An improved procedure for the three-component synthesis of benzo[g]chromene derivatives using basic ionic liquid

Article abstract of DOI:10.1002/jhet.747

A basic ionic liquid, 1-butyl-3-methyl imidazolium hydroxide ([bmim]OH), efficiently promotes a one-pot, three-component condensation of aromatic aldehydes, malononitrile or ethyl cyanoacetate, and 2-hydroxy-1,4-naphthoquinone to produce 4-aryl-5,10-dihyd

Full text of DOI:10.1002/jhet.747

1264
An Improved Procedure for the Three-Component Synthesis of
Benzo[g]chromene Derivatives Using Basic Ionic Liquid
Vol 48
Yi Yu, Hongyun Guo,* and Xiaojun Li
College of Chemical Engineering and Materials, Zhejiang University of Technology, Hangzhou
310014, People’s Republic of China
*E-mail: guohy63@163.com
Received July 21, 2010
DOI 10.1002/jhet.747
Published online 27 July 2011 in Wiley Online Library (wileyonlinelibrary.com).
A basic ionic liquid, 1-butyl-3-methyl imidazolium hydroxide ([bmim]OH), efficiently promotes a
one-pot, three-component condensation of aromatic aldehydes, malononitrile or ethyl cyanoacetate, and
2-hydroxy-1,4-naphthoquinone to produce 4-aryl-5,10-dihydro-4H-benzo[g]chromene-5,10-dione deriva-
tives in high yields at room temperature. This reaction does not involve any hazardous organic solvent
and toxic catalyst. The ionic liquid is recovered and recycled for subsequent reactions. Moreover, this
protocol has the advantages of easy work-up, short reaction time, high yields, and environmentally be-
nign procedure compared with the reported methods.
J. Heterocyclic Chem., 48, 1264 (2011).
INTRODUCTION
To the best of our knowledge, only few methods are
available for the preparation of 4-aryl-5,10-dihydro-4H-
benzo[g]chromene-5,10-dione derivatives [11–14], how-
ever, these methods have various drawbacks: reactions
require a long time, cannot be carried out one-step oper-
ation, harsh reaction conditions, high temperature, and
nonrecyclability. Therefore, it is desirable to develop a
more efficient and a general method for the synthesis of
4H-benzo[g]chromene derivatives.
Multicomponent reactions (MCRs) are a powerful
method for the synthesis of organic compounds, as the
products are formed in a single step, and diversity can
be achieved by simply varying each component [15].
Because of their easy operations and good results,
MCRs have attracted much attention [16,17].
Naturally occurring naphthoquinones comprise an im-
portant class of natural products with a wide range of
biological activity [1] arising from their capability to
cause DNA modification. Among the structurally diverse
naphthoquinone natural products, lapachol (a, Fig. 1)
and several 1,4- and 1,2-naphthoquinones are associated
with diverse biological activities [2] and are components
of antibacterial, fungicidal [3], antimalarial [4], trypano-
cidal, antiparasitic [5], and antitumoral [6] agents.
One of the most important lapachol derivatives with
antitumoral activity is a-lapachone (b, Fig. 1). Struc-
ture–activity relationship studies in lapachones have
shown that the modification to the C-ring [7] leads to
significant changes in bioactivities, which are important
in searching for possible lead compounds with more
potent pharmaceutical activity and less toxicity. On the
basis of biological properties, 1,4- and 1,2-naphthoqui-
nones are considered privileged structures in medicinal
chemistry [8], with the 1,4-naphthoquinones having
great cancer-preventing potential [9]. In addition, more
recent investigations have shown that a-lapachone is an
effective DNA topoisomerase II inhibitor and is a poten-
tial lead compound for the development of drugs for the
treatment of multidrug resistant cell lines with low
expressions of topoisomerase II [10].
Our recent interest has been in the development of
new synthetic methods on using ionic liquids as reaction
media and catalyst [18]. Herein, we would like to report
a highly efficient, convenient, and facile method for the
synthesis of 4-aryl-5,10-dihydro-4H-benzo[g]chromene-
5,10-dione derivatives in the presence of basic ionic liq-
uid [bmim]OH as catalyst at room temperature.
RESULTS AND DISCUSSION
Initially, the three-component reaction of benzalde-
hyde (1a, 1 mmol), malononitrile (2, 1 mmol), and 2-
C
V
2011 HeteroCorporation

November 2011 An Improved Procedure for the Three-Component Synthesis of Benzo[g]chromene
Derivatives Using Basic Ionic Liquid
1265
Table 2
Synthesis of 4H-benzo[g]chromene derivatives 4 using [bmim]OH as
catalyst in ethanol.
