Synthesis of some new 5-substituted-3-phenyl-4-thioxo-2-thiazolidinones and their fused thiopyrano[2,3-d[thiazole derivatives

Article abstract of DOI:10.1080/17415993.2015.1065405

The new 5-arylmethylene-3-phenyl-4-thioxo-2-thiazolidinone derivatives have been synthesized by condensation of ω-(4-formylphenoxy)acetophenone derivatives with 3-phenyl-4-thioxo-2-thiazolidinone, in good yields. The cycloaddition of the newly synthesized compounds to N-arylmaleimides, ethyl acrylate and ω-nitrostyrene has been studied. Under thermal reaction conditions [4+2] cycloaddition proceeds with complete site-and regioselectivity to yield the new fused thiopyrano[2,3-d]thiazole derivatives.

Full text of DOI:10.1080/17415993.2015.1065405

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Synthesis of some new 5-substituted-3-
phenyl-4-thioxo-2-thiazolidinones and
their fused thiopyrano[2,3-d]thiazole
derivatives
Mohamed Ahmed Badawya, Nadia Hanafy Metwallya & Doha Samir
Okpya
a Department of Chemistry, Faculty of Science, University of
Cairo, Giza, Egypt
Published online: 24 Jul 2015.
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To cite this article: Mohamed Ahmed Badawy, Nadia Hanafy Metwally & Doha Samir
Okpy (2015): Synthesis of some new 5-substituted-3-phenyl-4-thioxo-2-thiazolidinones
and their fused thiopyrano[2,3-d]thiazole derivatives, Journal of Sulfur Chemistry, DOI:
10.1080/17415993.2015.1065405
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Journal of Sulfur Chemistry, 2015
http://dx.doi.org/10.1080/17415993.2015.1065405
Synthesis of some new 5-substituted-3-phenyl-4-thioxo-2-
thiazolidinones and their fused thiopyrano[2,3-d]thiazole
derivatives
Mohamed Ahmed Badawy, Nadia Hanafy Metwally∗ and Doha Samir Okpy
Department of Chemistry, Faculty of Science, University of Cairo, Giza, Egypt
(Received 25 December 2014; accepted 19 June 2015)
The new 5-arylmethylene-3-phenyl-4-thioxo-2-thiazolidinone derivatives have been synthesized by con-
densation of ω-(4-formylphenoxy)acetophenone derivatives with 3-phenyl-4-thioxo-2-thiazolidinone, in
good yields. The cycloaddition of the newly synthesized compounds to N-arylmaleimides, ethyl acrylate
and ω-nitrostyrene has been studied. Under thermal reaction conditions [4 + 2] cycloaddition proceeds
with complete site- and regioselectivity to yield the new fused thiopyrano[2,3-d]thiazole derivatives.
Ph
N
O
S
O
N
R
S
O
H
Ar
5a-h
S
O
Ar
R
N
R
toluene
heat
R
N
S
N
+
Ph
O
O
4a-d
O
O
N
O
O
S
S
O
O
S
N Ph
Ph N
S
O
O
Keywords: ω-(4-formylphenoxy)acetophenones; 3-phenyl-4-thioxo-2-thiazolidinone; [4 + 2] cycload-
dition reaction; 5-[(4-benzoylmethoxy)phenylmethylene]-3-phenyl-4-thioxo-2-thiazolidinones; thiopyrano[2,3-
d]-thiazoles
1. Introduction
As a part of the general interest in heterocyclic synthesis that have been explored for devel-
oping pharmaceutically important compounds, thiazolidinones have been studied extensively
due to their ready accessibility, diverse chemical reactivity and broad spectrum of biological
*Corresponding author. Email: nhmmohamed@yahoo.com
© 2015 Taylor & Francis

2
M.A. Badawy et al.
activity.[1–10] Recently, it was established, that the modified 5-substituted thiazolidinone deriva-
tives exhibited diverse pharmacological activities.[11–13] In addition, thiopyrano[2,3-d]thiazole
derivatives are considered as novel anticancer lead compounds.[14–17] Also, heterocyclic sys-
tems having both thiazolidine and thiopyrano moieties have important applications in the
field of medicinal chemistry.[18–20] Our objective is that 3-phenyl-4-thioxo-2-thiazolidinones
are synthetic precursors of thiopyrano[2,3-d]thiazole compounds, which could imitate some
pharmacologically important molecular fragments of thiazolidinones. In continuation of our
previous studies on 4-thioxo-2-thiazolidines,[21–27] we report here the synthesis of some
new thiopyrano[2,3-d]thiazole derivatives, starting from ω-(4-formylphenoxy)acetophenone
derivatives and 3-phenyl-4-thioxo-2-thiazolidunone.
2. Results and discussion
Knoevenagel condensation of 3-phenyl-4-thioxo-2-thiazolidinone 1 with ω-(4-formylphenoxy)
acetophenone derivatives 2a–2c in glacial acetic acid afforded colored products 3a–3c
(Scheme 1). The structures of the isolated products 3a–3c were established by elemental analysis
and spectral data. For example, the IR spectrum of 3a showed absorption bands at νmax 1713,
1681 cm−1 due to CO groups, in addition to other absorption bands correlated to the assigned
structure. 1H NMR spectrum revealed a singlet signal at δ = 5.76 ppm due to methylene protons
and a singlet signal at δ = 8.32 ppm due to vinylic proton besides the other expected signals
for aromatic protons. In addition, an evidence to support the structural assignment was gained
from the 13C NMR spectrum of the same compound which showed two characteristic signals at
δ = 71.3 and 194.1 attributed to methylene and carbonyl carbon atoms. In addition, two char-
acteristic signals at δ = 171.4 and 193.8 assigned to the carbonyl and the thiocarbonyl carbon
atoms of thiazolidine ring, respectively, besides the other expected signals.
Also, our study is extended to explore the utility of compounds 3a–3c in the Diels–Alder reac-
tion with different dienophiles. Thus, heating equimolar amounts of colored compounds 3a,b
with N-arylmaleimides 4a–4d in toluene gave adducts 5a–5h (Scheme 2). The IR spectrum
of the isolated product 5b taken as a typical example of the prepared series, showed absorp-
tion bands at νmax 1765, 1716 and 1658 cm−1 corresponding to CO groups. Furthermore, the
1H NMR spectrum of this adduct showed two doublets at δ = 4.0 ppm with J values = 8.7
and 5.7 Hz attributed to H-6, in addition to two doublets at δ = 4.50 and 5.21 ppm with J val-
ues = 5.7 and 8.7 Hz, respectively, assigned to H-5 and H-7, besides the other expected signals.
1
The new adducts 5a–5h showed only one isomer in the H NMR spectra (see exp.) and the
Scheme 1. Synthesis of compounds 3a–3c.

