Introduction of O-sulfonated poly(4-vinylpyrrolidonium) chloride as a polymeric and reusable catalyst for the synthesis of xanthene derivatives

Article abstract of DOI:10.1039/c4ra04915b

O-Sulfonated poly(4-vinylpyrrolidonium) chloride is prepared from the reaction of poly(4-vinylpyrrolidone) [PVP], as a cheap and commercially available reagent, and neat chlorosulfonic acid at room temperature. A variety of techniques including infrared s

Full text of DOI:10.1039/c4ra04915b

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Introduction of O-sulfonated poly(4-
vinylpyrrolidonium) chloride as a polymeric and
Cite this: RSC Adv., 2014, 4, 38581
reusable catalyst for the synthesis of xanthene
derivatives
a
Farhad Shirini, Peyman Najafi Moghadam,b Simin Moayediab
*
and Mohadeseh Seddighia
O-Sulfonated poly(4-vinylpyrrolidonium) chloride is prepared from the reaction of poly(4-vinylpyrrolidone)
[PVP], as a cheap and commercially available reagent, and neat chlorosulfonic acid at room temperature. A
variety of techniques including infrared spectra (IR), thermal gravimetric analysis (TGA), scanning electron
microscopy (SEM), X-ray diffraction (XRD), pH analysis and Hammett acidity (Ho) were used to
characterize this solid acid. This polymeric reagent showed excellent catalytic activity for the synthesis of
xanthene derivatives including 1,8-dioxooctahydroxanthenes, 14-aryl-14H-dibenzo[a,j] xanthenes and
12-aryl-8,9,10,12-tetrahydrobenzo[a]xanthen-11-ones under solvent free conditions. The products were
formed in excellent yields over short reaction times and the catalyst can be reused several times without
any appreciable loss in its activity.
Received 24th May 2014
Accepted 31st July 2014
DOI: 10.1039/c4ra04915b
www.rsc.org/advances
One of the most widely used heterogeneous and polymeric
supports for numerous reagents and catalysts is cross-linked
Introduction
poly(vinylpyrrolidone) (PVP) because of its commercial avail-
ability, stability, reasonable high loading capacity, good physi-
cochemical structure and facile functionalization. It is One of
the most widely used excipients in pharmaceuticals, for
example as a binder in tablets, granulates and capsules. Stabi-
lizer of suspensions, ophthalmic preparation, sugar coating,
lm coating and miscellaneous applications are the other
applicabilities of this reagent.3 Also, it seems to an attractive
support to immobilize mineral acids because of the basic
nature of pyridyl group. Therefore, various PVP-supported
reagents have been designed to catalyze some of the organic
reactions.4–7
During the last decade, xanthenes and their derivatives have
been the subject of considerable levels of interest because of
their numerous applications in pharmaceutical and biological
research such as antimicrobial,8 antiviral,9 antitumor,10 and
anticancer11 activities. Additionally, these heterocyclic
compounds can be used in laser technology,12 uorescent
material for visualization of biomolecules,13 and also as
dyes.14,15 Thus, the synthesis of xanthene derivatives currently is
of much importance. The most common protocols for the one
pot multi-component preparation of symmetric and asym-
metric xanthenes are as follow:
¨
Replacement of conventional, toxic and polluting Bronsted and
Lewis acid catalysts with eco-friendly reusable heterogeneous
catalysts is an area of current interest. In this context, there has
been renewed interest in the synthesis of solid acid catalysts
that function as an acid under a solid state.1 These materials
have many advantages compared to traditional liquid acids
such as their efficiency, operational simplicity, easy recyclability
and recoverability, non-corrosive nature and friendly to the
environment, all factors which are important in industry.
Therefore, solid acid catalysts can play a signicant role in the
development of clean technologies.
Among various supports, polymers are becoming important
and useful tools in chemistry. Both soluble and cross-linked
polymers have been used as support materials in organic
synthesis. The soluble polymer supports provide a more
homogeneous reaction mixture, so they generally require a
more complicated separation procedure that limited their
common use, while the cross-linked materials can be separated
with simple ltration.2 One of the key goals in the design of a
new catalyst is to combine high efficiency of the catalyst with its
easy separation from the reaction products and the possibility
of recycling, so in this aspect cross-linked polymers create a
perspective type of support materials.
