N-Sulfonic acid poly(4-vinylpyridinium) hydrogen sulfate as an efficient and reusable solid acid catalyst for one-pot synthesis of xanthene derivatives in dry media under ultrasound irradiation

Article abstract of DOI:10.1016/j.ultsonch.2014.06.020

N-Sulfonic acid poly(4-vinylpyridinium) hydrogen sulfate catalyzed efficiently the synthesis of xanthene derivatives under ultrasonic irradiation at room temperature, which has prompted various concerns involving cost and environmental persistence. This methodology shows the effect of presence of anion hydrogen sulfate as an important and effective factor on the promotion of the one-pot multi-components and condensation reactions. The catalyst can be recovered by simple filtration and used for several times without a significant loss of catalytic activity.

Full text of DOI:10.1016/j.ultsonch.2014.06.020

Accepted Manuscript
N-sulfonic acid poly(4-vinylpyridinium) hydrogen sulfate as an efficient and
reusable solid acid catalyst for one-pot synthesis of xanthene derivatives in dry
media under ultrasound irradiation
Nader Ghaffari Khaligh, Farhad shirini
PII:
S1350-4177(14)00223-5
DOI:
http://dx.doi.org/10.1016/j.ultsonch.2014.06.020
ULTSON 2643
Reference:
Ultrasonics Sonochemistry
To appear in:
Received Date:
Revised Date:
Accepted Date:
2 June 2014
25 June 2014
26 June 2014
Please cite this article as: N.G. Khaligh, F. shirini, N-sulfonic acid poly(4-vinylpyridinium) hydrogen sulfate as an
efficient and reusable solid acid catalyst for one-pot synthesis of xanthene derivatives in dry media under ultrasound
irradiation, Ultrasonics Sonochemistry (2014), doi: http://dx.doi.org/10.1016/j.ultsonch.2014.06.020
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0
Graphical Abstract
N-sulfonic acid poly(4-vinylpyridinium)
hydrogen sulfate as an efficient and reusable
solid acid catalyst for one-pot synthesis of
xanthene derivatives in dry media under
ultrasound irradiation
Leave this area blank for abstract info.
Nader Ghaffari Khaligh*a, Farhad Shirinib
aResearch House of Professor Reza. Education Guilan, Rasht, District 1, 41569‐17139, Iran
bDepartment of Chemistry, College of Science, University of Guilan, Rasht, 41335-19141, Iran
SO3H
SO3H
N
N
N
Cl
HSO4
ClSO3H (neat)
H2SO4 (100%), dry CH2Cl2
N2, 2.5 h, 50oC
Dry CH2Cl2, 6 h, r.t.
n
n
n
NSPVPC
PVP
2 A
NSPVPHS
R
O
O
R
O
O
2 B
O
R
O
NSPVPHS, ))))))
Solvent-free, r.t.
R-CHO
+
O
A + C
O
R
O
O
O
O
B + C
O
O
O
OH
OH
O
B
C
A

1
N-sulfonic acid poly(4-vinylpyridinium) hydrogen sulfate as an efficient and
reusable solid acid catalyst for one-pot synthesis of xanthene derivatives in dry
media under ultrasound irradiation
Nader Ghaffari Khaligh∗a, Farhad shirinib
aResearch House of Professor Reza. Education Guilan, Rasht, District 1, 41569‐17139, Iran
bDepartment of Chemistry, College of Science, University of Guilan, Rasht, 41335-19141, Iran
ARTICLE INFO
ABSTRACT
Article history:
Received
N-sulfonic acid poly(4-vinylpyridinium) hydrogen sulfate catalyzed efficiently the synthesis of
xanthene derivatives under ultrasonic irradiation at room temperature, which has prompted various
concerns involving cost and environmental persistence. This methodology shows the effect of
presence of anion hydrogen sulfate as an important and effective factor on the promotion of the
one-pot muti-components and condensation reactions. The catalyst can be recovered by simple
filtration and used for several times without a significant loss of catalytic activity.
Received in revised form
Accepted
Available online
Keywords:
Ultrasound
Heterogeneous catalyst
Anion effect
.
Multi-component
Xanthene
———
∗ Corresponding author. Tel: +98-21-66431738; fax: +98-21-66934046; e-mail: ngkhaligh@guilan.ac.ir and ngkhaligh@gmail.com

