2,6-Disubstituted imidazo[2,1-b][1,3,4]thiadiazoles: Search for anticancer agents

Article abstract of DOI:10.1016/j.ejmech.2012.08.012

In this study, some novel 2,6-disubstituted imidazo[2,1-b][1,3,4] thiadiazoles 4 (a-i), 7 (a-p) and 11 (a-i) were synthesized from 5-substituted-1,3,4-thiadiazol-2-amine. The newly synthesized compounds 4a, 4b, 4c, 4e, 4g, 7j, 7l, 11b and 11c were evaluated in the National Cancer Institute for single dose in vitro primary cytotoxicity assay. Among the tested nine compounds, compound 4b (107166/760239) and 4c (107168/760240) were passed the criteria for activity in this assay and scheduled automatically for evaluation against the full panel of 60 human tumor cell lines at a minimum of five concentrations at 10-fold dilutions. 3-(2-(4-methoxyphenyl)imidazo[2,1-b][1,3,4] thiadiazol-6-yl)aniline (4c) exhibited significant in vitro anticancer activity against Non Small Cell Lung Cancer HOP-92 cell line (GI₅₀: 0.114 μM) and Renal Cancer CAKI-1 cell line (GI₅₀: 0.743 μM).

Full text of DOI:10.1016/j.ejmech.2012.08.012

European Journal of Medicinal Chemistry 56 (2012) 56e69
Contents lists available at SciVerse ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
2,6-Disubstituted imidazo[2,1-b][1,3,4]thiadiazoles: Search for anticancer agents
,
b
c
c
c
Malleshappa N. Noolvi a , Harun M. Patel , Sarita Kamboj , Amandeep Kaur , Vikas Mann
*
a Department of Pharmaceutical Chemistry, Shree Dhanvantary Pharmacy College, Kim (Surat) 3941110, Gujarat, India
b Department of Pharmaceutical Chemistry, R.C. Patel Institute of Pharmaceutical Education and Research, Shirpur(Dhule) 425405, Maharashtra, India
c Department of Pharmaceutical Chemistry, ASBASJSM College of Pharmacy, Bela (Ropar) 140111, Punjab, India
a r t i c l e i n f o
a b s t r a c t
Article history:
In this study, some novel 2,6-disubstituted imidazo[2,1-b][1,3,4]thiadiazoles 4 (aei), 7 (aep) and 11 (aei)
were synthesized from 5-substituted-1,3,4-thiadiazol-2-amine. The newly synthesized compounds 4a,
4b, 4c, 4e, 4g, 7j, 7l, 11b and 11c were evaluated in the National Cancer Institute for single dose in vitro
primary cytotoxicity assay. Among the tested nine compounds, compound 4b (107166/760239) and 4c
(107168/760240) were passed the criteria for activity in this assay and scheduled automatically for
evaluation against the full panel of 60 human tumor cell lines at a minimum of five concentrations at
10-fold dilutions. 3-(2-(4-methoxyphenyl)imidazo[2,1-b][1,3,4]thiadiazol-6-yl)aniline (4c) exhibited
Received 7 June 2012
Received in revised form
7 August 2012
Accepted 9 August 2012
Available online 16 August 2012
Keywords:
significant in vitro anticancer activity against Non Small Cell Lung Cancer HOP-92 cell line (GI50
0.114 M) and Renal Cancer CAKI-1 cell line (GI50: 0.743 M).
Ó 2012 Elsevier Masson SAS. All rights reserved.
:
Synthesis imidazo[2,1-b][1,3,4]thiadiazole
Anticancer agents
NCI
m
m
1. Introduction
small tumor burdens and it acts by stimulating the responsiveness
of lymphocytes to tumor antigens [1]. In addition, the imidazo[2,1-
b]thiadiazole derivatives of Levamisole have been reported as
potential antitumor agents (II) [2]. Later, antitumor activity of
5-formyl-6-arylimidazo-[2,1-b][1,3,4]thiadiazole sulfonamides (III)
were also reported [3] (Fig. 1).
In view of the above facts and in continuation of our search for
novel anticancer agents [13e17], we have further investigated the
potential of imidazo[2,1-b]thiadiazole as a supporting moiety for
a number of selected pharmacophoric functions. Since this hetero-
cycle constitutes the main part of levamisole, a well known immu-
nomodulator [18], the possibility of reducing the harmful effects of
the cytotoxic agents on the immune system could be seriously taken
into account. In fact, the aim of this research was to discover a lead
compound with a 2-fold action: first it could show antitumor activity
and later, through one of its metabolites, it could restore the
depressed immune system. With this in mind, in the present study
a new series of 2,6-disubstituted imidazo[2,1-b][1,3,4]thiadiazoles
have been synthesized and screened in vitro at NCI (National Cancer
Institute)eUSA for their anticancer properties (Fig. 1).
Cancer is undoubtedly a serious and potentially life-threatening
illness. Cancer chemotherapy has entered a new era of molecularly
targeted therapeutics, which is highly selective and not associated
with the serious toxicities of conventional cytotoxic drugs [1]. A
wide range of heterocyclic ring systems has been studied for the
development of novel chemical entities as a lead molecule in the
drug discovery paradigm. The anti-tumor potential of the 2-amino-
1,3,4-thiadiazole skeleton was recognized in the early 1950s [2] and
subsequently its fusion with the imidazo[2,1-b] ring system has
resulted in compounds with potential anticancer [3], antitubercular
[4], antibacterial [5], antifungal [6], anticonvulsant, analgesic [7],
and antisecretory [8] activities. Consequently, a large number of
imidazo[2,1-b][1,3,4]thiadiazole derivatives have been reported to
possess antitumor property [9e12].
Development of anticancer drugs with fewer or no side effects is
important for the treatment of cancer. The search for such potential
anticancer drugs have led to the discovery of synthetic small
molecules with anti-carcinogenic activity and limited harmful side
effects particularly with respect to the immune system. Alterna-
tively, stimulation of the body’s immune system could provide
a valuable support in cancer treatment, since it is capable of erad-
icating the neoplastic cells completely. Research in this area is
expanding rapidly and some promising leads have emerged.
Levamisole (I) appears to be the most effective in patients with
2. Chemistry
The synthetic route of the compound 4 (aei), 7 (aep) and 11 (ae
i) is outlined in Schemes1e3 respectively. The 2,6-disubstituted
imidazo[2,1-b][1,3,4]-thiadiazoles 4 (aei), 7 (aep) and 11 (aei)
were prepared by refluxing 5-substituted-1,3,4-thiadiazol-2-
* Corresponding author. Tel.: þ91 9417563874; fax: þ911881263655.
E-mail address: mnoolvi@yahoo.co.uk (M.N. Noolvi).
amine (2), (6) and (9) with substituted
a-bromoketones in dry
0223-5234/$ e see front matter Ó 2012 Elsevier Masson SAS. All rights reserved.
http://dx.doi.org/10.1016/j.ejmech.2012.08.012

