A green and efficient procedure for one-pot synthesis of xanthenes and acridines using silica boron-sulfuric acid nanoparticles (SBSANs) as a solid Lewis-protic acid

Article abstract of DOI:10.1007/s13738-012-0140-1

Silica boron-sulfuric acid nanoparticles (SBSANs) as a solid Lewis-protic acid have been found to be an efficient heterogeneous catalyst in the synthesis of xanthene and acridine derivatives. The SBSAN-catalyzed reaction between carbonyl compound (aldehyd

Full text of DOI:10.1007/s13738-012-0140-1

J IRAN CHEM SOC
DOI 10.1007/s13738-012-0140-1
ORIGINAL PAPER
A green and efficient procedure for one-pot synthesis of xanthenes
and acridines using silica boron–sulfuric acid nanoparticles
(SBSANs) as a solid Lewis-protic acid
•
Ali Khalafi-Nezhad Farhad Panahi
•
•
Somayeh Mohammadi Habib Ollah Foroughi
Received: 27 February 2012 / Accepted: 10 July 2012
Ó Iranian Chemical Society 2012
Abstract Silica boron–sulfuric acid nanoparticles
(SBSANs) as a solid Lewis-protic acid have been found to
be an efficient heterogeneous catalyst in the synthesis of
xanthene and acridine derivatives. The SBSAN-catalyzed
reaction between carbonyl compound (aldehyde/ketone/
ethyl orthoformate) and 5,5-dimethyl-1,3-cyclohexanedi-
one (dimedone) for synthesis of xanthene derivatives is
performed under mild conditions with the excellent iso-
lated yield. Also, we can apply a broad scope of carbonyl
compounds and amines for efficient synthesis of various
acridine derivatives in the presence of SBSAN catalyst. In
these multicomponent approaches the SBSAN catalyst can
be reused for several times without any treatment in its
catalytic activity.
The use of silica as substrate for preparation of solid
acids is the most popular strategy in industrials and
academic researches, due to ease of its availability and
functionalization [11–13]. Solid acids with sulfonic/sulfuric
acid groups based on silica have been used as heterogeneous
catalysts in a large number of organic processes [14–17].
It is noteworthy that, when sulfonic/sulfuric groups as
organic moieties have been grafted onto silica, their activity
and selectivity are decreased due to a decreasing in the
amount of reactant diffusion to the surface of catalyst
[18, 19]. Thus, one of the goals in the preparation of solid
acids is control of its reactivity with the ultimate goal of
preparation a heterogeneous catalyst with the versatility of a
homogenous catalyst in activity [20, 21]. One way that this
aim can be achieved is that, the silica support is selected in
nanometer scale, so the heterogeneous catalyst will even be
dispersible in solution as pseudo-homogenous catalyst to
form an emulsion to increase the velocity of reaction with
increasing the diffusion rate [22, 23]. The other way is
induction of Lewis acid sites’ influence on the protic sites of
catalysts which is known as Brønsted/Lewis acid synergy
(BLAS) [24]. According to the BLAS concept, the coordi-
nation of Lewis acid sites to the nearest connected donor
atom of protic sites (such as oxygen atom) has resulted in an
enhancement in the acidity of Brønsted sites [25]. As a
result, by use of these two most important strategies we can
improve the reactivity of solid acids.
Keywords Silica boron–sulfuric acid nanoparticles
(SBSANs) ꢀ Solid acid ꢀ Lewis-protic acid ꢀ Xanthenes ꢀ
Acridines
Introduction
Heterogeneous catalysts, especially solid acids have
attracted increasing interest in organic synthesis, because
they can provide a green and efficient media for organic
transformations [1–7]. Solid acid catalysts help us to design
a new procedure for excellent performing of acid-catalyzed
reactions, with maximum product efficiency and minimum
environmental impacts, as two important principles of
green chemistry [8–10].
Previously, we have introduced the silica boron–sulfuric
acid nanoparticles (SBSANs) as a new solid-acid catalyst
based on nanometer scale silica support with two Lewis
and protic acidic sites [26]. SBSAN catalyst has a nano-
particle nature and so its solution dispersibility has
improved to some extent. It also has two acidic sites, one
the protons of sulfuric acid group and other the boron
atoms as Lewis acid. It seems that, in SBSAN catalyst there
A. Khalafi-Nezhad (&) ꢀ F. Panahi ꢀ S. Mohammadi ꢀ
H. O. Foroughi
Department of Chemistry, Shiraz University,
71454 Shiraz, Islamic Republic of Iran
e-mail: khalafi@chem.susc.ac.ir
123

J IRAN CHEM SOC
is a BLAS effect between Lewis and protic acidic sites,
because its catalytic activity is decreased in donor solvents
and on the other hand it shows a good reactivity in solvent-
free conditions. The high reactivity of SBSAN catalyst
became interesting for our research group because it
effectively catalyzed the Ritter reaction as acid catalyzed at
room temperature and under solvent free condition with the
excellent results [26]. These interesting results prompted us
to check other acid-catalyzed reactions. In the current
study, we would like to present another important appli-
cation of SBSAN as an efficient heterogeneous catalyst for
synthesis of 1,8-dioxo-octahydroxanthenes and 1,8-dioxo-
decahydroacridines under mild condition.
Two categories of materials which can be obtained using
multicomponent reactions (MCRs) [27, 28] over an acid
catalyst are 1,8-dioxo-octahydroxanthenes and 1,8-dioxo-
decahydroacridines. Acridines, as a poly functionalized
1,4-dihydropyridine derivatives have attracted great interest
for their widespread applications including the treatment of
cardiovascular diseases, synthesizing of conjugated labels,
for DNA-binding, synthesizing of dyes, in construction of
fluorescent material for visualization of biomolecules, and in
laser technologies [29–34]. Xanthenes have received signif-
icant attention due to their biological and pharmaceutical
properties, such as antiviral effects, antibacterial properties,
antinociceptive, and anti-inflammatory activities [35–38].
For synthesis of these classes of compounds there are several
reports in the literature. Some of the catalysts which have
been used for promotion of these reactions are as follows:
InCl3ꢀ4H2O [39], diammonium hydrogen phosphate [40],
p-dodecylbenzenesulfonic acid [41], Fe3?-montmorillonite
[42], NaHSO4–SiO2 or silica chloride [43], amberlyst-15
[44], silica sulfuric acid (SSA) [45], tetrabutylammonium
hydrogen sulfate [46], 1-butyl-3-methylimidazolium hydro-
gen sulfate [47], montmorillonite K-10-supported [48],
silica-bonded s-sulfonic acid (SBSSA) [49], trichloroisoc-
yanuric acid [50], DABCO-bromine [51], silica-supported
polyphosphoric acid (PPA–SiO2) [52], and L-proline [53].
Although each of these methods has its benefits some of them
often suffer from one or more disadvantages. Using of only
reactive and conventional substrates, low yield, prolonged
reaction time, tedious work-up processes, expensive rea-
gents, and hazardous reaction conditions are most important
deficiencies associated with these methods [54–59].
Scheme 1 Synthetic rout for preparation of SBSAN catalyst
Results and discussion
This study was initiated with synthesis of SBSAN catalyst
based on our previous procedure [26]. The chemical pro-
cesses for the preparation of SBSAN catalyst is depicted in
Scheme 1.
According to the Scheme 1, SBSAN catalyst is prepared
in a two-step method. The main part of the synthetic route
for the preparation of SBSAN catalyst is the synthesis of
silica boric acid nanoparticles (SBAN). This material was
regularly produced during the modification of silica by
boric acid over the chemical vapor deposition (CVD)
process. The treatment of SBANs with chlorosulfonic acid
(ClSO3H) resulted in the formation of SBSAN catalyst.
The SBSAN catalyst has been fully characterized using
some different microscopic and spectroscopic techniques
[26].
Herein, a convenient and efficient method for synthesis
of 1,8-dioxo-octahydroxanthenes and 1,8-dioxo-decahy-
droacridines using SBSAN catalyst under solvent-free
condition is described. These conditions are appropriate for
applying a broad scope of carbonyl compounds and amines
for synthesis of new xanthene and acridine derivatives. In
this work, for the first time, ketones and ethyl orthoformate
were used as carbonyl group source for the synthesis of
new categories of xanthenes and acridines.
Due to the drastic reduction in catalytic activity of
SBSAN catalyst in coordinating solvents, it seems that the
boron atoms have a key role in the reactivity of this
catalyst. In accordance with the proposed structure for
SBSAN catalyst, Lewis acidity of the boron atoms is
only resulted from the tri-coordinated borons which are
123

