Efficient catalytic performance of calcined tungstophosphoric acid for the Claisen-Schmidt condensation under solvent-free reaction

Article abstract of DOI:10.14233/ajchem.2019.22219

Effect of calcination of tungstophosphoric acid catalyst was evaluated in terms of the synthesis of chalcone derivatives via Claisen-Schmidt condensation using the reaction of acetophenone and several substituted aldehydes. The catalyst was characterized before and after calcination by FT-IR to assess the effectiveness of the synthesis of the desired products. The calcined tungstophosphoric acid catalyst (HPW-CL) showed a better performance and high yield of Claisen-Schmidt products in a short period of time. It was also found out that the calcined tungstophosphoric acid provides a chemo selective, efficient and environmentally benign synthesis of chalcone in an excellent yield in a solvent-free system.

Full text of DOI:10.14233/ajchem.2019.22219

Asian Journal of Chemistry; Vol. 31, No. 11 (2019), 2579-2584
A
SIAN
J
OURNAL OF HEMISTRY
C
https://doi.org/10.14233/ajchem.2019.22219
Efficient Catalytic Performance of Calcined Tungstophosphoric Acid for
the Claisen-Schmidt Condensation under Solvent-Free Reaction
ABDULRAHMAN I. ALHARTHI
Department of Chemistry, College of Science and Humanities in Al-Kharj, Prince Sattam Bin Abdulaziz University, P.O. Box- 83, Al-Kharj
1
1942, Saudi Arabia
Corresponding author: E-mail: a.alharthi@psau.edu.sa
Received: 28 May 2019; Accepted: 6 July 2019;
Published online: 28 September 2019;
AJC-19589
Effect of calcination of tungstophosphoric acid catalyst was evaluated in terms of the synthesis of chalcone derivatives via Claisen-
Schmidt condensation using the reaction of acetophenone and several substituted aldehydes. The catalyst was characterized before and
after calcination by FT-IR to assess the effectiveness of the synthesis of the desired products. The calcined tungstophosphoric acid catalyst
(
HPW-CL) showed a better performance and high yield of Claisen-Schmidt products in a short period of time. It was also found out that
the calcined tungstophosphoric acid provides a chemo selective, efficient and environmentally benign synthesis of chalcone in an excellent
yield in a solvent-free system.
Keywords: Calcination, Tungstophosphoric acid, Claisen-Schmidt condensation, Chalcone derivatives.
super acid region in it. In another way, they have effective
redox properties [16]. Due to these qualities, fast multi-electron
redox transformation is possible under mild reaction conditions
[2]. Apart from that, heteropoly acids have a very high solub-
ility in polar solvents and exhibit high thermal stability in a
solid state [3,17,18]. Heteropoly acids have proved to be
INTRODUCTION
Many efforts have been made by the chemists as well as
the chemical industries over past two decades to avoid risk
during the synthesis of organic compounds either at the pilot
scale or the industry level. Significant use of various chemicals
during the process of synthesis in order to reduce environmen-
tal pollution is designated as a green chemistry approach [1].
In recent years, researchers have been constantly trying to find
new eco-friendly green solid catalysts for various organic trans-
formation reactions [2-5]. These included tungstophosphoric
stronger than common mineral acids (HCl, H
2
SO
4
, HNO , etc.)
3
in solution form. Tungstophosphoric acid is markedly stronger
than any other acids in this class such as phosphomolybdic
acid etc. [6,14,19]. Heteropoly acids also have the capability to
interact with polar as well as non-polar molecules due to the
pseudo liquid behaviour of the catalyst on the surface at even
low temperatures [1]. It was claimed that some solid heteropoly
acids and their salts, upon calcination around 300-400 ºC,
developed super acids sites and acidity was found more than
acid (H PW12O40), a solid acid catalyst, which possesses properties
of green chemistry, belongs to heteropoly acid and is therefore
convenient for wide varieties of organic synthesis [6].
3
Structurally, it is of Keggin type, having inorganic-cage
n-1
anions of the formula XM12
O
40 , where X is a heteroatom
100 % H
2
SO [20,21].
