Regioselective synthesis of pentacyclic heterocycles by sequential [3,3] sigmatropic rearrangement of 2-(4′-aryloxybut-2′-ynyl-mercapto)thiochromen-4-ones

Article abstract of DOI:10.1016/S0040-4020(03)00784-1

A number of 4-aryloxymethyl-7-chlorothiopyrano[2,3-b]thiochromen-5(2H)-ones are regioselectively synthesized in 80-85% yield by the Claisen rearrangement of 2-(4′-aryloxybut-2′-ynylmercapto)thiochromen-4-ones in refluxing chlorobenzene for 3 h. These products are then subjected to a second Claisen rearrangement in refluxing N,N-diethylaniline for 6 h to give hitherto unreported pentacyclic heterocycles in 50-55% yield.

Full text of DOI:10.1016/S0040-4020(03)00784-1

Tetrahedron 59 (2003) 5289–5293
Regioselective synthesis of pentacyclic heterocycles by sequential
[3,3] sigmatropic rearrangement of
2-(40-aryloxybut-20-ynyl-mercapto)thiochromen-4-ones
*
K. C. Majumdar, A. Bandyopadhyay and A. Biswas
Department of Chemistry, University of Kalyani, Kalyani 741 235, W.B., India
Received 17 December 2002; revised 22 April 2003; accepted 15 May 2003
Abstract—A number of 4-aryloxymethyl-7-chlorothiopyrano[2,3-b]thiochromen-5(2H)-ones are regioselectively synthesized in 80–85%
yield by the Claisen rearrangement of 2-(40-aryloxybut-20-ynylmercapto)thiochromen-4-ones in refluxing chlorobenzene for 3 h. These
products are then subjected to a second Claisen rearrangement in refluxing N,N-diethylaniline for 6 h to give hitherto unreported pentacyclic
heterocycles in 50–55% yield. q 2003 Elsevier Science Ltd. All rights reserved.
1. Introduction
2. Results and discussion
Our continued interest in the synthesis of different oxygen,1
nitrogen2 and sulfur3 heterocycles by the application of
sigmatropic rearrangements4 led us to synthesize a number
of hitherto unreported heterocyclic compounds derived
from 4-hydroxydithiocoumarin.5,6 This also included a
simple synthesis of the thieno[2,3-b]thiochromen-4-one
skeleton, an intermediate for the synthesis of a number of
drugs7 used for psycotic disturbances. Earlier we reported
the sequential [3,3] sigmatropic rearrangements of suitably
1,4-disubstituted but-2-ynes to give interesting results8–10
and this has prompted us to take a study on the sequential
[3,3] sigmatropic rearrangements of 2-(40-aryloxybut-20-
ynylmercapto)thiochromen-4-ones. Here we report the
results.
2-(40-Aryloxybut-20-ynylmercapto)-7-chlorothiochromen-
4-ones were prepared in 80–82% yield by the phase transfer
catalyzed alkylation11 of 7-chloro-4-hydroxydithio-
coumarin6 1 with a number of 1-aryloxy-4-chlorobut-2-
yne 2a–f in the presence of benzyltriethylammonium-
chloride (BTEAC) in 1% aqueous NaOH–CHCl3 for 5 h.
The same reaction if conducted under classical conditions of
refluxing in acetone in the presence of anhydrous potassium
carbonate for 6–8 h afforded the substrates 3a–f in lower
yields (55–70%) (Scheme 1).
The substrates 3a–f contain the but-2-ynylthioenone moiety
as well as the arylprop-2-ynylether moiety and thus offers
scope for two different possibilities of [3,3] sigmatropic
Scheme 1. Reagents and conditions: (i) BTEAC, aq. NaOH (1%), CHCl3, 5 h.
Keywords: [3,3] sigmatropic rearrangement; regioselective synthesis; sequential Claisen rearrangement; phase-transfer catalysis.
*
Corresponding author. Tel.: þ91-33-2582-7521; fax: þ91-33-25828282; e-mail: kcm@klyuniv.ernet.in
0040–4020/03/$ - see front matter q 2003 Elsevier Science Ltd. All rights reserved.
doi:10.1016/S0040-4020(03)00784-1

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K. C. Majumdar et al. / Tetrahedron 59 (2003) 5289–5293
Scheme 2. Reagents and conditions: C6H5Cl, 3 h, reflux.
