Synthesis of biscoumarin derivatives using poly(4-vinylpyridine)-supported dual acidic ionic liquid as a heterogeneous catalyst

Article abstract of DOI:10.1007/s00706-014-1156-2

A supported dual acidic ionic liquid catalyst was easily prepared from its starting materials (namely poly(4-vinylpyridine) and 1,4-butanesultone) and used as a highly efficient heterogeneous catalytic system for the synthesis of biscoumarin derivatives f

Full text of DOI:10.1007/s00706-014-1156-2

Monatsh Chem
DOI 10.1007/s00706-014-1156-2
ORIGINAL PAPER
Synthesis of biscoumarin derivatives using
poly(4-vinylpyridine)-supported dual acidic ionic liquid
as a heterogeneous catalyst
•
Kaveh Parvanak Boroujeni Parvin Ghasemi
•
Zahra Rafienia
Received: 7 June 2012 / Accepted: 10 January 2014
Ó Springer-Verlag Wien 2014
Abstract A supported dual acidic ionic liquid catalyst
was easily prepared from its starting materials (namely
poly(4-vinylpyridine) and 1,4-butanesultone) and used as a
highly efficient heterogeneous catalytic system for the
synthesis of biscoumarin derivatives from the reaction of
4-hydroxycoumarin with aliphatic and aromatic aldehydes.
The catalyst can be easily recovered and reused without
appreciable change in its efficiency.
difficult to handle, and corrosion problems. Thus, these
shortcomings make them a prime target for heterogeniza-
tion [6–9].
Coumarin is a fragrant chemical compound in the
benzopyrone chemical class, and it is found in many plants
[10]. There is widespread interest in the synthesis of cou-
marin and its derivatives owing to their diverse range of
biological properties such as anti-HIV, antibiotic, anti-
fungal, antibacterial, antioxidant, anticancer, and
anticoagulant [11–15]. Also, they have been used as fluo-
rescent brighteners, efficient laser dyes, and as additives in
food and cosmetics [16–18]. Biscoumarins are one of the
most important derivatives of coumarin. Among several
methods reported for the synthesis of biscoumarins [16,
19–21], two-component one-pot domino Knoevenagel-type
condensation/Michael reaction between aldehydes and
4-hydroxycoumarin is particularly popular. Catalysts that
have been used for this conversion include piperidine [22],
tetrabutylammonium bromide [23], I2 [24], sodium dodecyl
sulfate [25], ionic liquids [26–28], p-dodecylbenzenesulf-
onic acid/piperidine [29], NaHSO4 [30], and B(HSO4)3
[31]. However, most of the reported methods suffer from
one or more of the following drawbacks: low yields, long
reaction times, harsh reaction conditions, tedious work-up
leading to the generation of large amounts of toxic waste,
inefficiency when aliphatic aldehydes are used in the
reaction, and the use of unrecyclable, hazardous, or diffi-
cult-to-handle catalysts.
Keywords Biscoumarins ꢀ Aldehydes ꢀ
Poly(4-vinylpyridine)-supported ionic liquid ꢀ
One-pot synthesis ꢀ Heterogeneous catalysis
Introduction
Brønsted acidic ionic liquids have been widely applied in
many reactions as catalysts or dual catalyst–solvents. They
are designed to replace traditional mineral liquid acids such
as sulfuric acid and hydrochloric acid in chemical proce-
dures [1, 2]. Among them, SO3H-functionalized ionic
-
liquids possessing HSO4 as a counteranion find a broad
range of applications in organic synthesis because the
existence of both SO3H functional groups and hydrogen
sulfate counteranions can enhance their catalytic acidities
[3–5]. Although the catalytic ability of these ionic liquids
has been demonstrated successfully in many reactions,
most of them suffer from one or more of the following
drawbacks such as laborious work-up procedures, difficulty
of recovery and recycling, disposal of spent catalyst,
In a continuation of our work on the development of
efficient and environmentally benign procedures using
poly(vinylpyridine)-supported reagents and catalysts [32],
we found that poly(4-vinylpyridine-co-1-sulfonic acid
butyl-4-vinylpyridinium)hydrogen sulfate ([P4VPy–BuSO3
H]HSO4) is a good catalyst for the synthesis of 4,40-(a-
rylmethylene)bis(3-methyl-1-phenyl-1H-pyrazol-5-ols) [33].
K. Parvanak Boroujeni (&) ꢀ P. Ghasemi ꢀ Z. Rafienia
Department of Chemistry, Shahrekord University,
115, Shahrekord, Iran
e-mail: parvanak-ka@sci.sku.ac.ir
123

