Green chemistry preparation of MgO nanopowders: efficient catalyst for the synthesis of thiochromeno[4,3-b]pyran and thiopyrano[4,3-b]pyran derivatives

Article abstract of DOI:10.1080/17415993.2016.1149856

A mild and efficient method for the synthesis of thiochro meno[4,3-b]pyran and thiopyrano[4,3-b]pyran derivatives using MgO nanopowders as a catalyst is described. The MgO nanopowders were prepared via a green biosynthesis method using an extract of Rosma

Full text of DOI:10.1080/17415993.2016.1149856

Journal of Sulfur Chemistry
ISSN: 1741-5993 (Print) 1741-6000 (Online) Journal homepage: http://www.tandfonline.com/loi/gsrp20
Green chemistry preparation of MgO
nanopowders: efficient catalyst for the synthesis
of thiochromeno[4,3-b]pyran and thiopyrano[4,3-
b]pyran derivatives
Majid Ghashang, Syed Sheik Mansoor, Mohammad Reza Mohammad
Shafiee, Mahboubeh Kargar, Mohammad Najafi Biregan, Fateme Azimi &
Hadi Taghrir
To cite this article: Majid Ghashang, Syed Sheik Mansoor, Mohammad Reza Mohammad
Shafiee, Mahboubeh Kargar, Mohammad Najafi Biregan, Fateme Azimi & Hadi Taghrir (2016):
Green chemistry preparation of MgO nanopowders: efficient catalyst for the synthesis of
thiochromeno[4,3-b]pyran and thiopyrano[4,3-b]pyran derivatives, Journal of Sulfur Chemistry,
DOI: 10.1080/17415993.2016.1149856
To link to this article: http://dx.doi.org/10.1080/17415993.2016.1149856
Published online: 07 Mar 2016.
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Date: 09 March 2016, At: 03:56

JOURNAL OF SULFUR CHEMISTRY, 2016
http://dx.doi.org/10.1080/17415993.2016.1149856
Green chemistry preparation of MgO nanopowders: efficient
catalyst for the synthesis of thiochromeno[4,3-b]pyran and
thiopyrano[4,3-b]pyran derivatives
Majid Ghashanga, Syed Sheik Mansoorb, Mohammad Reza Mohammad Shafieea,
Mahboubeh Kargara, Mohammad Najafi Biregana, Fateme Azimia and Hadi Taghrira
aDepartment of Chemistry, Faculty of Sciences, Najafabad Branch, Islamic Azad University, Najafabad,
Esfahan, Iran; bResearch Department of Chemistry, Bioactive Organic Molecule Synthetic Unit, C. Abdul
Hakeem College, Melvisharam, Tamil Nadu, India
ABSTRACT
ARTICLE HISTORY
Received 13 September 2015
Accepted 30 January 2016
A mild and efficient method for the synthesis of thiochro-
meno[4,3-b]pyran and thiopyrano[4,3-b]pyran derivatives using
MgO nanopowders as a catalyst is described. The MgO nanopowders
were prepared via a green biosynthesis method using an extract of
Rosmarinus officinalis leaves and were characterized by Field Emis-
sion Scanning Electron Microscopy and X-ray diffraction analyses.
KEYWORDS
Rosmarinus officinalis leaves;
MgO nanopowders;
4H-pyran derivatives;
thiochromeno[4; 3-b]pyran;
thiopyrano[4; 3-b]pyran
CONTACT Majid Ghashang
ghashangmajid@gmail.com
Department of Chemistry, Faculty of Sciences,
Najafabad Branch, Islamic Azad University, Najafabad, Esfahan, Iran
Supplemental data for this article can be accessed here. http://dx.doi.org/10.1080/17415993.2016.1149856
© 2016 Taylor & Francis

