Tandem cyclization: One pot regioselective synthesis of thieno[3,2-c]quinolin-4(5H)-one derivatives

Article abstract of DOI:10.1016/S0040-4020(02)01303-0

A number of hitherto unreported 3-(aryloxyacetyl)-2,3-dihydro-5-alkylthieno[3,2-c]quinolin-4(5H)-ones are regioselectively synthesized in 80-90% yield from 4-(4′-aryloxybut-2′-ynyl)thioquinolin-2(1H)-ones by the oxidation with 1equiv. of m-CPBA at 0-5°C for 1h followed by heating under reflux in chloroform and subsequent treatment with 20% aqueous KOH. The substrate, sulfides were prepared by PTC alkylation of 4-mercaptoquinolin-2(1H)-one with 1-aryloxy-4-chlorobut-2-ynes.

Full text of DOI:10.1016/S0040-4020(02)01303-0

Tetrahedron 58 (2002) 10047–10052
Tandem cyclization: one pot regioselective synthesis
of thieno[3,2-c]quinolin-4(5H)-one derivatives
*
K. C. Majumdar and M. Ghosh
Department of Chemistry, University of Kalyani, Kalyani 741 235, W.B., India
Received 28 March 2002; revised 17 September 2002; accepted 10 October 2002
Abstract—A number of hitherto unreported 3-(ary0loxyacetyl)-2,3-dihydro-5-alkylthieno[3,2-c]quinolin-4(5H)-ones are regioselectively
synthesized in 80–90% yield from 4-(40-aryloxybut-2 -ynyl)thioquinolin-2(1H)-ones by the oxidation with 1 equiv. of m-CPBA at 0–58C for
1 h followed by heating under reflux in chloroform and subsequent treatment with 20% aqueous KOH. The substrate, sulfides were prepared
by PTC alkylation of 4-mercaptoquinolin-2(1H)-one with 1-aryloxy-4-chlorobut-2-ynes. q 2002 Elsevier Science Ltd. All rights reserved.
The Claisen rearrangement1 provides an excellent method
for the formation of carbon–carbon bonds.2–7 The present
importance of the Claisen rearrangement is partly due to its
application in the synthesis of oxygen,8 nitrogen9 and
sulfur10 heterocycles and partly because of the development
of several variants11–21 of its aliphatic counter part. We had
earlier developed a new ortho-Claisen rearrangement of
aryl propynyl sulfoxides22–25 and aryl propynyl amine
oxides,26–28 a variant of the aromatic Claisen rearrange-
ment for the construction of the five-membered heterocyclic
ring in benzo(b)thiophenes and indoles. This protocol was
found to be an excellent high yield one step process. Our
initial success in the application29–37 of this protocol and
also in the synthesis of quinolone-annulated heterocycles38,39
inspired us to investigate whether a five-membered
thiophene ring in the hitherto unreported thieno[3,2-c]-
quinolin-4(5H)-one system could be constructed via the
aforesaid sulfoxide rearrangement. Herein we report the
results.
1. Results and discussion
The starting materials for this study 3a–f were easily
Scheme 1.
Keywords: thieno[3,2-c]quinolin-4(5H)-one; sulfoxide rearrangement; modified Claisen rearrangement; Michael addition; regioselective synthesis.
*
Corresponding author. Tel.: þ91-33-5827521; fax: þ91-33-5828282; e-mail: kcm@klyuniv.ernet.in
0040–4020/02/$ - see front matter q 2002 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(02)01303-0

10048
K. C. Majumdar, M. Ghosh / Tetrahedron 58 (2002) 10047–10052
Scheme 2.
obtained in 70–85% yield by the phase transfer-catalysed
alkylation of 4-mercaptoquinolin-2(1H)-one with 1-aryl-
oxy-4-chlorobut-2-ynes in chloroform in the presence of
tetrabutyl ammonium bromide (TBAB) and 5% aqueous
NaOH for 10–12 h (Scheme 1).
Elemental analyses and mass spectroscopic data confirmed
that the product was isomeric with the starting sulfoxide 4c.
