Gold-film-catalysed hydrosilylation of alkynes by microwave-assisted, continuous-flow organic synthesis (MACOS)

Article abstract of DOI:10.1002/chem.200801610

Thin gold films on the surface of glass capillaries have proven to be highly active catalysts for the rapid hydrosilylation of alkynes that are flowed through the reactor while being heated by microwave irradiation. The films are able to be reused at least five times with no loss of activity and with no detectable levels of gold showing up in the hydrosilylated products.

Full text of DOI:10.1002/chem.200801610

FULL PAPER
DOI: 10.1002/chem.200801610
Gold-Film-Catalysed Hydrosilylation of Alkynes by Microwave-Assisted,
Continuous-Flow Organic Synthesis (MACOS)
Gjergji Shore and Michael G. Organ*[a]
Abstract: Thin gold films on the surface of glass capillaries have proven to be
highly active catalysts for the rapid hydrosilylation of alkynes that are flowed
through the reactor while being heated by microwave irradiation. The films are
able to be reused at least five times with no loss of activity and with no detectable
levels of gold showing up in the hydrosilylated products.
Keywords: catalysis
synthesis · gold · hydrosilylation ·
microwave
·
flow
Introduction
attempted to determine the catalytically active oxidation
state of Au and concluded that AuIII was more active than
AuI and that the most active catalyst in their studies was
“stabilized” AuIII on CeO2. With this in mind, we embarked
on the development of a suitable flow device and MACOS
protocol for the continuous-flow, general hydrosilylation of
alkynes.
Hydrometallation is a very powerful method to stereo- and
regioselectively create organometallic synthetic intermedi-
ates and products. In particular, hydrosilylation of alkynes is
useful for the preparation of: 1) stereodefined halides by
silyl/halide exchange of the corresponding vinylsilane, 2) or-
ganometallic cross-coupling partners, 3) polysiloxane build-
ing blocks, such as chlorosilanes, and 4) carbonyl derivatives
by Tamao oxidation. The most commonly used metal to cat-
alyse hydrosilylation is Pt (e.g., Karstedꢀs catalyst), which is
among the more expensive precious metals. Recently, Au,
which is less than half the price of Pt, has been investigated
for its applicability as a hydrosilylation catalyst. While gen-
erally less reactive than Pt, Au has been applied to the hy-
drosilylation of alkynes, carbonyls and imines.[1,2]
We were interested in developing a continuous hydrosily-
lation process employing microwave-assisted, continuous-
flow organic synthesis (MACOS)[3] and considered a gold
film on the surface of the reaction tube as a potential cata-
lyst for this application.[4] However, while supported gold
nanoparticles have been shown to be active in some prelimi-
nary hydrosilylation studies, metallic gold was observed to
be essentially inactive with the same substrates. Corma and
co-workers showed that AuIII from KAuCl4 was quite reac-
tive in the hydrosilylation of styrene, but reactivity ceased as
the salt decomposed over time to metallic Au.[1,5] They also
Results and Discussion
We began our investigation with the development of a
method to deposit robust gold films on the surface of capil-
laries to withstand the heat and physical wear-and-tear asso-
ciated with MACOS.[6] After some experimentation it was
determined that the most robust and catalytically-active
films resulted from a two-step deposition process.[7] First, a
very fine layer of densely-packed gold particles was deposit-
ed directly on the capillary wall from a diethylene glycol/
AuCl3 solution. A more random-appearing layer of gold-
nanoparticle clusters was then deposited on top of the first
layer from an aqueous sodium citrate solution.
The two layers and their differing morphology are clearly
visible on the SEM image of the resultant Au film
(Figure 1). As the process was being developed to produce
these films, the resultant prototypes were being tested in hy-
drosilylation reactions by using the conditions outlined in
Table 1. By means of this iterative process, it was found that
the first dense layer is necessary for good adhesion of the
film to the glass, which gives the film robustness, and the
top layer is necessary for high catalytic activity of the film
under MACOS conditions. The general hydrosilylation pro-
tocol outlined in Table 1 was tried on a variety of terminal
alkynes and it appears tolerant of many functional groups
[a] G. Shore, Prof. Dr. M. G. Organ
Department of Chemistry, York University
4700 Keele Street, Toronto, ON, M3J 1P3 (Canada)
Fax: ( +1)416-736-5936
E-mail: organ@yorku.ca
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.200801610.
Chem. Eur. J. 2008, 14, 9641 – 9646
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9641

cacious as hydrosilylating agents. Regioselectivity of the hy-
drometallation was high for placement of the silicon moiety
on the terminal carbon of the alkyne. Stereospecificity of
the hydrometallation was lowest when the substituent on
the alkyne was an alkyl chain (entries 1–6), but E selectivity
for the terminal silane product was always greater than 90
percent.
The temperature recorded during these hydosilylation re-
actions by the IR sensor (ꢀ1808C) in the Biotage Initiator
microwave primarily reflects the temperature of the gold
film as toluene is a poor absorber of microwave irradia-
tion.[8] To probe the necessity for microwave irradiation
during these studies, two con-
Figure 1. SEM images of the Au films prepared inside a glass capillary.
a) Image at ”5000 magnification. b) Image at ”60000 magnification
taken at the site of the arrow in panel (a). The arrow denotes a typical
Au nanoparticle cluster against the backdrop of much smaller, densely-
packed Au particles that coat the glass.
trol experiments were conduct-
Table 1. Hydrosilylation of terminal alkynes catalysed by gold-coated capillaries using MACOS.
ed (Table 1, entries 11 and 12).