J IRAN CHEM SOC
expected to be in the structure of this catalyst. In the
structure of SBSAN catalyst there are also protic acidic
sites which are related to the sulfonated boric acid and
also hydroxy groups of silica. One of the possible struc-
tures for SBSAN catalyst, considering to the observation
of B–O–B bond in the structure of this catalyst [26], is the
complex nature of boron atoms. In the proposed structure
for SBSAN, the counter ion of boronate complex is proton
ions, which can be the protic sites of SBSAN catalyst.
It is noticeable that the Lewis acidity of boron atoms
in the structure of SBSAN catalyst is increased due to the
presence of sulfonic group as electron withdrawing group
on the boron atoms. In SBSAN catalyst between protic
and Lewis sites there is a BLAS relationship, and perhaps
this is the reason why the SBSAN catalyst effec-
tively catalyzes the reactions under mild and solvent-less
conditions.
8-dioxo-octahydroxanthenes. The results of optimization
study are summarized in Table 1.
According to the Table 1, the reaction between benzal-
dehyde and dimedone was performed in the presence of
SBSAN catalyst at room temperature under solvent-free
condition with 87 % isolated yield after 12 h (Table 1,
entry 1). This reaction was also accomplished at 50 °C, and
95 % isolated yield of product was obtained after 2 h
(Table 1, entry 2). The increasing of temperature to 80 °C
did not have any effect on the reaction progress (Table 1,
entry 3), so we decided to select 50 °C as optimum tem-
perature for this reaction. The reaction was performed in
refluxing ethanol, but the yield of product was decreased to
some extent (Table 1, entry 4). In refluxing dichloro-
methane, the yield of desired product was enhanced to
85 % (Table 1, entry 5). In water as a green solvent, the
yield of product is decreased significantly, and only 43 %
yield of product was obtained (Table 1, entry 6). These
comparisons simply reveal the effect of donor solvents on
the catalytic activity of SBSAN. It can be seen that the
yield of 3a was decreased to 54 % when SBAN was used
To evaluate the catalytic activity of SBSAN catalyst in
these multicomponent reactions, the reaction between
benzaldehyde (1) and dimedone (2) was chosen as a model
to found optimization conditions for the preparation of 1,
Table 1 Optimization of reaction between benzaldehyde and dimedone
Entry
Catalyst
Solventa
T/°C
Time/h
Yield of 3a (%)b
1
SBSAN
SBSAN
SBSAN
SBSAN
SBSAN
SBSAN
SBAN
None
None
None
EtOH
CH2Cl2
H2O
r.t.
5
2
82 (87)c
95 (96)c
96 (97)c
82
2
50
3
80
2
4
Reflux
Reflux
Reflux
80
12
12
24
24
12
24
24
5
5
85
6
43
7
None
None
None
None
None
None
None
54
8
Silica
80
Trace
Trace
Traced
63
97e
68f
9
B(OH)3
Silica/B(OH)3
SSA
80
10
11
12
13
80
50
SBSAN
SBSAN
50
12
24
50
Amount of materials in all reactions: dimedone (2.2 mmol), benzaldehyde (1 mmol) and catalyst: SBSAN (0.05 g, 4.5 mol %), SBAN (0.1 g),
silica (0.1 g) and B(OH)3 (0.1 g)
a
5 mL of solvent was used
b
Isolated yield
c
The yields in practice are for time of 12 h
d
A mixture of silica (0.05 g) and B(OH)3 (0.05 g)
e
Amount of catalyst used: 0.075 g (6.75 mol%)
f
Amount of catalyst used: 0.025 g (2.25 mol%)
123

