Glycerin and CeCl3 7H2O: A new and efficient recyclable reaction medium for the synthesis of quinoxalines

Article abstract of DOI:10.1080/00397911.2010.533050

An efficient and environmentally benign process for the synthesis of quinoxalines has been developed using glycerine-cerium chloride as a reaction medium. This method is applicable to a variety of diketones and 1,2-phenylenediamines to afford the corresponding quinoxaline derivatives in excellent yields. The reaction medium was recovered and reused for further reactions without any problem. Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397911.2010.533050

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Glycerin and CeCl3 · 7H2O: A New and
Efficient Recyclable Reaction Medium for
the Synthesis of Quinoxalines
A. Venkat Narsaiah a & J. Kranthi Kumar a
a Organic Chemistry Division, Indian Institute of Chemical
Technology, Hyderabad, India
Accepted author version posted online: 30 Aug 2011.Published
online: 11 Nov 2011.
To cite this article: A. Venkat Narsaiah & J. Kranthi Kumar (2012): Glycerin and CeCl3 · 7H2O:
A New and Efficient Recyclable Reaction Medium for the Synthesis of Quinoxalines, Synthetic
Communications: An International Journal for Rapid Communication of Synthetic Organic Chemistry,
42:6, 883-892
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Synthetic Communications1, 42: 883–892, 2012
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2010.533050
GLYCERIN AND CeCl3 ꢀ 7H2O: A NEW AND EFFICIENT
RECYCLABLE REACTION MEDIUM FOR THE
SYNTHESIS OF QUINOXALINES
A. Venkat Narsaiah and J. Kranthi Kumar
Organic Chemistry Division, Indian Institute of Chemical Technology,
Hyderabad, India
GRAPHICAL ABSTRACT
Abstract An efficient and environmentally benign process for the synthesis of quinoxalines
has been developed using glycerine–cerium chloride as a reaction medium. This method is
applicable to a variety of diketones and 1,2-phenylenediamines to afford the corresponding
quinoxaline derivatives in excellent yields. The reaction medium was recovered and reused
for further reactions without any problem.
Keywords Cecl3 ꢀ 7H2O; diketones; glycerine; ortho-phenylenediamines; quinoxalines
INTRODUCTION
Quinoxalines are a versatile class of nitrogen-containing heterocyclic com-
pounds, and they constitute useful intermediates in organic synthesis. Quinoxaline
derivatives are well known in the pharmaceutical industry and have been shown
to possess a broad spectrum of biological activities including antibacterial, antiviral,
anti-inflammatory, anticancer, and kinase inhibitory activities.[1,2] In addition, quin-
oxaline derivatives have been evaluated as anthelmintic agents, semiconductors,
dyes, and biocides.[3] Therefore, a variety of synthetic strategies have been developed
for the preparation of substituted quinoxalines.
Received May 17, 2010.
Address correspondence to A. Venkat Narsaiah, Organic Chemistry Division, Indian Institute of
Chemical Technology, Hyderabad 500007, India. E-mail: vnakkirala2001@yahoo.com
883

884
A. V. NARSAIAH AND J. K. KUMAR
Conventionally, quinoxaline synthesis can be achieved by the reaction of ortho-
pheny lenediamine with two-carbon synthones such as a-dicarbonyls,[4–8] a-halogeno
carbonyls, a-hydroxycarbonyls, a-azocarbonyls, epoxides, and a,b-dihalides.[9–16]
Among the reported procedures, the most common method is the condensation of
aryl-1,2-diamine with 1,2-diketone in refluxing ethanol or acetic acid[17–22] or using
different catalysts and reaction conditions.[23–28] However, many of these methods
suffer from several drawbacks, such as drastic reaction conditions, use of polar sol-
vents [e.g., AcOH, EtOH, dimethylsulfoxide (DMSO)], expensive and toxic metal
catalysts [e.g., Pd(OAc)2 and RuCl2(PPh3)3–[2,2,6,6-tetramethylpiperidin-1-yl]oxyl
(TEMPO)], tedious workup procedures, and unsatisfactory yields, which limit their
use.[29–31] Therefore, the development of simple, convenient, environmentally benign,
and improved method for the synthesis of quinoxalines derivatives would certainly
be useful in generating combinatorial libraries for drug discovery. Recently, Silvera
et al. reported glycerine–CeCl3 ꢀ 7H2O as a new and efficient recyclable reaction
medium for the synthesis of bis(indole) methanes,[32] and we demonstrated this
system for the synthesis of Hantzsch pyridines.[33]
RESULTS AND DISCUSSION
Herein, we report an efficient and environmentally friendly protocol for the
synthesis of quinoxaline derivatives using glycerine–CeCl3 ꢀ 7H2O as a reaction
medium. Initially, we chose the benzil and 1,2-phenylenediamine as standard
reactants to establish the best reaction conditions for this transformation. In a
typical experiment, equimolar amounts of benzil and 1,2-phenylenediamine were
reacted in gylcerine (2 mL) using CeCl3 ꢀ 7H2O as catalyst to obtain the corre-
sponding product 2,3-diphenylquinoxaline (3a) in excellent yields, as shown in
the Scheme 1.