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M. GHASHANG ET AL.
1. Introduction
Heterocyclic systems containing sulfur atoms have found broad application in the
development of drugs such as antihyperglycemic,[1] pesticidal,[2] fungicides [3] and
other compounds. In particular, sulfur-containing heterocycles such as thiopyrans and
thiochromenes are of great interest because of their potent pharmacological and medicinal
properties.[4] On the other hand, 4H-pyran fragments are well known for their potential
pharmacological activities, such as antimicrobial,[5] antiflammatory,[6] and antiHIV.[7]
Having these results in hand, it occurred to us that incorporation of thiopyran and 4H-
pyran moieties into a single molecule may impart drug potential that is absent in the parent
substance. The first example of the synthesis of these types of compounds was done by
Eiden and Felbermeir in 1984 via cycloaddition reactions of 3-benzylidenethiochroman-4-
ones with enamines.[8] However, the simplest method for the synthesis of these molecules
was introduced by Nakib et al. by applying piperidine as catalyst in the reaction of
3-benzylidenethiochroman-4-ones with malononitrile.[9] In the literature, only a few
examples of these molecules have been synthesized. It is noticeable that the catalytic
reaction of 3-benzylidenechroman-4-one or α,αꢀ-bis (substituted-benzylidene) cycloalka-
nones with malononitrile is a well-known procedure similarly to the Nakib et al. reaction.
However, the sulfur analogues of these compounds needed to construct thiochromeno[4,3-
b]pyran and thiopyrano[4,3-b]pyran derivatives have not been investigated except for a few
examples.[10–14]
The exploration of these catalytic reactions depends on the preparation of metallic or
nano-metallic heterogeneous catalysts. Heterogeneous catalytic reactions have emerged as
green and environmentally friendly synthetic tools as they eliminate the need for multi-
step purifications. Therefore, the preparation and application of heterogeneous catalyst are
critical for the development of green synthesis technologies. In recent years, metal oxide
catalysts have attracted increased interest for use in organic reactions since they are non-
expensive and can be easily prepared in bulk and nanoscale. Most of them are insoluble
in water or common organic solvents. Thus, they are utilized as heterogeneous catalysts in
many organic transformations.[15–19] The MgO nanostructure is one of the basic metal
oxides that finds excellent applications as an active catalyst for various organic transforma-
tions due to its high surface area combined with reactive morphologies.[20] Considering
the importance of metal oxides for the preparation of organic compounds, it is surprising
that the preparation of thiochromeno[4,3-b]pyran and thiopyrano[4,3-b]pyran derivatives
using metal oxides has not yet been established.
In this article, we introduce MgO nanopowders as basic heterogeneous catalysts for the
synthesis of thiochromeno[4,3-b]pyran and thiopyrano[4,3-b]pyran derivatives as a green,
environmentally friendly catalyst prepared via a green biosynthesis method (Scheme 1).
2. Results and discussion
2.1. MgO characterization
MgO nanopowders were synthesized via a convenient and green method using an extract
of Rosmarinus officinalis leaves and MgCl2 as starting materials. R. officinalis extract is
known to be rich in carboxylic acids such as rosmarinic acid and carnosoic acid.[21] The

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3
Scheme 1. Synthesis of 2-amino-4,5-dihydro-4-arylthiochromeno[4,3-b]pyran-3-carbonitrile and
(8Z)-2-amino-8-arylidene-4,5,7,8-tetrahydro-4-arylthiopyrano[4,3-b]pyran-3-carbonitrile derivatives
over MgO nanopowders.
Scheme 2. Proposed mechanism for the preparation of MgO nanopowders.
carboxyl group is converted to the carboxylic anion following the addition of ammonia
solution. The presence of chelating agents such as carboxylic anions is the main reason for
the preparation of MgO nanopowders.
The proposed mechanism for the preparation of MgO nanopowders is shown in
Scheme 2.
The successful growth of MgO nanoparticles was first verified by a combination of Field
Emission Scanning Electron Microscopy (FE-SEM) and X-ray diffraction (XRD) analysis.
The XRD analysis of MgO nanopowders is shown in Figure 1. The XRD pattern indicates
that the MgO appears as a single phase with cubic structure. The pronounced diffraction
peaks related to the cubic phase of MgO are 43.0, 62.5, 74.9, and 78.9. The average crystal
size of the MgO nanopowders was calculated according to the Scherrer equation as 69 nm.
FE-SEM was used to study the morphology of the surface of the MgO nanopowders
(Figure 2). It was shown that the particles have a uniform and irregular morphology con-
sisting of homogeneous agglomerated particles with sizes on the nanoscale scale. Figure
3 shows the size distribution of MgO nanopowders determined by statistical design from
FE-SEM photographs. The average size of the nanoparticles was about 73 nm.