J IRAN CHEM SOC
as catalyst at 80 °C in solvent free condition (Table 1,
entry 7). The reaction did not carry out in the presence of
silica and boric acid (Table 1, entries 8 and 9). The same
result obtained when we used a mixture of silica and boric
acid as catalyst (Table 1, entry 10). These results have also
shown that the catalytic sites of SBAN are different from
silica and boric acid in normal form. Also, the yield of
desired product was obtained 63 %, when silica sulfuric
acid (SSA) was used as catalyst under the same condition
(Table 1, entry 11). This observation has also confirmed
that the reactivity of SBSAN has not resulted only from the
sulfuric acid groups.
reaction depended on the aldehyde, all aldehydes, espe-
cially aromatic types, were rapidly converted to the cor-
responding products with excellent isolated yields in short
reaction time (Table 2, entries 9–17). It seems that elec-
tron-withdrawing groups on the aryl ring increased the
reaction rate, so that 4-nitrobenzaldehyde as well as
3,4-dimethoxybenzaldehyde reacted with dimedone in the
presence of SBSAN catalyst (Table 2, entries 7 and 8).
Interestingly, the reaction of dimedone and terephthalde-
hyde has resulted in the production of compound 3q with
73 % isolated yield. This product has an aldehyde func-
tional group which can be used for synthesizing of dual-
polycyclic compounds or other compounds with a xanthene
structural motif (Table 2, entry 17).
The above results also confirmed that the boron atoms
have effect on catalytic activity of SBSAN and so the
existence of a BLAS between its protic and Lewis sites is
unavoidable. However, the nano-particle nature of silica
support should also be considered. It was seen that similar
results were obtained by increasing the amount of catalyst
(6.75 mol%) (Table 1, entry 12). As a result of decreasing
the amount of catalyst (2.25 mol%), both reaction time and
yield of product were changed (Table 1, entry 13). As
clearly shown in Table 1, the best results for this protocol
were obtained with catalyst loading of 4.5 mol% of
SBSAN at 50 °C in solvent free condition. With this effi-
cient protocol in our hand we set out to extend the scope of
the substrates and so some new 1,8-dioxo-octahydrox-
anthenes were synthesized under optimized conditions. The
results are depicted in Table 2.
Condensation reaction between dimedone, benzalde-
hyde, and aniline (4) was checked as a simple model
substrate for preparation of 1,8-dioxo-decahydroacridine
derivatives using SBSAN catalyst, and after only 1 h
the corresponding product was obtained with 96 %
isolated yield at 50 °C under solvent-free condition
(Scheme 2).
The above results encourage us to apply the SBSAN
catalyst in synthesis of new 1, 8-dioxo-decahydroacridine
derivatives (Table 3) using different carbonyl compounds
and amines.
In first selection, we used adenine and adenosine as
amine component to increase the structural diversity of
this process and these multicomponent reactions lead to
the formation of new nucleobase derivatives (Table 3,
entries 1 and 2). The functional group compatibility of
this reaction was highlighted using attached compounds or
functionalized groups by spacer with primary amines
(Table 3, entries 3 and 4). Another important feature of
this method is the use of ammonia (ammonium carbonate)
as an amine component to generate another class of
dihydropyridine derivative (Table 3, entry 5). To evaluate
the applicability of this protocol for aliphatic aldehydes
we also synthesized the compounds 5g and 5h using
1,3,5-trioxane and acetaldehyde, respectively (Table 3).
Although the SBSAN catalyst provides highly acidic
environment, we can synthesize the compound 5i with
good yield using thiophene-2-carbaldehyde as an acid-
sensitive substrate (Table 3). One of the most important
applications of this protocol is the use of ketones instead
of aldehydes to produce new derivatives of acridines
which may be biologically active (Table 3, entry 9). If a
cyclic ketone be used, the formed product is a spiro-
acridine (Table 3, entry 10).
SBSAN catalyst proved to be highly efficient and we
realized a good general applicability of the protocol due to
its significant functional group compatibility. One of the
most important applications of this catalyst system is in the
preparation of 1,8-dioxo-octahydroxanthenes whose cor-
responding aldehydes are aliphatic and have low boiling
point (Table 2, entries 2–4). An interesting application of
this protocol is the use of ethyl orthoformate as a carbonyl
group source and 9-ethoxy-3,4,6,7-tetrahydro-3,3,6,6-tet-
ramethyl-2H-xanthene 1,8(5H,9H)-dione as new ether
derivative of 1,8-dioxo-octahydroxanthenes was obtained
in the excellent yield (Table 2, entry 5). SBSAN catalyst
provides efficient conditions for utilization of ketones as
carbonyl component to produce xanthene derivatives with
high structure diversity. For example, by the use of acetone
as a simple ketone, 3,4,6,7-tetrahydro-3,3,6,6,9,9-hexam-
ethyl-2H-xanthene-1,8(5H,9H)-dione compound was pro-
duced (Table 2, entry 6). Cyclic ketones were also used
to generate the spiro-xanthenes as a new class of xanthene
derivatives (Table 2, entry 7). These compounds may
improve the biological activity of the 1,8-dioxo-octahy-
droxanthenes and/or create a new biological property for
application in medicinal chemistry in future. Under opti-
mized conditions by use of acetophenone any product was
observed (Table 2, entry 8). Although the progress of this
The recycling possibility of SBSAN catalyst was
examined by the reaction of benzaldehyde and dimedone
under optimizing conditions. When the reaction was
completed, the reaction mixture was washed with hot
ethanol and then catalyst separated by simple filtration.
123

J IRAN CHEM SOC
Table 2 One-pot Synthesis of 1, 8-dioxo-octahydroxanthenes using SBSAN catalyst under mild conditions
Entry
1
Substrate
Product
Time (h)
2
Yield (%)a
Mp (°C)
95
202–203
O
Lit: 201–203 [58]
O
O
O
3a
2
3
4
3
3
2
91
92
90
Oil
O
H
O
O
O
O
O
3b
Oil
O
CH3
O
O
H3C
H
O
3c
65–68
O
O
O
O
O
O
O
O
3d
5
6
7
3
4
5
91
90
91
Oil
Oil
Oil
O
O
OEt
O
O
3e
O
H3C
CH3
O
3f
O
O
O
O
3g
8
9
12
0
–
O
O
O
O
Me
Ph
O
3h
1
95
221–222
NO2
Lit: 222 [41]
O
O
NO2
O
3i
10
1
93
185–186
OMe
O
OMe
O
Lit: 184–186 [59]
O
MeO
OMe
O
3j
123

J IRAN CHEM SOC
Table 2 continued
Entry
11
Substrate
Product
Time (h)
1
Yield (%)a
95
Mp (°C)
243–244
O
OMe
Lit: 242–244 [49]
O
O
O
O
OMe
O
3k
12
13
14
1
94
93
93
184–185
O
N
Lit: 184–186 [49]
O
N
O
3l
2
226–227
O
Cl
O
Lit: 226–228 [59]
Cl
O
3m
1.5
169–170
O
NO2
O
Lit: 170–172 [49]
O
NO2
O
3n
15
1
92
230–231
O
Br
Lit: 230–232 [50]
O
O
Br
O
3o
16
2
90
203–204
O
CHO
O
O
3p
17
1
73
185–187
O
CHO
O
O
O
O
3q
Reaction condition: carbonyl compound (1 mmol), dimedone (2.2 mmol), and SBSAN (0.05 g, 4.5 mol%)
a
Isolated yield
The recycled catalyst was heated in oven at 100 °C for 2 h
and was saved for next run. The recycled catalyst could be
reused seven times without any treatment (Fig. 1).
After eight times of reusability we checked the sulfur
content of SBSAN catalyst using elemental analysis
instrument, and the results have shown that only 0.6 % of
123

