H3Mo12O40P-catalyzed one-pot synthesis of amidoalkyl naphthols

Article abstract of DOI:10.1080/00397910902885541

Solid H3Mo12O40P is used for an efficient one-pot synthesis of amidoalkyl naphthols using aromatic aldehydes,-naphthol, and urea or amides in carbon tetrachloride. The catalyst was efficiently recovered from the reaction mixture and reused with negligible loss of catalyst activity. Ambient conditions, simple workup, and good yield are some of the striking features of the present protocol.

Full text of DOI:10.1080/00397910902885541

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H3Mo12O40P-Catalyzed One-
Pot Synthesis of Amidoalkyl
Naphthols
Preeti Gawand a , Hrushikesh Deokar a , Bhushan
Langi a , Arun Yadav b & Atul Chaskar a c
a C. K. Thakur Research Centre, Navi Mumbai,
Maharashtra, India
b Institute of Science, Mumbai, India
c Dipartimento di Chimica, Materiali Ed Ingegneria
Chimica “Giulio Natta”, Politecnico di Milano, Italy
Version of record first published: 29 Oct 2009
To cite this article: Preeti Gawand, Hrushikesh Deokar, Bhushan Langi, Arun Yadav
& Atul Chaskar (2009): H3Mo12O40P-Catalyzed One-Pot Synthesis of Amidoalkyl
Naphthols, Synthetic Communications: An International Journal for Rapid
Communication of Synthetic Organic Chemistry, 39:23, 4171-4179
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Synthetic Communications1, 39: 4171–4179, 2009
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397910902885541
H3Mo12O40P-Catalyzed One-Pot Synthesis
of Amidoalkyl Naphthols
Preeti Gawand,1 Hrushikesh Deokar,1 Bhushan Langi,1
Arun Yadav,2 and Atul Chaskar1,3
1C. K. Thakur Research Centre, Navi Mumbai, Maharashtra, India
2Institute of Science, Mumbai, India
3Dipartimento di Chimica, Materiali Ed Ingegneria Chimica
‘‘Giulio Natta’’, Politecnico di Milano, Italy
Abstract: Solid H3Mo12O40P is used for an efficient one-pot synthesis of
amidoalkyl naphthols using aromatic aldehydes, b-naphthol, and urea or amides
in carbon tetrachloride. The catalyst was efficiently recovered from the reaction
mixture and reused with negligible loss of catalyst activity. Ambient conditions,
simple workup, and good yield are some of the striking features of the present
protocol.
Keywords: Amidoalkyl naphthols, aryl aldehyde, b-naphthol, one-pot reaction,
phosphomolybdic acid, urea or amides
INTRODUCTION
Multicomponent reactions (MCRs) have gained importance because of
their merits over two-component reactions, including the simplicity of a
one-pot procedure and wide variety of applications in organic and
medicinal chemistry.[1] Because these MCRs are one-pot processes in
which three or four accessible components react to form a single
product, the results of the MCRs can be achieved in a very fast, efficient,
and time-saving manner without isolation of any intermediate.[2]
Recently, there has been development of three- and, four-component
Received December 18, 2008.
Address correspondence to Atul Chaskar, C. K. Thakur Research Centre,
Navi Mumbai, Maharashtra, India 410206. E-mail: achaskar@rediffmail.com
4171

4172
P. Gawand et al.
Scheme 1. Synthesis of amidoalkyl naphthol.
reactions: the Biginelli,[3] Ugi,[4] Passerini,[5] Bucherer–Bergs,[6] and
Mannich[7] reactions.
Heteropolyacids (HPAs) are used as catalysts in various fine
chemical processes.[8] Compared to conventional organic and inorganic
acids, the HPAs are more active, as they have high acid strengths, low
reducibility, and thermal stability. Along with these characteristics, they
are noncorrosive and environmentally gentle. HPAs have attracted much
interest in synthetic chemistry because of their easy workup and minimi-
zation of waste due to recyclability and reuse.[9] HPAs are used in various
liquid-phase reactions such as alcohol dehydration, alkylation, and
esterification reactions.
In continuation of our interest in exploring new catalytic activities
of phosphomolybdic acid (H3Mo12O40P) in MCRs, herein we report a
simple and convenient method for the synthesis of amidoalkyl naphthols
by condensation of b-naphthol, aryl aldehyde, and urea or amide in the
presence of phosphomolybdic acid as a catalyst (Scheme 1).
RESULTS AND DISCUSSION
We have studied the effect of various organic solvents on the yield and
rate of the reaction. Organic solvents (viz. 1,4-dioxan, acetonitrile,
methanol, carbon tetrachloride, dichloromethane, tetrahydrofuran,
Table 1. Solvent effect on reaction of benzaldehyde, b-naphthol, and benzamide
catalyzed by H3Mo12O40P
Entry
Solvent
Time (h)
Yield (%)
1
2
3
4
5
6
7
8
1,4-Dioxan
Acetonitrile
Methanol
Carbon tetrachloride
Dichloromethane
Tetrahydrofurane
Chloroform
6
3
5
1.5
2
5
3
2
62
79
68
85
80
65
72
83
Ethylene dichloride

