ZrOCl2.8H2O in water: An efficient catalyst for rapid one-pot synthesis of pyridopyrazines, pyrazines and 2,3-disubstituted quinoxalines

Article abstract of DOI:10.1016/j.crci.2013.02.018

Zirconium(IV) oxide chloride was found to be a rapid and efficient catalyst for the synthesis of pyrazines and 2,3-disubstituted quinoxalines in water. A variety of pyridopyrazine and 2,3-disubstituted quinoxaline derivatives are readily prepared in high yields under green conditions by cyclocondensation of the desired 1,2-diamine and 1,2-diketone using a catalytic amount of zirconium(IV) oxide chloride in water. Less active diamines, such as 2,3- and 3,4-diaminopyridines took part in this protocol to provide the desired products in good to excellent yields.

Full text of DOI:10.1016/j.crci.2013.02.018

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CRAS2C-3724; No. of Pages 6
C. R. Chimie xxx (2013) xxx–xxx
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Full paper/Memoire
ZrOCl2Á8H2O in water: An efficient catalyst for rapid one-pot synthesis of
pyridopyrazines, pyrazines and 2,3-disubstituted quinoxalines
Ghasem Rezanejade Bardajee
Department of Chemistry, Payame Noor University, PO Box 19395–3697, Tehran, Iran
A R T I C L E I N F O
A B S T R A C T
Article history:
Zirconium(IV) oxide chloride was found to be a rapid and efficient catalyst for the
Received 10 February 2013
Accepted after revision 25 February 2013
Available online xxx
synthesis of pyrazines and 2,3-disubstituted quinoxalines in water.
A variety of
pyridopyrazine and 2,3-disubstituted quinoxaline derivatives are readily prepared in
high yields under green conditions by cyclocondensation of the desired 1,2-diamine and
1,2-diketone using a catalytic amount of zirconium(IV) oxide chloride in water. Less active
diamines, such as 2,3- and 3,4-diaminopyridines took part in this protocol to provide the
desired products in good to excellent yields.
Keywords:
Amines
Cyclization
´
ß 2013 Published by Elsevier Masson SAS on behalf of Academie des sciences.
Fused-ring systems
Homogeneous catalysis
Ketones
Nitrogen
1. Introduction
materials, organic semiconductors, cavitands, chemically
controllable switches, and DNA cleaving agents [6–8]. In
Quinoxaline and pyrazine derivatives represent an
imperative class of nitrogen-containing heterocycles as
they have received considerable interest from pharma-
ceutical to academic and industrial perspectives. For
example, drug formulations with the core of quinoxaline,
such as Lamprene, are currently available and they are
privileged structures in combinatorial drug discovery.
Besides their interesting therapeutic properties, such as
antiviral, antibacterial, anti-inflammatory, and antipro-
tozoal and as kinase inhibitors [1,2], they have also been
evaluated as anticancer, anthelmintic, antifungal, and
insecticidal agents [3]. The quinoxaline nucleus is a
part of several antibiotics, such as echinomycin, levo-
mycin, and actinomycin that are known to inhibit the
growth of Gram-positive bacteria and are active against
various transplantable tumours [4,5]. Furthermore, they
have found applications as dyes, electroluminescent
this regards, various strategies have been introduced for
the synthesis of these scaffolds, which include conden-
sation of arene-1,2-diamines with 1,2-ketones (I2, DMSO;
I2, MeCN; montmorillonite K-10; PEG-400; solid phase);
CAN; MeOH–AcOH (9:1); Ac2O, reflux; carbon-doped
MoO3–TiO2 (CMT); p-toluene sulfonic acid (PTSA) as
Brønsted acid catalyst in aqueous sodium p-toluene
sulfonate (NaPTS) solution (Brønsted acid hydrotrope-
combined catalyst (BAHC); lead (II) bromide; lithium
chloride), oxidative cyclization of
a-hydroxy ketones
with 1,2-diamines (MnO2; 1 mol% MnO2, microwaves;
Pd(OAc)2; MnO2–NaBH4; PEG-400), cyclization–oxida-
tion of phenacyl bromides with 1,2-diamines (HClO4–
silica gel), and oxidative coupling of epoxides with
ene-1,2-diamines [bismuth powder, Cu(OTf)2] [9–23].
