Aminothiophenedicarboxamides and dicyanothiopheneacetamides as effective synthetic molluscicides against Indoplanorbis exustus snail

Article abstract of DOI:10.1016/j.ejmech.2011.06.001

New thiophenedicarboxamide 2a-c and dicyanothiopheneacetamide 3a-c derivatives were synthesized and their bioactivity against Indoplanorbis exustus snails was evaluated. The I. exustus snail is a serious host of parasite of genus Schistosoma which infects cattle. Thus reduces livestock productivity and also acts as a source of cercarial dermatitis in human beings. The results obtained show a significant (P < 0.05) molluscicidal activity with LC ₅₀ = 0.6043 ppm for compound 2a and LC₅₀ = 0.6511 ppm for compound 3a.

Full text of DOI:10.1016/j.ejmech.2011.06.001

European Journal of Medicinal Chemistry 46 (2011) 4682e4686
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Short communication
Aminothiophenedicarboxamides and dicyanothiopheneacetamides as effective
synthetic molluscicides against Indoplanorbis exustus snail
,
a
b
b
Shrikant B. Kanawade a, Raghunath B. Toche a , Shivaraj P. Patil , Ashok E. Desai , Sapana S. Bhamare
*
a Organic Chemistry Research Center, Department of Chemistry, K. T. H. M. College, Gangapur Road, Nashik 422 002, MS, India1
b Department of Zoology, K. T. H. M. College, Gangapur Road, Nashik 422 002, MS, India1
a r t i c l e i n f o
a b s t r a c t
Article history:
New thiophenedicarboxamide 2aec and dicyanothiopheneacetamide 3aec derivatives were synthesized
and their bioactivity against Indoplanorbis exustus snails was evaluated. The I. exustus snail is a serious
host of parasite of genus Schistosoma which infects cattle. Thus reduces livestock productivity and also
acts as a source of cercarial dermatitis in human beings. The results obtained show a significant
(P < 0.05) molluscicidal activity with LC50 ¼ 0.6043 ppm for compound 2a and LC50 ¼ 0.6511 ppm for
compound 3a.
Received 27 March 2011
Received in revised form
1 June 2011
Accepted 1 June 2011
Available online 12 June 2011
Ó 2011 Elsevier Masson SAS. All rights reserved.
Keywords:
Thiophenedicarbonitrile
Thiophenedicarboxamide
Thiophenedicyanoacetamide
Molluscicidal activity
Indoplanorbis exustus snail
1. Introduction
used as a molluscicide in many parts of the world. But major demerit
of Bayluscide as a synthetic molluscicide is its toxicity to fish.
The freshwater snail Indoplanorbis exustus found across India
[1], Southeast Asia [2], Arabia and Africa [2], Central Asia
(Afghanistan) [3], is the intermediate host for parasite of genus
Schistosoma nasale, Schistosoma spindale and Schistosoma indicum
[2]. This snail is a hermaphroditic invasive species with high
fecundity and is responsible for the transmission of several
immature stages of the genus Schistosoma which infects cattle and
causes the reduction in livestock productivity, also causes cercarial
dermatitis among rural workers, particularly in India [4]. In spite of
its long history and wide geographical range, it is thought that
Indoplanorbis includes only a single species.
Schistosomiasis is an endemic parasitic disease in tropical and
subtropical regions that affect over 200 million people worldwide
and is second only to malaria having adverse effect on social and
economic development of the countries [5]. The control of snail
intermediate host is an effective means of reducing the disease
transmission. The early use of molluscicides in schistosomiasis
control was reviewed by Duncan et al. [6,7]. The synthetic
compound Bayluscide [8] is an ethanol amine salt of niclosamide
Quinolone derivatives [9], quinoline alkaloids [10] were
prepared and tested as molluscicides previously. Thiophene in
particular has been investigated by Royer et al. [11]; and reported
the effectiveness of some mono and polyhalogenated thiophene
carboxanilides against Biomphalaria glabrata snail. Other thiophene
containing compounds have also been evaluated [12]. Recently,
Fadda et al. [13] has reported the molluscicidal activity of new
thiophene, thiadiazole and pyrazolo derivatives. Such chemical
compounds reduce oxygen consumption level in glycolysis
pathway which consequently causes death of snails [14]. In our
previous article [15], we have synthesized quinolon-3-azoles and
tested against Machrochlamys indica snails which showed good
molluscicidal activity.
