Selective hydrosilylation of 1,3-diynes catalyzed by titania-supported platinum

Article abstract of DOI:10.1021/om201274v

Titania-supported platinum (mainly as Pt(II)) has been found to effectively catalyze the hydrosilylation of 1,3-diynes at 70 °C with low catalyst loading (0.25 mol %) under solvent-free conditions. Monohydrosilylation was achieved for diaryl-substituted d

Full text of DOI:10.1021/om201274v

Article
pubs.acs.org/Organometallics
Selective Hydrosilylation of 1,3-Diynes Catalyzed by Titania-
Supported Platinum
Francisco Alonso,*,† Robison Buitrago,‡ Yanina Moglie,† Antonio Sepulveda-Escribano,*,‡
́
and Miguel Yus†
†
́
́
Departamento de Quımica Organ
́
ica, Facultad de Ciencias, and Instituto de Sıntesis Organ
́
ica (ISO), Universidad de Alicante, Apdo.
99, E-03080 Alicante, Spain
‡
́
́
Departamento de Quımica Inorganica, Facultad de Ciencias, and Instituto Universitario de Materiales (IUMA), Universidad de
Alicante, Apdo. 99, E-03080 Alicante, Spain
S
* Supporting Information
ABSTRACT: Titania-supported platinum (mainly as Pt(II)) has
been found to effectively catalyze the hydrosilylation of 1,3-
diynes at 70 °C with low catalyst loading (0.25 mol %) under
solvent-free conditions. Monohydrosilylation was achieved for
diaryl-substituted diynes, whereas dialkyl-substituted diynes were
transformed into the corresponding dihydrosilylated products in
good yields. In every case, the process was proven to be highly
stereoselective, with syn addition of the silicon−hydrogen bond,
and regioselective, with the silicon moiety exclusively bonded to
the most internal carbon atom of the 1,3-diyne (β-E product), as
confirmed by X-ray crystallography.
limitations.7b In this study, the standard protocol adopted for
most reactions involved Karstedt’s catalyst in xylene at
temperatures between 125 and 140 °C for 1−3 days. The
combination of three diynes with six hydrosilanes allowed one
to conclude that bis-hydrosilylation adducts could be obtained
INTRODUCTION
■
Vinylsilanes1 are very versatile organosilicon compounds of
great interest in synthetic organic chemistry, with the
transition-metal-catalyzed cross-coupling reaction with vinyl
and aryl halides being one of the major applications of this type
of compound.2 Due to their particular nontoxicity, high
chemical stability, and relatively low molecular weight, these
organometalloids act as attractive alternatives to other organo-
metallic reagents (e.g., organotin, organoboron, or organozinc
counterparts). Vinylsilanes are most conveniently and straight-
forwardly prepared by the hydrosilylation of alkynes, a reaction
which proceeds with 100% atom efficiency.3 The control of the
regio- and stereochemistry of the process is, however, a
frequent difficulty encountered in the transition-metal-catalyzed
addition of heteroatom−hydrogen bonds across the carbon−
carbon triple bond,4 and in hydrosilylation in particular.5 In
general, the final outcome of the reaction will depend on the
catalyst, the alkyne, and the silane employed.
in high yields if the steric constraints were not too high.
Owing to our dedication to studying and understanding the
reactivity of active metals and nanoparticles,9 we reported the
hydrogen-transfer reduction of ketones catalyzed by highly
reusable platinum nanoparticles on carbon.10 More recently, we
demonstrated that platinum on titania catalyzed the hydro-
silylation of terminal and internal alkynes, bearing aryl and alkyl
as well as different functional groups, with three different
hydrosilanes to give the corresponding alkenylsilanes in high
yields and short reaction times (Scheme 1).11 Reactions were
performed in the absence of solvent, with exclusive syn addition
of the Si−H bond and a β/α regioselectivity of up to 94/6. In
contrast to previously reported heterogeneous platinum
catalysts, reactions proceeded in air, even at room temperature,
and the catalyst could be easily recovered and reused in several
cycles. As part of our research on organic reactions promoted
by platinum nanoparticles, we wish to present herein the results
attained on the selective mono- and dihydrosilylation of 1,3-
diynes catalyzed by Pt/TiO2 under solvent-free conditions.
