Facile synthesis of 1-naphthol azo dyes with nano Sio2/Hio4 under solvent-free conditions

Article abstract of DOI:10.4314/bcse.v27i3.13

Nano-silica supported periodic acid (nano-SPIA) has been utilized as a heterogeneous reagent for a highly efficient and one pot synthesis of azo dyes based on 1-naphthol under solvent-free conditions at room temperature. This method has some advantages, the reaction workup is very easy and the catalyst can be easily separated from the reaction mixture and one-pot procedure. The related products have been obtained in good to excellent yields, high purity and short reaction times. The structures of the products have been characterized by several techniques using UV-Vis, FT-IR, 1H NMR, 13C NMR and mass spectra.

Full text of DOI:10.4314/bcse.v27i3.13

Bull. Chem. Soc. Ethiop. 2013, 27(3), 439-445.
Printed in Ethiopia
DOI: http://dx.doi.org/10.4314/bcse.v27i3.13
ISSN 1011-3924
 2013 Chemical Society of Ethiopia
FACILE SYNTHESIS OF 1-NAPHTHOL AZO DYES WITH NANO SiO2/HIO4 UNDER
SOLVENT-FREE CONDITIONS
Abdolhamid Bamoniri1*, Ali Reza Pourali2 and S. Mohamad Reza Nazifi2*
1Departement of Organic Chemistry, Faculty of Chemistry, University of Kashan, Kashan, Iran
2School of Chemistry, Damghan University, Damghan, Iran
(Received January 17, 2013; revised May 13, 2013)
ABSTRACT. Nano-silica supported periodic acid (nano-SPIA) has been utilized as a heterogeneous reagent for
a highly efficient and one pot synthesis of azo dyes based on 1-naphthol under solvent-free conditions at room
temperature. This method has some advantages, the reaction workup is very easy and the catalyst can be easily
separated from the reaction mixture and one-pot procedure. The related products have been obtained in good to
excellent yields, high purity and short reaction times. The structures of the products have been characterized by
several techniques using UV-Vis, FT-IR, 1H NMR, 13C NMR and mass spectra.
KEY WORDS: Diazotization, Nano silica, Azo dyes, Solvent-free, Periodic acid
INTRODUCTION
In recent decades, organic color chemistry is undergoing very exciting development as a result
of the opportunities presented by dye applications in high technology fields: electronic devices,
linear and non linear optics, reprography, sensors and biomedical uses [1-4]. The acid-base
catalyzed processes are effective for the near quantitative formation of desired products. But its
main limitation is their environmental incompatibility, so nowadays the prohibition of the
environmental pollution is main issue in global of the world [5]. Aromatic diazonium salts are
important building blocks in the preparation of azo dyes which were synthesized via
diazotization of aryl amines using nitrous acid. Sodium or potassium nitrites are used as nitrous
acid sources because of the instability of free nitrous acid. Organic nitrite esters, such as t-butyl
nitrite and ethyl nitrite have been used as alternative sources of nitrous acid in organic solvents
[6, 7]. Recently HIO4/Al2O3 has been reported by Khalilzadeh as a new system for iodination of
activated aromatics and 1,3-dicarbonyl compounds [8]. There are a few reports for synthesis of
stable diazonium salts at room temperature by using supported reagents [9, 10]. The solvent-free
approach opens up numerous possibilities for conducting selective organic functional group
transformations more efficiently and expeditiously using a variety of supported reagents on
mineral oxides, inorganic substances or polymers [11]. Also azo dyes can be obtained under
solvent free condition [10, 12-14]. Synthesis of azo compounds with nanosized iron-promoted
reductive coupling of aromatic nitro compounds has been reported [15]. Here in, we wish to
report a convenient and one-pot method for diazotization and diazo coupling reactions using
nano silica supported periodic acid under solvent-free conditions at room temperature.
EXPERIMENTAL
Materials and instruments
Chemicals were purchased from Merck and Fluka chemical companies. All the products were
known and were identified by comparison of their physical and spectroscopic data with those of
authentic samples.
__________
*Corresponding author. E-mail: bamoniri@kashanu.ac.ir, mohamad_nazifi@yahoo.com

440
Abdolhamid Bamoniri et al.
IR spectra were recorded as KBr pellets on a Perkin-Elmer 781 spectrophotometer and an
1
Impact 400 Nicolet FT-IR spectrophotometer. H NMR and 13C NMR spectra were recorded on
a BrukerDRX-400 spectrometer with tetramethylsilane as internal reference. The scanning
electron microscopy (SEM) of nano particles were determined with VEGA/TESCAN scanning
electron microscope. Mass spectra were recorded on Micro Mass UKLTD spectra. The
transmission electron microscopy (TEM) was recorded whit Philips CM10-HT100KV. The X-
ray diffraction (XRD) patterns of materials were recorded by employing a Philips Xpert
MPDdiffractometer equipped with a Cu Kα anode (λ = 1.54 Å) in the 2θ range from 5 to 80◦.
