Role of basicity, calcinations, catalytic activity and recyclability of hydrotalcite in eco-friendly synthesis of coumarin derivatives

Article abstract of DOI:10.1016/j.molcata.2014.07.024

An efficient and simple protocol is described for synthesis of coumarin derivatives using Mg-Al-CO₃ and Ca-Al-CO₃ hydrotalcite as an environmental friendly and reusable heterogeneous catalyst under solvent free conditions. The catalysts were characterized by Hammett titration, SEM and XRD data. Present study revealed that catalytic activity and basicity depend on compositions of hydrotalcite. The calcined hydrotalcite with an Mg/Al of 3:1 derived from calcinations at 750 K was found to be suitable catalyst that gives the highest basicity and the best catalytic activity for this reaction. Catalyst allows short reaction time, high catalytic activity, easy to work up and is reusable. Step economy, atom efficiency and solvent free conditions are some important salient features of this protocol.

Full text of DOI:10.1016/j.molcata.2014.07.024

Journal of Molecular Catalysis A: Chemical 395 (2014) 251–260
Contents lists available at ScienceDirect
Journal of Molecular Catalysis A: Chemical
journal homepage: www.elsevier.com/locate/molcata
Role of basicity, calcinations, catalytic activity and recyclability of
hydrotalcite in eco-friendly synthesis of coumarin derivatives
a,b,∗
b,∗∗
, Dau D. Agarwala,b
Pramod K. Sahu
, Praveen K. Sahu
a
School of Studies in Chemistry, Jiwaji University, Gwalior 474011, Madhya Pradesh, India
Department of Industrial Chemistry, Jiwaji University, Gwalior 474011, Madhya Pradesh, India
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 19 May 2014
Received in revised form 12 July 2014
Accepted 14 July 2014
Available online 24 July 2014
An efficient and simple protocol is described for synthesis of coumarin derivatives using Mg–Al-CO3 and
Ca–Al-CO3 hydrotalcite as an environmental friendly and reusable heterogeneous catalyst under solvent
free conditions. The catalysts were characterized by Hammett titration, SEM and XRD data. Present study
revealed that catalytic activity and basicity depend on compositions of hydrotalcite. The calcined hydro-
talcite with an Mg/Al of 3:1 derived from calcinations at 750 K was found to be suitable catalyst that gives
the highest basicity and the best catalytic activity for this reaction. Catalyst allows short reaction time,
high catalytic activity, easy to work up and is reusable. Step economy, atom efficiency and solvent free
conditions are some important salient features of this protocol.
Keywords:
Calcination
Catalytic activity
Aging
©
2014 Elsevier B.V. All rights reserved.
Reusability
Coumarin derivatives
1
. Introduction
water, not reusable, higher catalyst loading, and relatively higher
temperature conditions.
Coumarins (chomene-2-ones, benzopyran-2-ones) are natu-
rally occurring classes of compound, which having variety of
pharmacological activity dependent on the substitution patterns
The drawback of ionic liquids is that it cannot be removed by
distillation and their limited solubility in water restricts their use.
They have high cost and also acute toxicity for aquatic organ-
ism and human [21]. Hydrotalcites (HTs) are synthetic or natural
layered materials made of positively charged two-dimensional
sheets of mixed hydroxides with water and exchangeable charge-
compensating anions [22]. Hydrotalcites are increasingly regarded
as a good alternative to the traditional homogenous base cata-
lysts such as NaOH and KOH for several base-catalyzed reactions
that are important for the pharmaceutical and fragrance industries
[23]. A well-documented example is the isomerization of eugenol
and safrole [24]. As far as green chemistry is concerned, hydro-
talcites offer several advantages over these corrosive, dissolved
catalysts, easy separation from the reaction mixture, recycling pos-
sibilities, decreased corrosion of the reactor, so forth [25]. The
range of applications of hydrotalcite base materials is virtually
unlimited. Hydrotalcites can be involved in the preparation of
catalysts dedicated to the production of H2 [26], wide range of
organic compounds [27] and production of biodiesel by trans-
esterification of triglycerides with methanol [28]. In addition to the
above numerous experimental investigations have been published
on the use of hydrotalcites for catalytic applications [29]. In present
communication, we have used hydrotalcite as catalyst led to for-
mation of high yield of coumarin derivatives under solvent free
conditions.
[
1]. Coumarins core structure represents a highly privileged and
biologically relevant molecular scaffold which occurs in many nat-
ural products. For example, autumnariol has been isolated from
onions of Eucomis autumnalis Greab (Liliaceae) [2]. A number of
related natural products, such as autumnariniol [3], alternariol
[
4], and altenuisol [5], have been isolated (Fig. 1) [6]. Recently
several synthetic procedures for the preparation of coumarin
derivatives have been reported using montmorillonite K-10 [7],
zinc [8], indium (III) chloride [9], TiCl4 [10], ZrCl4 [11], sulfated
zirconia [12], Lewis acidic chloroaluminate ionic liquid [13], bis-
muth nitrate [14], Wells–Dawson heteropolyacid [15], samarium
(
III) [16], PIDA/I -mediated [17], InCl [18], HClO ·SiO [19], DMAP
2
3
4
2
and Et N [20]. Literature survey demonstrated that reported meth-
3
ods have suffered drawbacks such as low yield, long duration, and
used hazardous solvent such as organic solvent as compared to
∗ Corresponding author at: School of Studies in Chemistry, Jiwaji University,
Gwalior 474011, Madhya Pradesh, India. Tel.: +91 9993932425.