We have examined the effect of temperature, amount of catalyst CeCl3 ꢀ 7H2O,
and reaction time using glycerine as a solvent. It was found that when using 0.5
equivalents of CeCl3 ꢀ 7H2O and 2.0 mL of glycerine at room temperature, the reac-
tion proceeded slowly and 70 % yield was obtained after stirring for 24 h. However,
when the mixture was heated at 60 ꢁC and 75 ꢁC, the desired product was obtained in
very good to excellent yields after 8 and 4 h, respectively. At higher temperature
(100 ꢁC), the reaction was completed within 4.0 h but in poor yield. The effect of
the amount of the catalyst was also studied. The observation shows that when
CeCl3 ꢀ 7H2O was used in 0.5 equivalents and 0.1 equivalents, the same yield was
obtained after 4 h of stirring at 75 ꢁC. On the other hand, using 1 equivalent of
CeCl3 ꢀ 7H2O was tested but there was no increase in yield or reduction in reaction
time. When the reaction was performed in glycerine without CeCl3 ꢀ 7H2O, at room
Scheme 1. General reaction for the synthesis of quinoxalines with aromatic-1,2-diamines.

SYNTHESIS OF QUINOXALINES
885
Scheme 2. General reaction for the synthesis of quinoxalines with alicyclic-1,2-diamines.
temperature or with heating, no product formation was observed. The ideal reaction
conditions for this condensation were 0.1 equivalent of CeCl3 ꢀ 7H2O (10 mol%) and
75 ꢁC in glycerine (Scheme 2 and Table 1).
This protocol was extended to other aromatic diketones, including benzil
and acenaphthylene-1,2-dione, and aliphatic carbonyls, including biacetyl. In a
similar manner, the aromatic diamines such as ortho-phenylene diamine (3a, 3e,
3m), 4-methylbenzene-1,2-diamine (3c and 3g), 4,5-dimethyl benzene-1,2-diamine
(3r, 3s, 3u), 4-notrobenzene-1,2-diamine (3j and 3n), pyridine-2,3-diamine (3b,
3f, 3q), 4-bromobenzene-1,2-diamine (3k, 3t, 3v), methyl-3,4-diaminobenzoate
(3i, 3o, 3p), and alicyclic diamine such as cyclo hexene-1,2-diamine (3d, 3h, 3l)
have been studied. The scope and generality of this procedure is illustrated with
respect to various diketo carbonyls and 1,2-diamines, and the results are presented
in Table 2. In general, the condensation takes place faster when the reaction was
carried out between aromatic diketones and ortho-phenylenediamines. In a similar
manner, the reaction between aliphatic diketones and alicyclic diamines was com-
paratively slower with lesser yields. All the reactions were completed within 4 to
6 h at 75 ꢁC. The products were obtained in 75% to 95% yields. The structures of
1
the products were identified by their H NMR, infrared (IR), and mass spectral
analysis.