4
5+
4+
6+
6+
(
P , Si ) and M is metal ion (W or Mo ) [7-9]. Heteropoly
Formation of α,β-unsaturated ketones through C-C bond
formation is known as Claisen-Schmidt condensation reaction
between acetophenone and aldehydes. The product so formed
is chalcone [21]. Chalcone derivatives belong to flavonoid family
and are an important medicinal scaffold for varieties of pharma-
cological applications including anticancer [22], anti-inflam-
acids also called as polyoxometalate compounds have increasing
demands recently [10-13]. Heteropoly acids have some remark-
able properties in the sense that they are low toxic, environ-
mentally friendly and cost-effective [14,15]. On the other hand,
heteropoly acids behave as strong Brønsted acids due to the
This is an open access journal, and articles are distributed under the terms of the Attribution 4.0 International (CC BY 4.0) License. This
license lets others distribute, remix, tweak, and build upon your work, even commercially, as long as they credit the author for the original
creation. You must give appropriate credit, provide a link to the license, and indicate if changes were made.

2
580 Alharthi
Asian J. Chem.
1
matory [23], antimalarial [24] and antitubercular [25]. Further-
more, they are important intermediates for useful synthesis
for pharmacologically important heterocycles [3].
Conventionally, Claisen-Schmidt condensation is carried
out in the presence of acid or base catalysts between aromatic
aldehydes and ketones. Numerous catalysts have been used
so far for the synthesis of chalcones in bases such as NaOH
1660 (C=O), 1602 (C=C,Ar); H NMR (DMSO, δ ppm): 7.79-
7.02 (10H, m, Ar-H), 7.05-6.96 (1H, d, J = 2 Hz, CH=CH),
13
6.68-6.24 (2H, d, J = 8.6 Hz, CH=CH); C NMR (DMSO, δ
ppm):188.40(C=O), 148.41 (1C, CH=CH), 141.44 (1C, CH=CH),
138.35, 136.40, 133.72, 132.23, 129.43, 128.33, 124.78, 122.68,
118.05, 115.00 (Ar-C).
3-(4-Hydroxy-3-methoxyphenyl)-1-phenylprop-2-en-
[
26], KOH [27], LiOH·H
such as dry HCl [30], RuCl
33], ionic liquids [4] and clay [34]. These mentioned catalysts
2
O [28], Ba(OH)
2
[29] and in acids
1-one (4a): Light yellow, m.p.: 82 ºC, m.f. C16
H
14
O ; FT-IR
3
-1
3
[31], TiCl [32], sulfonic acids
4
(cm , ATR); 3146 (C=C-H, Ar-H), 1662 (C=O), 1585 (C=C,
1
[
Ar); H NMR ( DMSO, δ, ppm): 9.23 (1H, s, OH), 7.07-7.05
have many shortcomings such as toxicity, corrosiveness, long
reaction times, generation of undesired products and high
temperature. Other drawbacks include low catalyst surface and
recovery, which have their implications on the fruitful C-C bond
formation during chalcone synthesis.
(8H, m, Ar-H) 6.93-6.92 (1H, d, J = 2 Hz), 6.16-6.14 (2H, d, J =
13
8.3 Hz); C NMR (DMSO, δ, ppm): 186.44 (C=O), 145.67
(1C, CH=CH), 138.54 (1C, CH=CH), 136.40, 133.72, 129.43,
128.33, 124.78, 122.68, 118.05, 115.00 (Ar-C), 56 (1C, OCH
3
).
3-(4-Chlorophenyl)-1-phenylprop-2-en-1-one (5a):White,
-1
In this work, a comparative study between the calcined
HPW-CL) and non-calcined tungstophosphoric acid (HPW)
m.p.: 118 ºC, m.f. C15H11OCl; FT-IR (cm ,ATR): 3196 (C=C-
1
(
H, Ar-H), 1680 (C=O), 1590 (C=C, Ar); H NMR (DMSO, δ
ppm): 8.15-7.27 (9H, m, Ar-H), 7.07-7.05 (1H, d, J = 12.9
as a catalyst for the C-C bond formation in a classical Claisen-
Schmidt condensation has been carried out to the fact that the
calcination increases the acidity of the catalyst which is required
for this type of reactions.
