Aqueous media preparation of 2-amino-4,6-diphenylnicotinonitriles using cellulose sulfuric acid as an efficient catalyst

Article abstract of DOI:10.1007/s11164-012-1008-9

A convenient approach to the synthesis of 2-amino-4,6- diphenylnicotinonitriles via four-component reaction of aromatic aldehydes, acetophenone derivatives, malononitrile and ammonium acetate is described. The reactions were done in water as solvent using cellulose sulfuric acid as catalyst. This simple protocol offer advantages such as shorter reaction times, simple work-up procedure, excellent yields and catalyst recovery.

Full text of DOI:10.1007/s11164-012-1008-9

Res Chem Intermed
DOI 10.1007/s11164-012-1008-9
Aqueous media preparation of 2-amino-4,6-
diphenylnicotinonitriles using cellulose sulfuric
acid as an efficient catalyst
•
Syed Sheik Mansoor Krishnamoorthy Aswin
•
•
Kuppan Logaiya Prasanna Nithiya Sudhan
Saleem Malik
•
Received: 18 October 2012 / Accepted: 27 December 2012
Ó Springer Science+Business Media Dordrecht 2013
Abstract A convenient approach to the synthesis of 2-amino-4,6-diphenylnicoti-
nonitriles via four-component reaction of aromatic aldehydes, acetophenone
derivatives, malononitrile and ammonium acetate is described. The reactions were
done in water as solvent using cellulose sulfuric acid as catalyst. This simple pro-
tocol offer advantages such as shorter reaction times, simple work-up procedure,
excellent yields and catalyst recovery.
Keywords Cellulose sulfuric acid Á 2-Amino-4,6-diphenylnicotinonitrile Á
Catalyst recovery Á Aqueous media preparation
Introduction
Multicomponent reactions (MCRs) have received substantial consideration from the
organic community for their innumerable advantages over conventional multistep
synthesis [1]. These reactions provide instantaneous access to large compound
libraries with diverse functionality [2–6]. Moreover, MCRs are both atom and step
economic as they avoid time consuming costly purification processes in addition to
the protection and deprotection steps [7].
The prevalence of pyridines in nature and their central role as versatile building
blocks in the synthesis of natural products as well as biologically active compounds
has led to a continued interest in the practical synthesis of pyridine derivatives
[8, 9]. The pyridine nucleus has also been found to be integral part of several potent
inhibitors of phosphodiesterase 4 (PDE4) that are known to be beneficial for the
potential treatment of asthma and chronic obstructive pulmonary disease (COPD)
S. S. Mansoor (&) Á K. Aswin Á K. Logaiya Á P. N. Sudhan Á S. Malik
Bioactive Organic Molecule Synthetic Unit, Research Department of Chemistry,
C. Abdul Hakeem College, Melvisharam 632 509, Tamil Nadu, India
e-mail: smansoors2000@yahoo.co.in
123

S. S. Mansoor et al.
[10, 11]. 2-Amino-3-cyanopyridine derivatives are known to have multiple
biological activities, such as anti-tumor activity [12], cardiotonic [13], anti-
inflammatory [14] and anti-parkinsonism properties [15]. 2-Amino-3-cyano-pyri-
dine derivatives were also reported as novel IKK-b inhibitors [14], A2A adenosine
receptor antagonists [15], potent inhibitor of HIV-1 integrase [16], and so on.
2-Amino-3-cyanopyridines are important and useful intermediates in preparing
variety of heterocyclic compounds [17, 18]. Therefore, the synthesis of these
compounds is of great significance.
A number of reports on this topic have appeared in the literature [19–27]. The
common method used in the preparation of 2-amino-4,6-diphenylnicotinonitrile
involves the chalcone or carbonyl compound condensation with malononitrile
and ammonium acetate by conventional heating in the presence of ethyl alcohol
as a solvent. Recently, the use of ultrasound [19], trifluoroethanol [20], ultrasonic
irradiation and grindstone technology [21], silica-bound N-propyl triethylenetetra-
mine sulfamic acid [22], microwave irradiation [23], ytterbium perfluorooctanoate
[24], ionic liquid ethylammonium nitrate [25], [Bmim]BF4 ionic liquid [26] and
liquid liquid phase transfer catalysis conditions [27] have been developed for the
synthesis of 2-amino-4,6-diphenylnicotinonitrile drivatives. However, some of these
procedures have certain limitations such as harsh reaction conditions, long reaction
time, toxic benzene as solvent, high temperature or microwave assistance, tedious
work-up, and low yields. However, a straightforward and efficient one-pot reaction
by catalysis in mild conditions is still limited. Hence, the development of novel
methods for the synthesis of 2-amino-3-cyanopyridines is of great importance
because of their potential biological and pharmaceutical activities.
During the course of our studies toward the development of new routes to the
synthesis of heterocyclic compounds, such as 3,4-dihydropyrimidin-2(1H)-ones/-
thiones/imines [28], b-amino ketone compounds [29], amidoalkyl naphthols [30]
and 1,4-dihydropyridine derivatives [31] by multi-component reactions, we herein
disclose a valid and an efficient procedure for the synthesis of 2-amino-4,6-
diphenylnicotinonitrile derivatives via condensation of aromatic aldehydes, ace-
tophenones, malononitrile and ammonium acetate in the presence of cellulose
sulfuric acid (CSA), as an inexpensive and biodegradable solid acid catalyst in H2O
at a temperature of 60 °C. To the best of our knowledge, the use of cellulose sulfuric
acid as a catalyst for the synthesis of 2-amino-4,6-diphenylnicotinonitriles
previously has not been reported.
In the recent years, being focused on green chemistry using environmentally
benign reagents and conditions is one of the most fascinating developments in
synthesis of widely used organic compounds. The use of water as a promising
solvent for organic reactions has received considerable attention in organic
synthesis owing to its green credentials [32, 33] and organic synthesis in aqueous
media offering key advantages such as rate enhancement and insolubility of the final
products, which facilitates their isolation by simple filtration.
Heterogeneous catalysts for the synthesis of fine chemicals have attracted
considerable interest from both environmental and economical points. The solid
acids have high turnover numbers and easily separated from reaction mixtures [34].
Several interesting biopolymers have been utilized as a support for catalytic
123