Corresponding author. Tel.: +91 9993932425.
E-mail addresses: sahu.chemistry@gmail.com, researchdata6@gmail.com
P.K. Sahu), praveensahu1234@gmail.com (P.K. Sahu).
∗
∗
(
http://dx.doi.org/10.1016/j.molcata.2014.07.024
381-1169/© 2014 Elsevier B.V. All rights reserved.
1

2
52
P.K. Sahu et al. / Journal of Molecular Catalysis A: Chemical 395 (2014) 251–260
Fig. 1. Natural occurring products with coumarins core.
Table 1
Optimization of hydrotalcite as a catalyst (Mg–Al-HT (Mg/Al = 3)).
to identify the best composition of Mg–Al mixed oxide catalysts
in the case of various reaction. A set of Mg–Al hydrotalcite-like
precursors with different Mg/Al atomic ratios was studied by Diez
et al. [35]. The optimum Mg/Al molar ratio is dependent on the
target reaction and more precisely, on the basic strength needed
to activate the reactant. In order to check the basicity effect of
hydrotalcite catalyst on the yield of the synthesized coumarin
derivatives, hydrotalcite with different metallic ratios of Mg–Al-
CO , Ca–Al-CO and their metal oxide were tried under solvent free
Entry
Catalyst loading (mg)
Time (min)
Yield (%)
1
2
3
4
5
10
20
50
75
100
120
90
30
30
30
52
74
97
97
96
3
3
conditions and concluded that (3:1) Mg–Al-CO , (3:1) Ca–Al-CO3
3
2
. Results and discussion
were more suited hydrotalcites to catalyze the reaction (Table 3).
The results show that basicity of hydrotalcite affected the reaction
time and yields of target product. Among all the metallic ratio
In order to evaluate the appropriate catalyst loading,
a
model reaction of resorcinol (0.0025 mol) and ethyl acetoacetate
of hydrotalcites, 3:1 ratio of hydrotalcite (Mg–Al-CO ) gives the
3
(
0.0025 mol) were carried out using 10 mg, 20 mg, 50 mg, 80 mg,
◦
highest yield with lower time.
and 100 mg of hydrotalcite as catalyst at 70 C. The catalyst load-
ing 50 mg was found to be the optimal quantity (Table 1). Catalyst
was reused and the results show that the hydrotalcite (Mg–Al-CO3)
can be reused as such without significant loss in yield (Table 2).
Reusability of catalyst reduces the cost of production. The pro-
cedure was efficient and greatly reduced the role of solvent thus
reducing environmental pollution. This procedure was easy to work
up because after completion of the reaction, mass was cooled to
room temperature and poured directly in cold water. Precipitate
was form and filtered easily. Solid was dissolved in ethanol and
filtered to separate hydrotalcite.
2.1. Recyclability and reusability of hydrotalcite
A model reaction has been carried out using of resorcinol
(0.0025 mol) and ethyl acetoacetate (0.0025 mol) for recyclability
and reusability of hydrotalcite as catalyst by incorporating 50 mg
of hydrotalcite catalyst. After completion of reaction, the contents
were filtered to recycle the hydrotalcite catalyst through what-
man filter 42. Recycled hydrotalcite washed with 5 mL ethanol to
II
remove organic impurities if any. Mg hydrotalcite catalyst can be
readily recovered and reused for at least four runs without any sig-
nificant loss of activity. XRD data of recovered hydrotalcite (Fig. 2)
which showed the similar profile as fresh catalyst which confirmed
that layered structure of hydrotalcite was maintained after the
reaction.
Basicity of hydrotalcite is a key for the preparation of material
with high performance [30]. It can be achieved by changing the
2
+
3+
nature of M /M metals [31]. As far as Mg–Al mixed oxides
of hydrotalcite is concerned, a correlation can be established
between the composition and the basicity: when the amount of
Al increases, the total number of basic sites decreases [25(a),32].
The decrease in basic site density observed in Mg–Al mixed
oxide derived from hydrotalcites when increasing the Al con-
tent is reported to be the reason for decreasing activity in the
Knoevenagel condensation reaction between glyceraldehydes
acetonide and ethyl acetoacetate [33]. The performance of Mg–Al
mixed oxide in the methanolysis of soybean oil was shown to be
dependent on the Mg/Al ratio [34]. Numerous authors have tried
2.2. Catalytic activity of hydrotalcite
By exploring the synthesis of coumarin derivatives the catalytic
activity has been observed, results are incorporated in Table 4.
Table 3
a
Effect of metal composition of hydrotalcite on yield of coumarin.
Entry
Ratio of hydrotalcite
Time (min)
Yield (%)
1
2
3
4
5
6
7
8
(2:1) Mg–Al-CO3
(3:1) Mg–Al-CO3
(4:1) Mg–Al-CO3
(2:1) Ca–Al-CO3
(3:1) Ca–Al-CO3
(4:1) Ca–Al-CO3
MgO
70
30
70
80
60
90
150
180
84
97
79
74
90
78
21
15
Table 2
a
Reusability of hydrotalcite (Mg–Al-HT, (Mg/Al = 3)).
Product
Fresh HT
97
Reuse (I)
95
Reuse (II)
95
Reuse (III)
93
Reuse (IV)
92
1a
CaO
a
Reaction conditions: resorcinol (0.0025 mol), ethyl acetoacetate (0.0025 mol),
◦
a
◦
Reaction conditions: solvent free conditions, heating at 70 C.
hydrotalcite (50 mg), heating at 70 C.

