Synthesis of S-functionalized thioesters using thioaroylate ions derived from carboxylic acids and tetrathiomolybdate via acyloxyphosphonium intermediates

Article abstract of DOI:10.1016/j.tet.2010.06.028

Thioaroylate ions generated in situ from acyloxyphosphonium salts and tetrathiomolybdate upon Michael addition or ring opening of three membered systems led to a facile synthesis of S-functionalized thioesters. While the ring opening of aziridines gave very good yield of the products, Michael addition and epoxide ring opening gave moderate yields.

Full text of DOI:10.1016/j.tet.2010.06.028

Tetrahedron 66 (2010) 7001e7011
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Synthesis of S-functionalized thioesters using thioaroylate ions derived from
carboxylic acids and tetrathiomolybdate via acyloxyphosphonium intermediates
*
Purushothaman Gopinath, Chanda Debasree, Ravindran Sasitha Vidyarini, Srinivasan Chandrasekaran
Department of Organic Chemistry, Indian Institute of science, Bangalore 560012, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Thioaroylate ions generated in situ from acyloxyphosphonium salts and tetrathiomolybdate upon Mi-
chael addition or ring opening of three membered systems led to a facile synthesis of S-functionalized
thioesters. While the ring opening of aziridines gave very good yield of the products, Michael addition
and epoxide ring opening gave moderate yields.
Received 27 April 2010
Received in revised form 6 June 2010
Accepted 9 June 2010
Available online 16 June 2010
Ó 2010 Elsevier Ltd. All rights reserved.
Keywords:
Carboxylic acids
Michael addition
Ring opening
Sulfur
Molybdenum
1. Introduction
have not been explored in organic synthesis as they are less
nucleophilic and hence less reactive. But, the thioesters obtained
Over the past few decades, extensive efforts have been made
to develop methodologies that form carbonesulfur bonds in the
synthesis of molecules with various biological applications. Al-
though a great deal of effort has been directed toward the use of
nucleophilic thiols1 for the formation of CeS bond, thioacids2
from thioacids as nucleophiles are synthetically more valuable
because of their widespread application in pharmaceutical
chemistry3 and also they serve as key intermediates in the syn-
thesis of various bioactive molecules.4 Moreover, thioesters are
used as coupling partners in organometallic reactions,5 building
E.W.G
O
O
O
R'
2-
CHCl3, rt
R'
PPh3
NBS
Ar
OH +
+
+
E.W.G
MoS4
Ar
S
Ar
S
1
X
Where X= O, NTs
O
R2
R1
R1
XH
Ar
S
R2
Scheme 1. General reaction scheme for the synthesis of thioesters.
blocks for the synthesis of heterocyclic compounds,6 and acyl
transfer7 reactions. Additionally the thioester functionality could
be readily transformed to a more versatile SH group under mild
reaction conditions.8
* Corresponding author. Tel.: þ91 80 2293 2404; fax: þ91 80 2360 2423; e-mail
address: scn@orgchem.iisc.ernet.in (S. Chandrasekaran).
0040-4020/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2010.06.028

7002
P. Gopinath et al. / Tetrahedron 66 (2010) 7001e7011
Table 1
Generally, the synthetic methods adopted for thioester forma-
Reaction of various Michael acceptors with thiobenzoate ion
tion are direct coupling of a thiol with the parent carboxylic acid and
an activating agent,9 or the coupling of thiol with acid anhydride9 or
acid chloride.9 Other methods include the reaction of thioacids with
suitable electrophilic reagents, such as alkyl halides,2a and Michael
acceptors.2b,2c,2f These methodologies, however, suffer from limi-
tations, such as the limited availability of starting thioacids and
thiols and also the practical difficulty associated in handling them.
In our earlier work we had shown the use of benzyl-
triethylammonium tetrathiomolybdate,10 (PhCH2N)2 MoS4 1 for the
in situ generation of thioaroylate ion from acyloxyphosphonium
intermediates.11 This methodology was used in the synthesis of
thioesters from alkyl halides12 and alcohols.13 In this paper, we
present our results on the application of our methodology to the
synthesis of S-functionalized thioesters (Scheme 1).
Entry Michael acceptors
Product
Time (h) Yield %
O
O
O
S
O
O
O
1
2
2
5
60
65
50
3a
3
O
S
S
2
4a
4
O
O
3
OMe
OMe
O
S
OH
5a
Bu- i
5
OEt
S
R
O
O
O
O
O
O
S
S
O
S
NH
O
O
4
0.5
52
6a
(ii) Fattyacid synthase
Inhibitor
(i) PC12 Inhibitor
6
NO2
NO2
Figure 1. Structure of some pharmacologically important Michael adducts.
2. Results and discussion
5
3
62
Ph
Ph
7
7a
2.1. Michael addition
CN
6
e
12
No reaction
The Michael adducts derived from conjugate addition with
thioacids as nucleophiles are present in a number of pharmaco-
logically important compounds (Fig. 1). These compounds are
generally synthesized3d,14 via multistep processes involving the
coupling of carboxylic acid with the corresponding thiol as the final
step due to the inaccessibility of the starting thioacids for Michael
addition reaction. In general, conjugate addition reaction with
thioacid as nucleophiles also requires longer reaction time in the
absence of a catalyst owing to their lower nucleophilicity. Thus, we
decided to explore our protocol for the formation of functionalized
thioesters through Michael addition in the same pot thereby
reducing the number of steps involved in the process.
8
Accordingly, benzoic acid 2a (1.0 equiv) was first treated with
PPh3 and NBS to form the corresponding activated intermediate
followed by the addition of reagent 1 to generate thioaroylate
ion,12,13 which on treatment with a Michael acceptor gave the
corresponding thioester 3ae7a in 50e65% yield (Scheme 2).
Figure 2. ORTEP diagram of compound 4h.
O
O
R'
E.W.G
2-
CHCl3, rt
PPh3
NBS
E.W.G
Ph
OH
2a
+
+
+
MoS4
+
Ph
S
R'
1
3a-7a (50-65%)
3-8
O
E.W.G
O
Br
PPh3
Ph
O
+
Ph
S
R'
1
1
O
S
S
O
O
O
S
S
O
Ph
S
Mo
+ MoS2
Ph
S
Ph
Mo
Ph
Ph
S
S
Ph
O
S
S
Scheme 2. Reaction of various Michael acceptors with thiobenzoate ion.

P. Gopinath et al. / Tetrahedron 66 (2010) 7001e7011
7003
Table 2
Using benzoic acid as the standard we then studied the re-
activity of other Michael acceptors to show the generality of the
methodology. It was observed that ethyl vinyl ketone gave maxi-
mum yield of the corresponding Michael adduct. Nitrostyrene and
methyl vinyl ketone also gave good yields of the corresponding
thioesters whereas methyl acrylate and cyclohexenone gave mod-
erate yields of the products. Acrylonitrile was inert to the reaction
conditions even after 12 h and gave no thioester product. The re-
sults of this study are summarized in Table 1.
Reaction of ethyl vinyl ketone 4 with various carboxylic acids
O
O
O
O
2-
CHCl3, rt
PPh
NBS
+
MoS4
+
R
OH
+
3
+
R
S
2h
1
2 (a-h)
4
4 (a-h)
Entry
Carboxylic acid
Product
Yield (%)
O
S
O
COOH
The methodology was then extended to other carboxylic acids
as well to show the synthetic versatility of the reaction, using ethyl
vinyl ketone as the standard Michael acceptor. The structure of
compound 4h was confirmed by single crystal X-ray analysis
(Fig. 2). The results of this study are summarized in Table 2.
The methodology was then extended to the synthesis of car-
bohydrate based thioesters to show the synthetic utility of our re-
1
63
4b
2b
O
O
O
action. At first, 1,2,3,4-tetra-O-acetyl-glucuronic15 acid
9 was
OH
S
S
treated with ethyl vinyl ketone under the same reaction conditions
(Scheme 3) to obtain the corresponding thioester 10 in 52% yield.
Subsequently a carbohydrate derived Michael acceptor16 11
(from glucose via glucol intermediate) was treated with benzoic
acid to give C-3 thioester 12 with high diastereoselectivity (dr 98:2)
in 60% yield. Similar reaction of phenyl acetic acid gave the thio-
ester 13 (dr 90:10) in 55% yield (Scheme 4). The stereochemistry at
the newly formed CeS bond was assigned based on COSY and
coupling constant values for 12 and by analogy for 13.
2
68
4c
2c
COOH
O
O
3
4
5
61
61
62
4d
OMe
2d
O
S
O
OMe
O
O
O
AcO
AcO
CHCl3, rt
2h
2-
AcO
+
PPh3
+
NBS
+
MoS4
+
R
OH
O
AcO
R
COOH
11
O
S
12 (R = Ph)
13 (R = PhCH2)
2e
4e
O
Scheme 4. Synthesis of C-3 thioesters 12 and 13 from glucol derived Michael acceptor,11.
COOH
O
S
O
Finally, we attempted an intramolecular reaction to synthesize
4f
g
-thiolactone 18 starting from
of C2 and C3 hydroxyl groups of
isopropylidene- -erythrose 15, which on further reaction with
L
-arabinose 14. Acetonide protection
L
-arabinose (Scheme 5) gave 2,3-O-
L
Cl
Wittig reagent, ethyl triphenylphosphoranylidineacetate, gave the
corresponding conjugated ester17 16 in 54% yield with Z isomer as
the major product. PDC oxidation of 16 gave the corresponding
carboxylic acid 17 in 62% yield. Compound 17 was then treated with
PPh3, NBS, and tetrathiomolybdate 1 to form the corresponding
thiolactone 18 (2:1 mixture of diastereomers) in 50% yield.
