DBSA catalyzed cyclotrimerization of acetophenones: An efficient synthesis of 1,3,5-triarylbenzenes under solvent-free conditions

Article abstract of DOI:10.1016/j.crci.2012.12.008

A facile method for the synthesis of 1,3,5-triarylbenzenes is developed via cyclotrimerization of acetophenones in the presence of 4-dodecylbenzenesulfonic acid (DBSA) as an efficient Bronsted acid catalyst under solvent-free conditions. This synthetic pr

Full text of DOI:10.1016/j.crci.2012.12.008

G Model
CRAS2C-3673; No. of Pages 5
C. R. Chimie xxx (2013) xxx–xxx
Contents lists available at SciVerse ScienceDirect
Comptes Rendus Chimie
www.sciencedirect.com
´
Full paper/Memoire
DBSA catalyzed cyclotrimerization of acetophenones: An efficient
synthesis of 1,3,5-triarylbenzenes under solvent-free conditions
*
Davinder Prasad, Amreeta Preetam, Mahendra Nath
Department of Chemistry, University of Delhi, 110007 Delhi, India
A R T I C L E I N F O
Article history:
A B S T R A C T
Received 31 July 2012
Accepted after revision 6 December 2012
A facile method for the synthesis of 1,3,5-triarylbenzenes is developed via cyclotrimer-
ization of acetophenones in the presence of 4-dodecylbenzenesulfonic acid (DBSA) as an
efficient Bronsted acid catalyst under solvent-free conditions. This synthetic protocol has
several advantages such as green reaction conditions, short reaction times, high atom
economy and good to excellent yields of the target products.
Available online xxx
Keywords:
DBSA
1,3,5-triarylbenzenes
Cyclotrimerization
Solvent-free conditions
Efficient synthesis
´
ß 2012 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.
1. Introduction
zirconocene bis(perfluoroctanesulfonate)s [20], ethylene-
diamine and trifluoroacetic acid [21]. Although these
The synthesis of
p
-conjugated 1,3,5-triarylbenzenes
processes have proved useful for the preparation of these
compounds, there are some limitations including low
yields, long reaction times, harsh reaction conditions, use
of hazardous organic solvents, expensive metal catalysts,
tedious workup procedures or requirement of special
apparatus. Therefore, the development of an efficient and
green methodology for the synthesis of 1,3,5-triarylben-
zenes is still in high demand.
In context to develop green synthetic strategies for the
sustainable development of the environment [22], there
has been a growing interest to perform chemical reactions
either in environmentally benign solvents such as water,
ionic liquids or under solvent-free conditions. Moreover,
high atom economy, use of preferred green reagents or
solvents and generation of non-toxic by-products during
the reaction also contribute to a clean and eco-friendly
protocol [23].
has received considerable attention in recent years due to
their wide range of applications in the field of electrode
devices [1], resisting materials [2], conducting polymers
[3] or light-emitting diodes [4]. In addition, these
molecules have also been used as potential building blocks
for the synthesis of buckminsterfullerenes [5], polycyclic
aromatic hydrocarbons (PAHs) [6], dendrimers [7] and
highly conjugated polyaromatics [8]. Consequently, a
number of synthetic methods have been developed
previously to construct 1,3,5-triarylbenzenes. The most
common strategies for their synthesis include the metal
catalyzed cyclotrimerization of alkynes [9], cross coupling
reactions of aryl halides with organometallic species [10]
and triple self-condensation of aryl methyl ketones in the
presence of an acidic catalyst such as PTSA [11], TiCl3(OTf)
[12], TiCl4 [13], Bi(OTf)3.4H2O [14], phosphomolybdic acid
[15], Nafion-H [16], potassium pyrosulfate and sulfuric
acid [17], Amberlyst-15 [18], H3PW12O40@nano-SiO2 [19],
Recently, DBSA has emerged as a cheap, non-hygro-
scopic, non-volatile and air-stable Brønsted acid surfac-
tant-combined catalyst for carrying out various organic
transformations in aqueous medium [24]. According to the
literature, 1,3,5-triarylbenzenes can be efficiently obtained
in high yields from acetophenones under the influence of
* Corresponding author.
E-mail address: mnath@chemistry.du.ac.in (M. Nath).
