Synthesis and anti-leishmanial activity of 5-(5-nitrofuran-2-yl)-1,3,4- thiadiazol-2-amines containing N-[(1-benzyl-1H-1,2,3-triazol-4-yl)methyl] moieties

Article abstract of DOI:10.1016/j.ejmech.2012.01.046

A novel series of 5-(5-nitrofuran-2-yl)-1,3,4-thiadiazol-2-amines were synthesized by introducing N-[(1-benzyl-1H-1,2,3-triazol-4-yl)methyl] moiety as a new functionality on the C-2 amine of thiadiazole ring via click chemistry. The title compounds namely, N-[(1-benzyl-1H-1,2,3-triazol-4-yl)methyl]-5-(5- nitrofuran-2-yl)-1,3,4-thiadiazol-2-amines (3a-n) were characterized by IR, NMR and MS spectra. These compounds were evaluated for their in vitro anti-leishmanial activity against promostigote form of the Leishmania major. Most compounds exhibited good anti-leishmanial activity against the promastigote form of L. major. The most active compound against promostigotes was found to be 4-methylbenzyl analog 3i, which significantly decreases the number of intracellular amastigotes per macrophage, percentage of macrophage infectivity and infectivity index.

Full text of DOI:10.1016/j.ejmech.2012.01.046

European Journal of Medicinal Chemistry 50 (2012) 124e128
Contents lists available at SciVerse ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Synthesis and anti-leishmanial activity of 5-(5-nitrofuran-2-yl)-1,3,4-thiadiazol-
2-amines containing N-[(1-benzyl-1H-1,2,3-triazol-4-yl)methyl] moieties
Azar Tahghighi a, Sepideh Razmi b, Mohammad Mahdavi c, Parham Foroumadi d, Sussan K. Ardestani b,
,d,
*
Saeed Emami e, Farzad Kobarfard f, Siavoush Dastmalchi a, Abbas Shafiee c, Alireza Foroumadi c
a Department of Medicinal Chemistry, School of Pharmacy, Tabriz University of Medical Sciences, Tabriz, Iran
b Institute of Biochemistry and Biophysics, Department of Biochemistry, University of Tehran, Tehran, Iran
c Faculty of Pharmacy and Pharmaceutical Sciences Research Center, Tehran University of Medical Sciences, Tehran, Iran
d Faculty of Pharmacy and Pharmaceutics Research Center, Kerman University of Medical Sciences, Kerman, Iran
e Department of Medicinal Chemistry and Pharmaceutical Sciences Research Center, Faculty of Pharmacy, Mazandaran University of Medical Sciences, Sari, Iran
f Department of Medicinal Chemistry, School of Pharmacy, Shahid Beheshti University of Medical Sciences, Tehran, Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
A novel series of 5-(5-nitrofuran-2-yl)-1,3,4-thiadiazol-2-amines were synthesized by introducing
N-[(1-benzyl-1H-1,2,3-triazol-4-yl)methyl] moiety as a new functionality on the C-2 amine of thiadiazole
ring via click chemistry. The title compounds namely, N-[(1-benzyl-1H-1,2,3-triazol-4-yl)methyl]-5-
(5-nitrofuran-2-yl)-1,3,4-thiadiazol-2-amines (3aen) were characterized by IR, NMR and MS spectra.
These compounds were evaluated for their in vitro anti-leishmanial activity against promostigote form of
the Leishmania major. Most compounds exhibited good anti-leishmanial activity against the promastigote
form of L. major. The most active compound against promostigotes was found to be 4-methylbenzyl
analog 3i, which significantly decreases the number of intracellular amastigotes per macrophage,
percentage of macrophage infectivity and infectivity index.
Received 28 November 2011
Received in revised form
22 January 2012
Accepted 24 January 2012
Available online 30 January 2012
Keywords:
Antileishmanial activity
5-Nitrofuran
1,3,4-Thiadiazole
1H-1,2,3-Triazole
Ó 2012 Elsevier Masson SAS. All rights reserved.
1. Introduction
treatment [2e4]. In addition, the development of the clinical
resistance and increase of co-infected leishmaniasis with AIDS in
Leishmaniasis is a major public health problem in new world
and causing morbidity and mortality in tropical and subtropical
regions of the world. According to WHO reports, it is estimated that
15e20 million infected and annually about three million people
will threaten worldwide [1]. The disease is caused by different
species of Leishmania sp. and transmitted by phelbotomine sand-
fly. It is manifested in three forms; visceral leishmaniasis, cuta-
neous leishmaniasis, muco-cutaneous leishmaniasis. In spite of the
importance of these tropical and subtropical infections, an effective
vaccine is not yet available. Some currently used drugs such as,
sodium stibogluconate (pentostam), meglumine antimonate (glu-
cantime), miltefosine, pentamidine and amphotericin B are toxic
and cause severe side effects such as pancreatitis and cardiac
toxicity. Moreover, they are expensive and required long-term
some regions is a serious problem [5]. Thus, the development of
new, efficient, cheap and safe drug for the treatment of leishman-
iasis is imperative. Substituted five-membered heterocyclic rings
have diverse antimicrobial activities. Recently, several furanyl and
thiophenyl azoles were synthesized and evaluated for their in vitro
anti-leishmanial activity [6].
