Vilsmeier-Haack reaction of α-oxo ketene dithioacetals to α-chlorovinyl/ethynyl ketene dithioacetals

Article abstract of DOI:10.1055/s-2004-834901

A range of α-oxo ketene dithioacetals 1 reacted with Vilsmeier reagent (POCl₃/DMF) to afford a-chlorovinyl ketene dithioacetals 2, With the treatment of NaOH in ethanol or methanol, the compounds 2 were transformed into the corresponding α-ethynyl ketene dithioacetals 3 in moderate to high yields.

Full text of DOI:10.1055/s-2004-834901

PAPER
85
Vilsmeier–Haack Reaction of a-Oxo Ketene Dithioacetals to a-Chlorovinyl/
Ethynyl Ketene Dithioacetals
V
ilsmeier–Haac
k
R
e
e
action of
w
a
-Oxo
K
etene Dit
e
hioacetals n Dong,* Yingchun Liu, Yulong Zhao, Yimei Qi, Zhuo Wang, Qun Liu*
Department of Chemistry, Northeast Normal University, Changchun, 130024, P. R. China
Fax +86(431)5098966; E-mail: dongdw663@nenu.edu.cn
Received 12 July 2004; revised 22 September 2004
developed a facile approach for the synthesis of 2H-pyr-
ans,18 substituted pyridines19 and a nonthiolic, odorless
thioacetalization reagent.20 As continuation of these stud-
ies, we intended to combine ketene dithioacetal and
alkyne together in the same molecule with the expectation
to develop highly valuable organic intermediates. We
herein wish to describe the complete investigation of the
Vilsmeier–Haack reactions of a-oxo ketene dithioacetals
to the novel a-chlorovinyl ketene dithioacetals and the
corresponding terminal alkynes.
Abstract: A range of a-oxo ketene dithioacetals 1 reacted with
Vilsmeier reagent (POCl3/DMF) to afford a-chlorovinyl ketene
dithioacetals 2. With the treatment of NaOH in ethanol or methanol,
the compounds 2 were transformed into the corresponding a-ethy-
nyl ketene dithioacetals 3 in moderate to high yields.
Key words: alkyne, a-ethynyl ketene dithioacetal, a-chlorovinyl
ketene dithioacetal, a-oxo ketene dithioacetal, Vilsmeier–Haack re-
action
Introduction
Results and Discussion
Alkynes are among the most important building blocks in
organic synthesis. The richness of this functional group
renders it extremely versatile as a synthon for the con-
struction of a diverse array of polysubstituted benzenes
1
Vilsmeier–Haack Reaction of a-Oxo Ketene
Thioacetals
and heterocycles.1–3 The transition metal-catalyzed [4+2] The reaction of Vilsmeier reagents with ketones contain-
benzannulation reaction of alkynes,4,5 the chemo- and ing methyl or methylene groups adjacent to the carbonyl
regiospecific formal [2+2+2] cyclotrimerization of group, reported in the late 1950’s by Anrnold and co-
alkynes,6,7 and the Dötz reaction of alkynes with a,b-un- workers, affords substituted b-chloroacrylaldehydes.21
8
saturated Fischer carbene complexes have been exten- Actually, the wide-ranging reactivity of Vilsmeier re-
sively reported. Also some work has focused on the agents extend far beyond the formylation of an activated
transformation of alkynes into other highly valuable inter- aromatic nucleus, which allows carbon-carbon bonds to
mediates, such as enynes, ynamines, ynones and acetylen- be formed in many other contexts. Our researches18–20 to-
22
ic sulfones.9–13 The utility of the alkynes in organic gether with other’s work has shown that the course of
synthetic chemistry, supramolecular chemistry and me- such reactions can often be controlled by substrates and
dicinal chemistry has become active project of researches, reaction conditions. In the present work, we investigated
however, the development of novel alkynes received less the Vilsmeier–Haack reactions of a range of a-oxo ketene
attention in literatures. General methods to synthesize dithioacetals with varied structures by controlling the feed
alkynes are realized from the dehydrohalogenation of vi- ratio of Vilsmeier reagent.
nyl halides, geminal dihalides or vicinal dihalides in the
presence of strong bases such as sodium amide (NaNH2).