1631-0748/$ – see front matter ß 2012 Acade´mie des sciences. Published by Elsevier Masson SAS. All rights reserved.
http://dx.doi.org/10.1016/j.crci.2012.12.008
Please cite this article in press as: Prasad D, et al. DBSA catalyzed cyclotrimerization of acetophenones: An efficient
synthesis of 1,3,5-triarylbenzenes under solvent-free conditions. C. R. Chimie (2013), http://dx.doi.org/10.1016/
j.crci.2012.12.008

G Model
CRAS2C-3673; No. of Pages 5
2
D. Prasad et al. / C. R. Chimie xxx (2013) xxx–xxx
Ar
yield within 6 hours (Table 1, entry 6). Interestingly, the
yield of the desired product (2a) did not improve
significantly by enhancing either the reaction temperature
or time (Table 1, entries 7 and 8); however, considerable
increase in the yield of 2a was observed with higher loads of
the catalyst (Table 1, entries 9 and 10). Thus, 20 mol% DBSA
was chosen as the optimal catalyst load for carrying out the
cyclotrimerization of acetophenone under solvent-free
conditions. Since then, the synthesis of 1,3,5-triphenylben-
zene (2a) has been recently accomplished [11] in 91% yield
by heating acetophenone with 10 mol% p-toluenesulfonic
acid (PTSA) at 130 8C for 10 hours. It was expected that
increasing the load of PTSA from 10 to 20 mol% might reduce
the reaction time as it is the case with DBSA. However, when
the experimentwas performed with20 mol% PTSA, only 60%
yieldof2awasobtainedafter3 hoursincontrastto94%yield
with 20 mol% DBSA under identical conditions (Table 1,
entries 10 and 11). Thus, it may be concluded that DBSA is a
better choice for the synthesis of 1,3,5-triarylbenzenes.
Indeed, a control experiment was performed in the absence
of DBSA under the same reaction conditions but no product
formation was observed, even after 24 hours (Table 1, entry
12), illustrating the catalytic role of DBSA in the formation of
1,3,5-triphenylbenzene (2a). Encouraged by these results
and to optimize the reaction conditions, the effect of
temperature on the formation of 1,3,5-triphenylbenzene
(2a)wasexamined. Thereactionatlowertemperaturessuch
as 80 8C and 100 8C was found to be sluggish and produced
poor yield of the desired product (2a) and the best results
were obtained when the reaction was carried out at 130 8C
(Table 1, entries 10, 13 and 14). Thus, the optimal condition
for a model reaction was found to be 20 mol% DBSA at 130 8C
temperature to generate 1,3,5-triphenylbenzene (2a) in 94%
yield (Table 1, entry 10).
DBSA
130 oC, 3 - 8 h
Ar COCH3
Ar
Ar
1a-n
2a-n
Scheme 1. DBSA catalyzed synthesis of 1,3,5-triarylbenzenes.
acidic catalysts. Hence, we thought to investigate the
synthesis of these molecules from aryl methyl ketones
using DBSA as an acidic catalyst.
To continue our efforts on the development of one-pot
syntheses [25] for various biologically important com-
pounds and owing to the material importance of 1,3,5-
triarylbenzenes, we wish to present herein a facile and
economical procedure for the synthesis of 1,3,5-triaryl-
benzenes via triple self-condensation of aryl methyl
ketones in the presence of DBSA as an efficient acidic
catalyst under solvent-free conditions (Scheme 1).
2. Results and discussion
In our initial study, we evaluated the scope of Yb(OTf)3,
Ln(OTf)3 and DBSA as acidic catalysts for the cyclotrimer-
ization of acetophenone at 130 8C under solvent-free
conditions (Table 1, entries 1, 5 and 6). Surprisingly, the
reaction catalyzed by 10 mol% Yb(OTf)3 gave the desired
1,3,5-triphenylbenzene (2a) as a white solid in only 16%
isolated yield after 18 hours (Table 1, entry 1). Further
attempts were unsuccessful to improve the yield of desired
product (2a) by increasing the reaction time, temperature or
catalytic load of Yb(OTf)3 (Table 1, entries 2–4). In contrast,
Ln(OTf)3 failed completely to catalyze this transformation
even after prolonged heating at 130 8C (Table 1, entry 5). On
the other hand, when 10 mol% DBSA were employedto carry
out this reaction under identical conditions, the desired
product, 1,3,5-triphenylbenzene (2a) was obtained in 61%
Under optimized reaction conditions, the cyclotrimer-
ization of acetophenones was further explored in order to
investigate the scope and limitations of the present
methodology by heating various aryl methyl ketones at
130 8C in the presence of 20 mol% DBSA under solvent-free
conditions. In general, the reaction proceeded smoothly
with a wide range of aryl methyl ketones carrying either
Table 1
Optimization of the reaction conditions for the formation of 1,3,5-
triphenylbenzene (2a) under solvent-free conditions.
