Hypervalent iodine(iii) sulfonate mediated synthesis of quinoxalines in liquid peg-400

Article abstract of DOI:10.1002/jccs.200900102

PEG-400[poly(ethylene glycol-400)] is used as a "green" recyclable solvent in the one-pot synthesis of quinoxalines by reaction with aryl ketones, hypervalent Iodine(III) Sulfonate, and o-phenylenediamines. Significant rate enhancements and improved yields have been observed.

Full text of DOI:10.1002/jccs.200900102

Journal of the Chinese Chemical Society, 2009, 56, 683-687
683
Communication
Hypervalent Iodine(III) Sulfonate Mediated Synthesis of Quinoxalines in
Liquid PEG-400
Pei-Ying Lina (
), Rei-Sheu Houb* (
), Huey-Min Wangb (
),
Iou-Jiun Kangc (
) and Ling-Ching Chena* (
)
aGraduate Institute of Pharmaceutical Sciences, College of Pharmacy, Kaohsiung Medical University,
Kaohsiung 807, Taiwan, R.O.C.
bChung Hwa University of Medical Technology, Tainan 717, Taiwan, R.O.C.
cDivision of Biotechnology and Pharmaceutical Research, National Health Research Institutes,
Miaoli County 350, Taiwan, R.O.C.
PEG-400[poly(ethylene glycol-400)] is used as a “green” recyclable solvent in the one-pot synthesis
of quinoxalines by reaction with aryl ketones, hypervalent Iodine(III) Sulfonate, and o-phenylenedi-
amines. Significant rate enhancements and improved yields have been observed.
Keywords: Hypervalent iodine; Quinoxalines; Poly(ethylene golycol).
INTRODUCTION
Nitrogen-containing heteroaromatic and heterocyclic
terials for ionic liquids) and their environmental safety is
still debated. Compared with PEG, however, toxicity and
environmental burden of ionic liquids are for the most part
unknown. Furthermore, the cost of ionic liquids is often
more expensive than that of PEG.11 To date some of the
more important reactions have been carried out and inves-
tigated in PEG, for example, Heck reaction,12 Lindlar
catalytic hydrogenation,13 asymmetric dihydroxylation,14
Baylis-Hillman reaction,15 Biginelli reaction,16 Suzuki-
Miyaura reaction, Stille cross-coupling reaction,17 Wacker
reaction,18 and asymmetric aldol reaction,19 etc.
compounds are indispensable structural units for both the
chemist and the biochemist. Quinoxalines constitute the
basis of many insecticides, fungicides, herbicides and
anthelmintics, as well as being important in human health
and as receptor antagonists.1,2 A number of methods have
been developed for the synthesis of substituted quinoxa-
lines involving condensation of 1,2-diamines with a-di-
ketones,3 1,4-addition of 1,2-diamines to diazenylbutenes,4
oxidation-trapping of a-hydroxy ketones with 1,2-diamine,5
cyclization-oxidation of phenacyl bromides and o-phenyl-
enediamines through solid-phase synthesis6 and oxidative
coupling of epoxides with ene-1,2-diamines.7 Neverthe-
less, most of these methods suffer from unsatisfactory
yields, difficult experimental procedures, expensive and
detrimental metal precursors and harsh reaction conditions.
Therefore, the development of improved methods for the
synthesis of quinoxaline derivatives has acquired rele-
vance to current research.
Poly(ethylene golycol) (PEG),8 a biologically accept-
able polymer used extensively in drug delivery and in bio-
conjugates as tools for diagnostics has been used as a sol-
vent medium support for various transformations.9 In re-
cent times ionic liquids have been in the forefront of re-
search, and several publications and reviews have already
appeared.10 Even though ionic liquids offer some advan-
tages, the tedious preparation of ionic liquids (and raw ma-
Recently, hypervalent iodine(III) reagents have been
used extensively in organic synthesis due to their low tox-
icity, ready availability and easy handling.20 In continua-
tion of our efforts to develop greener organic reaction pro-
cedures, we now report [hydroxyl(2,4-dinitrobenzenesul-
fonyloxy)iodo]benzene (HDNIB) mediated facile and effi-
cient synthesis of quinoxalines. The required HDNIB was
prepared in satisfactory yields from the reaction 2,4-dini-
trobenzenesulfonic acid with phenylidodine(III) diacetate
(PIDA).21 Treatment of aromatic ketones with HDNIB in
acetonitrile produced the a-[(2,4-dinitrobenzene)sulfo-
nyl]oxy ketone intermediates (2). Subsequent cyclocon-
densation by o-phenylenediamines in PEG-400 gave the
corresponding quinoxalines (3) in good yields (Scheme I).
RESULTS AND DISCUSSION
The 2,4-dinitrobenzenesulfonyloxy group located at

