Studies on sulfoxide rearrangement: Synthesis of dimedone-annelated heterocycles

Article abstract of DOI:10.1016/S0040-4020(02)00396-4

A number of 3-(4′-aryloxybut-2′-ynyl)thio-5,5-dimethyl cyclohex-2-enones are synthesized in 80-90% yield by phase transfer catalyzed reaction of 5,5-dimethyl-3-merca-ptocyclohex-2-enone with a number of 1-aryloxy-4-chlorobut-2-ynes. The sulfides are oxidized with 1equiv. of m-chloroperoxybenzoic acid and the resulting sulfoxides are then stirred at r.t. for 6-8h to give 2-aryloxymethyl-3-(m-chlorobenzoyloxy)-6,6-dimethyl-5,6,7-trihydro benzo(b)thiophene-4-ones in 70-80% yield.

Full text of DOI:10.1016/S0040-4020(02)00396-4

TETRAHEDRON
Pergamon
Tetrahedron 58 &2002) 4551±4554
Studies on sulfoxide rearrangement: synthesis of
dimedone-annelated heterocycles
K. C. Majumdarp and S. K. Samanta
Department of Chemistry, University of Kalyani, Kalyani, W.B. 741 235, India
Received 1 January 2002; revised 7 March 2002; accepted 4 April 2002
AbstractÐA number of 3-&40-aryloxybut-20-ynyl)thio-5,5-dimethyl cyclohex-2-enones are synthesized in 80±90% yield by phase transfer
catalyzed reaction of 5,5-dimethyl-3-merca-ptocyclohex-2-enone with a number of 1-aryloxy-4-chlorobut-2-ynes. The sul®des are oxidized
with 1 equiv. of m-chloroperoxybenzoic acid and the resulting sulfoxides are then stirred at r.t. for 6±8 h to give 2-aryloxymethyl-3-&m-
chlorobenzoyloxy)-6,6-dimethyl-5,6,7-trihydro benzo&b)thiophene-4-ones in 70±80% yield. q 2002 Published by Elsevier Science Ltd.
Aliphatic Claisen rearrangement1 has become a powerful
tool for carbon±carbon bond formation.2 Its importance is
partly due to the subsequent development of a series new
variants3 of the [3,3] sigmatropic rearrangement and partly
due to its versatile application in the synthesis of various
heterocycles using oxygen,4 nitrogen,5 and sulfur6 Claisen
rearrangements. Our recent work on the synthesis of various
heterocycles by the application of [3,3] sigmatropic
rearrangement7 motivated us to study the synthesis of
dimedone-annelated heterocycles.8 In continuation, we
undertook a study on the synthesis of dimedone-annelated
thiophene by the application of sulfoxide rearrangement, a
mild and simple methodology we had reported earlier.9
5,5-dimethyl-3-mercaptocyclohex-2-enone10 &1) with
a
number of 1-aryloxy-4-chlorobut-2-ynes &2a±g) in chloro-
form and 1% aqueous NaOH solution in the presence of
benzyltriethylammonium chloride at room temperature for
4 h &Scheme 1).
Substrate 3a was treated with 1 equiv. of 3-chloroperoxy-
benzoic acid in chloroform at 0±58C for 10 min. TLC
showed a highly polar single spot indicating the formation
of sulfoxide &4a). This product exhibited tendency to further
reorganization. The sulfoxide could not be isolated in the
pure form. It rearranged even during workup. Therefore, no
attempt was made to characterize the sulfoxide. The
reaction mixture was stirred for 6±8 h at room temperature
to give a single product. Its mass spectrum indicated the
incorporation of m-chloroperoxy unit as appendage. From
The starting materials &3a±g) for this study were prepared in
80±90% yield by the phase transfer catalyzed alkylation of
Scheme 1.
Keywords: [2,3] sigmatropic rearrangement; sulfoxide; m-chloroperoxybenzoic acid; 2-aryloxymethyl-3-&m-chlorobenzoyloxy)-6,6-dimethyl-5,6,7-trihydro
benzo&b)thiophene-4-ones; regioselective heterocyclization.
Corresponding author. Tel.: 191-33-582-7521; fax: 191-33-582-8282; e-mail: kcm@klyuniv.ernet.in
p
0040±4020/02/$ - see front matter q 2002 Published by Elsevier Science Ltd.