Cl
2f
COOH
O
O
S
S
O
O
6
7
4g
65
60
2g
2.2. Aziridine and epoxide ring opening
COOH
As further exploration of this methodology, we attempted the
ring opening of three membered heterocycles, such as aziridines
and epoxides to synthesize various S-2-functionalized thioesters,
which are present in a number of bioactive molecules (Fig. 3).
Unlike Michael addition presented earlier, nucleophilic ring open-
ing of epoxides and aziridines with thioacids as nucleophiles is less
common.
4h
NO2
NO2
2h
O
O
O
O
O
OAc
OAc
O
OAc
OAc
HO
AcO
CHCl3, rt
2h
2-
S
PPh3
+
NBS
+
+
MoS4
+
AcO
OAc
4
OAc
10
9
Scheme 3. Synthesis of glucuronic based Michael thioester 10.

7004
P. Gopinath et al. / Tetrahedron 66 (2010) 7001e7011
HO
OH
O
1.Me2C(OMe)2, TsOH, DMF;
2.NaIO4, H2O, hexane
HO
HO
O
MeO2CCH=PPh3
CH2Cl2
MeO2C
O
O
HO
OH
O
O
14
16
Z isomer (major)
15
6eq. PDC,
DMF, rt , 24hr
O
O
HO
S
O
O
MeO2C
CHCl3, rt
2h
2-
O
O
+
MoS4
PPh3
NBS
+
+
O
O
18
17
Scheme 5. Synthesis of thiolactone, 18 through intramolecular Michael addition.
Table 3
R1
Reaction of various carboxylic acids with aziridine 19
O
O
P
O
H
N
R2
S
S
R
Entry
Carboxylic acid
Product
Time (h) Yield (%)
O
O AZT
N
H
O
H
HS
O
O
O
S
COOH
AZT = 3'-azido-2', 3'-
dideoxy-thymidine
Ph
NHTs
1
5
5
88
83
(ii) Pro GSH and Anti HIV agent
(i) HIV Pronucleotide
2a
19a
O
COOH
Figure 3. Structures of some bioactive molecules containing S-2-functionalized
S
Ph
NHTs
thioesters.
2
3
2b
19b
Initially, we took commercially available chiral aziridine, ((S)-
(þ)-2-benzyl-1-(p-toluenesulfonyl)-aziridine) 19 for the ring
opening reaction. Thus reaction of benzoic acid, PPh3, NBS, and
tetrathiomolybdate, 1 in the presence of 19 gave the corresponding
functionalized thioester 19a in a highly regioselective fashion
(Scheme 6). The reaction was then carried out with other carboxylic
acids to show generality of the methodology. A variety of thioesters
were obtained in good yield and the results of this study are
summarized in Table 3.
O
O
OH
5.5
91
S
Ph
NHTs
19c
2c
COOH
O
S
Ph
NHTs
The reaction was then carried out with other activated aziridines
(20e25) prepared via Sharpless aziridination protocol.18 The ring
opening reactions were facile and the resultant thioesters were
obtained in good yield. The results of this study are summarized in
Table 4.
4
5
4
92
90
MeO
OMe
19d
2d
O
COOH
S
Ph
4.5
We were then interested in studying the reactivity profile of
thioaroylate ions toward bifunctionalised systems. For this study,
we initially synthesized a molecule containing both an aziridine
and a tosyl group. Thus, compound 27 synthesized from aziridino
alcohol 2619 on treatment with benzoic acid (1.05 equiv), PPh3
(1.1 equiv), NBS (1.1 equiv), and tetrathiomolybdate 1 (1.05 equiv)
gave thioester 28 in 74% yield. This results from initial ring opening
of aziridine (at the benzylic position) with the thioaroylate to give
27a followed by intramolecular displacement of the tosylate with
the amide nitrogen. However, in the presence of excess thioaroylate
ion, compound 27 gave the corresponding bisthioester 29 in 75%
yield. This can be rationalized by attack of thioaroylate at the
aziridine ring as well as displacement of the tosylate (Scheme 7).
2e
NHTs
19e
COOH
O
S
Ph
NHTs
6
5.5
87
Cl
2f
Cl
19f
We then attempted the ring opening of epoxides with thioar-
oylates to give the corresponding S-2-hydroxy thioesters. Accord-
ingly, benzoic acid 2a (1.0 equiv) PPh3, NBS, and tetrathiomolybdate
1 were stirred together to generate thiobenzoate ion which was
O
O
2-
CHCl3, rt
PPh3
NBS
Ph
OH
2a
+
+
+
MoS4
+
N
Ph
NHTs
Ph
S
5h
Ts
1
19
19a
Scheme 6. Ring opening of aziridine, 19 with thiobenzoate ion.

P. Gopinath et al. / Tetrahedron 66 (2010) 7001e7011
7005
Table 4
Table 5
Reaction of various aziridines with thiobenzoate ion
Reaction of various carboxylic acids with styrene epoxide
O
O
Ts
N
O
O
R1
O
2-
CHCl3, rt
2-
CHCl3-EtOH (1:1)
6h, rt
R2
Ph
OH + PPh3 NBS
+
+
PPh3
OH +
NBS
Ph
MoS4
+
+
MoS4
+
+
Ph
S
Ph
S
2a
R2
R1
30
NHTs
OH
1
30a
2a
1
20 - 25
20a - 25a
Entry
1
Carboxylic acid
Product
Yield (%)
62
Entry
Aziridine
Product
Time Yield
(h)
(%)
COOH
O
OH
Ph
NHTs
S
S
Ts
N
1
14
83
30a
2a
O
20a
20
Ph
COOH
O
OH
S
NHTs
2
3
65
62
Ph
N
N
Ts
2
3
2
4
85
88
2b
30b
S
21a
21
O
O
Ph
O
O
OH
NHTs
OH
S
Ts
S
Ph
30c
Ph
22
2c
22a
COOH
O
NHTs
OH
Ph
4
S
64
N
Ts
S
Ph
4
5
2
82
81
OMe
MeO
30d
23
O
23a
2d
NHTs
Ts
N
O
COOH
COOH
OH
Ph
12
5
6
63
59
S
S
O
2e
24a
24
Ph
30e
O
S
O
Ts
N
NHTs
S
OH
Ph
Ph
S
6
NHTs
6
80
Cl
+
O
Cl
2f
30f
25
Ph
25a
25a'
Reaction of cyclohexene oxide 31 under the reaction conditions
with benzoic acid gave the corresponding trans S-2-hydrox-
ycyclohexyl thioester 31a in 63% yield and similar reaction with
p-toluic acid provided the thioester 31b in 65% yield (Scheme 8).
In order to demonstrate the chemoselectivity of the reaction of
thioaroylate ion, we attempted ring opening of cyclohexadiene
then treated with styrene oxide to give the corresponding func-
tionalized thioester 30a in 62% yield in a highly regioselective
fashion by ring opening at the less substituted carbon. The reaction
was then carried out with other carboxylic acids as well and the
results of this study are summarized in Table 5.
O
Ts
N
S
Ts
N
O
Ts
S
N
Ph
OH
+
Et3N, 5h
OTs
(1.05 equiv)
CHCl3, rt, 5h
p-TsCl
CH2Cl2, rt
OTs
27a
27
26
O
S
CHCl3, rt, 8h
(2.2 equiv)
O
O
S
Ph
S
Ph
O
S
Ph
N
NHTs
Ts
28
29
Scheme 7. Reaction of aziridine tosylate, 27 with thiobenzoate ion.

7006
P. Gopinath et al. / Tetrahedron 66 (2010) 7001e7011
O
O
OH
CHCl3-EtOH (1:1)
S
2-
PPh3
NBS
O
MoS4
+
+
+
+
OH
R
6h, rt
R
1
31
Where R= H, 31a, 63%
31b,
2a
Where R= H,
CH3,
65%
CH3, 2b
Scheme 8. Ring opening of cyclohexene oxide with carboxylic acids.
derived trans-aziridino epoxide 32.20 When compound 32 was
treated with benzoic acid, PPh3, NBS, and tetrathiomolybdate 1, it
gave the corresponding aziridine ring opened product 32a in 80%
yield without affecting the epoxide unit (Scheme 9) as aziridines
are more reactive than epoxides.
4.2. General procedure for Michael addition (3ae7a, 4beh)
in one pot
To a well stirred solution of the corresponding carboxylic acid
(1.0 mmol), PPh3 (1.1 mmol), and NBS (1.1 mmol) in CHCl3 (5 mL)
O
O
O
CHCl3, rt
2-
PPh3
NBS
+
+
MoS4
+
Ph
+
OH
Ts
N
O
S
8h, 80%
2a
NHTs
1
32
Scheme 9. Chemoselective ring opening of aziridine in the presence of epoxide.
32a
3. Conclusions
(stirred for 10 min) was added benzyltriethylammonium tetra-
thiomolybdate 1 (2.0 mmol). The corresponding Michael acceptor
(2.0 mmol) was then added after 20 min and stirring was continued
for 2 h at room temperature (28 ꢀC). Diethyl ether (20 mL) was then
added to the reaction mixture followed by filtration through
a Celite pad. The residue was again extracted with CH2Cl2 (5 mL)
followed by extraction with diethyl ether (20 mL) and filtered again
through a Celite pad. The combined extract was evaporated and the
residue was purified by column chromatography on silica gel to
give the corresponding Michael adducts.
In conclusion, a variety of S-functionalized thioesters have been
synthesized from carboxylic acids and benzyltriethylammonium
tetrathiomolybdate 1 via acyloxyphosphonium intermediates by in
situ generation of thioaroylate ions. These thioaroylate ions on
further treatment with Michael acceptors and three membered
heterocycles gave the corresponding S-functionalized thioesters.
