Regio- and Stereoselective Synthesis of Functionalized Vinyl Sulfides Based on Pyridine-2-thiol and Propynoic Acid and Its Derivatives

Article abstract of DOI:10.1134/S1070428018120102

Regio- and stereoselective methods of synthesis of 3-(pyridin-2-ylsulfanyl)prop-2-enoic acid and alkyl (Z)-3-(pyridin-2-ylsulfanyl)prop-2-enoates have been developed on the basis of nucleophilic addition of pyridine-2-thiol to propynoic acid and alkyl propynoates. Reactions of alkyl (Z)-3-(pyridin-2-ylsulfanyl)prop-2- enoates with methyl iodide afforded 2-[(3-alkoxy-3-oxoprop-1-enyl)sulfanyl]-1-methylpyridinium iodides.

Full text of DOI:10.1134/S1070428018120102

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2018, Vol. 54, No. 12, pp. 1798–1802. © Pleiades Publishing, Ltd., 2018.
Original Russian Text © V.A. Potapov, R.S. Ishigeev, M.V. Musalov, S.V. Zinchenko, Yu.A. Chuvashev, T.N. Borodina, S.V. Amosova, 2018, published in
Zhurnal Organicheskoi Khimii, 2018, Vol. 54, No. 12, pp. 1784–1788.
Regio- and Stereoselective Synthesis
of Functionalized Vinyl Sulfides Based on Pyridine-2-thiol
and Propynoic Acid and Its Derivatives
V. A. Potapova,* R. S. Ishigeeva, M. V. Musalova, S. V. Zinchenkoa, Yu. A. Chuvasheva,
T. N. Borodinaa, and S. V. Amosovaa
a Favorskii Irkutsk Institute of Chemistry, Siberian Branch, Russian Academy of Sciences,
ul. Favorskogo 1, Irkutsk, 664033 Russia
*e-mail: v_a_potapov@irioch.irk.ru
Received August 22, 2018; revised September 25, 2018; accepted October 2, 2018
Abstract—Regio- and stereoselective methods of synthesis of 3-(pyridin-2-ylsulfanyl)prop-2-enoic acid and
alkyl (Z)-3-(pyridin-2-ylsulfanyl)prop-2-enoates have been developed on the basis of nucleophilic addition of
pyridine-2-thiol to propynoic acid and alkyl propynoates. Reactions of alkyl (Z)-3-(pyridin-2-ylsulfanyl)prop-2-
enoates with methyl iodide afforded 2-[(3-alkoxy-3-oxoprop-1-enyl)sulfanyl]-1-methylpyridinium iodides.
DOI: 10.1134/S1070428018120102
Pyridine ring is considered a pharmacohporic group
constituting a structural fragment of many medicinal
agents [1, 2]. Pyridine derivatives with sulfur-contain-
ing substituents were found to exhibit antiviral, anti-
tumor, anti-inflammatory, and anti-HIV activities
[3–6], whereas some pyridinium salts showed a high
antimicrobial activity [7, 8].
containing pharmacophoric groups seems to be
important.
We previously developed efficient methods for the
synthesis of vinyl chalcogenides by nucleophilic
addition of chalcogen-centered anions to alkynes
[13–18]. In this work we studied how the reaction
conditions (solvent, temperature, base) and substituent
at the triple bond affect the yield and product ratio in
the reactions of pyridine-2-thiol with propynoic acid
and alkyl proynoates with the goal of developing
efficient procedures for the preparation of function-
alized vinyl sulfides that are potential biologically
active compounds.
