Sulfuric acid ([3-(3-Silicapropyl)sulfanyl]propyl)ester as a recyclable catalyst for the synthesis of 4,4′-(Arylmethylene)bis(1H-pyrazol-5-ols)

Article abstract of DOI:10.1016/S1872-2067(10)60260-4

Sulfuric acid ([3-(3-silicapropyl)sulfanyl]propyl)ester is employed as a recyclable catalyst for the condensation reaction between aromatic aldehydes and 3-methyl-l-phenyl-5-pyrazolone. This condensation reaction was performed in ethanol under refluxing c

Full text of DOI:10.1016/S1872-2067(10)60260-4

CHINESE JOURNAL OF CATALYSIS
Volume 32, Issue 9, 2011
Online English edition of the Chinese language journal
Cite this article as: Chin. J. Catal., 2011, 32: 1477–1483.
RESEARCH PAPER
Sulfuric Acid ([3-(3-Silicapropyl)sulfanyl]propyl)ester
as a Recyclable Catalyst for the Synthesis of
4,4'-(Arylmethylene)bis(1H-pyrazol-5-ols)
Shekoofeh TAYEBI1, Mojtaba BAGHERNEJAD1, Dariush SABERI2, Khodabakhsh NIKNAM1,2,
1Department of Chemistry, Islamic Azad University, Gachsaran Branch, Gachsaran, Iran
2Department of Chemistry, Faculty of Sciences, Persian Gulf University, Bushehr 75169, Iran
*
Abstract: Sulfuric acid ([3-(3-silicapropyl)sulfanyl]propyl)ester is employed as a recyclable catalyst for the condensation reaction between
aromatic aldehydes and 3-methyl-l-phenyl-5-pyrazolone. This condensation reaction was performed in ethanol under refluxing conditions
giving 4,4'-alkylmethylene-bis(3-methyl-5-pyrazolones) in 74-90% yields. The heterogeneous catalyst was recycled and used in eleven runs
for the reaction between benzaldehyde and 3-methyl-l-phenyl-5-pyrazolone without losing catalytic activity.
Key words: sulfuric acid ([3-(3-silicapropyl)sulfanyl]propyl)ester; silica-bonded N-propyl sulfamic acid; 3-methyl-l-phenyl-5-pyrazolone;
aldehydes
The development of heterogeneous catalysts for organic
synthesis has become a major area of research. The potential
advantages of these materials over homogeneous systems
(simplified recovery, reusability, and the potential for incor-
poration in continuous reactors and microreactors) could lead
to novel, environmentally benign chemical procedures for
academia and industry [1,2]. The application of solid acids in
organic transformations is important because they have many
advantages including ease of handling, decreased reactor and
plant corrosion problems, and their disposal is more environ-
mentally friendly [3–21].
applied as alternatives to traditional sulfonic acid resins and
homogeneous acids for catalyzing chemical transformations
[3–8]. In continuation of our studies into the design and ap-
plication of solid acid catalysts in organic transformations
[7–21], we thus describe the application of sulfuric acid
([3-(3-silicapropyl)sulfanyl]propyl)ester (SASPSPE) as recy-
clable catalyst for the synthesis of 4,4'-alkylmethylene-
bis(3-methyl-5-pyrazolones) (Scheme 1).
Pyrazoles are an important class of bio-active drug targets in
the pharmaceutical industry as they are the core structure of
numerous biologically active compounds [22–24]. For exam-
ple; they exhibit anti-anxiety, antipyretic, analgesic and
anti-inflammatory properties. 2,4-Dihydro-3H-pyrazol-3-one
Several types of solid sulfonic acid functionalized silica
(both amorphous and ordered) have been synthesized and
O
OH
Cl
OH
SH
(MeO)3Si
O Si
O
SH
SiO2
OH
OH
SiO2
SiO2
toluene, reflux, 24 h
toluene, reflux, 18 h
O
O
ClSO3H
rt, 4 h
O-SO3H
O Si
S
SiO2
OH
O Si
S
O
O
SASPSPE
Scheme 1. Preparation of sulfuric acid ([3-(3-silicapropyl)sulfanyl]propyl)ester (SASPSPE).
Received 9 March 2011. Accepted 8 July 2011.
*Corresponding author. Tel: +98-771-4541494; Fax: +98-771-4545188; E-mail: niknam@pgu.ac.ir, khniknam@gmail.com
Copyright © 2011, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier BV. All rights reserved.
DOI: 10.1016/S1872-2067(10)60260-4

Shekoofeh TAYEBI et al. / Chinese Journal of Catalysis, 2011, 32: 1477–1483
derivatives including 4,4'-(arylmethylene)bis(3-methyl-1-
ethanol (30 ml) and dried at room temperature to obtain
SASPSPE as a cream powder (5.13 g). The sulfur content of
the samples by conventional elemental analysis was 15.51%
[7].
phenyl-1H-pyrazol-5-ols) have a broad spectrum of approved
biological activity and are used as anti-inflammatory [25],
antipyretic [26], gastric secretion stimulatory [27], antide-
pressant [28], antibacterial [29] and antifilarial agents [30].
