Reactions of electron-withdrawing thiophene 1,1-dioxides with furans. A novel reaction pathway

Article abstract of DOI:10.1007/s11172-006-0318-8

Reactions of thiophene dioxides containing electron-withdrawing substituents with furans were studied. The reactions with unsubstituted furan followed the inverse-electron-demand Diels-Alder mechanism. Subsequent elimination of sulfur dioxide from the add

Full text of DOI:10.1007/s11172-006-0318-8

7
12
Russian Chemical Bulletin, International Edition, Vol. 55, No. 4, pp. 712—717, April, 2006
Reactions of electronꢀwithdrawing thiophene 1,1ꢀdioxides with furans.
A novel reaction pathway
A. M. Moiseev, E. S. Balenkova, and V. G. Nenajdenkoꢀ
Department of Chemistry, M. V. Lomonosov Moscow State University,
1
Leninskie Gory, 119899 Moscow, Russian Federation.
Fax: +7 (495) 932 8846. Eꢀmail: nen@acylium.chem.msu.ru
Reactions of thiophene dioxides containing electronꢀwithdrawing substituents with furans
were studied. The reactions with unsubstituted furan followed the inverseꢀelectronꢀdemand
Diels—Alder mechanism. Subsequent elimination of sulfur dioxide from the adduct afforded
products of the tetrahydrobenzofuran series. The reactions with substituted furans gave
benzylcarbonyl compounds in high yields. The observed regiochemistry of the reaction was
explained in terms of the frontier orbital theory using the calculated orbital coefficients.
Key words: thiophene 1,1ꢀdioxides with electronꢀwithdrawing substituents, the Diels—Alder
reaction, substituted furans, benzylcarbonyl compounds.
The Diels—Alder reaction with furans as a 4πꢀcompoꢀ
dienophiles in [4+2] cycloaddition reactions with open
1
and cyclic 1,3ꢀdienes to give both monoꢀ and bisadducts.8
Because cycloaddition to various dienophiles is charꢀ
acteristic of furan and its derivatives, the possibility of
carrying out reactions with new electronꢀwithdrawing
thiophene dioxides we synthesized is of great interest. In
addition, reactions of thiophene dioxides with various
furans have not been adequately investigated: only a few
substituted thiophene dioxides have been studied and only
two examples of reactions with unsubstituted furan have
nent is a wellꢀstudied transformation. The theoretical
value and applications of furans in cycloaddition reacꢀ
tions is difficult to overestimate. The use of furans in
various cycloaddition reactions remains so far in demand
in all areas of synthetic organic chemistry. Furan derivaꢀ
tives show an important ability to react with various
dienophiles, giving [4+2] cycloadducts with a sixꢀmemꢀ
bered fragment capable of further transformations. Beꢀ
cause of this, they are successfully employed in the synꢀ
2
3
5a,9
thesis of natural compounds and macromolecules and
used as protective groups.
been reported.
4
Reactions of furans with thiophene 1,1ꢀdioxides are of
particular attention. In these reactions, halogenꢀ and
alkylꢀcontaining thiophene 1,1ꢀdioxides serve as dienes,
while furan acts as a dienophile. Intermediate cycloadducts
Results and Discussion
Taking into account that electronꢀwithdrawing thioꢀ
phene dioxides can act as dienophiles, we expected
the formation of 7ꢀoxabicyclo[2.2.1]heptꢀ5ꢀene (7ꢀoxaꢀ
bornene) derivatives, which are usual adducts of furan
with the bridging SO group undergo spontaneous elimiꢀ
2
nation of sulfur dioxide and a tandem rearrangement into
5
benzylcarbonyl compounds. Elimination of SO followed
2
1
by aromatization is a powerful driving force of this reacꢀ
tion that explains well the atypical behavior of furans as
with dienophiles.