13
Hz, CH=CH), 6.90-6.88 (1H, d, J = 12.8 Hz, CH=CH); C
NMR (DMSO, δ ppm): 189.75 (C=O), 143.07 (1C, CH=CH),
137.83, 135.62, 134.16, 134.03, 133.79, 131.37, 131.06, 129.45,
1
29.37, 129.33, 129.01 (Ar-C), 123.20 (1C, CH=CH).
EXPERIMENTAL
3
-(3-Chlorophenyl)-1-phenylprop-2-en-1-one (6a):
-1
White, m.p.: 78 ºC, m.f. C15
C=C-H,Ar-H), 1665 (C=O), 1602 (C=C,Ar); H NMR (DMSO,
δ ppm): 8.11-7.22 (9H, m, Ar-H), 7.47-7.29 (1H, d, J = 7.5
H11OCl; FT-IR (cm , ATR); 3162
All materials and chemicals were purchased from Sigma-
Aldrich. FT-IR spectra for the catalyst (tungstophosphoric acid)
and synthesized compounds were recorded using Thermo
Scientific iD5ATR diamond Nicolet iS 5 FT-IR Spectrometer.
1
(
13
Hz, CH=CH), 7.28-6.89 (1H, d, J = 7.8 Hz, CH=CH); C NMR
(DMSO, δ ppm): 185.47 (C=O), 148.29 (1C, CH=CH), 138.99,
-1
Data spacing was 0.482 cm with a single beam having OMINIC
software. Especially designed Thermocraft incorporated tube
furnace was used for calcination of the catalyst (tungstophos-
1
(
36.67, 133.89, 132.33, 129.44, 129.02, 128.40, 128.19, 125.79
Ar-C), 122.88 (1C, CH=CH).
1-Phenyl-3-(2,3,5-trimethoxyphenyl)prop-2-en-1-one
1
13
phoric acid). All compounds were elucidated by H and C
NMR spectra using BRUKER-PLUS (500 MHz) with tetra-
methylsilane (TMS) as an internal standard.
Calcination of tungstophosphoric acid: An accurately
.00 g of tungstophosphoric acid was weighed in a crucible.
The crucible containing tungstophosphoric acid was put in a
tube furnace at 300 ºC for 4 h in static air.
General Procedure for the synthesis of chalcones (3a-
4a) via Claisen-Schmidt condensation using tungstophos-
phoric acid: A mixture of substituted aldehyde (2 mmol) and
acetophenone (2 mmol) was stirred in the presence of calcined
or non-calcined tungstophosphoric acid with varying mol %
till the completion of reaction under solvent-free conditions.
TLC confirmed the completion of the reaction; the mixture
was filtered and washed with water to separate the catalyst (high
solubility of HPW in water). The product was obtained by
recrystallization with ethanol (Scheme-I).
-
1
(
3
(
(
7a):Yellow, m.p.: 142 ºC, m.f. C18
058 (C=C-H, Ar-H), 1669 (C=O), 1594 (C=C, Ar); H NMR
DMSO, δ ppm): 8.14-8.11 (1H, d, J = 15.75 Hz), 7.54-7.99
H
18
O
4
; FT-IR (cm , ATR);
1
13
7H, m, Ar-H), 7.45-7.44 (1H, d, J = 7.8 Hz); C NMR (DMSO,
5
δ, ppm): 190.57 (C=O), 138.99 (1C, CH=CH), 120.78 (1C,
CH=CH), 163.87, 161.92, 158.38, 132.94, 132.83, 129.74, 129.22,
1
(
28.68, 128.59, 128.42, 126.72, 106.68, 105.55 (Ar-C), 56.00
1C, OCH ), 55.48-56.54 (3C, OCH ).
,5-Diphenylpenta-2,4-dien-1-one (8a): Creamy white,
3
3
1
1
-1
m.p.: 110 ºC, m.f. C17
2C=C-H,Ar-H), 1664 (C=O), 1598 (C=C,Ar); H NMR (DMSO,
δ ppm) 7.46-7.22 (10H, m, Ar-H), 7.05 (1H, s, =CH), 7.03-
.02 (1H, d, J = 2.3 Hz), 6.36 (1H, d, J =1.0 Hz), 6.33 (1H, d,
H
14
O
4
; FT-IR (cm , ATR): 3156, 3080
1
(
7
13
J = 0.9 Hz); C NMR (DMSO, δ ppm): 176.45 (C=O), 139.23
1C, CH=CH), 121.43 (1C, CH=CH), 135.87, 130.88, 129.44,
29.14, 128.33, 128.02, 126.93, 125.66, 124.54 (Ar-C).