In recent years, significant attention have been aroused to ‘click
chemistry’ for their easy and efficient synthesis of 1,2,3-triazole
[7,8] that has occupied an important position in medicinal chem-
istry [9] owing to its chemotherapeutic effect such as antineoplasm
[10], antibacterial [11], antifungal [12], antitubercular [13], anti-HIV
[14] activities. On the other hand, 1,3,4-thiadiazole is well estab-
lished to have the excellent antiparasitic property and its attach-
ment to other heterocycles often changes the bioresponses,
depending upon the type of substituent and position of attachment
[15]. In our previous papers [16e18], we described the synthesis
and in vitro anti-leishmanial activity of a series of 5-(5-nitrofuran-
2-yl)-1,3,4-thiadiazoles 1 containing a cyclic amine at C-2 position
of thiadiazole (Fig. 1). Recently, we have focused our attention on
modification of the C-2 cyclic amine of the 5-(5-nitrofuran-2-yl)-
* Corresponding author. Faculty of Pharmacy and Pharmaceutical Sciences
Research Center, Tehran University of Medical Sciences, Tehran 14174, Iran.
Tel.: þ98 21 66954708; fax: þ98 21 66461178.
E-mail address: aforoumadi@yahoo.com (A. Foroumadi).
0223-5234/$ e see front matter Ó 2012 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2012.01.046

A. Tahghighi et al. / European Journal of Medicinal Chemistry 50 (2012) 124e128
125
Cyclic amine
3. Pharmacology
Acyclic amine
N
N
N
N
NHR
O2N
Primarily, the anti-promastigote activity of target compounds
3aen was evaluated by direct counting and MTT assay according to
the literature method [20]. The IC50s (50% inhibitory concentra-
tions) of compounds against promastigote form of Leishmania
major (vaccine strain MRHO/IR/75/ER, obtained from Pasteur
institute, Tehran, Iran) was determined. Two or more independent
experiments in triplicate were performed for each compound. The
IC50s were calculated by linear regression analysis, expressed in
mean values and presented in Table 1. Meglumine antimonate
(GlucantimeÒ) was used as a standard drug.
N
X
O2N
S
O
O
S
1
2
R = aminoalkyl, heteroarylalkyl,...
X = CH2, O, NH, NR
N
N
R
O2N
N
H
N
N
S
O
N
3
Also, the in vitro anti-amastigote activity of compounds was
determined in mouse peritoneal macrophages. Briefly, macro-
phages were placed on sterile glass cover slips in 24-well plates
(1 ꢀ 106/well). Then, the stationary phase promastigotes in RPMI
were added (2 ꢀ 106 parasites/well, three parasites/macrophage) to
macrophage monolayer and the plates were incubated for 2 h. After
removal of extracellular parasites by washing, new media con-
taining IC50 concentration of the compounds were added. Two sets
of experiments were carried out for each compound at 24 h.
Following these procedures, cells were fixed with methanol and
stained with Giemsa stain (Sigma). The infectivity index was
determined by multiplying the percentage of macrophages that
had at least one intracellular parasite by the average number of
intracellular parasites per infected macrophage (100 cells were
examined/well) [21]. The results of in vitro activity of selected
compounds against intramacrophage amastigotes of L. major are
depicted in Fig. 2.
Fig. 1. General structures of previously described compounds
designed compounds 3.
1 and 2, and new
1,3,4-thiadiazole-2-amines by introducing acyclic amines (Fig. 1,
structure 2) [19]. Accordingly, our strategy to achieve a novel anti-
leishmanial agent has focused on introducing N-[(1-benzyl-1H-
1,2,3-triazol-4-yl)methyl] moiety as a new functionality on the C-2
amine of thiadiazole ring via click chemistry. Thus, we report here
the synthesis and anti-leishmanial activity of N-[(1-benzyl-1H-
1,2,3-triazol-4-yl)methyl]-5-(5-nitrofuran-2-yl)-1,3,4-thiadiazol-2-
amines (3aen) (Fig. 1).
2. Chemistry
The synthetic pathway to achieve title compounds 3aen is
shown in Scheme 1. The alkyne derivative 5 was synthesized in 76%
yield by the reaction of 2-chloro-1,3,4-thiadiazole 4 with propargyl
amine in absolute ethanol. The benzyl azide intermediates 7 were
prepared in situ by the reaction of benzyl chlorides 6 with excess
NaN3 (1.5 equiv) in the presence of triethylamine in t-BuOH/water.