J IRAN CHEM SOC
1H and 13C NMR spectra were recorded on a Bruker
Avance 250 MHz spectrometer in DMSO or CDCl3 solu-
tion with TMS as an internal standard. FTIR spectroscopy
(Shimadzu FT-IR 8300 spectrophotometer) was employed
for the characterization of the compounds. Melting points
were determined in open capillary tubes in a Barnstead
Electrothermal 9100 BZ circulating oil melting point
apparatus. The reaction monitoring was accomplished by
TLC on silica gel PolyGram SILG/UV254 plates.
Chemical vapor deposition (CVD) process was used for
the synthesis of silica boric acid nanoparticles (SBANs).
In this way, a brief mixture of argon and oxygen gases
and the aerosols of the aqueous solution of boric acid
(*2.0 g mL-1) were injected into the solid silica supports
positioned inside a quartz tube located in a tubing furnace
at temperatures of about 600 °C. Silica boron–sulfuric acid
nanoparticles (SBSANs) are prepared from the reaction of
SBANs and chlorosulfonic acid (ClSO3H) based on pre-
vious procedure [26].
Scheme 2 Model substrates for synthesis of acridine using SBSAN
catalyst. Reaction conditions: benzaldehyde (1 mmol), dimedone
(2.2 mmol), and aniline (1 mmol)
sulfur of SBSAN catalyst was lost during this reaction.
These results are in good agreement with catalyst activity
of SBSAN catalyst after each recovery and no appreciable
loss in the catalytic activity of SBSAN catalyst could be
seen.
To compare the efficiency of our catalyst with the
reported catalysts for the synthesis of xanthenes, we have
tabulated the results of these catalysts for the synthesis of
compounds 3a, in Table 4.
General procedure for synthesis of 1,8-dioxo-
octahydroxanthenes using SBSAN catalyst
As shown in Table 4, our catalyst is superior to some of
the previously reported catalysts in terms of reaction con-
dition, reaction time, and yield. Furthermore, in spite of
most of the reported works, in our presented work, the
preparation of both xanthenes and acridine derivatives
using different carbonyl compounds have been achieved.
A mixture of 5,5-dimethyl-cyclohexane-dione (0.308 g,
2.2 mmol) and aldehyde (1 mmol) in 0.05 g of SBSAN at
50 °C was stirred in a round-bottomed flask for the spec-
ified time for each compound. After completion of the
reaction was confirmed by TLC, the reaction mixture was
washed with hot ethanol (2 9 10 mL), and SBSAN cata-
lyst was separated from the reaction mixture by filtration.
The products were purified by recrystallization in ethanol.
Conclusions
In summary, SBSAN with two protic and Lewis acidic sites
was found to be an effective catalyst for the preparation
of 1,8-dioxo-octahydroxanthene and 1,8-dioxo-9-aryl-10-
aryl-decahydroacridine derivatives under green condition.
By use of this heterogeneous catalyst in solvent-free
condition, we could apply a broad scope of carbonyl com-
pounds and amines to prepare a variety of xanthenes and
acridines with high structural diversity. This new approach
proceeded smoothly resulting in good to excellent yields.
The SBSAN catalyst was separated easily from the reaction
mixture by simple filtration. The use of SBSAN catalyst in
these reactions provides a better and practical alternative to
the existing procedures. Also, this procedure provides great
promise toward further useful applications in other new
multicomponent approach in future.
General procedure for synthesis of 1,8-dioxo-9-aryl-10-
aryl-decahydroacridine in the presence of SBSAN catalyst
In a round-bottomed flask a mixture of aldehyde (1 mmol),
dimedone (0.308 g, 2.2 mmol), amine (1 mmol), and
SBSAN (0.05 g) was stirred at room temperature for the
specified time for each compound. When the reaction was
completed (confirmed by TLC), the reaction mixture
was washed with hot ethanol (2 9 10 mL), and SBSAN
was separated from the reaction condition using a simple
filtration. The separated solid after filtration, was recrys-
tallized in ethanol to obtain pure product.
3,3,6,6-Tetramethyl-3,4,5,6,7,9-hexahydro-1H-xanthene-
1,8(2H)-dione (3b)
Yield: 93 %; yellow oil. IR (liquid): m = 2,861, 2,837,
1,640, 1,595 cm-1 1H NMR (250 MHz, CDCl3/TMS):
.
Experimental
d = 0.95 (s, 6H), 1.05 (s, 6H), 2.25–2.41 (m, 8H), 4.30
(s, 2H). 13C NMR (62.5 MHz, CDCl3/TMS): d = 27.3,
32.4, 35.0, 39.1, 46.1, 113.3, 157.6, 185. Anal. Calcd for
Chemicals were purchased from Fluka and Aldrich
Chemical Companies and used without further purification.
123

J IRAN CHEM SOC
Table 3 The synthesized acridine derivatives using SBSAN catalyst
Entry
1
Substrates
Product
Time/h
3
Yield (%)a
89
NO2
NO2
O
CHO
NH2
O
N
N
N
N
N
N
N
N
H
N
H
5b
2
NO2
3
87
CHO
O
O
NO2
NH2
N
N
N
N
N
N
N
N
N
O
O
HO
HO
HO
HO
HO
HO
5c
3
2
91
NO2
CHO
O
O
NO2
N
NH2
N
N
N
H
N
H
5d
4
2
90
Cl
N
CHO
O
O
Cl
N
NH2
N
5e
5f
5
6
2
4
93a
NO2
O
CHO
O
O
NO2
(NH4)2CO3
N
H
89
H
N
O
O
O
O
NH2
OMe
OMe
O
5g
5h
7
2
92
O
CH3
N
O
H3C
H
NH2
OMe
OMe
123

