Stereoselective synthesis of (E)- and (Z)-triethoxy(vinyl-d 2)silanes by hydrosilylation of acetylene-d 2

Article abstract of DOI:10.1021/om101127t

The hydrosilylation of deuterated acetylene with triethoxysilane can be directed to the synthesis of either cis or trans triethoxy(vinyl-d ₂)silanes by an appropriate choice of metal catalyst. In addition, we have demonstrated the viability of designing hydrosilylation-arylation sequential processes in which acetylene can be converted into styrenes or stilbenes using the same Pd catalyst for both reactions.

Full text of DOI:10.1021/om101127t

352 Organometallics 2011, 30, 352–355
DOI: 10.1021/om101127t
Stereoselective Synthesis of (E)- and (Z)-Triethoxy(vinyl-d2)silanes
by Hydrosilylation of Acetylene-d2
ꢀ
Alvaro Gordillo, Johan Forigua, Carmen Lopez-Mardomingo, and Ernesto de Jesus*
ꢀ
ꢀ
´
ꢀ
Departamento de Quımica Organica and Departamento de Quımica Inorganica, Universidad de Alcala,
´
ꢀ
ꢀ
ꢀ
28871 Alcala de Henares, Madrid, Spain
Received December 1, 2010
Scheme 1
Summary: The hydrosilylation of deuterated acetylene with
triethoxysilane can be directed to the synthesis of either cis or
trans triethoxy(vinyl-d2)silanes by an appropriate choice of
metal catalyst. In addition, we have demonstrated the viability
of designing hydrosilylation-arylation sequential processes in
which acetylene can be converted into styrenes or stilbenes
using the same Pd catalyst for both reactions.
Introduction
Therefore, the unequivocal determination of the reaction
stereochemistry requires the concurrent use of two different
isotopomers, the (E)- and (Z)-triethoxy(vinyl-d2)silanes (E)/
(Z)-1-d2 (Scheme 1).
There are only a few examples on the synthesis of deuter-
ated vinylsilanes, all of which contain alkyl substituents on
the silyl moiety.6,7 In this report, we describe the synthesis of
(E)- and (Z)-1-d2, which are good examples of stereochem-
ical control by the metal catalysts in the hydrosilylation
reaction.
Organosilicon compounds are valuable intermediates in a
variety of organic transformations.1 Research carried out
in the past few years on transition-metal-catalyzed cross-
coupling reactions has resulted in aryl- and alkenylsilanes
now being considered as good alternatives to their tin or
boron analogues.2 Alkenylsilanes are especially versatile for
palladium-catalyzed arylations, and they can afford styrenes
in at least two mechanistically different modes: a Hiyama-
type arylation at the C-Si functionality or a Heck coupling
trans to the C-Si bond followed by protodesilylation.3-5
The stereochemistry of these competing routes is different,
and they should therefore be distinguishable by isotopic
labeling of the vinylic hydrogen atoms. The complete eluci-
dation of the reaction stereochemistry requires differentia-
tion of the three vinylic protons (Scheme 1). These protons
can become theoretically distributed in the final product in a
maximum of six different ways (factorial of 3). H/D labeling
of one of the three vinylic hydrogen atoms can serve to
distinguish between three of these six possible distributions.
Results and Discussion
The few examples reported to date for the synthesis of
deuterated vinylsilanes are limited in scope, are incompatible
with silicon-alkoxy bonds, and suffer from partial selec-
tivity.6,7 The metal-catalyzed hydrosilylation of alkynes
circumvents the problems associated with the use of highly
reactive organometallic reagents and presents two additional
advantages: (a) a single methodology might serve to prepare
the mono-, di-, and trideuterated (vinyl-dn)SiR3 isotopolo-
gues from the appropriate combination of reagents, in other
words acetylene or acetylene-d2, HSiR3, or DSiR3; (b) addi-
tion of the hydrosilane to the alkyne (syn or anti) might be
controlled by the nature of the catalytic system and other
reaction parameters, thus allowing the synthesis to be direc-
ted to either the E or Z isotopic stereoisomers.8
*Corresponding author. E-mail: ernesto.dejesus@uah.es.