Time Yield
Products (h) (%)
Entry
Ar
X
1
2
C6H5A
CN
CN
CN
CN
CN
CN
CN
CN
4a
4b
4c
4d
4e
4f
4g
4h
4i
4j
4k
4l
4m
4n
1.0
0.8
2.0
0.8
1.5
2.0
0.6
0.9
2.0
1.0
0.7
1.0
2.0
3.0
91
92
80
88
79
81
93
89
78
85
88
82
78
70
4-ClAC6H4A
4-MeOAC6H4A
4-FAC6H4A
4-OHAC6H4A
4-CH3AC6H4A
4-NO2AC6H4A
3-BrAC6H4A
3
4
Figure 1. Examples of lapachol derivatives.
5
6
hydroxy-1,4-naphthoquinone (3, 1 mmol) was carried
out in different solvents in the presence of [bmim]OH
(10 mol%) at room temperature. As illustrated in Table
1, ethanol was preferred as the optimal solvent. More-
over, we found that the yield of this reaction was
affected by the temperature. When the temperature was
increased from 40 to 80ꢀC, the yield of product 4a was
decreased from 88 to 52% (Table 1, entries 7–9). We
believe that low reaction temperature in this reaction
suppress the formation of these side products, hence,
yield of the product increases. Therefore, the best tem-
perature for the reaction was room temperature.
7
8
9
4-OHA3-OCH3AC6H3A CN
10
11
12
13
14
2-ClAC6H4A
2,4-Cl2AC6H3A
2-NO2AC6H4A
4-ClAC6H4A
CN
CN
CN
COOEt
COOEt
4-CH3AC6H4A
be due to the less activity of ethyl caynoacetate than
malononitrile. However, when the aliphatic aldehyde was
applied to this reaction, no expected product was obtained,
we attribute this to the slow formation and unstable nature
of the alkylidenemalonitrile formed from the aliphatic
aldehydes examined. In a further study, alkylidenemaloni-
trile and 2-hydroxy-1,4-naphthoquinone was used in the
same conditions, no desired product was obtained, it may
be due to electronic effect. In this study, all the products
Based on the optimized reaction conditions, a series of
4-aryl-5,10-dihydro-4H-benzo[g]chromene-5,10-dione
derivatives were synthesized. The results were summar-
ized in Table 2, show that the three-component reaction
in the presence of 10 mol% [bmim]OH at room tempera-
ture gave the corresponding products in moderate to good
yields. It is obvious that this protocol could be applied to
various aromatic aldehydes with electron-withdrawing
groups or electron-donating groups. Besides, the results
suggest that the substrates bearing electron-withdrawing
groups have higher reactivity (higher yields and shorter
reaction time) than those bearing electron-donating
groups. So, it is concluded that the electronic nature of
the substituents on aldehydes has some effect on this reac-
tion. These three-component condensation reactions also
proceeded with ethyl caynoacetate (Table 2, entries 13–
14), in these cases, the reaction times are longer. It may
1
were characterized by mp, IR, H NMR, 13C NMR, and
elemental analyses.
As a green solvent or catalyst, the recovery and reuse of
ionic liquid are very important in green synthetic process.
Therefore, we studied on the reuse of [bmim]OH through
model reaction. As shown in Table 3, the ionic liquid [bmi-
m]OH could be successively recovered and reused for four
times without remarkable loss in the catalytic activity.
A reasonable mechanism for the formation of the
product 4 is outlined in Scheme 2. The reaction occurs
via initial formation of benzylidenemalononitrile in
quantitative yield by the Knoevenagel addition of malo-
nonitrile 2 to the aldehyde 1 and followed by loss of
water molecules. Subsequently, presumably involving
the ortho C-alkylation of 2-hydroxy-1,4-naphthoquinone
by reaction with the electrophilic C¼¼C double bond and
the nucleophilic addition of the OH group the CN moi-
ety producing the final benzo[g]chromene 4.
Table 1
Reaction conditions optimization for the synthesis of 4a.
Temperature
(ꢀC)
Time
(h)
Yield
(%)
Entry
Solvent
1
2
3
4
5
6
7
8
9
CHCl3
CH3CN
DMF
CH3OH
H2O
C2H5OH
C2H5OH
C2H5OH
C2H5OH
r.t.
r.t.
r.t.
r.t.
r.t.
r.t.
