Efficient synthesis of 4H-pyran derivatives using a polymeric catalyst based on PVP

Article abstract of DOI:10.1007/s13738-015-0687-8

A one-pot efficient method for the synthesis of 4H-pyran derivatives has been developed through a multi-component reaction of aldehydes, malononitrile, and 1,3-cyclic diketones using poly(vinylpyrrolidonium) hydrogen sulfate ([PVPH]HSO₄) as a h

Full text of DOI:10.1007/s13738-015-0687-8

J IRAN CHEM SOC
DOI 10.1007/s13738-015-0687-8
ORIGINAL PAPER
Efficient synthesis of 4H‑pyran derivatives using a polymeric
catalyst based on PVP
1
1
1
1
Farhad Shirini · Masoumeh Abedini · Susan Zarrabzadeh · Mohadeseh Seddighi
Received: 4 April 2015 / Accepted: 15 June 2015
©
Iranian Chemical Society 2015
Abstract A one-pot efficient method for the synthe-
sis of 4H-pyran derivatives has been developed through a
multi-component reaction of aldehydes, malononitrile, and
materials, laser dyes, optical brighteners, potential calcium
channel antagonists, and potent biodegradable agrochemi-
cals, as synthons of natural compounds, and occur in a
series of natural products [5–10].
1
,3-cyclic diketones using poly(vinylpyrrolidonium) hydro-
gen sulfate ([PVPH]HSO ) as a heterogeneous and reus-
Various types of methods including use of supported rea-
gents [11–17], ionic liquids [18–20], nano-catalysts [21–25],
and inorganic compounds [26–31] are reported for the
preparation of the synthesis of these types of compounds.
In spite of their own merits, some of these methodolo-
gies suffer from one or more drawbacks such as use of toxic
solvents, use of a large amounts of expensive or toxic cata-
lysts, tedious work-up, unsatisfactory yields of products
or long reaction times, and use of non-reusable catalysts.
Therefore, introduction of efficient and economical meth-
ods that solve these drawbacks is still under consideration.
Cross-linked poly(vinylpyrrolidone) (PVP) is one of
the most widely used polymeric supports for numerous
reagents and catalysts because of its stability, commercial
availability, reasonable high loading capacity, good physic-
ochemical structure, and facile functionalization. In recent
years and on the basis of these characteristics, various PVP-
supported reagents have been designed to catalyze some of
the organic reactions [32–38].
4
able catalyst. The synthesized polymeric catalyst has fully
been characterized by Fourier transform infrared spectra,
X-ray diffraction, scanning electron microscopy, thermal
gravimetric analysis, Hammett acidity (H ), and pH analy-
0
sis, which expose of the polymeric catalyst. This procedure
has the advantages of operational simplicity, mild condi-
tions, easy work-up, short reaction times, high yields of the
products, and reusability of the catalyst.
Keywords Poly(vinylpyrrolidone) ·
Poly(vinylpyrrolidonium) hydrogen sulfate ([PVPH]
HSO ) · 2-Amino-4H-pyran derivatives · Multi-component
4
reactions
Introduction
Tetrahydrobenzo[b]pyrans and their derivatives are impor-
tant class of heterocyclic compounds which have attracted
the attention of chemists because of their wide range of
useful biological and pharmacological properties, such as
antitumor, anticancer, antibacterial, antioxidant, diuretic,
and ant allergic [1–4] activities. These compounds can
be used as pigments, fluorescence markers, photoactive
In 1997, Vaidyanathan et al. reported a new modified
form of PVP which introduced as PVP-(H SO ) and Che-
2
4 n
hardoli and co-workers used this catalyst for the synthesis
of nitro phenol derivatives [33, 34]. They proposed a struc-
ture for this reagent in which N-atom is protonated but did
not provide any evidence to confirm their suggestion.
In continuation of our recently report on the applica-
tion of a new PVP-based catalyst in the synthesis of xan-
thene derivatives [39], we were interested to study the
applicability of poly(vinylpyrrolidonium) hydrogen sulfate
in the promotion of the synthesis of 2H-indazolo[2,1-b]
phthalazine-trione derivatives. Our studies on the structure
*
Farhad Shirini
fshirini@gmail.com; shirini@guilan.ac.ir
1
Department of Chemistry, College of Science,
University of Guilan, 41335 Rasht, Islamic Republic of Iran
1
3

J IRAN CHEM SOC
n
n
n
HSO4
OH
N
N
H SO 96 %
N
2
4
O
O
CH Cl , Ice bath, 2 h
2
2
Scheme 1 Preparation of [PVPH]HSO4
of the prepared reagent showed that the attributed struc-
ture by Chehardoli is incorrect and the reagent is not pro-
tected at N-atom and is actually protonated at O-atom.
