Friedel-Crafts alkylation of 4-hydroxycoumarin over silica-bonded 1,4-diaza-bicyclo[2.2.2] octane-sulfonic acid chloride as nanostructured heterogeneous catalyst

Article abstract of DOI:10.1139/cjc-2016-0258

A novel nanostructured heterogeneous catalyst, namely silica-bonded 1,4-diaza-bicyclo[2.2.2]octane-sulfonic acid chloride (SBDBSAC), has been synthesized and fully characterized by several techniques, including Fourier transform infrared spectroscopy (FTI

Full text of DOI:10.1139/cjc-2016-0258

Page 1 of 18
Friedel–Crafts alkylation of 4-hydroxycoumarin over silica-bonded
,4-diaza-bicyclo[2.2.2] octane-sulfonic acid chloride as
nanostructured heterogeneous catalyst
1
Ahmad Reza Moosavi-Zare*, Mohammad Ali Zolfigol, Ehsan Noroozizadeh, Abdolkarim
Zare and Mahmoud Zarei
,
Ahmad Reza Moosavi-Zare. Department of Chemistry, University of Sayyed Jamaleddin
Asadabadi, Asadabad, 6541835583, Iran.
Mohammad Ali Zolfigol, Ehsan Noroozizadeh, Mahmoud Zarei. Faculty of Chemistry, BuꢀAli
Sina University, Hamedan 6517838683, Iran.
Abdolkarim Zare. Departmentof Chemistry, Payame Noor University, I. R. Iran.
1
Corresponding author (Fax: +98 81323237451; Tel: 9881323237450; Eꢀmail:
2
moosavizare@yahoo.com). Corresponding author (Fax: +98 8138257407. Eꢀmail addresses:
mzolfigol@yahoo.com).
1

Page 2 of 18
ABSTRACT
A
novel nanostructured heterogeneous catalyst namely silicaꢀbonded 1,4ꢀdiazaꢀ
bicyclo[2.2.2]octaneꢀsulfonic acid chloride (SBDBSAC) has been synthesized, and fully
characterized by several techniques including Fourier transform infrared spectroscopy (FTꢀIR), Xꢀ
ray diffraction (XRD), thermal gravimetric analysis (TGA), differential thermal gravimetric
(DTG), scanning electron microscope (SEM) and energy dispersive Xꢀray analysis (EDX).
Afterward, the nanostructured catalyst has been utilized as an efficient catalyst for the synthesis of
bisꢀcoumarin derivatives by the condensation reaction of arylaldehydes with 4ꢀhydroxycoumarin
at 70 °C under solventꢀfree conditions.
Keywords:
Nanostructured
catalyst,
Heterogeneous,
Silicaꢀbonded
1,4ꢀdiazaꢀ
bicyclo[2.2.2]octaneꢀsulfonic acid chloride (SBDBSAC), Bisꢀcoumarin, Solventꢀfree.
2

Page 3 of 18
Graphical Abstract
Friedel–Crafts alkylation of 4-hydroxycoumarin over silica-bonded
1
,4-diaza-bicyclo[2.2.2] octane-sulfonic acid chloride as a
nanostructured heterogeneous catalyst
Ahmad Reza MoosaviꢀZare,* Mohammad Ali Zolfigol, Ehsan Noroozizadeh, Abdolkarim Zare,
Mahmoud Zarei
3

