Synthesis of novel 1,2,5-trisubstituted benzimidazoles as potential antitumor agents

Article abstract of DOI:10.1016/j.ejmech.2011.06.006

Novel methyl 1-(5-tert-butyl-1H-pyrazol-3-yl)-2-(aryl)-1H-benzo[d] imidazole-5-carboxylates 11 were synthesized by following a four-step strategy involving a nucleophilic aromatic displacement (S_NAr) and a solvent free approach as key steps for the formation of the desired products. Structure of intermediates and products were confirmed by X-ray diffraction as well as the tautomeric rearrangement suffered by the pyrazole moiety during the curse of the final cyclization process. Several of the obtained compounds were screened by the US National Cancer Institute (NCI) for their ability to inhibit 60 different human tumor cell lines. Products 11b and 11n exhibited the highest activity against a range of cancer cell lines with remarkable values in panels of Non-Small Cell Lung Cancer, Melanoma and Leukemia, with GI₅₀ range of 1.15-7.33 μM and 0.167-7.59 μM, respectively, and suitable LC ₅₀ with values greater than 100 μM.

Full text of DOI:10.1016/j.ejmech.2011.06.006

European Journal of Medicinal Chemistry 46 (2011) 4062e4070
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Synthesis of novel 1,2,5-trisubstituted benzimidazoles as potential
antitumor agents
,
a
a
a
b
b
Rodrigo Abonia a , Edwar Cortés , Braulio Insuasty , Jairo Quiroga , Manuel Nogueras , Justo Cobo
*
a Grupo de Investigación de Compuestos Heterocíclicos, Departamento de Química, Universidad del Valle, A.A. 25360 Cali, Colombia
b Departamento de Química Inorgánica y Orgánica, Universidad de Jaén, 23071 Jaén, Spain
a r t i c l e i n f o
a b s t r a c t
Article history:
Novel methyl 1-(5-tert-butyl-1H-pyrazol-3-yl)-2-(aryl)-1H-benzo[d]imidazole-5-carboxylates 11 were
synthesized by following a four-step strategy involving a nucleophilic aromatic displacement (SNAr) and
a solvent free approach as key steps for the formation of the desired products. Structure of intermediates
and products were confirmed by X-ray diffraction as well as the tautomeric rearrangement suffered by
the pyrazole moiety during the curse of the final cyclization process. Several of the obtained compounds
were screened by the US National Cancer Institute (NCI) for their ability to inhibit 60 different human
tumor cell lines. Products 11b and 11n exhibited the highest activity against a range of cancer cell lines
with remarkable values in panels of Non-Small Cell Lung Cancer, Melanoma and Leukemia, with GI50 range
Received 17 March 2011
Received in revised form
28 May 2011
Accepted 6 June 2011
Available online 14 June 2011
Keywords:
Nucleophilic aromatic substitution
Pyrazole derivatives
Trisubstituted benzimidazoles
Solvent free reaction conditions
Antitumor agents
of 1.15e7.33
m
M and 0.167e7.59
m
M, respectively, and suitable LC50 with values greater than 100
mM.
Ó 2011 Elsevier Masson SAS. All rights reserved.
1. Introduction
a proton-pump inhibitor (PPI) which prevents the stomach from
producing gastric acid [8], the Albendazole 3 is used for the treat-
ment of a variety of worm infestations [9] and compound 4 recently
synthesized showed an interestingly activity against several human
tumor cell lines [10].
The imidazole core is a common moiety in a large number of
natural products and pharmacologically active compounds [1].
Particularly, the benzimidazoles may be considered as structural
isosters of nucleotides owing to the fused heterocyclic nuclei in
their structures, interact easily with biopolymers and possess
potential activity for chemotherapeutic applications [2]. The
benzimidazole moiety itself is a crucial pharmacophore in modern
drug discovery [3], owing to the broad-spectrum of important
biological and pharmacological properties exhibited for a large
number of benzimidazole-containing compounds, such as anti-
ulcerative and antihypertensive [4a], antifungal [4b], antitumor
[4c,d], topoisomerase inhibitors [4e], antiallergic [5a] and selective
neuropeptide YY1 receptor antagonists [5b]. In addition, some
benzimidazole derivatives are effective against several human
viruses such as cytomegalovirus (HCMV) [6a], HIV [6b], RNA [6c]
and herpes (HSV-1) [6d].
The demonstrated practical applications of the benzimidazole
derivatives have prompted extensive studies for their synthesis.
Mainly, there are two general approaches for the synthesis of
benzimidazole derivatives. The first method involves the heating of
o-phenylenediamines and carboxylic acids [11] or their derivatives
(nitriles, chlorides, or orthoesters) [12] in the presence of a mineral
acid. The second one starts also with o-phenylenediamines but
using an aldehyde instead of the carboxylic acid. This reaction
proceeds in acidic media but in addition, an oxidative reagent is
required [13]. More recently, alternative Lewis acid-based catalysts
and environmentally friendly reaction conditions have been used
for the synthesis of a large number of benzimidazole derivatives
[14]. The pyrazole core is frequently found being part of the
structure of compounds of biological interest [15]. Some pyrazole-
oxime ethers were prepared and examined as cytotoxic agents and
particularly the activity of the 5-phenoxypyrazole derivative was
comparable to doxorubicin [15c]. Similarly, a series of amino-
pyrazoles were synthesized showing some of them significant
anticonvulsant activity [15d].
Fig. 1 shows some benzimidazole derivatives with biological
and practical activities. For example Omeprazole 1 is used for the
treatment of dyspepsia, peptic ulcer disease (PUD) and gastro-
esophageal reflux disease [7], the Lansoprazole 2 is used as
We have recently reported a one-pot procedure mediated by
* Corresponding author. Fax: þ57 2 3393248.
AmberlystÒ-15 for the synthesis of compound 4 (Fig. 1), and several
E-mail address: rodrigo.abonia@correounivalle.edu.co (R. Abonia).
0223-5234/$ e see front matter Ó 2011 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2011.06.006

R. Abonia et al. / European Journal of Medicinal Chemistry 46 (2011) 4062e4070
4063
Fig. 1. Some benzimidazole derivatives of biological interest.
Fig. 2. ORTEP drawing of the structure of compound 8-(N-acetyl) with 50% probability
ellipsoids.
new benzimidazole analogs bearing the quinolin-2-one pharma-
cophore in position 2 to be studied for antitumor activity [10].
Continuing with our current studies on the synthesis of potential
antitumor agents [10,15a,16], we felt that substituted benzimid-
azoles are worthy of further studies and therefore we planned the
synthesis of the new trisubstituted benzimidazole derivatives 11,
bearing a pyrazole residue at N-1, with the aim that the presence of
such substituent might improve the antitumor activity displayed by
compound 4.
corresponding methyl ester 6. Formation of compound 6 was
confirmed by the disappearing of the broad (CO2H) IR band
(present in compound 5 in the range of 3500-2500 cmꢀ1), and the
appearing of a new singlet at 3.99 ppm (3H, OCH3) in the 1H NMR
spectrum. This functional group interconversion was carried out to
improve the solubility and handling of the starting material 5 in
addition to setting the first substituent for the target products 11.
Treatment of the methyl ester 6 with the 5-amino-3-tert-
butylpyrazol (PzNH2) 7 in DMSO at room temperature afforded the
2. Results and discussion
corresponding amino-ester
8
via
a
nucleophilic aromatic
displacement (SNAr) of the fluorine atom. The presence of two NeH
absorption bands in the IR spectrum at 3371 and 3316 cmꢀ1
respectively, along with the full spectroscopic analysis confirmed
the insertion of the aminopyrazole fragment. At this point, the
second planed substituent for the target products 11 has been
inserted. Additionally, the N-acetylation of compound 8 by treat-
ment with acetic anhydride and growing single-crystals of this
product from a solution in EtOH and the study by X-ray diffraction
confirmed unambiguously the assigned structure for compound 8,
Fig. 2 [17].