The key step was 1,3-dipolar cycloaddition of alkyne 5 with benzyl
azides 7 using catalytic amount of copper iodide in t-BuOH/H2O at
room temperature. All of the compounds were characterized by IR,
NMR and MS spectra.
4. Results and discussion
For evaluation of anti-leishmanial properties of target
compounds, the in vitro activity was assessed against promastigote
(extracellular parasite) and amastigote (intramacrophage parasite)
forms of L. major. The IC50 values of compounds against promasti-
gotes are presented in Table 1. Generally, compounds 3aed, 3gei,
3k, and 3m showed good activity (IC50 values <26
by compound 3j with IC50 value of z33 M. The remaining
mM), followed
m
compounds exhibited weak or no activity against promastigotes
N
N
Cl
R
Table 1
O2N
Cl
Anti-promastigote activity (IC50, mM) of compounds 3aen.
S
O
6
4
N N
S
R
a
b
O2N
O
N
H
N
N
N
N
N
N
N
N
R
O2N
N
H
S
O
Compound
R
IC50 (mM)
7
5
3a
3b
3c
3d
3e
3f
3g
3h
3i
3j
3k
3l
3m
3n
H
2-F
4-F
2-Cl
3-Cl
4-Cl
2-Me
3-Me
19. 6 ꢁ 0.56
19.0 ꢁ 0.35
21.4 ꢁ 1.86
18.9 ꢁ 0.12
107.7 ꢁ 0.57
88.8 ꢁ 0.9
c
25.2 ꢁ 0.54
21. 9 ꢁ 0.89
12.2 ꢁ 0.66
32.7 ꢁ 0.31
17.4 ꢁ 0.76
103.5 ꢁ 0.58
19. 9 ꢁ 0.84
131.8 ꢁ 1.11
N
N
R
4-Me
O2N
N
H
N
N
S
O
4-NO2
2-F-6-Cl
2,3-Cl2
2,4-Cl2
3,4-Cl2
N
3a-n
Scheme 1. Synthesis of compounds 3aen. Reagents and conditions: (a) propargyl
amine, EtOH, reflux; (b) sodium azide, triethyl amine, t-BuOH, H2O; (c) CuI.
The IC50 of Glucantime was 68.3 mM.

126
A. Tahghighi et al. / European Journal of Medicinal Chemistry 50 (2012) 124e128
macrophage infectivity and infectivity index (Fig. 2A, B and C,
respectively). It is notable that 4-Methyl analog 3i which showed
potent activity against promastigotes was the most effective
compound against amastigotes as showed in the terms of amasti-
gote number per macrophage, the percentage of macrophage
infectivity and infectivity index.
In our previous studies [16e18], we have presented the
synthesis and in vitro anti-leishmanial activity of 5-(5-nitrofuran-
2-yl)-1,3,4-thiadiazoles against promastigote and amastigote
forms L. major strain, which several of them showed good activity
in both forms of promastigote and amastigote. Previous results
demonstrated that an amine substituent at C-2 position of 5-(5-
nitrofuran-2-yl)-1,3,4-thiadiazoles which connected to a distal
hydrophilic atom (O or N) has profound role in the biological
activity of these compounds. The distal amine could be a part of
cyclic amine (e.g. piperazine), acyclic amine (e.g. aminoalkylamine)
or nitrogen containing heteroaromatic linked to C-2 amine of
1,3,4-thiadiazol-2-amines. The former type of pendent amine can
be exemplified by pyrimidynyl methyl moiety [19]. In this study,
we described the synthesis and anti-leishmanial activity of a ser-
ies of 5-(5-nitrofuran-2-yl)-1,3,4-thiadiazol-2-amines containing
N-[(1-benzyl-1H-1,2,3-triazol-4-yl)methyl] residue. In this case,
1,2,3-triazole ring plays as nitrogen containing heterocycle in distal
position. From the results, it demonstrated that C-2 substituent is
the most flexible site for chemical modification and is an area
where it determines the potency and physicochemical properties of
5-(5-nitrofuran-2-yl)-1,3,4-thiadiazol-2-amines.
5. Conclusion
In summary, a series of N-[(1-benzyl-1H-1,2,3-triazol-4-yl)
methyl]-5-(5-nitrofuran-2-yl)-1,3,4-thiadiazol-2-amines
were
synthesized and evaluated for their in vitro inhibitory activity
against the Leishmania parasite. Most of the target compounds
exhibited good anti-leishmanial activity against the promastigote
form of L. major. The most active compound against promostigotes
was found to be 4-methylbenzyl analog 3i, which significantly
decreases the number of intracellular amastigotes per macrophage,
percentage of macrophage infectivity and infectivity index.