M.N. Noolvi et al. / European Journal of Medicinal Chemistry 56 (2012) 56e69
57
stretching band of the carboxylic acid function. The formation of
imidazothiadiazoles 4 (aei), 7 (aep) and 11 (aei) was indicated by
the absence of n NeH band w3200 in the IR spectra and appearance
of imidazo proton (CeH) around
d
w8.00 in 1H NMR spectra. The
13C NMR and Mass spectra of these compounds further confirmed
the assigned structures.
3. Pharmacology
3.1. Anticancer activity (NCI 60 DTP human tumor cell line
screening)
The screening of the compounds operated with the in vitro Cell
Line Screening Project (IVCLSP) which is a dedicated service,
providing direct support to the DTP anticancer drug discovery
program. It is a two stage process, beginning with the evaluation of
all compounds against the 60 cell lines at a single dose of 10ꢀ5 M.
The output from the single dose screen is reported as a mean graph
and is available for analysis by the compare program. Compounds
which exhibit significant growth inhibition are evaluated against
the 60 cell panel at five concentration level.
The tumor growth inhibition properties of the selected nine
compounds 4a, 4b, 4c, 4e, 4g, 7j, 7l, 11b and 11c with the NCI NSC-
codes 107164/760238, 107166/760239, 107168/760240, 107180/
760241, 108144/760535, 105053/758274, 105054/758274, 106805/
759798 and 10806/759799 were screened on human tumor cell
lines at 10ꢀ5 M concentration at the NCI, NIH, Bethesda, Maryland,
USA, under the drug discovery program of the NCI. Among the
tested compounds, compound 4b (107166/760239) and 4c (107168/
760240) were further screened for 5-log dose molar range as they
have shown prominent cell growth inhibition at 10ꢀ5 M concen-
tration against variety of cell lines.
3.2. Methodology of the in vitro cancer screen
The human cancer cell lines of the cancer screening panel are
grown in RPMI 1640 medium containing 5% fetal bovine serum at
Fig. 1. Reported and proposed antitumor 2,6-disubstituted imidazo[2,1-b][1,3,4]
thiadiazoles.
2 mM
L
-glutamine. For a typical screening experiment, cells are
ethanol. The ring nitrogen of the imino form of thiadiazole is
involved preferably on the nucleophilic displacement of bromine of
the a-bromoketones forming an intermediate. It undergoes further
cyclodehydration on heating with a suitable medium like ethanol,
DMF to afford imidazothiadiazoles in good yields. The cyclo-
dehydration involves intramolecular nucleophilic addition of the 2-
amino group to carbonyl functions of the intermediate followed by
the elimination of water as shown in Scheme 4. The physical data of
all the synthesized compounds is shown in Table 1.
inoculated into 96 well microtiter plates in 100
ml at plate densities
ranging from 5000 to 40,000 cells/well depending upon the
doubling time of individual cell lines. After cell inoculation, the
microtiter plates are incubated at 37 ꢁC, 5% CO2, 95% air and 100%
relative humidity for 24 h prior to addition of experimental drugs.
After 24 h, two plates of each cell lines are fixed in situ with TCA,
to represent a measurement of the cell population for each cell line
at the time of drug addition (Tz). Experimental drugs are solubi-
lized in dimethyl sulfoxide at 400-fold the desired final maximum
test concentration and stored frozen prior to use. At the time of
drug addition, an aliquot of frozen concentrate is thawed and
diluted to twice the desired final maximum test concentration with
The structures of synthesized compounds were established
on the basis of their spectral data. The formation of 2-
aminothiadiazoles 2, 6 and 9 was supported by the presence of
n
NeH band in the IR spectra w3200 and absence of carbonyl
complete medium containing 50 mg/ml gentamicin. Additional four,
Scheme 1. Synthesis of target compound 4(aei).

58
M.N. Noolvi et al. / European Journal of Medicinal Chemistry 56 (2012) 56e69
Scheme 2. Synthesis of target compound 7(aep).
10-fold or ½ log serial dilutions are made to provide a total of five
drug concentrations plus control. Aliquots of 100 l of these
different drug dilutions are added to the appropriate microtiter
wells already containing 100 l of medium, resulting in the
required final drug concentration.
Following drug addition, the plates are incubated for an addi-
tional 48 h at 37 ꢁC, 5% CO2, 95% air and 100% relative humidity. For
adherent cells, the assay is terminated by the addition of cold TCA.
test growth in the presence of drug at five concentration levels (Ti)],
the percentage growth is calculated at each of the drug concen-
trations levels. Percentage growth inhibition is calculated as:
m
m
½ðTi ꢀ TzÞ=ðC ꢀ TzÞꢂ ꢃ 100 for concentrations for which Ti ꢄ Tz
½ðTi ꢀ TzÞ=Tzꢂ ꢃ 100 for concentrations for which Ti < Tz
Three dose response parameters are calculated for each exper-
imental agent. Growth inhibition of 50% (GI50) is calculated from
[(Ti ꢀ Tz)/(C ꢀ Tz)] ꢃ 100 ¼ 50 which is the drug concentration
resulting in a 50% reduction in the net protein increase (as
measured by SRB staining) in control cells during the drug
incubation.
The drug concentration resulting in total growth inhibition (TGI)
is calculated from Ti ¼ Tz. The LC50 concentration of the drug
resulting in 50% reduction in the measured protein at the end of the
drug treatment as compared from [(Ti ꢀ Tz)/Tz] ꢃ 100 ¼ ꢀ50.
Values are calculated for each of these parameters if the level of
activity is reached; however, if the effect is not reached or is
exceeded, the value for that parameter is expressed as greater or
less than the maximum or minimum concentration tested [19e21].
Cells are fixed in situ by the gentle addition of 50
v) TCA (final concentration, 10% TCA) and incubated for 60 min at
ꢁC. The supernatant is discarded and the plates are washed five
times with tap water and air dried. Sulforhodamine (SRB) solution
(100 l) at 0.4% (w/v) in 1% acetic acid is added to each well, and
plates are incubated for 10 min at room temperature. After staining,
unbound dye is removed by washing five times with 1% acetic acid
and the plates are air dried. Bound stain is subsequently solubilized
with 10 mM trizma base, and the absorbance is read on an auto-
mated plate reader at a wavelength of 515 nm. For suspension cells,
the methodology is the same except that the assay is terminated by
ml of cold 50% (w/
4
m
fixing settled cells at the bottom by the wells by gentle adding 50 ml
of 80% TCA (final concentration 16% TCA). Using the seven absor-
bance measurements[time zero, (Tz), control growth, (C) and the
Scheme 3. Synthesis of target compounds 11(aei).

