Green method for the synthesis of polysubstituted chromene derivatives in ionic liquids

Article abstract of DOI:10.1080/00397911.2010.528128

In this article, the same reaction of aromatic aldehyde, malononitrile, and 2-(2,3-dihydrochromen-4-ylidene)malononitrile was performed in ionic liquids of [BMIm]BF₄ and [BMIm]Br, resulting in a green synthesis of 6H-benzo[c]chromene-8,8,10(7H)

Full text of DOI:10.1080/00397911.2010.528128

Synthetic Communications1, 42: 599–607, 2012
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2010.528128
GREEN METHOD FOR THE SYNTHESIS OF
POLYSUBSTITUTED CHROMENE DERIVATIVES IN
IONIC LIQUIDS
Mei-Mei Zhang,1 Jian-Rong Wu,2 Jie Zhou,2 and
Xiang-Shan Wang1,2
1Key Laboratory for Biotechnology on Medicinal Plants of Jiangsu Province,
Xuzhou Normal University, Xuzhou Jiangsu, China
2School of Chemistry and Chemical Engineering, Xuzhou Normal University,
Xuzhou Jiangsu, China
GRAPHICAL ABSTRACT
Abstract In this article, the same reaction of aromatic aldehyde, malononitrile, and
2-(2,3-dihydrochromen-4-ylidene)malononitrile was performed in ionic liquids of
[BMIm]BF4 and [BMIm]Br, resulting in a green synthesis of 6H-benzo[c]chromene-
8,8,10(7H)-tricarbonitrile and 6H-benzo[c]chromene-8,10-dicarbonitrile derivatives in
good yields. This procedure has the advantages of good yields, one pot, and environmental
friendliness.
Keywords Chromene; ionic liquids; malononitrile; synthesis
INTRODUCTION
Polysubstituted chromene derivatives are very important heterocyclic com-
pounds that frequently exhibit a variety of biological activities.[1] These activities
include anticancer,[2] anticoagulant,[3] and fungicidal activities.[4] They are also find
applications as pigments and potential biodegradable agrochemicals. Because of
their usefulness, the synthesis of these compounds has attracted a lot of interests.[5]
Ionic liquids have attracted increasing interest in the context of green synthesis
in the past few years. They were initially introduced as alternative green reaction
media because of their unique chemical and physical properties of nonvolatility, non-
flammability, thermal stability, and controlled miscibility.[6] The possibility of recy-
cling them and their low-vapor nature also ensure their utility in environmentally
Received May 6, 2010.
Address correspondence to Xiang-Shan Wang, School of Chemistry and Chemical Engineering,
Xuzhou Normal University, Xuzhou Jiangsu 221116, China. E-mail: xswang1974@yahoo.com
599

600
M. M. ZHANG ET AL.
Scheme 1. Reaction of 1, 2, and 2-(2,3-dihydrochromen-4-ylidene)malononitrile.
friendly technologies. They have been used as solvents for a large number of organic
transformations.[7] Another feature of ioꢀnic liquidsꢀis their ꢀalterable negative ions,
such as Clꢀ; Brꢀ; BF4ꢀ; PF6ꢀ; CF3SO3 ; CF3CO2 ; HSO4 ; OHꢀ; and CH3COꢀ2 .
Some of them are acidic media, such as BFꢀ4 ; PF6ꢀ; and HSO4ꢀ, while many ionic
liquids are basic, for example, Clꢀ, Brꢀ, and OHꢀ. Sometimes, they are used
not only as a green media but also as easily recyclable catalysts for many organic
reactions.[8]
As a continuation of our research devoted to the development of new methods
for the preparation of heterocycles in environmentally benign media,[9] we recently
performed the same reaction of aromatic aldehyde, malononitrile, and
2-(2,3-dihydrochromen-4-ylidene)malononitrile in [BMIm]BF4 and [BMIm]Br
with different products obtained. Herein, we report green syntheses of 6H-
benzo[c]chromene-8,8,10(7H)-tricarbonitrile and 6H-benzo[c] chromene-8,10-
dicarbonitrile derivatives using the same reactants by changing the negative anion
to control the pH value in ionic liquids.
