Ruthenium-catalysed hydrogenation of alkynylstannanes with migration of the stannyl group

Article abstract of DOI:10.1021/ja0458827

Molecular hydrogen adds to aliphatic and aromatic alkynylstannanes in the presence of a ruthenium catalyst, pushing the stannyl group to the adjacent carbon atom to give α-substituted vinylstannanes. This is the first achievement of hydrogenation of alkynylstannanes, which is applicable also to the deuteration affording precursors for an important class of deuterium-labeled compounds. Copyright

Full text of DOI:10.1021/ja0458827

Published on Web 10/01/2004
Ruthenium-Catalyzed Hydrogenation of Alkynylstannanes with Migration of
the Stannyl Group
Eiji Shirakawa,*,† Ryotaro Morita,‡ Teruhisa Tsuchimoto,‡ and Yusuke Kawakami‡
Department of Chemistry, Graduate School of Science, Kyoto UniVersity, Sakyo, Kyoto 606-8502, Japan, and
Graduate School of Materials Science, Japan AdVanced Institute of Science and Technology,
Tatsunokuchi, Ishikawa 923-1292, Japan
Received July 9, 2004; E-mail: shirakawa@kuchem.kyoto-u.ac.jp
Table 1. Ruthenium-Catalyzed Hydrogenation of
Monosubstituted vinylstannanes, whose stannyl groups can be
transformed to various organic groups (e.g., through the Kosugi-
Migita-Stille protocol),1 are versatile precursors for disubstituted
ethenes. Although â-substituted vinylstannanes with a trans or cis
configuration can be obtained through diverse types of transforma-
tion reactions,2 no simple method applicable to a wide range of
compounds is available for R-substituted vinylstannanes. Among
the reported methods, the addition of Sn-M (M ) Cu, Si, Al, Mg,
or Sn) bonds to terminal alkynes followed by hydrolysis of the
resulting C-M bonds seems to be the most reliable.3 However,
troublesome preparation and handling of the starting dimetallic
compounds make the method inconvenient.4,5 Here, we report a
new facile protocol for the synthesis of R-substituted vinylstannanes,
namely, the ruthenium-catalyzed hydrogenation of alkynylstannanes
accompanied by the migration of the stannyl group. To the best of
our knowledge, there has been no report on the hydrogenation of
alkynylstannanes, including 1,2-addition.2a
Tributyl(oct-1-yn-1-yl)tina
ruthenium
catalyst
additional
PBu3
time
(h)
conv.
(%)b
yield
(%)b
entry
1
2
Ru3(CO)12
Ru3(CO)12
RuH2(CO)(PBu3)3
Ru3(CO)12
RuH2(CO)(PPh3)3
RuH2(CO)(PPh3)3
RuCl2(CO)2(PBu3)2
[RuCl2(η6-p-cymene)]2
RuCl2(DMSO)4
none
+
-
-
+
+
-
-
+
+
- -
30
48
6
8
6
48
12
48
24
30
>99
>99
>99
>99
>99
>99
>99
>99
66
79
<1
92
85
92
19
87
24
10
<1
3
4c
5
6
7
8
9
10
8
a The experiment was carried out in DMSO (0.30 mL) at 80 °C under a
hydrogen atmosphere using tributyl(oct-1-yn-1-yl)tin (0.40 mmol) and a
ruthenium catalyst (5.0 mol % Ru) in the presence or absence of PBu3 (30
mol %). b Determined by GC. c Ru3(CO)12-PBu3 preheated in DMSO under
a hydrogen atmosphere at 80 °C for 24 h.
Treatment of tributyl(oct-1-yn-1-yl)tin (1a) with Ru3(CO)12 (5
mol % Ru) and tributylphosphine (30 mol %) under an atmosphere
of hydrogen in DMSO at 80 °C for 30 h gave a 79% yield of
2-tributylstannyl-1-octene (2a) but no oct-1-en-1-ylstannane, the
normal hydrogenation product of 1a (eq 1 and entry 1 of Table 1),
where the use of tributylphosphine is critical (entry 2). The
hydrogenation proceeded more smoothly with hydride complex,
RuH2(CO)(PBu3)3 (entry 3),6 whereas pretreatment of a Ru3(CO)12-
PBu3 complex in DMSO with a hydrogen gas also reduced the
reaction time (entry 4).7 The use of stable and commercially
available RuH2(CO)(PPh3)3, in combination with PBu3, also worked
(entry 5),8 whereas the absence of PBu3 resulted in a low yield
(entry 6). Carbon monoxide as a ligand was found to play an
important role (entry 7 vs entries 8 and 9), and no hydrogenation
product was generated without a ruthenium catalyst (entry 10).
