Green synthesis of 5 arylidene-2,4-thiazolidinedione, 5-benzylidene rhodanine and dihydrothiophene derivatives catalyzed by hydrated ionic liquid tetrabutylammonium hydroxide in aqueous medium

Article abstract of DOI:10.1080/17415993.2013.860142

An efficient synthesis of 5 arylidene-2,4-thiazolidinediones and 5-benzylidene rhodanines by the Knoevenagel condensation of 2,4- thiazolidinedione or rhodanine with aromatic aldehydes was studied. It proceeded smoothly in the presence of tetrabutylammonium hydroxide/H₂O-EtOH to afford the corresponding products in high yields at 50C. Also, a series of dihydrothiophene derivatives were synthesized via the four-component reaction of aldehyde, malonitrile, 2,4-thiazolidinedione, and piperidine in the presence of Bu₄NOH as a basic ionic liquid in aqueous medium. This new method offers several advantages, such as excellent yields, short reaction times, and simple procedure(Equation presented). 2013

Full text of DOI:10.1080/17415993.2013.860142

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Green synthesis of 5-arylidene-2,4-
thiazolidinedione, 5-benzylidene
rhodanine and dihydrothiophene
derivatives catalyzed by hydrated ionic
liquid tetrabutylammonium hydroxide
in aqueous medium
Ardeshir Khazaeia, Hojat Veisib, Maryam Safaeib & Hossein
Ahmadianb
a Faculty of Chemistry, Bu-Ali Sina University, P.O. Box
6517838683, Hamedan, Iran
b Department of Chemistry, Payame Noor University, 19395-4697
Tehran, Iran
Published online: 25 Nov 2013.
To cite this article: Ardeshir Khazaei, Hojat Veisi, Maryam Safaei & Hossein Ahmadian (2014) Green
synthesis of 5-arylidene-2,4-thiazolidinedione, 5-benzylidene rhodanine and dihydrothiophene
derivatives catalyzed by hydrated ionic liquid tetrabutylammonium hydroxide in aqueous medium,
Journal of Sulfur Chemistry, 35:3, 270-278, DOI: 10.1080/17415993.2013.860142
To link to this article: http://dx.doi.org/10.1080/17415993.2013.860142
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Journal of Sulfur Chemistry, 2014
Vol. 35, No. 3, 270–278, http://dx.doi.org/10.1080/17415993.2013.860142
Green synthesis of 5-arylidene-2,4-thiazolidinedione,
5-benzylidene rhodanine and dihydrothiophene derivatives
catalyzed by hydrated ionic liquid tetrabutylammonium
hydroxide in aqueous medium
Ardeshir Khazaeia∗, Hojat Veisib ∗, Maryam Safaeib and Hossein Ahmadianb
aFaculty of Chemistry, Bu-Ali Sina University, P.O. Box 6517838683, Hamedan, Iran; bDepartment of
Chemistry, Payame Noor University, 19395-4697 Tehran, Iran
(Received 31 July 2013; accepted 24 October 2013)
An efficient synthesis of 5-arylidene-2,4-thiazolidinediones and 5-benzylidene rhodanines by the Kno-
evenagel condensation of 2,4-thiazolidinedione or rhodanine with aromatic aldehydes was studied. It
proceeded smoothly in the presence of tetrabutylammonium hydroxide/H2O-EtOH to afford the corre-
sponding products in high yields at 50◦C. Also, a series of dihydrothiophene derivatives were synthesized
via the four-component reaction of aldehyde, malonitrile, 2,4-thiazolidinedione, and piperidine in the pres-
ence of Bu4NOH as a basic ionic liquid in aqueous medium. This new method offers several advantages,
such as excellent yields, short reaction times, and simple procedure.
O
R1
O
O
Bu4NOH
NH
H2O-EtOH, 50 °C
R2
+
NH
R1
R2
S
S
X
X
OH
N
R1: aryl, alkyl
R2: alkyl, H
X: O, S
O
H
N
N
O
H2N
NC
S
HN
O
CN
CN
Bu4NOH
H2O-EtOH, 50 °C
NH
+
+
+
RCHO
S
O
R
Keywords: rhodanines; 2,4-thiazolidinediones; dihydrothiophenes; ionic liquid
1. Introduction
The discovery of novel synthetic methodologies to facilitate the efficient preparation of com-
pounds of prominent utility is a pivotal focal point of research in modern organic chemistry.[1]
Thecontinualupsurgeinfacile, convenient, andnon-pollutingsyntheticproceduresurgeschemists
∗Corresponding authors. Emails: hojatveisi@yahoo.com; Khazaei_1326@yahoo.com
© 2013 Taylor & Francis

