Pd/C-catalyzed, copper-free Sonogashira coupling: One-pot synthesis of 1-aryl-4-(2-phenylethynyl)[1,2,4]triazolo[4,3-a]quinoxalines in water

Article abstract of DOI:10.1007/s00706-012-0904-4

Copper-free, Pd/C-catalyzed, one-pot reaction of 2,3-dichloroquinoxaline with hydrazine hydrate, bromine, phenylacetylene, and a variety of aldehydes provides an efficient and direct method for the preparation of 1-aryl-4-(2-phenylethynyl)[1,2,4]triazolo[4,3-a]quinoxalines in water at 70 C. This methodology involves the use of inexpensive reagents or catalysts, and thus permits a new and practical access to triazolo[4,3-a]quinoxalines.

Full text of DOI:10.1007/s00706-012-0904-4

Monatsh Chem (2013) 144:885–890
DOI 10.1007/s00706-012-0904-4
ORIGINAL PAPER
Pd/C-catalyzed, copper-free Sonogashira coupling: one-pot
synthesis of 1-aryl-4-(2-phenylethynyl)[1,2,4]triazolo[4,3-a]-
quinoxalines in water
•
Mohammad Bakherad Saeideh Jajarmi
Received: 1 June 2012 / Accepted: 14 December 2012 / Published online: 14 February 2013
Ó The Author(s) 2013. This article is published with open access at Springerlink.com
Abstract Copper-free, Pd/C-catalyzed, one-pot reaction
of 2,3-dichloroquinoxaline with hydrazine hydrate, bro-
mine, phenylacetylene, and a variety of aldehydes provides
an efficient and direct method for the preparation of 1-aryl-
4-(2-phenylethynyl)[1,2,4]triazolo[4,3-a]quinoxalines in water
at 70 °C. This methodology involves the use of inexpen-
sive reagents or catalysts, and thus permits a new and
practical access to triazolo[4,3-a]quinoxalines.
Typically, these coupling-cyclization reactions are car-
ried out using a palladium catalyst [e.g., Pd(PPh3)4,
(PPh3)2PdCl2, etc.] and a copper salt as the co-catalyst in the
presence of an amine base. The use of palladium on char-
coal as a catalytic system for the efficient Sonogashira
coupling of aryl halides with terminal alkynes has also been
reported [14–17]. Compared to the frequently used expen-
sive palladium catalysts [e.g., Pd(PPh3)4, (PPh3)2PdCl2,
etc.], Pd/C-based methods have an economic advantage,
and, hence, remain attractive for large or industrial scale
preparations.
Keywords Palladium catalyst Á Triazoloquinoxaline Á
Sonogashira reaction Á Phenylacetylene
In recent years, a variety of modifications have been
reported for this reaction, and significant progress has been
made [18–22]. The most important modification is the
elimination of the copper salt [23–27] since it can induce
Glaser-type homocoupling of terminal alkynes in the
presence of oxidants or air [28–30]. One of the powerful
tools used to combine economic aspects with the envi-
ronmental concerns is performing organic reactions in
water; this strategy consists of two or more synthetic steps,
which are carried out in water as a cheap, nontoxic, and
environmentally friendly solvent, in a one-step reaction,
without isolation of any intermediate, thus reducing time,
and saving money, energy, and raw materials [31–33].
Several examples of Pd-catalyzed Sonogashira reactions in
aqueous media have been reported [34–37].
Introduction
Quinoxaline and its derivatives show a broad spectrum of
biological activities including anti-tumor [1], anti-viral [2],
anti-tuberculosis [3], and anti-inflammatory [4] activities,
and, hence, are an important class of nitrogen-containing
heterocycles, and useful intermediates in organic synthesis
[5]. Furthermore, triazolo[4,3-a]quinoxalines have been
shown to be potent and selective adenosine receptor
ligands [6].
