Acid catalyzed efficient syntheses of aryl-5H-dibenzo[b,i]xanthene-5,7,12,14-(13H)-tetraones and 3,3-(arylmethylene)bis(2-hydroxynaphthalene-1,4-diones) and in vitro evaluation of their antioxidant activity

Article abstract of DOI:10.1002/jhet.1871

A simple and efficient synthesis of aryl-5H-dibenzo[b,i]xanthene-5,7,12,14-(13H)-tetraones and 3, 3-(arylmethylene)bis(2-hydroxynaphthalene-1,4-diones) by the condensation of aromatic aldehydes and 2-hydroxy-1,4-naphthoquinone under extremely mild conditi

Full text of DOI:10.1002/jhet.1871

Month 2014
Acid Catalyzed Efficient Syntheses of Aryl-5H-dibenzo[b,i]xanthene-
5,7,12,14-(13H)-tetraones and 3,3-(Arylmethylene)bis(2-hydroxynaphthalene-
1,4-diones) and In Vitro Evaluation of their Antioxidant Activity
*
Jitender M. Khurana, Anshika Lumb, Ankita Chaudhary, and Bhaskara Nand
Department of Chemistry, University of Delhi, Delhi 110007, India
*
E-mail: jmkhurana1@yahoo.co.in
Received June 2, 2012
DOI 10.1002/jhet.1871
Published online 00 Month 2014 in Wiley Online Library (wileyonlinelibrary.com).
O
O
O
Ar
O
O
OH
+
H2SO4, EtOH, reflux
or
bmim[HSO4]
ArCHO
O
O
O
Ar
O
O
H2SO4
H2SO4, EtOH, reflux
or
bmim[HSO4]
EtOH/H2O
reflux
OH
HO
O
A simple and efficient synthesis of aryl-5H-dibenzo[b,i]xanthene-5,7,12,14-(13H)-tetraones and 3,
3-(arylmethylene)bis(2-hydroxynaphthalene-1,4-diones) by the condensation of aromatic aldehydes and
2-hydroxy-1,4-naphthoquinone under extremely mild conditions using catalytic amount of H2SO4 or in
the presence of acidic ionic liquid 1-butyl-3-methylimidazolium hydrogen sulphate, which could be
recycled, has been reported. The radical scavenging capacity of the synthesized compounds has been
examined towards the stable free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH), and the compounds 2
were found to scavenge DPPH free radical efficiently.
J. Heterocyclic Chem., 00, 00 (2014).
INTRODUCTION
naphthoquinone scaffolds is an interesting challenge. In con-
tinuation of our work on the synthesis of heterocycles [8],
we have investigated the synthesis of 3,3-(arylmethylene)bis
(2-hydroxynaphthalene-1,4-diones) and 13-aryl-5H-dibenzo
[b,i] xanthene-5,7,12,14(13H)-tetraone derivatives under acidic
conditions or by using task-specific ionic liquid, 1-butyl-3-
methylimidazolium hydrogen sulphate (bmim[HSO4]).
Molecules with the quinone structure constitute an interest-
ing class of compounds in organic chemistry, because of their
biological properties and industrial applications [1]. Among
the quinones, naphthoquinones are considered as privileged
structures in medicinal chemistry as they act as intermediates
for the synthesis of biologically active heterocycles [2], which
are employed for the treatment of various diseases [3]. They
are usually colored, yellow or brown, and thus play important
roles as dyes in pigmentation. 2-Hydroxy-1,4-naphthoquinone
(Lawsone) is the principal natural dye in the leaves of henna
(1.0–1.4%), Lawsonia inermis [4]. Henna has been used
for more than 4000 years not only as a hair dye but also as
body paint and tattoo dye. A series of related naphthoquinone
pigments (streptocarpone, a-dunnione, dunniol, and
dunnione) from Streptocarpus dunnii have been isolated and
characterized [5,6].
The generation of free radicals during metabolic
processes is responsible for human conditions such as
aging, cancer, atherosclerosis, arthritis, viral infection,
stroke, and myocardial infarction. Antioxidants act as a
major defense against radical-mediated toxicity by inhibiting
the free radicals. In recent years, compounds that exhibit 2,
2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging
activity are receiving attention [7].
