4-(Succinimido)-1-butane sulfonic acid as a br?nsted acid catalyst for synthesis of pyrano[4,3-b]pyran derivatives under solvent-free conditions

Article abstract of DOI:10.1016/j.cclet.2014.10.009

4-(Succinimido)-1-butane sulfonic acid as an efficient and reusable Br?nsted acid catalyzed the synthesis of pyrano[4,3-b]pyran derivatives under solvent-free conditions. The catalyst can be prepared by mixing succinimide and 1,4-butanesultone that is mor

Full text of DOI:10.1016/j.cclet.2014.10.009

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CCLET 3115 1–5
Chinese Chemical Letters xxx (2014) xxx–xxx
Contents lists available at ScienceDirect
Chinese Chemical Letters
journal homepage: www.elsevier.com/locate/cclet
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Original article
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4-(Succinimido)-1-butane sulfonic acid as a Bronsted acid catalyst for
synthesis of pyrano[4,3-b]pyran derivatives under solvent-free
conditions
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Q1 Nader Ghaffari Khaligh
Research House of Professor Reza, Education Guilan, Rasht, District 1, 41569-17139, Iran
A R T I C L E I N F O
A B S T R A C T
Article history:
4-(Succinimido)-1-butane sulfonic acid as an efficient and reusable Bro¨nsted acid catalyzed the
synthesis of pyrano[4,3-b]pyran derivatives under solvent-free conditions. The catalyst can be prepared
by mixing succinimide and 1,4-butanesultone that is more simple and safer than the preparation of
succinimide sulfonic acid. This method has the advantages of high yield, clean reaction, simple
methodology and short reaction time. The catalyst could be recycled without significant loss of activity.
ß 2014 Nader Ghaffari Khaligh. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All
rights reserved.
Received 8 July 2014
Received in revised form 26 August 2014
Accepted 12 September 2014
Available online xxx
Keywords:
Bro¨nsted acid
Pyrano[4,3-b]pyran
4-Hydroxy-6-methylpyran-2-one
Three-component reaction
One-pot condensation
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1. Introduction
through wastewater or sludge discharging. Solid acids as economic 31
and ecologically benign catalysts have offered unique properties 32
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Pyridone and pyran structural units are widely occurring in
various molecules exhibiting a wide range of biological activities
and important advantages over the homogeneous inorganic acids 33
in organic synthesis in recent years; for example, operational 34
simplicity, environmental compatibility, nontoxic, low cost, and 35
ease of isolation [10–15]. However, they have some disadvantages, 36
for example, although zeolites demonstrate higher activity, their 37
reactions typically give a variety of undesired by-products due to 38
the higher temperatures employed and metal triflates are costly 39
and moisture sensitive and also some of the catalysts require the 40
special efforts to prepare [16]. Ion exchange resins are limited in 41
application because they are thermally unstable above 120 8C in 42
and serve as
a specific nonnucleoside reverse transcriptase
inhibitor of HIV-1 [1,2], inotropic and vasodilatatory drugs [3],
antitumors and antioxidants [4,5], rhinovirus 3C protease inhibi-
tors [6], anticancers [5,7], potential antiviral and antileishmanial
agents [8]. Also compounds containing a 2-pyridone moiety fused
with a substituted pyran ring are reported as a Ca2+ inhibitor [9],
active against multidrug resistant KB-VI cancer cells and a selective
cytotoxicity profile [10]. Therefore, a variety of synthetic strategies
have been developed for the preparation of dihydropyrano[4,3-
b]pyran derivatives that often proceeds through the formation of
the intermediate Knoevenagel products and their subsequent
reactions with 4-hydroxy-6-methylpyran-2-one [11] or a multi-
component reaction of pyrone with malononitrile and various
aromatic aldehydes [9].
the acid form [17].
