Study of the Rh2(OAc)4- or BF3·OEt2-mediated reaction of thioacetic S-acid with α-diazocarbonyl compounds

Article abstract of DOI:10.1002/ejoc.200210592

The Rh₂(OAc)₄-catalyzed reaction of methyl aryldiazo-acetates with thioacetic S-acid gives exclusively the S-H insertion products in high yields, while the corresponding reaction mediated by BF₃·OEt₂ gives O-est

Full text of DOI:10.1002/ejoc.200210592

FULL PAPER
Study of the Rh2(OAc)4- or BF3·OEt2-Mediated Reaction of Thioacetic S-Acid
with α-Diazocarbonyl Compounds
Wengang Yao,[a] Mingyi Liao,[a] Xiaomei Zhang,[a] Hao Xu,[a] and Jianbo Wang*[a]
Keywords: Carbenoids / Diazo compounds / Insertion / Lewis acids
The Rh2(OAc)4-catalyzed reaction of methyl aryldiazo- ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
acetates with thioacetic S-acid gives exclusively the S−H
insertion products in high yields, while the corresponding re-
action mediated by BF3·OEt2 gives O-esters. The mechanism
of the reaction is discussed.
Germany, 2003
Introduction
Results and Discussion
Methyl phenyldiazoacetate 1a was used as the first sub-
strate in this investigation (Scheme 1). When the diazo com-
pound was slowly added to a stirring solution under reflux
of freshly distilled thioacetic S-acid in CH2Cl2 containing 1
mol % Rh2(OAc)4, the reaction was complete within 60 min
to give a single product, which was isolated in 93% yield.
Spectroscopic data confirmed that the product was S-ester
3a, which was formed through normal SϪH insertion by
an RhIIϪcarbene. When the same substrate was reacted,
however, with thioacetic S-acid in the presence of 30 mol %
of BF3·OEt2 in CH2Cl2 at room temperature, an unexpected
product, methyl α-acetoxyphenyl acetate 4a, was isolated.
The structure of 4a was confirmed by spectral data and by
the comparison with a sample prepared independently by
OϪH insertion catalyzed by Rh2(OAc)4 of 1a into acetic
acid.[5] In the BF3·OEt2-catalyzed reaction, careful inspec-
The SϪH insertion of diazo carbonyl compounds with
thiols is a synthetically useful reaction that can introduce a
sulfur-containing substituent adjacent to the carbonyl
group of ketones or esters.[1] Similarly to the corresponding
OϪH insertions of alcohols,[2] this type of insertion reac-
tion can be promoted by photolysis or by transition metal
catalysis. It has been reported by McKervey et al. that the
Rh2(OAc)4-catalyzed reaction of diazo carbonyl com-
pounds with thiophenol gives α-phenylthio ketones and es-
ters in good yields.[3] The intramolecular SϪH insertion re-
action is also known to be highly efficient.[4] Although the
SϪH insertion into thiols and the OϪH insertion into the
OϪH bond of carboxylic acids have been well investi-
gated,[5] the corresponding reactions of α-diazo carbonyl
compounds with thiocarboxylic acids have received only
limited attention. In 1977, Sheehan et al. reported the pho-
toinduced reaction of 6-diazopenicillinate with thiocarbox-
ylic acids, from which the S-esters were obtained in moder-
ate yields.[6] In 1978, Thomas and coworkers reported the
reaction between that same diazo compound and thioacetic
acid in the presence of BF3·OEt2. In Thomas’s case, the
corresponding S-ester was isolated in low yield.[7] Since
thiocarboxylic acids may exist as a tautomeric mixture of
thiol and thione forms,[8] it is interesting to investigate the
chemoselectivity of this reaction. Here we report our study
on the reaction of thioacetic S-acid with α-diazo carbonyl
compounds, catalyzed by an RhII catalyst and a Lewis acid.
1
tion of the H NMR spectra of the reaction mixture before
purification revealed that O-ester 5 was formed initially.
[a]
Key Laboratory of Bioorganic Chemistry and Molecular
Engineering of Ministry of Education, Department of Chemical
Biology, College of Chemistry,
Peking University, Beijing 100871, China
Fax: (internat) ϩ 86-10/6275-1708
E-mail: wangjb@pku.edu.cn
Supporting information for this article is available on the
WWW under http://www.eurjoc.org or from the author.