-(Indolin-3-yl)-1-phenylprop-2-en-1-one (9a): Light
(
1
3
-1
brown, m.p.: 188 ºC, m.f. C17
H15NO; FT-IR (cm , ATR): 3042
1
(C=C-H,Ar-H), 1628 (C=O), 1611 (C=C,Ar); H NMR (DMSO,
δ, ppm): 12.15 (1H, s, NH, 3-indole), 8.30-8.29 (1H, d, J =
3
=
.15, 3-indole), 8.12-8.10 (1H, d, J = 7.65 Hz), 7.53 (1H, d, J
7.9 Hz), 7.29-7.21 (9H, m,Ar-H); C NMR (DMSO, δ, ppm):
13
Scheme-I: Claisen-Schmidt condensation reaction between acetophenone
185.44 (C=O), 138.93 (1C, CH=CH), 137.52 (1C, CH=CH),
24.58, 123.93, 122.59, 121.29, 118.63, 112.88 (Ar-C).
-Phenyl-3-(1H-pyrrol-2-yl)prop-2-en-1-one (10a):
and aldehydes using tungstophosphoric acid
1
1
Spectroscopic data
-1
Brown, m.p.: 142 ºC, m.f. C13H11NO; FT-IR (cm , ATR): 3100
1
3
-(Phenyl)-1-phenylprop-2-en-1-one (3a):White, m.p.:
(C=C-H, Ar-H), 1646 (C=O), 1583 (C=C, Ar). H NMR
-1
6
5 ºC, m.f. C15
H12O; FT-IR (cm , ATR): 3060 (C=C-H, Ar-H),
(DMSO, δ, ppm): 11.73 (1H, s, NH, 2-pyrrole), 8.07-8.06 (1H,

Vol. 31, No. 11 (2019)
Efficient Catalytic Performance of Calcined Tungstophosphoric Acid for the Claisen-Schmidt Condensation 2581
d, J = 8.55, ), 8.04-8.02 (1H, d, J = 8.55 Hz), 7.65-7.55 (8H, m,
Ar-H); C NMR (DMSO, δ, ppm): 188.88 (C=O), 138.79 (1C,
CH=CH), 134.76 (1C, CH=CH), 133.00, 129.60, 129.17, 128.40,
13
HPW
HPW-CL
124.79, 116.90, 115.05, 111.08 (Ar-C).
1
-Phenyl-3-(pyridine-2yl)prop-2-en-1one (11a): Light
-1
yellow, m.p.: 71 ºC, m.f. C11H14NO; FT-IR (cm , ATR): 3058
C=C-H, Ar-H), 1669 (C=O), 1594 (C=C, Ar); H NMR
1
(
(
=
DMSO, δ ppm): 8.49-7.09 (9H, m, Ar-H), 6.97-6.94(1H, t, J
1
693.53
13
7.3 Hz, CH=CH), 6.87-6.85(1H, t, J = 6.3 Hz, CH=CH); C
8
81.53
3
121.23
NMR (DMSO, δ ppm): 186.41 (C=O), 141.49 (1C, CH=CH),
963.76
1
075.35
1
1
39.65, 138.76, 137.89, 135.54, 132.34, 130.90, 129.71,
28.36, 126.32 (Ar-C), 121.62 (1C, CH=CH).
7
38.82
1
614.51
3
461.71
885.73
1
-Phenylhex-2-en-1-one (12a): White, m.p.: 29 ºC, m.f.