Herein we wish to report the results of this study and the
results obtained from the preparation of 2H-indazolo[2,1-b]
phthalazine-trione using this reagent as the catalyst.
General procedure for the synthesis of 4H‑pyran
derivatives
To a mixture of the aldehyde (1 mmol), dimedone
or 1,3-cyclohexadione (1 mmol), and malononitrile
(1.2 mmol) in H O:EtOH (7:3, 5 mL), [PVPH]HSO
2
4
(14 mg, 3.5 mol%) was added and the resulting mixture
was stirred at 80 °C. After completion of the reaction [mon-
itored by TLC: n-hexane: ethyl acetate (9:3)], the reaction
mixture was cooled and filtered to separate the catalyst
and product. After, warm EtOH (5 mL) was added to solve
the product and filtrate to separate the catalyst. For further
purification, products were recrystallized from ethanol.
Experimental
Materials
Chemicals were purchased from Fluka, Merck, and Aldrich
chemical companies. Cross-linked poly(vinylpyrrolidone)
was purchased from BASF, the chemical company, Ger-
many. All products were characterized by comparing their
physical constants, and IR and NMR spectroscopy with
authentic samples and those reported in the literature.
The FT-IR spectra were run on a VERTEX 70 Bruker
company (Germany). Thermogravimetric analyses (TGA)
were performed on TG/DTA6300 Sll-Nonotechnology
company (Japan). Samples were heated from 25 to 800 °C
Results and discussion
Catalyst characterization
FT‑IR analysis
The infrared spectra of PVP and [PVPH]HSO are shown
4
−
1
at ramp 10 °C min under N atmosphere. Scanning
in Fig. 1. As it can be seen, the modification of PVP to
2
electron microphotographs (SEM) were obtained on a
SEM-Philips XL30. Wide-angle X-ray diffraction (XRD)
measurements were performed at room temperature on a
Siemens D-500 X-ray diffractometer (Germany), using Ni-
filtered Co-Kα radiation (λ = 0.15418 nm).
[PVPH]HSO increased the number of vibrational modes
and brought completely different FT-IR spectrum.
4
In the case of [PVPH]HSO , the broad band around
4
−1
2600–3700 cm can be attributed to the OH stretching of
the HSO groups. Additional bands at 1179, 1068, 882, and
4
−
1
5
79 cm are assigned to the S=O asymmetric and sym-
Catalyst preparation [PVPH]HSO4
metric stretching, S–OH bending, and symmetric S–O
stretching vibrations, respectively [39]. Furthermore, in this
−
−
1
H SO (0.55 mL, 96 %) was added to a suspension of
spectra, the bands at 1431 (C–N) and 652 (N–C=O) cm
2
4
1
powdered poly(vinylpyrrolidone) (1 g) [cross-linked
poly(vinylpyrrolidone) with MW > 1,000,000] in 25 mL
dry CH Cl over a period of 15 min in an ice bath. After
are disappeared, and a moderate absorption at 1644 cm
which can be related to the internal imine groups of the
pendant rings of the polymer is appeared [39].
2
2
the addition was completed, the mixture was stirred for
additional 2 h under the same conditions. Then the mixture
was filtered and the solid residue was washed with diethyl
Powder X‑ray diffraction
ether (10 mL) and dried at 80 °C to afford [PVPH]HSO as
The XRD patterns of the PVP and [PVPH]HSO samples
4
4
a pale yellow powder (Scheme 1).
are shown in Fig. 2. As shown in this figure, incorporation
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J IRAN CHEM SOC
Fig. 1 FT-IR spectra of PVP
and [PVPH]HSO4
Fig. 2 XRD patterns of PVP and [PVPH]HSO4
Fig. 3 TGA curves for PVP and [PVPH]HSO4
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J IRAN CHEM SOC
of H SO leads to some changes in the diffractogram of
loss appears after 400 °C. Therefore, the molecular decompo-
sition of the catalyst occurred after 400 °C.
2
4
PVP. The PVP diffraction exhibits a diffused background
pattern with two diffraction halos appeared around 2θ equal
to 13 and 24 indicating that the polymer is amorphous [40].