Michael addition, when carried out in an intramolecular fashion
gave the thiolactone 18 thereby demonstrating the synthetic
utility of the methodology. We have also described the synthesis
of C-3 sugar thioesters 12 and 13 via conjugate addition of
benzoic/phenyl acetic acid derived thioaroylates to Michael ac-
ceptor 11. Aziridine and epoxide ring opening on the other hand
gave the corresponding S-2-sulfanamido and S-2-hydroxy
thioesters.
4.2.1. S-(3-Oxobutyl) benzothioate (3a). Colorless liquid. Yield:
0.125 g, 60%; IR (Neat): 1717, 1661, 1208, 915 cmꢁ1 1H NMR
;
(300 MHz, CDCl3):
d 7.97e7.93 (m, 2H), 7.60e7.54 (m, 1H),
7.48e7.21 (m, 2H), 3.26 (t, J¼6.6 Hz, 2H), 2.88 (t, J¼6.6 Hz, 2H), 2.18
(s, 3H); 13C NMR (75 MHz, CDCl3): 206.3, 191.9, 136.9, 133.4, 128.6,
127.2, 43.4, 29.9, 22.8; HRMS m/z: calcd for C11H12O2SNaþ
[MþNaþ]: 231.0456; found: 231.0455.
4. Experimental section
4.1. General
4.2.2. S-(3-Oxopentyl) benzothioate (4a). Colorless liquid. Yield:
0.144 g, 65%; IR (Neat): 1714, 1663, 1209 cmꢁ1; 1H NMR (400 MHz,
CDCl3): 7.96e7.94 (m, 2H), 7.59e7.55 (m, 1H), 7.46e7.42 (m, 2H),
3.27 (t, J¼6.8 Hz, 2H), 2.85 (t, J¼6.8 Hz, 2H), 2.45 (q, J¼7.2 Hz, 2H),
1.08 (t, J¼7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3): 209.2, 191.9,
136.9, 133.4, 128.6, 127.1, 42.0, 36.6, 22.9, 7.7; HRMS m/z: calcd for
C12H14O2SNaþ [MþNaþ]: 245.0612; found: 245.0606.
All reactions were carried out in oven-dried apparatus using
dry solvents under anhydrous conditions, unless otherwise noted.
Reaction mixtures were stirred magnetically unless otherwise
stated. Commercial grade solvents were distilled and dried
according to literature procedures (‘Purification of laboratory
chemicals’, 3rd ed.; Perrin, D.D., Armarego, W.L.F; Pergamon
Press: Oxford, 1988). Analytical TLC was performed on commer-
cial plates coated with silica gel GF254 (0.25 mm). Silica gel
(230e400 mesh) was used for column chromatography. Yields
refer to chromatographically and spectroscopically (1H NMR)
homogeneous materials, unless otherwise stated. NMR spectra
were recorded on 300 or 400 MHz instruments and calibrated
using residual undeuterated solvent as an internal reference. The
following abbreviations explain the multiplicity s¼singlet,
d¼doublet, t¼triplet, q¼quartet, m¼multiplet, br¼broad. IR
spectra were recorded on a FT-IR spectrometer. High-resolution
mass spectra (HRMS) were recorded on a Micromass Q-TOF mass
spectrometer.
4.2.3. S-(3-Oxocyclohexyl) benzothioate (6a). Colorless liquid. Yield:
0.122 g, 52%; IR (Neat): 1712, 1683, 1210, 913 cmꢁ1 1H NMR
;
(300 MHz, CDCl3): 7.95e7.91 (m, 2H), 7.60e7.55 (m, 1H), 7.47e7.42
(m, 2H), 4.11e4.07 (m, 1H), 2.87e2.84 (m, 1H), 2.82e2.36 (m, 4H),
2.30e2.23 (m, 1H), 2.14e1.87 (m, 2H); 13C NMR (75 MHz, CDCl3):
207.8,190.5,136.8,133.5,128.6,127.2, 47.3, 41.6,40.9, 31.2, 24.3;HRMS
m/z: calcd for C13H14O2SNaþ [MþNaþ]: 257.0612; found: 257.0601.
4.2.4. S-(3-Oxopentyl) 4-methylbenzothioate (4b). Colorless liquid.
Yield: 0.149 g, 63%; IR (Neat): 1715, 1659, 1410, 1212 cmꢁ1; 1H NMR
(400 MHz, CDCl3): 7.84 (d, J¼8.2 Hz, 2H), 7.23 (d, J¼8.2 Hz, 2H), 3.26
(t, J¼6.8 Hz, 2H), 2.84 (t, J¼6.8 Hz, 2H), 2.44 (q, J¼7.3 Hz, 2H), 2.40

P. Gopinath et al. / Tetrahedron 66 (2010) 7001e7011
7007
(s, 3H), 1.07 (t, J¼7.3 Hz, 3H); 13C NMR (100 MHz, CDCl3): 209.3,
191.5, 144.3, 134.3, 129.2, 127.2, 42.1, 36.0, 22.7, 21.6, 7.6; HRMS m/z:
calcd for C13H16O2SNaþ [MþNaþ]: 259.0769; found: 259.0764.
diethyl ether (20 mL) and filtered again through a Celite pad. The
combined extract was evaporated and the residue was purified by
column chromatography on silica gel to give compound 10 as
a colorless liquid (0.240 g, 52%).
4.2.5. S-(3-Oxopentyl) 2-phenylethanethioate (4c). Colorless liquid.
Yield: 0.161 g, 68%; IR (Neat): 1712, 1689, 1410, 1018 cmꢁ1; 1H NMR
(400 MHz, CDCl3): 7.35e7.25 (m, 5H), 3.80 (s, 2H), 3.05 (t, J¼6.8 Hz,
2H), 2.70 (t, J¼6.8 Hz, 2H), 2.37 (q, J¼7.3 Hz, 2H), 1.03 (t, J¼7.3 Hz,
3H); 13C NMR (75 MHz, CDCl3): 209.0, 197.3, 133.4, 129.4, 128.6,
127.4, 50.4, 41.7, 35.9, 23.1, 7.6; HRMS m/z: calcd for C13H16O2SNaþ
[MþNaþ]: 259.0761; found: 259.0769.
[a
]
25 þ23.3 (c 1.7, CHCl3); IR (Neat): 1759, 1714, 1685, 1370, 1216,
D
1041 cmꢁ1
;
1H NMR (300 MHz, CDCl3):
d
5.77 (d, J¼7.8 Hz, 1H),
5.32e5.09 (m, 3H), 4.15 (d, J¼9.3 Hz,1H), 3.08e3.02 (m, 2H), 2.71 (t,
J¼6.6 Hz, 2H), 2.43 (q, J¼7.2 Hz, 2H), 2.14 (s, 3H), 2.06 (s, 3H), 2.05
(s, 3H), 2.03 (s, 3H) 1.06 (t, J¼7.2 Hz, 3H); 13C NMR (100 MHz,
CDCl3): d 209.0, 195.2, 169.8, 169.3, 169.1, 168.7, 91.2, 77.9, 71.9, 70.1,
68.9, 41.1, 35.9, 22.2, 20.7, 20.6, 20.5, 7.6; HRMS m/z: calcd for
C19H26O11SNaþ [MþNaþ]: 485.1094; found: 485.1100.
4.2.6. S-(3-Oxopentyl) 4-methoxybenzothioate (4d). Colorless liq-
uid. Yield: 0.143 g, 61%; IR (Neat): 1715, 1654, 1602, 1168 cmꢁ1 1H
;
4.4. Synthesis of 4,5-di-O-acetyl-3-benzoyl-2-deoxy-3-thio-D-
ribo-hexopyanoso-1,5-lactone 12
NMR (300 MHz, CDCl3): 7.93 (d, J¼9.3 Hz, 2H), 6.92 (d, J¼9.3 Hz, 2H),
3.86 (s, 3H), 3.25 (t, J¼6.9 Hz, 2H), 2.84 (t, J¼6.9 Hz, 2H), 2.43 (q,
J¼7.2 Hz, 2H), 1.07 (t, J¼7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3):
209.3,190.4,163.9,129.9,129.4,113.8, 55.5, 42.3, 36.1, 22.9, 7.7; HRMS
m/z: calcd for C13H16O3SNaþ [MþNaþ]: 275.0718; found: 275.0708.
To a well stirred solution of benzoic acid 2a (0.122 g, 1.0 mmol),
PPh3 (0.288 mg, 1.1 mmol), and NBS (0.196 g, 1.1 mmol) in CHCl3
(5 mL) (stirred for 10 min) was added benzyltriethylammonium
tetrathiomolybdate
1 (1.22 g, 2.0 mmol). Michael acceptor, 11
4.2.7. (E)-S-(3-Oxopentyl) 3-phenylprop-2-enethioate (4e). Color-
less liquid. Yield: 0.151 g, 61%; IR (Neat): 1714, 1656, 1615,
(0.482 g, 2.0 mmol) was then added after 20 min and stirring was
continued for 2 h at room temperature (28 ꢀC). Diethyl ether (20 mL)
was then added to the reaction mixture followed by filtration
through a Celite pad. The residue was again extracted with CH2Cl2
(5 mL) followed by extraction with diethyl ether (20 mL) and filtered
again througha Celite pad. Thecombinedextract wasevaporatedand
the residue was purified by column chromatography on silica gel to
give the corresponding adduct 12 as a colorless liquid (0.220 g, 60%).
1038 cmꢁ1
;
1H NMR (400 MHz, CDCl3): 7.60 (d, J¼15.8 Hz, 1H),
7.55e7.51 (m, 2H), 7.41e7.39 (m, 2H), 6.69 (d, J¼15.8 Hz,1H), 3.21 (t,
J¼6.8 Hz, 2H), 2.82 (t, J¼6.8 Hz, 2H), 2.44 (q, J¼7.3 Hz, 2H), 1.08 (t,
J¼7.3 Hz, 3H); 13C NMR (100 MHz, CDCl3): 209.2, 189.8, 140.6, 134.0,
130.5, 128.9, 128.3, 124.8, 42.0, 36.0, 22.9, 7.7; HRMS m/z: calcd for
C14H16O2SNaþ [MþNaþ]: 271.0769; found: 271.0768.