Melting points obtained with a Yanagimoto micro melting point apparatus. The purity
determination of the substrates and reaction monitoring were accomplished by TLC on silica-gel
polygramSILG/UV 254 plates (Merck Company).
Preparation of nano silica supported periodic acid
10 mL of 70% aqueous solution HIO4 was added to 1 g of nano silica gel and stirred for 30 min.
°
After filtration from unreacted periodic acid, it was heated at 50 C for 1 h under vacuum to
afford nano-SPIA as a free flowing powder.
Typical procedure
A mixture of aniline (1 mmol, 0.093 g), nano-SPIA (0.05 g) and sodium nitrite (2 mmol, 0.138
g) were ground in a mortar for 10 min to obtain a homogeneous mixture. Then, a few drops of
water were gradually added to this mixture and it was ground for 10 min until the gas evolution
completely finished. 1-Naphthol (1 mmol, 0.144 g) was added to the diazonium salt and it was
ground for 10 min. The reaction progress was monitored by thin layer chromatography (TLC)
using a mixture of ethyl acetate and n-hexane (1:9 v/v) as solvent. Furthermore, purification of
the product was performed by column chromatography using n-hexane and ethyl acetate.
°
°
Corresponding azo dyes were obtained in 78% yield (product A, m.p.: 136 C, lit. [16] 136 C
and product B, m.p.: 206 °C, lit. [16] 204 °C).
The selected spectral data
2-(2-(4-Nitrophenyl)diazenyl) naphth-1-ol. UV-Vis: λmax CHCl3 = 498, 295 nm; IR (KBr):
3441, 3030, 2935, 1609, 1512, 1442, 1332, 1270, 1110, 756 cm-1; 1H NMR (400 MHz, CDCl3)
δ: 16.15 (s, 1H), 8.41 (d, J = 7.6 Hz, 1 H), 8.33 (d, J = 8.8 Hz, 2H), 7.8 (d, J = 7.2 Hz, 1H), 7.7
(d, J = 8.8 Hz, 2H), 7.55 (t, J = 9.2 Hz, 1H), 7.45 (t, J = 9.2 Hz, 1H), 6.85 (d, J = 8.4 Hz, 1H),
6.71 (d, J = 8.4 Hz, 1H) ppm. 13C NMR (CDCl3, 100 MHz) δ: 168.40, 143.59, 138.86, 138.36,
133.55, 130.19, 129.79, 128.59, 128.50, 128.03, 125.32, 124.00, 121.64, 119.18 ppm.
4-(2-(4-Nitrophenyl)diazenyl) naphth-1-ol. UV-Vis: λmax CHCl3 = 490, 315 nm; IR (KBr): 3441,
3033, 1635, 1444, 1526, 1352, 1188, 1266, 756, 827 cm-1; 1H NMR (400 MHz, CDCl3) δ: 8.53
(s,1 H), 8.4 (d, J = 7.6 Hz, 1H), 8.33 (d, J = 8.41 Hz, 2H), 8.09 (d, J = 9.6 Hz, 1H), 7.77 (d, J =
8.4 Hz, 1H), 7.58 (t, J = 9.2 Hz, 1H), 7.42 (t, J = 9.2 Hz, 1H), 7 (d, J = 8.41 Hz, 2H), 6.7 (d, J =
9.6 Hz, 1H) ppm; mass spectra: 294 (M+ 1, 10), 293 (M+, 48), 263 (12), 171 (10), 143 (92), 115
+
(61), 92 (17), 76 (9), 65 (12) m/z.
2-(2-(4-Chlorophenyl)diazenyl) naphth-1-ol. IR (KBr) cm-1: 3438, 3032, 1626, 1491, 1448,
1209, 1254, 1096, 822, 749 cm-1; 1H NMR (400 MHz, CDCl3) δ: 16.11 (s,1 H), 8.32 (d, J = 8.0
Hz, 1H) 7.77 (d, J = 8.8 Hz, 2H), 7.62 (d, J = 8.0 Hz, 1H), 7.38 (d, J = 8.8 Hz, 2H), 7.31-7.25
(m, 2H), 7.04-6.83 (dd, J = 9.6 Hz, 2H) ppm; 13C NMR (CDCl3, 100 MHz) δ: 172.29, 145.75,
Bull. Chem. Soc. Ethiop. 2013, 27(3)

Synthesis of 1-naphthol azo dyes with nano SiO2/HIO4 under solvent-free conditions
441
142.19, 131.69, 130.21, 127.63, 125.56, 124.75, 124.19, 123.62, 122.59, 120.73, 119.15,
116.53 ppm.