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1. Introduction
Due to the spectroscopic properties, xanthene derivatives were used as dyes [1-3], in laser technologies [4], and in fluorescent
materials for visualization of biomolecules [5]. Also a variety of natural and synthetic xanthene and benzoxanthene derivatives have the
potential biological and pharmaceutical properties [6-11]. Because of these significant features there has been a continuous interest in
the synthesis of these types of compounds and consequently numerous approaches have been reported for their synthesis [12-24]. The
main synthetic method for the preparation of xanthenes is based on the three-component condensation in the presence of a Brönsted or
Lewis acid. Even though various procedures were reported, some of them suffer from the disadvantages including low yields, prolonged
reaction times, use of very expensive catalysts, the formation of by-products, use of an excess of reagents/catalysts, corrosion as well as
waste acid pollution problems and use of toxic organic solvents. Therefore, there is still scope for development of a safer, more
convenient and efficient method.
Ultrasound as an eco-environmental technology in green chemistry has advantageous over the traditional thermal methods as
enhanced reaction rates, formation of purer products, improved yields, suppression of side products, increased selectivities, easier
experimental procedures, and use of milder conditions [25-28]. A survey of the literature reveales that a number of researchers have
demonstrated the efficacy of sonication under solvent-free conditions but at least one of the phases of the reaction mixture was a liquid
[29-31]. In addition, the use of heterogeneous catalysts in dry media can contribute to improve the production process, eliminating or
transforming unwanted and/or toxic byproducts avoiding the need for tedious separation.
Supported reagents have been the subject of increasing levels of attention in organic chemistry [32,33]. They can be readily
recovered from the reaction mixture and reused. Among the various supports available for synthetic reagents, poly(4-vinylpyridine)
cross-link with divinylbenzen P(4-VP) is one of the most commonly used heterogeneous polymeric supports in organic chemistry.
Recently, it was used as a support for the preparation of solid acid catalysts [34-40].
2. Experimental Section
2.1. Materials
Unless specified, all chemicals were analytical grade and purchased from Merck, Aldrich and Fluka Chemical Companies and used
without further purification. Products were characterized by their physical constant and comparison with authentic samples. The purity
determination of the substrates and reaction monitoring were accompanied by TLC using silica gel SIL G/UV 254 plates.
2.2. Instrumentation
The purity determination of the products was accomplished by TLC and GC-MS on an Agilent GC-Mass-6890 instrument under 70
eV conditions. The FT-IR spectra were recorded on a Perkin Elmer 781 Spectrophotometer using KBr pellets for solid and neat for
liquid samples in the range of 4000-400 cm-1. In all the cases the 1H and 13C NMR spectra were recorded with Bruker Avance 300 MHz
instrument. All chemical shifts are quoted in parts per million (ppm) relative to TMS using deuterated solvent. Microanalyses were
performed on a Perkin- Elmer 240-B microanalyzer. Melting points were recorded on a Büchi B-545 apparatus in open capillary tubes.

