A search of novel antimicrobial based on benzimidazole and 2-pyridone heterocycles

Article abstract of DOI:10.1007/s00044-011-9782-2

The increasing incidence of bacterial drug resistance imposes a new search on existing antimicrobial drugs leading to the development of new bioactive molecules. In continuation to this, the present article deals with the synthesis and antimicrobial activity of 1-(1-(1H-benzo [d]imidazol-2-yl)ethylideneamino)- 6-(arylideneamino)-4-(2-hydroxyphenyl)-2-oxo-1,2-dihydropyridine-3, 5-dicarbonitriles (4a-k). All newly synthesized compounds have been evaluated against two gram positive bacteria (Staphylococcus aureus, Streptococcus pyogenes), two gram negative bacteria (Escherichia coli, Pseudomonas aeruginosa), and three fungi (Candida albicans, Aspergillus niger, Aspergillus clavatus) using serial broth dilution method. Compounds reported in the present article bearing chloro and hydroxy groups exhibit very good to excellent antimicrobial activity. All the newly synthesized compounds have been characterized by IR, ¹H NMR, ¹³C NMR, and mass spectra. Springer Science+Business Media, LLC 2011.

Full text of DOI:10.1007/s00044-011-9782-2

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res
DOI 10.1007/s00044-011-9782-2
ORIGINAL RESEARCH
A search of novel antimicrobial based on benzimidazole
and 2-pyridone heterocycles
•
N. C. Desai Amit M. Dodiya Niraj R. Shihory
•
Received: 30 May 2011 / Accepted: 4 August 2011
Ó Springer Science+Business Media, LLC 2011
Abstract The increasing incidence of bacterial drug
resistance imposes a new search on existing antimicrobial
drugs leading to the development of new bioactive mole-
cules. In continuation to this, the present article deals with
the synthesis and antimicrobial activity of 1-(1-(1H-benzo
[d]imidazol-2-yl)ethylideneamino)-6-(arylideneamino)-4-(2-
hydroxyphenyl)-2-oxo-1,2-dihydropyridine-3,5-dicarbonitr-
iles (4a–k). All newly synthesized compounds have been
evaluated against two gram positive bacteria (Staphylo-
coccus aureus, Streptococcus pyogenes), two gram negative
bacteria (Escherichia coli, Pseudomonas aeruginosa), and
three fungi (Candida albicans, Aspergillus niger, Asper-
gillus clavatus) using serial broth dilution method. Com-
pounds reported in the present article bearing chloro and
hydroxy groups exhibit very good to excellent antimicro-
bial activity. All the newly synthesized compounds have
antimicrobials seriously threatens their effectiveness for
therapy of both bacterial and fungal infections. Literature
survey has indicated that the benzimidazole nucleus is an
essential part of many clinically useful chemotherapeutic
agents. For example, thiabendazol, triclabendazole, and
mebendazole are effective anthelmintic agents (Reynold,
1993). Chlormidazole is used in the treatment of fungal
infectionsofskin(Reynold, 1993). Enviroximeisaneffective
drug against rhinovirus (Reynold, 1993). Methyl 2-benzim-
idazolecarbamate (carbendazim, FB642) is an anticancer
agent that induces apoptosis of cancer cells (Hao et al., 2002).
The versatility of benzimidazole and its potential to
yield derivatives with a wide range of biological activities
has made it a useful structure for further molecular
exploration. The substituents at 1- and 2-positions of this
heterocycle have been intensively studied and this led to
derivatives with good antiviral activity. It is well known
that several 1,2-disubstituted benzimidazoles (Wallis and
O’Sullivan 1963; Porcari et al., 1998; Victor et al., 1997;
Garuti et al., 1998; Swayze et al., 1993; Gardiner et al.,
1995) are potent inhibitors of RNA viruses and this effect
prompted intensive efforts to prepare and evaluate other
derivatives. Recent observations suggest that substituted
benzimidazoles are the structural isosters of nucleotide
owing to fused heterocyclic nuclei in their structure. This
allows them to interact easily with biopolymers (Haugwitz
et al., 1982; Hisano et al., 1982). Some benzimidazole
nucleosides, particularly 5,6-dichlorobenzimidazole-1-b-
D-ribofuranoside (DRB) and its 2-substituted derivatives
showed activity against human cytomegalovirus (Devivar
et al., 1994). 2-Trifluorobenzimidazoles are potent decou-
plers of oxidative phosphorylation in mitochondria.
Recently, antiprotozoal activity of substituted 2-trifluoro-
benzimidazoles has also been reported (Navarette et al.,
2001).
1
been characterized by IR, H NMR, 13C NMR, and mass
spectra.