4-(2-(4-Chlorophenyl)diazenyl) naphth-1-ol. IR (KBr): 3438, 3032, 1618, 1491, 1448, 1209,
1
1254, 1096, 822, 749 cm-1; H NMR (400 MHz, CDCl3) δ: 8.83 (s, 1H), 8.32 (d, J = 8.0 Hz,
1H), 8.22 (d, J = 8.8 Hz, 1H), 7.77 (d, J = 8.8 Hz, 2H), 7.62 (d, J = 8.0 Hz, 1H), 7.38 (d, J = 8.8
Hz, 2H), 7.31-7.25 (m, 2H), 6.57 (d, J = 8.8 Hz, 1H) ppm. 13C NMR (CDCl3, 100 MHz) δ:
170.59, 144.33, 140.10, 133.39, 133.01, 129.76, 128.94, 128.69, 128.19, 125.89, 124.33,
121.75, 119.93.
4-(2-Phenyl)diazenyl) naphth-1-ol. IR (KBr): 3441, 3033, 1635, 1444, 1526, 1352, 1188, 1266,
756, 827 cm-1. 1H NMR (400 MHz, CDCl3) δ: 15.69 (s, NH), 8.18 (d, J = 7.6 Hz, 1H), 8.11 (d, J
= 9.2 Hz, 2H), 7.50 (m, 1H), 7.48 (t, J = 7.6 Hz, 1H). 7.43 (d, J = 9.2 Hz, 2H), 7.32 (t, J = 7.6
Hz, 1H), 6.89 (d, J = 9.6 Hz, 1H), 6.82 (d, J = 9.6 Hz, 1H) ppm. 13C NMR (100 MHz, CDCl3) δ:
161.33, 160.67, 141.84, 136.71, 133.31, 129.53, 128.33, 128.15, 124.80, 122.19, 122.06,
121.61, 114.78, 55.64 ppm. Mass spectra: 249 (M++1, 22), 248 (M+, 95), 171 (25), 144 (14),
145 (88), 115 (59), 77 (31), 51 (10) m/z.
RESULTS AND DISCUSION
In continuation of our previous studies on the application of supported reagents in organic
syntheses [17-30], we studied the conversion of primary aromatic amines to the corresponding
azo dyes by using nano silica supported periodic acid as a acidic source for diazotization and
diazo coupling with sodium nitrite under solvent-free conditions at room temperature (Scheme
1).
+ N2 IO4
-
OH
OH
Ar
1-naphthol
N N
Nano SiO2-HIO4
Ar-NH2
NaNO2
Room temperature
Solvent free
Room temperature
Solvent free
+
Stable
N
N
A
B
Ar
Scheme 1. General preparation procedure of azo dyes.
At first, we prepared nano-SPIA by reacting nano silica gel with a 70% aqueous solution of
HIO4. According to the SEM and TEM images and XRD pattern, the particle size of nano-SPIA
is presented 35 nm (Figure 1).
c
b
Figure 1. The SEM (a) and TEM (b) images and XRD (c) pattern of nano-SPIA.
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Abdolhamid Bamoniri et al.
Then mixture of p-nitro aniline (1 mmol) and sodium nitrite (1 mmol) in the presence of
various amounts of nano-SPIA were ground, we have obtained the related diazonium salt in
excellent yield using 0.05 g of nano-SPIA (Table 1).
Table 1. Preparation of phenyl diazonium periodate. In the presence of various amount of nano-SPIAa.
Ent.
1
Time (min)
Catalyst (g)
0.03
Yield (%)
45
40
35
30
30
47
59
78
89
89
2
0.04
3
0.045
0.05
4
5
0.06
a p-nitroaniline (1 mmol) and sodium nitrite (2 mmol) were used.
After preparation of diazonium salt, 1-naphthol (1mmol) was added to them and stirred for
10 min. The whole process of diazotization was performed in 30 minutes. The crude product
was extracted with dichloromethane. Then the solvent was evaporated by rotary evaporator at
reduced pressure and the crude product was purified by flash column chromatography. By this
procedure, 2-(2-(4-nitrophenyl)diazenyl) naphth-1-ol as product A and 4-(2-(4-nitrophenyl)
diazenyl) naphth-1-ol as product B were obtained with 89% isolated yield. We used the same
conditions for the conversion of other aromatic amines to the related azo dyes and we obtained
the products in good to excellent yields (Table 2).