43
Green Chemistry with its 12 principles would like to increases 44
the efficiency of synthetic methods, to use less toxic solvents, 45
reduce the stages of the synthetic routes and minimize waste as far 46
as practically possible [18]. One of the key areas of green chemistry 47
is the replacement of hazardous solvents with environmentally 48
benign ones or the elimination of solvents altogether [18–20]. 49
By changing the methodologies of organic synthesis health and 50
safety will be advanced in the small scale laboratory level but 51
also will be extended to the industrial large scale production 52
processes through the new techniques. Another beneficiary of 53
course will be the environment through the use of less toxic 54
reagents, minimization of waste and more biodegradable by-pro- 55
Homogeneous inorganic acids and alkali such as sulfuric acid,
potassium hydroxide and sodium hydroxide can act as the
catalysts in organic transformations. However, these catalysts
have some disadvantages: they are strongly corrosive and
nonrenewable and may easily cause environmental pollution
E-mail address: author@university.edu.
ducts [21–23].
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http://dx.doi.org/10.1016/j.cclet.2014.10.009
1001-8417/ß 2014 Nader Ghaffari Khaligh. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
Please cite this article in press as: N.G. Khaligh, 4-(Succinimido)-1-butane sulfonic acid as a Bro¨nsted acid catalyst for synthesis of
pyrano[4,3-b]pyran derivatives under solvent-free conditions, Chin. Chem. Lett. (2014), http://dx.doi.org/10.1016/j.cclet.2014.10.009

G Model
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N.G. Khaligh / Chinese Chemical Letters xxx (2014) xxx–xxx
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Recently, succinimide sulfonic acid was synthesized and their
application in the variety of organic transformations was
investigated [24]. Herein, a new Bro¨nsted acid, namely, 4-
(succinimido)-1-butane sulfonic acid (SBSA) is introduced and
its application in the promotion of the synthesis of dihydropyr-
ano[4,3-b]pyran derivatives is described. The present study is
developed as a new preparative procedure for this class of
heterocyclic scaffolds by utilizing SBSA under solvent-free
conditions.
6.31 (s, 1H, CH), 7.19 (brs, 2H, NH2), 7.19–7.22 (m, 2H, ArH),
7.31–7.34 (m, 2H, ArH).
2-Amino-4-(4-bromophenyl)-7-methyl-5-oxo-4,5-dihydropyr-
ano[4,3-b]pyran-3-carbonitrile (2d): Colorless solid; mp 225–
227 8C; IR (KBr, cmꢀ1): nmax 3381, 3322, 3197, 2921, 2204, 1712,
1676, 1643, 1611, 1596, 1384, 1263, 1141, 1095, 1036, 972; 1H
NMR (400 MHz, DMSO-d6): d 2.21 (s, 3H, CH3), 4.31 (s, 1H, CH), 6.27
(s, 1H, CH), 7.18 (d, 2H, J = 8.0 Hz, ArH), 7.25 (s, 2H, NH2), 7.46 (d,
2H, J = 8.0 Hz, ArH).
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4,40-(1,4-Phenylene)bis(2-amino-7-methyl-5-oxo-4,5-dihy-
dropyrano[4,3-b]pyran-3-carbonitrile) (2m): Colorless solid; mp
256–258 8C; IR (KBr, cmꢀ1): nmax 3372, 3317, 3196, 2196, 1699,
66
67
2. Experimental
1673, 1614, 1463, 1383; 1H NMR (400 MHz, DMSO-d6):
d
2.16 (s,
6H, 2CH3), 4.19 (s, 2H, 2CH), 6.22 (s, 2H, 2CH), 7.06 (s, 4H, Ar-H),
7.13 (brs, 4H, 2NH2); 13C NMR (100 MHz, DMSO-d6):
18.9, 35.5,
2.1. General
d
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79
Chemicals were purchased from Fluka AG, Merck and Synthetic
Chemicals Ltd. Reaction monitoring and purity determination of
the products were accomplished by TLC or GC–MS on an Agilent
GC-Mass-6890 instrument under 70 eV conditions. IR and FTIR
Spectra were obtained using a Perkin-Elmer spectrometer 781 and
Bruker Equinox 55 using KBr pellets for solid and neat for liquid
samples in the range of 4000–400 cmꢀ1. In all the cases the 1H NMR
spectra were recorded with Bruker Avance 400 MHz instrument
using. Mass spectra were recorded with PESciex model API
3000 instrument. Microanalyses were performed on a Perkin-
Elmer 240-B microanalyzer. Melting points were recorded on a
Bu¨chi B-545 apparatus in open capillary tubes.
