Catalytic performance of a Keplerate-type, giant-ball nanoporous isopolyoxomolybdate as a highly efficient recyclable catalyst for the synthesis of biscoumarins

Article abstract of DOI:10.1515/znb-2015-0151

In continuation of our previous works on the application of (NH₄)₄₂[Mo^VI ₇₂Mo^V ₆₀O₃₇₂(CH₃COO)₃₀(H₂O)₇₂], a Keplerate-type giant-ball n

Full text of DOI:10.1515/znb-2015-0151

Z. Naturforsch. 2016; aop
ACbaolgthaalseymtDicavopodenriaf*o, ArhmmadaNnakcheaeioanfdaNilKooefarpTalveakroali-tHeos-etinyi pe,
giant-ball nanoporous isopolyoxomolybdate
as a highly efficient recyclable catalyst for
the synthesis of biscoumarins
DOI 10.1515/znb-2015-0151
settings. Catalysts of this type have the potential to make
the processes in which they are applied cleaner, safer,
higher-yielding, and relatively inexpensive [1–4]. Poly-
oxometalates (POMs) are a large family of metal-oxygen
clusters of early transition metals. These compounds have
stimulated many current research activities in a broad
range of fields such as catalysis, magnetism, materials
science and biomedicine [5–8]. Such a stimulation is due
to diverse and highly modifiable sizes, shapes, charge den-
sities, acidities and reversible redox potentials of POMs [9,
10]. In recent years, the synthesis of nanotubular mate-
rials consisting of POMs such as POMs-including titania
nanotubes [11] and POMs-organic hybrid nanotubes [12]
has been a subject of increasing interest. These new types
of nanotubes show not only the functional properties of
POMs but also the advantages of tubular systems in the
application, for example, of catalytic and photochemical
properties [11–13].
Received September 11, 2015; accepted November 26, 2015
Abstract: In continuation of our previous works on the
application of (NH4)42[MoVI72MoV60O372(CH3COO)30(H2O)72],
a Keplerate-type giant-ball nanoporous isopolyoxomolyb-
date, as a catalyst for a series of organic transformations, in
this paper, we discovered that this new attractive catalyst
has high catalytic activity in the synthesis of biscoumarins
prepared by the reaction of 4-hydroxycoumarin and aro-
matic or aliphatic aldehydes in refluxing ethanol. The
catalyst was prepared according to a previously published
literature procedure using inexpensive and readily avail-
able starting materials. Furthermore, the catalyst could be
recovered conveniently and reused efficiently such that a
considerable catalytic activity still could be achieved after
fifth run. Other beneficial features of this new synthetic
approach include short reaction time, high yields, clean
reaction profiles, and a simple work-up procedure.
Giant nanosized porous Keplerate-type POMs,
Keywords: biscoumarin; giant-ball nanoporous isopoly- reported for the first time by Müller and co-workers [14],
oxomolybdate; Keplerate; {Mo132}.
show a large variety of applications in fundamental and
applied science, such as in modeling passive cation trans-
port through membranes, encapsulation, nanoseparation
chemistry, and magnetic and optics properties [15, 16]. In
spite of these valuable properties, to the authors’ knowl-
edge, there are only three references in the literature on
the use of giant nanosized porous POMs as a catalyst in
organic transformations [17–19].
Coumarins are a large group of heterocycles with
diverse and interesting biological activities. These com-
pounds are reported to possess significant anticoagulant,
insecticidal, antihelminthic, hypnotic, antifungal, and
HIV protease inhibition activities [20–24]. Biscoumarins,
the bridge substituted dimers of 4-hydroxycoumarin, have
enormous potential as anticoagulants [25, 26]. A number
of biscoumarins have also been found to be urease inhibi-
tors [27].
