Design and synthesis of 4,5-diaryl/heteroarylthiophene-2-carboxylic acid derivatives and evaluation of their biological activities

Article abstract of DOI:10.1515/hc-2016-0131

Synthesis, characterization and biological activity of novel 4,5-diaryl/heteroaryl thiophene-2-carboxylic acid derivatives are described. Aryl/heteroaryl esters were converted to substituted thiophene esters via a Vilsmeier-Haack reaction, which were then hydrolyzed to 4,5-diaryl/heteroaryl thiophene-2-carboxylic acid derivatives 8a-h. All products were characterized by ¹H NMR, ¹³C NMR, IR and MS. Antibacterial activity of the synthesized compounds against two Gram-positive and two Gram-negative bacteria, as well as their anticancer activity against PC-3 cell line (human prostate cancer cell lines) were evaluated.

Full text of DOI:10.1515/hc-2016-0131

Heterocycl. Commun. 2017; 23(1): 9–14
Preliminary Communication
Ananda Mohan Arasavelli, Ganapavarapu Sharma Veera Raghava and Siddaiah Vidavalur*
Design and synthesis of 4,5-diaryl/
heteroarylthiophene-2-carboxylic acid derivatives
and evaluation of their biological activities
DOI 10.1515/hc-2016-0131
Received August 22, 2016; accepted November 9, 2016; previously
published online February 7, 2017
non-steroidal anti-inflammatory drugs (NSAIDs) such as
tiaprofenic acid [12] (1) and tenidap [13] (2) (Figure 1) are
used for treatment of pain and inflammatory disorders.
The thiophenyl group mimics the phenyl group [14].
According to our recent review, 3,5-disubstituted
thiophene-2-carboxylic acid derivatives [15] and 2,5-disub-
stituted thiophene-3-carboxylic acid derivatives [16] have
been synthesized and their anti-HCV and anti-TB activities
evaluated. Furthermore, such derivatives have been devel-
oped as antibacterial agents [17]. However, synthesis and
biological evaluation of 4,5-diaryl/heteroarylthiophene-
2-carboxylic acid derivatives remain largely unexplored.
In the present study, we report the synthesis of novel 4,5-
diaryl/heteroarylthiophene-2-carboxylic acid derivatives
through the Vilsmeier-Haack reaction, their spectral char-
acterization and biological activity.
Abstract: Synthesis, characterization and biological
activity of novel 4,5-diaryl/heteroaryl thiophene-2-car-
boxylic acid derivatives are described. Aryl/heteroaryl
esters were converted to substituted thiophene esters
via a Vilsmeier-Haack reaction, which were then hydro-
lyzed to 4,5-diaryl/heteroaryl thiophene-2-carboxylic acid
1
derivatives 8a–h. All products were characterized by H
NMR, 13C NMR, IR and MS. Antibacterial activity of the
synthesized compounds against two Gram-positive and
two Gram-negative bacteria, as well as their anticancer
activity against PC-3 cell line (human prostate cancer cell
lines) were evaluated.
Keywords: PC-3 cancer cell line; thiophene esters; thio-
phene-2-carboxylic acid; Vilsmeier-Haack reaction.
Initially, aromatic ketones 5a–h were obtained from
4-chlorophenylacetic acid (3) and aromatic esters 4a–h
(Scheme 1). The Vilsmeier-Haack reaction is typically
used for formylation of aromatic and heteroaromatic com-
pounds [18, 19]. In this study, the ethanones 5a–h were
allowed to react with phosphorus oxychloride and N,N-
Introduction
Sulfur-containing heterocycles possess diverse properties dimethylformamide to yield chloro acrylaldehyde deriva-
such as antibacterial [1], antifungal [2], anti-HIV [3], anti- tives 6a–h. In the next step, these products were allowed
microbial [4] and antipsoriatic [5] activities. In particular, to react with ethyl mercaptoacetate in the presence of a
a thiophene system plays a crucial role in drug discov- sodium tert-butoxide to yield substituted thiophene esters
ery of BACE1 inhibitory [6], antibacterial [7], anticancer 7a–h, which were then hydrolyzed to the desired products
[8], antitubercular [9], anti-inflammatory [10] and anti- 8a–h.
HIV agents [11]. Currently, several thiophene-containing
S
*Corresponding author: Siddaiah Vidavalur, Department of Organic
O
Chemistry and FDW, Andhra University, Visakhapatnam 530003,
Cl
O
O
Andhra Pradesh, India, e-mail: gvrs276@gmail.com
Ananda Mohan Arasavelli: Department of Organic Chemistry,
Dr. B.R. Ambedkar University, Srikakulam, Etcherla 532410, Andhra
Pradesh, India; and Department of Chemistry, Jawaharlal Nehru
Technological University Kakinada, Kakinada 533003, Andhra
Pradesh, India
OH
OH
S
N
O
H2N
1
2
Tiaprofenic acid
Tenidap
Ganapavarapu Sharma Veera Raghava: Department of Chemistry,
GIT, GITAM University, Visakhapatnam 530045, Andhra Pradesh,
India
Figure 1ꢀThiophene based non-steroidal anti-inflammatory drugs 1
and 2.