RESULTS AND DISCUSSION
In the present study, we report “one-pot” syntheses of
aryl-5H-dibenzo[b,i]xanthene-5,7,12,14-(13H)-tetraones
(1a–i) and 3,3-(arylmethylene)bis (2-hydroxynaphthalene-
1,4-diones) (2a–k) by condensation of 2-hydroxynaphtha-
lene-1,4-dione and aromatic aldehydes catalyzed by sulfuric
acid in ethanol under reflux or in task-specific ionic liquid
bmim[HSO4] under different conditions. These compounds
were also screened for their in vitro antioxidant activity by
using DPPH radical scavenging assay.
The reaction conditions were optimized by attempting
the condensation of 4-chlorobenzaldehyde (1.0 mmol)
and 2-hydroxy-1,4-naphthoquinone (2.0 mmol) in the
presence of acids such as HCl, H2SO4, HNO3, and AcOH
in different media and at different temperatures. The results
are summarized in Table 1. The best yield of 13-(4-chloro-
phenyl)-5H-dibenzo[b,i]xanthene-5,7,12,14 (13H)-tetraone
(1a), which is 89%, was achieved when the reaction was
carried out in ethanol in the presence of 0.20 mmol of
Considering the importance of naphthoquinone deriva-
tives, development of new methods for the synthesis of
© 2014 HeteroCorporation

J. M. Khurana, A. Lumb, A. Chaudhary, and B. Nand
Vol 000
Table 1
Optimization of reaction conditions.
Run
Reaction media
Temp. (ꢀC)
Catalyst
H2SO4
mol%
Time (h)
Product (% Yield)
1
2
3
4
5
6
7
8
CHCl3
CH3CN
DMF
EtOH
EtOH
EtOH + H2O (1:1)
H2O
EtOH
EtOH
EtOH
60
80–85
110
15
15
15
15
20
20
20
25
20
20
20
5.0
5.0
5.0
2.5
2.0
0.5
7
2.0
5.0
5.0
5.0
1a (30)b,c
1a (30)b,c
1a (25)b,c
1a (78)
H2SO4
H2SO4
H2SO4
H2SO4
H2SO4
H2SO4
H2SO4
CH3COOH
HNO3
70–80
70–80
70–80
100
70–80
70–80
70–80
70–80
1a (89)
2a (93)
2a (56)b,c
1a (87)
9
10
11
1a (30)b,c
1a (20)b,c
d
EtOH
HCl
–
aMolar ratio, 4-chlorobenzaldehyde:2-hydroxy-1,4-naphthoquinone, 1:2.
bIncomplete reaction.
cYields after column chromatography.
dNumber of spots on TLC.
H2SO4 (Table 1, entry 5) under reflux. We observed that
the yields were affected by the amount of H2SO4 used, and
optimum yield was obtained using 0.20 mmol of H2SO4. The
reactions in the presence of HCl, AcOH, and HNO3 and in
solvents such as MeCN, CHCl3, and DMF were sluggish
and incomplete. Interestingly, when the reaction was per-
formed in EtOH–H2O (1:1, v/v), in the presence of 0.20 mmol
of H2SO4 under reflux, it resulted in the formation of the
intermediate product 3,3-(4-chlorophenyl)methylenebis(2-
hydroxynaphthalene-1,4-dione) (2a) in 93% yield in 30 min
(Table 1, entry 6), which did not undergo further cyclization
under these conditions. However, this condensation reaction
was not complete even after 7 h when attempted in water,
although it resulted in the formation of 2a (56%). It is thus
obvious that the course of the reaction can be controlled by
changing the solvent system (Scheme 1).
2-hydroxy-1,4-naphthoquinone and resulted in the formation
of 1 using H2SO4 as catalyst in ethanol under reflux (method
A, Table 2) and 2 using H2SO4 as catalyst in ethanol–H2O
(1:1, v/v) under reflux (Table 3) in high yields.
