Convenient one pot synthesis of some novel derivatives of thiazolo[2,3-b]dihydropyrimidinone possessing 4-methylthiophenyl moiety and evaluation of their antibacterial and antifungal activities

Article abstract of DOI:10.1016/j.ejmech.2006.09.003

A series of new 2-(arylidene/5-arylfurfurylidene)-5-(4-methylthiophenyl)-6-carbethoxy-7- methyl-5H-thiazolo[2,3-b]pyrimidin-3(1H)-ones 2 and 3 have been synthesized by a three component (MCR) reaction involving 4-(4-methylthiophenyl)-5-carbethoxy-6-methyl-3,4-dihydropyrimidin-2(1H)- thione 1, monochloroacetic acid and arylaldehydes/arylfurfuraldehydes, respectively. The newly synthesized compounds were well characterized by elemental analysis, IR, ¹H NMR and mass spectral studies. The newly synthesized compounds were screened for their antibacterial and antifungal activities and have exhibited moderate to excellent growth inhibition of bacteria and fungi. The results of such studies have been discussed in this paper.

Full text of DOI:10.1016/j.ejmech.2006.09.003

European Journal of Medicinal Chemistry 42 (2007) 380e385
http://www.elsevier.com/locate/ejmech
Original article
Convenient one pot synthesis of some novel derivatives
of thiazolo[2,3-b]dihydropyrimidinone possessing
4-methylthiophenyl moiety and evaluation of
their antibacterial and antifungal activities
a
b
Mithun Ashok a, , Bantwal Shivarama Holla , Nalilu Suchetha Kumari
*
a Department of Post-Graduate Studies and Research in Chemistry, Mangalore University, Mangalagangothri 574 199, Karnataka, India
b Department of Biochemistry, K.S. Hegde Medical Academy, Nithyananda Nagar, Deralakatte, Mangalore 574 263, Karnataka, India
Received 18 January 2006; received in revised form 24 July 2006; accepted 9 September 2006
Available online 27 October 2006
Abstract
A series of new 2-(arylidene/5-arylfurfurylidene)-5-(4-methylthiophenyl)-6-carbethoxy-7-methyl-5H-thiazolo[2,3-b]pyrimidin-3(1H )-ones 2
and 3 have been synthesized by a three component (MCR) reaction involving 4-(4-methylthiophenyl)-5-carbethoxy-6-methyl-3,4-dihydropyri-
midin-2(1H )-thione 1, monochloroacetic acid and arylaldehydes/arylfurfuraldehydes, respectively. The newly synthesized compounds were well
1
characterized by elemental analysis, IR, H NMR and mass spectral studies. The newly synthesized compounds were screened for their anti-
bacterial and antifungal activities and have exhibited moderate to excellent growth inhibition of bacteria and fungi. The results of such studies
have been discussed in this paper.
Ó 2006 Elsevier Masson SAS. All rights reserved.
Keywords: Thiazolo[2,3-b]dihydropyrimidinones; 4-Methylthiophenyl; Antibacterial; Antifungal
1. Introduction
constitute a superior tool for diversity-oriented and complex-
ity-generating organic synthesis for drug discovery [4].
Multi-component reactions (MCRs) are theoretically useful
organic reactions involving three or more starting materials
which react to give a product [1]. They are one of the most im-
portant protocols in organic synthesis and medicinal chemistry
[2]. They constitute a major part in the present day organic
synthesis with advantages ranging from lower reaction times,
increased reaction rates to higher yields and reproducibility.
The diversity, efficiency and rapid access to small and highly
functionalized organic molecules make this approach of cen-
tral current interest in the construction of combinatorial librar-
ies and optimization in drug discovery process [3]. They
The 3,4-dihydropyrimidin-2(1H )-ones have recently
emerged as important target molecules due to their therapeutic
and pharmacological properties [5] such as antiviral [6], anti-
mitotic [7], anticarcinogenic [8], antihypertensive [9] and note-
worthy, as calcium channel modulators [10]. Additionally, their
particular structure has been found in natural marine alkaloid
batzelladine A and B which are the first low molecular weight
natural products reported in the literature to inhibit the binding
of HIV gp-120 to CD4 cells, so disclosing a new field to-
wards the development of AIDS therapy [11]. Thiazoles and
their derivatives are also found to be associated with various
biological activities such as antibacterial, antifungal and anti-
inflammatory [12e15]. Prompted by the chemotherapeutic
importance of pyrimidine derivatives and in a view to synthe-
size bioactive molecules [16], it was contemplated to synthe-
size a series of novel fused pyrimidine derivatives possessing
* Corresponding author.