However, many of these methods suffer from several
drawbacks such as the use of strong oxidizing agents and
expensive metal catalysts, and also the yields are far from
satisfactory. Therefore, the development of a simple,
convenient, and general approach would certainly be
E-mail address: rezanejad@pnu.ac.ir.
1631-0748/$ – see front matter ß 2013 Published by Elsevier Masson SAS on behalf of Acade´mie des sciences.
http://dx.doi.org/10.1016/j.crci.2013.02.018
Please cite this article in press as: Bardajee, GR., ZrOCl2Á8H2O in water: An efficient catalyst for rapid one-pot synthesis
of pyridopyrazines, pyrazines and 2,3-disubstituted quinoxalines. C. R. Chimie (2013), http://dx.doi.org/10.1016/
j.crci.2013.02.018

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G.R. Bardajee / C. R. Chimie xxx (2013) xxx–xxx
O
R
R
NH2
NH2
N
R
R
useful in generating combinatorial libraries for drug
discovery.
ZrOCl2 (25 mol%)
Water, heat
+
Y
Y
Over the past decade, zirconium compounds have been
found to play an ever-increasing role in organic synthesis,
which has been recognized by a number of excellent
review articles and books covering various aspects of
zirconium compounds as the catalysts or reagents in
synthetic organic chemistry [24,25].
O
X
X
N
2a-f
3a-p
1a-e
X and Y = C or N
R = Aliphatic or Aromatic
Scheme 1. General route for the synthesis of desired heterocycles.
Herein, we set out to explore a new green synthetic
method for the synthesis of 2,3-disubstituted quinoxa-
lines, pyrazines and pyridopyrazines via zirconium(IV)
oxide chloride-catalyzed condensation of related 1,2-
diamines and 1,2-dicarbonyl compounds in water.
A survey of the literature shows that there are not
many reports on the synthesis of pyridopyrazine deriva-
tives [15]. The most convenient method for the synthesis
of these compounds is the reaction of 2,3- and 3,4-
diaminopyridines with different diketones. The problem
is that these diaminopyridines are almost unreactive
toward diketones in normal conditions. Herein, our
contribution is intended to extend the scope of available
methods for the synthesis of pyridopyrazines, pyrazines
and 2,3-disubstituted quinoxalines, and to describe the
application of a new transition metal-based catalyst in
their synthesis.
showed that excellent conversion of the starting
material into the product was achieved in 2 h by using
ZrOCl2Á8H2O as a catalyst under refluxing water. In a
typical procedure, the reaction of 2,3-diaminopyridine
1a (1.0 mmol, 1.0 equiv) and benzil 2a (1 mmol, 1 equiv)
in the presence of ZrOCl2Á8H2O (25 mol%) under reflux-
ing water for 2 h afforded compound 3a in 92% yield
(Table 1, entry 1). The proposed mechanism for the
synthesis of 3a in the presence of ZrOCl2 is shown in
Scheme 2.
In order to show the generality and scope of this new
protocol, a variety of 1,2-diamines and 1,2-diketones were
examined. The results are summarized in Table 1 (entries
1–16). Most of the reactions proceeded very cleanly and no
undesirable side products were observed. The results
showed that besides electron-rich diamines, such as
ethylene dimine and 1,2-phenylene diamine, the elec-
tron-deficient ones, such as 2,3-diaminopyridine and 3,4-
diaminopyridine can provide the desired products in good
to excellent yields (Table 1, entries 1–15). Furthermore,
our protocol proved to be a good route for the synthesis of
multifunctional and highly conjugated pyrazines (Table 1,
entries 4, 8, 9, 11 and 12).
2. Result and discussion
In continuation of our efforts in applying metal oxides
in organic synthesis [26,27], we tried ZrOCl2Á8H2O-
catalyzed condensation reaction of 1,2-diamines and
1,2-diketones for the preparation of the corresponding
pyridopyrazines, pyrazines, and 2,3-disubstituted quinox-
alines (Scheme 1).
Finally, we investigated the recycling of reaction
media in a subsequent reaction, for example, in the
reaction of o-phenylenediamine (1e) with benzil (2a),
and ZrOCl2 was reused five times without any appreci-
able loss of activity.
