A general and highly regio and stereoselective method for the synthesis of (E)-2-(2-arylvinyl)-3,1-benzoxathiin-4-ones through palladium-copper catalysis

Article abstract of DOI:10.1039/b102306n

A palladium-copper-catalysed procedure for the synthesis of (E)-2-(2-arylvinyl)-3,1-benzoxathiin-4-ones 5a-5h is developed. 3-[2-(Methoxycarbonyl)phenylthio]propyne 2 reacts with aryl iodides 3a-3h in the presence of bis(triphenylphosphine)palladium(II) dichloride, copper(I) iodide and triethylamine in acetonitrile to furnish the disubstituted alkynes 4a-4h in good yields (70-84%). These on alkaline hydrolysis and subsequent cyclisation of the carboxylic acids formed with copper(I) iodide (20 mol%) and triethylamine in tetrahydrofuran under reflux afford (E)-2-(2-arylvinyl)-3,1-benzoxathiin-4-ones 5a-5h in 61-70% yield rather than the expected benzoxathiepinones 6. The reactions of (E)-2-(2-arylvinyl)-3,1-benzoxathiin-4-ones 5a and 5g with nucleophites and the hydrogenation of compounds 5a, 5b and 5d are also studied.

Full text of DOI:10.1039/b102306n

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A general and highly regio and stereoselective method for the
synthesis of (E )-2-(2-arylvinyl)-3,1-benzoxathiin-4-ones through
palladium–copper catalysis
1
Bidisha Nandi and Nitya G. Kundu*
Department of Organic Chemistry, Indian Association for the Cultivation of Science, Jadavpur,
Calcutta, 700 032, India.; Fax: ϩ91-33-473-2805
Received (in Cambridge, UK) 12th March 2001, Accepted 21st May 2001
First published as an Advance Article on the web 4th July 2001
A palladium–copper-catalysed procedure for the synthesis of (E)-2-(2-arylvinyl)-3,1-benzoxathiin-4-ones 5a–5h
is developed. 3-[2-(Methoxycarbonyl)phenylthio]propyne 2 reacts with aryl iodides 3a–3h in the presence of
bis(triphenylphosphine)palladium() dichloride, copper() iodide and triethylamine in acetonitrile to furnish the
disubstituted alkynes 4a–4h in good yields (70–84%). These on alkaline hydrolysis and subsequent cyclisation of the
carboxylic acids formed with copper() iodide (20 mol%) and triethylamine in tetrahydrofuran under reflux afford
(E)-2-(2-arylvinyl)-3,1-benzoxathiin-4-ones 5a–5h in 61–70% yield rather than the expected benzoxathiepinones 6.
The reactions of (E)-2-(2-arylvinyl)-3,1-benzoxathiin-4-ones 5a and 5g with nucleophiles and the hydrogenation of
compounds 5a, 5b and 5d are also studied.
triethylamine in THF for 24 h in an argon atmosphere.
2-(2-Arylvinyl)-3,1-benzoxathiin-4-ones 5a–5h were formed
in a completely regio- and stereoselective manner instead of
the expected seven-membered heterocyclic compounds, i.e.
Introduction
3,1-Benzoxathiin-4-one1 is a unique heterocyclic structure
derived from 2-(hydroxymethylthio)benzoic acid. The synthesis
and reactivity of benzoxathiin-4-ones have not been extensively
studied so far and only a few routes are available for the
synthesis of substituted or unsubstituted 3,1-benzoxathiin-4-
ones.2–10
benzooxathiepinones 6, as shown in Scheme 1 and Table 1.
A recent trend in organic synthesis has been to develop
different carbocyclic11 and heterocyclic12 structures through
palladium-catalysed reactions.13 The rapid development in this
area has stimulated us to carry out syntheses of various benzo-
fused heterocyclic compounds of biological interest. We have
utilised the palladium-catalysed reactions of aryl iodides with a
nucleophilic group at the ortho position and terminal alkynes to
generate various benzofused heterocyclic structures.14–18
In another approach, by using prop-2-ynyloxy or prop-2-
ynylamino aromatic compounds with an ortho nucleophilic
group and aryl iodides under palladium–copper-catalysed con-
ditions and subsequent cyclisation of the disubstituted alkynes
generated, we could easily succeed in synthesising benzofused
heterocyclic structures with two heteroatoms.19–22
In continuation of these studies, we report here a novel
strategy for the synthesis of (E)-2-(2-arylvinyl)-3,1-benz-
oxathiin-4-ones 5a–5h starting from 3-[2-(methoxycarb-
onyl)phenylthio]propyne 2 and aryl iodides, 3a–3h, using
palladium- and copper-mediated reactions.23
Scheme 1 Reagents and conditions: (i) K2CO3, propargyl bromide,
acetone, reflux, 16 h; (ii) (PPh3)2PdCl2 (3.5 mol%), CuI (6 mol%), Et3N;
CH3CN, rt, 24 h; (iii) 5 M methanolic KOH, rt, 2 h; (iv) HCl (1:1);
(v) CuI (20 mol%), Et3N, THF, reflux, 24 h.
Results and discussion
3-[2-(Methoxycarbonyl)phenylthio]propyne 2 reacted with aryl
Role of catalyst, co-catalyst, base and solvent
iodides 3a–3h, under Sonogashira cross-coupling reaction
conditions,24 in the presence of bis(triphenylphosphine)-
palladium() dichloride (3.5 mol%), copper() iodide (6 mol%)
and triethylamine (4 equiv.) in acetonitrile at room temperature
for 24 h in an argon atmosphere to yield the disubstituted
alkynes 4a–4h. The disubstituted alkynes 4a–4h were then
hydrolysed with 5 M methanolic KOH solution by stirring
at room temperature for 2 h followed by acidification [dil.
HCl (1:1)] to the carboxylic acids, which were then heated
under reflux in the presence of copper() iodide (20 mol%) and
In the C-arylation step, a combination of bis(triphenyl-
phosphine)palladium() dichloride (3.5 mol%) (catalyst) and
CuI (6 mol%) (co-catalyst) was the most desired catalytic
system. It was found that in the absence of bis(triphenyl-
phosphine)palladium() dichloride, no disubstituted alkynes
were formed. We have also explored other palladium catalysts,
e.g. (PPh3)4Pd, Pd(OAc)2 along with PPh3, and found that yields
were not appreciable. Copper() iodide was the essential co-
catalyst, since in its absence very poor yields of the C-arylated
DOI: 10.1039/b102306n
J. Chem. Soc., Perkin Trans. 1, 2001, 1649–1655
This journal is © The Royal Society of Chemistry 2001
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Table 1 Palladium-catalysed arylation of 2 and the subsequent copper-catalysed cyclisation leading to (E)-2-(2-arylvinyl)-3,1-benzoxathiin-4-ones
5a–5h (Scheme 1)a
Entry
Aryl iodides (Ar)
Disubstituted alkynes, 4a–4h, yield (%)b
2-(2-Arylvinyl)-3,1-benzoxathiin-4-ones 5a–5h, yield (%)c
1
2
3
4
5
6
7
8
Ph, 3a
4a (77)
4b (77)
4c (81)
4d (76)
4e (75)
4f (84)
4g (78)
4h (70)
5a (63)
5b (62)
5c (67)
5d (70)
5e (65)
5f (68)
5g (63)
5h (61)
p-MeC6H4, 3b
o-MeOC6H4, 3c
p-MeOC6H4, 3d
1-Naphthyl, 3e
2-Naphthyl, 3f
m-ClC6H4, 3g
2-Thienyl, 3h
a Unless otherwise stated, disubstituted alkynes 4a–4h were synthesised by stirring a mixture of an aryl halide 3a–3h and 2 in the presence of
bis(triphenylphosphine)palladium() dichloride (3.5 mol%), copper() iodide (6 mol%) and triethylamine (4 equiv.) in acetonitrile at rt for 24 h in an
argon atmosphere. b Yields are based on 2. c Yields are based on the disubstituted alkynes 4a–4h.
