Highly convergent one-pot four-component regioselective synthesis of 4H-benzo[f]chromenes via annulation of β-oxodithioesters

Article abstract of DOI:10.1016/j.tet.2011.11.051

Highly efficient regioselective protocol for the synthesis of hitherto unreported 4H-benzo[f]chromenes has been developed by one-pot four-component coupling of aromatic aldehydes, β-naphthol, β-oxodithioesters, and primary alcohols in the presence of InCl

Full text of DOI:10.1016/j.tet.2011.11.051

Tetrahedron 68 (2012) 1247e1252
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journal homepage: www.elsevier.com/locate/tet
Highly convergent one-pot four-component regioselective synthesis of 4H-benzo
[f]chromenes via annulation of
b
-oxodithioesters
*
Subhasis Samai, Ganesh Chandra Nandi, Maya Shankar Singh
Department of Chemistry, Faculty of Science, Banaras Hindu University, Varanasi 221005, U.P., India
a r t i c l e i n f o
a b s t r a c t
Article history:
Highly efficient regioselective protocol for the synthesis of hitherto unreported 4H-benzo[f]chromenes
Received 27 September 2011
Received in revised form 19 November 2011
Accepted 19 November 2011
Available online 27 November 2011
has been developed by one-pot four-component coupling of aromatic aldehydes,
b-naphthol, b-ox-
odithioesters, and primary alcohols in the presence of InCl3. This transformation presumably proceeds
via domino Knoevenagel condensation/Michael addition/intramolecular cyclodehydration/trans-
esterification sequence creating four new bonds and one stereocenter in a single operation. Further,
alcohol plays dual role as a reactant as well as reaction medium.
Keywords:
Ó 2011 Elsevier Ltd. All rights reserved.
Four-component reaction
Indium trichloride (InCl3)
Benzo[f]chromene
b
-Oxodithioesters
Transesterification
1. Introduction
chemical biology and drug discovery; due to their straightforward
experimental procedures and flexible, convergent, and atom effi-
Molecules with chromene framework are important synthetic
targets both in pharmaceutical industry as well as in academic
laboratories displaying rich chemistry and numerous applica-
tions.1,2 They are widely present as key structural motifs in many
natural products, such as alkaloids, flavonoids, tocopherols, and
anthocyanins.3 Moreover, suitably substituted chromenes have
been found to exert wide spectrum of biological activities, such as
antibacterial, anti-inflammatory, anti-HIV, antioxidant, and anal-
gesic properties.4,5 In addition, 4H-chromenes also find applications
as cosmetics, pigments,6 biodegradable agrochemicals,7 and po-
tential inhibitors of EAAT1 (Excitatory amino acid transporters) and
Bcl-2 (B-cell lymphoma-2) family proteins.8 Recent SAR studies on
4H-chromene derivatives reveal that they have been used in the
cient nature. Although, several synthetic methods for the synthesis
of 4H-chromenes employing various strategies have been re-
ported,11,12 most of them suffer from some limitations, such as low
yields, poor selectivity, expensive and/or harmful catalysts, and te-
dious work-up. Therefore, more general, efficient, and viable routes
with operational simplicity for the synthesis of chromene de-
rivatives are very much desirable because of their importance as
substructures in a broad range of natural and synthetic products,
and would be of great relevance to both synthetic and medicinal
chemists.
In recent years, indium trichloride emerged as a highly efficient
and effective mild Lewis acid catalyst performing a variety of
chemical transformations in chemo-, regio-, and stereoselective
fashion due to its air and water compatibility and operational
treatment of human inflammatory TNF a-mediated diseases, such as
rheumatoid and psoriatic arthritis, hypertension, asthma, ischemia,
simplicity.13
b
-Oxodithioesters, which were not commercially
sourced, were prepared according to reported procedures.14 The
utility of -oxodithioesters as versatile intermediates in organic
synthesis has been well recognized.15 Recently,
-oxodithioesters
and urinary incontinence.9
The development of chemical methodologies that provide
maximum structural complexity and diversity with a minimum
number of synthetic steps to assemble compounds with interesting
properties is a key facet of modern drug discovery. Multicomponent
reactions10 (MCRs) have become important tools for the creation of
molecular complexity and diversity with predefined functionality in
b
b
have got much attention as a key intermediates in the synthesis of
various important bio-active frameworks, such as dihydropyr-
imidinone,16 pyridopyrimidinone,16 pyrazole,17 benzo[a]quinoli-
zine-4-thione,18 2H-chromene-2-thione,19 thiochromen-5-ones,20a
and thiophenes.20b Therefore, as a part of our incessant research
efforts with multicomponent reactions,21 we became intrigued in
scouting the use of b-oxodithioester as one of the component to
develop a more generalized synthetic strategy for the construction
of benzo[f]chromene frameworks.
* Corresponding author. Tel.: þ91 542 2307321; fax: þ91 542 2369951; e-mail
address: mssinghbhu@yahoo.co.in (M.S. Singh).
0040-4020/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2011.11.051

1248
S. Samai et al. / Tetrahedron 68 (2012) 1247e1252
2. Results and discussion
InCl3 loading was examined (Table 1, entries 7e9), and it was found
that 10 mol % of InCl3 provided the maximum yield in minimum
time (Table 1, entry 7). Further, the effect of different solvents, such
as CH3CN, THF, and H2O was also investigated at their reflux tem-
peratures in the presence of 10 mol % of InCl3, which were found to
be ineffective (Table 1, entries 10e12). The addition of phase
transfer catalyst tetrabutyl ammonium hydrogen sulfate also did
not make any difference in aqueous medium. In addition, the above
test reaction was also performed under solvent-free conditions, but
no desired product was obtained (Table 1, entry 13). Thus, the best
yield, cleanest reaction, and most facile work-up were achieved
employing 10 mol % of InCl3 in refluxing ethanol.
