Reductive cleavage of azo compounds by zinc and ammonium chloride

Article abstract of DOI:10.1081/SCC-120030694

Azo compounds are reduced to corresponding anilines with zinc dust in the presence of ammonium chloride in methanol at room temperature.

Full text of DOI:10.1081/SCC-120030694

This article was downloaded by: [Fordham University]
On: 13 January 2013, At: 06:42
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer
House, 37-41 Mortimer Street, London W1T 3JH, UK
Synthetic Communications: An International Journal
for Rapid Communication of Synthetic Organic
Chemistry
Publication details, including instructions for authors and subscription information:
http://www.tandfonline.com/loi/lsyc20
Reductive Cleavage of Azo Compounds by Zinc and
Ammonium Chloride
a
a
a
M. B. Sridhara , G. R. Srinivasa & D. Channe Gowda
a
Department of Studies in Chemistry, University of Mysore, Manasagangotri, Mysore,
Karnataka, 570 006, India
Version of record first published: 21 Aug 2006.
To cite this article: M. B. Sridhara , G. R. Srinivasa & D. Channe Gowda (2004): Reductive Cleavage of Azo Compounds by
Zinc and Ammonium Chloride, Synthetic Communications: An International Journal for Rapid Communication of Synthetic
Organic Chemistry, 34:8, 1441-1446
To link to this article: http://dx.doi.org/10.1081/SCC-120030694
PLEASE SCROLL DOWN FOR ARTICLE
Full terms and conditions of use: http://www.tandfonline.com/page/terms-and-conditions
This article may be used for research, teaching, and private study purposes. Any substantial or systematic
reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to
anyone is expressly forbidden.
The publisher does not give any warranty express or implied or make any representation that the contents
will be complete or accurate or up to date. The accuracy of any instructions, formulae, and drug doses
should be independently verified with primary sources. The publisher shall not be liable for any loss, actions,
claims, proceedings, demand, or costs or damages whatsoever or howsoever caused arising directly or
indirectly in connection with or arising out of the use of this material.

w
SYNTHETIC COMMUNICATIONS
Vol. 34, No. 8, pp. 1441–1446, 2004
Reductive Cleavage of Azo Compounds by
Zinc and Ammonium Chloride
*
M. B. Sridhara, G. R. Srinivasa, and D. Channe Gowda
Department of Studies in Chemistry, University of Mysore,
Manasagangotri, Mysore, Karnataka, India
ABSTRACT
Azo compounds are reduced to corresponding anilines with zinc dust
in the presence of ammonium chloride in methanol at room
temperature.
Key Words: Azo compounds; Reductive cleavage; Ammonium chlor-
ide; Zinc dust; Anilines.
INTRODUCTION
Reductive cleavage of azo compounds is a key step in organic chemistry.
Numerous reagents have been developed for the reductive cleavage of azo
*
Correspondence: D. Channe Gowda, Department of Studies in Chemistry, University
of Mysore, Manasagangotri, Mysore, Karnataka 570 006, India; Fax: 091-0821-
2
421263 or 2518835; E-mail: dcgowda@yahoo.com.
441
1
DOI: 10.1081/SCC-120030694
0039-7911 (Print); 1532-2432 (Online)
www.dekker.com
Copyright # 2004 by Marcel Dekker, Inc.

ORDER
REPRINTS
1
442
Sridhara, Srinivasa, and Gowda
However, these methods suffer from one or more
[
1–6]
compound to anilines.
limitations. Currently, we wish to report our novel observation on the
ammonium chloride mediated reductive cleavage of azo compounds to corres-
ponding anilines in the presence of low cost zinc dust (Sch. 1).
The reduction of azo compounds to corresponding anilines in the pre-
sence of zinc dust and ammonium chloride was completed within 5–20 min
at ambient temperature. The course of reaction was monitored by thin layer
chromatography and IR spectra. The reduced products were obtained in
good yields and the products were characterized by comparison of their melt-
ing points, TLC, and IR spectra with authentic samples. The disappearance of
21
a strong absorption band between 1630 and 1575 cm due to the –N 55 N–
stretching and the appearance of a strong absorption band between 3500
2
and 3300 cm due to the –NH group clearly showed that the azo compounds
1
2
had been cleaved into their substituted anilines. Table 1 showed that many
functional groups such as OCH , OH, COOH, CH , COCH , SO Na, and halo-
gens are tolerated during the cleavage step.
3
3
3
3
A control experiment was carried out using azo compounds with
ammonium chloride, in the absence of zinc, the formation of anilines could
not be detected. Methanol was found to be the best solvent.
In summary, this article describes a simple protocol to cleaved azo com-
pounds in their corresponding anilines with good yields in the presence
Zn-NH Cl.
4
EXPERIMENTAL
Materials
Azo compounds were purchased from Aldrich Chemical Company
Sigma-Aldrich, UK) or prepared according to standard procedures reported
(
[
9]
earlier. All of the solvents used were analytical grade or were purified
according to standard procedures. Thin layer chromatography was carried
out on silica gel plates obtained from Whatman Inc. The melting points
Scheme 1.