The condensation of 4-chlorobenzaldehyde and 2-hydroxy-
1,4-naphthoquinone was also attempted in the presence of
task-specific ionic liquid, bmim[HSO4]. The condensation
could be achieved successfully at 70ꢀC by using 20mol%
Scheme 1
O
O
Ar
O
O
O
O
H2SO4, EtOH,
OH
reflux
or
bmim[HSO4]
Ar
2
+
ArCHO
O
1a-i
H2SO4
H2SO4, EtOH,
O
O
O
O
reflux
EtOH/H2O
reflux
or
Subsequently, reactions of various aromatic aldehydes
containing electron-withdrawing and electron-donating
substituents showed equal ease towards condensation with
bmim[HSO4]
OH
HO
2a-k
Table 2
Synthesis of aryl-5H-dibenzo[b,i]xanthene-5,7,12,14-(13H)-tetraones (1).
Method A
Method B
Method C
Time (min) Yield (%)
mp (ꢀC)
(Obsd.)
mp (ꢀC)
(Lit.)
Product
Ar
Time (h)
Yield (%)
Time (h)
Yield (%)
1a
1b
1c
1d
1e
1f
1g
1h
1i
4-ClC6H4
4-BrC6H4
4-CH3OC6H4
C6H5
4-CH3C6H4
2-ClC6H4
4-CF3C6H4
4-FC6H4
2.0
2.5
2.5
3.0
2.5
2.0
2.5
3.0
2.0
89
87
90
88
91
86
89
85
88
1.5
2.0
1.0
2.0
1.5
1.0
2.0
2.0
1.0
86
84
88
88
84
85
85
86
89
30
35
25
40
30
35
40
45
30
91
93
94
91
88
90
91
92
93
330–332
328–330
320–322
300–302
304–306
304–306
324–326
276–278
290–292
330–332[9]
333–335[9]
–
305–307[9]
304–307[9]
307–309[9]
–
270–272[9]
283–285[10]
2-BrC6H4
Method A: H2SO4, EtOH, reflux.
Method B: bmim[HSO4], 70ꢀC.
Method C: H2SO4, EtOH, reflux, cyclization of 2.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2014
Syntheses of Aryl-5H-dibenzo[b,i]xanthene-5,7,12,14-(13H)-tetraones, 3,3-
(Arylmethylene)bis(2-hydroxynaphthalene-1,4-diones) and their Antioxidant Activity
Table 3
Synthesis of 3,3-(arylmethylene)bis(2-hydroxynaphthalene-1,4-dione) derivatives (2) by condensation of aldehydes and 2-hydroxy-1,4-naphthoquinone in
EtOH/H2O (1:1) using H2SO4 as the catalyst.
Product
Ar
4-ClC6H4
4-BrC6H4
4-CH3OC6H4
C6H5
4-CH3C6H4
2-ClC6H4
4-CF3C6H4
4-FC6H4
2-BrC6H4
2-CH3OC6H4
3-ClC6H4
Time (min)
Yield (%)
mp (ꢀC) (Obsd.)
mp (ꢀC) (Lit.)
2a
2b
2c
2d
2e
2f
2g
2h
2i
30
25
20
15
20
20
25
30
20
15
30
93
90
86
90
94
89
91
87
89
91
89
188–190
214–216
220–222
202–204
174–176
218–220
188–190
190–192
210–212
212–214
224–226
180–182[11]
216–218[11]
220–222[11]
202–204[11]
170–172[11]
215–217[9]
–
193–195[9]
–
2j
2k
–
231–233[9]
of bmim[HSO4] and led to the formation of 1a in 86% yield.
However, the reaction at room temperature remained incom-
plete and gave a mixture of 1a and 2a. Other substituted
aldehydes also underwent condensation successfully under
these conditions, and the corresponding aryl-5H-dibenzo[b,
i]xanthene-5,7,12,14(13H)-tetraones (1a–i) were obtained
in high yields (Table 2, method B). The recovered ionic
liquid could be recycled for three cycles before losing
activity (Fig. 1). Synthesis of xanthene derivatives (1a–i)
could also be achieved by dehydration of the initially formed
2a–i in ethanol under reflux using H2SO4 as a catalyst or in
the presence of bmim[HSO4] at 70ꢀC (Table 2, method C).