Keywords Benzimidazole Á 2-pyridone Á
Antimicrobial activity
Introduction
Development of antimicrobial agents for the chemotherapy
of bacterial and fungal infections represents one of the
most remarkable achievements of this century. Unfortu-
nately, the increasing emergence of acquired resistance to
N. C. Desai (&) Á A. M. Dodiya Á N. R. Shihory
Medicinal Chemistry Division, Department of Chemistry,
Bhavnagar University, Mahatma Gandhi Campus, Bhavnagar
364 002, India
e-mail: dnisheeth@rediffmail.com
123

Med Chem Res
2-pyridone is found to possess useful pharmacological
activities, such as analgesic (Ozturk et al., 2001), antima-
larial (Abadi et al., 1999), anti-HIV (Storck et al., 2005),
phytotoxic (Evidente et al., 2006), and antitumoral (Cocco
et al., 2003) properties. Functionalized pyridin-2(1H)-ones
have been used as versatile intermediates in the synthesis of a
wide range of nitrogen-containing heterocycles, such as
pyridine, quinolizidine, and indolizidine alkaloids (Torres
et al., 2005; Jauasinghe et al., 2006). In addition, benz-
imidazole and 2-pyridone derivatives have played a crucial
role in the theoretical development of heterocyclic chemistry
and are also used extensively in organic synthesis.
oxo-1,2-dihydropyridine-3,5-dicarbonitriles 4a–k has been
carried out in three steps. First step involves condensation
of 1-(1H-benzo[d]imidazol-2-yl)ethanone 1 with 2-hy-
drazinylacetyl cyanide in alcohol (99.9%) to give 2-(2-(1-
(1H-benzo[d]imidazol-2-yl)ethylidene)hydrazinyl)acetyl
cyanide 2. Second step involves cyclization of 2-(2-(1-
(1H-benzo[d]imidazol-2-yl)ethylidene)hydrazinyl)acetyl
cyanide 2 and 2-(2-hydroxy- benzylidene)malononitrile in
the presence of catalytic amount of piperidine to furnish
1-(1-(1H-benzo[d]imidazol-2-yl)ethylideneamino)-6-amino-
4-(2-hydroxyphenyl)-2-oxo-1,2-dihydropyridine-3,5-dicar-
bonitrile 3. Finally, it is condensed with different aryl alde-
hydes to form final compounds 4a–k, as shown in Scheme 1.
Compound 1-(1-(1H-benzo[d]imidazol-2-yl)ethylideneamino)-
6-(benzylideneamino)-4-(2-hydroxyphenyl)-2-oxo-1,2-dihy-
O
CH3
1
OH
O
N
dropyridine-3,5-dicarbonitrile 4a is characterized by IR, H
NMR, 13C NMR, and mass spectra.
N
N
N
Cl
N
CN
Perampanel
1H-NMR data
Cl
Bendamustine
It can be seen from the chemical structure of compound 4a
that different pairs of carbon e.g., C-3 and C-6, C-4 and
C-5, C-13 and C-17, C-14 and C-16 are attached to
chemically equivalent protons, which appeared at
d = 7.59, 7.22, 7.83, and 7.52 ppm, respectively. Proton
attached to C-15 position appeared as a multiplet at
7.54 ppm due to mutual coupling with C-14 and C-16,
while proton attached to C-27 also appeared as a multiplet
at d = 7.80 ppm due to mutual coupling with C-26 and
C-28. Proton attached to C-28 also appeared as a multiplet
at d = 6.96 ppm due to mutual coupling with C-27 and
C-29. Protons of C-26 and C-29 appeared as a doublet at
d = 6.72 and 7.21 ppm, respectively. Proton of hydroxyl
group at C-25 appeared as a singlet at d = 5.70 ppm.
Protons of methyl group appeared as a singlet at
d = 1.3 ppm, while proton of benzylidene group appeared
as a singlet at d = 9.20 ppm. Proton of secondary amine
present in benzimidazole nucleus appeared as a singlet at
d = 12.8 ppm.
Bendamustine (INN, trade names Ribomustin and Tre-
anda; also known as SDX-105) is nitrogen mustard used in
the treatment of chronic lymphocytic leukemias (CLL)
(Kath et al., 2001) and lymphomas. It belongs to the family
of drugs called alkylating agents. It is also being studied for
the treatment of sarcoma. Perampanel is a drug developed
by Eisai Co., which acts as a selective antagonist for
AMPA subtype of ionotropic glutamate receptors. It is
being researched for several possible clinical applications
including the treatment of Parkinson’s disease (Gottwald
and Aminoff 2008). Enlightened by these findings our
group has decided to search new antimicrobials by modi-
fying the second position of benzimidazole. In the present
article, we are interested in synthesizing hybrid antimi-
crobial agents and therefore, we have clubbed both moie-
ties (i.e., benzimidazole and 2-pyridone) in one frame
work. The well versed pharmacological properties of
benzimidazole and 2-pyridone has inspired our research
group (Desai et al., 2010, 2011) for the synthesis of two
moieties in a single frame for further search of novel
antimicrobial agents. Thus, a series of 1-(1-(1H-benzo[d]
imidazol-2-yl)ethylideneamino)-6-(arylideneamino)-4-(2-
hydroxyphenyl)-2-oxo-1,2-dihydropyridine-3,5-dicarbonitriles
(4a–k) are synthesized and tested for their antimicrobial
activity.
13C NMR data
The final compound 4a possesses benzimidazole and
2-oxo-pyridone nucleus. Chemical shifts of carbons of final
compound vary from d = 176.5 to 12.2 ppm. Carbon
nuclei under the influence of a strong electronegative
environment appeared downfield, e.g., C-23 carbonyl,
which is present in pyridine nucleus had a chemical shift
value of d = 176.5 ppm. While C-20 appeared at
d = 169.0 ppm due to the presence of highly electroneg-
ative C:N group present on both the sides of carbon atom.
