One-pot synthesis of quinoxalines from reductive coupling of 2-nitroanilines and 1,2-diketones using indium

Article abstract of DOI:10.1016/j.tet.2015.01.007

The one-pot reduction-cyclization of 2-nitroanilines and 1,2-diketones to give quinoxalines was investigated. Using indium and an appropriate acid such as acetic acid or indium(III) chloride, various quinoxaline derivatives including 2,3-dialkylquinoxalines, 2,3-diphenylquinoxalines, 2,3-di-2-thiophenylquinoxalines, 2,3-di(pyridin-2-yl)quinoxalines, and dibenzo[a,c]phenazines were synthesized in moderate to excellent yield.

Full text of DOI:10.1016/j.tet.2015.01.007

Tetrahedron xxx (2015) 1e12
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Tetrahedron
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One-pot synthesis of quinoxalines from reductive coupling of 2-
nitroanilines and 1,2-diketones using indium
Ahra Go a, Geunsoo Lee a, Jaeho Kim a, Seolhee Bae a, Byung Min Lee b,
,
Byeong Hyo Kim a
*
a Department of Chemistry, Kwangwoon University, Seoul 139-701, Republic of Korea
b Korea Research Institute of Chemical Technology, Taejon 305-600, Republic of Korea
a r t i c l e i n f o
a b s t r a c t
Article history:
The one-pot reduction-cyclization of 2-nitroanilines and 1,2-diketones to give quinoxalines was investigated.
Using indium and an appropriate acid such as acetic acid or indium(III) chloride, various quinoxaline de-
rivatives including 2,3-dialkylquinoxalines, 2,3-diphenylquinoxalines, 2,3-di-2-thiophenylquinoxalines, 2,3-
di(pyridin-2-yl)quinoxalines, and dibenzo[a,c]phenazines were synthesized in moderate to excellent yield.
Ó 2015 Elsevier Ltd. All rights reserved.
Received 6 November 2014
Received in revised form 6 January 2015
Accepted 7 January 2015
Available online xxx
Keywords:
Indium
N-Heterocycles
Reduction-triggered cyclization
One-pot quinoxaline synthesis
1. Introduction
characteristics of indium must be an attractive merit. Thus, the
application of indium metal for various reductive organic trans-
Organic compounds containing the quinoxaline moiety have
received considerable synthetic attention because of their in-
teresting biological properties. Quinoxaline derivatives are not only
widely distributed in nature, but they have been synthesized by
many research groups and many of these compounds exhibit
a broad spectrum of biological activity including antibacterial,1e3
antifungal,4,5 antiviral,6 anticancer,7 antituberculosis,8 antimalar-
ial,9 and anti-inflammatory properties.1,3 A typical approach to the
quinoxaline ring is the condensation of 1,2-arylenediamines with
1,2-dicarbonyl compounds in ethanol or acetic acid.10 Recently
developed synthetic methods include the use of I2,11,12 sulfamic acid
(SA),13 Montmorillonite K-10,14 silica-bonded S-sulfonic acid
formations has been pursued by many synthetic groups recently.27
Accordingly, we have developed various indium-mediated re-
ductive reactions during the past decade focusing in particular on
nitroarenes including reductive cyclization reactions to prepare
nitrogen-containing heterocyclic compounds.28 New and efficient
one-pot indium-mediated syntheses of nitrogen containing het-
erocycles include 2,1-benzisoxazoles,28a benzimidazoles,28b qui-
nolines,28c indazoles,28d,e oxazoles,28f indoles,28g,h and pyrroles.28i
While 1,2-aryl diamines are the most commonly used starting
substrates for the synthesis of quinoxalines, an extension of our
indium-mediated reductive reaction to 2-nitroaryl amines would
offer a more diverse one-pot synthetic approach to quinoxalines.
Therefore, we examined the one-pot reductive heterocyclization
using a 2-nitroaryl amine and 1,2-dicarbonyl compound in the
presence of indium to accomplish a coupling reaction giving the
quinoxaline. Herein, we report the simple and efficient trans-
formation for preparation of quinoxalines from 2-nitroaryl amines,
which have rarely been used as substrates for quinoxaline
synthesis.
(SSA),15 H6P2W18 62$24H2O,16 InCl3,17 MnCl2,11 CuSO4$5H2O,18
O
ionic liquid,19 ceric ammonium nitrate (CAN),20 Ga(OTf)3,21 TiO2,22
and graphite.23 In addition, the use of phenacyl bromides,24 diaz-
oketones,25 and 2-(phenylethynyl)benzaldehydes in place of 1,2-
dicarbonyl compounds has also appeared in the recent literature.26
Traditionally used reducing metal reagents such as iron, tin, and
zinc metals are getting more unforgiving to use because of envi-
ronmental issues. Since environmental issues are becoming in-
creasingly important to human endeavors, the green chemistry
2. Results and discussion
Based on our previous efforts in indium-mediated hetero-
cyclization reactions, trial experiments were carried out to
* Corresponding author. Fax: þ82 2 942 4635; e-mail address: bhkim@kw.ac.kr
(B.H. Kim).
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2
A. Go et al. / Tetrahedron xxx (2015) 1e12
determine the optimum reaction conditions. Acetic acid or indiu-
m(III) chloride, InCl3, was applied as an acid additive in various
aprotic and protic solvents. Initial experiments of 2-nitroaniline
(1 equiv) with 2,3-butanedione (1 equiv) in the presence of acetic
acid produced a mixture of the desired 2,3-dimethylquinoxaline (3)
and further reduced 2,3-dimethyl-1,2,3,4-tetrahydroquinoxaline
(4) regardless of the solvent (entries 1e4), which was somewhat
unexpected and disappointing. Formation of 4 may come from
further in situ reduction of 3, which implied that a moderation of
the reaction conditions to prevent formation of 4 was necessary.
Therefore, we tried the reaction with InCl3, which was not as active
as acetic acid in our previous indium-mediated heterocyclization
reactions. As expected, application of InCl3 led to a slower reaction,
and consequently, formation of 4 was retarded and the yield of the
quinoxaline was improved. However, the problem with the for-
mation of 4 was not completely solved. If the amount of InCl3 was
doubled, the amount of 4 increased from a trace to 19% even with
a shortened reaction time, as shown in entries 8 and 9 in Table 1.
Therefore, another trial experiment was performed to suppress the
formation of 4 by increasing the amount of 2,3-butanedione. For-
tunately, the formation of 4 was effectively suppressed, and the
desired product was obtained in high yield (entries 10, 11). After
careful control experiments changing the molar ratio of substrates,
indium, and InCl3, we determined optimized reaction conditions
(method A1); i.e., 2-nitroaniline (1 equiv)/2,3-butanedione
(2 equiv)/indium (5 equiv)/InCl3 (1.2 equiv) in methanol at reflux
(entry 11, Table 1).
which was the de-iodinated product, 2,3-dimethylquinoxaline as
well as the over-reduced product, 6-iodo-2,3-
dimethyltetrahydroquinoxaline. De-iodination presumably in-
volved electron transfer processes in the reductive cyclization,
which was similar to our previous reports on other indium-
mediated heterocyclization reactions.28
To extend our newly designed synthetic method to various
quinoxaline derivatives from 2-nitroanilines and other 1,2-
diketones, cyclizations of substituted 2-nitroanilines with 1,2-
diphenyl-1,2-ethanedione (benzil) were carried out under the op-
timized reaction conditions that had been used for heterocycliza-
tion of substituted 2-nitroanilines with 2,3-butanedione.
Cyclization of 2-nitroaniline and benzil (2 equiv) with indium
(5 equiv)/InCl3 (1.2 equiv) in methanol at reflux was completed
within 20 min in quantitative NMR yield. Unfortunately, there was
a problem in the isolation of pure product; i.e., the diphenyl-
substituted quinoxaline product and starting substrate, benzil had
the same TLC Rf value (Rf¼0.40, 30% ethyl acetate/hexane solution),
and consequently, flash column chromatography was not practical
for product purification. Therefore, as an excess of benzil should be
avoided, control experiments using a 1 to 1 M ratio of 2-nitroaniline
and benzil with varying molar amounts and/or kinds of reagents
were performed. After several control experiments, modified re-
action conditions were identified, which solved the separation is-
sue; i.e., 2-nitroaniline (1 equiv)/benzil (1 equiv)/indium (5 equiv)/
InCl3 (1 equiv) in methanol at reflux (method A2). In addition to
these modified conditions, use of an appropriate amount of acetic
Table 1
Formation of 2,3-dimethylquinoxalines in the presence of In/AcOH or InCl3 under various reaction conditions
Entry
Molar equiv (eq)
Solvent (mL)/
Temp (ꢀC)
Time (h)
Yielda (%)
1
2
In
Additive
3
4
1
2
3
4
5
6
7
8
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
2
2
4
4
4
4
4
4
4
4
5
5
5
5
5
AcOH(10)
AcOH(10)
AcOH(10)
AcOH(10)
InCl3(1)
InCl3(1)
InCl3(1)
InCl3(1)
InCl3(2)
EA(5)/reflux
Toluene(5)/80
ACN(5)/50
MeOH(5)/reflux
EA(5)/reflux
THF:H2O(3:3)/50
MeOH(5)/reflux
MeOH(5)/reflux
MeOH(5)/reflux
MeOH(5)/reflux
MeOH(5)/reflux
MeOH(5)/reflux
0.5
0.5
17
0.5
16
18
2.5
1
0.5
2.5
1.5
7
58
37
28
34
13
7
31
Trace
Trace
19
55
39b
77b
21
28
72b
73b
55b
90
9
10
11
12
InCl3(1)
InCl3(1.2)
InCl3(1)
d
91 (87c)
88
d
d
a
GC yield with an internal standard (octane).
1e8% of 1,2-diaminobenzene was observed.
Isolated yield.
b
c
Using the optimized reaction conditions, method A1, hetero-
acid in toluene solvent was equally effective as the above-
mentioned method A2; i.e., 2-nitroaniline (1 equiv)/benzil
(1 equiv)/indium (5 equiv)/AcOH (5 equiv) in toluene at 80 ꢀC
(method B1). With use of excess AcOH (10 equiv), the 2,3-diphenyl-
1,2,3,4-tetrahydroquinoxaline byproduct was encountered. Since
method B1 was as productive as method A2, both conditions were
applied to the synthesis of 2,3-diphenylquinoxaline derivatives,
and the results are summarized in Table 3. In most cases, both
methods worked equally well, and moderate to good yields of the
desired 2,3-diphenylquinoxaline derivatives were obtained re-
gardless of the nature and position of substituents, although the
reaction time was somewhat longer with method B1 compared to
method A2.
cyclizations of various substituted 2-nitroaniline derivatives with
2,3-butanedione (2 equiv) were initially examined in the presence
of indium (5 equiv)/InCl3 (1.2 equiv) in methanol at reflux to test
the synthetic scope of the reaction (Table 2). In most cases, cycli-
zation reactions delivered the quinoxalines from the 2-
nitroanilines in excellent yield, 68e95%, within 50e140 min.
Electronic effects of substituents appeared to have little effect on
the yield; however, an alkyl substituent (entries 2e4, Table 2)
prolonged the reaction time regardless of its position compared to
electron-withdrawing substituents such as halo, trifluoromethyl, or
cyano groups (entries 7e14). In the case of the iodo-substituted 2-
nitroaniline (entry 11), traces of by-products were observed, one of
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A. Go et al. / Tetrahedron xxx (2015) 1e12
3
Table 2
Synthesis of 2,3-dimethylquinoxalines in the presence of indium and InCl3 (method A1)
Entry
1
Substrate
Time (min)
90
Product
Yielda (%)
87
Entry
8
Substrate
Time (min)
60
Product
Yielda (%)
92
2
150
89
9
60
92
3
4
5
140
140
90
82
88
95
10
11
12
50
60
80
93
80b,c,d
89
6
120
60
68
91
13
14
80
50
93
96
7
a
Isolated yield.
A dehalogenated product was observed.
2,3-Dimethyl-1,2,3,4-tetrahydroquinoxaline was observed.
6-Iodo-2,3-dimethyl-1,2,3,4-tetrahydroquinoxaline was observed.
b
c
d
Table 3
Synthesis of 2,3-diphenylquinoxaline derivatives in the presence of In/InCl3 or In/AcOH
Entry
1
Substrate
Time (min)
Product
Method Yielda (%) Entry
Substrate
Time (min)
Product
Method Yielda (%)
30
30
A
B
85
85
8
9
40
110
A
B
63
75
2
3
4
100
25
A
B
89
87
40
100
A
B
63
75
35
40
A
B
71
87
10
11
40
70
A
B
76b
87b
30
50
A
B
85
90
50
270
A
B
75b
86b
(continued on next page)
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4
A. Go et al. / Tetrahedron xxx (2015) 1e12
Table 3 (continued )
Entry
Substrate
Time (min)
Product
Method Yielda (%) Entry
Substrate
Time (min)
Product
Method Yielda (%)
5
50
12h
A
B
90
90
12
60
100
A
B
75
59
6
50
12h
A
B
65
64
13
14
50
140
A
B
73
72
7
45
100
A
B
86
87
40
100
A
B
74
80
a
Isolated yield.