2.1. Chemistry
The design of our target compounds 11 implied that one of these
three substituents were a pyrazole residue (Pz) owing to the
aforementioned activity displayed by this moiety and aimed for
a positive synergistic effect by the presence of both pyrazole and
benzimidazole pharmacophores forming part of the same struc-
ture. The strategy used for the synthesis of the new benzimidazoles
11 is outlined in Scheme 1.
To start with, the methylation of the commercially available 4-
fluoro-3-nitrobenzoic acid 5 by treatment with dry methanol in
the presence of concentrated sulfuric acid afforded the
Due to the starting pyrazole 7 was not commercially available it
required being synthesized by a solvent-free heating of a mixture of
4,4-dimethyl-3-oxopentanonitrile and hydrazine hydrate as
described in Scheme 2 [18].
Subsequently, reduction of the nitro group performed by
treatment of the amino-ester 8 with the Ni-Raney/hydrazine
hydrate reagent led to the formation of the key diamine deriva-
tive 9, Scheme 1. The disappearing of the two absorption nitro
bands in the IR spectrum at 1541 and 1352 cmꢀ1 along with the full
spectroscopic analysis confirmed this process. To complete the
synthesis of our target compounds 11, a mixture of the diamine 9
(1 mmol) and 4-bromobenzaldehyde 10a (1 mmol) was initially
refluxed in ethanol. After 4 h of heating the desired product 11a was
obtained in only 40% yield. Pursuing for a yield improvement, the
reaction was repeated by heating the starting materials for 1 h at
140 ꢁC without solvent. The crude was purified by column
Scheme 1. Four-step synthesis of 1,2,5-trisubstituted benzimidazoles 11.
Scheme 2. Synthesis of pyrazole 7.

4064
R. Abonia et al. / European Journal of Medicinal Chemistry 46 (2011) 4062e4070
Scheme 4. Obtention of the 9-(N,N-diacetyl) derivative from treatment of diamine 9
with Ac2O.
Scheme 3. Synthesis of benzimidazole 11a from the reaction of diamine
4-bromobenzaldehyde 10a.
9 and
chromatography on silica gel using a mixture CHCl3/CH3OH as
eluent affording the desired compound 11a. This apparently simple
change of the reaction conditions improved the yield up to 92%.
The main spectroscopic feature of the structure of compound 11a
corresponded to the presence of only one NeH functionality with IR
and 1H NMR signals at 3374 cmꢀ1 and 13.03 ppm, respectively.
Although the presence of the free NH functionality in the pyrazolic
moiety of the diamine 9 might suppose a possible competence to
form the isomeric seven-membered diazepine ring 12a as showed
in Scheme 3, single-crystals were obtained from a solution in EtOH
and the study by X-ray diffraction unambiguously confirmed the
assigned structure for compound 11a, Fig. 3 [19].
derivative was obtained as unique product but not the expected
9-(N-acetyl) intermediate as shown in Scheme 4.
According to the crystalline structure withdrawn from X-ray
diffraction and depicted in Fig. 3, it is remarkable that the pyrazole
moiety of the imidazole 11a suffered a tautomeric rearrangement
during the course of the cyclization process. Comparing the posi-
tion of the pyrazole NH functionality in 7 and the 8-(N-acetyl)
derivative with the structure of the Fig. 3, clearly it is observed that
the NH shifted toward the adjacent nitrogen atom (N13) in the final
product 11a. A spatial PzNH/NH2 correlation found in the NOESY
spectrum of the diamine 9 also indicates that isomerization have
not proceeded yet and confirms that the tautomerization pro-
ceeded during the cyclization toward product 11, probably caused
by the temperature and the acidic conditions. This kind of isom-
erization in pyrazoles has previously been reported [20]. Once
established the best reaction conditions and the correct structure
In an attempt to block the 1-NH functionality of diamine 9 to try
to address the reaction selectively toward the formation of the
triazepine system type 12, diamine 9 was treated with acetic
anhydride at reflux. Unfortunately the undesired 9-(N,N-diacetyl)
Fig. 3. ORTEP drawing of the structure 11a with 50% probability ellipsoids.

R. Abonia et al. / European Journal of Medicinal Chemistry 46 (2011) 4062e4070
4065
Table 1
Analytical data for products 11aen.
Entry
Ar
Compounds 11
Yielda (%)
Mp ꢁC
Table 2
In vitro testing expressed as growth inhibition of cancer cells by compounds 11b and
11n.
a
b
c
d
e
f
g
h
i
j
k
l
m
n
4-BrC6H4
4-ClC6H4
4-CH3C6H4
4-CH3OC6H4
4-FC6H4
3,4,5-(CH3O)3C6H2
2-HOC6H4
2-HOe4-OCH3C6H3
4-(CH3)2NC6H4
3,4-(CH3O)2C6H3
C6H5
92
94
85
91
90
89
81
87
83
88
89
65
64
87
261e262
248e249
258e259
244e245
261e262
209e210
224e225
252e253
291e292
211e212
257e258
221e222
254e255
254e256
Panel/cell line
Compoundsa
11b
11n
b
c
b
c
GI50
TGI
LC50
M)
GI50
TGI
M)
LC50
M)
(m
M)
(
mM)
(
m
(m
M)
(
m
(
m
Leukemia
RPMI-8226
SR
CCRF-CEM
HL-60(TB)
K-562
3.93
3.23
4.91
4.03
4.20
5.48
19
>100
>100
11.2
>100
>100
>100
>100
>100
>100
>100
>100
0.167
10.0
0.585
0.322
1.73
0.987
>100
>100
d
>100
>100
>100
>100
>100
>100
4-CF3C6H4
1,3-Benzodioxol-5-yl
2-Oxo-1,2-dihydroquinolin-3-yl
>100
>100
MOLT-4
0.445
a
Isolated yield.
Non-small cell lung cancer
EKVX
HOP-62
3.06
>100
21
44
>100
>100
>100
>100
>100
>100
>100
>100
>100
5.8
>100
>100
>100
>100
>100
>100
d
>100
>100
>100
>100
>100
>100
d
3.41
4.09
3.42
2.95
3.21
1.15
0.996
7.00
2.78
0.630
0.928
d
for benzimidazole 11a, this procedure was extended to other
aldehydes 10ben to evaluate the generality of this methodology. In
all cases reactions proceeded with the same behavior and yields in
the range of 64e94%. Table 1 summarizes the main analytical data
for products 11aen.
NCI-H226
NCI-H23
NCI-H460
NCI-H522
HOP-92
36
8.81
20.3
8.02
86.4
94.5
NCI-H322M
A549/ATCC
10.4
4.03
0.929
>100
>100
>100
>100
>100
2.2. Anticancer activity
Colon
COLO 205
HCT-116
HCT-15
HT29
KM12
SW-620
HCC-2998
2.29
3.47
4.36
3.65
2.12
3.24
3.90
6.04
12.3
>100
15.4
6.07
>100
19.8
0.463
0.563
>100
>100
>100
>100
>100
d
>100
>100
>100
>100
d
>100
>100
>100
>100
>100
>100
>100
1.74
d
The two-stage screening process started with the evaluation of
six of the obtained compounds (i.e. 9, 9-(diacetyl), 11b, 11d, 11h and
11n) selected by NCI, against 60 cell lines at a single dose of 1.0 mM.
The output from the single dose screen was reported as a mean
graph available for analysis by the COMPARE program [21]. The
results of the primary assay suggested that compounds 11b and 11n
(Fig. 4), were declared as active.