However, the major product (71%) of the reaction of
thiophene dioxide 1a with furan (Scheme 1) was 4,7ꢀdiꢀ
chloroꢀ3a,7aꢀdihydroꢀ1ꢀbenzofuran (2). Thus, we isolated
for the first time an intermediate with the stable furan
ring, which opened up new potentialities of this reaction.
We assumed that this is also valid for other electronꢀ
withdrawing substituents in the thiophene ring.
6
dienophiles. It is known that thiophene dioxides conꢀ
taining no strong electronꢀwithdrawing groups behave like
electronꢀwithdrawing dienes, reacting with dienophiles
with elimination of SO to give the cyclohexadiene system.
2
Earlier,7 we have developed a convenient route to
thiophene dioxides containing electronꢀwithdrawing subꢀ
stituents. We have also studied the behavior of some of
the compounds obtained in reactions with 1,3ꢀdienes and
found that these compounds are reactive dienophiles, in
contrast to thiophene dioxides containing no strong elecꢀ
tronꢀwithdrawing substituents. For instance, they act as
Indeed, thiophene dioxides 1b—d containing strong
electronꢀwithdrawing SO Me and CN groups easily reꢀ
2
acted with furan in CH Cl at room temperature in 1 h.
2
2
The thiophene dioxides acted as dienes, which was eviꢀ
dent from the evolution of SO in all cases; however, the
2
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 687—692, April, 2006.
066ꢀ5285/06/5504ꢀ0712 © 2006 Springer Science+Business Media, Inc.
1

Thiophene 1,1ꢀdioxides and furans
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 4, April, 2006
713
Scheme 1
Scheme 2
products obtained were structurally different from comꢀ
pound 2.
According to 2D NMR data (NOESY, COSY, HMBC,
and HSQC), the compounds obtained contain two furan
fragments and have a structure of 5ꢀ(2ꢀfuryl)tetrahydroꢀ
benzofurans. The NOESY correlations for compound 3a
are shown below as an example.
i. 1. Furan; 2. Isomerization.
Thiophene R1
dioxide
R2
Product
Yield
(%)
1b
Cl
SO Me
3a
3b
3c
41
33
72
2
1c
Br
SO Me
2
1d
Me
CN
The first step of this transformation is the inverseꢀ
electronꢀdemand Diels—Alder reaction. Cycloaddition
reactions of this type are known to be controlled by the
highest occupied molecular orbitals (HOMO) of a dienoꢀ
phile and the lowest unoccupied molecular orbitals
1
1,12
(
LUMO) of a diene.
To interpret the observed
regioselectivity, we used quantumꢀchemical data for the
8
c,13
LUMO of thiophene 1,1ꢀdioxides
and for the HOMO
1
1,12
of furan.
In terms of the frontier molecular orbital
regioselectivity is due to overlap of the moꢀ
1
c,11
The formation of the furan ring fused with the sixꢀ
theory,
1
membered ring was also detected by H NMR spectroꢀ
lecular orbitals with the highest coefficients of both
the diene and dienophile in the transition state of the
Diels—Alder reaction of thiophene dioxide with furan.
The resulting strict orientation of the diene and the
dienophile in the transition state makes the reaction exꢀ
tremely regioselective and predetermines the respective
arrangement of the substituents in reaction products.
A reaction of thiophene 1,1ꢀdioxide 1b with furan is shown
in Scheme 3 as an example (the orbital coefficients are
indicated). The regiochemistry of adducts obtained from
other substituted thiophene dioxides is much the same.8c
The formation of products 3a—c is probably due to a
reaction of dihydrobenzofurans (Diels—Alder adducts)
with an excess of furan. Reactions of thiophene dioxides
scopy: The signals for two protons in this furan ring are
separate from other signals and appear as two characterisꢀ
tic doublets (J = 6.5 Hz). To specify the exact configuraꢀ
tions of the compounds obtained, we correlated the couꢀ
pling constants corresponding to all the protons in the
cyclohexane ring with the characteristic constants for subꢀ
stituted cyclohexanes.1 The H(7) and H(4) protons were
unambiguously located in axial positions because they
showed only two vicinal couplings with characteristic conꢀ
stants of 10.4 and 11.1 Hz, respectively. Thus, the reacꢀ
tion yields the thermodynamically most stable isomer in
which all substituents are equatorial.
