Cyanoacetamide in heterocyclic chemistry: Synthesis, antitumor and antioxidant activities of some new benzothiophenes

Article abstract of DOI:10.1002/jhet.634

Cyanoacylation of 2-amino-tetrahydrobenzothiophene-3-carboxylate ethyl ester with 3-(3,5-dimethyl-1H-pyrazol-1-yl)-3-oxopropanenitrile afforded cyanoacetamide 2. The later was utilized as key intermediate for the synthesis of 3-substituted 2-iminocoumarin

Full text of DOI:10.1002/jhet.634

1280
Cyanoacetamide in Heterocyclic Chemistry: Synthesis, Antitumor
and Antioxidant Activities of Some New Benzothiophenes
Vol 48
Serry A. A. El Bialya and Moustafa A. Goudab*
aDepartment of Pharmaceutical Organic Chemistry, Faculty of Pharmacy,
Mansoura University, Mansoura 35516, Egypt
bDepartment of Chemistry, Faculty of Science, Mansoura University,
El-Gomhoria Street, Mansoura 35516, Egypt
*E-mail: dr_mostafa_chem@yahoo.com
Received July 1, 2010
DOI 10.1002/jhet.634
Published online 2 August 2011 in Wiley Online Library (wileyonlinelibrary.com).
Cyanoacylation of 2-amino-tetrahydrobenzothiophene-3-carboxylate ethyl ester with 3-(3,5-dimethyl-
1H-pyrazol-1-yl)-3-oxopropanenitrile afforded cyanoacetamide 2. The later was utilized as key interme-
diate for the synthesis of 3-substituted 2-iminocoumarins 3–6 and acrylamides 7a, b via Knoevenagel
condensation with 2-hydroxy-1-naphthaldehyde; 2-hydroxybenzaldehyde; 1-nitrosonaphthalen-2-ol; 7-
hydroxy-5-methoxy-2-methyl-4-oxo-4H-chromene-6-carbaldehyde; 4-dimethylamino-benzaldehyde; and
4-piperidin-1-yl-benzaldehyde in EtOH/piperidine. The derivatives 7a, b did not afford the pyrazoles
8a, b upon treating with phenyl hydrazine. Furthermore, coupling of 2 with 4-amino-1,5-dimethyl-2-
phenyl-1H-pyrazol-3(2H)-one and 4,6-dimethyl-1H-pyrrolo[2,3-b]pyridin-3-amine afforded the hydra-
zone derivatives 9 and 10, respectively. The later derivative 10 was cyclized in acetic acid to afford the
pyridopyrazolotriazine 11. Finally, 2 was treated with dimethylformamide-dimethylacetal (DMF-DMA)
to afford the dimethylaminoacrylamide 12 which underwent transamination with 4,6-dimethyl-1H-pyr-
rolo[2,3-b]pyridin-3-amine to afford the pyrazole 13. Cyclization of compound 13 in acetic acid or pyri-
dine was unsuccessful. The antitumor and antioxidant activities of the synthesized products were
evaluated; several were found to exhibit promising antioxidant activities.
J. Heterocyclic Chem., 48, 1280 (2011).
INTRODUCTION
pyridines are of special importance due to the reported
biological activities [22], including antibacterial [23],
anti-inflammatory [24], antiviral [25], antitumor [26],
and antiparasitic [27] profiles. On the other hand, 2-
amino-thiophene-3-carboxylates have been reported to
possess analgesic activities [28]. The corresponding 5-
carboxamido-4-hydroxy-3-(b-D-ribofuranosyl) thiophene-
2-carbonic acid derivatives were investigated as viru-
cides and virostatic agents [29]. Furthermore,
thieno[2,3-d]pyrimidine derivatives [30], showed an
interesting biological properties including antihyperten-
sive [31], antiallergenic [32], antitumor [33], antiviral
[33], anti-HIV-1 [33], and analgesic [34] activities.
These biological data prompted us to synthesize
some new coumarin and pyrazole derivatives incorpo-
rated with 2-amino-thiophene-3-carboxylate moiety
starting from 2-amino-tetrahydrobenzothiophene-3-car-
boxylate ethyl ester to investigate their antitumor and
antioxidant activities.
