Structural diversity of interaction products of mucochloric acid and its derivatives with 1,2-ethanedithiol

Article abstract of DOI:10.1016/j.tet.2010.10.047

The synthesis and characterization of previously unknown sulfur-containing products from the reaction of mucochloric acid (3,4-dichloro-5-hydroxy-2(5H)- furanone) and its 5-alkoxy derivatives with 1,2-ethanedithiol is reported. Under basic and acidic cond

Full text of DOI:10.1016/j.tet.2010.10.047

Tetrahedron 66 (2010) 9945e9953
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Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Structural diversity of interaction products of mucochloric acid and its derivatives
with 1,2-ethanedithiol
,
b
a
a
Almira R. Kurbangalieva a , Olga A. Lodochnikova , Nadezhda F. Devyatova , Evgeny A. Berdnikov ,
*
Oleg I. Gnezdilov c, Igor A. Litvinov b, Galina A. Chmutova a
a A.M. Butlerov Chemical Institute at Kazan Federal University, Kremlyovskaya St. 18, Kazan 420008, Russian Federation
b A.E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Center of the Russian Academy of Sciences, Arbuzov St. 8, Kazan 420088, Russian Federation
c E.K. Zavoisky PhysicaleTechnical Institute, Kazan Scientific Center of the Russian Academy of Sciences, Sibirsky tract, 10/7, Kazan 420029, Russian Federation
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 26 July 2010
Received in revised form 25 September 2010
Accepted 18 October 2010
Available online 22 November 2010
The synthesis and characterization of previously unknown sulfur-containing products from the reaction
of mucochloric acid (3,4-dichloro-5-hydroxy-2(5H)-furanone) and its 5-alkoxy derivatives with 1,2-
ethanedithiol is reported. Under basic and acidic conditions both SH-groups of the reagent show nu-
cleophilic activity, leading to the formation of substitution products of different structural types. Novel
fused (7-hydroxy-2,3-dihydro[1,4]dithiino[2,3-c]furan-5(7H)-one) and spiro (9-chloro-6-methoxy-7-
oxa-1,4-dithiaspiro[4.4]nonan-8-one) bicyclic compounds, as well as various bis-thioethers have been
obtained and characterized by NMR spectroscopy and single crystal X-ray diffraction.
Ó 2010 Elsevier Ltd. All rights reserved.
Dedicated to the memory of Dr. Alexander I.
Movchan
Keywords:
Mucochloric acid
Lactones
2(5H)-Furanones
1,2-Ethanedithiol
Sulfur heterocycles
Diastereomers
1. Introduction
O
O
2
Cl
Cl
Cl
Cl
2(5H)-Furanone derivatives are naturally occurring and ex-
tremely useful heterocyclic compounds in various branches of
medicine, agriculture, technology, and organic synthesis.1 One of
3
4
OH
H
O
5
OH
H
O
1b
the most important representatives of unsaturated
g-lactones is
1a
mucochloric acid (3,4-dichloro-5-hydroxy-2(5H)-furanone),
1
well-known as a commercially available starting material with
a range of reactivity.2 Due to the propensity of compound 1 for
cycle-chain tautomerism2,3 (Fig. 1) and the presence of different
reaction centers, this heterocycle is widely used as a versatile
building block for the preparation of a variety of interesting
compounds.
Despite the large number of publications devoted to reactions of
1 and its derivatives with O-, N-, C-, and P-nucleophiles, the re-
activity toward sulfur-containing reagents is scarcely explored.4e8
Recently, in connection with our ongoing projects related to the
Fig. 1. Cycle-chain tautomerism of mucochloric acid 1.
synthesis and investigation of the structure and properties of sul-
fur- and selenium-containing derivatives of chemically and bi-
ologically active heterocycles, we have studied reactions of 1 and
some of its ethers and thioethers with various thiols,9e11 and
selenophenols.12 It was shown that by conducting reactions of 1
with thiols under basic or acidic conditions it is possible to selec-
tively introduce different SR groups into specific positions of the g-
lactone ring (atoms C(3), C(4), and C(5)) and to obtain pure
regioisomers of thioethers of the 2(5H)-furanone series.9,12
In a further effort to reveal the potential of 1 as a useful building
block for the synthesis of new sulfur heterocycles, we initiated
* Corresponding author. Tel.: þ7 843 233 7462; fax: þ7 843 233 7416; e-mail
a
study into the reactivity of 1 toward sulfur-containing
address: almira.kurbangalieva@ksu.ru (A.R. Kurbangalieva).
0040-4020/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2010.10.047

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A.R. Kurbangalieva et al. / Tetrahedron 66 (2010) 9945e9953
binucleophilic reagents, which are very attractive for the synthesis
of both mono- and bicyclic 2(5H)-furanone based products. To the
best of our knowledge there are only a few reports in the literature
of the use of 3,4-dihalo-2(5H)-furanones in the construction of
sulfur-containing heterocyclic compounds (Fig. 2).10,13,14
(6.45 ppm), a broad signal for the proton of the hydroxy group
(4.0e5.5 ppm), and a multiplet for the methylene protons, char-
acteristic for the AA0BB0 spin system in the range of 3.1e3.5 ppm.
Structure determination by single crystal X-ray diffraction identi-
fied
3 as 2,3-dichloro-3-(1,3-dithiolan-2-yl)prop-2-enoic acid
(Fig. 3). According to the X-ray data the five-membered ring of 3 in
the crystal has an ‘envelope’ conformation: the S(8)C(4)S(5)C(6)
fragment is planar within 0.02 Ǻ, the atom C(7) deviates from the
plane by 0.648(7) Ǻ. In the crystal, pairs of molecules are linked
through strong hydrogen bonds between the carboxyl groups to
form dimers. The parameters of the O(2)eH(2).O(1) hydrogen
bonds are: P(2)eO(2) 0.91(9) Ǻ, O(2).O(1) 2.621(8) Ǻ, H(2).O(1)
1.72(10) Ǻ, :O(2)eH(2).O(1) 172(10)ꢁ.
O
O
O
S
S
S
S
Cl
S
Cl
Cl
O
O
O
N
CHCOOR
C(CH3)2
H OCH3
S
O
Fig. 2. Sulfur-containing fused heterocycles derived from substituted 2(5H)-furanones.
