Synthesis of novel arylthio derivatives of mucochloric acid

Article abstract of DOI:10.1080/10426500601015989

Stable reaction products of mucochloric acid with aromatic and heterocyclic thiols were synthesized and characterized. Under basic conditions the reactions proceeded with the substitution of the chlorine atom(s) by arylthiogroup(s), while in an acidic med

Full text of DOI:10.1080/10426500601015989

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Phosphorus, Sulfur, and Silicon
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Synthesis of Novel Arylthio
Derivatives of Mucochloric Acid
A. R. Kurbangalieva a , N. F. Devyatova a , A. V.
Bogdanov a , E. A. Berdnikov a , T. G. Mannafov a , D.
B. Krivolapov b , I. A. Litvinov b & G. A. Chmutova c
a Aleksandr Mikhailovich Butlerov Chemical Institute,
Kazan State University , Kazan, Russia
b Aleksander Erminingeldovich Arbuzov Institute of
Organic and Physical Chemistry, Kazan Scientific
Center of the Russian Academy of Sciences , Kazan,
Russia
c A. M. Butlerov Chemical Institute, Kazan State
University , Kazan, Russia
Published online: 30 Jan 2007.
To cite this article: A. R. Kurbangalieva , N. F. Devyatova , A. V. Bogdanov , E. A.
Berdnikov , T. G. Mannafov , D. B. Krivolapov , I. A. Litvinov & G. A. Chmutova (2007)
Synthesis of Novel Arylthio Derivatives of Mucochloric Acid, Phosphorus, Sulfur, and
Silicon and the Related Elements, 182:3, 607-630, DOI: 10.1080/10426500601015989
To link to this article: http://dx.doi.org/10.1080/10426500601015989
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Phosphorus, Sulfur, and Silicon, 182:607–630, 2007
Copyright © Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500601015989
Synthesis of Novel Arylthio Derivatives
of Mucochloric Acid
A. R. Kurbangalieva
N. F. Devyatova
A. V. Bogdanov
E. A. Berdnikov
T. G. Mannafov
Aleksandr Mikhailovich Butlerov Chemical Institute,
Kazan State University, Kazan, Russia
D. B. Krivolapov
I. A. Litvinov
Aleksander Erminingeldovich Arbuzov Institute of Organic
and Physical Chemistry, Kazan Scientific Center of the Russian
Academy of Sciences, Kazan, Russia
G. A. Chmutova
A. M. Butlerov Chemical Institute, Kazan State University,
Kazan, Russia
Stable reaction products of mucochloric acid with aromatic and heterocyclic thi-
ols were synthesized and characterized. Under basic conditions the reactions pro-
ceeded with the substitution of the chlorine atom(s) by arylthiogroup(s), while
in an acidic medium the hydroxy group at C was substituted. Different types
5
of new sulfur-containing products of di- and trisubstitution on the basis of mu-
cochloric acid were obtained. In one case a new acyclic product—di-p-tolyl-2,3-bis-
(p-tolylthio)butanedithioate—was isolated. The structure of all synthesized com-
1
13
pounds was confirmed by IR, H, and C NMR spectroscopy; three compounds
were characterized by single crystal X-ray diffraction.
Keywords Furanone; mucochloric acid; single crystal X-ray diffraction; sulfur; thioether
Received August 19, 2005; accepted August 22, 2006.
The grants given to A. R. Kurbangalieva and N. F. Devyatova by the Russian Ministry
of Education and Science and U.S. Civilian Research and Development Foundation BRHE
(REC-007, No. Y2-C-07-17) are gratefully acknowledged. This research was supported by
grants from the Russian Foundation for Basic Research (grant No. 04-03-32156). The
authors are thankful to Dr. E. G. Yarkova for recording the IR spectra and to Dr. O. A.
Lodochnikova for assistance in X-ray analysis.
Address correspondence to A. R. Kurbangalieva, Department of Chemistry, Kazan
State University, 18 Kremlyovskaya Street, Kazan, 420008 Republic of Tatarstan,
Russian Federation. E-mail: almira@ksu.ru
607

608
A. R. Kurbangalieva et al.
INTRODUCTION
In recent years heterocyclic polyfunctional compounds have attracted
considerable attention due to the wide spectrum of their biological activ-
ity. One of these systems is mucochloric acid 1-3,4-dichloro-5-hydroxy-
2(5H)-furanone, which is a commercially available polyfunctional hete-
rocycle with high reactivity. Due to the presence of such reactive sites as
a double bond, a lactone ring, two chlorine atoms, and a hydroxy-group
mucochloric acid and its derivatives can react with nucleophilic as well
as with electrophilic reagents. This allows the introduction of different
functional groups into the lactone ring and to obtain new compounds
with practically useful properties.1−10
It was shown earlier that chlorine atoms in positions 3 and 4 of the
lactone ring are subjected to substitution in reactions of mucochloric
acid with simple aliphatic and aromatic thiols11,12 and selenophenols13
under basic conditions; in the presence of inorganic acids the hy-
droxy group is substituted.14−16 Nucleophilic substitution in an alkaline
medium (a water–alcohol solution of potassium hydroxide) gives mainly
4-arylthiosubstituted derivatives, while 3,4-disubstituted derivatives of
mucochloric acid are formed when an excess of the nucleophilic reagent
is used.12
The main aim of the present work was the investigation of reactions
of mucochloric acid with arylthiols under basic and acidic conditions
in order to obtain pure regioisomers of sulfur-containing derivatives of
the furanone series. Moreover, of particular interest are reactions of
mucochloric acid with heterocyclic thiols and the synthesis of different
di- and triarylthioderivatives. The reaction products were characterized
by 13C NMR spectroscopy and single crystal X-ray diffraction. IR and
1H NMR spectroscopy were also used for the structure identification of
the compounds. Identity and purity of the compounds were controlled
by TLC as well as elemental analysis.
RESULTS AND DISCUSSION
Mucochloric acid 1 formed with arylthiols products 3–8 resulting from
substitution of the chlorine atom in 4-position. The reaction was carried
out in diethyl ether in the presence of triethylamine with an equimolar
ratio of reagents and catalyst11 (Scheme 1).
The new products 3–8 are stable solid compounds; their composition
was determined by elemental analysis, and the position of the arylthio
group was proven by the spectral data presented in Table I.
Characteristic features of the IR spectra of products 3–8 are a broad
band of medium intensity in the range 3100–3400 cm−1 assigned to