(1) (a) Colvin, E. W. In Comprehensive Organometallic Chemistry II,
Vol. 11; Abel, E. W.; Stone, F. G. A.; Wilkinson, G., Eds.; Pergamon:
Oxford, 1995; pp 313-354. (b) Hosomi, A.; Miura, K. In Comprehensive
Organometallic Chemistry III: From Fundamentals to Applications, Vol.
9; Crabtree, R. H, Mingos, D. M. P., Eds.; Elsevier: Oxford, 2007;
pp 297-339.
(2) (a) Denmark, S. E.; Sweis, R. F. In Metal-Catalyzed Cross-
Coupling Reactions, Vol. 1, 2nd ed.; de Meijere, A, Diederich, F., Eds.;
Wiley-VCH: Weinheim, 2004; Chapter 4, pp 163-216. (b) Denmark, S. E.;
Butler, C. R. Chem. Commun. 2009, 20–33.
(3) (a) Jeffery, T. Tetrahedron Lett. 1999, 40, 1673–1676. (b) Itami, K.;
Mitsudo, K.; Kamei, T.; Koike, T.; Nokami, T.; Yoshida, J.-i. J. Am. Chem.
Soc. 2000, 122, 12013–12014. (c) Kikukawa, K.; Ikenaga, K.; Kono, K.;
Toritani, K.; Wada, F.; Matsuda, T. J. Organomet. Chem. 1984, 270, 277–
282. (d) Karabelas, K.; Hallberg, A. J. Org. Chem. 1986, 51, 5286–5290. (e)
Karabelas, K.; Hallberg, A. J. Org. Chem. 1988, 53, 4909–4914. (f)
Karabelas, K.; Hallberg, A. J. Org. Chem. 1989, 54, 1773–1776.
(4) (a) Hagiwara, E.; Gouda, K.-I.; Hatanaka, Y.; Hiyama, T.
Tetrahedron Lett. 1997, 38, 439–442. (b) Tamao, K.; Kobayashi, K.; Ito,
Y. Tetrahedron Lett. 1989, 30, 6051–6054.
We initially tested a series of prototypical Pt, Rh, Pd,
and Ru catalysts for the hydrosilylation of acetylene in neat
triethoxysilane under conditions compatible with the subse-
quent use of acetylene-d2 (a closed vessel containing a
(6) Hydrogenation of ethynyl(trimethyl)silane with dideuterium:
Marciniec, B.; Kujawa, M.; Pietraszuk, C. Organometallics 2000, 19,
1677–1681.
(7) (a) Metallation at the vinyl group followed by hydrolysis of the
metal-carbon bond with deuterium oxide: Soderquist, J. A.; Hassner,
A. J. Organomet. Chem. 1981, 217, 151–156. (b) Atagi, L. M.; Mayer, J. M.
Polyhedron 1995, 14, 113–125. (c) Alvisi, D.; Blart, E.; Bonini, B. F.;
Mazzanti, G.; Ricci, A.; Zani, P. J. Org. Chem. 1996, 61, 7139–7146.
(8) Marciniec, B. Hydrosilylation: A Comprehensive Review on Recent
Advances; Springer: Berlin, 2009.
ꢀ
ꢀ
ꢀ
(5) (a) Gordillo, A.; de Jesus, E.; Lopez-Mardomingo, C. Chem. Com-
ꢀ
ꢀ
mun. 2007, 4056–4058. (b) Gordillo, A.; de Jesꢀus, E.; Lopez-Mardomingo, C.