Trace amount of dehalogenated product was observed.
b
Heterocyclizations of various substituted 2-nitroanilines with
modified conditions of B1 with 10 equiv of acetic acid in methanol
was determined to give the best results; i.e., 2-nitroaniline (1 equiv)/
2,20-thenil (1 equiv)/indium (5 equiv)/AcOH (10 equiv) in methanol
(method B2) at reflux. With these modified reaction conditions,
method B2 at reflux, various 2,3-di-2-thiophenylquinoxaline de-
rivatives were successfully prepared in reasonable yields with re-
duced reaction times compared to the previous 2,3-
dimethylquinoxaline or 2,3-diphenylquinoxaline syntheses (Table 4).
2,20-thenil were also examined as an extension of our new method.
Unfortunately, trialexperiments usingthe conditionsof method A2or
B1 did not work well and gave poor yields of the desired product. In
the case of method A, the reaction time was quite prolonged, while
method B1 had a physical problem of coagulation of the reaction
mixture probably because of insoluble polymeric byproduct forma-
tion. Therefore, several additional control experiments were run, and
Table 4
Synthesis of 2,3-di-2-thiophenylquinoxalines in the presence of indium and acetic acid in methanol (method B2 at reflux)
Entry
1
Substrate
Time (min)
15
Product
Yielda (%)
47
Entry
8
Substrate
Time (min)
15
Product
Yielda (%)
85
2
3
4
5
6
20
20
40
50
53b
65b
87
9
10
11
12
15
10
20
5
56
76c
46c
75
86
20
15
53b
90
13
14
10
20
87
7
48b
a
Isolated yield.
10 mL of MeOH was used.
A dehalogenated product was observed.
b
c
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A. Go et al. / Tetrahedron xxx (2015) 1e12
5
Polypyridyl heterocyclic compounds that can bridge two or more
remote metal centers have received considerable attention in recent
coordination chemistry. As metal complexes with polypyridyl li-
gands could be useful for molecular materials such as electrical
conductors, electrochemiluminescent materials, and host-guest
molecules,29 the synthesis of 2,3-di(pyridin-2-yl)quinoxaline de-
rivatives was also attempted using our newly developed synthetic
method. Among the methods examined, method B2 [2-nitroaniline
(1 equiv)/2,20-pyridil (1 equiv)/indium (5 equiv)/AcOH (10 equiv) in
methanol] at 50 ꢀC gave the best results for the synthesis of 2,3-
di(pyridin-2-yl)quinoxalines as summarized in Table 5. In the case
of reactions of non- or alkyl-substituted 2-nitroaniline with 2,20-
pyridil (Table 5, entries 1e4), yields were lower because of forma-
tion of several by-products including the over-reduced byproduct,
alkyl substituted 1,2,3,4-tetrahydroquinoxaline.
synthesized from 2-nitroaniline and 9,10-phenanthrenequinone
using our method. Therefore, our synthetic method was
tried for the synthesis of dibenzo[a,c]phenazines. Among the
conditions developed in this work, the method B2 conditions
[2-nitroaniline
(1
equiv)/9,10-phenanthrenequinone/indium
(5 equiv)/AcOH (10 equiv) in methanol] at reflux exhibited the
best results, which are summarized in Table 6. Some of the re-
actions encountered purification problems in the flash column
chromatography due to the poor solubility of the product dibenzo
[a,c]phenazine derivatives in the eluant solvent (Table 6, entries 6,
7, 8, 9, 10, 11, 13, 14). In these cases, the following dry sample
loading technique was applied. The crude reaction product
(1 mmol scale) was dissolved in 30 mL of chloroform, and 1.5 g of
silica gel was added; the solvent was then evaporated until the
silica gel was completely dry. The product absorbed on dry silica
Table 5
Synthesis of 2,3-di(pyridin-2-yl)quinoxalines in the presence of indium and acetic acid in methanol (method B2 at 50 ꢀC)
Entry
1
Substrate
Time (min)
110
Product
Yielda (%)
47b
Entry
8
Substrate
Time (min)
110
Product
Yielda (%)
56
2
3
4
5
6
180
130
120
45
45b
50b
45b
78
9
10
11
12
13
14
120
50
50
70d
60d
70
50
170
190
70
60
80c
71
83
7
80
78
a
Isolated yield.
b
c
Over-reduced by-product was observed.
Recrystallized from ethyl acetate/hexane.
A dehalogenated product was observed.
d
Dibenzo[a,c]phenazines, quinoxaline based molecules that
was loaded onto the column and was eluted by adding a mixture
of ethyl acetate/hexane as eluant solvent. An initial 5% ethyl ac-
etate/hexane ratio was gradually increased to 20% for the
have interesting photophysical properties and can be the chem-
ical moiety of mesogeneous liquid crystals,30 could also be
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6
A. Go et al. / Tetrahedron xxx (2015) 1e12
separation. Using method B2 at reflux, various dibenzo[a,c]
phenazines were effectively synthesized even though some of the
reactions delivered relatively lower yields.
and another set of conditions used indium/AcOH. Based on these
two fundamental conditions, other reaction parameters such as
the ratio of reagents, solvent, and reaction temperature were
varied to obtain optimized yields.
Table 6
Synthesis of dibenzo[a,c]phenazines in the presence of indium and acetic acid in methanol (method B2 at reflux)
Entry
1
Substrate
Time (min)
5
Product
Yielda (%) Entry
Substrate
Time (min)
10
Product
Yielda (%)
66
80
8
2
3
4
5
6
10
84
9
60
50
20
25
74d
40c,e
80c,e
81
8
78
10
11
12
5
79
12h
56b,c
12h
12h
72
13
14
12h
10
68
50
7
48b,c
a
Isolated yield.
2-Nitroaniline derivative (w10%) was recovered.
Toluene was used as solvent.
30 mL of solvent was used.
A dehalogenated product was observed.
b
c
d
e
3. Conclusions
4. Experimental section
In conclusion, we have developed an efficient method for the
one-pot reduction-cyclization of 2-nitroanilines and 1,2-
diketones to produce quinoxalines. This method enables the
preparation of various quinoxaline derivatives such as 2,3-
4.1. General considerations
Most chemical reagents were purchased from SigmaeAldrich Co.
(St. Louis, MO, USA) and were used without further purification. Sol-
dialkylquinoxalines,
2,3-diphenylquinoxalines,
2,3-di-2-
vents were purchased and dried using standard methods. 1H and 13
C
thiophenylquinoxalines, 2,3-di(pyridin-2-yl)quinoxalines, and
dibenzo[a,c]phenazines, which are expected to be biologically
interesting compounds or useful molecular materials. In the
study, several modified conditions were applied depending on
the starting substrate: one set of conditions used indium/InCl3
NMR spectra were recorded at 400 and 100 MHz, respectively (JEOL,
Tokyo, Japan). Chemicalshifts are reported inparts per million relative
to residual solvent as an internal standard. GCeMS spectra were
recorded on an Agilent 6890N GC connected to an Agilent 5975 mass
selective detector (HewlettePackard Co., Palo Alto, CA, USA). Infrared
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A. Go et al. / Tetrahedron xxx (2015) 1e12
7
(IR) spectra were recorded using an MB104 FTIR (ABB Bomem, Inc.,
Zurich, Switzerland). Elemental analysis data were obtained with
a Thermo Scientific Flash 2000 (Thermo Fisher Scientific, Waltham,
MA, USA). Melting points were determined on an electrothermal
apparatus and were uncorrected. All major products were isolated by
flash column chromatography on silica gel (230e400 mesh ATSM,
purchased from Merck & Co., Inc. (Whitehouse Station, NJ, USA)) using
a mixed solvent eluant (ethyl acetate/hexane).
IR (KBr) 3019, 2987, 2931, 1616, 1499, 1223, 1155 cmꢂ1; GCeMS m/z
(rel intensity) 218 (Mþ, 100), 203 (18), 175 (38), 136 (23), 93 (12).
4.2.6. 6-Fluoro-2,3-dimethylquinoxaline (10).31h Yield 91%. Yellow
solid, mp 110e111 ꢀC (lit.31h mp 108e110 ꢀC). TLC (10% ethyl acetate/
dichloromethane) Rf 0.44; 1H NMR (400 MHz, CDCl3)
d
7.96 (dd, 1H,
J¼9.1, 5.7 Hz), 7.60 (dd, 1H, J¼9.1, 2.7 Hz), 7.43e7.40 (m, 1H), 2.72 (s,
3H), 2.71 (s, 3H); 13C NMR (100 MHz, CDCl3)
d
162.1 (d, J¼249.5 Hz),
154.4, 152.8 (d, J¼2.9 Hz), 141.7 (d, J¼12.8 Hz), 138.2, 130.2 (d,
J¼9.9 Hz), 118.8 (d, J¼25.7 Hz), 112.0 (d, J¼21.5 Hz), 23.1, 23.0; IR
4.2. General procedure for the indium-mediated reductive
cyclization of 2-nitroanilines to prepare quinoxalines
(KBr) 3117, 3033, 2995, 2968, 2918, 1620, 1491, 1328, 1214 cmꢂ1
;
GCeMS m/z (rel intensity) 176 (Mþ, 90), 135 (100), 108 (11), 94 (31).
A mixture of the 2-nitroaniline derivative (1.0 mmol), dione (1.0
or 2.0 mmol), indium (0.574 g, 5.0 mmol), and acetic acid (0.300 g,
5 mmol or 0.600 g, 10 mmol) or indium chloride (0.221 g,1 mmol or
0.265 g, 1.2 mmol) in methanol (5 mL) or toluene (5 mL) was stirred
at 50 ꢀC, 80 ꢀC, or reflux under a nitrogen atmosphere. After com-
pletion of the reaction, the reaction mixture was diluted with ethyl
acetate (30 mL), filtered through Celite, and the filtrate was poured
into 10% NaHCO3 (30 mL) and extracted with ethyl acetate
(30 mLꢁ3). The combined organic extracts were dried over MgSO4,
filtered, and concentrated. The residue was eluted with ethyl ace-
tate/hexane (v/v¼10/90) through a silica gel column to give the
corresponding pure quinoxaline. Quinoxaline structures were
characterized by 1H NMR, 13C NMR, FTIR, and GCeMS, and were
mostly known compounds. For unknown compounds, elemental
analysis data were additionally obtained.
4.2.7. 6-Chloro-2,3-dimethylquinoxalin (11).31bee Yield 92%. Yellow
solid, mp 92e93 ꢀC (lit.31b mp 85e86 ꢀC). TLC (10% ethyl acetate/
dichloromethane) Rf 0.50; 1H NMR (400 MHz, CDCl3)
d
7.94 (d, 1H,
J¼2.2 Hz), 7.88 (d, 1H, J¼8.8 Hz), 7.58 (dd, 1H, J¼8.8, 2.2 Hz), 2.71 (s,
3H), 2.71 (s, 3H); 13C NMR (100 MHz, CDCl3)
154.5, 153.7, 141.3,
d
139.5,134.3,129.6,129.5,127.3, 23.1, 23.08; IR (KBr)3094, 3065, 3045,
3024, 2951, 2914,1603,1482,1324,1178,1064 cmꢂ1; GCeMS m/z (rel
intensity) 194 (Mþþ2, 34), 192 (Mþ, 100), 151 (99), 110 (24), 75 (20).
4.2.8. 6-Bromo-2,3-dimethylquinoxaline (12).31i Yield 93%. Pale or-
ange solid, mp 87e88 ꢀC. TLC (10% ethyl acetate/dichloromethane)
Rf 0.48; 1H NMR (400 MHz, CDCl3)
d
8.14 (d, 1H, J¼2.2 Hz), 7.83 (d,
1H, J¼9.0 Hz), 7.73 (dd, 1H, J¼9.0, 2.2 Hz), 2.72 (s, 3H), 2.71 (s, 3H);
13C NMR (100 MHz, CDCl3)
154.5, 153.9, 141.7, 139.8, 132.3, 130.7,
d
129.7,122.4, 23.2, 23.19; IR (KBr) 3086, 3063, 3042, 3019, 2997, 2949,
2914, 1597, 1479, 1395, 1322, 1176 cmꢂ1; GCeMS m/z (rel intensity)
238 (Mþþ2, 95), 236 (Mþ, 100), 195 (79), 154 (20), 116 (11), 75 (32);
HRMS (EI) calcd for C10H9BrN2 235.9949, found 235.9952.
