Efficient one-pot syntheses of dibenzo[a, i]xanthene-diones and evaluation of their antioxidant activity

Article abstract of DOI:10.1139/v2012-033

Facile and convenient procedures for the synthesis of dibenzo[a,i]xanthene- diones have been described. The process employs one-pot condensation of aldehydes, 2-hydroxynaphthalene-1,4-dione, and 2-naphthol/2,7- dihydroxynaphthalene/2,6-dihydroxynaphthalene using catalytic sulfuric acid in water under reflux. Task-specific ionic liquid, 1-butyl-3-methylimidazolium hydrogen sulfate ([bmim]HSO₄), has also been found to be an effective catalyst for this transformation. The protocols defined herein prove to be efficient in terms of high yields, operational simplicity, easy workup, and short reaction time. Also, these compounds were screened for antioxidant activity by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay.

Full text of DOI:10.1139/v2012-033

739
Efficient one-pot syntheses of dibenzo[a,i]
xanthene-diones and evaluation of their
antioxidant activity
Jitender M. Khurana, Ankita Chaudhary, Anshika Lumb, and Bhaskara Nand
Abstract: Facile and convenient procedures for the synthesis of dibenzo[a,i]xanthene-diones have been described. The proc-
ess employs one-pot condensation of aldehydes, 2-hydroxynaphthalene-1,4-dione, and 2-naphthol/2,7-dihydroxynaphthalene/
2,6-dihydroxynaphthalene using catalytic sulfuric acid in water under reflux. Task-specific ionic liquid, 1-butyl-3-methylimi-
dazolium hydrogen sulfate ([bmim]HSO4), has also been found to be an effective catalyst for this transformation. The proto-
cols defined herein prove to be efficient in terms of high yields, operational simplicity, easy workup, and short reaction
time. Also, these compounds were screened for antioxidant activity by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scav-
enging assay.
Key words: benzoxanthene, synthesis in water, task-specific ionic liquid, antioxidant activity, DPPH assay.
Résumé : On décrit une méthode simple et commode de synthèse des dibenzo[a,i]xanthènediones. Le procédé implique
l’utilisation d’une condensation monotope d’aldéhydes, de 2-hydroxynaphtalène-1,4-dione et de 2-naphtol/2,7-dihydroxy-
naphtalène/2,6-dihydroxynaphtalène, en faisant appel à une catalyse par l’acide sulfurique dans l’eau, sous reflux. On a
trouvé que le liquide ionique à tâche spécifique, le sulfate acide du 1-butyl-3-méthylimidazolium ([bmim]HSO4) peut aussi
être utilisé comme catalyseur efficace pour cette transformation. Les protocoles définis dans ce travail se sont avérés effica-
ces en termes de rendements élevés, simplicité d’opération, facilité d’extraction et de temps de réaction court. De plus, l’ac-
tivité antioxydante de tous ces composés a été examinée par le biais de l’essai au piégeage du radical 2,2-diphényl-1-
picrylhydrazyle (DPPH).
Mots‐clés : benzoxanthène, synthèse en milieu aqueux, liquide ionique à tâche spécifique, activité antioxydante, essai au
DPPH.
[Traduit par la Rédaction]
polyethylene glycol, and water, has gained significant impe-
tus owing to environmental concerns. The advantages of con-
ducting organic reactions in water include an enhancement in
rate, ease of operation, and an improved safety profile.13
Also, organic reactions in water exhibit unique reactivity and
selectivity that is different from reactions in organic sol-
vents.14 In continuation of our studies on the development of
new routes for the heterocyclic systems,15 we have investi-
gated the synthesis of dibenzo[a,i]xanthene-8,13-diones in
aqueous medium and task-specific ionic liquid. Moreover,
phenolic- and quinone-based compounds are known to show
potent antioxidant activity that is attributed to their redox
properties.16 Therefore, we decided to screen the synthesized
dibenzoxanthene-diones for their antioxidant activity by 2,2-
diphenyl-1-picrylhydrazyl radical (DPPH) scavenging assay.
Introduction
Xanthenes and benzoxanthenes, being the structural motifs
of a large number of naturally occurring as well as synthetic
derivatives, hold a prominent position in medicinal chemis-
try.1 Benzoxanthenes exhibit a broad spectrum of biological
activities such as antiviral,2 antibacterial,3 anti-inflammatory,
and 4 zoxazolamine antagonists,5 as well as efficacy in photo-
dynamic therapy.6 These compounds can also be used as
dyes,7 pH-sensitive fluorescent materials for visualization of
biomolecules,8 and in laser technologies.9 Moreover, natural
and synthetic xanthenes and xanthones are also known for
their antioxidant activity.10 However, limited methods have
been reported for the synthesis of dibenzo[a,i]xanthene-diones.11
Development of improved and environmentally benign method-
ologies for the synthesis of xanthenes containing naphthoqui-
none fragments is an interesting challenge.
Results and discussion
Multicomponent reactions (MCRs)12 have emerged as an
efficient and powerful tool for the synthesis of heterocyclic
scaffolds and are useful for the construction of diverse chem-
ical libraries of “druglike” molecules. The design of MCRs
in nontoxic and nonvolatile media, such as ionic liquids,
We report herein an efficient synthetic route for the syn-
thesis of 14-aryl-14H-dibenzo[a,i]xanthene-8,13-diones in
aqueous media using H2SO4 as catalyst under reflux and
also by utilizing the task-specific ionic liquid, 1-butyl-3-
Received 12 October 2011. Accepted 30 April 2012. Published at www.nrcresearchpress.com/cjc on 22 August 2012.
J.M. Khurana, A. Chaudhary, A. Lumb, and B. Nand. Department of Chemistry, University of Delhi, Delhi 110007, India.
Corresponding author: Jitender M. Khurana (e-mail: jmkhurana@chemistry.du.ac.in).
Can. J. Chem. 90: 739–746 (2012)
doi:10.1139/V2012-033
Published by NRC Research Press

740
Can. J. Chem. Vol. 90, 2012
methylimidazolium hydrogen sulfate ([bmim]HSO4), at 60 °C.