684 J. Chin. Chem. Soc., Vol. 56, No. 4, 2009
Lin et al.
Scheme I
Table 1. Synthesis of quinoxalines 3a-m
the a position to a carbonyl group represents an increas-
ingly important entity in both mechanistic and synthetic or-
ganic chemistry. One reason for this importance is that 2,4-
dinitrobenzenesulfonyloxy group is a good leaving group,
and this accounts for the considerable synthetic utility as-
sociated with this group in functionalization of carbonyl
compounds.
Entry
Ar
R1
R2
Product Yield (%)
1
C6H5
4-MeC6H4
4-MeOC6H4
4-FC6H4
4-ClC6H4
4-BrC6H4
C6H5
H
H
H
H
H
H
H
H
H
H
Me
H
H
H
H
3a
3b
3c
3d
3e
3f
91
87
85
88
84
86
87
90
92
89
87
90
86
2
3
H
4
H
5
H
6
H
As shown in Scheme I, our experiments involving a
one-pot procedure for the preparation of quinoxalines (3)
by cyclocondensation of o-phenylenediamines with a-sul-
fonyloxy aryl ketone (2) in PEG-400 at room temperature
were successful. PEG-400 acts as a solvent medium and an
activator in the cyclocondensation reaction. The results are
summarized in the Table 1. An array of aryl ketones having
electron-donating and –withdrawing substituents on the ar-
omatic ring attached to carbonyl carbon reacted with o-
phenylenediamine to afford 2-aryl substituted quinoxalines
(3b-3f) in good yields. The reaction proceeds likewise with
aryl ketones having heteroaryl group attached to carbonyl
carbon to give the corresponding 2-heteroaryl substituted
quinoxalines (3j-3l) in 89%, 87% and 90% yields, respec-
7
Me
C6H5
C6H5
H
3g
3h
3i
8
C6H5
9
C6H5
10
11
12
13
2-Pyridyl
2-Furyl
3j
H
3k
3l
2-Thienyl
2-Naphthyl
H
H
3m
tively. When the reaction was conducted in the classical
molecular solvent, such as acetonitrile, the preparation of
2-phenylquinoxaline (3a) needs refluxing for 6 h; however,
in PEG-400, the reaction took place at room temperature
for 30 min and gave a higher yield (Table 2).
The PEG-400 can be typically recovered by extract-
Table 2. Effect of solvent on the cyclocondensation of á-sulfonyloxy aryl ketone (2a-c) with
o-phenylenediamine to form 3a-c
Reaction temperature Reaction time
Entry
Solvent
Quinoxline 3
Yield (%)
(°C)
(h)
1
2
3
4
5
6
MeCN
PEG-400
MeCN
80
25
80
25
80
25
6
0.5
6
3a
3a
3b
3b
3c
3c
80
91
78
87
77
85
PEG-400
MeCN
0.5
6
PEG-400
0.5

