Desulfurization-oxygenation of chiral 1,3-thiazolidine-2-thiones and 1,3-oxazolidine-2-thiones using propylene oxide and microwave irradiation

Article abstract of DOI:10.1055/s-0032-1317525

An efficient method for the desulfurization-oxygenation of 1,3-thiazolidine-2-thiones and 1,3-oxazolidine-2-thiones using propylene oxide and employing microwave irradiation is described. This strategy of oxygenation of the thiocarbonyl group provides an attractive methodology to prepare chiral 1,3-thiazolidin-2-ones and 1,3-oxazolidin-2-ones from the corresponding precursors in good yields. Copyright

Full text of DOI:10.1055/s-0032-1317525

LETTER
▌2835
lDetteersulfurization–Oxygenation of Chiral 1,3-Thiazolidine-2-thiones and 1,3-
Oxazolidine-2-thiones Using Propylene Oxide and Microwave Irradiation
Preparation of 1,3-Thiazolidine-2-thiones and 1,3-Ox
a
azolidine-2-thiones
b
b
a
a
Leticia Minor-Villar, Rodolfo Tello-Aburto, Horacio F. Olivo, Aydee Fuentes, Moises Romero-Ortega*
a
Departamento de Química Orgánica, Facultad de Química, Universidad Autónoma del Estado de México, Toluca, México
Fax +52(722)2173890; E-mail: mromeroo@uaemex.mx
b
Medicinal and Natural Products Chemistry, The University of Iowa, Iowa City, IA 52242, USA
Received: 17.08.2012; Accepted after revision: 10.10.2012
6
aldol processes. Further reports have shown that both
chlorotitanium enolates of 1,3-thiazolidine-2-thiones 2
Abstract: An efficient method for the desulfurization–oxygenation
of 1,3-thiazolidine-2-thiones and 1,3-oxazolidine-2-thiones using
propylene oxide and employing microwave irradiation is described.
and 1,3-oxazolidine-2-thiones 3 (Figure 1) provide excel-
9
This strategy of oxygenation of the thiocarbonyl group provides an lent levels of diastereoselectivity in aldol reactions. For
attractive methodology to prepare chiral 1,3-thiazolidin-2-ones and example, the syn-Evans and syn-non-Evans propionate al-
1
,3-oxazolidin-2-ones from the corresponding precursors in good dol sulfur adducts can be accessed depending on the
yields.
amount of Lewis acid and base used and they have the re-
Key words: thiazolidinethiones, oxazolidinethiones, thiazolidi- markable advantage of easier removal of the auxiliary af-
1
0
nones, propylene oxide, chiral auxiliaries.
ter completion of the chiral induction. Such a feature has
great merits in the synthesis of complicated and fragile
molecules containing different functionalities.
Chiral auxiliary based processes have a prominent posi-
tion among the most reliable strategies for accessing a ste-
Recently, we encountered some problems in the purifica-
tion of the N-enoyl imide derivatives during our work on
the 1,4-addition of organocuprates to N-enoyl thiazolidi-
1
reoisomer in enantiomerically pure form. Chiral
2
auxiliaries such as oxazolidin-2-ones 1, thiazolidine-2-
11
nethiones and oxazolidinethiones. This problem was at-
3
4
thiones 2, and oxazolidine-2-thiones 3 (Figure 1) have
become a superb tool for the stereoselective construction
of carbon–carbon bonds and have reached tremendous
success. Nevertheless, the diastereoselectivity imparted
tributed to the high nucleophilicity of the sulfur atom
present in the thiocarbonyl group reacting intramolecular-
ly with the unsaturation during chromatography. Palomo
described the rearrangement of the sulfur atom in the thio-
carbonyl of N-enoyl oxazolidinethiones when Lewis acids
5
by boron enolates of N-acetyl oxazolidin-2-ones is low.
However, the problem has been solved by employing its
12
are present. This rearrangement was employed for the
6
sulfur analogues. Additionally, the use of oxazolidin-2-
preparation of β-mercapto carbonyl derivatives. Eventual-
ly, we solved the purification problem by adding some tri-
ethylamine to the eluent during flash column
chromatography or avoiding the chromatographic step by
a simple recrystallization.
ones 1 has also attracted attention because of their antimi-
7
crobial activity as antibiotics. There are a few oxazolidi-
nones currently in clinical trials.8
O
O
O
It has been reported that thiocarbonyl compounds undergo
desulfurization to generate the corresponding carbonyl
compounds when treated with a variety of oxidizing re-
O
NH
O
NH
Bn
O
NH
Ph
13
agents. During the course of our studies, a method was
reported for the syntheses of chiral 1,3-thiazolidin-2-ones
1
a
1b
1c
1
4
4
from 1,3-thiazolidine-2-thiones 2. 4-Substituted thia-
S
S
O
zolidinethiones were treated with bromoethanol in etha-
nol with sodium ethoxide as a base. The yields of the
products were in the range of 45% (R = Me) to 85% (R =
Ph). Another method appeared in the patent literature,
where 4-benzylthiazolidinethione was transformed to the
corresponding thiazolidinone utilizing propylene oxide
and trifluoroacetic acid. However, the yield of the thia-
S
NH
R
O
NH
R
S
NH
R
2
3
4
Figure 1
1
5a
zolidinone was extremely low (2.5%). Calo et al. re-
Nagao reported that tin enolates of N-acyl-1,3-thiazoli- ported very good yields for the preparation of 4-
dine-2-thiones could participate in highly stereoselective isopropylthiazolidinone (4a; 87%) and 4-methylthiazolid-
inone (4d; 91%) utilizing also trifluoroacetic acid and 1-
1
5b
butene oxide.
Also, the 4-phenylthiazolidinone has
SYNLETT 2012, 23, 2835–2839
Advanced online publication: 09.11.2012
been reported to be obtained in 38–67% yields utilizing
aqueous hydrogen peroxide and sodium hydroxide at
room temperature for two hours. There are a few other
0
9
3
6
-
5
2
1
4
1
4
3
7
-
2
0
9
6
DOI: 10.1055/s-0032-1317525; Art ID: ST-2012-S0696-L
Georg Thieme Verlag Stuttgart · New York
16
©