Page 4 of 18
Introduction
Coumarins are an important group of heterocyclic compounds, because they have been
1
extensively applied in pharmaceutical, fragrance and agrochemical industries. Moreover,
coumarins derivatives can act as cytoatatic agent and decrease HIV reactivity in cell, so these
compounds with circle structure container heteroatom oxygen can be applied as agent
2
candidate for the cancer therapy. Another example of this class of compounds is 18ꢀkDa
3
protein which introduced as an inhibitor against activity of 2,3ꢀepoxide reductase. Bisꢀ
coumarins have been also used as antibiotics, coagulants, antitumor drugs, HIV protease
4
–7
inhibitors as well as additives in food and cosmetics. The condensation reaction of
arylaldehydes with 4ꢀhydroxycoumarin is the best route for the preparation of bisꢀcoumarins.
8
Several catalysts have been reported for this reaction such as tetrabutylammonium bromide,
9
10
11
molecular iodine, [bmin]BF , SO Hꢀfunctionalized ionic liquid, sodium dodecyl
4
3
1
2
13
14
15
sulfate, piperidine, nꢀdodecylbenzene sulfonic acid (DBSA), nano silica chloride,
1
6
17
ruthenium (III) chloride hydrate and Zn (proline) . Nevertheless, some of the previous
2
methods for the synthesis of bisꢀcoumarins are associated with one or more of the following
drawbacks: (ii) the use of expensive catalysts, (ii) application of volatile organic solvents, (iii)
long reaction times, and (iv) low yields. Hence, it is very important for us to develop
efficient and costꢀeffective catalysts and procedures with high novelty for the synthesis
of these valuable compounds.
We have recently introduced sulfonic acid functionalized imidazolium salts (SAFIS) as a new
category of ionic liquids, in which a SꢀN bond has formed in the imidazole and applied them
1
8
as organocatalysts or organoreagents for the preparation of bis(indolyl)methans, Nꢀsulfonyl
1
9
20,21
22
23
imines,
nitro aromatic compounds,
1ꢀamidoalkylꢀ2ꢀnaphthols,
benzimidazoles,
2
4
25
xanthenes, 1ꢀcarbamatoalkylꢀ2ꢀnaphthols, 4,4'ꢀ(arylmethylene)ꢀbis(3ꢀmethylꢀ1ꢀphenylꢀ1Hꢀ
2
6
27
28
pyrazolꢀ5ꢀ ol)s, tꢀbutyl aryl carbamates, 1,2,4,5ꢀtetrasubstituted imidazoles, βꢀacetamido
4

Page 5 of 18
2
9
30
ketones and hexahydroquinolines. In continuation of our previous studies on the
1
8ꢀ31
preparation and applications of acidic ILs and solid salts in organic transformations
and as
a part of our efforts to develop these categories of catalysts, we have prepared and
characterized silicaꢀbonded 1,4ꢀdiazaꢀbicyclo[2.2.2]octaneꢀsulfonic acid chloride (SBDBSAC)
as nanostructured compound in which an acidic ionic liquid based on 1,4ꢀdiazaꢀ
bicyclo[2.2.2]octane ring bonded to silica (Figure 1).
«
Figure 1»
We used SBDBSAC as a highly efficient, stable, reusable and heterogeneous nanocatalyst for
the synthesis of bisꢀcumarins from arylaldehydes and 4ꢀhydroxycoumarin, at 70 °C in the
absence of solvent (Scheme 1).
«
Scheme 1»
Results and discussion
At first, 1,4ꢀdiazaꢀbicyclo[2.2.2]octane was reacted with (3ꢀchloropropyl)triethoxysilane
under reflux conditions to give I. After that, I was reacted with silica in refluxed toluene for 8
hours to afford II. At the end, silicaꢀbonded 1,4ꢀdiazaꢀbicyclo[2.2.2]octaneꢀsulfonic acid
chloride (SBDBSAC) was synthesized via reaction of II with ClSO H in chloroform (Scheme
3
3
2
2
).
«
Scheme 2»
Identification of SBDBSAC structure was studied by FTꢀIR, XRD, TG, DTG, EDX, and SEM
analysis.
In the IR spectrum of the catalyst (Figure 2), the peak related to OꢀH stretching of the SO H group
3
ꢀ1
ꢀ1
was appeared at 2250ꢀ3600 cm . The vibrational mode of OꢀSO was observed at 1318 cm .
2
«
Figure 2»
The Xꢀray diffraction analysis (XRD) (Figure 3) pattern of SBDBSAC in a domain of 0ꢀ90
degree is shown in Figure 3. The XRD pattern showed diffraction lines of a high crystalline
5

