Trimethylsilyl chloride promoted selective desulfurization of thiocarbonyls to carbonyls with hydrogen peroxide

Article abstract of DOI:10.1055/s-0030-1258283

In the presence of hydrogen peroxide and trimethylsilyl chloride, thiocarbonyls desulfurize to the corresponding carbonyls. The safe, operationally simple, general reaction gives excellent yields in short reaction times with no side reactions and excellent regioselectivity, which makes this process an attractive, environmentally benign alternative for the desulfurization of thiocarbonyls

Full text of DOI:10.1055/s-0030-1258283

4
282
PAPER
Trimethylsilyl Chloride Promoted Selective Desulfurization of Thiocarbonyls
to Carbonyls with Hydrogen Peroxide
D
K
esulfurization of
i
Thioca
u
rbonyls to C
m
arbonyls ars Bahrami,*a,b Mohammad Mehdi Khodaei,*a,b Maryam Tajika
a
Department of Chemistry, Razi University, Kermanshah 67149-67346, Iran
Fax +98(831)4274559; E-mail: kbahrami2@hotmail.com; E-mail: mmkhoda@razi.ac.ir
b
Nanoscience and Nanotechnology Research Center (NNRC), Razi University, Kermanshah 67149-67346, Iran
Received 23 August 2010; revised 8 September 2010
spread use as a catalyst in organic transformations,5–7 to
the best of our knowledge, there are no reports on TMSCl-
mediated selective desulfurization of thiocarbonyls.
Abstract: In the presence of hydrogen peroxide and trimethylsilyl
chloride, thiocarbonyls desulfurize to the corresponding carbonyls.
The safe, operationally simple, general reaction gives excellent
yields in short reaction times with no side reactions and excellent re-
gioselectivity, which makes this process an attractive, environmen-
tally benign alternative for the desulfurization of thiocarbonyls.
As part of an ongoing program directed towards the devel-
opment of efficient reagents for use under mild condi-
tions, and following our recent interest in the use of
Key words: protecting groups, thiocarbonyls, desulfurization, tri-
methylsilyl chloride, hydrogen peroxide
8
hydrogen peroxide in organic synthesis, we report an en-
vironmentally sound, reasonably simple and efficient
method that enables thiocarbonyls to be economically
desulfurised to their oxo-analogues using H O in the
2
2
Protecting groups are important tools in organic synthesis,
and they have found extensive use in many different areas
of complex syntheses of natural products, biomolecules,
presence of TMSCl, in excellent yields (Scheme 1).
S
C
O
C
1
2 2
30% H O –TMSCl
and materials. Crucial features of protecting groups are
R1
R2
R1
R2
EtOH, 25 °C
their ease of preparation and removal as well as their rel-
ative stability toward different reaction conditions.
R1 = alkyl, aryl
2
R
= alkyl, aryl, aryl-NH, H, Ph-NMe, piperidyl
The conversion of thiocarbonyls into carbonyls has at-
tracted the interest of organic chemists since the early
Scheme 1 Reagents and conditions: H O (2 mmol), TMSCl (1
mmol), EtOH, 25 °C.
2
2
1
9th century, first for the quantitative determination of
compounds containing the thiocarbonyl moiety and, later,
for synthetic and mechanistic studies.
To choose the most appropriate medium for this transfor-
mation, we examined the reaction of N-phenyl benzothio-
amide as a model compound in a range of solvents, such
as acetonitrile, ethanol, chloroform, diethyl ether, and eth-
yl acetate. Ethanol and acetonitrile were found to be the
most efficient solvents in terms of reaction times and
product yields. To optimize the reaction conditions fur-
A variety of methods for C=S → C=O conversion have
been developed, including oxidative procedures with
2
3
inorganic and organic reagents, and hydrolytic proce-
4
dures, of which those catalyzed by metal ions are the
most widely used.
However, many of these approaches suffer from limita- ther, the effects of changing the amount of H O and
2
2
tions such as high toxicity, vigorous reaction conditions, TMSCl were examined with N-phenyl benzothioamide in
unsatisfactory yields, tedious work up, or use of a large ethanol at room temperature. As shown in Table 1, the
excess of reagents. Thus, a practical, efficient, and greener
alternative for this important transformation is desirable.
