Simple synthesis of 5-amino-8-nitro-7-aryl-3,7-dihydro-2H-thiazolo[3,2-a]pyridine-6-carboxamide derivatives

Article abstract of DOI:10.1080/17415993.2018.1494175

An easy, efficient, and environmentally benign synthesis of new class of thiazolopyridine carboxamide derivatives is reported via one-pot, multi-component reaction of 2-(nitromethylene)thiazolidine derived from the addition of cysteamine hydrochloride to nitro ketene dithioacetal with aromatic aldehydes and cyanoacetamide using catalytic amount of triethylamine (Et₃N) in ethanol/water at reflux in good to excellent yields.

Full text of DOI:10.1080/17415993.2018.1494175

Journal of Sulfur Chemistry
ISSN: 1741-5993 (Print) 1741-6000 (Online) Journal homepage: http://www.tandfonline.com/loi/gsrp20
Simple synthesis of 5-amino-8-nitro-7-aryl-3,7-
dihydro-2H-thiazolo[3,2-a]pyridine-6-carboxamide
derivatives
Fahimeh Sadat Hosseini, Shima Nasri & Mohammad Bayat
To cite this article: Fahimeh Sadat Hosseini, Shima Nasri & Mohammad Bayat (2018): Simple
synthesis of 5-amino-8-nitro-7-aryl-3,7-dihydro-2H-thiazolo[3,2-a]pyridine-6-carboxamide
derivatives, Journal of Sulfur Chemistry, DOI: 10.1080/17415993.2018.1494175
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JOURNAL OF SULFUR CHEMISTRY
https://doi.org/10.1080/17415993.2018.1494175
Simple synthesis of 5-amino-8-nitro-7-aryl-3,7-
dihydro-2H-thiazolo[3,2-a]pyridine-6-carboxamide
derivatives
Fahimeh Sadat Hosseini, Shima Nasri and Mohammad Bayat
Department of Chemistry, Faculty of Science, Imam Khomeini International University, Qazvin, Iran
ABSTRACT
ARTICLE HISTORY
Received 7 January 2018
Accepted 24 June 2018
An easy, efficient, and environmentally benign synthesis of new class
of thiazolopyridine carboxamide derivatives is reported via one-pot,
multi-component reaction of 2-(nitromethylene)thiazolidine derived
from the addition of cysteamine hydrochloride to nitro ketene
dithioacetal with aromatic aldehydes and cyanoacetamide using cat-
alytic amount of triethylamine (Et3N) in ethanol/water at reflux in
good to excellent yields.
KEYWORDS
Thiazolopyridine
carboxamide;
multi-component reaction;
2-(nitromethylene)
thiazolidine; cysteamine
hydrochloride; nitro ketene
dithioacetal; aromatic
aldehydes; cyanoacetamide
1. Introduction
Heterocycles are essential building blocks that are frequently used in the pharmaceutical
[1,2]. Biologically active molecules containing various heteroatoms such as nitrogen and
sulfur, always drawn the attention of chemists and pharmacologists over the years mainly
because of their broad range of bioactivities [3,4]. The presence of heteroatoms results in
significant changes in the cyclic molecular structure due to the availability of unshared
pairs of electrons and the difference in electronegativity between heteroatoms and carbon
[5,6]. Therefore, organo S- and N-heterocycles have been under investigation for a long
time on account of their synthetic diversity and therapeutic relevance [7].
Among these heterocycles, derivatives of thiazolopyridines have been reported to fur-
nish various biological activities such as anticancer [8], anti-inflammatory, antifungal [9],
antimicrobial and antihypertensive [10,11].
Ketene dithioacetals are versatile intermediates in organic synthesis [12] and the enam-
ines derived from nitro ketene dithioacetal are widely used for the synthesis of a variety of
CONTACT Mohammad Bayat
m.bayat@sci.ikiu.ac.ir, bayat_mo@yahoo.com
© 2018 Informa UK Limited, trading as Taylor & Francis Group