Moreover, the corresponding 4,4'-(arylmethylene)bis(1H-
pyrazol-5-ols) are applied as fungicides [31], pesticides [32],
insecticides [33], and dyestuffs [34–36], and as chelating and
extraction reagents for different metal ions [37,38]. The con-
ventional chemical approach to 4,4'-(arylmethylene)bis(3-
methyl-1-phenyl-pyrazol-5-ols) involves the successive Kno-
evenagel synthesis of the corresponding arylidenepyrazolones
and its base-promoted Michael reaction as well as the one-pot
tandem Knoevenagel-Michael reaction of arylaldehydes with
1.2 General procedure for the synthesis of
4,4'-(arylmethylene)bis(1H-pyrazol-5-ols)
A mixture of aromatic aldehyde (1 mmol), 5-methyl-
2-phenyl-2,4-dihydro-3H-pyrazol-3-one (2 mmol), and
SASPSPE (0.1 g) in ethanol (10 ml) were added to a flask and
heated under reflux for an appropriate time. After completion
of the reaction, as indicated by thin layer chromatography
(TLC, silica gel SILG/UV 254 plates), the reaction mixture was
washed with warm ethanol (30 ml × 3). After cooling, the crude
products were precipitated. The crude products were purified
by recrystallization from ethanol (95%). The recovered catalyst
was washed with diethyl ether, dried, and reused in subsequent
runs.
two
equivalents
of
5-methyl-2-phenyl-2,4-dihydro-
3H-pyrazol-3-one performed under various reaction conditions
[39,40]. The first set of procedures is concerned with the ca-
talysis of the components with piperidine in ethanolic solution
[41,42]. The second set of methods involves the non-catalyzed
tandem Knoevenagel-Michael reaction under neutral condi-
tions in either ethanol [43] or benzene [44] solutions. Although
the corresponding 4,4'-(arylmethylene)bis(1H-pyrazol-5-ols)
are obtained in reliable 70%–90% yields, the reaction requires
3–12 h of initial reflux and a further 24 h under ambient tem-
perature to reach completion. Recently, sodium dodecyl sulfate
[45], an electrocatalytic procedure [46], CAN [47], and sil-
ica-bonded S-sulfonic acid [17] were reported for the synthesis
The infrared (IR) spectra were obtained on a Shimadzu
IR-435. The 1H NMR was carried out on a Bruker Avance (300
MHz or DRX 500 MHz) or Bruker Ultrashield (400 MHz).
Melting points were determined using a Melting Point SMP1
apparatus in open capillary tubes and are uncorrected. All the
products were characterized by comparing their spectral (IR,
1H NMR), TLC, and physical data with those reported in the
literature [34–48]
of
4,4'-(arylmethylene)bis(3-methyl-1-phenyl-1H-pyrazol-
4,4'-(Phenylmethylene)bis(3-methyl-1-phenyl-1H-pyraz
ol-5-ol) (3a). White cream solid; recrystallized from ethanol;
mp 170–172 oC (171–172 oC [45]). IR (KBr, cm–1): 3400 (br),
3080 (w), 2900 (w), 1593 (s), 1494 (vs), 1410 (s), 1275 (s),
1020 (m), 730 (vs), 690 (s). 1H NMR (300 MHz, DMSO-d6): į
2.32 (6H, s), 4.96 (1H, s), 7.17–7.27 (7H, m), 7.44 (4H, t, J =
7.72 Hz), 7.71 (4H, d, J = 7.91 Hz), 13.96 (2H, br, OH). 13C
NMR (75 MHz, DMSO-d6): į 33.13, 120.52, 125.55, 125.88,
127.17, 128.12, 128.90, 142.22, 146.29.
5-ols). However, most of these methods suffer from at least one
limitation that may include moderate yields, long reaction
times, harsh reaction conditions, or tedious workup procedures.
1 Experimental
1.1 Catalyst preparation
1.1.1 3-(3-Silicapropylthio)-1-propanol
4,4'-[(4-Methylphenyl)methylene]bis(3-methyl-1-phenyl
-1H-pyrazol-5-ol) (3b). White solid; recrystallized from
o
o
3-Chloro-1-propanol (5 mmol, 0.473 g) was added to a
magnetically stirred mixture of 3-mercaptopropylsilica (10 g)
in toluene (30 ml) and then a few drops of triethyl amine was
added and the resulting mixture was refluxed for 24 h. The
mixture was filtered and the solid was washed with ethanol (20
ml × 3) and then dried in an oven. 3-(3-Silicapropylthio)-
1-propanol was obtained as a cream powder (10.3 g).
ethanol; mp 202–204 C (203 C [40]). IR (KBr, cm–1): 3440
(br), 3075 (w), 2830 (w), 1590 (s), 1495 (vs), 1408 (s), 1294 (s),
1
1020 (m), 800 (m), 744 (vs), 688 (s). H NMR (300 MHz,
DMSO-d6): į 2.24 (3H, s), 2.30 (6H, s), 4.90 (1H, s), 7.07 (2H,
d, J = 8.29 Hz), 7.13 (2H, d, J = 8.10 Hz), 7.24 (2H, t, J = 7.35
Hz), 7.44 (4H, t, J = 7.72 Hz), 7.70 (4H, d, J = 7.91 Hz), 13.93
(2H, br, OH). 13C NMR (75 MHz, DMSO-d6): į 18.55, 32.39,
114.85, 120.47, 125.49, 128.08, 128.89, 132.27, 137.39,
146.18, 155.49.
