Palladium-Catalyzed Silylation of Aryl Chlorides with Bulky Dialkoxydisilanes

Article abstract of DOI:10.1055/s-0039-1690877

Arylsilanes bearing a bulky alkoxy group on the silicon were synthesized from aryl chlorides and dialkoxydisilanes under reaction conditions utilizing SingaCycle-A3 as a palladium precatalyst and lithium benzoate in wet DMA. This report proposes the first direct and catalytic method for introducing tert -butoxy- or 1-adamantyloxysilyl groups onto various aryl moieties through the silylation reaction.

Full text of DOI:10.1055/s-0039-1690877

SYNLETT
0
9
3
6
-
5
2
1
4
1
4
3
7
-
2
0
9
6
©
Georg Thieme Verlag Stuttgart · New York
2020, 31, A–E
letter
A
en
Synlett
K. Fukui et al.
Letter
Palladium-Catalyzed Silylation of Aryl Chlorides with Bulky
Dialkoxydisilanes
iPr
iPr
Keitaro Fukui
Hayate Saito
N
N
iPr
Cl Pd
iPr
O
0
0
0
0-
0
0
0
2-4
5
4
9-7
9
1
7
Jun Shimokawa*
Hideki Yorimitsu*
0
0
0
0-
0
0
0
2-4
0
2
3-4
6
4
0
NH
0
0
0
0-0
0
0
2-0
1
5
3-1
8
8
8
Cl
Si
Si Si
cat. SingaCycle-A3
LiOBz, wet DMA
OtBu
Department of Chemistry, Graduate School of Science,
Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
shimokawa@kuchem.kyoto-u.ac.jp
+
R
R
tBuO
OtBu
100 °C, 12 h
up to 84%
yori@kuchem.kyoto-u.ac.jp
R = electron-withdrawing
electron-neutral
Received: 02.03.2020
Accepted after revision: 18.03.2020
Published online: 02.04.2020
icon source for our cross-coupling-type silylation reaction.
Compound 5 can be easily prepared in one step, and this
3b
DOI: 10.1055/s-0039-1690877; Art ID: st-2020-u0123-l
reagent is now commercially available. Among the previ-
ously reported conditions for silylation between an aryl ha-
Abstract Arylsilanes bearing a bulky alkoxy group on the silicon were
synthesized from aryl chlorides and dialkoxydisilanes under reaction
conditions utilizing SingaCycle-A3 as a palladium precatalyst and lithi-
um benzoate in wet DMA. This report proposes the first direct and cat-
alytic method for introducing tert-butoxy- or 1-adamantyloxysilyl
groups onto various aryl moieties through the silylation reaction.
5d,7g,7i–l
lide and a dialkoxydisilane
, Denmark’s seminal work
was the first and only method to introduce an alkoxysilyl
group (Scheme 1, eq. 1) wherein aryl bromide 1 reacted
with diethoxydisilane 2 using a PdCl /JohnPhos catalytic
2
5d
system to give arylsilane 3. As such, introduction of a silyl
group with a more bulky tertiary alkoxy group such as tBuO
has yet to be reported. Herein, we report our research on a
Key words palladium, alkoxysilane, disilane, arylsilane
palladium-catalyzed method for introducing a tBuOMe Si
2
Due to their unique chemical reactivity and potential
synthetic utility, organosilicon compounds have frequently
been the target of synthetic studies. In the current frame-
group through the silylation of aryl chloride with the corre-
sponding disilane 5 (Scheme 1, eq. 2).
1
1) Denmark’s seminal work on silylation with diethoxydisilane
work of organic synthesis, silicon functional groups should
become more balanced in terms of stability and ease of ac-
tivation. Some are rather too stable for facile transforma-
tions; others are too labile to manage during standard syn-
thetic manipulations. Therefore, prompting better balances
between stability and ease of activation would widen the
possibility of using silyl groups as alternative key functional
groups in organic synthesis. One of the promising solutions
to this dilemma is the use of bulky alkoxy substituents to
1.5 equiv
Si Si
EtO
OEt
Br
2
Si
OEt
3.0 equiv iPr2EtN
5 mol% PdCl2
0 mol% JohnPhos
EtO2C
EtO2C
1
1
3
NMP, rt, 30 min
2
) This work
2
balance them. Our research focus has thus turned to a
1.5 equiv
Si Si
3,4
tBuOMe Si group, as a candidate for such a balanced func-
2
tBuO
OtBu
Cl
5
Si
tional group. The special feature of this silyl group is its ex-
ceptional stability against water or bases in contrast to oth-
er labile primary or secondary alkoxy silyl groups. This silyl
group is therefore expected to serve as a reliable functional
group that can survive during multistep synthetic transfor-
mations. We accordingly focused on the development of a
OtBu
1.5 equiv LiOBz
3 mol% SingaCycle-A3
mol% H2O
EtO2C
a: 0.5 mmol
(0.17 M)
EtO2C
5
4
6a
DMA, 100 °C, 12 h
Scheme 1 Catalytic alkoxysilylation of aryl halide with dialkoxydisilane
general method to introduce a tBuOMe Si group via silyla-
2
tion of aryl halides. Typical silylation reagents for aryl ha-
lides include hydrosilanes, silylboranes, and disilanes.
We chose to employ the corresponding disilane 5 as the sil-
As a result of our optimization of palladium-catalyzed
silylation of ethyl p-chlorobenzoate (4a) with disilane 5, we
eventually devised the standard conditions for the reaction:
5
6
5d,7
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2020. Thieme. All rights reserved. Synlett 2020, 31, A–E
Georg Thieme Verlag KG, Rüdigerstraße 14, 70469 Stuttgart, Germany