PII: S0040-4020&02)00396-4

4552
K. C. Majumdar, S. K. Samanta / Tetrahedron 58 )2002) 4551±4554
Scheme 2.
its elemental analysis and spectroscopic data, the product
was characterized as 3-&m-chlorobenzoyloxymethyl)-2-
phenoxymethyl-6,6-dimethyl-5,6,7-trihydrobenzo&b)thio-
phene-4-one 5a. Encouraged by this result, other substrates
3b±g were similarly treated to give products 5b±g in 70±
80% yields &Scheme 2). The formation of products 5a±g
from the substrates 3a±g may be easily explained by the
facile oxidation of 3a±g with 1 equiv. of 3-chloroperoxy-
benzoic acid to the corresponding sulfoxides 4a±g. A [2,3]
sigmatropic rearrangement of the vinyl propargyl sulfoxides
&4a±g) may give unstable allenesulfenates &6a±g) which
may then undergo a [3,3] sigmatropic rearrangement giving
intermediates &7a±g). In intermediates &7a±g), the carbonyl
function and ±SH group are suitably juxtaposed to give
thioketols &8a±g). An SN2/displacement in 9a±g may afford
the ®nal products 5a±g &pathway a). Alternatively, inter-
mediate 8a±g could have provided 10a±g by an internal
Michael addition &pathway b). However, no such product
&10a±g) was obtained &Scheme 3).
Sulfoxide rearrangements reported earlier usually require
re¯uxing9a in CCl4. In the present instance, room tempera-
ture stirring brings about the sulfoxide rearrangement.
Incorporation of m-chlorobenzoyloxy unit as an appendage
was earlier observed only in the case of amine±oxide
rearrangement.
The reaction described here is found to be general. The
oxidation step is chemoselective as the other sensitive func-
tionalities remain unaffected by m-chloroperoxybenzoic
acid. This as a mild and simple method for the synthesis
of the hydroaromatic system 6,6-trihydro benzo&b)thio-
phene-4-ones.
1. Experimental
Melting points were measured on a sulfuric acid bath and
are uncorrected. UV absorption spectra were recorded in
Scheme 3.

K. C. Majumdar, S. K. Samanta / Tetrahedron 58 )2002) 4551±4554
4553
EtOH on a Hitachi 200-20 Spectrophotometer. IR spectra
were run on KBr disks on a Perkin±Elmer 1330 apparatus.
1H NMR, 13C NMR and DEPT Spectra were determined for
solutions in CDCl3 with TMS as internal standard on a
Bruker 300 &300 MHz) instrument. Elemental analyses
and recording of mass spectra were carried out by RSIC
&CDRI) Lucknow on a [JEOL D-300 &El)] instrument. Silica
gel &60±120 mesh), Spectrochem, India, was used for
chromatographic separation. Petroleum ether refers to the
fraction boiling between 60 and 808C.
&s, 1H, vCH), 6.81±6.89 &m, 4H, Ph); MS m/z 330 &M1);
Anal. calcd for C19H22O3S: C, 69.06; H, 6.71; found C,
68.94; H, 6.53%.
1.1.5. 3-'40-'40-Methylphenoxy)-20-ynylthio)-5,5-dimethyl-
cyclohex-2-enone '3e). Yield 88%; viscous liquid; lmax
;
:
221, 285 nm; nmax: 1130, 1580, 1650, 2970 cm21 1H
NMR &CDCl3, 300 MHz): d 1.05 &s, 6H, 2Me), 2.24 &s,
3H, PhMe), 2.28 &s, 4H, CH2CO, vCCH2), 3.58±3.59 &t,
Jˆ1.9 Hz, 2H, SCH2), 4.64±4.65 &t, Jˆ1.9 Hz, 2H, OCH2),
5.94 &s, 1H, vCH), 6.81±6.84 &d, Jˆ12 Hz, 2H, Ph), 7.06±
7.09 &d, Jˆ12 Hz, 2H, Ph); MS m/z 314 &M1); Anal. calcd
for C19H22O2S: C, 72.57; H, 7.05; found C, 72.39; H, 6.87%.
1.1. General procedure for the synthesis of 3a±g
To
a mixture of 1-aryloxy-4-chlorobut-2-yne 2a±g
1.1.6.
dimethylcyclohex-2-enone '3f). Yield 85%; viscous liquid;
max: 227, 282 nm; nmax: 1140, 1580, 1650, 2980 cm21; 1H
NMR &CDCl3, 300 MHz): d 1.05 &s, 3H, Me), 1.07 &s, 3H,
Me), 2.25 &s, 2H, CH2CO), 2.33 &s, 2H, vCCH2), 3.58±3.59
&t, Jˆ1.9 Hz, 2H, SCH2), 4.68±4.69 &t, Jˆ1.9 Hz, 2H,
OCH2), 5.94 &s, 1H, vCH), 6.92±7.31 &m, 3H, Ph); MS
m/z 368, 370, 372 &M1); Anal. calcd for C18H18Cl2O2S: C,
58.54; H, 4.91; found C, 58.52; H, 4.71%.