In these experiments, the same
Au capillaries placed in an oil
bath set to deliver the same
temperature
as
recorded
during the MACOS runs. In
both cases, percentage conver-
sion was significantly curtailed
as these runs produced only
25% of the product that was
obtained with microwave irra-
diation. The reason for this
could be that the true temper-
ature during MACOS is much
higher than that indicated by
the microwaveꢀs IR sensor
and/or there is an electronic
effect that positively promotes
the reaction by the current
that is being generated in the
metal film by the oscillating
microwave field.
To probe the robustness and
reuseability of the gold film,
the reaction in entry 10
(Table 1) was repeated five
separate times by using the
same capillary and the per-
centage conversion in succes-
sion was 52, 91, 75, 80 and
72%. While there appears to
be no significant deviation
from performance in this
study, it has been reported that
gold laid down on the outside
of glass chips “evaporates”
during microwave irradia-
tion.[9] Perhaps the hydrosilyla-
Entry
Alkyne
R=
Silane
Product
4 Z [%]
Conversion [%][a]
(yield [%])[b]
R1SiH=
3 E [%]
5a [%]
ACHTREUNG
1
2
3
4
5
6
7
8
CH3CH2CH2CH2
CH3CH2CH2CH2
HOCH2CH2
HOCH2CH2
ClCH2CH2CH2
ClCH2CH2CH2
Ph
Ph
CH3OCH2
CH3OCH2
CH3OCH2
Et3SiH
Ph3SiH
Et3SiH
Ph3SiH
Et3SiH
Ph3SiH
Et3SiH
Ph3SiH
Et3SiH
Ph3SiH
Et3SiH
Ph3SiH
Et3SiH
Ph3SiH
Et3SiH
Ph3SiH
(a) 82
(b) 80
(c) 84
(d) 85
(e) 75
(f) 93
(g) 92
(h) 90
(i) 96
(j) 98
(i) 98
(j) 98
(k) 90
(l) 98
(m) 93
(n) 97
(o) 81
(p) 98
(q) 97
(r) 97
(s) 100
(t) 96
(u) 100
(v) 100
(w) 74
(x) 76
9
6
6
4
4
3
4
2
4
1
1
1
1
1
1
1
2
1
1
1
0
0
0
0
0
0
9
82 (70)
78 (68)
82 (69)
85 (74)
77 (68)
78 (70)
86 (78)
91 (80)
84 (76)
88 (80)
28 (ND)
20 (ND)
87 (75)
85 (74)
82 (74)
86 (78)
62 (54)
68 (58)
88 (80)
82 (72)
56 (45)
80 (66)
75 (60)
66 (60)
72 (62)
58 (50)
14
10
11
21
4
4
8
0
1
1
1
9
1
6
2
17
1
2
9
10
11[c]
12[d]
13
14
15
16
17
18
19
20
21
22
23
24
25
26
CH3OCH2
HOCH2
HOCH2
NCCH2CH2CH2
NCCH2CH2CH2
CH3CH(OH)
CH3CH(OH)
PhCH2OCH2
PhCH2OCH2
ClCH2CH2CH2
NC CH2CH2CH2
CH3OCH2
Et3SiH
Ph3SiH
Et3SiH
Ph3SiH
2
0
4
0
0
26
24
Ph2SiClH[e]
Ph2SiClH[e]
Ph2SiClH[e]
Ph2SiClH[e]
Ph2SiClH[e]
Ph2SiClH[e]
PhCH2OCH2
3-thiophenyl
TMS-
[a] Percentage conversion was determined by analysis of the NMR spectrum of the reaction mixture effluent
as it exited the capillary. [b] Percentage yield was determined by collecting a known volume of reaction efflu-
ent, removing the solvent in vacuo and purifying the crude product by silica-gel chromatography. [c] Control
experiment: To probe the role of microwave irradiation, the identical reaction to entry 9 was run through an
oil bath at 1928C (i.e., no microwave irradiation was involved at all). [d] Control experiment: To probe the
role of microwave irradiation, the identical reaction to entry 10 was run through an oil bath at 1958C (i.e., no
À
microwave irradiation was involved at all). [e] The silanol corresponding to the silyl chloride (i.e., SiPh2OH)
was isolated following silica-gel chromatography and yields were calculated on this basis. TMS=trimethylsilyl.
including cyano, alcohols, chlorides, aromatics/heteroaro-
matics and ethers. Of note, free alcohols that were remote
from the alkyne (entries 3 and 4) or right next to it (en-
tries 13, 14, 17 and 18) were equally well tolerated. Triethyl-,
triphenyl- and chlorodiphenyl silane all proved equally effi-
tion solution is cooling the film sufficiently to increase its
lifetime and reactivity. Additionally, these product samples
were collected directly from the capillary (crude) and sub-
mitted to inductively coupled plasma mass spectrometry
(ICP-MS). The technique has a lower level of detection
9642
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Chem. Eur. J. 2008, 14, 9641 – 9646

Gold-Film-Catalysed Hydrosilylation of Alkynes
FULL PAPER
General procedure for the hydrosilylation by MACOS: A stock solution
containing the terminal alkyne (2.0 mmol, 2.0 equiv) and hydrosilane
(1.0 mmol, 1.0 equiv) in toluene (0.6–0.7 mL, total mixture volume is
1.0 mL) was prepared. After the continuous-flow microwave system was
primed with toluene, an aliquot (1.0 mL) of the homogenous stock solu-
tion was taken up in a Hamilton gastight syringe and connected to the re-
actor system with the aid of Microtight fittings. The syringe was placed in
a Harvard 22 syringe pump that was set to deliver 20 mLminÀ1 and the
single-mode microwave was programmed to heat constantly; the power
level was controlled manually so as to keep the temperature constant at
the specified levels. The output from the reactor was fed into a sealed
vial that was charged with 75 psi of air to create backpressure in the
system; the eluent was analysed by 1H NMR spectroscopy immediately
after the reaction to obtain chemical conversion. A known volume of the
crude reaction mixture (typically 0.7–0.8 mL) was collected and the prod-
uct purified by silica-gel chromatography. Below, the specific reactions
leading to each product along with spectral characterization of the major
E isomer are detailed (unless indicated otherwise).
