Nano SbCl5.SiO2: An efficient catalyst for the synthesis of quinoxaline derivatives at room temperature under solventless condition

Article abstract of DOI:10.4067/S0717-97072015000100017

Nano SbCl₅.SiO₂ as an eco-friendly and efficient nanocatalyst was applied for quinoxaline derivatives preparation with improved yield. In this protocol, α-diketones and 1,2-diamines were condensed in the presence of nanocatalyst at room temperature under solventless conditions. The method gave good yields of quinoxaline derivatives in short reaction times in comparison with earlier methods. Using nontoxic and inexpensive materials, simple work-up, short reaction times and high yields of the products are the advantages of this method.

Full text of DOI:10.4067/S0717-97072015000100017

J. Chil. Chem. Soc., 60, Nº 1 (2015)
NANO SbCl5.SiO2: AN EFFICIENT CATALYST FOR THE SYNTHESIS OF QUINOXALINE DERIVATIVES AT
ROOM TEMPERATURE UNDER SOLVENTLESS CONDITION
ABDOLHAMID BAMONIRI*a, BIBI FATEMEH MIRJALILIb, HASSAN KARBASIZADEHa
a)Department of Organic Chemistry, Faculty of Chemistry, University of Kashan, Kashan, I.R.Iran
b) Department of Chemistry, Faculty of Science, Yazd University, Yazd, I.R.Iran
ABSTRACT
Nano SbCl5.SiO2 as an eco-friendly and efficient nanocatalyst was applied for quinoxaline derivatives preparation with improved yield. In this protocol,
α-diketones and 1,2-diamines were condensed in the presence of nanocatalyst at room temperature under solventless conditions. The method gave good yields of
quinoxaline derivatives in short reaction times in comparison with earlier methods. Using nontoxic and inexpensive materials, simple work-up, short reaction times
and high yields of the products are the advantages of this method.
Keywords: nano SbCl5.SiO2, nano-catalyst, quinoxaline derivatives, solventless, green condensation reactions
INTRODUCTION
The quinoxaline moiety is an important structural motif in the preparation
of substances with pronounced biological activities1.The quinoxaline core
is presented in many drugs with antitumor2-3, anticancer4, antiamoebic5,
anticonvulsant6, antimalarial7, antioxidant8 and anti- protozoal activity9. Some
fluorescent dyes10, electroluminescent materials11, chemically controllable
switches12, and organic semiconductors also contain the quinoxaline moiety13.
Because of important applications of quinoxaline compounds in both medicinal
and industrial fields, a number of protocols have been developed for the
synthesis of quinoxaline derivatives. Improved methods have been reported
Scheme 1. Condensation of benzil with 1,2-phenylenediamine in the
presence of nano SbCl5.SiO2 at room temperature under solventless conditions
by using different catalysts such as gallium(III) triflate14, montmorillonite
K1015, sulfamic acid16, cupric sulfate pentahydrate17, Zn (l-proline)18, I219,20, Ni
nanoparticles21, cellulose sulfuric acid (CSA)22, silica sulfuric acid (SSA)23,
EXPERIMENTAL
sulfated titania24, Zn2+-montmorillonite K10 clay25, L-proline26, HClO4.SiO227
,
Ruthenium catalyst28, acidic ionic liquids29, β-cyclodextrin30, methanol/acetic
acid31 and the absence of any catalyst in water32,33 have been used for the
preparation of quinoxalines.
Material
Chemicals were purchased from the Merck Chemical Company in high
purity. The IR spectra were recorded on FT-IR Magna 550 nicolet using with
KBr plates. 1H-NMR spectra were obtained using a Bruker Avance 400 MHz
DRX spectrometer. Melting points were determined without correction using
a Büchi melting point B-540 Buchi apparatus. SEM and TEM analysis were
carried out on VEGA/TESCAN scanning electron microscope and Leo 912AB
OMEGA transmission electron microscopy, respectively.The X-ray diffraction
(XRD) patterns of materials were prepared by employing a Philips Xpert MPD
diffractometer equipped with a Cu Kα anode (λ = 1.54 A˚) in the 2θ range from
5 to 80°.
However, most of the reported methodologies still have certain limitations
such as expensive and air sensitive catalysts, toxicity and high boiling point of
solvents and restrictions for large scale applications. Critical product isolation
procedures, large amounts of catalysts and highly toxic wastes in scaling up for
industrial applications leading to environmental issues are other limitations.
Thus, the development of a simple and efficient method under solventless
conditions for constructing these heterocycles has been advocated.
