Catalytic performance of heteropolyacids as efficient and eco-friendly catalysts for the one-pot synthesis of benzopyran derivatives

Article abstract of DOI:10.1080/15533174.2010.522659

An efficient and improved procedure for the synthesis of benzopyran derivatives has been achieved with Keggin-type and Preyssler-type heteropolyacids (HPA) catalysts in one-pot reaction under solvent-free conditions. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/15533174.2010.522659

Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 40:916–921, 2010
Copyright © Taylor & Francis Group, LLC
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2010.522659
Catalytic Performance of Heteropolyacids as Efficient and
Eco-Friendly Catalysts for the One-Pot Synthesis of
Benzopyran Derivatives
Masoumeh Zakeri,1 Majid M. Heravi,1 Hossein A. Oskooie,1
and Fatemeh F. Bamoharram2
1Department of Chemistry, School of Sciences, Alzahra University, Vanak, Tehran, I. R. Iran
2Department of Chemistry, School of Sciences, Islamic Azad University, Khorasan Branch,
Mashhad, I. R. Iran
in solution.[8,9] They were used as industrial catalysts for sev-
An efficient and improved procedure for the synthesis of ben-
zopyran derivatives has been achieved with Keggin-type and
Preyssler-type heteropolyacids (HPA) catalysts in one-pot reaction
under solvent-free conditions.
eral liquid-phase reactions such as esterification, etherification,
hydration and dehydration, de-esterification, and condensation
reactions.[10]
In continuation of our interest in the application of het-
eropolyacids as versatile catalysts for a variety of organic
transformations,[11−17] we would like to report an effective
method to produce benzopyran derivatives in high yields, cat-
alyzed by Preyssler type and Keggin type heteropolyacids, under
solvent-free conditions (Scheme 1). Our findings indicated that
both HPA catalysts are effective for the synthesis of these com-
pounds in high yields. The major aim described in this work
is to design and develop the applications of HPAs with their
exclusive properties.
Keywords 1,3-hexanedione, salicylaldehyde, benzopyran deriva-
tives, heteropolyacids, solvent-free condition
INTRODUCTION
Benzopyran and its derivatives have attracted considerable
attention for organic and medicinal chemists because of their
useful biological and pharmacological properties such as an-
tibacterial, antitumor, antiallergic, anticoagulant, spasmolytic,
diuretic, and potassium channel activators.[1−3] Pyrans and their
derivatives are also key synthons[4] in the fields of pharma-
ceuticals, cosmetics, and perfumes. The biological importance
of this group of compounds has evoked widespread interest in
the development of new methodologies. Recently, benzopyran
derivatives have been synthesized by the reaction of substituted
salicylaldehydes with dimedone catalyzed by KF/Al2O3[5] or tri-
ethylbenzylammoium chloride (TEBA).[6] Considering the im-
portance and wide range applications of these compounds, an
easy and practical preparation method has still remained a chal-
lenging task. Development of methods using heteropolyacids
(HPAs) as solid and green catalysts for fine organic synthetic
processes related to fine chemicals, such as flavors, pharmaceu-
ticals, and food industries have been under attention in the last
EXPERIMENTAL
Materials and Methods
Melting points were measured by using the capillary tube
method with an electro thermal 9200 apparatus. 1HNMR spec-
tra were recorded on a Bruker AQS AVANCE-300MHz spec-
trometer using TMS as an internal standard (CDCl3 solution).
IR spectra were recorded using KBr disk on the FT-IR Bruker
Tensor 27. All products were well characterized by compar-
ison with authentic samples by TLC, spectral, and physical
data.
decade.[7] HPAs were reported to be more active catalysts than General Procedure
conventional inorganic and organic acids for various reactions
A mixture of substituted salicylaldehyde (2 mmol, 0.24 g),
substituted 1, 3-hexanedione (4 mmol, 0.56 g), and heteropoly-
acid (0.03 mmol) were mixed and stirred for 20 min at room
temperature. Temperature was raised to 120◦C and maintained
for the specified time (Table 3). After completion of the reaction
(monitored by thin-layer chromatography, TLC), the reaction
mixture was diluted with water (10 mL) and stirred for 5 min at
Received 9 January 2010; accepted 28 July 2010.
Address correspondence to Majid M. Heravi, Department of Chem-
istry, School of Sciences, Alzahra University, Vanak, Tehran, I. R. Iran.
E-mail: mmh1331@yahoo.com
916