6. Experimental protocols
Fig. 2. In vitro activity of selected compounds against intramacrophage amastigotes of
L. major. (A) The mean number of amastigotes per macrophage after treatment with
selected compounds for 24 h. (B) The percentage of infected macrophages after
treatment. (C) Infectivity index of macrophages cultured 24 h in presence of selected
compound. The infectivity index was determined by multiplying the percentage of
macrophages that had at least one intracellular parasite by the average number of
intracellular parasite per infected macrophage (100 cells were examined/well).
6.1. Chemistry
All starting materials, reagents and solvents were purchased
from Merck AG Chemical. The intermediate 2-chloro-5-
(5-nitrofuran-2-yl)-1,3,4-thiadiazole (4) was prepared from 5-
nitrofurfurylidene diacetate according to the previously described
method [16]. Melting points were determined on a Kofler hot stage
apparatus and are uncorrected. The IR spectra were obtained on
a Shimadzu 470 spectrophotometer (potassium bromide dicks). 1H
NMR spectra were recorded on a Varian unity 500 and 400 spec-
(IC50 ꢂ 88.8
mM). 4-Methyl analog 3i was the most potent
compound in the terms of anti-promastigote activity. Based on
structural points of view, introduction of different substituents on
pendent benzyl group could not improve the activity with the
exception of 4-methyl substitution which slightly increased the
anti-promastigote activity. Among the halogenated compounds,
derivatives having 2-halo- substitutions (compounds 3b, 3d, 3k
and 3m) exhibited significant activity. Thus, the introduction of
halogen on 3-position of benzyl moiety could be tolerated but
3-chloro substituent decreased anti-promostigote activity (as in
trometer and chemical shifts (d) are reported in parts per million
(ppm) relative to tetramethylsilane (TMS) as an internal standard.
The mass spectra were run on an Agilent 6410 LC-MS or a Finigan
TSQ-70 spectrometer (Finigan, USA) at 70 eV. Elemental analyses
were carried out on CHN-O rapid elemental analyzer (GmbH-Ger-
many) for C, H and N, and the results are within ꢁ0.4% of the
theoretical values. Merck silica gel 60 F254 plates were used for
analytical TLC.
compounds 3e, 3l, and 3n with IC50 values >100 mM, respectively).
Compounds 3a-d, 3h, 3i, 3k, and 3m having good inhibition
against promastigotes were also evaluated for their activity
against amastigote form of L. major in marine peritoneal macro-
phages (Fig. 2). All tested compounds significantly decreased the
number of intracellular amastigotes per macrophage, percentage of
6.1.1. Synthesis of 5-(5-nitrofuran-2-yl)-N-(prop-2-ynyl)-1,3,4-
thiadiazol-2-amine (5)
A mixture of compound 4 (0.1 g, 0.43 mmol) with propargyl
amine (0.03 mL, 0.43 mmol) in absolute ethanol (7 mL) was

A. Tahghighi et al. / European Journal of Medicinal Chemistry 50 (2012) 124e128
127
refluxed for 24 h. The completion of reaction was detected by TLC.
The solvent was evaporated under reduced pressure and the
resulting product was purified using silica gel column chromatog-
raphy eluting with CHCl3 and then EtOAc. Compound 5 was ob-
reduced pressure. Compound 3d was obtained as a yellow solid.
Yield 67%; m.p 185e186 ꢃC; MS (m/z, %) 419 ([M þ 2]þ, 9), 417 (Mþ,
24), 264 (8), 216 (8), 178 (24), 138 (9), 127 (35), 125 (100), 99 (7),
89(20), 82 (15); IR (KBr, cmꢄ1) 3235,1618,1533,1493,1351; 1H NMR
tained as a yellow solid. Yield 76%; m.p 204e206 ꢃC; IR (KBr, cmꢄ1
)
(DMSO-d6, 500 MHz) d 8.84 (br s, 1H, eNHe), 8.14 (s, 1H, triazole),
3299, 3207, 2121, 1566, 1345; 1H NMR (CDCl3, 400 MHz)
d
7.45
7.85 (d, 1H, J ¼ 3.8 Hz, furan), 7.51 (d, 1H, J ¼ 7.6 Hz, phenyl),
7.39e7.34 (m, 3H, furan and phenyl), 7.21 (d, 1H, J ¼ 7.6 Hz, phenyl),
5.7 (s, 2H, eCH2-), 4.63 (d, 2H, J ¼ 5 Hz, eCH2e); Anal. calcd for
C16H12ClN7O3S: C, 45.99; H, 2.89; N, 23.47. Found: C, 46.14; H, 3.1; N,
23.44.
(d, 1H, J ¼ 4 Hz, furan), 7.16 (d, 1H, J ¼ 4 Hz, furan), 4.27 (br s, 2H,
eCH2e), 2.35 (s, 1H, ^CH). Anal. calcd for C9H6N4O3S: C, 43.20; H,
2.42; N, 22.39. Found: C, 43.53; H, 2.54; N, 22.12.