RESULTS AND DISCUSSION
Treatment of aromatic aldehyde
1
with malononitrile
2
and
2-(2,3-dihydrochromen-4-ylidene)malononitrile 3 in [BMIm]BF4 at room tempera-
ture produced the corresponding 9-amino-7-aryl-6H-benzo[c]chromene-8,8,10(7H)-
tricarbonitrile 4 in good yields (Scheme 1). It is an unaromatized benzo[c]chromene
moiety; we think the pH value in ionic liquid media plays a key role in the reaction.
The CNꢀ may be lost by eliminating the hydrogen atom in the adjacent carbon atom.
As our assumption, to change the negative ions in the ionic liquid from BFꢀ4 to Brꢀ,
[BMIm]Br was selected to perform the same reaction. To our delight, the design
proceeded smoothly and provided excellent yields of aromatized 9-amino-7-aryl-
6H-benzo[c]chromene-8,10-dicarbonitrile derivatives 5 at 50 ꢁC (Scheme 1).
These alterable conditions were applied for the conversion of various kinds of
aromatic aldehydes into the corresponding benzo[c]chromene analogs (Table 1,
entries 1–13). Among these analogs, the yields of 4 or 5 were not sensitive to the elec-
tronic properties of the aromatic ring in the presence of electron-withdrawing groups
(such as halide and nitro) or electron-donating groups (such as the alkoxyl group).
They all gave the desired 6H-benzo[c]chromene-8,8,10(7H)-tricarbonitrile 4 in the
acidic ionic liquid of [BMIm]BF4 (Table 1, entries 1–6), while in the basic [BMIm]Br
they yielded aromatized 6H-benzo[c]chromene-8,10-dicarbonitrile derivatives
(Table 1, entries 7–13). All the compounds were characterized by 1H NMR, infrared
(IR), and high resolution mass spectrometry (HRMS).

POLYSUBSTITUTED CHROMENE DERIVATIVES
601
Table 1. Synthetic results of 4 and 5 in ionic liquidsa
Entry
Ar
Products
Time (h)
Yields (%)b
1
2
4-NO2C6H4
2-BrC6H4
3-BrC6H4
4a
4b
4c
4d
4e
4f
10
8
93
92
90
93
85
88
87
88
88
90
93
89
90
3
7
4
3,4-(CH3O)2C6H3
3,5-(CH3O)2C6H3
2,4,5-(CH3O)3C6H2
3,5-(CH3O)2C6H3
3-BrC6H4
10
12
11
8
5
6
7
5a
5b
5c
5d
5e
5f
8
8
9
2,3-(CH3O)2C6H3
4-ClC6H4
2-ClC6H4
8
10
11
12
13
6
7
2,4-Cl2C6H3
2,3-Cl2C6H3
9
5g
8
aReaction conditions: 1 (2 mmol) 2 (0.139 g, 2.1 mmol), 2-(2,3-dihydrochromen-4-ylidene)
malononitrile (0.392 g, 2 mmol), and 2 mL [BMIm][BF4], or [BMIm]Br.
bIsolated yields.
At completion, monitored by thin-layer chromatography (TLC), the reaction
mixture was allowed to reach room temperature. A little amount of water (5 mL)
was added to the mixture, and the crude product was isolated by filtration. The water
in the filtrate was removed by distillation under reduced pressure, and the ionic
liquid in the residue was then recovered for reuse by evaporating it at 80 ꢁC for sev-
eral hours in a vacuum. Investigations using 4-nitrobenzaldehyde, 2, and 3 as model
substrates showed the successfull reuse of the recycled ionic liquid. Even in the
fourth round, the yield of the product 4a is fairly good (91%).
Although the detailed mechanism of the reaction has not been clarified, the for-
mation of benzo[c]chromene derivatives 4 and 5 can be tentatively explained by the
Scheme 2. Possible mechanism for the formation of products 4 and 5.