The use of inorganic solid acids as heterogeneous catalyst have received
considerable importance in organic synthesis34. Because of easy handling,
enhanced reaction rates, high selectivity and easy separation of the products
that such processes permitting the recycling and reuse of catalyst with
operational and economical advantages. Antimony pentachloride (SbCl5), a
thin, colored and fuming liquid, is used in industry and organic synthesis35.
Since it fumes in air and reacts with moisture to form HCl, its handling and
usability in the liquid form is laborious. Thus, the supported form is indeed
preferable. It has been claimed that the supported SbCl5 is a solid superacid.
SbCl5 is used extensively in organic synthesis as a Lewis acid for enhancing
a variety of organic reactions such as Friedel-Crafts alkylation36, electrophilic
additions to alkenes and 1,3- dienes37 and aromatization of enamine38.
In continuation of our investigation on application of solid acids in organic
synthesis 39-44, we have used nano SbCl5.SiO2 for the synthesis of quinoxalines
by condensation of benzil derivatives (1) with 1,2-phenylenediamine
derivatives (2) in good to excellent yields (Scheme 1). The effect of solvent,
molar ratio of reactants, amount of catalyst, temperature and time of reaction
were investigated.
Preparation of catalyst
The catalyst was prepared by stirring a mixture of SbCl5 (0.7 ml) and nano
silica gel (20 nm, 1 g) in 5 ml chloroform for 1 h at room temperature. The
slurry was filtered and washed with chloroform (2×5 ml). The obtained solid
(62% w/w nano SbCl5.SiO2) was dried at ambient temperature for 2 h and then
stored in a dry container45.
General procedure for the synthesis of quinoxalines under solventless
conditions
A mixture of 1,2-phenylenediamine derivative (1 mmol), 1,2-diketones
(1 mmol) and nano SbCl5.SiO2 (62%w/w ) (0.15 g) was stirred at room
temperature under solventless condition. The reaction was monitored by TLC
(n-hexane:ethyl acetate, 7:3). After completion of the reaction, the mixture was
washed with chloroform (2×5 mL) and filtered to recover the catalyst. The
solvent was evaporated and the crude product was recrystallized from ethanol
(5 mL) to afford pure quinoxaline derivatives.
.
Spectroscopic data
2,3-diphenylquinoxaline (Table 1, 3a)
M.p. = 123–124 0C (123-125 °C [46]).1H NMR (CDCl3, TMS, 400 MHz):δ
7.3 (m, 6H); 7.52 (d, 4H, J =7.35 Hz); 7.76 (dd, 2H, J =3.3 Hz, J =3.45 Hz);
8.19 (dd, 2H, J =3.3 Hz, J =3.45 Hz) ppm; 13C NMR(CDCl3, TMS, 100 MHz):
128.27, 128.8, 129.26, 129.88, 129.93, 139.18, 141.29, 153.5 ppm.
6-methyl-2,3-diphenylquinoxaline (Table 1, 3b)
M.p. = 119–121 0C (118-120 °C [47]). 1H NMR (CDCl3, TMS, 400 MHz):
e-mail: bamoniri@kashanu.ac.ir
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J. Chil. Chem. Soc., 60, Nº 1 (2015)
δ 2.5 (s, 3H); 7.25 (m, 6H); 7.55 (m, 4H); 7.59 (d, J =8.75 Hz, 1H); 7.98 (s,
1H); 8.02 (d, J =8.5 Hz, 1H), ppm; 13C NMR (CDCl , TMS, 100 MHz): 21.94,
127.15, 128.12, 128.22, 128.51, 129.35, 131.28,3 138.27, 138.65, 139.25,
140.22, 152.40, 153.25 ppm.
δ 3.72 (s, 4H); 7.24-7.35 ( 6H, m), δ 7.41 (4H, dd, J=7.9 and 1.8 Hz) ppm; 13
C
NMR(CDCl3, TMS, 100 MHz): 43.27, 128.24, 129.72, 131.86, 139.43, 164.81
ppm.
2,3-Di-p-tolylquinoxaline (Table 1, 3k )
6-nitro-2,3-diphenylquinoxaline (Table 1, 3c)
M.p. = 146–147 0C (147-148 °C [19]). 1H NMR (CDCl , TMS, 400 MHz):
δ 2.33(s, 6H), 7.21 (d, J= 7.9, 4H), 7.48 (d, J= 8.0, 4H), 7.636 (m, 2H), 8.19 (m,
2H) ppm; 13C NMR(CDCl , TMS, 100 MHz): 21.27, 128.24, 128.75, 129.66,
129.83, 135.63, 138.44, 1430.83, 153.71 ppm.