After modification of PVP by H SO , the first peak (2θ
SEM analysis
2
4
around 13) is disappeared, and the broad peak at 2θ around
4 is slightly reduced. These observations imply that the
crystallinity of PVP is decreased after reaction with H SO
The samples of PVP and [PVPH]HSO were also ana-
4
2
lyzed by scanning electron microscopy (SEM) with var-
ious magnifications for determining the particle shape,
surface morphology, and size distribution, as repre-
sented in Fig. 4. These images show that with chemi-
cal modification, the primary morphology of PVP was
completely changed and the particles were aggregated.
It should be noted that after the reaction of PVP with
H SO , the polymer became swollen which increased
2
4
[
39].
Thermal analysis
The thermal stability of PVP and [PVPH]HSO was deter-
4
mined by TGA curves, as shown in Fig. 3. The TGA curve
of PVP displayed a weight loss below 120 °C which is cor-
responding to the loss of the physically adsorbed water and
2
4
the surface area of the catalyst and finally its catalytic
activity.
bonded H O within the gallery of PVP. The large proportion of
2
polymer underwent degradation in the range of 370–430 °C.
pH analysis
The TGA analysis of [PVPH]HSO is completely different
4
from PVP. The first weight loss which appeared at <120 °C
attributed to the loss of moisture contents. In addition, this
catalyst showed two major weight loss, the first weight loss
occurs after 220 °C, which can be result of the thermal decom-
position of the sulfonic groups [39], and the second weight
To 12.5 mL of an aqueous solution of NaCl (1 M) with a
primary pH 5.65, [PVPH]HSO (0.25 g) was added and the
4
resulting mixture was stirred for 2 h at room temperature
after which the pH of the solution decreased to 1.30. This
+
is equal to a loading of 2.5 mmol H /g of the catalyst [39].
Fig. 4 SEM micrographs of [PVPH]HSO (a–c) and PVP (d–f)
4
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J IRAN CHEM SOC
ꢀ
ꢁ
+ꢂ ꢃ
Hammett acidity
H = pK(I) + log [I] / IH
0
aq
s
s
The Hammett acidity method is an effective way to the
acidity strength of an acid in organic solvents, using UV–
Vis technique [39]. The Hammett function is defined as
The pK (I) is the pK value of aqueous solution of
aq a
+
the indicator, and [IH ] and [I] are the molar concen-
s
s
trations of protonated and unprotonated forms of the
indicator in the solvent. According to Lambert–Beer’s
+
Law, the value of [I] /[IH ] can be determined and cal-
s
s
culated through UV–Visible spectrum. For this purpose,
4
-nitroaniline (pK(I)aq = 0.99) as the basic indicator
and CCl as the solvent were chosen. As can be seen in
4
Fig. 5, the maximal absorbance of the unprotonated form
of the indicator was observed at 330 nm in CCl . When
4
[
PVPH]HSO as a catalyst was added to the indicator
4
solution, the absorbance of the unprotonated form of the
indicator decreased, which indicated that the indicator
+
was partially in the form of [IH ]. The obtained results
are listed in Table 1.
Catalytic activity
After preparation and characterization of [PVPH]HSO and
4
in continuation of our research program on the preparation
and use of new catalysts in organic transformations [24,
39], we were interested to study the synthesis of 4H-pyran
derivatives in the presence of this reagent as a new hetero-
geneous polymeric catalyst.
Fig. 5 Absorption spectra of 4-nitroaniline (Blank) and [PVPH]
HSO (catalyst) in CCl
4
4
Table 1 Calculation of Hammett acidity function (H ) for [PVPH]
0
HSO4
In order to optimize the reaction conditions, the reaction
of 4-chlorobenzaldehyde, malononitrile, and dimedone as a
model reaction was studied at different conditions and the
results are tabulated in Table 2.
+
Entry
Catalyst
Amax
[I] (%)
[IH ] (%)
H0
s
s
1
2
–
1.329
0.326
100
0
–
[PVPH]HSO4
24.52
75.48
0.502
To illustrate the catalytic activity of [PVPH]HSO , in
4
the controlled blank experiments, under the same reaction
conditions, the model reaction was also carried out in the
presence of PVP and H SO . The results showed that the
Condition for UV–Visible spectrum measurement: solvent: CCl ,
4
−4
indicator: 4-nitroaniline [pK(I)aq = 0.99], 1.44 × 10
mol/L
(
10 mL); catalyst: [PVPH]HSO (10 mg), 25 °C
4
2
4
Table 2 Effect of temperature,
and amounts of the catalyst and
solvent in the promotion of the
Yields (%) b
Entry
Catalyst (mg)
Solvent
EtOH
Time (min)
Temperature (°C)
1
2
3
4
5
6
7
8
9
14 (3.5 mol%)
70
120
55
30
12
13
60
42
13
22
23
39
91
50
90
92
96
93 c
30
90
96
91
95
92
80
80
80
80
80
80
r.t.