rearrangement. The aliphatic Claisen rearrangement has
lower activation energy as the aromatic counterpart has its
aromatic sextet disturbed in the transition state. Therefore,
substrate 3a was heated in chlorobenzene (1328C) and the
reaction was monitored by TLC. Complete conversion was
achieved in 3 h giving a white solid, mp 1028C, isolated in
80% yield. The product 4a was characterized from its
elemental analysis and spectroscopic data as 7-chloro-4-(40-
methylphenoxymethyl)thiopyrano[2,3-b]thiochromen-
5(2H)-one. Substrates 3b–f under similar treatment gave
products 4b–f in 80–85% yields (Scheme 2). The
formation of products 4a–f from substrates 3a–f may be
easily explained by an initial [3,3] sigmatropic rearrange-
ment followed by rapid enolization to give intermediate
allenyl thiol 6, [1,5] hydrogen shift and 6p-electrocyclic
ring closure may finally give products 4a–f (Scheme 2).
showed a tendency to decomposition and no tractable
product was obtained. Substrate 4a was next heated in
refluxing N,N-diethylaniline for 6 h to give a crystalline
solid, mp 1458C (50%). This was characterized as 8a
(Scheme 3) from its elemental analysis and spectral data. Its
1H NMR spectrum showed d 1.78 (s, 3H, CH3), 2.30 (s, 3H,
CH3), 2.83–2.91 (dd, 1H, J¼12.0, 13.0 Hz, SCH2), 2.98–
3.04 (dd, 1H, J¼4.0, 13.0 Hz, SCH2), 3.46–3.52 (dd, 1H,
J¼4.0, 12.0 Hz, 1H of ring junction), 6.85–7.42 (m, 5H,
ArH); 8.42 (d, 1H, J¼8.5 Hz, ArH). Substrates 4b–f were
also similarly treated to give products 8b–f. The stereo-
chemistry of the furothiopyran ring juncture of 8 can only be
surmised from the molecular model (Dreiding model) of the
molecules which show a strain free cis arrangement
(Scheme 3).
The formation of products 8a–f can be mechanistically
explained by an initial [3,3] sigmatropic rearrangement in
4a–f to give dienone 9, enolization converts 9 into 10 which
may then undergo a 5-exo cyclization to give 8 (Scheme 4).
A close examination of products 4a–f reveals that these still
contain an allyl aryl ether moiety well situated for a second
Claisen rearrangement. Substrate 4a was heated in 1,2-
dichlorobenzene in the presence of a catalytic amount of
aniline and after 14 h, a new compound was obtained. This
was characterized as 10 (Scheme 4) from its elemental
analysis and spectroscopic data. Its 1H NMR spectrum
revealed-d 2.17 (s, 3H, CH3), 3.30–3.64 (m, 2H, SCH2),
4.34–4.36 (m, 1H, allylic H), 5.19 (s, 1H, one exocyclic H),
6.08 (s, 1H, one exocyclic H), 6.60–6.72 (m, 5H, ArH),
8.36–8.39 (d, 1H, J¼8.5 Hz, ArH). This compound was
subjected to cyclization by (i) pyridine hydrotribromide, (ii)
hexamine hydrotribromide, (iii) H2SO4. The compound
In conclusion, we have executed the sequential Claisen
Scheme 3. Reagents and conditions: N,N-diethylaniline, reflux, 6 h.
Scheme 4.

K. C. Majumdar et al. / Tetrahedron 59 (2003) 5289–5293
5291
rearrangement, at the present instance a thio-Claisen
rearrangement of propynyl vinyl sulfide followed by an
oxy-Claisen rearrangement of allyl phenyl ether. This
methodology represents a straight forward approach for
the construction of the furothiopyran ring system. This has
been applied for the synthesis of pentacyclic heterocycles
from 2-(40-aryloxybut-20-enylmercapto)thiochromen-4-
ones.
3.1.3. 7-Chloro-2-[4-(30,50-dimethylphenoxybut-20-
ynylthio)][1]benzothiopyran-4-one (3c). White solid, mp
1038C; yield 80% (1.92 g); UV (EtOH) lmax: 219
(log 1¼4.26), 271 (log 1¼4.48), 337 (log 1¼4.18) nm; IR
(KBr) nmax: 1600, 1580, 1290 cm21; 1H NMR (500 MHz): d
2.23 (s, 6H, 2CH3); 3.83 (t, 2H. J¼2.0 Hz, –SCH2), 4.66 (t,
2H, J¼2.0 Hz, –OCH2), 6.53–7.47 (m, 6H, ArH); 8.38 (d,
1H, J¼8.5 Hz, ArH); HRMS (EI) m/z: 402 (2.1), 400 (14.9,
Mþ), 279 (34), 173 (92.55), 172 (72.3), 122 (100), 121
(58.5), 107 (100), 91 (34%). Anal. calcd for C21H17ClO2S2:
C, 63.00; H, 4.25%. Found C, 63.21; H, 4.19%.
