Synthesis of aryltriethoxysilanes via rhodium(I)-catalyzed cross-coupling of aryl electrophiles with triethoxysilane

Article abstract of DOI:10.1016/j.tet.2007.02.103

The general and efficient silylation of aryl halides has been developed utilizing triethoxysilane and a rhodium catalyst. The substrate scope is broad and includes ortho-, meta-, and para-substituted electron-rich and -deficient aryl iodides. In addition, the silylation of aryl bromides and fluoroalkanesulfonates proceeded in the presence of tetra-n-butylammonium iodide.

Full text of DOI:10.1016/j.tet.2007.02.103

Tetrahedron 63 (2007) 4087–4094
Synthesis of aryltriethoxysilanes via rhodium(I)-catalyzed
cross-coupling of aryl electrophiles with triethoxysilane
*
Miki Murata, Hiyoruki Yamasaki, Tsukasa Ueta, Masayuki Nagata, Masanori Ishikura,
Shinji Watanabe and Yuzuru Masuda
Department of Materials Science, Kitami Institute of Technology, 165 Koencho, Kitami 090-8507, Japan
Received 19 January 2007; revised 22 February 2007; accepted 23 February 2007
Available online 25 February 2007
Abstract—The general and efficient silylation of aryl halides has been developed utilizing triethoxysilane and a rhodium catalyst. The sub-
strate scope is broad and includes ortho-, meta-, and para-substituted electron-rich and -deficient aryl iodides. In addition, the silylation of aryl
bromides and fluoroalkanesulfonates proceeded in the presence of tetra-n-butylammonium iodide.
Ó 2007 Elsevier Ltd. All rights reserved.
1. Introduction
applicability to polyfunctionalized substrates and is difficult
to suppress competing formation of di- and triarylsilanes.
Arylsiloxanes and their hypervalent derivatives are versatile
reagents for carbon–carbon1–6 and carbon–heteroatom bond
formation,7 and provide an alternative to the reaction of
organotin or -boron compounds. Much attention has been
focused on the use of aryltrialkoxysilanes in palladium-
catalyzed aryl–aryl coupling with aryl halides1,2 and
palladium-3 or rhodium-catalyzed conjugate addition to
a,b-unsaturated carbonyl compounds.4,5 The 1,2-addition
to aldehydes5 and the Heck-type reaction6 are also important
methods for carbon–carbon bond formation. Therefore, the
supply of various functionalized aryltrialkoxysilanes has
become more and more necessary for modern organic
synthesis. The most common method for the synthesis of
aryltriethoxysilanes is based on the reaction of tetraalkyl
orthosilicate with aryl Grignard or lithium reagent (Fig. 1,
Route A).8 However, the protocol has lacked the wide
The palladium(0)-catalyzed cross-coupling reaction of met-
alloidhydridewith organic halides has emergedas apowerful
and atom-economical method for the synthesis of organo-
metalloids. The metalations of organic halides using various
metalloid hydrides, including silicon,9–11 germanium,12
tin,13 and boron compounds,14 have been extensively stud-
ied. In 1997, we demonstrated the first examples of the silyl-
ation of aryl halides 2 with triethoxysilane 1 to provide
aryltriethoxysilanes 3 (Route B).9a Although the reaction
conditions were mild to permit the synthesis of functional-
ized arylsiloxanes 3, the electronic and steric characteristics
of substrateshad a significant impact on the reactions; i.e., the
starting halides were restricted to aryl iodides having elec-
tron-donating groups at para-position. Thereafter, the palla-
dium(0)-catalyzed silylation using 1 has been extended to
aryl bromides and chlorides by other groups,9b,c but there
was no example of the efficient silylation of ortho-substituted
or electron-deficient aryl halides, that is to say, the above
problems were invincible. Further, in the palladium(0)-cata-
lyzed silylation of other hydrosilanes, similar limitation was
pointed out.10
Route A
Ar MgX
Mg
Si(OEt)4
Ar
X
Ar Si(OEt)3
3
2
As a consequence of our reinvestigation of the silylation of
aryl halides 2 using triethoxysilane 1, we found that a rho-
dium(I) complex was one of the efficient catalysts.15,16
Herein, we present a full report of the rhodium(I)-catalyzed
silylation of aryl halides that enables the synthesis of
ortho-, meta-, and para-substituted electron-rich and -poor
arylsiloxanes 3, and successful application of facile aryl
fluoroalkanesulfonates to this reaction. Our present
method overcomes a number of limitations of the
H
Si(OEt)3
1
Route B
Pd catalyst / R3N
Figure 1. Synthesis of aryltriethoxysilanes.
Keywords: Arylsilanes; Hydrosilane; Silylation; Rhodium catalyst.
* Corresponding author. Tel.: +81 157 26 9438; fax: +81 157 26 4973;
e-mail: muratamk@mail.kitami-it.ac.jp
0040–4020/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2007.02.103

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M. Murata et al. / Tetrahedron 63 (2007) 4087–4094
palladium(0)-catalyzed silylation and is the most general
system that is available to date.
8), and pyridine and KOAc completely inhibited the silyla-
tion (entries 7 and 9). Several solvents were tested, and
DMF proved to be the most effective solvent, while the use
of other solvents resulted in slower conversion to product
3a (entries 10–13). Under similar reaction condition to that
used for the above silylation of 2a, replacing the leaving
group of aryl halides with the corresponding bromide 2b
gave lower yields of the desired arylsilane 3a accompanied
by a considerable amount of ethyl benzoate 4a (entry 14).