1 Introduction
The development of heterogeneous catalysts and how they
affect specific transformations in chemical synthesis has
become a major area of research. The potential advantages
of these materials over homogeneous systems, in terms of
their simplified recovery and reusability, could potentially
allow for the development of environmentally benign
chemical procedures in both academic and industrial
*Corresponding author: Abolghasem Davoodnia, Department of
Chemistry, Mashhad Branch, Islamic Azad University, 91735-413
Mashhad, I.R. Iran, Fax: +98-51-38424020, E-mail: adavoodnia@
mshdiau.ac.ir; adavoodnia@yahoo.com
Ahmad Nakhaei and Niloofar Tavakoli-Hoseini: Department
of Chemistry, Mashhad Branch, Islamic Azad University, 91735-413
Mashhad, I.R. Iran
These compounds are generally synthesized via the
reaction of 4-hydroxycoumarin with aldehydes in the
presence of various Brønsted and Lewis acidic catalysts
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2ꢀ
ꢀA. Davoodnia et al.: Catalytic performance of a Keplerate-type, giant-ball nanoporous isopolyoxomolybdate
R
OH
O
OH
O
OH
O
O
{Mo132
}
+
R
H
EtOH, reflux
O
O
O
1
2a–l
3a–l
Scheme 1:ꢀ{Mo132} catalyzed synthesis of biscoumarins ({Mo132} ꢂ≡ꢂ (NH4)42[MoVI72MoV60O372(CH3COO)30(H2O)72]).
Table 1:ꢀOptimization of reaction conditions for the synthesis of
such as Brønsted-acidic ionic liquids based on ammonium
[28], imidazolium [29], and benzimidazolium [30] cations,
[P4VPy-BuSO3H]HSO4, a supported acidic ionic liquid
[31], TiO2-SO3H [32], tetrabutylammonium hexatungstate
[TBA]2[W6O19] [33], RuCl3·nH2O [34], I2 [35], and sulfonated
rice husk ash (RHA-SO3H) [36]. Catalyst-free synthesis of
these compounds with long reaction times has also been
reported [37].
compound 3e catalyzed by {Mo132}.a
Entryꢁ Catalyst (g)ꢁ Solvent
ꢁ
T (°C) ꢁ
Timeꢁ
(min)
Isolated
yield (%)
1
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
None
None
0.07
0.07
0.02
0.04
0.06
0.07
0.02
0.04
0.06
0.07
0.07
0.07
0.08
0.02
0.04
0.06
0.07
0.02
0.04
0.06
0.07
0.02
0.04
0.06
0.07
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
H2O
ꢂ
ꢂ
Refluxꢂ
Refluxꢂ
90ꢂ
90ꢂ
45ꢂ
45ꢂ
50ꢂ
45ꢂ
30ꢂ
30ꢂ
45ꢂ
20ꢂ
15ꢂ
10ꢂ
25ꢂ
30ꢂ
20ꢂ
45ꢂ
40ꢂ
30ꢂ
25ꢂ
45ꢂ
35ꢂ
30ꢂ
25ꢂ
60ꢂ
50ꢂ
35ꢂ
25ꢂ
10
17
27
29
14
32
69
81
23
52
88
97
89
83
97
15
38
77
85
16
41
78
89
10
28
63
76
2
EtOH
3
Solvent-freeꢂ 110
Solvent-freeꢂ 130
ꢂ
ꢂ
4
During the course of our recent studies directed
towards the development of practical and environmen-
tally friendly procedures for the synthesis of organic
compounds using reusable catalysts [38–46], we investi-
gated the application of (NH4)42[MoVI72MoV60O372(CH3COO)30
(H2O)72], a Keplerate-type giant-ball nanoporous isopoly-
oxomolybdate denoted as {Mo132}, as a catalyst for a series
of organic transformations. This new reusable catalyst
performed well and showed a high level of catalytic activ-
ity in the synthesis of 1,2,4,5-tetrasubstituted imidazoles,
1,8-dioxo-octahydroxanthenes and 1,8-dioxodecahy-
droacridines [18, 19]. This fact prompted us to investigate
the catalytic activity of this material in the synthesis of
biscoumarins (Scheme 1). For the first time, this ball-
shaped POM has been characterized using the transmis-
sion electron microscopy (TEM) image by Polarz et al.
[47]. The TEM picture clearly shows a periodic structure
with an average size of approximately 3 nm in diameter.
This experimentally obtained diameter fits nicely with the
theoretical value for the inner diameter of this ball-shaped
POM that was calculated to be 2.9 nm [14, 48].
