Application of directed metalation in synthesis. Part 8: Interesting example of chemoselectivity in the synthesis of thioaurones and hydroxy ketones and a novel anionic ortho-Fries rearrangement used as a tool in the synthesis of thienopyranones and thiafluorenones

Article abstract of DOI:10.1016/j.tet.2005.07.050

Chemoselective synthesis of thioaurones or 3-hydroxy benzo[b]thiophen-2- aryl ketones, 1-hydroxy naphtho[2,1-b]thiophen-2-aryl ketones and chalcones from N,N-diethyl-ortho-methyl sulfanyl aryl amides were described. (Benzo[b]thiophen-2-yl) alkylates and (naphtho[2,1-b]thiophen-2-yl) alkylates undergo a novel anionic ortho-Fries rearrangement leading to (3-hydroxy benzo[b]thiophen-2-yl) and (1-hydroxy naphtho[2,1-b]thiophen-2-yl) alkyl ketones. The hydroxy ketones were used as intermediates in the synthesis of wide range of benzothienopyranones and thiafluorenones.

Full text of DOI:10.1016/j.tet.2005.07.050

Tetrahedron 61 (2005) 9007–9017
Application of directed metalation in synthesis.
Part 8: Interesting example of chemoselectivity in the synthesis of
thioaurones and hydroxy ketones and a novel anionic ortho-Fries
rearrangement used as a tool in the synthesis of thienopyranones
and thiafluorenones*
b
Tarun Kanti Pradhan,a Asish Dea, and Jacques Mortier
*
aDepartment of Organic Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 072, India
b
´ ´ ´ ´ ´
Unite de Chimie organique moleculaire et macromoleculaire, Faculte des sciences et techniques, Universite du Maine,
Avenue Olivier Messiaen, 72085 Le Mans Cedex 9, France
Received 19 May 2005; revised 4 July 2005; accepted 15 July 2005
Available online 3 August 2005
Dedicated to Professor N. B. Chapman on his 90th birthday
Abstract—Chemoselective synthesis of thioaurones or 3-hydroxy benzo[b]thiophen-2-aryl ketones, 1-hydroxy naphtho[2,1-b]thiophen-2-
aryl ketones and chalcones from N,N-diethyl-ortho-methyl sulfanyl aryl amides were described. (Benzo[b]thiophen-2-yl) alkylates and
(naphtho[2,1-b]thiophen-2-yl) alkylates undergo a novel anionic ortho-Fries rearrangement leading to (3-hydroxy benzo[b]thiophen-2-yl)
and (1-hydroxy naphtho[2,1-b]thiophen-2-yl) alkyl ketones. The hydroxy ketones were used as intermediates in the synthesis of wide range
of benzothienopyranones and thiafluorenones.
q 2005 Elsevier Ltd. All rights reserved.
1. Introduction
2-position were obtained through a novel intramolecular
anionic rearrangement.
We have earlier demonstrated2–6 the usefulness of directed
metalation7 in providing regiocontrolled access to con-
tiguously substituted thiophene and benzene, which are key
intermediates in the synthesis of condensed heterocycles
incorporating a fused thiophene ring. In continuation of this
work, we have reported1 in a recent communication, two
novel high-yielding syntheses of 3-hydroxybenzo[b]thio-
phenes carrying acyl function in the 2-position termed as
hydroxy ketones 1. Either thioaurones (also known as hemi-
thioindigo) 2 or hydroxy ketones 1a–e and 1h–r, including
several chalcones can be chemoselectively synthesized via
the same one-pot reaction involving a common thioindoxyl
32,3 intermediate, while 3-hydroxybenzo[b]thiophene 1f–g
and 1s–t carrying an alkyl carbonyl substituent in the
The interesting and unprecedented switch of chemo-
selectivity observed during the formation of hydroxy
ketones 1a–e and 1h–r and the novel anionic ortho-Fries
rearrangement observed during the formation of hydroxy
alkyl ketones 1f–g and 1s–t lead to products that are
intermediates1 in the synthesis of benzothieno[3,2-b]-
pyranones. The latter are important synthetic targets
because of the interesting biological activities shown by
members of this class of compounds.8–10 Thioaurones have
a wide range of applications.11 They are employed in dyes,
cosmetics, aqueous jet-printing ink and as photochromic
materials.12 It was therefore, necessary to examine the scope
of these reactions by examining a wider range of substrates.
* Part 7: see Ref. 1.
2. Results and discussion
Keywords: Directed metalation; Chemoselectivity; Thioaurones; Chalcone;
Anionic ortho-Fries rearrangement; Benzothienopyranone.
A consequence of the development of expedient synthesis of
thioindoxyls 32,3 from readily available N,N-diethyl aryl
carboxamides 4a–d2,3,7 was the easy accessibility of
*
Corresponding author. Tel.: C91 33 2473 4971x403; fax: C91 33 2473
2805; e-mail: ocad@mahendra.iacs.res.in
0040–4020/$ - see front matter q 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2005.07.050

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T. K. Pradhan et al. / Tetrahedron 61 (2005) 9007–9017
Scheme 1. Reagents and conditions: (i) SOCl2/benzene/reflux; (ii) N,N-diethyl amine/benzene/rt; (iii) s-BuLi/TMEDA/THF/(SCH3)2/K78 8C to rt; (iv) LDA
(1.5 equiv)/THF/K78 8C to rt; (v) LDA (2.5 equiv)/THF/R1CHO (1.1 equiv)/K10 to 0 8C; (vi) LDA (1.5 equiv)/THF/R1CHO (1.1 equiv)/K10 to 0 8C.
thioaurones 2 in a one-pot reaction in high yields. In
comparison to the one-pot synthesis of thioaurones reported
by Cabbidu,13 the one-pot synthesis developed in our
laboratory (Scheme 1a and b) allows a wider variation of
substituents in the final products. The starting amide 4a–d
were converted into its ortho-methyl sulfanyl derivative
5a–d via standard protocol of directed ortho-lithiation and
quenching with dimethyldisulfide. The resulting methyl-
sulfanyl derivatives 5a–d2,3,7 were treated with LDA at 0 8C
and after stirring for 1 h at that temperature, a solution of the
aryl aldehyde or cinnamaldehyde (1.2 equiv) in tetra-
hydrofuran was added while the temperature of the reaction
mixture was maintained at 0 8C. Acidic work up after
stirring for further 2 h at that temperature afforded a red
crystalline material, and the crude reaction product was
purified by column chromatography over silica gel to afford
the thioaurones 2 in good to excellent yields (Table 1). In
common with the observation of Cabbidu,13 we found that
attempted one-pot synthesis of thioaurones using alkyl
aldehydes were accompanied by the formation of intractable
materials, presumably resulting out of polymeric self-
condensation of the aldehydes.
these compounds were assigned as the (3-hydroxybenzo[b]
thiophen-2-yl) (1a–e and 1h–o) and (1-hydroxy
naphtho[2,1-b]thiophen-2-yl) (1p–r) aryl ketone structures
(Scheme 2a and b).
Exclusive formation of the hydroxy aryl ketones was
assured when the aryl aldehyde was used in excess followed
by stirring the reaction mixture at room temperature for
several hours. The plausible reaction mechanism (Scheme 3)
requires the formation of thioindoxyl 3 as the common
intermediate for both the thioaurones and the hydroxy
ketones. The ionic intermediate 6 is formed by sequential
deprotonation at the 2-position of 3 and subsequent attack
Table 1. Thioaurones or hemi-thioindigo
Entry
Compound
R
R1
Yield
(%)
2a
2b
2c
2d
2e
2f
H
H
p-ClC6H4
79
CH]CHPh 75
Ph 76
CH]CHPh 80
Ph
p-ClC6H4
2-thienyl
OMe
OMe
SMe
SMe
SMe
SMe
The crude thioaurones were occasionally accompanied by
trace amounts of another compound, which could be
separated by careful column chromatography over silica
gel. Existence of intramolecular hydrogen bonding between
hydroxyl and carbonyl functions present in these com-
pounds, was evident from the peaks at 3440–3425 cmK1
and at 1590 cmK1 in their IR spectra. Additional corrobora-
tion for the presence of hydrogen bonding was provided by
the 1H NMR spectra, which displayed signals due to
hydrogen bonded OH as a slightly broad one proton singlet
at around 13.5 ppm. From analytical and spectroscopic data
78
80
92
2g
2h
CH]CHPh 78
2i
Ph
p-ClC6H4
2-thienyl
82
93
88
2j
2k
2l
CH]CHPh 79

T. K. Pradhan et al. / Tetrahedron 61 (2005) 9007–9017
9009
Scheme 2. Reagents and conditions: (i) LDA (1.5 equiv)/THF/K78 8C to rt; (ii) LDA (2.5 equiv)/THF/R1CHO (2.2 equiv)/K10 8C to rt; (iii) LDA (1.5 equiv)/
THF/R1CHO (2.2 equiv)/K10 8C to rt.
