Regiochemical aspects of the platinum oxide catalyzed hydrosilylation of alkynes

Article abstract of DOI:10.1055/s-2007-983742

The platinum-catalyzed hydrosilylation of unsymmetrical substituted arylalkynes with various hydrosilanes was investigated and the reaction selectivity of various para-substituted substrates was compared with that of their corresponding orthosubstituted derivatives. We showed that heterogeneous platinum oxide is a very efficient catalyst for such hydrosilylations and that H-Si bond addition proceeds in a stereoselective cis-fashion. The regioselectivity was found to be under the control of the ortho-substituent rather than due to the nature of the platinum catalyst. Arylalkynes with an ortho-substituent provided predominantly to exclusively α-selectivity, regardless of the electronic nature of the substituent. The precise contributions of steric, electronic, and coordinative factors controlling the regioselectivity of the H-Si bond addition are discussed. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1055/s-2007-983742

SPECIAL TOPIC
2025
Regiochemical Aspects of the Platinum Oxide Catalyzed Hydrosilylation of
Alkynes
Regiochemical
As
b
pects of the
P
d
latinum
O
xi
a
de
C
atalyze
l
d Hydr
l
osilyla
a
tion of
A
lk
h
ynes Hamze, Olivier Provot, Jean-Daniel Brion, Mouâd Alami*
Laboratoire de Chimie Thérapeutique, BioCIS – CNRS (UMR 8076), Univ. Paris Sud XI, Faculté de Pharmacie, rue J. B. Clément,
92296 Châtenay-Malabry Cedex, France
Fax +33(1)46835828; E-mail: mouad.alami@u-psud.fr
Received 20 February 2007
With terminal alkynes (R2 = H), industrial catalysts such
Abstract: The platinum-catalyzed hydrosilylation of unsymmetri-
as Speier’s catalyst (H2PtCl6) and Karstedt’s catalyst
[Pt2(dvtms)3; dvtms = divinyltetramethyldisiloxane] have
the advantages of excellent turnover numbers, however,
cal substituted arylalkynes with various hydrosilanes was investi-
gated and the reaction selectivity of various para-substituted
substrates was compared with that of their corresponding ortho-
substituted derivatives. We showed that heterogeneous platinum the selectivity observed when using these catalysts is usu-
ally low.5 The platinum–phosphine complexes
oxide is a very efficient catalyst for such hydrosilylations and that
H–Si bond addition proceeds in a stereoselective cis-fashion. The
regioselectivity was found to be under the control of the ortho-sub-
tion but the reactivity decreases in the order H2PtCl6 >
stituent rather than due to the nature of the platinum catalyst. Aryl-
[PtCl2(PPh3)2] and [Pt(PPh3)4] also catalyze hydrosilyla-
PtCl2(PPh3)2 > Pt(PPh3)4. Platinum complexes with bulky
alkynes with an ortho-substituent provided predominantly to
phosphine ligands (e.g., [Pt(PCy3)], [Pt(Pt-Bu3)]) show
improved b-regioselectivity.6 Recently, the use of N-het-
erocyclic carbene platinum(0) complexes has produced
good b-selectivity allowing the synthesis of E-vinyldisil-
oxanes.7 Excellent yields and b-selectivity can also be
achieved by using ligand-free platinum catalysts (Pt/C, Pt/
silica gel)8,9 providing a significant cost advantages over
homogeneous and elaborate platinum complexes. If solu-
tions to the problems associated with the hydrosilylation
of terminal alkynes mediated by platinum catalysts are
satisfactory in favor of the b-isomers, the reaction with
unsymmetrical internal alkynes, particularly those with
one or two aromatic rings, has received scant attention,8
probably because of the difficulty in controlling the re-
gioselectivity of the H–Si bond addition. Therefore, the
search for new selective procedures and more selective
catalysts presents an interesting challenge.
exclusively a-selectivity, regardless of the electronic nature of the
substituent. The precise contributions of steric, electronic, and co-
ordinative factors controlling the regioselectivity of the H–Si bond
addition are discussed.
Key words: hydrosilylation, platinum oxide, vinylsilane, alkyne
Alkenylsilanes are a class of organosilicon compounds
commonly used in organic synthesis.1 The lack of toxici-
ty, high chemical stabilities, and low molecular weight of
organosilanes make them ideal compounds for palladium-
catalyzed cross-coupling reactions. Therefore, there has
been a great impetus to assemble vinylsilanes in a rapid,
selective, and atom-economical fashion.2 The hydrosily-
lation of alkynes remains the simplest and most straight-
forward method for their preparation.3 The main difficulty
with this transformation concerns the control of both the
stereo- and regiochemistry of the alkenylsilane products.
Metal-mediated H–Si bond addition to alkynes is com-
monly employed for this purpose and it is well known to
occur in a stereoselective manner.4 A large number of
transition metals have been used (e.g., Pd, Pt, Rh, Ru,
etc.). Of these, platinum catalysts, which tolerated a wide
range of functional substituents, hold certain supremacy
and they are now routinely used for the cis-hydrosilylation
of alkynes. Two regioisomers, a and b, can be formed
(Scheme 1) and their ratio changes depending on the plat-
inum catalyst, the alkyne, and the silane employed.
It is well known that the regioselectivity of metalloid hy-
dride addition to alkynes is governed by electronic and
steric factors as well as chelating considerations.3 Previ-
ously, we described the palladium-catalyzed hydrostanna-
tion of aryl-substituted alkynes.10 We demonstrated that
ortho substituents on one side of the two aromatic rings
directed the regioselectivity of H-Sn bond addition what-
ever the electronic nature of the substituent. It occurred to
us that this unprecedented ortho-directing effect could be
extended to control the regiochemistry of the platinum-
catalyzed hydrosilylation of internal aryl-substituted
alkynes. Herein, we wish to detail our results11 towards
the platinum oxide catalyzed hydrosilylation of internal 1-
arylalk-1-ynes as well as diarylacetylenes to provide
trisubstituted vinylsilanes of defined stereochemistry. The
selectivity issues of this reaction mediated by platinum
oxide have been studied extensively and contributions of
steric, electronic, and coordinative factors controlling this
regioselectivity are discussed.
R1
R2
R1
R2
α
β
H-SiY3
[Pt]
R1
R2
+
Y3Si
H
H
SiY3
α-isomer
β-isomer
Scheme 1
SYNTHESIS 2007, No. 13, pp 2025–2036
x
x.
x
x
.
2
0
0
7
Advanced online publication: 18.06.2007
DOI: 10.1055/s-2007-983742; Art ID: C02507SS
© Georg Thieme Verlag Stuttgart · New York

2026
A. Hamze et al.
SPECIAL TOPIC
α
β
Hydrosilylation of 1-Arylalk-1-ynes
H-SiY3
C5H11
[Pt], neat
60 °C, 1 h
R
1
In our initial screening experiments, ethyl 4-hept-1-ynyl-
benzoate (1a) (Scheme 2) was used as a model substrate
to evaluate the effects of various platinum catalysts and
the results are summarized in Table 1. The addition of tri-
ethylsilane (1.5 equiv) to 1a was examined in the presence
of platinum complexes (5 mol%) at 60 °C without sol-
vent. With the exception of tetrakis(triphenylphos-
phine)platinum(0) (entry 1), all the ligand-free platinum
catalysts examined were found to be active in the cis-hy-
drosilylation of 1a, providing a- and b-isomers with
markedly similar selectivity and efficiency (entries 2–5).
R
C5H11
C5H11
R
+
Y3Si
SiY3
3
β-isomer
2
α-isomer
Scheme 2
The triple bond polarization induced by a para p-electron- To compare the catalytic activities of platinum oxide and
withdrawing group resulted mainly in a-selectivity as ob- platinum(II) chloride versus the metal-catalyzed hydrosi-
served in the hydrostannation reaction.10a Performing the lylation reaction, we tested a series of other catalysts, in-
reaction in tetrahydrofuran had no significant change on cluding Pd2(dba)3, Pd/C, NiCl2(PPh3)2, RhCl(PPh3)3,
the a-regioselectivity (a/b 82:18), but the yield of the re- Grubbs’ I, and RuHCl(CO)(PPh3)3. With the exception of
action decreased significantly (65% cf. 92%, entry 5). Hy- palladium on carbon, which gave a mixture of compounds
drosilylation of ethyl 2-hept-1-ynylbenzoate (1b) was resulting from the reduction of the triple bond, the use of
next investigated to determine the impact of the ortho sub- other catalysts did not promote any transformation.
stituent on the regioselectivity. We were pleased to find
that the reaction also occurred in a syn-fashion affording
exclusively a single a-isomer (entries 7–10) still demon-
strating the ortho-directing effect concept. In contrast to
As the nature of the hydrosilane can impact the reaction
selectivity,8 we next examined the hydrosilylation of
alkynes 1a,b with a series of hydrosilanes. The results are
summarized in Table 2.
platinum oxide or platinum(II) chloride, the use of
Reactions of 1a and 1b carried out with silanes gave sim-
hexachloroplatinic acid or platinum on carbon catalysts
ilar yields ranging from 82% [(EtO)Me2SiH] to 96%
(entries 7 and 8), however, furnished a notable amount of
(PhMe2SiH) and 70% [(EtO)3SiH] to 94% (EtOMe2SiH),
the reduced side product, which was formed from a com-
respectively. Moreover, all the hydrosilanes examined
peting platinum-catalyst-catalyzed direct semi-reduction
with 1a showed comparable a-selectivity (entries 1–5).
With alkyne 1b, the ortho-substituent regiocontrol effect
again provided significant a-isomer preference except in
the case of (EtO)3SiH (entry 9). The most efficient silane
is triethylsilane, leading to exclusive formation of the a-
isomer. In contrast with the literature,8 significantly it
seems that the distribution of a/b-adducts in the platinum
of the alkyne bond.12 Consequently, reaction in the pres-
ence of this heterogeneous catalyst proved to be high
yielding (cf. entries 9 and 10). In addition, platinum oxide,
which is less expensive than platinum(II) chloride, is eas-
ily removed from the reaction medium by simple filtra-
tion. Therefore, it was used as a catalyst of choice in the
continuation of this study.
Table 1 Hydrosilylation with Triethylsilane (Y = Et) of Substituted 1-Arylhept-1-ynes 1a,b Using Various Platinum Catalysts
Entry
Alkyne
Platinum catalyst
Ratioa 2/3 (a/b)
Yieldb (%)
1
2
3
4
5
Pt(PPh3)4
H2PtCl6
Pt/C
PtCl2
PtO2
–
0
87c
91c
88c
92c
EtO2C
C5H11
84:16
80:20
83:17
83:17
1a
6
7
8
9
10
Pt(PPh3)4
H2PtCl6
Pt/C
PtCl2
PtO2
–
0
70e
ndf
72
100:0d
100:0d
100:0
100:0
C5H11
COOEt
90
1b
a The product distribution was determined by 1H NMR on the crude reaction mixture.
b Isolated yield.
c Isolated yield of an inseparable mixture of a- and b-isomers.
d Contaminated with the corresponding alkene resulting from semi-reduction of the alkyne 1b.
e Isolated yield of pure 2b after flash column chromatography.
f Not determined.
Synthesis 2007, No. 13, 2025–2036 © Thieme Stuttgart · New York

SPECIAL TOPIC
Regiochemical Aspects of the Platinum Oxide Catalyzed Hydrosilylation of Alkynes
2027
Table 3 Hydrosilylation with Triethylsilane (Y = Et) of Various
Substituted 1-Arylhept-1-ynes 1 Using Platinum Oxide Catalyst
Table 2 Platinum Oxide Catalyzed Hydrosilylation of Substituted
1-Arylhept-1-ynes 1a,b Using Various Silanes
Entry Alkyne Hydrosilane H-SiY3 Ratioa 2/3 (a/b) Yieldb (%)
Entry
Ratioa 2/3
(a/b)
Yieldb (%)
R
C5H11
1
2
3
4
5
1a
Et3SiH
83:17
80:20
77:23
88:12
67:33
92
96
88
85
82
PhMe2SiH
Ph2MeSiH
(EtO)3SiH
(EtO)Me2SiH
1
c
d
e
f
R
1
2
H
65:35
97:3
71
83
62
95
92
90
82
68
90
80
82
NO2
CHO
CF3
CO2Et
Br
6
7
8
9
10
1b
Et3SiH
100:0
95:5
93:7
75:25
95:5
90c
85
90
70
94
3
85:15
84:16
83:17
82:18
65:35
73:27
77:23
70:30
78:22
PhMe2SiH
Ph2MeSiH
(EtO)3SiH
(EtO)Me2SiH
4
5
a
g
h
i
a The product distribution was determined by 1H NMR on the crude
reaction mixture.
