Synthesis and Pharmacological Investigations of Novel Pyrazolyl and Hydrazonoyl Cyanide Benzimidazole Entities

Article abstract of DOI:10.1002/jhet.3522

Various novel benzimidazole entities linked to pyrazolyl and hydrazonoyl cyanide substrates carrying aryl and heteroaryl groups (8a–e to 10a–e) were synthesized using new route syntheses and were focused on their pharmacological evaluation as one of the m

Full text of DOI:10.1002/jhet.3522

Month 2019
Synthesis and Pharmacological Investigations of Novel Pyrazolyl and
Hydrazonoyl Cyanide Benzimidazole Entities
a
Mohamed E. Khalifa,
Adil A. Gobouri,a Fahad M. Kabli,a Tariq A. Altalhi,a Abdulraheem S. A. Almalki,a and
*
Amira M. Elemshatyb
aDepartment of Chemistry, Faculty of Science, Taif University, Taif 21974, Saudi Arabia
bSoil, Water & Environment Research Institute, Agricultural Research Center, Giza, Egypt
*E-mail: mohamedezzat200@hotmail.com; mohamedezzat@tu.edu.sa
Received October 22, 2018
DOI 10.1002/jhet.3522
Published online 00 Month 2019 in Wiley Online Library (wileyonlinelibrary.com).
Various novel benzimidazole entities linked to pyrazolyl and hydrazonoyl cyanide substrates carrying aryl
and heteroaryl groups (8a–e to 10a–e) were synthesized using new route syntheses and were focused on their
pharmacological evaluation as one of the most important factors for the determination of the activity of these
synthesized compounds. The obtained benzimidazoles’ series were fully characterized and exhibited remark-
able pharmacological activity upon in vitro screening for their antibacterial activity against strains of selected
pathogenic Gram-positive bacteria (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli)
comparing with Ampicillin and Kanamycin as standard antibacterial agents and against human liver cancer
cell lines (HepG2) as antitumor agents as well.
J. Heterocyclic Chem., 00, 00 (2019).
INTRODUCTION
RESULTS AND DISCUSSION
Prevalence of infectious and malignant diseases has
increased as much as the need for antimicrobial and
antitumor agents, which are great importance for human
survival [1]. The promising therapeutic potential of
organic compounds containing benzimidazole scaffold as
a core unit could be traced back to 19th century [2] and
is found to exhibit various biological and pharmaceutical
activities such as antibacterial [3], antifungal [4], antiviral
[5,6], antioxidant [7], anticancer [8], analgesic [9], anti-
inflammatory [10], antitubercular [11], antihelminthic
[12], anticonvulsant [13], antiulcer [14], angiotensin-II
receptor antagonists [15], antihypertensive [16], and to
fluconazole against Candida albicans [4]. The
combination of several types of hetero moieties into one
vessel could produce a novel entity with enhanced
bioactivities [17]. Based on the aforementioned reported
findings, we have planned to synthesize a novel series of
benzimidazole scaffolds derived from 2-(bromomethyl)-
1H-benzimidazole (1) followed by their in vitro
antibacterial as well as their antioxidant activity and
antitumor activity against HepG2 cell line human
hepatocyte carcinoma.
Encouraged by our interest to design and synthesize
potent biologically active compounds based on
heterocyclic moieties containing sulfur and nitrogen
compounds [18–22], benzimidazole derivatives have
attracted our attention as important class of biological
characteristics and clinical applications. Herein we report
the synthesis of new benzimidazole derivatives starting
from 2-(bromomethyl)-1H-benzimidazole (1) followed by
functionalized reactions using new route syntheses and
study their potential as bioactive compounds as described
through this work.
Chemistry.
In the current scenario, the starting
compound 2-(bromomethyl)-1H-benzimidazole (1) was
synthesized according to the reported method by the
reaction of o-phenylenediamine with 2-bromoacetic acid
[23–25]. A series of interesting reactions has been
performed
2-(bromomethyl)-1H-benzimidazole (1). Thus, reaction
of 2-(bromomethyl)-1H-benzimidazole (1) with
based
on
the
reactivity
of
the
hydrazine hydrate gave the functionalized hydrazide
derivative 2-(hydrazineylmethyl)-1H-benzimidazole (2)
as depicted in Scheme 1, which is considered as
© 2019 Wiley Periodicals, Inc.

M. E. Khalifa, A. A. Gobouri, F. M. Kabli, T. A. Altalhi, A. S. A. Almalki, and A. M. Elemshaty Vol 000
precursor for novel hydrazineyl and pyrazolone
benzimidazoles.
2-(hydrazineylmethyl)-1H-benzimidazole (2) in the
presence of sodium ethoxide (Schemes 3–5). In
traditional way, the Knorr pyrazole synthesis was
reported widely using an acid catalyst [31], as the β-keto
esters acted as Michael donors and hence underwent
cycloaddition reaction with hydrazineyl derivative to
obtain pyrazolone derivatives [32–34]. As a new route,
using basic catalyst, the mechanism of the reaction was
assumed to go on the pathway in order to afford the
hydrazono intermediate before cyclization to obtain the
target pyrazolone derivatives (8a–e) as basic heterocyclic
nucleus as illustrated in Scheme 3 and Figure 1.
The infrared (IR) spectrum of the hydrazide (2) revealed
intense IR bands at 3358, 3244 cmꢀ1 (NH, NH2), 1547
cmꢀ1 (NH bending), 1614 cmꢀ1 (C═N), and 1418 cmꢀ1
1
(CH2 bending). The H NMR spectrum of (2) displayed
singlet signal at δ 4.65 ppm due to the methylene protons
(2H, CH2–NH), δ 7.12–7.46 ppm due to the aromatic
protons, and singlet at δ 10.21 ppm due to the NH–
benzimidazole proton.
Thus, two-step reaction was performed in order to
synthesize a new set of 2-((1H-benzimidazol-2-yl)methyl)-
4-(2-arylhydrazineylidene)-3,5-disubstituted
pyrazolyl
Unlikely the routine methodology, the condensation
reaction of the hydrazide compound (2) with (6a–e and/or
7a–e) was going without further internal cyclization to
afford 2-oxo (and/or amino)acetohydrazonoyl cyanide
derivatives (9a–e and 10a–e) as shown by Schemes 4 and
5. To the best of our knowledge, the strongly deactivating
action of nitrile group than acetyl group as Pi-acceptors
might explain this phenomenon. The nitrile group tended
to polarize the electron density from the adjacent Pi
system and hence hindered its reduction and cyclization
afterwards.
derivatives using aryldiazenyl derivatives (5a–e to 7a–e),
but unexpected results were obtained as being explained
later on. Firstly, various methods were reported for the
preparation of the aryldiazenyl derivatives (5a–e to 7a–e)
[26–30]. In this study, we were going to prepare the target
intermediate agents by azo coupling reaction of active
methylene compounds (3a–c) (i.e., ethyl acetoactate, ethyl
cyanoacetate, and malononitrile) with different freshly
prepared aryl/heteryl diazonium salts (4a–e) in mild
conditions (Scheme 2).
