Synthesis and anti-inflammatory evaluation of methylene bridged benzofuranyl imidazo[2,1-b][1,3,4]thiadiazoles

Article abstract of DOI:10.1016/j.ejmech.2007.06.023

A series of 6-substituted and 5,6-disubstituted 2-(6-methyl-benzofuran-3-ylmethyl)-imidazo[2,1-b][1,3,4]thiadiazoles have been synthesized. The new compounds have been tested for their in vivo analgesic, anti-inflammatory activities. Qualitative SAR studies indicate that the chloro substitution in the imidazole ring and introduction of formyl group at C-5 position of the imidazole ring increased the anti-inflammatory and analgesic activity. All the newly synthesized compounds have been characterized by spectral data and ORTEP diagram of one of the intermediates 6-(4-chlorophenyl)-2-(6-methyl-benzofuran-3-ylmethyl)-5-morpholin-4-ylmethyl imidazo[2,1-b][1,3,4]thiadiazole is reported herein.

Full text of DOI:10.1016/j.ejmech.2007.06.023

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European Journal of Medicinal Chemistry 43 (2008) 1721e1729
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Original article
Synthesis and anti-inflammatory evaluation of methylene bridged
benzofuranyl imidazo[2,1-b][1,3,4]thiadiazoles
b
b
b
V.B. Jadhav a, M.V. Kulkarni a, , V.P. Rasal , S.S. Biradar , M.D. Vinay
*
a Department of Chemistry, Karnatak University, Dharwad e 580 003, Karnataka, India
b Department of Pharmacology, K.L.E. Society’s College of Pharmacy, Belguam e 590 001, Karnataka, India
Received 10 April 2007 ; received in revised form 22 June 2007; accepted 28 June 2007
Available online 12 July 2007
Abstract
A series of 6-substituted and 5,6-disubstituted 2-(6-methyl-benzofuran-3-ylmethyl)-imidazo[2,1-b][1,3,4]thiadiazoles have been synthesized.
The new compounds have been tested for their in vivo analgesic, anti-inflammatory activities. Qualitative SAR studies indicate that the chloro
substitution in the imidazole ring and introduction of formyl group at C-5 position of the imidazole ring increased the anti-inflammatory and
analgesic activity. All the newly synthesized compounds have been characterized by spectral data and ORTEP diagram of one of the interme-
diates 6-(4-chlorophenyl)-2-(6-methyl-benzofuran-3-ylmethyl)-5-morpholin-4-ylmethyl imidazo[2,1-b][1,3,4]thiadiazole is reported herein.
Ó 2007 Elsevier Masson SAS. All rights reserved.
Keywords: Imidazo[2,1-b][1,3,4]thiadiazoles; Anti-inflammatory; Analgesic activity
1. Introduction
antagonist of a-2-adrenoreceptor [13]. Recently we have re-
ported many benzofuran derivatives as good anti-inflammatory
agents [14,15].
It was envisaged that these two active pharmacophores, if
linked together would generate novel molecular templates
which are likely to exhibit interesting biological properties
in animal models. The above cited applications prompted us
to synthesize a series of new compounds reported in this paper.
Imidazo[2,1-b]-1,3,4-thiadiazole derivatives have been of
interest to the medicinal chemists for many years because of
their anticancer [1], antitubercular [2], antibacterial [3], anti-
fungal [4], anticonvulsant, analgesic [5], and antisecretory
[6] activities. Moreover, much interest has also been focused
on the anti-inflammatory [7], cardiotonic [8], diuretic [9],
and herbicidal [10] activities displayed by compounds incor-
porating this heterocyclic system. Because the imidazo[2,1-b]-
1,3,4-thiadiazole system is similar in part to Levamisole,
a well known immunomodulator [11] the possibility of reduc-
ing the harmful effects of the cytotoxic agents on the immune
system also appears to be very attractive. Biheterocycles con-
taining benzofuran with pyridine, thiadiazoles and chromone
[12] rings have been found to exhibit antimicrobial, psychotro-
pic and anti-inflammatory activities. For example, Efaroxan
2. Chemistry
Benzofuran-3-acetic acid 1 required for the present work
has been synthesized by the alkali hydrolysis of 7-methyl-
4-bromomethyl coumarins [16], which upon reaction with
thiosemicarbazide in presence of POCl3 yielded 5-(6-methyl-
benzofuran-3-ylmethyl)-[1,3,4]thiadiazol-2-yl-amine 3. The
imidazo[2,1-b][1,3,4]thiadiazole 5 was obtained by the con-
densation of 3 with a-bromoarylketones 4 under reflux in
dry ethanol (Scheme 1). Mannich reaction of 5 with cyclic sec-
ondary amine morpholine and formaldehyde in presence of
catalytic amount of acetic acid yielded derivative 6. Vilsmeiere
Haack reaction of imidazothiadiazole 5 in DMF and POCl3
(2-imidazolinyl-2,3-dihydrobenzofuran) is
a well known
* Corresponding author. Tel.: þ91 836 2770476; fax: þ91 836 2747884.
E-mail address: drmvk274@yahoo.co.in (M.V. Kulkarni).
0223-5234/$ - see front matter Ó 2007 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2007.06.023

1722
V.B. Jadhav et al. / European Journal of Medicinal Chemistry 43 (2008) 1721e1729
NH2
O
OH
S
N
H
N
i
N
NH2
H2N
O
H3C
O
S
H3C
1
2
3
O
Br
ii
R
4
N
N
S
S
R
R
N
N
N
N
N
O
iii
O
H3C
O
H3C
6a-c
5a-c
R = Br, Cl, NO2 : a = Cl, b = Br, c = NO2
Scheme 1. Synthesis of benzofuranyl thiadiazoles. Reagents and conditions: (i) POCl3, reflux, 30 min, KOH.; (ii) Dry EtOH, reflux, 24 h, Na2CO3; (iii) Morpho-
line, HCHO, AcOH, MeOH, reflux, 8 h.
furnished 5-formyl derivative 7 (Scheme 2). The aldehyde
functional group in compound 7 has been utilized to synthe-
size corresponding alcohols, oxime and nitrile derivatives.
The reduction of aldehyde 7 by NaBH4 in methanol at room
temperature yielded the respective carbinols 8 in good yields.
hydrochloride in pyridine gave corresponding oxime 9, which
on dehydration with acetic anhydride produced the nitrile 10
in moderate yields. Structures of all the newly synthesized
compounds are well supported by spectral data such as IR,
NMR, Mass and Elemental analysis. Compound 6a has been
confirmed by X-ray diffraction studies.