E-mail address: mithun4l@rediffmail.com (M. Ashok).
0223-5234/$ - see front matter Ó 2006 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2006.09.003

M. Ashok et al. / European Journal of Medicinal Chemistry 42 (2007) 380e385
381
4-methylthiophenyl moiety and study their biological proper-
ties. Results of such studies are discussed in this paper.
a one pot multi-component reaction involving 1, monochloro-
acetic acid and the corresponding arylaldehyde/arylfurfuralde-
hyde in presence of anhydrous sodium acetate in acetic acide
acetic anhydride medium (Scheme 1). The structures of some
of the newly synthesized compounds have been established on
the basis of elemental analysis, IR, 1H NMR and mass spectral
studies. The results of such studies have been discussed in this
paper (Table 1).
2. Chemistry
4-(4-Methylthiophenyl)-5-carbethoxy-6-methyl-3,4-dihy-
dropyrimidin-2(1H )-thione 1 was synthesized in a one pot Bi-
ginelli reaction involving 4-methylthiobenzaldehyde, ethyl
acetoacetate and thiourea in presence of SnCl2$2H2O catalyst
according to the procedure reported in the literature [17]. The
characterization data of the above synthesized compound have
been given in Section 6. This compound was used further in
order to synthesize a series of novel N-bridged heterocycles.
The title compounds i.e. 2-(arylidene/5-arylfurfurylidene)-
5-(4-methylthiophenyl)-6-carbethoxy-7-methyl-5H-thiazolo
[2,3-b]-pyrimidin-3-ones 2 and 3 have been synthesized in
3. Biological activity
3.1. Antibacterial studies
The newly synthesized compounds were screened for their
antibacterial activity against four bacterial strains namely
Escherichia coli (ATCC-25922), Staphylococcus aureus
SCH3
SCH3
SnCl2.2H2O
EtO2C
H3C
CHO
EtO2C
H3C
NH2
NH
Abs. Alcohol, Reflux
6 h
+
N
H
S
H2N
S
O
1
SCH3
EtO2C
H3C
NH
N
H
S
1
ClCH2CO2H/ NaOAc
AcOH/ Ac2O
R'
CHO
CHO
O
R
SCH3
SCH3
O
O
EtO2C
H3C
EtO2C
H3C
N
N
S
S
O
N
N
R'
R
2
3
R = 4-SCH3, 4-OCH3, 4-Cl, 4-F, 4-OH, 2,4-Cl2, 4-OH-3-OCH3, 4-F-3-OPh, 3,4-OCH2O
R' = 4-NO2, 4-Cl, 4-Br, 2,4-Cl2
Scheme 1.