In this study, we have allowed 1 and its 5-alkoxy derivatives to
react with 1,2-ethanedithiol under basic and acidic catalytic con-
ditions, and observed the formation of previously unknown sulfur-
containing compounds.
2. Results and discussion
Previously, it was shown that in the presence of acids,
mucochloric acid 1 and some of its derivatives react with S-nucle-
ophiles with the substitution of the hydroxy group at the C(5) atom
of the lactone ring.6,8,9 Reaction of 1 with 1,2-ethanedithiol was
examined in the presence of concentrated sulfuric acid (from 2 to
30 mol %) and p-toluenesulfonic acid, as well as in polyphosphoric
acid medium. We also conducted a series of experiments using
various proportions of reagents and different heating times in order
to optimize the reaction conditions. Two stable products 2 and 3
were isolated in all cases in nearly the same yields (Scheme 1).
Fig. 3. A fragment of crystal packing in the crystal of compound 3.
O
O
HS
O
SH
Cl
Cl
Cl
OH
S
Cl
O
O
H2SO 4,
benzene
Cl
Cl
H S
O
S
3
S
H
47%
Cl
Cl
25 O
3
4
2
39%
1. p-TolSH
O
O
H
OH
HS
O
p-TolS
p-TolS
SH
H2SO4,
aq. KOH
1
STol-p
Cl
O
O
O
Cl
Cl
2. HCl
H
H S
OH
benzene
S
H
70%
4
5
68%
Scheme 1. Reactions of 1 and thioether 4 with 1,2-ethanedithiol in an acidic medium.
IR and NMR spectroscopic analysis indicated the absence of free
OH- and SH-groups in product 2. The 1H NMR spectrum of 2 in
acetone-d6 displays two singlets of equal intensity for the methine
proton at 6.59 and 6.60 ppm and two AA0BB0 multiplets for the
methylene protons in the range of 2.99e3.10 ppm, that provides
evidence for the formation of two diastereomers in a 1:1 ratio. The
results of the elemental analysis and mass spectrometry confirmed
the proposed structure of the bis-thioether 2. It is notable that the
similar compound with the eOeCH2eCH2eSe chain, connecting
two 2(5H)-furanone units, has been described previously as the
only product of the reaction of 1 with 2-mercaptoethanol under
acidic conditions.6,10
We assume that the reaction of 1 with 1,2-ethanedithiol in an
acidic medium proceeds according to the following mechanism
(Scheme 2):
Under acidic conditions, the increasing electrophilicity of atom
C(5) in the protonated form of mucochloric acid directs the nu-
cleophilic attack of 1,2-ethanedithiol to this position of the lactone
ring, which is followed by the elimination of a water molecule and
of a proton to form the product of monosubstitution (A). Pre-
sumably, after the protonation of the carbonyl oxygen of com-
pound (A) an attack of the second sulfur atom onto the electron
deficient carbon atom and proton elimination occur, thus,
dithiolanylprop-2-enoic acid 3 may be formed. Bis-thioether 2
may be generated as the result of the attack of the thiol group in
the compound (A) at the carbon atom C(5) in the protonated form
of mucochloric acid (Scheme 2).
There is no furanone ring in the second product 3 according to
the spectroscopic data. In the IR spectrum of compound 3, the
absorption band of the g-lactone carbonyl group is not observed
and instead, a narrow intense band appeared at 1688 cmꢀ1 typical
for the stretching vibrations of the C]O group of carboxylic acids in
the dimer state. In the 1H NMR spectrum of the compound 3 in
DMSO-d6 there is a singlet for the proton at the saturated carbon
Interestingly, a similar reaction of 1,2-ethanedithiol with fur-
anone 4, obtained from the reaction of 1 with 4-methylthiophenol
in alkaline medium,9 required more prolonged heating; the only
product isolated from this reaction was bis-thioether 5 (Scheme 1).

A.R. Kurbangalieva et al. / Tetrahedron 66 (2010) 9945e9953
9947
It should be noted that bicyclic product 6 was also isolated from
the reaction of compound 1 with 1,2-ethanedithiol under conditions
in which phenols,15 thiophenols,9 and 2-mercaptoacetic acid11 give
O
O
O
HS
Cl
Cl
Cl
Cl
Cl
Cl
H
SH
SH
O
O
O
SH
-H3O
substitution of the chlorine atom in the 3-position of the g-lactone
H
S
H
A
OH
OH
H
2
ring (aqueous solution of potassium hydroxide and subsequent
acidification of the reaction mixture). However, the reactions carried
out in the presence of base (triethylamine or potassium hydroxide)
are accompanied byconsiderable polymerization, that decreases the
yield of pure final product 6. The TLC analysis of reaction mixtures
showed that the only reaction product is compound 6.
Bicycle 6 undergoes an intermolecular dehydratation by heating
in benzene in the presence of catalytic amounts of sulfuric acid and
gives the compound 7 (Scheme 3). The IR spectrum of 7 shows the
absorption band of the lactone carbonyl group at 1748 cmꢀ1 and
a band of medium intensity at 1618 cmꢀ1, assigned to the stretching
vibrations of the C]C bond of the furanone ring. As evidenced by
1H NMR spectrum, which displays two singlets for the methine
proton at C(5) at 6.35 and 6.40 ppm, and two multiplets for the two
different ABCD spin systems of the methylene protons in the range
of 3.33e3.50 ppm, the compound 7 is present as a 1:1 mixture of
diastereomers.
1
H
O
O
O
Cl
Cl
Cl
Cl
Cl
Cl
H
OH
S
O
O
- H
SH
S
H
S
H
S
3
A
O
O
O
O
Cl
Cl
Cl
Cl
Cl
Cl
O
Cl
Cl
O
S
O
O
S
HS
-H3O
OH
S
H
H
H
2
H
A
2
Scheme 2. Proposed mechanism of the reaction in an acidic medium.