Aqueous media preparation of 2-amino-4,6-diphenylnicotinonitriles
applications, such as alginate [35], gelatin [36, 37], starch [38] and chitosan [39]
derivatives. Cellulose and its derivatives, have some unique properties, which make
them attractive alternatives for conventional synthetic organic or inorganic supports
for catalytic applications [40]. The most frequently synthesized and used cellulose
derivatives with functionalization patterns of high uniformity are important not only
for comparison with statistically modified celluloses, but are particularly important
as products with new properties and applications. Their importance also lies with
respect to questions that remain open about the solution structure of cellulose
derivatives and for the design of supra molecular architectures and has been widely
studied during the past decades because of it is a biodegradable material and a
renewable resource [41]. Thus, biopolymers are attractive candidates in the search
for such solid support catalysts [42].
Cellulose sulfuric acid is easily prepared from the treatment of inexpensive
cellulose with chlorosulfonic acid [43]. Recently, cellulose sulfuric acid has
been utilized as a biopolymeric solid support acid catalyst for the synthesis of
a-aminonitriles [43], quinolines [44], imidazoline, oxazolines, thiazolines [45],
benzoxanthene derivatives [46], a-aminophosphonates [47], substituted pyrroles
[48], 6-chloro-8-substituted-9H-purines [49], 1,4-dihydropyridines [50] and Ugi
reaction [51].
Results and discussion
To find out the suitable conditions for the reaction, a series of experiments were
performed with the standard reaction of benzaldehyde 1a, acetophenone 2a,
malononitrile 3, and ammonium acetate as a model reaction (Scheme 1).
Effect of catalyst
Our initial work started with screening of catalyst loading so as to identify optimal
reaction conditions for the synthesis of 2-amino-4,6-diphenylnicotinonitrile deriv-
atives. A mixture of benzaldehyde 1a (1 mmol), acetophenone 2a (1 mmol),
O
CHO
NC
CH3
CN
NH4OAc
+
+
Cellulose-SO3H
CN
H2N
N
1
2
3
4
Scheme 1 Synthesis of 2-amino-4,6-diphenylnicotinonitrile (optimizing the reaction)
123

S. S. Mansoor et al.
malononitrile 3 (1 mmol), and ammonium acetate (1 mmol) were stirred at 60 °C
together with 5 ml water without catalyst. The yield was only 38 % (Table 1, Entry
1) after 7 h of the reaction. The same reaction was carried out in the presence of a
catalytic amount of 0.015 mmol of cellulose–SO3H under similar conditions. The
yield of the product was increased to 66 % within 5 h. (Entry 2). Increasing the
quantity of the catalyst to 0.03, 0.04 and 0.05 mmol gave the corresponding product
in 72, 87 and 95 % yields in 3.5, 3 and 2.5 h, respectively. Use of just 0.05 mmol
was sufficient to drive the reaction forward; larger amounts of the catalyst did not
improve the results. Although the use of 0.06 mmol of cellulose–SO3H permitted
the reaction time to be decreased to 1.5 h and also the yield decreased to 88 %
(Entry 6). A possible explanation for the low product yield is that the starting
material or the product may have been destroyed during the reaction when an excess
amount (0.06 mmol) of cellulose–SO3H was used in the reaction. Hence 0.05 mmol
of cellulose–SO3H was sufficient to catalyze the reaction effectively.
Effects of the solvents
We try to optimize the model process mentioned above by detecting the efficiency of
several classic solvents chosen as the medium for comparison. In each case, the
substrates were mixed together with 5 ml solvent under high speed stirring conditions
at 60 °C. Among the tested solvents such as methanol, ethanol, acetonitrile, THF,
dichloromethane, water and solvent-free conditions, the formation of product 4a was
more facile and proceeded to give not only in high yield but also with high reaction
rate in water (95 % yield in 2.5 h) (Table 2, entry 7).
Polar protic solvents such as ethanol and methanol afforded moderate yields of
desired products but took comparatively longer reaction time (Table 1, entries 1 and
2). When the reaction was performed in acetonitrile, THF and dichloromethane
(DCM), unfortunately, the desired product was only obtained in 42, 45 and 35 %
yield respectively (Table 1, entries 3, 4, 5). In solvent-free conditions the desired
product 4a was obtained in low yield 76 % (Table 1, entry 6). The results show that
water as solvent is effective for good yield (Table 2, entry 7).
Table 1 The reaction of benzaldehyde, acetophenone, malononitrile and ammonium acetate: effect of
catalysis
Entry
Catalyst
Amount (mmol)
Time (h)
Yield (%)a
1
2
3
4
5
6
Cellulose–SO3H
Cellulose–SO3H
Cellulose–SO3H
Cellulose–SO3H
Cellulose–SO3H
Cellulose–SO3H
0.00
0.015
0.03
0.04
0.05
0.06
7.0
5.0
3.5
3.0
2.5
1.5
38
66
72
87
95
88
Reaction conditions: benzaldehyde (1 mmol), acetophenone (1 mmol), malononitrile (1 mmol) and
ammonium acetate (1 mmol) and water (5 ml) at 60 °C
a
Isolated yields
123

