ORGANIC
LETTERS
2
001
Vol. 3, No. 5
63-764
Addition Reaction of Dialkyl Disulfides
to Terminal Alkynes Catalyzed by a
Rhodium Complex and
7
Trifluoromethanesulfonic Acid
Mieko Arisawa and Masahiko Yamaguchi*
Department of Organic Chemistry, Graduate School of Pharmaceutical Sciences,
Tohoku UniVersity, Aoba, Sendai 980-8578, Japan
Received January 6, 2001
ABSTRACT
Addition of dialkyl disulfides to terminal alkynes is catalyzed by a rhodium−phosphine complex and trifluoromethanesulfonic acid giving
Z)-bis(alkylthio)olefins stereoselectively.
(
Metal-catalyzed cis-addition reaction of disulfides to alkynes
was first reported by Ogawa and Sonoda. Although high
When 1-octyne is treated with dibutyl disulfide (1 equiv)
1
in the presence of RhH(PPh ) (3 mol %), tris(p-methoxy-
3
4
yields are obtained in the case of aromatic disulfides,
aliphatic disulfides are not studied in detail. A method
involving the metal-catalyzed addition of bis(triisopropylsilyl)
disulfide followed by alkylation was developed for the
phenyl)phosphine (12 mol %), and trifluoromethanesulfonic
acid (3 mol %) in refluxing acetone for 10 h, (Z)-1,2-bis-
(butylthio)-1-octene is obtained in 95% yield (Table 1, entry
1
1). The (Z)-stereochemistry of the double bond is deter-
2
synthesis of the alkyl derivatives. Several related transfor-
mined by NOE, and no trace of its isomer is detected by
NMR analysis of the crude product. The rhodium complex
and trifluoromethanesulfonic acid are essential for the
addition, and no reaction occurs in the absence of either of
the reagents (entries 1, 2, and 3). Addition of a triphen-
ylphosphine, especially that with electron-donating substit-
uents, improves the yield (entries 4-9). Bidentate phosphines
mations are also known. Alkyl disulfides add to alkynes via
photoinitiated free radical mechanism giving isomeric mix-
3
tures of the products. 1,4-Dithiepines are obtained by the
4
cleavage of 1,2-dithiolanes with acetylides. As an extension
of our recent investigations on the catalytic use of transition
metal complexes and sulfuric acid derivatives in organic
5
synthesis, we describe here that the direct cis-addition of
(entries 12-15), tributylphosphine (entry 16), and triphenyl
dialkyl disulfides to terminal alkynes can be catalyzed by a
rhodium-phosphine complex and trifluoromethanesulfonic
acid.
phosphite (entry 17) are not very effective. The catalytic
6
+
activities of RhCl(PPh
3
)
3
,
)
[RhCl(cod)]
,6 Pd(OAc)
, PdCl
, and NiCl (dppp) are very low even in
2
,
Rh (cod)-
-
BF
4
, Pd
2
(dba)
3
, Pd(PPh
3
4
2
2
(PPh
3 2
) ,
RuClH(CO)(PPh
3
)
3
2
(1) Kuniyasu, H.; Ogawa, A.; Miyazaki, S.-I.; Ryu, I.; Kambe, N.;
Sonoda, N. J. Am. Chem. Soc. 1991, 113, 9796. Ogawa, A.; Kuniyasu, H.;
Sonoda, N.; Hirao, T. J. Org. Chem. 1997, 62, 8361.
the presence of trifluoromethanesulfonic acid and tris(p-
(
2) Gareau, Y.; Orellana, A. Synlett 1997, 803.
(3) Heiba, E. I.; Dessau, R. M. J. Org, Chem. 1967, 32, 3837. Also see
(5) Addition of phosphine to alkyne: Arisawa, M.; Yamaguchi, M. J.
Am. Chem. Soc. 2000, 122, 2387. Arisawa, M.; Yamaguchi, M. AdV. Synth.
Cat. 2001, 343, 27. Beckmann rearrangement: Arisawa, M.; Yamaguchi,
M. Org. Lett. 2001, 3, 311.
the followings for the addition of diselenides to alkynes. Ogawa, A.;
Yokoyama, H.; Yokoyama, K.; Masawaki, T.; Kambe, N.; Sonoda, N. J.
Org. Chem. 1991, 56, 5721. Back, T. G.; Krishna, M. V. J. Org. Chem.
1
988, 53, 2533.
4) Tazaki, M.; Kumakura, M.; Nagahama, S.; Takagi, M. J. Chem. Soc.,
Chem. Commun. 1995, 1763.
(6) RhCl(PPh)3 and Pd(PPh3)4 are not effective for the addition of dibutyl
disulfide to 1-octyne under the reaction conditions reported by Ogawa and
Sonoda.1
(
1
0.1021/ol015521l CCC: $20.00 © 2001 American Chemical Society
Published on Web 02/15/2001