3. Experimental
3.1.4. 7-Chloro-2-[4-(40-tert.butylphenoxybut-20-ynyl-
thio)][1]benzothiopyran-4-one (3d). White solid, mp
588C; yield 80% (2.0 g); UV (EtOH) lmax: 217
Melting points are uncorrected. UV absorption spectra were
recorded on a UV–VIS Spectrophotometer Shimadzu
Model No. UV-2401PC (absolute ethanol). IR spectra
were run as KBr discs on a Perkin–Elmer 1330 apparatus
and FTIR spectrophotometer Perkin–Elmer Model
(log 1¼4.25), 270 (log 1¼4.49), 336 (log 1¼4.15) nm; IR
(KBr) nmax: 1622, 1584, 1306 cm21; 1H NMR (300 MHz): d
1.27 (s, 9H, C(CH3)3); 3.84 (t, 2H. J¼2.0 Hz, –SCH2), 4.67
(t, 2H, J¼2.0 Hz, –OCH2), 6.83–7.49 (m, 7H, ArH); 8.38
(d, 1H, J¼8.5 Hz, ArH); HRMS (EI) m/z: 430 (3.2), 428
(6.4, Mþ), 413 (5.1), 279 (27.7), 150 (100), 136 (87.2), 135
(100), 107 (100), 95 (79.8), 91 (60.6%). Anal. calcd for
C23H21ClO2S2: C, 64.41; H, 4.90%. Found C, 64.60; H,
4.65%.
1
No.L120-000A. H NMR spectra were recorded in CDCl3
with TMS as internal standard on a Bruker DPX-300
(300 MHz) and Bruker DRS-600 (500 MHz) spectrometers.
Elemental analyses and mass spectras were recorded on a
[JEOL D-300 (El)] instrument by RSIC(CDRI) Lucknow.
Silica gel (60–120) was obtained from Spectrochem.
Extracts were dried over anhydrous Na2SO4.
3.1.5. 7-Chloro-2-[4-(40-methoxyphenoxybut-20-ynyl-
thio)][1]benzothiopyran-4-one (3e). White solid, mp
928C; yield 82% (1.98 g); UV (EtOH) lmax: 218
3.1. Alkylation of 7-chloro-4-hydroxydithiocoumarin
To a mixture of 7-chloro-4-hydroxydithiocoumarin
(6 mmol) and 1-aryloxy-4-chlorobut-2-yne (9 mmol) in
chloroform (50 mL) is added a solution of TBAB
(0.25 mmol) or (BTEAC) (0.9 mmol) in 1% aq. NaOH
(50 mL) and the mixture was stirred at room temperature for
a period of 5 h. The mixture was then diluted with water
(100 mL) and extracted with CHCl3 (3£25 mL), brine
(3£25 mL) and dried (Na2SO4). The solvent was removed
in vacuo and the residual crude mass was purified by
chromatography over silica gel using benzene–petroleum
ether (1:2) as eluent to afford the following compounds.
(log 1¼4.24), 271 (log 1¼4.43), 336 (log 1¼4.14) nm; IR
(KBr) nmax: 1600, 1582, 1270 cm21; 1H NMR (300 MHz): d
3.72 (s, 3H, –OCH3), 3.83 (t, 2H, J¼2.0 Hz, –SCH2), 4.64
(t, 2H, J¼2.0 Hz, –OCH2), 6.73–7.48 (m, 7H, ArH), 8.39
(d, 1H, J¼8.5 Hz, ArH); HRMS (EI) m/z: 404 (5.3), 402
(10.6, Mþ), 279 (22.3), 124 (100), 123 (62.7), 109 (100), 95
(22.3%). Anal. calcd for C20H15ClO3S2: C, 59.62; H,
3.72%. Found C, 59.70; H, 3.60%.
3.1.6. 7-Chloro-2-[4-(40-chloro-30,50-dimethylphenoxy-
but-20-ynylthio)][1]benzothiopyran-4-one (3f). White
solid, mp 1208C; yield 82% (2.15 g); UV (EtOH) lmax
212 (log 1¼4.25), 261 (log 1¼4.46), 340 (log 1¼4.18) nm;
IR (KBr) nmax: 1600, 1582, 1270 cm21 1H NMR
:
3.1.1. 7-Chloro-2-[4-(40-methylphenoxybut-20-ynyl-
thio)][1]benzothiopyran-4-one (3a). White solid, mp
;
958C; yield 80% (1.85 g); UV (EtOH) lmax
:
219
(300 MHz): d 2.28 (s, 6H, 2CH3), 3.83 (t, 2H, J¼2.0 Hz,
–SCH2), 4.64 (t, 2H, J¼2.0 Hz, –OCH2), 6.62–7.48 (m,
5H, ArH), 8.37 (d, 1H, J¼8.5 Hz, ArH); HRMS (EI) m/z:
438 (1.6), 436 (4.4), 434 (5.3, Mþ), 279 (15.9), 256 (60.2),
156 (100), 129 (45.7), 121 (100), 97 (71.3), 91 (94.7%).