products were observed. Triethylamine was the base of
choice in the C-arylation reaction since the use of other
bases like pyridine, potassium carbonate or sodium acetate led
to very low yields of the products. Acetonitrile was the desired
solvent in the C-arylation reaction. Triethylamine itself could
not be used as the solvent due to the poor solubility of many
compounds in it. When DMF was used as solvent, it led to
formation of much polymeric material.
the range δH 6.19–6.53 (dd, J ≈15.6, 6 Hz) and δH 6.87–7.13
(d, J ≈ 15.6 Hz) whereas the C-2 proton in the heterocyclic
ring (SCH) displayed a doublet in the range of δH 6.11–6.29
(J ≈ 6 Hz) firmly establishing the structure of 2-(2-aryl-
vinyl)-3,1-benzoxathiin-4-ones, 5a–5h. Furthermore, 13C NMR
spectra together with DEPT (135) experiments provided
additional support in favour of the stuctures of 5a–5h; the
characteristic peaks for methylenic carbons were absent, thus
excluding the formation of any seven-membered heterocyclic
structures 6.
Cyclisation
The heteroannulation process was completely regio- and
stereoselective. Only six-membered heterocyclic compounds
were formed instead of the expected seven-membered hetero-
cycles, i.e. benzoxathiepinones 6. The stereochemistry around
the double bond was assigned the E-configuration on the
basis of the coupling constants (15 Hz) of the two vinylic
protons.
Copper() iodide and triethylamine were the essential reagents
needed for the cyclisation. In the absence of any of these
reagents, no benzoxathiinones were obtained. Also, 20 mol% of
copper() iodide was found to be the optimum needed for the
cyclisation reaction. Any less or more of this catalyst led to a
decline in the yield. The use of other bases, e.g. pyridine or
potassium carbonate, was not found to be satisfactory since
either no product or a very poor yield of the product was then
observed. THF was the best solvent for cyclisation. The use of
other solvents, like acetonitrile, DMF or triethylamine, gave
poor yields of the cyclised products due to either solubility
problems or the formation of polymeric materials.
The allenic intermediates 7 25 were formed in all the cases due
to the alkaline hydrolysis of compounds 4a–4h, as was detected
by IR, 1H NMR and 13C NMR spectroscopy. The crude allenes
were used immediately for cyclisation.26 Some of the allenic
compounds, however, could be isolated, purified and character-
ised fully from spectral (IR, 1H NMR and 13C NMR) evidence
and elementary analysis. In the IR spectra, the C᎐C᎐C stretch-
᎐ ᎐
Nature and characterisation of the products
ing frequencies27 were found to be in the range νmax 1936.4–1932
cmϪ1. In the 1H NMR spectra, the two allenic hydrogens
appeared as doublets at δH 6.27–6.49 (J 6 Hz) and δH 6.39–6.73
(J 6 Hz). Finally, in the 13C NMR spectra, a characteristic peak
for the central carbon of the allenic species27 in the range
δC 208.7–213.6 firmly established the formation of the allenic
compounds 7 in the reaction sequence. The cyclisation of
the isolated allenic compounds 7a–d under the conditions
described in Scheme 1 afforded the desired 3,1-benzoxathiin-4-
ones 5a, 5b, 5c and 5f.
The disubstituted alkynes synthesised, 4a–4h, were stable and
could be stored at room temperature for a long time. However, a
brown colour developed when they were kept in solvents like
CHCl3, diethyl ether, or methanol for a long time. The 3,1-
benzoxathiin-4-ones 5a–5h formed were very sensitive to light,
air and heat. A pure sample of compound 5b, on storage in air
at room temperature for 2 days, developed a deep brown colour.
Hence, it should preferably be stored in a brown bottle in the
cold.
All the acyclic and cyclic products synthesised were well
1
characterised by spectral (IR, H NMR and 13C NMR) evi-
dence and elemental analysis. The structures of the disubsti-
tuted alkynes 4a–4h were established from the following
observations.
In the IR spectra of compounds 4a–4h, the stretching fre-
quency at νmax 3247.9 cmϪ1 (᎐C-H) was absent and the band
᎐
᎐
corresponding to the COOMe group was in the range νmax
Reactivity of (E )-2-(2-arylvinyl)-3,1-benzoxathiin-4-ones 5a–5h
1
1714–1705 cmϪ1. In the H NMR spectra, triplets correspond-
ing to the acetylenic hydrogen were absent and the methylenic
protons displayed a singlet at δH 3.73–3.96. All the other pro-
tons were at appropriate positions. In the 13C NMR spectra,
together with DEPT experiments, the methylenic carbons were
seen in the range δC 21.8–22.3. The structures of the cyclic
products 5a–5h were deduced from spectral (IR, 1H NMR and
(E)-2-(2-Arylvinyl)-3,1-benzoxathiin-4-ones 5a–5h are stable in
neutral aq. methanolic solution at room temperature as well as
at higher temperatures (60–80 ЊC). The heterocyclic ring
remained intact when a methanolic solution of compound 5b
was refluxed under acidic conditions (6 M HCl). On alkaline
hydrolysis, however, compound 5a opened up with the form-
ation of thiosalicylic acid and cinnamaldehyde 8a (Scheme 2).
Catalytic hydrogenation of compounds 5a, 5b and 5d was
carried out with palladium on activated charcoal at atmos-
pheric pressure in ethyl acetate. Hydrogenolysis of the
13C NMR) and analytical data. The IR specta revealed the C᎐O
᎐
stretching frequency in the range νmax 1732.5–1720 cmϪ1, indi-
cating the presence of a six-membered heterocyclic ring. In the
1H NMR spectra, the two vinylic hydrogens appeared in
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Scheme 2 Reagents and conditions: (i) 5 M KOH, MeOH, reflux, 12 h; (ii) dil. HCl (1:1); (iii) Pd/C (10%), H2 (1 atm), ethyl acetate, rt, 48 h;
(iv) NaOMe, MeOH, reflux, 15 h; (v) PhNH2, benzene, reflux, 15 h.
compounds was observed with the formation of the saturated
acyclic products 9a, 9b and 9c respectively (Scheme 2).
On reaction of (E)-2-[2-(m-chlorophenyl)vinyl]-3,1-benz-
oxathiin-4-one 5g with sodium methoxide in methanol, the
disulfide 10 was formed along with m-chlorocinnamaldehyde 8g
(Scheme 2).