M.p. = 186–188 0C (185-187 °C [47]).1H NMR (CDCl , TMS, 400 MHz):
δ 7.34 (m, 6H); 7.55 (d, J =6.75 Hz, 4H); 8.32 (d, J =9.23 3HZ, 1H); 8.49 (d, J
=7 HZ, 1H); 9.05 (s, 1H), ppm; 13C NMR (CDCl3, TMS, 100 MHz): 125.45,
128.32, 129.28, 129.58, 129.74, 129.83, 130.45, 138.36, 138.57, 139.97,
143.52, 147.74 ppm.
RESULTS AND DISCUSSION
2,3-bis(4-methoxyphenyl)quinoxaline (Table 1, 3d)
M.p. = 146–148 0C (145-147 °C [46]). 1H NMR (CDCl , TMS,400 MHz):
δ 3.81(s, 6H); 6.86 (d, J =8.25 Hz, 4H); 7.48 (d, J =8.25 Hz,34H); 7.53 (m, 2H);
8.1 (m, 2H), ppm; 13C NMR (CDCl , TMS,100 MHz): 55.12, 111.57, 127.47,
128.53, 130.15, 131.45, 140.78, 1533.23, 159.58 ppm.
XRD, SEM and TEM analysis of catalyst
The structure of the prepared catalyst was identified by powder XRD.
X-ray patterns of the nano SbCl5.SiO2 were recorded. The XRD of nano SiO2
showed no considerable peaks of crystallinity (Figure 1a). However, the XRD
of nano SbCl .SiO2 (Figure 1b) showed small amount of crystallinity with the
characteristic5peaks. To obtain a visual image of the nano SbCl5.SiO2, scanning
electron microscopy (SEM) and transmission electron microscopy (TEM) were
carried out. by SEM and TEM images, some information about the morphology
of the catalyst nano particles was obtained as presented in (Figure 2a-d). As can
be seen from the figure, the sample shows a nano crystalline structure.
2,3-bis(4-methoxyphenyl)-6-methylquinoxaline (Table 1, 3e)
M.p. = 124–126 0C (125-127 °C [47]). 1H NMR (CDCl3, TMS, 400 MHz):
δ 2.65 (s, 3H); 3.72 (s, 6H); 6.56 (d, J =8.75 Hz, 4H); 7.42 (d, J =8.5 Hz,
4H); 7.55 (d, J =8.5 Hz, 1H); 7.85 (s, 1H), 8.1 (d, J =8.5 Hz, 1H) ppm; 13C
NMR (CDCl3, TMS, 100 MHz): 21.25, 55.47, 112.25, 127.48, 128.27, 130.78,
131.43, 131.56, 139.72, 140.08, 141.12, 152.19, 152.75, 160.12 ppm.
2,3-bis(4-methoxyphenyl)-6-nitroquinoxaline (Table 1, 3f)
M.p. = 191–193 0C (192-194 °C [47]).1H NMR (CDCl3, TMS, 400 MHz):
δ 3.81 (s, 6H); 6.72 (d, J = 8 Hz, 4H); 7.53–7.58 (m, 4H), 8.15 (d, J = 9.25 Hz,
1H), 8.35 (d, J = 9.25 Hz, 1H), 8.95(s, 1H) ppm; 13C NMR (CDCl3, TMS, 100
MHz): 55.25, 113.15, 122.74, 124.49, 130.25, 130.41, 131.74, 131.82, 144, 46,
155.74, 155.89, 160.90 ppm.
Synthesis of quinoxalines in the presence of nano SbCl5.SiO2 under
solventless conditions
To demonstrate the generality and scope of this method, we examined the
reaction of 1,2-diamine with a number of differently substituted 1,2-diketone
under solventless conditions. The results of this study are presented in table 1.
Quinoxaline derivatives were synthesized over nano SbCl5.SiO2using
various 1,2-diketones and 1,2-diamines at room temperature; the results
are presented in table 1. As shown in table 1, all reactions have proceeded
very efficiently at room temperature and no undesirable side-reactions were
observed, although the yields were highly dependent on the substrate used. The
effects of electron deficiency and of the nature of sustituents on the aromatic
ring of diamine and diketone on the yield of quinoxalines were small. For
instance, electron-donating substituents present in diamine part, increased the
yields of products, whereas the effect is reverse with the electron-withdrawing
substituents (Table 1). On the other hand, electron-donating substituents with
aromatic 1,2-diketone decreased the product yields. However, the variations in
the yields were very little. The results summarized in table 1 clearly indicate the
scope of the reaction with respect to the synthesis of quinoxaline derivatives on
nano SbCl .SiO2 supported catalyst. The proposed mechanism for synthesis of
quinoxalin5e may be visualized to occur via reactions as depicted in scheme 2.