(LLD) of d=50 ppm and no gold was detected in the prod-
ucts. The capillaries do, however, darken over time. Given
the continued activity of the film and the apparent lack of
its degradation products in the product stream, it could be
that it is the organic matter in the flow stream that is being
gradually charred and deposited on the surface of this in-
tensely hot metal film.
Conclusion
In summary, we have shown that capillaries coated with
gold films comprised of a dense, regular layer of gold parti-
cles covered by an irregular amorphous one are highly
active for the flow hydrosilylation of terminal alkynes.
These films have shown good reliability and robustness in
our studies, which indicates that they are useful for a contin-
uous process.
(E)-1-(Triethylsilyl)-1-hexene (3a): 1-Hexyne and triethylsilane were re-
acted by following the general hydrosilylation procedure and 800 mL of
the crude reaction mixture were collected. Purification by flash chroma-
tography (pentane) afforded 110.0 mg of
3a (70% yield including minor isomers).
1H NMR (400 MHz, CDCl3): d=6.08 (dt,
J=18.7, 6.3 Hz, 1H), 5.56 (dt, J=18.7,
1.5 Hz, 1H), 2.14–2.21 (m, 2H), 1.32–1.49
Experimental Section
(m, 4H), 0.88–0.96 (m, 12H), 0.60 ppm (q,
Microwave irradiation experiments: All MACOS experiments were per-
formed in 1180 mm borosilicate capillaries, by using a single mode Biot-
age Smith Initiator Synthesizer operating at a frequency of 2.45 GHz
with irradiation power from 0 to 300 W. The capillary was fed reactants
from Hamilton gastight syringes attached to a Harvard 22 syringe pump
preset to the desired flow rate. The system was connected to a sealed col-
lection vial, in which a pressurized air line was attached to create back-
pressure (pressure inside the system reached 75 psi). The temperatures
reported were measured by the IR sensor built into the microwave cham-
ber on the outer surface of capillaries. All reagents and solvents were
purchased from commercial sources and used without additional purifica-
tion. Column chromatography purifications were carried out by using the
flash technique on silica gel 60 (200–400 mesh). 1H NMR spectroscopy
was run by using a Bruker Advance 400 MHz instrument and all spectra
were calibrated to d=7.26 ppm for the signal from the residual proton of
the deuterated chloroform solvent; 13C NMR spectra were calibrated to
the middle carbon signal of the triplet for deuterated chloroform (d=
77.00 ppm).
J=7.9 Hz, 6H); 13C NMR (100 MHz, CDCl3): d=144.8, 125.4, 36.8, 31.0,
22.2, 14.1, 7.5, 3.6 ppm; spectra matched those found in the literature.[10]
(E)-1-(Triphenylsilyl)-1-hexene (3b): 1-Hexyne and triphenylsilane were
reacted by following the general hydrosilylation procedure and 750 mL of
the crude reaction mixture were collect-
ed. Purification by flash chromatography
(5% ethyl acetate in hexane) afforded
174.5 mg of 3b (68% yield including
minor isomers). 1H NMR (400 MHz,
CDCl3): d=7.69–7.78 (m, 6H), 7.45–7.58
(m, 9H), 6.32 (m, 2H), 2.31–2.39 (m, 2H), 1.35–1.59 (m, 5H), 1.05 ppm
(t, J=7.2 Hz, 2H); 13C NMR (100 MHz, CDCl3): d=154.0, 136.3, 135.3,
129.6, 128.0, 123.4, 37.0, 31.0, 22.5, 14.2 ppm; spectra matched those
found in the literature.[11,12]
(E)-1-(Triethylsilyl)-1-buten-4-ol (3c): 3-Butyne-1-ol and triethylsilane
were reacted by following the general hydrosilylation procedure and
580 mL of the crude reaction mixture were collected. Purification by flash
chromatography (20% ethyl acetate in
General procedure for creating the Au film coating inside of 1180 mm
(ID) capillaries: Boronsilicate capillaries (1180 mm ID) were filled with a
0.1 mmolmLÀ1 solution of AuCl3 in diethylene glycol, capped at both
ends and placed inside a muffle furnace; the temperature was gradually
increased to 1808C. After 30 min, capillaries were taken out and rinsed
with acetone.
The second deposition mixture was prepared by mixing a 0.2 mmolmLÀ1
aqueous solution of AuCl3 (0.5 mL) with a 5% aqueous solution of triso-
dium citrate·2H2O (0.5 mL). The monocoated capillaries were filled with
this mixture, capped at both ends and left to develop at RT for another
30 min. After this time, capillaries were calcinated at 4008C before use in
MACOS.
hexane) afforded 72 mg of 3c (69% yield
including
minor
isomers).