We then examined a treatment with an additional equal
amount of tetra-n-butylammonium iodide (TBAI), and the si-
lylation proceeded selectively (entry 15).10d Unfortunately,
aryl chloride did not have enough reactivity; i.e., the reaction
of 2c resulted in only 19% conversion and 9% GC yield of
product (entry 16). From the synthetic point of view, the
use of aryl fluoroalkanesulfonates, such as aryl triflates
(X¼OSO2CF3, OTf) and nonaflates (X¼OSO2(CF2)3CF3,
ONf), as aryl electrophiles 2 have some advantages, in part
due to the easy access from phenols.17,18 Although we have
failed in all attempts at the silylation of aryl fluoroalkanesul-
fonates usingthe previous palladium catalyst system, the rho-
dium(I)-catalyzed silylation of aryl triflate 2d and nonaflate
2e could be carried out in good yield when an additional
iodide ion and a reaction temperature of 100 ꢀC were
required (entries 17 and 20). While Rh(acac)(cod) was found
to be effective catalyst for the reactions of 2d, [Rh(cod)-
(MeCN)2]BF4 was ineffective (entry 19).19
2. Results and discussion
In our initial screening experiments, triethoxysilane 1 and
ethyl 4-iodobenzoate 2a were used as substrates for discov-
ery of suitable reaction conditions. The results of screening
of catalyst systems are summarized in Table 1. Treatment
of 2a (1.0 equiv) with 1 (2 equiv) and triethylamine (3 equiv)
in the presence of a rhodium(I) catalyst (3 mol % of rhodium
metal) in DMF at 80 ꢀC was found to lead to the desired ethyl
4-(triethoxysilyl)benzoate 3a. The formation of ethyl benzo-
ate 4a by reduction of the starting 2a was the major side
reaction. As we reported previously, the palladium-catalyzed
reaction of such electron-deficient aryl iodide gave only 23%
yield of the silylated product 3a due to a strong tendency to
produce 4a. [RhCl(cod)]2 was found to exhibit catalytic ac-
tivity, although the yield was moderate (entry 1). Compared
with the chloride complex, cationic [Rh(cod)(MeCN)2]BF4
and acetylacetonato rhodium complexes, Rh(acac)(cod)
and Rh(acac)(CO)2, showed much higher catalytic activity
affording the product 3a in ca. 90% yield (entries 2–4). While
these phosphine-free rhodium complexes proved to be effec-
tive catalysts for the silylation of 2a, phosphine-containing
RhCl(PPh3)3 did not show good catalytic activity (entry 5).
Other conditions in the silylation of 2a were then examined
using [RhCl(cod)]2 as a catalyst. For the present reaction of
2a, tertiary amines were found to be effective as bases ana-
logous to the previous palladium-catalyzed silylation (entry
6); however, K2CO3 decreased theyield and selectivity (entry
The results obtained with representative aryl halides and tri-
flates 2 are listed in Table 2. The presence of functional
groups, such as CO2Et (entry 1), COMe (entries 2–4), and
CN (entry 18), in the starting 2 did not interfere with the
Table 1. Reaction of aryl electrophiles 2a–e with triethoxysilane 1 under various conditionsa
+
+
(EtO)3Si
CO2Et
CO2Et
(EtO)3Si
H
X
CO2Et
1
2a-e
3a
4a
Entry
2, X¼
Catalyst
Base
Solvent
Yieldb (%)
3a
4a
1
2
3
4
5
6
7
8
2a, X¼I
[RhCl(cod)]2
[Rh(cod)(MeCN)2]BF4
Rh(acac)(cod)
Rh(acac)(CO)2
RhCl(PPh3)3
[RhCl(cod)]2
[RhCl(cod)]2
[RhCl(cod)]2
[RhCl(cod)]2
[RhCl(cod)]2
[RhCl(cod)]2
[RhCl(cod)]2
[RhCl(cod)]2
[Rh(cod)(MeCN)2]BF4
[Rh(cod)(MeCN)2]BF4
[Rh(cod)(MeCN)2]BF4
Rh(acac)(cod)
Rh(acac)(cod)
[Rh(cod)(MeCN)2]BF4
Rh(acac)(cod)
Et3N
Et3N
Et3N
Et3N
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
NMP
MeCN
Dioxane
Toluene
DMF
DMF
DMF
DMF
DMF
DMF
DMF
76
88
92
90
15
75
0
22
0
30
28
0
16
12
4
3
Et3N
35
15
6
i-Pr2NEt
Pyridine
K2CO3
KOAc
Et3N
Et3N
Et3N
Et3N
Et3N
Et3N
Et3N
Et3N
Et3N
Et3N
Et3N
19
57
46
17
20
15
49
6
10
3
12
6
9
10
11
12
13
14
15c
16c,d
17c,d
18d
19c,d
20c,d
0
2b, X¼Br
2c, X¼Cl
40
90
9
92
6
2d, X¼OTf
0
90
2e, X¼ONf
4
a
Reactions of 2 (0.25 mmol) with 1 (0.50 mmol) were carried out at 80 ꢀC for 1 h in 1 mL of solvent by using a catalyst (3 mol % of rhodium metal) and a base
(0.75 mmol).
b
c
d
GLC yields are based on 2.
The reaction was performed in the presence of n-Bu4NI (0.25 mmol).
At 100 ꢀC for 16 h.