1.1.2 SASPSPE
4,4'-[(4-isopropylphenyl)methylene]bis(3-methyl-1-phen
yl-1H-pyrazol-5-ol) (3c). White cream solid; recrystallized
from ethanol; mp 132–134 oC. IR (KBr, cm–1): 3435 (br), 3080
(w), 2920 (w), 2830 (w), 1590 (s), 1495 (vs), 1408 (s), 1380
(m), 1365 (m), 1294 (s), 1020 (m), 779 (m), 744 (s), 688 (s). 1H
NMR (500 MHz, DMSO-d6): į 1.16 (6H, d, J = 6.9 Hz), 2.31
To a mixture of 3-(3-silicapropylthio)-1-propanol (5 g) in
chloroform (20 ml), chlorosulfonic acid (0.19 g, 1.65 ml) was
added dropwise at 0 °C over 2 h. After the addition was com-
plete the mixture was stirred for 2 h until HCl gas evolution
was stopped. Then, the mixture was filtered and washed with

Shekoofeh TAYEBI et al. / Chinese Journal of Catalysis, 2011, 32: 1477–1483
(6H, s), 2.79–2.85 (1H, m), 4.90 (1H, s), 7.13 (2H, d, J = 8.2
4,4'-[(2-Chlorophenyl)methylene]bis(3-methyl-1-phenyl-
Hz), 7.18 (2H, d, J = 8.1 Hz), 7.23 (2H, t, J = 7.25 Hz), 7.43
(4H, t, J = 7.3 Hz), 7.72 (4H, d, J = 7.9 Hz), 12.30 (1H, br, OH),
14.03 (1H, s, OH). 13C NMR (125 MHz, DMSO-d6): į 12.51,
24.78, 33.70, 33.84, 121.39, 126.40, 126.93, 127.93, 129.77,
140.57, 146.72, 147.14. Anal. Calcd for C30H30N4O2 (%): C,
75.29; H, 6.32; N, 11.71. Found: C, 75.12; H, 6.35; N, 11.54.
4,4'-[(3,4,5-Trimethoxyphenyl)methylene]bis(3-methyl-1
-phenyl-1H-pyrazol-5-ol) (3d). White cream solid; recrystal-
lized from ethanol; mp 195–197 oC. IR (KBr, cm–1): 3447 (br),
3085 (w), 2885 (w), 1585 (s), 1490 (vs), 1443 (s), 1410 (s),
1318 (m), 1262 (m), 1122 (m), 898 (m), 850 (s), 790 (vs), 690
(s). 1H NMR (500 MHz, DMSO-d6): į 2.33 (6H, s), 3.62 (3H,
s), 3.69 (6H, s), 4.85 (1H, s), 6.69 (2H, s), 7.24 (2H, t, J = 7.25
Hz), 7.43 (4H, t, J = 7.81 Hz), 7.71 (4H, d, J = 7.91 Hz), 14.29
(1H, s, OH). 13C NMR (125 MHz, DMSO-d6): į 12.61, 34.76,
56.70, 60.80, 105.81, 121.59, 126.45, 129.78, 136.86, 138.29,
139.62, 147.03, 153.42. Anal. Calcd for C30H30N4O5 (%): C,
68.42; H, 5.74; N, 10.64. Found: C, 68.19; H, 5.59; N, 10.38.
4,4'-[(2-Hydroxyphenyl)methylene]bis(3-methyl-1-phen
yl-1H-pyrazol-5-ol) (3e). White solid; recrystallized from
1H-pyrazol-5-ol) (3h). White solid; recrystallized from etha-
o
nol; mp 235–237 oC (236–237 C [45]). IR (KBr, cm–1): 3450
(br), 3070 (w), 2910 (w), 1610 (m), 1555 (s), 1495 (vs), 1395
1
(m), 1360 (m), 1300 (s), 835 (m), 740 (s), 690 (s). H NMR
(400 MHz, DMSO-d6): į 2.29 (6H, s), 5.14 (1H, s), 7.22–7.33
(4H, m), 7.40 (1H, d, J = 7.82 Hz), 7.44 (4H, t, J = 7.57 Hz),
7.70 (4H, d, J = 7.57 Hz), 7.80 (1H, d, J = 7.06 Hz), 13.92 (2H,
br, OH). 13C NMR (100 MHz, DMSO-d6): į 32.41, 120.67,
123.62, 126.92, 128.05, 128.93, 129.45, 130.32, 135.94,
137.36, 140.60, 141.18.
