Knoevenagel reaction catalyzed by a reusable Br?nsted acid based on 1-alkyl-1, 2, 4-triazolium tetrafluoroborate

Article abstract of DOI:10.2174/1570178614666171017164516

The Knoevenagel reaction is one of the most useful methods for the synthesis of α, β- unsaturated nitriles. We disclose an efficient protocol for the Knoevenagel reaction of aldehydes with malononitrile catalyzed by 1-alkyl-1, 2, 4-triazolium salts to aff

Full text of DOI:10.2174/1570178614666171017164516

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Letters in Organic Chemistry, 2018, 15, 133-138
RESEARCH ARTICLE
ISSN: 1570-1786
eISSN: 1875-6255
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Factor:
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Knoevenagel Reaction Catalyzed by a Reusable Brønsted Acid Based on
1-Alkyl-1,2,4-triazolium Tetrafluoroborate
BENTHAM
S
CIENCE
Elango Kandasamy1,*, Sankaranarayanan Nagarajan2 and Tanveer M. Shaikh3,*
1Department of Sciences, Amrita School of Engineering Coimbatore, Amrita Vishwa Vidyapeetham, Amrita University,
2
3
Coimbatore, India; Deapetment of S&H, PSN Engineering College, Melathediyoor, Tirunelveli, India; Department of
Chemistry, CNCS, Mekelle University, Mekele, Ethiopia
Abstract: The Knoevenagel reaction is one of the most useful methods for the synthesis of α,β-
unsaturated nitriles. We disclose an efficient protocol for the Knoevenagel reaction of aldehydes with
A R T I C L E H I S T O R Y
malononitrile catalyzed by 1-alkyl-1,2,4-triazolium salts to afford the corresponding products in excel-
lent yields. The important feature of this reaction is the catalyst; 1-alkyl-1,2,4-triazolium salts are recy-
cled and reused. Furthermore, the reaction conditions are environment friendly and do not produce any
hazardous waste.
Received: April 24, 2017
Revised: July 26, 2017
Accepted: October 03, 2017
DOI:
10.2174/1570178614666171017164516
Keywords: Aldehyde, benzylidenemalononitrile, Brønsted acid, ionic liquids, Knoevenagel reaction, reusable catalyst, tria-
zolium salts.
1. INTRODUCTION
[19] polymers, [20] polyacrylonitrile, polyacrylamide, zeo-
lites, [21] hydroxyapatite, [22] hydrotalcite, [23] MCM, [24]
and chitosan hydrogel have been reported [25]. However,
most of the catalytic methods are associated with certain
drawbacks such as high temperature, prolonged reaction
time, low yields and use of toxic reagents. In recent years,
the concept of heterogeneous catalysts [26] has received
considerable attention due to environmental issues and haz-
ardous waste.
C-C bond forming reactions are among the most studied
methods in the field of organic chemistry because of their
immediate applications in the synthesis of molecular com-
plexity [1]. Among them, the Knoevenagel condensation is
one of the important C-C bond forming reactions [2]. Par-
ticularly, the reaction of aldehydes or ketones with an active
methylene group in the presence of a base catalyst leads to
the formation of α,β-unsaturated compounds. Moreover,
such derivatives are associated with large applications in
cosmetics and in the pharmaceutical industry as therapeutic
drugs [3].
In this context, many chemists have shown interest in us-
ing ionic liquids [27] as catalysts to overcome such draw-
backs. Despite these significant developments in Knoevenagel
reaction, eco-friendly reagents and shorter reaction times are
still in demand. As part of our research interest to develop new
ionic liquids and their applications in synthetic reactions, [28]
we recently reported an efficient process for the preparation
of 2,3-dihydroquinazoline derivatives [28c]. In this article
we wish to report an efficient protocol for the Knoevenagel
condensation catalyzed by 1-alkyl-1,2,4-triazolium based 2a
and 2b Bronsted acidic ionic liquid Scheme 1.