Subsequently, a secondary screening process was performed in
order to determine the cytostatic activity of compounds 11b and
11n against the 60 cell panel representing leukemia, melanoma and
cancers of the lung, colon, brain, ovary, breast, prostate and kidney.
The testing results were expressed according to the following three
parameters: GI50 which is the molar concentration of the
compounds required to inhibit the growth of that cell lines by 50%
(relative to untreated cells). TGI as the molar concentration that
causes total growth inhibition, and LC50 which is a parameter of
cytotoxicity and reflects the molar concentration needed to kill 50%
of the cells [22]. Compounds 11b and 11n were evaluated at five
1.34
1.29
d
>100
d
d
CNS
SF-295
SF-539
U251
SF-268
SNB-19
SNB-75
2.48
2.54
4.13
3.29
4.31
2.14
8.98
8.95
22.7
17.8
>100
>100
0.521
>100
>100
>100
>100
1.23
4.12
0.652
2.13
7.59
5.42
25.5
>100
>100
>100
>100
>100
>100
>100
>100
91.9
>100
41.5
12.6
Melanoma
LOX IMVI
MALME-3M
MDA-MB-435
SK-MEL-5
UACC-257
UACC-62
SK-MEL-2
M14
SK-MEL-28
3.70
3.25
1.19
2.02
4.97
2.01
3.89
2.90
3.38
14.5
15.6
5
5.1
22.9
7.78
18.1
8.22
0.429
>100
0.505
0.186
0.967
0.463
>100
0.758
0.552
1.24
2.63
d
d
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
2.30
d
d
2.25
d
concentration levels (100, 10, 1.0, 0.1 and 0.01 mM). The test con-
15.5
d
sisted of a 48 h continuous drug exposure protocol using a sulfo-
rhodamide B (SRB) protein assay to estimate cell growth. Details of
this evaluation method and the complementary information
related to the activity pattern over all cell lines have been published
[23]. Table 2 shows that compound 11b displayed the most
remarkable activity against 58 human tumor cell lines, being HOP-
Ovarian
IGROV1
3.64
2.35
3.40
2.72
7.33
25
>100
0.915
>100
>100
>100
>100
>100
0.965
6.27
d
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
OVCAR-3
OVCAR-4
NCI/ADR-RES
OVCAR-8
OVCAR-5
SK-OV-3
6.13
>100
7.35
58.2
60.1
31
5.29
1.79
d
92 (Non-Small Cell Lung Cancer; GI50 ¼ 1.15
m
M; LC50 > 100
m
M) and
12.9
3.71
28.5
MDA-MB-435 (Melanoma; GI50 ¼ 1.19 M; LC50 ¼ 0.505
m
mM) the
Renal
A498
ACHN
2.26
3.00
2.25
1.57
4.34
6.94
3.35
3.62
9.76
9.34
12.8
5.77
27.7
>100
0.858
>100
>100
0.569
>100
>100
>100
>100
13.6
76.9
>100
90.5
8.86
>100
55.8
>100
>100
>100
>100
>100
>100
>100
>100
>100
0.476
2.16
5.61
16.9
CAKI-1
RXF 393
SN12C
TK-10
UO-31
786-0
44.1
32
0.533
5.81
>100
>100
Prostate
DU-145
3.70
25.8
>100
2.37
>100
>100
(continued on next page)
Fig. 4. Active compounds 11b and 11n after screening performed by the NCI.

4066
R. Abonia et al. / European Journal of Medicinal Chemistry 46 (2011) 4062e4070
Table 2 (continued )
spectra were recorded on a Bruker Avance 400 spectrophotometer
operating at 400 MHz and 100 MHz respectively, using CDCl3 and
DMSO-d6 as solvents and tetramethylsilane as internal standard.
Mass spectra were run on an SHIMADZU-GCMS 2010-DI-2010
spectrometer (equipped with a direct inlet probe) operating at
70 eV. Microanalyses were performed on an Agilent elemental
analyzer and the values are within ꢂ0.4% of the theoretical values.
Silica gel aluminum plates (Merck 60 F254) were used for analytical
TLC. The starting aldehydes 10aen and 4-fluoro-3-nitrobenzoic
acid 5 were purchased from Aldrich, Fluka and Acros (analytical
reagent grades) and were used without further purification.
Panel/cell line
Compoundsa
11b
11n
b
c
b
c
GI50
TGI
M)
15.7
LC50
M)
GI50
TGI
M)
LC50
M)
(m
M)
(
m
(
m
(
mM)
(
m
(
m
PC-3
Breast
MCF7
MDA-MB-231/ATCC
BT-549
T-47D
MDA-MB-468
HS 578T
2.93
>100
2.27
>100
>100
2.79
4.62
3.35
3.64
2.40
1.72
12.3
27
11.2
>100
7.98
7.86
>100
>100
0.595
>100
>100
>100
>100
4.13
4.88
>100
20.5
0.619
>100
>100
66.2
>100
>100
34.1
>100
>100
>100
>100
>100
>100
4.1. Synthesis of methyl 4-fluoro-3-nitrobenzoate (6)
a
Data obtained from NCI’s in vitro disease-oriented human tumor cell lines
screen [22].
A mixture of acid 5 (1.85 g, 1 mol), methanol (15 mL) and 96%
H2SO4 (1 mL) was heated under reflux with stirring for 2 h. The
reaction progress was monitored by TLC and after complete
disappearance of the starting material 5 the solvent was concen-
trated under vacuum to one half of the original volume. The solid
formed was collected by filtration and washed with methanol
(2 ꢃ 0.5 mL), to afford compound 6. White solid, 88% yield; m.p:
b
GI50 was 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.
Determined at five concentration levels (100, 10, 1.0, 0.1 and 0.01 M).
m
most sensitive strains. Likewise, compound 11n displayed the most
remarkable activity against 40 human tumor cell lines, thirteen of
97e98 ꢁC. FTIR (cmꢀ1): 3065, 2961, 1716 (C]O), 1619 (C]C), 1541
n
them with GI50 values under 1.0
of the Leukemia panel (GI50 ¼ 0.167 and GI50 ¼ 0.322
tively) were the most sensitive strains with LC50 values greater than
100 M. Products 11b and 11n showed significant activity against
other cell lines from the different panels of cancer types, with GI50
range of 1.15e7.33 M and 0.167e7.59 M, respectively.
m
M. The HL-60(TB) and RPMI-8226
and 1352 (NO2), 1126 (CeO); 1H NMR (CDCl3)
7.40 (bt, 1H, J ¼ 8.7 Hz), 8.34 (m, 1H), 8.75 (bd, 1H, J ¼ 7.0 Hz) ppm;
13C NMR (CDCl3)
d 3.99 (s, 3H, OCH3),
mM, respec-
d
52.9 (OCH3), 118.7 (d, J ¼ 21.3 Hz), 127.2 (d,
m
J ¼ 4.1 Hz, Cq), 127.8 (d, J ¼ 1.3 Hz), 136.5, 136.6 (Cq), 158.1 (d,
J ¼ 269.9 Hz, Cq), 164.1 (C]O) ppm. MS (EI) m/z (%): 199 (100, Mþ),
184 (42),168 (14, M ꢀ OCH3). Anal. Calcd. for C8H6FNO4: C, 48.25; H,
3.04; N, 7.03. Found: C, 48.50; H, 3.17; N, 6.99.
m
m
In general, compound 11n showed higher activity than
compound 11b for most cell lines. Moreover, compound 11n has
a framework closer to the active imidazole 4 (Fig. 1), than
compound 11b. These findings are probably related to the presence
of the 2-oxo-1,2-dihydroquinolin-3-yl moiety in the structure of
both compounds 11n and 4, which have recently been recognized
as convenient pharmacophore for development of new compounds
with antitumor properties [24]. The cytotoxic effects associated
with compounds 11b and 11n were measured as LC50 displaying
4.2. Synthesis of methyl 4-[(3-tert-butyl-1H-pyrazol-5-yl)amino]-
3-nitrobenzoate (8)
A
mixture of 3-tert-butyl-1H-pyrazol-5-amine 7 (0.139 g,
1 mmol), methyl ester 6 (0.199 g, 1 mmol) and DMSO (2 mL) was
stirred at ambient temperature during 2 h. After complete disap-
pearance of the starting materials (monitored by TLC), the solid
formed was collected by filtration and washed with MeOH/H2O (1/
2) (3 ꢃ 2 mL), to afford compound 8. Orange solid, 76% yield; m.p:
values greater than 100 mM for most of the cell lines evaluated,
indicating a low toxicity of these compounds for normal human cell
lines, as required for development of potential antitumor agents.