In this regard, we initially attempted the condensa-
tion of 2,3-diaminopyridine (1a) and benzil (2a, PhCO-
COPh) as
a model reaction under various reaction
conditions. The optimization of the reaction conditions
Zr(IV)
+
..
HO H
Ph
Ph
O
H2N
Ph
Ph
N
1- Nucleophilic addition to carbonyl
2- Proton exchange
+
..
O
2a
H2N
H2N
N
1a
N
O
A
-H2O
Ph
Ph
N
Ph
Ph
N
N
1- Nucleophilic addition to carbonyl
..
H2N
2- Proton exchange
3- Deletion of water
N
N
3a
O
+
B
Zr(IV)
Scheme 2. Proposed mechanism for the formation of 3a from starting materials in the presence of ZrOCl2.
Please cite this article in press as: Bardajee, GR., ZrOCl2Á8H2O in water: An efficient catalyst for rapid one-pot synthesis
of pyridopyrazines, pyrazines and 2,3-disubstituted quinoxalines. C. R. Chimie (2013), http://dx.doi.org/10.1016/
j.crci.2013.02.018

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3
Table 1
Synthesis of desired heterocyclic derivatives catalyzed by ZrOCl2Á8H2O in water.
NH2
NH2
NH2
NH2
NC NH2
NH2
NH2
NH2
N
N
1a
NC NH2
NH2
1c
1b
1e
1d
Entry
1
Diamine 1
Dicarbonyl 2
Product 3a
Time (h)
2
Yield (%)b
1a
92
N
Ph
Ph
O
N
N
3a
O
2a
2
3
1a
1a
2
3
93
88
F
F
O
O
2b
N
N
3b
N
F
F
OMe
OMe
O
O
2c
N
N
N
N
3c
OMe
OMe
OMe
4
5
1a
1b
2.5
85
86
N
O
N
O
3d
2d
2c
3
N
N
N
3e
OMe
F
6
1b
2b
2a
2.5
88
N
N
N
N
3f
F
7
8
1b
1b
2.5
2.5
91
87
N
N
3g
O
O
N
N
N
N
3h
3i
2e
9
1b
1c
2d
2.5
1
86
95
N
N
10
2a
N
N
3j
11
1c
2d
1
91
N
N
3k
Please cite this article in press as: Bardajee, GR., ZrOCl2Á8H2O in water: An efficient catalyst for rapid one-pot synthesis
of pyridopyrazines, pyrazines and 2,3-disubstituted quinoxalines. C. R. Chimie (2013), http://dx.doi.org/10.1016/
j.crci.2013.02.018

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G.R. Bardajee / C. R. Chimie xxx (2013) xxx–xxx
Table 1 (Continued )
NH2
NH2
NH2
NC NH2
NH2
NH2
N
N
1a
NH2
NH2
NC NH2
NH2
1b
1e
1d
1c
Entry
12
Diamine 1
Dicarbonyl 2
Product 3a
Time (h)
1
Yield (%)b
90
1d
O
O
Me
Me
NC
NC
N
N
3l
Me
Me
2f
13
14
1e
1e
2a
1
2
97
92
N
N
3m
2c
OMe
N
N
3n
OMe
F
15
1e
1e
2b
1
95
98
N
N
3o
3p
F
16
2f
0.5
N
N
Me
Me
a
All reactions were run under the following conditions: 1,2-diamine 1 (1 mmol, 1 equiv), diketone 2 (1.0 mmol, 1 equiv) and catalyst (25 mol%) in
refluxing water (2 mL) were heated for appropriate times.
b
Isolated yield.
3. Conclusions
of the products were followed by TLC on silica gel plates
(Merck, silica gel 60 F254, ready to use), using dichlor-
omethane:methanol (9:1) or n-hexane:ethyl acetate (1:3)
as eluents. The eluent for column chromatography was the
same as for TLC.
In summary, we successfully developed a simple,
efficient and eco-friendly method for the synthesis of
pyridopyrazines, pyrazines and quinoxalines from 1,2-
diamines and various 1,2-diketones using the cheap and
readily available ZrOCl2Á8H2O catalyst. Not only the
electron-rich diamines (ethylene dimine and 1,2-pheny-
lene diamine), but also the electron-deficient ones (2,3-
diaminopyridine and 3,4-diaminopyridine), provided the
desired products in good to excellent yields in water as a
green solvent.