5
H2O
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
Refluxꢂ
Refluxꢂ
Refluxꢂ
Refluxꢂ
Refluxꢂ
Refluxꢂ
Refluxꢂ
Refluxꢂ
6
H2O
7
H2O
8
H2O
9
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
MeOH
MeOH
MeOH
MeOH
CHCl3
CHCl3
CHCl3
CHCl3
CH3CN
CH3CN
CH3CN
CH3CN
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
50
ꢂ
ꢂ
r.t.
Refluxꢂ
Refluxꢂ
Refluxꢂ
Refluxꢂ
Refluxꢂ
Refluxꢂ
Refluxꢂ
Refluxꢂ
Refluxꢂ
Refluxꢂ
Refluxꢂ
Refluxꢂ
Refluxꢂ
aReaction conditions: 4-hydroxycoumarin (1) (2 mmol) and
4-cholorobenzaldehyde (2e) (1 mmol).
2 Results and discussion
catalyst in refluxing EtOH or H2O (entries 1 and 2) or in
the presence of the catalyst under solvent-free conditions
The catalyst {Mo132} was characterized by FT-IR and UV/ at high temperatures (entries 3 and 4), indicating that the
Vis spectroscopy as reported in our previous work [19]. catalyst and solvent are necessary for the reaction. As can
At the beginning of this study, 4-chlorobenzaldehyde be seen from Table 1, among the tested solvents such as
(2e) was employed as the model aldehyde and reacted H2O, EtOH, MeOH, CHCl3, CH3CN, and also solvent-free
with 4-hydroxycoumarin (1). In order to get the effective conditions and various amounts of the catalyst, the reac-
reaction conditions, the reaction was optimized in terms tion was more facile and proceeded to give the highest
of various parameters such as catalyst amount, effect of yield, using 0.07 g of {Mo132} in EtOH at reflux temperature
solvent and influence of temperature (Table 1). Low yields (entry 12). All subsequent reactions were carried out in
of the product 3e were obtained in the absence of the these optimized conditions.
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A. Davoodnia et al.: Catalytic performance of a Keplerate-type, giant-ball nanoporous isopolyoxomolybdateꢃ ꢃ3
Encouraged by the remarkable results obtained with (Fig. 2b–e) were almost identical to that of the fresh cata-
the above reaction conditions, and in order to show the lyst (Fig. 2a), which indicated that the structure of the
generality and scope of this new protocol, we extended catalyst was unchanged by the reaction.
the reaction of 4-hydroxycoumarin (1) with a range of
Although we did not investigate the reaction mech-
other aromatic or aliphatic aldehydes 2a–l under the anism, a plausible mechanism for this reaction may
optimized reaction conditions, and the results are sum- proceed as depicted in Scheme 2. On the basis of our previ-
marized in Table 2. As shown, all reactions proceed very ous reports [18, 19], it is reasonable to assume that several
cleanly to give the corresponding biscoumarins 3a–l in accessible Mo sites and NH4 groups in {Mo132} could act as
high yields over short reaction times. Purity checks with Lewis acid and Brönsted acid centers, respectively, and
1
melting points, TLC and the H NMR spectroscopic data therefore promote the necessary reactions. The catalyst
reveal that only one product is formed in all cases and no would play a significant role in increasing the electrophilic
undesirable side products are observed. The structures character of the electrophiles in the reaction. According to
1
of all known products 3a–l were deduced from their H this mechanism, the {Mo132} catalyst would facilitate the
NMR and FT-IR spectral data and a comparison of their formation of intermediates I, II and III. Under these condi-
melting points with those of authentic samples. For tions, however, attempts to isolate the proposed interme-
1
example, as shown in Fig. 1, the H NMR spectrum of 3f diates failed even after careful monitoring of the reactions.
1
in CDCl3 showed a sharp H NMR signal at δ ꢀ=ꢀ 6.09 ppm
for the methine proton along with two sharp singlets in
the down-field region of the spectrum at δ ꢀ=ꢀ 11.35 and
11.57 ppm for hydroxyl groups as well as the signals in the 3 Conclusion
aromatic region due to 12 aromatic protons, indicating the
formation of the compound 3f.
