Tandem knoevenagel-michael reaction of 1-Phenyl-3-methyl-5-pyrazolone with aldehydes using 3-aminopropylated silica gel as an efficient and reusable heterogeneous catalyst

Article abstract of DOI:10.1080/00397911.2011.555589

3-Aminopropylated silica gel is introduced as an efficient, reusable, and thermally stable heterogeneous catalyst for tandem Knoevenagel-Michael reaction of 1-phenyl-3-methyl-5-pyrazolone with aldehydes. Short reaction times, mild reaction conditions, eas

Full text of DOI:10.1080/00397911.2011.555589

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Tandem Knoevenagel–Michael Reaction
of 1-Phenyl-3-methyl-5-pyrazolone with
Aldehydes Using 3-Aminopropylated
Silica Gel as an Efficient and Reusable
Heterogeneous Catalyst
Sara Sobhani a , Ali-Reza Hasaninejad b , Mahdi Faal Maleki a & Zahra
Pakdin Parizi a
a Department of Chemistry, College of Sciences, Birjand University,
Birjand, Iran
b Department of Chemistry, Faculty of Sciences, Persian Gulf
University, Bushehr, Iran
Accepted author version posted online: 27 Dec 2011.Published
online: 09 Apr 2012.
To cite this article: Sara Sobhani , Ali-Reza Hasaninejad , Mahdi Faal Maleki & Zahra Pakdin Parizi
(2012): Tandem Knoevenagel–Michael Reaction of 1-Phenyl-3-methyl-5-pyrazolone with Aldehydes
Using 3-Aminopropylated Silica Gel as an Efficient and Reusable Heterogeneous Catalyst, Synthetic
Communications: An International Journal for Rapid Communication of Synthetic Organic Chemistry,
42:15, 2245-2255
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Synthetic Communications1, 42: 2245–2255, 2012
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2011.555589
TANDEM KNOEVENAGEL–MICHAEL REACTION
OF 1-PHENYL-3-METHYL-5-PYRAZOLONE WITH
ALDEHYDES USING 3-AMINOPROPYLATED
SILICA GEL AS AN EFFICIENT AND REUSABLE
HETEROGENEOUS CATALYST
Sara Sobhani,1 Ali-Reza Hasaninejad,2 Mahdi Faal Maleki,1
and Zahra Pakdin Parizi1
1Department of Chemistry, College of Sciences, Birjand University,
Birjand, Iran
2Department of Chemistry, Faculty of Sciences, Persian Gulf University,
Bushehr, Iran
GRAPHICAL ABSTRACT
Abstract 3-Aminopropylated silica gel is introduced as an efficient, reusable, and thermally
stable heterogeneous catalyst for tandem Knoevenagel–Michael reaction of 1-phenyl-3-
methyl-5-pyrazolone with aldehydes. Short reaction times, mild reaction conditions, ease
of recovery, and catalyst reusability make this method a new, economical, and waste-free
chemical process for the efficient synthesis of bis(pyrazolyl)methanes.
Keywords Bis(pyrazolyl)methane; heterogeneous catalysts; pyrazolone; silica-supported
catalysts; solid bases
INTRODUCTION
Pyrazoles are an important class of bioactive drug targets in the
pharmaceutical industry. They are the core structure of numerous biologically active
compounds.[1] For example, they exhibit anti-anxiety, antipyretic, analgesic, and
anti-inflammatory properties. 2,4-Dihydro-3H-pyrazol-3-one derivatives including
4,40-(arylmethylene)bis(3-methyl-1-phenyl-1H-pyrazol-5-ols), which have a broad
Received July 5, 2010.
Address correspondence to Sara Sobhani, Department of Chemistry, College of Science, Birjand
University, Birjand 414, India. E-mail: ssobhani@birjand.ac.ir; sobhanisara@yahoo.com
2245