50
100
80
80
80
a
model reaction.
14
H O
2
14
H O:EtOH(3:7)
2
14
H O:EtOH(1:1)
2
14
H O:EtOH(7:3)
2
14
Solvent-free
14
H O:EtOH(7:3)
2
14
H O:EtOH(7:3)
2
14
H O:EtOH(7:3)
2
1
1
1
0
1
2
8 (2 mol%)
20 (5 mol%)
H O:EtOH(7:3)
2
H O:EtOH(7:3)
2
25 (6.25 mol%)
H O:EtOH(7:3)
2
a
b
c
Reaction conditions: 4-chlorobenzaldehyde (1 mmol); malononitrile (1.2 mmol); and dimedone (1 mmol)
GC yield
Xanthene derivative is obtained
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J IRAN CHEM SOC
Table 3 Reaction of 4-chlorobenzaldehyde with malononitrile and
Further, the scope of this one-pot reaction was
extended by replacing 1,3-cyclohexadione with dime-
done under the same reaction conditions as described
above, and the corresponding products were obtained in
good yields during acceptable reaction times (Table 4,
entries 15–21).
It is important to note that some of the reactions were
also tested in larger scales without any difficulty by using
only 14 mg (3.5 mol%) of the catalyst. For example,
the reaction of 4-chlorobenzaldehyde (Table 4, entry 3,
dimedone in the presence of PVP, H SO , and [PVPH]HSO under
2
4
4
optimized conditions
Entry Reagent (amounts of the reagent) Time (min) Yield (%)
1
2
3
PVP (14 mg)
120
120
Trace
Trace
96
H SO (2.5 mmol)
2
4
[PVPH]HSO (14 mg, 3.5 mol%) 12
4
3
mmol) was investigated in the presence of 3.5 mol% of
O
O
the catalyst. The reaction was completed within 15 min and
the desired product was obtained in 95 % yield.
ArCHO
NCCH CN
2
R
Finally and in order to show the excellent catalytic
activity of this catalyst in comparison with the previ-
ously reported ones, we compared the results of the
synthesis of 4H-pyran derivative of benzaldehyde in
R
[
PVPH]HSO (14 mg, 3.5 mol%)
4
o
H O : EtOH (7:3), 80 C
2
the presence of [PVPH]HSO and other reagents with
4
respect to the amounts of the used catalysts, reaction
times, yields of the products, and reusability of the cata-
lysts (Table 5).
It should be mentioned that although in some of these
cases, the compared reaction is completed in the presence
of lower amounts of the catalysts (Table 5, entries 1, 5, 8),
these methods suffer from difficulty and/or use of expen-
sive starting materials in the preparation of the catalyst.
In the separate study, we have also compared
the stability of [PVPH]HSO4 with o-sulfonated
O
Ar
CN
R
R
O
NH2
Scheme 2 Synthesis of 2-amino-4H-pyran derivatives in the pres-
ence of [PVPH]HSO
model reaction catalyzed by PVP and H SO led to smaller
poly(vinylpyrrolidonium) chloride ([PVP-SO H]Cl) and
2
4
3
amounts of the products during longer reaction times
find that our new catalyst is very stable in the presence of
moisture, so that even after several days, it is not destroyed
and its color is not changed at all (Fig. 6).
(
Table 3).
On the basis of these studies, the best reaction condi-
tions are selected as shown in Scheme 2.
It should be noted that in the absence of solvent, only
the xanthene derivatives were obtained as the products
of the reaction (Table 2, entry 6). Also, no significant
increase in the yields of the products was observed when
the reaction temperature was raised from 80 to 100 °C
Reusability of the catalyst
In the next step, the reusability of the catalyst was investi-
gated with the model reaction under the optimized conditions.
After the separation of the product, the catalyst was washed
with diethyl ether, dried, and reused for the same reaction.
This process was carried out over six runs and all reactions
led to the desired products with high efficiency (Fig. 7).
(
Table 2, entry 9). Similarly, the use of higher amounts of
the catalyst did not improve the reaction yield (Table 2,
entries 11, 12).