2836
L. Minor-Villar et al.
LETTER
reports on the conversion of thiazolidine-2-thiones to thi-
Table 1 Desulfurization–Oxygenation of 1,3-Thiazolidine-2-thi-
azolidin-2-ones, but they are not related to chiral auxilia- ones
ries.17 White and Kawasaki also prepared a 1,3-
S
O
thiazolidin-2-one as found in a marine sponge metabolite
latrunculin A. In this context, we decided to investigate
a practical method to prepare chiral 1,3-thiazolidin-2-ones
O
18
S
NH
R
S
NH
R
+
1
00 °C
S
sealed tube
4
auxiliaries based on the desulfurization–oxygenation re-
2
a–e
4a–e
action of 1,3-thiazolidine-2-thiones 2 avoiding the use of
highly corrosive trifluoroacetic acid.
Entry
Substrate
Product
Yield (%)
We selected chiral thiazolidinethiones 2a–e and oxazoli-
dinethiones 3a–e because they are the most widely used
auxiliaries to accomplish the highest asymmetric induc-
tions and because their syntheses are accomplished in two
steps following known procedures. Reduction of the cor-
S
O
S
NH
i-Pr
S
NH
i-Pr
1
71
1
9
responding amino acid to the amino alcohol and expo-
sure of the amino alcohol to carbon disulfide in KOH
2a
4a
2
0
S
S
S
O
O
O
delivered thiazolidinethiones 2a–d in excellent yields.
Thiazolidinethione 2e was prepared from the correspond-
ing trans-1-amino-2-indanol according to our proce-
dure.3d We found that stirring thiazolidinethiones 2a–e
with propylene oxide in a sealed tube immersed in an oil
bath at 100 °C delivered after 48 hours the corresponding
thiazolidin-2-ones 4a–e in good yields 71–86% (Table 1).
Reducing the reaction time delivered the products in low-
er yields.
S
NH
Bn
S
NH
2
3
4
86
78
80
Bn
2b
4b
S
NH
Ph
S
NH
Ph
The methodology was extended for the desulfurization–
oxygenation of chiral oxazolidine-2-thiones 3a–e to oxa-
zolidin-2-ones 1a–e. Chiral oxazolidine-2-thiones 3a–e
were prepared from the corresponding amino alcohols us-
ing carbon disulfide in the presence of potassium carbon-
ate and hydrogen peroxide.21 These chiral auxiliaries
reacted equally well with propylene oxide under thermal
conditions for 48 hours to give the corresponding 1,3-ox-
azolidin-2-ones 1a–e in good yields (80–92%; Table 2).
2c
4c
S
NH
S
NH
2d
4d
S
O
We found that propylene oxide is a general reagent for this
transformation and the use of N-unsubstituted 1,3-thia-
zolidine-2-thione 2 was critical for the successful ex-
change of the thiocarbonyl for a carbonyl group. When N-
acetyl derivative of thiazolidinethione 2e was subjected to
the same desulfurization reaction conditions with propyl-
ene oxide, no product was observed. All four chiral auxil-
iaries can be easily distinguished by the chemical shift of
S
NH
S
NH
H
H
H
H
5
76
2e
4e
ones 3a–e under conventional thermal conditions, the re-
action time required for the reaction to complete could be
long (48 h). In this context, the use of high-power micro-
wave irradiation offers a complementary technology to
improve the efficiency of energy transfer to the reaction
mixture. In the last two decades fast microwave heating
has been shown to accelerate a large number of organic
transformations. In this respect, the desulfurization–ox-
ygenation process was investigated in chloroform using
sealed vessels and microwave heating. The reaction time
was set to 60 minutes and the temperature at 150 °C. The
investigated substrates 2c, 2d, 3b, 3c and 3e, were
smoothly transformed in very good yields to thiazolidin-
their carbonyl or thiocarbonyl carbon atom in 1 C NMR
3
(Figure 2).
O
S
S
O
O
NH
S
NH
O
NH
S
NH
2
2
1
a
2a
200.8 ppm
3a
189.5 ppm
4a
175.8 ppm
1
60.4 ppm
Figure 2 Chemical shifts in 13C NMR
2-ones 4c, 4d and oxazolidin-2-ones 1b, 1c and 1e, re-
spectively, under the microwave-assisted method (Table
Although the process occurred in a general and good to
very good yielding fashion with all the investigated 1,3-
thiazolidine-2-thiones 2a–e and 1,3-oxazolidine-2-thi-
3
). The reaction workup consisted simply in evaporation
23
of the solvent and 2-methylthiirane.
Synlett 2012, 23, 2835–2839
© Georg Thieme Verlag Stuttgart · New York

