Silica sulfuric acid/ethylene glycol as an efficient catalyst for the synthesis of benzo[4,5]imidazo[1,2-a]pyrimidine-3-carbonitrile derivatives

Article abstract of DOI:10.1080/00397911.2019.1652322

A simple and efficient eco-friendly method was developed for the synthesis of new benzo[4,5]imidazo[1,2-a]pyrimidine-3-carbonitrile derivatives in excellent yields. The synthesis was achieved through the reaction of 2-aminobenzimidazole, aldehydes and act

Full text of DOI:10.1080/00397911.2019.1652322

Synthetic Communications
An International Journal for Rapid Communication of Synthetic Organic
Chemistry
ISSN: 0039-7911 (Print) 1532-2432 (Online) Journal homepage: https://www.tandfonline.com/loi/lsyc20
Silica sulfuric acid/ethylene glycol as
an efficient catalyst for the synthesis of
benzo[4,5]imidazo[1,2-a]pyrimidine-3-carbonitrile
derivatives
Wahid M. Basyouni, Samir Y. Abbas, Nagwa M. Abdelazeem, Khairy A. M. El-
Bayouki & Mohamed Y. El-Kady
To cite this article: Wahid M. Basyouni, Samir Y. Abbas, Nagwa M. Abdelazeem, Khairy A.
M. El-Bayouki & Mohamed Y. El-Kady (2019): Silica sulfuric acid/ethylene glycol as an efficient
catalyst for the synthesis of benzo[4,5]imidazo[1,2-a]pyrimidine-3-carbonitrile derivatives, Synthetic
Communications, DOI: 10.1080/00397911.2019.1652322
To link to this article: https://doi.org/10.1080/00397911.2019.1652322
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SYNTHETIC COMMUNICATIONSV
https://doi.org/10.1080/00397911.2019.1652322
Silica sulfuric acid/ethylene glycol as an efficient catalyst
for the synthesis of benzo[4,5]imidazo[1,2-a]pyrimidine-3-
carbonitrile derivatives
Wahid M. Basyounia, Samir Y. Abbasa, Nagwa M. Abdelazeema,
Khairy A. M. El-Bayoukia, and Mohamed Y. El-Kadyb
aOrganometallic and Organometalloid Chemistry Department, National Research Centre, Cairo, Egypt;
bChemistry Department, Faculty of Science, Ain Shams University, Cairo, Egypt
ABSTRACT
ARTICLE HISTORY
Received 19 February 2019
A simple and efficient eco-friendly method was developed for the
synthesis of new benzo[4,5]imidazo[1,2-a]pyrimidine-3-carbonitrile
derivatives in excellent yields. The synthesis was achieved through
the reaction of 2-aminobenzimidazole, aldehydes and active nitriles
(malononitrle or ethyl cyanoacetae) in the presence of silica sulfuric
acid/ethylene glycol. This protocol offers very short reaction times (in
some cases, reaction times were reduced to five minutes), high
yields and low cost. This method thus provides an improvement
over the existing methods.
KEYWORDS
2-Aminobenzimidazole; ben-
zo[4,5]imidazo[1,2-a]pyrimi-
dine; nitrile compounds;
silica sulfuric acid
GRAPHICAL ABSTRACT
Introduction
Most of natural and synthetic heterocyclic compounds have been identified as potential
drug candidates with a wide range of biological activities.[1–6] Therefore, the organic
chemistry was interested in the synthetic community of medicinal chemistry, combina-
torial chemistry and diversity oriented synthesis was directed to develop new and an
efficient synthetic methods for heterocyclic compounds.[7–11]
CONTACT Wahid M. Basyouni
w_basyouni2002@yahoo.com; Samir Y. Abbas
samiryoussef98@yahoo.com
Organometallic and Organometalloid Chemistry Department, National Research Centre, Cairo, Egypt.
Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/lsyc.
