Recyclable CMK-5 supported sulfonic acid as an environmentally benign catalyst for solvent-free one-pot construction of coumarin through Pechmann condensation

Article abstract of DOI:10.1016/j.molcata.2014.04.013

Sulfonic acid modified nanostructured CMK-5 is used as an alternative to conventional acid catalysts in the von Pechmann condensation of a neat mixture of substituted phenols with ethyl acetoacetate leading to the formation of coumarin derivatives at 130 °C. In comparison, CMK-5-SO₃H showed a greater activity than some other homogeneous and heterogeneous catalysts. Additionally, the catalyst is reused repeatedly for 6 reaction cycles without any evidence of loss of activity, confirming the stability of the covalent bonding of acidic centers. The methodology presented offers reusable strategy for the efficient synthesis of coumarin, simplicity in operation, and green aspects by avoiding toxic conventional catalysts and solvents.

Full text of DOI:10.1016/j.molcata.2014.04.013

Accepted Manuscript
Title: Recyclable CMK-5 supported sulfonic acid as an
environmentally benign catalyst for solvent-free one-pot
construction of coumarin through Pechmann condensation
Author: Daryoush Zareyee Mahshad Serehneh
PII:
S1381-1169(14)00151-4
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.molcata.2014.04.013
MOLCAA 9075
To appear in:
Journal of Molecular Catalysis A: Chemical
Received date:
Revised date:
Accepted date:
12-1-2014
25-3-2014
12-4-2014
Please cite this article as: D. Zareyee, M. Serehneh, Recyclable CMK-5 supported
sulfonicacid as an environmentally benigncatalystforsolvent-free one-potconstruction
of coumarin through Pechmann condensation, Journal of Molecular Catalysis A:
Chemical (2014), http://dx.doi.org/10.1016/j.molcata.2014.04.013
This is a PDF file of an unedited manuscript that has been accepted for publication.
As a service to our customers we are providing this early version of the manuscript.
The manuscript will undergo copyediting, typesetting, and review of the resulting proof
before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that
apply to the journal pertain.

Recyclable CMK-5 supported sulfonic acid as an environmentally benign catalyst for
solvent-free one-pot construction of coumarin through Pechmann condensation
Daryoush Zareyee1, and Mahshad Serehneh
Department of Chemistry, Qaemshahr Branch, Islamic Azad University, Qaemshahr, Iran
Abstract: Sulfonic acid modified nanostructured CMK-5 is used as an alternative to
conventional acid catalysts in the von Pechmann condensation of a neat mixture of substituted
phenols with ethyl acetoacetate leading to the formation of coumarin derivatives at 130°C. In
comparison, CMK-5-SO3H showed a greater activity than some other homogeneous and
heterogeneous catalysts. Additionally, the catalyst is reused repeatedly for 6 reaction cycles
without any evidence of loss of activity, confirming the stability of the covalent bonding of
acidic centers. The methodology presented offers reusable strategy for the efficient synthesis of
coumarin, simplicity in operation, and green aspects by avoiding toxic conventional catalysts and
solvents.
Keywords: Pechmann condensation; Coumarins; Solvent-free; CMK-5; Heterogeneous sulfonic
acid.
1. Introduction
Coumarins occupy an important place in the realm of natural products and synthetic organic
chemistry. Their applications range from additive in foods, perfumes, cosmetics, pharmaceuticals
and in the preparation of insecticides [1], optical brighteners [2] and dispersed fluorescent and
tunable laser dyes [3]. In addition, some coumarins have varied bioactivities, such as, inhibitory
of platelet aggregation [4], antibacterial [5], anticancer [6], and inhibitory of HIV-1 protease [7].
Coumarins also act as intermediate for the synthesis of furocoumarins, chromones, coumarones
1 Corresponding author. Tel.:+98 123 214 5048; Fax: +98 123 214 5050.
E-mail address: zareyee@gmail.com, zareyee.d@qaemshahriau.ac.ir
1
Page 1 of 15