0
The reaction is of the general character: other elecꢀ
tronꢀwithdrawing thiophene 1,1ꢀdioxides also gave tricyꢀ
clic products 3b,c in high yields (Scheme 2).
containing strong electronꢀwithdrawing groups (SO Me,
2
CO Me, and CN) gave functionalized dihydrobenzoꢀ
2
With unsymmetrical thiophene 1,1ꢀdioxides containꢀ
ing two different substituents, two regioisomeric adꢀ
ducts can be obtained. However, only one of the posꢀ
sible regioisomers was isolated for each thiophene diꢀ
oxide 1b—d.
furans. The double bond in these products is activated for
nucleophilic addition: its interaction with an excess of
furan (Michael addition) followed by migration of the
double bond yields compounds 3a—c. Such a type of the
1
4
Michael addition of furans is well known; the driving

7
14
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 4, April, 2006
Moiseev et al.
Scheme 3
force of the migration is the formation of an aromatic
structure. Similar migrations catalyzed by rhodium(III)
chloride have been described earlier15 for furan systems.
Variation in the amount of furan (1, 1.5, and 0.5 equiv.)
did not change the pathway of this reaction: we isolated
only products 3a—c and the unreacted thiophene diꢀ
oxides 1b—d.
Scheme 4
To investigate the general character and regioselectivity
of this process with respect to the furan component, we
used 2ꢀmethylfuran (sylvan), 2,5ꢀdimethylfuran, and meꢀ
thyl furanꢀ2ꢀcarboxylate in the reaction.
We found that these reagents exclusively yield benzylꢀ
carbonyl compounds, in contrast to the reactions with
unsubstituted furan. Apparently, intermediate products in
these cases, more rapidly undergo opening into the correꢀ
sponding carbonyl compounds (for 2,5ꢀdimethylfuran, the
Michael addition is impossible).
Using a number of thiophene dioxides with electronꢀ
withdrawing substituents 1a—f and substituted furans, we
obtained previously unknown benzylcarbonyl compounds
Thiophene
dioxide
R1
R2
1
e
Br
CO Me
2
1f
Me
SO2Me
1
g
SO Me
SO Me
4
a—g (Scheme 4).
2
2
The reaction opens up wide possibilities for the synꢀ
R1
R2
R3
Comꢀ
Yield
thesis of functionalized benzylcarbonyl compounds; variaꢀ
tion of thiophene dioxides and furans allows one to obtain
carbonyl compounds with various substituents.
pound
(%)
4a
Cl
Cl
Br
Br
Me
Cl
SO Me
H
H
H
H
H
H
Me
91
81
70
88
95
96
93
4b
4c
4d
4e
2
SO Me
2
It should be noted that the regioselectivity of the addiꢀ
tion of sylvan and methyl furanꢀ2ꢀcarboxylate to all
thiophene dioxides was 100%. We detected no adducts
due to addition at the double bond with the methyl group.
In this case, the observed regioselectivity can be explained
by favorable electronic and steric effects. Thus, for
thiophene dioxide 1b and 2ꢀmethylfuran (5a), addition
involved the side without the methyl group (Scheme 5).