The first Knoevenagel condensation was reported in 1894
employing an acid catalyst [4]. Over the past decades, a con-
siderable number of alternative processes have been devel-
oped [5]. Methods involving transition metal catalysts such
as Ni(NO2)2, [6] Yb(OTf)3, [7] Li(OH)2, [8] Ti(OiPr)4, [9]
ZnCl2, [10] BiCl3, [11] CdI2, [12] other Lewis acids and acid
catalysts have been reported [13]. Other protocols employ
metal oxides, [14] CaO [15] and bimetal oxides of Zn-Mg
[16] and Mg–Fe [17a]. In addition to these catalytic proc-
esses, few other metal-free strategies were utilized, for ex-
ample N-methyl morpholine based ionic liquids (ILs), [17b]
silica-supported amine functionalized mesoporous silica,
NH4(OAc)2, N-heterocycle piperazine, thiourea, pyridine,
piperidine, L-proline, and lipase [18]. Similarly, solid bases,
O
CN
CN
catalyst 2a or 2b
CN
CN
R
R
H
H2O:EtOH
Scheme (1). Knoevenagel reaction of aldehydes and malononitrile.
*Address correspondence to these authors at the Department of Sciences, Amrita
School of Engineering Coimbatore, Amrita Vishwa Vidyapeetham, Amrita
University, Coimbatore, India; Tel/Fax: +91 4222685622/+91 422 2686274;
E-mail: elangoomc@gmail.com; and Department of Chemistry, CNCS,
Mekelle University, Makele, Ethiopia; E-mail: tanveerchem1@gmail.com
2. RESULTS AND DISCUSSION
Based on our previous findings, we deliberately carefully
chose 1-alkyltriazolium salts to investigate the Knoevenagel
1875-6255/18 $58.00+.00
© 2018 Bentham Science Publishers

134 Letters in Organic Chemistry, 2018, Vol. 15, No. 2
Kandasamy et al.
N
N
hyde also yielded condensation product in 88% yield. How-
ever, the reaction of malononitrile with heterocyclic alde-
hydes, such as pyridine-2-carboxaldehyde and furfuralde-
hyde was found to be slow and resulted in very poor product
yields. It is important to note that ketones failed to give any
Knoevenagel product employing our optimized reaction
conditions.
N
N
N
N
H
H
H
H
Br
Br
1a
1b
N
N
N
N
N
N
Next, we explored the reusability of triazolium salts 2a
and 2b employing benzaldehyde (10 mmol) and malononi-
trile (10 mmol) as starting material; the results are described
in Table 3. After completion of first cycle of experiment, the
catalyst (ionic liquid 2a or 2b) was recovered from the reac-
tion mixture. The ionic liquids (2a or 2b) were recovered
using a simple filtration technique. Subsequently the excess
of water and ethanol was removed by vacuum. The crude
residue was then washed with a mixture of hexane:ethyl ace-
tate (4:1) and further dried over vacuum for an hour. The
recycled ionic liquid 2a and 2b were then investigated for a
1st cycle; interestingly, excellent yields of product were ob-
served within 10 min (Table 3, entry 2). Subsequently, simi-
lar results were found for the 2nd and 3rd cycle.
H
H
BF4
BF4
H
H
2a
2b
Fig. (1). 1-Alkyl-1,2,4-triazolium salt-based protic ionic liquids.
condensation reaction. Initially, we focused our study on
finding suitable reaction conditions employing ionic liquids
1a or 1b (Fig. 1). However, it was observed that the Knoeve-
nagel product was obtained in lower yields (<35%) along
with the formation of undesired products with 1a or 1b at 70°C,
where water was used as the reaction medium. In order to
select the proper catalyst, we further prepared derivatives
1-alkyl-1,2,4-triazolium tetrafluoroborate (2a and 2b) from
the corresponding triazolium bromo salts of 1a and 1b,
respectively, using an anion exchange method. We then
carried out Knoevenagel condensations by exposing
benzaldehyde and malononitrile as test substrates to catalyst
2a or 2b (2 mol%) in the absence of solvent. The results
obtained are presented in Table 1. However, the reaction was
extremely slow and the starting material was recovered after
12 hours. It was noted that the reaction was improved with
the use of 5 mol% of catalyst in polar solvents. Reaction
times improved dramatically upon addition of ethanol in
addition to water (entry 4). In this case, product 4 was
isolated in 85% and 89% respectively within 30 min. The
variation in solvent ratio was not found to be useful over the
existing results. Interestingly, increasing the amount of
catalyst to 10 mol% and under neat conditions resulted in a
yield of 80% and 84% of 4 respectively. Then the reaction
was performed in a mixture of solvent (1:1 EtOH:H2O),
which resulted in the desired product in 88% and 95% yields
respectively within 10 min. Consistent with our previous
observations in ionic liquid reactions, the reaction failed to
give any product in the control experiment (catalyst absent).