An aromatic compound carrying hydroxyl and acyl
substituents on two contiguous carbons can act as key
intermediates for annulating a pyranone ring on to the
existing core (vide infra). While hydroxy ketones 1a–e and
1h–r can now be easily obtained from 5a–d, it was not
possible to synthesize alkyl hydroxy ketones 1f–g and 1s–t
in the same way because of the polymerisation of the
starting aldehydes under the reaction condition as stated
above. We could however, synthesize the latter via a novel
anionic ortho-Fries rearrangement. Anionic ortho-Fries
rearrangement14 under directed metalation condition, as
originally reported by Snieckus14 consists of directed
Scheme 3. Reagents and conditions: (i) LDA (2.5 equiv)/THF/R1CHO
lithiation at the ortho-position of an O-carbamate sub-
stituent followed by intramolecular rearrangement in the
(1.1 equiv)/K10 to 0 8C; (ii) aq HCl; (iii) R1CHO (1.1 equiv)/K10 8C to rt.
absence electrophile quench. We report here, similar
rearrangement undergone by an ortho-deprotonated alkyl
carboxylate species 8a–d (Scheme 4a and b). Alkyl
carboxylates have no directing power in directed metalation
by the incipient carbanion on the carbonyl carbon of the aryl
aldehyde. Acidic work up, after keeping the reaction
mixture at 0 8C for 1 h, results in dehydration affording
the thioaurones 2. When the reaction mixture was stirred at
room temperature in the presence of excess aryl aldehyde
Table 2. Hydroxy ketones
Entry
Compound
R
R1
Yield
(%)
for 5–6 h, it has sufficient time to undergo Cannizzaro type
hydride transfer resulting in the formation of the 1,3-
dicarbonyl compound 7, which subsequently enolises to the
hydroxy ketone 1a–e and 1h–r (Table 2). The transfer of
hydride to the aldehyde during the formation of the hydroxy
ketone is clearly evident from the exclusive formation of the
latter when excess aldehyde is used. It was however,
difficult to isolate the alcohol that should form con-
comitantly with the hydride transfer. The proposed mode
of hydride transfer was inferred from GC analysis of the
crude reaction product obtained for the synthesis of the
compound 1a (RZH) from o-methylsulfanyl benzamide
and benzaldehyde. GC analysis of the crude reaction
product contained a peak with the same retention time as
that of benzyl alcohol whose gas chromatogram was run
separately. Benzyl alcohol was then added to the crude
reaction product and the GC of the mixture was run
separately. The GC trace did not show any additional peaks
and an increase of the height of the peaks, which was earlier
surmised as that of benzyl alcohol, was observed.
Occurrence of the Cannizzaro-type hydride transfer was
thus, confirmed and an interesting switch of chemo-
selectivity is thus, observed between elimination product 2
and the 1,3-dicarbonyl compound 7 depending upon the
reaction conditions.
1a
1b
1c
1d
1e
1f
1g
1h
1i
1j
1k
1l
1m
1n
1o
H
H
H
H
H
H
H
OMe
OMe
OMe
OMe
SMe
SMe
SMe
SMe
Ph
p-ClC6H4
2-thienyl
93
89
93
p-OMeC6H4 91
CH]CHPh
Me
Et
95
67
73
91
93
90
89
91
93
90
88
Ph
p-ClC6H4
2-thienyl
CH]CHPh
Ph
p-ClC6H4
2-thienyl
CH]CHPh
1p
1q
1r
1s
1t
Ph
90
93
85
55
63
p-ClC6H4
CH]CHPh
Me
Et

9010
T. K. Pradhan et al. / Tetrahedron 61 (2005) 9007–9017
1e, 1k and 1r is amply demonstrated in the expedient
synthesis of pyranones 10a–b and fluorenone 10c
(Scheme 5a and b), respectively. Previously, Mustafa syn-
thesized this class of compounds from 1f17 by first
converting them into chalcones through reaction with aryl
aldehydes followed by treatment with seleniumdioxide.15,16
We could obtain the chalcones in one step from 5 and
cinnamaldehyde, which were then converted into pyranone
derivatives 10a–c by usual treatment with seleniumdioxide
in dry isoamyl alcohol.
Treatment of 1f and 1g with oil-free sodium hydride
(2.5 equiv) in dry THF was followed by addition of ethyl
formate and stirring for 10 h at room temperature. Addition
of water and acidification with 2 N HCl after most of the
solvent was evaporated, afforded the crude cyclised product
11a–b, which were purified by column chromatography
over silica gel. We found that 2-hydroxy-3-methyl-2,3-
dihydro benzo[4,5]thieno[3,2-b]pyran-4-one (11b) remains
as 1:1 mixture of diasteromers. The hydroxy compounds
11a and 11b were dehydrated with p-toluenesulfonic acid in
benzene to afford 12a and 12b, respectively, in 90 and 95%
yields (Scheme 6).
Scheme 4. Reagents and conditions: (i) NaH/THF/R1COCl/rt; (ii) LDA/
THF/K80 8C to rt.
reactions since nucleophilic substitution reaction occurs in
the presence of alkyl lithium. However, for our purpose, we
could take advantage of the acidic nature of the proton in the
a-position to the ring sulfur atom in benzo[b]thiophene,
allowing smooth deprotonation at that position, with LDA.
Treatment of thioindoxyl 3a2,3 and 3d3 with acetyl and
propionyl chloride in THF in the presence of oil-free sodium
hydride afforded 8a, 8b,1 8c and 8d in excellent yields.
When the compounds 8a–d were treated with LDA in THF
at K80 8C, deprotonation indeed took place in the position
a to the ring sulfur atom, as expected. Usual acidic work up
after keeping the reaction mixture at room temperature for
6 h afforded the rearranged products 1f–g and 1s–t in very
good yields (Table 2). A trace amount of 3a and 3d were
also formed, which were separated by column chromato-
graphy over silica gel.
The hydroxy ketone 1f was also used as an intermediate in
the synthesis of ethyl benzo[4,5]thieno[3,2-b]pyran-4-one-
2-carboxylate8 (13) and benzo[4,5]thieno[3,2-b]pyran-4-
one-3-carboxaldehyde (14) in very good yields. Compound
13 was obtained in 85% yield when 1f was treated with oil
free sodium hydride in THF followed by diethyl oxalate
while treatment of 1f with dimethyl formamide and
phosphorus oxychloride afforded 14 in 68% yield
(Scheme 6).
Several of the hydroxy ketones obtained by the above two
routes served as key intermediates in the annulation of a
g-pyranone ring onto the benzo[b]thiophene or naphtho
[2,1-b]thiophene core. Bubbling dry HCl gas into a dry
ethanolic solution of 1e, 1k, 1o and 1r afforded dihydropyr-
anones 9a,1 9b, 9c and dihydrothiafluorenone 9d, respect-
ively, (Scheme 5a and b) in excellent yields.
3. Conclusion
The one-pot reaction of N,N-diethyl-ortho-methylsulfanyl
aryl amides with aryl aldehydes in the presence of LDA
associated with an interesting switch of chemoselectivity is
yet another example of usefulness of directed metalation as
a methodology in synthetic aromatic and heteroaromatic
chemistry. While one of the alternative products, thio-
aurones have a multitude of applications, the other
The usefulness of the chemoselective synthesis of chalcones
Scheme 5. Reagents and conditions: (i) Dry ethanol/dry HCl (g); (ii) SeO2/dry isoamyl alcohol/reflux.

T. K. Pradhan et al. / Tetrahedron 61 (2005) 9007–9017
9011
Scheme 6. Reagents and conditions: (i) NaH/THF/HCO2Et; (ii) PTSA/benzene/reflux; (iii) NaH/THF/(CO2Et)2; (iv) DMF/POCl3.
alternative products 3-hydroxy-2-ketoaryl benzo[b]thio-
phenes and 1-hydroxy-2-ketoaryl naphtho[2,1-b]thiophenes
are important synthetic intermediates. A novel anionic
ortho-Fries rearrangement described in this paper, has led to
3-hydroxy-2-ketoalkyl benzo[b]thiophenes, which are used
as intermediates in the synthesis of benzothienopyranones
having different types of substitution in g-pyranone ring.
left after evaporation of the solvent was purified by column
chromatography [eluent: ethyl acetate–petroleum ether
(1/15)], yellow solid, yield 0.43 g, 79%, mp 162–165 8C
(ethyl acetate–petroleum ether). IR (KBr) nmax: 1678,
1
1580 cmK1; H NMR (300 MHz, CDCl3) dH: 7.95 (1H, d,
JZ7.7 Hz), 7.89 (1H, s), 7.64–7.56 (3H, m), 7.51–7.43 (3H,
m), 7.33 (1H, d, JZ7.7 Hz); 13C (75 MHz, CDCl3) dC:
188.8, 146.1, 136.5, 135.8, 133.3, 133.1, 132.4, 132.4,
131.1, 130.6, 129.2, 129.2, 127.5, 126.1, 124.3. Anal. Calcd
for C15H9ClOS: C, 66.05; 3.33%. Found C, 66.28; 3.41%.
4. Experimental
4.1.2. 2-(3-Phenylallylidene)benzo[b]thiophen-3-one
(2b). Prepared from 5a (0.45 g, 2 mmol) in THF (5 mL),
LDA (5 mmol) in THF (15 mL) and cinnamaldehyde
(0.32 g, 2.4 mmol) in THF (5 mL). Purified by column
chromatography [eluent: ethyl acetate–petroleum ether
(1/13)], red solid, yield 0.39 g, 75%, mp 138–140 8C
(ethyl acetate–petroleum ether). IR (KBr) nmax: 1662,
4.1. General
Melting points (uncorrected) were recorded in open
capillaries on a hot stage apparatus. H NMR (300 MHz)
1
and 13C NMR (75 MHz) spectra were recorded in
deuteriochloroform on a Bruker DPX-300 spectrometer.
Chemical shifts (d) are expressed in ppm using tetra-
methylsilane as internal standard. IR spectra were recorded
on FTIR-8300 and SHIMADZU spectrometers, for solids in
KBr discs and for liquids by placing a thin layer of the
sample between two KBr discs. Commercially available
solvents were purified by distillation. Diethyl ether and
tetrahydrofuran were kept overnight over potassium
hydroxide and subsequently purified further by the
benzophenone ketyl method. Dinethyl sulfate was washed
with water and kept over anhydrous potassium carbonate
before use. Both n- and s-butyl lithium were prepared by
slow addition of the appropriate halide to the freshly
prepared dispersion of lithium in n-hexane (for n-butyl
lithium) or cyclohexane (for s-butyl lithium) under
sonication. Petroleum ether has boiling point 60–80 8C.
Silica gel (60–120 mesh) was used for column
chromatography.
