An expedient route to highly functionalized 2H-chromene-2-thiones via ring annulation of β-oxodithioesters catalyzed by InCl3 under solvent-free conditions

Article abstract of DOI:10.1016/j.tet.2010.11.055

A convenient and one-pot synthesis of 3-aroyl/heteroaroyl-2H-chromene-2- thiones and benzo[f]2H-chromene-2-thiones has been developed by the condensation of β-oxodithioesters and salicylaldehydes/α-hydroxynaphthaldehydes in the presence of indium trichlor

Full text of DOI:10.1016/j.tet.2010.11.055

Tetrahedron 67 (2011) 584e589
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journal homepage: www.elsevier.com/locate/tet
An expedient route to highly functionalized 2H-chromene-2-thiones via ring
annulation of
b-oxodithioesters catalyzed by InCl3 under solvent-free conditions
*
Rajiv Kumar Verma, Girijesh K. Verma, Keshav Raghuvanshi, Maya Shankar Singh
Department of Chemistry, Faculty of Science, Banaras Hindu University, Varanasi 221005, India
a r t i c l e i n f o
a b s t r a c t
Article history:
A convenient and one-pot synthesis of 3-aroyl/heteroaroyl-2H-chromene-2-thiones and benzo[f]2H-
Received 23 September 2010
Received in revised form 9 November 2010
Accepted 16 November 2010
Available online 20 November 2010
chromene-2-thiones has been developed by the condensation of
b-oxodithioesters and salicylaldehydes/
a-hydroxynaphthaldehydes in the presence of indium trichloride under solvent-free conditions. The
reaction is operationally facile, readily scalable, and offers rapid entry into differentially substituted
chromene-2-thione scaffolds.
Ó 2010 Elsevier Ltd. All rights reserved.
Keywords:
3-Substituted-2H-chromene-2-thiones
Benzo[f]2H-chromene-2-thiones
b-Oxodithioesters
Indium trichloride
Solvent-free condition
1. Introduction
chromene-2-thiones and benzo[f]2H-chromene-2-thiones via ring
annulation of b-oxodithioesters.
Coumarins (2H-chromene-2-ones) are among the best known
oxygen heterocycles and are present as a structural motif in nu-
merous natural products including edible vegetables and fruits.1
Thus, interest in their chemistry continues unabated because of
the broad range of biological activity displayed by this class of
compounds.2 Because of the great relevance to both synthetic and
medicinal chemists, and diverse pharmacological properties of
coumarins, several elegant strategies3 for their synthesis involving
different types of catalysts have been developed.4 However, the
reports5 on the synthesis of chromene-2-thiones are limited and
suffer with many drawbacks, such as limitation of applicable
2. Results and discussion
A careful survey of literature at this stage revealed that b-oxo-
dithioesters 3 have been utilized as an unprecedented substrate for
the synthesis of chromene-2-thiones by Singh et al.5 We therefore
became interested in devising more general synthetic strategy
utilizing
construction of chromene-2-thiones 5 (Scheme 4). To further add
diversity to coumarin motif, the -oxodithioesters 3 were also
b-oxodithioesters 3 as the versatile templates for the
b
subjected to ring annulation with 2-hydroxy-1-naphthaldehyde 7
to afford benzo[f]2H-chromene-2-thiones 8 in good yields (Scheme
4). The new methodology allows facile introduction of substituents
at 3-position of chromene-2-thiones and flexibility for the con-
struction of novel benzo[f]2H-chromene-2-thione frameworks. The
b-ketoesters, expensive catalysts, harsh reaction conditions, multi-
step synthesis or low chemical yield, and lacking generality.
Recently, indium trichloride has emerged as a powerful Lewis
acid catalyst imparting high regio- and chemo-selectivity in various
chemical transformations,6 due to its low toxicity, air and water
compatibility, operational simplicity, and remarkable ability to
suppress side reactions in acid sensitive substrates. In continuation
of our interest in designing various heterocycles7 by the de-
velopment of new methodology, we report here remarkable cata-
lytic activity of InCl3 in the presence of urea under solvent-free
conditions for the facile synthesis of highly functionalized 2H-
desired
b
-oxodithioesters8 3 have been prepared in good yields
(Table 1) by stirring ketones 1 with dimethyl trithiocarbonate 2 in
the presence of sodium hydride in DMF/hexane (1:4) solvent
mixture at room temperature (Scheme 1).
Our initial attempts to synthesize chromene-2-thione, involving
the reaction of methyl-3-hydroxy-3-(p-methoxyphenyl)-prop-2-ene-
dithioate 3a and salicylaldehyde 4a in the presence of InCl3 (20 mol %)
at 100 ꢀC under solvent-free condition (Scheme 2) furnished the de-
sired chromene-2-thione 5a in very low yield, and surprisingly 3-
substituted coumarin 6a was formed as a major product (Table 2, entry
1). In order to confirm this observation, we carried out a series of
* Corresponding author. Fax: þ91 542 2368127; e-mail address: mssinghbhu@
yahoo.co.in (M.S. Singh).
0040-4020/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2010.11.055

R.K. Verma et al. / Tetrahedron 67 (2011) 584e589
p-MeO.C6H4
585
Table 1
Synthesis of
p-MeO.C6H4
p-MeO.C6H4
OHC
b
-oxodithioesters (3aeg)
O
InCl3 (20 mol%)
Urea, 100
solvent-free
O
O
+
+
Entry
Ar
Mp (ꢀC)
Yielda (%)
C
HO
MeS
S
O
O
O
S
3a
3b
3c
3d
3e
3f
4-MeO$C6H4
4-Me$C6H4
2-Furyl
74e75
54e55
51e52
49e50
72e73
73
68
70
80
75
72
45
4a
, trace
6a
3a
5a, 92%
Scheme 3. Synthesis of 2H-chromene-2-thiones in presence of urea.
2-Thienyl
4-Cl$C6H4
C6H5
after 6 h of heating. After prolonged heating (24 h) the b-oxodi-
57e58
103e104
thioester decomposed extensively (monitored by TLC). Based on
the above observations, it may be concluded that InCl3 is acting as
catalyst and urea as promoter. Thus, a more concise approach was
exploited by carrying out the above model reaction in the presence
of urea (1.2 equiv) under similar condition resulting 5 in excellent
yields (Table 4). Though, the roles of urea in these transformations
in not very clear, higher yields of chromene-2-thiones 5 were
obtained in the presence of urea, which probably inhibits the hy-
drolysis of chromene-2-thione.
3g
h
5-Ferrocenyl
a
Yield of isolated pure product.
O
S
O
S
NaH
+
SMe
Ar
CH3
Ar
MeS SMe DMF / n-hexane
3
2
stir, RT, 2-3 h
1
Scheme 1. Synthesis of
b
-oxodithioesters.