ꢀ The reaction of aldehydes (1 eq.) with cyclic 1,3-dicarbonyl
compounds (2 eq.) for the preparation of 1,8-
dioxooctahydroxanthenes.
aDepartment of Chemistry, College of Sciences, University of Guilan, 41335, Rasht,
Iran. E-mail: shirini@guilan.ac.ir; Fax: +98 131 3233262; Tel: +98 131 3233262
bDepartment of Chemistry, Faculty of Sciences, Urmia University, Urmia, Iran
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ꢀ The reaction of aldehydes (1 eq.) with b-naphthol (2 eq.) for
the preparation of 14-aryl-14H-dibenzo[a,j] xanthenes.
ꢀ The reaction of aldehydes (1 eq.) with b-naphthol (1 eq.)
and cyclic 1,3-dicarbonyl compounds (1 eq.) for the preparation
of 12-aryl-8,9,10,12-tetrahydrobenzo[a]xanthen-11-ones.
A variety of catalysts such as FeCl3 6$H2O,16 sulfamic acid,17
Scheme 1 Preparation of the catalyst ([PVP-SO3H] Cl).
amberlyst-15,18 silica sulfuric acid,19 selectuor™,20 poly-
22
tungstozincate acid,21 H3PW12O40
,
I2,23 pTSA,24 cellulose
80 ꢁC to afford [PVP-SO3H] Cl as a pale yellow powder
(Scheme 1).
sulfonic acid,25 NH2SO3H,26 b-cyclodextrin,27 nano-TiO2,28
saccharin sulfonic acid,29 succinimide-N-sulfonic acid,30 poly(4-
vinylpyridinium)hydrogen sulfate [P(4-VPH)HSO4],31 SO3H-
MCM-41,32
1-butyl-3-methylimidazolium
General procedure for the synthesis of 1,8-
dioxooctahydroxanthenes
functionalized
hydrogen sulfate [bmim][HSO4],33 trityl chloride (TrCl),34
silica-bonded S-sulfonic acid (SBSSA),35 N-sulfonic acid poly(4-
vinylpyridinium) chloride,36 PVPP-BF3,37 have been used to
facilitate the preparation of xanthene derivatives. Although
these procedures provide an improvement, many of them suffer
from disadvantages such as long reaction times, harsh reaction
conditions, need to excess amounts of the reagent, use of
organic solvents, use of toxic reagents and non-recoverability of
the catalyst. Additionally, only some of them are useful for the
synthesis of all of the above mentioned xanthenes. Therefore,
introduction of simple, efficient and mild procedures with
easily separable and reusable solid catalysts to overcome these
problems is still in demand.
A mixture of dimedone or cyclohexadione (2.1 mmol), aldehyde
(1 mmol) and [PVP-SO3H] Cl (10 mg) was stirred in an oil-bath at
120 ꢁC under solvent-free conditions. Aer completion of the
reaction (monitored by TLC), the reaction mixture was cooled,
EtOH (10 mL) was added and the catalyst was removed by
ltration. Then, water was added and the precipitated product
was collected by ltration in high purity.
General procedure for the synthesis of 14-aryl-14H-dibenzo
[a,j] xanthenes
A mixture of b-naphthol (2 mmol), aldehyde (1 mmol) and [PVP-
SO3H] Cl (40 mg) was stirred in an oil-bath at 120 ꢁC under
solvent-free conditions. Aer completion of the reaction
(monitored by TLC) the reaction mixture was cooled to room
temperature, EtOH (10 mL) was added to it and ltered to
separate the catalyst. Then the crude product was recrystallized
from EtOH to give the pure product.
Experimental section
Reagents and materials
Chemicals were purchased from Fluka, Merck, and Aldrich
chemical companies. Cross-linked poly(4-vinylpyrrolidone) we
purchased it from BASF the chemical company, Germany. All
yields refer to the isolated products. Products were character-
ized by comparison of, their physical constants, IR and NMR
spectroscopy with authentic samples and those reported in the
literature.
General procedure for the synthesis of 12-aryl-8,9,10,12-
tetrahydrobenzo[a]xanthen-11-ones
A mixture of b-naphthol (0.144 g, 1 mmol), dimedone or cyclo-
hexadione (1.2 mmol), aldehyde (1 mmol) and [PVP-ꢁSO3H] Cl
(40 mg) was stirred and heated in an oil-bath at 120 C for an
appropriate period of time. Aer completion of the reaction, as
monitored with TLC, the reaction mixture was cooled to room
temperature, EtOH (10 mL) was added to it and ltered to
separate the catalyst. Then the crude product was recrystallized
from EtOH to give the pure product.