1H NMR
(400 MHz, CDCl3): d=6.05 (dt, J=18.7,
6.4 Hz, 1H), 5.72 (dt, J=18.7, 1.3 Hz, 1H),
1.63 (brs, 1H), 0.95 (t, J=8.0 Hz, 9H),
0.59 ppm (q, J=8.0 Hz, 6H); 13C NMR (100 MHz, CDCl3) d 144.1, 130.3,
61.7, 40.5, 7.5, 3.5 ppm; spectra matched those found in the literature.[12]
(E)-1-(Triphenylsilyl)-1-buten-4-ol (3d): 3-Butyne-1-ol and triphenylsi-
lane were reacted by following the general hydrosilylation procedure and
650 mL of the crude reaction mixture were
collected. Purification by flash chromatog-
raphy (25% ethyl acetate in hexane) af-
Synthesis of benzyl propargyl ether: Benzyl alcohol (5.0 g, 46.3 mmol)
and propargyl bromide (13.7 g, 92.6 mmol) were added sequentially to a
solution of KOH (10.4 g, 185 mmol) in dry DMSO (60 mL) at 08C. The
mixture was left stirring at RT for 2 h before being diluted with Et2O
(200 mL) and H2O (100 mL). The organic layer was separated, washed
with H2O (4”50 mL), dried over anhydrous Na2SO4, filtered and concen-
trated in vacuo. Flash chromatography (10% ethyl acetate in hexane) fol-
lowed by distillation (2.5 mmHg, 808C) afforded benzyl propargyl ether
(4.8 g, 71%) as a clear liquid.[8] 1H NMR (400 MHz, CDCl3): d=7.30 (m,
5H), 4.64 (s, 2H), 4.21 (d, J=2.0 Hz, 2H), 2.49 ppm (t, J=2.0 Hz, 1H);
13C NMR (100 MHz, CDCl3): d=137.6, 128.4, 128.1, 127.9, 79.8, 74.5,
71.5, 57.0 ppm.
forded 159 mg of 3d (74% yield including
minor isomers). 1H NMR (400 MHz,
CDCl3): d=7.52–7.67 (m, 6H), 7.36–7.49 (m, 9H), 6.39 (dt, J=18.5,
1.2 Hz, 1H), 6.19 (dt, J=18.5, 6.4 Hz, 1H), 3.75 (t, J=6.3 Hz, 2H), 2.6
(qd, J=6.3, 1.2 Hz, 2H), 1.55 ppm (brs, 1H); 13C NMR (100 MHz,
CDCl3): d=149.6, 136.4, 135.1, 130.2, 128.4, 127.9, 61.9, 40.3 ppm; spectra
matched those found in the literature.[12]
(E)-5-Chloro-1-(triethylsilyl)-1-pentene
(3e): 5-Chloro-1-pentyne and triethylsi-
lane were reacted by following the gener-
al hydrosilylation procedure and 650 mL
Chem. Eur. J. 2008, 14, 9641 – 9646
ꢁ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
9643

M. G. Organ and G. Shore
of the crude reaction mixture were collected. Purification by flash chro-
matography (20% dichloromethane in pentane) afforded 94 mg of 3e
(68% yield including minor isomers). 1H NMR (400 MHz, CDCl3): d=
6.01 (dt, J=18.8, 6.2 Hz, 1H), 5.64 (dt, J=18.8, 1.4 Hz, 1H), 3.63 (t, J=
6.7 Hz, 2H), 2.48 (q, J=6.7 Hz, 2H), 1.98 (q, J=6.7 Hz, 2H), 0.92 (t, J=
8.0 Hz, 9H), 0.58 ppm (q, J=8.0 Hz, 6H); 13C NMR (100 MHz, CDCl3):
d=146.2, 127.9, 44.4, 34.2, 31.7, 7.5, 3.7 ppm; spectra matched those
found in the literature.[13]
(E)-1-(Triethylsilyl)-1-propen-3-ol (3k): Prop-
argyl alcohol and triethylsilane were reacted by
following the general hydrosilylation procedure
and 900 mL of the crude reaction mixture were
collected. Purification by flash chromatography (15% ethyl acetate in
hexane) afforded 115.8 mg of 3k (75% yield including minor isomers).
1H NMR (400 MHz, CDCl3): d=6.16 (dt, J=19.0, 4.1 Hz, 1H), 5.84 (dt,
J=19.0, 1.6 Hz, 1H), 4.14 (dd, J=4.1, 1.6 Hz, 2H), 2.62 (brs, 1H), 0.92
(t, J=8.0 Hz, 9H), 0.56 ppm (q, J=8.0 Hz, 6H); 13C NMR (100 MHz,
CDCl3): d=146.1, 125.7, 65.4, 7.4, 3.5 ppm; spectra matched those found
in the literature.[13]
(E)-5-Chloro-1-(triphenylsilyl)-1-pentene (3 f): 5-Chloro-1-pentyne and
triphenylsilane were reacted by follow-
ing the general hydrosilylation proce-
dure and 750 mL of the crude reaction
mixture were collected. Purification by
flash chromatography (12% dichloro-
(E)-1-(Triphenylsilyl)-1-propen-3-ol (3l): Propargyl alcohol and triphe-
nylsilane were reacted by following the general hydrosilylation procedure
and 750 mL of the crude reaction mixture were
methane in hexane) afforded 189.7 mg
collected. Purification by flash chromatography
of 3 f (70% yield including minor isomers). 1H NMR (400 MHz, CDCl3):
d=7.62–7.68 (m, 6H), 7.46–7.58 (m, 9H), 6.42 (dt, J=18.5, 1.3 Hz, 1H),
6.28 (dt, J=18.5, 6.0 Hz, 1H), 3.66 (t, J=6.7 Hz, 2H), 2.47 (q, J=6.7 Hz,
2H), 2.05 ppm (q, J=6.7 Hz, 2H); 13C NMR (100 MHz, CDCl3): d=
151.1, 136.1, 134.8, 129.7, 128.0, 125.4, 44.6, 34.1, 31.5 ppm; spectra
matched those found in the literature.[12]
(15% EtOAc in hexane) afforded 174.0 mg of
3l (74% yield including minor isomers).
