Modified clays as efficient acid-base catalyst systems for diazotization and diazocoupling reactions

Article abstract of DOI:10.1081/SCC-120016343

Diazotization and diazocoupling reactions of aniline and its substituted derivatives with phenol and other aromatic amines over ecofriendly clay catalysts is described. This inexpensive, non-corrosive and reusable catalysts were found to exhibit bifunctional catalytic properties for these reactions. No considerable decrease in the efficiency of the catalysts were observed after five cycles of operation. The new method totally avoids the use of acids and alkalies.

Full text of DOI:10.1081/SCC-120016343

This article was downloaded by: [Tulane University]
On: 23 August 2013, At: 23:07
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
Modified Clays as Efficient Acid–Base Catalyst Systems
for Diazotization and Diazocoupling Reactions
a
a
a
Damodaran Bahulayan , Litka John & Malathy Lalithambika
a
Clays and Clay Minerals Division, Regional Research Laboratory (CSIR), Kerala, India
Published online: 17 Aug 2006.
To cite this article: Damodaran Bahulayan , Litka John & Malathy Lalithambika (2003) Modified Clays as Efficient Acid–Base
Catalyst Systems for Diazotization and Diazocoupling Reactions, Synthetic Communications: An International Journal for Rapid
Communication of Synthetic Organic Chemistry, 33:6, 863-869, DOI: 10.1081/SCC-120016343
To link to this article: http://dx.doi.org/10.1081/SCC-120016343
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained
in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no
representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the
Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and
are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and
should be independently verified with primary sources of information. Taylor and Francis shall not be liable for
any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever
or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of
the Content.
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. Terms & Conditions of access and use can be found at http://
www.tandfonline.com/page/terms-and-conditions

MARCEL DEKKER, INC. • 270 MADISON AVENUE • NEW YORK, NY 10016
©
2003 Marcel Dekker, Inc. All rights reserved. This material may not be used or reproduced in any form without the express written permission of Marcel Dekker, Inc.
Õ
SYNTHETIC COMMUNICATIONS
Vol. 33, No. 6, pp. 863–869, 2003
Modified Clays as Efficient Acid–Base
Catalyst Systems for Diazotization and
Diazocoupling Reactions
Damodaran Bahulayan,* Litka John, and
Malathy Lalithambika
Clays and Clay Minerals Division, Regional Research
Laboratory (CSIR), Kerala, India
ABSTRACT
Diazotization and diazocoupling reactions of aniline and its
substituted derivatives with phenol and other aromatic amines over
ecofriendly clay catalysts is described. This inexpensive, non-
corrosive and reusable catalysts were found to exhibit bifunctional
catalytic properties for these reactions. No considerable decrease in
the efficiency of the catalysts were observed after five cycles of opera-
tion. The new method totally avoids the use of acids and alkalies.
*
Correspondence: Damodaran Bahulayan, Clays and Clay Minerals Division,
Regional Research Laboratory (CSIR), Trivandrum, 695 019, India; E-mail:
bahulayan@yahoo.com.
8
63
DOI: 10.1081/SCC-120016343
Copyright & 2003 by Marcel Dekker, Inc.
0039-7911 (Print); 1532-2432 (Online)
www.dekker.com

MARCEL DEKKER, INC. • 270 MADISON AVENUE • NEW YORK, NY 10016
©
2003 Marcel Dekker, Inc. All rights reserved. This material may not be used or reproduced in any form without the express written permission of Marcel Dekker, Inc.
8
64
Bahulayan, John, and Lalithambika
Key Words: Diazotization; Diazocoupling; Bifunctional; Clays;
Green.
Diazotization and diazocoupling reactions are important class of
organic reactions, which are currently performed with mineral acids and
[1,2]
alkalies as catalysts.
These conventional acid–base catalyzed
processes are effective for the near quantitative formation of the desired
products. But the main limitation of such synthetic processes is their
environmental incompatibility. The acidic and basic effluents from the
laboratory and industry produce permanent damage to the environment
[
3]
and disturb the ecological balance. In recent years, clay based catalysts
are reported to be effective for performing many of the acid–base
catalyzed organic reactions in
manner.
a
As part of our ongoing research programme for exploring
better environmentally benign
[4,5]
the bifunctional catalytic properties of clay based layered silicates, here
we describe a new process for diazotization and diazocoupling reactions in
which acidic and basic catalysts are required in a sequential manner.
We have studied the performance of three clay based catalysts
denoted as KK, GB and K10 for the said reactions. Out of this, KK
and GB are procured from local sources and belong to kaolinite and
bentonite variety respectively. K10 is procured from Aldrich and used
as such.
In the present synthesis, the amine was first made into a paste
ꢀ
with clay catalyst and it was then cooled to 0 C (Sch. 1). This
amine clay mixture was then diazotized with dil. NaNO2 solution.
Scheme 1.