4
M. GHASHANG ET AL.
Figure 1. XRD pattern MgO nanopowders.
Table 1. Optimization of reaction conditions.
Entry
Catalyst (mmol)
T (°C)
Solvent (5 mL)
Time (h)
Yield (%)a
1
2
3
4
5
6
7
8
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
1
80
Solvent free
n-Hexane
CH3CN
EtOAc
CH2Cl2
H2O
EtOH/H2O (50%)
EtOH
EtOH
24
24
24
24
24
10
10
10
5
–
–
Reflux
Reflux
80
Reflux
80
15
10
–
30
45
88
83
85
35
20
80
Reflux
Reflux
Reflux
Reflux
Reflux
9
10
11
12
0.5
0.1
0.05
EtOH
EtOH
EtOH
9
15
24
aIsolated yield (%).
2.2. Catalytic evaluation
Initially, the catalytic preparation of 2-amino-4,5-dihydro-4-arylthiochromeno
[4,3-b]pyran-3-carbonitrile over MgO nanopowders was chosen as a model reaction for
investigation. A variety of solvents including EtOH, H2O, CH2Cl2, EtOAc, n-hexane, and
CH3CN as well as solvent-free conditions were screened and the results are summarized
in Table 1. No yield of the product was obtained in nonpolar solvents under solvent-free
conditions (Table 1, Entries 1, 2, and 5). However, the product was obtained in low yield
in polar aprotic solvents and in aqueous media (Table 1, Entries 3, 4, and 6). Finally, the
use of ethanol produced the highest product yield of 88% (Table 1, Entry 8). Changing the
amount of catalyst produced no obvious experimental advantage. For example, a further
increase in the catalyst loading did not improve the reaction yield (Table 1, Entries 9 and
10).
Using the optimized reaction conditions in hand (Table1, Entry 8), a variety of 2-amino-
4,5-dihydro-4-arylthiochromeno[4,3-b]pyran-3-carbonitrile derivatives (Scheme 1) were
synthesized and the results are summarized in Table 2. A variety of 3-benzylidene-2,3-
dihydrothiochromen-4-ones with ortho, meta, and para substitutions on the benzene ring

JOURNAL OF SULFUR CHEMISTRY
5
Figure 2. FE-SEM photographs of MgO nanopowders.

6
M. GHASHANG ET AL.
Figure 3. The size distribution of MgO nanopowders.
were examined. Substrates with nitro and halogen substituents tolerated the reaction con-
ditions very well and gave excellent yields in shorter reaction times than those with methyl
and methoxy groups (Table 2).
As a continuation of this study, the synthesis of (8Z)-2-amino-8-arylidene-4,5,7,8-
tetrahydro-4-arylthiopyrano[4,3-b]pyran-3-carbonitrile derivatives over MgO nanopow-
ders was also examined. The results showed good reactivity and provided the products in
high yields (Table 2, Entries 11–15).
Based on the results and the reported literature,[10–14] a proposed mechanism for the
preparation of the entitled compounds is shown in Scheme 3. Two sites may be activated
by MgO; the carbonyl through the Lewis acid site (Mg atom) and the active methylene
of malononitrile by deprotonation with basic sites (O atom). Michael addition of depro-
tonated active methylene to the activated α,β-unsaturated carbonyl compound generates
the intermediate (a). The intramolecular cyclization and subsequent tautomerization of
intermediate (a) afforded the targeted molecules.
In conclusion, nanopowders of MgO were synthesized by a simple and cost-effective
biosynthesis method using MgCl2 and R. officinalis leaves extract solution. FE-SEM
micrographs show the agglomeration of fine particles having crystalline sizes of about
73 nm.
MgO nanopowders showed a very high reactivity in the synthesis of thiochromeno[4,3-
b]pyran and thiopyrano[4,3-b]pyran derivatives and provides good yields of pure prod-
ucts.
3. Experimental
All reagents were purchased from Merck and Aldrich and used without further purifi-
cation. All products were characterized using their spectral (1H NMR, and 13C NMR)