4,4'-[(4-Flurophenyl)methylene]bis(3-methyl-1-phenyl-1
H-pyrazol-5-ol) (3i). White solid; recrystallized from ethanol;
mp 181–183 oC (182 oC [40]). IR (KBr, cm–1): 3445 (br), 3080
(w), 2882 (w), 1590 (s), 1495 (vs), 1401 (m), 1380 (s), 1308
(m), 1121 (m), 902 (s), 842 (m), 788 (s), 690 (s). 1H NMR (500
MHz, DMSO-d6): į 2.31 (6H, s), 4.95 (1H, s), 7.09 (2H, t, J =
8.75 Hz), 7.22-7.28 (4H, m), 7.43 (4H, t, J = 7.65 Hz), 7.70 (4H,
d, J = 7.90 Hz), 12.48 (1H, br, OH), 13.91 (1H, s, OH). 13C
NMR (125 MHz, DMSO-d6): į 12.43, 33.32, 115.51, 115.68,
121.42, 126.45, 129.74, 129.78, 129.85, 129.92, 139.07,
147.11, 162.50.
o
o
ethanol; mp 227–229 C (230–231 C [46]). IR (KBr, cm–1):
3400 (br), 3060 (w), 2920 (w), 2830 (w), 1605 (s), 1575 (s),
4,4'-[(4-Nitrophenyl)methylene]bis(3-methyl-1-phenyl-1
H-pyrazol-5-ol) (3j). Yellow solid; recrystallized from ethanol;
mp 225–227 oC (224–226 oC [45]). IR (KBr, cm–1): 3440 (br),
3090 (w), 2920 (w), 1595 (s), 1495 (vs), 1410 (s), 1340 (m),
744 (s), 689 (s). 1H NMR (400 MHz, DMSO-d6): į 2.28 (6H, s),
5.06 (1H, s), 7.18 (2H, t, J = 7.06 Hz), 7.38 (4H, t, J = 7.31 Hz),
7.45 (2H, d, J = 8.32 Hz), 7.64 (4H, d, J = 7.82 Hz), 8.10 (2H, d,
J = 8.58 Hz), 13.81 (2H, br, OH). 13C NMR (100MHz,
DMSO-d6): į 34.45, 121.91, 124.65, 127.03, 129.92, 130.25,
147.20, 147.58, 151.63.
1
1455 (vs), 1225 (m), 750 (s), 690 (s). H NMR (500 MHz,
DMSO-d6): į 2.28 (6H, s), 5.16 (1H, s), 6.70 (1H, t, J = 7.5 Hz),
6.74 (1H, d, J = 7.5 Hz), 6.96 (1H, t, J = 7.0 Hz), 7.22 (2H, t, J
= 7.3 Hz), 7.42 (4H, t, J = 7.9 Hz), 7.57 (1H, d, J = 7.2 Hz),
7.71 (4H, d, J = 7.8 Hz). 13C NMR (125 MHz, DMSO-d6): į
12.73, 28.15, 115.66, 119.42, 121.37, 126.18, 127.65, 129.71,
147.16, 154.68.
4,4'-[(2-Bromophenyl)methylene]bis(3-methyl-1-phenyl-
1H-pyrazol-5-ol) (3f). White cream solid; recrystallized from
ethanol; mp 198–200 oC. IR (KBr, cm–1): 3440 (br), 3060 (w),
2920 (w), 1605 (s), 1560 (s), 1495 (vs), 1395 (m), 1365 (m),
4,4'-[(3-Nitrophenyl)methylene]bis(3-methyl-1-phenyl-1
H-pyrazol-5-ol) (3k). Pale yellow solid; recrystallized from
1
o
1300 (m), 830 (m), 744 (s), 690 (s). H NMR (500 MHz,
ethanol; mp 151–153 C (149–150 C [45]). IR (KBr, cm–1):
o
DMSO-d6): į 2.31 (6H, s), 5.10 (1H, s), 7.13 (1H, t, J = 7.25
Hz), 7.23 (2H, t, J = 7.0 Hz), 7.33 (1H, t, J = 7.3 Hz), 7.42 (4H,
t, J = 7.9 Hz), 7.56 (1H, d, J = 7.8 Hz), 7.71 (4H, d, J = 7.9 Hz),
7.86 (1H, m), 12.68 (1H, br, OH), 13.92 (1H, s, OH). 13C NMR
(125 MHz, DMSO-d6): į 13.08, 35.21, 121.49, 123.54, 126.43,
128.30, 129.16, 129.76, 131.44, 133.64, 138.21, 146.78. Anal.