K. Parvanak Boroujeni et al.
We now wish to report that [P4VPy–BuSO3H]HSO4 is also an
efficient catalyst for the synthesis of biscoumarins by two-
component one-pot domino Knoevenagel-type condensation/
Michael reaction between various aliphatic and aromatic
aldehydes and 4-hydroxycoumarin.
aldehydes with 4-hydroxycoumarin (Table 1). Initially, to
optimize the reaction conditions, we tried to convert
benzaldehyde (1 mmol) to 3,30-benzylidenebis(4-hy-
droxycoumarin) with 4-hydroxycoumarin (2 mmol) and
[P4VPy–BuSO3H]HSO4 in the presence of various sol-
vents at different temperatures. It was observed that this
reaction goes well at 90 °C in toluene. Afterwards, to
optimize the quantity of [P4VPy–BuSO3H]HSO4,
0.05–0.15 mmol of the catalyst was used in the this
reaction. It was found that 0.1:1 mmol ratio of catalyst to
benzaldehyde was sufficient to obtain 3,30-benzylidene-
bis(4-hydroxycoumarin) in 93 % yield within 0.8 h. Then,
under optimal conditions, a wide variety of aromatic
aldehydes (containing both electron-withdrawing and
electron-donating groups, entries 1–8), heteroaromatic
aldehydes such as 2-furyl- and 2-thienylcarbaldehyde
(entries 9, 10), and aliphatic aldehydes (entries 11, 12)
Results and discussion
[P4VPy–BuSO3H]HSO4 was prepared from the reaction of
poly(4-vinylpyridine) (P4VPy, 2 % divinylbenzene) with
1,4-butanesultone followed by treatment with H2SO4. The
acidic sites loading in [P4VPy–BuSO3H]HSO4 obtained by
means of acid–base titration was found to be 1.7 mmol/g
(Scheme 1).
In order to explore the catalytic activity of [P4VPy–
BuSO3H]HSO4, we studied the condensation reaction of
Scheme 1
Table 1 Synthesis of biscoumarin derivatives
H
H
R
H
O
O
O
O
O
[P4VPy-BuSO3H]HSO4
(0.1 mmol)
RCHO
+
2
Toluene / 90 °C
O
O
O
O
Entry
R
Time/h
Yield/%a
M.p. (Lit. m.p.)/°C
1
C6H5
0.8
0.9
1
93
92
91
94
95
91
95
95
90
90
91
92
232–234 (230–232 [25])
268–270 (266–268 [25])
243–245 (242–244 [24])
258–260 (256–258 [25])
233–235 (228–230 [25])
223–225 (222–224 [24])
236–238 (235 [30])
2
4-CH3-C6H4
4-OCH3-C6H4
4-Cl-C6H4
3
4
0.8
0.9
1
5
3-Cl-C6H4
6
4-OH-C6H4
3-NO2-C6H4
4-NO2-C6H4
2-Furanyl
7
0.7
0.6
0.8
0.9
1
8
233–235 (232–234 [24])
203–205 (202 [24])
9
10
11
12
2-Thienyl
206–209 (210 [24])
C6H5CH2CH2
C6H5CH=CH
190–193 (190 [22])
1
279–281 (278 [22])
All products are known compounds and were identified by comparison of their physical and spectral data with those of the authentic samples
a
Isolated yields
123

Synthesis of biscoumarin derivatives
were treated with 4-hydroxycoumarin to give the corre-
sponding biscoumarin products. As shown in Table 1, the
aromatic aldehydes with electron-withdrawing groups
reacted faster than the aromatic aldehydes with electron-
dontaing groups. This observation can be rationalized on
the basis of the mechanism in Scheme 2. The aldehyde is
first activated by [P4VPy–BuSO3H]HSO4. Nucleophilic
addition of 4-hydroxycoumarin to activated aldehyde fol-
lowed by loss of H2O generates intermediate I, which is
further activated by [P4VPy–BuSO3H]HSO4. Then, 1,4-
nucleophilic addition of a second molecule of 4-hy-
droxycoumarin to activated intermediate I, in a Michael-
type addition, affords the biscoumarin product. The elec-
tron-withdrawing groups substituted on aromatic aldehyde
in intermediate I increase the rate of 1,4-nucleophilic
addition reaction because of the alkene LUMO is at lower
energy in their presence compared with electron-donating
groups [34].
responsible for the catalytic properties, [P4VPy–
BuSO3H]HSO4 was added to toluene and the mixture
was stirred at 90 °C for 2 h. Then, the catalyst was fil-
tered off and the filtrate was analyzed for its acid
content, which showed a negligible release of the acidic
sites. The filtrate was found to be inactive in the con-
densation of 4-hydroxycoumarin with aldehydes. These
observations indicate that [P4VPy–BuSO3H]HSO4 is
stable under the reaction conditions, and there is no
leaching of acid moieties during reactions.
The recovered [P4VPy–BuSO3H]HSO4 can be washed
with toluene and used again at least five times without any
noticeable loss of catalytic activity (Scheme 3).
In conclusion, [P4VPy–BuSO3H]HSO4 is an efficient
heterogeneous acid catalyst for the synthesis of biscoum-
arin derivatives under modest conditions. The significant
advantages of this methodology are high yields, short
reaction times, simple work-up procedure, easy preparation
and handling of the catalyst, and minimization of cost and
waste generation owing to reuse and recycling of the
catalyst.
To find out whether the reaction takes place in the
solid matrix of [P4VPy–BuSO3H]HSO4 or whether the
acidic sites simply released in the reaction medium are
Scheme 2
Scheme 3
Run No.
Yield /%
1
2
3
4
5
93
93
92
90
90
123

K. Parvanak Boroujeni et al.
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Typical procedure for synthesis of biscoumarins
To a solution of benzaldehyde (1 mmol), 4-hydroxy-
coumarin (2 mmol), and 3 cm3 toluene was added [P4VPy–
BuSO3H]HSO4 (0.1 mmol) and the resulting mixture was
magnetically stirred at 90 °C. The progress of the reaction
was monitored by TLC. After the completion of the reac-
tion, the catalyst was filtered off and washed with toluene
(2 9 5 cm3) and the filtrate was concentrated on a rotary
evaporator under reduced pressure. The crude product was
recrystallized from ethanol to give 3,30-benzylidenebis(4-
hydroxycoumarin).
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Acknowledgments The author thanks the Research Council of
Shahrekord University for partial support of this work.
123