The glycerin=CeCl3 ꢀ 7H2O mixture can be successfully reused up to five times
with excellent results. Accordingly, treatment of benzil (1) with ortho-phenylenedia-
mine (2) in presence of 10 mol% of CeCl3 ꢀ 7H2O in glycerine at 75 ꢁC afforded
2,3-diphenyl quinoxalines (3a) in 95 % yield (entry 1, Table 2). The product 3a
was simply extracted with ethyl acetate (2 ꢂ 10 mL), and the glycerin=CeCl3 ꢀ 7H2O
mixture was reused for further reactions up to four times without any problem.
The product was obtained in 95, 93, 93, and 90% yields respectively in successive
cycles.
Table 1. Optimization of reaction conditions for the synthesis of quinoxalines
Entry
Solvent
CeCl3 ꢀ 7H2O
Temp. (ꢁC)
Time (h)
Yield (%)
1
2
3
4
5
6
7
8
Glycerin
Glycerin
Glycerin
Glycerin
Glycerin
Glycerin
Glycerin
Glycerin
0.5
0.5
0.5
0.5
0.1
1.0
24
8.0
4.0
4.0
4.0
4.0
24
70
78
95
80
95
95
0
rt
60
75
100
75
75
rt
0
0
24
0
75

886
A. V. NARSAIAH AND J. K. KUMAR
Table 2. Glycerin- and CeCl3 ꢀ 7H2O-catalyzed synthesis of quinoxalines
No.
a
Diamine
Diketone
Product (3a–3v)a
Reaction time (h)
Yieldb (%)
95
4.0
b
c
4.0
4.0
6.0
92
95
88
d
e
f
5.0
5.0
5.0
6.0
5.0
6.0
5.0
5.5
4.5
90
84
85
75
83
81
83
85
92
g
h
i
j
k
l
m
n
5.5
84
86
85
o
p
q
5.0
5.0
5.0
86
(Continued )

SYNTHESIS OF QUINOXALINES
887
Table 2. Continued
No.
Diamine
Diketone
Product (3a–3v)a
Reaction time (h)
Yieldb (%)
r
s
6.0
5.0
85
91
t
5.0
4.0
4.5
85
95
86
u
v
aAll the products were identified by their 1H NMR, IR, and mass.
bYields were isolated and not optimized.
CONCLUSION
In conclusion, we have demonstrated an efficient and environmentally friendly
protocol for the synthesis of quinoxalines using new catalyst system
a
(glycerine–CeCl3 ꢀ 7H2O) via the coupling of diketo carbonyls with 1,2-diamines.
The method is very simple, clean, and applicable to a variety of reactants such as
aromatic, hetero aromatic, aliphatic, and alicyclic systems.
EXPERIMENTAL
Melting points were recorded on Buchi R-535 apparatus. IR spectra were
recorded on a Perkin-Elmer Fourier transform (FT)–IR 240-c spectrophotometer
using KBr optics. 1H NMR spectra were recorded on Gemini-200 and Varian
Bruker-300 spectrometers in CDCl3 using tetramethylsilane (TMS) as internal
standard. Mass spectra were recorded on a Finnigan MAT 1020 mass spectrometer
operating at 70 eV.
General Procedure for the Synthesis of Quinoxalines
The catalyst CeCl3 ꢀ 7H2O (37 mg, 0.1 mmol) were added to a mixture of dike-
tone (210 mg, 1.0 mmol) and diamine (128 mg, 1.1 mmol) in glycerine (2.0 mL) at
room temperature. The resulting reaction mixture was stirred at 75 ꢁC for a period
of 4 to 6 h (Table 2). The progress of the reaction was monitored by thin layer chro-
matography (TLC). After completion of the reaction, as indicated by TLC, the reac-
tion mixture was cooled to room temperature. Ethyl acetate (10 mL) was added to
the reaction mixture and stirred well, the ethyl acetate layer was separated by decan-
tation, and the process was repeated. The combined organic layers were washed with

888
A. V. NARSAIAH AND J. K. KUMAR
water and brine, dried over Na2SO4, and concentrated under reduced pressure to
afford the crude products, which were purified by column chromatography using sil-
1
ica gel (60–120 mesh). All the pure products were identified by their IR, H NMR,
and mass spectroscopic data.