6.1.2. General procedure for the synthesis of compounds 3aen
A mixture of 1.3 mmol of Et3N, 0.9 mmol of sodium azide and
1.1 mmol of appropriate benzyl chloride 6 in 4 mL of water and 4 mL
of t-BuOH was stirred vigorously for 30 min at room temperature.
Then, 0.5 mmol of compound 5 and 7% mol of CuI were added into
the mixture and stirred for 24e56 h at room temperature. The
completion of reaction was detected by TLC. The reaction mixture
was diluted with water, cooled in ice. A brown precipitate was
formed, filtrated and washed three times with 20 mL of cold water.
The resulting product was purified using silica gel column
chromatography.
6.1.2.5. N-((1-(3-Chlorobenzyl)-1H-1,2,3-triazol-4-yl)methyl)-5-(5-
nitrofuran-2-yl)-1,3,4-thiadiazol-2-amine (3e). The resulting product
was purified using silica gel column chromatography eluting with
CHCl3 and then EtOAc. Compound 3e was obtained as an orange
solid. Yield 71%; m.p 195e196 ꢃC; IR (KBr, cmꢄ1) 3241, 1550, 1510,
1489, 1352; 1H NMR (DMSO-d6, 400 MHz)
d
8.82 (t, 1H, J ¼ 5.6 Hz,
eNHe), 8.2 (s, 1H, triazole), 7.83 (d, 1H, J ¼ 3.6 Hz, furan), 7.41e7.38
(m, 3H, phenyl), 7.34 (d, 1H, J ¼ 3.6 Hz, furan), 7.28e7.25 (m, 1H,
phenyl), 5.61 (s, 2H, eCH2-), 4.63 (d, 2H, J ¼ 5.6 Hz, eCH2-). Anal.
calcd for C16H12ClN7O3S: C, 45.99; H, 2.89; N, 23.47. Found: C, 45.80;
H, 2.63; N, 23.75.
6.1.2.1. N-((1-Benzyl-1H-1,2,3-triazol-4-yl)methyl)-5-(5-nitrofuran-2-
yl)-1,3,4-thiadiazol-2-amine (3a). The resulting product was purified
using silica gel column chromatography eluting with CHCl3 and then
EtOAc containing 2% methanol. Compound 3a was obtainþed as
a yellow solid. Yield: 76%; m.p 180e182 ꢃC; MS (m/z, %) 383 (M , 69),
368 (26), 353 (7), 339 (7), 313 (16), 292 (10), 264 (28), 236 (13), 212
(9), 201 (9), 183 (13), 144 (27), 104 (7), 91(100), 82 (10), 65 (8), 57
(10), 43(8); IR (KBr, cmꢄ1) 3200, 1542, 1489, 1459, 1358; 1H NMR
6.1.2.6. N-((1-(4-Chlorobenzyl)-1H-1,2,3-triazol-4-yl)methyl)-5-(5-
nitrofuran-2-yl)-1,3,4-thiadiazol-2-amine (3f). The resulting product
was purified using silica gel short column chromatography eluting
with CHCl3 and then EtOAc. Compound 3f was obtained as an orange
solid. Yield 35%; m.p 212e213 ꢃC; IR (KBr, cmꢄ1) 3202, 1566, 1530,
1462, 1353. 1H NMR (DMSO-d6, 500 MHz)
d
8.83 (t, 1H, J ¼ 5.4 Hz,
eNHe), 8.18 (s, 1H, triazole), 7.86 (d, 1H, J ¼ 4 Hz, furan), 7.44 (d, 2H,
J ¼ 8.4 Hz, phenyl), 7.36 (d,1H, J ¼ 4 Hz, furan), 7.34 (d, 2H, J ¼ 8.4 Hz,
phenyl), 5.6 (s, 2H, eCH2-), 4.63 (d, 2H, J ¼ 5.4 Hz, eCH2-). Anal. calcd
for C16H12ClN7O3S: C, 45.99; H, 2.89; N, 23.47. Found: C, 46.72; H,
3.12; N, 23.48.
(DMSO-d6, 400 MHz)
d 8.81 (br s, 1H, eNHe), 8.16 (s, 1H, triazole),
7.84 (d, 1H, J ¼ 3.6 Hz, furan), 7.38e7.30 (m, 6H, furan and phenyl),
5.59 (s, 2H, eCH2-), 4.63 (d, 2H, J ¼ 5.2 Hz, eCH2-); Anal. calcd for
C16H13N7O3S: C, 50.12; H, 3.42; N, 25.57. Found: C, 49.84; H, 3.61; N,
25.82.