Similarly, the reaction of compound 5g with aniline in a
refluxing solution in benzene afforded the disulfide of the
corresponding amide, 11 and m-chlorocinnamaldehyde 8g
(Scheme 2).
iodides were prepared according to the procedure given for the
synthesis of iodobenzene.28a 2-Iodothiophene,28b 2,5-diiodo-
thiophene,28b and 5-iodo-2,4-dimethoxypyrimidine28c were
synthesised according to the known procedures. IR spectra
(neat or KBr pellets) were recorded on a Shimadzu FTIR 8300.
1H NMR spectra for CDCl3 solution were recorded at 300 MHz
on Bruker DPX 300 and Varian EM 360 spectrophotometers,
respectively. 13C NMR spectra were recorded at 75 MHz on a
Bruker DPX 300 spectrophotometer.
Synthesis of 3-[2-(methoxycarbonyl)phenylthio]propyne 2
Conclusions
Methyl thiosalicylate 1 (9.04 mmol) in acetone (20 cm3) was
stirred with K2CO3 (9.04 mmol) at room temperature under
argon atmosphere for 4 h. Propargyl (prop-2-ynyl) bromide
(9.04 mmol) was added slowly to the reaction mixture and stir-
ring was continued for 1 h at room temperature followed by
reflux for 16 h. The solvent was removed and the residue was
diluted with water (10 cm3). This was extracted with CHCl3
(3 × 15 cm3), the extract was washed with water (5 cm3), dried
(anh. Na2SO4), and the solvent was removed. The crude prod-
uct obtained was purified by column chromatography on silica
gel with the eluent being 8:1 light petroleum–CHCl3 to afford
compound 2 as a white solid in 84% yield, mp 95 ЊC (Found:
C, 64.17; H, 4.95. C11H10O2S requres C, 64.05; H, 4.88%);
Although a number of versatile routes for synthesis of 3,1-
benzoxathiin-4-ones have been devised,2–10 most of them are
either direct condensation of aldehydes with thiosalicylic acid
or thermal decomposition procedures. In almost all cases, yields
were not good enough. Also, the lack of a variety of functional
groups in the products synthesised was observed. To the best
of our knowledge, no palladium-catalysed method has so far
been developed for the synthesis of 2-substituted 3,1-
benzoxathiin-4-ones. We have described, for the first time, a
palladium-mediated and copper-catalysed synthesis of (E)-2-
(2-arylvinyl)-3,1-benzoxathiin-4-ones from easily available
starting materials. The excellent regio- and stereoselectivity
exhibited by the procedure make it highly attractive. Further-
more, a vinylic functionality with a variety of aromatic sub-
stituents has been accommodated without affecting the main
heteroannulation process. The method is operationally simple,
does not involve any toxic reagent, and could be carried out
under mild conditions. Also, 2-(2-arylvinyl)-3,1-benzoxathiin-
4-ones could be of potential biological significance because
of the presence of various active functionalities (e.g., vinyl,
lactone, sulfur moieties) in the molecular domain.
νmax (KBr)/cmϪ1 3247.9, 2150.0, 1701.1, 1587.3, 1564.2; δH (300
᎐
MHz; CDCl ) 2.2 (t, J 2.7 Hz, 1H, C᎐CH), 3.63 (d, J 2.7 Hz,
᎐
3
2H, SCH2), 3.9 (s, 3H, COOCH3), 7.18 (td, J 7.2 and 1.8 Hz,
1H, ArH), 7.43–7.51 (m, 2H, ArH), 7.98 (d, J 8.1 Hz, 1H,
ArH); δC (CDCl3) 20.4, 52.1, 79.2, 124.2, 124.4, 125.6, 127.3,
131.2, 132.4, 140.1, 166.6; δC (CDCl3; DEPT 135) 20.6 (inverted),
52.3, 79.4, 124.6, 125.9, 131.4, 132.7.
Typical procedure for the synthesis of 3-[2-(methoxycarbonyl)-
phenylthio]-1-phenylpropyne 4a
Experimental
A mixture of iodobenzene 3a (2.42 mmol), (PPh3)2PdCl2 (0.07
mmol, 3 mol%), CuI (0.14 mmol, 6 mol%) and Et3N (9.68
mmol) in CH3CN (10 cm3) was stirred at room temperature for
0.5 h in an argon atmosphere. Compound 2 (2.42 mmol) was
added slowly to the reaction mixture, which was then stirred at
room temperature for 20 h. After removal of the solvent under
reduced pressure, the residue was diluted with water (5 cm3) and
extracted thoroughly with CHCl3 (3 × 20 cm3). The organic
Mps are uncorrected. Reactions were performed under argon
atmosphere. Bis(triphenylphosphine)palladium() dichloride
was obtained from Aldrich Chemical Co., Milwaukee, Wiscon-
sin, USA, and copper() iodide fron Merck–Schuchardt. Light
petroleum used was the fraction boiling between 60–80 ЊC.
Column chromatography was performed on silica gel (60–120
mesh). TLC was done on 60F-254 precoated sheets. Aryl
J. Chem. Soc., Perkin Trans. 1, 2001, 1649–1655
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layer was washed with water (2 × 5 cm3), dried (anh. Na2SO4),
and the solvent was distilled off. A brown gum was obtained
which was purified by column chromatography on silica gel
with the eluent being 1:1 CHCl3–light petroleum to furnish
compound 4a as a white solid, mp 79 ЊC (Found: C, 72.23; H,
5.03. C17H14O2S requires C, 72.31; H, 4.99%); νmax (KBr)/cmϪ1
1710.7, 1589.2, 1562.2; δH (300 MHz; CDCl3) 3.79 (s, 2H,
SCH2), 3.81 (s, 3H, COOCH3), 7.08–7.17 (m, 4H, ArH), 7.25–
7.28 (m, 2H, ArH), 7.37–7.47 (m, 2H, ArH), 7.9 (d, J 7.8 Hz,
1H, ArH); δC (CDCl3) 22.1, 42.5, 83.9, 85.1, 119.6, 123.3, 124.8,
126.4, 128.4, 128.6, 131.7, 132.1, 132.9, 141.1, 167.2; δC (CDCl3;
DEPT 135) 21.8 (inverted), 52.3, 124.5, 126.2, 128.1, 128.3,
131.4, 131.8, 132.6.
Hz, 1H, ArH), 7.58–7.65 (m, 3H, ArH), 7.76 (s, 1H, ArH), 7.88
(dd, J 7.8 and 1.5 Hz, 1H, ArH); δC (CDCl3) 22.2, 52.6, 84.3,
85.4, 120.6, 124.8, 126.4, 126.9, 127.0, 127.9, 128.1, 128.3,
128.8, 131.8, 132.0, 133.0, 133.2, 133.3, 141.1, 167.2; δC (CDCl3;
DEPT 135) 21.9, 52.3, 124.6, 126.2, 126.6, 126.8, 127.8, 128.0,
128.6, 131.5, 131.7, 132.7.
1-(3-Chlorophenyl)-3-[2-(methoxycarbonyl)phenylthio]propyne
4g. White solid, mp 80 ЊC (Found: C, 64.39; H, 4.09. C17H13-
ClO2S requires C, 64.44; H, 4.13%); νmax (KBr)/cmϪ1 1710.7,
1591.2, 1562.2; δH (300 MHz; CDCl3) 3.88 (s, 2H, SCH2), 3.91
(s, 3H, COOCH3), 7.15–7.27 (m, 4H, ArH), 7.33 (s, 1H, ArH),
7.51 (d, J 7 Hz, 2H, ArH), 8.00 (d, J 7.5 Hz, 1H, ArH);
δC (CDCl3) 21.9, 52.6, 82.5, 86.4, 124.9, 126.4, 127.9, 128.9,
129.9, 130.2, 131.8, 131.9, 133.0, 134.4, 140.8, 167.2; δC (CDCl3;
DEPT 135) 21.7, 52.3, 124.6, 126.1, 128.6, 129.6, 130.0, 131.5,
131.7, 132.7.