The melting points were recorded using a Buchi B540
melting point apparatus and are uncorrected. 1H and 13
C
NMR spectra were recorded at room temperature on a
Bruker AC 300, 400 or 500 MHz spectrometers using
CDCl3 or DMSO-d6 as the NMR solvents. 1H NMR spectra
are referenced to tetramethylsilane (0.00 ppm) and 13C
NMR spectra are referenced from the solvent central
peak (for example, 77.23 ppm for CDCl3). Chemical shifts
are given in ppm. IR spectra were taken as KBr pellets
4. Experimental method
using
a Jasco 4200 FT-IR spectrophotometer. IR is
reported as characteristic bands (cmÀ1) at their maxi-
mum intensity.
4.1. General
Commercial grade of 1,2-phenylenediamine, diamino-
pyridines, 1,2-dicarbonyl compounds and zirconium(IV)
oxide chloride were purchased from Sigma–Aldrich, Merck
and Acros organics companies. The solvents were of
analytical grade and used as received. Silica gel (Merck,
grade 9385, 230–400 mesh, 60 A8) for column chromatog-
raphy was used as received. All other reagents were
purchased from Merck and used as received unless
otherwise noted. The course of the synthesis and purity
4.2. General procedure for the synthesis of compounds 3a–3p
For the synthesis of entitled heterocycles, a round
bottom flask equipped with a stir bar was charged
with 1,2-phenylenediamine (1.0 mmol), 1,2-diketones
(1.0 mmol), water (2 mL) and zirconium(IV) oxide chloride
(25 mol%). The resulting mixture was heated in an oil bath
at 100 8C for the appropriate time, and the course of the
Please cite this article in press as: Bardajee, GR., ZrOCl2Á8H2O in water: An efficient catalyst for rapid one-pot synthesis
of pyridopyrazines, pyrazines and 2,3-disubstituted quinoxalines. C. R. Chimie (2013), http://dx.doi.org/10.1016/
j.crci.2013.02.018

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5
reaction was monitored using TLC on silica gel. Finally, the
reaction mixture was cooled and the crude mixture was
purified by column chromatography or crystallization to
give the desired product. The authenticity of the products
was established by comparing their melting points with
data of the literature and by analyzing the spectroscopic
data of 1H and 13C NMR and IR [9–16,26,27].
4.3.6. 2,3-Bis(4-fluorophenyl)pyrido[3,4-b]pyrazine (3f)
Yield 88%; orange solid, mp: 132–134 8C. IR (KBr)
y
(cmÀ1): 3049, 1597, 1509, 1381, 1325, 1230, 835. 1H NMR
(500 MHz, CDCl3)
7.96 (d, J = 5.8 Hz, 1H), 8.83 (d, J = 5.8 Hz, 1H), 9.58 (s, 1H).
13C NMR (75 MHz, CDCl3)
(ppm): 165.3, 165.2, 162.0,
d (ppm): 7.07 (m, 4H), 7.51–7.55 (m, 4H),
d
161.8, 156.6, 154.4, 154.0, 147.5, 143.5, 136.2, 134.1, 132.0,
131.8, 131.8, 131.7, 121.2, 115.9, 115.6. Anal. Calcd for
C19H11F2N3 (319.3): C, 71.47; H, 3.47; N, 13.16. Found: C,
71.64; H, 3.59; N, 13.33.
4.3. Spectral data for compounds 3a–3p
4.3.1. 2,3-Diphenylpyrido[2,3-b]pyrazine (3a)
Yield 92%; yellow solid, mp: 141–143 8C. IR (KBr)
(cmÀ1): 3056, 1544, 1430, 1384, 1332, 1068, 1019, 780,
697. 1H NMR (500 MHz, DMSO, d6)
(ppm): 7.31–7.49 (m,
10H), 7.86 (dd, J = 8.2, 4.1 Hz, 1H), 8.56 (dd, J = 8.2, 1.2 Hz,
1H) 9.14 (m, 1H). 13C NMR (125 MHz, CDCl3)
(ppm):
y
4.3.7. 2,3-Diphenylpyrido[3,4-b]pyrazine (3g)
Yield 91%; white solid partial to green, mp: 170–172 8C.
