Cationic palladium complex-catalyzed hydrosilylative cross-coupling of alkynes with alkenes. 1,4-addition of triehlorosilane to form 4-silyl-1-butene framework

Article abstract of DOI:10.1246/bcsj.80.1814

A new hydrosilylative cross-coupling reaction of a variety of alkynes with several alkenes, which is catalyzed by a cationic palladium complex A (1 mol %) without or with added PPh₃ ligand, was studied systematically. The reaction using HSiCl₃ as an addend afforded more or less two types of products consisting of four possible derivatives, R¹CH=CR ²-CHR³-CHR⁴-SiCl₃, which always contained 4-trichlorosilyl-l-butene frameworks, in acceptable combined yields. The coupling pattern was dependent both on the precatalyst A in the absence or presence of PPh₃ [also P(C₆F₅)₃] and on the combination of the alkyne and alkene counterpart employed. A possible catalytic cycle that involves an initial hydropalladation of an alkyne, followed by a facile and specific carbopalladation of an alkene, is proposed. At the same time, the lack of regioselectivity in the latter step is noted. The effect of the added phosphine ligand on the coupling pattern is briefly discussed.

Full text of DOI:10.1246/bcsj.80.1814

1814 Bull. Chem. Soc. Jpn. Vol. 80, No. 9, 1814–1823 (2007)
ꢀ 2007 The Chemical Society of Japan
Cationic Palladium Complex-Catalyzed Hydrosilylative
Cross-Coupling of Alkynes with Alkenes.
1,4-Addition of Trichlorosilane to Form 4-Silyl-1-butene Framework
Takamitsu Shimamoto, Motoharu Chimori, Hiroaki Sogawa, Yuki Harada,
¯
ꢀ
Masaharu Aoki, and Keiji Yamamoto
Department of Materials Science and Environmental Engineering, Tokyo University of Science, Yamaguchi,
1-1-1 Daigaku-Dori, Sanyo-Onoda, Yamaguchi 756-0884
Received March 8, 2007; E-mail: kyamamoto ji@yahoo.co.jp
A new hydrosilylative cross-coupling reaction of a variety of alkynes with several alkenes, which is catalyzed by a
cationic palladium complex A (1 mol %) without or with added PPh3 ligand, was studied systematically. The reaction
using HSiCl3 as an addend afforded more or less two types of products consisting of four possible derivatives,
R1CH=CR2–CHR3–CHR4–SiCl3, which always contained 4-trichlorosilyl-1-butene frameworks, in acceptable com-
bined yields. The coupling pattern was dependent both on the precatalyst A in the absence or presence of PPh3 [also
P(C6F5)3] and on the combination of the alkyne and alkene counterpart employed. A possible catalytic cycle that
involves an initial hydropalladation of an alkyne, followed by a facile and specific carbopalladation of an alkene, is pro-
posed. At the same time, the lack of regioselectivity in the latter step is noted. The effect of the added phosphine ligand
on the coupling pattern is briefly discussed.
Ample research activities in the transition metal complex-
catalyzed hydrosilylation of alkenes and alkynes are still
focused on achieving either chemo-, regio-, or stereoselective
hydrosilylation as well as to obtain an insight into mechanisms
of the reaction. Catalytic hydrosilylation is a versatile synthetic
method for obtaining organosilicon compounds. The value of
this hydrosilylation has been further augmented by protocols
for converting the silyl group in the products to other function-
al groups.1
Among a variety of catalysts so far studied, late transition
metal complexes, especially those of groups 8–10, have been
found to play a key role in providing effective catalyst precur-
sors. The catalytic reaction is generally thought to proceed by
either hydrometalation (Chalk–Harrod mechanism) or silyl-
metalation (so-called modified Chalk–Harrod mechanism) as
one of the key steps in the catalytic cycles that depend on both
transition metals and hydrosilanes employed.2
ynes,8c,g and alkadienes,8f,10a–d it is worthy to note that trialkyl-
silanes must be used as addends in these cases, and HSiMen-
Cl3ꢁn (n ¼ 0{2) but none of trialkylsilanes are applicable for
our studies (Scheme 1; vide infra).5,12
The unique findings have originated from the fact that, when
Cat. A (0.5 mol%)
HSiCl3 (1 M, CH2Cl2)
H
X
X
si
rt, 0.1 h, (95% yield)
(exothermic)
B: X = (EtO2C)2C
Cat. A (0.5 mol%)
HSiCl3 (1 M, CH2Cl2)
H
X
X
si
rt, 12h, (80% yield)
We have been studying the palladium complex-catalyzed
hydrosilylation of alkynes, which involves primarily non-
conventional reaction categories other than 1,2-addition of a
hydrosilane to the substrate.3 Specifically, dimerization–hydro-
silylation of 1-alkynes is catalyzed by a bulky palladium(II)
complex as a precatalyst,4 and the cyclization–hydrosilylation
of 1,6-alkadiynes or 1,6-alkenynes5,6 as well as the competi-
tive, yet intriguing, cyclization–hydrosilylation of 1-alkene-
6,11-diynes7 have been realized using a cationic palladium(II)
complex. A key mechanistic feature of these transformations
appears to involve catalytic cycles driven by a hydridopalla-
dium species, for which simple hydrosilylation is suppressed.
Although there are a variety of examples of the late transi-
tion metal (Rh,8 Ni,9 Pd,10 and Pt11) complex-catalyzed cycli-
zation–hydrosilylation of ꢀ,!-alkadiynes,8a,e,g,9a,11b alken-
C: X = (MeO2C)2C
Cat. A (1 mol%)
Me
a
HSiCl3 (1 M, CH2Cl2)
rt, 6 h, (73% yield)
Me
b
Me
si
D
H
H
si
a
+
:
b
8
92
Scheme 1. Facile cyclization of 1,6-enynes.
Published on the web September 13, 2007; doi:10.1246/bcsj.80.1814

T. Shimamoto et al.
Bull. Chem. Soc. Jpn. Vol. 80, No. 9 (2007) 1815
HSiCl3 is an addend, a palladium complex, [Pd(ꢁ3-C3H5)-
(cod)]þ[PF6]ꢁ (A) (cod = 1,5-cyclooctadiene) can catalyze
the cyclization–hydrosilylation of a 1-hepten-6-yne (B) evi-
dently much faster than that of the corresponding 1,6-hepta-
diyne (C), as indicated in Scheme 1.6 An intramolecular com-
petitive cyclization of endiyne D reinforces this fact.7 As such,
it seems possible to develop a reaction between an alkyne with
an alkene, i.e., an intermolecular version of cyclization–hydro-
silylation of ꢀ,!-alkenynes as mentioned above. Herein, we
report that the cationic palladium complex A catalyzes a selec-
tive cross-coupling of alkynes with alkenes, which occurs
under hydrosilylation conditions.13
Table 1. Effect of Phosphorus Ligand on the Reaction
(Eq. 2)a)
Entry Ligand (L)
L/Pd Yield/%b)
Composition
(1b + 2b):3b
1
PPh3
PPh3
P(p-Tol)3
P(tm-tp)3
P(C6F5)3
(ArO)3Pf)
(PhO)3P
(EtO)3P
C6H11O3Pg)
C6H11O3Pg)
1
2
1
1
1
1
1
1
1
2
58
50
26
42
55
49
34
21
46
52
3:97
4:96
10:90
53:47
85e):15
7:93
2c)
3
d)
4
5
6
7
8
9
10
9:91
29:71
23:77
12:88
Results and Discussion
With the above findings in hand, we carried out a reaction of
a mixture of phenylacetylene (1.0 mmol) and 1-hexene (1, 3, or
5 equiv) with HSiCl3 (1 M, CH2Cl2, 1 mL) (1 M = 1 mol dmꢁ3
in the presence of the catalyst [Pd(ꢁ3-C3H5)(cod)]þ[PF6]ꢁ (A)
(0.01 mmol, 1 mol %), under an argon atmosphere at 50 ꢂC for
1–4 h in a 5 mL screw-capped test tube. The reaction mixture
immediately turned clear dark-brown in color and then pale
brown, and a black precipitate, which is indicative of a final
stage of the reaction, formed. The mixture was either subjected
directly to a bulb-to-bulb distillation, in vacuo, to isolate reac-
tion products containing a moisture-sensitive trichlorosilyl
group or treated immediately with excess dry ethanol and tri-
ethylamine in CH2Cl2 at 0 ꢂC for 2 h to isolate the correspond-
ing triethoxy derivative of the hydrosilylative cross-coupling
products. In the latter case, two major products were obtained
in 70% combined yield after a usual work up, as indicated
in Eq. 1. It was also found that use of excess 1-hexene (3
equiv) resulted in a better yield of the cross-coupling products,
whereas product ratios of 1a (ꢀ-1)14 to 2a (ꢀ-2)14 (ca. 60:40)
did not change (see, Experimental).
a) 1-Hexene (3 equiv) to phenylacetylene was used. b) Isolat-
ed as triethoxysilyl derivatives. c) 1-Hexene (5 equiv) was
used. d) A bowl-shaped phosphine (Ref. 16). e) 1b:2b =
82:18. f) Ar = 2,4-Di-t-butylphenyl. g) Trimethylolpropane
phosphite.
However, once triphenylphosphine (1 equiv) was added to
the precatalyst A, the same reaction as above exhibited a quite
different reaction pattern after 3 h, as shown in Eq. 2. The
initial hydropalladation appears to attach the palladium center
to the ꢂ-position of phenylacetylene exclusively, resulting in
coupling product 3a (ꢂ-1),14 which was isolated as triethoxy-
silyl derivative 3b in 58% isolated yield.
Cat. A + PPh3
EtOH/Et3N
0 °C
(1 mol%) (1 equiv)
Bu
+
Ph
HSiCl3,CH2Cl2, 50 °C
H
Bu
ð2Þ
β
Cat. A (1 mol%)
EtOH/Et3N
1
+
others
Ph
Bu
+
Ph
H
si
HSiCl3,CH2Cl2, 50 °C
0 °C
si = SiCl3 : 3a
si = Si(OEt)3 : 3b (58% yield)
H
H
H
H
ð1Þ
Being interested in the reversed regioselectivity giving 3b
(ꢂ-1), we investigated the effects of other phosphorus ligands
for the precatalyst A on the regiocontrol of this reaction. All
results obtained are listed in Table 1. Several features may
be seen from Table 1. In the case of PPh3, the molar ratios
of phosphine ligand (L) to A (L/Pd = 1 or 2) had the little
effect on the product composition (1b + 2b):3b (Entries 1
and 2), whereas P(p-tolyl)3 and much bulkier, so-called
α
α
Ph
si
Ph
si
+
2
Bu
1
Bu
si = SiCl3 :
1a
1b
(60:40)
2a
2b
si = Si(OEt)3 :
(70% yield)
Since we have already confirmed that the initial step of
cyclization–hydrosilylation of substrate D (Scheme 1) must
take place at the alkyne site (path b rather than path a), the
result obtained here may be understood as follows: hydropal-
ladation initially occurs with phenylacetylene at an ꢀ-position
regioselectively,14 forming an alkenylpalladium intermediate.