In conclusion, in this paper, we showed that {Mo132}, a
To test the recyclability of {Mo132}, after completion of Keplerate-type giant-ball nanoporous isopolyoxomolyb-
the model reaction, the catalyst was recovered according date, as a highly effective heterogeneous catalyst effec-
to the procedure described in the Experimental section. tively catalyzes the reaction of 4-hydroxycoumarin and
The separated catalyst was dried at 60 °C under vacuum aromatic or aliphatic aldehydes in refluxing ethanol.
for 1 h before being reused in a similar reaction. The cata- This method provided the biscoumarins products in high
lyst could be used at least five times without changing the yields over short reaction time, following a facile work-up
yield of the product significantly (97 % for 1st use; 97 % for process. The catalyst is inexpensive and easily obtained,
2nd use; 96 % for 3rd use; 95 % for 4th use; 93 % for 5th use). stable and storable, easily recycled and reused for several
Furthermore, the FT-IR spectra of the recovered catalyst cycles with consistent activity.
Table 2:ꢀ{Mo132} catalyzed synthesis of biscoumarins.a
Entryꢁ
R
ꢁ
Productsbꢁ
Timeꢁ
(min)
Isolatedꢁ
yield (%)ꢁ
M.p. (°C)
Foundꢁ
Reported
1
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
C6H5
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
3a
3b
3c
3d
3e
3f
3g
3h
3i
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
13ꢂ
10ꢂ
12ꢂ
12ꢂ
10ꢂ
8ꢂ
13ꢂ
8ꢂ
8ꢂ
8ꢂ
92ꢂ
95ꢂ
95ꢂ
93ꢂ
97ꢂ
95ꢂ
93ꢂ
93ꢂ
96ꢂ
94ꢂ
97ꢂ
92ꢂ
231–233ꢂ
286–288ꢂ
264–267ꢂ
204–205ꢂ
253–255ꢂ
213–214ꢂ
269–271ꢂ
246–248ꢂ
233–236ꢂ
232–234ꢂ
210–212ꢂ
143–145ꢂ
226–229 [29]
Not reported [36]
263–266 [29]
201–203 [30]
252–254 [32]
214.5 [37]
266–269 [30]
250–252 [30]
236–238 [34]
233–235 [34]
206–209 [35]
144–146 [32]
2
3-BrC6H4
4-BrC6H4
2-ClC6H4
4-ClC6H4
4-FC6H4
4-MeC6H4
3
4
5
6
7
8
4-MeOC6H4 ꢂ
9
3-O2NC6H4
4-O2NC6H4
2-Thienyl
n-Pr
ꢂ
ꢂ
ꢂ
ꢂ
10
11
12
3j
3k
3l
11ꢂ
14ꢂ
aReaction conditions: 4-hydroxycoumarin (1) (2 mmol), aldehyde 2a–l (1 mmol), {Mo132} (0.07 g), EtOH (5 mL), reflux.
bAll the products were characterized by their FT-IR and 1H NMR spectral data and by comparison of their melting points with those of authen-
tic samples.
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4ꢀ ꢀA. Davoodnia et al.: Catalytic performance of a Keplerate-type, giant-ball nanoporous isopolyoxomolybdate
Fig. 1:ꢀThe 1H NMR spectrum of compound 3f in CDCl3.
4 Experimental section
4.1 Chemicals and apparatus
All chemicals were available commercially and used
without additional purification. The catalyst was syn-
thesized according to the literature. Melting points were
recorded using a Stuart SMP3 melting point apparatus.
The FT-IR spectra of the products were obtained with KBr
disks, using a Tensor 27 Bruker spectrophotometer. The
1H NMR (400 and 500 MHz) spectra were recorded using
Bruker 400 and 500 spectrometers.
4.2 General experimental procedure for
the synthesis of biscoumarins 3a–l
catalyzed by {Mo132}
A mixture of 4-hydroxycoumarin (1) (2 mmol), aromatic
or aliphatic aldehyde 2a–l (1 mmol), {Mo132} (0.07 g) as
a catalyst in ethanol (5 mL) was heated under reflux for
the appropriate time. The reaction was monitored by TLC.