J IRAN CHEM SOC
Table 3 continued
Entry
Substrates
Product
Time/h
2
Yield (%)a
89
8
S
S
O
O
O
O
O
O
O
NH2
N
NO2
O
NO2
5i
9
5
90
H3C
CH3
N
NH2
OMe
OMe
5j
10
5
88b
O
(NH4)2CO3
N
H
5k
Reaction conditions: aldehyde (1 mmol), dimedone (2.2 mmol), amine (1 mmol), and SBSAN (0.05 g)
a
Isolated yield
b
2 mmol of (NH4)2CO3 was used
32.3, 35.0, 50.3, 99.3, 155.3, 162.4, 195. Anal. Calcd for
C18H24O3 (288.38): C, 74.97; H, 8.39; found: C, 74.91; H,
8.33.
3,3,6,6-Tetramethyl-9-propyl-3,4,5,6,7,9-hexahydro-1H-
xanthene-1,8(2H)-dione (3d).
Yield: 91 %; yellow solid; mp 65–68 °C. IR (KBr):
m = 2,863, 2,829, 1,640, 1,599 cm-1. 1H NMR (250 MHz,
CDCl3/TMS): d = 0.62 (t, J = 1.0 Hz, 3H), 0.87 (s, 6H),
1.01 (s, 6H), 1.52–1.60 (m, 4H), 2.75–2.82 (m, 8H), 4.26
(t, J = 1.8 Hz, 1H). 13C NMR (62.5 MHz, CDCl3/TMS):
d = 14.1, 20.1, 28.1, 32.5, 37.1, 44.8, 51.0, 115.3, 152.6,
192.2. Anal. Calcd for C20H28O3 (316.43): C, 75.91; H,
8.92; found: C, 75.87; H, 8.89.
Fig. 1 Catalytic recovery times of SBSAN catalyst for eight runes.
Reaction condition: benzaldehyde (2 mmol), dimedone (4.4 mmol),
SBSAN (0.1 g), solvent free and 50 °C. Reaction time = 2 h
C17H22O3 (274.35): C, 74.42; H, 8.08; found: C, 74.35; H,
8.01.
9-Ethoxy-3,3,6,6-tetramethyl-3,4,5,6,7,9-hexahydro-1H-
xanthene-1,8(2H)-dione (3e)
3,3,6,6,9-Pentamethyl-3,4,5,6,7,9-hexahydro-1H-xanthene-
1,8(2H)-dione (3c)
Yield: 90 %; colorless oil. IR (liquid): m = 2,850, 2,828,
1,645, 1,597, 1,121 cm-1 1H NMR (250 MHz, CDCl3/
.
TMS): d = 0.88 (s, 6H), 0.89 (s, 6H), 1.07 (t, J = 2.3 Hz,
3H), 2.30–2.50 (m, 8H), 3.60–3.66 (m, 2H), 5.41 (s, 1H).
13C NMR (62.5 MHz, CDCl3/TMS): d = 17.4, 27.5, 31.1,
44.0, 52.5, 69.1, 111.3, 152.4, 196.5. Anal. Calcd for
C19H26O4 (318.41): C, 71.67; H, 8.23; found: C, 71.61; H,
8.21.
Yield: 89 %; pale yellow oil. IR (liquid): m = 2,860, 2,831,
1,645, 1,596 cm-1 1H NMR (250 MHz, CDCl3/TMS):
.
d = 0.98 (t, J = 1.3 Hz, 3H), 1.06 (s, 12H), 2.09–2.10
(m, 4H), 2.24–2.25 (m, 4H), 5.01 (q, J = 1.2, 2.1, 1H). 13
NMR (62.5 MHz, CDCl3/TMS): d = 21.1, 24.3, 29.1,
C
123

J IRAN CHEM SOC
Table 4 Comparison of the results of the synthesis of compound 3a, using SBSAN catalyst with those obtained by the reported catalysts
Entry
Catalyst and conditions
3a
References
Time (h)
Yield (%)
1
2
SBSAN, Solvent-free, 50 °C
[bmim][BF4]/InCl3, 80 °C
Silica chloride, CH3CN, reflux
Silica sulfuric acid, solvent free, 100 °C
Montmorillonite K10, solvent free, 100 °C
SBSSA, EtOH, reflux
2
5
95
95
90
97
82
98
95
90
93
83
This work
[39]
3
6
[43]
4
1
[45]
5
2
[48]
6
10
2
[49]
7
Trichloroisocyanuric acid, EtOH, reflux
DABCO-bromine, H2O, reflux
PPA–SiO2, solvent-free, 140 °C
L-proline, DCE, 60 °C
[50]
8
1
[51]
9
0.5
6
[52]
10
[53]
3,3,6,6,9,9-Hexamethyl-3,4,5,6,7,9-hexahydro-1H-
xanthene-1,8(2H)-dione (3f)
4-(3,3,6,6-Tetramethyl-1,8-dioxo-2,3,4,5,6,7,8,9-
octahydro-1H-xanthen-9-yl)benzaldehyde (3q)
Yield: 88 %; yellow oil. IR (liquid): m = 3,327, 2,856,