Carbons C-18 and C-21 appeared at 117.4 and 119.4 ppm,
Results and discussion
The synthesis of 1-(1-(1H-benzo[d]imidazol-2-yl)ethy-
lideneamino)-6-(arylideneamino)-4-(2-hydroxyphenyl)-2-
123

Med Chem Res
O
CH3
Scheme 1 Synthesis of
compounds 4a–k
O
NH
N
N
N
CN
CH3
H2N
CN
CH2
+
Ethanol
NH
NH
O
NH
2
Reflux, 3 h
1
OH
Ethanol
CN
Piperidine
Reflux, 3 h
CN
HO
CN
HO
CN
O
N
CH3
Ethanol
Reflux, 5 h
O
CH3
N
N
CN
N
CHO
N
N
CN
NH
N
NH
NH2
R
4a-k
3
R
R = Different substituents
Antimicrobial activity
respectively, due to the presence of –C:N group, while
carbons of –C:N group i.e., C-19 and C-22 appeared at
the same value of 119.7 ppm. Carbon of pyridone ring
C-10 appeared at 153.8 ppm due to attachment with two
nitrogen atoms. Carbon of benzylidene group C-11
appeared at d = 152.3 ppm. Carbon of methyl group C-9
appeared at d = 12.2 ppm. Carbon C-8 showed signal at
d = 149.0 ppm due to the presence of methyl group.
Hydroxyl group is attached to C-25 carbon due to which
the signal appeared at d = 153.6 ppm. Carbons of both
phenyl rings appeared between 114.8 and 141.5 ppm,
respectively. Carbon C-1 which is benzimidazole nucleus
and between two nitrogen atoms appeared at high field at
147.2 ppm. Carbon C-4 appeared at 122.3 ppm due to
mutual coupling with C-3 and C-5, while carbon C-5
appeared at 123.4 ppm due to mutual coupling with C-4
and C-5. Other carbons of benzimidazole nucleus (C-2,
C-3, C-6, and C-7) appeared between 113.1 and
127.1 ppm. The structure and carbon numbering of com-
pound 4a is described in Fig. 1.
Many of the newly synthesized compounds are found to
exhibit good to excellent antimicrobial activity. From
antimicrobial activity data (Table 1), it is observed that
compounds 4a (–H), 4d (4-OH), 4g (–2-Cl), and 4i (4-N,N-
(CH3)2) are most active compounds. For antibacterial
activity, compounds 4a and 4h possess good activity
against E. coli, compound 4a contains unsubstituted phenyl
ring while 4h contains chloro substitution, when we replace
it with 4-N,N-(CH3)2 group in 4i, the activity is enhanced
and it possesses very good activity against E. coli. Com-
pounds 4i (4-N,N-(CH3)2) and 4j (4-OH, 3-OCH3) possess
good activity against P. aeruginosa. When we remove the
substitution in compound 4a, it possesses very good
activity against P. aeruginosa. It is our observation that
when replacement of chloro group takes place in com-
pound 4g, it possesses excellent activity against P. aeru-
ginosa. Compounds 4a (–H), 4d (-4-OH), 4j (-4-OH,
-3-OCH3), and 4k (-3,4,5-(OCH3)2 possess good activity
against S. aureus. While compounds 4b (-2-OH), 4c
(-3-OH), and 4e (-3-NO2) possess very good activity
against S. aureus, and compounds 4g (-2-Cl), 4h (4-Cl),
and 4i (-4-N,N-(CH3)2) possess excellent activity against S.
aureus. Compounds 4a (-H) and 4i (4-N,N-(CH3)2) possess
good activity against S. pyogenes, at the same time if we
replace the substitution with 4-hydroxy group in compound
4d, it possesses very good activity against S. pyogenes. For
antifungal activity, compounds 4b (-2-OH), 4c (-3-OH), 4d
(-4-OH), 4e (-3-NO2), 4f (-4-NO2), and 4h (-4-Cl) possess
good activity against C. albicans. The substitution takes
place in compound 4a by (4-N,N-(CH3)2) as a result,
we got 4i which possesses very good activity against
22
HO
CN
O
25
26
28
21
CH
8
3
9
3
23
20
N
2
27
4
5
N
24
N
1
18
10
29
NH
7
CN
19
N
6
17
12
11
16
15
13
14
Fig. 1 Carbon numbering of compound-4a
123

Med Chem Res
C. albicans. Compounds 4a (-H) and 4g (-4-Cl) possess
good activity against A. niger. Compounds 4d (-4-OH) and
4k (-3,4,5-(OCH3)2) possess good activity against
A. clavatus. Thus, we have discussed and compared anti-
bacterial and antifungal activities based on standard drugs
ampicillin and griseofulvin, respectively.