The reaction of pyridine-2-thiol with propynoic
acid at room temperature in methylene chloride or
acetonitrile quantitatively afforded 3-(pyridin-2-ylsul-
fanyl)prop-2-enoic acid as a mixture of Z and E
isomers 1 and 2 at a ratio of ~1:3 (CH2Cl2) or ~5:6
(MeCN); i.e., in both solvents, E isomer 2 was formed
Vinyl chalcogenides are widely used as building
blocks and intermediate products in modern organic
synthesis [9–13]. They are generally prepared by
nucleophilic addition of organylchalcogenolate or chal-
cogenide anions to alkynes [9–18]. Of particular im-
portance are vinyl sulfides capable of being involved
in radical addition, polymerization, and copolymeriza-
tion reactions [10–13]. The addition of pyridine-2-thiol
to acetylene, phenylacetylene, and diacetylene was
reported to produce the corresponding 2-(ethenyl-
sulfanyl)pyridine derivatives [12]. The synthesis of
new potentially biologically active vinyl sulfides
Scheme 1.
O
Solvent, 20–25°C
+
+
COOH
OH
N
SH
N
S
N
S
HC
COOH
1
2
Solvent: CH2Cl2, MeCN, MeOH.
1798

REGIO- AND STEREOSELECTIVE SYNTHESIS OF FUNCTIONALIZED VINYL SULFIDES
1799
Scheme 2.
Solvent, 20–25°C
+
COOR
N
S
N
S
O
COOR
+
3, 5
4, 6
OR
N
SH
HC
NaOH, ROH, –18°C
3, 5
3, 4, R = Me; 5, 6, R = Et; solvent: CH2Cl2, MeCN, MeOH.
Scheme 3.
I–
I–
MeI, MeCN, 100°C
COOR
+
3, 5
N
S
N
S
Me
COOR
Me
7, 9
8, 10
3, 7, 8, R = Me; 5, 9, 10, R = Et.
as the major product (Scheme 1). When the reaction
was carried out in methanol, the major product was Z
isomer 1 (ratio 1/2 ~4:3).
activity. For this purpose, compounds 3 and 5 were
reacted with methyl iodide. The formation of pyridi-
nium salts was observed when sulfides 3 and 5 were
heated methyl iodide in boiling methanol or aceto-
nitrile; however, under these conditions, the conver-
sion was fairly low, so that it was difficult to isolate the
target products. We succeeded in attaining the com-
plete conversion by heating the reactants in a sealed
ampule at 100°C (Scheme 3). In this case, 2-[(3-al-
koxy-3-oxoprop-1-en-1-yl)sulfanyl]-1-methylpyridini-
um iodides were isolated in quantitative yield as mix-
tures of Z and E isomers; the ratio 7/8 was ~5:1, and
9/10, ~4:1. The reactions of propynoic acid deriva-
tives 1 and 2 with methyl iodide under similar con-
ditions led to the formation of mixtures of products
which were difficult to separate.
Likewise, pyridine-2-thiol reacted with methyl and
ethyl propynoate at room temperature in methylene
chloride, acetonitrile, methanol, or ethanol to give the
corresponding alkyl 3-(pyridin-2-ylsulfanyl)prop-2-
enoates 3‒6 in quantitative yield; the products were
mixtures of Z and E isomers, the former prevailing
(Scheme 2). For example, the Z/E-isomer ratio 3/4 was
2:1 in methylene chloride and 5:2 in acetonitrile.
Thus, the reactions of pyridine-2-thiol with alkyl
propynoates in the absence of a catalyst are regioselec-
tive but not stereoselective. The reaction of pyridine-2-
thiol with propynoic acid in methylene chloride and
acetonitrile gives preferentially E isomer 2 (Scheme 1),
whereas its reactions with alkyl propynoates in the
same solvents lead to the formation of Z isomers 3 and
5 as the major products (Scheme 2).
The structure of the isolated compounds was
1
proved by H and 13C NMR and mass spectra and
elemental analyses. The mass spectra of 1‒6 contained
the molecular ion peaks, but the most abundant was
[PySC2H2]+ ion with m/z 136. Analysis of the MS data
showed that the main fragmentation pathway of com-
pounds 1–6 under electron impact is elimination of the
In order to improve the stereoselectivity of the
addition of pyridine-2-thiol to alkyl propynoates, the
reactions were carried out on cooling to –15 to –18°C
in the presence of a catalytic amount of sodium
hydroxide (NaOH, 5 mol %) in methanol (with methyl
propynoate) and ethanol (with ethyl propynoate); the
reaction mixtures were then stirred at room tem-
perature. As a result, we isolated in high yields (97‒
98%) the corresponding Z-isomeric esters 3 and 5
(Scheme 2).