In order to establish solvent-free conditions, we subjected
this condensation reaction employing to 15-20 mol% of
catalyst; no significant change was observed. Similarly, other
solvents such as DMF, DMSO and acetonitrile afforded the
desired product in 60-77% yields.
3. EXPERIMENTAL
Melting points of the reported compounds were measured
in DALAL instruments, India and are uncorrected. IR spec-
tra were recorded on a Bruker Vector 22 FT-IR spectrometer
operating at 400-4000 cm-1 using KBr pellets. Elemental
analyses of the compounds were obtained from thermoquest
1
CE instrument CHNS-O, EA/110 model. H NMR spectra
were recorded at 400 MHz and 13C NMR spectra at 100
MHz on a Bruker AVANCE FT NMR instrument using
CDCl3 and DMSO-d6 as standard solvents. Electrospray
ionization mass spectrometry (ESI-MS) spectra were re-
corded on a Waters Q-TOF Premier mass spectrometer.
3.1. Synthesis of 1-propyl-1,2,4-triazolium Bromide (1a)
by a Quaternization Method
A 50 mL three-necked flask was equipped with a mag-
netic bar. The flask was charged with 100 mmol of 1-propyl-
1,2,4-triazole (11.1g) and toluene (10 mL). To this reaction
mixture 100 mmol of tert-butyl bromide (13.7 g) was added
slowly. Then the resulting mixture was subjected to heating
at 80ºC for 16 h under nitrogen atmosphere. After comple-
tion of the reaction, the reaction mixture was allowed to cool
at room temperature. Upon cooling, the immiscible layer was
solidified, which was filtered using sintered funnel. The ob-
tained solid product was washed with hexane (2 x 15 mL)
and dried over vacuum for 1 hour at 50ºC. The product 1a
was obtained in 88% yield and in pure form.
Having identified suitable reaction conditions for
Knoevenagel reaction, we next explored this protocol to
study various aldehydes. A reaction of alkyl-substituted ben-
zaldehydes with malononitrile resulted in the formation of
corresponding products in 77-95% yields. Reactions of
malononitrile with various hydroxy substituted aldehydes led
to the formation of the desired product without any side reac-
tion or over oxidation. Next, benzaldehydes substituted with
a variety of halo groups were examined, such as fluoro,
chloro, and bromo; all reacted to afford the corresponding
products in excellent yield. Interestingly, 4-nitro benzalde-
3.1.1. 1-propyl-1,2,4-triazolium bromide (1a)
Yield: 88% (1.6 g) colorless solid. Anal.Calcd. For
C5H10BrN3 (191.01): C, 31.27; H, 5.25; Br, 41.60; N, 21.88;
Found: C, 31.11; H, 5.13; N, 21.74,1H NMR (CDCl3, 400
MHz): δ, ppm: 14.26 (bs, 1H, NH), 10.91 (s, 1H, 5-CH),
8.90 (s, 1H, 3-CH), 4.57 (t, 2H, J = 8.0 Hz N-CH2-), 2.05 (m,
2H, -CH2-CH3), 1.0 (t, 3H, J = 10.0 Hz, CH3). 13C NMR
(CDCl3, 100 MHz): δ, ppm: 142.14 (C-5), 141.12 (C-3),
54.02 (N-CH2), 22.44 (-CH2-CH3), 10.74 (-CH3).

Knoevenagel Reaction Catalyzed by a Reusable Brønsted Acid
Letters in Organic Chemistry, 2018, Vol. 15, No. 2 135
Table 1. Evaluation of reaction parametersa.