The 1H NMR and IR spectra of 5c indicated the presence of
a terminal olefin and a hydroxyl function with signals at d
5.92 (s, 1H); d 5.98 (s, 1H) and at d 3.9 (s, 1H), but showed
no evidence for the presence of sulfoxide or acetylenic
linkage. The monothiohemiacetal structure 5c for this
product was assigned on the basis of spectral data. As
compounds 5a–f showed tendency of decomposition and
we failed to isolate compounds 5a,b and 5d–f in the
pure state, the products 5a–f were treated with 20%
aqueous potassium hydroxide to give stable products 9a–f
(Scheme 2). The products 9a–f were characterized from
their elemental analyses and spectroscopic data.
This alkylation when attempted under classical condition by
refluxing in acetone in the presence of anhydrous potassium
carbonate did not afford any tractable product.
The sulfides 3a–f were characterized from their elemental
analyses and spectroscopic data. The IR spectra of the
sulfides 3a–f exhibited nmax at 1640–1650 cm21 for the
amide carbonyl function which establishes the alkylation
preference for sulfur over oxygen. Compound 3a showed a
three-proton singlet at d 3.71 due to NCH3 group, a two
proton-triplet at d 3.79 due to SCH2 group and a two-proton
triplet at d 4.66 due to OCH2 group. It also showed a signal
at d 6.61 (s, 1H, C3H). The sulfides 3a–f were oxidised to
the corresponding sulfoxides by slow addition of 1 equiv. of
m-chloroperbenzoic acid in CHCl3 at 0–58C over a period
of 1 h. A highly polar single spot on TLC indicated the
formation of the sulfoxides. The sulfoxides were found to be
unstable and showed a tendency to undergo reorganization
even during work up. Therefore, no attempt was made to
characterize these sulfoxides. The thermally labile crude
sulfoxides 4a–f were refluxed in chloroform for 2 h leading
to the quantitative formation of new compounds 5a–f in
93–96% yields, which were found to be somewhat unstable.
We could only isolate compound 5c in the pure state.
Compound 9a exhibited nmax at 1640 cm21 for the amide
carbonyl function. 1H NMR of 9a showed a double doublet
at d 3.62–3.67 (J¼9.5, 11 Hz, 1H) for (–SCH–), and
another double doublet at d 3.75–3.78 (J¼6.5, 11 Hz, 1H)
for (–SCH–). It also showed a double doublet at d 4.82–
4.85 (J¼6.5, 9.5 Hz, 1H) for the (C3H), a doublet at d 4.96–
4.99 (J¼17 Hz, 1H) for (–CO–CH–OAr) and another
doublet at d 5.04–5.07 (J¼17 Hz, 1H) for (CO–CH–OAr).
13C NMR and DEPT experiment also supports the formation
of 9a. DEPT experiment showed the presence of one methyl
group, two CH2 group and nine CH groups which confirmed
the proposed structure of 9a.
Final confirmation of structure 9 was arrived at by

K. C. Majumdar, M. Ghosh / Tetrahedron 58 (2002) 10047–10052
10049
intermediate thiol 8, containing an enone moiety favourably
juxtaposed for the formation of the product monothio-
hemiacetal 5. The compounds 5a–f in the presence of a base
may suffer ring opening and then via an intramolecular
Michael addition of the thiophenolate to the enone moiety
may afford the products 9a–f (Scheme 4).
The whole operation if desired can be conducted in a single
pot. The methodology described here is a general one for
the synthesis of thieno[3,2-c]quinolin-4(5H)ones. This is an
exceedingly mild and simple synthesis for this type of
fused thieno heterocycles. This is also an example of the
application of sulfoxide rearrangement in heterocyclic
system.
2. Experimental
The melting points were recorded on sulfuric acid bath and
are uncorrected. UV absorption spectra were recorded in
ethanol on a Hitachi 200-20 spectrometer. IR spectra were
run for KBr disks on a Perkin–Elmer-FT IR spectrometer.
1H NMR, 13C NMR and DEPT experiments were
determined for solutions in deuteriochloroform with
SiMe4 as internal standard on a BRUKER 500 MHz
Spectrometer at the Bose Institute (Calcutta). Elemental
analyses and mass spectra were recorded at CDRI
(LUCKNOW) on a (JEOL D-300 (El)) instrument. Silica
Scheme 3.
dehydrogenation of compound 9a with DDQ in boiling
xylene to afford product 10 (Scheme 3).
