A new synthetic approach for functional triisopropoxyorganosilanes using molecular building blocks

Article abstract of DOI:10.1016/j.tet.2013.04.130

We report an efficient synthetic approach for well-designed organic-bridged alkoxysilanes, which allow the formation of highly functional organosilica hybrids under mild sol-gel conditions. A series of molecular building blocks containing a triisopropoxys

Full text of DOI:10.1016/j.tet.2013.04.130

Tetrahedron 69 (2013) 5312e5318
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
A new synthetic approach for functional triisopropoxyorganosilanes
using molecular building blocks
,
b
,
a
c
c
Yoshifumi Maegawa a , Minoru Waki , Akinari Umemoto , Toyoshi Shimada ,
*
,
b
Shinji Inagaki a
a Toyota Central R&D Labs., Inc., Nagakute, Aichi 480-1192, Japan
b Japan Science and Technology Agency (JST), ACT-C, Nagakute, Aichi 480-1192, Japan
c Department of Chemical Engineering, Nara National College of Technology, 22 Yata-cho, Yamatokoriyama, Nara 639-1080, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
We report an efficient synthetic approach for well-designed organic-bridged alkoxysilanes, which allow
the formation of highly functional organosilica hybrids under mild solegel conditions. A series of mo-
lecular building blocks containing a triisopropoxysilyl group were synthesized and used in cross-
coupling reactions. The triisopropoxysilyl group showed a good tolerance for various organic trans-
formations. 1,4-Diketo-3,6-dithienylpyrrolo[3,4-c]pyrrole-bridged triisopropoxysilane was successfully
prepared, allowing rapid formation of organosilica hybrid without loss of functionality under mildly
acidic conditions.
Received 19 March 2013
Received in revised form 26 April 2013
Accepted 27 April 2013
Available online 2 May 2013
Keywords:
Organosilica
Alkoxysilane
Ó 2013 Elsevier Ltd. All rights reserved.
Molecular building block
Cross-coupling
Solegel polymerization
1. Introduction
the synthesis of a series of molecular building blocks containing
allylsilyl groups for synthesis of solegel precursors with highly
Organosilica hybrid materials, such as periodic mesoporous
organosilicas (PMOs)1,2 and polysilsesquioxanes (PSQs)3,4 have re-
ceived considerable attention in the fields of catalysis, adsorbents,
and optical devices.5e7 These materials are typically prepared by
acid- or base-catalyzed hydrolysis and polycondensation (solegel
polymerization) of organic-bridged alkoxysilanes (R[Si(OR0)3]n,
nꢀ2, R: organic group, R0: Me, Et). The eSi(OMe)3 and eSi(OEt)3
groups are most frequently used for alkoxysilane precursors be-
cause they are readily hydrolyzed and condensed under mildly
acidic or basic conditions to form stable siloxane networks. How-
ever, the high reactivity of Si(OMe)3 and Si(OEt)3 has limited the
design and synthesis of alkoxysilane precursors with highly func-
tional organic groups (R) and caused formidable problems during
work-up and purification using silica gel chromatography.8e10
Recently, Shimada et al. found that allylsilyl (R[Si(CH2CH]
CH2)m(OEt)]3-m]n; m¼1e3) groups behaved as the synthetic
equivalent of alkoxysilyl groups, and were stable enough to allow
purification using silica gel chromatography.11,12 They also reported
functional organic groups via palladium-catalyzed coupling reac-
tions.13e15 However, the allylsilyl groups were hydrolyzed and
condensed under harsher conditions, such as high temperatures or
high concentrations of acid or base, or in the presence of expensive
Lewis acids, which sometimes damaged the functional organic
groups and/or caused undesired SieC bond cleavage in the
organosilane.16e18
Organosilanes with bulky alkoxysilyl groups, such as iso-
propoxysilyl [eSi(Oi-Pr)3] have been used only to a limited extent
to date, but have potential as ideal solegel precursors because of
their medium stability and reactivity due to the steric bulk of the
alkoxy group on the silicon atom.19e21 However, synthetic meth-
odologies have been limited to alkoxy exchange reactions of un-
stable chlorosilanes and/or less bulky alkoxysilanes.22 Here, we
report the preparation of a series of molecular building blocks
containing triisopropoxysilyl groups and the synthesis of highly
functional organosilica precursors via cross-coupling reaction of
the building blocks (Scheme 1). The isopropoxysilyl group was
found to show a good tolerance for various organic trans-
formations. The resulting organosilica precursor was successfully
hydrolyzed and condensed to form an organosilica hybrid without
loss of functionality under mildly acidic conditions.
* Corresponding author. Tel.: þ81 561 71 7139; fax: þ81 561 63 6507; e-mail
address: ymaegawa@mosk.tytlabs.co.jp (Y. Maegawa).
0040-4020/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2013.04.130

Y. Maegawa et al. / Tetrahedron 69 (2013) 5312e5318
5313
Table 1
Synthesis of halogen-substituted molecular building blocks containing one or two
triisopropoxysilyl groupsa
Entry
1
Substrate
Product
Yield %
86
Scheme 1. Synthetic method for functional organic-bridged triisopropoxysilanes using
molecular building blocks.
2. Results and discussion
2
85
83
First, we sought a suitable bulky alkoxysilyl group for the
building blocks. 2-Methoxyethoxysilyl and tert-butoxysilyl groups,
in addition to the isopropoxysilyl group, were introduced by
hydrosilylation of allylbromobenzene with trichlorosilane in the
presence of [PtCl2(C2H4)]2, followed by alkoxylation using appro-
priate alcohols in the presence of pyridine in CH2Cl2 (Scheme 2).23
The triisopropoxysilyl group was efficiently introduced and showed
sufficient stability during general work-up and silica gel chroma-
tography. The bulkier linear tris(2-methoxyethoxy)silyl group was
not retained during the reaction and purification, giving a complex
mixture that contained none of the target compound. The in-
troduction of the bulkier branched tri(tert-butoxy)silyl group failed
due to steric hindrance during the alkoxylation reaction.
3b
4
5
86
85
6b
84
a
Reagents and conditions: (i) allylhalobenzene (1 equiv), HSiCl3 (3.3 equiv),
Scheme 2. Synthesis of bromobenzene-based molecular building blocks containing
various bulky alkoxysilyl groups.
[PtCl2(C2H4)]2 (0.25 mol
% Pt), rt, overnight, (ii) i-PrOH (4.5 equiv), pyridine
(4.5 equiv), CH2Cl2, 0 ꢂCert, 6 h.
b
[(Bu4N)2PtCl6] (0.1 mol % Pt) was used as a catalyst.