Spectral Data for All Compounds
2,3-Diphenylquinoxaline (3a). IR (KBr): t 3384, 3056, 2934, 1659, 1595,
1541, 1474, 1442, 1394, 1344, 1248, 1216, 1174, 1053, 977, 925, 872, 798, 768, 725,
1
696 cmꢃ1; H NMR (CDCl3): d 7.25–7.35 (m, 6H), 7.45–7.55 (m, 4H), 7.75 (q, 2H,
J ¼ 6.0 Hz), 8.35 (d, 2H, J ¼ 6.0 Hz); EIMS m=z (%): 283 (mþ1 100), 256 (10), 205
(10), 179 (35), 140 (28), 128 (18), 104 (10), 91 (15), 79 (50), 76 (20), 52 (10).
2,3-Diphenylpyrido-[2,3-b]-pyrazine (3b). IR (KBr): t 3413, 3058, 2923,
2853, 1592, 1549, 1433, 1385, 1338, 1242, 1189, 1123, 1070, 1020, 973, 922, 806,
1
776, 740, 698 cmꢃ1; H NMR (CDCl3): d 7.25–7.40 (m, 6H), 7.45–7.55 (m, 2H),
7.58–7.63 (m, 2H), 7.75 (q, 1H, J ¼ 6.5 Hz), 8.50 (dd, 1H, J ¼ 3.5, 10.0 Hz),
9.12–9.20 (m, 1H); EIMS m=z (%): 284 (mþ1 100), 281 (12), 270 (15), 242 (20),
223 (10), 205 (10), 189 (15), 179 (35), 159 (20), 145 (20), 117 (30), 103 (40), 82
(56), 77 (10), 51 (10).
6-Methyl-2,3-diphenylquinoxaline (3c). IR (KBr): t 3419, 3054, 2922,
1665, 1591, 1485, 1447, 1342, 1250, 1208, 1172, 1060, 1022, 978, 875, 832, 773,
699 cmꢃ1 1H NMR (CDCl3): d 2.63 (s, 3H), 7.25–7.35 (m, 5H), 7.45–7.55 (m,
;
5H), 7.89–8.08 (m, 3H).; EIMS m=z (%): 297 (mþ1 100), 145 (20), 105 (15), 60 (20).
2,3-Diphenyl-4a,5,6,7,8,8a-hexahydroquinoxaline (3d). IR (KBr): t 3386,
2937, 2856, 1661, 1595, 1552, 1488, 1443, 1316, 1288, 1262, 1212, 1174, 1089, 1056,
1
979, 916, 850, 793, 766, 741, 695 cmꢃ1; H NMR (CDCl3): d 1.35–1.45 (m, 3H),
1.50–1.62 (m, 2H), 1.85–1.95 (m, 1H), 2.50 (d, 1H, J ¼ 6.0 Hz), 2.80 (d, 1H,
J ¼ 3.0 Hz), 7.15–7.28 (m, 6H), 7.32–7.42 (m, 4H); EIMS m=z (%): 289 (mþ1 100),
288 (10), 241 (10), 171 (10), 165 (15), 151 (10), 104 (60), 102 (30), 79 (25), 67 (35),
54 (10).
2,3-Dimethylquinoxaline (3e). IR (KBr): t 3380, 2941, 2885, 1647, 1428,
1
1397, 1324, 1208, 1164, 1044, 989, 922, 856, 762 cmꢃ1; H NMR (CDCl3): d 2.72
(s, 6H), 7.60–7.70 (m, 2H), 7.90–8.01 (m, 2H); EIMS m=z (%): 158 (mþ 70), 143
(10), 130 (10), 118 (10), 117 (100), 102 (10), 90 (15), 89 (12), 77 (20), 76 (35), 75
(12), 61 (12), 50 (18), 41 (10).