1H NMR (400 MHz, CDCl3): d=7.52–7.58 (m,
6H), 7.38–7.50 (m, 9H), 6.26 (dt, J=18.8, 1.7 Hz, 1H), 5.89 (dt, J=18.8,
3.9 Hz, 1H), 4.48 (dd, J=3.9, 1.7 Hz, 2H), 1.68 ppm (brs, 1H); 13C NMR
(100 MHz, CDCl3): d=150.8, 136.1, 134.5, 129.8, 128.1, 122.7, 65.2 ppm;
spectra matched those found in the literature.[12,15]
(E)-1-(Triethylsilyl)-2-phenylethene (3g): Phenylacetylene and triethylsi-
lane were reacted by following the general hydrosilylation procedure and
620 mL of the crude reaction mixture were
(E)-6-(Triethylsilyl)hex-5-enenitrile (3m): Hex-5-ynenitrile and triethylsi-
lane were reacted by following the general hydrosilylation procedure and
700 mL of the crude reaction mixture
collected. Purification by flash chromatogra-
phy (10% dichloromethane in pentane) af-
were collected. Purification by flash
forded 106.0 mg of 3g (78% yield including
chromatography (10% ethyl acetate in
hexane) afforded 108 mg of 3m in 74%
minor isomers). 1H NMR (400 MHz, CDCl3):
d=7.42–7.47 (m, 2H), 7.30–7.37 (m, 2H),
yield
including
minor
isomers).
7.21–7.27 (m, 1H), 6.88 (d, J=19.5 Hz, 1H), 6.41 (d, J=19.5 Hz, 1H),
0.98 (t, J=8.0 Hz, 9H), 0.68 ppm (q, J=8.0 Hz, 6H); 13C NMR
(100 MHz, CDCl3): d=144.8, 138.5, 128.8, 127.9, 126.5, 125.9, 7.7,
3.8 ppm; spectra matched those found in the literature.[14]
1H NMR (400 MHz, CDCl3): d=5.94
(dt, J=18.7, 6.2 Hz, 1H), 5.64 (dt, J=
18.7, 1.5 Hz, 1H), 2.35 (t, J=7.2 Hz, 2H), 2.26–2.31 (m, 2H), 1.77 (t, J=
7.2 Hz, 2H), 0.92 (t, J=8.0 Hz, 9H), 0.56 ppm (q, J=8.0 Hz, 6H);
13C NMR (100 MHz, CDCl3): d=146.1, 128.8, 119.6, 35.7, 24.6, 16.6, 7.4,
3.5 ppm; spectra matched those found in the literature.[12]
(E)-1-(Triphenylsilyl)-2-phenylethene (3h): Phenylacetylene and triphe-
nylsilane were reacted by following the general hydrosilylation procedure
and 620 mL of the crude reaction mixture
(E)-6-(Triphenylsilyl)hex-5-enenitrile (3n): Hex-5-ynenitrile and triphe-
nylsilane were reacted by following the general hydrosilylation procedure
and 700 mL of the crude reaction mix-
were collected. Purification by flash chroma-
tography (10% dichloromethane in pentane)
afforded 209 mg of 3h (80% yield including
minor isomers). H NMR (400 MHz, CDCl3):
ture were collected. Purification by
flash chromatography (20% ethyl ace-
1
d=7.61–7.68 (m, 6H), 7.28–7.56 (m, 14H),
7.10 ppm (d, J=2.0 Hz, 2H); 13C NMR (100 MHz, CDCl3): d=149.1,
138.1, 136.1, 134.6, 129.8, 128.8, 128.6, 128.1, 127.3, 122.9 ppm; spectra
matched those found in the literature.[12,14]
tate in hexane) afforded 191.0 mg of 3n
(78% yield including minor isomers).
1H NMR (400 MHz, CDCl3): d=7.58–
7.63 (m, 6H), 7.38–7.51 (m, 9H), 6.38 (dt, J=18.5, 1.5 Hz, 1H), 6.18 (dt,
J=18.5, 6.0 Hz, 1H), 2.41–2.46 (m, 2H), 2.37 (t, J=7.3 Hz, 2H),
1.87 ppm (t, J=7.3 Hz, 2H); 13C NMR (100 MHz, CDCl3): d=150.0,
136.0, 134.6, 129.8, 127.9, 126.5, 119.6, 35.5, 24.3, 16.6 ppm; spectra
matched those found in the literature.[12]
(E)-3-Methoxy-1-(triethylsilyl)-1-propene (3i): Propargyl methyl ether
and triethylsilane were reacted by following the general hydrosilylation
procedure and 800 mL of the crude reaction
mixture were collected. Purification by flash
chromatography (15% dichloromethane in
(E)-1-(Triethylsilyl)-1-buten-3-ol (3o): 3-Butyne-2-ol and triethylsilane
were reacted by following the general hydrosilylation procedure and
900 mL of the crude reaction mixture were col-
pentane) afforded 112.6 mg of 3i (76% yield
including minor isomer 4i). 1H NMR
(400 MHz, CDCl3): d=6.09 (dt, J=18.9, 4.9 Hz, 1H), 5.84 (dt, J=18.9,
1.5 Hz, 1H), 3.97 (dd, J=4.9, 1.5 Hz, 2H), 3.34 (s, 3H), 0.93 (t, J=
8.0 Hz, 9H), 0.57 ppm (q, J=8.0 Hz, 6H); 13C NMR (100 MHz, CDCl3):
d=143.4, 128.6, 75.8, 57.9, 7.5, 3.6 ppm; spectra matched those found in
the literature.[12]
lected. Purification by flash chromatography
(15% ethyl acetate in pentane) afforded 90 mg of
3o (54% yield including minor isomers).