3
Sonication was performed in Bandelin Sonorex reactor with a frequency of 35 kHz and a nominal power of 200 W, built-in heating, 30-
80 ºC thermostatically adjustable. The reaction vessel placed inside the ultrasonic bath containing water.
2.3. A General procedure for the synthesis of xanthene derivatives by grinding and heating method
A mixture of aldehyde (1 mmol) and the desired substrates {2-naphthol (2 mmol), 2-hydroxynaphthalene-1,4-dione (2 mmol),
mixture of 2-naphthol (1 mmol) and indane-1,3-dione(1 mmol) or 2-hydroxynaphthalene-1,4-dione (1 mmol) and indane-1,3-dione(1
mmol); according to Scheme 1} was heated and mixed in the presence of NSPVPHS (10 mg) [40] at 60 °C by grinding under solvent-
free conditions. The progress of the reaction was monitored by TLC. After completion of the reaction, the product was extracted with
Et2O (3 × 5 mL) and the catalyst was recovered and was dried at 65°C under vacuum to remove moisture, and then was reused. The
combined ethereal solution was concentrated under vacuum to afford the crude product. The highly pure product was obtained by
recrystallization from EtOH. The products were characterized by IR, NMR spectroscopic data and elemental analysis. The melting point
of known compounds is compared with reported values [36-38 and 41-46].
2.4. A General procedure for the synthesis of xanthene derivatives by sonochemical method
A mixture of aldehyde (1 mmol) and the desired substrates {2-naphthol (2 mmol), 2-hydroxynaphthalene-1,4-dione (2 mmol),
mixture of 2-naphthol (1 mmol) and indane-1,3-dione (1 mmol) or 2-hydroxynaphthalene-1,4-dione (1 mmol) and indane-1,3-dione (1
mmol); according to Scheme 1} were mixed in the presence of NSPVPHS (10 mg) at room temperature under ultrasound irradiation.
The progress of the reaction was monitored by TLC. After completion of the reaction, the product was extracted with Et2O (3 × 5 mL)
and the catalyst was recovered and was dried at 65°C under vacuum to remove moisture, and then was reused. The combined ethereal
solution was concentrated under vacuum to afford the crude product. The highly pure product was obtained by recrystallization from
EtOH.
2.5. Hydrolysis of catalyst in aqueous media
The reaction of NSPVPHS with water is important because water was produced as a by-product through the condensation reaction
and also moisture was observed about 12% due to absorption of physisorbed water molecules before drying. After drying, the content of
water of NSPVPHS was 1.2% using Karl–Fischer titration method. On the other hand, analysis showed one equivalent point for
neutralization in curve of titration, therefore it seems that the slow hydrolysis of catalyst in aqueous solution may be presented by the
following equation (Scheme 2).
2.6. Acivation procedure for the recycled catalyst
The recovered catalyst collected from different experiments was washed successively with Et2O and acetone. Then catalyst was
dried in vacuum at room temperature and it was stirred with chlorosulfonic acid and then sulfuric acid in dry CH2Cl2 to recover its
activity.
2.7. Spectral data for new compounds

4
NO2
O
O
O
O
O
13-(4-Nitrophenyl)-5H-dibenzo[b,i]xanthene-5,7,12,14(13H)-tetraone
Orange powder, m.p. >320 °C; IR (KBr) νmax = 3030, 1660,1600 cm-1; 1H NMR (300 MHz, DMSO-d6): δ = 5.45 (s, 1H, CH), 7.14–
8.16 (m, 12H, ArH) ppm; MS (m/z, %): 463 (M+, 25), 418 (M+-NO2, 40), 313 (M+- NO2-C6H4-CHO, 100); Anal. Calcd (%) for
C27H13NO7: C, 69.98; H, 2.83; N, 3.02. Found: C, 69.93; H, 2.80; N, 3.06.
OMe
O
O
O
O
O
13-(4-methoxyphenyl)-5H-dibenzo[b,i]xanthene-5,7,12,14(13H)-tetraone
Brown-redish powder, m.p. >320 °C; IR (KBr) νmax = 3080, 1660, 1605, 1230, 1020 cm-1; 1H NMR (300 MHz, DMSO-d6): δ = 3.81
(s, 3H, CH3), 5.11 (s, 1H, CH), 7.15-7.67 (m, 10H, ArH), 8.02-8.10 (m, 2H, ArH) ppm; MS (m/z, %): 448 (M+, 35), 420 (M+-CHO,
100), 313 (M+-MeO-C6H4-CHO, 65); Anal. Calcd (%) for C28H16O6: C, 75.00; H, 3.57. Found: C, 74.92; H, 3.52.
NO2
O
O
13-(4-Nitrophenyl)-indeno[1,2-b]naphtho[1,2-e]pyran-12(13H)-one
Yellow solid, mp 262-264 °C. IR (KBr) νmax = 3035, 1665,1608 cm-1; 1H NMR (300 MHz, DMSO-d6): δ = 5.57 (s, 1H, CH), 7.31-
7.87 (m, 11H, ArH), 7.93-8.07 (m, 3H, ArH) ppm; MS (m/z, %): 405 (M+, 30), 360 (M+-NO2, 45), 255 (M+- NO2-C6H4-CHO, 100);
Anal. calcd for C26H15NO4: C, 77.03; H, 3.73; N, 3.46. found: C, 76.88; H, 3.69; N, 3.52.
3. Results and discussion
Part of our research is aiming to show the potential ability of the ultrasound irradiation as a green source of energy for organic
synthesis under solvent-free conditions [25-28]. Poly(4-vinylpyridinium) hydrogen sulfate was prepared and used in the variety of
organic transformations [36 and 38]. Very recently, The synthesis of N-sulfonic acid poly(4-vinylpyridinium) chloride [NSPVPC] and
its applications in the chemoselective 1,1-diacetate protection and deprotection of aldehydes [34] and N-Boc protection of amines [35]
was described. Herein, and in continuation of these studies, we wish to report the application of another analogue of Solid Acid
Functionalized Poly(4-vinylpyridine) [SAFPVP], namely, N-sulfonic acid poly(4-vinylpyridinium) hydrogen sulfate (NSPVPHS) [40]

