Facile and green synthesis of triarylmethanes using silica sulfuric acid as a reusable catalyst under solvent-free conditions

Article abstract of DOI:10.1016/j.crci.2011.02.009

A facile and environmentally-benign protocol has been developed for the synthesis of triarylmethanes (TAMs) from the reaction of different arenes and aldehydes in the presence of silica sulfuric acid (SSA) as a heterogeneous and reusable catalyst under solvent-free conditions. Easy work-up, short reaction times, high yields, high selectivity, mild and green conditions are other salient features of this method.

Full text of DOI:10.1016/j.crci.2011.02.009

C. R. Chimie 14 (2011) 934–943
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Full paper/Memoire
Facile and green synthesis of triarylmethanes using silica sulfuric acid
as a reusable catalyst under solvent-free conditions
a
a
a
I. Mohammadpoor-Baltork a, , M. Moghadam , S. Tangestaninejad , V. Mirkhani ,
*
K. Mohammadiannejad-Abbasabadi a, M.A. Zolfigol b
a Catalysis Division, Department of Chemistry, University of Isfahan, Isfahan 81746-73441, Iran
b Department of Chemistry, Bu-Ali Sina University, Hamadan 65175, Iran
A R T I C L E I N F O
A B S T R A C T
Article history:
A facile and environmentally-benign protocol has been developed for the synthesis of
triarylmethanes (TAMs) from the reaction of different arenes and aldehydes in the
presence of silica sulfuric acid (SSA) as a heterogeneous and reusable catalyst under
solvent-free conditions. Easy work-up, short reaction times, high yields, high selectivity,
mild and green conditions are other salient features of this method.
Received 2 November 2010
Accepted after revision 17 February 2011
Available online 8 September 2011
Keywords:
´
ß 2011 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.
Triarylmethanes
Silica sulfuric acid
Reusable catalyst
Solvent-free
Veratrole
1. Introduction
cetic acid (TFA) [9]), sulfuric acid [10], [Ir(COD)Cl]2-SnCl4
[11], AuCl3 or AuCl3/AgOTf [12], Cu(OTf)2 [13], FeCl3 [14],
Triarylmethyl derivatives are an important class of
organic compounds which have received considerable
attention in recent years due to their wide range of
activities and interesting properties [1–3]. Some TAM
derivatives have been known to exhibit antioxidant
properties, antitumor activity and inhibitory activity
toward the histidine protein kinase [4]. These compounds
have also been used as dyes [5,6] and as protecting groups
for nucleosides and carbohydrates [3,7]. Due to their
importance, considerable attention has been paid to
develop efficient methods for the synthesis of TAMs.
Several synthetic methods such as Suzuki-Miyaura
coupling of diarylmethyl carbonates with arylboronic
acids in the presence of [Pd(h3-C3H5)Cl]2-DPPPent (1,5-
bis(diphenylphosphino) pentane) catalyst [8] and alkyl-
ation of arenes with aromatic aldehydes catalyzed by
trifluoromethanesulfonic acid (TFSA) or TFSA-trifluoroa-
Yb(OTf)3 [15] and AcBr/ZnBr2/SiO2 [16] have been devel-
oped for the preparation of TAMs. However, in spite of their
potential utility, most of the reported methods require
high reaction temperatures [8,11,14], long reaction times
[8,9,12,14,15] and excess amounts of catalyst [9,10] for
successful reactions. Further, the use of toxic organic
solvents [9,10,12–14,16], a corrosive catalyst [10] and
formation of a side product [9] limit the usefulness of some
of these methods, especially in large scale operation and
lead to serious environmental and safety problems.
Another disadvantage of the existing methods is that the
catalysts are destroyed during the work-up procedure and
can not be recovered and reused [8–16]. Consequently, the
design of simple, efficient and green approaches for the
synthesis of TAMs is still in demand.
In recent years, the use of solid acid catalysts has gained
considerable attention in
a wide range of organic
transformations [17–20]. The ease of separation, recovery
and re-use render the processes employing solid acid
catalysts as green and economically viable processes.
Among several solid acid catalysts used in organic
* Corresponding author.
E-mail address: imbaltork@sci.ui.ac.ir (I. Mohammadpoor-Baltork).
1631-0748/$ – see front matter ß 2011 Acade´mie des sciences. Published by Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.crci.2011.02.009

I. Mohammadpoor-Baltork et al. / C. R. Chimie 14 (2011) 934–943
935
reactions, silica sulfuric acid is one of the most attractive,
because of its reusability, environmental compatibility,
low cost, non-toxicity and operational simplicity. Due to
these advantages, silica sulfuric acid has been used as an
efficient catalyst in some important organic transforma-
tions [21–27]. This catalyst is prepared easily by the
reaction of silica gel with chlorosulfonic acid [21].
In continuation of our interest towards development of
useful synthetic methodologies [28–31], herein we wish to
report a facile and environmentally-friendly method for
the synthesis TAMs using silica sulfuric acid as a safe,
inexpensive and reusable solid acid catalyst under solvent-
free conditions (Scheme 1).
given in Table 3. After completion of the reaction as
indicated by TLC (n-hexane/ethyl acetate 10:4), the
reaction mixture was cooled to room temperature and
absolute EtOH (2 Â 5 mL) was added. The catalyst was
filtered by simple filtration and the crude product was
purified by recrystallization from EtOH or EtOH/H2O.
2.3. Physical and spectroscopic data
1,2-Dimethoxy-4-((3,4-dimethoxyphenyl)(phenyl)-
methyl)benzene (Table 2, compound 3a). Mp 122–124 8C; IR
(KBr):
1265, 1224, 1138, 1074, 1026, 958, 871, 817, 744, 704. 1H–
NMR (500 MHz, CDCl3): (ppm) 7.32 (2H, t, J = 7.6 Hz, 3,5-
n
(cmÀ1) 2999, 2960, 1589, 1512, 1463, 1448, 1340,
d
H phenyl), 7.22 (1H, t, J = 7.5 Hz, 4-H phenyl), 7.13 (2H, d,
J = 7.4 Hz, 2,6-H phenyl), 6.79 (2H, d, J = 8.3 Hz, 5-H
veratryl), 6.68 (2H, d, J = 1.7 Hz, 2-H veratryl), 6.51 (2H,
dd, J = 8.2 Hz, J = 1.9 Hz, 6-H veratryl), 5.45 (1H, s, Ar3CH),
3.86 (6H, s, OCH3), 3.77 (6H, s, OCH3). 13C–NMR (125 MHz,
2. Experimental
Silica sulfuric acid (SSA) was prepared according to the
literature [21]. The chemicals used in this work were
purchased from Fluka and Merck chemical companies. The
CDCl3):
d 148.85, 147.56, 144.36, 136.79, 129.30, 128.26,
progress of reactions was monitored by TLC using 0.25 mm
126.27, 121.47, 112.94, 111.01, 55.96, 55.89, 55.85. MS (EI,
70 eV) (m/z, %): 365.16 ([M + 1]+, 21.07), 364.16 (M+,
85.95), 333.14 (100), 287.16 (46.9), 227.15 (22.93), 165.08
(35.33), 143.18 (34.50), 115.02 (29.75), 77.00 (24.59). Anal.