Using benzaldehyde 1a, b-naphthol 2, and 3-oxo-3-phenyldi-
thiopropionic acid methyl ester 3a in equimolar amounts as
model system, a comprehensive review of reaction conditions we
tested for the synthesis of benzo[f]chromene 4a and are summa-
rized in Table 1. It is worth note that, under all reaction conditions
tested, we did not observe even a trace of our expected product 5,
which suggest that as the compound 5 is formed, it immediately
undergoes transesterification under the reaction conditions to give
benzo[f]chromene 4a (Scheme 1).
Table 1
Our literature survey at this stage revealed that there are no
reports on the use of InCl3 as catalyst in the synthesis of benzo[f]
chromene derivatives by the coupling of aromatic aldehydes,
Optimization of reaction conditions for the synthesis of 4aa
Ph
S
OH
+
O
S
b-naphthol, and b-oxodithioesters. With these results in hand, we
OEt
Reaction
conditions
PhCHO
+
next utilized a variety of substrates to explore the synthetic scope
and generality of this cascade reaction and to generate a small li-
brary of functionalized benzo[f]chromenes 4. Representative re-
sults are shown in Table 2.
Ph
SMe
O
4a
Ph
1a
3a
2
Entry
Catalyst (mol %)
Solvent
Time (h)
Yieldb (%), 4a
1
2
3
4
5
6
7
8
None
p-TSA (10)
Et3N (10)
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
CH3CN
THF
6
4
4
4
4
4
4
4
4
4
4
24
6
dc
dc
dc
dc
61
Table 2
Synthesis of 4H-benzo[f]chromenes 4
L-Proline (10)
Ar1
S
InCl3
SnCl2$2H2O (10)
CuBr2 (10)
InCl3 (10)
InCl3 (5)
InCl3 (15)
InCl3 (10)
InCl3 (10)
InCl3 (10)
InCl3 (10)
O
S
OH
+
(10 mol %)
35
79
62
77
OR
Ar2
Ar1 CHO
+
Ar2
SMe
ROH
O
4
80 oC
1
3
2
9
10
11
12
13
dd
dd
dc
dc
Product
Ar1
Ar2
R
Time (h)
Yielda (%)
H2O
None
4a
4b
4c
4d
4e
4f
4g
4h
4i
C6H5
C6H5
C6H5
C6H5
C6H5
C2H5
4.0
3.5
4.0
3.5
3.5
3.5
4.0
4.5
3.5
4.5
3.0
4.0
3.5
3.0
4.0
3.0
4.0
4.5
4.5
6.0
79
65
75
77
71
63
65
68
83
79
81
69
68
75
58
65
76
63
68
0
4-MeC6H4
4-NO2C6H4
4-FC6H4
C6H5
2-ClC6H4
2-OMeC6H4
4-OHC6H4
C6H5
4-MeC6H4
C6H5
4-OMeC6H4
3-ClC6H4
4-MeC6H4
C6H5
C2H5
C2H5
C2H5
C2H5
C2H5
C2H5
C2H5
C2H5
C2H5
C2H5
C2H5
C2H5
C2H5
CH3
a
Reaction of benzaldehyde 1a (1 mmol), b-naphthol 2 (1 mmol), and 3-oxo-3-
phenyldithiopropionic acid methyl ester 3a (1 mmol).
b
Isolated pure yields.
No desired product.
Complex reaction mixture.
4-OMeC6H4
4-OMeC6H4
4-OMeC6H4
4-OMeC6H4
4-ClC6H4
4-ClC6H4
2-Thienyl
2-Thienyl
2-Thienyl
2-Thienyl
C6H5
2-Thienyl
4-OMeC6H4
C6H5
2-Thienyl
C6H5
c
d
4j
4k
4l
CHO
O
S
OH
+
+
Ph
SMe
4m
4n
4o
4p
4q
4r
4s
4t
3a
2
1a
InCl3
EtOH
C6H5
C6H5
C6H5
C6H5
CH3
CH3
n-C4H9
n-C4H9
i-Pr
(10 mol %) 80 o
C
Trans esterification
C6H5
a
Isolated yields.
S
S
SMe
OEt
Notably, a wide range of aromatic aldehydes bearing electron-
withdrawing as well as electron-donating groups and various
O
5
Ph
O
4a
Ph
b-oxodithioesters were well tolerated, and proceeded smoothly
under the optimized reaction conditions. Further, to expand the
scope of this protocol and to gain more clear insight into the re-
action, we also carried out the above test reaction in different al-
cohols, such as MeOH, n-BuOH, and i-PrOH (Table 2, products
4oet). Primary alcohols provided the products in moderate to good
yields, whereas sterically hindered secondary alcohol i-PrOH did
not provide any trace of the desired product, but it led to a complex
mixture of several very close spots on the TLC plate, which could
not be isolated, thus limiting the scope of the reaction to some
extent.
Scheme 1. Synthesis of benzo[f]chromene 4a.