P.K. Sahu et al. / Journal of Molecular Catalysis A: Chemical 395 (2014) 251–260
253
Table 4
Catalytic activity of hydrotalcite for synthesis of coumarin derivatives.
a
Mp. ( C)c
◦
Mg–Al-CO3
Time (min)
Hydrotalcite
Yield (%)
Ca–Al-CO3
Time (min)
Hydrotalcite
Yield (%)b
Product
Phenol
b
1
a
182–183
30
97
92
60
90
1b
238–239
282–283
180–181
261–262
40
45
85
88
86
82
1
1
1
c
35
35
50
89
91
83
50
55
60
d
e
1f
151–152
25
93
30
90
1g
160–161
30
95
35
88

2
54
P.K. Sahu et al. / Journal of Molecular Catalysis A: Chemical 395 (2014) 251–260
Table 4 (Continued)
Mp. ( C)c
◦
Mg–Al-CO3
Time (min)
Hydrotalcite
Yield (%)
Ca–Al-CO3
Time (min)
Hydrotalcite
Yield (%)b
Product
Phenol
b
2
154–155
45
95
45
87
a
◦
Reaction was carried out using ethyl acetoacetate (0.0025 mol) and phenols (0.0025 mol) under solvent free conditions at 70 C.
Isolated yield.
Melting point was uncorrected.
b
c
It shows that hydrotalcite (Mg–Al-CO ) catalyzed the reaction
efficiently with excellent yield and shorter time compared to
calcined catalyst was shaken with 1 mL solution of Hammett indica-
tor in methanol and left to equilibrate. Color of catalyst was noted.
The base strength is quoted as being stronger than weakest indica-
tor which exhibits a color change. In benzoic acid titration method,
0.1 g of catalyst was suspended in 2 mL of phenolphthalein indica-
tor solution (0.01 mg/mL toluene). It was then stirrer for 0.5 h and
titrated against 0.01 M benzoic acid in toluene solution until pink
color change to colorless. The total basicity was, thus determined.
All samples prepared in our study had the basic strength in the
range of 9.3–15.0. The basicity of the catalysts with different Mg/Al
molar ratios was shown in Fig. 3. The main basic sites with H in the
range of 7.2–9.8 and the other sites with H in the range of 9.8–15.0
were observed, thus suggesting the calcined hydrotalcites contain
different types of surface basic sites. Di Cosimo et al. [44] suggested
that pure MgO possesses strong basic sites consisting predomi-
3
Ca–Al-CO3 type hydrotalcite. It has been previously suggested that
although the basic site density decreases with increasing Al con-
tent the relative proportion of strongly basic site increases [36,37].
On the other hand, Since Al is more electronegative than Mg, an
increase in Al should increase the average electronegativity of the
catalyst and thus a decrease in the average electronic density of the
unsaturated framework oxygens could be expected, with the cor-
responding effect on their basicity and catalytic activity [38–40].
As a result, the basicity and catalytic activity increased with elevat-
ing of Mg/Al molar ratio. However, when the Mg/Al molar ratio has
exceeds 3.0, the catalytic activity decreases. It may be due to the
formation of new weaker basic sites and thus decrease of strong
basic site amount.
nantly of O2 and calcined hydrotalcites contain surface basic sites.
Our experimental results on the Hammett titration method consis-
tent with this viewpoint. It indicates a wide basic site distribution
as far as the basicity is concerned.
−
Methodology involves the reaction of phenols/naphthol
(
0.0025 mol) and ethyl acetoacetate (0.0025 mol) using hydrotal-
cite (Mg–Al-CO ) as a catalyst under solvent free conditions at
3
◦
7
0 C (Scheme 1). Reaction was completed within few minutes
with excellent yield (Table 5) and the synthesized compounds
were characterized by comparing the observed spectral data and
physical properties with those of authentic samples [10,16]. A
variety of electron donating and electron withdrawing groups
on phenol have been studied by preparing coumarin derivatives.
There is no significant effect of electron donating and electron
withdrawing subsituents on yield and time and resultant yield
was obtained between ranges 82 and 97% within time range 30
and 50 min.
The total basicity of the hydrotalcite (catalyst) was increased
gradually with the Mg/Al molar ratio and reach up to the maximum
value at the Mg/Al molar ratio of 3.0. But basicity was decreased
when further increase the molar ratio of Mg/Al, which resulted in a
loss of the catalytic activity. Qualitatively similar trends were also
reported by other researchers [37,45]. Nakatsuka et al. [37] found
that the basicity measured by titration with benzoic acid reached a
maximum for Mg/Al ratio of about 2.6. Also, Fishel and Davis [45]
measured the number of basic sites by TPD of CO2 and a maximum
of the basic site density was observed at Mg/Al ratio of 3.0.
Best results were obtained with 3.0 HT, therefore basicity of
2.3. Basicity of hydrotalcite
3
.0 HT calcined at different temperatures was measured with the
Basicity of the catalyst was determined using Hammett indica-
tor and benzoic acid titration method [41–43]. In this, 25 mg of the
same method; the results are illustrated in Fig. 4. From this figure,
it can be seen that the maximum basicity (reaching 3.6 mmol/g)
is found at a calcinations temperature of 750 K and a low level of
basicity is observed below 573 K and above 750 K. The increased
Fig. 2. XRD pattern of recovered hydrotalcite.