Substituted cyanoacetamides are important intermedi-
ates in the synthesis of a variety of agrochemicals, dyes,
and pharmacologically active compounds [1]. Coumarin
and their derivatives have attracted the attention of or-
ganic and medicinal chemists, as several of which are
excellent scaffolds with proven multiple biological
activities [2–9]. Recently the anti-inflammatory/antioxi-
dant activities of several new coumarin derivatives with
a 7-azomethine linkage have been reported [10]. The
pyrazole nucleus has pronounced pharmacological appli-
cations as antianxiety, antipyretic [11], analgesic, and
anti-inflammatory drugs [12–14]. Certain alkyl pyrazoles
show significant bactericidal and fungicidal activities
[15]. Fused heterocycles containing pyrazolopyridine
systems have been prepared and found to exhibit biolog-
ical and medicinal activities including anxiolytic, [16],
antiviral, [17,18], antileishmanial [19], antitumor [20],
and anti-inflammatory [21] profiles. In particular, thieno-
C
V
2011 HeteroCorporation

November 2011
Cyanoacetamide in Heterocyclic Chemistry: Synthesis, Antitumor
and Antioxidant Activities of Some New Benzothiophenes
1281
Scheme 1
RESULTS AND DISCUSSION
4H-chromene-6-carbaldehyde in ethanol/piperidine afforded
3-substituted-2-iminocoumarines 3–6 (Scheme 2).
Chemistry. Based on the chemistry of ethyl 2-
amino-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxy-
late (1), different 3-substituted-2-iminocoumarins 3–6,
pyrazoles 9–11, and 13 were synthesized (Schemes 1–
5). The starting ethyl 2-(2-cyanoacetylamino)-4,5,6,7-tet-
rahydrobenzo[b]thiophene-3-carboxylate (2) was ob-
tained in a high yield and purity via cyanoacetylation of
Furthermore, treatment of 2 with 4-(dimethylacrylami-
de)benzaldehyde and 4-(piperidin-1-yl)benzaldehyde fur-
nished the acrylamide derivatives 7a, b. Our attempts to
synthesize the pyrazoles 8a, b via treatment of 7a, b
with phenyl hydrazine were unsuccessful (Scheme 3).
Moreover, coupling of 2 with 1,5-dimethyl-3-oxo-2-
phenyl-2,3-dihydro-1H-pyrazole-4-diazonium
and 4,6-dimethyl-1H-pyrazolo[3,4-b]pyridine-3-diazo-
chloride
ethyl
2-amino-4,5,6,7-tetrahydrobenzo[b]thiophene-3-
carboxylate (1) [35], with 3-(3,5-dimethyl-1H-pyrazol-1-
yl)-3-oxopropanenitrile [36] through the modification of
the reported procedures [37,38] (Scheme 1). The structure
2 was established by the spectral data. The IR spectrum
nium chloride yielded the hydrazone derivatives 9 and
10, respectively. Compound 10 was cyclized in acetic
acid to give the corresponding pyrazolopyridotriazine 11
(Scheme 4).
ꢀ
showed a characteristic absorption bands at t ¼ 2258 and
Finally, the enamine derivative 12 was synthesized
via condensation of 2 with dimethylformamide-dimethy-
lacetal (DMF-DMA) in dioxane. Transamination of 12
with 4,6-dimethyl-1H-pyrazolo[3,4-b]pyridin-3-amine in
dioxane/piperidine afforded ethyl 2-(2-cyano-3-(4,6-di-
methyl-1H-pyrazolo[3,4-b]pyridin-3-ylamino)acrylamido)-
4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxylate (13).
Our attempt to cyclize the enamine 13 to the corre-
sponding pyrazolopyridodiazine 14 in acetic acid or
pyridine was unsuccessful; compound 14 was a bio-
isoster of 11. The structure assignments of new
1654 cmꢀ1 due to cyano and amidic carbonyl groups. In
1
addition, its H NMR displayed a singlet at d 3.64 ppm,
which corresponds to methylene group of cyanoacetamide,
whereas the amide NH group resonates at d 11.9 ppm.
Finally, the product was confirmed by the mass spectrum
that displayed the molecular ion peak at m/z 292, which
matches with its molecular formula C14H16N2O3S.
Knoevenagel condensation of 2 with 2-hydroxy-1-
naphthaldehyde, 2-hydroxybenzaldehyde, 1-nitrosonaph-
thalen-2-ol and 7-hydroxy-5-methoxy-2-methyl-4-oxo-
Scheme 2
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DOI 10.1002/jhet

1282
S. A. A. El Bialy and M. A. Gouda
Vol 48
Scheme 3
compounds were based on their elemental analysis and
spectral data.
three singlet signals at d 3.16, 3.19, and 8.15 ppm attrib-
utable for dimethylaminomethine moiety.