Synthesis of Quinoxalines in Liquid PEG-400
J. Chin. Chem. Soc., Vol. 56, No. 4, 2009 685
ing out the product first and the recovered solvent can be
reused without loss activity.
2-(4-Methoxyphenyl)quinoxaline (3c)
mp 97-98 °C (Lit.,22 99-100 °C). IR (KBr) n: 3057,
2360, 954, 759 cm-1; 1H NMR (CDCl3) d: 3.90 (s, 3H), 7.07
(dd, J = 2.0, 6.8 Hz, 2H), 7.68-7.77 (m, 2H), 8.09 (t, J = 8.0
Hz, 2H), 8.15-8.18 (m, 2H), 9.28 (s, 1H); 13C NMR (CDCl3,
100 MHz) d: 55.3, 114.5, 128.9, 129.0, 129.1, 129.3,
130.1, 141.1, 142.2, 143.0, 151.4, 161.4; EI-MS m/z (rela-
tive intensity) 236 (M+), 221, 209, 193, 166.
In conclusion, we have described a novel and effi-
cient method for the synthesis of quinoxalines using PEG-
400 as reaction medium. The important features of this pro-
cedure are enhanced reaction rate, mild reaction condition,
high yields and green aspects such as avoiding hazardous
organic solvents, toxic catalysts and waste, ease of recov-
ery and reuse of this novel reaction medium.
2-(4-Fluorophenyl)quinoxaline (3d)
mp 119-120 °C (Lit.,22 120-121 °C). IR (KBr) n:
3048, 2361, 956, 755 cm-1; 1H NMR (CDCl3) d: 7.22-7.28
(m, 2H), 7.72-7.81 (m, 2H), 8.11-8.14 (m, 2H), 8.18-8.22
(m, 2H), 9.29 (s, 1H); 13C NMR (CDCl3, 100 MHz) d:
116.3, 129.1, 129.4, 129.5, 130.3, 132.8, 132.9, 141.4,
142.1, 142.8, 150.7, 165.4; EI-MS m/z (relative intensity)
225, 224 (M+), 197, 196.
EXPERIMENTAL SECTION
All melting points are uncorrected. The IR spectra
were recorded on a Shimadzu IR-27 G spectrophotometer.
1H NMR and 13C NMR spectra were recorded on a Varian
Unity Plus 400 MHz. Chemical shifts (d) were measured in
ppm with respect to TMS. MS were obtained on a JEOL
JMS D-300 instrument.
2-(4-Chlorophenyl)quinoxaline (3e)
General procedure for the synthesis of quinoxalines
(3)
mp 134 °C. IR (KBr) n: 3056, 2360, 955, 760 cm-1; 1H
NMR (CDCl3) d: 7.52-7.55 (m, 2H), 7.74-7.82 (m, 2H),
8.11-8.17 (m, 4H), 9.30 (s, 1H); 13C NMR (CDCl3, 100
MHz) d: 128.7, 129.1, 129.3, 129.5, 129.7, 130.4, 135.1,
136.5, 141.6, 142.1, 142.8, 150.5; EI-MS m/z (relative in-
tensity) 242, 240 (M+), 213, 205, 178, 151; Anal. Calcd for
C14H9ClN2: C, 69.86; H, 3.77; N, 11.64. Found: C, 69.75;
H, 3.68; N, 11.78.
To a solution of aryl ketone (1) (1.0 mmol) in ace-
tonitrile (20 mL), was added HDNIB (1.2 mmol) and re-
fluxed for 1 h. After removal of acetonitrile, Then PEG (2
g), o-phenylenediamine (1.0 mmol) and sodium carbonate
(0.6 mmol) were added to the reaction mixture and was
stirred at room temperature for 0.5 h to complete the reac-
tion. Subsequently, the reaction mixture was extracted with
Et2O (3 ´ 5 mL). The remaining PEG suspension was fil-
tered and reused for further runs. The combined ethereal
solution was evaporated under reduced pressure. The re-
sulting residue was chromatographed on silica gel using
ethyl acetate as eluent to give 3.
2-(4-Bromophenyl)quinoxaline (3f)
mp 128 °C. IR (KBr) n: 3057, 2359, 955, 760 cm-1; 1H
NMR (CDCl3) d: 7.68-7.71 (m, 2H), 7.74-7.82 (m, 2H),
8.07-8.15 (m, 4H), 9.29 (s, 1H); 13C NMR (CDCl3, 100
MHz) d: 124.9, 128.9, 129.1, 129.5, 129.7, 130.4, 132.3,
135.6, 141.6, 142.7, 150.6; EI-MS m/z (relative intensity)
287, 286, 285 (M+), 284, 205, 178, 151; Anal. Calcd for
C14H9BrN2: C, 58.97; H, 3.18; N, 9.82. Found: C, 59.23; H,
3.26; N, 9.74.
2-Phenylquinoxaline (3a)
mp 74-75 °C (Lit.,22 75-76 °C). IR (KBr) n: 3119,
1614, 1560, 1076 cm-1; 1H NMR (CDCl3) d: 7.55-7.58 (m,
3H), 7.74-7.82 (m, 2H), 8.11-8.22 (m, 4H), 9.34 (s, 1H);
13C NMR (CDCl3, 100 MHz) d: 127.5, 128.5, 129.1, 129.5,
129.6, 130.1, 130.2, 136.8, 141.5, 142.3, 143.3, 151.8; EI-
MS m/z (relative intensity) 206 (M+), 179, 152.
2-(4-Methylphenyl)quinoxaline (3b)
mp 92-93 °C (Lit.,22 90-91°C). IR (KBr) n: 3053,
952, 748 cm-1; 1H NMR (CDCl3) d: 2.46 (s, 3H), 7.38 (dd, J
= 0.8, 8.8 Hz, 2H), 7.71-7.80 (m, 2H), 8.09-8.16 (m, 4H),
9.32 (s, 1H); 13C NMR (CDCl3, 100 MHz) d: 21.4, 127.4,
129.0, 129.3, 129.5, 129.8, 130.2, 133.9, 140.5, 141.4,
142.3, 143.3, 151.8; EI-MS m/z (relative intensity) 220
(M+), 193, 192.
2-Methyl-3-phenyl-quinoxaline (3g)
mp 55 °C (Lit.,23 56 °C). IR (KBr) n: 3058, 2359,
1558, 1342, 816, 764 cm-1; 1H NMR (CDCl3) d: 2.78 (s,
3H), 7.46-7.54 (m, 3H), 7.63-7.75 (m, 4H), 8.04-8.12 (m,
2H); 13C NMR (CDCl3, 100 MHz) d: 24.3, 128.2, 128.4,
128.8, 128.9, 129.1, 129.6, 138.9, 140.8, 141.1, 152.4,
154.8; EI-MS m/z (relative intensity) 220 (M+), 219, 179,
151.
2,3-Diphenylquinoxaline (3h)
mp 123-124 °C (Lit.,24 126-127 °C). IR (KBr) n:
3054, 2922, 1539, 1344, 768, 729 cm-1; 1H NMR (CDCl3)
d: 7.32-7.40 (m, 6H), 7.52-7.54 (m, 4H), 7.75 (m, dd, J =