MARCEL DEKKER, INC. • 270 MADISON AVENUE • NEW YORK, NY 10016
©
2003 Marcel Dekker, Inc. All rights reserved. This material may not be used or reproduced in any form without the express written permission of Marcel Dekker, Inc.
Diazotization and Diazocoupling Reactions
865
The diazonium-clay complex formed was subsequently coupled with
phenol or amine. The azo dye thus formed was separated from the cat-
alyst by extracting it into alcohol or acetone and from where it was
recovered by removal of the solvent under vacuum. The generality of
the process is proved by performing the reaction with all the three cata-
lysts and with different amines and coupling agents. In almost all the
cases, the isolated yield of the pure products were found to be near
quantitative (Table 1). A notable high yield of the azo coupled product
was obtained in the case of a weakly basic amine like p-nitro aniline,
which gave >80% yield for the dye in the present synthesis (Entry 7,
Table 1).
Table 1. Diazotization and diazocoupling reactions of aniline and its substituted
derivatives with phenol and aniline over KK, GB and K10.
%
Yield*
Coupling
agent
Entry
1
Amine
Product
K.K. G.B. K10
97
94
96
99
94
97
91
88
92
2
3
4
94
98
94
5
6
96
92
96
95
91
89
7
88
90
81
8
9
93
91
80
95
91
81
89
90
80
1
*
0
Isolated pure products.

MARCEL DEKKER, INC. • 270 MADISON AVENUE • NEW YORK, NY 10016
©
2003 Marcel Dekker, Inc. All rights reserved. This material may not be used or reproduced in any form without the express written permission of Marcel Dekker, Inc.
8
66
Bahulayan, John, and Lalithambika
Control reactions were carried out with the same reagents in the
presence of mineral acids like HCl and bases by following
the conventional procedure for comparing the yields. All substrates
except p-nitro aniline yielded the corresponding dye in the range of
75–80% and are found to be slightly less than the same obtained
from the present clay based process. For p-nitro aniline, the conversion
was found to be <50%.
Recyling ability of the catalysts were also studied. For this purpose,
the catalysts after the removal of the azo dyes were washed several times
ꢀ
with acetone and dried at 110 C in an air oven for 1 h. These oven dried
ꢀ
samples were then calcined at 450 C for 3 h in a furnace and used for
performing the reactions. This process was repeated 5 times and no
considerable decrease in the yield of the azo dyes were observed. The
results obtained for the recycling reactions of aniline and phenol is
given in Table 2.
A plausible mechanism proposed for the present method is given in
Sch. 2). After the formation of the diazonium-clay complex, the edge
(
hydroxyls of the clay platelets are believed to get converted into
þ
–
ONa species by consuming the Na ions from NaNO solution used
2
for diazotization. This –ONa species helps to maintain the pH of
the medium neutral or slightly alkaline for a quantitative coupling
of the diazonium ion with the coupling agent.
In conclusion, we have developed a highly efficient ‘green’
methodology for diazotization and diazocoupling reactions by employing
clay catalysts with better recycling options and totally avoids the use of
acids, alkalies and toxic solvents.
Table 2. Results of the recycling reactions with GB and KK.
%
Yield*
Coupling
agent
Catalyst
G.B.
Amine
0 cycle I cycle II cycle III cycle IV cycle
99
90
88
97
99
90
88
96
97
89
88
96
97
89
85
95
97
89
85
95
G.B.
K.K
K.K.
*
Isolated pure products.