Antibacterial activity
The newly synthesized compounds are screened for their
antibacterial activity against gram positive bacteria
Staphylococcus aureus (MTCC-96) and Streptococcus py-
ogenes (MTCC-442) and gram negative Escherichia coli
(MTCC-443) and Pseudomonas aeruginosa (MTCC-
1688)]. Antibacterial activity is carried out by serial broth
dilution method (Ghalem and Mohamed, 2009; Desai and
Trivedi, 1993; Al-Bayati and Al-Mola, 2008; Desai and
Dodiya, 2011). The standard strains which are used for
antimicrobial activity are procured by The Institute of
Microbial Technology, Chandigarh. Compounds (4a–
k) are screened for their antibacterial activity in triplicate
sets against E. coli, S. aureus, P. aeruginosa, and S. py-
ogenes at different concentrations of 1000, 500, 200, 100,
50, 25 lg/ml as shown in (Table 1). The drugs found to be
active in primary screening are similarly diluted to obtain
100, 50, 25, 12.5 lg/ml concentrations. 10 lg/ml suspen-
sions are further inoculated on appropriate media and
growth is noted after 24 and 48 h. The lowest concentra-
tion, which shows no growth after spot subculture is con-
sidered as MIC for each drug. The highest dilution showing
at least 99% inhibition is taken as MIC. The test mixture
should contain 108 cells/ml. The standard drug used in
present study is ‘‘ampicillin’’ for evaluating antibacterial
activity which shows 100, 100, 250, and 100 lg/ml MIC
against E. coli, P. aeruginosa, S. aureus, and S. pyogenes,
respectively. For bacterial growth, in the present protocol,
we have used Muller Hinton broth at 37°C in aerobic
condition for 24–48 h.
Antifungal activity
Same compounds are tested for antifungal activity in trip-
licate sets against Candida albicans, Aspergillus niger and
Aspergillus clavatus at various concentrations of 1000,
500, 200, and 100 lg/ml as shown in (Table 1). Results are
recorded in the form of primary and secondary screening.
Synthesized compounds are diluted to at 1000 lg/ml con-
centration, as a stock solution. Synthesized compounds
which are found to be active in this primary screening are
further tested in second set of dilution against all micro-
organisms. Lowest concentration, which shows no growth
after spot subculture is considered as MIC for each drug.
Highest dilution showing at least 99% inhibition is taken as
123

Med Chem Res
MIC. Test mixture should contain 108 spores/ml MIC.
Griseofulvin is used as a standard drug for antifungal
activity, which shows 500, 100, and 100 lg/ml MIC
against C. albicans, A. niger, and A. clavatus, respectively.
Results of antimicrobial evaluation of derivatives (4a–
k) are shown in (Table 1). For fungal growth, in the present
protocol, we have used Sabouraud’s dextrose broth at 22°C
in aerobic condition for 72 h.
Preparation of 1-(1-(1H-benzo[d]imidazol-2-
yl)ethylideneamino)-6-amino-4-(2-hydroxyphenyl)-2-oxo-
1,2- dihydropyridine-3,5-dicarbonitrile (3)
A mixture containing 2-(2-(1-(1H-benzo[d]imidazol-2-
yl)ethylidene)hydrazinyl)acetyl cyanide (2) (0.01 mol),
2-(2-hydroxybenzylidene)malononitrile (0.01 mol) and
two drops of piperidine as catalytic amount in ethanol
(95%) (50 ml) was refluxed for 3 h. Mixture was then
cooled to room temperature and diluted with water. Crys-
tals formed were filtered, air dried, and recrystallized from
aqueous dimethyl formamide. Yield: 77%; m.p.:
215–217°C; IR (KBr) (m, cm-1): 3438 (–NH2, amine), 3389
(O–H, Ar–OH), 3335 ([N–H, 2° amine), 3051 (–C–H, Ar–
H), 2925 (–C–H, –CH3), 2207, 2211 (–C:N), 1634, 1562
(–C=C–, –C=N– aromatic ring stretching), 1681 ([C=O);
1H NMR (DMSO-d6) d (ppm): 1.4 (s, 3H, Ar–C(CH3)=N–),
5.46 (s, 1H, Ar–OH), 6.71-7.46 (m, 8H, Ar–H), 8.6 (s, 2H,
–NH2–), 12.1 (s, 1H, –NH–); 13C NMR (DMSO-d6) d
(ppm): 13.4, 115.8, 115.4, 115.2, 117.4, 121.4, 123.2,
128.9, 130.4, 134.5, 151.7, 153.8, 156.8, 159.5,
160.1,169.4; MS: m/z 409 (M?). Anal. calcd. For
C22H15N7O2, C, 64.54; H, 3.69; N, 23.95%. Found: C,
63.95; H, 3.12; N, 23.33.
Statistical analysis
Standard deviation value is expressed in terms of SD. On
the basis of calculated value using ANOVA method, it has
been observed that differences below 0.0001 level
(P B 0.001) are considered as statistically significant.
Experimental section
Melting points are determined in open capillaries in elec-
trical apparatus and are uncorrected. Monitoring of the
progress of all reactions and homogeneity of the synthe-
sized compounds is carried out by TLC. Elemental analysis
(% C, H, N) is carried out by Perkin-Elmer 2400 CHN
analyzer. IR spectra of all compounds has been recorded on
General synthesis of 1-(1-(1H-benzo[d]imidazol-2-
yl)ethylideneamino)-6-(arylbenzylideneamino)-4-(2-
hydroxyphenyl)-2-oxo-1,2-dihydropyridine-3,5-
dicarbonitriles (4a–k)
1
Perkin-Elmer FT-IR spectrophotometer in KBr. H NMR
and 13C NMR spectra are recorded on Bruker (400 MHZ)
spectrometer using DMSO-d6 as solvent and TMS as
internal standard. Chemical shifts are reported in parts per
million (ppm). Mass spectra are scanned on Schimadzu
LCMS 2010 spectrophotometer.