In this paper we report the synthesis and molluscicidal
activity of thiophenedicyanoacetamide and thiophenedicarbox-
amide derivatives. These compounds showed very high mollusci-
cidal activity even at very minute (ppm) concentration. Though
these compounds are very effective as molluscicides, may have
more adverse effect to the environment. However, this work is only
at the preliminary stage until we find some more suitable effective
thiophene moieties. Then we can enhance our study to evaluate the
biodegradability as well as its effect on other living organisms.
Unsubstituted analogue of (1) is reported in literature [16e19];
* Corresponding author. Tel.: þ91 0253 2571376; fax: þ91 0253 2577341.
E-mail address: raghunath_toche@rediffmail.com (R.B. Toche).
1
Affiliated to University of Pune, Pune 411 007, India.
0223-5234/$ e see front matter Ó 2011 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2011.06.001

S.B. Kanawade et al. / European Journal of Medicinal Chemistry 46 (2011) 4682e4686
4683
while its derivatives are still unknown in literature which showed
very good molluscicidal activity in present communication.
and 3a exhibited the highest toxic action with LC50 ¼ 0.6043 ppm
and 0.6511 ppm respectively. In the series of thiophene dicarbox-
amides 2aec and dicyanothiopheneacetamides 3aec, compound
2a showed higher molluscicidal activity with LC50 value
(0.6043 ppm) at 10e40 ppm concentration while, compound 3a
showed highest molluscicidal activity with LC50 value (0.6511 ppm)
at 0.02e0.08 ppm concentration. The activity at this minimal
amount may be due to the presence of carboxanilide and two nitrile
functionalities attached to the thiophene ring. It was also observed
that the presence of chlorine substituent may enhance the bio-
logical activity more than the difluoro and bis-trifluoromethyl
groups (Tables 1 and 2 entries) attached to the phenyl ring. Simi-
larly, we have evaluated the toxicity of compounds 1aec and 4aeb,
which did not show any toxic action at all against I. exustus snail.
During the exposure period, the effusion of the gelatinous material
was observed from snails under influence of the tested compounds.
This fact may reveal the mode of their toxic action is through the
physical interference of cell membranes, resulting in hindering
their functions and cause of subsequent death.
Compounds 2a and 3a (LC50 ¼ 0.6043 ppm and 0.6511 ppm
resp.) seemed to be promising and after some modifications will be
considered in future study. The I. exustus snails had been recently
considered as one of the most serious pests in Nashik District (MS,
India). Therefore, control measures are necessary. The
manufacturing of these compounds is inexpensive, hence can be
considered as futher molluscicides because of their higher activity
at ppm concentration.
2. Chemistry
The starting precursor 1aec was synthesized by Gewald reac-
tion of aryl-3-oxopropanenitrile, malononitrile and elemental
sulfur in excellent yield [16e19]. Direct conversion of thiophene-
2,4-dicarbonitriles 1aec to thiophene-2,4-dicarboxamides 2aec
was achieved in quantitative yield by stirring in conc. H2SO4 [20,21]
at room temperature. The structures of compounds 1aec and 2aec
were established by spectroscopic and analytical characterization
e.g. IR of 1a showed presence of nitrile stretching at 2198 cmꢀ1 is
also confirmed by 13C NMR spectrum clearly showed two isolable
nitrile carbons at
d 114.9 and 115.1 ppm. These nitrile peaks were
lost in compound 2a and new IR absorption bands are observed at
1668 cmꢀ1 (CO stretch) and 3169e3327 cmꢀ1 (NH stretch) due to
conversion of nitrile to amide. 1H NMR of compound 1a showed
a broad singlet at
broad singlets at
d
8.37 ppm for NH2 and that for 2a showed three
d
4.82, 6.84 ppm for two amide NH2 and 7.69 ppm
for one free amine NH2 protons. Compounds 1aec when stirred in
acetic anhydride in presence of catalytic conc. H2SO4 afforded
dicyanothiopheneacetamide 3aec in 85e90% yield. Compound 3a
showed absorption bands at 2216 cmꢀ1 for nitrile group, was
further confirmed by 13C NMR which showed two nitrile carbons at
d
112.9 and 113.7 ppm and also its mass spectrum showed molec-
ular ion peak, m/z ¼ 301 (Mþ, 100%). The 1H NMR spectrum of 3a
revealed two singlets at d 2.31 and 12.63 ppm due to protons of CH3
and NH respectively. Thienopyrimidine 4aeb was obtained from
dicarboxamide 2a, by refluxing in acid chlorides in acetic acid
(Scheme 1). Compound 4a showed IR absorption bands at
1665 cmꢀ1 for amide CO and 3489, 3468 cmꢀ1 for amide NH2 as
well as its 1H NMR spectrum assigned based on three singlets at
4. Conclusion
The polysubstituted thiophene derivatives having potential
molluscicidal activity can be obtained by simple and convenient
method of preparation having satisfactory yields. The series of
thiophene dicarboxamides and thiophenedicyanoacetamides
showed significantly potent activities against I. exustus snails. In
addition, the infection rate and prepatent period of I. exustus snails
were remarkably controlled on exposure to the tested thio-
phenedicarboxamide and thiophenedicyanoacetamide derivatives.