Aqueous media preparation of 2-amino-4,6-diphenylnicotinonitriles
Table 2 The reaction of benzaldehyde, acetophenone, malononitrile and ammonium acetate: effect of
solvent
Entry
Solvent
Amount of
catalyst (mmol)
Time (h)
Yield (%)a
1
2
3
4
5
6
7
Ethanol
Methanol
Acetonitrile
THF
0.05
0.05
0.05
0.05
0.05
0.05
0.05
4.0
4.0
8.0
6.0
8.0
5.0
2.5
70
65
42
45
35
76
95
DCM
None
Water
Reaction conditions: benzaldehyde (1 mmol), acetophenone (1 mmol), malononitrile (1 mmol) and
ammonium acetate (1 mmol) in water (5 ml) in the presence of Cellulose–SO3H (0.05 mmol) at 60 °C
a
Isolated yields
Table 3 Optimisation of temperature using cellulose–SO3H (0.05 mmol) as catalyst in water
Entry
Temperature (oC)
Time (h)
Yield (%)a
1
2
3
4
5
40
50
60
70
80
3.5
3.0
2.5
2.5
2.5
70
88
95
86
80
Reaction conditions: benzaldehyde (1 mmol), acetophenone (1 mmol), malononitrile (1 mmol) and
ammonium acetate (1 mmol) in water (5 ml) in the presence of cellulose–SO3H (0.05 mmol)
a
Isolated yields
Effects of reaction temperature
In order to further improve the yield of the reaction, we tried to perform the
experiments in 40, 50, 60, 70 and 80 °C. It was observed that a lower reaction
temperature led to a lower yield. As shown in Table 3, entry 3, we found that high
temperature could improve the reaction yield and shorten the reaction time. As
shown in Table 3, entry 5, the model reaction preceded in a considerably lower
yield under 80 °C due to remove of ammonia from reaction vessel in high
temperature. With having these results in hand, we selected the water as solvent for
the one-pot reaction of aromatic aldehydes, malononitrile, acetophenones and
ammonium acetate to give corresponding 2-amino-4,6-diphenylnicotinonitrile
derivatives at 60 °C.
Reusability of the catalyst
The reusability of the catalyst is one of the most important benefits and makes
it useful for commercial applications. Thus the recovery and reusability of cellulose–
123

S. S. Mansoor et al.
Table 4 The effect of recyclability of cellulose–SO3H (0.05 mmol) catalyst on the product 4a yield
Entry
Cycle
Time (h)
Yield (%)a
1
2
3
4
0
1
2
3
2.5
2.5
2.5
2.5
95
93
92
90
Reaction conditions: benzaldehyde (1 mmol), acetophenone (1 mmol), malononitrile (1 mmol) and
ammonium acetate (1 mmol) in water (5 ml) in the presence of cellulose–SO3H (0.05 mmol)
a
Isolated yields
R1
O
CHO
NC
CH3
CN
NH4OAc
+
+
Cellulose-SO3H
(0.05 mmol)
Water, 60oC
CN
H2N
N
R2
R1
1
2
3
4a - 4t
R2
Scheme 2 Synthesis of various 2-amino-4,6-diphenylnicotinonitrile derivatives
SO3H was investigated. After completion of the reaction, the reaction mixture was
cooled to ambient temperature, CH2Cl2 was added, and the cellulose–SO3H was filtered
off. The recycled catalyst has been examined in the next run. The cellulose–SO3H
catalyst could be reused four times without any loss of its activity (Table 4).
Synthesis of various 2-amino-4,6-diphenylnicotinonitrile derivatives
With the optimized reaction conditions in hand, we proceeded to investigate the
scope of the reaction by employing a wide range of aromatic aldehydes and
acetophenones in the process (Scheme 2) (Table 5). The reaction performed
well, providing the corresponding 2-amino-4,6-diphenylnicotinonitrile derivatives
in good to high yields, demonstrating the generality of the method and its good
tolerance of both electron-withdrawing and electron-donating substituents on the
aromatic ring of the aldehyde. For example, aromatic aldehydes containing electron-
donating substituents, including 4-OCH3 and 4-CH3 reacted with acetophenone
derivatives, including 4-Br, 4-Cl and 4-F acetophenone under the optimized
conditions, to provide the corresponding products in good to high yields (Table 5,
entries 4, 8, 9, 14 and 15). Furthermore, aromatic aldehydes containing electron-
withdrawing substituents, including 4-Cl, 4-F and 4-NO2 reacted with 4-Br, 4-F,
123