Scheme 1
1784
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
DOI: 10.1002/ejoc.200200592
Eur. J. Org. Chem. 2003, 1784Ϫ1788

Rh2(OAc)4- or BF3·OEt2-Mediated Reaction of Thioacetic S-Acid with α-Diazocarbonyl Compounds
FULL PAPER
The CϭS group in 5 was readily replaced by a CϭO group
Next, we extended this investigation to other diazo car-
during the workup and column chromatography bonyl compounds 6a؊c. In contrast to the reaction of
1
(Scheme 2). Moreover, from the H NMR spectrum of the methyl arylacetate 1, the Rh2(OAc)4-catalyzed reaction of
crude product, we determined that the thioester 3a was the ethyl diazoacetate 6a gave a complex mixture of products.
minor product. Interestingly, if the reaction time was pro- We also have tried Rh2(O2CCF3)4 as the catalyst, but it gave
longed from 10 min to 12 h, the S-ester 3a became the main a similar complex mixture. When the reaction was cata-
product. It is likely that the excess thioacetic S-acid can lyzed, however, by BF3·OEt2, the O-ester 7a was isolated
further attack the initially formed O-ester 5 or α-acetoxy- as the main product (Scheme 3). We found 7a to be stable
phenyl acetate 4a to give 3a. To substantiate this hypothesis, under normal workup and separation conditions. Diazo-
isolated 4a was treated with excess thioacetic S-acid in acetates 6b and 6c gave similar results, although in the case
CH2Cl2 containing BF3·OEt2. We found that 4a was con- of 6c the yield was somewhat low. The structures of 7a؊c
verted slowly into 3a. This transformation was accelerated were confirmed by spectral data, and by comparison of 7b
by the addition of Et3N to the reaction mixture.
with benzyl α-S-thioacetoxyacetic ester, which was prepared
by the reaction of thioacetic S-acid with benzyl chloro-
acetate under basic conditions.
Scheme 2
Another pathway for the formation of 3a in the
BF3·OEt2-catalyzed reaction is an intramolecular re-
arrangement of 5. Since 5 could not be isolated in a pure
form, we could not confirm this pathway experimentally.
To demonstrate the generality of the reaction, we investi-
gated the reaction of thioacetic S-acid with other methyl
arylacetates under conditions of Rh2(OAc)4 or BF3·OEt2
catalysis, and the results are summarized in Table 1. We see
that Rh2(OAc)4-catalyzed reactions all give the SϪH-inser-
tion products in good to excellent yields, while the
BF3·OEt2-catalyzed reactions gave the methyl α-acetoxy-
phenylacetates 4a؊f in low to moderate yields. Various
amounts of 3a؊f were detected from the reaction mixture
when BF3·OEt2 was used as the catalyst.
Scheme 3
These experimental results raise intriguing questions re-
garding the reaction mechanism. Although there is evidence
to show that simple thiocarboxylic acids may exist as an
equilibrium between thiol form 2 and thione form 8 in solu-
tion, it is generally believed that the thiol structure pre-
dominates (Scheme 4).[8] By observing the 13C NMR spec-
trum, we confirmed that a catalytic amount of Rh2(OAc)4
or BF3·OEt2 does not change thioacetic acid, which shows
a peak at δ ϭ 194.09 ppm in CDCl3 at room temperature.
Based on this information, we suggest that for both
Rh2(OAc)4- and BF3·OEt2-catalyzed reactions, the
thioacetic acid participates in the reaction in its thiol
form 2.