Table 2
DBSA catalyzed cyclotrimerization of aryl methyl ketones to form 1,3,5-
triarylbenzenes under solvent-free conditionsa.
Entry
Catalysts
Catalyst
Temp
Time
(h)
Yield
(%)a
Entry
Ar
Products
Time (h)
Yield (%)b
load (mol%)
(8C)
1
Yb(OTf)3
Yb(OTf)3
Yb(OTf)3
Yb(OTf)3
Ln(OTf)3
DBSA
10
10
10
20
10
10
10
10
15
20
20
–
130
130
150
130
130
130
150
130
130
130
130
130
100
80
18
24
18
18
24
6
16
25
28
1
C6H5
2a
2b
2c
2d
2e
2f
3
4
94
95
86
76
72
90
79
88
76
88
92
74
70
70
2
2
p-FC6H4
3
3
p-ClC6H4
4
4
30
b
4
p-BrC6H4
4
5
5
p-IC6H4
4
6
61
62
64
71
94
6
m-ClC6H4
m-BrC6H4
3,4-Cl2C6H3
m-CH3C6H4
p-CH3C6H4
p-PhC6H4
4-cyclohexylphenyl
m-CF3C6H4
Fluoren-2-yl
4
7
DBSA
6
7
2g
2h
2i
4
8
DBSA
24
3
8
3
9
DBSA
9
8
10
11
12
13
14
DBSA
3
10
11
12
13
14
2j
8
PTSA
3
60
b
2k
2l
3
–
24
3
10
4
DBSA
20
20
22
c
2m
2n
DBSA
3
8
a
a
Isolated yield.
Reaction conditions: aryl methyl ketone (3 mmol), DBSA (0.6 mmol),
b
c
No product formation.
130 8C temperature.
b
Trace amount of product.
Isolated yields of pure products.
Please cite this article in press as: Prasad D, et al. DBSA catalyzed cyclotrimerization of acetophenones: An efficient
synthesis of 1,3,5-triarylbenzenes under solvent-free conditions. C. R. Chimie (2013), http://dx.doi.org/10.1016/
j.crci.2012.12.008

G Model
CRAS2C-3673; No. of Pages 5
D. Prasad et al. / C. R. Chimie xxx (2013) xxx–xxx
3
H
OH
O
O
-O3S
OH
+
Ar
I
SO3H
H
Ar
Ar
Ar
O
H
Ar
O
Ar
-H2O
+
-O3S
Ar
II
OH
Aryl methyl
ketone
I
Ar
IV
III
HO3S
H
+
O
OH
H
O
O
Ar
Ar
Ar
Ar
HO
H
-
Ar
SO3
-H2O
Ar
Ar
Ar
Ar
SO3H
O
+
Ar
V
Ar
I
H
+
O
Ar
OH
HO
Ar
-O3S
H
intramolecular
cyclization
Ar
Ar
H
-H2O
Ar
Ar
Ar
Ar
Ar
Ar
Ar
Ar
VI
VII
1,3,5-Triarylbenzene
SO3H = DBSA
Scheme 2. Plausible reaction mechanism for the synthesis of 1,3,5-triarylbenzenes.