Alternatively, alkynes can be synthesized from the con-
version of ketones via the action of phosphorus pentachlo-
a-Oxo ketene dithioacetals have been extensively investi-
gated and reviewed as versatile organic synthons.23,24 Our
most recent work has revealed that the reaction of a-oxo
ketene thioacetal 1b with an equimolar amount of Vils-
meier reagent DMF/POCl3 at room temperature could
ride and subsequent treatment with strong bases. The
yields of the reaction, however, are very low.14,15 In 1975,
give a-chlorovinyl ketene dithioacetals 2b (Table 1, entry
Mironov and co-workers first reported the reaction of
2) in almost quantitative yield.20 The reaction conditions
acetylpyrroles with Vilsmeier reagent DMF/POCl3 to give
previously used were applied to the Vilsmeier reactions of
chlorovinyl derivatives, which with subsequent alkali
a-oxo ketene dithioacetals 1a and 1c–l. Consequently, a
treatment led to the corresponding alkynes.16 Following
range of a-chlorovinyl ketene dithioacetals 2 were ob-
the similar procedure, Jiang and coworkers synthesized
tained in very high yields. The structures of substrates and
alkyne porphyrins.17 Recently, we engaged in the Vils-
products, reaction conditions and product yields are sum-
marized in Table 1.
meier–Haack reactions of a-oxo ketene thioacetals and
It is observed that the group R1 of a-oxo ketene dithioac-
etals 1 plays a very important role in the Vilsmeier–Haack
SYNTHESIS 2005, No. 1, pp 0085–0091
Advanced online publication: 02.11.2004
x
x
.
x
x
.2
0
0
4
reaction. On the one hand, the nature of R1 determines the
DOI: 10.1055/s-2004-834901; Art ID: F09904SS
© Georg Thieme Verlag Stuttgart · New York
reactivity of a-oxo ketene dithioacetals 1 to react with

86
D. Dong et al.
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Vilsmeier reagent. In some cases, a-oxo ketene dithioace- On the other hand, R1 has a great effect on the stabilities
tals 1a–f containing R1 as COMe or COOMe (entries 1–6) of the resulting a-chlorovinyl ketene dithioacetals 2.
can be converted into the corresponding a-chlorovinyl Compounds 2b–f can be kept in desiccator for one month
ketene dithioacetals 2a–f in very high yields (up to without any chemical change, indicating they are quite
99.3%). The halogenation reaction can also take place in stable. However, compound 2a is less stable, and that is
the cases of 1h–j (entry 7–10), however, the halogenation one of the reasons to synthesize the compound at lower
products are too unstable to be readily obtained. However, temperature in comparison to its analogue 2b. On heating
no reaction was observed occurring in the case of 1k in the water, compounds 2a–f are easily hydrolyzed to af-
(entry 11). The reactivity of a-oxo ketene dithioacetals ford the corresponding substrates 1a–f. Compounds 2a
1 seems to follow their R1 sequence as -H > -COMe ª
and 2g–j are very unstable and quickly go black with the
-COOMe > -NO2, provided with the same alkylthio group. release of heat in neat even at ambient temperature. Ap-
Generally, the electron-donating groups at the neighbor- parently, the stability of a-chlorovinyl ketene dithioace-
ing position to the carbonyl group will activate the carbo- tals 2 significantly increases with the presence of electron-
nyl compounds and facilitate the Vilsmeier reaction. withdrawing R2. Moreover, it is observed that the stability
Therefore, the electron-withdrawing R1 in our studied sys- of a-chlorovinyl ketene dithioacetals 2 containing the
tem does not favor the Vilsmeier reaction, however, the same R1 group varies with alkylthio groups. For example,
electron-donating effect from alkylthio group should be in the cases of 2a–d, the stability follows the sequence of
taken into accounts. That is why some a-oxo ketene alkylthio groups as SMe ª S(CH2)4S > S(CH2)3S >
dithioacetals with weak electron-withdrawing R1 such as S(CH2)2S. Actually, the relative stabilities of compounds
COMe or COOMe could result in a-chlorovinyl ketene 2a, 2b and 2d were investigated according to the calcula-
dithioacetals, whereas a-oxo ketene dithioacetal with very tions based on the density functional theory (DFT)25 and
strong electron- withdrawing R1 such as NO2 could not some preliminary results were obtained which will be
undergo the halogenation reaction.
published in due course.