and 2-acylresorcinols [8]. Their properties turn coumarins in very interesting to organic chemists,
and several strategies for their synthesis were already reported.
A variety of methods, such as Pechmann [9], Perkin [10], Claisen [11], Knoevenagel [12],
Reformatsky [13] and Wittig [14], have been developed to synthesize coumarins. Among these,
Pechmann reaction, a two component (phenol and β-ketoester) coupling under acid catalysis, is a
very valuable protocol for coumarin ring synthesis. In the conventional production of coumarins
by the Pechmann reaction, concentrated sulfuric acid is used as the catalyst [15]. Several other
acid catalysts, like P2O5 [16], AlCl3 [17], trifluoroacetic acid [18], InCl3 [19], ZrCl4 [20], and
BiCl3 [21], are known to affect this condensation. It may also utilize transition metal catalysis
[22], ionic liquids [23], and microwave irradiation [24]. However, some of these procedures
suffer from sever drawbacks including the use of a large amounts of catalyst, for example
sulfuric acid, 10-12 equiv., trifluoroacetic acid, 3-4 equiv., elevated temperature, long reaction
times and poor yields. Furthermore, the disposal of acidic waste leads to environmental
pollution. For these reasons, there have been several attempts in the literature to find alternative
and environmentally benign synthesis routs.
The use of solid acids in organic synthesis and in industrial manufacture of materials is of
increasing importance since they provide green alternatives to homogenous catalysts. Nafion-H
[25], Amberlyst-15 [26], Montmorillonite clay [27,28], heteropoly acids [29], sulfamic acid [30],
sulfated zirconia [31], mesoporous zirconium phosphate [32], and Periodic mesoporous silica
chloride [33], have been employed for this purpose in the Pechmann condensation. Although
these catalysts are suitable for synthetic conditions, however, some of these procedures are
associated with one or more disadvantages like poor thermal stability, lack of reproducibility,
complex separation, low surface area, less water tolerance ability and large amount of solid
2
Page 2 of 15

support and tedious workup process which would eventually result in the generation of a large
amount of toxic waste. To improve the above mentioned problems, it is important to investigate
new methods using less hazardous reagents and solvents or even without harmful organic
solvents. Along this line, sulfonic acid groups immobilized on solid supports have generated
considerable interest, because they combine in a single solid, both the special chemical reactivity
of the organofunctional groups and attractive properties including a mechanically structure, high
surface area and large ordered pores [34-47]. In this context, we have recently developed a
variety of water-tolerant sulfonic acid based nanoreactors based on ordered nanoporous silica for
the von Pechmann reaction to satisfy both recyclability and reactivity. Detailed study revealed
that mesoporous solid sulfonic acid nanoreactor SBA-15-Ph-PrSO3H was a reusable,
hydrophobic and easily recyclable catalyst for the von Pechmann synthesis of coumarins [48].
Very recently, we have used ordered nanoporous carbonaceous sulfonic acid (CMK-5-SO3H)
with high surface area, narrow pore size distribution and large pore volume as a recoverable
heterogeneous catalyst in some organic transformations [49,50]. Keeping in view the importance
of Pechmann condensation and heterogeneous catalysis, and along the line of our studies in the
application of new solid acid catalysts in chemical transformations, herein we wish to report a
new method for the one-pot synthesis of coumarins using catalytic amounts of nanostrustured
CMK-5-SO3H under solvent-free reaction conditions (Scheme 1) (See supporting information for
experimental procedures for the synthesis of CMK-5 and CMK-5-SO3H, TGA, BJH, N2 ads-des,
TEM, and XRD diagrams for CMK-5 and CMK-5-SO3H).
3
Page 3 of 15

SO3H
SO3H
SO3H
CMK-5
O
O
O
OH
(3 mol%)
O
R
H2O
R
OEt
130 oC, Solvent-free
CH3
Scheme 1: Synthesis of coumarin derivatives using CMK-5-SO3H under solvent-free reaction
conditions.
2. Results and discussion
First, we examined the catalytic activity of various Bronsted acids in a model reaction of
resorcinol with ethyl acetoacetate (Table 1). As expected, condensation did not proceed without
catalyst (Table 1, entry 1). It can be seen that homogenous unrecoverable catalysts such as
H2SO4 (Table 1, entry 2), and p-toluene sulfonic acid (Table 1, entry 3) are less efficient.
Remarkably, it is also clearly seen from these data that no yield of the corresponding 7-hydroxy-
4-methyl coumarin was obtained when amorphous silica and SBA-15 were employed as catalysts
(Table 1, entries 4,5). Interestingly, the yield was dramatically increased using a hydrophobic
nanocatalyst SBA-15-Ph-PrSO3H and random pore carbon-SO3H (Table 1, entries 6,7).
Additionally, the reaction was very sluggish using non-sulfonated CMK-5 and the corresponding
product isolated in only 10% yield after 60 min (Table 1, entry 8). Finally, we observed that the
reaction was very efficient in the presence of as low as 3 mol% of CMK-5-SO3H and the
corresponding coumarin product was formed in excellent yield after 20 min (Table 1, entry 9).
This study clearly showed that CMK-5-SO3H exhibits higher activity under the same reaction
4
Page 4 of 15