Table 2. Ruthenium-Catalyzed Hydrogenation of
Alkynylstannanesa
time
(h)
yield
(%)b
entry
R
ligand
product
1
2
3
4
5
Hex (1a)
i-Pr (1b)
PBu3
PBu3
PBu3
PBu3
PBu3
PBu3
PBu3
PBu3
PBu3
PN
6
32
12
30
14
48
6
16
24
4
4
4
4
4
24
4
24
89
77
78
65
71
70
65
38e
8
89
81
25f
52h
55i
77
65
52
2a
2b
2c
2d
2e
2f
2g
2h
2i
HO(CH2)4 (1c)
MeOCO(CH2)4 (1d)
Me2NCO(CH2)4 (1e)
NC(CH2)3 (1f)
EtO (1g)
Bu3SnCtC (1h)
Ph (1i)
Ph (1i)
4-MeOC6H4 (1j)
4-CF3C6H4 (1k)
4-CF3C6H4 (1k)
4-BrC6H4 (1l)
2-MeC6H4 (1m)
3-thienyl (1n)
1-cyclohexenyl (1o)
6
7c
8d
9
10
11
12
13
14
15
16
17
2i
2j
PN
PN
2k
2k
2l
2m
2n
2o
PNg
PN
PN
PN
PNg
a The reaction was carried out in DMSO (0.30 mL) at 80 °C under a
hydrogen atmosphere using alkynylstannane (0.40 mmol), RuH2(CO)(PPh3)3
(5.0 mol %), and a ligand (30 mol % PBu3 or 10 mol % PN). b Isolated
yield based on the alkynylstannane. c Toluene was used as a solvent instead
of DMSO. d 1,4-Dioxane was used as a solvent instead of DMSO. e With
73% conversion of 1h. f A mixture of 1,2-addition products (58:42 E:Z)
was produced in 53% yield. g PN (20 mol %) was used. h A mixture of
1,2-addition products (60:40 E:Z) was produced in 25% yield. i A mixture
of 1,2-addition products (43:57 E:Z) was produced in 35% yield.
The RuH2(CO)(PPh3)3-PBu3 catalyst, which has shown the best
compatibility between catalytic activity and availability thus far,
was applicable also to various aliphatic alkynylstannanes (entries
1-8 of Table 2), where functional groups, such as hydroxy, ester,
amide, and cyano, were tolerated. For a bisstannylbutadiyne, an
acceptable selectivity for monohydrogenation was observed at 73%
conversion, though the yield was rather low (entry 8). In contrast
to aliphatic alkynylstannanes, tributyl(phenylethynyl)tin (1i) was
hydrogenated only in a low yield with RuH2(CO)(PPh3)3-PBu3
(entry 9). After thorough investigation, we found N,N-dimethyl-2-
diphenylphosphinobenzylamine (PN) to be an effective ligand for
1i and other phenylethynylstannanes substituted with an electron-
donating or -withdrawing group at the para or ortho position in
addition to a heteroarylethynylstannane (entries 10-16).9 Although
an electron-withdrawing substituent induced 1,2-hydrogenation to
† Kyoto University.
‡ Japan Advanced Institute of Science and Technology.
9
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J. AM. CHEM. SOC. 2004, 126, 13614-13615
10.1021/ja0458827 CCC: $27.50 © 2004 American Chemical Society

C O M M U N I C A T I O N S
React. 1997, 50, 1-652. (c) Fugami, K.; Kosugi, M. Top. Curr. Chem.
2002, 219, 87-130.
a considerable extent, the use of an increased amount of PN
improved the selectivity (compare entries 12 and 13). A dienyl-
stannane was obtained from a stannylenyne in moderate yield (entry
17).
