Synthesis of quinoxaline derivatives using TiO2 nanoparticles as an efficient and recyclable catalyst

Article abstract of DOI:10.5012/bkcs.2011.32.10.3720

TiO₂ nanoparticles were synthesized and characterized by SEM and XRD techniques. The TiO₂ nanoparticles were employed as a recyclable, inexpensive and efficient catalyst for the synthesis of substituted quinoxalines in high to excellent yields and in relatively short duration.

Full text of DOI:10.5012/bkcs.2011.32.10.3720

3720 Bull. Korean Chem. Soc. 2011, Vol. 32, No. 10
Heshmatollah Alinezhad et al.
http://dx.doi.org/10.5012/bkcs.2011.32.10.3720
2
Synthesis of Quinoxaline Derivatives Using TiO Nanoparticles as an
Efficient and Recyclable Catalyst
†
Heshmatollah Alinezhad, Mahmood Tajbakhsh, Fatemeh Salehian, and Pourya Biparva
,‡,*
†
†
§
†
Faculty of Chemistry, University of Mazandaran, Babolsar, Iran
‡
*
Nanotechnology Biotechnology Research Group, University of Mazandaran, Babolsar, Iran. E-mail: heshmat@umz.ac.ir
§
Research Department of Chromatography, Iranian Academic Center for Education, Culture and Research (ACECR),
Urmia Branch, Urmia, Iran
Received August 8, 2011, Accepted August 25, 2011
TiO
were employed as a recyclable, inexpensive and efficient catalyst for the synthesis of substituted quinoxalines
in high to excellent yields and in relatively short duration.
2 2
nanoparticles were synthesized and characterized by SEM and XRD techniques. The TiO nanoparticles
2
Key Words : TiO Nanoparticles, Quinoxalines, o-Phenelendiamines, 1,2-Diketones
Introduction
synthetic strategies have been developed for the preparation
of substituted quinoxalines by condensation of aryl 1,2-
diamines with ketones, α-halo-β-ketoesters, α-hydroxyketones
In recent years, transition metal nanoparticles are used as
efficient catalysts for various synthetic organic transforma-
tions due to their high surface area to volume ratio and
coordination sites which are mainly responsible for their
15-19
and 1,2-diketones.
A number of methods have been
reported for the generating quinoxaline derivatives using
20
3
stoichiometric or catalytic Lewis acids such as Ga(OTf) ,
1,2
catalytic activity.
21
alumina, SBA-Pr-SO
22
23
3 3
H and Bi(OTf) . Different hetero-
Titanium dioxide nanoparticles (nano-TiO
2
) are certainly
2
geneous transition-metal catalysts such as sulfated TiO -
24 25
P25, Ni nanoparticles, Fe
26
nanoparticles, and ZrO
one of the most interesting metal oxides because it has
surface properties which enable organic reactions to occur. It
has been proved to be a good catalyst because of its high
activity, non-toxicity, strong oxidizing power, easy avail-
O
3 4
2
/
27
x y
M O /MCM-41 have been used for this purpose.
Nevertheless, some of these methods suffer from long
reaction time, low product yields, expensive and detrimental
metal precursors for preparation of catalyst, using complex
or poorly available catalyst and harsh reaction conditions
which limit their use.
3-5
ability, reusability, and long term stability. Likewise, nano-
titanium dioxide is a versatile material for various kinds of
industrial applications related to catalysis, photocatalysis for
28
pollutant elimination or organic synthesis, photovoltaics,
As part of our research on chemical transformations, we
here report the preparation of a recyclable and highly
effective homogeneous nanocatalyst TiO for the synthesis
6
sensors, and paints. In order to prepare nanocrystalline TiO
with significant properties, several processes have been
developed over the last decade and can be classified as liquid
2
2
of substituted quinoxalines in high to excellent yields in
dichloroethane at room temperature (Scheme 1).
7 8
process (hydrothermal, sol-gel ), solid state processing
9 10
routes (mechanical alloying/milling, mechanochemical ),
1
1
and other routes such as laser ablation. From the above
methods, the sol-gel method is normally used for preparation
of nanometer TiO powder.