The IR spectra of 3–6, 9–11, and 13 showed character-
Biological activity.
Antitumor.
ꢀ1
ꢀ
istic absorption bands within the t ¼ 1677–1624 cm
region corresponding to the stretching vibration of ester
and amidic groups. The absence of the absorption band
corresponding to CN stretching frequency of the com-
pound 2 clearly confirmed the formation of 3–6 and 11.
The 1H NMR of the newly synthesized compounds
showed signals within the d 1.23–1.35 ppm (t, 3H,
CH3), d 4.16–4.38 ppm (q, 2H, OCH2), d 1.62–1.89
ppm (m, 4H, C5A2H, C6A2H), d 2.68–2.91 ppm (m,
4H, C4A2H, C7A2H), d 11.3–12.10 ppm (br, s, 1H,
NHACO) due to ethyl carboxylate, tetrahydrobenzene,
and COANH moieties, respectively. Also, compounds
7a, b displayed a singlet signal at d 8.46 and 8.48 ppm,
respectively, due to methine proton. Furthermore, com-
pound 9 displayed two singlet signals at d 2.55, 3.15
ppm corresponding to two methyl groups. Moreover,
compounds 10, 11, and 14 showed two singlet signals
within d 2.92–3.01 and 3.09–3.19 ppm regions due to
two methyl groups. Finally, compound 12 displayed
Effect of drugs on the viability of Ehrlich ascites cells
in vitro. Twelve thiophene derivatives were tested for
cytotoxicity against well-known established model Ehr-
lich ascites cells (EAC) in vitro [39]. The ED100, ED50,
and ED25 values of the active compounds are summar-
ized in Table 1. The data showed clearly that most of
compounds have weak activities.
Antioxidant activity assay. The antioxidant activity of
the newly synthesized compounds was evaluated by
Lissi procedures (1999) [40]. The data clearly showed
that compounds 2 and 9 have good activities, whereas
compounds 7a, b and 12 exhibited moderate activities.
On the other hand, the other compounds showed weak
activities. Thus, it has been appeared that introduction
of cyanoacetamide, antipyrine, 4-dimethylaminobenzal,
4-piperidinobenzal, and dimethyl-aminomethine moieties
enhances the antioxidant properties of 2-aminobenzo-
thiophene derivative (Table 2).
Scheme 4
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

November 2011
Cyanoacetamide in Heterocyclic Chemistry: Synthesis, Antitumor
and Antioxidant Activities of Some New Benzothiophenes
1283
Scheme 5
EXPERIMENTAL
yl)-3-oxopropanenitrile (2.28 g, 14 mmol) in benzene (20 mL)
was refluxed for 5 h. The solvent was evaporated under vac-
uum, and the residue was crystallized from ethanol to afford
All melting points are recorded on Gallenkamp electric melt-
ing point apparatus and are uncorrected. The IR spectra (KBr) t
(90%) of 2; M.p. 110 C; white powder; IR (KBr) t (cmꢀ1),
ꢀ
ꢁ
ꢀ
(cmꢀ1) were recorded on a Perkin Elmer Infrared Spectropho-
tometer Model 157. The 1H NMR spectra were recorded on a
Bruker 400 MHz spectrometer using the indicated solvents
using TMS as an internal reference, at the Georgia State Uni-
versity, Atlanta, GA. The mass spectra were recorded on 70 eV
with Kratos MS equipment. Elemental analyses (C, H, and N)
were carried out at the Microanalytical Center of Cairo Univer-
sity, Giza, Egypt. 2-Amino-4,5,6,7-tetrahydro-benzo[b]thio-
phene-3-carboxylic acid ethyl ester (1) was prepared according
to the procedures reported in the literature [35].
3259 (NH); 2258 (CN); 1697, 1654 (2C¼¼O); 1H NMR (400
MHz, CHCl3): d, 1.36 (t, 3H, CH3, J ¼ 6.9), 1.76–1.78 (m,
4H, C5A2H, C6A2H), 2.63–2.75 (m, 4H, C4A2H, C7A2H),
3.64 (s, 2H, CH2CO), 4.34 (q, 2H, CH2O, J ¼ 6.9), 11.92 (s,
1H, NHACO); ms: (m/z, %): 294 (Mþþ2, 3.2); 292 (Mþ,
25.7); 206 (65.2); 178 (16.7); 151 (14.3); 123 (10.5); 91
(19.7); 68 (100). Anal Calcd for C14H16N2O3S: C, 57.52; H,
5.52; N, 9.58; Found C, 57.63; H, 5.58; N, 9.67.