Yield: 73 %; white solid; mp 185-187 °C. IR (KBr):
m = 2,859, 2,831, 1,645, 1,561 cm-1. 1H NMR (250 MHz,
CDCl3/TMS): d = 0.96 (s, 6H), 1.06 (s, 6H), 2.17–2.51
(m, 8H), 4.70 (s, 1H), 7.07 (t, J = 0.9 Hz, 2H), 7.26
(q, J = 1.2, 1.0 Hz, 2H), 11.84 (s, 1H). 13C NMR
(62.5 MHz, CDCl3/TMS): d = 27.7, 30.0, 40.0, 45.0, 50.1,
113.1, 129.5, 129.7, 130.8, 144.7, 156.5, 191.4, 197.8.
Anal. Calcd for C24H26O4 (378.46): C, 76.17; H, 6.92;
found: C, 76.12; H, 6.88.
2,832, 1,643, 1,593 cm-1 1H NMR (250 MHz, CDCl3/
.
TMS): d = 0.98 (s, 6H), 1.00 (s, 6H), 1.18 (s, 3H), 1.22
(s, 3H), 2.05–2.35 (m, 6H). 13C NMR (62.5 MHz, CDCl3/
TMS): d = 14.1, 20.2, 28.7, 32.4, 42.7, 50.3, 60.6, 64.1,
101.1, 176.4, 199.5. Anal. Calcd for C22H30O3 (342.47): C,
77.16; H, 8.83; found: C, 77.00; H, 8.78.
30,30,60,60-Tetramethyl-30,40,60,70-
tetrahydrospiro[cyclohexane-1,90-xanthene]-
10,80(20H,50H)-dione (3g)
10-(1H-Benzo[d]imidazol-7-yl)-3,3,6,6-tetramethyl-9-(2-
nitrophenyl)-3,4,6,7,9,10-hexahydroacridine-1,8(2H,5H)-
dione (5b)
Yield: 91 %; yellow oil. IR (liquid): m = 3,312, 2,993,
2,891, 1,637, 1,547 cm-1 1H NMR (250 MHz, CDCl3/
.
Yield: 91 %; pale yellow solid; mp 245–247 °C. IR (KBr):
m = 3,243, 3,085, 1,615, 1,591, 1,550, 1,461, 1,330 cm-1
.
TMS): d = 0.98–1.02 (m, 12H), 1.16–1.32 (m, 6H), 2.08
(s, 4H), 2.13–2.22 (m, 8H). 13C NMR (62.5 MHz, CDCl3/
TMS): d = 13.6, 22.2, 27.4, 31.94, 42.3, 55.6, 100.1,
176.4, 199.5. Anal. Calcd for C19H26O3 (302.41): C, 75.46;
H, 8.67; found: C, 75.36; H, 8.59.
1H NMR (250 MHz, DMSO-d6/TMS): d = 1.05 (s, 6H),
1.12 (s, 6H), 2.41–2.51 (m, 8H), 5.4 (s, 1H), 7.14
(d, J = 3.2 Hz, 1H), 7.26 (q, J = 2.0, 1.5 Hz, 1H), 7.33
(q, J = 2.7, 1.3 Hz, 1H), 7.80 (d, J = 1.5 Hz, 1H), 8.29
(d, J = 3.2 Hz, 2H), 9.80 (brs, 1H). 13C NMR (62.5 MHz,
DMSO-d6/TMS): d = 27.3, 33.1, 55.4, 56.0, 109.9, 119.1,
126.5, 127.5, 129.8, 130.4, 134.5, 137.6, 148.1, 149.0,
150.3, 151.4, 164.2, 192.1. Anal. Calcd for C30H30N4O4
(510.58): C, 70.57; H, 5.92; N, 10.97; found: C, 70.49; H,
5.87; N, 10.95.
9-(Anthracen-9-yl)-3,3,6,6-tetramethyl-3,4,5,6,7,9-
hexahydro-1H-xanthene-1,8(2H)-dione (3p)
Yield: 92 %; yellow solid; mp 203–204 °C. IR (KBr):
m = 2,967, 1,670, 1,265, 1,057, 853 cm-1 1H NMR
.
(250 MHz, DMSO-d6/TMS): d = 0.97 (s, 6H), 1.03
(s, 6H), 2.46–2.83 (m, 8H), 4.68 (s, 1H), 7.33–7.49
(m, 4H), 7.80–7.84 (m, 4H), 8.12 (s, 1H). 13C NMR
(62.5 MHz, DMSO-d6/TMS): d = 15.9, 22.5, 27.8, 51.7,
52.7, 108.1, 124.9, 125.4, 126.2, 127.4, 128.7, 129.9,
130.5, 138.1, 160.3, 196.5. Anal. Calcd for C31H30O3
(450.57): C, 82.64; H, 6.71; found: C, 82.57; H, 6.65.
10-(1-((2R,3R,4S,5R)-3,4-Dihydroxy-5-(hydroxy-
methyl)tetrahydrofuran-2-yl)-1H-benzo[d]imidazol-4-yl)-
3,3,6,6-tetramethyl-9-(4-nitrophenyl)-3,4,6,7,9,10-
hexahydroacridine-1,8(2H,5H)-dione (5c)
Yield: 88 %; pale yellow solid; mp [300 °C. IR (KBr):
m = 3,125, 2,968, 2,881, 1,635, 1,591, 1,564, 1,473, 1,447,
123

