Synthesis of xanthenediones by silica supported orthophosphoric acid (H3PO4·SiO2)

Article abstract of DOI:10.14233/ajchem.2018.21498

The novel protocol was developed for the synthesis of xanthenediones by silica supported orthophosphoric acid (H3PO4·SiO2) as a heterogeneous catalyst. The reported protocol is simple, scalable, mild and effective for the synthesis of xanthenediones. The (H3PO4·SiO2) catalyst demonstrated excellent catalytic activity for various substituted aromatic aldehydes. This catalyst can be reused four times without much loss in catalytic activity.

Full text of DOI:10.14233/ajchem.2018.21498

Asian Journal of Chemistry; Vol. 30, No. 10 (2018), 2343-2346
A
SIAN
J
OURNAL OF HEMISTRY
C
https://doi.org/10.14233/ajchem.2018.21498
Synthesis of Xanthenediones by Silica Supported Orthophosphoric Acid (H3PO4·SiO2)
1,*
2
1
3,*
RAHUL S. PATIL , SURESH S. SHENDAGE , UDAY P. LAD and UTTAM B. MORE
1Department of Chemistry, Yashwantrao Chavan College of Science, Karad-415 124, India
2KET’S Vinayak Ganesh Vaze College of Arts, Science and Commerce, Mithagar Road, Mulund (E), Mumbai-400 081, India
3Department of Chemistry, Sadguru Gadage Maharaj College, Karad-415 110, India
*Corresponding authors: Fax: +91 2164 271356; Tel: +91 2164 271356; E-mail: rspatilorg@gmail.com; uttambmore@rediffmail.com
Received: 5 June 2018;
Accepted: 16 July 2018;
Published online: 31 August 2018;
AJC-19071
The novel protocol was developed for the synthesis of xanthenediones by silica supported orthophosphoric acid (H3PO4·SiO2) as a
heterogeneous catalyst. The reported protocol is simple, scalable, mild and effective for the synthesis of xanthenediones. The (H3PO4·SiO2)
catalyst demonstrated excellent catalytic activity for various substituted aromatic aldehydes. This catalyst can be reused four times
without much loss in catalytic activity.
Keywords: Xanthenediones, Heterogeneous catalysis, H3PO4·SiO2, Condensation reaction.
and cyanuric chloride [10]. However these methods require
harsh reaction conditions, long reaction time, low yields, use
toxic and expensive catalysts. So in preparation of xanthene-
diones, novel methods are desirable, which overcomes afore
mentioned drawbacks.
INTRODUCTION
In recent years the xanthene fascinated considerable
interest to organic synthesis since it exhibits antibacterial,
antiviral, anticoagulant, anticancer, diuretic, spasmolytic and
anti-inflammatory properties [1,2]. Besides, these compounds
have been explored for agricultural bactericidal activity and
photodynamic therapy [3,4]. Xanthenediones are integral part
of number of natural products [5]. The presence of pyran ring
in xanthenediones makes it as versatile synthons [6]. Moreover,
their applications are explored in cosmetics, pigments, laser
technologies [7,8] and in fluorescent material for revelation
of biomolecules [9,10].
In synthesis of xanthenediones, usually acid or base catalyzed
condensation of suitable active methylene group containing
carbonyl compounds with aldehydes is carried out [11]. In
literature different methods have been reported for synthesis
of xanthenediones such as condensation of active methylene
compounds with aldehydes catalyzed by sulfuric acid or hydro-
chloric acid [12], TiO2/SO42– [13], polyaniline p-toluenesulfo-
nate [14], PPA-SiO2 [15], Amberlyst-15 [16], Fe3+-montmori-
llonite [17], NaHSO4-SiO2 or silica chloride [18], cellulose-
sulfuric acid [19], InCl3/ionic liquid [20], Dowex-50W [21],
ZrOCl2·8H2O4, trimethylsilyl chloride (TMSCl) [22], ω-4°-
ammoniumalkyl sulfonate [23], polytungstozincate acid [24]
Heterogeneous catalysis has more advantages than homo-
geneous catalysis because in industrial practice, the removal
of the product and recovery of the catalysts are comparatively
easier. The development of nonmetallic heterogeneous catalyst
is essential due to their advantage of nominal product contami-
nation from metal release during reaction. Recently, silica
supported catalysts such as HClO4/SiO2 [25], H3PO4·SiO2 [26]
and ionic liquid prompted microwave irradiation [27] have
been used by various research group for organic transformation.
Herein, we report silica supported orthophosphoric acid as a
novel heterogeneous, reusable catalyst for synthesis of xanthen-
ediones. To the best of our knowledge, catalyst (H3PO4·SiO2)
has not been reported earlier for synthesis of xanthenediones
(Scheme-I). This catalyst was found to be highly efficient, recycl-
able and environmentally benign for synthesis of xanthene-
diones.
EXPERIMENTAL
All commercially available reagents were used as received
without further purification. 1H NMR spectra were recorded
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2344 Patil et al.
Asian J. Chem.
R1
TABLE-1
CHO
R3
R2
OPTIMIZATION OF REACTION PARAMETERS
FOR SYNTHESIS OF XANTHENEDIONESa
OCH3
H3PO4. SiO2
R3
2
O
O
Ethanol, reflux
CHO
R2
O
O
R1
H3PO4. SiO2
Solvent
2
O
O
O
Reflux
Scheme-I: Synthesis of xanthendiones by silica supported ortho-H3PO4
O
O
OCH3
O
on a BrukerAC-400 (400 MHz) spectrometer with TMS as an
internal standard.
Catalyst
amount
(mg)
S.
No.
Time
(min)
Yieldb
(%)
Solvent
Temp.
Synthesis of silica supported orthophosphoric acid:
Silica supported orthophosphoric acid catalyst was prepared
by reported method [26]. In typical procedure suspension of
(5 g) SiO2 in 30 mL choloroform was obtained. Then 3.5 g of
orthophosphoric acid was added to above suspension of SiO2
and stirred at room temperature for 2 h. This reaction mass was
concentrated by heating at 100 °C to get free-flowing powder.
This powder was washed with water and finally with 50 mL
of ethanol and dried at 110 °C to get a desired catalyst.
General procedure for the synthesis of xanthenediones:
Aldehyde, dimedone (1:2 mmol) and 30 mg catalyst was refluxed
at 80 °C in ethanol. Completion of reaction was monitored on
TLC. After completion of reaction, product was filtered to
remove catalyst. Product was purified by column chromato-
graphy (ethyl acetate and petroleum ether). Product were charac-
terized by melting points were compared with the literature
and proved by spectroscopic data.
1
2
3
4
5
6
7
8
9
Ethanol
Ethanol
Ethanol
Ethanol
Ethanol
Ethanol
Water
Reflux
Reflux
Reflux
Reflux
Reflux
Room temp.
Reflux
Reflux
30
30
30
20
10
30
30
10
10
30
20
10
30
30
30
30
30
30
94
88
70
81
45
16
31
61
73
DMSO
DMF
Reflux
aReaction condition: p-methoxy benzaldehyde (1 mmol), dimedone (2
mmol), Ethanol (5 mL), Catalyst (H3PO4·SiO2) and temperature reflux
bIsolated yield.
results shows that the higher reaction temperature, the more
efficiently the reaction could proceed. The various solvents
such as water, DMSO, DMF and ethanol have been tried for
these reaction Table-1 entries 7-9). The reaction gave high
yield of corresponding product in presence of ethanol. The opti-
mized reaction conditions are catalyst: 30 mg (H3PO4·SiO2),
solvent: ethanol, time 30 min and temperature: reflux.
RESULTS AND DISCUSSION
Reaction between 4-methoxybenzaldehyde and dimedone
was used as model reaction for optimization of reaction condi-
tions (Table-1).As shown in Table-1, the reaction could proceed
efficiently in presence of 30 mg silica supported orthophos-
phoric acid as heterogeneous catalyst (Table-1 entries 1-3).
The reaction temperature effects on the yields of the products
were studied by performing the condensation reaction at room
temperature and reflux, respectively (Table-1 entries 4-6). The
Then at above optimized conditions, various aldehydes
were studied and the results are presented in Table-2. The
catalyst (H3PO4·SiO2) was found to be worked effectively for
substituted and unsubstituted benzaldehyde (Table-2 entries
1-13). Electron-withdrawing substituents bearing aromatic
aldehydes reacted smoothly in short time as compared to
electron donationg subtituents (Table-2 entries 3-13). We have
also investigated activity of catalyst for cinnamaldehyde which
TABLE-2
SUBSTRATE STUDY
S. No.
1
R1
H
R2
H
R3
Time (min)
30
Product
Yieldb (%)
94
O
O
H
H
O
2
3
H
H
H
30
40
O
O
91
92
O
Cl
Cl
H
O
O
O