M. Murata et al. / Tetrahedron 63 (2007) 4087–4094
4089
Table 2. Silylation of various aryl electrophiles 2 with triethoxysilane 1a
Rh(I)catalyst / Et3N
DMF
(EtO)3Si
+
(EtO)3Si
+
H
X
H
R
R
R
1
2
3
4
Entry
1
Aryl electrophiles 2
Product 3
Catalystb
A
Condition
Yieldc (%)
78
2b
3a
80 ꢀC, 1 hd
O
O
I
2f
3f
2
3
4
(EtO)3Si
A
B
B
80 ꢀC, 2 h
75
84
76
Me
Me
2f
3f
3f
80 ꢀC, 2 h
O
100 ꢀC, 16 hd
2g
TfO
Me
2h
80 ꢀC, 2 h
86
90
(9)
(3)
3h
5
6
7
8
A
A
B
B
(EtO)3Si
I
80 ꢀC, 2 h
(EtO)3Si
I
OMe 2i
OMe 2j
OMe
3i
3i
3i
100 ꢀC, 16 hd
100 ꢀC, 16 hd
Br
2k
TfO
OMe
3l
I
(EtO)3Si
(EtO)3Si
2l
9
A
A
80 ꢀC, 2 h
80 ꢀC, 2 h
81
87
Me
Me
2m
3m
I
10
MeO
MeO
(EtO)3Si
I
2n
3n
11
12
A
B
80 ꢀC, 2 h
80 ꢀC, 2 h
72
92
CF3
2n
CF3
3n
Br
2o
13
14
3n
3n
A
B
80 ꢀC, 2 hd
80 ꢀC, 2 hd
70
89
CF3
2o
Br
(EtO)3Si
F
F
2p
3p
15
16
17
18
A
B
A
B
80 ꢀC, 16 hd
80 ꢀC, 16 hd
80 ꢀC, 2 hd
76
85
80
88
F
F
2p
3p
3q
2q
(EtO)3Si
(EtO)3Si
Br
N
N
100 ꢀC, 16 hd
2r
3r
TfO
TfO
CN
Cl
CN
Cl
100 ꢀC, 16 hd
71
3s
19
(EtO)3Si
B
2s
a
All reactions of 2 with 1 (2 equiv) were carried out in DMF by using 3 mol % of the rhodium complex and Et3N (3 equiv).
A: [Rh(cod)(MeCN)2]BF4. B: Rh(acac)(cod).
Isolated yields are based on 2. Those in parentheses are GLC yields.
b
c
d
The reaction was performed in the presence of n-Bu4NI (1 equiv).

4090
M. Murata et al. / Tetrahedron 63 (2007) 4087–4094
Table 3. Effect of other hydrosilanes a
outcome of the present reaction. The previous methods via
Grignard reagents or organolithiums should require the pro-
tection of functional groups frequently.8 Furthermore, in
contrast to the previous palladium-catalyzed silylation,9,10
both the yield and the selectivity in the reaction of aryl
iodides 2 (X¼I) were almost independent of the electronic
and steric requirement. In fact, the differences in the yields
and on the selectivity among aryl iodides having electron-
donating (entry 6) or -withdrawing groups (entry 2, 3, 11,
and 12) were not particularly large. Additionally, sterically
hindered 2l and 2m (entries 9 and 10) were also coupled
with 1 without any difficulty. On the other hand, the silyla-
tion of heteroaryl bromides 2q (entry 17) and electron-
deficient 2b, 2o, and 2p (entries 1 and 13–16) proceeded
smoothly in the presence of TBAI; however, the coupling
of electron-rich 4-bromoanisole 2j was problematic and
starting aryl bromide was recovered (entry 7). Similarly, in
the case of aryl triflate 2 (X¼OTf), the silylation of elec-
tron-deficient substrates could be accomplished (entries 4,
18, and 19); however, the presence of the electron-donating
substituent remarkably decreased the yield of 3 (entry 8).
Compared with the cationic [Rh(cod)(MeCN)2]BF4,
Rh(acac)(cod) showed much higher catalytic activity (en-
tries 3, 12, 14, and 16). As a whole, the desired products 3
were contaminated with small amounts of the reduced by-
products 4 in any case, but their isolation was very easy;
i.e., the desired 3 and reduced arenes 4 were purely separated
by bulb-to-bulb distillation. Accordingly, the present reac-
tion provides a simple and widely available procedure for
synthesizing aryltriethoxysilanes 3.
[Rh(cod)(MeCN)2]BF4 / Et3N
2a
+
H
R3Si
DMF
1a-e
+
4a
R3Si
CO2Et
5a-e
Entry
Hydrosilane
Catalystb
Yieldc (%)
5
4a
1
2
3
4
5
6
7
(MeO)2MeSi–H (1a)
Et3Si–H (1b)
A
B
A
B
A
A
A
40
18
53
5
16
0
19
59
47
39
20
(Me2N)3Si–H (1c)
Cl3Si–H (1d)
Cl2MeSi–H (1e)
Trace
Trace
0
a
Reactions of 2a (0.25 mmol) with hydrosilane (0.50 mmol) were carried
out at 80 ꢀC for 4 h in 1 mL of DMF by using 3 mol % of the rhodium
complex and Et3N (0.75 mmol).
A: [Rh(cod)(MeCN)2]BF4. B: Rh(acac)(cod).