241e242 ꢁC. FTIR (cmꢀ1): 3371 (NH), 3316 (NH), 3117, 2955, 1705
n
(C]O), 1625 (C]N), 1532 and 1323 (NO2), 1122 (CeO); 1H NMR
(CDCl3) 1.39 (s, 9H, tBu), 3.95 (s, 3H, OCH3), 5.98 (s, 1H, PzeCH),
3. Conclusion
d
8.06 (d, 1H, J ¼ 9.1 Hz), 8.13 (dd, 1H, J ¼ 9.1 Hz, J ¼ 1.8 Hz), 8.94 (d,
The design of a four-step synthesis of novel 1,2,5-trisubstituted
benzimidazoles 11, and studies on their cytotoxic activity have been
performed. The X-ray diffraction analysis confirmed not only the
formation of the expected products 11 but also revealed that the
pyrazole moiety suffered a tautomeric rearrangement during the
course of the cyclization process. The antitumor assays showed
that, among the six compounds selected and evaluated by the NCI,
benzimidazoles 11b and 11n exhibited the highest activity against
a range of cancer cell lines with remarkable values in panels of Non-
Small Cell Lung Cancer, Melanoma and Leukemia. The relative
activity values for the different evaluated strains also showed that
imidazole 11n presented a higher activity than imidazole 11b,
probably due to the presence of the 2-oxo-1,2-dihydroquinolin-3-yl
pharmacophore in its structure. Studies conducting to evaluate the
presence of this pharmacophore on the activity of some other of our
structures are currently in progress by the NCI.
1H, J ¼ 1.8 Hz), 10.07 (bs, 1H, PzeNH) ppm, the aniline NH is
missing; 13C NMR (CDCl3)
d 30.0 (tBu), 31.2 (Cq, tBu), 52.2 (OCH3),
94.9 (PzeCH), 117.2, 119.5 (Cq), 128.9, 132.1 (Cq), 136.2, 144.3 (Cq),
148.0 (Cq), 154.6 (Cq), 165.5 (C]O) ppm. MS (EI) m/z (%): 318 (100,
Mþ), 287 (15, M ꢀ CH3). Anal. Calcd. for C15H18N4O4: C, 56.60; H,
5.70; N, 17.60. Found: C, 56.54; H, 5.83; N, 17.46.
4.3. Synthesis of methyl 3-amino-4-[(3-tert-butyl-1H-pyrazol-5-yl)
amino]benzoate (9)
A mixture of methyl ester 8 (0.477 g, 1.5 mmol), hydrazine
hydrate (0.225 g, 4.5 mmol), Ni-Raney (0.070 g) and methanol
(15 mL) was heated to reflux with stirring for 1 h. Then the hot
mixture was filtered and the solvent was concentrated under
vacuum to one quarter of the original volume. After cooling the solid
formed was collected by filtration and recrystallized from methanol,
to afford compound 9. White solid, 94% yield; m.p: 190e191 ꢁC. FTIR
4. Experimental
n
(cmꢀ1): 3366 broad (NH2), 3293 (NH), 2963,1702 (C]O),1601 (C]
N), 1574, 1494, 1307, 1211 (CeO), 763; 1H NMR (DMSO-d6)
1.25 (s,
d
Melting points were determined on a Büchi melting point
apparatus and are uncorrected. IR spectra were recorded on a Shi-
madzu FTIR 8400 spectrophotometer in KBr disks. 1H and 13C NMR
9H, tBu), 3.73 (s, 3H, OCH3), 4.97 (s, 2H, NH2), 5.70 (s, 1H, PzeCH),
7.18 (d,1H, J ¼ 8.2 Hz), 7.26 (s,1H), 7.44 (s,1H, NH), 7.65 (bs,1H),11.81
(s, 1H, PzeNH) ppm; 13C NMR (DMSO-d6)
d 30.40 (tBu), 31.07 (Cq,

R. Abonia et al. / European Journal of Medicinal Chemistry 46 (2011) 4062e4070
4067
tBu), 51.66 (OCH3), 91.61 (PzeCH), 113.6, 115.5, 119.6 (Cq), 120.0,
135.5 (Cq), 135.9 (Cq), 150.5 (Cq), 153.1 (Cq), 167.1 (C]O) ppm. MS
(EI) m/z (%): 288 (100, Mþ), 272 (21), 257 (15), 246 (17), 215 (26),190
(17),121 (15),107 (15). Anal. Calcd. for C15H20N4O2: C, 62.48; H, 6.99;
N, 19.43. Found: C, 62.33; H, 7.07; N, 19.60.
142.4 (Cq), 143.7 (Cq), 153.3 (Cq), 155.6 (Cq), 167.0 (C]O) ppm. MS
(EI) m/z (%): 410/408 (37/100, Mþ), 397/395 (5/16), 393 (31), 379/
377 (14/35), 353/351 (5/14), 299 (20). Anal. Calcd. for C22H21ClN4O2:
C, 64.62; H, 5.18; N, 13.70. Found: C, 64.70; H, 5.00; N, 13.59.
4.5.3. Methyl 1-(5-tert-butyl-1H-pyrazol-3-yl)-2-(4-methylphenyl)-
4.4. Obtention of methyl 3-acetamido-4-(1-acetyl-3-tert-butyl-1H-
pyrazol-5-ylamino)benzoate (9-N,N-diacetyl)
1H-benzo[d]imidazole-5-carboxylate (11c)
Pale yellow solid. FTIR
2861, 1679 (C]O), 1614 (C]C), 1562 (C]N), 1508, 1472, 1440, 1307,
1227, 820, 747; 1H NMR (DMSO-d6)
1.30 (s, 9H, tBu), 2.32 (s, 3H,
n
(cmꢀ1): 3394 (NH), 3143, 2965, 2221,
A mixture of the diamino-ester 9 (0.288 g, 1 mmol) and acetic
anhydride (0.5 mL) was heated at 45 ꢁC during 5 min. After
complete disappearance of the starting material 9 (monitored by
TLC), the excess of acetic anhydride was removed under vacuum.