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S. SOBHANI ET AL.
Figure 1. 3-Aminopropylated silica gel (AP-SiO2).
spectrum of approved biological activity, are being used as anti-inflammatory,
antipyretic, gastric secretion stimulatory, antidepressant, antibacterial, and antifilar-
ial agents.[2] Moreover, the corresponding 4,40-(arylmethylene)bis(1H-pyrazol-5-ols)
are applied as fungicides, pesticides, insecticides, dyestuffs, and chelating and
extracting reagents for different metal ions.[3] The conventional chemical approach
to 4,40-(arylmethylene)bis(3-methyl-1-phenyl-pyrazol-5-ols) involves the successive
Knoevenagel synthesis of the corresponding arylidenepyrazolones and its base-
promoted Michael reaction.[3a],[3b],[4] One-pot tandem Knoevenagell–Michael
reaction of aldehydes with 2 equivalents of 5-methyl-2-phenyl-2,4-dihydro-3H-
pyrazol-3-one, which can be performed under a variety of reaction conditions, is
another approach for achieving these important scaffolds.[5] However, most of the
methods suffer from at least one limitation that may include moderate yields, long
reaction times, harsh reaction conditions, high temperature, use of unrecyclable
catalyst, or tedious workup procedures.
Use of heterogeneous solid base catalysts is of current interest in chemistry and
industry because solid bases offer many advantages such as simplicity in handling,
more environmentally safe disposal, and less industrial corrosion problems.[6] Amine
functionalized silica gel such as 3-aminopropylated silica gel (AP-SiO2) is one of the
organic–inorganic hybrid materials that have been applied as effective solid base cat-
alysts in organic transformations.[7] In these types of solid base catalysts, the reactive
centers are highly mobile, similar to those of homogeneous catalysts, and at the same
time these species have the advantage of being recyclable in the same fashion as
heterogeneous catalysts.
As part of our ongoing program directed toward the development of new
methods in organic reactions,[8] herein we introduce 3-aminopropylated silica gel
(AP-SiO2)[7a],[9] (Fig. 1) as an efficient catalyst for tandem Knoevenagel–Michael
reaction of 2 equivalents of 1-phenyl-3-methyl-5-pyrazolone with various aldehydes.
RESULTS AND DISCUSSIONS
At first, to find the best solvent, a series of reactions of benzaldehyde (1 equiva-
lent) with 1-phenyl-3-methyl-5-pyrazolone (1, 2 equivalents) were studied in different
solvents in the presence of AP-SiO2(30 mol%) at room temperature (Table 1, Entries
2–6). Among solvents investigated, CH3CN was the best medium for the present
reaction (entry 2). Under the same reaction conditions, when 20 mol% of the catalyst
was used, the desired product was obtained after a longer reaction time (entry 1). To
show the role of the catalyst, similar reactions in the absence of the catalyst or in the
presence of SiO2 were examined. These reactions led to the formation of the desired
product (2a) in good yields but after a long reaction time (Table 1, Entries 7 and 8).