Calcd for C23H24O4: C, 75.80; H, 6.64. Found: C, 75.37; H,
6.67.
pre-coated silica gel plates. Melting points were deter-
mined using Stuart Scientific SMP2 apparatus and are
uncorrected. 1H and 13C NMR (500 and 125 MHz) spectra
were recorded on a Bruker-AC 500 spectrometer in CDCl3
using TMS as internal standard. FT-IR spectra were
obtained as KBr pellets using a Nicolet-Impact 400D
instrument in the range of 400–4000 cmÀ1. Elemental
analysis was done on LECO, CHNS-932. Mass spectra were
recorded on a Platform II spectrometer from Micromass; EI
mode at 70 eV.
1-(Bis(3,4-dimethoxyphenyl)methyl)-3-nitrobenzene (Ta-
ble 2, compound 3b). Mp 154–155.5 8C; IR (KBr):
3084, 3003, 2947, 1589, 1516, 1463, 1342, 1028, 916, 869,
736. 1H–NMR (500 MHz, CDCl3):
(ppm) 8.05–8.08 (1H, m,
n )
(cmÀ1
d
4-H 3-nitrophenyl), 8.00 (1H, s, 2-H 3-nitrophenyl), 7.44–
7.46 (2H, m, 5,6-H 3-nitrophenyl), 6.81 (2H, d, J = 8.3 Hz, 5-
H veratryl), 6.65 (2H, d, J = 2.0 Hz, 2-H veratryl), 6.57 (2H,
dd, J = 8.3 Hz, J = 2.0 Hz, 6-H veratryl), 5.53 (1H, s, Ar3CH),
3.86 (6H, s, OCH3), 3.77 (6H, s, OCH3). 13C–NMR (125 MHz,
2.1. General procedure for the synthesis of
diveratrylmethanes (DVMs) under solvent-free conditions
A mixture of veratrole 1 (402 mg, 3 mmol), aldehyde
(1 mmol) and SSA (150 mg, 0.39 mmol) was heated at 65 8C
for the appropriate time according to Table 2. The progress
of the reaction was checked by TLC (n-hexane/ethyl
acetate 10:4). After completion of the reaction, the mixture
was cooled to room temperature and absolute EtOH
(2 Â 5 mL) was added. The catalyst was filtered by simple
filtration and the pure product was obtained by recrystal-
lization from EtOH (In the case of liquid products, the crude
material was purified by column chromatography on silica
gel).
CDCl3):
d 149.16, 148.44, 148.04, 146.68, 135.35, 135.17,
129.12, 124.05, 121.51, 121.39, 112.72, 111.26, 55.91,
55.59. MS (EI, 70 eV) (m/z, %): 410.12 ([M + 1]+, 25.86),
409.11 (M+, 100), 378.06 (46.26), 287.18 (40.23), 226.13
(9.99), 152.10 (7.33), 139.08 (6.90), 76.93 (21.83). Anal.
Calcd for C23H23NO6: C, 67.47; H, 5.66; N, 3.42. Found: C,
67.34; H, 5.64; N, 3.42.
4-((2-Chlorophenyl)(3,4-dimethoxyphenyl)methyl)-1,2-
dimethoxybenzene (Table 2, compound 3c). Mp 136–
137 8C; IR (KBr):
1514, 1465, 1413, 1332, 1263, 1139, 1026, 960, 869,
763, 704, 642. 1H–NMR (500 MHz, CDCl3):
(ppm) 7.38
n
(cmÀ1) 3078, 2997, 2933, 1589,
d
2.2. General procedure for the synthesis of TAMs under
solvent-free conditions
(1H, dd, J = 5.3 Hz, J = 3.7 Hz, 3-H 2-chlorophenyl), 7.17
(1H, t, J = 3.5 Hz, 4-H 2-chlorophenyl), 7.16 (1H, t,
J = 3.6 Hz, 5-H 2-chlorophenyl), 6.96 (1H, dd, J = 5.5 Hz,
J = 3.1 Hz, 6-H 2-chlorophenyl), 6.78 (2H, d, J = 8.3 Hz, 5-H
veratryl), 6.64 (2H, d, J = 1.9 Hz, 2-H veratryl), 6.54 (2H, dd,
J = 8.3 Hz, J = 1.9 Hz, 6-H veratryl), 5.84 (1H, s, Ar3CH), 3.86
(6H, s, OCH3), 3.77 (6H, s, OCH3). 13C–NMR (125 MHz,
A mixture of arene (3 mmol), aldehyde (1 mmol) and
SSA (200 mg, 0.52 mmol) was heated at 65 8C for the time
CDCl3):
d 148.93, 147.69, 142.01, 135.39, 134.54, 130.91,
129.65, 127.71, 126.55, 121.51, 113.03, 110.97, 55.86,
52.55. MS (EI, 70 eV) (m/z, %): 400.07 ([M + 2]+, 44.57),
398.07 (M+, 76.71), 367.05 (77.12), 287.09 (59.72), 143.05
(100), 127.53 (54.09), 100.91 (32.58), 76.90 (12.69). Anal.
Calcd for C23H23ClO4: C, 69.26; H, 5.81. Found: C, 69.17; H,
5.78.
Scheme 1.

936
I. Mohammadpoor-Baltork et al. / C. R. Chimie 14 (2011) 934–943
4-((2,4-Dichlorophenyl)(3,4-dimethoxyphenyl)methyl)-
1,2-dimethoxybenzene (Table 2, compound 3d). Mp 151–
152 8C IR (KBr):
(cmÀ1) 3072, 2999, 2933, 1587, 1516,
1463, 1328, 1250, 1138, 1028, 960, 866, 815, 754, 638. 1H–
NMR (500 MHz, CDCl3): (ppm) 7.39 (1H, d, J = 2.2 Hz, 3-H
2,4-dichlorophenyl), 7.15 (1H, dd, J = 8.5 Hz, J = 2.2 Hz, 5-H
2,4-dichlorophenyl), 6.88 (1H, d, J = 8.4 Hz, 6-H 2,4-
dichlorophenyl), 6.78 (2H, d, J = 8.3 Hz, 5-H veratryl),
6.61 (2H, d, J = 2 Hz, 2-H veratryl), 6.51 (2H, dd,
J = 8.3 Hz, J = 2.0 Hz, 6-H veratryl), 5.76 (1H, s, Ar3CH),
3.86 (6H, s, OCH3), 3.77 (6H, s, OCH3). 13C–NMR (125 MHz,
121.45, 112.79, 111.14, 56.10, 55.90. MS (EI, 70 eV) (m/z,
%): 393.14 ([M + 1]+, 60.45), 392.13 (M+, 99.25), 361.11
(97.76), 287.09 (94.03), 255.06 (47.56), 164.97 (54.48),
127.80 (40.86), 114.88 (51.49), 100.91 (41.60), 78.87
(32.09), 76.89 (30.04). Anal. Calcd for C24H24O5: C,
73.45; H, 6.16. Found: C, 73.33; H, 6.15.
n
d
4-((4-Fluorophenyl)(3,4-dimethoxyphenyl)methyl)-1,2-
dimethoxybenzene (Table 2, compound 3 h). Mp 124–
125 8C; IR (KBr):
1446, 1330, 1263, 1159, 1095, 1026, 958, 858, 790, 750.