Table 1 Effect of the Amount of H
rization of N-Phenyl Benzothioamide
2
O
2
and TMSCl on the Desulfu-
a
In oxidation processes, the use of a number of non-envi-
ronmental oxidants (for example, heavy metals or per-
acids) is very common, although other compounds have
been sought that are not detrimental to the environment. In
this context, the application of hydrogen peroxide (H O )
as an oxidant is useful because water is the sole expected
by-product. Furthermore, hydrogen peroxide is a safe,
readily available, and cheap reagent.
S
O
HN
HN
2
2
b
Entry
TMSCl (mmol) 30% H O (mmol) Yield (%)
2 2
1
2
3
0
4
3
2
0
23
0.7
1
75
It is well known that trimethylsilyl chloride (TMSCl) is an
efficient Lewis acid, however, although it has found wide-
96
4
1
trace
SYNTHESIS 2010, No. 24, pp 4282–4286
x
x.
x
x
.
2
0
1
0
a
Reaction conditions: N-phenyl benzothioamide (1 mmol), 2 min,
5 °C.
Isolated yield.
Advanced online publication: 05.10.2010
DOI: 10.1055/s-0030-1258283; Art ID: Z21310SS
Georg Thieme Verlag Stuttgart · New York
2
b
©

PAPER
Desulfurization of Thiocarbonyls to Carbonyls
4283
best result (96% yield) was obtained by carrying out the the thioamide was recovered), thus, TMSCl is only effec-
reaction with a 1:2 molar ratio of thioamide to H O in the tive in the presence of H O (Table 1, entry 4).
2
2
2
2
presence of 1 mmol TMSCl for two minutes. It should be
noted that the use of TMSCl is essential for the success of
the reaction, because H O alone oxidized the thioamides
With the optimized conditions in hand, we investigated
the scope and generality of this transformation with vari-
ous thioamides. The results are shown in Table 2. All the
reactions proceeded smoothly and rapidly to give the cor-
2
2
rather slowly (Table 1, entry 1).
As a control reaction, the desulfurization of N-phenyl ben- responding amides in excellent yields. Both electron-rich
zothioamide to the corresponding amide with TMSCl (1 and electron-deficient thioamides worked well, with most
mmol) was found to proceed extremely slowly (98% of leading to excellent yields of products.
Table 2 Selective Desulfurization of Thiocarbonyl Compoundsa
S
C
O
C
R1
R2
R1
R2
Entry Substrate
Product
Time (min) Yield (%)b Mp (°C)
Lit mp (°C) Ref.
S
O
HN
O
1
2
5
96
96
93
93
158–162 163
9
9
HN
S
HN
S
2
3
155
157–158
HN
O
12
6
195–197 198–199
9
HN
NO2
HN
NO2
S
O
4
139
140–143
10
O2N
O2N
HN
HN
S
O
5
HN
HN
2
90
163–165 164–165
11
S
N
O
N
O2N
O2N
6
10
5
92
95
104
168
106–107
168
9
9
Me
Me
S
O
7
HN
Br
HN
Br
S
N
O
N
O2N
2
O N
8
4
92
120
122–125
12
S
HN
S
O
HN
O
9
9
8
96
92
82
83–84
126
13
14
1
1
0
1
124
N
NH2
N
NH2
COOH
COOH
O
O
4
88
132
135
15
S
O
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4
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K. Bahrami et al.
PAPER
a
Table 2 Selective Desulfurization of Thiocarbonyl Compounds (continued)
S
C
O
C
R1
R2
R1
R2
Entry Substrate
Product
Time (min) Yield (%)b Mp (°C)
Lit mp (°C) Ref.
S
O
1
1
2
3
3
9
95
92
Oil
Oil
16
14
O
O
179
180–182
S
S
O
O
1
1
4
5
93
210
213
17
S
S
5
6
2
5
91
92
80
50
84
49
14
14
S
O
S
O
1
a
The products were characterized by comparison of their spectroscopic and physical data with authentic samples synthesized by reported pro-
cedures.
b
Pure isolated product.
Notably, sterically hindered thioamide, such as N-methyl- intermediate that undergoes sulfur extrusion. It is impor-
4
-nitro-N-phenylbenzothioamide, gave the desired amide tant that the by-product of the oxidant system, trimethyl-
in excellent yield (Table 2, entry 6). According to the re- silyl alcohol, is soluble in water and thus will not
sults, primary, secondary, and tertiary thioamides all un- contaminate product, i.e, simple extraction or recrystalli-
dergo this reaction with equal efficiency.
zation of product from a mixture of ethanol and water can
remove it easily.
