Facile synthesis of benzotriazole derivatives using nanoparticles of organosilane-based nitrite ionic liquid immobilized on silica and two room-temperature nitrite ionic liquids

Article abstract of DOI:10.1080/00397911.2012.744840

Nanoparticles of organosilane-based nitrite ionic liquid immobilized on silica, 1-butyl-3-methylimidazolium nitrite, and 1-(3-trimethoxysilylpropyl)-3- methylimidazolium nitrite were used as effective reagents for the preparation of benzotriazole derivatives from 1,2-diaminobenzenes at room temperature under mild solvent-free conditions. These ionic liquids play as nitrosonium sources in this procedure.1,2-Diaminobenzene derivatives have been treated with ionic liquids to give the related diaminobenzenes in very good to excellent yields in short reaction times. Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications for the full experimental and spectral details.

Full text of DOI:10.1080/00397911.2012.744840

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Facile Synthesis of Benzotriazole
Derivatives Using Nanoparticles of
Organosilane-Based Nitrite Ionic Liquid
Immobilized on Silica and Two Room-
Temperature Nitrite Ionic Liquids
Hassan Valizadeh a , Hamid Gholipour a & Manzar Mahmoodian a
a Department of Chemistry , Faculty of Sciences, Azarbaijan Shahid
Madani University , Tabriz , Iran
Published online: 08 Jul 2013.
To cite this article: Hassan Valizadeh , Hamid Gholipour & Manzar Mahmoodian (2013) Facile
Synthesis of Benzotriazole Derivatives Using Nanoparticles of Organosilane-Based Nitrite Ionic Liquid
Immobilized on Silica and Two Room-Temperature Nitrite Ionic Liquids, Synthetic Communications:
An International Journal for Rapid Communication of Synthetic Organic Chemistry, 43:20, 2801-2808,
DOI: 10.1080/00397911.2012.744840
To link to this article: http://dx.doi.org/10.1080/00397911.2012.744840
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Synthetic Communications1, 43: 2801–2808, 2013
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2012.744840
FACILE SYNTHESIS OF BENZOTRIAZOLE DERIVATIVES
USING NANOPARTICLES OF ORGANOSILANE-BASED
NITRITE IONIC LIQUID IMMOBILIZED ON SILICA AND
TWO ROOM-TEMPERATURE NITRITE IONIC LIQUIDS
Hassan Valizadeh, Hamid Gholipour, and
Manzar Mahmoodian
Department of Chemistry, Faculty of Sciences, Azarbaijan Shahid Madani
University, Tabriz, Iran
GRAPHICAL ABSTRACT
Abstract Nanoparticles of organosilane-based nitrite ionic liquid immobilized on silica,
1-butyl-3-methylimidazolium nitrite, and 1-(3-trimethoxysilylpropyl)-3-methylimidazolium
nitrite were used as effective reagents for the preparation of benzotriazole derivatives from
1,2-diaminobenzenes at room temperature under mild solvent-free conditions. These ionic
liquids play as nitrosonium sources in this procedure.1,2-Diaminobenzene derivatives have
been treated with ionic liquids to give the related diaminobenzenes in very good to excellent
yields in short reaction times.
Supplementary materials are available for this article. Go to the publisher’s online
edition of Synthetic Communications1 for the full experimental and spectral details.
Keywords Benzotriazole; nanoparticles; nitrite ionic liquid; task-specific ionic liquid
Received August 20, 2012.
Address correspondence to Hassan Valizadeh, Department of Chemistry, Faculty of Science,
P.O. Box 53714-161, Azarbaijan Shahid Madani University, Tabriz, Iran. E-mail: hvalizadeh2@
yahoo.com
2801

2802
H. VALIZADEH, H. GHOLIPOUR, AND M. MAHMOODIAN
INTRODUCTION
Heterocyclic compounds containing nitrogen atoms are some of the most
effective antimicrobial drugs used for cancer therapy.[1,2] Benzotriazole and 1,2,4-
benzotriazole derivatives are an interesting class of heterocycles[3] and have become
the most rapidly expanding group of antifungal compounds because of the advan-
tage of low toxicity, high oral bioavailability, and broad-spectrum activity.[4–6]
Moreover, several benzotriazoles inhibit the growth of some microorganisms, and
some benzotriazole derivatives show anti-inflammatory properties.[7] The diazotiza-
tion of 1,2-diaminobenzenes in an acidic solution is the major route to synthesis of
benzotriazoles. There are some reports on synthesis of benzotriazoles from 1,2-
diaminobenzene as the main precursor in the literature.[8,9] In addition, Wan et al.
reported that some benzotriazole derivatives exhibiting antibacterial activity.[10]
Ionic liquids have attracted chemists’ interest because of their physical and chemical
properties.[11,12] Many of these compounds, known as task-specific ionic liquids
(TSILs), are able to play multiple roles as catalyst and=or reagent and solvent. TSILs
contain functional groups that are covalently bonded to cation or anion in these com-
pounds. TSILs have been increasingly used in synthetic organic chemistry.[13–17]
Wang et al. reported the synthesis of N-(a-alkoxyalkyl) benzotriazoles using acidic
ionic liquid as catalyst at room temperature.[18] Shi and coworkers synthesized a var-
iety of substituted benzotriazolesvia the [3 þ 2] annulation click reaction of benzynes
and azides.[19] The biological significances of these classes of heterocycles and impor-
tant features of ionic liquids for the synthesis of organic compounds impelled us to
synthesize benzotriazole derivatives using TSILs. Herein, we report our preliminary
results on the synthesis of benzotriazoles 2a–j using task-specific nitrite ionic liquids.
Three ionic liquids (1-butyl-3-methylimidazolium nitrite, 1-(3-trimethoxysilylpropyl)-
3-methylimidazolium nitrite, and nanoparticles of organosilane-based nitrite ionic
liquid immobilized on silica) were used in this procedure (Scheme 1).
Scheme 1. Synthesis of benzotriazoles using TSILs.

SYNTHESIS OF BENZOTRIAZOLE DERIVATIVES
2803
Scheme 2. Proposed mechanism for synthesis of benzotriazolesfrom 1,2-diaminobenzene using TSILs as
nitrosonium sources.
RESULTS AND DISCUSSION
We started our investigation using equimolar amounts of 1,2-diaminobenzene,
1-butyl-3-methylimidazolium nitrite, IL-1, and AcOH at 0–5 ꢀC without using any
solvent. Benzotriazole 2a was synthesized in 42% yield. The reaction was examined
in several protic and aprotic solvents such as EtOH, MeOH, dimethylformaide
(DMF), dimethylsulfoxide (DMSO), CHCl3, and CH3CN at different temperatures.
The best result was achieved in protic solvents at 0–70 ꢀC. Other acids such as hydro-
chloric acid and p-toluenesulfonic acid produced the product in a moderate yield. The
best result was obtained when the reaction was carried out in the presence of 25 mol%
acetic acid. In the absence of acid, no formation of the desired product was observed.
Acetic acid (25 mol%) was required as the optimum amount of catalyst and increasing
the amount of catalyst did not improve the yields but decreasing the amount of cata-
lyst decreased the yield. The reaction was also carried out in AcOH=H2O at 0–70 ꢀC.
Good yield (77%) of product was achieved under this condition, and the best ratio of
aromaticdiamine and IL-1 was found to be 1:1.3. These conditions were chosen as
optimum for this reaction. To demonstrate the generality, we next tested different aro-
matic diamine precursors under these optimized reaction conditions, and the results
are summarized in Table 1. As can be seen, the reaction shows good compatibility with
different aromatic diamine precursors. All of these substrates gave clean reactions
under mild conditions. However, aromatic diamines containing electron-withdrawing
groups afforded related benzotriazoles in greater yields in shorter reaction times. Very
recently we reported two TSILs as nitrosonium sources for the nitrosation and diazo-
tization reactions.[13,14,20] We examined these TSILs as a nitrosonium sources in the
described reaction and compared the results (Table 1). We examined the effectiveness
of these ionic liquids as nitrosonium sources in this procedure under optimized con-
ditions. The results showed that the synthesis of 1,2,3-benzotriazoles in the presence
of nanoparticles of organosilane-based nitrite ionic liquid immobilized on silica was
occurred in greater yields and in shorter reaction times in comparison with other
examined TSILs. The proposed mechanism is shown in Scheme 2.

2804
H. VALIZADEH, H. GHOLIPOUR, AND M. MAHMOODIAN
Table 1. Synthesis ofbenzotriazoles using TSILs
M.P (ꢀC)
Time (min)
Yielda (%)
Product
number Found
Reported
[Ref.]
Entry
1
Product
IL-1 IL-2 IL-3 IL-1 IL-2 IL-3
2a
2b
2c
95–96
96–97 [21]
35
35
30
35
30
29
24
25
77
83
81
80
81
83
85
88
86
2
3
207–208
209 [22]
156–157 157–159 [22] 35
129–130 132–133 [23] 32
4
5
2d
2e
30
35
28
30
83
81
83
78
87
88
228–230 228–229 [25] 33
6
7
2f
136–138 136–138 [23] 33
156–158 156–157 [26] 30
35
30
32
30
75
73
75
74
80
78
2 g
8
9
2 h
2i
263–265 264–266 [27] 30
246–248 248–250 [28] 35
182–184 183–184 [29] 35
30
35
35
30
30
30
82
80
87
80
78
80
85
86
89
10
2j
aIsolated yield.
CONCLUSIONS
In conclusion, it was found that immobilized nitrite ionic liquid and two room-
temperature task-specific nitrite ionic liquids are convenient reagents for the synthesis
of 1,2,3-benzotriazoles under solvent-free conditions. These ionic liquids are efficient

