Malononitrile-Catalyzed and Highly Selective Method for the Synthesis of 2-((E)-1,3-Diarylallylidene)malononitriles in Ionic Liquid

Article abstract of DOI:10.1080/00397910902730903

The green and highly selective reactions of aromatic aldehydes, malononitrile, and 2-(1-arylethylidene)malononitriles in ionic liquid of [bmim+]Br- at 50C unexpectedly gave 2-((E)-1,3-diarylallylidene)malononitriles. The modification of the reaction used

Full text of DOI:10.1080/00397910902730903

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Malononitrile-Catalyzed and
Highly Selective Method for
the Synthesis of 2-((E)-1,3-
Diarylallylidene)malononitriles
in Ionic Liquid
Xiang-Shan Wang a b , Mei-Mei Zhang b , Qing Li a
Chang-Sheng Yao a
a School of Chemistry and Chemical Engineering,
Xuzhou Normal University, Xuzhou Jiangsu, China
&
b Key Laboratory of Biotechnology for Medical Plant,
Xuzhou Normal University, Xuzhou Jiangsu, China
Published online: 03 Aug 2009.
To cite this article: Xiang-Shan Wang , Mei-Mei Zhang , Qing Li & Chang-Sheng Yao
(2009) Malononitrile-Catalyzed and Highly Selective Method for the Synthesis of 2-
((E)-1,3-Diarylallylidene)malononitriles in Ionic Liquid, Synthetic Communications: An
International Journal for Rapid Communication of Synthetic Organic Chemistry, 39:17,
3045-3059
To link to this article: http://dx.doi.org/10.1080/00397910902730903
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Synthetic Communications1, 39: 3045–3059, 2009
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397910902730903
Malononitrile-Catalyzed and Highly Selective
Method for the Synthesis of
2-((E)-1,3-Diarylallylidene)malononitriles
in Ionic Liquid
Xiang-Shan Wang,1,2 Mei-Mei Zhang,2 Qing Li,1 and
Chang-Sheng Yao1
1School of Chemistry and Chemical Engineering, Xuzhou Normal
University, Xuzhou Jiangsu, China
2Key Laboratory of Biotechnology for Medical Plant, Xuzhou Normal
University, Xuzhou Jiangsu, China
Abstract: The green and highly selective reactions of aromatic aldehydes, malo-
nonitrile, and 2-(1-arylethylidene)malononitriles in ionic liquid of [bmimþ]Brꢀ
at 50ꢁC unexpectedly gave 2-((E)-1,3-diarylallylidene)malononitriles. The modifi-
cation of the reaction used 10 mol% malononitrile as catalyst at 90ꢁC in
[bmimþ][BF4ꢀ]. A possible reaction mechanism for the formation of the product
was proposed based on further experimental results. 2-((E)-1,3-Diarylallylidene)
malononitriles were not detected at all in the designed reaction of aromatic
aldehyde and 2-(1-arylethylidene)malononitriles at the same reaction conditions.
Keywords: 2-(1-Arylethylidene)malononitrile, 1,3-diarylallylidenemalononitrile,
ionic liquid, malononitrile, synthesis
INTRODUCTION
Ionic liquids are generally salts of quaternary ammonium species with
poorly coordinating ions and liquids at temperature less than 100ꢁC; they
Received October 1, 2008.
Address correspondence to Xiang-Shan Wang, School of Chemistry and
Chemical Engineering, Xuzhou Normal University, Xuzhou Jiangsu 221116,
China. E-mail: xswang1974@yahoo.com
3045

3046
X.-S. Wang et al.
Scheme 1. Reaction of 1, 3, and 2 in ionic liquid of [bmim]Br.
have attracted increasing interest in the context of green synthesis in
recent times. Ionic liquids were initially introduced as alternative green
reaction media because of their unique chemical and physical properties:
nonvolatility, nonflammability, thermal stability, and controlled miscibil-
ity.[1,2] The possibility of recycling them and the low vapor frame also
ensure their use in environmentally friendly technologies. They have
recently attracted considerable interest as solvents for a large number
of organic reactions because they are immiscible with many organic
solvents.[3–9] As a part of our ongoing program to apply ionic liquids
as green media in organic synthesis,[10,11] herein we report an improved
reaction of aromatic aldehyde and 2-(1-arylethylidene)malononitrile in
ionic liquid for the synthesis of 2-((E)-1,3-diarylallylidene)malononitriles
catalyzed by malononitrile. This reaction has advantages of good yield,
operational simplicity, and good selectivity.
We have previously reported an improved and green synthesis of
2-amino-4,6-diarylcyclohexa-2,4-diene-1,1,3-tricarbonitrile derivatives in
water.[12] However, the desired 2,6-dicyanoaniline moieties were not
detected in this triethylbenzylammonium chloride (TEBAC)=water
system. To obtain these acceptor–donor–acceptor (A-D-A) systems in a
multicomponent reaction, we performed a three-component reaction of
aromatic aldehyde, malononitrile, and 2-(1-arylethylidene)malononitrile
in ionic liquid of [bmimþ] Brꢀ at 50ꢁC. Unexpectedly, it gave the highly
selective product of 2-((E)-1,3-diarylallylidene)malononitrile rather than
2,6-dicyanoaniline moiety or cyclohexa-2,4-diene-1,1,3-tricarbonitrile
derivative (Scheme 1).
RESULTS AND DISCUSSION
According to the structure of product, the malononitrile may attend to
the reaction but lose at last, so we try to obtain the product 4 without