602
M. M. ZHANG ET AL.
pathway presented in Scheme 2. The product I may be formed first from a Knoeve-
nagel condensation of aromatic aldehyde and malononitrile. In the following step,
the Michael addition reaction between 3 and I takes place to produce intermediate
II, followed by intramolecular cyclization to form III. Then III isomerizes to give
the unaromatized benzo[c]chromenes 4. The deprotonation in basic ionic liquid fol-
lowed by the elimination of CNꢀ may take place in the last step to afford the final
aromatized 6H-benzo[c]chromene derivatives 5.
EXPERIMENTAL
Melting points were determined in open capillaries and are uncorrected. IR
spectra were recorded on a Tensor 27 spectrometer in KBr pellets. 1H NMR spectra
was obtained from a solution in dimethylsulfoxide (DMSO-d6) with Me4Si as inter-
nal standard using a Bruker-400 spectrometer. HRMS analyses were carried out
using a Bruker micro-TOF-Q-MS analyzer.
General Procedure for the Synthesis of 9-Amino-7-aryl-6H-benzo[c]-
chromene-8,8,10(7H)-tricarbonitrile 4
A dry 50-mL flask was charged with aromatic aldehyde (2.0 mmol), malononi-
trile (0.139 g, 2.1 mmol), 2-(2,3-dihydrochromen-4-ylidene)malononitrile (0.392 g,
2.0 mmol), and ionic liquid of [BMIm][BF4] (2 mL). The reaction mixture was stirred
at room temperature for 7–12 h, and then a small amount of water (5 mL) was added
to the mixture. The generated yellow solid was filtered off. The water in the filtrate
was removed by distillation under reduced pressure, and the ionic liquid in the resi-
due could be reused by evaporation at 80 ꢁC for 4 h in a vacuum. The crude yellow
products were washed with water and purified by recrystallization from EtOH and
water, then dried at 80 ꢁC for 2 h under a vacuum to give 4.
9-Amino-7-(4-nitrophenyl)-6H-benzo[c]chromene-8,8,10(7H)-tricarboni-
trile (4a). Mp 180–181 ꢁC; IR (KBr, n, cmꢀ1): 3530, 3423, 3322, 3197, 3080, 2921,
2828, 2210, 1646, 1606, 1576, 1518, 1489, 1457, 1350, 1246, 1224, 1109, 1014, 829,
1
784, 773, 713; H NMR (400 MHz, DMSO-d6, d, ppm): 4.43 (d, J ¼ 15.2 Hz, 1H,
CH2), 4.58 (d, J ¼ 15.2 Hz, 1H, CH2), 5.14 (s, 1H, CH), 6.96 (d, J ¼ 8.0 Hz, 1H,
ArH), 7.09 (t, J ¼ 7.6 Hz, 1H, ArH), 7.30 (t, J ¼ 7.2 Hz, 1H, ArH), 7.69 (t, J ¼ 8.8 Hz,
3H, ArH), 8.00 (s, 2H, NH2), 8.34 (d, J ¼ 8.8 Hz, 2H, ArH). HRMS (ESI, m=z) calcd
for C22H13N5NaO3 (M þ Naþ) 418.0916, found 418.0903.
9-Amino-7-(2-bromophenyl)-6H-benzo[c]chromene-8,8,10(7H)-tricarbo-
nitrile (4b). Mp 221–224 ꢁC; IR (KBr, n, cmꢀ1): 3385, 3321, 3207, 3065, 2923, 2847,
2216, 1657, 1607, 1588, 1489, 1470, 1458, 1376, 1282, 1246, 1218, 1112, 1025, 784,
1
766, 732; H NMR (400 MHz, DMSO-d6, d, ppm): 4.31 (d, J ¼ 15.2 Hz, 1H, CH2),
4.61 (d, J ¼ 15.6 Hz, 1H, CH2), 5.00 (s, 1H, CH), 6.95 (d, J ¼ 7.6 Hz, 1H, ArH),
7.11 (t, J ¼ 7.6 Hz, 1H, ArH), 7.30 (t, J ¼ 7.6 Hz, 1H, ArH), 7.41 (dd, J ¼ 19.2 Hz,
J0 ¼ 8.0 Hz, 2H, ArH), 7.49 (t, J ¼ 7.6 Hz, 1H, ArH), 7.68 (d, J ¼ 8.0 Hz, 1H,
ArH), 7.83 (d, J ¼ 8.0 Hz, 1H, ArH), 8.05 (s, 2H, NH2). HRMS (ESI, m=z) calcd.