40
60
80
2
2
2
2
2
2
6
6
6
56
90
CONCLUSIONS
85
77
In summary, the highly functionalized 4H-benzo[g]-
chromene derivatives are of intense attention because of
their potential for biological activities, and thus an effi-
cient procedure for their synthesis is of high importance.
The present procedure using a basic ionic liquid,
Trace
91
88
79
52
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

1266
Y. Yu, H. Guo, and X. Li
Vol 48
Table 3
Studies on the reuse of [bmim]OH in the preparation of 4a.
128.5, 130.0, 130.9, 131.1, 131.8, 134.1, 134.5, 143.1, 149.0,
158.4, 177.1, 182.5. Anal. calcd. For C20H11ClN2O3: C, 66.22;
H, 3.06; N, 7.72. Found: C, 66.15; H, 3.01; N, 7.84.
2-Amino-4-(4-methoxyphenyl)-5,10-dioxo-5,10-dihydro-4H-
benzo[g]chromene-3-carbonitrile (4c). This compound was
obtained as orange powder with mp 244ꢁ246ꢀC (Lit. [11]
247ꢁ248ꢀC); IR vmax (KBr): 3406, 3333, 2199, 1668, 1596,
Round
1
2
3
4
5
Yield (%)
91
89
90
87
75
1462, 1331, 1244, 1204 cmꢁ1 1H NMR (DMSO-d6):d 3.71
;
[bmim]OH, in place of conventional bases provides a
selective, high yielding one-pot synthesis of highly func-
tionalized 4H-benzo[g]chromene through a three-compo-
nent condensation process. The other advantages of this
procedure are the use of no hazardous organic solvent in
the reaction and the reusability of ionic liquids.
(3H, s, OCH3), 4.56 (1H, s, CH), 6.84ꢁ8.05 (10H, m, ArH
and NH2); 13C NMR (DMSO-d6): d 35.8, 55.8, 58.0, 114.1,
119.5, 122.2, 125.8, 126.1, 128.9, 130.7, 131.2, 134.1, 134.5,
136.0, 148.6, 158.3, 177.0, 182.7. Anal. Calcd for
C21H14N2O4: C, 70.39; H, 3.94; N, 7.82; Found: C, 70.31; H,
3.98; N, 7.90.
2-Amino-4-(4-fluorophenyl)-5,10-dioxo-5,10-dihydro-4H-ben-
zo[g]chromene-3-carbonitrile (4d). This compound was
obtained as orange powder with mp 290ꢁ292ꢀC (Lit. [12]
286ꢁ288ꢀC); IR vmax (KBr): 3420, 3189, 2205, 1668, 1600,
EXPERIMENTAL
1
1509, 1411, 1363, 1245, 1205 cmꢁ1; H NMR (DMSO-d6): d
4.64 (1H, s, CH), 7.11ꢁ8.06 (10H, m, ArH and NH2); 13C
NMR (DMSO-d6): d 35.8, 57.3, 115.1, 119.2, 121.6, 125.7,
126.0, 129.6, 129.7, 130.6, 131.0, 134.1, 134.5, 139.7, 148.9,
158.3, 176.8, 182.5. Anal. Calcd for C20H11FN2O3: C, 69.36;
H, 3.20; N, 8.09; Found: C, 69.28; H, 3.25; N, 8.12.
Melting points were determined with a X-4 microscopic
melting-point apparatus and were uncorrected. IR spectra were
1
recorded on a NEXUS 670 spectrometer in KBr. H NMR and
13C NMR spectra were measured on a BRUKER AVANCE-II
500-MHz spectrometer using TMS as an internal standard and
DMSO-d6 as solvent. Elemental analyses were performed on
FLASH EA 1112 elemental analyzer.
2-Amino-4-(4-hydroxyphenyl)-5,10-dioxo-5,10-dihydro-
4H-benzo[g]chromene-3-carbonitrile (4e). This compound
was obtained as orange powder with mp 255ꢁ257ꢀC (Lit. [11]
258ꢁ260ꢀC); IR vmax (KBr): 3403, 3195, 2203, 1670, 1610,
The synthesis of this task-specific ionic liquid has been car-
ried out from a similar method in the literature [19]. The ionic
liquid was formed quantitatively and in high purity as assessed
by 1H NMR. All other chemicals (AR grade) were commer-
cially available and used without further purification.