JOURNAL OF SULFUR CHEMISTRY
7
Table 2. Synthesis of 2-amino-4,5-dihydro-4-arylthiochromeno[4,3-b]pyran-3-carbonitrile and (8Z)-
2-amino-8-arylidene-4,5,7,8-tetrahydro-4-arylthiopyrano[4,3-b]pyran-3-carbonitrile derivatives over
MgO nanopowders.
Entry
Product structure
Product
Time (h)
Yield (%)a
M.p. (°C)
1
a1
10
88
193–195
2
3
a2
12
15
80
75
211–213
207–209
a3
4
5
a4
15
12
79
82
223–225
a5
214–216
231–233
6
7
a6
10
90
86
a7
9
224–226
(continued).

8
M. GHASHANG ET AL.
Table 2. Continued.
Entry
Product structure
Product
Time (h)
10
Yield (%)a
82
M.p. (°C)
207–209
8
a8
9
a9
a10
b1
12
77
94
95
202–204
249–251
228–230
10
11
8
15
12
13
b2
17
20
87
91
239–241
245–247
b3
14
b4
15
89
251–253
aIsolated yield.
data. The X-ray powder diffraction patterns were measured with D8, Advance, Bruker,
axs, diffractometer using Cu-Kα irradiation. FE-SEM was taken by a Hitachi S-4160 pho-
tograph to examine the shape and morphology of the samples. The NMR spectra were
recorded on a Bruker Avance DPX 400 MHz instrument. The spectra were measured in

JOURNAL OF SULFUR CHEMISTRY
9
Scheme 3. Proposed mechanism for the preparation of thiochromeno[4,3-b]pyran derivatives.
DMSO-d6 relative to TMS (0.00 ppm). TLC was performed on silica gel Polygram SIL
G/UV 254 plates. R. officinalis leaves were collected from Esfahan province in Iran.
3.1. Preparation of MgO nanostructure
Initially, 20 g of R. officinalis leaves was washed in running tap water, ground and inserted
into a 250 balloon flask containing 100 mL of de-ionized water and 50 mL of ethanol. The
mixture was refluxed for 4 h and the extract was filtered to cut off the unrequited bodies.
The extract was combined with 20 mL of aqueous ammonia (37%).
Next, to a solution of MgCl2 (30 mmol) in 100 mL of water, plant extract (100 mL) was
slowly poured drop-wise under vigorous magnetic stirring and the resulting precipitate
was filtered, washed with water several times, dried, and calcinated at 500°C for 2 h.
3.2. Preparation of (Z)-3-arylidenethiochroman-4-one and
(3Z,5Z)-3,5-diarylidene-tetrahydrothiopyran-4-one derivatives [22]
Tetrahydrothiopyran-4-one or thiochroman-4-one (1 mol) was dissolved in chloroform
(20 mL), then the aromatic aldehyde (1 mol) and piperidine (0.5 mL) were added, and the