Furthermore, we found that this reaction is similarly ef-
fective for a range of thioketones and thioesters, yielding
the corresponding products in excellent yields (Table 2,
entries 11–16). Steric effects did not influence the yield
significantly, for example, in the reaction of thiocamphor
H2O2
+
Me3Si Cl
HO
O
SiMe3
– HCl
S
S
H
OH
..
.
.
+
HO
O
SiMe3
+ N
N
N
– HO—SiMe3
(
Table 2, entry 13) and fluorene-9-thione (Table 2, entry
H
1
9
5), the corresponding products were obtained in 92 and
1% yields, respectively. Surprisingly, several functional-
ities, such as nitro, carboxyl, sulfur, halide, and pyridine
were tolerated under these reaction conditions.
Ho18 has reported that a combination of TMSCl and hy-
drogen peroxide gives trimethylsilyl hydroperoxide,
O
S
H
S
O+
.
.
O
N
– H+
N
–
1/8 S8
H
H
H
Scheme 2 Proposed mechanism for the desulfurization of thio-
which possesses a bonding arrangement similar to that amides
found in percarboxylic acids. Both of these types of com-
pounds are made up of soft acid–soft base pairs with re-
In conclusion, a practical and efficient desulfurization of
thioamides, thioketones, and thioesters has been achieved.
spect to the O–O linkage.
The proposed mechanism for the desulfurization of thioa- Short reaction times, excellent yields, operational sim-
mides is shown in Scheme 2. Nucleophilic attack of H O2 plicity, generality, no side reactions, and excellent regio-
2
on TMSCl makes the oxygen atom more electrophilic. selectivity make the process attractive for the green
Thus, the mechanism probably proceeds through a cyclic synthesis of the target compounds.
Synthesis 2010, No. 24, 4282–4286 © Thieme Stuttgart · New York

PAPER
Desulfurization of Thiocarbonyls to Carbonyls
4285
The thiocarbonyls are either commercially available or were pre-
pared as follows: thioamides from the reaction of the corresponding
24, 1527. (b) Hall, J.; Satchell, D. P. N. J. Chem. Soc.,
Perkin Trans. 2 1975, 1351. (c) Micallef, J. V.; Satchell, D.
P. N. J. Chem. Soc., Perkin Trans. 2 1982, 971.
(d) Micallef, J. V.; Satchell, D. P. N. J. Chem. Soc., Perkin
Trans. 2 1982, 1379. (e) Chalais, S.; Cornelis, A.; Laszlo,
P.; Mathy, A. Tetrahedron Lett. 1985, 26, 2327.
(f) Narasimhamurthy, N.; Samuelson, A. G. Tetrahedron
Lett. 1986, 27, 3911.
19
amides with P S , thioketones and thioesters from the reaction of
4
10
2
0
the corresponding carbonyl compounds with Lawesson’s reagent.
Melting points were determined in a capillary tube and are not cor-
rected. H NMR and C NMR spectra were recorded with a Bruker-
00 NMR spectrometer using TMS as internal standard.
1
13
2
Desulfurization of Thiocarbonyls to Carbonyls; General Proce-
dure
(5) (a) Yoshihiro, Y.; Matsumoto, N.; Hamasaki, R.; Tanabe, Y.
Tetrahedron Lett. 1999, 40, 4227. (b) Sabitha, G.; Reddy,
G. S. K. K.; Reddy, C. S.; Yadav, J. S. Synlett 2003, 858.
(c) Dabkowski, W.; Tworowska, I.; Michalski, J.; Cramer, F.
Chem. Commun. 1997, 877. (d) Prakash, G. K. S.; Mathew,
T.; Panja, C.; Olah, G. A. J. Org. Chem. 2007, 72, 5847.
(e) Ryabukhin, S. V.; Plaskon, A. S.; Ostapchuk, E. N.;
Volochnyuk, D. M.; Tolmachev, A. A. Synthesis 2007, 417.
(f) Ryabukhin, S. V.; Plaskon, A. S.; Volochnyuk, D. M.;
Tolmachev, A. A. Synthesis 2006, 3715.
(6) (a) Corey, E. J.; Boaz, N. W. Tetrahedron Lett. 1985, 26,
6015. (b) Bertz, S. H.; Miao, G.; Rossiter, B. E.; Snyder, J.
P. J. Am. Chem. Soc. 1995, 117, 11023. (c) Terang, N.;
Mehta, B. K.; Ila, H.; Junijappa, H. Tetrahedron 1998, 54,
12973. (d) Iwai, T.; Ito, T.; Mizumo, T.; Ishino, Y.