Table 1. The reaction of methyl aryldiazoacetate 1 with thioacetic
S-acid
Entry
Diazo substrate
Catalyst[a]
3:4[b]
Main product
yield (%)[c]
Scheme 4
1
2
3
4
5
6
7
8
1a
1a
1b
1b
1c
1c
1d
1d
1e
1e
1f
Rh2(OAc)4
BF3·OEt2
Rh2(OAc)4
BF3·OEt2
Rh2(OAc)4
BF3·OEt2
Rh2(OAc)4
BF3·OEt2
Rh2(OAc)4
BF3·OEt2
Rh2(OAc)4
BF3·OEt2
100:0
16:84
100:0
14:86
100:0
11:89
100:0
50:50
100:0
25:75
100:0
20:80
93
43
77
64
85
41
89
37[d]
79
24
57
59
We propose that the mechanism of the reaction of methyl
aryldiazoacetate with thioacetic S-acid, catalyzed by
Rh2(OAc)4, proceeds through a typical SϪH insertion by
RhIIϪcarbene 9 (Scheme 5). It has been suggested that an
XϪH (X ϭ O, S, N, etc.) insertion reaction of a diazocar-
bonyl compound, catalyzed by a transition metal complex,
follows a stepwise processes in which nucleophilic attack of
a heteroatom X at the electrophilic metal carbene forms an
ylide, which subsequently undergoes 1,2-rearrangement to
transfer a proton from X to the carbon atom to give
the formal insertion product.[1,2,9] For the reaction of
9
10
11
12
1f
[a]
[b]
1 mol % Rh2(OAc)4 or 30 mol % BF3·OEt2 was used.
The
ratio was determined from a 1H NMR spectrum of the crude prod-
uct. Isolated yield. Yield refers to compound 4.
[c]
[d]
Eur. J. Org. Chem. 2003, 1784Ϫ1788
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 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1785

W. Yao, M. Liao, X. Zhang, H. Xu, J. Wang
FULL PAPER
RhIIϪcarbene with thioactic S-acid, however, it is more
likely that direct insertion into the SϪH bond occurs, be-
cause the electron-withdrawing acetyl group decreases the
electron density of the sulfur atom, and thus makes it
less nucleophilic toward the electron-deficient carbenoid
carbon atom.
Conclusions
We have carried out a study on the reaction of thioacetic
S-acid with α-diazo carbonyl compounds under conditions
of Rh2(OAc)4 or BF3·OEt2 catalysis. We found the reaction
to be dependant on both the diazo substrate and the cata-
lysts used. The Rh2(OAc)4-catalyzed reaction of methyl
aryldiazoacetate with thioacetic S-acid, which may find its
utility in organic synthesis, gave a good yield of the S-ester.
Experimental Section
General Remarks: All reactions were performed under a nitrogen
atmosphere in flame-dried reaction flasks, and the components
were added by syringe. All solvents were distilled prior to use.
CH3COSH was purchased from Aldrich, and was distilled with col-
lection of the fraction boiling at 88Ϫ92 °C. CH2Cl2 was distilled
from CaH2. BF3·Et2O was distilled before use. For chromatogra-
phy, 100Ϫ200 mesh silica gel (Qindao, China) was employed. 1H
and 13C NMR spectra were recorded at 200 MHz and 50 MHz with
a Varian Mercury 200 spectrometer. Chemical shifts are reported
in ppm using tetramethylsilane as the internal standard. IR spectra
were recorded with a Nicolet 5MX-S infrared spectrometer. Mass
spectra were obtained on a VG ZAB-HS mass spectrometer.
Scheme 5
The BF3·OEt2-catalyzed reaction follows a different
mechanism. The BF3·OEt2 unit complexes with the car-
bonyl group of the diazo compound,[1] followed by nucleo-
philic attack of thioacetic S-acid’s carbonyl-group oxygen
atom to generate 11, which deprotonates to give 5.
General Procedure for the Rh2(OAc)4-Catalyzed Reaction of Diazo
Compounds with Thioacetic S-Acid: CH3COSH (1.0 mmol) and
Rh2(OAc)4 (ഠ 0.005 mmol) were dissolved in CH2Cl2 (5 mL). The
solution was heated under gentle reflux under N2. To this solution
was added dropwise a solution of diazo compound (0.5 mmol) in
CH2Cl2 (5 mL) over 30 min. The reflux was continued for 30 min
after addition. CH2Cl2 (20 mL) was added, and the solution was
washed with 1  NaOH and then with brine. A typical work-up
gave a crude product that was purified on a silica gel column elut-
ing with petroleum ether/diethyl ether (40:1). The structures of the
products were confirmed by IR, 1H NMR and 13C NMR spec-
troscopy and mass spectrometry.
