Conversion of thiiranes to β-chlorothioacetates catalyzed with CoCl2

Article abstract of DOI:10.1081/SCC-120021514

Cobalt (II) chloride catalyzes the ring opening of thiiranes with acetyl chloride to produce vicinal chlorothioesters in good yields.

Full text of DOI:10.1081/SCC-120021514

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Conversion of Thiiranes to β-Chlorothioacetates
Catalyzed with CoCl2
N. Iranpoor a , H. Firouzabadi a & A. A. Jafari a
a Chemistry Department, College of Sciences, Shiraz University, Shiraz, Iran
Published online: 17 Aug 2006.
To cite this article: N. Iranpoor , H. Firouzabadi & A. A. Jafari (2003): Conversion of Thiiranes to β-Chlorothioacetates
Catalyzed with CoCl2 , Synthetic Communications: An International Journal for Rapid Communication of Synthetic Organic
Chemistry, 33:13, 2321-2327
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SYNTHETIC COMMUNICATIONSÕ
Vol. 33, No. 13, pp. 2321–2327, 2003
Conversion of Thiiranes to
b-Chlorothioacetates Catalyzed with CoCl2
*
N. Iranpoor, H. Firouzabadi, and A. A. Jafari
*
Chemistry Department, College of Sciences, Shiraz
University, Shiraz, Iran
ABSTRACT
Cobalt (II) chloride catalyzes the ring opening of thiiranes with acetyl
chloride to produce vicinal chlorothioesters in good yields.
Key Words: Thiirane; b-Chlorothioacetate; Acetyl chloride; CoCl2.
Due to the ready polymerization of thiiranes, ring-opening reactions
of this class of compounds are rarely studied. The reaction of thiiranes
are limited to the reaction with primary alcohols in the presence of highly
acidic catalysts such as BF3, HCl orH SO4,[1,2] which occurs at high
2
*Correspondence: N. Iranpoor and H. Firouzabadi, Chemistry Department,
College of Sciences, Shiraz University, Shiraz, 71454, Iran; E-mail: iranpoor@
chem.susc.ac.ir, firouzabadi@chem.susc.ac.ir.
2321
DOI: 10.1081/SCC-120021514
Copyright & 2003 by Marcel Dekker, Inc.
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2322
Iranpoor, Firouzabadi, and Jafari
Scheme 1.
temperature with extensive Polymerization[1,3] to produce b-alkoxy
mercaptans in low yields.
This reaction with boiling acetic acid is reported to produce a mix-
ture of monomeric and dimeric acetoxy mercaptans.[4] We have also
reported the use of catalysts such as Ce(IV),[5] DDQ,[6] I2, and
I2/PVP[7] for ring opening dimmerization of thiiranes to their b,b0-
dialkoxy- ordiacetoxy disulfides. Although the ring opening of epoxides
with acyl chlorides has been reported in the presence of different cata-
lysts,[8,9] but to the best of ourknowledge, this catalyzed eraction with
thiiranes has not been studied yet.
In this work, we report on the synthesis of b-chlorothioesters
from the reaction of thiiranes catalyzed with Co(II) as anhydrous
CoCl2 (Sch. 1).
We first studied the reactions of styrene sulfide (1a) and epichlorohy-
drine (1f ) as examples of activated and deactivated thiiranes with acetyl
chloride in the presence of different Lewis acids as catalyst and also in the
absence of catalyst. The reaction of styrene episulfide (1a) with acetyl
chloride in the absence of catalyst occured in CH2Cl2 at room tempera-
ture and after 6 h produced a mixture of 2a and 3a (60%) with the ratio of
88:12. However the reaction of epichlorohydrine (1f ) with acetyl chloride
did not produce any product under these conditions (Table 1).
We then studied the catalytic effect of different Lewis acids on
these reactions. The results of Table 1 show that, among the studied
catalysts in this work, the presence of CoCl2, not only improves
the yield and the regioselectivity of the reaction of styrene oxide (1a)
with acetyl chloride, but also greatly affects the reaction’s time. The
role of catalyst for this transformation is also demonstrated in the
reaction of epichlorohydrine (1f ). This epoxide which does not react
with acetyl chloride in the absence of catalyst, reacts in the presence
of 0.05 molar equivalents of anhydrous Co(II) chloride and produces
the corresponding thioacetates (2f/3f ) in 81% yield with absolute
chemoselectivity of 0/100.