d
4.54, 6.21 and 12.04 ppm due to protons for CH2, primary amide
NH2 and secondary amide NH groups respectively. Mass spectrum
of 4a showed molecular ion peak, m/z ¼ 376 (MþNa, 20%) and base
peak, at m/z ¼ 79 (100%).
3. Biological evaluation
5. Experimental
3.1. Molluscicidal activity
Melting points were determined on a Gallenkamp melting point
apparatus. The 1H (300 MHz) and 13C (75 MHz) NMR spectra were
recorded on a Varian XL-300 spectrometer. Chemical shifts were
reported in ppm relative to tetramethylsilane (TMS), and
The toxicity of compounds 1aec, 2aec, 3aec, 4aeb against I.
exustus snails was evaluated and results with calculated half lethal
dose (LC50) in ppm were shown in Tables 1 and 2. Compounds 2a
O
O
RCOCl, AcOH
reflux, 8-10 h
Ar
NH2
NH2
Ar
conc. H2SO4
NH
H2N
rt
stirr, 4-6 h
O
H2N
R
Ar: 2a: 4-ClC6H4
N
S
S
O
2a-c
4a-b
90-94%
CN
Ar
NC
65-70%
4a; R = CH2Cl
4b; R = CH3
NH2
S
1a-c
Ar: a: 4-ClC6H4
b: 3,5-(CF3)2C6H3
c: 2,4-F2C6H3
CN
Ar
NC
O
Ar: a: 4-ClC6H4
Ac2O, H2SO4
b: 3,5-(CF3)2C6H3
c: 2,4-F2C6H3
CH3
N
S
rt
H
stirr, 1-1.5 h
3a-c
85-90%
Scheme 1. a) Compounds (2aec) and (3aec) have been successfully synthesized from polysubstituted thiophene (1aec) by conventional method and compound (4aeb) obtained
from compound (2a). b) Compounds (2aec) and (3aec) exhibited significant molluscicidal activity against Indoplanorbis exustus snail whereas (1aec) and (4aeb) found completely
inactive.

4684
S.B. Kanawade et al. / European Journal of Medicinal Chemistry 46 (2011) 4682e4686
Table 1
Molluscicidal activity of thiophenedicarboxamide (2aec) against Indoplanorbis exustus, (10 snail’s concentration) after 24 h exposure at ambient temperature 24 ꢂ 1 ꢁC.
Compd
Dose in ppm
% mortality
LC50 (ppm ꢂ S.E.)
Regression eqn Y ¼ a þ bx
Heterogenicity
Variance
Fiduacial limit
2a
Control
10
0
0
e
e
e
e
e
m1 ¼ ꢀ1.2005
m2 ¼ ꢀ2.7989
20
30
40
20
30
50
0.6043 ꢂ 0.4078
Y ¼ 3.3001 e 0.7791(x)
3.0636
0.1663
2b
2c
Control
10
20
30
40
0
20
30
60
60
e
e
e
e
e
m1 ¼ ꢀ2.4808
m2 ¼ ꢀ1.2700
0.7506 ꢂ 0.3089
Y ¼ 2.0403 e 2.0418(x)
3.5620
0.0954
Control
10
20
30
40
0
20
40
60
70
e
e
e
e
e
0.6067 ꢂ 0.5028
Y ¼ 1.8094 e 2.3115(x)
3.0457
0.2528
m1 ¼ ꢀ2.7684
m2 ¼ ꢀ0.7976
The data are the average of three replicates and significant at P < 0.05.
multiplicities were given as
s
(singlet), bs (broad singlet),
85.8, 114.9, 115.1, 129.5, 130.5, 135.2, 150.9, 198.3; MS: m/z (%) 259
(Mþ, 33), 261 (M þ 2, 11); Anal. Calcd for C12H6ClN3S (259.71) C,
55.50%; H, 2.33%; N, 16.18%; Found: C, 55.38%; H, 2.15%; N, 16.32%.
d (doublet), t (triplet), q (quartet), or m (multiplet). The solvents for
NMR spectra were DMSO-d6 and CDCl3 unless otherwise stated.