(2) trans-Alk-1-en-1-ylstannanes can be obtained by transmetalation between
the corresponding alkenylmetals with trialkyltin halides or by hydrostan-
nylation of terminal alkynes: (a) Davies, A. G. Organotin Chemistry,
2nd ed.; Wiley-VCH: Weinheim, Germany, 2004; Chapter 8.1.1, pp 114-
116 and references therein. For cis-alkenylstannanes through hydrozir-
conation of alkynylstannanes followed by hydrolysis, see: (b) Lipshutz,
B. H.; Keil, R.; Barton, J. C. Tetrahedron Lett. 1992, 33, 5861-5864.
For transition-metal-catalyzed carbostannylation of acetylene, see: (c)
Shirakawa, E.; Yoshida, H.; Kurahashi, T.; Nakao, Y.; Hiyama, T. J. Am.
Chem. Soc. 1998, 120, 2975-2976. (d) Shirakawa, E.; Yamasaki, K.;
Yoshida, H.; Hiyama, T. J. Am. Chem. Soc. 1999, 121, 10221-10222.
(e) Yoshida, H.; Shirakawa, E.; Kurahashi, T.; Nakao, Y.; Hiyama, T.
Organometallics 2000, 19, 5671-5678.
The corresponding deuteration is also possible. Thus, 1,1-
dideuterio-2-stannyl-1-alkenes (2′), with perfect deuteration ratios,
were obtained under a deuterium atmosphere with hydrogen-free
catalysts (eq 2).10 Note that deuterated alkynylstannanes, which can
be easily transformed to an important class of deuterium-labeled
compounds, were prepared using a highly accessible deuterium
source, such as molecular deuterium. The cross-coupling reaction,1,11
the addition to an aldehyde after transmetalation with n-butyl-
lithium,12 or the deuteriolysis of 2′a afforded a phenylated,
hydroxymethylated, or deuterated product, respectively, with the
intact dCD2 moiety (Scheme 1).13 Hydrogenation products also
should be converted into various alkenes in similar ways.
(3) For the addition of Sn-Cu bonds, see: (a) Piers, E.; Chong, J. M. J.
Chem. Soc., Chem. Commun. 1983, 934-935. (b) Oehlschlager, A. C.;
Hutzinger, M. W.; Aksela, R.; Sharma, S.; Singh, S. M. Tetrahedron Lett.
1990, 31, 165-168. (c) Singer, R. D.; Hutzinger, M. W.; Oehlschlager,
A. C. J. Org. Chem. 1991, 56, 4933-4938. (d) Barbero, A.; Cuadrado,
P.; Fleming, I.; Gonza´lez, M.; Pulido, F. J. J. Chem. Soc., Chem. Commun.
1992, 351-352. For Sn-Si bonds, see: (e) Ritter, K. Synthesis 1989,
218-221. For Sn-Al bonds, see: (f) Sharma, S.; Oehlschlager, A. C. J.
Org. Chem. 1989, 54, 5064-5073. For Sn-Mg bonds, see: (g) Matsubara,
S.; Hibino, J.; Morizawa, Y.; Oshima, K.; Nozaki, H. J. Organomet. Chem.
1985, 285, 163-172. For Sn-Sn bonds, see: (h) Mitchell, T. N.; Kwetkat,
K.; Rutschow, D.; Schneider, U. Tetrahedron 1989, 45, 969-
978.
(4) For other methods for the synthesis of R-substituted vinylstannanes, see:
(a) Verlhac, J.-B.; Kwon, H.; Pereyre, M. J. Chem. Soc., Perkin Trans. 1
1993, 1367-1368. (b) Bellina, F.; Carpita, A.; De Santis, M.; Rossi, R.
Tetrahedron 1994, 50, 4853-4872. (c) Shirakawa, E.; Nakao, Y.; Hiyama,
T. Chem. Commun. 2001, 263-264. (d) Shirakawa, E.; Nakao, Y.;
Tsuchimoto, T.; Hiyama, T. Chem. Commun. 2002, 1962-1963.
(5) Although the reaction of trialkyltin chlorides with R-substituted vinyl-
metals, derived from the corresponding alkenyl halides, must be one of
the most straightforward ways to R-substituted vinylstannanes, examples
of easily available 2-halo-1-alkene are limited.