2
F. S. HOSSEINI ET AL.
Scheme 1. Synthetic scheme for the products 5a-l.
S- and N-heterocyclic compounds in the past several years [13–24]. In continuation of our
research interests regarding the development of the synthetic utility of ketene dithioacetals
and cyclic N,S-ketene acetals on the basis of our previous endeavors in exploring novel and
practical MCRs to synthesize useful heterocyclic compounds, herein we report a simple
and efficient synthesis of a new class of thiazolopyridine carboxamide derivatives via a one-
pot, multi-component reaction of 2-(nitromethylene)thiazolidine as a cyclic N,S-ketene
acetal (derived from the addition of cysteamine hydrochloride to nitro ketene dithioac-
etal), aromatic aldehydes and cyanoacetamide in the presence of Et3N in EtOH/H2O as a
green medium at reflux.
2. Results and discussion
In this work, we would like to report the results of our studies involving the reaction of cys-
teamine hydrochloride 1 and nitro ketene dithioacetal 2 proceeds in one-pot under mild
conditions, in EtOH/H2O (1:1) at reflux to produce the 2-(nitromethylene)thiazolidine
6 in excellent yields. Next, the sequential one-pot addition of aromatic aldehydes 3,
cyanoacetamide 4, and catalytic amounts of Et3N, successfully gave the 5-amino-8-nitro-
7-aryl-3,7-dihydro-2H-thiazolo[3,2-a]pyridine-6-carboxamide derivatives 5 in good to
excellent yields (Scheme 1).
This reaction was very clean and free from side reactions in the presence of catalytic
amount of Et3N in EtOH/H2O as a green medium at reflux. In the absence of a catalyst, the
reaction did not yield any product even after long reaction times. We explored the scope of
this reaction by varying the structure of the aromatic aldehydes. The reaction proceeds
under the same reaction conditions to afford a series of thiazolopyridine carboxamide
derivatives 5 in 74–93% yields. The results are shown in Table 1.
The structures of compounds 5a-l (Table 1) were confirmed by IR, 1H NMR, 13C NMR
and mass spectra. The IR spectrum of 5a exhibit absorption bands due to two NH2 groups
(3460, 3396, 3340 and 3220 cm−1) and absorption bands due to two C O groups (1770
=
and 1646 cm−1) and as well as 1572, 1219, 1490 and 1325 cm−1 due to the Ar, C–N and
NO2 groups.
1H NMR spectrum (DMSO-d6) of 5a revealed two singlets for the NH2 (amine) and
NH2 (amide) groups (δ 6.61, 7.90 ppm, respectively), one singlet for the methine proton
(δ 5.28 ppm), one singlet for OCH3 group (3.79 ppm), characteristic multiplets for CH2S
and CH2N groups (.3.34–3.39, 4.15–4.36 ppm, respectively) and two doublets (δ 7.46,

JOURNAL OF SULFUR CHEMISTRY
3
Table 1. Products 5a-l.
Entry
1
ArCHO
Product
Time (h)
1.5
Yield (%)
93
2
1.5
78
3
1.5
87
4
2.5
80
5
1
87
(continued).

4
F. S. HOSSEINI ET AL.
Table 1. Continued.
Entry
6
ArCHO
Product
Time (h)
1
Yield (%)
90
7
3
83
8
5
80
9
2
85
10
3
82

JOURNAL OF SULFUR CHEMISTRY
5
Table 1. Continued.
Entry
11
ArCHO
Product
Time (h)
5
Yield (%)
74
12
2.5
77
Note: Cysteamine hydrochloride (1 mmol), nitro ketene dithioacetal (1 mmol), aromatic aldehyde (1 mmol) and cyanoac-
etamide (1 mmol) were used.
1
Scheme 2. H and 13C NMR chemical shift of 5a.
7.81 ppm) for the aromatic region which completely in accord with the assigned structure.
The 1H-decoupled 13C NMR spectrum (DMSO-d6) of 5a showed 14 distinct resonances
which was consistent with proposed structure (Scheme 2). The characteristic signal due to
the methane carbon was discernible (at δ 28.2 ppm). There are two signals for CH2S and
CH2N groups (at δ = 39.1 and 51.1 ppm, respectively) and two signals at δ 82.9, 157.7 ppm

