethyl 3,4-Diphenylthieno[2,3-b]thiophene-2,5-dicarboxylate
(1f).
This compound was obtained as colorless crystals (ethanol),
mp 142-143 °C ([15]: 135 °C); ir (potassium bromide): CH
2987, 2941, CO 1703 cm ; uv: λ max 271 nm (ε 25,100); H
This compound was obtained as light yellow crystals (diethyl
3
-1
1
ether), mp 174-176 °C; ir (potassium bromide): CH 2989, CO
3
-1
1
nmr (deuteriochloroform): δ 1.38 (t, 6H, CH , J = 7.1 Hz), 2.86
1732, CHAr 694 cm ; uv: λ max 326 nm (ε 7,030); H nmr (deu-
teriochloroform): δ 1.08 (t, 3H, CH , J = 7.0 Hz), 1.20 (t, 3H,
3
13
(s, 6H, CH ), 4.35 ppm (q, 4H, CH , J = 7.1 Hz); C nmr: δ 14.4
3
2
3
(2 CH ), 21.2 (2 CH ), 61.0 (2 CH ), 130.7 (2 CAr), 138.9 (CAr),
CH , J = 7.0 Hz), 4.16 (m, 4H, CH ), 6.98 ppm (m, 10H, C H );
C nmr: δ 13.9 (2 CH ), 60.7 (2 CH ), 126.8 (4 CAr), 127.6 (4
3 2
3
3
2
3 2 6 5
13
142.6 (2 CAr), 152.1 (CAr), 176.3 ppm (2 CO ).
2
Anal. Calcd. for C H O S : C, 53.85; H, 5.13. Found: C,
53.98; H, 5.28.
CAr), 129.1 (2 CAr), 131.6 (2 CAr), 140.5 (2 CAr), 141.8 (CAr),
149.7 (CAr), 153.5 (2 CAr), 168.6 ppm (2 CO ).
14 16
4 2
2
Anal. Calcd. for C H O S : C, 66.05; H, 4.59. Found: C,
65.93; H, 4.77.
24 20
4 2
1-(5-Acetyl-3,4-dimethyl-thieno[2,3-b]thiophen-2-yl)-ethanone
(1b).
Diethyl 4-Methyl-3-oxo-2,3-dihydrothieno[2,3-b]thiophene-2,5-
dicarboxylate (1g).
This compound was obtained as colorless crystals (ethanol),
mp 160-161 °C; ([8]: 157-158 °C); ir (potassium bromide): CH
3
-1
1
2996, 2962, CO 1671 cm ; uv: λ max 288 nm (ε 10,100); H
This compound was obtained as colorless crystals (ethanol),
nmr (deuteriochloroform): δ 2.57 (s, 6H, COCH ), 2.87 ppm (s,
mp 72-74 °C; ir (potassium bromide): CH 2984, 2941, CO 1735,
3
3
13
-1
6H, CH ); C nmr: δ 15.1 (2 CH ), 30.1 (2 CH ), 139.9 (2 CAr),
1713, 1693 cm ; uv: λ max 313 nm (ε 6,940), λ max 247 nm (ε
3
3
3
1
143.6 (CAr), 144.8 (2 CAr), 151.6 (CAr), 191.3 ppm (2 CO).
Anal. Calcd. for C H O S : C, 57.14; H, 4.76. Found: C,
10,380); H nmr (deuteriochloroform): δ 1.35 (m, 6H, CH ), 2.72
3
13
(s, 3H, CH ), 3.83 (s, 1H, CH), 4.29 ppm (m, 4H, CH ); C nmr:
12 12
2
2
3
2
57.03; H, 4.81.
δ 13.5 (CH ), 14.2 (CH ), 15.4 (CH ), 37.4 (CH), 61.2 (CH ),
3 3 3 2
62.1 (CH ), 136.9 (CAr), 141.5 (CAr), 148.3 (CAr), 151.3 (CAr),
2
3,4-Dimethylthieno[2,3-b]thiophene-2,5-dicarbonitrile (1c).
167.6 (CO ), 168.3 (CO ), 208.1 ppm (CO).
2
2
This compound was obtained as light brown crystals (ethanol),
Anal. Calcd. for C H O S : C, 49.68; H, 4.46. Found: C,
13 14
5 2
mp 225 °C; ([18]: 220-222 °C); ir (potassium bromide): CH
49.72; H, 4.59.
3
-1
2964, CN 2213 cm ; uv: λ max 259 nm (ε 44,200): λ max 222
Diethyl 3-Amino-4-tert-butylthieno[2,3-b]thiophene-2,5-dicar-
boxylate (1h).
1
nm (ε 12,400); H nmr (deuteriochloroform): δ 2.69 ppm (s, 6H,
13
CH ); C nmr: δ 14.8 (2 CH ), 108.5 (2 CAr), 113.3 (2CN),
3
3
134.1 (CAr), 143.1 (2CAr), 150.8 ppm (CAr).
This compound was obtained as light yellow crystals (acetoni-
Anal. Calcd. for C H N S : C, 55.04; H, 2.75; N, 12.84.
Found: C, 54.82; H, 2.92; N, 12.97.
trile), mp 124 °C; ir (potassium bromide): NH 3489, 3346,
10
6
2
2
2
-1
1596, CH 2978, 2959, CO 1683, 1665 cm ; uv: λ max 292 nm
3
1
(ε 22,800): λ max 230 nm (ε 14,200); H nmr (deuteriochloro-
Diethyl 3-Phenylthieno[2,3-b]thiophene-2,5-dicarboxylate (1d).
This compound was obtained as colorless crystals (ethanol),
form): δ 1.37 (m, 6H, CH ), 1.61 (s, 9H, C(CH ) ), 4.36 (m, 4H,
3
3 3
13
CH ), 6.29 ppm (broad s, 2H, NH ); C nmr: δ 14.1 (CH ), 14.5
2
2
3
mp 106-108 °C ([12] : 94-96 °C); ir (potassium bromide): CH
(CH ), 31.7 (3 C(CH ) ), 35.3 (C(CH ) ), 60.3 (CH ), 61.1
(CH ), 119.9 (CAr), 134.9 (CAr), 138.5 (CAr), 144.5 (CAr),
2
3
3 3 3 3 3 2
-1
2986, 2942, CO 1735, 1701, CHAr 730, 704 cm ; uv: λ max 308
1
nm (ε 3,120): λ max 259 nm (ε 7,960); H nmr (deuteriochloro-
145.1 (CAr), 157.7 (CAr), 166.2 (CO ), 167.3 ppm (CO ).
2 2