Compounds 4b–4h were synthesised from aryl iodides 3b–
3h according to the procedure followed for the synthesis of
compound 4a.
3-[2-(Methoxycarbonyl)phenylthio]-1-(p-tolyl)propyne
4b.
White solid, mp 92 ЊC (Found: C, 73.02; H, 5.26. C18H16O2S
requires C, 72.94; H, 5.44%); νmax(KBr)/cmϪ1 1705.0, 1585.4,
1566.1, 1508.2; δH (300 MHz; CDCl3) 2.30 (s, 3H, ArCH3), 3.88
(s, 2H, SCH2), 3.90 (s, 3H, COOCH3), 7.05 (d, J 8.1 Hz, 2H,
ArH), 7.18 (t, J 7.5 Hz, 1H, ArH), 7.24 (d, J 7.8 Hz, 2H, ArH),
7.48 (td, J 7.2 and 1.2 Hz, 1H, ArH), 7.54 (d, J 6.9 Hz, 1H,
ArH), 7.99 (dd, J 7.5 and 1.2 Hz, 1H, ArH); δC (CDCl3) 21.8,
22.2, 52.6, 84.0, 84.2, 120.2, 124.8, 126.5, 128.0, 129.4, 131.7,
132.0, 132.9, 137.7, 138.7, 167.2; δC (CDCl3; DEPT 135) 21.5,
21.9 (inverted), 52.3, 124.5, 126.2, 129.1, 131.4, 131.7, 132.6,
137.3.
3-[2-(Methoxycarbonyl)phenylthio]-1-(2-thienyl)propyne 4h.
White solid, mp 86 ЊC (Found: C, 70.19; H, 4.73. C15H12O2S
requires C, 70.28; H, 4.72%); νmax (KBr)/cmϪ1 1706.9, 1585.4,
1564.2; δH (300 MHz; CDCl3) 3.93 (s, 3H, COOCH3), 3.96 (s,
2H, SCH2), 7.23 (td, J 7.8 and 1.2 Hz, 1H, ArH), 7.41 (dd, J 8.4
and 1.5 Hz, 1H, ArH), 7.45–7.48 (m, 2H, ArH), 7.54 (td, J 8.1
and 1.5 Hz, 1H, ArH), 7.61 (d, J 7.8 Hz, 1H, ArH), 8.03 (dd,
J 7.8 and 1.2 Hz, 1H, ArH); δC (CDCl3) 22.2, 52.6, 84.2, 85.4,
120.5, 124.8, 126.4, 127.1, 127.9, 128.1, 128.8, 131.8, 133.0,
141.1, 167.3; δC (CDCl3; DEPT 135) 21.9 (inverted), 52.3, 124.5,
126.1, 126.6, 127.8, 128.6, 131.5, 132.7.
3-[2-(Methoxycarbonyl)phenylthio]-1-(2-methoxyphenyl)-
propyne 4c. White solid, mp 99 ЊC (Found: C, 69.14; H,
5.09. C18H16O3S requires C, 69.2; H, 5.16%); δH (300 MHz;
CDCl3) 3.83 (s, 3H, ArOCH3), 3.95 (s, 2H, SCH2), 3.98 (s, 3H,
ArH), 6.83 (d, J 8.1 Hz, 2H, ArH), 7.2–7.41 (m, 3H, ArH),
7.75 (d, J 7.5 Hz, 2H, ArH), 8.06 (dd, J 7.5 and 1.2 Hz, 1H,
ArH).
Typical procedure for the synthesis of (E )-2-styryl-3,1-
benzoxathiin-4-one 5a
3-[2-(Methoxycarbonyl)phenylthio]-1-phenylpropyne 4a (1.4
mmol) was stirred with a methanolic solution of potassium
hydroxide (5 M; 25 cm3) at room temperature for 2 h in an
argon atmosphere. After the removal of methanol under
reduced pressure, the residue was diluted with water (5 cm3),
acidified with dil. HCl (1:1) and extracted with diethyl ether
(3 × 30 cm3). The combined organic layer was washed with
water (5 cm3) and dried (anh. Na2SO4). The crude product
obtained was then heated under reflux with CuI (0.28 mmol;
20 mol%) and Et3N (2.86 mmol) in THF (20 cm3) in an argon
atmosphere for 24 h. After removal of the solvent and Et3N, the
residue was purified by column chromatography on silica gel
(60–120 mesh) with the eluent being 1:1 CHCl3–light petroleum
to furnish 5a as a light yellow solid, mp 96 ЊC (Found: C, 71.59;
H, 4.54. C16H12O2S requires C, 71.61; H, 4.50%); νmax (KBr)/
cmϪ1 1726.2, 1593.1, 1541.0; δH (300 MHz; CDCl3) 6.14 (d, J 6
3-[2-(Methoxycarbonyl)phenylthio]-1-(4-methoxyphenyl)-
propyne 4d. White solid, mp 65 ЊC (Found: C, 69.04; H, 5.06.
C18H16O3S requires C, 69.2; H, 5.16%); νmax (KBr)/cmϪ1 1705.0,
1604.7, 1585.4, 1564.2; δH (300 MHz; CDCl3) 3.77 (s, 3H,
ArOCH3), 3.88 (s, 2H, SCH2), 3.91 (s, 3H, COOCH3), 6.78
(d, J 8.76 Hz, 2H, ArH), 7.2 (td, J 7.2 and 1.2 Hz, 1H, ArH),
7.29 (d, J 8.7 Hz, 2H, ArH), 7.47–7.57 (m, 2H, ArH), 7.99
(dd, J 7.7 and 1.2 Hz, 1H, ArH); δC (CDCl3) 21.8, 52.2,
55.2, 83.0, 83.4, 113.8, 115.0, 124.3, 126.1, 129.6, 131.3, 132.5,
131.3, 132.5, 133.1, 140.7, 159.5, 166.8; δC (CDCl3; DEPT 135)
21.9 (inverted), 52.3, 55.4, 114.0, 124.5, 126.2, 131.4, 132.6,
133.2.
Hz, 1H, SCH), 6.32 (dd, J 15.6 and 6 Hz, 1H, CH᎐CHPh), 6.87
᎐
(d, J 15.6 Hz, 1H, CH᎐CHPh), 7.22–7.27 (m, 5H, ArH), 7.34
᎐
(d, J 7.2 Hz, 2H, ArH), 7.41 (t, J 7.2 Hz, 1H, ArH), 8.12 (d,
J 7.8 Hz, 1H, ArH); δC (CDCl3) 82.4, 122.0, 124.7, 127.2, 127.4,
128.0, 129.2, 129.4, 133.1, 134.2, 135.4, 135.81, 138.6, 164.2;
δC (CDCl3; DEPT 135) 82.1, 121.7, 126.9, 127.2, 127.7, 128.9,
129.1, 132.8, 133.9, 135.5.