Although the hydrosilylation of monoynes has been
extensively studied,3,5,6 research on the hydrosilylation of
diynes with monohydrosilanes is scanty.7 Some studies have
been devoted to the hydrosilylation of 1,3-diynes with bis-
hydrosilanes directed to the formation of polymers, in which
silane functionalities cross-link the chains7a or are alternating
with two α-vinylidene moieties.7b The rhodium- and nickel-
catalyzed hydrosilylation of 1,3-diynes aimed at the asymmetric
synthesis of allenes has been described by Tillack et al.8 To the
best of our knowledge, there is only one article which deals in
detail with the mono- and dihydrosilylation of 1,3-diynes, run
as model reactions to determine any steric or electronic
Received: December 23, 2011
Published: March 6, 2012
© 2012 American Chemical Society
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to apply a reaction temperature of 70 °C with the catalyst
consisting of calcined platinum on titania in all cases.
Scheme 1. Hydrosilylation of Terminal Alkynes Catalyzed by
Pt/TiO2
Characterization of the Calcined Pt/TiO2 Catalyst.
Figure 1 shows two TEM micrographs obtained for the fresh
calcined Pt/TiO2 catalyst. Very small (1−2 nm) platinum
clusters (darker spots) with a narrow size distribution can be
seen homogenously dispersed on the surface of the TiO2
crystals. The XPS spectrum in the Pt 4f region for this catalyst
is shown in Figure 2. It can be deconvoluted into four peaks,
two of them (those placed at lower binding energies)
corresponding to the Pt 4f7/2 level and the others to the Pt
4f5/2 level. The peaks arising from the Pt 4f7/2 level are centered
at 71.6−71.8 and 73.5−73.7 eV, which can be assigned to
oxidized platinum species. An accurate assignment of the peaks
is not easy, as the binding energies of the core electrons are
affected not only by the metal oxidation state but also by the
ligand atoms to which they are coordinated. The binding
energy of the Pt 4f7/2 level for Pt(IV) coordinated to six
chlorine atoms (as in the H2PtCl6 precursor compound) is
reported to be 75.3 eV (for K2PtCl6), but it decreases to 74.8
eV for PtO2 and to 74.2 eV for Pt(OH)4. Additionally, the Pt
4f7/2 level for PtCl2 is about 73.4 eV, whereas that for Pt(OH)2
is about 72.4 eV.13 Thus, the XPS analysis of the catalyst reveals
that it contains two different kinds of Pt(II) species, although
the presence of some remaining Pt(IV) cannot be discarded.14
This indicates, on one side, that reductive decomposition of the
metal precursor has taken place upon impregnation, by which
the parent Pt(IV) is reduced to Pt(II). On the other hand, this
surface decomposition is accompanied by both total (XPS band
at around 71.7 eV) and partial (band centered at around 73.6
eV) dechlorination. This is confirmed by the data in Table 2,
where it can be seen that the surface atomic Cl/Pt ratio in the
fresh catalyst is 1.24, much lower than the value corresponding
to the starting metal precursor.
RESULTS AND DISCUSSION
■
Screening of the Catalysts. The platinum catalysts were
prepared by the impregnation method (see the Experimental
Section). The hydrosilylation of 1,4-diphenylbuta-1,3-diyne
(1a) with triethylsilane (2a) was used as the model reaction at
two different temperatures, with noncalcined and calcined
catalysts (Table 1). Since solvent-free organic synthesis is one
of the most promising steps toward waste prevention and
environmental protection, all reactions were carried out in the
absence of solvent.12 In a control experiment, the titania
support was shown to be inactive in this reaction (Table 1,
entry 1). Both noncalcined and calcined Pt/TiO2 provided the
expected product in quantitative conversion, though the
reaction with the latter was somewhat faster (Table 1, entries
2 and 3). The bimetallic Pt−Pd catalyst exhibited low catalytic
activity (Table 1, entry 4), whereas that of Pt−Sn behaved
similarly to noncalcined Pt/TiO2 (Table 1, compare entries 2
and 5). A decrease in the conversion and longer reaction times
were noted at room temperature, irrespective of the catalyst, for
a 1/1 or 2/1 diyne/silane stoichiometry (Table 1, entries 6−
10). A 1.5/1 diyne/silane ratio, however, shortened the reaction
times and gave excellent conversion with calcined Pt/TiO2
(Table 1, entries 11 and 12). Unfortunately, the latter
conditions were not as effective when extended to other
substrates. Therefore, we decided that it was more convenient
Hydrosilylation of 1,3-Diynes Catalyzed by Pt/TiO2.
An array of differently substituted diynes was subjected to the
hydrosilylation reaction under the optimized reaction con-
ditions (0.25 mol % Pt/TiO2, 70 °C, neat). We first studied the
hydrosilylation of symmetrically substituted diaryl diynes.