Journal of Sulfur Chemistry
3
Scheme 2. Synthesis of compounds 5a–5h.
isolated adduct 5a studied by density functional theory (DFT). Thus, the geometrical structure
of compound 5a has been fully optimized at the B3LYP/6-31G(d) level of DFT theory. The
optimized geometries of the lowest energy endo and exo adducts are depicted in Figure 1. The
corresponding total and relative energies in vacuum and in acetic acid are given. It is obvious that
the exo-cycloadduct is more stable than the endo-cycloadduct by about 0.89 and 0.78 kcal/mol
in vacuum and in acetic acid, respectively.
Based on the above collective data, the structure 5 was assigned for the isolated products.
Similarly, cycloaddition of 3a,b with acrylonitrile 6a and ethyl acrylate 6b in refluxing toluene
gave the corresponding thiopyrano[2,3-d]thiazole derivatives 7a–7d (Scheme 3). The struc-
tures of 7a–7d were assigned on the basis of the obtained elemental analysis and spectral data
(see exp.). The formation of compounds 7a–7d can be explained in terms of [4 +2] cycloaddition
to conjugated thiocarbonyl moiety.
Figure 1. Optimized geometries of the lowest energy endo and exo adducts of 5a.

4
M.A. Badawy et al.
Scheme 3. Synthesis of compounds 7a–7d.
Scheme 4. Synthesis of compound 9.
Also, 3-phenyl-4-thioxo-2-thiazolidineone 1 undergoes condensation with terephthaldehyde 8
in glacial acetic acid and in the presence of sodium acetate in 2:1 molar ratio to afford compound
9 in good yield (Scheme 4).
The structure of the isolated product 9 was established by the elemental analysis and spectral
data. IR spectrum of 9 showed absorption band νmax 1680 cm−1 due to the carbonyl group.
1
It’s H NMR spectrum revealed a singlet signal at δ = 8.34 ppm due to vinylic protons. The
mass spectrum showed correct molecular ion peak at m/z = 516 (M+). The [4 +2] cycloaddition
reaction of compound 9 with some dienophiles was also investigated. Thus, refluxing of 9 with
N-arylmaleimides 4a–4d in 1:2 molar ratio in acetic acid gave adducts 10a–10d (Scheme 5). The
structure of the adducts was confirmed on the basis of their elemental analysis and spectral data
(see exp.)
Similarly, the reaction of 9 with acrylonitrile 6a and ethylacrylate 6b under the same reac-
tion conditions gave colorless cycloadducts 11a,b (Scheme 6). The structure of the adducts was
confirmed on the basis of their elemental analysis and spectral data (see exp.).
Condensation of 1 with 4,4ꢀ-(pentane-1,5-diylbisoxy)dibenzaldehyde 12 in glacial acetic acid
in the presence of sodium acetate in 1:1 or 1:2 molar ratio gave a mixture of mono- and bis-
3-phenyl-4-thioxo-2-thiazolidinone derivative 13 and 14, respectively, which were separated by
crystallization from ethanol (Scheme 7).
Some reactions were performed on mono- and bis-3-phenyl-4-thioxo-2-thiazolidinones. Thus,
compound 14 undergoes [4 +2] cycloaddition reaction in refluxing toluene in 1:2 molar ratio
with some dienophiles such as N-arylmaleimides 4a–4d, acrylonitrile 6a and ethylacrylate 6b
afforded the bis-adducts 15 and 16, respectively (Scheme 8). The structure of the isolated bis-
adducts was confirmed based on their elemental analysis and spectral data (see exp.).
1
All the new adducts 7, 10, 11, 15 and 16 showed only one isomer in the H NMR spectra
(see exp.) and this seems logic, since the endo-cycloadduct is obtained as a kinetically con-
trolled product at room temperature, but under thermal conditions it is transformed into the
exo-cycloadduct which is a thermally stable controlled product.

Journal of Sulfur Chemistry
5
Scheme 5. Synthesis of compounds 10a–10d.
Scheme 6. Synthesis of compounds 11a,b.
Scheme 7. Synthesis of compounds 13 and 14.
Moreover, mono 5-arylmethylene-3-phenyl-4-thioxo-2-thiazolidinone derivative 13 con-
densed with some active methylene compounds such as 2-thioxo-4-thiazolidinone and
3-phenyl-4-thioxo-2-thiazolidinone to give compounds 17 and 14, respectively (Scheme 9). The