Compounds 5b–5h were synthesised from 4b–4h following
the procedure for the synthesis of 5a.
3-[2-(Methoxycarbonyl)phenylthio]-1-(1-naphthyl)propyne 4e.
White solid, mp 85 ЊC (Found: C, 75.81; H, 4.83. C21H16O2S
requires C, 75.87; H, 4.85%); νmax (KBr)/cmϪ1 1714.6, 1585.4,
1560.0; δH (300 MHz; CDCl3) 3.73 (s, 3H, COOCH3), 3.73 (s,
2H, SCH2), 7.02 (t, J 7.5 Hz, 1H, ArH), 7.18 (t, J 7.5 Hz, 1H,
ArH), 7.27–7.35 (m, 3H, ArH), 7.42–7.48 (m, 2H, ArH), 7.57–
7.62 (m, 2H, ArH), 7.85 (d, J 7.8 Hz, 1H, ArH), 7.98–8.01 (m,
1H, ArH); δC (CDCl3) 22.3, 25.6, 82.0, 90.1, 120.9, 124.9, 125.6,
126.6, 126.8, 127.1, 128.0, 128.7, 129.2, 130.9, 131.8, 133.0,
133.5, 133.8, 141.0, 167.2; δC (CDCl3; DEPT 135) 22.3, 52.65,
124.9, 125.6, 126.6, 126.8, 127.1, 128.6, 129.2, 130.9, 131.8,
133.0.
(E )-2-[2-(p-Tolyl)vinyl]-3,1-benzoxathiin-4-one 5b. Light
yellow solid, mp 89 ЊC (Found: C, 72.35; H, 5.01. C17H14O2S
requires C, 72.31; H, 4.99%); νmax (KBr)/cmϪ1 1728.1, 1589.2,
1512.2; δH (300 MHz; CDCl3) 2.35 (s, 3H, ArCH3), 6.22 (d,
J 6.3 Hz, 1H, SCH), 6.36 (dd, J 15.9 and 6.3 Hz, 1H,
3-[2-(Methoxycarbonyl)phenylthio]-1-(2-naphthyl)propyne 4f.
White solid, mp 90 ЊC (Found: C, 76.01; H, 4.92. C21H16O2S
requires C, 75.87; H, 4.85%); νmax (KBr)/cmϪ1 1708.8, 1591.2,
1564.2; δH (300 MHz; CDCl3) 3.79 (s, 3H, COOCH3), 3.81 (s,
2H, SCH2), 7.08 (td, J 7.2 and 1.2 Hz, 1H, ArH), 7.27–7.34 (m,
3H, ArH), 7.38 (td, J 8.4 and 1.5 Hz, 1H, ArH), 7.46 (d, J 8.1
CH᎐CHAr), 6.92 (d, J 15.9 Hz, 1H, CH᎐CHAr), 7.16 (d, J 7.8
᎐ ᎐
Hz, 2H, ArH), 7.31–7.37 (m, 4H, ArH), 7.5 (td, J 9 and 1.2 Hz,
1H, ArH), 8.2 (d, J 8.1 Hz, 1H, ArH); δC (CDCl3) 20.3, 81.2,
119.5, 124.8, 125.7, 125.9, 126.5, 128.4, 129.0, 131.6, 132.6,
134.4, 137.3, 138.0, 162.8; δC (CDCl3; DEPT 135) 20.3, 81.2,
119.5, 125.7, 125.9, 126.5, 128.4, 131.6, 132.6, 134.3.
1652
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(E )-2-[2-(2-Methoxyphenyl)vinyl]-3,1-benzoxathiin-4-one 5c.
White solid, mp 99 ЊC (Found: C, 68.4; H, 4.71. C17H14O3S
requires C, 68.43; H, 4.73%); νmax (KBr)/cmϪ1 1728.1, 1596.9;
δH (300 MHz; CDCl3) 3.78 (s, 3H, ArOCH3), 6.16 (dd, J 6.6
and 1.2 Hz, 1H, SCH), 6.42 (dd, J 15.9 and 6.6 Hz, 1H,
1-(2-Carboxyphenylthio)-3-phenylpropa-1,2-diene 7a. White
solid, mp 156 ЊC (Found: C, 71.51; H, 4.43. C16H12O2S requires
C, 71.61; H, 4.50%); νmax (KBr)/cmϪ1 1936.4, 1681.8, 1593.1,
1573.8; δH (300 MHz; CDCl ) 6.36 (d, J 6 Hz, 1H, CH᎐C᎐
᎐ ᎐
3
CHAr), 6.39 (d, J 6 Hz, 1H,CH᎐C᎐CHAr), 7.12–7.2 (m, 2H,
᎐ ᎐
CH᎐CHAr), 6.81–6.9 (m, 2H, CH᎐CHAr, ArH), 7.18–7.29 (m,
ArH), 7.26–7.3 (m, 4H, ArH), 7.46–7.48 (m, 1H, ArH), 7.57 (d,
J 7.8 Hz, 1H, ArH), 7.98 (d, J 7.8 Hz, 1H, ArH); δC (CDCl3)
94.0, 120.3, 129.7, 131.7, 132.5, 132.7, 133.4, 133.9, 136.8,
137.6, 137.9, 146.2, 173.3, 213.6.
᎐
᎐
4H, ArH), 7.35–7.45 (m, 2H, ArH), 8.13 (dd, J 7.8 and 1.2 Hz,
1H, ArH); δC (CDCl3) 55.8, 83.2, 111.4, 121.0, 122.6, 124.3,
124.7, 127.1, 128.2, 130.5, 131.3, 133.0, 134.0, 138.9, 157.8,
164.4; δC (CDCl3; DEPT 135) 55.5, 82.9, 111.1, 120.8, 122.3,
126.8, 127.7, 127.9, 128.4, 130.2, 131.0, 132.7, 133.8.
1-(2-Carboxyphenylthio)-3-(p-tolyl)propa-1,2-diene 7b. White
solid, mp 149 ЊC (Found: C, 72.19; H, 4.85. C17H14O2S
requires C, 72.31; H, 4.99%); νmax (KBr)/cmϪ1 1932.5, 1678.0,
1585.4, 1562.2; δH (300 MHz; CDCl3) 2.33 (s, 3H, ArCH3), 6.38
(E )-2-[2-(4-Methoxyphenyl)vinyl]-3,1-benzoxathiin-4-one 5d.
Light yellow solid, mp 91 ЊC (Found: C, 68.45; H, 4.72.
C17H14O3S requires C, 68.43; H, 4.73%); νmax (KBr)/cmϪ1
1724.2, 1602.7, 1571.9; δH (300 MHz; CDCl3) 3.73 (s, 3H,
ArOCH3), 6.11 (d, J 6.6 Hz, 1H, SCH), 6.19 (dd, J 15.6 and 6.6
Hz, 1H, CH᎐CHAr), 6.78–6.84 (m, 3H, CH᎐CHAr, ArH),
(d, J 6 Hz, 1H, CH᎐ C᎐CHAr), 6.41 (d, J 6 Hz, 1H, CH᎐
᎐
᎐
᎐
C᎐CHAr), 7.07 (d, J 8.1 Hz, 1H, ArH), 7.13 (d, J 8.1 Hz,
᎐
1H, ArH), 7.2–7.24 (m, 3H, ArH), 7.5 (t, J 7.2 Hz, 1H,
ArH), 7.63 (d, J 7.8 Hz, 1H, ArH), 8.06 (d, J 7.8 Hz, 1H,
ArH); δC (CDCl3) 21.7, 88.9, 124.4, 124.7, 125.7, 126.8,
127.5, 129.2, 129.7, 130.0, 132.0, 132.6, 137.9, 168.6, 208.7;
δC (CDCl3; DEPT 135) 21.9, 89.0, 124.9, 127.0, 127.7, 129.4,
129.9, 132.2, 132.8.