[a
]
26 þ24.5 (c 0.8, CHCl3); IR (Neat): 1749, 1669, 1213, 906 cmꢁ1
;
D
1H NMR (400 MHz, CDCl3):
d 7.94e7.92 (m, 2H), 7.64e7.60 (m, 1H),
4.2.8. S-(3-Oxopentyl) 4-chlorobenzothioate (4f). Colorless liquid.
Yield: 0.167 g, 65%; IR (Neat): 1716, 1664, 1588, 1206, 915 cmꢁ1; 1H
NMR (400 MHz, CDCl3): 7.90e7.87 (m, 2H), 7.46e7.40 (m, 2H), 3.27
(t, J¼6.8 Hz, 2H), 2.85 (t, J¼6.8 Hz, 2H), 2.45 (q, J¼7.2 Hz, 2H),1.08 (t,
J¼7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3): 209.1, 190.8, 139.8, 135.2,
128.9, 128.5, 41.9, 36.0, 23.0, 7.7; HRMS m/z: calcd for
C12H13ClO2SNaþ [MþNaþ]: 279.0222; found: 279.0223.
7.50e7.46 (m, 2H), 5.32 (t, J¼3.2 Hz, 1H), 4.77 (dd, J1¼4.0 Hz,
J2¼7.6 Hz, 1H), 4.57 (ddd, J1¼3.2 Hz, J2¼6.0 Hz, J3¼10.4 Hz, 1H), 4.40
(d, J¼4.0 Hz, 2H), 3.06 (dd, J1¼6.0 Hz, J2¼18.0 Hz, 1H), 2.95 (dd,
J1¼10.4 Hz, J2¼18.0 Hz, 1H), 2.19 (s, 3H), 2.15 (s, 3H); 13C NMR
(100 MHz, CDCl3): 189.1, 170.2, 169.7, 166.7, 135.9, 134.2, 128.9,
127.4, 78.3, 67.8, 63.2, 36.9, 32.7, 29.7, 20.7; HRMS m/z: calcd for
C17H18O7SNaþ [MþNaþ]: 389.0671; found: 389.0659.
4.2.9. S-(3-Oxopentyl) 3-methylbenzothioate (4g). Colorless liquid.
Yield: 0.146 g, 62%; IR (Neat): 1715, 1658, 1247, 1151 cmꢁ1; 1H NMR
(400 MHz, CDCl3): 7.74 (d, J¼6.8 Hz, 2H), 7.39e7.26 (m, 2H), 3.26 (t,
J¼6.8 Hz, 2H), 2.84 (t, J¼6.8 Hz, 2H), 2.45 (q, J¼7.2 Hz, 2H), 2.40 (s,
3H), 1.08 (t, J¼7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3): 209.3, 192.1,
138.5,136.9,134.2,128.5,127.6,124.4, 42.1, 36.0, 22.9, 22.1, 7.7; HRMS
m/z: calcd for C13H16O2SNaþ [MþNaþ]: 259.0769; found: 259.0772.
4.5. Synthesis of 4,5-di-O-acetyl-2-deoxy-3-phenylacetyl-3-
thio-D-ribo- hexopyanoso-1,5-lactone 13
The same procedure as that for compound 12 was followed.
27
Yield: 0.231 g, 55%; [
a
]
þ13.9 (c 1.6, CHCl3); IR (Neat): 1748,
1697,1372,1222,1033 cmꢁ1D; 1H NMR (400 MHz, CDCl3):
d 7.38e7.25
(m, 5H), 5.20 (t, J¼3.4 Hz, 1H), 4.67 (q, J¼3.9 Hz, 1H), 4.32 (d, J¼3.9,
2H), 4.30e4.27 (m, 1H), 3.84 (s, 2H), 2.91 (dd, J1¼6.0 Hz, J2¼18.0 Hz,
1H), 2.78 (dd, J1¼10.4 Hz, J2¼18.0 Hz, 1H), 2.13 (s, 3H), 2.05 (s, 3H);
4.2.10. S-(3-Oxopentyl) 3-nitrobenzothioate (4h). Light yellow solid.
Yield: 0.160 g, 60%; mp 72 ꢀC; IR (Neat): 1713, 1651, 1531,
1348 cmꢁ1
;
1H NMR (300 MHz, CDCl3): 8.77 (t, J¼2.1 Hz, 1H),
13C NMR (100 MHz, CDCl3):
d 195.0, 170.1, 169.6, 166.5, 132.4, 129.6,
8.45e8.41 (m, 1H), 8.28e8.25 (m, 1H), 7.67 (t, J¼8.0 Hz, 1H), 3.34 (t,
J¼6.3 Hz, 2H), 2.89 (t, J¼6.3 Hz, 2H), 2.47 (q, J¼7.2 Hz, 2H), 1.09 (t,
J¼7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3): 208.7, 189.9, 148.4, 138.2,
129.9, 127.5, 122.1, 41.6, 36.0, 23.3, 7.6; HRMS m/z: calcd for
C12H13NO4SNaþ [MþNaþ]: 290.0463; found: 290.0449.
128.8, 127.8, 78.1, 67.4, 63.1, 50.4, 37.1, 32.4, 20.6; HRMS m/z: calcd
for C18H20O7SNaþ [MþNaþ]: 403.0827; found: 403.0828.
4.6. Synthesis of (4R,5R)-5-((Z)-2-(methoxycarbonyl)vinyl)-
2,2-dimethyl-1,3-dioxolane-4-carboxylic acid 17
4.3. Synthesis of S-3-oxopentanyl 1,2,3,4-tetra-O-acetyl-b-D-
glucopyranosiduronthioate 10
To a solution of compound 16 (188 mg, 1 mmol) in DMF (10 ml)
was added PDC (2.25 g, 6.0 mmol). The solution was stirred for 24 h
at room temperature. Solvent was removed under vacuum; ethyl
acetate (20 mL) was added to the residue and filtered through
a Celite pad. The solvent was evaporated to give compound 17 as
a colorless liquid (0.219 g, 95%).
To a well stirred mixture of 1,2,3,4-tetra-O-acetyl-b-D-gluco-
pyranuronic acid 9 (0.362 g, 1.0 mmol), PPh3 (0.288 g, 1.1 mmol),
and NBS (0.196 g, 1.1 mmol) in CHCl3 (5 mL) (stirred for 10 min) was
added benzyltriethylammonium tetrathiomolybdate
2.0 mmol). Ethyl vinyl ketone (0.2 mL, 2.0 mmol) was then added
after 20 min and stirring was continued for 2 h at room tempera-
ture (28 ꢀC). Diethyl ether (20 mL) was then added to the reaction
mixture followed by filtration through a Celite pad. The residue was
again extracted with CH2Cl2 (5 mL) followed by extraction with
1 (1.22 g,
[
a
]
23 þ15.8 (c 1.9, CHCl3); IR (Neat): 3235,1724,1221,1204 cmꢁ1
;
D
1H NMR (300 MHz, CDCl3):
d
8.7 (broad s, 1H), 6.16 (dd, J1¼6.9 Hz,
J2¼11.4 Hz, 1H) 5.92 (dd, J1¼1.5 Hz, J2¼11.4 Hz, 1H) 5.80 (dt,
J1¼1.5 Hz, J2¼6.9 Hz, 1H) 4.86 (d, J¼7.5 Hz, 1H), 3.67 (s, 3H), 1.55 (s,
3H), 1.35 (s, 3H); 13C NMR (75 MHz, CDCl3):
d 174.3, 165.8, 143.0,

7008
P. Gopinath et al. / Tetrahedron 66 (2010) 7001e7011
122.8, 117.7, 76.6, 75.0, 51.7, 26.7, 25.3; HRMS m/z: calcd for
C10H14O6Naþ [MþNaþ]: 253.0688; found: 253.0682.
[
a
]
26 ꢁ15.1 (c 4.05, CHCl3); IR (Neat): 3294, 2921, 1645, 1159 cmꢁ1
;
D
1H NMR (300 MHz, CDCl3): 7.58 (d, J¼7.8 Hz, 2H), 7.36e7.18 (m,
10H), 6.99e6.97 (m, 2H), 4.80 (d, J¼6.9 Hz, 1H), 3.76 (s, 2H),
3.63e3.52 (m, 1H), 3.00e2.86 (m, 2H), 2.76 (d, J¼6.6 Hz, 2H), 2.41
(s, 3H); 13C NMR (75 MHz, CDCl3): 197.4, 143.2, 137.3, 136.3, 133.2,
129.5, 129.3, 128.7, 128.6, 127.6, 127.0, 126.8, 55.0, 50.4, 40.7, 33.2,
21.5; HRMS m/z: calcd for C24H25NO3S2Naþ [MþNaþ]: 462.1174;
found: 462.1171.
4.7. Methyl 2-((3aS, 6aR)-tetrahydro-2,2-dimethyl-4-
oxothieno[3,4-d]dioxol-6-yl)acetate 18
To a well stirred solution of 17 (0.23 g, 1 mmol), PPh3 (0.288 mg,
1.1 mmol), and NBS (0.196 g, 1.1 mmol) in CHCl3 (5 mL) (stirred for
10 min) was added benzyltriethylammonium tetrathiomolybdate 1
(0.913 g,1.5 mmol). The reaction mixture was stirred for 2 h at room
temperature (28 ꢀC). Diethyl ether (20 mL) was then added to the
reaction mixture followed by filtration through a Celite pad. The
residue was again extracted with CH2Cl2 (5 mL) followed by ex-
traction with diethyl ether (20 mL) and filtered again through
a Celite pad. The combined extract was evaporated and the residue
was purified by column chromatography on silica gel to give the
Michael adduct 18 (0.123 g, 50%) as a mixture of diastereomers (2:1).
