A. Gupta et al. / Tetrahedron 70 (2014) 2141e2150
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Cyanoacetic acid (217 mg, 2.55 mmol) was added at room temperature
followed by the addition of piperidine (0.08 mL, 0.85 mmol) and the
resulting red solution was refluxed overnight. Solvent was removed
and the residue was dissolved in ethyl acetate and washed with 2 N
HCl followed by water and brine. The organic layer was dried over
anhydrous Na2SO4 and recovered to get crude solid, which was sub-
jected to column chromatography on silica gel (chloroform/methanol
8:2) to get title compound 1 (270 mg, 51%) as a deep red solid; mp
278e283 ꢃC; Rf (20% methanol/chloroform) 0.29; IR (thin solid film,
cmꢀ1) 3434 (br d), 3063, 3028, 2957, 2927, 2872, 2208, 1590, 1516,
1493, 1447, 1363, 1320, 1246, 1186, 826, 793, 753, 696; dH (400 MHz,
CD3SOCD3) 8.19 (1H, s), 7.82 (1H, s), 7.60e7.56 (3H, m), 7.31e7.27 (4H,
m), 7.06e7.01 (6H, m), 6.96e6.94 (2H, m), 4.13e4.11 (2H, m),1.94e1.87
(1H, m),1.25e1.14 (8H, m), 0.80 (3H, t, J 7.5 Hz), 0.74 (3H, t, J 6.8 Hz); dC
(100.6 MHz, CD3SOCD3) 165.3, 149.4, 147.6, 147.4, 145.4, 144.4, 144.1,
144.0, 134.4, 130.3, 129.2, 126.9, 124.9, 124.1, 123.7, 121.0, 120.0, 119.6,
113.2, 107.9, 51.1, 40.0, 30.4, 28.3, 23.9, 23.1, 14.4, 10.9; HRMS (EI): Mþ,
found 629.2197. C38H35N3O2S2 requires 629.2165.
added to a 1:1 solvent mixture (25 mL) of acetic acid and chloro-
form in a 100 mL round bottom flask followed by the addition of N-
iodosuccinimide (266 mg, 1.18 mmol) at room temperature. The
resulting reaction solution was stirred overnight at room temper-
ature in the absence of light. The reaction mixture was worked up
with water and chloroform, and the organic layer was separated,
washed with 20% sodium thiosulphate followed by water, brine,
dried over anhydrous Na2SO4 and recovered to get title compound 9
(360 mg, 78%) as a dark brown solid that was used as such for the
next step; mp 63e65 ꢃC; IR (thin solid film, cmꢀ1) 2954, 2926, 2851
(eCeH str), 1652 (eC]O str), 1511, 1467 (AreC]C str), 1407, 1277,
1248,1091,1019, 799; dH (400 MHz, CD2Cl2) 9.84 (1H, s), 7.71 (1H, s),
7.46e7.42 (2H, m), 7.33 (1H, s), 7.08e7.05 (2H, m), 4.03 (2H, t, J
6.6 Hz), 1.84e1.78 (2H, m), 1.50e1.46 (2H, m), 1.39e1.34 (4H, m),
0.94e0.90 (3H, m); dC (100.6 MHz, CDCl3) 183.2, 158.6, 147.8, 143.7,
141.0, 131.2, 124.9, 123.7, 121.4, 120.8, 120.7, 115.9, 115.7, 68.7, 31.7,
29.3, 25.8, 22.8, 14.2; HRMS (APCI): Mþ, found 508.9977.
C21H20INO2S2 requires 508.9975.