Secondly, the aryl/heteryl hydrazonyl derivatives (5a–e
Generally, the IR spectra of derivatives (8–10) revealed
characteristic IR bands at 3738–3740 cmꢀ1 (NHstr.),
3264–3850 cmꢀ1 (NH2, 10a–e), 2913–3164 (NH–
hydrazo), 1653–1735 cmꢀ1 (CO pyrazolone, 8a–e) and
1642–1688 cmꢀ1 (CO amide, 9a–e), 2175–2228 cmꢀ1
to
7a–e)
were
allowed
to
react
with
Scheme 1. Synthesis of 2-(hydrazineylmethyl)-1H-benzimidazole (2).
1
(CN, 9a–e and 10a–e). The H NMR spectrum displayed
singlet signal at 2.27–2.72 ppm due to the methyl protons
(3H, CH3 pyrazolone ring, 8a–e) and singlet at 12.16–
12.45 ppm due to the NH–benzimidazole proton.
Scheme 2. Preparation of the aryldiazenyl derivatives (5a–e to 7a–e).
Scheme 3. Synthesis of 2-arylhydrazineylidene-3,5-disubstituted pyrazolyl derivatives (8a–e).
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Month 2019
Novel Benzimidazole Entities: Synthesis and Pharmacological Investigations
Scheme 4. Synthesis of 2-oxoacetohydrazonoyl cyanide derivatives (9a–e).
Scheme 5. Synthesis of 2-aminoacetohydrazonoyl cyanide derivatives (10a–e).
Figure 1. Mechanism of formation of compounds (8a–e).
PHARMACOLOGICAL EVALUATION
The novel synthesized
compounds (8 to 10a–e, 100 μg/mL in DMSO) were
subjected in vitro to antibacterial assay using disc
diffusion method against two streams of pathogenic
microorganisms Escherichia coli (Gram-negative bacteria)
and Staphylococcus aureus (Gram-positive bacteria) in the
media of nutrient agar [35]. The antibacterial activity was
expressed by measuring the inhibition zone in mm, and
the bactericides Ampicillin and Kanamycin respectively
were served as positive reference standards (Fig. 1). It was
shown that most of the tested compounds exhibited broad-
spectrum antimicrobial activities against both Gram-
positive bacteria and Gram-negative bacteria, with
inhibition percentage in the range of 50% to 78%.
Antimicrobial performance.
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M. E. Khalifa, A. A. Gobouri, F. M. Kabli, T. A. Altalhi, A. S. A. Almalki, and A. M. Elemshaty Vol 000
Presence of strong electron withdrawing group (e.g.,
compound 9d) showed higher activity against E. coli
(Gram-negative bacteria), while most of the synthesized
compounds exhibited moderate to good activity against
S. aureus (Gram-positive bacteria).
and the reaction between DPPH, and antioxidant can be
monitored by the decrease in absorbance of the violet
colored free radical. Inhibition percentages of DPPH
radical by tested compounds were plotted in Figure 3,
and the measure of drug’s potency in terms of half-
maximal effective concentration (EC50) values was
plotted in Figure 4, which referred to the compound
concentration where 50% of its maximal effect was
observed. The resonance phenomena of double bonds and
lone pair electrons on nitrogen may lead to radical
formation in more than one site, especially on the
benzene ring attached to the nitro group (highly electron
withdrawing group) that enabled the benzene ring to
convert to a radical form and forms a new covalent bond
with another radical (e.g., 8a, 8b, 8d, 8e, 10b, 10c, and
10e – the highest DPPH values and the lowest EC50
values). This may explain the good antioxidant and
scavenging activities of the tested compounds. The
presence of pyrazole and benzimidazole rings in one
compound (e.g., 8a–e) and fewer rings in others gave
them the advantage over other structures. This conclusion
was also supported by previously reported results [39].
The plotted data in Figure 2 showed that most of the
tested compounds exhibited variable antimicrobial
activities from nil to moderate to high depending on their
chemical structure. It is obviously clear that the presence
of strong electron withdrawing group (e.g., nitro group)
linked to the phenyl function (e.g., compounds 8d, 9d,
and 10d) showed higher activity against Gram-positive
bacteria (i.e., S. aureus) than the positive control
(Kanamycin). Introducing a phenyl function enhanced the
reactivity against S. aureus (Gram-positive bacteria),
where the action of phenyl nucleus was referred to its
ability to form unstable complexes on the cell membrane
and hence inactivating intracytoplasm enzymes [36,37].
Most of the synthesized compounds exhibited nil to
moderate activity against E. coli (Gram-negative bacteria)
comparing with its positive control (Ampicillin).
Antioxidant potential of the synthesized compounds.
The method DPPH (2,2-diphenyl-1-picrylhydrazyl) free
radical scavenging assay incorporating a metastable free
radical was used to provide accurate expression for the
antioxidant activity of the synthesized compounds
comparing with the intracellular scavenging activity of
Cytotoxicity evaluation.
All synthesized compounds
were screened in vitro for possible potential antitumor
molecules against human liver cancer cell line (HepG2)
and showed variable anticancer activity. Neutral red (NR)
technique was used to evaluate the cytotoxic effects of
gradient concentration (100 to 500 μg/mL) of tested
compounds in terms of cell viability, where the lower
values showed higher antitumor potency (Fig. 5). The
Trolox
(6-hydroxy-2,5,7,8-tetramethylchromane-2-
carboxylic acid) as standard agent [38]. That is capable of
accepting hydrogen radicals from antioxidants in solution
Figure 2. Antimicrobial activity of the novel benzimidazole derivatives against selected pathogenic bacteria. [Color figure can be viewed at
wileyonlinelibrary.com]
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Month 2019
Novel Benzimidazole Entities: Synthesis and Pharmacological Investigations
Figure 3. Inhibition percentage of DPPH radical by novel synthesized benzimidazoles compared with Trolox. [Color figure can be viewed at
wileyonlinelibrary.com]
Figure 4. EC50: concentration of novel synthesized benzimidazoles that give half-maximal response compared with Trolox. [Color figure can be viewed
at wileyonlinelibrary.com]
half-maximal inhibitory concentration (IC50) values that
measured the potency of the compound in inhibiting a
specific biological function relative to Doxorubicin
(25.66 μg/mL) were evaluated and plotted in Figure 6.