Arylthio Derivatives of Mucochloric Acid
609
SCHEME 1
the stretching vibrations of the hydroxy group, a strong band at 1760–
1780 cm−1 assigned to the stretching vibrations of the C O bond of the
γ -lactone, and a narrow intensive band in the range 1580–1600 cm−1
typical for the C C bonds of the aromatic system. In the IR spectra of
most of the products, the absorption band ν(C O) was present either as
a doublet (a strong signal at 1760–1780 cm−1 and a weak signal in the
range 1730–1750 cm−1) or as broad unsplit band. The comparison of the
IR spectrum of mucochloric acid 1 with the IR spectra of compounds 3–8
gave evidence that the reaction proceeded with retention of the lactone
ring.
In the 1H NMR spectra of products 3–8, there were three main types
of signals: a singlet for the methine proton at C5 (5.6–6.2 ppm); a mul-
tiplet in the range 7.0–8.0 ppm, characteristic for the aromatic protons,
and a signal for the proton of the hydroxy group. The signal for the OH
proton appeared as a broad singlet in the range 2.5–4.5 ppm in solu-
tions of compounds 3–8 in CDCl3 and at 8.1 ppm in the spectrum of
compound 3, which were recorded in DMSO-d6 (Table I).
The location of the arylthio group was determined by comparison of
the 13C NMR spectra of furanones 1 and 3 in DMSO-d6 with those of
the model compounds A and B (Scheme 2).17,18
SCHEME 2

610
A. R. Kurbangalieva et al.
TABLE I Spectroscopic Data of Synthesized Compounds 2–24
No.
IR (ν cm−1), 1H NMR (δ ppm), and 13C NMR (δ ppm)
2
2988 (C5-H), 2940 (CH2), 2912 (CH3), 1792 (C O), 1642 (C C); 1H NMR (CDCl3,
200 MHz): 1.51 (t, 3 JHH = 7.1 Hz, 3H, CH3), 4.01 (dq, 3 JHH = 7.1 Hz,
2 JHH = −9.4 Hz, 1H, CH2), 4.11 (dq, 3 JHH = 7.1 Hz, 2 JHH = −9.4 Hz, 1H, CH2),
1
6.03 (s, 1H, C5-H); 13C{ H} NMR (CDCl3, 50 MHz): 14.2 (CH3); 65.6 (CH2);
100.3 (C5); 123.6 (C3); 147.1 (C4); 162.7 (C2)
3
3272 (OH), 1782, 1748 (C O), 1592, 1492 (C Carom); 1H NMR (CDCl3): 2.39 (s,
3H, CH3), 3.98 (br s, 1H, OH), 5.77 (s, 1H, C5-H), 7.22, 7.49 (AAꢀBBꢀ, N = 7.5 Hz,
4H, Harom); (DMSO-d6): 2.35 (s, 3H, CH3), 5.99 (s, 1H, C5-H), 7.53, 7.28 (AAꢀBBꢀ,
1
N = 8.1 Hz, 4H, Harom), 8.17 (s, 1H, OH); 13C{ H} NMR (DMSO-d6, 75 MHz):
20.8 (CH3), 97.0 (C5), 118.0 (C3), 121.7, 130.2, 134.7, 140.2 (Carom), 157.6 (C4),
164.3 (C2)
4
3368 (OH), 1740 (C O), 1584 (C Carom); 1H NMR (CDCl3): 1.25 (t, 3 JHH = 7.6 Hz,
3H, CH3), 2.69 (q, 3 JHH = 7.6 Hz, 2H, CH2), 3.50 (br s, 1H, OH), 5.80 (s, 1H,
C5-H), 7.25, 7.52 (AAꢀBBꢀ, N = 7.9 Hz, 4H, Harom
)
5
6
7
8
9
3248 (OH), 1754, 1732 (C O), 1584 (C Carom); 1H NMR (CDCl3): 3.22 (br s, 1H,
OH), 5.57 (s, 1H, C5-H), 7.4–8.4 (m, 7H, naphthyl)
3400 (OH), 1772, 1738, 1700 (C O), 1588 (C Carom); 1H NMR (CDCl3): 4.31 (br s,
1H, OH), 5.80 (s, 1H, C5-H), 7.57, 7.41 (AAꢀBBꢀ, N = 8.7 Hz, 4H, Harom
)
3352 (OH), 1742 (C O), 1592 (C Carom); 1H NMR (CDCl3): 4.03 (br s, 1H, OH),
5.79 (s, 1H, C5-H), 7.48, 7.56 (AAꢀBBꢀ, N = 8.6 Hz, 4H, Harom
)
3244 (OH), 1762, 1736 (C O), 1590 (C Carom); 1H NMR (CDCl3): 4.69 (br s, 1H,
OH), 5.79 (s, 1H, C5-H), 7.2-7.8 (m, 4H, Harom
)
1766 (C O), 1588 (C Carom); 1H NMR (CDCl3): 1.08 (t, 3 JHH = 7.1 Hz, 3H, CH3),
3.28 (dq, 3 JHH = 7.1 Hz, 2 JHH = −9.2 Hz, 1H, CH2), 3.70 (dq, 3 JHH = 7.1 Hz,
2 JHH = −9.2 Hz, 1H, CH2), 5.51 (s, 1H, C5-H), 7.4–7.6 (m, 4H, Harom
)
10 3120 (OH), 1762 (C O), 1632 (C N), 1594, 1498 (C Carom); 1H NMR (CDCl3):
2.37 (s, 3H, CH3), 3.49 (br s, 1H, OH), 5.77 (s, 1H, C5-H), 6.61 (s, 1H, H
7.2–8.0 (m, 5H, Harom
C ),
)
11 3136 (OH), 1768 (C O), 1648 (C N), 1596, 1500 (C Carom); 1H NMR (CDCl3):
2.18 (s, 3H, CH3), 3.46 (br s, 1H, OH), 5.89 (s, 1H, C5-H), 7.4–7.9 (m, 10H, Harom
12 1770 (C O), 1622 (C C), 1595, 1492 (C Carom); 1H NMR (CDCl3): 2.34 (s, 3H,
CH3), 6.03 (s, 1H, C5-H), 7.16, 7.38 (AAꢀBBꢀ, N = 8.1 Hz, 4H, Harom); 13C NMR
)
(CDCl3, 50 MHz): 21.3 (qt, 1
J
CH
= 127.0 Hz, 3
J
CH
= 4.4 Hz, CH3), 86.1 (d,
1 JCH = 171.3 Hz, C5), 122.3 (d, 3
J
CH = 3.2 Hz, C3), 121.8 (t, 3
J
J
CH = 5.0 Hz, CiS),
130.2 (ddq, 1
J
CH = 159.8 Hz, 3
J
CH = 5.4 Hz, CmS), 135.9 (dd, 1
CH = 164.0 Hz,
3 JCH = 5.9 Hz, CoS), 141.1 (m, CpS), 149.2 (d, 2
CH = 5.5 Hz, C4), 163.8 (s, C2)
J
13 1768 (C O), 1624 (C C), 1591, 1502 (C Carom); 1H NMR (CDCl3): 6.1 (s, 1H,
C5-H), 7.4–8.6 (m, 7H, Naphthyl)
14 1790 (C O), 1624 (C C), 1597 (C Carom); 1H NMR (CDCl3): 6.03 (s, 1H, C5-H),
7.32, 7.42 (AAꢀBBꢀ, N= 7.8 Hz, 4H, Harom
)
15 1772 (C O), 1624 (C C), 1592 (C Carom); 1H NMR (CDCl3): 6.10 (s, 1H, C5-H),
7.2–7.8 (m, 4H, Harom
)
16 1772 (C O), 1626 (C C), 1592, 1494 (C Carom); 1H NMR (CDCl3): 3.89 (s, 1H,
OCH3), 6.07 (s, 1H, C5-H), 6.94, 7.50 (AAꢀBBꢀ, N= 8.9 Hz, 4H, Harom
)
17 3300 (O-H), 1762 (C O), 1680 (C C), 1588, 1492 (C Carom); 1H NMR (DMSO-d6):
6.23 (s, 1H, C5-H), 7.1–7.6 (m, 5H, Harom), 8.50 (s, 1H, O-H)
(Continued on next page)