d
IR (KBr)
1024, 808, 696. 1H NMR (500 MHz, CDCl3)
7.55 (m, 10H), 7.99 (d, J = 5.7 Hz, 1H), 8.83 (d, J = 5.7 Hz,
1H), 9.60 (s, 1H). 13C NMR (75 MHz, CDCl3)
(ppm): 157.9,
y
(cmÀ1): 3047, 2963, 1590, 1542, 1383, 1326,
d
(ppm): 7.34–
d
156.5, 155.3, 154.9, 150.0, 139.1, 138.7, 136.5, 130.6, 130.6,
130.0, 129.9, 128.9, 126.8.
d
155.3, 154.4, 147.3, 143.5, 138.2, 136.3, 129.8, 129.8, 129.7,
129.4, 128.4, 121.3.
4.3.2. 2,3-Bis(4-fluorophenyl)pyrido[2,3-b]pyrazine (3b)
Yield 93%; yellow solid, mp: 140–142 8C. IR (KBr)
(cmÀ1): 2925, 1728, 1597, 1548, 1508, 1446, 1386, 1331,
1226, 832. 1H NMR (500 MHz, CDCl3)
(ppm): 7.02–7.09
(m, 4H), 7.53–7.63 (m, 4H), 7.72 (q, J = 8.3 Hz, 1H), 8.49 (dd,
J = 8.3, 1.7 Hz, 1H), 9.17 (dd, J = 4.1, 1.7 Hz, 1H) 13C NMR
y
4.3.8. Dibenzo[f,h]pyrido[3,4-b]quinoxaline (3h)
Yield 87%; yellow solid, mp: 216–218 8C. IR (KBr)
(cmÀ1): 3025, 2921, 1600, 1499, 1387, 1343, 1216, 1041,
828, 754, 719. 1H NMR (300 MHz, CDCl3)
(ppm): 7.69–
y
d
d
7.84 (m, 4H), 8.07 (d, J = 5.7 Hz, 1H), 8.48 (d, J = 7.8 Hz, 2H),
8.86 (d, J = 6.0 Hz, 1H), 9.30 (d, J = 7.8 Hz, 2H), 9.73 (s, 1H).
13C NMR (75 MHz, CDCl3)
d (ppm): 155.1, 146.2, 143.9,
136.9, 135.9, 132.8, 131.5, 131.0, 130.5, 129.5, 129.4, 128.2,
128.1, 127.0, 126.5, 123.9, 123.0, 122.9, 121.3.
(75 MHz, CDCl3)
d (ppm): 165.2, 165.1, 161.9, 161.8, 154.9,
154.3, 153.3, 149.7, 138.0, 136.1, 134.4, 134.3, 134.0, 133.9,
132.3, 132.2, 131.8, 131.7, 125.4, 115.8, 115.6, 115.5, 115.3.
Anal. Calcd for C19H11F2N3 (319.3): C, 71.47; H, 3.47; N,
13.16. Found: C, 71.64; H, 3.59; N, 13.38.
4.3.9. Acenaphtho[1,2-b]pyrido[3,4-e]pyrazine (3i)
4.3.3. 2,3-Bis(4-methoxyphenyl)pyrido[2,3-b]pyrazine (3c)
Yield 86%; orange solid, mp: 245–247 8C. IR (KBr)
(cmÀ1): 3031, 2922, 1611, 1569, 1424, 1296, 1103, 961,
830, 771. 1H NMR (300 MHz, CDCl3)
(ppm): 7.82 (m, 2H),
7.97 (d, J = 5.7 Hz, 1H), 8.11 (m, 2H), 8.37 (m, 2H), 8.79 (d,
J = 8.7 Hz, 1H), 9.54 (s, 1H). 13C NMR (75 MHz, CDCl3)
y
Yield 88%; yellow solid, mp: 137–139 8C. IR (KBr)
(cmÀ1): 2933, 2839, 1605, 1513, 1447, 1384, 1251, 1175,
1023, 833. 1H NMR (300 MHz, CDCl3)
(ppm): 3.84 (d, 6H),
y
d
d
6.85–6.91 (m, 4H), 7.53–7.68 (m, 5H), 8.45 (dd, J = 8.4,
1.8 Hz, 1H), 9.11 (dd, J = 4.2, 1.8 Hz, 1H). 13C NMR (75 MHz,
d
(ppm): 157.5, 155.2, 154.0, 147.0, 144.1, 137.1, 136.3,
130.8, 130.6, 130.0, 129.9, 128.8, 128.7, 122.9, 122.4, 122.0.
