Synthesis of 1,3-Oxazine-4-thione Derivatives through an Efficient, Rapid and Green Method Catalyzed by L-Proline in Aqueous Medium

Full text of DOI:10.1080/00304948.2018.1468984

Organic Preparations and Procedures International
The New Journal for Organic Synthesis
ISSN: 0030-4948 (Print) 1945-5453 (Online) Journal homepage: http://www.tandfonline.com/loi/uopp20
Synthesis of 1,3-Oxazine-4-thione Derivatives
through an Efficient, Rapid and Green Method
Catalyzed by L-Proline in Aqueous Medium
Razieh Mohebat, Arezoo Mojahedi & Afshin Yazdani-Elah-Abadi
To cite this article: Razieh Mohebat, Arezoo Mojahedi & Afshin Yazdani-Elah-Abadi (2018)
Synthesis of 1,3-Oxazine-4-thione Derivatives through an Efficient, Rapid and Green Method
Catalyzed by L-Proline in Aqueous Medium, Organic Preparations and Procedures International,
50:4, 424-431, DOI: 10.1080/00304948.2018.1468984
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Organic Preparations and Procedures International, 50:424–431, 2018
# 2018 Taylor & Francis Group, LLC
ISSN: 0030-4948 print / 1945-5453 online
DOI: 10.1080/00304948.2018.1468984
Synthesis of 1,3-Oxazine-4-thione Derivatives
through an Efficient, Rapid and Green Method
Catalyzed by L-Proline in Aqueous Medium
Razieh Mohebat,1 Arezoo Mojahedi,1 and
Afshin Yazdani-Elah-Abadi2,3,4
aDepartment of Chemistry, Yazd Branch, Islamic Azad University,
Yazd, Iran;
bDepartment of Chemistry, Payame Noor University, Tehran 19395-
3697, Iran;
cResearch Center of Environmental Chemistry, Payame Noor University,
Ardakan, Yazd, Iran;
dDepartment of Biology, Science and Art University, Yazd, Iran
The development of environmentally friendly and economical methods for the synthesis
of biologically active heterocycles using readily available reagents remains a significant
challenge in organic synthesis.1–5 In this context, organocatalysis has emerged as a
powerful methodology in organic synthesis for the preparation of both simple and com-
plex bioactive heterocycles6–11 Organocatalysts offer improved stability, lack of sensi-
tivity to moisture and oxygen, ready availability, low cost, lower toxicity and metal-free
reaction conditions. Among organocatalysts, L-proline is a readily obtainable naturally
occurring amino acid and is easy to obtain in high enantiomeric purity. It has been
reported as an eco-friendly catalyst for the synthesis of several heterocycles.12–17
Multi-component reactions (MCRs) have considerable ecological interest for use in
the synthesis of biologically important compounds. The design of novel MCRs for the
synthesis of diverse heterocycles has become as an important topic for medicinal and
organic chemists.18–22
Heterocyclic compounds, especially nitrogen- and oxygen-containing heterocyclic
molecules in five and six-membered rings, play key roles in medicinal chemistry.23,24
Among them, oxazines and their derivatives are significant due a diversity of biological
functions.25–27 Both natural and synthetic oxazines exhibit a wide range of biological
activities, including anticoagulant activity,28 fungicidal activities,29 a-amino-3-hydroxy-
5-methyl-4-isoxazolepropionic acid receptor modulation activities,30 as well as anal-
gesic and antispasmodic activities.31
In continuation of our research on MCRs and our ongoing program for the synthe-
sis of complex organic compounds based on green chemistry protocols,32–36 we now
report an efficient and green synthesis of 1,3-oxazine-4-thiones in the presence of
Received 25 November 2017; in final form 18 March 2018.
Address correspondence to Razieh Mohebat, Department of Chemistry, Yazd Branch, Islamic
Azad University, Yazd, Iran. E-mail: mohebat@iauyazd.ac.ir
424

1,3-Oxazine-4-thiones
425
Scheme 1. Synthesis of 1,3-oxazine-4-thione derivatives.
L-proline as an effective and bifunctional organocatalyst in aqueous medium at 50 ꢀC
(Scheme 1).