Characterization
The FT-IR spectra were run on a VERTEX 70 Bruker company
(Germany). Thermogravimetric analyses (TGA) were performed
on TG/DTA6300 Sll-Nonotechnology Company (Japan). Samples
ꢂ1
ꢁ
ꢁ
The spectral data of the selected compounds are as follow:
9-(2-Mehtoxyphenyl)-3,3,6,6-tetramethyl-1,8-dioxooctahydro
were heated from 25 to 800 C at ramp 10 C min under N2
atmosphere. Scanning election microphotographs (SEM) were
obtained on a SEM-Philips XL30. Wide-angle X-ray diffraction
(XRD) measurements were performed at room temperature on a
Siemens D-500 X-ray diffractometer (Germany), using Ni-ltered
Co-Ka radiation (l ¼ 0.15418 nm).
1
xanthene. H NMR (400 MHz, CDCl3): d ¼ 0.97 (s, 6H), 1.11 (s,
6H), 2.14 and 2.23 (d, J ¼ 16.4 Hz, 2H), 2.39 and 2.48 (d, J ¼ 17.4
Hz, 2H), 3.79 (s, 3H), 4.87 (s, 1H), 6.77 (d, J ¼ 8 Hz, 1H), 6.89 (dt,
J1 ¼ 7.4 Hz, J2 ¼ 1.2 Hz, 1H), 7.12 (m, 1H), 7.43 (dd, J1 ¼ 7.4 Hz,
J2 ¼ 1.6 Hz, 1H) ppm.
9-(3-Bromophenyl)-1,8-dioxo-octahydroxanthene. 1H NMR
(400 MHz, CDCl3): d ¼ ; 1.95–2.1 (m, 4H), 2.30–2.44 (m, 4H),
Catalyst preparation [PVP-SO3H] Cl
Chlorosulfonic acid (1.2 mL, 18 mmol) was added to a 2.55–2.63 (m, 2H), 2.66–2.73 (m, 2H), 4.79 (s, 1H), 7.11 (t, J ¼ 7.6
suspension of powdered poly(4-vinylpyrrolidone) (2.0 g) [cross- Hz, 1H), 7.26 ¼ 7.36 (m, 3H) ppm; 13C NMR (100 MHz, CDCl3): d
linked poly(4-vinylpyrrolidone) with MW > 1 000 000] in 10 mL ¼ 20.3, 27.2, 31.6, 36.9, 116.3, 122.3, 127.7, 129.6, 131.0, 146.6,
dry CH2Cl2 over a period of 15 min. The mixture was stirred at 164.3, 196.4 ppm.
room temperature for 5 h and then the mixture was ltered. The
solid residue was washed with ethyl acetate (20 mL) and dried at (400 MHz, CDCl3): d ¼ 1.99–2.10 (m, 4H), 2.30–2.45 (m, 4H),
9-(3-Mehtoxyphenyl)-1,8-dioxo-octahydroxanthene. 1H NMR
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2.54–2.71 (m, 4H), 3.81 (s, 3H), 4.83 (s, 1H), 6.69–6.71 (dd, J1 ¼
8.0 Hz, J2 ¼ 1.6 Hz, 1H), 6.89–6.95 (m, 2H), 7.17 (t, J ¼ 8.0 Hz,
1H) ppm; 13C NMR (100 MHz, CDCl3): d ¼ 20.3, 27.2, 31.5, 37.0,
55.2, 111.5, 114.5, 116.8, 121.0, 129.0, 146.0, 159.4, 164.0, 196.5
ppm.
14-(2-Chlorophenyl)-14H-dibenzo[a,j]xanthenes. 1H NMR
(300 MHz, CDCl3): d ¼ 6.85 (s, 1H), 6.93–6.99 (m, 2H), 7.30 (d, J
¼ 7.1 Hz, 1H), 7.44(d, J ¼ 7.6 Hz, 1H), 7.48 (t, J ¼ 7.5 Hz, 2H),
7.54(d, J ¼ 8.8 Hz, 2H), 7.67 (t, J ¼ 7.5 Hz, 2H), 7.83–7.87 (m,
4H), 8.79 (d, J ¼ 8.5 Hz, 2H) ppm; 13C NMR (75 MHz, CDCl3): d ¼
34.6, 117.9, 118.0, 123.4, 124.3, 126.8, 127.7, 127.8, 128.5, 129,
129.5, 130.1, 130.8, 131.6, 131.7139.5, 148.9 ppm.