10
M. GHASHANG ET AL.
reaction mixture stirred and refluxed for 5 h. After completion of the reaction, the sol-
vent was evaporated and the crude product was washed with water two times and finally
crystallized in ethanol.
3.3. General procedure for preparation thiopyran derivatives
The starting materials A and B (Scheme 1) were prepared according to the reported
literature.[22] A mixture of A or B (Scheme 1, 1 mmol), malononitrile (1.5 mmol), MgO
(0.25 mmol), and 5 mL of ethanol was stirred magnetically under reflux conditions for the
appropriate time as mentioned in Table 2. After completion of the reaction as detected
by TLC, the reaction mixture was cooled to room temperature. After dissolving the
crude product in boiling ethanol to separate the heterogeneous catalyst, the product was
recrystallized from ethanol to yield a pure product.
3.3.1. Selected spectral data
3.3.1.1. 2-Amino-4,5-dihydro-4-phenylthiochromeno[4,3-b]pyran-3-carbonitrile (Table
1
2, Product a1). H-NMR (400 MHz, DMSO-d6): δ = 3.07 (d, J = 15.0 Hz, 1H), 3.31 (d,
J = 15.0 Hz, 1H), 4.18 (s, 1H, CH|), 4.96 (s, 2H, NH2), 7.17–7.53 (m, 9H) ppm; 13C NMR
(100 MHz, DMSO-d6): δ = 27.1, 42.2, 60.8, 108.2, 119.3, 126.3, 127.1, 127.4, 128.4, 128.7,
129.2, 131.4, 132.3, 132.6, 137.5, 142.3, 159.1, 163.1 ppm. Found: C, 71.94; H, 4.67; N, 8.99;
S, 10.16% C19H14N2OS; requires: C, 71.67; H, 4.43; N, 8.80; S, 10.07%.
3.3.1.2. 2-Amino-4,5-dihydro-4-p-tolylthiochromeno[4,3-b]pyran-3-carbonitrile (Table
1
2, Product a2). H-NMR (400 MHz, DMSO-d6): δ = 2.27 (s, 3H, CH3), 3.05
(d, J = 15.3 Hz, 1H), 3.29 (d, J = 15.3 Hz, 1H), 4.24 (s, 1H, CH), 5.21 (s, 2H, NH2), 7.08
(d, J = 7.8 Hz, 2H), 7.14 (d, J = 7.8 Hz, 2H), 7.20–7.32 (m, 3H), 7.39 (d, J = 7.7 Hz, 1H),
ppm; 13C NMR (100 MHz, DMSO-d6): δ = 21.6, 27.2, 42.1, 60.7, 108.3, 119.7, 126.1, 126.6,
127.5, 129.5, 131.5, 132.3, 132.7, 137.9, 140.2, 142.1, 159.2, 163.0 ppm. Found: C, 72.49; H,
5.05; N, 8.67; S, 9.79% C20H16N2OS; requires: C, 72.26; H, 4.85; N, 8.43; S, 9.65%.
3.3.1.3. 2-Amino-4,5-dihydro-4-(4-methoxyphenyl)thiochromeno[4,3-b]pyran-3-
1
carbonitrile (Table 2, Product a3). H-NMR (400 MHz, DMSO-d6): δ = 3.06 (d,
J = 15.2 Hz, 1H), 3.30 (d, J = 15.2 Hz, 1H), 3.71 (s, 3H, OCH3), 4.23 (s, 1H, CH), 5.68 (s,
2H, NH2), 6.96 (d, J = 7.9 Hz, 2H), 7.20–7.32 (m, 5H), 7.38 (d, J = 7.7 Hz, 1H), ppm; 13
C
NMR (100 MHz, DMSO-d6): δ = 27.3, 42.2, 55.6, 60.3, 108.1, 114.9, 119.4, 124.9, 126.5,
127.9, 130.8, 132.4, 132.6, 138.1, 142.5, 159.3, 160.4, 163.1 ppm. Found: C, 69.21; H, 4.89;
N, 8.34; S, 9.36% C20H16N2O2S; requires: C, 68.94; H, 4.63; N, 8.04; S, 9.20%.
3.3.1.4. 4-(4-tert-Butylphenyl)-2-amino-4,5-dihydrothiochromeno[4,3-b]pyran-
1
3-carbonitrile (Table 2, Product a4). H-NMR (400 MHz, DMSO-d6): δ = 1.25 (s, 9H,
C(CH3)3), 3.09 (d, J = 15.0 Hz, 1H), 3.31 (d, J = 15.0 Hz, 1H), 4.28 (s, 1H, CH), 6.21 (s,
2H, NH2), 7.06 (d, J = 7.9 Hz, 2H), 7.16 (d, J = 7.9 Hz, 2H), 7.22–7.34 (m, 3H), 7.39 (d,
J = 7.7 Hz, 1H) ppm; 13C NMR (100 MHz, DMSO-d6): δ = 27.2, 31.4, 34.7, 42.3, 60.5,
108.6, 119.8, 123.4, 125.6, 126.1, 127.1, 131.4, 132.3, 132.5, 137.9, 142.2, 153.3, 159.1,
163.1 ppm. Found: C, 73.91; H, 6.11; N, 7.67; S, 8.74% C23H22N2OS; requires: C, 73.76;
H, 5.92; N, 7.48; S, 8.56%.