It is known that reactions of 1 with aliphatic and aromatic
thiols,4,7,9 2-mercaptoethanol,10 and2-mercaptoaceticacid,11 carried
out in acetone or diethyl ether in the presence of triethylamine, lead
to the formation of the products resulting from substitution of the
Interesting results were obtained in the reactions of 1,2-etha-
nedithiol with 5-alkoxy derivatives of mucochloric acid 8e10 in the
presence of triethylamine. While mucochloric acid 1 itself gives
bicyclic compound 6, reactions of 8e10 resulted in the formation
chlorine atom in the 4-position of the g-lactone ring. Under the same
conditions, reaction with 1,2-ethanedithiol results in substitution of
both of the chlorine atoms in the molecule of mucochloric acid 1 and
forms a novel bicyclic compound 6 (Scheme 3).
of 11e13 that combine
a bis-thioether moiety and two 2
(5H)-furanone fragments bridged through their carbon atoms S(4)
(Scheme 4). Judging from the 1H and 13C NMR spectra of the re-
O
O
O
O
HS
S
S
S
S
S
S
Cl
Cl
H2SO4
SH
O
O
O O
benzene
Et3N , acetone
or aq. KOH
O
H OH
OH
H
H
H
1
35-43%
6
7
84%
Scheme 3. Synthesis of 7-hydroxy-2,3-dihydro[1,4]dithiino[2,3-c]furan-5(7H)-one (6) and its anhydride 7.
In the 1H NMR spectrum of product 6 there are two doublets
action mixtures, bis-thioethers 11e13 are formed as 1:1 mixtures
of diastereomers. The ratio can be clearly evaluated from the 1H
NMR spectra of the methine protons at carbon atom C(5) of the
lactone ring by integration of the respective signals.
for the proton of the hydroxy group and for the methine proton
at 7.00 and 6.13 ppm, respectively, as well as a multiplet for the
ABCD spin system of the methylene protons in the range of
3.2e3.5 ppm. Compound 6 is the first representative of a new
type of the sulfur-containing fused bicyclic systemse2,3-dihydro
[1,4]dithiino[2,3-c]furan-5(7H)-ones. The structure was also de-
termined by single crystal X-ray diffraction. According to the
X-ray data, the six-membered ring of the molecule 6 is charac-
terized by the half-chair conformation (Fig. 4a). The S(1)C(8)C(9)
S(4) fragment is planar, the deviation of S(2) and S(3) atoms
from the plane is e0.290(4) Ǻ and 0.477(4) Ǻ, correspondingly.
The molecules of 6 in the crystal form infinite chains via hy-
drogen bonds H(1).P(5) 2.09(5) Ǻ, O(7).O(5) 2.811(4) Ǻ, :O
(7)eH(1).O(5) 162(4)ꢁ (Fig. 4b).
In the case of products 11 and 12, the diastereomeric mixtures
were separated into the individual components (meso 11a, 12a, and
DL 11b,12b) byfractionated crystallization fromtetrachloromethane.
The meso isomer 13a of isopropoxy derivative was also separated;
however, we have not managed to isolate the DL isomer 13b in pure
form. The individual diastereomeric forms of bis-thioethers 11e13
were characterized by 1H and 13C NMR spectroscopy; the chemical
shifts and all spinespin coupling constants are given in Section 3.3.
The methylene protons of the eSCH2CH2Se moiety form an
AA0BB0 spin system, giving rise to a pair of complex multiplets in the
1H NMR spectra of compounds 12 and 13. Spinespin coupling
Fig. 4. a) Molecular structure of compound 6 in the crystal. (b) The hydrogen bonding scheme for 6.

9948
A.R. Kurbangalieva et al. / Tetrahedron 66 (2010) 9945e9953
O
O
SHCH2CH2SH (0.5 mol)
Et3N (1 mol), acetone
8, 11 (73%) R = CH3
9, 12 (64%) R = C2H5
Cl
S
Cl
S
O
O
10, 13
(87%) R = CH(CH3)2
RO H
O
H OR
Cl
Cl
11-13
O
SHCH2CH2SH (1 mol)
H OR
8-10
O
O
O
H
O
Cl
Cl
S
8
for
Cl
S
S
O
O
Et3N (1 mol), acetone
S
H3COH
HOCH3
14 24%
HOCH3
11 39%
Scheme 4. Reactions of 5-alkoxy derivatives 8e10 with 1,2-ethanedithiol.
constants observed for meso isomers 12a and 13a are equal to
associatedwiththesulfuratom;atthesametimecorrespondingbond
lengths and bond angles are equal in all three molecules.
0
0
0
0
0
0
JAA ¼JBB ¼9.0 Hz, JAB¼JA B ¼ꢀ13.9 Hz, JA B¼JAB ¼6.0 Hz; and non-
equivalence of the diastereotopic methylene protons A and B is
Dd¼0.03 ppm. It is noteworthy that the 1H NMR spectra of the
methoxy derivatives 11, 11a, and 11b contain signals for the
eSCH2CH2Se protons in the form of a broad singlet due to very
small nonequivalence of the diastereotopic protons. A comparison
of the 1H NMR spectroscopic data for the two diastereomeric forms
of bis-thioethers 11e13 indicates that in the meso isomers, the
observed chemical shift of the methine proton at C(5) in the range
6.32e6.42 ppm is slightly lower than those of the DL isomers.
Isolated diastereomers of bis-thioethers 11e13 were crystallized
and their crystal structures were studied in detail by X-ray single
diffraction. Molecules of five isomers 11a, 11b, 12a, 12b, and 13a
were crystallized in different conformations, and the crystals were
of different shape and symmetry. Unusually the meso diastereomer
11a forms a clathrate with carbon tetrachloride in the trigonal
crystal system (space group Re3), in contrast bis-thioethers 11b,
12a, 12b, and 13a crystallize without incorporation of solvent in the
triclinic or monoclinic system (space groups Pꢀ1, P21/c, C2/c, P21/n,
respectively).
There are no centrosymmetric conformations for DL di-
astereomers, therefore they crystallize in a different way to that of
the meso isomers. Thus, 11b occupies the general position in the
crystal, and 12b is in a special position on the two-fold axis. Unlike
the other four isomers, 12b in the crystal adopts a gauche confor-
mation around the central C(6)eC(6)’ bond with the heterocyclic
fragments spatially close to each other (Fig. 7).
X-ray structure analysis revealed that meso diastereomer 11a in
contrast to the other studied molecules has unusual packing in the
crystal, forming a true clathrate with tetrachloromethane in host/
guest ratio¼3:1 (Fig. 8). The host molecules via SeH.O hydrogen
bonds form a three-dimensional associate with threefold sym-
metric channels, parallel to the c-axis, and the guest molecules are
situated on the trigonal axis and disordered over two equal posi-
tions, one atom of chlorine is exactly at the center of inversion.