14-(3-Nitrophenyl)-14H-dibenzo[a,j]xanthenes. 1H NMR (400
MHz, CDCl3): d ¼ 6.64 (s, 1H), 7.33 (t, J ¼ 8.0 Hz, 1H), 7.48 (t, J ¼
7.44, 2H), 7.55 (d, J ¼ 8.8, 2H), 7.65 (t, J ¼ 7.55 Hz, 2H), 7.84–7.90
(m, 6H), 8.35 (d, J ¼ 8.5 Hz, 2H), 8.46 (s, 1H) ppm; 13C NMR (100
MHz, CDCl3): d ¼ 38.1, 116.3, 118.5, 122.1, 122.4, 123.1, 125.0,
127.7, 129.5, 129.9, 130, 131.5, 131.8, 134.7, 147.4, 148.6, 149.2
ppm.
12-(2-Naphthyl)-9,9-dimethyl-8,9,10,12-octahydrobenzo[a]
1
xanthene-11-one. H NMR (400 MHz, CDCl3): d ¼ 0.96 (s, 3H),
1.14 (s, 3H), 2.32 and 2.36 (AB system, J ¼ 16.4 Hz, 2H), 2.61 (s,
2H), 5.92 (s, 1H), 7.28–7.44 (m, 5H), 7.50 (d, J ¼ 8 Hz, 1H), 7.67–
7.82 (m, 6H), 8.08 (d, J ¼ 8 Hz, 1H) ppm; 13C NMR (100 MHz,
CDCl3): d ¼ 27.2, 29.3, 32.3, 34.9, 41.5, 50.9, 114.1, 117.1, 117.6,
123.7, 124.9, 125.4, 125.7, 126.7, 127.1, 127.2, 127.4, 128.0,
128.4, 129.0, 131.4, 131.5, 132.1, 133.3, 142.1, 147.8, 164.0, 196.9
ppm.
Fig. 1 FT-IR spectra of PVP and [PVP-SO3H] Cl.
Results and discussion
Catalyst characterization
The infrared spectra of PVP and [PVP-SO3H] Cl are shown in
Fig. 1. As can be seen, presence of an extra sulfonic acid group
on the pyrrolidine nitrogen in the [PVP-SO3H] Cl increased the
number of vibrational modes and brought completely different
FTIR spectrum. In the case of [PVP-SO3H] Cl, the broad band
around 2600 to 3700 cmꢂ1 can be attributed to the OH
stretching of the SO3H group Additional bands at 1170, 1066,
882 and 578 cmꢂ1 are assigned to the S]O asymmetric and
symmetric stretching, S–OH bending and symmetric S–O
stretching vibrations, respectively.38,39 Furthermore, the bands
at 1429 (C–N) and 650 (N–C]O) cmꢂ1 are disappeared, a
moderate absorption at 1648 cmꢂ1 that corresponds to the
internal imine groups present in the pendant rings of the
polymer is appeared.6,7 These observations conrm the func-
tionalization of pyrrolidine oxygen with sulfonic acid.
Fig. 2 represents the X-ray diffraction (XRD) patterns of the
PVP and [PVP-SO3H] Cl samples. As shown in this gure,
incorporation of ClSO3H leads to some changes in the dif-
fractogram of PVP. The PVP diffraction exhibits a diffused
background pattern with two diffraction halos appeared around
2q equal to 13 and 22 indicating that the polymer is amor-
phous.40 Aer modication of PVP by ClSO3H the rst peak (2q
around 13) is disappeared, and the broad peak at 2q around 22
is slightly reduced. These observations imply that the crystalline
size of PVP is decreased aer reaction with ClSO3H.38
Fig. 2 XRD patterns of PVP in comparison of [PVP-SO3H] Cl.
The samples of PVP and [PVP-SO3H] Cl were also analyzed by
scanning electron microscopy (SEM) with various magnica-
tions for determining the size distribution, particle shape and
surface morphology, as represented in Fig. 3. These images
showed that with chemical modication the primary
morphology of PVP was completely changed and the particles
were aggregated. It should be noted that aer the reaction of
PVP with chlorosulfonic acid the polymer was became swollen.