Synthesis of Diarylallylidenemalononitrile
3047
Scheme 2. Reaction of 1a and 3a in ionic liquid without 2.
malononitrile by
a
reaction of the 2-chlorobenzaldehyde and
1-phenylethylidenemalononitrile in ionic liquid at the same reaction
conditions (Scheme 2), but it failed. It should be noted that the designed
reaction could take place in ordinary organic solvent.[13–15] However, a
base such as piperidine or triethylamine should be added; furthermore,
the yields of the reported reactions were poor (69–80%).
An interesting conclusion could be made that the malononitrile in
this reaction was a catalyst. Subsequently, the reaction of 2-chlorobenzal-
dehyde and 1-phenylethylidenemalononitrile was used as a model reac-
tion to optimize the conditions. A summary of the optimization
experiment is provided in Table 1. The results showed that no reaction
Table 1. Synthesis of 4a in ionic liquid at different reaction conditionsa
Entry
Temp. (ꢁC)
2 (mol%)
Ionic liquidb
Time (h)
Yieldc (%)
ꢀ
1
2
3
4
5
6
7
8
9
10
11
12
13
14
rt
10
10
5
10
20
10
10
10
[bmimþ][BF4ꢀ
[bmimþ][BF4ꢀ
[bmimþ][BF4ꢀ
[bmimþ][BF4ꢀ
[bmimþ][BF4ꢀ
[bmimþ][BF4ꢀ
[bmimþ][BF4
[emimþ]Br-
]
]
]
]
]
]
]
6
6
6
6
6
3
9
6
6
6
6
6
6
3
0
83
78
93
86
83
92
82
84
86
89
90
76
80
50
90
90
90
90
90
90
90
90
90
90
90
80
10
10
10
[pmimþ]Br-
[bmimþ]Br-
[emimþ][BF4 ꢀ
[pmimþ][BF4ꢀ
[bmimþ][BF4
Ethanol
]
ꢀ
10
Piperidined
Piperidine[13]
]
]
aReaction conditions: 1 mL ionic liquid, 2 mmol 2-chlorobenzaldehyde, and
2 mmol 1-phenylethylidenemalononitrile.
bbmim, 1-butyl-3-methylimidazolium; emim, 1-ethyl-3-methylimidazolium;
pmim, 1-methyl-3-propylimidazolium.
cIsolated yields.
dReaction conditions: 1 mL ionic liquid, 2 mmol 2-chlorobenzaldehyde, 2 mmol
1-phenylethylidenemalononitrile, 10 mol% piperidine.

3048
X.-S. Wang et al.
took place at room temperature (Table 1, entry 1). To our delight, the
reaction proceeded smoothly at 90ꢁC in good yield. Similar reactions
were then carried out in the presence of 5%, 10%, and 20 mol% of malo-
nonitrile. The results from Table 1 (entries 3, 4, and 5) showed that
10 mol% malononitrile at 90ꢁC in ionic liquid gave the best yield. Higher
loading of the catalyst did not improve the yield to a great extent. To find
the optimum reaction time, the reaction was carried out in ionic liquid of
[bmimþ] [BF4ꢀ] for 3, 6, or 9 h (Table 1, entries 4, 6, and 7), leading to 4a
in 83%, 93%, and 92% yield, respectively. Thus, the optimal reaction
temperature and reaction time are 90ꢁC and 6 h, respectively. Using
piperidine as basic catalyst only gave 4a in 76% in ionic liquid media.
Moreover, different ionic liquids were further investigated as shown in
Table 1. We concluded that the [bmimþ] [BF4ꢀ] was the best ionic liquid
for this reaction.
After the reaction was completed (monitored by thin-layer chroma-
tography, TLC), the reaction mixture was cooled to room temperature,
and then 5 mL water were added to the mixture. The solid was isolated
by filtration. The water in the filtrate was removed by evaporation at
reduced pressure, and the residue containing ionic liquid could be recov-
ered easily at 80ꢁC in vacuum after a few hours. The recovered ionic
liquid could be reused for the same reaction. Alternatively, the ionic
liquid was washed with ethyl acetate, followed by evaporation at 80ꢁC
in vacuum for a few hours, if it was used for other reactions with
different substrates. Investigations using 2-chlorobenzaldehyde and 1-
phenylethylidenemalononitrile as model substrates proved the successive
reuse of the recovered ionic liquid. Even in the fourth cycle, the yield
(92%) of product 4a is fairly good.
To extend the reaction (Scheme 3) to a library system, various kinds
of aromatic aldehydes 1 and 2-(1-arylethylidene)malononitriles 3 gave the
corresponding 2-((E)-1,3-diarylallylidene) malononitriles 4, and represen-
tative examples are shown in Table 2. All of 1 and 3 gave the
desired products in good yields, either bearing electron-withdrawing
groups (such as halide, nitro) or electron-donating groups (such as alkyl
group, or alkoxyl group) under the same reaction conditions. However,
Scheme 3. Reaction of 1 and 3 catalyzed by 2 in ionic liquid.