The formation of 5a–f from the sulfoxides 4a–f is easily
explained by the occurrence of a [2,3] sigmatropic
rearrangement in the sulfoxide 4 to give intermediate
allenyl sulfenate 6, which then may undergo a [3,3]sigma-
tropic rearrangement followed by enolisation leading to
Scheme 4.

10050
K. C. Majumdar, M. Ghosh / Tetrahedron 58 (2002) 10047–10052
gel ((60–120 mesh), Spectrochem, India) was used for
chromatographic separation. Silica gel G (E. Merck (India))
was used for TLC. Petroleum ether refers to the fraction
boiling between 60 and 808C.
5.27, N, 4.4. C20H17NO2S requires C, 71.64, H, 5.07, N,
4.17%).
2.1.4. 4-(40-o-Methylphenoxybut-20-ynylthio)-1-methyl-
quinolin-2(1H)-one (3d). Yield 85%; Viscous liquid; UV
(EtOH): lmax: 230, 331, 290 nm; IR (neat) nmax: 2976, 2940,
2.1. Preparation of sulfides, (3a–f) from 4-mercapto-
quinolin-2(1H)-ones
1
1650, 1580, 1488 cm21; H NMR (CDCl3, 500 MHz): d
2.21 (s, 3H, CH3), 3.7 (s, 3H, NCH3), 3.8 (t, J¼1.9 Hz, 2H,
SCH2), 4.7 (t, J¼1.9 Hz, 2H, OCH2), 6.63 (s, 1H, C3H),
6.88–6.82 (m, 2H, ArH), 7.11–7.08 (m, 2H, ArH), 7.25–
7.24 (m, 1H, ArH), 7.38–7.36 (d, J¼8.5 Hz, 1H, ArH),
7.61–7.58 (m, 1H, ArH), 7.83–7.81 (dd, J¼1.0, 8 Hz, 1H,
ArH); MS m/z 349 (Mþ); (Found: C, 72.48, H, 5.61, N, 3.74.
C21H19NO2S requires C, 72.2, H, 5.44, N, 4.01%).
A mixture of 1-alkyl-4-mercaptoquinolin-2(1H)-one
(0.57 g, 3 mmol) and 1-aryloxy-4-chloro-2-butyne
(3.5 mmol) was taken up in CHCl3 (50 mL). Tetrabutyl
ammonium bromide (TBAB) (250 mg) in 5% aqueous
NaOH (50 mL) was added and the mixture was stirred at
room temperature for 10–12 h. TLC confirmed complete
conversion of the starting material. It was then diluted with
water (50 mL) and the aqueous layer was extracted with
CHCl3 (50 mL£2). The combined organic layer was washed
with water (50 mL£2) followed by brine solution (50 mL)
and dried (Na2SO4). Removal of solvent gave the crude
gummy mass which was purified by column chroma-
tography over silica gel (Spectrochem, 60–120 mesh). The
pure products were obtained when the column was eluted
with ethyl acetate: benzene (1:9). Rf: 0.3 (ethyl acetate/
benzene (1:9)).
2.1.5. 4-(40-p-Methylphenoxybut-20-ynylthio)-1-methyl-
quinolin-2(1H)-one (3e). Yield 80%; viscous liquid; UV
(EtOH): lmax: 229, 292, 330 nm; IR (neat) nmax: 2970, 2938,
1
1640, 1582, 1490 cm21; H NMR (CDCl3, 500 MHz): d
2.25 (s, 3H, CH3), 3.7 (s, 3H, NCH3), 3.79 (t, J¼2 Hz, 2H,
SCH2), 4.65 (t, J¼2 Hz, 2H, OCH2), 6.62 (s, 1H, C3H),
6.83–6.80 (m, 2H, ArH), 7.05–7.03 (m, 2H, ArH), 7.25–
7.22 (m, 1H, ArH), 7.38–7.36 (d, J¼8.5 Hz, 1H, ArH),
7.61–7.58 (m, 1H, ArH), 7.83–7.81 (dd, J¼1.0, 8 Hz, 1H,
ArH); MS m/z 349 (Mþ); (Found: C, 72.46, H, 5.15, N, 4.3.