6
F. S. HOSSEINI ET AL.
Scheme 3. Plausible mechanism for the formation of product 5.
for two olefinic carbons (NH2CO-C9C-NH2). The 1H and 13C NMR spectra of 5b-l are
similar to that of 5a, except for the signals of aryl moieties.
The EI-MS of 5a displayed the molecular ion peak at m/z 376.5, which was in agreement
with the proposed structure.
The acceptable mechanism for this reaction is designated in Scheme 3. It is possible that
initially the formation of 2-(nitromethylene)thiazolidine 6 occurs through addition of cys-
teamine hydrochloride 1 to nitro ketene dithioacetal 2, while Knoevenagel condensation
between the aromatic aldehyde 3 and cyanoacetamide 4 would give intermediate 7. The 2-
(nitromethylene)thiazolidine 6 then adds to the Knoevenagel adduct 7 to give intermediate
8, which undergoes successive imine–enamine tautomerization, followed by N-cyclization
via attack of the secondary amino group to the cyano group, leading to the formation of 5.
3. Conclusion
In summary, we have developed a convenient, efficient, one-pot and multi-component
synthesis of thiazolopyridine carboxamide frameworks by the reaction of cysteamine
hydrochloride, nitro ketene dithioacetal, aromatic aldehydes and cyanoacetamide in the
presence of Et3N in EtOH/H2O at reflux. This strategy includes some advantages, such
as green methodoloy, simple experimental procedures, easy accessibility of reactants, high
atom economy, compatibility with various functional groups and good to excellent product
yields.
4. Experimental
4.1. General
All research chemicals (cysteamine hydrochloride, nitro ketene dithioacetal, aromatic alde-
hydes, cyanoacetamide and triethylamine) and solvents were purchased from Merck and