4.2.1. 2,3-Dimethylquinoxaline (5).19,31aef Yield 87%. Yellow solid,
mp 109e110 ꢀC (lit.31f mp 105 ꢀC). TLC (10% ethyl acetate/hexane) Rf
0.30; 1H NMR (400 MHz, CDCl3)
d
7.91 (dd, 2H, J¼6.3, 3.5 Hz), 7.59
(dd, 1H, J¼6.3, 3.5 Hz), 2.66 (s, 6H); 13C NMR (100 MHz, CDCl3)
d
153.4, 141.0, 128.7, 128.2, 23.1; IR (KBr) 3109, 3078, 3030, 2995,
4.2.9. 6-Iodo-2,3-dimethylquinoxaline (13).31g Yield 80%. Brown
solid, mp 77e78 ꢀC. TLC (10% ethyl acetate/dichloromethane) Rf
2953, 2914, 1490, 1398, 1164 cmꢂ1; GCeMS m/z (rel intensity) 158
(Mþ, 99), 117 (100), 76 (28), 50 (12).
0.47; 1H NMR (400 MHz, CDCl3)
d
8.38 (d, 1H, J¼1.9 Hz), 7.89 (dd,
1H, J¼8.8,1.9 Hz), 7.67 (d,1H, J¼8.8 Hz), 2.71 (s, 3H), 2.70 (s, 3H); 13
C
4.2.2. 5-Methyl-2,3-dimethylquinoxaline (6).31g Yield 89%. White
solid, mp 76e77 ꢀC. TLC (10% ethyl acetate/dichloromethane) Rf 0.28;
NMR (100 MHz, CDCl3) d 154.2, 154.1, 141.9, 140.2, 137.6, 137.4, 129.7,
94.1, 23.2, 23.16; IR (KBr) 3080, 3045, 3016, 2997, 2914, 1594, 1478,
1319, 1158 cmꢂ1; GCeMS m/z (rel intensity) 284 (Mþ,100), 243 (52),
202 (16), 116 (24), 75 (33); HRMS (EI) calcd for C10H9IN2 283.9810,
found 283.9804.
1H NMR (400 MHz, CDCl3)
d
7.74 (d, 1H, J¼8.4 Hz), 7.46 (m,1H), 7.41 (d,
1H, J¼6.8 Hz), 2.69(s,3H), 2.66(s,3H), 2.64(s,3H);13CNMR(100MHz,
CDCl3) d 152.7, 152.1, 141.0, 140.2, 136.6, 128.7, 128.4, 126.1, 23.3, 23.0,
17.1; IR (KBr) 3090, 3047, 3020, 2985, 2916, 2845, 1480, 1397, 1371,
1330 cmꢂ1; GCeMS m/z (rel intensity) 172 (Mþ,100),131 (55), 90 (27),
63 (10); HRMS (EI) calcd for C11H12N2 172.1000, found 172.1003.
4.2.10. 5-Trifluoromethyl-2,3-dimethylquinoxaline
89%. White solid, mp 83e84 ꢀC. TLC (10% ethyl acetate/dichloro-
methane) Rf 0.70; 1H NMR (400 MHz, CDCl3)
8.15 (d,1H, J¼8.4 Hz),
7.99 (d, 1H, J¼7.2 Hz), 7.69 (dd, 1H, J¼8.4, 7.2 Hz), 2.78 (s, 3H), 2.75
(s, 3H); 13C NMR (100 MHz, CDCl3)
154.5, 154.4, 141.0, 138.1, 132.8,
127.3, 127.2 (q, J¼29.6 Hz), 126.9 (q, J¼5.5 Hz), 123.7 (q, J¼272.2 Hz),
23.6, 23.1; IR (KBr) 3063, 2994, 2957, 2922, 1585, 1487, 1402, 1351,
1298, 1218, 1124, 1060 cmꢂ1; GCeMS m/z (rel intensity) 226 (Mþ,
76), 207 (8), 185 (100), 165 (8), 145 (18), 125 (11), 75 (8); HRMS (EI)
calcd for C11H9F3N2 226.0718, found 226.0718.
(14).31j Yield
d
4.2.3. 6-Methyl-2,3-dimethylquinoxaline (7).31bee Yield 88% (entry
4, Table 2). Yellow solid, mp 94e95 ꢀC (lit.31d mp 92e94 ꢀC). TLC
(10% ethyl acetate/dichloromethane) Rf 0.28; 1H NMR (400 MHz,
d
CDCl3)
d
7.86 (d, 1H, J¼8.3 Hz), 7.74 (s, 1H), 7.48 (dd, 1H, J¼8.3,
1.7 Hz), 2.70 (s, 6H), 2.55 (s, 3H); 13C NMR (100 MHz, CDCl3)
d
153.2,
152.4, 141.1, 139.4, 139.0, 130.9, 127.8, 127.2, 23.1, 23.0, 21.7; IR (KBr)
3042, 3020, 3018, 2995, 2920, 2858, 1498, 1329, 1165 cmꢂ1; GCeMS
m/z (rel intensity) 172 (Mþ, 100), 131 (90), 89 (33), 63 (11).
4.2.11. 6-Trifluoromethyl-2,3-dimethylquinoxaline
93%. White solid, mp 96e97 ꢀC. TLC (10% ethyl acetate/dichloro-
(15).31g Yield
4.2.4. 6-Methoxy-2,3-dimethylquinoxaline (8).31c Yield 95%. Pale
yellow solid, mp 100e101 ꢀC. TLC (10% ethyl acetate/dichloro-
methane) Rf 0.53; 1H NMR (400 MHz, CDCl3)
d 8.29 (s, 1H), 8.08 (d,
methane) Rf 0.15; 1H NMR (400 MHz, CDCl3)
d
7.21 (s, 2H), 3.95 (s,
159.8, 153.2, 150.5,
1H, J¼8.8 Hz), 7.84e7.82 (m, 1H), 2.77 (s, 3H), 2.76 (s, 3H); 13C NMR
6H), 2.61 (s, 6H); 13C NMR (100 MHz, CDCl3)
d
(100 MHz, CDCl3)
d
155.9, 155.2, 142.3, 140.1, 130.6 (q, J¼32.6 Hz),
142.4, 136.9, 129.2, 121.5, 106.1, 55.6, 23.0, 22.7; IR (KBr) 3069, 2989,
2918, 2839, 1617, 1496, 1376, 1335, 1218 cmꢂ1; GCeMS m/z (rel in-
tensity) 188 (Mþ, 100), 173 (13), 147 (50), 106 (49), 63 (21).
129.6, 126.4 (q, J¼4.3 Hz), 124.6 (q, J¼3.1 Hz), 123.8 (q, J¼271.0 Hz);
IR (KBr) 3136, 3067, 3035, 3007, 2951, 2930, 1404, 1364, 1318, 1272,
1195, 1118, 1058 cmꢂ1; GCeMS m/z (rel intensity) 226 (Mþ, 70), 207
(8), 185 (100), 145 (22), 125 (9), 75 (8); HRMS (EI) calcd for
4.2.5. 6,7-Dimethoxy-2,3-dimethylquinoxaline (9).31g Yield 68%.
Pale orange solid, mp 178e179 ꢀC. TLC (50% ethyl acetate/hexane) Rf
C11H9F3N2 226.0718, found 226.0716.
0.17; 1H NMR (400 MHz, CDCl3)
d
7.21 (s, 2H), 3.95 (s, 6H), 2.61 (s,
4.2.12. 6-Carbonitrile-2,3-dimethylquinoxaline (16).31g Yield 96%.
White solid, mp 205e206 ꢀC. TLC (10% ethyl acetate/
6H); 13C NMR (100 MHz, CDCl3)
d 151.7,150.6,137.7,106.2, 56.2, 22.7;
Please cite this article in press as: Go, A.; et al., Tetrahedron (2015), http://dx.doi.org/10.1016/j.tet.2015.01.007

8
A. Go et al. / Tetrahedron xxx (2015) 1e12
dichloromethane) Rf 0.45; 1H NMR (400 MHz, CDCl3)
d
8.32 (d, 1H,
(20% ethyl acetate/hexane) Rf 0.50; 1H NMR (400 MHz, CDCl3)
8.16 (s, 1H), 8.09 (d, 1H, J¼8.8 Hz), 7.69 (d, 1H, J¼8.8 Hz),
7.51e7.50 (m, 4H), 7.34e7.33 (m, 6H); 13C NMR (100 MHz, CDCl3)
154.2, 153.5, 141.4, 139.6, 138.7, 138.6, 135.6, 131.0, 130.4, 129.8,
129.7, 129.0, 128.9, 128.3, 128.2, 128.0; IR (KBr) 3059, 3036, 1674,
1597, 1470, 1447, 1342 cmꢂ1; GCeMS m/z (rel intensity) 318
(Mþþ2, 34), 316 (Mþ, 100), 213 (17), 178 (23), 151 (11), 110 (8),
75 (4).
J¼1.7 Hz), 8.05 (d, 1H, J¼8.5 Hz), 7.80 (dd, 1H, J¼8.5, 1.7 Hz), 2.78 (s,
3H), 2.77 (s, 3H); 13C NMR (100 MHz, CDCl3)
156.6, 155.8, 142.6,
140.1, 134.2, 129.9, 129.7, 118.2, 112.1, 23.4, 23.2; IR (KBr) 3113, 3069,
d
d
d
3032, 3003, 2957, 2920, 2225, 1573, 1493, 1397, 1328, 1166 cmꢂ1
;
GCeMSm/z (relintensity) 183(Mþ, 70),142(100),115 (8),102 (15), 75
(6), 50 (11); HRMS (EI) calcd for C11H9F3N2 183.0796, found 183.0796.
4.2.13. 2,3-Diphenylquinoxaline (17).32a Yield 85%. Pale white solid,
mp 128e129 ꢀC. TLC (30% ethyl acetate/hexane) Rf 0.40; 1H NMR
4.2.20. 6-Bromo-2,3-diphenylquinoxaline
(24).32a Yield
87%
(400 MHz, CDCl3)
d
8.18 (dd, 2H, J¼8.2, 3.6 Hz), 7.76 (dd, 2H, J¼8.2,
(method B1, entry 10, Table 3). Pale orange solid, mp 122e123 ꢀC.
3.6 Hz), 7.52e7.50 (m, 4H), 7.35e7.24 (m, 6H); 13C NMR (100 MHz,
TLC (20% ethyl acetate/hexane) Rf 0.45; 1H NMR (400 MHz, CDCl3)
CDCl3)
d
153.4, 141.2, 139.0, 129.9, 129.8, 129.1, 128.7, 128.2; IR (KBr)
d
8.29 (d, 1H, J¼2.0 Hz), 7.96 (d, 1H, J¼8.0 Hz), 7.76 (dd, 1H, J¼8.0,
2.0 Hz), 7.44e7.43 (m, 4H), 7.31e7.24 (m, 6H); 13C NMR (100 MHz,
CDCl3) 154.2, 153.7, 141.7, 139.9, 138.7, 138.6, 133.4, 131.4, 130.5,
3058, 3032, 1550, 1442, 1396, 1342 cmꢂ1; GCeMS m/z (rel intensity)
281 (Mþ, 100), 179 (55), 153 (16), 141 (19), 76 (26), 50 (10).
d
129.8, 129.7, 129.0, 128.2, 123.7; IR (KBr) 3059, 3036, 1593, 1470,
1342 cmꢂ1; GCeMS m/z (rel intensity) 362 (Mþþ2, 95), 360 (Mþ,
100), 257 (11), 178 (25), 151 (18), 75 (19).
4.2.14. 5-Methyl-2,3-diphenylquinoxaline
(method A2, entry 2, Table 3). White solid, mp 120e121 ꢀC. TLC
(20% ethyl acetate/hexane) Rf 0.45; 1H NMR (400 MHz, CDCl3)
8.00
(18).32a,b Yield
89%
d
(d,1H, J¼8.4 Hz), 7.66e7.62 (m, 1H), 7.59e7.56 (m, 3H), 7.53 (dd, 2H,
4.2.21. 6-Iodo-2,3-diphenylquinoxaline (25).32d Yield 86% (method
B1, entry 11, Table 3). Brown solid, mp 119e120 ꢀC. TLC (20% ethyl
J¼8.4, 2.0 Hz), 7.34e7.24 (m, 6H), 2.86 (s, 3H); 13C NMR (100 MHz,
CDCl3)
d
152.8, 151.7, 141.1, 140.3, 139.4, 139.3, 137.6, 130.1, 129.8,
acetate/hexane) Rf 0.42; 1H NMR (400 MHz, CDCl3)
d 8.60 (s, 1H),
129.6, 128.6, 128.2, 128.0, 126.9, 17.1; IR (KBr) 3058, 3032, 2958,
2920, 1570, 1470, 1442, 1346 cmꢂ1; GCeMS m/z (rel intensity) 296
(Mþ, 100), 193 (26), 165 (18), 147 (16), 89 (34).