4.8.4. (S)-S-(2-(4-Methylphenylsulfonamido)-3-phenylpropyl) 4-me-
thoxybenzothioate (19d). White solid. Yield: 0.419 g, 92%;
mp¼124 ꢀC; [
a]
D
26 ꢁ17.9 (c 3.30, CHCl3); IR (Neat): 3290, 2923, 1651,
1018 cmꢁ1; 1H NMR (300 MHz, CDCl3): 7.82 (d, J¼8.4 Hz, 2H), 7.59 (d,
J¼8.1 Hz, 2H), 7.28e7.22 (m, 3H), 7.15e7.12 (m, 2H), 7.04 (d, J¼8.1 Hz,
2H), 5.11 (d, J¼6.9 Hz, 1H), 3.88 (s, 3H), 3.69e3.59 (m, 1H), 3.14e2.86
(m, 4H), 2.23 (s, 3H); 13C NMR (75 MHz, CDCl3): 190.4, 164.1, 142.9,
137.4, 136.6, 129.5, 129.2, 128.7, 127.0, 113.8, 55.9, 55.6, 41.7, 32.3, 21.5;
HRMS m/z: calcd for C24H25NO4S2Naþ [MþNaþ]: 478.1123; found:
478.1127.
[a
]
24 ꢁ32.0 (c 0.6, CHCl3); IR (Neat): 2924, 1788, 1734, 1713, 1375,
D
1233 cmꢁ1; 1H NMR (300 MHz, CDCl3):
d 4.83e4.79 (m, 1.5H), 4.69
(d, J¼4.5 Hz, 0.5H), 4.64 (dd, J1¼4.8 Hz, J2¼0.6 Hz, 1H), 4.37e4.31
(m, 0.5H), 4.18 (t, J¼6.9 Hz, 1H), 3.75 (s, 1.5H), 3.73 (s, 3H), 3.09 (dd,
J1¼6.9 Hz, J2¼17.4 Hz, 0.5H), 2.96e2.86 (m, 2.5H), 1.48 (s, 3H), 1.46
4.8.5. (S,E)-S-(2-(4-Methylphenylsulfonamido)-3-phenylpropyl) 3-
phenylprop-2-enethioate (19e). White solid. Yield: 0.406 g, 90%;
(s, 1.5H), 1.39 (s, 4.5H); 13C NMR (75 MHz, CDCl3):
d
204.2, 170.4,
mp¼125 ꢀC; [
a]
ꢁ42.08 (c 2.46, CHCl3); IR (Neat): 3289, 2922,
26
D
112.8, 112.7, 85.1, 83.6, 80.4, 52.2, 52.1, 44.8, 41.3, 39.6, 35.5, 27.4,
26.0, 25.8; HRMS m/z: calcd for C10H14O5SNaþ [MþNaþ]: 269.0460;
found: 269.0468.
1614,1158, 1038 cmꢁ1; 1H NMR (300 MHz, CDCl3): 7.63 (d, J¼8.1 Hz,
2H), 7.58e7.43 (m, 3H), 7.42e7.41 (m, 3H), 7.27e7.09 (m, 6H), 6.59
(d, J¼15.6, 1H), 5.03 (d, J¼6.6 Hz, 1H), 3.67e3.59 (m, 1H), 3.12e2.83
(m, 4H), 2.31 (s, 3H); 13C NMR (100 MHz, CDCl3): 190.0, 143.1, 141.4,
137.3, 136.5, 133.8, 130.9, 129.5, 129.4, 129.0, 128.7, 128.5, 127.1,
126.8, 124.2, 55.7, 41.4, 32.5, 21.4; HRMS m/z: calcd for
C26H27NO3S2Naþ [MþNaþ]: 474.1174; found: 474.1156.
4.8. General procedure for aziridine ring opening (19aef and
20ae25a)
To a well stirred solution of the corresponding carboxylic acid
(1.2 mmol), PPh3 (1.3 mmol), and NBS (1.3 mmol) in CHCl3 (5 mL)
(stirred for 10 min) was added benzyltriethylammonium tetra-
thiomolybdate 1 (1.2 mmol). The aziridine (1.0 mmol) was then
added after 20 min and stirred at room temperature (28 ꢀC) until
the disappearance of the starting aziridine. Diethyl ether (20 mL)
was then added to the reaction mixture followed by filtration
through a Celite pad. The residue was again extracted with CH2Cl2
(5 mL) followed by extraction with diethyl ether (20 mL) and fil-
tered again through a Celite pad. The combined extract was evap-
orated and the residue was purified by column chromatography on
silica gel to give the corresponding product.
4.8.6. (S)-S-(2-(4-Methylphenylsulfonamido)-3-phenylpropyl)
4-
chlorobenzothioate (19f). White solid. Yield: 0.414 g, 90%;
mp¼53 ꢀC; [
a
]
D
26 ꢁ18.63 (c 2.95, CHCl3); IR (Neat): 3291, 2923, 1647,
1160 cmꢁ1
;
1H NMR (300 MHz, CDCl3): 7.78 (d, J¼8.7 Hz, 2H), 7.58
(d, J¼8.1 Hz, 2H), 7.42 (d, J¼8.7 Hz, 2H), 7.26e7.22 (m, 3H),
7.12e7.05 (m, 4H), 4.98 (d, J¼7.5 Hz, 1H), 3.74e3.59 (m, 1H),
3.13e3.10 (m, 2H), 2.99e2.85 (m, 2H), 2.29 (s, 3H); 13C NMR
(75 MHz, CDCl3): 190.6, 143.1, 140.2, 136.3, 129.5, 128.9, 128.7, 127.0,
126.9, 55.4, 41.5, 32.9, 21.4; HRMS m/z: calcd for C23H22ClNO3S2Naþ
[MþNaþ]: 482.0627; found: 482.0624.
4.8.7. S-(4-(4-Methylphenylsulfonamido)hexan-3-yl) benzothioate
4.8.1. (S)-S-(2-(4-Methylphenylsulfonamido)-3-phenylpropyl) ben-
(20a). White solid. Yield: 0.324 g, 83%; mp¼104 ꢀC; IR (Neat):
26
zothioate (19a). White solid. Yield: 0.374 g, 88%; mp¼72 ꢀC; [
a
]
3281, 1661, 1160, 909 cmꢁ1 1H NMR (300 MHz, CDCl3): 7.90e7.87
;
D
ꢁ17.5 (c 1.27, CHCl3); IR (Neat): 3287, 1664,1159, 912 cmꢁ1; 1H NMR
(300 MHz, CDCl3): 7.84 (d, J¼8.4 Hz, 2H), 7.60e7.57 (m, 3H),
7.47e7.41 (m, 2H), 7.26e7.22 (m, 3H), 7.14e7.11 (m, 2H), 7.03 (d,
J¼8.4 Hz, 2H), 5.01 (d, J¼6.9 Hz, 1H), 3.72e3.62 (m, 1H), 3.16e2.87
(m, 4H), 2.26 (s, 3H); 13C NMR (75 MHz, CDCl3): 191.8, 143.0, 136.4,
133.7, 129.5, 129.4, 128.7, 128.6, 127.8, 127.4, 127.0, 126.8, 55.6, 41.6,
32.5, 21.4; HRMS m/z: calcd for C23H23NO3S2Naþ [MþNaþ]:
448.1017; found: 448.1021.
(m, 2H), 7.82 (d, J¼7.8 Hz, 2H), 7.61e7.57 (m, 1H), 7.48e7.42 (m, 2H),
7.25 (d, J¼7.8 Hz, 2H), 4.84 (d, J¼9.3 Hz, 1H), 3.59e3.52 (m, 1H),
3.50e3.41 (m, 1H), 2.38 (s, 3H), 1.73e1.37 (m, 4H), 0.97e0.85 (m,
6H); 13C NMR (100 MHz, CDCl3): 191.0, 143.3, 137.8, 136.6, 133.5,
129.5, 128.6, 127.4,127.3, 58.2, 50.8, 25.4, 25.0, 21.5, 11.9,10.7; HRMS
m/z: calcd for C20H25NO3S2Naþ [MþNaþ]: 414.1174; found:
414.1173.
4.8.8. S-(2-(4-Methylphenylsulfonamido)cyclohexyl)
benzothioate
4.8.2. (S)-S-(2-(4-Methylphenylsulfonamido)-3-phenylpropyl) 4-meth-
(21a). White solid. Yield: 0.330 g, 85%; mp¼140 ꢀC; IR (Neat):
ylbenzothioate (19b). White solid. Yield: 0.364 g, 83%; mp¼80 ꢀC;
3285, 2939, 1642, 1328, 1159 cmꢁ1 1H NMR (300 MHz, CDCl3):
;
[a]
26 ꢁ22.7 (c 4.8, CHCl3); IR (Neat): 3293, 2924,1660,1160 cmꢁ1; 1H
7.79e7.73 (m, 2H), 7.63e7.54 (m, 3H), 7.46e7.41 (m, 2H), 6.92 (d,
J¼7.8 Hz, 2H), 5.26 (d, J¼6.9 Hz, 1H), 3.50e3.41 (m, 1H), 3.21e3.01
(m, 1H), 2.25 (s, 3H), 1.77e1.25 (m, 8H); 13C NMR (75 MHz, CDCl3):
193.4, 142.5, 136.4, 133.7, 129.6, 129.3, 128.4, 127.4, 126.8, 59.0, 46.4,
36.4, 32.5, 25.9, 24.5, 21.4; HRMS m/z: calcd for C20H23NO3S2Naþ
[MþNaþ]: 412.1017; found: 412.1037.