conditions and the catalyst loading. So CMK-5-SO3H is a good catalyst for the synthesis of
coumarin.
Table 1: Comparison of activity of some homogeneous and heterogeneous solid acid catalysts in
Pechmann condensation of resorcinol with ethyl acetoacetate.
Time Yield
Entry Catalyst
(min) (%)a,b
1
2
3
4
5
6
7
8
9
None
60
60
60
60
60
60
60
60
20
NR
30
H2SO4
p-TSOHc
35
SBA-15c
NR
NR
90
Silicagel
SBA-15-Ph-PrSO3Hd
random pore carbon-SO3Hd
CMK-5
84
10
CMK-5-SO3H
95
a. Isolated yields.
b. Conditions were as follows: resorcinol (1 mmol), ethyl acetoacetate (1 mmol), catalyst (∼ 3
mol %) at 130 °C.
c. 200 mg of SBA-15 or silica was used.
d. ∼ 7 mol % of SBA-15-Ph-PrSO3H was used.
Next, we investigated substrate generality in the CMK-5-SO3H catalyzed condensation of
substituted phenols and ethyl acetoacetate at 130°C under solvent-free reaction condition. The
reactions worked well and the results are illustrated in Table 2. Pyrogallol (Table 2, entry 1),
phloroglucinol (Table 2, entry 2), orcinol (Table 2, entry 3), 2,6-dihydroxy toluene (Table 2,
entry 4), and 3,5-dimethyl phenol (Table 2, entry 5) afforded excellent yields in short reaction
times. Hydroquinone (Table 2, entry 6), resorciniol (Table 2, entry 7), and substrates having
electron-donating groups in Para to the site of electrophilic substitution (Table 2, entries 8-10)
5
Page 5 of 15

also gave good yields in the slightly longer reaction times. 3-Methoxyphenol (Table 2, entry 9)
showed no detective demethylation under the given conditions. Interestingly, 3-aminophenol
reacted to provide the amino coumarin in good yield with high chemoselectivity (Table 2, entry
10). 1-Naphtol (Table 2, entry 11) requires a longer reaction time, due to the presence of another
phenyl rings. Noteworthy, One of the interesting feature of this procedure over most of the
previous heterogeneous and homogeneous systems, is the formation of 4-methylcoumarin in
acceptable yield from the reaction of unsubstituted phenol (Table 2, entry 12).
Table 2: Synthesis of coumarins using 3 mol% of CMK-5-SO3H under solvent-free reaction
conditions at 130 °C.
Entry
1
Substrate
Product a
Time (min)
20
Yield (%) b
OH
OH
HO
O
O
HO
OH
96
CH3
O
OH
OH
O
O
2
3
15
20
97
93
HO
HO
HO
OH
OH
CH3
O
CH3
CH3 CH3
HO
6
Page 6 of 15

CH3
CH3
HO
O
O
HO
OH
OH
4
30
88
CH3
O
H3C
H3C
O
5
6
25
25
20
30
30
35
89
90
95
86
89
91
CH3
CH3 CH3
O
O
OH
HO
HO
HO
HO
CH3
O
O
O
O
O
OH
OH
OH
OH
7
CH3
O
H3C
MeO
H2N
H3C
MeO
H2N
8
CH3
O
9
CH3
O
10
CH3
O
OH
O
11
12
45
92
60
CH3
O
O
OH
120
CH3
a. All products were characterized by comparison of their 1H, and 13C NMR spectra with those of
authentic samples.
b. Isolated yields after recrystallization.
Here it should be mentioned that the use of CMK-5-SO3H as a solid acid catalyst is
advantageous not only for its thermal stability, high water tolerance ability, easy sedimentation
property, and better catalytic activity, but also it is a reusable catalyst for Pechmann
condensation. The stability of the sulfonic acid groups during the reaction was conducted by
repeating the condensation of resorcinol over CMK-5-SO3H. In repeated experiments, the
catalyst washed with ethanol for three times and then the new substrates added. In six runs, the
yields of product were 95%, 92%, 92%, 90%,, 90% and 88% respectively, which verify that the
7
Page 7 of 15

