Dithieno[3,2-b:2’,3’-d]thiophene-2-carboxylic acid 23
The compound was prepared by modified literature
cooled to 230 ‡C and carbon dioxide (CO2) gas was bubbled
through the solution. The mixture was allowed to warm to
room temperature and stirred for 0.5 h before CO2 gas
introduction was stopped. After stirring for further 2 h, the
reaction was quenched by addition of water and 2 M aqueous
HCl (30 cm3). The mixture was extracted with ether
(3620 cm3). The combined organic layer was dried
(MgSO4), and the solvent was removed in vacuum. Column
chromatography (EtOH–ethyl acetate, 1 : 1) gave 24 (210 mg,
90%). Recrystallisation from EtOH–CHCl3 (1 : 1) afforded
needle-like crystals, whereas sublimation (150 ‡C, 1025 mbar,
4 h) afforded a colourless powder, mp 192–193 ‡C; vmax
(CDCl3, cm21) 2924, 2851, 2552, 1652, 1497, 1420, 1285,
1162, 908, 865, 808, 753, 688; dH(250 MHz, CDCl3–CD3OD)
0.75 (3 H, t, J 6.5, CH3), 1.13–1.29 (6 H, m, CH2), 1.60 (2 H, m,
CH2CH2Ar), 2.78 (2 H, t, J 7.0, CH2Ar), 6.88 (1 H, s, ArH),
7.26 (1 H, s, ArH); m/z (CI, NH3) 325.0387 (MzHz.
C15H17O2S3 requires 325.0390).
a
procedure.26 n-Butyllithium (1.6 M in hexane, 1.18 cm3,
1.88 mmol) was added dropwise to a solution of 215,18
(368 mg, 1.88 mmol) in THF (4 cm3) at 278 ‡C under N2.
The solution turned cloudy green within 10 min and was
allowed to warm up to room temperature. After 40 min, it was
cooled to approx. 240 ‡C. The cold solution was then
transferred to a syringe and added dropwise to dry ice in a
flask kept under N2. After warming up to room temperature,
water (30 cm3) and ether (40 cm3) were added. The organic
layer was separated and discarded. The aqueous layer was
acidified with HCl (10 M, 10 cm3). The yellow solid was
collected by suction filtration and recrystallised from 33%
acetic acid to give 23 as a fine yellow green powder (286 mg,
61%), mp 276 ‡C (compound sublimed, lit.26 275–277 ‡C); vmax
(KBr, cm21) 3090, 3823, 2559, 1652, 1504, 1428, 1311, 1265,
1164, 928, 750, 716, 602; dH(250 MHz, CDCl3) 7.31 (1 H, d, J
5.1), 7.56 (2 H, d, J 5.1), 7.94 (1 H, s).
General procedure for the preparation of the complex-
es. Carboxylic acid or tetrazole (3 equiv.) and 13 (1 equiv.)
were dissolved in hot ethanol (40 cm3 mmol21) to which a
certain amount of CHCl3 (5–10 cm3) had to be added as
cosolvent. After filtration of the hot solution and concentra-
tion, the crude product was crystallised from the solvent
(mixture) indicated for each complex.
2-Hexyldithieno[3,2-b:2’,3’-d]thiophene 22
To a stirred solution of 215 (339 mg, 1.73 mmol) in dry CH2Cl2
(50 cm3) was added hexanoyl chloride (0.25 cm3, 1.79 mmol).
The mixture was stirred for 0.5 h at room temperature, cooled
to 0 ‡C, and AlCl3 (267 mg, 2.0 mmol) was added portionwise.
The mixture was then allowed to warm to 25 ‡C and stirred for
18 h. The reaction was quenched by the addition of water
(30 cm3) and acidified with 2 M aqueous HCl (50 cm3). The
mixture was extracted with CH2Cl2 (2620 cm3). The organic
layers were combined, washed with water (30 cm3), dried
(MgSO4) and concentrated in vacuum. Column chromatogra-
phy (hexane–CH2Cl2, 1 : 1) afforded 1-(dithieno[3,2-b:2’,3’-
d]thiophen-2-yl)hexan-1-one (355 mg, 70%) as a colourless
solid, mp 140–141 ‡C (Found: C, 57.0; H, 4.8. C14H14S3O
requires C, 57.1; H, 4.8%); vmax (KBr, cm21) 2923, 2864, 1641,
1490, 1362, 1209, 703; dH(250 MHz, CDCl3) 0.89 (3 H, t, J 6.5,
CH3), 1.25 (4 H, br s, CH2), 1.78 (2 H, m, CH2), 2.93 (2 H, t, J
7.5, CH2CO), 7.32 (1 H, d, J 5.2), 7.52 (1 H, d, J 5.2), 7.91 (1 H,
s, ArH); dC(100 MHz, CDCl3) 13.9, 22.5, 24.7, 31.6, 39.0,
120.9, 125.5, 129.0, 130.9, 136.9, 141.2, 144.4, 144.9, 193.7; m/z
(EI) 294 (Mz, 28%), 238 (35), 223 (20), 195 (14), 175 (10), 163
(12), 151 (16), 123 (35), 83 (100); Rf(hexane–CH2Cl2, 1 : 1) 0.3.