1
1579, 1559 cmK1; H NMR (300 MHz, CDCl3) dH: 7.69
(1H, d, JZ11 Hz), 7.58 (1H, d, JZ7.9 Hz), 7.55–7.25 (8H,
m), 7.13–6.99 (2H, m); 13C (75 MHz, CDCl3) dC: 188.3,
145.6, 143.9, 136.3, 135.4, 133.3, 132.0, 130.0, 129.3,
129.3, 128.2, 127.9, 127.9, 127.1, 125.7, 124.6, 124.3. Anal.
Calcd for C17H12OS: C, 77.24; 4.58%. Found C, 77.11;
4.49%.
4.1.3. 2-Benzylidene-4-methoxybenzo[b]thiophen-3-one
(2c). Prepared in the same way from 5b (0.25 g, 1 mmol)
in THF (5 mL). LDA (2.2 mmol) in THF (10 mL) and
benzaldehyde (0.13 g, 1 mmol) in THF (3 mL). Purified by
column chromatography [eluent: ethyl acetate–petroleum
ether (1/15), yellow solid, yield 0.25 g, 76%, mp 160–
161 8C (ethyl acetate–petroleum ether). IR (KBr) nmax
:
1680, 1576 cmK1; H NMR (300 MHz, CDCl3) dH: 7.88
(1H, s), 7.71–7.68 (2H, m), 7.53–7.38 (4H, m), 7.07 (1H, d,
JZ7.7 Hz), 6.76 (1H, d, JZ8.2 Hz) 4.01 (3H, s); 13C
(75 MHz, CDCl3) dC: 187.1, 161.2, 148.7, 136.9, 134.8,
132.6, 131.2, 131.2, 130.6, 130.1, 129.3, 129.3, 118.9,
116.3, 108.3, 56.3. MS: (m/z) 267 (MCK1), 268 (MC), 269
(MCC1). Anal. Calcd for C16H12O2S: C, 71.62; 4.51%.
Found C, 71.75; 4.62%.
1
4.1.1. General synthesis of thioaurones taking 2-(4-
chlorobenzylidene)benzo[b]thiophen-3-one (2a) as
representative. To a well stirred solution of LDA
(5 mmol) in THF (15 mL), 5a (0.45 g, 2.4 mmol) in THF
(5 mL) was added by syringe while the temperature of the
reaction mixture was kept between K10 and 0 8C. After
stirring for 1 h, 4-chlorobenzaldehyde (0.34 g, 2.4 mmol) in
THF (5 mL) was added to the reaction mixture at the same
temperature. After stirring for 2 h at 0 8C, water (25 mL)
was added to the reaction mixture and the pH was
maintained between 4 and 5 by addition of 2 N HCl. After
extraction with chloroform the organic layer was washed
with water and dried (Na2SO4). The crude red solid residue
4.1.4. 4-Methoxy-2-(3-phenylallylidene) benzo[b]thio-
phen-3-one (2d). Prepared in the same way from 5b
(0.25 g, 1 mmol) in THF (5 mL), LDA (2.2 mmol) in THF
(10 mL) and cinnamaldehyde (0.13 g, 1 mmol). Purified by
column chromatography [eluent: ethyl acetate–petroleum
ether (1/13)] to afford thioaurone 2d as reddish crystalline

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T. K. Pradhan et al. / Tetrahedron 61 (2005) 9007–9017
material, yield 0.25 g, 80%, mp 180–182 8C (ethyl acetate–
petroleum ether). IR (KBr) nmax: 1664, 1585, 1572 cmK1
1H NMR (300 MHz, CDCl3) dH: 7.62–7.52 (3H, m), 7.47–
7.35 (4H, m), 7.19–6.97 (4H, m), 2.50 (3H, s, SCH3); 13C
(75 MHz, CDCl3) dC: 187.9, 160.0, 146.9, 145.3, 143.3,
136.4, 132.8, 132.5, 129.8, 129.2, 129.2, 128.2, 127.8,
127.8, 124.6, 120.0, 119.2, 14.2. Anal. Calcd for
C18H14OS2: C, 60.27; 3.48%. Found C, 60.39; 3.53%.
;
1H NMR (300 MHz, CDCl3) dH: 7.60–7.43 (4H, m), 7.40–
7.29 (3H, m), 7.09–6.90 (3H, m), 6.71 (1H, d, JZ8.2 Hz),
3.97 (3H, s, OCH3); 13C (75 MHz, CDCl3) dC: 186.4, 160.9,
147.7, 142.9, 136.6, 136.5, 133.3, 132.0, 129.7, 129.2,
129.1, 128.0, 127.8, 124.6, 116.4, 107.9, 96.4, 56.2. Anal.
Calcd for C18H14O2S: C, 73.44; 4.79%. Found C, 73.53;
4.85%.
4.1.9. 2-Benzylidene naphtho[2,1-b]thiophen-1-one (2i).
Prepared in the same way from 5d (0.27 g, 1 mmol) in THF
(5 mL), LDA (2.5 mmol) in THF (10 mL) and benzal-
dehyde (0.13 g, 1.2 mmol) in THF (3 mL). Purified by
column chromatography [eluent: ethyl acetate–petroleum
ether (1/14)], yellow solid, yield 0.24 g, 82%, mp 186–
4.1.5. 2-Benzylidene-4-methylsulfanyl benzo[b]thiophen-
3-one (2e). Prepared in the same way from 5c (0.27 g,
1 mmol), in THF (5 mL), LDA (2.5 mmol) in THF (10 mL)
and benzaldehyde (0.13 g, 1.2 mmol) in THF (3 mL).
Purified by column chromatography [eluent: ethyl acetate–
petroleum ether (1/9)], red solid, yield 0.22 g, 78%, mp
188 8C (ethyl acetate–petroleum ether). IR (KBr) nmax
:
1678, 1558 cmK1; H NMR (300 MHz, CDCl3) dH: 9.37
(1H, d, JZ8.5 Hz), 8.02–7.98 (2H, m), 7.86 (1H, d, JZ
8.1 Hz), 7.75–7.67 (3H, m), 7.55–7.40 (5H, m); 13C
(75 MHz, CDCl3) dC: 189.3, 150.5, 144.7, 136.6, 134.7,
134.4, 132.1, 131.7, 131.1, 131.1, 130.5, 130.0, 129.4,
129.4, 129.0, 128.8, 126.7, 123.5, 121.9. Anal. Calcd for
C19H12OS: C, 79.14; 4.19%. Found C, 79.26; 4.11%.
1
173–175 8C (ethyl acetate–petroleum ether). IR (KBr) nmax
:
1673, 1577 cmK1; H NMR (300 MHz, CDCl3) dH: 7.87
(1H, s), 7.68–7.65 (2H, m), 7.48–7.38 (4H, m), 7.19 (1H, d,
JZ7.6 Hz), 7.03 (1H, d, JZ7.6 Hz), 2.49 (3H, s, SCH3);
13C (75 MHz, CDCl3) dC: 187.3, 160.7, 147.1, 145.4, 134.4,
132.8, 131.7, 131.7, 131.1, 128.2, 128.2, 125.6, 124.3,
119.9, 118.7, 13.9. Anal. Calcd for C16H12OS2: C, 67.57;
4.25%. Found C, 67.56; 4.36%.
1
4.1.10. 2-(4-Chlorobenzylidene)naphtho[2,1-b]thiophen-
1-one (2j). Prepared from 5d (0.27 g, 1 mmol) in THF
(5 mL), LDA (2.5 mmol) in THF (10 mL) and 4-chloro-
benzadehyde (0.17 g, 1.2 mmol) in THF (3 mL). Purifi-
cation by column chromatography [eluent: ethyl acetate–
petroleum ether (1/14)] gave yellow solid, yield 0.3 g, 93%,
mp 216–218 8C (ethyl acetate–petroleum ether). IR (KBr)
4.1.6. 2-(4-Chlorobenzylidene)-4-methylsulfanyl benzo-
[b]thiophen-3-one (2f). Prepared from 5c (0.27 g, 1 mmol)
in THF (5 mL), LDA (2.5 mmol) in THF (10 mL) and
4-chlorobenzaldehyde (0.17 g, 1.2 mmol) in THF (3 mL).
Purification by column chromatography [eluent: ethyl
acetate–petroleum ether (1/15)] gave yellow solid, yield
0.25 g, 80%, mp 213–215 8C (ethyl acetate–petroleum
1
nmax: 1680, 1569 cmK1; H NMR (300 MHz, CDCl3) dH:
9.35 (1H, d, JZ8.4 Hz), 8.03 (1H, d, JZ8.6 Hz), 7.95 (1H,
s), 7.87 (1H, d, JZ8.2 Hz), 7.74–7.65 (3H, m), 7.56–7.44
(4H, m); 13C (75 MHz, CDCl3) dC: 189.2, 150.1, 136.8,
136.5, 133.2, 132.8, 132.4, 132.1, 132.1, 131.7, 131.6,
130.2, 129.7, 129.7, 128.9, 126.8, 123.7, 123.5, 121.9. Anal.
Calcd for C19H11ClOS: C, 70.69; 3.43%. Found C, 70.82;
3.52%.
ether). IR (KBr) nmax: 1655, 1581 cmK1 1H NMR
;
(300 MHz, CDCl3) dH: 7.81 (1H, s), 7.62–7.59 (2H, m),
7.49–7.42 (3H, m), 7.21 (1H, d, JZ7.7 Hz), 7.06 (1H, d, JZ
7.7 Hz), 2.54 (3H, s, SCH3); 13C (75 MHz, CDCl3) dC:
188.7, 160.1, 147.1, 145.4, 134.4, 132.8, 131.8, 131.8,
131.1, 129.2, 129.2, 125.6, 124.5, 119.9, 118.7, 13.8. Anal.
Calcd for C16H11ClOS2: C, 60.27; 3.48%. Found C, 60.39;
3.53%.