Page 6 of 18
◦
◦
◦
◦
◦
nature at about 2θ ≈ 9.1 , 18.8 , 19.4 , 20.0 and 26.6 . The crystallite size, which was
3
2
calculated by DebyeꢀScherrer’s formula [D=Kλ/ (βcosθ)], was at about 8.1 nm.
Figure 3»
The diagrams related to thermal gravimetric analysis (TGA) of SBISAC are depicted in
«
(
Figure 4). according to thermal gravimetric (TG) and differential thermal gravimetric (DTG)
3
2
diagrams, weight loss of the catalyst was occurred in one step, after 280 ºC.
«
Figure 4»
The energyꢀdispersive Xꢀray spectroscopy (EDX) of the nanocatalyst (Figure S1) proved the
presence of the expected elements in its structure, i.e. carbon, oxygen, nitrogen, sulfur,
chlorine and silicon.
The scanning electron microscope (SEM) micrographs of the catalyst showed that the particles
have not completely agglomerated. Particles of the catalyst were observed in nano scale which
is in good agreement with calculated size through to DebyeꢀScherrer’s equation (Figure 5).
«
Figure 5»
In the next step, to optimize the reaction conditions, as a model reaction, a mixture of 4ꢀ
chlorobenzaldehyde (1 mmol) and 4ꢀhydroxycoumarin (2 mmol) was stirred in the presence of
different amounts of SBDBSAC at range of 50 to 110 °C under solventꢀfree conditions. The
respective results are displayed in Table 1. As it can be seen in Table 1, 0.01 g (10 mol%) of
SBDBSAC was sufficient to catalyze the reaction at 70 °C. In these reaction conditions, the
expected bisꢀcoumarin was prepared in 95% yield within 12 min (Table 1, entry 3).
«
Table 1»
To investigate the efficacy and the generality of the catalyst, 4ꢀhydroxycoumarin was reacted
with various aromatic aldehydes (benzaldehyde as well as arylaldehyde containing electronꢀ
withdrawing groups, electronꢀdonating groups and halogens), under the optimized reaction
conditions (Table 2). As it is shown in Table 2, indicates that all reactions proceeded
6

Page 7 of 18
efficiently to give the expected bisꢀcoumarin derivatives in high yields and in short reaction
times. Therefore, SBDBSAC was a highly efficient and general catalyst for the synthesis of
bisꢀcoumarins.
+
The acidic content of SBDBSAC was characterized by the determination of its H of the
catalyst, through titration with NaOH (0.1 mol/L). For this purpose, SBDBSAC (0.01 g) was
titrated by 1.0 ml of NaOH (0.1 mol/L) and then mol% of catalyst was calculated.
«
Table 2»
To study recyclability of SBDBSAC, the reaction of 4ꢀchlorobenzaldehyde (2 mmol) with 4ꢀ
hydroxycoumarin (1 mmol) was performed using SBDBSAC (0.01 g, 10 mol%) at 70 °C.
After the reaction was completed, the reaction mixture was cooled to room temperature, ethyl
acetate (95%) (20 mL) was added, stirred and refluxed for 2 min. Afterward, the resulting
mixture was centrifuged for the separation of nanocatalyst from the product and remaining
starting materials. The remained catalyst was washed with hot ethyl acetate (10 mL), and dried
to use for the next run. Catalytic activity of SBDBSAC was restored within the limits of the
experimental errors for 4 successive recycle runs (Figure S2). The reused catalyst was also
characterized by IR and XRD analysis after its application in the reaction. IR and XRD
analysis of catalyst was same as this of the fresh catalyst (Figure S3 and Figure S4).
To compare the efficiency of the catalyst with the reported catalysts for the synthesis of
hexahydroquinolines, we have displayed the results of SBDBSAC to perform the condensation
reaction of 4ꢀchlorobenzaldehyde and 4ꢀhydroxycoumarin, in Table 3. As Table 3 indicates,
SBISAC has remarkably improved the synthesis of bisꢀcoumarins. The reaction time was shorter,
and the yield was higher when SBDBSAC was utilized.
7