6
b Isolated yield of an inseparable mixture of a- and b-isomers.
c Isolated yield of 2b.
7
Me
8
i-Pr
9
j
CH2OAc
OMe
oxide catalyzed hydrosilylation of 1-arylalk-1-ynes does
not depend on the silane employed.
10
11
k
l
OAc
Next we examined the hydrosilylation of various para-
substituted 1-arylhept-1-ynes 1a,d–l as well as their cor-
responding ortho-substituted derivatives 1b,m–u and the
selectivity issues were compared (Table 3).
C5H11
R
In order to establish a baseline regioselectivity control, the
reaction was first examined with the nonsubstituted
alkyne 1c and the H–Si bond addition occurred leading to
a mixture of vinylsilanes 2c and 3c in a 65:35 ratio (entry
1). This trend in a-selectivity is more marked with para-
substituted 1-arylhept-1-ynes bearing a p-electron-with-
drawing group, which induces strong polarization of the
C≡C bond (entries 2–6). Accordingly, less a-regioselec-
tivity was observed when switching to substrates 1h–l
with a para s-electron-donating group (entries 7–11). The
results in Table 3 exhibit how changing the position of the
substituent on the aromatic ring (from para to ortho) can
affect the product distribution. Total a-regioselectivity is
achieved with p-electron-withdrawing ortho-substituted
1-arylhept-1-ynes 1b,m–p, producing the vinylsilanes
2b,m–p and no observable b-isomers 3 (entries 12–16).
Similarly, we were pleased to observe high to exclusive
regioselectivity toward the formation of a-isomers 2q–u
from ortho-substituted 1-arylhept-1-ynes 1q–u bearing an
electron-donating group (entries 17–21). These results un-
ambiguously demonstrate the ortho-substituent regiocon-
trol concept in the platinum oxide mediated
hydrosilylation of 1-arylalk-1-ynes as was previously ob-
served in the palladium-catalyzed hydrostannation reac-
tion.10
12
13
14
15
16
17
18
19
20
21
m
n
o
b
p
q
r
NO2
CHO
CF3
100:0
100:0
100:0
100:0
95:5
90
71
71
90
89
63
83
74
92
76
CO2Et
Br
Me
85:15
81:19
100:0
91:9
i-Pr
s
CH2OAc
OMe
OAc
t
u
95:5
a The product distribution was determined by 1H NMR on the crude re
action mixture.
b Isolated yields of the mixture of vinylsilanes after column chromatog
raphy.
lenes 4 that constitute a real challenge. To our best knowl-
edge, the reaction with these substrates is not known,
probably because of the difficulty in controlling the regio-
selectivity.
Hydrosilylation of Diarylacetylenes
As can be seen in Table 4 (Scheme 3), the reaction pro-
ceeded with excellent regiocontrol and the corresponding
vinylsilanes 5 were isolated with a high to exclusive a-se-
lectivity. Diarylacetylenes with a para electron-donating
group 4e,f yielded an almost 1:1 mixture of the two regio-
Having established the ortho-directing effect in the plati-
num oxide mediated hydrosilylation of 1-arylalk-1-ynes,
we next examined the reaction in the cases of diarylacety-
Synthesis 2007, No. 13, 2025–2036 © Thieme Stuttgart · New York

2028
A. Hamze et al.
SPECIAL TOPIC
isomeric adducts 5e,f and 6e,f (entries 5 and 6), whereas Table 4 Hydrosilylation with Triethylsilane of Various Substituted
Diarylacetylenes 4 Using Platinum Oxide Catalyst
those with a para electron-withdrawing group 4a–d fa-
vored predominant formation of a-vinylsilanes 5a–d due
to the polarization of the C≡C bond (entries 1–4). ortho-
Substituted alkynes displayed much higher a-selectivity.
With substrates 4k,l bearing an electron-donating group
the a-selectivity increased from ~1:1 to ~9:1 (entries 11,
12). More interestingly, as expected total a-regioselectiv-
ity was observed with substrates 4g–j bearing an electron-
withdrawing group (entries 7–10).
Entry
Ratioa 5/6 Yieldb
R1
R2
(a/b)
(%)
4
a
b
c
d
e
f
R1
R2
H
1
2
3
4
5
6
NO2
80:20
74:26
77:23
72:28
42:58
46:54
80
82
95
65
70
67
CO2Et
CO2Et
CN
H
OMe
H
R2
α
β
H-SiEt3
[Pt], neat
60 °C, 1 h
R1
X
OMe
CH2OAc
H
4
H
R2
R2
R2
R1
X
X
R1
+
R1
Et3Si
SiEt3
5
6
7
8
g
h
i
NO2
H
100:0
100:0
100:0
100:0
80:20
92:8
92
72
74
80
64
68
α-isomer
β-isomer
CO2Et
CO2Et
CN
H
m: R1 = 4-CN, R2 = H, X = N 70%, α/β = 87:13
n: R1 = 2-CN, R2 = H, X = N 69%, α/β = 100:0
9
OMe
H
10
11
12
j
Scheme 3
k
l
OMe
H
CH2OAc
H
The efficiency of this platinum oxide-catalyzed hydrosi-
lylation was investigated with ortho- and para-substituted
substrates 4m,n containing a pyridyl moiety. It should be
noted that the presence of this heteroaromatic ring does
not affect the hydrosilylation reaction and gives mainly a-
adducts with a high levels of regiocontrol (cf. 4d and 4m).
As shown in Scheme 3, again the presence of an ortho-
substituent (e.g., CN) on one aromatic ring induced the
exclusive formation of a single a-isomer 5n.
a The product distribution was determined by 1H NMR on the crude
reaction mixture.
b Isolated yield of the mixture of vinylsilanes after column chroma-
tography; a- and b-isomers were unambiguously identified by NOE
NMR spectroscopy except in entries 5 and 6; interchangeable ratio.
even with the arylacetylene 7b bearing a 4-methoxycarbo-
nyl group (entry 2). Switching the ester group to the
ortho-position (entry 4) resulted in a ~1:1 mixture of the
two regioisomeric adducts 8d and 9d. This result clearly
shows that the ortho-directing effect, which is opposed to
steric effects, rebalances the isomeric distribution, thus in-
creasing the amount of a-products.
Hydrosilylation of Terminal Alkynes
Although the platinum-on-carbon and hexachloroplatinic
acid catalyzed hydrosilylation of terminal alkynes is well
known, no results using platinum oxide have been de-
scribed. To test its ability to catalyze the hydrosilylation
of terminal alkynes, we next examined the reaction with
terminal aryl- and alkyl-substituted alkynes (Tables 5
and 6).
H-SiEt3,
[Pt], neat,
60 °C, 1 h
α
β
R
Initial studies were carried out with terminal arylacety-
lenes 7 (Scheme 4, Table 5) and reactions proceed with
high chemical yields. As baseline control, similar isomer-
ic product distribution ratios were obtained for hydrosily-
lation of phenylacetylene with triethylsilane in the
presence of platinum oxide, platinum-on-carbon, or
Karstedt’s catalysts.8 The effect of aromatic ring substitu-
ents on the regioselectivity was examined for four repre-
sentative systems 7b–e. In these cases it was noted that
where steric effects are dominant, b-selectivity occurred,
7
R
R
+
Et3Si
SiEt3
9
8
Scheme 4
Synthesis 2007, No. 13, 2025–2036 © Thieme Stuttgart · New York

SPECIAL TOPIC
Regiochemical Aspects of the Platinum Oxide Catalyzed Hydrosilylation of Alkynes
2029
Table 5 Hydrosilylation with Triethylsilane of Various Arylacety-
lenes 7 Using Platinum Oxide Catalyst
In summary, we have demonstrated that heterogeneous
platinum oxide is a competent catalyst for the hydrosily-
lation of internal unsymmetrical arylalkynes as well as
terminal alkynes. The H–Si bond addition to substituted
1-arylalk-1-ynes and diarylacetylenes occurred at the a-
position leading preferentially to the a-silylated products
when an ortho-substituent was present on the aryl group
regardless of whether the ortho-substituent was an elec-
tron-donating or electron-withdrawing group. In compar-
ison, para-substituents showed a weaker a-silylation
directing effect. With terminal alkynes, the regioselectiv-
ity of the platinum-catalyzed hydrosilylation was found to
be governed by both steric and electronic factors, afford-
ing mainly b-isomers.
Entry
Arylacetylene 7
Ratioa 8/9 (a/b)
Yieldb (%)
R
1
2
3
4
5
a
b
c
H
15:85
24:76
18:82
52:48
38:62
86
98
96
84
97
4-CO2Me
4-OMe
2-CO2Me
2-OMe
d
e
a The product distribution was determined by 1H NMR on the crude
reaction mixture.
b Isolated yield of the mixture of vinylsilanes after column chromatog-
raphy.
1
IR spectra were recorded on a Perkin-Elmer 841 spectrometer. H
NMR and 13C NMR spectra were measured with a Bruker AC 200
and Bruker Avance 300. 1H NMR chemical shifts are referenced to
residual CHCl3 (d = 7.27). 13C chemical shifts are referenced to the
central peak of CDCl3 (d = 77.1). Elemental analyses were per-
formed with a Perkin-Elmer 240 analyzer. Analytical TLC were
performed on Merck precoated silica gel 60F plates. Merck silica
gel 60 (230–400 mesh) was used for column chromatography. All
solvents used in reactions were dried and purified according to stan-
dard procedures. Alkynes were prepared by Sonogashira
couplings14 of the corresponding halides and terminal alkynes under
standard conditions.
While the platinum oxide proved also to be an efficient
catalyst for the hydrosilylation of terminal alk-1-ynes 10,
the difference in the reactions conditions is significant.
Reaction with alkynes 7 required heating at 60 °C, where-
as with alk-1-ynes 10, 0 °C13 was found to be the optimal
reaction temperature (Scheme 5, Table 6). Under these
conditions, as with arylacetylenes 7, the hydrosilylation of
alk-1-ynes 10 was not selective producing mainly b-iso-
mers 12 even when coordinating oxygen atoms are at the
secondary propargylic position. In these cases, the ester
functionality impacts the regiochemistry of platinum ox-
ide mediated hydrosilylation differently compared to the
methyl ether group (cf. entries 2 and 3). In contrast, with
the less bulky primary propargyl acetate 10d (entry 4) the
regiochemical preference is reversed, demonstrating the
a-directing effect of the carbonyl-containing acetate.
1-Hept-1-ynyl-4-(trifluoromethyl)benzene (1f)
Yield: 83%.
1H NMR (300 MHz, CDCl3): d = 0.90 (t, J = 7.0 Hz, 3 H), 1.30–
1.70 (m, 6 H), 2.45 (t, J = 7.0 Hz, 2 H), 7.50 (d, J = 8.3 Hz, 2 H),
7.55 (d, J = 8.3 Hz, 2 H).
13C NMR (75 MHz, CDCl3): d = 14.0, 19.4, 22.2, 28.6, 31.1, 79.5,
93.4, 124.0 (q, J = 272 Hz), 125.1 (2), 128.0, 129.2 (q, J = 33.7 Hz),
131.7 (2).
19F NMR (188 MHz, CDCl3): d = –63.1.
H-SiEt3,
[Pt], neat,
0 °C, 1 h
Anal. Calcd for C14H15F3: C, 69.99; H, 6.29. Found: C, 69.85; H,
6.20.
β
R
α
R
+
R
Et3Si
11
SiEt3
10
1-Hept-1-ynyl-2-(trifluoromethyl)benzene (1o)
Yield: 80%.
12
1H NMR (300 MHz, CDCl3): d = 0.90 (t, J = 7.3 Hz, 3 H), 1.30–
1.70 (m, 6 H), 2.45 (t, J = 7.0 Hz, 2 H), 7.30 (t, J = 7.7 Hz, 1 H),
7.45 (t, J = 7.7 Hz, 1 H), 7.55 (d, J = 7.7 Hz, 1 H), 7.65 (d, J = 7.7
Hz, 1 H).