A mixture of compound 3 (0.01 mol), benzaldehyde
(0.01 mol), and ethanol (95%) (50 ml) was taken in a
round-bottom flask and refluxed for 5 h. Separated solid
was filtered, dried, and recrystallized from DMSO. Pro-
gress of the reaction and purity of compounds were rou-
tinely checked on TLC [aluminum sheet-silica gel G 60 (E.
Merck)] using chloroform–methanol (4:1 v/v) as mobile
phase and the spots were located by exposing the plates in
iodine chamber. Other compounds of this series (4a–
k) were prepared using the same method. Physical data and
characterized data of all compounds are recorded below.
1-(1H-benzo[d]imidazol-2-yl)ethanone (1) was prepared
by reported method (Stavros and Athanasios 2005).
Preparation of 2-(2-(1-(1H-benzo[d]imidazol-2-
yl)ethylidene)hydrazinyl)acetyl cyanide (2)
A mixture containing 1-(1H-benzo[d]imidazol-2-yl)etha-
none (1) (0.01 mol) and 2-hydrazinylacetyl cyanide
(0.01 mol) in alcohol (99.9%) (100 ml) was refluxed for
3 h and then cooled down to room temperature. Separated
crystals were filtered, air dried, and recrystallized from
ethanol (95%). Yield: 76%; m.p.: 165–167°C; IR (KBr) (m,
cm-1): 3333 ([N–H, 2° amine), 3054 (–C–H, Ar–H), 2922
(–C–H, –CH3), 2208, 2211 (–C:N), 1636, 1564 (–C=C–,
1-(1-(1H-benzimidazol-2-yl)ethylideneamino)-6-
(benzylideneamino)-4-(2-hydroxyphenyl)-2-oxo-1,2-
dihydropyridine-3,5-dicarbonitrile (4a)
1
–C=N– aromatic ring stretching), 1680 ([C=O); H NMR
Brown solid; Yield: 76%, m.p. 246–248°C; IR (KBr) (m,
cm-1): 3334 (N–H, 2° amine), 3043, 3052 (C–H, Ar–H),
3005, 2925 (C–H stretching, =CH and –CH3 group), 2206,
2210 (C:N), 3437 (O–H, Ar–OH), 1638, 1560 (C=C,
C=N aromatic ring stretching), 1681 ([C=O), 1448, 1457
(DMSO-d6) d (ppm): 1.2 (s, 3H, Ar–C(CH3)=N–),
6.89–7.71 (m, 4H, Ar–H), 9.3 (s, 1H, –NH–), 12.3 (s, 1H,
–NH–); 13C NMR (DMSO-d6) d (ppm): 12.8, 113.3, 115.2,
123.2 134.5, 146.8, 151.3, 155.4; MS: m/z 241 (M?). Anal.
calcd. For C12H11N5O, C, 59.74; H, 4.60; N, 29.03%.
Found.: C, 59.16; H, 4.12; N, 29.56.
1
(C–H bending, =CH and –CH3 group); H NMR (DMSO-
d6) d (ppm): 1.3 (s, 3H, Ar–C(CH3)=N–), 5.70 (s, 1H, Ar–
123

Med Chem Res
OH), 6.72–7.83 (m, 13H, Ar–H), 9.2 (s, 1H, Ar–CH=N–),
12.8 (s, 1H, –NH–); 13C NMR (DMSO-d6) d (ppm): 12.2,
113.1, 114.8, 117.4, 119.4, 119.7, 122.3, 123.4, 126.4,
127.1, 127.3, 128.1, 128.5, 129, 132.3, 136.2, 141.5, 147.2,
149, 153.6, 169, 176.5; MS: m/z 497 (M?). Anal. calcd. For
C29H19N7O2, C, 70.01; H, 3.85; N, 19.71%. Found: C,
70.08; H, 3.92; N, 19.78.
group), 2209, 2211 (C:N), 3438 (O–H, Ar–OH), 1638,
1561 (C=C, C=N aromatic ring stretching), 1682 ([C=O),
1445, 1462 (C–H bending, =CH and –CH3 group); 1H
NMR (DMSO-d6) d (ppm): 1.31 (s, 3H, Ar–C(CH3)=N–),
5.76 (s, 2H, Ar–OH), 6.63–7.45 (m, 12H, Ar–H), 9.23 (s,
1H, Ar–CH=N–), 12.7 (s, 1H, –NH–); 13C NMR (DMSO-
d6) d (ppm): 12.3, 113, 114, 114.8, 115.8, 117.4, 119.4,
119.7, 122.3, 123.4, 126.4, 128.1, 128.5, 129, 132.3, 134.2,
136.2, 147.2, 149, 153.6, 154.2, 169, 176.5; MS: m/z
513.15 (M?). Anal. calcd. For C29H19N7O3, C, 67.83; H,
3.73; N, 19.09%. Found: C, 67.89; H, 3.79; N, 19.16.