Then, clean insertion of 1-hexene, rather than the second phen-
ylacetylene molecule,4 into the resulting alkenylpalladium in-
termediate (carbopalladation) proceeds with a lack of regiose-
lectivity. As a result, both a terminally silylated product (des-
ignated as 1)14 and an internally silylated one (designated as
2)14 are formed, the former being predominant (vide infra).
There was found little dimerization–hydrosilylation product
of phenylacetylene.15
16
bowl-shaped, P(tm-tp)3 (L/Pd = 1) gave rise to lower and
even inverted regiocontrol, respectively (Entries 3 and 4).
Use of P(C6F5)3 (L/Pd = 1) gave a mixture of 1b and 2b as
major cross-coupling products (up to 85%) along with minor
3b (15%) (Entry 5). In addition, the ratio of 1b (ꢀ-1) to 2b
(ꢀ-2) was 82:18, which was better than that without added
PPh3 (60:40) (cf. Eq. 1). The increased yield and regiocontrol
using P(C6F5)3 as a ligand must arise from its strong electro-
negative influence.17
On the other hand, both triaryl phosphites and trialkyl phos-
phites generally scarcely affected the product composition.
Thus, (PhO)3P as well as bulky tris(2,4-di-t-butylphenyl) phos-

1816 Bull. Chem. Soc. Jpn. Vol. 80, No. 9 (2007)
Hydrosilylative Coupling of Alkynes with Alkenes
Table 2. Hydrosilylative Cross-Coupling of 1-Alkynes with 1-Alkenes Catalyzed by Complex A
H
H
R1
α
H
H
R1
α
R1
H
H
β
Cat. A
R2
R1
R2
H
R2
+
+
+
H
R2
H
HSiCl3, CH2Cl2
1
2
1
si
si
si
(3 equiv)
50 °C
Compositionb)
(ꢀ-1 + ꢀ-2):ꢂ-1
Entry
1c)
R1
R2
Time/h
1.5
Yield/%a)
70
C6H5
C6H5
C4H9
91 (60:40)
1a 2a
93 (78:22)
9
3a
7
2
3
4
C6H5
C4H9
C6H5
3
71
56
52
Ph
Ph
Ph
Ph
H
H
si
Ph
H
si
Ph
si
4a
5a
8a
6a
C5H11
3
89 (66:34)
11
27
—
Am
Am
Bu
Am
H
H
si
Bu
H
si
Bu
si
7a
9a
C5H11
2.5
73 (81:19)
Am
Am
Ph
Am
H
H
si
Ph
H
si
Ph
si
10a
ꢃ100 (88:12)d)
11a
12a
5
CO2Me
C4H9
4
40
CO2Me
CO2Me
CO2Me
H
Bu
H
H
Bu
si
si
si
Bu
13a
14a
15a
a) Combined yield as triethoxysilyl derivatives (b series). b) Glc analysis of trichlorosilyl derivatives
(a series). c) See, Eq. 1. d) Minor product estimated to be ꢀ-2.
phite gave a similar level of regiocontrol as ordinary triaryl-
phosphines (Entries 6 and 7), whereas two trialkyl phosphites
examined did not (Entries 8 and 9). However, the sterically
least-demanding trimethylolpropane phosphite (L/Pd = 2;
Entry 10) gave results similar to (PhO)3P. After all, the effect
of PPh3 added to precatalyst A on the reversal of regiocontrol
from ꢀ- to ꢂ-position in the hydropalladation of phenylacety-
lene is steric in origin. Significance of the observed reversal in
the regioselectivity will also be mentioned later.
Although the critical nature of a cationic palladium(II)-
catalyzed hydrosilylation is not clear yet, the scope and limita-
tions with regard of the present hydrosilylative cross-coupling
between alkynes and alkenes were examined: phenylacetylene,
1-heptyne, or methyl propiolate, respectively, was used as a
typical 1-alkyne, while 1-hexene or styrene was used as a 1-
alkene counterpart.
rene (Entry 2: 4a + 5a and 6a) did not substantially change.
Also, the product composition for 1-heptyne with 1-hexene
(Entry 3: 7a + 8a and 9a) and with styrene (Entry 4: 10a +
11a and 12a) exhibited only a trivial change. Thus, as for a
specific insertion step of 1-alkenes to the alkenylpalladium
intermediate, styrene may undergo insertion a little more selec-
tively, giving a terminal (ꢀ-1) product, than 1-hexene (4a vs.
1a, and 10a vs. 7a). However, the reaction of methyl propio-
late with 1-hexene was exceptional, and coupling products
13a and 14a were obtained exclusively. This was the highest
regioselectivity for 13a (ꢀ-1) (Entry 5) exhibited so far. It is
worthy to note that the isolated methyl 2-{1-[(triethoxysilyl)-
methyl]pentyl}propenoate (13b) is an immediate precursor,
by means of the Tamao–Fleming oxidation of alkenylsilanes,
to 3-butyl-2-methylenebutanolide,18a which may be a useful
building block (See, Experimental).
Hydrosilylative cross-coupling, which was catalyzed by
complex A alone, was carried out, and the results are listed
in Table 2. As is seen in Table 2, although the combined
yields were not optimal and moderate, the general trend in
the product composition, ((ꢀ-1 + ꢀ-2) and ꢂ-1),14 for phenyl-
acetylene with 1-hexene (Entry 1: cf. Eq. 1) and that with sty-
With the same combination of 1-alkynes and 1-alkenes as
shown in Table 2, the hydrosilylative cross-coupling was also
conducted using the cationic complex A with added PPh3 (1
equiv) as catalyst, and the results are listed in Table 3. As
can be seen, there was a preference for ꢂ-1 over ꢀ-114 (Entries
1, 2 (3a, 6a), and 3, 4 (9a, 12a)), and the combined yields were

T. Shimamoto et al.
Bull. Chem. Soc. Jpn. Vol. 80, No. 9 (2007) 1817
moderate yet acceptable. However, a similar coupling of meth-
yl propiolate with 1-hexene exhibited, despite the presence of
PPh3, mixed regioselectivity to afford both 13a (ꢀ-1) and 15a
(ꢂ-1) in a ratio 57:43 (Entry 5). Furthermore, use of an equi-
molar amount of P(C6F5)3 (L/Pd = 1) was found to enhance
the ratio of 13a:15a (75:25) (Entry 6). The same and rather
confusing trend as described here has also been found in the
case of phenylacetylene (Table 1, Entry 5).17 Consequently,
it is of interest to point out, in terms of the observed coupling
pattern, that methyl propiolate and phenylacetylene behave
quite similarly under the catalytic conditions examined. Final-
ly, the cross-coupling of methyl propiolate with styrene under
the same conditions as in Entry 6 took place in an exclusive ꢀ
regioselective manner, and the product ratio of 16a (ꢀ-1):17a
(ꢀ-2) was 81:19 (Entry 7). Again, isolated 16a is a possible
precursor to 2-methylene-3-phenylbutanolide18b by undergo-
ing the Tamao oxidation.
Table 3. Hydrosilylative Cross-Coupling of 1-Alkynes with
1-Alkenes Catalyzed by Cat. A + PPh3 (1 equiv)
R1
H
Cat. A + PPh3
Certain internal alkynes or alkenes as coupling components
can also be used in hydrosilylative cross-coupling catalyzed by
cationic complex A, without or with PPh3 under the conditions
given in Eq. 1 or Eq. 2. In Table 4, selected examples, which
circumvent potentially complex coupling pattern, giving most-
ly two products with moderate combined yields, are listed. The
reaction of phenylacetylene with (E)-3-hexene gave regioiso-
meric 3-ethyl-2-phenyl-4-trichlorosilyl-1-hexene (18a) and
(E)-3-ethyl-1-phenyl-4-trichlorosilyl-1-hexene (19a) in a ratio
of 80:20 with 50% combined isolated yield as triethoxysilyl
derivatives 18b and 19b (Entry 1). It is of interest that the ob-
served isomer ratio was significantly lowered than that of
(1a + 2a):3a = 91:9 using 1-hexene as a coupling partner
(see, Table 2, Entry 1). The fact that the two isomer ratios
above differ significantly may be explained in terms of a rever-
sible hydropalladation of phenylacetylene, which occurs prior
to the successive carbopalladation with (E)-3-hexene and 1-
hexane, respectively.19 In the coupling reaction of 3-hexyne
with allylbenzene, (E)-2-benzyl-3-ethyl-1-trichlorosilyl-3-hex-
ene (20a) and (E)-4-ethyl-7-phenyl-6-trichlorosilyl-3-heptene
(21a) were found in a ratio of 80:20, being isolated as
triethoxysilyl derivatives (20b and 21b) in 40% combined
yield (Entry 2). The hydrosilylative reaction of ethyl 2-butyno-
ate with 1-hexene catalyzed by complex A with added PPh3
(1 equiv) gave ethyl (Z)-2-[1-(trichlorosilyl)methyl]pentyl-
2-butenoate (22a) and ethyl (E)-3-methyl-4-(trichlorosilyl)-
methyl-2-octenoate (23a) in a ratio of 60:40 and in 64% com-
bined yield as triethoxysilyl derivatives (Entry 3). It was
found, in this particular case, that both compounds were con-
(1 mol%)
β
R2
R2
R1
+
+ others
H
HSiCl3, CH2Cl2
1
H
si
(3 equiv)
50 °C
Compositionb)
Entry
R1
R2
Time/h Yield/%a)
ꢂ-1
ꢀ-1c)
3a
91
6a
93
9a
92
12a
96
15a
43
15a
25
1a
9
4a
7
7a
1d)
2
C6H5
C6H5
C4H9
C6H5
3
58
61
55
64
51
38
40
0.5
4
3e)
4
C5H11 C4H9
C5H11 C6H5
CO2Me C4H9
8
10a
4
13a
57
13a
75
16a 17a
81:19
0.5
4
5
6f) CO2Me C4H9
7f) CO2Me C6H5
3
2
—
a) Combined yield as triethoxysilyl
derivatives (b series). b) Glc ana-
lysis of trichlorosilyl derivatives (a
series). c) Hard to characterize ꢀ-2
except Entry 5. d) See, Eq. 2. e) In
case of added P(C6F5)3 9a:7a =
78:22 (see, Ref. 17). f) P(C6F5)3
was employed instead of PPh3.