1,3-Oxazine-4-thione derivatives were synthesized via a two-step procedure: in the
first step, ammonium thiocyanate 1 (1 mmol) and acid chlorides 2 (1 mmol) were mixed
at 70 ꢀC (solvent-free) until, in less than 5 minutes, solids of benzoyl isothiocyanates 3
were formed. The second step involves the reaction between 3 and naphthols 4a-c in
the presence of L-proline in water to form the corresponding products 5, 6 and 7.
To find the best reaction conditions, the sequential one-pot three-component reac-
tion of ammonium thiocyanate (1 mmol), 3-nitrobenzoyl chloride (1 mmol) and 1-naph-
thol (1 mmol) was selected as a model reaction in the presence of different catalytic
systems. The yields and reaction times were monitored as functions of temperature and
molar ratio of catalyst. As shown in Table 1, after extensive screening, we found that
the best yields and time profiles were obtained when the reaction was carried out in the
presence of 20 mol % of L-proline as catalyst in H2O at 50 ꢀC, which afforded the cor-
responding 2-(3-nitrophenyl)-4H-naphtho[2,1-e][1,3]oxazine-4-thione 5d in 3 hours
with 93% yield (Table 1, entry 8). The reaction did not proceed efficiently in the
absence of solvent even after 4 hours at 50 ꢀC (Table 1, entry 12).
With the optimized conditions in hand, the scope and efficiency of the reaction
were explored for the synthesis of 1,3-oxazine-4-thione derivatives. The results are
summarized in Table 2. The extensive structural range of benzoyl chlorides afforded
the corresponding products in very good to excellent yields using L-proline as catalyst.
Benzoyl chlorides containing electron-withdrawing groups increased the rate of reaction
and gave higher yields (Entries 1-5, 10-13 and17-20) than those with electron-donating
groups (Entries 7-9, 15 and 16).
We also investigated the recycling of the catalyst under optimal reaction conditions
using a model reaction of ammonium thiocyanate, 3-nitrobenzoyl chloride and 1-naph-
thol (Figure 1). After completion of the reaction, the crude solid product was filtered
and washed with H2O (2 ꢁ 5 mL). The L-proline was thus removed from the reaction
medium by washing with H2O. Since the catalyst is soluble in water, the catalyst was
recovered by evaporation of the water, and washed with diethyl ether and reused for the
subsequent catalytic runs. The reactivity was without significant loss through the 2nd
run. In the 3rd, 4th and 5th runs, product yield was reduced slightly. That may be due

426
Mohebat et al.
Table 1
Optimization of the Reaction Conditions for the Synthesis of 5d
Entry
Catalyst (mol %)
Reaction conditions
Time (h)
Yield (%)a
1
2
3
4
5
6
7
8
DABCO (20)
Pyridine (20)
Triethylamine (20)
Imidazole (20)
Caffeine (20)
L-Proline(20)
L-Proline(20)
L-Proline(20)
L-Proline(20)
L-Proline(30)
L-Proline(10)
L-Proline(20)
H2O, 70 ꢀC
H2O, 70 ꢀC
H2O, 70 ꢀC
H2O, 70 ꢀC
H2O, 70 ꢀC
H2O, 70 ꢀC
H2O, 100 ꢀC
H2O, 50 ꢀC
H2O, rt
2
2
2
2
2
2
2
3
8
3
3
4
54
37
46
78
75
87
51
93
Trace
91
9
10
11
12
H2O, 50 ꢀC
H2O, 50 ꢀC
Solvent-free, 50 ꢀC
72
Trace
aIsolated yield.