6.1.2.7. N-((1-(2-Methylbenzyl)-1H-1,2,3-triazol-4-yl)methyl)-5-(5-
6.1.2.2. N-((1-(2-Fluorobenzyl)-1H-1,2,3-triazol-4-yl)methyl)-5-(5-
nitrofuran-2-yl)-1,3,4-thiadiazol-2-amine (3b). The resulting product
was purified using silica gel column chromatography eluting with
CHCl3 and then EtOAc. Compound 3b was obtained as a yellow solid.
nitrofuran-2-yl)-1,3,4-thiadiazol-2-amine
(3g). The
resulting
product was purified using silica gel column chromatography
eluting with CH2Cl2 and then EtOAc. Compound 3g was obtained as
a yellow solid. Yield 46%; m.p 179e183 ꢃC; MS (m/z, %) 397 (Mþ, 38),
292 (15), 279 (23), 264 (20), 226 (9), 212 (20), 203 (9), 185 (10), 167
(39), 158 (35), 149 (98), 118 (8), 105 (100), 79 (13), 57 (9); IR (KBr,
cmꢄ1) 3189, 1569, 1529, 1491, 1353; 1H NMR (DMSO-d6, 400 MHz)
Yield 72%; m.p 186e187 ꢃC; MS (ESI): 401.7 [M þ Hþ]. IR (KBr, cmꢄ1
)
3221, 1619, 1536, 1495, 1352; 1H NMR (DMSO-d6, 400 MHz)
d 8.8 (t,
1H, J ¼ 4.8 Hz, eNHe), 8.12 (s, 1H, triazole), 7.83 (d, 1H, J ¼ 3.6 Hz,
furan), 7.42e7.36 (m, 2H, phenyl), 7.33 (d, 1H, J ¼ 3.6 Hz, furan),
7.26e7.19 (m, 2H, phenyl), 5.65 (s, 2H, eCH2-), 4.62 (d, 2H, J ¼ 4.8 Hz,
eCH2-). Anal. calcd for C16H12FN7O3S: C, 47.88; H, 3.01; N, 24.43.
Found: C, 47.53; H, 2.81; N, 24.16.
d
8.81 (br s, 1H, eNHe), 8.1 (s, 1H, triazole), 7.85 (d, 1H, J ¼ 3.6 Hz,
furan), 7.69 (d, 1H, J ¼ 7.6 Hz, phenyl), 7.35 (d, 1H, J ¼ 3.6 Hz, furan),
7.24e7.18 (m, 2H, phenyl), 7.08 (d, 1H, J ¼ 7.6 Hz, phenyl), 5.6 (s,
2H, eCH2-), 4.63 (br s, 2H, eCH2-), 2.31 (s, 3H, CH3); Anal. calcd for
C17H15N7O3S: C, 51.38; H, 3.80; N, 24.67. Found: C, 51.09; H, 3.52; N,
24.44.
6.1.2.3. N-((1-(4-Fluorobenzyl)-1H-1,2,3-triazol-4-yl)methyl)-5-(5-
nitrofuran-2-yl)-1,3,4-thiadiazol-2-amine
(3c). The
resulting
product was extracted with 30 mL of CHCl3 and washed with water.
The organic layer was dried (Na2SO4) and evaporated under
reduced pressure. Compound 3c was obtained as an orange solid.
Yield 70%; m.p 197e200 ꢃC; MS (ESI): 401.7 [M þ Hþ]. IR (KBr,
cmꢄ1) 3243, 1543, 1508, 1490, 1352; 1H NMR (DMSO-d6, 400 MHz)
6.1.2.8. N-((1-(3-Methylbenzyl)-1H-1,2,3-triazol-4-yl)methyl)-5-
(5-nitrofuran-2-yl)-1,3,4-thiadiazol-2-amine (3h). The resulting
product was purified using silica gel column chromatography
eluting with CH2Cl2 and then EtOAc. Compound 3h was obtained as
an orange solid. Yield 55%; m.p 168e169 ꢃC; MS (ESI): 397.7
[M þ Hþ]. IR (KBr, cmꢄ1) 3180, 1545, 1491, 1352; 1H NMR (DMSO-d6,
d
8.82 (t, 1H, J ¼ 5 Hz, eNHe), 8.17 (s, 1H, triazole), 7.85 (d, 1H,
J ¼ 3.2 Hz, furan), 7.44e7.37(m, 2H, phenyl), 7.36 (d, 1H, J ¼ 3.2 Hz,
furan), 7.20 (t, 2H, J ¼ 8.8 Hz, phenyl), 5.58 (s, 2H, eCH2-), 4.63
(d, 2H, J ¼ 5 Hz, eCH2-). Anal. calcd for C16H12FN7O3S: C, 47.88; H,
3.01; N, 24.43. Found: C, 48.03; H, 3.01; N, 24.67.
400 MHz) d 8.81 (br s, 1H, eNHe), 8.14 (s, 1H, triazole), 7.84 (d, 1H,
J ¼ 4 Hz, furan), 7.34 (d, 1H, J ¼ 4 Hz, furan), 7.25 (t, 1H, J ¼ 7.6 Hz,
phenyl), 7.14e7.1(m, 3H, phenyl), 5.54 (s, 2H, eCH2-), 4.62 (br s, 2H,
eCH2-), 2.28 (s, 3H, CH3). Anal. calcd for C17H15N7O3S: C, 51.38; H,
3.80; N, 24.67. Found: C, 51.50; H, 3.87; N, 24.40.