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Conversion of Thiiranes to b-Chlorothioacetates
2323
Table 1. Effect of 0.05 molarequivalents of different catalysts in the
reaction of styrene sulfide (la) and epichlorohydrine (1f ) with acetyl
chloride in CH2Cl2 at room temperature.
Time
Entry Thiirane Catalyst (min)
Ratio of
3/2a
Product
% Yieldb
1
2
3
4
5
6
7
8
1a
1a
1a
1a
1a
1f
Non
AlCl3
600
5
3a þ 2a
3a þ 2a
3a þ 2a
3a þ 2a
3a þ 2a
90/10
90/10
90/10
88/12
98/2
60
40
20
35
85
c
c
FeCl3
ZnCl2
5
c
5
10
CoCl2
Non
CoCl2
600 No reaction
1f
240
2
3f þ 2f
0/100
10/90
81
37
c
1f
AlCl3
3e þ 2e
aIsomeric ratio was determined by GC and NMR analysis. bIsolated
yield of the mixture of isomers. The reaction completes quickly and
produces an unidentified polymeric material as major product.
The use of otherLewis acids in this study such as AICl , FeCl3, and
3
ZnCl2 do not show the pronounced effect of anhydrous CoCl2 on the
progress of the reaction. We therefore studied the ring opening reaction
of different thiiranes with acetyl chloride in the presence of anhydrous
CoCl2 in CH2Cl2 at room temperature (Table 2).
The reactions were occurred smoothly and furnished the correspond-
ing b-chloroacetates in good yields. The regioselectivity of the reaction is
controlled mainly by the electronic nature of the substituents on the
thiirane ring.
In the case of styrene sulfide, the presence of phenyl group as an
electron-releasing substituent favored the attack of chloride ion on the
benzylic carbon of the ring, however, in the case of electron-withdrawing
substituted thiiranes, the opposite attack is responsible for production of
the major isomer. The mechanism of the reaction is not clear, but the
activation of acetyl chloride with COCl2 followed by the attack of thiir-
ane sulfuratom can be suggested (Sch. 2).
The interaction of Co(II) with the oxygen of acetyl chloride could
both accelerate the reaction rate, and also affect the regioselectivity as it
was shown in Table 2.
In conclusion, the presence of Co(II) as catalyst, provides the
possibility of praparing b-chlorothioacetates from different thiiranes.
The role of this catalyst is well shown in the possiblity of reacting
thiiranes having electron-withdrawing substituents. The good to excellent
chemoselectivities and high yields of the reactions are also considerable.

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2324
Iranpoor, Firouzabadi, and Jafari
Table 2. Reaction of thiiranes with acetyl chloride in the presence of 0.05 mmol of
anhydrous CoCl2 as a catalyst.
Product
(isomeric ratio)a
Time, min
(Yield %)b
Entry
1
Thiiranes
i) PhCHClCH2(SCOCH3) (98%)
10 (85)
ii) PhCH(SCOCH3)CH2Cl (2%)
i) CH2¼CHCH2OCH2CHClCH2
(SCOCH3) (29%)
2
135 (94)
ii) CH2¼CHCH2OCH2CH(SCOCH3)
CH2Cl (71%)
3
i) (CH3)2CHOCH2CHClCH2
(SCOCH3) (30%)
110 (77)
ii) (CH3)2CHOCH2CH(SCOCH3)
CH2Cl (70%)
i) PhOCH2CHClCH2(SCOCH3) (24%)
4
5
210 (86)
180 (89)
ii) PHOCH2CH(SCOCH3)CH2Cl (76%)
i) CH2¼CH(CH3)CO2CHClCH2
(SCOCH3) (25%)
ii) CH2¼CH(CH3)CO2CH2CH(SCOCH3)
CH2Cl (75%)
i) ClCH2CH(SCOCH3)CH2Cl (100%)
6
7
240 (81)
30 (75)
i) CH3(CH2)3CHClCH2(SCOCH3) (55%)
ii) CH3(CH2)3CH(SCOCH3)CH2Cl (45%)
8
8 (87)
b
aDetermined by GC and NMR analysis. Total yield of the isomeric products.
Scheme 2.