activity of the catalyst remained unchanged throughout these six runs. For better investigation of
catalyst recyclability, we established an experiment by conducting successive condensation of
resorcinol with ethyl acetoacetate using CMK-5-SO3H in a shorter time (10 min). The yield of
corresponding product reached to 60% after 10 min. Gratifyingly, the catalyst was reused again
in six successive runs with no significant decreases in its efficiency, providing almost same
yields of the respective product (Figure 1).
Figure 1: Recyclability of the catalyst for the Pechmann condensation of resorcinol after 10
min.
In order to show whether the reaction is actually proceeding in a heterogeneous pathway or
whether it is conducting through a homogeneous manner, we performed a test, in which the
reaction of resorcinol with ethyl acetoacetate in the presence of CMK-5-SO3H were quenched
(by dilution with CH2Cl2) after 10 min and filtered off (≈60% conversion). Then CH2Cl2 was
evaporated and the residue was then allowed to further heating under solvent-free condition at
130 °C. We found that no further catalytic activity was observed upon the heating for 3h, thus
supporting the heterogeneous nature of the reaction.
3. Conclusions
8
Page 8 of 15

In summary, CMK-5-SO3H was shown to be an effective catalyst in solvent-free Pechmann
condensation. Furthermore, good to excellent yields of coumarin derivatives were obtained using
catalyst CMK-5-SO3H. The catalyst can be reused in six successive runs with no considerable
activity loss. Therefore, green and simple experimental procedure, solvent-free reaction
conditions, good yields of products, ease of work-up and recyclability of the catalyst, will make
the present method a useful and important addition to the present methodologies for the
Pechmann condensation.
4. Experimental
Chemicals were either prepared in our laboratories or were purchased from Alderich or Fluka
chemical companies. Reactions monitoring were accompanied by TLC on silica-gel polygram
1
SILG/UV 254 plates. The products are characterized by recording their H and 13C NMR
spectroscopy by using Bruker 250 or 400 MHz apparatus. Measurements of surface area and
pore size distribution were made using the Brunauer–Emmet–Teller (BET) method in a Quanta
Sorb machine. X-ray diffraction (XRD) patterns were recorded by an Xpert-Pro, X-ray
diffractometer using Cu Kα radiation. Transmission electron microscope, TEM (Philips CM-10)
was also used to obtain TEM image.
General procedure for the Pechmann condensation: In a round bottom flask, CMK-5-SO3H
(0.034g, 3mol%) was added to the mixture of phenolic compound (1 mmol) and ethyl
acetoacetate (1 mmol) at 130 °C and the reaction mixture stirred for the appropriate time (Table
2). The progress of reaction was monitored by TLC (eluent, n-hexane:ethyl acetate, 4:1). After
the completion of the reaction, the reaction mixture was diluted with ethanol and filtrated to
obtain the crude product. Compounds with purity below 95% were further purified using column
chromatography on silica gel and then recrystallized from hot ethanol to afford pure coumarin
9
Page 9 of 15

derivatives. All compounds were identified by comparison of 1H NMR, and 13C NMR with those
1
13
reported (see supporting information for copy of H and C spectra of products). Spectroscopic
data for selected examples listed below.
1
7,8-Dihydroxy-4-methyl-chromen-2-one (Entry 1): H NMR (400 MHz; DMSO-d6): δH = 2.36
13
(s, 3H), 6.14 (s, 1H), 6.8 (d, J = 8.8 Hz, 1H), 7.10 (d, J = 8.8 Hz, 1H), 9.7 (brs, 2H); C NMR
(100 MHz, DMSO-d6): δC = 18.7, 110.7, 112.6, 113.2, 115.9, 132.6, 143.8, 149.9, 154.4, 160.7.
1
5,7-Dihydroxy-4-methyl-chromen-2-one (Entry 2): H NMR (400 MHz; DMSO-d6): δH = 2.53
13
(s, 3H), 5.86 (s, 1H), 6.18 (s, 1H), 6.27 (s, 1H), 10.31 (s, 1H), 10.53 (s, 1H); C NMR (100
MHz, DMSO-d6): δC = 23.9, 94.9, 99.5, 102.5, 109.2, 155.4, 156.9, 158.4, 160.5, 161.5.
7-Hydroxy-4-methyl-chromen-2-one (Entry 7): 1H NMR (400 MHz; DMSO-d6): δH = 2.37 (brs,
3H), 6.14 (s, 1H), 6.71 (d, J = 2.4 Hz, 1H), 6.79-6.83 (dd, J = 8.8 Hz, J = 2.4 Hz, 1H), 7.59 (d, J
= 8.8 Hz, 1H), 10.55 (brs, 1H); 13C-NMR (100 MHz, DMSO-d6): δC = 18.6, 1026, 110.7, 112.5,
113.3, 127.1, 154.0, 155.3, 160.8, 161.6.
1
7-Amino-4-methyl-chromen-2-one (Entry 10): H NMR (400 MHz; DMSO-d6): δH = 2.27 (s,
3H), 5.87 (s, 1H), 6.07 (brs, 2H), 6.38 (d, J = 2.2 Hz, 1H), 6.54 (dd, J = 6Hz, J = 2.2 Hz, 1H),
7.38 (d, J = 8.5 Hz, 1H); 13C NMR (100 MHz, DMSO-d6): δC = 18.4, 98.9, 107.9, 109.3, 111.6,
126.7, 153.5, 154.2, 155.9, 161.2.
1
4-Methyl-benzo[h]chromen-2-one (Entry 11): H NMR (400 MHz; DMSO-d6): δH = 2.54 (s,
13
3H), 6.53 (s, 1H), 7.73-7.91 (m, 4H), 8.06-8.08 (m, 1H), 8.38-8.41 (m, 1H); C NMR (100
MHz, DMSO-d6): δC = 19.2, 114.4, 115.6, 121.8, 122.1, 122.7, 124.5, 127.9, 128.5, 129.2,
134.9, 150.2, 154.7, 160.1.
10
Page 10 of 15