D
NMR (300 MHz, CDCl3): 7.03 (d, J¼8.1 Hz, 2H), 7.59 (d, J¼8.1 Hz, 2H),
7.29e7.23 (m, 5H), 7.17e7.1 (m, 2H), 7.03 (d, J¼8.4 Hz, 2H), 5.04 (d,
J¼6.9 Hz,1H), 3.70e3.59 (m,1H), 3.14e2.87 (m, 4H), 2.43 (s, 3H), 2.27
(s, 3H); 13C NMR (75 MHz, CDCl3): 182.2, 144.7, 142.9, 137.2, 136.5,
129.5,129.4,128.7,127.5,127.0,126.8, 55.7, 41.6, 32.3, 21.7, 21.4; HRMS
m/z: calcd for C24H25NO3S2Naþ [MþNaþ]: 462.1174; found: 462.1160.
4.8.9. S-(6-(4-Methylphenylsulfonamido)cyclohex-3-en-1-yl) benzo-
4.8.3. (S)-S-(2-(4-Methylphenylsulfonamido)-3-phenylpropyl)
2-
thioate (22a). White solid. Yield: 0.341 g, 88%; mp¼100 ꢀC; IR
phenylethanethioate (19c). Colorless liquid. Yield: 0.399 g, 91%;
(Neat): 3281, 1661, 1158, 1092 cmꢁ1 1H NMR (300 MHz, CDCl3):
;

P. Gopinath et al. / Tetrahedron 66 (2010) 7001e7011
7009
7.81 (d, J¼8.4 Hz, 2H), 7.67e7.57 (m, 3H), 7.53e7.41 (m, 2H), 7.07 (d,
J¼8.4 Hz, 2H), 5.62 (s, 2H), 5.25 (br s, 1H), 3.88e3.81 (m, 1H),
3.61e3.51 (m, 1H), 2.65e2.53 (m, 2H), 2.43e2.12 (m, 2H), 2.32 (s,
3H); 13C NMR (75 MHz, CDCl3): 192.6, 142.9, 136. 4, 133.6, 129.4,
128.5, 127.7, 127.4, 126.8, 125.0, 124.8, 53.8, 42.1, 33.7, 30.5, 21.4;
HRMS m/z: calcd for C20H21NO3S2Naþ [MþNaþ]: 410.0861; found:
410.0869.
128.3, 128.0, 127.8, 127.4, 47.8, 43.9, 32.5, 21.6; HRMS m/z: calcd for
C
23H21NO3S2Naþ [MþNaþ]: 446.0861; found: 446.0859.
4.10. Synthesis of S,S0-(2-(4-methylphenylsulfonamido)-1-
phenylpropane-1,3-diyl) dibenzothioate, 29
To a well stirred solution of benzoic acid 2a (0.268 g, 2.2 mmol),
PPh3 (0.576 g, 2.2 mmol), and NBS (0.392 g, 2.2 mmol) in CHCl3
(8 mL) (stirred for 10 min) was added benzyltriethylammonium
tetrathiomolybdate 1 (1.34 g, 2.2 mmol). To this was added azir-
idine tosylate 27 (0.457 g, 1 mmol) and the reaction mixture was
stirred for 8 h at room temperature (28 ꢀC). Diethyl ether (30 mL)
was then added to the reaction mixture followed by filtration
through a Celite pad. The residue was again extracted with CH2Cl2
(10 mL) followed by extraction with diethyl ether (30 mL) and fil-
tered again through a Celite pad. The combined extract was evap-
orated and the residue was purified by column chromatography on
silica gel to give the corresponding bisthioester 29 as a white solid
(0.421 g, 75%).
4.8.10. S-(2-(4-Methylphenylsulfonamido)cyclopentyl) benzothioate
(23a). White solid. Yield: 0.307 g, 82%; mp¼137 ꢀC; IR (Neat):
3274,1660,1159 cmꢁ1; 1H NMR (300 MHz, CDCl3): 7.79 (d, J¼7.2 Hz,
2H), 7.66e7.58 (m, 3H), 7.48e7.43 (m, 2H), 7.00 (d, J¼7.2 Hz, 2H),
5.53 (d, J¼5.1 Hz, 1H), 3.76e3.67 (m, 1H), 3.48e3.38 (m, 1H), 2.22 (s,
3H), 2.19e2.09 (m, 2H), 1.86e1.54 (m, 4H); 13C NMR (100 MHz,
CDCl3): 193.2, 142.9, 137.3, 136.3, 133.7, 129.4, 128.5, 127.4, 127.1,
62.6, 46.4, 33.6, 29.4, 22.0, 21.4; HRMS m/z: calcd for
C19H21NO3S2Naþ [MþNaþ]: 398.0861; found: 398.0865.
4.8.11. S-(4-Methyl-3-(4-methylphenylsulfonamido)pentan-2-yl)
benzothioate (24a). White solid. Yield: 0.317 g, 81%; mp¼134 ꢀC; IR
Mp¼153 ꢀC; IR (Neat): 3282, 1666, 1597, 1208, 1158 cmꢁ1
;
1H
(Neat): 3286, 1658, 1158 cmꢁ1
;
1H NMR (300 MHz, CDCl3):
NMR (300 MHz, CDCl3): 7.93e7.90 (m, 2H), 7.82e7.79 (m, 2H),
7.66e7.55 (m, 4H), 7.48e7.21 (m, 9H), 7.01 (d, J¼8.4 Hz, 2H), 5.16 (d,
J¼3.6 Hz, 1H), 5.06 (d, J¼9.0 Hz, 1H), 4.16e4.07 (m, 1H), 3.24 (dd,
J1¼9.0 Hz, J2¼14.1 Hz, 1H), 3.04 (dd, J1¼5.1 Hz, J2¼14.1 Hz, 1H), 2.20
(s, 3H); 13C NMR (100 MHz, CDCl3): 191.6, 189.6, 143.1, 137.8, 136.8,
136.4, 133.7, 133.6, 129.4, 128.9, 128.6, 128.5, 128.4, 128.2, 127.5,
127.4, 127.2, 58.3, 52.4, 31.3; HRMS m/z: calcd for C30H27NO4S3Naþ
[MþNaþ]: 584.1000; found: 584.0987.
7.80e7.73 (m, 4H), 7.59e7.40 (m, 3H), 7.20 (d, J¼7.5 Hz, 2H), 4.99 (d,
J¼9.9 Hz, 1H), 3.91e3.85 (m, 1H), 3.48e3.36 (m, 1H), 2.37 (s, 3H),
1.93e1.87 (m, 1H), 1.26 (d, J¼7.2 Hz, 3H), 0.97 (d, J¼6.6 Hz, 6H); 13C
NMR (100 MHz, CDCl3): 191.0,143.0,138.8, 136.7,133.4,129.4,128.5,
127.2, 127.1, 63.2, 41.8, 31.0, 21.5, 20.5, 18.8, 16.9; HRMS m/z: calcd
for C20H25NO3S2Naþ [MþNaþ]: 414.1174; found: 414.1170.
4.8.12. S-(2-(4-Methylphenylsulfonamido)-1-phenylethyl)
benzo-
thioate (25a) and S-(2-(4-methylphenylsulfonamido)-2-phenylethyl)
4.11. General procedure for epoxide ring opening (30aef, 31a,
and 31b)
benzothioate (25a0). White solid. Yield: 0.311 g, 80%; mp¼119 ꢀC
(for mixture); (R1:R2¼4:3) IR (Neat): 3282, 1662, 1330, 1157 cmꢁ1
;
1H NMR (300 MHz, CDCl3): 7.90e7.84 (m, 2HR1þ2HR2), 7.74 (d,
J¼8.4 Hz, 2HR1), 7.63e7.55 (1HR1þ3HR2), 7.48e7.40 (m,
2HR1þ2HR2), 7.32e7.21 (m, 7HR1þ5HR2), 7.00 (d, J¼7.8 Hz, 2HR2),
5.51 (d, J¼6.3 Hz, 1HR2), 4.81e4.74 (m, 2HR2), 4.59e4.52 (m, 1HR1),
3.68e3.59 (m, 1HR1), 3.54e3.48 (m, 1HR1), 3.56e3.52 (m, 1HR2),
3.24 (dd, J1¼4.2 Hz, J2¼14.1 Hz, 1HR2), 2.40 (s, 3HR1), 2.24 (s, 3HR2);
13C NMR (75 MHz, CDCl3): 190.3, 143.5, 143.0, 140.1, 136.3, 133.8,
129.7, 129.3,; HRMS m/z: calcd for C20H23NO3S2Naþ [MþNaþ]:
412.1017; found: 412.1037.
To a well stirred solution of the corresponding carboxylic acid
(1.0 mmol), PPh3 (1.1 mmol), and NBS (1.1 mmol) in CHCl3eEtOH
(1:1) mixture (6 mL) (stirred for 10 min) was added benzyl-
triethylammonium tetrathiomolybdate 1 (1.2 mmol). The corre-
sponding epoxide (1.2 mmol) was then added after 20 min and
stirring was continued for 6 h at room temperature (28 ꢀC). Diethyl
ether (20 mL) was then added to the reaction mixture followed by
filtration through a Celite pad. The residue was again extracted with
CH2Cl2 (5 mL) followed by extraction with diethyl ether (20 mL)
and filtered again through a Celite pad. The combined extract was
evaporated and the residue was purified by column chromatogra-
phy on silica gel to give the corresponding product.
4.9. Synthesis of S-(phenyl(1-tosylaziridin-2-yl)methyl)
benzothioate 28
4.11.1. S-(2-Hydroxy-2-phenylethyl) benzothioate (30a). Colorless
To
a
well stirred solution of benzoic acid 2a (0.128 g,
liquid. Yield: 0.160 g, 62%; IR (Neat): 3448, 1660, 1207 cmꢁ1 1H
;
1.05 mmol), PPh3 (0.275 g, 1.05 mmol), and NBS (0.187 g,
1.05 mmol) in CHCl3 (5 mL) (stirred for 10 min) was added ben-
zyltriethylammonium tetrathiomolybdate 1 (0.639 g, 1.05 mmol).