The Sonogashira reaction catalyzed by palladium and
copper is a powerful and straightforward method for the
construction of arylated internal alkyne compounds [7–9].
These are important intermediates in organic synthesis and
for the preparation of natural products [10], biologically
active molecules [11], molecular electronics [12], and
polymers [13].
Recently, our group has prepared pyrrolo[2,3-b]quin-
oxaline derivatives under mild conditions in one-pot
reactions catalyzed by Pd–Cu [38–40]. We attempted to
make this overall approach more attractive synthetically by
examining the preparation of triazolo[4,3-a]quinoxalines
using a one-pot reaction of 2,3-dichloroquinoxaline,
hydrazine, aldehydes, bromine, and phenylacetylene cata-
lyzed by Pd/C without the use of copper as a co-catalyst in
water.
M. Bakherad (&) Á S. Jajarmi
School of Chemistry, Shahrood University of Technology,
Shahrood, Iran
e-mail: m.bakherad@yahoo.com
123

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M. Bakherad, S. Jajarmi
Results and discussion
bromine, and phenylacetylene in water at 70 °C to triaz-
olo[4,3-a]quinoxalines in moderate to good yields
(Table 2). When the less reactive acetylene, 1-hexyne,
1-octyne, and propargyl alcohol were used, Sonogashira
coupling could not be achieved. The reactions were carried
out under an argon atmosphere, and water was degassed
prior to use.
We reported the synthesis of new derivatives of triazolo[4,3-
a]quinoxalines via 10 % palladium/charcoal activated
(Merck catalyst) catalyzed one-pot reaction of 2,3-dichlo-
roquinoxaline, hydrazine, a suitable aldehyde, bromine, and
phenylacetylene at 70 °C by employing water as the reaction
medium. The use of water as a reaction medium represents
remarkable benefits since this green solvent is highly polar
and, therefore, immiscible with most organic compounds;
moreover, the water-soluble by-products reside, and sepa-
ration of the organic materials is thus easy.
Mechanistically, the formation of triazolo[4,3-a]quin-
oxalines 4 involves the following steps (Scheme 2):
(i) formation of 1-aryl-4-chloro[1,2,4]triazolo[4,3-a]quin-
oxalines from the cyclization of intermediate A catalyzed
by bromine [41]; and (ii) Sonogashira coupling reaction of
3 with phenyl acetylene.
Retrosynthetic analysis indicated that the desired 1-aryl-
4-(2-phenylethynyl)[1,2,4]triazolo[4,3-a]quinoxalines can
also be synthesized from 2,3-dichloroquinoxaline, hydra-
zine, a suitable aldehyde, and phenylacetylene as the
starting materials (Scheme 1).
Conclusion
For optimization of the reaction conditions, we studied
the effect of various reaction parameters including the
base, palladium catalyst, and temperature on the outcome
of the copper-free reaction of 2,3-dichloroquinoxaline (1
equiv.) with hydrazine hydrate (2 equiv.), benzaldehyde (1
equiv.), bromine (1 equiv.), and phenylacetylene (1 equiv.)
in the presence of 10 % Pd/C (5 mol %) and K2CO3 (2
equiv.) in water at 70 °C (Table 1).
The reaction was influenced significantly by the base
employed. It worked very well when inorganic bases such
as K2CO3 and KOH were used (entries 2 and 3), with
the best result obtained in the case of potassium carbon-
ate. Two of the organic bases used, triethylamine and
piperidine, also gave good yields (entries 5 and 8). It was
found that while PdCl2(PPh3)2, PdCl2/PPh3, PdCl2, and
Pd2(dba)3ÁCHCl3 all catalyzed the reaction without the aid
of any surfactant (entries 9–12), 10 % Pd/C turned out to
be the best catalyst in terms of yields (entry 2). When the
catalyst loading was decreased to 3 mol %, the yield of 4a
was 55 % (entry 13). Increasing the amount of palladium
catalyst did not increase the yield (entry 14). Decreasing
the temperature to 25 °C caused the yield to decrease to
35 % (entry 15).
