Reaction of hydrosilanes with alkynes catalyzed by gold nanoparticles supported on TiO2

Article abstract of DOI:10.1016/j.tet.2012.08.021

Gold nanoparticles supported on TiO₂ (0.8-1.4 mol %) catalyze the β-(E) regioselective hydrosilylation of a variety of functionalized terminal alkynes with alkylhydrosilanes in 1,2-dichloroethane (70 °C). The product yields are excellent, and the reaction times relatively short, while almost equimolar amounts of alkynes and hydrosilanes can be used. Minor side-products in up to 35% relative yield of cis-oxidative (dehydrogenative) disilylation, an unprecedented reaction pathway, are formed in the cases of the less hindered hydrosilanes and alkynes. Triethoxysilane reacts faster and affords apart from β-(E) addition products, minor α-hydrosilylation regio-isomers in upto 15% relative yield. Internal alkynes are generally less reactive or even unreactive. It is proposed that cationic Au(I) species stabilized by the support are the reactive catalytic sites, forming in the presence of hydrosilanes either silyl-Au(III)-H (hydrosilylation pathway) or Au(III)-disilyl species (dehydrogenative disilylation pathway). Regarding the mechanism of hydrosilylation, kinetic experiments are in agreement with silyl carbometallation of the triple bond in the rate determining step of the reaction.

Full text of DOI:10.1016/j.tet.2012.08.021

Tetrahedron 68 (2012) 8724e8731
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Reaction of hydrosilanes with alkynes catalyzed by gold nanoparticles supported
on TiO2
,
Androniki Psyllaki a, Ioannis N. Lykakis b, Manolis Stratakis a
*
a Department of Chemistry, University of Crete, Voutes, 71003 Iraklion, Greece
b Department of Chemistry, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 5 April 2012
Received in revised form 16 July 2012
Accepted 7 August 2012
Available online 14 August 2012
Gold nanoparticles supported on TiO2 (0.8e1.4 mol %) catalyze the b-(E) regioselective hydrosilylation of
a variety of functionalized terminal alkynes with alkylhydrosilanes in 1,2-dichloroethane (70 ꢀC). The
product yields are excellent, and the reaction times relatively short, while almost equimolar amounts of
alkynes and hydrosilanes can be used. Minor side-products in up to 35% relative yield of cis-oxidative
(dehydrogenative) disilylation, an unprecedented reaction pathway, are formed in the cases of the less
hindered hydrosilanes and alkynes. Triethoxysilane reacts faster and affords apart from
b-(E) addition
Keywords:
Hydrosilylation
Alkynes
Gold nanoparticles
Dehydrogenative disilylation
Heterogeneous catalysis
products, minor -hydrosilylation regio-isomers in upto 15% relative yield. Internal alkynes are generally
a
less reactive or even unreactive. It is proposed that cationic Au(I) species stabilized by the support are the
reactive catalytic sites, forming in the presence of hydrosilanes either silyleAu(III)eH (hydrosilylation
pathway) or Au(III)edisilyl species (dehydrogenative disilylation pathway). Regarding the mechanism of
hydrosilylation, kinetic experiments are in agreement with silyl carbometallation of the triple bond in
the rate determining step of the reaction.
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
The selective synthesis of vinyl silanes via hydrosilylation of
alkynes plays a crucial role in organic synthesis due to the signifi-
cance of such key-intermediates in a wide range of synthetic ap-
plications. Alkyne hydrosilylation is catalyzed by a variety of
cationic metals, including Pt, Pd, Rh, Ru, Ti, Co, Y, Ir, Ni as well as
organoelanthanide, and actinide complexes.1 Furthermore, alkyne
hydrosilylation can be promoted via free radicals.2 Generally, ter-
minal alkynes are more reactive substrates as compared to their
internal counterparts, although a remarkable progress has been
recently achieved.3 Terminal alkynes may provide three possible
regioisomeric adducts (Scheme 1) depending on the topology of
Scheme 1. Possible regio-isomeric products from the hydrosilylation of terminal
alkynes.
Although numerous metal-catalyzed hydrosilylation method-
ologies exist, surprisingly, no homogeneous Au(I)-catalyzed pro-
tocol is known. Based on a typical transition metal-catalyzed
hydrosilylation mechanism that involves oxidative insertion of
addition, the a-silyl, and the two diastereomeric b-(Z) and b-(E)
products. The observed selectivity depends on the nature of the
catalyst, the substitution of the alkyne and/or hydrosilane, the
solvent, and the reaction conditions. To account for the differences
in product selectivity, two main mechanisms have been proposed,
the ChalkeHarrod,4 mainly for the cases of Pt, Co, Ni, and Pd-
the metal into the
s
SieH bond, gold in the oxidation state of þ1
could reasonably be expected as an active catalyst, operating
through a Au(I)/Au(III) catalytic cycle. On the other hand, gold
nanoparticles have recently been recognized as active heteroge-
neous hydrosilylation catalysts, however, few reports appear in the
literature and the scope and limitations of this reaction has not
been studied. Caporusso and co-workers6 reported in 2005 the
solvent-free hydrosilylation of a single substrate (1-hexyne) using
as catalysts acetone-solvated gold nanoparticles supported on
catalyzed additions, which lead to
treeeOjima5 for Rh, Ru, Ir, Y, and Ti, that provide selectively or
unselectively the thermodynamically unfavorable -(Z) adducts.
b-(E) isomers, and the Crab-
b
carbon and
found, while the selectivity was close to 100% in favor of the
isomers. The same group extended their studies focusing again on
g
-alumina, at 70 ꢀC. Moderate to excellent yields were
-(E)
b
* Corresponding author. Fax: þ30 2810545001; e-mail address: stratakis@
chemistry.uoc.gr (M. Stratakis).
0040-4020/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2012.08.021

A. Psyllaki et al. / Tetrahedron 68 (2012) 8724e8731
8725
the hydrosilylation of 1-hexyne.7 A screening of the size of gold
nanoparticles obtained from gold vapor and acetone via the metal
vapor synthesis technique, and deposited on a variety of different
supports (C, Al2O3, Fe3O4, CeO2, TiO2, and ZrO2), was achieved. The
Table 1
Hydrosilylation/oxidative cis-disilylation of terminal alkynes catalyzed by Au/TiO2
best results were obtained in the presence of Au/g-Al2O3. In all
experiments, a 4/1 ratio of alkyne/silane was used. Corma and co-
workers reported8 that Au nanoparticles supported on CeO2 (5%
mol) catalyze the hydrosilylation of phenylacetylene in high yield
b
-(E)
Disilylation
Silane
Time/Yielda
and b
-(E) selectivity (70 ꢀC). The molar ratio of phenylacetylene to
1a (89%)
1c (90%)
1b (11%)
1d (10%)
Et3SiH
PhMe2SiH
3 h/83%
3 h/86%
the hydrosilanes was 3/1. Unfortunately, these studies were limited
to a single substrate (phenylacetylene). Surprisingly, a homoge-
neous Au(III)-based catalyst used in the same studies was active,
2a (90%)
3a (92%)
4a
2b (10%)
3b (8%)
d
Et3SiH
Et3SiH
Et3SiH
3 h/84%
2 h/82%
3 h/95%
and afforded unselectively a mixture of b-(E) and b-(Z) adducts.
Organ and Shore9 reported that thin gold film on the surface of
glass (boronsilicate) capillaries are active catalysts for the fast
hydrosilylation of terminal alkynes in a continuous-flow reactor
while being heated under microwave irradiation. In all experi-
ments, the molar ratio of alkyne to silane was 2/1. Regarding
product selectivity, the
b-(E) products were always predominating,
with -(Z) and -isomers being formed as side-products. The
b
a
temperature reached on the gold film inside the microwave appa-
ratus during the continuous-flow experiments was w185e195 ꢀC.