1H NMR (400 MHz, CDCl3): d=6.12 (dd, J=
19.0, 5.2 Hz, 1H), 5.74 (dd, J=19.0, 1.5 Hz, 1H),
4.24–4.28 (m, 1H), 2.08 (brs, 1H), 1.24 (d, J=6.6 Hz, 3H), 0.90 (t, J=
8.0 Hz, 9H), 0.55 ppm (q, J=8.0 Hz, 6H); 13C NMR (100 MHz, CDCl3):
d=151.3, 124.2, 70.7, 23.2, 7.4, 3.5 ppm; spectra matched those found in
the literature.[12]
(E)-3-Methoxy-1-(triphenylsilyl)-1-propene (3j): Propargyl methyl ether
and triphenylsilane were reacted by following the general hydrosilylation
procedure and 740 mL of the crude reaction
mixture were collected. Purification by flash
chromatography (14% ethyl acetate in
(E)-1-(Triphenylsilyl)-1-buten-3-ol (3p): 3-Butyne-2-ol and triphenylsi-
lane were reacted by following the general hydrosilylation procedure and
800 mL of the crude reaction mixture were collected. Purification by flash
chromatography (20% ethyl acetate in hexane)
hexane) afforded 195 mg of 3j (80% yield in-
cluding minor isomers). 1H NMR (400 MHz,
CDCl3): d=7.54–7.61 (m, 6H), 7.32–7.46 (m,
9H), 6.58 (dt, J=18.6, 1.4 Hz, 1H), 6.28 (dt, J=18.6, 4.6 Hz, 1H), 4.1
(dd, J=4.6, 1.4 Hz, 2H), 3.45 ppm (s, 3H); 13C NMR (100 MHz, CDCl3):
d=148.1, 136.2, 134.7, 129.7, 128.1, 125.3, 75.2, 58.5 ppm; spectra
matched those found in the literature.[12,15]
afforded 152 mg of 3p (58% yield including
minor isomers). 1H NMR (400 MHz, CDCl3):
d=7.58–7.64 (m, 6H), 7.40–7.53 (m, 9H), 6.52
(dd, J=18.7, 1.4 Hz, 1H), 6.28 (dd, J=18.7,
9644
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Gold-Film-Catalysed Hydrosilylation of Alkynes
FULL PAPER
4.5 Hz, 1H), 4.40–4.44 (m, 1H), 1.72 (d, J=2.6, 1H), 1.32 ppm (d, J=
6.1 Hz, 3H); 13C NMR (100 MHz, CDCl3): d=155.5, 136.1, 134.5, 129.7,
128.1, 121.7, 70.6, 23.2 ppm; spectra matched those found in the litera-
ture.[16]
ed. Purification by flash chromatography (20% ethyl acetate in pentane)
afforded 135.0 mg of 3t (66% yield including minor isomer 5t). H NMR
1
(400 MHz, CDCl3): d=7.59–7.68 (m, 4H), 7.38–7.51 (m, 6H), 6.25 (dt,
J=18.2, 6.0 Hz, 1H), 6.11 (dt, J=18.2, 1.1 Hz, 1H), 2.53 (brs, 1H), 2.32–
2.44 (m, 4H), 1.82 ppm (q, J=7.0 Hz, 2H); 13C NMR (100 MHz, CDCl3):
d=149.7, 135.5, 134.5, 130.1, 127.9, 127.2, 119.5, 35.2, 23.9, 16.5 ppm;
HRMS: m/z: calcd for C18H19NOSi: 293.1236; found: 293.1237.
(E)-3-Methoxy-1-(hydroxydiphenylsilyl)-1-propene
(3u):
Propargyl
methyl ether and chlorodiphenylsilane were reacted by following the
general hydrosilylation procedure and
720 mL of the crude reaction mixture were
collected. Purification by flash chromatog-
raphy (20% ethyl acetate in hexane) af-
(E)-3-Benzyloxy-1-(triethylsilyl)-1-propene (3q): Benzyl propargyl ether
and triethylsilane were reacted by following the general hydrosilylation
procedure and 660 mL of the crude reaction mixture were collected. Pu-
rification by flash chromatography (20% dichloromethane in pentane)
afforded 138.2 mg of 3q (80% yield including minor isomers). 1H NMR
(400 MHz, CDCl3): d=7.36–7.43 (m, 4H), 7.27–7.32 (m, 1H), 6.20 (dt,
J=19.0, 4.9 Hz, 1H), 5.88 (dt, J=19.0, 1.5 Hz, 1H), 4.57 (s, 2H), 4.10
(dd, J=4.9, 1.5 Hz, 2H), 0.99 (t, J=8.0 Hz, 9H), 0.62 ppm (q, J=8.0 Hz,
6H); 13C NMR (100 MHz, CDCl3): d=143.6, 138.4, 128.6, 128.4, 127.8,
127.6, 73.5, 72.3, 7.4, 3.6 ppm; spectra matched those found in the litera-
ture.[17]
forded 124 mg of 3u (60% yield, no other
isomers formed). 1H NMR (400 MHz,
CDCl3): d=7.62–7.66 (m, 4H), 7.38–7.46 (m, 6H), 6.26–6.41 (m, 2H),
4.06 (dd, J=3.0, 1.1 Hz, 2H), 3.39 (s, 3H), 2.49 ppm (brs, 1H); 13C NMR
(100 MHz, CDCl3): d=147.9, 135.4, 134.6, 130.3, 127.9, 125.7, 74.7,
58.3 ppm; elemental analysis calcd (%) for C16H18O2Si: C 71.07, H 6.71;
found,
C 71.10, H 6.55; HRMS: m/z: calcd for C16H18O2Si+NH4:
288.1420; found: 288.1425.
(E)-[(3-Benzyloxy)prop-1-enyl]hydroxydiphenylsilane (3v): Benzyl prop-
argyl ether and chlorodiphenylsilane were reacted by following the gen-
eral hydrosilylation procedure and 780 mL of the crude reaction mixture
were collected. Purification by flash chromatography (20% ethyl acetate
in hexane) afforded 162 mg of 3v (60% yield, no other isomers formed).