M.N. Noolvi et al. / European Journal of Medicinal Chemistry 56 (2012) 56e69
59
Scheme 4. Reaction mechanism of synthesized compounds 4(aei), 7(aep) and 11(aei).
3.3. Primary single high dose (10ꢀ5 M) full NCI 60 cell panel in vitro
assay
obtained by dividing the full panel MIDa (the average sensitivity of
all cell lines toward the test agent) by their individual subpanel
MIDb (the average sensitivity of all cell lines of a particular subpanel
toward the test agent). Ratios between 3 and 6 refer to moderate
selectivity; ratios greater than 6 indicate high selectivity toward the
corresponding cell line, while compounds not meeting either of
these criteria rated non-selective [21]. As per this criterion,
compounds 4b and 4c were found close to moderately selective
towards Breast Cancer subpanel with selectivity ratio of 1.41 and
1.71, whereas it was found to be non-selective against remaining
cell panel (Tables 2 and 3).
All the selected compounds submitted to National Cancer
Institute (NCI) for in vitro anticancer assay were evaluated for their
anticancer activity. Primary in vitro one dose anticancer assay was
performed in full NCI 60 cell panel representing leukemia, mela-
noma, lung, colon, brain, breast, ovary, kidney and prostate cancers
in accordance with the protocol of the NCI, USA. The compounds
were added at a single concentration (10ꢀ5 M) and the culture was
incubated for 48 h. End point determinations were made with
a
protein binding dye, sulforhodamine B. Results for each
compound were reported as a mean graph of the percent growth of
the treated cells when compared to the untreated control cells.
There after obtaining the results for one dose assay, analysis of
historical Development Therapeutics Programme (DTP) was per-
formed and compounds 4b and 4c which satisfied pre-determined
threshold inhibition criteria was selected for NCI full panel 5 dose
assays.
4. Conclusion
A new series of 2,6-disubstituted imidazo[2,1-b][1,3,4]thiadia-
zoles 4(aei), 7(aep) and 11(aei) were synthesized. Among all of
these derivatives, compounds 4a, 4b, 4c, 4e, 4g, 7j, 7l, 11b and 11c
were tested at a single dose of 10ꢀ5 M concentration at the NCI over
60 cell line panel, and compounds 4b and 4c were subsequently
tested in 5 dose testing mode. 3-(2-(4-methoxyphenyl)imidazo
[2,1-b][1,3,4]thiadiazol-6-yl)aniline (4c) exhibited significant anti-
cancer activity as compared to other tested compounds. This
compound demonstrated the most marked effects in the National
Cancer Institute’s 60 human tumor cell line in vitro screen on Non
3.4. In vitro 5 dose full NCI 60 cell panel assay and discussion
All the cell lines (about 60), representing nine tumor subpanels,
were incubated at five different concentrations (0.01, 0.1, 1, 10 &
100 mM). The outcomes were used to create log concentration Vs %
Small Cell Lung Cancer HOP-92 cell line (GI50: 0.114
Cancer CAKI-1 cell line (GI50: 0.743 M). In terms of selectivity ratio
mM) and Renal
m
growth inhibition curves and three response parameters (GI50, TGI
and LC50) were calculated for each cell line. The GI50 value (growth
inhibitory activity) corresponds to the concentration of the
compound causing 50% decrease in net cell growth, the TGI value
(cytostatic activity) is the concentration of the compound resulting
in total growth inhibition and LC50 value (cytotoxic activity) is the
concentration of the compound causing net 50% loss of initial cells
at the end of the incubation period of 48 h.
compounds 4b and 4c were interestingly more selective for Breast
Cancer cell lines than other cancer types. These preliminary
encouraging results of biological screening of the tested
compounds could offer an excellent framework in this field that
may lead to discovery of potent antitumor agent.
5. Experimental
Compound 4b (NSC: 107166/760239) exhibited high activity
against Non Small Cell Lung Cancer HOP-92 cell line (GI50
0.231 M), CNS Cancer SNB-75 cell line (GI50: 0.331 M) and Renal
Cancer A498 cell line (GI50: 0.365 M) as shown in Figs. 2 and 3.
Similarly compound under investigation 4c (NSC: 107168/760240)
exhibited significant anticancer activity against most of the tested
cell lines representing nine different subpanels with GI50 values
between 0.114 and 17.3 mM and found to be potential candidate of
the series as shown in Figs. 4 and 5. With regard to the sensitivity
against some individual cell lines the compound showed high
:
All chemicals and solvents were supplied by Merck, S.D. Fine
Chemical Limited, Mumbai. All the solvents were distilled and dried
before use. The reactions were monitored with the help of thin-
layer chromatography using pre-coated aluminum sheets with
GF254 silica gel, 0.2 mm layer thickness (E. Merck). Melting points of
the synthesized compounds were recorded on the Veego (VMP-
MP) melting point apparatus. IR spectrum was acquired on a Shi-
madzu Infra Red Spectrometer, (model FTIR-8400S). Both 1H NMR
(DMSO) and 13C NMR (DMSO) spectra of the synthesized
compounds were performed with Bruker Avance-II 400 NMR
Spectrometer operating at 400 MHz in SAIF, Punjab University
(Chandigarh). Chemical shifts were measured relative to internal
m
m
m
activity against Non Small Cell Lung Cancer HOP-92 cell line (GI50
0.114 M) and Renal Cancer CAKI-1 cell line (GI50: 0.743 M). The
criterion for selectivity of a compound depends upon the ratio
:
m
m

60
M.N. Noolvi et al. / European Journal of Medicinal Chemistry 56 (2012) 56e69
Table 1
Physical data of synthesized compounds 4(aei), 7(aep) and 11(aei).
No.
Compounds
Molecular Formula
NSC number
Yield (%)
71
Melting point (ꢁC)
4a
C17H13N3OS
107164/760238
192e197
4b
4c
4d
4e
4f
C17H13N3O3S
C17H14N4OS
C17H12BrN3OS
C18H15N3O2S
C17H11Cl2N3OS
C17H14N4OS
C17H13N3O2S
C17H12ClN3OS
C22H15N3S
107166/760239
76
79
66
77
77
75
75
76
67
176e182
212e216
220e224
242e247
232e236
228e232
234e237
252e257
263e266
107168/760240
NS
107180/760241
NS
4g
4h
4i
108144/760535
NS
NS
NS
7a
7b
7c
C22H14ClN3S
C22H14FN3S
NS
NS
62
61
271e274
261e264
7d
7e
7f
C22H13Cl2N3S
NS
NS
NS
NS
NS
59
61
71
68
62
255e259
265e268
273e276
268e272
250e254
C22H16N4S
C22H15N3O2S
C22H14BrN3S
C22H15N3OS
7g
7h

M.N. Noolvi et al. / European Journal of Medicinal Chemistry 56 (2012) 56e69
61
Table 1 (continued )
No.
Compounds
Molecular Formula
C22H14FN3S
NSC number
NS
Yield (%)
56
Melting point (ꢁC)
7i
7j
7k
7l
242e245
248e251
256e260
261e264
C22H13ClFN3S
C22H13F2N3S
C22H12Cl2FN3S
105053/758274
NS
59
61
64
105054/758274
7m
7n
C22H15FN4S
NS
NS
71
54
239e243
253e258
C22H14FN3O2S
7o
7p
C22H13BrFN3S
C22H14FN3OS
NS
NS
58
52
242e245
267e270
11a
C16H9ClN4O2S
NS
51
234e238
11b
11c
C16H9ClN4O4S
106805/759798
10806/759799
62
61
228e231
262e264
C16H10ClN5O2S
11d
C16H8BrClN4O2S
NS
49
251e254
11e
11f
C17H11ClN4O3S
C16H7Cl3N4O2S
NS
NS
54
58
234e238
271e274
11g
C16H10ClN5O2S
NS
59
241e245
11h
11i
C16H9ClN4O3S
C16H8Cl2N4O2S
NS
NS
61
68
254e258
264e268
NSC: National Service Code. NS: Not Selected.

62
M.N. Noolvi et al. / European Journal of Medicinal Chemistry 56 (2012) 56e69
Fig. 2. Five dose assay of compound 4b (107166/760239).

