Markovnikov-selective hydrosilylation of electron-deficient alkenes with arylsilanes catalyzed by mono(phosphine)palladium(0)

Article abstract of DOI:10.1021/om500964g

Markovnikov-selective hydrosilylation of electron-deficient alkenes with HSiPh₃ is catalyzed by a mono(phosphine)palladium(0) complex, Pd(η²:η²-C₆H₁₀O)(PMe₃) (1a). The hydrosilylation of acrylonitrile with HSiPh₃ at 30 °C proceeds to completion within 40 min in the presence of 5 mol % of 1a. The complex 1a also shows the catalytic activity for the hydrosilylation with mono- and diarylsilanes and monochlorosilane such as HSiPhMe₂, HSiPh₂Me, and HSiClMe₂. The hydrosilylation using para-substituted styrenes clearly shows the electron-withdrawing substituent promoting the reaction. Mechanistic studies indicate that the reaction is proceeding by a Chalk-Harrod mechanism with the reductive elimination of an (alkyl)(silyl)palladium(II) intermediate being the rate-determining step.

Full text of DOI:10.1021/om500964g

Article
pubs.acs.org/Organometallics
Markovnikov-Selective Hydrosilylation of Electron-Deficient Alkenes
with Arylsilanes Catalyzed by Mono(phosphine)palladium(0)
Nobuyuki Komine,* Makoto Abe, Ryoko Suda, and Masafumi Hirano
Department of Applied Chemistry, Graduate School of Engineering, Tokyo University of Agriculture and Technology, 2-24-16
Nakacho, Koganei, Tokyo 184-8588, Japan
S
* Supporting Information
ABSTRACT: Markovnikov-selective hydrosilylation of electron-
deficient alkenes with HSiPh3 is catalyzed by a mono(phosphine)-
palladium(0) complex, Pd(η2:η2-C6H10O)(PMe3) (1a). The hydro-
silylation of acrylonitrile with HSiPh3 at 30 °C proceeds to completion
within 40 min in the presence of 5 mol % of 1a. The complex 1a also
shows the catalytic activity for the hydrosilylation with mono- and
diarylsilanes and monochlorosilane such as HSiPhMe2, HSiPh2Me, and
HSiClMe2. The hydrosilylation using para-substituted styrenes clearly
shows the electron-withdrawing substituent promoting the reaction. Mechanistic studies indicate that the reaction is proceeding
by a Chalk−Harrod mechanism with the reductive elimination of an (alkyl)(silyl)palladium(II) intermediate being the rate-
determining step.
to give 2-(triphenylsilyl)propanenitrile exclusively within 40 min
(eq 1).
INTRODUCTION
■
Hydrosilylation is an important reaction in organic synthesis
and polymer chemistry and for the production of organosilicon
compounds. The addition of hydrosilane to alkenes normally
requires a transition-metal catalyst.1 Among many transition-
metal catalysts for hydrosilylation reported, platinum com-
pounds such as Speier’s and Karstedt’s catalysts are widely
believed to be very powerful catalysts and are often used
commercially.2 However, these catalysts generally show poor
activity toward electron-deficient alkenes such as acrylonitrile as
substrates in the hydrosilylations. Several catalytic α-selective
hydrosilylations of acylonitrile were already reported by use of
Rh, Pd, and Re catalysts.3 For example, in 1974 Tsuji and co-
workers reported α-selective hydrosilylation of acylonitrile
catalyzed by a Pd−phosphine system.3a Recently we found a
palladium(0) complex to catalyze hydrometalation of electron-
deficient alkenes and alkynes with transition-metal hydrides.4
Among the palladium(0) catalysts screened, mono(phosphine)-
palladium(0) complexes having a diallyl ether ligand, Pd(η2:η2-
C6H10O)L (1)5 was found to be the best catalyst.4c As one of
the new and important aspects of this chemistry, we now
evaluated this promising palladium(0) catalyst 1 for hydro-
silylations because hydrosilylations catalyzed by an isolated
mono(phosphine)palladium(0) complex are unprecedented
to the best of our knowledge.6 In this paper, we disclose
Markovnikov-selective hydrosilylations of electron-deficient
alkenes promoted by 1 under ambient conditions.