We then synthesized a variety of halogenated benzene-based
building blocks with triisopropoxysilyl groups attached, as shown
in Table 1. During this study, we found that allylhalobenzene was
readily prepared by halogenemagnesium exchange reaction of
bromobenzene derivatives with a mixture of i-PrMgCl and n-BuLi in
cyclopentyl methyl ether followed byallylationwith allyl bromide in
the presence of CuCN.24 Both hydrosilylation and isopropoxylation
of p- and m-allylbromobenzene proceeded successfully to give the
corresponding building blocks 1a and 1d in high yields of 86% and
85%, respectively (Table 1, entries 1 and 2). The bis-silylated building
block 1e could be synthesized from diallylated bromobenzene
(Table 1, entry 3). In this case, hydrosilylation proceeded effectively
in the presence of (Bu4N)2PtCl6 as a catalyst.25 A series of iodo-
benzene building blocks, 1feh, were also obtained under same re-
action conditions (Table 1, entries 4e6).
Magnesium-containing building blocks were obtained from the
iodobenzene-based building blocks (Table 2, entries 1e3). A
Grignard exchange reaction of 1f with i-PrMgCl$LiCl in a mixture of
1,4-dioxane/tetrahydrofuran (THF) (1:10 v/v) proceeded effectively
at ꢁ40 ꢂC for 4 h and gave the magnesium-containing building
block 2a quantitatively. It is notable that the triisopropoxysilyl
group was stable towards i-PrMgCl$LiCl and the resulting magne-
sium reagent, owing to its bulky structure. Interestingly, no reaction
occurred in the absence of 1,4-dioxane, and unreacted 1f was re-
covered. This may be attributed to the formation of a magnesium
complex between i-PrMgCl and the triisopropoxysilyl group. In-
deed, the use of excess i-PrMgCl in THF gave the corresponding 2a.
The addition of 1,4-dioxane affects the dissociation of the magne-
sium complex, as reported by Knochel’s group.26 m-Silylated (2b)
and bis-silylated (2c) Grignard reagents were also successfully
obtained from corresponding iodo-building blocks under the same
reaction conditions.
reagents. The transmetallation of 2a with 2-isopropoxy-4,4,5,5-
tetramethyl-1,3,2-dioxaborolane in a mixture of 1,4-dioxane/THF
(1:10 v/v) gave the borylated building block 2d in 93% yield (Table
2, entry 4). The reaction of 2a with trimethyltin chloride afforded
the trimethylstannylated building block 2e in a high yield of 87%
(Table 2, entry 5).
With key building blocks in hand, we then examined the utility
of the molecular building blocks as cross-coupling partners. The
halogen-substituted building blocks can be used as coupling re-
agents for SuzukieMiyaura27 and SonogashiraeHagihara cross-
coupling reactions.28 SuzukieMiyaura coupling between 1f and
2-thiophenboronic acid in the presence of Pd(PPh3)4 as a catalyst
gave the thiophene-substituted building block 2f in 71% yield
(Table 2, entry 6). Notably, in the reaction, the use of a basic
aqueous solution did not affect the hydrolysis of the triisopropox-
ysilyl group. The
a-proton on thiophene ring in 2f was readily
brominated using N-bromosuccinimide (NBS) to afford the bro-
mothiophene building block 2g in 81% yield (Table 2, entry 7). The
resulting 2g is a useful coupling partner for the construction of p-
conjugated thiophene bridging groups. SonogashiraeHagihara
coupling between 1a and 2-methyl-3-butyn-2-ol in the presence of
PdCl2(PPh3)2/CuI as a catalyst gave the ethynylated compound 2h in
86% yield (Table 2, entry 8). The resulting 2h can easily be depro-
tected using NaH to afford the terminal ethyne-substituted building
block 2i in 71% yield without decomposition of the triisopropox-
ysilyl group (Table 2, entry 9). The obtained 2i can then be used as
a coupling partner for SonogashiraeHagihara coupling and/or click
reactions with azide compounds.29
Materials based on 1,4-diketo-3,6-dithienylpyrrolo[3,4-c]pyr-
role (DTDPP) have attracted tremendous attention in the fields of
solar cells and field effect transistors because of their promising
optical and electrical properties.30,31 DTDPP-bridged silane
The magnesium-containing building blocks successfully un-
derwent transmetallation upon treatment with other metal

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Y. Maegawa et al. / Tetrahedron 69 (2013) 5312e5318
Table 2
Synthesis of functional molecular building blocks
Entry
Substrate
Product
Yield %
Quant.h
1a
1f
2a
1g
1h
Quant.h
Quant.h
3a
4b
2a
93
5c
6d
7e
2a
1f
2f
87
71
Scheme 3. Synthesis of DTDPP-bridged triisopropoxysilane 4a and triallylsilane 4b,
and preparation of organosilica films.
81
86
71
transition in the DTDPP unit, which indicated that the optical
properties of the DTDPP unit remained after formation of the
organosilica film (Fig. 1). However, the corresponding DTDPP-
bridged triallylsilane 4b did not form an organosilica film under
same solegel conditions. Unfortunately, the color of the sol faded
under highly acidic conditions (1 M in THF), and an organosilica
film did not form. This indicates decomposition of the
donoreacceptoredonor structure in the DTDPP skeleton during
preparation of the sol. The triisopropoxysilyl group proved to be
useful in the synthesis of functional organosilica hybrids without
loss of organic group functionality.
8f
1a
2h
9g
a
Reagents and conditions: i-PrMgCl$LiCl, 1,4-dioxane/THF (1:10), ꢁ40 ꢂC, 4 h.
2-Isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane, ꢁ40 ꢂCert, overnight.
Trimethyltin chloride, ꢁ40 ꢂCert, overnight.
b
c
d
e
f
Pd(PPh3)4, 2-thiopheneboronic acid, NaHCO3 aqueous, 1,4-dioxane, 85 ꢂC, 24 h.
NBS, DMF, rt, 2 h.
PdCl2(PPh3)2, CuI, 2-methyl-3-butyn-2-ol, Et3N, 80 ꢂC, 24 h.
NaH, toluene, 115 ꢂC, 1 h.
Conversion of substrates 1feh.
g
h
precursors were synthesized by cross-coupling reaction using
building blocks, as shown in Scheme 3. MigitaeKosugieStille cross-
coupling between 2e and dibrominated DTDPP gave the desired
DTDPP-bridged triisopropoxysilane 4a in high yield (85%).32,33 The
corresponding DTDPP-bridged triallylsilane 4b also synthesized
using triallylsilane building block 3 (see Experimental section).
Both functional precursors were purified by silica gel chromatog-
raphy and isolated in pure form.