B
Synlett
K. Fukui et al.
Letter
8
4
a (0.17 M), 1.5 equiv disilane 5, 3 mol% SingaCycle-A3 , 1.5
sluggish (entries 3, 4). With JohnPhos that gave a good re-
sult in Denmark’s report, a low conversion was observed
9
5d
equiv LiOBz , 5 mol% H O, DMA, 100 °C, 12 h. Table 1 shows
2
results associated with differences based on the deviations
listed. Under the standard conditions, arylsilane 6a was ob-
tained in 75% NMR yield (75% isolated yield) along with the
formation of the corresponding homocoupling product, di-
ethyl 1,1′-biphenyl-4,4′-dicarboxylate, in 4% yield. Pd-
PEPPSI-IPr was also applicable albeit with a slower reac-
tion rate (entry 2). When the ligand was changed to tBu-
DavePhos or CyJohnPhos, the reaction became even more
(entry 5).
The amount of the base heavily affected the reaction
outcome. With 0.1 equiv of LiOBz, the minimum necessary
amount for activating SingaCycle-A3, only a 13% yield of the
product was obtained (Table 1, entry 6). This is in contrast
with our previous report on the base-free silylation of aryl
chloride with silylsilatrane,7 in which we proposed the re-
action proceeds through the four-membered transition
10
m
Table 1 Optimization of Silylation Conditions
1.5 equiv
Si Si
tBuO
OtBu
Cl
Si
5
OtBu
1
3
5
.5 equiv LiOBz
mol% SingaCycle-A3
mol% H2O
EtO2C
a: 0.5 mmol
0.17 M)
EtO C
2
4
6a
DMA, 100 °C, 12 h
(
Entry
Deviations from the standard conditions
Yield (%)a
4
a
6a
75 (75b)
Biaryl
1
2
3
4
5
6
7
8
9
none
0
4
2
Pd-PEPPSI-IPr instead of SingaCycle-A3
7
20
12
57
59
84
12
5
65
48
49
17
13
3
3.0 mol% tBuDavePhos, 1.5 mol% Pd
3.0 mol% CyJohnPhos, 1.5 mol% Pd (dba)
3.0 mol% JohnPhos, 1.5 mol% Pd (dba)
0.1 equiv instead of 1.5 equiv LiOBz
Et N instead of LiOBz
2
(dba)
3
instead of SingaCycle-A3
3
2
3
instead of SingaCycle-A3
6
2
3
instead of SingaCycle-A3
<1
0
3
0
LiOAc instead of LiOBz
LiOPiv instead of LiOBz
55
53
12
54
31
71
50
0
1
1
10
11
12
13
14
15
Li
2
CO
3
instead of LiOBz
68
0
0
NaOBz instead of LiOBz
KOBz instead of LiOBz
NMP instead of DMA
11
43
<1
3
0
0
DMF instead of DMA
29
90
1,4-dioxane instead of DMA
0
iPr
iPr
iPr
iPr
N
N
N
N
iPr
Cl
iPr
iPr
iPr
Cl
Pd
O
Cl
Pd
N
NH
Cl
Pd-PEPPSI-IPr
SingaCycle-A3
PtBu2
PCy2
PtBu2
Me2N
tBuDavePhos
CyJohnPhos
JohnPhos
a
1
Determined by H NMR analysis using 1,3,5-trimethoxybenzene or mesitylene as an internal standard.
Isolated yield.
b
©
2020. Thieme. All rights reserved. Synlett 2020, 31, A–E