CO2Me
Ph
CO2Me
Ph
H
H
si
si
16a
17a
Table 4. Palladium-Catalyzed Hydrosilylative Cross-Coupling Using Internal Alkynes or Alkenes
R1
R2
R4
Cat. A (1 mol%)
R1
R2
+
H
R4
HSiCl3, CH2Cl2
50 °C, 6 h
R3
R3
SiCl3
Entry
1
Alkyne
Alkene
Products
R1
R2
R3
R4
Yield/%a)
50
Ratiob)
Phenylacetylene
(E)-3-Hexene
Allylbenzene
1-Hexene
18a
19a
20a
H
Ph
Et
Ph
H
Et
Et
H
Bnc)
H
Et
Et
Bnc)
H
Bu
Bu
Me, Prh)
18a:19a
80:20
20a:21a
80:20
22a:23a
60:40
—
2
3-Hexyne
Et
Et
Ef)
Me
H
40
21a
Et
3d)
4d)
Ethyl
2-butynoate
Phenylacetylene
22ae)
23ae)
24a
Me
Ef)
Ph
64
H
H
2-Methyl-
1-penteneg)
58i)
a) Combined yield as triethoxysilyl derivatives (b series). b) Determined by GLC peak ratios. c) Benzyl. d) Triphen-
ylphosphine (1 equiv) added. e) A regioisomer of hexene component as a contaminant. f) Ethoxycarbonyl.
g) 2-Methyl-1-hexene also gave coupling product 240a (see, text and Experimental). h) Diastereomeric isomer
not observed. i) Dimerization/hydrosilylation of phenylacetylene slightly observed.

1818 Bull. Chem. Soc. Jpn. Vol. 80, No. 9 (2007)
Hydrosilylative Coupling of Alkynes with Alkenes
taminated by a significant amount of regioisomers probably
from reversed insertion of 1-hexene component. However,
the major reaction pattern was basically akin to that of methyl
propiolate with 1-hexene (see, Table 3, Entry 5). Finally, the
coupling reaction of phenylacetylene with 2-methyl-1-pentene,
a typical 1,1-disubstituted alkene, under exactly the same con-
ditions as in Entry 3 was examined, and (E)-3-methyl-1-phen-
yl-3-(trichlorosilyl)methyl-1-hexene (24a) (ꢂ-1)14 was exclu-
sively obtained in 58% yield (Entry 4). This reaction is char-
acterized as a quaternary carbon bond-forming coupling reac-
tion. Also, 2-methyl-1-hexene reacted to afford (E)-3-methyl-
1-phenyl-3-(trichlorosilyl)methyl-1-heptene (240a) as a sole
product in 38% yield as a triethoxy derivative 24b0. However,
the coupling reaction of 3-hexyne with (E)-3-hexene was
found to be very sluggish, and the starting material was recov-
ered unchanged.
[Pd(η3-C3H5)(cod)]+ (A)
R1
R2
H
SiCl3
(α−1)
R1
HPd+Ln
(iii)
(A')
HSiCl3
R1
R2
R1
H
+
1
Pd Ln
HPd+Ln
II
H
(ii)
(i)
R1
Pd+Ln
α
Throughout the hydrosilylative cross-coupling reactions
presented here (Tables 1–4), various amounts of simple hydro-
silylation product from alkenes, but not from alkynes, were
usually obtained. In the case of allylbenzene, a large amount
of hydrosilylation products were obtained at the expense of
diminished cross-coupling with 3-hexyne (Table 4, Entry 2).
Finally, although palladium complex A-catalyzed hydro-
silylative cross-coupling of alkynes with alkenes is new, it is
obvious that, besides the regioselectivity at the alkyne site,
less than satisfactory regiocontrol for the incoming 1-alkene
partners was observed.
R2
I
Scheme 2. Proposed catalytic cycle.
strate by coordinating selectively to A0. The catalytic cycle
may be explained in terms of elementary steps (i)–(iii) in
Scheme 2. (i) Initial hydropalladation of the alkyne takes
place, either in an ꢀ-directing or in a ꢂ-directing manner, to
form an alkenylpalladium (I) (depicted ꢀ only for clarity).
(ii) The latter, in turn, undergoes a rapid and specific alkene
insertion, the direction of which is not regioselective without
added PPh3. (iii) The resulting homoallylic organopalladium
(II) (depicted ꢀ-1 only) terminates one catalytic cycle by
undergoing HSiCl3 ꢃ-metathesis, if any, to substitute the pal-
ladium center with a trichlorosilyl group, giving rise to cou-
pling product(s), and, at the same time, regenerating A0 as an
active catalyst.
The reason why the step (ii) proceeds so selectively, if not
regioselectively, may be explained as follows. Cationic alke-
nylpalladium I has a few ligands, exhibiting substantial elec-
trophilicity that promotes a facile electrophilic addition to al-
kenes (carbopalladation).23 It is emphasized that, even though
alkenes were utilized in three-fold equivalents to alkynes, the
observation of an exclusive alkene insertion to the alkenylpal-
ladium I in step (ii), rather than a successive alkyne insertion,4
is unprecedented.
Catalytic Process. On the basis of the above observations,
the coupling reaction has two salient features. Firstly, the use
of both catalyst precursor [Pd(ꢁ3-C3H5)(cod)]þ[PF6]ꢁ (A) and
HSiCl3 as a hydrosilylating addend is essential for the cross-
coupling of alkynes with alkenes to proceed. Although another
non-coordinating counter anion [BF4]ꢁ worked equally well,
use of other chlorinated hydrosilanes, HSiMenCl3ꢁn (n ¼ 1
or 2), gave rise to hydrosilylation of alkenes employed. An
attempted stoichiometric reaction of complex A with HSiCl3
(1 M, CH2Cl2) in CD2Cl2 showed that propene and SiCl4,20
both of which were detected by 1H and 29Si NMR (see, Exper-
imental),21 were evolved. However, no hydridopalladium spe-
cies was detected. It appears most probable that the HSiCl3
solution we have prepared is inevitably contaminated with
HCl, and that the presence of HSiCl3, HCl, and complex A
would have resulted in giving propene, SiCl4 and a hydridopal-
ladium species, [HPdþLn] (A0) (L = ligand, substrate, or sol-
vent),22 which may play a key role in the catalytic process, as
discussed below. Secondly, the coupling pattern of the hydro-
silylative reactions between alkynes and alkenes was dramati-
cally affected by using either catalyst precursor A or that
modified with added PPh3 (e.g., Eq. 1 vs. Eq. 2). Thus, a sim-
ple 1-alkyne undergoes hydropalladation, if reversible, with
the catalyst A0 containing PPh3, a ꢂ-substituted intermediate,
i.e., a distal alkenylpalladium intermediate, whereas reversed
hydropalladation proceeds with the catalyst A0 without PPh3
to form preferentially an ꢀ-substituted, proximal alkenylpalla-
dium one. These facts can be understood by a substantial
change in effective steric bulk of the active catalyst A0.
Given A0 plays a role in the reaction, as discussed above, a
possible catalytic process for the reaction is depicted in
Scheme 2. The initial step must be activation of an alkyne sub-
In conclusion, we conceptually studied a new hydrosilyla-
tive cross-coupling reaction of a variety of alkynes with sever-
al alkenes, which is catalyzed by a cationic palladium complex
A (1 mol %) in the absence or presence of an added PPh3
ligand. The reaction, using HSiCl3 as an addend, afforded
more or less two types of coupling products consisting of four
possible derivatives, R1CH=CR2–CHR3–CHR4–SiCl3, that al-
ways contain 4-trichlorosilyl-1-butene frameworks, in accept-
able combined yields.
Experimental
General. NMR spectra were recorded on a JEOL JNM FX
270 spectrometer (270 MHz for 1H and 67.8 MHz for 13C) in
CDCl3 or Bruker Avance 500 spectrometer (99.35 MHz for 29Si)
in CD2Cl2. Chemical shifts of the protons and the carbons are
reported in ꢄ and referenced to tetramethylsilane as an internal
standard. IR spectra were recorded on a JEOL JIR-WINSPEC

T. Shimamoto et al.
Bull. Chem. Soc. Jpn. Vol. 80, No. 9 (2007) 1819
50 spectrophotometer using a liquid film, absorptions being given
in wavenumbers (cmꢁ1). GLC analyses were conducted on a
Shimadzu GC-14B (equipped with programmed heating) chroma-
tograph connected with a C-R6A chromatopack recorder. Prepar-
ative column chromatography employing silica gel (hexane–ethyl
acetate) was performed according to the method of Still.24 Ele-
mental analyses for the representative cross-coupling products in
this study were performed by the Kyoto University Microanalysis
Center.
All moisture-sensitive manipulations were carried out under an
argon atmosphere. All reactions were conducted in a 5 mL screw-
capped testing tube containing a stirring bar. Dichloromethane
was used after distillation over diphosphorus pentaoxide. Absolute
ethanol and triethylamine distilled over calcium hydride were
used for ethoxylation of trichlorosilyl derivatives. Hexane was
distilled over sodium wire. Commercial trichlorosilane in an am-
poule (25 mL) was always used as an 1 M CH2Cl2 solution, which
was stored under argon in a 100-mL Schlenk tube. [Pd(ꢁ3-C3H5)-
(cod)]þ[PF6]ꢁ (A) was synthesized according to the literature
procedure.25 Triphenylphosphine was purified by recrystallization
from ethanol. All alkenes and alkynes were purchased from
Aldrich, Wako Chemicals, or Tokyo Chemical Ind. and used after
distillation under reduced pressure. As for the reactions, yields
have not been optimized.
dissolved in CH2Cl2 in an ice-cooled bath for 1 h. Salt Et3N/HCl
formed was removed by repeated trituration with cold hexane and
filtration through a short celite plug, and the filtrates were concen-
trated using a coolnit evaporator. The residual oil was purified
by a bulb-to-bulb distillation under a reduced pressure to give
products. If necessary, they were purified by a preparative GLC.
1
Spectral data for 1b: H NMR: ꢄ 0.834 (t, J ¼ 7:1 Hz, 3H), 0.86
(dd, J ¼ 15:2, 8.2 Hz, 1H), 0.95 (dd, J ¼ 15:2, 6.4 Hz, 1H), 1.20
(t, J ¼ 6:9 Hz, 9H), 1.3–1,4 (m, 6H), 2.81 (quint, J ¼ 6:8 Hz, 1H),
3.79 (q, J ¼ 6:9 Hz, 6H), 5.06 (d, J ¼ 1:0 Hz, 1H), 5.18 (d, J ¼
1
1:3 Hz, 1H), 7.2–7.4 (m, aromatic, 5H). 2b: H NMR: ꢄ 0.826 (t,
J ¼ 7:1 Hz, 3H), 1.22 (t, J ¼ 6:9 Hz, 9H), 1.43–1.53 (m, 6H), 2.35
(ddd, J ¼ 14:5, 10.7, 0.7 Hz, 1H), 2.93 (ddd, J ¼ 14:5, 4.0, 0.8
Hz, 1H), 3.84 (q, J ¼ 6:9 Hz, 6H), 5.06 (d, J ¼ 1:0 Hz, 1H),
5.27 (q, J ¼ 1:3 Hz, 1H), 7.2–7.4 (m, aromatic, 5H). Anal. Found:
C, 68.25; H, 9.51%. Calcd for C20H34O3Si (1b): C, 68.52; H,
9.78%.
The procedure was applied for all other cross-coupling reac-
tions catalyzed by the precursor A in the absence of PPh3: see,
Table 2.