Following our interest in the use of the readily available gold
nanoparticles supported on titania (Au/TiO2)10 as a powerful cata-
lyst for the selective isomerization of epoxides into allyl alcohols,11
cycloisomerization/oxidative dimerization of aryl propargyl
ethers,12 cycloisomerization of 1,6-enynes,13 and in the oxidative
cycloaddition of 1,1,3,3-tetramethyldisiloxane to alkynes,14 we fo-
cus in this manuscript on a detailed examination (scope and limi-
tations) of the Au/TiO2-catalyzed alkyne hydrosilylation. As it has
been noted above, so far the few alkyne hydrosilylation studies
involving catalysis by supported gold nanoparticles have been
limited to two specific substrates (1-hexyne and phenylacetylene),
with rather poor molecular economy as alkynes have been used in
3e4 M excess relative to the silanes.
5a (95%)
5b (4%)
Et3SiH
3 h/74%
6a (95%)
6c (88%)
6b (5%)
6d (12%)
Et3SiH
PhMe2SiH
2 h/91%
3 h/86%
7a
8a
d
d
Ph3SiHb
Ph3SiHb
12 h/85%
6 h/84%
9a (65%)
9c
9b (35%)
d
PhMe2SiH
Ph3SiHb
2 h/81%
12 h/78%
2. Results and discussion
We were pleased to find that by using almost equimolar
amounts of terminal alkynes and hydrosilanes and around
0.5e1.0 mol % catalyst loading, the hydrosilylation reactions go to
completion within 2e4 h at reflux in 1,2-dichloethane (DCE) as
solvent, under an inert atmosphere and strictly dry conditions. The
gold nanoparticles can be easily recovered at the end of the reaction
and reused with little deterioration of their activity. Since any
moisture present into the reaction system hydrolyzes the hydro-
silanes into the corresponding silanols and eventually their de-
hydration products 1,3-disiloxanes, we finally used 1.5e2
equivalents of silanes in all experiments to compensate their partial
competitive hydrolysis, as for simplicity the reactions were carried
out under open air conditions and the solvent was not exhaustively
dried prior to use. The hydrolytic dehydrogenative oxidation of
hydrosilanes into silanols/1,3-disiloxanes was independently found
in our hands to be catalyzed by Au/TiO2 under ambient conditions.
Several analogous heterogeneous catalytic examples have recently
appeared in the literature using hydroxyapatite-supported gold
nanoparticles,15 a nanoporous gold material,16 and a carbon nano-
tubeegold nanohybrid.17 Additionally, the reaction is purely het-
erogeneous in nature. ICP analysis revealed that the gold content in
the supernatant reaction solution was below parts per million level,
as shown in previous work from our group.12
10a (82%)
11a (87%)
10b (82%)
11b (13%)
PhMe2SiH
Et3SiH
3 h/83%
3 h/84%
a
Isolated overall yields after column chromatography.
1.4 mol % of catalyst was used.
b
terminal alkynes forming
b-(E) isomers.
a
-Isomers were formed in
-(Z)
some cases, however, always in <4% relative yield, while
b
isomers were not detected at all. The less hindered triethylsilane
and dimethylphenylsilane react faster (2e4 h) compared to the
bulky triphenylsilane, which requires up 12 h to drive the reactions
to completion. Worth mentioning are the reactions of propargyl
aryl ethers 1e4 in the presence of hydrosilanes that solely provide
hydrosilylation products, relative to their cyclization pathway into
2H-chromenes12 in the absence of silanes. Furthermore, no com-
petitive hydrosilylation was seen on the double bond of 1,6-enyne
11. To establish the selective reactivity of a triple bond relative to
a double CeC bond, we tested the hydrosilylation of styrene with
Et3SiH. Under prolonged heating at reflux (8 h), however, traces of
hydrosilylation products were seen.18
The examples from the hydrosilylation of a series of terminal
alkynes using a variety of alkyl-substituted hydrosilanes (trie-
thylsilane, dimethylphenylsilane, triphenylsilane) are presented in
Table 1. Our findings in brief reveal that Au/TiO2 is an excellent
catalyst for the regioselective cis-hydrosilylation of functionalized
To our surprise, in the reactions of triethylsilane and more
profoundly for dimethylphenylsilane, minor products resulting
from a syn-oxidative disilylation pathway were detected in up to
35% relative yield. Their amount depends on the steric

8726
A. Psyllaki et al. / Tetrahedron 68 (2012) 8724e8731
Table 2
requirements of silane and alkyne. We were able to isolate in two
cases such di-adducts (9b, 10b) in pure form by very careful column
chromatography and elucidate their stereochemistry by means of
NOE experiments. The relative yield of cis-disilanes is nearly in-
dependent of the concentration of the reacting silane (0.5e4
equivalents). In addition, di-adducts do not derive from an oxida-
tive silylation of mono-hydrosilylated products, but rather oxida-
tive cis-disilylation is competing with the hydrosilylation pathway.
Thus, pure alkenylsilanes are unreactive against hydrosilanes when
heating at reflux in the presence of Au/TiO2. For all other di-
adducts, being formed in minor amounts, purification was ex-
tremely difficult, however, were cleanly seen in the 1H NMR spec-
trum of the crude mixtures having a characteristic singlet olefinic
absorption in the region of 6.0e7.0 ppm, and by GCeMS. Triphe-
nylsilane did not provide any di-silylation products, apparently due
to steric reasons. To the best of our knowledge, this is the first ex-
ample in the literature that cis-disilyl products are formed via
double a oxidative addition of mono-hydrosilanes into an alkyne,
and is relevant to the Au/TiO2-catalyzed oxidative cycloaddition of
1,1,3,3-tetramethyldisiloxane to alkynes recently reported14 by our
group. Alternatively, cis-disilylation is known19 via the Pt or Pd-
catalyzed addition of 1,2-disilanes to alkynes, while to the best of
our knowledge there is one relevant example in the
diethyl(bipyridyl)nickel(II)-catalyzed addition of hydrosilanes to
internal alkynes, which provides competing pathways of hydro-
silylation and dehydrogenative cis-disilylation.20 This example is
limited, however, to activated hydrosilanes bearing at least two
chlorine substituents.
Hydrosilylation of terminal alkynes catalyzed by Au/TiO2 in the presence of
(EtO)3SiH
b
-(E)
a
-
Time/Yielda
2 h/91%
6e (90%)
13a (85%)
7b (90%)
6f (10%)
13b (15%)
7c (10%)
1 h/92%
2 h/92%
14a (86%)
8b (100%)
14b (14%)
1.5 h/75%
2 h/94%
d
a
Isolated yields of combined
b
-(E)þ
a-hydrosilylation products.
Internal alkynes (diphenylacetylene, 3-hexyne or 1-phenyl-1-
propyne) are unreactive even after prolonged heating at reflux.
The selective reactivity of terminal versus internal alkynes was
clearly shown in the hydrosilylation of diyne 12, which provides in
the presence of triethylsilane the addition product 12a (accompa-
nied by minor cis-disilylated 12b) in high yield without the internal
triple bond being affected (Scheme 2).
(stereochemistry of adducts proved by NOE experiments) in 95%
isolated yield (Scheme 3). Commenting on the case of 15, analogous
selectivity was reported in the homogeneous Pt(II)-catalyzed
hydrosilylation of internal aryl alkynes.22 The high reactivity of
internal alkyne 16 could be attributed to the highly polar nature of
its triple bond. Alami and co-workers23 have invoked triple bond
polarization arguments to rationalize the regiochemistry in the Pd-
catalyzed hydrostannylation of diaryl alkynes. On the other hand,
the absence of regioselectivity in the hydrosilylation of 16 is sur-
prising, taken into account the highly polar nature of its triple bond.
An explanation is provided in the mechanistic analysis below. For
comparison, the Ru and Pd-catalyzed hydrosilylation of 1624 and
structurally similar compounds yield selectively one regioisomer,
analogous to 16a.
Scheme 2. Selective hydrosilylation of the terminal versus an internal triple bond in
diyne 12.
We next focused on the use of triethoxysilane as a hydro-
silylation reagent (Table 2). The vinyl silyloxy hydrosilylation
products from alkynes and this specific silane are very useful in-
termediates for Pd-catalyzed cross coupling reactions21 with aryl or
vinyl halides. It was found that (EtO)3SiH (1.5e2 equiv) reacts
smoothly at 70 ꢀC with a variety of terminal alkynes affording
primarily products of the
b-(E) hydrosilylation pathway. However,
in contrast to trialkylsilanes, (EtO)3SiH additionally provides
a
-
isomers as side-products in up to 15% relative yield. Generally,
(EtO)3SiH reacts faster as compared to Et3SiH, and the reactions go
to completion within 0.5e2 h at reflux in DCE. While symmetrical
internal alkynes are either completely unreactive (3-hexyne), or
react extremely extremely slowly (diphenylacetylene yields
a hydrosilylation product in merely 8% relative yield after heating at
reflux for 72 h based on GCeMS analysis), hex-1-yn-1-ylbenzene
(15) and ethyl but-2-ynoate (16) were smoothly hydrosilylated,
with 15 forming the single regioisomer 15a (proof of structure by
NOE experiments) in 77% isolated yield (10 h, 70 ꢀC), while 16
provided after 30 min an equimolar mixture of 16a and 16b
Scheme 3. Hydrosilylation of some internal alkynes with (EtO)3SiH.

A. Psyllaki et al. / Tetrahedron 68 (2012) 8724e8731
8727
To draw mechanistic conclusions, a kinetic study in the com-
petitive hydrosilylation of some aryl acetylenes with triethylsilane
was performed. It was found that electron withdrawing sub-
stituents on the aryl ring accelerate the reaction rate relative to
electron donating substituents. The competitions were carried out
upon reacting an equimolar mixture of the competing acetylenes
with a limited amount of hydrosilane, at approximately 10e20%
conversion. Then the crude reaction mixture was analyzed by GC
and 1H NMR spectroscopy. For example, p-fluorophenylacetylene
(13) reacts 2.5 faster as compared to the parent phenylacetylene (6).
Furthermore, phenylacetylene reacts two times faster upon com-
peting with p-tolylacetylene (7), and 13 six times faster than the
methoxy-substituted 5. These results indicate the development of
a partial negative charge on the benzylic position of aryl acetylenes
in the transition state of the rate determining step of the reaction.
An analogous kinetic profile had been observed in the RuCl2(PPh3)3
catalyzed hydrosilylation of aryl acetylenes with HSiCl2Me.25
As supported gold nanoparticles on metal oxide surfaces contain
apart from Au0 oxidized Au species,26 we chose, based on the
preceding discussion in the introduction section of this article, AuI
as the most reasonable active catalytic sites of Au/TiO2 for hydro-
silylation.27 The AuIeAuIII redox catalytic cycles required for our
proposed mechanism shown in Scheme 4 are well documented in
hydride intermediate I and a molecule of hydrosilane (Scheme 4),
or by the dehydrogenative direct coupling of two hydrosilane
molecules with Au(I). Since there is no significant dependence on
the ratio of hydrosilylation/oxidative disilylation with the variation
of hydrosilane concentration (alkyne/hydrosilane ratio ranging
from 2/1 to 1/3), we tend to propose that the second option
(dehydrogenative direct coupling of two hydrosilane molecules
with Au) is more likely to occur. The first option (dehydrogenative
reaction among metal-hydride I and a molecule of hydrosilane)
should lead to an increase in the relative ratio of disilylation with
increasing hydrosilane concentration. The existence of metal disilyl
species of type IV is well documented by the reaction of 1,2-
disilanes19 with Pd or Pt, and hydrosilanes with Pt,31 while re-
cently a relevant specific example was presented32 in the in-
termolecular oxidative insertion of a Au(I) salt into a SieSi bond.
Additionally, Kumada has proposed20 in the Ni(II)-catalyzed
dehydrogenative disilylation of alkynes, an analogous disilylnickel
intermediate. The possibility that gold(0), as proposed in the cat-
alytic diboration of alkenes,33 are the catalytic sites cannot be ex-
cluded, however, it is rather unlikely in our opinion, as a stepwise
disilylation should not be expected to provide one geometrical
disilyl isomer.
the literature.28 Thus, oxidative insertion of AuI into the
s SieH
3. Conclusions
bond29 of the hydrosilane will generate an AuIIIehydride30 in-
termediate species I. Subsequently, I adds to the triple bond
through a silylmetallation path forming intermediate II via transi-
tion state TS1. The hydrometallation pathway (classical
ChalkeHarrod mechanism) to form III via TS2 is unlike. The reason
is that in TS1 a negative charge is developing on the more
substituted carbon of the alkyne, in agreement with the kinetic
profile of the hydrosilylation of aryl acetylenes presented above. On
the other hand, in TS2 a partial positive charge should develop at
the same position. The unselective reaction of 16, more likely im-
plies the participation of the two competing mechanisms (hydro-
metallation and silylmetallation). Formation of the oxidative
disilylation side-products might involve a gold(III)edisilyl species
IV, formed either by the dehydrogenative reaction among metal-
In conclusion, we have shown that Au/TiO2 (0.8e1.4 mol %) is
a highly efficient catalyst for the hydrosilylation of a wide variety of
functionalized alkynes forming primarily b-(E) addition products.
Terminal alkynes are significantly more reactive when compared to
internal alkynes. An unprecedented dehydrogenative minor cis-
oxidative disilylation pathway was uncovered for the cases of the
less hindered hydrosilanes and alkynes. In the Au/TiO2-catalyzed
hydrosilylation protocol there is no need to add the alkyne into
excess relative to the hydrosilane, since over-reaction with the
addition products (alkenylsilanes) is not observed. Our proposed
hydrosilylation mechanism requires a Au(I)eAu(III) redox catalytic
cycle, with a silylmetallation pathway predominating. The current
work extends the utility of a readily available catalyst (Au/TiO2)
toward new applications in organic chemistry.
4. Experimental section
4.1. General
The reactions were monitored by thin-layer chromatography
(TLC) carried out on silica gel plates (60F-254) with UV light as the
visualizing method and an acidic mixture of phosphomolybdic
acid/cerium(IV) sulfate accompanied by heating of the plate as
a developing system. Flash column chromatography was carried
out on SiO2 (silica gel 60, particle size 0.040e0.063 mm) with the
specified eluent. NMR spectra were recorded on a Bruker DPX-300
instrument. Electrospray ionization (ESI) mass spectrometry (MS)
experiments were performed with a GCeMS QP 5050 Shimadzu
single-quadrupole mass spectrometer. GC analyses and kinetics
were performed by using a Shimadzu GC-17A model equipped with
a 60 m HP-5 capillary column.
4.2. Synthesis of substrates
Alkynes 5e10, and 13e18 are commercially available. Aryl
propargyl ethers 1e4 were prepared in yields ranging from 89 to
95% by alkylation of the corresponding phenols as described in
a previous publication from our group.12 Enyne 1113 and diyne 1234
were prepared in 74% and 72% overall yield, respectively, by double
alkylation of dimethyl malonate (prenyl bromide, and propargyl
Scheme 4. Proposed mechanism for the Au/TiO2-catalyzed terminal alkyne
hydrosilylation.

8728
A. Psyllaki et al. / Tetrahedron 68 (2012) 8724e8731
bromide for 11, and 1-bromo-2-butyne, and propargyl bromide for
12), as described in the literature.
7.3, 3.3; MS (EI): 278 (33%), 249 (MþꢁEt, 33%), 209 (37%), 181
(100%), 153 (98%), 147 (53%), 123 (55%), 115 (57%), 97 (35%), 87
(98%), 77 (18%), 69 (47%), 59 (88%); %); HRMS: MþHþ, found
279.1778. C16H26O2SiþH, requires 279.1780.
4.3. Typical procedure for the Au/TiO2-catalyzed hydro-
silylation reaction
4.4.6. (Z)-(3-(4-Methoxyphenoxy)prop-1-ene-1,2-diyl)bis(-
triethylsilane) (2b). This compound was formed as a side-product
to 2a in 10% relative yield, and could not be separated from 2a as
they have similar Rf values. 1H NMR (300 MHz, CDCl3) characteristic
absoprtions: 6.77 (s, 1H), 4.50 (d, J¼1.5 Hz, 2H), 2.75 (s, 3H); MS
(EI): 392 (Mþ, 2%), 363 (MþꢁEt, 4%), 238 (34%), 209 (27%), 181
(23%), 153 (24%), 115 (83%), 87 (100%), 59 (88%).
To a vial containing phenylacetylene, 6 (67
mL, 0.6 mmol),
dimethylphenylsilane (0.155 mL,1.0 mmol), and 1,2-dichloroethane
(2 mL) were added Au/TiO2 (95 mg, 1 wt % in Au, w0.005 mmol).
The reaction was heated to 70 ꢀC for 2 h, and then the slurry was
filtered with the aid of dichloromethane (3 mL) through a short pad
of silica gel. The filtrate was evaporated under vacuum and the
residue was chromatographed with hexane as eluent to afford
a mixture containing 6c and 6d (135 mg, 86% yield) in a relative
ratio of 88/12.
4.4.7. (E)-Triethyl(3-(4-fluorophenoxy)prop-1-enyl)silane
(3a). Colorless oil. Rf (hexane/ethyl acetate¼10/1) 0.69; IR (neat,
cmꢁ1): 2952, 2909, 2874, 2359, 1504, 1456, 1369, 1294, 1198,
1096, 1070, 1015, 825, 804, 742, 717; 1H NMR (300 MHz, CDCl3):
6.98e6.92 (m, 2H), 6.88e6.82 (m, 2H), 6.21 (dt, J1¼19.0 Hz,
J2¼4.5 Hz, 1H), 5.98 (dt, J1¼19.0 Hz, J2¼1.5 Hz, 1H), 4.53 (dd,
J1¼4.5 Hz, J2¼1.5 Hz, 2H), 0.94 (t, J¼8.0 Hz, 9H), 0.60 (q, J¼8.0 Hz,
6H); 13C NMR (75 MHz, CDCl3): 156.9 (d, JCeF¼237.0 Hz), 154.8,
141.7, 129.3, 115.8 (d, JCeF¼2.0 Hz), 115.6 (d, JCeF¼17.0 Hz), 71.4,
7.3, 3.3; MS (EI): 266 (8%), 237 (MþꢁEt, 36%), 197 (46%), 169
(68%), 141 (46%), 115 (42%), 97 (35%), 87 (67%), 69 (44%), 59
(100%); HRMS: MþHþ, found 267.1575. C15H23FOSiþH, requires
267.1580.
4.4. Spectroscopic data of hydrosilylation products
4.4.1. (E)-Triethyl(3-phenoxyprop-1-enyl)silane35 (1a). Colorless oil.
Rf (hexane/ethyl acetate¼4/1) 0.71; 1H NMR (300 MHz, CDCl3):
7.30e7.25 (m, 2H), 6.97e6.90 (m, 3H), 6.24 (dt, J1¼19.0 Hz,
J2¼4.5 Hz, 1H), 5.98 (dt, J1¼19.0 Hz, J2¼1.5 Hz, 1H), 4.58 (dd,
J1¼4.5 Hz, J2¼1.5 Hz, 2H), 0.94 (t, J¼8.0 Hz, 9H), 0.68 (q, J¼8.0 Hz,
6H); 13C NMR (75 MHz, CDCl3): 158.6, 142.0, 129.4, 129.0, 120.7,
114.8, 70.8, 7.3, 3.3; MS (EI): 248 (9%), 219 (MþꢁEt, 56%), 179 (38%),
151 (100%), 123 (61%), 87 (58%), 69 (34%), 59 (67%); HRMS: MþHþ,
found 249.1671. C15H24OSiþH, requires 249.1674.
4.4.8. (Z)-(3-(4-Fluorophenoxy)prop-1-ene-1,2-diyl)bis(-
triethylsilane) (3b). This compound was formed as a side-product
to 3a in 8% relative yield, and could not be separated from 3a as
they have similar Rf values. 1H NMR (300 MHz, CDCl3) characteristic
absoprtions: 6.89 (s, 1H), 4.52 (br s, 2H); MS (EI): 351 (MþꢁEt, 17%),
269 (13%), 226 (16%), 169 (25%), 125 (27%), 115 (100%), 87 (96%), 59
(90%).
4.4.2. (Z)-(3-Phenoxyprop-1-ene-1,2-diyl)bis(triethylsilane)
(1b). This compound was formed as a side-product to 1a in 11%
relative yield, and could not be separated from 1a as they have
similar Rf values. 1H NMR (300 MHz, CDCl3) characteristic
absoprtions: 7.27e7.22 (m, 2H), 6.86e6.70 (m, 3H), 6.67 (s, 1H),
4.62 (br s, 2H), 0.90e0.97 (m, 18H), 0.65e0.71 (m, 12H); MS (EI):
333 (MþꢁEt, 17%), 179 (33%), 151 (29%), 115 (100%), 87 (91%), 59
(86%).
4.4.9. (E)-Triethyl(3-(4-methoxyphenoxy)-3-methylbut-1-enyl)silane
(4a). Colorless oil. Rf (hexane/ethyl acetate¼6/1) 0.48; IR (neat,
cmꢁ1): 2951, 2909, 2873, 1503, 1463, 1378, 1231, 1211, 1173, 1122,
1039, 996, 892, 842, 791, 773, 717; 1H NMR (300 MHz, CDCl3): 6.89
(d, J¼9.0 Hz, 2H), 6.74 (d, J¼9.0 Hz, 2H), 6.29 (d, J¼19.0 Hz, 1H), 5.67
(d, J¼19.0 Hz, 1H), 3.76 (s, 3H), 1.38 (s, 6H), 0.92 (t, J¼8.0 Hz, 9H),
0.59 (q, J¼8.0 Hz, 6H); 13C NMR (75 MHz, CDCl3): 155.1, 152.9, 149.4,
124.3, 123.5, 113.7, 80.5, 55.5, 26.7, 7.3, 3.4; MS (EI): 306 (Mþ, 1%),
182 (5%), 153 (62%), 140 (20%), 125 (100%), 109 (47%), 97 (62%), 81
(33%), 59 (46%); HRMS: MþHþ, found 307.2104. C18H30O2SiþH,
requires 307.2093.
4.4.3. (E)-Dimethyl(3-phenoxyprop-1-enyl)(phenyl)silane
(1c). Colorless oil. Rf (hexane/ethyl acetate¼10/1) 0.62; IR (neat,
cmꢁ1): 2954, 2358, 1598, 1494, 1426, 1367, 1301, 1240, 1153, 1111,
1030, 1015, 986, 784, 751, 729, 690; 1H NMR (300 MHz, CDCl3):
7.53e7.50 (m, 2H), 7.35e7.25 (m, 5H), 6.95e6.89 (m, 3H), 6.29 (dt,
J1¼19.0 Hz, J2¼4.0 Hz, 1H), 6.19 (dt, J1¼19.0 Hz, J2¼1.0 Hz, 1H), 4.59
(dd, J1¼4.0 Hz, J2¼1.0 Hz, 2H), 0.37 (s, 6H); 13C NMR (75 MHz,
CDCl3): 158.6, 142.4, 138.2, 133.8, 130.3, 129.4, 129.0, 127.8, 120.8,
114.8, 70.4, ꢁ2.7; MS (EI): 268 (6%), 253 (MþꢁMe, 13%), 213 (12%),
190 (6%), 175 (17%), 159 (14%), 151 (100%), 135 (68%), 121 (25%), 105
(17%), 91 (11%), 77(8%), 59 (67%); HRMS: MþHþ, found 269.1354.
C17H20OSiþH, requires 269.1361.
4.4.10. (E)-Triethyl(2-methoxystyryl)silane36 (5a). Colorless oil. Rf
(hexane) 0.31; 1H NMR (300 MHz, CDCl3): 7.55 (d, J¼7.5 Hz, 1H),
7.30 (d, J¼19.5 Hz, 1H), 7.23 (t, J¼7.5 Hz, 1H), 6.94 (t, J¼7.5 Hz, 1H),
6.87 (d, J¼7.5 Hz, 1H), 6.39 (d, J¼19.5 Hz, 1H), 3.85 (s, 3H), 0.99 (t,
J¼8.0 Hz, 9H), 0.68 (q, J¼8.0 Hz, 6H); 13C NMR (75 MHz, CDCl3):
156.4, 139.0, 128.9, 126.2, 126.0, 120.6, 120.0, 111.0, 55.5, 7.4, 3.6; MS
(EI): 248 (7%), 219 (MþꢁEt, 78%), 175 (100%), 147 (42%), 135 (8%), 59
(27%); HRMS: MþHþ, found 249.1687. C15H24OSiþH, requires,
249.1685.
4.4.4. (Z)-(3-Phenoxyprop-1-ene-1,2-diyl)bis(dimethyl(phenyl)si-
lane) (1d). This compound was formed as a side-product to 1c in
10% relative yield, and could not be separated from 1c as they have
similar Rf values. 1H NMR (300 MHz, CDCl3) characteristic absopr-
tions: 6.99 (s, 1H), 4.56 (d, J¼1.5 Hz, 2H), 0.33 (s, 6H), 0.21 (s, 6H);
MS (EI): 402 (Mþ, 1%), 387 (MþꢁMe, 3%), 309 (9%), 213 (18%), 159
(15%), 135 (100%).
4.4.11. (Z)-(1-(2-Methoxyphenyl)ethene-1,2-diyl)bis(triethylsilane)
(5b). This compound was formed as a side-product to 5a in w4%
relative yield, and was identified by GCeMS. MS (EI): 333 (MþꢁEt,
100%), 289 (9%), 233 (16%), 204 (22%), 176 (16%), 115 (42%), 87 (74%),
59 (65%).
4.4.5. (E)-Triethyl(3-(4-methoxyphenoxy)prop-1-enyl)silane
(2a). Colorless oil. Rf (hexane/ethyl acetate¼10/1) 0.60; IR (neat,
cmꢁ1): 2951, 2908, 2873, 2359, 1505, 1456, 1225, 1106, 1072, 1039,
1015, 822, 794, 717; 1H NMR (300 MHz, CDCl3): 6.85 (d, J¼7.0 Hz,
2H), 6.82 (d, J¼7.0 Hz, 2H), 6.22 (dt, J1¼19.0 Hz, J2¼4.5 Hz, 1H), 5.98
(dt, J1¼19.0 Hz, J2¼1.5 Hz, 1H), 4.52 (dd, J1¼4.5 Hz, J2¼1.5 Hz, 2H),
3.77 (s, 3H), 0.94 (t, J¼8.0 Hz, 9H), 0.59 (q, J¼8.0 Hz, 6H); 13C NMR
(75 MHz, CDCl3): 153.8, 152.9, 142.3, 128.8, 115.8, 114.5, 71.6, 55.7,
4.4.12. (E)-Triethyl(styryl)silane9 (6a). Colorless oil. Rf (hexane/
ethyl acetate¼10/1) 0.72; 1H NMR (300 MHz, CDCl3): 7.48 (d,
J¼7.0 Hz, 2H), 7.36 (t, J¼7.0 Hz, 2H), 7.27 (t, J¼7.0 Hz, 1H), 6.95 (d,

A. Psyllaki et al. / Tetrahedron 68 (2012) 8724e8731
8729
J¼19.0 Hz, 1H), 6.46 (d, J¼19.0 Hz, 1H), 1.03 (t, J¼8.0 Hz, 9H), 0.70 (q,
J¼8.0 Hz, 6H); 13C NMR (75 MHz, CDCl3): 144.8, 138.2, 128.5, 127.9,
126.3, 125.9, 7.4, 3.5; MS (EI): 218 (18%), 189 (MþꢁEt, 100%), 161
(89%), 131 (68%), 105 (38%), 59 (88%); HRMS: MþHþ, found
219.1564. C14H22SiþH, requires, 219.1569.
(32%), 160 (22%), 135 (100%); HRMS: MþHþ, found 367.2281.
C23H34Si2þH, requires, 367.2277.
4.4.20. (E)-Hept-1-enyltriphenylsilane39 (9c). Colorless oil. Rf (hex-
ane/ethyl acetate¼4/1) 0.58; 1H NMR (300 MHz, CDCl3): 7.66 (dd,
J1¼1.5 Hz, J2¼7.5 Hz, 6H), 7.53e7.44 (m, 9H), 6.36e6.27 (m, 2H),
2.37e2.33 (m, 2H), 1.59e1.54 (m, 2H), 1.45e1.40 (m, 4H), 1.01 (t,
J¼6.5 Hz, 3H); 13C NMR (75 MHz, CDCl3): 153.8, 136.1, 135.6, 130.2,
128.0, 123.3, 37.1, 31.6, 28.3, 22.6, 14.2; MS (EI): 356 (10%), 285
(94%), 207 (45%), 183 (100%), 146 (20%), 105 (78%), 78 (50%); HRMS:
MþHþ, found 357.2033. C25H28SiþH, requires, 357.2038.
4.4.13. (Z)-(1-Phenylethene-1,2-diyl)bis(triethylsilane)
(6b). This
compound was formed as a side-product to 6a in 5% relative yield,
and was identified by GCeMS, and by a characteristic absorption of
the olefinic hydrogen atom in the 1H NMR spectrum of the crude
reaction mixture at 7.01 ppm. MS (EI): 332 (1%), 303 (MþꢁEt, 36%),
163 (61%), 115 (53%), 87 (83%), 59 (100%).
4.4.21. (E)-(2-Cyclopropylvinyl)dimethyl(phenyl)silane40
(10a). Colorless oil. Rf (hexane/ethyl acetate¼10/1) 0.71; 1H NMR
(300 MHz, CDCl3): 7.57e7.52 (m, 2H), 7.38e7.33 (m, 3H), 5.84 (d,
J¼18.5 Hz, 1H), 5.57 (dd, J1¼18.5 Hz, J2¼8.5 Hz, 1H), 1.56e1.49 (m,
1H), 0.81e0.76 (m, 2H), 0.51e0.46 (m, 2H), 0.33 (s, 6H); 13C NMR
(75 MHz, CDCl3): 152.7, 139.3, 133.8, 128.8, 127.7, 124.1, 17.6, 7.4,
ꢁ2.4; MS (EI): 187 (MþꢁMe, 55%), 174 (90%), 159 (94%), 145 (59%),
135 (78%); HRMS: MþHþ, found 203.1252. C13H18SiþH, requires,
203.1256.
4.4.14. (E)-Dimethyl(phenyl)(styryl)silane9 (6c). Colorless oil. Rf
(hexane/ethyl acetate¼10/1) 0.68; 1H NMR (300 MHz, CDCl3):
7.73e7.69 (m, 2H), 7.55 (d, J¼7.5 Hz, 2H), 7.48e7.32 (m, 6H), 7.06 (d,
J¼19.0 Hz, 1H), 6.70 (d, J¼19.0 Hz, 1H), 0.55 (s, 6H); 13C NMR
(75 MHz, CDCl3): 145.4, 134.5, 134.0, 133.1, 129.1, 128.6, 128.3, 128.0,
127.2, 126.6, -2.4. MS (EI): 238 (33%), 223 (MþꢁMe, 55%), 145 (49%),
105 (38%), 91 (54%), 77 (58%), 58 (100%).
4.4.15. (Z)-(1-Phenylethene-1,2-diyl)bis(triethylsilane)
(6d). This
compound was formed as a side-product to 6c in 12% relative yield,
and could not be separated from 6c as they have identical Rf values.
1H NMR (300 MHz, CDCl3) characteristic absorptions: 6.91 (s, 1H),
0.35 (s, 6H), 0.33 (s, 6H); MS (EI): 357 (MþꢁMe, 8%), 294 (4%), 236
(21%), 135 (100%).
4.4.22. (Z)-(1-Cyclopropylethene-1,2-diyl)bis(dimethyl(phenyl)si-
lane) (10b). Colorless oil. Rf (hexane/ethyl acetate¼10/1) 0.66; IR
(neat, cmꢁ1): 3067, 2998, 2954, 2897, 2359, 2342, 1427, 1247, 1109,
1047, 1018, 807, 767, 726, 696; 1H NMR (300 MHz, CDCl3): 7.44e7.41
(m, 4H), 7.36e7.26 (m, 6H), 6.36 (s, 1H), 1.62e1.57 (m, 1H),
0.66e0.61 (m, 2H), 0.54e0.51 (m, 2H), 0.32 (s, 6H), 0.19 (s, 6H); 13C
NMR (75 MHz, CDCl3): 162.1, 143.2, 140.4, 136.8, 134.2, 133.9, 128.8,
128.7, 127.6, 127.6, 22.0, 7.6, ꢁ0.1, ꢁ0.5; MS (EI): 336 (Mþ, 1%), 321
(MþꢁMe, 1%), 197 (6%), 186 (18%), 158 (9%), 135 (100%); HRMS:
MþHþ, found 337.1807. C21H28Si2þH, requires, 337.1803.
4.4.16. (E)-(4-Methylstyryl)triphenylsilane37 (7a). White solid. Rf
(hexane/ethyl acetate¼10/1) 0.64; 1H NMR (300 MHz, CDCl3): 7.65
(d, J¼7.0 Hz, 6H), 7.52e7.40 (m, 9H), 7.23 (d, J¼8.0 Hz, 1H), 7.18 (d,
J¼8.0 Hz, 1H), 7.06 (d, J¼19.0 Hz, 1H), 6.97 (d, J¼19.0 Hz, 1H), 2.41 (s,
3H); 13C NMR (75 MHz, CDCl3): 148.9, 138.6, 136.1, 135.7, 134.7,
129.6, 129.3, 128.0, 126.8, 121.5, 21.3; MS (EI): 376 (27%), 298 (58%),
284 (29%), 221 (38%), 207 (15%), 196 (57%), 181 (100%), 155 (15%),
105 (52%), 77 (10%); HRMS: MþHþ, found 377.1721. C27H24SiþH,
requires, 377.1725.
4.4.23. (E)-Dimethyl 2-(3-methylbut-2-enyl)-2-(3-(triethylsilyl)allyl)
malonate (11a). Colorless oil. Rf (hexane/ethyl acetate¼4/1) 0.59; IR
(neat, cmꢁ1): 2952, 2912, 2874, 2359, 2342, 1735, 1456, 1435, 1288,
1231, 1194, 1169, 1071, 1013, 770, 719, 669; 1H NMR (300 MHz,
CDCl3): 5.85 (dt, J1¼19.0 Hz, J2¼7.0 Hz, 1H), 5.65 (d, J¼19.0 Hz, 1H),
4.95 (t, J¼7.5 Hz, 1H), 3.69 (s, 6H), 2.68 (d, J¼7.5 Hz, 2H), 2.60 (d,
J¼7.5 Hz, 2H), 1.70 (s, 3H), 1.60 (s, 3H), 0.91 (t, J¼8.0 Hz, 9H), 0.53 (q,
J¼8.0 Hz, 6H); 13C NMR (75 MHz, CDCl3): 171.6, 141.6, 135.6, 131.8,
117.6, 58.0, 52.2, 40.1, 31.2, 26.0, 17.9, 7.3, 3.4; MS (EI): 354 (Mþ, 1%),
325 (MþꢁEt, 28%), 257 (12%), 225 (79%), 199 (18%), 167 (20%), 135
(14%),117 (58%), 89 (57%), 69 (100%), 59 (48%); HRMS: MþHþ, found
355.2301. C19H34O4SiþH, requires, 355.2304.
4.4.17. (E)-2-Methyl-4-(triphenylsilyl)but-3-en-2-ol3 8
(8a). Colorless oil. Rf (hexane/ethyl acetate¼10/1) 0.22; 1H NMR
(300 MHz, CDCl3): 7.53e7.49 (m, 6H), 7.43e7.34 (m, 9H), 6.39 (d,
J¼19.0 Hz, 1H), 6.29 (d, J¼19.0 Hz, 1H), 1.34 (s, 6H); 13C NMR
(75 MHz, CDCl3): 159.0, 135.9, 134.5, 129.5, 127.9, 118.6, 72.4, 29.4;
MS (EI): 326 (MþꢁH2O, 28%), 248 (100%), 199 (92%), 181 (84%), 155
(19%), 129 (17%), 105 (74%), 79 (10%), 53 (16%); HRMS: MþHþ, found
345.1682. C23H24OSiþH, requires, 345.1675.
4.4.24. (Z)-Dimethyl 2-(2,3-bis(triethylsilyl)allyl)-2-(3-methylbut-2-
en-1-yl)malonate (11b). This compound was formed as a side-
product to 11a in 13% relative yield, and could not be separated
from 11a as they have identical Rf values. Yet, it was clearly iden-
tified by GCeMS, and in the 1H NMR spectrum of the crude reaction
mixture. 1H NMR (300 MHz, CDCl3) characteristic absoprtions: 6.16
(s, 1H), 4.93 (t, J¼7.5 Hz, 1H), 3.67 (s, 3H), 2.87 (s, 2H), 2.73 (m, 2H),
2.68 (d, J¼7.5 Hz, 2H), 1.66 (s, 3H), 1.55 (s, 3H), 0.77e0.60 (m, 12H);
MS (EI): 468 (Mþ, 1%), 439 (MþꢁEt, 36%), 225 (49%), 115 (45%), 87
(100%), 59 (88%).
4.4.18. (E)-Hept-1-enyl(dimethyl)phenylsilane39 (9a). Colorless oil.
Rf (hexane/ethyl acetate¼10/1) 0.58; 1H NMR (300 MHz, CDCl3):
7.57e7.53 (m, 2H), 7.39e7.35 (m, 3H), 6.15 (dt, J1¼6.0 Hz,
J2¼18.5 Hz, 1H), 5.78 (dd, J1¼18.5 Hz, J2¼1.5 Hz, 1H), 2.20e2.13 (m,
2H), 1.46e1.37 (m, 2H), 1.33e1.26 (m, 4H), 0.92 (t, J¼6.5 Hz, 3H),
0.34 (s, 6H); 13C NMR (75 MHz, CDCl3): 149.5, 139.4, 133.8, 128.8,
127.7, 127.1, 36.8, 31.5, 28.3, 22.5, 14.1, ꢁ2.4; MS (EI): 232 (7%), 217
(MþꢁMe, 75%),175 (8%),161 (58%),135 (49%),121 (100%),105 (27%),
59 (36%).
4.4.19. (Z)-Hept-1-ene-1,2-diylbis(dimethylphenylsilane)
(9b). Colorless oil. Rf (hexane/ethyl acetate¼10/1) 0.52; IR (neat,
cmꢁ1): 2956, 2925, 2856, 2359, 2341, 1616, 1427, 1246, 1112, 990,
817, 782, 727, 696; 1H NMR (300 MHz, CDCl3): 7.49e7.45 (m, 4H),
7.41e7.28 (m, 6H), 6.63 (s, 1H), 2.28 (t, J¼7.5 Hz, 2H), 1.43e1.38 (m,
2H), 1.32e1.22 (m, 4H), 0.89 (t, J¼7.5 Hz, 3H), 0.29 (s, 6H), 0.20 (s,
6H); 13C NMR (75 MHz, CDCl3): 162.1, 143.2, 140.4, 139.6, 134.2,
133.9, 128.8, 128.6, 127.6 (2C), 44.1, 31.7, 30.0, 22.5, 14.1, ꢁ0.2, ꢁ0.4;
MS (EI): 366 (Mþ, 1%), 351 (MþꢁMe, 6%), 310 (22%), 231 (28%), 197
4.4.25. (E)-Dimethyl
2-(but-2-ynyl)-2-(3-(triethylsilyl)allyl)malo-
nate (12a). Colorless oil. Rf (hexane/ethyl acetate¼4/1) 0.58; IR
(neat, cmꢁ1): 2951, 2908, 2873, 2341, 1608, 1509, 1457, 1415, 1236,
1196, 1178, 1010, 986, 825, 790, 778, 753, 714; 1H NMR (300 MHz,
CDCl3): 5.85 (dt, J1¼19.0 Hz, J2¼6.5 Hz, 1H), 5.73 (d, J¼19.0 Hz, 1H),
3.72 (s, 6H) 2.84 (d, J¼6.5 Hz, 2H), 2.74 (q, J¼2.5 Hz, 2H), 1.76 (t,
J¼2.5 Hz, 3H), 0.92 (t, J¼7.5 Hz, 9H), 0.53 (q, J¼7.5 Hz, 6H); 13C NMR
(75 MHz, CDCl3): 170.5, 141.0, 132.6, 78.8, 73.4, 57.4, 52.5, 39.9, 23.2,
7.3, 3.5, 3.4; MS (EI): 338 (Mþ, 1%), 309 (MþꢁEt, 40%), 249 (45%),

8730
A. Psyllaki et al. / Tetrahedron 68 (2012) 8724e8731
221 (7%), 161 (10%), 133, (44%), 117 (74%), 105 (35%), 89 (100%), 75
(26%), 59 (96%); HRMS: MþHþ, found 339.1988. C18H30O4SiþH,
requires, 339.1991.
(Mþ, 13%), 265 (77%), 236 (98%), 207 (37%), 190 (70%),163 (80%),145
(43%), 118 (100%), 89 (84%), 79 (37%), 63 (37%).
4.4.33. (E)-Triethoxy(3-ethynylstyryl)silane (14a). Colorless oil. Rf
(hexane/ethyl acetate¼4/1) 0.61; IR (neat, cmꢁ1): 3294, 2973, 2925,
2885, 1608, 1589, 1571, 1390, 1203, 1165, 1069, 992, 954, 829, 778;
1H NMR (300 MHz, CDCl3): 7.61 (s, 1H), 7.47e7.40 (m, 2H), 7.29 (d,
J¼7.5 Hz, 1H), 7.16 (d, J¼19.0 Hz,1H), 6.20 (d, J¼19.0 Hz, 1H), 3.89 (q,
J¼7.0 Hz, 6H), 3.08 (s, 1H), 1.27 (t, J¼7.0 Hz, 9H); 13C NMR (75 MHz,
CDCl3): 147.9, 137.8, 132.1, 130.4, 128.5, 127.1, 122.4, 119.2, 83.3, 77.3,
58.6,18.3; MS (EI): 290 (Mþ, 8%), 276 (7%), 244 (23%), 202 (29%),126
(60%), 79 (57%), 45 (100%); HRMS: MþHþ, found 291.1412.
C16H22O3SiþH, requires, 291.1416.
4.4.26. (Z)-Dimethyl 2-(2,3-bis(triethylsilyl)allyl)-2-(but-2-yn-1-yl)
malonate (12b). This compound was formed as a side-product to
12a in 8% relative yield, and could not be separated from 12a as they
have almost identical Rf values. Yet, it was clearly identified by
GCeMS, and in the 1H NMR spectrum of the crude reaction mixture.
1H NMR (300 MHz, CDCl3) characteristic absoprtions: 6.19 (s, 1H),
3.71 (s, 3H), 3.00 (s, 2H), 2.82 (q, J¼2.5 Hz, 2H), 1.75 (t, J¼2.5 Hz),
0.72e0.58 (m, 12H); MS (EI): 423 (MþꢁEt, 18%), 393 (6%), 247 (13%),
117 (36%), 87 (100%), 59 (89%).
4.4.27. (E)-Triethoxy(styryl)silane36 (6e). Colorless oil. Rf (hexane/
ethyl acetate¼4/1) 0.63; 1H NMR (300 MHz, CDCl3): 7.48 (d,
J¼7.5 Hz, 2H), 7.38e7.29 (m, 3H), 7.23 (d, J¼19.0 Hz, 1H), 6.19 (d,
J¼19.0 Hz, 1H), 3.90 (q, J¼7.0 Hz, 6H), 1.28 (t, J¼7.0 Hz, 9H); 13C NMR
(75 MHz, CDCl3): 149.1, 137.6, 128.7, 128.5, 126.8, 117.7, 58.6, 18.3;
MS (EI): 266 (Mþ, 6%), 251 (MþꢁMe, 24%), 222 (29%), 193 (27%), 176
(55%), 149 (68%), 147 (100%).
4.4.34. Triethoxy(1-(3-ethynylphenyl)vinyl)silane (14b). This com-
pound was formed as a side-product to 14a in 14% relative yield,
and could not be separated from 14a as they have almost identical
Rf values. 1H NMR (300 MHz, CDCl3) characteristic absoprtions: 6.13
(d, J¼2.5 Hz, 1H), 5.98 (d, J¼2.5 Hz, 1H), 3.85 (q, J¼7.0 Hz, 6H), 3.06
(s, 1H), 1.21 (t, J¼7.0 Hz, 9H); MS (EI): 290 (Mþ, 7%), 244 (23%), 202
(32%), 156 (30%), 135 (28%), 102 (31%), 79 (57%), 63 (58%).
4.4.28. Triethoxy(1-phenylvinyl)silane36 (6f). This known com-
pound was formed as a side-product to 6e in 10% relative yield,
and could not be separated from 12a as they have almost identical
Rf values. 1H NMR (300 MHz, CDCl3) characteristic absoprtions in
the crude reaction mixture: 6.15 (d, J¼2.5 Hz, 1H), 5.97 (d,
J¼2.5 Hz, 1H), 3.90 (q, J¼7.0 Hz, 6H), 1.27 (t, J¼7.0 Hz, 9H); MS (EI):
266 (Mþ, 3%), 251 (25%), 222 (49%), 207 (8%), 193 (46%), 176 (62%),
149 (81%), 147 (100%), 131 (51%), 119 (32%), 103 (40%), 91 (41%), 79
(74%), 63 (69%).
4.4.35. (E)-2-Methyl-4-(triethoxysilyl)but-3-en-2-ol (8b). Colorless
oil. Rf (hexane/ethyl acetate¼4/1) 0.50; IR (neat, cmꢁ1): 3341, 2973,
2930, 2359, 2341,1621,1426,1362,1221,1021, 960, 905, 835, 806, 785,
761, 714; 1H NMR (300 MHz, CDCl3): 6.53 (d, J¼19.0 Hz, 1H), 5.61 (d,
J¼19.0 Hz,1H), 3.82 (q, J¼7.0 Hz, 6H),1.30 (s, 6H),1.23 (t, J¼7.0Hz, 9H);
13C NMR (75 MHz, CDCl3): 159.4, 114.1, 72.0, 58.5, 29.2, 18.2; HRMS:
MþHþ, found 249.1522. C11H24O4SiþH, requires, 249.1522. MþꢁH2O,
found 231.1410. C11H22O3SiþH, requires, 231.1416.
4.4.36. (E)-Triethoxy(1-phenylhex-1-enyl)silane (15a). Colorless oil.
Rf (hexane/ethyl acetate¼6/1) 0.55; IR (neat, cmꢁ1): 2972, 2925,
2360, 2341, 1490, 1441, 1389,1166, 1100,1073, 954, 777, 719, 699; 1H
NMR (300 MHz, CDCl3): 7.32e7.26 (m, 2H), 7.21e7.13 (m, 3H), 6.37
(t, J¼7.0 Hz, 1H), 3.78 (q, J¼7.0 Hz, 6H), 2.08 (q, J¼7.0 Hz, 2H),
1.42e1.30 (m, 2H), 1.32e1.20 (m, 2H), 1.17 (t, J¼7.0 Hz, 9H), 0.83 (t,
J¼7.0 Hz, 3H); 13C NMR (75 MHz, CDCl3): 147.6, 140.5, 135.2, 128.5,
127.8, 125.7, 58.6, 31.5, 29.5, 22.3, 18.1, 13.9; MS (EI): 322 (Mþ, 19%),
278 (25%), 221 (14%), 163 (100%), 135 (60%), 119 (85%), 79 (42%), 63
(26%); HRMS: MþHþ, found 323.2035. C18H30O3SiþH, requires,
323.2042.
4.4.29. (E)-Triethoxy(4-fluorostyryl)silane (13a). Colorless oil. Rf
(hexane/ethyl acetate¼4/1) 0.56; IR (neat, cmꢁ1): 2974, 2927, 2886,
2359, 2340, 1601, 1507, 1411, 1390, 1294, 1228, 1157, 1070, 992, 954,
830, 795; 1H NMR (300 MHz, CDCl3): 7.47e7.42 (m, 2H), 7.17 (d,
J¼19.0 Hz, 1H), 7.05e6.99 (m, 2H), 6.08 (d, J¼19.0 Hz, 1H), 3.88 (q,
J¼7.0 Hz, 6H),1.27 (t, J¼7.0 Hz, 9H); 13C NMR (75 MHz, CDCl3): 163.0
(d, JCeF¼247.0 Hz), 147.7, 133.9 (d, JCeF¼3.0 Hz), 128.4 (d,
JCeF¼8.0 Hz), 117.5 (d, JCeF¼2.0 Hz), 115.4 (d, JCeF¼21.5 Hz), 58.6,
18.2; MS (EI): 284 (Mþ, 18%), 169 (MþꢁMe, 73%), 240 (75%), 211
(71%), 165 (86%), 147 (73%), 91 (100%); HRMS: MþHþ, found
285.1314. C14H21FO3SiþH, requires, 285.1322.
4.4.37. (E)-Ethyl 3-(triethoxysilyl)but-2-enoate41 (16a). Colorless
oil. Rf (hexane/ethyl acetate¼4/1) 0.41; 1H NMR (300 MHz, CDCl3):
6.31 (q, J¼2.0 Hz, 1H), 4.17 (q, J¼7.0 Hz, 2H), 3.83 (q, J¼7.0 Hz, 6H),
2.21 (d, J¼2.0 Hz, 3H), 1.29 (t, J¼7.0 Hz, 3H), 1.24 (t, J¼7.0 Hz, 9H);
13C NMR (75 MHz, CDCl3): 165.7, 151.2, 130.5, 59.8, 58.8, 18.2, 16.8,
14.3; MS (EI): 231 (MþꢁOEt, 68%), 202 (63%), 187 (100%), 163 (38%),
135 (44%), 79 (83%); HRMS: MþHþ, found 277.1463. C12H24O5SiþH,
requires, 277.1471.
4.4.30. Triethoxy(1-(4-fluorophenyl)vinyl)silane (13b). This known
compound was formed as a side-product to 13a in 15% relative
yield, and could not be separated from 13a as they have almost
identical Rf values. 1H NMR (300 MHz, CDCl3) characteristic
absoprtions: 6.10 (d, J¼2.5 Hz, 1H), 5.94 (d, J¼2.5 Hz, 1H), 3.86 (m,
6H), 1.20 (t, J¼7.0 Hz, 9H); MS (EI): 284 (Mþ, 15%), 269 (73%), 240
(74%), 211 (68%), 194 (35%), 165 (87%), 147 (73%), 118 (67%), 91
(100%), 79 (65%), 63 (58%).
4.4.38. (E)-Ethyl 2-(triethoxysilyl)but-2-enoate41 (16b). Colorless
oil. Rf (hexane/ethyl acetate¼4/1) 0.35; 1H NMR (300 MHz, CDCl3):
6.80 (q, J¼7.0 Hz, 1H), 4.21 (q, J¼7.0 Hz, 2H), 3.84 (q, J¼7.0 Hz, 6H),
2.05 (d, J¼7.0 Hz, 3H),1.31 (t, J¼7.0 Hz, 3H),1.22 (t, J¼7.0 Hz, 9H); 13C
NMR (75 MHz, CDCl3): 168.9, 154.4, 128.7, 60.1, 58.8, 18.1, 17.6, 14.3;
MS (EI): 231 (MþꢁOEt, 100%), 202 (31%), 187 (15%), 158 (44%), 119
(24%), 79 (47%); HRMS: MþHþ, found 277.1463. C12H24O5SiþH,
requires, 277.1471.
4.4.31. (E)-Triethoxy(4-methylstyryl)silane36 (7b). Colorless oil. Rf
(hexane/ethyl acetate¼4/1) 0.63; 1H NMR (300 MHz, CDCl3): 7.37
(d, J¼8.0 Hz, 2H), 7.19 (d, J¼19.0 Hz, 1H), 7.15 (d, J¼8.0 Hz, 2H), 6.11
(d, J¼19.0 Hz, 1H), 3.89 (q, J¼7.0 Hz, 6H), 2.35 (s, 3H), 1.27 (t,
J¼7.0 Hz, 9H); 13C NMR (75 MHz, CDCl3): 149.0, 138.7, 135.0, 129.2,
126.7, 116.3, 53.6, 21.2, 18.2; MS (EI): 280 (Mþ, 30%), 265 (MþꢁMe,
84%), 236 (100%), 190 (76%), 118 (98%).
4.4.32. (E)-Triethoxy(2-methoxystyryl)silane36 (7c). This known
compound was formed as a side-product to 7b in 10% relative yield,
and could not be separated from 7b as they have almost identical Rf
values. 1H NMR (300 MHz, CDCl3) characteristic absorptions: 6.13
(d, J¼2.5 Hz, 1H), 5.93 (d, J¼2.5 Hz, 1H), 2.33 (s, 3H); MS (EI): 280
Acknowledgements
We thank ProFI and Dr. Rabalakos for obtaining the HRMS
spectra, and professor N. Chaniotakis for assistance in recording the
FT-IR spectra.

A. Psyllaki et al. / Tetrahedron 68 (2012) 8724e8731
8731
21. (a) Denmark, S. E.; Liu, J. H.-C. Angew. Chem., Int. Ed. 2010, 49, 2978e2986; (b)
Nakao, Y.; Hiyama, T. Chem. Soc. Rev. 2011, 40, 4893e4901.
22. Hamze, A.; Provot, O.; Alami, M.; Brion, J.-D. Org. Lett. 2005, 7, 5625e5628.
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27. It is also possible that a partially positively charged multiatomic gold catalytic
center (cluster) may be invoked in the mechanism. Recently it was shown,
based on theoretical calculations, that the endothermic oxidative insertion of
Au(I) to the C-I bond of iodobenzene may become energetically favorable upon
considering a model Au38 nanoparticle, for which the developing positive
charge is almost equally distributed among all gold atoms: Corma, A.; Juarez, R.;
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Supplementary data
Copies of 1H and 13C NMR spectra of all compounds, as well as,
copies of MS spectra of key compounds. Supplementary data re-
lated to this article can be found at http://dx.doi.org/10.1016/
j.tet.2012.08.021.
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