ORDER
REPRINTS
Reductive Cleavage of Azo Compounds
1443

ORDER
REPRINTS
1
444
Sridhara, Srinivasa, and Gowda

ORDER
REPRINTS
Reductive Cleavage of Azo Compounds
1445
were determined by using a Thomas–Hoover melting point apparatus and are
uncorrected. IR spectra were recorded on a Shimadzu FTIR-8300
spectrometer.
Typical Procedure
A suspension of the azo compound (10 mmol) and zinc dust (10mmol) in
methanol (15mL) or suitable solvent (15mL) and ammonium chloride
(
20 mmol) was stirred under a nitrogen atmosphere at room temperature. After
the completion of the reaction (monitored by TLC) the reaction mixture was
filtered through a Celite pad and washed with solvent. The combined filtrate
and washings were concentrated, the residue dissolved in chloroform (30mL)
or diethyl ether and washed with saturated brine solution (30 mL Â 2) and
water. The organic layer was dried over anhydrous magnesium sulfate and con-
centrated. The residue was purified by preparative TLC or silica gel
chromatography.
ACKNOWLEDGMENT
The authors wish to thank the University Grants Commission, New Delhi,
India, for financial assistance.
REFERENCES
1
. Braude, E.; Linstead, R.P.; Mitchell, P.W.D.; Wooldridge, K.R.H. Hydro-
gen transfer. Part VIII. Metal catalyzed transfer hydrogenation of miscel-
laneous acceptors. J. Chem. Soc. 1954, 3595–3598.
2
3
. Stafford, W.H.; Los, M.; Thomson, N. The reduction of azo-compounds
with hydrazine. Chem. Ind. (London) 1956 (43), 1277.1.
. Ho, T.L.; Olah, G.A. Synthetic methods and reactions; 33. Palladium
catalyzed reductive cleavage of azoarenes and hydrazoarenes to amines
via hydrogen transfer from cyclohexene. Synthesis 1977, 169–170.
. Gilchrist, T.L. Reduction of N 55 N, N–N, N–O, and O–O bonds. In
Comprehensive Organic Synthesis; Trost, B.M., Fleming, I., Eds.; Perga-
mon Press: Oxford, 1991; Vol. 8, Ch. 2.2, 381–402.
4
5
. Jnaneshwara, G.K.; Sudalai, A.; Deshpande, V.H. Palladium catalyzed
transfer hydrogenation of azo compounds and oximes using ammonium
formate. J. Chem. Res. (S) 1998 (3), 160–161.

ORDER
REPRINTS
1
446
Sridhara, Srinivasa, and Gowda
6
. Gowda, D.C.; Gowda, S.; Abiraj, K. Rapid cleavage of azo compounds to
amine/s using Raney nickel and ammonium formate or formic acid. Ind. J.
Chem. 2003, 42B, 1774–1776.
7
8
9
. Vogel, A.I. Text Book of Practical Organic Chemistry; Addison Wesley
Longman Limited: UK, 1997; 1298–1398.
. The Merck Index, 11th Ed.; Budavari, S., Ed.; Merck & Co., Inc.: Rahway,
N.J., USA, 1989; 3247.
. Vogel, A.I.; Wating, A.; Wating, J. The small-scale preparation of azoben-
zene and of hydrazobenzene. J. Chem. Edu. 1958, 35, 40–41.
Received in India November 7, 2003

Request Permission or Order Reprints Instantly!
Interested in copying and sharing this article? In most cases, U.S. Copyright
Law requires that you get permission from the article’s rightsholder before
using copyrighted content.
All information and materials found in this article, including but not limited
to text, trademarks, patents, logos, graphics and images (the "Materials"), are
the copyrighted works and other forms of intellectual property of Marcel
Dekker, Inc., or its licensors. All rights not expressly granted are reserved.
Get permission to lawfully reproduce and distribute the Materials or order
reprints quickly and painlessly. Simply click on the "Request Permission/
Order Reprints" link below and follow the instructions. Visit the
U.S. Copyright Office for information on Fair Use limitations of U.S.
copyright law. Please refer to The Association of American Publishers’
(
AAP) website for guidelines on Fair Use in the Classroom.
The Materials are for your personal use only and cannot be reformatted,
reposted, resold or distributed by electronic means or otherwise without
permission from Marcel Dekker, Inc. Marcel Dekker, Inc. grants you the
limited right to display the Materials only on your personal computer or
personal wireless device, and to copy and download single copies of such
Materials provided that any copyright, trademark or other notice appearing
on such Materials is also retained by, displayed, copied or downloaded as
part of the Materials and is not removed or obscured, and provided you do
not edit, modify, alter or enhance the Materials. Please refer to our Website
User Agreement for more details.
Request Permission/Order Reprints
Reprints of this article can also be ordered at
http://www.dekker.com/servlet/product/DOI/101081SCC120030694