Fig. 3. Basicity of calcined hydrotalcite with different metal ratios.

P.K. Sahu et al. / Journal of Molecular Catalysis A: Chemical 395 (2014) 251–260
255
Table 5
Hydrotalcite (Mg–Al-HT) catalyzed synthesis of coumarin derivatives.
Yield (%)a
Time (min)
Mp. ( C) Found/Reported [Ref.]
◦
b
Entry
Products
Phenol
1
97
30
182–183/184–186 [10]
1
a
2
92
40
238–239/241–243 [55]
1
1
b
c
3
89
35
282–283/280–281 [55]
4
91
35
180–181/183–185 [16]
1
1
d
e
5
83
50
261–262/263–265 [11]
6
93
25
151–152/151–154 [16]
1
f

2
56
Table 5 (Continued)
Entry Products
P.K. Sahu et al. / Journal of Molecular Catalysis A: Chemical 395 (2014) 251–260
Yield (%)a
Time (min)
Mp. ( C) Found/Reported [Ref.]
◦
b
Phenol
7
95
30
160–161/163–164 [16]
1
g
8
95
45
154–155/155–157 [10]
a
Isolated yield
Melting point was uncorrected
b
phases [38,47]. The first one, below 500 K, is attributed to the loss of
interlayer water and the second, between 500 K and 750 K, to dehy-
droxylation and loss of the charge compensating anions [45,48, 49].
The acid–base properties and, as a consequence, the catalytic activ-
ity of these Mg–Al-HT depend on chemical composition and on
the conditions of the thermal treatment used to decompose the
hydrotalcite precursor, 723–800 K being the range that produce
the most active mixed oxides. Thus present studies have also been
demonstrated the similar results which are supported by above
literature.
2.4. Effect of aging time and catalytic activities
The SEM images of hydrotalcite samples at Mg/Al molar ratio of
Fig. 4. Basicity of 3.0 hydrotalcite at different temperature.
3.0 were recorded to observe the effect of aging time on the mor-
phology of the material. The micrographs at different aging times
are shown in Fig. 5. From the micrographs of hydrotalcite, a well-
developed layered and platelet structure of the hydrotalcite was
observed. However, a spongy type structure is exhibited due to
overlapping of such platelets. The SEM images of the hydrotalcite
basicity could be expected to correlate with an increase of the cata-
lyst activity [46]. The thermal decomposition of Mg–Al-HT at about
50 K gives rise to mixed oxides whose X-ray diffraction patterns
7
indicate a diffuse MgO-type structure with no segregate crystalline
Scheme 1. Preparation of coumarin derivatives.

P.K. Sahu et al. / Journal of Molecular Catalysis A: Chemical 395 (2014) 251–260
257
◦
Fig. 5. SEM image of hydrotalcite at a Mg/Al (3:1) at different aging time at 110 C.
showed a gradual crystallization during the hydrothermal treat-
ment conditions. The crystallinity of the hydrotalcite was observed
to be very poor at 0 h aging time and 110 C hydrothermal treatment
was found 24.87 nm as calculated using Scherrer formula [52]. More
intensive and sharper reflections of the (0 0 3) and (0 0 6) planes has
found at low 2ꢀ values (11–23 ). A typical SEM image of Mg–Al-CO3
◦
◦
temperature; however, as aging time increases from 0 to 10 h, the
crystallinity of the hydrotalcite also increased. These results con-
firmed an increase in the crystallinity of the hydrotalcite samples
at Mg/Al under hydrothermal treatment conditions.
hydrotalcite is shown in Fig. 6. This figure indicates the existence of
lamellar particles looks like rounded hexagonal shape and typical
of hydrotalcite like material. The material was found mesoporous
2
with the surface area 90 m /g.
The Ca:Al metal ratio was found in good agreement with the
initially taken metallic ratio. The observed value for Ca–Al-CO3
was 3:2:1. The P-XRD patterns for the LDHs Ca–Al-CO3 exhibits
features commonly shown by layered materials. There are nar-
row, symmetric, strong lines at low 2ꢀ values and weaker, less
2
.5. Characterization of hydrotalcite
Mg:Al atomic ratio was measured using X-ray microanalysis and
found 3.16, which is in good agreement with the metallic ratio
III
II
III
2−
(
3.0) taken in solution. The value of x [x = M /M + M ] was found
symmetric lines at high 2ꢀ value (Fig. 7) [53]. Presence of CO3
to 0.24, which suggest the purity of hydrotalcite [50]. Powder X-
anion in the interlayer gallery of the hydrotalcite is confirmed by
ray diffraction (P-XRD) pattern for sample Mg–Al-CO is shown
the characteristic basal spacing d003 = 3.38 A˚ . The lattice parame-
3
in Fig. 6. The presence of CO32 anion in the interlayer gallery of
−
ters a and c were calculated assuming 3R packing of the layers and
from the positions of doublet corresponding to plane 1 1 0 and 1 1 3,
0 0 3, 0 0 6, 0 0 9 reflections. Sharp intense peaks at low diffraction
the hydrotalcite is confirmed by the characteristic basal spacing
d003 = 7.76 A˚ . This indicates a gallery height of 2.96 A˚ (assuming a
◦
◦
◦
thickness of 4.8 A˚ for the cationic sheets). The material is reasonably
angles (peaks close to 2ꢀ = 11 , 24 , and 35 ; ascribed to diffrac-
crystalline and suggests a relatively well-ordered sheet arrange-
ment [51]. Diffraction peaks of the (0 0 3) basal plane that gives
the distance between the layers became sharper which indicates
higher crystallinity and order. This fact is supported by the increase
in the ratio of the intensities of the diffraction from the (0 0 6) basal
plane to that of the (0 0 3) one. The crystallite size of this sample
tion by basal planes (0 0 3), (0 0 6), and (0 0 9), respectively) and
◦
broad, less intense peaks at higher angles (peaks close to 2ꢀ = 38 ,
◦
◦
46 , and 60 ); ascribed to diffraction by (1 0 5), (1 0 8) and (1 1 0)
planes confirm the presence of hydrotalcite. The crystallite size of
this sample was found 47.025 nm. The crystallographic parame-
ter ‘a’ equals the average cation–cation distance in the brucite like

2
58
P.K. Sahu et al. / Journal of Molecular Catalysis A: Chemical 395 (2014) 251–260
Fig. 6. P-XRD pattern and SEM image of hydrotalcite (Mg–Al 3:1).