electron-donating or electron-withdrawing substituents
on the aromatic ring and provided the corresponding 1,3,5-
triarylbenzenes (2a–n) in good to excellent yields (Table
2). The acetophenones bearing electron-withdrawing
substituents, particularly halogens on the aromatic ring,
cyclotrimerized with high rates in short reaction times and
afforded products (2b–h) in 72–95% yields (Table 2, entries
2–8). In contrast, the acetophenones having electron-
donating substituents such as CH3 either at para- or meta-
position of the aromatic ring reacted sluggishly and
produced corresponding 1,3,5-triarylbenzene derivatives
(2i and 2j) in 76–88% yields after 8 hours (Table 2, entries 9
and 10). In the case of acetophenones containing halogens
at para-position of the aromatic ring, the yield of the
cyclotrimerized products was significantly reduced, with
decrease in the electronegativity of the halogen atoms
(Table 2, entries 2–5). Further, the yields of triarylbenzenes
varied with respect to the position of the substituents
attached to acetophenone. For example, m-haloacetophe-
nones provided high yields of the target 1,3,5-triarylben-
zene products than the p-haloacetophenones (Table 2,
entries 3 and 6; 4 and 7). On the other hand, m-
methylacetophenone afforded the desired product (2i) in
lower yield than p-methylacetophenone (Table 2, entries 9
and 10). In addition, the bulky aryl methyl ketones
provided lower yields of the corresponding products (2k,
2l and 2n) when compared to acetophenone (Table 2,
entries 1 and 11; 1 and 12; 1 and 14).
The proposed mechanism for the formation of 1,3,5-
triarylbenzenes is depicted in Scheme 2. The reaction
possibly proceeds through the protonation of aryl methyl
ketone to form intermediate (I) and (II) in the presence of
DBSA as an acidic catalyst. The reaction of these inter-
mediates in the next step affords
After subsequent dehydration and addition steps, it forms
an enol intermediate (VI) which on intramolecular 6-
b-hydroxy ketone (III).
p
-
electrocyclization followed by dehydration affords the
desired 1,3,5-triarylbenzenes.
The structures of all the synthesized compounds were
established on the basis of spectral data. In addition, X-ray
analysis of compound 2a further proved its structure to be
that of 1,3,5-triphenylbenzene (Fig. 1)1.
1
CCDC 867818 contains the supplementary crystallographic data for
the deposited structure. These data can be obtained free of charge from
the Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
Fig. 1. X-ray crystal structure of compound 2a.
Please cite this article in press as: Prasad D, et al. DBSA catalyzed cyclotrimerization of acetophenones: An efficient
synthesis of 1,3,5-triarylbenzenes under solvent-free conditions. C. R. Chimie (2013), http://dx.doi.org/10.1016/
j.crci.2012.12.008

G Model
CRAS2C-3673; No. of Pages 5
4
D. Prasad et al. / C. R. Chimie xxx (2013) xxx–xxx
Table 3
Comparative study of catalytic efficiency of DBSA with other reported catalysts for the formation of 1,3,5-tris(40-fluorophenyl)benzene (2b).
Entry
Catalysts (mol%)
Solvents
Time (h)
Temp (8C)
Yield (%)
[References]
1
2
3
4
5
PTSA (10)
–
24
18
9
143
90 [11]
79 [14]
80 [15]
75 [18]
95a
Bi(OTf)3.4H2O (2)
Phosphomolybdic acid (2)
Amberlyst-15 (25–30)
DBSA (20)
Toluene
Ethanol
Toluene
–
Reflux
Reflux
Reflux
130
10
4
a
Present work.
Furthermore, the catalytic efficiency of DBSA was
compared with that of other reported catalysts for the
formation of 1,3,5-tris(40-fluorophenyl)benzene, 2b (Table
3). Though, catalysts such as PTSA, Bi(OTf)3ꢀ4H2O and
phosphomolybdic acid are capable to generate the desired
product (2b) in 79–90% yields by using comparatively
lower catalyst loads but these procedures require either
prolonged reaction time, elevated temperature or inflam-
mable organic solvents to carry out the reaction (Table 3,
entries 1–3). In contrast, the present methodology requires
20 mol% DBSA to generate the corresponding product (2b)
in 95% yield at 130 8C within 4 hours under solvent-free
conditions (Table 3, entry 5). Hence, DBSA can be
considered as an efficient catalyst for the synthesis of
1,3,5-triarylbenzenes.
by thin layer chromatography (TLC), the reaction mixture
was cooled to room temperature and diluted with equal
volumes of saturated solution of NaHCO3 and brine
(5 mL + 5 mL). The resulting solution was extracted with
ethyl acetate (10 mL ꢂ 3) and the organic layers were
combined, dried over anhydrous Na2SO4 and evaporated
under reduced pressure to dryness. The crude product
obtained was purified by silica gel (60–120 mesh size)
column chromatography using 1–2% ethyl acetate in
heptane as the eluent to afford the desired products in
pure form.
