A highly regio- and stereoselective transition metal-catalyzed hydrosilylation of terminal alkynes under ambient conditions of air, water, and room temperature

Article abstract of DOI:10.1039/b302259e

A highly efficient and stereoselective hydrosilylation of terminal alkynes was developed at room temperature in air and water.

Full text of DOI:10.1039/b302259e

A highly regio- and stereoselective transition metal-catalyzed
hydrosilylation of terminal alkynes under ambient conditions of air,
water, and room temperature
Wei Wu and Chao-Jun Li*
Department of Chemistry, Tulane University, New Orleans, Louisiana, USA. E-mail: cjli@tulane.edu;
Fax: 504-865-5596; Tel: 504-865-5573
Received (in Corvallis, OR, USA) 25th February 2003, Accepted 21st April 2003
First published as an Advance Article on the web 6th June 2003
A highly efficient and stereoselective hydrosilylation of
terminal alkynes was developed at room temperature in air
and water.
(entry 1). The use of Pt(DVDS) (DVDS: 1,3-divinyl-1,1,3,3-tet-
ramethyldisiloxane) complex as a catalyst resulted in an
increase in both the product yield and the trans/cis ratio under
the same reaction conditions (entry 2). Notably, the use of
Pt(DVDS)–P [P: bis(diphenylphosphinomethylene)butylamine
(1) ] as catalyst led to a near quantitative yield and a 100%
stereoselectivity (trans) (entry 3). Rhodium-based catalysts
Catalytic hydrosilylation of alkynes is an important process
generating vinylsilanes that are important reagents for a number
10
1
of organic transformations such as Hiyama-type coupling,
coupling with aldehydes,2 and applications in controlling
[RhCl(PPh
Rh(COD) BF
yields and lower trans/cis selectivity. No reaction was observed
with Ru(CO)HCl(PPh and Ru(Cp) as catalysts under the
)
3
,
4
RhCl
·3H
O, Rh(COD)(PPh
)PF
,
and
3
3
2
3
6
3
various cation-cyclization processes. Since the first report of
2
] were also effective, but they led to both lower
catalytic hydrosilylation of alkynes using Speier’s catalyst,4
many catalysts have been developed for related transforma-
3
)
3
2
5
tions. Generally, these catalytic reactions are carried out in an
same reaction conditions. In addition, no a-addition product
was observed in any of these cases. Subsequently, various
terminal acetylenes were hydrosilylated under the standard
inert gas atmosphere and under anhydrous conditions. Recently,
there has been significant interest in developing carbon–carbon
6
11
bond formation reactions in water. Among these reactions is
conditions catalyzed by Pt(DVDS)–P (Table 2). The corre-
7
the addition of vinylboronic acids to aldehydes. Recently, we
sponding results catalyzed by Pt(DVDS) without the phosphine