C21H19NO2S requires C, 72.2, H, 5.44, N, 4.01%).
2.1.1. 4-(40-p-Chlorophenoxybut-20-ynylthio)-1-methyl-
quinolin-2(1H)-one (3a). Yield 80%; solid (white); mp
1348C; UV (EtOH): lmax: 231, 290, 332 nm; IR (KBr) nmax
;
:
2.1.6. 4-(40-Dimethylphenoxybut-20-ynylthio)-1-methyl-
quinolin-2(1H)-one (3f). Yield 70%; viscous liquid; UV
(EtOH): lmax: 230, 333 nm; IR (neat) nmax: 2974, 2940,
2976, 2941, 1646, 1580, 1494 cm21 1H NMR (CDCl3,
500 MHz): d 3.71 (s, 3H, NCH3), 3.79 (t, J¼1.9 Hz, 2H,
SCH2), 4.66 (t, J¼1.9 Hz, 2H, OCH2), 6.61 (s, 1H, C3H),
6.86–6.83 (m, 2H, ArH), 7.17–7.14 (m, 2H, ArH),
7.26–7.25 (m, 1H, ArH), 7.39–7.38 (d, J¼8.5 Hz, 1H,
ArH), 7.62–7.58 (m, 1H, ArH), 7.82–7.8 (dd, J¼1, 8 Hz,
1H, ArH); 13C NMR (CDCl3, 125 MHz): dC 23 (NCH3), 32
(C10 ), 59 (C40 ), 82 (C30 ), 84 (C20 ), 115 (C8), 117 (C600, C200), 122
(C5), 125 (C6), 127 (C4a), 128 (C300, C500), 129 (C400), 131 (C7),
132 (C3), 142 (C4), 144 (C8a), 157 (C100), 159 (C2). MS m/z
369, 371 (Mþ); (Found: C, 65.27, H, 4.11, N, 4.0.
C20H16ClNO2S requires C, 65.04, H, 4.33, N, 3.79%).
1
1640, 1580, 1490 cm21; H NMR (CDCl3, 500 MHz): d
2.21 (s, 3H, CH3), 2.23 (s, 3H, CH3), 3.69 (s, 3H, NCH3),
3.8 (t, J¼2 Hz, 2H, SCH2), 4.68 (t, J¼2 Hz, 2H, OCH2),
6.61 (s, 1H, C3H), 6.68–6.63 (m, 2H, ArH), 6.98–6.96 (m,
1H, ArH), 7.25–7.22 (m, 1H, ArH), 7.37–7.36 (d, J¼
8.5 Hz, 1H, ArH), 7.61–7.57 (m, 1H, ArH), 7.83–7.81 (dd,
J¼1.0, 8 Hz, 1H, ArH); MS m/z 363 (Mþ); (Found: C,
72.47, H, 5.56, N, 4.1. C22H21NO2S requires C, 72.72, H,
5.78, N, 3.85%).
2.2. General procedure for the oxidation and rearrange-
ment of 4-(40-aryloxybut-20ynylthio)-1-methylquinolin-
2(1H)-one
2.1.2. 4-(40-o-Chlorophenoxybut-20-ynylthio)-1-methyl-
quinolin-2(1H)-one (3b). Yield 75%; viscous liquid; UV
(EtOH): lmax: 230, 290, 331 nm; IR (neat) nmax: 2972, 2940,
1
1640, 1580, 1480 cm21; H NMR (CDCl3, 500 MHz): d
mCPBA (0.345 g, 50%, 1 mmol) in CHCl3 (50 mL) was
slowly added to a well-stirred solution of 4-(40-aryloxybut-
20-ynylthio)-1-methylquinolin-2(1H)-one (1 mmol) in
CHCl3 (30 mL) at 0–58C over a period of 30 min.
The mixture was stirred for half an hour more. Some
m-chloroperbenzoic acid separated as insoluble solid at this
low temperature. After completion of reaction (TLC
monitoring), the reaction mass was washed successively
with 5% Na2CO3 solution (50 mL£2) to remove the organic
acid, water (50 mL£2) and dried (Na2SO4). Sodium sulfate
was filtered off and the filtrate was refluxed for 2 h.