Furthermore, the assessment of radical scavenging activity
towards the DPPH radical was measured, and these com-
pounds were found to scavenge the DPPH free radical effi-
ciently.
which acted both as medium and catalyst. A further in-
crease in the amount of [bmim]HSO4 did not have any sig-
nificant effect on product yield and reaction time. The
condensation reactions of other diversely substituted aromatic
aldehydes with 2-naphthol and 2-hydroxy-naphthalene-1,4-
dione using 20 mol % of [bmim]HSO4 under the standar-
dized conditions gave excellent yields of the corresponding
xanthene derivatives (Table 1, method B, entries 1–11).
Also, on replacing 2-naphthol with 2,7- and 2,6-dihydroxy-
naphthalenes, the reactions underwent successful completion
in [bmim]HSO4 (Table 1, method B, entries 12–24). All at-
tempts to achieve bis condensation under these conditions
were unsuccessful.
We also examined the reusability of [bmim]HSO4 by
studying the catalytic activity of the recycled ionic liquid for
the synthesis of 1a. After separation of the product by filtra-
tion, the filtrate containing the ionic liquid was rinsed with
ether and further vacuumed to dryness at 90 °C for 2 h to
remove any moisture. The recovered [bmim]HSO4 was
reused directly for the next run. It was found that the ionic
liquid can be used for the reactions for up to three runs with-
out any appreciable loss of efficiency.
The reaction conditions were optimized by the reactions of
4-methoxybenzaldehyde (1.0 mmol), 2-naphthol (1.0 mmol),
and 2-hydroxynaphthalene-1,4-dione (1.0 mmol) in different
media in the presence of acid catalysts like HCl, HNO3,
CH3COOH, and H2SO4. The best result was obtained when
the reaction was carried out in water in the presence of a cat-
alytic amount of sulfuric acid (0.1 mmol) under reflux. The
reaction underwent completion in 30 min yielding 92% of
14-(4-methoxyphenyl)-14H-dibenzo[a,i]xanthene-8,13-dione (1a)
after a simple work up. In the absence of any catalyst, we
did not observe any product formation even after 16 h of
reflux. The synthesis of 1a in different solvents such as
EtOH, CH2Cl2, and CH3CN under reflux using H2SO4 as
catalyst yielded 85%, 40%,and 26% of 14-(4-methoxy-
phenyl)-14H-dibenzo[a,i]xanthene-8,13-dione (1a), respec-
tively. Subsequently reactions of variously substituted
aromatic aldehydes with 2-naphthol and 2-hydroxy-1,4-
naphthoquinone were carried out in water using 10 mol %
of H2SO4 as catalyst under reflux. The reactions proceeded
efficiently, yielding the corresponding xanthene derivatives
(1a–1k) in excellent yields (Scheme 1). The results have
been summarized in Table 1 (method A, entries 1–11).
This cyclocondensation reaction was then investigated with
different dihydroxynaphthalenes. The reaction of 4-methoxy-
To survey the possible biological activities of these highly
coloured
14-aryl-14H-dibenzo[a,i]xanthene-8,13-diones,
these compounds (Table 1, entries 1–24) were subjected to a
test of antioxidant activity. The antioxidant activity is repre-
sented by their capacities for scavenging the DPPH radical,
and the results are summarized in Table 2 and Fig. 1.
Among the synthesized dibenzoxanthene-diones, com-
pounds 2a–2k and 3a and 3b showed potent DPPH radical-
scavenging activity, comparable to that of the standard (buty-
lated hydroxyl toluene, BHT) at higher concentrations of the
tested compounds. Further, it was observed that the antioxi-
dant property of dibenzoxanthene-diones was enhanced by
introducing aldehydes having an electron-donating function-
ality.
benzaldehyde
(1.0
mmol),
2,7-dihydroxynaphthalene
(1.0 mmol), and 2-hydroxy-1,4-naphthoquinone (1.0 mmol)
in water using H2SO4 as catalyst under reflux yielded 91%
of
2-hydroxy-14-(4-methoxyphenyl)-14H-dibenzo[a,i]xan-
thene-8,13-dione (2a) after 30 min. Subsequently, reactions
of other aldehydes also yielded the corresponding novel xan-
thene derivatives (2a–2k) (Table 1, method A, entries 12–22)
in excellent yields. Replacement of 2,7-dihydroxynaphthalene
with 2,6-dihydroxynaphthalene also led to the successful con-
densation under similar conditions to afford novel xanthene
derivatives (3a–3b) in high yields (Table 1, method A, en-
tries 23 and 24). None of the reactions of 2,7-dihydroxynaph-
thalene and 2,6-dihydroxynaphthalenes showed the formation
of any bis-condensation product. Reactions using double molar
concentrations of aldehydes and 2-hydroxy-1,4-naphthoqui-
none with 2,7-dihydroxynaphthalene and 2,6-dihydroxynaph-
thalenes did not show formation of bis-condensation products
even after prolonged reaction times. Even reactions of initially
formed 2 with aldehyde and 2-hydroxy-1,4-naphthoquinone to
give bis-condensation products were unsuccessful. Reactions
using 1,5-, 1,6-, and 1,7-dihydroxynaphthalenes led to the
formation of 3,3′-(arylmethylene)bis(2-hydroxynaphthalene-
1,4-dione) derivatives rather than desired xanthene-diones.
Reactions were then attempted using task-specific acidic
ionic liquid [bmim]HSO4. It was observed that the reaction of
4-methoxybenzaldehyde (1.0 mmol), b-naphthol (1.0 mmol),
and 2-hydroxynaphthalene-1,4-dione (1.0 mmol) proceeded
efficiently in [bmim]HSO4 at 60 °C, yielding 91% of the
corresponding xanthene derivative 1a in 30 min without
any other catalyst. The effect of the amount of ionic liquid
on the reaction time and yields was also examined. A maximum
yield of 1a was obtained with 20 mol % of [bmim]HSO4,
Conclusion
In conclusion, we have devised efficient synthetic ap-
proaches for the synthesis of 14-aryl-14H-dibenzo[a,i]xan-
thene-8,13-dione
derivatives.
The
three-component
condensation has been proficiently performed in water as a
“green” solvent using H2SO4 as catalyst. The ionic liquid,
[bmim]HSO4 also efficiently catalyses the cyclocondensation
reaction. The antioxidant activity of these compounds was
evaluated by DPPH free-radical scavenging assay, and we
found them to be efficient DPPH free-radical scavengers.
Experimental
All the chemicals used were purchased from Sigma-Aldrich
and used as received. Silica gel 60 F254 (precoated aluminium
plates) from Merck was used to monitor reaction progress.
