Miceller-mediated phosphomolybdic acid: Highly effective reusable catalyst for synthesis of quinoline and its derivatives

Article abstract of DOI:10.1080/00397910903245141

A simple, efficient, and ecofriendly procedure has been developed for the synthesis of quinoline and its derivatives in a one-pot reaction of aniline with crotonaldehyde or methyl vinyl ketone using phosphomolybdic acid as solid acid catalyst in miceller media. The catalyst was easily recycled and reused. Copyrigh

Full text of DOI:10.1080/00397910903245141

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Miceller-Mediated Phosphomolybdic
Acid: Highly Effective Reusable Catalyst
for Synthesis of Quinoline and Its
Derivatives
a b
a
a
Atul Chaskar
, Vikas Padalkar , Kiran Phatangare , Bhushan
a
c
Langi & Chetan Shah
a
Department of Chemistry, Postgraduate and Research Centre, C. K.
Thakur College, Navi Mumbai, Maharashtra, India
b
Dipartimento di Chimica, Materiali Ed Ingegneria Chimica, “Giulio
Natta” Politecnico di Milano, Milan, Italy
c
Radiation and Photochemistry Division, Bhabha Atomic Research
Centre, Trombay, Mumbai, India
Version of record first published: 07 Jul 2010.
To cite this article: Atul Chaskar , Vikas Padalkar , Kiran Phatangare , Bhushan Langi & Chetan Shah
(2010): Miceller-Mediated Phosphomolybdic Acid: Highly Effective Reusable Catalyst for Synthesis
of Quinoline and Its Derivatives, Synthetic Communications: An International Journal for Rapid
Communication of Synthetic Organic Chemistry, 40:15, 2336-2340
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1
Synthetic Communications , 40: 2336–2340, 2010
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397910903245141
MICELLER-MEDIATED PHOSPHOMOLYBDIC ACID:
HIGHLY EFFECTIVE REUSABLE CATALYST FOR
SYNTHESIS OF QUINOLINE AND ITS DERIVATIVES
1
,2
1
Atul Chaskar, Vikas Padalkar, Kiran Phatangare,
1
1
Bhushan Langi, and Chetan Shah
Department of Chemistry, Postgraduate and Research Centre, C. K. Thakur
College, Navi Mumbai, Maharashtra, India
3
1
2
Dipartimento di Chimica, Materiali Ed Ingegneria Chimica, ‘‘Giulio Natta’’
Politecnico di Milano, Milan, Italy
3
Radiation and Photochemistry Division, Bhabha Atomic Research Centre,
Trombay, Mumbai, India
A simple, efficient, and ecofriendly procedure has been developed for the synthesis of quino-
line and its derivatives in a one-pot reaction of aniline with crotonaldehyde or methyl vinyl
ketone using phosphomolybdic acid as solid acid catalyst in miceller media. The catalyst
was easily recycled and reused.
Keywords: Aniline; heteropolyacid; miceller media; quinoline; vinyl aldehydes; vinyl ketones
INTRODUCTION
[
The Skraup procedure is a classical method for the synthesis of quinoline
1]
ꢀ
that involves use of a large amount of sulfuric acid at temperatures above 150 C,
and the reaction is violent. Many other methods have been developed for the syn-
thesis of quinoline, but most of these methods are not fully satisfactory with
[
2–4]
regards to yield, reaction conditions, generality, and operational simplicity.
Quinolines can be synthesized by the Doebner–Miller method, but the yield is poor
and the reaction involves a tedious isolation procedure from a complex reaction
[
5]
mixture.
Although the synthesis of quinoline using InCl on a silica-gel surface is simple
3
[
6]
and efficient under microwave radiation conditions, it has drawbacks, as conven-
tional heating under microwave irradiation induces the polymerization of vinyl
ketone, which ultimately reduces the yield of quinoline. Formation of quinoline
skeleton also has been attempted by the aid of transition metals such as palladium,
[7–11]
rhodium, ruthenium, and iron.
Received March 18, 2009.
Address correspondence to Atul Chaskar, Department of Chemistry, Postgraduate and Research
Centre, C. K. Thakur College, Navi Mumbai, Maharashtra, India. E-mail: achaskar@rediffmail.com
2
336

MICELLER-MEDIATED PHOSPHOMOLYBDIC ACID
2337
Scheme 1. Phosphomolybdic acid–catalyzed synthesis of substituted quinoline from aniline and
ꢀ
alkyl vinyl ketone or aldehyde. (i) Phosphomolybdic acid in toluene, miceller media, 80 C, 50 min.
ꢀ
(
ii) Phosphomolybdic acid in toluene, 100 C, 2 h.
The heteropolyacid (HPA) phosphomolybdic acid is an attractive catalyst not
only for oxidation but also for acid-catalyzed reactions. The poor solubility of HPA
in product media, however, improves product selectivity because of the
phase-transfer separation of reactants and products. The presence of a catalytic
amount of miceller media such as sodium dodecylsulfate (SDS) increases the rate
of reaction and yield. Due to this miceller media reaction, the mass is separated in
two phases, organic and aqueous acidic phase, which decreases the polymerization
[12,13]
of aldehydes and ketones.
Keeping in this mind, herein we report a one-pot, highly efficient synthesis of
quinoline and its derivatives by the reaction of aniline with a,b-unsaturated carbonyl
compounds using phosphomolybdic acid with miceller media (Scheme 1).
RESULTS AND DISCUSSION
In this reaction, the aniline solvated in phosphomolybdic acid forms one phase
and the carbonyl group in toluene forms another phase. The reaction occurs at the
interface and mass transfer is achieved due to micelles. By stirring the reaction mass
vigorously, the reaction rate increases even at low temperature. The product also is
solvated in the catalyst phase, making the product easy to isolate as HPA is insoluble
in toluene.
A wide range of substituted anilines and several alkyl vinyl ketones
were subjected to this process to obtain the corresponding quinolines in excellent
yields using miceller media. The results are presented in Table 1. Table 1 also
shows the effect of different parameters on the yield of product. In general, the
yields of quinoline were little affected by the nature of the substituents of the
aniline. The process involves Michelle addition of the aniline to a,b-unsaturated
carbonyl compound by using phosphomolybdic acid followed by cyclization
and aromatization.
Recovery and reusability of catalyst is the key feature for ecofriendly catalytic
processes. In this protocol, we have used HPA as a recyclable catalyst. After com-
pletion of reaction, the HPA was recovered. In the aqueous layer, ethyl acetate
was added, and this organic layer was dried over anhydrous sodium sulfate. The
ethyl acetate was concentrated under reduced pressure to isolate the product,
and the aqueous layer was evaporated under reduced pressure to isolate the HPA.
The HPA was reused two more times with negligible loss in activity.