The decrease of the IC50 value of the tested compound
indicated its higher efficiency against tumor cell.
As shown in Figures 5 and 6, the tested compounds
exhibited broad-spectrum antitumor activity in different
concentrations, where increasing the concentration lead to
less viability percentage and the IC50 values indicated the
medium to higher potency of compounds 9c, 9e, and
10a–e comparing with reference compound. The presence
of the antipyrinyl and the 4-phenyl function with a nitro
group (e.g., 8e, 10e, 8a, and 10a) increased the antitumor
activity because of their high antioxidant and free radical
scavenging activities. This structure may lead to radical
formation in more than one site, especially on the
benzene ring attached to the nitro group (e.g., 10a),
which is a highly electron withdrawing group that
enables the benzene ring to convert to a radical form and
formed a new covalent bond with another radical as
previously reported [40]. The biocompatibility of the
nitrile functionality [41] assisted the prevalence of
clinical nitrile-containing pharmaceuticals. It is well
known that the nitrile group should be activated by
adjacent structural elements such as electron withdrawing
groups to play the electrophilic role towards free
nucleophiles [42]. Subsequent release of cyanide from
alkylnitriles bearing an adjacent proton can be oxidized
in the liver to cyanohydrins [43]. The potential oxidation
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M. E. Khalifa, A. A. Gobouri, F. M. Kabli, T. A. Altalhi, A. S. A. Almalki, and A. M. Elemshaty Vol 000
Figure 5. Viability % of HepG2 cell line treated with novel synthesized benzimidazoles at 100, 250, and 500 μg/mL. [Color figure can be viewed at
wileyonlinelibrary.com]
Figure 6. IC50: half-maximal inhibitory concentration values relative to Doxorubicin. [Color figure can be viewed at wileyonlinelibrary.com]
and cyanide ejection likely explains the success of several
alkenenitrile-containing pharmaceuticals in this study.
cancer cell line (HepG2) using NR technique to evaluate
cytotoxic effects of gradient concentrations (100 to
500 μg/mL) of test compounds on human liver (HepG2)
cell line and in terms of cell viability and IC50 values.
The tested compounds exhibited acceptable efficiency
against human liver (HepG2) cell line. The increase in
efficiency among synthesized compounds may be due to
the presence of electron withdrawing substituent,
pyrazole, benzimidazole and antipyrinyl rings in one
compound and fewer rings in others.
CONCLUSIONS
The newly synthesized benzimidazole derivatives 8a–e
to 10a–e were prepared and fully characterized. They
exhibited variable in vitro antibacterial activities against
S. aureus (Gram-positive bacteria) and E. coli (Gram-
negative bacteria) comparing with Ampicillin and
Kanamycin as standard antibacterial agent related to their
chemical structure. The compounds 8a, 8b, 8d, 8e, 10b,
10c, and 10e showed more inhibition effect against
DPPH (the lowest EC50 values) compared with Trolox
(EC50 = 55.13) and other tested compounds. They were
screened for their antitumor activities against human liver
EXPERIMENTAL
Materials for chemical reactions.
All chemicals and
reagents used were analytical grade or chemically pure
and supplied by Sigma Aldrich Co., Darmstadt, Germany.
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Micro and spectroscopic analysis. All the synthesized
compounds were micro-analyzed satisfactorily for C, H,
and N by the PerkinElmer 2400 Analyzer, series II
(PerkinElmer Co., Shelton, UK); their results were found
to be in good agreement ( 0.3%) with the calculated
values. All of the corrected melting points are in degree
centigrade and measured using a Stuart SMP20 melting
point apparatus (Bibby Scientific Limited, Staffordshire,
UK). The IR spectra were recorded on a PerkinElmer
Alpha platinum-ATR spectrometer, the 1H NMR
(300 MHz) and 13C NMR (75 MHz) spectra were
recorded on a Varian Mercury VXR-300 spectrometer
(Varian Inc., Palo Alto, CA, USA), and the chemical shifts
were related to that of the solvent DMSO-d6 using TMS as
an internal standard. The EI-MS analysis was carried out
using TRACE GC Ultra Gas Chromatographs–mass
spectrometry, coupled with THERMO mass spectrometer
detector–ISQ Single Quadrupole Mass Spectrometer
(THERMO Scientific Corp., Waltham, MA, USA), and
was obtained by electron ionization at 70 eV, using a
spectral range of m/z 50–1000. All of the microanalyses
and spectral analyses were performed by the Micro
Analytical Centers of Taif University–Saudi Arabia [IR
spectra and high-resolution mass spectrometry (HRMS)],
Cairo University (1H NMR and 13C NMR), and National
Research Center–Egypt (mass spectra).
recrystallized from acetone to give red crystals. Yield
86%, mp 140–141°C (60°C [44], 59–61°C [45]).
Synthesis of 2-(hydrazineylmethyl)-1H-benzimidazole
(2).
A mixture of 2-(bromomethyl)-1H-benzimidazole
(1) (2.11 g, 10 mmol) and hydrazine hydrate 80%
(1.25 mL, 25 mmol) was heated under reflux for 2 h. The
reaction mixture allowed cooling at room temperature,
and the formed solid product was then recrystallized from
ethanol/water to obtain the 2-(hydrazineylmethyl)-1H-
benzimidazole (2) as yellow solid. Yield 62%, mp 175–
178°C (197–198°C [46], 114°C [47]).
General procedure for the synthesis of aryldiazenyl
derivatives (5a–e to 7a–e).
The corresponding aryl
diazonium chloride was prepared by adding cold sodium
nitrite solution (0.69 g in 15 mL H2O) to a cold
suspension of different aryl and hetaryl amines
(10 mmol) in concentrated HCl (4 mL) with stirring. To a
cold solution of 10 mmol the functionalized active
methylene compounds ethyl chloroacetate, ethyl
cyanoacetate, and malononitrile (5, 1.30 g; 6, 1.13 g; and
7, 0.66 g; respectively) in ethanol (20 mL) and sodium
acetate (1.6 g, 20 mmol), a cold aqueous solution from
the corresponding aryl diazonium chloride was added
dropwise with stirring at 0–5°C for 2 h. The solid
product obtained was filtered, washed with water
followed by cold ethanol, and then dried. The obtained
products were recrystallized from ethanol to give target
Biological analysis.