Anal. calcd for C21H16Cl2O2S2: C, 57.93; H, 3.67%. Found
C, 57.90; H, 3.63%.
(log 1¼4.25), 272 (log 1¼4.50), 336 (log 1¼4.16) nm; IR
(KBr) nmax: 1600, 1580, 1230 cm21; 1H NMR (300 MHz): d
2.27 (s, 3H, –CH3); 3.67 (t, 2H, J¼2.0 Hz, –SCH2), 4.62 (t,
2H, J¼2.0 Hz, –OCH2), 6.76–7.95 (m, 7H, ArH); 8.37 (d,
1H, J¼8.5 Hz, ArH); HRMS (EI) m/z: 388 (3.2), 386 (12.4,
Mþ), 279 (31.2), 122 (100), 121 (61.2), 107 (100), 91
(31.2%). Anal. Calcd for C20H15ClO2S2: C, 62.18; H,
3.89%. Found C, 62.07; H, 3.94%.
3.2. General procedure for rearrangement of compound
3a–f
3.1.2. 7-Chloro-2-[4-(40-chlorophenoxybut-20-ynyl-
thio)][1]benzothiopyran-4-one (3b). White solid, mp
1028C; yield 80% (2.0 g); UV (EtOH) lmax: 221
(log 1¼4.24), 271 (log 1¼4.43), 343 (log 1¼4.15) nm; IR
(KBr) nmax: 1600, 1580, 1260 cm21; 1H NMR (300 MHz): d
3.85 (t, 2H. J¼2.0 Hz, –SCH2), 4.81 (t, 2H, J¼2.0 Hz,
–OCH2), 6.82–7.51 (m, 7H, ArH); 8.42 (d, 1H, J¼8.5 Hz,
ArH); HRMS (EI) m/z:410 (2.4), 408 (4.6) 406 (6.8, Mþ),
279 (22.8), 128 (100), 127 (58.1), 109 (100), 91 (28.7%).
Anal. calcd for C19H12Cl2O2S2: C, 56.01; H, 2.94%. Found
C, 56.06; H, 2.98%.
The starting sulfide (0.5 g, 1.25 mmol) was refluxed in
chlorobenzene (4 mL) in an oil bath for 2 h. Chlorobenzene
was removed in vacuo and the residual mass was
chromatographed over silica gel. Elution of the column
with pet-ether (60–808C) removed the residual chloro-
benzene and then white solid was obtained by eluting the
column with benzene–petether (60–808C) 1:1.
3.2.1. 8-Chloro-4-(40-methylphenoxymethyl)thio-
pyrano[2,3-b]thiochromen-5-(2H)-one (4a). White solid,

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K. C. Majumdar et al. / Tetrahedron 59 (2003) 5289–5293
mp 1008C; yield 85% (410 mg); UV (EtOH) lmax: 240
(log 1¼4.22), 295 (log 1¼4.52), 336 (log 1¼3.93) nm; IR
(KBr) nmax: 1620, 1580, 1380 cm21; 1H NMR (500 MHz): d
2.25 (s, 3H, –CH3); 3.42 (d, 2H. J¼6.0 Hz, –SCH2), 5.50
(s, 2H, –OCH2), 6.15–6.17–7.47 (m, 7H, ArH); 8.28 (d,
1H, J¼8.5 Hz, ArH); HRMS (EI) m/z: 388 (4.3), 386 (8.5,
Mþ), 281 (100), 280 (58.5), 279 (100), 216 (14.9), 171
(21.3), 107 (77.6), 91 (17%). Anal. calcd for C20H15ClO2S2:
C, 62.18; H, 3.89%. Found C, 62.02; H, 3.90%.
l
max: 212 (log 1¼4.21), 261 (log 1¼4.51), 353 (log 1¼
3.92) nm; IR (KBr) nmax: 1610, 1586, 1380 cm21; 1H NMR
(300 MHz): d 2.29 (s, 6H, 2CH3), 3.42 (d, 2H. J¼6.0 Hz,
–SCH2), 5.03 (s, 2H, –OCH2), 6.12–7.47 (m, 5H, ArH);
8.27 (d, 1H, J¼8.5 Hz, ArH); HRMS (EI) m/z: 438 (0.75),
436 (2.2), 434 (1.9, Mþ), 281 (42.6), 280 (23.2), 279 (100),
256 (21.3), 156 (36.2), 121 (44.7), 106 (24.5), 91 (29.8%).