An interesting result was obtained from methyl pyroꢀ
mucate as a furan component and thiophene dioxides
CO Me
2
SO Me
2
4f
SO Me
SO Me
SO Me
2
2
4
g
SO Me
2
2
3
R = H (5a), Me (5b)
tion mixture in tetrachloroethylene to 100 °C resulted in
the complete conversion of the starting thiophene diꢀ
oxides and the quantitative formation of products 6a,b
(Scheme 6). Further heating of the reaction mixture in
boiling tetrachloroethylene for 1 h gave the target benzylꢀ
carbonyl compounds 7a,b in 87 and 90% yields, respecꢀ
tively. Apparently, isolation of substituted dihydrobenzoꢀ
1
b,g. Prolonged stirring of the reagents at room temperaꢀ
ture in CH Cl gave no products (monitoring by TLC),
2
2
while heating under reflux very slowly yielded a mixture
of two compounds. However, rapid heating of the reacꢀ

Thiophene 1,1ꢀdioxides and furans
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 4, April, 2006
715
Scheme 5
with thiophene dioxides exclusively gave functionalized
benzylcarbonyl compounds. The 100% regioselectivity of
the cycloaddition of thiophene dioxides to furans is due to
both orbital and steric factors.
Experimental
1H and 13C NMR spectra were recorded on a Varian
VXRꢀ400 spectrometer (400 and 100 MHz, respectively) in
CDCl , CD CN, and DMSOꢀd with Me Si as the internal
3
3
6
4
standard. TLC was carried out on Merck 60F254 plates; column
chromatography was carried out on silica gel (63—200 mesh,
Merck).
Commercial reagents were used. Thiophene 1,1ꢀdioxides
were prepared as described earlier.7
4
,7ꢀDichloroꢀ3a,7aꢀdihydroꢀ1ꢀbenzofuran (2). Freshly disꢀ
furans 6a,b became possible because of the presence of
the electronꢀwithdrawing ester group. Consequently,
higher temperatures were required for rearrangement into
benzylcarbonyl compounds.
tilled furan (1 mL, 15.7 mmol) was added at 0 °C to a vigorously
stirred solution of thiophene dioxide 1a (1 mmol, 185 mg) in dry
dichloromethane (10 mL). The reaction mixture was warmed to
room temperature and stirred for 12 h. The solvent and the
excess of furan were removed in vacuo. The residue was chroꢀ
matographed on silica gel with hexane—ethyl acetate (1 : 1)
as an eluent. The yield was 71%, colorless crystals, m.p.
Scheme 6
1
35—136 °C. Found (%): C, 50.81; H, 3.14. C H Cl O. Calcuꢀ
8 6 2
1
lated (%): C, 50.83; H, 3.20. H NMR (CDCl ), δ: 3.78—3.80
3
(
m, 1 H, C(3a)H); 5.25 (s, 1 H, C(7a)H); 5.29—5.31 (m,
1
6
H, CH=CH—O); 6.33 (d, 1 H, CH=CH—O, J = 3.1 Hz);
.41—6.43, 6.69—6.71 (both dd, 1 H each, C(5)H—CH,
13
C(6)H—CH, J = 1.8 Hz, J = 5.9 Hz). C NMR (CDCl ), δ:
3
5
7.9, 80.9, 88.2, 130.2, 134.5, 135.1, 135.3.
Reactions of thiophene dioxides 1b—d with an excess of furan
(
general procedure). Freshly distilled furan (1 mL, 15.7 mmol)
was added at 0 °C to a vigorously stirred solution or suspension
of thiophene dioxide 1b—d (1 mmol) in dry dichloromethane
(
10 mL). The reaction mixture was warmed to 15 °C, stirred
at this temperature for 1—2 h, and then left at ~20 °C for ~14 h
for the reaction to be completed. The solvent and the excess
of furan were removed in vacuo. The residue was chromatoꢀ
graphed on silica gel with hexane—ethyl acetate (1 : 1) as an
eluent.