Supplemental data for this article can be accessed on the publisher’s website.
ß 2019 National Research Centre

2
W. M. BASYOUNI ET AL.
Upon a comprehensive survey for the methods of preparation of benzo[4,5]imi-
dazo[1,2-a]pyrimidine derivatives, we found that the most methods are the one-pot
three-component condensation reactions of aminobenzimidazole, aldehydes and
dicarbonyl compounds (or active nitrles) in the presence of catalysts.[12–15] However,
some of these methodologies suffer from disadvantages, such as low yields, use of
high boiling solvents, excess of catalyst or special apparatus. Also, to our knowledge,
ethyl cyanoacetate was not used as active nitrle in this one-pot three-component
reaction. Thus, we decided to investigate a new, efficient, and an convenient method
for building new types of benzo[4,5]imidazo[1,2-a]pyrimidine derivatives.
Recently, there are interesting for the development of efficient methodologies that are
environmentally benign. The usage of catalysts has received great interest in the various
organic syntheses. Solid supported reagents are useful technique to improve the activity
and selectivity of the individual reagents, because this technique increase the surface area
of the reagent to manifold.[16] Silica sulfuric acid as solid acid is a versatile catalyst. They
make reaction processes more economic, more convenient and environmentally benign.
Silica sulfuric acid (SSA) successfully used as efficient heterogeneous catalysts for
many organic transformations due to different factors such as ease of preparation, low
cost, recycling and eases of handling. Owing to the numerous advantages associated
with this cheap and nonhazardous catalyst, under mild conditions, silica sulfuric acid
has been explored as a powerful catalyst for various organic transformations.[17]
We are reported the development of silica sulfuric acid as a simple and efficient cata-
lyst for the synthesis of tricyclic and tetarcyclic dihydropyrimidine derivatives,[18] highly
substituted piperidines[19] and 3,4,5-trisubstituted 2(5 H)-furanone derivatives[20] by a
one-pot multicomponent reaction under mild conditions. This reaction can be regarded
as an efficient approach for the preparation of synthetically and pharmaceutically
important compounds. This one-pot reaction has some important advantages such as
easy workup procedure, simple and readily available precursors, nontoxic and inexpen-
sive catalyst, and good to excellent yields.
This solid acid has also been used in synthesis of synthesis of substituted pyrroles,[21]
synthesis of 2,3-dihydroquinazolin-4(1H)-ones,[22] oxazolines and imidazolines,[23]
deprotection of oxime to carbonyls[24] and chemoselective detritylation of 50-tritylated
nucleosides.[25]
On the other hand, in modern organic synthesis, traditional volatile organic reaction
solvents are continuously replaced by environmentally benign solvents or used solvent-
free techniques for the syntheses of various heterocyclic compounds.[26–28]
In view of these facts and as a continuation of our previous efforts to develop new
synthetic methodologies, development of synthetic method that afforded high yields of
the target products by investigating new, convenient and efficient method for building
new types of benzo[4,5]imidazo[1,2-a]pyrimidine-3-carbonitrile derivatives was aimed
to investigate.
Result and discussion
In order to optimize the reaction conditions, 2-aminobenzimidazole, benzaldehyde, and
malononitrile were taken as model substrates (Scheme 1). In the initial study, when

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SYNTHETIC COMMUNICATIONSV
3
Ph
N
H
CN
N
Conditions
+
+ NC
Ph CHO
CN
NH2
N
H
N
N
H
NH2
1a
Scheme 1. Optimization of reaction conditions for the synthesis of benzo[4,5]imidazo[1,2-a]pyrimi-
dine-3-carbonitrile 1a.
Table 1. Results of benzo[4,5]imidazo[1,2-a]-pyrimidine-3-carbonitrile 1a with different catalysts
and solvents.