JOURNAL OF SULFUR CHEMISTRY
7
Aldrich and were used without further purification. The melting points were taken in an
open capillary tube using an electrotherma1 9100 apparatus. NMR spectra were recorded
with a Bruker DRX-300 Avance instrument (300 MHz for 1H and 75.4 MHz for 13C) with
DMSO as solvent. Chemical shifts are expressed in parts per million (ppm), and coupling
constant (J) are reported in hertz (Hz). IR spectra were recorded on a Bruker Tensor 27
spectrometer. Mass spectra were recorded with an Agilent 5975C VL MSD with Triple-
Axis Detector operating at an ionization potential of 70 eV. Elemental analyses for C, H
and N were performed using a PerkinElmer 2004 series [II] CHN elemental analyzer.
4.2. General procedure for the synthesis of product 5
The stoichiometric mixtures of cysteamine hydrochloride (0.113 g, 1 mmol), nitro ketene
dithioacetal (0.165 g, 1 mmol) and Et3N (140 μL, 1 mmol) in 10 mL of H2O/EtOH (1:1), in
50 mL flask, was stirred under reflux for 5 h. Next, aromatic aldehyde (1 mmol), cyanoac-
etamide (0.084 g, 1 mmol) and one drop Et3N as a catalyst were added at once, respectively,
and the solution was heated at reflux for the time given in Table 1. Upon completion
as monitored by TLC, the reaction mixture was cooled to room temperature and result-
ing solid product was filtered, washed with a small amount of H2O/EtOH (1:1) to give
product 5.
4.2.1. Methyl 4-(5-amino-6-carbamoyl-3,7-dihydro-8-nitro-2H-thiazolo[3,2-
a]pyridin-7-yl)benzoate (5a)
Red solid; yield: 0.350 g (93%); m.p. 253–255°C. 1H NMR (300 MHz, DMSO): δ 3.34–3.39
(m, 2H, CH2S), 3.79 (s, 3H, OCH3), 4.15–4.36 (m, 2H, CH2N), 5.28 (s, 1H, CH), 6.61
(s, 2H, NH2), 7.46 (d, 3JHH = 8.1 Hz, 2H, Ar), 7.81 (d, 3JHH = 8.1 Hz, 2H, Ar), 7.90 (s,
2H, NH2). 13C NMR (75.4 MHz, DMSO): δ 28.2 (CH), 39.1 (CH2S), 51.1 (CH2N), 52.4
=
=
(OCH3), 82.9, 123.3, 128.3, 128.5, 129.3, 149.2, 150.5, 157.7, 166.5 (C O), 171.1 (C O).
IR (KBr) (νmax/cm−1): 3460, 3396, 3340 and 3220 (NH2), 1717 (C O), 1646 (C O), 1572
(Ar), 1490 and 1325 (NO2), 1219 (C–N). MS (EI, 70 eV): m/z (%) = 376.5 (M+, 1.1), 316
(100), 285 (69), 229 (32), 199 (59), 171 (31), 129 (32), 101 (25), 60 (76). Anal. Calc. for
C16H16N4O5S (376.39): C, 51.06; H, 4.28; N, 14.89. Found: C, 51.5; H, 4.7; N, 14.6.
=
=
4.2.2. 5-Amino-7-(3-fluorophenyl)-3,7-dihydro-8-nitro-2H-thiazolo[3,2-a]pyridine-6-
carboxamide (5b)
1
Orange solid; yield: 0.262 g (78%); m.p. 256–258°C. H NMR (300 MHz, DMSO): δ
3.36–3.47 (m, 2H, CH2S), 4.13–4.37 (m, 2H, CH2N), 5.21 (s, 1H, CH), 6.62 (s, 2H, NH2),
6.93–7.29 (m, 4H, Ar), 7.91 (s, 2H, NH2). 13C NMR (75.4 MHz, DMSO): δ 28.2 (CH), 38.9
(CH2S), 51.1 (CH2N), 83.0, 113.6 (d, 2JCF = 21 Hz), 115.1 (d, 2JCF = 21 Hz), 123.4, 124.1,
130.3, 148.1, 149.2, 157.6, 161.0 (d, 1JCF = 243 Hz), 171.1 (C O). IR (KBr) (νmax/cm−1):
=
=
3439, 3346 and 3196 (NH2), 1636 (C O), 1562 (Ar), 1482 and 1329 (NO2), 1236 (C–N).
MS (EI, 70 eV): m/z (%) = 336.5 (M+, 9.3), 292 (100), 241 (93), 189 (24), 146 (31), 95
(13), 61 (32). Anal. Calc. for C14H13FN4O3S (336.34): C, 49.99; H, 3.90; N, 16.66. Found:
C, 49.9; H, 4.2; N, 16.5.