Calcd for C27H23BrN4O2 (%): C, 62.92; H, 4.50; Br, 15.50; N,
10.87. Found: C, 62.74; H, 4.54; N, 10.70.
3420 (br), 3085 (w), 2910 (w), 1595 (s), 1495 (vs), 1340 (s),
758 (m), 735 (s), 692 (s), 598 (m). 1H NMR (400 MHz,
DMSO-d6): į 2.35 (6H, s), 5.14 (1H, s), 7.26 (2H, t, J = 7.31
Hz), 7.45 (4H, t, J = 7.57 Hz), 7.60 (1H, t, J = 8.32 Hz),
7.68–7.74 (5H, m), 8.06–8.10 (2H, m), 13.91 (2H, br, OH). 13
C
NMR (100MHz, DMSO-d6): į 32.80, 120.63, 121.21, 121.70,
125.78, 125.81, 128.98, 129.71, 134.34, 137.39, 144.56,
146.30, 147.72.
4,4'-[(4-Chlorophenyl)methylene]bis(3-methyl-1-phenyl-
1H-pyrazol-5-ol) (3g). White solid; recrystallized from etha-
nol; mp 215–217 oC (210 oC [40]). IR (KBr, cm–1): 3430 (br),
3085 (w), 2920 (w), 1595 (s), 1490 (vs), 1410 (s), 1290 (m),
4,4'-[(4-Cyanophenyl)methylene]bis(3-methyl-1-phenyl-
1H-pyrazol-5-ol) (3l). Yellow solid; recrystallized from
o
o
ethanol; mp 210–212 C, (210–212 C [17]). IR (KBr, cm–1):
3420 (br), 3090 (w), 2921 (w), 2230 (m), 1595 (s), 1495 (vs),
1
1
804 (m), 742 (s), 690 (s). H NMR (300 MHz, DMSO-d6): į
1410 (s), 1290 (m), 810 (m), 750 (s), 690 (s). H NMR (400
2.30 (6H, s), 4.98 (1H, s) 7.22–7.28 (4H, m), 7.35 (2H, d, J =
8.48 Hz), 7.44 (4H, t, J =7.91 Hz), 7.71 (4H, d, J = 7.91 Hz),
13.90 (2H, br, OH). 13C NMR (75 MHz, DMSO-d6): į 32.56,
120.54, 125.62, 128.00, 128.90, 129.13, 130.56, 137.18,
141.14, 146.23.
MHz, DMSO-d6): į 2.33 (6H, s), 5.07 (1H, s), 7.25 (2H, t, J =
7.31 Hz), 7.42–7.46 (6H, m), 7.40 (4H, d, J = 7.82 Hz), 7.76
(2H, d, J = 8.32 Hz), 13.89 (2H, br, OH). 13C NMR (100 MHz,
DMSO-d6): į 33.23, 119.00, 120.61, 125.57, 128.38, 128.94,
133.36, 142.59, 148.15.

Shekoofeh TAYEBI et al. / Chinese Journal of Catalysis, 2011, 32: 1477–1483
4,4'-[(2-Naphthyl)methylene]bis(3-methyl-1-phenyl-1H-
18.54, 33.34, 120.70, 125.87, 126.68, 128.82, 134.52, 142.40,
pyrazol-5-ol) (3m). White solid; recrystallized from ethanol;
mp 206–208 oC. IR (KBr, cm–1): 3410 (br), 3030 (w), 1590 (s),
1490 (vs), 1392 (s), 1360 (m), 1280 (m), 1020 (m), 810 (m),
149.89, 154.26.
1,4-Diphenylene-4,4'-(methylene)bis(3-methyl-1-phenyl-
1H-pyrazol-5-ol) (4b). White cream solid; recrystallized from
ethanol; mp 214–216 C (218–220 C [48]). IR (KBr, cm–1):
1
o
o
780 (m), 740 (s), 690 (s); H NMR (500 MHz, DMSO-d6): į
2.36 (6H, s), 5.14 (1H, s), 7.24 (2H, t, J = 6.9 Hz), 7.41–7.45
(7H, m), 7.71–7.73 (5H, m), 7.81–7.85 (3H, m), 12.41 (1H, br,
OH), 13.93 (1H, s, OH); 13C NMR (125 MHz, DMSO-d6): į
12.50, 34.22, 121.46, 125.80, 126.30, 126.83, 127.36, 128.16,
128.52, 128.59, 129.79, 132.54, 133.73, 140.55, 147.19. Anal.
Calcd for C31H26N4O2 (%): C, 76.52; H, 5.39; N, 11.51; Found:
C, 76.35; H, 5.30; N, 11.46.