4.1.11. 2-Thiophen-2-ylmethylene naphtho[2,1-b]thio-
phen-1-one (2k). Prepared from 5d (0.27 g, 1 mmol) in
THF (5 mL), LDA (2.5 mmol) in THF (10 mL) and
thiophen-2-carboxaldehyde (0.13 g, 1.2 mmol) in THF
(3 mL). Purified by column chromatography [eluent: ethyl
acetate–petroleum ether (1/14)], yield 0.26 g, 88%, mp 180–
4.1.7. 4-Methylsulfanyl-2-(thiophen-2-yl)methylene
benzo[b]thiophen-3-one (2g). Prepared from 5c (0.27 g,
1 mmol) in THF (5 mL), LDA (2.5 mmol) in THF (10 m)
and thiophen-2-carboxaldehyde (6.13 g, 1 mmol) in THF
(3 mL). Purification by column chromatography [eluent:
ethyl acetate–petroleum ether (1/14)] gave yellow solid,
yield 0.26 g, 92%, mp 166–168 8C (ethyl acetate–petroleum
182 8C (ethyl acetate–petroleum ether). IR (KBr) nmax
:
1677, 1575 cmK1; H NMR (300 MHz, CDCl3) dH: 9.37
(1H, d, JZ8.5 Hz), 8.20 (1H, s), 8.02 (1H, d, JZ8.6 Hz),
7.87 (1H, d, JZ8.1 Hz), 7.73–7.64 (2H, m), 7.57–7.51 (3H,
m), 7.21–7.19 (1H, m); 13C (75 MHz, CDCl3) dC: 189.3,
149.6, 139.6, 136.5, 134.2, 132.7, 132.1, 131.9, 130.0,
128.9, 128.8, 126.8, 126.7, 124.8, 123.5, 123.5, 122.0. Anal.
Calcd for C17H10OS2: C, 69.36; H, 3.42%. Found C, 69.48;
H, 3.27%.
1
1
ether). IR (KBr) nmax: 1666, 1581, 1554 cmK1; H NMR
(300 MHz, CDCl3) dH: 8.05 (1H, s), 7.63 (1H, d, JZ
4.9 Hz), 7.48–7.42 (2H, m), 7.24–7.16 (2H, m), 7.04 (1H, d,
JZ7.9 Hz), 2.5 (3H, s, SCH3); 13C (75 MHz, CDCl3) dC:
188.1, 159.7, 145.5, 139.6, 134.6, 133.5, 132.7, 131.6,
130.7, 128.9, 125.6, 120.3, 119.3 14.2. Anal. Calcd for
C14H10OS3: C, 57.90; 3.47%. Found C, 57.78; 3.52%.
4.1.12. 2-(3-Phenyallylidene)naphtho[2,1-b]thiophen-1-
one (2l). Prepared from 5d (0.55 g, 2 mmol) in THF
(7 mL), LDA (5 mmol) in THF (15 mL) and cinnamalde-
hyde (0.31 g, 2.4 mmol) in THF (5 mL). Purification by
column chromatography [eluent: ethyl acetate–petroleum
ether (1/12)] gave red solid, yield 0.5 g, 79%, mp 243–
4.1.8. 4-Methylsulfanyl-2-(3-phenylallylidene)benzo[b]
thiophen-3-one (2h). Prepared from 5c (0.54 g, 2 mmol),
LDA (5 mmol) in THF (15 mL) and cinnamaldehyde (0.3 g,
2.5 mmol) in THF (5 mL). Purification by column chroma-
tography [eluent: ethyl acetate–petroleum ether (1/12)] gave
red solid, yield 0.48 g, 78%, mp 210–212 8C (ethyl acetate–
245 8C (ethyl acetate–petroleum ether). IR (KBr) nmax
:
1
1666, 1579, 1553 cmK1; H NMR (300 MHz, CDCl3) dH:
petroleum ether). IR (KBr) nmax: 1655, 1574, 1554 cmK1
;
9.37 (1H, d, JZ8.5 Hz), 8.02 (1H, d, JZ8.6 Hz), 7.87 (1H,

T. K. Pradhan et al. / Tetrahedron 61 (2005) 9007–9017
9013
d, JZ8.1 Hz), 7.78–7.67 (2H, m), 7.58–7.50 (4H, m), 7.43–
7.26 (3H, m), 7.18–7.05 (2H, m); 13C (75 MHz, CDCl3) dC:
189.2, 149.6, 144.4, 136.8, 134.4, 132.4, 132.2, 130.5,
130.4, 129.7, 129.7, 129.6, 129.5, 129.2, 128.4, 128.4,
127.0, 125.5, 125.1, 124.0, 122.5. Anal. Calcd for
C21H14OS: C,80.22; 4.49%. Found C, 80.35; H, 4.55%.
113.9, 109.1, 55.5. Anal. Calcd for C16H12O3S: C, 67.59; H,
4.25%. Found C, 67.43; H, 4.38%.
4.1.16. 1-(3-Hydroxy benzo[b]thiophen-2-yl)-3-phenyl
propenone (1e). Prepared in the same way from 5a
(0.45 g, 2 mmol) in THF (5 mL), LDA (5 mmol) in THF
(15 mL) and cinamaldehyde (0.53 g, 4 mmol) in THF
(5 mL). Purified by column chromatography [eluent: ethyl
acetate–petroleum ether (1/16)], red solid, yield 0.53 g,
95%, mp 139–141 8C (ethyl acetate–petroleum ether). IR
(KBr) nmax: 3420, 1576 cmK1; 1H NMR (300 MHz, CDCl3)
dH: 13.21 (1H, s, OH), 8.05 (1H, d, JZ7.8 Hz), 7.97 (1H, d,
JZ15.3 Hz), 7.79 (1H, d, JZ8.1 Hz), 7.69–7.66 (2H, m),
7.59–7.27, (5H, m), 7.09 (1H, d, JZ15.3 Hz); 13C (75 MHz,
CDCl3) dC: 185.6, 164.8, 144.2, 139.5, 134.2, 130.8, 130.5,
128.9, 128.9, 128.8, 128.8, 127.5, 124.7, 123.7, 123.2,
122.3, 111.6. MS: (MC) 280, (MCC1) 281. Anal. Calcd for
C17H12O2S: C, 72.83; H, 4.31%. Found C, 72.95; H, 4.43%.
4.1.13. General synthesis of hydroxy ketones taking
(4-chlorophenyl) (3-hydroxy benzo[b]thiophen-2-yl)
methanone (1b) as representative. To a well-stirred
solution of LDA (2.5 mmol) in THF (15 mL) kept at
K10 8C, 5a (0.22 g, 1 mmol) in THF (4 mL) was added by
syringe. The reaction mixture was stirred at that temperature
for 1 h followed by addition of p-chlorobenzaldehyde
(0.34 g, 2.4 mmol) in THF (5 mL). The reaction mixture
was then allowed to attain room temperature and stirred at
that temperature for 6 h. Work up consisted of addition of
water (25 mL) to the reaction mixture, maintenance of pH at
4–5 by dropwise addition of HCl (2 N) followed by
extraction with chloroform (3!20 mL). The organic layer
was washed with water (3!25 mL) and dried (Na2SO4).
Removal of solvent and purification by column chromato-
graphy [eluent: ethyl acetate–petroleum ether (1/17)] gave
yellow solid, yield 0.27 g, 89%, mp 136–138 8C (ethyl
4.1.17. General synthesis of aryl alkyl ketones taking
1-(3-hydroxy benzo[b]thiophen-2-yl) propan-1-one (1g)
as representative. To a well stirred solution of LDA
(2.5 mmol) in THF (10 mL) kept at K80 8C a solution of 8b
(0.41 g, 2 mmol) in THF (5 mL) was added by syringe and
after stirring for 30 min at that temperature the reaction
mixture was allowed to reach room temperature. After
stirring for another 6 h, 2 N HCl was added to the reaction
mixture followed by extraction with chloroform (3!
25 mL). The organic layer was washed with brine and
dried (Na2SO4). The residue left after removal of solvent
was purified by column chromatography [eluent: ethyl
acetate–petroleum ether (1/20)], amorphous solid, yield
acetate–petroleum ether). IR (KBr) nmax: 3446, 1589 cmK1
;
1H NMR (300 MHz, CDCl3) dH: 13.30 (1H, s, OH), 8.00–
7.84 (3H, m), 7.68 (1H, d, JZ8.1 Hz), 7.60–7.29, (4H, m);
13C (75 MHz, CDCl3) dC: 190.2, 165.5, 140.5, 138.9, 136.3,
130.3, 130.0, 129.7, 129.7, 128.9, 128.9, 127.3, 124.7,
123.9, 122.8. MS: (MC) 288.6. Anal. Calcd for
C15H9ClO2S: C, 62.39; H, 3.14%. Found C, 62.47; H,
3.23%.
0.30 g, 73%, mp 72 8C. IR (KBr) nmax: 3500, 1626 cmK1
;
1H NMR (300 MHz, CDCl3) dH: 12.28 (1H, s, OH), 7.99–
7.96 (1H, m), 7.78–7.71 (1H, m), 7.55–7.49 (1H, m), 7.43–
7.37 (1H, m), 2.84 (2H, q, JZ7.2 Hz, COCH2CH3), 1.30
(3H, t, JZ7.2 Hz, CH2CH3); 13C NMR (75 MHz, CDCL3)
dC: 200.0, 161.4, 138.8, 129.7, 124.7, 123.7, 123.2, 120.4,
110.9, 34.1, 8.1. Anal. Calcd for C11H10O2S: C, 64.05; H,
4.89%. Found: C, 64.16; H, 4.97%.