J IRAN CHEM SOC
1,365, 1,312, 1,225, 1,148, 991, 560 cm-1
.
1H NMR
192.4. Anal. Calcd for C23H26N2O4 (394.46): C, 70.03; H,
6.64; N, 7.10; found: C, 69.97; H, 6.61; N, 7.04.
(250 MHz, DMSO-d6/TMS): d = 1.03 (s, 6H), 1.10 (s, 6H),
2.30–2.42 (m, 8H), 3.65 (d, J = 4.2 Hz, 1H), 3.76–3.82 (m,
2H), 4.23 (d, J = 7.6 Hz, 1H), 4.63 (d, J = 8.7 Hz, 1H),
4.90 (s, 1H), 5.14 (brs, 3H), 5.82 (d, J = 1.3 Hz, 1H), 7.42
(d, J = 4.2 Hz, 2H), 8.16 (d, J = 5.2 Hz, 2H), 8.27 (s, 1H),
8.57 (s, 1H). 13C NMR (62.5 MHz, DMSO-d6/TMS):
d = 28.7, 51.4, 61.0, 74.0, 77.5, 84.1, 90.0, 112.2, 115.1,
118.3, 119.2, 129.1, 138.8, 147.1, 148.6, 149.3, 150.0, 151.1,
151.6. Anal. Calcd for C35H38N4O8 (642.70): C, 65.41; H,
5.96; N, 8.72; found: C, 65.38; H, 5.91; N, 8.70.
10-(4-Methoxyphenyl)-3,3,6,6-tetramethyl-3,4,6,7,9,10-
hexahydroacridine-1,8(2H,5H)-dione (5g)
Yield: 90 %; pale yellow solid; mp 156–158 °C. IR (KBr):
m = 3,347, 2,877, 2,824, 1,648, 1,583, 1,554, 1,354 cm-1
.
1H NMR (250 MHz, CDCl3/TMS): d = 0.93 (s, 6H), 0.94
(s, 6H), 2.04–2.21 (m, 8H), 3.60 (s, 3H), 5.21 (s, 2H), 6.77
(d, J = 3.2, 2H), 7.00 (d, J = 3.3, 2H). 13C NMR
(62.5 MHz, CDCl3/TMS): d = 35.8, 44.4, 50.6, 56.0, 97.5,
114.4, 126.6, 131.0, 157.5, 162.4, 197.6. Anal. Calcd for
C24H29NO3 (379.49): C, 75.96; H, 7.70; N, 3.69; found: C,
75.91; H, 7.64; N, 3.65.
3,3,6,6-Tetramethyl-9-(4-nitrophenyl)-10-(2-(piperaz-in-1-
yl)ethyl)-3,4,6,7,9,10-hexahydroacridine-1,8(2H, 5H)-
dione (5d)
Yield: 93 %; yellow solid; mp 233–235 °C. IR (KBr):
m = 3,131, 2,967, 2,875, 1,643, 1,590, 1,566, 1,489,
10-(4-Methoxyphenyl)-3,3,6,6,9-pentamethyl-3,4,6,7,9,10-
hexahydroacridine-1,8(2H,5H)-dione (5h)
1
1,451 cm-1. H NMR (250 MHz, CDCl3/TMS): d = 0.83
(s, 6H), 86 (s, 6H), 2.24–2.42 (m, 20H), 5.45 (s, 1H), 7.34 (d,
J = 8.3 Hz, 2H), 7.64 (d, J = 8.8 Hz, 2H). 13C NMR
(62.5 MHz, CDCl3/TMS): d = 27.3, 28.3, 32.8, 33.4, 43.1,
45.4, 50.3, 55.4, 65.4, 97.5, 114.0, 126.6, 140.0, 157.5, 162.4,
197.6. Anal. Calcd for C29H38N4O4 (506.64): C, 68.75; H,
7.56; N, 11.06; found: C, 68.71; H, 7.53; N, 11.01.
Yield: 92 %; pale yellow solid; mp 159–161 °C. IR (KBr):
m = 2,938, 2,829, 1,639, 1,589, 1,443, 1,335, 1,261,
1
1,045 cm-1. H NMR (250 MHz, CDCl3/TMS): d = 0.91
(s, 3H), 0.93 (s, 6H), 0.94 (s, 6H), 2.09–2.25 (m, 8H), 3.68 (s,
3H), 5.25 (s, 1H), 6.72 (d, J = 3.6 Hz, 2H), 7.08 (d,
J = 7.9 Hz, 2H). 13C NMR (62.5 MHz, CDCl3/TMS):
d = 28.3, 32.8, 43.1, 50.3, 55.4, 97.3, 114.4, 126.1, 131.0,
157.5, 162.4, 197.6. Anal. Calcd for C25H31NO3 (393.52): C,
76.30; H, 7.94; N, 3.56; found: C, 76.23; H, 7.89; N, 3.51.
9-(4-Chlorophenyl)-10-(2-(dimethylamino)ethyl)-3,3,6,
6-tetramethyl-3,4,6,7,9,10-hexahydroacridine-1,8(2H,5H)-
dione (5e)
9,90-(1,4-Phenylene)bis(10-(4-methoxyphenyl)-3,3,6,6-
tetramethyl-3,4,6,7,9,10-hexahydroacridine-1,8(2H,5H)-
dione) (5j)
Yield: 91 %; yellow solid; mp 217–219 °C. IR (KBr):
m = 2,868, 2,537, 1,644, 1,635, 1,601, 1,524, 1,326 cm-1
.
1H NMR (250 MHz, DMSO-d6/TMS): d = 1.00 (s, 6H),
1.11 (s, 6H), 2.17 (d, J = 1.8 Hz, 2H), 2.25–2.41 (m, 8H),
2.45 (d, J = 1.8 Hz, 3H), 2.61 (t, J = 2.6 Hz, 3H), 3.26
(t, J = 2.3 Hz, 2H), 5.17 (s, 1H), 7.09–7.18 (m, 2H),
7.34–7.43 (m, 2H). 13C NMR (62.5 MHz, DMSO-d6/
TMS): d = 27.3, 32.2, 41.0, 47.0, 51.5, 56.2, 66.5, 130.0,
131.1, 132.4, 136.4, 141.7, 161.2, 193.2. Anal. Calcd for
C27H35ClN2O2 (455.03): C, 71.27; H, 7.75; N, 6.16; found:
C, 71.21; H, 7.72; N, 6.13.
Yield: 90 %; yellow solid; mp 295–297 °C. IR (KBr):
m = 3,321, 2,865, 2,834, 1,675, 1,648, 1,586, 1,567, 1,432,
1,419, 1,324, 1,311, 1254, 1,044, 832, 768 cm-1. 1H NMR
(250 MHz, DMSO-d6/TMS): d = 1.02 (s, 12H), 1.03 (s,
12H), 2.21–2.48 (m, 16H), 3.45 (s, 6H), 5.2 (s, 2H),
6.91–6.99 (m, 4H), 7.28 (t, J = 5.7 Hz, 4H), 7.34–7.39 (m,
4H). 13C NMR (62.5 MHz, DMSO-d6/TMS): d = 28.0,
31.1, 50.5, 111.5, 115.0, 116.6, 129.4, 134.4, 138.0, 151.1,
154.0, 191.1. Anal. Calcd for C54H60N2O6 (833.06): C,
77.85; H, 7.26; N, 3.36; found: C, 77.81; H, 7.22; N, 3.34.
3,3,6,6-Tetramethyl-9-(3-nitrophenyl)-3,4,6,7,9,10-
hexahydroacridine-1,8(2H,5H)-dione (5f)
10,100-(1,4-Phenylene)bis(9-(4-bromophenyl)-3,3,6,6-
tetramethyl-3,4,6,7,9,10-hexahydroacridine-1,8(2H,5H)-
dione) (5k)
Yield: 95 %; white solid; mp 211–213 °C. IR (KBr):
m = 2,971, 2,929, 1,641, 1,592, 1,514, 1,453, 1,331 cm-1
.
1H NMR (250 MHz, CDCl3/TMS): d = 0.92 (s, 6H), 0.94
(s, 6H), 2.35–2.44 (m, 8H), 5.48 (s, 1H), 7.42 (q, J = 5.2,
2.3 Hz, 2H), 7.42 (q, J = 5.2, 2.3 Hz, 2H), 7.81 (d,
J = 3.6 Hz, 1H), 8.31 (d, J = 9.4 Hz, 1H), 9.27 (s, 1H).
13C NMR (62.5 MHz, CDCl3/TMS): d = 27.3, 31.2, 38.3,
42.5, 50.8, 110.6, 118.2, 124.9, 128.1, 134.6, 142.6, 148.9,
Yield: 87 %; yellow solid; mp 291–293 °C. IR (KBr):
m = 3,334, 3,312, 2,895, 2,879, 1,668, 1,653, 1,581, 1,554,
1,430, 1,412, 1,319, 1,308, 1,232, 1,040, 830, 776 cm-1
.
1H NMR (250 MHz, DMSO-d6/TMS): d = 0.98 (s, 12H),
1.08 (s, 12H), 2.37–2.41 (m, 16H), 5.19 (s, 2H), 7.01
123