3410 (br), 3020 (w), 1590 (s), 1490 (vs), 1410 (s), 1350 (s),
1
1290 (s), 1120 (s), 1020 (m), 850 (m), 745 (vs), 690 (s). H
NMR (500 MHz, DMSO-d6): į 2.29 (12H, s), 5.05 (2H, s), 7.17
(4H, s), 7.22 (4H, t, J = 7.1 Hz), 7.41 (8H, t, J = 7.8 Hz), 7.69
(8H, d, J = 7.9 Hz), 12.41 (2H, br, OH) 14.11 (2H, s, OH). 13
C
NMR (125MHz, DMSO-d6): į 12.51, 33.69, 121.50, 127.84,
129.72, 140.93, 147.07, 155.01. Anal. Calcd for C48H42N8O4
(%): C, 72.52; H, 5.32; N, 14.09. Found: C, 72.35; H, 5.29; N,
13.85.
4,4'-[(3-Pyridyl)methylene]bis(3-methyl-1-phenyl-1H-py
razol-5-ol) (3n). White cream solid; recrystallized from etha-
nol; mp 238–240 oC. IR (KBr, cm–1): 3410 (br), 3050 (w), 2900
(w), 1595 (s), 1490 (vs), 1410 (s), 1345 (m), 1280 (m), 1020
2 Results and discussion
1
(m), 850 (m), 790 (m), 745 (s), 695 (s); H NMR (500 MHz,
DMSO-d6): į 2.34 (6H, s), 5.05 (1H, s), 7.23 (2H, t, J = 7.1 Hz),
7.34 (1H, t, J = 6.0 Hz), 7.43 (4H, t, J = 7.5 Hz), 7.71–7.73 (5H,
m), 8.41 (1H, d, J = 3.6 Hz), 8.51 (1H, s), 12.10 (1H, br, OH),
14.12 (1H, br, OH); 13C NMR (125 MHz, DMSO-d6): į 12.54,
31.96, 104.68, 121.45, 124.22, 126.44, 129.76, 136.16, 138.25,
138.91, 147.04, 147.61, 149.32. Anal. Calcd for C26H23N5O2
(%): C, 71.38; H, 5.30; N, 16.01; Found C, 71.20; H, 5.25; N,
15.87.
To study the effect of catalyst loading on the condensation
reaction of aromatic aldehydes with 3-methyl-l-phenyl-
5-pyrazolone the reaction between benzaldehyde and
5-methyl-2-phenyl-2,4-dihydro-3H-pyrazol-3-one was chosen
as the model reaction (Table 1). The results show clearly that
SASPSPE is an effective catalyst for this condensation and in
the absence of SASPSPE the condensation reaction gave a very
low yield after 24 h. The optimal amount of SASPSPE was 0.1
g (3.4 mol%) per 1 mmol of aldehyde in refluxing ethanol.
Although the lower catalyst loading of 0.05 g of SASPSPE
accomplished this condensation, 0.1 g SASPSPE per 1 mmol
of aldehyde was optimum in terms of the reaction time and the
isolated yield. Also, the model reaction was examined using
optimum amounts and at room temperature, and we obtained a
GC yield of 55% for the corresponding product (Table 1, entry
11). In addition, the result of this condensation in the presence
4,4'-[(2-Thienyl)methylene]bis(3-methyl-1-phenyl-1H-p
yrazol-5-ol) (3o). White cream solid; recrystallized from
o
o
ethanol; mp 181–183 C (181–183 C [17]). IR (KBr, cm–1):
3420 (br), 3080 (w), 2920 (w), 1595 (s), 1490 (vs), 1410 (s),
1284 (s), 779 (vs), 690 (s). 1H NMR (400 MHz, DMSO-d6): į
2.32 (6H, s), 5.13 (1H, s), 6.75–6.77 (1H, m), 6.90–6.92 (1H,
m), 7.24–7.30 (3H, m), 7.45 (4H, t, J = 7.82 Hz), 7.71 (4H, d, J
= 7.82 Hz) 14.01 (2H, br, OH). 13C NMR (100MHz, DMSO-d6):
į 29.43, 120.58, 124.05, 124.15, 126.75, 128.94, 132.99,
134.13, 147.73.
Table 1 Condensation reaction of benzaldehyde with 5-methyl-2-
phenyl-2,4-dihydro-3H-pyrazol-3-one in the presence of different
amounts of catalysts
4,4'-[(2-Furyl)methylene]bis(3-methyl-1-phenyl-1H-pyr
azol-5-ol) (3p). White cream solid; recrystallized from ethanol;
mp 189–191 oC (181–183 oC [47]). IR (KBr, cm–1): 3420 (br),
3080 (w), 2920 (w), 1595 (s), 1490 (vs), 1410 (s), 1284 (s), 779
Entry
Catalyst
no catalyst
SASPSPE
SASPSPE
SASPSPE
SASPSPE
SBNPSA
H2SO4
Catalyst loading
—
Time (h) Yielda (%)
1
2
24
6.5
<10
70
78
90
89
90
1
0.05 g (0.017 mmol)
0.07 g (0.023 mmol)
0.1 g (0.034 mmol)
0.15 g (0.051 mmol)
0.2 g (0.068 mmol)
0.2 mmol
(vs), 690 (s). H NMR (400 MHz, DMSO-d6): į 2.31 (6H, s),
3
5.0
3.0
3.0
4.0
4.0
3.0
1.2
0.7
15.0
4.99 (1H, s), 6.12-6.14 (1H, m), 6.34-6.36 (1H, m), 7.25 (2H, t,
J = 6.0 Hz), 7.43–7.51 (5H, m), 7.71 (4H, d, J = 8.0 Hz), 12.46
(1H, br, OH), 13.85 (1H, s, OH). 13C NMR (100MHz,
DMSO-d6): į 28.22, 106.11, 109.88, 110.34, 120.43, 120.55,
125.60, 128.91, 131.92, 141.54.