Tetrahedron Lett. 2004, 45, 1083. (e) Kobayashi, K.;
Takanohashi, A.; Hashimoto, K.; Morikawa, O.; Konishi, H.
Tetrahedron 2006, 62, 3158. (f) Chen, Y.-J.; Huang, Y.-P.
Tetrahedron Lett. 2000, 41, 5233.
A mixture of thioamide (2 mmol), 30% H O (4 mmol, 0.4 mL) and
2
2
TMSCl (2 mmol) was stirred in EtOH (10 mL) at 25 °C for the ap-
propriate time (Table 2). A yellow solid (elemental sulfur, mp
1
20 °C) immediately precipitated. The progress of the reaction was
monitored by TLC to determine the necessary reaction times. Upon
completion of the reaction, the reaction mixture was filtered to re-
move the elemental sulfur and the filtrate was poured into H O (10
2
mL), extracted with EtOAc (4 × 5 mL), and the extract was dried
with anhydrous MgSO . The filtrate was evaporated under vacuum
4
to afford the analytically pure product. An identical procedure was
employed using thioketone or thioester (2 mmole), 30% H O (4
2
2
mmol, 0.4 mL) and TMSCl (2 mmol) for the desulfurization of
thioketones or thioesters.
All of products are known compounds, and were characterized by
1
13
comparison with authentic samples ( H and C NMR spectra, and
melting point).
(
7) (a) Yamanaka, M.; Nishida, A.; Nakagawa, M. J. Org.
Chem. 2003, 68, 3112. (b) Sakai, N.; Hirasawa, M.;
Hamajima, T.; Konakahara, T. J. Org. Chem. 2003, 68, 483.
(c) Jiang, B.; Si, Y. G. Tetrahedron Lett. 2003, 44, 6767.
(d) Ishino, Y.; Mihara, M.; Takeuchi, T.; Takemoto, M.
Tetrahedron Lett. 2004, 45, 3503. (e) Ryabukhin, S. V.;
Plaskon, A. S.; Volochnyuk, D. M.; Tolmachev, A. A.
Synlett 2004, 2287. (f) Yoshikawa, E.; Gevorgyan, V.;
Asao, N.; Yamamoto, Y. J. Am. Chem. Soc. 1997, 119, 6781.
8) (a) Bahrami, K. Tetrahedron Lett. 2006, 47, 2009.
Acknowledgment
We are thankful to the Razi University Research Council for partial
support of this work.
References
(1) (a) Hanessian, S.; Reddy, G. J.; Chahal, N. Org. Lett. 2006,
(
8
2
2
, 5477. (b) Jones, S. B.; He, L.; Castle, S. L. Org. Lett.
006, 8, 3757. (c) Va, P.; Roush, W. R. J. Am. Chem. Soc.
006, 128, 15960. (d) Fuwa, H.; Ebine, M.; Bourdelais, A.
(
b) Khodaei, M. M.; Bahrami, K.; Khedri, M. Can. J. Chem.
007, 85, 7. (c) Bahrami, K.; Khodaei, M. M.; Kavianinia, I.
2
Synthesis 2007, 547. (d) Khodaei, M. M.; Bahrami, K.;
Karimi, A. Synthesis 2008, 1682. (e) Bahrami, K.; Khodaei,
M. M.; Naali, F. J. Org. Chem. 2008, 73, 6835.
J.; Baden, D. G.; Sasaki, M. J. Am. Chem. Soc. 2006, 128,
6989.
1
(
2) (a) Rani, R.; Rahmanana, M. F.; Bhalerao, U. T.
Tetrahedron 1992, 48, 1953. (b) Dhar, D. N.; Bag, A. K.
Indian J. Chem., Sect. B: Org. Chem. Incl. Med. Chem.
(
5
f) Bahrami, K.; Khodaei, M. M.; Naali, F. Synlett 2009,
69. (g) Khodaei, M. M.; Bahrami, K.; Tirandaz, Y. J. Sulfur
Chem. 2009, 30, 581. (h) Bahrami, K.; Khodaei, M. M.;
Soheilizad, M. Synlett 2009, 2773. (i) Bahrami, K.;
Khodaei, M. M.; Soheilizad, M. J. Org. Chem. 2009, 74,
1
985, 24, 445. (c) Kristensen, R. B.; Thomsen, I.; Lawesson,
S.-O. Sulfur Lett. 1985, 3, 7. (d) Jorgensen, K. A.; Ghattas,
A.-B. A. G.; Lawesson, S.-O. Tetrahedron 1982, 38, 1163.