6.1.2.4. N-((1-(2-Chlorobenzyl)-1H-1,2,3-triazol-4-yl)methyl)-5-(5-
nitrofuran-2-yl)-1,3,4-thiadiazol-2-amine (3d). The resulting moist
solid was extracted with 40 mL of EtOAc and washed with water.
The organic layer was dried (Na2SO4) and evaporated under
6.1.2.9. N-((1-(4-Methylbenzyl)-1H-1,2,3-triazol-4-yl)methyl)-5-
(5-nitrofuran-2-yl)-1,3,4-thiadiazol-2-amine (3i). The resulting
product was purified using silica gel column chromatography

128
A. Tahghighi et al. / European Journal of Medicinal Chemistry 50 (2012) 124e128
eluting with CHCl3 and then EtOAc. Compound 3i was obtained as
an orange solid. Yield 61%; m.p 183e185 ꢃC; MS (ESI): 397.7
[M þ Hþ]. IR (KBr, cmꢄ1) 3235, 1618, 1537, 1496, 1350; 1H NMR
(s, 1H, phenyl), 7.47 (d, 1H, J ¼ 8.25 Hz, phenyl), 7.35 (d, 1H,
J ¼ 3.5 Hz, furan), 7.27 (d,1H, J ¼ 8.25 Hz, phenyl), 5.7 (s, 2H, eCH2-),
4.64 (br s, 2H, eCH2-); 13C NMR (DMSO-d6, 125 MHz):
d 169.3, 151.4,
(DMSO-d6, 500 MHz)
d
8.8 (t, 1H, J ¼ 5.35 Hz, eNHe), 8.12 (s, 1H,
147.6, 144.8, 143.6, 133.9, 133.7, 132.5, 131.9, 129.1, 127.9, 124.1, 115.2,
111.9, 50.0, 39.0; Anal. calcd for C16H11Cl2N7O3S: C, 42.49; H, 2.45;
N, 21.68. Found: C, 42.62; H, 2.63; N, 21.44.
triazole), 7.84 (d, 1H, J ¼ 4 Hz, furan), 7.36 (d, 1H, J ¼ 4 Hz, furan),
7.22 (d, 2H, J ¼ 8 Hz, phenyl), 7.17 (d, 2H, J ¼ 8 Hz, phenyl), 5.53
(s, 2H, eCH2-), 4.62 (d, 2H, J ¼ 5.35 Hz, eCH2-), 2.28 (s, 3H, CH3);
Anal. calcd for C17H15N7O3S: C, 51.38; H, 3.80; N, 24.67. Found: C,
51.21; H, 3.58; N, 24.97.
6.1.2.14. N-((1-(3,4-Dichlorobenzyl)-1H-1,2,3-triazol-4-yl)methyl)-5-
(5-nitrofuran-2-yl)-1,3,4-thiadiazol-2-amine (3n). The resulting
product was purified using silica gel column chromatography
eluting with CHCl3 and then EtOAc. Compound 3n was obtained as
a yellow solid. Yield 70%; m.p 189e191 ꢃC; MS (ESI): 451.6 [M þ Hþ].
IR (KBr, cmꢄ1) 3199, 1600, 1530, 1498, 1355; 1H NMR (DMSO-d6,
6.1.2.10. N-((1-(4-Nitrobenzyl)-1H-1,2,3-triazol-4-yl)methyl)-5-(5-
nitrofuran-2-yl)-1,3,4-thiadiazol-2-amine
(3j). The
resulting
product was purified using silica gel column chromatography
eluting with CHCl3 and then EtOAc. Compound 3j was obtained as
an orange solid. Yield 78%; m.p 234e236 ꢃC; MS (ESI): 428.7
[M þ Hþ]. IR (KBr, cmꢄ1) 3212, 1561, 1517, 1493, 1352; 1H NMR
400 MHz)
d
8.84 (t, 1H, J ¼ 5 Hz, eNHe), 8.22 (s, 1H, triazole), 7.85
(d, 1H, J ¼ 4 Hz, furan), 7.64 (d, 1H, J ¼ 8 Hz, phenyl), 7.61 (s, 1H,
phenyl), 7.35 (d, 1H, J ¼ 4 Hz, furan), 7.3 (d, 1H, J ¼ 8 Hz, phenyl),
5.62 (s, 2H, eCH2-), 4.62 (d, 2H, J ¼ 5 Hz, eCH2-). Anal. calcd for
C16H11Cl2N7O3S: C, 42.49; H, 2.45; N, 21.68. Found: C, 42.75; H, 2.71;
N, 21.37.