57.8, 98.0, 119.4, 127.5, 130.1, 136.6, 142.4, 158.6, 161.2, 161.9,
162.8, 174.8; MS(ESI): m/z [M+1]+ 483; Anal. Calcd. for
C26H18N4O6: C, 64.73; H, 3.73; N, 11.62%. Found: C, 64.62; H,
3.83; N, 11.78%.
3. Results and discussion
134
Part of our research is aiming to introduce the eco-efficient
methodology that allows decreasing the amount of waste and a
lesser use of hazardous materials is proposed. In preparation of
succinimide-N-sulfonic acid, chlorosulfonic acid was stirred with
succinimide to generate gaseous HCl [24]. However, it has the
disadvantage of using chlorosulfonic acid which causes severe
burns and reacts exothermically and violently with water
producing sulfuric acid, hydrochloric acid, and large quantities
of dense white acid fumes. Also it is very toxic by inhalation and
corrosive to metals. The present catalyst was prepared by mixing
succinimide and 1,4-butane sultone that is more simple and safer.
The synthesis of 4-(succinimido)-1-sulfonic acid involved stirring
same equivalents of succinimide and 1,4-butane sultone at
40–50 8C for 6 h. The present method does not use traditional
heater. Instead, 10 mirrors reflect the sunlight onto the 25 mL
round bottom flask. When the concentrated sunlight strikes the
round bottom flask, it heats the mixture of reaction to 40–60 8C.
The viscous liquid was washed by diethyl ether, and then a white
solid was obtained. The resulting SBSA was dried to constant
weight in vacuum. The structure was confirmed by IR, 1H NMR, and
13C NMR. The content of water of SBSA was 5.4% using Karl–Fischer
titration method. SBSA was soluble in DMSO, DMF, water,
methanol and ethanol; however it was immiscible with diethyl
ether, ethyl acetate, and dichloromethane. So the catalyst can be
separated conveniently from products by simple phase separations
(Scheme 1).
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168
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2.2. Synthesis of 4-(succinimido)-1-butane sulfonic acid (SBSA)
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Succinimide (0.99 g, 10 mmol) was added to 1,4-butane sultone
(1.5 mL 14.4 mmol) and stirred continuously for 10 h at 40–50 8C
by using solar energy to obtain 4-(succinimio)-1-butane sulfonic
acid as a white solid. The viscous liquid was washed by diethyl
ether for three times to remove any unreacted starting materials,
and then a white solid was obtained. The resulting SBSA was dried
to constant weight in vacuum at 60 8C. The white needles were
obtained by crystallization in a mixture of ethanol and water using
slow evaporation technique (2.12 g, yield 90.2%). Mp 222 8C (dec.);
IR (KBr, cmꢀ1): nmax 3140, 3090, 2980, 2940, 1740, 1640, 1600,
1460, 1380, 1190, 1120, 1040; 1H NMR (300 MHz, D2O):
d 1.75–
1.68 (m, 2H, –CH2–), 2.03–1.91 (m, 2H, –CH2–), 2.64 (s, 4H, –CH2–
CH2–, Succinimide), 2.95 (t, J = 7.4 Hz, –CH2–S), 4.23 (t, J = 6.9 Hz,
2H, –CH2–N); 13C NMR (75 MHz, D2O):
d 22.3 (C2 of butane), 28.2
(C3 of butane), 29.3 (CH2 of succinimide), 49.3 (N–CH2), 51.2
(S–CH2), 186.5 (C55O).