6
M.A. Badawy et al.
Scheme 8. Synthesis of compounds 15a–15d and 16a,b.
Scheme 9. Synthesis of compounds 17 and 14.

Journal of Sulfur Chemistry
7
structure of products 17 and 14 was established on their elemental analysis and spectral data
(see exp.).
3. Conclusion
The method reported here describes the synthesis of 5-(4-(2-(aryl)-2-oxoethoxy)benzylidene)-
3-phenyl-4-thioxothiazolidin-2-ones 3a–3c and reaction of latter compounds with N-
arylmaleimides 4a–4d in glacial acetic acid underwent 4 +2-cycloaddition reaction to give
1:1 cycloadducts 5a–5h. Also, the method describes the reaction of bis-3-phenyl-4-thioxo-
4-thioxo-2-thiazoldinones with some different dienophiles in refluxing toluene to give the
bis-cycloadducts.
4. Experimental
All melting points were determined on an Electrothermal (9100) apparatus and are uncorrected.
1
IR spectra were recorded as KBr pellets on a Perkin Elmer 1430 spectrophotometer. H NMR
spectra were recorded in deuterated dimethylsulfoxide at 300 MHz on a Varian Gemini NMR
spectrometer using tetramethylsilane as the internal reference and results are expressed as δ
values. 13C NMR spectra were recorded in dimethylsulfoxide (DMSO-d6) at 75.46 MHz on a
Varian Mercury VXR-300 NMR spectrometer using tetramethylsilane as the internal reference
and results are expressed as δ values. Mass spectra were taken on a Shimadzu GCMS-QP 1000
Ex mass spectrometer at 70 eV. Elemental analyses were carried out at the Microanalysis Center
of Cairo University. The starting compounds 2a–2c, and 12 were prepared according to lit.[26,29]
4.1. Preparation of 3-phenyl-4-thioxo-2-thiazolidinone 1
A mixture of 3-phenyl-2,4-thiazolidinedione (0.25 mol) and 20 g of phosphorus pentasulfide was
refluxed for 3 h in 200 ml dry dioxane. The mixture was filtered off and the dioxane was distilled
under reduced pressure to give pale yellow crystals of m.p. 110°C of compound 1.[28]
4.2. Preparation 5-(4-(2-(aryl)-2-oxoethoxy)benzylidene)-3-phenyl-4-
thioxothiazolidin-2-one 3a–3c
4.2.1. General procedure
To a solution of 1 (0.01 mol) in glacial acetic acid (25 ml) and fused sodium acetate (1.64 g,
0.02 mol), the appropriate aldehyde 2a–2c (0.01 mol) was added. The reaction mixture was
refluxed for 30 min on a water bath, cooled and then poured into cold water. The solid so formed
was filtered off and recrystallized from an ethanol and dioxane mixture to give compounds
3a–3c.
4.2.1.1. 5-[4-(2-Oxo-2-phenylethoxy)benzylidene]-3-phenyl-4-thioxo-2-thiazolidinone (3a).
1
Orange crystals (88%); m.p. 213°C; νmax/cm−1 (KBr) 1713, 1681 (CO); H NMR (DMSO-
d6) δ = 5.76 (s, 2H, CH2), 7.18-8.05 (m, 14H, Ar), 8.32 (s, 1H, CH). 13C NMR (DMSO-d6)
δ = 71.3, 115.0, 126.7, 127.8, 128.3, 128.6, 128.8, 129.0, 131.0, 132.7, 133.9, 134.2, 135.3,
146.8, 160.3, 171.4, 193.8 and 194.1. Anal. Calcd C24H17NO3S2 (431.52): C, 66.80; H, 3.97; N,
3.25; S, 14.86. Found: C, 66.96; H, 3.77; N, 3.48; S, 14.67.

8
M.A. Badawy et al.
4.2.1.2. 5-[4-(2-(4-Chlorophenyl)-2-oxoethoxy)benzylidene]-3-phenyl-4-thioxo-2-
thiazolidinone (3b). Orange crystals (72%); m.p. 242°C; νmax/cm−1 (KBr) 1713, 1681 (CO);
1H NMR (DMSO-d6) δ = 5.73 (s, 2H, CH2), 7.11–8.10 (m, 13H, Ar), 8.31 (s, 1H, CH). Anal.
Calcd C24H16ClNO3S2 (465.97): C, 61.86; H, 3.46; Cl, 7.61; N, 3.01; S, 13.76. Found: C, 61.67;
H, 3.64; Cl, 7.79; N, 3.28; S, 13.58.
4.2.1.3. 5-[4-(2-(4-Methoxyphenyl)-2-oxoethoxy)benzylidene]-3-phenyl-4-thioxo-2-
thiazolidinone (3c). Orange crystals (80%); m.p. 255°C; νmax/cm−1 (KBr) 1725, 1692 (CO);
1H NMR (DMSO-d6) δ = 3.97 (s, 3H, OCH3), 5.70 (s, 2H, CH2), 7.17–8.24 (m, 13H, Ar), 8.31
(s, 1H, CH). m/z = 462 (M+ +1, 4.7%), 399 (4.5%), 313 (10.3%), 284 (7.1%), 212 (100%), 165
(7.1%), 121 (31.8%), 91 (17.5%), 77 (98.9%). Anal. Calcd C25H19NO4S2: C, 65.06; H, 4.15; N,
3.03; S, 13.89. Found: C, 65.25; H, 4.34; N, 3.26; S, 13.71.
4.3. Preparation of compounds 5a–5h and 7a–7d
4.3.1. General procedure
A solution of equimolecular amounts (0.01 mol) of each of 3a,b and the appropriate dienophile in
toluene (30 ml) was refluxed for 1 h. The solid so formed was filtered off and recrystallized from
an ethanol and dioxane mixture. The physical constants together with spectral data of compounds
5a–5h and 7a–7d are shown below.
4.3.1.1. 8-[4-(2-Oxo-2-phenylethoxy)phenyl]-3,6-diphenyl-3,4a,7a,8-tetrahydro-pyrrolo
[3ꢀ,4ꢀ:5,6]-thiopyrano[2,3-d]thiazole-2,5,7(6H)-trione (5a). White crystals (59%); m.p. 162°C;
νmax/cm−1 (KBr) 1776, 1711, 1660 (CO); 1H NMR (DMSO-d6) δ = 4.0 (dd, 1H, J = 8.7, 5.7
Hz, H-6), 4.58 (d, 1H, J = 5.7 Hz, H-5), 5.17 (d, 1H, J = 8.7 Hz, H-7), 5.61 (s, 2H, CH2),
6.66–8.05 (m, 19H, Ar). m/z = 605 (M+ +1, 3.4%), 542 (3.7%), 474 (2.9%), 400 (3.3%),
312 (11.5%), 222 (3.8%), 173 (6.4%), 131 (5.1%), 105 (100%), 77 (74.9%). Anal. Calcd
C34H24N2O5S2: C, 67.53; H, 4.00; N, 4.63; S, 10.60. Found: C, 67.35; H, 4.18; N, 4.86; S,
10.44.
4.3.1.2. 8-[4-(2-Oxo-2-phenylethoxy)phenyl]-6-(4-methyl-phenyl)-3-phenyl-3,4a,7a,8-
tetrahydro-pyrrolo[3ꢀ,4ꢀ:5,6]thiopyrano[2,3-d]thiazole-2,5,7(6H)-trione (5b). Whitish yellow
1
crystals (58%); m.p. 145°C; νmax/cm−1 (KBr) 1765, 1716, 1658 (CO); H NMR (DMSO-d6)
δ = 2.31(s, 3H, CH3), 4.01 (dd, 1H, J = 8.7, 5.7 Hz, H-6), 4.50 (d, 1H, J = 5.7 Hz, H-5), 5.21
(d, 1H, J = 8.7 Hz, H-7), 5.58 (s, 2H, CH2), 6.51–7.88 (m, 18H, Ar). Anal. Calcd C35H26N2O5S2
(618.72): C, 67.94; H, 4.24; N, 4.53; S, 10.36. Found: C, 67.75; H, 4.44; N, 4.79; S, 10.17.
4.3.1.3. 6-(4-Methoxyphenyl)-8-[4-(2-oxo-2-phenylethoxy)phenyl]-3-phenyl-3,4a,7a,8-
tetrahydro-pyrrolo[3ꢀ,4ꢀ:5,6]thiopyrano[2,3-d]thiazole-2,5,7(6H)-trione (5c). Pale brown crys-
tals (61%); m.p. 167°C; νmax/cm−1 (KBr) 1779, 1710, 1665 (CO);1H NMR (DMSO-d6)
δ = 3.74 (s, 3H, OCH3), 4.04 (dd, 1H, J = 8.7, 5.7 Hz, H-6), 4.55 (d, 1H, J = 5.7 Hz, H-
5), 5.23 (d, 1H, J = 8.7 Hz, H-7), 5.63 (s, 2H, CH2), 6.54–8.04 (m, 18H, Ar). Anal. Calcd
C35H26N2O6S2 (634.72): C, 66.23; H, 4.13; N, 4.41; S, 10.10. Found: C, 66.04; H, 4.32; N, 4.66;
S, 10.30.
4.3.1.4. 6-(4-Chlorophenyl)-8-[4-(2-oxo-2-phenylethoxy)phenyl]-3-phenyl-3,4a,7a,8-
tetrahydro-pyrrolo[3ꢀ,4ꢀ:5,6]thiopyrano[2,3-d]thiazole-2,5,7(6H)-trione (5d). White crystals
1
(64%); m.p. 175°C; νmax/cm−1 (KBr) 1781, 1711, 1668 (CO); H NMR (DMSO-d6) δ = 4.04
(dd, 1H, J = 8.1, 5.7 Hz, H-6), 4.59 (d, 1H, J = 5.7 Hz, H-5), 5.34 (d, 1H, J = 8.1 Hz, H-7),