Table 1 Reactions of a-Oxo Ketene Dithioacetals 1 with Vilsmeier Reagent DMF–POCl3/PBr3
Entry
Substratea
R
R
R1
X
R2
Product
Reaction
time (h)
Reaction
Yields
temp. (ºC) (%)b
1
2
1a
1b
1c
1d
1e
1f
(CH2)2
(CH2)3
(CH2)4
COMe
COMe
COMe
COMe
CO2Me
CO2Me
H
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Br
Br
CCl=CH2
CCl=CH2
CCl=CH2
CCl=CH2
CO2Me
CO2Me
H
2a
2b
2c
2d
2e
2f
4
4
–5 to 0
r.t
83.1
99.3c
92.4
92.3
95.2
97.9
80.1
84.5
75.2
87.6
0
3
14
6
r.t
4
CH3
(CH2)2
CH3
r.t
5
4
r.t
6
(CH2)3
(CH2)2
(CH2)3
4
r.t
7
1g
1h
1i
2g
2h
2i
3
–5 to 0
–5 to 0
–5 to 0
r.t.
8
H
H
3
9
CH3
CH3
H
H
3
10
11
12
13
1j
CH2Ph CH2Ph
(CH2)3
H
H
2j
3
1k
1b
1d
NO2
NO2
2k
20
4
40–50
r.t.
(CH2)3
COMe
COMe
CBr=CH2 2b¢
CBr=CH2 2d¢
93.7
93.1
CH3
CH3
6
r.t.
a See ref.24
b Isolated yields over silica gel chromatography.
c See ref.20
Synthesis 2005, No. 1, 85–91 © Thieme Stuttgart · New York

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Vilsmeier–Haack Reaction of a-Oxo Ketene Dithioacetals
87
Following the similar procedure, we next investigated the groups that facilitate the reaction. The experimental re-
reactions of 1b and 1d with another Vilsmeier reagent sults reveal that NaOH is the most efficient base among
PBr3–DMF, respectively. Accordingly, a-bromo vinyl those examined and was selected as base in the following
ketene dithioacetals 2b¢ and 2d¢ were successfully ob- reactions. Also, the reaction media were examined in the
tained in 93.7% and 93.1% yields, respectively. Some of present work. It is found that the reaction could proceed
the results are also listed in Table 1 (entries 12 and 13).
smoothly in more polar solvents such as ethanol, metha-
nol, DMF, acetone and THF. By comparison, the protic
solvent ethanol was selected as the reaction solvent for the
following studies. In the cases of 3e–f, the reactions were
carried out in methanol rather than ethanol that could
2
Dehydrohalogenation ofa-Chlorovinyl Ketene
Dithioacetals
In this section, we investigated the elimination of hydro- cause the easterification between the substrate and the sol-
gen chloride of the above a-chlorovinyl ketene dithioace- vent. Under the optimized conditions, a range of a-chlo-
tals 2 with the treatment with a base. The reactions of 2 rovinyl ketene dithioacetals 2 was converted into the
were carried out under various conditions to optimize the corresponding alkynes 3 in good yields. Some of the re-
reaction yields. It is widely known that the dehydrohalo- sults are summarized in Table 2. Similarly, 3b¢ were suc-
genation of vinyl halide can be realized in the presence of cessfully synthesized from a-bromovinyl ketene
strong bases such as NaNH2. In our present work, we dithioacetal 2b¢. It should be mentioned that in the cases
found that a-chlorovinyl ketene dithioacetals 2 could be of 3g–j, the diethyl ether work-up extracts from the Vils-
converted into the corresponding terminal alkynes with meier–Haack reaction mixture of 1g–j were directly em-
the treatment of NaOH, KOH or even weak base such as ployed. To the best our knowledge, this is the first report
K2CO3 for the elimination of hydrochloride. The results on the synthesis of the ketene dithioacetals with a-ethynyl
are mainly attributed to the electron-donating alkylthio substituted group. Indeed, the a-ethynyl ketene dithioace-
Table 2 Synthesis of Terminal Alkynes 3 from a-Chlorovinyl Ketene Dithioacetals 2
Entry a
Substrate
R
R
R2
R3
Product
Reaction
time (h)
Reaction
temp. (ºC)
Yields
(%)b
1
2
2a
2b
2c
2d
2e
2f
(CH2)2
(CH2)3
(CH2)4
CCl=CH2
CCl=CH2
CCl=CH2
CCl=CH2
CO2Me
CO2Me
H
CCl=CH2
CCl=CH2
CCl=CH2
CCl=CH2
CO2Me
CO2Me
H
3a
3b
3c
3d
3e
3f
12
36
6
–5 to 0
r.t.