Triethylsilane (2a), triphenylsilane (2b), and trimethoxysilane
(2c) successfully added to 1,4-diphenylbuta-1,3-diyne (1a),
Table 1. Optimization of the Catalyst and Reaction Conditions
a
b
entry
cat.
1a/2a
T (°C)
t (h)
3aa (%)
1
TiO2
1/1
1/1
1/1
1/1
1/1
1/1
1/1
1/1
2/1
2/1
1.5/1
1.5/1
70
70
70
70
70
rt
24
3
0
>99
>99
10
2
Pt/TiO2 nc
Pt/TiO2 c
3
1
4
Pt−Pd/TiO2 c
Pt−Sn/TiO2 c
Pt/TiO2 nc
Pt/TiO2 c
24
3
5
>99
82
6
24
24
24
24
24
1
7
rt
82
8
Pt−Sn/TiO2 c
Pt/TiO2 nc
Pt/TiO2 c
rt
63
9
rt
87
10
11
12
rt
85
Pt/TiO2 nc
Pt/TiO2 c
rt
83
rt
1
>99
a
b
M/TiO2 (25 mg); c = calcined catalyst, nc = noncalcined catalyst. Conversion into 3aa determined by GC.
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leading to the monohydrosilylation products 3aa, 3ab, and 3ac,
respectively, in good to excellent yields (Table 3, entries 1−3).
The least sterically hindered Et3SiH, however, reacted much
more quickly than Ph3SiH and (MeO)3SiH. Then, different
substituents were introduced at the para position of the diyne
moiety in order to study any possible electronic effects. The
electron-rich substrate 1c furnished vinylsilane 3ca in higher
yield and shorter reaction time than for the electronically
neutral 1b (Table 3, entries 4 and 5). In contrast, the electron-
poor diyne 1d reacted sluggishly, producing 3da in moderate
yield (Table 3, entry 6). We must underline that the
dihydrosilylation of diaryl diynes failed even when using 5
equiv of the silane after prolonged heating (ca. 5% disilylated
product from 1a and 2a was detected). Taking into account the
regio- and stereochemistry of the reaction (see below), it seems
rather unlikely to accommodate two vicinal silane moieties in a
highly conjugated (and quite flat) 1,4-diarylbuta-1,3-diene
skeleton. The monohydrosilylation of symmetrically substituted
dialkyl diynes was proven to be elusive, leading to mixtures of
mono- and diaddition products. Nevertheless, the reaction
could be directed toward the dihydrosilylation by using an
excess of the silane under the standard conditions. Dialkyl
(1e)-, bis(chloroalkyl) (1f)-, and dicyclohexyl-substituted (1g)
diynes were nicely transformed into the corresponding
di(vinylsilanes) 3ea, 3fa, and 3ga, respectively, in good to
high yields (Table 3, entries 7−9). Finally, the reaction of
Et3SiH with the unsymmetrically substituted 5-phenylpenta-
2,4-diyn-1-ol (1h) readily afforded the silylated enyne 3ha in
good yield (Table 3, entry 10). All products in Table 3, with the
exception of the triphenylsilyl derivative 3ab,7b are new
compounds.
It is noteworthy that the monohydrosilylation of diynes was
highly regio- and stereoselective. The only products detected
arose from the syn addition of the Si−H bond across the
carbon−carbon triple bond, with the silicon atom bonded to
the most internal carbon atom of the diyne (Table 3, entries 1−
6). The presence of the (E)-2-trialkylsilylbut-1-en-3-yne moiety
was initially proposed on the basis of NOE experiments
effected for 3aa and unequivocally confirmed by X-ray
crystallographic analysis of the triphenylsilyl derivative 3ab
(Figure 3).15 The same regio- and stereochemical outcome was
observed in the dihydrosilylation of dialkyl-substituted 1,3-
diynes. In these cases, only one of the nine possible addition
products was selectively obtained containing the (E,E)-2,3-
bis(trialkylsilyl)buta-1,3-diene unit (Table 3, entries 7−9). The
unsymmetrically substituted diyne 5-phenylpenta-2,4-diyn-1-ol
(1h) followed a trend similar to that above, but the reaction
was further regioselective as the addition occurred uniquely on
the carbon−carbon triple bond of the propargyl alcohol
fragment (Table 3, entry 10). The favored formation of this
regioisomer could be due to an additional coordination of the
platinum species to the hydroxyl group. The same regiochem-
istry, but opposite stereochemistry, was noted by Trost et al. in
the ruthenium-catalyzed addition of ethoxydimethylsilane to a
furyl diynol, furnishing a cyclic vinylsiloxane.16 No selectivity
was observed when deca-1,3-diyn-1-ylbenzene was subjected to
the hydrosilylation reaction, forming two monoaddition and
one diaddition product. This fact reaffirms our proposal that
the unsymmetrically substituted diynol (1h) undergoes extra
coordination through the hydroxyl group.