Journal of Sulfur Chemistry
9
5.63 (s, 2H, CH2), 6.70–8.08 (m, 18H, Ar). m/z = 639 (M+ +1, 5.9%), 584 (6.9%), 541 (6.8%),
483 (4.7%), 387 (4.4%), 338 (6.0%), 257 (5.9%), 207 (22.5%), 151 (8.3%), 105 (100%), 77
(75.4%). Anal. Calcd C34H23ClN2O5S2: C, 63.89; H, 3.63; Cl, 5.55; N, 4.38; S, 10.03. Found:
C, 64.08; H, 3.45; Cl, 5.76; N, 4.66; S, 10.20.
4.3.1.5. 8-[4-(2-(4-Chlorophenyl)-2-oxoethoxy)phenyl]-3,6-diphenyl-3,4a,7a,8-tetrahydro-
pyrrolo[3ꢀ,4ꢀ:5,6]thiopyrano[2,3-d]thiazole-2,5,7(6H)-trione (5e). Whitish yellow crystals
1
(54%); m.p. 159°C; νmax/cm−1 (KBr) 1780, 1713, 1661 (CO); H NMR (DMSO-d6) δ = 4.03
(dd, 1H, J = 8.4, 6.3 Hz, H-6), 4.59 (d, 1H, J = 6.3 Hz, H-5), 5.35 (d, 1H, J = 8.4 Hz, H-7),
5.61 (s, 2H, CH2), 6.65–8.11 (m, 18H, Ar). Anal. Calcd C34H23ClN2O5S2 (639.14): C, 63.89; H,
3.63; Cl, 5.55; N, 4.38; S, 10.03. Found: C, 63.71; H, 3.46; Cl, 5.74; N, 4.55; S, 10.21.
4.3.1.6. 8-[4-(2-(4-Chlorophenyl)-2-oxoethoxy)phenyl]-3-phenyl-6-(4-methyl-phenyl)-3,4a,
7a,8-tetrahydro-pyrrolo[3ꢀ,4ꢀ:5,6]thiopyrano[2,3-d]thiazole-2,5,7(6H)-trione (5f). Pale yel-
low crystals (58%); m.p. 163°C; νmax/cm−1 (KBr) 1776, 1713, 1667 (CO); 1H NMR (DMSO-d6)
δ = 2.36 (s, 3H, CH3), 4.05 (dd, 1H, J = 9, 6 Hz, H-6), 4.63 (d, 1H, J = 6 Hz, H-5), 5.23 (d,
1H, J = 9 Hz, H-7), 5.67 (s, 2H, CH2), 6.67-8.15 (m, 17H, Ar). Anal. Calcd C35H25ClN2O5S2
(653.16): C, 64.36; H, 3.86; Cl, 5.43; N, 4.29; S, 9.82. Found: C, 64.16; H, 3.69; Cl, 5.60; N,
4.55; S, 9.99.
4.3.1.7. 8-[4-(2-(4-Chlorophenyl)-2-oxoethoxy)phenyl]-6-(4-methoxyphenyl)-3-phenyl-3,4a,
7a,8-tetraydropyrrolo[3ꢀ,4ꢀ:5,6]thiopyrano[2,3-d]thiazole-2,5,7(6H)-trione (5g). Pale yellow
1
crystals (60%); m.p. 181°C; νmax/cm−1 (KBr) 1778, 1713, 1668 (CO); H NMR (DMSO-d6)
δ = 3.86 (s, 3H, OCH3), 4.18 (dd, 1H, J = 9, 5.4 Hz, H-6), 4.66 (d, 1H, J = 5.4 Hz, H-
5), 5.27 (d, 1H, J = 9 Hz, H-7), 5.65 (s, 2H, CH2), 6.70–8.17 (m, 17H, Ar). Anal. Calcd
C35H25ClN2O6S2 (669.16): C, 62.82; H, 3.77; Cl, 5.30; N, 4.19; S, 9.58. Found: C, 63.0; H,
3.60; Cl, 5.48; N, 4.45; S, 9.38.
4.3.1.8. 6-(4-Chlorophenyl)-8-[4-(2-(4-chlorophenyl)-2-oxoethoxy)phenyl]-3-phenyl-3,4a,7a,
8-tetrahydro-pyrrolo[3ꢀ,4ꢀ:5,6]thiopyrano[2,3-d]thiazole-2,5,7(6H)-trione (5h). Pale yellow
1
crystals (64%); m.p. 200°C; νmax/cm−1 (KBr) 1783, 1712, 1660 (CO); H NMR (DMSO-d6)
δ = 4.23 (dd, 1H, J = 9, 6 Hz, H-6), 4.67 (d, 1H, J = 6 Hz, H-5), 4.84 (d, 1H, J = 9 Hz, H-7),
5.64 (s, 2H, CH2), 6.69–8.18 (m, 17H, Ar). Anal. Calcd C34H22Cl2N2O5S2 (673.58): C, 60.63;
H, 3.29; Cl, 10.53; N, 4.16; S, 9.52. Found: C, 60.44; H, 3.46; Cl, 10.35; N, 4.38; S, 9.70.
4.3.1.9. 2-Oxo-7-[4-(2-oxo-2-phenylethoxy)phenyl]-3-phenyl-3,5,6,7-tetrahydro-2H-
thiopyrano-[2,3-d]thiazole-6-carbonitrile (7a). Whitish yellow crystals (56%); m.p. 215°C;
1
νmax/cm−1 (KBr) 2219 (CN), 1713, 1654 (CO); H NMR (DMSO-d6) δ = 3.59–3.62 (m, 2H,
H-5), 4.03 (t, 1H, J = 5.7 Hz, H-6), 4.49 (d, 1H, J = 7.2 Hz, H-7), 5.66 (s, 2H, CH2), 7.09–8.13
(m, 14H, Ar). Anal. Calcd C27H20N2O3S2 (484.59): C, 66.92; H, 4.16; N, 5.78; S, 13.23. Found:
C, 66.74; H, 4.33; N, 5.52; S, 13.04.
4.3.1.10. 7-(4-(2-(4-Chlorophenyl)-2-oxoethoxy)phenyl)-2-oxo-3-phenyl-3,5,6,7-tetrahydro-
2H-thiopyrano[2,3-d]thiazole-6-carbonitrile (7b). Pale brown crystals (60%); m.p. 179°C;
1
νmax/cm−1 (KBr) 2218 (CN), 1711, 1660 (CO); H NMR (DMSO-d6) δ = 3.59–3.62 (m, 2H,
H-5), 4.03 (t, 1H, J = 5.1 Hz, H-6), 4.49 (d, 1H, J = 7.2 Hz, H-7), 5.66 (s, 2H, CH2), 7.09–8.13
(m, 13H, Ar). Anal. Calcd C27H19ClN2O3S2 (519.03): C, 62.48; H, 3.69; Cl, 6.83; N, 5.40; S,
12.35. Found: C, 62.67; H, 3.87; Cl, 6.66; N, 5.65; S, 12.19.