5
as a reusable heterogeneous catalyst in the promotion of the synthesis of xanthene derivatives in dry media at significantly milder
reaction conditions than those known in literature (Scheme 1). For that purpose, eco-efficient methodology as ultrasound irradiation that
allows decreasing the amount of waste and a better use of energy is proposed.
The reaction of 4-chloro-benzaldehyde (1 mmol) with 2-naphthol (A, 2 mmol) was taken as model and treated with NSPVPHS (10
mg) under different conditions including various solvents such as phMe, MeCN, EtOH, Et2O, THF, DCM, and water at room
temperature or reflux conditions; and also the model reaction was done at different temperatures in the absence of solvent (Scheme 3).
The reaction was not completed in the presence of solvents at reflux after 2 h and two products (I) and (II) were observed (IR and
GCMS) and the yield of the product (II) was low (32%). The significant increase was not observed in the yield of product (II) with
longer reaction times. The reaction was completed after 15 minutes under solvent-free conditions at 60 °C and 14-(4-chlorophenyl)-
14H-dibenzo[a,j]xanthene was obtained with yield 94%. The better catalytic activity of NSPVPHS under neat conditions compared to
that in solvents may be explained due to the better electrostatic effect of the ionic aggregates in the solid state to activate the substrates.
The poor results obtained in solvents may be reasonably included due to the competitive interaction of the solvent molecules with the
active sites of the catalyst and also the decreased diffusion of the substrates in the presence of the solvent.
In order to optimization, the model reaction was carried out in the presence of different amounts of NSPVPHS at 60 °C under
grinding and solvent-free conditions. The results showed that the reaction was not possible in the absence of the catalyst. Increasing the
amount of solid acid catalyst to 20 mg showed no significantly improvement in the yield (95%) and only the reaction time was
decreased slightly (12 min). It should be noted that when the reaction proceeded in solvent the reaction time became longer.
To survey the effect of ultrasonic irradiation, the model reaction was performed using NSPVPHS at room temperature under
ultrasonic irradiation. In general, ultrasound has chemical and mechanical effects. The majority of the advantages of the uses of
ultrasound in the processing of liquids can be directly related to the physical effects of acoustic cavitation: the formation, growth and
implosive collapse of bubbles in liquids irradiated with high-intensity ultrasound [47]. Since this work is a heterogeneous catalytic
system in dry media, it seems that the main effect of ultrasound can be due to its mechanical effect. The mechanical effects of
ultrasound allows penetration of reactants and/or release of materials from surface, degradation of large solid particles due to shear
forces induced by shock waves and microstreaming leads to reduction of particle size and increase of surface area and accelerated
motion of suspended particles leads to better mass transfer [48]. Frequencies below 50 kHz are generally preferred for the
heterogeneous systems due to the more intense mechanical effects [49]; hence, we selected 35 kHz for maximum sonication. Control
experiments showed the effect of a possible simultaneous thermal activation. 14-(4-Chlorophenyl)-14H-dibenzo[a,j]xanthene was
obtained in the presence of NSPVPHS (10 mg) at room temperature and 60 ºC under grinding method in 28% and 94% yield,
respectively, after 15 min (Table 1, entry 2). The reaction was subjected to ultrasonic irradiation initially for 2 min, but no product was
detected (TLC monitoring), sonication was then continued, product formation was noticed, and after 5 min the percentage of the
product formation was found 95% yield. Continuation of sonication for 15 min, did not affect the yield (Table 1, entry 2). It was
apparent that the ultrasound irradiation could accelerate the reaction. The need of just one third of reaction time (5 min vs. 15 min) and