Anhydrous ether (6 cm3) at 0 ‡C was added to separate batches
of LiAlH4 (160 mg, 4.2 mmol) and AlCl3 (133 mg, 1.0 mmol),
and the resulting mixtures were combined. To this mixture was
14b. Yield: 75% (from EtOH–CHCl3), yellow crystals, DSC:
K1/167 (DH –30 J g21)/K2/243 (DH 83 J g21)/Idecomp. (Found:
C, 65.4; H, 6.1; N, 6.6. C69H72N6O1562 H2O requires C, 65.7;
H, 6.1; N, 6.7%); lmax (CHCl3) 332 nm (e 88 000 M21 cm21);
vmax (KBr, cm21) 1640, 1584, 1538, 1504, 1379, 1124;
dH(500 MHz, CDCl3) 3.87 (9 H, s, OCH3), 3.92 (18 H, s,
OCH3), 4.16 (12 H, s, NCH2), 6.75 (6 H, s, ArH), 7.04 (3 H,
AB, J 16.0, LCH), 7.10 (3 H, AB, J 16.0, LCH), 7.52, 8.07 (266
H, AA’XX’, ArH), 10.12 (3 H, s, HA); dC(125 MHz, CDCl3,
15.1 mg/0.8 cm3) 45.5, 56.2, 61.0, 103.8, 125.4, 126.0, 127.7,
129.7, 129.9, 132.9, 134.8, 136.2, 138.2, 139.5, 153.5, 163.1,
173.5. After exposure of an NMR sample to sunlight for several
hours, a chloroform solution showed additional 1H NMR
signals for the (Z) isomer, dH(200 MHz, CDCl3) 3.87 (9 H, s,
OCH3), 3.92 (18 H, s, OCH3), 6.75 (6 H, s, ArH), 7.04 (3 H,
AB, J 16.0, LCH), 7.10 (3 H, AB, J 16.0, LCH), 7.52, 8.07 (266
H, AA’XX’, ArH).
14f. Yield: 57% (from EtOH–CHCl3), pale yellow crystals,
mp 265 ‡C; lmax (CHCl3–EtOH, 1 : 1) 314 nm; vmax (KBr,
) 2917, 2848, 1644, 1492, 1466, 1362, 1189, 838;
added
1-(dithieno[3,2-b:2’,3’-d]thiophen-2-yl)hexan-1-one
cm21
(127 mg, 0.43 mmol) in dry ether at 0 ‡C. The mixture was
allowed to warm to room temperature and then stirred for 3 h.
The reaction was quenched by the careful addition of ether
(2 cm3) and 2 M aqueous HCl (4 cm3). The product was
extracted by washing the gray precipitate with ether
(3610 cm3). The combined organic washings were dried
(MgSO4), and the solvent was removed in vacuum. Column
chromatography (hexane) afforded 22 (110 mg, 90%) as
transparent crystals, mp 52–53 ‡C (Found: C, 60.0; H, 5.8.
C14H16S3 requires C, 60.0; H, 5.8%); vmax (CDCl3, cm21) 2956,
2930, 2857, 817, 604; dH(250 MHz, CDCl3) 0.88 (3 H, t, J 6.5,
CH3), 1.25–1.46 (4 H, m, CH2), 1.73 (2 H, m, CH2), 2.90 (2 H, t,
J 7.0, CH2), 6.96 (1 H, s), 7.25 (1 H, d, J 5.3), 7.27 (1 H, d, J 5.3,
ArH); dC(100 MHz, CDCl3) 14.1, 22.6, 28.0, 30.9, 31.2, 31.6,
117.5, 120.7, 124.9, 128.7, 131.2, 140.1, 140.8, 147.3; m/z (EI)
281 (Mz, 7%), 211 (19), 209 (100); Rf(hexane) 0.5.
dH(500 MHz, CD3OD) 4.04 (12 H, s, NCH2), 7.38 (3 H, d, J
5.1), 7.59 (3 H, d, J 5.1), 7.83 (3 H, s, ArH), 8.52 (3 H, s, HA).
Additional signals could be assigned to ethanol and chloroform
that were included in crystals 14f.
14g. Yield: 80% (from MeOH–CH2Cl2), colourless crystals,
DSC: K1/114 (DH 33 J g21)/K2/171 (DH 2 J g21)/K3/191 (DH
16 J g21)/I (Found: C, 55.5; H, 5.25; N, 6.4. C60H66N6O6S962
H2O requires C, 55.8; H, 5.5; N, 6.5%); lmax (CHCl3) 322 nm;
n
max (KBr, cm21) 1584, 1499, 1288, 1155; dH(500 MHz, CDCl3)
0.89 (9 H, t, J 6.9, CH3), 1.21–1.41 (18 H, m), 1.72 (6 H, m,
CH2), 2.89 (6 H, t, J 7.5, CH2), 4.20 (12 H, s, NCH2), 6.97 (3 H,
s), 7.80 (3 H, s, ArH), 9.94 (3 H, s, HA), 12.78 (6 H, br s, NH);
dC(62.5 MHz, CDCl3) 14.1, 22.6, 28.7, 31.2, 31.6, 45.5, 117.6,
123.9, 125.3, 129.0, 134.3, 134.7, 139.4, 142.2, 142.4, 148.6,
162.9, 169.1.
6-Hexyldithieno[3,2-b:2’,3’-d]thiophene-2-carboxylic acid 24
20a. Yield: 77% (from EtOH–CHCl3), yellow crystals, mp
283–284 ‡C (decomp.) (Found: C, 67.6; H, 5.2; N, 22.65.
C63H60N18O3 requires C, 67.7; H, 5.4; N, 22.6%); lmax (CHCl3–
)
1647, 1640, 1602, 1577, 1507, 1251, 1176; dH(500 MHz,
To a solution of 22 (200 mg, 0.71 mmol) in dry THF (30 cm3) at
278 ‡C was added dropwise n-butyllithium (0.50 cm3, 15% in
hexane, 0.80 mmol). The reaction mixture was allowed to warm
to room temperature and was stirred for 0.5 h. It was then
MeOH, 24 : 1) 338 nm (e 65 000 M21 cm21); vmax (KBr, cm21
1632
J. Mater. Chem., 2001, 11, 1625–1633