In order to evaluate the most appropriate catalyst and its loading,
the above model reactionwas performed utilizing different catalysts
with varying loading percentages under different solvents and sol-
vent-free conditions (Table 3). After optimization, 20 mol % of InCl3
under solvent-free condition was found to be effective for the
progress of the reaction (Table 3, entry 3). Higher percentage loading
of the InCl3 did not increase the yield but lowered the reaction time
slightly (Table 3, entry 4). The effect of temperature was also studied
and the optimum temperature of the reaction was found to be
100 ꢀC, whereas lowering the temperature are detrimental to the
reaction resulting in lower yields and long reaction time.
Ar
O
Ar
Ar
S
R1
OHC
R1
R1
InCl3 (20 mol%)
O
O
+
+
°
100
C
O
S
HO
O
O
MeS
R2
R2
R2
solvent-free
3
4
5
6
Scheme 2. Reaction of b-oxodithioesters (3) with salicylaldehydes (4) in the absence
of urea.
Table 2
Reaction of
b-oxodithioesters (3) with salicylaldehydes (4)
Table 3
R1
R2
Products 5, 6 Yielda (%)
Optimization of the catalyst on model reactiona
Entry
Ar
1
2
3
4
5
6
7
4-MeO$C6H4
4-MeO$C6H4
4-MeO$C6H4
4-Me$C6H4
4-Me$C6H4
4-Cl$C6H4
C6H5
H
H
Br
H
NO2
H
H
OMe
H
H
H
5a (15)
5b (20)
5c (35)
5e (12)
5g (10)
5m (16)
5p (10)
6a (70)
6b (72)
6c (55)
6e (72)
6g (68)
6m (65)
6p (75)
Entry
Catalyst
Loading (mol %)
Solvent
Time (h)
Yieldb (%)
1
2
3
4
5
6
7
8
InCl3
InCl3
InCl3
InCl3
InCl3
InCl3
InCl3
SbCl3
SbCl3
SbCl3
SbCl3
PTA
10
15
20
25
20
20
20
15
20
25
20
5
Solvent-free
Solvent-free
Solvent-free
Solvent-free
CH3CN
EtOH
THF
Solvent-free
Solvent-free
Solvent-free
CH3CN
4
3
65
82
92
90
2.5
2.0
24
24
24
3.5
2.5
2.0
24
24
6
H
H
55
H
Trace
Trace
58
65
68
Trace
NRc
35
a
Yield of isolated pure product.
9
10
11
12
13
reaction using different b-oxodithioesters 3 and various salicylalde-
hydes 4, which provided corresponding chromene-2-ones 6 as the
major products (65e75%) along with respective chromene-2-thiones 5
as the minor ones (10e20%) except in the case of 5-bromosalicy-
laldehyde, where both 5 and 6 were obtained in moderate yields (Table
2, entry 3). The results are summarized in Table 2. The chromene-2-
ones 6 were characterized by comparing the physical, spectral, and
analytical data with the previous reports.9
CH3CN
Solvent-free
PTA
5
a
Reaction of methyl-3-hydroxy-3-(p-methoxyphenyl)-prop-2-enedithioate
(1 mmol), salicylaldehyde (1.2 mmol), and urea (1.2 mmol) under solvent-free
condition at 100 ꢀC and in solvents at its reflux temperature.
b
Isolated yields.
No reaction.
c
Then, we decided to perform the above reaction in the presence
of urea as per previous reports.5 Initially, the reaction of
b-oxodi-
To generate a small library of functionalized 3-substituted
thioester 3a (1.0 mmol) and salicylaldehyde 4a (1.2 mmol) as
a model reaction was performed in the presence of both InCl3 as
well as urea (20 mol % each) at 100 ꢀC under solvent-free condition
yielding both chromene-2-thione 5a (65%) and chromene-2-one 6a
(30%). The significant increase in the yield of 5a in the presence of
urea clearly indicates that somehow it prevents the formation of 6.
In order to further enhance the yield of chromene-2-thione 5a, we
carried out the above model reaction using equivalent amount of
urea. To our delight, chromene-2-thione 5a was formed as exclu-
sive product with trace of chromene-2-one 6a (Scheme 3). In order
to check the real effect of urea in the above cyclocondensation re-
chromene-2-thiones 5 using the optimized reaction condition, we
next utilized a variety of b-oxodithioesters 3 and salicylaldehydes 4
to explore the scope of this one-pot cyclocondensation reaction
(Scheme 4). A number of functional groups, such as bromo, nitro,
methoxy, and ethoxy in the salicylaldehyde component, and aryl, 2-
thienyl, 2-furyl, and
h b-position of the b-oxo-
5-ferrocenyl at the
dithioester are tolerated well under the reaction conditions to
provide structurally interesting chromene-2-thiones 5 in excellent
yields (Table 4). To further demonstrate the scope, and to explore
the limitations and generality of the reaction, the procedure was
extended to 2-hydroxy-1-naphthaldehyde 7 as cyclocondensation
action, a test reaction using b-oxodithioester 3a and salicylalde-
partner. Compound 7 was reacted with various b-oxodithioesters 3
hyde 4a was performed in the absence of InCl3 at 100 ꢀC under
solvent-free conditions utilizing urea in catalytic (20 mol %) as well
as in equivalent amounts separately. It was found that no conver-
sion to product was obtained under above both conditions even
under similar reaction conditions to afford benzo[f]2H-chromene-
2-thiones 8 in high yields (Scheme 4, Table 4), except in the case of
methyl 3-(
afforded 8g in moderate yield (Table 4, entry 24).Given the range of
h
5-ferrocenyl)-3-hydroxyprop-2-enedithioate 3g, which

586
R.K. Verma et al. / Tetrahedron 67 (2011) 584e589
2-oyl)-6-bromo-2H-chromene-2-thione 5k allowed for its struc-
Ar
S
R1
CHO
OH
tural verification by X-ray crystallography10 and thus, unambiguous
regiochemical confirmation (Fig. 1).
R1
O
Ar
O
R2
4
R2
3. Conclusion
5
InCl3, Urea
SF, 100
O
or
+
In conclusion, an efficient one-pot, ring annulation protocol for
MeS
S
C
or
Ar
a variety of chromene-2-thiones has been devised involving
b-
3
O
oxodithioesters under solvent-free conditions. To the best of our
knowledge, this is the first report of chromene-2-thione synthesis
via ring annulation using b-oxodithioesters as a C-2 synthon uti-
lizing InCl3 as catalyst. The advantages of this strategy are short
reaction time, high yields, mild reaction condition, easy purifica-
tion, and economic availability of the catalyst. A particularly at-
tractive feature of this approach is that depending on the structure
CHO
OH
O
S
8
7
Scheme 4. Synthesis of chromene-2-thiones.
of b-oxodithioesters, different substituents can be incorporated in
the 3-position. This method is suitable to library production, di-
versity-oriented synthesis, and drug discovery. Further studies to
Table 4
Synthesis of chromene-2-thiones
Entry Ar
R1
R2
Product Yielda (%)
extend the scope of b-oxodithioesters to diverse range of hetero-
1
2
3
4
5
6
7
8
4-MeO$C6H4
H
H
Br
NO2
H
H
NO2
H
H
OMe
H
H
H
OMe
H
H
OMe
H
H
OMe
H
OMe
OEt
H
5a
5b
5c
5d
5e
5f
92
92
90
80
90
89
78
94
90
95
85
82
87
92
88
86
60
75
72
80
76
73
75
50
cyclic compounds are in progress in our laboratory.
