Direct transformation of organosulfur compounds to organophosphorus compounds: Rhodium-catalyzed synthesis of 1-alkynylphosphine sulfides and acylphosphine sulfides

Article abstract of DOI:10.1016/j.tetlet.2011.02.112

A rhodium-catalyzed method for the synthesis of organophosphorus compounds directly from organosulfur compounds was developed. In the presence of RhH(PPh₃)₄ and depe, the reaction of 1-alkylthioalkynes with tetraethyldiphosphine disu

Full text of DOI:10.1016/j.tetlet.2011.02.112

Tetrahedron Letters 52 (2011) 2410–2412
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Direct transformation of organosulfur compounds to organophosphorus
compounds: rhodium-catalyzed synthesis of 1-alkynylphosphine sulfides
and acylphosphine sulfides
⇑
,
Mieko Arisawa, Takuya Watanabe, Masahiko Yamaguchi
Department of Organic Chemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba, Sendai 980-8578, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
A rhodium-catalyzed method for the synthesis of organophosphorus compounds directly from organosul-
fur compounds was developed. In the presence of RhH(PPh3)4 and depe, the reaction of 1-alkylthioalky-
nes with tetraethyldiphosphine disulfide gave 1-alkynylphosphine sulfides. The same complex catalyzed
the reaction of thioesters giving acylphosphine sulfides.
Received 28 January 2011
Revised 23 February 2011
Accepted 28 February 2011
Available online 2 March 2011
Ó 2011 Published by Elsevier Ltd.
The direct transformation of organosulfur compounds to orga-
nophosphorus compounds would be an interesting synthetic
method in organic chemistry. These organoheteroatom compounds
can exhibit important biological activity or physical properties, and
their synthesis would facilitate comparison and optimization of
function in a systematic way. Organophosphorus and organosulfur
compounds in general have been synthesized by independent
methods, and such heteroatom interconversion has rarely been
examined. Exceptions are the synthesis of 1-alkynylphosphonates
from alkynylsulfones, which was reported using mercury phos-
phates1 or trialkyl phosphites;2 the conversion of organosulfones3
or sulfoxides4 to phosphorus derivatives under strongly basic con-
ditions. Described in this study is the rhodium-catalyzed reaction
of 1-alkylthioalkynes with tetraalkyldiphosphine disulfides giving
1-alkynylphosphine sulfides. The use of sulfides as the organosul-
fur substrate and the employment of a transition metal catalyst
are novel aspects of this heteroatom manipulation. Also note that
the synthesis of alkynylphosphine sulfides has been rarely exam-
ined and the only reported example employed a sulfination reac-
tion of 1-alkynyldialkylphosphines.5 The conversion of
organosulfur compounds into organophosphorus compounds was
also examined in this Letter using thioesters and a thiobenzothiaz-
ole to give acylphosphine sulfides and a benzothiazoylphosphine
sulfide, respectively.
reactions were developed: SS/PP metathesis of thiophosphinates
to give other thiophosphinates;8 CH/PP metathesis of 1-alkynes
to give 1-alkynylphosphine;9 OH/PP metathesis of alcohols and
phenols to give phosphinyl esters;10 and CF/PP metathesis of acid
fluorides to give acylphosphine sulfides.11 We also found that a
rhodium catalyst could cleave the C–S bond of 1-alkylthioalky-
nes,12 thioesters,13 and
a
-thioketones.14 On the basis of these re-
sults, it was suggested that the P–P bond cleavage method could
be applied to the synthesis of organophosphorus compounds from
organosulfur compounds via C–S bond cleavage (Scheme 1).
When an equimolar mixture of 1-hexylthio-2-(2,4,6-trimethyl-
phenyl)ethyne and tetramethyldiphosphine disulfide15 in chloro-
benzene was heated in reflux for 12 h in the presence of
RhH(PPh3)4 (2 mol %) and 1,2-bis(diethylphosphino)ethane (depe,
4 mol %), 1-(2,4,6-trimethylphenyl)ethynyldimethylphosphine sul-
fide (88%) and hexyl dimethyldithiophosphinate (87%) were ob-
tained (Table 1, entry 1). The rhodium complex and depe were
both essential for the reaction, and no reaction occurred in the ab-
sence of either substance. The high efficiency of depe in this reaction
was observed, when compared with 1,2-bis(dimethylphosphi-
no)ethane (dmpe) (36%) and 1,2-bis(diphenylphosphino)ethane
(dppe) (16%). Even when using 10 mol % RhH(PPh3)4 and 20 mol %
phosphine, low yields (<10%) of the product were obtained using
other bidentate ligands, that is, dppm, dppp, and dppb, and mono-
dentate ligands, that is, (p-ClC6H4)3P and (p-MeOC6H4)3P. The use
of tetraethyldiphosphine disulfide 1 in place of tetramethyldiphos-
phine disulfide gave a similar result (entry 2). The reaction of
1-(phenylthio)alkyne with 1 gave the corresponding product in
We studied transition-metal-catalyzed methods for the synthe-
sis of organophosphorus compounds that employ P–P bond cleav-
age and the transfer of the phosphorus group to organic
compounds. We found that the addition reaction of diphosphine
disulfide occurs with allenes6 and aldehydes.7 Several metathesis
S
S
S
PEt2
S
Rh cat.
⇑
Corresponding author.
+
+
C
SR
Et2P PEt2
C
Et2P SR
E-mail address: yama@mail.pharm.tohoku.ac.jp (M. Yamaguchi).
Present address: WPI Research Center, Advanced Institute for Materials Research,
Tohoku University, Aoba, Sendai 980-8577 Japan.
Scheme 1.
0040-4039/$ - see front matter Ó 2011 Published by Elsevier Ltd.
doi:10.1016/j.tetlet.2011.02.112