Entry
Catalyst (mol)
None
PPA/SiO2 (0.11)
HClO4/SiO2 (0.11)
SSA (0.11)
SSA (0.11)
SSA (0.11)
SSA (0.11)
SSA (0.11)
SSA (0.11)
Solvent/ ꢀC
Time (min)
Yield (%)
1
2
3
4
5
6
7
8
(CH2OH)2/120
(CH2OH)2/120
(CH2OH)2/120
(CH2OH)2/120
H2O/ reflux
MeOH/reflux
EtOH/reflux
CHCl3/reflux
DMF
90
10
10
5
30
60
10
10
90
5
50
84
90
97
72
77
84
74
77
90
84
87
9
10
11
12
SSA (0.15)
SSA (0.05)
SSA (0.025)
(CH2OH)2/120
(CH2OH)2/120
(CH2OH)2/120
5
5
2-aminobenzimidazole was left to react with benzaldehyde and malononitrile in ethylene
glycol without catalyst (Table 1, entry 1); it was found that, the desired product ben-
zo[4,5]imidazo[1,2-a]pyrimidine-3-carbonitrile (1a) was obtained in low yield (50%)
even at prolonged reaction time.
As shown in Table 1, different catalysts and solvents were investigated with regard to
the best yield and low reaction times for the synthesize 2-amino-4-phenyl-1,4-dihydro-
benzo[4,5]-imidazo[1,2-a]pyrimidine-3-carbonitrile (1a). The reaction was carried out
by using various catalysts (namely PPA/SiO2, HClO4/SiO2 and SSA) alone to set up
standard reaction conditions in order to obtain the best catalyst as shown in Table 1.
From the obtained results, it was found that, the best catalyst in terms of yield and reac-
tion time was silica sulfuric acid (Table 1, entry 4). The attention was then focused
toward the effect of solvents on the yield of the one-pot assembly of the model.
Replacing ethylene glycol by H2O, CH3OH, C2H5OH, CHCl3, or DMF (Table 1, entry
5-9, respectively) produced the model 1a in yields lower than that of entry 4. Moreover,
upon studying the efficacy of the ratio of the catalyst (0.11, 0.15, 0.05, 0.025 mol) it was
noticed that 0.11 mol of the catalyst was the optimum ratio (Table 1, entry 4).
Optimized condition was established in ethylene glycol as a solvent, it gave the best
result with 97% yield of the required benzo[4,5]imidazo[1,2-a]pyrimidine-3-carbonitrile
1a (Table 1, entry 4). This remarkable activation in reaction rate prompted us to
explore the potential of this protocol for the synthesis of other 2-amino-4-aryl-1,4-dihy-
drobenzo[4,5]imidazo[1,2-a]-pyrimidine-3-carbonitrile derivatives.
Under optimized reaction conditions, the reusability of silica sulfuric acid was exam-
ined. The silica sulfuric acid is exists in the solid state and easily separated from reac-
tion mixture simply by filtration. The catalyst was washed with ethyl acetate and diethyl

4
W. M. BASYOUNI ET AL.
Table 2. The effect of reusability of SSA catalyst on the benzo[4,5]
imidazo[1,2-a]-pyrimidine-3-carbonitrile 1a yield.
Number of uses
Time (min)
Yield (%)
1
2
3
4
5
5
6
8
97
97
95
93
Ar
H
CN
NH2
N
SSA/(CH2OH)2,
120 °C
N
NH2
NC
CN
ArCHO
N
H
N
N
H
1a-f
Scheme 2. Reaction of 2-aminobenzimidazole and aldehydes with malononitrile.
Table 3. Reaction times and yields of the synthesis of 2-amino-benzo[4,5]imidazo[1,2-a]-pyrimidine-
3-carbonitriles 1a–f.
Found
Reported
Entry
1
Compd. No.
