Selective nitration of aromatic compounds catalyzed by Hβ zeolite using N2O5

Article abstract of DOI:10.1016/j.cclet.2012.05.016

A selective and efficient process for the electrophilic nitration is described using N₂O₅ as a green nitrating agent, Hβ zeolite as a solid acid catalyst and shape controlling agent under mild conditions.

Full text of DOI:10.1016/j.cclet.2012.05.016

Available online at www.sciencedirect.com
Chinese Chemical Letters 23 (2012) 809–812
www.elsevier.com/locate/cclet
Selective nitration of aromatic compounds catalyzed
by Hb zeolite using N O5
2
*
Xiao Ming Ma, Bin Dong Li , Lei Chen, Ming Lu, Chun Xu Lv
Chemical Engineering College, Nanjing University of Science and Technology, Nanjing 210094, China
Received 27 March 2012
Available online 12 June 2012
Abstract
A selective and efficient process for the electrophilic nitration is described using N
2 5
O as a green nitrating agent, Hb zeolite as a
solid acid catalyst and shape controlling agent under mild conditions.
2012 Bin Dong Li. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
#
2 5
Keywords: Selective nitration; Hb zeolite; N O ; Catalysis
Nitration of aromatic substrates is one of the widely studied organic reactions as nitro aromatic compounds are
industrially important intermediates during the synthesis of dyes, plastics and pharmaceuticals [1–4]. However, many
commercial processes to produce such materials still rely on technology that was developed many years ago. The
traditional method for nitration, involving a mixture of nitric acid and sulfuric acid, suffers from many disadvantages
including the generation of large quantities of corrosive waste and in many cases the production of mixtures of isomers
in which the most desirable one is not in high yield [5]. The obvious disadvantages of the commercial manufacturing
process currently used have stimulated much research aimed at development of environmental friendly and reusable
2
À
alternative procedures. Different solid acid catalysts tested so far included MoO /SiO [6–8], SO /SiO [9], WO –
3
2
4
2
3
2À
TiO /SiO [10], WO –SO /SnO [11], zeolite-based solid acid catalysts [12–15], melamine–(H SO ) [17] and
2
+
polyvinylpyrrolidone–(H SO ) [18]; other sources of NO were involved, such as nitronium salts in organic media
2
3
4
2
2
4 3
2
4 n
2
[
19], Zn(NO ) Á6H O [20], guanidinium nitrate [21], N O [22,23] and N O [24–27]; organic nitrating agents of e.g.
3
2
2
2
4
2 5
acetyl nitrates [13,16] and alkyl nitrates [21], other acids replacing sulfuric acid [28], etc., that generate less waste and
provide product mixtures in which the most desirable isomer (often the para-isomer) is much more abundant.
However, these processes are associated with the problems of leaching of acid from the support during reaction and
calcination, requiring long reaction time and high reaction temperature, and giving poor selectivity towards some
aromatic compounds.
The use of b zeolite in aromatic nitration is a subject of increasing interest, particularly with regard to unusual
regioselectivity [13,29–31]. Smith has shown that the b zeolite plays an important role in the selective mononitration
of toluene, where the para-selectivity of 67% by using benzoyl nitrate and the ortho–para isomer ratio of 0.23 by using
*
Corresponding author.
E-mail address: libindong@mail.njust.edu.cn (B.D. Li).
1001-8417/$ – see front matter # 2012 Bin Dong Li. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
http://dx.doi.org/10.1016/j.cclet.2012.05.016