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Conversion of Thiiranes to b-Chlorothioacetates
2325
EXPERIMENTAL
Infra red spectra were recorded on a Perkin Elmer IR-157 G and a
1
Perkin Elmer 781 spectrometer. H and 13C NMR spectra were recorded
on a Bruker Avance DPX-250.
General procedure for preparation of b-chlorothioacetates. To a solu-
tion of thiirane (l mmol) in CH2Cl2 (2 mL), acetyl chloride (1.2–2 mmol)
was added followed by the addition of anhydrous CoCl2 (0.05 mmol,
6.5 mg). The reaction mixture was stirred at room temperature for
0.1–4 h and monitored with GC or TLC analysis. After completion of
the reaction, diethyl ether (35 mL) was added. The organic layer was
separated and washed with water (20 mL) and dried over anhydrous
Na2SO4. Evaporation of the solvent followed by chromatography on a
short column of silica-gel using petroleum ether/ethyl acetate (8:2)
afforded the pure b-chlorothioacetates in 77–94% yield. The ratio of
each isomerwas determined by both GC and NMR analysis.
Thioacetate acid S-(2-chloro-2-phenyl-ethyl) ester (3a). IR (neat)
ꢀ 3095, 3060, 2850, 1705, 1505, 1469, 1369, 1250, 1150. 1H NMR
(CDCl3) ꢁ: 7.2–7.4 (5H, m), 4.9 (IH, t), 3.5 (2H, dd), 2.2 (3H, s).
13C NMR (CDCl3) ꢁ: 194.8, 140.4, 129.2, 128.6, 127.6, 62.3, 38.4, 30.9.
MS (70 eV): (M, 1.7%), (M þ 2, 0.6%), (M-Cl, 3.7%), (M-HCl, 0.8%),
(M-C2H2OS, 8.7%), (M-C2H3OS, 5.1%), (M-C2H4OS, 26.8%), (M-
C2H5OSCl, 10%), (M-C2H4OCl, 13.3%).
Thioacetate acid S-(2-chloro-cyclohexyl-ethyl) ester (3b). Colorless
oil. IR (neat) ꢀ 2925, 2870, 1700, 1450, 1360, 1270, 1238, 1225, 1215,
1
1130, 1010. H NMR (CDCl3) ꢁ: 3.95 (1H, m), 3.7 (IH, m), 2.3 (3H, s),
2.15–2.34 (2H, m), 1.75–1.82 (2H, m), 1.41–1.55 (4H, m). 13C NMR
(CDCl3) ꢁ: 194.4, 61.6, 48.95, 34.9, 31.5, 31.1, 24.7, 23.6. MS (70 eV);
(M, 2.8%), (M þ 2, 1%), (M-Cl, 1.2%), (M-HCl, 3.4%), (M-C2H4O5,
12.3%), (M-C2H3OCl, 2.3%), (M-C3H4OSCl, 2.3%), (M-C3H5OSCl,
29.6%), (M-C3H6OSCl, 14.6%).
Thioacetate acid S-(2-chloro-hexyl) ester (3d). Colorless oil. IR (neat)
1
ꢀ 2970, 2945, 2890, 2875, 1750, 1710, 1475, 1362, 1240, 1140. H NMR
(CDCl3) ꢁ: 3.7 (2H, m), 3.25 (IH, m), 2.3 (3H, s), 1.8–1.3 (6H, m), 0.9
(3H, t). 13C NMR (CDCl3) ꢁ: 195.4, 61.8, 48.1, 37.2, 30.9, 29.1, 22.7, 14.3.
MS (70 eV): (M, 0.1%), (M-HCl, 0.1%), (M-C2H3OS, 0.3%),
(M-C2H4OS, 0.3%), (M-C2H4OSCl, 0.9%).
Thioacetate acid S-(1-allyloxymethyl-2-chloro-ethyl) ester (2c).
Colorless oil. IR (neat) ꢀ 3090, 2995, 2885, 1700, 1435, 1360, 1240,
1
1130. H NMR (CDCl3) ꢁ: 5.87 (1H, m), 5.21 (2H, dd), 4 (3H, m), 3.75
(2H), 3.6 (2H, m), 2.3 (3H). 13C NMR (CDCl3) ꢁ: 194.5, 134.6, 117.8,
72.6, 68.4, 45.4, 44.4, 30.9. MS (70 eV): (M, 1%), (M þ 2, 0.4%), (M-HCl,