The solid formed was collected by filtration and washed with cold
ethanol (2 ꢃ 0.5 mL), to afford the 9-(N,N-diacetyl) derivative as
d
CH3), 3.88 (s, 3H, OCH3), 6.16 (s, 1H, PzeCH), 7.20 (d, 2H, AreH,
J ¼ 7.2 Hz), 7.36 (d,1H, 7-H, J ¼ 8.0 Hz), 7.51 (d, 2H, AreH, J ¼ 7.2 Hz),
7.90 (d, 1H, 6-H, J ¼ 8.4 Hz), 8.31 (s, 1H, 4-H), 12.98 (s, 1H, NH) ppm;
13C NMR (DMSO-d6)
d 21.3 (CH3), 30.3 (tBu), 31.4 (Cq, tBu), 52.5
(OCH3), 98.5 (PzeCH), 111.6 (C-7), 121.2 (C-4), 124.8 (C-6 and Cq),
127.0 (Cq), 129.2, 129.3, 140.4 (Cq), 140.7 (Cq), 142.4 (Cq), 144.0 (Cq),
154.5 (Cq), 155.4 (Cq), 167.0 (C]O) ppm. MS (EI) m/z (%): 388 (100,
Mþ), 387 (48), 373 (37, M ꢀ CH3), 357 (19, M ꢀ OCH3), 331 (14,
M ꢀ tBu), 271 (5), 171 (6). Anal. Calcd. for C23H24N4O2: C, 71.11; H,
6.23; N, 14.42. Found: C, 71.00; H, 6.40; N, 14.31.
white solid, 91% yield; m.p: 208e210 ꢁC. FTIR
n
(cmꢀ1): 3493
(AcNH), 3237 (NH), 2981, 2951, 1711 (C]O), 1671 br (2ꢃ C]O),
1602 (C]N, C]C),1561,1532,1290,1286, 1223 (CeO), 762; 1H NMR
(CDCl3)
d 1.30 (s, 9H, tBu), 2.27 (s, 3H, O]CCH3), 2.68 (s, 3H, O]
CCH3), 3.90 (s, 3H, OCH3), 5.82 (s, 1H, PzeCH), 7.15 (bs, 1H, NH), 7.39
(d, 1H, J ¼ 8.4 Hz), 7.94 (d, 1H, J ¼ 8.4 Hz), 8.15 (s, 1H), 9.62 (s, 1H,
AceNH) ppm; 13C NMR (CDCl3)
d
23.4 [(C]O)CH3], 23.6 [(C]O)
4.5.4. Methyl 1-(5-tert-butyl-1H-pyrazol-3-yl)-2-(4-methoxyphenyl)-
CH3], 29.5 (tBu), 32.7 (Cq, tBu), 52.0 (OCH3), 88.1 (PzeCH), 117.5,
124.3 (Cq), 126.6 (Cq), 128.1, 129.0, 139.1 (Cq), 146.0 (Cq), 165.7 (Cq),
166.2 (C]O), 169.4 (C]O), 175.0 (C]O) ppm. MS (EI) m/z (%): 372
(56, Mþ), 341 (6), 330 (63), 313 (39), 312 (40), 288 (100), 272 (26),
246 (20), 190 (63). Anal. Calcd. for C19H24N4O4: C, 61.28; H, 6.50; N,
15.04. Found: C, 61.50; H, 6.21; N, 14.93.
1H-benzo[d]imidazole-5-carboxylate (11d)
White solid. FTIR
1713 (C]O), 1614 (C]C), 1562 (C]N), 1509, 1481, 1434, 1362, 1290,
1257, 1232,1182, 837; 1H NMR (CDCl3)
1.29 (s, 9H, tBu), 3.82 (s, 3H,
n
(cmꢀ1): 3302 (NH), 3122, 3079, 2963, 2837,
d
OCH3), 3.96 (s, 3H, OCH3), 5.88 (s, 1H, PzeCH), 6.87 (d, 2H, AreH,
J ¼ 9.0 Hz), 7.46 (d, 1H, 7-H, J ¼ 8.0 Hz), 7.64 (d, 2H, AreH,
J ¼ 9.0 Hz), 8.02 (d, 1H, 6-H, J ¼ 8.0 Hz), 8.54 (s, 1H, 4-H), 11.05 (bs,
4.5. General procedure for the synthesis of imidazoles (11)
1H, NH) ppm; 13C NMR (CDCl3)
d 29.9 (tBu), 31.3 (Cq, tBu), 52.0
(OCH3), 55.3 (OCH3), 98.6 (PzeCH), 111.0 (C-7), 113.7, 121.6 (C-4),
121.9 (Cq), 124.8 (C-6), 125.1 (Cq), 130.9, 140.3 (Cq), 142.5 (Cq), 145.4
(Cq),154.3 (Cq),155.4 (Cq),161.0 (Cq),167.8 (C]O) ppm. MS (EI) m/z
(%): 404 (100, Mþ), 403 (27), 389 (27, M ꢀ CH3), 373 (11, M ꢀ OCH3),
347 (13, M ꢀ tBu), 179 (7). Anal. Calcd. for C23H24N4O3: C, 68.30; H,
5.98; N, 13.85. Found: C, 68.54; H, 5.80; N, 13.92.
A mixture of the diamino-ester 9 (0.288 g, 1 mmol) and the
corresponding arylaldehyde 10 (1.2 mmol) was heated at 140 ꢁC in
absence of solvent for 1e2 h. After complete disappearance of the
starting material 9 (monitored by TLC), the mixture was cooled at
ambient temperature and the residue was purified from column
chromatography on silica gel by using a CHCl3/CH3OH (40/1)
mixture as eluent, to afford pure compounds 11 after evaporation of
the solvent.
4.5.5. Methyl 1-(5-tert-butyl-1H-pyrazol-3-yl)-2-(4-fluorophenyl)-
1H-benzo[d]imidazole-5-carboxylate (11e)
White solid. FTIR
1616 (C]C), 1569 (C]N), 1511, 1484, 1436, 1363, 1287, 1230, 1083,
991, 844; 1H NMR (CDCl3)
1.30 (s, 9H, tBu), 3.97 (s, 3H, OCH3), 5.87
n
(cmꢀ1): 3208 (NH), 3121, 2966, 1722 (C]O),
4.5.1. Methyl 1-(5-tert-butyl-1H-pyrazol-3-yl)-2-(4-bromophenyl)-
1H-benzo[d]imidazole-5-carboxylate (11a)
d
White solid. FTIR
(C]O), 1650 (C]C), 1561 (C]N), 1545, 1278, 763; 1H NMR (DMSO-
d6) 1.30 (s, 9H, tBu), 3.87 (s, 3H, OCH3), 6.18 (s, 1H, PzeCH), 7.39 (d,
n
(cmꢀ1): 3374 (NH), 3315 (broad), 2964, 1697
(s, 1H, PzeCH), 7.05 (bt, 2H, AreH, J ¼ 8.8 Hz), 7.49 (d, 1H, 7-H,
J ¼ 8.4 Hz), 7.69 (dd, 2H, AreH, J ¼ 8.0 Hz, J ¼ 5.2 Hz), 8.06 (d, 1H, 6-
H, J ¼ 8.8 Hz), 8.55 (s, 1H, 4-H), 11.08 (bs, 1H, NH) ppm; 13C NMR
d
1H, 7-H, J ¼ 8.5 Hz), 7.53 (d, 2H, AreH, J ¼ 8.5 Hz), 7.61 (d, 2H, AreH,
(CDCl3) d 29.9 (tBu), 31.3 (Cq, tBu), 52.1 (OCH3), 98.5 (PzeCH), 111.1
J ¼ 8.3 Hz), 7.92 (d,1H, 6-H, J ¼ 8.5 Hz), 8.33 (s,1H, 4-H),13.03 (s,1H,
(C-7), 115.4 (d, J ¼ 22 Hz) 122.0 (C-4), 125.2 (C-6), 125.3 (Cq), 125.7
(d, Cq, J ¼ 3 Hz), 131.4 (d, J ¼ 8 Hz), 140.1 (Cq), 142.4 (Cq), 145.2 (Cq),
153.3 (Cq), 155.5 (Cq), 164.0 (d, Cq, J ¼ 249 Hz), 167.7 (C]O) ppm.
MS (EI) m/z (%): 392 (100, Mþ), 391 (32), 377 (26, M ꢀ CH3), 361 (33,
M ꢀ OCH3), 335 (10, M ꢀ tBu), 173 (5). Anal. Calcd. for C22H21FN4O2:
C, 67.33; H, 5.39; N, 14.28. Found: C, 67.54; H, 5.43; N, 14.09.