Results and Discussion
2
In this study, we prepared nano-TiO
method using titanium tetra-isopropoxide, deionized water,
ethanol and HNO under ultrasonic irradiation. The X-ray
diffraction pattern (Fig. 1) showed that the diffraction angle
and intensity of the characteristic peaks of the samples are
well consistent with the standard data for the TiO nano-
particle structure. The value of 52 nm was calculated from
XRD data for average particle diameter of this nanocrystal-
2
by the sol-gel
Quinoxaline derivatives have found applications as anti-
bacterial agents possessing a wide range of activities. For
example, echinomycin, leromycin and actinomycin have
proven to be an efficient antibacterial and growth-inhibiting
material. They exhibit a diverse range of biological proper-
3
2
12 13
ties, such as antitumor, cytotoxic, antiviral, anti-inflam-
1
4
matory, and kinase inhibitor properties.
29
Based on the significant applications of quinoxaline
compounds in both medicinal and industrial fields, several
lin TiO
2
using Scherrer’s equation. The nanoparticles
prepared were round in shape, with an average diameter of
Scheme 1. Synthesis of the quinoxaline derivatives using of nano-TiO .

Synthesis of Quinoxaline Derivatives Using TiO
2
Nanoparticles
Bull. Korean Chem. Soc. 2011, Vol. 32, No. 10 3721
Table 1. Formation of 2,3-Diphenylquinoxaline with Different
Catalysts
mol % of
Entry
Catalyst
Time (min) Yield (%)
catalyst
1
2
3
4
5
6
7
8
Nano-TiO
CM-TiO
5
5
15
35
60
45
25
60
25
15
99
90
87
89
89
93
95
99
Nano-ZnO
Nano-ZrO
Nano-SiO
Nano-TiO
Nano-TiO
Nano-TiO
5
5
5
Figure 1. X-ray diffraction pattern of TiO nanoparticles.
1
2
2.5
Reaction conditions: 1,2-phenylenediamine (1.1 equiv), benzyl (1.0
equiv), catalyst (different mol %), DCE, 25 C. Yields refer to isolated
pure products.
Table 2. Effect of the Solvent on the Synthesis of 2,3-Diphenyl-
quinoxaline Using a Catalytic Amount of Nano-TiO
Entry
Solvent
Time (min)
Yield (%)
1
2
3
4
5
DCE
DCM
CH CN
H O
15
90
99
90
90
40
85
120
120
120
EtOH
Reaction conditions: 1,2-phenylenediamine (1.1 mmol), benzil (1.0
mmol), TiO nanoparticles (2.5 mol %), solvent (5.0 mL), 25 °C. Yields
refer to isolated pure products.
Next, we studied the effect of nano-ZnO, nano-ZrO
nano-SiO on the quinoxaline formation (Table 1, entries 3-
). However, their catalytic activities were much lower than
nano-TiO
2
and
2
5
2
.
Figure 2. FE-SEM micrographs of synthesis TiO nanoparticle (a)
We also found that the amount of catalyst had an effective
influence on the reaction course. As shown in Table 1, 2.5
mol % of catalyst gave the best result (Table 1, entries 1 and
6-8).
low magnification, (b) high magnification.
50 nm as measured by field emission-scanning electron
microscopy (FE-SEM; Fig. 2), substantially consistent with
the results estimated from Scherrer’s formula. The results
showed that the sample prepared by this method has a
uniform distribution of spherical particles with no obvious
aggregation.
In order to optimize the protocol, we explored the
influence of different solvents such as DCE, CH
2 2
Cl , EtOH,
H O and CH CN (Table 2). The results clearly showed that
2 3
DCE is the most efficient solvent as the highest yield of 2,3-
diphenylquinoxaline was obtained.