H
O
H
catalyst,
CN
CN
CN
CN
solvent, time
1
4
3
Catalyst 2aꢀ
Catalyst 2bꢀ
Entryꢀ
Catalyst (mol%)ꢀ
Solventꢀ
Time (min)ꢀ
Yieldb (%)ꢀ
Time (min)ꢀ
Yieldb (%)ꢀ
1ꢀ
2ꢀ
2ꢀ
5ꢀ
--ꢀ
--ꢀ
12*ꢀ
12*ꢀ
1*ꢀ
30ꢀ
70ꢀ
75ꢀ
78ꢀ
85ꢀ
74ꢀ
65ꢀ
80ꢀ
88ꢀ
--ꢀ
12*ꢀ
12*ꢀ
1*ꢀ
1*ꢀ
30ꢀ
1*ꢀ
1*ꢀ
12*ꢀ
5ꢀ
35ꢀ
78ꢀ
76ꢀ
80ꢀ
89ꢀ
80ꢀ
72ꢀ
84ꢀ
95ꢀ
--ꢀ
3ꢀ
5ꢀ
H2Oꢀ
EtOHꢀ
4ꢀ
5ꢀ
1*ꢀ
5ꢀ
5ꢀ
H2O: EtOH (1:1)ꢀ
H2O: EtOH (2:1)ꢀ
H2O: EtOH (1:2)ꢀ
--ꢀ
30ꢀ
6ꢀ
5ꢀ
1*ꢀ
7ꢀ
5ꢀ
1*ꢀ
8ꢀ
10ꢀ
10ꢀ
--ꢀ
12*ꢀ
10ꢀ
9ꢀ
H2O: EtOH (1:1)ꢀ
H2O: EtOH (1:1)ꢀ
--ꢀ
10ꢀ
11ꢀ
12ꢀ
13ꢀ
14ꢀ
15ꢀ
16ꢀ
17ꢀ
1*ꢀ
--ꢀ
15ꢀ
15ꢀ
20ꢀ
20ꢀ
10ꢀ
10ꢀ
10ꢀ
12*ꢀ
15ꢀ
81ꢀ
94ꢀ
79ꢀ
84ꢀ
77ꢀ
70ꢀ
60ꢀ
12*ꢀ
10ꢀ
12*ꢀ
5ꢀ
82ꢀ
96ꢀ
80ꢀ
87ꢀ
77ꢀ
74ꢀ
65ꢀ
H2O: EtOH (1:1)ꢀ
--ꢀ
12*ꢀ
10ꢀ
H2O: EtOH (1:1)ꢀ
DMFꢀ
1*ꢀ
1*ꢀ
1*ꢀ
1*ꢀ
DMSOꢀ
1*ꢀ
CH3CNꢀ
1*ꢀ
aReaction conditions: benzaldehyde (1 mmol), malononitrile (1 mmol), catalyst, solvent; b isolated yields. *Reaction time in hours.
Table 2. Scope of the Knoevenagel reaction of aldehydes with malononitrilea.
H
O
CN
CN
catalyst 2a or 2b
CN
CN
H
R
R
H2O:EtOH
ꢀ
Catalyst 2aꢀ
Catalyst 2bꢀ
Entryꢀ
1ꢀ
Productbꢀ
Time (min)ꢀ
Yield (%)cꢀ
Time (min)ꢀ
Yield (%)cꢀ
CN
CN
15ꢀ
88ꢀ
10ꢀ
95ꢀ
ꢀ
CN
CN
2ꢀ
3ꢀ
35ꢀ
15ꢀ
77ꢀ
90ꢀ
15ꢀ
15ꢀ
83ꢀ
H3C
ꢀ
ꢀ
CN
CN
92ꢀ
(Table 2) Contd….

136 Letters in Organic Chemistry, 2018, Vol. 15, No. 2
Kandasamy et al.
Catalyst 2bꢀ
Catalyst 2aꢀ
Time (min)ꢀ
Entryꢀ
4ꢀ
Productbꢀ
Yield (%)cꢀ
79ꢀ
Time (min)ꢀ
Yield (%)cꢀ
CN
CN
15ꢀ
10ꢀ
10ꢀ
88ꢀ
MeO
MeO
ꢀ
CN
CN
5ꢀ
6ꢀ
7ꢀ
90ꢀ
71ꢀ
77ꢀ
5ꢀ
92ꢀ
82ꢀ
78ꢀ
OMe
ꢀ
CN
CN
45ꢀ
10ꢀ
10ꢀ
10ꢀ
HO
OMe
ꢀ
CN
CN
OH
ꢀ
ꢀ
CN
CN
8ꢀ
9ꢀ
10ꢀ
10ꢀ
10ꢀ
85ꢀ
91ꢀ
90ꢀ
10ꢀ
5ꢀ
88ꢀ
94ꢀ
95ꢀ
OH
CN
CN
ꢀ
CN
CN
10ꢀ
10ꢀ
F
ꢀ
ꢀ
CN
CN
11ꢀ
12ꢀ
20ꢀ
15ꢀ
90ꢀ
84ꢀ
10ꢀ
10ꢀ
92ꢀ
90ꢀ
Cl
Br
CN
CN
CN
ꢀ
CN
13ꢀ
15ꢀ
86ꢀ
10ꢀ
90ꢀ
Br
ꢀ
ꢀ
CN
CN
14ꢀ
15ꢀ
10ꢀ
10ꢀ
88ꢀ
88ꢀ
10ꢀ
10ꢀ
92ꢀ
95ꢀ
Cl
CN
CN
Cl
Cl
ꢀ
CN
CN
16ꢀ
15ꢀ
86ꢀ
10ꢀ
88ꢀ
NO2
ꢀ
ꢀ
CN
CN
17ꢀ
18ꢀ
24*ꢀ
24*ꢀ
20ꢀ
10ꢀ
24ꢀ
24ꢀ
25ꢀ
10ꢀ
N
CN
O
CN
ꢀ
ꢀ
ꢀ
19ꢀ
20ꢀ
Cyclohexanoneꢀ
Acetophenoneꢀ
30*ꢀ
30*ꢀ
--ꢀ
--ꢀ
--ꢀ
--ꢀ
aReaction conditions: aldehyde (1 mmol), malononitrile (1 mmol), catalyst 2a or 2b (10 mol%), ethanol:H2O (1:1); bproducts were characterized by mp, 1H- and 13C-NMR, GCMS;
cisolated yields. *Reaction time in hours.