J. Am. Chem. Soc. 2009, 131, 4584–4585.
r
pubs.acs.org/Organometallics
Published on Web 12/22/2010
2010 American Chemical Society

Note
Table 1. Hydrosilylation of Acetylene with Triethoxysilanea
Organometallics, Vol. 30, No. 2, 2011 353
Scheme 2. Sequential Hydrosilylation/C-C Coupling Reactions
Catalyzed by a Single Loading of the Pd Catalyst
yield (%)c
entry
catalyst
H2PtCl6
Karstedt
conditionsb
1
3
4
5
1
2
3
4
5
0.2 mol %, 25 °C, 3 h
0.2 mol %, 25 °C, 3 h
0.2 mol %, 5 °C, 6 h
0.2 mol %, 5 °C, 6 h
0.2 mol %, 5 °C, 6 h
0.1 mol %, 25 °C, 18 h
0.5 mol %, 25 °C, 18 h
0.2 mol %, 25 °C, 18 h
1 mol %, 120 °C, 24 h
1 mol %, 120 °C, 24 h
0.2 mol %, 120 °C, 24 h
49
39
70
70
76
74
54
5
7
2
4
4
7
6
19
30
10
15
13
8
7
3
7
6
H2PtCl6
Karstedt
[PtCl2(COD)]
Table 2. Hydrosilylation of Acetylene-d2 with Triethoxysilanea
6d,e [{RhCl(COD)}2]
7e
8d
9
[Rh(COD)2]BF4
[RhCl(PPh3)3]
Pd(OAc)2
10
11
[Pd2(dba)3]
[PdCl2(PPh3)2]
90
12e [PdCl2(PPh3)2]
0.02 mol %, 120 °C, 24 h 27
0.02 mol %, 120 °C, 24 h 93
0.001 mol %, 120 °C, 24 h 71
entry
catalyst
conditions
E:Z (%)b
13
[PdCl2(PTA)2]
14e [PdCl2(PTA)2]
1
2
3
4
5
6
[{RhCl(COD)}2]
[Rh(COD)2]BF4
Karstedt
[PdCl2(PPh3)2]
[PdCl2(PTA)2]
0.2 mol %, 25 °C, 18 h
0.2 mol %, 25 °C, 18 h
0.2 mol %, 5 °C, 6 h
97
97
94
88
93
7
3
3
6
12
7
93
15
[Cp*Ru(MeCN)3]PF6 1 mol %, 25 °C, 2 h
95
a Reaction conditions: HSi(OEt)3 (5.0 mmol), C2H2 (ca. 10.0 mmol).
See the Experimental Section for more details. All the conversions were
100% with respect to silane, except as otherwise stated. b Catalyst
concentration based on metal atoms. c Yields were determined by 1H
NMR analysis of the crude product. d NaI (0.25 mmol) was added.
e Partial conversion.
0.2 mol %, 120 °C, 24 h
0.2 mol %, 120 °C, 24 h
[Cp*Ru(MeCN)3]PF6 1 mol %, 25 °C, 2 h
a See Table 1 and Supporting Information for other reaction condi-
tions. b Determined by H NMR spectroscopy from integration of the
1
vinylic protons. For an accurate determination, the 13C satellites of the E
vinylic proton were used for integration in entries 1 and 2.
preloaded amount of acetylene at a pressure of around 1.5-2
bar measured at room temperature; see Supporting Informa-
tion for more details). Platinum catalysts afforded large
amounts of the usual side-products obtained during the
hydrosilylation of acetylene (3-5; Table 1, entries 1-5),
even at low temperatures. The conversions achieved with the
phosphane-free rhodium(I) complexes were lower, but for-
mation of the saturated products 4 and 5 was not observed
(Table 1, entries 6 and 7). Wilkinson’s catalyst was inactive
under these conditions (Table 1, entry 8), as were the
phosphane-free palladium compounds (Table 1, entries 9 and
10), probably due to hydrosilane-induced catalyst decomposi-
tion to Pd black.8 Remarkably, formation of the side-products
3-5 was suppressed when PPh3 or PTA (PTA = 1,3,5-triaza-7-
phosphaadamantane) complexes of palladium(II) (Table 1,
entries 11-14) or [Cp*Ru(MeCN)3]PF6 (Table 1, Cp* =
C5Me5, entry 15) were employed as catalysts.