Scheme 1. Transformations of Deuteration Product 2′a
(6) RuH2(CO)(PBu3)3, a new complex, was obtained through reduction of
RuCl3‚nH2O with NaBH4 in the presence of PBu3 followed by CO
bubbling in 40% yield in high purity but containing Bu3PdO (7% in
integral in 31P NMR). For reduction with NaBH4, see: (a) Mitsudo, T.;
Nakagawa, Y.; Watanabe, K.; Hori, Y.; Misawa, H.; Watanabe, H.;
Watanabe, Y. J. Org. Chem. 1985, 50, 565-571. For the introduction of
CO, see: (b) Harris, R. O.; Hota, N. K.; Sadavoy, L.; Yuen, J. M. C. J.
Organomet. Chem. 1973, 54, 259-264. For details, see the Supporting
Information.
(7) Under the same conditions, the reaction with a Ru3(CO)12-PBu3 catalyst
preheated in DMSO under a nitrogen atmosphere at 80 °C for 24 h did
not afford 2a at all after 8 h, but did so in 73% yield after 30 h.
(8) With the addition of PBu3 (6 equiv) at 80 °C, the peaks in the 31P NMR
data of RuH2(CO)(PPh3)3 in DMSO/THF (10/1) disappeared within 5 min,
and those of RuH2(CO)(PBu3)3 predominated after 2 h.
Although the reaction mechanism is unclear at present, the
migration of stannyl groups, in addition to the tendency for
ruthenium complexes to form vinylidene complexes upon reaction
with terminal alkynes14 or alkynylsilanes,15 may imply that
ruthenium-â-stannylvinylidene complexes, Rud•dC(SnBu3)R, are
possibly involved in the hydrogenation.
In conclusion, we have disclosed the first example of the
transition-metal-catalyzed hydrogenation of aromatic and aliphatic
alkynylstannanes. The hydrogenation, catalyzed by a ruthenium
complex, is accompanied by the migration of a stannyl group, giving
R-substituted vinylstannanes, which are otherwise not easily ac-
cessible. Studies on the mechanistic details, as well as application
of the system to other substrates, are in progress.
(9) In contrast to PBu3, PN failed to construct an active catalyst in combination
with Ru3(CO)12
.
(10) Although a 1,2-dideuterated product (∼5% yield estimated by GC) was
generated in the deuteration of phenylethynylstannane 1i, 2′i can be easily
obtained in a pure form through GPC chromatography.
(11) Han, X.; Stoltz, B. M.; Corey, E. J. J. Am. Chem. Soc. 1999, 121, 7600-
7605.
(12) Verlhac, J.-B.; Pereyre, M. J. Organomet. Chem. 1990, 391, 283-
288.
(13) The Wittig reaction using R3P+CD3‚X- should be one of the most common
methods for the introduction of a dCD2 moiety when the corresponding
carbonyl compounds are available. However, the Wittig reaction some-
times causes the loss and/or scrambling of deuterium atoms. For example,
see: (a) Hasselmann, D. Chem. Ber. 1974, 107, 3486-3493. (b) Dun˜ach,
E.; Halterman, R. L.; Vollhardt, P. C. J. Am. Chem. Soc. 1985, 107, 1664-
1671. (c) Casalnuovo, A. L.; RajanBabu, T. V.; Ayers, T. A.; Warren, T.
H. J. Am. Chem. Soc. 1994, 116, 9869-9882.
(14) For example, see: (a) Wakatsuki, Y.; Koga, N.; Yamazaki, H.; Morokuma,
K. J. Am. Chem. Soc. 1994, 116, 8105-8111. See also ref 15b,c.
Ruthenium-vinylidene complexes are known to be the key intermediates
of the addition reactions to terminal alkynes. For reviews, see: (b) Naota,
T.; Takaya, H.; Murahashi, S.-I. Chem. ReV. 1998, 98, 2599-2660. (c)
Trost, B. M.; Toste, F. D.; Pinkerton, A. B. Chem. ReV. 2001, 101, 2067-
2096.
(15) (a) Onitsuka, K.; Katayama, H.; Sonogashira, K.; Ozawa, F. J. Chem.
Soc., Chem. Commun. 1995, 2267-2268. (b) Katayama, H.; Ozawa, F.
Organometallics 1998, 17, 5190-5196. (c) Katayama, H.; Wada, C.;
Taniguchi, K.; Ozawa, F. Organometallics 2002, 21, 3285-3291.
Acknowledgment. This work was supported, in part, by Daicel
Chemical Industries, Ltd.
Supporting Information Available: Experimental procedures and
spectral analyses of all reaction products. This material is available
free of charge via the Internet at http://pubs.acs.org.
References
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