1H–NMR (500 MHz, CDCl3):
(ppm) 7.06–7.10 (2H, m, 3,5-
n
(cmÀ1) 2999, 2960, 1602, 1506, 1463,
d
CDCl3):
d
149.03, 147.85, 140.76, 135.15, 134.82, 132.77,
H 4-fluorophenyl), 6.97 (2H, t, J = 8.7 Hz, 2,6-H 4-fluor-
ophenyl), 6.79 (2H, d, J = 8.3 Hz, 5-H veratryl), 6.65 (2H, d,
J = 1.8 Hz, 2-H veratryl), 6.59 (2H, dd, J = 8.3 Hz, J = 1.6 Hz,
6-H veratryl), 5.43 (1H, s, Ar3CH), 3.86 (6H, s, OCH3), 3.77
131.74, 129.41, 126.83, 121.41, 112.89, 111.03, 55.89,
55.86, 52.16. MS (EI, 70 eV) (m/z, %): 436.09 (M+ +4, 2.40),
434.06 ([M + 2]+, 10.16), 432.08 (M+, 18.97), 365.07 (7.59),
287.12 (9.77), 139.05 (30.80), 94.00 (37.72), 78.99 (100),
77.00 (50.89). Anal. Calcd for C23H22Cl2O4: C, 63.75; H,
5.12. Found: C, 63.49; H, 5.09.
(6H, s, OCH3). 13C–NMR (125 MHz, CDCl3):
d 161.41(d,
4
1JCF = 243.3 Hz), 148.92, 147.66, 140.12 (d, JCF = 3.1 Hz),
3
136.58, 130.70 (d, JCF = 7.8 Hz), 121.36, 115.02 (d,
4-((4-Bromophenyl)(3,4-dimethoxyphenyl)methyl)-1,2-
dimethoxybenzene (Table 2, compound 3e). Mp 159–
2JCF = 21.0 Hz), 112.79, 111.05, 55.88, 55.85, 55.16. MS
(EI, 70 eV) (m/z, %): 383.09 ([M + 1]+, 62.03), 382.09 (M+,
85.56), 367.04 (28.87), 352.08 (62.03), 351.09 (82.88),
287.06 (73.53), 245.05 (73.55), 213.01 (56.08), 198.97
(66.27), 182.97 (78.04), 169.95 (72.16), 150.98 (67.84),
142.99 (89.02), 127.53 (100), 108.92 (69.02), 78.87 (79.22),
76.92 (69.02).
161 8C; IR (KBr):
1332, 1261, 1138, 1026, 947, 839, 804, 750, 572. 1H–NMR
(500 MHz, CDCl3): (ppm) 7.40 (2H, d, J = 8.5 Hz, 3,5-H 4-
n
(cmÀ1) 2995, 2931, 1587, 1524, 1462,
d
bromophenyl), 6.99 (2H, d, J = 8.4 Hz, 2,6-H 4-bromophe-
nyl), 6.79 (2H, d, J = 8.3 Hz, 5-H veratryl), 6.79 (2H, d,
J = 1.9 Hz, 2-H veratryl), 6.58 (2H, dd, J = 8.3 Hz, J = 1.9 Hz,
6-H veratryl), 5.39 (1H, s, Ar3CH), 3.86 (6H, s, OCH3), 3.77
1,2-Dimethoxy-4-((3,4-dimethoxyphenyl)(3-methoxy-
phenyl)methyl)benzene (Table 2, compound 3i). Mp 120–
(6H, s, OCH3). 13C–NMR (125 MHz, CDCl3):
d
148.96,
122 8C; IR (KBr):
1317, 1246, 1139, 1091, 1026, 958, 860, 767. 1H–NMR
(500 MHz, CDCl3): (ppm) 7.21 (1H, t, J = 8.0 Hz, 5-H 3-
n
(cmÀ1) 3010, 2935, 1602, 1581, 1463,
147.75, 143.49, 136.12, 131.34, 131.03, 121.39, 120.19,
112.80, 111.09, 55.90, 55.89, 55.38. MS (EI, 70 eV) (m/z, %):
444.13 ([M + 2]+, 43.50), 442.12 (M+, 49.72), 413.09
(38.42), 411.08 (40.11), 287.12 (58.76), 151.93 (33.05),
142.79 (100), 100.90 (33.90), 77.00 (22.18). Anal. Calcd for
d
methoxyphenyl), 6.78 (2H, d, J = 8.3 Hz, 5-H veratryl), 6.76
(1H, dd, J = 8.2 Hz, J = 2.2 Hz, 6-H 3-methoxyphenyl), 6.72
(1H, d, J = 7.7 Hz, 4-H 3-methoxyphenyl), 6.68–6.69 (3H, m,
2-H veratryl and 2-H 3-methoxyphenyl), 6.62 (2H, dd,
J = 8.3 Hz, J = 1.9 Hz, 6-H veratryl), 5.41 (1H, s, Ar3CH), 3.86
(6H, s, OCH3 of veratryl), 3.77 (6H, s, OCH3 of veratryl), 3.74
(3H, s, OCH3 of 3-methoxyphenyl). 13C–NMR (125 MHz,
C23H23BrO4: C, 62.31; H, 5.23. Found: C, 62.10; H, 5.22.
4-(Bis(3,4-dimethoxyphenyl)methyl)benzonitrile (Table
2, compound 3f). Mp 115–116 8C; IR (KBr):
2989, 2935, 2227, 1604, 1587, 1462, 1334, 1261, 1138,
1024, 960, 856, 810, 748. 1H–NMR (500 MHz, CDCl3):
n )
(cmÀ1
d
CDCl3): d 159.63, 148.83, 147.57, 146.01, 136.62, 129.16,
(ppm) 8.00–8.08 (1H, m, 3 or 5-H 4-cyanophenyl), 8.00
(1H, s, 3 or 5-H 4-cyanophenyl), 7.43–7.46 (2H, m, 2,6-H 4-
cyanophenyl), 6.80 (2H, d, J = 8.3 Hz, 5-H veratryl), 6.65
(2H, d, J = 2.0 Hz, 2-H veratryl), 6.57 (2H, dd, J = 8.2 Hz,
J = 2 Hz, 6-H veratryl), 5.53 (1H, s, Ar3CH), 3.86 (6H, s,
121.85, 121.44, 115.46, 112.89, 111.32, 111.00, 55.96,
55.88, 55.86, 55.13. MS (EI, 70 eV) (m/z, %): 395.10
([M + 1]+, 73.79), 394.10 (M+, 100), 364.07 (71.56),
363.07 (98.93), 287.05 (93.51), 257.06 (81.08), 241.05
(57.30), 225.05 (57.30), 181.07 (68.11), 152.01 (69.73),
138.97 (64.86), 114.99 (51.35), 94.87 (39.46), 76.98
(55.68). Anal. Calcd for C24H26O5: C, 73.08; H, 6.64. Found:
C, 72.89; H, 6.65.