6
the lower temperature (ca. 25 ºC vs. 60 ºC) showed that ultrasonic chemical activation clearly affected the course of the reaction
increasing its energy efficiency.
For exploring of the scope and efficiency of the NSPVPHS, 2-naphthol (A), 2-hydroxynaphthalene-1,4-dione (B) and indane-1,3-
dione (C) were condensed with a variety of aldehydes under the optimized reaction conditions. The results are summarized in Table 1.
The results showed that presence of the electron-withdrawing and electron-donating substituents on the aromatic ring of aldehydes have
influence on the reaction times and the yields. With electron releasing groups (-OMe) in the para-position of the aromatic aldehydes,
rate and yield of the reaction was decreased due to the electrophilic character of the carbonyl carbon became less for the electrophilic
attack (Table 1, entry 4). In the presence of electron-withdrawing groups (-NO2) in the para-position, electrophicity of the carbonyl
carbon is enhancing (Table 1, entry 5). The presence of a –NO2 group in the ortho position decreased both the rate and the yield of 14-
(2-nitrophenyl)-14H-dibenzo [a,j]xanthene. It seems be due to intramolecular interaction and steric interference (Table 1, entry 6).
Moreover, the presence of halogen on the aromatic ring of the aldehydes had a negligible effect on the reaction results (Table 1, entries
2,3). After the successful synthesis of the 14-aryl-14H-dibenzo[a,j]xanthenes, we decided to explore the synthesis of 13-aryl-5H-
dibenzo[b,i]xanthene-5,7,12,14(13H)-tetraone, 13-aryl-indeno[1,2-b]naphtho[1,2-e]pyran-12(13H)-one and 12-aryl-12H-indeno[1,2-
b]naphtho[3,2-e]pyran-5,11,13-trione derivatives using NSPVPHS as a versatile solid acid catalyst under similar conditions. When 2-
hydroxynaphthalene-1,4-dione (B) was applied in the reaction, the desired xanthenes were obtained in short reaction time and high
yields (Table 1, entries 8-13).
A search of the literature indicated that only few methods were available for the synthesis of indeno[1,2-b]naphtho[e]pyrans. It was
possible to prepare 13-aryl-indeno[1,2-b]-naphtha[1,2-e]pyran-12(13H)-ones employing silica chloride [44a], sulfamic acid [44b], ionic
liquids [45] and poly(4‐vinylpyridinium) hydrogen sulfate [46] as a catalyst under thermal solvent-free conditions. However, there were
several limitations to these procedures, such as high temperature, unsatisfactory yields and long reaction time.
In addition, synthesis of 12-aryl-12H-indeno[1,2-b]naphtho[3,2-e]pyran-5,11,13-triones by the three component reaction of 2-
hydroxynaphthalene-1,4-dione, aldehydes, and 2H-indene-1,3-dione under thermal solvent-free conditions in the presence of
poly(4‐vinylpyridinium) hydrogen sulfate as a soild acid [38] and acidic ionic liquids was reported [45].
Interestingly, ultrasound irradiation of a mixture of 2-naphthol (1mmol) and indane-1,3-dione (1 mmol) (A+C) or 2-
hydroxynaphthalene-1,4-dione (1 mmol) and indane-1,3-dione (1 mmol) (B+C) in presence of NSPVPHS at room temperature yielded
the asymmetric xanthenes (Table 1, entries 14-18 and 19-24). Therefore both symmetric and asymmetric derivatives of xanthenes can
be produced using this procedure (Scheme 1).
On the other hand, when comparing the results obtained using conventional heating method in the absence of solvent, with those
obtained by means of the ultrasonic method, we can conclude that both methods afford the respective xanthenes in a shorter time, with
good yields and with minimal environmental impact. In both cases the work-up method is relatively simple. In addition, ultrasonic
equipments are common in organic synthetic laboratories.