On the other hand, although a theoretical study suggests
that a CϭO bond is more stable than a CϭS bond in gen-
eral,[10] it is not clear why, in the BF3·OEt2-catalyzed reac-
tion of methyl phenyldiazoacetate, the CϭS bond in the
initially formed product 5 can be easily replaced by CϭO,
while the CϭS bond is relatively stable in 7a, 7b and 7c. In
the case of 5, we speculate that enolization occurs readily
because of the stabilizing effect of the phenyl ring. In the
enol structure 13, the thioacetyl group is close to the hy-
droxyl group. The ester group may accelerate the conversion
of CϭS to CϭO through neighboring-group participation
(Scheme 6). In O-esters 7a, 7b and 7c, the enolization is
more difficult because of lack of stabilization by a phenyl
ring. Consequently, in these cases, the O-esters with a CϭS
group are relatively stable.
General Procedure for the BF3·OEt2-Catalyzed Reaction of Diazo
Compounds with Thioacetic S-Acid: The diazo compound
(0.33 mmol) in CH2Cl2 (3 mL) was added dropwise over 5Ϫ10 min
at room temperature to a solution of CH3COSH (3.3 mmol) and
BF3·Et2O (0.1 mmol) dissolved in CH2Cl2 (2 mL). Stirring was
continued for another 5 min under N2 at room temperature, then
water (5 mL) and CH2Cl2 (20 mL) were added. The same procedure
as described above gave pure products whose structures were con-
firmed by IR, 1H NMR, and 13C NMR spectroscopy and mass
spectrometry.
Methyl (Acetylthio)(phenyl)acetate (3a):[11] From the Rh2(OAc)4-
catalyzed reaction: colorless oil, 93%. IR: ν˜ ϭ 2955, 1743, 1698,
1
1241, 1134, 786 cmϪ1. H NMR (CDCl3): δ ϭ 2.33 (s, 3 H), 3.72
(s, 3 H), 5.32 (s, 1 H), 7.29Ϫ7.38 (m, 5 H) ppm. 13C NMR (CDCl3):
δ ϭ 29.9, 51.0, 53.0, 128.3, 128.4, 129.9, 134.7, 170.4, 193.8 ppm.
MS: m/z ϭ 224 (2) [Mϩ], 192 (51), 182 (51), 150 (30), 123 (81), 90
(10), 77 (14), 43 (100).
Methyl (Acetyl)(phenyl)acetate (4a):[12] From the BF3·Et2O-cata-
lyzed reaction: colorless oil, 43%. IR: ν˜ ϭ 2955, 1757, 1233, 786
1
cmϪ1. H NMR (CDCl3): δ ϭ 2.20 (s, 3 H), 3.72 (s, 3 H), 5.93 (s,
1 H), 7.36Ϫ7.47 (m, 5 H) ppm. 13C NMR (CDCl3): δ ϭ 20.7, 52.6,
74.4, 127.6, 128.8, 129.2, 133.7, 169.3, 170.3 ppm. MS: m/z ϭ 208
(4) [Mϩ], 176 (31), 166 (52), 149 (62), 107 (100).
Scheme 6
1786
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Eur. J. Org. Chem. 2003, 1784Ϫ1788

Rh2(OAc)4- or BF3·OEt2-Mediated Reaction of Thioacetic S-Acid with α-Diazocarbonyl Compounds
FULL PAPER
Methyl (Acetylthio)(m-chlorophenyl)acetate (3b): From the 7.09Ϫ7.35 (m, 3 H) ppm. 13C NMR (CDCl3): δ ϭ 20.7, 52.7, 70.4,
Rh2(OAc)4-catalyzed reaction: colorless oil, 77%. IR: ν˜ ϭ 2954, 124.6, 126.3, 126.6, 134.0, 169.0, 170.2 ppm. MS: m/z ϭ 214 (3)
1
1743, 1698, 1132, 770 cmϪ1. H NMR (CDCl3): δ ϭ 2.36 (s, 3 H), [Mϩ], 182 (14), 172 (31), 155 (19), 113 (89), 96 (4), 85 (22), 43 (100).