General procedure for synthesis of 3-substituted-2-imino-
coumarines 3–6 and 4-substituted benzal cyanoacetamides
7a, b. A mixture of 2 (1.46 g, 5 mmol), piperidine (0.2 mL),
and 2-hydroxy-1-naphthaldehyde (0.86 g, 5 mmol); 2-hydroxy-
benzaldehyde (0.61 g, 5 mmol); 1-nitrosonaphthalen-2-ol (0.87
g, 5 mmol); 7-hydroxy-5-methoxy-2-methyl-4-oxo-4H-chro-
mene-6-carbaldehyde (1.17 g, 5 mmol); 4-(dimethylamino)ben-
zaldehyde (0.75 g, 5 mmol) or 4-(piperidin-1-yl)benzaldehyde
(0.95 g, 5 mmol) in ethanol (15 mL) was stirred at 80ꢁC. The
Synthesis of 2-(2-cyano-acetylamino)-4,5,6,7-tetrahydro-
benzo[b]thiophene-3-carboxylic acid ethyl ester (2). A mix-
ture of 1 (3.15 g, 14 mmol) and 3-(3,5-dimethyl-1H-pyrazol-1-
Table 1
In vitro cytotoxicity of benzothiophene derivatives (EAC, % dead).
% Dead
Table 2
ED100
(lg cmꢀ3
ED50
(lg cmꢀ3
ED25
(lg cmꢀ3
)
ABTS antioxidant activity assay of benzothiophene derivatives.
Compound No.
)
)
ABTS
5-FU
2
3
93
58
4
37
2.2
1.5
1.1
1.5
1.8
1
7.8
5.7
5.3
6.8
7
4.9
5.5
7.6
6.9
6.8
5.3
6.1
Compound No.
Absorbance of samples
% Inhibition
3.1
2.9
3.5
3.5
2.3
3
4
5
Control of ABTS
Ascorbic acid
0.506
0.081
0.193
0.417
0.392
0.345
0.38
0
83.99
61.85
17.58
22.52
31.81
24.9
6
2
3
4
5
7a
7b
9
10
11
12
13
1.7
2
2
3.9
3.6
3.6
2.8
3.2
6
1.8
1.2
1.7
7a
7b
9
0.3
0.304
0.18
40.71
39.92
64.42
22.33
29.64
41.3
10
11
12
13
0.393
0.356
0.297
0.388
ED100, ED50, and ED25 are the effective doses at 25, 50, and 100 lL,
respectively, of the compounds used. The % dead refers to the % of
the dead tumor cells, and 5-FU is 5-fluorouracil as a well known cyto-
toxic agent.
23.32
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S. A. A. El Bialy and M. A. Gouda
Vol 48
ꢁ
ꢀ
separated crystals was filtered, dried, and recrystallized from
the appropriate solvent to give compounds 3–7a, b,
respectively.
M.p. 266 C; red crystals; IR (KBr) t (cmꢀ1), 3433 (br, NH),
1
2917, 2854 (CAH aliphatic), 2204, (CN), 1652 (br, 2CO); H
NMR (400 MHz, DMSO-d6): d, 1.23 (t, 3H, CH3, J ¼ 6.8),
1.72–1.75 (m, 4H, C5A2H, C6A2H), 2.64–2.87 (m, 4H,
C4A2H, C7A2H), 3.17 (s, 3H, NACH3), 3.19 (s, 3H,
NACH3), 4.33 (q, 2H, OCH2, J ¼ 6.8), 7.15 (d, 2H, Ar-H, J
¼ 7.6), 8.91 (d, 2H, Ar-H, J ¼ 7.6), 8.46 (s, 1H, methine),
11.4 (br, s, 1H, NHACO); ms: (m/z, %): 255 (Mþ-[Etþ4H],
100), 199 (70.6), 180 (70.6), 179 (76.5), 171 (70.6), 157
(29.4), 156 (52.9), 116 (47.1), 77 (70.6). Anal. Calcd. for
C23H25N3O3S: C, 65.23; H, 5.95; N, 9.92; Found C, 65.01; H,
6.07; N, 10.02.