Among hydrosilanes, HSiPh3 is generally considered to be
an inert silane for hydrosilylation,1c,7 and this is the first
hydrosilylation of acrylonitrile with HSiPh3. The product was
recrystallized from Et2O with hexane and was characterized by
full spectroscopic data and elemental analysis. Figure 1 shows
the time-course curves for the hydrosilylation of acrylonitrile
with HSiPh3 catalyzed by Pd(η2:η2-C6H10O)L (L = PMe3 (1a),
PCy3 (1b), PPh3 (1c)). The product linearly increased until the
completion of the reactions. The PMe3 analogue showed the
best activity among the mono(phosphine)palladium complexes
Pd(η2:η2-C6H10O)L (L = PMe3 (1a), PCy3 (1b), PPh3 (1c))
screened (Figure 1).
The reaction rate diminished by the addition of 1 equiv of
PMe3 and was completely hampered in the presence of 2 equiv
of PMe3 (Figure 2). These results suggest the active catalyst is a
(monophosphine)palladium complex. Note that Karstedt-type
catalysts such as Pt2(dvd)3 and Pt(dvd)(PCy3)8 (dvd = 1,3-
divinyl-1,1,3,3-tetramethyldisiloxane) show virtually no catalytic
activity for this hydrosilylation under these optimized conditions.
Scope of Silanes. The scope of silanes in the hydro-
silylation of acrylonitrile catalyzed by 1a is given in Table 1.
RESULTS AND DISCUSSION
■
Reaction of Acrylonitrile with Triphenylsilane Catalyzed
by Mono(phosphine)palladium(0). The reaction of acryloni-
trile with HSiPh3 was catalyzed at 30 °C by the mono(phosphine)-
palladium(0) complex Pd(η2:η2-C6H10O)(PMe3) (1a; 5 mol %)
Received: September 21, 2014
© XXXX American Chemical Society
A
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Table 2. Hydrosilylation of Alkenes with Triphenylsilane
a
Catalyzed by Pd(η2:η2-C6H10O)(PMe3) (1a)
Figure 1. Hydrosilylation of acrylonitrile with triphenylsilane catalyzed
by mono(phosphine)palladium(0) complex, Pd(η2:η2-C6H10O)L
■
◆
▲
(L = PMe3 (1a, red ), PCy3 (1b, blue ), PPh3 (1c, green )).
Conditions: [HSiPh3]0 = 0.10 M, [acrylonitrile]0 = 0.10 M, [1] =
0.005 M, solvent C6D6, temperature 30 °C.
Figure 2. Effect of PMe3 added in hydrosilylation of acrylonitrile with
triphenylsilane catalyzed by the mono(trimethylphosphine)-
palladium(0) complex Pd(η2:η2-C6H10O)(PMe3) (1a): [PMe3] = 0
■
■
■
(red ), 0.005 (green ), 0.010 M (blue ). Conditions: [HSiPh3]0 =
0.10 M, [acrylonitrile]0 = 0.10 M, [1a] = 0.005 M, solvent C6D6,
temperature 30 °C.
Table 1. Hydrosilylation of Acrylonitrile with Hydrosilanes
a
Catalyzed by Pd(η2:η2-C6H10O)(PMe3) (1a)
entry
hydrosilane
time/h conversn/% yield/% 104(rate)/M s−1
1
2
3
4
5
6
HSiPh3
0.6
1.3
7
98
100
87
97
96
85
0
50
24
HSiPh2Me
HSiPhMe2
HSiEt3
3.7
8
22
HSiMe2Cl
HSi(OEt)3
1.2
97
74
0
25
a
13
100
Conditions: [hydrosilane]0 = 0.10 M, [acrylonitrile]0 = 0.10 M,
b
a
[1a] = 0.005 M, solvent C6D6, temperature 30 °C. [HSiPh3]0 = 0.30 M,
[1a] = 0.010 M. The yield was estimated by H NMR using hexa-
methyldisiloxane as an initial standard. Isolated yield.