7
In order to assess the efficiency of the present method in comparison with the reported methods for the preparation of xanthene
derivatives, compound 14-(phenyl)-14H-dibenzo[a,j] xanthene was synthesized applying the reported methods (Table 2). Compared
with data presented in the literature (Table 2), the systems reported here demand milder operation conditions (temperature and time) and
simpler experimental conditions (dry media) to reach much higher conversion for 14-(phenyl)-14H-dibenzo[a,j] xanthene. Madhav et
al. run this reaction at high temeprature (110-115 ºC) reaching of 91% and 81% yield in 1.5 h using sulfuric acid and cellulose sulfuric
acid, respectively, as catalyst (Table 2) [48]. In this work, the reaction was performed at room temperature and 60 ºC, with a
heterogeneous catalyst, in dry media needing significantly less time: 5-15 min vs. 90 min. These changes lead to remarkable process
intensification through a much more efficient use of energy and materials. In addition to use milder reaction conditions, room
temperature, solvent-free and dry media, we report an economic heterogeneous catalyst that can be easily prepared.
To examine the feasibility of a relatively large-scale synthesis, a mixture containing 10 mmol of each of the reactants was subjected
to the reaction conditions for 20 min leading to isolation of more than 90% of 14-(phenyl)-14H-dibenzo[a,j] xanthene.
The probable mechanism of the reaction is not fully established, but the formation of dibenzoxanthenes could be described by a
reaction sequence similar to the literature report [54]. NSPVPHS activates the aldehyde towards electrophilic attack of 2-naphthol (A),
2-hydroxynaphthalene-1,4-dione (B). Such activation through acid sites of catalyst, as depicted in the Scheme 4, along with
simultaneous sonication can provide the required activation energy for the reactants to overcome the transition state barrier at room
temperature, giving rise to Knoevenagel intermediate in shorter times (1 or 2 in Scheme 4). The reaction then is followed by
nucleophilic addition of the second of these fragments onto the Knoevenagel intermediate, which undergoes intramoleular cyclization to
produce the xanthene derivatives. Also under ultrasound irradiation, the increase in reaction rate might be due to an increase in the rate
of the breaking of C-OH and C-H bonds and elimination of H2O that is critical in this type of multi-component reactions.
The recycling of the catalyst is a valuable advantage of our method. The excellent yields was obtained for the synthesis of 14-(4-
chlorophenyl)-14H-dibenzo[a,j]xanthenes in the presence of recycled catalyst even after five cycles. It implied that NSPVPHS can be
reused without significant loss of activity (Fig. 1). In the other process, after completion of the reaction, the product was separated and
new substrates were added to the reaction vessel. The progress of the reaction was monitored by TLC at optimized reaction conditions
and this process was repeated for five runs. The results showed that the activity of catalyst was not decreased and the yields ranged from
95% to 92% in an average reaction time approximately 5 min.
The sulfuric acid leakage from the matrix was studied in the optimized reaction conditions. Any measurable leakage was not
observed under the optimized conditions. An activity loss of 3% was observed within the 5th use (in this case, a small amount of sulfuric
acid leakage was detected in the reaction medium and wash solutions). However, after 10 cycle repeated uses, the catalyst retained
about 92% of its initial activity (data not shown), attributed to strong interactions between the pyridyl units of poly(4-vinylpyridine) and
acid sites. When the yield drops, the catalyst can be activated to recover its activity by simple activation procedure.