382
M. Ashok et al. / European Journal of Medicinal Chemistry 42 (2007) 380e385
Table 1
Characterization data of compounds 2aei and 3aed
Compound
R/R0
Molecular formula
M.P. (ꢀC)
Yield (%)
Elemental analysis found (calculated)
C
H
N
2a
2b
2c
2d
2e
2f
4-SCH3
4-OCH3
4-Cl
C25H24N2O3S3
C25H24N2O4S2
C24H21ClN2O3S2
C24H21FN2O3S2
150e152
180e182
176e178
168e170
170e172
216e218
142e144
70e72
76
78
83
84
74
85
80
84
76
83
85
83
86
60.41 (60.46)
62.42 (62.48)
59.46 (59.43)
61.50 (60.52)
61.71 (61.78)
55.48 (55.49)
60.46 (60.47)
64.29 (64.27)
60.71 (60.71)
59.81 (59.88)
61.00 (61.03)
56.40 (56.47)
57.45 (57.44)
4.89 (4.87)
4.99 (5.03)
4.35 (4.36)
4.53 (4.52)
4.78 (4.75)
3.82 (3.88)
4.88 (4.87)
4.44 (4.49)
4.43 (4.48)
4.10 (4.13)
4.13 (4.21)
3.89 (3.89)
3.75 (3.79)
5.64 (5.64)
5.82 (5.83)
5.79 (5.78)
5.93 (5.98)
5.95 (6.00)
5.39 (5.39)
5.64 (5.64)
4.96 (5.00)
5.60 (5.66)
7.48 (7.48)
5.09 (5.08)
4.62 (4.70)
4.78 (4.78)
4-F
4-OH
C24H22N2O4S2
C24H20Cl2N2O3S2
C25H24N2O5S2
2,4-Cl2
4-OH-3-OCH3
4-F-3-OPh
3,4-OCH2O
4-NO2
2g
2h
2i
C30H25FN2O4S2
C25H22N2O5S2
C28H23N3O6S2
194e196
236e238
208e210
206e208
244e246
3a
3b
3c
3d
4-Cl
4-Br
C28H23ClN2O4S2
C28H23BrN2O4S2
C28H22Cl2N2O4S2
2,4-Cl2
(ATCC-25923), Pseudomonas aeruginosa (ATCC-27853) and
Klebsiella pneumoniae (Recultured) by disc diffusion method
[18,19]. The discs measuring 6.25 mm in diameter were
punched from Whatman No. 1 filter paper. Batches of 100
discs were dispensed in each screw capped bottles and steril-
ized by dry heat at 140 ꢀC for an hour. The test compounds
were prepared in different concentrations using dimethylfor-
mamide. Exactly 1 ml containing 100 times the amount of
chemical in each disc was added to each bottle, containing
100 discs. The discs of each concentration were placed in
nutrient agar medium inoculated with fresh bacterial strains
separately. The plates were incubated at 37 ꢀC for 24 h.
Ciprofloxacin was used as a standard drug. It has 16e
22 mm inhibition length for E. coli and 27e35 mm inhibition
length for S. aureus at a concentration of 10 mg/ml. Solvent
and growth controls were kept separately and the zone of in-
hibition and minimum inhibitory concentrations (MIC) were
measured. The antibacterial activity data are given in Table 2.
Aspergillus flavus (NCIM No. 524), Aspergillus fumigatus
(NCIM No. 902), Candida albicans (NCIM No. 3100), and
Penicillium marneffei (Recultured) by serial dilution method
[20,21]. Sabourauds agar (prepared by dissolving peptone
(1 g), D-glucose (4 g), and agar (2 g) in distilled water
(100 ml) and adjusting the pH to 5.7) was used as the medium
for fungal growth. Normal saline was used to make the spore
suspension of the fungal strains (i.e. a loopful of particular
fungal strain was transferred to 3 ml of saline in order to ob-
tain a suspension of the corresponding species). Twenty milli-
liters of the prepared Sabourauds agar media was poured into
each of the petri dishes. Excess of media was decanted and the
plates were dried by placing in an incubator for 1 h. Wells
were made on these seeded agar plates using an agar punch
and labeled. A 10 mg/ml solution of the test compounds in
DMSO was then added into each of these labeled wells. A
control was also prepared in the same way using DMSO.
The petri dishes were then incubated at 37 ꢀC for 3e4 days.
The zone of inhibition and minimum inhibitory concentrations
(MIC) were determined in comparison with the standard drug
Ciclopiroxolamine. The antifungal activity data are given in
Table 3.