8
F. S. HOSSEINI ET AL.
4.2.3. 5-Amino-7-(2-chlorophenyl)-3,7-dihydro-8-nitro-2H-thiazolo[3,2-a]pyridine-6-
carboxamide (5c)
1
Orange solid; yield: 0.306 g (87%); m.p. 249–251°C. H NMR (300 MHz, DMSO): δ
3.37–3.42 (m, 2H, CH2S), 4.22–4.36 (m, 2H, CH2N), 5.39 (s, 1H, CH), 6.37 (s, 2H, NH2),
7.13–7.46 (m, 4H, Ar), 7.90 (s, 2H, NH2). 13C NMR (75.4 MHz, DMSO): δ 28.0 (CH), 38.9
(CH2S), 50.9 (CH2N), 82.1, 122.6, 127.5, 128.7, 130.0, 132.3, 132.5, 141.6, 149.3, 158.0,
=
171.3 (C O). Anal. Calc. for C14H13ClN4O3S (352.80): C, 47.66; H, 3.71; N, 15.88. Found:
C, 76.3; H, 4.2; N, 15.5.
4.2.4. 5-Amino-3,7-dihydro-8-nitro-7-phenyl-2H-thiazolo[3,2-a]pyridine-6-
carboxamide (5d)
1
Orange solid; yield: 0.254 g (80%); m.p. 262–264°C. H NMR (300 MHz, DMSO): δ
3.32–3.38 (m, 2H, CH2S), 4.14–4.30 (m, 2H, CH2N), 5.16 (s, 1H, CH), 6.56 (s, 2H, NH2),
7.12–7.32 (m, 5H, Ar), 7.84 (s, 2H, NH2). 13C NMR (75.4 MHz, DMSO): δ 28.2 (CH), 39.1
=
(CH2S), 51.0 (CH2N), 83.6, 124.0, 126.9, 128.1, 128.3, 145.2, 149.1, 157.3, 171.3 (C O). IR
(KBr) (νmax/cm−1): 3433, 3344 and 3203 (NH2), 1636 (C O), 1563 (Ar), 1482 and 1325
=
(NO2), 1237 (C–N). MS (EI, 70 eV): m/z (%) = 318.5 (M+, 9.9), 274 (100), 241 (90), 198
(10), 171 (31), 128 (25), 102 (20), 61 (25). Anal. Calc. for C14H14N4O3S (318.35): C, 52.82;
H, 4.43; N, 17.60. Found: C, 53.3; H, 4.9; N, 17.4.
4.2.5. 5-Amino-7-(4-chlorophenyl)-3,7-dihydro-8-nitro-2H-thiazolo[3,2-a]pyridine-6-
carboxamide (5e)
1
Orange solid; yield: 0.306 g (87%); m.p. 245–247°C. H NMR (300 MHz, DMSO): δ
3.37–3.40 (m, 2H, CH2S), 4.13–4.34 (m, 2H, CH2N), 5.19 (s, 1H, CH), 6.60 (s, 2H, NH2),
7.26 (d, 3JHH = 8.4 Hz, 2H, Ar), 7.33 (d, 3JHH = 8.4 Hz, 2H, Ar), 7.89 (s, 2H, NH2). 13
C
NMR (75.4 MHz, DMSO): δ 28.2 (CH), 38.7 (CH2S), 51.1 (CH2N), 83.1, 123.5, 128.2,
130.0, 131.4, 144.2, 149.1, 157.5, 171.1 (C9 O). IR (KBr) (νmax/cm−1): 3466, 3360 and
=
3191 (NH2), 1631 (C O), 1561 (Ar), 1482 and 1332 (NO2), 1226 (C–N). Anal. Calc. for
C14H13ClN4O3S (352.80): C, 47.66; H, 3.71; N, 15.88. Found: C, 48.1; H, 4.0; N, 15.5.
4.2.6. 5-Amino-7-(4-bromophenyl)-3,7-dihydro-8-nitro-2H-thiazolo[3,2-a]pyridine-6-
carboxamide (5f)
1
Orange solid; yield: 0.357 g (90%); m.p. 250–252°C. H NMR (300 MHz, DMSO): δ
3.35–3.40 (m, 2H, CH2S), 4.13–4.32 (m, 2H, CH2N), 5.18 (s, 1H, CH), 6.60 (s, 2H, NH2),
7.27 (d, 3JHH = 8.4 Hz, 2H, Ar), 7.40 (d, 3JHH = 8.4 Hz, 2H, Ar), 7.89 (s, 2H, NH2). 13
C
NMR (75.4 MHz, DMSO): δ 28.2 (CH), 38.8 (CH2S), 51.1 (CH2N), 83.0, 120.0, 123.5,
=
130.4, 131.1, 144.6, 149.1, 157.5, 171.1 (C O). Anal. Calc. for C14H13BrN4O3S (397.25):
C, 42.33; H, 3.30; N, 14.10. Found: C, 42.8; H, 3.7; N, 13.8.
4.2.7. 5-Amino-3,7-dihydro-7-(3-methoxyphenyl)-8-nitro-2H-thiazolo[3,2-a]pyridine-
6-carboxamide (5 g)
Red solid; yield: 0.289 g (83%); m.p. 247–249°C. 1H NMR (300 MHz, DMSO): δ 3.34–3.40
(m, 2H, CH2S), 3.67 (s, 3H, OCH3), 4.13–4.34 (m, 2H, CH2N), 5.14 (s, 1H, CH), 6.58
3
3
(s, 2H, NH2), 6.71 (d, JHH = 8.1 Hz, 1H, Ar), 6.83 (d, JHH = 7.8 Hz, 1H, Ar), 6.91
(s, 1H, Ar), 7.13 (t, JHH = 8.1 Hz, 1H, Ar), 7.85 (s, 2H, NH2). 13C NMR (75.4 MHz,
3
DMSO): δ 28.2 (CH), 39.1 (CH2S), 51.1 (CH2N), 55.3 (OCH3), 83.5, 111.5, 114.9, 120.2,