OCH3), 3.76 (6H, s, OCH3). 13C–NMR (125 MHz, CDCl3):
d
149.15, 148.44, 148.03, 146.68, 135.35, 135.17, 129.13,
124.05, 121.52, 121.39, 112.70, 111.24, 55.91, 55.59. MS
(EI, 70 eV) (m/z, %): 390.07 ([M + 1]+, 73.79), 389.05 (M+,
100), 385.04 (83.5), 287.05 (86.44), 252.06 (64.41), 190.04
(62.15), 151.03 (57.63), 143.19 (65.54), 120.76 (67.80),
77.02 (29.38).
2-(Bis(3,4-dimeyhoxyphenyl)methyl)naphthalene (Table
2, compound 3j). Mp 133–135 8C; IR (KBr):
3005, 2954, 1629, 1587, 1462, 1365, 1261, 1184, 1028, 964,
862, 761. 1H–NMR (500 MHz, CDCl3):
(ppm) 7.81–7.83
n )
(cmÀ1
d
4-(Bis(3,4-dimethoxyphenyl)methyl)benzaldehyde (Table
(1H, m, 6-H naphthyl), 7.79 (1H, d, J = 8.5 Hz, 4-H
naphthyl), 7.73–7.75 (1H, m, 7-H naphthyl), 7.52 (1H, s,
1-H naphthyl), 7.46 (1H, d, J = 3.5 Hz, 5-H naphthyl), 7.44
(1H, d, J = 3.4 Hz, 8-H naphthyl), 7.36 (1H, dd, J = 8.5 Hz,
J = 1.6 Hz, 3-H naphthyl), 6.81 (2H, d, J = 8.3 Hz, 5-H
veratryl), 6.79 (2H, d, J = 1.9 Hz, 2-H veratryl), 6.69 (2H,
dd, J = 8.3, J = 1.9, 6-H veratryl), 5.65 (1H, s, Ar3CH), 3.88
(6H, s, OCH3), 3.79 (6H, s, OCH3). 13C–NMR (125 MHz,
2, compound 3 g). Mp 128–129 8C; IR (KBr):
2929, 2839, 1699, 1602, 1516, 1465, 1344, 1267, 1138,
1026, 858, 794, 756. 1H–NMR (500 MHz, CDCl3):
(ppm)
n
(cmÀ1) 2999,
d
9.99 (1H, s. CHO), 7.81 (2H, d, J = 8.2 Hz, 3,5-H 4-
formylphenyl), 7.3 (2H, d, J = 8.2 Hz, 2,6-H 4-formylphe-
nyl), 6.81 (2H, d, J = 8.3 Hz, 5-H veratryl), 6.65 (2H, d,
J = 2.0 Hz, 2-H veratryl), 6.59 (2H, dd, J = 8.3 Hz, J = 2.0 Hz,
6-H veratryl), 5.51 (1H, s, Ar3CH), 3.87 (6H, s, OCH3), 3.77
CDCl3):
d 148.97, 147.70, 142.07, 136.60, 133.49, 132.25,
(6H, s, OCH3). 13C–NMR (125 MHz, CDCl3):
151.61, 149.04, 147.89, 135.58, 134.82, 129.97, 129.77,
d
191.83,
128.09, 127.93, 127.84, 127.63, 127.60, 126.04, 125.66,
121.68, 113.05, 111.12, 56.13, 55.91, 55.90. MS (EI, 70 eV)

I. Mohammadpoor-Baltork et al. / C. R. Chimie 14 (2011) 934–943
937
(m/z, %): 415.11 ([M + 1]+, 69.51), 414.09 (M+, 100), 384.08
(63.11), 383.07 (91.97), 287.05 (80.00), 277.07 (65.88),
245.07 (57.06), 215.06 (52.94), 127.96 (61.18), 126.02
(71.18), 119.46 (68.24), 77.00 (25.29). Anal. Calcd for
%): 351.14 ([M + 2]+, 3.7) 350.14 ([M + 1]+, 23.53), 349.14
(M+, 100), 332.13 (22.15), 318.11 (37.13), 227.22 (98.53),
152.11 (57.72), 77.13 (14.98).
1,4-Bis(bis(4-methoxyphenyl)methyl)benzene (Table 3,
C27H26O4: C, 78.24; H, 6.32. Found: C, 77.95; H, 6.34.
compound 6b). Mp 114–116C; IR (KBr):
2951, 1608, 1581, 1462, 1301, 1246, 1111, 1033, 813, 759.
1H–NMR (500 MHz, CDCl3):
(ppm) 7.04–7.08 (12H, m,
n
(cmÀ1) 3001,
1,1-Bis(3,4-dimethoxyphenyl)butane (Table 2, com-
pound 3m). Oil; IR (KBr):
1463, 1425, 1259, 1141, 1028, 952, 856, 808, 754. 1H–NMR
(500 MHz, CDCl3): (ppm) 6.79 (4H, s, 5,6-H veratryl), 6.74
n
(cmÀ1) 2995, 2931, 1589,
d
2,2’,6,6’-H of anisyl and the hydrogens of terephthyl), 6.85
(8 H, d, J = 16.7 Hz, 3,3’,6,6’-H anisyl), 5.46 (2H, s, Ar3CH),
3.81 (12H, s, OCH3). 13C–NMR (125 MHz, CDCl3):
d 158.39,
142.76, 137.02, 130.70, 129.56, 114.06, 55.67, 55.30. MS
(EI, 70 eV) (m/z, %): 532.29 ([M + 2]+, 7.58), 531.26
([M + 1]+, 28.79), 530.26 (M+, 100), 423.20 (16.48),
303.14 (66.67), 227.19 (60.98), 152.10 (37.12), 121.18
(51.14), 77.17 (19.03). Anal. Calcd for C36H34O4: C, 81.48;
H, 6.46. Found: C, 81.36; H, 6.45.
d
(2H, s, 2-H veratryl), 3.88 (6H, s, OCH3), 3.87 (6H, s, OCH3),
3.81 (1H, t, J = 6.8 Hz, Ar2CH), 1.97 (2H, q, J = 7.7 Hz, CH2 (1)
of n-propyl), 1.29 (2H, sext, J = 7.6 Hz, CH2 (2) of n-propyl),
0.93 (3H, t, J = 7.3 Hz, CH3 of n-propyl). 13C–NMR
(125 MHz, CDCl3):
d 148.87, 147.36, 138.28, 119.58,
111.50, 111.24, 55.89, 50.17, 38.34, 21.19, 14.07. MS (EI,
70 eV) (m/z, %): 331.15 ([M + 1]+, 29.55), 330.14 (M+,
64.09), 288.13(62.27), 287.13 (84.55), 166.94 (90.91),
148.90 (100), 127.95 (61.82), 114.81 (66.36), 112.98
(85.91), 103.89 (65.91), 82.92 (80.45), 76.89 (49.09).