LETTER
Preparation of 1,3-Thiazolidine-2-thiones and 1,3-Oxazolidine-2-thiones
2837
We believe that the desulfurization–oxygenation reaction
of 1,3-thiazolidine-2-thiones 2 and 1,3-oxazolidine-2-thi-
ones 3 using propylene oxide, involves three reactive in-
termediates (Scheme 1). The nucleophilic sulfur atom
attacks the oxirane, opening the ring, forming an iminium
ion A. Intramolecular attack of the alkoxide ion to the im-
inium A generates the tetraheteroatom spiro intermediate
B. This high-energy intermediate undergoes ring opening
via iminium intermediate C to deliver propylene episul-
fide and the desired 1,3-thiazolidin-2-one or the 1,3-oxa-
zolidin-2-one. When a reaction was carried out in a sealed
Table 2 Desulfurization–Oxygenation of 1,3-Oxazolidine-2-thiones
S
O
O
O
NH
R
O
NH
R
+
1
00 °C
sealed tube
S
3a–e
1a–e
Entry
Substrate
Product
Yield (%)
S
O
1
NMR tube under thermal conditions, the H NMR signals
for the propylene episulfide could be observed in the spec-
tra.
O
NH
i-Pr
O
NH
1
80
i-Pr
3a
1a
S
S
S
O
O
O
O
S
S
O
O
NH
Bn
O
NH
S
X
O
2
3
4
87
92
84
H
X
NH
R
X
N
NH
Bn
R
R
3b
1b
B
A
O
NH
Ph
O
NH
Ph
S
O
3c
1c
X
NH
R
O
+
S
H
X
N
O
NH
O
NH
R
C
Scheme 1 Mechanism of the desulfurization–oxygenation reaction
3d
1d
S
O
In summary, we have developed a simple and highly effi-
cient synthetic route to prepare both 1,3-thiazolidin-2-
ones 4 and 1,3-oxazolidin-2-ones 1 via a desulfurization–
oxygenation process, using commercially available and
inexpensive propylene oxide. This methodology is partic-
ularly attractive using microwave conditions for brevity
and efficiency. The influence of endocyclic sulfur atom
on the reactivity of the non-racemic 1,3-thiazolidin-2-
ones 4 and their application in asymmetric synthesis are
under investigation.
O
NH
O
NH
H
H
H
H
5
83
3e
1e
Table 3 Desulfurization–Oxygenation using Microwave Irradiation
S
O
O
X
NH
R
X
NH
R
Acknowledgment
+
1
6
50 °C
0 min
S
Financial support for this research was provided by the Consejo Na-
cional de Ciencia y Tecnologia CONACyT (Clave 83731) and is
gratefully acknowledged. The authors wish to thank Prof. Joseph
M. Muchowski (UNAM) for helpful discussions and his interest in
our work.
Entry
Substrate
Product
Yield (%)
1
2
3
4
5
2c
2d
3b
3c
3e
4c
4d
1b
1c
1e
85
88
90
94
89
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Synlett 2012, 23, 2835–2839