Vol. 30, No. 10 (2018)
Synthesis of Xanthenediones by Silica Supported Orthophosphoric Acid (H3PO4·SiO2) 2345
CH3
4
CH3
H
H
H
H
60
80
91
89
O
O
O
5
CH(CH3)2
O
O
O
OCH3
6
7
OCH3
OCH3
H
H
H
45
60
93
89
O
O
O
OCH 3
OC H3
OCH3
O
O
O
NO2
O
O
8
9
H
H
H
NO2
H
NO2
30
60
45
90
86
91
O
NO2
O
O
H
O
NO2
O
O
10
NO2
H
O
OH
O
O
11
12
H
OH
H
H
70
45
85
92
O
OH
OH
H
O
O
O
N
13
N(CH3)2
H
H
55
87
O
O
O
aReaction conditions: Aromatic aldehyde (1 mmol), dimedone (2 mmol) H3PO4·SiO2 (30 mg), ethanol (2 mL), reflux time: 30 min. bIsolated yield.

2346 Patil et al.
Asian J. Chem.
TABLE-4
COMPARISON OF RESULTS USING (H3PO4·SiO2) CATALYST WITH RESULTS OBTAINED BY OTHER WORKERS
S. No.
Catalyst
(H3PO4·SiO2)
InCl3·4H2O
Reaction conditions
Ethanol, reflux
Ionic liquid/80 °C
EtOH (reflux)
CH3CN (reflux)
CH3CN (reflux)
Time (min)
30-80
240-600
360
Yield (%)
85-94
76-95
84-96
90-98
Ref.
This work
[2288]
1
2
3
4
5
Fe3+-montmorillonite
NaHSO4-SiO2
Amberlyst-15
[2299]
[1188]
[16]
16
360
300
90-96
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was easily recovered by filtration after washing with ethyl acetate
and drying at 80 °C. The recycled catalyst was used for the next.
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leaching of the catalyst. Thus catalyst, (H3PO4·SiO2) could be
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Run
Yieldb
1st
2nd
3rd
4th
5th
84
94
92
91
89
aReaction conditions: Aromatic aldehyde (1 mmol), dimedone (2
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bIsolated yield
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catalyst reported in this work is simple, more efficient and
less time consuming compared with other reported catalysts.
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for the synthesis of various substituted and unsubstituted
xanthenediones. In addition to this, low-cost, easy availability,
recyclability, low toxicity, stability of the catalyst, excellent
yields of products and short reaction time make this protocol
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ACKNOWLEDGEMENTS
The authors are thankful for Instrumentation Department,
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CONFLICT OF INTEREST
The authors declare that there is no conflict of interests
regarding the publication of this article.
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