4. Experimental
4-MeO$C6H4
4-MeO$C6H4
4-MeO$C6H4
4-Me$C6H4
4-Me$C6H4
4-Me$C6H4
2-Furyl
4.1. General
5g
5h
5i
All the reagents were commercial and purchased from Merck,
Aldrich and Fluka and were used as received. All 1H and 13C NMR
spectra were recorded on JEOL AL 300 FT-NMR spectrometer.
9
2-Furyl
2-Furyl
H
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Br
Br
H
H
H
H
H
H
5j
5k
5l
2-Thienyl
2-Thienyl
4-Cl$C6H4
4-Cl$C6H4
C6H5
Chemical shifts are given as
d value with reference to tetrame-
5m
5n
5o
5p
5q
8a
8b
8c
8d
8e
8f
thylsilane (TMS) as the internal standard. The IR spectra were
recorded on Varian 3100 FT-IR spectrophotometer. Mass spectra
were recorded at 70 eV ionizing voltage on a JEOL-D300 MS in-
strument. The C and H analyses were performed from microana-
lytical laboratory with an Exeter Analytical Inc. ‘Model CE-400 CHN
Analyzer’. X-ray diffraction was measured on Xcalibur Oxford CCD
Diffractometer. All the reactions were monitored by TLC using
precoated sheets of silica gel G/UV-254 of 0.25 mm thickness
(Merck 60F254) using UV light (254 nm/365 nm) for visualization.
C6H5
h
5-Ferrocenyl
H
4-MeO$C6H4
4-Me$C6H4
2-Furyl
2-Thienyl
4-Cl$C6H4
C6H5
2-Hydroxy-1-naphthaldehyde
edoe
edoe
edoe
edoe
edoe
h
5-Ferrocenyl edoe
8g
€
Melting points were determined with Buchi B-540 melting point
a
Isolated pure yields in the presence of urea.
apparatus and are uncorrected.
4.2. General procedure for the synthesis of b-oxodithioesters
(3aeg)
commercially available components for this protocol (b-oxodi-
thioesters and salicylaldehydes), the method should prove valuable
in the preparation of combinatorial libraries of functionalized
coumarin motifs.
Appropriate aryl/heteroaryl ketone 1 (10 mmol) was added to
a suspension of NaH (60% suspension in mineral oil, 0.80 g,
20 mmol) in DMF/hexane solvent mixture (1:4, 30 mL). Dimethyl
trithiocarbonate 2 (10 mmol) was slowly added to the reaction
mixture and stirred well for 2 h (in the case of acetylferrocene,
the reaction mixture was refluxed for 3 h to get the product).
After completion of the reaction (monitored by TLC), the reaction
mixture was washed with hexane to remove unreacted ketone
and dimethyl trithiocarbonate. Reaction mixture was acidified
with 1 N HCl (20 mL) to get the dithioesters precipitated. The
precipitated dithioester was extracted with dichloromethane
(2ꢁ30 mL) followed by washing with brine (2ꢁ25 mL) and dried
over anhydrous sodium sulfate. The solvent was evaporated
under vacuum and the residue obtained was purified by column
chromatography over silica gel using hexane as eluent to give
The structures were confirmed by spectral (IR, 1H, 13C, and mass)
and analytical studies. The absence of nitrogen in the CHN analyses
gave us a clue to the structural elucidation of the respective hith-
erto unknown coumarins. Importantly, the crystallinity of 3-(thien-
the corresponding
b-oxodithioester in high yield. The spectral
and analytical data of the
below.
b-oxodithioesters 3aeg are given
4.2.1. Methyl 3-hydroxy-3-(p-methoxyphenyl)-prop-2-enedithioate
(3a). Yellow solid, mp 74e75 ꢀC. IR (KBr): 3430, 1603, 1582, 1545,
Fig. 1. Ortep diagram for 3-(thien-2-oyl)-6-bromo-2H-chromene-2-thione 5k.
1503, 1430, 1232, 1180, 1052 cmꢂ1 1H NMR (300 MHz, CDCl3):
.

R.K. Verma et al. / Tetrahedron 67 (2011) 584e589
587
d
15.16 (s, 1H, OH), 7.86 (d, J¼8.7 Hz, 2H, ArH), 6.94 (dþs, J¼8.7 Hz,
(1ꢁ20 mL) and dried over anhydrous Na2SO4. The solvent was evap-
oratedundervacuumtogivetheproduct, whichwas purified either by
recrystallization from ethyl acetate or by column chromatography
over silica gel using increasing amount of ethyl acetate in hexane.
The spectral and analytical data for the compounds 5aeq and
8aeg are given below.
3H, ArHþHOlefin), 3.87 (s, 3H, OCH3), 2.65 (s, 3H, SCH3). 13C NMR
(75 MHz, CDCl3): d 215.5, 169.4, 162.7, 128.6, 126.1, 114.1, 107.0, 55.4,
16.9. FABMS (m/z): 241 (Mþþ1). Anal. Calcd for C11H12O2S2: C,
54.97%; H, 5.03%. Found: C, 54.88%; H, 4.91%.
4.2.2. Methyl 3-hydroxy-3-(p-methylphenyl)-prop-2-enedithioate (3b).
Yellow solid, mp 54e55 ꢀC. IR (KBr): 3382, 1654, 1584, 1560, 1529,
4.3.1. 3-(4-Methoxybenzoyl)-2H-chromene-2-thione
solid, mp 188e190 ꢀC. IR (KBr): 3058, 2928, 1657, 1600, 1559, 1257,
1170 cmꢂ1. 1H NMR (300 MHz, CDCl3):
(5a). Yellow
1502, 1456, 1421, 1236, 1184 cmꢂ1 1H NMR (300 MHz, CDCl3):
.
d
15.09 (s, 1H, OH), 7.77 (d, J¼8.1 Hz, 2H, ArH), 7.24 (d, J¼8.1 Hz, 2H,
d
7.91 (d, J¼8.7 Hz, 2H, ArH),
ArH), 6.94 (s, 1H, HOlefin), 2.65 (s, 3H, SCH3), 2.40 (s, 3H, ArCH3). 13
C
7.68e7.63 (m, 2H, ArH), 7.57 (s, 1H, ArH), 7.52 (d, J¼8.4 Hz, 1H, ArH),
7.39e7.34 (m, 1H, ArH), 6.93 (d, J¼8.7 Hz, 2H, ArH), 3.87 (s, 3H,
NMR (75 MHz, CDCl3): d 216.5,169.6, 142.6,131.5,129.4, 126.7, 107.5,
21.7, 17.0. FABMS (m/z): 225 (Mþþ1). Anal. Calcd for C11H12OS2: C,
OCH3). 13C NMR (75 MHz, CDCl3):
d 193.7, 190.8, 164.2, 156.9, 139.5,
58.89%; H, 5.39%. Found: C, 58.99%; H, 5.44%.