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ꢀꢀꢀꢂ
10ꢁ
ꢁA.M. Arasavelli et al.: Design and synthesis of 4,5-diaryl/heteroarylthiophene-2-carboxylic acid derivatives
Cl
Cl
Cl
Cl
O
O
O
(Me3Si)2NNa
THF, – 15°C
POCl3
CH3
Ar
Ar
O
HO
Ar
DMF, 120°C
4a–h
3
5a–h
(6a–h)
O
H
Cl
Cl
SH
EtO
O
O
1. 0.25 M NaOH
2. rt, 3 h, 0.1 mol HCl
O
OEt
HO
S
S
NaOBut
Ar
Ar
(7a–h)
8a–h
a: Ar = 2-furyl
e: Ar = 4-chlorophenyl
f: Ar = 4-nitrophenyl
g: Ar = phenyl
b: Ar = 4-pyridyl
c: Ar = 4-methylphenyl
d: Ar = 3-bromo-3-tert.butyl phenyl
h: Ar = 4-hydroxyphenyl
Scheme 1ꢀ
2-(4-Chlorophenyl)-1-(pyridin-4-yl)ethanone (5b)ꢁYield 47%;
Experimental
1
white solid; mp 210°C; H NMR (DMSO-d6): δ 8.8 (m, 2H, Ar-H), 7.95
(m, 2H, Ar-H), 7.4 (m, 2H, Ar-H), 7.25 (m, 2H, Ar-H), 4.25 (s, 2H, -CH2);
13C NMR (CDCl3, 75 MHz): δ 194.8, 152.8, 150.8, 146.4, 138.5, 133.7, 130.8,
122.7, 118.0, 46.7; IR: υ 3068.3 (Ar=CH str), 2973.8 (CH str), 1710.8 (CO
str), 1520.9, 1482.6 (Ar C=C str), 1422.3 (CN str), 826.4 (C-Cl str) cmꢀ−ꢀ1;
All reactions were monitored by thin-layer chromatography analy-
sis using silica gel plates (Kieselgel 60F254 Merck). Compounds were
visualized by irradiation with UV light (254 nm) after spraying with
a 10% sulfuric acid/methanol solution. Melting points were deter-
mined in open capillary tubes on a Boetius melting point appara-
tus and are uncorrected. The IR spectra were recorded using KBr
+
+
+
LC-MS: m/z 231 (M)ꢀ , 232, 233 [relative intensity Mꢀ /(Mꢀ+ꢀ2)ꢀ ꢀ=ꢀ3ꢀ:ꢀ1].
Anal. Calcd for C13H10ClNO: C, 67.39; H, 4.35; N, 6.06. Found: C, 67.41;
H, 4.29; N, 5.97.
pellets on a Bruker spectrophotometer. H NMR (300 MHz) and 13C
1
NMR (75 MHz) spectra were obtained at room temperature on a Var-
ian Gemini spectrometer. Mass spectra were recorded on a JEOL
SX102 mass spectrometer coupled with a liquid chromatography
system in electrospray time of flight (TOF) mode. Elemental analy-
sis was performed on a Perkin Elmer CHNS elemental analyzer. The
purity of compounds was determined using a reverse-phase Waters
HPLC system equipped with a C18 analytical column (4.6ꢀ×ꢀ75 mm).
Peaks were detected by UV absorption (254 nm) using a diode array
detector.
2-(4-Chlorophenyl)-1-(p-tolyl)ethanone (5c)ꢁYield 53%; white
1
solid; mp 1215°C; H NMR (DMSO-d6): δ 7.92 (m, 2H, Ar-H), 7.38 (m,
4H, Ar-H), 7.24 (m, 2H, Ar-H), 4.20 (s, 2H, -CH2), 2.20 (s, 3H, -CH3); 13
C
NMR (CDCl3): δ 196.2, 148.8, 138.6, 137.2, 135.4, 122.7, 118.0, 46.2, 25.3;
IR: υ 3088.7 (Ar=CH str), 2943.2 (CH str), 2847.0 (CH str), 1698.7 (CO
str), 1540.9, 1452.4 (Ar C=C str), 796.3 (C-Cl str) cmꢀ−ꢀ1; LC-MS (m/z): 244
+
+
+
(Mꢀ ), 245, 246 [relative intensity Mꢀ /(Mꢀ+ꢀ2)ꢀ ꢀ=ꢀ3ꢀ:ꢀ1]. Anal. Calcd for
C15H13ClO: C, 73.62; H, 5.35. Found: C, 73.56; H, 5.29.