Table 2
Preparation of 1,3-oxazine-4-thione Derivatives in the Presence of L-proline (20 mol%)
as Catalyst at 50 ꢀC in H2O
Time Yield
mp
mp[Lit]
(ꢀC)
Entry Naphthol
Ar group
Product (h) (%)a (Obs) (ꢀC)
1
2
3
4
5
6
7
8
4a
4a
4a
4a
4a
4a
4a
4a
4a
4b
4b
4b
4b
4b
4b
4b
4c
4c
4c
4c
4c
4-NO2-C6H4
4-Cl-C6H4
4-Br-C6H4
3-NO2-C6H4
5a
5b
5c
5d
3
3
3
3
3
3
4
4
4
3
3
3
3
3
4
4
3
3
3
3
3
97
91
96
93
90
95
90
88
86
95
95
93
91
93
88
85
92
88
87
90
85
166-167
118-120
124
141-143 Present work
157-158 Present work
105-106
117-119
111 Present work
125-127 Present work
170-172
122-123
149-150 Present work
172-174 Present work
105
132-134
167-16937
120-12237
122-12437
3,5-(NO2)2-C6H3 5e
C6H5
5f
107-10937
114-11637
4-Me-C6H4
3-Me-C6H4
2-Me-C6H4
4-NO2-C6H4
4-Br-C6H4
3-NO2-C6H4
5g
5h
5i
6a
6b
6c
9
10
11
12
13
14
15
16
17
18
19
20
21
169-17137
123-12537
3,5-(NO2)2-C6H3 6d
C6H5
6e
6f
6g
7a
7b
103-10537
132-13437
4-Me-C6H4
2-Me-C6H4
4-NO2-C6H4
3-NO2-C6H4
127-129 Present work
121
120-12237
108-110 Present work
130-131 Present work
146-148 Present work
3,5-(NO2)2-C6H3 7c
4-Br-C6H4
C6H5
7d
7e
114-116
114-11637
aIsolated yield.

1,3-Oxazine-4-thiones
427
to some loss of catalyst during the recovery processes, likely a consequence of solubil-
ity in the wash solvents. Even so, the maximum decrease in yields through 5 runs was
only 9% (Figure 1).
In summary, we have demonstrated an environmentally benign technique for the
synthesis of functionalized 1,3-oxazine-4-thionederivatives in excellent yields and puri-
ties from readily available starting materials by using a catalytic amount of L-proline as
a highly reactive, non-toxic and reusable catalyst, under conventional heating in aque-
ous medium.
Experimental Section
All melting points were determined on an Electrothermal 9100 apparatus and are uncor-
rected. IR spectra were recorded on a Shimadzu IR-470 spectrometer. Elemental analy-
ses for C, H, and N were performed using a Heraeus CHN-O-Rapid analyzer at the
Iranian Petroleum Central ResearchCompany. Mass spectra were recorded on an
Agilent Technology (HP) spectrometer operating at an ionization potential of 70 eV.
1
The H nuclear magnetic resonance (NMR) and 13C NMR spectra were recorded on
Bruker Avance 400 MHz spectrometer Bruker DRX-400 MHz Avance instruments with
CDCl3 as solvent. Thin-layer chromatography (TLC) was performed on silica-gel
Polygram SILG/UV 254 plates. All reagents and solvents were purchased from Merck
and Aldrich and used without further purification.
General Procedure for the Synthesis of 1,3-Oxazine-4-thione Derivatives(5, 6, 7)
Ammonium thiocyanate 1 (1 mmol) and acid chloride 2 (1 mmol) were mixedat 70 ꢀC
(solvent-free) until in less than 5 minutes a solid of benzoyl isothiocyanate 3 was
formed.37–39 Then, 1-naphthol 4a (1 mmol) was added into the reaction mixture and
finally, a solution of L-proline (20 mol %) in water (5 mL) was added and the reaction
mixture was stirred at 50 ꢀC for an appropriate time as shown in Table 2. Upon comple-
tion of the reaction, monitored by TLC(eluent: ethyl acetate/hexane, 1:2), the reaction
mixture was allowed to cool to room temperature. Then, the crude solid product was fil-
tered and washed with H2O (2 ꢁ 5 mL) to remove the catalyst. The resulting product
was dried and subsequently washed with 10 mL of diethyl ether to give the pure solid.
We also used 2-naphthol 4b and phenol 4c instead of 1-naphthol 4a in this procedure
(Scheme 1). The analytical and spectroscopic data for the unknown compounds are
as follows.
2-(3-Nitrophenyl)-4H-naphtho[2,1-e][1,3]oxazine-4-thione (5d). Pale yellow pow-
der; yield 93%, 0.311 g; mp 141-143 ꢀC; IR (KBr) (ꢀmax, cmꢂ1): 1662, 1575, 1527,
1
1378, 1338, 1278, 1216, 1108, 1026, 760; H NMR (400 MHz, CDCl3): dH 7.41 (d, 1H,
J ¼ 7.6 Hz, Ar-H), 7.54-7.59 (m, 3H, Ar-H),7.81 (d, 1H, J ¼ 8.0 Hz, Ar-H), 7.84-7.86
(m, 1H, Ar-H), 7.89-7.96 (m, 2H, Ar-H), 8.56-8.59 (m, 1H, Ar-H), 8.67 (d, 1H,
J ¼ 7.6 Hz, Ar-H); 13C NMR (100 MHz, CDCl3): dC 118.1, 120.9, 125.2, 125.4, 126.6,
126.7, 126.8, 128.2, 128.3, 130.0, 131.2, 134.7, 135.9, 146.3, 151.7, 163.2, 197.8; MS
(m/z, %): 334 (Mþ, 12).