2,3-dimethylquinoxaline (Table 1, 3g)
M.p. = 105–106 0C (105-107 °C [48]).1H NMR (CDCl3, TMS, 400 MHz):
δ 2.59 (s, 6H); 7.52–7.57 (m, 2H); 7.85–7.89 (m, 2H), ppm; 13C NMR (CDCl3,
TMS, 100 MHz): 23.08, 128.21, 128.48, 128.69, 140.95 ppm
2,3,6-trimethylquinoxaline (Table 1, 3h)
M.p. = 112–114 0C (113-115 °C [48]).1H NMR (CDCl3, TMS, 400 MHz):
δ 2.45 (s, 3H); 2.65 (s, 6H); 7.41 (d, J = 8.5, 1H); 7.68 (s, 1H); 7.81 (d, J = 8.25,
1H),ppm; 13C NMR(CDCl3, TMS, 100 MHz): 21.5, 23.58, 127.14, 127.45,
131.48, 139.17, 139.48, 141.56, 152.43 ppm.
2,3-dimethyl-6-nitroquinoxaline (Table 1, 3i)
M.p. = 130–131 0C (130-132 °C [48]).1H NMR (CDCl , TMS, 400 MHz):
δ 2.75 (s, 6H); 8.01 (d, J = 9 Hz, 1H); 8.34 (d, J = 9 Hz, 1H)3; 8.78 (s, 1H), ppm;
13C NMR(CDCl3, TMS, 100 MHz): 23.27, 122.24, 124.79, 129.86, 139.83,
143.63, 147.04, 156.27, 157.21 ppm.
2,3-dihydro-5,6-diphenylpyrazine (Table 1, 3j)
M.p. = 154–155 0C (154-156 °C [49]). 1H NMR (CDCl3, TMS, 400 MHz):
Fig. 1.The XRD pattern of (a) nano SiO2 and (b) nano SbCl5.SiO2
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J. Chil. Chem. Soc., 60, Nº 1 (2015)
Fig. 2.a) SEM image ofnano SiO2, b) SEM image of nano SbCl5.SiO2 ,c)
TEM image of nano SiO2, d) TEM image of nano SbCl5.SiO2
Scheme 2. Proposed mechanism for the synthesis of quinoxaline
derivatives
Table 1. Synthesis of quinoxaline derivatives from 1,2-diketones (1mmol) and 1,2-diamines (1mmol) in the presence of nano SbCl5.SiO2 (0.15 g)at room
temperature under solvent-less conditions
Time
(min)
YieldRef.
(%)
Enty
1, 2-diketone
1,2-diamine
Product
NH2
NH2
O
N
N
1
8
9946
9547
9147
O
3a
NH2
N
O
O
2
10
H3C
NH2
N
CH3
3b
NH2
NH2
N
N
O
O
3
15
O2N
NO2
3c
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J. Chil. Chem. Soc., 60, Nº 1 (2015)
H3CO
H3CO
H3CO
N
N
NH2
NH2
O
O
4
15
9546
H3CO
H3CO
3d
H3CO
N
N
NH2
O
5
25
9547
CH3
O
H3C
NH2
H3CO
H3CO
H3CO
3e
H3CO
N
N
NH2
NH2
O
O
6
20
35
8547
NO2
O2N
H3CO
H3CO
3f
O
N
N
NH2
NH2
NH2
7
9048
O
3g
N
N
O
8
25
40
9148
CH3
3h
O
H3C
O2N
NH2
N
N
NH2
NH2
O
9
8848
O
NO2
3i
NH2
NH2
N
N
O
10
10
9049
O
3j
Me
Me
Me
Me
NH2
NH2
N
O
11
15
9219
O
N
3k
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J. Chil. Chem. Soc., 60, Nº 1 (2015)
Optimization of the reaction conditions
ACKNOWLEDGEMENTS
Nano SbCl5.SiO2 with different loading of SbCl were used and it was
observed that as SbCl loading are increased from 105to 62% w/w, the yield
of quinoxalines also a5re increased. However, on further increasing the SbCl5
loading to 70 and 100 % w/w the yields are decreased with the formation of
side products. Thus 62% w/w of nano SbCl5.SiO2 was used as the preferred
catalyst for further studies (Table 2).
The authors are grateful to University of Kashan for supporting this work
by Grant No(159189- 19).
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SbCl5.SiO2
Number
Solvent
CH2C12
MeOH
EtOH
Time (min)
Yield (%)b
1
2
15
20
15
30
30
15
12
60
60
08
95
92
90
91
94
89
96
93
85
99
3
4
Et2O
5
THF
6
DMF
7
CH3CN
PhCH3
EtOAc
Solventless
8
9
10
aReaction conditions: 1,2-diketone (1 mmol), 1,2-phenylenediamine
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