An organosilica hybrid film was readily obtained from the
DTDPP-bridged triisopropoxysilane 4a by solegel polymerization
under mildly acidic conditions. A purple solution of the precursor
4a containing aqueous hydrochloric acid (HCl, 5 mM in THF) was
smoothly converted to a dark blue sol by stirring for only 45 min.
The color change indicated the formation of a soluble siloxane
oligomer in the sol. The obtained sol formed a solid organosilica
film by spin-coating and drying under reduced pressure. The
resulting organosilica film showed absorption maxima at 564 nm
and 609 nm, attributed to an intramolecular charge transfer
Fig. 1. UVevis absorption spectra of organosilica films prepared from DTDPP-bridged
silane precursors 4a and 4b.
3. Conclusions
In conclusion, we developed a novel synthetic route for p-con-
jugated organosilica precursors by using molecular building blocks
containing one or two triisopropoxysilyl groups. The synthesized
molecular building blocks could be used as coupling partners for
various palladium-catalyzed cross-coupling reactions. Indeed, opto-
and electroactive organosilanes were successfully synthesized and

Y. Maegawa et al. / Tetrahedron 69 (2013) 5312e5318
5315
isolated in pure form. Furthermore, one organosilane was readily
hydrolyzed and condensed to give an organosilica hybrid without
loss of functionality. This innovative approach is expected to extend
and complement the conventional approach using allylsilane-based
molecular building blocks and will lead to significant development
of organosilica hybrids.
chloride solution (2.0 M in THF) (16.2 mL, 32.4 mmol) and n-BuLi
solution (2.5 M in hexane) (25.8 mL, 64.5 mmol) were added
dropwise over a period of 30 min, respectively. The reaction mix-
ture was stirred for 8 h at ꢁ5 ꢂC. Copper (I) cyanide (723 mg,
8.0 mmol,10 mol % Cu) was added at once, and the reaction mixture
was stirred for 5 min at ꢁ5 ꢂC. Allyl bromide (10.2 mL, 120.6 mmol)
was then added dropwise over a period of 30 min at ꢁ5 ꢂC. It was
then allowed to reach room temperature and stirred for 15 h. The
precipitated magnesium salt was filtered off and the resulting or-
ganic phase was extracted with diethyl ether and washed with
saturated NH4Cl aqueous solution and brine and dried over anhy-
drous MgSO4, filtered, and concentrated under reduced pressure
affording title compound as a transparent light brown liquid (21.4 g,
96% yield), which was used without further purification. 1H NMR
4. Experimental
4.1. Methods and materials
All reactions were carried out under argon using standard high
vacuum and Schlenk-line techniques. Unless otherwise noted, all
materials, including dry solvents, were purchased from commercial
suppliers (SigmaeAldrich, Tokyo Chemical Industry Co., Ltd., and
Wako Pure Chemical Industries Ltd.) and used without further
purification.
(400 MHz, CDCl3)
5.83e5.94 (m, 1H), 7.27 (d, J¼1.6 Hz, 2H), 7.50 (t, J¼1.6 Hz, 1H).
d
3.33 (d, J¼6.8 Hz, 2H), 5.08e5.15 (m, 2H),
4.2.1.4. 1-Bromo-3,5-diallylbenzene. A 500 mL three-neck
round-bottom flask connected to a dropping funnel and dry ar-
Nuclear magnetic resonance (NMR) spectra were recorded on
a Jeol JNM-EXC400P spectrometer (400 MHz for 1H and 100 MHz
gon flow was charged with
a stir bar and 1-allyl-3,5-
for 13C). Chemical shifts are reported in
d
parts per million refer-
enced to an internal tetramethylsilane standard (
0.00) for 1H NMR
and chloroform-d (
77.0) for 13C NMR, respectively. Mass spectra
dibromobenzene (21.4 g, 77.5 mmol), dry cyclopentyl methyl
ether (100 mL). The mixture was cooled to ꢁ5 ꢂC, and iso-
propylmagnesium chloride solution (2.0 M in THF) (16.2 mL,
32.5 mmol) and n-BuLi solution (2.5 M in hexane) (25.8 mL,
64.5 mmol) were added dropwise over a period of 30 min, re-
spectively. The reaction mixture was stirred for 8 h at ꢁ5 ꢂC. Copper
(I) cyanide (705 mg, 7.8 mmol, 10 mol % Cu) was added at once, and
the reaction mixture was stirred for 5 min at ꢁ5 ꢂC. Allyl bromide
(10.2 mL, 120.6 mmol) was then added dropwise over a period of
30 min at ꢁ5 ꢂC. It was then allowed to reach room temperature
and stirred for 15 h. The precipitated magnesium salt was filtered
off and the resulting organic phase was extracted with diethyl ether
and washed with saturated NH4Cl aqueous solution and brine and
dried over anhydrous MgSO4, filtered, and concentrated under re-
duced pressure. The resulting crude residue was purified by bulb-
to-bulb distillation (150 Pa, 100 ꢂC) affording title compound as
a transparent colorless liquid (17.5 g, 96% yield). 1H NMR (400 MHz,
d
d
were recorded on a Micromass GCT Premier mass spectrometer (FI:
field ionization) and Micromass Q-TOF mass spectrometer (ESI:
electrospray ionization). Ultraviolet-visible (UVevis) absorption
spectra were measured using a Jasco V-670 spectrometer.
4.2. Synthetic procedures and characterization
4.2.1. Synthesis of allylhalobenzene derivatives
4.2.1.1. 1-Allyl-4-bromobenzene. A 200 mL three-neck round-
bottom flask connected to a dropping funnel and dry argon flow
was charged with
a stir bar, 1,4-dibromobenzene (15.0 g,
63.6 mmol), and dry cyclopentyl methyl ether (35 mL). The mixture
was cooled to ꢁ5 ꢂC, and isopropylmagnesium chloride solution
(2.0 M in THF) (12.7 mL, 25.4 mmol) and n-BuLi solution (1.6 M in
hexane) (31.8 mL, 50.9 mmol) were added dropwise over a period
of 30 min, respectively. The reaction mixture was stirred for 4 h at
ꢁ5 ꢂC. Copper (I) cyanide (285 mg, 3.18 mmol, 5 mol % Cu) was
added at once, and the reaction mixture was stirred for 5 min at
ꢁ5 ꢂC. Allyl bromide (10.8 mL, 127.7 mmol) was then added drop-
wise over a period of 30 min at ꢁ5 ꢂC. It was then allowed to reach
room temperature and stirred for 15 h. The precipitated magne-
sium salt was filtered off and the resulting organic phase was
extracted with diethyl ether and washed with saturated NH4Cl
aqueous solution and brine and dried over anhydrous MgSO4, fil-
tered, and concentrated under reduced pressure. The resulting
crude residue was purified by bulb-to-bulb distillation (150 Pa,
50 ꢂC) affording title compound as a transparent colorless liquid
CDCl3)
d
3.33 (d, J¼6.8 Hz, 4H), 5.05e5.11 (m, 4H), 5.86e5.96 (m,
2H), 6.92 (s, 1H), 7.25 (s, 2H). 13C NMR (100 MHz, CDCl3)
d
39.8,
116.5, 122.4, 127.7, 129.3, 136.5, 142.3. FI-HRMS m/z calcd for
C12H13Br (Mþ): 236.0201; found: 236.0204.