In conclusion, the chemistry outlined here provides a
simple, efficient, clean, and straightforward method for the
synthesis of triazolo[4,3-a]quinoxaline derivatives via the
copper-free, Pd/C-catalyzed reaction of readily available
dichloroquinoxaline with hydrazine, bromine, phenylacet-
ylene, and a variety of aldehydes in water. This
methodology does not involve the use of expensive
reagents or catalysts, and thus permits a new and practical
access to triazolo[4,3-a]quinoxalines.
Experimental
All the compounds (phenylacetylene, aldehydes, Pd/C)
were obtained from Merck. The reagents used were pur-
chased from commercial suppliers, and used without
further purification. Merck silica gel 60 was used for
chromatography (230–400 mesh). The IR spectra were
obtained as KBr pellets in the range of 400–4,000 cm-1 on
a Shimadzu Model 460 spectrophotometer. 1H NMR spectra
were recorded at 400 MHz, and 13C NMR spectra were
recorded at 100 MHz in DMSO-d6. The chemical shifts are
reported in ppm (d), and referenced to the residual proton
signal for DMSO-d6 (2.49 ppm). The coupling constants
(J) are reported in Hz. Mass spectrometric data (MS) were
In order to examine the scope of this reaction, com-
pound 1 was reacted with hydrazine, various aldehydes 2,
Scheme 1
Ph
N
N
N
N
N
N
Cl
Cl
N
Ph
+
+
N
N
N
H
CHAr
N
N
Ar
Ar
N
Cl
N
Cl
Cl
ArCHO
+
NH2NH2
NH2
N
N
H
N
123

Pd/C-catalyzed, copper-free Sonogashira coupling
887
Table 1 Effect of base and catalyst on the heterocyclization during the reaction of 2,3-dichloroquinoxaline (1) with hydrazine hydrate, bromine,
benzaldehyde, and phenylacetylenea
Ph
N
N
Cl
Cl
N
N
Cat, base
H2O, 70 oC
NH2NH2
+
PhCHO Br2
+
+
Ph
+
N
N
1
2a
4a
Ph
Entry
Catalyst/mol%
Base
Yield/%b
1
10 % Pd/C (5)
10 % Pd/C (5)
10 % Pd/C (5)
10 % Pd/C (5)
10 % Pd/C (5)
10 % Pd/C (5)
10 % Pd/C (5)
10 % Pd/C (5)
Cs2CO3
K2CO3
KOH
75
82
80
78
58
42
54
60
50
70
74
45
55
82
35
2
3
4
Na2CO3
5
Et3N
6
DIEAc
Pyridine
Piperidine
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
7
8
9
PdCl2 (5)/PPh3 (10)
PdCl2(PPh3)2 (5)
Pd(dba)2 (5)
10
11
12
13
14
15d
a
PdCl2 (5)
10 % Pd/C (3)
10 % Pd/C (10)
10 % Pd/C (5)
Reaction conditions: 1 (1.0 mmol), hydrazine hydrate (2.0 mmol), 2a (1.0 mmol), bromine (1.0 mmol), phenylacetylene (1.0 mmol), K2CO3
(2.0 mmol), 70 °C, 12 h
b
Isolated yields
c
Diisopropylethylamine
d
Reaction at 25 °C
1-Phenyl-4-(2-phenylethynyl)[1,2,4]triazolo[4,3-a]quinox-
aline (4a, C23H14N4)
obtained by electron ionization (EI, 70 eV) or electrospray
ionization (ESI).