ONE-POT SYNTHESIS OF BENZOPYRAN DERIVATIVES
917
R1
R1
O
O
OH
O
CHO
OH
HPA (0.03 mmol)
2
R
solvent-free, 120 °C
R1
R1
O
R
R1
R1
O
1
2
3
SCH. 1. Synthesis of benzopyran derivatives catalyzed by H14[NaP5W29MoO110] heteropolyacid, under solvent-free conditions.
80◦C. The product was filtered and purified by recrystallization of solvent was studied by carrying out the reactions in various
from ethanol.
solvents including ethanol, water, and acetonitrile, and solvent-
free condition. As presented in Table 1, the solvent free condition
resulted in higher yields.
RESULTS AND DISCUSSION
In study of reaction progress with TLC, we found that con-
To obtain some preliminary information on this synthetic re- version rates were affected by catalyst structure. In all cases the
action, initial experiments were performed with salicylaldehyde conversion rates were higher with H14[NaP5W29MoO110]. This
(1) and 5, 5- dimethyl-1, 3-cyclohexanedione (2, R1 =Me) as result is in agreement with expectation and earlier works on Big-
model substrates. When salicylaldehyde (2 mmol) was treated inelli reaction.[12,13] In this work, Preyssler-type heteropolyacid
with 5, 5- dimethyl-1, 3-cyclohexanedione (4 mmol) in the pres- gives higher yields of products than Keggin-type heteropoly-
ence of a catalytic amount of HPA (0.03 mmol) at 120◦C, acids. Unlike the Keggin-type heteropolyacids that have been
the desired product (3a) was obtained in 95% yield. In con- widely used as acid and oxidation catalysts for organic syn-
tinuation of our works, using heteropolyacids, which are low theses, the role of Preyssler catalyst is largely overlooked and
in toxicity, being highly stable towards humidity, being recy- there is not sufficient information. We believe that the Preyssler-
clable, air stable, and very well known in green chemistry, type form activates the pseudo liquid phases by maintaining the
we studied this reaction with heteropolyacids including Mo, concentration of reactant molecules in the appropriate pseudo
such as H3[PMo12O40], H4[PMo11VO40], H5[PMo10V2O40], liquid (solid bulk) phase, and this is due to the “oval” shape
H6[PMo9V3O40] and H14[NaP5W29MoO110]. Mixed addenda of the Preyssler-type in contrast to the “spherical” Keggin-type
Preyssler and Keggin catalysts are formed by the substitution of polyanions, which tend to be absorbing a greater number of
tungsten (VI) ion by Mo (VI). Interestingly, these catalysts, not reactant molecules.[18] The order of efficiency of these cata-
only catalyzed this reaction, but also showed higher yields than lysts is as follows: H14[NaP5W29MoO110] > H6[PMo9V3O40] >
H3[PW12O40] and H14[NaP5W30O110], which were used in our H5[PMo10V2O40] > H4[PMo11VO40] > H3[PMo12O40]. Thus,
earlier work.[17]
H14[NaP5W29MoO110] was selected as the catalyst of choice
The effects of various parameters such as solvent, catalyst for the synthesis of benzopyran. The results are represented in
type, time, and temperature of reactions were studied. The effect Table 2.
TABLE 1
TABLE 2
The results of the reaction of salicylaldehyde (1) and 5,
5-dimethyl-1, 3-cyclohexanedione (2) in the presence of
H14[NaP5W29MoO110] in different solvents
The results of the reaction of salicylaldehyde (1) and 5,
5-dimethyl-1, 3-cyclohexanedione (2) using different
heteropolyacids (0.03 mmol) under solvent-free conditions
Temperature
(◦C)
Time
(min)
Yield Entry
Heteropolyacid
Time (min)
Yield (%)a
Entry
Solvent
(%)
1
H3[PMo12O40]
60
60
60
60
20
70
70
80
85
95
1
2
3
4
EtOH
H2O
CH3CN
Solvent- free
reflux
reflux
reflux
120
60
20
60
20
80
80
85
95
2
3
4
5
H4[PMo11VO40]
H5[PMo10V2O40]
H6[PMo9V3O40]
H14[NaP5W29MoO110
]