3.2. Antifungal studies
The newly synthesized compounds were also screened for
their antifungal activity against four fungal strains namely
Table 2
Antibacterial activity data of the compounds 2aei and 3aed
Table 3
Antifungal activity data of the compounds 2aei and 3aed
Compound
S. aureus
P. aeruginosa
K. pneumoniae
E. coli
Compound
A. fumigatus
A. flavus
C. albicans
P. marneffei
2a
2b
10 (25)
12 (25)
13 (12.5)
24 (6)
12 (12.5)
21 (6)
12 (25)
10 (25)
10 (25)
17 (12.5)
12 (25)
11 (25)
18 (12.5)
10 (25)
10 (25)
12 (25)
10 (25)
18 (12.5)
11 (25)
18 (12.5)
2a
2b
12 (12.5)
21 (6)
10 (25)
17 (12.5)
12 (25)
10 (12.5)
20 (6)
12 (12.5)
12 (12.5)
10 (12.5)
20 (6)
2c
2d
10 (25)
18 (12.5)
12 (25)
12 (12.5)
10 (12.5)
15 (12.5)
13 (12.5)
23 (6)
10 (12.5)
20 (6)
2c
2d
11 (12.5)
20 (6)
11 (12.5)
19 (6)
18 (12.5)
10 (25)
10 (25)
2e
12 (12.5)
10 (12.5)
18 (12.5)
12 (12.5)
10 (12.5)
11 (12.5)
12 (12.5)
20 (6)
2e
10 (12.5)
11 (12.5)
21 (6)
10 (12.5)
12 (12.5)
10 (12.5)
20 (6)
12 (12.5)
10 (12.5)
19 (6)
2f
2g
18 (12.5)
20 (12.5)
19 (12.5)
10 (25)
2f
2g
11 (25)
2h
12 (12.5)
10 (12.5)
13 (12.5)
10 (12.5)
23 (6)
2h
12 (12.5)
12 (12.5)
17 (12.5)
10 (12.5)
12 (12.5)
10 (12.5)
22 (6)
18 (12.5)
12 (25)
12 (25)
19 (6)
2i
3a
2i
3a
11 (12.5)
12 (12.5)
19 (6)
10 (12.5)
11 (12.5)
11 (12.5)
20 (6)
10 (25)
12 (25)
3b
3c
3b
3c
17 (12.5)
18 (12.5)
18 (12.5)
18 (12.5)
18 (12.5)
19 (12.5)
19 (12.5)
19 (6)
20 (6)
20 (6)
3d
Standard
23 (6)
25 (6)
20 (6)
20 (6)
3d
Standard
18 (6)
20 (6)
Values in bracket are MIC values.
Values in bracket are MIC values.

M. Ashok et al. / European Journal of Medicinal Chemistry 42 (2007) 380e385
383
1
4. Results and discussion
1274 (C]S), 1178 (CeO); H NMR (CDCl3) d: 1.22 (t, 3H,
J ¼ 7.12 Hz, estereCH3), 4.12 (q, 2H, J ¼ 7.12 Hz, estere
CH2), 2.45 (s, 3H, CH3), 2.53 (s, 3H, SCH3), 5.42 (s, 1H,
CH), 7.18 (d, 2H, J ¼ 8.32 Hz, 4-methylthiophenyl), 7.34 (d,
2H, J ¼ 8.32 Hz, 4-methylthiophenyl), 7.65 (s, 1H, NH),
8.25 (s, 1H, NH); MS (m/z, %): 323 (Mþ þ 1, 100), 322
(Mþ, 18), 199 (31), 177 (20), 154 (36), 137 (22), 136 (37),
77 (19).
The antibacterial and antifungal screening revealed that all
the tested compounds 2aei and 3aed showed moderate to
good inhibition at 10 mg/ml concentration. The antibacterial
screening indicated that among the tested compounds, the
compound 2g showed excellent activity against three bacterial
strains namely S. aureus, P. aeruginosa and E. coli. It also
showed moderate activity against K. pneumoniae. The com-
pound 3c showed good activity against P. aeruginosa, K.
pneumoniae and E. coli whereas compound 3d showed good
activity against S. aureus, P. aeruginosa and K. pneumoniae.
The antifungal screening revealed that compound 2d
showed excellent activity against all the four fungal strains
namely A. fumigatus, A. flavus, C. albicans and P. marneffei.
The compound 2b also showed good activity against A. fumi-
gatus, A. flavus and C. albicans. In addition to this the com-
pounds 2h, 3c and 3d showed very good activity against A.
flavus, C. albicans and P. marneffei, respectively.