1H NMR (400 MHz, CDCl3): d=7.65–7.68 (m, 4H), 7.45–7.48 (m, 2H),
7.37–7.44 (m, 7H), 7.31–7.35 (m, 2H), 6.33–6.45 (m, 2H), 4.58 (s, 2H),
4.15 (dd, J=3.8, 1.1 Hz, 2H), 3.01 ppm (brs, 1H); 13C NMR (100 MHz,
CDCl3): d=145.0, 138.1, 135.4, 134.6, 130.5, 128.4, 127.9, 127.8, 127.6,
125.8, 72.5, 72.3 ppm; HRMS: m/z: calcd for C22H22O2Si+NH4: 364.1733;
found: 364.1747.
(E)-3-Benzyloxy-1-(triphenylsilyl)-1-propene (3r): Benzyl propargyl
ether and triphenylsilane were reacted by following the general hydrosi-
lylation procedure and 650 mL of the crude reaction mixture were collect-
ed. Purification by flash chromatography (15% ethyl acetate in hexane)
afforded 190 mg of 3r (72% yield including minor isomers). 1H NMR
(400 MHz, CDCl3): d=7.62–7.69 (m, 6H), 7.34–7.55 (m, 14H), 6.67 (dt,
J=18.7, 1.4 Hz, 1H), 6.37 (dt, J=18.7, 4.5 Hz, 1H), 4.7 (s, 2H), 4.26 ppm
(dd, J=4.6, 1.4 Hz, 2H); 13C NMR (100 MHz, CDCl3): d=148.3, 138.3,
136.2, 134.5, 129.6, 128.5, 128.1, 128.0, 127.8, 125.3, 72.8, 72.5 ppm; spec-
tra matched those found in the literature.[12]
(E)-Hydroxydiphenyl[2-(thiophen-3-yl)]vinylsilane (3w): 3-Ethynylthio-
phene and chlorodiphenylsilane were reacted by following the general
hydrosilylation procedure and 800 mL of the crude reaction mixture were
collected. Purification by flash chromatog-
raphy (30% dichloromethane in pentane)
afforded 118 mg of 3w (48%, minor
a
isomer 5w reported below). 1H NMR
(400 MHz, CDCl3): d=7.67–7.74 (m, 4H),
7.40–7.47 (m, 6H), 7.34–7.37 (m, 1H),
(E)-5-Chloro-1-(hydroxydiphenylsilyl)-1-pentene (3s): 5-Chloro-pentyne-
1 and chlorodiphenylsilane were reacted by following the general hydro-
silylation procedure and 640 mL of the crude reaction mixture were col-
lected. Purification by flash chromatography (15% ethyl acetate in pen-
tane) afforded 87.0 mg of 3s (45% yield, no other isomers formed).
1H NMR (400 MHz, CDCl3): d=7.62–7.66 (m, 4H), 7.38–7.47 (m, 6H),
6.31 (dt, J=19.2, 6.0 Hz, 1H), 6.09 (dt, J=19.2, 1.1 Hz, 1H), 3.57 (t, J=
6.0 Hz, 2H), 2.40 (q, J=7.0 Hz, 2H), 2.28 (brs, 1H), 1.95 ppm (q, J=
7.0 Hz, 2H); 13C NMR (100 MHz, CDCl3): d=150.9, 135.6, 134.5, 130.1,
127.9, 125.9, 44.4, 33.7, 31.1 ppm; HRMS: m/z: calcd for C17H19OClSi+
H: 303.0972; found: 303.0612.
7.25–7.33 (m, 2H), 7.12 (d, J=19.2 Hz, 1H), 6.55 (d, J=19.2 Hz, 1H),
2.51 ppm (s, 1H); 13C NMR (100 MHz, CDCl3): d=142.3, 141.5, 135.4,
134.7, 130.1, 127.9, 126.1, 124.9, 124.3, 122.8 ppm; HRMS: m/z: calcd for
C18H16OSSi: 308.0689; found: 308.0674; elemental analysis calcd (%) for
C18H16OSSi: C 70.09, H 5.23; found C 69.89, H 5.21.
a-Hydroxydiphenyl[1-(thiophen-3-yl)]vinylsilane
(5w): From the above crude reaction mixture,
34 mg of the minor isomer 5w was isolated (14%
yield). 1H NMR (400 MHz, CD2Cl2): d=7.64–7.70
(m, 4H), 7.39–7.50 (m, 6H), 7.26–7.31 (m, 1H),
7.17–7.35 (m, 2H), 6.36 (d, J=2.1 Hz, 1H), 5.69
(d, J=2.1 Hz, 1H), 2.71 ppm (brs, 1H); 13C NMR
(150 MHz, CD2Cl2): d=142.9, 141.2, 134.9, 134.7, 130.3, 130.1, 127.8,
126.2, 125.3, 121.9 ppm; HRMS: m/z: calcd for C18H16OSSi: 308.0691;
found: 308.0561; elemental analysis calcd (%) for C18H16OSSi: C 70.09,
H 5.23; found: C 69.97, H 5.11.
(E)-5-Cyano-1-(hydroxydiphenylsilyl)-1-pentene (3t): Hex-5-ynenitrile
and chlorodiphenylsilane were reacted by following the general hydrosi-
lylation procedure and 700 mL of the crude reaction mixture were collect-
(E)-1-(Hydroxydiphenylsilyl)-2-(trimethylsilyl)-
ethene (3x): Ethynyltrimethylsilane and chloro-
diphenylsilane were reacted by following the
Chem. Eur. J. 2008, 14, 9641 – 9646
ꢁ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
9645

M. G. Organ and G. Shore
general hydrosilylation procedure and 900 mL of the crude reaction mix-
ture were collected. Purification by flash chromatography (20% ethyl
acetate in pentane) afforded 109 mg of 3x (40% yield, minor a isomer
5x reported below). 1H NMR (400 MHz, CDCl3): d=7.62–7.68 (m, 4H),
7.40–7.49 (m, 6H), 6.89–7.05 (m, 2H), 2.44 (brs, 1H), 0.16 ppm (s, 9H);
13C NMR (100 MHz, CDCl3): d=157.3, 143.9, 135.5, 134.6, 130.0, 127.8,
À1.7 ppm; HRMS: m/z: calcd for C17H22OSi2: 298.1209; found: 298.1205;
elemental analysis calcd (%) for C17H22OSi2: C 68.40, H 7.43; found: C
68.63, H 7.37.