Ar
Time (min)
Yield %
97
Time (min)
Yield %
1a
Ph
5
5
6
2
3
3
5
3
90[29]
92[15]
91[30]
87[29]
90[15]
91[30]
2
1b
4-FC6H4
86
3
4
5
6
1c
1d
1e
1f
4-OHC6H4
3-OCH3C6H4
2,5-(OCH3)2-C6H3
naphthalen-2-yl
15
10
15
15
83
83
97
97
3
3
92[29]
92[30]
ether and a fresh reaction was then performed under the same condition. The silica sul-
furic acid could be used for at least four times without significant loss in product yield
(Table 2).
The scope and limitations of the present three-component reaction under optimized
conditions were explored using a variety of aldehydes. Thus, 2-aminobenzimidazole and
malononitrile were reacted with different aldehydes to afford the corresponding 2-
amino-4-aryl-1,4-dihydro benzo[4,5]imidazo[1,2-a]pyrimidine-3-carbonitrile derivatives
1a-f in good yields (83–97%) as shown in Scheme 2 and Table 3. Under identical condi-
tions, heterocyclic aldehydes such as 5-methylfuranal and 2-thiophene aldehyde gave
none of the corresponding 2-amino-4-hetrocycles-1,4-dihydro benzo[4,5]imidazo[1,2-
a]pyrimidine-3-carbonitrile derivatives.
1
Structure of the synthesized products 1a–f was deduced on the basis of IR, H NMR,
13C NMR spectroscopy and elemental analyses. Thus, their IR spectra exhibited charac-
terized absorption bands in 3480–3137 cmꢁ1 region corresponding to NH & NH2 func-
tional groups. Moreover, IR spectra exhibited strong absorption band around 2180 cmꢁ1
1
due to cyano functional group. H NMR spectrum of 1e as representative example
exhibited two singlet signals at: d ¼ 3.60 and 3.66 ppm for two methoxy protons, signal

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5
N
NH2
N
H
O
Ar
Ar
H
H
NC
CN
+
OC2H5
Ar CHO
N
N
CN
+
SSA/(CH2OH)2,
120 °C
N
N
O
N
N
O
H
H
3a-g
2a-g
Scheme 3. Reaction of 2-aminobenzimidazole and aldehydes with ethyl cyanoacetate.
Table 4. Reaction times and yields of benzo[4,5]imidazo[1,2-a]pyrimidine derivatives
2a–g and 3a–g.
Entry
1
Ar
Time (min)
35
Compd. No.
Yield %
Ph
2a
3a
2b
3b
2c
3c
2d
3d
2e
3e
2f
50
18
44
19
0
83
47
16
51
0
58
37
73
9
2
3
4
5
6
7
4–FC6H4
3–ClC6H4
35
35
50
80
10
60
3–OCH3C6H4
2,5–(OCH3)2–C6H3
3–NO2C6H4
3f
2g
3g
naphthalen-2-yl
at: d ¼ 5.34 ppm for CH proton of the pyrimidine ring (H-4). Also, the spectrum
revealed the presence of two broad signals at: d ¼ 6.73 and 8.28 ppm for the NH2 and
NH protons, respectively. 13C NMR spectrum supported these assignments and added a
strong evidence for these interpretations; where, 13C NMR spectrum revealed signals at:
55.7 and 56.3 ppm assigned to two methoxy carbons and signal at 49.5 ppm assigned to
CH carbon of pyrimidine ring (H-4).
Regarding to the effect of the aromatic aldehydes: The presence of 2,5-dimethoxy-
phenyl moiety (Table 3, entry 5) resulted the higher yield of the product (1e; 97%) with
compared to other aryl moieties followed by phenyl moiety (entry 2, 1a; 96%). 3-
methoxyphenyl moiety (1d, entry 4) had the same behavior of 4-hydroxyphenyl moiety
(1c, entry 3) towards this reaction (83%). 4-Fluorophenyl moiety (1b, entry 2) showed
result (86%). Naphthyl moiety (1f, entry 6) had the same behavior of 2,5-dimethoxy-
phenyl moiety towards this reaction (97%).