Arylthio Derivatives of Mucochloric Acid
611
TABLE I Spectroscopic Data of Synthesized Compounds 2–24
(Continued)
No.
IR (ν cm−1), 1H NMR (δ ppm), and 13— NMR (δ ppm)
18 3384 (O H), 1746 (C O), 1628 (C C), 1596, 1496 (C Carom); 1H NMR
(DMSO-d6): 2.29 (s, 3H, CH3), 2.33 (s, 3H, CH3), 5.95 (d, 3 JHH = 8.9 Hz, 1H,
C5-H), 7.16, 7.23 (AAꢀBBꢀ, N= 8.3 Hz, 4H, Harom), 7.24, 7.51 (AAꢀBBꢀ, N= 8.0
Hz, 4H, Harom), 7.93 (d, 3 JHH = 8.9 Hz, 1H, OH); 13C NMR (DMSO-d6, 50 ÃHz):
20.6 (q, 1
J
CH = 126.9 Hz, CH3), 20.8 (q, 1
CH = 126.9 Hz, CH3), 96.6 (d,
J
1 JCH = 179.3 Hz, C5), 116.3 (s, C3), 122.9, 128.4, 129.2, 130.0, 130.2, 134.7, 136.8,
140.0 (Carom), 166.8 (s, C4), 168.3 (s, C2)
19 3276 (O-H), 1770 (C O), 1600, 1492 (C Carom); 1H NMR (DMSO-d6, 200 MHz):
2.30 (s, 3H, CH3), 6.17 (s, 1H, C5-H), 7.20, 7.33 (AAꢀBBꢀ, N= 8.2 Hz, 4H, Harom),
8.47 (br s, 1H, OH); 13C{ H} NMR (DMSO-d6, 50 ÃHz): 20.7 (CH3), 97.5 (C5),
1
124.3 (C3), 125.9, 130.1, 131.3, 138.1 (Carom), 155.5 (C4), 165.8 (C2)
20 1768 (C O), 1652 (C C), 1596, 1492 (C Carom); 1H NMR (CDCl3): 2.33 (s, 3H,
CH3), 2.42 (s, 3H, CH3), 5.70 (s, 1H, C5-H), 7.0–7.6 (m, 8H, Harom); 13C{ H}
1
NMR (CDCl3, 50 MHz): 21.4, 21.4 (CH3), 96.1 (C5), 122.4 (C3), 123.7, 130.0 (CpS),
130.5, 130.6 (CmS), 135.5, 135.7 (CoS), 140.7, 141.2 (CiS), 156.8 (C4), 165.4 (C2)
21 1784 (C O), 1592, 1495 (C Carom); 1H NMR (CDCl3): 2.32 (s, 3H, CH3), 2.40 (s,
3H, CH3), 5.94 (s, 1H, C5-H), 6.8–7.5 (m, 8H, Harom
)
22 1790 (C O), 1670 (C Cfuranone), 1588, 1488 (C Carom); 1H NMR (CDCl3): 2.42 (s,
1H, CH3), 5.99 (s, 1H, C5-H), 6.2–7.5 (m, 9H, Harom
)
23 1766 (C O), 1592, 1494 (C Carom); 1H NMR (CDCl3, 200 MHz): 2.31 (s, 3H, CH3),
2.40 (s, 3H, CH3), 3.80 (s, 3H, OCH3), 5.65 (s, 1H, C5-H), 6.7–7.6 (m, 12H,
1
H
arom); 13C{ H} NMR (CDCl3, 50 MHz): 21.2, 21.4 (CH3), 55.4 (OCH3), 86.1
(C5), 120.4 (C3), 114.8, 117.5, 123.9, 127.9, 129.8, 130.5, 130.8, 135.3, 137.6,
138.0, 140.8, 161.4 (Carom), 164.6 (C4), 167.8 (C2)
24 1700 (C O), 1596, 1494 (C Carom); 1H NMR (CDCl3, 200 MHz): 2.33 (s, 6H, CH3),
2.38 (s, 6H, CH3), 4.16 (s, 2H, C-H), 7.0–7.5 (m, 16H, Harom); 13C{ H} NMR
1
(CDCl3, 50 MHz): 21.3, 21.4 (CH3), 58.6 (C-H), 123.8, 128.0 (CpS), 130.0, 130.1
(CmS), 134.5, 134.9 (CoS), 139.5, 139.9 (CiS), 193.1 (C O)
The characteristic changes of the chemical shifts of the ethylene car-
bon atoms on introducing the arylthio group—a significant downfield
shift for the signal Cα(C4) and an upfield shift for the signal Cβ(C3)—
prove the substitution of the chlorine atom at C4. Thioethers 4–8 and
the compound 9, which is the interaction product of 4-chlorothiophenol
with the ethyl ester of mucochloric acid 2, have similar structure. A
1
characteristic feature of the H NMR spectrum of compound 9 is the
presence of signals for the ethoxy group in the form of a triplet for
the methyl protons (δ 1.08 ppm) and two multiplets for the two di-
astereotopic methylene protons. The diastereotopy (ꢀδ 0.42 ppm) was
noticeably larger than in the ethyl ester of mucochloric acid 2 itself (ꢀδ
0.10 ppm).