Scheme 4.
+·
S
N
N
–[COOR]
S
COOR
1–6
A
m/z 136 (Irel 100%)
We also tried to obtain methylpyridinium salts as
water-soluble derivatives with potential biological
1, 2, R = H; 3, 4, R = Me; 5, 6, R = Et.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 54 No. 12 2018

POTAPOV et al.
1800
COOH or COOAlk group to form stable [1,3]thiazolo-
[3,2-a]pyridin-4-ium cation A (Scheme 4).
(Py), 122.90 (Py), 136.66 (Py), 141.45 (=CHS), 149.12
(Py), 154.92 (NCS), 168.13 (C=O).
1
E Isomer (2). H NMR spectrum, δ, ppm: 5.88 d
In summary, by studying the effects of the con-
ditions and substituent at the triple bond on the yield
and ratio of products of nucleophilic addition of pyri-
dine-2-thiol to propynoic acid and alkyl propynoates,
we have developed regio- and stereoselective methods
of synthesis of compounds 1‒10 in up to quantitative
yield. The obtained compounds are new promising
intermediate products for organic synthesis which also
attract interest as potential biologically active sub-
stances. The presence of reactive groups (vinylsul-
fanyl, ester, carboxy, nucleophilic nitrogen atom) in
their molecules provides the possibility of their further
functionalization and synthesis of new derivatives.
3
(1H, =CHC=O, J = 15.9 Hz), 6.92‒6.97 m (1H, Py),
7.04‒7.08 m (1H, Py), 7.40‒7.44 (1H, Py), 8.29‒
3
8.33 (1H, Py), 8.36 d (1H, =CHS, J = 15.9 Hz).
13C NMR spectrum, δC, ppm: 117.40 (=CH), 121.28
(Py), 122.85 (Py), 136.81 (Py), 141.66 (=CHS), 149.28
(Py), 153.68 (NCS), 166.62 (C=O).
Methyl (Z)-3-(pyridin-2-ylsulfanyl)prop-2-en-
oate (3). A solution of 0.17 g (2 mmol) of methyl
propynoate in 2 mL of methanol was added to a solu-
tion of 0.222 g (2 mmol) of pyridine-2-thiol and
0.005 g (0.1 mmol) of 85% NaOH in 8 mL of metha-
nol cooled to –15 to –18°C. The mixture was left to
stand for 16 h in a refrigerator (–18°C) and stirred for
6 h at room temperature, 0.006 g (0.11 mmol) of
ammonium chloride was added, and the mixture was
stirred for 1 h more. The solvent was distilled off on
a rotary evaporator, the residue was washed with
chloroform (10 mL), and the solution was filtered. The
filtrate was evaporated on a rotary evaporator, and the
residue was dried under reduced pressure. Yield 0.38 g
(97%), white powder, mp 53‒54°C (from MeOH).
1H NMR spectrum, δ, ppm: 3.76 s (3H, OCH3), 6.08 d
EXPERIMENTAL
The NMR spectra were recorded on a Bruker DPX-
400 spectrometer at 400.13 (1H) and 100.61 MHz (13C)
using CDCl3 as solvent and hexamethyldisiloxane as
reference. The mass spectra (electron impact, 70 eV)
were recorded on a Shimadzu GCMS-QP5050A instru-
ment with direct sample admission into the ion source.
The elemental analyses were obtained with a Thermo
Scientific Flash 2000 CHNS analyzer. The melting
points were measured on a Boetius PHMK 05 melting
point apparatus (Wagetechnik Rapido). The solvents
used were preliminarily dried and distilled.
3
(1H, =CHC=O, J = 10.2 Hz), 7.06‒7.12 m (1H, Py),
7.28‒7.32 m (1H, Py), 7.52‒7.59 m (1H, Py), 8.47‒
3
8.50 m (1H, Py), 8.56 d (1H, =CHS, J = 10.2 Hz).