Synthesis of Diarylallylidenemalononitrile
3049
Table 2. Malononitrile-catalyzed reactions of aromatic aldehydes and
2-(1-arylethylidene)malononitriles in ionic liquida
Entry
Ar
Ar0
Products Time (h) Yields (%)b
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
2-ClC6H4
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
4-BrC6H4
4-BrC6H4
4-BrC6H4
4-ClC6H4
4-CH3C6H4
4-CH3OC6H4
4-CH3OC6H4
4-CH3OC6H4
4-CH3OC6H4
4-CH3OC6H4
4a
4b
4c
4d
4e
4f
6
7
4
4
5
6
7
5
5
3
5
4
8
8
7
5
7
8
7
5
5
93
90
96
96
92
90
94
96
92
98
90
92
88
87
92
95
92
89
90
90
95
2-CH3OC6H4
2-NO2C6H4
4-Cl-2-NO2C6H3
2,4-Cl2C6H3
3-NO2C6H4
3,4-Cl2C6H3
2-ClC6H4
2,4-Cl2C6H3
2-NO2C6H4
2-ClC6H4
2,4-Cl2C6H3
3,4-(CH3)2C6H3
2,4-Cl2C6H3
2-ClC6H4
2-NO2C6H4
3,4-Cl2C6H3
4g
4h
4i
4j
4k
4l
4m
4n
4o
4p
4q
4r
4s
4t
3,4-(CH3O)2C6H3 2,4-(CH3)2C6H3
2-ClC6H4
2-ClC6H4
2-ClC6H4
2,4-(CH3)2C6H3
3-ClC6H4
4-FC6H4
4u
aReaction conditions: 1 mL ionic liquid, 2 mmol aromatic aldehyde 1, 0.2 mmol
malononitrile 2, and 2 mmol 2-(1-arylethylidene)malononitrile 3, 90ꢁC.
bIsolated yields.
we failed to give the corresponding products, using n-butyraldehyde,
n-heptaldehyde, and 3-indolealdehyde as reactants.
The structure of product 4h was further confirmed by x-ray diffraction
analysis, and the crystal structure of 4h is shown in Fig. 1.
Although the detailed mechanism of the reaction has not been
clarified yet, the formation of 4 can be tentatively explained by the path-
way presented in Scheme 4. A sequential reaction of the Knoevenagel
condensation and Michael addition reaction may take place, followed
by losing a molecule of 2 to give the final product 4.
To verify the mechanism, we performed each separate step of the
reaction. The Knoevenagel condensation product, 2-chlorophenylidenema-
lononitrile 5, was obtained in 92% yield; subsequently, product 5 was trea-
ted with 1-phenylethylidene malononitrile 3a in ionic liquid (Scheme 5). As
expected, intermediate product 5 reacted with 3a to smoothly give the

3050
X.-S. Wang et al.
Figure 1. Crystal structure of product 4h with positional disorder in 4-bromoben-
zene ring.
Scheme 4. Possible mechanism for the formation of products 4.
Scheme 5. Separate reactions of 1a, 2, and 3a in ionic liquid.

Synthesis of Diarylallylidenemalononitrile
3051
Scheme 6. Reaction of chalcone 6 with malonitrile in ionic liquid.
corresponding 4a. This result suggested that a Knoevenagel condensation
took place during the reaction.
Furthermore, treating chalcone 6 with malononitrile for 12 h in ionic
liquid at 90ꢁC (Scheme 6) gave the Michael addition product 7 in 82%
yield rather than the desired product 4, which was in accordance to that
of the reference reported.[16,17]
EXPERIMENTAL
Melting points were determined in open capillaries and are uncorrected.
Infrared (IR) spectra were recorded on a Tensor 27 spectrometer in KBr
pellets. 1H NMR spectra were obtained from solution in dimethy
sulfoxide (DMSO)-d6 with Me4Si as internal standard using an Inova-400
spectrometer. Elemental analyses were carried out using a Perkin-Elmer
2400 II analyzer.
General Procedure for the Syntheses of 2-((E)-1,3-Diarylallylidene)
malononitriles 4
A dry 50-mL flask was charged with aromatic aldehyde (2.0 mmol),
malononitrile (0.013 g, 0.2 mmol), 2-(1-arylethylidene)malononitrile
(2.0 mmol), and ionic liquid of [bmimþ][BF4ꢀ] (1 mL). The reaction
mixture was stirred at 90ꢁC for 3–8 h, and then 5 mL water were added
to the mixture. The solid was isolated by filtration. The water in the
filtrate was removed by evaporation at reduced pressure, and the ionic
liquid could be recovered easily at 80ꢁC in vacuum after a few hours.
The crude yellow products were washed with water and purified by
recrystallization from dimethyformanide (DMF) and water to give 4.