The condensation of aldehyde
6
with hydroxylamine
N
S
N
R
S
R
N
N
N
CN
N
O
H3C
O
H3C
10a-c
5a-c
iv
i
N
N
S
R
S
R
N
N
N
N
CHO
N
iii
OH
O
H3C
O
H3C
9a- c
7a-c
ii
N
S
R
N
N
OH
O
H3C
8a-c
R = Br, Cl, NO2 : a = Cl, b = Br, c = NO2
Scheme 2. Reagents and conditions: (i) DMF/POCl3, Na2CO3; (ii) NaBH4, MeOH, R.T; (iii) NH2OH, pyridine, reflux; (iv) Ac2O, reflux, 1 h.

V.B. Jadhav et al. / European Journal of Medicinal Chemistry 43 (2008) 1721e1729
1723
2.1. Spectral characterization
a sharp band around 2200 cmꢀ1 in the IR spectrum assigned
1
for nCN and there was no band due to nOeH. The H NMR
The formation of 2-aminothiadiazole (3) was supported by
the presence of nNeH band in the IR spectra and absence of
carbonyl stretching band of the carboxyl acid function. The
formation of imidazothiadiazole (5aec) was indicated by the
absence of nNeH band in the IR spectra and appearance of im-
idazole proton (C5eH) around d 7.90 in 1H NMR spectra. For-
mation of the Mannich bases (6aec) was corroborated by the
absence of imidazole proton and the appearance of a singlet
of the compound was the useful probe to check the formation
of the product as it reveals the absence of both the eOH and
azomethine protons.
3. Biological activity
3.1. Acute toxicity studies
1
around d 4.00 ppm in the H NMR spectra. Other aliphatic
For testing the acute toxicity potential of the test com-
pounds, albino rats of either sex weighing 25e30 g were se-
lected, separated into groups each containing six rats. The
dosage was varied from 100 up to 3000 mg kgꢀ1 body weight.
The rats were continuously observed for 8 h for any signs
of acute toxicity such as increasededecreased motor activity,
ataxia, tremors, convulsions, sedation, lacrimation, etc. After
24 h the rats were sacrificed, stomach, intestine, and liver
were inspected under the magnifying lenses for any ulcer-
haemorrhagic spots.
protons of the amine substituents resonated in the expected re-
gion as two triplets. Formation of these Mannich bases was
further supported by mass spectra and the structure of 6a
has been subsequently confirmed by the X-ray crystal diffrac-
tion studies (Fig. 1, CCDC Deposit no. 637482). IR spectra of
aldehyde 7 displayed a sharp band for carbonyl stretching fre-
quency (nc]o) around 1650 cmꢀ1 and signal due to C5eH of
imidazole was absent and a new signal for aldehydic proton
was observed around d 10 ppm in the 1H NMR spectrum,
thus substantiating the formation of imidazo[2,1-b][1,3,4]thia-
diazoles-5-carbaldehydes (7aec). The reduction products 8aec
3.2. Anti-inflammatory activity
showed the absence of carbonyl stretching frequency (nc]o
)
and the presence of broad band in the region 3150 cmꢀ1 for
nOeH in IR spectra. The 1H NMR showed the absence of signal
due to aldehydic proton, and the methylene protons resonated
as singlet at around d 5 ppm and OH proton was observed as
broad singlet. This data confirms the conversion of carbalde-
hyde 7 to imidazo[2,1-b][1,3,4]thiadizole-5-carbinols (8aec).
The absence of nC]O band and the presence of nOeH band
in the IR spectrum of the product supported the formation of
Fourteen of all the newly synthesized compounds were
screened for their in vivo inhibition of formalin induced paw
oedema in rats, which is one of the most acceptable test
procedures to evaluate anti-inflammatory agents [17]. Anti-
inflammatory activity exhibited by the compounds may be at-
tributed to the inhibition of cyclo oxygenase enzyme, which
plays a vital role in inflammation process [18]. The standard
used for the present anti-inflammatory activity testing is Ibupro-
fen. The test compounds were found to be significantly active.
1
oxime (9aec). H NMR spectra also confirmed the formation
of aldoximes where the signal for aldehydic proton was ab-
sent, the azomethine and the eOH proton (D2O exchangeable)
resonated around d 8.3 and 11.6 ppm, respectively. These
compounds on treatment with acetic anhydride readily con-
verted in to nitriles (10aec) and these are characterized by
3.3. Analgesic activity
Analgesic activity was measured by rat tail-flick method
used by D’Amour and Smith [19]. The reaction time was
Fig. 1. ORTEP diagram with 50% thermal ellipsoidal probability of compound 6a.

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V.B. Jadhav et al. / European Journal of Medicinal Chemistry 43 (2008) 1721e1729
Table 1a
Comparison of oedema volume at different time intervals of compounds 5ae10a
Compound
Oedema volume at different time intervals** ꢁ S.E
0 h
0.5 h
1 h
2 h
3 h
2.00 ꢁ 0.051
4 h
5 h
Control
0.5333 ꢁ 0.061
0.583 ꢁ 0.006
0.916 ꢁ 0.060
1.117 ꢁ 0.047
1.083 ꢁ 0.060
1.083 ꢁ 0.047
1.033 ꢁ 0.088
1.017 ꢁ 0.030
1.083 ꢁ 0.070
1.083 ꢁ 0.060
0.916 ꢁ 0.007
1.117 ꢁ 0.060
0.983 ꢁ 0.060
1.000 ꢁ 0.051
1.383 ꢁ 0.060
0.800 ꢁ 0.044
1.267 ꢁ 0.049
1.300 ꢁ 0.044
1.383 ꢁ 0.030
1.317 ꢁ 0.047
1.267 ꢁ 0.080
1.333 ꢁ 0.042
1.333 ꢁ 0.066
1.367 ꢁ 0.049
1.250 ꢁ 0.067
1.350 ꢁ 0.042
1.300 ꢁ 0.057
1.317 ꢁ 0.060
1.617 ꢁ 0.047
0.933 ꢁ 0.071
1.400 ꢁ 0.057*
1.450 ꢁ 0.034
1.400 ꢁ 0.025*
1.367 ꢁ 0.033**
1.417 ꢁ 0.079*
1.533 ꢁ 0.033
1.433 ꢁ 0.033
1.417 ꢁ 0.030*
1.383 ꢁ 0.040**
1.500 ꢁ 0.036
1.533 ꢁ 0.033
1.400 ꢁ 0.063*
1.783 ꢁ 0.054
2.117 ꢁ 0.070
2.150 ꢁ 0.056
Standard
5a
5b
1.017 ꢁ 0.047**
1.033 ꢁ 0.033**
1.567 ꢁ 0.055*
1.350 ꢁ 0.056**
1.267 ꢁ 0.042**
1.217 ꢁ 0.030**
1.350 ꢁ 0.022**
1.350 ꢁ 0.034**
1.583 ꢁ 0.054*
1.267 ꢁ 0.049**
1.550 ꢁ 0.022**
1.583 ꢁ 0.054*
1.283 ꢁ 0.047**
0.800 ꢁ 0.036**
0.966 ꢁ 0.066**
1.783 ꢁ 0.054*
1.183 ꢁ 0.030**
1.133 ꢁ 0.042**
1.133 ꢁ 0.033**
1.167 ꢁ 0.033**
1.150 ꢁ 0.042**
1.783 ꢁ 0.060*
1.083 ꢁ 0.030**
1.267 ꢁ 0.042**
1.800 ꢁ 0.036*
1.133 ꢁ 0.049**
0.800 ꢁ 0.036**
0.933 ꢁ 0.061**
1.883 ꢁ 0.074*
1.150 ꢁ 0.056**
1.100 ꢁ 0.025**
1.033 ꢁ 0.042**
1.100 ꢁ 0.036**
1.117 ꢁ 0.030**
1.900 ꢁ 0.057*
0.966 ꢁ 0.021**
1.167 ꢁ 0.049**
1.833 ꢁ 0.060*
1.033 ꢁ 0.042**
0.583 ꢁ 0.060**
0.900 ꢁ 0.051**
1.667 ꢁ 0.143**
1.080 ꢁ 0.030**
1.067 ꢁ 0.033**
1.017 ꢁ 0.074**
1.050 ꢁ 0.034**
1.100 ꢁ 0.057**
1.883 ꢁ 0.060*
0.883 ꢁ 0.047**
1.133 ꢁ 0.049**
1.483 ꢁ 0.065**
1.000 ꢁ 0.025**
5c
6a
6b
6c
7a
7b
8a
8b
9a
10a
Model: acute inflammation; method: carragennan induced oedema; test animal: albino rats; number of animals per group: 6; route of administration: oral; standard:
Ibuprofen (100 mg kgꢀ1); test compounds: 100 mg kgꢀ1. **P < 0.01, *P < 0.05. Statistical analysis: the statistical analysis was performed by one-way ANOVA
followed by Dunnet’s ‘t’ test.