4.2.5. 4-(4-(Hexyloxy)phenyl)-4H-dithieno[3,2-b:20,30-d]pyrrole
(7). 3,30-Dibromo-2,20-bithiophene (2.00 g, 6.17 mmol) was added
in toluene (100 mL) in a 250 mL round bottom flask followed by the
addition of sodium-tert-butoxide (1.42 g, 14.8 mmol) at room
4.2.8. 6-(4-(Diphenylamino)phenyl)-4-(4-(hexyloxy)phenyl)-4H-di-
thieno[3,2-b:20,30-d]pyrrole-2-carbaldehyde (10). Compound
9
(760 mg, 1.49 mmol) and 4-(diphenylamino)phenylboronic acid
(731 mg, 2.53 mmol) were added in 1:1 solvent mixture (40 mL)
of tetrahydrofuran and dimethoxyethane in a 100 mL round
bottom flask followed by the addition of potassium carbonate
(617 mg, 4.47 mmol) at room temperature. The reaction sus-
pension was stirred for 30 min followed by the addition of tet-
rakis(triphenylphosphine)palladium(0) (85.5 mg, 0.07 mmol) at
room temperature. The resulting yellow suspension was refluxed
overnight and solvent was evaporated off to get crude solid,
which was subjected to column chromatography on silica
(hexane/ethyl acetate 9:1) to afford title compound 10 (400 mg,
43%) as a yellowish-orange solid; mp 59e61 ꢃC; Rf (10% ethyl
acetate/hexane) 0.32; IR (thin solid film, cmꢀ1) 2917, 2849
(eCeH str), 1653 (eC]O str), 1587, 1509, 1492 (AreC]C str),
1409, 1280, 1248, 1028, 833, 753; dH (200 MHz, CD2Cl2) 9.86 (1H,
s), 7.65 (1H, s), 7.53e7.47 (2H, m), 7.35e7.00 (17H, m), 4.11e4.07
(2H, m), 2.02e1.96 (2H, m), 1.38e1.29 (6H, m), 0.97e0.90 (3H,
m); dC (100.6 MHz, CD2Cl2) 183.1, 158.4, 148.3, 147.4, 140.7, 131.5,
129.5, 129.2, 128.8, 127.7, 126.5, 124.9, 124.8, 124.7, 123.6, 122.9,
121.9, 116.3, 115.8, 112.1, 99.7, 68.7, 31.7, 29.8, 25.8, 22.8, 13.9;
HRMS (APCI): Mþ, found 626.2055. C39H34IN2O2S2 requires
626.2056.
temperature.
[1,10-Bis(diphenylphosphino)ferrocene]dichlor-
opalladium(II), complex with dichloromethane (97.9 mg,
0.12 mmol) was added to this reaction mixture followed by the
addition of 1,10-bis(diphenylphosphino)ferrocene (266 mg,
0.48 mmol) ligand at room temperature. The resulting reaction
mixture was stirred for 15 min followed by the addition of 4-
(hexyloxy)aniline (1.19 g, 6.17 mmol) at room temperature. Re-
action mixture was heated to reflux overnight and the solvent was
evaporated under reduced pressure to get crude solid, which was
subjected to column chromatography on silica (hexane/dichloro-
methane 9:1) to get title compound 7 (1.60 g, 73%) as a white solid;
mp 87e90 ꢃC; Rf (10% CH2Cl2/hexane) 0.77; IR (thin solid film,
cmꢀ1) 2949, 2928, 2857 (Ar eC-H str), 1516, 1468, 1405 (Ar eC]C
str), 1290, 1246, 814, 692; dH (400 MHz, CD2Cl2) 7.50e7.46 (2H, m),
7.19e7.17 (2H, m), 7.12e7.10 (2H, m), 7.06e7.02 (2H, m), 4.02 (2H, t),
1.85e1.77 (2H, m), 1.51e1.45 (2H, m), 1.39e1.34 (4H, m), 0.94e0.89
(3H, m); dC (100.6 MHz, CD2Cl2) 157.7, 144.6, 132.7, 124.3, 123.4,
116.2, 115.6, 112.2, 68.6, 31.7, 29.4, 25.8, 22.8, 13.9; HRMS (APCI):
Mþ, found 355.1061. C20H21NOS2 requires 355.1059.