1,2-Dimethoxy-4-(1-(3,4-dimethoxyphenyl)-2-phenyl-
2-((4-Chlorophenyl)(2-methoxy-5-methylphenyl)-
methyl)-1-methoxy-4-methylbenzene (Table 3, compound
6c). Mp 153–155 8C; IR (KBr):
1498, 1404, 1288, 1109, 1031, 885, 850, 752, 621. 1H–NMR
(500 MHz, CDCl3): (ppm) 7.25 (2H, d, J = 8.2 Hz, 2,6-H 4-
n
(cmÀ1) 3012, 2943, 1610,
propyl)benzene (Table 2, compound 3n). Oil; IR (KBr):
(cmÀ1) 3057, 2931, 1589, 1463, 1334, 1263, 1184, 1028,
856, 810, 761, 700. 1H–NMR (500 MHz, CDCl3):
(ppm)
n
d
chlorophenyl), 7.04 (4H, t, J = 9.2 Hz, 4,5-H anisyl), 6.82 (2
H, d, J = 8.2 Hz, 3,5-H 4-chlorophenyl), 6.63 (2 H, d,
J = 1.2 Hz, 2-H anisyl), 6.16 (1H, s, Ar3CH), 3.71 (6 H, s,
d
7.15–7.2 (4H, m, 2,3,5,6-H phenyl), 7.08 (1H, t, J = 6.9 Hz,
4-H phenyl), 6.96 (1H, dd, J = 8.2 Hz, J = 1.8 Hz, 6-H
veratyll), 6.88 (1H, d, J = 1.7 Hz, 2-H veratryl), 6.85 (1H,
d, J = 8.2 Hz, 5-H veratryl), 6.68 (1H, dd, J = 8.2 Hz,
J = 1.9 Hz, 5’-H veratyl), 6.61 (1H, d, J = 8.3 Hz, 4’-H
veratryl), 6.55 (1H, d, J = 1.8 Hz, 1’-H veratryl), 3.97 (1H,
d, J = 11.1 Hz, Ar2CH), 3.89 (3H, s, OCH3), 3.86 (3H, s, OCH3),
3.67 (3H, s, OCH3), 3.66 (3H, s, OCH3), 3.45–3.49 (1H, m,
PhCHCH3), 1.24 (3H, d, J = 6.8 Hz, CH3CHPh). 13C–NMR
OCH3), 2.25 (6H, s, Me). 13C–NMR (125 MHz, CDCl3):
d
155.63, 143.29, 132.30, 131.73, 131.09, 131.08, 129.71,
128.44, 128.18, 111.36, 56.36, 43.07, 21.21. MS (EI, 70 eV)
(m/z, %): 368.09 ([M + 2]+, 36.45) 367.09 ([M + 1]+, 26.07),
366.08 (M+, 100), 351.06 (28.76), 209.13 (52.04), 165.07
(61.65), 135.04 (65.85), 105.14 (65.94), 77.04 (31.80). Anal.
Calcd for C23H23ClO2: C, 75.30; H, 6.32. Found: C, 75.15; H,
6.33.
(125 MHz, CDCl3):
d
148.99, 148.26, 147.58, 146.94,
1-Methoxy-2-((2-methoxy-5-methylphenyl)(p-tolyl)-4-
methylbenzene (Table 3, compound 6d). Mp 119–120 8C; IR
146.06, 136.97, 136.78, 128.12, 127.69, 125.82, 120.25,
120.16, 112.20, 111.95, 111.45, 110.92, 58.39, 55.97,
55.91, 55.74, 55.69, 44.89, 21.93. MS (EI, 70 eV) (m/z, %):
393.06 ([M + 1]+, 2.04), 392.05 (M+, 7.72), 287.09 (100),
257.03 (75.72), 197.04 (62.17), 167.01 (64.78), 152.03
(71.30), 128.04 (72.17), 115.00 (80.43), 105.02 (90.87),
77.00 (85.65).
(KBr):
1107, 1029, 889, 806, 704. 1H–NMR (500 MHz, CDCl3):
n
(cmÀ1) 3007, 2922, 1608, 1566, 1496, 1313, 1236,
d
(ppm) 7.09 (2H, d, J = 7.9 Hz, 2-H 4-methylphenyl), 7.03
(2H, dd, J = 8.2 Hz, J = 1.9 Hz, 4-H anisyl), 6.99 (2H, d,
J = 8.0 Hz, 3-H 4-methylphenyl), 6.81 (2H, d, J = 8.2 Hz, 5-H
anisyl), 6.68 (2H, d, J = 2.0 Hz, 2-H anisyl), 6.18 (1H, s,
Ar3CH), 3.71 (6H, s, OCH3), 2.36 (3H, s, Me), 2.24 (6H, s,
1,4-Bis(bis(3,4-dimethoxyphenyl)methyl)benzene (4). Mp
173–176 8C; IR (KBr):
1463, 1332, 1263, 1186, 1028, 866, 788, 746. 1H–NMR
(500 MHz, CDCl3): (ppm) 7.4 (4H, s, 2,3,5,6-H terephthyl),
n
(cmÀ1) 2993, 2924, 1587, 1514,
methyl of anisyl). 13C–NMR (125 MHz, CDCl3):
d 155.73,
141.35, 135.38, 133.19, 131.16, 129.66, 129.58, 129.06,
127.84, 111.41, 56.49, 43.02, 21.51, 21.24. MS (EI, 70 eV)
(m/z, %): 347.23 ([M + 1]+, 24.58), 346.21 (M+, 90.83),
315.24 (63.33), 209.19 (31.46), 135.24 (47.29), 105.21
(100), 91.15 (42.57), 77.15 (22.5). Anal. Calcd for C24H26O2:
C, 83.20; H, 7.56. Found: C, 82.97; H, 7.55.
d
6.78 (4H, d, J = 8.3 Hz, 5,5’-H veratryl), 6.67 (4H, d,
J = 1.9 Hz, 2,2’-H veratryl), 6.61 (4H, dd, J = 8.3 Hz,
J = 1.8 Hz, 6,6’-H veratryl), 5.41 (2H, s, Ar3CH), 3.86 (12H,
s, OCH3), 3.76 (12H, s, OCH3). 13C–NMR (125 MHz, CDCl3):
d
148.81, 147.54, 142.27, 136.84, 129.14, 121.39, 112.94,
4-Chloro-2-((5-chloro-2-methoxyphenyl)(4-nitrophe-
nyl)methyl)-1-methoxybenzene (Table 3, compound 6e). Mp
110.96, 55.88, 55.85, 55.61. Anal. Calcd for C40H42O8: C,
73.83; H, 6.51. Found: C, 73.46; H, 6.49.