M. Arisawa et al. / Tetrahedron Letters 52 (2011) 2410–2412
2411
Table 1
the presence of RhH(PPh3)4 (5 mol %) and depe (10 mol %), (4-
methoxybenzoyl)diethylphosphine sulfide was obtained in 55%
yield along with 4-methylphenyl diethyldithiophosphinate in
51% yield (Scheme 3). The solvent effect of this reaction was small:
use of toluene (44%), THF (56%), DMF (47%), and chlorobenzene
(55%) gave comparable results, whereas no reaction occurred in
dichloroethane. Aliphatic thioesters also gave acylphosphine
sulfides.
Rhodium-catalyzed reaction of 1-thioalkynes with 1
RhH(PPh3)4 (4 mol%)
S
S
depe (8 mol%)
PhCl, refl., 12 h
+
SR'
R
Et2P PEt2
1
S
S
+
PEt2
R
Et2P SR'
In relation to our recent work on the synthesis of 2-thiobenzo-
thiazoles and 2-thiobenzoxazoles,16 the reaction of the heterocy-
clic compound was examined (Scheme 4). When 2-
tolylthiobenzothiazole was reacted with 1 under the same condi-
tions, (2-benzothiazolyl)diethylphosphine sulfide was obtained in
47% yield.
In summary, a rhodium-catalyzed method for the synthesis of
organophosphorus compounds from organosulfur compounds
was developed. 1-Alkylthioalkynes, thioesters, and 2-thiobenzo-
thiazole were converted into 1-alkynylphosphine sulfides, acyl-
phosphine sulfides, and (2-benzothiazolyl)phosphine sulfide,
respectively, by treatment with diphosphine disulfides. This meth-
od for the synthesis of organophosphorus compounds may be ap-
plied to various organosulfur compounds.
2
Entry
R
R0
Yield (%)
a
1
2
3
4
5
6
7
8
2,4,6-Me3C6H2
2,4,6-Me3C6H2
2,4,6-Me3C6H2
2,4,6-iPr3C6H2
2,6-Me2C6H3
2-MeC6H4
Ph
4-MeOC6H4
4-MeC6H4
4-ClC6H4
n-C6H13
n-C6H13
Ph
88
87
74
91
90
89
78
76
82
60
58
53
36
n-C6H13
n-C6H13
n-C6H13
n-C6H13
n-C6H13
n-C6H13
n-C6H13
n-C6H13
Ph
9
10
11
12
13
(i-Pr)3Si
(i-Pr)3Si
n- C5H11
b
n-C6H13
In a two-necked flask equipped with a reflux condenser were
placed RhH(PPh3)4 (4.0 mol %, 23 mg), tetraethyldiphosphine
disulfide 1 (0.5 mmol, 121 mg), and 1-hexylthio-2-(2,4,6-trimeth-
ylphenyl)ethyne (0.5 mmol, 130 mg) under an argon atmosphere.
Dry chlorobenzene (1 mL) and depe (8.0 mol %, 8.2 mg) were
added, and the solution was heated at reflux for 12 h. The solvent
was removed under reduced pressure, and the residue was purified
by flash column chromatography on silica gel giving [(2,4,6-tri-
methylphenyl)ethynyl]diethylphosphine sulfide (115.1 mg, 87%)
as colorless solids and hexyl diethyldithiophosphinate (95.6 mg,
80%) as pale yellow oil.
a
Tetramethyldiphosphine disulfide was used in place of 1. RhH(PPh3)4 (2 mol %),
depe (4 mol %).
b
RhH(PPh3)4 (8 mol %), depe (16 mol %).
74% yield (entry 3), and the effect of the sulfur substituent was not
great.
The reaction was applied to several aromatic 1-hexylthioalkynes