4.1.14. (3-Hydroxybenzo[b]thiophen-2-yl) (thiophen-2-
yl) methanone (1c). Prepared in the same way from 5a
(0.23 g, 1 mmol) in THF (5 mL), LDA (2.5 mmol) in THF
(15 mL) and thiophen-2-carboxaldehyde (0.23 g, 2.4 mmol)
in THF (5 mL). Purification by column chromatography
[eluent: ethyl acetate–petroleum ether (1/17)] gave yellow
solid, yield 0.23 g, 93%, mp 118 8C (ethyl acetate–
petroleum ether). IR (KBr) nmax: 3442, 1571 cmK1 1H
;
NMR (300 MHz, CDCl3) dH: 13.36 (1H, s, OH), 8.07 (1H,
d, JZ3.8 Hz), 7.98 (1H, d, JZ8.1 Hz), 7.70–7.67 (2H, m),
7.52–7.47 (1H, m), 7.38–7.33 (1H, m), 7.18–7.15, (1H, m);
13C (75 MHz, CDCl3) dC: 185.6, 164.8, 144.2, 139.5, 134.2,
130.8, 130.5, 128.9, 128.9, 128.8, 128.8, 127.5, 124.7,
123.7, 123.2, 122.3, 111.6. MS: (MC) 260, (MCC1) 261.
Anal. Calcd for C13H8O2S2: C, 59.98; H, 3.10%. Found C,
59.82; H, 3.23%.
4.1.18. (3-Hydroxy-4-methoxy benzo[b]thiophen-2-yl)
phenyl methanone (1h). Prepared according to the general
synthesis of hydroxy ketone 1b from 5b (0.22 g, 1 mmol) in
THF (5 mL), LDA (2.5 mmol) in THF (15 mL) and
benzaldehyde (0.25 g, 2.4 mmol) in THF (5 mL). Purifi-
cation by column chromatography [eluent: ethyl acetate–
petroleum ether (1/18)] gave yellow solid, yield 0.26 g,
91%, mp 138 8C (ethyl acetate–petroleum ether). IR (KBr)
1
nmax: 3421, 1589 cmK1; H NMR (300 MHz, CDCl3) dH:
14.27 (1H, s, OH), 8.03–8.00 (2H, m), 7.62–7.44 (4H, m),
7.29 (1H, d, JZ8.0 Hz), 6.79 (1H, d, JZ8.0 Hz), 4.04 (3H,
s, OCH3); 13C NMR (75 MHz, CDCl3) dC: 191.1, 167.6,
169.0, 138.6, 132.8, 131.9, 129.0, 129.0, 128.7, 128.7,
124.6, 122.5, 120.2, 115.5, 105.5, 56.3. MS (EI): (MC) 284,
(MCC1) 285. Anal. Calcd for C16H10O3S: C, 67.59; H,
4.25%. Found: C, 67.73; H, 4.33%.
4.1.15. (4-Methoxyphenyl) (3-hydroxy benzo[b]thio-
phen-2-yl) methanone (1d). Prepared in the same way
from 5a (0.223 g, 1 mmol) in THF (5 mL), LDA (2.5 mmol)
in THF (15 mL) and p-methoxybenzaldehyde (0.34 g,
2.5 mmol) in THF (5 mL). Purification by column chroma-
tography [eluent: ethyl acetate–petroleum ether (1/16)] gave
yellow solid, yield 0.24 g, 91%, mp 106 8C (ethyl acetate–
petroleum ether). IR (KBr) nmax: 3446, 1589 cmK1 1H
;
NMR (300 MHz, CDCl3) dH: 13.71 (1H, s, OH), 8.13–8.06
(3H, m), 7.76 (1H, d, JZ8.1 Hz), 7.58–7.53, (1H, m), 7.46–
2.41 (1H, m), 7.05–7.01 (2H, m), 3.92 (3H, s, OCH3); 13C
(75 MHz, CDCl3) dC: 190.2, 165.2, 163.3, 140.3, 130.8,
130.8, 130.6, 130.3, 129.9, 124.6, 123.8, 122.8, 113.9,
4.1.19. (4-Chlorophenyl) (3-hydroxy-4-methoxybenzo[b]
thiophen-2-yl)methanone (1i). Prepared in the same way
from 5b (0.25 g, 1 mmol) in THF (5 mL), LDA (2.5 mmol)
in THF (15 mL) and p-chlorobenzaldehyde (0.28 g,
2 mmol) in THF (5 mL). Purification by column

9014
T. K. Pradhan et al. / Tetrahedron 61 (2005) 9007–9017
chromatography [eluent: ethyl acetate–petroleum ether
(1/17)] gave yellow solid, yield 0.29 g, 93%, mp 158 8C
(ethyl acetate–petroleum ether). IR (KBr) nmax: 3435,
5c (0.27 g, 1 mmol) in THF (5 mmol), LDA (2.5 mmol) in
THF (15 mL) and 4-chlorobenzaldehyde (0.30 g, 2.5 mmol)
in THF (5 mL). Purification by column chromatography
[eluent: ethyl acetate–petroleum ether (1/17)] gave yellow
solid, yield 0.32 g, 93%, mp 211 8C (ethyl acetate–
1
1570 cmK1; H NMR (300 MHz, CDCl3) dH: 13.94 (1H,
s, OH), 7.74.7.71 (2H, m), 7.68 7.28.7.26, (3H, m), 7.04
(1H, d, JZ8.1 Hz), 6.55 (1H, d, JZ8.1 Hz), 3.80 (3H, s,
OCH3); 13C (75 MHz, CDCl3) dC: 189.5, 167.9, 159.0,
143.5, 139.2, 136.8, 132.1, 130.1, 130.1, 129.3, 129.3,
120.1, 115.5, 108.4, 105.6, 56.3. MS: (MC) 318, (MCC1)
319, (MCC2) 320. Anal. Calcd for C16H11ClO2S: C, 62.39;
H, 3.14%. Found C, 62.47; H, 3.23%.
petroleum ether). IR (KBr) nmax: 3433, 1583 cmK1 1H
;
NMR (300 MHz, CDCl3) dH: 14.54 (1H, s, OH), 7.99–7.95
(2H, m), 7.55–7.40, (4H, m), 7.09–7.07 (1H, m), 2.57 (3H, s,
SCH3); 13C (75 MHz, CDCl3) dC: 187.9, 169.9, 142.7,
140.6, 138.9, 136.0, 130.5, 129.8, 129.8, 129.2, 129.2,
129.0, 119.3, 118.5, 110.2, 14.7. Anal. Calcd for
C16H11ClO2S2: C, 57.39; H, 3.31%. Found C, 57.48; H,
3.38%.
4.1.20. (3-Hydroxy-4-methoxy benzo[b]thiophen-2-yl)
(thiophen-2-yl)methanone (1j). Prepared in the same way
from 5b (0.25 g, 1 mmol) in THF (5 mL), LDA (2.5 mmol)
in THF (15 mL) and thiophen-2-aldehyde (0.23 g,
2.2 mmol) in THF (5 mL). Purification by column chroma-
tography [eluent: ethyl acetate–petroleum ether (1/18)] gave
yellow solid, yield 0.26 g, 90%, mp 174–176 8C (ethyl
acetate–petroleum ether). IR (KBr) nmax: 3469, 1593,
4.1.24. (3-Hydroxy-4-methylsulfanyl benzo[b]thiophen-
2-yl) (thiophen-2-yl) methanone (1n). Prepared from 5c
(0.27 g, 1 mmol) in THF (5 mL), DA (2.5 mmol) in THF
(5 mL) and thiophene-2-carboxaldehyde (0.28 g, 2.2 mmol)
in THF (5 mL). Purification by column chromatography
(eluent: ethyl acetate–petroleum ether (1/17)] gave red
solid, yield 0.27 g, 90%, mp 182 8C (ethyl acetate–
1
1574 cmK1; H NMR (300 MHz, CDCl3) dH: 14.28 (1H,
s, OH), 8.08–8.07(1H, m), 7.73 (1H, dd, JZ0.9, 4.9 Hz),
7.49–7.44 (1H, m), 7.31–7.20 (2H, m), 6.78 (1H, d, JZ
7.8 Hz), 4.02 (3H, s, OCH3); 13C (75 MHz, CDCl3) dC:
181.8, 168.0, 158.9, 143.2, 142.9, 134.2, 132.7, 132.0,
128.8, 120.1, 115.6, 107.3, 105.7, 65.3. MS: (MCK1) 289,
(MC) 290, (MCC1) 291. Anal. Calcd for C14H10O3S2: C,
57.91; H, 3.47%. Found C, 57.78; H, 3.58%.
petroleum ether). IR (KBr) nmax: 3423, 1556 cmK1 1H
;
NMR (300 MHz, CDCl3) dH: 14.28 (1H, s, OH), 8.09 (1H,
d, JZ3.3 Hz), 7.74 (1H, d, JZ4.8 Hz), 7.45–7.41 (2H, m),
7.26–7.22 (1H, m), 7.09–7.06 (1H, m), 2.56 (3H, s, SCH3);
13C (75 MHz, CDCl3) dC: 180.4, 169.2, 142.0, 140.1, 133.7,
132.3, 130.2, 129.8, 128.3, 123.6, 119.2, 118.5, 105.2, 14.6.
Anal. Calcd for C14H10O2S3: C, 54.87; H, 3.29%. Found C,
54.99; H, 3.37%.
4.1.21. 1-(3-Hydroxy-4-methoxybenzo[b]thiophen-2-yl)-
3-phenyl propenone (1k). Prepared from 5b (0.51 g,
2 mmol) in THF (5 mL), LDA (5 mmol)in THF (15 mL)
and cinnamaldehyde (0.54 g, 4.4 mmol) in THF (5 mL).