Conditions: [hydrosilane]0 = 0.10 M, [acrylonitrile]0 = 0.10 M,
[1a] = 0.005 M, solvent C6D6, temperature 30 °C.
c
1
d
Mono- and diarylsilanes such as HSiPhMe2 and HSiPh2Me
also gave the corresponding product3a,9 in excellent yield with
complete Markovnikov selectivity. The monochlorosilane
HSiMe2Cl also reacted with acrylonitrile to give the
corresponding diorganochlosilane,3a whereas HSiEt3 and
HSi(OEt)3 did not give the hydrosilylation products. The
present hydrosilylation suggests that the acidic hydrosilane
promotes the reaction.10 This interesting nature compensates
traditional hydrosilylations.
Scope of Alkenes. Table 2 shows the substrate scope of
alkenes using HSiPh3. Electron-deficient monosubstituted
alkenes such as methyl vinyl ketone (entry 2) and methyl
acrylate (entry 3) produced the corresponding products in high
yields. In sharp contrast, electron-rich alkenes remained un-
reacted (entries 5−7). Consistent with this hypothesis, styrenes
with an electron-withdrawing group such as p-CF3 (σp = 0.54),
p-CN (σp = 0.66), and p-NO2 (σp = 0.78) encouraged the
B
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reaction (entry 8−10), while styrene (σp = 0.0) did not react
with HSiPh3 at all (entry 7). Disubstituted electron-deficient
alkenes also produced the products (entries 11−14). However,
dimethyl fumarate unexpectedly remained unreacted (entry 15).
Probably, this reaction requires a polarized CC bond or the
putative Pd(dimethyl fumarate)2(PMe3) species cannot react with
HSiPh3 (vide infra). In the reaction of ethyl isocrotonate (entry 13),
ethyl crotonate was observed (Figure 3). This E/Z isomerization
Figure 4a shows the effect of concentration of palladium(0)
catalyst on the reaction rate. The loading of 1a can be reduced
to 1 mol %, but the complete conversion takes longer to
achieve. When the concentration of 1a was increased to 5 and
10 mol %, the initial rate roughly increased 5 and 10 times,
suggesting a reaction first order in the catalyst concentration.
All of these reaction profiles appear to be similar to zero-order
reactions to the substrates, but actually the initial rate depends
on the HSiPh3 concentration, as shown in Figure 4b. Therefore,
a more precise understanding is that the dependence of the
initial rate on the HSiPh3 concentration is saturated when up to
0.10 M of HSiPh3 is employed under these conditions. On the
other hand, the reaction was diminished by the addition of
excess acrylonitrile (Figure 4c). This feature is discussed in the
following section.
When DSiPh3 (>95% D) was used in this reaction, the
deuterium atom was exclusively incorporated in the methyl
group of the product (eq 2).12 No isotope effect on the rate was
observed in this reaction.
Figure 3. Time course for the reaction of ethyl isocrotonate with
HSiPh3 in the presence of Pd(η2:η2-C6H10O)(PMe3) (1a): ethyl
◆
■
isocrotonate (blue ), ethyl crotonate (purple ×), HSiPh3 (red ),
◆
ethyl 2-(triphenylsilyl)butanate (green ). Conditions: [HSiPh3]0 =
In order to understand the reaction mechanism, the stoi-
0.10 M, [ethyl isocrotonate]0 = 0.10 M, [1a] = 0.005 M, solvent C6D6,
temperature 30 °C.
chiometric reactions of 1a with acrylonitrile was monitored by
1
the H NMR spectrum at 30 °C in benzene-d6. The treatment
of 1a with 2 equiv of acrylonitrile rapidly produced a 1:1
mixture of 1a and Pd(η2-CH2CHCN)2(PMe3) (2a) with the
liberation of dialyl ether in 52% yield (Scheme 1).
suggests the reversible insertion of an alkene into the Pd−H bond
and β-hydride elimination processes. This is consistent with a
Chalk−Harrod mechanism11 for the present hydrosilylation
reaction. Trisubstituted and 1,1-disubstituted alkenes also
remained unreacted, probably due to difficulty in coordination
(entries 16 and 17).