10 M.A. Badawy et al.
4.3.1.11. Ethyl 2-oxo-7-[4-(2-oxo-2-phenylethoxy)phenyl]-3-phenyl-3,5,6,7-tetrahydro-2H-
thiopyrano[2,3-d]thiazole-6-carboxylate (7c). Pale brown crystals (55%); m.p. 140°C;
1
νmax/cm−1 (KBr) 1720, 1713, 1658 (CO); H NMR (DMSO-d6) δ = 1.13 (t, 3H, J = 7.2 Hz,
CH3), 3.58–3.60 (m, 2H, H-5), 4.04 (t, 1H, J = 6.3 Hz, H-6), 3.72 (q, 2H, J = 6 Hz, CH2), 4.50
(d, 1H, J = 6.9 Hz, H-7), 5.69 (s, 2H, CH2), 7.06–8.16 (m, 14H, Ar). Anal. Calcd C29H25NO5S2
(531.64): C, 65.52; H, 4.74; N, 2.63; S, 12.06. Found: C, 65.72; H, 4.56; N, 2.87; S, 12.24.
4.3.1.12. Ethyl
7-(4-(2-(4-chlorophenyl)-2-oxoethoxy)phenyl)-2-oxo-3-phenyl-3,5,6,7-
tetrahydro-2H-thiopyrano[2,3-d]thiazole-6-carboxylate (7d). Pale brown crystals (58%); m.p.
109°C; νmax/cm−1 (KBr) 1720, 1713, 1661 (CO); 1H NMR (DMSO-d6) δ = 1.13 (t, 3H, J = 6.9
Hz, CH3), 3.58–3.60 (m, 2H, H-5), 4.04 (t, 1H, J = 5.1 Hz, H-6), 3.72 (q, 2H, J = 6 Hz, CH2),
4.50 (d, 1H, J = 6 Hz, H-7), 5.69 (s, 2H, CH2), 7.06–8.16 (m, 13H, Ar). m/z = 566 (M+ +1,
3.5%), 466 (6.1%), 391 (4.5%), 312 (11.2%), 236 (6.1%), 207 (9.2%), 135 (6.7%), 105 (100%),
77 (72.8%). Anal. Calcd C29H24ClNO5S2: C, 61.53; H, 4.27; Cl, 6.26; N, 2.47; S, 11.33. Found:
C, 61.34; H, 4.44; Cl, 6.45; N, 2.23; S, 11.50.
4.4. Preparation of 5,5ꢀ-[1,4-phenylenebis(methanylylidene)]bis(3-phenyl-4-thioxo-2-
thiazolidinone) (9)
To a solution of 1 (0.02 mol) in glacial acetic acid (25 ml) and anhydrous sodium acetate (1.64
g, 0.02 mol) terephthaldehyde 8 (0.01 mol) was added. The reaction mixture was refluxed for 30
min cooled and then poured into cold water. The solid so formed was filtered off and recrystal-
lized from dimethylformamide to give red crystals (83%); m.p. 290°C; νmax/cm−1 (KBr) 1680
(CO); 1H NMR (DMSO-d6) δ = 7.44–7.94 (m, 14H, Ar), 8.34 (s, 2H, 2CH); m/z = 516 (M+,
18%), 325 (46.2%), 296 (20.5%), 162 (30.8%), 122 (20.5%), 116 (17.9%), 110 (5.1%), 104
(30.8%), 89 (51.3%), 77 (43.6%), 66 (20.5%), 60 (100%). Anal. Calcd C26H16N2O2S4: C, 60.44;
H, 3.12; N, 5.42; S, 24.82. Found: C, 60.62; H, 3.32; N, 5.16; S, 25.01.
4.5. Preparation of cycloadducts 10a–10d and 11a,b
4.5.1. General procedure
To compound 9 (0.01 mol), suspended in glacial acetic acid (20 ml), were added N-
arylmaleimides 4a–4d, acrylonitrile 6a and ethyl acrylate 6b (0.02 mol). The mixture was
refluxed for 30 min, or till decolorization took place, then it was left overnight at room tem-
perature. The solid so formed was filtered off, and recrystallized from an ethanol and dioxane
mixture.
4.5.1.1. 8,8ꢀ-(1,4-Phenylene)bis(3,6-diphenyl-3,4a,7a,8-tetrahydro-pyrrolo-[3ꢀ,4ꢀ:5,6]
thiopyrano-[2,3-d]thiazole-2,5,7(6H)-trione) (10a). Pale yellow crystals (65%); m.p. 215°C;
νmax/cm−1 (KBr) 1702, 1662 (CO); 1H NMR (DMSO-d6) δ = 3.40 (m, 2H, H-6, H-6ꢀ), 4.82 (d,
2H, J = 6.3 Hz, H-5, H-5ꢀ), 5.16 (d, 2H, J = 8.7 Hz, H-7, H-7ꢀ), 7.21–7.61 (m, 24H, Ar). Anal.
Calcd C46H30N4O6S4 (863.01): C, 64.02; H, 3.50; N, 6.49; S, 14.86. Found: C, 64.20; H, 3.69;
N, 6.76; S, 14.69.
4.5.1.2. 8,8ꢀ-(1,4-Phenylene)bis(6-(4-methyl-phenyl)-3-phenyl-3,4a,7a,8-tetrahydro-pyrrolo-
[3ꢀ,4ꢀ:5,6]thiopyrano[2,3-d]thiazole-2,5,7(6H)-trione) (10b). Pale yellow crystals (60%); m.p.
222°C; νmax/cm−1 (KBr) 1702, 1660 (CO); 1H NMR (DMSO-d6) δ = 2.37 (s, 6H, 2CH3), 3.38
(m, 2H, H-6, H-6ꢀ), 4.85 (d, 2H, J = 6.3 Hz, H-5, H-5ꢀ), 5.11 (d, 2H, J = 8.7 Hz, H-7, H-7ꢀ),