612
A. R. Kurbangalieva et al.
The reactions of mucochloric acid with heterocyclic thiols with the
purpose to introduce sulfur as well as known pharmacophoric frag-
ments at the 2(5H)-furanone framework are of particular interest. To
the best of our knowledge, there is only one example of the reaction of
mucobromic acid and its methyl ester with disodium 2-oxo-1,3-dithiole-
4,5-dithiolate, leading to the formation of sulfur-containing hetero-
cyclic compounds.19 Reactions of mucochloric acid with 3-methyl-1-
phenylpyrazol-5-thiol and 4-benzoyl-3-methyl-1-phenylpyrazol-5-thiol
were carried out in analogy to the reaction outlined in Scheme 1. Prod-
1
ucts 10–11 showed similar IR and H NMR spectral data for the lac-
tone fragment as those previously described (Table I) and are novel
4-substituted derivatives of mucochloric acid (Scheme 3).
SCHEME 3
However, reactions with heterocyclic thiols were accompanied by
strong resinification of the reaction mixture, which is the reason for
low yields of pure final products 10 and 11.
The synthesis of 5-thiosubstituted derivatives of mucochloric acid
was performed by prolonged heating of 1 with arylthiols in benzene in
the presence of sulfuric acid according to 14 (Scheme 4):
SCHEME 4

Arylthio Derivatives of Mucochloric Acid
613
FIGURE 1 Molecular structure of 3,4-dichloro-5-[(4-methylphenyl)thio]-
2(5H)-furanone 12 in the crystal.
Products 12–16 were isolated with yields of 70–84%. IR spectra of
compounds 12–16 displayed bands for the aromatic system in the range
1500–1515 cm−1; an intensive band for the carbonyl group of the lactone
ring at 1768–1772 cm−1; and no absorption band for a hydroxy group,
1
characteristic of 1. Together with the H NMR data (a singlet for the
proton at saturated carbon C5 and a multiplet for aryl protons) and the
13C NMR data (Table I), they confirmed the substitution of the hydroxy
group at C5 in an acidic medium.
Products 12–16 are crystalline substances. The structure of 3,4-
dichloro-5-[(4-methylphenyl)thio]-2(5H)-furanone 12 was determined
by single crystal X-ray diffraction (Figure 1).
˚
In molecule 12, the furanone ring was planar within 0.009(2) A with
the carbonyl group and the chlorine atoms lying in the same plane.
˚
The C O bond length was 1.200(4) A (Table II). The conjugation in the
O C2-C3 C4 fragment was negligible as indicated by the bond lengths
˚
of C3 C4, 1.321(4), and the C2-C3, 1.459(5) A. In spite of the remark-
able steric repulsion between the chlorine atoms, which became evident
in the increased exocyclic bond angles Cl3C3C4 128.9(2)◦ and Cl4C4C3
127.9(2)◦, the double bond was not twisted (torsion angle Cl4C4C3Cl3
-1.5[4]◦). The torsion angle between the planes of the furanone and the
benzene rings was 63.5(1)◦. The bond angle C5S6C7 of 104.1(1)◦ suggests
some repulsion between these rings. Bond length and bond angles in
the molecule were as expected. Apparently, the crystal packing of 12
was determined by stacking interactions between the benzene rings.

614

615

616
A. R. Kurbangalieva et al.
FIGURE 2 Packing in the crystal of compound 12; projection is along the b-
axis.
The planes of the benzene rings of neighboring molecules were parallel
˚
with an interplanar distance of 3.385 A (Figure 2).
Thus, it was shown that in acidic and basic media, the attack of a
nucleophile goes to different centers; differences in regioselectivity are
connected with different mechanisms of reaction. We believe that in
the presence of triethylamine, the substitution of the halogen atom at
C4 proceeds according to the well-known scheme of nucleophilic vinyl