The melting points were determined on a Tropical Labequip
apparatus and are uncorrected. IR (KBr) spectra were re-
corded on PerkinElmer FTIR spectrophotometer and the val-
ues are expressed as nmax (cm–1). Absorbance measurements
were made using an Analytikjena Specord 250 spectropho-
tometer. Elemental analysis was performed by a Vario EL III
Elementar analyzer. Mass spectral data were recorded on a
Jeol-Accutof JMS-T100 mass spectrometer having a DART
Published by NRC Research Press

Khurana et al.
741
Scheme 1.
Table 1. Synthesis of dibenzo[a,i]xanthene-dione derivatives via a multicomponent condensation reaction.
Method A Method B
Time
(min)
Yield
Time
(min)
Yield
Entry
1
2
3
4
5
6
7
8
RCHO
4-CH3OC6H4
C6H5
R1
H
H
H
H
H
H
H
H
R2
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
OH
OH
Product
1a
1b
1c
1d
1e
(%)
92
91
89
91
90
92
90
90
89
89
88
92
91
89
91
90
92
90
90
91
89
88
90
88
(%)
91
89
88
89
90
90
91
89
90
89
87
91
89
88
89
90
90
91
89
89
87
86
89
88
mp (Obsd.)a
279–281
>300
254–256
>300
>300
>300
>300
280–282
>300
>300
284–295
>300
>300
>300
>300
>300
>300
>300
>300
>300
>300
>300
mp (lit.)
30
45
35
30
25
30
35
45
40
45
35
30
45
35
30
25
30
35
45
35
40
30
30
35
30
40
30
30
25
30
30
35
35
45
35
30
40
30
30
25
30
30
35
30
35
30
40
35
278–28011a
319–32011a
255–25611a
305–30611a
332–33311a
304–30511a
301–30211a
281–28211a
4-CH3C6H4
4-ClC6H4
4-O2NC6H4
3-O2NC6H4
2,4-Cl2C6H3
2-ClC6H4
4-FC6H4
2-Naphthyl
4-BrC6H4
4-CH3OC6H4
4-BrC6H4
4-CH3C6H4
4-ClC6H4
4-O2NC6H4
2-ClC6H4
(CH3)2CH
2-Thiophenyl
3-BrC6H4
C6H5
1f
1g
1h
1i
b
9
H
H
H
—
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
1j
—
1k
2a
2b
2c
2d
2e
294–29811c
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
H
—
—
—
—
—
—
—
—
—
—
—
—
—
2f
2g
2h
2i
2j
2,4-Cl2C6H3
4-CH3OC6H4
4-BrC6H4
2k
3a
3b
>300
>300
H
Note: Method A: Reaction in water under reflux H2SO4 (0.1 mmol). Method B: Reaction in [bmim]HSO4 at 60 °C.
aEthanol was used for recrystallization.
bKnown compound, but the mp is reported for the first time.
1
source. The H and 13C NMR spectra were recorded on a
Bruker Spectrospin spectrometer and a Jeol JNM ECX-400P
at 300 MHz and 400 MHz, respectively, using TMS as an in-
ternal standard. The chemical shift values are recorded on a d
scale, and the coupling constants (J) are in Hertz. [bmim]HSO4
was prepared by the reported procedure.17 The melting
point, IR, 1H NMR, and elemental analysis of all known
compounds were found to be identical with those described
in the literature.11
1,4-dione (1.0 mmol), H2SO4 (0.1 mmol), and 10 mL of
water was stirred magnetically under reflux for the appropri-
ate time as mentioned in Table 1. The progress of the reac-
tion was monitored by TLC using petroleum ether – ethyl
acetate (70:30, v/v) as eluent. After completion of the reac-
tion, the reaction mixture was allowed to cool to room tem-
perature. The precipitate formed was collected by filtration at
pump, washed with cold dilute ethanol and recrystallized
from ethanol to afford the pure xanthene derivative. The
products were identified by spectral analysis.
General procedure for the synthesis of 14-aryl-14H-
dibenzo[a,i]xanthene-8,13-dione derivatives
Method B
A mixture of aldehyde (1.0 mmol), 2-naphthol (or 2,7-/2,6-
dihydroxynaphthalene) (1.0 mmol), 2-hydroxynaphthalene-
1,4-dione (1.0 mmol), and [bmim]HSO4 (20 mol %) was
stirred magnetically in an oil bath maintained at 60 °C for
Method A
A mixture of aldehyde (1.0 mmol), 2-naphthol (or 2,7-/2,6-
dihydroxynaphthalene) (1.0 mmol), 2-hydroxynaphthalene-
Published by NRC Research Press

742
Can. J. Chem. Vol. 90, 2012
Table 2. 2,2-Diphenyl-1-picrylhydrazyl (DPPH) radical
scavenging activity (%) of 14-aryl-14H-dibenzo[a,i]
xanthene-8,13-dione derivatives.
expressed as an inhibition percentage and were calculated us-
ing the formula:
Radical scavenging activity ð%Þ
¼ ½ðA0 ꢀ A1Þ=A0 ꢁ 100ꢂ
where A0 is the absorbance of the control (blank, without
compound) and A1 is the absorbance of the compound. All
the tests were carried out in triplicate and the results were
averaged.
Scavenging activity (%)
Product
1a
1b
1c
1d
1e
0.4 (µmol/L)/mLa
60.23
23.12
54.03
33.00
10.43
16.23
43.12
25.72
8.14
0.8 (µmol/L)/mLa
79.88
37.03
71.43
45.89
14.69
25.43
70.00
54.23
15.26
8.34
1f
Spectral data
1g
1h
1i
14-(4-Methoxyphenyl)-14H-dibenzo[a,i]xanthene-8,13-dione
(1a)
1j
5.22
Orange solid, mp 279–281 °C (lit.11a 278–280 °C). UV
(4 × 10–5 mol/L solution in CHCl3) lmax (3): 338 nm
(1.26 × 104 L mol–1 cm–1). IR (nmax, cm–1, KBr): 2963,
1k
2a
2b
2c
2d
2e
17.62
68.23
55.14
56.58
63.61
14.08
53.44
57.00
47.57
38.00
45.94
40.73
79.00
54.51
87.43
28.38
87.54
74.59
81.38
71.38
32.11
69.03
76.87
66.55
57.92
48.86
51.88
89.88
78.00
89.01
1
2919, 2853, 1718, 1702, 1685, 1590, 1508, 1366, 1211. H
NMR (300 MHz, CDCl3) d: 8.09–8.02 (m, 2H, Ar), 7.92 (d,
J = 8.4 Hz, 1H, Ar), 7.81–7.67 (m, 3H, Ar), 7.52–7.33 (m,
4H, Ar), 7.31 (d, 2H, J = 8.7 Hz, Ar), 7.18 (s, 2H,Ar), 5.82
(s, 1H, CH), 3.60 (s, 3H, OCH3). Anal. calcd for C28H18O4:
C 80.37, H 4.34; found: C 80.35, H 4.32.
