Synthesis of novel 1,2,4-triazolyl coumarin derivatives as potential anticancer agents

Article abstract of DOI:10.1155/2018/5201374

A series of novel coumarin derivatives carrying 1,2,4-triazole or 1,2,4-triazolo[3,4-b][1,3,4]thiadiazole moieties were prepared and evaluated in vitro as anticancer in the human colon cancer (HCT116) cell line. The derivatives 4c and 8c exhibited marked anticancer activity with IC₅₀ values 4.363 and 2.656 μM, respectively. The molecular docking studies suggested possible interaction with tyrosine kinases (CDK2).

Full text of DOI:10.1155/2018/5201374

Hindawi
Journal of Chemistry
Volume 2018, Article ID 5201374, 8 pages
https://doi.org/10.1155/2018/5201374
Research Article
Synthesis of Novel 1,2,4-Triazolyl Coumarin Derivatives as
Potential Anticancer Agents
,
3
Lamya H. Al-Wahaibi ,1 Hanaa M. Abu-Melha,1 and Diaa A. Ibrahim2
1Department of Chemistry, College of Science, Princess Nourah Bint Abdulrahman University, Riyadh 11671, Saudi Arabia
2Department of Chemistry, Faculty of Science, Jazan University, Jazan, Saudi Arabia
3National Organization for Drug Control and Research, Cairo, Egypt
Correspondence should be addressed to Lamya H. Al-Wahaibi; lhalwahaibi@pnu.edu.sa
Received 22 June 2018; Accepted 29 August 2018; Published 14 October 2018
Academic Editor: Gabriel Navarrete-Vazquez
Copyright © 2018 Lamya H. Al-Wahaibi et al. -is is an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
A series of novel coumarin derivatives carrying 1,2,4-triazole or 1,2,4-triazolo[3,4-b][1,3,4]thiadiazole moieties were prepared and
evaluated in vitro as anticancer in the human colon cancer (HCT116) cell line. -e derivatives 4c and 8c exhibited marked
anticancer activity with IC50 values 4.363 and 2.656 µM, respectively. -e molecular docking studies suggested possible interaction
with tyrosine kinases (CDK2).
stress [12, 13]. Meanwhile, the coumarin derivatives ensaculin
[14] and AP2243 [15] are known acetylcholine esterase in-
hibitors which have been used clinically in treating Alz-
heimer’s disease for a long time.
1. Introduction
Coumarin (2H-1-benzopyran-2-one; 2H-chromen-2-one)
derivatives are a large class of important naturally occur-
ring and synthetic oxygen-containing heterocycles. -is type
of benzopyrone structure enables such derivatives to interact
with diversity of enzymes and receptors in organisms
through weak bond interactions, thereby exhibiting wide
potentiality as bioactive drugs [1]. More than 1300 coumarin
derivatives were identified as secondary metabolites from
plants, bacteria, and fungi [2]. Coumarin derivatives were
early recognized as important agents for the prevention and
treatment of diseases [3, 4]. Several coumarin-based de-
rivatives are currently used as anticoagulant drugs and as
rodenticides [5–7]. -e naturally occurring coumarins such
as novobiocin, chlorobiocin, and coumermycin have been
found to be an unprecedented class of antibiotics, specifically
against Gram-positive bacteria [8]. -e natural coumarin
derivatives possessing long-chain hydrocarbon substitutions
such as ammoresinol and ostruthin [9], grandivittin, aga-
syllin, and osthole displayed significant antibacterial activity
against clinically isolated Gram-positive and Gram-negative
bacterial strains [10, 11]. In addition, the coumarin glycoside
fraxin displayed free-radical scavenging effect and cell pro-
tective effect against hydrogen peroxide-mediated oxidative
Coumarin compounds as potential anticancer agents have
become a rapidly developing, extremely active, and attractive
topic. -e coumarin derivative STX 64, a potent estrogen
antagonist, is currently under clinical trials as anticancer
agents against breast carcinoma [16]. Moreover, auraptene
has been reported as anticancer agent against the liver, skin,
tongue, esophagus, and colon cancers [17] (Figure 1).
