Synthesis of a nitrite functionalized star-like poly ionic compound as a highly efficient nitrosonium source and catalyst for the diazotization of anilines and subsequent facile synthesis of azo dyes under solvent-free conditions

Article abstract of DOI:10.1016/j.dyepig.2015.02.007

Nitrite functionalized star-like poly ionic (NFSPI) compound was synthesized and used as a highly efficient nitrosonium source and catalyst for the conversion of aniline derivatives to diazonium salts. Azo dyes were prepared via in situ azo-coupling reaction of these diazoniums with active aromatic compounds under solvent-free conditions in very short reaction time in excellent yields. NFSPI plays dual role as a three-dimensional nitrosonium source and catalyst because of its poly ionic characteristic. The isolated products were confirmed with FT-IR spectrum, ¹H-NMR, ¹³C-NMR spectroscopy and CHNSO analysis. The structure of heterogeneous reagent and catalyst was confirmed by FT-IR spectrum, SEM images, EDX and CHNSO analysis. Yields and reaction times for the synthesis of a variety of products via this procedure were compared with reported values in literature.

Full text of DOI:10.1016/j.dyepig.2015.02.007

Accepted Manuscript
Synthesis of a nitrite functionalized star-like poly ionic compound as a highly efficient
nitrosonium source and catalyst for the diazotization of anilines and subsequent facile
synthesis of azo dyes under solvent-free conditions
Hassan Valizadeh, Ashkan Shomali, Jalal Ghorbani, Saeideh Noorshargh
PII:
S0143-7208(15)00043-1
10.1016/j.dyepig.2015.02.007
DYPI 4661
DOI:
Reference:
To appear in: Dyes and Pigments
Received Date: 20 December 2014
Revised Date: 6 February 2015
Accepted Date: 9 February 2015
Please cite this article as: Valizadeh H, Shomali A, Ghorbani J, Noorshargh S, Synthesis of a nitrite
functionalized star-like poly ionic compound as a highly efficient nitrosonium source and catalyst for the
diazotization of anilines and subsequent facile synthesis of azo dyes under solvent-free conditions, Dyes
and Pigments (2015), doi: 10.1016/j.dyepig.2015.02.007.
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ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
Synthesis of a nitrite functionalized star-like poly ionic compound as a highly
efficient nitrosonium source and catalyst for the diazotization of anilines and
subsequent facile synthesis of azo dyes under solvent-free conditions
Hassan Valizadeh , Ashkan Shomali, Jalal Ghorbani, Saeideh Noorshargh
Department of Chemistry, Faculty of Sciences, Azarbaijan Shahid Madani University, Tabriz, Iran.
Corresponding author: Tel: +98-41-33856447, Fax: +98-41-34327541; P.O. Box 53714-161; E-mail address:
hvalizadeh2@yahoo.com
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ACCEPTED MANUSCRIPT
Abstract
Nitrite functionalized star-like poly ionic (NFSPI) compound was synthesized and used as a
highly efficient nitrosonium source and catalyst for the conversion of aniline derivatives to
diazonium salts. Azo dyes were prepared via in situ azo-coupling reaction of these diazoniums
with active aromatic compounds under solvent-free conditions in very short reaction time in
excellent yields. NFSPI plays dual role as a three-dimensional nitrosonium source and catalyst
because of its poly ionic characteristic. The isolated products were confirmed with FT-IR
spectrum, 1H-NMR, 13C-NMR spectroscopy and CHNSO analysis. The structure of
heterogeneous reagent and catalyst was confirmed by FT-IR spectrum, SEM images, EDX and
CHNSO analysis. Yields and reaction times for the synthesis of a variety of products via this
procedure were compared with reported values in literature.
Keyword: Azo dyes; diazonium salts; heterogeneous catalyst; nitrite functionalized poly ionic,
solvent-free; star-like.
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1. Introduction
Aromatic azo compounds are very important chemical materials because of their widely
applications in industry as dyes and pigments [1], therapeutic agents [2] and drug deliveries [3].
Diazonium salts have been frequently used for the preparation of synthetic azo dyes [4]. Many
reports have been published for diazotization and also for azo-coupling reactions in literature [5-
7]. However, many of these reported methods suffer from one or more practical drawbacks
associated with hazardous reagents, long reaction times, less effective catalysts, formation of
side products and difficult and time consumed work-up procedure. To eliminate of some of these
explained limitations, in the present research we utilize a poly ionic heterogonous nitrosonium
source which plays the dual role as reagent and catalyst. The easy work-up procedure, very short
reaction times and also high yields of the products were achieved by using of this reagent.
Having the unique behavior of organic-inorganic composites, there are a lot of interests in
developing of the synthesis and applications of new structures of these compounds [8]. Recently,