measured at the end of 60, 90, 120 and 300 min after the ad-
ministration of the compound and the standard employed was
Nimesulide.
inflammation even at the end of 5 h. However, the correspond-
ing nitrile 10a was significantly active (Tables 1a and 1b).
These results obtained in these experiments are well sup-
ported by the analgesic activity data, which was evaluated
by the reaction time (in seconds) at various time intervals.
4. Results and discussion
4.3. Analgesic activity
4.1. Acute toxicity studies
The maximum reaction time observed in the case of the
standard was 9.683 s and many compounds synthesized during
the present investigation showed reaction times in the similar
range.
Amongst the substituted imidazothiadiazoles the chloro and
nitro compounds 5a and 5c showed reaction time of 9.633 and
9.900 s. The bromo compound 5b also did not exhibit any sig-
nificant activity.
All the compounds have shown good safety profile till the
highest dose. No adverse effect or mortality was detected in
albino rats up to 3 g kgꢀ1, p.o. of SPA during the 24 h obser-
vation period.
There was no sedation, convulsions and tremors upon in-
spection, no ulceration and no haemorrhagic spots were ob-
served. Postmortem examination of the stomach, and
intestine did not reveal any ulcer-haemorrhagic spots.
Amongst the substitution at C-5 the morpholinomethyl de-
rivative 6c and the C-5 formyl derivative were quite promising.
The nitrile 10a showed considerable protection.
4.2. Anti-inflammatory activity
Table 1b
Anti-inflammatory activities of compounds 5ae10a (% inhibition)
4.2.1. Carragennan induced rat paw oedema method
The present study reports the anti-inflammatory activity of
benzofuranyl imidazo[2,1-b][1,3,4]thiadiazoles derivatives
(5e10). When compared with the control all the compounds
showed reduction in oedema volume. Compounds 5 with no
substituents at C-5 in the imidazole ring showed similar range
of inhibition at the end of the 5 h except for the bromo
substituted compound 5b. The nitro derivative 5c showed a de-
layed onset of action but the inhibition was pronounced at the
end of third hour.
Amongst the various substituents at C-5 the best effects
were observed with formyl and hydroxymethyl groups 7 and
8. In these compounds also the bromo substituents has reduced
the activity to the considerable extent (12.41%) as observed in
7b. The conversion of the aldehyde at C-5 into oxime lead to
the compound 9, which also did not significantly inhibit the
Compound % Inhibition of inflammation at various time intervals
0.5 h
1 h
2 h
3 h
4 h
5 h
0.0
Control
0.0
42.15
8.38
6.00
0.00
4.77
8.38
3.6
0.0
0.0
0.0
0.0
Standard
5a
5b
42.30
13.44
10.32
13.41
15.46
12.36
5.19
42.90
42.06
12.00
24.28
28.93
31.74
24.28
24.28
11.21
28.93
13.06
11.21
28.04
60.00
51.66
10.85
40.85
43.35
43.35
41.65
42.50
10.85
45.85
36.65
10.00
43.35
66.14
55.91
11.05
45.67
48.03
51.20
48.03
47.23
10.25
54.33
44.87
11.05
51.20
72.86
58.13
22.46
49.76
50.37
52.69
51.16
48.83
12.41
58.93
47.30
31.00
53.48
5c
6a
6b
6c
7a
7b
3.6
11.37
12.36
14.47
7.20
1.15
9.61
2.38
6.00
4.77
8a
8b
9a
10a
5.19
13.41

V.B. Jadhav et al. / European Journal of Medicinal Chemistry 43 (2008) 1721e1729
1725
It can be seen that there is a good correlation between the
anti-inflammatory and the analgesic activity of the compounds
(Table 2).
5. Experimental
5.1. Chemistry
The melting points were determined by open capillaries on
a Buchi-apparatus and are uncorrected. The IR spectra were re-
corded on a Nicolet-Impact-410 FT-IR spectrometer, using
KBR pellets. 1H NMR and 13C NMR spectra were recorded, re-
spectively, on a Bruker 300 MHz and 75 MHz spectrometer, in
CDCl3 and DMSO-d6 using TMS, as an internal standardand the
values are expressed in d ppm.The mass spectra were recorded
using Agilent-single quartz LCeMS. The elemental analysis
was carried out using Heraus CHN rapid analyzer. All the chem-
icals purchased were of analytical reagent grade, and were used
without further purification unless otherwise stated.
