Novel stereoselective phase transfer catalytic synthesis and some applications of (E)-2-chlorovinylthioarenes and hetarenes

Article abstract of DOI:10.1080/10426500307930

A novel two-step method for the preparation of (E)-2-chlorovinyl-thioarenes (or hetarenes) from thiols and 1,1,2-trichloroethane in the phase transfer catalytic systems solid K₂CO₃/solid KI/18-crown-6/xylene and solid KOH/18-crown-6/

Full text of DOI:10.1080/10426500307930

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Phosphorus, Sulfur, and Silicon and the Related
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Novel Stereoselective Phase Transfer Catalytic
Synthesis and Some Applications of ( E )-2-
Chlorovinylthioarenes and Hetarenes
Kira Rubina a , Edgars Ābele a , Juris Popelis a , Solveiga Grinberga a , Pavel Arsenyan a &
Edmunds Lukevics a
a Latvian Institute of Organic Synthesis , Riga, Latvia
Published online: 27 Oct 2010.
To cite this article: Kira Rubina , Edgars Ābele , Juris Popelis , Solveiga Grinberga , Pavel Arsenyan & Edmunds Lukevics
(2003) Novel Stereoselective Phase Transfer Catalytic Synthesis and Some Applications of ( E )-2-Chlorovinylthioarenes and
Hetarenes, Phosphorus, Sulfur, and Silicon and the Related Elements, 178:3, 521-529
To link to this article: http://dx.doi.org/10.1080/10426500307930
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Phosphorus, Sulfur and Silicon, 2003, Vol. 178:521–529
C
Copyright 2003 Taylor & Francis
1042-6507/03 $12.00 + .00
DOI: 10.1080/10426500390170679
NOVEL STEREOSELECTIVE PHASE TRANSFER
CATALYTIC SYNTHESIS AND SOME APPLICATIONS
OF (E)-2-CHLOROVINYLTHIOARENES
AND HETARENES
¯
Kira Rubina, Edgars Abele, Juris Popelis, Solveiga Grinberga,
Pavel Arsenyan, and Edmunds Lukevics
Latvian Institute of Organic Synthesis, Riga, Latvia
(Received May 22, 2002; accepted August 29, 2002)
A novel two-step method for the preparation of ( E)-2-chlorovinyl-
thioarenes (or hetarenes) from thiols and 1,1,2-trichloroethane in
the phase transfer catalytic systems solid K2CO3/solid KI/18-crown-
6/xylene and solid KOH/18-crown-6/toluene has been developed. ( E)-
2-chlorovinylthioarenes were isolated in yields up to 98%. Utilization of
( E)-2-chlorovinylthioarenes in the Heck and Stille reactions has been
shown.
Keywords: Chlorovinylthioarenes; Heck reaction; phase transfer
catalytic system; Stille reaction
INTRODUCTION
Functionalized unsaturated sulfur containing compounds have been in-
vestigated as intermediates in organic synthesis.1 3 Among these com-
pounds 2-halovinyl sulfides have been extensively studied.4,5 For exam-
ple, 2-chlorovinyl sulfides are the excellent synthons for the preparation
of vinyl selenides6 or polyenediynes.7
The general methods for the synthesis of 2-chorovinyl sulfides are
based on the reaction of thiols or sodium thiolates with cis- or trans-1,2-
dichloroethenes5,8,9 or addition of terminal acetylenes to arylsulfenyl
chlorides in AcOH10,11 or EtOAc.12 2-Halovinylthioarenes were ob-
tained by the thermal decomposition of -arylmercaptoacrylic acids
in the presence of chlorine or bromine.13 Reactions of benzenethiolate
anions with several polychloroethanes also were studied.14 However,
The authors thank Latvian Council of Science for the financial support (Grant
No. 166).
Address correspondence to Kira Rubina, Latvian Institute of Organic Synthesis, 21
Aizkraukles Street, Riga, LV-1006, Latvia. E-mail: kira@osi.lanet.lv
521