1-(3-Bromo-5-(tert-butyl)phenyl)-2-(4-chlorophenyl)ethanone
1
(5d)ꢁYield 27%; white solid; mp 223°C; H NMR (DMSO-d6): δ 8.02
(d, 1H, Jꢀ=ꢀ7.6 Hz, Ar-H), 7.82 (d, 1H, Jꢀ=ꢀ8.2 Hz, Ar-H), 7.80 (s, 1H, Ar-H),
7.42 (m, 2H, Ar-H), 7.26 (m, 2H, Ar-H), 4.22 (s, 2H, -CH2), 1.32 (s, 9H,
-CH3); 13C NMR (CDCl3): δ 188.8, 148.8, 140.8, 135.2, 132.4, 128.8, 124.7,
118.8, 42.7, 36.7, 30.2; IR: υ 3048.7 (Ar=CH str), 2842.3 (CH str), 2758.4
(CH str), 1688.5 (CO str), 1540.9, 1452.4 (Ar C=C str), 845.2 (C-Cl str)
General procedure for synthesis of compounds 5a–h
A solution of 2-(4-chlorophenyl)acetic acid (3, 1 g, 5.8 mmol) in
THF (10 mL) was cooled to −ꢀ60°C and stirred for 10 min before
treatment with sodium bis(trimethylsilyl)amide (NaHMDS, 2.90 g,
10 mmol) and then stirred for 1 h at −ꢀ20°C. An aryl ester 4a–h
(5.8 mmol) was added and the mixture was stirred for 30 min at
−ꢀ15°C and then at room temperature for an additional 30 min. The
reaction progress was monitored by TLC. The reaction mass was
quenched with NH4Cl and extracted with ethyl acetate. The prod-
uct was purified by silica gel column chromatography eluting with
ethyl acetate.
+
+
cmꢀ−ꢀ1; LC-MS (m/z): (M)ꢀ at 364 and (Mꢀ+ꢀ2)ꢀ at 366 [relative inten-
+
+
sity Mꢀ /(Mꢀ+ꢀ2)ꢀ ꢀ=ꢀ3ꢀ:ꢀ1]. Anal. Calcd for C18H18BrClO: C, 59.12; H, 4.96.
Found: C, 59.11; H, 4.88.
2-(4-Chlorophenyl)-1-(2-hydroxyphenyl)ethanone
(5e)ꢁYield
52%; white solid; mp 197°C; 1H NMR (CDCl3): δ 7.89 (d, 2H, Jꢀ=ꢀ7.8 Hz,
Ar-H), 7.20–7.65 (m, 4H, Ar-H), 7.05 (dd, 1H, Jꢀ=ꢀ7.6 Hz, Ar-H), 6.75
(d, 1H, Jꢀ=ꢀ7.5 Hz, Ar-H), 6.05 (s, 1H, OH), 3.95 (s, 2H, -CH2); 13C NMR
(CDCl3): δ 189.2, 166.4, 148.3, 139.4, 133.0, 126.4, 119.0, 112.7, 36.7; IR:
υ 3426.8 (OH str), 3089.2 (Ar=CH str), 2972.7 (CH str), 1714.9 (CO str),
1574.1, 1462.0 (Ar C=C str), 871.0 (C-Cl str) cmꢀ−ꢀ1; LC-MS (m/z): 246
2-(4-Chlorophenyl)-1-(furan-2-yl)ethanone (5a)ꢁYield 54%; white
solid; mp 196°C; 1H NMR (CDCl3): δ 7.6 (d, 1H, Jꢀ=ꢀ7.5 Hz, Ar-H), 7.2–7.5
(m, 5H, Ar-H), 6.45 (d, 1H, Jꢀ=ꢀ7.8 Hz, Ar-H), 4.05 (s, 2H, -CH2); 13C NMR
(CDCl3): δ 188.6, 162.0, 150.7, 138.4, 132.9, 122.7, 114.0, 38.7; IR: υ 3072.1
+
+
+
(Mꢀ ), 247, 248 [relative intensity Mꢀ /(Mꢀ+ꢀ2)ꢀ ꢀ=ꢀ3ꢀ:ꢀ1]. Anal. Calcd for
C14H11ClO2: C, 68.16; H, 4.49. Found: C, 68.09; H, 4.41.
(Ar=CH str), 2882.7 (CH str), 1709.7 (CO str), 1518.2, 1475.7 (Ar C=C str),
1182.0 (C-O-C str), 862.9 (C-Cl str) cmꢀ−ꢀ1; LC-MS (m/z): 220 (M)ꢀ , 221, 2-(4-Chlorophenyl)-1-(4-nitrophenyl)ethanone (5f)ꢁYield 48%;
+
+
+
222 [relative intensity Mꢀ /(Mꢀ+ꢀ2)ꢀ ꢀ=ꢀ3ꢀ:ꢀ1]. Anal. Calcd for C12H9ClO2: C, White solid, mp: 199°C; 1H NMR (DMSO-d6): δ 8.60 (d, 2H, Jꢀ=ꢀ7.9 Hz,
65.32; H, 4.11. Found: C, 65.22; H, 4.06.