5.1.1. Synthesis of 5-(6-methyl-benzofuran-3-ylmethyl)-
[1,3,4]thiadiazol-2-yl-amine (3)
6-Methyl-benzofuran-3-acetic acid (19.2 g, 0.1 mol) and
thiosemicarbazide (9.1 g, 0.1 mol) in phosphorous oxychloride
(30 ml) were refluxed gently for 30 min. The solution was
cooled; water (90 ml) was added carefully. The separated solid
was filtered and suspended in water, and basified with aqueous
potassium hydroxide. The solid was filtered, washed with wa-
ter, dried and crystallized from mixture of DMF and ethanol
(9:1) to obtain a colorless solid in 65% yield. IR (KBr)
cmꢀ1 3281, 3102, 2960, 1635, 1521; 1H NMR (CDCl3,
300 MHz, TMS): d 2.39 (s, 3H, C6eCH3 of benzofuran),
4.21 (s, 2H, C3eCH2 of benzofuran), 7.00 (br s, 2H, NH2,
D2O exchangeable), 7.06 (d, 1H, J ¼ 5.9 Hz, C5eH of benzo-
furan), 7.36 (s, 1H, C7eH of benzofuran), 7.40 (d, 1H,
J ¼ 5.9 Hz, C4eH of benzofuran), 7.84 (s, 1H, C2eH of ben-
zofuran); LCeMS 246 [M þ H]. Anal. Calcd for
C12H11N3OS: C, 58.76; H, 4.52; N, 17.13. Found: C, 58.84;
H, 4.58; N, 17.16. M.p. 224e226 ꢂC (aq. DMF).
5.1.2. Synthesis of 2-(6-methyl-benzofuran-3-ylmethyl)-6-
phenyl-imidazo[2,1-b][1,3,4]thiadiazole (5): general
procedure
A mixture of equimolar quantities of 5-(6-methyl-benzofu-
ran-3-ylmethyl)-[1,3,4]thiadiazol-2-ylamine (0.01 mol) and ap-
propriately substituted bromoacetyl compound (0.01 mol) was
refluxed in dry ethanol for 24 h. The excess of solvent distilled
off and solid hydrobromide that separated was collected by fil-
tration, suspended in water and neutralized by aqueous sodium
carbonate solution to get free base (2). It was filtered, washed
with water, dried and recrystallized from suitable solvent.
5.1.2.1. 6-(4-Chlorophenyl)-2-(6-methyl-benzofuran-3-
ylmethyl)-imidazo[2,1-b][1,3,4]thiadiazole
(5a). Colorless
solid (chloroform); yield 60%; m.p. 162e164 ꢂC; IR (KBr)
cmꢀ1 3112, 3022, 2915, 1631, 1527, 1471; 1H NMR
(CDCl3, 300 MHz, TMS): d 2.44 (s, 3H, C6eCH3 of

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V.B. Jadhav et al. / European Journal of Medicinal Chemistry 43 (2008) 1721e1729
benzofuran), 4.38 (s, 2H, C3eCH2 of benzofuran), 7.16 (d,
1H, J ¼ 8.1 Hz, C5eH of benzofuran), 7.31 (s, 1H, C7eH
of benzofuran), 7.40 (d, 1H, J ¼ 8.1 Hz, C4eH of benzofu-
ran), 7.37 (d, 2H, J ¼ 7.8 Hz, C2, C6eH phenyl), 7.66 (s,
1H, C2eH of benzofuran), 7.65 (d, 2H, J ¼ 7.8 Hz, C3,
C5eH phenyl), 7.99 (s, 1H, C5eH imidazole); 13C NMR
(CDCl3, 75 MHz, TMS): d 22.1, 27.3, 109.9, 112.4, 114.5,
120.0, 121.7, 124.9, 125.0, 130.0, 130.01, 133.2, 135.9,
136.2, 136.2, 142.8, 145.6, 146.2, 156.5, 163.9; LCeMS
380 [M þ H]. Anal. Calcd for C20H14ClN3OS (%): C, 63.24;
H, 3.71; N, 11.06. Found: C, 63.29; H, 3.75; N, 11.10.
sodium sulfate. The solution was evaporated to dryness in vac-
uum and the residue was crystallized from appropriate solvent.
5.1.3.1. 6-(4-Chlorophenyl)-2-(6-methyl-benzofuran-3-ylmethyl)-
5-morpholin-4-ylmethyl-imidazo[2,1-b][1,3,4]thiadiazole (6a).
Colorless solid (chloroform þ petroleum ether); yield 65%;
m.p. 158e161 ꢂC; IR (KBr) cmꢀ1 3080, 2965, 1626; 1H
NMR (CDCl3, 300 MHz, TMS): d 2.46 (s, 3H, C6eCH3 of ben-
zofuran), 2.56 (t, 4H, J ¼ 4.0 Hz, C3, C5eH of morpholine),
3.71 (t, 4H, J ¼ 4.0 Hz, C2, C6eH of morpholine), 3.89 (s,
2H, CH2), 4.39 (s, 2H, C3eCH2 of benzofuran), 7.06 (d, 1H,
J ¼ 5.9 Hz, C5eH of benzofuran), 7.32 (s, 1H, C7eH of benzo-
furan), 7.38e7.41 (m, 3H, C4eH of benzofuran, C2, C6eH of
phenyl), 7.61 (s, 1H, C2eH of benzofuran), 7.89 (d, 2H,
J ¼ 6.0 Hz, C3, C5eH of phenyl); LCeMS 480 [M þ H].
Anal. Calcd for C25H23ClN4O2S (%): C, 62.69; H, 4.84; N,
11.70. Found: C, 62.78; H, 4.97; N, 11.82.
5.1.2.2. 6-(4-Bromophenyl)-2-(6-methyl-benzofuran-3-ylmethyl)-
imidazo[2,1-b][1,3,4]thiadiazole (5b). Colorless solid (ethanol);
yield 50%; m.p. 178e180 ꢂC; IR (KBr) cmꢀ1 3116, 2914, 1621,
1473, 1095; 1H NMR (CDCl3, 300 MHz, TMS): d 2.48 (s, 3H,
C6eCH3 of benzofuran), 4.37 (s, 2H, C3eCH2 of benzofuran),
7.09 (d, 1H, J ¼ 7.8 H, C5eH of benzofuran), 7.34 (s, 1H, C7e
H of benzofuran), 7.40 (d, 1H, J ¼ 7.80 Hz, C4eH of benzofu-
ran), 7.52 (d, 2H, J ¼ 8.1 Hz, C2, C6eH phenyl), 7.62 (s, 1H,
C2eH of benzofuran), 7.67 (d, 2H, J ¼ 8.1 Hz, C3, C5eH phe-
nyl), 7.97 (s, 1H, C5eH imidazole); 13C NMR (CDCl3,
75 MHz, TMS): d 22.0, 27.3, 109.7, 112.4, 114.7, 119.2,
121.7, 124.6, 124.9, 127.0, 127.01, 132.2, 132.2, 133.2, 135.9,
142.8, 145.4, 146.2, 156.3, 163.4; LCeMS 425 [M þ H].
