J. Am. Chem. Soc. 1998, 120, 8249-8250
Scheme 1
8249
The First Platinum(0)-Catalyzed Regio- and
Stereoselective Thiosilylation of Alkynes Using
Disulfides and Disilanes: A New Strategy for
Introducing Two Different Heteroatoms into
Carbon-Carbon Unsaturated Bonds
(3.0 mmol, 330.6 mg) in toluene (3 mL) in the presence of Pt-
(CH2dCH2)(PPh3)2 (34 mg, 1.5 mol % relative to sulfur) at 110
°C for 6 h resulted in complete disappearance of 1-octyne as
confirmed by GC.6 Subsequent additions of Et3N (10 mmol, 1.4
mL) and EtOH (10 mmol, 0.6 mL) to the reaction mixture
followed by purification by column chromatography on silica gel
(hexane/ether/Et3N ) 100/10/1) afforded analytically pure (Z)-
1-(triethoxysilyl)-2-(4′-chlorophenylthio)-1-octene (2c) regio- and
stereoselectively as pale yellow oil in 83% yield (1.04 g, 2.5
mmol) (eq 1). Surprising is the lack of addition of the disulfide
Li-Biao Han and Masato Tanaka*
National Institute of Materials and Chemical Research
Tsukuba, Ibaraki 305-8565, Japan
ReceiVed April 30, 1998
The chemistry for efficient construction of carbon-heteroatom
bonds by transition metal catalyzed addition of heteroatom
compounds to carbon-carbon unsaturated bonds is emerging
rapidly.1 Particularly interesting and challenging in this category
are those involving the regio- and stereoselective simultaneous
introductions of two different heteroatoms (E, E′, E * E′; Scheme
1), which enable versatile and elegant synthetic elaborations of
the adducts (1). However, all of the few reactions reported to
date2 have been performed by adopting the same protocol, using
directly the corresponding unsymmetrical E-E′ as reagents (path
a), in which a troublesome and time-consuming preparation of
the E-E′ linkage can be a serious drawback. On the other hand,
related symmetrical compounds (E-E and E′-E′) are generally
more accessible and easy to handle. Herein reported is a new
protocol for the synthesis of 1 by employing a mixture of two
symmetrical heteroatom compounds (path b); heating a mixture
of disulfides, disilanes, and alkynes in the presence of a platinum
catalyst realizes regio- and stereoselective thiosilylation of alkynes,
which readily affords synthetically versatile (Z)-1-silyl-2-thio-1-
alkenes in good yields.3,4 This thiosilylation reaction also appears
to represent the first metal-catalyzed addition of the group 14
element-chalcogen bond to unsaturated hydrocarbons with high
efficiencies.5
to the alkyne since such an addition reaction is known to proceed
in the presence of complex catalysts.5b The possible regio- and
stereoisomers of 2c were not formed either.7,8
As demonstrated in Table 1, the platinum-catalyzed thiosily-
lation could be readily applied to other terminal alkynes, yielding
the corresponding (Z)-1-silyl-2-thio-1-alkenes (2) in good yields
with excellent regio- and stereoselectivities. Besides 1-octyne,
the reaction of 3-phenyl-1-propyne and other functionalized
aliphatic alkynes such as those having chloro, cyano, siloxy, and
alkoxycarbonyl groups9 also proceeded efficiently affording the
adducts in high yields. Multiple silyl and thio groups could be
easily introduced regio- and stereoselectively to acetylenes having
more than one C-C triple bond. For example, the thiosilylation
of 1,8-nonadiyne using 1.1 equiv of the disulfide and (SiCl3)2
gave the corresponding product in 69% yield. Aromatic alkynes
such as phenylacetylene, 1-chloro-4-ethynylbenzene, and 4-ethy-
nyltoluene also reacted similarly and good yields of the thiosi-
lylation products were obtained. In contrast to alkynes, alkenes
were inert toward the reaction. Consequently, only an adduct
through the addition to the triple bond was obtained from
1-ethynylcyclohexene.10
In a typical experiment, heating a mixture of (4-ClC6H4S)2 (1.5
mmol, 430.8 mg), (SiCl3)2 (1.5 mmol, 403.3 mg), and 1-octyne
(1) (a) Collman, J. P.; Hegedus, L. S.; Norton, J. R.; Finke, R. G. Principles
and Applications of Organotransition Metal Chemistry; University Science
Books: Mill Valley, CA, 1987. (b) Parshall, G. W.; Ittel, S. D. Homogeneous
Catalysis; John Wiley & Sons: New York, 1992; pp 25-50. (c) Compre-
hensiVe Handbook on Hydrosilylation; Marciniec, B., Ed.; Pergamon Press:
Oxford, UK, 1992.