R1 = Cl, R2 = SO Me (6a, 7a); R1 = R2 = SO Me (6b, 7b)
7ꢀChloroꢀ5ꢀ(2ꢀfuryl)ꢀ4ꢀmethylsulfonylꢀ4,5,6,7ꢀtetrahydroꢀ1ꢀ
benzofuran (3a). The yield was 41%, a light yellow oil. Found (%):
C, 51.61; H, 4.33. C H ClO S. Calculated (%): C, 51.92;
2
2
1
3
13
4
Products 7a,b exist in the enol form, which was conꢀ
firmed by NMR and IR spectroscopy. For instance,
the IR spectra of the benzylcarbonyl compounds obꢀ
tained contain characteristic bands of the OH group at
1
H, 4.36. H NMR (CD CN), δ: 2.31—2.39, 2.70—2.77
3
(
both m, 1 H each, C(6)CH ); 2.99 (s, 3 H, SO Me);
2
2
3
.61—3.68, 4.94—4.98 (both m, 1 H each, C(5)H, C(7)H); 5.10
(
d, 1 H, CHSO C(4)H , J = 10.4 Hz); 6.36 (d, 1 H, C(3)H, J =
2 3
3
300 cm–1
Dihydrobenzofuran derivatives 6a,b are by themselves
.
6.5 Hz); 6.40 (m, 2 H, 4,3ꢀfuryl); 6.78 (d, 1 H, C(2)H, J =
1
3
6.5 Hz); 7.49 (br.s, 1 H, 5ꢀfuryl). C NMR (CD CN), δ:
3
interesting objects of investigation. Their oxidative aroꢀ
matization can afford substituted derivatives of benzoꢀ
furancarboxylic acids.
Thus, we studied the reactions of electronꢀwithdrawꢀ
ing thiophene 1,1ꢀdioxides with furans and isolated for
the first time previously postulated reaction intermediates.
In the case of thiophene dioxides containing strong elecꢀ
tronꢀwithdrawing groups, 5ꢀ(2ꢀfuryl)tetrahydrobenzoꢀ
furans were obtained. The reactions of substituted furans
39.7, 40.5, 43.2, 71.9, 79.6, 109.7, 111.8, 121.0, 130.2, 141.0,
1
41.9, 144.4.
ꢀBromoꢀ5ꢀ(2ꢀfuryl)ꢀ4ꢀmethylsulfonylꢀ4,5,6,7ꢀtetrahydroꢀ1ꢀ
7
benzofuran (3b). The yield was 33%, a yellow oil. Found (%):
C, 45.11; H, 3.69. C H BrO S. Calculated (%): C, 45.23;
1
3
13
4
1
H, 3.80. H NMR (CDCl ), δ: 1.92—1.99, 2.63—2.68 (both m,
3
1
H each, C(6)H ); 2.95 (s, 3 H, SO Me); 3.48—3.59, 3.72—3.80
2
2
(
both m,
1
H
each, C(5)H, C(7)H); 5.07 (d, 1 H,
CHSO C(4)H , J = 11.6 Hz); 5.11 (d, 1 H, CH, J = 4.6 Hz);
2
3
6.30 (br.s, 1 H, 5ꢀfuryl); 6.45, 6.67 (both d, 1 H each, C(2)H,

7
16
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 4, April, 2006
Moiseev et al.
C(3)H, J = 6.6 Hz). 13C NMR (CDCl ), δ: 36.6, 41.3, 42.3,
1
H NMR (CD COCD ), δ: 2.27, 3.17, 3.20 (all s, 3 H each,
3
3
3
6
3.2, 78.5, 99.2, 123.6, 129.1, 132.0, 133.8, 139.9, 142.8.
ꢀ(2ꢀFuryl)ꢀ7ꢀmethylꢀ4,5,6,7ꢀtetrahydroꢀ1ꢀbenzofuranꢀ4ꢀ
CH CO, 2 SO CH ); 4.49 (s, 2 H, CH ); 7.93 (d, 1 H, J =
3 2 3 2
5
1.9 Hz); 8.09 (dd, 1 H, J = 8.3 Hz, J = 1.9 Hz); 7.49 (d, 1 H,
13
carbonitrile (3c). The yield was 72%, a yellow oil. Found (%):
J = 8.3 Hz). C NMR (CD COCD ), δ: 19.9, 33.3, 33.9, 37.4,
3 3
C, 73.95; H, 5.43. C14H NO . Calculated (%): C, 73.99;
111.7, 120.9, 122.1, 126.8, 133.6, 134.9, 194.7.