M.N. Noolvi et al. / European Journal of Medicinal Chemistry 56 (2012) 56e69
63
Fig. 3. Five dose assay graph of compound 4b (107166/760239) against nine panel cancer cell line at NCI.
standard TMS (
d
: 0). Chemical shifts are reported in
d
scale (ppm).
(C]C),1452 (CH bend); 1H NMR (DMSO-d6)
d
ppm: 8.49 (s,1H, C-5-
Mass spectra of the synthesized compounds were recorded at MAT
120 in SAIF, Punjab University.
H, imidazole), 7.01e8.11 (m, 9H, AreH), 3.80 (s, 3H, OCH3); 13C NMR
(DMSO-d6)
d ppm: 163.0, 143.4, 140.5, 136.0, 133.1, 130.2, 129.3,
128.8, 127.5, 123.1, 122.0, 114.4, 55.9; HRMS (EI) m/z calcd for
5.1. Synthesis of 5-(4-methoxyphenyl)-1,3,4-thiadiazol-2-amine (2)
C17H13N3OS: 307.0779; found: 307.0775.
It is prepared as per the procedure given by G. Tu et al. [22].
5.2.2. 4-(2-(4-Methoxyphenyl)imidazo[2,1-b][1,3,4]thiadiazol-6-yl)
benzene-1,3-diol (4b)
5.2. General procedure for the synthesis of 2-(4-methoxyphenyl)-6-
substituted imidazo[2,1-b][1,3,4]thiadiazole (4aei)
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢀ1): 3635 (OeH strech), 3043 (CH
strech), 1565 (C]C), 1456 (CH bend); 1H NMR (DMSO-d6)
d ppm:
A mixture of 2 (0.1 mol) and 3(aei) (0.1 mol) was refluxed in dry
ethanol with few drops of DMF for 20e25 h. The excess of solvent
was distilled off and the solid hydrobromide that separated was
collected by filtration, suspended in water and neutralized by
aqueous sodium carbonate solution to get free base 4(aei). The
product was filtered, washed with water, dried and recrystallized
from ethanol.
12.02, 10.59 (s, 1H, 1H, OH), 8.41 (s, 1H, C-5-H, imidazoles), 6.22e
8.35 (m, 7H, AreH), 3.82 (s, 3H, OCH3); 13C NMR (DMSO-d6)
d
ppm: 163.4, 159.9, 156.7, 143.4, 140.5, 136.3, 130.3, 130.2, 123.1,
122.2, 114.4, 109.0, 104.1, 55.7; HRMS (EI) m/z calcd for
C17H13N3O3S: 339.0678; found: 339.0681.
5.2.3. 3-(2-(4-Methoxyphenyl)imidazo[2,1-b][1,3,4]thiadiazol-6-yl)
aniline (4c)
5.2.1. 2-(4-Methoxyphenyl)-6-phenylimidazo[2,1-b][1,3,4]
thiadiazole (4a)
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢀ1): 3384 and 3340 (NH2 strech),
3018 (CH strech), 1595 (C]C), 1449 (CH bend); 1H NMR (DMSO-d6)
This compound was prepared and purified as per the
above mentioned procedure: IR (KBr, cmꢀ1): 3064 (CH strech), 1570
d
ppm: 8.44 (s, 1H, C-5-H, imidazoles), 6.72e8.27 (m, 8H, AreH),

64
M.N. Noolvi et al. / European Journal of Medicinal Chemistry 56 (2012) 56e69
Fig. 4. Five dose assay of compound 4c (107168/760240).

M.N. Noolvi et al. / European Journal of Medicinal Chemistry 56 (2012) 56e69
65
Fig. 5. Five dose assay graph of compound 4c (107168/760240) against nine panel cancer cell line at NCI.
5.38 (s, 2H, NH2), 3.82 (s, 3H, OCH3); 13C NMR (DMSO-d6)
d
ppm:
125.6, 123.7, 122.4, 114.2, 55.6; HRMS (EI) m/z calcd for
163.7, 148.9, 143.4, 140.5, 136.7, 133.9, 130.1, 123.1, 122.9, 117.5, 116.3,
114.4, 55.5; HRMS (EI) m/z calcd for C17H14N4OS: 322.0888; found:
322.0892.
C18H15N3O2S: 337.0885; found: 337.0890.
5.2.6. 6-(2,4-Dichlorophenyl)-2-(4-methoxyphenyl)imidazo[2,1-b]
[1,3,4]thiadiazole (4f)
5.2.4. 6-(4-Bromophenyl)-2-(4-methoxyphenyl)imidazo[2,1-b]
[1,3,4]thiadiazole (4d)
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢀ1): 3076 (CH strech), 1578
(C]C), 1461 (CH bend), 654 (CeBr); 1H NMR (DMSO-d6)
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢀ1): 3063 (CH strech), 1564 (C]
C), 1457 (CH bend), 761 (CeCl); 1H NMR (DMSO-d6)
d
ppm: 8.41 (s,
1H, C-5-H, imidazoles), 6.88e8.36 (m, 7H, AreH), 3.82 (s, 3H,
OCH3); 13C NMR (DMSO-d6)
ppm: 163.9, 143.6, 140.4, 136.5, 135.7,
d
d
ppm: 8.41 (s, 1H, C-5-H, imidazoles), 7.20e7.84 (m, 8H, Are
133.7, 130.9, 130.3, 130.2, 128.1, 127.5, 123.1, 122.5, 114.4, 55.7; HRMS
(EI) m/z calcd for C17H11Cl2N3OS: 375.0000; found: 375.0004.
H), 3.86 (s, 3H, OCH3); 13C NMR (DMSO-d6)
d
ppm: 163.1,
143.3, 140.8, 136.9, 132.6, 130.2, 130.1, 123.1, 122.4, 114.6, 55.7;
HRMS (EI) m/z calcd for C17H12BrN3OS: 386.9884; found:
386.9889.
5.2.7. 4-(2-(4-Methoxyphenyl)imidazo[2,1-b][1,3,4]thiadiazol-6-yl)
aniline (4g)
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢀ1): 3367and 3352 (NH2 strech),
3089 (CH strech), 1586 (C]C), 1452 (CH bend); 1H NMR (DMSO-d6)
5.2.5. 2,6-Bis(4-methoxyphenyl)imidazo[2,1-b][1,3,4]thiadiazole
(4e)
This compound was prepared and purified as per the above
d
ppm: 8.39 (s, 1H, C-5-H, imidazoles), 7.11e8.20 (m, 8H, AreH),
5.63 (br s, 2H, NH2), 3.83 (s, 3H, OCH3); 13C NMR (DMSO-d6)
ppm: 163.4, 148.7, 143.8, 143.5, 140.6, 136.8, 130.6, 128.8, 123.3,
mentioned procedure: IR (KBr, cmꢀ1): 3046 (CH strech), 1556 (C]
C), 1454 (CH bend); 1H NMR (DMSO-d6)
d
ppm: 8.39 (s, 1H, C-5-H,
imidazoles), 6.88e8.36 (m, 8H, AreH), 3.82 (s, 6H, OCH3); 13C NMR
(DMSO-d6) ppm: 163.4, 160.7, 143.9, 140.4, 136.6, 130.4, 128.5,
d
122.2, 116.9, 114.1, 55.6; HRMS (EI) m/z calcd for C17H14N4OS:
322.0888; found: 322.0892.
d