Both the methods gave comparative yields. However, the
yields reported in Table 2, method C, are those obtained
using H2SO4 as catalyst under reflux.
Figure 2. Graphical representation of % DPPH radical scavenging activity
of compounds 2a-k and BHT as a function of concentration.
Hydroxyl naphthoquinone and its alkylated derivatives are
reported to show high antioxidant activity [12]. Therefore, we
screened in vitro antioxidant activity of naphthoquinone-
based compounds 1 and 2. Radical scavenging activity of
3,3-(arylmethylene)bis(2-hydroxynaphthalene-1,4-diones)
(2a–k) were measured at different concentrations (Fig. 2) by
using DPPH assay and compared with butylated hydroxy
toluene (BHT) as standard. The antioxidant activities of
compounds 1a–i could not be performed as these compounds
showed little solubility in the solvent system (methanol–
acetone). The compounds 2a–i showed good to moderate
radical scavenging activity, as compared with the standard
BHT (Table 4). The IC50 (mM) values of the compounds
2a, 2c, 2d, 2e, 2g, and 2k were found to be 61.00, 62.41,
35.01, 62.99, 80.93, and 60.86 respectively, which were
comparable with the standard (BHT) (Fig. 3). Among them,
compound 2d exhibited promising radical scavenging activ-
ity. The variation exhibited in DPPH scavenging capacity
could be attributed to the effect of different substituents,
and the results are summarized in Table 4.
CONCLUSION
In conclusion, we have reported an efficient acid cata-
lyzed synthesis of aryl-5H-benzo[b,i]xanthene-5,7,12,14
(13H)-tetraones and 3,3-(arylmethylene)bis(2-hydroxy
naphthalene-1,4-diones). The synthesis of aryl-5H-benzo
Figure 1. Recycling yields. Reactions of 2-hydroxy-1,4-naphthoquinone
and 4-chloro benzaldehyde and bmim[HSO4] (20 mol%).
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

J. M. Khurana, A. Lumb, A. Chaudhary, and B. Nand
Vol 000
Table 4
Antioxidant activity of the test compounds and standard using DPPH scavenging method – % DPPH radical scavenging activity.
% DPPH scavenging activity*
Compound
25 mM
22.95
50 mM
100 mM
200 mM
400 mM
IC50 (mM)
2a
2b
2c
2d
2e
52.07
35.25
49.81
67.98
47.03
25.36
41.42
38.58
31.93
36.84
46.27
85.92
62.82
54.44
70.64
97.11
64.61
33.41
58.49
46.29
42.06
49.91
60.02
86.79
78.23
74.90
90.1
93.64
87.15
95.32
97.11
88.16
65.49
79.61
74.13
61.85
76.01
80.46
87.43
61.00
89.00
62.41
35.01
62.99
278.08
80.93
184.79
167.20
96.29
60.86
11.93
13.02
13.47
38.00
25.34
14.11
22.62
20.31
19.27
28.00
30.80
78.42
97.11
76.59
41.17
69.54
53.27
54.96
61.84
70.54
89.19
2f
2g
2h
2i
2j
2k
BHT
*Each experiment was performed in triplicate, and the standard deviation was less than 10% of the mean.
DART source. The 1H NMR and 13C NMR spectra were recorded on
Jeol JNM ECX-400P at 400 MHz, using TMS as an internal standard.
The chemical shift values are recorded on d scale, and the coupling
constants (J) are in Hertz. Ionic liquid bmim[HSO4] was synthesized
according to a reported procedure [13]. The spectral data of the
known compounds are comparable with those reported in the literature.
General procedure for the synthesis of aryl-5H-dibenzo[b,i]
xanthene-5,7,12, 14(13H)-tetraones (1a–i).
Method A.
A mixture of aldehyde (1.0 mmol), 2-hydroxy-
1,4-naphthoquinone (2.0 mmol), H2SO4 (0.20mmol), and 10 mL
of EtOH was placed in a 50mL round-bottomed flask and stirred
under reflux. After completion of the reaction, as monitored by
TLC using CHCl3 as eluent (Table 2, method A), the reaction was
allowed to cool at room temperature, and the precipitate formed
was collected by filtration under vacuum. The solid was washed
with ethanol and dried to obtain pure aryl-5H-dibenzo[b,i]
xanthene-5,7,12,14(13H)-tetraone derivatives.