Typical Procedure for Eq. 2, and Table 1: (E)-1-Phenyl-3-
(triethoxysilyl)methyl-1-heptene (3b: ꢂ-1): A catalyst system
consisting of the palladium complex A and PPh3 (or other phos-
phorus ligand given in Table 1; 1 or 2 equiv) was employed, and
the reaction of phenylacetylene (1 mmol) and 1-hexene (3 mmol)
with HSiCl3 (1 M, CH2Cl2, 1 mL) was conducted at 50 ꢂC for
4 h, in exactly the same manner as for Eq. 1. The products of tri-
Catalytic Hydrosilylative Cross-Coupling of Alkynes with
Alkenes.26 Typical Procedure for Eq. 1: 2-Phenyl-3-(trichloro-
silyl)methyl-1-heptene (1a: ꢀ-1) and 2-phenyl-4-trichlorosilyl-1-
octene (2a: ꢀ-2): A mixture of phenylacetylene (1 mmol), 1-hex-
ene (3 mmol), and the catalyst A (1 ꢄ 10ꢁ2 mmol, 1 mol %) dis-
solved in dry CH2Cl2 (1 mL) was placed in a 5-mL screw-capped
test tube under an argon atmosphere. To this solution was added
HSiCl3 (1 M, CH2Cl2, 1 mL), and the mixture was heated at
50 ꢂC in a thermostated oil bath for 4 h. Color change of the reac-
tion mixture was diagnostic of the end-point of reaction. GLC
chlorosilyl derivatives were detected by GLC analysis (TR
¼
16:7 min (3a)), and isolated as triethoxy derivatives. In the case
of Eq. 2, the distilled product 3a was substantially a single one
(0.203 g, 58% yield). Spectral data for 3a: 1H NMR: ꢄ 0.89 (t,
J ¼ 6:6 Hz, 1H), 1.23–1.37 (m, 6H), 1.58 (dd, J ¼ 15:2, 8.9 Hz,
1H), 1.68 (dd, J ¼ 15:2, 5.3 Hz, 1H), 2.63 (qt, J ¼ 8:9, 5.3 Hz,
1H), 5.95 (dd, J ¼ 15:5, 9.2 Hz, 1H), 6.43 (d, J ¼ 15:5 Hz, 1H),
7.2–7.4 (m, aromatic, 5H). 3b: 1H NMR: ꢄ 0.80 (dd, J ¼ 15:2,
7.4 Hz, 1H), 0.87 (t, J ¼ 6:9 Hz, 3H), 0.89 (dd, J ¼ 15:2, 6.6
Hz, 1H), 1.20 (t, J ¼ 6:9 Hz, 9H), 1.17–1.45 (m, 6H), 2.31–2.45
(m, 1H), 3.80 (q, J ¼ 6:9 Hz, 6H), 6.06 (dd, J ¼ 15:7, 8.9 Hz,
1H), 6.33 (dd, J ¼ 15:7, 0.3 Hz, 1H), 7.1–7.4 (m, aromatic, 5H).
13C NMR: ꢄ 14.1, 17.5, 18.3, 22.7, 29.6, 37.6, 38.1, 58.3, 126.0,
126.6, 128.2, 128.4, 137.0, 138.0. Anal. Found: C, 68.56; H,
9.77%. Calcd for C20H34O3Si (3b): C, 68.52; H, 9.78%.
ꢅ
analysis of the reaction mixture (3 mm ꢄ 3 m column packed
with SE-30 grease on Celite (10%) under programmed heating
at a rate 10 ꢂC minꢁ1 from 100 ꢂC (for 2 min) to 280 ꢂC) revealed
clearly that the reaction was complete, and that the peak area ratio
of the cross-coupling products containing a trichlorosilyl group
(TR ¼ 17:0 (1a) and 17.2 (2a) min) was estimated to be 60:40.
A small amount of hydrosilylation products from 1-hexene, which
were usually neglected, were also obtained. The products were di-
rectly subjected to bulb-to-bulb distillation under reduced pressure
to give the regioisomeric products consisting of 1a and 2a
(0.223 g, 70% combined yield). Little change in the ratio 1a to
2a except combined yields was observed by using 1 or 5 equiv
of 1-hexene to phenylacetylene. They were separated by prepara-
tive GLC for the spectral identification. Spectral data for 1a:
1H NMR (270 MHz, CDCl3, TMS) ꢄ 0.85 (t, J ¼ 7:1 Hz, 3H),
1.2–1.4 (m, 6H), 1.67 (dd, J ¼ 15:5, 7.3 Hz, 1H), 1.79 (dd, J ¼
15:5, 6.9 Hz, 1H), 3.03 (quint, J ¼ 6:9 Hz, 1H), 5.12 (s, 1H),
5.29 (d, J ¼ 0:7 Hz, 1H), 7.3–7.4 (aromatic H, 5H). 13C NMR
(67.8 MHz): ꢄ 14.0, 22.6, 28.7, 29.8, 31.4, 39.1, 113.6, 126.9,
127.5, 128.3, 141.9, 151.8. Spectral data for 2a: 1H NMR: ꢄ
0.85 (t, J ¼ 7:1 Hz, 3H), 1.19 (quint, J ¼ 7:1 Hz, 1H), 1.45–1.65
(m, 6H), 2.55 (ddd, J ¼ 14:5, 10.2, 0.7 Hz, 1H), 3.09 (ddd, J ¼
14:5, 4.3, 0.7 Hz, 1H), 5.17 (d, J ¼ 0:7 Hz, 1H), 5.36 (q, J ¼
0:7 Hz, 1H), 7.3–7.4 (aromatic H, 5H). 13C NMR: ꢄ 13.8, 22.8,
27.4, 29.9, 34.1, 35.8, 115.4, 126.5, 127.8, 128.5, 139.7, 145.8.
The corresponding triethoxysilyl compounds 1b and 2b were
derived from 1a and 2a for analytical purpose. The distilled
sample obtained above was treated with an excess EtOH and Et3N
Spectral and Certain Analytical Data for All Products
Listed in Tables 2 and 3. Table 2, Entry 1: Phenylacetylene/
1-Hexene, Same as for Eq. 1: Table 2, Entry 2: Phenylacety-
lene/Styrene: 2,3-Diphenyl-4-trichlorosilyl-1-butene (4a: ꢀ-1):
1H NMR: ꢄ 2.04 (dd, J ¼ 15:2, 8.9 Hz, 1H), 2.15 (dd, J ¼ 15:2,
6.6 Hz, 1H), 4.27 (ddd, J ¼ 8:9, 6.6, 1.0 Hz, 1H), 5.27 (d, J ¼
1:0 Hz, 1H), 5.42 (s, 1H), 7.2–7.4 (aromatic H, 10H). 13C NMR:
ꢄ 30.8, 45.1, 113.9, 126.9 (ꢄ2), 127.1, 127.5, 128.1 (ꢄ2), 128.2
(ꢄ2), 128.6 (ꢄ2), 141.4, 141.7, 151.3.
2,3-Diphenyl-4-triethoxysilyl-1-butene (4b): 1H NMR: ꢄ 1.12
(t, J ¼ 6:9 Hz, 9H), 1.24 (dd, J ¼ 15:2, 9.2 Hz, 1H), 1.35 (dd, J ¼
15:2, 5.9 Hz, 1H), 3.63 (q, J ¼ 6:9 Hz, 6H), 4.09 (dd, J ¼ 8:7, 6.4
Hz, 1H), 5.27 (t, J ¼ 1:2 Hz, 1H), 5.33 (s, 1H), 7.1–7.3 (aromatic
H, 10H). Anal. Found: C, 71.31; H, 8.23%. Calcd for C22H30O3Si:
C, 71.31; H, 8.16%.
1
2,4-Diphenyl-4-trichlorosilyl-1-butene (5a: ꢀ-2): H NMR: ꢄ
2.85 (dd, J ¼ 11:5, 3.6 Hz, 1H), 3.06 (dd, J ¼ 13:9, 11.5 Hz, 1H),
3.42 (dd, J ¼ 13:9, 3.6 Hz, 1H), 4.94 (s, 1H), 5.13 (s, 1H), 7.2–7.4
(m, aromatic, 10 H). 13C NMR: ꢄ 34.8, 41.0, 115.6, 126.4 (ꢄ2),
127.3, 127.3, 128.5 (ꢄ4), 129.1 (ꢄ2), 135.5, 139.9, 144.9.

1820 Bull. Chem. Soc. Jpn. Vol. 80, No. 9 (2007)
Hydrosilylative Coupling of Alkynes with Alkenes
2,4-Diphenyl-4-triethoxysilyl-1-butene (5b): 1H NMR: ꢄ 1.14
(t, J ¼ 6:9 Hz, 9H), 2.31 (dd, J ¼ 11:4, 3.5 Hz, 1H), 2.86 (dd, J ¼
15:3, 11.4 Hz, 1H), 3.22 (dd, J ¼ 15:3, 3.5 Hz, 1H), 3.70 (q, J ¼
6:9 Hz, 6H), 4.79 (d, J ¼ 0:7 Hz, 1H), 5.05 (d, J ¼ 1:0 Hz, 1H),
7.2–7.4 (m, aromatic, 10H).
1H NMR: ꢄ 0.86 (t, J ¼ 6:9 Hz, 3H), 1.2–1.6 (m, 6H), 1.94 (dd,
J ¼ 15:2, 8.6 Hz, 1H), 2.06 (dd, J ¼ 15:2, 6.6 Hz, 1H), 2.27 (t,
J ¼ 6:9 Hz, 2H), 4.09 (q, J ¼ 6:8 Hz, 1H), 6.35 (t, J ¼ 1 Hz,
0.8H), 6.39 (t, J ¼ 1 Hz, 0.8H), 7.20–7.30 (m, aromatic, 5H). 2-
[1-Phenyl-2-(triethoxysilyl)ethyl]-1-heptene (10b): 1H NMR: ꢄ
0.87 (t, J ¼ 6:8 Hz, 3H), 1.09–1.23 (m, 6H), 1.22 (t, J ¼ 6:9 Hz,
9H), 1.30 (dd, J ¼ 15:2, 7.0 Hz, 1H), 1.40 (dd, J ¼ 15:2, 7.3 Hz,
1H), 2.08 (t, J ¼ 6:9 Hz, 2H), 3.80 (q, J ¼ 6:9 Hz, 6H), 3.99 (q,
J ¼ 6:9 Hz, 1H), 6.18 (s, 1H), 6.22 (s, 1H), 7.13–7.29 (m, aromat-
ic, 5H). 13C NMR: ꢄ 14.1, 18.2, 22.3, 22.5, 30.1, 31.7, 37.5, 41.3,
58.2, 125.8, 127.0, 128.1, 130.9, 146.4, 151.6.