᎐
᎐
7.22–7.29 (m, 4H, ArH), 7.42 (t, J 7.8 Hz, 1H, ArH), 8.11 (d,
J 7.5 Hz, 1H, ArH); δC (CDCl3) 55.7, 82.8, 114.6, 119.6, 124.7,
127.2, 128.0, 128.1, 128.8, 133.0, 134.1, 135.5, 138.8, 160.7,
164.4; δC (CDCl3; DEPT 135) 55.4, 82.5, 114.3, 119.3, 126.7,
127.7, 128.5, 132.2, 132.7, 133.8.
1-(2-Carboxyphenylthio)-3-(2-methoxyphenyl)propa-1,2-diene
7c. White solid, mp 132 ЊC (Found: C, 68.31; H, 4.69. C17H14-
O3S requires C, 68.43; H, 4.73%); νmax (KBr)/cmϪ1 1932.0,
1670.0, 1585.5; δH (300 MHz; CDCl3) 3.78 (s, 3H, ArOCH3),
(E )-2-[2-(1-Naphthyl)vinyl]-3,1-benzoxathiin-4-one 5e. White
solid, mp 120 ЊC (Found: C, 75.39; H, 4.41. C20H14O2S requires
C, 75.44; H, 4.43%); νmax (KBr)/cmϪ1 1730.0, 1585.3; δH (300
MHz; CDCl3) 6.26 (d, J 6 Hz, 1H, SCH), 6.51 (dd, J 15.6 and
6.27 (d, J 6 Hz, 1H, CH᎐C᎐CHAr), 6.73 (d, J 6 Hz, 1H,
᎐ ᎐
6 Hz, 1H, CH᎐CHAr), 7.11 (d, J 15.6 Hz, 1H, CH᎐CHAr),
᎐
᎐
CH᎐C᎐CHAr), 6.79–6.89 (m, 2H, ArH), 7.12–7.17 (m, 2H,
᎐ ᎐
7.31–7.42 (m, 5H, ArH), 7.5–7.67 (m, 4H, ArH), 7.87 (d, J 7.8
Hz, 1H, ArH), 8.24 (d, J 7.8 Hz, 1H, ArH).
ArH), 7.3–7.32 (m, 1H, ArH), 7.43 (t, J 7.2 Hz, 1H, ArH), 7.58
(d, J 7.8 Hz, 1H, ArH), 8.00 (d, J 7.5 Hz, 1H, ArH).
(E )-2-[2-(2-Naphthyl)vinyl]-3,1-benzoxathiin-4-one 5f. White
solid, mp 137 ЊC (Found: C, 75.41; H, 4.44. C20H14O2S requires
C, 75.44; H, 4.43%); νmax (KBr)/cmϪ1 1732.0, 1589.2; δH (300
MHz; DMSO-d6 ϩ CDCl3) 6.29 (d, J 6 Hz, 1H, SCH), 6.53
1-(2-Carboxyphenylthio)-3-(2-naphthyl)propa-1,2-diene 7d.
White solid, mp 154 ЊC (Found: C, 75.4; H, 4.41. C20H14O2S
requires C, 75.44; H, 4.43%); νmax (KBr)/cmϪ1 1932.5, 1678.0,
1596.9, 1585.4; δH (300 MHz; CDCl3) 6.49 (d, J 6 Hz, 1H,
(dd, J 15.6 and 6 Hz, 1H, CH᎐CHAr), 7.13 (d, J 15.6 Hz, 1H,
᎐
CH᎐C᎐CHAr), 6.62 (d, J 6 Hz, 1H, CH᎐C᎐CHAr), 7.24 (td,
᎐ ᎐ ᎐ ᎐
CH᎐CHAr), 7.33–7.39 (m, 2H, ArH), 7.47–7.55 (m, 3H, ArH),
᎐
J 7.2 and 1.2 Hz, 1H, ArH), 7.44–7.53 (m, 4H, ArH), 7.66–7.71
(m, 2H, ArH), 7.77–7.81 (m, 3H, ArH), 8.08 (dd, J 7.6 and 1.5
Hz, 1H, ArH); δC (CDCl3) 89.6, 98.0, 125.0, 125.2, 126.4, 126.7,
126.9, 127.3, 128.1, 128.2, 128.8, 130.7, 132.1, 132.8, 133.3,
133.9, 141.6, 168.7, 209.3; δC (CDCl3; DEPT 135) 89.3, 97.7,
124.7, 124.9, 126.1, 126.5, 126.6, 126.7, 127.8, 127.9, 128.5,
131.9, 132.5.
7.61 (d, J 8.7 Hz, 1H, ArH), 7.82 (d, J 7.8 Hz, 4H, ArH), 8.22
(d, J 7.8 Hz, 1H, ArH); δC (DMSO-d6 ϩ CDCl3) 32.5, 122.2,
123.7, 124.7, 126.9, 127.0, 127.2, 128.0, 128.1, 128.3, 128.6,
128.9, 132.8, 133.1, 133.8, 134.0, 134.1, 135.9, 138.7, 164.1; δC
(DMSO-d6 ϩ CDCl3; DEPT 135) 82.2, 121.9, 123.4, 126.6,
126.7, 126.9, 127.7, 127.8, 128.0, 128.3, 128.6, 132.8, 133.8,
135.6.
Reaction of compound 5a with alkali
(E )-2-[2-(3-Chlorophenyl)vinyl]-3,1-benzoxathiin-4-one 5g.
Light yellow solid, mp 101 ЊC (Found: C, 71.92; H, 4.14.
C16H11ClO2S requires C, 71.88; H, 4.15%); νmax (KBr)/cmϪ1
1728.2, 1595.7; δH (300 MHz; CDCl3) 6.16 (d, J 6 Hz, 1H,
Compound 5a (0.25 mmol) was refluxed with 5 M methanolic
KOH solution (7 cm3) for 12 h in an argon atmosphere. After
removal of the solvent under reduced pressure the residue was
diluted with water (2 cm3) followed by extraction with CHCl3
(3 × 5 cm3). The organic layer was dried (anh. Na2SO4) and the
solvent was distilled off. Cinnamaldehyde 8a was obtained as a
light yellow oil which was identical with an authentic sample.
The aqueous part was then acidified with dil. HCl (1:1) and the
precipitate was filtered off and dried in vacuo; a white solid was
obtained which was identified as thiosalicylic acid, mp 163 ЊC
(mp of an authentic sample was 165 ЊC).
SCH), 6.35 (dd, J 15.6 and 6 Hz, 1H, CH᎐CHAr), 6.91 (d,
᎐
J 15.6 Hz, 1H, CH᎐CHAr), 7.31–7.39 (m, 4H, ArH), 7.43 (s,
᎐
1H, ArH), 7.65 (d, J 7.2 Hz, 2H, ArH), 8.22 (d, J 7.5 Hz, 1H,
ArH).