13C NMR (75 MHz, CDCl3): d = 14.0, 19.5, 22.2, 28.1, 30.9, 76.7,
96.8, 118.2, 125.7 (q, J = 5.1 Hz), 127.1, 127.2 (q, J = 273.2 Hz),
131.2, 131.4 (q, J = 29.8 Hz), 133.9.
Scheme 5
Table 6 Hydrosilylation with Triethylsilane of Various Terminal
Alkynes 10 Using Platinum Oxide Catalyst
Entry
Alk-1-yne 10
Ratioa 11/12 (a/b) Yieldb (%)
19F NMR (188 MHz, CDCl3): d = –62.9.
1
2
3
4
a
b
c
C5H11
10:90
12:88
29:71
82:18
98
78
60
90
Anal. Calcd for C14H15F3: C, 69.99; H, 6.29. Found: C, 69.79; H,
6.15.
CH(OMe)Me
CH(OAc)Me
CH2OAc
4-(Pyridin-2-ylethynyl)benzonitrile (4m)
Yield: 67%.
d
1H NMR (300 MHz, CDCl3): d = 7.30 (m, 1 H), 7.60 (d, J = 7.8 Hz,
1 H), 7.65–7.80 (m, 5 H), 8.70 (d, J = 4.8 Hz, 1 H).
13C NMR (75 MHz, CDCl3): d = 87.0, 92.4, 112.3, 118.3, 123.5,
127.1, 127.5, 132.1 (2), 132.5 (2), 136.4, 142.5, 150.3.
a The product distribution was determined by 1H NMR on the crude
reaction mixture.
b Isolated yield of the mixture of vinylsilanes after column chromatog-
raphy.
Synthesis 2007, No. 13, 2025–2036 © Thieme Stuttgart · New York

2030
A. Hamze et al.
SPECIAL TOPIC
(E)-Triethyl[1-(4-nitrophenyl)hept-1-enyl]silane (2d)
Anal. Calcd for C14H8N2: C, 82.33; H, 3.95; N, 13.72. Found: C,
82.26; H, 3.74; N, 13.59.
Yield: 83%; ratio a/b ca. 97:3.
IR (neat): 2954, 2931, 2874, 1592, 1517, 1489, 1459, 1416, 1378,
1342, 1281, 1107, 1006, 974, 914, 856, 758, 732, 719, 701 cm–1.
1H NMR (200 MHz, CDCl3): major a-isomer 2d: d = 0.40–0.60 (m,
6 H), 0.95–1.20 (m, 12 H), 1.25–1.65 (m, 6 H), 2.05 (q, J = 6.9 Hz,
2 H), 6.20 (t, J = 7.1 Hz, 1 H), 7.25 (d, J = 8.8 Hz, 2 H), 8.35 (d,
J = 8.8 Hz, 2 H).
1H NMR (200 MHz, CDCl3): minor b-isomer 3d: d = 2.15–2.35 (m,
2 H).6.90 (s, 1 H). (Only the most significant resonances are listed.)
13C NMR (50 MHz, CDCl3): major a-isomer 2d: d = 2.7 (3), 7.0 (3),
13.8, 22.3, 28.9, 30.1, 31.2, 123.3 (2), 128.3 (2), 140.0, 144.2,
145.8, 151.1.
Hydrosilylation of Alkynes; General Procedure
In a 20-mL flask, PtO2 (11.35 mg, 0.05 mmol) and alkyne (1 mmol)
were placed under N2. Et3SiH (0.24 mL, 1.5 mmol) was introduced
via syringe and the mixture was stirred at 60 °C in an oil bath for 1
h. The residue was then purified by column chromatography (silica
gel) to yield the title adducts either as a single a-isomer or as a mix-
ture of inseparable a- and b-isomers.
Ethyl (E)-4-[1-(Triethylsilyl)hept-1-enyl]benzoate (2a)
Yield: 92%; ratio a/b ca. 83:17.
IR (neat): 2954, 2930, 2874, 1718, 1606, 1503, 1415, 1306, 1269,
1174, 1100, 1020, 973, 773, 731, 707 cm–1.
Anal. Calcd for C19H31NO2Si (333.54): C, 68.42; H, 9.37; N, 4.20.
Found: C, 68.23; H, 9.62; N, 4.23.
1H NMR (200 MHz, CDCl3): major a-isomer 2a: d = 0.40–0.60 (m,
6 H), 0.75–1.10 (m, 12 H), 1.10–1.35 (m, 6 H), 1.30 (t, J = 7.1 Hz,
3 H), 1.85 (q, J = 7 Hz, 2 H), 4.40 (q, J = 7.1 Hz, 2 H), 5.90 (t,
J = 7.0 Hz, 1 H), 6.90 (d, J = 8.4 Hz, 2 H), 7.95 (d, J = 8.4 Hz, 2 H).
(The presence of an a/b mixture of isomers complicates the spec-
trum.)
1H NMR (200 MHz, CDCl3): minor b-isomer 3a: d = 2.15–2.35 (m,
2 H), 6.70 (s, 1 H). (Only the most significant resonances are listed.)
13C NMR (50 MHz, CDCl3): major a-isomer 2a: d = 2.7 (2), 3.1, 7.1
(2), 7.3, 13.8, 14.2, 22.3, 29.4, 30.9, 31.2, 60.5, 127.4, 127.5 (2),
129.2 (2), 140.7, 143.4, 148.5, 166.5.
(E)-4-[1-(Triethylsilyl)hept-1-enyl]benzaldehyde (2e)
Yield: 62%; ratio a/b ca. 85:15.
IR (neat): 2953, 2931, 2874, 2727, 1703, 1600, 1563, 1459, 1415,
1302, 1237, 1208, 1164, 1103, 1005, 974, 912, 842, 820, 710 cm–1.
1H NMR (200 MHz, CDCl3): major a-isomer 2e: d = 0.40–0.60 (m,
6 H), 0.75–1.10 (m, 12 H), 1.20–1.55 (m, 6 H), 2.05 (q, J = 7.0 Hz,
2 H), 6.10 (t, J = 7.0 Hz, 1 H), 7.25 (d, J = 8.0 Hz, 2 H), 7.90 (d,
J = 8.0 Hz, 2 H),10.1 (s, 1 H). (The presence of an a/b mixture of
isomers complicates the spectrum.)
1H NMR (200 MHz, CDCl3): minor b-isomer 3e: d = 2.30–2.40 (m,
2 H), 6.90 (s, 1 H). (Only the most significant resonances are listed.)
Anal. Calcd for C22H36O2Si (360.61): C, 73.28; H, 10.06. Found: C,
73.10; H, 10.29.
13C NMR (50 MHz, CDCl3): major a-isomer 2e: d = 2.8 (2), 3.1, 7.1
(2), 7.3, 13.8, 22.2, 28.9, 30.0, 31.2, 128.2 (2), 129.5 (2), 133.8,
140.6, 143.6, 150.7, 191.8.
Ethyl (E)-2-[1-(Triethylsilyl)hept-1-enyl]benzoate (2b)
Yield: 90%.
IR (neat): 3062, 2953, 2932, 2874, 1726, 1596, 1567, 1460, 1441,
1416, 1366, 1286, 1267, 1243, 1172, 1162, 1124, 1044, 760, 711,
685 cm–1.
Anal. Calcd for C20H32OSi (316.56): C, 75.88; H, 10.19. Found: C,
75.75; H, 10.12.
1H NMR (200 MHz, CDCl3): d = 0.40–0.60 (m, 6 H), 0.75–0.60 (m,
12 H), 1.10–1.35 (m, 6 H), 1.20 (t, J = 7.1 Hz, 3 H), 1.75 (q, J = 7.3
Hz, 2 H), 4.00–4.30 (m, 2 H), 5.80 (t, J = 6.8 Hz, 1 H), 6.80 (d,
J = 7.6 Hz, 1 H), 7.10 (t, J = 7.6 Hz, 1 H), 7.30 (t, J = 7.6 Hz, 1 H),
7.75 (d, J = 7.6 Hz, 1 H).
13C NMR (50 MHz, CDCl3): d = 3.2 (3), 7.2 (3), 13.8, 14.2, 22.3,
28.7, 30.3, 31.4, 60.3, 125.1, 129.1, 129.6, 129.9, 130.9, 140.5,
141.4, 144.3, 167.4.
(E)-Triethyl{1-[4-(trifluoromethyl)phenyl]hept-1-enyl}silane
(2f)
Yield: 95%; ratio a/b ca. 84:16.
IR (neat): 2955, 2876, 1614, 1459, 1404, 1322, 1237, 1163, 1124,
1105, 1067, 1018, 913, 835, 713 cm–1.
1H NMR (200 MHz, CDCl3): major a-isomer 2f: d = 0.55–0.65 (q,
J = 6.6 Hz, 6 H), 0.80–1.00 (m, 12 H), 1.10–1.40 (m, 6 H), 1.90 (q,
J = 7.2 Hz, 2 H), 6.00 (t, J = 7.2 Hz, 1 H), 7.05 (d, J = 7.9 Hz, 2 H),
7.55 (d, J = 7.9 Hz, 2 H). (The presence of an a/b mixture of iso-
mers complicates the spectrum.)
Anal. Calcd for C22H36O2Si (360.61): C, 73.28; H, 10.06. Found: C,
73.12; H, 10.25.
1H NMR (200 MHz, CDCl3): minor b-isomer 3f: d = 2.25–2.35 (m,
2 H), 6.75 (s, 1 H), 7.35 (d, J = 7.6 Hz, 2 H), 7.50 (d, J = 7.6 Hz, 2
H). (Only the most significant resonances are listed.)
13C NMR (50 MHz, CDCl3): major a-isomer 2f: d = 2.8 (3), 7.2 (3),
14.0, 22.4, 29.1, 30.0, 31.3, 122.7 (2), 124.5 (q, J = 271.6 Hz),
127.9 (2), 140.2, 144.0, 147.3 (C-CF3 not seen).
19F NMR (188 MHz, CDCl3): major a-isomer 2f: d = –62.6.
19F NMR (188 MHz, CDCl3): minor b-isomer 3f: d = –62.8.
(E)-Triethyl(1-phenylhept-1-enyl)silane (2c)
Yield: 71%; ratio a/b ca. 65:35.
IR (neat): 2954, 2931, 2874, 1595, 1490, 1459, 1377, 1237, 1007,
718, 701 cm–1.
1H NMR (200 MHz, CDCl3): major a-isomer 2c: d = 0.60–0.80 (q,
J = 7.8 Hz, 6 H), 1.00–1.80 (m, 18 H), 2.10 (q, J = 7.1 Hz, 2 H),
6.10 (t, J = 7.0 Hz, 1 H), 7.15 (d, J = 8.3 Hz, 2 H), 7.25–7.60 (m, 3
H). (The presence of an a/b mixture of isomers complicates the
spectrum.)
1H NMR (200 MHz, CDCl3): minor b-isomer 3c: d = 2.45–2.60 (m,
2 H), 6.90 (s, 1 H). (Only the most significant resonances are listed.)
Anal. Calcd for C20H31F3Si (356.21): C, 67.37; H, 8.76. Found: C,
67.14; H, 8.55.
(E)-[1-(4-Bromophenyl)hept-1-enyl]triethylsilane (2g)
Yield: 90%; ratio a/b ca. 82:18.
13C NMR (50 MHz, CDCl3): mixture a/b: d = 2.8, 3.3, 7.2, 7.4, 13.9,
22.3, 22.4, 29.2, 29.5, 29.8, 30.8, 31.3, 32.2, 125.0, 126.3, 127.6 (2),
127.8, 128.0, 128.5, 138.6, 138.9 (b),141.1, 142.4, 143.1.
IR (neat): 2953, 2932, 2874, 1712, 1586, 1483, 1458, 1415, 1378,
1236, 1181, 1071, 1009, 973, 910, 818, 714 cm–1.
1H NMR (200 MHz, CDCl3): major a-isomer 2g: d = 0.55–0.65 (q,
J = 6.8 Hz, 6 H), 0.85–1.15 (m, 12 H), 1.00–1.30 (m, 6 H), 1.75 (q,
Anal. Calcd for C19H32Si (288.54): C, 79.09; H, 11.18. Found: C,
78.90; H, 11.23.