1-(1-(1H-benzo[d]imidazol-2-yl)ethylideneamino)-6-(2-
hydroxybenzylideneamino)-4-(2-hydroxyphenyl)-2-oxo-
1,2-dihydropyridine-3,5-dicarbonitrile (4b)
Brown solid; Yield: 72%, m.p. 237–238°C; IR (KBr) (m,
cm-1): 3338 (N–H, 2° amine), 3045, 3053 (C–H, Ar–H),
3008, 2926 (C–H stretching, =CH and –CH3 group), 2208,
2210 (C:N), 3439 (O–H, Ar–OH), 1638, 1560 (C=C,
C=N aromatic ring stretching), 1680 ([C=O), 1446, 1459
1-(1-(1H-benzimidazol-2-yl)ethylideneamino)-4-(2-
hydroxyphenyl)-6-(3-nitrobenzylidene-amino)-2-oxo-1,2-
dihydropyridine-3,5-dicarbonitrile (4e)
1
Yellow solid; Yield: 75%, m.p. 242-244°C; IR (KBr) (m,
cm-1): 3342 (N–H, 2° amine), 3046, 3056 (C–H, Ar–H),
3002, 2927 (C–H stretching, =CH and –CH3 group), 2209,
2211 (C:N), 3442 (O–H, Ar–OH), 1530 (N–O, Ar–NO2),
1646, 1571 (C=C, C=N aromatic ring stretching), 1679
([C=O), 1444, 1453 (C–H bending, =CH and –CH3
(C–H bending, =CH and –CH3 group); H NMR (DMSO-
d6) d (ppm): 1.31 (s, 3H, Ar–C(CH3)=N–), 5.75 (s, 2H,
2Ar–OH), 6.64–7.73 (m, 12H, Ar–H), 9.22 (s, 1H, Ar–
CH=N–), 12.8 (s, 1H, –NH–); 13C NMR (DMSO-d6) d
(ppm): 12.3, 113, 114.4, 114.8, 115.8, 119.4, 119.7, 121.2,
122.3, 123.4, 126.4, 128.1, 128.5, 128.7, 128.8, 129, 132.3,
136.2, 147.2, 149, 153.6, 154, 169, 176.5; MS: m/z 513.15
(M?). Anal. calcd. For C29H19N7O3, C, 67.83; H, 3.73; N,
19.09%. Found: C, 67.89; H, 3.80; N, 19.14.
1
group); H NMR (DMSO-d6) d (ppm): 1.31 (s, 3H, Ar–
C(CH3)=N–), 5.76 (s, H, Ar–OH), 6.67-8.01 (m, 12H, Ar–
H), 9.23 (s, 1H, Ar–CH=N–), 12.7 (s, 1H, –NH–); 13C
NMR (DMSO-d6) d (ppm): 12.3, 113, 114.1, 114.8, 117.4,
119.4, 119.7, 121.8, 122, 122.3, 123.4, 126.4, 128.1, 129,
129.3, 132.3, 133.1, 136.2, 142.3, 147.2, 148.1, 149, 153.6,
169, 176.5; MS: m/z 542.15 (M?). Anal. calcd. For
C29H18N8O4, C, 64.20; H, 3.34; N, 20.65%. Found: C,
64.25; H, 3.41; N, 20.71.
1-(1-(1H-benzimidazol-2-yl)ethylideneamino)-6-(3-
hydroxybenzylideneamino)-4-(2-hydroxyphenyl)-2-oxo-
1,2-dihydropyridine-3,5-dicarbonitrile (4c)
Dark brown solid; Yield:73%, m.p. 245–247°C; IR (KBr)
(m, cm-1): 3336 (N–H, 2° amine), 3041, 3054 (C–H, Ar–
H), 3001, 2927 (C–H stretching, =CH and –CH3 group),
2206, 2211 (C:N), 3437 (O–H, Ar–OH), 1638, 1560
(C=C, C=N aromatic ring stretching), 1683 ([C=O), 1444,
1455 (C–H bending, =CH and –CH3 group); 1H NMR
(DMSO-d6) d (ppm): 1.32 (s, 3H, Ar–C(CH3)=N–), 5.77 (s,
2H, 2Ar–OH), 6.63–7.41 (m, 12H, Ar–H), 9.23 (s, 1H, Ar–
CH=N–), 12.7 (s, 1H, –NH–); 13C NMR (DMSO-d6) d
(ppm): 12.3, 113, 114, 114.4, 114.6, 114.8, 117.4, 119.4,
119.7, 119.8, 122.3, 123.4, 126.4, 129, 129.9, 132.3, 136.2,
142.9, 147, 149, 153.6, 155.4, 169, 176.5; MS: m/z 513.15
(M?). Anal. calcd. For C29H19N7O3, C, 67.83; H, 3.73; N,
19.09%. Found: C, 67.88; H, 3.79; N, 19.16.