522
K. Rubina et al.
selectivity and yields of such reactions usually were low. The reac-
tion of PhSNa with CH2ClCHCl2 in DMF afforded the desired prod-
uct PhSCH CHCl in yield up to 11%, PhSCH CHSPh (27–58% yield)
being the main product.
The stereoselective synthesis of 2-chlorovinylthioarenes in good
preparative yields is solved in this article.
RESULTS AND DISCUSSION
We have developed a novel two-step phase transfer catalytic (PTC)
method for the preparation of (E)-2-chlorovinylthioarenes (or het-
arenes) from thiols and 1,1,2-trichloroethane (Scheme 1). The first step
included the synthesis of 2,2-dichloroethyl aryl (or hetaryl) sulfides
7–11 by the interaction of thiols 1–6 with 1,1,2-trichloroethane in the
PTC system solid K2CO3/solid KI/18-crown-6/xylene. The use of the
solid KOH in this process leads to the decomposition of the alkylating
agent 1,1,2-trichloroethane. 2,2-Dichloroethyl sulfides 7–11 in the solid
KOH/18-crown-6/toluene system stereoselectively afforded E-isomers
of 2-chlorovinylthioarenes (or hetarenes) in yields up to 98%.
SCHEME 1
Thiophenol (1) smoothly reacted with 1,1,2-trichloroethane in
K2CO3/KI/18-crown-6/xylene system giving 2,2-dichloroethylthio-
benzene (7) in excellent yield (92%). Similar reaction of 2-mercapto-
pyridine, 2-mercaptopyrimidine, and 2-mercaptobenzothiazole led to
the desired products in 54–58% yields. However, under described con-
ditions 2-mercaptopyrimidine formed the sulfide 9 as the hydrochloride
salt. After water addition the system has pH 6. The hydrolysis of the
salt by saturated aqueous solution of NaHCO3 (pH 9) was necessary
for isolation of free base 9. 2-(2,2-Dichloroethylthio)benzoxazole (10)
was obtained only in 11% yield. Thus, the reactivity of thiols 5, 6 is
correlated with the electron-donating properties of the heteroatom
in the ring. The benzimidazole thiol undergoes direct chlorovinyla-
tion in the system ClCH2CHCl2/K2CO3/KI/18-crown-6/xylene giving
2-(2-cholorovinylthio)benzimidazole (14) in 1% yield.

Novel Stereoselective Phase Transfer
523
The dehydrochlorination of 2,2-dichloroethyl derivatives 7, 8, 10,
11 occurred in the presence of KOH at the room temperature. The
2-chlorovinylthiohetarenes 12, 13, 15, 16 were isolated in 53–98%
yields. According to 1H NMR spectroscopic data the dehydrochlo-
rination step of reaction proceeded stereoselectively. The character-
istic doublet of the SCH group proton with J = 12.8–13.6 Hz
indicates that all the obtained products have E-configuration. 2-(2,2-
Dichloroethylthio)pyrimidine 9 underwent the full decomposition in the
system solid KOH/18-crown-6/toluene.
The further dehydrochlorination of 2-chlorovinylthiohetarenes 12,
13, 15, 16 did not occur under above described conditions and the
attempts to prepare the acetylenes of the type HetSC CH were
unsuccessful.
The synthesis of the 2-chlorovinylthiohetarenes can be realized also
as one-pot process. For example, the chlorovinylation of thiophenol
(1) readily proceeded in the system ClCH2CHCl2/K2CO3/KI/18-crown-
6 (molar ratio ClCH2CHCl2 : K2CO3 : KI : 18-crown-6 = 1 : 2.2 : 3 : 2 : 0.1)
in xylene with the subsequent treatment of reaction mixture with 4
equivalents of solid KOH. E-2-Chlorovinylthiobenzene 12 was obtained
in 88% yield.
The synthesized 2-chlorovinylthioarenes can be used in the stereose-
lective synthesis of different E-2-substituted vinyl sulfides (Scheme 2).
SCHEME 2
The utilization of E-2-chlorovinylthiobenzene (12) in the system
PhC CH/Pd(PPh3)4/CuI/Et3N/xylene afforded Heck type reaction15
product 17 in 43% yield. The Stille reaction16 of 2-chlorovinylthio-
benzene 12 with 2-methyl-5-tributylstannylthiophene in the Pd2(dba)3/
PPh3/CsF/18-crown-6/toluene system gave stereoselectively E-isomer
of 1-phenylthio-2-(5-methyl-2-thienyl)ethene in 42% yield. High