On the contrary, 1,2,4-triazole nucleus has been reported
to constitute the essential pharmacophore of various ther-
apeutically active agents possessing marked anti-
inflammatory [18, 19], antifungal [20, 21], and anticancer
[22, 23] activities. Moreover, the condensed triazolo het-
erocycles such as 1,2,4-triazolo[3,4-b] [1,3,4]thiadiazoles
were reported to exhibit significant antibacterial [24, 25] and
anticancer [26] activities.
Based on the abovementioned biological activities of
coumarin, 1,2,4-triazole, and 1,2,4-triazolo[3,4-b] [1,3,4]
thiadiazole derivatives, we report herein the synthesis and
evaluation of the anticancer activity of new series of cou-
marin derivatives carrying a 1,2,4-triazole or 1,2,4-triazolo
[3,4-b] [1,3,4]thiadiazole moieties.

2
Journal of Chemistry
a high anticancer activity (relative potency >50%) with IC50
values 4.363 and 2.656 µM, respectively. Meanwhile, com-
pounds 4a, 8a, and 8b displayed moderate anticancer ac-
tivity (relative potency 10–20%) with IC50 values 18.76,
25.630, and 15.296 µM. Compounds 4b, 5a, 5b, and 5c were
practically inactive (relative potency <10%).
O
O
O
H2NO2S
O
O
STX 64
O
Auraptene
Figure 1: ꢀe structures of coumarin-based anticancer drugs.
2.3. Molecular Docking Studies. To understand the mecha-
nism of action of the anticancer activities of the newly
synthesized compounds, we carried out molecular docking,
which is used to predict the binding mode of ligands within
the binding site of target proteins [33]. Taking into con-
sideration the previously reported tyrosine kinases (CDK2)
inhibitory activity of the structurally related chromene
anticancer agents genistein [34] and quercetin [35], we
docked the synthesized compounds in CDK2 active site. To
validate and specify the target protein for the antitumor
activity of newly synthesized triazolyl coumarin derivatives,
CDK2 protein was selected and downloaded from the
protein data bank (PDB ID: 1KE8) [36]. Docking studies of
compound 4c into the active site of CDK2 enzyme showed
two hydrogen bonds with THR160 and GLU81 and a good
electrostatic interaction with the active site (Figure 2).
Similarly, docking conformation of the active compound
8c showed good interactions with the active site residues of
this protein. Compound 8c formed two hydrogen bond
interactions between amino groups moiety, as it acts as
a hydrogen bond donor with the side chain of HIE84 and
ASP86 residues with strength of 45%. Furthermore, it
showed Van der Waals interaction with PHE80 and PHE82
(Figure 3). Finally, there was a good correlation between the
docking studies and the biological pro‹les.
2. Results and Discussion
2.1. Chemical Synthesis. ꢀe synthesis of the target triazolyl
coumarin derivatives is outlined in Scheme 1. ꢀe starting
material 2-(coumarin-4-yl) acetic acid 1 (2-(2-oxo-2H-
chromen-4-yl) acetic acid was prepared via reaction of citric
acid with phenol in sulfuric acid following the previously
reported procedures [27–29]. 2-(Coumarin-4-yl)acetic acid
1 was reacted with thiocarbohydrazide 2 in re-uxing
phosphoryl chloride to yield the target 3-[(coumarin-4-yl)
methyl]-4-amino-1H-1,2,4-triazole-5(4H)-thione 3 in 80%
yield. ꢀe reaction of the aminotriazole derivative 3 with
di‡erent aromatic aldehydes in propanol containing cata-
lytic amount of acetic acid yielded the corresponding ary-
lideneamino derivatives 4a–c. 4-Arylideneamino-1H-1,2,4-
triazole-5(4H)-thiones were reported to undergo oxidative
cyclization to their 1,2,4-triazolo[3,4-b][1,3,4]thiadiazole
analogues using di‡erent oxidizing agents such as iodine,
nitrobenzene, and ammonium cerium(IV) nitrate [30].