Arylthio Derivatives of Mucochloric Acid
617
substitution, which was shown earlier for related systems.20 Under
acidic conditions, the increasing electrophilicity of C5 in the protonated
form of mucochloric acid directs the nucleophilic attack of arylthiol
(RSH) to this position of the lactone ring, which is followed by the elimi-
nation of a water molecule and of a proton to form the 5-thiosubstituted
derivative of mucochloric acid.
The product of the chlorine substitution at C3—4-chloro-5-hydroxy-
3-phenoxy-2(5H)-furanone 17 (Scheme 5)—was obtained from the re-
action of compound 1 with phenol in an aqueous solution containing an
excess of potassium hydroxide.21 It was shown that the opening of the
lactone ring in the molecule of mucochloric acid and further attack of
the nucleophile at the carbon atom in α-position to the carboxy group
occurred in a basic medium; the cyclic product 17 was isolated after
acidification of the reaction mixture.21 It should be noted that in the
case of 4-methylthiophenol, the product of 3,4-disubstitution 18 is the
only compound formed under the same conditions: an aqueous solution
of alkali (4.1 mol), 4-methylthiophenol (3.4 mol), and 1 (1 mol).
SCHEME 5
The formation of the disubstitution product 3,4-di[(4-
methylphenyl)thio]-5-hydroxy-2(5H)-furanone 18 was revealed by
spectral data (Table I). Its crystal structure was determined by single
crystal X-ray diffraction (Figure 3).
As in 12, in 18 the furanone ring was planar. The carbonyl group
and the sulfur atoms were positioned in the plane of the heterocycle.
The corresponding bond length in the molecules of 12 and 18 coincided
within the experimental error (Table II). A twisting of the double bond
was not observed (torsion angle S6-C3 C4-S14 -2[1]◦), in spite of the even
greater increase of bond angles S6C3C4 135.7(7) and S14C4C3 126.2(6)◦.
The dihedral angles between the planes of the benzene rings and the
furanone ring in 18 were 67.9(5)◦ and 69.0(5)◦. Interestingly, a differ-
ence in sulfur bond angles (C3S6C7 103.3[5]◦, C4S14C15 100.8(4)◦) was
observed, most probably connected with a different steric strain of these
arylthio fragments. The presence of the hydroxy group at C5 determined

618
A. R. Kurbangalieva et al.
FIGURE 3 Molecular structure of 3,4-di[(4-methylphenyl)thio]-5-hydroxy-
2(5H)-furanone 18 and hydrogen bonds in crystal.
packing in the crystal. Theꢀmolecules of 18 formed infinite chains along
the b-axis via O5-H51· · ·O2 (1−x,−1/2+y,1/2−z) hydrogen bonds (O H
ꢀ
ꢀ
ꢀ
0.82, H· · ·O2 2.04, O5· · ·O2 2.79[1] A, O5-H51· · ·O2 is 154◦). It must be
noted that as in the case of 12, stacking interactions in the crystal be-
tween the benzene rings at S3 of neighboring molecules were observed
(Figure 4). The benzene rings of neighboring molecules, connected by a
center of symmetry, were parallel; the distance between the planes of
˚
˚
the rings was 3.69 A.
Variation of the reaction conditions allowed us to obtain the mono-
substitution product at C3 of the lactone ring 19. Thus, two products,
18 and 19, in a 1:1 ratio were isolated using the reagents in a 1:1:1 ratio
and the same order of their mixing.
The 1H NMR spectrum of 19 showed a singlet for the methine proton
at C5 (6.17 ppm), a singlet for methyl protons (2.30 ppm), signals of
aromatic protons (7.1–7.6 ppm), and a broad signal for the OH proton
(8.47 ppm) (Table I). The analysis of the 13C NMR spectrum of compound
19 reveald, that the introduction of the thiotolyl moiety in place of the
chlorine atom at C3 results in the shift of all signals of carbon atoms of
the lactone ring to a lower field compared to those of mucochloric acid
(Scheme 6).
Interestingly, when the order mixing the reagents was different,
viz. the alkaline solution of 1 was added dropwise to the alkaline
solution of 4-methylthiophenol (ratio 1:4-methylthiophenol:KOH of
1:1:2), products 18 and 19 were isolated in a ratio of 1:4. The mono-
substituted furanone 19 was the only product of the reaction when
the ratio of the reagents was 1:1:2 and when the alkaline solution of

Arylthio Derivatives of Mucochloric Acid
619
SCHEME 6
FIGURE 4 Packing in the crystal of compound 18; projection is along the b-
axis.

620
A. R. Kurbangalieva et al.
4-methylthiophenol was added dropwise to the alkaline solution of mu-
cochloric acid.
Thus we have found that the variation of the ratio of the reagents
and the order of their mixing affected the type and ratio of products of
the reaction of mucochloric acid with 4-methylthiophenol in potassium
hydroxide solution. Some suggestions can be offered for the explanation
of this fact. When the solution of potassium mucochlorate is added to
the alkaline solution of 4-methylthiophenol, in the moment of mixing
there is an excess of thiol, which can attack the molecule of mucochloric
acid at the two electrophilic centers C3 and C4; therefore, the disubsti-
tution product 18 is formed along with the monosubstitution product
19. On the contrary, when the alkaline solution of 4-methylthiophenol
is added dropwise to the solution of potassium mucochlorate, there is
a lack of S-nucleophile, which may cause the formation of only the α-
monosubstitution product 19.
Products of 4,5-disubstitution (compound 20) and 3,5-disubstitution
(compounds 21 and 22) were obtained for the first time under acidic
conditions from the reaction of 4-methylthiophenol with the furanones
3, 19, and 17, respectively (Scheme 7). Furanone 23 substituted in
the three position was synthesized in a similar manner. Under boiling
of 3,4-di[(4-methylphenyl)thio]-5-hydroxy-2(5H)-furanone 18 with 4-
methoxythiophenol in benzene in the presence of concentrated sulfuric
SCHEME 7