13C NMR spectrum, δC, ppm: 51.14 (CH3), 113.07
(=CH), 121.12 (Py), 122.88 (Py), 136.63 (Py), 141.95
(=CHS), 149.32 (Py), 154.68 (NCS), 166.73 (C=O).
Found, %: C 55.63; H 4.82; N 7.36; S 16.13.
C9H9NO2S. Calculated, %: C 55.37; H 4.65; N 7.17;
S 16.42.
(Z)- and (E)-3-(Pyridin-2-ylsulfanyl)prop-2-enoic
acids (1/2). A solution of 0.111 g (1 mmol) of pyridine-
2-thiol in 2 mL of methylene chloride was added
dropwise with stirring to a solution of 0.07 g (1 mmol)
of propynoic acid in 2 mL of methylene chloride. The
mixture was stirred for 6 h at room temperature, the
solvent was distilled off on a rotary evaporator, and
the residue was dried under reduced pressure. Yield
0.181 g (quantitative), white powder, mp 33‒34°C
(from CHCl3); a mixture of Z and E isomers at a ratio
of 1:3. Mass spectrum, m/z (Irel, %): 181 (20) [M]+,
137 (26) [PySC2H3]+, 136 (100) [PySC2H2]+, 111 (16)
[PySH]+, 79 (67) [C5H5N]+, 78 (75) [C5H4N]+, 67 (25)
[C4H5N]+, 51 (53) [C4H3]+, 39 (39) [C3H3]+. Found, %:
C 52.73; H 4.07; N 7.48; S 18.01. C8H7NO2S. Cal-
culated, %: C 53.02; H 3.89; N 7.73; S 17.70.
Methyl (E)-3-(pyridin-2-ylsulfanyl)prop-2-en-
oate (4). A solution of 0.17 g (2 mmol) of methyl
propynoate in 2 mL of methylene chloride was added
to a solution of 0.22 g (2 mmol) of pyridine-2-thiol in
8 mL of methylene chloride. The mixture was stirred
for 20 h at room temperature, the solvent was distilled
off, and the residue was dried under reduced pressure.
Yield 0.39 g (quantitative), colorless viscous oily
material, a mixture of Z and E isomers (ratio 3/4 ~2:1).
Mass spectrum, m/z (Irel, %): 195 (3) [M]+, 164 (4)
[M – C2H5O]+, 137 (6) [PySC2H3]+, 136 (100)
[PySC2H2]+, 111 (4) [PySH]+, 79 (11) [C5H5N]+, 78
(20) [C5H4N]+, 51 (12) [C4H3]+, 39 (9) [C3H3]+. Found,
%: C 55.09; H 4.47; N 6.98; S 16.17. C9H9NO2S. Cal-
culated, %: C 55.37; H 4.65; N 7.17; S 16.42.
1
Z Isomer (1). H NMR spectrum, δ, ppm: 5.87 d
3
(1H, =CHC=O, J = 10.2 Hz), 6.89‒6.94 m (1H, Py),
7.08‒7.12 m (1H, Py), 7.36‒7.40 m (1H, Py), 8.28‒
3
1
8.32 m (1H, Py), 8.26 d (1H, =CHS, J = 10.2 Hz).
E Isomer (4). H NMR spectrum, δ, ppm: 3.73 s
13C NMR spectrum, δC, ppm: 114.20 (=CH), 121.09
(3H, OCH3), 6.12 d (1H, =CHC=O, J = 15.9 Hz),
3
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 54 No. 12 2018

REGIO- AND STEREOSELECTIVE SYNTHESIS OF FUNCTIONALIZED VINYL SULFIDES
1801
7.09‒7.14 m (1H, Py), 7.21‒7.25 m (1H, Py), 7.55‒
7.60 m (1H, Py), 8.41‒8.44 m (1H, Py), 8.64 d (1H,
N 3.98; S 9.23. C10H12INO2S. Calculated, %: C 35.62;
H 3.59; N 4.15; S 9.51.