This increased the surface area of the catalyst and nally its
catalytic activity. Furthermore, in the SEM images of [PVP-
SO3H] Cl the pendant sulfonic groups were observed on the
surface PVP polymer.
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Fig. 3 SEM micrographs of PVP (a–c) and [PVP-SO3H] Cl (d–f).
The thermal stability of PVP and [PVP-SO3H] Cl was deter- which is corresponding to the loss of the physically adsorbed
mined by Thermogravimetric analysis (TGA) and differential water and bonded H2O within the gallery of PVP. The large
thermogravimetry analysis (DTGA) curves, as shown in Fig. 4. proportion of polymer underwent degradation in the range of
The TGA curve of PVP displayed a weight loss below 120 ꢁC 350–470 ꢁC. The TGA and DTG analysis of [PVP-SO3H] Cl show
four-stage decomposition, completely different from PVP. The
ꢁ
rst weight loss appeared at <120 C attributed to the loss of
moisture contents. The second weight loss which started from
200 ꢁC (210–280 ꢁC, Tmax ¼ 260 ꢁC) can be a result of the thermal
decomposition of the pendant sulfonic groups. The sulfonated
PVP moiety undergoes intermolecular bonding interactions in
the solid state, leading to the formation of a rigid network
structure which requires higher temperature for decomposi-
tion. This is conrmed by the third (310–360 ꢁC, Tmax ¼ 330 ꢁC)
and fourth (380–480 ꢁC, Tmax ¼ 430 ꢁC) decomposition stages.38
The DTGA-TGA data show that the [PVP-SO3H] Cl catalyst is
stable to 210 ꢁC.
The Hammett acidity method is an effective way to the
acidity strength of an acid in organic solvents, using UV-vis
technique.39 The Hammett function is dened as:
H0 ¼ pK (I)aq + log ([I]s/[IH+]s)
where the pK (I)aq is the pKa value of aqueous solution of the
indicator, and [IH+]s and [I]s are the molar concentrations of
protonated and unprotonated forms of the indicator in the
solvent, respectively. According to Lambert–Beer's Law, the
value of [I]s/[IH+]s can be determined and calculated through
UV-visible spectrum. For this purpose, 4-nitroaniline (pK(I)aq ¼
0.99) as the basic indicator and CCl4 as the solvent were chosen.
As can be seen in Fig. 5, the maximal absorbance of the
unprotonated form of the indicator was observed at 330 nm in
CCl4. When [PVP-SO3H] Cl as a solid acid catalyst was added to
Fig. 4 TGA curves (up) and DTGA curves (down) for PVP and [PVP-
SO3H] Cl.
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Scheme 2 Synthesis of 1,8-dioxooctahydroxanthenes catalyzed by
[PVP-SO3H] Cl.
Aer optimization of the reaction conditions and in order to
establish the effectiveness and the acceptability of the method,
we explored the protocol with a variety of simple readily avail-
able substrates under the optimal conditions. As presented in
Table 2, different aromatic aldehydes (containing electron-
withdrawing or electron-donating groups) were condensed
with cyclic 1,3-diketones (dimedone or 1,3-cyclohexadione)
under the optimal conditions in high yields and very short
Fig. 5 Absorption spectra of 4-nitroaniline (indicator) (a) and [PVP-
SO3H] Cl (catalyst) (b) in CCl4.
the indicator solution, the absorbance of the unprotonated
form of the indicator decreased, which indicated that the
indicator was partially in the form of [IH+]. These results
that have listed in Table 1, show the acidity strength of reaction times. As can be seen, the nature of the substituents on
[PVP-SO3H] Cl.
the aromatic ring did not show strongly obvious effects in terms
of yields and times under the selected reaction conditions,
while the steric effects increased the reaction times (Table 2,
entry 8).
To 25 mL of an aqueous solution of NaCl (1 M) with a
primary pH 5.6, [PVP-SO3H] Cl (0.5 g) was added and the
resulting mixture was stirred for 2 h at room temperature aer
which the pH of solution decreased to 1.21. This is equal to a
loading of 3.0 mmol H+ per gram of the catalyst.39
In the next step, [PVP-SO3H] Cl solid acid catalyst was used in
the condensation of b-naphthol with aldehydes leading to 14-
aryl-14H-dibenzo[a,j] xanthenes. Our observations showed that
under the same conditions used for the preparation of 1,8-
dioxooctahydroxanthenes, this reaction was not completed. We
found that higher amounts of the catalyst was need and 40 mg
[PVP-SO3H] Cl was adequate to accomplish the reaction effec-
tively at 120 ꢁC (Scheme 3). Under this optimum conditions,
various aldehydes were reacted with b-naphthol in short reac-
tion times with high yields that conrms the efficiency of this
method (Table 3).