J IRAN CHEM SOC
29. E. Antman, J. Muller, S. Goldberg, R. Macalpin, M. Rubenfire,
B. Tabatznik, C. Liang, F. Heupler, S. Achuff, N. Reichek,
E. Geltman, N.Z. Kerin, R.K. Neff, E.N. Raunwald, Engl. J. Med.
302, 1269 (1980)
30. M. Guazzi, M. Olivari, A. Polese, C. Fiorentini, F. Margrini,
P. Moruzzi, Clin Pharmacol Ther 22, 528 (1977)
31. R.S. Hornung, B.A. Gould, R.I. Jones, T.N. Sonecha, E.B. Raf-
erty, Am J Cardiol 51, 1323 (1983)
(t, J = 3.2 Hz, 4H), 7.24 (d, J = 4.1 Hz, 4H), 7.36
(t, J = 3.2 Hz, 4H). 13C NMR (62.5 MHz, DMSO-d6/
TMS): d = 27.4, 32.3, 51.3, 112.0, 117.1, 120.3, 130.4,
141.1, 153.3, 179.5. Anal. Calcd for C52H54Br2N2O4
(930.80): C, 67.10; H, 5.85; N, 3.01; found: C, 67.03; H,
5.81; N, 2.97.
32. E. Delfourne, C. Roubin, J. Bastide, J Org Chem 65, 5476 (2000)
33. J. Antonini, P. Polucci, A. Magnano, S. Martelli, J Med Chem 44,
3329 (2001)
Acknowledgments We acknowledge the financial support from
Shiraz University.
34. M.G. Ferlin, C. Mar-zano, G. Chiarelotto, F. Baccichetti,
F. Bordin, Eur J Med Chem 35, 827 (2000)
35. S.M. Menchen, S.C. Benson, J.Y.L. Lam, W. Zhen, D. Sun,
B.B. Rosenblum, S.H. Khan, M. Taing, U. S. Patent US6583168
2003, Chem. Abstr. 139, 54287f (2005)
36. R.C. Hunter, T. Beveridge, J. Appl. Environ. Microbiol. 71, 2501
(2005)
References
1. H.I. Ryoo, L.Y. Hong, S.H. Jung, D.P. Kim, J Mater Chem 20,
6419 (2010)
2. B.K. Gorityala, J. Ma, K.K. Pasunooti, S. Cai, X.W. Liu, Green
Chem 13, 573 (2011)
3. C. Tagusagawa, A. Takagaki, A. Iguchi, K. Takanabe,
J.N. Kondo, K. Ebitani, T. Tatsumi, K. Domen, Chem Mater 22,
3072 (2010)
4. T. Wang, R.D. Ma, L. Liu, Z.P. Zhan, Green Chem 12, 1576
(2010)
5. Y. Xu, W. Gu, D.L. Gin, J Am Chem Soc 126, 1616 (2004)
6. D.J. Lipomi, J.S. Panek, Org Lett 7, 4701 (2005)
7. S.V. Vyver, L. Peng, J. Geboers, H. Schepers, F.D. Clippel,
C.J. Gommes, B. Goderis, P.A. Jacobs, B.F. Sels, Green Chem
12, 1560 (2010)
8. M. Hino, K. Arata, Green Chem 3, 170 (2001)
9. K. Arata, Green Chem 11, 1719 (2009)
10. T. Okuhara, Chem Rev 102, 3641 (2002)
11. S. Wang, J.A. Guin, Chem. Commun. 2499 (2000)
12. M.H. Lim, C.F. Blanford, A. Stein, Chem Mater 10, 467 (1998)
13. S. Minakata, M. Komatsu, Chem Rev 109, 711 (2009)
14. B. Karimi, M. Khalkhali, J Mol Catal A: Chem 232, 113 (2005)
15. M.B. Gawande, V. Polshettiwar, R.S. Varma, R.V. Jayaram,
Tetrahedron Lett 48, 8170 (2007)
16. G.B. Brieva, M.P.D.F. Escrig, J.M.C. Martin, J.L.G. Fierro,
Green Chem 12, 1163 (2010)
17. M.P. Kapoor, W. Fujii, Y. Kasama, M. Yanagi, H. Nanbu,
L.R. Juneja, J Mater Chem 18, 4683 (2008)
18. P.D. Stevens, J.D. Fan, H.M.R. Gardinmalla, M. Yen, Org Lett 7,
2085 (2005)
19. T.J. Yoon, W. Lee, Y.S. Oh, New J Chem 27, 227 (2003)
20. Z.L. Lu, E. Lindner, H.A. Mayer, Chem Rev 102, 3543 (2002)
21. A.P. Wight, M.E. Davis, Chem Rev 102, 3589 (2002)
22. S. Banerjee, J. Das, R.P. Alvarez, S. Santra, New J Chem 34, 302
(2010)
23. S.D. Jackson, J.S.J. Hargreaves, D. Lennon, K.M.K. Yu,
S.C. Tsang, Catal. Appl. 161 (2003)
24. S. Li, A. Zheng, Y. Su, H. Zhang, L. Chen, J. Yang, C. Ye,
F. Deng, J Am Chem Soc 129, 11161 (2007)
37. E.F. Llama, C.D. Campo, M. Capo, M. Anadon, Eur J Med Chem
24, 391 (1989)
38. J.P. Poupelin, G. Saint-Rut, O. Foussard-Blanpin, G. Narcisse,
G. Uchida-Ernouf, R. Lacroix, Eur J Med Chem 13, 67 (1978)
39. X. Fan, X. Hu, X. Zhang, J. Wang, Can J Chem 83, 16 (2005)
40. F. Darviche, S. Balalaie, F. Chadegani, P. Salehi, Synth Commun
37, 1059 (2007)
41. T.S. Jin, J.S. Zhang, J.C. Xiao, A.Q. Wang, T.S. Li, Synlett. 866
(2004)
42. G. Song, B. Wang, H. Luo, L. Yang, Catal Commun 8, 673 (2007)
43. B. Das, P. Thirupathi, I. Mahender, K.R. Reddy, B. Ravikanth,
L. Nagarapu, Catal Commun 8, 535 (2007)
44. B. Das, P. Thirupathi, I. Mahender, V.S. Reddy, Y.K. Rao, J Mol
Catal A: Chem 2347, 233 (2006)
45. M. Seyyedhamzeh, P. Mirzaei, A. Bazgir, Dyes Pigm 76, 836
(2008)
46. H.N. Karade, M. Sathe, M.P. Kaushik, ARKIVOC 13, 252 (2007)
47. K. Niknam, M. Damya, J Chin Chem Soc 56, 659 (2009)
48. A. Sharifi, M.S. Abaee, A. Tavakkoli, M. Mirzaei, A. Zolfaghari,
Synth Commun 38, 2958 (2008)
49. K. Niknam, F. Panahi, D. Saberi, M. Mohagheghnejad, J. Het-
erocyclic Chem. 47, 292 (2010)
50. M.A. Bigdeli, F. Nemati, G.H. Mahdavinia, H. Doostmoham-
madi, Chin Chem Lett 20, 1275 (2009)
51. M. Bigdeli, Chin Chem Lett 21, 1180 (2010)
52. S. Kantevari, S.V.N. Vuppalapati, D.O. Biradar, L. Nagarapu,
J Mol Catal A: Chem 269, 53 (2007)
53. B. Das, J. Kashanna, R.A. Kumar, P. Jangili, Synth Commun 42,
2876–2884 (2012)
54. A.C. Cole, J.L. Jensen, I. Ntai, K.L.T. Tran, K.J. Weaver,
D.C. Forbes, J.J.H. Davis, J Am Chem Soc 124, 5962 (2002)
55. Z.Q. Tang, Y. Chen, C.N. Liu, K.Y. Cai, S.J. Tu, J. Heterocyclic
Chem. 47, 363–367 (2010)
56. T.S. Jin, J.S. Zhang, A.Q. Wang, T.S. Li, Synth Commun 35,
2339 (2005)
57. S. Rostamizadeh, A. Amirahmadi, N. Shadjou, A.M. Amani,
J. Heterocyclic Chem. 49, 111 (2011)
58. A. John, P.J.P. Yadav, S. Palaniappan, J Mol Catal A: Chem 248,
121 (2006)
59. M.T. Maghsoodlou, S.M. Habibi-Khorassani, Z. Shahkarami,
N. Maleki, M. Rostamizadeh, Chin Chem Lett 21, 686 (2010)
25. A. Corma, V. Fornes, F. Rey, Appl. Catal. 59, 267 (1990)
26. A. Khalafi-Nezhad, H.O. Foroughi, M.M. Doroodmand,
F. Panahi, J Mater Chem 21, 12842 (2011)
27. K.K. Pasunooti, C.N. Jensen, H. Chai, M.L. Leow, D.W. Zhang,
X.W. Liu, J Comb Chem 12, 577 (2010)
28. A. Khalafi-Nezhad, F. Panahi, Synthesis. 984 (2011)
123