2f
2g
2h
2i
14-Phenyl-14H-dibenzo[a,i]xanthene-8,13-dione (1b)
Orange solid, mp > 300 °C (lit.11a 319–320 °C). UV (4 ×
10–5 mol/L solution in CHCl3) lmax (3): 338 nm (2.26 ×
104 L mol–1 cm–1). IR (nmax cm–1) (KBr): 1224, 2854, 1612,
1630, 1589, 1363, 1282. 1H NMR (300 MHz, CDCl3) d:
8.17–8.10 (m, 2H, Ar), 8.00 (d, J = 8.1 Hz, 1H, Ar), 7.90–
7.75 (m, 3H, Ar), 7.60–7.39 (m, 6H, Ar), 7.20 (t, J =
14.7 Hz, 2H, Ar), 7.11–7.06 (m, 1H, Ar), 5.94 (s, 1H).
Anal. calcd for C27H16O3: C 83.49, H 4.15; found: C 83.47,
H 4.13.
2j
2k
3a
3b
BHTb
Note: A 0.1 mmol/L methanolic solution of DPPH was used
for all the experiments.
aThe solutions of compounds were prepared in a mixture of
methanol–acetone (1:1).
bButylated hydroxyl toluene (BHT) was used as a reference
compound.
14-(4-Methylphenyl)-14H-dibenzo[a,i]xanthene-8,13-dione
(Ic)
an appropriate time as mentioned in Table 1. After comple-
tion of the reaction as monitored by TLC using petroleum
ether – ethyl acetate (70:30, v/v) as eluent, the reaction mix-
ture was allowed to cool to room temperature and then
quenched with water (~5 mL). The precipitate formed was
collected by filtration at the pump, washed with cold dilute
ethanol, and recrystallized from ethanol to afford the pure
xanthene derivative. The filtrate was rinsed with ether, con-
centrated under reduced pressure, and dried at 90 °C to re-
cover the ionic liquid for subsequent reuse.
Orange solid, mp 254–256 °C (lit.11a 255–256 °C). UV
(4 × 10–5 mol/L solution in CHCl3) lmax (3): 333 nm
(1.47 × 104 L mol–1 cm–1). IR (nmax cm–1, KBr): 2920,
1
1665, 1637, 1591, 1577, 1364, 1286. H NMR (400 MHz,
CDCl3) d: 8.16 (d, J = 8.0 Hz, 1H, Ar), 8.11 (d, J =
7.6 Hz, 1H, Ar), 7.99 (d, J = 8.0 Hz, 1H, Ar), 7.89–7.76
(m, 3H, Ar), 7.60–7.42 (m, 4H, Ar), 7.29 (d, J = 8.0 Hz,
2H, Ar), 7.00 (d, J = 7.6 Hz, 2H, Ar), 5.90 (s, 1H, CH),
2.21 (s, 3H, CH3). Anal. calcd for C28H18O3: C 83.57, H
4.51; found: C 83.59, H 4.52.
DPPH free-radical scavenging assay
14-(4-Chlorophenyl)-14H-dibenzo[a,i]xanthene-8,13-dione
(1d)
A methanol solution of DPPH was used as a reagent for
the spectrophotometric assay with modifications.18 Solutions
of different concentrations of dibenzoxanthene-diones (i.e.,
0.8 and 0.4 (µmol/L)/mL) were prepared using a mixture of
methanol–acetone (1:1). One millilitre of a 0.1 mmol/L
methanolic solution of DPPH was added to 3 mL of the sol-
ution of the compounds and the mixture was shaken vigo-
rously using a vortex mixer. Absorbance was read against a
blank at 517 nm after incubation of the reaction mixtures for
60 min in the dark at room temperature. BHT was used as a
reference compound. The radical-scavenging activities were
Orange solid, mp > 300 °C (lit.11a 305–306 °C). UV (4 ×
10–5 mol/L solution in CHCl3) lmax (3): 336 nm (2.75 ×
104 L mol–1 cm–1). IR (nmax cm–1, KBr): 3046, 1667, 1637,
1591, 1577, 1367, 1286. 1H NMR (400 MHz, CDCl3) d:
8.18 (d, 1H, J = 7.6 Hz, Ar), 8.14 (d, J = 7.6 Hz, 1H, Ar),
7.91–7.77 (m, 4H, Ar), 7.62–7.45 (m, 4H, Ar), 7.34 (d, J =
8.4 Hz, 2H, Ar), 7.15 (d, J = 8.4 Hz, 2H, Ar), 5.90 (s, 1H,
CH). Anal. calcd for C27H15ClO3: C 76.69, H 3.58; found: C
76.67, H 3.57.
Published by NRC Research Press

Khurana et al.
743
Fig. 1. 2,2-Diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity (%) of 14-aryl-14H-dibenzo[a,i]xanthene-8,13-dione derivatives.
14-(4-Nitrophenyl)-14H-dibenzo[a,i]xanthene-8,13-dione
(1e)
14-(4-Fluorophenyl)-14H-dibenzo[a,i]xanthene-8,13-dione
(1i)
Orange solid, mp > 300 °C (decomp.). UV (4 × 10–5 mol/L
solution in CHCl3) lmax (3): 340 nm (2.52 × 104 L mol–1 cm–1).