GLC yields are based on 2a.
b
c
Ar Si(OEt)3
3
(EtO)3Si H
1
Rh
X
(EtO)3Si Rh
X
(EtO)3Si Rh X
Ar
H
8
6
Et3N
(EtO)3Si Rh
7
To verify the feasibility of the reaction on a common labora-
tory scale, the silylation of 2a was repeated on a 10 mmol
scale (see Section 4). In this case, the amounts of triethoxy-
silane 1, the catalyst, and the solvent were lowered. Reduc-
ing the amount of the reagents would be desirable to limit the
amount of waste generation from this procedure, especially
if the silylation was performed on a preparative scale. Actu-
ally, the present system was applied to the larger scale syn-
thesis of 3a without any difficulty.
Ar
X
2
Et3NH X
Figure 2. Plausible catalytic cycle for silylation of 2 with 1.
it seems also possible that aryl halide 2 added oxidatively to
the silyl hydrido species 6.11b At present, the mechanism in-
volving the Rh(V) intermediate cannot necessarily be ruled
out.
Finally, we examined the effect of other hydrosilanes under
our optimized conditions. These results are summarized in
Table 3. The use of 1a–c induced lowering of the selectivity
and prevented the formation of the desired arylsilanes 5a–c
(entries 1–5). Additionally, no coupling occurred with halo-
silanes 1d–e and the starting aryl iodide 2a was recovered
(entries 6 and 7). The present study demonstrates that tri-
ethoxysilane 1 selectively acted as a silicon source for the
coupling of aryl electrophiles 2.
Hydrogenolysis of 2, affording a reduced by-product 4,
would occur in the case that reductive elimination of halosi-
lane (EtO)3SiX from 6 or 8 proceeded. The effect of iodide
ion on the reaction of aryl bromide and triflate can be under-
stood in terms of the ligand exchange between iodide ion and
X of the rhodium(III) halide 6 or 8. Recently, Osakada and
co-workers have reported that RhI(H)[Si(OEt)3](PPh3)2
did not undergo coupling of their iodo and silyl ligands,
whereas the formation of (EtO)3SiCl from analogous
RhCl(H)[Si(OEt)3](PPh3)2 took place rapidly.20b In addi-
tion, bearing in mind the previously described result, in
which iodosilane added oxidatively to a transition metal
even in the presence of triethylamine,22 silyl(hydrido)rho-
dium(III) iodide (6, X¼I) may be more favorable for pre-
venting reductive elimination of halosilane (EtO)3SiX.
A plausible reaction pathway is shown in Figure 2, although
there is no clear experimental evidence. Initially, triethoxy-
silane 1 would add to the rhodium(I) catalyst to give a silyl
hydrido species 6,20 followed by reductive elimination of hy-
drogen halide HX, giving a silyl rhodium(I) complex 7. As
the deprotonation of silyl hydrido complexes in the presence
of a base has been known,21 the reductive elimination of HX
may occur with the aid of triethylamine. Then, oxidative ad-
dition of the aryl halide 2 would furnish an arylrhodium(III)
intermediate 8, and subsequent reductive elimination would
lead to the product 3 along with regeneration of the catalyst.
Bearing in mind the quite recently described result, however,
3. Conclusion
We have developed a general method for the silylation of
aryl halides using triethoxysilane as a silylating reagent.
The cross-coupling of aryl iodides with triethoxysilane in

M. Murata et al. / Tetrahedron 63 (2007) 4087–4094
4091
the presence of triethylamine and a catalytic amount of
[Rh(cod)(MeCN)2]BF4 or Rh(acac)(cod) provides the corre-
sponding aryltriethoxysilanes in high yield. The substrate
scope is significantly broader than previous palladium-cata-
lyzed silylation, and includes electron-deficient and ortho-
substituted aryl iodides. In the case of aryl bromides, the
efficient silylation proceeded by a treatment with an addi-
tional equal amount of tetra-n-butylammonium iodide. Ad-
ditionally, in the presence of Rh(acac)(cod) catalyst and
iodide anion, the silylation of aryl fluoroalkanesulfonates
was achieved.
1279, 1101 cmꢁ1. 1H NMR (CDCl3): d¼1.24 (t, J¼7.0 Hz,
9H), 1.47 (t, J¼7.0 Hz, 3H), 3.88 (q, J¼7.0 Hz, 6H), 4.39
(q, J¼7.0 Hz, 2H), 7.74 (d, J¼8.2 Hz, 2H), 8.04 (d,
J¼8.2 Hz, 2H). 13C NMR (CDCl3): d¼10.29, 14.16, 54.84,
56.96, 124.55, 128.05, 130.70, 132.94, 162.63. EIMS: m/z
(%)¼312 (5, [M+]), 267 (100), 253 (15), 239 (61), 223
(16), 195 (22), 183 (17), 163 (25), 147 (20). HRMS (EI):
m/z calcd for C15H24O5Si [M+]: 312.1393; found: 312.1392.
4.3.2. 4-(Triethoxysilyl)acetophenone (3f).9b Following
the typical procedure, 3f was prepared starting from 2f
(60.7 mg, 0.247 mmol) as a colorless oil. The product was
purified by distillation to afford 52.5 mg (75% yield). The
reaction of 2f (124.3 mg, 0.505 mmol) using Rh(acac)(cod)
catalyst instead of [Rh(cod)(MeCN)2]BF4 gave 120.4 mg
(84% yield) of the title compound. Also, the silylation of
2g (270.0 mg, 1.01 mmol) was carried out at 100 ꢀC using
Rh(acac)(cod) (0.03 mmol) and TBAI (1.0 mmol) to afford
214.8 mg (76% yield) of 3f. IR (neat): 2977, 2928, 2890,
4. Experimental
4.1. General information
All the experiments were carried out under an argon atmo-
sphere using oven-dried (120 ꢀC) glassware. IR spectra
were taken with a Perkin–Elmer System 2000 FTIR spec-
trometer. NMR spectra were recorded on a JNM-A500 spec-
trometer (1H, 500 MHz; 13C, 125 MHz). Chemical shifts of
1H NMR and 13C NMR signals reported d parts per million
referenced to CHCl3 (7.26 and 77.0) or an internal SiMe4.