for C24H13BrN4NaO (M þ Naþ) 451.0170; found 451.0192.

POLYSUBSTITUTED CHROMENE DERIVATIVES
603
9-Amino-7-(3-bromophenyl)-6H-benzo[c]chromene-8,8,10(7H)-tricarbo-
nitrile (4c). Mp 201–203 ꢁC; IR (KBr, n, cmꢀ1): 3442, 3311, 3201, 3057, 2212, 1648,
1621, 1573, 1488, 1429, 1373, 1275, 1238, 1215, 1179, 1156, 1111, 1075, 1041, 1018,
1
796, 763, 732; H NMR (400 MHz, DMSO-d6, d, ppm): 4.44 (d, J ¼ 11.6 Hz, 1H,
CH2), 4.57 (d, J ¼ 11.6 Hz, 1H, CH2), 4.90 (s, 1H, CH), 6.95 (d, J ¼ 8.0 Hz, 1H,
ArH), 7.10 (t, J ¼ 7.6 Hz, 1H, ArH), 7.30 (t, J ¼ 7.6 Hz, 1H, ArH), 7.37–7.46 (m,
2H, ArH), 7.61–7.69 (m, 3H, ArH), 7.94 (s, 2H, NH2). HRMS (ESI, m=z) calcd.
for C24H13BrN4NaO (M þ Naþ) 451.0170; found 451.0149.
9-Amino-7-(3,4-dimethoxyphenyl)-6H-benzo[c]chromene-8,8,10(7H)-tri-
carbonitrile (4d). Mp 216–218 ꢁC; IR (KBr, n, cmꢀ1): 3437, 3344, 3243, 2955, 2937,
2912, 2837, 2203, 1644, 1633, 1605, 1593, 1574, 1519, 1489, 1469, 1447, 1420, 1384,
1
1347, 1277, 1259, 1238, 1141, 1110, 1027, 781, 764; H NMR (400 MHz, DMSO-d6,
d, ppm): 3.72 (s, 3H, CH3O), 3.77 (s, 3H, CH3O), 4.45 (d, J ¼ 15.2 Hz, 1H, CH2),
4.54 (d, J ¼ 15.2 Hz, 1H, CH2), 4.78 (s, 1H, CH), 6.91–6.96 (m, 2H, ArH), 7.02 (d,
J ¼ 8.4 Hz, 2H, ArH), 7.09 (t, J ¼ 7.6 Hz, 1H, ArH), 7.28 (t, J ¼ 8.0 Hz, 1H, ArH),
7.62 (d, J ¼ 7.6 Hz, 1H, ArH), 7.90 (s, 2H, NH2). HRMS (ESI, m=z) calcd. for
C24H18N4NaO3 (M þ Naþ) 433.1477; found 433.1287.