CDCl3)
d (ppm): 160.7, 155.7, 154.2, 153.5, 149.8, 137.8,
135.8, 131.8, 131.2, 131.1, 130.7, 124.7, 113.9, 113.6, 55.3,
55.3.
4.3.10. 5,6-Diphenyl-2,3-dihydropyrazine (3j)
Yield 95%; white solid, mp: 154–156 8C. IR (KBr)
(cmÀ1): 3028, 2943, 2831, 1610, 1551, 1439, 1261, 986,
766, 698. 1H NMR (500 MHz, CDCl3)
(ppm): 3.69 (s, 4H),
y
4.3.4. Acenaphtho[1,2-b]pyrido[2,3-e]pyrazine (3d)
Yield 85%; yellow solid, mp: 225–227 8C. IR (KBr)
(cmÀ1): 3051, 1612, 1561, 1433, 1373, 1212, 1098, 1034,
826, 771. 1H NMR (300 MHz, CDCl3)
(ppm): 7.69–7.90 (m,
3H), 8.12 (dd, J = 8.2, 2.7 Hz, 2H), 8.40–8.57 (m, 3H), 9.12 (d,
J = 4.1 Hz, 1H). 13C NMR (75 MHz, CDCl3)
(ppm): 157.1,
y
d
7.23 (d, J = 7.8 Hz, 4H), 7.30 (m, 2H), 7.39 (d, J = 8.0 Hz, 4H).
d
13C NMR (75 MHz, CDCl3)
129.6, 137.7, 160.3.
d (ppm): 45.8, 127.9, 128.1,
d
154.9, 152.4, 150.6, 138.3, 137.2, 136.4, 131.2, 130.9, 130.2,
130.0, 129.9, 128.9, 128.7, 124.3, 123.3, 122.3. Anal. Calcd
for C17H9N3 (255.2): C, 79.99; H, 3.55; N, 16.46. Found: C,
79.75; H, 3.80; N, 16.52.
4.3.11. 8,9-Dihydroacenaphtho[1,2-b]pyrazine (3k)
Yield 91%; yellow solid, mp: 165–167 8C. IR (KBr)
y
(cmÀ1): 2929, 2838, 1671, 1627, 1483, 1429, 1329, 1111,
961, 824, 771. 1H NMR (300 MHz, CDCl3)
4H) 7.71 (m, 2H), 7.94–8.01 (m, 4H). 13C NMR (75 MHz,
CDCl3) (ppm): 158.6, 131.7, 130.6, 128.5, 128.3, 118.7,
d (ppm): 3.94 (s,
4.3.5. 2,3-Bis(4-methoxyphenyl)pyrido[3,4-b]pyrazine (3e)
d
Yield 86%; yellow solid partial to green, mp: 145–
118.6, 44.9.
147 8C. IR (KBr)
1383, 1248, 1173, 1028, 835. 1H NMR (500 MHz, CDCl3)
y
(cmÀ1): 3025, 2923, 1604, 1510, 1460,
d
4.3.12. 5,6-Dimethylpyrazine-2,3-dicarbonitrile (3l)
Yield 90%; white solid, mp: 162–164 8C. IR (KBr)
(ppm): 3.84 (S, 6H), 6.89 (d, J = 8.7 Hz, 2H), 7.52 (d,
J = 8.0 Hz, 2H), 7.93 (d, J = 5.7 Hz, 1H), 8.77 (d, J = 5.7 Hz,
y
(cmÀ1): 3006, 2239, 1770, 1717, 1536, 1389, 1197, 1123,
1H), 9.53 (s, 1H). 13C NMR (75 MHz, CDCl3)
d
(ppm): 160.9,
986, 793, 695. 1H NMR (500 MHz, CDCl3)
d
(ppm): 2.70 (s,
d (ppm): 158.4, 130.7,
160.6, 157.4, 154.9, 154.1, 146.9, 143.4, 136.2, 131.4, 131.2,
130.9, 130.8, 121.2, 113.9, 55.3.