Figure 3. IC50: concentration needed for reducing DPPH absorption by
50% at 517 nm. Values are average of 3 independent measurements for
each compound.
Method B.
Aldehyde (1.0 mmol) and 2-hydroxy-1,4-
naphthoquinone (2.0 mmol) were mixed thoroughly and placed in
a 50 mL round-bottomed flask containing 1 mL of bmim[HSO4].
The mixture was stirred at 70ꢀC for the appropriate time as
mentioned in Table 2, method B. After completion of the reaction
as monitored by TLC using CHCl3 as solvent, the mixture was
allowed to cool at room temperature and quenched with water
(5–7 mL). The precipitate thus formed was collected by filtration at
pump and washed with water and then with EtOH to afford pure
aryl-5H-dibenzo[b,i]xanthene-5,7,12,14(13H)-tetraone derivatives.
The filtrate was concentrated under reduced pressure and dried
at 100ꢀC to recover the ionic liquid for subsequent use. The ionic
liquid thus obtained was reused for successive reactions for three
more times without losing significant catalytic activity.
[b,i]xanthene-5,7,12,14(13H)-tetraones has also been
reported with the task-specific ionic liquid bmim[HSO4],
which acts as an effective catalyst and media for this trans-
formation. The antioxidant activity of the synthesized
compounds was screened by DPPH method, and IC50
(mM) values of the compounds 2a, 2c, 2d, 2e, 2g, and 2k
were found comparable with the standard (BHT).
EXPERIMENTAL
Method C.
3,3-(Arylmethylene)bis(2-hydroxy naphthalene-
All the chemicals used were purchased from Sigma-Aldrich
(Missouri, USA) and used as received. Silica gel 60 F254 (precoated
aluminium plates) from Merck (Mumbai, India) was used to monitor
reaction progress. Melting points were determined on a Tropical
Labequip apparatus and are uncorrected. IR (KBr) spectra were
recorded on Perkin-Elmer FTIR spectrophotometer, and the values
are expressed as nmax cmꢁ1. Absorbance measurements were made
using Analytikjena Specord 250 Spectrophotometer. Mass spectral
data were recorded on JEOL-AccuTOF mass spectrometer having a
1,4-dione) (2a–i) (1 mmol), H2SO4 (0.20 mmol), and EtOH
(10 mL) were placed in a 50 mL round-bottomed flask. The
mixture was refluxed for appropriate time as mentioned in
Table 2, method C. The precipitate formed was filtered at pump
and washed with EtOH to yield pure aryl-5H-dibenzo[b,i]
xanthene-5,7,12,14(13H)-tetraone derivatives. The aforementioned
condensation could also be effected in the presence of task-
specific ionic liquid bmim[HSO4] (1 mL) instead of H2SO4 by
heating at 70ꢀC.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2014
Syntheses of Aryl-5H-dibenzo[b,i]xanthene-5,7,12,14-(13H)-tetraones, 3,3-
(Arylmethylene)bis(2-hydroxynaphthalene-1,4-diones) and their Antioxidant Activity
General procedure for the synthesis of 3,3-(arylmethylene)
bis(2-hydroxy naphthalene-1,4-dione) (2a–k). A mixture of
aldehyde (1.0 mmol), 2-hydroxy-1,4-naphthoquinone (2.0mmol),
H2SO4 (0.20 mmol), and 10mL of EtOH–H2O (1:1, v/v) was
stirred magnetically under reflux in a 50 mL round-bottomed flask
for an appropriate time as mentioned in Table 3. The progress of
the reaction was monitored by TLC using ethyl acetate–petroleum
ether (60:40, v/v) as eluent. After completion, the reaction mixture
was allowed to cool at room temperature. The precipitate, thus
formed, was collected by filtration at pump and washed
with water followed by ethanol to yield pure 3,3-(arylmethylene)
bis(2-hydroxynaphthalene-1,4-dione) derivatives.