Ethyl 2-(2-cyano-3-(4-(piperidin-1-yl)phenyl)acrylamido)-
4,5,6,7-tetrahydrobenzo[b] thiophene-3-carboxylate (7b). Reaction
time 15 min, crystallized from DMF/EtOH to afford (94%) of
7a; mp 259 C; red crystals; IR (KBr) t (cmꢀ1), 3428 (br,
Ethyl 2-(3-imino-3H-benzo[f]chromene-2-carboxamido)-
4,5,6,7-tetrahydrobenzo[b] thiophene-3-carboxylate (3). Reaction
time 30 minꢁ, crystallized from DMF to afford (92%) of 3;
M.p. > 290 C; yellow powder; IR (KBr) t (cmꢀ1), 3378,
ꢀ
3322 (2NH), 2979, 2925 (CAH aliphatic), 1677, 1635 (2(CO),
1
1610 (C¼¼N); H NMR (400 MHz, DMSO-d6): d, 1.25 (t, 3H,
CH3, J ¼ 6.8), 1.68–1.82 (m, 4H, C5A2H, C6A2H), 2.75–2.88
(m, 4H, C4A2H, C7A2H), 4.22 (q, 2H, CH2O, J ¼ 6.8), 7.43–
8.03 (m, 7H, Ar-H, C4AH, coumarin), 8.91 (s, 1H, NH), 11.62
(br, s, 1H, NHACO); ms: (m/z, %): 413 (Mþ-[Etþ4H], 8.5),
366 (98.2), 151 (100), 141 (96), 140 (71.4), 139 (84), 118
(78.1), 61 (85.7). Anal. Calcd. for C25H22N2O4S: C, 67.25; H,
4.97; N, 6.27; Found C, 67.31; H, 5.03; N, 6.36.
ꢁ
ꢀ
Ethyl
2-(2-imino-2H-chromene-3-carboxamido)-4,5,6,7-
NH), 2917, 2853 (CAH aliphatic), 2204 (CN), 1650 (br,
2CO); H NMR (400 MHz, DMSO-d6): d, 1.33 (t, 3H, CH3, J
1
tetrahydrobenzo[b]thiophene-3-carboxylate (4). Reaction
time 10 min, crystallized from DMF to afford (81%) of 4; mp
¼ 7.2), 1.66–1.85 (m, 10H, C5A2H, C6A2H, 3CH2, piperi-
dine), 2.69–2.84 (m, 4H, C4A2H, C7A2H), 3.47–3.60 (m, 4H,
2CH2, piperidine), 4.34 (q, 2H, OCH2, J ¼ 6.8), 7.66 (d, 2H,
Ar-H, J ¼ 7.6), 8.15 (d, 2H, Ar-H, J ¼ 7.6), 8.48 (s, 1H,
methine), 12.10 (br, s, 1H, NHACO); ms: (m/z, %): 417 (Mþ-
[OEtþ3H], 48.1), 355 (33.3), 239 (29.6), 225 (11.1), 174
(100), 143 (33.3), 81 (25.9), 66 (37). Anal. Calcd. for
C26H29N3O3S: C, 67.36; H, 6.31; N, 9.06; Found C, 67.21; H,
6.37; N, 9.10.
General procedure for synthesis of 4,5,6,7-tetrahydroben-
zo[b]thiophenes (9) and (10). To a well-stirred cooled solu-
tion of 4-amino-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one
(1.02 g, 5 mmol) or 4,6-dimethyl-1H-pyrazolo[3,4-b]pyridin-3-
amine [41] (0.81 g, 5 mmol) in concentrated HCl (3 mL), a
solution of NaNO2 (0.35 g, 5.1 mmol in 5-mL H2O) was
added drop wise. The above cooled diazonium solution was
added slowly to a well-stirred solution of 2 (1.46 g, 5 mmol)
in pyridine (10 mL). The reaction mixture was stirred for 2 h.
The crude product was filtered off, dried well, and recrystal-
lized from EtOH-benzene to give 9 and from DMF to give 10,
respectively.