Anal. Calcd for C20H14BrN3OS (%): C, 56.61; H, 3.33; N,
9.90. Found: C, 56.65; H, 3.30; N, 9.94.
5.1.3.2. 6-(4-Bromophenyl)-2-(6-methyl-benzofuran-3-ylmethyl)-
5-morpholin-4-ylmethyl-imidazo[2,1-b][1,3,4]thiadiazole (6b).
Colorless solid (chloroform þ petroleum ether); yield 65%;
m.p. 128e131 ꢂC; IR (KBr) cmꢀ1 3091, 2930, 1646, 1455;
1H NMR (CDCl3, 300 MHz, TMS): d 2.48 (s, 3H, C6eCH3
of benzofuran), 2.57 (t, 4H, J ¼ 4.2 Hz, C3, C5eH of morpho-
line), 3.70 (t, 4H, J ¼ 4.2 Hz, C2, C6eH of morpholine), 3.89 (s,
2H, CH2), 4.40 (s, 2H, C3eCH2 of benzofuran), 7.09 (d, 1H,
J ¼ 6.0 Hz, C5eH of benzofuran), 7.33 (s, 1H, C7eH of benzo-
furan), 7.40 (d, 1H, J ¼ 6.0 Hz, C4eH of benzofuran), 7.57 (d,
2H, J ¼ 6.3 Hz, C2, C6eH of phenyl), 7.63 (s, 1H, C2eH of
benzofuran), 7.84 (d, 2H, J ¼ 6.2 Hz, C3, C5eH of phenyl).
Anal. Calcd for C25H23BrN4O2S (%): C, 57.36; H, 4.43; N,
10.70. Found: C, 57.42; H, 4.50; N, 10.78.
5.1.2.3. 6-(4-Nitrophenyl)-2-(6-methyl-benzofuran-3-ylmethyl)-
imidazo[2,1-b][1,3,4]thiadiazole (5c). Colorless soliꢀd1 (chlo-
roform); yield 60%; m.p. 162e164 ꢂC; IR (KBr) cm 2921,
1602, 1523, 1307; 1H NMR (CDCl3, 300 MHz, TMS):
d 2.49 (s, 3H, C6eCH3 of benzofuran), 4.41 (s, 2H, C3e
CH2 of benzofuran), 7.10 (d, 1H, J ¼ 7.80 Hz, C5eH of ben-
zofuran), 7.35 (s, 1H, C7eH of benzofuran), 7.41 (d, 1H,
J ¼ 7.80 Hz, C4eH of benzofuran), 7.95 (d, 2H,
J ¼ 8.70 Hz, C2, C6eH phenyl), 7.64 (s, 1H, C2eH of benzo-
furan), 8.26 (d, 2H, J ¼ 7.80 Hz, C3, C5eH phenyl), 8.13 (s,
1H, C5eH imidazole); 13C NMR (CDCl3, 75 MHz, TMS):
d 22.1, 27.3, 109.9, 112.4, 114.5, 120.0, 121.7, 124.9, 125.0,
130.0, 130.0, 133.2, 135.9, 136.2, 136.2, 142.8, 145.6,
146.2, 156.5, 163.9; LCeMS 391 [M þ H]. Anal. Calcd for
C20H14ClN3OS (%): C, 63.24; H, 3.71; N, 11.06. Found: C,
63.29; H, 3.75; N, 11.10.
5.1.3.3. 6-(4-Nitrophenyl)-2-(6-methyl-benzofuran-3-ylmethyl)-
5-morpholin-4-ylmethyl-imidazo[2,1-b][1,3,4]thiadiazole (6c).
Colorless solid (chloroform þ hexane); yield 59%; m.p.
104e106 ꢂC; IR (KBr) cmꢀ1 2925, 1608, 1527, 1307; 1H
NMR (CDCl3, 300 MHz, TMS): d 2.48 (s, 3H, C6eCH3 of
benzofuran), 2.60 (t, 4H, J ¼ 4.5 Hz, C3, C5eH of morpho-
line), 3.75 (t, 4H, J ¼ 4.4 Hz, C2, C6eH of morpholine),
5.11 (s, 2H, CH2), 4.42 (s, 2H, C3eCH2 of benzofuran),
7.12 (d, 1H, J ¼ 6.2 Hz, C5eH of benzofuran), 7.38 (s, 1H,
C7eH of benzofuran), 7.41 (d, 1H, J ¼ 6.2 Hz, C4eH of ben-
zofuran), 7.98 (d, 2H, J ¼ 7.0 Hz, C2, C6eH phenyl) 7.62 (s,
1H, C2eH of benzofuran), 8.23 (d, 2H, J ¼ 7.0 Hz, C3, C5eH
of phenyl). Anal. Calcd for C25H23N5O4S (%): C, 61.34; H,
4.74; N, 14.31. Found: C, 61.43; H, 4.83; N, 14.40.
5.1.3. Synthesis of [2-(6-methyl-benzofuran-3-ylmethyl)-
5-morpholine-4-ylmethyl-6-phenyl-imidazo[2,1-b]
[1,3,4]thiadiazole (6): general procedure
5.1.4. Synthesis of 2-(6-methyl-benzofuran-3-ylmethyl)-
6-phenyl-imidazo[2,1-b][1,3,4]thiadiazole-5-carbaldehyde
(7). VilsmeireHaack reaction: general procedure
VilsmeireHaack reagent was prepared by adding phosphoryl-
chloride (3 ml) in dimethyl formamide (20 ml) at 0 ꢂC with stir-
ring. Then appropriately substituted 2-(6-methyl-benzofuran-
3-ylmethyl)-6-phenyl-imidazo[2,1-b][1,3,4]thiadiazole (5aec,
0.01 mol) was added to the reagent and stirred at 0 ꢂC for
30 min. The mixture was further stirred for 2 h at room
2-(6-Methyl-benzofuran-3-ylmethyl)-6-phenyl-imi-
dazo[2,1-b][1,3,4]thiadiazole
5
(0.005 mol), morpholine
(0.006 mol), formaldehyde (1 ml) and acetic acid catalytic
amount in methanol (20 ml) was refluxed for 8 h (monitored
by TLC). The solution was diluted with water, extracted
with chloroform (3 ꢃ 30 ml), the combined chloroform extract
was washed with water (3 ꢃ 30 ml), and dried over anhydrous

V.B. Jadhav et al. / European Journal of Medicinal Chemistry 43 (2008) 1721e1729
1727
temperature and at 60 ꢂC for additional 2 h. The reaction mixture
was then poured in sodium carbonate solution and stirred at90 ꢂC
for 2 h. After cooling, the mixture was diluted with water, and ex-
tracted with chloroform. Chloroform layer was dried over anhy-
drous sodium sulfate. The residue obtained after removal of
chloroform was recrystallized from suitable solvent to get the
crystalline solid.
(0.001 mol) in dry methanol (20 ml) was added in small portions
sodium borohydride (0.0015 mol). The mixture was stirred at
room temperature for 2 h (monitored by TLC), poured over
icewater. The solid separated was collected by filtration, washed
with cold methanol, dried and crystallized from appropriate
solvent.