2,2-Diphenyl-1-picrylhydrazyl free radical scavenging
assay. Methanolic solution of DPPH was used as a reagent for
the spectrophotometric assay with modifications [14]. Solutions of
different concentration of synthesized compounds (i.e., 25–400 mM)
were prepared using a mixture of methanol–acetone (1:1). We
added 1 mL of 0.1 mM methanolic solution of DPPH to a 3mL
solution of the compounds, and the mixture was shaken vigorously
using vortex mixer. Absorbance was read against a blank at
517 nm after incubation of the reaction mixtures for 60 min in dark
at room temperature. BHT was used as a reference compound. The
radical scavenging activities were expressed as the inhibition
percentage and were calculated using the following formula:
(m, 2H, Ar), 7.93 (d, J = 7.32 Hz, 2H, Ar), 7.87–7.63 (m, 4H,
Ar), 7.54 (d, J = 7.8 Hz, 2H, Ar), 7.46–7.45 (m, 2H, Ar), 6.06
(s, 1H, ArCH), 4.44 (bs, OH, overlap with DMSO); 13C NMR
(100 MHz, DMSO-d6) d: 183.90, 181.66, 157.17, 146.67,
135.18, 133.63, 132.62, 130.40, 129.32, 126.55, 126.12,
122.65, 38.01; MS (ESI) m/z calcd. for C28H15F3O6: 504.08,
found: 505.15 [M+ + H].
3,3-(2-Bromophenyl)methylenebis(2-hydroxynaphthalene-
1,4-dione) (2i).
Yellow solid; IR (KBr, cmꢁ1) nmax: 3330,
1672, 1545, 1360, 1254; 1H NMR (400 MHz, DMSO-d6) d:
7.99 (d, J = 7.32 Hz, 2H, Ar), 7.92 (d, J = 7.32 Hz, 2H, Ar),
7.86–7.75 (m, 4H, Ar), 7.51 (d, J = 7.8 Hz, 1H, Ar), 7.32
(d, J = 7.32 Hz, 1H, Ar), 7.22–7.18 (m, 1H, Ar), 7.12–7.08
(m, 1H, Ar), 6.02 (s, 1H, ArCH), 3.98 (bs, OH, overlap with
DMSO); 13C NMR (100 MHz, DMSO-d6) d: 183.72, 181.53,
156.88, 140.46, 135.31, 133.76, 132.49, 132.40, 131.22,
130.34, 128.35, 127.60, 126.18, 124.24, 122.66, 39.34; MS (ESI)
m/z calcd. for C27H15BrO6: 514.01, found: 515.05 [M+ + H],
5.17.05 [M+ + H + 2].
Acknowledgments. A. L. thanks the University of Delhi for the
award of University Teaching Assistantship. A. C. and B. N.
thank the CSIR, New Delhi, for the grant of Junior/ Senior
Research Fellowships.
Radical scavenging activityð%Þ ¼ ½ðA0 ꢁ A1Þ=A0Þ ꢂ100ꢃ;
where A0 is the absorbance of the control (blank, without
compound) and A1 the absorbance of the compound. All
the tests were carried out in triplicate, and the results were
averaged.
Spectral data of some representative products are given in the
succeeding text.
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5,7,12,14(13H)-tetraone (1c). Red solid; IR (KBr, cmꢁ1) nmax
:
1
2928, 1688, 1671, 1591, 1213; H NMR (400 MHz, DMSO-d6)
d: 8.09–8.04 (m, 2H, Ar), 7.98–7.96 (m, 1H, Ar), 7.94–7.89
(m, 2H, Ar), 7.86–7.83 (m, 2H, Ar), 7.71–7.67 (m, 1H, Ar), 7.32
(d, J = 8.72 Hz, 2H), 6.77 (d, J = 8.44Hz, 2H), 5.02 (s, 1H,
ArCH), 3.69 (s, 3H, OCH3); MS (ESI) m/z calcd. for C28H16O6:
448.09, found: 449.12 [M+ + H].
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Sinica 2008, 15, 1837.
[5] Perez, A. L.; Lamoureux, G.; Sanchez-Kopper, A. Tetrahedron
Lett 2007, 48, 3735.