Knoevenagel Reaction Catalyzed by a Reusable Brønsted Acid
Letters in Organic Chemistry, 2018, Vol. 15, No. 2 137
Table 3. Reusable study in Knoevenagel condensation.
Catalyst 2aꢀ
Catalyst 2bꢀ
Entryꢀ
Cycleꢀ
Time (min)ꢀ
Yield (%)aꢀ
Time (min)ꢀ
Yield (%)aꢀ
1ꢀ
2ꢀ
3ꢀ
4ꢀ
Freshꢀ
1stꢀ
2ndꢀ
10ꢀ
10ꢀ
15ꢀ
20ꢀ
94ꢀ
91ꢀ
89ꢀ
88ꢀ
5ꢀ
5ꢀ
96ꢀ
94ꢀ
90ꢀ
85ꢀ
10ꢀ
15ꢀ
3rdꢀ
3.1.2. 1-propyl-1,2,4-triazolium tetrafluoroborate (2a)
bath. The course of the reaction was monitored by thin layer
chromatography (TLC). After completion of the reaction, the
mixture was cooled to room temperature and the precipitate
formed was separated by filtration. The residue was washed
with n-hexane (5 mLx2) and further dried in air to obtain
condensed products.
Yield: 89% (1.7 g) brown color semi solid. Anal. Calcd.
For C5H10BF4N3 (199.09): C, 30.18; H, 5.07; N, 21.12 Found:
1
C, 30.10; H, 5.00; N, 21.01; H NMR (CDCl3, 400 MHz):
δ11.64 (bs, 1H, NH), 10.86 (s, 1H, 5-CH), 8.77 (s, 1H, 3-
CH), 4.55 (t, 2H, N-CH2-), 2.05 (m, 2H, CH2-CH3), 1.0 (t, 3H,
CH3); 13C NMR (CDCl3, 100 MHz):δ 142.05 (C-5), 141.18
(C-3), 54.04 (N-CH2), 22.47 (-CH2-CH3), 10.73 (-CH3).
3.3.1. 2-benzylidenemalononitrile (Table 2, entry 1)
Yield: 95%; White solid; Mp: 82-84°C (Lit.27i 82-84°C);
FTIR (KBr, cm-1): 3090, 3069, 3028, 2930, 2219, 1550, 1561;
1H-NMR (400MHz, CDCl3): δ, ppm: 7.85 (d, J = 7.5 Hz,
2H), 7.72 (s, 1H), 7.57 (t, J = 5.0 Hz, 1H), (t, J = 5.0 Hz,
1H); 13C-NMR (100 MHz, CDCl3) δ, ppm: 159.7, 134.2,
130.5, 129.3, 113.2, 112.2, 82.5.
3.2. Synthesis of 1-propyl-1,2,4-triazolium Tetra-
fluoroborate (2a) by Anion Exchange Metathesis Method
A 50 mL flask was charged with 1-propyl-1,2,4-
triazolium bromide (1a) (10 mmol) and a mixture of solvents
CH2Cl2:CH3OH 10 mL (4:1). Then potassium tetrafluorobo-
rate (10 mmol) was added slowly to the above solution. The
resulting reaction mixture was stirred for 3 h at room tem-
perature. After completion of the reaction, the solution was
filtered and the solvents were removed under vacuum to give
2a.