89.5
78.6
76.2
72.8
85.1
90.3
70.9
70.2
62.7
61.6
85.9
83.3
80.7
89.6
88.4
3
40
4
CH3
(CH2)2
CH3
6
40
5
12
12
8
r.t
6
(CH2)3
(CH2)2
(CH2)3
r.t
7
2g
2h
2i
3g
3h
3i
r.t
8
H
H
8
r.t
9
CH3
CH2Ph
(CH2)2
CH3
H
H
8
r.t
10
11
12
13
14
15
2j
CH2Ph
H
H
3j
8
r.t
2a
2b
2c
2e
2f
CCl=CH2
CCl=CH2
CCl=CH2
CO2Me
CO2Me
C≡CH
C≡CH
C≡CH
CO2H
CO2H
3a¢
3b¢
3c¢
3e¢
3f¢
12
12
12
4
40
(CH2)3
(CH2)4
(CH2)2
(CH2)3
40
reflux
reflux
reflux
4
a 1.2 equimolar amount of NaOH is employed in entries 1–10, and 4.0 equimolar amount of NaOH is employed in entries 11–15.
b Isolated yields over silica gel chromatography.
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88
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Preparation of Compounds 2a–2j, 2b¢ and 2d¢; General Proce-
dure, (Preparation of 2b Described as a Typical Procedure)
The Vilsmeier reagent was prepared by adding POCl3 (12.00 mmol,
1.12 mL) dropwise to ice-cold anhyd N,N-dimethylformamide
(DMF, 10 mL) under stirring. The mixture was then stirred for 10–
15 min at 0 °C. To the above Vilsmeier reagent was added 1b (6.00
mmol, 1.30 g) as a solution in DMF (5 mL). Then the mixture was
allowed to warm to r.t. and stirred for about 4 h. After the starting
material was consumed (monitored by TLC), the reaction mixture
was poured over crushed ice (5.0 g) and stirred. A white solid was
precipitated and isolated by filtration. The crude product 2b was pu-
rified by chromatography over silica gel using Et2O–hexane (1:60)
as eluent.
tals 3 can be regarded as alkylthio substituted enynes
which might be applied as valuable organic intermediates.
It is worth noting that there exist interconversions among
a-oxo ketene dithioacetals 1, a-chlorovinyl ketene dithio-
acetals 2 and a-ethynyl ketene dithioacetals 3 as shown in
Scheme 1. For example, with the treatment of H2SO4
(several drops) in ethanol at ambient temperature, 3b
could be converted into 1b directly in 76% yield. Once
HCl was employed, 3b could be converted into 2b in 78%
yield. Then 2b could be hydrolyzed in ethanol (95%) on
heating to give 1b in 67% yield.
2,4-Dichloro-3-(1,2-ethylenedithio-methylene)-penta-1,4-diene
(2a)
White oil.
IR: 3105, 2926, 2854, 1617, 1529, 1463, 893 cm–1.
1H NMR (80 MHz): d = 3.40 (t, 4 H, SCH2), 5.44 (s, 2 H, C=CH),
5.64 (s, 2 H, C=CH).
13C NMR (500 MHz): d = 38.24 (2 × C), 118.98 (2 × C), 122.15,
137.36 (2 × C), 148.89.
MS: m/z = 240 [M + 1]+ 240.
Anal. Calcd for C8H8Cl2S2: C, 40.17; H, 3.37. Found: C, 40.24; H,
3.42.
Scheme 1
2,4-Dichloro-3-(1,3-propylenedithio-methylene)-penta-1,4-di-
ene (2b)
White solid; mp 79–81 °C.
IR: 3100, 2927, 1616, 1508, 1403, 903 cm–1.