The case of the Pd catalysts should be highlighted at this
point, as this metal is used more often for the hydrosilylation
of alkenes than alkynes. Furthermore, the turnover numbers
of up to 71 000 obtained with [PdCl2(PTA)2] (Table 1, entry
14) are particularly high for palladium9 and similar to those
described in the patent literature for platinum catalysts in
similar processes.10 This Pd catalyst may therefore be of
practical interest for the design of sequential processes in
which hydrosilylation is followed by a Pd-catalyzed trans-
formation of the alkenylsilane intermediate without the need
for a previous isolation. Many examples of hydrosilylation/
C-C coupling sequences have been published, although, to
the best of our knowledge, all these examples use different
catalysts for the hydrosilylation (usually Pt, Rh, or Ru) and
C-C bond-formation (Pd) steps.11,8 The potential of our
PTA-Pd complex in this respect is illustrated by the hydro-
silylation-single or double arylation sequences shown in
Scheme 2, where a single Pd loading of 0.02 mol % allows
acetylene to be converted into styrene 6 or stilbene 7 in high
yields. Moreover, the latter compound was isolated simply
by filtering the aqueous solution.5a
We subsequently applied the most efficient combinations
of catalyst and reaction conditions to the hydrosilylation of
acetylene-d2 (Table 2). [Cp*Ru(MeCN)3]PF6 was the only
catalyst to give a preferential net trans addition of the H-Si
bond to the acetylene, affording a 93:7 mixture of the Z and
E stereoisomers (Table 2, entry 6). In contrast, the COD rho-
dium complexes gave the E isomer with the highest selectivity
(97%; Table 2, entries 1 and 2). The E isomer is the product of
the cis silylmetalation initially expected in the widely accepted
Chalk-Harrod hydrosilylation mechanism,12 although the
possibility of an isomerization step was subsequently intro-
duced to justify the predominant trans hydrosilylation observed
under some circumstances.13 Trost and Ball have, however,
shown that [Cp*Ru(MeCN)3]PF6 is a general trans addition
(11) An example has been described in which a single bimetallic
Rh-Pd catalyst is used in a hydrosilylation/Hiyama cross-coupling
sequence: Thiot, C.; Schmutz, M.; Wagner, A.; Mioskowski, C.
Chem.;Eur. J. 2007, 13, 8971–8978.
(12) (a) Chalk, A. J.; Harrod, J. F. J. Am. Chem. Soc. 1965, 87, 16–21.
(b) Harrod, J. F.; Chalk, A. J. J. Am. Chem. Soc. 1965, 87, 1133–1133.
(13) (a) Ojima, I.; Clos, N.; Donovan, R. J.; Ingallina, P. Organo-
metallics 1990, 9, 3127–3133. (b) Tanke, R. S.; Crabtree, R. H. J. Am. Chem.
Soc. 1990, 112, 7984–7989.
(9) (a) Watanabe, H.; Asami, M.; Nagai, Y. J. Organomet. Chem.
1980, 195, 363–373. (b) Motoda, D.; Shinokubo, H.; Oshima, K. Synlett
2002, 1529–1531. (c) Kim, D. H.; Park, Y.-a. W. Bull. Korean Chem. Soc.
2006, 27, 27–28.
(10) (a) Preiss, T.; Friedrich, H.; Henkelmann, J. Patent EP1174433,
Mar 23, 2002. (b) Suzuki, E.; Okamoto, M.; Tajima, S.; Suzuki, H.; Harada,
K. Patent WO2003024979, Mar 27. 2003. (c) Okamoto, M.; Kiya, H.;
Yamashita, H.; Suzuki, E. Chem. Commun. 2002, 1634–1635.

354 Organometallics, Vol. 30, No. 2, 2011
Gordillo et al.
synthesized as reported elsewhere.16 All other reagents and
solvents (synthesis grade) were obtained from commercial
1
sources and used as received. H and 13C NMR spectra were
recorded with a Varian Mercury 300, Unity 300, or Unity 500
Plus spectrometer. Chemical shifts (δ, ppm) are quoted relative
to SiMe4 and were measured by internal referencing to the
1
deuterated solvent (13C or residual H resonances). Coupling
constants (J) are given in hertz. The Analytical Services of the
ꢀ
Universidad de Alcala recorded the EI mass spectra with a
Thermo Scientific ITQ 900 spectrometer.