5.1.5.1. [6-(4-Chlorophenyl)-2-(6-methyl-benzofuran-3-ylmethyl)-
imidazo[2,1-b][1,3,4]thiadiazol-5-yl]-methanol (8a). Colorless
solid (ethanol); yield 70%; m.p. 184e186 ꢂC; IR (KBr) cmꢀ1
5.1.4.1. 6-(4-Chlorophenyl)-2-(6-methyl-benzofuran-3-ylmethyl)-
imidazo[2,1-b][1,3,4]thiadiazole-5-carbaldehyde (7a). Brown
solid (benzene þ petroleum ether); yield 60%; m.p. 184e
1
3181, 2921, 1649, 1496, 1476; H NMR (CDCl3, 300 MHz,
1
186 ꢂC; IR (KBr) cmꢀ1 3105, 2917, 2837, 1648; H NMR
TMS): d 2.44 (s, 3H, C6eCH3 of benzofuran), 2.50 (br s, 1H,
OH, D2O exchangeable), 4.38 (s, 2H, C3eCH2 of benzofuran),
5.06 (s, 2H, C5eCH2eO of imidazole), 7.17 (d, 1H,
J ¼ 8.0 Hz, C5eH of benzofuran), 7.31 (s, 1H, C7eH of benzo-
furan), 7.40 (d, 1H, J ¼ 8.0 Hz, C4eH of benzofuran), 7.50 (d,
2H, J ¼ 7.9 Hz, C2, C6eH of phenyl), 7.65 (s, 1H, C2eH of ben-
zofuran), 7.70 (d, 2H, J ¼ 7.9 Hz, C3, C5eH of phenyl); LCeMS
410 [M þ H]. Anal. Calcd for C21H16ClN3O2S (%): C, 61.53; H,
3.93; N, 10.25. Found: C, 61.62; H, 4.01; N, 10.32.
(CDCl3, 300 MHz, TMS): d 2.43 (s, 3H, C6eCH3 of benzofu-
ran), 4.53 (s, 2H, C3eCH2 of benzofuran), 7.51 (d, 1H,
J ¼ 8.4 Hz, C5eH of benzofuran), 7.41 (d, 1H, J ¼ 8.4 Hz,
C4eH of benzofuran), 7.32 (s, 1H, C7eH of benzofuran),
7.70 (s, 1H, C2eH of benzofuran), 7.47 (d, 2H, J ¼ 8.0 Hz,
C2, C6eH of phenyl), 7.82 (d, 2H, J ¼ 8.4 Hz, C3, C5eH
of phenyl), 10.0 (s, 1H, CHO); 13C NMR (CDCl3, 75 MHz,
TMS): d 21.7, 27.2, 111.8, 114.3, 119.4, 124.3, 126.8, 127.0,
128.7, 129.4, 129.4, 130.6, 130.6, 131.0, 133.2, 136.5, 143.8,
154.4, 154.9, 166.9, 177.5; LCeMS 408 [M þ H]. Anal. Calcd
for C21H14ClN3O2S (%): C, 61.84; H, 3.46; N, 10.30. Found:
C, 61.97; H, 3.58; N, 10.45.
5.1.5.2. [6-(4-Bromophenyl)-2-(6-methyl-benzofuran-3-ylmethyl)-
imidazo[2,1-b][1,3,4]thiadiazol-5-yl]-methanol (8b). Colorless
solid (ethanol); yield 75%; m.p. 188e190 ꢂC; IR (KBr) cmꢀ1
1
3165, 2919, 1625, 1493; H NMR (CDCl3, 300 MHz, TMS):
5.1.4.2. 6-(4-Bromophenyl)-2-(6-methyl-benzofuran-3-ylmethyl)-
imidazo[2,1-b][1,3,4]thiadiazole-5-carbaldehyde (7b). Brown
solid (benzene); yield 60%; m.p. 208e210 ꢂC; IR (KBr) cmꢀ1
d 2.48 (s, 3H, C6eCH3 of benzofuran), 2.69 (br s, 1H, OH,
D2O exchangeable), 4.37 (s, 2H, C3eCH2 of benzofuran), 5.04
(s, 2H, C5eCH2eO of imidazole), 7.08 (d, 1H, J ¼ 8.0 Hz,
C5eH of benzofuran), 7.33 (s, 1H, C7eH of benzofuran), 7.39
(d, 1H, J ¼ 8.0 Hz, C4eH of benzofuran), 7.54 (d, 2H,
J ¼ 8.1 Hz, C2, C6eH of phenyl), 7.62 (s, 1H, C2eH of benzofu-
ran), 7.64 (d, 2H, J ¼ 8.1 Hz, C3, C5eH of phenyl); 13C NMR
(CDCl3, 75 MHz, TMS): d 22, 27.3, 54.4, 112.4, 114.7, 119.2,
122.2, 122.7, 124.5, 124.9, 129.3, 129.3, 132.2, 132.2, 133.2,
135.9, 142.8, 143.6, 145.1, 156.3, 164.1; LCeMS 455 [M þ H].
Anal. Calcd for C21H16BrN3O2S (%): C, 55.51; H, 3.55; N,
9.25. Found: C, 55.60; H, 3.67; N, 9.29. M.p. (alcohol), yield 75%.
1
3105, 3030, 2915, 2837, 1647; H NMR (CDCl3, 300 MHz,
TMS): d 2.48 (s, 3H, C6eCH3 of benzofuran), 4.54 (s, 2H,
C3eCH2 of benzofuran), 7.10 (d, 1H, J ¼ 8.0 Hz, C5eH of ben-
zofuran), 7.41 (d, 1H, J ¼ 8.0 Hz, C4eH of benzofuran), 7.35 (s,
1H, C7eH of benzofuran), 7.67 (s, 1H, C2eH of benzofuran),
7.64 (d, 2H, J ¼ 8.4 Hz, C2, C6eH of phenyl), 7.75 (d, 2H,
J ¼ 8.4 Hz, C3, C5eH of phenyl), 10.07 (s, 1H, CHO); LCe
MS 453 [M þ H]. Anal. Calcd for C21H14BrN3O2S (%): C,
55.76; H, 3.12; N, 9.29. Found: C, 55.85; H, 3.22; N, 9.18.