Conclusions
1H NMR (400 MHz): d = 2.20 (m, 2 H, CH2), 2.98 (t, 4 H, SCH2),
In summary, the Vilsmeier–Haack reactions of a-oxo
ketenedithioacetals 1 were investigated under various
conditions. A range of a-halovinyl ketene dithioacetals 2
was prepared from the reaction of a-oxo ketene dithioac-
etals 1 with Vilsmeier reagent (POCl3/DMF or PBr3/
DMF) in very high yields. With the treatment of NaOH in
ethanol or methanol, a-halovinyl ketene dithioacetals 2
were transformed into the corresponding a-ethynyl ketene
dithioacetals 3 in moderate to high yields. The a-function-
alized ketene dithioacetals 2 and 3 have the potential to be
used as important new intermediates in organic synthesis.
For example, 2b as electron-rich dienes might attend the
Diels–Alder reaction. The alkylthio and ethynyl substitu-
5.35 (s, 2 H, C=CH), 5.71 (s, 2 H, C=CH).
13C NMR (500 MHz): d = 23.93, 29.28 (2 × C), 120.44 (2 × C),
130.81, 134.58 (2 × C), 143.73.
MS: m/z = 253 [M+].
Anal. Calcd for C9H10Cl2S2: C, 42.69; H, 3.98. Found: C, 42.61; H,
4.04.
2,4-Dichloro-3-(1,4-butylenedithio-methylene)-penta-1,4-diene
(2c)
White solid; mp 120–122 °C.
IR: 3100, 2919, 2852, 1619, 1512, 1463, 899 cm–1.
1H NMR (400 MHz): d = 2.01 (m, 4 H, CH2), 3.10 (m, 4 H, SCH2),
ents at a and b positions to the carbon-carbon double bond 5.37 (s, 2 H, C=CH), 5.67 (s, 2 H, C=CH).
MS: m/z = 266 [M – 1]+.
of 3 are quite reactive groups, which makes this kind of
compounds good candidates to serve as precursors for fur-
ther synthetic transformations. The applications of a-
ethynyl ketene dithioacetals 3 and extension of the scope
of the methodology are currently under investigation in
our laboratory.
3-(Bis-methylsulfanyl-methylene)-2,4-dichloro-penta-1,4-diene
(2d)
White solid; mp 38–40 °C.
IR: 3103, 2922, 2854, 1618, 1507, 1411, 901cm–1.
1H NMR (400 MHz): d = 2.39 (s, 6 H, SCH3), 5.43 (s, 2 H, C=CH),
5.64 (s, 2 H, C=CH).
MS: m/z = 240 [M – 1]+.
All reagents were purchased from commercial sources and used
without treatment, unless otherwise indicated. DMF was dried over
anhyd P2O5. The products were purified by column chromatography
1
over silica gel. H NMR spectra and 13C NMR spectra were ob-
3-Chloro-2-(1,2-ethylenedithio-methylene)-but-3-enoic Acid
Methyl Ester (2e)
White solid; mp 72–74 °C.
IR: 2948, 1687, 1630, 1505, 1433, 1268, 911 cm–1.
1H NMR (400 MHz): d = 3.37 (t, 2 H, SCH2), 3.52 (t, 2 H, SCH2),
3.80 (s, 3 H, OCH3), 5.41 (s, 1 H, C=CH), 5.6 5 (s, 1 H, C=CH).
tained at 25 °C on a Bruker WP-80 spectrometer or a Varian spec-
trometer (Unity-400 or Inova-500 MHz) using CDCl3 (unless
otherwise indicated) as solvent and TMS as internal standard. Mass
spectra were recorded on a VG Platform mass spectrometer. IR
spectra (KBr) were recorded on a Magna-560 FTIR spectrophoto-
meter.
Synthesis 2005, No. 1, 85–91 © Thieme Stuttgart · New York

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Vilsmeier–Haack Reaction of a-Oxo Ketene Dithioacetals
89
13C NMR (500 MHz): d = 36.54, 39.75, 52.14, 115.13, 119.83,
3-(Bis-methylsulfanyl-methylene)-2,4-dibromo-penta-1,4-di-
ene (2d¢)
White solid; mp 44–46 °C.
IR: 3100, 2919, 1687, 1611, 1492, 903 cm–1.
1H NMR (400 MHz): 2.39 (s, 6 H, SCH3), 5.43 (s, 2 H, C=CH), 5.64
(s, 2 H, C=CH).
136.58, 164.78, 167.91.
MS: m/z = 236 [M – 1]+.
Anal. Calcd for C8H9O2S2Cl: C, 40.59; H, 3.83. Found: C, 40.43; H,
3.89.