Figure 1. TEM micrographs of the fresh calcined Pt/TiO2 catalyst.
Figure 2. XPS Pt 4f spectra of the fresh calcined Pt/TiO2 catalyst.
Table 2. Surface Atomic Ratios in the Fresh and Used
Calcined Pt/TiO2 Catalyst from XPS Analysis
atoms
fresh
used
Pt/Ti
O/Ti
Cl/Pt
0.030
2.970
1.239
0.013
2.531
1.190
Stability and Recycling of the Catalyst. The catalyst was
handled in air, and all the experiments were carried out without
air exclusion, with these being advantages that make the
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a
Table 3. Solvent-Free Mono- and Dihydrosilylation of 1,3-Diynes Catalyzed by Pt/TiO2
a
Reaction conditions: 1 (0.5 mmol), 2 (0.75 mmol, entries 1−6 and 10; 1.25 mmol, entries 7−9), Pt/TiO2 (25 mg, 0.25 mol %), neat, 70 °C.
Isolated yield.
b
procedure operationally simple. It is worthwhile mentioning
unchanged after the reaction, a strong decrease in the Pt/Ti
ratio was observed. In principle, this decrease could be ascribed
to sintering of the platinum particles upon reaction, giving rise
to less exposed surface. However, the mild temperature at
which the reaction was carried out rules out this possibility. It is
more likely to assume that platinum species are partially
leached from the surface during the reaction, yielding a lower
amount of surface platinum in the used catalyst. Furthermore,
the amount of surface chlorine also decreased after the reaction,
whereas the Cl/Pt ratio remained nearly constant. The leaching
of platinum was also confirmed by ICP-MS; the recovered
catalyst after a third cycle was shown to contain 22% of the
original platinum. Therefore, the decrease in the amount of
platinum in the catalyst seems to be the origin of the loss of
catalytic activity after successive reaction cycles.
that, despite the fact of the small amount of catalyst utilized (25
mg), it could be easily recovered by filtration and reused. We
were, however, somewhat disappointed with the recycling
capability, since the conversion drastically dropped in the third
run (100, 70, and 15%). These results largely differ from those
recorded by us in the hydrosilylation of terminal alkynes with a
similar catalyst,11 where reutilization was successfully extended
over four cycles without any apparent loss of activity (98, 98,
97, and 98%). In order to determine the origin of this loss of
activity, XPS analysis was also conducted on the used catalyst
after a third cycle. From a qualitative point of view, the XPS
spectrum is very similar to that of the fresh catalyst, though the
intensity of the platinum signal is lower (Figure 4). To try to
rationalize this difference, the surface atomic Pt/Ti and O/Ti
ratios, determined by XPS, are also reported in Table 2. It can
be seen that, whereas the O/Ti ratio remained practically
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EXPERIMENTAL SECTION
■
General Considerations. Degussa P25 TiO2 (60% anatase, 40%
rutile) with a surface area of 50 m2 g−1 (N2, −195 °C, BET method)
was used as support, after being calcined in air at 500 °C for 5 h. X-ray
photoelectron spectra (XPS) were acquired with a VG-Microtech
Multilab 3000 spectrometer equipped with a hemispherical electron
analyzer and a Mg Kα (h = 1253.6 eV, 1 eV = 1.602 × 10−19 J) 300 W
X-ray source. Conventional TEM analysis was carried out with a JEOL
Model JEM-210 electron microscope working at 200 kV and equipped
with a INCA Energy TEM 100 analytical system and a SIS Mega View
II camera. Samples for analysis were suspended in methanol and
placed on copper grids with a holey carbon film support.
Dyines 1a−g were prepared by homocoupling of the corresponding
terminal alkynes catalyzed by copper nanoparticles on titania.17 Diyne
1h was synthesized following a literature procedure.18 All other
materials and reagents were the best grade commercially available and
were used without further purification. All reactions were carried out
on a multireactor apparatus using the corresponding reactor tubes.