Aqueous media preparation of 2-amino-4,6-diphenylnicotinonitriles
Table 5 Synthesis of various 2-amino-4,6-diphenylnicotinonitriles derivatives in the presence of cel-
lulose–SO3H
Entry
R1
R2
Product
Time (h)
Yield (%)a
Mp (°C)
Found
Reported
1
H
H
4a
4b
4c
4d
4e
4f
2.5
2.5
2.0
2.5
2.5
2.0
2.0
3.0
3.0
2.0
2.0
2.0
2.0
3.0
3.0
2.5
2.5
2.5
2.0
2.0
95
95
96
90
93
96
95
89
90
95
94
96
95
88
89
94
93
94
92
94
185–187
174–176
170–172
180–182
241–243
181–182
230–232
216–218
204–206
234–236
206–208
202–204
218–220
202–204
195–197
226–228
172–174
194–196
196–198
208–210
185–187 [20]
175 [21]
2
H
4-Br
4-Br
4-Br
4-Cl
4-Cl
4-Cl
4-Cl
4-Cl
4-OH
4-OH
4-OH
4-F
3
4-F
172 [21]
4
4-OCH3
H
181 [21]
5
240–242 [22]
181 [21]
6
4-F
7
4-Cl
4-CH3
4-OCH3
4-Br
4-NO2
4-F
4g
4 h
4i
230–231 [22]
215–217 [22]
204–205 [22]
234–237 [19]
205–208 [19]
201–203 [19]
219–220 [23]
203–204 [22]
194–196 [22]
225–228 [19]
172–173 [23]
195–196 [23]
–
8
9
10
11
12
13
14
15
16
17
18
19
20
4j
4k
4l
4-Cl
4-CH3
4-OCH3
4-Br
4-Cl
4-Cl
4-F
4m
4n
4o
4p
4q
4r
4s
4-F
4-F
H
4-CH3
4-OCH3
4-NO2
4-NO2
4-Br
4t
–
Reaction conditions: substituted benzaldehyde (1 mmol), substituted acetophenone (1 mmol), malono-
nitrile (1 mmol) and ammonium acetate (1 mmol) in water (5 ml) in the presence of cellulose–SO3H
(0.05 mmol). All reactions were carried out at 60 °C
a
Isolated yields
4-Cl, 4-OH, 4-CH3, 4-OCH3 and 4-NO2 acetophenone and malononitrile under the
optimized conditions to afford the corresponding products in high yield (Table 5,
entries 3, 6, 7, 10–13 and 16–20).
The structures of isolated products 4a–4t were deducted by physical and
spectroscopic data such as: IR, 1H NMR and 13C NMR spectroscopy, and elemental
analysis. In IR spectra, symmetrical and unsymmetrical stretching frequency of NH2
is formed in region between m = 3,411–3,300 cm-1. The stretching vibration of
C–N in nitrile group was appeared in the region between m = 2,198–2,214 cm-1. In
the 1H NMR spectra in DMSO-d6 was shown the two singlet signals around
d = 5.46–6.98 and d = 7.16–7.28 ppm corresponding to NH2 group and C–H of
pyridine ring in 2-amino-4,6-diphenylnicotinonitriles. In the 13C NMR spectra, one
carbon link to C–C–N has chemical shift in d = 84.8–87.5 ppm because of
anisotropic effect of triple bond of nitrile group and the signal around d =
116.8–118.0 is assigned by one carbon of C–N of nitrile group.
123

S. S. Mansoor et al.
Experimental
General
All chemicals were purchased from Aldrich Chemical Co. and solvents were used
without further purification. Analytical thin-layer chromatography was performed
with E. Merck silica gel 60F glass plates. Visualisation of the developed
chromatogram was performed by UV light (254 nm). Column chromatography
was performed on silica gel 90, 200–300 mesh. Melting points were determined
1
with Shimadzu DS-50 thermal analyser. H nuclear magnetic resonance (NMR)
(500 MHz) and 13C NMR (125 MHz) spectra were obtained using Bruker DRX-500
Avance at ambient temperature, using tetramethylsilane (TMS) as internal standard.
Fourier-transform infrared (FT-IR) spectra were obtained as KBr discs on Shimadzu
spectrometer. Mass spectra were determined on a Varian—Saturn 2000 GC/MS
instrument. Elemental analysis were measured by means of Perkin Elmer 2400 CHN
elemental analyzer flowchart.
Preparation of cellulose sulfuric acid
To a magnetically stirred mixture of 5.0 g of cellulose in 20 ml of n-hexane, 1.0 g
of chlorosulfonic acid (9 mmol) was added drop wise at 0 °C during 2 h. HCl gas
was removed from the reaction vessel immediately. After the addition was
complete, the mixture was stirred for 2 h. Then the mixture was filtered and washed
with 30 ml of acetonitrile and dried at room temperature to afford 5.25 g of
cellulose sulfuric acid as a white powder. Sulfur content of the samples by
conventional elemental analysis, was 0.55 for cellulose sulfuric acid. The number of
H? sites on the cellulose–SO3H was determined by acid–base titration was
0.50 mequiv./g [43].
X-ray diffraction (XRD) for cellulose sulfuric acid
Powder X-ray diffraction measurements were performed using Advance diffract
meter made by a Bruker AXS company in Germany. Scans were taken with a 2h
step size of 0.04 and a counting time of 30 s at room temperature. Specimens for
XRD were prepared by compaction into a glass-backed aluminum sample holder.
Data was collected over a 2h range from 4° to 75°. The XRD pattern of cellulose
sulfuric acid is presented in Fig. 1.
Typical procedure for the synthesis of 2-amino-4,6-diphenylnicotinonitrile (4a)
in water
A mixture of benzaldehyde (1 mmol), acetophenone (1 mmol), malononitrile
(1 mmol) and ammonium acetate (1 mmol) in the presence of cellulose sulfuric acid
(0.05 mmol) was stirred in H2O (5 ml) at 60 °C in a 50 ml flask for the appropriate
time, as shown in Table 5. After completion of the reaction [thin-layer chroma-
tography (TLC) monitoring], the reaction mixture was cooled to ambient
123