Arylthio Derivatives of Mucochloric Acid
621
acid, only one product was isolated, which, according to the spectral
data (Table I), has the structure of 3,4-di[(4-methylphenyl)thio]-5-[(4-
methoxyphenyl)thio]-2(5H)-furanone 23.
In an attempt to obtain the product of 4,5-disubstitution 20
from 3,4-dichloro-5-[(4-methylphenyl)thio]-2-(5H)-furanone 12 and 4-
methylthiophenol under basic conditions with triethylamine as a base,
the acyclic product 24 was unexpectedly isolated (Scheme 8).
SCHEME 8
The IR spectrum of 24 showed the absorption band of the stretching
vibration of the carbonyl group at 1700 cm−1 (strongly shifted to lower
frequencies compared to the C O bands of γ -lactones) and two bands
in the range 1494 and 1596 cm−1, assigned to the stretching vibrations
of the aromatic system. The 1H NMR spectrum of 24 displayed a singlet
for methine protons at 4.16 ppm, two singlets for methyl protons at 2.38
and 2.33 ppm, and a multiplet for aromatic protons in the range 7.0–7.5
ppm (Table I). Structure determination by single crystal X-ray diffrac-
tion identified 24 as di-p-tolyl-2,3-bis-(p-tolylthio)butanedithioate (Fig-
ure 5).
There were two independent molecules A and B observed in the
crystal of 24. These independent molecules represent an enantiomeric
pair. Chiral centers in the molecule A had an RR configuration, and
in the molecule B, they had an SS configuration. The bond lengths
and bond angles in the independent molecules were identical within
experimental error (Table II). Both molecules slightly differed in con-
formation, with the maximal difference in the module of torsion angles
not exceeding 10◦.
Functional groups able to form hydrogen bonding were absent in
24, but there was a large number of aromatic substituents. There-
fore, the packing in the crystal of 24 was determined predominantly by
stacking interactions. Parallel arrangement of benzene rings C27÷C32

622
A. R. Kurbangalieva et al.
FIGURE 5 Molecular structure of the independent molecule A of compound
24 in the crystal.
of molecule A and C6÷C11 of molecule B was observed with an interpla-
˚
nar distance of 3.62 A (Figure 6).
Although for the moment it is difficult to explain the mechanism
of the formation of the acyclic product 24, we assume that this
compound may be formed according to the mechanism outlined in
Scheme 9.

Arylthio Derivatives of Mucochloric Acid
623
FIGURE 6 Packing in the crystal of compound 24; projection is along the b-
axis.
SCHEME 9

624
A. R. Kurbangalieva et al.
CONCLUSION
Reactions of mucochloric acid with aromatic and heterocyclic thiols
were carried out under basic and acidic conditions. Different regioiso-
mers as well as novel sulfur-containing products of trisubstitution and
various types of disubstitution products were obtained when reactions
were performed under different conditions.
EXPERIMENTAL
IR spectra were recorded on a Specord–M80 spectrometer in a solid
state (in Nujol); the thickness of cell was d = 0.1–0.12 mm. NMR spectra
were obtained on a Varian Unity–300 spectrometer at 299.94 MHz (1H)
and 75.13 MHz (13C) and a Varian Gemini–200 spectrometer at 200
MHz (1H) and 50.46 MHz (13C) at 25◦C with CDCl3, and DMSO-d6 was
taken as internal standards. TLC was performed using Silufol UV-254
plates, processed in an iodide camera, and was fixed in water. Acetone–
benzene 1:8 mixture was used as the eluent.
Mucochloric acid 1 was commercially available and was further re-
crystallised from water. M.p. 127◦C (m.p. 127◦C22). TLC, Rf 0.42.
3,4-Dichloro-5-ethoxy-2(5H)-furanone20 2 and 4-chloro-5-hydroxy-3-
phenoxy-2(5H)-furanone21 17 were synthesized according to the known
methods.
X-Ray Structure Determinations
The X-ray diffraction data for the crystals of 12, 18, and 24 were
collected on a CAD4 Enraf-Nonius automatic diffractometer using
˚
graphite-monochromated MoKα (λ = 0.71073 A) radiation. Details of
crystal data, data collection, and refinement are given in Table III.
The stability of the crystals and the experimental conditions were
checked every 2 h using three control reflections, while the orienta-
tion was monitored every 200 reflections by centering two standards.
No significant decay was observed. Corrections for Lorentz and polar-
ization effects were applied. Absorption correction was not applied.
The structure was solved by direct method using the SIR23 program
and refined by full matrix least-squares using SHELXL9724 program.
All non–hydrogen atoms were refined anisotropically. The positions of
the hydrogen atoms were idealized. All calculations were performed
on a PC using the WinGX25 program. Cell parameters, data collection,
and data reduction were performed on an Alpha Station 200 computer

Arylthio Derivatives of Mucochloric Acid
625
TABLE III Single-Crystal X-Ray Data for Structures of
Compounds 12, 18, and 24
12
18
24
Chemical formula
Chemical formula weight
Space group
C11H8O2SCl2
275.16
C18H16O3S2
344.45
C32H30O2S4
574.84
P21/a
P21/c
P21/n
Cell parameters
˚
a(A)
12.662(2)
7.167(2)
13.207(2)
101.77(1)
1173.3(3)
4
13.380(4)
6.271(4)
20.559(8)
103.75(3)
1676(1)
4
20.836(6)
9.860(2)
30.15(1)
105.69(5)
5962(6)
8
˚
b(A)
˚
c(A)
β(deg)
V (A )
3
˚
Z
Dx (mg m−3
F(000)
)
1.56
560
1.37
1.28
720
2288
Crystal color
Crystal form
Colorless
Prismatic
Yellow
Needle
Colorless
Prismatic
Crystal size (mm)
Diffractometer used
Radiation (A)
Temperature, (deg K)
Scan mode
0.8 × 0.6 × 0.5 0.9 × 0.06 × 0.02
0.4 × 0.4 × 0.2
Enraf-Nonius CAD-4
˚
0.71073
293
ω
θ
(deg)
26.29
7.05
Variable, 1–16.4
2504
22.77
3.15
26.32
3.32
max
Absorption correction
Not applied
μ(cm−1
)
Scan speed (deg · min−1
)
Recorded reflections
1766
568
5598
3525
Independent reflections
1659
with F2 ≥ 2σ(F2)
Rint
R1
R1 all data
ωR2
ωR2 all data
S
0.026
0.041
0.065
0.110
0.122
1.032
0.224
0.049
0.282
0.050
0.082
0.918
0.044
0.044
0.096
0.102
0.122
0.997
using the MoLEN26 program. All figures were made using the programs
ORTEP27 and PLATON.28
Crystallographic data for the structures of 12, 18, and 24 have
been deposited with the Cambridge Crystallographic Data Centre
as supplementary publication No. CCDC-607651, CCDC-607652, and
CCDC-607650, respectively. Copies of the data can be obtained free
of charge on application to CCDC, 12 Union Road, Cambridge,
CB2 1EZ, UK (fax: +44-1223-336-033; e-mail: deposit@ccdc.cam.ac.uk,
www:http://www.ccdc.cam.ac.uk).