Melting points were meassured with a Reichert Thermovar apparatus
and are uncorrected. NMR spectra were recorded on Bruker Avance
Figure 3. Plot showing the X-ray structure and atomic numbering for
compound 3ab.
1
300 and 400 spectrometers (300 and 400 MHz for H NMR; 75 and
100 MHz for 13C NMR) using CDCl3 as solvent and TMS as internal
standard; chemical shifts are given in (δ) parts per million and
coupling constants (J) in hertz. Infrared analysis was performed with a
Jasco 4100LE (Pike MIRacle ATR) spectrophotometer; wavenumbers
are given in cm−1. Mass spectra (EI) were obtained at 70 eV on an
Agilent 5973 spectrometer; fragment ions are given in m/z with
relative intensities (%) in parentheses. HRMS analyses were were also
carried out in the electron impact mode (EI) at 70 eV on a Finnigan
MAT95S spectrometer. The purity of volatile compounds and the
chromatographic analyses (GLC) were determined with a Hewlett-
Packard HP-6890 gas chromatograph and Agilent 5973 GC-MS
apparatus. Retention times (tr) were obtained with the latter under the
following conditions: 30 m HP5MS capillary column (0.25 mm
diameter, 0.25 μm film thickness), using helium (54.1 mL/min) as
carrier gas, Tinjector = 250 °C, Tcolumn = 60 °C (3 min), and 60−270 °C
(15 °C/min). Column chromatography was performed using 40−60
μm silica gel 60 (hexane or hexane/EtOAc as eluent). Thin-layer
chromatography was carried out on TLC aluminum sheets with silica
gel 60 F254 (Merck).
Typical Procedure for the Preparation of Pt/TiO2.14,19 The
Pt/TiO2 catalyst was prepared by the impregnation method with an
aqueous solution of H2PtCl6·6H2O (Aldrich) of the appropriate
concentration to achieve a Pt content of 1 wt %. The slurry (10 mL
Figure 4. XPS Pt 4f spectra of the reused Pt/TiO2 catalyst.
CONCLUSION
■
A series of monometallic and bimetallic catalysts based on
noncalcined and calcined platinum supported on titania have
been prepared by the impregnation method and tested in the
hydrosilylation of 1,3-diynes. The calcined Pt/TiO2 catalyst has
shown the best performance in this reaction at 70 °C with low
catalyst loading (0.25 mol %) under solvent-free conditions.
This catalyst has been characterized by TEM and XPS,
revealing the presence of platinum nanoparticles composed of
Pt(II) species uniformly dispersed on the support. A variety of
electronically different diaryl-substituted symmetric 1,3-diynes
have been monohydrosilylated with three different silanes in
moderate to excellent yields (55−98%), whereas several
structurally different dialkyl-substituted symmetric 1,3-diynes
successfully underwent dihydrosilylation (71−90%). The
successful monohydrosilylation of an unsymmetric diyne is
also reported. All reactions were highly stereo- and
regioselective, affording the corresponding monosilyl enynes
and disilyl dienes with exclusive E stereochemistry and with the
silicon atom bonded to the internal carbon atom of the
conjugated system. The reutilization of the catalyst is rather
limited due to some platinum leaching.
g
−1 of TiO2) was stirred for 12 h, and then excess solvent was removed
by heating at 90 °C under vacuum in a rotary evaporator. Finally, the
catalyst was dried at 110 °C for 24 h (the “noncalcined catalyst”) and
calcined at 400 °C for 5 h, with a heating rate of 3 °C min−1 (the
“calcined catalyst”).
General Procedure for the Hydrosilylation of 1,3-Diynes
Catalyzed by Pt/TiO2. The diyne (1, 0.5 mmol) and the hydrosilane
(2, 0.75 mmol, entries 1−6 and 10; 1.25 mmol, entries 7−9; Table 3)
were added to a reactor tube containing PtNPs/TiO2 (25 mg, 0.25
mol %) without solvent. The reaction mixture was warmed to 70 °C
without exclusion of air and monitored by TLC and/or GLC until
total conversion of the starting material. EtOAc (3 mL) was added to
the resulting mixture followed by filtration through Celite and washing
with additional EtOAc (4 mL). The crude reaction mixture was
purified by column chromatography (silica gel, hexane (hexane/EtOAc
90/10 for compound 3ha)), except compound 3ac, which was
unstable on silica gel, to give the corresponding silylated enynes 3.