a lot of attentions have been paid to the construction of three-dimensional molecules such as star-
like polymers due to their importance in drug-delivery [9], catalysis [10], etc. Liu et al. have
been reported the preparation of a three-dimensional star-like polymer that was prepared via
connection of linear polymers to a central reactive core [11]. The most of reported star-like
polymers are on the base of organic materials which are unstable, toxic, and non-ionic
compounds [12]. According to the some interesting characteristics of ionic liquids, synthesis of
three-dimensional star-like compounds based on ionic liquids could play an important role in
synthetic organic chemistry. In continuation of our work on the using of nitrite ionic liquid
immobilized on silica for the diazotization of aniline derivatives [13], herein we introduced a
new rapid and efficient method for this reaction and subsequent synthesis of azo dyes. In this
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study, NFSPI compound was used as a new nitrosonium source and catalyst for the efficient
diazotization of aniline derivatives and synthesis of azo dyes under solvent free conditions
(Scheme 1).
<<Scheme 1>>
2. Experimental
2.1. Materials and instrumentation
All reagents purchased from Merck Company and used without further purification. Infrared
1
spectra were recorded in KBr and determined on a Perkin Elmer FT-IR spectrometer. HNMR
and 13CNMR spectra were recorded on a Bruker Avance AC-400 MHz using DMSO-d6 or
CDCl3 as the deuterated solvent and TMS as internal standard. All melting point measured in
open glass-capillaries using a Stuart melting point apparatus. The morphology of the catalyst was
studied by field emission scanning electron microscopy using FESEM; Hitachi, model S-4160.
Structure of catalyst was confirmed by energy–dispersive X-ray analysis using EDX; Tescan;
model MIRA3FEG-SEM and elemental analysis was determined by CHNSO; Euro EA; model
EA3000.
2.2. Synthesis of silica nanoparticles
Ammonia solution 25% (750 µL, 10 mmol) and water (1.98 mL) were poured in a 250 mL round
bottom flask containing absolute methanol (100 mL). While stirring of the solution,
tetraethoxysilane, TEOS (11 ml, 50 mmol) was added slowly. The solution was stirred for three
days at ambient temperature. The silica nano particles was isolated and confirmed by scanning
electron microscopy image. FT-IR (KBr, cm-1): 3456 (Si-OH), 1639 (O-H), 1097 and 803 (Si-O).
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2.3. Synthesis of star-like poly ionic compound 8:
N,N,N',N'-Tetramethylethylenediamine (11 mmol) was added to a round bottom flask containing
acetonitrile (10 mL). While stirring, (3-chloropropyl)trimethoxysilane (10 mmol) was poured
into the solution dropwise. Then, the solution was stirred for three days at 80ºC to produce ionic
liquid 6. The unreacted materials were washed by acetonitrile. The resulted ionic liquid 6 and
silica nanoparticles were refluxed in acetonitrile for three days at 60ºC. The acetonitrile was
removed under reduced pressure at 40ºC to produce crude product 7. Isolated yield was 90%. FT-
IR (KBr, cm-1): 3451 (Si-OH), 2956 (C-H), 1637, 1486 (C-H), 1090 (SiO-H), 800 (Si-O). EDX:
Calcd. (%w): N/C= 0.259; Found (%): C, 16.93; N, 4.37; H, 3.92; %w N/C= 0.258. CHNSO:
Calcd. (%w): N/C= 0.259; Found (%): C, 16.93; N, 4.37; H, 3.92; N/C= 0.258. Then, 1,4-
dichlorobutane (10 mmol) and product 7 were added to acetonitrile (15 mL) and mixed
thoroughly. The mixture was refluxed at 80ºC for three days. Then the mixture was poured in
acetonitrile and stirred thoroughly and unreacted regents were removed by centrifuging. After
this, the product was reacted with diamine and then with 1,4-dichlorobutane under the above
described conditions to produce the product 8. The morphology and structure of the product was
confirmed and identified by scanning electron microscopy FE-SEM, FT-IR spectroscopy, EDX,
and CHNSO analysis. FT-IR (KBr, cm-1): 3442 (Si-OH), 2958 (C-H), 1638, 1486 (C-H), 1093
(SiO-H), 800 (Si-O). EDX: Calcd. (%w): N/C= 0.246. CHNSO: Calcd. N/C (%w) = 0.241;
Found (%): C, 17.76; N, 4.37; H, 4.24, N/C= 0.246
2.4. Synthesis of hydroxyl functionalized star-like poly ionic compound 9:
4-Chlorobutanol (10 mmol) was added into a solution of compound 8 in acetonitrile while
stirring and the mixture was refluxed for three days at 80ºC. Hydroxyl functionalized star–like
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poly ionic product 9 was isolated as the same work-up procedure which described for the
compound 8. The structure of product was confirmed by comparison of FT-IR spectroscopy of
compounds 8 and 9 (Figure 2, B). FT-IR (KBr, cm-1): 3420 (O-H), 2958 (C-H), 1636 (O-H),
1482 (C-H), 1402 (bending O-H), 1087 (Si-O), 951 (Si-OH), 801 (Si-O).
2.5. Synthesis of NFSPI compound 10:
Freshly prepared compound 9 (10 g) was added to an aqueous solution of sodium nitrite (15 ml).