230 C; yellow powder; IR (KBr) t (cmꢀ1), 3326 (NH), 3979,
ꢁ
ꢀ
3927 (CAH, aliphatic), 1675 (br, 2CO), 1615 (C¼¼N); 1H
NMR (400 MHz, DMSO-d6): d, 1.35 (t, 3H, CH3, J ¼ 7.2),
1.68–1.81 (m, 4H, C5A2H, C6A2H), 2.79–2.86 (m, 4H,
C4A2H, C7A2H), 4.38 (q, 2H, CH2O, J ¼ 7.2), 7.42–8.05 (m,
5H, Ar-H, C4AH, coumarin), 8.98 (s, 1H, NH), 11.44 (br, s,
1H, NHACO); ms: (m/z, %): 398 (2.4, Mþþ2), 396 (Mþ), 363
(24.9), 317 (100), 289 (2.6), 255 (1.5), 172 (88.1), 145 (27.7),
118 (51.1), 89 (35.7), 65 (24.9). Anal. Calcd. for
C21H20N2O4S: C, 63.62; H, 5.08; N, 7.07; Found C, 63.59; H,
5.19; N, 7.13.
Ethyl 2-(3-imino-3H-naphtho[2,1-b][1,4]oxazine-2-carbox-
amido)-4,5,6,7-tetrahydro-benzo[b]thiophene-3-carboxylate
(5). Reaction time 5 h, crystallized from DMF/MeOH to
ꢁ
ꢀ
afford (82%) of 5; M.p. 256 C; brown powder; IR (KBr) t
(cmꢀ1), 3386, 3342 (2NH), 2931, 2852 (CAH aliphatic), 1660
(br, 2CO), 1619 (C¼¼N); 1H NMR (400 MHz, DMSO-d6): d,
1.30 (t, 3H, CH3, J ¼ 6.8), 1.69–1.89 (m, 4H, C5A2H,
C6A2H), 2.70–2.91 (m, 4H, C4A2H, C7A2H), 4.27 (q, 2H,
CH2O, J ¼ 6.8), 7.42–8.22 (m, 6H, Ar-H), 8.93 (s, 1H, NH),
11.50 (br, s, 1H, NHACO). Anal. Calcd. for C24H21N3O4S: C,
64.41; H, 4.73; N, 9.39; Found C, 64.36; H, 4.68; N, 9.42.
Ethyl 2-(2-imino-5-methoxy-8-methyl-6-oxo-2,6-dihydro-
pyrano[3,2-g]chromene-3-carboxamido)-4,5,6,7-tetrahydro-
benzo[b]thiophene-3-carboxylate (6). Reaction time 30 min,
Ethyl 2-(2-cyano-2-(2-[1,5-dimethyl-3-oxo-2-phenyl-2,3-dihy-
dro-1H-pyrazol-4-yl]hydra-zono)acetamido)-4,5,6,7-tetrahy-
drobenzo[b]thiophene-3-carboxylate (9). Crystallized from
EtOH/benzene to afford (77%) of 9; M.p. 232ꢁC; redish brown
powder; IR (KBr) t (cmꢀ1), 3241 (br, NH), 2933, 2858 (CAH
ꢀ
crystallized from DMF/EtOH or benzene/EtOH to afford
(67%) of 6; M.p. 274 C; reddish brown powder; IR (KBr) t
aliphatic), 2204 (CN), 1671 (br, 3CO); 1H NMR (400 MHz,
DMSO-d6): d, 1.29 (t, 3H, CH3, J ¼ 6.8), 1.68–1.79 (m, 4H,
C5A2H, C6A2H), 2.55 (s, 3H, CH3), 2.63–2.77 (m, 4H,
C4A2H, C7A2H), 3.15 (s, 3H, NACH3), 4.16 (q, 2H, CH2O, J
¼ 6.8), 7.15–7.51 (m, 5H, Ar-H), 10.2 (br, s, 1H, NH), 11.30
(br, s, 1H, NHACO). Anal. Calcd. for C25H26N6O4S: C, 59.27;
H, 5.17; N, 16.59; Found C, 59.32; H, 5.25; N, 16.51.