Anal. calcd for C21H16Cl2O2S2: C, 57.93; H, 3.67%. Found
C, 57.88; H, 3.69%.
3.2.2. 8-Chloro-4-(40-chlorophenoxymethyl)thio-
pyrano[2,3-b]thiochromen-5-(2H)-one (4b). White solid,
mp 998C; yield 80% (407 mg); UV (EtOH) lmax: 242
(log 1¼4.21), 298 (log 1¼4.49), 355 (log 1¼3.96) nm; IR
(KBr) nmax: 1620, 1600, 1490 cm21; 1H NMR (500 MHz): d
3.42 (d, 2H. J¼6.0 Hz, –SCH2), 5.06 (s, 2H, –OCH2),
6.13–7.47 (m, 7H, ArH); 8.28 (d, 1H, J¼8.5 Hz, ArH);
HRMS (EI) m/z:410 (1.4), 408 (4.6), 406 (2.4, Mþ), 281
(52.3), 280 (34.5), 279 (100), 121 (36.8), 107 (23.4), 91
(25.6%). Anal. calcd for C19H12Cl2O2S2: C, 56.01; H,
2.94%. Found C, 56.08; H, 3.01%.
3.3. General procedure for rearrangement of 4-(aryl-
oxymethyl)thiopyrano[2,3-b]benzothiopyran-5(2H)ones
A mixture of compound (4a–f) (1 mmol) in N,N-diethyl-
aniline (5 mL) was refluxed for 4–6 h. The reaction mixture
was cooled, poured into ice-cold 6N HCl (30 mL), and
extracted with CHCl3 (3£20 mL).The CHCl3 layer was
washed with water and dried over Na2SO4. Removal of
CHCl3 gave a viscous liquid which was chromatographed
over silica gel. Elution of the column with 50% benzene–
petroleum ether furnished products 8a–f.
3.2.3. 8-Chloro-4-(30,50-dimethylphenoxymethyl)thio-
pyrano[2,3-b]thiochromen-5-(2H)-one (4c). White solid,
mp 1388C; yield 80% (402 mg); UV (EtOH) lmax: 220
(log 1¼4.21), 292 (log 1¼4.52), 351 (log 1¼3.97) nm; IR
(KBr) nmax: 1613, 1582, 1378 cm21; 1H NMR (300 MHz): d
2.25 (s, 6H, 2CH3); 3.42 (d, 2H. J¼6.0 Hz, –SCH2), 5.04 (s,
2H, –OCH2), 6.15–7.47 (m, 6H, ArH); 8.29 (d, 1H,
J¼8.5 Hz, ArH); HRMS (EI) m/z: 402 (2.1), 400 (4.3, Mþ),
281 (100), 280 (76.59), 279 (100), 216 (18.1), 171 (12.8),
122 (21.3), 107 (21.3), 91 (18.1%). Anal. calcd for
C21H17ClO2S2: C, 63.00; H, 4.25%. Found C, 62.19; H,
4.31%.
3.3.1. 10-Chloro-5b,13b-dihydro-4,13b-dimethylbenzo-
furo[3,2-c]thiopyrano[3,2-b]thiochromen-13-one (8a).
White solid, mp 1328C; yield 55% (212 mg); UV (EtOH)
l
max: 217 (log 1¼4.13), 275 (log 1¼4.37), 335 (log 1¼
4.98) nm; IR (KBr) nmax: 1620, 1570, 1420 cm21; 1H NMR
(300 MHz): d 1.78 (s, 3H, –CH3 of ring junction), 2.30 (s,
3H, ArCH3), 2.83–2.91 (dd, 1H, J¼12.0, 13.0 Hz, –SCH2),
2.98–3.04 (dd, 1H. J¼4.0, 13.0 Hz, –SCH2), 3.46–3.52
(dd, 1H, J¼4.0, 12.0 Hz, H of ring junction), 6.85–7.42 (m,
5H, ArH), 8.42 (d, 1H, J¼8.5 Hz, ArH); HRMS (EI) m/z:
388 (43.4), 386 (100, Mþ), 371 (43.2), 281 (38.6), 279
(71.2), 266 (32.3), 253 (48.8), 171 (22.3), 107 (19.2), 91
(26.3%). Anal. calcd for C20H15ClO2S2: C, 62.18; H,
3.89%. Found C, 62.05; H, 3.70%.