A control experiment verified that the reaction did not proceed
in the absence of catalyst (Table 1, entry 1). Initially, the above
model reaction was performed in the presence of different cata-
lysts, such as p-TSA, Et3N,
(10 mol % each) separately in refluxing ethanol. p-TSA, Et3N, and
-proline were found to be completely ineffective (Table 1, entries
L-proline, SnCl2$2H2O, CuBr2, and InCl3
L
2e4). SnCl2$2H2O and CuBr2 did catalyze the reaction to furnish the
desired product 4a albeit in low yields (Table 1, entries 5 and 6). To
our delight, InCl3 gave the desired benzo[f]chromene 4a in 79%
yield (Table 1, entry 7, Scheme 1). Encouraged by this result, we
then focused on optimizing the reaction conditions. Subsequently,
The structures of all the newly synthesized compounds were
well characterized from their satisfactory elemental and spectral
(IR, 1H, 13C NMR, and mass) studies. The mass spectra of these

S. Samai et al. / Tetrahedron 68 (2012) 1247e1252
1249
compounds displayed molecular ion peaks at the appropriate m/z
values. Finally, the structure of one representative compound 2-(4-
chlorophenyl)-4-phenyl-4H-benzo[f]chromene-3-carbothioic acid
O-ethyl ester 4i was confirmed unambiguously by the X-ray single
crystal diffraction analysis (Fig. 1).22
transesterification by the alcohol under the reaction conditions to
give benzo[f]chromene 4. The alternative rotamer B2 may undergo
cyclization via its two different routes II and III to furnish benzo[f]
chromene D and benzo[f]thiochromene E, respectively. During our
investigation, we did not observe a trace of D and E, and only 4 was
obtained exclusively thus, making this protocol highly regiose-
lective. This operationally simple and four-component domino
process concomitantly created two new CeC and two CeO bond
leading to chromene ring.
3. Conclusion
In summary, we have developed an efficient and highly con-
vergent one-pot four-component domino protocol for the synthesis
of functionalized benzo[f]chromenes in refluxing alcohol promoted
by InCl3 for the first time. It should be noted that alcohol plays dual
role as a reactant as well as reaction medium. This transformation
proceeds via Knoevenagel condensation/Michael addition/intra-
molecular cyclodehydration/transesterification sequence creating
four new bonds in highly chemo- and regioselective manner and
one stereocenter in a single operation. This method not only pro-
vides an excellent complement to benzo[f]chromenes synthesis,
but also avoids the use of hazardous reagents.
4. Experimental section
4.1. General
All starting materials were used as received without further
Fig. 1. ORTEP diagram of the compound 4i.
purification.
b-Oxodithioesters were prepared following known
procedure.14 Thin-layer chromatography (TLC) was performed
using silica gel 60 F254 precoated plates. Infrared (IR) spectra are
Although we have not established the mechanism of the re-
action experimentally, on the basis of above results, a plausible
reaction scenario for the formation of benzo[f]chromenes is out-
lined in Scheme 2. The reaction is supposed to proceed via the
measured in KBr, and wavelengths (n
) are reported in cmꢀ1. 1H and
13C NMR spectra were recorded on NMR spectrometers operating at
300 MHz, 200 MHz, and 75 MHz, 50 MHz, respectively. Chemical
shifts (d) are given in parts per million (ppm) using the residue
solvent peaks as reference relative toTMS. J values are given in hertz.
Mass spectra were recorded using electro spray ionization (ESI)
mass spectrometry. The C, H, and N analysis were performed from
micro analytical laboratory. The melting points are uncorrected.
4.2. General procedure for the synthesis of 4H-benzo[f]
chromene-3-carbothioic acid O-ethyl ester (4)
A mixture of aldehyde (1.0 mmol),
b-naphthol (1.0 mmol), and
b-oxodithioester (1.0 mmol) was placed in a 25 mL round bottom
flask containing 2 mL dry ethanol. InCl3 (22 mg, 10 mmol) was
added to it and the reaction mixture was heated at 80 ꢁC for the
stipulated period of time. After completion of the reaction (moni-
tored by TLC) ethanol was evaporated under reduced pressure. The
residue thus obtained was diluted with water (20 mL) and extrac-
ted with ethyl acetate (2ꢂ10 mL). The combined organic extract
was washed with brine and dried over anhydrous Na2SO4. The
solvent was evaporated under vacuum and the residue was purified
by column chromatography over silica gel using ethyl acetate and
n-hexane mixture (1:49) as eluent, which afforded the desired
product in excellent purity. The physical and spectral data of the
synthesized compounds are as follows.
Scheme 2. A plausible mechanism for the formation of benzo[f]chromene 4.
Michael acceptor ortho-quinonemethide intermediate (o-QM) A,
formed by the nucleophilic addition of
ortho-quinonemethide intermediate A is highly reactive and could
not be isolated at room temperature. The enol form of -oxodi-
thioester 3 attacks to A in a Michael-type fashion to produce an
open chain intermediate B1. B1 undergoes regiospecific O-cycliza-
tion via route I followed by dehydration to give the benzo[f]chro-
mene 5, which could not be isolated and immediately undergoes
b
-naphthol 2 to aldehyde 1.
4.2.1. 2,4-Diphenyl-4H-benzo[f]chromene-3-carbothioic acid O-ethyl
ester (4a). Colorless jelly; IR (KBr, nmax, cmꢀ1): 3065, 1705, 1059;
b
1H NMR (300 MHz, CDCl3,
d
ppm): 8.11 (d, J¼8.4 Hz, 2H),
7.89e7.81 (m, 3H), 7.63e7.59 (m, 2H), 7.46e7.37 (m, 9H), 5.87 (s,
1H), 3.99 (q, J¼7.2 Hz, 2H), 0.91 (t, J¼6.9 Hz, 3H); 13C NMR
(75 MHz, CDCl3,
d ppm): 166.9, 159.4, 152.2, 148.2, 146.6, 134.7,
131.5, 130.6, 129.9, 129.6, 129.2, 128.8, 128.7, 127.9, 127.3, 125.0,

1250
S. Samai et al. / Tetrahedron 68 (2012) 1247e1252
123.8, 122.6, 117.2, 115.6, 107.0, 60.5, 39.1, 13.5; ESI-MS: m/
z¼423.1 (Mþþ1). Anal. Calcd for C28H22O2S: C, 79.59; H, 5.25.