Aqueous media preparation of 2-amino-4,6-diphenylnicotinonitriles
Fig. 1 XRD pattern of cellulose–SO3H
temperature, CH2Cl2 was added, and the cellulose sulfuric acid was filtered off. The
filtrate was concentrated to dryness, and the crude solid product was crystallized
from EtOH to afford the pure 2-amino-4,6-diphenylnicotinonitrile (Table 5).
Spectral data for synthesized derivatives of 2-amino-4,6-diphenylnicotinonitrile
(4a–4t)
2-Amino-4,6-diphenylnicotinonitrile (4a)
IR (KBr, cm-1): 3,394 and 3,312 (NH2), 3,177 (ArH), 2,211 (CN). 1H NMR
(500 MHz, DMSO-d6) d: 8.04–8.16 (2H, m, ArH), 7.62–7.78 (3H, m, ArH),
7.40–7.47 (3H, m, ArH), 7.18 (1H, s, CH), 7.00 (2H, d, J = 8.4 Hz, ArH), 5.48 (2H,
s, NH2) ppm; 13C NMR (125 MHz, DMSO-d6) d: 86.4, 109.0, 114.2, 117.8, 127.8,
129.4, 129.9, 130.3, 130.5, 138.1, 155.0, 158.9, 160.8, 161.4 ppm; MS(ESI): m/z
272 (M ? H)?; Anal. Calcd for C18H13N3: C, 79.70; H, 4.80; N, 15.50 %. Found:
C, 79.66; H, 4.76; N, 15.44 %.
2-Amino-4-phenyl-6-(4-bromophenyl)nicotinonitrile (4b)
IR (KBr, cm-1): 3,388 and 3,308 (NH2), 3,165 (ArH), 2,214 (CN). 1H NMR
(500 MHz, DMSO-d6) d: 8.02–8.10 (2H, m, ArH), 7.65 (2H, d, J = 8.4 Hz, ArH),
7.50–7.55 (3H, m, ArH), 7.16 (1H, s, CH), 7.21 (2H, d, J = 8.4 Hz, ArH), 6.98 (2H,
s, NH2) ppm; 13C NMR (125 MHz, DMSO-d6) d: 87.2, 108.9, 113.9, 117.85 127.3,
129.1, 129.5, 130.3, 130.8, 138.0, 153.9, 159.4, 161.0, 162.1 ppm; MS(ESI): m/z
350.9 (M ? H)?; Anal. Calcd for C18H12BrN3: C, 61.73; H, 3.43; N, 12.00 %.
Found: C, 61.66; H, 3.49; N, 12.12 %.
123

S. S. Mansoor et al.
2-Amino-4-(4-fluorophenyl)-6-(4-bromophenyl)nicotinonitrile (4c)
IR (KBr, cm-1): 3,400 and 3,307 (NH2), 3,184 (ArH), 2,201 (CN). 1H NMR
(500 MHz, DMSO-d6) d: 8.11–8.12 (2H, m, ArH), 7.66 (2H, d, J = 8.4 Hz, ArH),
7.44–7.48 (2H, m, ArH), 7.25 (1H, s, CH), 7.11 (2H, d, J = 8.4 Hz, ArH), 6.96 (2H,
s, NH2) ppm; 13C NMR (125 MHz, DMSO-d6) d: 87.4, 108.5, 113.4, 118.0, 126.9,
128.9, 129.5, 130.1, 130.7, 138.1, 152.9, 157.9, 161.8, 162.6 ppm; MS(ESI): m/z
368.9 (M ? H)?; Anal. Calcd for C18H11BrFN3: C, 58.71; H, 2.99; N, 11.44 %.
Found: C, 58.70; H, 2.95; N, 11.40 %.
2-Amino-4-(4-methoxyphenyl)-6-(4-bromophenyl)nicotinonitrile (4d)
IR (KBr, cm-1): 3,402 and 3,303 (NH2), 3,180 (ArH), 2,201 (CN). 1H NMR
(500 MHz, DMSO-d6) d: 8.16–8.19 (2H, m, ArH), 7.60 (2H, d, J = 8.4 Hz, ArH),
7.41–7.46 (2H, m, ArH), 7.20 (1H, s, CH), 7.12 (2H, d, J = 8.4 Hz, ArH), 5.63 (2H,
s, NH2), 3.81 (3H, s, OCH3) ppm; 13C NMR (125 MHz, DMSO-d6) d: 87.0, 107.9,
114.2, 116.9, 128.0, 129.0, 129.8, 130.3, 130.6, 137.9, 155.5, 158.4, 161.8,
163.4 ppm; MS(ESI): m/z 380.9 (M ? H)?; Anal. Calcd for C19H14BrN3O: C,
60.01; H, 3.68; N, 11.05 %. Found: C, 60.00; H, 3.62; N, 11.02 %.
2-Amino-4-phenyl-6-(4-chlorophenyl)nicotinonitrile (4e)
IR (KBr, cm-1): 3,399 and 3,302 (NH2), 3,177 (ArH), 2,212 (CN). 1H NMR
(500 MHz, DMSO-d6) d: 8.04–8.09 (2H, m, ArH), 7.69 (2H, d, J = 8.4 Hz, ArH),
7.46–7.49 (3H, m, ArH), 7.21 (1H, s, CH), 7.17 (2H, d, J = 8.4 Hz, ArH), 5.60 (2H,
s, NH2) ppm; 13C NMR (125 MHz, DMSO-d6) d: 86.9, 111.5, 115.6, 117.8, 127.3,
128.6, 129.5, 130.3, 131.6, 138.1, 154.9, 158.9, 160.8, 161.4 ppm; MS(ESI): m/z
306.45 (M ? H)?; Anal. Calcd for C18H12ClN3: C, 70.71; H, 3.93; N, 13.75 %.
Found: C, 70.66; H, 3.90; N, 13.72 %.
2-Amino-4-(4-fluorophenyl)-6-(4-chlorophenyl)nicotinonitrile (4f)
IR (KBr, cm-1): 3,392 and 3,311 (NH2), 3,177 (ArH), 2,211 (CN). 1H NMR
(500 MHz, DMSO-d6) d: 8.11–8.15 (2H, m, ArH), 7.64 (2H, d, J = 8.4 Hz, ArH),
7.48–7.51 (2H, m, ArH), 7.19 (1H, s, CH), 7.11 (2H, d, J = 8.4 Hz, ArH), 5.69 (2H,
s, NH2) ppm; 13C NMR (125 MHz, DMSO-d6) d: 84.8, 110.5, 114.0, 116.9, 128.7,
129.3, 129.6, 131.0, 131.7, 138.1, 154.9, 158.9, 162.8, 164.4 ppm; MS(ESI): m/z
324.45 (M ? H)?; Anal. Calcd for C18H11FClN3: C, 66.78; H, 3.40; N, 12.98 %.
Found: C, 66.74; H, 3.36; N, 12.96 %.
2-Amino-4-(4-chlorophenyl)-6-(4-chlorophenyl)nicotinonitrile (4g)
IR (KBr, cm-1): 3,405 and 3,300 (NH2), 3,184 (ArH), 2,200 (CN). 1H NMR
(500 MHz, DMSO-d6) d: 8.00–8.06 (2H, m, ArH), 7.55 (2H, d, J = 8.4 Hz, ArH),
7.38–7.44 (2H, m, ArH), 7.19 (1H, s, CH), 7.14 (2H, d, J = 8.4 Hz, ArH), 5.62 (2H,
s, NH2) ppm; 13C NMR (125 MHz, DMSO-d6) d: 87.9, 110.5, 116.8, 127.7, 129.1,
123