4.2.1.5. 1-Allyl-4-iodobenzene. A 200 mL three-neck round-bot-
tom flask connected to a dropping funnel and dry argon flow was
charged with a stir bar,1-allyl-4-bromobenzene (12.0 g, 60.9 mmol),
and dry cyclopentyl methyl ether (30 mL). The mixture was cooled to
ꢁ5 ꢂC, and isopropylmagnesium chloride solution (2.0 M in THF)
(15.2 mL, 30.4 mmol) and n-BuLi solution (2.5 M in hexane) (24.4 mL,
61.0 mmol) were added dropwise over a period of 30 min, re-
spectively. The reaction mixture was stirred for 6 h at ꢁ5 ꢂC. The
resulting reaction mixture was then added dropwise to a solution of
iodine (23.2 g, 91.4 mmol) in THF (100 mL) at ꢁ78 ꢂC. It was then
allowed to reach room temperature and stirred for 18 h. The resulting
mixture was quenched with saturated NH4Cl aqueous solution at
0 ꢂC, and organic phase was extracted with diethyl ether and washed
with brine and dried over anhydrous MgSO4, filtered, and concen-
trated under reduced pressure. The resulting crude residue was pu-
rified by bulb-to-bulb distillation (150 Pa, 70 ꢂC) affording title
compound as a transparent colorless liquid (13.4 g, 90% yield). 1H
(12.2 g, 97% yield). 1H NMR (400 MHz, CDCl3)
2H), 5.03e5.09 (m, 2H), 5.87e5.97 (m, 1H), 7.05 (d, J¼8.4 Hz, 2H),
7.40 (t, J¼8.4 Hz, 2H). The same procedure was followed for the
synthesis of 1-allyl-3-bromobenzene as described below.
d
3.33 (d, J¼6.8 Hz,
4.2.1.2. 1-Allyl-3-bromobenzene. Transparent colorless liquid.
Yield: 93%. Bp: 150 Pa, 50 ꢂC. 1H NMR (400 MHz, CDCl3)
d 3.35 (d,
J¼6.8 Hz, 2H), 5.06e5.11 (m, 2H), 5.87e5.97 (m, 1H), 7.10e7.17 (m,
2H), 7.31e7.34 (m, 2H). 13C NMR (100 MHz, CDCl3)
d 39.7, 116.5,
122.4, 127.2, 129.1, 129.9, 131.6, 136.4, 142.3.
NMR (400 MHz, CDCl3)
d
3.33 (d, J¼6.6 Hz, 2H), 5.04e5.10 (m, 2H),
5.86e5.97 (m, 1H), 6.94 (d, J¼8.3 Hz, 2H), 7.61 (d, J¼8.3 Hz, 2H). The
same procedure was followed for the synthesis of 1-allyl-3-
iodobenzene and 1,3-diallyl-5-iodobenzene as described below.
4.2.1.3. 1-Allyl-3,5-dibromobenzene. A 500 mL three-neck
round-bottom flask connected to a dropping funnel and dry ar-
gon flow was charged with a stir bar, 1,3,5-tribromobenzene
(25.4 g, 80.7 mmol), and dry cyclopentyl methyl ether (120 mL).
The mixture was cooled to ꢁ5 ꢂC, and isopropylmagnesium
4.2.1.6. 1-Allyl-3-iodobenzene. Transparent colorless liquid. Yield:
87%. Bp: 150 Pa,100 ꢂC. 1H NMR (400 MHz, CDCl3)
d
3.33 (d, J¼6.4 Hz,

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Y. Maegawa et al. / Tetrahedron 69 (2013) 5312e5318
2H), 5.06e5.11 (m, 2H), 5.86e5.97 (m, 1H), 7.02 (t, J¼8.0 Hz, 1H), 7.15
(d, J¼8.0 Hz, 1H), 7.53 (d, J¼8.0 Hz, 1H), 7.54 (s, 1H). 13C NMR
127.8, 129.9, 134.6, 137.5, 145.0. FI-HRMS m/z calcd for C18H31IO3Si
(Mþ): 450.1087; found: 450.1091.
(100 MHz, CDCl3)
142.4.
d 39.7, 94.5, 116.5, 127.9, 130.1, 135.1, 136.5, 137.5,
4.2.2.5. 1,3-Bis(3-(triisopropoxysilyl)propyl)-5-bromobenzene
(1e). A 300 mL three-neck round-bottom flask connected to
a condenser and dry argon flow was charged with a stir bar, 1-
bromo-3,5-diallylbenzene (4.50 g, 19.0 mmol), dry diethyl ether
(12 mL), and dry CH2Cl2 (15 mL). After the addition of a solution of
4.2.1.7. 1,3-Diallyl-5-iodobenzene. Transparent colorless liquid.
Yield: 77%. Bp: 200 Pa, 110 ꢂC. 1H NMR (400 MHz, CDCl3)
3.30 (d,
d
J¼6.8 Hz, 4H), 5.05e5.11 (m, 4H), 5.85e5.95 (m, 2H), 6.96 (s, 1H),
7.38 (d, J¼1.2 Hz, 2H). 13C NMR (100 MHz, CDCl3)
d
39.6, 94.6, 116.4,
(Bu4N)2PtCl6 (17.0 mg, 19.0 mmol, 0.1 mol % Pt) in dry CH2Cl2 (3 mL),
128.3, 135.3, 136.5, 142.4. FI-HRMS m/z calcd for C12H13I (Mþ):
trichlorosilane (7.50 mL, 74.3 mmol) was then added dropwise over
a period of 15 min at 0 ꢂC. After complete addition of the tri-
chlorosilane, the temperature was progressively raised to room
temperature. The mixture was stirred overnight at room temper-
ature. The reaction mixture was concentrated under reduced
pressure and the residue was dissolved in dry CH2Cl2 (75 mL). The
resulting solution was then carefully added dropwise to a mixed
solution of dry 2-propanol (13.0 mL, 170 mmol) and dry pyridine
(14.0 mL, 170 mmol) in dry CH2Cl2 (100 mL) over a period of 30 min
at 0 ꢂC, and the resulting mixture was stirred for 3 h at room
temperature. The reaction mixture was then concentrated under
reduced pressure. The precipitated pyridinium salt was filtered off
and residue was extracted with hexane (300 mL). The combined
organic phase was concentrated under reduced pressure, and the
resulting crude residue was purified by silica gel chromatography
(eluent: hexane/EtOAc¼10:1) affording 1e as a transparent color-
284.0062; found: 284.0051.