Journal of Sulfur Chemistry 271
to increase the tools of their arsenal. Domino reactions have attracted particular attention over
the past few decades because of their high efficiency in the construction of complex molecular
frameworks.[2] Compared with step-wise reactions, this type of reaction minimizes waste since
the amount of solvents, reagents, adsorbents, and energy is dramatically decreased.[3] Domino
reactions are often accompanied by significant increases in molecular complexity and impres-
sive selectivity.[4] Ionic liquids (ILs) have attracted extensive research interest in recent years as
environmental benign solvents due to their favorable properties, like non-inflammability, negli-
gible vapor pressure, reusability, and high thermal stability.[5] They have also been referred to as
“designer solvents” as their physical and chemical properties can be adjusted by a careful choice
of cation and anion. Apart from this they exhibit acidic or basic properties. Combining these
unique properties of ILs they are emerging as attractive “green reaction media”.
Compounds containing the 2,4-thiazolidinedione and rhodanine ring have showed a wide
range of pharmacological activities, which includes antimicrobial,[6–8] anticonvulsant,[9]
antibacterial,[10] anti-viral,[11] and anti-diabetic.[12] Additionally, rhodanine-based molecules
have been popular as small molecule inhibitors of numerous targets such as Hepatitis C virus NS3
protease,[13] β-lactamase,[14] L-alanine ligase,[15] and cathepsin D.[16] The rhodanine moiety
has been synthesized by various methods such as the addition of isothiocyanate to mercaptoacetic
acid followed by acid-catalyzed cyclization, or the reaction of ammonia or primary amines with
carbon disulfide and chloroacetic acid in the presence of bases.[17] Condensation of aromatic
aldehydes or ketones at the nucleophilic C-5 active methylene has been performed using piperi-
dinium benzoate in refluxing toluene,[16] NH4OH/NH4Cl,[18] or sodium acetate in refluxing
glacial acetic acid.[19] Recently, Lee and Sim [20] reported the synthesis of 5-arylalkylidene
rhodanines in 60–82% yields by heating the reactants suspended in toluene at 110◦C for three
days. Sing et al. [21] reported the condensation of rhodanine with an aldehyde (0.1 mmol) by
heating in anhydrous EtOH (200 mL) for 6 h at 80◦C. Alternatively, rhodanine (0.1 mmol), ketone
(0.1 mmol), and NH4OAc (0.2 mmol) were refluxed in toluene (500 mL) for three days (61–92%
yields).
Sulfur-containing heterocyclic compounds are widespread in nature, and their applications to
biologically active pharmaceuticals, agrochemicals, and functional materials are becoming more
and more important. The development of new efficient methods to synthesize S-heterocycles with
structural diversity is one major interest of modern synthetic organic chemists. The dihydroth-
iophene moiety has been found in various natural products, biologically active compounds, and
synthetic intermediates.[22,23] Their preparations often require lengthy steps and suffer from
various drawbacks such as lower yields.[24,25] Sun et al. [26] have reported the synthesis of
dihydrothiophenes under stirring in the presence of acetonitrile. Recently, Shi et al. [27] reported
the synthesis of dihydrothiophene derivatives in ethanol under ultrasound irradiation. Obviously,
these methods involve long reaction times, high temperatures, use large quantities of organic sol-
vents and some give unsatisfactory yields. Therefore, it is useful to develop new methods, which
are simple and environmentally friendly for the synthesis of these compounds.
2. Result and discussions
In continuation of our interest in the organic synthesis [28], we wish to report here hydrated IL
tetrabutylammonium hydroxide 50% (TBAH) as an efficient and recyclable basic catalyst for the
synthesis of 5-arylidene-2,4-thiazolidinediones, 5-benzylidene rhodanines, and dihydrothiophene
derivatives in aqueous media (Scheme 1).
We first decided to examine the reaction between benzaldehyde and rhodanine in the presence
of Bu4NOH as basic IL in aqueous medium. The Knoevenagel condensation of the C-5 active