ꢁ
ꢀ
(cmꢀ1), 3320 (NH), 2983, 2927, 2850 (CAH aliphatic), 1673
(br, 4CO), 1602 (C¼¼N); 1H NMR (400 MHz, DMSO-d6): d,
1.34 (t, 3H, CH3, J ¼ 6.8), 1.62–1.75 (m, 4H, C5A2H,
C6A2H), 1.81 (s, 3H, CH3), 2.67–2.83 (m, 4H, C4A2H,
C7A2H), 3.92 (s, 3H, OCH3), 4.30 (q, 2H, OCH2, J ¼ 6.8),
6.55 (s, 1H, C10AH), 7.29 (s, 1H, C7AH), 8.30 (s, 1H,
C4AH), 9.23 (br, s, 1H, NH), 12.20 (br, s, 1H, NHACO); ms:
(m/z, %): 475 (Mþ-[Etþ4H], 13.0), 429 (83.9), 284 (100), 225
(34.8), 202 (8.7), 180 (19.6), 179 (89.1), 123 (23.9), 116 (3.4),
100 (26.1), 67 (78.3), 66 (30.4). Anal. Calcd. for
C26H24N2O7S: C, 61.41; H, 4.76; N, 5.51; Found C, 61.35; H,
4.82; N, 5.42.
Ethyl 2-(2-cyano-2-(2-(4,6-dimethyl-1H-pyrazolo[3,4-b]pyri-
din-3-yl)hydrazono) acetamido)-4,5,6,7-tetrahydrobenzo[b]-
thiophene-3-carboxylate ꢁ(10). Crystallized from DMF to afford
ꢀ
(69%) of 10; M.p. > 320 C; reddish brown powder; IR (KBr) t
(cmꢀ1), 3386, 3257, 3203 (NH2, NH), 3933, 2858 (CAH ali-
phatic), 1662, (2CO), 1629 (C¼¼N); 1H NMR (400 MHz,
DMSO-d6): d, 1.28 (q, 3H, CH3, J ¼ 7.2), 1.68–1.75 (m, 4H,
C5A2H, C6A2H), 2.69–2.83 (m, 4H, C5A2H, C6A2H), 2.95 (s,
3H, CH3), 3.15 (s, 3H, CH3), 4.36 (q, 3H, CH3, J ¼ 7.2), 7.40
(s, 1H, Ar-H), 7.07 (s, 1H, CH), 9.2 (br, s, 1H, NH), 10.2 (br, s,
Ethyl 2-(2-cyano-3-(4-(dimethylamino)phenyl)acrylamido)-4,5,
6,7-tetrahydrobenzo[b] thiophene-3-carboxylate (7a). Reaction
time 5 h, crystallized from DMF/EtOH to afford (92%) of 7a;
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

November 2011
Cyanoacetamide in Heterocyclic Chemistry: Synthesis, Antitumor
and Antioxidant Activities of Some New Benzothiophenes
1285
1H, NHAN¼¼C), 11.62 (br, s, 1H, NHACO); ms: (m/z, %): 467
(Mþþ2, 8.5), 456 (Mþ, 65.9), 419 (12.3), 392 (21.3), 345
(17.1), 241 (72.0), 215 (64.9), 179 (90.5), 151 (45.5), 146
(50.2), 133 (49.8), 133 (50.0), 131 (39.3), 119 (46.4), 91 (50.7),
78 (79.1), 77 (100). Anal. Calcd. for C22H23N7O3S: C, 56.76;
H, 4.98; N, 21.06; Found C, 56.83; H, 5.06; N, 21.18.
(National Cancer Institute, Cairo, Egypt), which contains Ehr-
lich cell. The cells were grown partially floating and attach in
a suspension culture (RPMI 1660 medium, Sigma Chemical,
St. Louis), supplemented with 10% foetal bovine serum
(GIBCO, UK). They were maintained at 37ꢁC in humidified
atmosphere with 5% CO2 for 2 h. The viability of the cell
used in control experiments (DMSO only without drug)
exceeded 95% as determined by microscopic examination
using a hemocytometer and trypan blue stain (stain only the
dead cells).
Antioxidant assay. Antioxidant activity determinations
were evaluated from the bleaching of ABTS-derived radical
cations. The radical cation was derived from ABTS [2,20-
azino-bis(3-ethyl benzothiazoline-6-sulfonic acid)] and was
prepared by the reaction of ABTS (60 lL) with MnO2 (3 mL,
25 mg mLꢀ1) in (5 mL) aqueous buffer solution (pH 7). After
shaking the solution for a few minutes, it was centrifuged and
filtered.