Anal. Calcd for C18H10N2O3S: C, 64.66; H, 3.01; N, 8.38; S, 9.59. Found: C,
64.90; H, 3.18; N, 8.60; S, 9.72.
2-(3,5-Dinitrophenyl)-4H-naphtho[2,1-e][1,3]oxazine-4-thione (5e). Pale yellow
powder; yield 90%, 0.341 g; mp 157-158 ꢀC; IR (KBr) (ꢀmax, cmꢂ1): 1659, 1594, 1532,

428
Mohebat et al.
1379, 1335, 1263, 1213, 1137, 1067, 766; 1H NMR (400 MHz, CDCl3): dH 7.43
(dd, 1H, J1 ¼ 7.6 Hz, J2 ¼ 1.2 Hz, Ar-H), 7.54-7.61 (m, 3H, Ar-H),7.84-7.89 (m, 2H, Ar-
H), 7.95-7.98 (m, 1H, Ar-H), 8.36-8.39 (m, 1H, Ar-H), 8.45 (d, 1H, J ¼ 8.0 Hz, Ar-H);
13C NMR (100 MHz, CDCl3): dC 118.0, 120.5, 123.1, 125.4, 126.1, 126.9, 127.0, 127.1,
128.3, 130.0, 133.1, 134.7, 145.9, 148.9, 161.3, 199.4; MS (m/z, %): 379 (Mþ, 9).
Anal. Calcd for C18H9N3O5S: C, 56.99; H, 2.39; N, 11.08; S, 8.45. Found: C,
57.12; H, 2.43; N, 11.29; S, 8.70.
2-(m-Tolyl)-4H-naphtho[2,1-e][1,3]oxazine-4-thione (5h). Yellow powder; yield
88%, 0.267 g; mp 111 ꢀC; IR (KBr) (ꢀmax, cmꢂ1): 1649, 1571, 1374, 1263, 1217, 1181,
1
1078, 762; H NMR (400 MHz, CDCl3): dH 2.39 (s, 3H, Me), 7.15 (s, 1H, Ar-H), 7.21-
7.26 (m, 1H, Ar-H), 7.34-7.44 (m, 4H, Ar-H), 7.69 (d, 1H, J ¼ 8.0 Hz, Ar-H), 7.79-7.85
(m, 1H, Ar-H), 8.06 (d, 1H, J ¼ 7.6 Hz, Ar-H), 8.21 (d, 1H, J ¼ 8.0 Hz, Ar-H); 13C
NMR (100 MHz, CDCl3): dC 21.3, 118.3, 121.3, 125.5, 126.1, 126.2, 126.4, 126.5,
127.5, 128.6, 129.2, 130.8, 131.3, 134.6, 146.9, 152.2, 165.4, 198.6; MS (m/z, %): 303
(Mþ, 23).
Anal. Calcd for C19H13NOS: C, 75.22; H, 4.32; N, 4.62; S, 10.57. Found: C, 75.11;
H, 4.50; N, 4.91; S, 10.68.
2-(o-Tolyl)-4H-naphtho[2,1-e][1,3]oxazine-4-thione (5i). Yellow powder; yield
86%, 0.261 g; mp 125-127 ꢀC; IR (KBr) (ꢀmax, cmꢂ1): 1646, 1585, 1377, 1273, 1215,
1
1149, 1076, 782; H NMR (400 MHz, CDCl3): dH 2.78 (s, 3H, Me),7.41-7.46 (m, 2H,
Ar-H), 7.55-7.58 (m, 4H, Ar-H), 7.83 (d, 1H, J ¼ 8.0 Hz, Ar-H), 7.94-8.01 (m, 2H, Ar-
H), 8.44 (d, 1H, J ¼ 7.6 Hz, Ar-H); 13C NMR (100 MHz, CDCl3): dC 22.1, 118.4,
121.3, 125.5, 126.2, 126.4, 126.5, 126.6, 127.1, 128.2, 128.8, 131.0, 131.3, 134.7,
146.9, 152.5, 165.8, 199.0; MS (m/z, %): 303 (Mþ, 14).