General Procedure for the Hydrosilylation of Acetylene. A
mixture of the appropriate catalyst (see below) and triethoxysi-
lane (0.97 mL, 5.00 mmol) was stirred for 30 min under an argon
atmosphere in a 125 mL pressure tube fitted with a Young valve
at 0 °C (25 °C for entries 9-14). Acetylene (ca. 300 mg, 11.5
mmol) was then introduced into the pressure tube as follows.
First, a 250 mL Schlenk tube was filled with acetylene at room
temperature and a pressure of 1 bar. The 125 mL pressure tube
was evacuated for a few seconds to avoid significant triethoxy-
silane evaporation and then cooled with liquid nitrogen. Finally,
the pressure tube and the Schlenk tube were connected to
one another to allow the acetylene to condense in the pressure
tube. Once the acetylene transfer was complete (ca. 1 min), the
pressure tube was disconnected, and the reaction continued at
the temperature and for the time indicated in Table 1. The tube
was then allowed to reach room temperature. The crude reaction
mixture was analyzed by 1H NMR spectroscopy, and the yields
of each product were obtained from the relative integration of
the ethenyl (1), ethenediyl (3), ethanediyl (4), or ethyl protons (5)
with respect to the ethoxy resonances.
Figure 1. 1H and 2H resonances of (E)- and (Z)-1-d2 in the
vinylic region.
catalyst whose peculiar behavior does not follow a Chalk-
Harrod-type mechanism.14,15
The (E)- and (Z)-1-d2 compounds have been characterized
by 1H, 2H, and 13C NMR spectroscopy and EI-MS spectro-
metry. The 1H and 2H resonances of their vinylic regions are
shown in Figure 1. The 1H and 2H chemical shifts observed
for the vinylic hydrogen nuclei match those of the corre-
sponding protons in the nondeuterated vinylsilane 1. On the
other hand, the observed HD couplings [∼3.1 Hz for H-
D(trans) in the E isomer and ∼2.3 Hz for the H-D(geminal)
in the Z isomer] are also in agreement with the J(HH) values
observed for 1 (20.8 and 13.8 Hz, respectively). Other charac-
terization details can be found in the Experimental Section
and Supporting Information.
Catalysts: entries 1 and 3: [H2PtCl6] xH2O (40.39% Pt con-
3
tent, 4.8 mg, 10 μmol); entries 2 and 4: [Pt2{O(SiMe2CHd
CH2)2}3] as a 0.1 M solution (based on Pt) in poly(dimethyl-
siloxane) (Karstedt catalyst, 0.10 mL, 10 μmol); entry 5:
[PtCl2(COD)] (3.7 mg, 10 μmol); entry 6: [{RhCl(COD)}2] (2.5
mg, 5.0 μmol) and NaI (37.5 mg, 0.25 mmol); entry 7: [Rh-
(COD)2]BF4 (10.2 mg, 25.0 μmol); entry 8: [RhCl(PPh3)3] (9.3
mg, 10 μmol) and NaI (37.5 mg, 0.25 mmol); entry 9: [Pd(OAc)2]
(11.2 mg, 50 μmol); entry 10: [Pd2(dba)3] (45.8 mg, 50.0 μmol);
entry 11: [PdCl2(PPh3)2] (7.0 mg, 10 μmol); entry 12: [PdCl2-
(PPh3)2] (0.70 mg, 1.0 μmol); entry 13: [PdCl2(PTA)2] (0.50 mg,
1.0 μmol); entry 14: [PdCl2(PTA)2] (0.025 mg, 0.05 μmol); entry
15: [Cp*Ru(MeCN)3]PF6 (25.2 mg, 50.0 μmol).
Conclusion
In summary, we have shown how the hydrosilylation of
(deuterated) acetylene can be directed toward the prepara-
tion of silanes bearing deuterated vinyl groups with the desired
stereochemistry. This provides a general tool for the elucida-
tion of mechanisms implying vinylsilanes. Incidentally, we
have demonstrated the viability of designing hydrosilylation-
arylation sequential processes in which acetylene can be con-
verted into styrenes or stilbenes using the same Pd catalyst for
both reactions. Additional experimental work is ongoing trying
to extend the synthetic utility of these Pd-catalyzed sequential
processes.