3-Chloro-2-(1,3-propylenedithio-methylene)-but-3-enoic Acid
Methyl Ester (2f)
MS: m/z = 333 [M – 1]+.
White solid; mp 66–68 °C.
IR: 3097, 2950, 1690, 1632, 1491, 1253, 916 cm–1.
Preparation of Compounds 3a–j, 3a¢–f¢; General Procedure,
(Preparation of 3b Described as a Typical Procedure)
To a 50mL round-flask, was added 2b (2.00 mmol, 0.51 g), EtOH
(15 mL) and a solution of NaOH (2.40 mmol, 0.10 g) in water (4
mL). The mixture was stirred at r.t. for 12 h. After the starting ma-
terial was consumed (monitored by TLC), the reaction mixture was
poured into water and stirred. A white solid was precipitated and
isolated by filtration. The crude product 3b was purified by chroma-
tography over silica gel using Et2O–hexane (1:80) as eluent.
1H NMR (400 MHz): d = 2.19 (m, 2 H, CH2), 2.99 (t, 4 H, SCH2),
2.78 (s, 3 H, OCH3), 5.33 (d, J = 1.2 Hz, 1 H, C=CH), 5.68 (d, J =
1.2 Hz, 1 H, C=CH).
13C NMR (500 MHz): d = 23.24, 29.03, 29.53, 51.84, 120.49,
123.21, 134.46, 163.51, 163.80.
MS: m/z = 250 [M – 1]+.
Compounds 3a, 3c–j and 3a¢–f¢ were prepared following the same
procedure. In the cases of 3g–j, the Et2O work-up extracts from the
Vilsmeier reaction mixture of 1g–j were directly used. In the cases
of 3a¢–f¢, 4 equimolar amount of NaOH was used.
Anal. Calcd for C9H11O2S2Cl: C, 43.11; H, 4.42. Found: C, 43.20;
H, 4.31.
3-Chloro-1,2-ethylenedithio-buta-1,3-diene (2g)
Colorless liquid.
IR: 3075, 2943, 1684, 1546, 1493, 1238, 901 cm–1.
1H NMR (80 MHz): d = 3.35 (m, 4 H, SCH2), 5.30 (s, 1 H, C=CH),
5.36 (s, 1 H, C=CH), 6.12 (s, 1 H, C=CH).
2-(2-Chloropent-1-en-4-yn-3-ylidene)-1,3-dithiolane (3a)
Colorless liquid.
IR: 3286, 2923, 2052, 1506, 1420 cm–1.
1H NMR (80 MHz): d = 3.43 (m, 4 H, SCH2), 3.53 (s, 1 H, C≡CH),
5.48 (s, 1 H, C=CH), 5.53 (s, 1 H, C=CH).
MS: m/z = 202 [M – 1]+.
3-Chloro-1,3-propylenedithio-buta-1,3-diene (2h)
Colorless liquid.
IR: 3057, 2935, 1679, 1491, 1253, 896 cm–1.
1H NMR (80 MHz): d = 2.08 (m, 2 H, CH2), 2.91 (t, 4 H, SCH2),
5.29 (d, J = 1.6 Hz, 1 H, C=CH), 5.42 (d, J = 1.6 Hz, 1 H, C=CH),
6.12 (s, 1 H, C=CH).
2-(2-Chloropent-1-en-4-yn-3-ylidene)-1,3-dithiane (3b)
Colorless liquid.
IR: 3285, 2925, 2857, 2083, 1620, 1493, 892 cm–1.
1H NMR (80 MHz): d = 2.20 (m, 2 H, CH2), 2.95 (m, 4 H, SCH2),
3.57 (s, 1 H, C≡CH), 5.32 (d, J = 1.6 Hz, 1 H, C=CH), 5.62 (d, J =
1.6 Hz, 1 H, C=CH).
MS: m/z = 192 [M – 1]+.
3-Chloro-1,1-bis-methylsulfanyl-buta-1,3-diene (2i)
Colorless liquid.
IR: 3120, 2921, 2853, 1683, 1544, 1486, 1067, 875 cm–1.
1H NMR (80 MHz): d = 2.35 (s, 3 H, SCH3), 2.42 (s, 3 H, SCH3),
5.50 (d, J = 1.6 Hz, 1 H, C=CH), 5.56 (d, J = 1.6 Hz, 1 H, C=CH),
5.97 (s, 1 H, C=CH).