General procedure for the synthesis of 4H-benzo[g]chro-
mene derivatives 4. The mixture of the aromatic aldehyde 1
(1 mmol), malononitrile or ethyl cyanoacetate 2 (1 mmol), 2-
1
1594, 1513, 1404, 1364, 1244, 1207 cmꢁ1; H NMR (DMSO-
d6):d 4.50 (1H, s, CH), 6.66ꢁ8.05 (10H, m, ArH and NH2),
9.35 (1H, s, OH); 13C NMR (DMSO-d6): d 35.8, 57.9, 115.2,
119.5, 122.4, 125.8, 126.2, 128.4, 129.0, 130.5, 131.1, 134.1,
134.6, 148.5, 156.4, 158.3, 177.0, 182.8. Anal. Calcd for
C20H12N2O4: C, 69.76; H, 3.51; N, 8.14; Found: C, 69.82; H,
3.55; N, 8.16.
hydroxy-1,4-naphthoquinone
3 (1 mmol), [bmim]OH (0.1
mmol) in EtOH (5 mL) was stirred at room temperature for
the appropriate time (monitored by thin-layer chromatogra-
phy). After completion of the reaction, the result mixture was
cooled to room temperature and poured into 10 mL of water.
The solid product was collected by filtration and recrystallized
from ethanol to give the pure compound 4. The filtrate was
extracted with diethyl ether several times to remove unreacted
starting materials and other organic contaminations. Then, the
water was evaporated under reduced pressure and dried to
recover the ionic liquid for subsequent use.
2-Amino-5,10-dioxo-4-p-tolyl-5,10-dihydro-4H-benzo[g]-
chromene-3-carbonitrile (4f). This compound was obtained as
orange powder with mp 246ꢁ248ꢀC (Lit. [11] 242ꢁ244ꢀC); IR
vmax (KBr): 3411, 3325, 3188, 2204, 1669, 1634, 1595, 1514,
1407, 1362, 1242, 1201 cmꢁ1 1H NMR (DMSO-d6): d 2.24
;
(3H, s, CH3), 4.56 (1H, s, CH), 7.09ꢁ8.05 (10H, m, ArH and
NH2); 13C NMR (DMSO-d6): d 20.5, 36.0, 57.5, 119.2, 122.1,
125.7, 126.0, 127.5, 129.0, 130.5, 131.0, 134.0, 134.5, 136.2,
140.6, 148.7, 158.2, 176.8, 182.5. Anal. Calcd for C21H14N2O3:
C, 73.68; H, 4.12; N, 8.18; Found: C, 73.59; H, 4.17; N, 8.12.
2-Amino-4-(4-nitrophenyl)-5,10-dioxo-5,10-dihydro-4H-
benzo[g]chromene-3-carbonitrile (4g). This compound was
obtained as orange powder with mp 236ꢁ238ꢀC (Lit. [11]
234ꢁ235ꢀC); IR vmax (KBr): 3439, 3401, 3332, 2202, 1668,
2-Amino-5,10-dioxo-4-phenyl-5,10-dihydro-4H-benzo[g]chro-
mene-3-carbonitrile (4a). This compound was obtained as or-
ange powder with mp 260ꢁ261ꢀC (Lit. [11] 261ꢁ262ꢀC); IR
vmax (KBr): 3401, 3325, 3193, 2199, 1670, 1601, 1405, 1365,
1245, 1205 cmꢁ1 1H NMR (DMSO-d6): d 4.61 (1H, s, CH),
;
1634, 1593, 1520, 1407, 1350, 1245, 1206 cmꢁ1 1H NMR
;
7.22ꢁ8.07 (11H, m, ArH, and NH2); 13C NMR (DMSO-d6): d
36.5, 57.5, 119.3, 122.1, 125.8, 126.0, 127.1, 127.8, 128.9,
130.7, 131.0, 134.2, 134.5, 143.8, 149.1, 158.6, 177.0, 182.8.
Anal. calcd. For C20H12N2O3: C, 73.16; H, 3.68; N, 8.53.
Found: C, 73.08; H, 3.62; N, 8.60.