Mass spectra were obtained at an ionization potential of
70 eV with a JEOL JMS-SX102 spectrometer. GLC analyses
were carried out with a Shimadzu GC-14B equipped with
a glass column (OV-17 on Chromosorb W, 2 m). GLC yields
were determined using suitable hydrocarbons as internal
standards.
1
1689, 1390, 1359, 1265, 1078 cmꢁ1. H NMR (CDCl3):
d¼1.25 (t, J¼7.0 Hz, 9H), 2.62 (s, 3H), 3.88 (q, J¼7.0 Hz,
6H), 7.78 (d, J¼8.3 Hz, 1H), 7.94 (d, J¼8.3 Hz, 1H). 13C
NMR (CDCl3): d¼18.19, 26.69, 58.88, 127.28, 135.02,
137.29, 138.31, 198.41. EIMS: m/z (%)¼282 (9, [M+]),
267 (100), 238 (69), 223 (18), 209 (14). HRMS (EI): m/z
calcd for C14H22O4Si [M+]: 282.1287; found: 282.1284.
4.3.3. Phenyltriethoxysilane (3h).8b Following the typical
procedure, 3h was prepared starting from 2h (203.8 mg,
1.00 mmol). The product was purified by distillation to af-
ford 206.8 mg (86% yield) as a colorless oil. IR (neat):
2976, 2928, 2886, 1594, 1483, 1431, 1391, 1295, 1168,
4.2. Materials
1129, 1103, 1080 cmꢁ1
.
1H NMR (CDCl3): d¼1.25 (t,
N,N-Dimethylformamide (DMF) was distilled from CaH2
before use. Hydrosilanes, aryl halides, triethylamine, and
tetra-n-butylammonium iodide (TBAI) were purchased
from commercial sources, and used without purification.
Aryl triflates were obtained from the corresponding phenols
and trifluoromethanesulfonic anhydride.17 All rhodium
complexes were commercial products except for [Rh(cod)-
(MeCN)2]BF4, which was prepared by the known method.23
J¼7.0 Hz, 9H), 3.88 (q, J¼7.0 Hz, 6H), 7.3–7.5 (m, 3H),
7.6–7.8 (m, 2H). 13C NMR (CDCl3): d¼18.12, 58.68,
127.78, 130.22, 131.08, 134.74. EIMS: m/z (%)¼240 (16,
[M+]), 195 (38), 181 (13), 162 (28), 147 (100), 139 (33),
135 (33). HRMS (EI): m/z calcd for C12H20O3Si [M+]:
240.1182; found: 240.1141.
4.3.4. 4-(Triethoxysilyl)anisole (3i).8b Following the typi-
cal procedure, 3i was prepared starting from 2i (57.7 mg,
0.247 mmol). The product was purified by distillation to af-
ford 59.9 mg (90% yield) as a colorless oil. IR (neat): 2975,
4.3. Synthesis of aryltriethoxysilane: typical procedure
[Rh(cod)(MeCN)2]BF4 (0.03 mmol), aryl electrophile 2
(1.0 mmol) (if a solid), and TBAI (1 mmol) (when aryl bro-
mide or triflate was used as 2) were placed in a test tube
capped with a septum rubber. The tube was evacuated and
backfilled with argon, and then charged with DMF (4 mL).
Triethylamine (3 mmol), 2 (1.0 mmol) (if a liquid), and tri-
ethoxysilane 1 (2 mmol) were added by a syringe through
the septum rubber. The reaction mixture was then stirred at
80–100 ꢀC. After the reaction, the mixture was diluted with
ether, washed three times with H2O to remove DMF, and
dried over Na2SO4. The solvent was removed under reduced
pressure, and the residue was purified by Kugelrohr distilla-
tion to give the desired aryltriethoxysilane 3.
2360, 1598, 1567, 1506, 1459, 1390, 1282, 1250 cmꢁ1
.
1H NMR (CDCl3): d¼1.24 (t, J¼7.0 Hz, 9H), 3.82 (s,
3H), 3.85 (q, J¼7.0 Hz, 6H), 6.92 (d, J¼8.5 Hz, 2H),
7.61 (d, J¼8.5 Hz, 2H). 13C NMR (CDCl3): d¼18.12,
54.89, 58.55, 113.57, 122.00, 136.37, 161.37. EIMS: m/z
(%)¼270 (52, [M+]), 255 (53), 225 (38), 211 (25), 181
(28), 169 (27), 149 (22), 147 (100), 135 (32). HRMS (EI):
m/z calcd for C13H22O4Si [M+]: 270.1287; found: 270.1261.