Table 2. Diazotization and diazo coupling reactions of some amines with 1-naphthol at room temperature.
M.p. (°C )
Reported [16]
Time
(min)
Entry
Amines
Yield (%)a
Yield (%)b
Found
A:136
B:206
A:160
B:178
A:154
B:176
A:174
B:286
A:182
B:293
A:158
B:194
A:189
B:265
A:165
B:245
A:178
B:289
A:136
B:204
A:162
B: 176
A:153
B:178
A:175
B:284
A:183
B:295
A:159
B:194
A:188
B:269
A:168
B:249
A:180
B:285
1
2
3
4
5
6
7
8
9
C6H5NH2
78
81
82
80
89
78
75
85
77
78
81
76
76
89
73
67
80
70
30
25
27
23
30
27
26
30
28
p-ClC6H4NH2
o-ClC6H4NH2
o-NO2C6H4NH2
p-NO2C6H4NH2
p-MeOC6H4NH2
p-BrC6H4NH2
o-MeC6H4NH2
p-MeC6H4NH2
a,bThe ratio of amine (mmol), NaNO2 (mmol), 1-naphthol (mmol) and nano-SPIA (g) was 1:2:1:0.05.
1
In H NMR spectrum of 2-(2-(4-nitrophenyl)diazenyl) naphth-1-ol, the (NH/OH) signal
around 16 ppm is deshielded more than those of other signals, due to bifurcated intramolecular
hydrogen bonds which are examples of hydrogen bonds involving one proton and two
1
acceptors. Also the H NMR spectra of product B, the singlet peak around δ = 8.5 ppm may be
attributed to bifurcated NH/N proton in azo-hydrazon forms.
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Synthesis of 1-naphthol azo dyes with nano SiO2/HIO4 under solvent-free conditions
443
The reusability of nano-SPIA was investigated for several times which indicated no
significant decrease in catalytic activity (Table 3).
Table 3. The reusability of catalyst
Reaction cycles
Yields (%)
1
2
3
4
5
89
89
78
59
47
To determining the stability of the diazonium salts, some aryl diazoniumnano-silica
periodates were stored in a desiccator at room temperature. After the specified times, 2-naphthol
was added to each salt and the reaction mixture was ground at room temperature for 10 min.
The products were extracted and the yields of azo dyes compared with the product provided
with the corresponding fresh diazonium salts (Table 4). Aryl diazoniumnano-silica periodate
with electron-withdrawing groups on aromatic ring are more stable than those with electron
donating groups because of the instability of the resulting aryl cation (Table 4). Also, we have
compared the stability of diazonium silica periodates versus diazonium nano-silica periodates
and found that the diazonium silica periodates have less stability (Table 5).
Table 4. The stability study of some aryl diazoniumnano silica periodate at room temperaturea.
Yield (%) after
Diazonium salt
N2+ IO4
Product
2a
30 min 1 day 2 days 3 days 4 days 5 days 6 days
-
91
90
93
96
88
85
90
93
85
80
86
90
80
76
81
85
75
61
77
79
52
50
70
73
35
30
65
69
-
-
N2+ IO4
2b
MeO
Cl
-
N2+ IO4
N2+ IO4
2c
O2N
2d
aThe yields refer to the isolated pure products after adding 2-naphthol into their corresponding diazonium salts
within the specified time.
Table 5. The stability study of some aryl diazonium silica periodate at room temperature.
Yield (%) after
Diazonium salt
Product
30 min 1 day
2 days
3 days 4 days 5 days 6 days
-
N2+ IO4
2a
2b
2c
85
80
83
73
75
78
50
43
32
70
25
22
48
20
-
-
-
-
-
MeO
Cl
N2+ IO4
43
74
-
N2+ IO4
37
24
O2N
N2+ IO4
2d
89
80
73
69
51
30
25
aThe yields refer to the isolated pure products after adding 2-naphthol into their corresponding diazonium salts
within the specified times.
CONCLUSION
Various aromatic amines including electron-withdrawing and electron-donating groups were
rapidly and efficiently converted to the related azo dyes under solvent-free conditions at room
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Abdolhamid Bamoniri et al.
temperature. Especially nano-SPIA proved to be a suitable catalyst affording the highest
stability of diazonium salts and yields. One reason for this behavior may be related to the
number of available active sites which in turn increases the catalytic activity. The solvent free
conditions employed in the present method, which make it environmentally friendly and make it
useful for industrial applications. Furthermore, it has other advantages such as mildness, low
cost, the reusability of catalyst, ease handling, short reaction times and simple experimental
procedure.
ACKNOWLEDGEMENT
The authors are grateful to Damghan University and the University of Kashan, Iran, for
supporting this work by Grant No (159189/25).
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