Synthesis 2007, No. 13, 2025–2036 © Thieme Stuttgart · New York

SPECIAL TOPIC
Regiochemical Aspects of the Platinum Oxide Catalyzed Hydrosilylation of Alkynes
2031
J = 7.2 Hz, 2 H), 5.80 (t, J = 7.1 Hz, 1 H), 6.65 (d, J = 8.4 Hz, 2 H),
7.25 (d, J = 8.4 Hz, 2 H). (The presence of an a/b mixture of iso-
mers complicates the spectrum.)
13C NMR (50 MHz, CDCl3): major a-isomer 2j: d = 2.7 (2), 3.2, 7.1
(2), 7.3, 13.8, 20.9, 22.3, 29.1, 29.8, 31.3, 66.2, 127.8 (2), 128.0 (2),
133.9, 140.6, 143.1, 143.4, 170.7.
1H NMR (200 MHz, CDCl3): minor b-isomer 3g: d = 0.55 (q,
J = 7.6 Hz, 6 H), 2.00–2.20 (m, 2 H), 6.45 (s, 1 H), 7.00 (d, J = 8.4
Hz, 2 H), 7.25 (d, J = 8.4 Hz, 2 H). (Only the most significant reso-
nances are listed.)
13C NMR (50 MHz, CDCl3): major a-isomer 2g: d = 2.8 (3), 7.1 (3),
13.8, 22.4, 29.1, 29.9, 31.3, 118.9, 129.3 (2), 131.0 (2), 137.5,
141.5, 143.7.
Anal. Calcd for C22H36O2Si (360.61): C, 73.28; H, 10.06. Found: C,
73.21; H, 10.15.
(E)-Triethyl[1-(4-methoxyphenyl)hept-1-enyl]silane (2k)
Yield: 80%; ratio a/b ca. 70:30.
IR (neat): 2952, 2873, 1606, 1506, 1463, 1416, 1377, 1282, 1242,
1174, 1104, 1039, 1006, 902, 826, 716 cm–1.
Anal. Calcd for C19H31BrSi (366.14): C, 62.11; H, 8.50. Found: C,
62.04; H, 8.48.
1H NMR (200 MHz, CDCl3): major a-isomer 2k: d = 0.70–0.90 (m,
6 H), 0.95–1.20 (m, 12 H), 1.20–1.60 (m, 6 H), 2.05 (q, J = 7.1 Hz,
2 H), 3.90 (s, 3 H), 6.05 (t, J = 7.1 Hz, 1 H), 6.95 (d, J = 8.5 Hz, 2
H), 7.35 (d, J = 8.5 Hz, 2 H). (The presence of an a/b mixture of iso-
mers complicates the spectrum.)
(E)-Triethyl[1-(4-tolyl)hept-1-enyl]silane (2h)
Yield: 82%; ratio a/b ca. 65:35.
IR (neat): 2953, 2930, 2874, 1701, 1606, 1508, 1458, 1416, 1378,
1237, 1180, 1108, 1006, 973, 910, 810, 717 cm–1.
1H NMR (200 MHz, CDCl3): minor b-isomer 3k: d = 2.45–2.55 (m,
2 H), 3.95 (s, 3 H), 6.80 (s, 1 H). (Only the most significant reso-
nances are listed.)
13C NMR (50 MHz, CDCl3): major a-isomer 2k: d = 2.9 (3), 7.3 (3),
14.0, 22.4, 29.1, 30.0, 31.3, 55.1, 113.3 (2), 128.7 (2), 135.3, 140.4,
143.5, 157.2.
1H NMR (200 MHz, CDCl3): major a-isomer 2h: d = 0.60–0.80 (q,
J = 7.9 Hz, 6 H), 1.00–1.20 (m, 12 H), 1.30–1.50 (m, 6 H), 2.10 (q,
J = 7.1 Hz, 2 H), 2.50 (s, 3 H), 6.30 (t, J = 7.0 Hz, 1 H), 7.00 (d,
J = 8.0 Hz, 2 H), 7.25 (d, J = 8.0 Hz, 2 H). (The presence of an a/b
mixture of isomers complicates the spectrum.)
1H NMR (200 MHz, CDCl3): minor b-isomer 3h: d = 2.50 (s, 3 H),
6.85 (s, 1 H), 7.30 (m, 4 H). (Only the most significant resonances
are listed.)
Anal. Calcd for C20H34OSi (318.24): C, 75.40; H, 10.76. Found: C,
75.29; H, 10.65.
(E)-4-[1-(Triethylsilyl)hept-1-enyl]phenyl Acetate (2l)
Yield: 82%; ratio a/b ca. 78:22.
13C NMR (50 MHz, CDCl3): major a-isomer 2h: d = 2.8 (3), 7.2 (3),
13.9, 21.0, 22.4, 29.2, 29.8, 31.3, 127.5 (2), 128.5 (2), 134.2, 139.9,
140.9, 143.1.
IR (neat): 2953, 2931, 2874, 1766, 1597, 1501, 1459, 1417, 1368,
1193, 1164, 1099, 1008, 916, 836, 716, 688 cm–1.
1H NMR (200 MHz, CDCl3): major a-isomer 2l: d = 0.70–0.90 (m,
6 H), 0.95–1.20 (m, 12 H), 1.20–1.60 (m, 6 H), 2.10 (q, J = 7.0 Hz,
2 H), 2.60 (s, 3 H), 6.25 (t, J = 7.0 Hz, 1 H), 6.85 (d, J = 8.4 Hz, 2
H), 7.35 (d, J = 8.4 Hz, 2 H). (The presence of an a/b mixture of iso-
mers complicates the spectrum.)
1H NMR (200 MHz, CDCl3): minor b-isomer 3l: d = 2.50–2.65 (m,
2 H), 2.60 (s, 3 H), 6.90 (s, 1 H), 7.60 (d, J = 8.5 Hz, 2 H). (Only the
most significant resonances are listed.)
Anal. Calcd for C20H34Si (302.24): C, 79.39; H, 11.33. Found: C,
79.26; H, 11.20.
(E)-Triethyl[1-(4-isopropylphenyl)hept-1-enyl]silane (2i)
Yield: 68%; ratio a/b ca. 73:27.
IR (neat): 2955, 2930, 2874, 1707, 1603, 1507, 1459, 1415, 1379,
1237, 1099, 1054, 1006, 972, 912, 827, 717, 699, 675 cm–1.
1H NMR (200 MHz, CDCl3): major a-isomer 2i: d = 0.60–0.80 (m,
6 H), 0.90–1.10 (m, 12 H), 1.00–1.50 (m, 12 H), 1.95–2.05 (q,
J = 7.0 Hz, 2 H), 2.85–3.05 (m, 1 H), 6.00 (t, J = 7.0 Hz, 1 H), 6.95
(d, J = 8.5 Hz, 2 H), 7.25 (d, J = 8.5 Hz, 2 H). (The presence of an
a/b mixture of isomers complicates the spectrum.)
1H NMR (200 MHz, CDCl3): minor b-isomer 3i: d = 2.40–2.50 (m,
2 H), 6.75 (s, 1 H). (Only the most significant resonances are listed.)
13C NMR (50 MHz, CDCl3): major a-isomer 2i: d = 2.8 (3), 7.2 (3),
13.8, 23.9, 26.8, 29.2, 29.8, 31.3, 33.5, 125.7 (2), 127.4 (2), 138.7,
140.1, 140.9, 143.0, 145.2.
13C NMR (50 MHz, CDCl3): major a-isomer 2l: d = 2.7 (2), 3.2, 7.1
(2), 7.3, 13.8, 21.0, 22.3, 29.1, 29.8, 31.3, 120.7 (2), 128.4 (2),
140.2, 140.4, 143.7, 148.3, 169.2.
Anal. Calcd for C21H34O2Si (346.58): C, 72.77; H, 9.89. Found: C,
72.57; H, 10.08.
(E)-Triethyl[1-(2-nitrophenyl)hept-1-enyl]silane (2m)
Yield: 90%.
IR (neat): 2954, 2931, 2874, 1608, 1569, 1524, 1459, 1416, 1347,
1296, 1237, 1161, 1142, 1080, 1008, 974, 914, 868, 851, 785, 755,
705, 686 cm–1.
1H NMR (200 MHz, CDCl3): d = 0.40–0.60 (m, 6 H), 0.60–0.95 (m,
12 H), 1.00–1.25 (m, 6 H), 1.75 (m, 2 H), 5.90 (t, J = 7.0 Hz, 1 H),
6.90 (dd, J = 7.5 Hz, J = 1.3 Hz, 1 H), 7.20 (td, J = 7.5 Hz, J = 1.3
Hz, 1 H), 7.40 (td, J = 7.5 Hz, J = 1.3 Hz, 1 H), 7.85 (dd, J = 7.5 Hz,
J = 1.3 Hz, 1 H).
Anal. Calcd for C22H38Si (330.63): C, 79.92; H, 11.58. Found: C,
79.55; H, 11.62.
(E)-4-[1-(Triethylsilyl)hept-1-enyl]benzyl Acetate (2j)
Yield: 90%; ratio a/b ca. 77:23.
IR (neat): 2953, 2931, 2874, 1742, 1603, 1508, 1459, 1416, 1378,
1361, 1224, 1179, 1109, 1018, 965, 912, 820, 716, 675 cm–1.
13C NMR (50 MHz, CDCl3): d = 3.2 (3), 7.0 (3), 13.8, 22.3, 28.6,
30.7, 31.3, 124.1, 126.2, 130.4, 132.2, 137.3, 138.7, 143.3, 148.0.
1H NMR (200 MHz, CDCl3): major a-isomer 2j: d = 0.40–0.60 (m,
6 H), 0.75–1.10 (m, 12 H), 1.35–1.85 (m, 6 H), 2.20 (q, J = 7.0 Hz,
2 H), 2.45 (s, 3 H), 5.40 (s, 2 H), 6.25 (t, J = 7.0 Hz, 1 H), 7.20 (d,
J = 8.0 Hz, 2 H), 7.60 (d, J = 8.0 Hz, 2 H). (The presence of an a/b
mixture of isomers complicates the spectrum.)
1H NMR (200 MHz, CDCl3): minor b-isomer 3j: d = 2.45 (s, 3 H),
2.50–2.65 (m, 2 H), 7.00 (s, 1 H). (Only the most significant reso-
nances are listed.)
Anal. Calcd for C19H31NO2Si (333.54): C, 68.42; H, 9.37; N, 4.20.
Found: C, 68.40; H, 9.40; N, 4.17.
(E)-2-[1-(Triethylsilyl)hept-1-enyl]benzaldehyde (2n)
Yield: 71%.
Synthesis 2007, No. 13, 2025–2036 © Thieme Stuttgart · New York

2032
A. Hamze et al.
SPECIAL TOPIC
IR (neat): 2955, 2932, 2875, 1780, 1693, 1595, 1465, 1415, 1379,
1285, 1266, 1239, 1196, 1180, 1095, 1006, 974, 926, 873, 825, 798,
717 cm–1.
Anal. Calcd for C20H34Si (302.24): C, 79.39; H, 11.33. Found: C,
79.21; H, 11.14.
(E)-Triethyl[1-(2-isopropylphenyl)hept-1-enyl]silane (2r)
Yield: 83%; ratio a/b ca. 81:19.
1H NMR (200 MHz, CDCl3): d = 0.40–0.60 (m, 6 H), 0.60–0.95 (m,
12 H), 1.00–1.35 (m, 6 H), 1.75 (q, J = 6.9 Hz, 2 H), 6.05 (t, J = 6.9
Hz, 1 H), 6.85 (d, J = 7.6 Hz, 1 H), 7.20 (t, J = 7.6 Hz, 1 H), 7.40
(td, J = 7.6 Hz, J = 1.2 Hz, 1 H), 7.85 (dd, J = 7.6 Hz, J = 1.2 Hz, 1
H), 10.05 (s, 1 H).
13C NMR (50 MHz, CDCl3): d = 2.8 (3), 7.0 (3), 13.7, 22.2, 28.4,
30.5, 31.3, 126.0, 126.9, 128.9, 132.7, 133.7, 137.4, 145.4, 147.5,
192.6.
IR (neat): 3062, 2955, 2931, 2874, 1603, 1481, 1459, 1380, 1362,
1177, 1082, 1008, 972, 944, 912, 757, 746, 715 cm–1.
