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succinimide (224 mg, 1.26 mmol) was added and the reaction flask
was pulled out of the ice bath, covered with aluminium foil in
order to protect the reaction mixture from light. The reaction was
continued at room temperature for 24 h. Then water was added
and the layers were separated. The aqueous layer was extracted
five times with chloroform, the combined organic layers were
washed with water, and dried over Na SO . After filtration, the sol-
8.6 Hz, 4H; benzene 2-H and 6-H), 7.51 (brs, 2H; imidazole 2-H),
7.39 (brs, 2H; imidazole 4-H), 3.94 (t, J=5.5 Hz, 4H; NCH CH ), 3.75
2
2
(s, 6H; NCH ), 3.66 (t, J=5.5 Hz, 4H; NCH CH ), 3.29 ppm (s, 6H;
3
2
2
13
OCH3); C NMR (126 MHz, CDCl ): d=162.8, 148.3, 131.5, 130.8,
3
129.4, 127.7, 125.4, 110.1, 96.1, 80.0, 70.2, 58.9, 42.2, 32.1 ppm (two
carbon atoms are missing); HRMS (ESI): calcd for C H N O :
3
6
33
6
4
+
613.2563 [M+H ]; found: 613.2567.
,5-Bis(2-methoxyethyl)-3,6-bis(5-((1-methyl-1H-imidazol-5-yl)-
ethyn-yl)thien-2-yl)-2,5-dihydropyrrolo[3,4-c]pyrrolo-1,4-dione
2
4
vents were evaporated and the products were purified as de-
scribed below.
2
3
,6-Bis(5-bromothien-2-yl)-2,5-bis(2-methoxyethyl)-2,5-dihydro-
pyrrolo[3,4-c]pyrrolo-1,4-dione (2b): Prepared from dye
250 mg, 0.60 mmol). Purified by column chromatography (silica,
(3b): Prepared from dye 2b (57 mg, 0.100 mmol). The reaction
mixture was diluted with water and extracted with five portions of
warm chloroform (product shows weak solubility). The combined
7
(
dichloromethane/acetone 97:3) and re-crystallized from toluene.
organic layers were washed with water and dried over MgSO . The
4
Product 2b (252 mg, 73%) was obtained as dark brown powder.
drying agent was filtered off and the solvents were evaporated.
The product was purified by using column chromatography (silica,
chloroform/methanol/triethylamine 980:20:1). The product was dis-
solved in a hot mixture of chloroform and methanol (9:1 v/v) and
precipitated by the addition of diethyl ether. The precipitate was
then filtered off and washed with diethyl ether. Compound 3b
1
M. p. 252–2548C; H NMR (500 MHz, CDCl ): d=8.51 (brs, 2H; thio-
3
phene 3-H), 7.21 (d, J=4.1 Hz, 2H; thiophene 4-H), 4.18 (t, J=
5
.9 Hz, 4H; NCH CH ), 3.68 (t, J=5.9 Hz, 4H; NCH CH ), 3.36 ppm
2
3
2
2
2
1
(
s, 6H; OCH3); C NMR (126 MHz, CDCl ): d=161.3, 139.5, 135.0,
3
1
31.5, 131.0, 119.4, 108.0, 70.4, 59.2, 42.1 ppm; HRMS (ESI): calcd
+
for C H Br N O S Na: 594.8972 [M+Na ]; found: 594.8976.
(41 mg, 66%) was obtained as a dark gray powder. M. p.>3008C
2
0
18
2
2
4 2
1
(
(
decomposition); H NMR (500 MHz, CDCl /[D]-trifluoroacetic acid
3
,6-Bis(5-bromofur-2-yl)-2,5-bis(2-methoxyethyl)-2,5-dihydropyr-
rolo-[3,4-c]pyrrolo-1,4-dione (2c): Prepared from dye 8 (231 mg,
.60 mmol). Purified by column chromatography (silica, dichloro-
3
[D]TFA) 4:1): d=8.73 (s, 2H; imidazole 2-H), 8.42 (d, J=4.1 Hz, 2H;
thiophene 3-H), 7.69 (s, 2H; imidazole 4-H), 7.60 (d, J=4.1 Hz, 2H;
thiophene 4-H), 4.37 (t, J=5.4 Hz, 4H; NCH CH ), 4.04 (s, 6H;
0
methane/acetone 99:1!97:3) and re-crystallized by slow addition
2
2
NCH ), 3.92 (t, J=5.4 Hz, 4H; NCH CH ), 3.53 ppm (s, 6H; OCH );
of MeOH to a solution of the product in a small amount of hot
3
2
2
3
13
C NMR (126 MHz, CDCl /[D]TFA 4:1): d=162.5, 141.6, 135.9, 135.7,
CHCl . Product 2c (290 mg, 89%) was obtained as dark brown,
3
3
1
135.6, 131.3, 126.7, 123.7, 118.8, 109.8, 91.7, 79.5, 70.1, 59.1, 41.8,
crystalline powder. M. p.>2208C (decomposition); H NMR
+
3
4.7 ppm;. HRMS (ESI): calcd for C H N O S : 625.1692 [M+H ];
32 29 6 4 2
(
600 MHz, CDCl ): d=8.26 (brs, 2H; furan 3-H), 6.63 (d, J=3.7 Hz,
3
found: 625.1678.