Infrared spectra were recorded in KBr pellets on a Shimadzu FTIR-
8400S spectrophotometer. Mass spectra were recorded on a Shi-
madzu LC-MS QP 2010A mass spectrometer with an ionization
potential of 70 eV. Elemental analyses were performed on Thermo
Quest Flash 1112 Series EA analyzer. Reactions were monitored by
thin layer chromatography, carried out on 0.2 mm silica gel 60 F254
(Merck) plates using UV light (254 and 366 nm) for detection.
Common reagent grade chemicals were commercially available and
used without further purification or prepared by standard litera-
ture procedures.
5.1.2. 5-Amino-3-(3,5-bis(trifluoromethyl)phenyl)thiophene-2,4-
dicarbonitrile (1b)
Colourless solid. (Yield 85%, 3.00 g), m.p. 230e231 ꢁC (MeOH); IR
(KBr): V=cmꢀ1 ¼ 3398; 3327 (NH2), 2206 for two (CN), 1618 (Ar C]
C); 1HNMR:(DMSO-d6),
d8.19(s, 2H, Ar), 8.26(s,1H, Ar-H), 8.48(bs, 2H,
NH2); MS: m/z (%) 361 (Mþ, 80); Anal. Calcd for C14H5F6N3S (361.27): C,
46.54%; H, 1.40%; N, 11.63%; Found: C, 46.45%; H, 1.36%; N, 11.70%.
5.1.3. 5-Amino-3-(2,4-difluorophenyl)thiophene-2,4-dicarbonitrile (1c)
Brown solid. (Yield 85%, 2.22 g), m.p. 244e246 ꢁC (EtOH:DMF,
8:2); IR (KBr): V=cmꢀ1 ¼ 3387; 3292 (NH2), 2204 for two (CN),
1629 (Ar C]C); 1H NMR: (DMSO-d6),
d 7.27e7.34 (m, 1H, Ar-H),
5.1. General procedure for the synthesis of 5-amino-(4-aryl)
thiophene-2,4-dicarbonitrile (1aec)
7.49e7.68 (m, 2H, Ar-H), 8.43 (bs, 2H, NH2); MS: m/z (%) 260
(M ꢀ 1, 40); Anal. calcd for C12H5F2N3S (261.25): C, 55.17%; H, 1.93%;
N, 16.08%; Found C, 55.09%; H, 1.99%; N, 16.22%.
These compounds were synthesized by the known literature
method [16e19,22] and recrystallized from appropriate solvents.
5.1.1. 5-Amino-3-(4-chlorophenyl)thiophene-2,4-dicarbonitrile (1a)
Yellow solid. (Yield 90%, 2.33 g), m.p. 292e294 ꢁC (EtOH:DMF,
8:2); IR (KBr): V=cmꢀ1 ¼ 3383; 3304 (NH2), 2198 for two (CN),1630
5.2. General procedure for the synthesis of 4-arylthiophene-
dicarboxamide (2aec)
(ArC]C); 1HNMR: (DMSO-d6),
d
7.57 (d, J ¼8.4 Hz, 2H, Ar-H), 7.62 (d,
Compound 1aec (2.59 g, 0.01 mol) was stirred in conc. H2SO4
(10 mL) at room temperature for about 4e6 h (TLC check
J ¼ 8.4 Hz, 2H, Ar-H), 8.37 (bs, 2H, NH2); 13C NMR: (DMSO-d6),
d 85.7,
Table 2
Molluscicidal activity of dicyanothiopheneacetamide (3aec) against Indoplanorbis exustus, (10 snail’s concentration) after 24 h exposure at ambient temperature 24 ꢂ 1 ꢁC.
Compd
Dose in ppm
% mortality
LC50 (ppm ꢂ S.E.)