1H NMR (200 MHz, CDCl3): major a-isomer 2r: d = 0.60–0.80 (m,
6 H), 0.90–1.10 (m, 12 H), 1.00–1.30 (m, 12 H), 1.70–1.80 (m, 2 H),
2.85–2.95 (m, 1 H), 6.85 (t, J = 7.2 Hz, 1 H), 6.70 (dd, J = 8.5 Hz,
J = 1.2 Hz, 1 H), 6.90–7.15 (m, 3 H). (The presence of an a/b mix-
ture of isomers complicates the spectrum.)
1H NMR (200 MHz, CDCl3): minor b-isomer 3r: d = 1.95–2.05 (m,
2 H), 6.85 (s, 1 H). (Only the most significant resonances are listed.)
Anal. Calcd for C20H32OSi (316.56): C, 75.88; H, 10.19. Found: C,
76.01; H, 10.30.
(E)-Triethyl{1-[2-(trifluoromethyl)phenyl]hept-1-enyl}silane
(2o)
Yield: 71%.
13C NMR (50 MHz, CDCl3): major a-isomer 2r: d = 3.4 (3), 7.2 (3),
13.9, 22.4, 23.4, 24.7, 29.0, 29.9, 31.4, 125.0 (2), 125.0, 127.9,
139.1, 140.2, 140.7, 143.5, 145.4.
IR (neat): 2955, 2876, 1603, 1574, 1459, 1313, 1257, 1164, 1125,
1058, 1034, 1014, 955, 913, 870, 766, 716, 681, 649 cm–1.
1H NMR (300 MHz, CDCl3): d = 0.45–0.65 (m, 6 H), 0.80–1.00 (m,
12 H), 1.10–1.40 (m, 6 H), 1.65–1.90 (m, 2 H), 6.00 (dd, J = 7.9 Hz,
J = 5.8 Hz, 1 H), 6.95 (d, J = 7.9 Hz, 1 H), 7.30 (t, J = 7.9 Hz, 1 H),
7.45 (t, J = 7.9 Hz, 1 H), 7.70 (d, J = 7.9 Hz, 1 H).
13C NMR (75 MHz, CDCl3): d = 3.8 (3), 7.2 (3), 14.0, 22.4, 28.7,
30.9, 31.5, 124.9 (q, J = 177.8 Hz), 125.4, 126.1 (q, J = 4.9 Hz),
129.5, 131.1, 138.3, 142.5, 144.1 (q, J = 1.6 Hz) (one C missing).
19F NMR (188 MHz, CDCl3): d = –59.7.
Anal. Calcd for C22H38Si (330.63): C, 79.92; H, 11.58. Found: C,
79.72; H, 11.58.
(E)-2-[1-(Triethylsilyl)hept-1-enyl]benzyl Acetate (2s)
Yield: 74%.
IR (neat): 2954, 2931, 2874, 1743, 1606, 1484, 1459, 1417, 1378,
1360, 1224, 1104, 1019, 965, 757, 714, 679 cm–1.
1H NMR (200 MHz, CDCl3): d = 0.40–0.60 (m, 6 H), 0.75–1.10 (m,
12 H), 1.00–1.35 (m, 6 H), 1.65–1.80 (m, 2 H), 2.00 (s, 3 H), 4.90
(s, 2 H), 5.95 (t, J = 6.9 Hz, 1 H), 6.75 (dd, J = 8.0 Hz, J = 1.1 Hz,
1 H), 7.00–7.25 (m, 2 H), 7.30 (m, 1 H).
13C NMR (50 MHz, CDCl3): d = 3.0 (3), 7.1 (3), 13.8, 20.8, 22.3,
29.5, 30.3, 31.3, 64.1, 125.6, 127.6, 127.9, 128.3, 132.2, 138.8,
142.1, 144.4, 171.4.
Anal. Calcd for C20H31F3Si (356.21): C, 67.37; H, 8.76. Found: C,
67.27; H, 8.65.
(E)-[1-(2-Bromophenyl)hept-1-enyl]triethylsilane (2p)
Yield: 89%; ratio a/b ca. 95:5.
Anal. Calcd for C22H36O2Si (360.61): C, 73.28; H, 10.06,. Found: C,
73.22; H, 10.00.
IR (neat): 2953, 2930, 2874, 1609, 1462, 1429, 1416, 1377, 1237,
1072, 1047, 1019, 973, 943, 911, 856, 754, 729, 714, 683 cm–1.
(E)-Triethyl[1-(2-methoxyphenyl)hept-1-enyl]silane (2t)
Yield: 92%; ratio a/b ca. 91:9.
1H NMR (200 MHz, CDCl3): major a-isomer 2p: d = 0.55–0.65 (m,
6 H), 0.85–1.15 (m, 12 H), 1.20–1.60 (m, 6 H), 1.95 (m, 2 H), 6.05
(t, J = 6.3 Hz, 1 H), 6.90 (dd, J = 7.4 Hz, J = 1.8 Hz, 1 H), 7.05 (td,
J = 7.4 Hz, J = 1.8 Hz, 1 H), 7.25 (td, J = 7.4 Hz, J = 1.4 Hz, 1 H),
7.60 (dd, J = 1.4 Hz, 1 H).
1H NMR (200 MHz, CDCl3): minor b-isomer 3p: d = 2.15–2.25 (m,
2 H), 6.85 (s, 1 H). (Only the most significant resonances are listed.)
13C NMR (50 MHz, CDCl3): major a-isomer 2p: d = 3.3 (3), 7.3 (3),
14.0, 22.5, 28.5, 29.3, 31.5, 122.8, 126.8 (2), 128.3, 132.4, 140.0,
143.7, 144.3.
IR (neat): 2952, 2873, 2833, 1593, 1577, 1487, 1433, 1377, 1240,
1160, 903, 844, 783 cm–1.
1H NMR (200 MHz, CDCl3): major a-isomer 2t: d = 0.60–0.90 (m,
6 H), 0.80–1.10 (m, 12 H), 1.20–1.55 (m, 6 H), 2.05 (q, J = 7.0 Hz,
2 H), 3.85 (s, 3 H), 6.10 (t, J = 7.1 Hz, 1 H), 6.90–7.05 (m, 3 H),
7.15–7.35 (m, 1 H). (The presence of an a/b mixture of isomers
complicates the spectrum.)
1H NMR (200 MHz, CDCl3): minor b-isomer 3t: d = 2.25–2.35 (m,
2 H), 3.90 (s, 3 H), 6.90 (s, 1 H). (Only the most significant reso-
nances are listed.)
Anal. Calcd for C19H31BrSi (366.14): C, 62.11; H, 8.50. Found: C,
61.89; H, 8.21.
13C NMR (50 MHz, CDCl3): major a-isomer 2t: d = 3.3 (3), 7.2 (3),
13.9, 22.2, 30.0 (2), 31.6, 54.7, 110.0, 120.1, 126.5, 129.2, 131.8,
137.4, 143.2, 156.0.
(E)-Triethyl[1-(2-tolyl)hept-1-enyl]silane (2q)
Yield: 63%; ratio a/b ca. 88:12.
IR (neat): 2953, 2930, 2874, 1601, 1605, 1482, 1458, 1416, 1378,
1236, 1180, 1106, 1008, 973, 942, 909, 799, 754 cm–1.
Anal. Calcd for C20H34OSi (318.24): C, 75.40; H, 10.76. Found: C,
75.29; H, 10.65.
1H NMR (300 MHz, CDCl3): major a-isomer 2q: d = 0.55–0.65 (q,
J = 7.8 Hz, 6 H), 0.80–1.00 (m, 12 H), 1.15–1.45 (m, 6 H), 1.85 (q,
J = 7.2 Hz, 2 H), 2.20 (s, 3 H), 6.00 (t, J = 7.2 Hz, 1 H), 6.80 (m, 1
H), 7.10–7.30 (m, 3 H). (The presence of an a/b mixture of isomers
complicates the spectrum.)
1H NMR (200 MHz, CDCl3): minor b-isomer 3q: d = 2.30 (s, 3 H),
6.75 (s, 1 H). (Only the most significant resonances are listed.)
13C NMR (75 MHz, CDCl3): major a-isomer 2q: d = 3.2 (3), 7.3 (3),
14.0, 19.9, 22.5, 28.8, 30.2, 31.5, 125.2, 125.3, 126.6, 129.6, 134.5,
139.1, 142.2, 143.1.
(E)-2-[1-(Triethylsilyl)hept-1-enyl]phenyl Acetate (2u)
Yield: 76%; ratio a/b ca. 95:5.
IR (neat): 2954, 2931, 2874, 1765, 1599, 1481, 1459, 1444, 1416,
1367, 1204, 1172, 1097, 1038, 1008, 974, 913, 816, 750, 713, 675
cm–1.
1H NMR (200 MHz, CDCl3): major a-isomer 2u: d = 0.70–0.90 (m,
6 H), 1.00–1.20 (m, 12 H), 1.30–1.60 (m, 6 H), 2.15 (q, J = 7.0 Hz,
2 H), 6.30 (t, J = 7.0 Hz, 1 H), 2.50 (s, 3 H), 7.15–7.25 (m, 1 H),
Synthesis 2007, No. 13, 2025–2036 © Thieme Stuttgart · New York

SPECIAL TOPIC
Regiochemical Aspects of the Platinum Oxide Catalyzed Hydrosilylation of Alkynes
2033
7.30–7.60 (m, 3 H). (The presence of an a/b mixture of isomers
13C NMR (75 MHz, CDCl3): major a-isomer 5c: d = 3.1 (3), 7.3 (3),
complicates the spectrum.)
14.4, 55.1, 60.8, 113.5 (2), 127.5 (2), 127.6, 129.8, 130.0 (2), 130.9
(2), 138.5, 140.6, 149.2, 158.7, 166.8.
1H NMR (200 MHz, CDCl3): minor b-isomer 3u: d = 6.80 (s, 1 H).
(Only the most significant resonance is listed.)
13C NMR (50 MHz, CDCl3): major a-isomer 2u: d = 3.1 (3), 7.1 (3),
13.8, 20.7 (CH3), 22.4, 28.9, 30.4, 31.3, 122.3, 125.9, 125.4, 129.5,
135.4, 135.8, 145.1, 147.2, 168.8.
Anal. Calcd for C24H32O3Si (396.21): C, 72.68; H, 8.13. Found: C,
72.31; H, 7.99.
(E)-4-[2-Phenyl-1-(triethylsilyl)vinyl]benzonitrile (5d)
Yield: 65%; ratio a/b ca. 72:28.
Anal. Calcd for C21H34O2Si (346.58): C, 72.77; H, 9.89. Found: C,
73.00; H, 9.72.
IR (neat): 2953, 2909, 2875, 2227, 1602, 1572, 1495, 1458, 1447,
1415, 1208, 1163, 1107, 1074, 1005, 966, 938, 838, 752, 736, 717,
693 cm–1.
1H NMR (200 MHz, CDCl3): major a-isomer 5d: d = 0.50–0.70 (m,
6 H), 0.90 (t, J = 8.1 Hz, 9 H), 6.80 (s, 1 H), 6.70–7.05 (m, 6 H),
7.10–7.30 (m, 1 H), 7.50 (d, J = 8.3 Hz, 2 H). (The presence of an
a/b mixture of isomers complicates the spectrum.)
1H NMR (200 MHz, CDCl3): minor b-isomer 6d: d = 6.70 (s, 1 H).
(Only the most significant resonance is listed.)
13C NMR (50 MHz, CDCl3): major a-isomer 5d: d = 2.6 (3), 7.1 (3),
109.3, 119.0, 127.4, 128.3 (2), 128.7 (2), 129.7 (2), 136.5 (2), 136.8,
141.7, 142.4, 148.9.
(E)-Triethyl[1-(4-nitrophenyl)-2-phenylvinyl]silane (5a)
Yield: 80%; ratio a/b ca. 80:20.
IR (neat): 3069, 3024, 2956, 2910, 2891, 1807, 1595, 1515, 1494,
1379, 1341, 1279, 1080, 1000, 922, 857, 757, 735, 720, 694 cm–1.