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2.3. The preparation of 2-amino-4-aryl-7-methyl-5-oxo-4,5-
dihydropyrano[4,3-b]pyran-3-carbonitriles (2)
To evaluate the effect of the amount of SBSA, condensation of
4-hydroxy-6-methylpyran-2-one, 4-nitrobenzaldehyde (1e) and
malononitrile was carried out in presence of different amounts
of (2.1%, 4.2% and 8.5 mol%) under solvent-free conditions
(Scheme 2). It was observed that 4.2 mol% of SBSA was an
optimum amount for this model reaction to furnish the desired
product in high yield. Increasing the amount of the catalyst beyond
4.2 mol% did not increase the yield noticeably. Also the different
99
In a 25 mL round bottom flask a mixture of 4-hydroxy-6-
methylpyran-2-one (1.0 mmol), aromatic aldehyde (1.0 mmol),
malononitrile (1.0 mmol) were mixed in presence of 4-(succini-
mido)-1-butane sulfonic acid (10 mg) at 60 8C under solvent-free
condition for appropriate time. After completion of the reaction
(monitored by TLC), the reaction mixture was cooled to room
temperature and water was added and the solid precipitated was
filtered to separate the catalyst. Water was evaporated under
reduced pressure and the catalyst was recovered and used for the
next run. The solid product was recrystallized from ethanol to yield
the pure product.
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2-Amino-4-(4-fluorophenyl)-7-methyl-5-oxo-4,5-dihydropyr-
ano[4,3-b]pyran-3-carbonitrile (2c): Colorless solid; mp 221–
223 8C; IR (KBr, cmꢀ1): nmax 3369, 3317, 3195, 2924, 2194,
1715, 1678, 1641, 1618, 1591, 1378, 1259, 1138, 1091, 1032, 978;
Scheme 1. Synthesis of 4-(succinimido)-1-butane sulfonic acid (SBSA) by using
1H NMR (400 MHz, DMSO-d6):
d 2.19 (s, 3H, CH3), 4.28 (s, 1H, CH),
solar energy.
Please cite this article in press as: N.G. Khaligh, 4-(Succinimido)-1-butane sulfonic acid as a Bro¨nsted acid catalyst for synthesis of
pyrano[4,3-b]pyran derivatives under solvent-free conditions, Chin. Chem. Lett. (2014), http://dx.doi.org/10.1016/j.cclet.2014.10.009

G Model
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N.G. Khaligh / Chinese Chemical Letters xxx (2014) xxx–xxx
3
NO2
OH
O
NO2
O
CN
CN
SBSA
CN
+
+
O
Different parameters
H3C
O
H3C
NH2
O
CHO
2(a-l)
1(a-l)
Scheme 2. Synthesis of 2-amino-4-aryl-7-methyl-5-oxo-4,5-dihydropyrano[4,3-b]pyran-3-carbonitrile derivatives in presence of SBSA under various reaction conditions.
169
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191
192
193
194
195
196
197
198
199
200
reaction temperatures (r.t. ꢀ80 8C) were analyzed and the results
O
H
O
H
showed that 88% of 2-amino-4-(4-nitrophenyl)-7-methyl-5-oxo-
4,5-dihydropyrano[4,3-b]pyran-3-carbonitrile was offered in the
presence of 4.2 mol% SBSA at 60 8C within 60 min. Higher
temperatures caused more spots on the TLC and it seems that
by-products were obtained. The reaction was not completed at
60 8C even after 4 h in absence of SBSA and only 38% of 2e was
offered.
N
N
H3C
CH3
H3C
CH3
Scheme 3. Tautomerisation with formation of a quinonoid structure.