Page 8 of 18
2
. Experimental
.1.General
2
All chemicals were purchased from Merck or Fluka Chemical Companies. The known products
were identified by comparison of their melting points and spectral data with those reported in the
literature. Progress of the reactions was monitored by TLC using silica gel SIL G/UV 254 plates.
1
13
The H NMR (400 MHz) and C NMR (100 MHz) were recorded on a Bruker Avance DPX FTꢀ
NMR spectrometer (δ in ppm). Melting points were recorded on a Büchi Bꢀ545 apparatus in open
capillary tubes. Thermal gravimetry (TG) and differential thermal gravimetric (DTG) were
analyzed by a Perkin Elmer (Model: Pyris 1). TG/DTG analysis (25 to 600 °C, temperature
ꢀ1
increase rate of 10 °C. min , nitrogen atmosphere). The crystal structure of synthesized materials
was determined by an Xꢀray diffractometer (Italstructure ADP2000 XRD diffractometer) at
ambient temperature.
2
.2. The procedure for the preparation of SBDBSAC
A mixture of 1,4ꢀdiazaꢀbicyclo[2.2.2]octane (0.56 g, 5 mmol), (3ꢀchloropropyl)triethoxysilane
1.125 g, 5 mmol) and acetone (15 mL) in a 50 mL roundꢀbottomed flask connected to a reflux
(
condenser, was stirred for 12 hours under reflux conditions. In the next step, the obtained white
precipitate, was filtered to separate from acetone, and reacted with silica (0.3 g, 5 mmol) in
refluxed toluene (15 mL) for 8 hours. After removing of the solvent, the resulted product was
added to a 50 mL roundꢀbottomed flask in an ice water bath (0 °C), and a solution of
chlorosulfonic acid (5 mmol) in chloroform (10 mL) was added dropwise to it, and stirred for 2
hours. Afterward, the residue was triturated with chloroform (3×10 mL), and dried under powerful
vacuum at 90 °C to give silicaꢀbonded 1,4ꢀdiazaꢀbicyclo[2.2.2]octane acid chloride (SBDBSAC)
as a white precipitate in 95 % yield.
8

Page 9 of 18
2
.3. General procedure for the preparation of bisꢀcoumarins
SBDBSAC (0.01 g, 10 mol%) was added to a mixture of 4ꢀhydroxycoumarin (0.324 g, 2 mmol)
and arylaldehyde (1 mmol) in a 25 mL roundꢀbottomed flask, and the resulting mixture was
initially stirred magnetically at 70 ºC, and after that the reaction mixture was solidified, it was
stirred with a small rod at same temperature. After the reaction was completed, as monitored by
TLC, the reaction mixture was cooled to room temperature, ethyl acetate (95%) (20 mL) was
added to it, stirred and refluxed for 3 min. Then, the mixture was centrifuged for the separation of
catalyst from the product and the remaining starting materials. The solvent of the reaction mixture
was evaporated, and the precipitate was purified by recrystallization from ethanol (95%) to give
the desired product. In this work, the catalyst was recovered and reused for 4 times without any
significant changes in the yield and the reaction time.
Conclusions
In summary, we have synthesized silicaꢀbonded 1,4ꢀdiazaꢀbicyclo[2.2.2]octaneꢀsulfonic acid
chloride (SBDBSAC) as a nanostructured heterogeneous catalyst, and fully characterized it by
several techniques including Fourier transform infrared spectroscopy (FTꢀIR), Xꢀray
diffraction (XRD), thermal gravimetric analysis (TGA), differential thermal gravimetric
(
DTG), scanning electron microscope (SEM) and Energy dispersive Xꢀray analysis (EDX).
SBDBSAC was successfully tested as a reusable, stable, general and heterogeneous catalyst
for the condensation reaction between arylaldehydes and 4ꢀhydroxycoumarin to provide bisꢀ
coumarins.
Acknowledgements
The authors gratefully acknowledge the BuꢀAli Sina University and Iran National Science Foundation
(
INSF) (The Grant of Allameh Tabataba'i's Award, Grant Number BN093) and Sayyed Jamaleddin
Asadabadi University for providing support to this work.
9