1-(1-(1H-benzimidazol-2-yl)ethylideneamino)-4-(2-
hydroxyphenyl)-6-(4-nitrobenzylidene-amino)-2-oxo-1,2-
dihydropyridine-3,5-dicarbonitrile (4f)
Dark yellow solid; Yield: 73%, m.p. 239–241°C; IR (KBr)
(m, cm-1): 3338 (N–H, 2° amine), 3046, 3059 (C–H, Ar–
H), 3003, 2928 (C–H stretching, =CH and –CH3 group),
2213, 2215 (C:N), 3441 (O–H, Ar–OH), 1528 (N–O, Ar–
NO2), 1638, 1570 (C=C, C=N aromatic ring stretching),
1681 ([C=O), 1444, 1456 (C–H bending, =CH and –CH3
1
group); H NMR (DMSO-d6) d (ppm): 1.33 (s, 3H, Ar–
C(CH3)=N–), 5.77 (s, H, Ar–OH), 6.70–8.03 (m, 12H, Ar–
H), 9.25 (s, 1H, Ar–CH=N–), 12.71 (s, 1H, –NH–); 13C
NMR (DMSO-d6) d (ppm): 12.3, 113, 114, 114.8, 117.4,
119.4, 119.7, 122.3, 123.2, 123.4, 126.4, 127.9, 128.1, 129,
132.3, 136.2, 147.2, 147.5, 149,149.9, 153.6, 169, 176.5;
MS: m/z 542.15 (M?). Anal. calcd. For C29H18N8O4, C,
64.20; H, 3.34; N, 20.65%. Found: C, 64.26 H, 3.42; N,
20.71%.
1-(1-(1H-benzimidazol-2-yl)ethylideneamino)-6-(4-
hydroxybenzylideneamino)-4-(2-hydroxyphenyl)-2-oxo-
1,2-dihydropyridine-3,5-dicarbonitrile (4d)
Reddish-brown solid; Yield: 70%, m.p. 236–237°C; IR
(KBr) (m, cm-1): 3338 (N–H, 2° amine), 3043, 3056 (C–H,
Ar–H), 3011, 2927 (C–H stretching, =CH and –CH3
123

Med Chem Res
1-(1-(1H-benzimidazol-2-yl)ethylideneamino)-6-(2-
chlorobenzylideneamino)-4-(2-hydroxyphenyl)-2-oxo-1,2-
dihydropyridine-3,5-dicarbonitrile (4g)
114.8, 117.4, 119.4, 119.7, 122.3, 123.4, 126.4, 127.8,
128.1, 129, 129.7, 132.3, 136.2, 147.2, 149, 153, 169,
176.5; MS: m/z 540.20 (M?). Anal. calc. For C31H24N8O2 :
C, 68.88%; H, 4.47%; N, 20.73%. Found:C, 68.82%; H,
4.54%; N, 20.79%.
Orange solid; Yield: 69%, m.p. 237–239°C; IR (KBr) (m,
cm-1): 3340 (N–H, 2° amine), 3049, 3061 (C–H, Ar–H),
2993, 2925 (C–H stretching, =CH and –CH3 group), 2208,
2212 (C:N), 3438 (O–H, Ar–OH), 760 (C–Cl, Ar–Cl),
1636, 1568 (C=C, C=N aromatic ring stretching), 1683
([C=O), 1446, 1456 (C–H bending, =CH and –CH3
1-(1-(1H-benzimidazol-2-yl)ethylideneamino)-6-(4-
hydroxy-3-methoxybenzylideneamino)-4-(2-
hydroxyphenyl)-2-oxo-1,2-dihydropyridine-3,5-
dicarbonitrile (4j)
1
group); H NMR (DMSO-d6) d (ppm): 1.32 (s, 3H, Ar–
C(CH3)=N–), 5.76 (s, H, Ar–OH), 6.68–7.72 (m, 12H, Ar–
H), 9.24 (s, 1H, Ar–CH=N–), 12.7 (s, 1H, –NH–); 13C
NMR (DMSO-d6) d (ppm): 12.3, 113, 114, 114.3, 114.8,
117.4, 119.4, 119.7, 122.3, 123.4, 126.4, 126.5,
128.1,128.3, 128.7, 129, 132.3, 133.5, 136.2, 141.7, 147.2,
149, 153.6, 169, 176.5; MS: m/z 531.12 (M?). Anal. calc.
For C29H18ClN7O2: C, 65.48%; H, 3.41%; N, 18.43%.
Found : C, 65.55; H, 3.48; N, 18.55%.
Reddish-brown solid; Yield: 75%, m.p. 234–236°C; IR
(KBr) (m, cm-1): 3340 (N–H, 2° amine), 3047, 3058 (C–H,
Ar–H), 3009, 2925 (C–H stretching, =CH and –CH3
group), 2213, 2211 (C:N), 3442 (O–H, Ar–OH), 1636,
1566 (C=C, C=N aromatic ring str.), 1683 ([C=O), 1117,
1030, (C–O–C, Ar–O–CH3), 2845 (C–H, O–CH3), 1450,
1465 (C–H bending, =CH and –CH3 group); 1H NMR
(DMSO-d6) d (ppm): 1.32 (s, 3H, Ar–C(CH3)=N–), 5.49 (s,
2H, Ar–OH), 6.70–7.59 (m, 11H, Ar–H), 9.26 (s, 1H, Ar–
CH=N–), 12.7 (s, 1H, –NH–), 3.90 (s, 3H, Ar–OCH3); 13
C
1-(1-(1H-benzimidazol-2-yl)ethylideneamino)-6-(4-
chlorobenzylideneamino)-4-(2-hydroxyphenyl)-2-oxo-1,2-
dihydropyridine-3,5-dicarbonitrile (4h)
NMR (DMSO-d6) d (ppm): 12.3, 42.4, 113, 113.8, 114.1,
114.8, 116.7, 117.4, 119.4, 119.7, 120.4, 122.3, 123.4,
126.4, 128.10, 129, 132.3, 135.1, 136.2, 139.5, 146, 147.2,
149, 153.6, 169, 176.5; MS: m/z 543.17 (M?). Anal. calc.