Aer the successful application of [PVP-SO3H] Cl as a solid
acid catalyst in the synthesis of symmetric xanthenes, we
decided to use it in the synthesis of 12-aryl-8,9,10,12-tetrahy-
drobenzo[a]xanthen-11-ones as asymmetric xanthenes. For this
purpose and to obtain the optimum reaction conditions, the
reaction between 4-chlorobenzaldehyde, b-naphthol and dime-
done to its corresponding xanthene was investigated as a model
reaction in different conditions. We found that the best result
was obtained using 1 mmol aldehyde, 1 mmol b-naphthol, 1.2
mmol dimedone and 40 mg [PVP-SO3H] Cl at 120 ꢁC under
solvent-free conditions (Scheme 4). Subsequently, to reveal the
generality of this method, the condensation was carried out
with a variety of substrates using [PVP-SO3H] Cl under the
optimal conditions. The results show that these conversions
were also occurred with excellent yields in very short times
(Table 4).
Catalytic activity
On the basis of the information obtained from the above
mentioned studies, we anticipated that O-sulfonated poly(4-
vinylpyrrolidonium) chloride can be used as an efficient cata-
lyst for the promotion of the reactions which need the use of an
acidic catalyst to speed up. So we were interested to investigate
the applicability of this reagent in the preparation of the
xanthenes derivatives.
At rst, we focused our attention to study the synthesis of
1,8-dioxooctahydroxanthenes. For optimization of the reaction
conditions, the condensation of 4-chlorobenzaldehyde with
dimedone (5,5-dimethyl-1,3-cyclohexanedione) to the corre-
sponding product was selected as a model reaction and the
various conditions using different amounts of catalyst at
various temperatures under solvent-free conditions were
examined. Finally the optimal reaction conditions for this
reaction was as follow: 1 mmol aldehyde, 2.1 mmol dimedone
and 10 mg [PVP-SO3H] Cl as catalyst at 120 ꢁC under solvent-free
conditions (Scheme 2). Any further increase of the catalyst or
temperature did not improve the reaction time and yield.
Table 1 Calculation of Hammett acidity function (H0) for [PVP-SO3H]-
Cla
In order to highlight the merits of our newly developed
procedures, we have compared our result obtained from the
synthesis of 9-phenyl-3,3,6,6-tetramethyl-1,8-dioxo-octahy-
droxanthenes, 14-phenyl-14H-dibenzo[a,j]xanthenes and 12-(4-
chlorophenyl)-9,9-dimethyl-8,9,10,12-tetrahydrobenzo[a] xanthene-
11-one catalyzed by [PVP-SO3H] Cl with other results reported
in the literature. As shown in Table 5, this method is superior in
Catalyst
Amax
[I]s %
[IH+]s %
H0
—
2.2254
0.0374
100
1.68
0
—
ꢂ0.78
[PVP-SO3H] Cl
98.32
a
Condition for UV-visible spectrum measurement: solvent: CCl4,
indicator: 4-nitroaniline (pK (I)aq ¼ 0.99), 1.44 ꢃ 10ꢂ4 mol Lꢂ1 (10
mL); catalyst: [PVP-SO3H] Cl (10 mg), 25 ꢁC.