MS: m/z = 216 [M – 1]+.
2-(2-Chloropent-1-en-4-yn-3-ylidene)-1,3-dithiepane (3c)
White solid; mp 50–52 °C.
IR: 3286, 2912, 2010, 1691, 1514, 898 cm–1.
1H NMR (80 MHz): d = 1.95 (m, 4 H, CH2), 2.99 (m, 4 H, SCH2),
3.50 (s, 1 H, C≡CH), 5.25 (d, J = 1.6 Hz, 1 H, C=CH), 5.53 (d, J =
1.6 Hz, 1 H, C=CH).
MS: m/z = 180 [M – 1]+.
3-Chloro-1,1-bis-benzylsulfanyl-buta-1,3-diene (2j)
Colorless liquid.
IR: 3060, 3028, 2923, 1604, 1545, 1494, 1453, 887, 701 cm–1.
1H NMR (80 MHz): d = 3.97 (s, 2 H, SCH2), 4.10 (s, 2 H, SCH2),
5.32 (d, J = 1.6 Hz, 1 H, C=CH), 5.45 (d, J = 1.6 Hz, 1 H, C=CH),
6.21 (s, 1 H, C=CH), 7.28 (m, 10 H, ArH).
MS: m/z = 230 [M – 1]+ 230.
3-[Bis(methylthio)methylene]-2-chloropent-1-en-4-yne (3d)
Colorless liquid.
IR: 3286, 2923, 2854, 2080, 1623, 1424, 902 cm–1.
1H NMR (80 MHz): d = 2.40 (s, 3 H, SCH3), 2.49 (s, 3 H, SCH3),
3.55 (s, 1 H, C≡CH), 5.42 (d, J = 1.6 Hz, 1 H, C=CH), 5.60 (d, J =
1.6 Hz, 1 H, C=CH).
13C NMR (CDCl3, 500 MHz): d = 17.73, 18.32, 80.87, 85.44,
118.65, 120.89, 135.37, 151.02.
2,4-Dibromo-3-(1,3-propylenedithio-methylene)-penta-1,4-di-
ene (2b¢)
White solid; mp 72–74 °C.
IR: 3100, 2919, 1687, 1611, 1492, 903 cm–1.
1H NMR (400 MHz): d = 2.15 (m, 2 H, CH2), 2.98 (t, 4 H, SCH2),
5.80 (d, J = 1.2 Hz, 2 H, C=CH), 5.93 (d, J = 1.2 Hz, 2 H, C=CH).
13C NMR (500 MHz): d = 23.77, 29.18 (2 × C), 124.90, 125.12,
126.53, 133.31 (2 × C), 142.83.
MS: m/z = 204 [M + 1]+.
Anal. Calcd for C8H9ClS2: C, 46.93; H, 4.43. Found: C, 47.01; H,
4.49.
Methyl 2-(1,3-Dithiolan-2-ylidene)but-3-ynoate (3e)
White solid; mp 109–110 °C.
IR: 3259, 2360, 1683, 1485, 1275, 1194, 1008 cm–1.
Anal. Calcd for C9H10Br2S2: C, 31.60; H, 2.95. Found: C, 31.51; H,
2.86.
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1H NMR (500 MHz): d = 3.44–3.46 (m, 2 H, SCH2), 3.54–3.57 (m,
2 H, SCH2), 3.65 (s, 1 H, C≡CH), 3.82 (s, 3 H, CH3O).
13C NMR (500 MHz): d = 36.83, 40.64, 52.70, 80.06, 85.55, 98.55,
165.64, 174.89.
2-(Penta-1,4-diyn-3-ylidene)-1,3-dithiane (3b¢)
White solid; dp 108–110 °C.
IR: 3271, 2925, 2092, 1638, 1486 cm–1.
1H NMR (400 MHz): d = 2.20 (m, 2 H, CH2), 3.03 (t, 4 H, SCH2),
3.47 (s, 2 H, C≡CH).
MS: m/z = 201 [M + 1]+.
Anal. Calcd for C8H8O2S2: C, 47.98; H, 4.03. Found: C, 47.80; H,
3.90.
13C NMR (500 MHz): d = 23.16, 29.10 (2 × C), 79.49 (2 × C), 83.79
(2 × C), 95.82, 158.41.
Anal. Calcd for C9H8S2: C, 59.96; H, 4.47. Found: C, 60.02; H,
4.51.