5. Supplementary data
Experimental procedures for the synthesis of CMK-5 and CMK-5-SO3H, TGA, BJH, N2 ads-des,
and XRD diagrams for CMK-5 and CMK-5-SO3H, TEM image for recovered catalyst and copy
1
of H and 13C spectra for products and general procedure for the synthesis of coumarins is
available.
Acknowledgements
The authors acknowledge the Islamic Azad University of Qaemshahr Research Councils for
support of this work.
References
[1] R.O. Kennedy, R.D. Zhorenes, Coumarins: Biology, Applications and Mode of Action;
Wiley and Sons: Chichester, 1997.
[2] M. Zahradnik, The Production and Application of Fluorescent Brightening Agents:Wiley and
Sons, 1990.
[3] R.D.H. Murray, J. Mendez, S.A. Brown, The Natural Coumarins: Occurrence, Chemistry and
Biochemistry; Wiley and Sons: New York, 1982.
[4] G. Cravetto, G.M. Nano, G. Plamisanom, S. Tagliapietra, Tetrahedron: Asymmetry 12 (2001)
707.
[5] O. Kayser, H. Kolodziej, Planta Med. 63 (1997) 508.
[6] C.J. Wang, Y.J. Hsieh, C.Y. Chu, Y.L. Lin, T.H. Tseng, Cancer Lett. 183 (2002) 163.
[7] S. Kirkiacharian, D.T. Thuy, S. Sicsic, R. Bakhchinian, R. Kurkjian, T. Tonnaire, Il Farmaco
57 (2002) 703.
[8] S.M. Sethna, N.P. Kong, Chem. Rev. 36 (1945) 1.
[9] V.H. Pechmann, C. Duisberg, Chem. Ber. 17 (1884) 929.
11
Page 11 of 15

[10] W.H. Perkin, W. Sr. Henry, J. Chem. Soc. 28 (1875) 10.
[11] N. Carins, L.M. Harwood, D.P. Astles, J. Chem. Soc.; Perkin Trans. (1994) 3101.
[12] G. Jones, Org. React. 15 (1967) 204.
[13] R.L. Shriner, Org. React. 1 (1942) 15.
[14] N.S. Narasimahan, R.S. Mali, M.V. Brave, Synthesis (1979) 906.
[15] E.C. Horning, Organic Synthesis, Vol. III, Wiley: New York, 1955, 281.
[16] H. Simmonis, P. Remmert, Chem. Ber. 47 (1914) 2229.
[17] S.M. Sethna, N.M. Shah, R.C. Shah, J. Chem. Soc. (1938) 228.
[18] L.L. Woods, J. Sapp, J. Org. Chem. 27 (1962) 3703.
[19] D.S. Bose, A.P. Rudradas, M. Hari Babu, Tetrahedrion Lett. 43 (2002) 9195.
[20] G.V.M. Sharma, J.J. Reddy, P.S. Lakshmi, P.R. Krishna, Tetrahedron Lett. 46 (2005) 6119.
[21] S.K. De, R.A. Gibbs, Synthesis (2005) 1231.
[22] T. Nguyen Van, S. Debenedetti, N. De Kimpe, Tetrahedron Lett. 44 (2003) 4199.
[23] M.K. Potdur, S.S. Mohile, M.M. Salunkhe, Tetrahedron Lett. 42 (2001) 9285.
[24] A.D. Hoz, M. Andres, E. Vazquez, Synlett (1999) 602.
[25] D.A. Chaudhari, Chem. Ind. (1983) 568.
[26] E.A. Gunnewegh, A.J. Hoefnegal, H. Van Bekkum, J. Mol. Catal. A: Chem. 100 (1995) 87.
[27] S. Frere, V. Thiery, T. Besson, Tetrahedron Lett. 42 (2001) 2791.
[28] T. Li, Z. Zhang, F. Yang, C. Fu, J. Chem. Res. (1998) 38.
[29] G.P. Romanelli, D. Bennardi, D.M. Ruiz, G. Baronetti, H.J. Thomasb, J.C. Autino,
Tetrahedron Lett. 45 (2004) 8935.
[30] P.R. Singh, D.U. Singh, S.D. Samant, Synlett (2004) 1909.
[31] B. Tyagi, M.K. Mishra, R.V. Jasra, J. Mol. Catal. A: Chem. 276 (2007) 47.
12
Page 12 of 15