C
Synlett
K. Fukui et al.
Letter
current transformation, though the exact reason is unclear.
Thus, the conditions in Table 1, entry 1 were confirmed to
be optimal.
1
.5 equiv
Si Si
tBuO
OtBu
Cl
Si
5
OtBu
R
1.5 equiv LiOBz
R
3
5
mol% SingaCycle-A3
mol% H2O
1.5 equiv
Si Si
4
: 0.5 mmol
6
EtO
OEt
DMA, 100 °C, 12–60 h
Cl
2
Si
(
0.17 M)
OEt
1
3
.5 equiv LiOBz
mol% SingaCycle-A3
EtO2C
4a: 0.5 mmol
0.17 M)
5 mol% H2O
EtO2C
1%a
Si
Si
Si
3
6
DMA, 100 °C, 12 h
OtBu
OtBu
OtBu
OtBu
OtBu
(
6b
NC
6c
6d
O
O
6
9%
77%
84%
1.5 equiv
Si Si
O
O
Si
Si
Si
7
Si
OtBu
O
H
1.5 equiv LiOBz
3 mol% SingaCycle-A3
F3C
EtO2C
8
46%
6
e
6f
6g
5
mol% H2O
O
6
6%
68%
60%
DMA, 100 °C, 20 h
Scheme 3 Silylation with diethoxy- or diadamantyloxydisilane. a Deter-
mined by GC analysis.
Si
Si
Si
OtBu
OtBu
OtBu
O
Scheme 2 shows the substrate scope under the opti-
mized conditions. Silylation products were obtained in
good yields when the para position was substituted with
B
F
O2N
6
h
6i
24% (51%)a
6j
O
2
7% (69%)a
0%
75% recovered SM)
(
11
electron-withdrawing groups such as acetyl (6b ), cyano
12
(
6c ), benzoyl (6d), CF (6e), and formyl (6f). A naphthyl
3
Si
Si
Si
substituent was also applicable (6g). It is intriguing that the
Bpin substituent in 6h survived the reaction conditions al-
though some decomposition, probably at the boron unit,
was observed during purification on silica gel. Fluoro-sub-
stituted product 6i was obtained albeit with a loss of the
material and was obtained in only a 24% yield. With a nitro
group, none of product 6j was observed while most of the
aryl chloride starting material was recovered. With an elec-
tron-donating methyl (6d) or methoxy (6h) substituents,
conversion was very sluggish. Product bearing m-ethoxy-
carbonyl group (6n) or m-cyano group (6o) was obtained in
moderate yield. The ortho substitution seems to be retard-
ing the silylation, and no ethoxycarbonyl product 6p was
observed. Heteroaromatic substrate (2-chloroquinoline) or
alkenyl chloride (4-tert-butyl-1-chlorocyclohex-1-ene)
gave no corresponding silylated product.
OtBu
OtBu
OtBu
tBuO
6
k
MeO
(
6l
Si
6
m
4%b
trace
47% recovered SM)
42%
2
EtO2C
EtO2C
Si
NC
Si
Si
OtBu
OtBu
OtBu
6
n
6o
6p
5
5%
60%
0%
79% recovered SM)
(
Scheme 2 Scope of reaction with respect to aryl chloride. Reagents and
conditions: 4 (0.5 mmol, 0.17 M), 5 (1.5 equiv), SingaCycle-A3 (3 mol%),
LiOBz (1.5 equiv), H O (5 mol%), DMA, 100 °C, 12–60 h. Isolated yields
are given. Determined by H NMR analysis using 1,3,5-trimethoxyben-
zene or mesitylene as an internal standard. SingaCycle-A3 (6 mol%).
2
a
1
b
state. The screening of bases disclosed Et N to be ineffective
in the current transformation (entry 7). Lithium acetate or
pivalate showed a lower efficiency compared to benzoate
3
[Pd0]
11
BzO Si
15
Ar Cl
4
oxidative
addition
(entries 8, 9). A much lower yield was observed with lithi-
reductive
elimination
II
um carbonate, indicating the importance of carboxylate
bases (entry 10). Sodium and potassium benzoates did not
give better yields than lithium benzoate (entries 11, 12).
Other solvents were also examined. The reaction efficiency
is similar in NMP (entry 13), and a slower reaction was ob-
served in DMF (entry 14). The reaction completely stopped
in 1,4-dioxane (entry 15). Under strictly dehydrated condi-
tions, the reduced conversion rate was observed to indicate
the importance of water for the reproducible results in the
Ar [Pd ] Cl
12
LiO
O
II
BzO [Pd ] Si
Ph
14
ligand
exchange
reductive
elimination
oxidative
addition
LiCl
Ar Si
6
Si
Ar [PdIV] Si
Si Si
5
OBz13
Scheme 4 Proposed reaction mechanism
©
2020. Thieme. All rights reserved. Synlett 2020, 31, A–E