Journal of Sulfur Chemistry 11
7.19–7.59 (m, 22H, Ar). Anal. Calcd C48H34N4O6S4 (891.06): C, 64.70; H, 3.85; N, 6.29; S,
14.39. Found: C, 64.50; H, 3.68; N, 6.02; S, 14.56.
4.5.1.3. 8,8ꢀ-(1,4-Phenylene)bis(6-(4-methoxyphenyl)-3-phenyl-3,4a,7a,8-tetrahydro-pyrrolo-
[3ꢀ,4ꢀ:5,6]thiopyrano[2,3-d]thiazole-2,5,7(6H)-trione) (10c). Pale yellow crystals (60%); m.p.
214°C; νmax/cm−1 (KBr) 1701, 1659 (CO);1H NMR (DMSO-d6) δ = 3.80 (s, 6H, 2OCH3), 4.68
(m, 2H, H-6, H-6ꢀ), 5.13 (d, 2H, J = 6.0 Hz, H-5, H-5ꢀ), 5.15 (d, 2H, J = 8.7 Hz, H-7, H-7ꢀ),
6.51–7.66 (m, 22H, Ar). Anal. Calcd C48H34N4O8S4 (923.06): C, 62.46; H, 3.71; N, 6.07; S,
13.89. Found: C, 62.63; H, 3.88; N, 6.30; S, 13.71.
4.5.1.4. 8,8ꢀ-(1,4-Phenylene)bis(6-(4-chlorophenyl)-3-phenyl-3,4a,7a,8-tetrahydro-pyrrolo-
[3ꢀ,4ꢀ:5,6]thiopyrano[2,3-d]thiazole-2,5,7(6H)-trione) (10d). Pale yellow crystals (61%); m.p.
230°C; νmax/cm−1 (KBr) 1701, 1659 (CO); 1H NMR (DMSO-d6):δ = 4.75 (m, 2H, H-6, H-6ꢀ),
5.12 (d, 2H, J = 6 Hz, H-5, H-5ꢀ), 5.18 (d, 2H, J = 8.7 Hz, H-7, H-7ꢀ), 6.53–7.70 (m, 22H, Ar).
Anal. Calcd C46H28Cl2N4O6S4 (931.89): C, 59.29; H, 3.03; Cl, 7.61; N, 6.01; S, 13.76. Found:
C, 59.48; H, 3.20; Cl, 7.44; N, 6.25; S, 13.94.
4.5.1.5. 7,7ꢀ-(1,4-Phenylene)bis(2-oxo-3-phenyl-3,5,6,7-tetrahydro-2H-thiopyrano-[2,3-d]
thiazole-6-carbonitrile) (11a). Pale yellow crystals (56%); m.p. 210°C; νmax/cm−1 (KBr) 2218
(CN), 1663 (CO); 1H NMR (DMSO-d6) δ = 3.42–3.47 (m, 4H, H-5, H-5ꢀ), 4.16–4.20 (m, 2H,
H-6, H-6ꢀ), 4.62–4.67 (m, 2H, H-7, H-7ꢀ), 7.40–7.76 (m, 14H, Ar). Anal. Calcd. C32H22N4O2S4
(622.79): C, 61.71; H, 3.56; N, 9.00; S, 20.59. Found: C, 61.89; H, 3.74; N, 9.22; S, 20.78.
4.5.1.6. Diethyl
7,7ꢀ-(1,4-phenylene)bis(2-oxo-3-phenyl-3,5,6,7-tetrahydro-2H-thiopyrano
[2,3-d] thiazole-6-carboxylate) (11b). Pale yellow crystals (52%); m.p. 195°C; νmax/cm−1
(KBr) 1720, 1616 (CO); 1H NMR (DMSO-d6) δ = 1.13 (t, 6H, J = 7.2 Hz, 2CH3), 3.21–3.33
(m, 4H, H-5, H-5ꢀ), 3.38 (q, 4H, J = 7.2 Hz, 2CH2), 3.99–4.01 (m, 2H, H-6, H-6ꢀ), 4.40 (d, 2H,
J = 8.1 Hz, H-7, H-7ꢀ), 6.90–7.82 (m, 14H, Ar). m/z = 716 (M+, 17.8%), 607 (22.2%), 568
(21.6%), 453 (18.2%), 309 (48.6%), 255 (21.6%), 156 (18.2%), 103 (27.5%), 77 (100%). Anal.
Calcd C36H32N2O6S4: C, 60.31; H, 4.50; N, 3.91; S, 17.89. Found: C, 60.50; H, 4.67; N, 3.65;
S, 17.72.
4.6. Preparation of compounds 13 and 14
To a solution of 1 (0.01 mol) in glacial acetic acid (25 ml) and anhydrous sodium acetate (1.64 g,
0.02 mol), 4,4ꢀ-(pentan-1-diybisoxy)dibenzaldehyde 12 (0.01 mol) was added. The reaction mix-
ture was refluxed for 1 h, cooled and then poured into cold water. The solid so formed was filtered
off and crystallized from ethanol to afford mono compound 13 and the insoluble compound is
recrystallized from an ethanol and dioxane mixture to afford compound 14.
4.6.1. 4-((5-(4-((2-Oxo-3-phenyl-4-thioxothiazolidin-5-ylidene)methyl)phenoxy)-pentyl)oxy)-
benzaldehyde (13)
1
Orange crystals (30%); m.p. 110°C; νmax/cm−1 (KBr) 2869 (CHO), 1714 (CO); H NMR
(DMSO-d6) δ = 1.81 (m, 2H, CH2), 1.89 (m, 4H, 2CH2), 4.10 (m, 4H, 2CH2), 7.10–7.87 (m,
13H, Ar), 8.30 (s, 1H, CH), 9.86 (s, 1H, CHO); m/z = 503 (M+, 12%), 443 (12%), 415 (18.1%),
312 (38.6%), 297 (9.6%), 284 (10.8%), 193 (26.5%), 163 (21.7%), 150 (67.5%), 121 (51.8%),
105 (34.9%), 77 (61.4%), 69 (100%). Anal. Calcd. C28H25NO4S2: C, 66.78; H, 5.0; N, 2.78; S,
12.73. Found: C, 66.95; H, 5.20; N, 2.50; S, 12.91.