9-Amino-7-(3,5-dimethoxyphenyl)-6H-benzo[c]chromene-8,8,10(7H)-tri-
carbonitrile (4e). Mp 216–218 ꢁC; IR (KBr, n, cmꢀ1): 3274, 3029, 3015, 2975, 2930,
2887, 2837, 2218, 1609, 1590, 1574, 1561, 1481, 1468, 1453, 1431, 1365, 1336, 1309,
1220, 1205, 1158, 1130, 1075, 1062, 1024, 887, 828, 762; 1H NMR (400 MHz, CDCl3,
d, ppm): 3.05 (d, J ¼ 11.2 Hz, 1H, CH2), 3.84–3.87 (m, 1H, CH2), 3.33 (s, 6H,
2CH3O), 4.27–4.31 (m, 1H, CH), 6.57–6.66 (m, 3H, ArH), 6.97 (d, J ¼ 8.4 Hz, 1H,
ArH), 7.11–7.13 (m, 1H, ArH), 7.51–7.55 (m, 1H, ArH), 8.39 (d, J ¼ 8.4 Hz, 1H,
NH2), 10.82 (s, 1H, NH2). HRMS (ESI, m=z) calcd. for C24H18N4NaO3 (M þ Naþ)
433.1477; found 433.1294.
9-Amino-7-(2,4,5-trimethoxyphenyl)-6H-benzo[c]chromene-8,8,10(7H)-
tricarbonitrile (4f). Mp 216–218 ꢁC; IR (KBr, n, cmꢀ1): 3443, 3422, 2998, 2949,
2927, 2224, 1656, 1608, 1581, 1528, 1512, 1471, 1453, 1438, 1299, 1276, 1230,
1
1210, 1048, 1026, 826, 764; H NMR (400 MHz, DMSO-d6, d, ppm): 3.15–3.26
(m, 1H, CH2), 3.44–3.62 (m, 1H, CH2), 3.74 (s, 3H, CH3O), 3.79 (s, 3H, CH3O),
3.82 (s, 3H, CH3O), 3.94–3.98 (m, 1H, CH), 6.75 (s, 1H, ArH), 6.95 (d, J ¼ 8.4 Hz,
1H, ArH), 7.07–7.11 (m, 2H, ArH), 7.25 (s, 1H, ArH), 7.42–7.47 (m, 1H, ArH),
7.92–7.94 (m, 1H, NH2). HRMS (ESI, m=z) calcd. for C25H20N4NaO4 (M þ Naþ)
463.1382; found 463.1367.
General Procedure for the Synthesis of 9-Amino-7-aryl-6H-benzo[c]-
chromene-8,10-dicarbonitrile derivatives 5
A dry 50-mL flask was charged with aromatic aldehyde (2.0 mmol), malononi-
trile (0.139 g, 2.1 mmol), 2-(2,3-dihydrochromen-4-ylidene)malononitrile (0.392 g,
2.0 mmol), and ionic liquid of [BMIm]Br (2 mL). The reaction mixture was stirred
at 50 ꢁC for 6–9 h and then cooled down to room temperature. A small amount of
water (5 mL) was added to the mixture, and the generated yellow solid was filtered
off. The water in the filtrate was removed by distillation under reduced pressure,

604
M. M. ZHANG ET AL.
and the ionic liquid in the residue could be reused by being evaporated at 80 ꢁC for
4 h in a vacuum. The crude yellow products were washed with water, purified by
recrystallization from DMF and water, and then dried at 80 ꢁC for 2 h under vacuum
to give 5.
9-Amino-7-(3,5-dimethoxyphenyl)-6H-benzo[c]chromene-8,10-dicarbo-
nitrile (5a). Mp 281–282 ꢁC; IR (KBr, n, cmꢀ1): 3363, 3341, 3241, 2942, 2844, 2216,
1641, 1608, 1562, 1488, 1452, 1434, 1372, 1300, 1261, 1206, 1166, 1068, 1000, 944,
1
835, 760; H NMR (400 MHz, DMSO-d6, d, ppm): 3.79 (s, 6H, 2CH3O), 4.65 (s,
2H, CH2), 6.55 (d, J ¼ 2.0 Hz, 2H, NH2), 6.65 (t, J ¼ 2.0 Hz, 1H, ArH), 6.80 (s,
2H, ArH), 7.09 (d, J ¼ 7.6 Hz, 1H, ArH), 7.23 (t, J ¼ 7.2 Hz, 1H, ArH), 7.48 (t,
J ¼ 8.4 Hz, 1H, ArH), 8.31 (d, J ¼ 8.0 Hz, 1H, ArH). HRMS (ESI, m=z) calcd. for
C23H18N3O3 (M þ Hþ) 384.1384; found 384.1327.