686 J. Chin. Chem. Soc., Vol. 56, No. 4, 2009
Lin et al.
2.4, 9.2 Hz, 2H), 8.20 (dd, J = 2.4, 8.8 Hz, 2H); 13C NMR
(CDCl3, 100 MHz) d: 128.2, 128.7, 129.1, 129.7, 129.9,
139.0, 141.1, 153.4; EI-MS m/z (relative intensity) 282
(M+), 178, 152, 140, 77.
129.5, 130.3, 133.3, 134.0, 134.0, 141.5, 142.3, 143.4,
151.6; EI-MS m/z (relative intensity) 256 (M+), 202, 153,
126.
6-Methyl-2,3-diphenylquinoxaline (3i)
ACKNOWLEDGEMENT
mp 118-119 °C (Lit.,24 116-117 °C). IR (KBr) n:
3055, 2940, 1617, 1199, 1020, 699 cm-1; 1H NMR (CDCl3)
d: 2.60 (s, 3H), 7.30-7.33 (m, 6H), 7.49-7.52 (m, 4H), 7.58
We gratefully acknowledge the National Council Sci-
ence of Republic of China for financial support of this
work.
(dd, J = 2.4, 11.2 Hz, 1H), 8.06 (d, J = 11.2 Hz, 1H); 13
C
NMR (CDCl3, 100 MHz) d: 21.8, 127.9, 128.1, 128.5,
128.6, 129.7, 129.7, 132.2, 139.1, 140.3, 142.2, 152.4,
153.2; EI-MS m/z (relative intensity) 296 (M+), 192, 165,
89.
Received April 14, 2009.
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