Accordingly, the arylideneamino derivatives 4a–c were
successfully cyclized to their 1,2,4-triazolo[3,4-b][1,3,4]
thiadiazole analogues 5a–c by the action of iodine in ace-
tonitrile. ꢀe 1,2,4-triazolo[3,4-b][1,3,4]thiadiazole ana-
logues 5a–c were also independently synthesized in slightly
lower yields by the reaction of the aminotriazole derivative 3
with the corresponding aromatic carboxylic acid via heating
in phosphoryl chloride. ꢀe reaction of compound 3 with
carbon disul‹de in pyridine under re-ux furnished 6-
mercapto-1,2,4-triazolo[3,4-b][1,3,4]thiadiazole analogue 6
in 78% yield. ꢀe mercapto derivative 6 was further reacted
with iodomethane in dry N,N-dimethylformamide (DMF),
in the presence of anhydrous potassium carbonate to yield
the methylthio analogue 7. ꢀe reaction of the methylthio
analogue 7 with di‡erent primary aromatic amines via
prolonged heating in DMF resulted in replacement of the
methylthio group with an arylamino substituent leading to
the 6-arylamino derivatives 8a–c in reasonable yields
(Scheme 1; Table 1). ꢀe structures of the newly synthesized
3. Materials and Methods
Melting points (°C) were measured in open-glass capillaries
using a Gallenkamp melting point apparatus and are un-
corrected. IR spectra were recorded in potassium bromide
discs on a Shimadzu FTIR 8101 PC infrared spectropho-
tometer. ꢀe NMR spectra were recorded on a BRUKER
VX-500 NMR spectrometer. 1H spectra were run at
500 MHz, and 13C spectra were run at 125 MHz in deu-
terated dimethylsulphoxide (DMSO-d6) using TMS as an
internal standard. Electron impact mass spectra were
recorded on a Shimadzu GCMS-QP 1000 EX mass spec-
trometer at 70 eV. Elemental analyses were performed using
a Vario LIII CHNS analyzer, and the analytical data (C, H &
N) were in agreement with the proposed structures within
0.4% of the theoretical values. ꢀe biological evaluation of
the products was carried out in the Medical Mycology
Laboratory of the Regional Center for Mycology and Bio-
technology of Al-Azhar University, Cairo, Egypt.
1H NMR, 13C
compounds were established based on IR,
NMR, and mass spectral data.
2.2. In Vitro Anticancer Activity. ꢀe antitumor activity of
compounds 4a–c, 5a–c, and 8a–c was investigated against
the human colorectal cancer cell line (HCT116) following
the previously reported colorimetric cytotoxicity assay of
Skehan et al. [31]. ꢀe results of the preliminary cytotoxic
activity of compounds 4a–c, 5a–c, and 8a–c and the anti-
cancer drug doxorubicin [32] are shown in Table 2.
3.1. 3-[(Coumarin-4-yl)methyl]-4-amino-1H-1,2,4-triazole-5
(4H)-thione 3. Phosphoryl chloride (5 g) was added drop-
wise to an ice-cold mixture of 2-(coumarin-4-yl) acetic acid
1 (1.06 g, 0.01 mole) and thiocarbohydrazide 2 (2.04 g, 0.01
mole) with stirring, and the mixture was then heated under
ꢀe analysis of the IC50 values on the HCT116 cell line
(Table 2) revealed that the compounds 4c and 8c exhibited

Journal of Chemistry
3
S
S
Ar
H2N
N
N
OH
N
NH
NH
N
O
O
O
N
H
N
H
N
POCl3
ArCHO
4a–c
+
H2N
NH2
S
2
O
O
O
O
1
3
HS
I2/MeCN
S
S
H2N
N
N
Ar
N
NH
N
S
N
N
N
O
CS2/Pyridine
ArCOOH
POCl3
N
N
N
6
O
3
O
O
MeI/K2CO3
O
O
DMF
5a–c
Ar
S
HN
S
S
N
N
N
N
ArNH2
DMF
N
N
N
N
7
8a–c
O
O
O
O
Scheme 1: Synthesis of the target triazolyl coumarin derivatives.
Table 1: Crystallization solvents, melting points, yield percentages, molecular formulae, and molecular weights of compounds 3, 4a–c, 5a–c,
6, and 7.
Comp. no.
Ar
Cryst. solvent
M.p. (°C)
Yield (%)
Mol formula (mol. wt.)