Purification by column chromatography [eluent: ethyl
acetate–petroleum ether (1/16)] gave red solid, yield
0.54 g, 89%, mp 164–166 8C (ethyl acetate–petroleum
4.1.25. 1-(3-Hydroxy-4-methylsulfanyl benzo[b]thio-
phen-2-yl)-3-phenyl propenone (1o). Prepared from 5c
(0.54 g, 2 mmol) in THF (5 mL), LDA (5 mmol) in THF
(15 mL) and cinamaldehyde (0.66 g, 5 mmol) in THF
(5 mL). Purification by column chromatography [eluent:
ethyl acetate–petroleum ether (1/16)] gave red solid, yield
0.54 g, 88%, mp 183 8C (ethyl acetate–petroleum ether). IR
1
ether). IR (KBr) nmax: 3421, 1633, 1572 cmK1; H NMR
1
(300 MHz, CDCl3) dH: 13.86 (1H, s, OH), 7.94 (1H, d, JZ
15.5 Hz), 7.66–7.63 (2H, m), 7.49–7.41 (3H, m), 7.32–7.26
(2H, m), 7.06 (1H, d, JZ15.3 Hz), 6.79 (1H, d, JZ8.0 Hz),
4.03 (3H, s, OCH3); 13C (75 MHz, CDCl3) dC: 184.5, 158.9,
144.0, 142.6, 134.9, 131.9, 131.1, 129.7, 129.0, 129.0,
128.9, 128.9, 128.8, 128.7, 120.7, 116.0, 105.6, 56.3. MS:
(MC) 310, (MCC1) 311, (MCC2) 312. Anal. Calcd for
C18H14O3S: C, 69.66; H, 4.55%. Found C, 69.80; H, 4.63%.
(KBr) nmax: 3421, 1613, 1578 cmK1; H NMR (300 MHz,
CDCl3) dH: 14.51 (1H, s, OH), 7.82 (1H, d, JZ15.4 Hz),
7.56–7.52 (2H, m), 7.43–7.32 (5H, m), 6.98–6.96 (1H, m),
6.87 (1H, d, JZ15.4 Hz), 2.57 (3H, s, SCH3); 13C (75 MHz,
CDCl3) dC: 181.9, 171.6, 143.8, 142.5, 140.9, 134.8, 131.1,
130.9, 129.3, 129.3, 128.9, 128.9, 127.8, 122.1, 119.6,
119.3, 111.2, 15.0. Anal. Calcd for C18H14O2S2: C, 66.23;
H, 4.32%. Found C, 66.35; H, 4.38%.
4.1.22. (3-Hydroxy-4-methylsulfanylbenzo[b]thiophen-
2-yl)phenyl methanone (1l). Prepared from 5c (0.27 g,
1 mmol) in THF (5 mL), LDA (2.5 mmol) in THF (15 mL).
Purification by column chromatography [eluent: ethyl
acetate–petroleum ether (1/17)] gave yellow solid, yield
0.27 g, 91%, mp 144 8C (ethyl acetate–petroleum ether. IR
(KBr) nmax: 3440, 1585 cmK1; 1H NMR (300 MHz, CDCl3)
dH: 14.62 (1H, s, OH), 8.03–8.00 (2H, m), 7.59–7.50 (3H,
m), 7.43–7.41 (2H, m), 7.07–7.03 (1H, m), 2.55 (3H, s,
SCH3); 13C NMR (75 MHz, CDCl3) dC: 189.3, 169.6, 142.8,
140.4, 137.7, 132.5, 130.3, 128.7, 128.7, 128.3, 128.3,
126.3, 119.2, 118.5, 108.7, 14.7. Anal. Calcd for
C16H12O2S2: C, 63.97; H, 4.03%. Found: C, 63.85; H,
4.11%.
4.1.26. (1-Hydroxy naphtho[2,1-b]thiophen-2-yl) phenyl
methanone (1p). Prepared from 5d (0.27 g, 1 mmol) in
THF (5 mL), LDA (2.5 mmol) in THF (15 mL) and
benzaldehyde (0.25 g, 2.5 mmol) in THF (5 mL). Purifi-
cation by column chromatography [eluent: ethyl acetate–
petroleum ether (1/16)] gave yellow solid, yellow 0.27 g,
90%, mp 142 8C (ethyl acetate–petroleum ether). IR (KBr)
1
nmax: 3444, 1590 cmK1; H NMR (300 MHz, CDCl3) dH:
14.14 (1H, s, OH), 9.16 (1H, d, JZ8.1 Hz), 8.06–8.03 (2H,
m), 7.91–7.84 (2H, m), 7.69–7.54 (6H, m); 13C NMR
(75 MHz, CDCl3) dC: 191.5, 167.6, 141.6, 138.4, 132.5,
131.4, 131.2, 130.3, 128.7, 128.7, 128.5, 128.4, 128.4,
127.8, 126.1, 124.4, 124.1, 120.6, 110.0. Anal. Calcd for
C19H12O2S: C, 74.98; H, 3.97%. Found: C, 74.86; H, 3.89%.
4.1.23. (4-Chlorophenyl) (3-hydroxy-4-methylsulfanyl
benzo[b]thiophen-2-yl) methanone (1m). Prepared from
4.1.27. (4-Chlorophenyl) (1-hydroxy naphtho[2,1-b]thio-
phen-2-yl) methanone (1q). Prepared from 5d (0.27 g,

T. K. Pradhan et al. / Tetrahedron 61 (2005) 9007–9017
9015
1 mmol) in THF (5 mL), LDA (2.5 mmol) in THF (15 mL)
and p-chlorobenzaldehyde (0.35 g, 2.5 mmol) in THF
(5 mL). Purification by column chromatography [eluent:
ethyl acetate–petroleum ether (1/17)] gave yellow solid,
yield 0.31 g, 93%, mp 213 8C (ethyl acetate–petroleum
After stirring the reaction mixture for 1 h, acetyl chloride
(0.5 g, 7 mmol) was added to it and stirring was continued
for 10 h at room temperature followed by removal of solvent
under reduced pressure. The residue left was decomposed
with water and extracted with diethyl ether (15!3 mL). The
organic layer was washed with water and dried (Na2SO4).
The residue left after removal of solvent was purified by
column chromatography [eluent: ethyl acetate–petroleum
ether (1/20)] to afford clear liquid, yield 0.71 g, 89%. IR
ether). IR (KBr) nmax: 3433, 1583 cmK1 1H NMR
;
(300 MHz, CDCl3) dH: 14.07 (1H, s, OH), 9.18 (1H, d,
JZ8.4 Hz), 8.02–7.90 (4H, m), 7.74–7.50, (5H, m); 13C
(75 MHz, CDCl3) dC: 191.5, 167.9, 141.6, 139.6, 138.9,
136.7, 131.7, 131.2, 130.3, 130.3, 129.8, 129.8, 129.0,
128.5, 127.9, 126.3, 124.4, 120.6, 110.3. Anal. Calcd for
C19H11ClO2S: C, 67.35; H, 3.37%. Found C, 67.48; H,
3.33%.
1
(Neat) nmax: 1764 cmK1; H NMR (300 MHz, CDCl3) dH:
7.83–7.80 (1H, m), 7.74–7.71 (1H, m), 7.44–7.39 (3H, m),
2.40 (3H, s COCH3); 13C NMR (75 MHz, CDCl3) dC: 168.3,
140.7, 136.9, 132.1, 125.2, 124.3, 122.9, 120.4, 111.9, 21.0.
Anal. Calcd for C10H8O2S: C, 62.68; H, 4.19%. Found: C,
62.60; H, 4.26%.
4.1.28. 1-(1-Hydroxy naphtho[2,1-b]thiophen-2-yl)-3-
phenyl propenone (1r). Prepared from 5d (0.55 g,
2 mmol) in THF (5 mL), LDA (5 mmol) in THF (15 mL)
and cinamaldehyde (0.66 g, 5 mmol) in THF (5 mL).
Purification by column chromatography [eluent: ethyl
acetate–petroleum ether (1/15)] gave red solid, yield
0.56 g, 85%, mp 171 8C (ethyl acetate–petroleum ether).
4.1.32. (Naphtho[2,1-b]thiophen-1-yl) acetate (8c). Pre-
pared in the same way from 3d (2 g, 10 mmol) in THF
(15 mL), sodium hydride (0.6 g, 15 mmol) in THF (25 mL)
and acetyl chloride (1.2 g, 15 mmol). Purified by column
chromatography [eluent: ethyl acetate–petroleum ether
IR (KBr) nmax: 3425, 1630, 1578 cmK1
;
1H NMR
(1/20)], clear liquid, yield 2.2 g, 93%. IR (Neat) nmax:
1
(300 MHz, CDCl3) dH: 13.80 (1H, s, OH), 9.11 (1H, d,
JZ8.3 Hz), 7.94–7.68 (3H, m), 7.66–7.52 (5H, m), 7.42–
7.23 (3H, m), 7.07 (1H, d, JZ15.4 Hz); 13C (75 MHz,
CDCl3) dC: 185.6, 166.9, 143.9, 140.2, 134.4, 131.3, 131.2,
130.9, 130.2, 129.0, 129.0, 128.7, 128.7, 128.3, 127.8,
126.2, 124.6, 124.4, 122.5, 120.9, 112.3. Anal. Calcd for
C21H14O2S: C, 76.34; H, 4.27%. Found C, 76.49; H, 4.33%.
1779 cmK1; H NMR (300 MHz, CDCl3) dH: 8.62 (1H, d,
JZ8.2 Hz), 7.85–7.80 (1H, m), 7.78–7.59 (2H, m), 7.56–
7.38 (3H, m), 2.37 (3H, s COCH3); 13C NMR (75 MHz,
CDCl3) dC: 168.6, 143.6, 135.9, 132.0, 129.1, 129.0, 126.9,
126.5, 126.4, 125.8, 123.4, 121.3, 112.3, 22.0. Anal. Calcd
for C14H10O2S: C, 69.40; H, 4.26%. Found: C, 69.53; H,
4.33%.