4
5
6
7
44c
8
H2SO4
1.0 mmol
44c
45c
47c
55d
1,3-Diphenylene-4,4'-(methylene)bis(3-methyl-1-phenyl-
1H-pyrazol-5-ol) (4a). White cream solid; recrystallized from
9
H2SO4
4.0 mmol
10
11
H2SO4
10.0 mmol
o
o
ethanol; mp 191–192 C (190–194 C [48]). IR (KBr, cm–1):
3405 (br), 3015 (w), 1599 (s), 1402 (vs), 1279 (vs), 1025 (m),
788 (m), 753 (vs), 683 (vs). 1Ǿ ȃȂȇ (400 MHz, DMSO-d6): į
2.25 (12Ǿ, s), 4.86 (2Ǿ, s), 7.07–7.67 (24Ǿ, m), 12.45 (2Ǿ, br,
ȅǾ) 14.08 (2Ǿ, s, ȅǾ). 13C ȃȂȇ (100 125MHz, DMSO-d6): į
SASPSPE
0.1 g (0.034 mmol)
Reaction conditions: benzaldehyde 1 mmol, 5-methyl-2-phenyl-2,4-
a
dihydro-3H-pyrazol-3-one 2 mmol, EtOH 10 ml, reflux conditions. Iso-
b
c
lated yield. Silica-bonded N-propyl-sulfamic acid (SBNPSA) [8]. The
same yield was obtained for the by-product. dGC yield of the conversion
at room temperature.

Shekoofeh TAYEBI et al. / Chinese Journal of Catalysis, 2011, 32: 1477–1483
Ph
N
Me
Ph
Ar
OH
HO
Me
Me
N
N
SASPSPE
EtOH, Reflux
N
Ar-CHO + 2
N
N
N
O
Me
N
OHC
N
Me
N
OH
Me
HO
SASPSPE
Ph
Ph
Ph
+
4
N
ꢀ
1
EtOH, Reflux
2
O
N
3a 3p
Me
Me
OHC
Ph
Scheme 2. The condensation of aromatic aldehydes with 3-methyl-l-
N
N
2
N
Ph
phenyl-5-pyrazolone upon catalysis by SASPSPE.
N
OH
HO
4a, 4b
Ph
of commercially available sulfuric acid is shown in Table 1.
Therefore, we employed optimized conditions for the con-
densation reaction of various aryl aldehydes with 3-methyl-
Scheme 3. The condensation of terephthaldehyde with 3-methyl-l-
phenyl-5-pyrazolone catalyzed by SASPSPE.
l-phenyl-5-pyrazolone
to
give
the
corresponding
4,4'-(arylmethylene)bis(3-methyl-1-phenyl-1H-pyrazol-5-ols)
(Scheme 2).
Cinnamyl aldehyde was reacted with 3-methyl-1-phenyl-
5-pyrazolone under the optimized conditions but gave a mix-
ture of products.
As shown in Table 2, both the aromatic and heteroaromatic
aldehydes react with 3-methyl-l-phenyl-5-pyrazolone to afford
4,4'-(arylmethylene)-bis-(3-methyl-1-phenyl-1H-pyrazol-5-ols)
in excellent yields. On the other hand, benzaldehydes with
electron-donating or electron-withdrawing groups, i.e. methyl,
iso-propyl, and 3,4,5-trimethoxybenzaldehyde (Table 2, entries
2–4) or 4-nitro, 3-nitro, and 4-cyano-benzaldehyde (Table 2,
entries 10–12) condense into the corresponding
4,4'-(arylmethylene)-bis-(3-methyl-1-phenyl-1H-pyrazol-5-ols)
3b–3d and 3j–3l in high yields. The acid sensitive substrates
3-pyridine carbaldehyde, thiophene-2-carbaldehyde, and fur-
fural (Table 2, entries 14–16) were converted into the corre-
sponding products 3n, 3o, and 3p in 84%, 74%, and 75% yields,
respectively. 2-Naphthyl carbaldehyde was converted into the
corresponding product 3m in 88% yield (Table 2, entry 13).
The practical synthetic efficiency of this reaction was high-
lighted by the reaction of terephthaldehyde and isophthalde-
hyde with 3-methyl-1-phenyl-5-pyrazolone to give structurally
complex pyrazol-5-ol derivatives (4a and 4b, Scheme 3).