For C30H21N7O4 : C, 66.29%; H, 3.89%; N, 18.04%.
Found: C, 66.34%; H, 3.94%; N, 18.09%.
Light brown solid; Yield: 68%, m.p. 230–231°C; IR (KBr)
(m, cm-1): 3339 (N–H, 2° amine), 3047, 3062 (C–H, Ar–
H), 3001, 2925 (C–H stretching, =CH and –CH3 group),
2210, 2213 (C:N), 3439 (O–H, Ar–OH), 758 (C–Cl, Ar–
Cl), 1634, 1565 (C=C, C=N aromatic ring stretching), 1680
([C=O), 1444, 1455 (C–H bending, =CH and –CH3
1-(1-(1H-benzimidazol-2-yl)ethylideneamino)-4-(2-
hydroxyphenyl)-2-oxo-6-(3,4,5-
1
group); H NMR (DMSO-d6) d (ppm): 1.33 (s, 3H, Ar–
trimethoxybenzylideneamino)-1,2-dihydropyridine-3,5-
dicarbonitrile (4k)
C(CH3)=N–), 5.77 (s, H, Ar–OH), 6.69–7.74 (m, 12H, Ar–
H), 9.25 (s, 1H, Ar–CH=N–), 12.7 (s, 1H, –NH–); 13C
NMR (DMSO-d6) d (ppm): 12.3, 113, 114, 114.8, 117.4,
119.4, 122.3, 123.4, 126.4, 128.1, 128.7, 129, 132.3, 133.7,
136.2, 139.5, 147.2,149, 153.6, 169, 176.5; MS: m/z 531.12
(M?). Anal. calc. For C29H18ClN7O2 : C, 65.48%; H,
3.41%; N, 18.43%. Found: C, 65.54%; H, 3.47%; N,
18.49%.
Dark brown solid; Yield: 79%, m.p. 229–231°C; IR (KBr)
(m, cm-1): 3339 (N–H, 2° amine), 3049, 3062 (C–H, Ar–
H), 2998, 2927 (C–H stretching, =CH and –CH3 group),
2210, 2213 (C:N), 3439 (O–H, Ar–OH), 1636, 1566
(C=C, C=N aromatic ring str.), 1679 ([C=O), 2852 (C–H,
O–CH3), 1116 (C–O–C, Ar–O–CH3), 1445, 1454 (C–H
1
bending, =CH and –CH3 group); H NMR (DMSO-d6) d
1-(1-(1H-benzimidazol-2-yl)ethylideneamino)-6-(4-
(dimethylamino)benzylideneamino)-4-(2-hydroxyphenyl)-
2-oxo-1,2-dihydropyridine-3,5-dicarbonitrile (4i)
(ppm): 1.33 (s, 3H, Ar–C(CH3)=N–), 5.50 (s, 1H, Ar–OH),
6.65–7.61 (m, 10H, Ar–H), 9.24 (s, 1H, Ar–CH=N–), 12.7
(s, 1H, –NH–), 3.91 (s, 3H, Ar–OCH3), 3.94 (s, 6H, Ar–
OCH3); 13C NMR (DMSO-d6) d (ppm): 12.3, 42.3, 105.2,
113, 114.8, 117.4, 119.2, 122.3, 123.4, 126.4, 128.1, 129,
132.3, 135, 136.2, 147, 149.3, 153, 169, 177; MS: m/z
587.19 (M?). Anal. calc. For C32H25N7O5 : C, 65.41%; H,
4.29%; N, 16.69%. Found:C, 65.46%; H, 4.34%; N,
16.73%.
Brown solid; Yield: 80%, m.p. 250–252°C; IR (KBr) (m,
cm-1): 3339 (N–H, 2° amine), 3046, 3055 (C–H, Ar–H),
2998, 2927 (C–H stretching, =CH and –CH3 group), 2210,
2214 (C:N), 3439 (O–H, Ar–OH), 1636, 1566 (C=C,
1
C=N aromatic ring stretching), 1677 ([C=O); H NMR
(DMSO-d6) d (ppm): 1.32 (s, 3H, Ar–C(CH3)=N–), 5.73 (s,
H, Ar–OH), 6.70–7.59 (m, 12H, Ar–H), 9.24 (s, 1H, Ar–
Acknowledgments The authors thank Department of Chemistry,
Bhavnagar University, Bhavnagar for providing research facilities
and the authors also thank University Grants Commission, New Delhi
CH=N–), 12.8 (s, 1H, –NH–), 2.55 (s, 6H, –N–(CH3)2; 13
C
NMR (DMSO-d6) d (ppm): 12.2, 43.6, 112.3, 113, 114.1,
123

Med Chem Res
for providing UGC-meritorious scholarship to one of the authors
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