HCl (37%, 3 mL) was added slowly to the mixture while stirring at 0-5ºC. The mixture was
filtered off and washed with cold water (20 mL) and the crude product 10 was dried under
vacuum at room temperature. Functional group conversion was confirmed by comparison of the
FT-IR spectra of compounds 9 and 10 (Figure 2, B). FT-IR (KBr, cm-1): 3440 (SiO-H), 2958 (C-
H), 1637 (O-H), 1483 (C-H), 1384 (N=O), 1090 (Si-O), 952 (Si-OH), 801 (Si-O).
2.6. General procedure for the synthesis of azo dyes 3a-t
Aniline derivative was added to a vessel containing HCl 37% (0.5 ml) and the mixture was
º
stirred in ice bath at 0-5 C. Then, NFSPI 10 was added to the mixture and grinded at room
temperature for the times shown in Table 2 to produce the related diazonium salt. The phenolate
compound was added slowly to the mixture to produce the desired azo dye at 0-5ºC. After
completion of the reaction, ethyl acetate was added to the reaction mixture and stirred
thoroughly. Then, poly ionic compound 9 was filtered off and the crude azo dye was isolated by
evaporation of ethyl acetate. For more purification, crude product was recrystallized from
ethanol/H2O. The products were characterized by their FT-IR, 1H-NMR and 13C-NMR spectra.
2.7. Spectroscopic and analytical data
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2.7.1. 4-(3-Nitrophenylazo) phenol (3a)
C12H9N3O3 [14]: FT-IR (KBr, cm-1): 3416, 1623, 1591, 1338, 730. 1H NMR (400 MHz, DMSO-
d6) δ (ppm): 8.78 (s, 1H); 8.36 (1H, d, J = 5.2 Hz); 8.20 (1H, d, J = 5.4 Hz); 7.92 (1H, m), 7.84
(2H. d, J = 8.1 Hz); 7.01 (2H, d, J = 8.1 Hz); 5.34 (1H, s-br); 13C NMR (100 MHz, DMSO-d6) δ
(ppm): 154.0, 152.5, 149.5, 129.2, 128.8, 128.3, 128.0, 124.3, 124.0, 123.1, 122.7. Anal. Calc.
for C12H9N3O3: C, 59.26; H, 3.70; N, 17.28%. Found: C, 59.27; H, 3.72; N, 17.25%.
2.7.2. 4-(4-Bromophenylazo) phenol (3b)
1
C12H9N2BrO [14]: FT-IR (KBr, cm-1): 3399, 1627, 713, 533. H NMR (400 MHz, DMSO-d6) δ
(ppm): 7.80 (1H, d, J = 8.1 Hz); 7.74 (2H, m); 7.66 (2H, m); 7.57 (1H, m); 7.39 (1H, m); 6.95
(1H, m); 13C NMR (100 MHz, DMSO-d6) δ (ppm): 153.3, 151.5, 133.3, 132.5, 132.1, 130.7,
127.3, 124.0, 123.1, 122.7, 122.1, 115.7. Anal. Calc. for C12H9N2BrO: C, 51.98; H, 3.25; N,
10.11%. Found: C, 51.96; H, 3.29; N, 10.10%.
2.7.3. 4-(4-Chlorophenylazo) phenol (3c)
1
C12H9N2ClO [14]: FT-IR (KBr, cm-1): 3400, 1556, 839, 719. H NMR (400 MHz, DMSO-d6) δ
(ppm): 8.01 (1H, d, J = 4.3 Hz); 7.81(2H, m); 7.73 (1H, d, J = 8.2 Hz); 7.60 (1H, d, J = 8.2 Hz);
13
7.54 (2H, m); 6.96 (1H, d, J = 8.2 Hz); C NMR (100 MHz, DMSO-d6) δ (ppm): 153.6, 153.1,
133.2, 133.1, 132.7, 131.5, 127.0, 125.8, 124.9, 123.2, 123.7, 116.4. Anal. Calc. for
C12H9N2ClO: C, 61.93; H, 3.87; N, 12.04%. Found: C, 61.99; H, 3.80; N, 12.09%.
2.7.4. 4-Phenylazophenol (3d)
1
C12H10N2O [14]: FT-IR (KBr, cm-1): 3190, 1579, 720. H NMR (400 MHz, DMSO-d6) δ (ppm):
8.26-8.21 (2H, d, J = 10.4 Hz); 7.83 (2H, d, J = 8.1 Hz); 7.66 (2H, t, J = 10.4 Hz); 7.28 (1H, t, J
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13
= 10.4 Hz); 7.01 (2H, d, J = 8.1 Hz); 5.31 (1H, s-br); C NMR (100 MHz, DMSO-d6) δ (ppm):
161.3, 152.8, 146.3, 131.8, 129.1, 125.5, 124.7, 122.0, 116.4, 116.1. Anal. Calc. for C12H10N2O:
C, 72.73; H, 5.05; N, 14.14%. Found: C, 72.68; H, 5.11; N, 14.12%.
2.7.5. 4-((3-Bromo-4-methyl)phenylazo) phenol (3e)
1
C12H11N2BrO [14]: FT-IR (KBr, cm-1): 3298, 1579, 721, 572. H NMR (400 MHz, DMSO-d6) δ
(ppm): 7.82 (2H, d, J = 8.2 Hz); 7.73 (1H, s); 7.53(1H, d, J = 8.2 Hz); 7.30 (1H, d, J = 8.2 Hz);
7.04 (2H, dd, J1 = 4.1 Hz, J2 = 12.4 Hz); 2.37 (3H, s); 13C NMR (100 MHz, DMSO-d6) δ (ppm):
146.3, 145.8, 143.2, 131.5, 128.2, 124.2, 125.2, 124.1, 118.1, 116.8, 115.3, 21.9. Anal. Calc. for
C12H11N2BrO: C, 53.61; H, 3.78; N, 9.62%. Found: C, 53.67; H, 3.81; N, 9.66%.
2.7.6. 4-(4-Nitrophenylazo) resorcinol (3f)
C12H9N3O4 [5]: FT-IR (KBr, cm-1): 3440 (bs), 3366, 1619, 1610. 1H NMR (400 MHz, CDCl3) δ
(ppm): 12.23 (OH, s); 8.83 (OH, s); 7.75 (2H, d, J = 8.19 Hz); 7.83 (2H, d, J = 8.19 Hz); 7.74
(1H, d, J = 8.12 Hz); 6.62 (1H, dd, J = 8.12 and 2.48 Hz); 6.32 (1H, d, J = 2.48 Hz,); 13C NMR
(100 MHz, CDCl3) δ (ppm): 156.22, 148.73, 148.12, 145.16, 131.41, 128.35, 127.38, 121.31,
111.69, 104.18. Anal. Calc. for C12H9N3O4: C, 55.59; H, 3.47; N, 16.21%. Found: C, 55.62; H,
3.51; N, 16.28%.
2.7.7. 2-Nitro-4-(4-chlorophenylazo) phenol (3g)
C12H8N3ClO3 [15]: FT-IR (KBr, cm-1): 3432, 1623, 1510, 1120. 1H NMR (400 MHz, DMSO-d6)
δ (ppm): 12.67 (OH, s); 8.33 (1H, s); 7.71 (2H, d, J = 8.3 Hz); 7.43 (4H, m); 13C NMR (100
MHz, DMSO-d6) δ (ppm): 168.21, 150.47, 138.53, 137.71, 132.71, 128.40, 128.04, 124.55,
122.43, 115.47. Anal. Calc. for C12H8N3ClO3: C, 51.89; H, 2.88; N, 15.13%. Found: C, 51.92; H,
2.79; N, 15.19%.
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2.7.8. 2-Nitro-4-(4-methylphenylazo) phenol (3h)
1
C13H11N3O3 [15]: FT-IR (KBr, cm-1): 3459, 2970, 1629, 1480, 1133. H NMR (400 MHz,
13
DMSO-d6) δ (ppm): 8.40-6.7 (7H, m); 2.17 (3H, s); C NMR (100 MHz, DMSO-d6) δ (ppm):