8.00 (dd, 1H, J¼8.0, 2.0 Hz), 7.87 (d, 1H, J¼8.0 Hz), 7.50 (d, 4H,
J¼8.0 Hz), 7.37e7.31 (m, 6H); 13C NMR (100 MHz, CDCl3)
d 154.0,
153.9, 141.9, 140.3, 138.7, 138.6, 138.6, 138.1, 130.4, 129.8, 129.7,
129.0, 128.9, 128.3, 128.2, 95.6; IR (KBr) 3059, 3036, 1589, 1542,
1465, 1342 cmꢂ1; GCeMS m/z (rel intensity) 408 (Mþ, 100), 281
(16), 202 (6), 178 (23), 140 (9), 75 (18).
4.2.15. 6-Methyl-2,3-diphenylquinoxaline
(method B1. entry 4, Table 3). Pale yellow solid, mp 116e117 ꢀC. TLC
(20% ethyl acetate/hexane) Rf 0.45; 1H NMR (400 MHz, CDCl3)
8.06
(19).32a,b Yield
90%
d
(d, 1H, J¼8.8 Hz), 7.95 (s, 1H), 7.59 (d, 1H, J¼8.8 Hz), 7.51e7.44 (m,
4.2.22. 2,3-Diphenylquinoxaline-6-carbonitrile (26).32d Yield 75%
(method A2, entry 12, Table 3). White solid, mp 181e182 ꢀC. TLC
4H), 7.33e7.31 (m, 6H), 2.60 (s, 3H); 13C NMR (100 MHz, CDCl3)
d
153.2, 152.5, 141.2, 140.4, 139.7, 139.2, 132.2, 129.8, 129.7, 128.7,
(20% ethyl acetate/hexane) Rf 0.45; 1H NMR (400 MHz, CDCl3)
d
8.53
(s, 1H), 8.24 (d, 1H, J¼8.0 Hz), 7.89 (d, 1H, J¼8.0 Hz), 7.54e7.53 (m,
4H), 7.41e7.34 (m, 6H); 13C NMR (100 MHz, CDCl3)
155.9, 155.3,
128.6, 128.5, 128.2, 128.0, 21.9; IR (KBr) 3060, 3032, 2957, 2920,
2986, 1620, 1539, 1485, 1446, 1346 cmꢂ1; GCeMS m/z (rel intensity)
296 (Mþ, 100), 192 (17), 165 (10), 148 (8), 89 (17).
d
142.5, 140.2, 138.1, 138.0, 135.0, 130.7, 130.6, 129.8, 129.7, 129.6,
129.5, 128.4, 118.1, 113.1; IR (KBr) 3058, 3028, 2229, 1447, 1396,
1342 cmꢂ1; GCeMS m/z (rel intensity) 316 (Mþ, 100), 213 (17), 178
(22), 151 (11), 110 (8), 75 (10).
4.2.16. 6-Methoxy-2,3-diphenylquinoxaline (20).32a Yield 90%. Yel-
low solid, mp 156e157 ꢀC. TLC (20% ethyl acetate/hexane) Rf 0.35;
1H NMR (400 MHz, CDCl3)
d
8.05 (d, 1H, J¼8.8 Hz), 7.48e7.42 (m,
6H), 7.34e7.32 (m, 6H), 3.93 (s, 3H); 13C NMR (100 MHz, CDCl3)
160.8, 153.3, 150.9, 142.7, 139.2, 139.1, 137.4, 130.1, 129.8, 128.4,
4.2.23. 5-Trifluoromethyl-2,3-diphenylquinoxaline
(27).32e Yield
d
73% (method A2, entry 13, Table 3). White solid, mp 129e130 ꢀC.
128.2, 128.1, 123.3, 106.4; IR (KBr) 3058, 3031, 2962, 1939, 1616,
1485, 1350, 1203 cmꢂ1; GCeMS m/z (rel intensity) 312 (Mþ, 100),
297 (26), 269 (25), 209 (11), 106 (28), 63 (22).
TLC (20% ethyl acetate/hexane) Rf 0.70; 1H NMR (400 MHz, CDCl3)
d
8.50 (s, 1H), 8.29 (d,1H, J¼8.0 Hz), 7.94 (d,1H, J¼8.0 Hz), 7.55e7.52
(m, 4H), 7.40e7.34 (m, 6H); 13C NMR (100 MHz, CDCl3)
d
155.4,
154.8, 142.2, 140.1, 138.4, 138.3, 131.5 (q, J¼33.3 Hz), 130.3, 129.8,
129.3, 129.2, 128.4, 128.3, 127.2 (q, J¼4.4 Hz), 125.5 (q, J¼3.0 Hz),
123.7 (q, J¼273.8 Hz); IR (KBr) 3062, 3032, 1574, 1470, 1441,
1304 cmꢂ1; GCeMS m/z (rel intensity) 350 (Mþ, 100), 310 (18), 248
(10), 185 (12), 165 (8), 145 (18), 125 (11), 75 (8).
4.2.17. 6,7-Dimethoxy-2,3-diphenylquinoxaline (21).32c Yield 65%
(method A2, entry 6, Table 3). White solid, mp 254e255 ꢀC. TLC (30%
ethyl acetate/hexane) Rf 0.65; 1H NMR (400 MHz, CDCl3)
d
7.41e7.40
(m, 6H), 7.26e7.24 (m, 6H), 3.99 (s, 6H); 13C NMR (100 MHz, CDCl3)
d
152.9, 151.0, 139.4, 138.4, 129.8, 128.3, 128.2, 106.7, 56.4; IR (KBr)
3062, 3030, 2930, 1679, 1590, 1450, 1267, 1205 cmꢂ1; GCeMS m/z
4.2.24. 6-Trifluoromethyl-2,3-diphenylquinoxaline
80% (method B1, entry 14, Table 3). White solid, mp 135e136 ꢀC. TLC
(20% ethyl acetate/hexane) Rf 0.53; 1H NMR (400 MHz, CDCl3)
8.50
(s, 1H), 8.29 (d, 1H, J¼8.8 Hz), 7.94 (d, 1H, J¼8.8 Hz), 7.53 (m, 4H),
7.36 (m, 6H); 13C NMR (100 MHz, CDCl3)
154.0, 153.3, 140.8, 138.8,
138.0, 133.4, 130.3, 129.6, 126.3, 129.2, 128.4, 128.3, 128.1, 127.9 (q,
J¼5.3 Hz), 123.6 (q, J¼273.8 Hz); IR (KBr) 3062, 3036, 1450, 1404,
1323, 1130 cmꢂ1; GCeMS m/z (rel intensity) 350 (Mþ, 100), 310 (18),
185 (10), 145 (22), 125 (9), 75 (8).
(28).32c Yield
(rel intensity) 342 (Mþ, 100), 298 (20), 136 (15), 93 (10).
d
4.2.18. 6-Fluoro-2,3-diphenylquinoxaline (22).10 Yield 87% (method
B1, entry 7, Table 3). Yellow solid, mp 133e134 ꢀC (lit.10 mp
108e110 ꢀC). TLC (20% ethyl acetate/hexane) Rf 0.50; 1H NMR
d
(400 MHz, CDCl3)
d
8.17e8.15 (m, 1H), 7.80 (dd, 1H, J¼9.1, 2.8 Hz),
7.55e7.52 (m, 5H), 7.34e7.34 (m, 6H); 13C NMR (100 MHz, CDCl3)
d
162.8 (d, J¼251.0 Hz), 154.2, 152.8 (d, J¼2.9 Hz), 141.9 (d,
J¼13.0 Hz), 138.7 (d, J¼9.7 Hz), 138.4, 131.2 (d, J¼9.9 Hz), 129.8,
129.0, 128.8, 128.3, 120.3 (d, J¼25.7 Hz), 112.6 (d, J¼21.5 Hz); IR
(KBr) 3058, 3036, 1470, 1442, 1346 cmꢂ1; GCeMS m/z (rel intensity)
300 (Mþ, 100), 197 (33), 150 (11), 94 (11).
4.2.25. 2,3-Di-2-thiophenylquinoxaline (29).33a Yield 47%. Pale yel-
low solid, mp 131e132 ꢀC (lit.33a mp 129 ꢀC). TLC (30% ethyl acetate/
hexane) Rf 0.69; 1H NMR (400 MHz, CDCl3)
d
7.99 (dd, 2H, J¼8.02,
3.4 Hz), 7.64 (dd, 2H, J¼8.02, 3.4 Hz), 7.42 (m, 2H), 7.16 (m, 2H), 6.96
(m, 2H); 13C NMR (100 MHz, CDCl3)
146.6, 141.4, 140.6, 130.1,
129.3, 128.9, 128.8, 127.6; IR (KBr) 3094, 3070, 1523, 1423,
4.2.19. 6-Chloro-2,3-diphenylquinoxaline
(method B1, entry 8, Table 3). Yellow solid, mp 122e123 ꢀC. TLC
(23).32a Yield
75%
d
Please cite this article in press as: Go, A.; et al., Tetrahedron (2015), http://dx.doi.org/10.1016/j.tet.2015.01.007

A. Go et al. / Tetrahedron xxx (2015) 1e12
9
1234 cmꢂ1; GCeMS m/z (rel intensity) 294 (Mþ, 100), 261 (16), 185
2H), 7.04 (m, 2H); 13C NMR (100 MHz, CDCl3)
d
147.4, 146.8, 141.2,
(22), 141 (7).
141.1, 141.0, 139.3, 133.6, 131.1, 130.1, 129.7, 129.5, 129.4, 129.2, 128.6,
127.6, 124.0; IR (KBr) 3097, 3074, 1597, 1523, 1431, 1335 cmꢂ1
;
4.2.26. 5-Methyl-2,3-di-2-thiophenylquinoxaline (30).33b Yield 53%.
Pale yellow solid, mp 133e134 ꢀC. TLC (30% ethyl acetate/hexane) Rf
GCeMS m/z (rel intensity) 376 (Mþþ2, 98), 374 (Mþ, 100), 341 (14),
265 (14), 184 (23), 140 (29), 109 (10), 75 (17); Anal. Calcd for
0.76; 1H NMR (400 MHz, CDCl3)
d
7.82 (d, 1H, J¼8.0 Hz), 7.54e7.46
C16H9BrN2S2: C, 51.48; H, 2.43; N, 7.50; S, 17.18. Found: C, 51.46; H,
2.37; N, 7.51; S, 17.05.
(m, 2H), 7.41 (m, 1H), 7.39 (m, 1H), 7.24 (m, 1H), 7.13 (m, 1H), 6.99
(m, 1H), 6.93 (m, 1H), 2.73 (s, 3H); 13C NMR (100 MHz, CDCl3)
d
145.7, 145.2, 142.6, 141.3, 140.5, 139.8, 137.2, 130.1, 129.8, 129.1,
4.2.33. 6-Iodo-2,3-di-2-thiophenylquinoxaline (37). Yield 46%. Yel-
low solid, mp 147e149 ꢀC. TLC (30% ethyl acetate/hexane) Rf 0.40;
129.0,128.5,127.6,127.5,126.6,17.0; IR (KBr) 3101, 3070, 2970, 2927,
1601, 1427, 1227 cmꢂ1; GCeMS m/z (rel intensity) 308 (Mþ, 100),
275 (18), 198 (21), 89 (14).
1H NMR (400 MHz, CDCl3)
d
8.41 (d, 1H, J¼1.5 Hz), 7.86 (dd, 1H,
J¼8.8, 1.5 Hz), 7.68 (d, 1H, J¼8.8 Hz), 7.44 (m, 2H), 7.19 (m, 2H), 6.96
(m, 2H); 13C NMR (100 MHz, CDCl3)
147.1,147.0,141.2,141.1,141.08,
d
4.2.27. 6-Methyl-2,3-di-2-thiophenylquinoxaline (31).33b Yield 87%
(entry 4, Table 4). Pale yellow solid, mp 143e144 ꢀC. TLC (30% ethyl
141.07, 139.6, 138.8, 137.7, 130.0, 129.6, 129.5, 129.4, 129.2, 127.6,
95.9; IR (KBr) 3101, 3074, 1589, 1523, 1431, 1331 cmꢂ1; GCeMS m/z
(rel intensity) 420 (Mþ, 100), 311 (10), 293 (9), 202 (8), 184 (30), 140
(18), 75 (37); Anal. Calcd for C16H9IN2S2: C, 45.72; H, 2.16; N, 6.67; S,
15.26. Found: C, 45.71; H, 2.08; N, 6.61; S, 15.21.
acetate/hexane) Rf 0.59; 1H NMR (400 MHz, CDCl3)
d 7.88 (d, 1H,
J¼8.5 Hz), 7.78 (s, 1H), 7.47 (d, 1H, J¼8.5 Hz), 7.40 (m, 2H), 7.14 (m,
2H), 6.97e6.94 (m, 2H), 2.51 (s, 3H); 13C NMR (100 MHz, CDCl3)
d
146.5, 145.7, 141.7, 141.5, 140.8, 140.7, 139.1, 132.5, 129.2, 129.0,
128.7, 128.5, 128.3, 127.7, 127.54, 127.50, 21.9; IR (KBr) 3101, 3074,
2950, 2920, 1620, 1523, 1431, 1335, 1234 cmꢂ1; GCeMS m/z (rel
intensity) 308 (Mþ, 100), 275 (15), 198 (23), 89 (14).