Anal. Calcd for C19H13NOS: C, 75.22; H, 4.32; N, 4.62; S, 10.57. Found: C, 75.39;
H, 4.45; N, 4.38; S, 10.34.
3-(3-Nitrophenyl)-1H-naphtho[1,2-e][1,3]oxazine-1-thione (6c). Pale yellow pow-
der; yield 93%, 0.311 g; mp 149-150 ꢀC; IR (KBr) (ꢀmax, cmꢂ1): 1653, 1612, 1581,
1
1527, 1344, 1294, 1156, 1056, 713; H NMR (400 MHz, CDCl3): dH 7.40 (dd, 1H,
J1 ¼ 8.8 Hz, J2 ¼ 2.4 Hz, Ar-H), 7.52-7.58 (m, 2H, Ar-H), 7.75-7.76 (m, 1H, Ar-H),
7.79 (d, 1H, J ¼ 8.0 Hz, Ar-H), 7.86-7.93 (m, 2H, Ar-H), 7.96 (d, 1H, J ¼ 8.8 Hz, Ar-
H), 8.53-8.61 (m, 2H, Ar-H); 13C NMR (100 MHz, CDCl3): dC 118.6, 120.7, 125.1,
126.0, 126.8, 127.7, 127.8, 128.0, 129.7, 129.9, 131.4, 131.7, 133.7, 135.8, 148.1,
148.4, 163.3, 199.2; MS (m/z, %): 334 (Mþ, 8).
Anal. Calcd for C18H10N2O3S: C, 64.66; H, 3.01; N, 8.38; S, 9.59. Found: C,
64.52; H, 3.14; N, 8.27; S, 9.71.
3-(3,5-Dinitrophenyl)-1H-naphtho[1,2-e][1,3]oxazine-1-thione (6d). Yellow pow-
der; yield 91%, 0.345 g; mp 172-174 ꢀC; IR (KBr) (ꢀmax, cmꢂ1): 1644, 1615, 1596,
1
1540, 1339, 1273, 1167, 1070, 756; H NMR (400 MHz, CDCl3): dH 7.40 (dd, 1H,
J1 ¼ 2.0 Hz, J2 ¼ 8.8 Hz, Ar-H), 7.54-7.60 (m, 2H, Ar-H), 7.77 (d, 1H, J ¼ 1.6 Hz, Ar-
H), 7.88-7.94 (m, 2H, Ar-H), 7.98 (d, 1H, J ¼ 8.8 Hz, Ar-H), 8.34-8.35 (m, 1H, Ar-H),
8.39 (d, 1H, J ¼ 2.0 Hz, Ar-H); 13C NMR (100 MHz, CDCl3): dC 118.5, 120.2, 122.9,
126.4, 127.0, 127.8, 127.9, 129.9, 130.0, 131.8, 133.3, 133.6, 147.7, 148.8, 161.3,
198.9; MS (m/z, %): 379 (Mþ, 10).
Anal. Calcd for C18H9N3O5S: C, 56.99; H, 2.39; N, 11.08; S, 8.45. Found: C,
57.14; H, 2.63; N, 11.25; S, 8.58.
3-(o-Tolyl)-1H-naphtho[1,2-e][1,3]oxazine-1-thione (6g). Yellow powder; yield
85%, 0.258 g; mp 127-129 ꢀC; IR (KBr) (ꢀmax, cmꢂ1): 1639, 1593, 1501, 1296, 1233,

1,3-Oxazine-4-thiones
429
94
92
90
88
86
84
82
80
78
Run 1
93
Run 2
93
Run 3
90
Run 4
88
Run 5
84
Product (%)
Figure 1. The investigation of the recycling of L-proline.
1
1150, 1041, 728; H NMR (400 MHz, CDCl3): dH 2.54 (s, 3H, CH3), 7.36-7.40 (m, 2H,
Ar-H), 7.50-7.55 (m, 2H, Ar-H), 7.71 (d, 1H, J ¼ 2.4 Hz, Ar-H), 7.85-7.91 (m, 2H, Ar-
H), 7.94 (d, 1H, J ¼ 8.8 Hz, Ar-H), 8.06-8.09 (m, 1H, Ar-H), 8.26 (d, 1H, J ¼ 8.0 Hz,
Ar-H); 13C NMR (100 MHz, CDCl3): dC 22.0, 118.8, 121.4, 125.7, 125.9, 126.5, 127.0,
127.7, 128.5, 128.8, 129.4, 130.7, 131.8, 132.0, 134.8, 141.4, 148.5, 166.0, 199.3; MS
(m/z, %): 303 (Mþ, 5).