Regression eqn Y ¼ a þ bx
Heterogenicity
Variance
Fiduacial limit
3a
Control
0.02
0.04
0.06
0.08
0
20
40
60
80
e
e
e
e
e
m1 ¼ ꢀ1.6597
m2 ¼ ꢀ1.9677
0.6511 ꢂ 0.0786
Y ¼ 5.0131 e 2.6986(x)
2.2224
0.0061
3b
3c
Control
0.02
0.04
0.06
0.08
0
20
30
50
70
e
e
e
e
e
m1 ¼ ꢀ1.6563
m2 ¼ ꢀ2.08232
0.7403 ꢂ 0.1087
Y ¼ 4.6902 e 4.193(x)
2.3725
0.0118
Control
0.02
0.04
0.06
0.08
0
20
40
50
60
e
e
e
e
e
m1 ¼ ꢀ1.6375
m2 ¼ ꢀ2.1275
0.7628 ꢂ 0.1250
Y ¼ 4.8324 e 0.7971(x)
2.1042
0.0156
The data are the average of three replicates and significant at P < 0.05.

S.B. Kanawade et al. / European Journal of Medicinal Chemistry 46 (2011) 4682e4686
4685
hexane:ethyl acetate, 1:1). The reaction mass was then added over
(250 mL) crushed ice and neutralized with saturated NaHCO3
(30 mL) solution. The crude solid separated was filtered, washed
with water, dried and recrystallized or purified by either appro-
priate solvent or from column chromatography (Hexane:ethyl
acetate 6:4).
(CH),2216fortwo(CN),1703(C]O),1622(ArC]C);1HNMR:(DMSO-
d6), 2.33 (s, 3H, CH3), 8.35e8.38 (m, 3H, Ar-H),12.73 (s,1H, NH); MS:
d
m/z (%) 402 (M ꢀ 2, 100). Anal. Calcd for C16H7F6N3OS (403.30): C,
47.65%; H, 1.75%; N, 10.42%; Found: C, 47.52%; H, 1.64%; N, 10.38%.
5.3.3. N-(3,5-dicyano-4-(2,4-difluorophenyl)thiophen-2-yl)
acetamide (3c)
5.2.1. 5-Amino-3-(4-chlorophenyl)thiophene-2,4-dicarboxamide (2a)
Pale yellow crystals. (Yield 90%, 2.65 g), m.p. 200e202 ꢁC
(EtOH); IR (KBr): V=cmꢀ1 ¼ 3475; 3345 for (NH2), 3327, 3306,
3252, 3169 for two amide (NH2), 1668, 1672 for two amide (C]O),
Colourless amorphous solid. (Yield 85%, 2.57 g), m.p. 310e312 ꢁC
(Hexane:ethyl acetate 2:1); IR (KBr): V=cmꢀ1 ¼ 3267; (NH), 3211
(CH), 2216 for two (CN), 1699 for (C]O), 1618 (Ar C]C); 1H NMR:
(DMSO-d6), d 2.31 (s, 3H, CH3), 7.33e7.75 (m, 3H, Ar-H), 12.67 (s, 1H,
1564, 1479, 1384; 1H NMR (DMSO-d6),
d
4.82 (bs, 2H, amide NH2),
NH); MS: m/z (%) 302 (M ꢀ 1, 70); Anal. Calcd for C14H7F2N3OS
(303.29): C, 55.44%; H, 2.33%; N,13.85%; Found: C, 55.58%; H, 2.26%;
N, 13.71%.
6.84 (bs, 2H, amide NH2), 7.38 (d, J ¼ 8.3 Hz, 2H, Ar-H), 7.56 (d,
J ¼ 8.3 Hz, 2H, Ar-H), 7.69 (bs, 2H, NH2); 13C NMR (DMSO-d6),
d
109.3, 114.7, 129.2, 131.1, 133.6, 134.3, 139.0, 162.9, 163.0, 166.8;
MS: m/z (%) 296 (M þ 1, 50), 298 (M þ 2, 15). Anal. Calcd for
C12H10ClN3O2S (295.74): C, 48.73%; H, 3.41%; N, 14.21%; Found: C,
48.82%; H, 3.62%; N, 14.12%.