(E)-(1,4-Diphenylbut-1-en-3-yn-2-yl)triethylsilane (3aa): yellow
1
oil; Rf 0.55 (hexane); tr 17.69; H NMR (400 MHz, CDCl3) δ 8.00
(d, J = 10.0 Hz, 2H), 7.48−7.42 (m, 2H), 7.40−7.24 (m, 6H), 6.83 (s,
1H), 1.04 (t, J = 10.4 Hz, 9H), 0.82 (q, J = 10.4 Hz, 6H); 13C NMR
(75 MHz, CDCl3) δ 145.2, 137.8, 131.2, 128.8, 128.4, 128.3, 128.2,
̃
127.8, 124.4, 120.8, 100.4, 90.8, 7.4, 3.1; IR (neat) ν 3058, 2952, 2909,
2873, 1595, 1488, 1237, 1017, 1004, 752, 733, 719 cm−1; MS (70 eV)
m/z (%) 319 [M+ + 1, 100%], 318 [M+, 28], 289 (19), 261 (29), 259
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(22), 233 (31), 232 (11), 231 (47), 202 (14), 187 (12), 183 (10), 131
(69), 129 (12), 115 (12), 105 (13), 87 (25), 59 (23); HRMS calcd for
C22H26Si 318.1804, found 318.1813.
(400 MHz, CDCl3) δ 5.59 (t, J = 6.6 Hz, 2H), 3.52 (t, J = 6.6 Hz, 4H),
2.02−1.91 (m, 4H), 1.82−1.71 (m, 4H), 1.54−1.44 (m, 4H), 0.94 (t, J
= 8.0 Hz, 18H), 0.58 (q, J = 8.0 Hz, 12H); 13C NMR (75 MHz,
(E)-(1,4-Diphenylbut-1-en-3-yn-2-yl)triphenylsilane (3ab):.7b yel-
low solid; mp 98.5−101.5 °C; Rf 0.58 (hexane/EtOAc, 9:1); 1H NMR
(400 MHz, CDCl3) δ 7.97 (d, J = 8.0 Hz, 2H), 7.71 (dd, J = 8.0, 1.4
Hz, 6H), 7.44−7.23 (m, 12H), 7.21−7.16 (m, 5H), 6.97 (s, 1H); 13C
NMR (75 MHz, CDCl3) δ 149.6, 137.5, 136.4, 133.2, 131.2, 129.8,
̃
CDCl3) δ 141.4, 138.4, 44.9, 32.6, 30.0, 26.7, 7.6, 3.9; IR (neat) ν
2952, 2873, 1456, 1416, 1119, 1016, 717, 654 cm−1; MS (70 eV) m/z
(%) 462 [M+, 5%], 161 (27), 123 (34), 122 (10), 121 (97), 119 (25),
115 (78), 95 (14), 93 (35), 91 (13), 88 (10), 87 (100), 79 (10), 59
(41); HRMS calcd for C24H48Cl2Si2 462.2672, found 462.2664.
[(1E,3E)-1,4-Dicyclohexylbuta-1,3-diene-2,3-diyl]bis-
(triethylsilane) (3ga): colorless oil; Rf 0.88 (hexane); tr 19.25; 1H
NMR (400 MHz, CDCl3) δ 5.40 (d, J = 9.6 Hz, 2H), 2.16−2.05 (m,
2H), 1.72−1.44 (m, 12H), 1.21−1.12 (m, 4H), 1.09−1.05 (m, 4H),
0.94 (t, J = 8.0 Hz, 18H), 0.57 (q, J = 8.0 Hz, 12H); 13C NMR (75
MHz, CDCl3) δ 145.2, 137.3, 39.3, 33.2, 32.9, 26.3, 26.0, 25.9, 7.82,
129.1, 128.9, 128.2, 127.9, 127.8, 123.9, 118.1, 102.0, 91.3; IR (neat) ν
̃
3049, 1580, 1485, 1426, 1108, 754, 740, 698, 688 cm−1; MS (70 eV)
m/z (%) 463 [M+ + 1, 13%], 462 [M+, 32], 384 (18), 383 (14), 307
(13), 260 (24), 259 (100), 202 (13), 181 (23), 105 (10); HRMS calcd
for C34H26Si 462.1804, found 462.1811.