MARCEL DEKKER, INC. • 270 MADISON AVENUE • NEW YORK, NY 10016
©
2003 Marcel Dekker, Inc. All rights reserved. This material may not be used or reproduced in any form without the express written permission of Marcel Dekker, Inc.
Diazotization and Diazocoupling Reactions
867
Scheme 2.
EXPERIMENTAL
General
The montmorilonite K10 clay catalyst was procured from
Aldrich Chemicals and used as such. The kaolinite clay used for the prep-
aration of catalyst (K.K.) was collected from the diagentic clay deposits of
Quilon district, Kerala, India. The bentonite clay used for the
preparation of catalyst (G.B.) was procured from Ashapura mines of
Gujarat State, India. The amines were procured from E-Merck (India)
Limited and used as such. Azo dyes formed were systematically
1
characterized by GC–MS, H NMR and IR spectral analyses.
Preparation of the Kaolinite Clay Catalyst KK
The raw clay was first subjected to coning and quartering to obtain a
sample which is representative of the bulk. This was then subjected to
slacking to remove soluble impurities and is then sieved using À350
mesh. The fine grained clay particle obtained was dried and powdered.
ꢀ
It was then calcined at 550 C (metakaolinization) for 4 h. The
metakaolinized sample was then activated with 2 M HCl in the solid to
liquid ratio 1:4 (400 mL 2 M HCl for 100 g clay) for a period of 45 min and
filtered. It was then washed thoroughly with distilled water for
ꢀ
removing chloride ions and dried in an air oven at 110 C for 2 h.

MARCEL DEKKER, INC. • 270 MADISON AVENUE • NEW YORK, NY 10016
©
2003 Marcel Dekker, Inc. All rights reserved. This material may not be used or reproduced in any form without the express written permission of Marcel Dekker, Inc.
8
68
Bahulayan, John, and Lalithambika
ꢀ
Then acid activated clay was again calcined at 400 C for a period of 3 h and
used for the reaction. SiO 55.8%, Al O 25.69%, Fe O 2.24%, TiO
2
2
3
2
3
2
1.93%, Na O 0.08%, K O 0.26%, Loss on ignition (LOI) 8.45%,
Ho 0.03 mmol/g and Surface area (B.E.T.) 53.634 m /g.
2 2
2
Preparation of Bentonite Clay Catalyst GB
The bentonite clay (GB) was collected from Ashapura mines of
Gujarat State, India and purified by adopting the same procedure
mentioned above for KK. The À350 fractions collected was dried and
ꢀ
calcined at 450 C for 4 h and used as such for reaction. SiO 56.19%,
2
Al O 15.56%, Fe O 7.59%, TiO 0.79%, CaO 5.68%, MgO 4.98%,
2
3
2
3
2
Loss on ignition (LOI) 14.2%, Ho 0.043 mmol/g and Surface area
(
2
B.E.T.) 98.30 m /g.
Representative Procedure for Diazotization and Diazocoupling
Reactions
In a typical experiment, 4.67 g of (0.05 mol) of aniline was adsorbed
ꢀ
on 8 g of clay (KK) catalyst and cooled to 0 C. To this, 4.34 g (0.1 mol)
of NaNO i n 15 mL HO was added dropwise for a period of 1 h. After
the addition of NaNO , 4.67 g (0.05 mol) of phenol was added to this ice
2
2
2
cold diazonium clay complex and was brought to room temperature with
constant stirring and kept at room temperature for 1 h. The reaction
mixture was then repeatedly extracted into alcohol. The alcohol extracts
evaporation under vacuum afforded 1.
À1
Selected data for 1: IR(KBr cm ): 1625 (–N¼N–), 3400 (OH), UV
1
(
ꢀmax nm) 415. H NMR (CDCl /DMSO, 300 MHz). ꢁ9.8 (s, 1H, –OH),
3
8
1
.1–8.4 (m, 4H, phenyl), 7.3–6.9 (m, 5H, phenyl), GC–MS OV 101, Rt
À1
þ
0.57 min m/z. 198 (M ) 2. (IR KBr cm ) 1621 (–N¼N–) 3425 (NH ),
2
1
UV (ꢀmax nm) 420, H NMR (CDCl /DMSO 300 MHz): ꢁ3.8 (s, 2H,
3
–
1
NH ), 8.1–8.3 (m, 4H, phenyl), 7.2–6.9 (m, 5H, phenyl), GC–MS OV
2
þ
À1
01 Rt 10.53 min m/z 197 (M ). 3. IR(KBr cm ): 1625 (–N¼N–), UV
1
(
6
ꢀmax nm) 420, H NMR (CDCl /DMSO) ꢁ2.96 (s, 6H, 2 ꢁ CH ),
3
3
.72–7.36 (m, 9H, 2 ꢁ C H ), GC–MS OV 101, Rt 12.77 min; m/z 225
6
5
þ À1
(
M ). 4. IR(KBr cm ): 1625 (–N¼N–), 3411 (OH), UV (ꢀmax nm) 415.
3 3
1
H NMR (CDCl /DMSO) ꢁ2.1 (s, 3H, CH ), 9.8 (s, 1H, –OH), 8.1–8.3
m, 4H, phenyl), 7.1–7.4 (m, 4H, phenyl), GC–MS OV 101, Rt 11.22 min;
(
þ
À1
m/z 212 (M ). 5. IR(KBr cm ) 3400–3450 (OH), 1621 (–N¼N–), 1510,
1
1
340 (NO ), UV (ꢀmax nm) 270, 390. H NMR ꢁ8.1–8.3 (m, 4H, phenyl),
2