All used kits for biochemical
aryldiazenyl reaction intermediates (5a–e to 7a–e).
Ethyl-2-(2-(4-nitrophenyl)hydrazineylidene)-3-oxobutanoate
parameters were supplied by Diagnostic Company,
Maidenhead, UK. All chemicals used were supplied by
Gibco®Life Technologies, Waltham, MA, USA. The
biological tests were performed by the Microbiology
Units, Agricultural Research Center and Soil, Water &
Environment Research Institute, Giza, Egypt. Human
transformed cell lines from liver (HepG2) were obtained
from Egyptian company for vaccine and serum
(VACSERA, Cairo, Egypt). The statistical package for
XLFIT5 software (IDBS, London, England) was used for
the statistical analyses.
Neutral red reagent. A quantity of 0.33 g of NR desorb
solution (1% glacial acetic acid and 50% ethanol made in
water) was added to 100 mL H2O2 filter sterilized and
stored at room temperature, protected from light. On the
day of use, the reagent was diluted in media to obtain a
final concentration of 33 μg/mL.
(5a).
Yield 87%, brown solid, mp 158–160°C (145–
146°C [26], 120°C [27]).
Ethyl-3-oxo-2-(2-(p-tolyl)hydrazineylidene)butanoate (5b).
Yield 76%, reddish brown solid, mp 89–90°C (78°C [48],
66°C [49]).
Ethyl-2-(2-(4-acetylphenyl)hydrazineylidene)-3-
oxobutanoate (5c).
Yield 58%, brown solid, mp 134–
136°C (126°C [28]).
Ethyl-2-(2-(3,4-dichlorophenyl)hydrazineylidene)-3-
oxobutanoate (5d). Yield 70%, reddish brown solid, mp
96–98°C. IR: νmax = 3156–2931 (═CH aromatic), 2986
(NH–hydrazo), 1698 (CO ester), 1627 (CO acetyl), 1582
1
(C═N), 1462 (CH2) and 1366 (CH3) cmꢀ1. H NMR: δ/
ppm = 1.30 (q, 2H, CH2 aliphatic), 2.27 (s, 3H, CH3),
3.65 (t, 3H, CH3), 6.74–7.41 (m, 3H, Ar–H), 12.60 (s,
1H, NH–hydrazo). 13C NMR: δ/ppm = 12.8, 28.2, 61.4,
115.6, 118.1, 123.4, 128.6, 129.1, 131.7, 142.4, 168.4,
196.4. MS (m/z, %): 304.12 (M + 1, 32.20). HRMS calc.
for C12H12Cl2N2: 302.0225, found: 302.0221. Anal.
Calcd. for C12H12Cl2N2 (303.14): C, 47.55; H, 3.99; N,
9.24. Found: C, 47.16; H, 3.74; N, 9.11 [50].
General procedure for the synthesis of 2-(bromomethyl)-
1H-benzimidazole
(1).
The
2-bromomethyl
benzimidazole (1) was prepared according to the
literature procedure [23–25], where o-phenylenediamine
(2.16 g, 20 mmol) was dissolved in 30–40 mL of 4M
HCl by heating. The bromoacetic acid (4.16 g, 30 mmol)
was added thoroughly, and then the reaction mixture was
boiled under reflux for 5 h. The mixture was neutralized
with ammonia, and the solid product was filtered, washed
with water, and dried. The obtained product was
Ethyl
2-((1,5-dimethyl-3-oxo-2-phenylpyrazolidin-4-yl)
diazenyl)-3-oxobutanoate (5e). Yield 61%, reddish brown
solid, mp 191°C (179–181°C [51], 169°C [52]).
Ethyl-2-cyano-2-(2-(4-nitrophenyl)hydrazineylidene)acetate
(6a). Yield 89%, reddish brown solid, mp 177–179°C
(173–174°C [53]).
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Ethyl-2-cyano-2-(2-(p-tolyl)hydrazineylidene)acetate (6b).
Yield 60%, yellow solid, mp 120–122°C (105°C [29]).
Ethyl-2-(2-(4-acetylphenyl)hydrazineylidene)-2-cyanoacetate
benzimidazole 2 (1.62 g, 10 mmol) and aryldiazenyl
derivatives 5a–e to 7a–e (10 mmol) was refluxed in the
presence of sodium ethoxide (0.23 g Na/20 mL EtOH,
10 mmol) and ethanol for 6 h. The reaction mixture was
then poured onto ice-cold water containing a few drops
of dilute hydrochloric acid for neutralization. The solid
product obtained was filtered off, washed with cold
water, dried, and recrystallized from proper solvent.
2-((1H-Benzimidazol-2-yl)methyl)-5-methyl-4-(2-(4-
nitrophenyl)hydrazineylidene)-2,4-dihydro-3H-pyrazol-3-one
(8a). Yield 59%, brown solid, mp 204–206°C (EtOH/
(6c).
Yield 67%, brown solid, mp 148–149°C (110–
11°C, acetic acid [54]).
Ethyl-2-cyano-2-(2-(3,4-dichlorophenyl)hydrazineylidene)
acetate (6d). Yield 60%, yellow solid, mp 171–172°C.
IR: νmax = 3210–2980 (═CH aromatic, –CH aliphatic),
3070 (NH–hydrazo), 2212 (CN), 1739 (CO ester), 1591
1
(C═N), 1450 (CH2) and 1408 (CH3) cmꢀ1. H NMR: δ/
ppm = 1.35 (q, 2H, CH2 aliphatic), 3.87 (t, 3H, CH3),
6.58–7.67 (m, 3H, Ar–H), 13.60 (s, 1H, NH–hydrazo).
13C NMR: δ/ppm = 12.9, 61.8, 110.6, 115.3, 116.3,
118.1, 123.4, 129.2, 131.7, 142.5, 161.7. MS (m/z, %):
287.31 (M + 1, 28.11). HRMS calc. for C11H9Cl12N3O2:
285.0072, found: 285.0069. Anal. Calcd. for
C11H9Cl12N3O2 (286.11): C, 46.18; H, 3.17; N, 14.69.
Found: C, 45.87; H, 2.84; N, 14.44 [30].
Ethyl-2-cyano-2-(2-(1,5-dimethyl-3-oxo-2-phenyl-2,3-
dihydro-1H-pyrazol-4-yl)hydrazineylidene)acetate (6e).
Yield 64%, red solid, mp 167–168°C (162–164°C [55]).