Procedure for the Pd-Catalyzed Sequential Hydrosilylation-
Vinylation Reactions. A solution of [PdCl2(PTA)2] (0.40 mg,
0.8 μmol) and triethoxysilane (0.77 mL, 4.00 mmol) was stirred
for 30 min at 25 °C under an argon atmosphere in a 125 mL
pressure tube fitted with a Young valve. Acetylene (ca. 300 mg,
11.5 mmol) was then introduced into the pressure tube as de-
scribed above, and the reaction continued for 24 h at 120 °C. The
reaction mixture was then allowed to cool to room temperature,
and the yield on 1 (93%) estimated by 1H NMR. Compounds 6
and 7 were synthesized from this crude product as follows.
Compound 6. 4-Bromoacetophenone (0.2031 g, 1.00 mmol),
PEG 2000 (2.4 g), and a 0.5 M aqueous solution of NaOH
(12.0 mL) were added to the 125 mL pressure tube containing
the crude product 1. The reaction mixture was stirred for 5 h
at 140 °C, then allowed to cool to room temperature and
extracted with ethyl acetate (3 ꢀ 20 mL). The combined organic
layers were dried over MgSO4, and after filtration, the solvent
was eliminated in a rotary evaporator connected to a water
aspirator pump. The product was purified to analytical grade
by flash chromatography with hexane/ethyl acetate (6:1)
(Rf = 0.30) on silica gel. Compound 6 was obtained as a
colorless oil (0.133 g, 91%). See the Supporting Information
for NMR data.
Experimental Section
General Experimental Procedures. All reactions were carried
out in air using conventional pressure tubes fitted with a Young
valve. THF was purified by flash column chromatography and
collected under argon, using an MBraun MB SPS solvent
purification device. Deionized water (type II quality) was ob-
tained using a Millipore Elix 10 UV water purification system.
[PdCl2(PTA)2] (PTA=1,3,5-triaza-7-phosphaadamantane) was
(14) Trost, B. M.; Ball, Z. T. J. Am. Chem. Soc. 2005, 127, 17644–
17655.
(15) A mechanism has been proposed in which the oxidative addition
of the hydrosilane is concerted with hydride insertion: Chung, L. W.;
Wu, Y.-D.; Trost, B. M.; Ball, Z. T. J. Am. Chem. Soc. 2003, 125, 11578–
11582.
Compound 7. 4-Bromoacetophenone (0.2031 g, 1.00 mmol),
0.6 equiv of the crude product 1 (0.13 g, 0.6 mmol assuming a
purity of 93%), and a 0.5 M aqueous solution of NaOH (5.0 mL)
were added to a 15 mL Ace pressure tube. The reaction mixture
(16) Alyea, E. C.; Ferguson, G.; Kannan, S. Polyhedron 1998, 17,
2727–2273.

Note
Organometallics, Vol. 30, No. 2, 2011 355
was stirred for 24 h at 120 °C and then allowed to cool to room
temperature. Stilbene 7 was isolated as a white solid by simple
filtration of the aqueous solution at room temperature. The
product can be purified to analytical grade by flash chromatog-
raphy with hexane/ethyl acetate (6:1) (Rf = 0.35) on silica gel
(0.1295 g, 98%). See the Supporting Information for NMR
data.