143.15, 132.27, 130.81, 130.41, 130.23, 130.03, 128.76, 128.34, 124.66, 121.80, 120.86, 120.28,
116.67. Anal. Calc. for C13H11N3O3: C, 60.70; H, 4.28; N, 16.34%. Found: C, 60.68; H, 4.31; N,
16.28%.
2.7.9. 1-(4-Methylphenylazo)-2-naphthol (3i)
1
C17H14N2O [15]: FT-IR (KBr, cm-1): 3419, 2940, 1627, 1489, 1344. H NMR (400 MHz,
DMSO-d6) δ (ppm): 15.29 (1H, s); 8.39 (1H, d, J = 8.2 Hz); 7.91 (1H, d, J = 9.1 Hz); 7.80 (3H,
m); 7.66 (1H, t, J = 8.2 Hz); 7.32 (1H, t, J = 7.2 Hz); 7.21 (2H, d, J = 8.2 Hz); 6.79 (1H, d, J =
9.1 Hz); 2.26 (3H, s); 13C NMR (100 MHz, CDCl3) δ (ppm): 164.1, 144.51, 140.21, 139.19,
130.46, 129.71, 128.23, 126.72, 126.36, 123.33, 122.61, 121.19, 20.32. Anal. Calc. for
C17H14N2O: C, 77.86; H, 5.34; N, 10.69%. Found: C, 77.83; H, 5.38; N, 10.71%.
2.7.10. 1-(4-Bromophenylazo)-2-naphthol (3j)
1
C16H11N2BrO [14]: FT-IR (KBr, cm-1): 3415, 1611, 729, 522. H NMR (400 MHz, DMSO-d6) δ
(ppm): 8.55 (1H, d, J = 8.2 Hz); 8.11 (1H, d, J = 1.6 Hz); 7.96 (1H, d, J = 9.4 Hz); 7.80 (2H, d, J
= 8.2 Hz); 7.62 (2H, t, J = 8.2 Hz); 7.51 (1H, d, J = 10.1 Hz); 7.45 (1H, d, J = 10.1 Hz); 6.965
(1H, d, J = 9.4 Hz); 13C NMR (100 MHz, CDCl3) δ (ppm): 148.6, 148.1, 147.6, 138.2, 135.2,
132.7, 132.5, 130.9, 130.3, 130.1, 129.4, 129.1, 128.8, 127.7, 126.1, 125.9. Anal. Calc. for
C16H11N2BrO: C, 58.71; H, 3.36; N, 8.56%. Found: C, 58.73; H, 3.39; N, 8.51%.
2.7.11. 1-(3-Nitrophenylazo)-2-naphthol (3k)
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C16H11N3O3 [14]: FT-IR (KBr, cm-1): 3378, 1624, 1512, 1332, 718. 1H NMR (400 MHz, DMSO-
d6) δ (ppm): 8.53 (1H, s); 8.51 (1H, d, J = 8.3 Hz); 8.21 (1H, d, J = 8.3 Hz); 8.03 (2H, d, J = 8.3
Hz); 7.86 (1H, t, J = 9.8 Hz); 7.71 (2H, t, J = 8.3 Hz); 7.64 (1H, d, J = 8.3 Hz); 7.50 (1H, t, J =
7.5 Hz); 7.21 (1H, t, J = 7.4 Hz); 6.75 (1H, d, J = 8.3 Hz); 13C NMR (100 MHz, CDCl3) δ: 134.6,
130.3, 130.2, 129.9, 128.4, 128.4, 128.1, 127.7, 126.4, 125.9, 123.9, 123.5, 121.5, 121.3, 119.3,
118.7. Anal. Calc. for C16H11N3O3: C, 65.53; H, 3.75; N, 14.33%. Found: C, 65.57; H, 3.79; N,
14.39%.
2.7.12. 1-(4-Nitrophenylazo)-2-naphthol (3l)
1
C16H11N3O3 [5]: FT-IR (KBr, cm-1): 3411 (bs), 1650, 1613. H NMR (400 MHz, CDCl3) δ
(ppm): 12.16 (OH, s), 8.58 (1H, dd, J = 8.13 and 2.03 Hz); 7.85 (2H, d, J = 7.88 Hz); 7.68 (2H,
d, J = 7.88); 7.51 (1H, d, J = 7.28 Hz); 7.49 (1H, d, J = 7.28 Hz); 7.45 (1H, dd, J = 7.95 and 2.02
Hz); 7.43 (1H, dt, J = 7.65 and 1.99 Hz); 7.42 (1H, dt, J = 7.75 and 1.97 Hz); 13C NMR (100
MHz, CDCl3) δ (ppm): 143.33, 137.30, 134.15, 131.15, 128.47, 127.87, 124.12, 121.33, 120.13,
119.35, 119.23, 117.14, 115.71, 111.18. Anal. Calc. for C16H11N3O3: C, 65.53; H, 3.75; N,
14.33%. Found: C, 65.54; H, 3.72; N, 14.41%.
2.7.13. 1-(4-Chlorophenylazo)-2-naphthol (3m)
C16H11N2ClO [14]: FT-IR (KBr, cm-1): 3330, 1628, 829, 720. 1H NMR (400 MHz, DMSO-d6) δ
(ppm): 8.54 (1H, d, J = 8.1 Hz); 8.15 (1H, d, J = 12.0 Hz); 7.94 (1H, d, J = 9.4 Hz); 7.84 (2H, d,
J = 8.1 Hz); 7.62 (2H, t, J = 8.1 Hz); 7.50 (1H, d, J = 10.0 Hz); 7.43 (1H, d, J = 10.0 Hz); 6.95
(1H, d, J = 9.4 Hz); 13C NMR (100 MHz, CDCl3) δ (ppm): 149.7, 148.2, 147.6, 138.5, 134.1,
132.4, 132.1, 130.6, 130.4, 130.1, 128.4, 128.2, 127.7, 127.5, 126.1, 124.3. Anal. Calc. for
C16H11N2ClO: C, 67.96; H, 3.89; N, 9.91%. Found: C, 67.99; H, 3.92; N, 9.95%.
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2.7.14. N,N-dimethyl-4-(phenylazo) aniline (3n)
1
C14H15N3 [15]: FT-IR (KBr, cm-1): 1618, 1524, 1518, 1460. H NMR (400 MHz, CDCl3) δ
(ppm): 77.63 (2H, d, J = 7.89 Hz); 7.36 (5H, m); 6.76 (2H, d, J = 7.89 Hz); 3.58 (6H, s); 13C
NMR (100 MHz, CDCl3) δ (ppm): 134.52, 128.73, 126.43, 125.45, 123.31, 120.27, 117.46,
114.41, 35.52. Anal. Calc. for C14H15N3: C, 74.66; H, 6.67; N, 18.67%. Found: C, 74.65; H,
6.69; N, 18.64%.
2.7.15. N,N-dimethyl-4-(4-nitrophenylazo) aniline (3o)
1
C14H14N4O2 [16]: FT-IR (KBr, cm-1): 1617, 1511, 1469, 1546, 1332. H NMR (400 MHz,
CDCl3) δ (ppm): 7.73 (2H, d, J = 8.12 Hz); 7.70 (2H, d, J = 8.12); 7.66 (2H, d, J = 7.96 Hz);
13
6.69 (2H, d, J = 7.96 Hz); 3.51 (6H, s); C NMR (100 MHz, CDCl3) δ (ppm): 156.43, 135.58,
128.43, 126.59, 125.34, 122.43, 121.17, 117.84, 116.21, 34.32. Anal. Calc. for C14H14N4O2: C,
62.22; H, 5.18; N, 20.74%. Found: C, 62.27; H, 5.21; N, 20.71%.
2.7.16. N,N-dimethyl-4-(2-chloro-4-nitrophenylazo) aniline (3p)
C14H13N4ClO2 [16]: FT-IR (KBr, cm-1): 1631, 1520, 1471, 1539, 1329.1H NMR (400 MHz,
CDCl3) δ (ppm): 8.33 (1H, dd, J = 2.5 and 0.4 Hz); 8.14 (1H, dd, J = 9.0 and 2.4 Hz,); 7.99 (2H,
13
m); 7.79 (1H, d, J = 8.9 Hz); 6.82 (2H, m); 3.16 (6H, s); C NMR (125 MHz, CDCl3) δ (ppm):
153.1, 152.0, 147.9, 143.4, 133.0, 128.9, 126.9, 123.6, 117.1, 112.8, 41.6. Anal. Calc. for
C14H13N4ClO2: C, 55.17; H, 4.27; N, 18.39%. Found: C, 55.19; H, 4.26; N, 18.41%.
2.7.17. 3-Formyl-2-(2-carboxylicacidphenylazo)1H-indol (3q)
1
C16H11N3O3 [17]: FT-IR (KBr, cm-1): 3412, 3100, 1650, 1537, 1350; H NMR (400 MHz,
CDCl3) δ (ppm): 11.91 (1H, s); 11.15 (1H, s); 9.75 (1H, s); 8.27 (2H, d, J = 7.69 Hz); 7.91 (d, J
11