133.1,133.0,132.1,128.6,128.4,125.7,119.9,116.6,114.0, 55.5. FABMS
(m/z): 297 (Mþþ1). Anal. Calcd for C17H12O3S: C, 68.90%; H, 4.08%.
Found: C, 68.99%; H, 4.28%.
4.2.3. Methyl 3-(furan-2-yl)-3-hydroxyprop-2-enedithioate (3c).
Yellow solid, mp 51e52 ꢀC. IR (KBr): 3058, 3009, 1666, 1592, 1251
cmꢂ1.1H NMR (300 MHz, CDCl3):
d
14.69 (s,1H, OH), 7.57 (s,1H, ArH),
4.3.2. 3-(4-Methoxybenzoyl)-8-methoxy-2H-chromene-2-thione
7.13 (d, J¼3.6 Hz, 1H, ArH), 6.92 (s, 1H, HOlefin), 6.56 (s, 1H, ArH), 2.64
(5b). Yellow solid, mp 141e143 ꢀC. IR (KBr): 3064, 2925, 1648, 1597,
(s, 3H, SCH3). 13C NMR (75 MHz, CDCl3):
d
216.6, 159.1, 148.5, 145.6,
1547, 1267, 1172 cmꢂ1 1H NMR (300 MHz, CDCl3):
. d 7.90 (d,
115.1, 112.7, 106.3, 17.0. FABMS (m/z): 201 (Mþþ1). Anal. Calcd for
J¼8.7 Hz, 2H, ArH), 7.54 (s, 1H, ArH), 7.27 (d, J¼8.4 Hz, 1H, ArH),
C8H8O2S2: C, 47.98%; H, 4.03%. Found: C, 47.92%; H, 4.10%.
7.17e7.10 (m, 2H, ArH), 6.92 (d, J¼8.7 Hz, 2H, ArH), 4.01 (s, 3H,
OCH3), 3.87 (s, 3H, OCH3). 13C NMR (75 MHz, CDCl3):
d 192.9, 190.8,
4.2.4. Methyl 3-hydroxy-3-(thiophen-2-yl)-prop-2-enedithioate (3d).
Yellow solid, mp 49e50 ꢀC. IR (KBr): 3058, 3009, 1666, 1592, 1251
164.2, 146.9, 146.7, 139.7, 133.2, 132.1, 128.5, 125.7, 120.7, 119.5, 114.4,
114.0, 56.2, 55.5. FABMS (m/z): 327 (Mþþ1). Anal. Calcd for
C18H14O4S: C, 66.24%; H, 4.32%. Found: C, 66.37%; H, 4.21%.
cmꢂ1 1H NMR (300 MHz, CDCl3):
. d 15.04 (s, 1H, OH), 7.73 (d,
J¼3.3 Hz, 1H, ArH), 7.56 (d, J¼4.8 Hz, 1H, ArH), 7.12 (dd, J¼4.5, 4.2 Hz,
1H, ArH), 6.86 (s, 1H, HOlefin), 2.65 (s, 3H, SCH3). 13C NMR (75 MHz,
4.3.3. 6-Bromo-3-(4-methoxybenzoyl)-2H-chromene-2-thione
CDCl3):
d
215.6, 164.0, 138.3, 130.9, 129.2, 128.3, 106.9, 16.9. FABMS
(5c). Yellow solid, mp 207e208 ꢀC. IR (KBr): 3050, 2921, 1659, 1601,
(m/z): 217 (Mþþ1). Anal. Calcd for C8H8OS3: C, 44.41%; H, 3.73%.
1553, 1261, 1234, 1174 cmꢂ1. 1H NMR (300 MHz, CDCl3):
d 7.89 (d,
Found: C, 44.52%; H, 3.61%.
J¼9.0 Hz, 2H, ArH), 7.74e7.70 (m, 2H, ArH), 7.46 (s, 1H, ArH), 7.40 (d,
J¼8.7 Hz, 1H, ArH), 6.94 (d, J¼9.0, 2H, ArH), 3.88 (s, 3H, OCH3). 13
C
4.2.5. Methyl 3-(p-chlorophenyl)-3-hydroxyprop-2-enedithioate (3e).
Yellow solid, mp 72e73 ꢀC. IR (KBr): 3429, 2922, 1591, 1555, 1485,
NMR (75 MHz, CDCl3): d 193.0, 190.3, 164.5, 155.7, 140.4, 135.7,
132.2, 131.3, 130.5, 128.3, 121.5, 118.5, 118.3, 114.2, 55.6. FABMS (m/
z): 377 (Mþþ2). Anal. Calcd for C17H11BrO3S: C, 54.41%; H, 2.95%.
Found: C, 54.53%; H, 3.09%.
1415, 1229, 1092 cmꢂ1. 1H NMR (300 MHz, CDCl3):
d
15.04 (s, 1H, OH),
7.81 (d, J¼8.7 Hz, 2H, ArH), 7.41 (d, J¼8.7 Hz, 2H, ArH), 6.89 (s, 1H,
Holefin), 2.66 (s, 3H, SCH3). 13C NMR (75 MHz, CDCl3):
d 217.7, 167.6,
138.2, 132.9, 129.0, 128.1, 107.6, 17.3. FABMS (m/z): 245 (Mþþ1). Anal.
4.3.4. 3-(4-Methoxybenzoyl)-6-nitro-2H-chromene-2-thione
Calcd for C10H9ClOS2: C, 49.07%; H, 3.71%. Found: C, 49.14%; H, 3.59%.
(5d). Orange solid, mp 208e209 ꢀC. IR (KBr): 3752, 3066, 2926, 1654,
1601, 1535, 1240, 1151 cmꢂ1. 1H NMR (300 MHz, CDCl3):
d 8.48 (s, 1H,
4.2.6. Methyl 3-hydroxy-3-phenyl-prop-2-enedithioate (3f). Yellow
solid, mp 55e56 ꢀC. IR (KBr): 3731,1585,1559,1489,1451,1392,1298,
ArH), 8.46 (s, 1H, ArH), 7.89 (d, J¼8.7 Hz, 2H, ArH), 7.63e7.58 (m, 2H,
ArH), 6.95 (d, J¼8.7 Hz, 2H, ArH), 3.89 (s, 3H, OCH3). 13C NMR (75 MHz,
1236, 1055 cmꢂ1. 1H NMR (300 MHz, CDCl3):
d
15.08 (s, 1H, OH), 7.88
CDCl3): d 192.2, 189.6, 164.6, 159.3, 145.1, 144.6, 141.3, 132.1, 130.7,
(d, J¼6.9 Hz, 2H, ArH), 7.51e7.44 (m, 3H, ArH), 6.96 (s, 1H, Holefin),
127.9, 127.3, 123.9, 120.1, 117.6, 114.2, 55.6. FABMS (m/z): 342 (Mþþ1).
2.66 (s, 3H, SCH3). 13C NMR (75 MHz, CDCl3):
d
217.3, 169.4, 134.2,
HRMS (ESIþ) Calcd for C17H11NO5S: 341.0357. Found: 341.0346.