1H NMR (200 MHz, CDCl3): major a-isomer 5a: d = 0.55 (q,
J = 8.1 Hz, 6 H), 0.85 (t, J = 8.1 Hz, 9 H), 6.80–6.95 (m, 4 H), 7.05
(d, J = 8.7 Hz, 2 H), 7.15 (s, 1 H), 7.20–7.30 (m, 1 H), 8.10 (d,
J = 8.7 Hz, 2 H). (The presence of an a/b mixture of isomers com-
plicates the spectrum.)
1H NMR (200 MHz, CDCl3): minor b-isomer 6a: d = 6.80 (s, 1 H),
7.85 (d, J = 8.9 Hz, 2 H). (Only the most significant resonances are
listed.)
Anal. Calcd for C21H25NSi (319.52): C, 78.94; H, 7.89, N, 4.38.
Found: C, 78.50; H, 8.11; N, 4.39.
13C NMR (50 MHz, CDCl3): major a-isomer 5a: d = 2.8 (3), 7.1 (3),
123.9 (2), 127.5, 128.0 (2), 128.3 (2), 129.3 (2), 136.5, 140.1, 142.2,
145.9, 151.3.
(E)-Triethyl[1-(4-methoxyphenyl)-2-phenylvinyl]silane (5e)
and (E)-Triethyl[2-(4-methoxyphenyl)-1-phenylvinyl]silane
(6e)
Anal. Calcd for C20H25NO2Si (339.51): C, 70.75; H, 7.42; N, 4.13.
Found: C, 70.42; H, 7.55; N, 4.20.
Yield: 70%; ratio a/b ca. 42:58.
IR (neat): 2951, 2909, 2874, 2834, 1604, 1571, 1506, 1461, 1416,
1281, 1242, 1176, 1103, 1035, 1005, 965, 920, 896, 829, 769, 752,
716, 698 cm–1.
1H NMR (200 MHz, CDCl3): major isomer: d = 4.15 (s, 3 H). (The
presence of an a/b mixture of isomers complicates the spectrum.)
(Only the most significant resonance is listed.)
Ethyl (E)-4-[2-Phenyl-1-(triethylsilyl)vinyl]benzoate (5b)
Yield: 82%; ratio a/b ca. 74:26.
IR (neat): 2953, 2906, 2874, 1716, 1605, 1561, 1493, 1366, 1207,
1100, 1006, 967, 771, 757, 730, 703, 692 cm–1.
1H NMR (200 MHz, CDCl3): major a-isomer 5b: d = 0.70–0.90 (m,
6 H), 1.15 (t, J = 8.1 Hz, 9 H), 1.40–1.60 (t, J = 7.1 Hz, 3 H), 4.45–
4.60 (q, J = 7.1 Hz, 2 H), 6.95 (s, 1 H), 6.90–7.20 (m, 6 H), 7.20–
7.40 (m, 1 H), 8.10 (d, J = 8.3 Hz, 2 H). (The presence of an a/b
mixture of isomers complicates the spectrum.)
1H NMR (200 MHz, CDCl3): minor b-isomer 6b: d = 7.90 (d,
J = 8.4 Hz, 2 H). (Only the most significant resonance is listed.)
13C NMR (50 MHz, CDCl3): major a-isomer 5b: d = 2.8 (3), 7.1 (3),
14.2, 60.7, 127.3, 127.7 (2), 127.9 (2), 128.6, 129.4 (2), 129.9 (2),
136.9, 139.2, 143.2, 148.7, 166.6.
1H NMR (200 MHz, CDCl3): minor isomer: d = 4.00 (s, 3 H). (Only
the most significant resonance is listed.)
(E)-4-[2-Phenyl-1-(triethylsilyl)vinyl]benzyl Acetate (5f) and
(E)-4-[2-Phenyl-2-(triethylsilyl)vinyl]benzyl Acetate (6f)
Yield: 67%; ratio a/b ca. 54:46.
IR (neat): 3024, 2953, 2910, 2874, 1741, 1599, 1572, 1508, 1492,
1416, 1378, 1224, 1018, 1006, 965, 818, 777, 756, 730, 700 cm–1.
1H NMR (200 MHz, CDCl3): major isomer: d = 0.50–0.70 (q,
J = 8.1 Hz, 6 H), 0.90 (t, J = 8.1 Hz, 9 H), 2.00 (s, 3 H), 5.10 (s, 2
H), 6.75 (s, 1 H), 6.80–7.00 (m, 6 H), 7.05–7.20 (m, 3 H). (The pres-
ence of an a/b mixture of isomers complicates the spectrum.)
Anal. Calcd for C23H30O2Si (366.57): C, 75.36; H, 8.25. Found: C,
75.11; H, 8.52.
1H NMR (200 MHz, CDCl3): minor isomer: d = 2.95 (s, 3 H), 4.90
(s, 2 H), 6.70 (s, 1 H). (Only the most significant resonances are list-
ed.)
13C NMR (50 MHz, CDCl3): mixture 5f and 6f: d = 2.7 (6), 7.2 (6),
20.8, 20.9, 65.8, 66.1, 125.5, 127.0, 127.1, 127.4, 127.7, 127.8,
128.4, 128.6, 129.4, 129.6, 133.1, 134.4, 137.2, 138.1, 139.0, 143.0,
143.1, 143.5, 144.7, 170.7.
Ethyl (E)-4-[2-(4-Methoxyphenyl)-1-(triethylsilyl)vinyl]ben-
zoate (5c)
Yield: 95%; ratio a/b ca. 77:23.
IR (neat): 2953, 2906, 2874, 2836, 1716, 1604, 1508, 1462, 1366,
1270, 1248, 1174, 1100, 1019, 1005, 968, 945, 892, 856, 827, 775,
705 cm–1.
1H NMR (300 MHz, CDCl3): major a-isomer 5c: d = 0.50–0.70 (m,
6 H), 0.80–1.00 (m, 9 H), 1.30 (t, J = 7.1 Hz, 3 H), 3.65 (s, 3 H),
4.30 (q, J = 7.1 Hz, 2 H), 6.55 (d, J = 8.9 Hz, 2 H), 6.65 (s, 1 H),
6.75 (d, J = 8.9 Hz, 2 H), 7.00 (d, J = 8.5 Hz, 2 H), 7.95 (d, J = 8.5
Hz, 2 H). (The presence of an a/b mixture of isomers complicates
the spectrum.)
(E)-Triethyl[1-(2-nitrophenyl)-2-phenylvinyl]silane (5g)
Yield: 92%.
IR (neat): 3062, 3023, 2954, 2909, 2875, 1607, 1568, 1520, 1342,
1302, 1238, 1006, 962, 939, 853, 786, 753, 691 cm–1.
1H NMR (200 MHz, CDCl3): d = 0.90 (m, 6 H), 1.10 (t, J = 8.0 Hz,
9 H), 6.95 (s, 1 H), 7.00–7.10 (m, 2 H), 7.15–7.35 (m, 4 H), 7.50 (td,
J = 8.1 Hz, J = 1.5 Hz, 1 H), 7.65 (td, J = 7.4 Hz, J = 1.5 Hz, 1 H),
8.25 (d, J = 8.1 Hz, 1 H).
1H NMR (200 MHz, CDCl3): minor b-isomer 6c: d = 7.15 (s, 1 H).
(Only the most significant resonance is listed.)
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A. Hamze et al.
SPECIAL TOPIC
13C NMR (50 MHz, CDCl3): d = 3.3 (3), 7.1 (3), 123.9, 124.7,
126.6, 127.2 (2), 128.8 (2), 130.3, 133.3, 137.0, 138.7, 139.5, 140.3,
147.6.
1H NMR (200 MHz, CDCl3): minor a-isomer 6k: d = 3.85 (s, 3 H).
(Only the most significant resonances are listed.)
13C NMR (50 MHz, CDCl3): major a-isomer 5k: d = 3.2 (3), 7.2 (3),
54.9, 110.4, 120.8, 126.7, 126.9, 127.6, 127.8, 127.9, 128.4, 128.9,
132.0, 137.9, 138.5, 140.8, 156.0.
Anal. Calcd for C20H25NO2Si (339.51): C, 70.75; H, 7.42; N, 4.13.
Found: C, 70.11; H, 7.70; N, 4.02.
Anal. Calcd for C21H28OSi (324.19): C, 77.72; H, 8.70. Found: C,
77.64; H, 8.64.
Ethyl (E)-2-[2-Phenyl-1-(triethylsilyl)vinyl]benzoate (5h)
Yield: 72%.
IR (neat): 3059, 2953, 2908, 2875, 1709, 1596, 1566, 1494, 1286,
1266, 1244, 1171, 1131, 1044, 766, 754, 710, 691 cm–1.
(E)-2-[2-Phenyl-1-(triethylsilyl)vinyl]benzyl Acetate (5l)
Yield: 68%; ratio a/b ca. 92:8.
1H NMR (200 MHz, CDCl3): d = 0.50–0.70 (m, 6 H), 0.85 (t, J = 8.1
Hz, 9 H), 1.10 (t, J = 7.1 Hz, 3 H), 3.95–4.20 (m, 2 H), 6.70 (s, 1 H),
6.75–7.05 (m, 6 H), 7.15 (t, J = 7.5 Hz, 1 H), 7.30 (t, J = 7.5 Hz, 1
H), 7.85 (d, J = 7.7 Hz, 1 H).
13C NMR (50 MHz, CDCl3): d = 3.2 (3), 7.2 (3), 14.0, 60.5, 125.5,
126.6, 127.8, 128.1, 128.8, 129.0, 129.3, 130.4, 131.3, 131.9, 137.0,
139.7, 143.8, 144.7, 167.0.
IR (neat): 3062, 3022, 2953, 2910, 2875, 1799, 1739, 1601, 1571,
1494, 1459, 1443, 1416, 1379, 1360, 1224, 1073, 1018, 964, 839,
802, 754, 716, 691 cm–1.
1H NMR (200 MHz, CDCl3): major a-isomer 5l: d = 0.55–0.75 (q,
J = 8.1 Hz, 6 H), 0.90 (t, J = 8.1 Hz, 9 H), 1.70 (s, 3 H), 4.75 (d,
J = 12.5 Hz, 1 H), 4.85 (d, J = 12.5 Hz, 1 H), 6.80 (s, 1 H), 6.80–
6.90 (m, 2 H), 6.95–7.10 (m, 4 H), 7.15–7.35 (m, 3 H). (The pres-
ence of an a/b mixture of isomers complicates the spectrum.)
Anal. Calcd for C23H30O2Si (366.57): C, 75.44; H, 8.25. Found: C,
75.11; H, 8.41.
1H NMR (200 MHz, CDCl3): minor a-isomer 6l: d = 5.10 (s, 1 H).
(Only the most significant resonance is listed.)
Ethyl (E)-2-[2-(4-Methoxyphenyl)-1-(triethylsilyl)vinyl]ben-
zoate (5i)
Yield: 74%.
13C NMR (50 MHz, CDCl3): major a-isomer 5l: d = 3.2 (3), 7.2 (3),
20.6, 64.3, 126.1, 127.4, 127.6, 128.0 (2), 128.5, 129.2 (2), 129.3,
131.7, 137.4, 140.1, 141.4, 142.3, 170.6.
IR (neat): 2952, 2908, 2874, 2836, 1719, 1604, 1566, 1508, 1462,
1441, 1417, 1366, 1287, 1266, 1244, 1177, 1130, 1075, 1036, 1008,
964, 941, 889, 853, 824, 767, 750, 709 cm–1.
Anal. Calcd for C23H30O2Si (366.57): C, 75.36; H, 8.25. Found: C,
75.21; H, 8.04.
1H NMR (300 MHz, CDCl3): d = 0.40–0.60 (m, 6 H), 0.75 (t, J = 7.7
Hz, 9 H), 1.10 (t, J = 7.1 Hz, 3 H), 3.50 (s, 3 H), 3.85–4.10 (m, 2 H),
6.40 (d, J = 8.8 Hz, 2 H), 6.45 (s, 1 H), 6.60 (d, J = 8.8 Hz, 2 H),
6.75 (d, J = 7.7 Hz, 1 H), 6.95–7.10 (t, J = 7.7 Hz, 1 H), 7.15–7.25
(t, J = 7.7 Hz, 1 H), 7.70 (d, J = 7.7 Hz, 1 H).