4.1.29. 1-(1-Hydroxy naphtho[2,1-b]thiophen-2-yl)
ethan-1-one (1s). Prepared according to the general
synthesis of aryl alkyl ketone from 8c (0.24 g, 1 mmol) in
THF (5 mL) and LDA (1.5 mmol) in THF (10 mL). Purified
by column chromatography [eluent: ethyl acetate–
petroleum ether (1/20)], amorphous solid, yield 0.13 g,
55%, mp 67 8C. IR (KBr) nmax: 3470, 1630 cmK1; 1H NMR
(300 MHz, CDCl3) dH: 13.6 (1H, s, OH), 8.97 (1H, d, JZ
8.0 Hz), 7.87–7.84 (2H, m), 7.63–7.51 (3H, m), 2.47 (3H, s,
COCH3); 13C NMR (75 MHz, CDCL3) dC: 199.3, 164.5,
139.4, 131.7, 131.3, 130.5, 128.9, 127.7, 126.6, 126.4,
124.8, 121.1, 111.3, 18.8. Anal. Calcd for C14H10O2S: C,
69.40; H, 4.16%. Found: C, 69.23; H, 4.28%.
4.1.33. (Naphtho[2,1-b]thiophen-1-yl) propionate (8d).
Prepared in the same way from 3d (2 g, 10 mmol) in THF
(15 mL), sodium hydride (0.6 g, 15 mmol) in THF (25 mL)
and propionylchloride (1.5 g, 15 mmol). Purified by column
chromatography [eluent: ethyl acetate–petroleum ether
(1/20)], clear liquid, yield 2.3 g, 96%. IR (Neat) nmax
:
1
1764 cmK1; H NMR (300 MHz, CDCl3) dH: 8.84 (1H, d,
JZ8.2 Hz), 7.98 (1H, d, JZ7.6 Hz), 7.80–7.57 (5H, m),
2.89 (2H, s COCH2), 1.47 (3H, s CH3); 13C NMR (75 MHz,
CDCl3) dC: 171.4, 143.0, 135.2, 131.3, 128.4, 128.3, 126.1,
125.7, 125.1, 122.8, 120.6, 111.5, 27.9, 8.4. Anal. Calcd for
C15H12O2S: C, 70.29; H, 4.72%. Found: C, 70.33; H, 4.81%.
4.1.34. General synthesis of dihydropyranones from
chalcones taking 9-methoxy-2-phenyl-2,3-dihydro-
benzo[4,5]thieno[3,2-b]pyran-4-one (9b) as representa-
tive. Dry HCl gas was bubbled through a solution of 1k
(0.31 g, 1 mmol) in ethanol (20 mL) for 4 h. After removal
of most of the ethanol under reduced pressure, the reaction
mixture was diluted with chloroform, the organic layer was
washed with water and dried (Na2SO4). Residue left after
removal of solvent was purified by column chromatography
[eluent: ethyl acetate–petroleum ether (1/4)], white solid,
yield 0.26 g, 87%, mp 182 8C (ethyl acetate–petroleum
4.1.30. 1-(1-Hydroxynaphtho[2,1-b]thiophen-2-yl) pro-
pan-1-one (1t). Prepared in the same way from 8d (0.26 g,
1 mmol) in THF (5 mL), LDA (1.5 mmol) in THF (10 mL).
Purified by column chromatography [eluent: ethyl acetate–
petroleum ether (1/20)], solid material, yield 0.16 g, 63%,
mp 88 8C. IR (KBr) nmax: 3483, 1633 cmK1 1H NMR
;
(300 MHz, CDCl3) dH: 13.0 (1H, s, OH), 9.10 (1H, d, JZ
8.4 Hz), 7.93–7.86 (2H, m), 7.70–7.55 (3H, m), 2.89–2.81
(2H, m, COCH2CH3), 1.39–1.29 (3H, m, CH2CH3); 13C
NMR (75 MHz, CDCL3) dC: 199.9, 164.6, 139.5, 131.5,
131.2, 130.6, 128.7, 127.9, 126.5, 126.4, 124.7, 121.2,
111.6, 34.3, 8.7. Anal. Calcd for C15H12O2S: C, 70.29; H,
4.72%. Found: C, 70.45; H, 4.83%.
1
ether). IR (KBr) nmax: 1665 cmK1; H NMR (300 MHz,
CDCl3) dH: 7.56–7.54 (2H, m), 7.48–7.37 (4H, m), 7.35–
7.32 (1H, m), 6.77 (1H, d, JZ8.1 Hz), 5.82 (1H, d, JZ
12.0 Hz, OCHCH2), 3.94 (3H, s, OCH3) 3.10–2.99 (2H, m,
COCH2CH); 13C NMR (75 MHz, CDCl3) dC: 186.5, 167.7,
161.9, 158.1, 143.4, 138.6, 131.0, 129.1, 128.9, 128.9,
126.3, 120.4, 116.3, 114.4, 105.6, 82.7, 56.2, 43.7. Anal.
Calcd for C18H14O3S: C, 69.66; H, 4.55%. Found: C, 69.59;
H, 4.48%.
4.1.31. General synthesis of alkanoic acid aryl ester
taking (benzo[b]thiophen-3-yl) acetate as example (8a).
A solution of 3a (0.60 g, 4 mmol) in THF (10 mL) was
added dropwise to a magnetically stirred suspension of oil
free sodium hydride (0.30 g, 6 mmol) in THF (10 mL).

9016
T. K. Pradhan et al. / Tetrahedron 61 (2005) 9007–9017
4.1.35. 9-Methylsulfanyl-2-phenyl-2,3-dihydrobenzo[4,
5]thieno[3,2-b]pyran-4-one (9c). Prepared from 1o
(0.16 g, 0.5 mmol) in ethanol (20 mL). Purification by
column chromatography [eluent: ethyl acetate–petroleum
ether (1/4)] gave solid material, yield 0.14 g, 90%, mp 170–
dioxide (0.23 g, 2.2 mmol). Red solid, yield 0.18 g, 55%,
mp 225 8C (ethyl acetate–petroleum ether). IR (KBr) nmax
:
1632 cmK1; H NMR (300 MHz, CDCl3) dH: 8.96 (1H, d,
JZ8.1 Hz), 8.00–7.95 (3H, m), 7.92 (1H, d, JZ8.7 Hz),
7.83(1H, d, JZ8.7 Hz), 7.76–7.71 (1H, m), 7.66–7.58 (4H,
m), 6.95 (1H, s); 13C NMR (75 MHz, CDCl3) dC: 188.3,
174.5, 163.6, 155.4, 139.1, 131.6, 13.4, 131.2, 129.9, 129.2,
129.2, 128.8, 128.5, 127.8, 126.2, 126.2, 126.1, 123.4,
123.2, 121.0, 108.8. MS: (MCC1) 329.14. Anal. Calcd for
C21H12O2S: C, 76.81; H, 3.68%. Found: C, 76.73; H, 3.59%.
1
172 8C (ethyl acetate–petroleum ether). IR (KBr) nmax
;
:
1670 cmK1 1H NMR (300 MHz, CDCl3) dH: 7.56–7.46
(2H, m), 7.42–7.28 (5H, m), 6.98 (1H, d, JZ7.5 Hz), 5.77
(1H, dd, JZ3.7, 13.0 Hz, OCHCH2), 3.07–2.84 (2H, m,
COCH2CH), 2.45 (3H, s, SCH3); 13C NMR (75 MHz,
CDCl3) dC: 185.9, 161.6, 142.1, 138.6, 137.8, 129.1, 128.6,
128.6, 128.4, 126.1, 125.7, 119.2, 119.1, 114.7, 82.7, 43.4,
14.5. Anal. Calcd for C18H14O2S2: C, 66.23; H, 4.32%.
Found: C, 66.13; H, 4.27%.
4.1.40. 2-Hydroxy-2,3-dihydro benzo[4,5]thieno[3,2-b]
pyran-4-one (11a). To a well stirred suspension of oil-
free sodiumhydride (0.12 g, 2.5 mmol) in THF (10 mL) a
solution of 1f (0.2 g, 1 mmol) in THF (5 mL) was added
under external cooling. After 15 min ethyl formate (0.1 g,
2 mmol) was added to the reaction mixture, which was
stirred at room temperature for another 10 h. Residue left
after removal of most of the solvent under reduced pressure
was decomposed with water, acidified with dilute HCl,
extracted with chloroform and dried (Na2SO4). Purified by
column chromatography [eluent: ethyl acetate–petroleum
ether (1/5)], white solid, yield 0.18 g, 85%, mp 117 8C
(ethyl acetate–petroleum ether). IR (KBr) nmax: 3280,
4.1.36. 10-Phenyl-9,10-dihydro-11-oxa-7-thiabenzo[c]
fluoren-8-one (9d). Prepared from 1r (0.33 g, 1 mmol) in
ethanol (20 mL). Purification by column chromatography
[eluent: ethyl acetate–petroleum ether (1/4)] gave solid
material, yield 0.30 g, 93%, mp 158 8C (ethyl acetate–
petroleum ether). IR (KBr) nmax: 1668 cmK1 1H NMR
;
(300 MHz, CDCl3) dH: 8.81 (1H, d, JZ7.6 Hz), 7.87–7.79
(2H, m), 7.70 (1H, d, JZ8.8 Hz), 7.56–7.39 (7H, m), 5.58
(1H, dd, JZ3, 13.5 Hz, OCHCH2), 3.21–2.87 (2H, m,
COCH2CH); 13C NMR (75 MHz, CDCl3) dC: 186.3, 162.1,
141.3, 138.5, 132.3, 130.4, 129.5, 128.9, 128.8, 128.8,
128.4, 127.5, 126.1, 126.1, 125.9, 123.8, 121.2, 117.7,
114.3, 83.1, 43.8. Anal. Calcd for C21H14O2S: C, 76.34; H,
4.27%. Found: C, 76.11; H, 4.38%.