N-(4-Nitrophenyl)carbonohydrazonoyl dicyanide (7a).
Yield 85%, yellow solid, mp 206–208°C (214°C [29]).
N-p-Tolylcarbonohydrazonoyl dicyanide (7b). Yield 61%,
DMF). IR: νmax = 3264–2848 (NH, ═CH aromatic, –CH
aliphatic), 3101 (NH–hydrazo), 1677 (CO pyrazolone),
1594 (C═N), 1449 (CH2) and 1410 (CH3) cmꢀ1 1H
.
NMR: δ/ppm = 1.22 (s, 2H, CH2 aliphatic), 2.16 (s, 3H,
CH3 pyrazolone ring), 6.58–8.31 (m, 8H, Ar–H), 12.24
(s, 1H, NH–benzimidazole ring), 13.45 (s, 1H, NH–
hydrazo). 13C NMR: δ/ppm = 12.5, 51.1, 113.4 (2C),
115.9 (2C), 122.5 (2C), 124.2 (2C), 128.2, 137.7, 139.3
(2C), 141.1, 148.6, 149.7, 169.5. MS (m/z, %): 378.34
(M + 1, 3.11). Anal. Calcd. for C18H15N7O3 (377.36): C,
57.29; H, 4.01; N, 25.98. Found: C, 57.13; H, 4.15; N,
25.79.
2-((1H-Benzimidazol-2-yl)methyl)-5-methyl-4-(2-(p-tolyl)
hydrazineylidene)-2,4-dihydro-3H-pyrazol-3-one (8b). Yield
yellow solid, mp 189–190°C (158°C [29]).
N-(4-Acetylphenyl)carbonohydrazonoyl dicyanide (7c).
57%, brownish yellow solid, mp >250°C (acetic acid).
IR: νmax = 3278–2850 (NH, ═CH aromatic, –CH
aliphatic), 3164 (NH–hydrazo), 1691 (CO pyrazolone),
Yield 65%, brown solid, mp 190–192°C. IR:
νmax = 3216–2956 (═CH aromatic), 3050 (NH–hydrazo),
2217 (CN), 1671 (CO acetyl), 1595 (C═N) and 1409
1636 (C═N), 1460 (CH2) and 1407 (CH3) cmꢀ1 1H
.
1
(CH3) cmꢀ1. H NMR: δ/ppm = 3.85 (s, 3H, CH3), 7.16–
7.84 (m, 4H, Ar–H), 12.85 (s, 1H, NH–hydrazo). 13C
NMR: δ/ppm = 26.4, 81.4, 111.6 (2C), 115.2 (2C), 129.9
(2C), 131.2, 147.2, 197.8. MS (m/z, %): 213.10 (M + 1,
57.13). HRMS calc. for C11H8N4O: 212.0698, found:
212.0694. Anal. Calcd. for C11H8N4O (212.21): C, 62.26;
H, 3.80; N, 26.40. Found: C, 61.91; H, 3.56; N, 26.30.
NMR: δ/ppm = 1.24 (s, 2H, CH2 aliphatic), 2.27 (s, 3H,
CH3 pyrazolone ring), 2.50 (s, 3H, CH3), 6.58–8.31 (m,
8H, Ar–H), 12.24 (s, 1H, NH–benzimidazole ring), 13.45
(s, 1H, NH–hydrazo). 13C NMR: δ/ppm = 11.3, 21.1,
51.4, 115.7 (2C), 116.3 (2C), 122.6 (2C), 129.1 (2C),
128.2, 137.6, 139.2 (2C), 140.4, 141.1, 148.6, 169.5. MS
(m/z, %): 345.4 (M ꢀ 1, 44.52). Anal. Calcd. for
C19H18N6O (346.39): C, 65.88; H, 5.24; N, 24.26.
N-(3,4-Dichlorophenyl)carbonohydrazonoyl
(7d).
dicyanide
Yield 68%, yellow solid, mp 198–199°C (193–
196°C [56]).
Found: C, 65.71; H, 5.11; N, 24.19.
N-(1,5-Dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-
yl)carbonohydrazonoyl dicyanide (7e). Yield 62%, yellow
2-((1H-Benzimidazol-2-yl)methyl)-4-(2-(4-acetylphenyl)
hydrazineylidene)-5-methyl-2,4-dihydro-3H-pyrazol-3-one
(8c). Yield 63%, brown solid, mp 119–120°C (EtOH/
solid, mp >250°C. IR: νmax = 3227–2941 (═CH
aromatic), 3105 (NH–hydrazo), 2224 (CN), 1634 (CO
DMF). IR: νmax = 3576–2992 (NH, NH2, ═CH aromatic,
–CH aliphatic), 2918 (NH–hydrazo), 1735 (CO
pyrazolone), 1668 (CO acetyl), 1594 (C═N), 1463 (CH2)
pyrazolone), 1594 (C═N) and 1405 (CH3) cmꢀ1 1H
.
NMR: δ/ppm = 3.14 (s, 3H, CH3), 3.90 (s, 3H, CH3),
7.15–7.82 (m, 5H, Ar–H), 11.47 (s, 1H, NH–hydrazo).
13C NMR: δ/ppm = 12.5, 34.7, 81.8, 113.2 (2C), 116.2,
122.7, 124.2 (2C), 129.5 (2C), 131.8, 133.1, 160.2. MS
(m/z, %): 280.28 (M+, 97.0). HRMS calc. for C11H8N4O:
280.1073, found: 280.1070. Anal. Calcd. for C14H12N6O
(280.29): C, 59.99; H, 4.32; N, 29.98. Found: C, 59.84;
H, 4.21; N, 29.80 [57].
1
and 1420 (CH3) cmꢀ1. H NMR: δ/ppm = 1.24 (s, 2H,
CH2 aliphatic), 2.27 (s, 3H, CH3 pyrazolone ring), 2.50
(s, 3H, CH3), 6.58–8.31 (m, 8H, Ar–H), 12.24 (s, 1H,
NH–benzimidazole ring), 13.45 (s, 1H, NH–hydrazo).
13C NMR: δ/ppm = 11.4, 26.1, 51.4, 115.7 (4C), 123.2
(2C), 128.5 (2C), 129.2, 131.3, 138.9 (2C), 141.3, 147.2,
148.4, 169.5, 196.8. MS (m/z, %): 375.34 (M + 1, 12.2).
Anal. Calcd. for C20H18N6O2 (374.40): C, 64.16; H,
General procedure for the synthesis of 2-((1H-
benzimidazol-2-yl)methyl)-4-(2-arylhydrazineylidene)-3,5-
disubstituted pyrazolyl derivatives (8a–e to 10a–e).
