A new method for synthesis of S-aryl-O-alkyl thiolcarbonates: Selenium-catalyzed reaction of alcohols with carbon monoxide and diaryl disulfides

Article abstract of DOI:10.1016/j.tetlet.2005.08.108

A unique catalytic ability of selenium has been developed. When alcohols were allowed to react with diaryl disulfides in the presence of a catalytic amount of selenium under a pressurized carbon monoxide, S-aryl-O-alkyl thiolcarbonates were obtained in moderate to good yields.

Full text of DOI:10.1016/j.tetlet.2005.08.108

Tetrahedron
Letters
Tetrahedron Letters 46 (2005) 7415–7417
A new method for synthesis of S-aryl-O-alkyl
thiolcarbonates: selenium-catalyzed reaction of alcohols
with carbon monoxide and diaryl disulfides
Yutaka Nishiyama,* Ken Maehira, Junko Nakase and Noboru Sonoda*
Department of Applied Chemistry, Faculty of Engineering, Kansai University, Suita, Osaka 564-8680, Japan
Received 4 July 2005; revised 10 August 2005; accepted 19 August 2005
Available online 9 September 2005
Abstract—A unique catalytic ability of selenium has been developed. When alcohols were allowed to react with diaryl disulfides in
the presence of a catalytic amount of selenium under a pressurized carbon monoxide, S-aryl-O-alkyl thiolcarbonates were obtained
in moderate to good yields.
Ó 2005 Elsevier Ltd. All rights reserved.
The development of the process to replace the use of
phosgene as a carbonylating reagent has received con-
siderable attention in recent years in organic and indus-
trial points of view. Carbon monoxide is one of the
promising agents for the replacement of phosgene; the
development of new methods for the carbonylation of
various organic compounds with carbon monoxide
could have a great impact in organic chemistry.1 Thiol-
carbonates were widespread used as synthetic inter-
mediates,2,3 polymerization initiators,4 heat stabilizers
for polymers,5 precursors to polymercaptanes,6 bio-
active compounds,7 and radiographic contrast agent.8
Although many methods for the synthesis of thiolcar-
bonates have already been reported, there are some dis-
advantages of these methods: (i) the use of poisonous
phosgene and carbonyl sulfide, (ii) the need of intoler-
able odorous thiol, (iii) the use of chloro thioformate
having unstable against moisture, and (iv) multi-step
procedures.3b–r,9,10 In this letter, we wish to report a
facile method for the synthesis of S-aryl-O-alkyl thiol-
carbonates by the selenium-catalyzed reaction of alco-
hols with diaryl disulfides and carbon monoxide
(Scheme 1).11
The treatment of ethyl alcohol with diphenyl disulfide in
the presence of a catalytic amount of selenium (0.1
equiv) under the pressurized carbon monoxide (25 atm)
at 25 °C for 6 h gave S-phenyl-O-ethyl thiolcarbonate
(1) in almost quantitative yield (entry 1). The yield
of 1 was diminished when the reaction was carried out
under lower reaction temperature and carbon monoxide
pressure. It is possible to reduce the amount of selenium
still further under longer reaction time (15 h) giving 1
in 89% yield (entry 2). In order to know the application
of the reaction, various alcohols were reacted with
diphenyl disulfide and carbon monoxide (Table 1). The
yields of product were influenced by the steric effect of
alcohol used. S-Phenyl-O-methyl, S-phenyl-O-ethyl,
and S-phenyl-O-butyl thiolcarbonates were formed by
the reaction of methyl, ethyl, and butyl alcohol with
diphenyl disulfide and carbon monoxide in good to
excellent yields (entries 1, 3, and 4). Similarly, benzyl
alcohol was coupled with diphenyl disulfide and carbon
monoxide to give S-phenyl-O-benzyl thiolcarbonate in
77% yield (entry 5). When i-propyl alcohol was allowed
to react with diphenyl disulfide and carbon monoxide
under the similar reaction conditions to that of primary
alcohol, the yield of S-phenyl-O-i-propyl thiolcarbonate
was low (13%), however, the product yield was
improved by using hash reaction conditions (at 80 °C,
for 13 h under CO (70 atm)) (entries 6 and 7). Similarly,
cyclohexyl alcohol was coupled with diphenyl disulfide
and carbon monoxide giving S-phenyl O-cyclohexyl
thiolcarbonate in moderate yield (entry 8). S-Phenyl-
O-tert-butyl thiolcarbonate was not obtained on the
reaction of tert-butyl alcohol (entry 9).
cat. Se
O
ROH
Scheme 1.
+ ArSSAr + CO
ROCSAr
*
Corresponding authors. Tel.: +81 6 6368 1121; fax: +81 6 6339
4026; e-mail: nishiya@ipcku.kansai-u.ac.jp
0040-4039/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2005.08.108