(E)-Triethoxy(vinyl-d2)silane, (E)-1-d2. (E)-1-d2 was obtained
as a colorless oil in 52% yield and with 97% stereoselectivity
after distillation (1H NMR evidence) using the conditions of
entry 1 (see Figures S1 and S2 in the Supporting Information for
13C and 2H NMR spectra). 1H NMR (CDCl3, 300 MHz): δ 1.21
(t, 3JHH = 6.9 Hz, 9 H; CH3), 3.81 (q, 3JHH = 6.9 Hz, 6 H; CH2),
5.97 (1:1:1 triplet, 3JHD = 3.0 Hz, 1 H; CHD). 2H NMR (CDCl3,
77 MHz): δ 6.16 (s, 1 D; CHD), 5.93 (d, 3JDH=3.1 Hz, 1 D; CDSi).
13C{1H} NMR (CDCl3, 75 MHz): δ 18.2 (CH3), 58.5 (CH2), 128.7
Synthesis of (E)- and (Z)-Triethoxy(vinyl-d2)silane. We fol-
lowed the general procedure described above for the hydrosilyla-
tion of nondeuterated acetylene starting from triethoxysilane
(0.97 mL, 5.00 mmol) and acetylene-d2 (190 mL at ca. 1.7 bar,
13 mmol). Acetylene-d2 was obtained from CDN isotopes (http://
www.cdnisotopes.com/) and transferred directly from the cylinder
containing 1 L of gas at 1 bar of pressure to three 190 mL pre-
ssure tubes so that three different experiments could be carried
out in parallel. Thus, the three reaction tubes containing the
silane and the catalyst under vacuum were connected simulta-
neously to the cylinder and cooled with liquid nitrogen as ex-
plained above. Once condensation of acetylene-d2 into the pre-
ssure tubes was complete (approximately 1 min), the cylinder
valve was closed and the tubes were allow to reach room tem-
perature, before disconnecting, to equilibrate their gas pressures.
The specific conditions employed for each experiment are de-
scribed in Table 2. The crude product was purified by dis-
tillation under vacuum (ca. 0.15 mbar) at room temperature to a
trap cooled with liquid nitrogen. The silanes were characterized by
NMR spectroscopy.
(1:1:1 triplet, 1JCD = 21.7 Hz; CDSi), 136.7 (1:1:1 triplet, 1JCD
23.6 Hz; CHD). EI-MS (70 eV): m/z (%) 193.05 [Mþ].
=
(Z)-Triethoxy(vinyl-d2)silane, (Z)-1-d2. (Z)-1-d2 was obtained
as a colorless oil contaminated with 7% of the E isomer using the
conditions of entry 6 (see Figures S3 and S4 in the Supporting
Information for 13C and 2H NMR spectra). 1H NMR (CDCl3,
300 MHz): δ 1.21 (t, 3JHH = 6.9 Hz, 9 H; CH3), 3.81 (q, 3JHH
=
6.9 Hz, 6 H; CH2), 6.07 (1:1:1 t, 3JHD = 2.31 Hz, 1 H; CHD). 2H
=
NMR (CDCl3, 77 MHz): δ 6.03 (s, 1 D; CHD), 5.93 (d, 3JDH
3.1 Hz, 1 D; CDSi). 13C{1H} NMR (CDCl3, 75 MHz): δ 18.17
(CH3), 58.47 (CH2), 128.69 (1:1:1 t, JCD = 21.7 Hz; CDSi),
1
136.66 (1:1:1 t, 1JCD = 23.6 Hz; CHD). EI-MS (70 eV): m/z (%)
193.05 (12) [Mþ].
Acknowledgment. We gratefully acknowledge finan-
ꢀ
cial support by the Ministerio de Ciencia e Innovacion
(CTQ2008-02918/BQU). We also thank the Ministerio de
ꢀ
Educacion y Ciencia for a FPU Fellowship to A.G. and
Catalysts: Entry 1: [{RhCl(COD)}2] (2.5 mg, 5.0 μmol) and
NaI (37.5 mg, 0.25 mmol); entry 2: [Rh(COD)2]BF4 (10.2 mg,
25.0 μmol); entry 3: 0.1 m of the Karstedt catalyst in poly-
(dimethylsiloxane) ([Pt2{O(SiMe2CHdCH2)2}3], 0.10 mL, 10
μmol); entry 4: [PdCl2(PPh3)2] (7.0 mg, 10.0 μmol); entry 5:
[PdCl2(PTA)2] (1.0 mg, 2.0 μmol); entry 6: [Cp*Ru(MeCN)3]-
PF6 (25.2 mg, 50.0 μmol).
ꢀ
Fundacion Carolina for a Fellowship to J.F.
Supporting Information Available: 1H and 13C{1H} NMR
2
data for compounds 1, 6, and 7 and H and 13C{1H} NMR
spectra for (E)- and (Z)-1-d2 are available free of charge via the
Internet at http://pubs.acs.org.