MS: m/z = 180 [M – 1]+.
Methyl 2-(1,3-Dithian-2-ylidene)but-3-ynoate (3f)
White solid; mp104–106 °C.
IR: 3262, 2338, 1688, 1470, 1278, 1194, 997 cm–1.
1H NMR (500 MHz): d = 2.21–2.24 (m, 2 H, CH2), 2.97 (t, J = 7.0
Hz, 2 H, SCH2), 3.05 (t, J = 7.0 Hz, 2 H, SCH2), 3.67 (s, 1 H,
C≡CH), 3.80 (s, 3 H, CH3O).
13C NMR (500 MHz): d = 23.45, 29.76, 29.94, 52.48, 79.10, 86.57,
106.47, 164.67, 170.65.
2-(Penta-1,4-diyn-3-ylidene)-1,3-dithiepane (3c¢)
White solid; dp 70–72 °C.
IR: 3256, 2927, 2091, 1645, 1490 cm–1.
1H NMR (80 MHz): d = 1.97 (m, 4 H, CH2), 3.02 (m, 4 H, SCH2),
3.37 (s, 2 H, C≡CH).
MS: m/z = 215 [M + 1]+.
2-(1,3-Dithiolan-2-ylidene)but-3-ynoic Acid (3e¢)
Anal. Calcd for C9H10O2S2: C, 50.44; H, 4.70. Found: C, 50.27, H,
4.61.
White solid; dp 144–146 °C.
IR: 3282, 2952, 2823, 2097, 1665, 1471, 1415, 1278, 1250 cm–1.
2-(Prop-2-ynylidene)-1,3-dithiolane (3g)
Colorless liquid.
IR: 2925, 2854, 2089, 1548 cm–1.
1H NMR (80 MHz): d = 3.36 (d, J = 2.0 Hz, 1 H, C≡CH), 3.43 (m,
4 H, SCH2), 5.52 (d, J = 2.0 Hz, 1 H, C=CH).
1H NMR (DMSO, 400 MHz): d = 3.46 (m, 2 H, SCH2), 3.56 (m, 2
H, SCH2) 3.66 (s, 1 H, C≡CH).
MS: m/z = 166 [M – 1]+.
2-(1,3-Dithian-2-ylidene)but-3-ynoic Acid (3f¢)
White solid; dp 140–142 °C.
IR: 3443, 2362,2091, 1657, 1424, 1279, 1189 cm–1.
MS: m/z [M – 1]+.
2-(Prop-2-ynylidene)-1,3-dithiane (3h)
Colorless liquid.
IR: 3283, 2998, 2901, 2827, 2087, 1586 cm–1.
1H NMR (DMSO, 400 MHz): d = 2.24 (m, 2 H, CH2), 2.97 (t, 2 H,
J = 6.8 Hz, SCH2), 3.07 (t, 2 H, J = 6.8 Hz, SCH2), 3.69 (s, 1 H,
C≡CH).
1H NMR (400 MHz): d = 2.17 (m, 2 H, CH2), 2.94 (t, 2 H, SCH2),
3.01 (t, 2 H, SCH2), 3.41 (d, J = 2.0 Hz, 1 H, C≡CH), 5.70 (d, J =
2.0 Hz, 1 H, C=CH).
13C NMR (DMSO, 500 MHz): d = 22.87, 29.23, 29.49, 80.13,
89.21, 106.77, 165.26, 168.20.
Anal. Calcd: for C8H8O2S2: C, 47.98; H, 4.03. Found: C, 47.95; H,
4.09.
MS: m/z = 156 [M – 1]+.
1,1-Bis(methylthio)but-1-en-3-yne (3i)
Colorless liquid.
Acknowledgment
IR: 3312, 2955, 2923, 2853, 2095, 1645, 1463, 1377, 901 cm–1.
1H NMR (80 MHz): d = 2.35 (s, 3 H, SCH3), 2.42 (s, 3 H, SCH3),
3.40 (d, J = 2.0 Hz, 1 H, C≡CH), 5.47 (d, J = 2.0 Hz, 1 H, C=CH).
Financial supports of this research by NNSFC (20272008) and the
Key Project of Chinese Ministry of Education (03059) are greatly
acknowledged.
1,1-Bis(benzylthio)but-1-en-3-yne (3j)
Colorless liquid.
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