Ar-H), 7.92 (m, 4H, Ar-H), 7.57 (d, 2H, Jꢀ=ꢀ8.2 Hz, Ar-H), 4.05 (s, 2H,
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A.M. Arasavelli et al.: Design and synthesis of 4,5-diaryl/heteroarylthiophene-2-carboxylic acid derivativesꢀ
ꢀ11
-CH2); 13C NMR (CDCl3): δ 192.0, 153.3, 149.2, 145.4, 136.7, 133.6, 129.5, (d, 1H, Jꢀ=ꢀ7.5 Hz, Ar-H), 7.62 (s, 1H, Ar-H), 7.48 (m, 2H, Ar-H), 7.40 (m,
121.6, 117.0, 44.3; IR: υ 3052.8 (Ar=CH str), 2890.2 (CH str), 1702.3 (CO 2H, Ar-H), 6.52 (dd, 1H, Ar-H), 6.23 (d, 1H, Jꢀ=ꢀ7.7 Hz, Ar-H), 2.95 (q, 2H,
str), 1603.1, 1522.8 (Ar C=C str), 826.4 (C-Cl str) cmꢀ−ꢀ1; LC-MS (m/z): Jꢀ=ꢀ13.1 Hz, OCH2), 1.72 (t, 3H, Jꢀ=ꢀ8.1 Hz, CH3); 13C NMR (CDCl3): δ 165.7,
+
+
+
275 (Mꢀ ), 277 [relative intensity Mꢀ /(Mꢀ+ꢀ2)ꢀ ꢀ=ꢀ3ꢀ:ꢀ1]. Anal. Calcd for 154.3, 148.8, 146.8, 140.8, 135.2, 132.4, 128.8, 124.7, 118.8, 106.2; IR: υ
C14H10ClNO3: C, 60.99; H, 3.66; N, 5.08. Found: C, 60.91; H, 3.61; 3097.9 (Ar=CH str), 1761.9 (CO str), 1568.7, 1530.2 (Ar C=C str), 1059.6
N, 4.99.
+
(C-S-C str), 838.1 (C-Cl str) cmꢀ−ꢀ1; LC-MS (m/z): 332 (Mꢀ ), 334 [relative
+
+
intensity Mꢀ /(Mꢀ+ꢀ2)ꢀ ꢀ=ꢀ3ꢀ:ꢀ1].
2-(4-Chlorophenyl)-1-phenylethanone (5g)ꢁYield 50%; white
solid; mp 189°C; H NMR (CDCl3): δ 7.94 (d, 2H, Jꢀ=ꢀ7.8 Hz, Ar-H), 7.52
1
(dd, 1H, Jꢀ=ꢀ7.1 Hz, Ar-H), 7.32 (d, 2H, Jꢀ=ꢀ7.9 Hz, Ar-H), 7.08 (m, 4H, General procedure for hydrolysis of compounds 7a–h
Ar-H), 4.08 (s, 2H, -CH2); 13C NMR (CDCl3): δ 188.0, 143.6, 137.1, 135.3,
(preparation of 8a–h)
122.0, 118.0, 46.3; IR: υ 3059.2 (Ar=CH str), 2896.2 (CH str), 1696.5 (CO
str), 1578.9, 1478.9 (Ar C=C str), 810.9 (C-Cl str) cmꢀ−ꢀ1; LC-MS (m/z):
The ester 7a–h (0.3 g, 0.9 mmol) was dissolved in methanol (3 mL)
+
+
+
230 (Mꢀ ), 232 [relative intensity Mꢀ /(Mꢀ+ꢀ2)ꢀ ꢀ=ꢀ3ꢀ:ꢀ1]. Anal. Calcd for
and the solution was treated with water (0.6 mL) and solid NaOH
(0.25 mol). The mixture was stirred for 3 h at ambient tempera-
ture, acidified with HCl (0.1 m), concentrated and the residue was
extracted with ethyl acetate. The acid 8a–h was purified by silica gel
chromatography eluting with ethyl acetate and petroleum ether.
C14H11ClO: C, 72.89; H, 4.81. Found: C, 72.81; H, 4.71.
2-(4-Chlorophenyl)-1-(4-hydroxyphenyl)ethanone
(5h)ꢁYield
43%; white solid; mp 198°C; 1H NMR (CDCl3): δ 8.34 (d, 2H, Jꢀ=ꢀ7.2 Hz,
Ar-H), 7.28 (m, 4H, Ar-H), 7.04 (d, 2H, Jꢀ=ꢀ8.2 Hz, Ar-H), 5.81 (s, 1H, OH),
3.82 (s, 2H, -CH2); 13C NMR (CDCl3): δ 192.6, 160.2, 142.1, 134.8, 134.0,
128.0, 128.7, 119.2, 40.2; IR: υ 3409.7 (OH str), 3053.7 (Ar=CH str), 2925.3
(CH str), 1708.9 (CO str), 1549.2, 1473.0 (Ar C=C str), 840.0 (C-Cl str)
4-(4-Chlorophenyl)-5-(furan-2-yl)thiophene-2-carboxylic acid
1
(8a)ꢁYield 54%; white solid; mp 201°C; H NMR (DMSO-d6): δ 13.41
(s, 1H, COOH), 7.74 (d, 1H, Jꢀ=ꢀ7.4 Hz, Ar-H), 7.62 (s, 1H, Ar-H), 7.48 (m,
2H, Ar-H), 7.40 (m, 2H, Ar-H), 6.52 (dd, 1H, Jꢀ=ꢀ8.1 Hz, Ar-H), 6.23 (d,
1H, Jꢀ=ꢀ7.9 Hz, Ar-H); 13C NMR (DMSO-d6): δ 187.9, 159.4, 149.1, 146.7,
cmꢀ−ꢀ1; LC-MS (m/z): 246 (Mꢀ ), 248 [relative intensity Mꢀ /(Mꢀ+ꢀ2)ꢀ ꢀ=ꢀ3ꢀ:ꢀ1].