SYNTHESIS OF BIS(PRAZOLYL)METHANES
2247
Table 1. Effect of reaction media on the preparation of 3a from tandem Knoevenagel–Michael reaction
of 1-phenyl-3-methyl-5-pyrazolone (2) with benzaldehyde catalyzed by 3-aminopropylated silica gel
(AP-SiO2)
Entry
Catalyst
Solvent
Time
Yielda (%)
1
2
3
4
5
6
7
8
AP-SiO2
AP-SiO2
AP-SiO2
AP-SiO2
AP-SiO2
AP-SiO2
—
CH3CN
CH3CN
H2O
1.5 h
10 min
24 h
90b
98
90
75
90
80
70
75
n-Hexane
Toluene
CH2Cl2
CH3CN
CH3CN
20 h
1.5 h
0.5 h
24 h
SiO2
24 h
aIsolated yield. Conditions: benzaldehyde=pyrazolone=catalyst (AP-SiO2) 1:2:0.3 (except for entry 1),
room temperature.
bConditions: benzaldehyde=pyrazolone=catalyst (AP-SiO2) 1:2:0.2.
Then, a range of different aldehydes (2a–o) were subjected to react with
1-phenyl-3-methyl-5-pyrazolone (1) under the optimized reaction conditions
(Scheme 1, Table 2).
As shown in Table 2, different aromatic, heteroaromatic, and aliphatic alde-
hydes reacted with 1 in the presence of 30 mol% of 3-aminopropylated silica gel
(AP-SiO2) in short reaction times (5–45 min) to afford bis(pyrazolyl)methanes
(3a–o) in good yields.
The ability to recycle and reuse AP-SiO2 was also studied in this system. For
this purpose, after performing the preparation reaction of bis(pyrazolyl)methane
3a under the reaction conditions described in Table 2, the catalyst was recovered
by filtration, washed with EtOH, and then reused for a consecutive run under similar
conditions. The average isolated yield for the five consecutive runs was 92.6%, which
clearly showed the practical reusability of this catalyst (Fig. 2). This reusability
demonstrates the good stability and turnover of AP-SiO2 under the employed con-
ditions. It is worth to note that the recyclability test was stopped after five runs.
We propose a plausible mechanism for the formation of bis(pyrazolyl)-
methanes 3 as the reaction of aldehydes with 1-phenyl-3-methyl-5-pyrazolone cata-
lyzed by AP-SiO2 (Scheme 2). The first step involves the formation of benzylidene 4
Scheme 1. Tandem Knoevenagel–Michael reaction of 1-phenyl-3-methyl-5-pyrazolone with aldehydes
catalyzed by AP-SiO2.

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S. SOBHANI ET AL.
Table 2. Synthesis of bis(pyrazolyl)methanes 3a–o
Entry
Aldehyde
Product
Time (min)
Yielda (%)
1
2
3a
10
98
3b
3c
10
95
95
3
4
5
6
5
3d
3e
3f
10
98
97
96
5
15
7
8
3 g
15
15
96
3 h
98
(Continued )

SYNTHESIS OF BIS(PRAZOLYL)METHANES
2249
Table 2. Continued
Entry
Aldehyde
Product
Time (min)
Yielda (%)
9
3 i
30
97
90
95
10
11
3j
45
10
3k
12
13
3 l
30
15
90
90
3 m
14
15
3n
3o
20
10
90
95
aIsolated yield. Conditions: aldehyde=pyrazolone=catalyst (AP-SiO2) 1:2:0.3, room temperature. All of
the products are known.[5]
by the nucleophilic addition of 1-phenyl-3-methyl-5-pyrazolone to imine (formed by
the reaction of aldehyde and AP-SiO2) followed by dehydration. Then, the second
molecule of 1-phenyl-3-methyl-5-pyrazolone is added to 4 in Michael addition
fashion to give bis(pyrazolyl)methanes 3.
CONCLUSION
In conclusion, 3-aminopropylated silica gel (AP-SiO2) is introduced as an
efficient and heterogeneous catalyst for tandem Knoevenagel–Michael reaction of
1-phenyl-3-methyl-5-pyrazolone with various aldehydes. Ease of recovery and

2250
S. SOBHANI ET AL.
Figure 2. Reusability of AP-SiO2 as a catalyst for the preparation of bis(pyrazolyl)methane 3a.
catalyst reusability make this method an economic and waste-free chemical process
for the efficient synthesis of a variety of bis(pyrazolyl)methanes. Short reaction
times, simple workup, and mild reaction conditions are the other advantageous of
the present methodologies.
Scheme 2. Plausible mechanism for the formation of bis(pyrazolyl)methanes 3.