12 M.A. Badawy et al.
4.6.2. 5,5ꢀ-(((Pentane-1,5-diylbis(oxy))bis(4,1-phenylene))bis(methanylylidene))-bis(3-
phenyl-4-thioxo-2-thiazolidinone) (14)
Red crystals (46%); m.p. 165°C; νmax/cm−1 (KBr) 1714 (CO); 1H NMR (DMSO-d6) δ = 1.82
(m, 2H, CH2), 1.84 (m, 4H, 2CH2), 4.10 (m, 4H, 2CH2), 7.11–7.70 (m, 18H, Ar), 8.26 (s,
2H, 2CH); m/z = 694 (M+, 18.8%), 380 (3.1%), 313 (10.7%), 284 (10.7%), 209 (13.8%), 193
(10.7%), 165 (3.6%), 150 (24.1%), 135 (32.1%), 119 (38.4%), 104 (37.1%), 91 (36.2%), 77
(100%). Anal. Calcd C37H30N2O4S4: C, 63.95; H, 4.35; N, 4.03; S, 18.45. Found: C, 63.77; H,
4.54; N, 4.31; S, 18.65.
4.7. Preparation of compounds 15a–15d and 16a,b
4.7.1. General procedure
To compound 14 (0.01 mol), suspended in glacial acetic acid (20 ml), N-arylmaleimides 4a–4d,
acrylonitrile 6a or ethyl acrylate 6b (0.02 mol) was added. The mixture was refluxed for 30 min
or till decolorization took place, then it was left overnight at room temperature. The solid so
formed was filtered off and recrystallized from an ethanol and dioxane mixture.
4.7.1.1. 8,8ꢀ-((Pentane-1,5-diylbis(oxy))bis(4,1-phenylene))bis(3,6-diphenyl-3,4a,7a,8-
tetrahydro-pyrrolo[3ꢀ,4ꢀ:5,6]thiopyrano[2,3-d]thiazole-2,5,7(6H)-trione) (15a). Pale yellow
crystals (56%); m.p. 176°C; νmax/cm−1 (KBr) 1710, 1661 (CO); 1H NMR (DMSO-d6) δ = 1.78–
1.80 (m, 2H, CH2), 1.84–1.90 (m, 4H, 2CH2), 4.01–4.04 (m, 4H, 2CH2), 4.07–4.411 (m, 2H, H-6,
H-6ꢀ), 4.57 (d, 2H, J = 5.7 Hz, H-5, H-5ꢀ), 5.16 (d, 2H, J = 8.7 Hz, H-7, H-7ꢀ), 6.67–7.55 (m,
28H, Ar). Anal. Calcd C57H44N4O8S4 (1041.24): C, 65.75; H, 4.26; N, 5.38; S, 12.32. Found: C,
65.95; H, 4.45; N, 5.12; S, 12.49.
4.7.1.2. 8,8ꢀ-((Pentane-1,5-diylbis(oxy))bis(4,1-phenylene))bis(3-phenyl-6-(4-methyl-phenyl)-
3,4a,7a,8-tetrahydro-pyrrolo[3ꢀ,4ꢀ:5,6]thiopyrano[2,3-d]thiazole-2,5,7(6H)-trione) (15b). Pale
1
yellow crystals (58%); m.p. 156°C; νmax/cm−1 (KBr) 1710, 1664 (CO); H NMR (DMSO-d6)
δ = 1.78–1.80 (m, 2H, CH2), 1.85–1.93 (m, 4H, 2CH2), 2.37 (s, 6H, 2CH3), 4.0–4.01 (m, 4H,
2CH2), 4.06–4.18 (m, 2H, H-6, H-6ꢀ), 4.54 (d, 2H, J = 5.7 Hz, H-5, H-5ꢀ), 5.14 (d, 2H, J = 8.7
Hz, H-7, H-7ꢀ), 6.69–7.59 (m, 26H, Ar). Anal. Calcd C59H48N4O8S4 (1069.29): C, 66.27; H,
4.52; N, 5.24; S, 11.99. Found: C, 66.45; H, 4.35; N, 5.49; S, 12.18.
4.7.1.3. 8,8ꢀ-((Pentane-1,5-diylbis(oxy))bis(4,1-phenylene))bis(6-(4-methoxyphenyl)-3-phenyl
-3,4a,7a,8-tetrahydro-pyrrolo[3ꢀ,4ꢀ:5,6]thiopyrano[2,3-d]thiazole-2,5,7(6H)-trione) (15c). Pale
yellow crystals in a yield of 56%; m.p. 160°C; IR (KBr, ν cm−1):1718, 1660 (CO); 1H
NMR (DMSO-d6) δ = 1.80–1.86 (m, 2H, CH2), 1.89–1.92 (m, 4H, 2CH2), 3.87 (s, 6H,
2OCH3), 4.04–4.06 (m, 4H, 2CH2), 4.09–4.12 (m, 2H, H-6, H-6ꢀ), 4.57 (d, 2H, J = 5.7
Hz, H-5, H-5ꢀ), 5.13 (d, 2H, J = 8.7 Hz, H-7, H-7ꢀ), 6.70–7.61 (m, 26H, Ar). Anal. Calcd.
C59H48N4O10S4 (1101.29): C, 64.35; H, 4.39; N, 5.09; S, 11.64. Found: C, 64.54; H, 4.21;
N, 5.36; S, 11.48.
4.7.1.4. 8,8ꢀ-((Pentane-1,5-diylbis(oxy))bis(4,1-phenylene))bis(6-(4-chlorophenyl)-3-phenyl-
3,4a,7a,8-tetrahydro-pyrrolo[3ꢀ,4ꢀ:5,6]thiopyrano[2,3-d]thiazole-2,5,7(6H)-trione) (15d). Pale
1
yellow crystals (60%); m.p. 186°C; νmax/cm−1 (KBr) 1716, 1618 (CO); H NMR (DMSO-
d6):δ = 1.79–1.86 (m, 2H, CH2), 1.91–2.09 (m, 4H, 2CH2), 4.01–4.04 (m, 4H, 2CH2), 4.07–4.11
(m, 2H, H-6, H-6ꢀ), 4.61 (d, 2H, J = 5.7 Hz, H-5, H-5ꢀ), 5.17 (d, 2H, J = 8.4 Hz, H-7, H-7ꢀ),
6.73–7.62 (m, 26H, Ar); m/z = 1108 (M+, 20.7%), 979 (19.2%), 693 (17.2%), 328 (20.7%),