To this was added the corresponding aziridine tosylate 27
(0.457 g, 1 mmol) and the reaction mixture was stirred for 5 h at
room temperature (28 ꢀC). Diethyl ether (20 mL) was then added
to the reaction mixture followed by filtration through a Celite
pad. The residue was again extracted with CH2Cl2 (5 mL) followed
by extraction with diethyl ether (20 mL) and filtered again
through a Celite pad. The combined extract was evaporated and
the residue was purified by column chromatography on silica gel
to give the corresponding aziridine thioester 28 (0.313 g, 74%) as
a white solid.
NMR (300 MHz, CDCl3): 8.01e7.98 (m, 2H), 7.62e7.57 (m, 1H),
7.49e7.29 (m, 7H), 4.94 (dd, J1¼3.6 Hz, J2¼8.4 Hz, 1H), 3.54 (dd,
J1¼8.4 Hz, J2¼13.8, 1H), 3.30 (dd, J1¼8.4 Hz, J2¼13.8 Hz, 1H), 2.72 (br
s, 1H); 13C NMR (75 MHz, CDCl3): 192.4, 142.5, 133.6, 128.7, 128.6,
128.0, 127.4, 125.8, 73.4, 38.0; HRMS m/z: calcd for C15H14O2SNaþ
[MþNaþ]: 281.0612; found: 281.0606.
4.11.2. S-(2-Hydroxy-2-phenylethyl) 4-methylbenzothioate (30b).
White solid. Yield: 0.150 g, 65%; mp¼63 ꢀC; IR (Neat): 3402, 1657,
1606, 914 cmꢁ1
;
1H NMR (300 MHz, CDCl3): 7.88 (d, J¼8.1 Hz, 2H),
7.47e7.40 (m, 2H), 7.37e7.23 (m, 5H), 4.94e4.89 (m, 1H), 3.51 (dd,
J1¼3.6 Hz, J2¼14.1 Hz, 1H), 3.28 (dd, J1¼8.4 Hz, J2¼14.1 Hz, 1H), 2.86
(d, J¼3.6 Hz, 1H), 2.41 (s, 3H); 13C NMR (100 MHz, CDCl3): 192.6,
145.1, 143.1, 134.7, 129.8, 129.1, 128.5, 128.0, 126.3, 73.9, 38.4, 22.2;
HRMS m/z: calcd for C16H16O2SNaþ [MþNaþ]: 295.0769; found:
295.0767.
Mp¼104 ꢀC; IR (Neat): 1665, 1597, 1327, 1162 cmꢁ1
;
1H NMR
(400 MHz, CDCl3): 7.86e7.85 (m, 2H), 7.62 (d, J¼8.0 Hz, 2H),
7.59e7.56 (m, 1H), 7.46e7.42 (m, 2H), 7.21e7.18 (m, 5H), 7.10 (d,
J¼8.0 Hz, 2H), 4.66 (d, J¼7.6 Hz, 1H), 3.26e3.22 (m, 1H), 2.81 (d,
J¼6.8 Hz, 1H), 2.38e2.33 (m, 1H), 2.35 (s, 3H); 13C NMR (100 MHz,
CDCl3): 189.7, 144.3, 136.8, 136.2, 134.5, 133.8, 129.5, 128.7, 128.6,
4.11.3. S-(2-Hydroxy-2-phenylethyl) 2-phenylethanethioate (30c).
Colorless liquid. Yield: 0.169 g, 62%; IR (Neat): 3371, 1677,

7010
P. Gopinath et al. / Tetrahedron 66 (2010) 7001e7011
1018 cmꢁ1; 1H NMR (300 MHz, CDCl3): 7.36e7.25 (m, 10H), 4.80 (d,
J¼9.0 Hz, 1H), 3.86 (s, 2H), 3.31 (dd, J1¼4.2 Hz, J2¼14.1 Hz, 1H), 3.09
(dd, J1¼9.0 Hz, J2¼14.1 Hz, 1H), 2.51 (br s, 1H); 13C NMR (100 MHz,
CDCl3): 198.4, 142.8, 133.8, 130.1, 129.2, 129.0, 128.5, 128.0, 126.3,
73.7, 50.9, 36.7; HRMS m/z: calcd for C16H16O2SNaþ [MþNaþ]:
295.0769; found: 295.0768.
ether (20 mL) and filtered again through a Celite pad. The combined
extract was evaporated and the residue was purified by column
chromatography on silica gel to give the corresponding aziridine
thioester 32a (0.322 g, 80%) as a white solid.
Mp¼104 ꢀC; IR (Neat): 3288, 1660, 1159, 911 cmꢁ1
;
1H NMR
(400 MHz, CDCl3): 7.83e7.80 (m, 2H), 7.67 (d, J¼8.0 Hz, 2H),
7.61e7.58 (m, 1H), 7.47e7.42 (m, 2H), 7.11 (d, J¼8.0 Hz, 2H), 5.47 (d,
J¼8.8 Hz, 1H), 3.78e3.73 (m, 1H), 3.51e3.43 (m, 1H), 2.55 (dd,
J1¼5.4 Hz, J2¼16.0 Hz, 1H), 2.48e2.42 (m, 1H), 2.34 (m, 1H), 2.34 (s,
3H), 2.10e1.99 (m, 2H); 13C NMR (100 MHz, CDCl3): 191.2, 143.0,
138.3, 136.3, 133.8, 129.6, 128.6, 127.4, 126.6, 52.1, 51.3, 51.2, 39.4,
30.8, 28.6, 21.5; HRMS m/z: calcd for C20H21NO4S2Naþ [MþNaþ]:
426.0810; found: 426.0804.
4.11.4. S-(2-Hydroxy-2-phenylethyl) 4-methoxybenzothioate (30d).
White solid. Yield: 0.184 g, 64%; mp¼45 ꢀC; IR (Neat): 3436, 1601,
1168 cmꢁ1
;
1H NMR (300 MHz, CDCl3): 7.98 (d, J¼9.0 Hz, 2H),
7.48e7.29 (m, 5H), 6.94 (d, J¼9.0 Hz, 2H), 4.94e4.92 (m,1H), 3.87 (s,
3H), 3.52 (dd, J1¼3.6 Hz, J2¼14.1 Hz, 1H), 3.28 (dd, J1¼3.6 Hz,
J2¼14.1 Hz, 1H), 2.87 (d, J¼2.0 Hz, 1H); 13C NMR (100 MHz, CDCl3):
191.1, 164.1, 142.7, 129.7, 128.6, 128.0, 125.9, 113.9, 73.6, 55.6, 38.0;
HRMS m/z: calcd for C16H16O2SNaþ [MþNaþ]: 311.0718; found:
311.0706.
Compounds 5a21 and 7a21 are reported.
Crystallographic data (excluding structure factors) for the
structures (4h) in this paper have been deposited with the Cam-
bridge Crystallographic Data Centre as supplementary publication
nos. CCDC-731527. Copies of the data can be obtained, free of
charge, on application to CCDC, 12 Union Road, Cambridge CB2 1EZ,
UK, (fax: þ44 (0)1223 336033 or e-mail: deposit@ccdc.cam.ac.Uk).
4.11.5. (E)-S-(2-Hydroxy-2-phenylethyl) 3-phenylprop-2-enethioate
(30e). White solid. Yield: 0.179 g, 63%; mp¼59 ꢀC; IR (Neat): 3448,
1652, 1615, 1042 cmꢁ1
;
1H NMR (300 MHz, CDCl3): 7.66 (d,
J¼15.9 Hz, 1H), 7.57e7.31 (m, 10H), 6.76 (d, J¼15.9 Hz, 1H),
4.94e4.91 (m, 1H), 3.48 (dd, J1¼3.9 Hz, J2¼14.1 Hz, 1H), 3.26 (dd,
J1¼8.4 Hz, 1H, J2¼14.1 Hz, 1H), 2.78 (d, J¼3.0 Hz, 1H); 13C NMR
(100 MHz, CDCl3): 190.5, 142.6, 141.4, 134.0, 130.9, 129.1, 128.6,
125.9, 124.6, 73.5, 38.1; HRMS m/z: calcd for C17H16O2SNaþ
[MþNaþ]: 307.0769; found: 307.0763.
Acknowledgements
P.G. thanks Council of Scientific and Industrial Research (CSIR),
New Delhi for a Senior Research Fellowship and S.C.N. thanks De-
partment of Science and Technology (DST), New Delhi for the J.C.
Bose Fellowship.
4.11.6. S-(2-Hydroxy-2-phenylethyl) 4-chlorobenzothioate (30f).
White solid. Yield: 0.173 g, 59%; mp¼59 ꢀC; IR (Neat): 3457, 1666,
1588, 1206 cmꢁ1; 1H NMR (300 MHz, CDCl3): 7.93 (d, J¼8.4 Hz, 2H),
7.47e7.30 (m, 7H), 4.95e4.92 (m, 1H), 3.54 (dd, J1¼3.6 Hz,
J2¼13.8 Hz, 1H), 3.31 (dd, J1¼8.4 Hz, J2¼13.8 Hz, 1H), 2.66 (d,
J¼3.3 Hz, 1H); 13C NMR (100 MHz, CDCl3): 191.5, 142.7, 140.4, 135.3,
129.3, 129.0, 128.9, 128.4, 126.1, 73.6, 38.3; HRMS m/z: calcd for
C16H17ClO2SNaþ [MþNaþ]: 315.0222; found: 315.0210.
Supplementary data
Copies of the 1H, and 13C NMR spectra for all new compounds
are attached. Supplementary data associated with this article can
be found in the online version at doi:10.1016/j.tet.2010.06.028.