NH) ppm; 13C NMR (DMSO-d6)
d 30.2 (tBu), 31.5 (Cq, tBu), 52.5
(OCH3), 98.5 (PzeCH), 111.8 (C-7), 121.4 (C-4), 124.3 (Cq), 125.1 (C-
6), 125.2 (Cq), 129.0 (Cq), 131.2, 131.8, 140.5 (Cq), 142.3 (Cq), 143.6
(Cq), 153.4 (Cq), 155.6 (Cq), 167.0 (C]O) ppm. MS (EI) m/z (%): 454/
452 (100/98, Mþ), 439/437 (24/24, M ꢀ CH3), 423/421 (25/25,
M ꢀ OCH3), 397 (11), 395 (14). Anal. Calcd. for C22H21BrN4O2: C,
58.29; H, 4.67; N, 12.36. Found: C, 58.20; H, 4.75; N, 12.29.
4.5.6. Methyl 1-(5-tert-butyl-1H-pyrazol-3-yl)-2-(3,4,5-trimethoxy-
phenyl)-1H-benzo[d]imidazole-5-carboxylate (11f)
4.5.2. Methyl 1-(5-tert-butyl-1H-pyrazol-3-yl)-2-(4-chlorophenyl)-
White solid. FTIR
1716 (C]O), 1616 (C]C), 1568 (C]N), 1504, 1433, 1359, 1302, 1211,
1088, 771, 694; 1H NMR (CDCl3)
1.30 (s, 9H, tBu), 3.74 (s, 6H, OCH3),
n
(cmꢀ1): 3310 (NH), 3194, 3135, 3106, 2963, 2864,
1H-benzo[d]imidazole-5-carboxylate (11b)
White solid. FTIR
(C]O), 1614 (C]C), 1565 (C]N), 1470, 1292, 1227, 1091, 830; 1H
NMR (DMSO-d6) 1.31 (s, 9H, tBu), 3.88 (s, 3H, OCH3), 6.19 (s, 1H,
n
(cmꢀ1): 3292 (NH), 2960, 2925, 2850, 1715
d
3.87 (s, 3H, OCH3), 3.97 (s, 3H, OCH3), 6.00 (s, 1H, PzeCH), 6.97 (s, 2H,
AreH), 7.40 (d, 1H, 7-H, J ¼ 8.0 Hz), 8.03 (dd, 1H, 6-H, J ¼ 8.4 Hz,
J¼ 1.6Hz),8.55(bd,1H,4-H,J¼ 1.2Hz),11.10(bs,1H, NH)ppm; 13CNMR
d
PzeCH), 7.40 (d, 1H, 7-H, J ¼ 8.5 Hz), 7.48 (d, 2H, AreH, J ¼ 8.0 Hz),
7.61 (d, 2H, AreH, J ¼ 8.0 Hz), 7.92 (d, 1H, 6-H, J ¼ 8.5 Hz), 8.34 (s,
(CDCl3)
d
30.0 (tBu), 31.3 (Cq, tBu), 52.1 (OCH3), 56.0 (2ꢃ OCH3), 60.9
1H, 4-H), 13.02 (s, 1H, NH) ppm; 13C NMR (DMSO-d6)
d
30.3 (tBu),
(OCH3), 98.8 (PzeCH),106.7,110.8 (C-7),121.9(C-4),124.6 (Cq),125.1 (C-
6), 125.3 (Cq), 139.7 (Cq), 140.4 (Cq), 142.3 (Cq), 145.5 (Cq), 152.9 (Cq),
154.0 (Cq),155.6 (Cq),167.7 (C]O) ppm. MS (EI) m/z(%): 464 (100, Mþ),
31.5 (Cq, tBu), 52.5 (OCH3), 98.5 (PzeCH), 111.8 (C-7), 121.4 (C-4),
125.1 (Cq),125.1 (C-6),128.7 (Cq),128.9,131.0,135.5 (Cq),140.6 (Cq),

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R. Abonia et al. / European Journal of Medicinal Chemistry 46 (2011) 4062e4070
463 (15), 449 (32, M ꢀ CH3), 433 (9, M ꢀ OCH3), 407 (13, M ꢀ tBu), 403
(8), 389 (15), 333 (8), 181 (11). Anal. Calcd. for C25H28N4O5: C, 64.64; H,
6.08; N, 12.06. Found: C, 64.72; H, 5.96; N, 12.20.
31.3 (Cq, tBu), 52.1 (OCH3), 55.7 (OCH3), 55.9 (OCH3), 98.7 (PzeCH),
110.6 (C-7), 110.8 (Cq), 112.1, 121.6 (C-4), 122.0 (Cq), 122.6, 124.8,
125.1 (C-6), 140.4 (Cq), 142.4 (Cq), 145.5 (Cq), 148.5 (Cq), 150.6 (Cq),
154.2 (Cq), 155.5 (Cq), 167.7 (C]O) ppm. MS (EI) m/z (%): 434 (100)
[Mþ], 419 (24) [M ꢀ CH3], 403 (25) [M ꢀ OCH3], 299 (2) [M ꢀ 135].
Anal. Calcd. for C24H26N4O4: C, 66.34; H, 6.03; N, 12.89. Found: C,
66.50; H, 6.10; N, 12.73.
4.5.7. Methyl 1-(5-tert-butyl-1H-pyrazol-3-yl)-2-(2-hydroxyphenyl)-
1H-benzo[d]imidazole-5-carboxylate (11g)
Pale yellow solid. FTIR
2969, 1697 (C]O), 1624 (C]C), 1568 (C]N), 1485, 1317, 1301, 1231,
804, 759; 1H NMR (CDCl3)
1.37 (s, 9H, tBu), 4.00 (s, 3H, OCH3), 6.14
n
(cmꢀ1): 3324 (broad, OH and NH), 3138,
d
4.5.11. Methyl 1-(5-tert-butyl-1H-pyrazol-3-yl)-2-phenyl-1H-benzo
(s, 1H, PzeCH), 6.65 (td, 1H, AreH, J ¼ 8.4 Hz, J ¼ 1.2 Hz), 7.04 (dd,
1H, 7-H, J ¼ 8.0 Hz, J ¼ 1.6 Hz), 7.13 (dd, 1H, AreH, J ¼ 8.4 Hz,
J ¼ 1.2 Hz), 7.30 (bt, 2H, AreH, J ¼ 8.4 Hz), 8.05 (dd, 1H, 6-H,
J ¼ 8.0 Hz, J ¼ 1.6 Hz), 8.51 (bd,1H, 4-H, J ¼ 0.8 Hz),12.48 (s, 1H, NH),
[d]imidazole-5-carboxylate (11k)
Pale yellow solid. FTIR
2865, 1715 (C]O), 1646, 1616 (C]C), 1568 (C]N), 1503, 1476, 1434,
1359, 1299, 1251, 1211, 1088, 772, 695; 1H NMR (CDCl3)
1.35 (s, 9H,
n
(cmꢀ1): 3190 (NH), 3135, 3105, 2963,
d
(signal for OH is missing) ppm; 13C NMR (CDCl3)
d
29.9 (tBu), 31.5
tBu), 3.99 (s, 3H, OCH3), 5.88 (s, 1H, PzeCH), 7.36e7.46 (m, 3H,
AreH), 7.52 (d, 1H, 7-H, J ¼ 8.5 Hz), 7.72 (d, 2H, AreH, J ¼ 8.5 Hz),
8.06 (dd, 1H, 6-H, J ¼ 8.5 Hz, J ¼ 1.6 Hz), 8.59 (bd, 1H, 4-H,
(Cq, tBu), 52.2 (OCH3), 99.3 (PzeCH), 110.7 (C-7), 112.0 (Cq), 118.0,
118.2, 120.9 (C-4), 125.5 (C-6), 125.7 (Cq), 127.2, 132.1, 139.4 (Cq),
139.8 (Cq), 145.2 (Cq), 152.9 (Cq), 156.2 (Cq), 159.6 (Cq), 167.5 (C]