Fig. 7. P-XRD and pattern and SEM image of hydrotalcite (Ca–Al 3:1).
2
.6. Plausible mechanism
layers, while parameter ‘c’ is three times the distance from the cen-
ter of one layer to the next and is controlled mostly by the size
and orientation of the interlayer anion and the electrostatic forces
operating between the interlayer anion and the layers. SEM (Fig. 7)
of the material shows high crystallinity. The particles of hydrotal-
cite Ca–Al-CO3 clearly exhibit the hexagonal shape; however, big
needle shape particles are also visible.
A plausible mechanism for formation of product 1 shown in
Scheme 2. It is suggested that the lone pair of electrons of the phe-
nolic OH group attacks at the carbonyl carbon of ethoxy moiety of
ester (ethyl acetoester) with the elimination of alcohol molecule
to give intermediate A. The intermediate A undergoes ring clo-
sure through electrophilic attack of the ␲-electrons at the activated
Scheme 2. Plausible reaction mechanism.

P.K. Sahu et al. / Journal of Molecular Catalysis A: Chemical 395 (2014) 251–260
259
carbonyl carbon by active metal center of hydrotalcite to form inter-
mediate B. The intermediate B then undergoes elimination of one
water molecule to give target product 1.
(TLC analysis using ethyl acetate:petroleum ether, 1:3), the reac-
tion mixture was cooled to room temperature and poured in cold
water. The solid mass was filtered. It was dissolved in ethanol and
filtered. The solid hydrotalcite got separated as solid. The filtrate
having product soluble in ethanol was concentrate to crystallize the
product. Hydrotalcite was washed with ethanol to remove organic
impurity.
3
. Conclusion
It can be concluded that synthesis coumarin derivatives have
been developed using hydrotalcite (Mg–Al-CO ), reusability of cat-
3
alyst and ease of work-up make the method advantageous. The
catalytic activities of the calcined hydrotalcite show a striking
correlation with their corresponding basic properties and com-
position of metal content affected the yield of target molecules.
The prepared catalyst were characterized with Hammett indicator-
benzene carboxylic acid titration, SEM and XRD showing the strong
4.4. Compound 1a
◦
−1
White powder, mp. 182–183 C; IR (KBr) (ꢁmax, cm ): 3260
(OHstr), 3080 (C Hstr), 1690 (C Ostr). H NMR (400 MHz, CDCl3): ıH
1
2.65 (s, 3H, Me), 6.41 (s, 1H, C CH), 6.64 (d, J = 8.4 Hz, 1H, ArH), 7.24
(s, 1H, ArH), 7.57 (d, J = 7.76 Hz, 1H, ArH), 8.9 (s, 1H, OH); 13C NMR
(100 MHz, CDCl3): 23.09, 102.96, 111.80, 115.02, 131.95, 137.56,
153.46, 157.22, 162.27, 165.55; EIMS: m/z: Calculated for C10H8O3
2−
basic sites in double layers and coordinatively unsaturated O ion
acting as basic sites in the calcined hydrotalcite may be responsi-
ble for their catalytic activity. The crystallization of hydraotalcite
was significantly affected by hydrothermal treatment temperature
and time. Conversion of reactant depends on the number of fac-
tors such as molar ratios of metal ions, calcination temperature,
and crystallinity depends on the aging time. The crystallization
of hydrotalcite (Mg/Al molar ratio = 3.0) was significantly affected
by the aging time (0–10 h). This is first attempt to synthesize the
coumarin derivatives using heterogeneous catalyst (hydrotalcite).
The main advantages of this methodology are the short reaction
times, simple catalyst system, higher yields, higher catalytic activ-
ity, solvent free conditions and good reusability.
+
176, Found [M] 176; C, H and N analyses Calculated for C 68.18, H
4.54, Found C 68.25, H 4.59.
4.5. Compound 1b
White solid, mp 238–239 C; 1H NMR (400 MHz; DMSO-d ): ıH
◦
6
2.35 (s, 3H, Me), 6.30 (s, 1H, C CH), 6.46 (d, J = 8.4 Hz, 1H, ArH), 7.20
(d, J = 8.4 Hz, 1H, ArH), 9.26 (s, 2H, OH); 13C NMR (100 MHz, DMSO-
d ): 23.1, 110.7, 111.2, 111.5, 117.6, 133.4, 151.46, 152.6, 165.4;
6
EIMS: m/z: Calculated for C10H O 192, Found [M]+ 192; C, H and
8
4
N analyses Calculated for C 62.50, H 4.20, Found C 62.63, H 4.39.