132.0, 128.7, 126.8, 108.0, 17.2. FABMS (m/z): 211 (Mþþ1). Anal. Calcd
for C10H10OS2: C, 57.11%; H, 4.79%. Found: C, 57.14%; H, 4.69%.
4.3.5. 3-(4-Methylbenzoyl)-2H-chromene-2-thione
solid, mp 171e172 ꢀC. IR (KBr): 3041, 2922, 1660, 1604, 1556, 1239,
1164 cmꢂ1. 1H NMR (300 MHz, CDCl3):
7.83 (d, J¼8.1 Hz, 2H, ArH),
7.68e7.51 (m, 4H, ArH), 7.39e7.37 (m, 1H, ArH), 7.26 (d, J¼8.1 Hz,
2H, ArH), 2.42 (s, 3H, ArCH3). 13C NMR (75 MHz, CDCl3):
193.7,
(5e). Yellow
4.2.7. Methyl
(3g). Violet solid, mp 103e104 ꢀC. IR (KBr): 2974, 1599, 1559, 1482,
1392, 1055, 761 cmꢂ1. 1H NMR (300 MHz, CDCl3):
15.05 (s, 1H, OH),
6.60 (s,1H, HOlefin), 4.81 (d, J¼1.8 Hz, 2H, HCp), 4.54 (d, J¼1.5 Hz, 2H, HCp),
3-(h
5-ferrocenyl)-3-hydroxyprop-2-enedithioate
d
d
d
192.0, 157.1, 145.2, 139.3, 133.0, 129.9, 129.4, 128.5, 125.9, 125.6,
120.0, 116.5, 21.8. FABMS (m/z): 281 (Mþþ1). Anal. Calcd for
C17H12O2S: C, 72.83%; H, 4.31%. Found: C, 72.91%; H, 4.29%.
4.22 (s, 5H, HCp), 2.62 (s, 3H, SCH3). 13C NMR (75 MHz, CDCl3):
d 212.2,
176.3,107.4, 72.0, 70.4, 70.1, 68.0,16.6. FABMS (m/z): 318 (Mþþ1). Anal.
Calcd for C14H14FeOS2: C, 52.84%; H, 4.43%. Found: C, 52.99%; H, 4.58%.
4.3.6. 3-(4-Methylbenzoyl)-8-methoxy-2H-chromene-2-thione
4.3. General procedure for the synthesis of 2H-chromene-2-
thiones (5) and benzo[f]2H-chromene-2-thiones (8)
(5f). Yellow solid, mp 164e165 ꢀC. IR (KBr): 3054, 2961, 2922, 1658,
1604, 1564, 1241, 1158 cmꢂ1. 1H NMR (300 MHz, CDCl3):
d
7.82 (d,
J¼8.1 Hz, 2H, ArH), 7.55 (s, 1H, ArH), 7.18e7.11 (m, 5H, ArH), 4.01 (s,
3H, OCH3), 2.41 (s, 3H, ArCH3). 13C NMR (75 MHz, CDCl3):
193.0,
A mixture of
b-oxodithioester 3 (1.0 mmol), substituted salicy-
d
laldehyde 4 (or 2-hydroxy-1-naphthaldehyde 7) (1.2 mmol), and urea
(1.2 mmol) was reacted in the presence of InCl3 (20 mol %, 0.2 mmol,
0.044g)withconstantstirringat100ꢀC.Theheatingwascontinuedtill
the completion of the reaction (2e3 h, monitoredbyTLC). Thereaction
mixture was treated with water (20 mL) and extracted with ethyl
acetate (2ꢁ20 mL). The organic layer was washed with brine
192.1, 146.9, 145.0, 139.9, 133.5, 133.1, 129.8, 129.6, 126.0, 120.9,
119.3, 114.5, 56.4, 21.9. FABMS (m/z): 311 (Mþþ1). Anal. Calcd for
C18H14O3S: C, 69.66%; H, 4.55%. Found: C, 69.81%; H, 4.25%.
4.3.7. 3-(4-Methylbenzoyl)-6-nitro-2H-chromene-2-thione
(5g). Yellow solid, mp 233e234 ꢀC. IR (KBr): 3722, 1662, 1606, 1547,

588
R.K. Verma et al. / Tetrahedron 67 (2011) 584e589
1290, 1151 cmꢂ1
ArH), 7.82 (d, J¼8.1 Hz, 2H, ArH), 7.63e7.59 (m, 2H, ArH), 7.29e7.25
(m, 2H, ArH), 2.43 (s, 3H, ArCH3). 13C NMR (75 MHz, CDCl3):
192.1,
190.7, 159.3, 145.7, 144.6, 141.2, 132.5, 130.9, 129.8, 129.6, 127.4,
123.9, 120.1, 117.6, 21.8. FABMS (m/z): 326 (Mþþ1). Anal. Calcd for
C17H11NO4S: C, 62.76%; H, 3.41%; N, 4.31%. Found: C, 62.55%; H,
3.25%; N, 4.45%.
.
1H NMR (300 MHz, CDCl3):
d
8.49e8.47 (m, 2H,
7.30e7.25 (m, 1H, ArH), 7.20e7.15 (m, 2H, ArH), 4.02 (s, 3H, OCH3).
13C NMR (75 MHz, CDCl3):
192.7, 191.3, 147.1, 146.5, 140.3, 138.9,
134.2, 134.1, 131.0, 129.2, 126.0, 120.7, 119.9, 114.5, 56.3. FABMS (m/
z): 331 (Mþþ1). Anal. Calcd for C17H11ClO3S: C, 61.73%; H, 3.35%.
Found: C, 61.61%; H, 3.39%.
d
d
4.3.15. 3-Benzoyl-8-ethoxy-2H-chromene-2-thione
solid, mp 164e165 ꢀC. IR (KBr): 2924, 2855, 1661, 1564, 1459, 1235,
1166 cmꢂ1. 1H NMR (300 MHz, CDCl3):
(5o). Orange
4.3.8. 3-(Furan-2-oyl)-2H-chromene-2-thione (5h). Orange crys-
tals, mp 164e165 ꢀC. IR (KBr): 3118, 2923, 1657, 1604, 1557, 1465,
d
7.93 (d, J¼7.2 Hz, 2H, ArH),
7.57 (s, 2H, ArH), 7.45 (t, 2H, ArH), 7.26 (d, J¼6.3 Hz, 1H, ArH),
1252, 1173 cmꢂ1 1H NMR (300 MHz, CDCl3):
. d 7.67e7.50 (m, 5H,
7.18e7.10 (m, 2H, ArH), 4.25 (q, 2H, OCH2),1.53 (t, 3H, CH3). 13C NMR
ArH), 7.39e7.26 (m, 2H, ArH), 6.59 (dd, J¼1.2, 2.1 Hz, 1H, ArH). 13C
(75 MHz, CDCl3): d 192.9, 192.3, 147.2, 146.1, 139.4, 135.7, 133.8,
NMR (75 MHz, CDCl3):
d
193.2, 179.5, 157.0, 151.7, 147.5, 138.0, 133.6,
133.7, 129.5, 128.6, 125.7, 120.7, 119.5, 115.8, 65.1, 14.6. FABMS (m/z):
311 (Mþþ1). Anal. Calcd for C18H14O3S: C, 69.66%; H, 4.55%. Found:
C, 69.75%; H, 4.51%.