810
X.M. Ma et al. / Chinese Chemical Letters 23 (2012) 809–812
R
R
N O / CH Cl
2
2
5
2
NO2
Hβ zeolite
i
t
R=H, F, Cl, Br, Me, Et, Pr, Bu,
Scheme 1. Nitration of simple aromatics using N catalyzed by Hb zeolite.
2 5
O
acetyl nitrate have been achieved [13]. The method for aromatic nitration using NO /O catalyzed by b zeolite gives
2
3
excellent conversion of a wide variety of aromatic compounds under mild conditions (Kyodai nitration) [30,31].
However, use of ozone adds to the cost of the process. And the method where ozone is employed most likely involves
dinitrogen pentoxide (N O ), a highly active nitrating agent.
2
5
Previously, we reported two mild, efficient and eco-friendly nitration processes: (1) using MoO /SiO [8] as
3
2
catalyst and (2) using rare earth metal triflates [32] as catalyst, which gave the corresponding nitro products with high
yield but low para-selectivity. Therefore, we have attempted to develop a selective process which uses N O as the
2
5
highly active nitrating agent and Hb zeolite as a solid acid catalyst as well as shape controlling agent to improve the
para-selectivity. Now, we report the substantial process in this letter.
In our study, the nitration of toluene using N O in the presence of Hb zeolite was examined (Scheme 1). The
2
5
addition order of the agents had a remarkable effect on the para-selectivity of the process. As shown in Table 1, the best
order (entry 5, 6) should be conducted by pre-mixing the Hb zeolite with CH Cl and then successively adding the
nitrating agent (N O /CH Cl solution) and toluene. In this cases, the best o/p ratio ( para-selectivity) is 0.59 with the
2
2
2
5
2
2
high conversion of 97%. The results showed that Hb zeolite could promote the reaction and the isomer proportion
moved to the orientation to favor the para-isomer, which indicated that the formation of electrophilic nitronium ions
+
NO ) from N O and the interaction of the reactants were conducted predominantly inside the Hb zeolite channels.
(
Although entry 4 in Table 1 shows good selectivity but with low conversion, that because of the heat released when
2
2 5
N O /CH Cl solution contacted with Hb zeolite directly which caused the decomposition of N O . Therefore, pre-
2
2
5
2
2 5
mixing the Hb zeolite with CH Cl is a necessary procedure. Although the higher conversion (98%) was obtained by
2
2
adding the N O /CH Cl solution added to a prepared mixture of Hb zeolite and toluene (entry 2), the para-selectivity
2
5
2
2
was very low (o/p ratio = 1.12). This was caused that N O transferred into the zeolite channels incompletely, and the
2
5
reaction was taken place mainly on the surface of catalyst showed low para-selectivity.
Fig. 1 shows the effect of the catalyst amount on the nitration selectivity. Even with as little as 0.05 g Hb, the
reaction showed remarkable para-selectivity with high conversion, and the best result has been obtained since 0.2 g
Hb zeolite was involved (conversion is 97%; o/p ratio is 0.59). Increasing the catalyst amount provides an increased
+
pore volume and a greater number of catalytic sites. Consequently, a greater proportion of NO2 can be generated
inside the channels, leading to the increased para-selectivity. So 0.2 g Hb zeolite was used in subsequent experiments.
By means of the optimized reaction conditions, extended investigation on a variety of other aromatic compounds
was studied (Scheme 1). The results were summarized in Table 2. As the results shown in Table 2, this new process is
Table 1
a
The effect of order of addition of reagents on the nitration of toluene.
b
b
b
Entry
Order of addition
Time (min)
Conversion (%)
Product isomers (%)
o/p
Ortho
Meta
Para
1
2
3
4
5
6
A–B–C
10
30
10
30
10
30
86
98
46
51
85
97
51.4
51.3
34.1
36.0
35.0
36.3
2.5
2.8
1.8
1.9
1.8
1.8
46.1
45.9
64.1
62.1
63.2
61.9
1.11
1.12
0.53
0.58
0.55
0.59
A–B–C
A–C–B
A–C–B
A–D–C–B
A–D–C–B
a
Reaction conditons: A = Hb (0.2 g), B = toluene (5 mmol, 0.46 g), C = N
Calculated from original GC data.
2
O
5
/CH
2
Cl
2
(5 mmol/5 mL), D = CH Cl
2
2
(2 mL), 20 8C.
b

X.M. Ma et al. / Chinese Chemical Letters 23 (2012) 809–812
811
Fig. 1. The effect of catalyst amount (Hb zeolite) on toluene nitration using N
5.0 mmol/5.0 mL), Hb (0.2 g) with 2 mL CH Cl , 30 min, 20 8C.
2
O
5
. Reaction conditions: toluene (5.0 mmol), N
2
O
5
/CH
2
Cl
2
(
2
2
Table 2
a
Nitration of various aromatics using N
2
O
5
catalyzed by Hb zeolite.
b
b
b
c
Entry
R
Conversion (%)
Product isomers (%)
o/p
o/p
Ortho
Meta
Para
1
2
3
4
5
6
7
F
100
99
21.3
29.6
33.4
–
–
78.7
70.4
66.6
–
0.27
0.42
0.50
–
0.48
0.78
0.82
–
Cl
Br
H
–
92
–
100
100
98
–
Et
i
28.7
16.8
11.2
2.2
3.6
2.9
69.1
79.6
85.9
0.42
0.21
0.13
0.83
0.35
0.16
Pr
t
Bu
100
a
2 5 2 2
Reaction conditions: substrate (5.0 mmol), N O /CH Cl (5.0 mmol/5.0 mL), Hb (0.2 g), 30 min, 20 8C. All products are known and identified
by comparison using GC with authentic samples.
b
Determined by original GC data.
c
Data from Ref. [32].
suitable for a range of moderate active aromatics, high conversions were obtained in all of the cases under mild
reaction conditions, accompanied with a better para-selectivity compared with the data from Ref. [32].
In conclusion, we have developed a selective and efficient process for the nitration of simple aromatic compounds
by using N O and Hb zeolite. This method can give high para-selectivity under mild conditions and is suitable for
2
5
scale-up. The combination of Hb zeolite and N O seems to be a new direction for environmental chemistry in
2
5
nitration.
1
. Experimental
The Hb zeolite (Si/Al ratio is 25) was purchased from Nankai University Catalyst Co. Ltd., and the rest chemicals
were purchased from Sinopharm Chemical Reagent Co. Ltd. and used without further purification; N O was prepared
2
5
according to the procedure of Ref. [25]. All products are known and identified by comparison using GC with authentic
samples.
General procedure: To a cooled (0 8C) stirring mixture of the Hb zeolite (0.2 g) and CH Cl (2 mL), a solution of
2
2
N O (5 mmol) and CH Cl (5 mL) was added slowly; then toluene (5 mmol) was introduced into the tube drop by
2
5
2
2
drop. The reaction was carried out at 20 8C for 1 h, then the catalyst was filtered off and washed with some CH Cl ,
2
2