[3] E. Comer, M. G. Organ, J. Am. Chem. Soc. 2005, 127, 8160.
[4] For a vapour-phase Pt-based flow reactor, see: M. Okamoto, H.
Kiya, H. Yamashita, E. Suzuki, Chem. Commun. 2002, 1634.
[5] For another hydrosilylation processes that uses gold particles, see:
A. M. Caporusso, L. A. Aronica, E. Schiavi, E. , G. Martra, G. Vi-
tulli, P. Salvadori, J. Organomet. Chem. 2005, 690, 1063.
[6] G. Shore, S. Morin, M. G. Organ, Angew. Chem. 2006, 118, 2827;
Angew. Chem. Int. Ed. 2006, 45, 2761; G. Shore, S. Morin, D. Mallik,
M. G. Organ, Chem. Eur. J. 2008, 14, 1351; G. Shore, M. G. Organ,
Chem. Commun. 2008, 838.
a-1-(Hydroxydiphenylsilyl)-1-(trimethylsilyl)ethene (5x): From the above
crude reaction mixture, 26 mg of 5x were also obtained (10% yield).
1H NMR (400 MHz, CDCl3): d=7.60–7.65 (m, 4H),
7.38–7.46 (m, 6H), 6.63 (d, J=5.0 Hz, 1H), 6.41 (d,
J=5.0 Hz, 1H), 2.30 (brs, 1H), 0.08 ppm (s, 9H);
13C NMR (100 MHz, CDCl3): d=150.7, 145.3, 135.9,
134.5, 129.8, 127.8, À0.48 ppm; HRMS: m/z: calcd for
C17H22OSi2: 298.1209; found: 298.1222; elemental
analysis calcd (%) for C17H22OSi2: C 68.40, H 7.43;
found: C 68.20, H 7.47.
[7] Boronsilicate capillaries (1180 mm ID) were filled with
a
0.1 mmolmLÀ1 solution of AuCl3 in diethylene glycol, capped at
both ends and placed inside a muffle furnace; the temperature was
gradually increased to 1808C. After 30 min, the capillaries were
taken out and rinsed with acetone. For best results, this procedure
could be repeated two to three more times. Then an aqueous mix-
ture was prepared by mixing a 0.2 mmolmLÀ1 aqueous solution of
AuCl3 (0.5 mL) with a 5% aqueous solution of sodium citrate
(0.5 mL). The capillaries were filled with the mixture, capped at
both ends and left to develop at room temperature for another
30 min. After rinsing with acetone, the capillaries were calcinated at
4008C before use.
Gold analysis: After removing the solvent in vacuo, the sample was accu-
rately weighed, ashed and then digested in Aqua Regia (1:3 nitric acid to
hydrochloric acid). Following digestion, the sample was cooled to RT, di-
luted to a known volume with high purity RO water and then analysed
by ICP-MS by using an HP/Agilent 4500 ICP-MS. The ICP-MS was cali-
brated prior to the sample analysis by using NIST traceable standards for
gold.
[8] We expect that the temperature inside the capillary is actually
higher, perhaps significantly so, than the value read by the IR
sensor in the microwave cavity. Currently, we are unable to record
temperatures inside of the capillary, which would be more accurate.
[9] P. He, S. J. Haswell, P. D. I. Fletcher, Lab Chip 2004, 4, 38.
[10] L. D. Field, A. J. Ward, J. Organomet. Chem. 2003, 681, 91.
[11] T. H. Chan, K. Koumaglo, J. Organomet. Chem. 1985, 285, 109.
[12] H. Aneetha, W. Wu, J. G. Verkade, Organometallics 2005, 24, 2590.
[13] R. Takeuchi, S. Nitta, D. Watanabe, J. Org. Chem. 1995, 60, 3045.
[14] a) J. W. Faller, D. G. D’Alliessi, Organometallics 2002, 21, 1743;
b) L. D. Field, A. J. Ward, J. Organomet. Chem. 2003, 681, 91.
[15] E. Lukevics, R. Ya. Sturkovich, O. A. Pudova, J. Organomet. Chem.
1985, 292, 151.
Acknowledgements
M.G.O. wishes to thank the Natural Sciences and Engineering Research
Council of Canada (NSERC) for operating funds to support this project
(Grant No. CRDPJ 338330–06), and G.S. is grateful to the Ontario Grad-
uate Scholarship (OGS) Program for salary support.
[16] K. Kahle, P. J. Murphy, J. Scott, R. Tamagni, J. Chem. Soc. Perkin
Trans. 1 1997, 997.
[17] W. Wu, C. J. Li, Chem. Commun. 2003, 1668.
[1] A. Corma, C. Gonzꢂlez-Arellano, M. Iglesias, F. Sꢂnchez, Angew.
Chem. 2007, 119, 7966; Angew. Chem. Int. Ed. 2007, 46, 7820.
[2] D. Lantos, M. Contel, S. Sanz, A. Bodor, I. T. Horvath, J. Organo-
met. Chem. 2007, 692, 1799; B. M. Wile, R. MacDonald, M. J. Fergu-
son, M. Stradiotto, Organometallics 2007, 26, 1069.
Received: August 5, 2008
Published online: September 24, 2008
9646
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Chem. Eur. J. 2008, 14, 9641 – 9646