4.2.34. 5-Trifluoromethyl-2,3-di-2-thiophenylquinoxaline
(38). Yield 75%. Yellow solid, mp 145e146 ꢀC. TLC (20% ethyl ace-
tate/hexane) Rf 0.50; 1H NMR (400 MHz, CDCl3)
d 8.22 (d, 1H,
J¼8.5 Hz), 8.04 (m, 1H), 7.72 (m, 1H), 7.53 (m, 2H), 7.43 (dd, 1H,
4.2.28. 6-Methoxy-2,3-di-2-thiophenylquinoxaline
86%. Yellow solid, mp 138e139 ꢀC. TLC (30% ethyl acetate/hexane)
Rf 0.60; 1H NMR (400 MHz, CDCl3)
7.87 (d, 1H, J¼7.1 Hz), 7.40 (m,
2H), 7.28 (m, 2H), 7.12 (m, 2H), 6.95 (m, 2H), 3.90 (s, 3H); 13C NMR
(100 MHz, CDCl3) 161.0, 146.6, 144.0, 142.3, 141.6, 141.4, 137.5,
137.3, 129.8, 129.1, 128.7, 128.2, 127.6, 127.5, 123.6, 106.0, 55.8; IR
(KBr) 3097, 3074, 2958, 2935, 1616, 1485, 1211 cmꢂ1; GCeMS m/z
(rel intensity) 324 (Mþ, 100), 309 (9), 291 (9), 281 (8), 200 (18), 106
(11), 63 (12).
(32).33b Yield
J¼3.8 Hz), 7.33 (d, 1H, J¼3.8 Hz), 7.10 (dd, 1H, J¼4.8, 3.8 Hz), 7.00
(dd, 1H, J¼4.8, 3.8 Hz); 13C NMR (100 MHz, CDCl3)
d 146.9, 146.8,
d
141.9, 140.5, 140.1, 137.4, 137.3, 130.0, 129.9 (q, J¼45.0 Hz), 129.6,
128.9 (q, J¼271.7 Hz), 128.6, 128.2 (q, J¼5.2 Hz), 127.6 (q, J¼5.2 Hz),
d
127.2, 124.8, 122.1; IR (KBr) 3101, 3074, 1523, 1423, 1296, 1138 cmꢂ1
;
GCeMS m/z (rel intensity) 362 (Mþ, 100), 341 (36), 329 (14), 253
(34), 171 (11), 109 (16); Anal. Calcd for C17H9F3N2S2: C, 56.34; H,
2.50; N, 7.73. Found: C, 56.41; H, 2.37; N, 7.51.
4.2.35. 6-Trifluoromethyl-2,3-di-2-thiophenylquinoxaline
(39). Yield 87%. Yellow solid, mp 144e145 ꢀC. TLC (30% ethyl ace-
4.2.29. 6,7-Dimethoxy-2,3-di-2-thiophenylquinoxaline
(33).33c Yield 53%. Yellow solid, mp 147e148 ꢀC. TLC (30% ethyl
tate/hexane) Rf 0.78; 1H NMR (400 MHz, CDCl3)
d
8.30 (s, 1H), 8.09
(d, 1H, J¼8.8 Hz), 7.80 (d, 1H, J¼8.8 Hz), 7.47 (m, 2H), 7.25 (m, 2H),
6.98 (m, 2H); 13C NMR (100 MHz, CDCl3)
148.5, 147.9, 141.6, 140.9,
acetate/hexane) Rf 0.48; 1H NMR (400 MHz, CDCl3)
d
7.39e7.37 (m,
2H), 7.28 (s, 2H), 7.10e7.09 (m, 2H), 6.95e6.94 (m, 2H), 3.98 (s, 6H);
13C NMR (100 MHz, CDCl3)
153.1, 141.8, 137.9, 135.3, 128.6, 128.1,
d
d
140.8, 131.5 (q, J¼33.1 Hz), 130.0, 129.9, 129.8, 129.7, 128.7, 127.7,
127.5, 106.4, 56.4; IR (KBr) 3080, 3005, 2933, 2832, 1653, 1616, 1498,
127.6, 126.8 (q, J¼4.4 Hz), 125.6 (q, J¼3.3 Hz), 125.0, 123.6 (q,
1210 cmꢂ1; GCeMS m/z (rel intensity) 354 (Mþ, 100), 93 (8).
J¼273.1 Hz); IR (KBr) 3085, 3074, 1523, 1415, 1342, 1122 cmꢂ1
;
GCeMS m/z (rel intensity) 362 (Mþ, 100), 329 (16), 253 (23), 109
(14); Anal. Calcd for C17H9F3N2S2: C, 56.34; H, 2.50; N, 7.73; S, 17.70.
Found: C, 56.13; H, 2.53; N, 7.77; S, 17.91.
4.2.30. 6-Fluoro-2,3-di-2-thiophenylquinoxaline (34). Yield 90%.
Pale yellow solid, mp 139e141 ꢀC. TLC (30% ethyl acetate/hexane) Rf
0.52; 1H NMR (400 MHz, CDCl3)
d
8.05 (dd,1H, J¼9.1, 5.7 Hz), 7.68 (dd,
1H, J¼9.1, 2.6 Hz), 7.50 (m, 3H), 7.24 (m, 2H), 7.03 (m, 2H); 13C NMR
4.2.36. 6-Carbonitrile-2,3-di-2-thiophenylquinoxaline
48%. Yellow solid, mp 139e141 ꢀC. TLC (30% ethyl acetate/hexane) Rf
0.32; 1H NMR (400 MHz, CDCl3)
8.40 (s, 1H), 8.12 (d, 1H, J¼8.5 Hz),
7.83 (d, 1H, J¼8.5 Hz), 7.56 (d, 2H, J¼4.4 Hz), 7.36 (d, 2H, J¼3.7 Hz),
7.07e7.05 (m, 2H); 13C NMR (100 MHz, CDCl3)
148.9, 148.3, 141.9,
(40). Yield
(100 MHz, CDCl3)
d
161.0,146.6,144.0,142.8 (d, J¼242.5 Hz),141.6 (d,
J¼14.9 Hz), 137.39 (d, J¼25.7 Hz), 136.7, 129.8, 129.1, 128.9 (d,
J¼8.3 Hz), 128.7, 128.2, 127.6, 127.5, 123.6, 106.0; IR (KBr) 3093, 3078,
1616,1477,1307,1203cmꢂ1; GCeMS m/z (rel intensity) 312 (Mþ,100),
279 (24), 203 (35), 158 (9), 109 (11), 94 (8); Anal. Calcd for
d
d
140.8, 140.5, 139.5, 134.5, 130.7, 130.43, 130.40, 130.2, 130.1, 130.0,
127.8, 127.7, 118.0, 113.1; IR (KBr) 3101, 3074, 2229, 1520, 1427, 1334,
1230 cmꢂ1; GCeMS m/z (rel intensity) 319 (Mþ, 100), 286 (16), 210
(24), 109 (16); Anal. Calcd for C17H9N3S2: C, 63.93; H, 2.84; N, 13.16;
S, 20.08. Found: C, 63.85; H, 2.76; N, 13.14; S, 19.80.
C16H9FN2S2: C, 61.52; H, 2.90;N, 8.97. Found: C, 61.58; H, 2.78; N, 8.68.
4.2.31. 6-Chloro-2,3-di-2-thiophenylquinoxaline (35).33d Yield 85%
(entry 8, Table 4). Pale yellow solid, mp 151e152 ꢀC. TLC (30% ethyl
acetate/hexane) Rf 0.65; 1H NMR (400 MHz, CDCl3)
d
8.40 (s, 1H),
8.12 (d, 1H, J¼8.5 Hz), 7.83 (m, 1H), 7.56 (m, 2H), 7.36 (m, 2H),
7.07e7.04 (m, 2H); 13C NMR (100 MHz, CDCl3)
147.4, 146.7, 141.1,
141.0,140.8,140.0,137.5,137.3,135.8,131.0,130.0,129.7,129.5,129.4,
4.2.37. 2,3-Di(pyridin-2-yl)quinoxaline (41).31j Yield 47%. Pale yel-
low solid, mp 185e187 ꢀC (lit.31j mp 188e191 ꢀC). TLC (30% ethyl
d
acetate/hexane) Rf 0.50; 1H NMR (400 MHz, CDCl3)
d 8.36 (m, 2H),
129.1, 127.7; IR (KBr) 3097, 3070, 1601, 1524, 1431, 1335 cmꢂ1
;
8.21 (m, 2H), 7.94 (m, 2H), 7.80 (m, 4H), 7.22 (d, 2H, J¼7.6 Hz); 13C
GCeMS m/z (rel intensity) 330 (Mþþ2, 58), 328 (Mþ, 100), 295 (17),
NMR (100 MHz, CDCl3) d 157.4, 152.4, 148.6, 141.1, 136.6, 130.5,
219 (18), 184 (17), 140 (14), 109 (9), 75 (8).
129.4, 124.2, 122.9; IR (KBr) 3058, 3009, 1589, 1481, 1350 cmꢂ1
;
GCeMS m/z (rel intensity) 284 (Mþ, 100), 256 (21), 179 (24), 142
4.2.32. 6-Bromo-2,3-di-2-thiophenylquinoxaline (36). Yield 76%.
Yellow solid, mp 153e154 ꢀC. TLC (30% ethyl acetate/hexane) Rf
(13), 78 (16).
0.65; 1H NMR (400 MHz, CDCl3)
d
8.25 (d, 1H, J¼1.7 Hz), 7.92 (d, 1H,
4.2.38. 5-Methyl-2,3-di(pyridin-2-yl)quinoxaline (42).34a Yield 45%.
Orange solid, mp 96e98 ꢀC. TLC (30% ethyl acetate/hexane) Rf 0.50;
J¼8.8 Hz), 7.77 (dd, 1H, J¼8.9, 1.8 Hz), 7.51 (m, 2H), 7.28e7.26 (m,
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10
A. Go et al. / Tetrahedron xxx (2015) 1e12
1H NMR (400 MHz, CDCl3)
d
8.38 (m, 1H), 8.31 (m, 1H), 8.15 (m, 1H),
acetate/hexane) Rf 0.50; 1H NMR (400 MHz, CDCl3)
8.36 (m, 2H), 8.09 (m, 1H), 7.97 (m, 2H), 7.90 (m, 1H), 7.86e7.80 (m,
2H), 7.27e7.24 (m, 2H); 13C NMR (100 MHz, CDCl3)
157.1, 157.0,
d 8.41 (m, 1H),
8.06 (m, 1H), 7.96 (m, 1H), 7.87e7.80 (m, 2H), 7.70 (m, 1H), 7.65 (m,
1H), 7.25e7.23 (m, 2H), 2.88 (s, 3H); 13C NMR (100 MHz, CDCl3)
d
d
157.8, 157.7, 152.0, 150.9, 148.5, 148.2, 141.1, 140.2, 137.7, 137.0,
153.2, 152.7, 149.8, 148.6, 148.5, 141.6, 139.8, 136.7, 136.6, 134.0,
131.6, 130.6, 124.2, 124.1, 123.2, 123.1; IR (KBr) 3175, 3097, 1623,
1502, 1338,1250 cmꢂ1; GCeMS m/z (rel intensity) 363 (Mþþ2, 100),
361 (Mþ, 100), 341 (36), 329 (14), 253 (34), 171 (11), 109 (16).
136.6, 130.3, 130.2, 127.1, 124.3, 124.1, 122.9, 122.8, 17.1; IR (KBr)
3055, 3008, 2951, 2924, 1589, 1474, 1350 cmꢂ1; GCeMS m/z (rel
intensity) 298 (Mþ, 100), 270 (12), 192 (8), 148 (11), 89 (12).