SYNTHESIS OF BENZOTRIAZOLE DERIVATIVES
2805
nitrisonium sources. Our methodology offers several advantages including mild reac-
tion conditions, cleaner reaction, good yields of products, and a simple experimental
and isolated procedure, which make it a useful and attractive process for the synthesis
of benzotriazoles.
EXPERIMENTAL
All reagents were purchased from Merck Company and used without further
purification. Infrared (IR) spectra were recorded in KBr and were determined on a
1
Perkin Elmer FT-IR spectrometer. H and 13C NMR spectra were recorded on a
Bruker Avance AC 400-MHz instrument using dimethylsulfoxide (DMSO-d6) or CDCl3
as the deuterated solvents and tetramethylsilane (TMS) as internal standard. All melting
points measured in open glass capillaries using a Stuart melting a point apparatus.
General Procedure
Aromatic diamine (50 mmol) and freshly prepared 1-butyl-3-methylimidazolium
nitrite,[14] 1-(3-trimethoxysilylpropyl)-3-methylimidazolium nitrite,[20] or nanoparti-
cles of organosilane-based nitrite ionic liquid immobilized on silica[24] (65 mmol) were
added to water (5 mL) and mixed thoroughly at 0–5 ꢀC. Then glacial acetic acid
(25 mol%) was added to the mixture continuously and the temperature rose rapidly
to 70–80 ꢀC. The mixture was stirred at this temperature for a time as shown in
Table 1. In the case of using IL-1 and IL-2 the precipated products were filtered
and washed three times with cold water to afford the crude benzotriazole derivative.
In the case of IL-3, after filtration of the mixture, the remained solid was washed
with chloroform or acetone and then the organic solvent was evaporated. The crude
products were recrystallized with charcoal from ethanol or ethyl acetate–hexane.
1H-Benzo[d][1,2,3]triazole (2a)
Mp 95–96 ꢀC, 96–97 ꢀC[21]; FT-IR (KBr, cmꢁ1): 1208 (N N), 1575 (C C),
=
=
1
=
1624 (C C), 3083 (¼C-H), 3146 (N-H); H NMR (400 MHz, CDCl3) d (ppm):
7.50 (d, J ¼ 6.75 Hz, 2H), 7.98 (d, J ¼ 6.75 Hz, 2H), 13.92 (s, NH); 13C NMR
(100 MHz, CDCl3) d (ppm): 113.3, 127.0, 139.8 (6C, Ph).
5-Nitro-1H-benzo[d][1,2,3]triazole (2b)
Mp 207–208 ꢀC, 209 ꢀC[22]; FT-IR (KBr, cmꢁ1): 1219 (N N), 1354 (N O),
=
=
1490 (N O), 1521 (C C), 1624 (C C), 3093 (¼C-H), 3577 (N-H); 1H NMR
=
=
=
3
4
(400 MHz, CDCl3) d (ppm): 7.38 (dd, J ¼ 8.21 Hz and J ¼ 1.86 Hz, 1H), 8.12 (d,
J ¼ 8.21 Hz, 1H), 8.38 (d, J ¼ 1.86 Hz, 1H); 13C NMR (100 MHz, CDCl3) d (ppm):
123.65, 123.80, 126.8, 127.1, 133.0, 146.5.
5-Chloro-1H-benzo[d][1,2,3]triazole (2c)
Mp 156–157 ꢀC, 157–159 ꢀC[22]; FT-IR (KBr, cmꢁ1): 1204 (N N), 1558 (C C),
=
=
1626 (C C), 3039 (¼C-H), 3448 (N-H); 1H NMR (400 MHz, DMSO-d 6) d
=

2806
H. VALIZADEH, H. GHOLIPOUR, AND M. MAHMOODIAN
3
4
(ppm): 7.47 (dd, J ¼ 8.8 Hz and J ¼ 1.6 Hz, 1H), 7.99 (d, J ¼ 8.8 Hz, 1H), 8.06 (s,
1H);13C NMR (100 MHz, DMSO-d 6) d (ppm): 115.2, 117.0, 126.1, 130.3, 138.3, 139.4.
5-Benzoyl-1H-benzo[d][1,2,3]triazole (2d)
Mp 129–130 ꢀC, 132–133 ꢀC[23]; FT-IR (KBr, cmꢁ1): 1205 (N N), 1608 (C C),
=
=
1629 (C C), 1662 (C O), 3127 (N-H); 1H NMR (400 MHz, CDCl3) d (ppm):
7.29–8.45 (m, 8H, Ar), 12.64 (s, NH); 13C NMR (100 MHz, CDCl3) d (ppm):
116.8, 128.7 (2C, Ar), 129.5, 130.0 (3C, Ar), 132.7, 139.7 (2C, Ar), 145.6 (2C, Ar),
=
=
=
195.1 (C O).
4-Nitro-1H-benzo[d][1,2,3]triazole (2e)
Mp 228–230 ꢀC, 228–229 ꢀC[25]; FT-IR (KBr, cmꢁ1): 1210 (N N), 1348 (N O),
=
=
1
=
=
1524 (N O), 1630 (C C), 3025 (¼C-H), 3172 (N-H); H NMR (400 MHz, CDCl3) d
3
4
(ppm): 7.72 (t, J ¼ 8.21 Hz, 1H), 8.38 (dd, J ¼ 8.20 Hz and J ¼ 1.84 Hz, 1H), 8.48
3
4
(dd, J ¼ 8.23 Hz and J ¼ 1.84 Hz, 1H); 13C NMR (100 MHz, CDCl3) d (ppm):
122.61, 122.86, 127.0, 127.1, 131.5, 147.5.
5-Methyl-1H-benzo[d][1,2,3]triazole (2f)
Mp 136–138 ꢀC, 136–138 ꢀC[23]; FT-IR (KBr, cmꢁ1): 1201 (N N), 1626 (C C),
=
=
1
3083 (¼C-H), 3188 (N-H); H NMR (400 MHz, CDCl3) d (ppm): 2.35 (s, 3H), 7.31
(dd, 3J ¼ 8.19 Hz and 4J ¼ 1.79 Hz, 1H), 8.09 (d, J ¼ 8.19 Hz, 1H), 8.38 (d,
J ¼ 1.79 Hz, 1H); 13C NMR (100 MHz, CDCl3) d (ppm): 22.43, 120.15, 122.8,
125.8, 128.1, 135.0, 146.5.
5,6-Dimethyl-1H-benzo[d][1,2,3]triazole (2g)
Mp 156–158 ꢀC, 156–157 ꢀC[26]; FT-IR (KBr, cmꢁ1): 1215 (N N), 1615 (C C),
=
=
1
2905 (aliphatic C-H), 3089 (¼C-H), 3193 (N-H); H NMR (400 MHz, CDCl3) d
(ppm): 2.33 (s, 3H), 2.36 (s, 3H), 7.35 (s, 1H), 7.41 (s, 1H); 13C NMR (100 MHz,
CDCl3) d (ppm): 22.54, 23.89, 121.25, 124.8, 126.1, 128.8, 137.5, 145.4.
5,6-Dichloro-1H-benzo[d][1,2,3]triazole (2h)
Mp 263–265 ꢀC, 264–266 ꢀC[27]; FT-IR (KBr, cmꢁ1): 1212 (N N), 1625 (C C),
3079 (¼C-H), 3184 (N-H); 1H NMR (400 MHz, CDCl3) d (ppm): 7.68 (s, 1H), 7.79 (s,
1H); 13C NMR (100 MHz, CDCl3) d (ppm): 123.2, 126.6, 127.7, 130.8, 137.9, 146.5.
=
=
5,6-Dibromo-1H-benzo[d][1,2,3]triazole (2i)
Mp 246–248 ꢀC, 246–250 ꢀC[28]; FT-IR (KBr, cmꢁ1): 1211 (N N), 1640 (C C),
3065 (¼C-H), 3181 (N-H); 1H NMR (400 MHz, CDCl3) d (ppm): 7.65 (s, 1H), 7.77 (s,
1H); 13C NMR (100 MHz, CDCl3) d (ppm): 122.2, 125.6, 126.7, 130.6, 136.8, 146.1.
=
=

SYNTHESIS OF BENZOTRIAZOLE DERIVATIVES
2807
5,6-Diflouro-1H-benzo[d][1,2,3]triazole (2j)
Mp 182–184 ꢀC, 183–184 ꢀC[29]; FT-IR (KBr, cmꢁ1): 1216 (N N), 1618 (C C),
3071 (¼C-H), 3184 (N-H); 1H NMR (400 MHz, CDCl3) d (ppm): 7.81 (s, 1H), 7.87 (s,
1H); 13C NMR (100 MHz, CDCl3) d (ppm): 126.2, 127.6, 128.1, 131.6, 139.0, 147.9.
=
=
SUPPORTING INFORMATION
1
Melting points, FT-IR, and H and 13C NMR spectra are available online.
ACKNOWLEDGMENT
The partial financial assistance from the Research Vice Chancellor of
Azarbaijan Shahid Madani University is gratefully acknowledged.
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