1727 cmK1 1H NMR (300 MHz, acetone-d6) dH: 7.97–
;
7.87 (2H, m), 7.62–7.57 (1H, m), 7.51–7.46 (1H, m), 6.19–
6.17 (1H, m, OCHOH), 3.12–3.05 (2H, m, COCH2); 13C
NMR (75 MHz, acetone-d6) dC: 196.3, 155.7, 141.5, 138.4,
131.7, 129.7, 125.8, 123.2, 122.7, 102.7, 44.7. Anal. Calcd
for C11H8O3S: C, 59.99; H, 3.66%. Found: C, 79.76; H,
3.75%.
4.1.37. General synthesis of pyranones from chalcones
taking 2-phenylbenzo[4,5]thieno[3,2-b]pyran-4-one
(10a) as representative. Selenium dioxide (0.23 g,
2.2 mmol) and 1e (0.28 g, 1 mmol) were heated under
reflux in dry isoamyl alcohol (3 mL) for 15 h. The reaction
mixture was filtered when hot. Most of the solvent of filtrate
was removed under reduced pressure and the solid
precipitate, which separated was filtered and washed with
1:1 mixture of ethyl acetate and petroleum ether and
crystallized from ethyl acetate. Yield 0.17 g, 63%, mp
4.1.41. 2-Hydroxy-3-methyl-2,3-dihydro benzo[4,5]
thieno[3,2-b]pyran-4-one (11b). Prepared in the same
way from 1g (0.21 g, 1 mmol) in THF (5 mL), sodium
hydride (0.12 g, 2.5 mmol) in THF (10 mL) and ethyl
formate (0.1 g, 2 mmol). Purification by column chroma-
tography [eluent: ethyl acetate–petroleum ether (1/5)],
white solid (obtained as a 1:1 diasteromeric mixture),
yield 0.20 g, 89%, mp 140–150 8C (ethyl acetate–petroleum
1
178 8C. IR (KBr) nmax: 1635 cmK1; H NMR (300 MHz,
ether). IR (KBr) nmax: 3265, 1632 cmK1 1H NMR
;
CDCl3) dH: 8.18 (1H, d, JZ7.5 Hz), 7.96–7.90 (3H, m),
7.62–7.52 (5H, m), 6.95 (1H, s); 13C NMR (75 MHz,
CDCl3) dC: 187.5, 174.9, 163.1, 153.7, 139.2, 131.5, 131.3,
129.2, 129.0, 129.0, 126.2, 126.1, 125.3, 124.8, 123.9,
121.9, 109.0. MS: (MCC1) 278.07. Anal. Calcd for
C17H10O2S: C, 73.31; H, 3.62%. Found: C, 73.53; H, 3.39%.
(300 MHz, acetone-d6) dH: 7.94–7.83 (2H, m), 7.59–7.52
(1H, m), 7.48–7.44 (1H, m), 6.07–6.06 (1/2H, d, OCHOH),
5.76–5.73 (1/2H, d, OCHOH), 3.17–3.13 (1/2H, m, COCH),
2.84–2.77 (1/2H, m, COCH), 1.27–1.22 (3H, m, CH3); 13
C
NMR (75 MHz, acetone-d6) dC: 205.4, 129.3, 129.0, 124.9,
124.8, 123.8, 123.8, 122.7, 122.5, 103.2, 101.2, 47.3, 45.9,
11.0, 8.6. Anal. Calcd for C12H10O3S: C, 61.52; H, 4.30%.
Found: C, 61.65; H, 4.43%.
4.1.38. 9-Methoxy-2-phenylbenzo[4,5]thieno[3,2-b]
pyran-4-one (10b). Prepared in the same way from 1k
(0.31 g, 1 mmol) and selenium dioxide (0.23 g, 2.2 mmol).
Red solid, yield 0.18 g, 58%, mp 203 8C (ethyl acetate–
4.1.42. Benzo[4,5]thieno[3,2-b]pyran-4-one (12a). In a
round bottom flask fitted with Dean-stark water separator
11a (0.22 g, 1 mmol) and catalytic amount of p-toluene
sulphonic acid was heated under reflux in benzene (10 mL)
for 3 h. Residue left after removal of most of the solvent was
followed by extraction with diethyl ether, washed with
water and dried (Na2SO4). Residue left after removal of
solvent was purified by column chromatography [eluent:
ethyl acetate–petroleum ether (1/5)] to afford colorless
solid, yield 0.18 g, 93%, mp 167 8C (ethyl acetate–
petroleum ether). IR (KBr) nmax: 1628 cmK1 1H NMR
;
(300 MHz, CDCl3) dH: 8.00–7.91 (2H, m), 7.55–7.52 (3H,
m), 7.49–7.42 (2H, m), 6.99 (1H, s), 6.88 (1H, d, JZ
6.9 Hz), 4.10 (3H, s, OCH3); 13C NMR (75 MHz, CDCl3)
dC: 189.5, 177.3, 174.6, 156.6, 140.9, 139.3, 131.3, 131.1,
130.0, 128.9, 128.9, 125.8, 125.8, 123.4, 115.7, 107.7,
105.6, 55.8. MS: (MCC1) 309.05. Anal. Calcd for
C18H12O3S: C, 70.11; H, 3.92%. Found: C, 69.93; H, 4.03%.
petroleum ether). IR (KBr) nmax: 1633, 1622 cmK1 1H
;
4.1.39. 10-Phenyl-11-oxa-7-thiabenzo[c]fluoren-8-one
(10c). Prepared from 1r (0.33 g, 1 mmol) and selenium
NMR (300 MHz, CDCl3) dH: 8.06–7.78 (4H, m), 7.68–7.35
(2H, m); 13C NMR (75 MHz, CDCl3) dC: 198.7, 161.3,

T. K. Pradhan et al. / Tetrahedron 61 (2005) 9007–9017
9017
153.3, 140.7, 138.7, 136.4, 132.6, 129.5, 125.2, 122.6,
122.2. Anal. Calcd C11H6O2S: C, 65.33; H, 2.99%. Found:
C, 65.45; H, 3.13%.
References and notes
1. Part 7. Pradhan, T. K.; De, A. Tetrahedron Lett. 2005, 46,
1493.
2. Mukherjee, C.; De, A. Synlett 2002, 325.
3. Mukherjee, C.; Kamila, S.; De, A. Tetrahedron 2003, 59,
4767.
4.1.43. Benzo[4,5]thieno[3,2-b]pyran-4-one-3-carboxal-
dehyde (14). To an externally cooled and stirred mixture
of 1f (0.4 g, 2 mmol) in DMF (3 mL), phosphoryl chloride
(1 mL) was added. The reaction mixture was allowed to
reach room temperature and after stirring at that temperature
for 13 h, was poured into crushed ice and extracted with
chloroform. The organic phase was washed with water and
dried (Na2SO4). Residue left after removal of solvent was
purified by column chromatography [eluent: ethyl acetate–
petroleum ether (1/4)] gave white solid, yield 0.32 g, 68%,
4. Pradhan, T. K.; Ghosh, S. C.; De, A. ARKIVOC 2003, 158. Part
(ix).
5. Pradhan, T. K.; De, A. Heterocycles 2005, 65, 1491.
6. Kamila, S.; Mukherjee, C.; Mondal, S. S.; De, A. Tetrahedron
2003, 59, 1339.
7. Snieckus, V. Chem. Rev. 1990, 90, 879.
8. Wright, J. B.; Johnson, H. G. J. Med. Chem. 1973, 16, 861.
9. Cairns, H.; Fitzmaurice, C.; Hunter, D.; Johnson, P. B.; King,
J.; Lee, T. B.; Lord, G. H.; Minshull, R.; Cox, J. S. G. J. Med.
Chem. 1972, 15, 583.
mp 133 8C (ethyl acetate–petroleum ether). IR (KBr) nmax
:
1675, 1648 cmK1; 1H NMR (300 MHz, acetone-d6) dH: 9.73
(1H, s, CHO), 8.23–7.58 (4H, m), 7.13 (1H, s); 13C NMR
(75 MHz, acetone-d6) dC: 200.3, 184.3, 165.5, 143.9, 136.2,
130.5, 128.3, 124.2, 124.1, 122.9, 121.7, 103.7. Anal. Calcd
for C12H6SO3: C, 62.10; H, 2.63%. Found: C, 62.48; H,
2.33%.
10. Falliers, C. J. J. Allergy 1971, 47, 298.
11. For various application of thioaurones. Ahlheim, M.;
Barzoukas, M.; Bedworth, P. V.; Blanchard-Desce, M.; Fort,
A.; Hu, Z.-Y.; Marder, S. R.; Perry, J. W.; Runser, C.; Staehlin,
B.; Zysset, B. Science 1996, 271, 335.
12. Steinle, W.; Ru¨ck-Braun, K. Org. Lett. 2002, 5, 141.
13. Cabbidu, M. G.; Cabbidu, S.; Cadoni, E.; de Montis, S.;
Fattuoni, C.; Melis, S.; Usai, M. Synthesis 2002, 875.
14. Sibi, M. P.; Snieckus, V. J. Org. Chem. 1983, 48, 1935.
15. Mustafa, A.; Mohamed, S.; Zayed, A. D. J. Am. Chem. Soc.
1956, 78, 6174.
Acknowledgements
Thanks for financial assistance are due to Royal Society of
Chemistry (UK) and Council of Scientific and Industrial
Research (New Delhi) to A. D. T. K. P. thanks Council of
Scientific and Industrial Research (New Delhi) for Junior
and Senior Research Fellowships.
16. Mustafa, A.; Asker, W.; Hishmat, O. H.; Ali, M. I.; Mansour,
A.-K. E.; Abed, N. M.; Khalil, K. M. A.; Samy, S. M.
Tetrahedron 1965, 21, 849.
17. Smiles, S.; McClelland, L. W. J. Chem. Soc. 1921, 119, 1810.