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Table 2 synthesis of 1,8-dioxooctahydroxanthenes in the presence of [PVP-SO3H] Cl
Mp (ꢁC)
Found
Entry
Ar
R
Time (min)
Yielda (%)
Reported
1
2
3
4
5
6
7
8
C6H5–
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
H
H
H
H
H
H
H
H
3
3
3
3
3
4
3
20
9
3
3
3
3
3
2
2
2
2
94
95
92
95
94
91
95
92
93
96
90
91
96
92
95
94
94
95
198–200
229–231
282–284
235–237
198–200
185–186
190–191
251–252
162–164
220–222
262–264
247–249
281–283
278–280
286–288
190–192
281–283
250–252
201–202 (ref. 20)
230–232 (ref. 20)
281–282 (ref. 36)
236–238 (ref. 16)
205–207 (ref. 41)
188–190 (ref. 42)
192–194 (ref. 30)
251–252 (ref. 36)
164–165 (ref. 36)
222 (ref. 41)
265–267 (ref. 43)
248–249 (ref. 36)
282–285 (ref. 43)
280–281 (ref. 36)
284–285 (ref. 27)
192–194 (ref. 43)
280–282 (ref. 43)
254–256 (ref. 43)
4-ClC6H4–
3-BrC6H4–
4-BrC6H4–
3-CH3C6H5–
2-CH3OC6H5–
3-CH3OC6H5–
2-NO2C6H4–
3-NO2C6H4–
4-NO2C6H4–
C6H5–
2-ClC6H4–
4-ClC6H4–
3-BrC6H4 –
4-BrC6H4–
3-CH3OC6H5–
3-NO2C6H4–
4-NO2C6H4–
9
10
11
12
13
14
15
16
17
18
a
Isolated yields.
Scheme 3 Synthesis of 14-aryl-14H-dibenzo[a,j] xanthenes catalyzed
by [PVP-SO3H] Cl.
the term of the reaction time. Furthermore, this avoids some of
the disadvantages associated with the other procedures such as
toxic reagents, organic solvents and low yields.
Scheme
4
Synthesis
of
12-aryl-8,9,10,12-tetrahydrobenzo[a]
xanthen-11-ones catalyzed by [PVP-SO3H] Cl.
To check the reusability of the catalyst, the reaction of 4-
chlorobenzaldehyde (1 mmol) with dimedone (2.1 mmol) under
the optimized reaction conditions was studied again. When the
reaction completed, ethyl acetate was added and the catalyst
was separated by ltration. The recovered catalyst was washed
with ethyl acetate, dried and reused for the same reaction. This
process was carried out over ve runs and all reactions were led
to the desired products without signicant changes in terms of
Table 3 Synthesis of 14-aryl-14H-dibenzo[a,j] xanthenes in the presence of [PVP-SO3H] Cl
Mp (ꢁC)
Found
Entry
Ar
Time (min)
Yielda (%)
Reported
1
2
3
4
5
6
7
8
9
10
C6H5–
6
18
5
7
7
40
20
3
4
10
93
90
96
94
96
90
92
96
94
94
184–186
208–211
288–291
187–189
295–297
250–252
196–198
212–214
313–315
135–137
184–185 (ref. 37)
206–209 (ref. 36)
290–292 (ref. 37)
190–191 (ref. 28)
296–298 (ref. 19)
258–259 (ref. 37)
199–201 (ref. 36)
211–212 (ref. 37)
312–313 (ref. 37)
130–133 (ref. 36)
2-ClC6H4–
4-ClC6H4–
3-BrC6H4–
4-BrC6H4–
2-CH3OC6H5–
4-CH3OC6H5–
3-NO2C6H4–
4-NO2C6H4–
4-OHC6H4–
a
Isolated yields.
38586 | RSC Adv., 2014, 4, 38581–38588
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Table 4 Synthesis of 12-aryl-8,9,10,12-tetrahydrobenzo[a] xanthen-11-ones catalyzed by [PVP-SO3H] Cl
Mp (ꢁC)
Found
Entry
Ar
R
Time (min)
Yielda (%)
Reported
1
2
3
4
5
6
7
8
9
10
4-ClC6H4–
CH3
CH3
CH3
CH3
CH3
CH3
CH3
H
5
10
4
20
10
30
10
10
10
35
94
93
96
91
94
93
95
93
94
93
185–187
163–165
179–181
159–161
198–200
149–151
214–216
201–203
199–201
262–264
185–187 (ref. 26)
161–164 (ref. 34)
180–182 (ref. 36)
163–165 (ref. 44)
201–203 (ref. 34)
150–151 (ref. 22)
213–215 (ref. 36)
205–206 (ref. 22)
208–209 (ref. 45)
269–270 (ref. 45)
3-BrC6H4–
4-BrC6H4–
2-CH3OC6H5–
4-CH3OC6H5–
4-OHC6H4–
2-Naphtyl-
4-ClC6H4–
4-BrC6H4–
4-OHC6H4–
H
H
a
Isolated yields.