Scheme 1
Mechanistic Study. In order to obtain mechanistic
information for the present hydrosilylation, a kinetic inves-
tigation of the stoichiometric reactions was carried out.
Figure 4. Effect of concentration of palladium(0) catalyst and substrates on the reaction rate. (a) Effect of concentration of Pd(η2:η2-
■
■
●
C6H10O)(PMe3) (1a). Conditions: [HSiPh3]0 = 0.10 M, [acrylonitrile]0 = 0.10 M, [1a] = 0.001 (red ), 0.005 (green ), 0.010 M (blue ) . (b)
■
■
●
Effect of concentration of HSiPh3. Conditions: [HSiPh3]0 = 0.050 (blue ), 0.10 (green ), 0.20 M (red ), [acrylonitrile]0 = 0.10 M, [1a] =
0.005 M. (c) Effect of concentration of acrylonitrile. Conditions: [HSiPh3]0 = 0.10 M, [acrylonitrile]0 = 0.050 (blue ), 0.10 (green ), 0.20 M (red ),
■
●
▲
[1a] = 0.005 M. Legend: (a) yields calculated on the basis of HSiPh3; (b) yields calculated on the basis of acrylonitrile.
C
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With 4 equiv of acrylonitrile, 2a was formed in 94% yield
with the liberation of diallyl ether in 95% yield. In these reac-
tions, the acrylonitrile resonances were broadened, suggesting
the presence of dynamic behavior, and 2a was formed as a 6:4
mixture of isomers. Complex 2a was isolated as an analytically
pure white powder of an isomeric mixture in 1:0.73 ratio by
the reaction of 1 with 5 equiv of acrylonitrile in hexane in
would insert into the Pd−H rather than Pd−Si bond. The
polarization of the coordinating alkene gives a rise to the regio-
specific insertion reaction. The isotope experiment suggests
reductive elimination being the rate-determining step. The
major resting state of the active catalyst is probably the
bis(alkene)palladium(0) species.
1
quantitative yield. The complex 2a was characterized by H,
CONCLUSION
■
13C{1H}, and 31P{1H} NMR spectra, COSY and HETCOR,
and elemental analysis. These isomers are assignable to the
diastereomers that arise from the prostereogenic faces of two
acrylonitrile ligands at the Pd(0) center.13 On the other hand,
1a did not react with HSiPh3 at all under these conditions.
The treatment of 2a with HSiPh3 (1 equiv/Pd) at 30 °C in
benzene-d6 produced the hydrosilylation product in 106% yield
within 10 min. Complex 2a can be used as a catalyst precursor
for the hydrosilylation. The reaction of acrylonitrile (0.1 M)
with HSiPh3 (0.1 M) is catalyzed by 2a (5 mol %) to give the
Markovnikov product in 100% yield within 50 min at 30 °C.
The catalytic activity of 2a was exactly as same as that of 1a (cf.
Figure 2). However, with 0.5 M of acrylonitrile, the reaction is
significantly suppressed and yields the hydrosilylation product
only in 84% yield after 190 min. This nature is also the same
feature as 1a, suggesting the prior dissociation of an
acrylonitrile fragment.
In summary, the catalytic hydrosilylation of electron-deficient
alkenes can be achieved by mono(phosphine)palladium(0)
complexes in complete Markovnikov selectivity.
EXPERIMENTAL SECTION
■
General Considerations. All procedures described in this paper
were carried out under a nitrogen or argon atmosphere by use of
Schlenk and vacuum line techniques. Benzene and hexane were dried
and purified using a Glass Contour Ultimate Solvent System. Benzene-
d6 was dried over sodium wire and stored under vacuum, and it was
purified by vacuum distillation prior to use. HSiPh3, HSiPh2Me,
HSiPhMe2, HSiMe2Cl, HSiEt3, HSi(OEt)3, diallyl ether, and alkenes
were purchased from TCI or Aldrich. The mono(phosphine)-
palladium(0) complexes Pd{η2:η2-(CH2CHCH2)2O}(PR3) (R =
Me (1a), Cy (1b), Ph (1c))5 and DSiPh315 were prepared by literature
1
2
procedures with modification. H, H, 13C{1H}, and 31P{1H} NMR
1
spectra were measured on a 400 MHz (for H) NMR spectrometer.