3.2.4. 8-Chloro-4-(40-tert.butylphenoxymethyl)thio-
pyrano[2,3-b]thiochromen-5-(2H)-one (4d). White solid,
mp 748C; yield 80% (427 mg); UV (EtOH) lmax: 221
(log 1¼4.18), 291 (log 1¼4.48), 343 (log 1¼3.91) nm; IR
(KBr) nmax: 1617, 1582, 1383 cm21; 1H NMR (300 MHz): d
1.27 (s, 9H, C(CH3)3); 3.42 (d, 2H. J¼6.0 Hz, –SCH2), 5.05
(s, 2H, –OCH2), 6.15–7.46 (m, 7H, ArH); 8.28 (d, 1H,
J¼8.5 Hz, ArH); HRMS (EI) m/z: 430 (1.8), 428 (4.5, Mþ),
281 (100), 280 (75.9), 279 (100), 252 (39.4), 224 (26.6), 150
(37.2), 135 (100), 107 (68.1), 91 (28.7%). Anal. calcd for
C23H21ClO2S2: C, 64.41; H, 4.90%. Found C, 64.25; H,
4.78%.
3.3.2. 10-Chloro-5b,13b-dihydro-4-chloro-13b-methyl-
benzofuro[3,2-c]thiopyrano[3,2-b]thiochromen-13-one
(8b). White solid, mp 1458C; yield 50% (202 mg); UV
(EtOH) lmax: 205 (log 1¼4.18), 271 (log 1¼4.42), 311
(log 1¼4.00)nm; IR (KBr) nmax: 1620, 1580, 1450 cm21
;
1H NMR (300 MHz): d 1.79 (s, 3H, –CH3 of ring junction),
2.84–2.92 (dd, 1H, J¼12.0, 13.0 Hz, –SCH2), 2.99–3.05
(dd, 1H, J¼4.0, 13.0 Hz, –SCH2), 3.51–3.56 (dd, 1H,
J¼4.0, 12.0 Hz, H of ring junction), 6.89–7.45 (m, 5H,
ArH); 8.45 (d, 1H, J¼8.5 Hz, ArH); HRMS (EI): m/z: 410
(23.4), 408 (71.3), 406 (100, Mþ), 393 (23.4), 391 (33), 373
(19.1), 281 (24.1), 279 (59.6), 266 (70.2), 253 (47.9), 170
(21.3), 110 (19.1%). Anal. calcd for C19H12Cl2O2S2: C,
56.01; H, 2.94%. Found C, 56.10; H, 3.06%.
3.2.5. 8-Chloro-4-(40-methoxylphenoxymethyl)thio-
pyrano[2,3-b]thiochromen-5-(2H)-one (4e). White solid,
mp 1028C; yield 80% (404 mg); UV (EtOH) lmax: 223
(log 1¼4.20), 292 (log 1¼4.51), 353 (log 1¼3.96) nm; IR
(KBr) nmax: 1610, 1586, 1380 cm21; 1H NMR (300 MHz): d
3.42 (d, 2H. J¼6.0 Hz, –SCH2), 3.74 (s, 3H, –OCH3), 5.03
(s, 2H, –OCH2), 6.14–7.47 (m, 6H, ArH); 8.28 (d, 1H,
J¼8.5 Hz, ArH); HRMS (EI) m/z: 404 (3.8), 402 (9, Mþ),
281 (100), 280 (68.1), 279 (100), 216 (28.7), 171 (17), 124
(56.4), 109 (38.5%). Anal. calcd for C20H15ClO3S2: C,
59.62; H, 3.72%. Found C, 59.43; H, 3.68%.
3.3.3. 10-Chloro-5b,13b-dihydro-3,5,13b-trimethyl-
benzofuro[3,2-c]thiopyrano[3,2-b]thiochromen-13-one
(8c). White solid, mp 1948C; yield 50% (200 mg); UV
(EtOH) lmax: 211 (log 1¼4.14), 275 (log 1¼4.38), 336
(log 1¼3.95) nm; IR (KBr) nmax: 1622, 1580, 1307 cm21
;
1H NMR (300 MHz): d 1.72 (s, 3H, –CH3 of ring junction);
2.28 (s, 3H, ArCH3), 2.32 (s, 3H, ArCH3), 2.73–2.81 (dd,
1H, J¼12.0, 13.0 Hz, –SCH2), 2.95–3.01 (dd, 1H, J¼4.0,
13.0 Hz, –SCH2), 3.42–3.47 (dd, 1H, J¼4.0, 12.0 Hz, H of
ring junction), 6.55–7.45 (m, 5H, ArH); 8.46 (d, 1H,
J¼8.5 Hz, ArH); HRMS (EI) m/z: 402 (65.9), 400 (100,
3.2.6. 8-Chloro-4-(40-chloro-30,50-dimethylphenoxy-
methyl)thiopyrano[2,3-b]thiochromen-5-(2H)-one (4f).