ligand are also included in parentheses for comparison.
Although both catalysts provided excellent yields of the
hydrosilylation product in each case, the use of Pt(DVDS)–P as
catalyst provided better trans selectivity in all cases and
complete trans selectivity was observed with most terminal
alkynes (entries 1, 7, 9, 11, 13, 15). Notably, the presence of a
reported a transition metal-catalyzed addition of vinylsilane
derivatives to aldehydes and a,b-unsaturated carbonyl com-
8
pounds, as well as coupling of vinylsilane derivatives with aryl
9
halides in air and water. A limitation of this method is the
requirement for preforming vinylsilane derivatives under the
standard anhydrous conditions. A method for hydrosilylation of
alkynes in aqueous media would be highly desirable. Herein, we
wish to report a highly effective as well as regio- and
stereoselective hydrosilylation of terminal alkynes under ambi-
ent conditions of air, water, and room temperature (Scheme
Table 2 Catalytic hydrosilylation of alkynes in air and water
trans/cis/aa
Yield (%)b
Entry
Alkyne
1
).
To begin our study, phenylacetylene was reacted with
triethylsilane in water, with a variety of catalysts being
examined (Table 1). The use of H PtCl as a catalyst led to 86%
1
2
100 : 0 : 0
(91 : 9 : 0)
97
(96)
2
6
3
4
96 : 4 : 0
(80 : 20 : 0)
92
(91)
isolated yield of the hydrosilylation product as a mixture of
trans and cis geometrical isomers in 3 h at room temperature
5
6
95 : 5 : 0
(81 : 19 : 0)
90
(90)
7
8
100 : 0 : 0
(73 : 27 : 0)
92
(92)
9
100 : 0 : 0
98
1
0
(74 : 26 : 0)
(98)
Scheme 1
11
100 : 0 : 0
95
1
2
(67 : < 1 : 33)
(93)
Table 1 Catalyst-screening for alkyne-hydrosilylation in water
13
100 : 0 : 0
93
1
4
(82 : 18 : 0)
(93)
Yield
(%)
a
15
100 : 0 : 0
(93 : 7 : 0)
95
(89)
Entry Alkyne
Catalyst
PtCl
Pt(DVDS)
Pt(DVDS)–P
trans/cis/a-
1
6
1
2
3
4
5
6
7
8
9
Phenylacetylene
H
2
6
74 : 26 : 0
91 : 9 : 0
100 : 0 : 0
85 : 18 : 0
77 : 23 : 0
81 : 19 : 0
84 : 16 : 0
—
86
93
98
90
88
91
92
0
Phenylacetylene
Phenylacetylene
Phenylacetylene
Phenylacetylene
Phenylacetylene
Phenylacetylene
Phenylacetylene
Phenylacetylene
1
1
7
8
91 : 9 : 0
(55 : 45 : 0)
95
(96)
RhCl(PPh
RhCl ·3H
Rh(COD)(PPh
Rh(COD) BF
Ru(CO)HCl(PPh
Ru(Cp)
3 3
)
2
O
3
3
)PF
6
19
20
35 : 65 : 0
(45 : 55 : 0)
92
(92)
2
4
3 3
)
2
2
1
2
93 : 7 : 0
(86 : 14 : 0)
95
(93)
2
—
0
All reactions were carried out at room temperature on a 1 mmol scale in 3
a
1
h. Isolated yields are reported. trans/cis/a-ratios were measured by
H
Pt(DVDS)–P as catalyst; results of using Pt(DVDS) as catalyst are in
parentheses. Determined by H NMR and/or GCMS. Isolated yields.
a
1
b
NMR and/or GCMS.
1
668
CHEM. COMMUN., 2003, 1668–1669
This journal is © The Royal Society of Chemistry 2003