Chloroform was evaporated under reduced pressure to give
a yellow crystalline solid 5c in almost quantitative yield.
Products 5a,b and 5d–f could not be obtained in pure state
due to their tendency of decomposition. These were
therefore used for the next step without characterization.
3.71 (s, 3H, NCH3), 3.8 (t, J¼1.95 Hz, 2H, SCH2), 4.68
(t, J¼1.95 Hz, 2H, OCH2), 6.61 (s, 1H, C3H), 6.86–6.83
(m, 2H, ArH), 7.17–7.14 (m, 2H, ArH), 7.25–7.23 (m,
1H, ArH), 7.39–7.38 (d, J¼8.5 Hz, 1H, ArH), 7.63–7.57
(m, 1H, ArH), 7.82–7.8 (dd, J¼1.0, 8 Hz, 1H, ArH);
MS m/z 369, 371 (Mþ); (Found: C, 64.84, H, 4.1, N,
3.93. C20H16ClNO2S requires C, 65.04, H, 4.33, N,
3.79%).
2.1.3. 4-(40-Phenoxybut-20-ynylthio)-1-methylquinolin-
2(1H)-one (3c). Yield 75%; Viscous liquid; UV (EtOH):
l
max: 230, 296, 333 nm; IR (neat) nmax: 2975, 2940, 1645,
1580, 1490 cm21; H NMR (CDCl3, 500 MHz): d 3.7 (s,
3H, NCH3), 3.80 (t, J¼1.9 Hz, 2H, SCH2), 4.68 (t, J¼
1.9 Hz, 2H, OCH2), 6.62 (s, 1H, C3H), 6.95–6.92 (m, 3H,
ArH), 7.27–7.22 (m, 3H, ArH), 7.38–7.36 (d, J¼8.5 Hz,
1H, ArH), 7.61–7.58 (m, 1H, ArH), 7.83–7.81 (dd, J¼1.0,
8 Hz, 1H, ArH); MS m/z 335 (Mþ); (Found: C, 71.42, H,
1
2.2.1. Compound (5c). Yield 90%; solid; mp 1128C; UV
(EtOH): lmax: 350, 240, 367 nm; IR (KBr) nmax: 3200,

K. C. Majumdar, M. Ghosh / Tetrahedron 58 (2002) 10047–10052
10051
2910,1620 cm21; 1H NMR (CDCl3, 500 MHz): d 3.7 (s, 3H,
NCH3), 3.9 (brs, 1H, OH), 4.26 (d, J¼10 Hz, 1H), 4.38 (d,
J¼10 Hz, 1H), 5.92 (s, 1H), 5.98 (s, 1H), 6.78 (d, J¼9 Hz,
1H, ArH), 6.87–7.05 (m, 3H, ArH), 7.19–7.4 (m, 4H, ArH),
8.2 (d, J¼9 Hz, 1H, ArH); MS m/z 351 (Mþ); (Found: C,
68.12; H, 4.6, N, 4.21. C20H17NO3S requires C, 68.37; H,
4.84, N, 3.98%).
4.61, N, 3.76. C20H17NO3S requires C, 68.37, H, 4.84, N,
3.98%).
2.3.4. 3-(20-Methylphenoxyacetyl)-2,3-dihydro-5-methyl-
thieno[3,2-c]quinolin-4(5H)-one (9d). Yield 90%; solid;
mp 1748C; UV (EtOH): lmax: 320, 220, 201 nm; IR (KBr)
n
max: 2990, 2945, 1730, 1640, 1485 cm21 1H NMR
;
(CDCl3, 500 MHz): d 2.28 (s, 3H, CCH3), 3.69 (s, 3H,
NCH3), 3.66–3.62 (dd, J¼9.5, 11 Hz, 1H, SCH2), 3.76–
3.72 (dd, J¼6.5, J¼11 Hz, 1H, SCH2), 4.85–4.83 (dd,
J¼6.5, 9.5 Hz, 1H, C3H), 4.96–4.93 (d, J¼17 Hz, 1H,
OCH2), 5.03–4.97 (d, J¼17 Hz, 1H, OCH2), 6.78–6.77 (d,
J¼8 Hz, 1H, ArH), 6.9–6.89 (d, J¼7.5 Hz, 1H, ArH),
7.15–7.13 (d, J¼7.5 Hz, 2H, ArH), 7.27–7.24 (m, 1H,
ArH), 7.38–7.36 (d, J¼8.5 Hz, 1H, ArH), 7.49–7.48 (d,
J¼8 Hz, 1H, ArH), 7.62–7.59 (m, 1H, ArH); MS m/z 365
(Mþ); (Found: C, 68.79, H, 5.45, N, 3.57. C21H19NO3S
requires C, 69.04, H, 5.2, N, 3.83%).