+
+
+
Anal. Calcd for C14H11ClO2: C, 68.16; H, 4.49. Found: C, 68.09; H, 4.41.
137.7, 136.0, 135.5, 134.5, 130.8, 129.4, 127.6, 122.3, 119.7, 114.6; IR:
υ
3417.4 (OH str), 3057.5 (Ar=CH str), 1739.5 (CO str), 1621.8, 1520.4,
1478.4 (Ar C=C str), 1139.0 (C-S-C str), 857.0 (C-Cl str) cm−ꢀ1; LC-MS
General procedure for synthesis of compounds 6a–h
+
+
+
(m/z): 303.36 (Mꢀ ), 305.33 [relative intensity Mꢀ /(Mꢀ+ꢀ2)ꢀ ꢀ=ꢀ3ꢀ:ꢀ1].
Anal. Calcd for C15H9ClO3S: C, 59.12; H, 2.98; S, 10.52. Found: C, 59.11;
H, 2.87; S, 10.51.
POCl3 (0.86 g, 5.65 mmol) was added at 0°C to DMF (0.49 g, 6.78 mmol)
and the mixture was allowed to warm to room temperature and
stirred for 30 min. The mixture was cooled again to 0°C, treated with
compound 5a–h (0.5 g, 2.26 mmol) and the resulting reaction mass
was stirred for 1 h at 0°C and then at 70°C for 4 h, quenched with
sodium acetate and extracted with dichloromethane. The extract
was dried over sodium sulfate and concentrated. The residue of 6a–h
was used for the next step without purification. As a representative
example, the structure of 3-chloro-2-(4-chlorophenyl)-3-(furan-2-yl)
acrylaldehyde (6a) was confirmed on the basis of the following ana-
lytical data: yield 45%; white solid; mp 203°C; 1H NMR (CDCl3): δ 9.2
(s, 1H, CHO), 7.6 (d, 1H, Jꢀ=ꢀ7.6 Hz, Ar-H), 7.2–7.5 (m, 5H, Ar-H), 6.45 (d,
1H, Jꢀ=ꢀ8.3 Hz, Ar-H); 13C NMR (CDCl3): δ 210.3, 162.0, 150.7, 138.4, 135.5,
132.9, 122.7, 112.0; IR (KBr): υ 3062.2 (Ar=CH str), 1752.8 (CO str), 1518.2,
1475.7 (Ar-C=C str), 1164.2 (C-O-C str), 862.9 (C-Cl str) cmꢀ−ꢀ1; LC-MS
4-(4-Chlorophenyl)-5-(pyridin-4-yl)thiophene-2-carboxylic acid
1
(8b)ꢁYield 55%; light yellowish solid; mp 210°C; H NMR (DMSO-
d6): δ 13.41 (s, 1H, COOH, D2O exchangeable), 8.54 (dd, 2H, Jꢀ=ꢀ7.4 Hz,
Ar-H), 7.82 (s, 1H, Ar-H), 7.42 (d, 2H, Jꢀ=ꢀ8.2 Hz, Ar-H), 7.30 (m, 2H,
Ar-H), 7.20 (m, 2H, Ar-H); 13C NMR (CDCl3): δ 187.9, 159.4, 153.2, 149.4,
146.9, 136.3, 136.0, 135.8, 134.1, 132.6, 130.6, 129.9, 129.8, 123.8, 121.5,
120.7, 114.1, 113.8, 55.2; IR: υ 3417.4 (OH str), 3057.5 (Ar=CH str), 1739.3
(CO str), 1622.31, 1564.93, 1479.72 (Ar C=C str), 1138.8 (C-S-C str), 829.4
+
(C-Cl str) cmꢀ−ꢀ1; LC-MS (m/z): 315.78 (Mꢀ ), 316.17, 317.35 [relative inten-
+
+
sity Mꢀ /(Mꢀ+ꢀ2)ꢀ ꢀ=ꢀ3ꢀ:ꢀ1]. Anal. Calcd for C16H10ClNO2S: C, 60.86; H, 3.19;
N, 4.44; S, 10.15. Found: C, 60.81; H, 3.1; N, 4.39; S, 10.11.
+
+
+
4-(4-Chlorophenyl)-5-(p-tolyl)thiophene-2-carboxylic acid (8c)ꢁ
(m/z): 265 (M)ꢀ , 267.23 [relative intensity Mꢀ /(Mꢀ+ꢀ2)ꢀ ꢀ=ꢀ3ꢀ:ꢀ1].