4
. Experimental
4.6. Compound 1c
Colorless solid, mp 282–283 C; 1H NMR (400 MHz; DMSO-d6):
◦
4.1. General
ıH 2.47 (s, 3H, Me), 6.36 (s, 1H, C CH), 6.89–6.92 (m, 2H, ArH), 9.82
(s, 1H, OH), 10.12 (s, 1H, OH); C NMR (100 MHz, DMSO-d6): 23.09,
The 1H NMR spectra were measured by BRUKER AVANCE II 400
13
NMR spectrometer with tretramethylsilane as an internal standard
102.9, 111.8, 115.0, 131.9, 137.5, 153.46, 157.22, 162.27, 165.55;
EIMS: m/z: Calculated for C10H8O4 192, Found [M]+ 192; C, H and
N analyses Calculated for C 62.50, H 4.20, Found C 62.59, H 4.12.
◦
1
at 20–25 C; data for H NMR are reported as follow: chemical shift
ppm), integration, multiplicity (s, singlet; d, doublet; t, triplet; q,
(
quartet; m, multiplet and br, broad), coupling constant (Hz). IR
spectra were recorded by SHIMADZU, IR spectrometer of sample
dispersed in KBr pellet and are reported in terms of frequency of
absorption (cm ). Elemental analysis was performed by a Carlo-
Erba EA1110 CNNO-S analyzer. E-Merck pre-coated TLC plates,
RANKEM silica gel G for preparative thin-layer chromatography
were used. Melting points were determined on electrical melting
point apparatus in open capillary and were uncorrected. Phenol,
naphthol and ethyl acetoacetate were purchased from Himedia,
Mumbai India and used without any purification.
4.7. Compound 1d
−1
Colorless solid, mp 180–181 C; 1H NMR (400 MHz; DMSO-d ):
◦
6
ıH 2.40 (s, 3H, Me), 6.33 (s, 1H, C CH), 6.81–6.89 (m, 3H, ArH),
1
3
10.12 (s, 1H, OH); C NMR (100 MHz, DMSO-d ): 14.04, 23.1, 115.0,
6
116.0, 128.1, 151.23, 157.23, 162.99, 165.9, 171.8; EIMS: m/z: Calcu-
+
lated for C10H NO 205.17, Found [M+H] 206; C, H and N analyses
7
4
Calculated for C 58.54, H 3.44, N 6.83 Found C 58.41, H 3.59, N 6.88.
.8. Compound 1e
Colorless solid, mp 261–262 C; 1H NMR (400 MHz; DMSO-
4
4.2. Preparation of hydrotalcite
◦
The catalyst hydrotalcite was synthesized using literature pro-
d6): ıH 2.11 (s, 3H, CH3), 2.46 (s, 3H, Me), 6.39 (s, 1H, C CH),
6.80 (d, J = 8.4 Hz, 1H, ArH), 7.41 (d, J = 8.4 Hz, 1H, ArH), 10.3 (brs,
1H); C NMR (100 MHz, DMSO-d6): 14.04, 23.11, 115.03, 116.07,
122.9, 151.3, 157.2, 162.9, 165.9, 171.8; EIMS: m/z: Calculated for
C11H10O3 190.2, Found [M]+ 190; C, H and N analyses Calculated
for C 69.46, H 5.30, Found C 69.61, H 5.36.
cedure [54].
Typical procedure. Mixed salt solutions containing Ca2+/Mg2+
13
3
+
and Al in molar ratios of 3:1 were taken. pH of the solution was
raised to 8.5 using 25% NH OH. The thick white slurry was aged and
4
autogenous pressure in an autoclave to achieve small particle size
and high surface area. The precipitate was filtered ad washed with
◦
deionized water and dried at 110 C.
4.9. Compound 1f
White solid, mp 151–152 C; 1H NMR (400 MHz; DMSO-d6): ıH
◦
4.3. One-pot three component reaction
2
.40 (s, 3H, Me), 6.33 (s, 1H, C CH), 6.61 (d, J = 8.4 Hz, 1H, ArH),
13
Typical procedure for synthesis of coumarin. A mixture of phe-
7.2 (s, 1H, ArH), 7.51 (d, J = 7.76 Hz, 1H, ArH), 10.12 (s, 1H, OH);
C
nols (0.0025 mol) and dicarbonyl (0.0025 mol) were heated at
NMR (100 MHz, DMSO-d6): 23.09, 102.8, 110.8, 111.9, 115.1, 132.5,
137.6, 153.5, 162.3, 165.6; EIMS: m/z: Calculated for C10H7NO4
205.17, Found [M+H]+ 206; C, H and N analyses Calculated for C
58.54, H 3.44, N 6.83 Found C 58.41, H 3.59, N 6.88.
◦
7
5
0 C under solvent free conditions using hydrotalcite (Mg–Al-CO ,
3
0 mg) as a catalyst. The time taken by different phenols in reac-
tion was as mentioned in Table 4. After completion of the reaction

2
60
P.K. Sahu et al. / Journal of Molecular Catalysis A: Chemical 395 (2014) 251–260
[15] G.P. Romanelli, D. Bennardi, D.M. Ruiz, G. Baronetti, H.J. Thomas, J.C. Autino,
4
.10. Compound 1g
Tetrahedron Lett. 45 (2004) 8935.
[
16] S.S. Bahekara, D.B. Shinde, Tetrahedron Lett. 45 (2004) 7999.