The IR spectra were measured on a Fourier transform spectrometer.
The elemental analyses were performed on a CHN analyzer.
Hydrosilylation of Electron-Deficient Alkenes Catalyzed by
Mono(phosphine)palladium(0) Complexes. As a typical proce-
dure, the hydrosilylation of acrylonitrile with triphenylsilane is given.
NMR Tube Reaction. In an NMR tube containing 410 μL of C6D6
were placed 90.7 μL of a 0.066 M C6D6 solution of 1/1 mixture of
acrylonitrile (0.060 mmol) and HSiPh3 (0.060 mmol). To this was
added a solution of hexamethyldisiloxane (0.067 M, 50 μL,
0.034 mmol) as an internal standard. After the addition of a C6D6
solution of Pd{η2:η2-(CH2CHCH2)2O}(PMe3) (1a; 0.060 M,
50 μL, 0.0030 mmol) to form a 6.0 mM solution of acrylonitrile
and HSiPh3, the reaction was monitored by 1H NMR at 30 °C, and the
yields were periodically estimated by 1H NMR. The final yield of
2-(triphenylsilyl)propanenitrile was 97%.
With this fundamental information about the Pd species in
hand, we have monitored the behavior of 1a in catalysis by
31P{1H} NMR. In the catalytic reaction of acrylonitrile (0.1 M)
with HSiPh3 (0.1 M) in the presence of 1a (10 mol %) as the
catalyst precursor, 1a rapidly converted into a new singlet
species at δ −16.1 in the 31P{1H} NMR along with 2a. No
1
hydride species were observed in the H NMR. After com-
pletion of the reaction, all species converted to 1a.14 Un-
fortunately, although the new transient species was difficult to
characterize, it was confirmed to be a resting state.
All of these results are consistent with the Chalk−Harrod
mechanism11 shown in Scheme 2. First of all, complex 1a is
Schlenk Tube Reaction. A reaction mixture of acrylonitrile
(26.0 μL, 0.397 mmol), HSiPh3 (100.3 mg, 0.3852 mmol), and 1a
(2.6 mg, 0.0093 mmol) in C6D6 (2 mL) was vigorously stirred at room
temperature for 12 h. After filtration by Celite pad, the mixture was
concentrated by an evaporator to dryness to give a crude product.
The crude product was purified by recrystallization from diethyl
ether with a small amount of hexane to give colorless crystals of
2-(triphenylsilyl)propanenitrile in 35% yield (42.3 mg, 0.135 mmol).
1H NMR (400 MHz, C6D6, 30 °C): δ 1.04 (d, 3H, J = 7.4 Hz,
CH3), 2.07 (q, 1H, J = 7.4 Hz, CH), 7.13 (m, 9H, m,p-C6H5), 7.57 (m,
6H, o-C6H5). 13C{1H} NMR (101 MHz,C6D6, 30 °C): δ 10.1 (CH3),
13.1 (CH), 122.6 (CN), 128.0 (C6H5), 130.7 (C6H5), 131.6 (C6H5),
136.3 (C6H5). Anal. Calcd for C21H19NSi: C, 80.46; H, 6.11; N, 4.47.
Found: C, 80.03; H, 6.40; N, 4.63.
Scheme 2. Proposed Catalytic Cycle
Methyl 2-(Triphenylsilyl)propanate. The yield was estimated as
1
100% by H NMR. This compound was isolated as a white solid in
1
74% yield by column chromatography. H NMR (400 MHz, C6D6,
30 °C): δ 1.41 (d, JHH = 7.4 Hz, 1H, Me), 2.97 (q, JHH =7.4 Hz, 1H,
CHMeCO2Me), 3.11 (s, 3H, CO2Me), 7.0−7.3 (m, 9H, m,p-C6H5),
7.6−7.8 (m, 6H, o-C6H5). 13C{1H} NMR (101 MHz, C6D6, 30 °C): δ.