Found: 79.87; H, 5.45.
(75 MHz, CDCl3, d ppm): 167.1,160.5,158.0, 155.9, 148.3,133.8, 131.4,
131.1, 130.5, 130.4, 128.3, 127.8, 126.6, 124.4, 123.5, 121.0, 117.8, 117.2,
113.2, 110.9, 107.1, 60.1, 55.5, 55.3, 32.9, 14.1; ESI-MS: m/z¼483.1
(Mþþ1). Anal. Calcd for C30H26O4S: C, 74.66; H, 5.43. Found: C,
74.83; H, 5.59.
4.2.2. 2-Phenyl-4-p-tolyl-4H-benzo[f]chromene-3-carbothioic acid
O-ethyl ester (4b). Pale yellow jelly; IR (KBr, nmax, cmꢀ1): 3066,1702,
1065; 1H NMR (200 MHz, CDCl3,
d
ppm): 8.00 (d, J¼7.2 Hz, 1H),
4.2.8. 4-(4-Hydroxypheyl)-2-(4-methoxyphenyl)-4H-benzo[f] chro-
mene-3-carbothioic acid O-ethyl ester (4h). Yellow jelly; IR (KBr,
nmax, cmꢀ1): 3599, 3070, 1702, 1067; 1H NMR (300 MHz, CDCl3,
7.80e7.73 (m, 2H), 7.68e7.45 (m, 4H), 7.41e7.17 (m, 4H), 7.14e6.95
(m, 4H), 5.72 (s, 1H), 4.18 (q, J¼7.2 Hz, 2H), 2.25 (s, 3H), 1.18 (t,
J¼7.2 Hz, 3H); 13C NMR (50 MHz, CDCl3,
d
ppm): 167.3, 151.1, 148.3,
d
ppm): 8.00 (d, J¼8.4 Hz, 1H), 7.80e7.73 (m, 2H), 7.47 (d, J¼8.4 Hz,
141.9,136.4,135.6,131.6,131.0,130.6,130.1,129.8, 129.4,128.9,128.7,
128.5,128.3,127.9,127.1,126.8,126.5,124.9,123.6,123.3,117.4,108.9,
60.8, 39.5, 21.1, 14.0; ESI-MS: m/z¼437.1 (Mþþ1). Anal. Calcd for
C29H24O2S: C, 79.78; H, 5.54. Found: C, 80.04; H, 5.69.
3H), 7.37e7.33 (m, 1H), 7.29e7.25 (m, 3H), 6.93 (d, J¼8.4 Hz, 2H),
6.67 (d, J¼8.4 Hz, 2H), 5.66 (s, 1H), 4.72 (s, 1H), 4.04 (q, J¼7.2 Hz,
2H), 3.84 (s, 3H), 1.03 (t, J¼7.2 Hz, 3H); 13C NMR (75 MHz, CDCl3,
d
ppm): 167.6, 160.7, 158.2, 154.1, 148.1, 137.7, 131.4, 130.9, 130.6,
129.4, 128.6, 128.4, 127.3, 126.8, 124.6, 123.2, 117.4, 117.2, 115.2, 113.1,
107.5, 60.3, 55.3, 38.3, 13.8; ESI-MS: m/z¼469.2 (Mþþ1). Anal. Calcd
for C29H24O4S: C, 74.34; H, 5.16. Found: C, 73.59; H, 5.34.
4.2.3. 4-(4-Nitrophenyl)-2-phenyl-4H-benzo[f]chromene-3-
carbothioic acid O-ethyl ester (4c). Pale yellow jelly; IR (KBr, nmax
,
cmꢀ1): 3069, 1704, 1062; 1H NMR (300 MHz, CDCl3,
d
ppm): 8.02 (d,
J¼8.4 Hz, 1H), 7.80e7.74 (m, 2H), 7.48e7.34 (m, 9H), 7.24e7.20 (m,
2H), 7.13e7.09 (m, 1H), 5.76 (s, 1H), 3.98 (q, J¼8.1 Hz, 2H), 0.94 (t,
4.2.9. 2-(4-Chlorophenyl)-4-phenyl-4H-benzo[f]chromene-3-
carbothioic acid O-ethyl ester (4i). Yellow solid; mp 174e175 ꢁC; IR
(KBr, nmax, cmꢀ1): 3059, 1700, 1065; 1H NMR (300 MHz, CDCl3,
J¼7.2 Hz, 3H); 13C NMR (75 MHz, CDCl3,
d ppm): 167.1, 158.2, 148.2,
145.1,135.1,131.4,130.9, 129.4, 128.8, 128.6,128.4, 128.3, 127.9,127.7,
126.9, 126.8, 126.5, 124.6, 123.2, 117.1, 116.9, 108.3, 60.2, 39.1, 13.5;
ESI-MS: m/z¼468.2 (Mþþ1). Anal. Calcd for C28H21NO4S: C, 71.93;
H, 4.53; N, 3.00. Found: C, 71.70; H, 4.79; N, 3.12.
d
ppm): 8.01 (d, J¼8.4 Hz,1H), 7.80e7.52 (m, 2H), 7.46e7.32 (m, 9H),
7.24e7.20 (m, 2H), 7.14e7.09 (m, 1H), 5.75 (s, 1H), 4.02 (q, J¼7.2 Hz,
2H), 1.02 (t, J¼7.2 Hz, 3H); 13C NMR (75 MHz, CDCl3,
d ppm): 166.7,
157.1, 148.0, 144.9, 135.5, 133.5, 131.4, 130.8, 130.3, 128.9, 128.4,
128.3, 128.0, 126.9, 126.6, 124.7, 123.2, 117.0, 116.8, 108.6, 60.5, 39.1,
13.6; ESI-MS: m/z¼457.1 (Mþþ1). Anal. Calcd for C28H21ClO2S: C,
73.59; H, 4.63. Found: C, 73.95; H, 4.39.