2.3. General procedure for the intramolecular Michael
addition, preparation of compounds 9a–f
The compounds 5a–f were treated with aqueous 20% KOH
solution (2 mL). Within 3–5 min, a white solid separated
out in excellent yield. These were filtered off, dried and
recrystallized from chloroform–hexane to give white
crystalline solids 9a–f.
2.3.1. 3-(40-Chlorophenoxyacetyl)-2,3-dihydro-5-methyl-
thieno[3,2-c]quinolin-4(5H)-one (9a). Yield 89%; solid;
mp 1168C; UV (EtOH): lmax: 319, 229, 202 nm; IR (KBr)
2.3.5. 3-(40-Methylphenoxyacetyl)-2,3-dihydro-5-methyl-
thieno[3,2-c]quinolin-4(5H)-one (9e). Yield 85%; solid;
mp 1328C; UV (EtOH): lmax: 319, 219, 202 nm; IR (KBr)
n
max: 2990, 2942, 1730, 1640, 1480 cm21 1H NMR
;
(CDCl3, 500 MHz): d 3.69 (s, 3H, NCH3), 3.67–3.62 (dd,
J¼9.5, 11 Hz, 1H, SCH2), 3.78–3.75 (dd, J¼6.5, 11 Hz,
1H, SCH2), 4.85–4.82 (dd, J¼6.5, 9.5 Hz, 1H, C3H), 4.99–
4.96 (d, J¼17 Hz, 1H, OCH2), 5.07–5.04 (d, J¼17 Hz, 1H,
OCH2), 6.89–6.87 (d, J¼9 Hz, 2H, ArH), 7.22–7.21 (d,
J¼9 Hz, 2H, ArH), 7.28–7.26 (d, J¼8 Hz, 1H, ArH), 7.38–
7.36 (d, J¼8.5 Hz, 1H, ArH), 7.49–7.48 (d, J¼8 Hz, 1H,
ArH), 7.62–7.59 (m, 1H, ArH); 13C NMR (CDCl3,
125 MHz): dC 29 (NCH3), 34 (C2), 54 (C3), 72 (C11), 114
(C6), 116 (C60 , C20 ), 122 (C9), 125 (C8), 126 (C9a), 127 (C40 ),
128 (C30 , C50 ), 129 (C3a), 131 (C7), 139 (C9b), 153 (C5a), 156
(C10 ), 158 (C4), 204 (C10); MS m/z 385,387 (Mþ); (Found:
C, 62.05, H, 3.9, N, 3.87. C20H16ClNO3S requires C, 62.33,
H, 4.15, N, 3.63%).
n
max: 2990, 2940, 1730, 1642, 1490 cm21 1H NMR
;
(CDCl3, 500 MHz): d 2.28 (s, 3H, CCH3), 3.69 (s, 3H,
NCH3), 3.67–3.64 (dd, J¼11, 9.5 Hz, 1H, SCH2), 3.74–
3.72 (dd, J¼6.5, 11 Hz, 1H, SCH2), 4.86–4.84 (dd, J¼6.5,
9.5 Hz, 1H, C3H), 4.95–4.93 (d, J¼17 Hz, 1H, OCH2),
5.03–4.97 (d, J¼17 Hz, 1H, OCH2), 6.78–6.77 (d, J¼8 Hz,
1H, ArH), 6.9–6.89 (d, J¼7.5 Hz, 1H, ArH), 7.15–7.13 (d,
J¼7.5 Hz, 2H, ArH), 7.27–7.25 (m, 1H, ArH), 7.38–7.36
(d, J¼8.5 Hz, 1H, ArH), 7.5–7.48 (d, J¼8 Hz, 1H, ArH),
7.62–7.59 (m, 1H, ArH); MS m/z 365 (Mþ); (Found: C,
69.29, H, 5.43, N, 4.08. C21H19NO3S requires C, 69.04, H,
5.2, N, 3.83%).