(E)-(1,4-Diphenylbut-1-en-3-yn-2-yl)trimethoxysilane (3ac): or-
ange oil; Rf 0.23 (hexane/EtOAc, 9/1); tr 16.87; 1H NMR (400
MHz, CDCl3) δ 8.04 (d, J = 8.0 Hz, 2H), 7.50−7.46 (m, 2H), 7.37−
7.31 (m, 6H), 7.19 (s, 1H), 3.72 (s, 9H); 13C NMR (75 MHz, CDCl3)
δ 149.1, 137.2, 132.6, 131.5, 129.5, 129.4, 128.5, 128.4, 124.1, 112.3,
4.17; IR (neat) ν
̃
2949, 2922, 2873, 1457, 1447, 1015, 720, 687 cm−1;
MS (70 eV) m/z (%) 446 [M+, 11%], 417 (11), 302 (14), 301 (29),
273 (15), 214 (13), 116 (12), 115 (100), 87 (79), 59 (30); HRMS
calcd for C28H54Si2 446.3764, found 446.3769.
(E)-5-Phenyl-3-(triethylsilyl)pent-2-en-4-yn-1-ol (3ha): yellow oil;
̃
99.7, 89.3, 51.5; IR (neat) ν 3055, 2941, 2841, 1595, 1488, 1443, 1188,
1
1076, 810, 754, 688 cm−1; MS (70 eV) m/z (%) 325 [M+ + 1, 28%],
324 [M+, 100], 293 (14), 277 (16), 262 (15), 261 (16), 218 (24), 217
(34), 204 (41), 203 (33), 202 (44), 201 (12), 200 (12), 121 (58), 107
(14), 91 (59), 61 (11); HRMS calcd for C19H20O3Si 324.1182, found
324.1190.
Rf 0.41 (hexane/EtOAc, 9/1); tr 15.72; H NMR (300 MHz, CDCl3)
δ 7.42−7.36 (m, 2H), 7.34−7.28 (m, 3H), 6.31 (t, J = 5.7 Hz, 1H),
4.55 (d, J = 5.7 Hz, 2H), 2.04 (s, 1H), 1.01 (t, J = 7.8 Hz, 9H), 0.74 (q,
J = 7.8 Hz, 6H); 13C NMR (75 MHz, CDCl3) δ 150.3, 137.6, 131.2,
̃
128.3, 127.9, 123.9, 98.6, 88.0, 62.8, 7.2, 2.8; IR (neat) ν 3311, 2952,
2909, 2874, 1597, 1456, 1415, 1377, 1237, 754, 734, 719, 689 cm−1;
MS (70 eV) m/z (%) 271 [M+, 29%], 244 (12), 243 (38), 215 (34),
197 (11), 187 (18), 175 (32), 169 (17), 159 (26), 147 (40), 140 (38),
139 (78), 137 (50), 131 (37), 129 (15), 128 (15), 127 (14), 116 (12),
115 (87), 105 (13), 103 (48), 101 (15), 88 (11), 87 (100), 77 (12), 75
(58), 59 (43), 57 (12), 47 (13), 45 (12); HRMS calcd for C17H24OSi,
272.1596, found 272.1599.
(E)-(1,4-Di-p-tolylbut-1-en-3-yn-2-yl)triethylsilane (3ba): yellow
1
oil; Rf 0.40 (hexane); tr 19.35; H NMR (300 MHz, CDCl3) δ 7.92
(d, J = 8.0 Hz, 2H), 7.35 (d, J = 8.0 Hz, 2H), 7.21−7.11 (m, 4H), 6.78
(s, 1H), 2.36 (s, 6H), 1.04 (t, J = 8.0 Hz, 9H), 0.82 (q, J = 8.0 Hz,
6H); 13C NMR (75 MHz, CDCl3) δ 144.7, 138.3, 137.9, 135.3, 131.1,
129.1, 128.9, 128.8, 121.6, 119.5, 100.3, 90.4, 21.5, 21.4, 7.4, 3.1; IR
̃
(neat) ν 3052, 2952, 2910, 2873, 1582, 1456, 1412, 1016, 1004, 812,
730, 718, 696 cm−1; MS (70 eV) m/z (%) 347 [M+ + 1, 31%], 346
[M+, 100], 289 (18), 287 (14), 261 (17), 259 (31), 215 (11), 197
(10), 173 (22), 145 (52), 87 (14), 59 (16); HRMS calcd for C24H30Si
346.2117, found 346.2125.
ASSOCIATED CONTENT
■
S
* Supporting Information
Figures giving TEM micrographs of the calcined Pt/TiO2
(E)-[1,4-Bis(4-methoxyphenyl)but-1-en-3-yn-2-yl]triethylsilane
1
catalyst, H and 13C NMR spectra of the silylated enynes 3,
1
(3ca): yellow oil; Rf 0.59 (hexane/EtOAc, 9:1); tr 23.76; H NMR
and the NOESY spectrum of compound 3aa and a CIF file
giving crystallographic data for 3ab. This material is available
free of charge via the Internet at http://pubs.acs.org.