2838
L. Minor-Villar et al.
LETTER
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(
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3
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removed under reduced pressure. The residue was purified
by silica gel flash column chromatography eluting with
hexanes–EtOAc (4:1) for 1,3-thiazolidin-2-ones and
hexanes–EtOAc (3:2) for 1,3-oxazolidin-2-ones to give
analytically pure products 4 and 1, respectively.
(
(
(
b) Jones, R. N.; Moet, G. J.; Sader, H. S.; Mendes, R. E.;
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(
(
(
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(4S)-Isopropyl-1,3-thiazolidin-2-one (4a): was obtained as
a white solid after purification by flash column
(
2
4
chromatography; mp 75–76 °C (CH Cl –hexanes); [α]
2
2
D
1
+19.2 (c = 0.5, CHCl ). H NMR (300 MHz, CDCl ): δ =
3
3
6.96 (br, 1 H), 3.60–3.68 (dt, J = 7.8, 15.3 Hz, 1 H), 3.35 (dd,
J = 7.5, 10.9 Hz, 1 H), 3.16 (dd, J = 8.2, 10.9 Hz, 1 H), 1.77–
1.89 (m, 1 H), 1.01 (d, J = 6.7 Hz, 3 H), 0.96 (d, J = 6.7 Hz,
1
3
(
13) (a) Shibahara, F.; Suenami, A.; Yoshida, A.; Murai, T.
Chem. Commun. 2007, 2354. (b) Mohammadpoor-Baltork,
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3 H). C NMR (75 MHz, CDCl ): δ = 175.8, 61.4, 32.5,
3
32.4, 18.7, 18.1. HRMS: m/z calcd for C H NOS: 145.0556;
6
11
found: 145.0562.
591. (c) Kim, Y. H.; Chung, B. C.; Chang, S. Tetrahedron
(4S)-4-Benzyl-1,3-thiazolidin-2-one (4b): was obtained as
Lett. 1985, 26, 1079. (d) Jorgensen, K. A.; El-Wassimy, M.
T. M.; Lawesson, S. O. Tetrahedron 1983, 39, 469.
a white solid after purification by flash column
2
5
D
chromatography; mp 69–70 °C (CH Cl –hexanes); [α] –
2
2
1
(e) Kochhar, K. S.; Cottrell, D. A.; Pinnick, H. W.
9.6 (c = 0.5, CHCl ). H NMR (300 MHz, CDCl ): δ = 7.23–
3 3
Tetrahedron Lett. 1983, 24, 1323.
7.36 (m, 3 H), 7.16–7.20 (m, 2 H), 6.01 (br, 1 H), 4.07 (m, 1
(14) Deng, X.; Chen, N.; Wang, Z.; Li, X.; Hu, H.; Xu, J.
Phosphorus, Sulfur Silicon 2011, 186, 1563.
H), 3.43 (dd, J = 7.2, 11.1 Hz, 1 H), 3.17 (dd, J = 6.3, 11.1
1
3
Hz, 1 H), 2.93 (m, 2 H). C NMR (75 MHz, CDCl ): δ =
3
(
15) (a) Sattigery, V. J.; Palle, V. P.; Khera, M. K.; Reddy, R.;
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174.8, 136.4, 129.0, 128.9, 127.1, 56.5, 40.9, 34.3. HRMS:
m/z calcd for C H NOS: 193.0556; found: 193.0555.
1
0
11
(4R)-Phenyl-1,3-thiazolidin-2-one (4c): was obtained as a
2
(
1
008023336, 2008; Chem. Abstr. 2008, 148, 308571.