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= 7.47 Hz, 2H); 7.79 (2H, m); 7.47 (2H, m); 13C NMR (100 MHz, CDCl3) δ (ppm): 164.25,
161.13, 134.32, 131.28, 130.83, 128.47, 127.91, 125.73, 125.62, 124.49, 124.06, 123.33, 121.52,
120.21, 116.79, 115.42. Anal. Calc. for C16H11N3O3: C, 65.53; H, 3.75; N, 14.33%. Found: C,
65.51; H, 3.73; N, 14.31%.
2.7.18. 3-Formyl-2-(phenylazo)1H-indol (3r)
1
C15H11N3O [17]: FT-IR (KBr, cm-1): 1785, 1624, 1533, 1122; H NMR (400 MHz, CDCl3) δ
(ppm): 11.89 (1H, s); 9.82 (1H, s); 8.22 (1H, dd, J = 7.59 and 2.08 Hz); 7.31 (1H, dd, J = 7.43
and 2.04 Hz); 7.55 (2H, m); 7.21 (2H, m); 7.03 (3H, m); 13C NMR (100 MHz, CDCl3) δ (ppm):
162.54, 131.44, 130.72, 125.96, 124.45, 123.13, 122.64, 122.13, 121.25, 121.02, 117.42, 115.15,
112.74. Anal. Calc. for C15H11N3O: C, 72.29; H, 4.42; N, 16.87%. Found: C, 72.28; H, 4.39; N,
16.84%.
2.7.19. 2-(4-Chlorophenylazo) naphthol (3s)
1
C16H11N2ClO [18]: FT-IR (KBr, cm-1): 3418 (bs), 3012, 1629, 1471, 1428, 1218, 812, 738. H
NMR (400 MHz, CDCl3) δ (ppm): 16.42 (1H, s); 8.22 (1H, d, J = 8.2 Hz); 7.57 (2H, d, J = 8.5
Hz); 7.12 (1H, d, J = 8.2 Hz); 7.13 (2H, d, J = 8.5 Hz); 7.00 (2H, m); 6.98 (2H, dd, J = 9.6 Hz);
13C NMR (100 MHz, CDCl3) δ (ppm): 173.19, 146.45, 140.19, 131.76, 130.11, 127.43, 125.26,
124.65, 124.09, 123.52, 122.19, 120.93, 119.25, 116.53. Anal. Calc. for C16H11N2ClO: C, 67.96;
H, 3.89; N, 9.91%. Found: C, 67.97; H, 3.87; N, 9.95%.
2.7.20. 4-(4-Chlorophenylazo) naphthol (3t)
1
C16H11N2ClO: FT-IR (KBr, cm-1) [18]: 3448 (bs), 3012, 1628, 1481, 1439, 1212, 812, 733. H
NMR (400 MHz, CDCl3) δ (ppm): 8.88 (1H, s,); 8.42 (1H, d, J = 8.1 Hz); 8.12 (1H, d, J = 8.6
Hz); 7.67 (2H, d, J = 8.6 Hz); 7.52 (1H, d, J = 8.1 Hz); 7.18 (2H, d, J = 8.6 Hz); 7.05 (2H, m);
12