JOURNAL OF SULFUR CHEMISTRY
9
123.8, 129.5, 146.7, 149.1, 157.3, 159.2, 171.2 (C O). IR (KBr) (νmax/cm−1): 3438, 3346
and 3196 (NH2), 1633 (C O), 1557 (Ar), 1484 and 1337 (NO2), 1237 (C–N). MS (EI,
=
=
70 eV): m/z (%) = 348.5 (M+, 11.8), 304 (75), 241 (100), 201 (22), 44 (20). Anal. Calc. for
C15H16N4O4S (348.38): C, 51.71; H, 4.63; N, 16.08. Found: C, 51.3; H, 4.9; N, 15.7.
4.2.8. 5-Amino-3,7-dihydro-7-(3,4-dimethoxyphenyl)-8-nitro-2H-thiazolo[3,2-
a]pyridine-6-carboxamide (5 h)
Red solid; yield: 0.302 g (80%); m.p. 223–225°C. 1H NMR (300 MHz, DMSO): δ 3.36–3.43
(m, 2H, CH2S), 3.66 (s, 3H, OCH3), 3.67 (s, 3H, OCH3), 4.15–4.32 (m, 2H, CH2N), 5.09
(s, 1H, CH), 6.53 (s, 2H, NH2), 6.71–6.80 (m, 2H, Ar), 7.00 (s, 1H, Ar), 7.83 (s, 2H, NH2).
13C NMR (75.4 MHz, DMSO): δ 28.2 (CH), 38.7 (CH2S), 51.0 (CH2N), 55.9 (OCH3), 83.7,
=
112.2, 112.8, 119.9, 124.2, 137.8, 147.9, 148.4, 149.1, 156.9, 171.3 (C O). Anal. Calc. for
C16H18N4O5S (378.40): C, 50.78; H, 4.79; N, 14.81. Found: C, 50.4; H, 5.2; N, 14.6.
4.2.9. 5-Amino-3,7-dihydro-8-nitro-7-(4-nitrophenyl)-2H-thiazolo[3,2-a]pyridine-6-
carboxamide (5i)
1
Orange solid; yield: 0.308 g (85%); m.p. 235–237°C. H NMR (300 MHz, DMSO): δ
3.33–3.40 (m, 2H, CH2S), 4.16–4.37 (m, 2H, CH2N), 5.37 (s, 1H, CH), 6.68 (s, 2H, NH2),
7.60 (d, 3JHH = 8.7 Hz, 2H, Ar), 7.97 (s, 2H, NH2), 8.09 (d, 3JHH = 8.7 Hz, 2H, Ar). 13
C
NMR (75.4 MHz, DMSO): δ 28.2 (CH), 39.1 (CH2S), 51.1 (CH2N), 82.4, 122.9, 123.6,
=
129.4, 146.5, 149.2, 152.7, 158.1, 171.0 (C O). Anal. Calc. for C14H13N4O5S (363.35): C,
46.28; H, 3.61; N, 19.27. Found: C, 46.0; H, 3.8; N, 18.9.
4.2.10. 5-Amino-3,7-dihydro-8-nitro-7-(2-nitrophenyl)-2H-thiazolo[3,2-a]pyridine-6-
carboxamide (5j)
1
Yellow solid; yield: 0.297 g (82%); m.p. 245–247°C. H NMR (300 MHz, DMSO): δ
3.34–3.39 (m, 2H, CH2S), 4.18–4.39 (m, 2H, CH2N), 5.64 (s, 1H, CH), 6.65 (s, 2H, NH2),