White powder, mp 160–161 C; 1H NMR (400 MHz; DMSO-d ):
◦
6
[17] J. Li, H. Chen, D.Z. Negrerie, Y. Du, K. Zhao, RSC Adv. 3 (2013) 4311.
[18] R.K. Verma, G.K. Verma, G. Shukla, M.S. Singh, RSC Adv. 2 (2012) 2413.
[19] M. Maheswara, V. Siddaiah, G.L.V. Damu, Y.K. Rao, C.V. Rao, J. Mol. Catal. A:
Chem. 255 (2006) 49.
ıH 2.46 (s, 3H, Me), 3.89 (s, 1H, OCH ), 6.36 (s, 1H, C CH), 6.80–6.91
3
m, 2H, ArH), 9.82 (s, 1H, OH); 1 C NMR (100 MHz, DMSO-d ): 23.7,
3
(
5
6
7.2, 103.2, 111.8, 113.9, 152.0, 154.5, 159.4, 163.2, 166.6; EIMS:
[
20] K.C. Majumdar, S. Samanta, I. Ansary, B. Roy, RSC Adv. 2 (2012) 2137.
m/z: Calculated for C11H10O3 206.19, Found [M]+ 206; C, H and N
[21] (a) M. Matzke, S. Stolte, K. Thiele, T. Juffernholz, J. Arning, J. Ranke, U. Welzbier-
mann, B. Jastorff, Green Chem. 9 (2007) 1198;
analyses Calculated for C 64.07, H 4.89 Found C 64.19, H 5.03.
(
(
b) D. Kralisch, A. Stark, S. Korsten, G. Kreisel, B. Ondruschka, Green Chem. 7
2005) 301;
4
.11. Compound 2
(c) T. Pham, C. Cho, Y. Yun, Water Res. 44 (2010) 352.
[
22] G. Centi, S. Perathoner, Microporous Mesoporous Mater. 107 (2008) 3.
◦
−1
[23] S.K. Sharma, P.A. Parikh, R.V. Jarra, J. Mol. Catal. A: Chem. 278 (2007)
35.
[24] C.M. Jinesh, C.A. Antonyraj, S. Kannan, Catal. Today 141 (2009) 176.
[25] (a) A. Corma, S. Iborra, S.S. Miquel, J. Primo, J. Catal. 173 (1998) 315;
White powder, mp 154–155 C; IR (KBr) (ꢁmax, cm ): 1675
1
1
(
C
Ostr). H NMR (400 MHz, CDCl ): ıH 2.71 (s, 3H, Me), 6.51 (s, 1H,
3
C
1
1
CH), 7.03–7.63 (m, 6H, ArH); 13C NMR (100 MHz, CDCl ): 23.17,
3
(
b) K. Motocura, N. Fujita, K. Mori, T. Mizugaki, K. Ebitani, K. Htsukawa, K.
02.56, 111.65, 122.22, 122.92, 123.68, 126.40, 126.79, 127.98,
Kanedar, Chem. Eur. J. 12 (2006) 8228.
37.43, 141.26, 154.04, 162.59, 165.44; EIMS: m/z: Calculated for
[
26] M. Turco, G. Bagnasco, U. Costantino, F. Marmottini, T. Montanari, G. Ramis, G.
Busca, J. Catal. 228 (2004) 56.
C14H10O2 210, Found [M]+ 210; C, H and N analyses Calculated for
C 80.01, H 4.76, Found C 80.05, H 4.81.
[
[
[
27] B.F. Sels, D.E. De Vos, P.A. Jacobs, Catal. Rev. Sci. Eng. 43 (2001) 443.
28] Y. Xi, R.J. Davis, J. Catal. 254 (2008) 190.
29] S.K. Yun, T.J. Pinnavaia, Chem. Mater. 7 (1995) 348.
Acknowledgements
[30] B.M. Choudary, M.L. Kantam, V. Neeraja, K.K. Rao, F. Figueras, L. Delmotte, Green
Chem. 3 (2001) 257.
[
31] (a) S.K. Sharma, P.A. Parikh, R.V. Jasra, J. Mol. Catal. A: Chem. 278 (2007) 135;
b) V.R.L. Constantino, T. Pinnavaia, J. Inorg. Chem. 34 (1995) 883.
[32] (a) A. Corma, V. Fornes, R.M. Martinaranda, F. Rey, J. Catal. 134 (1992) 58;
b) M.J. Climent, A. Corma, S. Iborra, J. Primo, J. Catal. 151 (1995) 60.
33] C.O. Veloso, C.N. Perez, B.M. De Souza, E.C. Lima, A.G. Dias, J.L.F. Monteiro, C.A.
Henriques, Microporous Mesoporous Mater. 107 (2008) 23.
We are grateful thanks to Dr. Yogesh Sharma, Water India Ltd.,
Delhi and SIAF Facility, Punjab University, Chandigarh for spectral
analytical data.
(
(
[
References
[34] W.L. Xie, H. Peng, L.G. Chen, J. Mol. Catal. A: Chem. 246 (2006) 24.
[
[
35] V.K. Diez, C.R. Apesteguia, J.I. Di Cosimo, J. Catal. 215 (2003) 220.