2,3-Dimethylpyrido-[2,3-b]-pyrazine (3f). IR (neat): t 3376, 2994, 2947,
1641, 1599, 1560, 1461, 1395, 1313, 1238, 1191, 1151, 1108, 1041, 995, 918, 830,
1
796, 713, 680 cmꢃ1; H NMR (CDCl3): d 2.78 (s, 3H), 2.83 (s, 3H), 7.58–7.68 (m,
1H), 8.35 (d, 1H, J ¼ 5.0 Hz), 9.05 (d, 1H, J ¼ 3.0 Hz).; EIMS m=z (%): 159 (mþ
48), 144 (10), 118 (58), 105 (12), 91 (15), 77 (52), 61 (100), 50 (18), 41 (66).
2,3,6-Trimethylquinoxaline (3g). IR (KBr): t 3388, 2940, 1620, 1563, 1494,
1
1442, 1399, 1367, 1325, 1255, 1200, 1113, 1044, 988, 832, 769, 677 cmꢃ1; H NMR
(CDCl3): d 2.58 (s, 3H), 2.70 (s, 6H), 7.45 (d, 1H, J ¼ 7.0 Hz), 7.70 (s, 1H), 7.83
(d, 1H, J ¼ 7.0 Hz); EIMS m=z (%): 173 (mþ1 100), 146 (10), 132 (10), 91 (25), 76 (15).

SYNTHESIS OF QUINOXALINES
889
1
2,3-Dimethyl-4a,5,6,7,8,8a-hexahydroquinoxaline (3h). H NMR (CDCl3):
d 0.92 (s, 6H), 1.30–1.45 (m, 4H), 1.55–1.70 (m, 6H); EIMS m=z (%): 164 (mþ 100),
140 (20), 114 (10), 98 (10), 82 (10), 56 (10), 43 (15).
Methyl-2,3-Dimethylquinoxaline-6-carboxylate (3i). IR (KBr): t 3384,
2943, 2886, 1712, 1658, 1442, 1400, 1343, 1307, 1263, 1198, 1095, 1046, 992, 918,
1
854, 765, 695 cmꢃ1; H NMR (CDCl3): d 2.75 (s, 6H), 3.99 (s, 3H), 7.98 (d, 1H,
J ¼ 6.5 Hz), 8.25 (d, 1H, J ¼ 6.5 Hz), 8.68 (s, 1H); EIMS m=z (%): 217 (mþ 100),
191 (20), 177 (12), 102 (25).
2,3-Dimethyl-6-nitroquinoxaline (3j). IR (KBr): t 3383, 2941, 1617, 1525,
1
1403, 1342, 1197, 1163, 1111, 1045, 995, 919, 847, 821, 744, 711, 675 cmꢃ1; H
NMR (CDCl3): d 2.80 (s, 6H), 8.09 (d, 1H, J ¼ 7.0 Hz), 8.44 (d, 1H, J ¼ 7.0 Hz),
8.88 (s, 1H); EIMS m=z (%): 204 (mþ1 100), 194 (10), 179 (10), 171 (15), 164 (10),
158 (10), 155 (15), 145 (20), 112 (10), 72 (10).
6-Bromo-2,3-dimethylquinoxaline (3k). IR (KBr): t 3406, 3085, 3020,
2950, 1597, 1573, 1480, 1440, 1415, 1398, 1366, 1322, 1250, 1159, 1127, 1054,
1
1015, 963, 913, 889, 828, 777, 707, 671 cmꢃ1; H NMR (CDCl3): d 2.72 (s, 6H),
7.70 (d, 1H, J ¼ 7.0 Hz), 7.82 (d, 1H, J ¼ 7.0 Hz), 8.12 (s, 1H); EIMS m=z (%): 237
(mþ 100), 211 (10), 171 (10), 155 (20), 145 (10), 115 (10).