524
K. Rubina et al.
efficiency of above system was recently demonstrated in the synthe-
sis of unsymmetric diynes.17
EXPERIMENAL
1H and 13C NMR spectra were recorded on a Varian 200 Mercury spec-
trometer (200 MHz) using CDCl3 as a solvent and HMDSO as the in-
ternal standard. Mass spectra were registered on a GC-MS HP 6890
(70 eV) apparatus. GC analysis was performed on a Chrom-5 instru-
ment equipped with a flame-ionization detector using a glass column
packed with 5% OV-101/Chromosorb W-HP (80–100 mesh, 1.2 m
3 mm). Thiols 1–6, 1,1,2-trichloroethane, 18-crown-6 and palladium cat-
alysts (Acros) were used without purification.
General Method of Synthesis of
2,2-Dichloroethylthioarenes(or Hetarenes) 7–11
2,2-Dichloroethylthiobenzene (7)
1,1,2-Trichloroethane (4.1 ml, 44 mM) was added under stirring to
the mixture of thiophenol (2.20 g, 20 mM), K2CO3(8.28 g, 60 mM), KI
(6.64 g, 40 mM), and 18-crown-6 (528 mg, 2 mM) in 25 ml of xylene. The
reaction mixture was refluxed 2 h (GC-MS control), cooled, and filtered.
The solvent was evaporated under reduced pressure. The residue was
purified by column chromatography using hexane: ethyl acetate (5 : 1)
as eluent. Yield of 7 was 3.8 g (98%). Compounds 8–10 (see Table I)
were similarly prepared.
General Method of Synthesis of
E-2-Chlorovinylthioarenes (or Hetarenes) 12, 13, 15, 16
2-Chlorovinylthiobenzene (12)
Finely powdered KOH (1.12 g, 10 mM) was added to the solution of
7 (2.07 g, 10 mM) and 18-crown-6 (264 mg, 1 mM) in 25 ml of toluene.
Reaction mixture was stirred 45 min (GC-MS control) at room tem-
perature, filtered, and evaporated. The residue was purified by column
chromatography using hexane: toluene (2 : 1) as eluent. The yield of
12 was 1.67 g (98%). Compounds 13–16 (see Table I) were similarly
prepared.
One-Pot Synthesis of E-2-Chlorovinylthiobenzene (12)
from Thiophenol (1)
1,1,2-Trichloroethane (4.1 ml, 44 mM) was added under stirring to a
mixture of thiophenol (2.20 g, 20 mM), K2CO3 (8.28 g, 60 mM), KI