with different aryl groups, and arylethynylphosphine sulfides were
obtained in high yields (entries 1–10). The electronic effect of the p-
substituent was small (entries 7–10). A notable observation was
that 1-hexylthioalkynes without ortho-subsutituents underwent
the C–P bond formation reaction (entries 7–10). Our previous reac-
tion of aromatic 1-alkylthioalkynes generally required the 2,6-di-
methyl group on the aromatic ring to suppress alkyne
oligomerization.12 The broader scope of this reaction may be as-
cribed to the use of diethylphosphinyl reagents, which effectively
trapped thiols and disulfides. The reactions of 1-hexylthio-2-tri-
isopropylsilylethyne and 1-phenylthio-2-triisopropylsilylethyne
gave the corresponding products in 58% and 53% yields, respec-
tively (entries 11 and 12). An aliphatic 1-hexylthioalkyne, however,
gave a lower yield of the product as shown by the reaction of 1-hex-
ylthio-1-heptyne, which may be due to catalyst deactivation (entry
13).
Tetraphenyldiphosphine dioxide reacted with 1-hex-
ylthioalkyne giving the phosphine oxide in 61% yield along with
S-hexyl diphenylthiophosphinate in 51% yield (Scheme 2).
At this stage it was considered interesting whether such metal-
catalyzed transformation to organophosphorus compounds could
be applied to other organosulfur compounds, and thioesters were
found to undergo the reaction. When S-(4-tolyl) 4-methoxybenzo-
thioate and 1 (1 equiv) were reacted in refluxing chlorobenzene in
RhH(PPh3)4 (5 mol%)
S
S
O
C
depe (10 mol%)
PhCl, refl., 6 h
+
Me
Et2P PEt2
R
S
O
C
S
PEt2
S
Et2P
+
R
S
Me
R = MeO 55%
51%
50%
53%
Me2N
RhH(PPh3)4 (5 mol%)
depe (10 mol%)
S
S
O
C
+
OMe
Et2P PEt2
R
S
PhCl, refl., 6 h
O
C
S
S
Et2P
+
S
OMe
R
PEt2
R = n-C11H23
1-adamantyl
47%
41%
46%
44%
Scheme 3.
RhH(PPh3)4 (4 mol%)
RhH(PPh3)4 (5 mol%)
depe (10 mol%)
O
O
Ph2P PPh2
S
S
N
depe (8 mol%)
+
)
+
Me
S
S(n-C6H13
Et2P PEt2
PhCl, refl., 6 h
PhCl, refl., 12 h
S
S
N
S
Et2P
O
PPh2
O
PEt2
S
+
S
Me
+
Ph2P S(n-C6H13
)
61%
51%
47%
47%
Scheme 2.
Scheme 4.

2412
M. Arisawa et al. / Tetrahedron Letters 52 (2011) 2410–2412
2. Yatsumonji, Y.; Ogata, A.; Tsubouchi, A.; Takeda, T. Tetrahedron Lett. 2008, 49,
Acknowledgments
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This work was supported by Grant-in-Aid for Scientific Re-
search (No. 21229001), the GCOE program, and the WPI Initiative
from JSPS. M.A. expresses her thanks for financial support from
the Grant-in-Aid for Scientific Research from MEXT (No.
22689001) and also to the Naito Foundation.
10. Arisawa, M.; Yamaguchi, M. Tetrahedron Lett. 2010, 51, 4840.
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Supplementary data
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.tetlet.2011.02.112.
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