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6.47 (1H, d, J = 8.6 Hz); 13C NMR (100 MHz, CDCl3) δ (ppm): 172.59, 143.43, 141.11, 132.30,
132.01, 129.66, 128.84, 128.69, 128.19, 125.89, 125.33, 122.75, 118.83. Anal. Calc. for
C16H11N2ClO: C, 67.96; H, 3.89; N, 9.91%. Found: C, 67.97; H, 3.87; N, 9.95%.
3. Results and discussions
3.1. Ionic liquid 6 was synthesized via the reaction of 3-chloropropyletrimethoxysilane and
N,N,N',N'-tetramethylethylenediamine in acetonitrile at 80ºC in 95% yield (Scheme 2). Then the
ionic liquid was immobilized on nanosilica. The immobilization was confirmed by comparison
of the FT-IR spectroscopy and EDX analysis of compounds 7 and 8 (Figure 3, A). Compound 8
was achieved by increasing of the length of the ionic chain via the four subsequent reactions of
compound 7 with 1,4-dichlorobutane and N,N,N',N'-tetramethylethylenediamine. The structure
of compound 8 was confirmed by FT-IR spectrum, FE-SEM image, EDX and CHNSO analysis
(Figure 1, B and Figure 2, A). The EDX analysis showed the existence of elements C, N, Si, Cl
and O in the structure of 8 (Figure 3, B). Experimental N:C ratio were calculated from EDX and
CHNSO analysis. Comparison of N:C ratio in two structure 7, 8 was used for approving of the
growth of the ionic chain in poly ionic compound 8. Theoretical calculation of the N:C ratio for
compounds 7 and 8 showed that this ratio should be decreased by the growth of poly ionic chain.
N:C ratios (respectively from EDX and CHNSO analysis) for compounds 7 (0.259 and 0.258)
and 8 (0.241 and 0.246) was confirmed the growth of poly ionic chain.
<<Scheme 2>>
Compound 8 was reacted with 4-chlorobuthanol in acetonitrile at 80ºC for 3 days to afford the
hydroxyl functionalized star-like poly ionic compound 9. Hydroxy to nitrite functional group
interconversion was occurred using sodium nitrite in the presence of HCl at 0-5ºC in 5 min. This
13