To choose the most appropriate medium in this hetero-
cyclization reaction and to understand the influence of
different variables in this reaction, several components were
studied. We accomplished the reaction under standard
conditions employing o-phenylenediamine (1.1 mmol) and
benzil (1.0 mmol) as a representative model in the presence
of a catalytic amount of different titanium dioxides [com-
To investigate the generality of this method, various 1,2-
diketones were reacted with different substituted o-phenyl-
enediamines (Table 3). In general, all reactions were very
clean and the quinoxaline derivatives were obtained in high
to excellent yields under the optimized reaction conditions.
1
13
All products were characterized by IR, H and C-NMR and
MS spectra, melting point and compared with literature data.
As summarized in Table 3, both electron-rich and elec-
tron-deficient o-phenylenediamines were effective in this
process. When o-phenylenediamines are substituted at the 4-
position with electron-donating (ED) groups, higher rates
and yields are observed than the ones bearing electron-
withdrawing (EW) groups at that position. For example, 4-
nitro-1,2-phenylenediamine afforded the product in 90 min
with 80% yield (entry 4), whereas methyl and methoxy
mercially available bulk TiO
ally sol-gel-prepared TiO nanoparticles (Nano-TiO
room temperature in dichloroethane (DCE) to afford the
corresponding 2,3-diphenylquinoxaline (Table 1, entries 1
and 2). The Nano-TiO was found to be superior to the CM-
TiO in terms of yields and reaction times. Nano-TiO gave
,3-diphenylquinoxaline in excellent yield within 15 min,
while CM-TiO afforded it in longer time (35 min).
2
2
(CM-TiO ), and convention-
2
2
)] at
2
2
2
2
2

3
722 Bull. Korean Chem. Soc. 2011, Vol. 32, No. 10
Table 3. Synthesis of Quinoxaline Derivatives Catalyzed by Nano-TiO
Entry 1,2-Diamine 1,2-Diketone Product
Heshmatollah Alinezhad et al.
mp ( C)
Ref.
Literature)
Time (min) Yield (%)
(
15
1
99 (97)
128-130 (130-131)
20
(15)
2
15
95
114-116 (116-117)
20
3
15
97
160-162 (156-158)
30
4
90
80
188-191 (190-192)
20
5
90
91
137-139 (140-142)
20
6
45
70
168-170 (168-172)
25
7
8
9
30
30
40
95
91
93
240-242 (242-245)
230-232 (233-235)
242-244 (245-246)
23
31
26
1
0
20
25
35
90
91
90
227-229 (228-230)
32
11
220-221
-
12
245-247
-

Synthesis of Quinoxaline Derivatives Using TiO
2
Nanoparticles
Bull. Korean Chem. Soc. 2011, Vol. 32, No. 10 3723
Table 3. Continued
Time
min)
mp ( C)
Entry
1,2-Diamine
1,2-Diketone
Product
Yield (%)
Ref.
(
(Literature)
13
14
15
60
96
147-149 (148-150)
124-126 (125-127)
161-163
33
60
92
33
90
94
33
16
10
97
188-190 (190-191)
26
17
10
92
183-185 (184-185)
26
18
30
99
203-206 (203-204)
31
19
20
21
22
23
20
40
75
15
70
93
93
91
90
90
132-134 (131-132)
114-116 (112-114)
128-130
34
34
-
76-77 (78-79)
26
130-132 (132-134)
26
Reaction conditions: 1,2-phenylenediamine (1.1 mmol), 1,2-diketone (1 mmol), Nano-TiO (2.5 mol %), DCE, 25 C. Products were characterized by
IR, H, C-NMR and mass spectroscopy and melting point. Yields refer to isolated products. Reaction was recorded on 10 mmol scale.

3
724 Bull. Korean Chem. Soc. 2011, Vol. 32, No. 10
Heshmatollah Alinezhad et al.