The compounds, 2a–g and 2i–l are known and their
spectral and analytical data are found to be in agreement
with the reported data [11,14,16,18] while the characteri-
zation data of unknown compounds (2h, 2m and 2n) are
given below.
3. Conclusion
4.1.1. 1,3,5-Tris(30,40-dichlorophenyl)benzene (2h)
In summary, we have developed an efficient method for
the synthesis of various 1,3,5-triarylbenzenes via cyclo-
trimerization of aryl methyl ketones. The reaction worked
well with acetophenones bearing either electron-donating
or electron-withdrawing substituents. The notable fea-
tures of the present protocol are operational simplicity,
high atom economy, short reaction times, good to excellent
yields of the target products and most importantly, water
as the only by-product generated in the reaction.
White solid; mp 280 8C; yield: 94%. IR (Nujol):
1377, 1137, 1026, 860, 816, 718, 695 cmꢁ1 1H NMR
(400 MHz, DMSO-d6): 8.28 (dd, J1 = 9.15 Hz, J2 = 2.20 Hz,
3H, ArH), 8.04 (s, 3H, ArH), 7.95 (dd, J1 = 8.05 Hz,
J2 = 2.20 Hz, 3H, ArH), 7.74 (d, J = 8.79 Hz, 3H, ArH) ppm;
ESI-MS: m/z = 514 [M + H]+; Anal. calcd for C24H12Cl6.H2O:
C, 54.28; H, 2.66. Found: C, 54.05; H, 2.45.
n 1459,
;
d
4.1.2. 1,3,5-Tris(30-trifluoromethylphenyl)benzene (2m)
White solid; mp 280 8C; yield: 70%. IR (CHCl3):
n 2926,
4. Experimental
1599, 1459, 1401, 1359, 1330, 1281, 1234, 1165, 1125, 1099,
1074, 1042, 911, 872, 801, 704, 674, 661, 621 cmꢁ1; 1H NMR
All the chemicals were purchased from Sigma-Aldrich
and used without further purification. The progress of the
reactions was monitored by thin layer chromatography
(TLC) using silica gel 60 F254 (pre-coated aluminium
sheets) from Merck. TLC spots were visualized by UV-light
irradiation followed by iodine. NMR spectra were obtained
in CDCl3 or DMSO-d6 on a Jeol ECX 400 MHz NMR
spectrometer and chemical shifts are expressed in parts
per million (ppm). Infrared spectra were recorded on a
Perkin Elmer IR spectrometer and absorption maxima
(400 MHz, CDCl3): d 7.92 (bs, 3H, ArH), 7.87 (d, J = 7.32 Hz,
3H, ArH), 7.79 (s, 3H, ArH), 7.69–7.61 (m, 6H, ArH) ppm; 13
C
2
NMR (100 MHz, CDCl3):
d
141.47 (d, JCꢁF = 24.92 Hz),
3
3
131.74 (d, JCꢁF = 32.59 Hz), 131.10 (d, JCꢁF = 31.63 Hz)
130.71, 129.49, 125.88, 124.60(d, 4JCꢁF = 3.83 Hz), 124.14(d,
4JCꢁF = 2.88 Hz), 124.09 (d, 1JCꢁF = 272.20 Hz) ppm; ESI-MS:
m/z = 549 [M + K]+; Anal. calcd for C27H15F9.0.5H2O: C,
62.44; H, 3.10. Found: C, 62.71; H, 3.08.
4.1.3. 1,3,5-Tris(9H-fluoren-2-yl)benzene (2n)
(vmax
)
are given in cmꢁ1
.
The melting points were
Pale yellow solid; mp 156 8C; yield: 70%. IR (Nujol):
1458, 1377, 1301, 1153, 824, 766, 732 cmꢁ1 1H NMR
(400 MHz, CDCl3): 7.93–7.89 (m, 9H, ArH), 7.84 (d,
n
determined in open capillary tubes on Buchi M-560
melting point apparatus and are uncorrected.