(DMSO-d6):d 4.82 (1H, s, CH), 7.48ꢁ8.18 (10H, m, ArH and
NH2); 13C NMR (DMSO-d6): d 36.2, 56.4, 118.9, 120.3,
Scheme 1
2-Amino-4-(4-chlorophenyl)-5,10-dioxo-5,10-dihydro-4H-ben-
zo[g]chromene-3-carbonitrile (4b). This compound was
obtained as orange powder with mp 250ꢁ252ꢀC (Lit. [11]
249ꢁ252ꢀC); IR vmax (KBr): 3410, 3331, 3194, 2203, 1668,
1
1595, 1411, 1363, 1244, 1205 cmꢁ1; H NMR (DMSO-d6): d
4.65 (1H, s, CH), 7.37ꢁ8.07 (10H, m, ArH and NH2); 13C
NMR (DMSO-d6): d 36.0, 57.1, 119.5, 121.2, 125.8, 126.1,
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

November 2011 An Improved Procedure for the Three-Component Synthesis of Benzo[g]chromene
Derivatives Using Basic Ionic Liquid
1267
Scheme 2
122.0, 122.3, 125.6, 126.0, 130.0, 130.6, 130.8, 134.0, 134.3,
134.7, 145.7, 148.0, 149.2, 158.3, 176.7, 182.6. Anal. Calcd
for C20H11N3O5: C, 64.35; H, 2.97; N, 11.26; Found: C,
64.28; H, 2.95; N, 11.32.
130.8, 131.9, 132.2, 132.9, 134.1, 134.5, 140.1, 149.5, 158.3,
176.6, 182.3. Anal. Calcd for C20H10Cl2N2O3: C, 60.48; H,
2.54; N, 7.05; Found: C, 60.37; H, 2.59; N, 7.09.
2-Amino-4-(2-nitrophenyl)-5,10-dioxo-5,10-dihydro-4H-ben-
zo[g]chromene-3-carbonitrile (4l). This compound was
obtained as orange powder with mp 242ꢁ244ꢀC; IR vmax
(KBr): 3431, 3338, 3218, 2205, 1667, 1634, 1592, 1361, 1248,
2-Amino-4-(3-bromophenyl)-5,10-dioxo-5,10-dihydro-4H-
benzo[g]chromene-3-carbonitrile (4h). This compound was
obtained as orange powder with mp 257ꢁ258ꢀC (Lit. [11]
259ꢁ260ꢀC); IR vmax (KBr): 3408, 3332, 3192, 2200, 1654,
1199 cmꢁ1
;
1H NMR (DMSO-d6): d 5.39 (1H, s, CH),
1634, 1593, 1406, 1364, 1246, 1206 cmꢁ1
;
1H NMR (DMSO-
7.46ꢁ8.05 (10H, m, ArH and NH2); 13C NMR (DMSO-d6): d
31.0, 55.8, 118.6, 121.2, 124.0, 125.8, 126.0, 128.4, 130.6,
130.7, 131.3, 133.7, 134.2, 134.6, 137.8, 148.5, 149.0, 158.8,
176.7, 182.6. Anal. Calcd for C20H11N3O5: C, 64.35; H, 2.97;
N, 11.26; Found: C, 64.25; H, 2.91; N, 11.30.
d6): d 4.64 (1H, s, CH), 7.26ꢁ8.06 (10H, m, ArH and NH2); 13C
NMR (DMSO-d6): d 36.2, 57.0, 119.1, 120.8, 121.8, 125.7,
126.1, 127.0, 130.0, 130.3, 130.6, 130.9, 134.1, 134.4, 146.3,
149.2, 158.3, 176.7, 182.6. Anal. Calcd for C20H11BrN2O3: C,
58.99; H, 2.72; N, 6.88; Found: C, 58.88; H, 2.76; N, 6.80.
2-Amino-4-(4-hydroxy-3-methoxyphenyl)-5,10-dioxo-5,10-
dihydro-4H-benzo[g]chromene-3-carbonitrile (4i). This com-
pound was obtained as orange powder with mp 243ꢁ245ꢀC;
IR vmax (KBr): 3515, 3398, 3334, 3199, 2202, 1668, 1594,
Ethyl2-Amino-4-(4-chlorophenyl)-5,10-dioxo-5,10-dihydro-
4H-benzo[g]chromene-3-carbonitrile (4m). This compound
was obtained as orange powder with mp 189ꢁ191ꢀC; IR vmax
(KBr): 3463, 3419, 3307, 2983, 1681, 1657, 1612, 1519, 1275,
1
1196 cmꢁ1; H NMR (DMSO-d6): d 1.11 (3H, t, J ¼ 7.0 Hz,
1514, 1363, 1245, 1205 cmꢁ1
;
1H NMR (DMSO-d6): d 3.73
CH3), 3.98 (2H, q, J ¼ 7.0 Hz, CH2), 4.88 (1H, s, CH),
7.29ꢁ8.05 (10H, m, ArH and NH2); 13C NMR (DMSO-d6): d
13.5, 34.1, 59.0, 76.1, 124.4, 125.8, 127.9, 128.3, 129.4, 130.0,
130.3, 130.6, 131.0, 132.4, 134.0, 134.4, 143.9, 148.6, 158.9,
167.5, 176.9, 182.7. Anal. Calcd for C22H16ClNO5: C, 64.48;
H, 3.94; N, 3.42; Found: C, 64.35; H, 3.89; N, 3.46.