2338
A. CHASKAR ET AL.
Table 1. Quinoline derivatives produced by using phosphomolybdic acid with and without miceller media
Yield (%)
a
b
Entry
R
R
1
R
2
Product
With miceller
Without miceller
1
2
3
4
5
6
7
8
9
H
p-Cl
CH
CH
CH
CH
CH
CH
CH
CH
CH
H
3
3
3
3
3
3
3
3
3
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
2a
2b
2c
2d
2e
2f
89
87
88
89
88
94
91
81
79
91
87
89
92
92
94
97
83
80
84
81
82
82
81
87
85
79
74
85
82
83
86
86
88
90
81
76
m-Cl
p-Me
m-Me
p-OMe
o-OMe
2g
2h
2i
p-NO
2
m-NO
H
2
1
1
1
1
1
1
1
1
1
0
1
2
3
4
5
6
7
8
2j
p-Cl
m-Cl
p-Me
H
2k
2l
H
H
2m
2n
2o
2p
2q
2r
m-Me
p-OMe
o-OMe
H
H
H
p-NO
m-NO
2
H
2
H
a
b
ꢀ
The reaction mixture was stirred at 80 C for 50 min with miceller media.
ꢀ
The reaction mixture was stirred at 100 C for 2 h without miceller media.
EXPERIMENTAL
General Remarks
All commercial reagents were used as received without any purification, and all
solvents were of reagent grade. The reaction was monitored by thin-layer chromato-
graphy (TLC) on 0.25-mm E-Merck silica-gel 60 F254 precoated plates, which were
visualized with ultraviolet (UV) light. Melting points were taken in open capillaries.
The infrared (IR) spectra were recorded on a Perkin-Elmer 257 spectrometer using
1
13
KBr discs. H NMR and C NMR spectra were recorded on a VXR 300-MHz
instrument using tetramethylsilane (TMS) as an internal standard.
General Procedure
Aniline (0.1 mol) was added to the solution of phosphomolybdic acid
0.001 mol) dissolved in 8 ml of water and 0.001 mol of sodium dodecylsulfate
miceller). To this, crotonaldehyde (0.15 mol) was added with 10 ml of toluene,
and the mixture was vigorously stirred at 80 C for 1 h. After completion of
the reaction, the lower layer was separated and basified using a sodium bicar-
bonate solution, and the product was extracted with ethyl acetate. Ethyl acetate
was dried over sodium sulfate and concentrated to get a crude product, which
was further purified by column chromatography over silica gel in EtOAc and
hexane (1:9).
(
(
ꢀ

MICELLER-MEDIATED PHOSPHOMOLYBDIC ACID
2339
Representative Data (2j)
ꢁ
1 1
IR (KBr): 1600, 1505, 1420, 818 cm . H NMR (CDCl ): d 2.18 (s, 3H), 7.18
3
(
1
d, 1H, J ¼ 8.6 Hz), 7.39 (m, 1H), 7.61 (m, 1H), 7.71 (d, 1H, J ¼ 8.6 Hz), 7.85 (d,
H, J ¼ 7.2 Hz), 8.00 (d 1H, J ¼ 7.2 Hz) ppm. CMR (CDCl ): d 26, 122, 127, 128,
3
1
H, 6.34; N, 9.78. Found: C, 84.01; H, 6.28; N, 9.72.
29, 130, 132, 137, 148, 160 ppm. Elemental analysis for C H N: Calcd. C, 83.88;
9
1
0
CONCLUSION
In summary, we have developed an efficient, simple, and practical method for
the synthesis of quinoline and its derivatives. The reaction is catalyzed by safe,
stable, easily prepared phosphomolybdic acid and has been carried out in miceller
media. The process has several advantages over many reported literature proce-
dures from economical and environmental points of view, such as operational
simplicity, short reaction time, excellent yield of the product, and recyclability of
the catalyst.
We believe that this will provide a better and more practical alternative to the
existing methodologies for the synthesis of quinoline and its derivatives.
ACKNOWLEDGMENTS
The authors are grateful to the University Grant Commission, New Delhi, and
the University of Mumbai for financial support. Thanks go to Dr. S. T. Gadade,
principal, C. K. Thakur College, for providing laboratory and other facilities.
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2
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