DRX-400 AVANCE spectrometer in CDCl or DMSO as
Table 4. Comparison of the Catalyst Effects in the Synthesis of 2,3-
Diphenyel-quinoxaline at Room Temperature
3
solvent. Melting points were determined on an electro-
thermal apparatus and were uncorrected. Mass spectra were
obtained on an Agilent technologies instrument and IR
spectra were determined on a Shimadzu instrument. Powder
X-ray diffraction data were obtained using ShimadzuXD-D1
diffractometer using Cu Kα radiation (λ = 1.5418 Å). Nano-
size and morphology of the ZnO nanoparticles were observed
under TESCAN MV2300T/40 Field Emission-Scanning
Electron Microscope (FE-SEM).
mol % of Time
Yield
(%)
Entry
Catalyst
Ref.
catalyst
(min)
1
2
3
4
5
Nano-TiO
TiO -SO
2.5
5
15
5
99
99
98
95
94
-
24
25
26
35
Nano-Ni
10
10
12
10
150
15
Nano-Fe O
Nano-TiO
Synthesis of Nanocatalyst. In a typical process, 5 mL of
titanium tetra-n-butoxide was dissolved in 5 mL anhydrous
alcohol, and ultrasonically dispersed to produce a mixture.
Table 5. Recycling of TiO Nanoparticles
Run No.
1
2
3
4
Meanwhile, 5 mL of water and 1 mL of HNO
added to another 20 mL of absolute ethanol in turn to form
an ethanol-nitric acid-water mixture solution. The Ti(OBu)
OH solution was slowly added dropwise to the ethanol-
3
(65%) were
Time (min)
Yield (%)
15
95
15
92
17
89
17
87
4
-
Yields refer to isolated products.
2 5
C H
nitric acid-water solution under ultrasonic irradiation in a
sonication cell in 15 min to carry out a hydrolysis. Then, a
semitransparent sol was gained after continuously ultrason-
ing for 1 h. Subsequently, the sonication was conducted so
substituted 1,2-phenylenediamines gave the expected quin-
oxaline in 15 min with 95 and 97% yield, respectively
entries 2 and 3). Substituted benzil also reacted smoothly
(
o
that the temperature was raised from 25 to 80 C at the end
with 1,2-phenylenediamines, to give high yielded of the
corresponding quinoxalines (Table 3, entries 13-18).
of the reaction. The obtained precipitates were separated by
filtering, washing for several times with de-ionized water
In order to show the advantages and limitations of this
protocol, we have compared some of our results with those
o
and anhydrous alcohol, drying at 70 C in the air for about
reported in the literature (Table 4). Nano-TiO
catalyst for this reaction in terms of the amount of catalyst
and reaction time in comparison with other catalysts.
Although nano-TiO was previously used as a catalyst for
this reaction (entry 5), but their preparation of nanoparticles
required the use of TiCl which liberates HCl as a toxic
2
is an effective
12 h to produce dry gel powder after grinding. Finally, nano-
TiO
2
was obtained by calcined the dry gel precursor at 480
C for 2 h in air. The TiO nanoparticles were characterized
by FE-SEM and XRD techniques.
Typical Procedure for Synthesis of Quinoxaline Deri-
vatives. Nano-TiO (0.002 g, 2.5 mol %) was added to a
o
2
2
4
2
waste as well as the use of higher amount of catalyst (12
mol %) compared to our method (entry 1).
mixture of o-phenylenediamine (0.124 g, 1.1 mmol) and
benzil (0.21 g, 1 mmol) in 5 mL of DCE and the mixture was
stirred at room temperature. After completion of the reaction
(as monitored by TLC), the catalyst was filtered, washed
with dichloromethane. The solvent was removed under
reduced pressure, and crude product was purified by
recrystallization from ethanol or acetone/water, in some
cases by column chromatography on silica gel with n-
hexane:EtOAC (20:1) as an eluent to afford the pure product
The reusability of the catalyst was investigated. After
completing the model reaction, the catalyst was recovered
by filtration, washed with dichloromethane, and dried at 70
o
C in air. The regenerated catalyst was used for consecutive
runs under the same substrate and reaction conditions. The
recycling results show that the catalyst was still highly
efficient after the fourth run (Table 5).