2
4
H; furan 4-H), 4.31 (t, J=6.0 Hz, 4H; NCH CH ), 3.65 (t, J=6.0 Hz,
2 2
13
H; NCH CH ), 3.37 ppm (s, 6H; OCH ); C NMR (151 MHz, CDCl3):
2,5-Bis(2-methoxyethyl)-3,6-bis(5-((1-methyl-1H-imidazol-5-yl)-
ethyn-yl)fur-2-yl)-2,5-dihydropyrrolo[3,4-c]pyrrolo-1,4-dione (3c):
Prepared from dye 2c (54 mg, 0.100 mmol). The reaction mixture
was diluted with water and extracted with five portions of warm
chloroform (product shows weak solubility). The combined organic
2
2
3
d=160.6, 146.1, 132.5, 126.5, 122.3, 115.6, 106.4, 70.9, 59.0,
1.6 ppm; HRMS (ESI): calcd for C H Br N O Na: 562.9429
4
20
18
2
2
6
+
[M+Na ]; found: 562.9418.
layers were washed with water and dried over MgSO . The drying
4
General procedure for the preparation of dyes 3a–3c by
Sonogashira coupling
agent was filtered off and the solvents were evaporated. The prod-
uct was purified by using column chromatography (silica, chloro-
form/methanol/triethylamine 98:1:1). The product was dissolved in
a hot mixture of chloroform and methanol (9:1 v/v) and precipitat-
ed by addition of diethyl ether. The precipitate was then filtered
off and washed with diethyl ether. Compound 3c (47 mg, 80%)
In a Schlenck flask containing a magnetic stirring bar, the corre-
sponding bromoderivative 2a, 2b, or 2c (0.100 mmol), copper(I)
iodide (1.9 mg, 0.010 mmol), and tetrakis(triphenylphosphine)palla-
dium(0) (5.8 mg, 0.005 mmol) were placed. The vessel was evacuat-
ed and backfilled with argon (three times) and anhydrous de-
gassed THF was added (5 mL) followed by 5-ethynyl-1-methylimi-
dazole (30 mL, 0.300 mmol) and dry triethylamine (56 mL,
1
was obtained as a dark green powder. M. p.>4008C; H NMR
(
(
500 MHz, CDCl /[D]TFA 4:1): d=8.77 (s, 2H; imidazole 2-H), 8.26
d, J=4.0 Hz, 2H; furan 3-H), 7.76 (s, 2H; imidazole 4-H), 7.21 (d,
3
J=4.0 Hz, 2H; furan 4-H), 4.50 (t, J=5.7 Hz, 4H; NCH CH ), 4.03 (s,
2
2
0
.400 mmol). The vessel was tightly closed and again carefully
6
H; NCH ), 3.96 (t, J=5.7 Hz, 4H; NCH CH ), 3.55 ppm (s, 6H;
3 2 2
evacuated (until the mixture start to boil) and backfilled with
argon (three times). The content of the flask was stirred for 16 h at
13
OCH3); C NMR (126 MHz, CDCl /[D]TFA 4:1): d=161.8, 145.1,
3
1
5
38.4, 136.1, 134.5, 124.6, 123.3, 122.4, 118.2, 108.6, 88.4, 79.6, 70.8,
8.9, 41.9, 34.7 ppm; HRMS (ESI): calcd for C H N O : 593.2149
7
08C (above the boiling point). The products were then purified as
described below.
,5-Bis(2-methoxyethyl)-3,6-bis(4-((1-methyl-1H-imidazol-5-yl)-
32
29
6
6
+
[M+H ]; found: 593.2153.
2
ethyn-yl)phenyl)-2,5-dihydropyrrolo[3,4-c]pyrrolo-1,4-dione (3a):
Prepared from dye 2a (56 mg, 0.100 mmol). The reaction mixture
was diluted with water and extracted with five portions of di-
chloromethane. The combined organic layers were washed with
water and dried over Na SO . The drying agent was filtered off and
the solvents were evaporated. The residue was dissolved in di-
chloromethane and filtered through a layer of silica gel by using
a mixture of dichloromethane/methanol 8:2 as the eluting system.
The solvents were evaporated and the solid was dissolved in hot
CHCl3 and precipitated by the addition of an excess amount of
Preparation of salts 4a–4c
Salt 4a: Compound 3a (31 mg, 0.050 mmol) was dissolved in di-
chloromethane (5 mL). Iodomethane (155 mL, 2.5 mmol) was added
and the obtained mixture was heated to reflux for 24 h. Due to in-
complete conversion of the starting material (according to TLC)
a second portion of iodomethane (155 mL, 2.5 mmol) was added
and the reaction was heated to reflux for another 24 h. The result-
ing suspension was cooled down and the precipitate was filtered
off and washed with dichloromethane and diethyl ether. The crude
product was dissolved in hot methanol and precipitated by the ad-
dition of an excess of diethyl ether. After filtration and drying salt
2
4
MeOH. After filtration, product 3a (53 mg, 87%) was obtained as
1
a red powder. M. p. 264–2668C; H NMR (500 MHz, CDCl ): d=8.01
3
(
AA’BB’, J=8.6 Hz, 4H; benzene 3-H and 5-H), 7.63 (AA’BB’, J=
&
&
Chem. Eur. J. 2015, 21, 1 – 11
8
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