A plausible reaction mechanism was suggested in which silica sulfuric acid can serve
as a Lewis acidic catalyst for Knoevenagel condensation of activated aldehyde with
malononitrile which leads to the formation of 2-arylidenemalononitrile intermediates. 2-
Amino benzimidazole was reacted with the latter intermediates in the Michael way to
generate intermediates, which subjected to cyclization, leading to the formation of the
desired 2-amino-1,4-dihydrobenzo[4,5]imidazo[1,2-a]pyrimidine-3-carbonitrile deriva-
tives 1a–f (Table 4).

6
W. M. BASYOUNI ET AL.
O
CN
O
S
H
H
O
S
NC
H
COOC2H5
Ar
O
O
O
H
O
COOC2H5
O
Ar
H
Ar
I
N
O
S
H
O
NH2
N
H
O
Ar
Ar
N
H
Ar
H
H
CN
CN
N
N
CN
- H2
COOC2H5
NH2
N
N
O
N
II
N
N
H
O
H
3
2
Scheme 4. A plausible mechanism for the one-pot synthesis of benzo[4,5]imidazo[1,2-a]pyrimidine
derivatives 2a–g and 3a–g.
After the successful application of silica sulfuric acid/ethylene glycol in the synthesis
of 2-amino-4-aryl-1,4-dihydrobenzo[4,5]- imidazo[1,2-a]pyrimidine-3-carbonitrile deriv-
atives 1a–f, this catalyst was also applied in the three-component condensation of ethyl
cyanoacetate with 2-aminobenzimidazole and different aldehydes, leading to two prod-
ucts, as shown in Scheme 3. Structures of the obtained products were elucidated by
1
careful inspection of their spectral data. IR spectra showed bands for cyano group. H
NMR spectra showed absence of the ester and amino groups. The obtained products
were confirmed as 1,2,3,4-tetrahydrobenzo [4,5]imidazo[1,2-a]-pyrimidine-3-carbonitrile
derivatives 2a–g and their oxizied form 1,2-dihydrobenzo[4,5]imidazo[1,2-a]-pyrimi-
dine-3-carbonitrile derivatives 3a–g. In all cases (except 3-chlorobenzaldehyde), the
majority products were the 1,2,3,4-tetrahydrobenzo[4,5]imidazo[1,2-a]pyrimidine-3-car-
bonitrile derivatives 2 while 1,2-dihydrobenzo[4,5]imidazo [1,2-a]pyrimidine-3-carboni-
trile derivatives 3 were observed as a sole product in case of product 3c. Under
identical conditions, heterocyclic aldehydes such as 5-methylfuranal and 2-thiophene
aldehyde gave none of the corresponding benzo[4,5]imidazo[1,2-a]pyrimidine-3-carbon-
itrile derivatives.
1
Structures of products 2a–g and 3a–g were deduced on the basis of IR, H & 13C
NMR spectroscopy and correct elemental analyses. IR spectrum of 2d, as representative
example, exhibited the absorption bands at 3432, 2232 and 1675 cmꢁ1 for imino, cyano
1
and carbonyl functional groups, respectively. H NMR spectrum of 2d as representative
example exhibited singlet signal at: d ¼ 3.83 ppm for methoxy protons. CH protons of
pyrimidine ring (H-3 and H-4) were observed as two doublet signals at: d ¼ 5.89 and
1
7.49 ppm while in H NMR spectrum of 3d, CH proton signals of pyrimidine ring were
not observed. 13C NMR spectra for the products 2 and 3 supported these assignments
and added a strong evidence for these interpretations.