The literature contains afewexamples of similar three-dimensional
associates, having a cavity filled with guest molecules, including CCl4,
CHCl3, however, host molecules are connected by classical hydrogen
bonds.16e18 The major difference between clathrate CCl4/11a and
the structures described earlier, is that the walls of the 3D channels in
clathrate CCl4/11a are linked together via CeH.O interactions.
The hydrogen atom at atom C(5) and the oxygen atom O(2) of the
carbonyl group participate in hydrogen bonding, each bis-thioether
molecule is found to be connected with four neighboring molecules,
The crystals of individual diastereomers grown under identical
conditions from the tetrachloromethane solution have different
forms: compound 11a crystallizes in the form of hexagonal prisms,
11bdplates, 12adplates, 12bdcubic prisms and 13adrounded
plates. Photographs of the crystals obtained are shown in Fig. 5.
Fig. 5. Photographs of the crystals of individual diastereomers grown from the tetrachloromethane solution: (a) 11a, (b) 11b, (c) 12a, (d) 12b, (e) 13a.
The molecules of all three meso forms (11a, 12a, 13a) in the
crystals were in the special position in the center of symmetry (in
the center of bonds C(6)eC(6)’), and as a result one half of mole-
cules was crystallographically independent. The conformational
flexibility of the eSCH2CH2Se fragments allows the molecules 11a,
12a, 13a to adopt different conformations in the crystal (Fig. 6).
Atoms Cl(1) and C(6) of the molecules 11a and 13a are in an anti-
orientation, in the case of molecule 12a a syn-orientation is observed.
Considering the spatial arrangement of structural fragments relative
to the plane of one of the five-membered rings, the alkoxy-group and
second 2(5H)-furanone ring lie on one side of the plane in the mol-
ecule 11a, and on the other side in the molecule 12a. In the molecule
13a both five-membered rings and the bis-thioether fragment are all
situated in one plane. The aforementioned conformational differ-
ences become apparent only in a variation of the torsion angles
that apparently provide sufficient stabilization of the channel walls.
The parameters of the C(5)eH(5).O(2) hydrogen bonds are as fol-
lows: S(5)eO(5) 0.92 Ǻ, S(5).O(2) 3.426(4) Ǻ, H(5).O(2) 2.47 Ǻ,
:S(5)eH(5).O(2) 164ꢁ.
Reactions of 5-alkoxy derivatives of mucochloric acid 8e10 with
1,2-ethanedithiol in the presence of triethylamine were carried out
under different ratios of reagents. Bis-thioethers 11e13 were the
only products formed using a ratio of ether/1,2-ethanedithiol/
triethylamine of 2:1:2. The same compounds were isolated from
the reactions of ethers 9 and 10 with 1,2-ethanedithiol with re-
agents in a 1:1:1 ratio. However, two products, bis-thioether 11 and
the novel spiro compound 14, were obtained in the case of the
methoxy derivative 8 and an equimolar reagent ratio (Scheme 4).
The 1H NMR spectrum of the isolated compound 14 shows the
presence of one diastereomer. Since other possible diastereomer

A.R. Kurbangalieva et al. / Tetrahedron 66 (2010) 9945e9953
9949
Fig. 6. Molecular structure of meso isomers in the crystal: (a) 11a, (b) 12a, (c) 13a.
Fig. 7. Molecular structure of DL isomers in the crystal: (a) 11b, (b) 12b.
was not detected in the reaction mixture, the formation of spi-
rocyclic compound 14 is likely to occur stereospecifically.
As a mechanism for the observed formation of the unexpected
product 14, we can propose an initial nucleophilic substitution of
the chlorine atom at the 4-position by the 1,2-ethanedithiol,
followed by addition of the free sulfhydryl group to the olefinic
double bond of furanone ring to give spiro bicyclic compound 14
(Scheme 5). Understandably, bis-thioethers 11e13 are formed as
a result of interaction of both SH-groups of S,S-binucleophile with
two molecules of alkoxy derivatives 8e10.

9950
A.R. Kurbangalieva et al. / Tetrahedron 66 (2010) 9945e9953
Fig. 9. Molecular structure of bicycle 14 in the crystal (R,R-isomer is shown).
11e13 were obtained under basic and acidic conditions. The di-
astereomeric mixtures 11e13 were separated into the individual
components by fractional crystallization. The molecular and crystal
structure of eight sulfur-containing compounds derived from
mucochloric acid were studied by single crystal X-ray diffraction.
Fig. 8. The fragment of the crystal packing of 11a; projection is on the z0 plane. The
CeH.O interactions are shown as dashed lines.
O
O
O
H
Cl
Cl
SH
Cl
S
,
Et3N
HS
HS
O
O
O
S
HS
Cl
- Et3NHCl
S
H
H3CO H
8
H
OCH3
OCH3
14
O
O
O
O
Cl
Cl
Et3N
Cl
S
Cl
S
Cl
S
O
O
H3CO H
8
O
O
- Et3NHCl
H3CO H
OCH3
H
H
OCH3
11
Scheme 5. A possible mechanism for the formation of compounds 11e13 and 14.
According to the X-ray data, spiro adduct 14 is represented by the
RR,SS-diastereomer in the examined crystal. The five-membered
lactone exists in an ‘envelope’ conformation, the C(6)O(7)C(8)C(9)
fragment is planar within 0.002(3) Ǻ, the atom C(5) deviates from the
plane by 0.675(3) Ǻ (Fig. 9). The atoms C(2) and C(3) of the sulfur-
containing heterocycle are disordered over two positions with equal
occupancy, that correspond to the coexistence of two ‘envelope’
conformations for this five-membered cycle in the crystal. One con-
formation is characterized by the planar S(1)C(5)S(4)C(3B) fragment
(within 0.016(3) Ǻ) with deviation of C(2B) atom from the plane of
0.77(2) Ǻ, and second one has the planar S(4)C(5)S(1)C(2A) fragment
(within 0.042(3) Ǻ) with deviation of C(3A) atom of 0.64(2) Ǻ.