SYNTHESIS OF BIS(PRAZOLYL)METHANES
2251
EXPERIMENTAL
Chemicals were purchased from Merck and Fluka Chemical Companies.
AP-SiO2 was prepared by known procedures.[7] The loading of the organic groups
was calculated from the nitrogen content (1.30%) by elemental analysis performed
with a Heraeus CHN Rapid analyzer. Thermogravimetric analyses (TGA) revealed
that the catalyst is thermally stable and thus does not release organic fragments
almost until 125 ꢀC. All of the products are known and were identified by their spec-
tral data. Infrared (IR) spectra were run on a Perkin-Elmer 780 instrument. NMR
spectra were recorded on Bruker Avance DPX 250, 400, and 500 instrument. Mass
spectra were recorded on a Shimadzu GCMS-QP5050A instrument. The purity of
the products and the progress of the reactions were accomplished by thin-layer
chromatography (TLC) on silica-gel polygram SILG=UV254 plates.
General Procedure for the Synthesis of Bis(pyrazolyl)methanes
3-Aminopropylated silica gel (AP-SiO2) (3.22 g, 0.93 mmol=g, 3 mmol) was
added to a stirring solution of aldehyde (10 mmol) and pyrazolone 1 (20 mmol) in
CH3CN (10 mL). The mixture was stirred at room temperature for an appropriate
time (Table 2). The catalyst was recovered by filtration, washed with EtOH, and then
reused for a consecutive run under the same reaction conditions. The filtrate was
concentrated under reduced pressure to give the crude product. The pure product
(3a–o) was obtained by crystallization from ethanol.
Spectral Data for Selected Products
4,4’-(Phenylmethylene)bis(3-methyl-1-phenyl-pyrazol-5-ol)
(3a). 1H
NMR (DMSO-d6, 500 MHz): d 2.30 (s, 6 H), 4.95 (s, 1 H), 7.17–7.27 (m, 1 H),
7.44 (t, 4 H, J ¼ 7.72 Hz), 7.71 (d, 4 H, J ¼ 7.91 Hz), 13.96 (brs, 2 H) ppm; 13C
NMR (DMSO-d6, 125 MHz): d 12.0, 33.5, 121.3, 126.4, 126.5, 127.7, 128.7, 129.5,
137.4, 142.5, 146.8 ppm; IR (KBr): t 3430 (O–H) cmꢁ1; mp 168–170 ꢀC; MS: m=z
(%) ¼ 436 (0.18), 262 (48), 174 (31).
4,4’-[(3-Nitrophenyl)methylene]
bis(3-methyl-1-phenyl-pyrazol-5-ol)
(3b). 1H NMR (DMSO-d6, 400 MHz): d 2.35 (s, 6 H), 5.14 (s, 1 H), 7.26 (t, 2 H,
J ¼ 7.31 Hz), 7.45 (t, 4 H, J ¼ 7.57 Hz), 7.60 (t, 1 H, J ¼ 8.3 Hz), 7.68–7.74 (m, 5
H), 8.06–8.10 (m, 2 H), 13.91 (brs, 2 H) ppm; 13C NMR (DMSO-d6, 100 MHz): d
32.8, 120.6, 121.2, 121.7, 125.8, 125.8, 129.0, 129.7, 134.3, 137.4, 144.6, 146.3,
147.7 ppm; IR (KBr): 3420 (O–H) cmꢁ1; mp 151–153 ꢀC; MS: m=z (%) ¼ 307 (7.0),
174 (30.8).
4,4’-[(4-Bromophenyl)methylene] bis(3-methyl-1-phenyl-pyrazol-5-ol)
(3c). 1H NMR (DMSO-d6, 400 MHz): d 2.32 (s, 6 H), 4.95 (s, 1 H), 7.19, 7.52 (d,
2 H, J ¼ 8.0 Hz), 7.23–7.26 (m, 2 H), 7.42–7.48 (m, 6 H), 7.69 (d, 4 H, J ¼ 7.6 Hz),
13.87 (brs, 2 H) ppm; 13C NMR (DMSO-d6, 100 MHz): d 12.1, 33.0, 119.5, 121.0,
126.1, 129.34, 130.0, 131.4, 142.1, 146.7 ppm; mp 215 ꢀC; MS: m=z (%) ¼ 340
(10.5), 342 (10.5), 174 (29.5).