66
M.N. Noolvi et al. / European Journal of Medicinal Chemistry 56 (2012) 56e69
Table 2
Table 3
NCI in vitro selectivity ratio of compound 4b (107166/760239) at five dose level in
M.
NCI in vitro selectivity ratio of compound 4c (107168/760240) at five dose level in
mM.
m
Panel
Cell line
GI50
Panel
Cell line
GI50
Concentration Subpanel Selectivity
Concentration Subpanel Selectivity
per cell line
MIDb
ratio
per cell line
MIDb
ratio
MIDa:MIDb
MIDa:MIDb
Leukemia
CCRF-CEM
HL-60
MOLT-4
RPMI-8226
SR
5.08
3.86
3.04
2.08
2.17
2.69
1.95
1.88
0.231
1.43
3.23
2.02
1.88
5.82
4.37
1.76
5.13
2.95
3.61
3.96
2.42
2.16
1.83
3.57
0.331
1.70
2.58
1.32
3.68
2.61
2.85
2.14
4.98
3.47
2.23
2.54
1.38
3.43
2.63
2.94
1.70
1.72
0.365
3.52
2.07
1.09
2.58
3.46
1.44
1.95
4.37
1.98
Leukemia
CCRF-CEM
HL-60
MOLT-4
RPMI-8226
SR
A549/ATCC
EKVX
HOP-62
1.77
1.77
3.00
1.28
3.27
5.84
1.01
3.12
0.114
1.53
4.90
7.15
3.36
1.63
7.08
1.08
3.51
5.26
4.27
5.34
6.08
4.13
2.88
2.51
12.4
1.07
7.65
3.38
1.74
5.48
2.58
5.35
3.76
2.19
17.3
2.92
2.65
3.40
1.54
8.54
4.97
4.46
2.72
4.70
1.11
4.50
0.743
1.38
4.18
7.56
1.46
1.20
6.79
2.20
1.58
2.33
3.88
1.37
1.83
3.77
3.24
0.77
1.32
2.21
1.69
1.18
Non small cell
lung cancer
A549/ATCC
EKVX
Non small cell
lung cancer
HOP-62
HOP-92
NCI-H226
NCI-H322M
NCI-H460
NCI-H522
COLO 2005
HCC-2998
HCT-116
HCT-15
HT 29
KM 12
SW-620
SF-268
SF-295
SF-539
SNB-19
SNB-75
U251
LOX IMVI
MALME-3M
M14
MDA-MB-435
SK-MEL-2
SK-MEL-28
UACC-257
UACC-62
HOP-92
1.91
NCI-H226
NCI-H23
NCI-H322M
NCI-H460
NCI-H522
COLO 2005
HCC-2998
HCT-116
HCT-15
HT 29
KM 12
SW-620
SF-268
SF-295
SF-539
SNB-19
SNB-75
U251
LOX IMVI
MALME-3M
M14
MDA-MB-435
SK-MEL-2
SK-MEL-28
SK-MEL-5
UACC-257
UACC-62
3.18
Colon cancer
Colon cancer
3.94
2.00
0.64
1.26
4.66
5.10
0.80
0.73
CNS cancer
Melanoma
CNS cancer
Melanoma
2.87
0.88
4.96
0.76
Ovarian cancer IGROV1
OVCAR-3
OVCAR-4
OVCAR-5
OVCAR-8
NCI/ADR-RES
SK-OV-3
786-0
A498
Ovarian cancer IGROV1
OVCAR-3
2.40
2.03
1.05
1.24
OVCAR-4
OVCAR-5
OVCAR-8
NCI/ADR-RES
SK-OV-3
786-0
A498
4.04
3.20
0.93
1.17
Renal cancer
ACHN
Renal cancer
CAKI-1
RXF-393
SN12C
TK-10
ACHN
CAKI-1
RXF-393
SN12C
TK-10
UO-31
Prostate cancer PC-3
DU-145
MCF-7
MDA-MB-81/ATCC 1.37
3.16
1.79
0.80
1.41
UO-31
Breast cancer
Prostate cancer PC-3
DU-145
Breast cancer
3.99
2.19
0.94
1.71
HS-5787
BT-549
T-47D
1.92
2.36
1.63
1.50
2.53
MCF-7
MDA-MB-281/ATCC
HS-5787
BT-549
T-47D
MDA-MB-468
MIDa
MDA-MB-468
For calculation of Selectivity Ratio, GI50 is converted into
m
M
concentration.
MIDa
MIDa ¼ Average sensitivity of all cell line in
m
M. MIDb ¼ Average sensitivity of all cell
line of a particular subpanel in
m
M.
For calculation of Selectivity Ratio, GI50 is converted into
m
M
concentration.
MIDa ¼ Average sensitivity of all cell line in
m
M. MIDb ¼ Average sensitivity of all cell
line of a particular subpanel in mM.
5.2.8. 2-(2-(4-Methoxyphenyl)imidazo[2,1-b][1,3,4]thiadiazol-6-yl)
phenol (4h)
This compound was prepared and purified as per the above
AreH), 3.84 (s, 3H, OCH3); 13C NMR (DMSO-d6)
d ppm: 163.0, 155.8,
143.9, 140.7, 136.5, 130.2, 128.6, 123.0, 122.6, 121.4, 120.4, 116.4,
114.4, 55.8; HRMS (EI) m/z calcd for C17H13N3O2S: 323.0728; found:
323.0731.
mentioned procedure: IR (KBr, cmꢀ1): 3619 (OeH strech), 3103 (CH
strech), 1593 (C]C), 1458 (CH bend); 1H NMR (DMSO-d6)
d
ppm:
10.7 (s, 1H, OH), 8.43 (s, 1H, C-5-H, imidazoles), 7.20e8.23 (m, 8H,