6.2. General procedure for the synthesis of 2-(arylidene)-
5-(4-methylthiophenyl)-6-carbethoxy-7-methyl-5H-
thiazolo[2,3-b]pyrimidin-3-ones (2aei)
A mixture of thione (1) (10 mmol), monochloroacetic acid
(15 mmol), anhydrous sodium acetate (2 g), glacial acetic acid
(20 ml), acetic anhydride (15 ml) and arylaldehyde (10 mmol)
were heated to reflux for 3 h. The reaction mixture was cooled
to room temperature and poured into crushed ice with vigorous
stirring. The precipitated solid was filtered under suction,
washed with cold water and recrystallized from glacial acetic
acid. The characterization data of these compounds are given
in Table 1.
5. Conclusions
This article reports a convenient one pot multi-component
synthesis of some thiazolo[2,3-b]pyrimidinones in good yield
along with their antimicrobial activities. The antimicrobial
screening suggests that all the newly synthesized compounds
showed moderate to good activity against the tested organ-
isms. Among the newly synthesized compounds, the one car-
rying 4-bromophenylfuranyl moiety showed the most
promising antibacterial and antifungal activity.
Compound 2a: IR (KBr) n/cmꢁ1: 2976 (CeH), 1710
1
(C]O), 1606 (C]N), 1541 (C]C), 1159 (CeO); H NMR
(CDCl3) d: 1.22 (t, 3H, J ¼ 7.12 Hz, estereCH3), 4.14 (q,
2H, J ¼ 7.12 Hz, estereCH2), 2.44 (s, 3H, CH3), 2.51 (s,
3H, SCH3), 2.52 (s, 3H, SCH3), 6.18 (s, 1H, CH), 7.17 (d,
2H, J ¼ 8.36 Hz, 4-methylthiophenyl), 7.33 (d, 2H,
J ¼ 8.36 Hz, 4-methylthiophenyl), 7.23 (d, 2H, J ¼ 8.36 Hz,
4-methylthiophenyl), 7.38 (d, 2H, J ¼ 8.36 Hz, 4-methylthio-
phenyl), 7.71 (s, 1H, exocyclic CH); MS (m/z, %): 497
(Mþ þ 1, 100), 496 (Mþ, 90), 451 (30), 373 (75), 362 (10),
317 (5), 307 (10), 289 (10), 239 (2), 232 (2), 201 (5), 180
(10), 175 (10), 154 (55), 136 (40), 120 (5), 105 (5).
6. Experimental protocols
Melting points were determined by open capillary method
and are uncorrected. The IR spectra (in KBr pellets) were re-
corded on a Shimadzu FT-IR 157 spectrophotometer. 1H NMR
spectra were recorded on a Bruker AMX-400 (400 MHz) spec-
trophotometer using TMS as an internal standard. The mass
spectra were recorded on a Jeol JMS-D 300 mass spectrometer
operating at 70 eV. The purity of the compounds was checked
by thin layer chromatography (TLC) on silica gel plate using
n-hexane and ethyl acetate (4:1, v/v).
Compound 2b: IR (KBr) n/cmꢁ1: 2973 (CeH), 1710
1
(C]O), 1610 (C]N), 1549 (C]C), 1165 (CeO); H NMR
(CDCl3) d: 1.22 (t, 3H, J ¼ 7.12 Hz, estereCH3), 4.14 (q,
2H, J ¼ 7.12 Hz, estereCH2), 2.44 (s, 3H, CH3), 2.51 (s,
3H, SCH3), 3.89 (s, 3H, OCH3), 6.18 (s, 1H, CH), 7.01 (d,
2H, J ¼ 8.64 Hz, 4-methoxyphenyl), 7.17 (d, 2H,
J ¼ 8.36 Hz, 4-methylthiophenyl), 7.33 (d, 2H, J ¼ 8.36 Hz,
4-methylthiophenyl), 7.43 (d, 2H, J ¼ 8.64 Hz, 4-methoxy-
phenyl), 7.71 (s, 1H, exocyclic CH); MS (m/z, %): 481
(Mþ þ 1, 100), 480 (Mþ, 50), 435 (10), 407 (10), 357 (75),
329 (2), 307 (20), 289 (15), 273 (2), 201 (2), 175 (5), 164
(10), 154 (55), 136 (40), 120 (5), 107 (10).