4.2.6. 4-(4-(Hexyloxy)phenyl)-4H-dithieno[3,2-b:20,30-d]pyrrole-2-
carbaldehyde (8). Compound 7 (600 mg, 1.69 mmol) was added to
ethylene dichloride (25 mL) in a 100 mL round bottom flask followed
by the addition of dimethylformamide (129 mg, 1.77 mmol) at room
temperature. The resulting reaction solution was cooled to 0 ꢃC and
POCl3 (0.46 mL, 5.07 mmol) was added drop wise. The reaction mix-
ture was allowed to warm to room temperature and refluxed over-
night. Reaction mixture was cooled down and worked up with
saturated sodium acetate solution and chloroform. The organic layer
was washed twice with water followed by brine, dried over Na2SO4
and recovered to yield titlecompound8 (350 mg, 54%)asayellowsolid,
which was used as such for the next step; mp 104e106 ꢃC; IR (thin
solid film, cmꢀ1) 2929, 2856 (eC-H str), 1653 (eC]O str), 1511, 1467,
1407 (AreC]C str),1356,1292,1247,1143, 833, 801, 713; dH (400 MHz,
CD2Cl2) 9.84 (1H, s), 7.74 (1H, s), 7.50e7.46 (2H, m), 7.43e7.42 (1H, m),
7.13e7.11 (1H, m), 7.09e7.05 (2H, m), 4.03 (2H, t), 1.85e1.78 (2H, m),
1.51e1.46 (2H, m), 1.39e1.34 (4H, m), 0.94e0.90 (3H, m); dC
(100.6 MHz, CDCl3) 183.2, 158.4, 148.7, 144.1, 140.7, 131.7, 128.8, 124.8,
124.5, 120.8, 116.4, 115.8, 112.1, 68.6, 31.7, 29.4, 25.8, 22.8, 14.2; HRMS
(APCI): Mþ, found 383.1009. C21H21NO2S2 requires 383.1008.
4.2.9. 2-Cyano-3-(6-(4-(diphenylamino)phenyl)-4-(4-(hexyloxy)phe-
nyl)-4H-dithieno[3,2-b:20,30-d]pyrrol-2-yl)acrylic acid (2). Compound
10 (400 mg, 0.64 mmol) was added in 1:1 solvent mixture (20 mL) of
chloroform and acetonitrile in a 100 mL RB flask at room tempera-
ture. Cyanoacetic acid (218 mg, 2.56 mmol) was added at room
temperature followed by the addition of piperidine (0.03 mL,
0.32 mmol), and the resulting red solution was refluxed overnight.
Solvent was removed and the residue was dissolved in ethyl acetate
and washed with 2 N HCl followed by water and brine. The organic
layer was dried over anhydrous Na2SO4 and recovered to get crude
solid, which was subjected to column chromatography on silica
(chloroform/methanol 8:2) to get title compound 2 (150 mg, 34%) as
a deep cherry powder; mp 250e254 ꢃC; Rf (20% methanol/chloro-
form) 0.35; IR (thin solid film, cmꢀ1) 3447 (br d), 3028, 2929, 2858,
2209, 1590,1512,1493, 1369,1326,1278, 1247,1167, 832, 753, 696; dH
(400 MHz, CD3SOCD3) 8.20 (1H, s), 7.78 (1H, s), 7.59e7.57 (2H,
m), 7.53e7.51 (2H, m), 7.47 (1H, s), 7.30e7.26 (4H, m), 7.07e7.04 (4H,
m), 7.02e6.99 (4H, m), 6.92e6.90 (2H, m), 3.97 (2H, t, J 6.5 Hz),
1.72e1.65 (2H, m), 1.42e1.35 (2H, m), 1.29e1.24 (4H, m), 0.85e0.82
(3H, m); dC (100.6 MHz, CD3SOCD3) 165.2, 157.9, 147.8, 147.7, 147.3,
146.2, 144.0, 143.3, 135.2, 131.6, 130.3, 130.2, 128.8, 127.3, 125.0, 124.9,
124.2, 123.4, 122.5, 119.8, 116.2, 114.9, 108.0, 104.6, 68.7, 31.6, 29.3,
4.2.7. 4-(4-(Hexyloxy)phenyl)-6-iodo-4H-dithieno[3,2-b:20,30-d]pyr-
role-2-carbaldehyde (9). Compound 8 (350 mg, 0.91 mmol) was