7.41–7.78 (m, 4H, Ar), 8.27 (s, 2H, NH2). 13C NMR (75.4 MHz, DMSO): δ 28.1 (CH), 34.9
(CH2S), 51.2 (CH2N), 80.9, 122.9, 124.0, 128.8, 131.3, 134.5, 138.4, 149.0, 150.4, 158.4,
=
170.9 (C O). Anal. Calc. for C14H13N4O5S (363.35): C, 46.28; H, 3.61; N, 19.27. Found:
C, 46.8; H, 3.9; N, 19.0.
4.2.11. 5-Amino-3,7-dihydro-7-(4-hydroxyphenyl)-8-nitro-2H-thiazolo[3,2-
a]pyridine-6-carboxamide (5k)
1
Yellow solid; yield: 0.247 g (74%); m.p. 246–248°C. H NMR (300 MHz, DMSO): δ
3.35–3.41 (m, 2H, CH2S), 4.15–4.29 (m, 2H, CH2N), 5.02 (s, 1H, CH), 6.47 (s, 2H, NH2),
6.58 (d, 3JHH = 7.8 Hz, 2H, Ar), 7.08 (d, 3JHH = 7.8 Hz, 2H, Ar), 7.78 (s, 2H, NH2), 9.17
(s, 1H, OH). 13C NMR (75.4 MHz, DMSO): δ 28.1 (CH), 38.4 (CH2S), 51.0 (CH2N), 84.0,
=
115.0, 124.4, 129.1, 135.6, 148.9, 156.3, 156.8, 171.3 (C O). Anal. Calc. for C14H14N4O4S
(334.35): C, 50.29; H, 4.22; N, 16.76. Found: C, 50.8; H, 4.8; N, 16.5.
4.2.12. 5-Amino-3,7-dihydro-7-(4-methoxyphenyl)-8-nitro-2H-thiazolo[3,2-
a]pyridine-6-carboxamide (5 l)
Red solid; yield: 0.268 g (77%); m.p. 245–247°C. 1H NMR (300 MHz, DMSO): δ 3.36–3.46
(m, 2H, CH2S), 3.84 (s, 3H, OCH3), 4.13–4.33 (m, 2H, CH2N), 5.09 (s, 1H, CH), 6.53
3
3
(s, 2H, NH2), 6.76 (d, JHH = 8.7 Hz, 2H, Ar), 7.21 (d, JHH = 8.4 Hz, 2H, Ar), 7.86

10
F. S. HOSSEINI ET AL.
(s, 2H, NH2). 13C NMR (75.4 MHz, DMSO): δ 28.2 (CH), 38.3 (CH2S), 51.1 (CH2N),
=
55.4 (OCH3), 81.8, 108.5, 113.4, 129.1, 138.1, 149.1, 152.1, 157.9, 171.3 (C O). IR (KBr)
(νmax/cm−1): 3432, 3341, 3257 and 3198 (NH2), 1638 (C O), 1561 (Ar), 1487 and 1336
=
(NO2), 1237 (C–N). MS (EI, 70 eV): m/z (%) = 348.5 (M+, 4.4), 305 (46), 288 (100), 257
(77), 218 (23), 201 (76), 171 (19), 146 (29), 60 (28). Anal. Calc. for C15H16N4O4S (348.38):
C, 51.71; H, 4.63; N, 16.08. Found: C, 51.4; H, 4.9; N, 16.3.
Disclosure statement
No potential conflict of interest was reported by the authors.
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