5.4. General procedure for the synthesis of oxo-thienopyrimidine-6-
dicarboxamides (4ae4b)
A
mixture of compound 5-amino-3-(4-chlorophenyl)thio-
5.2.2. 5-Amino-3-(3,5-bis(trifluoromethyl)phenyl)thiophene-2,4-
dicarboxamide (2b)
phene-2,4-dicarboxamide 2a (0.01 mol) and various acid chlorides
(0.01 mol) were stirred at 115 ꢁC in glacial acetic acid (4 mL) for
10e12 h (TLC check chloroform:methanol, 8:1). Excess of acetic
acid was distilled off under vacuum and residue obtained was
poured over crushed ice (15 mL), filtered and dried. The solid was
then purified by column chromatography (60e120 mesh) in
chloroform:methanol (8:2) as an eluent.
Colourless amorphous solid. (Yield 92%, 3.65 g); m.p.
190e192 ꢁC (Hexane:ethyl acetate 6:4); IR (KBr): V=cmꢀ1 ¼ 3497;
3364 for (NH2), 3308, 3284 for two amide (NH2), 1656 for amide
(C]O); 1H NMR (CDCl3),
d 4.67 (bs, 2H, amide NH2), 4.98 (bs, 2H,
amide NH2), 6.87e7.95 (m, 3H, Ar-H), 8.03 (bs, 2H, NH2); MS: m/z
(%) 398 (M þ 1, 100); Anal. Calcd for C14H9F6N3O2S (397.30): C,
42.32%; H, 2.28%; N, 10.58%; Found: C, 42.20%; H, 2.34%; N, 10.41%.
5.4.1. 2-(Chloromethyl)-5-(4-chlorophenyl)-3,4-dihydro-4-oxothieno
[2,3-d]pyrimidine-6-carboxamide (4a)
5.2.3. 5-Amino-3-(2,4-difluorophenyl)thiophene-2,4-dicarboxamide
(2c)
Colourless amorphous solid. (Yield 70%, 2.47 g), m.p.
267e269 ꢁC (AcOH); IR (KBr): V=cmꢀ1 ¼ 3489; 3468 for amide
Green amorphous solid. (Yield 94%, 2.80 g); m.p. 264e265 ꢁC
(Hexane:ethyl acetate 6:4); IR (KBr): V=cmꢀ1 ¼ 3484; 3357 for
(NH2), 3312, 3289 for two amide (NH2), 1662 for amide (C]O); 1H
(NH2), 1665 (C]O), 1630 (Ar C]C); 1H NMR: (DMSO-d6),
d 4.54 (s,
2H, CH2), 6.21 (bs, 2H, amide NH2), 7.36 (d, J ¼ 8.3 Hz, 2H, Ar-H), 7.51
(d, J ¼ 8.3 Hz, 2H, Ar-H), 12.04 (bs, 1H, NH); 13C NMR: (DMSO-d6),
NMR (DMSO-d6),
d
6.15 (bs, 2H, amide NH2), 6.38 (bs, 2H, amide
d 166.0, 164.9, 163.4, 143.2, 136.8, 133.7, 133.1, 131.6, 128.9, 125.6,
NH2), 7.22e7.52 (m, 3H, Ar-H), 12.06 (bs, 2H, NH2); MS: m/z (%) 297
(Mþ, 50). Anal. Calcd for C14H9F6N3O2S (297.28): C, 48.48%; H,
3.05%; N, 14.13%; Found: C, 48.31%; H, 3.16; N%, 14.24%.
120.2, 42.4; MS: m/z (%) 376 (MþNa
, 20); Anal. Calcd for
C14H9Cl2N3O2S (353.00): C, 47.47%; H, 2.56%; N, 11.86%; Found: C,
47.31%; H, 2.42%; N, 11.76%.
5.3. General procedure for the synthesis of 4-aryl-dicyanothio
pheneacetamide (3aec)
5.4.2. 2-Methyl-5-(4-chlorophenyl)-3,4-dihydro-4-oxothieno[2,3-
d]pyrimidine-6-carboxamide (4b)
Off white amorphous solid. (Yield 65%, 2.07 g), m.p. 277e280 ꢁC
(EtOH: DMF); IR (KBr): V=cmꢀ1 ¼ 3490; 3470 for amide (NH2),
1668 for amide (C]O), 1629 for (Ar C]C) cmꢀ1; 1H NMR: (DMSO-
To compound 1aec (0.01 mol) and acetic anhydride (5 mL),
a drop of conc. H2SO4 was added and then stirred at room
temperature for 1e1.5 h (TLC check hexane:ethyl acetate, 2:1).