168–170 8C; IR (KBr):
1435, 1402, 1290, 1240, 1120, 1068, 1026, 887, 835, 794,
702, 644. 1H–NMR (500 MHz, CDCl3):
(ppm) 8.16 (2H, d,
n
(cmÀ1) 3007, 2935, 1593, 1485,
1-(Bis(4-methoxyphenyl)methyl)-3-nitrobenzene (Table
3, compound 6a). Oil; IR (KBr):
1593, 1485, 1402, 1242, 1120, 1028, 808, 702. 1H–NMR
(500 MHz, CDCl3): (ppm) 8.10–8.12 (1H, m, 4-H 3-
nitrophenyl), 8.03 (1H, s, 2-H 3-nitrophenyl), 7.45–7.50
(2H, m, 5,6-H 3-nitrophenyl), 7.05 (4H, d, J = 8.7 Hz, 2,6-H
of anisyl), 6.90 (4H, d, J = 8.7 Hz, 3,5-H anisyl), 5.59 (1H, s,
Ar3CH), 3.85 (6H, s, OCH3). 13C–NMR (125 MHz, CDCl3):
n
(cmÀ1) 3007, 2937,
d
J = 8.6 Hz, 2, 6-H 4-nitrophenyl), 7.26 (2H, dd, J = 8.7 Hz,
J = 2.3 Hz, 4-H anisyl), 7.23 (2H, d, J = 8.7 Hz, 5-H anisyl),
6.86 (2H, d, J = 8.7 Hz, 3, 5-H 4-nitrophenyl), 6.72 (2H, d,
J = 2.3 Hz, 2-H anisyl), 6.15 (1H, s, Ar3CH), 3.72 (6 H, s,
d
OCH3). 13C–NMR (125 MHz, CDCl3):
d 156.06, 150.83,
d
147.04, 132.34, 130.25, 129.99, 128.53, 125.96, 123.96,
112.51, 56.29, 44.03. MS (EI, 70 eV) (m/z, %): 420.95
([M + 4]+, 12.25), 418.96 ([M + 2]+, 68.42), 417.98 ([M + 1]+,
158.85, 148.85, 147.40, 135.85, 135.31, 130.62, 129.33,
124.48, 121.87, 114.47, 55.70, 55.30. MS (EI, 70 eV) (m/z,

938
I. Mohammadpoor-Baltork et al. / C. R. Chimie 14 (2011) 934–943
23.48), 416.95 (M+, 100), 381.98 (90.28), 155.10 (93.93),
121.14 (78.95). Anal. Calcd for C21H17Cl2NO4: C, 60.30; H,
4.10; N, 3.35. Found: C, 60.17; H, 4.12; N, 3.34.
2-((4-Chlorophenyl)(2,4,6-trimethoxyphenyl)-1,3,5-tri-
methoxybenzene (Table 3, compound 6 h). Mp 164–
165 8C; IR (KBr):
1332, 1228, 1060, 950, 875, 813, 677. 1H–NMR (500 MHz,
CDCl3): (ppm) 7.11 (2H, d, J = 8.5 Hz, 2-H 4-chloro-
n
(cmÀ1) 2999, 2937, 1587, 1489,
4-Chloro-2-((5-chloro-2-methoxyphenyl)(2-chlorophe-
nyl)methyl)-1-methoxybenzene (Table 3, compound 6f). Mp
d
139–140 8C; IR (KBr):
1317, 1242, 1120, 1026, 893, 810, 754, 638. 1H–NMR
(500 MHz, CDCl3): (ppm) 7.41 (1H, dd, J = 7.8 Hz,
n
(cmÀ1) 3062, 2935, 1593, 1485,
phenyl), 6.98 (2H, d, J = 8.5 Hz, 3-H 4-chlorophenyl), 6.17
(1H, s, Ar3CH), 6.11 (4H, s, 3,5-H trimethoxyphenyl), 3.79
(6 H, s, OCH3), 3.53 (12H, s, OCH3). 13C–NMR (125 MHz,
d
J = 1.4 Hz, 6-H 2-chlorophenyl), 7.23 (2H, dd, J = 8.8 Hz,
J = 2.6 Hz, 4-H anisyl), 7.2 (1H, dd, J = 5.9 Hz, J = 1.9 Hz, 4-H
2-chlorophenyl), 7.17 (1H, dd, J = 7.4 Hz, J = 1.4 Hz, 5-H 2-
chlorophenyl), 6.87 (1H, dd, J = 7.6 Hz, J = 1.7 Hz, 3-H 2-
chlorophenyl), 6.76 (2H, d, J = 8.7 Hz, 5-H anisyl), 6.69 (2H,
d, J = 2.6 Hz, 2-H anisyl), 6.41 (1H, s, Ar3CH), 3.72 (6 H, s,
CDCl3): d 159.80, 159.36, 144.41, 129.64, 129.25, 127.05,
113.75, 91.84, 56.10. 55.17, 36.63. MS (EI, 70 eV) (m/z, %):
460.11 ([M + 2]+, 25.56), 458.09 (M+, 67.78), 290.14
(100.00), 179.19 (60.56), 125.17 (49.72), 77.13 (18.06).
Anal. Calcd for C25H27ClO6: C, 65.43; H, 5.93. Found: C,
64.98; H, 5.94.
OCH3). 13C–NMR (125 MHz, CDCl3):
d 156.33, 140.52,
134.95, 132.87, 130.42, 130.18, 129.81, 128.28, 128.07,
126.92, 125.75, 112.48, 56.45, 41.31. MS (EI, 70 eV) (m/z,
%): 410.06 ([M + 4]+, 12.11), 408.07 ([M + 2]+, 34.54),
406.08 (M+, 35.57), 155.13 (71.65), 125.08 (100), 91.12
(37.63). Anal. Calcd for C21H17Cl3O2: C, 61.86; H, 4.20.
Found: C, 61.68; H, 4.17.
3. Results and discussion
Initially, the effect of different parameters such as
solvent, the amount of catalyst, temperature and reactant
ratio were examined in the reaction of veratrole (1) with
3-nitrobenzaldehyde (2b) in the presence of SSA as a
model reaction (Table 1). The model reaction was
performed in solvents such as EtOH, CH3CN, CHCl3 and
acetone and also under solvent-free conditions (entries
1–5). The reaction under solvent-free conditions gave the
best result (entry 5). To determine the appropriate molar
ratio of veratrole to aldehyde, the model reaction was
investigated with different molar ratios of reactants and
the best result was obtained with 3:1 molar ratio of
veratrole to aldehyde (entry 5). Using lower amount of
veratrole resulted in lower yields (entry 6), while higher
amount of veratrole did not improve the reaction time
and yield (entry 7). To find the optimized amount of silica
sulfuric acid, the reaction was carried out in the presence
2-((4-Bromophenyl)(2,4,6-trimethoxyphenyl)-1,3,5-tri-
methoxybenzene (Table 3, compound 6 g). Mp 149–151 8C;
IR (KBr):
1058, 950, 873, 810, 596. 1H–NMR (500 MHz, CDCl3):
n
(cmÀ1) 3005, 2939, 1591, 1485, 1332, 1228,
d
(ppm) 7.30 (2H, d, J = 8.4 Hz, 2-H 4-bromophenyl), 6.97
(2H, d, J = 8.3 Hz, 3-H 4-bromophenyl), 6.20 (1H, s, Ar3CH),
6.15 (4H, s, 3,5-H trimethoxyphenyl), 3.83 (6 H, s, OCH3),
3.56 (12H, s, OCH3). 13C–NMR (125 MHz, CDCl3):
d 160.20,
159.79, 145.40, 130.41, 130.13, 118.16, 113.95, 92.18,
56.50, 55.59, 37.07. MS (EI, 70 eV) (m/z, %): 504.21
([M + 2]+, 2.57), 502.13 (M+, 2.64), 179.11 (14.18), 69.07
(64.25), 71.13 (21.77), 55.07 (100.00). Anal. Calcd for
C25H27BrO6: C, 59.65; H, 5.41. Found: C, 59.48; H, 5.43.