133.3, 128.6, 125.8, 120.1, 119.7, 116.6, 112.8. FABMS (m/z): 257
(Mþþ1). Anal. Calcd for C14H8O3S: C, 65.61%; H, 3.15%. Found: C,
65.55%; H, 3.35%.
4.3.16. 3-Benzoyl-2H-chromene-2-thione (5p). Yellow solid, mp
4.3.9. 3-(Furan-2-oyl)-8-methoxy-2H-chromene-2-thione
171e172 ꢀC. IR (KBr): 3060, 2924, 1663, 1602, 1555, 1243, 1166 cmꢂ1
.
(5i). Orange crystals, mp 169e170 ꢀC. IR (KBr): 2928, 1657, 1600,
1H NMR (300 MHz, CDCl3):
8H, ArH). 13C NMR (75 MHz, CDCl3):
d
d
7.95e7.92 (m, 2H, ArH), 7.67e7.25 (m,
193.6, 192.3, 157.0, 139.0,
1559, 1257, 1170 cmꢂ1
.
1H NMR (300 MHz, CDCl3):
d
7.61 (d,
J¼6.3 Hz, 1H, ArH), 7.59 (s, 1H, ArH), 7.29e7.11 (m, 4H, ArH), 6.57
135.6, 133.9, 133.7, 133.2, 129.6, 128.7, 128.5, 125.9, 120.0, 116.7.
FABMS (m/z): 267 (Mþþ1). Anal. Calcd for C16H10O2S: C, 72.16%; H,
3.78%. Found: C, 72.29%; H, 3.59%.
(dd, J¼1.5, 1.8 Hz, 1H, ArH), 4.01 (s, 3H, OCH3). 13C NMR (75 MHz,
CDCl3):
d 192.5, 179.6, 151.7, 147.5, 146.7, 138.3, 133.7, 125.7, 120.4,
120.1, 119.6, 114.7, 112.8, 56.3. FABMS (m/z): 287 (Mþþ1). Anal.
Calcd for C15H10O4S: C, 62.93%; H, 3.52%. Found: C, 62.69%; H, 3.31%.
4.3.17. 3-
mp 250e252 ꢀC (decomp.). IR (KBr): 3090, 2927, 1727, 1635, 1447,
1363, 1264, 1170 cmꢂ1 1H NMR (300 MHz, CDCl3):
7.96 (s, 1H,
h
5-Ferrocenoyl-2H-chromene-2-thione (5q). Violet solid,
4.3.10. 3-(Furan-2-oyl)-6-bromo-2H-chromene-2-thione
.
d
(5j). Yellow crystals, mp 198e199 ꢀC. IR (KBr): 3119, 1639, 1552,
ArH), 7.63e7.57 (m, 2H, ArH), 7.41e7.25 (m, 2H, ArH), 4.86 (br s, 2H,
1460, 1363, 1240, 1174 cmꢂ1. 1H NMR (300 MHz, CDCl3):
d
7.75e7.70
Hcp), 4.64 (br s, 2H, Hcp), 4.29 (s, 5H, Hcp). 13C NMR (75 MHz, CDCl3):
(m, 2H, ArH), 7.63 (s,1H, ArH), 7.51 (s,1H, ArH), 7.38 (d, J¼8.7 Hz,1H,
d 193.8, 192.3, 141.7, 135.6, 133.9, 133.7, 129.6, 128.7, 125.9, 116.7,
ArH), 7.28 (d, J¼3.3 Hz, 1H, ArH), 6.60e6.59 (m, 1H, ArH). 13C NMR
82.3, 73.4, 70.9, 70.4. FABMS (m/z): 375 (Mþþ1). Anal. Calcd for
(75 MHz, CDCl3):
d
192.4,179.0,155.7,151.5,147.6,138.8,135.9,131.7,
C20H14FeO2S: C, 64.19%; H, 3.77%. Found: C, 64.35%; H, 3.51%.
130.6, 121.2, 120.2, 118.4, 118.2, 112.9. FABMS (m/z): 337 (Mþþ2).
HRMS (ESIþ) Calcd for C14H7BrO3S: 333.9299. Found 333.9210.
4.3.18. 3-(4-Methoxybenzoyl)-benzo[f]2H-chromene-2-thione
(8a). Yellow solid, mp 246e247 ꢀC. IR (KBr): 1662, 1596, 1547, 1259,
4.3.11. 3-(Thien-2-oyl)-6-bromo-2H-chromene-2-thione
1203 cmꢂ1. 1H NMR (300 MHz, CDCl3):
d 8.34 (s, 1H, ArH), 8.23 (d,
(5k). Yellow crystal, mp 202e203 ꢀC. IR (KBr): 3054, 2923, 1639,
J¼8.1 Hz, 1H, ArH), 8.11 (d, J¼9.0 Hz, 1H, ArH), 7.96 (d, J¼8.4 Hz, 3H,
1601, 1549, 1236, 1162 cmꢂ1. 1H NMR (300 MHz, CDCl3):
d 7.77e7.69
ArH), 7.74e7.63 (m, 3H, ArH), 6.95 (d, J¼8.7 Hz, 2H, ArH), 3.88 (s, 3H,
(m, 3H, ArH), 7.64 (d, J¼3.3 Hz, 1H, ArH), 7.50 (s, 1H, ArH), 7.39 (d,
OCH3). 13C NMR (75 MHz, CDCl3):
d 192.6, 191.2, 164.3, 157.6, 141.0,
J¼8.7 Hz, 1H, ArH), 7.13 (t, 1H, ArH). 13C NMR (75 MHz, CDCl3):
139.1, 135.0, 134.5, 132.2, 130.6, 129.5, 129.2, 128.9, 128.6, 127.0, 121.6,
116.4, 115.2, 114.0, 113.8, 55.5. FABMS (m/z): 347 (Mþþ1). Anal. Calcd
for C21H14O3S: C, 72.81%; H, 4.07%. Found: C, 72.59%; H, 3.92%.
d
192.4, 183.7, 155.7, 142.5, 139.6, 135.9, 135.1, 131.2, 131.1, 130.6,
128.4, 121.2, 118.5, 118.2. FABMS (m/z): 353 (Mþþ2). Anal. Calcd for
C14H7BrO2S2: C, 47.87%; H, 2.01%. Found: C, 47.63%; H, 2.32%.