3052
X.-S. Wang et al.
Data
2-((E)-3-(2-Chlorophenyl)-1-phenylallylidene)malononitrile 4a
Pale yellow crystals; mp 151–153ꢁC. IR (KBr): 3059, 2223, 1606, 1587,
1561, 1527, 1487, 1470, 1445, 1339, 1280, 1182, 1101, 1079, 1041, 967,
768, 734, 719, 703, 683 cmꢀ1
.
1H NMR (DMSO-d6) d: 7.18
(d, J ¼ 15.6 Hz, 1H, CH ¼), 7.47–7.50 (m, 5H, ArH þCH ¼), 7.60–7.66
(m, 4H, ArH), 8.00–8.02 (m, 1H, ArH). 13C NMR (DMSO-d6) d: 84.1,
113.1, 114.0, 125.6, 127.3, 128.6, 129.0, 130.7, 131.7, 132.2, 132.46,
132.54, 133.3, 134.9, 143.6, 169.5. MS (m=z): 290 (Mþ, 42), 255 (100),
227 (25), 178 (17). Anal. Calcd. for C18H11ClN2: C, 74.36; H, 3.81; N,
9.64. Found: C, 74.52; H, 3.70; N, 9.68.
2-((E)-3-(2-Methoxylphenyl)-1-phenylallylidene)malononitrile 4b
Pale yellow crystals; mp 136–138ꢁC. IR (KBr): 3015, 2968, 2940, 2840,
2221, 1600, 1530, 1480, 1438, 1329, 1309, 1255, 1180, 1160, 1116, 1048,
1
1029, 978, 871, 763, 714, 701 cmꢀ1. H NMR (DMSO-d6) d: 3.78 (s,
3H, CH3O), 7.01–7.05 (m, 1H, ArH), 7.08–7.11 (m, 2H, ArH),
7.45–7.49 (m, 3H, ArH þCH ¼), 7.58–7.65 (m, 4H, ArH), 7.72 (d,
J ¼ 15.6 Hz, 1H, CH ¼). Anal. Calcd. for C19H14N2O: C, 79.70; H,
4.93; N, 9.78. Found: C, 79.57; H, 5.10; N, 9.90.
2-((E)-3-(2-Nitrophenyl)-1-phenylallylidene)malononitrile 4c
Pale yellow crystals; mp 149–150ꢁC. IR (KBr): 3067, 2223, 1607, 1569,
1524, 1487, 1441, 1352, 1321, 1299, 1214, 1165, 1102, 972, 855, 773,
1
749, 723, 699 cmꢀ1. H NMR (DMSO-d6) d: 7.30 (d, J ¼ 15.6 Hz, 1H,
CH ¼), 7.45 (d, J ¼ 15.6 Hz, 1H, CH ¼), 7.55–7.73 (m, 6H, ArH),
7.84–7.87 (m, 1H, ArH), 7.99 (d, J ¼ 8.0 Hz, 1H, ArH), 8.08 (d,
J ¼ 8.4 Hz, 1H, ArH). Anal. Calcd. for C18H11N3O2: C, 71.75; H, 3.68;
N, 13.95. Found: C, 71.72; H, 3.78; N, 13.79.
2-((E)-3-(4-Chloro-2-Nitrophenyl)-1-phenylallylidene)malononitrile 4d
Pale yellow crystals; mp 179–181ꢁC. IR (KBr): 3108, 3081, 2229, 1598,
1561, 1521, 1468, 1445, 1335, 1264, 1205, 1095, 1027, 972, 927, 877,
848, 777, 759, 737, 708 cmꢀ1
.
1H NMR (DMSO-d6) d: 7.24
(d, J ¼ 15.6 Hz, 1H, CH ¼), 7.51 (d, J ¼ 15.6 Hz, 1H, CH ¼), 7.54–7.65
(m, 5H, ArH), 7.75 (dd, J ¼ 8.4 Hz, J’ ¼ 2.0 Hz, 1H, ArH), 8.10–8.12