3
=CHS, J = 15.9 Hz). 13C NMR spectrum, δC, ppm:
1
Z Isomer (7). H NMR spectrum, δ, ppm: 3.74 s
51.26 (CH3), 116.31 (=CH), 121.25 (Py), 122.77 (Py),
136.73 (Py), 141.90 (=CHS), 149.74 (Py), 153.60
(NCS), 165.16 (C=O).
(3H, OCH3), 4.47 s (3H, NCH3), 6.35 d (1H,
3
3
=CHC=O, J = 9.7 Hz), 7.75 d (1H, =CHS, J =
9.7 Hz), 8.02‒8.06 m (1H, Py), 8.33‒8.37 m (1H, Py),
8.55‒8.60 m (1H, Py), 9.35‒9.39 m (1H, Py).
13C NMR spectrum, δC, ppm: 47.50 (NCH3), 51.69
(OCH3), 119.59 (=CH), 125.31 (Py), 129.59 (Py),
137.55, 144.73, 147.37 (Py, =CHS), 156.06 (NCS),
165.47 (C=O).
Ethyl (Z)-3-(pyridin-2-ylsulfanyl)prop-2-enoate
(5) was synthesized as described above for compound
3 using ethanol as solvent. Yield 98%, white powder,
mp 61‒62°C (from EtOH). 1H NMR spectrum, δ, ppm:
3
3
1.31 t (3H, CH3, J = 7.1 Hz), 4.24 q (2H, CH2, J =
3
1
7.1 Hz), 6.08 d (1H, =CHC=O, J = 10.3 Hz), 7.08‒
E Isomer (8). H NMR spectrum, δ, ppm: 3.72 s
7.13 m (1H, Py), 7.28‒7.32 m (1H, Py), 7.56‒7.61 m
(1H, Py), 8.47‒8.51 m (1H, Py), 8.51 d (1H, =CHS,
3J = 10.3 Hz). 13C NMR spectrum, δC, ppm: 14.21
(CH3), 60.28 (CH2), 113.77 (=CH), 121.19 (Py),
123.13 (Py), 136.71 (Py), 141.78 (=CHS), 149.50 (Py),
155.13 (NCS), 166.68 (C=O). Found, %: C 56.63;
H 5.11; N 6.92; S 15.61. C10H11NO2S. Calculated, %:
C 57.39; H 5.30; N 6.69; S 15.32.
(3H, OCH3), 4.45 s (3H, NCH3), 6.44 d (1H,
3
3
=CHC=O, J = 15.2 Hz), 7.68 d (1H, =CHS, J =
15.2 Hz), 7.96‒8.03 m (2H, Py), 8.50‒8.54 m (1H,
Py), 9.40‒9.44 m (1H, Py). 13C NMR spectrum, δ,
ppm: 47.26 (NCH3), 51.83 (OCH3), 121.60 (=CH),
124.85 (Py), 128.04 (Py), 138.12, 144.38, 147.48 (Py,
=CHS), 154.46 (NCS), 163.02 (C=O).
(Z)- and (E)-2-[(3-Ethoxy-3-oxo-prop-1-en-1-yl)-
sulfanyl]-1-methylpyridinium iodides (9/10) were
synthesized in a similar way. Yield quantitative, dark
yellow viscous oilu material, a mixture of Z and E
isomers at a ratio of 4:1. Found, %: C 37.33; H 3.82;
N 4.16; S 8.92. C11H14INO2S. Calculated, %: C 37.62;
H 4.02; N 3.99; S 9.13.
Ethyl (E)-3-(pyridin-2-ylsulfanyl)prop-2-enoate
(6) was synthesized as described above for compound
4. Colorless viscous oily material; mixture of Z and E
isomers, ratio 5/6 2:1 (quantitative overall yield).