Page 10 of 18
References
1] Hinman, J. W.; Hoeksema, H.; Caron E. L. Jackson, W.G. J. Am. Chem. Soc. 1956, 78,
072.
2] (a) Li, B. J.; Chiang, C. C.; Hsu, L. Y. J. Chin, Chem. Soc. 2010, 57, 742; (b) Wu, L. Q.;
[
1
[
Yang, C. G.; Wu Y. F.; Yang, L. M. J. Chin. Chem. Soc. 2009, 56, 606; (c) Tsai T. W.; Wang, E.
C. J. Chin. Chem. Soc. 2004, 51, 1019.
[
[
3] Wallin R.; Hutson, S. M. Trends Mol. Med. 2004, 10, 299.
4] Su, C. X.; Mouscadet, J. F.; Chiang, C. C.; Tsai H. J.; Hsu, L. Y. Chem. Pharm. Bull. 2006,
5
4, 682.
[
[
5] Manolov, I.; MaichleꢀMoessmer, C.; Nicolova I.; Danchev, N. Arch. Pharm. 2006, 339, 319.
6] Khan, K.M.; Iqbal, S.; Lodhi, M. A.; Maharvi, G.M.; Ullah, Z.; Choudhary, M.I.;
Rahman A.U.; Perveen, S. Bioorg. Med. Chem. 2004, 12, 1963.
[
[
[
7] Li, W.; Wang, Y.; Wang, Z.; Dai L.; Wang, Y. Catal. Lett. 2011, 141, 1651.
8] Khurana J. M.; Kumar, S. Tetrahedron Lett. 2009, 50, 4125.
9] Kidwai, M.; Bansal, V.; Mothsra, P.; Saxena, S.; Somvanshi, R. K.; Day S.; Singh, T. P. J.
Mol. Catal. A: Chem. 2007, 268, 76.
[
[
[
[
10] Khurana J. M.; Kumar, S. Monatsh Chem. 2010, 141, 56.
11] Li, W.; Wang, Y.; Wang, Z.; Dai L.; Wang, Y.; Catal Lett. 2011, 141, 1651.
12] Mehrabi H.; Abusaidi, H. J. Iran. Chem. Soc. 2010, 7, 890.
13] Khan, K. M.; Iqbal, S.; Lodhi, M. A.; Maharvi, G. M.; Ullah, Z.; Choudhary, M. Iq.;
UrꢀRahman A.; Perveen, SH. Bioorg. Med. Chem. 2004, 12, 1963.
[
[
14] Pawar, B.; Shinde V.; Chaskar, A. Green and Sustainable Chemistry, (GSC), 2013, 3, 56.
15] Karimian, R.; Piri, F.; Safari A. A.; Davarpanah, S. J. Journal of Nanostructure in
Chemistry (JNSC), 2013, 3, 52.
1
0