White solid; yield 283 mg (82 %); m.p.: 280–282 °C;
Rf = 0.53; IR (KBr): m = 2,200, 1,650 cm-1 1H NMR
;
Typical procedure for the synthesis of 1-aryl-4-
(2-phenylethynyl)[1,2,4]triazolo[4,3-a]quinoxalines
4a–4k
(400 MHz, DMSO-d6): d = 7.32–7.42 (m, 4H), 7.45–7.55
(m, 4H), 7.67 (d, J = 4.8 Hz, 1H), 7.81 (d, J = 4.1 Hz,
1H), 7.86–7.92 (m, 3H), 8.05–8.08 (m, 1H) ppm; 13C NMR
(100 MHz, DMSO-d6): d = 85.26, 96.37, 123.80, 127.55,
127.85, 128.11, 128.21, 128.70, 128.95, 129.22, 129.55,
129.76, 130.45, 132.10, 132.45, 138.92, 142.17, 145.11,
149.12 ppm; MS (EI, 70 eV): m/z (%) = 346 ([M?], 100),
269 (52), 245 (22), 167 (16); HRMS (ESI): m/z =
346.1201.
A mixture of 199 mg 2,3-dichloroquinoxaline (1.0 mmol),
0.1 cm3 hydrazine hydrate (99 %, 2.0 mmol), a suitable
aldehyde (1.0 mmol), and 0.05 cm3 bromine (1.0 mmol)
were stirred in 5 cm3 H2O at room temperature under an
argon atmosphere for 30 min. Phenylacetylene (0.11 cm3,
1 mmol), 53 mg Pd/C (10 %, 0.05 mmol), and 276 mg
K2CO3 (2.0 mmol) were added, and the resulting solution
was heated at 70 °C for 12 h, and then cooled to room
temperature. The reaction mixture was filtered, and the
filtrate was concentrated in vacuo. The residue was
purified by chromatography, eluting with CHCl3/CH3OH
(98:2) to afford the pure product (Table 2).
1-(2-Nitrophenyl)-4-(2-phenylethynyl)[1,2,4]triazolo-
[4,3-a]quinoxaline (4b, C23H13N5O2)
White solid; yield 367 mg (94 %); m.p.: 284–286 °C;
Rf = 0.55; IR (KBr): m = 2,200, 1,600, 1,540, 1,340 cm-1
;
1H NMR (400 MHz, DMSO-d6): d = 7.56–7.63 (m, 3H),
7.73–7.75 (m, 1H), 7.80–7.87 (m, 3H), 7.95 (dd, J = 6.4,
123

888
M. Bakherad, S. Jajarmi
Table 2 Synthesis of triazolo[4,3-a]quinoxalines 4a–4ka
Ph
N
N
Cl
Cl
N
N
Pd/C
NH2NH2
+
ArCHO
Br2
+
+
+
Ph
K2CO3, H2O
70 °C
N
N
1
2a 2k
-
4a 4k
-
Ar
Entry
Ar
Product
Yield/%b
1
C6H5
4a
4b
4c
4d
4e
4f
82
94
74
94
76
85
83
86
75
80
81
2
2-NO2–C6H4
3-NO2–C6H4
4-NO2–C6H4
2-F–C6H4
3
4
5
6
4-F–C6H4
7
2-Cl–C6H4
4g
4h
4i
8
4-Cl–C6H4
9
2,6-Cl2–C6H3
4-CH3–C6H4
4-CH3O–C6H4
10
11
a
4j
4k
Reaction conditions: 1 (1.0 mmol), hydrazine hydrate (2.0 mmol), 2a–2k (1.0 mmol), phenylacetylene (1.0 mmol), bromine (1.0 mmol),
K2CO3 (2.0 mmol), 10 % Pd/C (5 mol %), 5 cm3 degassed water, 70 °C, 10 h
b
Isolated yields
N
N
Cl
Cl
Scheme 2
N
N
Cl
N
N
Cl
N
Br2, H2O
H2O
NH2NH2
ArCHO
+
+
N
N
H
Ar
N
1
2a-2k
A
Ar
3
Pd/C
Ph
Ph
Cl
N
N
N
Pd
N
Pd
N
N
-Pd(0)
Ph
N
N
K2CO3
N
N
N
N
Ar
Ar
Ar
4a-4k
C
B
2.0 Hz, 2H), 8.05–8.10 (m, 2H), 8.16–8.19 (m, 2H) ppm;
13C NMR (100 MHz, DMSO-d6): d = 85.39, 96.45,
121.36, 122.72, 127.45, 128.25, 128.35, 128.47, 128.66,
129.42, 129.58, 129.68, 131.36, 132.45, 132.60, 135.54,
142.36, 145.78, 149.25 ppm; MS (EI, 70 eV): m/z
(%) = 391 ([M?], 100), 345 (32), 314 (51), 290 (21),
169 (24); HRMS (ESI): m/z = 391.1037.