4.85; N, 22.45. Found: C, 64.01; H, 4.58; N, 22.13.
2-((1H-Benzimidazol-2-yl)methyl)-4-(2-(3,4-dichlorophenyl)
hydrazineylidene)-5-methyl-2,4-dihydro-3H-pyrazol-3-one
An
equimolar
ratio
of
2-(hydrazineylmethyl)-1H-
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2019
Novel Benzimidazole Entities: Synthesis and Pharmacological Investigations
(8d). Yield 59%, dark brown solid, mp 85–86°C (EtOH/
DMF). IR: νmax = 3264–2854 (NH, ═CH aromatic, –CH
aliphatic), 3058 (NH–hydrazo), 1660 (CO pyrazolone),
1590 (C═N), 1463(CH2) and 1388 (CH3) cmꢀ1. 1H NMR:
δ/ppm = 1.30 (s, 2H, CH2 aliphatic), 2.27 (s, 3H, CH3
pyrazolone ring), 6.58–8.31 (m, 7H, Ar–H), 12.45 (s, 1H,
2-(2-((1H-Benzimidazol-2-yl)methyl)hydrazineyl)-N-(4-
acetylphenyl)-2-oxoacetohydrazonoyl cyanide (9c).
Yield
76%, dark brown solid, mp 134–135°C (EtOH/DMF). IR:
νmax = 3263–2920 (NH, ═CH aromatic, –CH aliphatic),
3101 (NH–hydrazo), 2217 (CN), 1665 (CO amide), 1594
1
(C═N) and 1426 (CH2) cmꢀ1. H NMR: δ/ppm = 2.51
NH–benzimidazole ring), 13.60 (s, 1H, NH–hydrazo). 13
C
(s, 2H, CH2 aliphatic), 3.86 (s, 3H, CH3), 7.16–7.88 (m,
8H, Ar–H; 2H hydrazide), 12.41 (s, 1H, NH–
benzimidazole ring), 12.85 (s, 1H, NH–hydrazo). 13C
NMR: δ/ppm = 26.2, 51.4, 106.2, 110.6, 115.2 (4C),
123.2 (2C), 129.9 (2C), 131.2, 138.9 (2C), 141.4, 147.2,
162.9, 196.8. MS (m/z, %): 376.92 (M + 1, 12.16). Anal.
Calcd. for C19H17N7O2 (375.39): C, 60.79; H, 4.56; N,
NMR: δ/ppm = 11.5, 51.4, 115.4, 115.6, 118.1, 123.2
(2C), 123.4, 128.6, 129.1, 131.7, 138.9 (2C), 141.3, 142.4,
148.4, 169.5, 196.4. MS (m/z, %): 401.92 (M + 1, 16.15).
Anal. Calcd. for C18H14Cl2N6O (401.25): C, 53.88; H,
3.52; N, 20.94. Found: C, 53.67; H, 3.40; N, 20.81.
2-((1H-Benzimidazol-2-yl)methyl)-4-(2-(1,5-dimethyl-3-oxo-
2-phenylpyrazolidin-4-yl)hydrazineylidene)-5-methyl-2,4-
26.12. Found: C, 60.62; H, 4.44; N, 25.97.
2-(2-((1H-Benzimidazol-2-yl)methyl)hydrazineyl)-N-(3,4-
dichlorophenyl)-2-oxoacetohydrazonoyl cyanide (9d). Yield
dihydro-3H-pyrazol-3-one (8e).
Yield 58%, dark brown
solid, mp 131–132°C (EtOH/DMF). IR: νmax = 3264–
2854 (NH, ═CH aromatic, –CH aliphatic), 2922 (NH–
hydrazo), 1653 (CO pyrazolone), 1602 (C═N), 1443
65%, yellowish brown solid, mp 116–117°C (EtOH/
H2O). IR: νmax = 3212–2920 (NH, ═CH aromatic, –CH
aliphatic), 2983 (NH–hydrazo), 2220 (CN), 1688 (CO
1
(CH2) and 1379 (CH3) cmꢀ1. H NMR: δ/ppm = 1.63 (s,
amidic), 1588 (C═N), 1461(CH2) and 1376 (CH3) cmꢀ1
.
2H, CH2 aliphatic), 2.16 (s, 3H, CH3), 2.72 (s, 3H, CH3),
2.89 (s, 3H, CH3), 7.14–7.95 (m, 10H, Ar–H), 12.32 (s,
1H, NH–benzimidazole ring). 13C NMR: δ/ppm = 11.5,
15.1, 43.3, 51.4, 53.1, 61.7, 115.4 (2C), 123.2 (2C),
128.9, 128.6 (2C), 128.1, 131.8 (2C), 134.5, 138.9 (2C),
141.4, 148.3, 169.4, 169.7. MS (m/z, %): 442.29 (M ꢀ 2,
15.12). Anal. Calcd. for C23H24N8O2 (444.50): C, 62.15;
1H NMR: δ/ppm = 3.87 (s, 2H, CH2 aliphatic), 6.58–8.87
(m, 7H, Ar–H; 2H hydrazide), 12.32 (s, 1H, NH–
benzimidazole ring), 13.60 (s, 1H, NH–hydrazo). 13C
NMR: δ/ppm = 51.4, 106.2, 110.6, 115.1 (2C), 116.3,
118.1, 123.4, 123.0 (2C), 129.2, 131.7, 138.9 (2C),
141.4, 142.5, 162.9. MS (m/z, %): 403.31 (M + 1,
20.01). Anal. Calcd. for C17H13Cl2N7O (402.24): C,
50.76; H, 3.26; N, 24.38. Found: C, 50.65; H, 3.12; N,
H, 5.44; N, 25.21. Found: C, 61.91; H, 5.23; N, 25.08.
2-(2-((1H-Benzimidazol-2-yl)methyl)hydrazineyl)-N-(4-
nitrophenyl)-2-oxoacetohydrazonoyl cyanide (9a).
Yield
24.19.
57%, dark brown solid, mp 116–117°C (EtOH/DMF). IR:
νmax = 3263–2853 (NH, ═CH aromatic, –CH aliphatic),
3103 (NH–hydrazo), 2220 (CN), 1656 (CO amide), 1593
2-(2-((1H-Benzimidazol-2-yl)methyl)hydrazineyl)-N-(1,5-
dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)-2-
oxoacetohydrazonoyl cyanide (9e).