Journal of Sulfur Chemistry 13
255 (17.2%), 194 (17.2%), 127 (27.6%), 97 (34.5%), 71 (34.5%), 63 (100%). Anal. Calcd
C57H42Cl2N4O8S4: C, 61.67; H, 3.81; Cl, 6.39, N, 5.05; S, 11.55. Found: C, 61.85; H, 3.63;
Cl, 6.20; N, 5.32; S, 11.75.
4.7.1.5. 7,7ꢀ-((Pentane-1,5-diylbis(oxy))bis(4,1-phenylene))bis(2-oxo-3-phenyl-3,5,6,7-
tetrahydro-2H-thiopyrano[2,3-d]thiazole-6-carbonitrile) (16a). Pale yellow crystals (58%);
m.p. 117°C; νmax/cm−1 (KBr) 2218 (CN), 1624 (CO); 1H NMR (DMSO-d6) δ = 1.80–1.84 (m,
2H, CH2), 1.89–1.92 (m, 4H, 2CH2), 4.01–4.05 (m, 4H, 2CH2), 4.08–4.11 (m, 4H, H-5, H-5ꢀ),
4.41–4.54 (m, 2H, H-6, H-6ꢀ), 4.92 (d, 2H, J = 8.7 Hz, H-7, H-7ꢀ), 6.73–7.62 (m, 18H, Ar).
Anal. Calcd C43H36N4O4S4 (801.02): C, 64.47; H, 4.53; N, 6.99; S, 16.01. Found: C, 64.30; H,
4.70; N, 6.73; S, 16.20.
4.7.1.6. Diethyl
7,7ꢀ-((pentane-1,5-diylbis(oxy))bis(4,1-phenylene))bis(2-oxo-3-phen-yl-
3,5,6,7-tetrahydro-2H-thiopyrano[2,3-d]thiazole-6-carboxylate) (16b). Pale yellow crystals
1
(54%); m.p. 127°C; νmax/cm−1 (KBr) 1720, 1630 (CO); H NMR (DMSO-d6) δ = 1.11 (t,
6H, J = 7.2 Hz, 2CH3), 1.59–1.62 (m, 2H, CH2), 1.79–1.81 (m, 4H, 2CH2), 3.11–3.15 (m,
4H, H-5, H-5ꢀ), 3.37–3.41 (m, 4H, CH2), 3.39 (q, 4H, J = 4.8 Hz, 2CH2), 3.97–3.99 (m,
2H, H-6, H-6ꢀ), 4.42 (d, 2H, J = 8.1 Hz, H-7, H-7ꢀ), 6.88–7.55 (m, 18H, Ar). Anal. Calcd.
C47H46N2O8S4 (894.21): C, 63.06; H, 5.18; N, 3.13; S, 14.33. Found: C, 62.78; H, 5.37;
N, 3.40; S, 14.16.
4.8. Preparation of compounds 17 and 14
To compound 13 (0.01 mol), suspended in glacial acetic acid (20 ml), each of 2-thioxo-4-
thiazolidinone or 3-phenyl-4-thioxo-2-thiazolidinone (0.01 mol) was added. The mixture was
refluxed for 30 min and then it was left overnight at room temperature. The precipitate so formed
was filtered off and recrystallized from ethanol and/or dimethylformamide.
5,5ꢀ-(((Pentane-1,5-diylbis(oxy))bis(4,1-phenylene))bis(methanylylidene))-bis(3-phenyl-4-
thioxo-2-thiazolidinone) (14): Red crystals (64%); m.p. 165°C.
4.8.1. 5-(4-((5-(4-((4-Oxo-2-thioxothiazolidin-5-ylidene)methyl)phenoxy)pentyl)-
oxy)benzylid-ene)-3-phenyl-4-thioxo-2-thiazolidinone (17)
1
Red crystals (54%); m.p. 266°C; νmax/cm−1 (KBr) 3223 (NH), 1680, 1645 (CO); H NMR
(DMSO-d6) δ = 1.64–1.69 (m, 2H, CH2), 1.79–1.89 (m, 4H, 2CH2), 3.37–3.46 (m, 4H,
2CH2), 7.07–7.94 (m, 15H, Ar), 8.40 (s, 2H, 2CH), 12.50 (s, 1H, NH). Anal. Calcd
C31H26N2O4S4 (618.80): C, 60.17; H, 4.24; N, 4.53; S, 20.72. Found: C, 60.35; H, 4.42;
N, 4.79; S, 20.54.
5. Computational method
Molecular orbital calculations were carried out using the Gaussian 09W package.[30] Geome-
tries of the studied 4-thiazolidinone derivatives were fully optimized using Becke’s hybrid
Hartree–Fock (HF) density functional method [31,32] with the Lee–Yang–Parr (LYP) correlation
functional [33] and the 6-31G(d) basis set [B3LYP/6-31G(d)]. Vibrational frequency calculations
were performed at the same level of theory to confirm the local minima. Solvation effect was
introduced by the self consistent reaction field method, via the polarizable continuum model [34]
implemented in the Gaussian program.

14 M.A. Badawy et al.
Disclosure statement
No potential conflict of interest was reported by the authors.
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