Aqueous media preparation of 2-amino-4,6-diphenylnicotinonitriles
129.5, 130.3, 131.0, 140.1, 154.9, 158.9, 161.2, 163.4 ppm; MS(ESI): m/z 340.90
(M ? H)?; Anal. Calcd for C18H11Cl2N3: C, 63.55; H, 3.24; N, 12.36 %. Found: C,
63.52; H, 3.22; N, 12.30 %.
2-Amino-4-(4-methylphenyl)-6-(4-chlorophenyl)nicotinonitrile (4h)
IR (KBr, cm-1): 3,411 and 3,309 (NH2), 3,179 (ArH), 2,213 (CN). 1H NMR
(500 MHz, DMSO-d6) d: 8.04–8.16 (2H, m, ArH), 7.58 (2H, d, J = 8.4 Hz, ArH),
7.42–7.49 (2H, m, ArH), 7.19 (1H, s, CH), 7.00 (2H, d, J = 8.4 Hz, ArH), 5.69 (2H,
s, NH2), 2.22 (3H, s, CH3) ppm; 13C NMR (125 MHz, DMSO-d6) d: 85.5, 111.5,
116.8, 127.5, 128.9, 129.4, 130.3, 132.0, 141.1, 156.2, 158.9, 162.0, 163.2 ppm;
MS(ESI): m/z 320.45 (M ? H)?; Anal. Calcd for C19H14ClN3: C, 71.37; H, 4.38; N,
13.15 %. Found: C, 71.32; H, 4.32; N, 13.14 %.
2-Amino-4-(4-methoxyphenyl)-6-(4-chlorophenyl)nicotinonitrile (4i)
IR (KBr, cm-1): 3,401 and 3,311 (NH2), 3,172 (ArH), 2,198 (CN). 1H NMR
(500 MHz, DMSO-d6) d: 8.08–8.10 (2H, m, ArH), 7.61 (2H, d, J = 8.4 Hz, ArH),
7.44–7.46 (2H, m, ArH), 7.20 (1H, s, CH), 7.11 (2H, d, J = 8.4 Hz, ArH), 5.60 (2H,
s, NH2), 3.79 (3H, s, OCH3). 13C NMR (125 MHz, DMSO-d6) d: 87.5, 108.9, 117.0,
128.0, 129.0, 129.6, 130.3, 131.0, 139.7, 153.9, 160.8, 162.5. MS(ESI): m/z 336.45
(M ? H)?; Anal. Calcd for C19H14ClN3O: C, 67.97; H, 4.17; N, 12.52 %. Found:
C, 67.90; H, 4.12; N, 12.58 %.
2-Amino-4-(4-bromophenyl)-6-(4-hydroxyphenyl)nicotinonitrile (4j)
IR (KBr, cm-1): 3,388 and 3,355 (NH2), 3,339 (OH), 3,222 (ArH), 2,200 (CN). 1H
NMR (500 MHz, DMSO-d6) d: 8.14 (2H, d, J = 8.4 Hz, ArH), 7.54 (2H, d,
J = 8.4 Hz, ArH), 7.16 (1H, s, CH), 7.07 (2H, d, J = 8.4 Hz, ArH), 7.03 (2H, d,
J = 8.4 Hz, ArH), 6.87 (2H, s, NH2), 9.82 (s, 1 H, OH) ppm; 13C NMR (125 MHz,
DMSO-d6) d: 87.4, 108.9, 115.4, 116.8, 127.7, 129.1, 130.3, 132.0, 140.1, 154.9,
158.9, 160.8, 162.0 ppm; MS(ESI): m/z 366.90 (M ? H)?; Anal. Calcd for
C18H12N3BrO: C, 59.03; H, 3.28; N, 11.48 %. Found: C, 59.02; H, 3.24; N,
11.44 %.
2-Amino-4-(4-nitrophenyl)-6-(4-hydroxyphenyl)nicotinonitrile (4k)
IR (KBr, cm-1): 3,404 and 3,300 (NH2), 3,339 (OH), 3,170 (ArH), 2,210 (CN). 1H
NMR (500 MHz, DMSO-d6) d: 8.09–8.18 (2H, m, ArH), 7.66 (2H, d, J = 8.4 Hz,
ArH), 7.39–7.45 (2H, m, ArH), 7.22 (1H, s, CH), 7.00 (2H, d, J = 8.4 Hz, ArH),
6.93 (2H, s, NH2) 9.90 (s, 1 H, OH) ppm; 13C NMR (125 MHz, DMSO-d6) d: 86.9,
110.5, 115.6, 116.8, 124.7, 127.1, 129.5, 130.3, 131.5, 137.9, 154.9, 158.9, 160.8,
162.0 ppm; MS(ESI): m/z 333 (M ? H)?; Anal. Calcd for C18H12N4O3: C, 65.06;
H, 3.61; N, 16.87 %. Found: C, 65.02; H, 3.60; N, 16.84 %.
123