Upon completion of the transformation, the catalyst was
removed by filtration of the hot suspension. The catalyst
Fig. 2:ꢀFT-IR spectra of a fresh catalyst {Mo132} (run 1, a) and recovered
catalysts (runs 2–5, b–e) for the synthesis of compound 3e in the
model reaction.
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A. Davoodnia et al.: Catalytic performance of a Keplerate-type, giant-ball nanoporous isopolyoxomolybdateꢃ ꢃ5
{Mo132
}
H
O
O
R
O
O
O
O
H
{Mo132
}
{Mo132
}
R
H
OH
- H2O
2a-l
O
O
O
H
O
1
I
O
O
{Mo132
}
R
III
R
O
OH
O
O
O
R
O
O
O
O
O
II
{Mo132
}
OH
O
OH
O
O
O
3a-l
Scheme 2:ꢀPlausible mechanism for the {Mo132}-catalyzed formation of biscoumarins 3a–l.
was washed with a small portion of hot ethanol. After 4.3.3 3,3′-((4-Bromophenyl)methylene)bis(4-hydroxy-
cooling, the combined filtrate was allowed to stand at
room temperature. The precipitated solid was collected
2H-chromen-2-one) (3c) (Table 2, entry 3)
by filtration, and recrystallized from ethanol to give com- IR (KBr disk): ν ꢀ=ꢀ 3432, 3071, 1666, 1616, 1558, 1491, 1354,
−1
pounds 3a–l in high yields.
1096, 762 cm . – 1H NMR (400 MHz, CDCl3, 25 °C, TMS): δ ꢀ=ꢀ
6.04 (s, 1H, CH), 7.12 (dd, J ꢀ=ꢀ 8.6, 1.2 Hz, 2H, arom-H), 7.37–
7.48 (m, 6H, arom-H), 7.63–7.69 (m, 2H, arom-H), 8.00–8.12
(m, 2H, arom-H), 11.33 (s br, 1H, OH), 11.56 (s br, 1H, OH).
4.3 FT-IR and 1H NMR data
4.3.1 3,3′-(Phenylmethylene)bis(4-hydroxy-
2H-chromen-2-one) (3a) (Table 2, entry 1)
4.3.4 3,3′-((2-Chlorophenyl)methylene)bis(4-hydroxy-
2H-chromen-2-one) (3d) (Table 2, entry 4)
IR (KBr disk): ν ꢀ=ꢀ 3430, 3059, 1672, 1618, 1562, 1493, 1352,
−1
1098, 761 cm . – 1H NMR (500 MHz, CDCl3, 25 °C, TMS): δ ꢀ=ꢀ IR (KBr disk): ν ꢀ=ꢀ 3436, 3074, 1650, 1565, 1497, 1471, 1454,
6.14 (s, 1H, CH), 7.25–7.50 (m, 9H, arom-H), 7.64–7.70 (m, 1353, 1307, 1277, 1101, 767 cm . – 1H NMR (400 MHz, CDCl3,
−1
2H, arom-H), 8.00–8.14 (m, 2H, arom-H), 11.33 (s, 1H, OH), 25 °C, TMS): δ ꢀ=ꢀ 6.17 (s, 1H, CH), 7.24–7.45 (m, 7H, arom-H),
11.57 (s, 1H, OH).
7.48 (d, J ꢀ=ꢀ 7.2 Hz, 1H, arom-H), 7.64 (td, J ꢀ=ꢀ 7.8, 1.2 Hz, 2H,
arom-H), 8.00–8.10 (m, 2H, arom-H), 10.96 (br, 1H, OH),
11.67 (s br, 1H, OH).
4.3.2 3,3′-((3-Bromophenyl)methylene)bis(4-hydroxy-
2H-chromen-2-one) (3b) (Table 2, entry 2)
IR (KBr disk): ν ꢀ=ꢀ 3434, 3069, 1664, 1610, 1566, 1498, 1471, 4.3.5 3,3′-((4-Chlorophenyl)methylene)bis(4-hydroxy-
−1
1353, 1312, 1099, 764 cm . – 1H NMR (400 MHz, CDCl3, 25 °C,
2H-chromen-2-one) (3e) (Table 2, entry 5)
TMS): δ ꢀ=ꢀ 6.09 (s, 1H, CH), 7.15–7.50 (m, 9H, arom-H), 7.65–
7.72 (m, 2H, arom-H), 8.05 (d, J ꢀ=ꢀ 8.0 Hz, 1H, arom-H), 8.11 (d, IR (KBr disk): ν ꢀ=ꢀ 3429, 3072, 1668, 1618, 1562, 1491, 1454,
−1
1
J ꢀ=ꢀ 8.0 Hz, 1H, arom-H), 11.33 (s, 1H, OH), 11.61 (s, 1H, OH).