Page 11 of 18
[
16] Tabatabaeian, K.; Heidari, H.; Khorshidi, A.; Mamaghani M.; Mahmoodi, N. O. J. Serb.
Chem. Soc. 2012, 77, 407.
[
[
17] Siddiqui, Z. N.; Forooq, F. Catal. Sci. Technol. 2011, 1, 810.
18] Zolfigol, M. A.; Khazaei, A.; MoosaviꢀZare A. R.; Zare, A. Org. Prep. Proced. Int. 2010, 42,
9
5.
[
[
19] Zolfigol, M. A.; Khazaei, A.; MoosaviꢀZare A. R.; Zare, A. J. Iran. Chem. Soc. 2010, 7, 646.
20] Khazaei, A.; Zolfigol, M. A.; MoosaviꢀZare A. R.; Zare, A. Scientia Iranica: Trans. C:
Chem. Chem. Engin. 2010, 17, 31.
21] Zolfigol, M. A.; Khazaei, A.; MoosaviꢀZare, A. R.; Zare, A.; Kruger, H. G.; Asgari, Z.;
Khakyzadeh V.; KazemꢀRostami, M. J. Org. Chem. 2012, 77, 3640.
22] Zolfigol, M. A.; Khazaei, A.; MoosaviꢀZare, A. R.; Zare A.; Khakyzadeh, V. Appl. Catal A:
Gen. 2011, 400, 70.
23] Khazaei, A.; Zolfigol, M. A.; MoosaviꢀZare, A. R.; Zare, A.; Ghaemi, E.; Khakyzadeh, V.;
Asgari Z.; Hasaninejad, A. Scientia Iranica: Trans. C: Chem. Chem. Engin. 2011, 18, 1365.
24] Zolfigol, M. A.; Khakyzadeh, V.; MoosaviꢀZare, A. R.; Zare, A.; Azimi, S. B.; Asgari Z.;
Hasaninejad, A. C. R. Chim. 2012, 15, 719.
[
[
[
[
[
[
25] Zare, A.; Yousofi T.; MoosaviꢀZare, A. R. RSC. Adv. 2012, 2, 7988.
26] Khazaei, A.; Zolfigol, M. A.; MoosaviꢀZare, A. R.; Asgari, Z.; Shekouhy, M.; Zare A.
Hasaninejad, A. RSC. Adv. 2012, 2, 8010.
27] Zolfigol, M. A.; Khakyzadeh, V.; MoosaviꢀZare, A. R.; Chehardoli, G.; DerakhshanꢀPanah,
F.; Zare A.; Khaledian, O. Scientia Iranica: Trans. C: Chem. Chem. Engin. 2012, 19, 1584.
28] Zolfigol, M. A.; Khazaei, A.; MoosaviꢀZare, A. R.; Zare, A.; Asgari, Z.; Khakyzadeh V.;
Hasaninejad, A. J. Ind. Eng. Chem. 2013, 19, 721.
[
[
1
1

Page 12 of 18
[
29] Zare, A.; HekmatꢀZadeh, T.; MirzaeiꢀMonfared, S.; Merajoddin, M.; TorabiꢀMonfared, H.;
Zolfigol, M. A.; MoosaviꢀZare, A. R.; Rostami, E.; Mokhlesi, M.; DerakhshanꢀPanah, F.; Porbahi
S.; Balandeh, S. S. Afr. J. Chem. 2012, 65, 63.
[
30] Zare, A.; Abi, F.; MoosaviꢀZare, A. R.; Beyzavi, M. H.; Zolfigol, M. A. J. Mol. Liq. 2013,
78, 113.
31] a) MoosaviꢀZare, A. R.; Zolfigol, M. A.; Zarei, M.; Zare A.; Khakyzadeh, V. J. Mol. Liq.
015, 211, 373; b) MoosaviꢀZare, A. R.; Zolfigol, M. A.; Zarei, M.; Zare A.; Afsar, J. Appl. Catal.
A: Gen. 2015, 505, 224.
32] MoosaviꢀZarea, A. R.; Zolfigol, M. A.; Noroozizadeh, E.; SalehiꢀMoratab, R.; Zarei, M. J.
Mol.Catal. A: Chem. 2016, 420, 246.
1
[
2
[
[
[
[
33] Zolfigol, M. A.; MoosaviꢀZare, A. R.; Zarei, M. C. R. Chimie, 2014, 17, 1264.
34] Karmakar, B.; Nayak, A.; Banerji, J. Tetrahedron Lett. 2012, 53, 4343.
35] Shamsaddini, A.; Sheikhhosseini E. International Journal of Organic Chemistry, 2014, 4,
1
35.
36] Singh, P.; Kumar, P.; Katyal, A.; Kalra, R.; Dass. S. K.; Prakash, S.; Chandra, R. Catal Lett.
010, 134, 303.
[
2
1
2

Page 13 of 18
O
O
Cl
Si
N
O
N
Cl
SO H
3
Figure 1. The structure of silicaꢀbonded 1,4ꢀdiazaꢀbicyclo[2.2.2]octane ꢀsulfonic acid chloride
SBDBSAC).
(
Figure 2. FTꢀIR spectrum of SBDBSAC.
1
3