White solid, mp 1768C; yield 80% (432 mg); UV (EtOH)

K. C. Majumdar et al. / Tetrahedron 59 (2003) 5289–5293
5293
Mþ), 385 (61.7), 367 (27.7), 281 (25.5), 279 (64.9), 266
(24.5), 256 (32.9), 171 (40.4), 135 (47.9), 95 (27.7%). Anal.
calcd for C21H17ClO2S2: C, 63.00; H, 4.25%. Found C,
63.20; H, 4.17%.
obtained when column was eluted with benzene–ethyl-
acetate (19:1).
3.4.1. 8-Chloro-2,3-dihydro-4-exomethylene-3-(40-
methyl-20-hydroxyphenyl)thiopyrano[2,3-b]thiochrom-
4-en-5-one (10). White solid, mp 1708C; yield 40%
3.3.4. 10-Chloro-5b,13b-dihydro-4-tert.butyl-13b-
methylbenzofuro[3,2-c]thiopyrano[3,2-b]thio-chromen-
13-one (8d). White solid, mp 2038C; yield 53% (225 mg);
UV (EtOH) lmax: 218 (log 1¼4.11), 275 (log 1¼4.34), 336
(70 mg); UV (EtOH) lmax
(log 1¼4.25), 357 (log 1¼4.73) nm; IR (KBr) nmax: 1620,
1560, 1310 cm21 1H NMR (300 MHz): d 2.17 (s, 3H,
:
208 (log 1¼4.02), 220
;
(log 1¼3.95) nm; IR (KBr) nmax: 1625, 1582, 1299 cm21
1H NMR (300 MHz): d 1.30 (s, 9H, –C(CH3)3); 1.78 (s, 3H,
;
ArCH3), 3.30–3.64 (m, 2H, –SCH2), 4.34–4.36 (m, 1H,
–SCH2CH), 5.19 (s, 1H, vCH2), 6.08 (s, 1H, vCH2),
6.60–6.72 (m, 5H, ArH), 8.36–8.39 (d, 1H, J¼8.5 Hz,
ArH); HRMS (EI) m/z: 388 (0.53), 386 (2.8, Mþ), 256
(20.2), 149 (25.5), 141 (14.9), 129 (21.3), 113 (24.5), 111
(24.5), 97 (43.6), 85 (100%). Anal. calcd for C20H15ClO2S2:
C, 67.70; H, 4.23%. Found C, 67.20; H, 4.00%.
–CH3 of ring junction), 2.85–2.93 (dd, 1H, J¼12.0,
13.0 Hz, –SCH2), 3.02–3.08 (dd, 1H, J¼4.0, 13.0 Hz,
–SCH2), 3.48–3.53 (dd, 1H, J¼4.0, 12.0 Hz, H of ring
junction), 6.88–7.44 (m, 5H, ArH); 8.45 (d, 1H, J¼8.5 Hz,
ArH); HRMS (EI) m/z:430 (28.7), 428 (100, Mþ), 413
(81.9), 395 (20.8), 371 (34), 281 (43.6), 279 (77.6), 266
(23.4), 253 (14.9), 161 (21.3), 97 (19.1%). Anal. calcd for
C23H21ClO2S2: C, 64.41; H, 4.90%. Found C, 64.26; H,
5.00%.
Acknowledgements
We thank the CSIR (New Delhi) for financial assistance.
One of us (A. Biswas) is grateful to CSIR for a Junior
Research Fellowship.
3.3.5. 10-Chloro-5b,13b-dihydro-4-methoxy-13b-
methylbenzofuro[3,2-c]thiopyrano[3,2-b]thio-chromen-
13-one (8e). White solid, mp 708C; yield 50% (200 mg);
UV (EtOH) lmax: 217 (log 1¼4.18), 275 (log 1¼4.35), 336
1H NMR (300 MHz): d 1.78 (s, 3H, –CH3 of ring junction),
2.86–2.94 (dd, 1H, J¼12.0, 13.0 Hz, –SCH2), 3.00–3.06
(dd, 1H, J¼4.0, 13.0 Hz, –SCH2), 3.48–3.53 (dd, 1H,
J¼4.0, 12.0 Hz, H of ring junction), 3.77 (s, 3H, –OCH3),
6.73–7.44 (m, 6H, ArH), 8.44 (d, 1H, J¼8.5 Hz, ArH);
HRMS (EI) m/z: 404 (39.4), 402 (100, Mþ), 387 (31.9), 369
(19.2), 279 (22.3), 266 (14.9), 253 (14.9), 171 (14.9), 150
(20.2), 109 (14.9%). Anal. calcd for C20H15ClO3S2: C,
59.62; H, 3.72%. Found C, 59.80; H, 3.60%.