8
4. Conclusions
This work presents the research to intensify the synthesis of xanthene derivatives using a catalytic amount of NSPVPHS solid acid
in dry media under ultrasound irradiation, which results in a more efficient use of energy and materials (no solvent, heterogeneous
catalyst). Thus, this work offers a practical alternative to conventional heating in traditional catalysis and brings important
improvements in the search of new routes to synthesis of xanthene and its derivatives in high added value chemicals and less
environmental impact. Compared with traditional methods, the present methodology has exhibited several advantages such as: the
accelerated reaction rate and excellent yields, minimizing the energy consumption, no side reactions, ease of preparation and handling
of the catalyst, cost efficiency (use of inexpensive catalyst with lower loading) and simple experimental procedure, mild conditions.
Recovery and reuse of NSPVPHS is also satisfactory, which demonstrates the green aspect of the methodology.
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11
Table captions
Table 1. Synthesis of the xanthenes derivatives are catalyzed in the presence of NSPVPHS under grinding and solvent-free conditions.
Table 2. Comparison of our results with the results obtained by other groups in the synthesis of 14-(phenyl)-14H-dibenzo[a,j] xanthene.

12
Table 1. Synthesis of the xanthenes derivatives are catalyzed in the presence of NSPVPHS.a
Entry
Aldehyde
Grinding and heating methodb
Ultrasound methodc
Melting point (°C)
Found
Time (min)
15
Yield (%)d
95
Time (min)
Yield (%)d
Reported [Ref.]
183-185 [36,41]
290-292 [36,41]
296-298 [36,41]
203-206 [36,41]
312-313 [36,41]
293 [36,41]
198-200 [37]
305-307 [42,43]
330-332 [42,43]
304-307 [42,43]
333-335 [42,43]
-
1
C6H5-CHO
5
97
95
96
90
95
88
91
95
95
95
93
90
95
90
94
94
89
95
92
94
92
91
88
95
185-186
293-295
297-298
206-208
310-312
296-298
202-204
301-304
>320
2
4-Cl-C6H4-CHO
4-Br-C6H4-CHO
4-MeO-C6H4-CHO
4-NO2-C6H4-CHO
2-NO2-C6H4-CHO
Furfural
15
94
5
3
15
93
5
4
20
88
8
5
10
92
8
6
15
86
5
7
15
89
5
8
C6H5-CHO
22
92
10
5
9
4-Cl-C6H4-CHO
4-Me-C6H4-CHO
4-Br-C6H4-CHO
4-MeO-C6H4-CHO
4-NO2-C6H4-CHO
C6H5-CHO
15
95
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
22
94
10
5
301-303
>320
15
90
18
88
8
>320
12
92
6
>320
-
15
88
5
208-210
229-231
195-197
230-232
262-264
311-314
230-232
>320
202-203 [44]
225-226 [44]
192-193 [44]
225-226 [44]
-
4-Cl-C6H4-CHO
4-Me-C6H4-CHO
4-MeO-C6H4-CHO
4-NO2-C6H4-CHO
C6H5-CHO
18
91
8
15
91
5
20
85
8
10
93
5
15
90
5
311-314 [38]
>330 [38]
4-Cl-C6H4-CHO
4-Br-C6H4-CHO
4-Me-C6H4-CHO
4-MeO-C6H4-CHO
4-NO2-C6H4-CHO
15
91
5
15
90
5
>330 [38]
18
88
8
198-200
311-313
>320
314-316 [38]
309-311 [38]
>330 [38]
25
78
12
12
94
5
a Products were characterized by 1H NMR, IR and melting point and also by comparison with the reported in literature data.
b Reaction conditions: aldehyde, 1.0 mmol; substrate {2-naphthol (2 mmol), 2-hydroxynaphthalene-1,4-dione (2 mmol), mixture of
2-naphthol (1 mmol) and indane-1,3-dione(1 mmol) or 2-hydroxynaphthalene-1,4-dione (1 mmol) and indane-1,3-dione(1 mmol);
according to Scheme 1}; NSPVPHS, 10 mg; 60 °C, grinding under solvent-free conditions.
c
Reaction conditions: aldehyde, 1.0 mmol; substrate {2-naphthol (2 mmol), 2-hydroxynaphthalene-1,4-dione (2 mmol), mixture of
2-naphthol (1 mmol) and indane-1,3-dione(1 mmol) or 2-hydroxynaphthalene-1,4-dione (1 mmol) and indane-1,3-dione(1 mmol);
according to Scheme 1}; NSPVPHS, 10 mg; room temperature and under ultrasound irradiation.
d Isolated yields.