-1
C
12
H14O; FT-IR (cm ,ATR): 3573 (C=C-H,Ar-H), 1681 (C=O),
1
073.83
1
0
971.99 738.82
1
597 (C=C, Ar); H NMR (DMSO, δ ppm): 7.96-7.24 (5H, m,
Ar-H), 7.22-7.16 (1H, q, J = 7.1 Hz, CH=CH), 7.14-7.10 (1H, t,
J= 8.5 Hz, CH=CH), 2.50 (2H, s, CH ), 2.36 (2H, s, CH ), 0.91
); C NMR (DMSO, δ ppm): 188.78 (C=O), 140.35
1C, CH=CH), 138.43, 136.72, 129.47, 127.51, (Ar-C), 120.89
1C, CH=CH), 34.45, 23.56 (2C, 2 × CH ), 14.23 (1C, CH ).
-Phenyldec-2-en-1-one (13a): White, m.p.: 38 ºC; m.f.
4000
3500
3000
2500
2000
1500
1000
500
–1
Wavenumber (cm )
Fig. 1. FT-IR spectra of non-calcined (HPW) and calcined (HPW-CL)
2
2
13
(
(
(
3H, s, CH
3
Progression in percentage yields of the desired product was
found increased, as the mol % of the catalyst increased by two
units in each reaction. The percentage yield of product and
time of completion of the reaction with each mol % of the
catalyst (HPW-CL or HPW) were studied. The maximum yield
%) of 98 % was observed using 8 % of HPW-CL with the
expense of 10 min only, while 10 mol % was utilized applying
HPW as a catalyst to get 82 % within 45 min (Table-1, Fig. 2).
2
3
1
-
1
C
(
(
16
H22O. FT-IR (cm , ATR): 3572 (C=C-H, Ar-H), 1683
C=O), 1597 (C=C, Ar); H NMR (DMSO, δ ppm): 7.88-7.86
5H, m, Ar-H), 7.30-7.27 (1H, d, J = 7.3 Hz, CH=CH), 7.26-
1
(
7
0
1
.24 (1H, d, J = 8.6 Hz, CH=CH), 2.64-2.36 (12H, s, 6 × CH
2
),
); C NMR (DMSO, δ ppm): 191.62 (C=O),
41.53 (1C, CH=CH), 129.47, 129.03, 127.50 (Ar-C), 121.92
), 15.18 (1C, CH ).
-Phenylhept-2-en-1-one (14a): Creamy white, m.p.: 42
13
.77 (3H, s, CH
3
(1C, CH=CH), 39.94-39.44 (6C, CH
2
3
1
TABLE-1
-1
OPTIMIZATION BASED ON THE AMOUNT OF CALCINED
HPW-CL) AND NON-CALCINED TUNGSTOPHOSPHORIC
ACID (HPW) AND OTHER CATALYSTS FOR THE SYNTHESIS
OF MODEL REACTION (4a) BETWEEN ACETOPHENONE (1)
AND 4-HYDROXY-3-METHOXY BENZALDEHYDE (2)
ºC, m.f. C13H16O. FT-IR (cm ,ATR): 3572 (C=C-H,Ar-H), 1681
(
1
(
C=O), 1597 (C=C, Ar); H NMR (DMSO, δ ppm): 7.88-7.87
(2 × 1H, d, J = 7.0 Hz, CH=CH), 7.30-7.25 (5H, m,Ar-H),2.99-
13
2.50 (2H, s, 3 × CH
2
), 0.89 (3H, s, CH ); C NMR (DMSO, δ
3
1
2
ppm): 191.28 (C=O), 138.44 (1C, CH=CH), 133.95, 129.47,
27.52, (Ar-C), 122.54 (1C, CH=CH), 39.92-39.42 (2C, 3 ×
CH ), 12.98 (1C, CH ).
Entry
Catalyst (mol %)
HPW-CL (2)
HPW-CL (4)
HPW-CL (6)
HPW-CL (8)
HPW-CL (10)
HPW (2)
Yield (%)
72
Solvents Time (min)
1
1
2
3
4
5
6
7
8
9
–
–
–
–
–
–
–
–
–
120
100
50
10
12
150
125
80
50
45
78
87
98
91
51
65
68
79
82
45
40
50
2
3
RESULTS AND DISCUSSION
Catalyst characterization: From the FT-IR spectrum of
non-calcined HPW, the well-defined sharp and strong absorption
HPW (4)
HPW (6)
HPW (8)
HPW (10)
-1
bands at 1073.83 and 971.99 cm were clearly identified as
P-O and W=O stretching vibrations respectively, whereas at
-1
10
–
8
85.73 cm stretching modes of vibration for W-OW were also
11
12
13
NaOH (10)
H SO (10)
EtOH
EtOH
EtOH
240
300
150
observed (Fig. 1). These bands are a clear indication of the
Keggin type structure of HPW [7,8].