M.N. Noolvi et al. / European Journal of Medicinal Chemistry 56 (2012) 56e69
67
5.2.9. 6-(4-Chlorophenyl)-2-(4-methoxyphenyl)imidazo[2,1-b]
[1,3,4]thiadiazole (4i)
5.4.5. 4-(2-(Biphenyl-4-yl)imidazo[2,1-b][1,3,4]thiadiazol-6-yl)
aniline (7e)
This compound was prepared and purified as per the
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢀ1): 3321 and 3289 (NH2
strech), 3101 (CH strech), 1564 (C]C), 1459 (CH bend); 1H NMR
above mentioned procedure: IR (KBr, cmꢀ1): 3087 (CH strech), 1589
(C]C), 1454 (CH bend), 726 (CeCl); 1H NMR (DMSO-d6)
d
ppm:
8.34 (s, 1H, C-5-H, imidazoles), 6.97e7.80 (m, 8H, AreH), 3.80 (s,
3H, OCH3); 13C NMR (DMSO-d6)
ppm: 163.8, 143.9, 140.2, 136.7,
(DMSO-d6)
d
ppm: 8.46 (s, 1H, C-5-H, imidazoles), 7.12e8.32 (m,
ppm: 149.3, 146.8, 145.6, 145.1,
d
13H, AreH); 13C NMR (DMSO-d6)
d
134.4, 131.2, 130.2, 129.4, 128.9, 123.1, 122.8, 114.7, 55.9; HRMS (EI)
m/z calcd for C17H12ClN3OS: 341.0390; found: 341.0394.
139.2, 136.4, 130.2, 129.3, 128.0, 127.9, 127.5, 127.0, 123.8, 122.1,
119.1; HRMS (EI) m/z calcd for C22H16N4S: 368.1096; found:
368.1092.
5.3. Synthesis of 5-(2-substituted biphenyl-4-yl)-1,3,4-thiadiazol-
2-amine (6)
5.4.6. 4-(2-(Biphenyl-4-yl)imidazo[2,1-b][1,3,4]thiadiazol-6-yl)
benzene-1,3-diol (7f)
It is prepared as per the procedure given by G. Tu et al.
[22].
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢀ1): 3538 (OH strech), 3078 (CH
strech), 1591 (C]C), 1456 (CH bend); 1H NMR (DMSO-d6)
d
ppm:
11.21 (s, 1H, OH), 10.31 (s, 1H, OH), 8.49 (s, 1H, C-5-H, imidazoles),
7.01e8.23 (m, 12H, AreH); 13C NMR (DMSO-d6)
ppm: 161.9, 159.6,
5.4. General procedure for the synthesis of 2-(2-substituted biphenyl-
4-yl)-6-substituted imidazo[2,1-b][1,3,4]thiadiazole 7(aep)
d
148.3, 146.8, 144.1, 139.2, 133.3, 132.4, 130.2, 129, 128.9, 127.6, 127.2,
124.3, 116.1, 114.0, 112.6; HRMS (EI) m/z calcd for C22H15N3O2S:
385.0885; found: 385.0889.
A mixture of 6 (0.1 mol) and substituted phenacyl bromides
(0.1 mol) was refluxed in dry ethanol with few drops of DMF for
20e25 h. The excess of solvent was distilled off and the solid
hydrobromide that separated was collected by filtration, suspended
in water and neutralized by aqueous sodium carbonate solution to
get free base 7(aep). The product was filtered, washed with water,
dried and recrystallized from ethanol.
5.4.7. 2-(Biphenyl-4-yl)-6-(4-bromophenyl)imidazo[2,1-b][1,3,4]
thiadiazole (7g)
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢀ1): 3122 (CH strech), 1562 (C]
C), 1464 (CH bend), 630 (CeBr); 1H NMR (DMSO-d6)
d
ppm: 8.49 (s,
1H, C-5-H, imidazoles), 7.18e8.01 (m, 13H, AreH); 13C NMR (DMSO-
d6) ppm: 149.3, 146.8, 145.1, 139.2, 135.4, 133.1, 132.0, 130.2, 129.3,
5.4.1. 2-(Biphenyl-4-yl)-6-phenylimidazo[2,1-b][1,3,4]thiadiazole
(7a)
d
This compound was prepared and purified as per the above
128.0, 127.9, 127.4, 126.2, 124.1, 121.3; HRMS (EI) m/z calcd for
C22H14BrN3S: 431.0092; found: 431.0096.
mentioned procedure: IR (KBr, cmꢀ1): 3029 (CH strech), 1596 (C]
C), 1462 (CH bend); 1H NMR (DMSO-d6)
d
ppm: 8.54 (s, 1H, C-5-H,
imidazoles), 7.39e8.16 (m, 14H, AreH); 13C NMR (DMSO-d6)
d
ppm:
5.4.8. 2-(2-(Biphenyl-4-yl)imidazo[2,1-b][1,3,4]thiadiazol-6-yl)
phenol (7h)
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢀ1): 3611 (OH strech), 3088
(CH strech), 1568 (C]C), 1457 (CH bend); 1H NMR (DMSO-d6)
148.3, 145.8, 144.1, 140.2, 136.0, 133.4, 130.5, 129.2, 128.7, 128, 127.9,
127.6, 126.5, 125.2, 122.3; Mass (EI) m/z: 354.1730 [M þ 1].
5.4.2. 2-(Biphenyl-4-yl)-6-(4-chlorophenyl)imidazo[2,1-b][1,3,4]
thiadiazole (7b)
d
ppm: 8.43 (s, 1H, C-5-H, imidazoles), 7.10e8.23 (m, 13H, AreH);
This compound was prepared and purified as per the above
13C NMR (DMSO-d6)
d
ppm: 149.3, 146.8, 144.1, 139.2, 135.4,
mentioned procedure: IR (KBr, cmꢀ1): 3064 (CH strech), 1571 (C]
133.5, 132.1, 130.8, 129.7, 128.6, 127.4, 126.2, 124.3, 122.8, 120.5,
118.8; HRMS (EI) m/z calcd for C22H15N3OS: 369.0936; found:
369.0940.
C), 1457 (CH bend), 751 (CeCl); 1H NMR (DMSO-d6)
d
ppm: 8.38 (s,
1H, C-5-H, imidazoles), 7.01e8.11 (m, 13H, AreH); 13C NMR (DMSO-
d6) ppm: 148.3, 146.8, 143.1, 139.2, 135.3, 133.4, 132.1, 130.3, 129.2,
d
129.0, 128.9, 127.9, 127.6, 126.2, 120.3; HRMS (EI) m/z calcd for
C22H14ClN3S: 387.0597; found: 387.0594.
5.4.9. 2-(2-Fluorobiphenyl-4-yl)-6-phenylimidazo[2,1-b][1,3,4]
thiadiazole (7i)
This compound was prepared and purified as per the above
5.4.3. 2-(Biphenyl-4-yl)-6-(4-fluorophenyl)imidazo[2,1-b][1,3,4]
thiadiazole (7c)
mentioned procedure: IR (KBr, cmꢀ1): 3111 (CH strech), 1574
(C]C), 1466 (CH bend), 1110 (CeF); 1H NMR (DMSO-d6)
d
ppm:
8.56 (s, C-5-H, imidazoles), 7.01e8.34 (m, 13H, AreH); 13C NMR
(DMSO-d6) ppm: 163.2, 147.3, 144.1, 139.5, 138.2, 136, 136.0,
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢀ1): 3076 (CH strech), 1598 (C]
C), 1459 (CH bend), 1210 (CeF); 1H NMR (DMSO-d6)
d
ppm: 8.48 (s,
1H, C-5-H, imidazoles), 6.89e8.01 (m, 13H, AreH); 13C NMR
(DMSO-d6) ppm: 163.9, 148.3, 145.8, 143.1, 141.2, 134.4, 131.2,
d
132, 131.2, 130.2, 129, 128.7, 127.9, 127.6, 126.5, 123.6, 122.3,
118.4; HRMS (EI) m/z calcd for C22H14FN3S: 371.0892; found:
371.0896.
d
130.6, 129.6, 128.9, 127.9, 127.6, 127.2, 122.3, 118.0; HRMS (EI) m/z
calcd for C22H14FN3S: 371.0892; found: 371.0896.
5.4.10. 6-(4-Chlorophenyl)-2-(2-fluorobiphenyl-4-yl)imidazo[2,1-
b][1,3,4]thiadiazole (7j)
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢀ1): 3034 (CH strech), 1601 (C]
C), 1468 (CH bend), 1214 (CeF), 780 (CeCl); 1H NMR (DMSO-d6)
5.4.4. 2-(Biphenyl-4-yl)-6-(2,4-dichlorophenyl)imidazo[2,1-b]
[1,3,4]thiadiazole (7d)
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢀ1): 3011 (CH strech), 1584 (C]
C), 1457 (CH bend), 721 (CeCl); 1H NMR (DMSO-d6)
d
ppm: 8.54 (s,
1H, C-5-H, imidazoles), 7.39e8.16 (m,12H, AreH); 13C NMR (DMSO-
d6) ppm: 148.3, 145.8, 143.1, 139.2, 136.7, 134.6, 132.4, 131.9, 130.3,
d
ppm: 8.41 (s, 1H, C-5-H, imidazoles), 7.31e8.34 (m, 12H, AreH);
13C NMR (DMSO-d6)
d
ppm: 163.2, 148.3, 144.1, 139.5, 138.2,
d
135.3,134, 132.1, 131, 130.3, 129.2, 129, 128.9, 127.9, 126.6, 124.6,
121.3, 118.4; HRMS (EI) m/z calcd for C22H13ClFN3S: 405.0503;
found: 405.0508.
129.2, 128.3, 128.0, 127.9, 127.4, 126.4, 125.2, 121.3; HRMS (EI) m/z
calcd for C22H13Cl2N3S: 421.0207; found: 421.0211.

