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16). Very high alpha selectivity (94%) could also be obtained with trimethylacetylene (entry 10). Similar alpha
selectivity has been reported previously for a Pd(PPh3)2Cl2-catalyzed hydrostannylation [12,13]. With the other
alkynes, including allyl propargyl ether (entry 12), benzyl propargyl ether (entry 14), 1-ethynylcyclohexan-1-ol (entry
15), propargyl alcohol (entry 20) and 3-butyn-1-ol (entry 22), interestingly, almost complete or complete trans
vinyltriphenylsilane products were obtained. It is not quite clear what caused this selectivity change at the moment.
The oxygen atom in the substrate might be responsible for this observation. Finally, in common with most
hydrosilylation of alkynes, the presence of a hydroxyl or alkenyl group can tolerate in this protocol (entries 11, 12 and
17–22).
In conclusion, a highly effective and regio- and stereoselective hydrosilylation of terminal alkynes was developed
by using the Pt(DVDS)–P(t-Bu)3 complex as catalyst. In most cases, only trans products or alpha products were
obtained exclusively or selectively.
1. Experimental
A xylenes solution of Pt(DVDS) and P(t-Bu)3 were obtained from Aldrich. 1H and 13C NMR spectra were recorded
on a Varian Unity 400 or 300 MHz spectrometer. 1H NMR spectra are referenced to the residual CHCl3 peak (d 7.27) in
CDCl3, and 13C NMR spectra are referenced to CDCl3 (d 77.23). GC–MS data were recorded on a Varian Saturn 2100
GC/MS System. Combustion analyses were performed on a PE 2400 elemental analyzer.
1.1. In situ synthesis of metal complexes
To a xylenes solution of Pt(DVDS) (1 mL containing 2% Pt) was added P(t-Bu)3 (1.0 equiv. per Pt). The mixture
was stirred at 65 8C for 10 min, and cooled to room temperature. This solution was stored under argon and used within
1 month.
1.2. Reaction of 1-heptyne with 1,1,3,3-tetrmethyldisiloxane
To 1-heptyne (2 mmol) solution of THF (0.5 mL) was added 1,1,3,3-tetrmethyldisiloxane (1 mmol) under argon.
The reaction mixture was stirred at 20 8C for 30 min after addition of the catalyst (1 mol.%). The crude reaction
mixture was concentrated in vacuum and was purified by column chromatography on silica gel column. (GC–MS:
retention time for the isomeric products from hydrosilylation of 1-heptyne with 1,1,3,3-tetramethyldisiloxane (min):
Z,Z: 12.0; Z,E: 12.11, E,E: 12.27; Z,a: 12.39; E,a: 12.5)
1.3. General procedure for the hydrosilylation reactions
To an alkyne (1 mmol) solution of THF (1 mL) was added silane (1.1 equiv.) under argon. And the reaction mixture
was stirred at 20 8C for 20–30 min after addition of the catalyst (1 mol.%). The crude reaction mixture was
concentrated in vacuum and was purified by column chromatography on silica gel column.
1.4. (E,E)-1,1,3,3-tetramethyl-1,3-bis(1-heptenyl)disiloxane
1H NMR (CDCl3, 400 MHz): d 0.12 (s, 12H), 0.90 (t, 6H, J = 8.8 Hz), 1.28–1.43 (m, 12H), 2.08–2.14 (m, 4H), 5.61
(dt, 2H, J = 18.7, 1.3 Hz), 6.11 (dt, 2H, J = 18.7 Hz, 6.2 Hz). 13C NMR (CDCl3, 100 MHz): d 1.1, 14.3, 22.8, 28.5,
31.7, 36.8, 129.5, 148.3. Anal. Calcd. for C18H38OSi2: C, 66.18; H, 11.73. Found: C, 65.84; H, 11.98.
References
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