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11
3.3.1.5. 2-Amino-4-(4-chlorophenyl)-4,5-dihydrothiochromeno[4,3-b]pyran-3-
1
carbonitrile (Table 2, Product a5). H-NMR (400 MHz, DMSO-d6): δ = 3.08
(d, J = 15.2 Hz, 1H), 3.29 (d, J = 15.2 Hz, 1H), 4.31 (s, 1H, CH), 6.35 (s, 2H, NH2),
7.22–7.47 (m, 8H) ppm; 13C NMR (100 MHz, DMSO-d6): δ = 27.3, 42.2, 60.3, 108.6,
119.4, 125.8, 127.6, 128.1, 128.9, 131.4, 132.4, 132.7, 135.7, 137.9, 142.3, 159.0, 163.2 ppm.
Found: C, 64.92; H, 3.93; N, 8.14; S, 9.31% C19H13ClN2OS; requires: C, 64.68; H, 3.71; N,
7.94; S, 9.09%.
3.3.1.6. 2-Amino-4-(2,4-dichlorophenyl)-4,5-dihydrothiochromeno[4,3-b]pyran-3-
1
carbonitrile (Table 2, Product a6). H-NMR (400 MHz, DMSO-d6): δ = 3.12 (d,
J = 15.6 Hz, 1H), 3.37 (d, J = 15.6 Hz, 1H), 4.34 (s, 1H, CH), 6.89 (s, 2H, NH2), 7.15–7.54
(m, 7H) ppm; 13C NMR (100 MHz, DMSO-d6): δ = 27.2, 42.5, 60.4, 108.7, 119.3, 125.9,
127.5, 127.8, 129.1, 128.5, 131.4, 132.3, 132.6, 133.2, 137.9, 135.3, 142.2, 159.2, 163.3 ppm.
Found: C, 59.12; H, 3.29; N, 7.40; S, 8.41% C19H12Cl2N2OS; requires: C, 58.92; H, 3.12; N,
7.23; S, 8.28%.
3.3.1.7. 2-Amino-4-(3,4-dichlorophenyl)-4,5-dihydrothiochromeno[4,3-b]pyran-3-
1
carbonitrile (Table 2, Product a7). H-NMR (400 MHz, DMSO-d6): δ = 3.15 (d,
J = 15.4 Hz, 1H), 3.41 (d, J = 15.4 Hz, 1H), 4.37 (s, 1H, CH), 6.74 (s, 2H, NH2), 7.21–7.50
(m, 7H) ppm; 13C NMR (100 MHz, DMSO-d6): δ = 27.2, 42.4, 60.3, 108.7, 119.4, 125.8,
127.3, 128.7, 129.3, 129.9, 131.4, 132.4, 132.7, 133.9, 133.8, 138.2, 141.9, 159.4, 163.2 ppm.