13.4 (CH3), 28.8 (CH3), 50.7 (CH), 128.1 (C6H5), 130.0 (C6H5),
133.4 (C6H5), 136.6 (C6H5), 175.6 (CO). Anal. Calcd: C, 76.26; H,
6.40. Found: C, 76.07; H, 6.35.
converted into Pd(η2-CH2CHCN)(PMe3) (A), which is in
equilibrium with bis(acrylonitrile)palladium(0) species 2a.
Complex 2a was isolated by the stoichiometric reaction in
hexane. In the presence of PMe3, the active species A would
give bis(phosphine)palladium(0) (B). These 16e species 2a
and B must be much more stable than A, but they can
reversibly give A. Now A gives C by the oxidative addition of
HSiPh3. Since we have observed a Z to E isomerization of
alkene during the hydrosilylation, the coordinating alkene
3-(Trimethylsilyl)-2-butanone. The yield was estimated as 93%
1
by NMR. H NMR (400 MHz, C6D6, 30 °C): δ 1.65 (dm, JHH =6.7
Hz, 3H, CHMeCOMe), 1.65 (s, 3H, CHMeCOMe), 4.44 (q, JHH =6.7
Hz, 1H, CHMeCOMe), 7.1−7.2 (m, 9H, m,p-C6H5), 7.7−7.8 (m, 6H,
o-C6H5). 13C{1H} NMR (101 MHz, C6D6, 30 °C): δ 11.2 (CH3),
D
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23.2 (CH), 103.6 (CH3), 128.2 (C6H5), 130.3 (C6H5), 135.2 (C6H5),
135.7 (C6H5), 147.8 (CO).
JHP = 11 Hz, PMe3), 2.66 (br d, 2H, JHH = 11 Hz, CHHCHCN:
trans to CN), 2.99 (distorted br t, 2H, JHH = 11 Hz, CH2CHCN),
3.03 (distorted br d, 2H, JHH = 13 Hz, CHHCHCN: cis to CN).
13C{1H} NMR (101 MHz, C6D6, 20 °C): δ 15.8 (d, JCP = 23 Hz,
PMe3), 42.5 (s, CH2CHCN), 59.9 (br s, CH2CHCN), 120.9 (s,
CH2CHCN). 31P{1H} NMR (162 MHz, C6D6, 21 °C): δ −23.9 (s).
Methyl 2-(Triphenylsilyl)butanate. The yield was estimated as
1
96% by NMR. H NMR (400 MHz, C6D6, 30 °C): δ 0.94 (t, JHH
=
7.2 Hz, 3H, CH2CH3), 1.71 (dqd, JHH = 14.3, 7.2, 2.7 Hz, 1H,
CH(SiPh3)CHH), 2.21 (ddq, JHH = 14.3, 12.0, 7.2, 2.7 Hz, 1H,
CH(SiPh3)CHH), 2.91 (dd, JHH = 12.0, 2.8 Hz, 1H, CH), 3.13 (s, 3H,
CO2Me), 7.0−7.3 (m, 9H, m,p-C6H5), 7.6−7.8 (m, 6H, o-C6H5).
13C{1H} NMR (101 MHz, C6D6, 30 °C): δ 15.3 (CH3), 22.9 (CH2),
38.5 (CH), 50.6 (CH3), 128.1 (C6H5), 130.0 (C6H5), 133.5 (C6H5),
136.6 (C6H5), 174.9 (CO).
Ethyl 2-(Triphenylsilyl)butanate. The yield was estimated as
84% by NMR. 1H NMR (400 MHz, C6D6, 30 °C): δ 0.72 (t, JHH = 7.2
Hz, 3H, CH2CH3), 0.97 (t, JHH = 7.2 Hz, 3H, CO2CH2CH3), 1.72
1
These coupling constants in H NMR were evaluated by iteration of
gNMR for Windows (5.0.6.0).