The possibility of recycling the catalyst SASPSPE was
examined using the reaction of benzaldehyde and
5-methyl-2-phenyl-2,4-dihydro-3H-pyrazol-3-one under the
optimized conditions. Upon completion, the reaction mixture
was washed with warm ethanol (30 ml × 3). The recovered
catalyst was washed with diethyl ether, dried, and reused for
subsequent runs. The recycled catalyst was reused eleven times
without any additional treatment. No observation of any ap-
preciable loss in the catalytic activity of SASPSPE was ob-
served (Fig. 1).
Table 2 Preparation of 4,4'-(arylmethylene)-bis-(3-methyl-1-phenyl-1H-pyrazol-5-ols) derivatives catalyzed by SASPSPE in ethanol under reflux condi-
tions
Entry
1
Ar (1)
C6H5-
Product
3a
Time (h)
3.0
2.3
3.5
3.3
3.5
2.6
2.2
2.4
2.5
2.0
2.3
2.1
3.0
3.0
4.0
4.0
4.0
4.0
Yielda (%)
90
mp (oC)
170–172 (171–172 [45])
202–204 (203 [40])
132–134
2
4-Me-C6H4-
4-iso-Pr-C6H4-
3,4,5-(MeO)3-C6H2-
2-HO-C6H4-
2-Br-C6H4-
4-Cl-C6H4-
2-Cl-C6H4-
4-F-C6H4-
3b
3c
89
3
88
4
3d
3e
89
195–197
5
83
227–229 (230–231 [46])
198–200
6
3f
78
7
3g
85
215–217 (210 [40])
235–237 (236–237 [45])
181–183 (182 [40])
225–227 (224–226 [45])
151–153 (149–150 [45])
210–212 (210–212 [17])
206–208
8
3h
3i
77
9
86
10
11
12
13
14
15
16
17
18
4-O2N-C6H4-
3-O2N-C6H4-
4-(CN)-C6H4-
2-C10H7-
3j
88
3k
3l
87
89
3m
3n
3o
88
3-pyridyl-
84
238–240
2-thienyl-
74
181–183 (181–183 [17])
189–191 (189–190 [47])
191–192 (190–194 [48])
214–216 (218–220 [48])
2-furyl-
3p
4a
75
3-OHC-C6H4-
4-OHC-C6H4-
82
4b
86
Reaction conditions: aromatic aldehyde 1 mmol, 5-methyl-2-phenyl-2,4-dihydro-3H-pyrazol-3-one 2 mmol, catalyst SASPSPE 0.1 g, EtOH 10 ml, reflux
conditions. aIsolated yield.

Shekoofeh TAYEBI et al. / Chinese Journal of Catalysis, 2011, 32: 1477–1483
13 Niknam K, Zolfigol M A, Chehardoli G, Dehghanian M. Chin
100
80
60
40
20
0
J Catal, 2008, 29: 901
14 Niknam K, Zolfigol M A, Sadabadi T. J Iran Chem Soc, 2007,
4: 199
15 Niknam K, Zolfigol M A, Hossieninejad Z, Daneshvar N. Chin
J Catal, 2007, 28: 591
16 Niknam K, Zolfigol M A, Sadabadi T, Nejati A. J Iran Chem
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17 Niknam K, Saberi D, Sadegheyan M, Deris A. Tetrahedron
Lett, 2010, 51: 692
18 Niknam K, Saberi D, Baghernejad M. Phosphorus Sulfur Sili-
con Relat Elem, 2010, 185: 875
1
2
3
4
5
6
7
8
9 10 11 12
Run
19 Niknam K, Panahi F, Saberi D, Mohagheghnejad M. J Het-
erocycl Chem, 2010, 47: 292
Fig. 1. Recyclability of SASPSPE as a catalyst in the condensation
reaction between benzaldehyde (1 mmol) and 5-methyl-2-phenyl-
2,4-dihydro-3H-pyrazol-3-one (2 mmol) in the presence of 0.1 g of
SASPSPE in refluxing ethanol. Reaction time 3 h.
20 Niknam K, Saberi D, Mohagheghnejad M. Molecules, 2009,
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21 Niknam K, Saberi D, Baghernejad B. Chin Chem Lett, 2009,
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22 McDonald E, Jones K, Brough P A, Drysdale M J, Workman P.
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3 Conclusions
23 Elguero J. In: Katritzky A R, Rees C W, Scriven E F V eds.
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Pergamon Press, 1996
We prepared new 4,4'-(arylmethylene)-bis-(3-methyl-
1-phenyl-1H-pyrazol-5-ols) by a tandem condensation reaction
between aromatic aldehydes and two equivalents of
24 Elguero J, Goya P, Jagerovic N, Silva A M S. Targets
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5-methyl-2-phenyl-2,4-dihydro-3H-pyrazol-3-one
in
the
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26 Behr L C, Fusco R, Jarboe C H. In: Weissberger A Ed. The
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Acknowledgments
We are grateful to the Islamic Azad University Research
Council for partial support of this work.
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