In order to evaluate the generality of this model reaction, a
range of 2-amino-4-aryl-7-methyl-5-oxo-4,5-dihydropyrano[4,3-
b]pyran-3-carbonitriles 2a–m were prepared under optimized
reaction conditions in presence of SBSA (Table 1). The aryl
aldehydes which possess electron-donating and electron-with-
drawing substituents and heteryl aldehydes provided desired
dihydropyrano[4,3-b]pyrans in good to high yields without
involving any side products (Table 1, entries 1–13). However,
aliphatic aldehydes did not undergo pyranization even within long
reaction time and elevated temperature; TLC and GC–MS analysis
of the reaction mixture showed numerous products. The electron-
donating substituents caused lower yields and longer reaction
times than electron-withdrawing substituents (Table 1, entries 5,
7, 9 and 10). 4,40-(1,4-Phenylene)bis(2-amino-7-methyl-5-oxo-
4,5-dihydropyrano[4,3-b]pyran-3-carbonitrile) 2m was obtained
in 80% yield when terephthaldehyde 1m was reacted with
malononitrile and 4-hydroxy-6-methylpyran-2-one in molar ratio
1.0:2.0:2.0 under optimized reaction conditions (Table 1, entry 13).
4-Dimethylaminobenzaldehyde failed to give the corresponding
pyran derivative and the starting materials were quantitatively
recovered under the same conditions (Table 1, entry 14). The
explanation for this result may be due to the strong electron-
donating dimethylamino group which will reduce the reactivity.
A degree of tautomerisation may occur with formation of a
quinonoid structure as shown in Scheme 3 and thus decrease the 201
reactivity of the aldehyde group [25].
New products were characterized by IR, 1H NMR, 13C NMR, 203
MASS spectra and elemental analysis and known products were 204
characterized by IR and 1H NMR and comparison of their melting 205
202
points with those of authentic samples.
206
SBSA was isolated and could be recycled up to five times 207
without any significant loss of activity (Table 1, entry 5). The 208
proposed mechanism for the formation of the product via tandem 209
Knoevenagel-cyclo condensation is outlined in Scheme 4. Carbonyl 210
group of aldehyde (1) was activated by Bro¨nsted acid SBSA. Next, 211
nucleophilic attack of the malononitril on the carbonyl carbon was 212
caused to form intermediate arylidene malononitrile. Subsequent 213
Michael addition of 4-hydroxy-6-methylpyran-2-one followed by 214
cyclization afforded the product (2).
215
To validate the proposed mechanism, the synthesis of 2b was 216
carried out in two steps. Firstly, 4-chlorobenzylidene malononitrile 217
was prepared by the condensation of 4-chlorobenzaldehyde 1b 218
and malononitrile in presence of SBSA. Then product of the first 219
step was reacted with 4-hydroxy-6-methylpyran-2-one in pres- 220
ence of SBSA to give the product 2b (87%) in 45 min. This fact 221
Table 1
Synthesis of 2-amino-4-aryl-7-methyl-5-oxo-4,5-dihydropyrano[4,3-b]pyran-3-carbonitriles in the presence of SBSA.a
Q3
Entry
Substrate (1)
Product (2)
Time (min)
Yield (%)b
Mp (8C)
Ref.
Found
Reported
1
C6H5–CHO
a
b
c
d
e
f
80
80
236
236–238
231–232
223–225
218–220
216–218
223–225
205–207
216
[21]
[22]
[8]
2
4-Cl–C6H4–CHO
75
84
228–230
221–223
225–227
220–222
218–220
210–212
217–219
218–220
198–202
118–120
238–240
256–258
–
3
4-F–C6H4–CHO
70
82
4
4-Br–C6H4–CHO
80
84
[8]
5
4-NO2–C6H4–CHO
4-CH3–C6H4–CHO
4-CH3O–C6H4–CHO
3-Br–C6H4–CHO
60 (60, 60, 60, 62)c
88 (88, 88, 86, 86)c
[28]
[29]
[26]
[27]
[28]
[27]
[5]
6
90
95
72
70
69
74
70
78
74
85
–
7
g
h
i
8
70
9
3-NO2–C6H4–CHO
3,4-(CH3O)2–C6H3–CHO
Furfural
62
234–236
198–202
223–224
242–244
–
10
11
12
13
14
j
95
k
l
80
2-Thiophene carbaldehyde
1,4-(CHO)2–C6H4
4-Dimethylaminobenzaldehyde
80
[5]
m
n
90
–
120
–
–
a
Reaction conditions: 4-hydroxy-6-methylpyran-2-one (1.0 mmol), aromatic aldehyde (1.0 mmol); malononitrile (1.0 mmol); SBSA (4.2 mol%); 60 8C; solvent-free.