3-'40-'20,40-Dichlorophenoxy)-20-ynylthio)-5,5-
&1 mmol) and 3-mercapto-5,5-dimethyl cyclohex-2-enone
&1 mmol) 2a±g in chloroform &100 mL) was added to a
solution of benzyltriethylammonium chloride &BTEAC,
0.5 g, 1.8 mmol) in 1% aqueous NaOH &100 mL) and the
mixture was magnetically stirred at room temperature for
4 h. The reaction mixture was then diluted with water
&50 mL). Chloroform layer was taken out and washed with
2N HCl &20 mL), brine &20 mL), water &20 mL) and dried
&Na2SO4). Evaporation of chloroform left a gummy residue
which was subjected to column chromatography. Elution of
the column with benzene afforded compounds 3a±g.
l
1.1.7. 3-'40-'20-Methylphenoxy)-20-ynylthio)-5,5-dimethyl-
cyclohex-2-enone '3g). Yield 86%; viscous liquid; lmax
;
:
220, 282 nm; nmax: 1130, 1570, 1640, 2980 cm21 1H
1.1.1. 3-'40-Phenoxybut)-20-ynylthio)-5,5-dimethylcyclo-
hex-2-enone '3a). Yield 90%; viscous liquid; lmax: 218,
NMR &CDCl3, 300 MHz): d 1.05 &s, 6H, 2Me), 2.22 &s,
3H, PhMe), 2.25 &s, 2H, CH2CO), 2.33 &s, 2H, vCCH2),
3.58 &brs, 2H, SCH2), 4.70 &brs, 2H, OCH2), 5.94 &s, 1H,
vCH), 6.87±7.17 &m, 4H, Ph); MS m/z 314 &M1); Anal.
calcd for C19H22O2S: C, 72.57; H, 7.05; found C, 72.49; H,
6.89%.
285 nm; nmax: 1140, 1590, 1660, 2980 cm21 1H NMR
;
&CDCl3, 300 MHz): d 1.05 &s, 3H, Me), 1.07 &s, 3H, Me),
2.25 &s, 2H, CH2CO), 2.42 &s, 2H, vCCH2), 3.57±3.59 &t,
Jˆ1.9 Hz, 2H, SCH2), 4.77±4.78 &t, Jˆ1.9 Hz, 2H, OCH2),
5.93 &s, 1H, vCH), 6.92±7.30 &m, 5H, Ph); MS m/z 300
&M1); Anal. calcd for C18H20O2S: C, 71.97; H, 6.71; found
C, 72.12; H, 6.49%.
1.2. General procedure for the oxidation and subsequent
rearrangement of 3-'40-aryloxybut-20-ynylthio)-5,5-
dimethylcyclohex-2-enone '5a±g)
1.1.2. 3-'40-'20-Chlorophenoxy)-20-ynylthio)-5,5-dimethyl-
cyclohex-2-enone '3b). Yield 87%; viscous liquid; lmax
;
:
218, 282 nm; nmax: 1130, 1580, 1650, 2970 cm21 1H
A solution of m-CPBA [5 mmol, 1.91 g &45%)] in chloro-
form &100 mL) was slowly added to a well stirred solution
of the sul®de &3a±g) &5 mmol) in chloroform &50 mL) at
0±58C over a period of 10 min. The reaction mixture was
stirred at room temperature for an additional 6±8 h before
being washed with 10% aqueous Na2CO3 &3£25 mL) and
dried &Na2SO4). Removal of the solvent gave a crude mass
which was puri®ed by column chromatography over silica
gel. Elution of the column by 70% benzene±petroleum ether
gave compounds &5a±g).
NMR &CDCl3, 300 MHz): d 1.05 &s, 3H, Me), 1.07 &s, 3H,
Me), 2.26 &s, 2H, CH2CO), 2.29 &s, 2H, vCCH2), 3.57±3.58
&t, Jˆ1.9 Hz, 2H, SCH2), 4.75±4.76 &t, Jˆ1.9 Hz, 2H,
OCH2), 5.92 &s, 1H, vCH), 6.93±7.37 &m, 4H, Ph); MS
m/z 334, 336 &M1); Anal. calcd for C18H19ClO2S: C,
64.59; H, 5.72; found C, 64.50; H, 5.52%.