918
M. ZAKERI ET AL.
The corresponding products were obtained in good to excel- The results (in optimum conditions) for H14[NaP5W29MoO110
]
lent yields. The results are summarized in Table 3. (best catalyst) are shown in Figure 1. The results indi-
In order to obtain the best reaction temperature, the effect cated that there is an increase in the percentage of pro-
of reaction temperature on the yield of products was studied. duced benzopyran with increase in the reaction temperature
TABLE 3
Synthesis of 1-oxo-hexahydroxanthene derivatives catalyzed by H14[NaP5W29MoO110
]
Mp (◦C)
Entry
3a
Aldehydes
Products
R1
Time (min) Yield (%)a
20 95
Found
(Lit)
2–OHC6H4CHO
CH3
209–211 206–208[4]
H3C
O
CH3
OH
O
CH3
CH3
O
OH
3b
3c
3d
2–OH–5–NO2C6H4CHO
2–OH–5–ClC6H4CHO
2–OH–5–BrC6H4CHO
CH3
CH3
CH3
18
90
205–208 205–207[4]
H3C
CH3
O
NO2
OH
O
CH3
O
CH3
OH
H3C
25
85
238–239 238–239[4]
251–253 253–255[4]
(Continued on next page)
CH3
O
Cl
OH
O
CH3
O
CH3
OH
H3C
20
90
CH3
O
Br
OH
O
CH3
O
CH3
OH

ONE-POT SYNTHESIS OF BENZOPYRAN DERIVATIVES
919
TABLE 3
Synthesis of 1-oxo-hexahydroxanthene derivatives catalyzed by H14[NaP5W29MoO110] (Continued)
Mp (◦C)
R1 Time (min) Yield (%)a Found
(Lit)
Entry
3e
Aldehydes
Products
2–OH–5–FC6H4CHO
CH3
CH3
CH3
20
30
25
92
90
85
227–230 225–227[19]
226–228 222–224[5]
230–232 230–231[19]
H3C
CH3
O
OH
O
F
CH3
O
CH3
OH
H3C
3f
2–OH–5–MeC6H4CHO
CH3
O
CH3
OH
O
CH3
O
CH3
OH
3g
2–OH–3–MeOC6H4CHO
H3C
CH3
O
OH
O
CH3
CH3
O
H
MeO
OH
H
3h
2–OHC6H4CHO
H
25
90
244–247 245–247[4]
O
OH
O
H
O
H
OH
(Continued on next page)

920
M. ZAKERI ET AL.
TABLE 3
Synthesis of 1-oxo-hexahydroxanthene derivatives catalyzed by H14[NaP5W29MoO110] (Continued)
Mp (◦C)
Entry
3i
Aldehydes
Products
R1
H
Time (min)
40
Yield (%)a
85
Found
245–247
(Lit)
2–OH–5–ClC6H4CHO
245–247[4]
H
H
O
OH
Cl
O
H
O
H
OH
3j
2–OH–5–BrC6H4CHO
H
35
88
236–240
235–236[4]
H
H
O
OH
Br
O
H
O
H
OH
100
90
90
80
70
60
50
40
30
20
10
80
70
60
2-OH-5-B rC 6H4
2-OH-5-C lC 6H4
2-OH-5-NO 2C 6H4
2-OH-C 6H4
50
40
30
20
10
0
0
60
H3
H4
H5
H6
80
100
120
HP A
Temperature (°C)
FIG. 2. Comparison catalytic performance of keggin heteropolyacids on prod-
ucts’ yield.
FIG. 1. Effect of the reaction temperature on products yield of salicylalde-
hyde (1) and 5, 5-dimethyl-1, 3-cyclohexanedione derivatives in the reactions
catalyzed by H14[NaP5W29MoO110].
up to 120◦C. This behavior was generally quiet for all of the used CONCLUSION
catalysts. The optimum reaction temperature has been found to
Preyssler-type heteropolyacid H14[NaP5W29MoO110] is a
highly efficient solid acid catalyst for the synthesis of benzopy-
ran derivatives under solvent-free conditions. The short reaction
times, simple work-up in isolation of the products in high yields
with high purity, mild reaction conditions, and reusability of
catalyst are some advantages of this protocol.
be 120◦C under solvent-free conditions.
Comparison of H6[PMo9V3O40], H5[PMo10V2O40],
H4[PMo11VO40], and H3[PMo12O40] showed that the higher
activity could be achieved with H6[PMo9V3O40]. The results
are represented in Figure 2.

ONE-POT SYNTHESIS OF BENZOPYRAN DERIVATIVES
921
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