5.1.4.3. 6-(4-Nitrophenyl)-2-(6-methyl-benzofuran-3-ylmethyl)-
imidazo[2,1-b][1,3,4]thiadiazole-5-carbaldehyde (7c). Brown
solid (benzene); yield 65%; m.p. 190e192 ꢂC; IR (KBr)
cmꢀ1 2922, 1654, 1603, 1524, 1307; 1H NMR (CDCl3,
300 MHz, TMS): d 2.49 (s, 3H, C6eCH3 of benzofuran),
4.40 (s, 2H, C3eCH2 of benzofuran), 7.11 (d, 1H,
J ¼ 8.0 Hz, C5eH of benzofuran), 7.40 (d, 1H, J ¼ 8.0 Hz,
C4eH of benzofuran), 7.33 (s, 1H, C7eH of benzofuran),
7.64 (s, 1H, C2eH of benzofuran), 7.98 (d, 2H, J ¼ 8.5 Hz,
C2, C6eH of phenyl), 8.28 (d, 2H, J ¼ 8.5 Hz, C3, C5eH
of phenyl), 10.12 (s, 1H, CHO); LCeMS 419 [M þ H].
Anal. Calcd for C21H14N4O4S (%): C, 60.28; H, 3.37; N,
13.39. Found: C, 60.40; H, 3.45; N, 13.44.
5.1.5.3. [6-(4-Nitrophenyl)-2-(6-methyl-benzofuran-3-ylmethyl)-
imidazo[2,1-b][1,3,4]thiadiazol-5-yl]-methanol (8c). Colorless
solid (ethanol); yield 72%; m.p. 172e174 ꢂC; IR (KBr) cmꢀ1
1
3179, 2921, 1620, 1523, 1307; H NMR (CDCl3, 300 MHz,
TMS): d 2.45 (s, 3H, C6eCH3 of benzofuran), 2.75 (br s, 1H,
OH, D2O exchangeable), 4.36 (s, 2H, C3eCH2 of benzofuran),
5.20 (s, 2H, C5eCH2eO of imidazole), 7.10 (d, 1H, J ¼ 7.8 Hz,
C5eH of benzofuran), 7.36 (s, 1H, C7eH of benzofuran), 7.40
(d, 1H, J ¼ 7.8 Hz, C4eH of benzofuran), 7.98 (d, 2H,
J ¼ 8.6 Hz, C2, C6eH of phenyl), 7.60 (s, 1H, C2eH of benzo-
furan), 8.30 (d, 2H, J ¼ 8.6 Hz, C3, C5eH of phenyl). Anal.
Calcd for C21H16N4O4S (%): C, 59.99; H, 3.84; N, 13.33. Found:
C, 60.10; H, 3.92; N, 13.25.
5.1.5. Synthesis of [2-(6-methyl-benzofuran-3-ylmethyl)-6-
phenyl-imidazo[2,1-b][1,3,4]thiadiazole-5-yl]-methanol (8):
general procedure
5.1.6. Synthesis of 2-(6-methyl-benzofuran-3-ylmethyl)-6-
phenyl-imidazo[2,1-b][1,3,4]thiadiazole-5-carbaldehyde
oxime (9): general procedure
To a stirred solution of 2-(6-methyl-benzofuran-3-ylmethyl)-
6-phenyl-imidazo[2,1-b][1,3,4]thiadiazole-5-carbaldehyde 7
A mixture of 2-(6-methyl-benzofuran-3-ylmethyl)-6-phenyl-
imidazo[2,1-b][1,3,4]thiadiazole-5-carbaldehyde 7 (0.001 mol)

1728
V.B. Jadhav et al. / European Journal of Medicinal Chemistry 43 (2008) 1721e1729
and hydroxyl amine hydrochloride (0.0012 mol) was refluxed in
pyridine (10 ml) for 6 h (monitored by TLC), the cooled mixture
was then poured over ice and the precipitate was collected by fil-
tration, washed with water, aqueous ethanol, dried and recrystal-
lized from appropriate solvent to yield the corresponding
aldoximes.
d6, 300 MHz, TMS): d 2.43 (s, 3H, C6eCH3 of benzofuran),
4.65 (s, 2H, C3eCH2 of benzofuran), 7.12 (d, 1H, J ¼ 5.8 Hz,
C5eH of benzofuran), 7.43 (s, 1H, C7eH of benzofuran),
7.55 (d, 1H, J ¼ 5.8 Hz, C4eH of benzofuran), 7.64 (d, 2H,
J ¼ 6.4 Hz, C2, C6eH of phenyl), 7.97 (d, 2H, J ¼ 6.4 Hz,
C3, C5eH of phenyl), 8.03 (s, 1H, C2eH of benzofuran);
LCeMS 405 [M þ H]. Anal. Calcd for C21H13ClN4OS (%):
C, 62.30; H, 3.24; N, 13.84. Found: C, 62.40; H, 3.35; N, 13.97.
5.1.6.1. 6-(4-Chlorophenyl)-2-(6-methyl-benzofuran-3-ylmethyl)-
imidazo[2,1-b][1,3,4] thaidiazole-5-carbaldehyde oxime (9a).
Yellow solid (ethanol); yield 58%; m.p. 246e248 ꢂC; IR
5.1.7.2. 6-(4-Bromophenyl)-2-(6-methyl-benzofuran-3-ylmethyl)-
imidazo [2,1-b][1,3,4]thiadiazole-5-carbonitrile (10b). Yellow
solid (chloroform); yield 68%; m.p. 165e167 ꢂC; IR (KBr)
cmꢀ1 3068, 2917, 2225, 1630, 1602; 1H NMR (DMSO-d6,
300 MHz, TMS): d 2.40 (s, 3H, C6eCH3 of benzofuran), 4.62
(s, 2H, C3eCH2 of benzofuran), 7.15 (d, 1H, J ¼ 6.0 Hz, C5e
H of benzofuran), 7.42 (s, 1H, C7eH of benzofuran), 7.53 (d,
1H, J ¼ 6.0 Hz, C4eH of benzofuran), 7.62 (d, 2H,
J ¼ 6.5 Hz, C2, C6eH of phenyl), 7.95 (d, 2H, J ¼ 6.5 Hz,
C3, C5eH of phenyl), 7.99 (s, 1H, C2eH of benzofuran);
LCeMS 450 [M þ H]. Anal. Calcd for C21H13BrN4OS (%):
C, 56.13; H, 2.92; N, 12.47. Found: C, 56.21; H, 3.00; N, 12.54.
1
(KBr) cmꢀ1 3258, 3098, 2921, 1621, 1535, 1498; H NMR
(DMSO-d6, 300 MHz, TMS): d 2.39 (s, 3H, C6eCH3 of benzo-
furan), 4.55 (s, 2H, C3eCH2 of benzofuran), 7.08e8.10 (m, 8H,
C5, C4, C7, C2eH of benzofuran, C2, C6, C3, C5eH of phe-
nyl), 8.33 (s, 1H, CHN), 11.60 (br s, 1H, OH, D2O exchange-
able). Anal. Calcd for C21H15ClN4O2S (%): C, 59.64; H, 3.58;
N, 13.25. Found: C, 59.74; H, 3.70; N, 13.30.