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functionalizations were confirmed by comparison of the FT-IR spectra of compounds 8, 9 and 10
(Figure 2, B). The signal at 1384 cm-1 in FT-IR spectrum of product 10 was related to N=O bond
and signal O-H was weaker in the FT-IR spectrum of compound 10 in comparison with FT-IR
spectrum of the compound 9.
<<Figure 1>>
<<Figure 2>>
<<Figure 3>>
3.2. Reactions
The freshly prepared compound 10 was examined as a nitrosonium source for the diazotization
of aniline derivatives. Diazotization of p-nitroaniline (1mmol) in the presence of HCl 37% (2
mmol) at 0-5ºC was chosen as a typical reaction. Subsequent azo coupling reaction was used as
the confirmation of the formation of diazonium product. So, sodium β-naphthoxide was added to
the reaction mixture after diazotization for possible azo-coupling reaction and production of
related azo dye, 3l. Product 3l was formed via this procedure and its structure was confirmed by
13
1H-NMR and C-NMR spectroscopy. Using of different amount of compound 10 was used for
optimization of value of this reagent and it was found that, 1.5 g of this compound was required
to achieve the highest yield of 3l from the reaction of p-nitroaniline (10 mmol) in the shortest
reaction time. The using of higher amounts of reagent 10 had no effect on the reaction efficiency.
The generality of this promising reaction was evaluated by employing a variety of aniline
derivatives and subsequent reaction with some phenoxides. The corresponding results were
shown in Table 1. Reaction times and yields for the preparation of diazoniumes and the azo dyes
were gathered in Table 2. As seen from Table 2, the reaction proceeded smoothly to afford the
14

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corresponding dyes in excellent yields for anilines bearing electron-withdrawing as well as
electron donating substituents. The products were purified by recrystallization with ethanol/H2O
and were identified by their spectroscopic and elemental analysis data. The reaction times and
yields were compared with those reported in the literatures (Table 2). As it can be seen from
Table 2, in comparison with reported reagents, compound 10 is more effective and the reactions
were accrued in higher yields and in shorter reaction times. So, this reagent acts as a catalyst in
this procedure because of its highly ionic characteristic.
<<Table 1>>
<<Table 2>>
In summary, a highly efficient method has been developed for the diazotization reaction of
anilines using nitrite functionalized poly ionic star-like compound under solvent-free conditions.
Our new introduced nitrosonium ion source is the best because it gave excellent yields in most of
the cases. No by-products were formed in this new method and the purification of the desired azo
dye is easier. Further work in this direction is in progress in our laboratory and will be reported
in due course of time.
Acknowledgment
The partial financial assistance from the Research Vice Chancellor of Azarbaijan Shahid Madani
University is gratefully acknowledged.
References
15

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Table 1
.
Diazotization of anilines using nitrite functionalized star-like poly ionic compound and subsequent
synthesis of azo dyes.
Product
number
Entry Amine
Coupling reagent
Product
NH2
1
3a
OH
O2N
2
3
3b
3c
Br
NH2
OH
OH
Cl
NH2
HO
N
4
5
3d
3e
NH2
NH2
OH
OH
N
Me
O2N
Cl
Br
OH
6
7
3f
NH2
NH2
HO
OH
3g
NO2
OH
8
9
3h
Me
Me
NH2
NO2
OH
3i
NH2

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Table 1. (Continued)
Product
number
Entry
Amine
Coupling reagent
Product
OH
10
3j
3k
3l
Br
NH2
OH
OH
OH
NH2
11
12
13
O2N
O2N
NH2
3m
Cl
NH2
14
15
3n
3o
NH2
NMe2
NMe2
O2N
O2N
NH2
NH2
16
17
3p
3q
NMe2
CHO
Cl
COOH
NH2
N
H

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Table 1. Continued
Product
number
Entry
Amine
Coupling reagent
Product
CHO
N
18
19
3r
NH2
N
N
H
OH
3s
OH
20
3t
Cl
NH2

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Table 2. Comparison of the melting point, reaction times and yields with
reported values.
Entry Product
number
M.P (°C)
Reported
[Ref.]
Time (min)
Yielda (%)
Found
Diazonium Azo Found Reported
dyes
[Ref.]
salts
1
2
166-167 167-169 [14]
216-217 216-218 [14]
189-191 188-190 [14]
159-160 160-163 [4b]
248-250 248-250 [14]
197-198 196-198 [5]
163-165 165-167 [15]
145-146 144-146 [15]
131-132 130-132 [19]
169-170 169-171 [19]
194-196 194 [20]
5
5
5
98%
87%
84%
88%
82%
98%
93%
89%
91%
98%
97%
94%
89%
84%
81%
86%
98%
98%
97%
95%
98% [14]
67% [14]
37% [14]
-
3a
3b
3c
3d
3e
3f
5
3
5
5
4
5
-
5
5
5
42% [14]
89% [5]
80% [15]
78% [15]
82% [19]
81% [19]
90% [20]
89% [5]
80% [19]
84% [5]
57% [16]
82% [16]
94% [17]
91% [17]
89% [18]
89% [18]
6
5
10
10
10
15
10
-
7
10
10
10
10
5
3g
3h
3i
8
9
10
11
12
13
14
15
16
17
18
19
20
3j
3k
3l
250-251 250-252 [5]
158-159 157-159 [19]
107-108 108-112 [5]
228-230 229-230 [16]
192-193 191-192 [16]
192-194 192-195 [17]
190-192 191-194 [17]
181-183 182 [18]
5
10
15
15
15
10
10
15
15
15
10
5
3m
3n
3o
3p
3q
3r
3s
10
10
5
5
10
10
293-295 293 [18]
3t
a isolated yields

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Figure 1. A) FE-SEM image of nanosilica; B) FE-SEM image of immobilized compound 8; C) FE-SEM image of
hydroxyl functionalized 9.

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Figure 2: A) FT-IR spectrum of nanosilica and poly ionic 8; B) FT-IR spectrum of poly ionic compounds 8, 9 and
10.

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Figure 3. A) EDX analysis of compound 7; B) EDX analysis of compound 8.

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Scheme 1: Diazotization of anilines using NFSPI and subsequent synthesis of azo dyes.

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Scheme 2. Synthesis of nitrite functionalized star-like poly ionic compound.

ACCEPTED MANUSCRIPT
Highlights
•
•
•
Star-like nitrite functionalized poly ionic compound is a highly efficient
heterogeneous catalyst for the diazotization of anilines.
Azo dyes were synthesized using this catalyst in excellent yields under solvent-
free conditions.
We introduced new nitrosonium ion source and it is the best because it gave
excellent yields without any by-products.
.