[32] A. Sinhamahapatra, N. Sutradhar, S. Pahari, H.C. Bajaj, A.B. Panda, Appl. Catal. A: Gen.
394 (2011) 93.
[33] B. Karimi, H. Behzadnia, Catal. Commun. 12 (2011) 1432.
[34] R.D. Badley, W.T. Ford, J. Org. Chem. 54 (1989) 5437.
[35] G. Olah, P.S. Iyer, G.K. Surya, Synthesis (1986) 513.
[36] I.K. Mbaraka, B.H. Shanks, J. Catal. 244 (2006) 78.
[37] B. Rac, A. Molnar, P. Forgo, M. Mohai, I. Bertoti, J. Mol. Catal. A: Chem. 244 (2006) 46.
[38] L. Peng, A. Philippaerts, X. Ke, J. Van Noyen, F. De Clippel, G. Van Tendeloo, P. A.
Jacobs, B. F. Sels, Catal. Today 150 (2010) 140.
[39] K. Hou, A. Zhang, L. Gu, M. Liu, X. Guo, J. Coll. Interface Sci. 377 (2012) 18.
[40] A. Aldana-Pérez, L. Lartundo-Rojas, R. Gómez, M.E. Niño-Gómez, Fuel, 100 (2012) 128.
[41] F. Liu, J. Sun, Q. Sun, L. Zhu, L. Wang, X. Meng, C. Qi, F-S. Xiao, Catal. Today, 186
(2012) 115.
[42] L. Geng, G. Yu, Y. Wang, Y. Zhu, Appl. Catal. A: Gen. 427–428 (2012) 137.
[43] R. Liu, X. Wang, X. Zhao, P. Feng, Carbon 46 (2008) 1664.
[44] B. Chang, J. Fu, Y. Tian, X. Dong, J. Phys. Chem. C, 117 (2013) 6252.
[45] R. Xing, Y. Liu, Y. Wang, L. Chen, H. Wu, Y. Jiang, M. He, P. Wu, Micropor. Mesopor.
Mater. 105 (2007) 41.
[46] S.H. Joo, J. Choi, I. Oh, J. Kwak, Z. Liu, O. Terasaki, R. Ryoo, Nature 412 (2001) 169.
[47] M. Kurk, M. Jaroniec, T.-W. Kim, R. Ryoo, Chem. Mater. 15 (2003) 2815.
[48] B. Karimi, D. Zareyee, Org. Lett. 10 (2008) 3989.
[49] D. Zareyee, M.S. Ghandali, M.A. Khalilzadeh, Catal. Lett. 141 (2011) 1521.
[50] D. Zareyee, P. Alizadeh, M.S. Ghandali, M.A. Khalilzadeh, Chem. Paper 7 (2013) 713.
13
Page 13 of 15

Research highlights
ꢀ efficient synthesis of coumarins with green and simple experimental procedure
ꢀ Solvent-free reaction conditions
ꢀ Exceedingly simple workup and uncomplicated recovery (six reaction cycles)
Outstanding thermal stability of CMK-5-SO3H
14
Page 14 of 15

Graphical Abstract
SO3H
SO3H
SO3H
CMK-5
O
O
O
OH
(3 mol%)
O
R
H2O
R
OEt
130 oC, Solvent-free
CH3
15
Page 15 of 15