9-Amino-7-(3-bromophenyl)-6H-benzo[c]chromene-8,10-dicarbonitrile
(5b). Mp 254–255 ꢁC; IR (KBr, n, cmꢀ1): 3461, 3360, 3243, 2850, 2218, 1666, 1643,
1607, 1586, 1570, 1553, 1494, 1468, 1436, 1386, 1295, 1265, 1228, 1155, 1077, 1013,
985, 833, 809, 757, 741; 1H NMR (400 MHz, DMSO-d6, d, ppm): 4.62 (s, 2H, CH2),
6.86 (s, 2H, NH2), 7.10 (d, J ¼ 8.0 Hz, 1H, ArH), 7.24 (t, J ¼ 7.6 Hz, 1H, ArH), 7.39
(d, J ¼ 8.4 Hz, 2H, ArH), 7.49 (t, J ¼ 7.2 Hz, 1H, ArH), 7.77 (d, J ¼ 8.0 Hz, 2H,
ArH), 8.31 (d, J ¼ 7.6 Hz, 1H, ArH). HRMS (ESI, m=z) calcd. for C21H12BrN3ONa
(M þ Naþ) 424.0061; found 424.0059.
9-Amino-7-(2,3-dimethoxyphenyl)-6H-benzo[c]chromene-8,10-dicarbo-
nitrile (5c). Mp 286–288 ꢁC; IR (KBr, n, cmꢀ1): 3465, 3329, 3227, 2983, 2930, 2842,
2207, 1631, 1607, 1583, 1562, 1474, 1432, 1369, 1297, 1266, 1211, 1159, 1118, 1083,
1
1003, 942, 862, 802, 758; H NMR (400 MHz, DMSO-d6, d, ppm): 3.60 (s, 3H,
CH3O), 3.89 (s, 3H, CH3O), 4.50 (dd, J ¼ 18.8 Hz, J0 ¼ 13.2 Hz, 2H, CH2), 6.80 (s,
2H, NH2), 6.82–6.84 (m, 1H, ArH), 7.09 (d, J ¼ 8.0 Hz, 1H, ArH), 7.22–7.25 (m,
3H, ArH), 7.48 (t, J ¼ 7.2 Hz, 1H, ArH), 8.35 (d, J ¼ 7.6 Hz, 1H, ArH). HRMS
(ESI, m=z) calcd. for C23H18N3O3 (M þ Hþ) 384.1384; found 384.1340.
9-Amino-7-(4-chlorophenyl)-6H-benzo[c]chromene-8,10-dicarbonitrile
(5d). Mp 245–246 ꢁC; IR (KBr, n, cmꢀ1): 3467, 3356, 3246, 2852, 2219, 1645, 1608,
1586, 1555, 1498, 1437, 1362, 1295, 1265, 1228, 1094, 1017, 986, 838, 810, 754; H
1
NMR (400 MHz, DMSO-d6, d, ppm): 4.61 (s, 2H, CH2), 6.85 (s, 2H, NH2), 7.10
(d, J ¼ 8.0 Hz, 1H, ArH), 7.24 (t, J ¼ 7.6 Hz, 1H, ArH), 7.44–7.50 (m, 3H, ArH),
7.63 (d, J ¼ 8.4 Hz, 2H, ArH), 8.31 (d, J ¼ 8.0 Hz, 1H, ArH). HRMS (ESI, m=z)
calcd. for C21H12ClN3ONa (M þ Naþ) 380.0567; found 380.0569.