3
—
4-OHC6H4
4-MeOC6H4
4-OH,3-MeOC6H3
4-OHC6H4
4-MeOC6H4
4-OH,3-MeOC6H3
—
EtOH
DMF/EtOH
DMF/EtOH
DMF/EtOH
DMF
226–229
248–250
255–257
240–243
271–273
282–284
266–268
236–239
244–246
273–275
264–267
283–285
80
60
66
54
74
62
48
78
85
64
75
55
C12H10N4O2S (274.30)
C19H14N4O3S (378.40)
C20H16N4O3S (392.43)
C20H16N4O4S (408.43)
C19H12N4O3S (376.39)
C20H14N4O3S (390.42)
C20H14N4O4S (406.41)
C13H8N4O2S2 (316.36)
C14H10N4O2S2 (330.38)
C19H13N5O3S (391.40)
C19H12ClN5O2S (409.85)
C19H14N6O4S2 (454.48)
4a
4b
4c
5a
5b
5c
6
DMF
DMF
Dioxan
7
—
EtOH
8a
8b
8c
4-OHC6H4
4-ClC6H4
4-H2NSO2C6H4
DMF/EtOH
DMF/EtOH
DMF/EtOH
reflux for one hour. -e excess phosphoryl chloride was
distilled off under reduced pressure. -e resulted residue was
triturated with dry pyridine (2 mL), and ice-cold water
(250 mL) was added and the mixture was kept for 10
minutes. -e precipitated crude product was filtered, washed
with water, and crystallized from ethanol to yield 2.2 g (80%)
(C�S), 161.30 (C�O), 154.14, 150.14, 146.94, 132.55, 126.54,
124.62, 118.12, 117.10, 114.20 (Coumarin-C & Triazole C3),
29.67 (CH2). EI-MS (m/z) � 274. Anal. calcd. for
C12H10N4O2S, %: C, 52.54; H, 3.67; N, 20.43. Found, %: C,
52.36; H, 3.43; N, 20.28.
−1
of 3 as light brown powder. IR (cm ): 3280 (NH), 3169, 3155
(NH2), 2895 (Aliphatic CH), 1715 (C�O). 1H NMR: δ 13.81
(s, 1H, NH), 7.64 (t, J � 7.5 Hz, 1H, Coumarin-H), 7.63 (d,
J � 8.4 Hz, 1H, Coumarin-H), 7.47 (d, J � 8.6 Hz, 1H), 7.34 (t,
J � 7.5 Hz, 1H, Coumarin-H), 6.14 (s, 1H, Coumarin-H),
5.20 (s, 2H, NH2), 3.86 (s, 2H, CH2). 13C NMR: δ 172.90
3.2. 3-[(Coumarin-4-yl)methyl]-4-arylideneamino-1H-1,2,4-
triazole-5(4H)-thione 4a–c. A mixture of 3-[(coumarin-4-yl)
methyl]-4-amino-1H-1,2,4-triazole-5(4H)-thione 3 (274 mg,
1 mmol) and the appropriate aromatic aldehyde (1 mmol), in
isopropyl alcohol (25 mL) containing three drops of acetic

4
Journal of Chemistry
Table 2: Cytotoxic activity of compounds 4a–c, 5a–c, and 8a–c
126.57, 124.88, 124.44, 118.03, 117.09, 115.01, 114.43,
109.04 (Coumarin-C, N�CH, Ar–C & Triazole C3),
56.14 (OCH3), 30.15 (CH2). EI-MS (m/z) � 408. Anal.
calcd. for C20H16N4O4S, %: C, 58.81; H, 3.95; N, 13.72.
Found, %: C, 58.66; H, 3.73; N, 13.46.
against the human colorectal cancer cell line (HCT116).
Comp. no.