S. S. Mansoor et al.
2-Amino-4-(4-fluorophenyl)-6-(4-hydroxyphenyl)nicotinonitrile (4l)
IR (KBr, cm-1): 3,397 and 3,307 (NH2), 3,339 (OH), 3,184 (ArH), 2,201 (CN). 1H
NMR (500 MHz, DMSO-d6) d: 8.08–8.14 (2H, m, ArH), 7.58 (2H, d, J = 8.4 Hz,
ArH), 7.35–7.43 (2H, m, ArH), 7.22 (1H, s, CH), 7.06 (2H, d, J = 8.4 Hz, ArH),
6.94 (2H, s, NH2), 9.94 (s, 1 H, OH) ppm; 13C NMR (125 MHz, DMSO-d6) d: 86.5,
111.5, 115.0, 116.9, 126.9, 128.9, 129.4, 130.3, 131.5, 137.9, 154.9, 158.9, 160.5,
162.6 ppm; MS(ESI): m/z 306 (M ? H)?; Anal. Calcd for C18H12FN3O: C, 70.82;
H, 3.93; N, 13.77 %. Found: C, 70.80; H, 3.90; N, 13.74 %.
2-Amino-4-(4-chlorophenyl)-6-(4-fluorophenyl)nicotinonitrile (4m)
IR (KBr, cm-1): 3,399 and 3,307 (NH2), 3,184 (ArH), 2,201 (CN). 1H NMR
(500 MHz, DMSO-d6) d: 8.06–8.13 (2H, m, ArH), 7.72 (2H, d, J = 8.4 Hz, ArH),
7.34–7.46 (2H, m, ArH), 7.18 (1H, s, CH), 7.14 (2H, d, J = 8.4 Hz, ArH), 6.97 (2H,
s, NH2) ppm; 13C NMR (125 MHz, DMSO-d6) d: 87.5, 111.2, 115.3, 117.7, 127.6,
129.0, 129.5, 130.2, 130.7, 139.0, 153.9, 158.9, 160.8, 162.0 ppm; MS(ESI): m/z
324.45 (M ? H)?; Anal. Calcd for C18H11ClFN3: C, 66.78; H, 3.40; N, 12.98 %.
Found: C, 66.74; H, 3.38; N, 12.90 %.
2-Amino-4-(4-methylphenyl)-6-(4-fluorophenyl)nicotinonitrile (4n)
IR (KBr, cm-1): 3,402 and 3,307 (NH2), 3,184 (ArH), 2,201 (CN). 1H NMR
(500 MHz, DMSO-d6) d: 8.14-8.19 (2H, m, ArH), 7.77 (2H, d, J = 8.4 Hz, ArH),
7.37–7.47 (2H, m, ArH), 7.25 (1H, s, CH), 7.09 (2H, d, J = 8.4 Hz, ArH), 6.00 (2H,
s, NH2), 2.22 (s, 3H, CH3) ppm; 13C NMR (125 MHz, DMSO-d6) d: 86.0, 110.0,
114.4, 116.9, 128.0, 129.0, 129.6, 130.2, 130.6, 139.0, 155.2, 159.4, 160.4,
162.2 ppm; MS(ESI): m/z 304 (M ? H)?; Anal. Calcd for C19H14FN3: C, 75.25; H,
4.62; N, 13.86 %. Found: C, 75.22; H, 4.60; N, 13.84 %.
2-Amino-4-(4-methoxyphenyl)-6-(4-fluorophenyl)nicotinonitrile (4o)
IR (KBr, cm-1): 3,398 and 3,307 (NH2), 3,184 (ArH), 2,201 (CN). 1H NMR
(500 MHz, DMSO-d6) d: 7.98–8.08 (2H, m, ArH), 7.76 (2H, d, J = 8.4 Hz, ArH),
7.44–7.55 (2H, m, ArH), 7.28 (1H, s, CH), 7.20 (2H, d, J = 8.4 Hz, ArH), 5.58 (2H,
s, NH2), 3.36 (s, 3H, OCH3) ppm; 13C NMR (125 MHz, DMSO-d6) d: 85.7, 108.9,
115.6, 117.5, 126.0, 128.9, 129.6, 130.3, 131.0, 141.1, 154.4, 158.4, 160.8,
162.1 ppm; MS(ESI): m/z 320 (M ? H)?; Anal. Calcd for C19H14FN3O: C, 71.47;
H, 4.39; N, 13.17 %. Found: C, 71.44; H, 4.33; N, 13.18 %.
2-Amino-4-(4-bromophenyl)-6-phenylnicotinonitrile (4p)
IR (KBr, cm-1): 3,411 and 3,307 (NH2), 3,184 (ArH), 2,201 (CN). 1H NMR
(500 MHz, DMSO-d6) d: 7.88–8.00 (2H, m, ArH), 7.78 (2H, d, J = 8.4 Hz, ArH),
7.33–7.44 (3H, m, ArH), 7.18 (1H, s, CH), 7.16 (2H, d, J = 8.4 Hz, ArH), 6.94 (2H,
s, NH2) ppm; 13C NMR (125 MHz, DMSO-d6) d: 87.0, 110.5, 114.0, 116.9, 126.9,
123