4.2.39. 6-Methyl-2,3-di(pyridin-2-yl)quinoxaline (43).34b Yield 50%
(entry 3, Table 5). Yellow solid, mp 143e144 ꢀC (lit.33c mp 146 ꢀC).
TLC (30% ethyl acetate/hexane) Rf 0.50; 1H NMR (400 MHz, CDCl3)
4.2.45. 6-Iodo-2,3-di(pyridin-2-yl)quinoxaline
White solid, mp 143e144 ꢀC. TLC (30% ethyl acetate/hexane) Rf
0.50; 1H NMR (400 MHz, CDCl3)
8.58 (s, 1H), 8.28 (m, 2H), 7.98 (d,
1H, J¼8.8 Hz), 7.91e7.84 (m, 4H), 7.76e7.74 (m, 2H), 7.19e7.15 (m,
3H); 13C NMR (100 MHz, CDCl3)
157.1, 157.0, 153.0, 152.9, 148.6,
148.5, 141.8, 140.2, 139.3, 138.3, 136.7, 136.7, 130.5, 124.2, 124.1,
(49). Yield 60%.
d
d
8.31 (m, 2H), 8.05 (d, 1H, J¼8.5 Hz), 7.93 (s, 1H), 7.87 (m, 2H), 7.74
(m, 2H), 7.59 (d, 1H, J¼8.5), 7.16 (m, 2H), 2.55 (s, 3H); 13C NMR
d
(100 MHz, CDCl3)
d 147.2, 144.7, 130.3, 126.7, 126.6, 126.1, 126.0,
125.4, 125.4, 119.3, 119.2, 118.8, 118.5, 118.3, 118.1, 118.0, 117.6, 117.5,
123.2, 123.1, 96.4; IR (KBr) 3054, 1585, 1475, 1348, 1077 cmꢂ1
;
21.6; IR (KBr) 3059, 3005, 2955, 2928, 1585, 1435, 1311 cmꢂ1
;
GCeMS m/z (rel intensity) 409 (Mþ, 100), 282 (31), 75 (9); Anal.
Calcd for C18H11IN4: C, 52.70; H, 2.70; N, 13.66. Found: C, 52.58; H,
2.64; N, 13.67.
GCeMS m/z (rel intensity) 298 (Mþ, 100), 270 (16), 193 (8), 148 (13),
89 (14), 78 (12).
4.2.40. 6-Methoxy-2,3-di(pyridin-2-yl)quinoxaline
78%. White solid, mp 194e195 ꢀC. TLC (30% ethyl acetate/hexane) Rf
0.50; 1H NMR (400 MHz, CDCl3)
8.43 (m, 1H), 8.40 (m, 1H), 8.11
(44).34c Yield
4.2.46. 5-Trifluoromethyl-2,3-di(pyridin-2-yl)quinoxaline
(50). Yield 70%. Pale yellow solid, mp 139e140 ꢀC. TLC (30% ethyl
d
acetate/hexane) Rf 0.50; 1H NMR (400 MHz, CDCl3)
d 8.31 (m, 2H),
(m, 1H), 7.90e7.86 (m, 1H), 7.81 (m, 1H), 7.79 (m, 1H), 7.77 (m, 1H),
8.23 (d, 1H, J¼7.8 Hz), 8.17 (m, 1H), 8.07 (d, 1H, J¼7.1 Hz), 7.90 (m,
7.53 (m, 1H), 7.48 (m, 1H), 7.27e7.21 (m, 2H), 3.99 (s, 3H); 13C NMR
1H), 7.83e7.74 (m, 3H), 7.17 (m, 2H); 13C NMR (100 MHz, CDCl3)
(100 MHz, CDCl3)
d
161.2, 157.5, 157.4, 152.3, 149.9, 148.7, 148.6,
d 157.4, 156.6, 153.3, 152.3, 148.6, 148.0, 137.0, 136.9, 136.7, 133.6,
142.8, 137.3, 136.52, 136.51, 130.3, 124.2, 124.1, 124.0, 122.9, 122.7,
106.6, 55.8; IR (KBr) 3051, 3005, 2966, 2943, 1620, 1586, 1494, 1357,
1213 cmꢂ1; GCeMS m/z (rel intensity) 313 (Mþ, 100), 299 (21), 271
(29).
128.9, 128.4 (q, J¼5.0 Hz), 128.1, 127.0 (q, J¼3.9 Hz), 126.4 (q,
J¼279.5 Hz), 124.9, 123.8 (q, J¼48.7 Hz), 123.4, 123.1; IR (KBr) 3055,
3008, 1628, 1589,1473,1323, 1130 cmꢂ1; GCeMS m/z (rel intensity);
351 (Mþ, 100), 332 (20), 78 (9); Anal. Calcd for C19H11F3N4: C, 64.77;
H, 3.15; N, 15.90. Found: C, 64.73; H, 3.04; N, 15.69.
4.2.41. 6,7-Dimethoxy-2,3-di(pyridin-2-yl)quinoxaline (45). Yield
80%. Brown solid (recrystallized from ethyl acetate/hexane), mp
234e236 ꢀC. TLC (60% ethyl acetate/hexane) Rf 0.24; 1H NMR
4.2.47. 6-Trifluoromethyl-2,3-di(pyridin-2-yl)quinoxaline (51). Yield
71%. Pale yellow solid, mp 132e133 ꢀC. TLC (30% ethyl acetate/
(400 MHz, CDCl3)
d
8.38e8.37 (m, 2H), 7.74e7.67 (m, 4H), 7.45 (s,
hexane) Rf 0.50; 1H NMR (400 MHz, CDCl3)
d
8.55 (s, 1H), 8.36 (m,
3H), 8.04e7.98 (m, 3H), 7.86 (m, 2H), 7.27 (m, 2H); 13C NMR
(100 MHz, CDCl3) 156.8, 156.7, 154.4, 153.8, 148.6, 148.5, 142.1,
2H), 7.17e7.16 (m, 2H), 4.02 (s, 6H); 13C NMR (100 MHz, CDCl3)
d
157.6, 153.4, 150.0, 148.9, 138.6, 136.5, 124.3, 122.7, 106.8, 56.5; IR
d
(KBr) 3055, 3005, 2936, 2833, 1730, 1499, 1222 cmꢂ1; GCeMS m/z
140.0, 136.8, 136.7, 132.2 (q, J¼33.1 Hz), 130.6, 127.3 (q, J¼4.4 Hz),
126.1 (q, J¼3.0 Hz), 124.2, 124.1, 123.6 (q, J¼273.1 Hz), 123.32,
123.30; IR (KBr) 3055, 3008, 1620, 1587, 1472, 1359 cmꢂ1; GCeMS
m/z (rel intensity) 351 (Mþ, 100), 324 (13), 176 (7), 78 (16); Anal.
Calcd for C19H11F3N4: C, 64.77; H, 3.15; N, 15.90. Found: C, 64.73; H,
3.05; N, 15.69.
(rel intensity) 343 (Mþ, 100), 327(10), 299 (17); Anal. Calcd for
C
20H16N4O2: C, 69.76; H, 4.68; N, 16.27. Found: C, 69.33; H, 4.65; N,
15.94.
4.2.42. 6-Fluoro-2,3-di(pyridin-2-yl)quinoxaline (46). Yield 78%.
Orange solid, mp 95e96 ꢀC. TLC (30% ethyl acetate/hexane) Rf 0.50;
1H NMR (400 MHz, CDCl3)
d
8.31 (m, 2H), 8.16 (m, 1H), 8.08 (d, 1H,
4.2.48. 6- Carbonitrile-2,3-di(pyridin-2-yl)quinoxaline (52). Yield
83%. Pale yellow solid, mp 132e133 ꢀC. TLC (30% ethyl acetate/
J¼7.8 Hz), 7.89e7.84 (m, 2H), 7.79e7.72 (m, 3H), 7.17 (m, 2H); 13C
NMR (100 MHz, CDCl3)
d
153.3 (d, J¼239.2 Hz), 141.4, 124.7, 124.53
hexane) Rf 0.50; 1H NMR (400 MHz, CDCl3)
d
8.59 (d, 1H, J¼2.0 Hz),
(d, J¼24.0 Hz), 124.51, 124.503, 124.50 (d, J¼24 Hz), 120.03, 120.01,
119.94,119.93,119.91 (d, J¼9.1 Hz),119.90,119.87,111.4 (d, J¼3.3 Hz),
111.2 (d, J¼2.5 Hz), 108.2, 107.4; IR (KBr) 3172, 3098, 1645, 1515,
1415, 1340, 1245 cmꢂ 1; GCeMS m/z (rel intensity) 301 (Mþ, 100),
274 (18), 197 (12), 78 (8); HRMS (EI) calcd for C18H11FN4 302.0968,
found 302.0929.
8.36 (m, 2H), 8.31 (d, 1H, J¼8.5 Hz), 8.03 (m, 2H), 7.96 (m, 1H),
7.87e7.85 (m, 2H), 7.30e7.26 (m, 2H); 13C NMR (100 MHz, CDCl3)
d
156.6, 156.5, 154.9, 154.3, 148.6, 148.58, 142.4, 140.1, 136.8, 136.79,
135.2, 131.1, 130.9, 124.2, 124.16, 123.5, 123.46, 118.0, 113.8; IR (KBr)
3057, 3004, 2230, 1587, 1473, 1349 cmꢂ1; GCeMS m/z (rel intensity)
308 (Mþ,100), 281 (7), 78 (11); Anal. Calcd for C19H11N5: C, 73.77; H,
3.58; N, 22.64. Found: C, 73.41; H, 3.61; N, 23.08.
4.2.43. 6-Chloro-2,3-di(pyridin-2-yl)quinoxaline (47).31j Yield 56%
(entry 8, Table 5). Pale brown solid, mp 360e362 ꢀC (lit.31j mp
362e369 ꢀC). TLC (30% ethyl acetate/hexane) Rf 0.50; 1H NMR
4.2.49. Dibenzo[a,c]phenazine (53).15,35a,b Yield 80%. Pale yellow
solid, mp 224e225 ꢀC (lit.15 mp 225e226 ꢀC). TLC (30% ethyl ace-
(400 MHz, CDCl3)
J¼8.8 Hz), 7.88 (m, 2H), 7.77e7.72 (m, 2H), 7.69 (dd, 1H, J¼8.8,
2.2 Hz), 7.19e7.15 (m, 2H); 13C NMR (100 MHz, CDCl3)
157.1, 157.0,
d
8.29 (m, 2H), 8.15 (d, 1H, J¼2.2 Hz), 8.08 (d, 1H,
tate/hexane) Rf 0.74; 1H NMR (400 MHz, CDCl3)
d
9.33 (d, 2H,
J¼7.8 Hz), 8.48 (d, 2H, J¼7.8 Hz), 8.28 (m, 2H), 7.83e7.67 (m, 6H);
13C NMR (100 MHz, CDCl3)
142.4, 142.1, 142.0, 130.3, 130.2, 129.7,
d
d
153.2, 152.6, 149.8, 148.6, 141.3, 139.6, 137.0, 136.7, 136.2, 131.5,
130.5, 128.2, 126.9, 125.1, 124.2, 123.1; IR (KBr) 3056, 3005, 1603,
1587, 1478, 1349 cmꢂ1; GCeMS m/z (rel intensity) 319 (Mþþ2, 69),
362 (Mþ, 100), 341 (36), 329 (14), 253 (34), 171 (11), 109 (16).
129.4, 127.9, 126.2, 122.9; IR (KBr) 3059, 3032, 1605, 1501,
1357 cmꢂ1; GCeMS m/z (rel intensity) 280 (Mþ, 100), 251 (4), 140
(13).
4.2.50. 10-Methyldibenzo[a,c]phenazineꢀ (54).35c Yield 84%. Orange
solid, mp 222e223 ꢀC (lit.35c mp 223 C). TLC (20% ethyl acetate/
4.2.44. 6-Bromo-2,3-di(pyridin-2-yl)quinoxaline (48).31j Yield 70%.
Orange solid, mp 100e101 ꢀC (lit.31j mp 95e96 ꢀC). TLC (30% ethyl
hexane) Rf 0.54; 1H NMR (400 MHz, CDCl3)
d 9.29 (m, 2H), 8.44 (m,
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A. Go et al. / Tetrahedron xxx (2015) 1e12
11
2H), 8.07 (d, 1H, J¼8.0 Hz), 7.73e7.58 (m, 6H), 2.95 (s, 3H); 13C NMR
1454, 1357 cmꢂ1; GCeMS m/z (rel intensity) 360 (Mþþ2, 100), 358
(Mþ, 100), 279 (26), 266 (20), 251 (11), 207 (13), 179 (15), 139 (19),
79 (49).