3.75(s, 3 H), 5.29 (s, 1 H), 7.27Ϫ7.40 (m, 4 H) ppm. 13C NMR
(CDCl3): δ ϭ 29.9, 50.3, 53.2, 126.6, 128.5, 128.6, 130.0, 134.6,
136.9, 169.8, 193.2 ppm. MS: m/z ϭ 258 (1) [Mϩ], 226 (9), 216
(13), 184(6), 157 (15), 84 (76), 77 (1), 43 (100). HRMS calcd. for
C11H11O3SCl [Mϩ] 258.0117; found 258.0114.
HRMS calcd. for C9H10O4S [Mϩ] 214.0299; found 214.0292.
Methyl (Acetylthio)(1-naphthyl)acetate (3f): From the Rh2(OAc)4-
catalyzed reaction: colorless oil, 57%. IR: ν˜ ϭ 2953, 1743, 1694,
1132 cmϪ1 1H NMR (CDCl3): δ ϭ 2.38 (s, 3 H), 3.72 (s, 3 H),
.
6.09 (s, 1 H), 7.38Ϫ8.05 (m, 7 H) ppm. 13C NMR (CDCl3): δ ϭ
29.8, 48.2, 53.2, 123.1, 125.3, 126.0, 126.8, 127.0, 129.0, 129.3,
130.7, 130.8, 134.0, 170.7, 194.0 ppm. MS: m/z ϭ 274 (30) [Mϩ],
242 (54), 232 (32), 200 (55), 173 (62), 171 (100). HRMS calcd. for
C15H14O3S [Mϩ] 274.0663; found 274.0658.
Methyl (Acetyl)(m-chlorophenyl)acetate (4b): From the BF3·Et2O-
catalyzed reaction: colorless oil, 64%. IR: ν˜ ϭ 2956, 1751, 1232
1
cmϪ1. H NMR (CDCl3): δ ϭ 2.21 (s, 3 H), 3.74 (s, 3 H), 5.90 (s,
1 H), 7.34Ϫ7.48 (m, 4 H) ppm. 13C NMR (CDCl3): δ ϭ 20.7, 52.8,
73.6, 125.7, 127.6, 129.4, 130.0, 134.7, 135.5, 168.8, 170.1 ppm.
MS: m/z ϭ 242 (1.5) [Mϩ], 210 (4), 200 (11), 183 (10), 141(9), 124
(2), 111 (7), 77 (6), 43 (100). HRMS calcd. for C11H11O4Cl [Mϩ]
242.0345; found 242.0340.
Methyl (Acetyl)(1-naphthyl)acetate (4f): From the BF3·Et2O-cata-
lyzed reaction: colorless oil, 59%. IR: ν˜ ϭ 2955, 1748, 1229, 1055
1
cmϪ1. H NMR (CDCl3): δ ϭ 2.20 (s, 3 H), 3.69 (s, 3 H), 6.68 (s,
1 H), 7.43Ϫ8.19 (m, 7 H) ppm. 13C NMR (CDCl3): δ ϭ 20.7, 52.7,
72.4, 123.7, 125.2, 126.1, 126.9, 127.5, 128.8, 129.9, 130.1, 131.0,
134.0, 169.6, 170.3 ppm. MS: m/z ϭ 258 (20) [Mϩ], 226 (9), 216
(11), 199 (10), 157 (100). HRMS calcd. for C15H14O4 [Mϩ]
258.0892; found 258.0888.
Methyl (Acetylthio)(p-chlorophenyl)acetate (3c): From the
Rh2(OAc)4-catalyzed reaction: colorless oil, 85%. IR: ν˜ ϭ 2957,
1
1740, 1696 cmϪ1. H NMR (CDCl3): δ ϭ 2.35 (s, 3 H), 3.74 (s, 3
H), 5.29 (s, 1 H), 7.30Ϫ7.40 (m, 4 H) ppm. 13C NMR (CDCl3):
δ ϭ 29.9, 50.2, 53.1, 129.0, 129.7, 133.5, 134.4, 169.9, 193.4 ppm.
MS: m/z ϭ 258 (3) [Mϩ], 226 (30), 216 (27), 184 (16), 157 (44),
123 (7), 111 (12), 84(100). HRMS calcd. for C11H11O3SCl [Mϩ]
258.0117; found 258.0122.