13
2
1
H, 5.77. H NMR (CDCl ), δ: 1.61 (br.s, 1 H); 2.12 (s, 3 H,
1ꢀ[2ꢀMethylꢀ3,6ꢀbis(methylsulfonyl)phenyl]acetone (4g). The
yield was 93%, colorless crystals, m.p. 221 °C. Found (%):
C, 47.01; H, 4.99. C12H16O S . Calculated (%): C, 47.35;
3
Me); 2.24 (d, 1 H, J = 1.8 Hz); 3.47 (br.d, 1 H, J = 1.8 Hz);
4
4
(
.99, 5.59 (both br.s, 1 H each); 6.26, 6.40 (both br.s, 1 H each,
5
2
1
,3ꢀfuryl); 6.53—6.55, 6.69—6.71 (both m, 1 H each); 6.76—6.78
H, 5.30. H NMR (CD COCD ), δ: 2.32, 2.64, 3.17, 3.25 (all s,
3 3
dd, 1 H, J = 1.8 Hz, J = 5.3 Hz). 1 C NMR (CD CN), δ:
3
3 H each, CH , CH CO, 2 SO CH ); 4.58 (s, 2 H, CH ); 8.11,
3 3 2 3 2
3
13
3
1
9.7, 40.5, 43.2, 71.9, 79.6, 109.7, 111.8, 121.0, 130.2, 141.0,
41.9, 144.4.
8.17 (both d, 1 H each, J = 8.2 Hz). C NMR (DMSOꢀd ), δ:
6
15.9, 29.7, 43.2, 43.7, 43.8, 126.8, 127.6, 136.7, 139.6, 143.9,
134.9, 203.9.
Synthesis of benzylcarbonyl compounds (general procedure).
An appropriate furan (5 mmol) (2,5ꢀdimethylfuran in the synꢀ
thesis of 3g and 2ꢀmethylfuran in the other cases) was added
at 0 °C to a solution of thiophene dioxide (1 mmol) in diꢀ
chloromethane (5 mL). The reaction mixture was kept at this
temperature for 1 h and concentrated in vacuo. The residue was
dissolved in CH Cl , passed through a layer of silica gel (1—2 g),
Reactions of thiophene 1,1ꢀdioxides 1b,g with methyl furanꢀ
2ꢀcarboxylate (5c) (general procedure). A solution of thiophene
dioxide (1 mmol) and ester 5c (1.1 mmol) in tetrachloroethylene
(10 mL) was rapidly heated to 100 °C. The workup described
above for compounds 4a—g gave esters 6a,b. When the reaction
mixture was refluxed at ~120 °C prior to workup, esters 7a,b
were obtained.
2
2
and concentrated.
1
ꢀ(2,5ꢀDichlorophenyl)acetone (4a). The yield was 91%, a
Methyl 7ꢀchloroꢀ4ꢀmethylsulfonylꢀ3a,7aꢀdihydroꢀ1ꢀbenzofuꢀ
ranꢀ2ꢀcarboxylate (6a). The yield was 100%, a light yellow oil.
Found (%): C, 45.31; H, 3.79. C H ClO S. Calculated (%):
colorless oil. Found (%): C, 53.11; H, 3.80. C H Cl O. Calcuꢀ
lated (%): C, 53.23; H, 3.97. H NMR (CDCl ), δ: 2.23 (s, 3 H,
9
8
2
1
3
11 11
5
1
CH CO); 3.81 (s, 2 H, CH ); 7.19—7.21 (m, 2 H); 7.30—7.32
C, 45.44; H, 3.81. H NMR (CDCl ), δ: 2.93, 3.77 (both s,
3
2
3
13
(
m, 1 H). C NMR (CDCl ), δ: 29.2, 48.3, 128.9, 129.0, 130.1,
3 H each, CO CH , SO CH ); 4.43—4.47 (d, 1 H, C(3a)H, J =
3
2
3
2
3
1
31.4, 132.0, 133.7, 201.6.