4.3.5. 2-Tolyltriethoxysilane (3l).8b Following the typical
procedure, 3l was prepared starting from 2l (54.1 mg,
0.248 mmol). The product was purified by distillation to af-
ford 51.1 mg (81% yield) as a colorless oil. IR (neat): 2975,
2928, 2886, 1594, 1442, 1391, 1285, 1167, 1138, 1103,
4.3.1. Ethyl 4-(triethoxysilyl)benzoate (3a).9a The typical
procedure was followed using 2b (229.1 mg, 1.00 mmol)
and TBAI (1.0 mmol). The product was purified by distilla-
tion to afford 243.1 mg (78% yield) as a colorless oil. IR
(neat): 2977, 2928, 2361, 1720, 1558, 1445, 1391, 1367,
1079 cmꢁ1. H NMR (CDCl3): d¼1.25 (t, J¼7.0 Hz, 9H),
1
2.51 (s, 3H), 3.86 (q, J¼7.0 Hz, 6H), 7.1–7.2 (m, 2H),
7.32 (t, J¼7.3 Hz, 1H), 7.72 (d, J¼7.3 Hz, 1H). 13C NMR
(CDCl3): d¼18.17, 22.39, 58.48, 124.64, 129.69, 129.82,
130.46, 136.46, 144.51. EIMS: m/z (%)¼254 (68, [M+]),

4092
M. Murata et al. / Tetrahedron 63 (2007) 4087–4094
209 (65), 195 (25), 181 (22), 162 (74), 147 (100), 135 (50),
119 (67). HRMS (EI): m/z calcd for C13H22O3Si [M+]:
254.1338; found: 254.1323.
to afford 46.9 mg (80% yield) as a colorless oil. IR (neat):
2977, 2929, 2890, 1578, 1561, 1395, 1167, 1138,
1
1080 cmꢁ1. H NMR (CDCl3): d¼1.26 (t, J¼7.0 Hz, 9H),
3.89 (q, J¼7.0 Hz, 6H), 7.29 (dd, J¼7.4, 4.9 Hz, 1H), 7.95
(d, J¼7.4 Hz, 1H), 8.65 (d, J¼4.9 Hz, 1H), 8.83 (s, 1H).
13C NMR (CDCl3): d¼18.04, 58.80, 123.07, 126.55,
142.36, 151.05, 154.99. EIMS: m/z (%)¼241 (54, [M+]),
240 (100), 226 (18), 212 (27), 196 (88), 147 (29), 182 (25).
HRMS (EI): m/z calcd for C11H19O3NSi [M+]: 241.1134;
found: 241.1112.
4.3.6. 2-(Triethoxysilyl)anisole (3m).8b Following the typi-
cal procedure, 3m was prepared starting from 2m (231.0 mg,
0.987 mmol). The product was purified by distillation to af-
ford 231.6 mg (87% yield) as a colorless oil. IR (neat):
2975, 2928, 2891, 1592, 1573, 1476, 1429, 1391, 1244,
1
1168, 1104, 1081 cmꢁ1. H NMR (CDCl3): d¼1.23 (t, J¼
7.0 Hz, 9H), 3.83 (s, 3H), 3.88 (q, J¼7.0 Hz, 6H), 6.85 (d,
J¼8.2 Hz, 1H), 6.96 (dd, J¼7.0, 7.0 Hz, 1H), 7.40 (dd, J¼
8.2, 7.0 Hz, 1H), 7.65 (d, J¼7.0 Hz, 1H). 13C NMR
(CDCl3): d¼18.20, 55.09, 58.65, 109.62, 119.30, 120.48,
132.14, 137.54, 164.37. EIMS: m/z (%)¼270 (42, [M+]),
255 (33), 181(42), 151 (33), 147 (100), 139 (40). HRMS (EI):
m/z calcd for C13H22O4Si [M+]: 270.1287; found: 270.1274.
4.3.10. 4-(Triethoxysilyl)benzonitrile (3r).9a Following
the typical procedure, the silylation of 2r (248.2 mg,
0.988 mmol) was carried out at 100 ꢀC using Rh(acac)(cod)
(0.03 mmol) and TBAI (1.0 mmol) to afford 230.0 mg (88%
yield) of 3r as a colorless oil. IR (neat): 2977, 2231, 1444,
1390, 1296 cmꢁ1. 1H NMR (CDCl3): d¼1.25 (t, J¼7.0 Hz,
9H), 3.88 (q, J¼7.0 Hz, 6H), 7.65 (d, J¼8.3 Hz, 2H), 7.78
(d, J¼8.3 Hz, 2H). 13C NMR (CDCl3): d¼18.16, 59.04,
113.93, 131.12, 135.23, 137.88, 159.74. EIMS: m/z (%)¼
265 (43, [M+]), 250 (17), 220 (100), 206 (46), 192 (20),
176 (34), 164 (62). HRMS (EI): m/z calcd for C13H19O3NSi
[M+]: 265.1134, found: 265.1144.
4.3.7. 3-(Triethoxysilyl)benzotrifluoride (3n). Following
the typical procedure, 3n was prepared starting from 2n
(137.4 mg, 0.505 mmol). The product was purified by distil-
lation to afford 111.6 mg (72% yield) as a colorless oil. The
reaction of 2n (136.7 mg, 0.503 mmol) using Rh(acac)(cod)
catalyst instead of [Rh(cod)(MeCN)2]BF4 gave 143.4 mg
(92% yield) of the title compound. Also, the silylation of
2o (227.1 mg, 1.01 mmol) was carried out at 80 ꢀC using
TBAI (1.0 mmol) to afford 218.8 mg (70% yield) of 3n,
and the reaction of 2o (113.7 mg, 0.505 mmol) using
Rh(acac)(cod) catalyst gave 139.5 mg (89% yield) of 3n.