Ethyl (O-Thioacetyl)acetate (7a): From the BF3·Et2O-catalyzed re-
˜
action: light-yellow oil, 92%. IR: ν ϭ 2254, 1755, 1194, 1080 (Cϭ
S), 651 cmϪ1 1H NMR (CDCl3): δ ϭ 1.27 (t, J ϭ 7.2 Hz, 3 H),
.
Methyl (Acetyl)(p-chlorophenyl)acetate (4c): From the BF3·Et2O-
catalyzed reaction: colorless oil, 41%. IR: ν˜ ϭ 2919, 1749, 1225,
787 cmϪ1. 1H NMR (CDCl3): δ ϭ 2.21 (s, 3 H), 3.73 (s, 3 H), 5.90
(s, 1 H), 7.34Ϫ7.42 (m, 4 H) ppm. 13C NMR (CDCl3): δ ϭ 20.7,
52.7, 73.7, 128.9, 129.0, 132.2, 135.3, 168.9, 170.1 ppm. MS: m/z ϭ
242 (6) [Mϩ], 210 (21), 200 (30), 183 (29), 141 (97), 124 (3), 111(9),
77 (17), 43 (100). HRMS calcd. for C11H11O4Cl [Mϩ] 242.0345;
found 242.0348.
2.64 (s, 3 H), 4.21 (q, J ϭ 7.2 Hz, 2 H), 5.00 (s, 2 H) ppm. 13C
NMR (CDCl3): δ ϭ 14.1, 33.9, 61.5, 67.1, 166.7, 219.2 ppm. MS:
m/z ϭ 162 (20) [Mϩ], 117 (13), 104 (29), 83 (6.5), 59 (100), 43(99).
HRMS calcd. for C6H10O3S [Mϩ] 162.0350; found 162.0357.
Benzyl (O-Thioacetyl)acetate (7b): From the BF3·Et2O-catalyzed
reaction: colorless oil, 86%. IR: ν˜ ϭ 2958, 1765, 1287, 1176, 1079
1
(CϭS), 808 cmϪ1. H NMR (CDCl3): δ ϭ 2.57 (s, 3 H), 5.00 (s, 2
H), 5.13 (s, 2 H), 7.28 (s, 5 H) ppm. 13C NMR (CDCl3): δ ϭ 33.8,
67.0, 67.1, 115.9, 128.4, 128.52, 128.58, 128.6, 134.9, 166.5,
219.1 ppm. MS: m/z ϭ 224 (8) [Mϩ], 168 (15), 148 (14), 108 (13),
91 (100). HRMS calcd. for C11H12O3S [Mϩ] 224.0507; found
224.0500.
Methyl (Acetylthio)(p-methoxyphenyl)acetate (3d): From the
Rh2(OAc)4-catalyzed reaction: colorless oil, 89%. IR: ν˜ ϭ 2955,
1741, 1695, 1512, 1253 cmϪ1. 1H NMR (CDCl3): δ ϭ 2.34 (s, 3 H),
3.73 (s, 3 H), 3.79 (s, 3 H), 5.27 (s, 1 H), 6.86 (d, J ϭ 9.0 Hz, 2 H),
7.30 (d, J ϭ 9.0 Hz, 2 H) ppm. 13C NMR (CDCl3): δ ϭ 29.9, 50.4,
53.0, 55.2, 114.3, 126.5, 129.5, 159.6, 170.6, 194.1 ppm. MS: m/z ϭ
254 (2) [Mϩ], 222 (15), 212 (4), 179 (13), 151 (20), 119 (7.83), 86
(100), 84 (100). HRMS calcd. for C12H14O4S [Mϩ] 254.0612;
found 254.0627.
Menthyl (O-Thioacetyl)acetate (7c): From the BF3·Et2O-catalyzed
reaction: colorless oil, 44%. IR: ν˜ ϭ 2959, 1750, 1196, 1080 (Cϭ
1
S), 650 cmϪ1. H NMR (CDCl3): δ ϭ 0.74Ϫ2.39 (m, 18 H), 2.66
(s, 3 H), 4.77 (dt, J ϭ 11, 4.4 Hz, 1 H), 5.01 (s, 2 H) ppm. 13C
NMR (CDCl3): δ ϭ 16.2, 20.7, 21.9, 23.4, 26.2, 31.4, 33.9, 34.1,
40.6, 46.9, 67.2, 75.8, 166.3 ppm. MS: m/z ϭ 272 (3) [Mϩ], 138
(84), 123 (39), 109 (9), 95 (100), 81 (86). HRMS calcd. for
C14H24O3S [Mϩ] 272.1446; found 272.1445.