2
4
ZnCl (10)
2
1
2
When HPW was calcined, slight changes of intensity were
observed. This may be due to the loss of water (Fig. 1). The
Reaction conditions were optimized to 100 % conversion; Isolated
yield.
-1
W=O band was shifted from 971.99 to 963.76 cm , whereas
-1
W-O-W band changed from 885.73 to 881.53 cm . This revealed
that the Keggin type structure of HPW was not affected by the
calcination at 300 ºC and it remained intact after the calcination.
Optimization of reaction conditions: A model reaction
was set up by taking 4-hydroxy-3-methoxy benzaldehyde
From the above results, the optimum mol% for HPW-CL
and HPW was found 8 and 10 %, respectively. Selecting any
mol% of non-calcined (HPW) as well as calcined (HPW-CL)
catalysts has many differences in terms of yield and reaction
completion time. The difference in these results shows that
the HPW-CL acid is more efficient than HPW in relation to
the C-C bond formation in Claisen-Schmidt condensation. It
seems that the amount and the nature of the catalyst play
significant role in the yield and time of product formation.
However, it was evident that the calcination of tungstophos-
(vanillin) and acetophenone as reactants to observe the perfor-
mance of calcined and non-calcined tungstophosphoric acid
catalyst under the solvent-free condition for effective Claisen-
Schmidt condensation via C-C bond formation. There was no
observation of any product formation in the absence of a catalyst.

2
582 Alharthi
Asian J. Chem.
phoric acid led to enhance the activity of bronsted acid which
increased the catalytic performance towards condensation reac-
leads to degradation of some reactants and there was no improve-
ment in yield. Therefore, it can be claimed that the low reaction
temperature was a positive factor in the efficiency of this procedure.
To establish the scope of both forms of tungstophosphoric
acid HPW-CL and HPW, various aldehydes (aromatic, hetero-
cyclic, aliphatic) with acetophenone reactions were performed
to get the product in excellent yields (Table-2). Condensation
product (chalcone) was also obtained by using aromatics where
heterocyclic aldehydes exhibited higher yields in a less time
compared to aliphatic aldehydes under the influence of both
forms of catalysts. This might be due to the hydrocarbon chain
tions [6]. Furthermore, 10 mol% of NaOH, H
2
SO
4
and ZnCl
2
in ethanol were used as catalysts for the reaction of Claisen
Schmidt condensation. As a result, they revealed a moderate
yield compare to the HPW and HPW-CL (Table-1, entries 11,
1
2 and 13).
Effect of temperature was not critically observed, as there
was no solvent used under catalytic reactions. Generally, room
temperature to 50 ºC was considered to complete the reaction
depending on reactants. It was observed that a high temperature
TABLE-2
CALCINED (HPW-CL) AND NON-CALCINED (HPW) TUNGSTOPHOSPHORIC ACID (8 mol %) CATALYZED
CLAISEN-SCHMIDT CONDENSATION REACTION FOR C-C BOND FORMATION DURING CHALCONE SYNTHESIS
Time (min)
HPW-CL
Yield (%)
HPW-CL
Entry
1
R1
R2
Product
HPW
45
HPW
77
H
3a
20
88
OH
OCH3
2
H
4a
10
40
98
88
Cl
3
4
H
H
5a
6a
15
15
40
60
92
85
89
70
Cl
OCH3
5
H
7a
25
40
95
89
H CO
3
OCH3
6
7
H
H
8a
9a
30
20
85
60
86
91
62
78
N
H
8
9
H
H
10a
11a
20
75
55
97
88
75
92
N
H
120
N
H C
3
10
11
12
H
H
H
12a
13a
14a
50
45
60
80
75
75
75
72
65
56
60
H C
3
H C
3
100

Vol. 31, No. 11 (2019)
Efficient Catalytic Performance of Calcined Tungstophosphoric Acid for the Claisen-Schmidt Condensation 2583
Conclusion
100
This study presents an easy technique to enhance the catal-
ytic activity of tungstophosphoric acid through calcination
HPW
HPW-Cl
90
80
70
60
50
without any support. The calcined catalyst worked efficiently
for the C-C bond formation in Claisen-Schmidt condensation
under a solvent-free condition in high yield with limited time
as compared to non-calcined catalyst. Thus, this method has a
wider scope to improve the yield in a clean reaction state. Calcined
tungstophosphoric acid could be a useful catalyst for a variety
of condensation reactions, where the high demand of the acidic
medium is required.