272 A. Khazaei et al.
O
R1
O
O
Bu4NOH
NH
H2O-EtOH, 50 °C
R2
+
NH
R1
R2
S
S
X
X
OH
N
R1: aryl, alkyl
R2: alkyl, H
X: O, S
O
H
N
N
O
H2N
NC
S
HN
O
CN
CN
Bu4NOH
H2O-EtOH, 50 °C
NH
+
+
+
RCHO
S
O
R
Scheme 1. Synthesis of 5-arylidene-2,4-thiazolidinediones, 5-benzylidene rhodanines, and
dihydrothiophene derivatives.
Table 1. Synthesis of 5-arylidene-2,4-thiazolidinediones and 5-benzylidene rhodanines.
Entry
Product
Yield (%)
Mp (◦C)
202–204
Mp/Ref.
O
1
95
199–202 [29]
NH
S
S
O
2
3
4
90
90
90
240–241
250–253
234–235
240 [29]
250–252 [30–36]
235 [29]
NH
S
O
O
NH
S
S
MeO
MeO
S
O
NH
O
O
NH
S
5
6
92
85
261–263
178–179
263–264 [21]
S
NO2
O
NH
180 [29]
S
O
NO2
(Continued).

Journal of Sulfur Chemistry 273
Table 1. Continued.
Entry
Product
Yield (%)
85
Mp (◦C)
184–185
Mp/Ref.
O
7
185–186 [30–36]
NH
S
HO
S
O
8
92
281–282
281 [29]
NH
S
HO
O
O
Cl
Cl
9
95
90
230–232
213–214
231.5–232.5 [30–36]
NH
S
S
Cl
S
O
10
215 [29]
NH
Cl
O
O
11
95
90
85
90
225–227
265–266
271–272
280–281
224–230 [29]
270 [21]
NH
S
S
Cl
S
O
12
NH
Cl
O
O
13
273–274 [30–36]
NH
S
N
S
O
14
281 [29]
NH
O
S
N
methylene of rhodanine with aromatic aldehydes proceeded smoothly in the presence of 1 mL of
basic Bu4NOH (50%) at 50◦C for 1.5 h, and the results are summarized in Table 1. It shows that
the aromatic aldehydes having different substituents, such as hydroxyl, chloro, nitro, methoxy,
etc., were converted to the corresponding products in high yields.
Hence, we decided to study the catalytic activity of the recycled catalyst in the synthesis of
5-benzylidene rhodanines. After the separation of products, the catalyst was reused in the next
run without further purification. The reaction medium can be recycled at least three times without
significant decrease in the yields, which ranged from 85% to 90%.

274 A. Khazaei et al.
Table 2. One-pot four-component synthesis a variety of dihydrothiophene.
Entry
Product
Yield (%)
Mp (◦C)
221–223
Mp (◦C)/Ref.
N
O
H2N
NC
S
S
S
HN
O
1
70
220–222 [26]
N
O
H2N
HN
O
2
3
4
60
70
40
206–208
301–302
211–213
206–208 [27]
299–301 [26]
210–212 [26]
NC
Cl
N
O
H2N
NC
HN
O
Cl
N
O
H2N
NC
S
HN
O
OMe
S
N
O
H2N
NC
HN
O
5
65
210–212
209–211 [26]
NO2
S
N
O
H2N
NC
HN
O
6
65
227–229
230–233 [26]
OH
(Continued).