Page 14 of 18
Figure 3. XRD diagram of SBDBSAC in comparison with other components of the catalyst.
Figure 4. Thermal gravimetric (TG) and derivative thermal gravimetric (DTG) analysis of
1
4

Page 15 of 18
◦
◦
SBISAC at range of 25–600 C, with a temperature increase rate of 10 C.
Figure 5. The SEM images of of SBDBSAC.
1
5

Page 16 of 18
Scheme 1. The preparation of Bisꢀcoumarin catalyzed by SBDBSAC.
Scheme 2. The preparation of silicaꢀbonded 1,4ꢀdiazaꢀbicyclo[2.2.2]octane ꢀsulfonic acid
chloride (SBDBSAC).
Table 1. Effect of the catalyst amount and temperature on the reaction between 4ꢀ
hydroxycoumarin and 4ꢀchlorobenzaldehyde.
a
Entry
Catalyst
Catalyst amount (g)
Temp.(ºC)
Time (min)
Yield (%)
1
2
3
4
5
6
7
SBDBSAC
SBDBSAC
SBDBSAC
SBDBSAC
SBDBSAC
SBDBSAC
SBDBSAC
0.006
0.008
0.01
0.02
0.01
0.01
0.01
70
70
50
35
12
12
40
12
12
65
72
95
95
50
95
95
70
70
50
90
110
a
Isolated yield.
1
6

Page 17 of 18
Table 2. The solventꢀfree synthesis of bisꢀcoumarins from arylaldehydes, 4ꢀhydroxycoumarin
and catalyzed by SBDBSAC at 70 °C.
a
Entry
1
R
Time (min)
12
Yield (%)
95
Mp. ºC (Lit.)
257ꢀ260 (259ꢀ261) [33]
4
2
ꢀClC H
6
4
4
2
3
4
5
6
7
8
9
ꢀClC H
12
14
10
10
10
12
12
15
17
18
15
17
93
89
93
90
92
90
89
87
85
88
86
90
218ꢀ220 (224ꢀ226) [15]
232ꢀ234 (230ꢀ231) [33]
238ꢀ240 (232ꢀ234) [15]
205ꢀ207 (204) [34]
6
C H
6
5
4
2
3
ꢀNO C H
2 6
4
4
4
ꢀNO C H
2
6
ꢀNO C H
236ꢀ238 (234ꢀ236) [15]
268ꢀ270 (266ꢀ268) [15]
262ꢀ264 (260ꢀ262) [33]
262ꢀ264 (266ꢀ268) [15]
247ꢀ249 (246ꢀ248) [15]
187ꢀ190 (188ꢀ191) [33]
275ꢀ277 (270ꢀ274) [33]
203ꢀ206 197–201 [33]
2
6
4
ꢀBrC H
6 4
4
ꢀCNC H
6 4
4
ꢀMeC H
6 4
1
1
1
0
1
2
3
4
ꢀOMeC H
6 4
1
ꢀEthylbenzene
C H N
5
4
1
C H S
4
3
a
Isolated yield.
1
7

Page 18 of 18
Table 3. Comparison of the results on the codcensation reaction of 4ꢀchlorobenzaldehyde and 4ꢀ
hydroxycoumarin catalyzed by SBDBSAC with those obtained by the recently reported catalysts.
a
Time
Yield
(%)
Reaction Condition
Catalyst loading
25 mol%
Ref.
(min)
DBSA, ethanolꢀwater (1:1), reflux
60
85
76
93
93
85
35
35
12
8
DBSA, ethanolꢀwater (1:1),
MW irradiations
2
5 mol%
5.5
150
45
SDS, H O, 70 ºC
20 mol%
10 mol%
10 mol%
2
TBAB, H O, reflux
2
TBAB, solventꢀfree, 120 ºC
40
8
Phosphotungstic acid, solventꢀfree,
1
5 mol%
20
12
93
95
36
8
0 ºC
b
SBDBSAC, solventꢀfree, 70 ºC
10 mol%
ꢀ
a
b
Isolated yield. Our work.
1
8