Anal. Calcd for C19H13NOS: C, 75.22; H, 4.32; N, 4.62; S, 10.57. Found: C, 75.39;
H, 4.50; N, 4.46; S, 10.81.
2-(3-Nitrophenyl)-4H-benzo[e][1,3]oxazine-4-thione (7b). Yellow powder; yield
88%, 0.250 g; mp 108-110 ꢀC; IR (KBr) (ꢀmax, cmꢂ1): 1650, 1591, 1522, 1339, 1316,
1
1290, 1248, 1108, 1054, 750; H NMR (400 MHz, CDCl3): dH 7.26 (d, 2H, J ¼ 8.0 Hz,
Ar-H), 7.34 (t, 1H, J ¼ 7.6 Hz, Ar-H), 7.48 (t, 2H, J ¼ 8.0 Hz, Ar-H), 7.76 (t, 1H,
J ¼ 8.0 Hz, Ar-H), 8.50-8.56 (m, 2H, Ar-H); 13C NMR (100 MHz, CDCl3): dC 121.5,
122.9, 125.1, 126.6, 126.9, 128.0, 129.7, 129.9, 131.4, 135.8, 148.4, 150.5, 163.1,
199.6; MS (m/z, %): 284 (Mþ, 19).
Anal. Calcd for C14H8N2O3S: C, 59.15; H, 2.84; N, 9.85; S, 11.28. Found: C,
59.37; H, 3.04; N, 9.89; S, 11.51.
2-(3,5-Dinitrophenyl)-4H-benzo[e][1,3]oxazine-4-thione (7c). Yellow powder;
yield 87%, 0.286 g; mp 130-131 ꢀC; IR (KBr) (ꢀmax, cmꢂ1): 1657, 1593, 1542, 1333,
1
1311, 1292, 1267, 1136, 1065, 756; H NMR (400 MHz, CDCl3): dH 7.27-7.29 (m, 2H,
Ar-H), 7.35-7.39 (m, 1H, Ar-H), 7.48-7.50 (m, 2H, Ar-H), 7.79 (d, 1H, J ¼ 7.6 Hz, Ar-
H), 8.52-8.55 (m, 1H, Ar-H); 13C NMR (100 MHz, CDCl3): dC 121.4, 122.9, 126.9,
128.7, 129.8, 129.9, 130.7, 131.4, 131.9, 133.3, 148.8, 150.1, 161.2, 198.4; MS (m/z,
%): 329 (Mþ, 7).
Anal. Calcd for C14H7N3O5S: C, 51.06; H, 2.14; N, 12.76; S, 9.74. Found: C,
51.39; H, 2.03; N, 12.83; S, 9.93.
2-(4-Bromophenyl)-4H-benzo[e][1,3]oxazine-4-thione (7d). Yellow powder; yield
90%, 0.286 g; mp 146-148 ꢀC; IR (KBr) (ꢀmax, cmꢂ1): 1660, 1584, 1384, 1277, 1220,
1
1195, 1072, 743; H NMR (400 MHz, CDCl3): dH 7.22-7.24 (m, 1H, Ar-H),7.28-7.33
(m, 1H, Ar-H),7.44-7.48 (m, 2H, Ar-H),7.66-7.70 (m, 2H, Ar-H),8.07-8.10 (m, 2H, Ar-

430
Mohebat et al.
H); 13C NMR (100 MHz, CDCl3): dC 121.5, 121.6, 126.0, 128.4, 128.8, 129.5, 131.6,
131.8, 131.9, 135.4, 147.7, 150.7, 164.5, 199.2; MS (m/z, %): 318 (Mþ, 15).
Anal. Calcd for C14H8BrNOS: C, 52.85; H, 2.53; N, 4.40; S, 10.08. Found: C,
53.07; H, 2.25; N, 4.14;S, 10.27.
Acknowledgment
We gratefully acknowledge financial support from the Research Council of the Islamic
Azad University of Yazd.
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