4.3.19. 3-(4-Methylbenzoyl)-benzo[f]2H-chromene-2-thione
4.3.12. 3-(Thien-2-oyl)-8-methoxy-2H-chromene-2-thione
(8b). Yellow solid, mp 264e265 ꢀC. IR (KBr): 2925, 1654, 1603,
(5l). Yellow solid, mp 167e168 ꢀC. IR (KBr): 3025, 1632, 1602, 1549,
1395, 1201, 790 cmꢂ1. 1H NMR (300 MHz, CDCl3):
d 8.36 (s, 1H, ArH),
1405,1234,1158 cmꢂ1. 1H NMR (300 MHz, CDCl3):
d
7.74 (d, J¼4.5 Hz,
8.24 (d, J¼8.1 Hz, 1H, ArH), 8.11 (d, J¼9.3 Hz, 1H, ArH), 7.96 (d,
J¼8.1 Hz, 1H, ArH), 7.89 (d, J¼8.1 Hz, 2H, ArH), 7.75e7.61 (m, 3H,
ArH), 7.27 (d, J¼10.8 Hz, 2H, ArH), 2.43 (s, 3H, ArCH3). 13C NMR
1H, ArH), 7.65 (d, J¼3.3 Hz, 1H, ArH), 7.57 (s, 1H, ArH), 7.31e7.25 (m,
1H, ArH), 7.18e7.10 (m, 3H, ArH), 4.01 (s, 3H, OCH3). 13C NMR
(75 MHz, CDCl3):
d
192.6, 184.9, 146.2, 144.2, 143.1, 138.5, 135.6, 134.9,
(75 MHz, CDCl3): d 192.6, 192.3, 157.0, 145.1, 139.1, 134.6, 133.2,
127.9, 125.0, 121.2, 120.1, 119.7, 111.5, 56.1. FABMS (m/z): 303 (Mþþ1).
130.6, 129.9, 129.7, 129.5, 129.2, 128.9, 128.8, 127.0, 121.6, 116.5,
115.2, 21.8. FABMS (m/z): 331 (Mþþ1). HRMS (ESIþ) Calcd for
C21H14O2S: 330.0714. Found 330.0735.
HRMS (ESIþ) Calcd for C15H10O3S2: 302.0071. Found 302.0054.
4.3.13. 3-(4-Chlorobenzoyl)-2H-chromene-2-thione
crystals, mp 184e186 ꢀC. IR (KBr): 3093, 3045, 1663, 1611, 1233
cmꢂ1 1H NMR (300 MHz, CDCl3):
7.85 (d, J¼8.7 Hz, 2H, ArH),
7.72e7.60 (m, 3H, ArH), 7.54e7.51 (m, 1H, ArH), 7.42 (d, J¼8.4 Hz,
2H, ArH), 7.39e7.37 (m, 1H, ArH). 13C NMR (75 MHz, CDCl3):
193.5,
191.0, 157.2, 140.3, 138.8, 134.0, 133.5, 131.0, 129.2, 128.6, 126.1, 119.7,
116.6. FABMS (m/z): 301 (Mþþ1). Anal. Calcd for C16H9ClO2S: C,
63.90%; H, 3.02%. Found: C, 63.85%; H, 3.11%.
(5m). Yellow
4.3.20. 3-(Furan-2-oyl)-benzo[f]2H-chromene-2-thione (8c). Yellow
.
d
solid, mp 252e253 ꢀC. IR (KBr): 1641, 1558, 1462, 1284, 1170 cmꢂ1
.
1H NMR (300 MHz, CDCl3):
d
8.39 (s, 1H, ArH), 8.25 (d, J¼8.1 Hz, 1H,
d
ArH), 8.11 (d, J¼9.0 Hz, 1H, ArH), 7.96 (d, J¼7.8 Hz, 1H, ArH),
7.76e7.62 (m, 4H, ArH), 7.33 (d, J¼3.6 Hz, 1H, ArH), 6.61e6.59 (m,
1H, ArH). 13C NMR (75 MHz, CDCl3):
d 192.3,179.9,157.7,151.8,147.5,
137.7,134.9,130.6,130.0,129.2, 129.0, 128.8,127.0,121.6,120.1,116.4,
115.0, 112.8. FABMS (m/z): 307 (Mþþ1). Anal. Calcd for C18H10O3S:
C, 70.57%; H, 3.29%. Found: C, 70.69%; H, 3.41%.
4.3.14. 3-(4-Chlorobenzoyl)-8-methoxy-2H-chromene-2-thione
(5n). Yellow solid, mp 176e177 ꢀC. IR (KBr): 2966, 2932, 1674, 1568,
1468, 1376, 1236, 1169 cmꢂ1. 1H NMR (300 MHz, CDCl3):
d
7.85 (d,
4.3.21. 3-(Thien-2-oyl)-benzo[f]2H-chromene-2-thione (8d). Yellow
solid, mp 267e268 ꢀC. IR (KBr): 3058, 1634, 1554, 1407, 1352, 1198
J¼8.1 Hz, 2H, ArH), 7.59 (s, 1H, ArH), 7.42 (d, J¼8.1 Hz, 2H, ArH),

R.K. Verma et al. / Tetrahedron 67 (2011) 584e589
589
cmꢂ1 1H NMR (300 MHz, CDCl3):
. d 8.37 (s, 1H, ArH), 8.23 (d,
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Afantitis, A.; Detsi, A.; Igglessi-Markopoulou, O.; Markopoulos, J. Synthesis
2004, 1775e1782; (g) Audisio, D.; Messaoudi, S.; Brion, J.-D.; Alami, M. Eur. J.
Org. Chem. 2010, 1046e1051; (h) Heravi, M. M.; Sadjadi, S.; Oskooie, H. A.;
Shoar, R. H.; Bamoharram, F. F. Catal. Commun. 2007, 9, 470e474; (i) Oyamada,
J.; Kitamura, T. Tetrahedron 2006, 62, 6918e6925; (j) Taksande, K.; Borse, D. S.;
Lokhande, P. Synth. Commun. 2010, 40, 2284e2290.
J¼8.4 Hz, 1H, ArH), 8.12 (d, J¼9.0 Hz, 1H, ArH), 7.96 (d, J¼7.5 Hz, 1H,
ArH), 7.78e7.63 (m, 5H, ArH), 7.15e7.12 (m, 1H, ArH). 13C NMR
(75 MHz, CDCl3): d 192.2, 184.6, 176.7, 157.7, 151.3, 147.4, 135.6, 135.1,
134.9, 129.3, 129.2, 129.0, 128.4, 127.0, 121.6, 116.5, 112.8. FABMS (m/
z): 323 (Mþþ1). Anal. Calcd for C18H10O2S2: C, 67.06%; H, 3.13%.
Found: C, 66.91%; H, 3.26%.
4.3.22. 3-(4-Chlorobenzoyl)-benzo[f]2H-chromene-2-thione
(8e). Yellow solid, mp 254e255 ꢀC. IR (KBr): 3066, 2933, 1660, 1561,
1387, 1204, 1169 cmꢂ1. 1H NMR (300 MHz, CDCl3):
d 8.40 (s, 1H, ArH),
8.25 (d, J¼8.4 Hz, 1H, ArH), 8.13 (d, J¼9.3 Hz, 1H, ArH), 7.98e7.90 (m,
3H, ArH), 7.74e7.64 (m, 3H, ArH), 7.44 (d, J¼8.4 Hz, 2H, ArH). 13C
NMR (75 MHz, CDCl3þDMSO-d6):
d 192.7, 191.7, 164.0, 158.6, 141.2,
139.0, 135.1, 134.5, 133.5, 130.3, 130.2, 129.6, 128.5, 128.4, 128.1, 126.5,
121.3, 115.5, 114.1. FABMS (m/z): 351 (Mþþ1). Anal. Calcd for
C20H11ClO2S: C, 68.47%; H, 3.16%. Found: C, 68.26%; H, 3.09%.