4.2.4. 4-(4-Fluorophenyl)-2-phenyl-4H-benzo[f]chromene-3-
carbothioic acid O-ethyl ester (4d). Pale brown jelly; IR (KBr, nmax
,
cmꢀ1): 3067, 1701, 1058; 1H NMR (300 MHz, CDCl3,
d
ppm): 7.96 (d,
J¼8.4 Hz, 1H), 7.81e7.75 (m, 2H), 7.50e7.34 (m, 10H), 6.93e6.88 (m,
4.2.10. 2-(4-Chlorophenyl)-4-p-tolyl-4H-benzo[f]chromene-3-
carbothioic acid O-ethyl ester (4j). Pale brown solid; mp
170e171 ꢁC; IR (KBr, nmax, cmꢀ1): 3065, 1703, 1065; 1H NMR
2H), 5.75 (s, 1H), 3.99 (q, J¼6.9 Hz, 2H), 0.93 (t, J¼6.9 Hz, 3H); 13C
NMR (75 MHz, CDCl3, d ppm): 167.1, 158.3, 148.1, 140.9, 135.0, 131.4,
130.7, 129.8, 129.7, 129.6, 128.8, 128.5, 127.8, 126.9, 124.8, 123.0,
117.2, 116.7, 115.4, 115.1, 108.1, 60.3, 38.4, 13.5; ESI-MS: m/z¼441.2
(Mþþ1). Anal. Calcd for C28H21FO2S: C, 76.34; H, 4.80. Found: C,
76.59; H, 4.95.
(300 MHz, CDCl3,
d
ppm): 8.01 (d, J¼8.4 Hz, 1H), 7.80e7.74 (m, 2H),
7.45e7.28 (m, 9H), 7.04 (d, J¼7.5 Hz, 2H), 5.71 (s, 1H), 4.02 (q,
J¼6.9 Hz, 2H), 2.23 (s, 3H), 1.02 (t, J¼6.9 Hz, 3H); 13C NMR (75 MHz,
CDCl3,
d ppm): 166.8, 157.0, 148.0, 142.0, 136.2, 135.5, 133.6, 131.4,
130.9, 130.4, 129.2, 128.8, 128.4, 128.1, 128.0, 126.9, 124.7, 123.2,
117.0, 108.8, 60.4, 38.7, 21.0, 13.7; ESI-MS: m/z¼471.2 (Mþþ1). Anal.
Calcd for C29H23ClO2S: C, 73.95; H, 4.92. Found: C, 73.61; H, 5.09.
4.2.5. 2-(4-Methoxyphenyl)-4-phenyl-4H-benzo[f]chromene-3-
carbothioic acid O-ethyl ester (4e). Pale yellow jelly; IR (KBr, nmax
,
cmꢀ1): 3057, 1700, 1066; 1H NMR (300 MHz, CDCl3,
d
ppm): 8.02 (d,
J¼8.4 Hz, 1H), 7.79e7.73 (m, 2H), 7.48e7.34 (m, 6H), 7.23e7.19 (m,
3H), 7.12 (d, J¼7.2 Hz, 1H), 6.93 (d, J¼8.4 Hz, 2H), 5.73 (s, 1H), 4.04
(q, J¼7.2 Hz, 2H), 3.83 (s, 3H), 1.03 (t, J¼6.9 Hz, 3H); 13C NMR
4.2.11. 4-Phenyl-2-thienyl-4H-benzo[f]chromene-3-carbothioic acid
O-ethyl ester (4k). Red jelly; IR (KBr, nmax, cmꢀ1): 3065, 1702, 1065;
1H NMR (300 MHz, CDCl3,
d
ppm): 7.98 (d, J¼8.1 Hz, 1H), 7.81e7.76
(75 MHz, CDCl3,
d
ppm): 167.3, 160.7, 158.4, 148.2, 145.2, 130.6,
(m, 2H), 7.52e7.37 (m, 7H), 7.24e7.19 (m, 2H), 7.14e7.05 (m, 2H),
5.74 (s, 1H), 4.16 (q, J¼7.2 Hz, 2H), 1.17 (t, J¼6.9 Hz, 3H); 13C NMR
128.7, 128.4, 128.2, 126.8, 126.5, 124.6, 123.1, 117.2, 113.1, 107.3, 60.3,
55.3, 39.2, 14.1; ESI-MS: m/z¼453.2 (Mþþ1). Anal. Calcd for
C29H24O3S: C, 76.96; H, 5.35. Found: C, 77.19; H, 5.49.
(75 MHz, CDCl3, d ppm): 167.0,150.9,148.1,144.5,135.3, 131.4, 130.8,
130.5, 128.8, 128.6, 128.5, 128.3, 128.2, 127.0, 126.9, 126.6, 124.7,
123.1, 117.1, 117.0, 108.4, 60.6, 39.6, 13.8; ESI-MS: m/z¼429.1
(Mþþ1). Anal. Calcd for C26H20O2S2: C, 72.87; H, 4.70. Found: C,
72.61; H, 4.88.