6.1. General procedure for the synthesis of 4-(4-
methylthiophenyl)-5-carbethoxy-6-methyl-3,4-
dihydropyrimidin-2(1H )-thione (1)
Compound 2c: IR (KBr) n/cmꢁ1: 2969 (CeH), 1710
(C]O), 1608 (C]N), 1548 (C]C), 1155 (CeO), 823 (Ce
A mixture of 4-methylthiobenzaldehyde (3.0 mmol), ethyl
acetoacetate
1
(3.0 mmol),
thiourea
(3.6 mmol)
and
Cl); H NMR (CDCl3) d: 1.22 (t, 3H, J ¼ 7.12 Hz, estere
SnCl2$2H2O (0.6 mmol) in ethanol medium were heated to
reflux for 6 h. The resulting solution was cooled to room tem-
perature and poured into crushed ice with vigorous stirring.
The resulting solid was filtered under suction, washed with
cold ethanol and recrystallized from hot ethanol. This com-
pound was obtained as lemon yellow shining micro-crystals.
Yield: 91%, m.p. 150e152 ꢀC, IR (KBr) n/cmꢁ1: 3311 (Ne
H), 3185 (NeH), 2985 (CeH), 1706 (C]O), 1571 (C]C),
CH3), 4.14 (q, 2H, J ¼ 7.12 Hz, estereCH2), 2.44 (s, 3H,
CH3), 2.51 (s, 3H, SCH3), 6.18 (s, 1H, CH), 7.17 (d, 2H,
J ¼ 8.36 Hz, 4-methylthiophenyl), 7.33 (d, 2H, J ¼ 8.36 Hz,
4-methylthiophenyl), 7.41 (d, 2H, J ¼ 8.72 Hz, 4-chloro-
phenyl), 7.47 (d, 2H, J ¼ 8.72 Hz, 4-chlorophenyl), 7.71 (s,
1H, exocyclic CH); MS (m/z, %): 485 (Mþ þ 1, 70), 484
(Mþ, 25), 415 (30), 373 (40), 345 (5), 317 (5), 201 (10),
180 (15), 115 (5).

384
M. Ashok et al. / European Journal of Medicinal Chemistry 42 (2007) 380e385
Compound 2e: IR (KBr) n/cmꢁ1: 3396 (OeH), 2976 (Ce
J ¼ 3.72 Hz, furaneH), 6.98 (d, 1H, J ¼ 3.72 Hz, furaneH),
7.17 (d, 2H, J ¼ 8.36 Hz, 4-methylthiophenyl), 7.33 (d, 2H,
J ¼ 8.36 Hz, 4-methylthiophenyl), 7.49 (s, 1H, exocyclic
CH), 7.51 (d, 2H, J ¼ 8.68 Hz, 4-chlorophenyl), 7.66 (d, 2H,
J ¼ 8.68 Hz, 4-chlorophenyl); MS (m/z, %): 551 (Mþ þ 1,
100), 550 (Mþ, 55), 505 (12), 477 (15), 429 (30), 427 (80),
397 (10), 234 (20), 154 (15), 136 (10), 107 (5).
H), 1710 (C]O), 1608 (C]N), 1546 (C]C), 1158 (CeO);
1H NMR (CDCl3) d: 1.21 (t, 3H, J ¼ 7.12 Hz, estereCH3),
4.12 (q, 2H, J ¼ 7.12 Hz, estereCH2), 2.44 (s, 3H, CH3),
2.51 (s, 3H, SCH3), 6.15 (s, 1H, CH), 7.16 (d, 2H,
J ¼ 8.36 Hz, 4-methylthiophenyl), 7.20 (d, 2H, J ¼ 8.64 Hz,
4-hydroxyphenyl), 7.26 (s, 1H, OH), 7.31 (d, 2H,
J ¼ 8.36 Hz, 4-methylthiophenyl), 7.49 (d, 2H, J ¼ 8.64 Hz,
4-hydroxyphenyl), 7.71 (s, 1H, exocyclic CH); MS (m/z, %):
467 (Mþ þ 1, 100), 466 (Mþ, 30), 451 (5), 415 (30), 373
(40), 345 (5), 317 (5), 302 (2), 277 (2), 247 (2), 201 (10),
180 (15), 175 (15), 128 (2), 115 (5), 89 (2).