Isolated yield.
Recycled SBSA.
b
c
d
Reaction conditions: 4-hydroxy-6-methylpyran-2-one (2.0 mmol), aromatic aldehyde (1.0 mmol); malononitrile (2.0 mmol); SBSA (4.2 mol% g); 60 8C; solvent-free.
Please cite this article in press as: N.G. Khaligh, 4-(Succinimido)-1-butane sulfonic acid as a Bro¨nsted acid catalyst for synthesis of
pyrano[4,3-b]pyran derivatives under solvent-free conditions, Chin. Chem. Lett. (2014), http://dx.doi.org/10.1016/j.cclet.2014.10.009

G Model
CCLET 3115 1–5
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N.G. Khaligh / Chinese Chemical Letters xxx (2014) xxx–xxx
Scheme 4. The proposed mechanism for the synthesis of 2-amino-4-aryl-7-methyl-5-oxo-4,5-dihydropyrano[4,3-b]pyran-3-carbonitriles in presence of [BBMIm](HSO4)2 at
60 8C.
Table 2
Q4
Comparison of the present method with other reported strategies for the synthesis of 2-amino-4-phenyl-7-methyl-5-oxo-4,5-dihydropyrano[4,3-b]pyran-3-carbonitrile.
Entry
Catalyst
Conditions
Time (min)
Yield (%)
Ref.
1
2
NH4OAc (10 mol%)
Neat, r.t.
10
180
60
94
85
79
77
65
76a
89
94
94
92
88
[5]
[bmim][BF4] (1.5 g)
80 8C
MeOH, reflux
100 8C
H2O, 80 8C
EtOH, r.t.
[8]
3
Piperidine (1–2 drops)
[28]
[30]
[31]
[32]
[33]
[34]
[35]
[36]
This work
4
1,1,3,3-N,N,N,N-Tetramethylguanidinium trifluoroacetate (TMGT) (1 mol%)
60
5
–
10.5 h
8 h
30
6
KF-Al2O3
7
MgO (0.25 g)
H2O/EtOH, reflux
H2O, reflux
Neat, 60 8C
H2O, 80 8C
Neat, 60 8C
8
H6P2W18O62ꢁ18H2O (1 mol%)
[BBMIm](HSO4)2 (500 mg)
Thiourea dioxide (TUD)
SBSA (4.2 mol%)
60
9
35
10
11
40
60
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250
251
252
253
254
255
256
257
258
259
260
261
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283
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290
222
provided the evidence in support of the intermediate arylidene
malononitrile proposed pathway.
223
224
225
226
227
228
The comparison of the present methodology with previously
reported procedures for the synthesis of 2a is shown in Table 2. As
can be seen, the reaction catalyzed by SBSA at 60 8C give a
comparable yield, requires less amount of catalyst and less time
than other protocols and also it is reusable.
229
4. Conclusion
230
231
232
233
234
235
236
237
In conclusion, a novel Bro¨nsted acid is introduced and its
catalytic activity was investigated for the synthesis of 2-amino-4-
aryl-7-methyl-5-oxo-4,5-dihydropyrano[4,3-b]pyran-3-carboni-
trile derivatives under solvent-free conditions. To prepare of the
catalyst, solar energy was applied for the first time and hazardous
material namely chlorosulfonic acid was avoided. The current
method has the advantages of simple experimental procedure,
good to high yield of products, and reusability of the catalyst.
238
Acknowledgment
239 Q2
240
The author is thankful to the Research House of Professor Reza,
Education Guilan for the partial support of this work.
241
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Please cite this article in press as: N.G. Khaligh, 4-(Succinimido)-1-butane sulfonic acid as a Bro¨nsted acid catalyst for synthesis of
pyrano[4,3-b]pyran derivatives under solvent-free conditions, Chin. Chem. Lett. (2014), http://dx.doi.org/10.1016/j.cclet.2014.10.009