(300 MHz, CDCl3) δ 8.02 (d, J = 8.4 Hz, 2H), 7.42 (d, J = 8.7 Hz,
2H), 6.96−6.87 (m, 4H), 6.75 (s, 1H), 3.85 (s, 3H), 3.84 (s, 3H), 1.06
(t, J = 7.8 Hz, 9H), 0.82 (q, J = 7.6 Hz, 6H); 13C NMR (75 MHz,
CDCl3) δ 159.6, 159.3, 143.8, 132.6, 131.2, 130.3, 117.7, 116.9, 114.0,
̃
113.5, 99.7, 39.9, 55.3, 7.4, 3.1; IR (neat) ν 3050, 2952, 2873, 1603,
AUTHOR INFORMATION
Corresponding Author
*E-mail: falonso@ua.es (F.A.); asepul@ua.es (A.S.-E.).
Notes
■
1505, 1287, 1171, 1031, 1022, 827, 729, 718, 696 cm−1; MS (70 eV)
m/z (%) 379 [M+ + 1, 33%], 378 [M+, 100], 247 (14), 189 (18), 161
(35), 59 (12); HRMS calcd for C24H30SiO2 378.2015, found 378.2022.
(E)-{1,4-Bis[4-(trifluoromethyl)phenyl]but-1-en-3-yn-2-yl}-
1
triethylsilane (3da): yellow oil; Rf 0.51 (hexane); tr 16.79; H NMR
The authors declare no competing financial interest.
(400 MHz, CDCl3) δ 8.06 (d, J = 8.0 Hz, 2H), 7.65 (d, J = 8.4 Hz,
2H), 7.62 (d, J = 8.4 Hz, 2H), 7.54 (d, J = 8.0 Hz, 2H), 6.92 (s, 1H),
1.06 (t, J = 7.2 Hz, 9H), 0.86 (q, J = 7.2 Hz, 6H); 13C NMR (75 MHz,
CDCl3) δ 144.6, 140.8, 131.6, 130.3 (q, 1JC−F = 42 Hz, CF3), 129.8 (q,
ACKNOWLEDGMENTS
This work was generously supported by the Spanish Ministerio
■
2
1JC−F = 42 Hz, CF3), 129.0 127.8, 125.9 (q, JC−F = 23 Hz, CCF3),
de Ciencia e Innovacio
́
n (MICINN; CTQ2007-65218,
3
3
CTQ2011-24151, and Consolider Ingenio 2010-CSD2007-
00006), the Generalitat Valenciana (GV; PROMETEO/2009/
002 and PROMETEO/2009/039), and FEDER. Y.M. thanks
the ISO of the Universidad de Alicante for a grant. R.B.
acknowledges the Universidad de Alicante, CAM, and Union
Fenosa for his grant (UF2007-X9159987F).
125.5 (q, JC−F = 15 Hz, CH), 125.4 (q, JC−F = 15 Hz, CH), 124.1,
122.3 (q, 2JC−F = 23 Hz, CCF3), 99.8, 99.4, 7.4, 2.8; IR (neat) ν
̃
2955,
2876, 1613, 1320, 1164, 1124, 1105, 1066, 1015, 839, 733, 720, 700
cm−1; MS (70 eV) m/z (%) 455 [M+ + 1, 24%], 454 [M+, 77], 435
(14), 425 (22), 398 (10), 397 (37), 369 (23), 321 (21), 320 (89), 319
(14), 227 (36), 200 (16), 199 (100), 151 (38), 115 (42), 87 (51);
HRMS calcd for C24H24F6Si 454.1551, found 454.1541.
(7E,9E)-Hexadeca-7,9-diene-8,9-diylbis(triethylsilane) (3ea): col-
orless oil; Rf 0.91 (hexane); tr 18.09; H NMR (400 MHz, CDCl3) δ
5.60 (t, J = 6.4 Hz, 2H), 2.01−1.85 (m, 4H), 1.35−1.21 (m, 16H),
0.94 (t, J = 8.0 Hz, 18H), 0.93 (t, J = 8.0 Hz, 6H), 0.58 (q, J = 8.0 Hz,
12H); 13C NMR (75 MHz, CDCl3) δ 140.4, 139.8, 32.0, 31.0, 29.6,
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