Stoichiometric Reaction of 2a with Triphenylsilane. In an
NMR tube containing HSiPh3 (9.04 mg, 0.0347 mmol) were placed
500 μL of C6D6 and a solution of hexamethyldisiloxane (0.37 M,
10 μL, 0.0037 mmol) as an internal standard. After the addition of a
C6D6 solution of bis(acrylonitrile)palladium(0) complex 2a (0.346 M,
100 μL, 0.0346 mmol), the reaction was monitored by 1H and 31P{1H}
1
(dqd, JHH = 14.3, 7.2, 2.7 Hz, 1H, CH(SiPh3)CHH), 2.22 (ddq, JHH
=
NMR at 30 °C, and the yields were periodically estimated by H
14.3, 12.0, 7.2, 2.7 Hz, 1H, CH(SiPh3)CHH), 2.90 (dd, JHH = 12.0, 2.3
Hz, 1H, CH), 3.66 (dq, JHH = 10.8, 7.2 Hz 1H, CO2CHHMe), 3.82
(dq, JHH = 10.8, 7.2 Hz 1H, CO2CHHMe), 7.0−7.3 (m, 9H, m,p-
C6H5), 7.6−7.8 (m, 6H, o-C6H5). 13C{1H} NMR (101 MHz, C6D6, 30 °C):
δ 13.7 (CH3), 15.0 (CH2), 22.5 (CH2), 38.1 (CH), 59.6 (CH3), 127.8
(C6H5), 129.7 (C6H5), 133.3 (C6H5), 136.4 (C6H5), 174.2 (CO).
Methyl 3-Phenyl-2-(trimethylsilyl)propanoate. The yield was
estimated as 68% by NMR. 1H NMR (400 MHz, C6D6, 30 °C): δ 2.99
NMR. The final yield of 2-(triphenylsilyl)propanenitrile was 106%.
ASSOCIATED CONTENT
■
S
* Supporting Information
1
A figure giving the H NMR spectrum and gNMR simulation
for 2a. This material is available free of charge via the Internet
at http://pubs.acs.org.
(s, 3H, CO2Me), 3.04 (dd, JHH = 14.9, 2.3 Hz, CH), 3.42 (dd, JHH
=
12.0, 2.3 Hz, CH(SiPh3)CHH), 3.56 (dd, JHH = 14.3, 2.3 Hz,
CH(SiPh3)CHH), 7.1−7.2 (m, 14H, C6H5), 7.6−7.8 (m, 6H, o-C6H5).
13C{1H} NMR (101 MHz, C6D6, 30 °C): δ 35.1 (CH3), 38.8 (CH2),
50.7 (CH3), 126.5 (C6H5), 127.9 (C6H5), 128.5 (C6H5), 128.7 (C6H5),
130.2 (C6H5), 133.1(C6H5), 136.6(C6H5), 142.4 (C6H5),174.5 (CO).
1-Nitro-4-[1-methyl-1-(trimethylsilyl)ethyl]benzene. The
AUTHOR INFORMATION
Corresponding Author
*N. K.: e-mail, komine@cc.tuat.ac.jp; tel and fax, +81 423 887 044.
Notes
■
The authors declare no competing financial interest.
1
yield was estimated as 81% by NMR. H NMR (400 MHz, C6D6,
30 °C): δ 1.29 (d, 3H, JHH = 7.4 Hz, CH3), 2.83 (q, 1H, JHH = 7.4 Hz,
CH), 6.51 (d, 2H, JHH = 8.9 Hz, C6H4NO2), 7.1−7.2 (m, 9H, m,p-
C6H5Si), 7.63 (m, 6H, o-C6H5Si), 7.67 (d, 2H, JHH = 8.9 Hz,
C6H4NO2). 13C{1H} NMR (101 MHz, C6D6, 30 °C): δ 17.1 (CH3),
29.2 (CH), 123.2 (C6H5), 129.1 (C6H5), 130.1 (C6H5), 133.1 (C6H5),
135.4 (C6H5), 136.6 (C6H5), 146.1 (C6H5),146.1 (CO).