These data include MOL files and InChIKeys of the most important
compounds described in this article.
4.11.7. S-(2-Hydroxycyclohexyl) benzothioate (31a). Colorless liq-
References and notes
uid. Yield: 0.149 g, 63%; IR (Neat): 3421, 1659, 912 cmꢁ1 1H NMR
;
(300 MHz, CDCl3): 7.99e7.96 (m, 2H), 7.61e7.56 (m, 1H), 7.48e7.43
(m, 2H), 3.67e3.53 (m, 2H), 2.48 (d, J¼3.9 Hz, 1H), 2.19e2.11 (m,
2H), 1.83e1.73 (m, 2H), 1.61e1.26 (m, 4H); 13C NMR (100 MHz,
CDCl3): 192.7, 136.9, 133.6, 128.6, 127.5, 73.3, 0.3, 35.2, 32.2, 25.9,
24.1; HRMS m/z: calcd for C13H16O2SNaþ [MþNaþ]: 259.0769;
found: 259.0771.
1. (a) Vijaikumar, S.; Pitchumani, K. J. Mol. Cat. A: Chem. 2004, 217, 117; (b) Jai-
singhani, H. G.; Khadilkar, B. M. Synth. Commun. 1999, 29, 3693; (c) Mariola, Z.
B.; Rafal, K.; Jacek, S. Tetrahedron 2005, 61, 5235; (d) Sibi, M. P.; Manyem, S.
Tetrahedron 2000, 56, 8033; (e) Fan, R. H.; Hou, X. L. J. Org. Chem. 2003, 68, 726;
(f) Bae, J. H.; Shin, S. H.; Park, C. S.; Lee, W. K. Tetrahedron 1999, 55, 10041.
2. (a) Yamamoto, H.; Fukazu, N.; Tanaka, M.; Kobayashi, S. Jpn. Kokai Tokkyo Koho
2004, 9p; (b) Li, H.; Zu, L.; Wang, J.; Wang, W. Tetrahedron Lett. 2006, 47, 3145;
(c) Li, H.; Wang, J.; Zu, L.; Wang, W. Tetrahedron Lett. 2006, 47, 2585; (d) Fanjul,
S.; Hulme, A. N.; White, J. W. Org. Lett. 2006, 8, 4219; (e) Roy, C.; Li, T.; Krasik, P.;
Gilbert, M. J.; Pelletier, C.; Gagnon, D.; Robert, E.; Ducharme, J.; Storer, R.;
Lavallee, J. F. Bioorg. Med. Chem. Lett. 2002, 12, 3141; (f) Busque, F.; March, P. D.;
Figueredo, M.; Font, J.; Gonzalez, L. Eur. J. Org. Chem. 2004, 1492; (g) Hu, L.; Zhu,
H.; Du, D. M.; Xu, J. J. Org. Chem. 2007, 72, 4543.
3. (a) Bjorn, H. T.; Ben, F. L.; Adriaan, M. J. Chem. Commun. 2007, 5, 489; (b) Field, L.
Synthesis 1972, 101; (c) Haslam, E. Tetrahedron 1980, 36, 2409; (d) Koizumi, N.;
Takegawa, S.; Iwashita, S.; Kawachi, T.; Inoue, F.; Honma, S.; Takahashi, H.;
Mieda, M.; Ueda, K. PCT Int. Appl., 1994, 65 p. (e) Yang, Z. N.; Fan, M.; Yang, X. S.;
Yu, Z. W.; Hao, X. J. Chin. J. Chem. 2008, 26, 547.
4. (a) Chakor, N.; Dallavalle, S.; Musso, L.; Moretti, M. Tetrahedron Lett. 2008, 49,
5056; (b) Tius, M. A.; Astrab, D. P. Tetrahedron Lett. 1989, 30, 2333; (c) Luond, R.
M.; Walker, J.; Neier, R. W. J. Org. Chem. 1992, 57, 5005.
5. (a) Villalobos, J. M.; Srogl, J.; Liebeskind, L. S. J. Am. Chem. Soc. 2007, 129, 15734;
(b) Prokopcova, H.; Pisani, L.; Kappe, C. O. Synlett 2007, 43; (c) Morita, A.; Ku-
wahara, S. Org. Lett. 2004, 8, 1613; (d) Lengar, A.; Kappe, C. O. Org. Lett. 2004, 6,
771; (e) Alphonse, F. A.; Suzenet, F.; Keromnes, A.; Lebert, B.; Guillaumet, G.
Synlett 2002, 447.
6. Ibarra, A. C.; Mendoza, M.; Orellana, G.; Quiroga, M. L. Synthesis 1989, 560.
7. (a) Mukaiyama, T.; Araki, M.; Takei, H. J. Am. Chem. Soc. 1973, 95, 4763; (b)
Anderson, R.; Henrick, C. A.; Rosenblum, L. D. J. Am. Chem. Soc. 1974, 96, 3654;
(c) Sviridov, A. F.; Ermolenko, M. S.; Yashunsky, D. V.; Kochetkov, N. K. Tetra-
hedron Lett. 1983, 24, 4355.
8. Greene, T. W.; Wuts, P. G. M. Protective Groups in Organic Synthesis; John Wiley:
New York, NY, 1999; p 454.
9. (a) McGarvey, G. J.; Williams, M. J.; Hiner, R. N.; Matsubra, Y.; Oh, T. J. Am. Chem. Soc.
1986, 108, 4943; (b) McCoy, J. G.; Johnson, H. D.; Singh, S.; Bingman, C. A.; Lei, I. K.;
Thorson, J. S.; Phillips, G. N. Prot. Str. Func. Bio. 2009, 74, 50; (c) Zeiba, A.; Suwinska,
4.11.8. S-(2-Hydroxycyclohexyl) 4-methylbenzothioate (31b). White
solid. Yield: 0.163 g, 65%; mp¼69 ꢀC; IR (Neat): 3420, 1653,
913 cmꢁ1; 1H NMR (300 MHz, CDCl3): 7.87 (d, J¼8.1 Hz, 2H), 7.24 (d,
J¼8.1 Hz, 2H), 3.65e3.49 (m, 2H), 2.61 (br s, 1H), 2.41 (s, 3H),
2.19e2.10 (m, 2H), 1.82e1.72 (m, 2H), 1.60e1.25 (m, 4H); 13C NMR
(100 MHz, CDCl3): 192.8, 144.9, 134.9, 129.7, 128.0, 73.8. 50.6, 35.6,
32.7, 26.4, 24.6, 22.2; HRMS m/z: calcd for C14H18O2SNaþ [MþNaþ]:
273.0925; found: 273.0933.
4.12. Synthesis of S-(4-(4-methylphenylsulfonamido)-7-
oxabicyclo[4.1.0]heptan-3-yl) benzothioate, 32a
To a well stirred solution of benzoic acid 2a (0.128 g, 1.05 mmol),
PPh3 (0.275 g, 1.05 mmol), and NBS (0.187 g, 1.05 mmol) in CHCl3
(5 mL) (stirred for 10 min) was added benzyltriethylammonium
tetrathiomolybdate 1 (0.639 g, 1.05 mmol). To this was added the
corresponding aziridine epoxide, 32 (0.265 g, 1 mmol) and the re-
action mixture was stirred for 8 h at room temperature (28 ꢀC).
Diethyl ether (20 mL) was then added to the reaction mixture fol-
lowed by filtration through a Celite pad. The residue was again
extracted with CH2Cl2 (5 mL) followed by extraction with diethyl

P. Gopinath et al. / Tetrahedron 66 (2010) 7001e7011
7011
K. Heterocycles 2008, 75, 2649; (d) Peterson, M. J.; Marchal, C.; Loughlin, W. A.;
Jenkins, I. D.; Healy, P. C.; Almesaker, A. Tetrahedron 2006, 63, 1395.
10. Prabhu, K. R.; Devan, N.; Chandrasekaran, S. Synlett 2002, 1762.
11. (a) Froyen, P. Phosphorus Sulfur Silicon 1994, 89, 57; (b) Froyen, P. Phosphorus
Sulfur Silicon 1994, 91, 145; (c) Sucheta, K.; Reddy, G. S. R.; Ravi, D.; Rama Rao, N.
Tetrahedron Lett. 1994, 25, 4415; (d) Froyen, P. Synth. Commun. 1995, 25, 959; (e)
Froyen, P. Phosphorus Sulfur Silicon 1995, 102, 253.
14. Wang, X.; Zhao, G.; Chen, Y.; Xu, X.; Zhong, W.; Wang, L.; Li, S. Bioorg. Med.
Chem. Lett. 2009, 19, 770.
15. Malkinson, J. P.; Falconer, R. A.; Toth, I. J. Org. Chem. 2000, 65, 5249.
16. Jorglis, P.; Lichtenthaler, F. W. Tetrahedron Lett. 1982, 23, 3781.
17. Argyopoulos, N. K.; Panagiotidis, T. D.; Gallos, J. K. Tetrahedron: Asymmetry 2006,
17, 829.
18. Jeong, J. U.; Tao, B.; Sagasser, I.; Henniges, H.; Sharpless, K. B. J. Am. Chem. Soc.
1998, 120, 6844.
12. Gopinath, P.; Vidyarini, R. S.; Chandrasekaran, S. J. Org. Chem. 2009, 74,
6291.
19. Linge, M.; Peng, J.; Qihan, Z.; Jiaxi, X. Tetrahedron: Asymmetry 2005, 16, 3718.
20. Sureshkumar, D.; Maity, S.; Chandrasekaran, S. J. Org. Chem. 2006, 71, 61653.
21. Kreutzkamp, N.; Peschel, H. Pharmazie 1970, 25, 5.
13. Gopinath, P.; Vidyarini, R. S.; Chandrasekaran, S. Eur. J. Org. Chem. 2009,
6043.