7a,8,9,10,11,11a-Hexahydroacenaphtho-[1,2-b]-quinoxaline
(3l). IR
(KBr): t 3387, 3064, 2938, 1661, 1592, 1449, 1323, 1211, 1172, 1110, 1045, 996,
1
927, 874, 794, 719, 641 cmꢃ1; H NMR (CDCl3): d 1.48–1.62 (m, 3H), 1.90–2.05
(m, 3H), 2.55 (d, 2H, J ¼ 6.0 Hz), 3.08–3.18 (m, 2H), 7.68 (t, 2H, J ¼ 6.0 Hz), 7.95
(d, 4H, J ¼ 6.0 Hz).
Acenaphtho-[1,2-b]-quinoxaline (3m). IR (KBr): t 3386, 2939, 2856, 1646,
1428, 1299, 1208, 1108, 1043, 992, 923, 857, 758 cmꢃ1; 1H NMR (CDCl3): d 7.71 (d,
2H, J ¼ 6.0 Hz), 7.83 (t, 2H, J ¼ 6.0 Hz), 8.08 (d, 2H, J ¼ 6.0 Hz), 8.18 (d, 1H,
J ¼ 6.0 Hz), 8.41 (d, 2H, J ¼ 6.0 Hz).
6-Nitro-2,3-diphenylquinoxaline (3n). IR (KBr): t 3381, 3061, 2937, 1660,
1594, 1518, 1448, 1398, 1341, 1210, 1170, 1111, 1050, 995, 980, 907, 874, 767, 720,
1
698 cmꢃ1; H NMR (CDCl3): d 7.30–7.45 (m, 6H), 7.95 (d, 4H, J ¼ 7.0 Hz), 8.25
(d, 1H, J ¼ 7.0 Hz), 8.54 (d, 1H, J ¼ 7.0 Hz), 9.08 (s, 1H); EIMS m=z (%): 328
(mþ1 65), 298 (30), 265 (25), 255 (20), 233 (45), 225 (20), 211 (35), 194 (10), 178
(35), 171 (40), 164 (10), 149 (10), 131 (15), 115 (20), 105 (100), 75 (30).
Methyl-2,3-diphenylquinoxaline-6-carboxylate (3o). IR (KBr): t 3384,
1
2942, 1715, 1651, 1445, 1309, 1256, 1178, 1107, 1045, 920, 856, 761, 677 cmꢃ1; H
NMR (CDCl3): d 4.02 (s, 3H), 7.30–7.40 (m, 6H), 7.48–7.58 (m, 4H), 8.16 (d, 1H,
J ¼ 7.0 Hz), 8.34 (d, 1H, J ¼ 7.0 Hz), 8.87 (s, 1H).; EIMS m=z (%): 341 (mþ1 100),
267 (10), 253 (10), 232 (10), 190 (15), 110 (20), 60 (20).
Methylacenaphtho-[1,2-b]-quinoxaline-9-carboxylate (3p). IR (KBr): t
3360, 2923, 2853, 1709, 1618, 1517, 1435, 1368, 1299, 1231, 1105, 1046, 986, 907,
1
824, 763 cmꢃ1; H NMR (CDCl3): d 4.05 (s, 3H), 7.87 (t, 2H, J ¼ 7.0 Hz), 8.10 (d,
2H, J ¼ 7.0 Hz), 8.20 (d, 1H, J ¼ 7.0 Hz), 8.30 (d, 1H, J ¼ 7.0 Hz), 8.43 (d, 2H,
J ¼ 7.0 Hz), 8.39 (s, 1H); EIMS m=z (%): 313 (mþ1 20), 279 (10), 265 (10), 247

890
A. V. NARSAIAH AND J. K. KUMAR
(20), 237 (25), 219 (45), 207 (35), 191 (100), 177 (25), 171 (30), 167 (25), 160 (10), 149
(10), 131 (15), 115 (30).
Compound (3q). IR (KBr): t 3383, 2940, 2850, 1620, 1563, 1494, 1442, 1399,
1
1367, 1325, 1255, 1200, 1158, 1113, 1095, 1044, 988, 907, 833, 769, 677 cmꢃ1; H
NMR (CDCl3): d 7.68–7.72 (m, 1H), 7.82–7.90 (m, 2H), 8.12–8.18 (m, 2H), 8.40
(d, 1H, J ¼ 6.0 Hz), 8.01–8.10 (m, 2H), 9.12 (s, 1H); EIMS m=z (%): 255 (mþ 25),
233 (56), 225 (18), 211 (33), 194 (15), 178 (30), 171 (65), 149 (20), 131 (25), 115
(15), 105 (100), 75 (28).