1351, 1310, 1094, 766 cm . – H NMR (400 MHz, CDCl3,
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25 °C, TMS): δ ꢀ=ꢀ 6.06 (s, 1H, CH), 7.18 (dd, J ꢀ=ꢀ 8.8, 0.8 Hz, 4.3.10 3,3′-((4-Nitrophenyl)methylene)bis(4-hydroxy-
2H, arom-H), 7.31 (d, J ꢀ=ꢀ 8.8 Hz, 2H, arom-H), 7.38–7.47 (m,
4H, arom-H), 7.63–7.69 (m, 2H, arom-H), 8.01 (d, J ꢀ=ꢀ 7.6 Hz,
2H-chromen-2-one) (3j) (Table 2, entry 10)
1H, arom-H), 8.09 (d, J ꢀ=ꢀ 7.6 Hz, 1H, arom-H), 11.35 (s br, IR (KBr disk): ν ꢀ=ꢀ 3413, 3060, 1663, 1600, 1564, 1522, 1491,
−1
1H, OH), 11.56 (s br, 1H, OH).
1453, 1352, 1313, 1099, 786 cm . – 1H NMR (400 MHz, CDCl3,
25 °C, TMS): δ ꢀ=ꢀ 6.14 (s, 1H, CH), 7.40–7.50 (m, 6H, arom-
H), 7.70 (t, J ꢀ=ꢀ 7.6 Hz, 2H, arom-H), 8.02 (d, J ꢀ=ꢀ 7.6 Hz, 1H,
arom-H), 8.11 (d, J ꢀ=ꢀ 8.0 Hz, 1H, arom-H), 8.21 (d, J ꢀ=ꢀ 8.8
Hz, 2H, arom-H), 11.40 (s, 1H, OH), 11.60 (s, 1H, OH).
4.3.6 3,3′-((4-Fluorophenyl)methylene)bis(4-hydroxy-
2H-chromen-2-one) (3f) (Table 2, entry 6)
IR (KBr disk): ν ꢀ=ꢀ 3458, 3066, 1672, 1562, 1507, 1453, 1352,
−1
1
1310, 1102, 765 cm . – H NMR (400 MHz, CDCl3, 25 °C,
TMS): δ ꢀ=ꢀ 6.09 (s, 1H, CH), 7.05 (t, J ꢀ=ꢀ 8.4 Hz, 2H, arom-H),
7.20–7.25 (m, 2H, arom-H), 7.40–7.50 (m, 4H, arom-H), 7.67
(td, J ꢀ=ꢀ 8.0, 1.6 Hz, 2H, arom-H), 8.03 (d, J ꢀ=ꢀ 7.6 Hz, 1H,
arom-H), 8.11 (d, J ꢀ=ꢀ 7.6 Hz, 1H, arom-H), 11.35 (s, 1H, OH),
11.57 (s, 1H, OH).
4.3.11 3,3′-(Thiophen-2-ylmethylene)bis(4-hydroxy-
2H-chromen-2-one) (3k) (Table 2, entry 11)
IR (KBr disk): ν ꢀ=ꢀ 3429, 3068, 1661, 1565, 1496, 1452, 1346,
−1
1
1309, 1267, 1216, 1098, 761 cm . – H NMR (400 MHz,
CDCl3, 25 °C, TMS): δ ꢀ=ꢀ 6.23 (s, 1H, CH), 6.88–6.91 (m,
1H, arom-H), 6.97–7.00 (m, 1H, arom-H), 7.25 (dt, J ꢀ=ꢀ 5.2,
1.2 Hz, 1H, arom-H), 7.40–7.48 (m, 4H, arom-H), 7.66 (td,
J ꢀ=ꢀ 8.6, 1.6 Hz, 2H, arom-H), 8.06 (d br, J ꢀ=ꢀ 7.2 Hz, 1H,
arom-H), 8.09 (d br, J ꢀ=ꢀ 7.2 Hz, 1H, arom-H), 11.32 (s, 1H,
4.3.7 3,3′-((4-Methylphenyl)methylene)bis(4-hydroxy-
2H-chromen-2-one) (3g) (Table 2, entry 7)
IR (KBr disk): ν ꢀ=ꢀ 3423, 3057, 2998, 1671, 1605, 1564, 1493, OH), 11.83 (s, 1H, OH).