IR (nmax cm–1, KBr): 2923, 2852, 2699, 1661, 1637, 1590,
Orange solid, mp > 300 °C (lit.11a 332–333 °C). UV (4 ×
10–5 mol/L solution in CHCl3) lmax (3): 336 nm (2.43 ×
104 L mol–1 cm–1). IR (nmax cm–1, KBr): 2914, 1703, 1663,
1
1
1502, 1368, 1214. H NMR (400 MHz, DMSO-d6) d: 7.93–
1635, 1590, 1518, 1349, 1212. H NMR (400 MHz, CDCl3)
7.83 (m, 3H, Ar), 7.80–7.75 (m, 1H, Ar), 7.60–7.42 (m,
4H, Ar), 7.37–7.33 (m, 2H, Ar), 7.29–7.18 (m, 4H, Ar),
5.91 (s, 1H, CH). Anal. calcd for C27H15FO3: C 79.79, H
3.72; found: C 79.76, H 3.70.
d: 8.20 (d, J = 7.6 Hz, 1H, Ar), 8.15 (d, J = 7.6 Hz, 1H, Ar),
8.05 (d, J = 8.8 Hz, 2H, Ar), 7.97–7.79 (m, 4H, Ar), 7.66–
7.46 (m, 6H, Ar), 6.05 (s, 1H, CH). Anal. calcd for
C27H15NO5: C 74.82, H 3.49, N 3.23; found: C 74.84, H
3.51, N 3.24.
14-(2-Naphthyl)-14H-dibenzo[a,i]xanthene-8,13-dione (1j)
Yellow solid, mp > 300 °C (decomp.). UV (4 × 10–5 mol/L
solution in CHCl3) lmax (3): 340 nm (2.25 × 104 L mol–1 cm–1).
IR (nmax cm–1, KBr): 2925, 1635, 1586, 1365, 1216. 1H
NMR (400 MHz, DMSO-d6) d: 8.23 (d, J = 7.56 Hz, 1H,
Ar), 8.13 (d, J = 8.48 Hz, 1H, Ar), 8.016 (d, J = 9.20 Hz,
1H, Ar), 7.93–7.84 (m, 4H, Ar), 7.77–7.62 (m, 5H, Ar),
7.44–7.32 (m, 5H, Ar), 5.91 (s, 1H, CH). 13C NMR
(100 MHz, DMSO-d6) d: 178.28, 177.91, 156.70, 147.33,
141.58, 135.57, 133.18, 132.28, 131.97, 130.92, 130.86,
130.63, 130.26, 129.22, 128.98, 128.54, 128.26, 127.97,
127.82, 127.68, 127.23, 126.69, 126.41, 125.96, 125.02,
124.05, 117.92, 117.00, 115.88, 35.62. MS (ESI) m/z calcd
for C31H18O3: 438.13; found: 439.20 [M+ + H]. Anal. calcd
for C31H18O3: C 84.92, H 4.14; found: C 84.90, H 4.12.
14-(3-Nitrophenyl)-14H-dibenzo[a,i]xanthene-8,13-dione
(1f)
Orange solid, mp > 300 °C (lit.11a 304–305 °C). UV (4 ×
10–5 mol/L solution in CHCl3) lmax (3): 337 nm (2.50 ×
104 L mol–1 cm–1). IR (nmax cm–1, KBr): 2922, 1702, 1656,
1
1637, 1575, 1529, 1347, 1214. H NMR (400 MHz, CDCl3)
d: 8.21 (d, J = 8.0 Hz, 1H, Ar), 8.13 (d, J = 8.1 Hz, 1H, Ar),
8.10 (s, 1H, Ar), 8.00–7.82 (m, 6H, Ar), 7.66–7.61 (m, 2H,
Ar), 7.52–7.41 (m, 3H, Ar), 6.06 (s, 1H, CH). Anal. calcd for
C27H15NO5: C 74.82, H 3.49, N 3.23; found: C 74.80, H
3.46 H 3.20.
14-(2,4-Dichlorophenyl)-14H-dibenzo[a,i]xanthene-8,13-
dione (1g)
Orange solid, mp > 300 °C (lit.11a 301–302 °C). UV (4 ×
10–5 mol/L solution in CHCl3) lmax (3): 340 nm (2.75 ×
104 L mol–1 cm–1). IR (nmax cm–1, KBr): 3056, 1662, 1637,
14-(4-Bromophenyl)-14H-dibenzo[a,i]xanthene-8,13-dione
(1k)
Orange solid, mp 284–295 °C (lit.11c 294–298 °C). UV
(4 × 10–5 mol/L solution in CHCl3) lmax (3): 339 nm
(2.25 × 104 L mol–1 cm–1). IR (nmax cm–1, KBr): 3075,
1
1591, 1577, 1466, 1362, 1288. H NMR (400 MHz, CDCl3)
d: 8.20 (d, J = 7.8 Hz, 1H Ar), 8.15–8.11 (m, 2H, Ar), 7.89–
7.79 (m, 3H, Ar), 7.65–7.43 (m, 4H, Ar), 7.32–7.26 (m, 2H,
Ar), 7.10 –7.03(m, 1H, Ar), 6.15 (s, 1H, CH). Anal. calcd for
C27H14Cl2O3: C 70.91, H 3.09; found: C 70.89, H 3.06.
1
1704, 1663. H NMR (300 MHz, DMSO-d6) d: 8.18– 8.11
(m, 2H, Ar). 7.93–7.86 (m, 3H, Ar), 7.80 (t, J = 7.6 Hz,
1H, Ar), 7.62–7.50 (m, 2H, Ar), 7.45–7.40 (m, 2H, Ar).
7.34–7.26 (m, 4H, Ar), 5.87 (s, 1H, CH). Anal. calcd for
C27H15BrO3: C 69.39, H 3.24; found: C 69.37, H 3.22.
14-(2-Chlorophenyl)-14H-dibenzo[a,i]xanthene-8,13-dione
(1h)
Orange solid, mp 280–282 °C (lit.11a 281–282 °C). UV
(4 × 10–5 mol/L solution in CHCl3) lmax (3): 338 nm
(2.51 × 104 L mol–1 cm–1). IR (nmax cm–1, KBr): 3068,
2-Hydroxy-14-(4-methoxyphenyl)-14H-dibenzo[a,i]
xanthene-8,13-dione (2a)
Orange solid, mp > 300 °C (decomp.). UV (4 × 10–5 mol/L
solution in CHCl3) lmax (3): 357 nm (1.08 × 104 L mol–1
cm–1). IR (nmax cm–1, KBr): 3297, 2924, 1700, 1650, 1627,
1
1666, 1638, 1591, 1577, 1361, 1289. H NMR (300 MHz,
CDCl3) d: 8.23–8.12 (m, 2H, Ar), 8.14 (d, J = 7.5 Hz, 1H,
Ar), 7.87–7.78 (m, 3H, Ar), 7.63–7.26 (m, 6H, Ar), 7.09–
7.00 (m, 2H, Ar), 6.20 (s, 1H, CH). Anal. calcd for
C27H15ClO3: C 76.69, H 3.58; found: C 76.66, H, 3.56.