Synthesis of Diarylallylidenemalononitrile
3053
(m, 2H, ArH). Anal. Calcd. for C18H10ClN3O2: C, 64.39; H, 3.00; N,
12.52. Found: C, 64.51; H, 3.11; N, 12.55.
2-((E)-3-(2,4-Dichlorophenyl)-1-phenylallylidene)malononitrile 4e
Pale yellow crystals; mp 129–130ꢁC. IR (KBr): 3060, 2223, 1604, 1581,
1531, 1488, 1469, 1442, 1389, 1325, 1305, 1280, 1214, 1143, 1100, 1049,
.
972, 887, 844, 817, 756, 699 cmꢀ1 1H NMR (DMSO-d6) d: 7.10 (d,
J ¼ 15.6Hz, 1H, CH ¼), 7.53–7.66 (m, 7H, ArH þCH ¼), 7.73 (d,
J ¼ 2.0 Hz, 1H, ArH), 8.08 (d, J ¼ 8.8 Hz, 1H, ArH). Anal. calcd. for
C18H10Cl2N2: C, 66.48; H, 3.10; N, 8.61. Found: C, 66.35; H, 3.17; N, 8.55.
2-((E)-3-(3-Nitrophenyl)-1-phenylallylidene)malononitrile 4f
Pale yellow crystals; mp 169–171ꢁC. IR (KBr): 3087, 2227, 1607, 1547,
.
1530, 1478, 1354, 1099, 985, 812, 777, 738, 702 cmꢀ1 1H NMR
(DMSO-d6) d: 7.12 (d, J ¼ 16.0 Hz, 1H, CH ¼), 7.54–7.76 (m, 7H, ArH
þCH ¼), 8.22 (d, J ¼ 7.6 Hz, 1H, ArH), 8.28 (dd, J ¼ 8.0 Hz,
J’ ¼ 2.0 Hz, 1H, ArH), 8.57 (s, 1H, ArH). Anal. calcd. for C18H11N3O2:
C, 71.75; H, 3.68; N, 13.95. Found: C, 71.88; H, 3.59; N, 13.79.
2-((E)-3-(3,4-Dichlorophenyl)-1-phenylallylidene)malononitrile 4g
Pale yellow crystals, mp 190–192ꢁC. IR (KBr): 3058, 3027, 2228, 1609,
1585, 1547, 1529, 1488, 1472, 1443, 1394, 1343, 1317, 1272, 1215, 1135,
1
1105, 1074, 1029, 982, 810, 779, 748, 699 cmꢀ1. H NMR (DMSO-d6) d:
6.92 (d, J ¼ 15.2 Hz, 1H, CH ¼), 7.51–7.53 (m, 2H, ArH), 7.61–7.76 (m,
6H, ArH þ CH ¼), 8.08 (d, J ¼ 2.0 Hz, 1H, ArꢀH). Anal. calcd. for
C18H10Cl2N2: C, 66.48; H, 3.10; N, 8.61. Found: C, 66.44; H, 3.22; N, 8.45.
2-((E)-1-(4-Bromophenyl)-3-(2-chlorophenyl)allylidene)
malononitrile 4h
Pale yellow crystals, mp 180–184ꢁC. IR (KBr): 3061, 2221, 1602, 1561,
1532, 1485, 1469, 1444, 1391, 1338, 1323, 1286, 1098, 1071, 1039, 1011,
1
966, 824, 766, 750 cmꢀ1. H NMR (DMSO-d6) d: 7.16 (d, J ¼ 15.6 Hz,
1H, CH ¼), 7.47–7.55 (m, 5H, ArH), 7.58 (d, J ¼ 15.6 Hz, 1H, CH ¼),
7.85 (d, J ¼ 8.4 Hz, 2H, ArH), 8.01–8.03 (m, 1H, ArH). 13C NMR
(DMSO-d6) d: 83.7, 113.3, 114.1, 127.5, 128.6, 128.9, 129.4, 129.5,
130.7, 131.9, 132.3, 133.3, 134.8, 143.6, 170.8. MS (m=z): 370 (Mþ, 10),