2252
S. SOBHANI ET AL.
4,4’-[(4-Nitrophenyl)methylene]
bis(3-methyl-1-phenyl-pyrazol-5-ol)
(3d). 1H NMR (DMSO-d6, 500 MHz): d 2.35 (s, 6 H), 5.13 (s, 1 H), 7.25–7.27 (m,
2 H), 7.44 (t, 4 H, J ¼ 7.0 Hz), 7.52 (d, 2 H, J ¼ 8.1 Hz), 7.71 (d, 4 H, J ¼ 7.6 Hz),
8.17 (d, 2 H, J ¼ 8.2 Hz), 13.86 (brs, 2 H) ppm; 13C NMR (DMSO-d6, 125 MHz):
d 34.1, 56.9, 121.5, 124.2, 126.6, 129.5, 129.8, 146.8, 147.2, 151.2 ppm; IR (KBr): t
3056 (O–H) cmꢁ1; mp 229–231 ꢀC; MS: m=z (%) ¼ 307 (9.2), 174 (18.3).
4,4’-[(4-Chlorophenyl)methylene] bis(3-methyl-1-phenyl-pyrazol-5-ol)
(3e). 1H NMR (DMSO-d6, 500 MHz): d 2.32 (s, 6 H), 4.97 (s, 1 H), 7.26 (d, 4 H,
J ¼ 8.2 Hz), 7.34 (d, 2 H, J ¼ 8.0 Hz), 7.44 (t, 4 H, J ¼ 7.1 Hz), 7.71 (d, 4 H,
J ¼ 7.6 Hz), 12.40 (brs, 1 H), 13.87 (brs, 1 H) ppm; 13C NMR (DMSO-d6,
125 MHz): d 33.4, 40.1, 121.4, 126.4, 128.9, 129.8, 130.0, 131.4, 142.0, 147.1 ppm;
IR (KBr): t 3044 (OꢁH) cmꢁ1; mp 212–214 ꢀC; MS: m=z (%) ¼ 296 (6.3), 174 (14.0).
4,4’-[(2-Chlorophenyl)methylene] bis(3-methyl-1-phenyl-pyrazol-5-ol)
(3f). 1H NMR (DMSO-d6, 400 MHz): d 2.29 (s, 6 H), 5.14 (s, 1 H), 7.22–7.33 (m,
4 H), 7.40 (d, 1 H, J ¼ 7.8 Hz), 7.44 (t, 4 H, J ¼ 7.6 Hz), 7.70 (d, 4 H, J ¼ 7.6 Hz),
7.80 (d, 1 H, J ¼ 7.1 Hz), 13.92 (brs, 2 H) ppm; 13C NMR (DMSO-d6, 100 MHz):
d 32.4, 120.7, 123.6, 126.9, 128.0, 128.9, 129.4, 130.3, 135.9, 137.4, 140.6,
141.2 ppm; IR (KBr): t 3450 (OꢁH) cmꢁ1; mp 235–237 ꢀC; MS: m=z (%) ¼ 296
(6.6), 185 (12.2).
4,4’-[(3-Methyl)methylene] bis(3-methyl-1-phenyl-pyrazol-5-ol) (3g).
1H NMR (DMSO-d6, 400 MHz): d 2.25 (s, 3 H), 2.31 (s, 6 H), 4.91 (s, 1 H), 6.98
(d, 1 H, J ¼ 7.6 Hz), 7.06 (s, 1 H), 7.07 (d, 1 H, J ¼ 6.8 Hz), 7.16 (t, 1 H, J ¼ 7.2 Hz),
), 7.25 (t, 2 H, J ¼ 7.2 Hz), 7.44 (t, 4 H, J ¼ 7.6 Hz), 7.71 (d, 4 H, J ¼ 7.6 Hz), 13.98
(brs, 2 H) ppm; 13C NMR (DMSO-d6, 100 MHz): d 12.1, 21.7, 33.6, 121.0, 124.8,
126.0, 127.1, 128.2, 128.5, 129.4, 137.5, 142.7, 146.7 ppm; IR (KBr): t 3023 (OꢁH)
cmꢁ1; mp 193–194 ꢀC; MS: m=z (%) ¼ 276 (28.4), 174 (21.0).
4,4’-[(4-Methoxy)methylene] bis(3-methyl-1-phenyl-pyrazol-5-ol) (3h).
1H NMR (DMSO-d6, 250 MHz): d 2.12 (s, 6 H), 3.72 (s, 3 H), 4.73 (s, 1 H), 6.77
(d, 2 H, J ¼ 8.7 Hz), 7.08–7.12 (m, 4 H), 7.21–7.28 (m, 4 H), 7.54 (d, 4 H, J ¼ 7.9 Hz)
) ppm; 13C NMR (DMSO-d6, 63 MHz): d 11.6, 32.4, 54.9, 105.0, 113.5, 120.4, 125.4,
128.1, 128.9, 129.2, 134.6, 137.9, 146.1, 157.5 ppm; IR (KBr): t 3060 (OꢁH) cmꢁ1
;
mp 176–177 ꢀC; MS: m=z (%) ¼ 466 (0.2, [Mþ]), 292 (100), 174 (32).
4,4’-[(4-Hydroxyphenyl)methylene]bis(3-methyl-1-phenyl-pyrazol-5-ol)
(3i). 1H NMR (DMSO-d6, 500 MHz): d 2.31 (s, 6 H), 4.86 (s, 1 H), 6.67 (d, 2 H,
J ¼ 8.0), 7.06 (d, 2 H, J ¼ 8.5 Hz), 7.24 (t, 2 H, J ¼ 7.0 Hz), 7.44 (t, 4 H, J ¼ 8.0 Hz),
), 7.72 (d, 4 H, J ¼ 8.0 Hz), 9.16 (brs, 1 H, OH), 12.40 (brs, 1 H, OH), 13.95 (brs, 1 H,
OH) ppm ; 13C NMR (DMSO-d6, 125 MHz): d 12.5, 33.2, 115.7, 121.4, 126.4, 128.9,
129.8, 133.2, 143.6, 147.0, 156.4 ppm; IR (KBr): t 3420 (OꢁH) cmꢁ1; mp
150–151 ꢀC; MS: m=z (%) ¼ 296 (30.2), 174 (91.4).
4,4’-[(2-Hydroxyphenyl)methylene]bis(3-methyl-1-phenyl-pyrazol-5-ol)
(3j). 1H NMR (DMSO-d6, 250 MHz): d 2.28 (s, 6 H), 5.16 (s, 1 H), 6.66–6.75 (m, 2
H), 6.97 (t, 1 H, J ¼ 7.7 Hz), 7.22 (t, 2 H, J ¼ 7.2 Hz), 7.42 (t, 4 H, J ¼ 7.7 Hz), 7.55
(d, 1 H, J ¼ 7.2 Hz), 7.69 (d, 4 H, J ¼ 8.1 Hz) ppm; 13C NMR (DMSO-d6, 63 MHz): d
11.8, 27.3, 104.5, 114.9, 118.6, 120.6, 125.5, 126.9, 128.8, 128.9, 129.3, 137.5, 146.3,

SYNTHESIS OF BIS(PRAZOLYL)METHANES
2253
153.9, 157.5 ppm; IR (KBr): t 3064 (OꢁH) cmꢁ1; mp 230–231 ꢀC; MS: m=z
(%) ¼ 452 (0.2, [Mþ]), 278 (5), 174 (34).
4,4’-[(2-Naphthyl)methylene] bis(3-methyl-1-phenyl-pyrazol-5-ols) (3k).
1H NMR (DMSO-d6, 400 MHz): 2.49 (s, 6 H), 5.29 (s, 1 H), 7.35 (t, 2 H, J ¼ 7.2 Hz),
7.42 (d, 1 H, J ¼ 8.4 Hz), 7.45–7.48 (m, 2 H), 7.50 (t, 4 H, J ¼ 7.6 Hz), 7.73 (d, 4 H,
J ¼ 7.6 Hz), 7.76 (s, 1 H), 7.84–7.88 (m, 3 H) ppm; 13C NMR (DMSO-d6, 100 MHz):
d 11.4, 33.1, 105.5, 122.3, 125.5, 126.1, 126.5, 126.7, 127.5, 127.8, 128.3, 128.4, 129.6,
132.2, 133.3, 135.9, 139.1, 146.5 ppm; IR (KBr): t 3055 (OꢁH) cmꢁ1; mp 194
(dec.)ꢀC. C31H26N4O2: calcd. C, 76.52; H, 5.39; N, 11.51. Found: C, 76.48; H,
5.39; N, 11.49.
4,4’-[(2-Thienyl)methylene] bis(3-methyl-1-phenyl-pyrazol-5-ol) (3 l).
1H NMR (DMSO-d6, 500 MHz): d 2.38 (s, 6 H), 5.11 (s, 1 H), 6.90 (d, 2 H,
J ¼ 8.5 Hz), 7.09–7.48 (m, 7 H), 7.77–7.85 (m, 4 H), 13.56 (brs, 2 H) ppm; 13C
NMR (DMSO-d6, 125 MHz): d 12.5, 33.2, 121.3, 125.0, 125.1, 128.2, 128.6, 131.5,
131.9, 134.2, 139.8, 144.3, 154.9 ppm; IR (KBr): t 3420 (OꢁH) cmꢁ1; mp
190–192 ꢀC; MS: m=z (%) ¼ 268 (100), 174 (71).
4,4’-[(2-Furyl)methylene]bis(3-methyl-1-phenyl-pyrazol-5-ol) (3 m). 1H
NMR (DMSO-d6, 500 MHz): d 2.27 (s, 6 H), 4.95 (s, 1 H), 6.09 (s, 1 H), 6.31 (s, 1
H), 7.20 (t, 2 H, J ¼ 7.4 Hz), 7.39 (t, 4 H, J ¼ 8.0 Hz), 7.47 (s, 1 H), 7.67 (d, 4 H,
J ¼ 8.0 Hz), (brs, 2 H) ppm; 13C NMR (DMSO-d6, 125 MHz): d 12.1, 28.8, 106.7,
110.9, 121.1, 126.2, 129.5, 142.1, 146.5, 154.7 ppm; IR (KBr): t 3430 (OꢁH) cmꢁ1
mp 189–190 ꢀC; MS: m=z (%) ¼ 252 (100), 174 (64).
;
4,4’-[(iso-Propyl)methylene]bis(3-methyl-1-phenyl-pyrazol-5-ol)
(3n).
1H NMR (DMSO-d6, 500 MHz): d 0.84 (d, 6 H, J ¼ 7.9 Hz), 2.21 (s, 6 H),
2.55–2.69 (m, 1 H), 7.40–7.48 (m, 4 H), 7.71–7.43 (m, 4 H), 11.93 (bs, 1 H), 13.64
(bs, 1 H) ppm; IR (KBr): t 3428 (OꢁH) cmꢁ1; mp 210–212 ꢀC; MS: m=z
(%) ¼ 228 (21), 174 (33), 77 (100).
4,4’-[(N-Buthyl)methylene]bis(3-methyl-1-phenyl-pyrazol-5-ol) (3o). 1H
NMR (DMSO-d6, 400 MHz): d 0.85 (t, 3 H, J ¼ 7.2 Hz), 1.16–1.19 (m, 2 H),
1.27–1.32 (m, 2 H), 2.92 (s, 6 H), 2.50 (s, 1 H), 7.33 (t, 2 H, J ¼ 7.2 Hz), 7.49 (t, 4
H, J ¼ 8.0 Hz), 7.68 (d, 4 H, J ¼ 8.0 Hz) ppm;13C NMR (DMSO-d6, 100 MHz): d
10.9, 14.3, 22.4, 28.28, 30.0, 31.7, 106.4, 122.6, 127.9, 129.7, 135.0, 145.7,
158.6 ppm; IR (KBr): t 3420 (OꢁH) cmꢁ1; mp 125–127 ꢀC; MS: m=z (%) ¼ 243
(23.3), 174 (100). C25H28N4O2: calcd. C, 72.09, H, 6.78, N, 13.45. Found: C,
72.12; H, 6.80; N, 13.40.
ACKNOWLEDGMENT
We are thankful to Birjand University Research Council and Persian Gulf
University for their support.

2254
S. SOBHANI ET AL.
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