Novel Stereoselective Phase Transfer
525
TABLE I Synthesis of Dichloroethyl 7–11 (ArSH: ClCH2CHl2 : K2CO3 : KI :
18-crown-6 = 1 : 2.2 : 3 : 2 : 0.1) and Chlorovinyl 12–16 (ArSCH2CHCl2 : KOH :
18-crown-6 = 1 : 3 : 0.1) Derivatives
Yield of
ArSCH2CHCl2, chlorination,
Dehydro-
Yield of,
ArSCH CHCl,
%
Alkylation,
h
No.
Ar
No.
%
h
No.
1
2.0
7a
92
2.0
12a
98
2
3
4
2.0
8
9
58
55
—
5.0
2.5
—
13
—
14
69
6.0
4.0
0
—
1b
5
6
11.0
5.0
10
11
11
54
2.0
0.7
15
16
53
95
a7 and 12 were prepared previously.14
bThe benzimidazole thiol undergoes direct chlorovinylation in the system ClCH2CHCl2/
K2CO3/KI/18-crown-6/xylene.
(6.64 g, 40 mM), and 18-crown-6 (528 mg, 2 mM) in 25 ml of xylene. The
reaction mixture was refluxed 2 h (GC-MS control) and cooled. Finely
powdered KOH (4.48 g, 80 mM) was added to the reaction mixture under
vigorous stirring. The reaction mixture was stirred 7 h (GC-MS control)
at room temperature, filtered, and evaporated. The residue was puri-
fied by column chromatography using hexane : toluene (2 : 1) as eluent.
The yield of 12 was 3.0 g (88%).
Palladium Catalyzed Synthesis of
E-1-henylthio-4-phenylbut-1-en-3-yne (17)
Tetrakis(triphenylphosphine) palladium (58 mg, 0.05 mM) was added
at room temperature under an argon atmosphere to a solution of 12
(170 mg, 1 mM) in xylene (1 ml). The mixture was stirred for an addi-
tional 45 min. A solution of phenylacetylene (102 mg, 1 mM) in triethy-
lamine (303 mg, 3 mM) was added followed by copper iodide (20 mg,
0.1 mM). The reaction mixture was refluxed 10 h, phenyl acetylene

526

527

528
K. Rubina et al.
(102 mg, 1 mM) was once more added, and then refluxed for an addi-
tional 10 h (GC-MS control), cooled to the room temperature, filtered,
and isolated by column chromatography, using hexane as eluent. Prod-
uct 17 was isolated in 42% yield (100 mg). M.p. 80–81 C.
MS (Irel, %) m/z: 236 (M+, 100), 235 (57), 234 (42), 221 (18), 203 (21),
202 934), 191 (21), 1134 (11), 126 (17), 121 (26), 115 (33), 89 (12), 77
(27), 63 (13), 51 (35), 39 (13).
1H NMR (CDCl3/HMDSO) ppm: 6.28 and 6.57 (both d, 2H, J = 12.8
Hz, CH CH); 7.34 (m, 3H, Ph); 7.52 (m, 2H, Ph).
13C NMR (CDCl3) ppm: 73.9 and 81.5 (C C); 121.8 (SC); 127.2
(PhCH); 128.2; 128.3; 128.4; 129.2; 129.5; 131.6; 132.5.
Palladium Catalyzed Synthesis of
E-1-phenylthio-2-(5-methyl-2-thienyl)ethene (18)
The mixture of 12 (170 mg, 1 mmol), tris(dibenzylideneacetone)dipall-
adium (0) (13.7 mg, 0.015 mM), and triphenylphosphine (15.7 mg,
0.06 mM) in toluene (1.5 ml) were stirred for 5 min in an atmosphere of
argon at room temperature. 18-Crown-6 (26 mg, 0.1 mM), dry cesium
fluoride (334 mg, 2.2 mM), and 2-methyl-5-tributylstannylthiophene
(273 mg, 1 mmol) were added to the reaction mixture under stirring
under argon. The reaction was carried out under vigorous stirring at
reflux temperature for 20 h with GC-MS control, cooled, filtered, and
isolated by column chromatography using hexane:ethyl acetate (1 : 1)
as eluent in 43% yield (106 mg).
MS (Irel, %) m/z: 232 (M+, 100), 217 (M+-Me, 14), 199 (17), 187 (33),
185 (31), 173 (13), 153 (15), 140 (12), 121 (54), 111 (32), 97 (10), 77 (30),
51 (30), 39 (18).
1H NMR (CDCl3/HMDSO) ppm: 2.44 (s, 3H, Me); 6.54 (d, 1H, J =
15.3 Hz, thienyl-CH); 6.60 (d, 1H, J = 2.4 Hz, H-4); 6.71 (d, 1H, J =
2.4 Hz, H-3); 6.80 (d, 1H, J = 15.3 Hz, SCH); 7.31–7.4 (m, 5H, Ph).
13C NMR (CDCl3) ppm: 15.5 (Me); 120.3 (SC); 125.3 (C-thienyl);
125.5; 126.7; 126.9; 129.1; 134.9; 135.5; 139.2; 139.4.
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