1.1.3. 3-'40-'40-Chlorophenoxy)-20-ynylthio)-5,5-dimethyl-
cyclohex-2-enone '3c). Yield 85%; viscous liquid; lmax
;
:
227, 282 nm; nmax: 1140, 1580, 1650, 2970 cm21 1H
NMR &CDCl3, 300 MHz): d 1.05 &s, 3H, Me), 1.09 &s, 3H,
Me), 2.25 &s, 2H, CH2CO), 2.28 &s, 2H, vCCH2), 3.57±3.58
&t, Jˆ1.9 Hz, 2H, SCH2), 4.65±4.67 &t, Jˆ1.9 Hz, 2H,
OCH2), 5.92 &s, 1H, vCH), 6.84±6.89 &d, Jˆ12 Hz, 2H,
Ph), 7.22±7.25 &d, Jˆ12 Hz, 2H, Ph); MS m/z 334, 336
&M1); Anal. calcd for C18H19ClO2S: C, 64.59; H, 5.72;
found C, 64.43; H, 5.61%.
1.2.1. 2-Phenoxymethyl-3-'30-chlorobenzoyloxymethyl)-
6,6-dimethyl-5,6,7-trihydrobenzo'b)thiophene-4-ones
'5a). Yield 85%; viscous liquid; lmax: 219, 275 nm; nmax
;
:
1120, 1590, 1610, 1680, 2920 cm21 1H NMR &CDCl3,
300 MHz): d 1.05 &s, 6H, 2Me), 2.30 &s, 2H, CH2CO),
2.52 &s, 2H, vCCH2), 3.99 &brs, 2H, CH2OAr), 4.70 &brs,
2H, CH2±OCO), 6.70±7.33 &m, 9H, Ph); MS m/z 454, 456
&M1); Anal. calcd for C25H23ClO4S: C, 66.00; H, 5.09;
found C, 66.21; H, 5.12%.
1.1.4.
methylcyclohex-2-enone '3d). Yield 80%; viscous liquid;
max: 225, 285 nm; nmax: 1140, 1580, 1640, 2970 cm21; 1H
3-'40-'40-Methoxyphenoxy)-20-ynylthio)-5,5-di-
l
1.2.2.
2-'20-Chlorophenoxy)-3-'30-chlorobenzoyloxy-
NMR &CDCl3, 300 MHz): d 1.05 &s, 3H, Me), 1.08 &s, 3H,
Me), 2.25 &s, 2H, CH2CO), 2.38 &s, 2H, vCCH2), 3.58 &brs,
2H, SCH2), 3.77 &s, 3H, ±OMe), 4.62 &brs, 2H, OCH2), 5.94
methyl)-6,6-dimethyl-5,6,7-trihydrobenzo'b)thiophene-
4-ones '5b). Yield 70%; viscous liquid; lmax: 218, 273 nm;
n
max: 1120, 1580, 1620, 1690, 2920 cm21; 1H NMR &CDCl3,

4554
K. C. Majumdar, S. K. Samanta / Tetrahedron 58 )2002) 4551±4554
300 MHz): d 1.05 &s, 6H, 2Me), 2.30 &s, 2H, CH2CO), 2.52
&s, 2H, vCCH2), 4.00 &brs, 2H, CH2OAr), 4.75 &brs, 2H,
CH2±OCvO), 6.67±7.39 &m, 8H, Ph); MS m/z 488, 490,
492 &M1); Anal. calcd for C25H22Cl2O4S: C, 61.36; H, 4.53;
found C, 61.23; H, 4.39%.
8H, Ph); MS m/z 468, 470 &M1); Anal. calcd for
C26H25ClO4S: C, 66.58; H, 5.37; found C, 66.43; H, 5.23%.
Acknowledgements
We are thankful to the CSIR &New Delhi) for ®nancial
assistance. One of us &S. K. S.) is grateful to the CSIR
&New Delhi) for a fellowship.
1.2.3.