2-[2-Phenyl-2-(trichlorosilyl)ethyl]-1-heptene(11a:ꢀ-2) could
only be assigned as a minor component in a mixture with 10a:
1H NMR: ꢄ 0.55 (d, J ¼ 2 Hz, 0.2H), 5.58 (d, J ¼ 2 Hz, 0.2H),
diagnostic vinylidene protons. (E)-2-Phenyl-1-trichlorosilyl-3-
nonene (12a: ꢂ-1): 1H NMR: ꢄ 0.87 (t, J ¼ 6:8 Hz, 3H), 1.20–
1.40 (m, 6H), 1.89 (dd, J ¼ 15:2, 6.9 Hz, 1H), 1.95 (dd, J ¼ 15:2,
8.4 Hz, 1H), 1.99 (m, 2H), 3.65–3.74 (m, 1H), 5.56 (dd, J ¼ 14:2,
6.2 Hz, 1H), 5.57 (dd, J ¼ 14:2, 6.2 Hz, 1H), 7.20–7.30 (m, aro-
matic, 5H). 13C NMR: ꢄ 14.0, 22.5, 28.8, 31.4, 31.7, 32.3, 43.5,
126.7, 127.1, 128.7, 131.6, 132.6, 144.3. (E)-2-Phenyl-1-trieth-
oxysilyl-3-nonene (12b): 1H NMR: ꢄ 0.86 (t, J ¼ 6:9 Hz, 3H),
1.10–1.30 (m, 6H), 1.15 (t, J ¼ 6:9 Hz, 9H), 1.30 (dd, J ¼ 15:2,
7.1 Hz, 1H), 1.40 (dd, J ¼ 15:2, 7.3 Hz, 1H), 1.96 (q, J ¼ 6:9
Hz, 2H), 3.69 (q, J ¼ 6:9 Hz, 6H), 3.51 (q, J ¼ 7:6 Hz, 1H), 5.41
(dtd, J ¼ 14:2, 6.6, 1.0 Hz, 1H), 5.60 (ddt, J ¼ 14:2, 7.3, 1.3 Hz,
1H), 7.15–7.28 (m, aromatic, 5H). 13C NMR: ꢄ 14.1, 18.2, 22.5,
29.1, 31.5, 32.4, 32.5, 43.1, 58.2, 125.8, 127.4, 128.2, 129.1,
135.5, 146.9.
(E)-1,3-Diphenyl-4-trichlorosilyl-1-butene(6a: ꢂ-1): 1H NMR:
ꢄ 2.03 (dd, J ¼ 15:2, 7.3 Hz, 1H), 2.07 (dd, J ¼ 15:2, 7.9 Hz, 1H),
3.93 (q, J ¼ 7:7 Hz, 1H), 6.32 (dd, J ¼ 15:8, 7.9 Hz, 1H), 6.49
(d, J ¼ 15:8 Hz, 1H), 7.2–7.4 (aromatic H, 10H).
(E)-1,3-Diphenyl-4-triethoxysilyl-1-butene (6b): 1H NMR: ꢄ
1.148 (t, J ¼ 6:9 Hz, 9H), 1.24 (dd, J ¼ 15:2, 7.3 Hz, 2H), 1.28
(dd, J ¼ 15:2, 7.9 Hz, 1H), 3.60 (q, J ¼ 6:9 Hz, 1H), 3.70 (q, J ¼
6:9 Hz, 6H), 6.37 (d, J ¼ 15:8 Hz, 1H), 6.41 (dd, J ¼ 15:8, 5.6 Hz,
1H), 7.15–7.35 (aromatic H, 10H). 13C NMR: ꢄ 18.2 (ꢄ3), 43.5
(ꢄ2), 58.3 (ꢄ3), 126.2 (ꢄ2), 126.9, 127.5 (ꢄ2), 128.3, 128.4
(ꢄ4), 135.9, 137.7, 146.0.
(E)-1,4-Diphenyl-4-triethoxysilyl-1-butene (60b: ꢂ-2) was sep-
arated by column chromatography (Silica gel, hexane–ethyl ace-
tate 2%) from a mixture with 6b: 1H NMR: ꢄ 1.153 (t, J ¼ 6:9
Hz), 2.32 (dd, J ¼ 10:1, 5.4 Hz), 2.76 (centered m), 3.70 (q, J ¼
6:9 Hz), 6.14 (dt, J ¼ 15:8, 6.8 Hz), 6.32 (d, J ¼ 15:5 Hz), 7.15–
7.35 (aromatic H). 13C NMR ꢄ 18.2 (ꢄ3), 33.7, 34.1, 58.8 (ꢄ3),
126.0 (ꢄ2), 126.7, 126.9, 127.9 (ꢄ2), 128.3 (ꢄ2), 128.7 (ꢄ2),
130.2, 130.4, 137.9, 141.4.
Table 2, Entry 3 and Table 3, Entry 3: 1-Heptyne/1-Hexene:
2-Pentyl-3-(trichlorosilyl)methyl-1-heptene (7a: ꢀ-1): 1H NMR:
ꢄ 0.88 (t, J ¼ 7:4 Hz, 3H), 0.89 (t, J ¼ 7:4 Hz, 3H), 1.2–1.6 (m,
12H), 1.43 (dd, J ¼ 14:2, 6.3 Hz, 1H), 2.00 (t, J ¼ 7:4 Hz, 2H),
2.12 (dd, J ¼ 14:2, 9.6 Hz, 1H), 2.49 (quint, J ¼ 7:1 Hz, 1H),
4.82 (s), 4.86 (s).
2-Pentyl-3-(triethoxysilyl)methyl-1-heptene (7b): 1H NMR: ꢄ
0.81 (dd, J ¼ 14:4, 7.6 Hz, 1H), 0.87 (t, J ¼ 7:3 Hz, 6H), 0.88 (dd,
J ¼ 14:4, 7.4 Hz, 1H), 1.15–1.30 (br m, 12H), 1.22 (t, J ¼ 6:9 Hz,
9H), 1.95 (quint, J ¼ 7:9 Hz, 2H), 2.06 (m, 1H), 3.83 (q, J ¼
6:9 Hz, 6H), 4.69 (br s, 1H), 4.74 (s, 1H). 13C NMR: ꢄ 14.1,
18.3, 20.2, 22.6, 23.2, 22.7, 27.4, 28.4, 31.0, 35.1, 35.7, 41.1,
58.5, 109.8, 149.1.
Table 2, Entry 5 and Table 3, Entries 5 and 6: Methyl Pro-
piolate/1-Hexene: Methyl 2-{1-[(trichlorosilyl)methyl]pentyl}-
propenoate (13a: ꢀ-1): 1H NMR: ꢄ 0.89 (t, J ¼ 7:0 Hz, 3H),
1.15–1.35 (m, 6H), 1.55 (dd, J ¼ 15:5, 8.1 Hz, 1H), 1.62 (dd, J ¼
15:5, 6.1 Hz, 1H), 2.62 (m, 1H), 3.76 (s, 3H), 5.64 (br s, 1H), 6.27
(d, J ¼ 1:0 Hz, 1H).
Methyl 2-{1-[(triethoxysilyl)methyl]pentyl}propenoate (13b):
1H NMR: ꢄ 0.86 (t, J ¼ 6:9 Hz, 3H), 0.91 (d, J ¼ 7:6 Hz, 2H),
1.21 (t, J ¼ 6:9 Hz, 9H), 1.2–1.3 (m, 6H), 2.78 (quint, J ¼ 7:2
Hz, 1H), 3.74 (s, 3H), 3.79 (q, J ¼ 6:9 Hz, 6H), 5.54 (brs, 1H),
6.17 (d, J ¼ 1 Hz, 1H). Diastereotopic hydrogens (2H) are not
resolved. 13C NMR: ꢄ 14.1, 16.7, 18.2, 22.7, 29.4, 36.2, 36.3, 51.6,
58.3, 124.0, 145.4, 167.7. IR (neat): 2973.7, 2927.5, 2885.0,
2734.6, 1724.1, 1627.7, 1437.7, 1390.4, 1274.7, 1201.5, 958.5
cmꢁ1. Anal. Found C, 57.90; H, 9.49%. Calcd for C16H32O5Si: C,
57.79; H, 9.70%.
2-Pentyl-4-trichlorosilyl-1-octene (8a: ꢀ-2): Diagnostic signals
were hardly separated.
2-Pentyl-4-triethoxysilyl-1-octene (8b): 1H NMR: ꢄ 0.87 (t,
J ¼ 7:3 Hz, 3H), 0.89 (t, J ¼ 6:9 Hz, 3H), 0.98 (m, 1H), 1.10–
1.50 (m, 12H), 1.22 (t, J ¼ 6:9 Hz, 9H), 1.99 (dd, J ¼ 14:2, 7.3
Hz, 1H), 2.10 (t, J ¼ 7:3 Hz, 2H), 2.30 (dd, J ¼ 14:2, 3.3 Hz, 1H),
3.82 (q, J ¼ 6:9 Hz, 6H), 4.69 (s, 1H), 4.72 (s, 1H). 13C NMR: ꢄ
14.1, 16.7, 18.3, 22.8, 23.2, 27.5, 28.4, 29.7, 31.7, 32.1, 35.1,
35.5, 58.3, 107.7, 154.3.
Methyl 2-[2-(trichlorosilyl)hexyl]propenoate (14a:ꢀ-2): Spec-
tral data of 14a were obtained only for reference. Methyl 2-[2-
(triethoxysilyl)hexyl]propenoate (14b): 13C NMR: ꢄ 14.1, 16.7,
18.3, 22.8, 29.3, 35.8, 36.5, 51.7, 58.5, 125.5, 140.1, 167.8.
Methyl (E)-4-(trichlorosilyl)methyl-2-octenoate (15a: ꢂ-1):
1H NMR: ꢄ 0.87 (t, J ¼ 7:0 Hz, 3H), 1.27 (centered m, 6H), 1.70
(dd, J ¼ 15:5, 6.3 Hz, 1H), 1.91 (dd, J ¼ 15:5, 8.9 Hz, 1H), 2.90
(tt, J ¼ 8:7, 5.9 Hz, 1H), 3.77 (s, 3H), 5.86 (dd, J ¼ 15:5, 0.7
Hz, 1H), 6.75 (dd, J ¼ 15:5, 9.2 Hz, 1H).
1
(E)-5-(Trichlorosilyl)methyl-6-dodecene (9a: ꢂ-1): H NMR:
ꢄ 0.88 (t, J ¼ 6:9 Hz, 6H), 1.2–1.4 (m, 12H), 1.45 (dd, J ¼ 15:2,
9.2 Hz, 1H), 1.55 (dd, J ¼ 15:2, 5.3 Hz, 1H), 1.98 (q, J ¼ 6:9 Hz,
2H), 2.32–2.44 (m, 1H), 5.15 (dd, J ¼ 15:2, 8.9 Hz, 1H), 5.46 (dd,
J ¼ 15:2, 6.9 Hz, 1H).