626
A. R. Kurbangalieva et al.
General Procedure for the Preparation of Furanones (3–11)
To a solution of mucochloric acid (1.00 g, 6 mmol) in absolute ether
with intense stirring was added dropwise a solution of thiol (6 mmol)
in ether and an ether solution of triethylamine (6 mmol). Weak warm-
ing of the reaction mixture and the formation of a white precipitate
of (C2H5)3N·HCl was observed. The precipitate was filtered off and
washed with ether (20 mL). The combined filtrates were evaporated
to dryness and the obtained residue was crystallized from benzene.
3-Chloro-5-hydroxy-4-[(4-methylphenyl)thio]-2(5H)-
furanone (3)
Yield 1.32 g (86%), m.p. 126◦C, TLC Rf: 0.36. Anal. calcd. for
C11H9ClO3S: C, 51.47; H, 3.53; Cl, 13.81; S, 12.49%. Found: C, 51.28;
51.10; H, 3.27, 3.24; Cl, 13.36, 13.22; S, 12.23, 12.29%.
3-Chloro-4-[(4-ethylphenyl)thio]-5-hydroxy-2(5H)-furanone (4)
Yield 1.14 g (70%), m.p. 112◦C, TLC Rf: 0.39. Anal. calcd. for
C12H11ClO3S: C, 53.24; H, 4.10; Cl, 13.10; S, 11.84%. Found: C, 53.32,
53.35; H, 4.27, 4.31; Cl, 13.79, 14.06; S, 12.10, 12.16%.
3-Chloro-5-hydroxy-4-[(1-naphthyl)thio]-2(5H)-furanone (5)
Yield 0.47 g (27%), m.p. 179◦C, TLC Rf: 0.30. Anal. calcd. for
C14H9ClO3S: C, 57.44; H, 3.10; Cl, 12.11; S, 10.95%. Found: C, 57.32,
57.64; H, 3.18, 3.14; Cl, 12.68; S, 11.22, 11.22%.
3-Chloro-4-[(4-chlorophenyl)thio]-5-hydroxy-2(5H)-
furanone (6)
Yield 1.63 g (98%), m.p. 138◦C, TLC Rf: 0.71. Anal. calcd. for
C10H6Cl2O3S: C, 43.34; H, 2.18; Cl, 25.59; S, 11.57%. Found: C, 45.69;
H, 3.94; Cl, 25.37; S, 11.29%.
4-[(4-Bromophenyl)thio]-3-chloro-5-hydroxy-2(5H)-
furanone (7)
Yield 1.79 g (93%), m.p. 158◦C, TLC Rf: 0.41. Anal. calcd. for
C10H6BrClO3S: C, 37.35; H, 1.88; Br, 24.85; Cl, 11.02; S, 9.97%. Found:
C, 36.52, 36.27; H, 1.28, 1.42; Br, 23.62, 23.52; Cl, 10.49, 10.45; S, 9.70,
9.67%.

Arylthio Derivatives of Mucochloric Acid
627
4-[(3-Bromophenyl)thio]-3-chloro-5-hydroxy-2(5H)-
furanone (8)
Yield 1.10 g (57%), m.p. 108◦C (from hexane), TLC Rf: 0.39. Anal.
calcd. for C10H6BrClO3S: Br, 24.85; Cl, 11.02; S, 9.97%. Found: Br, 23.42;
Cl, 10.39; S, 9.62%.
3-Chloro-4-[(4-chlorophenyl)thio]-5-etoxy-2(5H)-furanone (9)
This was synthesized from ether 2 (6 mmol) and 4-chlorothiophenol
following a general procedure. Yield 1.70 g (93%), m.p. 72◦C (from
petroleum ether), TLC Rf: 0.68. Anal. calcd. for C12H10Cl2O3S: C, 47.23;
H, 3.30; Cl, 23.23; S, 10.51%. Found: C, 49.95; H, 4.33; Cl, 22.77; S,
10.90%.
3-Chloro-5-hydroxy-4-[(3-methyl-1-phenylpyrazolyl-5)thio]-2(5
H)-furanone (10).
Yield 0.87 g (45%), m.p. 185◦C, TLC Rf: 0.46.
4-[(4-Benzoyl-3-methyl-1-phenylpyrazolyl-5)thio]-3-chloro-5-
hydroxy-2(5H)-furanone (11)
Yield 1.23 g (48%), m.p. 128◦C, TLC Rf: 0.29. Anal. calcd. for
C21H15ClN2O4S: C, 59.09; H, 3.54; Cl, 8.31; S, 7.51%. Found: C, 58.60;
H, 3.91; Cl, 9.78; S, 6.64%.
General Procedure for the Preparation of Furanones (12–16)
and (20–23)
A solution of mucochloric acid (5.77 g, 34.2 mmol), thiophenol (34.2
mmol), and concentrated sulfuric acid (0.7 mL) in benzene (75 mL) was
refluxed in a round-bottom flask supplied with a reflux condenser and
adapter for the azeotropic evaporation of water for 3 h. After cooling to
r.t. the benzene solution was washed with water until neutral reaction
and dried over MgSO4. The solvent was evaporated, and the residue
was mixed with petroleum ether and cooled to −10–0◦C. The solid thus
obtained was filtered and crystallized from hexane.
3,4-Dichloro-5-[(4-methylphenyl)thio]-2(5H)-furanone (12)
Yield 7.81 g (83%), m.p. 46◦C, TLC Rf: 0.80. Anal. calcd. for
C11H8Cl2O2S: C, 48.02; H, 2.93; Cl, 25.77; S, 11.65%. Found: C, 47.34;
H, 2.44; Cl, 26.30; S, 14.27%.
3,4-Dichloro-5-[(1-naphthyl)thio]-2(5H)-furanone (13)
Yield 7.55 g (71%), m.p. 122◦C (from CCl4), TLC Rf: 0.77.