13C NMR (75 MHz, CDCl3): d = 3.3 (3), 7.4 (3), 14.2, 55.1, 60.6,
113.3 (2), 125.5, 129.0, 129.5, 130.5 (2), 130.6, 132.1, 136.6, 141.1,
145.1, 158.4, 167.3 (one C missing).
(E)-4-(2-Pyridin-2-yl-1-(triethylsilyl)vinyl]benzonitrile (5m)
Yield: 61%.
IR (neat): 2957, 2910, 2890, 2228, 1605, 1582, 1565, 1496, 1459,
1435, 1414, 1379, 1265, 1233, 1163, 1109, 1050, 1002, 966, 932,
907, 891, 844, 775, 737, 718, 697 cm–1.
1H NMR (200 MHz, CDCl3): d = 0.50–0.65 (q, J = 7.1 Hz, 6 H),
0.90 (t, J = 7.1 Hz, 9 H), 6.50 (d, J = 8.0 Hz, 1 H), 6.90–7.00 (m, 1
H), 6.95 (s, 1 H), 7.05 (d, J = 8.5 Hz, 2 H), 7.20–7.30 (td, J = 7.6
Hz, J = 1.8 Hz, 1 H), 7.50 (d, J = 8.5 Hz, 2 H), 8.45 (m, 1 H).
13C NMR (75 MHz, CDCl3): d = 2.5 (3), 7.1 (3), 109.4, 118.9,
121.8, 123.6, 127.8 (2), 132.3 (2), 135.4, 140.3, 146.3, 148.4, 149.2,
155.0.
Anal. Calcd for C24H32O3Si (396.21): C, 72.68; H, 8.13. Found: C,
72.55; H, 8.01.
(E)-2-[2-Phenyl-1-(triethylsilyl)vinyl]benzonitrile (5j)
Yield: 80%.
Anal. Calcd for C20H24N2Si (320.17): C, 74.95; H, 7.55; N, 8.74.
Found: C, 74.77; H, 7.36; N, 8.58.
IR (neat): 3061, 3023, 2953, 2910, 2875, 2224, 1597, 1572, 1494,
1459, 1416, 1379, 1208, 1076, 1006, 963, 938, 875, 795, 745, 717,
692 cm–1.
1H NMR (200 MHz, CDCl3): d = 0.60–0.80 (m, 6 H), 1.00 (t, J = 8.0
Hz, 9 H), 6.85–7.00 (m, 2 H), 7.00 (s, 1 H), 7.05–7.40 (m, 5 H),
7.40–7.50 (m, 2 H).
13C NMR (50 MHz, CDCl3): d = 3.1 (3), 7.2 (3), 111.2, 118.1,
126.1, 127.5, 128.0 (2), 128.5, 129.0 (2), 132.5, 133.2, 136.7, 140.0,
141.9, 147.6.
(E)-4-[2-Pyridin-2-yl-2-(triethylsilyl)vinyl]benzonitrile (6m)
Yield: 9%.
IR (neat): 2953, 2910, 2874, 2227, 1602, 1582, 1560, 1501, 1463,
1426, 1410, 1378, 1278, 1238, 1174, 1148, 1091, 1049, 1005, 974,
943, 887, 826, 788, 721 cm–1.
1H NMR (200 MHz, CDCl3): d = 0.50–0.65 (q, J = 7.9 Hz, 6 H),
0.90 (t, J = 7.9 Hz, 9 H), 6.65 (m, 1 H), 6.70 s, 1 H), 6.80 (d, J = 8.6
Hz, 2 H), 7.00–7.10 (m, 1 H), 7.30 (d, J = 8.6 Hz, 2 H), 7.50 (td,
J = 7.5 Hz, J = 1.5 Hz, 1 H), 8.55 (m, 1 H).
Anal. Calcd for C21H25NSi (319.52): C, 78.94; H, 7.89; N, 4.38.
Found: C, 78.71; H, 8.20; N, 4.34.
13C NMR (75 MHz, CDCl3): d = 3.0 (3), 7.3 (3), 110.4, 118.9,
121.0, 122.5, 129.7 (2), 131.7 (2), 136.3, 138.3, 141.7, 148.7, 149.9,
161.3.
(E)-Triethyl[1-(2-methoxyphenyl)-2-phenylvinyl]silane (5k)
Yield: 64%; ratio a/b ca. 80:20.
IR (neat): 3056, 2951, 2909, 2874, 2833, 1592, 1576, 1486, 1460,
1434, 1416, 1377, 1292, 1272, 1242, 1180, 1110, 1073, 1049, 1029,
1006, 966, 947, 919, 883, 846, 800, 749, 714, 691 cm–1.
Anal. Calcd for C20H24N2Si (320.17): C, 74.95; H, 7.55; N, 8.74.
Found: C, 74.71; H, 7.28; N, 8.55.
1H NMR (200 MHz, CDCl3): major a-isomer 5k: d = 0.50–0.70 (q,
J = 8.1 Hz, 6 H), 0.90 (t, J = 8.1 Hz, 9 H), 3.65 (s, 3 H), 6.75–6.85
(m, 3 H), 6.90–7.20 (m, 7 H). (The presence of an a/b mixture of
isomers complicates the spectrum.)
(E)-2-[2-Pyridin-2-yl-1-(triethylsilyl)vinyl]benzonitrile (5n)
Yield: 69%.
IR (neat): 3061, 2954, 2910, 2876, 2224, 1582, 1566, 1458, 1435,
1425, 1379, 1265, 1237, 1192, 1175, 1151, 1096, 1006, 964, 934,
904, 876, 824, 794, 761, 742, 717, 705 cm–1.
Synthesis 2007, No. 13, 2025–2036 © Thieme Stuttgart · New York

SPECIAL TOPIC
Regiochemical Aspects of the Platinum Oxide Catalyzed Hydrosilylation of Alkynes
2035
1H NMR (200 MHz, CDCl3): d = 0.50–0.65 (q, J = 8.1 Hz, 6 H),
0.90 (t, J = 8.1 Hz, 9 H), 6.60 (dt, J = 7.9 Hz, J = 0.9 Hz, 1 H), 6.90–
6.95 (m, 1 H), 7.05 (s, 1 H), 7.00–7.10 (d, J = 9.2 Hz, 1 H), 7.20–
7.30 (m, 2 H), 7.40–7.60 (m, 2 H), 8.40 (m, 1 H).
13C NMR (75 MHz, CDCl3): d = 3.0 (3), 7.2 (3), 110.8, 118.2,
122.0, 123.3, 126.2, 127.8, 132.8, 133.2, 135.8, 141.7, 144.1, 147.5,
149.4, 155.0.
Methyl (E)-2-[1-(Triethylsilyl)vinyl]benzoate (8d) and Methyl
(E)-2-[2-(Triethylsilyl)vinyl]benzoate (9d)
Yield: 84%; ratio a/b ca. 52:48.
IR (neat): 2951, 2909, 2875, 1722, 1598, 1566, 1458, 1433, 1416,
1289, 1252, 1190, 1163, 1126, 1074, 1043, 1009, 967, 927, 840,
812, 783, 768 cm–1.
1H NMR (300 MHz, CDCl3): mixture 8d and 9d: d = 0.30–0.50 (m,
12 H), 0.60–0.75 (t, J = 7.7 Hz, 9 H), 0.75–0.85 (t, J = 7.7 Hz, 9 H),
3.60 (s, 3 H), 3.65 (s, 3 H), 5.35 (d, J = 3.0 Hz, 1 H), 5.40 (d, J = 3.0
Hz, 1 H), 6.10 (d, J = 19.2 Hz, 1 H), 6.80 (d, J = 7.3 Hz, 1 H), 6.95–
7.10 (m, 2 H), 7.15–7.30 (m, 2 H), 7.35–7.50 (m, 2 H), 7.55–7.70
(m, 2 H).
Anal. Calcd for C20H24N2Si (320.17): C, 74.95; H, 7.55; N, 8.74.
Found: C, 74.79; H, 7.35; N, 8.60.
(E)-Triethyl(styryl)silane (9a)
Yield: 86%; ratio a/b ca. 15:85.
IR (neat): 3300, 2953, 2910, 2875, 1603, 1494, 1457, 1415, 1378,
1238, 1014, 989, 974, 826, 785, 734 cm–1.
1H NMR (200 MHz, CDCl3): major b-isomer 9a: d = 0.65 (q,
J = 6.8 Hz, 6 H), 1.00 (t, J = 6.8 Hz, 9 H), 6.45 (d, J = 19.3 Hz, 1
H), 6.95 (d, J = 19.3 Hz, 1 H), 7.15–7.30 (m, 3 H), 7.30–7.40 (m, 2
H).
13C NMR (75 MHz, CDCl3): mixture 8d and 9d: d = 3.4 (3), 3.5 (3),
7.3 (3), 7.4 (3), 51.7, 52.0, 125.7, 126.8, 127.2, 127.3, 128.5, 128.8,
129.0, 129.6, 129.9, 130.2, 131.1, 131.9, 140.6, 143.8, 147.0, 151.8,
168.0, 168.4.
Anal. Calcd for C16H24O2Si (276.15): C, 69.51; H, 8.75. Found: C,
69.42; H, 8.67.
1H NMR (200 MHz, CDCl3): minor a-isomer 8a: d = 5.60 (d,
J = 3.1 Hz, 1 H), 5.90 (d, J = 3.1 Hz, 1 H). (Only the most signifi-
cant resonances are listed.)
(E)-Triethyl[2-(2-methoxyphenyl)vinyl]silane (9e)
Yield: 97%; ratio a/b ca. 38:62.
IR (neat): 2952, 2909, 2874, 2834, 1596, 1486, 1462, 1436, 1415,
1327, 1288, 1242, 1178, 1161, 1105, 1092, 1049, 1030, 1006, 972,
929, 834, 802, 784, 747, 720 cm–1.
1H NMR (300 MHz, CDCl3): major b-isomer 9e: d = 0.30–0.50 (m,
6 H), 0.60–0.75 (m, 9 H), 3.70 (s, 3 H), 6.30 (d, J = 19.4 Hz, 1 H),
6.70–6.90 (m, 2 H), 7.00–7.15 (m, 1 H), 7.25 (d, J = 19.4 Hz, 1 H),
7.45 (dd, J = 7.7 Hz, J = 1.7 Hz, 1 H).
1H NMR (300 MHz, CDCl3): minor b-isomer 8e: d = 3.65 (s, 3 H),
5.50 (d, J = 3.4 Hz, 1 H), 5.75 (d, J = 3.4 Hz, 1 H). (Only the most
significant resonances are listed.)
13C NMR (75 MHz, CDCl3): major b-isomer 9e: d = 53.1, 136.9.
(Only the most significant resonances are listed.)
13C NMR (75 MHz, CDCl3): minor a-isomer 8e: d = 52.4, 126.1
(=CH2). (Only the most significant resonances are listed.)
13C NMR (50 MHz, CDCl3): major b-isomer 9a: d = 3.6 (3), 7.3 (3),
125.8, 126.3 (2), 128.0 (2), 128.7, 138.6, 145.0.
Anal. Calcd for C14H22Si (218.15): C, 76.99; H, 10.15. Found: C,
76.77; H, 10.04.
Methyl (E)-4-[2-(Triethylsilyl)vinyl]benzoate (9b)
Yield: 98%; ratio a/b ca. 24:76.
IR (neat): 2952, 2874, 1721, 1605, 1458, 1435, 1409, 1274, 1243,
1193, 1176, 1106, 1016, 988, 969, 864, 842, 806, 782, 753 cm–1.
1H NMR (200 MHz, CDCl3): major b-isomer 9b: d = 0.55–0.75 (q,
J = 7.9 Hz, 6 H), 0.90 (t, J = 7.9 Hz, 9 H), 3.80 (s, 3 H), 6.50 (d,
J = 19.2 Hz, 1 H), 6.85 (d, J = 19.2 Hz, 1 H), 7.40 (d, J = 8.3 Hz, 2
H), 7.90 (d, J = 8.3 Hz, 2 H).
1H NMR (200 MHz, CDCl3): minor a-isomer 8b: d = 0.55–0.75 (q,
J = 7.8 Hz, 6 H), 0.85 (t, J = 7.8 Hz, 9 H), 3.78 (s, 3 H), 5.55 (d,
J = 3.0 Hz, 1 H), 5.80 (d, J = 3.0 Hz, 1 H), 7.10 (d, J = 8.5 Hz, 2 H),
7.85 (d, J = 8.5 Hz, 2 H).