2,3,6,7-Tetramethylquinoxaline (3r). IR (KBr): t 3383, 2940, 2850, 1620,
1563, 1494, 1442, 1399, 1367, 1325, 1255, 1200, 1158, 1113, 1095, 1044, 988, 907,
1
833, 769, 677 cmꢃ1; HNMR (CDCl3): d 7.68–7.72 (m, 1H), 7.82–7.90 (m, 2H),
8.12–8.18 (m, 2H), 8.40 (d, 1H, J ¼ 6.0 Hz), 8.01–8.10 (m, 2H), 9.12 (s, 1H); EIMS
m=z (%): 255 (mþ 25), 233 (56), 225 (18), 211 (33), 194 (15), 178 (30), 171 (65),
149 (20), 131 (25), 115 (15), 105 (100), 75 (28).
9,10-Dimethylacenaphtho-[1,2-b]-quinoxaline (3s). IR (KBr): t 3386,
1
2939, 2856, 1646, 1428, 1299, 1208, 1108, 1043, 992, 923, 857, 758 cmꢃ1; H NMR
(CDCl3): d 2.52 (s, 6H), 7.81 (t, 2H, J ¼ 6.0 Hz), 7.90 (s, 2H), 8.20 (d, 2H, J ¼ 6.0 Hz),
8.39 (d, 2H, J ¼ 6.0 Hz); EIMS m=z (%): 282 (mþ 100), 256 (25), 221 (10), 195 (15),
171 (10), 136 (20), 111 (10), 84 (20).
9-Bromoacenaphtho-[1,2-b]-quinoxaline (3t). IR (KBr): t 3341, 3056,
2937, 2879, 1642, 1571, 1495, 1408, 1384, 1315, 1254, 1201, 1159, 1101, 1094,
1005, 975, 908, 846, 761, 679 cmꢃ1 1H NMR (CDCl3): d 7.50–7.60 (m, 2H),
;
7.80–7.99 (m, 6H), 8.30 (s, 1H); EIMS m=z (%): 333 (mþ1 100), 253 (40), 230 (10),
204 (10), 180 (10), 152 (10), 126 (15), 104 (20), 81 (10), 56 (20).
6,7-Dimethyl-2,3-diphenylquinoxaline (3u). IR (KBr): t 3386, 2939, 2856,
1
1646, 1428, 1299, 1208, 1108, 1043, 992, 923, 857, 758 cmꢃ1; H NMR (CDCl3): d
2.52 (s, 6H), 7.81 (t, 2H, J ¼ 6.0 Hz), 7.90 (s, 2H), 8.20 (d, 2H, J ¼ 6.0 Hz), 8.39 (d,
2H, J ¼ 6.0 Hz); EIMS m=z (%): 310 (mþ 25), 233 (10), 156 (100), 132 (20), 105
(30), 94 (10), 76 (25), 68 (15), 56 (10).
6-Bromo-2,3-diphenylquinoxaline (3v). IR (KBr): t 3408, 3056, 2935,
1662, 1590, 1506, 1486, 1445, 1348, 1252, 1204, 1185, 1061, 1008, 973, 895, 812,
1
779, 632 cmꢃ1; H NMR (CDCl3): d 7.25–7.40 (m, 6H), 7.50–7.75 (m, 5H), 8.50
(d, 1H, J ¼ 6.0 Hz), 9.19 (brs, 1H); EIMS m=z (%): 360 (mþ 100), 281 (15), 204
(20), 127 (30), 104 (10), 76 (20), 56 (20).
ACKNOWLEDGMENT
J. K. K. is thankful to the University Grants Commission, New Delhi, for
providing a fellowship.

SYNTHESIS OF QUINOXALINES
891
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