3054
X.-S. Wang et al.
289 (100), 254 (25), 227 (20). Anal. calcd. for C18H10BrClN2: C, 58.49; H,
2.73; N, 7.58. Found: C, 58.62; H, 2.70; N, 7.54.
Crystal Data for 4h
C36H20Br2Cl2N4; M ¼ 739.28, pale yellow block crystals, 0.28 ꢂ 0.26 ꢂ
0.12 mm, orthorhombic, space group
P
nma, a ¼ 20.900(4), b ¼
˚
3
ꢁ
˚
7.0710(11), c ¼ 10.9170 (18) A, a ¼b ¼c ¼ 90 , V ¼ 1613.4(5) A , Z ¼ 2,
Dc ¼ 1.522 gꢃcmꢀ3. F (000) ¼ 736, m (MoKa) ¼ 2.710 mmꢀ1. Intensity data
were collected on a CCD area detector with graphite monochromated
˚
MoKa radiation (k ¼ 0.71073 A) using phi and omega scans mode with
2.10ꢁ <h < 26.26ꢁ. A total of 1782 unique reflections were measured,
and 1058 reflections with I > 2r (I) were used in the refinement. Structure
solved by direct methods and expanded using Fourier techniques. The final
cycle of full-matrix least squares technique to R ¼ 0.0494 and wR ¼ 0.1146.
2-((E)-1-(4-Bromophenyl)-3-(2,4-dichlorophenyl)allylidene)malononitrile 4i
Pale yellow crystals; mp 170–172ꢁC. IR (KBr): 3072, 2224, 1607, 1578,
1527, 1485, 1468, 1388, 1336, 1317, 1213, 1187, 1148, 1103, 1069, 1050,
976, 911, 827, 777, 729 cmꢀ1
.
1H NMR (DMSO-d6) d: 7.08 (d,
J ¼ 15.6 Hz, 1H, CH ¼), 7.51–7.60 (m, 4H, ArH þCH ¼), 7.72 (d,
J ¼ 2.0 Hz, 1H, ArH), 7.85 (d, J ¼ 8.4 Hz, 2H, ArH), 8.06 (d, J ¼ 8.4 Hz,
1H, ArH). Anal. calcd. for C18H9BrCl2N2: C, 53.50; H, 2.24; N, 6.93.
Found: C, 53.51; H, 2.17; N, 6.78.
2-((E)-1-(4-Bromophenyl)-3-(2-nitrophenyl)allylidene)malononitrile 4j
Pale yellow crystals; mp 170–172ꢁC. IR (KBr): 3061, 2222, 1607, 1586,
1569, 1519, 1486, 1441, 1395, 1348, 1269, 1211, 1100, 1074, 1011, 968,
855, 829, 789, 745, 700 cmꢀ1. 1H NMR (DMSO-d6) d: 7.32 (d, J¼ 15.6 Hz,
1H, CH), 7.42 (d, J¼ 15.6 Hz, 1H, CH), 7.53 (d, J¼ 7.2 Hz, 2H, ArH),
7.69–7.73 (m, 1H, ArH), 7.82–7.88 (m, 3H, ArH), 7.98 (d, J¼ 7.6 Hz, 1H,
ArH), 8.10 (d, J¼ 8.0Hz, 1H, ArH). Anal. calcd. for C18H10BrN3O2: C,
56.86; H, 2.65; N, 11.05; Found: C, 56.80; H, 2.66; N, 10.94.
2-((E)-1-(4-Chlorophenyl)-3-(2-chlorophenyl)allylidene)malononitrile 4k
Pale yellow crystals; mp 163–165ꢁC. IR (KBr): 3062, 2220, 1604, 1565,
1
1532, 1469, 1337, 1317, 1288, 1091, 1040, 1013, 828, 769, 756 cmꢀ1. H

Synthesis of Diarylallylidenemalononitrile
3055
NMR (DMSO-d6) d: 7.17 (d, J ¼ 15.6 Hz, 1H, CH), 7.48–7.56 (m, 3H,
ArH), 7.59 (d, J ¼ 15.6 Hz, 1H, CH), 7.61 (d, J ¼ 8.4 Hz, 2H, ArH), 7.72
(d, J ¼ 8.4 Hz, 2H, ArH), 8.02–8.04 (m, 1H, ArH). Anal. calcd. for
C18H10Cl2N2: C, 66.48; H, 3.10; N, 8.61. Found: C, 66.30; H, 3.19; N, 8.65.
2-((E)-3-(2,4-Dichlorophenyl)-1-(4-methylphenyl)allylidene)
malononitrile 4l
Pale yellow crystals; mp 128–130ꢁC. IR (KBr): 3066, 3031, 2222, 1606,
1584, 1547, 1517, 1499, 1471, 1387, 1342, 1303, 1210, 1187, 1146, 1109,
1
1047, 989, 949, 858, 820, 761, 726 cmꢀ1. H NMR (DMSO-d6) d: 7.13 (d,
J ¼ 15.6Hz, 1H, CH), 7.41–7.45 (m, 4H, ArH), 7.55–7.58 (m, 2H, ArH
þCH), 7.71 (s, 1H, ArH), 8.04 (d, J ¼ 8.8 Hz, 1H, ArH). Anal. calcd. for
C19H12Cl2N2: C, 67.27; H, 3.57; N, 8.26. Found: C, 67.11; H, 3.69; N, 8.29.
2-((E)-3-(3,4-Dimethylphenyl)-1-(4-methoxylphenyl)allylidene)
malononitrile 4m
Pale yellow crystals; mp 127–128ꢁC. IR (KBr): 3015, 2968, 2943, 2218,
1604, 1593, 1524, 1493, 1460, 1442, 1416, 1382, 1342, 1298, 1237, 1205,
1
1176, 1103, 1021, 965, 845, 818 cmꢀ1. H NMR (DMSO-d6) d: 2.24 (s,
3H, CH3), 2.26 (s, 3H, CH3), 3.87 (s, 3H, CH3O), 6.93 (d, J ¼ 15.6 Hz,
1H, CH), 7.15–7.17 (m, 2H, ArH), 7.23–7.25 (m, 1H, ArH), 7.43–7.51
(m, 5H, ArH þCH). Anal. calcd. for C21H18N2O: C, 80.23; H, 5.77; N,
8.91. Found: C, 80.35; H, 5.70; N, 8.93.
2-((E)-3-(2,4-Dichlorophenyl)-1-(4-methoxylphenyl)allylidene)
malononitrile 4n
Pale yellow crystals; mp 187–188ꢁC. IR (KBr): 3052, 2221, 1604, 1583,
1497, 1471, 1346, 1309, 1267, 1181, 1103, 1024, 995, 948, 874, 836,
1
812 cmꢀ1. H NMR (DMSO-d6) d: 3.87 (s, 3H, CH3O), 7.16–7.21 (m,
3H, ArH þCH), 7.54–7.60 (m, 4H, ArH þCH), 7.75 (d, J ¼ 2.0 Hz,
1H, ArH), 8.06 (d, J ¼ 8.8 Hz, 1H, ArH). Anal. calcd. for C19H12Cl2N2O:
C, 64.24; H, 3.41; N, 7.89. Found: C, 64.20; H, 3.53; N, 7.80.
2-((E)-3-(2-Chlorophenyl)-1-(4-methoxylphenyl)allylidene)malononitrile 4o
Pale yellow crystals; mp 110–112ꢁC. IR (KBr): 3009, 2222, 1602, 1574,
1521, 1504, 1470, 1442, 1342, 1312, 1265, 1186, 1031, 1000, 953, 841,