4.2.6. 4-(2-Chlorophenyl)-2-(4-methoxyphenyl)-4H-benzo[f]chro-
mene-3-carbothioic acid O-ethyl ester (4f). Pale yellow jelly; IR (KBr,
nmax, cmꢀ1): 3057, 1701, 1059; 1H NMR (300 MHz, CDCl3,
d ppm):
8.24 (d, J¼8.1 Hz, 1H), 7.95e7.74 (m, 2H), 7.50 (d, J¼8.7 Hz, 3H),
7.36e7.31 (m, 4H), 7.09e7.04 (m, 2H), 6.94 (d, J¼8.7 Hz, 2H), 6.12 (s,
1H), 4.04 (q, J¼5.4 Hz, 2H), 3.85 (s, 3H), 1.05 (t, J¼7.2 Hz, 3H); 13C
4.2.12. 4-(4-Methoxyphenyl)-2-thienyl-4H-benzo[f]chromene-3-
carbothioic acid O-ethyl ester (4l). Red jelly; IR (KBr, nmax, cmꢀ1):
3067, 1699, 1067; 1H NMR (300 MHz, CDCl3,
d ppm): 7.97
NMR (75 MHz, CDCl3,
d
ppm): 167.3, 160.7, 148.3, 143.0, 132.0, 131.7,
(d, J¼8.4 Hz,1H), 7.84e7.74 (m, 3H), 7.51e7.35 (m, 4H), 7.31e7.24 (m,
1H), 7.07e6.98 (m, 2H), 6.76 (d, J¼8.7 Hz, 2H), 5.69 (s, 1H), 4.16 (q,
J¼7.2 Hz, 2H), 3.70 (s, 3H), 1.16 (t, J¼7.2 Hz, 3H); 13C NMR (75 MHz,
131.3, 131.2, 130.3, 129.6, 129.0, 128.4, 127.8, 127.5, 127.0, 124.7,
123.5, 117.3, 113.3, 107.2, 60.5, 55.4, 36.1, 13.8; ESI-MS: m/z¼487.1
(Mþþ1). Anal. Calcd for C29H23ClO3S: C, 71.52; H, 4.76. Found: C,
71.79; H, 4.66.
CDCl3,
d ppm): 167.1, 158.2, 148.0, 147.6, 147.0, 131.9, 130.4, 129.2,
128.7, 128.5, 128.3, 126.8, 126.6, 124.7,124.4,123.9, 119.0,117.1, 114.2,
113.8, 60.6, 55.1, 38.8, 14.1; ESI-MS: m/z¼459.1 (Mþþ1). Anal. Calcd
for C27H22O3S2: C, 70.71; H, 4.84. Found: C, 70.99; H, 4.99.
4.2.7. 2-(4-Methoxyphenyl)-4-(2-methoxyphenyl)-4H-benzo[f]chro-
mene-3-carbothioic acid O-ethyl ester (4g). Pale yellow jelly. IR (KBr,
nmax, cmꢀ1): 3057, 1699, 1067; 1H NMR (300 MHz, CDCl3,
d
ppm):
4.2.13. 4-(3-Chlorophenyl)-2-thienyl-4H-benzo[f]chromene-3-
8.27 (d, J¼8.4 Hz, 1H), 7.76e7.68 (m, 2H), 7.49e7.44 (m, 3H),
7.37e7.29 (m, 3H), 7.09 (d, J¼7.2 Hz, 1H), 6.94e6.81 (m, 4H), 6.08 (s,
1H), 3.98e3.91 (m, 5H), 3.84 (s, 3H), 1.02 (t, J¼6.9 Hz, 3H); 13C NMR
carbothioic acid O-ethyl ester (4m). Pale yellow jelly; IR (KBr, nmax
cmꢀ1): 1067, 1702, 1065; 1H NMR (300 MHz, CDCl3,
ppm): 7.92
(d, J¼8.1 Hz, 1H), 7.83e7.78 (m, 2H), 7.54e7.48 (m, 2H), 7.41e7.7.37
,
d

S. Samai et al. / Tetrahedron 68 (2012) 1247e1252
1251
(m, 3H), 7.25e7.24 (m, 1H), 7.14e7.06 (m, 4H), 5.73 (s, 1H), 4.18 (q,
NMR (50 MHz, CDCl3,
d
ppm): 167.3, 151.1, 148.3, 144.7, 135.6, 131.6,
J¼7.2 Hz, 2H), 1.19 (t, J¼7.2 Hz, 3H); 13C NMR (75 MHz, CDCl3,
131.0, 130.6, 129.0, 128.6, 128.3, 127.1, 126.8, 124.8, 123.3, 117.3,
108.8, 64.7, 39.8, 30.5, 19.2, 13.8; ESI-MS: m/z¼457.2 (Mþþ1). Anal.
Calcd for C28H24O2S2: C, 73.65; H, 5.30. Found: C, 73.93; H, 5.12.
d
ppm): 166.8, 151.5, 148.1, 146.5, 134.2, 131.4, 130.8, 129.7, 129.2,
128.6, 128.3, 127.8, 127.1, 127.0, 126.8, 126.4, 124.9, 122.8, 117.1, 116.2,
107.6, 60.8, 39.3, 13.8; ESI-MS: m/z¼463.1 (Mþþ1). Anal. Calcd for
C26H19ClO2S2: C, 67.45; H, 4.14. Found: C, 67.67; H, 4.36.
Acknowledgements
4.2.14. 2-Thienyl-4-p-tolyl-4H-benzo[f]chromene-3-carbothioic acid
This work was carried out under financial support from the
Council of Scientific and Industrial Research (Grant 01(2260)/08/
EMR-II) and the Department of Science and Technology (Grant
SR/S1/OC-66/2009), New Delhi. S.S. and G.C.N. are thankful to the
Council of Scientific and Industrial Research (CSIR), New Delhi, for
their senior research fellowship (SRF).