5.1.6.2. 6-(4-Bromophenyl)-2-(6-methyl-benzofuran-3-ylmethyl)-
imidazo[2,1-b][1,3,4] thaidiazole-5-carbaldehyde oxime (9b).
Colorless solid (ethanol); yield 61%; m.p. 240e242 ꢂC; IR
1
(KBr) cmꢀ1 3265, 3098, 2922, 1620, 1535, 1495; H NMR
(DMSO-d6, 300 MHz, TMS): d 2.40 (s, 3H, C6eCH3 of benzo-
furan), 4.58 (s, 2H, C3eCH2 of benzofuran), 7.09e8.00 (m, 8H,
C5, C4, C7, C2eH of benzofuran, C2, C6, C3, C5eH of phe-
nyl), 8.30 (s, 1H, CHN), 11.60 (br s, 1H, OH, D2O exchange-
able); LCeMS 468 [M þ H]. Anal. Calcd for C21H15BrN4O2S
(%): C, 53.97; H, 3.24; N, 11.99. Found: C, 54.10; H, 3.35;
N, 12.08.
5.1.7.3. 6-(4-Nitrophenyl)-2-(6-methyl-benzofuran-3-ylmethyl)-
imidazo [2,1-b][1,3,4]thiadiazole-5-carbonitrile (10c). Yel-
low solid (chloroform); yield 63%; m.p. 174e174 ꢂC; IR
1
(KBr) cmꢀ1 3118, 2917, 2225, 1630, 1602, 1530, 1317; H
NMR (DMSO-d6, 300 MHz, TMS): d 2.44 (s, 3H, C6eCH3
of benzofuran), 4.58 (s, 2H, C3eCH2 of benzofuran), 7.12
(d, 1H, J ¼ 6.80 Hz, C5eH of benzofuran), 7.45 (s, 1H,
C7eH of benzofuran), 7.52 (d, 1H, J ¼ 6.80 Hz, C4eH of
benzofuran), 7.98 (d, 2H, J ¼ 8.0 Hz, C2, C6eH of phenyl),
8.25 (d, 2H, J ¼ 8.0 Hz, C3, C5eH of phenyl), 8.00 (s, 1H,
C2eH of benzofuran). Anal. Calcd for C21H13N5O3S (%):
C, 60.71; H, 3.15; N, 16.86. Found: C, 60.80; H, 3.23; N,
16.93.
5.1.6.3. 6-(4-Nitrophenyl)-2-(6-methyl-benzofuran-3-ylmethyl)-
imidazo[2,1-b][1,3,4] thaidiazole-5-carbaldehyde oxime (9c).
Colorless solid (ethanol); yield 60%; m.p. 224e226 ꢂC; IR
1
(KBr) cmꢀ1 3265, 3100, 2918, 1618, 1525, 1310; H NMR
(DMSO-d6, 300 MHz, TMS): d 2.42 (s, 3H, C6eCH3 of benzo-
furan), 4.48 (s, 2H, C3eCH2 of benzofuran), 7.12e8.40 (m,
4H, C5, C4, C7, C2eH of benzofuran), 7.98 (d, 2H,
J ¼ 8.2 Hz, C2, C6eH of phenyl), 8.25 (d, 2H, J ¼ 8.2 Hz,
C3, C5eH of phenyl) 8.35 (s, 1H, CHN), 11.62 (br s, 1H,
OH, D2O exchangeable). Anal. Calcd for C21H15N5O4S (%):
C, 58.19; H, 3.49; N, 16.16. Found: C, 58.27; H, 3.57; N, 16.24.
5.2. Pharmacology
5.2.1. Animals
Albino rats of Wister strain (150e200 g) and Swiss albino
mice (25e30 g) of either sex were procured from the central
animal house of the institute. They were housed in standard
polypropylene cages and kept under controlled room temper-
ature (24 ꢁ 2 ꢂC; relative humidity 60e70%) in a 12 h
lightedark cycle. The rats were given a standard laboratory
diet and water ad libitum. Food was withdrawn 12 h before
and during the experimental hours. All experimental protocols
were approved by the institutional animal ethics committee.
5.1.7. Synthesis of 2-(6-methyl-benzofuran-3-ylmethyl)-6-
phenyl-imidazo[2,1-b][1,3,4]thiadiazole-5-carbonitrile (10):
general procedure
The 2-(6-methyl-benzofuran-3-ylmethyl)-6-phenyl-imi-
dazo[2,1-b][1,3,4]thiadiazole-5-carbaldehyde oxime
9
(0.001 mol) was suspended in acetic anhydride (10 ml) and
refluxed for 1 h. Poured over cold water, neutralized by so-
dium carbonate solution, the solid that separated was col-
lected by filtration, washed repeatedly with water, dried
and recrystallized from appropriate solvent.
5.2.2. Acute toxicity studies
For testing the acute toxicity potential of the test com-
pounds, albino rats of either sex weighing 25e300 g were se-
lected, separated into groups each containing six rats. The
dosage was varied from 100 up to 3000 mg kgꢀ1 body weight.
The rats were continuously observed for 8 h for any signs
of acute toxicity such as increasededecreased motor activity,
ataxia, tremors, convulsions, sedation, lacrimation, etc. After
5.1.7.1. 6-(4-Chlorophenyl)-2-(6-methyl-benzofuran-3-ylmethyl)-
imidazo[2,1-b][1,3,4]thiadiazole-5-carbonitrile (10a). Yellow
solid (chloroform þ pꢀet1roleum ether); yield 61%; m.p. 154e
1
156 ꢂC; IR (KBr) cm 3068, 2917, 2212; H NMR (DMSO-

V.B. Jadhav et al. / European Journal of Medicinal Chemistry 43 (2008) 1721e1729
1729
24 h the rats were sacrificed, stomach, intestine, and liver were
inspected under the magnifying lenses for any ulcer-haemor-
rhagic spots.
Acknowledgements
The authors thank the University Sophisticated Instrumen-
tation Centre, Karnatak University, Dharwad for IR, NMR and
analytical data. One of the authors Mr. Vithal B. Jadhav is
grateful to the Karnatak University, Dharwad for University
Research Studentship.
5.2.3. Anti-inflammatory activity
For the antiinflammatory activity the animals were divided
into different groups as shown in Tables 1a and b. Acute in-
flammation was produced by subplantar injection of 0.1 ml
of 1% suspension of carrageenan with 2% gum acacia in nor-
mal saline, in the right hind paw of the rats, 1 h after oral ad-
ministration of the drugs. The paw volume was measured
plethysmometrically (Ugo Basile, Italy) at 0 and 3 h after
the carrageenan injection. The difference between the two
readings was taken as the volume of oedema and the percent-
age anti-inflammatory activity was calculated. Aspirin
100 mg kgꢀ1, p.o. suspended in 2% gum acacia was used as
the standard drug.
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