In conclusion, we have reported that the utilization of 1,2-etha-
nedithiol in the reactions with 1 and its derivatives allows us to sig-
nificantly expand the synthetic resources of mucochloric acid and to
obtain previously unknown sulfur heterocycles. In all experiments
performed under various conditions, both SH-groups of the reagent
show a nucleophilic activity, leading to the formation of substitution
products of different structural types; compounds with free thiol
group have not been detected. Novel sulfur-containing fused 6, 7 and
spiro 14 bicyclic compounds, and the product of the lactone ring-
opening reaction 3 were described. Several bis-thioethers with
a eSCH2CH2Se chain, connecting two 2(5H)-furanone units 2, 5,
3. Experimental section
3.1. General
IR spectra were recorded on a SpecordeM80 spectrometer in
a solid state (in Nujol); the thickness of cell was d¼0.1e0.12 mm.
NMR spectra were obtained on a Varian Unitye300 spectrometer at
299.94 MHz (1H) and a Bruker Avancee400 spectrometer at
400.13 MHz (1H), and 100.62 MHz (13C) at 25ꢁS with acetone-d6
taken as internal standard. Thin-layer chromatography was per-
formed using Silufol UV-254 plates (Kavalier, Czech Republic), ace-
toneebenzene 1:5 mixture was used as the eluent. Spots were
visualized with a UV lamp at 254 nm or iodine vapor. Silica gel 60
(Fluka, 70e230 mesh, 0.063e0.200 mm) was used for open column
chromatography. The melting points were measured on a Boetius
hot stage and were not corrected. Mucochloric acid 1 (Shostka
Chemical Reagents Plant, Ukraine) was commercially available and
was further recrystallized from water, mp 127 ꢁS. TLC Rf 0.62.
4-Chloro-5-hydroxy-3-(4-methylphenylsulfanyl)-2(5H)-furanone9
(4), 3,4-dichloro-5-methoxy-2(5H)-furanone19 (8), 3,4-dichloro-5-
ethoxy-2(5H)-furanone20 (9), 3,4-dichloro-5-isopropoxy-2(5H)-
furanone19 (10) were synthesized according to the known methods.
All solvents were purified and distilled by standard procedures.

A.R. Kurbangalieva et al. / Tetrahedron 66 (2010) 9945e9953
9951
3
3
3
3
0
0
0
0
0
0
3.2. X-ray structure determinations
JAA ¼ JAB ¼ JA B¼ JBB ¼6.0 Hz, 4O, eSSOAOBeSOA OB Se), 4.0e5.5
(br s, 1O, PO), 6.45 (s, 1O, SeO) ppm. 13S NMR (75 MHz, DMSO-
d6): 52.38 (CH2), 65.38 (SO2), 101.84 (S(4)eO), 123.41 (C(2)eCl),
The X-ray diffraction data for the crystals of 3, 6, and 14 were
collected on a CAD 4 EnrafeNonius automatic diffractometer using
graphite monochromated radiation, and for the crystals 11a, 11b,
12a, 12b, and 13a on a Smart Apex II automatic diffractometer using
graphite monochromated radiation. The structures were solved by
direct methods using the SIR21 program and refined by full-matrix
least-squares using SHELXL9722 program. All the non-hydrogen
atoms were refined with anisotropic atomic displacement param-
eters. H atoms bonded to carbon were constrained as riding atoms,
with CeH set to 0.95 Ǻ. The hydroxy H atoms were located from
a difference Fourier map and the OeH bond length set to 0.85 Ǻ.
The molecules 11a,12a,13a in the crystals are in the special position
in the center of symmetry, the molecule 11b occupies the general
position in the crystal, and the molecule 12b is in a special position
on the two-fold axis. The SSl4 molecules in the crystal 11a are
situated on the trigonal axis and disordered over two equal posi-
tions, one atom of chlorine is exactly at the center of inversion. All
figures were made using the program PLATON.23 Crystallographic
data (excluding structure factors) for the structures 3, 6, 11a, 11b,
12a, 12b, 13a, 14 reported in this paper have been deposited with
the Cambridge Crystallographic Data Center as supplementary
publication numbers CCDC 611247, 611248, 720830, 720831,
720828, 720832, 720829, and 720827, respectively. Copies of the
data can be obtained, free of charge, on application to CCDC, 12
Union Road, Cambridge CB2 1EZ, UK, (fax: þ44 (0)1223 336033 or
e-mail: deposit@ccdc.cam.ac.uk).
d
153.12 (S(3)eCl), 163.31 (S(1)]P) ppm. C6H6Cl2O2S2 (245.15):
calcd. C 29.40, H 2.47, Cl 28.92, S 26.16; found C 29.62, H 2.38, Cl
29.03, S 26.02.
3.3.2. 5,50-(Ethane-1,2-diyldisulfanediyl)bis[4-chloro-3-(4-methyl-
phenyl-sulfanyl)furan-2(5H)-one] (5). A solution of compound 4
(1.00 g, 3.9 mmol), 1,2-ethanedithiol (0.16 mL, 1.95 mmol), and
concentrated sulfuric acid (0.02 mL) in benzene (35 mL) was
refluxed in a round-bottom flask supplied with a reflux condenser
and adapter for the azeotropic evaporation of water for 30 h. After
cooling, the reaction mixture was evaporated to dryness under
reduced pressure, and the brown oily residue was purified by col-
umn chromatography (acetoneebenzene, 1:5). From the first non-
polar fraction, product 5 was obtained as a 1:1 mixture of di-
astereomers and recrystallized from tetrachloromethane to yield
0.75 g (68%) of a white precipitate. The second fraction contained
unreacted starting material
147e149 ꢁC. TLC Rf 0.82. IR
: 1760 (S]P), 1592 (S]Slactone), 1491
(C]Carom) cmꢀ1 1H NMR (300 MHz, acetone-d6):
2.33 (s, 12H,
4 (0.12 g, 12% recovery). Mp
n
.
d
CH3), 2.91e2.95 (m, 8O, eSO2SO2e), 6.46 (s, 2O, S(5)eO), 6.47 (s,
2O, S(5)eO), 7.21, 7.40 (AA0BB0, N¼8.0 Hz, 16H, Harom) ppm.
C24H20Cl2O4S4 (571.58): calcd. C 50.43, H 3.53, Cl 12.41, S 22.44;
found C 50.36, H 3.57, Cl 12.44, S 22.44.