Anal. Calcd for C15H24OSi (248.16): C, 72.52; H, 9.74. Found: C,
72.14; H, 9.48.
(E)-Triethyl(hept-1-enyl)silane (12a)
Yield: 98; ratio a/b ca. 10:90.
13C NMR (50 MHz, CDCl3): major b-isomer 9b: d = 3.4 (3), 7.2 (3),
52.0, 126.2 (2), 129.2, 129.7, 129.8 (2), 142.7, 143.7, 166.9.
IR (neat): 2954, 2927, 2874, 1616, 1459, 1416, 1378, 1237, 1014,
991, 922, 781, 717 cm–1.
1H NMR (300 MHz, CDCl3): major b-isomer 12a: d = 0.40–0.50 (q,
J = 7.3 Hz, 6 H), 0.80–0.95 (m, 12 H), 1.15–1.40 (m, 6 H), 1.95–
2.10 (m, 2 H), 5.45 (dt, J = 18.7 Hz, J = 1.5 Hz, 1 H), 5.95 (dt,
J = 18.7 Hz, J = 6.2 Hz, 1 H).
1H NMR (300 MHz, CDCl3): minor a-isomer 11a: d = 5.20 (td,
J = 3.0 Hz, J = 0.9 Hz, 1 H), 5.50 (m, 1 H). (Only the most signifi-
cant resonances are listed.)
Anal. Calcd for C16H24O2Si (276.15): C, 69.51; H, 8.75. Found: C,
69.48; H, 8.74.
(E)-Triethyl[2-(4-methoxyphenyl)vinyl]silane (9c)
Yield: 96%; ratio a/b ca. 18:82.
IR (neat): 2952, 2908, 2874, 2835, 1606, 1570, 1508, 1462, 1441,
1416, 1332, 1294, 1249, 1171, 1106, 1037, 1010, 986, 843, 789,
749, 717 cm–1.
1H NMR (200 MHz, CDCl3): major b-isomer 9c: d = 0.55–0.75 (q,
J = 7.9 Hz, 6 H), 0.85 (t, J = 7.9 Hz, 9 H), 3.70 (s, 3 H), 6.50 (d,
J = 19.2 Hz, 1 H), 6.85 (d, J = 19.2 Hz, 1 H), 7.40 (d, J = 8.3 Hz, 2
H), 7.90 (d, J = 8.3 Hz, 2 H).
1H NMR (200 MHz, CDCl3): minor a-isomer 8c: d = 3.68 (s, 3
H),5.40 (d, J = 3.2 Hz, 1 H), 5.75 (d, J = 3.2 Hz, 1 H). (Only the
most significant resonances are listed.)
13C NMR (75 MHz, CDCl3): major b-isomer 12a: d = 3.5 (3), 7.4
(3), 14.1, 22.5, 28.5, 31.4, 37.0, 125.4, 148.8.
Anal. Calcd for C13H28Si (212.20): C, 73.50; H, 13.28. Found: C,
73.19; H, 13.07.
(E)-Triethyl(3-methoxybut-1-enyl)silane (12b)
Yield: 78%; ratio a/b ca. 12:88.
13C NMR (50 MHz, CDCl3): major b-isomer 9c: d = 3.7 (3), 7.4 (3),
52.3, 113.9 (2), 123.4, 127.5 (2), 131.6, 144.3, 159.6.
IR (neat): 2953, 2910, 2875, 2818, 1675, 1619, 1458, 1416, 1371,
1323, 1232, 1199, 1110, 1079, 1012, 992, 972, 910, 849, 778, 718
cm–1.
1H NMR (200 MHz, CDCl3): major b-isomer 12b: d = 0.40–0.50
(m, 6 H), 0.80–0.95 (m, 9 H), 1.10 (d, J = 6.3 = Hz, 3 H), 3.20 (s, 3
Anal. Calcd for C15H24OSi (248.16): C, 72.52; H, 9.74. Found: C,
72.38; H, 9.56.
Synthesis 2007, No. 13, 2025–2036 © Thieme Stuttgart · New York

2036
A. Hamze et al.
SPECIAL TOPIC
H), 3.55–3.70 (q, J = 6.3 Hz, 1 H), 5.65 (d, J = 18.9 Hz, 1 H), 5.85
(dd, J = 18.9 Hz, J = 6.3 Hz, 1 H).
1H NMR (300 MHz, CDCl3): minor a-isomer 11d: d = 3.15 (s, 3 H),
5.35 (dd, J = 2.9 Hz, J = 0.7 Hz, 1 H). (Only the most significant
resonances are listed.)
13C NMR (75 MHz, CDCl3): major b-isomer 12b: d = 3.3 (3), 7.3
(3), 21.1, 56.0, 80.6, 127.7, 148.9.
(2) Trost, B. M. Science 1991, 254, 1471.
(3) An excellent overview of the addition of metalloid hydrides
to alkynes appeared recently, see: Trost, B. M.; Ball, Z. T.
Synthesis 2005, 853.
(4) For recent advances in the metal-catalyzed hydrosilylation
of alkynes, see: (a) Arico, C. S.; Cox, L. R. Org. Biomol.
Chem. 2004, 2, 2558. (b) Trost, B. M.; Ball, Z. T. J. Am.
Chem. Soc. 2001, 123, 12726. (c) Kawanami, Y.; Sonoda,
Y.; Mori, T.; Yamamoto, K. Org. Lett. 2002, 4, 2825.
(d) Maifeld, S. V.; Tran, M. N.; Lee, D. Tetrahedron Lett.
2005, 46, 105. (e) Faller, J. W.; D’Alliessi, D. G.
Organometallics 2002, 21, 1743. (f) Kawanami, Y.;
Yamamoto, K. Synlett 1995, 1232. (g) Uno, T.;
Wakayanagi, S.; Sonoda, Y.; Yamamoto, K. Synlett 2003,
1997. (h) Denmark, S. E.; Wang, Z. Org. Lett. 2001, 3,
1073. (i) Katayama, H.; Taniguchi, K.; Kobayashi, M.;
Sagawa, T.; Minami, T.; Ozawa, F. J. Organomet. Chem.
2002, 645, 192.
Anal. Calcd for C11H24OSi (200.16): C, 65.93; H, 12.07. Found: C,
65.79; H, 11.99.
(E)-1-Methyl-3-(triethylsilyl)allyl Acetate (12c)
Yield: 60%; ratio a/b ca. 29:71.
IR (neat): 2954, 2911, 2876, 1740, 1623, 1458, 1417, 1369, 1235,
1135, 1043, 1009, 950, 849, 780, 718 cm–1.
1H NMR (200 MHz, CDCl3): major b-isomer 12c: d = 0.40–0.55
(m, 6 H), 0.80–0.95 (m, 9 H), 1.30 (d, J = 6.6 = Hz, 3 H), 2.10 (s, 3
H), 3.30–5.50 (m, 1 H), 5.75 (dd, J = 19.0 Hz, J = 1.3 Hz, 1 H), 6.00
(dd, J = 19.0 Hz, J = 5.0 Hz, 1 H).
1H NMR (300 MHz, CDCl3): minor a-isomer 11c: d = 2.05 (s, 3 H),
5.90 (m, 1 H). (Only the most significant resonances are listed.)
13C NMR (75 MHz, CDCl3): major b-isomer 12c: d = 3.1 (3), 7.3
(3), 20.0, 21.1, 72.5, 126.7, 146.0, 170.3.
(5) (a) Speier, J. L. Adv. Organomet. Chem. 1979, 17, 407.
(b) Lewis, L. N.; Sy, K. G.; Bryant, G. L. Jr.; Donahue, P. E.
Organometallics 1991, 10, 3750.
(6) (a) Green, M.; Spencer, J. L.; Stone, G. A. F.; Tsipis, C. A.
J. Chem. Soc., Dalton Trans. 1977, 1525. (b) Tsipis, C. A.
J. Organomet. Chem. 1980, 187, 427. (c) Tsipis, C. A. J.
Organomet. Chem. 1980, 188, 53. (d) Takahasi, K.;
Minami, T.; Ohara, Y.; Hiyama, T. Tetrahedron Lett. 1993,
34, 8263. (e) Denmark, S. E.; Wang, Z. G. Org. Lett. 2001,
3, 1073. (f) Murphy, P. J.; Spencer, J. L.; Procter, G.
Tetrahedron Lett. 1990, 31, 1051.
Anal. Calcd for C12H24O2Si (228.15): C, 63.10; H, 10.59. Found: C,
62.80; H, 10.40.
(E)-3-(Triethylsilyl)allyl Acetate (11d)
Yield: 90%; ratio a/b ca. 88:12.
(7) De Bo, G.; Berthon-Gelloz, G.; Tinant, B.; Markó, I. E.
Organometallics 2006, 25, 1881.
(8) Chauhan, M.; Hauck, B. J.; Keller, L. P.; Boudjouk, P. J.
Organomet. Chem. 2002, 645, 1.
(9) Jiménez, R.; Martínez-Rosales, J. M.; Cervantes, J. Can. J.
Chem. 2003, 81, 1370.
(10) (a) Liron, F.; Le Garrec, P.; Alami, M. Synlett 1999, 246.
(b) Alami, M.; Liron, F.; Gervais, M.; Peyrat, J. F.; Brion, J.
D. Angew. Chem. Int. Ed. 2002, 41, 1578. (c) Liron, F.;
Gervais, M.; Peyrat, J. F.; Alami, M.; Brion, J. D.
Tetrahedron Lett. 2003, 44, 2789. For the hydrostannation
of enynes and related compounds see: (d) Alami, M.; Ferri,
F. Synlett 1996, 755. (e) Ferri, F.; Alami, M. Tetrahedron
Lett. 1996, 37, 7971. (f) Bujard, M.; Ferri, F.; Alami, M.
Tetrahedron Lett. 1998, 39, 4243. (g) Hamze, A.; Provot,
O.; Brion, J.-D.; Alami, M. J. Org. Chem. 2007, 72, 3868.
(11) Hamze, A.; Provot, O.; Alami, M.; Brion, J.-D. Org. Lett.
2005, 7, 5625.
IR (neat): 2954, 2912, 2876, 1742, 1624, 1459, 1417, 1374, 1226,
1005, 845, 779, 720 cm–1.
1H NMR (200 MHz, CDCl3): major b-isomer 11d: d = 0.40–0.55
(m, 6 H), 0.80–0.95 (m, 9 H), 2.00 (s, 3 H), 4.60 (t, J = 1.5 Hz, 2 H),
5.35 (m, 1 H), 5.80 (m, 1 H).
1H NMR (300 MHz, CDCl3): minor a-isomer 12d: d = 2.02 (s, 3 H),
4.55 (dd, J = 5.1 Hz, J = 1.5 Hz, 2 H). (Only the most significant
resonances are listed.)
13C NMR (75 MHz, CDCl3): major b-isomer 11d: d = 3.3 (3), 7.3
(3), 20.9, 68.1, 126.6, 143.3, 170.6.
Anal. Calcd for C11H22O2Si (214.14): C, 61.63; H, 10.34. Found: C,
61.51; H, 10.10.
Acknowledgment
(12) Treatment of 2b with Et3SiH (1.5 equiv) in the presence of
H2PtCl6 or Pt/C (5 mol%) at 60 °C for a prolonged time (3 h)
did not promote any protodesilylation of 2b, indicating that
the reduced side product was formed from starting material
1b.
(13) Performing the hydrosilylation of 10a at 60 °C led to a
mixture of a- (10%) and b-isomers (23%) together with the
protodesilylated product (67%).
The CNRS is gratefully thanked for support of this research.
References
(1) (a) Colvin, E. W. Silicon Reagents in Organic Synthesis;
Academic Press: London, 1988. (b) Oshima, K. In Science
of Synthesis, Vol. 2; Fleming, I., Ed.; Georg Thieme Verlag:
Stuttgart, 2002, 685. (c) The Chemistry of Organosilicon
Compounds; Patai, S.; Rappaport, Z., Eds.; Wiley:
Chichester, 1998, Chap. 3.
(14) Alami, M.; Ferri, F.; Linstrumelle, G. Tetrahedron Lett.
1993, 34, 6403.
Synthesis 2007, No. 13, 2025–2036 © Thieme Stuttgart · New York