(E)-5-(Triethoxysilyl)methyl-6-dodecene(9b):1H NMR:ꢄ 0.69
(dd, J ¼ 15:2, 7.3 Hz, 1H), 0.73 (dd, J ¼ 15:2, 6.6 Hz, 1H), 0.87
(t, J ¼ 6:9 Hz, 3H), 0.88 (t, J ¼ 6:6 Hz, 3H), 1.15–1.30 (m, 12H),
1.22 (t, J ¼ 6:9 Hz, 9H), 1.96 (q, J ¼ 6:9 Hz, 2H), 2.16 (m, 1H),
3.80 (q, J ¼ 6:9 Hz, 6H), 5.23 (ddt, J ¼ 15:2, 8.6, 0.7 Hz, 1H),
5.34 (dt, J ¼ 15:2, 6.4 Hz, 1H) 13C NMR: ꢄ 14.1 (ꢄ2), 17.6, 18.3,
22.6, 22.7, 29.3, 29.7, 31.4, 32.5, 37.5, 37.7, 58.2, 128.8, 136.3.
Anal. Found: C, 66.51, H, 11.79%. Calcd for C19H40O3Si: C,
66.22, H, 11.70%.
Methyl (E)-4-(triethoxysilyl)methyl-2-octenoate (15b):
1H NMR: ꢄ 0.73 (dd, J ¼ 15:2, 6.9 Hz, 1H), 0.80 (dd, J ¼ 15:2,
6.9 Hz, 1H), 0.87 (t, J ¼ 6:9 Hz, 3H), 1.21 (t, J ¼ 6:9 Hz, 9H),
1.2–1.3 (m, 6H), 2.4 (m, 1H), 3.72 (s, 3H), 3.80 (q, J ¼ 6:9 Hz,
6H), 5.78 (dd, J ¼ 15:5, 1.0 Hz, 1H), 6.83 (dd, J ¼ 15:5, 8.9 Hz,
1H). 13C NMR: ꢄ 14.0, 16.5, 18.2, 22.6, 29.4, 36.4, 37.4, 51.4,
58.4, 119.3, 155.1, 167.4. IR (neat): 2973.7, 2927.5, 2885.0,
Table 2, Entry 4 and Table 3, Entry 4: 1-Heptyne/Styrene:
2-[1-Phenyl-2-(trichlorosilyl)ethyl]-1-heptene (10a: ꢀ-1):
1726.0, 1654.6, 1435.8, 1269.9, 1104.0, 1081.9, 959.4 cmꢁ1
.

T. Shimamoto et al.
Bull. Chem. Soc. Jpn. Vol. 80, No. 9 (2007) 1821
Anal. Found C, 57.74; H, 9.40%. Calcd for C16H32O5Si: C, 57.79;
H, 9.70%.
ponent (presumably, ꢀ-2 and ꢂ-2), spectral data of the latter
two being obtained only for diagnostic signals.
Table 3, Entry 7: Methyl Propiolate/Styrene: Methyl 2-[(1-
phenyl-2-triethoxysilyl)ethyl]propenoate (16b: ꢀ-1): 1H NMR:
ꢄ 1.13 (t, J ¼ 6:9 Hz, 9H), 1.20 (dd, J ¼ 15:2, 8.9 Hz, 0.85H), 1.28
(dd, J ¼ 15:2, 6.6 Hz, 0.85H), 3.64 (q, J ¼ 6:9 Hz, 6H), 3.65 (s,
3H), 4.14 (t, J ¼ 7:9 Hz, 0.85H), 5.76 (br s, 0.85H), 6.27 (s,
0.85H). 7.10–7.25 (m, aromatic, 5H). 13C NMR: ꢄ 17.2, 18.1, 41.2,
51.7, 58.2, 125.1, 126.3, 128.0, 128.1, 145.4, 153.6, 167.3.
Methyl 2-[(2-phenyl-2-triethoxysilyl)ethyl]propenoate (17b:
ꢀ-2) could only be detected as a minor component in a mixture
with 16b: 1H NMR: ꢄ 2.51 (dd, J ¼ 15:5, 3.6 Hz, 0.15H), 2.96
(dd, J ¼ 15:5, 3.3 Hz, 0.15H) (diastereotopic hydrogens), 3.70 (t,
J ¼ 3:5 Hz, 0.15H) (a benzylic hydrogen), 5.26 (d, J ¼ 1:3 Hz,
0.15H), 5.95 (d, J ¼ 1:3 Hz, 0.15H) (vinylidene hydrogens).
Spectral Data for Products Listed in Table 4. Table 4,
Entry 1: Phenylacetylene/(E)-3-Hexene: 3-Ethyl-2-phenyl-4-
trichlorosilyl-1-hexene (18a: ꢀ): 1H NMR: ꢄ 0.95 (t, J ¼ 7:6 Hz,
3H), 1.02 (t, J ¼ 7:1 Hz, 3H), 1.33 (ddd, J ¼ 9:2, 4.3, 2.6 Hz, 1H),
3.17 (dt, J ¼ 10:6, 2.5 Hz, 1H), 5.07 (s, 1H), 5.45 (s, 1H) 7.20–
7.40 (m, aromatic, 5H). Diastereotopic methylene hydrogens (4H)
could not be resolved. 13C NMR: ꢄ 12.5, 14.5, 17.5, 22.2, 39.5,
44.8, 114.4, 126.7 (ꢄ2), 127.6, 128.5 (ꢄ2), 142.5, 148.0 (a threo
isomer would be formed).
Table 4, Entry 4: Phenylacetylene/2-Methyl-1-pentene:
(E)-3-Methyl-1-phenyl-3-(trichlorosilyl)methyl-1-hexene (24a:
ꢂ-1): 1H NMR: ꢄ 0.90 (t, J ¼ 7:3 Hz, 3H), 1.22–1.32 (m, 2H),
1.35 (s, 3H), 1.51–1.57 (m, 2H), 1.77 (d, J ¼ 15:3 Hz, 1H), 1.79
(d, J ¼ 15:3 Hz, 1H), 6.20 (d, J ¼ 16:4 Hz, 1H), 6.33 (br d, J ¼
16:4 Hz, 1H). 13C NMR: ꢄ 14.5, 17.6, 25.5, 38.0, 39.0, 46.6,
126.2, 127.2, 127.5, 128.6, 131.9, 138.0.
(E)-3-Methyl-1-phenyl-3-(triethoxysilyl)methyl-1-hexene
1
(24b): H NMR: ꢄ 0.87 (t, J ¼ 7:3 Hz, 3H), 0.90 (br s, 2H), 1.19
(t, J ¼ 6:9 Hz, 9H), 1.20 (s, 3H), 1.24–1.33 (m, 2H), 1.38–1.51
(m, 2H), 3.80 (q, J ¼ 6:9 Hz, 6H), 6.24 (d, J ¼ 16:5 Hz, 1H), 6.30
(d, J ¼ 16:5 Hz, 1H), 7.17 (t, J ¼ 7:3 Hz, 1H), 7.28 (t, J ¼ 7:3 Hz,
2H), 7.36 (d, J ¼ 7:3 Hz, 2H). 13C NMR: ꢄ 14.8, 17.9, 18.2 (ꢄ3),
24.3, 26.1, 37.7, 46.1, 58.2 (ꢄ3), 125.2, 126.0 (ꢄ2), 126.5, 128.4
(ꢄ2), 138.3, 141.5. 13C NMR: ꢄ 14.1, 23.2, 25.4, 26.6, 38.0, 38.9,
44.0, 126.2, 127.2, 127.5, 128.6, 132.0, 138.0.
Table 4, Entry 4, Footnote g: Phenylacetylene/2-Methyl-1-
hexene: (E)-3-Methyl-1-phenyl-3-(trichlorosilyl)methyl-1-hep-
1
tene (240a: ꢂ-1): H NMR: ꢄ 0.89 (t, J ¼ 6:9 Hz, 3H), 1.22–1.31
(m, 4H), 1.35 (s, 3H), 1.53–1.58 (m, 2H), 1.77 (d, J ¼ 15:2 Hz,
1H), 1.79 (d, J ¼ 15:2 Hz, 1H), 6.22 (d, J ¼ 16:3 Hz, 1H), 6.33 (d,
J ¼ 16:3 Hz, 1H), 7.20–7.45 (m, aromatic, 5H).
(E)-3-Ethyl-1-phenyl-4-trichlorosilyl-1-hexene (19a: ꢂ):
1H NMR: ꢄ 0.91 (t, J ¼ 7:4 Hz, 3H), 1.09 (t, J ¼ 7:4 Hz, 3H), 2.54
(ddt, J ¼ 9:6, 7.6, 4.6 Hz, 1H), 6.10 (dd, J ¼ 15:5, 9.6 Hz, 1H),
6.43 (d, J ¼ 15:5 Hz, 1H), 7.20–7.35 (m, aromatic, 5H). Diaster-
eotopic hydrogens (5H) hardly be assigned. 13C NMR: ꢄ 12.3,
13.5, 19.8, 26.2, 41.7, 44.8, 126.3 (ꢄ2), 127.0, 127.6 (ꢄ2), 131.5,
132.0, 137.2.
Table 4, Entry 2: 3-Hexyne/Allylbenzene: (E)-2-Benzyl-3-
ethyl-1-trichlorosilyl-3-hexene (20a): 1H NMR: ꢄ 0.93 (t, J ¼
7:6 Hz, 3H), 0.97 (t, J ¼ 7:6 Hz, 3H), 1.52 (dd, J ¼ 15:5, 5.1 Hz,
1H), 1.61 (dd, J ¼ 15:5, 9.1 Hz, 1H), 1.92 (q, J ¼ 7:6 Hz, 2H),
1.98 (quint, J ¼ 7:3 Hz, 2H), 2.6 (m, 1H), 5.20 (t, J ¼ 7:1 Hz,
1H), 7.1–7.3 (m, aromatic, 5H). Benzylic protons were hardly
assigned.
(E)-4-Ethyl-7-phenyl-6-trichlorosilyl-3-heptene (21a):
1H NMR: ꢄ 0.83 (t, J ¼ 7:6 Hz, 3H), 0.94 (t, J ¼ 7:6 Hz, 3H), 1.77
(m, 1H), 1.91 (q, J ¼ 7:3 Hz, 2H), 1.98 (quint, J ¼ 7:3 Hz, 2H),
2.15 (dd, J ¼ 14:2, 8.9 Hz, 1H), 2.46 (dd, J ¼ 14:2, 6.1 Hz, 1H),
2.73 (dd, J ¼ 14:2, 7.6 Hz, 1H), 2.99 (dd, J ¼ 14:2, 6.1 Hz, 1H),
5.22 (t, J ¼ 7:1 Hz, 1H), 7.1–7.3 (m, aromatic 5H).
(E)-3-Methyl-1-phenyl-3-(triethoxysilyl)methyl-1-heptene
(240b): 1H NMR: ꢄ 0.87 (t, J ¼ 6:9 Hz, 3H), 0.90 (br s, 2H), 1.15–
1.31 (m, 4H), 1.19 (t, J ¼ 6:9 Hz, 9H), 1.20 (s, 3H), 1.40–1.53 (m,
2H), 3.80 (q, J ¼ 6:9 Hz, 6H), 6.24 (d, J ¼ 16:2 Hz, 1H), 6.30 (d,
J ¼ 16:2 Hz, 1H), 7.20–7.45 (m, aromatic, 5H). 13C NMR: ꢄ 14.2,
18.3, 18.8, 23.4, 24.4, 26.1, 26.9, 37.6, 43.5, 58.2, 125.3, 126.0,
128.4, 138.0, 141.5. Anal. Found: C, 69.43; H, 10.05%. Calcd for
C21H36O3Si: C, 69.18; H, 9.95%.