;
d
J = 7.32 Hz, 3H, ArH), 7.77 (d, J = 8.05 Hz, 3H, ArH), 7.58 (d,
J = 7.32 Hz, 3H, ArH), 7.43–7.39 (m, 3H, ArH), 7.35–7.31 (m,
3H, ArH), 4.01 (s, 6H, CH2) ppm; 13C NMR (100 MHz,
4.1. General procedure for the synthesis of 1,3,5-
triarylbenzenes (2a–n)
CDCl3):
d 143.95, 143.48, 142.58, 141.34, 141.16, 139.81,
A
mixture of acetophenone (3 mmol) and DBSA
126.82, 126.79, 126.20, 125.06, 125.03, 123.98, 120.17,
120.01, 37.00 ppm; ESI-MS: m/z = 593 [M + Na]+; Anal.
calcd for C45H30: C, 94.70; H, 5.30. Found: C, 94.48; H, 5.30.
(0.6 mmol) was heated at 130 8C in a preheated oil bath
for 3–8 hours. After completion of the reaction as indicated
Please cite this article in press as: Prasad D, et al. DBSA catalyzed cyclotrimerization of acetophenones: An efficient
synthesis of 1,3,5-triarylbenzenes under solvent-free conditions. C. R. Chimie (2013), http://dx.doi.org/10.1016/
j.crci.2012.12.008

G Model
CRAS2C-3673; No. of Pages 5
D. Prasad et al. / C. R. Chimie xxx (2013) xxx–xxx
5
(d) Y. Xu, Y. Pan, Q. Wu, H. Wang, P. Liu, J. Org. Chem. 76 (2011)
8472 ;
Acknowledgements
(e) A. Goswami, T. Ito, S. Okamoto, Adv. Synth. Catal. 349 (2007)
2368 ;
(f) D. Cicero, A. Lembo, A. Leoni, P. Tagliatesta, New J. Chem. 33 (2009)
2162 ;
(g) A. Ciammaichella, A. Leoni, P. Tagliatesta, New J. Chem. 34 (2010)
2122.
This work is supported by the University of Delhi, India
under the scheme to strengthen R&D Doctoral Research
Programme. We are thankful to Central Instrumentation
Facility, University of Delhi, India for providing NMR and
single crystal X-ray data. Amreeta Preetam is grateful to
CSIR, New Delhi, India for providing JRF.
[10] (a) S. Shi, Y. Zhang, J. Org. Chem. 72 (2007) 5927 ;
(b) L. Bai, J.X. Wang, Adv. Synth. Catal. 350 (2008) 315 ;
(c) M. Mora, C. Jimenez-Sanchidrian, J.R. Ruiz, Appl. Organometal.
Chem. 22 (2008) 122 ;
Appendix A. Supplementary data
(d) S. Paul, J.H. Clark, Green Chem. 5 (2003) 635.
[11] Y. Zhao, J. Li, C. Li, K. Yin, D. Ye, X. Jia, Green Chem. 12 (2010) 1370.
[12] N. Iranpoor, B. Zeynizaded, Synlett (1998) 1079.
[13] Z. Li, W.H. Sun, X. Jin, C. Shao, Synlett (2001) 1947.
[14] F. Ono, Y. Ishikura, Y. Tada, M. Endo, T. Sato, Synlett (2008) 2365.
[15] K. Phatangare, V. Padalkar, D. Mhatre, K. Patil, A. Chaskar, Synth.
Commun. 39 (2009) 4117.
Supplementary data associated with this article can be
found, in the online version, at http://dx.doi.org/10.1016/
j.crci.2012.12.008.
[16] T. Yamato, C. Hideshima, M. Tashiro, G.K.S. Prakash, G.A. Olah, Catal.
Lett. 6 (1990) 341.
[17] D.B. Clapp, A.A. Morton, J. Am. Chem. Soc. 58 (1936) 2172.
[18] A. Kumar, M. Dixit, S.P. Singh, R. Raghunandan, P.R. Maulik, A. Goel,
Tetrahedron Lett. 50 (2009) 4335.
[19] R. Ghanbaripour, I. Mohammadpoor-Baltork, M. Moghadam, A.R.
Khosropour, S. Tangestaninejad, V. Mirkhani, Polyhedron 31 (2012)
721.