4.2.2. Synthesis of molecular building blocks containing bulky al-
koxysilyl group
4.2.2.1. 1-Bromo-4-(3-(triisopropoxysilyl)propyl)benzene (1a). A
500 mL three-neck round-bottom flask connected to a condenser
and dry argon flow was charged with a stir bar, 1-allyl-4-
bromobenzene (12.0 g, 60.9 mmol), and [PtCl2(C2H4)]2 (4.0 mg,
6.8 m
mol, 0.25 mol % Pt). The mixture was cooled to 0 ꢂC, and tri-
chlorosilane (20.0 mL, 198 mmol) was then added dropwise over
a period of 15 min at 0 ꢂC. After complete addition of the tri-
chlorosilane, the temperature was progressively raised to room
temperature. The mixture was stirred for 18 h at room temperature.
The reaction mixture was concentrated under reduced pressure
and the residue was dissolved in dry CH2Cl2 (50 mL). The resulting
solution was then carefully added dropwise to a mixed solution of
dry 2-propanol (21.0 mL, 274 mmol) and dry pyridine (22.2 mL,
274 mmol) in dry CH2Cl2 (200 mL) over a period of 30 min at 0 ꢂC,
and the resulting mixture was stirred for 6 h at room temperature.
The reaction mixture was then concentrated under reduced pres-
sure. The precipitated pyridinium salt was filtered off, and residue
was extracted with hexane (300 mL). The combined organic phase
was concentrated under reduced pressure, and the resulting crude
residue was purified by silica gel chromatography (eluent: hexane/
EtOAc¼10:1) affording 1a as a transparent colorless liquid (21.2 g,
less liquid (10.2 g, 83% yield). 1H NMR (400 MHz, CDCl3)
d 0.58e0.62
(m, 4H), 1.18 (d, J¼6.4 Hz, 36H), 1.65e1.73 (m, 4H), 2.56 (t, J¼8.0 Hz,
4H), 4.19 (sept, J¼6.4 Hz, 6H), 6.88 (s, 1H), 7.12 (d, J¼1.4 Hz, 2H). 13C
NMR (100 MHz, CDCl3)
d 11.7, 24.9, 25.6, 38.9, 64.9, 122.0, 127.6,
128.8, 144.6. FD-HRMS m/z calcd for C30H57BrO6Si2 (Mþ): 648.2877;
found: 648.2869. The same procedure was followed for the syn-
thesis of compound 1h as described below.
4.2.2.6. 1,3-Bis(3-(triisopropoxysilyl)propyl)-5-iodobenzene
(1h). Transparent colorless liquid. Yield: 84%. 1H NMR (400 MHz,
CDCl3)
4H), 2.53 (t, J¼7.6 Hz, 4H), 4.19 (sept, J¼6.0 Hz, 6H), 6.92 (s, 1H), 7.33
(s, 2H). 13C NMR (100 MHz, CDCl3)
11.7, 24.9, 25.6, 38.8, 64.9, 94.3,
d
0.57e0.62 (m, 4H), 1.18 (d, J¼6.0 Hz, 36H), 1.64e1.72 (m,
86% yield). 1H NMR (400 MHz, CDCl3)
d 0.57e0.61 (m, 2H), 1.17 (d,
J¼6.4 Hz, 18H), 1.67e1.71 (m, 2H), 2.58 (t, J¼7.2 Hz, 2H), 4.18 (sept,
d
J¼6.4 Hz, 3H), 7.04 (d, J¼8.8 Hz, 2H), 7.37 (d, J¼8.8 Hz, 2H). 13C NMR
128.3, 134.8, 144.7. ESI-HRMS m/z calcd for C30H57INaO6Si2
(100 MHz, CDCl3)
d 11.6, 25.0, 25.6, 38.6, 64.9, 119.3, 130.3, 131.2,
(MþNaþ): 719.2623; found: 719.2668.
141.5. FI-HRMS m/z calcd for C18H31BrO3Si (Mþ): 402.1226; found:
402.1224. The same procedure was followed for the synthesis of
compounds 1d, 1f, and 1g as described below.
4.2.2.7. 4-(3-(Triisopropoxysilyl)propyl)phenylmagnesium chlo-
ride (2a). A 20 mL Schlenk flask connected to dry argon flow was
charged with a stir bar, 1f (247 mg, 0.55 mmol), and dry THF (5 mL).
The mixture was cooled to ꢁ40 ꢂC, and isopropylmagnesium
chloride lithium chloride complex solution (1.3 M in THF) (0.85 mL,
1.10 mmol) and dry 1,4-dioxane (0.50 mL) were added dropwise
over a period of 5 min, respectively. The reaction mixture was
stirred for 4 h at ꢁ40 ꢂC. Conversion of starting material was check
by 1H NMR after the quenching water. The same procedure was
followed for the preparation of compound 2b and 2c.
4.2.2.2. 1-Bromo-3-(3-(triisopropoxysilyl)propyl)benzene
(1d). Transparent colorless liquid. Yield: 85%. 1H NMR (400 MHz,
CDCl3)
2H), 2.60 (t, J¼7.6 Hz, 2H), 4.19 (sept, J¼6.4 Hz, 3H), 7.08e7.15 (m,
2H), 7.28e7.32 (m, 2H). 13C NMR (100 MHz, CDCl3)
11.9, 25.2, 25.9,
d
0.58e0.62 (m, 2H), 1.18 (d, J¼6.4 Hz, 18H), 1.67e1.75 (m,
d
39.1, 65.2, 122.6, 127.5, 129.0, 130.0, 131.9, 145.2. FI-HRMS m/z
calcd for C18H31BrO3Si (Mþ): 402.1226; found: 402.1211.