3056
X.-S. Wang et al.
755 cmꢀ1
.
1H NMR (DMSO-d6) d: 3.87 (s, 3H, CH3O), 7.17 (d,
J ¼ 8.8 Hz, 2H, ArH), 7.26(d, J ¼ 15.6 Hz, 1H, CH), 7.48–7.51 (m, 2H,
ArH), 7.54–7.59 (m, 4H, ArH þCH), 8.01–8.03 (m, 1H, ArH). Anal.
calcd. for C19H13ClN2O: C, 71.14; H, 4.08; N, 8.73. Found: C, 71.03;
H, 4.18; N, 8.80.
2-((E)-1-(4-Methoxylphenyl)-3-(2-nitrophenyl)allylidene)malononitrile 4p
Pale yellow crystals; mp 188–190ꢁC. IR (KBr): 3084, 3004, 2972, 2839,
2223, 1602, 1569, 1518, 1439, 1420, 1345, 1292, 1254, 1210, 1177, 1103,
1
1025, 983, 857, 838, 794, 749, 704 cmꢀ1. H NMR (DMSO-d6) d: 3.87
(s, 3H, CH3O), 7.16 (d, J ¼ 8.4 Hz, 2H, ArH), 7.36 (d, J ¼ 15.6 Hz, 1H,
CH), 7.42 (d, J ¼ 15.6 Hz, 1H, CH), 7.57 (d, J ¼ 8.4 Hz, 2H, ArH),
7.70–7.71 (m, 1H, ArH), 7.85–7.89 (m, 1H, ArH), 7.98 (d, J ¼ 8.0 Hz,
1H, ArH), 8.10 (d, J ¼ 8.0 Hz, 1H, ArH). Anal. calcd. for C19H13N3O3:
C, 68.88; H, 3.95; N, 12.68. Found: C, 69.01; H, 3.87; N, 12.57.
2-((E)-3-(3,4-Dichlorophenyl)-1-(4-methoxylphenyl)allylidene)
malononitrile 4q
Pale yellow crystals; mp 161–163ꢁC. IR (KBr): 3029, 2966, 2842, 2223,
1606, 1573, 1550, 1526, 1505, 1471, 1386, 1343, 1317, 1294, 1255, 1213,
1
1179, 1135, 1105, 1030, 981, 924, 836, 815, 727, 675 cmꢀ1. H NMR
(DMSO-d6) d: 3.87 (s, 3H, CH3O), 6.99 (d, J ¼ 15.6 Hz, 1H, CH), 7.15
(d, J ¼ 8.4 Hz, 2H, ArH), 7.51 (d, J ¼ 8.4 Hz, 2H, ArH), 7.59 (d,
J ¼ 15.6 Hz, 1H, CH), 7.68–7.75 (m, 2H, ArH), 8.06 (s, 1H, ArH). Anal.
calcd. for C19H12Cl2N2O: C, 64.24; H, 3.41; N, 7.89. Found: C, 64.38; H,
3.43; N, 7.82.
2-((E)-3-(3,4-Dimethoxylphenyl)-1-(2,4-dimethylphenyl)allylidene)
malononitrile 4r
Pale yellow crystals; mp 138–140ꢁC. IR (KBr): 3002, 2966, 2933, 2837,
2218, 1611, 1591, 1574, 1518, 1461, 1439, 1418, 1342, 1302, 1284, 1241,
1
1171, 1140, 1024, 970, 858, 820, 799, 773 cmꢀ1. H NMR (DMSO-d6)
d: 2.15 (s, 3H, CH3), 2.38 (s, 3H, CH3), 3.79 (s, 3H, CH3O), 3.82 (s,
3H, CH3O), 6.71 (d, J ¼ 15.2 Hz, 1H, CH), 7.02 (d, J ¼ 8.8 Hz, 1H,
ArH), 7.14 (d, J ¼ 8.0 Hz, 1H, ArH), 7.20 (d, J ¼ 7.6 Hz, 1H, ArH),
7.25–7.30 (m, 3H, ArH), 7.46 (d, J ¼ 15.2 Hz, 1H, CH). Anal. calcd.
for C22H20N2O2: C, 76.72; H, 5.85; N, 8.13. Found: C, 76.60; H, 5.77;
N, 8.25.