36] D. Tichit, M.H. Lhouty, A. Guida, B.H. Chiche, F. Figueras, A. Auroux, B. Bartalini,
E. Garrone, J. Catal. 151 (1995) 1995.
[1] (a) I. Kostova, Curr. Med. Chem. 5 (2005) 29;
(
(
(
b) F. Borges, F. Roleira, N. Milhazes, L. Santana, E. Uriarte, Curr. Med. Chem. 12
2005) 887;
c) J.M. Schmidt, G.B. Tremblay, M. Page, J. Mercure, M. Feher, R. Dunn-Dufault,
[
37] T. Nakatsuka, T.H. Kawasaki, S. Yamashita, S. Kohjiya, Bull. Chem. Soc. Jpn. 52
(
1979) 2449.
[
[
38] W.T. Reichle, S.Y. Kang, D.S. Everhardt, J. Catal. 101 (1986) 352.
39] P. Mustrowski, L. Chmielarz, E. Bozek, M. Sawalha, F. Roessner, Mater. Res. Bull.
M.G. Peter, P.R. Redden, J. Med. Chem. 46 (2003) 1289;
(
(
d) J. Pandey, A.K. Jha, K. Hajela, Bioorg. Med. Chem. 12 (2004) 2239;
e) J.M. Sayer, Y. Haruhiko, A.W. Wood, A.H. Conney, D.M. Jerina, J. Am. Chem.
39 (2004) 263.
[
[
40] J. Shen, M. Tu, C. Hu, J. Solid State Chem. 137 (1998) 295.
41] D.G. Cantrell, L.J. Gillie, A.F. Lee, K. Wilson, Appl. Catal. A: Gen. 287 (2005)
Soc. 104 (1982) 5562;
(
(
(
f) Y.A.G.P. Gunawardana, N.S. Kumar, M.U.S. Sultanbawa, Phytochemistry 18
1979) 1017;
g) B.I. Alo, A. Kandil, P.A. Patil, M.J. Sharp, M.A. Snieckus, V. Siddiqui, J. Org.
1
83.
42] J.M. Fraile, N. Garcia, J.A. Mayoral, E. Pires, L. Rodan, Appl. Catal. A: Gen. 364
2009) 87.
[
(
Chem. 56 (1991), and Refs. 6–10 cited therein 3763.
[
[
43] H.J. Hattori, Jpn. Petrol. Inst. 47 (2004) 67.
44] J.J. Di Cosimo, V.K. Di’ez, M. Xu, E. Iglesia, C.R. Apesteguia, J. Catal. 178 (1998)
[
[
[
[
[
2] H.W.T. Sidwell, L. Fritz, C. Tamm, Helv. Chim. Acta 54 (1971) 207.
3] C. Tamm, Arzneim. -Forsch. 22 (1972) 1776.
4] H. Raistrick, C.E. Stilkings, R. Thomas, Biochemistry 55 (1953) 421.
5] R.W. Pero, D. Harvan, M.C. Blois, Tetrahedron Lett. 14 (1973) 945.
6] W. Steglich, B. Fugmann, S. Lang-Fugmann, ROMPP Encyclopedia of Natural
Products, B. Eds.; Thieme: Stuttgart, (1997).
499.
[
[
45] C.T. Fishel, R. Davis, Langmuir 10 (1994) 159.
46] P. Kustrowski, D. Sulkowska, L. Chmielarz, R. Dziembaj, Appl. Catal. A: Gen. 302
(
2006) 317.
47] (a) A.L. McKenzie, C.T. Fishel, R.J. Davis, J. Catal. 138 (1992) 547;
b) F. Rey, V. Fornés, J.M. Rojo, J. Chem. Soc.: Faraday Trans. 83 (1992) 2233.
[
[
[
7] S. Frere, V. Thiery, T. Besson, Tetrahedron Lett. 42 (2001) 2791.
8] S.P. Chavan, K. Shivasankar, R. Sivappa, R. Kale, Tetrahedron Lett. 43 (2002)
(
[
[
[
[
[
[
[
[
48] W.T. Reichle, Chemtech 16 (1986) 58.
8
583.
49] A. Takagaki, K. Iwatani, S. Nishimura, K. Ebitani, Green Chem. 12 (2010) 578.
50] F. Cavani, F. Trifiro, A. Vaccari, Catal. Today 11 (1991) 173.
51] F.M. Labojos, V. Rives, M.A. Ulibarri, J. Mater. Sci. 27 (1992) 1546.
52] A.S. Bookin, A. Dritis, Clays Clay Miner. 41 (1993) 551.
53] K.R. Kottapalli, G. Monique, S.V. Jaime, F. Francois, J. Catal. 173 (1998) 115.
54] S. Gupta, D.D. Agarwal, S. Banerjee, Indian J. Chem.: Sect. A 47 (2008) 1004.
55] L. Wang, J. Xia, H. Tian, C. Qian, Y. Ma, Indian J. Chem. 42B (2003) 2097.
[9] S.D. Bose, A.P. Rudradas, M.H. Babu, Tetrahedron Lett. 43 (2002) 9195.
[
[
10] H. Valizadeha, A. Shockravi, Tetrahedron Lett. 46 (2005) 3501.
11] G.V.M. Sharma, J.J. Reddy, P.S. Lakshmi, P.R. Krishna, Tetrahedron Lett. 46 (2005)
1
9.
[
[
[
12] J.C. Rodríguez-Domínguez, G. Kirsch, Tetrahedron Lett. 47 (2006) 3279.
13] M.K. Potdar, S.S. Mohile, M.M. Salunkhe, Tetrahedron Lett. 42 (2001) 9285.
14] V.M. Alexander, R.P. Bhat, S.D. Saman, Tetrahedron Lett. 46 (2005) 6957.