[6] Inoue, K.; Ueda, S.; Nayeshiro, H.; Inouye, H. Chem Pharm
Bull 1982, 30, 2265.
13-(4-Trifluoromethylphenyl)-5,7,12,14-tetrahydrodibenzo[b,i]
xanthene-5,7,12,14 (13H)-tetraone (1g). Red solid; IR (KBr,
1
cmꢁ1) nmax: 2940, 1689, 1668, 1592, 1218; H NMR (400 MHz,
[7] Hossain, S. U.; Bhattacharya, S. Bioorg Med Chem Lett 2007,
17, 1149.
DMSO-d6) d: 8.14–8.11 (m, 2H, Ar), 8.04–8.02 (m, 2H, Ar),
7.97–7.90 (m, 4H, Ar), 7.78–7.72 (m, 1H, Ar), 7.54–7.48 (m, 2H,
Ar), 7.29–7.25 (m, 1H, Ar), 5.31 (s, 1H, ArCH); MS (ESI)
m/z calcd. for C28H13F3O5: 486.07, found: 489.10 [M+ + H].
3,3-(4-Chlorophenyl)methylenebis(2-hydroxynaphthalene-
[8] (a) Khurana, J. M.; Nand, B.; Kumar, S. Synth Commun
2011, 41, 405; (b) Khurana, J. M.; Magoo, D. Tetrahedron Lett 2009,
50, 4777; (c) Khurana, J. M.; Kumar, S.; Tetrahedron Lett 2009, 50,
4125; (d) Khurana, J. M.; Nand B.; Saluja, P. Tetrahedron 2010, 66,
5637; (e) Khurana, J. M.; Chaudhary, A.; Nand, B.; Lumb, A. Tetrahedron
Lett 2012, 53, 3018.
[9] Yuling, L.; Baixiang, D.; Xiaoping, X.; Daqing, S.; Shunjun, J.
Chin. J. Chem. 2009, 27, 1563.
[10] Tisseh, Z. N.; Azimi, S. C.; Mirzaei, P.; Bazgir, A. Dyes and
pigments 2008, 79, 273.
[11] Tisseh, Z. N.; Bazgir, A. Dyes and pigments 2009, 83, 258.
[12] Vinothkumar, S. P.; Murali, K.; Gupta, J. K. J. Pharm Res
2010, 3, 2784.
[13] Wang, W.; Shao, L.; Cheng, W.; Yang J.; He, M. Catal
Commun, 2008, 9, 337.
[14] (a) Koleva, N.; VanBeek, T. A.; Linssen, J. P. H.; Groot, A.
D.; Evastatieva, L. N. Phytochem Anal 2002, 13, 8; (b) Miliauskas, G.;
Venskutonis, P.; VanBeek, T. A.; Food Chem, 2004, 85, 231.
1,4-dione) (2a).
Yellow solid; IR (nmax cmꢁ1) (KBr): 3332,
1673, 1651, 1365, 1298; 1H NMR (400MHz, DMSO-d6):
d = 7.99 (d, J = 7.32 Hz, 2H, Ar), 7.92 (d, J = 7.32Hz, 2H, Ar),
7.88–7.75 (m, 4H, Ar), 7.33–7.30 (m, 2H, Ar), 7.20–7.14 (m, 2H,
Ar), 6.07 (s, 1H, ArCH), 4.06 (bs, OH, overlap with DMSO); 13
C
NMR (100 MHz, CDCl3): d = 183.22, 181.02, 156.40, 138.36,
134.78, 133.22, 132.76, 132.01, 130.47, 129.84, 128.56, 127.54,
126.56, 126.09, 125.67, 122.03, 36.27; MS (ESI) m/z calcd. for
C27H15ClO6: 470.06, found: 471.10 [M+ + H], 473.10 [M+ + H + 2].
3,3-(4-Trifluromethylphenyl)methylenebis(2-hydroxynaphthalene-
1,4-dione) (2g). Yellow solid; IR (KBr, cmꢁ1) nmax: 3340, 1651,
1
1594, 1348, 1300; H NMR (400MHz, DMSO-d6) d: 7.99–7.97
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet