Aluminum nitrate and silica sulfuric acid as efficient nitrating media for the mononitration of phenols under mild and heterogeneous conditions

Article abstract of DOI:10.1139/V09-081

A variety of phenol derivatives were successfully nitrated via combination of Al(NO₃)₃-9H₂O and silica sulfuric acid in the presence of wet SiO₂ (50% w/w) in dichloromethane at room temperature with moderate-to-good yields.

Full text of DOI:10.1139/V09-081

1144
Aluminum nitrate and silica sulfuric acid as
efficient nitrating media for the mononitration of
phenols under mild and heterogeneous conditions
Arash Ghorbani-Choghamarani, Hamid Goudarziafshar, Mohsen Nikoorazm, and
Somaieh Yousefi
Abstract: A variety of phenol derivatives were successfully nitrated via combination of Al(NO3)3Á9H2O and silica sulfuric
acid in the presence of wet SiO2 (50% w/w) in dichloromethane at room temperature with moderate-to-good yields.
Key words: nitration, phenol, heterogeneous conditions, aluminum nitrate [Al(NO3)3Á9H2O], silica sulfuric acid (SiO2–OSO3H).
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Resume : Operant a la temperature ambiante, dans le dichloromethane et faisant appel a une combinaison de Al(NO3)2Á9H2O
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et d’acide sulfurique lie a de la silice, en presence de SiO2 humide (50 % w/w), on a realise avec succes la nitration des derives
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du phenol, avec des rendements allant de moderes a bons.
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Mots-cles : nitration, phenol, conditions heterogenes, nitrate d’aluminium [Al(NO3)2Á9H2O], acide sulfurique lie a de la si-
lice (SiO2–OSO3H).
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[Traduit par la Redaction]
Therefore, we decided to design new heterogeneous media
for the selective mononitration of phenolic compounds.
Introduction
Nitrophenols have been identified in the atmospheric gas
phase and in cloud and rainwater.1 Nitration of organic sub-
strates is a widely studied reaction of great industrial signifi-
cance, as many nitro-compounds are extensively utilized and
act as intermediates for the manufacture of plastics, dyes,
perfumes, drugs, and pharmaceuticals.2 However, nitration
in a manufacturing process requires the use of potent mix-
tures of concentrated or fuming nitric acid with sulfuric
acid, leading to excessive acid-waste streams and added
expense.3 Nitrophenols are very important organic intermedi-
ates, and hence, it is still interesting to develop regiospecific
pollution-free nitrating procedures for phenolic compounds
under mild conditions.4 Even though various nitrating
reagents for the nitration of phenols have been emerged in
the recent years,5–10 many of these methods still suffer from
some drawbacks, including low selectivity, low yields of
products, tedious work-up, toxicity, and expensive reagents.
Recent research has demonstrated that the heterogeneous
reagent systems have many advantages, such as simple ex-
perimental procedures, mild reaction conditions, and minimi-
zation of chemical waste as compared with the liquid-phase
counterparts.11–16
Result and discussion
In this article, we report a new, simple, cheap, and con-
venient protocol for the mononitration of phenols using
SiO2–OSO3H and Al(NO3)3Á9H2O in the presence of wet
SiO2 (50% w/w) under mild and heterogeneous conditions.
Silica sulfuric acid can be readily prepared via the reported
procedure by Zolfigol (Scheme 1).17
A wide variety of substituted phenols were nitrated by
silica sulfuric acid (SiO2–OSO3H) (I) and aluminum nitrate
[Al(NO3)3Á9H2O] (II) in the presence of wet SiO2 (50%, w/w)
in dichloromethane (Scheme 2).
The nitration reactions were performed at room tempera-
ture with moderate-to-good yields, and the results are sum-
marized in Table 1.
The mixing of the nitrating agents and phenols in
dichloromethane and stirring the resulting heterogeneous
mixture at room temperature can selectively produce mono-
nitrated phenols. Highly pure mononitrophenols can be ob-
tained by flash column chromatography. A combination of
aluminum nitrate nine hydrate and silica sulfuric acid can
act as a solid nitrating agent, which can be readily weighed,
handled, and used in the presence of moist SiO2. Water mol-
ecules or wet SiO2 are necessary for the nitration of phenols.
Therefore, we think that wet SiO2 acts as a heterogeneous
effective surface area for in situ generation of HNO3.
In summary, herein, we report an efficient method for the
selective nitration of phenols under mild and heterogeneous
conditions with acceptable yields. Furthermore, this method
exhibits substrate versatility, mild reaction conditions, easy
and clean work-up of products.
Received 27 February 2009. Accepted 28 May 2009. Published
on the NRC Research Press Web site at canjchem.nrc.ca on
27 July 2009.
A. Ghorbani-Choghamarani,1 H. Goudarziafshar,
M. Nikoorazm, and S. Yousefi. Department of Chemistry,
Faculty of Science, Ilam University, P.O. Box 69315516 Ilam,
Iran.
1Corresponding author (e-mail: arashghch58@yahoo.com).
Can. J. Chem. 87: 1144–1147 (2009)
doi:10.1139/V09-081
Published by NRC Research Press