(100/MHz, CDCl3)
d 142.2, 141.7, 141.2, 140.9, 137.7, 131.9, 131.7,
130.6, 130.2, 130.0, 129.9, 129.5, 129.3, 127.7, 127.1, 127.2, 126.0,
122.8, 122.76, 122.7, 17.4; IR (KBr) 3055, 3028, 2947, 2920, 1604,
1497, 1447, 1354 cmꢂ1; GCeMS m/z (rel intensity) 294 (Mþ, 100),
147 (9).
4.2.57. 11-Iododibenzo[a,c]phenazine (61). Yield 80% (Toluene was
used as solvent). Yellow solid, mp 232e234 ꢀC. TLC (30% ethyl ac-
etate/hexane) Rf 0.75; 1H NMR (400 MHz, CDCl3)
d
9.28 (m, 2H),
8.70 (s, 1H), 8.51 (m, 2H), 7.99 (m, 2H), 7.75 (m, 4H); 13C NMR
(100 MHz, CDCl3) 142.7, 141.1, 138.4, 135.3, 135.2, 132.1, 130.7,
130.6, 130.2, 130.0, 128.5, 128.0, 126.3, 126.2, 125.0, 124.8, 123.0,
4.2.51. 11-Methyldibenzo[a,c]phenazine (55).15 Yield 79% (entry 4,
Table 6). Yellow solid, mp 222e223 ꢀC (lit.15 mp 218e220 ꢀC). TLC
d
(20% ethyl acetate/hexane) Rf 0.47; 1H NMR (400 MHz, CDCl3)
d
9.31
(d, 2H, J¼7.2 Hz), 8.49 (m, 2H), 8.14 (d, 1H, J¼7.8 Hz), 8.01 (s, 1H),
7.72e7.61 (m, 5H), 2.63 (s, 3H); 13C NMR (100 MHz, CDCl3)
142.1,
110.6, 110.0, 95.7; IR (KBr) 3070, 3036, 1600, 1492, 1450, 1357 cmꢂ1
;
d
GCeMS m/z (rel intensity) 406 (Mþ, 100), 305 (17), 279 (31), 203
(10), 139 (10); Anal. Calcd for C20H11IN2: C, 59.13; H, 2.73; N, 6.90.
Found: C, 58.64; H, 2.75; N, 6.86.
141.6, 140.7, 140.2, 132.3, 131.9, 131.7, 130.33, 130.31, 130.0, 129.9,
128.9, 128.8, 128.0, 127.9, 127.7, 126.1, 126.0, 122.8, 122.7, 22.0; IR
(KBr) 3058, 3020, 2918, 2947, 2850, 1502, 1357 cmꢂ1; GCeMS m/z
(rel intensity) 294 (Mþ, 100), 147 (9).
4.2.58. 10-Trifluoromethyldibenzo[a,c]phenazine (62).35h Yield 81%.
Yellow solid, mp 197e198 ꢀC (lit.35h mp 195e196 ꢀC). TLC (20% ethyl
4.2.52. 11-Methoxydibenzo[a,c]phenazine (56).35d Yield 56% (Tolu-
ene was used as solvent). Pale yellow solid, mp 201e203 ꢀC. TLC
acetate/hexane) Rf 0.61; 1H NMR (400 MHz, CDCl3)
d 9.29 (d, 1H,
J¼7.6 Hz), 9.19 (d, 1H, J¼7.8 Hz), 8.40 (m, 3H), 8.14 (d, 1H, J¼7.1 Hz),
(20% ethyl acetate/hexane) Rf 0.72; 1H NMR (400 MHz, CDCl3)
d
9.31
(m, 2H), 8.59e8.51 (m, 2H), 8.13 (d, 1H, J¼9.3 Hz), 7.72 (m, 4H),
7.50e7.36 (m, 2H), 4.12 (s, 3H); 13C NMR (100 MHz, CDCl3)
160.8,
7.81 (m, 1H), 7.74e7.66 (m, 3H), 7.62 (m, 1H); 13C NMR (100 MHz,
CDCl3)
d 142.7, 142.4, 141.7, 138.6, 133.7, 132.2, 132.1, 130.9, 130.8,
d
129.7 (q, J¼29.8 Hz), 129.5, 128.3, 128.2, 127.9 (q, J¼5.0 Hz), 127.8 (q,
J¼5.2 Hz), 126.2, 126.1 (q, J¼273.5 Hz), 125.3, 122.9, 122.7, 119.8; IR
(KBr) 3067, 3028, 1504, 1450, 1315, 1125 cmꢂ1; GCeMS m/z (rel
intensity) 348 (Mþ, 100), 327 (15), 164 (8).
143.7, 142.1, 140.2, 138.7, 132.0, 131.3, 130.5, 130.4, 130.2, 129.9,
129.5, 127.8, 127.7, 126.0, 125.7, 124.1, 122.8, 122.76, 105.8, 55.9; IR
(KBr) 3070, 3012, 2959, 2936, 1623, 1501, 1361, 1203 cmꢂ1; GCeMS
m/z (rel intensity) 310 (Mþ, 100), 297 (71), 281 (10), 267 (39), 253
(9), 240 (9), 207 (14), 190 (8), 155 (16), 133 (14), 111 (10), 97 (17), 79
(32), 57 (42).
4.2.59. 11-Trifluoromethyldibenzo[a,c]phenazine (63).35h Yield 68%.
Yellow solid, mp 192e193 ꢀC (lit.35h mp 190e192 ꢀC). TLC (20% ethyl
acetate/hexane) Rf 0.72; 1H NMR (400 MHz, CDCl3)
d
9.10 (m, 2H),
8.42 (s, 1H), 8.32 (d, 2H, J¼7.8 Hz), 8.19 (d, 1H, J¼8.8 Hz), 7.82 (m,
1H), 7.65 (m, 2H), 7.56 (m, 2H); 13C NMR (100 MHz, CDCl3)
143.8,
4.2.53. 11,12-Dimethoxydibenzo[a,c]phenazine (57).35e Yield 72%.
Pale yellow solid, mp 252e253 ꢀC. TLC (30% ethyl acetate/hexane)
d
Rf 0.72; 1H NMR (400 MHz, CDCl3)
d
9.28e9.27 (m, 2H), 8.53e8.52
(m, 2H), 7.70e7.67 (m, 4H), 7.49e7.47 (m, 2H), 4.16 (s, 6H); 13C NMR
(100 MHz, CDCl3) 153.4, 140.2, 139.9, 131.4, 130.5, 129.4, 127.7,
143.3, 142.7, 140.6, 132.3, 132.0, 130.9, 130.8 (q, J¼28.7 Hz), 130.7,
130.6, 129.5, 128.0, 127.9, 127.5 (q, J¼4.6 Hz), 126.5, 126.3, 125.2,
124.9 (q, J¼2.9 Hz), 122.8, 122.7, 122.5; IR (KBr) 3070, 3024, 1604,
1454, 1335 cmꢂ1; GCeMS m/z (rel intensity) 348 (Mþ, 100), 174 (8).
d
125.5, 122.9, 106.3, 56.5; IR (NaCl) 3065, 3015, 2929, 1493, 1429,
1361, 1216 cmꢂ1; GCeMS m/z (rel intensity) 340 (Mþ,100), 297 (28),
254 (10), 176 (13).
4.2.60. 11-Carbonitriledibenzo[a,c]phenazine (64). Yield 50%. Yel-
low solid, mp 275e276 ꢀC. TLC (20% ethyl acetate/hexane) Rf 0.56;
4.2.54. 11-Fluorodibenzo[a,c]phenazine (58).35c Yield 48%. Yellow
solid, mp 224e225 ꢀC (lit.35c mp 226 ꢀC). TLC (20% ethyl acetate/
1H NMR (400 MHz, CDCl3)
d
9.37 (m,1H), 9.35 (d,1H, J¼8.5 Hz), 8.69
(s, 1H), 8.57 (m, 2H), 8.39 (d, 1H, J¼8.8 Hz), 7.95 (d, 1H, J¼8.3 Hz),
7.85 (m, 2H), 7.77 (m, 2H); 13C NMR (100 MHz, CDCl3)
136.6, 135.7,
hexane) Rf 0.79; 1H NMR (400 MHz, CDCl3)
d
9.27 (d, 1H, J¼6.8 Hz),
d
9.25 (d, 1H, J¼6.8 Hz), 9.12e9.05 (m, 3H), 8.51 (s, 1H), 8.23 (m, 1H),
133.3,132.4,131.5,131.3,131.0,129.8,129.5,128.3,128.2,128.1,127.4,
127.2, 126.9, 126.6, 124.0, 123.1, 123.0, 112.9, 111.3; IR (KBr) 3062,
3043, 2225, 1731, 1600, 1446, 1353 cmꢂ1; GCeMS m/z (rel intensity)
305 (Mþ, 100), 279 (6), 152 (6); Anal. Calcd for C21H11N3: C, 82.61; H,
3.63; N, 13.76. Found: C, 82.51; H, 3.81; N, 13.25.
7.84 (m, 1H), 7.74 (m, 1H), 7.68 (m, 1H), 7.58 (m, 1H); 13C NMR
(100 MHz, CDCl3)
d
162.8 (d, J¼252.4 Hz), 142.8 (d, J¼10.8 Hz),
142.6, 141.8, 139.4, 132.2, 131.8, 131.5 (d, J¼9.9 Hz), 130.5, 130.2,
130.1, 129.9, 127.9, 127.8, 127.4, 126.4, 126.0, 122.8, 120.6 (d,
J¼26.5 Hz), 112.3 (d, J¼20.7 Hz); IR (KBr) 3056, 3018, 1624, 1500,
1357, 1211 cmꢂ1; GCeMS m/z (rel intensity) 298 (Mþ, 100), 149 (9).
Acknowledgements
4.2.55. 11-Chlorodibenzo[a,c]phenazine (59).15,35def Yield 74% (en-
try 9, Table 6). Yellow solid, mp 248e249 ꢀC (lit.35f mp 246e247 ꢀC).
TLC (20% ethyl acetate/hexane) Rf 0.71; 1H NMR (400 MHz, CDCl3)
This work was supported by Kwangwoon University in 2014.
References and notes
d
9.37 (m, 2H), 8.58 (m, 2H), 8.30 (m, 2H), 7.79 (m, 5H); 13C NMR
1. Badran, M. M.; Abouzid, K. A. M.; Hussein, M. H. M. Arch. Pharm. Res. 2003, 26,
107e113.
2. Griffith, R. K.; Chittur, S. V.; Chen, Y. C. Med. Chem. Res. 1992, 2, 467e473.
3. El-Gendy, A. A.; El-Meligie, S.; El-Ansry, A.; Ahmedy, A. M. Arch. Pharm. Res.
1995, 18, 44e47.
(100 MHz, CDCl3)
d 137.9, 137.8, 130.9, 130.7, 130.6, 130.5, 129.1,
129.0, 128.3, 128.28, 128.2, 128.1, 128.0, 126.4, 126.3, 126.2, 125.3,
125.0, 124.5, 123.0; IR (KBr) 3062, 3024, 1605, 1489, 1450,
1357 cmꢂ1; GCeMS m/z (rel intensity) 316 (Mþþ2, 38), 314 (Mþ,
100), 277 (7), 157 (10), 139 (8).
4. Reddy-Sastry, C. V.; Shrinivas-Rao, K.; Krishanan, V. S. H.; Rastogi, K.; Jain, M. L.;
Narayanan, G. Indian J. Chem. 1990, 54, 808e815.
5. El-Hawash, S. A.; Habib, N. S.; Franki, N. H. Pharmazie 1999, 54, 808e815.
6. Westphal, G.; Wasiki, H.; Zielinski, U.; Weberr, F. G.; Tonew, M.; Tonew, E.
Pharmazie 1977, 35, 570e571.
7. Monge, A.; Martinez-Crespo, F. J.; Lopez de Cerain, A.; Palop, J. A.; Narro, S.;
Senador, V.; Marin, A.; Sainz, Y.; Gonzalez, M.; Hamilton, E.; Barker, A. J. J. Med.
Chem. 1995, 38, 4488e4495.
8. Michael, J. W.; Ben-Hadda, T.; Kotchevan, A. T.; Ramdani, A.; Touzani, R.; El-
kadiri, S.; Hakkou, A.; Boukka, M.; Elli, T. Molecules 2002, 7, 641e656.
9. Rangisetty, J. B.; Gupta, C. N.; Prasad, A. L.; Srinavas, P.; Sridhar, N.; Perimoo, P.;
Veeranjaneyulu, A. J. Pharm. Pharmacol. 2001, 53, 1409e1413.
