A convenient method for the oxidation of aromatic amines to nitro compounds using tetra-n-alkylammonium bromates

Article abstract of DOI:10.1081/SCC-120039488

Tetra-n-propyl and tetra-n-butylammonium bromates were used for the oxidation of a variety of aromatic amines to nitro compounds. Reaction condition and recovery simple and yield of products high.

Full text of DOI:10.1081/SCC-120039488

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A Convenient Method for
the Oxidation of Aromatic
Amines to Nitro Compounds
Using Tetra‐n‐alkylammonium
Bromates
Satya Sandhya Das a , Utpal Nath a , Dibakar Deb a
& Pranab J. Das a
a Department of Chemistry, Gauhati University,
Guwahati, 781014, India
Published online: 30 Mar 2009.
To cite this article: Satya Sandhya Das , Utpal Nath , Dibakar Deb & Pranab J.
Das (2004) A Convenient Method for the Oxidation of Aromatic Amines to Nitro
Compounds Using Tetra‐n‐alkylammonium Bromates, Synthetic Communications:
An International Journal for Rapid Communication of Synthetic Organic Chemistry,
34:13, 2359-2363, DOI: 10.1081/SCC-120039488
To link to this article: http://dx.doi.org/10.1081/SCC-120039488
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SYNTHETIC COMMUNICATIONSw
Vol. 34, No. 13, pp. 2359–2363, 2004
A Convenient Method for the Oxidation of
Aromatic Amines to Nitro Compounds
Using Tetra-n-alkylammonium Bromates
Satya Sandhya Das, Utpal Nath, Dibakar Deb, and
*
Pranab J. Das
Department of Chemistry, Gauhati University, Guwahati, India
ABSTRACT
Tetra-n-propyl and tetra-n-butylammonium bromates were used for the
oxidation of a variety of aromatic amines to nitro compounds. Reaction
condition and recovery simple and yield of products high.
Key Words: Aromatic amines; Nitro compounds; Quaternary ammonium
salts; Oxidants.
INTRODUCTION
Quaternary ammonium salts, as phase transfer catalysts have been used to
catalyze oxidation of a variety of substrates using oxidants such as O2,[1]
*
Correspondence: Pranab J. Das, Department of Chemistry, Gauhati University,
Guwahati 781014, India; E-mail: pjd123@sify.com.
2359
DOI: 10.1081/SCC-120039488
0039-7911 (Print); 1532-2432 (Online)
www.dekker.com
Copyright # 2004 by Marcel Dekker, Inc.

2360
Das et al.
NaOCl,[2] H2O2,[3] KMnO4, and others.[4,5] In our search for low cost,
sensitive, and easy to handle oxidizing agents, we found that the tetra-n-
alkylammonium bromates prepared from the corresponding tetra-n-alkyl-
ammonium bromides by using chlorine gas in an alkaline medium are useful
for the oxidation of organic substrates. Direct oxidation of aromatic amines to
nitro compounds were reported by using many reagents.[6–11] However, these
methods of oxidation had limitations due to formation of side products formed
mainly from the partial oxidation of the amines, giving moderate yields. In the
present study, the versatility of the tetra-n-propylammonium bromates and
tetra-n-butylammonium bromates as oxidizing agents is established by the
fact that several aromatic amines could be oxidized to the nitro compounds
using simple reaction techniques. Further, work up was simple and the
products were obtained in high yields (Sch. 1; Table 1).
EXPERIMENTAL
General Procedure for Conversion of Tetra-n-
alkylammonium Bromides to Bromates
10 mmol of tetra-n-alkylammonium bromide was dissolved in 50 mL of
5% aqueous NaOH and chlorine gas was passed through the solution till a
yellow oil separated, which solidified on standing. The yellow solid was filt-
ered and dried. Neutralizing the filtrate with acetic acid, precipitated more
products. Using this procedure, both the tetra-n-propyl ammonium bromate
and tetra-n-butylammonium bromate were prepared. Tetra-n-propylammo-
nium bromate (m.p. 1148C, yield 74%) Found: C, 46.2%; H, 9.15%; N,
1
4.18%; requires C, 45.86%; H, 8.92%; N, 4.46%. H-NMR d (CDCl3) 1.2
(3H, t) 2.3 (m, 2H), 4.5 (t, 2H) and tetra-n-butylammonium bromate (m.p.
61–638C, yield 70–75%). Found: C, 50.86%; H, 9.92%; N, 3.93%; requires
C, 51.88%; H, 9.73%; N; 3.78%. 1H-NMR, d (CDCl3) 1.3 (3H, t), 2.3
(m, 2H), 4.8 (t, 2H).
Scheme 1. Oxidation of aromatic amines to nitro compounds.

Oxidation of Aromatic Amines to Nitro Compounds
2361

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Das et al.

Oxidation of Aromatic Amines to Nitro Compounds
General Procedure for the Oxidation
2363
1 mmol of aromatic amine was dissolved in 20 mL of glacial acetic acid
followed by addition of 2 mmol of the tetra-n-alkylammonium bromate and
5 mL of 6 N H2SO4. The solution was refluxed and monitored by TLC. The
reaction was brought to room temperature and poured on crushed ice and
solid filtered. Solid was purified by dissolving in ethanol and poured over
water. The same reaction was also performed by using tetra-n-butylammonium
bromate and similar results were obtained. The products were identified by
[12]
comparing melting points of the products with those found in literature
1
and by comparision of H-NMR spectra. In conclusion, we have devised a
simple method for the preparation of tetra-n-alkylammonium bromates and
used them for the oxidation of aromatic amines to nitro compounds in high
yields.
REFERENCES
1. Neumann, R.; Sasson, Y.J. J. Chem. Soc. Chem. Comm. 1985, 616.
2. Do, J.S.; Chou, T.C. Ind. Eng. Chem. 1990, 29, 1095.
3. Barak, G.; Sasson, Y.J. J. Chem. Soc. Chem. Comm. 1987, 1266.
4. Dehmlow, E.V.; Cyrankiewiez, R. J. Chem. Res. (S) 1990, 24.
5. Kalsi, P.S.; Kaur, P.P.; Singh, J.; Chabra, B. Chem. Ind. (Lond) 1987, 394.
6. Holmes, R.R.; Bayer, R.P. J. Am. Chem. Soc. 1960, 82, 3454.
7. Mckillop, A.; Tarbin, J.A. Tetrahedron Lett. 1983, 24, 1505.
8. Emmons, W.D. J. Am. Chem. Soc. 1957, 79, 5528.
9. Bachman, G.B.; Strawn, K.G. J. Org. Chem. 1968, 33, 131.
10. Keinan, E.; Mazur, Y. J. Org. Chem. 1977, 42, 844.
11. Nielsen, A.T.; Atkins, R.L.; Norris, W.P.; Coon, C.L.; Sitzmanns, M.
J. Org. Chem. 1980, 45, 2341.
12. Clarke, H.T.; Haynes, B. A Handbook of Organic Analysis, Indian Ed.;
Edward Arnold Publishers Ltd.: London, 1986.
Received in India March 8, 2004