(E )-2-[2-(2-Thienyl)vinyl]-3,1-benzoxathiin-4-one 5h. White
solid, mp 128 ЊC (Found: C, 61.18; H, 3.61. C14H10O2S2 requires
C, 61.28; H, 3.67%); νmax (KBr)/cmϪ1 1720.4, 1585.4, 1564.2;
δH (300 MHz; CDCl3) 6.18 (d, J 6 Hz, 1H, SCH), 6.23 (dd,
Hydrogenation of (E )-2-(2-arylvinyl)-3,1-benzoxathiin-4-ones. A
typical procedure
J 15.6 Hz, 1H, CH᎐CHAr), 6.99–7.01 (m, 1H, ArH), 7.07–7.12
᎐
(m, 2H, CH᎐CHAr, ArH), 7.27 (d, J 4.5 Hz, 1H, ArH), 7.36 (d,
᎐
J 7.5 Hz, 2H, ArH), 7.51 (td, J 7.8 and 1.2 Hz, 1H, ArH), 8.2
(dd, J 7.5 and 0.9 Hz, 1H, ArH).
Styryl-3,1-benzoxathiin-4-one 5a (0.18 mmol) in dry ethyl
acetate (5 cm3) was hydrogenated in the presence of palladium
on activated charcoal (10%; 0.06 mmol) at room temperature
under atmospheric pressure for 48 h. After completion of the
reaction, the catalyst was removed by filtration, washed with
ethyl acetate (20 cm3), and the solvent was distilled off. The
residue was purified by preparative TLC, using light petroleum–
ethyl acetate (1:2) as the eluent, to yield 1-(2-carboxyphenyl-
thio)-3-phenylpropane 9a as a pale yellow solid (90%), mp
Isolation of the allenic intermediates 7a–d
Allenic acids were formed by the hydrolysis of the disubstituted
alkynes 4 with methanolic KOH, acidification with dil. HCl and
extraction with diethyl ether (see under 5a). Some of them were
isolated as pure compounds by crystallisation (diethyl ether–
light petroleum) of the crude products formed.
J. Chem. Soc., Perkin Trans. 1, 2001, 1649–1655
1653

View Article Online
121 ЊC (Found: C, 70.59; H, 5.91. C16H16O2S requires C, 70.55;
H, 5.92%); νmax (KBr)/cmϪ1 1681.8, 1585.4, 1562.2; δH (300
MHz; CDCl3) 1.94–2.04 (m, 2H, SCH2CH2), 2.73 (t, J 7.2 Hz,
2H, CH2Ar), 2.85 (t, J 7.2 Hz, 2H, SCH2), 7.06–7.24 (m, 7H,
ArH), 7.35 (t, J 7.5 Hz, 1H, ArH), 8.04 (d, J 7.8 Hz, 1H, ArH),
8.88 (br s, 1H, COOH).
Acknowledgements
Grateful acknowledgement is made of a Royal Society of
Chemistry Journals Grants for International Authors to N. G.
K. which made his visit (May–June, 2000) to various research
institutes and universities in the UK and Europe possible.
Compounds 9b and 9c were synthesised from 5b and 5d
following the procedure for 9a.
References
1-(2-Carboxyphenylthio)-3-(p-tolyl)propane 9b. Light yellow
solid, mp 118 ЊC (Found: C, 71.41; H, 6.38. C17H18O2S requires
C, 71.29; H, 6.33%); νmax (KBr)/cmϪ1 1689.5, 1585.4, 1560.3;
δH (300 MHz; CDCl3) 1.92–2.02 (m, 2H, SCH2CH2), 2.25 (s,
3H, ArCH3), 2.7 (t, J 7.5 Hz, 2H, CH2Ar), 2.85 (t, J 7.5 Hz,
2H, SCH2), 7.00–7.03 (m, 3H, ArH), 7.12 (t, J 8.1 Hz, 1H,
ArH), 7.17–7.2 (m, 2H, ArH), 7.37 (td, J 7.5 and 1.5 Hz, 1H,
ArH), 8.05 (dd, J 7.8 and 1.5 Hz, 1H, ArH); δC (CDCl3) 20.0,
28.3, 30.6, 33.5, 123.1, 125.3, 127.2, 127.4, 128.1, 131.5, 132.0,
134.5, 136.9, 141.3, 169.1; δC (CDCl3; DEPT 135) 20, 28.7
(inverted), 30.5 (inverted), 33.5 (inverted), 123, 125.1, 127.5,
128.1, 131.5, 132.1
1 J. K. Landquist, Six-membered Ring Systems in Comprehensive
Organic Chemistry, ed. D. H. Barton and W. D. Ollis, Pergamon
Press, Oxford, 1st edn., 1979, vol. 4, p. 1051.
2 D. T. Mowry, W. H. Yanko and E. L. Ringwald, J. Am. Chem. Soc.,
1947, 69, 2358.
3 S. Senning and S.-O. Lawesson, Ark. Kemi, 1961, 17, 261.
4 D. C. Dittmer and E. S. Whitman, J. Org. Chem., 1969, 34, 2004.
5 S. Oae and T. Numata, Tetrahedron, 1974, 30, 2641.
6 J. C. Grivas, J. Org. Chem., 1976, 41, 1325.
7 V. Tripathi, P. Venkataramani and G. Mehta, J. Chem. Soc., Perkin
Trans. 1, 1979, 36.
8 S. Wolfe, P. M. Kazmeir and H. Aukshi, Can. J. Chem., 1979, 57,
2404.
9 Y. Uchida, Y. Kabayashi and S. Kozuka, Bull. Chem. Soc. Jpn., 1981,
54, 1781.
10 K. Okumura, K. Shiki, S. Sonoda, Y. Koga, K. Shioji, T. Kitamura,
Y. Fujiwara and Y. Yokomori, Bull. Chem. Soc. Jpn., 2000, 73,
155.
1-(2-Carboxyphenylthio)-3-(4-methoxyphenyl)propane
9c.
White solid, mp 113 ЊC (Found: C, 67.61; H, 5.97. C17H18O3S
requires C, 67.52; H, 6.00%); νmax (KBr)/cmϪ1 1679.9, 1585.4,
1564.2; δH (300 MHz; CDCl3) 1.91–2.00 (m, 2H, SCH2CH2),
2.68 (t, J 7.2 Hz, 2H, CH2Ar), 2.84 (t, J 7.2 Hz, 2H, SCH2),
3.72 (s, 3H, ArOCH3), 6.76 (d, J 8.4 Hz, 2H, ArH), 7.03–
7.18 (m, 4H, ArH), 7.36 (td, J 7.5 and 1.2 Hz, 1H, ArH),
8.04 (dd, J 7.8 and 1.2 Hz, 1H, ArH); δC (CDCl3) 30.2, 31.7,
34.4, 55.6, 114.3, 124.3, 126.3, 126.9, 129.8, 132.9, 133.5,
134.1, 143.0, 158.4, 171.4; δC (CDCl3; DEPT 135) 30.2
(inverted), 31.6 (inverted), 34.4 (inverted), 55.6, 114.3, 124.3,
126.2, 129.8, 132.9, 133.5.