Resulting reaction mixture was poured over crushed ice and stirred
overnight. The separated solid was filtered, washed with cold
water, dried in vacuum and purified by column chromatography
(Hexane:ethyl acetate 2:1).
d6),
d 2.14 (s, 3H, CH3), 6.32e6.54 (bs, 2H, amide NH2), 7.34 (d,
J ¼ 8.4 Hz, 2H, Ar-H), 7.49 (d, J ¼ 8.4 Hz, 2H, Ar-H), 11.29 (bs, 1H,
NH); MS: m/z (%) 318 (M ꢀ 1, 25), 320 (M þ 1, 8.33); Anal. Calcd for
C14H10ClN3O2S (319.77): C, 52.59%; H, 3.15%; N, 13.14%; Found: C,
52.48%; H, 3.21%; N, 13.21%.
5.3.1. N-(3,5-dicyano-4-(4-chlorophenyl)thiophen-2-yl)acetamide (3a)
Pale yellow amorphous solid. (Yield 90%, 2.72 g), m.p.
298e300 ꢁC (Hexane:ethyl acetate 8:2); IR (KBr): V=cmꢀ1 ¼ 3267;
(NH), 2216 for two (CN), 1703 for (C]O), 1625 (Ar C]C); 1H NMR:
5.5. Molluscicidal activity tests
The molluscicidal ativity tests were carried out by determina-
tion of half lethal concentration LC50 of each compound under
investigation. I. exustus snails were collected from Godavari river in
Nashik, District Nashik (MS, India) and acclimatized to a laboratory
conditions for 3 weeks. Then, snails were examined to ensure that
they were free from parasitic infection. Molluscicidal effect of the
new compounds were evaluated by inclusion of an inert solvent to
help the dissolution of samples. The compounds 1aec, 2aec, 3aec
and 4aeb were separately dissolved in a small amount of DMF
(w0.5 mL) and added to dechlorinated water to obtain a series of
concentrations ranging from 0.02 to 40 ppm of each compound
under investigation. Then, 10 snails having the same size were
selected and used in each experiment and maintained in the tested
(DMSO-d6),
d
2.31 (s, 3H, CH3), 7.64 (d, J ¼ 8.7 Hz, 2H, Ar-H), 7.73 (d,
J ¼ 8.7 Hz, 2H, Ar-H), 12.63 (s, 1H, NH); 13C NMR (DMSO-d6),
d 22.3,
92.7, 96.4, 112.9, 113.7, 129.0, 129.4, 130.3, 135.0, 147.8, 153.1, 170.2;
MS: m/z (%) 301 (Mþ, 20), 303 (M þ 2, 6.66); Anal. Calcd for
C14H8ClN3OS (301.75): C, 55.72%; H, 2.67%; N, 13.93%; Found: C,
55.66%; H, 2.52%; N, 13.75%.
5.3.2. N-(3,5-dicyano-4-(3,5-bis(trifluoromethyl)phenyl)thiophen-
2-yl)acetamide (3b)
White amorphous solid. (Yield 88%, 3.55 g); m.p. 272e274 ꢁC
(Hexane:ethyl acetate 2:1); IR (KBr): V=cmꢀ1 ¼ 3261; (NH), 3227

4686
S.B. Kanawade et al. / European Journal of Medicinal Chemistry 46 (2011) 4682e4686
[2] L. Liu, M. MH Mondal, M.A. Idris, H.S. Lokman, P.R.V.J. Rajapakse,
solution under laboratory condition at room temperature for 24 h.
Each experiment was repeated three times and the mean number
of killed snails counted by for each concentration as shown in
Tables 1 and 2. Snails were considered dead if they remained
motionless. A control condition was taken by placing 10 snails in
dechlorinated water containing DMF (w0.5 mL) which showed no
harmful effect. These bioassays are in accordance with the WHO
guidelines and Finney’s method [23,24]. Compounds 1aec and
4aec did not show any activity at all against these snails.
F. Satrija, J.L. Diaz, E.S. Upatham, S.W. Attwood, Parasit. Vectors
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Acknowledgements
Author thanks to CSIR, New Delhi for financial assistance, Dept.
of Chemistry; University of Pune for spectroscopic and analytical
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Appendix. Supplementary data
Supplementary data related to this article can be found online at
doi:10.1016/j.ejmech.2011.06.001.
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