IR (neat): 2978, 2930, 2892, 1607, 1511, 1393, 1329, 1275,
4.3.11. 4-Chloro(triethoxysilyl)benzene (3s).9a Following
the typical procedure, the silylation of 2s (257.6 mg,
0.937 mmol) was carried out at 100 ꢀC using Rh(acac)(cod)
(0.03 mmol) and TBAI (1.0 mmol) to afford 174.2 mg (71%
yield) of 3s as a colorless oil. IR (neat): 2975, 2888, 2360,
1
1699, 1583, 1557, 1485, 1443, 1389, 1296, 1261 cmꢁ1. H
1169, 1131, 1078 cmꢁ1
.
1H NMR (CDCl3): d¼1.26 (t,
NMR (CDCl3): d¼1.17 (t, J¼7.0 Hz, 9H), 3.79 (q, J¼
7.0 Hz, 6H), 7.28 (d, J¼8.5 Hz, 2H), 7.54 (d, J¼8.5 Hz,
2H). 13C NMR (CDCl3): d¼18.12, 58.75, 128.06, 129.53,
136.13, 136.70. EIMS: m/z (%)¼274 (3, [M+]), 239 (27),
229 (44), 185 (15), 173 (25), 162 (31), 147 (100), 135 (9).
HRMS (EI): m/z calcd for C12H19O3ClSi [M+]: 274.0792;
found: 274.0792.
J¼7.0 Hz, 9H), 3.89 (q, J¼7.0 Hz, 6H), 7.50 (t, J¼7.6 Hz,
1H), 7.68 (d, J¼7.6 Hz, 1H), 7.85 (d, J¼7.6 Hz, 1H), 7.92
(s, 1H). 13C NMR (CDCl3): d¼17.86, 58.71, 124.17 (q,
J¼272.4 Hz), 126.71 (q, J¼4.1 Hz), 127.97, 129.94 (q,
J¼32.1 Hz), 131.08 (q, J¼2.1 Hz), 132.68, 137.89. EIMS:
m/z (%)¼308 (2, [M+]), 293 (15), 263 (100), 249 (38), 235
(15), 219 (26), 207 (49), 191 (24), 181 (56), 163 (18), 154
(24), 147 (26). HRMS (EI): m/z calcd for C13H19F3O3Si
[M+]: 308.1056; found: 308.1083.
4.3.12. Ethyl 4-(methyldimethoxysilyl)benzoate (5a). The
typical procedure was followed using 1a as a silicon source
and aryl iodide 2a. IR (neat): 2978, 2838, 1720, 1391,
1
4.3.8. 3,4-Difluorophenyltriethoxysilane (3p). The typical
procedure was followed using 2p (47.5 mg, 0.246 mmol)
and TBAI (0.25 mmol). The product was purified by dis-
tillation to afford 51.4 mg (76% yield) as a colorless oil.
Also, the reaction of 2p (97.1 mg, 0.503 mmol) using
Rh(acac)(cod) catalyst instead of [Rh(cod)(MeCN)2]BF4
gave 117.7 mg (85% yield) of the title compound. IR
(neat): 2978, 2929, 2891, 1607, 1511, 1392, 1275, 1168,
1280, 1090 cmꢁ1. H NMR (CDCl3): d¼0.40 (s, 3H), 1.40
(t, J¼7.3 Hz, 3H), 3.57 (s, 6H), 4.39 (q, J¼6.8 Hz, 2H),
7.70 (d, J¼7.9 Hz, 2H), 8.05 (d, J¼7.9 Hz, 2H). 13C NMR
(CDCl3): d¼ꢁ5.21, 14.31, 50.59, 61.03, 128.66, 131.86,
133.95, 139.49, 166.61. EIMS: m/z (%)¼254 (7, [M+]), 239
(100), 209 (20), 181 (10), 119 (7), 105(35). HRMS (EI): m/z
calcd for C12H18O4Si [M+]: 254.0974, found: 254.1003.
1
1089 cmꢁ1. H NMR (CDCl3): d¼1.25 (t, J¼7.0 Hz, 9H),
4.3.13. Ethyl 4-(triethylsilyl)benzoate (5b). The typical
procedure was followed using 1b as a silicon source and
aryl iodide 2a. IR (neat): 2955, 1721, 1599, 1588, 1557,
3.86 (q, J¼7.0 Hz, 6H), 7.18 (dt, J¼10.3, 7.9 Hz, 1H),
7.39 (br s, 1H), 7.46 (t, J¼10.3 Hz, 1H). 13C NMR
(CDCl3): d¼18.29, 59.05, 117.42 (d, J¼15.5 Hz), 123.60
(dd, J¼18.5, 2.1 Hz), 131.4 (d, J¼4.1 Hz), 131.5 (d,
J¼4.1 Hz), 150.47 (dd, J¼250.3, 12.4 Hz), 152.18 (dd,
J¼251.4, 12.4 Hz). EIMS: m/z (%)¼276 (15, [M+]), 261
(17), 231 (100), 217 (31), 203 (16), 187 (27), 175 (53),
162 (55), 147 (71). HRMS (EI): m/z calcd for C12H18F2O3Si
[M+]: 276.0994; found: 276.0980.
1
1463, 1416, 1389, 1367, 1278 cmꢁ1. H NMR (CDCl3):
d¼0.81 (q, J¼7.7 Hz, 6H), 0.96 (t, J¼7.6 Hz, 9H), 1.39 (t,
J¼7.3 Hz, 3H), 4.38 (q, J¼7.1 Hz, 2H), 7.56 (d, J¼7.9 Hz,
2H), 8.00 (d, J¼7.9 Hz, 2H). 13C NMR (CDCl3): d¼3.17,
7.30, 14.34, 60.86, 128.34, 130.58, 134.11, 143.88, 166.86.