68
M.N. Noolvi et al. / European Journal of Medicinal Chemistry 56 (2012) 56e69
5.4.11. 2-(2-Fluorobiphenyl-4-yl)-6-(4-fluorophenyl)imidazo[2,1-b]
[1,3,4]thiadiazole (7k)
5.5. 5-(2-Chloro-5-nitrophenyl)-1,3,4-thiadiazol-2-amine (9)
This compound was prepared and purified as per the above
It is prepared as per the procedure given by G. Tu et al. [22].
mentioned procedure: IR (KBr, cmꢀ1): 3121 (CH strech), 1573 (C]
C), 1461 (CH bend), 1174 (CeF); 1H NMR (DMSO-d6)
d
ppm: 8.51
(s, 1H, C-5-H, imidazoles), 7.21e8.41 (m, 12H, AreH); 13C NMR
(DMSO-d6) ppm: 165.9, 162.2, 146.3, 143.1, 138.5, 136.2, 135, 133,
5.6. General procedure for the synthesis of 2-(2-chloro-5-
nitrophenyl)-6-substituted imidazo[2,1-b][1,3,4]thiadiazole 11(aei)
d
130.2, 129, 128.6, 127.6, 127.9, 126.6, 125.6, 123.3, 118.4, 116.0;
HRMS (EI) m/z calcd for C22H13F2N3S: 389.0798; found: 389.0794.
A mixture of 9 (0.1 mol) and 10 (aei) (0.1 mol) was refluxed in
dry ethanol with few drops of DMF for 20e25 h. The excess of
solvent was distilled off and the solid hydrobromide that separated
was collected by filtration, suspended in water and neutralized by
aqueous sodium carbonate solution to get free base 11(aei). The
product was filtered, washed with water, dried and recrystallized
from ethanol.
5.4.12. 6-(2,4-Dichlorophenyl)-2-(2-fluorobiphenyl-4-yl)imidazo
[2,1-b][1,3,4]thiadiazole (7l)
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢀ1): 3321 and 3279 (NH2
strech), 3041 (CH strech), 1593 (C]C), 1463 (CH bend), 1134 (Ce
F), 752 (CeCl); 1H NMR (DMSO-d6)
d
ppm: 8.44 (s, 1H, C-5-H,
imidazoles), 7.24e8.39 (m, 11H, AreH); 13C NMR (DMSO-d6)
ppm: 163.2, 148.3, 144.1, 139.5, 138.2, 136.7, 135.6, 134.9, 132.9,
5.6.1. 2-(2-Chloro-5-nitrophenyl)-6-phenylimidazo[2,1-b][1,3,4]
thiadiazole (11a)
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢀ1): 3064 (CH strech), 1589 (C]
C), 1549 and 1348 (NO2), 1458 (CH bend), 756 (CeCl); 1H NMR
d
130.3,130, 129.2, 129, 128.0, 127.9, 127.6, 126.3, 126.6, 124.3, 118.4;
HRMS (EI) m/z calcd for C22H12Cl2FN3S: 439.0113; found:
439.0118.
(DMSO-d6)
d
ppm: 8.46 (s,1H, C-5-H, imidazoles), 7.15e8.23 (m, 8H,
ppm: 174.1, 148.5, 144.1, 141.3, 139.18,
AreH); 13C NMR (DMSO-d6)
d
5.4.13. 4-(2-(2-Fluorobiphenyl-4-yl)imidazo[2,1-b][1,3,4]
thiadiazol-6-yl)aniline (7m)
138.2, 135.0, 133.2, 130.2, 129.7, 128.3, 127.5, 124.2, 123.3; HRMS (EI)
m/z calcd forC16H9ClN4O2S: 356.0135; found: 356.0139.
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢀ1): 3334 and 3298 (NH2 strech),
3021 (CH strech), 1576 (C]C), 1462 (CH bend), 1075 (CeF); 1H NMR
5.6.2. 4-(2-(2-Chloro-5-nitrophenyl)imidazo[2,1-b][1,3,4]
thiadiazol-6-yl)benzene-1,3-diol (11b)
(DMSO-d6)
d
ppm: 10.21 (s, 2H, NH2), 8.34 (s, 1H, C-5-H, imidaz-
ppm: 162.2,
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢀ1): 3612 (OH strech), 3078 (CH
strech), 1598 (C]C), 1552 and 1346 (NO2), 1458 (CH bend), 741 (Ce
oles), 7.02e8.21 (m, 12H, AreH); 13C NMR (DMSO-d6)
d
148.6, 144.3, 143.1, 138.5, 136.2, 134, 132, 130.2, 129, 128.3, 127.9,
126.6, 124.0, 123.6, 122.3, 118.4, 116.1; HRMS (EI) m/z calcd for
C22H15FN4S: 386.1001; found: 386.1005.
Cl); 1H NMR (DMSO-d6)
d
ppm:3545 (OH strech), 8.38 (s, 1H, C-5-H,
imidazoles), 7.18e8.01 (m, 6H, AreH); 13C NMR (DMSO-d6)
d
ppm:
173.1, 161.9, 159.6, 151.5, 148.1, 141.3, 139.18, 136.2, 135.3, 132.2,
129.3, 126.2, 123.3, 118.1, 115.0, 112.6; HRMS (EI) m/z calcd for
C16H9ClN4O4S: 388.0033; found: 388.0038.
5.4.14. 4-(2-(2-Fluorobiphenyl-4-yl)imidazo[2,1-b][1,3,4]
thiadiazol-6-yl)benzene-1,3-diol (7n)
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢀ1): 3564 (s, 1H, OH), 3131 (CH
strech), 1584 (C]C), 1462 (CH bend), 1170 (CeF); 1H NMR (DMSO-
5.6.3. 3-(2-(2-Chloro-5-nitrophenyl)imidazo[2,1-b][1,3,4]
thiadiazol-6-yl)aniline (11c)
d6)
d
ppm: 12.1 (s, 1H, OH), 11.3 (s, 1H, OH), 8.41 (s, 1H, C-5-H,
ppm:
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢀ1): 3345 and 3301 (NH2 strech),
3071 (CH strech), 1591 (C]C), 1554 and 1342 (NO2), 1459 (CH
imidazoles), 7.11e8.31 (m, 11H, AreH); 13C NMR (DMSO-d6)
d
163.9, 160.2, 158.6, 146.3, 143.1, 138.5, 137.2, 135, 133.3, 131.5, 130.2,
129, 127.6, 126.6, 124.6, 122.3, 118.4, 116, 111.0, 109.6; HRMS (EI) m/z
calcd for C22H14FN3O2S: 403.0791; found: 403.0795.
bend), 741 (CeCl); 1H NMR (DMSO-d6)
d
ppm: 10.21 (s, 2H, NH2),
8.42 (s, 1H, C-5-H, imidazoles), 7.01e8.28 (m, 7H, AreH); 13C NMR
(DMSO-d6) ppm: 173.1, 152.9, 149.5, 146.1, 141.3, 139.18, 138.2,
d
5.4.15. 6-(4-Bromophenyl)-2-(2-fluorobiphenyl-4-yl)imidazo[2,1-
b][1,3,4]thiadiazole (7o)
135.8, 133.2, 131.0, 129.3, 126.2, 124.3, 120.7, 119.5, 115.2; HRMS (EI)
m/z calcd for C16H10ClN5O2S: 371.0244; found: 371.0249.
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢀ1): 3123 (CH strech), 1593 (C]
C), 1462 (CH bend), 1079 (CeF), 653 (CeBr); 1H NMR (DMSO-d6)
5.6.4. 6-(4-Bromophenyl)-2-(2-chloro-5-nitrophenyl)imidazo[2,1-
b][1,3,4]thiadiazole (11d)
d
ppm: 8.44 (s, 1H, C-5-H, imidazoles), 7.31e8.31 (m, 12H, AreH);
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢀ1): 3079 (CH strech), 1590 (C]
C), 1555 and 1346 (NO2), 1452 (CH bend), 731 (CeCl), 631 (CeBr);
13C NMR (DMSO-d6)
d
ppm: 163.6, 153.3, 148.1, 140.5, 138.2, 135.8,
133.1, 132.0, 130, 129.2, 129, 128.3, 126.9, 125.6, 123.6, 123.1, 122.3,
118.4; HRMS (EI) m/z calcd for C22H13BrFN3S: 448.9998; found:
448.9994.
1H NMR (DMSO-d6)
d
ppm: 8.34 (s, 1H, C-5-H, imidazoles), 7.12e
8.28 (m, 7H, AreH); 13C NMR (DMSO-d6)
d
ppm: 172.1, 149.5,
143.1, 141.3, 138.18, 137.2, 134.1, 133.0, 132.2, 130.3, 129.3, 127.2,
126.1, 124.3; HRMS (EI) m/z calcd for C16H8BrClN4O2S: 433.9240;
found: 433.9246.
5.4.16. 2-(2-(2-Fluorobiphenyl-4-yl)imidazo[2,1-b][1,3,4]
thiadiazol-6-yl)phenol (7p)
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢀ1): 3561 (OH strech), 3067 (CH
strech), 1583 (C]C), 1462 (CH bend), 1188 (CeF); 1H NMR (DMSO-
5.6.5. 2-(2-Chloro-5-nitrophenyl)-6-(4-methoxyphenyl)imidazo
[2,1-b][1,3,4]thiadiazole (11e)
d6)
d
ppm: 11.12 (s, 1H, OH), 8.41 (s, 1H, C-5-H, imidazoles), 7.11e
ppm: 161.8, 158.2,
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢀ1): 3078 (CH strech), 1594 (C]
C), 1554 and 1342 (NO2), 1452 (CH bend), 769 (CeCl); 1H NMR
8.31 (m, 12H, AreH); 13C NMR (DMSO-d6)
d
148.3, 142.1, 139.5, 136.2, 134, 130.1, 131.5, 130, 129.2, 128, 127.9,
126.6, 124.6, 122.3, 121.8, 120.5, 118.8, 116.4; HRMS (EI) m/z calcd for
C22H14FN3OS: 387.0842; found: 387.0846.
(DMSO-d6)
d
ppm: 8.38 (s, 1H, C-5-H, imidazoles), 6.98e8.23 (m,
ppm: 173.1, 162.6, 149.5, 143.1,
7H, AreH); 13C NMR (DMSO-d6)
d