Methyl (Acetyl)(p-methoxyphenyl)acetate (4d): From the BF3·Et2O-
catalyzed reaction: colorless oil, 37%. IR: ν˜ ϭ 2957, 1747, 1515,
1233, 760 cmϪ1 1H NMR (CDCl3): δ ϭ 2.18 (s, 3 H), 3.72 (s, 3
.
H), 3.81 (s, 3 H), 5.88 (s, 1 H), 6.91 (d, J ϭ 8.8 Hz, 2 H), 7.37 (d,
J ϭ 8.8 Hz, 2 H) ppm. 13C NMR (CDCl3): δ ϭ 20.7, 52.5, 55.3,
74.1, 114.2, 125.9, 129.1, 160.3, 169.6, 170.4 ppm. MS: m/z ϭ 238
(30) [Mϩ], 206 (77), 196 (19), 179 (50), 137 (100). HRMS calcd. for
C12H14O5 [Mϩ] 238.0841; found 238.0842.
Preparation of Benzyl (Acetylthio)acetate:[13] ClCH2CO2Bn (1.84 g,
10 mmol) in THF (2 mL) was added dropwise to a solution of
CH3COSH (760 mg, 10 mmol) and NaOH (400 mg, 10 mmol) dis-
sloved in THF (5 mL). After the addition was complete, the solu-
tion was stirred overnight. The reaction mixture was extracted with
CH2Cl2, and then the organic solution was washed with water and
dried by Na2SO4. Evaporation of the solvent gave a crude product
that was purified on a silica gel column (petroleum ether/Et2O,
40:1) to give a colorless oil (1.92 g, 86%). IR: ν˜ ϭ 2935, 1750, 1696,
Methyl (Acetylthio)(3-thienyl)acetate (3e): From the Rh2(OAc)4-ca-
talyzed reaction: colorless oil, 79%. IR: ν˜ ϭ 2953, 1742, 1696, 1132
1
cmϪ1. H NMR (CDCl3): δ ϭ 2.35 (s, 3 H), 3.76 (s, 3 H), 5.45 (s,
1 H), 7.06Ϫ7.32 (m, 3 H) ppm. 13C NMR (CDCl3): δ ϭ 29.9, 45.9,
53.0, 124.0, 126.5, 127.2, 134.3, 170.1, 193.6 ppm. MS: m/z ϭ 230
(7) [Mϩ], 198 (54), 188 (39), 156 (26), 129 (60), 43 (100). HRMS
calcd. for C9H10O3S2 [Mϩ] 230.0071; found 230.0065.
1
1291, 1132 cmϪ1. H NMR (CDCl3): δ ϭ 2.38 (s, 3 H), 3.75 (s, 2
H), 5.12 (s, 2 H), 7.36 (s, 5 H) ppm. 13C NMR (CDCl3): δ ϭ30.0,
31.5, 67.5, 128.2, 128.4, 128.6, 135.4, 168.5, 193.5 ppm. MS: m/z ϭ
224 (3) [Mϩ], 181 (27), 148 (2), 136 (3), 107 (10), 91 (100). HRMS
Methyl (Acetyl)(3-thienyl)acetate (4e): From the BF3·Et2O-cata-
lyzed reaction: colorless oil, 24%. IR: ν˜ ϭ 2955, 1750, 1229 cmϪ1
.
1H NMR (CDCl3): δ ϭ 2.12 (s, 3 H), 3.68 (s, 3 H), 5.98 (s, 1 H), calcd. for C11H12O3S [Mϩ] 224.0507; found 224.0501.
Eur. J. Org. Chem. 2003, 1784Ϫ1788
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 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1787

W. Yao, M. Liao, X. Zhang, H. Xu, J. Wang
FULL PAPER
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Received October 23, 2002
1788
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2003, 1784Ϫ1788