3H), 8.03–8.06 (m, 1H) ppm; 13C NMR (100 MHz, DMSO-
d6): d = 85.26, 96.35, 121.10, 122.45, 127.52, 128.45,
129.26, 129.45, 129.64, 129.88, 130.20, 131.36, 132.25,
132.45, 142.36, 145.56, 148.92, 149.55 ppm;MS(EI, 70 eV):
m/z (%) = 391 ([M?], 100), 345 (35), 314 (43), 290 (26), 167
(21); HRMS (ESI): m/z = 391.1042.
1-(4-Nitrophenyl)-4-(2-phenylethynyl)[1,2,4]triazolo-
[4,3-a]quinoxaline (4d, C23H13N5O2)
1-(3-Nitrophenyl)-4-(2-phenylethynyl)[1,2,4]triazolo-
[4,3-a]quinoxaline (4c, C23H13N5O2)
White solid; yield 367 mg (94 %); m.p.: 293–295 °C;
White solid; yield 289 mg (74 %); m.p.: 274–276 °C;
Rf = 0.54; IR (KBr): m = 2,210, 1,620, 1,540, 1,320 cm-1
;
Rf = 0.52; IR (KBr): m = 2,230, 1,610, 1,530, 1,340 cm-1
;
1H NMR (400 MHz, DMSO-d6): d = 7.40 (d, J = 8.4 Hz,
1H), 7.55–7.61 (m, 4H), 7.68–7.71 (m, 1H), 7.80–7.86 (m,
1H NMR (400 MHz, DMSO-d6): d = 7.28 (s, 1H), 7.35–7.40
(m, 2H), 7.46–7.52 (m, 3H), 7.54–7.60 (m, 3H), 7.64–7.71 (m,
2H), 8.11–8.18 (m, 3H), 8.55 (d, J = 8.2 Hz, 2H) ppm; 13
C
123

Pd/C-catalyzed, copper-free Sonogashira coupling
889
NMR (100 MHz, DMSO-d6): d = 84.95, 96.35, 116.61,
120.60, 124.75, 126.02, 128.50, 129.68, 130.72, 131.29,
132.14, 132.85, 134.87, 135.97, 136.09, 145.33, 148.53,
149.46 ppm; MS (EI, 70 eV): m/z (%) = 391 ([M?], 100),
345 (40), 314 (47), 290 (18), 168 (29); HRMS (ESI):
m/z = 391.1047.
(100 MHz, DMSO-d6): d = 85.01, 96.20, 116.25, 120.63,
126.18, 127.49, 128.34, 129.68, 129.85, 130.60, 131.27,
132.45, 132.83, 136.03, 136.46, 136.80, 145.11, 149.14 ppm;
MS (EI, 70 eV): m/z (%) = 382 ([M?][37Cl], 32), 380
([M?][35Cl], 100), 345 (30), 303 (62), 279 (26), 168 (20);
HRMS (ESI): m/z = 380.0850.