IC50 (µM)
Relative potency∗
4a
13.865
44.704
4.363
18.76%
5.82%
59.62%
2.01%
0.98%
6.65%
10.15%
17.00%
97.93%
100%
4b
4c
5a
129.259
266.089
39.133
25.630
15.296
2.656
3.3. 6-Aryl-3-[(coumarin-4-yl)methyl]-[1,2,4]triazolo[3,4-b]
5b
[1,3,4]thiadiazole 5a–c
5c
8a
3.3.1. Method A. To a suspension of the arylideneamino
analogues 4a–c (50 mmol), in dry acetonitrile (70 mL), io-
dine (1.27 g, 50 mmol) was added, the reaction mixture was
heated under reflux, and the reaction progression was
monitored by TLC using ethyl acetate : hexane (9 :1) as
mobile phase. Upon completion of the reaction, the reaction
mixture was poured onto ice-cold water (200 mL), and
a solution of sodium thiosulfate was added to destroy excess
iodine. -e greenish precipitate thus formed was filtered,
washed with ethyl acetate, and recrystallized from DMF-
EtOH.
8b
8c
Doxorubicin
2.601
∗Compared to doxorubicin.
acid, was heated under reflux for 7 hours. On cooling, the
precipitated crude products were filtered, dried, and recrys-
tallized from DMF-EtOH to afford compounds 4a–c as
yellowish brown powders.
−1
4a: IR (cm ): 3361 (OH), 3231 (NH), 3055 (Aromatic
CH), 2860 (Aliphatic CH), 1720 (C�O), 1625 (N�CH).
1H NMR: δ 13.68 (s, 1H, NH), 9.75 (s, 1H, OH), 8.31
(s, 1H, N�CH), 7.70 (t, J � 7.6 Hz, 1H, Coumarin-H),
7.44–7.50 (m, 4H, Coumarin-H & Ar–H), 7.23 (t,
J � 7.6 Hz, 1H, Coumarin-H), 6.88 (d, J � 7.5 Hz, 2H, 2H,
Ar–H), 6.24 (s, 1H, CH, Coumarin-H), 3.92 (s, 2H,
CH2). 13C NMR: δ 172.35 (C�S), 161.20 (C�O), 157.24,
154.27, 153.24, 146.07, 145.56, 132.42, 132.10, 127.09,
126.54, 124.21, 118.07, 117.08, 115.15, 114.44
(Coumarin-C, N�CH, Ar–C & Triazole C3), 30.15
(CH2). EI-MS (m/z) � 378. Anal. calcd. for C19H14N4O3S,
%: C, 60.31; H, 3.73; N, 14.81. Found, %: C, 60.26; H, 3.83;
N, 14.38.
3.3.2. Method B. A mixture of the appropriate carboxylic
acid (50 mmol), 3-[(coumarin-4-yl)methyl]-4-amino-1H-
1,2,4-triazole-5(4H)-thione 3 (1.37 g, 50 mmol), and phos-
phoryl chloride (5 mL) was heated under reflux for 1 hour.
On cooling, crushed ice (100 g) was cautiously added, and
the mixture was stirred for 30 minutes. -e separated crude
product was filtered, washed with water then with saturated
sodium hydrogen carbonate solution and finally with water,
dried, and crystallized from DMF-EtOH.
−1
5a: IR (cm ): 3361 (OH), 3110 (Aromatic CH), 2885
(Aliphatic CH), 1720 (C�O), 1650 (C�N). 1H NMR: δ
9.25 (s, 1H, OH), 7.77 (d, J � 8.4 Hz, 2H, Coumarin-H),
7.65–7.33 (m, 4H, Coumarin-H & Ar–H), 6.91 (d,
J � 7.4 Hz, 2H, Ar–H), 6.29 (s, 1H, Coumarin-H), 4.14
(s, 2H, CH2). 13C NMR: δ 165.54, 161.26, 159.55, 157.24,
154.41, 145.76, 142.95, 132.38, 132.18, 126.81, 124.21,
123.63, 117.90, 117.30, 117.04, 112.59 (Coumarin-C,
Ar–C & Triazolo[3,4-b][1,3,4]thiadiazole-C), 30.02
(CH2). EI-MS (m/z) � 376. Anal. calcd. for
C19H12N4O3S, %: C, 60.63; H, 3.21; N, 14.89. Found, %:
C, 60.36; H, 3.53; N, 15.16.