Table 5 Comparison of the results obtained from the synthesis of 9-phenyl-3,3,6,6-tetramethyl-1,8-dioxooctahydro xanthenes, 14-phenyl-
14H-dibenzo[a,j]xanthenes, 12-(4-chlorophenyl)-8,9,10,12-octahydrobenzo[a]xanthene-11-one in the presence of [PVP-SO3H] Cl with those
obtained using other catalysts
Product
Catalyst (loading)
Reaction conditions
Time (min)
Yield (%)
FeCl3$6H2O (10 mol%)
Amberlyst-15 (200 mg)
80 ꢁC/[bmim][BF4]
Reux/CH3CN
6 h
5 h
60
60
40
5 h
10 h
35
3 h
10 h
10
92 (ref. 16)
92 (ref. 18)
97 (ref. 19)
95 (ref. 20)
94 (ref. 21)
94 (ref. 25)
96 (ref. 27)
92 (ref. 30)
85 (ref. 33)
98 (ref. 35)
97 (ref. 36)
94 (This work)
Silica sulfuric acid (30 mg)
Selectuor™ (10 mol%)
Polytungstozincate acid (50 mg)
Cellulose sulfonic acid (50 mg)
b-cyclodextrin (1 mmol)
Succinimide-N-sulfonic acid (5.6 mol%)
[bmim][HSO4] (42 mol%)
SBSSA (30 mg)
80 ꢁC/Solvent free
120 ꢁC/Solvent free
80 ꢁC/Solvent free
110 ꢁC/Solvent free
60 ꢁC/H2O
80 ꢁC/Solvent free
80 ꢁC/Solvent free
Reux/EtOH
N-sulfonic acid PVP Cl (20 mg)
[PVP-SO3H] Cl (10 mg)
100 ꢁC/Solvent free
120 ꢁC/Solvent free
3
Sulfamic acid (10 mol%)
125 ꢁC/Solvent free
80 ꢁC/Solvent free
80 ꢁC/Solvent free
120 ꢁC/Solvent free
100 ꢁC/Solvent free
80 ꢁC/Solvent free
100 ꢁC/Solvent free
120 ꢁC/Solvent free
120 ꢁC/Solvent free
8 h
45
60
70
55
60
30
90
6
93 (ref. 17)
89 (ref. 19)
81 (ref. 21)
94 (ref. 29)
94 (ref. 31)
90 (ref. 32)
80 (ref. 36)
94 (ref. 37)
93 (This work)
Silica sulfuric acid (30 mg)
Polytungstozincate acid (50 mg)
Saccharin sulfonic acid (15 mol%)
P(4-VPH)HSO4 (10 mg)
SO3H-functionalized MCM-41 (20 mg)
N-sulfonic acid PVP Cl (20 mg)
PVPP-BF3 (50 mg)
[PVP-SO3H] Cl (40 mg)
H3PW12O40 (5 mol%)
I2 (10 mol%)
pTSA (20 mol%)
NH2SO3H (20 mol%)
TrCl (7 mol%)
N-sulfonic acid PVP Cl (20 mg)
[PVP-SO3H] Cl (40 mg)
60 ꢁC/Solvent free
60 ꢁC/Solvent free
120 ꢁC/Solvent free
120 ꢁC/Solvent free
110 ꢁC/Solvent free
130 ꢁC/Solvent free
120 ꢁC/Solvent free
60
60
35
95
45
30
5
92 (ref. 22)
95 (ref. 23)
86 (ref. 24)
84 (ref. 26)
90 (ref. 34)
90 (ref. 36)
94 (This work)
the reaction times and yields which clearly demonstrates prac- loss of activity. Furthermore, high reaction rates, no side reac-
tical recyclability of this catalyst (Fig. 6). tions, ease of preparation and handling of the catalyst, simple
The simple and efficient preparation of symmetric and experimental procedure, use of inexpensive and reusable catalyst
asymmetric xanthenes including 1,8-dioxooctahydroxanthenes, with lower loading and solvent free conditions are the other
14-aryl-14H-dibenzo[a,j] xanthenes and 12-aryl-8,9,10,12-tetra- advantages of this method. Further studies on some more
hydrobenzo[a]xanthen-11-ones. The catalyst shows high thermal practical applications of the [PVP-SO3H] Cl catalyst in the other
stability and was recovered and reused without any noticeable organic reactions are currently underway in our laboratory.
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38588 | RSC Adv., 2014, 4, 38581–38588
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