Tamao Oxidation of Methyl 2-{1-[(Triethoxysilyl)methyl]-
pentyl}propenoate (13b). Preparation of 2-Triethoxysilyl-1-
octene (25): In a 100-mL three-necked round-bottomed flask,
under an argon atmosphere, was placed a solution of 1-octyne
(5.50 g, 50 mmol) and HSi(OEt)3 (8.25 g, 50 mmol) dissolved in
CH2Cl2 (50 mL). To this solution, cooled in an ice-water bath,
ꢀ
ꢀ
was added [Ru(cp )(NCMe)3]þ[PF6]ꢁ (cp = pentamethylcyclo-
pentadienyl)27 (252.2 mg, 0.5 mmol; 1 mol %), and the mixture
was stirred magnetically at room temperature for 2 h. The solvent
was removed by evaporation, and the residue was distilled in
vacuo to give crude products (11.2 g, 82% crude yield), GLC anal-
ysis of which revealed 25 and (E)-1-triethoxysilyl-1-octene28 in a
ratio of 90:10. Redistillation gave a purer sample (8.9 g, 65%), the
isomer ratio being unchanged. 2-Triethoxysilyl-1-octene (25):
1H NMR: ꢄ 0.88 (t, J ¼ 6:6 Hz, 3H), 1.23 (t, J ¼ 6:9 Hz, 9H),
1.23–1.32 (m, 6H), 1.38–1.50 (m, 2H), 2.14 (tt, J ¼ 7:8, 1.5 Hz,
1.8H), 3.82 (q, J ¼ 6:9 Hz, 6H), 5.63 (dt, J ¼ 3:3, 1.0 Hz, 0.9H),
5.72 (dt, J ¼ 3:3, 1.6 Hz, 0.9H). Diagnostic signals for (E)-1-
triethoxysilyl-1-octene: 2.28 (qd, J ¼ 7:3, 1.0 Hz, 0.2H), 5.29 (dt,
J ¼ 14:2, 1.3 Hz, 0.1H), 6.52 (dt, J ¼ 14:2, 7.6 Hz, 0.1H).
13C NMR: ꢄ 14.1, 18.2, 22.6, 28.6, 29.1, 31.7, 36.0, 58.4, 129.0,
143.8.
Table 4, Entry 3: Ethyl 2-Butynoate/1-Hexene: Ethyl (Z)-
2-[1-(triethoxysilyl)methyl]pentyl-2-butenoate (22b: ꢀ-1):
1H NMR: ꢄ 0.86 (t, J ¼ 6:9 Hz, 3H), 0.9–1.3 (m, 6H), 1.21 (t, J ¼
6:9 Hz, 9H), 1.30 (t, J ¼ 7:3 Hz, 3H), 1.58 (d, J ¼ 7:2 Hz, 2H),
1.89 (d, J ¼ 7:3 Hz, 3H), 2.57 (quint, J ¼ 7:2 Hz, 1H), 3.79 (q,
J ¼ 6:9 Hz, 6H), 4.21 (q, J ¼ 7:3 Hz, 2H), 5.87 (q, J ¼ 7:3 Hz,
1H). Diastereotopic hydrogens (2H) are not resolved. 13C NMR:
ꢄ 14.1, 14.3, 15.5, 16.7, 18.2, 22.7, 29.6, 36.2, 38.9, 58.2, 59.8,
133.0, 138.1, 168.6. Ethyl (E)-3-methyl-4-(triethoxysilyl)meth-
1
yl-2-octenoate (23b: ꢂ-1): H NMR: ꢄ 0.86 (t, J ¼ 6:9 Hz, 3H),
1.0–1.6 (m, 6H), 1.13 (d, J ¼ 7:6 Hz, 2H), 1.21 (t, J ¼ 6:9 Hz,
9H), 1.28 (t, J ¼ 7:3 Hz, 3H), 2.07 (s, 3H), 2.34 (m, 1H), 3.79 (q,
J ¼ 6:9 Hz, 6H), 4.15 (q, J ¼ 7:3 Hz, 2H), 5.69 (s, 1H). Diastereo-
topic hydrogens (2H) are not resolved. 13C NMR: ꢄ 14.0, 14.4,
18.2, 18.3, 20.5, 23.0, 28.4, 30.9, 40.9, 58.5, 59.4, 116.5, 160.0,
166.8. Both compounds were found to be contaminated by a sig-
nificant amount (in a ratio ca. 5:1 by GLC analysis) of respective
regioisomers resulting from reversed insertion of 1-hexene com-
Tamao Oxidation of 25: According to the literature proce-
dure,29 the following conditions were examined (see, Scheme 3)
as a controlling experiment using 25, affording 2-octanone in
1
moderate yields: H NMR: ꢄ 0.88 (t, J ¼ 6:9 Hz, 3H), 1.24–1.34
(m, 6H), 1.56 (br quint, J ¼ 7:3 Hz, 2H), 2.14 (s, 3H), 2.42 (t,
J ¼ 7:4 Hz, 2H). a) Ac2O–H2O2 (12 equiv)/KHF2 (3 equiv)/no
KHCO3/DMF/rt, 7 h: Yield of 2-octanone 45%. b) H2O2 (6
equiv)/KHF2 (3 equiv)/no KHCO3/MeOH–THF/60 ꢂC, 7 h:

1822 Bull. Chem. Soc. Jpn. Vol. 80, No. 9 (2007)
Hydrosilylative Coupling of Alkynes with Alkenes
was utilized as an internal standard for the extent of propene
evolution, which ceased completely in 5 h. 29Si NMR of this final
sample exhibited a signal at ꢄ ꢁ18:5 characteristic of SiCl4.1c
Oxidant
KHF2, KHCO3
Solvent, Temp, Time
Si(OEt)3
This work was partly supported by a Grant-in-Aid from
the Japan Society of Promotion of Sciences (No. 15550099),
to which the authors’ thanks are due. We thank Professors
Y. Tsuji (Kyoto University) and K. Goto (The University of
Tokyo) for their generous gift of a bowl-shaped phosphine,
P(tm-tp)3. We also thank UBE Scientific Analysis Laboratory,
Inc. for 29Si NMR measurements.
(4 mmol)
(Yield)
O
Scheme 3. Oxidative cleavage of alkenylsilane.
49%. c) H2O2 (6 equiv)/KHF2 (1 equiv)/KHCO3 (1 equiv)/
MeOH–THF/reflux, 6 h: 57%.
Supporting Information
Thus, conditions a) and c) were adopted for the oxidation
of 13b.
The chemical names (9CI) and CAS Registry Numbers for the
cross-coupling products, which have appeared in our preliminary
communication (see, Ref. 13). This material is available free of
charge on the Web at http://www.csj.jp/journals/bcsj/.
Tamao Oxidation of 13b: d) In a similar manner as in a),
30% H2O2 (0.41 g, 12 mmol) and Ac2O (1.23 g, 12 mmol) were
added to a mixture of 13b (0.67 g, 2.0 mmol) and KHF2 (0.47 g,
6.0 mmol) dissolved in DMF (10 mL), and the whole mixture
was stirred at room temperature for 14 h. The mixture was treated
with a 10% NaHSO3 solution (20 mL) and then extracted thor-
oughly with ether. After a usual work-up, the residual organic lay-
er was purified by column chromatography to afford a colorless
oil. Spectral data of this product indicate methyl 2-[1-(hydroxy-
methyl)pentyl]propenoate (0.09 g, 24%): 1H NMR: ꢄ 0.88 (t,
J ¼ 6:9 Hz, 3H), 1.20–1.34 (m, 4H), 1.50 (brq, J ¼ 7:2 Hz, 2H),
1.74 (t, J ¼ 5:9 Hz, OH); disappeared by added D2O), 2.76 (dq,
J ¼ 8:2, 5.6 Hz, 1H), 3.67 (t, J ¼ 5:9 Hz, 2H), 3.72 (s, 3H), 5.62
(d, J ¼ 1:0 Hz, 1H), 6.30 (d, J ¼ 1:0 Hz, 1H). IR: 3429, 2955,
2932, 2872, 2860, 1721 cmꢁ1. Acetylation of this unexpected ꢆ-
hydroxy carboxylic ester did form methyl 2-[1-(acetoxymethyl)-
pentyl]propenoate: 1H NMR: ꢄ 0.88 (t, J ¼ 6:9 Hz, 3H), 1.27
(centered m, 4H), 1.53 (br q, 2H), 2.02 (s, 3H), 2.92 (quint, J ¼
6:9 Hz, 1H), 3.77 (s, 3H), 4.10 (dd, J ¼ 10:9, 7.3 Hz, 1H), 4.15
(dd, J ¼ 10:9, 6.3 Hz, 1H), 5.59 (br s, 1H), 6.30 (s, 1H). 13C NMR:
ꢄ 13.9, 20.9, 22.6, 29.2, 30.3, 40.2, 51.9, 66.5, 126.0, 140.6, 167.3,
171.0. IR: 2956, 2933, 2873, 2861, 1742, 1722, 1240 cmꢁ1. e) In a
similar manner as in c), 30% H2O2 (0.41 g, 12 mmol) was added to
a mixture of 13b (1.13 g, 3.4 mmol), KHF2 (0.32 g, 4.1 mmol), and
KHCO3 (0.51 g, 5.1 mmol) dissolved in MeOH (25 mL) and THF
(25 mL), and the whole mixture was stirred at room temperature
for 12 h. The mixture was treated with a saturated Na2S2O3 solu-
tion (20 mL) and then extracted thoroughly with ether. After a
usual work-up, the residual organic layer was purified by column
chromatography to afford colorless oil, 3-butyl-2-methylene-
butanolide18a (0.12 g, 25% yield): 1H NMR: ꢄ 0.92 (t, J ¼ 7:2
Hz, 3H), 1.20–1.50 (m, 6H), 2.98–3.10 (m, 1H), 3.98 (dd, J ¼ 8:9,
5.9 Hz, 1H), 4.02 (dd, J ¼ 9:8, 5.9 Hz, 1H), 5.59 (d, J ¼ 2:6 Hz,
1H), 6.27 (d, J ¼ 2:6 Hz, 1H).
References
1
For reviews, see: a) I. Ojima, The Hydrosilylation Reaction
in The Chemistry of Organic Silicon Compounds, ed. by S. Patai,
Z. Rappoport, Wiley Interscience, New York, 1989, Vol. 2,
pp. 1479–1526. b) B. Marciniec, J. Gulinski, W. Urbaniak,
Z. W. Kornetka, in Comprehensive Handbook on Hydrosilylation,
ed. by B. Marciniec, Pergamon Press, Oxford, 1992. c) M. A.
Brook, Silicon in Organic, Organometallic, and Polymer Chemis-
try, John Wiley & Sons, New York, 2000. d) K. Yamamoto, T.