9
287. (j) Bahrami, K.; Khodaei, M. M.; Farrokhi, A.
(
1
e) Kim, Y. H.; Chung, B. C.; Chang, H. S. Tetrahedron Lett.
985, 26, 1079. (f) Varma, R. S.; Kumar, D. Synth.
Tetrahedron 2009, 65, 7658. (k) Bahrami, K.; Khodaei, M.
M.; Tirandaz, Y. Synthesis 2009, 369.
Commun. 1999, 29, 1333. (g) Movassagh, B.; Lakouraj, M.
M.; Ghodrati, K. Synth. Commun. 2000, 30, 2353.
(
9) Mohammadpoor-Baltork, I.; Memarian, H. R.; Bahrami, K.
Monatsh. Chem. 2004, 135, 411.
10) Elson, K. E.; Jenkinsb, I. D.; Loughlin, W. A. Tetrahedron
Lett. 2004, 45, 2491.
11) Al-Awadi, H.; Ibrahim, M. R.; Dib, H. H.; Al-Awadi, N. A.;
Ibrahim, Y. A. Tetrahedron 2005, 61, 10507.
12) Rahman, A.-U.; Basha, A.; Waheed, N. Tetrahedron Lett.
(
h) Mohammadpoor-Baltork, I.; Khodaei, M. M.; Nikoofar,
(
(
(
K. Tetrahedron Lett. 2003, 44, 591. (i) Mohammadpoor-
Baltork, I.; Memarian, H. R.; Hajipour, A. R.; Bahrami, K.
Bull. Korean Chem. Soc. 2003, 24, 1002.
(
3) (a) Tamagaki, S.; Hatanaka, I.; Kozuka, S. Bull. Chem. Soc.
Jpn. 1977, 50, 3421. (b) Ley, S. V.; Meerholz, C. A.;
Barton, D. H. R. Tetrahedron Lett. 1980, 21, 1785.
1
976, 17, 219.
(
(
13) Gajda, T.; Zwierzak, I. Synthesis 1981, 1005.
14) Olah, C. A.; Arvanaghi, M.; Ohannesian, L.; Surya, P. G. K.
Synthesis 1984, 785.
15) Dictionary of Organic Compounds, 5th ed., Vol. 1;
Buckingham, J., Ed.; Chapman and Hall: London, 1982, 19.
16) Lajis, N. Pertanika 1985, 8, 67.
17) Masuda, R.; Hojo, M.; Ichi, T.; Sasano, S.; Kobayashi, T.;
Kuroda, C. Tetrahedron Lett. 1991, 32, 1195.
18) Ho, T. L. Synth. Commun. 1979, 9, 37.
(c) Cussans, N. J.; Ley, S. V.; Barton, D. H. R. J. Chem. Soc.,
Perkin Trans. 1 1980, 1650. (d) Abuzar, S.; Sharma, S.;
Iyer, R. N. Indian J. Chem., Sect. B: Org. Chem. Incl. Med.
Chem. 1980, 19, 211. (e) Kochhar, K. S.; Cottrell, D. A.;
Pinnick, H. W. Tetrahedron Lett. 1983, 24, 1323.
(
(
(
(
f) Tabüchi, T.; Nojima, M.; Kusabayashi, S. J. Chem. Soc.,
Perkin Trans. 1 1991, 3043. (g) Tabüchi, T.; Nojima, M.;
Kusabayashi, S. J. Chem. Soc., Chem. Commun. 1990, 625.
4) (a) Ellis, J.; Frier, R. D.; Schibeci, R. A. Aust. J. Chem. 1971,
(
(
Synthesis 2010, No. 24, 4282–4286 © Thieme Stuttgart · New York

4
286
K. Bahrami et al.
PAPER
Scheibye, S.; Nilsson, N. H.; Lawesson, S.-O. Bull. Soc.
Chim. Belg. 1978, 87, 223. (c) Pedersen, B. S.; Scheibye, S.;
Clausen, K.; Lawesson, S.-O. Bull. Soc. Chim. Belg. 1978,
87, 293.
(
(
19) Scheeren, J. W.; Ooms, P. H. J.; Nivard, R. J. F. Synthesis
973, 149.
20) (a) Fieser, L. F.; Fieser, M. Reagents for Organic Synthesis,
Vol. 1; Wiley: New York, 1967, 333. (b) Pedersen, B. S.;
1
Synthesis 2010, No. 24, 4282–4286 © Thieme Stuttgart · New York