11 Some selected references: (a) Y. Zhang and E.-i. Negishi, J. Am.
Chem. Soc., 1989, 111, 3454; (b) B. M. Trost and S. Shi, J. Am. Chem.
Soc., 1993, 115, 12491; (c) N. C. Ihle and C. H. Heathcock, J. Org.
Chem., 1993, 58, 560; (d ) G. Balme and D. Bouyssi, Tetrahedron,
1994, 50, 403; (e) E. Negishi, C. Coperet, S. Ma, S.-Y. Liou and
F. Liu, Chem. Rev., 1996, 96, 365; ( f ) R. C. Larock, Q. Tian
and A. A. Pletnev, J. Am. Chem. Soc., 1999, 121, 3238.
12 (a) Some selected references: L. S. Hegedus, Angew. Chem., Int. Ed.
Engl., 1988, 27, 1113; (b) T. Sakamoto, Y. Kondo and H. Yamanaka,
Heterocycles, 1988, 27, 2225; (c) J. H. Tidwell, D. R. Senn and
S. L. Buchwald, J. Am. Chem. Soc., 1991, 113, 4685; (d ) R. G.
Anderson and J. E. Backvall, J. Am. Chem. Soc., 1992, 114, 8696;
(e) B. M. Trost and M. C. McIntosh, J. Am. Chem. Soc., 1995, 117,
7255; ( f ) J. M. Zenner and R. C. Larock, J. Org. Chem., 1999, 64,
7312.
13 For palladium-catalysed reactions, see: (a) R. F. Heck, Palladium
Reagents in Organic Synthesis, Academic Press, London, 1985;
(b) G. D. Daves, Jr. and A. Hallberg, Chem. Rev., 1989, 89, 1433;
(c) A. de Meijere and F. E. Meyer, Angew. Chem., Int. Ed. Engl.,
1994, 33, 2379; (d ) J. Tsuji, Palladium Reagents and Catalysis, Wiley,
Chichester, 1995; (e) J. L. Malleron, J. C. Fiaud and J. Y. Legos,
Handbook of Palladium-Catalysed Organic Reactions, Academic
Press, London, 1997.
Synthesis of 10
A solution of 5g (0.33 mmol) in methanol was heated under
reflux with sodium methoxide (0.82 mmol) in an argon atmos-
phere for 15 h. After usual work-up, the residue was purified by
column chromatography on silica gel with the eluent being 1:1
CHCl3–light petroleum to furnish the disulfide 10 as a white
solid in 82% yield, mp 128 ЊC (Found: C, 57.58; H, 4.18.
C16H14O4S2 requires C, 57.46; H, 4.22%); νmax (KBr)/cmϪ1
1710.7, 1587.3, 1562.2; δH (300 MHz; CDCl3) 3.88 (s, 6H,
ArCOOCH3), 7.2 (td, J 7.5 and 1.5 Hz, 2H, ArH), 7.44–7.53
(m, 4H, ArH), 7.95 (dd, J 7.8 and 1.2 Hz, 2H, ArH);
δC (CDCl3) 35.8, 52.6, 125.2, 127.0, 128.5, 131.7, 133.0, 140.6,
167.0; δC (CDCl3; DEPT 135) 35.4, 52.3, 124.8, 126.6, 131.4,
132.7.
14 (a) N. G. Kundu, M. Pal, J. S. Mahanty and S. K. Dasgupta,
J. Chem. Soc., Chem. Commun., 1992, 41; (b) N. G. Kundu, M. Pal,
J. S. Mahanty and M. De, J. Chem. Soc., Perkin Trans. 1, 1997, 2815.
15 (a) N. G. Kundu and M. Pal, J. Chem. Soc., Chem. Commun., 1993,
86; (b) N. G. Kundu, M. Pal and B. Nandi, J. Chem. Soc., Perkin
Trans. 1, 1998, 561.
16 (a) N. G. Kundu, J. S. Mahanty, P. Das and B. Das, Tetrahedron
Lett., 1993, 34, 1625; (b) J. S. Mahanty, M. De, P. Das and N. G.
Kundu, Tetrahedron, 1997, 53, 13397.
Synthesis of the disulfide 11
17 (a) M. W. Khan and N. G. Kundu, Synlett, 1997, 1435; (b) N. G.
Kundu, M. W. Khan and J. S. Mahanty, J. Chem. Res. (S), 1999,
460; N. G. Kundu, M. W. Khan and J. S. Mahanty, J. Chem.
Res. (M), 1999, 1901; (c) N. G. Kundu, M. W. Khan and
R. Mukhopadhyay, Tetrahedron, 1999, 55, 12361.
18 M. De, D. P. Majumdar and N. G. Kundu, J. Indian Chem. Soc.,
1999, 76, 665.
19 (a) C. Chowdhury and N. G. Kundu, Chem. Commun., 1996, 1067;
(b) C. Chowdhury, G. Chaudhuri, S. Guha, A. K. Mukherjee and
N. G. Kundu, J. Org. Chem., 1998, 63, 1863.
20 G. Chaudhuri and N. G. Kundu, J. Chem. Soc., Perkin Trans. 1,
2000, 775.
21 (a) G. Chaudhuri, C. Chowdhury and N. G. Kundu, Synlett., 1998,
1273; (b) N. G. Kundu, G. Chaudhuri and A. Upadhyay, J. Org.
Chem., 2001, 66, 20.
22 B. Nandi and N. G. Kundu, Org. Lett., 2000, 2, 235.
23 A preliminary account has appeared: N. G. Kundu and B. Nandi,
Synlett, 2001, 415.
24 K. Sonogashira, Y. Tohda and V. Hagihara, Tetrahedron Lett., 1975,
4467.
25 (a) For propargyl-to-allenic isomerisation, see: P. J. Garratt and
A mixture of compound 5g (0.25 mmol) and aniline (0.75
mmol) in benzene (5 cm3) was heated under reflux for 15 h in an
argon atmosphere. The resulting reaction mixture was then
diluted with water (5 cm3) and the benzene layer was separated.
This was washed successively with dil. HCl (2 × 3 cm3) and with
water (2 × 5 cm3) and dried (anh. Na2SO4). After removal of
the solvent, a brown residue was obtained which was purified by
column chromatography on silica gel (60–120 mesh) with the
eluent being 1:1 CHCl3–light petroleum to afford m-chloro-
cinnamaldehyde 8g and compound 11 as a white solid, mp
246 ЊC (lit.,29 248 ЊC) (Found: C, 68.25; H, 4.37; N, 6.18. Calc.
for C26H20N2O2S2: C, 68.39; H, 4.41; N, 6.13%); νmax (KBr)/cmϪ1
3288.4, 1849.0, 1598.9; δH (300 MHz; DMSO-d6) 7.11 (t, J 7.2
Hz, 2H, ArH), 7.33–7.38 (m, 6H, ArH), 7.49 (t, J 7.8 Hz, 2H,
ArH), 7.13–7.77 (m, 8H, ArH), 10.53 (s, 2H, NH); δC (DMSO-
d6) 120.9, 121.0, 124.8, 127.1, 129.3, 129.5, 132.2, 135.5, 137.4,
139.7, 166.5; δC (DMSO-d6; DEPT 135) 120.7, 124.5, 126.8,
129.0, 129.2, 131.9.
1654
J. Chem. Soc., Perkin Trans. 1, 2001, 1649–1655

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