O) ppm. MS (EI) m/z (%): 390 (100, Mþ), 389 (41), 375 (24, M ꢀ CH3),
373 (48, M ꢀ OH), 359 (6, M ꢀ OCH3), 333 (6, M ꢀ tBu), 317 (15), 299
(23), 172 (54). Anal. Calcd. for C22H22N4O3: C, 67.68; H, 5.68; N,
14.35. Found: C, 67.75; H, 5.54; N, 14.49.
J ¼ 1.0 Hz), 10.24 (bs, 1H, NH) ppm; 13C NMR (CDCl3)
d 29.9 (tBu),
31.3 (Cq, tBu), 51.9 (OCH3), 98.6 (PzeCH), 111.1 (C-7), 122.1 (C-4),
125.0 (C-6), 125.3 (Cq), 128.1, 129.4, 129.9, 140.1 (Cq), 142.7 (Cq),
145.7 (Cq), 150.4 (Cq), 154.3 (Cq), 155.1 (Cq), 167.6 (C]O) ppm. MS
(EI) m/z (%): 374 (100, Mþ), 373 (54), 359 (36, M ꢀ CH3), 343 (27,
M ꢀ OCH3), 317 (19, M ꢀ tBu), 179 (13), 164 (80), 136 (24). Anal.
Calcd. for C22H22N4O2: C, 70.57; H, 5.92; N, 14.96. Found: C, 70.54;
H, 6.00; N, 15.07.
4.5.8. Methyl 1-(5-tert-butyl-1H-pyrazol-3-yl)-2-(3-hydroxy-4-
methoxyphenyl)-1H-benzo[d]imidazole-5-carboxylate (11h)
Pale yellow solid. FTIR
1712 (C]O), 1608 (C]C), 1502 (C]N), 1435, 1302, 1287, 1221, 1127,
760; 1H NMR (DMSO-d6)
1.33 (s, 9H, tBu), 3.63 (s, 3H, OCH3), 3.89 (s,
n
(cmꢀ1): 3301 (broad OH and NH), 2963,
4.5.12. Methyl 1-(5-tert-butyl-1H-pyrazol-3-yl)-2-(4-(trifluoro-
methyl)phenyl)-1H-benzo[d]imidazole-5-carboxylate (11l)
d
3H, OCH3), 6.24 (s,1H, PzeCH), 6.82 (d,1H, AreH, J ¼ 8.0 Hz), 7.10 (d,
1H, AreH, J ¼ 2.0 Hz), 7.25 (dd,1H, AreH, J ¼ 8.4 Hz, J ¼ 2.0 Hz), 7.30
(d, 1H, 7-H, J ¼ 8.4 Hz), 7.89 (dd, 1H, 6-H, J ¼ 8.4 Hz, J ¼ 1.6 Hz), 8.30
(bd, 1H, 4-H, J ¼ 1.6 Hz), 9.61 (s, 1H, OH), 13.08 (s, 1H, NH) ppm; 13C
White solid. FTIR
1615 (C]C), 1564 (C]N), 1511, 1434, 1321, 1163, 1127, 848, 753; 1H
NMR (CDCl3) 1.32 (s, 9H, tBu), 3.99 (s, 3H, OCH3), 5.94 (s, 1H,
n
(cmꢀ1): 3284 (NH), 3135, 2970, 1692 (C]O),
d
PzeCH), 7.50 (d, 1H, 7-H, J ¼ 8.6 Hz), 7.62 (d, 2H, AreH, J ¼ 8.3 Hz),
7.85 (d, 2H, AreH, J ¼ 8.3 Hz), 8.10 (dd, 1H, 6-H, J ¼ 8.5 Hz,
J ¼ 1.2 Hz), 8.60 (bd, 1H, 4-H, J ¼ 0.8 Hz), 11.17 (bs, 1H, NH) ppm; 13C
NMR (DMSO-d6) d 30.3 (tBu), 31.5(Cq, tBu), 52.5 (OCH3), 55.6(OCH3),
98.8 (PzeCH), 111.3 (C-7), 112.8, 115.9, 120.5 (Cq), 120.8 (C-4), 123.0,
124.5 (C-6), 124.7 (Cq), 141.0 (Cq), 142.4 (Cq), 144.2 (Cq), 147.5 (Cq),
149.1 (Cq), 154.6 (Cq), 155.5 (Cq), 167.1 (C]O) ppm. MS (EI) m/z (%):
420 (0.53, Mþ), 405 (0.12, M ꢀ CH3), 389 (0.1, M ꢀ OCH3), 363 (0.11,
M ꢀ tBu), 288 (0.15), 32 (28), 28 (100). Anal. Calcd. for C23H24N4O4: C,
65.70; H, 5.75; N, 13.33. Found: C, 65.64; H, 5.60; N, 13.49.
NMR (CDCl3) d 29.9 (tBu), 31.4 (Cq, tBu), 52.2 (OCH3), 98.5 (PzeCH),
111.3 (C-7), 122.3 (C-4), 125.1 (q, CH, J ¼ 4 Hz), 125.6 (C-6), 128.9 (2ꢃ
CH and 1Cq), 129.0 (q, CF3, J ¼ 209 Hz), 131.9 (q, CqeF, J ¼ 38 Hz),
133.1 (Cq), 140.2 (Cq), 142.4 (Cq), 144.8 (Cq), 152.6 (Cq), 155.8 (Cq),
167.6 (C]O) ppm. MS (EI) m/z (%): 442 (100, Mþ), 441 (51), 427 (25,
M ꢀ CH3), 411 (50, M ꢀ OCH3), 385 (9, M ꢀ tBu), 198 (19), 188 (64),
171 (20), 156 (37), 129 (28). Anal. Calcd. for C23H21F3N4O2: C, 62.44;
H, 4.78; N, 12.66. Found: C, 62.53; H, 4.64; N, 12.69.
4.5.9. Methyl 1-(5-tert-butyl-1H-pyrazol-3-yl)-2-(4-(dimethylamino)
phenyl)-1H-benzo[d]imidazole-5-carboxylate (11i)
White solid. FTIR
1711 (C]O), 1609 (C]C), 1567 (C]N), 1513, 1483, 1433, 1291, 1235,
1203, 826; 1H NMR (CDCl3)
1.30 (s, 9H, tBu), 2.99 [s, 6H, N(CH3)2],
n
(cmꢀ1): 3131 (NH), 3100, 2964, 2922, 2851,
4.5.13. Methyl 2-(benzo[d] [1,3]dioxol-5-yl)-1-(5-tert-butyl-1H-
d
pyrazol-3-yl)-1H-benzo[d]imidazole-5-carboxylate (11m)
3.96 (s, 3H, OCH3), 5.94 (s,1H, PzeCH), 6.61 (d, 2H, AreH, J ¼ 9.2 Hz),
7.37 (d, 1H, 7-H, J ¼ 8.4 Hz), 7.58 (d, 2H, AreH, J ¼ 9.2 Hz), 7.96 (dd,
1H, 6-H, J ¼ 8.4 Hz, J ¼ 1.6 Hz), 8.50 (d,1H, 4-H, J ¼ 1.2 Hz), (signal for
Pale yellow solid. FTIR
1618 (C]C), 1566 (C]N), 1507, 1473, 1437, 1300, 1241, 1029; 1H
NMR (CDCl3) 1.29 (s, 9H, tBu), 3.97 (s, 3H, OCH3), 5.91 (s, 1H,
n
(cmꢀ1): 3316 (NH), 2961, 1725 (C]O),
d
PzNH is missing) ppm; 13C NMR (CDCl3)
d
30.0 (tBu), 31.3 (Cq, tBu),
PzeCH), 5.99 (s, 2H, OCH2O), 6.78 (d, 1H, AreH, J ¼ 8.4 Hz), 7.19 (bd,
1H, AreH, J ¼ 1.6 Hz), 7.21 (dd, 1H, AreH, J ¼ 8.4 Hz, J ¼ 1.6 Hz), 7.46
(d, 1H, 7-H, J ¼ 8.4 Hz), 8.03 (dd, 1H, 6-H, J ¼ 8.4 Hz, J ¼ 1.6 Hz), (bd,
40.1 [N(CH3)2], 52.0 (OCH3), 98.7 (PzeCH), 110.6, 111.2 (C-7), 116.5
(Cq), 121.1 (C-4), 124.3 (C-6), 124.7 (Cq), 130.3, 140.6 (Cq), 142.6 (Cq),
145.3 (Cq), 151.3 (Cq), 155.1 (Cq), 155.4 (Cq), 167.9 (C]O) ppm. MS
(EI) m/z (%): 417 (100, Mþ), 416 (22), 403 (15), 402 (22, M ꢀ CH3), 386
(6, M ꢀ OCH3), 360 (13, M ꢀ tBu). Anal. Calcd. for C24H27N5O2: C,
69.04; H, 6.52; N, 16.77. Found: C, 68.94; H, 6.65; N, 16.69.