(2) Representative E-E′ additions: (Si-Sn) (a) Mitchell, T. N.; Schneider,
U. J. Organomet. Chem. 1991, 407, 319 and references therein. (B-S) (b)
Ishiyama, T.; Nishijima, K.; Miyaura, N.; Suzuki, A. J. Am. Chem. Soc. 1993,
115, 7219. (Si-Se, Ge-S, and Ge-Se) (c) Tsumuraya, T.; Ando, W.
Organometallics 1989, 8, 2286. (d) Ogawa, A.; Sonoda, N. Yuki Gosei Kagaku
Kyokaishi (J. Synth. Org. Chem. Jpn.) 1993, 51, 815. (P-Se) (e) Han, L.-B.;
Choi, N.; Tanaka, M. J. Am. Chem. Soc. 1996, 118, 7000. (B-Sn) (f)
Onozawa, S.-y.; Hatanaka, Y.; Choi, N.; Tanaka, M. Organometallics 1997,
16, 5389. (B-Si) (g) Onozawa, S.-y.; Hatanaka, Y.; Tanaka, M. Chem.
Commun. 1997, 1229. (h) Suginome, M.; Nakamura, H.; Ito, Y. Angew. Chem.,
Int. Ed. Engl. 1997, 36, 2516. For other relevant studies, see: (i) Ishiyama,
T.; Matsuda, N.; Murata, M.; Ozawa, F.; Suzuki, A.; Miyaura, N. Organo-
metallics 1996, 15, 713 and references therein.
(3) Conventional synthesis of 1-silyl-2-thioalkenes via radical addition of
ArSH to ethynylsilanes: (a) Komarov, N. V.; Torosh, O. G. IzV. Akad. Nauk
SSSR Ser. Khim. 1967, 3, 690. Via cross-coupling of bromoalkenylsilanes
with PhSSnR3: (b) Carpita, A.; Rossi, R., Scamuzzi, B. Tetrahedron Lett.
1989, 30, 2699. Other methods: (c) Hase, T. A.; Lahtinen, L. J. Organomet.
Chem. 1982, 240, 9. (d) Chou, S.-S. P.; Chao, M.-H. Tetrahedron Lett. 1995,
36, 8825.
(4) For applications in cyclopentenone annulations, see: (a) Magnus, P.;
Quagliato, D. J. Org. Chem. 1985, 50, 1621. Vinylsilanes and vinyl sulfides
are useful synthetic intermediates. For vinylsilanes: (b) Horn, K. A. Chem.
ReV. 1995, 95, 1317. For vinyl sulfides, see ref 4a and references therein.
(5) Palladium-catalyzed additions of strained thia- and selenadigermiranes
to acetylene and PhSeSiMe3 to phenylacetylene have been briefly described
in refs 2c and 2d. For related pioneering studies, see: (a) Ogawa, A.; Takeba,
M.; Kawakami, J.-i, Ryu, I.; Kambe, N.; Sonoda, N. J. Am. Chem. Soc. 1995,
117, 7564. (b) Kuniyasu, H.; Ogawa, A.; Miyazaki, S.; Ryu, I.; Sonoda, N. J.
Am. Chem. Soc. 1991, 113, 9796.
Mechanistic investigations revealed that a novel platinum-
catalyzed disproportionation reaction of a disulfide (ArS)2 with
(6) The 2-(arylthio)-1-(trichlorosilyl)-1-alkenes (1) could be isolated by
Kugelrohr distillation, e.g., 1a in 63% yield.
1
(7) Weak vinylic signals could be found in the H NMR spectrum of the
crude reaction mixture. However, they are not due to either other isomers of
the major adduct or the adduct of the disulfides but seems due to an entirely
different side product derived from one molecule of silyl sulfide and two
molecules of alkynes. See the Supporting Information for details.
(8) Pt(PPh3)4 also worked as efficient catalyst to give 2c in 76% yield. In
contrast, complexes such as Pt(PPh2Me)4, Pt(cod)2, PtCl2(PPh3)2, Pd2(dba)3,
PdCl2(PhCN)2, and PdCl2(PPh3)2 did not show any catalytic activity, and an
attempted reaction using Pd(PPh3)4 produced a rather complicated result.
Among disulfides screened for the reaction of 1-octyne, (4-ClC6H4S)2 gave
the highest yield of the adduct (1c, 95%), followed by (PhS)2 (1a, 65%) and
(4-MeC6H4S)2 (1b, 52%). However, formation of an analogous adduct could
not be confirmed in the reaction with (c-C6H11S)2. As for disilane compounds,
use of (SiMe3)2, (SiClMe2)2, (SiFMe2)2, (SiPhMe2)2, or [Si(OMe)3]2 in place
of (SiCl3)2 did not form the corresponding adducts under similar reaction
conditions.
(9) Cleavage of C-O bonds by silyl sulfides is known. See: Armitage, D.
A. In The Silicon-Heteroatom Bond; Patai, S., Rappoport, Z., Eds.; John
Wiley & Sons: Chichester, 1991; pp 213-243.
(10) The relatively low yield was due to rather extensive formation of a
side product as described in ref 7.
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