Aqueous media preparation of 2-amino-4,6-diphenylnicotinonitriles
128.5, 129.0, 130.3, 131.4, 139.5, 155.7, 158.5, 160.4, 161.9 ppm; MS(ESI): m/z
350.90 (M ? H)?; Anal. Calcd for C18H12BrN3: C, 61.73; H, 3.43; N, 12.00 %.
Found: C, 61.70; H, 3.40; N, 12.02 %.
2-Amino-4-(4-chlorophenyl)-6-(4-methylphenyl)nicotinonitrile (4q)
IR (KBr, cm-1): 3,395 and 3,312 (NH2), 3,180 (ArH), 2,208 (CN). 1H NMR
(500 MHz, DMSO-d6) d: 8.16–8.19 (2H, m, ArH), 7.64 (2H, d, J = 8.4 Hz, ArH),
7.40–7.47 (2H, m, ArH), 7.24 (1H, s, CH), 7.16 (2H, d, J = 8.4 Hz, ArH), 6.95 (2H,
s, NH2), 2.18 (3H, s, CH3) ppm; 13C NMR (125 MHz, DMSO-d6) d: 86.4, 109.4,
114.4, 117.4, 127.4, 129.4, 129.9, 130.1, 130.6, 139.1, 155.2, 158.5, 160.5,
162.4 ppm; MS(ESI): m/z 320.45 (M ? H)?; Anal. Calcd for C19H14ClN3: C,
71.37; H, 4.38; N, 13.15 %. Found: C, 71.34; H, 4.35; N, 13.12 %.
2-Amino-4-(4-chlorophenyl)-6-(4-methoxyphenyl)nicotinonitrile (4r)
IR (KBr, cm-1): 3,392 and 3,307 (NH2), 3,184 (ArH), 2,201 (CN). 1H NMR
(500 MHz, DMSO-d6) d: 7.99-8.07 (2H, m, ArH), 7.78 (2H, d, J = 8.4 Hz, ArH),
7.35-7.42 (2H, m, ArH), 7.22 (1H, s, CH), 7.09 (2H, d, J = 8.4 Hz, ArH), 6.88 (2H,
s, NH2), 3.28 (3H, s, OCH3) ppm; 13C NMR (125 MHz, DMSO-d6) d: 85.9, 107.9,
114.6, 117.8, 126.9, 128.9, 129.7, 130.5, 131.0, 141.1, 153.9, 158.9, 160.7,
161.9 ppm; MS(ESI): m/z 336.45 (M ? H)?; Anal. Calcd for C19H14ClN3O: C,
67.97; H, 4.17; N, 12.52 %. Found: C, 67.94; H, 4.16; N, 12.44 %.
2-Amino-4-(4-fluorophenyl)-6-(4-nitrophenyl)nicotinonitrile (4s)
IR (KBr, cm-1): 3,408 and 3,312 (NH2), 3,188 (ArH), 2,207 (CN). 1H NMR
(500 MHz, DMSO-d6) d: 8.01–8.09 (2H, m, ArH), 7.69 (2H, d, J = 8.4 Hz, ArH),
7.49–7.55 (2H, m, ArH), 7.29 (1H, s, CH), 7.19 (2H, d, J = 8.4 Hz, ArH), 5.46 (2H,
s, NH2) ppm; 13C NMR (125 MHz, DMSO-d6) d: 87.7, 108.8, 113.6, 118.2, 127.0,
128.5, 129.4, 130.3, 130.9, 138.2, 152.7, 157.8, 161.6, 162.7 ppm; MS(ESI): m/z
335 (M ? H)?; Anal. Calcd for C18H11FN4O2: C, 64.67; H, 3.29; N, 16.76 %.
Found: C, 64.58; H, 3.28; N, 16.77 %.
2-Amino-4-(4-bromophenyl)-6-(4-nitrophenyl)nicotinonitrile (4t)
IR (KBr, cm-1): 3,399 and 3,317 (NH2), 3,179 (ArH), 2,214 (CN). 1H NMR
(500 MHz, DMSO-d6) d: 8.08–8.15 (2H, m, ArH), 7.66 (2H, d, J = 8.2 Hz, ArH),
7.47–7.55 (2H, m, ArH), 7.18 (1H, s, CH), 7.16 (2H, d, J = 8.4 Hz, ArH), 5.51 (2H,
s, NH2) ppm; 13C NMR (125 MHz, DMSO-d6) d: 84.4, 110.4, 114.0, 116.7, 128.6,
129.4, 129.8, 131.2, 131.8, 138.3, 154.7, 158.8, 162.9, 164.6 ppm; MS(ESI): m/z
395.9 (M ? H)?; Anal. Calcd for C18H11BrN4O2: C, 54.69; H, 2.78; N, 14.18 %.
Found: C, 54.64; H, 2.76; N, 14.15 %.
123

S. S. Mansoor et al.
Conclusions
In summary, cellulose–SO3H efficiently catalyzed the synthesis of 2-amino-4,6-
diarylnicotinonitriles via a four component condensation reaction. The simplicity of
this procedure, together with the eco-friendly, non-volatile, easy-to-handle, non-
hazardous and recyclable nature of catalyst, represents the main advantages of this
method. We expect this method will find extensive applications in the field of
combinatorial chemistry, diversity-oriented synthesis and drug discovery.
Acknowledgments The authors are thankful to the Management of C. Abdul Hakeem College,
Melvisharam—632509 (T.N), India for the support. The authors also thankful to Dr. W. Abdul Hameed,
Principal, and Dr. M. S. Dastageer, Head of the Research Department of Chemistry for the facilities and
support from the DST-FIST (Government of India) sponsored Department. The authors wish to thank to
Dr. A. Abdul Rahuman, Unit of Nanotechnology and Bioactive Natural Products, for useful discussion
and encouragement.
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