b) Calo, V.; Nacci, A.; Volpe, A. Gazz. Chim. Ital. 1997,
27, 283.
white solid after purification by flash column
24
chromatography; mp 162–164 °C (CH Cl –hexanes); [α]
2 2 D
1
–86.4 (c = 0.5, CHCl ). H NMR (300 MHz, CDCl ): δ =
3 3
(
16) Kitoh, S.-I.; Kubota, A.; Kunimoto, K.-K.; Kuwae, A.;
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7.61 (br, 1 H), 7.32–7.39 (m, 5 H), 4.94 (td, J = 0.9, 7.5 Hz,
1 H), 3.68 (dd, J = 7.5, 11.0 Hz, 1 H), 3.26 (dd, J = 7.7, 11.0
13
(
17) (a) Wilmore, B. H.; Cassidy, P. B.; Warters, R. L.; Roberts,
J. C. J. Med. Chem. 2001, 44, 2661. (b) D’Amico, J. J.;
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Hz, 1 H). C NMR (75 MHz, CDCl ): δ = 174.2, 139.9,
3
128.3, 127.8, 125.5, 58.4, 37.0. HRMS: m/z calcd for
C H NOS: 179.0399; found: 179.0390.
9
9
2
5, 1503.
(4R)-Methyl-1,3-thiazolidin-2-one (4d): was obtained as a
(
(
18) White, J. D.; Kawasaki, M. J. Org. Chem. 1992, 57, 5292.
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Org. Synth. 1985, 63, 136.
white solid after purification by flash column
2
4
D
chromatography; mp 40–42 °C (CH Cl –hexanes); [α]
2
2
1
+12.80 (c = 0.5, CHCl ). H NMR (300 MHz, CDCl ): δ =
3
3
(
20) (a) Delaunay, D.; Toupet, L.; Le Corre, M. J. Org. Chem.
6.70 (br, 1 H), 3.99–4.06 (m, 1 H), 3.47 (dd, J = 7.2, 10.8 Hz,
1 H), 3.04 (dd, J = 7.2, 10.8 Hz, 1 H), 1.34 (d, J = 6.2 Hz, 3
1
995, 60, 6604. (b) Galvez, E.; Romea, P.; Urpi, F. Org.
1
3
Synth. 2009, 86, 70. (c) Crimmins, M. T.; Christie, H. S.;
Hughes, C. O. Org. Synth. 2011, 88, 364. (d) Morales-Nava,
H). C NMR (75 MHz, CDCl ): δ = 175.4, 51.2, 36.5, 20.5.
3
(4R,5S)-Indano[1,2-d]-1,3-thiazolidine-2-one (4e): was
Synlett 2012, 23, 2835–2839
© Georg Thieme Verlag Stuttgart · New York

LETTER
Preparation of 1,3-Thiazolidine-2-thiones and 1,3-Oxazolidine-2-thiones
2839
obtained as a white solid after purification by flash column
(dd, J = 7.5, 17.0 Hz, 1 H), 3.20 (dd, J = 3.0, 17.0 Hz, 1 H).
2
3
13
chromatography; mp 195–196 °C (CH Cl –hexanes); [α]
C NMR (125 MHz, CDCl –DMSO): δ = 173.1, 140.3,
2
2
D
3
1
+
3.2 (c = 0.5 CHCl ). H NMR (500 MHz, CDCl –DMSO):
139.4, 128.2, 126.9, 124.5, 124.3, 63.0, 46.7. HRMS: m/z
3
3
δ = 8.21 (br, 1 H), 7.37–7.39 (m, 1 H), 7.24–7.31 (m, 3 H),
.17 (d, J = 7.5 Hz, 1 H), 4.67 (td, J = 3.0, 7.5 Hz, 1 H), 3.48
calcd for C H NOS: 191.0399; found: 191.0393.
1
0
9
5
©
Georg Thieme Verlag Stuttgart · New York
Synlett 2012, 23, 2835–2839

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