After optimization of the reaction conditions, efficiency
of this procedure was examined using different types of
aldehydes and the results are summarized in Table 4. In all
cases, various substituted aromatic aldehydes, containing
electron-donating or electron-withdrawing groups, were
reacted successfully and gave the corresponding products
in high yields during short reaction times. However, aro-
matic aldehydes with electron-donating groups needed
longer reaction times to provide high yields of the corre-
sponding products.
Conclusion
In conclusion, we have developed a simple and effective
method for the synthesis of biologically and pharmacologi-
cally active 4H-pyran derivatives using [PVPH]HSO as a
heterogeneous catalyst in appropriate times with excellent
yields. This catalytic system offers advantages such as mild
reaction conditions, short reaction times, high yields of the
4
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J IRAN CHEM SOC
Table 4 Synthesis of 2-amino
Yield(%)a
Entry
Aldehyde
C H CHO
R
Time (min)
M.P. (°C)
Observed
-
4H-pyran derivatives using
[
PVPH]HSO as the catalyst
Reported
Ref.
4
1
2
3
4
5
6
7
8
9
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
10
11
12
15
12
23
54
25
20
24
13
13
16
28
96
96
96
94
93
95
93
89
94
93
97
96
88
90
230–232
202–204
211–213
214–216
206–209
193–195
200–203
213–215
220–222
224–226
177–179
212–214
180–183
258–260
227–229
200–203
213–215
214–215
206–208
197–199
206–208
210–212
216–218
226–228
179–180
207–210
182–184
258–260
[41]
[16]
[41]
[42]
[41]
[41]
[41]
[42]
[41]
[16]
[42]
[41]
[42]
[14]
6
5
4-FC H CHO
6
4
4-ClC H CHO
6
4
2-ClC H CHO
6
4
4-BrC H CHO
6
4
4-CH OC H CHO
3
6
4
4-HOC H CHO
6
4
4-(CH ) NC H CHO
3
2
6
4
4-CH C H CHO
3
6
4
10
11
12
13
14
4-CNC H CHO
6 4
4-NO C H CHO
2
6
4
3-NO C H CHO
2
6
4
PhCH=CHCHO
CHO
15
16
17
18
19
20
21
4-ClC H CHO
H
H
H
H
H
H
H
13
15
22
28
14
22
35
92
96
89
91
89
88
90
220–222
214–216
235–237
188–190
230–232
235–237
253–255
224–226
210–212
232–233
190–192
234–236
234–236
254–255
[14]
[14]
[14]
[43]
[14]
[43]
[14]
6
4
2-ClC H CHO
6
4
4-CH C H CHO
3
6
4
4-CH OC H CHO
3
6
4
4-NO C H CHO
2
6
4
4-CNC H CHO
6
4
CHO
Reaction conditions: aldehyde (1 mmol), malononitrile (1.2 mmol), dimedone or 1,3-cyclohexadione
(
a
1 mmol), catalyst (14 mg, 3.5 mol%), water:ethanol (7:3 = 5 mL), 80 °C
Isolated yields
Table 5 Comparison of the results obtained for the synthesis of 4H-pyran derivative of benzaldehyde using [PVPH]HSO with the other cata-
4
lysts reported in the literature
Entry
Catalyst amount (mol%)
Solvent
Recovery
Time (min)
Yield (%)
Ref.
1
2
3
4
5
6
7
8
9
Fe O @SiO /DABCO (5 mg)
H Oa
6
25
25
17
60
10
50
13
35
15
10
90
90
93
86
80
86
80
96
97
96
[44]
3
4
2
2
(SBPPSP) (4.3)
H O:EtOH
3
[45]
2
CA-SiO (16)
H O:EtOH
–
[11]
2
2
Fe O /SiO -Met Nps (30 mg)
H O:EtOH
6
[25]
3
4
2
2
[γ-Fe O @Hap-Si(CH ) AMP)] (1.5)
H O
10
3
[15]
2
3
2 3
2
SO 2 /MCM-41(25 mg)
−
EtOH
[16]
4
PPA-SiO (10 mg)
H O
3
[12]
2
2
SB-DABCO (6)
EtOH
15
–
[14]
SiO -Pr-SO H (3 mg)
H O
[17]
2
3
2
b
1
0
[PVPH]HSO (14 mg, 3.5 mol%)
H O:EtOH
6
This work
4
2
Reaction conditions: benzaldehyde (1 mmol), dimedone (1 mmol), malononitrile (1.2 mmol), reflux
a
8
0 °C
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3

J IRAN CHEM SOC
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