M.N. Noolvi et al. / European Journal of Medicinal Chemistry 56 (2012) 56e69
69
139.3, 137.18, 136.2, 130.2, 129.3, 128.3, 126.5, 123.2, 122.3, 116.8,
55.8; HRMS (EI) m/z calcd for C17H11ClN4O3S: 386.0240; found:
386.0244.
(DMSO-d6)
d
ppm: 8.38 (s, 1H, C-5-H, imidazoles), 6.68e7.98 (m,
ppm: 173.1, 149.5, 144.1, 139.3,
7H, AreH); 13C NMR (DMSO-d6)
d
138.18, 136.2, 134.3, 132.1, 130.2, 129.3, 128.9, 127.3, 126.2, 124.3;
HRMS (EI) m/z calcd for C16H8Cl2N4O2S: 389.9745; found: 389.9749.
5.6.6. 2-(2-Chloro-5-nitrophenyl)-6-(2,4-dichlorophenyl)imidazo
[2,1-b][1,3,4]thiadiazole (11f)
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢀ1): 3029 (CH strech), 1595 (C]
C), 1555 and 1349 (NO2), 1456 (CH bend), 721 (CeCl); 1H NMR
Acknowledgments
The authors are thankful to Director General, Department of
Science and Technology, New Delhi for funding the project
(Grant.No.SR/FT/LS-0024/2008). We are also greateful of NCI, NIH,
Bethesda, Maryland, USA for anticancer screening.
(DMSO-d6)
d
ppm: 8.41 (s, 1H, C-5-H, imidazoles), 6.88e8.12 (m,
ppm: 172.1, 149.5, 145.1, 141.3,
6H, AreH); 13C NMR (DMSO-d6)
d
139.18, 136.2, 135.7, 132.6, 131.9, 130.2, 129.3, 128.0, 127.3, 126.2,
125.4, 123.3; HRMS (EI) m/z calcd for C16H7Cl3N4O2S: 423.9355;
found: 423.9359.
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5.6.7. 4-(2-(2-Chloro-5-nitrophenyl)imidazo[2,1-b][1,3,4]
thiadiazol-6-yl)aniline (11g)
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢀ1):3368 and 3228 (NH2 strech),
3089 (CH strech), 1595 (C]C), 1556 and 1345 (NO2), 1459 (CH
bend), 721 (CeCl); 1H NMR (DMSO-d6)
d
ppm: 11.21 (s, 2H, NH2),
8.39 (s, 1H, C-5-H, imidazoles), 7.01e8.12 (m, 7H, AreH); 13C NMR
(DMSO-d6) ppm: 173.1, 147.5, 145.6, 143.1, 141.3, 139.18, 137.2,
d
132.2, 130.3, 129.3, 127.2, 125.0, 122.3, 118.1; HRMS (EI) m/z calcd for
C16H10ClN5O2S: 371.0244; found: 371.0249.
5.6.8. 2-(2-(2-Chloro-5-nitrophenyl)imidazo[2,1-b][1,3,4]
thiadiazol-6-yl)phenol (11h)
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢀ1): 3583 (OH strech), 3021 (CH
strech), 1579 (C]C), 1558 and 1344 (NO2), 1450 (CH bend), 763 (Ce
Cl); 1H NMR (DMSO-d6)
d
ppm: 12.34 (s, IH, OH), 8.49 (s, 1H, C-5-H,
imidazoles), 6.96e8.12 (m, 7H, AreH); 13C NMR (DMSO-d6)
d
ppm:
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173.1, 159.2, 149.5, 144.1, 141.3, 139.18, 136.2, 134.5, 132.1, 130.2,
129.3, 128.2, 126.3, 125.8, 122.5, 119.8; HRMS (EI) m/z calcd for
C16H9ClN4O3S: 372.0084; found: 372.0089.
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5.6.9. 2-(2-Chloro-5-nitrophenyl)-6-(4-chlorophenyl)imidazo[2,1-
b][1,3,4]thiadiazole (11i)
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢀ1): 3084 (CH strech), 1590 (C]
C), 1558 and 1342 (NO2), 1458 (CH bend), 764 (CeCl); 1H NMR