(3H, s, OCH3), 4.51 (1H, s, CH), 6.65ꢁ8.05 (9H, m, ArH and
NH2), 8.91 (1H, s, OH); 13C NMR (DMSO-d6): d 35.9, 55.7,
57.8, 112.0, 115.4, 119.4, 120.1, 122.2, 125.7, 125.9, 130.5,
131.0, 134.0, 134.4, 134.5, 145.7, 147.4, 148.4, 158.2, 176.9,
182.6. Anal. Calcd for C21H14N2O5: C, 67.38; H, 3.77; N,
7.48; Found: C, 67.28; H, 3.79; N, 7.53.
2-Amino-4-(2-chlorophenyl)-5,10-dioxo-5,10-dihydro-4H-ben-
zo[g]chromene-3-carbonitrile (4j). This compound was obtained
as orange powder with mp 240ꢁ242ꢀC (Lit. [11] 236ꢁ239ꢀC);
IR vmax (KBr): 3434, 3329, 3215, 2192, 1664, 1636, 1595, 1365,
Ethyl 2-Amino-5,10-dioxo-4-p-tolyl-5,10-dihydro-4H-ben-
zo[g]chromene-3-carbonitrile (4n). This compound was
obtained as orange powder with mp 211ꢁ214ꢀC; IR vmax (KBr):
3465, 3315, 2991, 2923, 1679, 1661, 1612, 1507, 1273, 1194
1
cmꢁ1; H NMR (DMSO-d6): d 1.12 (3H, t, J ¼ 7.0 Hz, CH3),
1246, 1202 cmꢁ1
;
1H NMR (DMSO-d6): d 5.15 (1H, s, CH),
2.21 (3H, s, CH3), 3.99 (2H, q, J ¼ 7.0 Hz, CH2), 4.87 (1H, s,
CH), 7.03ꢁ8.05 (10H, m, ArH and NH2); 13C NMR (DMSO-
d6): d 13.5, 20.5, 34.0, 59.0, 76.6, 125.3, 125.8, 126.0, 127.9,
128.6, 129.0, 130.1, 130.5, 131.0, 134.0, 134.5, 135.5, 141.9,
148.4, 158.9, 167.7, 177.0, 182.7. Anal. Calcd for C23H19NO5:
C, 70.94; H, 4.92; N, 3.60; Found: C, 70.80; H, 4.89; N, 3.54.
7.23ꢁ8.07 (10H, m, ArH and NH2); 13C NMR (DMSO-d6): d
33.5, 56.3, 118.8, 121.3, 125.8, 126.1, 127.8, 128.7, 129.4, 130.5,
130.6, 130.9, 132.0, 134.1, 134.6, 140.9, 149.5, 158.4, 176.8,
182.4. Anal. Calcd for C20H11ClN2O3: C, 66.22; H, 3.06; N,
7.72; Found: C, 66.15; H, 3.01; N, 7.78.
2-Amino-4-(2,4-dichlorophenyl)-5,10-dioxo-5,10-dihydro-4H-
benzo[g]chromene-3-carbonitrile (4k). This compound was
obtained as orange powder with mp 286ꢁ288ꢀC; IR vmax
(KBr): 3467, 3341, 3168, 2201, 1664, 1631, 1591, 1364, 1247,
Acknowledgment. We thank the Education Department of Zhe-
jiang Province (NO.20060811) for the financial support of this work.
REFERENCES AND NOTES
1200 cmꢁ1
;
1H NMR (DMSO-d6): d 5.13 (1H, s, CH),
7.32ꢁ8.07 (9H, m, ArH and NH2); 13C NMR (DMSO-d6): d
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