Yield 65%, brown
(C═N), 1447(CH2) and 1326, 1507 (NO2) cmꢀ1 1H
.
solid, mp 219–220°C (dioxane). IR: νmax = 3212–2854
(NH, ═CH aromatic, –CH aliphatic), 2913 (NH–
hydrazo), 2175 (CN), 1732 (CO pyrazolone), 1642 (CO
NMR: δ/ppm = 2.27 (s, 2H, CH2 aliphatic), 6.65–8.31
(m, 8H, Ar–H; 2H hydrazide), 12.32 (s, 1H, NH–
benzimidazole ring), 13.65 (s, 1H, NH–hydrazo). 13C
NMR: δ/ppm = 51.4, 106.1, 110.6, 113.2 (2C), 115.3
(2C), 123.2 (2C), 124.9 (2C), 137.6 (2C), 138.9 (2C),
141.4, 149.0. MS (m/z, %): 378.78 (M+, 1.37). Anal.
Calcd. for C17H14N8O3 (378.35): C, 53.97; H, 3.73; N,
amidic), 1602 (C═N), 1461 (CH2) and 1379 (CH3) cmꢀ1
.
1H NMR: δ/ppm = 2.19 (s, 2H, CH2 aliphatic), 3.15 (s,
3H, CH3), 3.90 (s, 3H, CH3), 7.16–8.85 (m, 9H, Ar–H;
2H hydrazide), 12.32 (s, 1H, NH–benzimidazole ring),
12.85 (s, 1H, NH–hydrazo). 13C NMR: δ/ppm = 12.4,
34.8, 51.4, 106.2, 110.6, 115.1 (2C), 116.1, 122.7, 123.0
(2C), 123.8 (2C), 129.2 (2C), 131.6, 133.7, 138.8 (2C),
141.4, 160.5, 162.9. MS (m/z, %): 443.87 (M+, 7.96).
Anal. Calcd. for C22H21N9O2 (443.47): C, 59.58; H,
29.62. Found: C, 53.68; H, 3.60; N, 29.51.
2-(2-((1H-Benzimidazol-2-yl)methyl)hydrazineyl)-2-oxo-N-
(p-tolyl)acetohydrazonoyl cyanide (9b). Yield 59%, brown
solid, mp 98–99°C (benzene). IR: νmax = 3220–2982
(NH, ═CH aromatic, –CH aliphatic), 2918 (NH–
hydrazo), 2215 (CN), 1678 (CO amide), 1597 (C═N),
4.77; N, 28.43. Found: C, 59.41; H, 4.58; N, 28.22.
2-(2-((1H-Benzimidazol-2-yl)methyl)hydrazineyl)-2-amino-
1471 (CH2) and 1378 (CH3) cmꢀ1
.
1H NMR: δ/
N-(4-nitrophenyl)acetohydrazonoyl cyanide (10a).
Yield
ppm = 2.51 (s, 2H, CH2 aliphatic), 3.30 (s, 3H, CH3),
7.19–7.41 (m, 8H, Ar–H; 2H hydrazide), 12.16 (s, 1H,
NH–benzimidazole ring), 12.95 (s, 1H, NH–hydrazo).
13C NMR: δ/ppm = 21.3, 51.4, 106.2, 110.6, 115.2 (2C),
116.3 (2C), 123.2 (2C), 129.9 (2C), 131.2, 138.9 (2C),
140.6, 141.4, 162.9. MS (m/z, %): 346.67 (M ꢀ 1,
21.19). Anal. Calcd. for C18H17N7O (347.38): C, 62.24;
H, 4.93; N, 28.23. Found: C, 62.11; H, 4.79; N, 28.08.
63%, dark brown solid, mp 128–129°C (EtOH). IR:
νmax = 3740 (NH2), 3263–2853 (NH, ═CH aromatic, –
CH aliphatic), 3103 (NH–hydrazo), 2220 (CN), 1680
(CO amidic), 1589 (C═N), 1447 (CH2) and 1310, 1502
(NO2) cmꢀ1 1H NMR: δ/ppm = 3.43 (s, 2H, CH2
.
aliphatic), 6.59–8.31 (m, 8H, Ar–H; 2H hydrazide), 12.43
(s, 1H, NH–benzimidazole ring), 13.61 (s, 1H, NH–
hydrazo). 13C NMR: δ/ppm = 51.4, 66.4, 110.6, 113.2
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

M. E. Khalifa, A. A. Gobouri, F. M. Kabli, T. A. Altalhi, A. S. A. Almalki, and A. M. Elemshaty Vol 000
(2C), 115.2 (2C), 123.0 (2C), 124.6 (2C), 134.2, 136.8,
138.7 (2C), 141.4, 149.1. MS (m/z, %): 378.28 (M + 1,
0.84). Anal. Calcd. for C17H15N9O2 (377.37): C, 54.11;
H, 4.01; N, 33.41. Found: C, 53.90; H, 4.15; N, 33.26.
2-(2-((1H-Benzimidazol-2-yl)methyl)hydrazineyl)-2-amino-
N-(p-tolyl)acetohydrazonoyl cyanide (10b). Yield 68%, dark
amino), 12.41 (s, 1H, NH–benzimidazole ring), 13.52 (s,
1H, NH–hydrazo). 13C NMR: δ/ppm = 12.5, 34.9, 51.1,
110.6, 115.2 (2C), 115.6, 116.2, 122.9, 123.0 (2C), 124.0
(2C), 129.3 (2C), 131.2, 134.1, 138.7 (2C), 141.4, 152.6,
161.2. MS (m/z, %): 442.20 (M+, 100.0). Anal. Calcd. for
C22H22N10O (442.49): C, 59.72; H, 5.01; N, 31.66.
Found: C, 59.58; H, 4.88; N, 31.45.
brown solid, mp 104–105°C (benzene). IR: νmax = 3739
(NH2), 3231–3057 (NH, ═CH aromatic, –CH aliphatic),
2914 (NH–hydrazo), 2215 (CN), 1605 (C═N), 1453
Antibacterial evaluation.
Disc diffusion method was
used to evaluate the antibacterial activity of the
synthesized compounds [58]. Both Kanamycin (30 μg/mL)
and Ampicillin (10 μg/mL) were aseptically used as
positive standard reference for Gram-positive strains and
Gram-negative strains. The inhibition clear zones (mm)
were recorded in all samples and equal zero in no-
inhibition results. The method is explained in details in
Data S1.