812
X.M. Ma et al. / Chinese Chemical Letters 23 (2012) 809–812
which was added to the filtrate. The CH Cl solution was washed with a few portions of saturated NaHCO solution,
2
2
3
then several times with water, dried with MgSO , and examined by GC.
4
Acknowledgments
We are grateful for the financial support from the National Natural Science Foundation of China-Academy of
Engineering Physics (No. 10976014), the Natural Science Foundation of Jiangsu Province (No. BK2011697) and
Independent Scientific Research Special Plan of NJUST (No. 2011YBXM06).
References
[
[
[
[
[
[
[
[
[
1] G.A. Olah, R. Malhotra, S.C. Narang, Nitration: Methods and Mechanisms, VCH, New York, 1989.
2] J.P. Agrawal, R.D. Hodgson, Organic Chemistry of Explosive, John Wiley Sons Ltd., 2007.
3] J.P. Agrawal, High Energy Materials propellants, Explosives and Pyrotechnics, John Wiley Sons Ltd., 2010.
4] R.W. Millar, A.W. Arber, R.M. Endsor, et al. J. Energ. Mater. 29 (2011) 88.
5] J. Clark, Chemistry of Waste Minimization, 2nd ed., Chapman & Hall, London, 1995.
6] S.K. Maurya, M.K. Gurjar, K.M. Malshe, et al. Green Chem. 5 (2003) 720.
7] S.B. Umbarkar, A.V. Biradar, S.M. Mathew, et al. Green Chem. 8 (2006) 488.
8] X.M. Ma, B.D. Li, C.X. Lv, et al. Catal. Lett. 141 (2011) 1814.
9] M.A. Zolfigol, E. Madrakian, E. Ghaemi, Molecules 7 (2002) 734.
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
10] S.M. Kemdeo, V.S. Sapkal, G.N. Chaudhari, J. Mol. Catal. A: Chem. 323 (2010) 70.
11] A.S. Khder, A.I. Ahmed, Appl. Chem. A: Gen. 354 (2009) 153.
12] B.M. Choudary, M. Sateesh, M.L. Kantam, et al. Chem. Commun. (2000) 25.
13] K. Smith, A. Musson, G.A. DeBoos, J. Org. Chem. 63 (1998) 8448.
14] S.N. Nagy, J. Phys. Org. Chem. 7 (1994) 385.
15] T. Esakkidurai, K. Pitchumani, J. Mol. Catal. A: Chem. 185 (2000) 305.
16] S. Bernasconi, G. Pringruber, A. Kogelbauer, et al. J. Catal. 219 (2003) 231.
17] M.L. Kantam, B.M. Choudary, N.S. Kumar, et al. J. Mol. Catal. A: Chem. 229 (2005) 67.
18] G. Chehardoli, M.A. Zolfigol, S.B. Azimi, et al. Chin. Chem. Lett. 22 (2011) 827.
19] S. Uemura, A. Toshimitsu, M. Okano, J. Chem. Soc., Perkin Trans. 1 (1978) 1076.
20] F. Nemati, H. Kiani, Chin. Chem. Lett. 21 (2010) 403.
21] J.M. Smith, H. Liu, D.E. Resasco, Stud. Surf. Sci. Catal. 111 (1997) 199.
22] D.B. Akolekar, G. Lemay, A. Sayari, et al. Res. Chem. Intermed. 21 (1995) 7.
23] A. Ghorbani-Choghamarani, H. Goudarziafshar, M. Nikoorazm, et al. Chin. Chem. Lett. 22 (2011) 1431.
24] R.P. Claridge, N.L. Lancaster, R.W. Millar, et al. J. Chem. Soc., Perkin Trans. 2 (1999) 1815.
25] R.R. Bak, A.J. Smallridge, Tetrahedron Lett. 42 (2001) 6767.
26] A.J. Hill, R.W. Millar, J.P.B. Sandall, Org. Biomol. Chem. 2 (2004) 90.
27] H.Z. Zhi, J. Luo, C.X. Lv, et al. Chin. Chem. Lett. 20 (2009) 379.
28] C.L. Coon, W.G. Blucher, M. Hill, J. Org. Chem. 38 (1973) 4243.
29] K. Smith, T. Gibbins, R.W. Millar, et al. J. Chem. Soc., Perkin Trans. 1 (2000) 2753.
30] X. Peng, H. Suzuki, C. Lu, Tetrahedron Lett. 42 (2001) 4357.
31] X. Peng, H. Suzuki, Org. Lett. 3 (2001) 3431.
32] X.M. Ma, B.D. Li, M. Lu, et al. Chin. Chem. Lett. 23 (2012) 73.