ꢀ(5ꢀChloroꢀ2ꢀmethylsulfonylphenyl)acetone (4b). The yield
13.7 Hz); 5.52 (d, 1 H, C(7a)H, J = 13.7 Hz); 6.23 (d, 1 H, J =
3.1 Hz); 6.36 (d, 1 H, J = 6.9 Hz); 6.81—6.83 (dd, 1 H, J =
1
13
was 81%, colorless crystals, m.p. 140—141 °C. Found (%):
1.6 Hz, J = 6.9 Hz). C NMR (DMSOꢀd ), δ: 40.1, 48.3, 52.0,
6
C, 48.51; H, 4.82. C H ClO S. Calculated (%): C, 48.68;
118.6, 128.3, 131.9, 136.5, 147.1, 148.9, 161.0.
10
11
3
1
H, 4.49. H NMR (CDCl ), δ: 2.31 (s, 3 H, CH CO); 3.01 (s,
Methyl 3ꢀ(5ꢀchloroꢀ2ꢀmethylsulfonylphenyl)ꢀ2ꢀhydroxyꢀ
acrylate (7a). The yield was 87%, a dark oil. Found (%): C, 45.12;
H, 3.66. C H ClO S. Calculated (%): C, 45.44; H, 3.81.
3
3
3
7
H, SO CH ); 4.25 (s, 2 H, CH ); 7.20 (d, 1 H, J = 2.1 Hz);
.45 (dd, 1 H, J = 2.1 Hz, J = 8.6 Hz); 7.94 (d, 1 H, J = 8.6 Hz).
2 3 2
1
1
11
5
1
3
1
C NMR (CDCl ), δ: 30.1, 44.4, 48.1, 128.6, 131.6, 133.4,
H NMR (DMSOꢀd ), δ: 3.20, 3.83 (both s, 3 H each, CO CH ,
6 2 3
3
1
36.3, 137.5, 140.0, 204.9.
SO CH ); 7.16 (s, 1 H, CH=C); 7.58—7.61 (m, 1 H, Ar); 7.97
2 3
1
ꢀ(5ꢀBromoꢀ2ꢀmethylsulfonylphenyl)acetone (4c). The yield
(d, 1 H, Ar, J = 8.4 Hz); 8.34 (d, 1 H, Ar, J = 1.8 Hz); 10.61 (s,
13
was 70%, a colorless oil. Found (%): C, 41.34; H, 3.80.
C H BrO S. Calculated (%): C, 41.25; H, 3.81. H NMR
1 H, OH). C NMR (DMSOꢀd ), δ: 45.4, 51.5, 118.0, 129.7,
6
1
130.6, 130.9, 139.8, 140.0, 145.1, 163.9.
10
11
3
(
(
2
(
CDCl ), δ: 2.31 (s, 3 H, CH CO); 3.03 (s, 3 H, SO CH ); 4.22
Methyl 4,7ꢀbis(methylsulfonyl)ꢀ3a,7aꢀdihydroꢀ1ꢀbenzofuranꢀ
2ꢀcarboxylate (6b). The yield was 100%, a yellow oil. Found (%):
C, 43.13; H, 4.36. C H O S . Calculated (%): C, 43.10;
3
3
2
3
s, 2 H, CH ); 7.19 (d, 1 H, J = 2.0 Hz); 7.41 (dd, 1 H, J =
2
13
.0 Hz, J = 8.5 Hz); 7.90 (d, 1 H, J = 8.5 Hz). C NMR
1
2
14
7 2
1
CDCl ), δ: 29.8, 44.0, 47.9, 128.3, 131.1, 133.2, 135.8, 137.1,
H, 4.22. H NMR (DMSOꢀd ), δ: 3.23, 3.29, 3.71 (all s,
3
6
1
39.4, 206.1.