−1
4b: IR (cm ): 3274 (NH), 3060 (Aromatic CH), 2880
(Aliphatic CH), 1710 (C�O), 1650 (C�N). 1H NMR: δ
13.66 (s, 1H, NH), 8.32 (s, 1H, N�CH), 7.63 (t,
J � 8.1 Hz, 1H, Coumarin-H), 7.54–7.45 (m, 4H,
Coumarin-H & Ar–H), 7.26 (t, J � 8.1 Hz, 1H,
Coumarin-H), 7.07 (d, J � 8.4 Hz, 2H, Ar–H), 3.92 (s,
2H, CH2), 3.82 (s, 3H, OCH3). 13C NMR: δ 172.36
(C�S), 161.19 (C�O), 158.91, 154.06, 153.06, 146.08,
145.56, 132.40, 129.54, 128.11, 126.54, 124.26, 118.03,
117.08, 114.44, 113.69 (Coumarin-C, N�CH, Ar–C &
Triazole C3), 55.33 (OCH3), 30.17 (CH2). EI-MS
(m/z) � 392. Anal. calcd. for C20H16N4O3S, %: C,
61.21; H, 4.11; N, 14.28. Found, %: C, 60.86; H, 3.93; N,
14.16.
−1
5b: IR (cm ): 3090 (Aromatic CH), 2980 (Aliphatic
1
CH), 1710 (C�O), 1655 (C�N). H NMR: δ 7.89 (d,
J � 8.4 Hz, 2H, Ar–H), 7.65–7.64 (m, 2H, Coumarin-H),
7.49 (d, J � 8.3 Hz, 1H, Coumarin-H), 7.32 (t, J � 7.8 Hz,
1H, Coumarin-H), 7.03 (d, J � 8.4 Hz, 2H, Ar–H), 6.28
(s, 1H, Coumarin-H), 4.14 (s, 2H, CH2), 3.88 (s, 3H,
OCH3). 13C NMR: δ 165.51, 161.33, 159.53, 157.24,
154.25, 145.79, 142.95, 132.37, 131.94, 126.84, 125.56,
124.02, 117.83, 117.02, 114.86, 112.62 (Coumarin-C,
Ar–C & Triazolo[3,4-b][1,3,4]thiadiazole-C), 55.32
(OCH3), 30.02 (CH2). EI-MS (m/z) � 390. Anal. calcd.
for C20H14N4O3S, %: C, 61.53; H, 3.61; N, 14.35. Found,
%: C, 61.26; H, 3.33; N, 14.09.
−1
4c: IR (cm ): 3341 (OH), 3214 (NH), 3065 (Aromatic
CH), 2886 (Aliphatic CH), 1715 (C�O), 1650 (C�N).
1H NMR: δ 13.29 (s, 1H, NH), 8.96 (s, 1H, OH), 8.37 (s,
1H, N�CH), 7.63–7.46 (m, 4H, Coumarin-H & Ar–H),
7.33 (t, J � 7.9 Hz, 1H, Coumarin-H), 7.13 (s, 1H,
Coumarin-H), 7.10–6.87 (m, 1H, Ar–H), 6.32 (s, 1H,
Coumarin-H), 3.93 (s, 2H, CH2), 3.86 (s, 3H, OCH3).
13C NMR: δ 172.33 (C�S), 161.20 (C�O), 154.06,
151.98, 147.71, 147.41, 146.08, 145.56, 132.29, 127.20,

Journal of Chemistry
5
(a)
(b)
Figure 2: (a) 2D and (b) 3D interactions of compound 4c with ATP active site of CDK2, which showed hydrogen bond and electrostatic
interactions.
(a)
(b)
Figure 3: (a) 2D and (b) 3D interactions of compound 8c with ATP active site of CDK2, which showed hydrogen bond and electrostatic
interactions.