4.2.2.3. 1-Iodo-4-(3-(triisopropoxysilyl)propyl)benzene
4.2.2.8. 4-(4,4,5,5-Tetramethyl-1,3,2-dioxaborolan-2-yl)-1-(3-
(triisopropoxysilyl)propyl)benzene (2d). A 20 mL Schlenk flask
connected to dry argon flow was charged with a stir bar and
2a (0.55 mmol) in dry THF/dry 1,4-dioxane (6.35 mL). The mixture
was cooled to ꢁ40 ꢂC, 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-
(1f). Transparent colorless liquid. Yield: 86%. 1H NMR (400 MHz,
CDCl3)
d
0.57e0.61 (m, 2H), 1.17 (d, J¼6.4 Hz, 18H), 1.57e1.73 (m,
2H), 2.57 (t, J¼7.6 Hz, 2H), 4.18 (sept, J¼6.4 Hz, 3H), 6.92 (d,
J¼8.4 Hz, 2H), 7.57 (d, J¼8.4 Hz, 2H). 13C NMR (100 MHz, CDCl3)
d
11.6, 24.9, 25.6, 38.7, 64.9, 90.5, 130.7, 137.2, 142.2. FI-HRMS m/z
dioxaborolane (225 mL, 1.10 mmol) was added one-portion. It was
calcd for C18H31IO3Si (Mþ): 450.1087; found: 450.1065.
then allowed to reach room temperature and stirred for 18 h. The
resulting mixture was quenched with saturated NH4Cl aqueous
solution at 0 ꢂC, and organic phase was extracted with diethyl ether
and washed with brine and dried over anhydrous MgSO4, filtered,
and concentrated under reduced pressure affording 2d as a trans-
parent colorless liquid (230 mg, 93% yield). 1H NMR (400 MHz,
4.2.2.4. 1-Iodo-3-(3-(triisopropoxysilyl)propyl)benzene
(1g). Transparent colorless liquid. Yield: 85%. 1H NMR (400 MHz,
CDCl3)
d
0.57e0.61 (m, 2H), 1.18 (d, J¼6.0 Hz, 18H), 1.66e1.74 (m,
2H), 2.57 (t, J¼7.6 Hz, 2H), 4.19 (sept, J¼6.0 Hz, 3H), 6.99 (d,
J¼8.0 Hz, 1H), 7.12 (d, J¼8.0 Hz, 1H), 7.50 (d, J¼8.0 Hz, 1H), 7.53 (s,
CDCl3)
d
0.59e0.63 (m, 2H), 1.17 (d, J¼6.0 Hz, 18H), 1.33 (s, 12H),
1H). 13C NMR (100 MHz, CDCl3)
d 11.6, 24.9, 25.6, 38.7, 64.9, 94.4,
1.69e1.76 (m, 2H), 2.64 (t, J¼7.6 Hz, 2H), 4.18 (sept, J¼6.0 Hz, 3H),

Y. Maegawa et al. / Tetrahedron 69 (2013) 5312e5318
5317
7.18 (d, J¼8.0 Hz, 2H), 7.71 (d, J¼8.0 Hz, 2H). 13C NMR (100 MHz,
with a stir bar, 1a (7.13 g, 17.6 mmol), PdCl2(PPh3)2 (495 mg,
0.71 mmol), CuI (135 mg, 0.70 mmol), and dry Et3N (70 mL). After
the mixture was stirred for 1 min at room temperature, 2-methyl-
3-butyn-2-ol (2.10 mL, 21.5 mmol) was added. The temperature
was progressively raised to 80 ꢂC and then the reaction mixture was
stirred for 20 h. The reaction mixture was then concentrated under
reduced pressure and the resulting crude residue was purified by
silica gel chromatography (eluent: hexane/EtOAc¼10:1) affording
2h as a transparent light yellow liquid (6.21 g, 86% yield). 1H NMR
CDCl3)
d 11.7, 24.5, 24.8, 25.5, 39.5, 64.8, 83.6, 128.0, 133.8, 134.7,
146.0. FI-HRMS m/z calcd for C24H43BO5Si (Mþ): 450.2973; found:
450.2978.
4.2.2.9. 4-(3-(Triisopropoxysilyl)propyl)-1-(trimethylstannyl)ben-
zene (2e). A 100 mL two-neck round-bottom flask connected to dry
argon flow was charged with a stir bar and 2a (3.33 mmol) in dry
THF/dry 1,4-dioxane (38 mL). The mixture was cooled to ꢁ40 ꢂC,
trimethyltin chloride (1.33 g, 6.67 mmol) was added one-portion. It
was then allowed to reach room temperature and stirred for 18 h.
The resulting mixture was quenched with saturated NH4Cl aqueous
solution at 0 ꢂC, and organic phase was extracted with diethyl ether
and washed with brine and dried over anhydrous MgSO4, filtered,
and concentrated under reduced pressure affording 2e as a trans-
parent colorless liquid (1.41 g, 87% yield). Compound 2e was used
(400 MHz, CDCl3)
d
0.57e0.61 (m, 2H), 1.17 (d, J¼6.4 Hz, 18H), 1.61
(s, 6H), 1.66e1.74 (m, 2H), 2.62 (t, J¼7.6 Hz, 2H), 4.18 (sept, J¼6.4 Hz,
3H), 7.10 (d, J¼8.4 Hz, 2H), 7.31 (d, J¼8.4 Hz, 2H). 13C NMR (100 MHz,
CDCl3) d 11.6, 24.8, 25.5, 31.5, 39.0, 64.8, 65.6, 82.3, 93.0,119.8,128.5,
131.5, 143.0. FI-HRMS m/z calcd for C23H38O4Si (Mþ): 406.2539;
found: 406.2545.
without further purification. 1H NMR (400 MHz, CDCl3)
d 0.27 (t,
4.2.2.13. 1-Ethynyl-4-(3-(triisopropoxysilyl)propyl)benzene
(2i). A 300 mL three-neck round-bottom flask connected to a con-
denser and dry argon flow was charged with a stir bar, 2h (10.0 g,
24.6 mmol), and dry toluene (150 mL). After the mixture was stirred
for 5 min at room temperature, sodium hydride (60%, dispersion in
paraffin liquid, 195 mg, 4.88 mmol) was added. The temperature
was progressively raised to 115 ꢂC and then the reaction mixture
was stirred for 1 h. The reaction mixture was then concentrated
under reduced pressure and the resulting crude residue was puri-
fied by silica gel chromatography (eluent: hexane/CHCl3¼2:1)
affording 2i as a transparent light yellow liquid (6.08 g, 71% yield).