Mass spectrum, m/z (Irel, %): 209 (3) [M]+, 164 (4)
[M – C2H5O]+, 137 (6) [PySC2H3]+, 136 (100)
[PySC2H2]+, 111 (4) [PySH]+, 79 (12) [C5H5N]+, 78
(21) [C5H4N]+, 51 (9) [C4H3]+, 39 (7) [C3H3]+. Found,
%: C 56.11; H 5.13; N 6.48; S 15.59. C10H11NO2S.
Calculated, %: C 57.39; H 5.30; N 6.69; S 15.32.
1
Z Isomer (9). H NMR spectrum, δ, ppm: 1.21 t
3
3
(3H, CH3, J = 7.1 Hz), 4.12 q (2H, OCH2, J =
7.1 Hz), 4.42 s (3H, NCH3), 6.27 d (1H, =CHC=O,
3
3J = 9.7 Hz), 6.59 d (1H, =CHS, J = 9.7 Hz), 7.97‒
8.01 m (1H, Py), 8.28‒8.33 m (1H, Py), 8.45‒8.50 m
(1H, Py), 9.30‒9.35 m (1H, Py). 13C NMR spectrum,
δC, ppm: 13.97 (CH3), 48.15 (NCH3), 61.09 (CH2),
120.01 (=CH), 125.96 (Py), 130.47 (Py), 138.32,
145.35, 147.78 (Py, =CHS), 155.99 (NCS), 165.61
(C=O).
1
E Isomer (6). H NMR spectrum, δ, ppm: 1.30 t
(3H, CH3, 3J = 7.1 Hz), 4.23 q (2H, CH2, 3J = 7.1 Hz),
6.12 d (1H, =CHC=O, 3J = 15.9 Hz), 7.08‒7.12 m (1H,
Py), 7.26‒7.30 m (1H, Py), 7.54‒7.59 m (1H, Py),
3
7.47–8.51 m (1H, Py), 8.54 d (1H, =CHS, J =
15.9 Hz). 13C NMR spectrum, δC, ppm: 13.80 (CH3),
62.20 (CH2), 117.18 (=CH), 121.37 (Py), 123.04 (Py),
136.81 (Py), 141.71 (=CHS), 149.98 (Py), 154.11
(NCS), 165.01 (C=O).
1
E Isomer (10). H NMR spectrum, δ, ppm: 1.19 t
3
3
(3H, CH3, J = 7.1 Hz), 4.15 q (2H, OCH2, J =
7.1 Hz), 4.40 s (3H, NCH3), 6.36 d (1H, =CHC=O,
3J = 15.2 Hz), 6.69 d (1H, =CHS, 3J = 15.2 Hz), 7.90–
7.97 m (2H, Py), 8.50‒8.55 m (1H, Py), 9.35‒9.40 m
(1H, Py). 13C NMR spectrum, δC, ppm: 13.88 (CH3),
48.02 (NCH3), 61.29 (CH2), 120.11 (=CH), 125.58
(Py), 130.40 (Py), 138.12, 145.15, 147.97 (Py, =CHS),
154.61 (NCS), 163.03 (C=O).
(Z)- and (E)-2-[(3-Methoxy-3-oxoprop-1-en-1-
yl)sulfanyl]-1-methylpyridinium iodides (7/8).
A mixture of 0.195 g (1 mmol) of compound 3, 0.43 g
(3 mmol) of methyl iodide, and 1 mL of acetonitrile
was heated for 4 h at 100°C in a sealed ampule. The
solvent and excess methyl iodide were distilled off ion
a rotary evaporator, and the residue was dried under
reduced pressure. Yield 0.337 g (quantitative), dark
yellow viscous oily material, a mixture of Z and E
isomers at a ratio of 5:1. Found, %: C 35.34; H 3.78;
This study was performed under financial support
by the Russian Science Foundation (project no. 18-13-
00372). The spectral measurements were performed
using the facilities of the Baikal Joint Analytical Cen-
ter, Siberian Branch, Russian Academy of Sciences.
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POTAPOV et al.
10. Trofimov, B.A. and Amosova, S.V., Sulfur Rep., 1984,
1802
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