−1
1
1352, 1309, 1095, 764 cm . – H NMR (400 MHz, CDCl3,
25 °C, TMS): δ ꢀ=ꢀ 2.36 (s, 3H, CH3), 6.09 (s, 1H, CH), 7.14
(ABq, JAB ꢀ=ꢀ 8.4 Hz, 4H, arom-H), 7.38–7.45 (m, 4H, arom-H), 4.3.12 3,3′-(Butane-1,1-diyl)bis(4-hydroxy-2H-chromen-
7.65 (td, J ꢀ=ꢀ 8.6, 1.6 Hz, 2H, arom-H), 8.02 (d br, J ꢀ=ꢀ 7.2 Hz,
1H, arom-H), 8.09 (d br, J ꢀ=ꢀ 7.2 Hz, 1H, arom-H), 11.34 (s br,
1H, OH), 11.53 (s br, 1H, OH).
2-one) (3l) (Table 2, entry 12)
IR (KBr disk): ν ꢀ=ꢀ 3460, 3060, 1687, 1615, 1537, 1460, 1406,
−1
1376, 1353, 1179, 1107, 755 cm . – 1H NMR (400 MHz, CDCl3,
25 °C, TMS): δ ꢀ=ꢀ 0.97 (t, J ꢀ=ꢀ 7.2 Hz, 3H, CH3), 1.37 (sex, J ꢀ=ꢀ
4.3.8 3,3′-((4-Methoxyphenyl)methylene)bis(4-hydroxy- 7.2 Hz, 2H, CH2), 2.30–2.50 (m, 2H, CH2), 4.53 (t, J ꢀ=ꢀ 8.0 Hz,
2H-chromen-2-one) (3h) (Table 2, entry 8)
1H, CH), 7.35–7.42 (m, 4H, arom-H), 7.58–7.64 (m, 2H, arom-
H), 8.02 (dd, J ꢀ=ꢀ 8.2, 1.2 Hz, 2H, arom-H), 11.23 (s, 1H, OH),
IR (KBr disk): ν ꢀ=ꢀ 3427, 3002, 1671, 1605, 1564, 1510, 1353, 12.06 (s, 1H, OH).
−1
1
1259, 1094, 769 cm . – H NMR (500 MHz, CDCl3, 25 °C,
TMS): δ ꢀ=ꢀ 3.83 (s, 3H, OCH3), 6.08 (s, 1H, CH), 6.87 (d, Acknowledgments: This work was supported by Islamic
2H, J ꢀ=ꢀ 8.7 Hz, arom-H), 7.16 (d, 2H, J ꢀ=ꢀ 8.7 Hz, arom-H), Azad University, Mashhad Branch, as a research project.
7.40–7.50 (m, 4H, arom-H), 7.65 (t, 2H, J ꢀ=ꢀ 7.9 Hz, arom-H),
8.04 (s br, 1H, arom-H), 8.09 (s br, 1H, arom-H), 11.32 (s,
1H, OH), 11.54 (s, 1H, OH).
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Z. Naturforsch.ꢃ
ꢃ2016 | Volume x | Issue x(b)
Graphical synopsis
Abolghasem Davoodnia, Ahmad
Nakhaei and Niloofar Tavakoli-Hoseini
Catalytic performance of a Keplerate-
type, giant-ball nanoporous isopoly-
oxomolybdate as a highly efficient
recyclable catalyst for the synthesis
of biscoumarins
DOI 10.1515/znb-2015-0151
Z. Naturforsch. 2016; x(x)b: xxx–xxx
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