1
1591, 1377, 1210. H NMR (400 MHz, DMSO-d6) d: 9.90
(s, 1H, OH), 8.18 (d, J = 7.56 Hz, 1H, Ar), 7.94 (d, J =
7.56 Hz, 1H, Ar), 7.86–7.62 (m, 4H, Ar), 7.44 (d, J =
Published by NRC Research Press

744
Can. J. Chem. Vol. 90, 2012
1
8.96 Hz, 1H, Ar), 7.20–7.17 (m, 3H, Ar), 6.97–6.95 (m,
1H, Ar), 6.74 (d, J = 8.72 Hz, 2H, Ar), 5.45 (s, 1H, CH),
3.58 (s, 3H, OCH3). 13C NMR (100 MHz, DMSO-d6) d:
177.98, 177.78, 157.95, 156.70, 156.35, 147.42, 135.77,
135.35, 132.32, 131.57, 130.63, 130.34, 130.25, 129.57,
129.32, 128.66, 126.03, 124.56, 117.74, 116.14, 115.16,
113.88, 105.55, 55.10, 34.03. MS (ESI) m/z calcd for
C28H18O5: 434.12; found: 435.20 [M+ + H].
1210. H NMR (400 MHz, DMSO-d6) d: 9.99 (s, 1H, OH),
8.23 (d, J = 7.76 Hz, 1H, Ar), 8.10 (d, J = 8.68 Hz, 2H, Ar),
7.98–7.67 (m, 5H, Ar), 7.62 (d, 2H, J = 8.68 Hz, Ar), 7.52 (d,
J = 8.72 Hz, 2H, Ar), 7.19 (s, 1H, Ar), 7.02–7.00 (m, 1H, Ar),
5.70 (s, 1H, CH). 13C NMR (100 MHz, DMSO-d6) d: 177.56,
177.29, 156.88, 156.51, 150.62, 147.31, 146.12, 134.98,
132.07, 131.60, 130.54, 130.46, 129.91, 128.42, 125.87,
124.51, 123.54, 117.74, 114.38, 113.74, 113.47, 105.17, 35.1.
MS (ESI) m/z calcd for C27H15NO6: 449.09; found: 450.10
[M+ + H].
2-Hydroxy-14-(4-bromophenyl)-14H-dibenzo[a,i]xanthene-
8,13-dione (2b)
Orange solid, mp > 300 °C(decomp.). UV (4 × 10–5 mol/L
solution in CHCl3) lmax (3): 344 nm (1.62 × 104 L mol–1 cm–1).
IR (nmax cm–1, KBr): 3307, 2923, 1701, 1654, 1627, 1379,
2-Hydroxy-14-(2-chlorophenyl)-14H-dibenzo[a,i]xanthene-
8,13-dione (2f)
Orange solid, mp > 300 °C (decomp.). UV (4 × 10–5 mol/L
solution in CHCl3) lmax (3): 358 nm (2.36 × 104 L mol–1 cm–1).
IR (nmax cm–1, KBr): 3298, 2924, 1700, 1623, 1591, 1375,
1
1210; H NMR (400 MHz, DMSO-d6) d: 9.93 (s, 1H, OH),
8.17 (d, J = 7.76 Hz, 1H, Ar), 7.95 (d, J = 7.80 Hz, 1H,
Ar), 7.85–7.64 (m, 4H, Ar), 7.45 (d, J = 8.68 Hz, 1H, Ar),
7.39–7.16 (m, 5H, Ar), 6.99–6.96 (m, 1H, Ar), 5.50 (s, 1H,
CH). 13C NMR (100 MHz, DMSO-d6) d: 178.19, 177.93,
157.26, 157.84, 147.80, 143.26, 135.53, 132.61, 131.99,
131.74, 131.23, 131.00, 130.85, 130.54, 130.05, 128.95,
126.38, 124.94, 120.27, 118.20, 115.62, 114.65, 114.20,
105.77, 35.03. MS (ESI) m/z calcd for C27H15BrO4: 482.02;
found: 483.02 [M+ + H], 485.02 [M+ + H + 2].
1
1210. H NMR (400 MHz, DMSO-d6) d: 9.91 (s, 1H, OH),
8.22 (d, J = 7.8 Hz, 1H, Ar), 7.95 (d, J = 7.92 Hz, 1H, Ar),
7.88–7.64 (m, 4H, Ar), 7.43 (d, J = 8.72 Hz, 1H, Ar), 7.32–
7.06 (m, 5H, Ar), 7.01–6.99 (m, 1H,Ar), 5.79 (s, 1H, CH).
MS (ESI) m/z calcd for C27H15ClO4: 438.07; found: 439.07
[M+ + H], 441.07 [M+ + H + 2].
2-Hydroxy-14-(isopropyl)-14H-dibenzo[a,i]xanthene-8,13-
dione (2g)
Orange solid, mp > 300 °C (decomp.). UV (4 × 10–5 mol/L
solution in CHCl3) lmax (3): 355 nm (2.38 × 104 L mol–1 cm–1).
IR (nmax cm–1, KBr): 3354, 2966, 1702, 1625, 1591, 1570,
2-Hydroxy-14-(4-methylphenyl)-14H-dibenzo[a,i]xanthene-
8,13-dione (2c)
Orange solid, mp > 300 °C (decomp.). UV (4 × 10–5 mol/L
solution in CHCl3) lmax (3): 349 nm (1.19 × 104 L mol–1 cm–1).
IR (nmax cm–1, KBr): 3359, 2924, 1701, 1653, 1629, 1592,
1
1398, 1211. H NMR (400 MHz, DMSO-d6) d: 9.93 (s, 1H,
OH), 8.09 (d, J = 7.36 Hz, 1H, Ar), 7.99 (d, J = 7.32 Hz,
1H, Ar), 7.83–7.76 (m, 3H, Ar), 7.67–7.63 (m, 1H, Ar),
7.34–7.28 (m, 2H, Ar), 7.05–7.02 (m, 1H, Ar), 4.51 (s, 1H,
CH), 2.04 (m, 1H, CH(CH3)2), 0.86 (d, J = 6.88 Hz, 3H,
CH3), 0.63 (d, J = 6.88 Hz, 3H, CH3). 13C NMR (100 MHz,
DMSO-d6) d: 178.84, 177.77, 159.38, 156.67, 148.64,
135.03, 132.33, 131.24, 130.47, 130.28, 130.20, 128.42,
125.88, 124.01, 117.65, 115.74, 113.63, 113.33, 104.77,
34.57, 33.39, 20.75, 17.71. MS (ESI) m/z calcd for
C24H18O4: 370.12; found: 371.17 [M+ + H].