Journal of Sulfur Chemistry 275
Table 2. Continued.
Entry
Product
Yield (%)
Mp (◦C)
Mp (◦C)/Ref.
N
O
H2N
S
HN
O
NC
7
70
201–202
202–204 [26]
CH3
S
N
O
H2N
NC
HN
O
8
9
45
60
221–223
227–229
220–222 [26]
227–228 [27]
Br
N
H2N
NC
S
S
HN
O
O
N
O
H2N
NC
S
HN
O
10
50
209–211
209–210 [27]
N
We have developed this method for the condensation of various aldehydes with 2,4-
thiazolidinedione in ethanol at 50◦C for 2 h with excellent yields (85–92%). The reactions were
compatible with various substituents such as nitro, methyl, chloro, hydroxyl, methoxy, etc. No
any significant substituents effect was observed in regarding the reaction time and yield of product
(Table 1).
Using this catalyst we were able to conduct one-pot four-component synthesis of a variety of
dihydrothiophene by reaction of piperidine (1 mmol), 1,3-thiazolidinedione (1 mmol), malononi-
trile (1 mmol), and a variety of aldehydes (1 mmol) according to Scheme 1. The desired products
(Table 2) were obtained in good yields.
To test the scope of the substrates, we used different aromatic aldehydes with either electron
withdrawing or electron-donating groups (Table 2, Entries 1–8). In addition, reactions with hete-
rocyclic aldehydes (Table 2, Entries 9 and 10) can also be carried out smoothly. The results were
excellent in terms of yields and product purity using ethanol-H2O as solvent (Table 2).
We also propose a reaction mechanism for the preparation of dihydrothiophenes catalyzed by
TBAH50%asillustratedinScheme2. First, thearylidenemalononitrile I islikelyformedviainitial
condensation of the aromatic aldehyde with malononitrile, which is catalyzed by TBAH. The sec-
ond step is a Michael addition of the carbanion of 1,3-thiazolidinedione to arylidenemalononitrile
I to yield adduct II. Then, piperidine attacks the carbonyl group of thiazolidinedione to open its

276 A. Khazaei et al.
ring to form sulfide anion III, which in turn intramolecularly attacks one of the two cyano groups
to form a sulfur-containing five-membered ring intermediate IV. Finally, the dihydrothiophene
V was produced through imine-enamine tautomerization (Scheme 2).
O
O
Bu4NOH
NH
NH
CN
S
S
O
NC
H
O
O
NH
R
S
CN
CN
CN
Bu4NOH
RCH
C
II
RCHO
+
O
CN
H
N
I
N
O
N
O
N
O
H2N
NC
HN
S
R
S
N
HN
O
S
HN
O
HN
O
C
H
NC
NC
R
R
V
IV
III
Scheme 2. The propose mechanism for the preparation of dihydrothiophenes.
3. Conclusion
In conclusion, TBAH has a high synthetic utility, because it is reusable and shows high activ-
ity in the Knoevenagel condensation of different aromatic aldehydes with 2,4-thiazolidinedione
and rhodanine with good yields for the synthesis of the corresponding 5-aryilidene-2,4-
thiazolidinediones and 5-benzylidene rhodanines. Also, we have developed a facile and efficient
protocol for the one-pot four-component synthesis of dihydrothiophene derivatives in aqueous
media. The major advantages of the present method are much faster reactions, easy work up
procedure and good to excellent yields, and it avoids the use of hazardous organic solvents and
toxic catalysts.
4. Experimental
4.1. General procedure for the preparation of 5-aryilidene-2,4-thiazolidinediones and
5-benzylidene rhodanines
Amixtureofaromaticaldehyde(1 mmol), 2,4-thiazolidinedioneorrhodanine(1 mmol)andTBAH
(1 mL, 50%) were mixed in EtOH-H2O (1:1, 3 mL). The reaction mixture was stirred at 50◦C
in an oil bath for 1.5 h. The progress of reaction was monitored on TLC. After completion of
reaction, the resulting precipitate was filtered and washed with ethanol to afford the pure product
as solid in good to excellent yields. The known products were characterized by comparing the 1H
NMR and melting point data with those reported in the literature.

Journal of Sulfur Chemistry 277
4.2. General procedure for the preparation of dihydrothiophene derivatives
A mixture of piperidine (1 mmol), 1,3-thiazolidinedione (1 mmol), malononitrile (1 mmol), alde-
hyde (1 mmol), and TBAH (1 mL, 50%) were mixed in aqueous ethanol (1:1, 4 mL). The reaction
mixture was stirred at 50◦C condition for 2 h. The progress of reaction was monitored on TLC.
After the completion of the reaction, the resulting precipitate was filtered and washed with ethanol
and water to afford the pure product as solid in good to excellent yields. The known products
were characterized by comparing the 1H NMR and melting point data with those reported in the
literature.
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