Ghorbani-Choghamarani et al.
1145
Table 1. Mononitration of phenols to their corresponding nitro derivatives using silica sulfuric acid (I), Al(NO3)3Á9H2O (II), and wet SiO2
(50% w/w) in dichloromethane at room temperature.
Scheme 1. Preparation of silica sulfuric acid (SiO2–OSO3H).
Scheme 2. Mononitration of phenol derivatives.
Published by NRC Research Press

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Can. J. Chem. Vol. 87, 2009
Table 1. Concluded.
2-Nitro-4-iso-propylphenol
Experimental section
1
Yellow oil. H NMR (400 MHz, CDCl3) d: 10.48 (s, 1H),
7.94 (s, 1H), 7.47–7.49 (d, 1H, J = 7.6 Hz), 7.09–7.11 (d,
1H, J = 8.8 Hz), 2.89–2.96 (septet, 1H, J = 8 Hz), 1.25–
1.27 (d, 6H, J = 8 Hz) ppm. 13C NMR (100 MHz, CDCl3)
d: 153.3, 141.2, 136.4, 133.3, 121.9, 119.7, 33.1, 23.7 ppm.
The chemicals and solvents were purchased from Fluka,
Merck, and Aldrich chemical companies and were used
without further purifications.
Mononitration of 4-chloro-3-methylphenol with silica
sulfuric acid, Al(NO3)3Á9H2O, and wet SiO2 (a typical
procedure)
2-Nitro-4-phenoxyphenol
1
Yellow oil. H NMR (400 MHz, CDCl3) d: 10.41 (s, 1H),
A
suspension of 4-chloro-3-methylphenol (0.142 g,
7.7–7.71 (m, 1H), 7.34–7.4 (m, 3H), 7.16–7.18 (m, 2H),
6.99–7.0 (m, 2H) ppm. 13C NMR (100 MHz, CDCl3) d:
156.6, 151.2, 149.8, 133.3, 130.1, 129.6, 124.1, 121.1,
118.6, 113.6 ppm.
1 mmol), silica sulfuric acid (0.225 g), wet SiO2 (50% w/w,
0.2 g), and Al(NO3)3Á9H2O (0.143 g, 0.5 mmol) in CH2Cl2
(5 mL) was stirred at room temperature for 110 min (the
progress of the reaction was monitored by TLC) and then
filtered. Anhydrous Na2SO4 (1.5 g) was added to the filtrate.
After 15 min, the resulting mixture was also filtered; CH2Cl2
was removed by distillation in a water bath. Crude product
was purified by flash silica-gel column chromatography
using CH2Cl2 as eluent and pure product obtained in 60%
yield (0.112 g). Crystalline pale yellow solid, mp 130–
2-tert-Buthyl-4-methyl-2-nitrophenol
Crystalline pale yellow solid, mp 89–90 8C. 1H NMR
(400 MHz, CDCl3) d: 11.43 (s, 1H), 7.79 (s, 1H), 7.38 (s,
1H), 2.32 (s, 3H), 1.43 (s, 9H) ppm. 13C NMR (100 MHz,
CDCl3) d: 153.1, 140.2, 136.1, 133.8, 128.6, 122.2, 35.4,
29.3, 20.7 ppm.
1
132 8C. H NMR (400 MHz, CDCl3) d: 10.46 (s, 1H), 8.10
2-Methoxy-4-methyl-2-nitrophenol
(s, 1H), 7.27 (s, 1H), 7.07 (s, 1H), 2.43 (s, 3H) ppm. 13C
NMR (100 MHz, CDCl3) d: 153.4, 147.6, 131.8, 125.8,
124.5, 121.4, 20.8 ppm.
Crystalline pale yellow solid, mp 75–77 8C. 1H NMR
(400 MHz, CDCl3) d: 10.64 (s, 1H), 7.49 (s, 1H), 6.96 (s,
1H), 3.94 (s, 3H), 2.34 (s, 3H) ppm. 13C NMR (100 MHz,
CDCl3) d: 149.6, 144.3, 133.4, 128.9, 122.0, 119.2, 115.2,
56.6, 20.9 ppm.
4-tert-Buthyl-2-nitrophenol
Yellow oil. H NMR (400 MHz, CDCl3) d: 10.49 (s, 1H),
1
8.07 (s, 1H), 7.63–7.66 (d, 1H, J = 8.8 Hz), 7.09–7.12 (d,
1H, J = 8.8 Hz), 1.33 (s, 9H) ppm. 13C NMR (100 MHz,
CDCl3) d: 153.0, 143.6, 135.4, 132.9, 120.8, 119.5, 34.3,
31.0 ppm.
Acknowledgment
This work was supported by the research facilities of Ilam
University, Ilam, Iran.
Published by NRC Research Press