EIMS: m/z (%)¼264 (3, [M+]), 235 (85), 207 (100), 133
(8), 115 (3), 104 (45), 57 (4). HRMS (EI): m/z calcd for
C15H24O2Si [M+]: 264.1546, found: 264.1523.
4.3.9. 3-Pyridyltriethoxysilane (3q).9a The typical proce-
dure was followed using 2q (39.5 mg, 0.250 mmol) and
TBAI (0.25 mmol). The product was purified by distillation
4.3.14. Ethyl 4-tris(dimethylamino)silylbenzoate (5c).
The typical procedure was followed using 1d as a silicon

M. Murata et al. / Tetrahedron 63 (2007) 4087–4094
4093
8. (a) Selin, T. G.; West, R. J. Am. Chem. Soc. 1962, 84, 1856; (b)
Manoso, A. S.; Ahn, C.; Soheili, A.; Handy, C. J.; Correia, R.;
Seganish, W. M.; DeShong, P. J. Org. Chem. 2004, 69, 8305;
(c) Lee, A. S.-Y.; Chang, Y.-T.; Chu, S.-F.; Tsao, K.-W.
Tetrahedron Lett. 2006, 47, 7085.
9. For the synthesis of aryltrialkoxysilanes, see: (a) Murata, M.;
Suzuki, K.; Watanabe, S.; Masuda, Y. J. Org. Chem. 1997,
62, 8569; (b) Manoso, A. S.; DeShong, P. J. Org. Chem.
2001, 66, 7455; (c) Komuro, K.; Ishizaki, K.; Suzuki, H.
Touagousei-kenkyu-nenpo 2003, 6, 24.
source and aryl iodide 2a. IR (neat): 3545, 2838, 1722, 1464,
1279, 1176, 1091 cmꢁ1
.
1H NMR (CDCl3): d¼1.39 (t,
J¼7.0 Hz, 3H), 2.52 (s, 18H), 4.38 (q, J¼7.1 Hz, 2H),
7.63 (d, J¼7.9 Hz, 2H), 7.99 (d, J¼7.9 Hz, 2H). 13C NMR
(CDCl3): d¼14.33, 38.01, 60.80, 128.17, 130.53, 135.17,
142.83, 166.93. EIMS: m/z (%)¼309 (53, [M+]), 265
(100), 264 (25), 221 (33), 148 (15), 72 (16). HRMS (EI):
m/z calcd for C15H27O2N3Si [M+]: 309.1873, found:
309.1904.
10. For other examples of the palladium(0)-catalyzed silylation of
organic halides, see: (a) Murata, M.; Watanabe, S.; Masuda, Y.
Tetrahedron Lett. 1999, 40, 9255; (b) Denmark, S. E.;
Kallemeyn, J. M. Org. Lett. 2003, 5, 3483; (c) Yamanoi, Y.
J. Org. Chem. 2005, 70, 9607; (d) Murata, M.; Ohara, H.;
Oiwa, R.; Watanabe, S.; Masuda, Y. Synthesis 2006, 1771.
11. Quite recently, platinum- and rhodium-catalyzed silylations
using Et3SiH have been reported: (a) Hamze, A.; Provot, O.;
Alami, M.; Brion, J.-D. Org. Lett. 2006, 8, 931; (b)
Karshtedt, D.; Bell, A. T.; Tilley, T. D. Organometallics
2006, 25, 4471; (c) Yamanoi, Y.; Nishihara, H. Tetrahedron
Lett. 2006, 47, 7157.
4.4. Procedure for the large-scale preparation
of aryltriethoxysilane
A flask with a septum inlet was charged with Rh(acac)(cod)
(62 mg, 0.2 mmol) and a magnetic stirring bar, and then
flushed with nitrogen. DMF (10 mL), Et3N (4.2 mL,
30 mmol), 2a (2.82 g, 10 mmol), and 1 (2.8 mL, 15 mmol)
were added by syringe. After being stirred for 16 h at
80 ꢀC, the mixture was extracted with ether (20 mL). The
extract was washed with H2O (10 mL), dried over Na2SO4,
and concentrated. The residue was purified by Kugelrohr
distillation to give 2.38 g (78% yield) of 3a.
12. Nakamura, T.; Kinoshita, H.; Shinokubo, H.; Oshima, K. Org.
Lett. 2002, 4, 3165.
13. Murata, M.; Watanabe, S.; Masuda, Y. Synlett 2000, 1043.
14. (a) Murata, M.; Watanabe, S.; Masuda, Y. J. Org. Chem. 1997,
62, 6458; (b) Murata, M.; Oyama, T.; Watanabe, S.; Masuda, Y.
J. Org. Chem. 2000, 65, 164; (c) Murata, M.; Oyama, T.;
Watanabe, S.; Masuda, Y. Synthesis 2000, 778; (d) Baudoin,
Acknowledgements
This work was partially supported by a Grant-in-Aid for En-
couragement of Young Scientists (B) from the Ministry of
Education, Culture, Sports, Science and Technology, Japan
(No. 16750069).
ꢀ
ꢀ
O.; Guenard, D.; Gueritte, F. J. Org. Chem. 2000, 65, 9268;
(e) Murata, M.; Oyama, T.; Watanabe, S.; Masuda, Y. Synth.
ꢁ
Commun. 2002, 32, 2513; (f) Broutin, P.-E.; Cern˜a, I.;
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