J¼27.6 Hz, 9H), 0.62e0.66 (m, 2H), 1.18 (d, J¼6.4 Hz, 18H), 1.69e1.76
(m, 2H), 2.61 (t, J¼8.0 Hz, 2H), 4.19 (sept, J¼6.4 Hz, 3H), 7.17 (d,
J¼7.6 Hz, 2H), 7.40 (d, J¼7.6 Hz, 2H). 13C NMR (100 MHz, CDCl3)
d
ꢁ9.6, 11.9, 25.1, 25.6, 39.4, 64.8, 128.4, 135.7, 138.6, 142.7. ESI-
HRMS m/z calcd for C21H40NaO3SiSn (MþNaþ): 511.1666; found:
511.1679.
4.2.2.10. 4-(Thiophen-2-yl)-1-(3-(triisopropoxysilyl)propyl)ben-
zene (2f). A 500 mL three-neck round-bottom flask connected to
a condenser and dry argon flow was charged with a stir bar, 1f
(6.60 g, 14.7 mmol), 2-thiopheneboronic acid (2.82 g, 22.0 mmol),
sodium hydrogen carbonate (2.46 g, 29.3 mmol), dry 1,4-dioxane
(220 mL), and degassed distilled water (22 mL). After the mixture
was stirred for 10 min at room temperature, Pd(PPh3)4 (400 mg,
0.35 mmol, 2.4 mol % Pd) was added one-portion under argon flow.
The temperature was progressively raised to 85 ꢂC and then the
reaction mixture was stirred for 24 h. The reaction mixture was
then concentrated under reduced pressure and the resulting crude
residue was purified by silica gel chromatography (eluent: hexane/
CHCl3¼1:1) affording 2f as a transparent light yellow liquid (4.24 g,
1H NMR (400 MHz, CDCl3)
d
0.57e0.62 (m, 2H), 1.17 (d, J¼6.0 Hz,
18H), 1.69e1.73 (m, 2H), 2.63 (t, J¼8.0 Hz, 2H), 3.03 (s, 1H), 4.18
(sept, J¼6.0 Hz, 3H), 7.12 (d, J¼8.4 Hz, 2H), 7.39 (d, J¼8.4 Hz, 2H). 13C
NMR (100 MHz, CDCl3) d 11.6, 24.8, 25.6, 39.1, 64.9, 76.4, 83.9, 119.2,
128.5, 132.0, 143.6. FI-HRMS m/z calcd for C20H32O3Si (Mþ):
348.2121; found: 348.2129.
4.2.3. Synthesis of molecular building blocks containing triallylsilyl
group
4.2.3.1. 1-Iodo-4-(3-(triallylsilyl)propyl)benzene. A 300 mL three-
neck round-bottom flask connected to a condenser and dry argon
flow was charged with a stir bar, 1-allyl-4-iodobenzene (6.0 g,
71% yield). 1H NMR (400 MHz, CDCl3)
d 0.61e0.66 (m, 2H), 1.18 (d,
J¼6.4 Hz, 18H), 1.70e1.78 (m, 2H), 2.64 (t, J¼7.6 Hz, 2H), 4.19 (sept,
J¼6.4 Hz, 3H), 7.06 (dd, J¼5.2 Hz, 3.6 Hz, 1H), 7.18 (d, J¼8.0 Hz, 2H),
7.23 (dd, J¼5.2 Hz,1.2 Hz,1H), 7.26 (dd, J¼3.6 Hz, 0.8 Hz,1H), 7.51 (d,
24.6 mmol), and [PtCl2(C2H4)]2 (7.25 mg, 12.3 mmol, 0.1 mol % Pt).
The mixture was cooled to 0 ꢂC, and trichlorosilane (15.0 mL,
149 mmol) was then added dropwise over a period of 15 min at 0 ꢂC.
After complete addition of the trichlorosilane, the temperature was
progressively raised to room temperature. The mixture was stirred
for 15 h at room temperature. The reaction mixture was concen-
trated under reduced pressure and the residue was dissolved in dry
diethyl ether (10 mL). The mixture was cooled to 0 ꢂC, and allyl-
magnesium bromide solution (1.0 M in diethyl ether, 98.0 mL,
98.0 mmol) were added dropwise over a period of 30 min. The re-
action mixture was stirred for 20 h at room temperature. The
resulting mixture was quenched with saturated NH4Cl aqueous
solution at 0 ꢂC, and organic phase was extracted with diethyl ether
and washed with brine and dried over anhydrous MgSO4, filtered,
and concentrated under reduced pressure. The resulting crude res-
idue was purified by bulb-to-bulb distillation (130 Pa, 90 ꢂC)
affording title compound as a transparent colorless liquid (5.73 g,
J¼8.0 Hz, 2H). 13C NMR (100 MHz, CDCl3)
d 11.7, 25.0, 25.5, 38.9,
64.8, 122.5, 124.2,125.8, 127.8, 129.0, 131.8, 142.0, 144.5. FI-HRMS m/
z calcd for C22H34O3SSi (Mþ): 406.1988; found: 406.1977.
4.2.2.11. 4-(5-Bromothiophen-2-yl)-1-(3-(triisopropoxysilyl)pro-
pyl)benzene (2g). A 100 mL two-neck round-bottom flask con-
nected to dry argon flow was charged with a stir bar, 2f (1.05 g,
2.58 mmol), and dry DMF (30 mL). After the mixture was stirred for
10 min at 0 ꢂC, N-bromosuccinimide (636 mg, 3.57 mmol) was
added one-portion under argon flow. The reaction mixture was
stirred for 2 h at room temperature. The organic phase was
extracted with hexane and concentrated under reduced pressure.
The resulting crude residue was purified by silica gel chromatog-
raphy (eluent: hexane/EtOAc¼10:1) affording 2g as a transparent
light yellow liquid (1.01 g, 81% yield). 1H NMR (400 MHz, CDCl3)
59% yield). 1H NMR (400 MHz, CDCl3)
d 0.60e0.63 (m, 2H), 1.58 (d,
d
0.61e0.65 (m, 2H), 1.18 (d, J¼6.4 Hz, 18H), 1.69e1.77 (m, 2H), 2.63
J¼8.0 Hz, 6H), 1.56e1.66 (m, 2H), 2.55 (t, J¼8.0 Hz, 2H), 4.84e4.89
(m, 6H), 5.70e5.81 (m, 3H), 6.91 (d, J¼8.0 Hz, 2H), 7.59 (d, J¼8.0 Hz,
2H). FI-HRMS m/z calcd for C18H25ISi (Mþ): 396.0770; found:
396.0766.
(t, J¼7.6 Hz, 2H), 4.19 (sept, J¼6.4 Hz, 3H), 6.99 (s, 2H), 7.17 (d,
J¼8.4 Hz, 2H), 7.40 (d, J¼8.4 Hz, 2H). 13C NMR (100 MHz, CDCl3)
d
11.7, 25.0, 25.6, 38.9, 64.8, 110.7, 122.6, 125.5, 129.1, 130.7, 131.1,
142.6, 146.1. FI-HRMS m/z calcd for C22H33BrO3SSi (Mþ): 484.1103;
found: 484.1096.