1
1378, 1212. H NMR (400 MHz, DMSO-d6) d: 9.94 (s, 1H,
OH), 8.19 (d, J = 7.76 Hz, 1H, Ar), 7.96 (d, J = 7.76 Hz,
1H, Ar), 7.88–7.64 (m, 4H, Ar), 7.47 (d, J = 8.72 Hz, 1H,
Ar), 7.23–7.19 (m, 3H, Ar), 7.00–6.98 (m, 3H, Ar), 5.48 (s,
1H, CH), 2.13 (s, 3H, CH3). 13C NMR (100 MHz, DMSO-
d6) d: 178.25, 178.08, 157.07, 156.75, 141.09, 136.32,
135.66, 132.69, 131.93, 130.91, 130.65, 130.59, 129.70,
129.43, 129.00, 128.81, 126.37, 124.91, 118.09, 116.38,
115.41, 114.19, 105.99, 34.98, 20.98. MS (ESI) m/z calcd
for C28H18O4: 418.12; found: 419.12 [M+ + H].
2-Hydroxy-14-(thienyl)-14H-dibenzo[a,i]xanthene-8,13-
dione (2h)
2-Hydroxy-14-(4-chlorophenyl)-14H-dibenzo[a,i]xanthene-
8,13-dione (2d)
Orange solid, mp > 300 °C (decomp.). UV (4 × 10–5 mol/L
solution in CHCl3) lmax (3): 347 nm (2.10 × 104 L mol–1 cm–1).
IR (nmax cm–1, KBr): 3295, 1698, 1658, 1624, 1589, 1381,
Orange solid, mp > 300 °C (decomp.). UV (4 × 10–5 mol/L
solution in CHCl3), lmax (3): 354 nm (1.76 × 104 L mol–1 cm–1).
IR (nmax cm–1, KBr): 3227, 1618, 1597, 1377, 1212. 1H
NMR (400 MHz, DMSO-d6) d: 9.93 (s, 1H, OH), 8.19 (d,
J = 7.76 Hz, 1H, Ar), 7.95 (d, J = 7.80 Hz, 1H, Ar),
7.87–7.64 (m, 4H, Ar), 7.46 (d, J = 8.68 Hz, 1H, Ar),
7.31–7.17 (m, 5H, Ar), 6.99–6.97 (m, 1H, Ar), 5.52 (s,
1H, CH). 13C NMR (100 MHz, DMSO-d6) d: 178.20,
177.94, 157.26, 156.85, 147.82, 142.84, 135.54, 132.62,
132.00, 131.73, 131.00, 130.85, 130.56, 130.04, 128.96,
128.82, 126.38, 124.95, 118.19, 115.70, 114.73, 114.21,
105.77, 34.94; MS (ESI) m/z calcd for C27H15ClO4: 438.07;
found: 439.10 [M+ + H], 441.10 [M+ + H + 2].
1
1213. H NMR (400 MHz, DMSO-d6) d: 9.99 (s, 1H, OH),
8.18 (d, J = 7.76 Hz, 1H, Ar), 7.99 (d, J = 7.32 Hz, 1H,
Ar), 7.89–7.87 (m, 2H, Ar), 7.82 (d, J = 8.72 Hz, 1H, Ar),
7.70–7.66 (m, 1H, Ar), 7.46 (d, J = 9.16 Hz, 1H, Ar),
7.27–7.22 (m, 2H, Ar), 7.05 (dd, J1,2 = 2.28 Hz, J1,3
=
8.72 Hz, 1H, Ar), 6.89–6.82 (m, 2H, Ar), 5.87 (s, 1H,
CH). MS (ESI) m/z calcd for C25H14O4S: 410.06; found:
411.06 [M+ + H].
2-Hydroxy-14-(3-bromophenyl)-14H-dibenzo[a,i]xanthene-
8,13-dione (2i)
Orange solid, mp > 300 °C (decomp.). UV (4 × 10–5 mol/L
solution in CHCl3) lmax (3): 340 nm (2.25 × 104 L mol–1 cm–1).
IR (nmax cm–1, KBr): 3329, 2926, 1700, 1626, 1569, 1592,
2-Hydroxy-14-(4-nitrophenyl)-14H-dibenzo[a,i]xanthene-
8,13-dione (2e)
Orange solid, mp > 300 °C (decomp.). UV (4 × 10–5 mol/L
solution in CHCl3) lmax (3): 349 nm (2.25 × 104 L mol–1 cm–1).
IR (nmax cm–1, KBr): 3306, 2924, 1702, 1628, 1592, 1379,
1376, 1208. H NMR (400 MHz, DMSO-d6) d: 10.01 (s,
1H, OH), 8.20 (d, J = 7.36 Hz, 1H, Ar), 7.98 (d, J =
6.60 Hz, 1H, Ar), 7.93–7.75 (m, 3H, Ar), 7.70 (m, 1H, Ar),
1
Published by NRC Research Press

Khurana et al.
745
7.50–7.48 (m, 2H, Ar), 7.32–7.15 (m, 4H, Ar), 7.03 (dd, J1,2
=
3-Hydroxy-14-(4-bromophenyl)-14H-dibenzo[a,i]xanthene-
2.20 Hz, J1,3 = 8.80 Hz, 1H, Ar), 5.55 (s, 1H, CH). 13C
NMR (100 MHz, DMSO-d6) d: 177.67, 177.37, 156.81,
156.46, 147.41, 145.90, 134.97, 132.08, 131.49, 131.10,
130.60, 130.52, 130.43, 130.00, 129.63, 128.42, 127.61,
125.86, 124.47, 121.61, 117.73, 114.98, 113.96, 113.70,
105.19, 34.79. MS (ESI) m/z calcd for C27H15BrO4:
482.02; found: 483.02 [M+ + H], 485.02 [M+ + H + 2].