4.3.23. 3-Benzoyl-benzo[f]2H-chromene-2-thione (8f). Yellow solid,
mp 241e242 ꢀC. IR (KBr): 3047, 2925, 1657, 1553, 1394, 1202, 1155
cmꢂ1 1H NMR (300 MHz, CDCl3):
. d 8.38 (s, 1H, ArH), 8.25 (d,
J¼8.1 Hz, 1H, ArH), 8.12 (d, J¼9.0 Hz, 1H, ArH), 7.99e7.95 (m, 3H,
ArH), 7.75e7.59 (m, 4H, ArH), 7.50e7.45 (m, 2H, ArH). 13C NMR
(75 MHz, CDCl3): d 192.7,192.5, 160.6, 157.7, 141.1, 138.8, 135.7, 134.8,
133.9, 130.0, 129.7, 129.2, 129.0, 128.7, 127.0, 123.7, 121.7, 116.5,115.2.
FABMS (m/z): 317 (Mþþ1). Anal. Calcd for C20H12O2S: C, 75.93%; H,
3.82%. Found: C, 75.82%; H, 3.91%.
4.3.24. 3-
violet solid, mp 242e243 ꢀC (decomp.). IR (KBr): 3051, 1635, 1549,
1413, 1348, 1191 cmꢂ1 1H NMR (300 MHz, CDCl3):
8.42 (s, 1H,
h
5-Ferrocenoyl-benzo[f]2H-chromene-2-thione (8g). Dark
5. (a) Singh, O. M.; Devi, N. S.; Thokchom, D. S.; Sharma, G. J. Eur. J. Med. Chem.
2010, 45, 2250e2257; (b) Singh, O. M.; Devi, N. S. J. Org. Chem. 2009, 74,
3141e3144; (c) Xu, X.; Hu, Y. J. Heterocycl. Chem. 2006, 43, 71e73.
.
d
ArH), 8.27 (d, J¼8.4 Hz, 1H, ArH), 8.11 (d, J¼9.0 Hz, 1H, ArH), 7.97 (d,
J¼7.8 Hz, 1H, ArH), 7.77e7.72 (m, 1H, ArH), 7.67e7.63 (m, 2H, ArH),
4.86 (s, 2H, Hcp), 4.64 (s, 2H, Hcp), 4.35 (s, 5H, Hcp). 13C NMR
6. Reviews for indium Lewis acids: (a) Yadav, J. S.; Antony, A.; George, J.; Reddy,
B. V. S. Eur. J. Org. Chem. 2010, 591e605; (b) Frost, C. G.; Chauhan, K. K. J.
Chem. Soc., Perkin Trans. 1 2000, 3015e3019; (c) Fringuelli, F.; Piermatti, O.;
Pizzo, F.; Vaccaro, L. Curr. Org. Chem. 2003, 7, 1661e1689; (d) Frost, C. G.;
Hartley, J. P. Mini-Rev. Org. Chem. 2004, 1, 1e7; (e) Zhang, Z.-H. Synlett 2005,
711e712; (f) Zhang, Y.; Li, P.; Wang, M.; Wang, L. J. Org. Chem. 2009, 74,
4364e4367; (g) Nandi, G. C.; Samai, S.; Kumar, R.; Singh, M. S. Tetrahedron
2009, 65, 7129e7134; (h) Kumar, R.; Nandi, G. C.; Verma, R. K.; Singh, M. S.
Tetrahedron Lett. 2010, 51, 442e445; (i) Nandi, G. C.; Samai, S.; Singh, M. S.
Synlett 2010, 1133e1137.
7. (a) Nandi, G. C.; Samai, S.; Kumar, R.; Singh, M. S. Tetrahedron Lett. 2009, 50,
7220e7222; (b) Samai, S.; Nandi, G. C.; Kumar, R.; Singh, M. S. Tetrahedron Lett.
2009, 50, 7096e7098; (c) Samai, S.; Nandi, G. C.; Singh, P.; Singh, M. S. Tetra-
hedron 2009, 65, 10155e10161; (d) Samai, S.; Nandi, G. C.; Singh, M. S. Tetra-
hedron Lett. 2010, 51, 5555e5558; (e) Kumar, R.; Raghuvanshi, K.; Verma, R. K.;
Singh, M. S. Tetrahedron Lett. 2010, 51, 5933e5936; (f) Nandi, G. C.; Samai, S.;
Singh, M. S. J. Org. Chem. 2010, 75, 7785e7795.
(75 MHz, CDCl3):
d 196.4, 192.2, 157.5, 139.0, 134.6, 130.6, 129.3,
129.0, 128.8, 128.4, 127.0, 121.4, 116.5, 114.9, 77.9, 73.2, 70.9, 70.4.
FABMS (m/z): 425 (Mþþ1). Anal. Calcd for C24H16FeO2S: C, 67.94%;
H, 3.80%. Found: C, 67.67%; H, 3.91%.
Acknowledgements
This work was carried out under financial support from Council
of Scientific and Industrial Research (Grant 01(2260)/08/EMR-II)
and Department of Science and Technology (Grant SR/S1/OC-66/
2009), New Delhi. R.K.V. is grateful to Council of Scientific and In-
dustrial Research (CSIR), New Delhi for senior research fellowship
and G. K.V. is thankful to University Grants Commission (UGC), New
Delhi for junior research fellowship.
8. Samuel, R.; Asokan, C. V.; Suma, S.; Chandran, P.; Retnamma, S.; Anabha, E. R.
Tetrahedron Lett. 2007, 48, 8376e8378 and references therein.
9. (a) Rao, H. S. P.; Sivakumar, S. J. Org. Chem. 2006, 71, 8715e8723; (b) Specht, D.
P. Tetrahedron 1982, 38, 1203e1211; (c) Buu-Hoi, N. P. Bull. Soc. Chim. Fr. 1958, 3,
361e363.
10. Crystal data for 5k: C14H7BrO2S2, yellow, M¼351.24, monoclinic, space group P
References and notes
3
ꢀ
ꢀ
21/n, a¼9.3601(3), b¼10.4053(3), c¼13.5327(4) A, V¼1314.91 A ,
m¼3.
436 cmꢂ1, Z¼4, T¼293 K, F000¼996, R¼0.0394, wR2¼0.0948. The CCDC de-
1. (a) Hepworth, J. D.; Gabbutt, C. D.; Heron, B. N. In Comprehensive Heterocyclic
Chemistry II; Pergamon: Oxford, 1996; Vol. 5, p 301; (b) Deans, F. M. Naturally
position number: CCDC 783653.