1H, 4-H, J ¼ 1.2 Hz), 11.54 (bs, 1H, NH) ppm; 13C NMR (CDCl3)
d 8.53
(tBu), 31.3 (Cq, tBu), 52.2 (OCH3), 98.6 (PzeCH), 101.5 (OCH2O),
108.2, 109.6, 111.1(C-7), 121.7 (C-4), 123.2 (Cq), 124.1, 124.9 (C-6),
125.1 (Cq), 140.3 (Cq), 142.3 (Cq), 145.0 (Cq), 147.6 (Cq), 149.2 (Cq),
154.0 (Cq), 155.6 (Cq), 167.8 (C]O) ppm. MS (EI) m/z (%): 418 (100,
Mþ), 417 (41), 403 (42, M ꢀ CH3), 387 (21, M ꢀ OCH3), 361 (22,
M ꢀ tBu), 194 (22), 179 (27). Anal. Calcd. for C23H22N4O4: C, 66.02;
H, 5.30; N, 13.39. Found: C, 65.94; H, 5.17; N, 13.50.
4.5.10. Methyl 1-(5-tert-butyl-1H-pyrazol-3-yl)-2-(3,4-dimethoxy-
phenyl)-1H-benzo[d]imidazole-5-carboxylate (11j)
White solid. FTIR
(C]O), 1650, 1617 (C]C), 1566 (C]N), 1504, 1474, 1439, 1359, 1305,
1218, 1089, 765, 695; 1H NMR (CDCl3)
1.32 (s, 9H, tBu), 3.79 (s, 3H,
n
(cmꢀ1): 3195 (NH), 3137, 2965, 2850, 1716
d
4.5.14. Methyl 1-(5-tert-butyl-1H-pyrazol-3-yl)-2-(2-oxo-1,2-
OCH3), 3.91 (s, 3H, OCH3), 3.97 (s, 3H, OCH3), 5.96 (s, 1H, PzeCH),
6.83 (d, 1H, AreH, J ¼ 8.4 Hz), 7.28 (bd, 1H, AreH, J ¼ 2.0 Hz), 7.30
(dd, 1H, AreH, J ¼ 8.4 Hz, J ¼ 2.0 Hz), 7.42 (d, 1H, 7-H, J ¼ 8.4 Hz),
8.03 (dd, 1H, 6-H, J ¼ 8.4 Hz, J ¼ 1.6 Hz), 8.55 (bd, 1H, 4-H,
dihydroquinolin-3-yl)-1H-benzo[d]imidazole-5-carboxylate (11n)
Pale yellow solid. FTIR
n
(cmꢀ1): 3290 (broad 2ꢃ NH), 3173, 2963,
2866, 1721 (C]O), 1662 C]O, 1614 (C]C), 1568 (C]N), 1516, 1434,
1310, 1285, 1216, 1086, 751; 1H NMR (DMSO-d6)
3.92 (s, 3H, OCH3), 6.23 (s, 1H, PzeCH), 7.25 (t, 1H, AreH, J ¼ 8.5 Hz),
d 1.26 (s, 9H, tBu),
J ¼ 0.8 Hz), 11.26 (bs, 1H, NH) ppm; 13C NMR (CDCl3)
d 30.0 (tBu),

R. Abonia et al. / European Journal of Medicinal Chemistry 46 (2011) 4062e4070
4069
F. Hernández-Luis, R. Cedillo, J. González, A. Martínez-Fernández,
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[11] (a) M.R. Grimmet, in: A.R. Katritzky, C.W. Rees (Eds.), Comprehensive
Heterocyclic Chemistry, Vol. 5, 1984, p. 457;
7.33 (d, 1H, AreH, J ¼ 8.4 Hz), 7.58 (t, 1H, AreH, J ¼ 8.5 Hz), 7.78 (d,
1H, 7-H, J ¼ 8.4 Hz), 7.81 (d, 1H, AreH, J ¼ 8.8 Hz), 8.00 (dd, 1H, 6-H,
J ¼ 8.4 Hz, J ¼ 1.6 Hz), 8.36 (bd, 1H, 4-H, J ¼ 1.6 Hz), 8.42 (s, 1H,
AreH), 12.05 (s, 1H, NH), 12.72 (s, 1H, NH) ppm; 13C NMR (DMSO-d6)
d
30.3 (tBu), 31.3 (Cq, tBu), 52.6 (OCH3), 95.6 (PzeCH), 112.2 (C-7),
(b) J.B. Wright, Chem. Rev. 48 (1951) 396e541.
115.4,119.0 (Cq), 121.4 (C-4), 122.7, 124.6 (Cq), 124.7 (Cq), 125.1 (C-6),
129.2, 132.1, 138.6 (Cq), 139.9 (Cq), 142.5 (Cq), 142.9, 144.4 (Cq), 151.7
(Cq), 154.3 (Cq), 160.1 (C]O), 167.1 (C]O) ppm. MS (EI) m/z (%): 441
(0.2, Mþ), 440 (0.6), 424 (18), 423 (62), 422 (21), 409 (28), 408 (99),
407 (12), 381 (14), 368 (13), 309 (18), 189 (100), 169 (79), 155 (31),
141 (27). Anal. Calcd. for C25H23N5O3: C, 68.01; H, 5.25; N, 15.86.
Found: C, 67.94; H, 5.37; N, 15.92.
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Acknowledgments
The authors wish to credit The Developmental Therapeutics
Program (DTP) of the National Cancer Institute of the United States
(U.S.) for performing the screening of compounds. This work was
supported financially by Colciencias, Universidad del Valle, Con-
sejería de Innovación, Ciencia y Empresa (Junta de Andalucía,
Spain) and The Universidad de Jaén. Authors thank "Servicios
Técnicos de Investigación de la Universidad de Jaén" and the staff
for data collection.
(h) X. Han, H. Ma, Y. Wang, ARKIVOC xiii (2007) 150e154.
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AppendixSupplementary material
(h) M.M. Heravi, S. Sadjadi, H.A. Oskooie, R.H. Shoar, F.F. Bamoharram, Catal.
Commun. 9 (2008) 504e507;
(i) H. Sharghi, O. Asemani, R. Khalifeh, Synth. Commun. 38 (http://www.
informaworld.com/smpp/
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.ejmech.2011.06.006.
titlewcontent¼t713597304wdb¼allwtab¼issueslistwbranches¼38-
v382008) 1128e1136. (j) R. Trivedi, S.K. De, R.A. Gibbs, J. Mol. Catal. A: Chem.
245 (2006) 8e11;
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