13
Table 2. Comparison of our results with the results obtained by other groups in the synthesis of 14-(phenyl)-14H-dibenzo[a,j] xanthene.
Yield (%)a
Entry
Catalyst
Amount of catalyst (mg)
Temp. (°C)
Time (h)
Ref.
1
p-TSA
17.2
9.7
10
125
4
89
93
94
94
91
81
75
94
89
78
94
95
14
2
Sulfamic acid
125
8
24
3
Poly(4-vinylpyridinium) hydrogen sulfate
Succinimide-N-sulfonic acid
Sulfuric acid
100
55 min
35 min
1.5
36
4
10
80
38
5
10
110-115b
50
6
Cellulose sulfuric acid
Montmorillonitr K10
Amberlyst-15
80
110-115
1.5
50
7
300
10
120
3
51
8
125
2
52
9
Silica sulfuric acid
Dowex-50W
80
110-115
1.5
53
10
11
12
100
10
100
1.5
54
NSPVPHS
60
15 min
5 min
This work
This work
NSPVPHS
10
Utrasonic method at r.t.
a Isolated yields.
b Solvent: acetic acid.

14
Figure captions
Fig. 1. Synthesis of 14-(4-chlorophenyl)-14H-dibenzo[a,j]xanthenes under ultrasound irradiation in presence of recycled NSPVPHS
within 5 min under ultrasound irradiation.

15
Fig. 1. Synthesis of 14-(4-chlorophenyl)-14H-dibenzo[a,j]xanthenes under ultrasound irradiation in presence of recycled NSPVPHS
within 5 min under ultrasound irradiation.

16
Scheme captions
Scheme 1. NSPVPHS catalyzed synthesis of xanthenes under grinding and solvent-free conditions.
Scheme 2. The proposed equation for the slow hydrolysis of catalyst in aqueous media.
Scheme 3. The Elucidation of catalytic activity of N-sulfonic acid poly(4-vinylpyridinium) hydrogen sulfate (NSPVPHS).
Scheme 4. A plausible mechanism for synthesis of xanthene derivatives in the presence of NSPVPHS under solvent free
conditions.

17
R
2 A
(Table 1, entries 1-7)
(Table 1, entries 8-13)
O
R
O
O
O
O
2 B
O
R
NSPVPHS (10 mg), )))))
Solvent-free, r.t.
R-CHO
+
O
(Table 1, entries 14-18)
(Table 1, entries 19-24)
A + C
O
R
O
O
O
O
B + C
O
O
O
OH
OH
O
B
C
A
Scheme 1. NSPVPHS catalyzed synthesis of xanthenes under grinding and solvent-free conditions.

18
N
NH
NH
+
2 HSO4
+
H2O
HSO4
N
SO3H
Scheme 2. The proposed equation for the slow hydrolysis of catalyst in aqueous media.

19
Cl
Cl
Cl
OH
NSPVPHS
+
+
Different conditions
O
II
OH
HO
H
O
I
A
Scheme 3. The Elucidation of catalytic activity of N-sulfonic acid poly(4-vinylpyridinium) hydrogen sulfate (NSPVPHS).

20
(A)
(B)
O
O
HO
HO
R
H+ from NSPVPHS
O
O
R
O
O
O
R
O
H
) ) ) ) )
)))))
-H2O (B)
(A)
-H
2O
O
R
O
O
R
) ) ) ) )
(Table 1, entries 8-13)
(Table 1, entries 1-7)
)))))
R
O
R
O
O
HO
OH
(C)
(2)
(1)
) ) ) ) )
)))))
-H
O
(C)
O
O
2O
-H2O
(Table 1, entries 14-18)
(Table 1, entries 19-24)
Scheme 4. A plausible mechanism for synthesis of xanthene derivatives in the presence of NSPVPHS under solvent free
conditions.

21
Highlights
•
•
Introducing new solid acid catalyst for organic transformations
Showing the important supporting role of anion hydrogen sulfate on selectivity of the products of
xanthene derivatvies
•
•
•
Application of ultrasonic method as a green source of energy
Generality of the method, high yields and high reaction rates
Recoverability and reusability solid acid catalyst