CONFLICT OF INTEREST
The authors declare that there is no conflict of interests
regarding the publication of this article.
2
4
6
8
10
Catalyst (mol %)
Fig. 2. Effect of mol % of catalysts HPW and HPW-CL on the yield of
REFERENCES
model compound 4a
1
2
3
4
5
.
.
.
.
.
M. Dabiri and S. Bashiribod, Molecules, 14, 1126 (2009);
https://doi.org/10.3390/molecules14031126.
J.H. Clark, Acc. Chem. Res., 35, 791 (2002);
https://doi.org/10.1021/ar010072a.
J.K. Rajput and G. Kaur, Tetrahedron Lett., 53, 646 (2012);
https://doi.org/10.1016/j.tetlet.2011.11.109.
H. Qian, D. Liu and C. Lv, Ind. Eng. Chem. Res., 50, 1146 (2011);
https://doi.org/10.1021/ie101790k.
J. Li, J. Feng, M. Li, Q. Wang, Y. Su and Z. Jia, Solid State Sci., 21, 1
attached to CHO functional group that hinders towards the
condensation reaction.Also, the liquid nature of aliphatic alde-
hydes and products after condensation were difficult to convert
into the solid state resulting in a slightly lower yield.
Moreover, attempts were made to understand the effect
of structure, product yield and time of reaction; however, there,
could not be found any significant correlation between them
except the fact that the compounds bearing aliphatic substituent
were found to have a lower yield and a longer reaction time.
Plausible mechanism: A probable mechanism for C-C
bond formation in Claisen-Schmidt condensation reaction (3a-
(
2013);
https://doi.org/10.1016/j.solidstatesciences.2013.04.005.
I.V. Kozhevnikov, Chem. Rev., 98, 171 (1998);
https://doi.org/10.1021/cr960400y.
L.P. Kazanskii and M.A. Fedotov, ed.: D.B. Brown, Mixed-Valence
Compounds: Theory and Applications in Chemistry, Physics, Geology,
and Biology, Springer Science & Business Media, England, vol. 58, p.
6
7
.
.
1
4a) is presented in Scheme-II.
383 (2012).
8
9
1
.
.
W. Klemperer and W. Shum, J. Am. Chem. Soc., 99, 3544 (1977);
https://doi.org/10.1021/ja00452a080.
W. Klemperer and W. Shum, J. Am. Chem. Soc., 100, 4891 (1978);
https://doi.org/10.1021/ja00483a044.
0. T. Okuhara, N. Mizuno and M. Misono, Catalytic Chemistry of Hetero-
poly Compounds, In: Advances in Catalysis, Elsevier, vol. 41, pp. 113-
252 (1996).
1
1
1
1. A. Corma, Chem. Rev., 95, 559 (1995);
https://doi.org/10.1021/cr00035a006.
2. D. Friesen and D. Gibson, Chem. Commun., 5, 543 (1998);
https://doi.org/10.1039/a800381e.
3. M. Misono and N. Nojiri, Appl. Catal., 64, 1 (1990);
https://doi.org/10.1016/S0166-9834(00)81550-X.
4. H. Firouzabadi and A. Jafari, J. Iran. Chem. Soc., 2, 85 (2005).
5. I.V. Kozhevnikov, Russ. Chem. Rev., 56, 811 (1987);
https://doi.org/10.1070/RC1987v056n09ABEH003304.
6. M. Misono, Catal. Rev., Sci. Eng., 29, 269 (1987);
https://doi.org/10.1080/01614948708078072.
1
1
1
1
7. M. Timofeeva,A. Demidov,A. Davydov and I. Kozhevnikov, J. Mol. Catal.,
7
9, 21 (1993);
https://doi.org/10.1016/0304-5102(93)85087-A.