Synthesis of Amidoalkyl Naphthols
4173
Table 2. Synthesis of amido alkyl naphthols in the presence of catalytic amounts
of H3Mo12O40P
Time Yield
(h) (%)
Entry Aldehyde
Urea=amide
Product
1
H2NÀCOÀNH2
1.5
2.5
2
85
82
83
80
2
3
4
H2NÀCOÀNH2
H2NÀCOÀNH2
H2NÀCOÀNH2
4
5
H2NÀCOÀNH2
2
84
(Continued )

4174
P. Gawand et al.
Table 2. Continued
Time Yield
(h) (%)
Entry Aldehyde
Urea=amide
Product
6
H3CÀCOÀNH2
1.5
84
7
H3CÀCOÀNH2
H3CÀCOÀNH2
H3CÀCOÀNH2
3
81
8
2.5
82
9
3.5
81
10
H3CÀCOÀNH2
2
83
(Continued )

Synthesis of Amidoalkyl Naphthols
4175
Table 2. Continued
Time Yield
(h) (%)
Entry Aldehyde
Urea=amide
Product
11
PhÀCOÀNH2
2
84
12
PhÀCOÀNH2
3
82
13
PhÀCOÀNH2
3
83
14
PhÀCOÀNH2
4
79
15
PhÀCOÀNH2
3
81
(Continued )

4176
P. Gawand et al.
Table 2. Continued
Time Yield
(h) (%)
Entry Aldehyde
Urea=amide
Product
16
H2NÀCOÀNH2
3
79
17
H2NÀCOÀNH2
2.5
85
18
H3CÀCOÀNH2
2.5
78
chloroform, and ethylene dichloride) were selected for the study. The best
result was obtained with carbon tetrachloride (Table 1).
Various aromatic aldehydes were refluxed with b-naphthol and urea
or amides in CCl4, in the presence of a catalytic amount of H3Mo12O40P.
The corresponding amido alkyl naphthols were obtained in good to
excellent yield. The results are summarized in Table 2.
The aromatic aldehyde with an electron-withdrawing group reacted
much faster than the aromatic aldehyde bearing an electron-donating
group. However, the type of the substituent on the aromatic aldehydes
does not show much effect on the yield of the product. The electron-
donating as well as electron-withdrawing substituents on the aromatic
ring resulted in good to excellent yields.
The effectiveness of catalyst was investigated. The reactions of
para-substituted aromatic aldehyde such as p-methylbenzadehyde, p-
methoxybenzaldehyde, and m-nitrobenzaldehyde were studied, and reac-
tions resulted in good yield with enhanced rate of reaction without any
side products.

Synthesis of Amidoalkyl Naphthols
CONCLUSION
4177
In conclusion, a one-pot, simple, and efficient process to afford
diversified amidoalkyl naphthols via three-component reaction of
b-naphthol, aryl aldehyde, and urea or amide using phosphomolybdic
acid as catalyst was developed. The process has several advantages over
reported literature from economical and environmental points of view,
such as operational simplicity, mild reaction conditions, good yield of
the product, recyclability, and reuse of catalyst.
EXPERIMENTAL
All commercial reagents are used as received without purification, and all
solvents were reagent grade. The reaction mixture was stirred magneti-
cally in a round-bottomed flask and was monitored by thin-layer chro-
matography (TLC) using 0.25-mm Merck silica-gel 60 F254 precoated
plates, which were visualized with ultra violet (UV) light. Melting points
were taken in open capillaries. The infrared (IR) spectra were recorded
on a Perkin-Elmer 257 spectrometer using KBr discs. 1H NMR and
13C NMR spectra in dimethyl sulfoxide (DMSO-d6) were recorded on
a VXR 300-MHz instrument using tetramethylsilane (TMS) as internal
standard.
General Experimental Procedure
A mixture of aromatic aldehyde (1 mmol), b-naphthol (1 mmol), urea or
amides (1 mmol), and phosphomolebdic acid (0.0002 mol) in CCl4 was
refluxed for the appropriate time as indicated in Table 2. After
completion of reaction, as indicated by TLC, the solvent was removed
under pressure. The solid was washed with water and recrystallized
from ethanol.
Representative Spectral Data (11)
IR (KBr): 3385, 2900, 1640, 1530, 1418, 1320, 1259, 1060, 978,
1
815 cmÀ1. H NMR (DMSO-d6 d-ppm): 5.1 (s, 1H, OH), 6.79 (s, 1H),
6.98 (d, 1H), 7.20–7.50 (m, 15H), 7.8 (s, 1H, NH). CMR (DMSO-
d6 d-ppm): 167, 153.5, 138, 135, 134, 132.50, 131, 130, 129, 128.80,
128.40, 128, 127.50, 127, 126.50, 126, 125.80, 125.50, 125, 124.50, 122,
119, 115, 54.

4178
P. Gawand et al.
ACKNOWLEDGMENTS
We gratefully acknowledge the financial support from the University
Grants Commission, New Delhi, and the University of Mumbai. We
thank Dr. S. T. Gadade, principal, C. K. Thakur College, for providing
all the facilities.
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