The plausible reaction mechanism (Scheme 4) was suggested in which silica sulfuric
acid can serve as a Lewis acidic catalyst for Knoevenagel condensation of the aldehyde
with ethyl cyanoacetate which lead to the formation of arylidene ethyl cyanoacetate
intermediates I. The imino-group of the 2-aminobenzimidazole was reacted with the lat-
ter intermediates in the Michael way, leading to generate the intermediates II, which

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SYNTHETIC COMMUNICATIONSV
7
subjected to loss a molecule of ethanol (from reacting the amino- group with the
ester- group) to form the intermediates which undergoes cyclization, leading to forma-
tion of the desired products 2-oxo-4-aryl-1,2,3,4-tetrahydrobenzo[4,5]imidazo[1,2-a]pyr-
imidine-3-carbonitrile derivatives 2a–g which underwent dehydrogenation afforded the
2-oxo-4-aryl-1,2-dihydrobenzo[4,5]- imidazo[1,2-a]pyrimidine-3-carbonitrile deriva-
tives 3a–g.
Conclusion
In conclusion, the present investigation demonstrated a novel catalyst (Silica sulfuric
acid/ethylene glycol) for the synthesis of benzo[4,5] imidazo[1,2-a]pyrimidine-3-carbon-
itrile. Silica sulfuric acid/ethylene glycol catalyst was able to modify the reaction proto-
col and successfully benzo[4,5] imidazo[1,2-a]pyrimidine-3-carbonitrile derivatives were
obtained in high yield and high purity with short reaction times via the three-compo-
nent condensation reactions of 2-aminobenzimidazole, aldehydes and active nitriles
(malononitrle or ethyl cyanoacetae). Silica sulfuric acid/ethylene glycol catalyst offer sev-
eral advantages such as simplicity, mild reaction conditions, high yields, and little envir-
onmental impact. Hence, it can be applied for the synthesis of other
heterocyclic compounds.
Experimental section
General procedure for synthesis of the 2-amino-benzo [4,5]imidazo[1,2-a]
pyrimidine-3-carbonitrile derivatives 1a-f
To the mixture of 2-aminobenzimidazole (1 mmol), malononitrile (1 mmol) and the
desired aldehyde (namely benzaldehyde, 4-fluorobenzaldehyde, 4-hydroxybenzalde-
hyde, 3-methoxybenzaldehyde, 2,5-dimethoxybenzadehyde and 2-naphthaldehyde)
(1 mmol) in ethylene glycol (5 mL), SSA (42.6 mg, 0.11 mol %) was added. The mix-
ture was heated at 120 ꢀC for an appropriate time (Table 2). After completion of the
reaction (TLC), 10 mL EtOAc was added to the reaction mixture and the catalyst
was recovered by filtration. The organic layer was dried over Na2SO4; the solvent
was evaporated and purified by recrystallization from ethanol to give com-
pounds 1a–g
2-Amino-4-(4-hydroxyphenyl)-1,4-dihydrobenzo[4,5] imidazo[1,2-a]pyrimidine-3-
carbonitrile (1c)
Yield 83%; m.p. 222 ꢀC; IR: ꢀ/cmꢁ1: 3481, 3382, 3326 (OH, NH2 & NH), 2911
1
(CH-aliph), 2188 (CꢂN), 1679 (C ¼ N); H NMR (400 MHz, DMSO): d/ppm ¼ 5.13 (s,
1H, CH), 6.75 (m, 3H, Ar-H & NH2), 6.94 (m, 1H, Ar-H), 7.00 (t, 1H, Ar-H), 7.11 (d,
2H, Ar-H), 7.21 (d, 1H, Ar-H), 7.65 (d, 1H, Ar-H), 7.85 (d, 1H, Ar-H), 8.58 (br, 1H,
OH); 13C NMR (101 MHz, DMSO): 53.5, 63.1, 112.8, 115.8 (2C), 116.5, 119.7, 120.3,
123.8, 127.8 (2C), 129.8, 133.6, 144.1, 149.4, 152.3, 157.6; Anal. calcd for C17H13N5O
(303.32): C, 67.32; H, 4.32; N, 23.09; Found: C, 67.46; H, 4.29; N, 22.98%