(yield: 0.28 g (99%)). The product was characterized by IR,
1
13
Conclusion
H, C-NMR and mass spectrums, melting point and com-
pared with literature data. Furthermore, we accomplished
the reaction in large scale synthesis of 2,3-diphenylquino-
xaline with 11 mmol of o-phenylenediamine, 10 mmol of
2
In summary, TiO nanoparticles with diameter of 50 nm
was successfully synthesized via sol-gel method and used as
eco-friendly (non-toxic, recyclable), easily available, inex-
pensive and efficient homogeneous catalyst for the synthesis
of quinoxaline derivatives in high to excellent yields with
relatively short reaction times. The simplicity of operation,
easy work-up procedure, and high yields are some other
advantageous.
2
benzil and 2.5 mol % nano-TiO . Usual work-up and puri-
fication afforded a white solid of 2,3-diphenylquinoxaline at
the same time (2.73 g, 9.70 mmol, 97%).
Some of the selected compounds’ spectroscopic data
2,3-Diphenylquinoxaline. (Table 3, entry 1) IR (KBr):
−
1
1
3051, 1630, 1528, 1348, 772 cm ; H NMR (400 MHz,
CDCl ): δ 8.19-8.23 (m, 2H), 7.78-7.83 (m, 2H), 7.52-7.57
(m, 4H), 7.34-7.41 (m, 6H); C NMR (400 MHz, CDCl
53.49 (C), 141.25 (C), 139.09 (C), 129.98 (CH), 129.85
3
13
Experimental
3
): δ
1
Starting materials used in the reactions were supplied
commercially from Aldrich or Merck Chemical Co. Nuclear
magnetic resonance spectra were recorded on a Bruker
(CH), 129.22 (CH), 128.82 (CH), 128.29 (CH); MS: m/z
+
(EI) 282 (M ), 205, 140, 127, 103, 76, 50.
Acenaphtho[1,2-b]quinoxaline. (Table 3, entry 7) IR

Synthesis of Quinoxaline Derivatives Using TiO
2
Nanoparticles
Bull. Korean Chem. Soc. 2011, Vol. 32, No. 10 3725
(
KBr): 3060, 1640, 1614, 1571, 1480, 1431, 1297, 1205,
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−
1 1
1
8
7
103, 835, 768, 760 cm ; H NMR (400 MHz, CDCl
3
): δ
4
7, 6213.
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.42 (d, 2H, J = 7.2 Hz), 8.21-8.24 (m, 2H), 8.10 (d, 2H, J =
3
13
.2 Hz), 7.84 (t, 2H, J = 7.2 Hz), 7.76-7.79 (m, 2H);
): δ 154.08 (C), 141.26 (C), 136.51
C), 131.80 (C), 130.01 (C), 129.59 (CH), 129.49 (CH),
29.24 (CH), 128.67 (CH), 121.88 (CH); MS: m/z (EI) 254
C
4
NMR (400 MHz, CDCl
3
(
6
. Klyachko, N. L.; Klibanov, A. M. Appl. Biochem. Biotechnol.
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+
M ), 227, 200, 151, 127, 100, 77.
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−
1 1
3
035, 1608, 1501, 1356, 1039, 770, 748 cm ; H NMR (400
): δ 9.39 (dd, 2H, J = 6.4, J = 1.6 Hz), 8.55 (d,
H, J = 7.6 Hz), 8.32-8.35 (m, 2H), 7.85-7.88 (m, 2H), 7.79-
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3
2
1
3
9. (a) Kim, D. H.; Hong, H. S.; Kim, S. J.; Song, J. S.; Lee, K. S. J.
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7
.82 (m, 2H), 7.73-7.77 (m, 2H); C NMR (400 MHz,
CDCl ): δ 142.41 (C), 142.16 (C), 132.02 (C), 130.28 (CH),
29.73 (CH), 129.44 (CH), 127.91 (CH), 126.25 (CH),
3
1
10. (a) Guimaraes, J. L. Abbate, M.; Betim, S. B.; Alves, M. C. M. J.
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Sci. 2000, 463, L609.
+
22.89 (CH); MS: m/z (EI) 280 (M ), 253, 225, 176, 140, 50.