628
A. R. Kurbangalieva et al.
5-[(4-Chlorophenyl)thio]-3,4-dichloro-2(5H)-furanone (14)
Yield 8.49 g (84%), m.p. 80◦C, TLC Rf: 0.79. Anal. calcd. for
C10H5Cl3O2S: C, 40.64; H, 1.71; Cl, 35.98; S, 10.85%. Found: C, 40.38;
H, 1.73; Cl, 36.85; S, 11.70%.
5-[(3-Bromophenyl)thio]-3,4-dichloro-2(5H)-furanone (15)
Yield 8.60 g (74%), m.p. 58◦C (from a hexane/CCl4 mixture), TLC Rf:
0.80. Anal. calcd. for C10H5BrCl2O2S: C, 35.33; H, 1.48; Br, 23.50; Cl,
20.85; S, 9.43%. Found: C, 31.19; H, 1.33; Br, 20.89; Cl, 18.54; S, 11.79%.
3,4-Dichloro-5-[(4-methoxyphenyl)thio]-2(5H)-furanone (16)
Yield 8.26 g (83%), m.p. 67◦C, TLC Rf: 0.69. Anal. calcd. for
C11H8Cl2O3S: C, 45.38; H, 2.77; Cl, 24.35; S, 11.02%. Found: C, 46.19,
46.48; H, 3.83, 3.65; Cl, 23.61; S, 14.41%.
Synthesis of 3,4-Di[(4-methylphenyl)thio]-5-hydroxy-2(5
H)-furanone (18)
To a solution of 4-methylthiophenol (2 g, 16.1 mmol) and potassium
hydroxide (1.09 g, 19.4 mmol) in water (2.5 mL) was added mucochloric
acid (1.2 g, 4.7 mmol) slowly with intense stirring. A weak warming of
the reaction mixture and the formation of a precipitate was observed.
The precipitate was filtered off, and dissolved in water, and the solution
was acidified by diluted hydrochloric acid. The bright yellow solid thus
obtained was filtered and recrystallized from a benzene/petroleum ether
mixture (the ratio was 2:1). Yield 1.05 g (65%), m.p. 158◦C, TLC Rf:
0.84. Anal. calcd. for C18H16O3S2: C, 62.76; H, 4.68; S, 18.62%. Found:
C, 62.19; H, 4.82; S, 21.32%.
Synthesis of 4-Chloro-5-hydroxy-3-[(4-methylphenyl)thio]-2(5
H)-furanone (19)
To a solution of mucochloric acid (2.47 g, 14.6 mmol) and potassium
hydroxide (0.82 g, 14.6 mmol) in water (10 mL) was added slowly with
intense stirring a solution of 4-methylthiophenol (1.81 g, 14.6 mmol)
and potassium hydroxide (0.82 g, 14.6 mmol) in water (20 mL). Weak
warming of the reaction mixture and the formation of a precipitate were
observed. The precipitate was filtered off and dissolved in water, and
the solution was acidified by diluted hydrochloric acid. The obtained oil
was recrystallized from carbon tetrachloride. Yield 2.51 g (67%), m.p.
95◦C, TLC Rf: 0.29. Anal. calcd. for C18H16ClO3S: C, 51.46; H, 3.53; Cl,
13.81; S, 12.49%. Found: C, 51.37; H, 3.60; Cl, 13.60; S, 15.06%.

Arylthio Derivatives of Mucochloric Acid
629
3-Chloro-4,5-di[(4-methylphenyl)thio]-2(5 H)-furanone (20)
This was synthesized following the general procedure from furanone
3 (0.8 g, 3.1 mmol) and 4-methylthiophenol. Yield 0.65 g (58%), m.p.
113◦C, TLC Rf: 0.90.
4-Chloro-3,5-di[(4-methylphenyl)thio]-2(5 H)-furanone (21)
This was synthesized following the general procedure from furanone
19 (0.8 g, 3.1 mmol) and 4-methylthiophenol. Yield 0.69 g (61%), m.p.
90◦C. Anal. calcd. for C18H15ClO2S2: C, 59.57; H, 4.17%. Found: C, 61.03;
H, 3.61%.
4-Chloro-5-[(4-methylphenyl)thio]-3-phenoxy-2(5 H)-furanone
(22)
This was synthesized following the general procedure from furanone
17 (2.0 g, 8.3 mmol) and 4-methylthiophenol. Yield 2.0 g (73%), m.p.
88◦C. Anal. calcd. for C17H13ClO3S: C, 61.35; H, 3.94%. Found: C, 62.54;
H, 3.92%.
3,4-Di[(4-methylphenyl)thio]-5-[(4-methoxylphenyl)thio]-2(5
H)-furanone (23)
This was synthesized following the general procedure from furanone
18 (0.8 g, 2.3 mmol) and 4-methoxythiophenol. Yield 0.62 g (57%), m.p.
109◦C (from hexane / CCl4), TLC Rf: 0.67.
Synthesis of Di-p-tolyl-2,3-bis-(p-tolylthio)butanedithioate (24)
To a solution of furanone 12 (1.18 g, 4.3 mmol) in absolute ether
(10 mL) with intense stirring was added dropwise a solution of 4-
methylthiophenol (0.53 g, 4.3 mmol) in ether and an ether solution of
triethylamine (0.60 mL, 4.3 mmol). The precipitated (C2H5)3N•HCl was
filtered off and washed with ether (20 mL). The filtrate was evaporated,
and the obtained white solid residue was crystallized from petroleum
ether. Yield 0.57 g (69%), m.p. 107◦C, TLC Rf: 0.76. Anal. calcd. for
C32H30O2S4: C, 66.86; H, 5.26; S, 22.31%. Found: C, 67.01; H, 5.16; S,
22.13%.
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