Found: C, 59.11; H, 3.31; N, 7.39; S, 8.38% C19H12Cl2N2OS; requires: C, 58.92; H, 3.12; N,
7.23; S, 8.28%.
3.3.1.8. 2-Amino-4-(3-chlorophenyl)-4,5-dihydrothiochromeno[4,3-b]pyran-3-
1
carbonitrile (Table 2, Product a8). H-NMR (400 MHz, DMSO-d6): δ = 3.09 (d,
J = 15.2 Hz, 1H), 3.31 (d, J = 15.2 Hz, 1H), 4.32 (s, 1H, CH), 6.42 (s, 2H, NH2), 7.21–7.48
(m, 8H) ppm; 13C NMR (100 MHz, DMSO-d6): δ = 27.2, 42.1, 60.1, 108.3, 125.7, 126.9,
127.5, 127.8, 128.4, 129.3, 130.6, 131.5, 132.4, 132.8, 138.3, 141.5, 159.1, 163.1 ppm. Found:
C, 64.89; H, 3.88; N, 8.15; S, 9.25% C19H13ClN2OS; requires: C, 64.68; H, 3.71; N, 7.94; S,
9.09%.
3.3.1.9. 2-Amino-4-(2-chlorophenyl)-4,5-dihydrothiochromeno[4,3-b]pyran-3-
1
carbonitrile (Table 2, Product a9). H-NMR (400 MHz, DMSO-d6): δ = 3.04 (d,
J = 15.1 Hz, 1H), 3.27 (d, J = 15.1 Hz, 1H), 4.32 (s, 1H, CH), 6.37 (s, 2H, NH2), 7.21–7.47
(m, 8H) ppm; 13C NMR (100 MHz, DMSO-d6): δ = 27.1, 42.2, 60.3, 108.2, 119.2, 125.9,
127.1, 128.4, 129.0, 130.7, 130.8, 131.4, 132.4, 132.7, 132.9, 138.1, 142.2, 159.2, 163.1 ppm.
Found: C, 64.90; H, 3.86; N, 8.17; S, 9.23% C19H13ClN2OS; requires: C, 64.68; H, 3.71; N,
7.94; S, 9.09%.
3.3.1.10. 2-Amino-4,5-dihydro-4-(3-nitrophenyl)thiochromeno[4,3-b]pyran-3-
1
carbonitrile (Table 2, Product a10). H-NMR (400 MHz, DMSO-d6): δ = 3.17 (d,
J = 15.3 Hz, 1H), 3.37 (d, J = 15.3 Hz, 1H), 4.48 (s, 1H, CH), 6.79 (s, 2H, NH2), 7.21–7.32
(m, 3H) 7.39–7.46 (m, 2H), 7.79 (d, J = 7.8 Hz, 1H), 8.18–8.22 (m, 2H) ppm; 13C NMR
(100 MHz, DMSO-d6): δ = 27.2, 42.3, 61.1, 108.8, 119.8, 122.7, 125.3, 126.1, 127.5, 129.9,