2.3.6. 3-(20,50-Dimethylphenoxyacetyl)-2,3-dihydro-5-
methylthieno[3,2-c]quinolin-4(5H)-one (9f). Yield 90%;
solid; mp 1568C; UV (EtOH): lmax: 320, 219, 202 nm; IR
(KBr) nmax: 2988, 2942, 1733, 1641, 1484 cm21; 1H NMR
(CDCl3, 500 MHz): d 2.23 (s, 3H, CCH3), 2.28 (s, 3H,
CCH3), 3.68 (s, 3H, NCH3), 3.66–3.64 (dd, J¼11, 9.5 Hz,
1H, OCH2), 3.73–3.71 (dd, J¼6.6, 11 Hz, 1H, SCH2),
4.85–4.83 (dd, J¼6.6, 9.5 Hz, 1H, C3H), 4.97–4.95 (d, J¼
17 Hz, 1H, OCH2), 5.04–4.98 (d, J¼17 Hz, 1H, OCH2),
6.66–6.64 (d, J¼8 Hz, 1H, ArH), 6.7–6.69 (d, J¼7.5 Hz,
1H, ArH), 7.02–7.0 (d, J¼7.5 Hz, 1H, ArH), 7.25–7.23 (m,
1H, ArH), 7.37–7.35 (d, J¼8.5 Hz, 1H, ArH), 7.49–7.47
(d, J¼8 Hz, 1H, ArH), 7.61–7.58 (m, 1H, ArH); MS m/z
379 (Mþ); (Found: C, 69.41, H, 5.79, N, 3.45. C22H21NO3S
requires C, 69.65, H, 5.54, N, 3.69%).
2.3.2. 3-(20-Chlorophenoxyacetyl)-2,3-dihydro-5-methyl-
thieno[3,2-c]quinolin-4(5H)-one (9b). Yield 90%; solid;
mp 1488C; UV (EtOH): lmax: 319, 230, 202 nm; IR (KBr)
n
max: 2980, 2940, 1730, 1642, 1481 cm21 1H NMR
;
(CDCl3, 500 MHz): d 3.69 (s, 3H, NCH3), 3.67–3.62 (dd,
J¼9.5, 11 Hz, 1H, SCH2), 3.78–3.75 (dd, J¼6.5, 11 Hz,
1H, SCH2), 4.85–4.82 (dd, J¼6.5, 9.5 Hz, 1H, C3H), 4.99–
4.96 (d, J¼17 Hz, 1H, OCH2), 5.07–5.04 (d, J¼17 Hz, 1H,
OCH2), 6.88–6.86 (d, J¼9 Hz, 2H, ArH), 7.21–7.2 (d,
J¼9 Hz, 2H, ArH), 7.28–7.25 (d, J¼8 Hz, 1H, ArH), 7.38–
7.36 (d, J¼8.5 Hz, 1H, ArH), 7.49–7.48 (d, J¼8 Hz, 1H,
ArH), 7.62–7.59 (m, 1H, ArH); MS m/z 385,387 (Mþ);
(Found: C, 62.09, H, 4.38, N, 3.89. C20H16ClNO3S requires
C, 62.33, H, 4.15, N, 3.63%).