MARCEL DEKKER, INC. • 270 MADISON AVENUE • NEW YORK, NY 10016
©
2003 Marcel Dekker, Inc. All rights reserved. This material may not be used or reproduced in any form without the express written permission of Marcel Dekker, Inc.
Diazotization and Diazocoupling Reactions
869
6
2
.7–7.36 (m, 4H, nitrophenyl), GC–MS OV 101, Rt 11.30 min; m/z
þ
43 (M ).
ACKNOWLEDGMENT
D.B. thanks SERC, Department of Science and Technology,
Govt. of India for providing financial support under FAST TRACK
Scheme for Young Scientists (SR/FTP/CS-17/2000).
REFERENCES
1
2
3
4
5
. Zollinger, H. Azo and Diazo Chemistry, Aliphatic and Aromatic
Compounds, Interscience Publishers Ltd.: London, 1961.
. Saunders, K.H.; Allen, R.L.M. Aromatic Diazo Compounds; 3rd Edn;
Edward Arnold (Publishers) Ltd.: London, 1985.
. Clark, J.H. Chemistry of Waste Minimization; Ed. Chapman and
Hall: London, 1995.
. Clark, J.H. Catalysis of Organic Reactions by Supported Inorganic
Reagents; VCH: New York, 1994.
. (a) Cornilis, A.; Laszlo, P. Synlett. 1994, 155; (b) Clark, J.H.;
Macquarrie, D.J. Chem. Commun. 1998, 853; (c) Clark, J.H.;
Macquarrie, D.J. Org. Process Res. Dev. 1997, 1, 149; (d) Varma,
R.S.; Naicker, K.P.; Aschberger J. Synth. Commun. 1999, 29, 2823;
(
e) Meshram, H.M.; Sumithra, G.; Reddy. G.S.; Ganesh, Y.S.S.;
Yadav, J.S. Synth. Commun. 1999, 29, 2807; (f ) Hui-Yan Duan; Jian-
Xian-Xin Wang; Jong-Shunghi. Synth. Commun. 1999, 29, 3197;
(
g) Mojtahedi, M.M.; Saidi, M.R.; Bolourtchian, M.; Heravi, M.M.
Synth. Commun. 1999, 29, 3283; (h) Freeman, B.A.; Smith, K.M.
Synth. Commun. 1999, 29, 1843; (i) Lalithambika, M.; Sukumar. R.;
Bahulayan. D.; Sabu, K.R.; Bull. Catal. Soc. India 1999, 9, 155;
(
j) Bahulayan, D.; Sukumar, R.; Sabu, K.R.; Lalithambika, M. Green
Chemistry 1999, 1, 191; (k) Choudhary, B.M.; Sateesh, M.;
Lakshmikantam, M.; Koteesara Rao, K.; Ramprasad, K.V.;
Raghavan, K.V.; Sharma, J.A.R.P. Chem. Commun. 2000, 25;
(
4
l) Samajdar, S.; Becker, F.R.; Naik, B.K. Tetrahedron Letters 2000,
1, 8017; (m) Bahulayan, D.; Narayan, G.; Sreekumar, V.;
Lalithambika, M. Synth. Commun. 2002, 32, 3565.
Received in the Netherlands March 22, 2002

MARCEL DEKKER, INC. • 270 MADISON AVENUE • NEW YORK, NY 10016
©
2003 Marcel Dekker, Inc. All rights reserved. This material may not be used or reproduced in any form without the express written permission of Marcel Dekker, Inc.