3 H each, 2 SO CH , CO CH ); 4.51—4.53 (d, 1 H, C(3a)H,
2
3
2
3
Methyl 4ꢀbromoꢀ2ꢀ(2ꢀoxopropyl)benzoate (4d). The yield
J = 13.9 Hz); 5.52 (d, 1 H, C(7a)H, J = 13.9 Hz); 6.35, 6.39
(both d, 1 H each, J = 3.3 Hz, J = 7.1 Hz); 6.85—6.87 (dd, 1 H,
was 88%, a yellow oil. Found (%): C, 41.34; H, 3.80.
1
13
C H BrO . Calculated (%): C, 41.25; H, 3.81. H NMR
J = 1.8 Hz, J = 7.1 Hz). C NMR (DMSOꢀd ), δ: 40.9, 48.5,
1
1
11
3
6
(
CDCl ), δ: 2.31 (s, 3 H, CH CO); 3.86 (s, 3 H, CO CH ); 4.09
52.8, 119.1, 129.1, 132.5, 137.0, 147.9, 149.4, 163.5.
3
3
2
3
(
2
(
1
s, 2 H, CH ); 7.37 (d, 1 H, J = 2.0 Hz); 7.51 (dd, 1 H, J =
.0 Hz, J = 8.3 Hz); 7.92 (d, 1 H, J = 8.3 Hz). C NMR
Methyl 3ꢀ[2,5ꢀbis(methylsulfonyl)phenyl]ꢀ2ꢀhydroxyacrylate
(7b). The yield was 90%, colorless crystals, m.p. 211 °C.
Found (%): C, 43.20; H, 4.14. C H O S . Calculated (%):
2
13
CDCl ), δ: 29.6, 48.5, 52.1, 122.7, 123.3, 127.5, 130.2, 131.0,
3
12 14
7 2
1
34.6, 169.4, 205.8.
ꢀ(5ꢀMethylꢀ2ꢀmethylsulfonylphenyl)acetone (4e). The yield
C, 43.10; H, 4.22. H NMR (DMSOꢀd ), δ: 3.06, 3.83, 3.89
6
1
(all s, 3 H each, CO CH , 2 SO CH ); 7.22 (s, 1 H, CH=C);
2
3
2
3
was 95%, a colorless oil. Found (%): C, 58.41; H, 6.12.
7.63—7.65 (m, 1 H, Ar); 8.09 (d, 1 H, Ar, J = 8.6 Hz); 8.38
(d, 1 H, Ar, J = 2.0 Hz); 11.23 (s, 1 H, OH). C NMR
1
13
C11H14O S. Calculated (%): C, 58.38; H, 6.24. H NMR
3
(
CDCl ), δ: 2.29 (s, 3 H, CH CO); 2.38 (s, 3 H, CH );
(DMSOꢀd ), δ: 45.9, 52.0, 119.1, 130.1, 132.8, 133.7, 140.5,
3
3
3
6
2
7
.99 (s, 3 H, SO CH ); 4.23 (s, 2 H, CH ); 7.00 (s, 1 H);
.26, 7.87 (both d, 1 H each, J = 8.1 Hz). C NMR
141.9, 146.0, 165.4.
2
3
2
1
3
(
1
CDCl ), δ: 20.9, 29.6, 44.0, 47.9, 128.6, 129.7, 133.7, 135.6,
3
This work was financially supported by the Russian
Foundation for Basic Research (Project No. 06ꢀ03ꢀ
32510ꢀa) and the Foundation for Assistance to Home
Science.
44.3, 205.4.
,5ꢀ[Bis(methylsulfonyl)phenyl]acetone (4f). The yield
2
was 96%, colorless crystals, m.p. 201 °C. Found (%): C, 45.51;
H, 4.82. C11H14O S . Calculated (%): C, 45.50; H, 4.86.
5
2

Thiophene 1,1ꢀdioxides and furans
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 4, April, 2006
717
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Received February 14, 2006