1
Yield 57% white solid; mp 213°C; H NMR (DMSO-d6): δ 13.21 (s, 1H,
COOH, D2O exchangeable), 7.76 (s, 1H, Ar-H), 7.38 (d, 2H, Jꢀ=ꢀ7.8 Hz,
Ar-H), 7.26 (d, 2H, Jꢀ=ꢀ7.9 Hz, Ar-H), 7.18 (m, 4H, Ar-H) 2.2 (s, 3H,
CH3); 13C NMR (CDCl3): δ 174.0, 162.4, 145.3, 135.1, 132.5, 130.6, 129.4,
128.5, 128.3, 126.4, 127.2, 127.9, 126.4, 30.0, 23.2; IR: υ 3484.26 (OH str),
General procedure for the preparation of compounds 7a–h
Ethyl mercaptoacetate (0.112 g, 9.3 mmol) was added at 0°C to a solu- 3048.4 (Ar=CH str), 1739.4 (CO str), 1621.7, 1556.9, 1478.4 (Ar C=C str),
+
tion of sodium tert-butoxide (0.06 g, 9.3 mmol) in ethanol (1.5 mL) 1139.0 (C-S-C str), 830.8 (C-Cl str) cmꢀ−ꢀ1; LC-MS (m/z): 328.82 (M)ꢀ ,
+
+
and the mixture was stirred at the same temperature for 30 min, 329.37, 330.37 [relative intensity Mꢀ /(Mꢀ+ꢀ2)ꢀ ꢀ=ꢀ3ꢀ:ꢀ1]. Anal. Calcd for
then treated with compound 6a–h and the stirring was continued C18H13ClO2S: C, 65.75; H, 3.99; S, 9.75. Found: C, 65.69; H, 3.91; S, 9.69.
overnight followed by reflux for an additional 2 h. The reaction
mass was quenched with water and extracted with dichlorometh- 5-(3-Bromo-5-(tert-butyl)phenyl-4-(4-chlorophenyl)thiophene-
1
ane. The extract was concentrated affording compound 7a–h that 2-carboxylic acid (8d)ꢁYield 61%; white solid; mp 216°C; H NMR
was used without further purification. As a representative example, (DMSO-d6): δ 13.25 (s, 1H, COOH, D2O exchangeable), 7.78 (s, 1H,
the structure of ethyl 4-(4-chlorophenyl)-5-(furan-2-yl)thiophene- Ar-H), 7.52 (s, 1H, Ar-H), 7.40 (m, 3H, Ar-H), 7.26 (dd, 2H, Jꢀ=ꢀ7.6 Hz,
2-carboxylate (7a) was confirmed based on the following analytical Ar-H), 7.08 (d, 1H, Jꢀ=ꢀ8.4 Hz, Ar-H), 1.05 (s, 9H, (CH3)3); 13C NMR
1
data: yield 45%; yellowish solid; mp 198°C; H NMR (CDCl3): δ 7.74 (CDCl3): δ 175.0, 162.1, 148.3, 145.4, 141.6, 139.6, 135.1, 132.3, 128.9, 128.5,
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12ꢁ
127.8, 127.7, 126.9, 115.3, 29.9, 23.9; IR: υ 3496.2 (OH str), 3058.4 (Ar=CH Ar-H), 7.82 (s, 1H, Ar-H), 7.42 (d, 2H, Jꢀ=ꢀ8.2 Hz, Ar-H), 7.30 (m, 2H,
str), 1724.4 (CO str), 1547.9, 1459.4 (Ar C=C str), 1048.9 (C-S-C str), 820.7 Ar-H), 7.20 (m, 2H, Ar-H); 13C NMR (CDCl3): δ 186.7, 164.1, 148.7, 146.4,
+
+
(C-Cl str) cmꢀ−ꢀ1; LC-MS (m/z): 449.8 (Mꢀ ), 451.3 [relative intensity Mꢀ / 141.3, 139.4, 131.7, 130.4, 127.2, 116.7, 112.8; IR: υ 3486.8 (OH str), 3067.1
+
(Mꢀ+ꢀ2)ꢀ ꢀ=ꢀ3ꢀ:ꢀ1]. Anal. Calcd for C21H18BrClO2S: C, 56.08; H, 4.03; S, 7.13. (Ar=CH str), 1708.5 (CO str), 1564.9, 1462.8 (Ar C=C str), 1052.0 (C-S-C
+
Found: C, 55.98; H, 4.07; S, 7.09.
str), 840.0 (C-Cl str) cmꢀ−ꢀ1; LC-MS (m/z): 330 (Mꢀ ), 331, 332 [relative
+
+
intensity Mꢀ /(Mꢀ+ꢀ2) ꢀ ꢀ=ꢀ3ꢀ:ꢀ1]. Anal. Cacld for C17H11ClO3S: C, 61.73; H,
4-(4-Chlorophenyl)-5-(2-hydroxyphenyl)thiophene-2-carboxylic 3.35; S, 9.69. Found: C, 61.69; H, 3.29; S, 9.61.