1
1
2
8. V. Chuvaev, K. Popov and V. Spitsyn, Dokl. Akad. Nauk SSSR, 255, 892
(
1980).
Scheme-II: Plausible mechanism involved in C-C bond formation in Claisen-
9. G.A. Olah, G.K.S. Prakash and J. Sommer, Superacids, John Wiley & Sons:
NewYork, Chichester, Brisbane, Toronto, Singapore, pp. 1073-1074 (1985).
0. K. Nowiñska, R. Fiedorow and J.Adamiec, J. Chem. Soc., Faraday Trans.,
Schmidt condensation reaction
8
7, 749 (1991);
Either the calcined (HPW-CL) or non-calcined (HPW)
catalyst activates the lone pair electron of the oxygen atom of
aldehydes carbonyl groups (2), which facilitates the double
bond of acetophenone (1) to attack and form β-hydroxyl
compounds intermediate which finally undergoes dehydration
to form the desired product 3a-14a.
https://doi.org/10.1039/FT9918700749.
2
2
1. T. Okuhara, T. Nishimura, H. Watanabe and M. Misono, J. Mol. Catal.,
7
4, 247 (1992);
https://doi.org/10.1016/0304-5102(92)80242-9.
2. A. Alcantara, J.M. Marinas and J. Sinisterra, Tetrahedron Lett., 28,
1515 (1987);
https://doi.org/10.1016/S0040-4039(01)81030-3.

2
584 Alharthi
Asian J. Chem.
2
2
2
2
3. Y. Xia, Z.Y. Yang, P. Xia, K.F. Bastow, Y. Nakanishi and K.H. Lee,
Bioorg. Med. Chem. Lett., 10, 699 (2000);
https://doi.org/10.1016/S0960-894X(00)00072-X.
4. H.K. Hsieh, L.T. Tsao, J.P. Wang and C.N. Lin, J. Pharm. Pharmacol.,
28. X. Bu, L. Zhao and Y. Li, Synthesis, 1246 (1997);
https://doi.org/10.1055/s-1997-1348.
29. S. Bhagat, R. Sharma, D.M. Sawant, L. Sharma and A.K. Chakraborti,
J. Mol. Catal. A Chem., 244, 20 (2006);
https://doi.org/10.1016/j.molcata.2005.08.039.
30. T. Narender, K.P. Reddy, Shweta, K. Srivastava, D.K. Mishra and S.K.
Puri, Org. Lett., 9, 5369 (2007);
https://doi.org/10.1021/ol702187m.
31. T. Szell and I. Sohar, Can. J. Chem., 47, 1254 (1969);
https://doi.org/10.1139/v69-207.
32. L.J. Mazza and A. Guarna, Synthesis, 41 (1980);
https://doi.org/10.1055/s-1980-28916.
5
2, 163 (2000);
https://doi.org/10.1211/0022357001773814.
5. N. Yadav, S.K. Dixit, A. Bhattacharya, L.C. Mishra, M. Sharma, S.K.
Awasthi and V.K. Bhasin, Chem. Biol. Drug Des., 80, 340 (2012);
https://doi.org/10.1111/j.1747-0285.2012.01383.x.
6. M.N. Gomes, R.C. Braga, E.M. Grzelak, B.J. Neves, E. Muratov, R. Ma,
L.L. Klein, S. Cho, G.R. Oliveira, S.G. Franzblau and C.H. Andrade,
Eur. J. Med. Chem., 137, 126 (2017);
https://doi.org/10.1016/j.ejmech.2017.05.026.
33. T. Narender and K.P. Reddy, Tetrahedron Lett., 48, 3177 (2007);
https://doi.org/10.1016/j.tetlet.2007.03.054.
34. Q. Xu, Z. Yang, D. Yin and F. Zhang, Catal. Commun., 9, 1579 (2008);
https://doi.org/10.1016/j.catcom.2008.01.007.
2
7. N.J. Lawrence, D. Rennison, A.T. McGown, S. Ducki, L.A. Gul, J.A.
Hadfield and N. Khan, J. Comb. Chem., 3, 421 (2001);
https://doi.org/10.1021/cc000075z.