1-(2-Fluorophenyl)-4-(2-phenylethynyl)[1,2,4]triazolo-
[4,3-a]quinoxaline (4e, C23H13FN4)
1-(2,6-Dichlorophenyl)-4-(2-phenylethynyl)[1,2,4]triazolo-
[4,3-a]quinoxaline (4i, C23H12Cl2N4)
White solid; yield 276 mg (76 %); m.p.: 305–307 °C;
White solid; yield 310 mg (75 %); m.p.: 267–269 °C;
Rf = 0.50; IR (KBr): m = 2,250, 1,570 cm-1 1H NMR
;
Rf = 0.57; IR (KBr): m = 2,210, 1,620 cm-1 1H NMR
;
(400 MHz, DMSO-d6): d = 7.20 (s, 1H), 7.35–7.43 (m,
4H), 7.57–7.64 (m, 4H), 7.82–7.86 (m, 2H), 8.21 (d,
J = 8.0 Hz, 2H) ppm; 13C NMR (100 MHz, DMSO-d6):
d = 85.80, 96.42, 116.62, 122.26, 122.92, 124.85, 127.70,
128.37, 128.81, 129.21, 130.35, 130.56, 133.51, 133.65,
141.52, 146.23, 146.56, 149.55, 160.42 ppm; MS (EI,
70 eV): m/z (%) = 364 ([M?], 100), 345 (27), 287 (62),
263 (42), 167 (25); HRMS (ESI): m/z = 364.1152.
(400 MHz, DMSO-d6): d = 7.20 (s, 1H), 7.40–7.48 (m,
4H), 7.55–7.62 (m, 3H), 7.75–7.78 (m, 2H), 8.12–8.15 (m,
1H), 8.17–8.20 (m, 1H) ppm; 13C NMR (100 MHz,
DMSO-d6): d = 85.35, 96.23, 127.80, 127.95, 128.44,
128.84, 128.92, 129.10, 129.25, 129.54, 130.92, 131.44,
132.35, 132.74, 133.55, 138.22, 142.62, 145.84, 149.12 ppm;
MS (EI, 70 eV): m/z (%) = 418 ([M?][37Cl2], 12), 416
([M?][37Cl][35Cl], 53), 414 ([M?][35Cl2], 100), 381 (23),
339 (65), 313 (30), 269 (32), 168 (15); HRMS (ESI):
m/z = 414.0475.
1-(4-Fluorophenyl)-4-(2-phenylethynyl)[1,2,4]triazolo-
[4,3-a]quinoxaline (4f, C23H13FN4)
White solid; yield 309 mg (85 %); m.p.: 313–315 °C;
Rf = 0.51; IR (KBr): m = 2,230, 1,590 cm-1 1H NMR
;
1-(4-Methylphenyl)-4-(2-phenylethynyl)[1,2,4]triazolo-
[4,3-a]quinoxaline (4j, C24H16N4)
(400 MHz, DMSO-d6): d = 7.20 (s, 1H), 7.35–7.41 (m,
2H), 7.55–7.62 (m, 2H), 7.78–7.82 (m, 2H), 7.90–7.98 (m,
4H), 8.15–8.19 (m, 2H) ppm; 13C NMR (100 MHz,
DMSO-d6): d = 85.82, 96.44, 116.36, 116.45, 122.32,
126.22, 127.32, 128.24, 128.55, 128.74, 128.92, 129.20,
130.35, 130.47, 132.10, 132.21, 142.30, 145.25, 149.25,
162.92 ppm; MS (EI, 70 eV): m/z (%) = 364 ([M?], 100),
345 (32), 287 (67), 263 (35), 167 (29); HRMS (ESI):
m/z = 364.1144.