9-Amino-7-(2-chlorophenyl)-6H-benzo[c]chromene-8,10-dicarbonitrile
(5e). Mp 280–282 ꢁC; IR (KBr, n, cmꢀ1): 3466, 3353, 3242, 2848, 2214, 1641, 1608,
1586, 1557, 1491, 1451, 1368, 1300, 1275, 1226, 1160, 1121, 1047, 985, 948, 878, 812,
1
762, 744; H NMR (400 MHz, DMSO-d6, d, ppm): 4.45 (d, J ¼ 13.2 Hz, 1H, CH2),
4.51 (d, J ¼ 13.2 Hz, 1H, CH2), 6.91 (s, 2H, NH2), 7.10 (d, J ¼ 8.0 Hz, 1H, ArH),
7.24 (t, J ¼ 16.0 Hz, 1H, ArH), 7.46–7.61 (m, 4H, ArH), 7.71 (d, J ¼ 8.0 Hz, 1H,
ArH), 8.36 (d, J ¼ 8.0 Hz, 1H, ArH). HRMS (ESI, m=z) calcd. for C21H12ClN3ONa
(M þ Naþ) 380.0567; found 380.0571.

POLYSUBSTITUTED CHROMENE DERIVATIVES
605
9-Amino-7-(2,4-dichlorophenyl)-6H-benzo[c]chromene-8,10-dicarbonit-
rile (5f). Mp 245–246 ꢁC; IR (KBr, n, cmꢀ1): 3456, 3351, 3243, 3185, 2221, 1671,
1640, 1607, 1588, 1563, 1491, 1434, 1385, 1301, 1262, 1225, 1104, 1061, 1031, 986,
1
820, 763, 733; H NMR (400 MHz, DMSO-d6, d, ppm): 4.47 (d, J ¼ 13.2 Hz, 1H,
CH2), 4.53 (d, J ¼ 13.2 Hz, 1H, CH2), 6.97 (s, 2H, NH2), 7.10 (d, J ¼ 8.0 Hz, 1H,
ArH), 7.24 (t, J ¼ 7.6 Hz, 1H, ArH), 7.48–7.54 (m, 2H, ArH), 7.65 (d, J ¼ 8.4 Hz,
1H, ArH), 7.93 (d, J ¼ 8.0 Hz, 1H, ArH), 8.35 (d, J ¼ 8.0 Hz, 1H, ArH). HRMS
(ESI, m=z) calcd. for C21H11Cl2N3ONa (M þ Naþ) 414.0177; found 414.0178.
9-Amino-7-(2,3-dichlorophenyl)-6H-benzo[c]chromene-8,10-dicarbonit-
rile (5g). Mp > 295 ꢁC; IR (KBr, n, cmꢀ1): 3386, 2850, 2211, 1626, 1606, 1584, 1557,
1489, 1432, 1406, 1364, 1302, 1278, 1231, 1186, 1156, 1105, 1047, 925, 819, 806, 768,
1
742; H NMR (400 MHz, DMSO-d6, d, ppm): 4.47 (d, J ¼ 13.2 Hz, 1H, CH2), 4.53
(d, J ¼ 13.2 Hz, 1H, CH2), 6.98 (s, 2H, NH2), 7.10 (d, J ¼ 8.0 Hz, 1H, ArH), 7.25
(t, J ¼ 7.6 Hz, 1H, ArH), 7.47–7.52 (m, 2H, ArH), 7.57 (t, J ¼ 8.0 Hz, 1H, ArH),
7.85 (d, J ¼ 8.0 Hz, 1H, ArH), 8.36 (d, J ¼ 7.2 Hz, 1H, ArH). HRMS (ESI, m=z)
calcd. for C21H12Cl2N3O (M þ Hþ) 392.0357; found 392.0365.
CONCLUSION
In summary, this article describes an efficient and green method for the
synthesis of polysubstituted chromene derivatives in ionic liquids. The structure of
all the obtained substances has been characterized by spectral methods including
1
IR, H NMR and HRMS. This procedure has the advantages of good yields, one
pot, and environmental friendliness.
ACKNOWLEDGMENTS
We are grateful to the National Natural Science Foundation of China
(20802061), the Natural Science Foundation (08KJD150019), and the Qing Lan
Project (08QLT001) of Jiangsu Education Committee for financial support.
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