1
1
1-Methyl-dibenzo[a,c]phenazine. (Table 3, entry 11) IR
−
1
1
11. Matsubara, M.; Yamaki, T.; Itoh, H.; Abe, H.; Asai, K. Jpn. J.
Appl. Phys. 2003, 42, (5A Pt 2) L479.
(
KBr): 3065, 1623, 1503, 1361, 755, 709 cm ; H NMR
400 MHz, CDCl ): δ 9.35-9.38 (m, 2H), 8.53 (d, 2H, J = 8
Hz), 8.19 (d, 1H, J = 7.2 Hz), 8.19 (d, 1H, J= 8.4 Hz), 8.07
s, 1H), 7.76-7.79 (m, 2H), 7.71-7.75 (m, 2H), 7.65-7.68 (m,
(
3
1
2. Corona, P.; Carta, A.; Loriga, M.; Vitale, G.; Paglietti, G. Eur. J.
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(
13
1
H), 2.68 (s, 3H); C NMR (400 MHz, CDCl
C), 142.14 (C), 141.62 (C), 140.69 (C), 140.35 (C), 132.38
CH), 131.96 (C), 131.77 (C), 130.35 (C), 130.31 (C),
30.12 (CH), 129.99 (CH), 22.08 (CH ); MS: m/z (EI) 294
3
): δ 142.19
1
(
1
(
7
1
3
+
(
M ), 240, 190, 147, 90.
Dibenzo[a,c]phenazine-11-yl-phenyl-methanone. (Table
, entry 12) IR (KBr): 3068, 1656, 1601, 1328, 1257, 749,
1
1
2
3
7
7
7
7
−
1 1
00 cm ; H NMR (400 MHz, CDCl
.6 Hz), 9.37 (d, 1H, J = 8 Hz), 8.71 (s, 1H), 8.59 (d, 2H, J =
.6 Hz), 8.35-8.47 (m, 2H), 7.99 (d, 2H, J = 7.2 Hz), 7.63-
3
): δ 9.45 (d, 1H, J =
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49, 7386.
13
.88 (m, 5H), 7.59 (t, 2H, J = 7.2 Hz); C NMR (400 MHz,
): δ 195.90 (C), 143.72 (C), 141.06 (C), 137.97 (C),
37.37 (C), 132.93 (CH), 132.86 (CH), 132.63 (C), 132.21
C), 131.04 (CH), 130.80 (CH), 130.23 (CH), 129.93 (CH),
2
1. Mohsenzadeh, F.; Aghapoor, K.; Darabi, H. R. J. Braz. Chem.
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3
1
2
2. Mohammadi Ziarani, Gh.; Badiei, A.; Haddadpour, M. International
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(
1
29.45 (CH), 128.59 (CH), 128.16 (CH), 126.74 (CH),
23. Yadav, J. S.; Reddy, B. V. S.; Premalatha, K.; Shankar, K. S.
Synthesis 2008, 3787.
126.39 (CH), 123.05 (CH), 123.03 (CH); MS: m/z (EI) 384
+
24. Krishnakumar, B.; Velmurugan, R.; Jothivel, S.; Swaminathan, M.
Catal. Commun. 2010, 11, 997.
(
M ), 307, 279, 227, 201, 175, 151, 105, 77.
,3-Bis(4-bromophenyl)quinoxaline. (Table 3, entry 16)
IR (KBr): 3049, 1587, 1540, 1485, 1394, 1340, 1066, 829,
2
2
5. Kumar, A.; Kumar, S.; Saxena, A.; De, A.; Mozumdar, S. Catal.
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84.
−1 1
7
60 cm ; H NMR (400 MHz, CDCl
3
): δ 8.16-8.20 (m, 2H),
2
7
.80-7.84 (m, 2H), 7.52-7.55 (m, 4H), 7.41-7.44 (m, 4H);
13
C NMR (400 MHz, CDCl
3
): δ 151.9, 141.3, 137.7, 131.7,
1
1
31.4,130.4, 129.2, 123.7; MS: m/z (EI) 440 (M+2), 438
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Acknowledgments. Financial support of this work from
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Wang, Y.; Lindsley, C. W. Tetrahedron Lett. 2004, 45, 4873.
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