White solid; yield 288 mg (80 %); m.p.: 218–220 °C;
Rf = 0.52; IR (KBr): m = 2,220, 1,600 cm-1 1H NMR
;
(400 MHz, DMSO-d6): d = 2.39 (s, 3H), 7.36 (d,
J = 8.0 Hz, 2H), 7.50–7.62 (m, 4H), 7.70–7.77 (m, 3H),
8.08–8.14 (m, 2H), 8.40–8.46 (m, 2H) ppm; 13C NMR
(100 MHz, DMSO-d6): d = 22.62, 85.12, 96.21, 116.25,
120.53, 124.62, 126.10, 128.42, 128.60, 129.52, 129.92,
130.62, 132.34, 132.45, 138.40, 140.92, 141.52, 145.22,
149.62 ppm; MS (EI, 70 eV): m/z (%) = 360 ([M?], 100),
345 (21), 283 (64), 259 (24), 168 (22); HRMS (ESI):
m/z = 360.1343.
1-(2-Chlorophenyl)-4-(2-phenylethynyl)[1,2,4]triazolo-
[4,3-a]quinoxaline (4g, C23H13ClN4)
White solid; yield 315 mg (83 %); m.p.: 276–278 °C;
Rf = 0.56; IR (KBr): m = 2,250, 1,600 cm-1 1H NMR
;
1-(4-Methoxyphenyl)-4-(2-phenylethynyl)[1,2,4]triazolo-
[4,3-a]quinoxaline (4k, C24H16N4O)
(400 MHz, DMSO-d6): d = 7.35 (s, 1H), 7.43–7.52 (m,
4H), 7.60–7.70 (m, 4H), 8.06–8.12 (m, 2H), 8.40 (d,
J = 8.0 Hz, 2H) ppm; 13C NMR (100 MHz, DMSO-d6):
d = 85.65, 96.53, 123.42, 127.53, 127.65, 128.21, 128.32,
128.42, 128.65, 129.25, 129.64, 130.36, 130.54, 132.25,
132.36, 132.46, 138.65, 142.35, 145.65, 149.58 ppm; MS
(EI, 70 eV): m/z (%) = 382 ([M?][37Cl], 31), 380
([M?][35Cl], 100), 345 (35), 303 (57), 279 (21), 167
(25); HRMS (ESI): m/z = 380.0850.
White solid; yield 304 mg (81 %); m.p.: 250–252 °C;
Rf = 0.51; IR (KBr): m = 2,200, 1,620 cm-1 1H NMR
;
(400 MHz, DMSO-d6): d = 3.90 (s, 3H), 7.20 (d,
J = 8.7 Hz, 2H), 7.41–7.52 (m, 3H), 7.54–7.62 (m, 3H),
7.67–7.70 (m, 1H), 7.75–7.81 (m, 2H), 8.06 (d,
J = 8.4 Hz, 2H) ppm; 13C NMR (100 MHz, DMSO-d6):
d = 55.92, 85.15, 96.20, 116.12, 122.36, 124.51, 126.15,
128.21, 128.42, 128.52, 128.95, 129.55, 129.78, 130.54,
132.32, 132.45, 140.48, 145.23, 149.65 ppm; MS (EI,
70 eV): m/z (%) = 376 ([M?], 100), 345 (21), 299 (64),
275 (27), 269 (32), 168 (27); HRMS (ESI): m/z =
376.1360.
1-(4-Chlorophenyl)-4-(2-phenylethynyl)[1,2,4]triazolo-
[4,3-a]quinoxaline (4h, C23H13ClN4)
White solid; yield 326 mg (86 %); m.p.: 289–291 °C;
Rf = 0.55; IR (KBr): m = 2,240, 1,600 cm-1 1H NMR
;
(400 MHz, DMSO-d6): d = 7.41–7.45 (m, 1H), 7.55–7.63
(m, 4H), 7.65–7.69 (m, 1H), 7.71–7.77 (m, 3H), 7.85 (d,
J = 8.0 Hz, 2H), 8.11–8.18 (m, 2H) ppm; 13C NMR
Acknowledgments We are grateful to the Research Council of
Shahrood University of Technology for the financial support of this
work.
123

890
M. Bakherad, S. Jajarmi
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author(s) and the source are credited.
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