8,13-dione (3b)
Orange solid, mp > 300 °C (decomp.). UV (4 × 10–5 mol/L
solution in CHCl3) lmax (3): 348 nm (1.48 × 104 L mol–1 cm–1).
IR (nmax cm–1, KBr): 3309, 2925, 1624, 1591, 1370, 1214.
1H NMR (400 MHz, DMSO-d6) d: 9.78 (s, 1H, OH), 8.16
(d, J = 7.80 Hz, 1H, Ar), 7.93 (d, J = 7.76 Hz, 1H, Ar),
7.86–7.82 (m, 2H, Ar), 7.76 (d, J = 9.16 Hz, 1H, Ar), 7.66–
7.56 (m, 2H, Ar), 7.35–7.26 (m, 4H, Ar), 7.14 (d, J =
6.32 Hz, 1H, Ar), 7.14 (dd, J1,2 = 2.32 Hz, J1,3 = 9.16 Hz,
1H, Ar), 5.66 (s, 1H, CH). 13C NMR (100 MHz, DMSO-d6)
d: 178.08, 177.94, 156.85, 156.59, 145.19, 143.64, 135.47,
133.73, 131.90, 131.67, 131.20, 130.75, 130.57, 128.88,
128.41, 125.54, 124.89, 124.66, 120.19, 117.91, 116.63,
115.37, 110.65, 34.92. MS (ESI) m/z calcd for C27H15 BrO4:
482.02; found: 483.10 [M+ + H], 485.10 [M+ + H +2].
2-Hydroxy-14-(phenyl)-14H-dibenzo[a,i]xanthene-8,13-
dione (2j)
Orange solid, mp > 300 °C (decomp.). UV (4 × 10–5 mol/L
solution in CHCl3) lmax (3): 354 nm (1.96 × 104 L mol–1 cm–1).
IR (nmax cm–1, KBr): 3311, 2925, 1618, 1592, 1376, 1211.
1H NMR (400 MHz, DMSO-d6) d: 9.95 (s, 1H, OH), 8.11
(d, J = 7.32 Hz, 1H, Ar), 7.94 (d, J = 6.60 Hz, 1H, Ar),
7.87–7.83 (m, 2H, Ar), 7.77 (d, J = 8.80 Hz, 1H, Ar),
7.66–7.62 (m, 1H, Ar), 7.46 (d, J = 8.80 Hz, 1H, Ar),
7.33 (d, J = 7.36 Hz, 2H, Ar), 7.24–7.18 (m, 3H, Ar),
References
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7.09–7.06 (m, 1H, Ar), 7.00 (dd, J1,2 = 2.20 Hz, J1,3
=
8.76 Hz, 1H, Ar), 5.51 (s, 1H, CH). 13C NMR (100 MHz,
DMSO-d6) d: 177.70, 177.51, 156.65, 156.34, 147.29,
143.47, 135.07, 132.19, 131.40, 130.39, 130.18, 130.12,
129.27, 128.43, 128.37, 126.60, 125.86, 124.38, 117.61,
115.76, 114.77, 113.66, 105.33, 34.89. MS(ESI) m/z calcd
for C27H16O4: 404.10; found: 405.10[M+ + H].
2-Hydroxy-14-(2,4-dichlorophenyl)-14H-dibenzo[a,i]
xanthene-8,13-dione (2k)
Orange solid, mp > 300 °C (decomp.). UV (4 × 10–5 mol/L
solution in CHCl3) lmax (3): 350 nm (1.30 × 104 L mol–1 cm–1).
IR (nmax cm–1, KBr): 3338, 2926, 1702, 1627, 1593, 1572,
1
1466, 1450, 1378, 1213. H NMR (400 MHz, DMSO-d6) d:
9.96 (s, 1H, OH), 8.23 (d, J = 7.72 Hz, 1H, Ar), 7.98 (d, J =
6.60 Hz, 1H, Ar), 7.90–7.84 (m, 2H, Ar), 7.79 (d, J =
8.76 Hz, 1H, Ar), 7.71–7.76 (m, 1H, Ar), 7.47–7.42 (m,
3H, Ar), 7.27–7.24 (m, 2H, Ar), 7.05 (dd, J1,2 = 2.20 Hz,
J1,3 = 8.80 Hz, 1H, Ar), 5.79 (s, 1H, CH). 13C NMR
(100 MHz, DMSO-d6) d: 177.54, 177.35, 156.80, 156.51,
147.45, 139.61, 135.04, 133.53, 133.32, 132.47, 132.04,
131.55, 130.48, 130.37, 130.03, 129.79, 128.91, 128.39,
127.60, 125.77, 124.52, 117.61, 113.73, 105.48, 32.93. MS
(ESI) m/z calcd for C27H14Cl2O4: 472.03; found: 473.03 [M+ +
H], 475.03 [M+ + H + 2].
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3-Hydroxy-14-(4-methoxyphenyl)-14H-dibenzo[a,i]
xanthene-8,13-dione (3a)
Orange solid, mp > 300 °C (decomp.). UV (4 × 10–5 mol/L
solution in CHCl3) lmax (3): 355 nm (1.36 × 104 L mol–1 cm–1).
IR (nmax cm–1, KBr): 3386, 2926, 1624, 1516, 1371, 1290.
1H NMR (400 MHz, DMSO-d6) d: 9.76 (s, 1H, OH), 8.16
(d, J = 7.80 Hz, 1H, Ar), 7.94–7.85 (m, 3H, Ar), 7.75 (d, J =
9.10 Hz, 1H, Ar), 7.66–7.57 (m, 2H, Ar), 7.23 (d, J =
8.72 Hz, 2H, Ar), 7.13 (d, J = 6.32 Hz, 1H, Ar), 7.06–7.03
(m, 1H, Ar), 6.73 (d, J = 9.64 Hz, 2H, Ar), 5.62 (s, 1H,
CH), 3.57 (s, 3H, OCH3). 13C NMR (100 MHz, DMSO-d6)
d: 178.78, 178.09, 158.26, 156.70, 155.51, 145.21, 136.57,
135.63, 133.72, 131.77, 130.87, 130.67, 129.93, 128.97,
128.09, 125.82, 124.89, 124.82, 120.04, 117.94, 117.57,
116.27, 114.22, 110.57, 55.43, 34.49. MS (ESI) m/z calcd
for C28H18O5: 434.12; found: 435.12 [M+ + H].
Published by NRC Research Press

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