hydroxyl group did not affect the reaction (entries 7–12). Except
in entry 12, no a-product was observed with either catalyst in
any case. Interestingly, the use of trimethylsilylacetylene
J. Organomet. Chem., 2002, 645, 1; B. M. Trost and Z. T. Ball, J. Am.
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2
002, 4, 4163.
6
7
C. J. Li and T. H. Chan, Organic Reactions in Aqueous Media, John
Wiley & Sons, New York, 1997; Organic Synthesis in Water; P. A.
Grieco, Ed., Thomson Science, Glasgow, 1998.
(entries 19, 20) led to a switch of the trans/cis selectivity. It is
not yet clear what caused this selectivity change.
M. Sakai, H. Hayashi and N. Miyaura, Organometallics, 1997, 20,
4
1
229; Y. Takaya, M. Ogasawara and T. Hayashi, Tetrahedron Lett.,
998, 39, 8479. For examples of addition of other vinyl reagents, see: C.
J. Li, Acc. Chem. Res., 2002, 35, 533; C. J. Li, T. S. Huang, S.
Venkatraman, Y. Meng, D. Kort, R. Ding, D. Wang and T. Nguyen,
Pure Appl. Chem., 2001, 73, 1315; T. S. Huang, S. Venkatraman, Y.
Meng, D. Wang and C. J. Li, J. Am. Chem. Soc., 2001, 121, 7451; C. J.
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8 T. S. Huang and C. J. Li, Chem. Commun., 2001, 2348; see also: S. Oi,
Y. Honma and Y. Inoue, Org. Lett., 2002, 4, 667.
9 S. Venkatraman, T. S. Huang and C. J. Li, Adv. Synth. Catal., 2002, 344,
399; T. S. Huang and C. J. Li, Tetrahedron Lett., 2002, 43, 403.
0 Preparation of ligand 1: [cf. Y. Uozumi and Y. Nakai, Org. Lett., 2002,
In conclusion, a highly effective and stereoselective hydro-
silylation of terminal alkynes was developed under ambient
conditions of air, water, and at room temperature. Hydroxylated
alkynes could be hydrosilylated directly. In all cases except for
trimethylsilylacetylene, trans-products were obtained exclu-
sively or selectively. Synthetic applications of the reaction are
currently under investigation.
1
4
, 2997] To a three-necked 100 mL round bottomed flask, paraf-
We are grateful to NASA (NAD-1-02070/NCC3-946) and
the NSF for partial support of our research.
ormaldehyde (0.23 g, 7.1 mmol) and 20 mL of degassed methanol were
added under a flow of nitrogen gas. Then, 1.35 mL of diph-
enylphosphine were introduced to the reaction mixture via a syringe.
After the mixture was stirred at room temperature for 2 h, butylamine
Notes and references
(250 mg, 3.53 mmol) dissolved in methanol (10 mL) and toluene (20
1
Y. Hatanaka and T. Hiyama, Synlett, 1991, 845; M. E. Mowery and P.
DeShong, Org. Lett., 1999, 1, 2137; S. E. Denmark and L. Neuville,
Org. Lett., 2000, 2, 3221.
mL) was added via a syringe. The mixture was heated to 60–70 °C and
stirred overnight. Removal of all volatiles after cooling gave the product
1
as a viscous liquid (yield, 89%). H NMR (CDCl
3
, 400 MHz, ppm): d
2
3
M. C. McIntosh and S. M. Weinreb, J. Org. Chem., 1991, 56, 5010.
T. A. Blumenkopf and L. E. Overman, Chem. Rev., 1986, 86, 7; S. E.
Denmark, K. L. Habermas, G. A. Hite and T. K. Jones, Tetrahedron,
7.54–7.21 (m, 20H), 3.61 (d, J = 3.2 Hz, 4H), 2.88 (t, J = 7.6 Hz, 2H),
1.39 (m, 2H), 1.21 (m, 2H), 0.83 (t, J = 7.2 Hz, 3H). 13C NMR (CDCl
100 MHz, ppm): d 131.8, 131.7, 131.4, 131.3, 129.0, 128.9, 128.7,
3
,
3
1
1986, 42, 2821; E. J. Corey and W. L. Seibel, Tetrahedron Lett., 1986,
128.6, 56.6, 56.5, 56.4, 56.3, 28.8, 28.6, 20.6, 20.4, 14.3, 14.2.
P
+
27, 905.
(CDCl
3 2
) d 227.47. HRMS for (M 2 PPh ): calc’d. 284.1562, found
4
5
J. L. Speier, J. A. Webster and G. H. Bernes, J. Am. Chem. Soc., 1957,
9, 974.
284.1567.
7
11 A general reaction procedure follows: to a mixture of triethylsilane (1
mmol) and terminal alkyne (1 mmol) in 3 mL of water, under vigorous
stirring at room temperature, were slowly added 30 µL of Pt(DVDS)–P
complex (in xylene) [the complex was prepared by reacting Pt(DVDS)
with equimolar ligand 1 at 65 °C for 15 min]. The stirring was continued
for 3 h after complete addition of the catalyst solution. Then the reaction
mixture was extracted with ether and the solvent was removed in vacuo.
The crude product was purified by column chromatography on silica gel
(eluent: hexane–ethyl acetate) to afford the product.
For recent examples, see: F. Wang and D. C. Neckers, J. Organomet.
Chem., 2003, 665, 1; D. Motoda, H. Shinokubo and K. Oshima, Synlett,
2002, 1529; M. Martin, E. Sola, F. J. Lahoz and L. A. Oro,
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CHEM. COMMUN., 2003, 1668–1669
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