12
M. GHASHANG ET AL.
131.5, 132.4, 132.6, 134.7, 138.1, 148.3, 148.7, 159.1, 163.4 ppm. Found: C, 63.09; H, 3.79;
N, 11.74; S, 8.94% C19H13N3O3S; requires: C, 62.80; H, 3.61; N, 11.56; S, 8.82%.
3.3.1.11. (8Z)-2-amino-8-benzylidene-4,5,7,8-tetrahydro-4-phenylthiopyrano[4,3-b]
1
pyran-3-carbonitrile (Table 2, Product b1). H-NMR (400 MHz, DMSO-d6): δ = 2.97
(d, J = 15.7 Hz, 1H), 3.25 (d, J = 15.7 Hz, 1H), 3.54 (d, J = 15.8 Hz, 1H), 3.69 (d,
J = 15.8 Hz, 1H), 4.11 (s, 1H, CH), 6.56 (s, 2H, NH2), 7.14 (s, 1H) 7.23–7.41 (m, 10H)
ppm; 13C NMR (100 MHz, DMSO-d6): δ = 27.9, 28.7, 43.1, 56.5, 114.7, 120.2, 124.7, 126.8,
127.4, 127.6, 128.3, 128.9, 129.6, 129.9, 136.2, 142.1, 144.9, 159.2 ppm. Found: C, 73.86; H,
5.17; N, 7.89; S, 9.07% C22H18N2OS; requires: C, 73.71; H, 5.06; N, 7.82; S, 8.95%.
3.3.1.12. (8Z)-8-(4-methylbenzylidene)-4-(4-methylphenyl)-2-amino-4,5,7,8-
1
tetrahydrothiopyrano[4,3-b]pyran-3-carbonitrile (Table 2, Product b2). H-NMR
(400 MHz, DMSO-d6): δ = 2.25 (s, 3H, CH3), 2.36 (s, 3H, CH3), 2.96 (d, J = 15.9 Hz,
1H), 3.22 (d, J = 15.9 Hz, 1H), 3.57 (d, J = 16.1 Hz, 1H), 3.75 (d, J = 16.1 Hz, 1H), 4.16
(s, 1H, CH), 6.83 (s, 2H, NH2), 7.05–7.27 (m, 9H) ppm; 13C NMR (100 MHz, DMSO-d6):
δ = 21.3, 21.5, 40.9, 43.7, 56.8, 113.9, 120.4, 121.4, 126.9, 127.6, 128.7, 129.1, 129.6, 132.7,
136.9, 140.1, 144.8, 145.1, 153.4, 160.1 ppm. Found: C, 74.77; H, 6.02; N, 7.41; S, 8.49%
C24H22N2OS; requires: C, 74.58; H, 5.74; N, 7.25; S, 8.30%.
3.3.1.13. (8Z)-8-(4-methoxybenzylidene)-4-(4-methoxyphenyl)-2-amino-4,5,7,8-
1
tetrahydrothiopyrano[4,3-b]pyran-3-carbonitrile (Table 2, Product b2). H-NMR
(400 MHz, DMSO-d6): δ = 2.97 (d, J = 15.8 Hz, 1H), 3.24 (d, J = 15.8 Hz, 1H), 3.59 (d,
J = 15.9 Hz, 1H), 3.78 (d, J = 15.9 Hz, 1H), 3.80 (s, 3H, OCH3), 3.84 (s, 3H, OCH3), 4.11
(s, 1H, CH), 6.85–6.98 (m, 6H), 7.14–7.22 (m, 5H) ppm; 13C NMR (100 MHz, DMSO-d6):
δ = 41.2, 43.7, 55.8, 56.7, 56.9, 113.7, 120.5, 121.4, 124.8, 125.3. 127.6, 129.1, 129.6, 136.9,
140.1, 145.1, 153.4, 156.7, 157.9, 160.1 ppm. Found: C, 69.07; H, 5.52; N, 6.93; S, 7.84%
C24H22N2O3S; requires: C, 68.88; H, 5.30; N, 6.69; S, 7.66%.
3.3.1.14. (8Z)-8-(4-tert-butylbenzylidene)-4-(4-tert-butylphenyl)-2-amino-4,5,7,8-
1
tetrahydrothiopyrano[4,3-b]pyran-3-carbonitrile (Table 2, Product b4). H-NMR
(400 MHz, DMSO-d6): δ = 1.26 (s, 9H), 1.37 (s, 9H), 3.00 (d, J = 16.0 Hz, 1H), 3.28 (d,
J = 16.0 Hz, 1H), 3.55 (d, J = 16.2 Hz, 1H), 3.73 (d, J = 16.2 Hz, 1H), 4.17 (s, 1H, CH),
6.77 (s, 2H, NH2), 6.99–7.14 (m, 7H), 7.23 (d, J = 7.8 Hz, 2H) ppm; 13C NMR (100 MHz,
DMSO-d6): δ = 28.1, 29.3, 31.2, 31.5, 34.7, 35.2, 43.4, 57.1, 115.1, 120.2, 125.4, 125.7, 126.8,
128.7, 129.2, 130.0, 131.9, 137.0, 140.2, 144.8, 145.1, 153.4, 159.2 ppm. Found: C, 76.79; H,
7.56; N, 6.21; S, 6.99% C30H34N2OS; requires: C, 76.56; H, 7.28; N, 5.95; S, 6.81%.
Disclosure statement
No potential conflict of interest was reported by the authors.
Funding
We are thankful to the Islamic Azad University, Najafabad Branch research council for partial
support of this research.

JOURNAL OF SULFUR CHEMISTRY
13
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