Compound 3c: IR (KBr) n/cmꢁ1: 2974 (CeH), 1710
(C]O), 1610 (C]N), 1549 (C]C), 1162 (CeO), 754 (Ce
1
Br); H NMR (CDCl3) d: 1.21 (t, 3H, J ¼ 7.12 Hz, estere
CH3), 4.12 (q, 2H, J ¼ 7.12 Hz, estereCH2), 2.44 (s, 3H,
CH3), 2.54 (s, 3H, SCH3), 6.16 (s, 1H, CH), 6.83 (d, 1H,
J ¼ 3.68 Hz, furaneH), 6.85 (d, 1H, J ¼ 3.68 Hz, furaneH),
7.17 (d, 2H, J ¼ 8.36 Hz, 4-methylthiophenyl), 7.33 (d, 2H,
J ¼ 8.36 Hz, 4-methylthiophenyl), 7.48 (s, 1H, exocyclic
CH), 7.57 (d, 2H, J ¼ 8.72 Hz, 4-bromophenyl), 7.62 (d, 2H,
J ¼ 8.72 Hz, 4-bromophenyl); MS (m/z, %): 597 (Mþ þ 2,
100), 595 (Mþ, 90), 549 (10), 523 (20), 521 (15), 473 (50),
471 (40), 460 (10), 307 (80), 289 (40), 278 (10), 165 (5),
154 (75), 137 (40), 136 (50), 120 (10), 107 (15), 89 (15), 77
(10).
Compound 2i: IR (KBr) n/cmꢁ1: 2980 (CeH), 1710
1
(C]O), 1610 (C]N), 1542 (C]C), 1160 (CeO); H NMR
(CDCl3) d: 1.21 (t, 3H, J ¼ 7.12 Hz, estereCH3), 4.12 (q,
2H, J ¼ 7.12 Hz, estereCH2), 2.44 (s, 3H, CH3), 2.51 (s,
3H, SCH3), 6.05 (s, 2H, OCH2O), 6.15 (s, 1H, CH), 6.88 (d,
1H, Jo ¼ 8.12 Hz, 3,4-methylenedioxyphenyl), 6.94 (d, 1H,
Jm ¼ 1.64 Hz, 3,4-methylenedioxyphenyl), 7.01 (dd, 1H,
Jo ¼ 8.12 Hz, Jm ¼ 1.64 Hz, 3,4-methylenedioxyphenyl), 7.16
(d, 2H, J ¼ 8.36 Hz, 4-methylthiophenyl), 7.31 (d, 2H,
J ¼ 8.36 Hz, 4-methylthiophenyl), 7.64 (s, 1H, exocyclic
CH); MS (m/z, %): 495 (Mþ þ 1, 100), 494 (Mþ, 15), 465
(10), 449 (15), 421 (10), 405 (5), 371 (60), 343 (5), 315
(15), 275 (5), 215 (5), 201 (10), 178 (18), 175 (16), 136 (5),
115 (5), 89 (5).
Acknowledgements
The authors are thankful to the Head, CDRI, Lucknow and
the Head, SAIF, IISc, Bangalore for providing the mass and 1H
NMR spectral data.
6.3. General procedure for the synthesis of 2-(5-
arylfurfurylidene)-5-(4-methylthiophenyl)-6-carbethoxy-
7-methyl-5H-thiazolo[2,3-b]pyrimidin-3-ones (3aed)
References
A mixture of thione (1) (10 mmol), monochloroacetic acid
(15 mmol), anhydrous sodium acetate (2 g), glacial acetic acid
(20 ml), acetic anhydride (15 ml) and 5-aryl-furan-2-carboxal-
dehyde (10 mmol) were heated to reflux for 3 h. The reaction
mixture was cooled to room temperature and poured into
crushed ice with vigorous stirring. The precipitated solid
was filtered under suction, washed with cold water and recrys-
tallized from glacial acetic acid. The characterization data of
these compounds are given in Table 1.
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1371 (symm. NO2), 1160 (CeO); H NMR (CDCl3) d: 1.21
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