1
acid (8e)ꢁYield 56%; white solid; mp 218°C; H NMR (DMSO-d6): δ
11.56 (s, 1H, COOH), 8.12 (s, 1H, Ar-H), 7.62 (d, 2H, Jꢀ=ꢀ7.4 Hz, Ar-H),
7.37 (m, 3H, Ar-H), 7.14 (dd, 2H, Jꢀ=ꢀ7.1 Hz, Ar-H), 6.85 (d, 1H, Jꢀ=ꢀ7.8 Hz,
Antibacterial activity
Ar-H), 6.44 (s, 1H, Ar-OH); 13C NMR (CDCl3): δ 174.3, 162.3, 145.3, 142.3,
135.7, 132.9, 130.2, 128.7, 128.0, 126.4, 125.9, 122.9, 118.3; IR: υ 3476.2
Two Gram-positive (Bacillus sphaericus and Staphylococcus aureus)
(OH str), 3436.0 (OH str), 3068.4 (Ar=CH str), 1704.1 (CO str), 1558.9,
and two Gram-negative (Pseudomonas vulgaris and Escherichia coli)
organisms were used for this study. Pseudomonas aeruginosa (MTCC
6642) and E. coli were obtained from Microbial Type Culture Collec-
tion, IMTECH, Chandigarh, India. Clinical isolates of S. aureus and
B. sphaericus, were obtained from Microbiology laboratory of Global
Hospital, Hyderabad, India. Ciprofloxacin was used as standard ref-
erence. Compounds 8a–h were tested for antibacterial activity in
vitro by agar well diffusion method [20]. The bacterial strains were
reactivated from stock cultures by incubating the inoculated broths
at 37°C for 24 h in an incubator. Final inoculums containing 106 colo-
nies (1ꢀ×ꢀ106 CFU/mL) were added aseptically to Mueller-Hinton agar
medium and poured into sterile Petri dishes. One hundred microliters
of each test extract from stock concentrations (1 mg/mL) were added
to the wells (8 mm) punched on agar surface. Plates were incubated
in a bacterial incubator overnight at 37°C. The activity was evaluated
by measuring the diameter of inhibition zone (Table 1). Compounds
8a and 8b show considerable activity against E. coli.
1452.4 (Ar C=C str), 1099.4 (C-S-C str), 864.1 (C-Cl str) cmꢀ−ꢀ1; LC-MS
+
+
+
(m/z): 330.8 (Mꢀ ), 332.3 [relative intensity Mꢀ /(Mꢀ+ꢀ2)ꢀ ꢀ=ꢀ3ꢀ:ꢀ1]. Anal.
Calcd for C17H11ClO3S: C, 61.73; H, 3.35; S, 9.69. Found: C, 61.69; H,
3.36; S, 9.61.
4-(4-Chlorophenyl)-5-(4-nitrophenyl)thiophene-2-carboxylic
acid (8f)ꢁYield: 59%. Light yellow solid, mp 220°C; 1H NMR (CDCl3):
δ 13.26 (s, 1H, COOH), 8.06 (s, 1H, Ar-H), 7.73 (d, 2H, Jꢀ=ꢀ7.6 Hz, Ar-H),
7.24 (d, 2H, Jꢀ=ꢀ8.3 Hz, Ar-H), 7.12 (m, 2H, Ar-H) 6.87 (m, 2H, Ar-H); 13
C
NMR (75 MHz, CDCl3): δ 178.8, 160.2, 152.5, 143.2, 140.5, 137.3, 134.7,
131.7, 127.8, 123.8, 117.8; IR: υ 3424.4 (OH str), 3078.1 (Ar=CH str),
1724.8 (CO str), 1558.8, 1464.1 (Ar C=C str), 1145.3 (C-S-C str), 845.4
+
(C-Cl str) cmꢀ−ꢀ1. LC-MS (m/z): 359 (Mꢀ ), 360, 361 [relative intensity
+
+
Mꢀ /(Mꢀ+ꢀ2)ꢀ ꢀ=ꢀ3ꢀ:ꢀ1]. Anal. Calcd for C17H10 ClNO4S: C, 56.75; H, 2.80; N,
3.89; S, 8.91. Found: C, 56.68; H, 3.81; N, 3.81; S, 8.89.
4-(4-Chlorophenyl)-5-phenylthiophene-2-carboxylic acid (8g)ꢁ
Yield 61%; white solid; mp 208°C; 1H NMR (DMSO-d6): δ 13.41 (s, 1H,
COOH, D2O exchangeable), 8.54 (dd, 2H, Jꢀ=ꢀ7.4 Hz, Ar-H), 7.82 (s, 1H,
Ar-H), 7.42 (d, 2H, Jꢀ=ꢀ8.1 Hz, Ar-H), 7.30 (m, 2H, Ar-H), 7.20 (m, 2H,
Ar-H); 13C NMR (CDCl3): δ 172.4, 160.5, 150.7, 139.8, 139.3, 135.6, 131.6,
Anticancer activity
128.7, 122.5, 115.4; IR: υ 3452.5 (OH str), 3027.7 (Ar=CH str), 1717.4 (CO Cisplatin and MTT (3,4,5-dimethylthiazol-2-yl-2-5-diphenyltetrazo-
str), 1579.7, 1482.7 (Ar C=C str), 1126.7 (C-S-C str), 864.9 (C-Cl str) cmꢀ−ꢀ1; lium bromide) were procured from Sigma Aldrich (USA). PC-3 (human
+
+
+
LC-MS (m/z): 314 (M)ꢀ , 316 [relative intensity of Mꢀ /(Mꢀ+ꢀ2)ꢀ ꢀ=ꢀ3ꢀ:ꢀ1]. prostate cancer cell line) was procured from NCCS (Pune, India).