Table 1
Optimization of the reaction conditions for the SSA catalyzed reaction of veratrole 1 with 3-nitrobenzaldehyde 2b.
Entry
SSA (mg)
Veratrole (mmol)
Aldehyde (mmol)
Solvent
T (8C)
Time (min)
Yield (%)a
1
2
150
150
150
150
150
150
150
200
100
–
3
1
1
1
1
1
1
1
1
1
1
1
1
1
EtOH
Reflux
Reflux
Reflux
Reflux
65
60
60
60
60
15
20
15
15
20
60
15
20
25
13
15
23
45
94
71
94
94
80
5
3
CH3CN
3
3
Acetone
4
3
CHCl3
5
3
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
6
2.5
3.5
3
65
7
65
8
65
9
3
65
10
11
12
13
3
65
150
150
150
3
75
94
82b
46b
3
50
3
RT
a
Isolated yield.
b
No further progress was observed even after 2 h.

I. Mohammadpoor-Baltork et al. / C. R. Chimie 14 (2011) 934–943
939
Table 2
Synthesis of diveratrylmethanes from the reaction of veratrole with aldehydes catalyzed by SSA under solvent-free conditionsa.
Entry
RCHO
Product
Time (min)
Yield (%)b
1
2
PhCHO (2a)
3a
3b
3c
3d
3e
3f
20
15
20
18
15
20
8
78
3-NO2C6H4CHO (2b)
2-ClC6H4CHO (2c)
2,4-(Cl)2C6H3CHO (2d)
4-BrC6H4CHO (2e)
4-NCC6H4CHO (2f)
4-OHCC6H4CHO (2g)
4-FC6H4CHO (2h)
94
3
95
4
82
5
91
6
92
7c
8
3g
3h
3i
86
20
25
25
60
60
10
10
85
9
3-CH3OC6H4CHO (2i)
2-Naphtaldehyde (2j)
4-HOC6H4CHO (2k)
4-CH3OC6H4CHO (2l)
n-PrCHO (2m)
85
10
11d
12d
13e
14e
3j
87
3k
3l
Traces
Traces
93
3m
3n
2-Phenylpropionaldehyde (2n)
94
a
Reaction conditions: 3 mmol veratrole, 1 mmol aldehyde, 150 mg SSA at 65 8C.
Isolated yield.
b
c
Reaction condition: 1 mmol terephthalaldehyde 2g and 2.5 mmol veratrole 1.
The starting materials were recovered from the reaction mixture.
Reaction of aliphatic aldehydes were preformed at room temperature.
d
e
of different amounts of the catalyst. Maximum yield was
obtained with 150 mg of the catalyst (entry 5). Further
increase in amount of silica sulfuric acid did not affect the
product yield (entry 8), but a lower amount of the
catalyst led to lower yield (entry 9). Indeed in the absence
of the catalyst, the desired product was obtained in only
5% yield after 1 h (entry 10). Furthermore, the effect of
reaction temperature was examined (entries 11–13) and
we found that 65 8C is the optimal temperature (entry 5)
and the reaction was incomplete at lower temperatures
even after 2 h (entries 12 and 13). The model reaction was
also carried out in the presence of sulfuric acid under
similar experimental conditions (molar ratio and tem-
perature); the corresponding triarylmethane 3b was
obtained in only 26% yield. Further, SSA as a solid acid,
in comparison with sulfuric acid, offers the advantages of
easy separation, non-corrosiveness and low pollution
effects.
Encouraged by our initial studies, we then investigat-
ed the generality and versatility of this method. A wide
range of aromatic aldehydes were investigated for their
reaction with veratrole in the presence of SSA under the
optimized reaction conditions and the results are
summarized in Table 2. The type of substituents on the
aromatic aldehydes has significant influence on the yield
of the product and reaction time. The aldehydes with
electron-withdrawing groups (entries 2–9) afforded the
desired products in high yields within short reaction
times, while an aromatic ring with electrondonating
groups, such as hydroxy and methoxy groups failed to
produce the products and the starting materials were
recovered from the reaction mixture (entries 11 and 12).
It is important to note that 2-naphthaldehyde did not
yield the corresponding TAM in the reaction with
veratrole in the presence of sulfuric acid and only starting
materials were recovered from the reaction mixture [10].
In contrast, the reaction of 2-naphthaldehyde with
veratrole was performed efficiently in the presence of
SSA within 25 min to afford the desired TAM in 87% yield
(entry 10). More gratifyingly, this method is suitable not
only for aromatic aldehydes, but also for aliphatic
aldehydes, such as butanal with 93% yield and 2-
phenylpropionaldehyde with 94% yield (entries 13 and
14). Another noteworthy feature of our protocol lies in the
reaction of dialdehyde such as terephthalaldehyde (2g)
with veratrole. Using a 2.5:1 molar ratio of veratrole to
terephthalaldehyde, only one aldehyde moiety reacted
selectively and the corresponding TAM was obtained in
86% yield. When veratrole was used in large excess (7
equiv. with respect to terephthalaldehyde), both alde-
hyde groups reacted and the desired product was
obtained in 77% yield (Scheme 2). Such selectivity can
be considered as an important practical achievement in
the synthesis of TAMs.
The probable reaction pathway for SSA catalyzed
synthesis of TAMs using veratrole and aldehydes is shown
in Scheme 3. The reaction proceeds via a series of
prototropic shift. The aldehyde is first activated by

940
I. Mohammadpoor-Baltork et al. / C. R. Chimie 14 (2011) 934–943
CHO
CHO
OMe
OMe
MeO
OMe
OMe
SSA, Solvent-free
+
65 oC, 8 min
MeO
CHO
1 (2.5 mmol)
2g (1 mmol)
3g (86%)
MeO
MeO
OMe
CHO
OMe
OMe
OMe
SSA, Solvent-free
65 oC, 60 min
+
MeO
MeO
OMe
OMe
CHO
1 (7 mmol)
4 (77%)
2g (1 mmol)
Scheme 2.
O
_
+
O
H
R
SiO2
O3SO
MeO
MeO
R
H
H
R
A
MeO
MeO
OMe
OMe
SiO2
OSO3H
R
H
MeO
MeO
OH
R
+
_
B
H
SiO2
MeO
MeO
OMe
O3SO
_
+
OMe
SiO2
O3SO
MeO
MeO
E
_
R
SiO2
O3SO
R
OH
+
MeO
MeO
OH2
MeO
C
MeO
+
D
SiO2
OSO3H
Scheme 3.
protonation with SSA to give A. Nucleophilic attack of
veratrole on A affords B and then C which in turn is
activated by the catalyst to afford D. Nucleophilic attack of
second molecule of veratrole to D gives E which is
subsequently converted to the desired product and
releases the catalyst for the next catalytic cycle.