1
(CH2) and 1390 (CH3) cmꢀ1. H NMR: δ/ppm = 2.49 (s,
3H, CH3), 3.88 (s, 2H, CH2 aliphatic), 7.20–7.38 (m, 8H,
Ar–H; 2H amino), 12.40 (s, 1H, NH–benzimidazole
ring), 12.95 (s, 1H, NH–hydrazo). 13C NMR: δ/
ppm = 21.3, 51.4, 66.4, 110.6, 115.2 (2C), 116.1 (2C),
123.0 (2C), 124.6 (2C), 131.2, 136.8, 138.7 (2C), 140.1,
141.5. MS (m/z, %): 346.49 (M+, 1.26). Anal. calcd. for
C18H18N8 (346.40): C, 62.41; H, 5.24; N, 32.35. Found:
Antitumor
evaluation. Cell
culture.
Human
C, 62.30; H, 5.05; N, 32.18.
2-(2-((1H-Benzimidazol-2-yl)methyl)hydrazineyl)-N-(4-
acetylphenyl)-2-aminoacetohydrazonoyl cyanide (10c). Yield
transformed cell lines from liver (HepG2) were
maintained in RPMI-1640 supplemented with 100 μg/mL
streptomycin, 100 μg/mL penicillin, and 10% (w/v) heat-
inactivated fetal bovine serum in a humidified 5% (v/v)
CO2 atmosphere at 37°C.
52%, reddish brown solid, mp 108–109°C (EtOH). IR:
νmax = 3738 (NH2), 3231–3056 (NH, ═CH aromatic, –
CH aliphatic), 2914 (NH–hydrazo), 2185 (CN), 1665
(CO acetyl), 1594 (C═N), 1426(CH2) and 1390 (CH3)
Cytotoxicity assay.
Neutral red assay was used to
evaluate the cytotoxicity effects of prepared compounds
[59]. Method is explained in details in Data S1. The
percentage of cell death is expressed according to
Equation 1:
1
cmꢀ1. H NMR: δ/ppm = 2.45 (s, 3H, CH3), 3.31 (s, 2H,
CH2 aliphatic), 7.39–7.59 (m, 8H, Ar–H; 2H amino),
12.32 (s, 1H, NH–benzimidazole ring). 13C NMR: δ/ppm:
26.3, 51.1, 110.6, 116.1, 115.2 (2C), 116.2 (2C), 123.0
(2C), 129.6 (2C), 131.2, 138.8 (2C), 141.4, 143.5, 152.6,
197.0. MS (m/z, %): 375.16 (M + 1, 20.5). Anal. Calcd.
for C19H18N8O (374.41): C, 60.95; H, 4.85; N, 29.93.
Abs540 treated sample
%Cell death ¼
ꢁ100:
(1)
Abs540 treated sample
The data are based on three independent experiments.
Found: C, 60.71; H, 4.79; N, 29.81.
2-(2-((1H-Benzimidazol-2-yl)methyl)hydrazineylidene)-2-
Antioxidant potential.
The tested compounds were
tested for their antioxidant potential according to the
reported technique [60]. The technique is explained in
details and provided in Data S1. The antioxidant abilities
were expressed as μM Trolox equivalents. Each sample
was analyzed in triplicate. The percentage inhibition of
the DPPH radical by the samples was calculated
according to Equation 2.
amino-N-(3,4-dichlorophenyl)acetohydrazonoyl
(10d).
cyanide
Yield 65%, brownish yellow solid, mp 138–
139°C (dioxane). IR: νmax = 3740 (NH2), 3227–3172
(NH, ═CH aromatic, –CH aliphatic), 3048 (NH–
hydrazo), 2224 (CN), 1594 (C═N) and 1455 (CH2)
1
cmꢀ1. H NMR: δ/ppm = 3.90 (s, 2H, CH2 aliphatic),
7.15–7.66 (m, 8H, Ar–H; 2H amino), 12.32 (s, 1H, NH–
benzimidazole ring), 12.99 (s, 1H, NH–hydrazo). 13C
NMR: δ/ppm = 50.9, 110.5, 115.2 (2C), 115.6, 115.8,
118.2, 123.0 (2C), 123.4, 129.3, 131.2, 138.8 (2C), 141.5
(2C), 142.4, 152.6. MS (m/z, %): 401.08 (M+, 18.4).
Anal. Calcd. for C17H14Cl2N8 (401.26): C, 50.89; H,
3.52; N, 27.93. Found: C, 50.72; H, 3.38; N, 27.79.
2-(2-((1H-Benzimidazol-2-yl)methyl)hydrazineylidene)-2-
amino-N-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-
½Ab ꢀ Aaꢂ
Inhibition% ¼
ꢁ100:
(2)
Ab
where Ab is the absorption of the blank sample
(t = 0 min) and Aa is the absorption of the tested com-
pounds or standard substance solution (t = 30 min).
The EC50 value defined as the concentration of antioxi-
dant in the reactive system necessary to decrease the ini-
tial DPPH concentration by 50% and was calculated from
the data obtained.
Calculation of IC50. The IC50 values (50% cell viability
maximum inhibition concentration) of the tested and
control compound (Doxorubicin) were calculated using
XLFIT5 software (IDBS) and expressed in μg mLꢀ1 at
95% confidence intervals.
pyrazol-4-yl)acetohydrazonoyl cyanide (10e).
Yield 66%,
brown solid, mp 204–205°C (dioxane). IR: νmax = 3738
(NH2), 3197–2919 (NH, ═CH aromatic, –CH aliphatic),
3103 (NH–hydrazo), 2228 (CN), 1636 (CO pyrazolone),
1595 (C═N), 1450 (CH2) and 1403 (CH3) cmꢀ1 1H
.
NMR: δ/ppm = 2.20 (s, 2H, CH2 aliphatic), 3.14 (s, 3H,
CH3), 3.90 (s, 3H, CH3), 7.15–7.82 (m, 8H, Ar–H; 2H
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2019
Novel Benzimidazole Entities: Synthesis and Pharmacological Investigations
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Acknowledgments. This work was funded by the King
Abdulaziz City for Science and Technology (KACST)–Saudi
Arabia (project no. 1-17-01-022-0006). The authors acknowledge
support from the Scientific Research Unit of Taif University,
Saudi Arabia.
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CONFLICT OF INTEREST
The authors declare no conflict of interest. The founding
sponsors had no role in the design of the study; in the
collection, analyses, or interpretation of data; in the
writing of the manuscript; and in the decision to publish
the results.
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J Mol Med 2005, 15, 259.
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SUPPORTING INFORMATION
Additional supporting information may be found online
in the Supporting Information section at the end of the
article.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet