Green and efficient synthesis of novel bispyrazoles through a tandem Knoevenagel and Michael type reaction using nanowire zinc oxide as a powerful and recyclable catalyst

Article abstract of DOI:10.3906/kim-1404-54

Zinc oxide nanowires (ZnO NWs) were prepared and characterized by scanning electron microscopy, powder X-ray diffraction, and transmission electron microscopy analyses. ZnO NWs were then employed as heterogeneous and recyclable catalyst for green synthesi

Full text of DOI:10.3906/kim-1404-54

Turk J Chem
2015) 39: 1069 – 1077
Turkish Journal of Chemistry
(
http://journals.tubitak.gov.tr/chem/
¨
˙
⃝
c TUBITAK
Research Article
doi:10.3906/kim-1404-54
Green and efficient synthesis of novel bispyrazoles through a tandem Knoevenagel
and Michael type reaction using nanowire zinc oxide as a powerful and recyclable
catalyst
∗
Khalil ESKANDARI, Bahador KARAMI , Saeed KHODABAKHSHI, Seyyed Jafar HOSEINI
Department of Chemistry, Yasouj University, Yasouj, Iran
Received: 17.04.2014
•
Accepted/Published Online: 10.08.2014
•
Printed: 30.10.2015
Abstract: Zinc oxide nanowires (ZnO NWs) were prepared and characterized by scanning electron microscopy, powder
X-ray diffraction, and transmission electron microscopy analyses. ZnO NWs were then employed as heterogeneous and
recyclable catalyst for green synthesis of some new and known bispyrazole derivatives through a tandem Knoevenagel
and Michael type addition reaction of aromatic aldehyde and pyrazolone. The synthetic method is operationally simple
and affords product with high yields in short reaction times.
Key words: Zinc oxide nanowire, bispyrazole, aldehyde, green synthesis, nanocatalyst
1
. Introduction
The discovery of new synthetic strategies to facilitate the efficient and green preparation of organic compounds
is a vital issue of research in modern organic chemistry.1
−3
During the past decade, many attempts have been
made to approach this aim,4 which frequently focused on the preparation of organic compounds via one-pot
multicomponent reactions.8,9 Among the categories of nanoscience, nanocatalysis has an important part that
has recently gained much attention from chemists. Nanocatalysts have distinguishing features compared to the
bulk ones. For example, nanosized systems dramatically increase the contact between reactants and catalysts.10
Among safe and environmentally friendly nanomaterials, ZnO nanomaterials have emerged as safe and efficient
−7
catalysts in organic reactions.1
effective way to prevent waste production in chemical reactions.1
Pharmaceutically, pyrazoles are small di-aza heterocyclic compounds that have a wide domain of approved
1−13
Replacement of toxic organic solvents by safe and clean ones is another
4−16
biological activity, such as antianxiety, antipyretic, analgesic, and anti-inflammatory properties.1
7−20
In regard
to this background, synthesis of pyrazole derivatives has attracted considerable interest among some organic and
pharmaceutical chemists. So far, several synthetic routes to bispyrazoles have been presented in the literature. In
recent studies, some research groups focused on catalyzed synthesis of bispyrazoles in which aromatic aldehydes
condense with pyrazolones in various conditions.2
1−30
Despite the significant synthetic potential and ecological
advantages, some of the present methods suffer from drawbacks including long reaction times, low product yield,
and use of extra tools and unrecyclable catalysts. Above all, herein, we wish to report a convenient, green,
′
and efficient approach to 4,4 -(arylmethylene)bis(1H -pyrazol-5-ol)s syntheses using recyclable ZnO nanowires
in aqueous media.
∗
Correspondence: karami@mail.yu.ac.ir
1
069

ESKANDARI et al./Turk J Chem
2
. Results and discussion
ZnO nanowire was synthesized and characterized by X-ray diffraction (XRD) pattern and scanning electron
microscopy (SEM). The morphology of the ZnO nanowires was studied by scanning electron microscopy (SEM).
Figure 1 shows the typical SEM image of ZnO nanowires synthesized by the solvothermal method. The ZnO
nanowires have a diameter of about 20 nm and a length of a few micrometers.
The XRD spectrum of the ZnO nanowires is shown in Figure 2. ZnO nanowires exhibited prominent
100), (002), and (101) peaks corresponding to a ZnO wurtzite structure.31
(
Figure 1.
Scanning electron microscopy of ZnO
Figure 2. X-ray diffraction spectra of ZnO nanowires.
nanowires.
Furthermore, transmission electron microscopy (TEM) analysis was performed for detailed characteriza-
tion of the ZnO NWs’ structure (Figure 3). The TEM image reveals that the ZnO nanowire has a homogeneous
diameter size of about 20 nm that does not vary significantly along the wire length.
Figure 3. TEM image of the ZnO nanowires grown by solvothermal synthesis method.
1070

ESKANDARI et al./Turk J Chem
In continuation of our previous studies on development of green synthetic methodologies for the prepa-
ration of organic compounds,3
2−35
herein we report a new green condition for the synthesis of some novel and
′
known 4,4 -(arylmethylene)bis(1H -pyrazol-5-ol) 3 from the condensation reaction of aromatic aldehydes 1 with
pyrazolone 2 in the presence of catalytic amounts of ZnO NWs (Scheme 1).
To optimize the reaction conditions, the treatment of benzaldehyde 1a with 2 was selected as a model
(
Scheme 2).
Scheme 1. Synthesis of bispyrazoles by employing ZnO NWs.
Scheme 2. The model reaction to optimize the conditions.
From the perspective of green chemistry, an equal mixture of H2 O/EtOH (1:1) was used as the reaction
medium. It should be noted that reaction progress in absolute water and/or absolute ethanol was not better
than that of the mixture of these solvents. From the different ratios of H2 O/EtOH mixtures, H2 O/EtOH (1:1)
mixture was considered the most effective ratio. Initially, the model reaction was established under reflux in an
equal mixture of H2 O/EtOH (1:1) in the presence of various amounts of ZnO NWs. This reaction was firstly
examined in the absence of catalyst that did not show any appreciable progress even after 120 min. Upon
screening, the results clearly showed that the reaction proceeded efficiently when 2 mol% of ZnO NWs were
added. Moreover, increasing the catalyst amount did not improve the results (Figure 4).
The reaction was also established at room temperature in an equal mixture of H2 O/EtOH (1:1) in
the presence of ZnO NWs (2 mol%); however, the results showed that at room temperature no reaction took
place even after 120 min. Afterwards, the feasibility of the reaction was further studied with various aromatic
aldehydes under optimized conditions, which successfully led to products with high yields in short reaction
times. The results are listed in Table 1.
1
071

ESKANDARI et al./Turk J Chem
Figure 4. The effect of catalyst amount on synthesis of compound 3a. Reaction time: 20 min.
Table 1. Synthesis of bispyrazoles 3 using ZnO NWs (2 mol%).
a
◦
Entry Ar
Time (min)
Yield (%) Mp ( C)/(Reported)
3
3
3
a
b
c
C6H5
20
20
30
90
88
86
162–164 (171–172) 21
190–192 (-)
2,4-(OMe)2-C6H3
3-OEt-4-OH-C6H3
212–213 (-)
3
3
d
e
30
15
90
90
228–230 (-)
218–220 (-)
3f
30
85
242–244 (-)
3
3
3
3
3
3
g
h
i
2,4-(Cl)2-C6H3
3-NO2-C6H5
4-NO2-C6H5
4-Me-C6H5
2-Cl-C6H5
20
15
15
30
15
20
30
86
90
90
88
90
84
90
228–230 (227–229) 21
161–163 (151–153) 21
226–228 (225–227) 21
203–205 (202–204) 21
238–240 (235–237) 21
165–167 (176–177) 21
174–176 (173–175) 21
j
k
l
4-MeO-C6H5
3-Br-C6H5
3
m
a
Isolated yields.
As can be seen from Table 1, the nature of the substituents on the aromatic ring showed no important
effects in terms of reaction time or product yields under the optimized conditions mentioned above. In fact, the
aromatic aldehyde bearing both electron donating/withdrawing groups reacted well with compound 2. When
the aliphatic aldehydes were replaced, however, the reactions were unsuccessful. It seems that the problem in
the case of aliphatic ones is likely to be enolyzed.
In the final study, the recyclability of the ZnO NWs was investigated upon the synthesis of model
compound 3a. In this case, after being recovered, the catalyst was reused for the next reaction and it was
1072

ESKANDARI et al./Turk J Chem
observed that the system did not show an apparent loss in catalytic activity of the ZnO NWs during 4 cycles
(
Figure 5).
Figure 5. Recyclability of the catalyst. Reaction time: 20 min.
To compare the present method with ones previously reported in the literature, Table 2 provides brief
data. According to the results summarized in Table 2, the merits of the presented method are confirmable due
to its efficiency in the generation of desired compounds in higher yield and shorter reaction time than the other
ones.
Table 2. Comparison of present work with other methods reported in the literature for synthesis of 3a.
Entry Conditions
Time (min) Yield (%) [Lit.]
a
21
1
2
3
5
4
6
7
SBSSA (0.1 g), EtOH, Reflux
SASPSPE (0.1 g), EtOH, Reflux
Cellulose sulfuric acid (0.2 g), H2O/EtOH, Reflux 120
Electrolysis, EtOH, NaBr (0.1 g), 20 C
120
180
80
90
74
82
86
b
22
2
3
◦
24
25
33
60
60
20
c
4
◦
[Dsim]AlCl (1 mol%), 50 C
Sodium dodecyl sulfate (5 mol%), H O, Reflux
2
86.8 26
90d
ZnO NWs (2 mol%), H2O/EtOH, Reflux
a
b
c
Silica-bonded S-sulfonic acid. Sulfuric acid ([3-(3-silicapropyl)sulfanyl]propyl)ester. 1,3-disulfonic acid imidazolium
d
tetrachloroaluminate. Present work.
A sequence of reactions such as Knoevenagel condensation followed by Michael type addition takes place
during the formation of the product 3. The proposed mechanism for the ZnO catalyzed synthesis of bispyrazols
3
is depicted in Scheme 3. In the first step, the reaction undergoes the Knoevenagel condensation between
aldehyde 1 and pyrazolone 2 to generate α, β -unsaturated adduct. Subsequent 1,4-addition of 2 on α, β -
unsaturated adduct followed by [1,3]-sigmatropic proton shift led to the formation of the target molecule 3.
In conclusion, we have demonstrated the efficiency of ZnO NWs as heterogeneous catalyst for the
condensation reaction between aromatic aldehyde and 3-methyl-1-phenyl-5-pyrazolone in a molar ratio of 1:2,
respectively. The major advantages of the present method are its excellent yields, short reaction times, simple
experimental procedure, and low catalyst loading, and the recyclability of the ZnO NWs, which make this
method more attractive and in accordance with sustainable chemistry.
1
073

ESKANDARI et al./Turk J Chem
Scheme 3. A plausible reaction mechanism for ZnO catalyzed synthesis of 3.
3
. Experimental
Chemicals were purchased from Merck and Aldrich chemical companies. SEM studies of the nanostructures
were carried out with a JEOL JEM 3010 instrument operating at an accelerating voltage of 300 kV. XRD (D8 ,
Advance, Bruker, AXS) patterns were obtained for characterization of the heterogeneous catalyst. TEM study
of the nanostructures was carried out with a JEOL JEM 3010 instrument operating at an accelerating voltage
of 300 kV. Melting points were measured on an electro thermal KSB1N apparatus. IR spectra were recorded
in the matrix of KBr with a JASCO FT-IR-680 plus spectrometer. H NMR and 13 C NMR spectra were
recorded on a FT-NMR Bruker AVANCE UltraShield Spectrometer at 300.13 (400.13 and 250.13 MHz for a few
products) and 76.46 MHz (100.62 and 62.6 MHz for a few products), respectively, in DMSO-d6 as the solvent in
the presence of tetra methyl silane as the internal standard. TLC was performed on TLC-grade silica gel-G/UV
1
254 nm plates. All of the products were isolated, purified, and deduced from their elemental analyses (C, H,
N), IR, 1 H NMR, and 13 C NMR spectral data.
3
.1. Preparation of ZnO NWs
ZnO nanowires were obtained by a slight modification of the method reported in the literature.36,37 First 0.315
g (1.43 mmol) of zinc acetate dihydrate [Zn(OAc)2 .2H2 O] was dissolved in 66 mL of ethanol and then 1.67 g
(
41 mmol) of NaOH was added followed by stirring for 1.5 h to make it dissolve at room temperature. The
◦
resulting cloudy solution was sealed in a 70 mL Teflon-lined stainless-steel autoclave and heated at 120 C for
2
4 h. The autoclave was then allowed to cool down to room temperature. White precipitate was collected by
074
1

ESKANDARI et al./Turk J Chem
centrifugation and washed with water and ethanol several times until the washing solution was free of NaOH.
The average diameter of the ZnO nanowires is ∼20 nm with lengths going up to a few micrometers.
′
3
.2. Synthesis of 4,4 -(arylmethylene)bis(1H-pyrazol-5-ol) using ZnO NWs
A solution of the aromatic aldehyde 1 (1 mmol), the pyrazolone 2 (2 mmol), and ZnO NWs (2 mol%) in
EtOH/H2 O (1:1, 10 mL) was stirred under reflux for a stipulated time. The progress of the reaction was
checked by TLC. After completion, the reaction mixture was cooled to room temperature and solvent was
evaporated under reduced pressure. The precipitate was dried and dissolved in hot EtOH to separate the
catalyst. The product 3 was obtained after recrystallization from EtOH and no further purification was needed.
3
.3. Representative spectral data
′
4
,4 -(Phenylmethylene)bis(3-methyl-1-phenyl-1H-pyrazol-5-ol) (3a): Light yellow crystals; FT-IR (KBr) ( υ¯ max ,
cm 1): 3424 (OH), 3062 (sp2 C–H), 2917 (sp3 C–H), 1598 (C=N), 1498 (C=C), 1284 (Ar–O), 755, 692
monosub. Ph); 1 H NMR (400.13 MHz, DMSO-d6) δ (ppm): 13.96 (s, 1H, OH), 12.39 (s, 1H, OH), 7.71 (d,
J = 8.4 Hz, 4H, aromatic CH), 7.45 (t, J = 8.4 Hz, 4H, aromatic CH), 7.31–7.24 (m, 6H, aromatic CH),
.20–7.17 (m, 1H, aromatic CH), 5.00 (s, 1H, CH), 2.33 (s, 6H, 2CH3); 13 C NMR (100.62 MHz, DMSO-d6) δ
ppm): 157.6, 146.4, 140.7, 136.9, 128.8, 128.3, 127.1, 126.4, 126.2, 121.3, 105.7, 33.6, 11.5; Anal. calcd. for
−
(
7
(
C27 H24 N4 O2 : C, 74.29; H, 5.54; N, 12.84; found: C, 74.31; H, 5.50; N, 12.82%.
′
4
,4 -((2,4-Dimethoxyphenyl)methylene)bis(3-methyl-1-phenyl-1H-pyrazol-5-ol) (3b): Yellow crystals; FT-
IR (KBr) ( υ¯ max , cm 1): 3428 (OH), 2996 (sp2 C–H), 2958 (sp3 C–H), 1613 (C=N), 1503, 1460 (C=C), 1294,
−
1
1
209 (Ar–O), 1122, 1041 (C–O); 1 H NMR (300.13 MHz, DMSO-d6) δ (ppm): 14.35 (s, 1H, OH), 12.38 (s,
H, OH), 7.69 (d, J = 7.8 Hz, 4H, aromatic CH), 7.50–7.39 (m, 5H, aromatic CH), 7.22 (t, J = 7.2 Hz, 2H,
aromatic CH), 6.46 (t, J = 8.4 Hz, 2H, aromatic CH), 5.09 (s, 1H, CH), 3.79 (s, 3H, OCH3), 3.69 (s, 3H,
OCH3), 2.26 (s, 6H, 2CH3); 13 C NMR (76.46 MHz, DMSO-d6) δ (ppm): 158.8, 156.7, 146.1, 137.6, 137.4,
137.3, 137.1, 136.7, 133.6, 131.9, 128.8, 125.4, 122.9, 120.5, 104.1, 98.2, 55.4, 55.0, 26.9, 11.6; Anal. calcd. for
C29 H28 N4 O4 : C, 70.15; H, 5.68; N, 11.28; found: C, 70.22; H, 5.62; N, 11.25%.
′
4
,4 -((3-Ethoxy-4-hydroxyphenyl)methylene)bis(3-methyl-1-phenyl-1H-pyrazol-5-ol) (3c): Chocolate crys-
−
1
2
3
tals; FT-IR (KBr) ( υ¯ max , cm ): 3420, 3219 (OH), 2985 (sp C–H), 2927 (sp C–H), 1596 (C=N), 1498 (C=C),
275, 1214 (Ar–O), 1126, 1043 (C–O); 1 H NMR (300.13 MHz, DMSO-d6) δ (ppm): 13.97 (s, 1H, OH), 12.36
s, 1H, OH), 8.67 (s, 1H, OH), 7.69 (d, J = 8.1 Hz, 4H, aromatic CH), 7.42 (t, J = 7.8 Hz, 4H, aromatic CH),
1
(
7
3
.22 (t, J = 7.2 Hz, 2H, aromatic CH), 6.82 (s, 1H, aromatic CH), 6.66 (s, 2H, aromatic CH) 4.82 (s, 1H, CH),
1
3
.90 (q, J = 6.9 Hz, 2H, CH2), 2.29 (s, 6H, 2CH3), 1.25 (t,J = 6.9 Hz, 3H, CH3).
C NMR (76.46 MHz,
DMSO-d6) δ (ppm): 146.1, 145.1, 142.6, 137.3, 137.0, 133.1, 131.6, 128.9, 125.5, 120.5, 119.7, 115.2, 113.4,
63.9, 32.7, 14.7, 11.6; Anal. calcd. for C29 H28 N4 O4 : C, 70.15; H, 5.68; N, 11.28; found: C, 70.19; H, 5.57; N,
11.26%.
′
4
,4 -(Naphthalen-1-ylmethylene)bis(3-methyl-1-phenyl-1H-pyrazol-5-ol) (3d): Navajo white crystals; FT-
IR (KBr) ( υ¯ max , cm 1): 3419 (OH), 3062 (sp2 C–H), 2922 (sp3 C–H), 1608 (C=N), 1542, 1497 (C=C), 1132
−
(
Ar–O); 1 H NMR (300.13 MHz, DMSO-d6) δ (ppm): 13.15 (s, 1H, OH), 12.19 (s, 1H, OH), 8.00–7.90 (m, 2H,
aromatic CH), 7.81–7.70 (m, 6H, aromatic CH), 7.53–7.41 (m, 7H, aromatic CH), 7.15–7.25 (m, 2H, aromatic
CH), 5.61 (s, 1H, CH), 2.25 (s, 6H, 2CH3); 13 C NMR (76.46 MHz, DMSO-d6) δ (ppm): 146.0, 144.1, 140.6,
1
075

ESKANDARI et al./Turk J Chem
137.3, 136.7, 133.6, 130.7, 128.8, 128.7, 127.0, 125.9, 125.7, 125.3, 125.2, 123.5, 119.9, 105.6, 30.9, 11.9, 11.8;
Anal. calcd. for C31 H26 N4 O2 : C, 76.52; H, 5.39; N, 11.51; found: C, 76.57; H, 5.33; N, 11.48%.
′
4
,4 -([1,1’-biphenyl]-4-ylmethylene)bis(3-methyl-1-phenyl-1H-pyrazol-5-ol) (3e): Navajo white crystals;
−
FT-IR (KBr) ( υ¯ max , cm 1): 3444 (OH), 3026 (sp2 C–H), 2922 (sp3 C–H), 1599 (C=N), 1580, 1499 (C=C),
1
1
294 (Ar–O), 818 (para-disub. Ph); 1 H NMR (300.13 MHz, DMSO-d6) δ (ppm): 14.05 (s, 1H, OH), 12.48 (s,
H, OH), 7.74 (d, J = 7.8 Hz, 4H, aromatic CH), 7.62–7.55 (m, 4H, aromatic CH), 7.46–7.34 (m, 9H, aromatic
CH), 7.23 (t, J = 7.2 Hz, 2H, aromatic CH), 5.01 (s, 1H, CH), 2.35 (s, 6H, 2CH3); 13 C NMR (76.46 MHz,
DMSO-d6) δ (ppm): 146.3, 141.5, 140.0, 137.9, 137.4, 137.3, 128.9, 128.8, 127.8, 127.1, 126.5, 125.5, 120.5,
104.9, 104.6, 32.8, 11.6; Anal. calcd. for C33 H28 N4 O2 : C, 77.32; H, 5.51; N, 10.93; found: C, 77.38; H, 5.43;
N, 10.84%.
′
4
,4 -((1H-indol-3-yl)methylene)bis(3-methyl-1-phenyl-1H-pyrazol-5-ol) (3f): Yellow crystals; mp: 242–
44 C; FT-IR (KBr) ( υ¯ max , cm ): 3470 (OH, NH), 3042 (sp2 C–H), 2920 (sp3 C–H), 1618 (C=N), 1540,
488 (C=C), 1136 (Ar–O); 1 H NMR (400.13 MHz, DMSO-d6) δ (ppm): 12.65 (s, 2H, 2OH), 9.85 (s, 1H, NH),
.13–8.11 (m, 2H, aromatic CH), 8.06 (s, 1H, aromatic CH), 8.05–8.01 (m, 3H, aromatic CH), 7.60–7.58 (m,
H, aromatic CH), 7.42 (t,J = 7.6 Hz, 4H, aromatic CH), 7.32–7.29 (m, 3H, aromatic CH), 7.15 (t,J = 7.6 Hz,
H, aromatic CH), 3.49 (s, 1H, CH), 2.39 (s, 6H, 2CH3); 13 C NMR (100.62 MHz, DMSO-d6) δ (ppm): 162.7,
50.8, 138.9, 138.2, 136.9, 136.4, 128.6, 128.1, 123.8, 123.4, 122.0, 118.5, 118.0, 112.8, 112.2, 18.5, 12.9; Anal.
◦
−1
2
1
8
1
1
1
calcd. for C29 H25 N5 O2 : C, 73.25; H, 5.30; N, 14.73; found: C, 73.31; H, 5.23; N, 14.66%.
′
4
,4 -((2,4-Dichlorophenyl)methylene)bis(3-methyl-1-phenyl-1H-pyrazol-5-ol) (3g): Bisque crystals, mp:
28–229 C; FT-IR (KBr) ( υ¯ max , cm ): 3420 (OH), 3057 (sp2 C–H), 2920 (sp3 C–H), 1597 (C=N), 1572,
◦
−1
2
1
500, 1470 (C=C), 1189 (Ar–O); 1 H NMR (250.13 MHz, DMSO-d6) δ (ppm): 13.95 (s, 1H, OH), 12.67 (s, 1H,
OH), 7.72–7.65 (m, 5H, aromatic CH), 7.53 (d, J = 2.0 Hz, 1H, aromatic CH), 7.44–7.36 (m, 5H, aromatic
CH), 7.22 (t, J = 7.2 Hz, 2H, aromatic CH), 5.05 (s, 1H, CH), 2.26 (s, 6H, 2CH3); 13 C NMR (62.89 MHz,
DMSO-d6) δ (ppm): 148.3, 147.1, 146.0, 137.3, 134.9, 128.8, 125.4, 120.5, 119.2, 111.6, 111.5, 104.9, 104.6,
31.7, 11.6; Anal. calcd. for C27 H22 Cl2 N4 O2 : C, 64.17; H, 4.39; N, 11.09; found: C, 64.20; H, 4.30; N, 10.98%.
Acknowledgment
The authors are grateful to the Iranian Nanotechnology Initiative Council for its financial support.
References
1
2
3
4
5
6
7
8
9
.
.
.
.
.
.
.
.
.
Okandeji, B. O.; Sello, J. K. J. Org. Chem. 2009, 74, 5067–5070.
Ruijter, E.; Scheffelaar, R.; Orru, R. V. A. Angew. Chem., Int. Ed. 2011, 50, 6234–6246.
Born, D. V.; Herscheid, J. K. D. M.; Orru, R. V. A.; Vugts, D. J. Chem. Commun. 2013, 49, 4018–4020.
Silveira, C. C.; Boeck, P.; Braga, A. L. Tetrahedron Lett. 2000, 41, 1867–1869.
Silveira, C. C.; Mendes, S. R.; Martins, G. M.; Schlosser, S. C.; Kaufman, T. S. Tetrahedron 2013, 69, 9076–9085.
Habibi, A.; Eskandari, K.; Alizadeh, A. Phosphorus Sulfur Silicon Relat. Elem. 2012, 187, 1109–1117.
Karami, B.; Eskandari, K.; Azizi, M. Lett. Org. Chem. 2013, 10, 722–732.
Okandeji, B. O.; Gordon, J. R.; Sello, J. K. J. Org. Chem. 2008, 73, 5595–5597.
Ruijter, E.; Orru, R. V. A. Drug Discovery Today: Technol. 2013, 10, 15–20.
1
0. Polshettiwar, V.; Varma, R. S. Green Chem. 2010, 12, 743–754.
1076

ESKANDARI et al./Turk J Chem
1
1
1
1
1
1
1
1
1
1. Bhattacharyya, P.; Pradhan, K.; Paul, S.; Das, A. R. Tetrahedron Lett. 2012, 53, 4687–4691.
2. Karami, B.; Eskandari, K.; Khodabakhshi, S.; Hoseini, S. J.; Hashemian, F. RSC Adv. 2013, 3, 23335–23342.
3. Ghosh, P. P.; Dasach, A. R. J. Org. Chem. 2013, 78, 6170–6181.
4. Gu, Y. Green Chem. 2012, 14, 2091–2128.
5. Chanda, A.; Fokin, V. V. Chem. Rev. 2009, 109, 725–748.
6. Karami, B.; Hoseini, S. J.; Eskandari, K. Ghasemi, A. Nasrabadi, H. Catal. Sci. Technol. 2012, 2, 331–338.
7. Sugiura, S.; Ohno, S.; Ohtani, O.; Izumi, K.; Kitamikado, T.; Asai, H.; Kato, K. J. Med. Chem. 1977, 20, 80.
8. Rosiere, C. E.; Grossman, M. I. Science 1951, 113, 651–651.
9. Bailey, D. M.; Hansen, P. E.; Hlavac, A. G.; Baizman, E. R.; Pearl, J.; Defelice, A. F.; Feigenson, M. E. J. Med.
Chem. 1985, 28, 256–260.
2
0. Chauhan, P. M. S.; Singh, S.; Chatterjee, R. K. Ind. J. Chem. Sect. B: Org. Chem. Incl. Med. Chem. 1993, 32,
8
58–861.
2
2
2
2
2
1. Niknam, K.; Saberi, D.; Sadegheyan, M.; Deris, A. Tetrahedron Lett. 2010, 51, 692–694.
2. Tayebi, S.; Baghernejad, M.; Saberi, D.; Niknam, K. Chin. J. Catal. 2011, 32, 1477–1483.
3. Mosaddegh, E.; Hassankhani, A.; Baghizadeh, A. J. Chil. Chem. Soc. 2010, 55, 419–420.
4. Elinson, M. N.; Dorofeev, A. S.; Nasybullin, R. F.; Nikishin, G. I. Synthesis 2008, 12, 1933–1937.
5. Khazaei, A.; Zolfigol, M. A.; Moosavi-Zare, A. R.; Asgari, Z.; Shekouhy, M.; Zare, A.; Hasaninejad, A. RSC Adv.
2
012, 2, 8010–8013.
2
2
6. Wang, W.; Wang, S. X.; Qin, X. Y.; Li, J. T. Synth. Commun. 2005, 35. 1263–1269.
7. Sujatha, K.; Shanthi, G.; Selvam, N. P.; Manoharan, S.; Perumal, P. T.; Rajendran, M. Bioorg. Med. Chem. Lett.
2
009, 19, 4501–4503.
8. Hasaninejad, A.; Shekouhy, M.; Zare, A.; Hoseini-Ghattali, S. M. S.; Golzar, N. J. Iran. Chem. Soc. 2011, 8,
11–423.
2
4
2
3
3
3
3
3
3
3
3
9. Gouda, M. A.; Abu-Hashem, A. A. Green Chem. Lett. Rev. 2012, 5, 203–209.
0. Eynde, J. J. V.; Mutonkole, K.; Haverbeke, Y. V. Ultrason. Sonochem. 2001, 8, 35–39.
1. Zervos, M.; Karipi, C.; Othonos, A. Nanoscale Res. Lett. 2012, 7, 175–182.
2. Karami, B.; Eskandari, K.; Khodabakhshi, S. Arkivoc 2012, 9, 76–84.
3. Karami, B.; Eskandari, K.; Ghasemi, A. Turk. J. Chem. 2012, 36, 601–613.
4. Karami, B.; Eskandari, K.; Gholipour, S.; Jamshidi, M. Org. Prep. Proced. Int. 2013, 45, 220–226.
5. Eskandari, K.; Karami, B.; Khodabakhshi, S. Catal. Commun. 2014, 54, 124–130.
6. Cao, H. L.; Qian, X. F.; Gong, Q. W.; Du, M.; Ma, X. D.; Zhu, Z. K. Nanotechnol. 2006, 17, 3632–3636.
7. Gomathi, A.; Hoseini, S. J.; Rao, C. N. R. J. Mater. Chem. 2009, 19, 988–995.
1
077