In order to show the efficiency and applicability of this
method further, the reaction of other arenes such as

I. Mohammadpoor-Baltork et al. / C. R. Chimie 14 (2011) 934–943
941
anisole and its derivatives with aldehydes catalyzed by SSA
under solvent-free conditions was also investigated. As
shown in Table 3, treatment of a series of aldehydes with
anisole and its derivatives in the presence of catalytic
amount of SSA provided the corresponding TAM in high
yields.
In view of green chemistry, we then turned our
attention towards the reusability of the catalyst. The
reusability of SSA was examined through a series of
sequential reaction of veratrole with 3-nitrobenzaldehyde.
After completion of the reaction, EtOH was added and SSA
catalyst was separated by simple filtration and dried at
Table 3
Synthesis of TAMs from the reaction of arenes with aldehydes catalyzed by SSA under solvent-free conditionsa.
Entry
1
Ar-H
Ar’CHO
Product
Time (min)
25
Yield (%)b
91
CHO
MeO
OMe
2c
60
93
OHC
2g
MeO
OMe
6b
3
15
94
4
15
89

942
I. Mohammadpoor-Baltork et al. / C. R. Chimie 14 (2011) 934–943
Table 3 (Continued )
Entry
5
Ar-H
Ar’CHO
Product
Time (min)
25
Yield (%)b
86
6
25
87
95
94
MeO
OMe
CHO
7
5
Br
OMe
2e
5d
8
5
a
Reaction conditions: 3 mmol arene, 1 mmol aldehyde, 200 mg SSA at 65 8C.
Isolated yield.
b
c
The reaction was carried out with 7 mmol anisole and 1 mmol terephthalaldehyde in the presence of 350 mg of SSA.
70 8C. The recovered catalyst was reused in subsequent
reactions without significant decrease in its activity even
after five runs (Table 4).
In conclusion, we have developed a novel and facile
method for the synthesis of TAMs in the presence of SSA as
a cheap, safe, easy to handle and heterogeneous catalyst
under solvent-free conditions. In addition, operational
simplicity, mild reaction conditions, high yields, fast
reaction, reusability of the catalyst and green synthesis
avoiding toxic solvents are noteworthy advantages and
make this method economic and environmentally-benign
for the synthesis of TAMs.

I. Mohammadpoor-Baltork et al. / C. R. Chimie 14 (2011) 934–943
943
Table 4
Reusability of SSA in synthesis of DVMs.
Run
Time (min)
Yield (%)a
1
2
3
4
5
6
15
15
15
15
20
20
94
94
92
90
88
87
a
Isolated yield.
[15] S. Genovese, F. Epifano, C. Pelucchini, M. Curini, Eur. J. Org. Chem. 8
(2009) 1132.
Acknowledgements
[16] M. Kodomari, M. Nagamatsu, M. Akaike, T. Aoyama, Tetrahedron Lett.
49 (2008) 2537.
[17] J.H. Clark, Acc. Chem. Res. 35 (2002) 791.
[18] A. Corma, Chem. Rev. 95 (1995) 559.
[19] A. Cornelis, P. Laszlo, Synlett. (1994) 155.
Financial support of this work by Center of Excellence of
Chemistry and Research Council of University of Isfahan is
gratefully acknowledged.
[20] S.E. Sen, S.M. Smith, K.A. Sullivan, Tetrahedron 55 (1999) 12657.
[21] M.A. Zolfigol, Tetrahedron 57 (2001) 9509.
[22] M.A. Zolfigol, I. Mohammadpoor-Baltork, B.F. Mirjalili, A. Bamoniri,
Synlett (2003) 1877.
[23] H. Wu, Y. Shen, L.Y. Fan, Y. Wan, D.Q. Shi, Tetrahedron 62 (2006)
7995.
References
[1] V. Nair, S. Thomas, S.C. Mathew, K.G. Abhilash, Tetrahedron 62 (2006)
6731.
[2] H. Wulff, G.A. Gutman, M.D. Cahalan, K.G. Chandy, J. Biol. Chem. 276
(2001) 32040.
[3] M.S. Shchepinov, V.A. Korshun, Chem. Soc. Rev. 32 (2003) 170.
[4] M. Yamato, K. Hashigaki, Y. Yasumoto, J. Sakai, R.F. Luduena, A. Bane-
rjee, S. Tsukagoshi, T. Tashiro, T. Tsuruo, J. Med. Chem. 30 (1987) 1897.
[5] D.F. Duxbury, Chem. Rev. 93 (1993) 381.
[6] P. Rys, H. Zollinger, Fundamentals of the Chemistry and Application of
Dyes, Wiley-Interscience, New York, 1972.
[24] P. Salehi, M.A. Zolfigol, F. Shirini, M. Baghbanzadeh, Curr. Org. Chem. 10
(2006) 2171.
[25] M.A. Zolfigol, P. Salehi, M. Shiri, A. Sayadi, A. Abdoli, H. Keypour, M.
Rezaeivala, K. Niknam, E. Kolvari, Mol. Divers. 12 (2008) 203.
[26] I. Mohammadpoor-Baltork, V. Mirkhani, M. Moghadam, S. Tangesta-
ninejad, M.A. Zolfigol, M. Abdollahi-Alibeik, A.R. Khosropour, H. Kargar,
S.F. Hojati, Catal. Commun. 9 (2008) 894.
[27] J.T. Li, X.T. Meng, B. Bai, M.X. Sun, Ultason. Sonochem. 17 (2010) 14.
[28] I. Mohammadpoor-Baltork, M. Abdollahi-Alibeik, Can. J. Chem. 83
(2005) 110.
[7] T.W. Greene, P.G.M. Wuts, Protective Groups in Organic Synthesis. 3rd
ed., Wiley, New York, 1999.
[8] J.Y. Yu, R. Kuwano, Org. Lett. 10 (2008) 973.
[29] I. Mohammadpoor-Baltork, M. Moghadam, S. Tangestaninejad, V. Mir-
khani, M.A. Zolfigol, S.F. Hojati, J. Iran. Chem. Soc. 5 (2008) S65.
[30] V. Mirkhani, I. Mohammadpoor-Baltork, M. Moghadam, S. Tangesta-
ninejad, M. Abdollahi-Alibeik, H. Kargar, Appl. Catal. A Gen. 325 (2007)
99.
[9] S. Saito, T. Ohwada, K. Shudo, J. Am. Chem. Soc. 117 (1995) 11081.
[10] R. Goossens, M. Smet, W. Dehaen, Tetrahedron Lett. 43 (2002) 6605.
[11] S. Poder, J. Choudhury, U.K. Roy, S. Roy, J. Org. Chem. 72 (2007) 3100.
[12] V. Nair, K.G. Abhilash, N. Vidya, Org. Lett. 7 (2005) 5857.
[13] J. Esquivias, R.G. Arrayas,J.C. Carretero,Angew. Chem. Int. Ed. 45 (2006) 629.
[14] Z. Li, Z. Duan, J. Kang, H. Wang, L. Yu, Y. Wu, Tetrahedron 64 (2008)
1924.
[31] I. Mohammadpoor-Baltork, M. Moghadam, S. Tangestaninejad, V. Mir-
khani, S.F. Hojati, Polyhedron 27 (2008) 750.