2-'40-Chlorophenoxy)-3-'30-chlorobenzoyloxy-
methyl)-6,6-dimethyl-5,6,7-trihydrobenzo'b)thiophene-
4-ones '5c). Yield 71%; viscous liquid; lmax: 226, 274 nm;
n
max: 1130, 1590, 1610, 1690, 2930 cm21; 1H NMR &CDCl3,
300 MHz): d 1.06 &s, 6H, 2Me), 2.31 &s, 2H, CH2CO), 2.51
&s, 2H, vCCH2), 4.98±3.99 &t, Jˆ2 Hz, 2H, CH2OAr),
4.67±4.68 &t, Jˆ2 Hz, 2H, CH2±OCvO), 6.81±6.86 &m,
4H, Ph), 7.23±7.27 &m, 4H, Ph); MS m/z 488, 490, 492
&M1); Anal. calcd for C25H22Cl2O4S: C, 61.36; H, 4.53;
found C, 61.31; H, 4.31%.
References
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4-ones '5d). Yield 72%; viscous liquid; lmax: 219, 273 nm;
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n
max: 1130, 1580, 1620, 1690, 2960 cm21; 1H NMR &CDCl3,
300 MHz): d 1.06 &s, 6H, 2Me), 2.26 &s, 2H, CH2CO), 2.52
&s, 2H, vCCH2), 3.77 &s, 3H, ±OMe), 3.99±4.00 &t,
Jˆ2 Hz, 2H, CH2OAr), 4.63±4.65 &t, Jˆ2 Hz, 2H, CH2±
OCvO), 6.69±7.25 &m, 8H, Ph); MS m/z 484, 486 &M1);
Anal. calcd for C26H25ClO5S: C, 64.38; H, 5.18; found C,
64.31; H, 4.98%.
1.2.5.
2-'40-Methylphenoxy)-3-'30-chlorobenzoyloxy-
methyl)-6,6-dimethyl-5,6,7-trihydrobenzo'b)thiophene-
4-one '5e). Yield 70%; viscous liquid; lmax: 222, 275 nm;
n
max: 1120, 1560, 1610, 1690, 2960 cm21; 1H NMR &CDCl3,
300 MHz): dH 1.05 &s, 6H, 2Me), 2.24 &s, 2H, CH2CO), 2.29
&s, 3H, PhMe), 2.52 &s, 2H, vCCH2), 3.99 &brs, 2H,
CH2OAr), 4.70 &brs, 2H, CH2±OCvO), 6.69±7.98 &m,
8H, Ph); 13C NMR &CDCl3, 300 MHz): dc 20.85, 28.14,
28.21, 34.705, 38.66, 45.65, 51.32, 56.12, 74.13, 84.53,
99.08, 99.65, 114.94, 115.26, 128.69, 130.27, 130.46,
130.53, 130.50, 131.50, 131.59, 133.23, 134.16, 154.52,
170.50 &ester carbonyl) 197.96 &keto carbonyl); MS m/z
468, 470 &M1); Anal. calcd for C26H25ClO4S: C, 66.58; H,
5.37; found C, 66.49; H, 5.22%.
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1.2.6. 2-'20,40-Dichlorophenoxy)-3-'30-chlorobenzoyloxy-
methyl)-6,6-dimethyl-5,6,7-trihydrobenzo'b)thiophene-
4-ones '5f). Yield 80%; mp 1108C; lmax: 221, 285 nm; nmax
;
:
8. Majumdar, K. C.; Samanta, S. K. Tetrahedron 2001, 57,
4955±4958.
1130, 1570, 1600, 1690, 2940 cm21 1H NMR &CDCl3,
300 MHz): d 1.07 &s, 6H, 2Me), 2.31 &s, 2H, CH2CO),
2.57 &s, 2H, vCCH2), 3.99 &brs, 2H, CH2OAr), 4.77 &brs,
2H, CH2±OCO), 6.68±7.38 &m, 7H, Ph); MS m/z 522, 524,
526 &M1); Anal. calcd for C25H21Cl3O4S: C, 57.31; H, 4.04;
found C, 57.52; H, 3.89%.
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1.2.7.
2-'20-Methylphenoxy)-3-'30-chlorobenzoyloxy-
methyl)-6,6-dimethyl-5,6,7-trihydrobenzo'b)thiophene-
4-ones'5g). Yield 78%; viscous liquid; lmax: 222, 287 nm;
n
max: 1120, 1570, 1610, 1680, 2950 cm21; 1H NMR &CDCl3,
300 MHz): d 1.06 &s, 6H, 2Me), 2.28 &s, 2H, CH2CO), 2.29
&s, 3H, PhMe), 2.52 &s, 2H, vCCH2), 3.92 &brs, 2H,
CH2OAr), 4.65 &brs, 2H, CH2±OCvO), 6.69±7.58 &m,
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