ACKNOWLEDGMENTS
■
We thank Prof. S. Komiya for useful discussion and Ms.
S. Kiyota for elemental analysis. We also thank Mr. R. Ito for
the preliminary experiments. A part of this work was supported
by a JSPS Grant-in-Aid for Scientific Research on Innovative
Areas “3D Active-Site Science”: Grant No. 26105003.
1-Cyano-4-[1-methyl-1-(trimethylsilyl)ethyl]benzene. The
1
yield was estimated as 80% by NMR. H NMR (400 MHz, C6D6,
30 °C): δ 1.32 (d, 3H, JHH = 7.4 Hz, CH3), 2.82 (q, 1H, JHH = 7.4 Hz,
CH), 6.50 (d, 2H, JHH = 8.0 Hz, C6H4CN), 6.85 (d, 2H, JHH = 8.0 Hz,
C6H4CN), 7.1−7.2 (m, 9H, m,p-C6H5Si), 7.36 (m, 6H, o-C6H5Si).
1-Trifluoro-4-[1-methyl-1-(trimethylsilyl)ethyl]benzene. The
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1
yield was estimated as 40% by NMR. H NMR (400 MHz, C6D6,
30 °C): δ 1.43 (d, 3H, JHH = 7.4 Hz, CH3), 2.93 (q, 1H, JHH = 7.4 Hz,
CH), 6.74 (d, 2H, JHH = 8.0 Hz, C6H4CF3), 7.1−7.2 (m, 9H, m,p-
C6H5Si), 7.42 (d, 2H, JHH = 8.0 Hz, C6H4 CF3), 7.58 (m, 6H, o-
C6H5Si).
2-(Triphenylsilyl)propanenitrile-d. The yield was estimated as
1
97% by NMR. H NMR (400 MHz, C6D6, 30 °C): δ 1.04 (dm, 2H,
JHH = 6.8 Hz, CH2D), 2.11 (t, 1H, JHH = 6.8 Hz, CH), 7.13 (m, 9H,
m,p-C6H5), 7.57 (m, 6H, o-C6H5). 2H NMR (62 MHz, C6H6, 20 °C):
δ 0.99 (br, 1D, CH2D).
Synthesis of Bis(acrylonitrile)palladium(0) Complex 2a. The
mono(phosphine)palladium(0) complex 1a (73.6 mg, 0.262 mmol)
was placed in a Schlenk tube under nitrogen, and hexane (10 mL) was
added. Then acrylonitrile (86 μL, 1.31 mmol) was added to the
solution, giving a white participate immediately. After the mixture was
stirred for 30 min, the white precipitate was filtered, washed with
hexane, and dried under vacuum. Yield: 55.9 g (0.194 mmol, 74%),
Anal. Calcd for C9H15N2PPd: C, 37.45; H, 5.24; N, 9.71. Found: C,
37.20; H, 4.98; N, 9.68. Data for the major isomer of 2a are as follows.
1H NMR (400 MHz, C6D6, 21 °C): δ 0.84 (d, 9H, JHP = 8.0 Hz,
PMe3), 2.71 (br d, 2H, JHH = 11 Hz, CHHCHCN: trans to CN),
2.90 (br t, 2H, JHH = 11 Hz, CH2CHCN), 3.13 (br d, 2H, JHH = 11
Hz, CHHCHCN: cis to CN). 13C{1H} NMR (101 MHz, C6D6,
20 °C): δ 15.6 (d, PMe3, JCP = 23 Hz), 41.6 (br s, CH2CHCN),
60.4 (br s, CH2CHCN), 120.9 (s, CH2CHCN). 31P{1H} NMR
(162 MHz, C6D6, 21 °C): δ −23.3 (s). Data for the minor isomer of
1
2a are as follows. H NMR (400 MHz, C6D6, 21 °C): δ 0.80 (d, 9H,
E
DOI: 10.1021/om500964g
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
between Homogeneous and Heterogeneous Catalysis (ISHHC-16),
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2
(12) The D NMR of the product in benzene indicated exclusive
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DOI: 10.1021/om500964g
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