Synthesis of ethyl 2-(8-amino-2,4-dimethyl-1,5,6,8a,9-pen-
taazafluorene-7-carboxamido)-4,5,6,7-tetrahydrobenzo[b]-
thiophene-3-carboxylate (11). A suspension of 10 (2.33 g, 5
mmol) in acetic acid (10 mL) was refluxed for 7 h; the reac-
tion mixture was poured into ice-cold water. The formed pre-
cipitate was filtered off, dried, and recrystallized from DMF to
afford (80%) of 11; M.p. > 320ꢁC; reddish brown powder; IR
(KBr) t (cmꢀ1), 3241 (NH), 2933, 2858 (CAH aliphatic),
ꢀ
2204 (CN), 1671 (br, 2CO); H NMR (400 MHz, DMSO-d6):
1
d, 1.31 (t, 3H, CH3, J ¼ 6.8), 1.66–1.71 (m, 4H, C5A2H,
C6A2H), 2.68–2.80 (m, 4H, C5A2H, C6A2H), 2.92 (s, 3H,
CH3), 3.19 (s, 3H, CH3), 4.30 (q, 2H, CH2O, J ¼ 6.8), 7.38 (s,
1H, CAH), 10.3 (br, s, 2H, NH2), 12.01 (br, s, 1H, NHACO).
Anal. Calcd. for C22H23N7O3S: C, 56.76; H, 4.98; N, 21.06;
Found C, 56.65; H, 4.93; N, 20.11.
The absorbance (A control) of the resulting green–blue solu-
tion (ABTS radical solution) was recorded at kmax 734 nm.
The absorbance (A test) was measured on the addition of (20
lL of 1 mg mLꢀ1) solution of the tested sample in spectro-
scopic grade MeOH/buffer (1:1 v/v) to the ABTS solution.
The inhibition ratio (%) was calculated using the following
formula:
Synthesis of ethyl 2-(2-cyano-3-(dimethylamino)acryla-
mido)-4,5,6,7-tetrahydro-benzo[b]thiophene-3-carboxylate
(12). A mixture of 2 (1.46 g, 5 mmol), DMF-DMA (0.66 g,
5.5 mmol) in dioxane (20 mL) was refluxed for 3 h, cooled.
and poured into ice water. The formed precipitate was filtered
off and crystallized from ethanol to afford (69%) of 12; M.p.
% Inhibition ¼ ½AðcontrolÞ ꢀ AðtestÞ=AðcontrolÞꢂ ꢃ 100 (1)
240 C; yellow powder; IR (KBr) t (cmꢀ1), 3235 (NH), 2939
ꢁ
ꢀ
Ascorbic acid (20 lL, 2 mM) solution was used as standard
antioxidant (positive control). Blank sample was run using sol-
vent without ABTS (Table 2).
(CAH aliphatic), 2184 (CN), 1668, 1624 (2CO); 1H NMR
(400 MHz, DMSO-d6): d, 1.31 (q, 3H, CH3, J ¼ 7.2), 1.63–
1.73 (m, C5A2H, C6A2H), 2.63–2.86 (m, C5A2H, C6A2H),
3.16 (s, 3H, NACH3), 3.19 (s, 3H, NACH3), 4.26 (q, 2H,
CH2O, J ¼ 7.2), 8.15 (s, 1H, methine), 11.5 (br, s, 1H,
NHACO); ms: (m/z, %): 349 (Mþþ2, 1.0), 347 (Mþ, 0.7), 301
(2.3), 259 (1.4), 225 (0.5), 206 (2.0), 178 (3.1), 151 (1.7), 123
(100), 80 (14.4). Anal. Calcd. for C17H21N3O3S: C, 58.77; H,
6.09; N, 12.09; Found C, 58.81; H, 6.18; N, 12.01.
Acknowledgments. The authors are grateful to Dr. A. A. Fara-
hat, Department of Pharmaceutical Organic Chemistry, Faculty
of Pharmacy, University of Mansoura, Egypt, for spectral meas-
urements, and he is greatly acknowledged.
Synthesis of ethyl 2-(2-cyano-3-(4,6-dimethyl-1H-pyr-
rolo[2,3-b]pyridin-3-ylamino) acrylamido)-4,5,6,7-tetrahydro-
benzo[b]thiophene-3-carboxylate (13). A mixture of 12 (1.74
REFERENCES AND NOTES
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ꢁ
ꢀ
3383, 3280, 3236 (3NH), 2937, 2885 (CAH aliphatic), 2186
(CN), 1662 (br, 2CO), 1618 (C¼¼N); 1H NMR (400 MHz,
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Journal of Heterocyclic Chemistry
DOI 10.1002/jhet