[20] G.P. Zhang, R.H. Qiu, X.H. Xu, H.H. Zhou, Y.F. Kuang, S.H. Chen, Synth.
Commun. 42 (2012) 858.
[21] S.L. Zhang, Z.F. Xue, Y.R. Gao, S. Mao, Y.Q. Wang, Tetrahedron Lett. 53
(2012) 2436.
[22] P. Tundo, P. Anastas, D.S. Black, J. Breen, T. Collins, S. Memoli, J.
Miyamoto, M. Polyakoff, W. Tumas, Pure Appl. Chem. 72 (2000)
1207.
[23] S.L.Y. Tang, R.L. Smith, M. Poliakoff, Green Chem. 7 (2005) 761.
[24] (a) K. Manabe, S. Kobayashi, Org. Lett. 1 (1999) 1965 ;
(b) K. Manabe, S. Iimura, X.M. Sun, S. Kobayashi, J. Am. Chem. Soc. 124
(2002) 11971 ;
References
[1] M.J. Plater, M. McKay, T. Jackson, J. Chem. Soc., Perkin Trans. 1 (2000)
2695.
[2] Y. Shirota, J. Mater. Chem. 15 (2005) 75.
[3] (a) E. Rebourt, B. Pepin-Donat, E. Dinh, Polymer 36 (1995) 399 ;
(b) A. Viallat, B. Pepin-Donat, Macromolecules 30 (1997) 4679 ;
(c) L.R. Tsai, C.W. Li, Y. Chen, J. Polym. Sci.: Part A: Polym. Chem. 46
(2008) 5945.
[4] I.A. Khotina, O.E. Shmakova, D.Y. Baranova, N.S. Burenkova, A.A. Gurs-
kaja, P.M. Valetsky, L.M. Bronstein, Macromolecules 36 (2003)
8353.
[5] M.J. Plater, M. Praveen, Tetrahedron Lett. 38 (1997) 1081.
[6] V.S. Iyer, M. Wehmeier, J.D. Brand, M.A. Keegstra, K. Mullen, Angew.
Chem., Int. Ed. 36 (1997) 1603.
[7] (a) X.Y. Cao, X.H. Liu, X.H. Zhou, Y. Zhang, Y. Jiang, Y. Cao, Y.X. Cui, J. Pei,
J. Org. Chem. 69 (2004) 6050 ;
(b) E.J. Juarez-Perez, C. Vinas, F. Teixidor, R. Santillan, N. Farfan, A.
Abreu, R. Yepez, R. Nunez, Macromolecules 43 (2010) 150.
[8] B.P. Dash, R. Satapathy, E.R. Gaillard, J.A. Maguire, N.S. Hosmane, J. Am.
Chem. Soc. 132 (2010) 6578.
[9] (a) K. Yoshida, I. Morimoto, K. Mitsudo, H. Tanaka, Tetrahedron 64
(2008) 5800 ;
(c) K. Manabe, Y. Mori, S. Kobayashi, Tetrahedron 57 (2001)
2537.
[25] (a) B.P. Mathew, M. Nath, J. Heterocycl. Chem. 46 (2009) 1003 ;
(b) D. Prasad, M. Nath, Catal. Sci. Technol. 2 (2012) 93 ;
(c) R.K. Bhatt, S. Sharma, M. Nath, Monatsh. Chem. 143 (2012) 309 ;
(d) D. Prasad, M. Nath, J. Heterocycl. Chem. 49 (2012) 628 ;
(e) D. Prasad, A. Preetam, M. Nath, RSC Adv. 2 (2012) 3133 ;
(f) D. Prasad, A. Preetam, M. Nath, C. R. Chim. 15 (2012) 675.
(b) G. Hilt, C. Hengst, W. Hess, Eur. J. Org. Chem. (2008) 2293 ;
(c) V. Cadierno, S.E. Garcia-Garrido, J. Gimeno, J. Am. Chem. Soc. 128
(2006) 15094 ;
Please cite this article in press as: Prasad D, et al. DBSA catalyzed cyclotrimerization of acetophenones: An efficient
synthesis of 1,3,5-triarylbenzenes under solvent-free conditions. C. R. Chimie (2013), http://dx.doi.org/10.1016/
j.crci.2012.12.008