O-ethyl ester (4n). Red jelly; IR (KBr, nmax, cmꢀ1): 3062, 1701, 1067;
1H NMR (300 MHz, CDCl3,
(m, 2H), 7.51e7.36 (m, 5H), 7.29e7.24 (m, 2H), 7.07e7.00 (m, 3H),
5.70 (s, 1H), 4.15 (q, J¼6.9 Hz, 2H), 2.22 (s, 3H), 1.17 (t, J¼6.9 Hz, 3H);
d
ppm): 7.99 (d, J¼8.4 Hz, 1H), 7.79e7.74
13C NMR (75 MHz, CDCl3,
d ppm): 167.1, 150.9, 148.0, 141.7, 136.2,
135.4, 131.4, 130.8, 130.5, 129.2, 128.7, 128.5, 128.3, 128.0, 126.9,
126.6, 124.7, 123.1, 117.2, 117.1, 108.6, 60.6, 39.2, 21.0, 13.8; ESI-MS:
m/z¼443.2 (Mþþ1). Anal. Calcd for C27H22O2S2: C, 73.27; H, 5.01.
Found: C, 73.56; H, 4.89.
Supplementary data
X-ray structure and crystallographic information file (CIF) for
compound 4i. Supplementary data related to this article can be
found online at doi:10.1016/j.tet.2011.11.051.
4.2.15. 2,4-Diphenyl-4H-benzo[f]chromene-3-carbothioic acid O-
methyl ester (4o). Pale orange solid; mp 84e85 ꢁC; IR (KBr, nmax
,
cmꢀ1): 3065, 1703, 1065; 1H NMR (300 MHz, CDCl3,
d ppm): 8.01 (d,
References and notes
J¼8.1 Hz, 1H), 7.80e7.75 (m, 2H), 7.51e7.34 (m, 11H), 7.23e7.20 (m,
1H), 7.14e7.09 (m, 1H), 5.76 (s, 1H), 3.50 (s, 3H); 13C NMR (75 MHz,
1. (a) Shen, H. C. Tetrahedron 2009, 65, 3931; (b) Ferreira, S. B.; da Silva, F.; de, C.;
Pinto, A. C.; Gonzaga, D. T. G.; Ferreira, V. F. J. Heterocycl. Chem. 2009, 46, 1080;
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J.; Wang, M.; Lin, L.; Feng, X. Eur. J. Org. Chem. 2011, 137; (e) Moon, D.; Kim, M.;
Kang, S.; Choi, Y.; Park, S.; Kim, G. Cancer Lett. 2010, 292, 111; (f) Moafi, L.; Ahadi,
S.; Bazgir, A. Tetrahedron Lett. 2010, 51, 6270.
CDCl3,
d ppm):167.6, 145.0, 129.6, 128.8, 128.5, 128.2, 127.8, 126.9,
126.6, 124.7, 123.2, 117.2, 108.0, 97.2, 51.3, 39.2; ESI-MS: m/z¼409.1
(Mþþ1). Anal. Calcd for C27H20O2S: C, 79.38; H, 4.93. Found: C,
79.68; H, 4.77.
2. (a) Sun, W.; Cama, L. D.; Birzin, E. T.; Warrier, S.; Locco, L.; Mosley, R.; Ham-
mond, M. L.; Rohrer, S. P. Bioorg. Med. Chem. Lett. 2006, 16, 1468; (b) Stachulski,
A. V.; Berry, N. G.; Low, A. C. L.; Moores, S. L.; Row, E.; Warhurst, D. C.; Adagu, I.
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67, 1799.
4.2.16. 4-Phenyl-2-thienyl-4H-benzo[f]chromene-3-carbothioic acid
O-methyl ester (4p). Brown solid; mp 120e121 ꢁC; IR (KBr, nmax
,
cmꢀ1): 3065, 1701, 1065; 1H NMR (300 MHz, CDCl3,
d ppm): 7.98 (d,
J¼8.4 Hz, 1H), 7.81e7.76 (m, 2H), 7.56 (d, J¼3.0 Hz, 1H), 7.49e7.37
(m, 6H), 7.22e7.06 (m, 4H), 5.75 (s, 1H), 3.68 (s, 3H); 13C NMR
(75 MHz, CDCl3,
d
ppm): 167.5, 151.3, 148.1, 144.5, 135.3, 131.4, 130.8,
3. (a) Bohm, B. A.; Choy, J. B.; Lee, A. Y.-M. Phytochemistry 1989, 28, 501; (b) Ia-
cobucci, G. A.; Sweeny, J. G. Tetrahedron 1983, 39, 3005; (c) Gill, M. Aust. J. Chem.
1995, 48, 1; (d) Parmar, V. S.; Jain, S. C.; Bisht, K. S.; Jain, R.; Taneja, P.; Jha, A.;
Tyagi, O. D.; Prasad, A. K.; Wengel, J.; Olsen, C. E.; Boll, P. M. Phytochemistry
1997, 46, 597.
130.6, 128.9, 128.5, 128.1, 126.9, 126.7, 124.7, 123.1, 117.1, 109.4, 107.9,
51.6, 39.6; ESI-MS: m/z¼415.1 (Mþþ1). Anal. Calcd for C25H18O2S2:
C, 72.43; H, 4.38. Found: C, 72.63; H, 4.59.
4. (a) McKee, T. C.; Fuller, R. W.; Covington, C. D.; Cardellina, J. H. II; Gulakowski,
R. J.; Krepps, B. L.; McMahon, J. B.; Boyd, M. R. J. Nat. Prod. 1996, 59, 754; (b)
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4.2.17. 2-(4-Methoxyphenyl)-4-phenyl-4H-benzo[f]chromene-3-
carbothioic acid O-methyl ester (4q). Yellow solid; mp 188e189 ꢁC;
IR (KBr, nmax, cmꢀ1): 1H NMR (200 MHz, CDCl3,
d ppm): 8.00 (d,
ꢀ ꢀ
(d) Garino, C.; Bihel, F.; Pietrancosta, N.; Laras, Y.; Quelever, G.; Woo, I.; Klein, P.;
J¼6.0 Hz, 1H), 7.78e7.71 (m, 2H), 7.47e7.42 (m, 2H), 7.41e7.37 (m,
2H), 7.35e7.29 (m, 2H), 7.22e7.20 (m, 2H), 7.16e7.08 (m, 2H), 6.92
(d, J¼8.6 Hz, 2H), 5.71 (s, 1H), 3.82 (s, 3H), 3.52 (s, 3H); 13C NMR
Bain, J.; Boucher, J.-L.; Kraus, J.-L. Bioorg. Med. Chem. Lett. 2005, 15, 135.