−1
5c: IR (cm ): 3380 (OH), 3098 (Aromatic CH), 2975
ice-cold water (100 mL), and the mixture was slightly
acidified with hydrochloric acid. -e precipitated crude
product was filtered, washed with water, dried, and crys-
tallized from dioxin to yield 2.47 g (78%) of 6 as orange
1
(Aliphatic CH), 1720 (C�O), 1655 (C�N). H NMR: δ
8.81 (s, 1H, OH), 7.75 (d, J � 7.8 Hz, 1H, Coumarin-H),
7.62–7.38 (m, 3H, Coumarin-H), 7.33–6.97 (m, 2H,
Ar–H), 6.31 (s, 1H, Coumarin-H), 4.13 (s, 2H, CH2), 3.86
(s, 3H, OCH3). 13C NMR: δ 166.96, 161.27, 157.28, 154.25,
149.20, 147.64, 145.80, 143.00, 132.30, 126.82, 125.94,
124.44, 124.17, 117.83, 117.02, 116.40, 115.14, 112.62
(Coumarin-C, Ar–C & Triazolo[3,4-b][1,3,4]thiadiazole-
C), 55.96 (OCH3), 30.04 (CH2). EI-MS (m/z) � 406. Anal.
calcd. for C20H14N4O4S, %: C, 59.11; H, 3.47; N, 13.79.
Found, %: C, 59.26; H, 3.31; N, 13.49.
−1
crystals. IR (cm ): 2985 (Aliphatic CH), 1715 (C�O), 1660
1
(C�N). H NMR: δ 7.69 (d, J � 7.9 Hz, 1H, Coumarin-H),
7.64 (t, J � 8.1 Hz, 1H, Coumarin-H), 7.50 (d, J � 8.1 Hz, 1H,
Coumarin-H), 7.35 (t, J � 7.9 Hz, 1H, Coumarin-H), 6.21 (s,
1H, Coumarin-H), 5.65 (s, 1H, SH), 4.12 (s, 2H, CH2). 13
C
NMR: δ 161.74, 160.93, 156.21, 154.22, 145.79, 144.86,
132.18, 126.65, 124.07, 117.88, 117.01, 112.52 (Coumarin-C
& Triazolo[3,4-b][1,3,4]thiadiazole-C), 29.71 (CH2). EI-MS
(m/z) � 316. Anal. calcd. for C13H8N4O2S2, %: C, 49.36; H,
2.55; N, 17.71. Found, %: C, 49.26; H, 2.38; N, 17.49.
3.4. 3-[(Coumarin-4-yl)methyl]-6-mercapto[1,2,4]triazolo
[3,4-b][1,3,4]thiadiazole 6. Carbon disulfide (2 mL) and
few drops of triethylamine were added to a solution of 3-
[(coumarin-4-yl)methyl]-4-amino-1H-1,2,4-triazole-5(4H)-
thione 3 (2.74 g, 0.01 mol) in pyridine (30 mL), and the
mixture was heated under reflux at 100°C with stirring for 6
hours. On cooling, the reaction mixture was poured onto
3.5. 3-[(Coumarin-4-yl)methyl]-6-methylthio[1,2,4]triazolo
[3,4-b][1,3,4]thiadiazole 7. To a solution of 3-[(coumarin-
4-yl)methyl]-6-mercapto[1,2,4]triazolo[3,4-b][1,3,4]thiadia-
zole 6 (1.58 g, 50 mmol) in DMF (10 mL), iodomethane
(1.14 gm, 80 mmol) and anhydrous potassium carbonate

6
Journal of Chemistry
(0.69 gm, 50 mol) were added, and the mixture was stirred at
room temperature for 4 hours. Water (15 mL) was added,
and the mixture was stirred for further 30 minutes. -e
precipitated crude product was filtered, washed with water,
dried, and crystallized from ethanol to yield 1.4 gm (85%) of
Coumarin-H), 7.33 (t, J � 7.9 Hz, 1H, Coumarin-H),
7.06 (d, 2H, J � 8.5 Hz, 2H, Ar–H), 6.40 (s, 2H, NH2),
6.18 (s, 1H, Coumarin-H), 4.13 (s, 2H, CH2). 13C NMR:
δ 161.30, 159.00, 157.16, 154.25, 145.77, 142.93, 140.36,
136.91, 132.21, 127.81, 126.84, 124.11, 120.93, 117.76,
117.07, 112.60 (Coumarin-C, Ar–C & Triazolo[3,4-b]
[1,3,4]thiadiazole-C), 29.83 (CH2). EI-MS (m/z) � 454.