8
W. M. BASYOUNI ET AL.
General procedure for the synthesis of the 1,2,3,4-
tetrahydrobenzo[4,5]imidazo[1,2-a]pyrimidine-3-carbonitrile derivatives 2a-g and
1,2-dihydrobenzo[4,5]imidazo[1,2-a] pyrimidine-3-carbonitrile derivatives 3a-g
To the mixture of 2-aminobenzimidazole (1 mmol), ethyl cyanoacetate (1 mmol) and the
desired aldehyde (namely benzaldehyde, 4-fluorobenzaldehyde, 3-chlorobenzaldehyde, 3-
methoxybenzaldehyde, 2,5-dimethoxybenzaldehyde, 3-nitrobenzaldehyde or 2-naphthal-
dehyde) (1 mmol) in ethylene glycol (5 mL), SSA (42.6 mg, 0.11 mol %) was added. The
mixture was heated at 120 ꢀC for an appropriate time (Table 3). After completion of the
reaction (TLC), 10 mL EtOAc was added to the reaction mixture and the catalyst was
recovered by filtration. The organic layer was dried over Na2SO4; the solvent was evapo-
rated. The mixture of two products was separated by column chromatography on silica-
gel using pet. ether/ethyl acetate (60/40) as eluent.
4-(3-Methoxyphenyl)-2-oxo-1,2,3,4-tetrahydrobenzo[4,5]imidazo[1,2-a] pyrimidine-
3-carbonitrile (2d)
Yield 47%; m.p.323 ꢀC; IR: ꢀ/cmꢁ1: 3432 (NH), 2923 (CH-aliph), 2232 (CN), 1675 (C¼O),
1
1601 (C¼N); H NMR (400 MHz, DMSO): d/ppm ¼ 3.83 (s, 3H, OCH3), 5.89 (d, 1H,
J ¼ 8.2 Hz, CH), 6.96 (t, 1H, J ¼ 7.7 Hz,), 7.10–7.40 (m, 7H, Ar-H þ NH), 7.49 (d, 1H,
J ¼ 7.8 Hz, CH), 7.67 (t, 1H, J ¼ 7.8 Hz, Ar-H); 13C NMR (101 MHz, DMSO): 56.0, 113.2,
114.1, 115.2, 117.8, 120.5, 122.2, 126.2, 127.9, 130.9, 131.6, 148.9, 155.8, 160.2; Anal. Calcd
for C18H14N4O2 (318.33): C, 67.91; H, 4.43; N, 17.60; Found: C, 68.07; H, 4.39; N, 17.72%.
4-(3-Methoxyphenyl)-2-oxo-1,2-dihydropyrimido[1,2-a]benzimidazole-3-
carbonitrile (3d)
Yield 16%; m.p. 294 ꢀC; IR: ꢀ/cmꢁ1: 3301 (NH), 2204 (CꢂN), 1694 (C¼O), 1637
1
(C¼N); H NMR (400 MHz, DMSO): d/ppm ¼ 3.83 (s, 3H, OCH3), 7.11 (m, 2H, Ar-
H), 7.20–7.30 (m, 2H, Ar-H), 7.37–7.50 (m, 2H, Ar-H), 7.61 (d, 1H, J ¼ 7.9 Hz, Ar-H),
8.03 (br, 1H, NH), 8.41 (d, 1H J ¼ 7.9 Hz, Ar-H); 13C NMR (101 MHz, DMSO): 55.7,
80.0, 111.8, 114.3, 115.6, 116.1, 119.5, 121.3, 122.5, 125.4, 127.9, 129.8, 132.3, 140.0,
152.2, 153.3, 159.4, 161.0, 166.6; Anal. Calcd for C18H12N4O2 (316.31): C, 68.35; H,
3.82; N, 17.71; Found: C, 68.43; H, 3.78; N, 17.58%.
Funding
This work was supported by National Research Center, Egypt through Ph.D. degree.
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