5. (a) Shanthi, G.; Perumal, P. T.; Rao, U.; Sehgal, P. K. Indian J. Chem. 2009, 48B,
1319; (b) Johnson, A. J.; Kumar, R. A.; Rasheed, S. A.; Chandrika, S. P.; Chan-
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7. Hafez, E. A. A.; Elnagdi, M. H.; Elagamey, A. G. A.; El-Taweel, F. M. A. A. Het-
erocycles 1987, 26, 903.
(50 MHz, CDCl3,
d ppm): 167.8, 160.8, 158.5, 148.2, 145.2, 131.4,
130.9, 130.6, 128.8, 128.4, 128.2, 127.0, 126.9, 126.5, 124.6, 123.2,
117.3,117.2,113.2,107.1, 55.3, 51.3, 39.2; ESI-MS: m/z¼439.1 (Mþþ1).
Anal. Calcd for C28H22O3S: C, 76.69; H, 5.06. Found: C, 76.94; H, 5.23.
8. (a) Erichsen, M. N.; Huynh, T. H. V.; Abrahamsen, B.; Bastlund, J. F.; Bundgaard,
C.; Monrad, O.; Bekker-Jensen, A.; Nielsen, C. W.; Frydenvang, K.; Jensen, A. A.;
Bunch, L. J. Med. Chem. 2010, 53, 7180; (b) Doshi, J. M.; Tian, D.; Xing, C. J. Med.
€
€
4.2.18. 2,4-Diphenyl-4H-benzo[f]chromene-3-carbothioic acid O-bu-
Chem. 2006, 49, 7731; (c) Skommer, J.; Wlodkowic, D.; Matto, M.; Eray, M.;
Pelkonen, J. Leukemia Res. 2006, 30, 322.
tyl ester (4r). Pale red jelly; IR (KBr, nmax, cmꢀ1): 3065, 1735, 3065;
9. (a) Shi, D.; Mou, J.; Zhuang, Q.; Wang, X. J. Chem. Res. 2004, 821; (b) Pirotte, B.;
Fontaine, J.; Lebrun, P. Curr. Med. Chem. 1995, 2, 573; (d) Atwal, K. S. Curr. Med.
Chem. 1996, 3, 27.
1H NMR (300 MHz, CDCl3,
d
ppm): 8.02 (d, J¼7.2 Hz, 1H), 7.78e7.73
(m, 2H), 7.48e7.33 (m, 10H), 7.24e7.11 (m, 3H), 5.76 (s, 1H), 3.92 (t,
J¼6.0 Hz, 2H), 1.25e1.24 (m, 2H), 1.01e0.95 (m, 2H), 0.76 (t,
€
10. (a) Ugi, I. Pure Appl. Chem. 2001, 73, 187; (b) Domling, A. Chem. Rev. 2006, 106,
€
€
17; (c) D’Souza, D. M.; Muller, T. J. J. Chem. Soc. Rev. 2007, 36, 1095; (d) Domling,
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2007, 36, 484.
J¼6.3 Hz, 3H); 13C NMR (75 MHz, CDCl3,
d ppm): 167.2, 158.2, 148.1,
145.1, 135.2, 131.4, 130.9, 129.4, 128.9, 128.8, 128.4, 128.3, 127.8,
126.9, 126.5, 124.6, 123.2, 117.1, 117.0, 108.3, 64.3, 39.1, 30.1, 18.9,
13.6; ESI-MS: m/z¼451.2 (Mþþ1). Anal. Calcd for C30H26O2S: C,
79.97; H, 5.82. Found: C, 79.62; H, 5.99.
11. (a) Zhou, J. F.; Tu, S. J.; Gao, Y.; Ji, M. Chin. J. Org. Chem. 2001, 21, 742; (b) Peng, Y.;
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Synlett 2003, 2001; (e) Balalaie, S.; Bararjanian, M.; Amani, A. M.; Movassagh, B.
Synlett 2006, 263; (f) Jin, T.-S.; Wang, A.-Q.; Wang, X.; Zhang, J.-S.; Li, T.-S.
Synlett 2004, 871; (g) Gao, S.; Tsai, C. H.; Tseng, C.; Yao, C. -F. Tetrahedron 2008,
64, 9143; (h) Hekmatshor, R.; Majedi, S.; Bakhtiari, K. Catal. Commun. 2008, 9,
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O-butyl ester (4s). Red jelly; IR (KBr, nmax, cmꢀ1): 3067, 1729, 1067;
1H NMR (200 MHz, CDCl3,
d
ppm): 8.00 (d, J¼8.2 Hz, 1H), 7.82e7.76
(m, 2H), 7.52e7.47 (m, 3H), 7.42e7.29 (m, 4H), 7.23e7.19 (m, 2H),
7.16e7.12 (m, 1H), 7.09e7.05 (m, 1H), 5.76 (s, 1H), 4.10 (t, J¼6.6 Hz,
2H), 1.52e1.34 (m, 2H), 1.21e1.13 (m, 2H), 0.89 (t, J¼7.2 Hz, 3H); 13C

1252
S. Samai et al. / Tetrahedron 68 (2012) 1247e1252
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