Hayashi, Hydrosilylation of Olefins in Transition Metals for
Organic Synthesis, ed. by M. Beller, C. Bolm, Wiley-VCH,
New York, 1998, Vol. 2, pp. 120–131. e) K. Yamamoto, T.
Hayashi, Hydrosilylation of Olefins in Transition Metals for
Organic Synthesis, 2nd ed., ed. by M. Beller, C. Bolm,
Wiley-VCH, New York, 2004, Vol. 2, pp. 167–181.
2
a) A. J. Chalk, J. F. Harrod, J. Am. Chem. Soc. 1965, 87,
16. b) M. A. Schroeder, M. S. Wrighton, J. Organomet. Chem.
1977, 128, 345. c) S. Sakaki, M. Ogawa, Y. Musashi, T. Arai,
J. Am. Chem. Soc. 1994, 116, 7258. d) S. Sakaki, N. Mizoe, M.
Sugimoto, Organometallics 1998, 17, 2510; For a relevant review,
see: J. Y. Corey, J. Braddock-Wilking, Chem. Rev. 1999, 99, 175.
3 For a review on addition of metalloid hydrides to alkynes,
see: B. M. Trost, Z. T. Ball, Synthesis 2005, 853.
4
5
Y. Kawanami, K. Yamamoto, Synlett 1995, 1232.
a) Y. Kawanami, K. Yamamoto, 43rd Symposium on
Organometallic Chemistry, Osaka: Japan, 1996, Abstr., No. PB114.
b) T. Uno, S. Wakayanagi, Y. Sonoda, K. Yamamoto, Synlett
2003, 1997.
6
S. Wakayanagi, T. Shimamoto, M. Chimori, K.
Yamamoto, Chem. Lett. 2005, 34, 160.
T. Shimamoto, T. Hirano, H. Nishimoto, K. Yamamoto,
Chem. Lett. 2006, 35, 846.
Stoichiometric Reaction of [Pd(ꢀ3-C3H5)(cod)]þ[PF6]ꢀ (A)
7
ꢅ
with HSiCl3.21 In a 5 mm ꢄ 180 mm NMR tube, which has
a joint to connect with the vacuum line (0.27 Pa), were placed
under nitrogen a cationic palladium complex A (20.0 mg, 5 ꢄ
10ꢁ2 mmol) and CD2Cl2 (0.70 mL), and the resulting solution
was subjected twice to freeze-thawing. To this solidified solution
was added a chilled HSiCl3 stock solution (50 mL, 1 M CH2Cl2,
5 ꢄ 10ꢁ2 mmol), and the mixture was immediately subjected
once to freeze-thawing. The tube was sealed under vacuum. The
1H NMR measurement of this sample at probe temperature (25 ꢂC)
was conducted at given time intervals to detect the evolution of
free propene, while the mixture solution began soon to darken
and became eventually turbid. The signal of CH2Cl2 (ꢄ 5.33)
8
a) I. Ojima, R. J. Donovan, W. R. Shay, J. Am. Chem. Soc.
1992, 114, 6580. b) I. Ojima, A. T. Vu, J. V. McCullagh, A.
Kinoshita, J. Am. Chem. Soc. 1999, 121, 3230. c) I. Ojima,
A. T. Vu, S.-Y. Lee, J. V. McCullagh, A. C. Moralee, M.
Fujiwara, T. H. Hoang, J. Am. Chem. Soc. 2002, 124, 9164.
d) T. Muraoka, I. Matsuda, K. Itoh, Tetrahedron Lett. 1998, 39,
7325. e) T. Muraoka, I. Matsuda, K. Itoh, Organometallics
2002, 21, 3650. f) C. Liu, R. A. Widenhoefer, Organometallics
2002, 21, 5666. g) H. Chakrapani, C. Liu, R. A. Widenhoefer,
Org. Lett. 2003, 5, 157.
9
a) K. Tamao, K. Kobayashi, Y. Ito, J. Am. Chem. Soc.

T. Shimamoto et al.
Bull. Chem. Soc. Jpn. Vol. 80, No. 9 (2007) 1823
1989, 111, 6478. b) K. Tamao, K. Kobayashi, Y. Ito, Synlett
1992, 539. c) For a related Ni0-catalyzed dimerization of
1-alkynes, see: M. F. Lappert, T. A. Nile, S. Takahashi, J.
Organomet. Chem. 1974, 72, 425.
two alkynes.
18 a)
3-Butyl-2-methylenebutanolide = 4-Butyl-3-methyl-
ene-4,5-dihydro-2(3H)furanone: E. Roeder, H. Krauss, Ann. Chim.
1992, 177. b) 2-Methylene-3-phenylbutanolide: H. Nishiyama, H.
Yokoyama, S. Narimatsu, K. Itoh, Tetrahedron Lett. 1982, 23,
1267.
19 Reversivility of the hydropalladation in the Pd-catalyzed
alkadiynes has not been established. However, reversible silylpal-
ladation in the case of alkadienes under similar reaction conditions
are discussed. See: X. Wang, H. Chakrapani, C. N. Stengone,
R. A. Widenhoefer, J. Org. Chem. 2001, 66, 1755.
20 With regard to this discussion, Hayashi et al. have ob-
served that the reaction of [Pd(ꢁ3-C3H5)Cl]2 with HSiEt3 in the
presence of a diphosphine generates a Pd0L2 species together with
ClSiEt3 and propene. The reaction with HSiCl3 and PPh3 should
also produce a Pd0 species. See: Y. Uozumi, H. Tsuji, T. Hayashi,
J. Org. Chem. 1998, 63, 6137; Hydrosilylation of 1,5- and 1,3-
cyclooctadiene has long been known to be catalyzed easily
by various types of Pt catalysts: K. Yamamoto, M. Kumada,
J. Organometal. Chem. 1968, 13, 131.
21 Stoichiometric reactions of ꢇ-allylic palladium(II) com-
plexes containing phosphorus ligand or N-heterocyclic carbene
ligand with HSiCl3 will be discussed elsewhere: N. Takaoka,
B.S. Thesis, Tokyo University of Science, Yamaguchi, 2004.
22 K. K. Hii, Hydridopalladium Complexes in Handbook of
Organopalladium Chemistry for Organic Synthesis, ed. by E.
Negishi, Wiley Intersciece, New York, 2002, Vol. 1, pp. 81–90.
23 A cationic arylpalladium species is known to undergo a
facile alkene insertion in the Mizoroki–Heck reaction: F. Ozawa,
T. Hayashi, J. Am. Chem. Soc. 1991, 113, 1417; For a relevant
review, see: T. Nishikata, N. Miyaura, Shokubai 2005, 47, 619.
24 W. C. Still, M. Kahn, A. Mitra, J. Org. Chem. 1978,
43, 2923.
10 a) R. A. Widenhoefer, M. A. DeCarli, J. Am. Chem. Soc.
1998, 120, 3805. b) R. A. Widenhoefer, A. Vadehra, Tetrahedron
Lett. 1999, 40, 8499. c) R. A. Widenhoefer, C. N. Stengone,
J. Org. Chem. 1999, 64, 8681. d) N. S. Perch, R. A. Widenhoefer,
J. Am. Chem. Soc. 1999, 121, 6960. e) C. N. Stengone, R. A.
Widenhoefer, Tetrahedron Lett. 1999, 40, 1451. f) N. S. Perch,
P. Kisanga, R. A. Widenhoefer, Organometallics 2000, 19,
2541. g) X. Wang, H. Chakrapani, C. N. Stengone, R. A.
Widenhoefer, J. Org. Chem. 2001, 66, 1755. h) X. Wang, S. Z.
Stankovich, R. A. Widenhoefer, Organometallics 2002, 21, 901.
11 a) J. W. Madine, X. Wang, R. A. Widenhoefer, Org. Lett.
2001, 3, 385. b) X. Wang, H. Chakrapani, J. A. Madine, M. A.
Keyerleber, R. A. Widenhoefer, J. Org. Chem. 2002, 67, 2778.
12 For a discussion about the mechanistic crossover, see: a) Y.
Maruyama, K. Yamamura, T. Sagawa, H. Katayama, F. Ozawa,
Organometallics 2000, 19, 1308. b) F. Ozawa, J. Organomet.
Chem. 2000, 611, 332.
13 For a preliminary report, see: T. Shimamoto, M. Chimori,
H. Sogawa, K. Yamamoto, J. Am. Chem. Soc. 2005, 127, 16410.
14 In the chemical formula, the designations ꢀ or ꢂ and 1 or 2
refer to the carbopalladation that occur at ꢀ or ꢂ position of the 1-
alkyne employed, and C–Si bond occurring at terminal or internal
carbon of the 1-alkene counterpart, respectively.
15 Immediate reaction products consist of ꢀ’s (> 90%), a
little ꢂ isomer (<5%) and others on the basis of GLC analysis,
the latter two being hardly isolated at this stage.
16
A
bowl-shaped phosphine, P(tm-tp)3 = tris{2,200,6,600-
tetramethyl-m-terphenyl-50-yl}-phosphine: a) K. Goto, Y. Ohzu,
H. Sato, T. Kawashima, Phosphorus, Sulfur Silicon Relat. Elem.
2002, 177, 2179. b) O. Niyomura, T. Iwasawa, N. Sawada, M.
Tokunaga, Y. Obora, Y. Tsuji, Organometallics 2005, 24, 3468.
An intriguing nature of a Rh complex that contains P(tm-tp)3 in
the hydrosilylation of ketones is discussed by Tsuji et al.
25 D. A. White, Inorg. Synth. 1972, 13, 61.
26 Throughout this section, all chemical names for the prod-
ucts of hydrosilylative cross-coupling of alkynes with alkenes
are given on the basis of common 4-organosilyl-1-butene frame-
works, R1CH=CR2–CHR3–CHR4–SiX3 (X ¼ Cl or OEt) and
not consonant with those by CAS (9CI).
27 B. M. Trost, Z. T. Ball, J. Am. Chem. Soc. 2001, 123,
12726, and references cited therein.
28 M. R. Chaulagain, G. M. Mahandru, J. Montgomery,
Tetrahedron 2006, 62, 7560.
17 In this regard, it should be mentioned that, in the hydro-
silylative cross-coupling of 1-heptyne with 1-hexene (3 equiv)
in the presence of catalyst A, P(C6F5)3 caused very rapid conver-
sion at room temperature, giving rise to products (55% yield) in 7a
(ꢀ-1):9a (ꢂ-1) = 22:78 (see, Table 3, Entry 3, footnote e). Thus,
the fact that phenylacetylene, (1b (ꢀ-1) + 2b (ꢀ-2)):3b (ꢂ-1) =
85:15 (Table 1, Entry 5), and 1-heptyne show contrasting regiose-
lectivities well reinforces that P(C6F5)3 as a ligand exhibits a
reversed electronic effect on the hydropalladation step for these
29 K. Tamao, N. Ishida, T. Tanaka, M. Kumada, Organo-
metallics 1983, 2, 1694.