3.3.3. 7-Hydroxy-2,3-dihydro[1,4]dithiino[2,3-c]furan-5(7H)-one
(6). The compound 6 was obtained by two methods:
3.3. General procedure of the synthesis of compounds 2, 3,
5e7, 11e14
Method A. To
5.9 mmol) in absolute acetone (10 mL) with intense stirring was
added dropwise solution of 1,2-ethanedithiol (0.50 mL,
a solution of mucochloric acid 1 (1.00 g,
a
3.3.1. 5,50-(Ethane-1,2-diyldisulfanediyl)bis(3,4-dichlorofuran-2(5H)-
one) (2) and (2Z)-2,3-dichloro-3-(1,3-dithiolan-2-yl)prop-2-enoic
acid (3). A solution of mucochloric acid 1 (1.50 g, 8.9 mmol), 1,2-
ethanedithiol (0.74 mL, 8.9 mmol), and concentrated sulfuric acid
(0.05 mL) in benzene (35 mL) was heated at reflux for 3 h, the water
produced being removed by means of a DeaneStark apparatus. A
purple precipitate was formed during the reaction. After cooling of
the reaction mixture to room temperature the purple precipitate
was filtered off. The benzene solution was washed with water until
neutral, then dried over MgSO4. The solution was concentrated
down to a small volume, and a light yellow precipitate was thus
obtained. Both isolated precipitates contain two substances
according to the TLC analysis. Purple and light yellow precipitates
were combined and multiply washed with acetone at room tem-
perature. Thus, practically insoluble in acetone compound 2 as a 1:1
mixture of diastereomers (measured by 1H NMR spectroscopy) and
readily soluble in acetone compound 3 were separated from each
other.
5.9 mmol) in acetone (8 mL), and a solution of triethylamine
(0.82 mL, 5.9 mmol) in acetone (4 mL). The reaction mixture was
refluxed for 6 h and the formation of a white precipitate of
(S2O5)3N$OSl was observed. The precipitate was filtered off and
washed with acetone. The combined filtrates were evaporated to
dryness and the obtained oil was purified by column chromatog-
raphy (acetoneebenzene, 1:4). Evaporation of the main fraction,
followed by recrystallization from water gave 6 (0.48 g, 43%) as
colorless crystals.
Method B. To a solution of mucochloric acid (1.50 g, 8.9 mmol)
and potassium hydroxide (0.50 g, 8.9 mmol) in water (10 mL) was
added slowly with intense stirring a solution of 1,2-ethanedithiol
(0.74 mL, 8.9 mmol), and potassium hydroxide (0.50 g, 8.9 mmol) in
water (7 mL). An additional amount of KOH (0.25 g, 4.5 mmol) was
added to the reaction mixture to bring up the pH (z10) and the
stirring was continued for 2 h at room temperature. The solution
was acidified with diluted hydrochloric acid to about pH¼2e3 and
further evaporated to dryness. The obtained dark oil was washed
with acetone and thus isolated precipitate of potassium chloride
was filtered off. After evaporating the acetone the resulting residue
was recrystallized from carbon tetrachloride to afford 6 (0.59 g,
Compound (2). White solid, yield 0.55 g (47%), mp 174e178 ꢁC.
TLC Rf 0.83. IR n
: 1792 (S]P), 1628 (S]Slactone) cmꢀ1. EIMS: m/
z¼395.9 [M]þ. 1H NMR (300 MHz, acetone-d6):
d 2.99e3.10 (m, 8O,
eSSO2eSO2Se), 6.59 (s, 2O, S(5)eO), 6.60 (s, 2O, S(5)eO) ppm.
C10H6Cl4O4S2 (396.10): calcd. C 30.32, H 1.53, Cl 35.80, S 16.19;
found C 30.48, H 1.67, Cl 35.75, S 16.20. When the diastereomeric
mixture 2 was heated under reflux with chloroform and the in-
soluble part was filtered off, one diastereomer as a white powder
was obtained from the filtrate. Mp 175e176 ꢁC. 1H NMR (300 MHz,
35%), mp 147e148 ꢁC. TLC Rf 0.52. IR
n: 3344 (PO), 1728 (S]P),
1648 (S]Slactone
)
cmꢀ1 1H NMR (300 MHz, acetone-d6):
.
d
3.25e3.35 (m, 2H, eSO2eS), 3.36e3.45 (m, 2H, eSO2eS), 6.13 (d,
3JO,O¼8.7 Hz, 1H, S(5)eH), 7.00 (d, JO,O¼8.7 Hz, 1H, PO) ppm.
C6H6O3S2 (190.24): calcd. C 37.88, H 3.18, S 33.71; found C 38.11, H
3.08, S 33.65.
3
2
3
3
0
0
0
0
acetone-d6):
d
3.03, 3.06 (m, 2JAB¼ JA B ¼e13.9 Hz, JAB ¼ JA B¼6.1 Hz,
3
3
JAA ¼ JBB ¼9.0 Hz, 4O, eSSOAOBeSOA OB Se), 6.59 (s, 1O, S(5)eO)
3.3.4. 7,70-Oxybis(2,3-dihydro[1,4]dithiino[2,3-c]furan-5(7H)-one)
(7). A solution containing compound 6 (92 mg, 0.48 mmol) and one
drop of concentrated sulfuric acid in benzene (25 mL) was heated at
reflux for 2 h, the water produced being removed by means of
a DeaneStark apparatus. The cooled reaction mixture was washed
with water until neutral, then dried over MgSO4. The solvent was
0
0
0
0
ppm.
Compound (3). White crystalline solid, yield 0.28 g (39%), mp
166e167 ꢁC (recrystallized from benzene). TLC Rf 0.49. IR
3300e3100 (br, PO), 1688 (S]P), 1548 (S]S) cmꢀ1 1H NMR
3.24, 3.40 (m, JAB¼ JA B ¼ꢀ9.0 Hz,
n
:
.
2
2
0
0
(300 MHz, DMSO-d6):
d

9952
A.R. Kurbangalieva et al. / Tetrahedron 66 (2010) 9945e9953
evaporated to dryness, and the residue was recrystallized from
(5)eH) ppm. 13S {1H} NMR (100 MHz, acetone-d6):
32.21 (SCH2), 66.90 (OCH2), 102.50 (S(5)), 119.21 (C(3)), 156.78
(S(4)), 165.45 (S(2)) ppm.
d
¼16.34 (CH3),
benzeneepetroleum ether mixture to give 7 (74 mg, yield 84%) as
a white solid. Mp 165e166 ꢁC. TLC Rf 0.35. IR
n
: 1748 (S]P), 1618
(S]Slactone) cmꢀ1. 1H NMR (300 MHz, acetone-d6):
d
3.33e3.39 (m,
4H, eSO2eS), 3.44e3.50 (m, 4H, eSO2eS), 6.35, 6.40 (s, 2H, (5)eH)
ppm. C12H10O5S4 (362.47): calcd. C 39.76, H 2.78, S 35.39; found C
39.88, H 2.64, S 35.37.