(DMSO-d6, 400 MHz)
d
8.84 (t, 1H, J ¼ 5 Hz, eNHe), 8.26e8.2 (m,
3H, triazole and phenyl), 7.83 (d, 1H, J ¼ 3.8 Hz, furan), 7.53 (d, 2H,
J ¼ 8.4 Hz, phenyl), 7.34 (d,1H, J ¼ 3.8 Hz, furan), 5.78 (s, 2H, eCH2-),
4.64 (d, 2H, J ¼ 5 Hz, eCH2-). Anal. calcd for C16H12N8O5S: C, 44.86;
H, 2.82; N, 26.16. Found: C, 44.97; H, 2.63; N, 26.26.
Acknowledgment
6.1.2.11. N-((1-(2-Chloro-6-fluorobenzyl)-1H-1,2,3-triazol-4-yl)
This work was supported by grants from the Research Council of
Tehran University of Medical Sciences and Iran National Science
Foundation (INSF).
methyl)-5-(5-nitrofuran-2-yl)-1,3,4-thiadiazol-2-amine
(3k). The
resulting product was purified using silica gel column chromatog-
raphy eluting with CHCl3 and then EtOAc. Compound 3k was ob-
tained as a yellow solid. Yield 73%; m.p 207e208 ꢃC; MS (m/z, %) 437
([M þ 2]þ, 20), 435 (Mþ, 52), 292 (7), 264 (41), 234 (43), 212 (12),198
(24), 196 (74), 161 (20), 156 (34), 145 (92), 143(100), 107 (21), 82 (15);
IR (KBr, cmꢄ1) 3215, 1615, 1534, 1496, 1352; 1H NMR (DMSO-d6,
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1H, J ¼ 3.95 Hz, furan), 7.53e7.48 (m, 1H, phenyl), 7.42 (d, 1H,
J ¼ 8 Hz, phenyl), 7.36 (d, 1H, J ¼ 3.95 Hz, furan), 7.33 (d, 1H, J ¼ 8 Hz,
phenyl), 5.72 (s, 2H, eCH2-), 4.62 (d, 2H, J ¼ 5.2 Hz, eCH2-); 13C NMR
(DMSO-d6, 125 MHz) d: 169.2, 151.4, 147.6, 144.8, 143.3, 134.9, 131.9,
131.8, 125.9, 123.8, 120.8, 115.1, 114.9, 111.9, 44.4, 39.0; Anal. calcd for
C16H11ClFN7O3S: C, 44.09; H, 2.54; N, 22.50. Found: C, 44.42; H, 2.44;
N, 22.21.
6.1.2.12. N-((1-(2,3-Dichlorobenzyl)-1H-1,2,3-triazol-4-yl)methyl)-5-
(5-nitrofuran-2-yl)-1,3,4-thiadiazol-2-amine (3l). The resulting
product was purified using silica gel column chromatography
eluting with CH2Cl2 and then EtOAc. Compound 3l was obtained as
an orange solid. Yield 69%; m.p 220e222 ꢃC; MS (ESI): 451.6
[M þ Hþ]. IR (KBr, cmꢄ1) 3195, 1589, 1527, 1498, 1353; 1H NMR
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(DMSO-d6, 400 MHz)
d
8.82 (t, 1H, J ¼ 5 Hz, eNHe), 8.16 (s, 1H,
triazole), 7.84 (d, 1H, J ¼ 3.6 Hz, furan), 7.65 (d, 1H, J ¼ 8 Hz, phenyl),
7.38 (t, 1H, J ¼ 8 Hz, phenyl), 7.34 (d, 1H, J ¼ 3.6 Hz, furan), 7.14
(d, 1H, J ¼ 8 Hz, phenyl), 5.75 (s, 2H, eCH2-), 4.62 (d, 2H, J ¼ 5 Hz,
eCH2-). Anal. calcd for C16H11Cl2N7O3S: C, 42.49; H, 2.45; N, 21.68.
Found: C, 42.27; H, 2.31; N, 21.85.
6.1.2.13. N-((1-(2,4-Dichlorobenzyl)-1H-1,2,3-triazol-4-yl)methyl)-5-
(5-nitrofuran-2-yl)-1,3,4-thiadiazol-2-amine (3m). The resulting
moist solid was heated in hot acetone and filtrated. Then, the
organic phase was dried (Na2SO4) and concentrated under reduced
pressure. Compound 3m was obtained as a yellow solid. Yield 72%;
m.p 154e155 ꢃC; MS (ESI): 451.6 [M þ Hþ]. IR (KBr, cmꢄ1) 3200,
1619, 1540, 1493, 1356; 1H NMR (DMSO-d6, 500 MHz)
d: 8.83 (br s,
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1H, eNHe), 8.16 (s, 1H, triazole), 7.85 (d, 1H, J ¼ 3.5 Hz, furan), 7.7