Synthesis of Diarylallylidenemalononitrile
3057
2-((E)-3-(2-Chlorophenyl)-1-(2,4-dimethylphenyl)allylidene)
malononitrile 4s
Pale yellow crystals; mp 158–160ꢁC. IR (KBr): 3062, 2225, 1604, 1561,
1534, 1495, 1462, 1437, 1338, 1310, 1284, 1237, 1210, 1160, 1083, 1039,
1
963, 815, 763, 741, 726, 706 cmꢀ1. H NMR (DMSO-d6) d: 2.17 (s, 3H,
CH3), 2.37 (s, 3H, CH3), 7.02 (d, J ¼ 15.6 Hz, 1H, CH), 7.04–7.23 (m,
2H, ArH), 7.27 (s, 1H, ArH), 7.47–7.54 (m, 3H, ArH), 7.59 (d,
J ¼ 15.6 Hz, 1H, CH), 8.02–8.04 (m, 1H, ArH). Anal. calcd. for
C20H15ClN2: C, 75.35; H, 4.74; N, 8.79. Found: C, 75.30; H, 4.91; N,
8.97.
2-((E)-1-(3-ssssChlorophenyl)-3-(2-chlorophenyl)allylidene)
malononitrile 4t
Pale yellow crystals; mp 141–143ꢁC. IR (KBr): 3064, 2226, 1602, 1562,
1526, 1466, 1436, 1409, 1333, 1312, 1283, 1194, 1112, 1079, 1051, 1037,
1
888, 849, 794, 775, 722, 704, 695 cmꢀ1. H NMR (DMSO-d6) d: 7.17
(d, J ¼ 15.6 Hz, 1H, CH), 7.49–7.57 (m, 4H, ArH), 7.59 (d, J ¼ 15.6 Hz,
1H, CH), 7.65–7.75 (m, 3H, ArH), 8.04–8.05 (m, 1H, ArH). Anal. calcd.
for C18H10Cl2N2: C, 66.48; H, 3.10; N, 8.61. Found: C, 66.49; H, 3.20; N,
8.49.
2-((E)-3-(2-Chlorophenyl)-1-(4-fluorophenyl)allylidene)
malononitrile 4u
Pale yellow crystals; mp 136–138ꢁC. IR (KBr): 3051, 2223, 1603, 1562,
1532, 1466, 1340, 1285, 1238, 1210, 1159, 1094, 1043, 974, 838, 804,
763 cmꢀ1
.
1H NMR (DMSO-d6) d: 7.17 (d, J ¼ 15.6 Hz, 1H, CH),
7.47–7.54 (m, 5H, ArH), 7.59 (d, J ¼ 15.6 Hz, 1H, CH), 7.64–7.67 (m,
2H, ArH), 8.01–8.04 (m, 1H, ArH). Anal. calcd. for C18H10ClFN2: C,
70.02; H, 3.26; N, 9.07. Found: C, 69.90; H, 3.37; N, 9.00.
CONCLUSION
In conclusion, we have discovered a green and highly selective method for
the syntheses of 2-((E)-1,3-diarylallylidene)malononitriles by the reaction
of aromatic aldehyde and 2-(1-arylethylidene)malononitrile in ionic
liquid using 10 mol% malononitrile as catalyst. The noteworthy features
of this procedure are mild reaction conditions, good yield, operational

3058
X.-S. Wang et al.
simplicity, and an environmentally friendly procedure. Meanwhile,
[bmimþ] [BF4ꢀ] could be reused for several rounds without significant
loss of activity.
ACKNOWLEDGMENTS
We are grateful to the National Natural Science Foundation of China
(20802061), the Natural Science Foundation (08KJD150019), and Qing
Lan Project (08QLT001) of Jiangsu Education Committee for financial
support.
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