3.3.7. 4,40-(Ethane-1,2-diyldisulfanediyl)bis(3-chloro-5-iso-
propoxyfuran-2(5H)-one) (13). Compound 13 was synthesized as
described above for compound 11 from isopropoxyfuranone 10
(1.00 g, 4.7 mmol) and 1,2-ethanedithiol (0.20 mL, 2.35 mmol) in
the presence of triethylamine (0.66 mL, 4.70 mmol). Re-
crystallization from mixture of tetrachloromethane and hexane
(4:1) afforded a crystal sample of 13 (0.91 g, 87%) as a 1:1 mixture of
diastereomers (measured by 1H NMR spectroscopy).
3.3.5. 4,40-(Ethane-1,2-diyldisulfanediyl)bis(3-chloro-5-methoxy-
furan-2(5H)-one) (11). 1,2-Ethanedithiol (0.23 mL, 2.73 mmol) and
triethylamine (0.76 mL, 5.46 mmol) were added to a stirred solu-
tion of ether 8 (1.00 g, 5.46 mmol) in acetone (15 mL). The reaction
mixture was refluxed for 2 h. The precipitate of (S2O5)3N$OSl was
filtered off and washed with acetone. The combined filtrates were
evaporated to dryness and the obtained yellow oil was purified by
column chromatography (acetoneebenzene, 1:5). Evaporation of
the main fraction, followed by recrystallization from a mixture of
tetrachloromethane and benzene (3:1) afforded a crystal sample of
11 (0.77 g, 73%) as a 1:1 mixture of diastereomers (measured by 1H
NMR spectroscopy). The separation of two diastereomers is de-
scribed below.
Compound 13 mp 147e154 ꢁC. TLC Rf 0.71. 1H NMR (400 MHz,
acetone-d6):
d
1.29 (d, 3JO,O¼6.1 Hz,12O, SH3),1.34 (d, 3JO,O¼6.1 Hz,
12O, SH3), 3.57e3.73 (m, 8O, eSO2Se), 4.25 (septet, 3JO,O¼6.1 Hz,
4H, OCH), 6.406 (s, 2H, S(5)eH), 6.417 (s, 2H, S(5)eH) ppm. 13S
{1H} NMR (100 MHz, acetone-d6):
d 23.40, 23.41, 24.53, 24.54 (CH3),
32.00, 32.05 (SCH2), 75.73, 75.75 (OSO), 101.82, 101.83 (S(5)),
119.50, 119.64 (C(3)), 156.62, 156.77 (S(4)), 165.52, 165.53 (S(2))
ppm. C16H20Cl2O6S2 (443.36): calcd. C 43.34, H 4.55, Cl 15.99, S
14.46; found C 43.31, H 3.49, Cl 15.97, S 14.43.
Compound 11 mp 97e100 ꢁC. TLC Rf 0.59. 1H NMR (400 MHz,
Compound 13a meso isomer, mp 147e148 ꢁC. IR
n: 1760 (S]P),
acetone-d6):
d
3.598 (s, 6H, OCH3), 3.602 (s, 6H, OCH3), 3.65 (br s,
1590 (S]Slactone) cmꢀ1. 1H NMR (400 MHz, acetone-d6):
d
1.29 (d,
3
8H, eSO2eCH2e), 6.323 (s, 2H, S(5)eH), 6.328 (s, 2H, S(5)eH)
ppm. C12H12Cl2O6S2 (387.26): calcd. C 37.22, H 3.12, Cl 18.31, S
16.56; found C 37.32, H 3.24, Cl 18.27, S 16.52.
3JO,O¼6.1 Hz, 6O, SH3), 1.34 (d, JO,O¼6.1 Hz, 6O, SH3), 3.64, 3.67
(AA0BB0, JAA ¼JBB ¼9.0 Hz, JAB¼JA B ¼e13.9 Hz, JA B¼JAB ¼6.3 Hz, 4O,
0
0
0
0
0
0
eSO2Se), 4.25 (septet, 3JO,O¼6.1 Hz, 2H, OCH), 6.406 (s, 2H, S(5)e
Compound 11a meso isomer, mp 80 ꢁC. IR
n
: 1755 (S]P), 1590
(S]Slactone) cmꢀ1. 1H NMR (400 MHz, acetone-d6):
3.598 (s, 6H,
OCH3), 3.65 (br s, 4H, eSO2eCH2e), 6.323 (s, 2H, S(5) eH) ppm.
13S {1H} NMR (100 MHz, acetone-d6):
32.14 (CH2), 56.82 (SO3),
H) ppm. 13S {1H} NMR (100 MHz, acetone-d6):
d 23.40, 24.53 (CH3),
d
32.00 (SCH2), 75.73 (OSO), 101.82 (S(5)), 119.64 (C(3)), 156.62
(S(4)), 165.53 (S(2)) ppm.
d
103.03 (S(5)), 119.32 (C(3)), 156.58 (S(4)), 165.40 (S(2)) ppm.
Compound 11a forms the clathrate with tetrachloromethane with
a 3:1 host/guest ratio. 3(C12H12Cl2O6S2)$CCl4 (1315.59): calcd. Cl
26.95; found Cl 27.31.
3.3.8. The separation of diastereomeric bis-thioethers 11e13. The
separation of compounds 11e13 was achieved by the method of
fractional crystallization in combination with manual sorting of
the crystals under a microscope. The sample containing the
mixture of two isomers was dissolved in an excess of tetra-
chloromethane by heating and left for slow evaporation at room
temperature. In one to two days the first portion of the crystals
were separated by filtration, washed with cold tetrachloro-
methane, and dried. The isolated crystals appeared under the
microscope as well-faceted quite large crystals that have typical
forms of hexagonal prisms (11a), plates (12a) or rounded plates
(13a). The preferentially grown diastereomer in all three cases of
bis-thioethers was the meso form as verified by X-ray single dif-
fraction analysis. The subsequent crystallization from mother li-
quors led to the precipitation of the mixture of two diastereomers
(as evidenced by 1H NMR spectroscopy) that can be sorted out
manually under microscope. Thus, the small plates of DL isomer
11b and the cubic prisms of 12b were obtained. The last portion of
grown crystals represents exclusively the pure DL isomers 11b and
12b. Unfortunately, all our attempts to crystallize and isolate the
DL diastereomer of isopropoxy bis-thioether 13 were unsuccessful.