7416
Y. Nishiyama et al. / Tetrahedron Letters 46 (2005) 7415–7417
Table 1. Synthesis of S-phenyl-O-alkyl thiolcarbonatesa
Se + CO
SeCO
ROH / Base
cat. Se
Et3N
ArS-
CO
O
ROH
+ PhSSPh + CO
ROCSPh
THF
25 oC, 6 h
Entry
ROH
Yield/%b
ROCSe- Base.H+
1
C2H5OH
C2H5OH
CH3OH
C4H9OH
PhCH2OH
(CH3)2CHOH
(CH3)2CHOH
c-C6H11OH
100
89
100
93
77
13
76
56
Trace
ArSSe-
(4)
2c
3
O
(2)
4
5
6
7d
8d
9
ArSSAr
ArSCOR
ArS-
O
(1)
ArSSeCOR
(CH3)3COH
O
a ROH (5 mmol), PhSSPh (5 mmol), Se (0.5 mmol), Et3N (5 mmol),
THF (2.5 mL), and CO (25 atm) at 25 °C for 5 h.
b GC yields based on alcohol.
(3)
Scheme 2.
c Se (0.1 mmol) at 25 °C 15 h.
d CO (70 atm) at 80 °C for 13 h.
the corresponding thiolcarbonate was not obtained (en-
try 8).12
Although we cannot clearly determine the catalytic reac-
tion pathway for the synthesis of thiolcarbonates, cata-
lytic cycle shown in Scheme 2 was suggested for the
reaction. Nucleophilic addition of alcohol on selenium
carbonyl, which was generated in situ by the reaction
of elemental selenium with carbon monoxide under the
basic conditions, formed selenolate (2) species as the first
step in the reaction. The attack of 2 on sulfur atom of
diaryl disulfide gave the intermediate (3) and arylthio-
late. Aryl thiolate attacked on carbonyl carbon of inter-
mediate 3 to give thiolcarbonate (1) and selenolate (4).
Selenolate (4) was reacted with carbon monoxide to
regenerate selenium carbonyl and arylthiolate.13
To know the scope and limitation of selenium-catalyzed
synthesis of S-aryl-O-alkyl thiolcarbonates, various dia-
ryl disulfides were reacted with ethyl alcohol and carbon
monoxide in the presence of a catalytic amount of sele-
nium. The results summarized in Table 2 showed that
the reaction is amenable to the synthesis of various
S-aryl-O-ethyl thiolcarbonates. In the case of di(3-meth-
ylphenyl), di(4-methylphenyl), di(4-bromophenyl), di(4-
chlorophenyl), di(4-methoxy-phenyl), and di(2-napthyl)
disulfide, the reaction proceeded efficiently giving the
corresponding S-aryl-O-ethyl thiolcarbonates in good
to excellent yields (entries 3–7 and 9). For the sterically
hindered disulfide, di(2-methylphenyl), and di(2,6-dim-
ethylphenyl) disulfide, the product yield was low (entries
1 and 2). For the reaction of di(4-nitrophenyl) disulfide,
In summary, from the viewpoint of simple operation,
mild reaction conditions, and good yields, the present
reaction provides a useful method for synthesis of S-
aryl-O-alkyl thiolcarbonates Furthermore, application
of the reaction and elucidation of the reaction pathway
are now in progress.
Table 2. Synthesis of S-aryl-O-ethyl thiolcarbonatesa
cat. Se
Et3N
O
Acknowledgement
C2H5OH
+
ArSSAr + CO
C2H5OCSAr
THF
25 oC, 6 h
This research was supported by a Grant-in-Aid for
Science Research (No. 15550096) and Research and
Development Organization of Industry-University
Cooperation from the Ministry of Education, Culture,
Sports, Science and Technology of Japan.
Entry
Ar
Yield/%b
1
2-CH3C6H4
32
Trace
98
2c
3
2,6-(CH3)2C6H3
3-CH3C6H4
4-CH3C6H4
4-ClC6H4
4
5
6
7
8c
9
95
100
100
87
Trace
97
References and notes
4-BrC6H4
4-CH3OC6H4
4-O2NC6H4
2-C10H7
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