(log 1¼4.00) nm; IR (KBr) nmax: 1610, 1580, 1305 cm21
;
References
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(b) Ziegler, F. E. Chem. Rev. 1988, 88, 1423. (c) Ziegler, F. E.
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2. Thyagarajan, B. S. Advances in Heterocyclic Chemistry;
Academic, 1967; Vol. 8. p 143.
3. Morin, L.; Lebaud, J.; Paquer, D.; Chaussin, D.; Barillier, D.
Phosphorous Sulfur 1979, 7, 69.
4. (a) Majumdar, K. C.; Chatterjee, P.; Saha, S. Tetrahedron Lett.
1998, 39, 7147–7148. (b) Majumdar, K. C.; Biswas, P.
Tetrahedron 1999, 55, 1449–1456. (c) Majumdar, K. C.;
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(d) Majumdar, K. C.; Samanta, S. K. Synthesis 2002,
120–125. (e) Majumdar, K. C.; Samanta, S. K. Tetrahedron
Lett. 2002, 43, 2119–2121. (f) Majumdar, K. C.; Ghosh, S. K.
Tetrahedron Lett. 2002, 43, 2123–2125.
3.3.6. 10-Chloro-5b,13b-dihydro-4-chloro-3,5,13b-tri-
methylbenzofuro[3,2-c]thiopyrano[3,2-b] thiochromen-
13-one (8f). White solid, mp 1928C; yield 54% (235 mg);
UV (EtOH) lmax: 212 (log 1¼4.18), 261 (log 1¼4.42), 337
1H NMR (300 MHz): d 1.72 (s, 3H, –CH3 of ring junction),
2.34 (s, 3H, ArCH3), 2.38 (s, 3H, ArCH3), 2.72–2.80 (dd,
1H, J¼12.0, 13.0 Hz, –SCH2), 2.92–2.98 (dd, 1H, J¼4.0,
13.0 Hz, –SCH2), 3.43–3.48 (dd, 1H, J¼4.0, 12.0 Hz, H of
ring junction), 6.76–7.40 (m, 3H, ArH), 8.44 (d, 1H,
J¼8.5 Hz, ArH); HRMS (EI) m/z: 438 (11.7), 436 (71.3),
434 (87.2, Mþ), 419 (44.7), 401 (35.1), 281 (50), 279 (100),
266 (37.2), 253 (30.9), 169 (22.4), 97 (24.5%). Anal. calcd
for C21H16Cl2O2S2: C, 57.93; H, 3.67%. Found C, 57.89; H,
3.63%.
(log 1¼4.00) nm; IR (KBr) nmax: 1610, 1580, 1305 cm21
;
5. Majumdar, K. C.; Khan, A. T.; Saha, S. SynLett 1991,
595–596.
6. Majumdar, K. C.; Khan, A. T.; Saha, S. Synth. Commun. 1992,
22, 901–912.
7 Sandoz Ltd Neth. Appl. 6411476 (C1, C O7d), April 9, 1965;
Swiss Appl. October 8, 1963 and July 29, 1964, p 12; Chem.
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8. Majumdar, K. C.; Das, U. J. Org. Chem. 1998, 63,
9997–10000.
3.4. General procedure for the preparation of compound
10
9. Majumdar, K. C.; Kundu, U. K.; Ghosh, S. K. Org. Lett. 2002,
4, 2629–2631.
10. Majumdar, K. C.; Kundu, U. K.; Ghosh, S. J. Chem. Soc.,
Perkin Trans. 1 2002, 2139–2140.
Compounds 4a (0.52 mmol) in presence of catalytic amount
N,N-diethyl aniline for 14 h. The reaction mixture was then
cooled and directly subjected to column chromatography
over silica gel. o-dichlorobenzene and N,N-diethyl aniline
were eluted out with petroleum ether. The product 10 was
11. (a) Starks, C. M.; Liotta, C. Phase Transfer-catalysis;
Academic: New York, 1978. (b) Dehmlow, E. V.; Dehmlow,
S. S. Phase Transfer-Catalysis; 3rd ed. VCH: New York,
1993.