Compound 11b DL isomer, mp 99 ꢁC. 1H NMR (400 MHz, acetone-
d6):
d
3.602 (s, 6H, OCH3), 3.65 (br s, 4H, eSO2eCH2e), 6.328 (s, 2H,
32.24 (CH2),
S(5)eH) ppm. 13S {1H} NMR (100 MHz, acetone-d6):
d
56.91 (SO3), 103.08 (S(5)), 119.24 (C(3)), 156.69 (S(4)), 165.39
(S(2)) ppm.
3.3.6. 4,40-(Ethane-1,2-diyldisulfanediyl)bis(3-chloro-5-ethoxyfuran-
2(5H)-one) (12). Compound 12 was synthesized as described above
for compound 11 from ethoxyfuranone 9 (1.00 g, 5.08 mmol) and
1,2-ethanedithiol (0.21 mL, 2.5 mmol) in the presence of triethyl-
amine (0.71 mL, 5.08 mmol). Recrystallization from tetrachloro-
methane gave a crystal sample of 12 (0.67 g, 64%) as a 1:1 mixture
of diastereomers (measured by 1H NMR spectroscopy).
Compound 12 mp 83e86 ꢁC. TLC Rf 0.65. 1H NMR (400 MHz,
3
acetone-d6):
d
1.30 (t, X-part of ABX3-system, JO,O¼7.1 Hz, 12H,
CH3), 3.60e3.70 (m, 8H, eCH2Se), 3.83e3.98 (m, AC-part of ABX3-
system, 8H, OCH2), 6.358 (s, 2H, C(5)eH), 6.370 (s, 2H, C(5)eH)
ppm. C14H16Cl2O6S2 (415.31): calcd. C 40.49, H 3.88, Cl 17.07, S
15.44; found C 40.13, H 3.65, Cl 17.00, S 15.52.
3.3.9. (RR,SS)-9-Chloro-6-methoxy-7-oxa-1,4-dithiaspiro[4.4]nonan-
8-one (14). 1,2-Ethanedithiol (0.31 mL, 3.63 mmol) and triethyl-
amine (0.51 mL, 3.63 mmol) were added to a stirred solution of
ether 8 (0.66 g, 3.63 mmol) in acetone (20 mL). The reaction mix-
ture was refluxed for 1 h. The precipitate of (S2O5)3N$OSl was
filtered off and washed with acetone. The combined filtrates were
evaporated to dryness and the obtained yellow oil was purified by
column chromatography (hexaneediethyl ether, 1:3). From the first
non-polar fraction, product 14 was obtained and recrystallized
from a mixture of tetrachloromethane and hexane (2:1) to yield
0.21 g (24%) of colorless crystals. Second fraction contained bis-
Compound 12a meso isomer, mp 110 ꢁC. 1H NMR (400 MHz,
acetone-d6):
d
1.30 (t, X-part of ABX3-system, 3JH,H¼7.1 Hz, 6H, CH3),
3.65, 3.68 (AA0BB0, JAA ¼JBB ¼9.0 Hz, JAB¼JA B ¼ꢀ13.9 Hz,
0
0
0 0
0
0
JA B¼JAB ¼ꢀ6.0 Hz, 4H, eCH2Se), 3.90, 3.93 (both m, AB-part of
ABX3-system, 2JAB¼e9.4 Hz, JAX¼3JBX¼7.1 Hz, 4H, OCH2), 6.358 (s,
3
2H, C(5)eH) ppm. 13C {1H} NMR (100 MHz, acetone-d6):
d 16.34
(CH3), 32.14 (SCH2), 66.87 (OCH2), 102.49 (S(5)), 119.36 (C(3)),
156.64 (S(4)), 165.46 (S(2)) ppm.
Compound 12b DL isomer, mp 91e92 ꢁC. 1H NMR (400 MHz,
acetone-d6):
d
1.30 (t, X-part of ABX3-system, 3JHH¼7.2 Hz, 6H, CH3),
3.64, 3.68 (AA0BB0, JAA ¼JBB ¼6.0 Hz, JAB¼JA B ¼e13.9 Hz,
thioether 11 (0.70 g, 39%). Mp 74e76 ꢁC. TLC Rf 0.65. IR
(S]P) cmꢀ1. 1H NMR (300 MHz, acetone-d6):
3.37e3.55 (m, 4H,
eSO2eSO2e), 3.61 (s, 3H, OSH3 ), 5.25 (s, 1H, S(3)eH), 5.65 (s, 1H,
n
: 1790
0
0
0 0
0
0
JA B¼JAB ¼9.0 Hz, 4H, eCH2Se), 3.90, 3.93 (both m, AB-part of ABX3-
d
system, 2JAB¼e9.5 Hz, 3JAX¼3JBX¼7.2 Hz, 4H, OCH2), 6.370 (s, 2H, C

A.R. Kurbangalieva et al. / Tetrahedron 66 (2010) 9945e9953
9953
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Acknowledgements
The financial support from the Tatarstan Academy of Sciences
(No 03e13/2009 (G)), Ministry of Science and Education of Russian
Federation (GK No 02.740.11.0633) and RFBR (grant No 09e03e
00696ea) is gratefully acknowledged.
Supplementary data
Supplementary data associated with this article (including single
crystal X-ray data and refinement parameters, selected geometrical
parameters of the individual isomers of bis-thioethers 11e13 and
Checkcif Reports of compounds) can be found in online version.
Supplementary data related to this article can be found online at
doi:10.1016/j.tet.2010.10.047. These data include MOL files and
InChiKeys of themost importantcompoundsdescribedinthis article.
12. Kurbangalieva, A. R.; Bogdanov, A. V.; Movchan, A. I.; Chmutova, G. A. Zh. Org.
Khim. 2004, 40, 1263e1265.
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