Anal. Calcd for C17H11ClO2S: C, 64.86; H, 3.52; S, 10.19. Found: C, 64.81; Compounds 8a–h were screened for anticancer activity following
H, 3.49; S, 10.11.
a reported protocol [21] and the results are summarized in Table 2.
The cell line was grown in the RPMI-1640 with 2 mmol L-glutamine,
4-(4-Chlorophenyl)-5-(4-hydroxyphenyl)thiophene-2-carbox- supplemented with 10% FBS, penicillin (100 IU/mL) and strepto-
1
ylic acid (8h)ꢁYield 59%; white solid; mp 213°C; H NMR (DMSO- mycin (100 μg/mL) at 37°C in a humidified incubator with 5% CO2
d6): δ 13.41 (s, 1H, COOH, D2O exchangeable), 8.54 (dd, 2H, Jꢀ=ꢀ7.2 Hz, atmosphere. The cell line was passaged twice weekly for maintaining
Table 1ꢀAntibacterial activity.
No. ꢁ Compounds ꢁ Zone of inhibition (diameter, mm) 0.4 mg/mL
ꢁ
Bacillus sphaericus (ꢂ+ꢂve)ꢁ Staphylococcus aureus (ꢂ+ꢂve)ꢁ Pseudomonas vulgaris (ꢂ−ꢂve)ꢁ Escherichia coli (ꢂ−ꢂve)
1
2
3
4
5
6
7
8
9
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
5a
5b
5c
5d
5e
5f
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
15ꢂ ꢂ0.2
11ꢂ ꢂ0.2
18ꢂ ꢂ0.4
14ꢂ ꢂ0.2
16ꢂ ꢂ0.3
NI
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
07ꢂ ꢂ0.3
NI
10ꢂ ꢂ0.2
12ꢂ ꢂ0.3
11ꢂ ꢂ0.2
08ꢂ ꢂ0.2
NI
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
17ꢂ ꢂ0.4
09ꢂ ꢂ0.2
NI
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
20ꢂ ꢂ0.4
25ꢂ ꢂ0.5
18ꢂ ꢂ0.3
09ꢂ ꢂ0.2
NI
10ꢂ ꢂ0.2
NI
NI
12ꢂ ꢂ0.3
11ꢂ ꢂ0.2
09ꢂ ꢂ0.2
07ꢂ ꢂ0.2
35ꢂ ꢂ0.4
5g
5h
16ꢂ ꢂ0.4
12ꢂ ꢂ0.2
11ꢂ ꢂ0.3
36ꢂ ꢂ0.5
11ꢂ ꢂ0.2
31ꢂ ꢂ0.5
Ciprofloxacinꢃ 28ꢂ ꢂ0.2
NI, No inhibition.
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A.M. Arasavelli et al.: Design and synthesis of 4,5-diaryl/heteroarylthiophene-2-carboxylic acid derivativesꢀ
ꢀ13
Table 2ꢀAnticancer activity of title compounds against PC-3.
Compoundsꢁ
ꢁ
% of cell death at various concentrations (μg/mL)ꢁ
IC50 (μg/mL)
2.0ꢁ
5.0ꢁ
10.0ꢁ
25.0
8a
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
28.9ꢃ
29.72ꢃ
47.28ꢃ
29.98ꢃ
26.47ꢃ
20.34ꢃ
30.88ꢃ
33.33ꢃ
22.38ꢃ
37.72ꢃ
34.62ꢃ
56.38ꢃ
37.48ꢃ
38.24ꢃ
36.37ꢃ
35.04ꢃ
42.89ꢃ
44.24ꢃ
50.73ꢃ
41.35ꢃ
58.65ꢃ
38.24ꢃ
49.27ꢃ
40.31ꢃ
44.11ꢃ
51.27ꢃ
49.36ꢃ
61.27ꢃ
60.27ꢃ
59.71ꢃ
36.37ꢃ
62.48ꢃ
41.91ꢃ
61.76ꢃ
61.27ꢃ
64.17ꢃ
10
17
8b
8c
6
8d
18
8e
9.6
4.5
15.2
6.8
25
8f
8g
8h
Cisplatin
subconfluent state. MTT was used as cell viability assay [22]. Cispl-
atin, a known anticancer drug, was used as a reference. The treated
and untreated cells were washed with PBS (phosphate buffer saline)
and MTT (100 μg/mL) was added and the mixture was incubated at
37°C for 5 h. The MTT was then removed and the formazan crystals
were dissolved by adding DMSO. The absorbance at 540 nm for via-
ble cells was measured. The absorbance from the untreated cells was
defined as 100% viable cells. The % viable cells were plotted (Y-axis)
against concentration (X-axis). The IC50 values was interpolated from
the graph. Compounds 8c and 8h show good activity and further
work is in progress.
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Acknowledgments: We acknowledge the financial support
of Dr. B. R. Ambedkar University, Srikakulam. The finan-
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istry, GITAM University is also acknowledged.
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