6H). 13C NMR (125 MHz, CDCl3)
113.6, 23.3.
Please cite this article in press as: Bardajee, GR., ZrOCl2Á8H2O in water: An efficient catalyst for rapid one-pot synthesis
of pyridopyrazines, pyrazines and 2,3-disubstituted quinoxalines. C. R. Chimie (2013), http://dx.doi.org/10.1016/
j.crci.2013.02.018

G Model
CRAS2C-3724; No. of Pages 6
6
G.R. Bardajee / C. R. Chimie xxx (2013) xxx–xxx
4.3.13. 2,3-Diphenylquinoxaline (3m)
Appendix A. Supplementary data
Yield 97%; white solid, mp: 121–123 8C. IR (KBr)
(cmÀ1): 3048, 2923, 1544, 1441, 1336, 765, 691. 1H NMR
(500 MHz, CDCl3) (ppm): 7.32–7.38 (m, 6H), 7.52 (d,
J = 7.8 Hz, 4H), 7.77 (q, J = 6.4 Hz, 2H), 8.18 (q, J = 9.5 Hz,
2H). 13C NMR (75 MHz, CDCl3)
(ppm): 153.5, 141.2,
y
Supplementary data associated with this article can be
found, in the online version, at http://dx.doi.org/10.1016/
j.crci.2013.02.018
d
d
139.0, 129.9, 129.8, 129.2, 128.8, 128.2.
References
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4.3.14. 2,3-Bis(4-methoxyphenyl)quinoxaline (3n)
Yield 92%; white solid, mp: 145–147 8C. IR (KBr)
y
(cmÀ1): 2932, 2836, 1605, 1510, 1462, 1344, 1291, 1244,
1173, 1026, 832. 1H NMR (300 MHz, CDCl3)
(s, 6H), 6.88 (d, J = 8.7 Hz, 4H), 7.50 (d, J = 8.7 Hz, 4H), 7.72
(m, 2H), 8.13 (m, 2H). 13C NMR (75 MHz, CDCl3)
(ppm):
d (ppm): 3.83
d
160.1, 153.0, 141.0, 131.5, 131.2, 129.5, 129.0, 113.7,
55.3.
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4.3.15. 2,3-Bis(4-fluorophenyl)quinoxaline (3o)
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161.
Yield 95%; white solid, mp: 133–135 8C. IR (KBr)
(cmÀ1): 3063, 1600, 1510, 1476, 1395, 1342, 1227, 1158,
1051, 842, 763. 1H NMR (300 MHz, CDCl3)
(ppm): 7.03–
7.09 (m, 4H), 7.49–7.54 (m, 4H), 7.80 (q, J = 9.6 Hz, 1H),
8.16 (q, J = 9.0 Hz, 1H). 13C NMR (75 MHz, CDCl3)
(ppm):
y
d
d
164.8, 161.5, 152.1, 141.2, 135.0, 134.9, 131.8, 131.7,
130.2, 129.1, 115.6, 115.4. Anal. Calcd for C20H12F2N2
(318.3): C, 75.46; H, 3.80; N, 8.80. Found: C, 75.58; H, 3.71;
N, 8.91.
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4.3.16. 2,3-Dimethylquinoxaline (3p)
Yield 98%; white solid, mp: 102–104 8C. IR (KBr)
(cmÀ1): 2998, 1564, 1484, 1433, 1393, 1321, 1206, 1161,
982, 760. 1H NMR (500 MHz, CDCl3)
(ppm): 2.69 (s, 6H),
7.63 (d, J = 6.3 Hz, 2H), 7.94 (d, J = 6.1 Hz, 2H). 13C NMR
y
d
(125 MHz, CDCl3)
23.1.
d (ppm): 153.3, 141.0, 128.7, 128.2,
Acknowledgments
[27] G.R. Bardajee, R. Malakooti, I. Abtin, H. Atashin, Micropor. Mesopor.
Mat. 169 (2013) 67.
We are grateful to the PNU for funding this work.
Please cite this article in press as: Bardajee, GR., ZrOCl2Á8H2O in water: An efficient catalyst for rapid one-pot synthesis
of pyridopyrazines, pyrazines and 2,3-disubstituted quinoxalines. C. R. Chimie (2013), http://dx.doi.org/10.1016/
j.crci.2013.02.018