Anal. calcd. for C19H14N6O4S2, %: C, 50.21; H, 3.10; N,
18.49. Found, %: C, 50.51; H, 3.25; N, 18.29.
−1
7 as yellow crystalline powder. IR (cm ): 2979 (Aliphatic
CH), 1710 (C�O), 1640 (C�N). 1H NMR: δ 7.70 (d,
J � 7.8 Hz, 1H, Coumarin-H), 7.64 (t, J � 8.2 Hz, 1H,
Coumarin-H), 7.50 (d, J � 8.2 Hz, 1H, Coumarin-H), 7.34 (t,
J � 7.9 Hz, 1H, Coumarin-H), 6.27 (s, 1H, Coumarin-H),
4.11 (s, 2H, CH2), 2.67 (s, 3H, CH3). 13C NMR: δ 166.94,
160.93, 154.24, 153.69, 145.79, 141.83, 131.92, 126.66, 124.39,
117.88, 117.01, 112.50 (Coumarin-C & Triazolo[3,4-b][1,3,4]
thiadiazole-C), 30.30 (CH2), 15.48 (CH3). EI-MS (m/z) �
330. Anal. calcd. for C14H10N4O2S2, %: C, 50.90; H, 3.05; N,
16.96. Found, %: C, 50.66; H, 2.88; N, 17.19.
4. Conclusions
In the current study, a novel series of triazolyl coumarin
derivatives were synthesized and evaluated as anticancer
agents against human colorectal cancer cell line (HCT116).
-e compounds 4c and 8b exhibited marked cytotoxic ac-
tivity with 59.62 and 97.93% relative potency, respectively,
compared to the potent anticancer drug doxorubicin. -e
molecular docking studies of the active compounds revealed
that these compounds might act via inhibition of tyrosine
kinases (CDK2). -e active compounds are considered to be
good candidates as newer anticancer agents, and further
studies including preparation of newer analogues and tox-
icity testing are required for optimization of the activity
which are being undertaken.
3.6. 3-[(Coumarin-4-yl)methyl]-6-arylamino[1,2,4]triazolo
[3,4-b][1,3,4]thiadiazole 8a–c. 4-Aminophenol, 4-chlor-
oaniline, or 4-aminobenzenesulfonamide (50 mmol) was
added to a solution of compound 7 (1.56 g, 50 mmol), in
DMF (10 mL) containing few drops of 37% hydrochloric
acid, and the mixture was heated under reflux for 10 hours.
-e excess DMF was then distilled off in vacuo, and the solid
residue was triturated with water (20 mL). -e separated
solid precipitate was filtered, washed with water, and
crystallized from DMF-Ethanol to yield compounds 8a–c as
reddish brown crystals.
Data Availability
-e data used to support the findings of this study are
available from the corresponding author upon request.
−1
8a: IR (cm ): 3351 (OH), 3244 (NH), 3065 (Aromatic
CH), 2880 (Aliphatic CH), 1714 (C�O), 1650 (C�N).
1H NMR: δ 9.95 (s, 1H, NH), 9.24 (s, 1H, OH),
7.70–7.40 (m, 3H, Coumarin-H), 7.33 (t, J � 8.1 Hz, 1H,
Coumarin-H), 7.01 (d, J � 8.4 Hz, 2H, Ar–H), 6.81 (d,
J � 8.4 Hz, 2H, Ar–H), 6.20 (s, 1H, Coumarin-H), 4.12
(s, 2H, CH2). 13C NMR: δ 161.25, 159.00, 156.71, 154.25,
153.86, 145.79, 142.43, 133.77, 132.37, 126.84, 124.89,
123.98, 117.83, 117.02, 115.27, 112.62 (Coumarin-C,
Ar–C & Triazolo[3,4-b][1,3,4]thiadiazole-C), 29.84
(CH2). EI-MS (m/z) � 391. Anal. calcd. for
C19H13N5O3S, %: C, 58.30; H, 3.35; N, 17.89. Found, %:
C, 58.61; H, 3.18; N, 17.59.
Conflicts of Interest
-e authors declare that they have no conflicts of interest.
Acknowledgments
-e authors would like to thank the Deanship of Scientific
Research, Princess Nourah Bint Abdulrahman University,
for funding this study (Research Project No. 37-S-178).
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