2.3.3. 3-(Phenoxyacetyl)-2,3-dihydro-5-methylthieno-
[3,2-c]quinolin-4(5H)-one (9c). Yield 80%; solid; mp
1408C; UV (EtOH): lmax: 319, 229, 202 nm; IR (KBr)
2.4. General procedure for the dehydrogenation of
compound 9a, preparation of compound 10
n
max: 2981, 2943, 1728, 1645, 1490 cm21
;
1H NMR
The compound 9a (200 mg, 0.51 mmol) was refluxed with
2,3-dichloro-5,6-dicyano-1,4-benzoquinone (0.56 mmol) in
dry xylene (15 mL) for 2 h. The reaction mixture was
cooled, filtered and the residue was washed with CHCl3
(100 mL). The filtrate was washed successively with 10%
KOH solution, water (three times) and finally dried over
anhydrous sodium sulfate. The CHCl3 solution was then
filtered through a silica gel column and the column was
washed with CHCl3 (300 mL). From the elutes, CHCl3 and
(CDCl3, 500 MHz): d 3.69 (s, 3H, NCH3), 3.66–3.63 (dd,
J¼9.5, 11 Hz, 1H, SCH2), 3.77–3.75 (dd, J¼6.6, 11 Hz,
1H, SCH2), 4.85–4.83 (dd, J¼6.6, 9.5 Hz, 1H, C3H),
5.03–4.99 (d, J¼17 Hz, 1H, OCH2); 5.08–5.05 (d, J¼
17 Hz, 1H, OCH2), 6.91–6.78 (m, 2H, ArH), 7.17–7.14
(m, 2H, ArH), 7.27–7.24 (m, 2H, ArH), 7.38–7.36
(d, J¼8.5 Hz, 1H, ArH), 7.51–7.49 (m, 1H, ArH), 7.62–
7.59 (m, 1H, ArH); MS m/z 351 (Mþ); (Found: C, 68.6, H,

10052
K. C. Majumdar, M. Ghosh / Tetrahedron 58 (2002) 10047–10052
18. Johnson, W. S.; Gravestock, M. B.; Parry, R. J.; Myers, R. F.;
Bryson, T. A.; Miles, H. J. Am. Chem. Soc. 1971, 93,
4330–4332.
xylene were removed under vacuum. The solid obtained
was purified by recrystallization from chloroform–pet ether
(60–80) mixture.
19. Felix, D.; Gschwend-Steen, K.; Wick, A. E.; Eschensoser, A.
Helv. Chim. Acta 1969, 52, 1030–1042.
2.4.1. Compound (10). Yield 90%; solid; mp 1318C; UV
(EtOH): lmax: 348, 333, 283, 229 nm; IR (KBr) nmax: 3083,
20. Ireland, R. E.; Mueller, R. H. J. Am. Chem. Soc. 1972, 94,
5897–5898.
1
1700, 1640, 1491 cm21; H NMR (CDCl3, 500 MHz): d
3.78 (s, 3H, NCH3), 5.35 (brs, 2H, OCH2), 7.26–6.89 (m,
4H, ArH), 7.64–7.3 (m, 3H, ArH), 7.67 (s, 1H, C2H), 7.85–
7.88 (m, 1H, ArH); MS m/z 383, 385 (Mþ); (Found: C,
62.41, H, 3.91, N, 3.41. C20H14ClNO3S requires C, 62.66,
H, 3.65, N, 3.65%).
21. Pereira, S.; Srebnik, M. Aldrichim. Acta 1993, 26, 17–29.
22. Majumdar, K. C.; Thyagarajan, B. S. J. Chem. Soc., Chem.
Commun. 1972, 83.
23. Majumdar, K. C.; Thyagarajan, B. S. Int. J. Sulfur Chem.
1972, 2A, 93.
24. Majumdar, K. C.; Thyagarajan, B. S. Int. J. Sulfur Chem.
1972, 2A, 67.
Acknowledgements
25. El-Osta, B.; Majumdar, K. C.; Thyagarajan, B. S.
J. Heterocyclic Chem. 1973, 10 107.
We thank the CSIR (New Delhi) for financial assistance and
the University of Kalyani for providing laboratory facilities.
26. Hillard, J. B.; Reddy, K. V.; Majumdar, K. C.; Thyagarajan,
B. S. Tetrahedron Lett. 1974, 23, 1999.
27. Hillard, J. B.; Reddy, K. V.; Majumdar, K. C.; Thyagarajan,
B. S. J. Heterocycl. Chem. 1974, 11, 369.
28. Thyagarajan, B. S.; Majumdar, K. C. J. Heterocycl. chem.
1975, 12, 43.
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