4.2.56. 11-Bromodibenzo[a,c]phenazine (60).35g Yield 40% (Toluene
was used as solvent). Yellow solid, mp 274e276 ꢀC (lit.35g mp
276 ꢀC). TLC (20% ethyl acetate/hexane) Rf 0.60; 1H NMR (400 MHz,
CDCl3)
d
9.36 (m, 2H), 8.54 (m, 3H), 8.18 (m, 1H), 7.92 (m, 1H), 7.78
135.3,133.3,131.6,131.5,130.7,
(m, 4H); 13C NMR (100 MHz, CDCl3)
d
130.6, 130.0, 129.9, 128.1, 127.8, 126.5, 126.4, 126.3, 125.1, 123.8,
123.7, 123.1, 123.0, 122.9, 117.4; IR (KBr) 3053, 3024, 1605, 1496,
Please cite this article in press as: Go, A.; et al., Tetrahedron (2015), http://dx.doi.org/10.1016/j.tet.2015.01.007

12
A. Go et al. / Tetrahedron xxx (2015) 1e12
10. Zhao, Z.; Wisnoski, D. D.; Wolkenberg, S. E.; Leister, W. H.; Wang, Y.; Lindsley, C.
W. Tetrahedron Lett. 2004, 45, 4873e4876.
Chim. Acta 2003, 348, 263e270; (c) Jung, O. S.; Park, S. H.; Kim, Y. J.; Lee, Y. A.;
Jang, H. G.; Lee, U. Inorg. Chim. Acta 2001, 312, 93e99.
11. Bhosale, R. S.; Sarda, S. R.; Ardhapure, S. S.; Jadhav, W. N.; Bhusare, S. R.; Pawar,
30. (a) Babuin, J.; Foster, J.; Williams, V. E. Tetrahedron Lett. 2003, 44, 7003e7005;
(b) Foster, E. J.; Babuin, J.; Nguyen, N.; Williams, V. E. Chem. Commun. 2004,
2052e2053; (c) Foster, E. J.; Lavigueur, C.; Ke, Y. C.; Williams, V. E. J. Mater.
Chem. 2005, 15, 4062e4068; (d) Foster, E. J.; Jones, R. B.; Lavigueur, C.; Williams,
V. E. J. Am. Chem. Soc. 2006, 128, 8569e8574; (e) Gautrot, J. E.; Hodge, P. Polymer
2007, 48, 7065e7077; (f) Lavigueur, C.; Foster, E. J.; Williams, V. E. J. Am. Chem.
Soc. 2008, 130, 11791e11800; (g) Estrada, L. A.; Neckers, D. C. Org. Lett. 2011, 13,
3304e3307.
R. P. Tetrahedron Lett. 2005, 46, 7183e7186.
12. More, S. V.; Sastry, M. N. V.; Wang, C. C.; Yao, C. F. Tetrahedron Lett. 2005, 46,
6345e6348.
13. Heravi, M. M.; Bakhtiari, K.; Tehrani, M. H.; Javadi, N. M.; Oskooie, H. A. Arkivoc
2006, 16e22.
14. Hasaninejad, A.; Zare, A.; Mohammadizadeh, M. R.; Shekouhy, M. Arkivoc 2008,
28e35.
15. Niknam, K.; Saberi, D.; Mohagheghnejad, M. Molecules 2009, 14, 1915e1926.
16. Debasish, B.; Sanghamitra, M.; Robert, R. R.; Bimal, K. B. Molecules 2010, 15,
4207e4212.
17. Darabi, H. R.; Aghapoor, K.; Mohsenzadeh, F.; Jalali, M. R.; Talebian, S.; Ebadi-
Nia, L.; Khatamifar, E.; Aghahee, A. Bull. Korean Chem. Soc. 2011, 32, 213e218.
18. Wen, X. G.; Hui, L. J.; Jiu, X. C.; Fan, C.; Jin, C. D.; Hua, Y. W. J. Braz. Chem. Soc.
2009, 20, 1e6.
19. Darabi, H. R.; Tahoori, F.; Aghapoor, K.; Mohsenzadeh, F. J. Braz. Chem. Soc. 2008,
19, 1646e1652.
20. Hasaninejad, A.; Zare, A.; Mahammadizadeh, M. R.; Karami, Z. J. Iran. Chem. Soc.
31. (a) Despinoy, C.; Lloyd, D.; Mcnab, H.; Reed, D. Tetrahedron 1998, 54,
9667e9676; (b) Li, Z.; Li, W.; Sun, Y.; Huang, H.; Ouyang, P. J. Heterocycl. Chem.
2008, 45, 285e288; (c) Ajaikumar, S.; Pandurangan, A. Appl. Catal. A: Gen. 2009,
357, 184e192; (d) Darabi, H. R.; Aghapoor, K.; Mohsenzadeh, F.; Taala, F.; Asa-
dollahnejad, N.; Badiei, A. Catal. Lett. 2009, 133, 84e89; (e) Aghapoor, K.; Darabi,
H. R.; Mohsenzadeh, F.; Balavar, Y.; Daneshyar, H. Trans. Met. Chem. 2010, 35,
49e53; (f) Padmavathy, K.; Nagendrappa, G.; Geetha, K. V. Tetrahedron Lett.
2011, 52, 544e547; (g) Landquist, J. K.; Stacey, G. J. J. Chem. Soc. 1953,
2822e2830; (h) Zhang, L.; Qiu, B.; Li, X.; Wang, X.; Li, J.; Zhang, Y.; Liu, J.; Li, J.;
Shen, J. Molecules 2006, 11, 988e999; (i) Morales-Castellanos, J. J.; Ramirez-
Hernandez, K.; Gomez-Flores, N.; Rodas-Suarez, O. R.; Peralta-Cruz, J. Molecules
2012, 17, 5164e5176; (j) Ji, Y.; Brueckl, T.; Baxter, R. D.; Fujiwara, Y.; Seiple, I. B.;
Su, S.; Blackmond, D. G.; Baran, P. S. Proc. Natl. Acad. Sci. U.S.A. 2011, 108,
14411e14415.
32. (a) Zhang, C.; Xu, Z.; Zhang, L.; Jiao, N. Tetrahedron 2012, 68, 5258e5262; (b)
Urban, S.; Ortega, N.; Glorius, F. Angew. Chem., Int. Ed. 2011, 50, 3803e3806; (c)
Baumann, N. Ger. Offen. 1976, DE 2525674 A1 19760102. (d) Rtishchev, N. I.;
Dobrodei, A. N.; El’tsov, A. V. Russ. J. Gen. Chem. 1999, 69, 1658e1668; (e) Sykes,
A.; Tatlow, J. C. J. Chem. Soc. 1952, 4078e4079.
33. (a) Zhuo, F. F.; Xie, W. W.; Yang, Y. X.; Zhang, L.; Wang, P.; Yuan, R.; Da, C. S. J.
Org. Chem. 2013, 78, 3243e3249; (b) Joel, K.; Matthew, D.; Dan, S.; Hai-Ying,
H.; Alexander, K.; Bronek, P. PCT Int. Appl. 2005, WO 2005007099 A2
2009, 6, 153e158.
21. Mahesh, R.; Dhar, A. K.; Sasank, T. V. N. V. T.; Thirunavukkarasu, S.; Devadoss, T.
Chin. Chem. Lett. 2011, 22, 389e392.
22. Fang, D.; Gong, K.; Fei, Z.; Zhou, X.; Liu, Z. Catal. Commun. 2008, 9, 317e320.
23. Kadam, H. K.; Khan, S.; Kunkalkar, R. A.; Tilve, S. G. Tetrahedron Lett. 2013, 54,
1003e1007.
24. Meshram, H. M.; Kumar, G. S.; Ramesh, P.; Reddy, B. C. Tetrahedron Lett. 2010, 51,
2580e2585.
25. Martin, L. J.; Marzinzik, A. L.; Ley, S. V.; Baxendale, I. R. Org. Lett. 2011, 13,
320e323.
26. Rustagi, V.; Agggarwal, T.; Verma, A. K. Green Chem. 2011, 13, 1640e1643.
27. (a) Yamamoto, K.; Oshima, K. Main Group Metals in Organic Synthesis; Wiley-
VCH: Weinheim, Germany, 2004, Vol. 1, pp 323e386; (b) Li, C. J.; Chan, T. H.
Organic Reactions in Aqueous Media; Wiley-Interscience: New York, NY, 1997;
pp 65e114; (c) Li, C. J. Tetrahedron 1996, 52, 5643e5668; (d) Podlech, J.; Maier,
T. C. Synthesis 2003, 5, 633e655; (e) Nair, V.; Ros, S.; Jayan, C. N.; Pillai, B. S.
Tetrahedron 2004, 60, 1959e1982; (f) Kumar, S.; Pervinder, K.; Vijay, K. Curr. Org.
Chem. 2005, 9, 1205e1235.
28. (a) Kim, B. H.; Jin, Y.; Jun, Y. M.; Han, R.; Baik, W.; Lee, B. M. Tetrahedron Lett.
2000, 41, 2137e2140; (b) Kim, B. H.; Han, R.; Kim, J. S.; Jun, Y. M.; Baik, W.; Lee,
B. M. Heterocycles 2004, 62, 41e54; (c) Han, R.; Chen, S.; Lee, S. J.; Qi, F.; Wu, X.;
Kim, B. H. Heterocycles 2006, 68, 1675e1684; (d) Han, R.; Son, K. I.; Ahn, G. H.;
Jun, Y. M.; Lee, B. M.; Park, Y.; Kim, B. H. Tetrahedron Lett. 2006, 47, 7295e7299;
(e) Ahn, G. H.; Lee, J. J.; Jun, Y. M.; Lee, B. M.; Kim, B. H. Org. Biomol. Chem. 2007,
5, 2472e2485; (f) Lee, J. J.; Kim, J.; Jun, Y. M.; Lee, B. M.; Kim, B. H. Tetrahedron
2009, 65, 8821e8831; (g) Kim, J. S.; Han, J. H.; Lee, J. J.; Jun, Y. M.; Lee, B. M.;
Kim, B. H. Tetrahedron Lett. 2008, 49, 3733e3738; (h) Han, R.; Chen, S.; Lee, S. J.;
Qi, F.; Wu, X.; Kim, B. H. Heterocycles 2013, 87, 155e162; (i) Lee, H. S.; Kim, B. H.
Tetrahedron Lett. 2013, 69, 6698e6708.
ꢀ
ꢀ
ꢀ
ꢀ
20050127. (c) Szekelyhidi, Z.; Pato, J.; Waczeka, F.; Banhegyi, P.; Hegymegi-
ꢀ
ꢀ
ꢀ
Barakonyi, B.; Ero}s, D.; Meszaros, G.; Hollosy, F.; Hafenbradl, D.; Obert, S.;
Klebl, B.; Keri, G.; Or}fi, L. Bioorg. Med. Chem. Lett. 2005, 15, 3241e3246; (d)
ꢀ
Bhattacharya, T.; Sarma, T. K.; Samanta, S. Catal. Sci. Technol. 2012, 2,
2216e2220.
34. (a) Polson, M. I. J.; Howell, S. L.; Flood, A. H.; Burrell, A. K.; Blackman, A. G.;
Gordon, K. C. Polyhedron 2004, 23, 1427e1439; (b) Zhang, X. Z.; Wang, J. X.; Bai,
L. Synth. Commun. 2011, 41, 2053e2063; (c) Bauer, S.; Brahm, R.; Dietrich, R.
Patentschrift 1978, CH 599569 A5 19780531.
35. (a) Samanta, S.; Dasgupta, A.; Mallik, A. K. Monatsh. Chem. 2014, http://dx.doi.
org/10.1007/s00706-014-1242-5; (b) Tajbakhsh, M; Bazzar, M.; Ramzanian, S.
F.; Tajbakhsh, M. Appl. Clay Sci. 2014, 89, 178e185; (c) Suschitzky, H. J. Chem.
Soc. 1953, 3042e3044; (d) Bauer, S.; Kluepfel, K. W.; Faust, R. J. Ger. Offen. 1971,
DE 2027467 A 19711209. (e) Heacock, R. A.; Hutzinger, O. J. Chem. Soc. 1963,
3574e3578; (f) Karami, B.; Khodabakhshi, S. J. Chil. Chem. Soc. 2013, 58,
1655e1658; (g) Soleymani, R.; Niakan, N.; Tayeb, S.; Hakimi, S. Orient. J. Chem.
2012, 28, 687e701; (h) Campbell, J. B. Ger. Offen. 1977, DE 2631888 A1
19770203.
29. (a) Wang, X. L.; Bi, Y. F.; Liu, G. C.; Lin, H. Y.; Hu, T. L.; Bu, X. H. Cryst. Eng.
Commun. 2008, 10, 349e356; (b) Granifo, J.; Garland, M. T.; Baggio, R. Inorg.
Please cite this article in press as: Go, A.; et al., Tetrahedron (2015), http://dx.doi.org/10.1016/j.tet.2015.01.007