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2326
Iranpoor, Firouzabadi, and Jafari
0.1%), (M-C2H3OS, 0.3%), (M-C2H4O, 1.9%), (M-C3H6O, 5.6%), (M-
C3H5O, 0.7%).
Thioacetate acid S-(2-chloro-l-isopropoxymethyl-ethyl) ester (2e).
Colorless oil. IR (neat) ꢀ 2980, 2940, 2880, 1705, 1475, 1435, 1385,
1
1375, 1360, 13420, 1290, 1180, 1135, 1020. H NMR (CDCl3) ꢁ: 3.5–3.7
(2H þ 3H, complex), 2.3 (3H, s), 1.15 (6H, d). 13C NMR (CDCl3) ꢁ:
194.7, 72.6, 66.4, 45.7, 44.5, 30.8, 22.3. MS (70 eV): (M, 0.5%), (M þ 2,
0.2%), (M-HCl, 0.2%), (M-C3H8O, 1.4%), (MC5H11OCl, 13.3%).
Thioacetate acid S-(2-chloro-l-chloromethyl-ethyl) ester (2f ).
Colorless oil. IR (neat) ꢀ 2960, 2892, 1700, 1435, 1365, 1275, 1115.
1H NMR (CDCl3) ꢁ: 4 (1H, m), 3.9 (2H, m), 3.75 (2H), 2.3 (3H).
13C NMR (CDCl3) ꢁ: 198, 46.7, 44, 30.6. MS (70 eV): (M, 1.6%), (M-
Cl, 0.3%), (M-HCl, 0.6%), (M-C2H3OS, 0.7%), (M-C2H4OS, 1.3%),
(M-C2H3OCl, 3.1%).
Thioacetate acid S-(2-chloro-1-phenoxymethyl-ethyl) ester (2g).
Colorless oil. IR (neat) ꢀ 3063, 3042, 1930, 1880, 1695, 1600, 1590,
1495, 1460, 1430, 1385, 1355, 1300, 1290, 1240, 1175, 1130, 1080, 1055,
1035. 1H NMR (CDCl3) ꢁ: 7.22–7.57 (2H, m), 6.87–6.97 (3H, m), 4.3 (2H,
m), 4.1 (1H, m), 3.8 (2H), 2.3 (3H). 13C NMR (CDCl3) ꢁ: 194.1, 158.5,
130, 121.9, 115.1, 66.5, 45, 44.2, 31. MS (70 eV): (M, 3.1%), (M þ 2,
1.2%), (M-Cl, 0.5%), (M-HCl, 0.3%), (M-C6H5O, 12.2%),
(M-C8H8O2, 0.6%), (M-C2H3O5, 0.6%), (M-C5H7OSCl, 42.8%).
2-Methyl-acrylic acid 2-acetylsulfanyl-3-chloro-propyl ester (2h).
2965, 2940, 1730, 1705, 1635, 1460, 1440, 1410, 1380, 1360, 1325, 1300,
1150, 1020. 1H NMR (CDCl3) ꢁ: 6.15 (1H, dd), 5.5 (IH, dd), 4.3 (3H, m),
3.7 (2H, m), 2.3 (3H, s), 1.9 (3H, s). 13C NMR (CDCl3) ꢁ: 192.4, 166,
136.1, 126.1, 63, 44.4, 44, 30.7, 18.7. MS (70 eV): (M, 0.5%), (M þ 2,
0.2%), (M-Cl, 0.1%), (M-HCl, 0.3%), (M-C2H4OS, 0.5%),
(M-C4H6O2, 4%), (M-C2H5OSCl, 0.7%).
ACKNOWLEDGMENT
The authors appreciate the Research Council of Shiraz University for
partial support of this work.
REFERENCES
1. Synder, H.R.; Stewart, J.M.; Ziegler, J.B. J. Am. Chem. Soc. 1974,
69, 2675.

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Conversion of Thiiranes to b-Chlorothioacetates
2327
2. Synder, H.R.; Stewart, J.M. US Patent, 2,497,422, 1950; Chem. Abst.
1950, 44, 4025.
3. Kwart, H.; Hewig, J.A. J. Chem. Soc. 1963, 85, 1508.
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Received in the Netherlands October 16, 2002

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