3.3.2. 2-(4-methylbenzylidene)malononitrile (Table 2, en-
try 2)
Yield: 83%; white solid; Mp: 134-135°C (lit.27g) 134-
135°C); FTIR (KBr, cm-1): 3030, 2955, 2920, 2219, 1585,
1
1550; H-NMR (400MHz, CDCl3): δ, ppm:7.80 (d, J = 8.3
Hz, 2H), 7.70 (s, 1H), 7.35 (d, J = 8.3 Hz, 2H); 13C-NMR
(100 MHz, CDCl3) δ, ppm: 159.9, 146.5, 130.6, 130.5,
128.9, 113.9, 112.5, 81.5.
3.2.1. 1-propyl-1,2,4-triazolium tetrafluoroborate (2a)
Yield: 89% (1.7 g) brown color semi solid. Anal. Calcd.
For C5H10BF4N3 (199.09): C, 30.18; H, 5.07; N, 21.12
1
Found: C, 30.10; H, 5.00; N, 21.01; H NMR (CDCl3, 400
3.3.3. 2-(4-chlorobenzylidene)malononitrile (Table 2, entry
11)
MHz): δ, ppm: 11.64 (bs, 1H, NH), 10.86 (s, 1H, 5-CH),
8.77 (s, 1H, 3-CH), 4.55 (t, 2H, N-CH2-), 2.05 (m, 2H, CH2-
CH3), 1.0 (t, 3H, CH3); 13C NMR (CDCl3, 100 MHz):δ, ppm:
142.05 (C-5), 141.18 (C-3), 54.04 (N-CH2), 22.47 (-CH2-
CH3), 10.73 (-CH3).
Yield: 92%, white solid; Mp: 162-163°C (Lit.3, 161-
163°C); FTIR (KBr, cm-1): 3105, 3081, 3072, 3039, 2232,
1
1580, 1555; H-NMR (400MHz, CDCl3): δ, ppm: 7.83 (d, J
= 8.4 Hz, 2H), 7.71 (s, 1H), 7.50 (d, J = 8.4 Hz, 2H); 13C-
NMR (100 MHz, CDCl3) δ, ppm: 158.2, 141.1, 131.7, 130.0,
129.2, 117.2, 112.6, 111.6, 86.9.
3.2.2. 1-butyl-1,2,4-triazolium tetrafluoroborate (2b)
Yield: 84% (1.8 g) brown color semi solid. Anal. Calcd.
For C6H12BF4N3 (213.11): C, 33.84; H, 5.68; N, 19.73
Found: C, 33. 79; H, 5.76; N, 19.65;1H NMR (DMSO-d6,400
MHz):δ 10.18 (s, 1H, 4-NH), 9.62 (t, 1H, 5-CH), 8.76 (s, 1H,
3-CH), 4.3 (t,2H, CH2-CH2-CH2-CH3), 1.8 (dd,2H, CH2-
CH2-CH2-CH3), 1.2 (m, 2H, CH2-CH2-CH2-CH3), 0.85 (t,
3H, CH2-CH2-CH2-CH3). ES-MS m/z: 126.19 [M-BF4]+
CONCLUSION
A convenient approach for Knoevenagel reaction was
developed, utilising catalytic amounts of 1-alkyltriazolium
salts. A variety of aldehyde derivatives underwent smooth
reactions with malononitrile under optimized reaction condi-
tions and affording desired products in excellent yields.
3.3. General Procedure for the Knoevenagel Condensa-
tion (Table 2)
CONSENT FOR PUBLICATION
A 10 mL flask was charged with 1:1 mixture of water
and ethanol (2mL), benzaldehyde (1.06 g, 10 mmol) and
malononitrile (0.66g, 10 mmol). To this reaction mixture
ionic liquid catalyst 1-alkyl-1,2,4-triazolium tetrafluorobo-
rate (10 mol%) (alkyl = propyl and butyl) was added slowly.
Then the reaction mixture was heated to 70 °C using an oil
Not applicable.
CONFLICT OF INTEREST
The authors declare no conflict of interest, financial or
otherwise.

138 Letters in Organic Chemistry, 2018, Vol. 15, No. 2
Kandasamy et al.
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ACKNOWLEDGEMENTS
The authors thank the Science and Engineering Research
Board (DST-SERB, SR/FT/CS-60/2011), India for providing
research fund.
SUPPLEMENTARY MATERIAL
Supplementary material is available on the publisher’s
website along with the published article.
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