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(10) Barletta, B.; Bolzacchini, E.; Meinardi, S.; Orlandi, M.; Rin-
done, B. Environ. Sci. Technol. 2000, 34 (11), 2224–2230.
doi:10.1021/es990844m.
(11) Zolfigol, M. A.; Salehi, P.; Ghorbani-Choghamarani, A.;
Shahamirian, M. Synth. Commun. 2007, 37 (11), 1817–1823.
doi:10.1080/00397910701316276.
References
(1) Heal, M. R.; Harrison, M. A. J.; Cape, J. N. Atmos. Environ.
2007, 41 (17), 3515–3520. doi:10.1016/j.atmosenv.2007.02.
003.
(2) Mallick, S.; Parida, K. M. Catal. Commun. 2007, 8 (10),
1487–1492. doi:10.1016/j.catcom.2006.12.023.
(12) Mohammadpoor-Baltork, I.; Tangestaninejad, S.; Hojati, S.
F. J. Iran. Chem. Soc. 2008, 5, S65.
(3) Yi, W.-B.; Cai, C. Synth. Commun. 2006, 36 (20), 2957–
2961. doi:10.1080/00397910600773700.
(13) Zolfigo, M.; Amani, K.; Ghorbani-Choghamarani, A.;
Hajjami, M.; Ayazinasrabadi, R.; Jafari, S. Catal. Commun.
2008, 9 (8), 1739–1744. doi:10.1016/j.catcom.2008.01.029.
(14) Zolfigol, M.; Shirini, F.; Ghorbani-Choghamarani, A.
Synthesis 2006, 2043–2046. doi:10.1055/s-2006-942396.
(15) Mohammadpoor-Baltork, I.; Ghorbani-Choghamarani, A.;
Baghbanzadeh, M. J. Iran. Chem. Soc. 2006, 3, 73.
(16) Zolfigol, M. A.; Amani, K.; Hajjami, M.; Ghorbani-
Choghamarani, A. Monatsh. Chem. 2008, 139 (8), 895–899.
doi:10.1007/s00706-008-0868-6.
(17) Zolfigol, M. A. Tetrahedron 2001, 57 (46), 9509–9511.
doi:10.1016/S0040-4020(01)00960-7.
(18) Zolfigol, M.; Shirini, F.; Ghorbani-Choghamarani, A. Phos-
phorus Sulfur Silicon 2003, 178 (9), 2019–2025. doi:10.
1080/10426500390228701.
(4) Selvam, J. J. P.; Suresh, V.; Rajesh, K.; Reddy, S. R.;
Venkateswarlu, Y. Tetrahedron Lett. 2006, 47 (15), 2507–
2509. doi:10.1016/j.tetlet.2006.02.057.
(5) Nandurkar, N. S.; Bhanushali, M. J.; Jagtap, S. R.; Bhanage,
B. M. Ultrason. Sonochem. 2007, 14 (1), 41–45. doi:10.
1016/j.ultsonch.2006.01.005. PMID:16563845.
(6) Anuradha, V.; Srinivas, P. V.; Aparna, P.; Rao, J. M. Tetra-
hedron Lett. 2006, 47 (28), 4933–4935. doi:10.1016/j.tetlet.
2006.05.017.
(7) Heravi, M. M.; Benmorad, T.; Bakhtiari, K.; Bamoharram,
F. F.; Oskooie, H. H. J. Mol. Catal. Chem. 2007, 264 (1-2),
318–321. doi:10.1016/j.molcata.2006.09.014.
(8) Rajagopal, R.; Srinivasan, K. V. Synth. Commun. 2003, 33
(6), 961–966. doi:10.1081/SCC-120016360.
(9) Budde, C. L.; Beyer, A.; Munir, I. Z.; Dordick, J. S.;
Khmelnitsky, Y. L. J. Mol. Catal., B Enzym. 2001, 15 (1-3),
55–64. doi:10.1016/S1381-1177(01)00004-2.
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