4.2.3.2. 4-(3-(Triallylsilyl)propyl)-1-(trimethylstannyl)benzene
(3). A 100 mL two-neck round-bottom flask connected to dry argon
flow was charged with a stir bar, 1-iodo-4-(3-(triallylsilyl)propyl)
benzene (2.32 g, 5.85 mmol), and dry THF (16 mL). The mixture was
4.2.2.12. 1-(3-Hydroxy-3-methyl-1-butynyl)-4-(3-(triisopropox-
ysilyl)propyl)benzene (2h). A 500 mL three-neck round-bottom
flask connected to a condenser and dry argon flow was charged

5318
Y. Maegawa et al. / Tetrahedron 69 (2013) 5312e5318
cooled to 0 ꢂC, and isopropylmagnesium chloride solution (2.0 M in
THF) (6.0 mL, 12.0 mmol) was added dropwise over a period of
5 min. The reaction mixture was stirred for 8 h at 0 ꢂC. Then, tri-
methyltin chloride (2.40 g, 12.0 mmol) was added one-portion. It
was then allowed to reach room temperature and stirred for 15 h.
The resulting mixture was quenched with saturated NH4Cl aqueous
solution at 0 ꢂC, and organic phase was extracted with diethyl ether
and washed with brine and dried over anhydrous MgSO4, filtered,
and concentrated under reduced pressure affording 3 as a trans-
parent colorless liquid (2.50 g, 99% yield). Compound 3 was used
4.2.5. Preparation of DTDPP-bridged organosilica film. DTDPP-
bridged organosilane 4a (12.4 mg, 10.6 mol) was dissolved in THF
(3.4 mL) and then 2 mol/L HCl aqueous solution (8.5 L) was added
to the solution (5 mM in THF). The mixture was stirred at room
temperature for 45 min. The sol solution was coated on a quartz
glass plate by spin-coating (1000 rpm, 30 s) and dried under re-
duced pressure to give an organosilica film.
m
m
Acknowledgements
without further purification. 1H NMR (400 MHz, CDCl3)
d 0.28 (t,
The authors thank Mr. S. Kajiya and Mr. K. Yagi (Toyota Central
R&D Labs., Inc.) for FI-HRMS and ESI-HRMS measurement.
J¼24.8 Hz, 9H), 0.64e0.68 (m, 2H), 1.58 (d, J¼8.4 Hz, 6H), 1.62e1.68
(m, 2H), 2.59 (t, J¼7.6 Hz, 2H), 4.83e4.89 (m, 6H), 5.71e5.81 (m,
3H), 7.15 (d, J¼8.0 Hz, 2H), 7.41 (d, J¼8.0 Hz, 2H). 13C NMR (100 MHz,
References and notes
CDCl3)
d
ꢁ9.6, 11.5, 19.5, 25.7, 39.9, 113.5, 128.2, 134.3, 135.8, 138.8,
142.4. FI-HRMS m/z calcd for C21H34SiSn (Mþ): 434.1452; found:
€
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4.2.4. Synthesis of DTDPP-bridged organosilane
4.2.4.1. 3,6-Bis(5-(4-(triisopropoxysilyl)propyl)phenylthiophen-2-
yl)-2,5-bis(2-ethylhexyl)pyrrolo[3,4-c]pyrrole-1,4-dione (4a). A 100
mL two-neck round-bottom flask connected to a condenser and dry
argon flow was charged with a stir bar, 2e (420 mg, 0.86 mmol),
3,6-di(2-bromothien-5-yl)-2,5-bis(2-ethylhexyl)pyrrolo[3,4-c]pyr-
role-1,4-dione (198 mg, 0.29 mmol), tris(dibenzylideneacetone)
dipalladium(0) (13.3 mg, 0.015 mmol, 10 mol % Pd), tri(2-furyl)
phosphine (14.6 mg, 0.058 mmol, 20 mol %), and dry THF (30 mL).
The temperature was progressively raised to 70 ꢂC and then the
reaction mixture was stirred for 20 h. The reaction mixture was
then concentrated under reduced pressure and the resulting crude
residue was purified by flash chromatography (eluent: hexane/
EtOAc¼40:1) affording 4a as a dark blue tacky solid (289 mg, 85%
11. Shimada, T.; Aoki, K.; Shinoda, Y.; Nakamura, T.; Tokunaga, N.; Inagaki, S.;
Hayashi, T. J. Am. Chem. Soc. 2003, 125, 4688e4689.
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yield). 1H NMR (400 MHz, CDCl3)
d 0.62e0.66 (m, 4H), 0.87 (t,
J¼6.8 Hz, 6H), 0.91 (t, J¼7.2 Hz, 6H), 1.19 (d, J¼6.4 Hz, 36H),
1.24e1.42 (m, 16H), 1.72e1.80 (m, 4H), 1.90e2.00 (m, 2H), 2.67 (t,
J¼7.6 Hz, 4H), 4.03e4.13 (m, 4H), 4.20 (sept, J¼6.4 Hz, 6H), 7.23 (d,
J¼8.4 Hz, 4H), 7.42 (d, J¼4.0 Hz, 2H), 7.58 (d, J¼8.4 Hz, 4H), 8.96 (d,
J¼4.0 Hz, 2H). 13C NMR (100 MHz, CDCl3)
d 10.6, 11.8, 14.1, 23.1, 23.7,
25.0, 25.6, 28.6, 30.4, 39.0, 39.2, 46.0, 64.9, 108.0, 124.0, 126.0, 128.3,
129.3, 130.7, 136.8, 139.8, 143.8, 150.0, 161.7. ESI-HRMS m/z calcd for
C66H100N2NaO8S2Si2 (MþNaþ): 1191.6357; found: 1191.6323. The
same procedure was followed for the synthesis of DPP-bridged
triallylsilane (4b) as described below.
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d 0.64e0.68 (m,
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6H), 7.22 (d, J¼8.0 Hz, 4H), 7.44 (d, J¼4.0 Hz, 2H), 7.59 (d, J¼8.0 Hz,
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14.1, 19.5, 23.1, 23.6, 25.5, 28.5, 30.3, 39.2, 39.6, 45.9, 108.0,
113.6124.0, 126.0, 128.3, 129.2,130.7,134.2,136.8,139.7,143.4,149.8,
161.6. ESI-HRMS m/z calcd for C66H88N2NaO2S2Si2 (MþNaþ):
1083.5724; found: 1083.5712.