D
Synlett
K. Fukui et al.
Letter
Other dialkoxydisilanes could also be used for this si-
lylation reaction (Scheme 3). 1,2-Diethoxy-1,1,2,2-te-
tramethyldisilane (2), which was reactive under Denmark’s
conditions, reacted similarly under our optimized condi-
tions. However, product 3 was not stable enough for chro-
matographic purification, and the yield (61%) was deter-
mined by gas chromatography. Also, we have synthesized
In conclusion, conditions for palladium-catalyzed silyla-
tion reaction between aryl chlorides and bulky dialkoxydis-
ilanes were developed. These NHC-Pd-catalyzed conditions
newly allowed the introduction of bulky tert-alkoxysilyl
groups to arenes bearing electron-neutral or electron-with-
drawing substituents.
5d
1
,2-bis(adamantan-1-yloxy)-1,1,2,2-tetramethyldisilane(7)
Funding Information
13
as a crystalline dialkoxydisilane. Under the standard con-
ditions, 7 could also be applied to the silylation reaction of
This work was supported by the Japan Society for the Promotion of
Science (JSPS KAKENHI Grant Numbers JP16H04109, JP18H04254,
JP18H04409, JP19H00895, JP18J22838), and partly by Core Research
for Evolutional Science and Technology (JST CREST Grant Number JP-
MJCR19R4), Japan. J.S. thanks the support from the Kyoto University
Research Development Program (ISHIZUE 2019). H.Y. thanks The Asa-
4a to afford 8 in 46% yield.
Bromides and iodides were examined for our silylation
reaction (Table 2). Under the standard conditions for aryl
chloride, bromide 9 and iodide 10 were converted into the
corresponding arylsilane 6a only in 27% and 3% respective
yields (entries 1, 2). In the presence of additional LiCl, yields
were slightly improved (27% to 48% for bromide 9 and 3% to
hi Glass Foundation for financial support.
K
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Acknowledgment
portance of chloride ion is not clear in the current state.
A plausible reaction mechanism for the silylation is
shown in Scheme 4. Pd(0) species 11 generated from the
precatalyst would be subjected to oxidative addition to
yield 12. Maji reported a mechanistic investigation by DFT
calculations for his palladium-catalyzed C–H silylation with
hexamethyldisilane, in which the chloride substituent on
Pd(II) was replaced with a carboxylate to facilitate the acti-
vation of the disilane to give a Pd(IV) intermediate.14 Keep-
ing in mind that carboxylate bases were indispensable for
the current silylation, the reaction of 12 with disilane 5
would similarly form Pd(IV) carboxylate species 13 and re-
The authors thank Mr. Kohsuke Yoshikawa (Rakuhoku High School,
Kyoto) for his assistance for the synthesis of 1,2-bis(adamantan-1-
yloxy)-1,1,2,2-tetramethyldisilane (7). The authors thank Tokyo
Chemical Industry Co., Ltd. for a generous donation of 1,2-di-tert-bu-
toxy-1,1,2,2-tetramethyldisilane (5).
Supporting Information
Supporting information for this article is available online at
https://doi.org/10.1055/s-0039-1690877.
S
u
p
p
orti
n
g Inform ati
o
n
S
u
p
p
orti
n
g Inform ati
o
n
References and Notes
15
ductive elimination to generate arylsilane 6. Finally, re-
ductive elimination from 14 would generate silyl carboxyl-
ate 15 and Pd(0) species 11 to close the catalytic cycle.
(1) (a) Organosilicon Chemistry; Hiyama, T.; Oestreich, M., Ed.;
Wiley-VCH: Weinheim, 2019. (b) Hiyama, T. In Organometallics
in Synthesis: Third Manual; Schlosser, M., Ed.; Wiley: Hoboken,
2013, 373. (c) Science of Synthesis, Vol. 4; Fleming, I., Ed.;
Table 2 Applications to Aryl Bromide and Iodide
Thieme: Stuttgart, 2002. (d) Brook, M. A. Silicon in Organic,
Organometallic, and Polymer Chemistry; Wiley: New York, 2000.
(
e) Organosilicon Chemistry Set: From Molecules to Materials;
1
.5 equiv
Si Si
Auner, N.; Weis, J., Ed.; Wiley-VCH: Weinheim, 1994.
tBuO
OtBu
5
(
(
(
2) (a) Tamao, K.; Kobayashi, K.; Ito, Y. Tetrahedron Lett. 1989, 30,
X
Si
1
3
5
.5 equiv LiOBz
OtBu
6
8
051. (b) Denmark, S. E.; Sweis, R. F. Acc. Chem. Res. 2002, 35,
35. (c) Li, L.; Navasero, N. Org. Lett. 2004, 6, 3091.
mol% SingaCycle-A3
mol% H2O
EtO2C
EtO2C
additive
3) (a) Martin, S. E. S.; Watson, D. A. J. Am. Chem. Soc. 2013, 135,
0
.5 mmol (0.17 M)
(X = Br)
0 (X = I)
6a
DMA, 100 °C, 12 h
1
2
3330. (b) Saito, H.; Nogi, K.; Yorimitsu, H. Angew. Chem. Int. Ed.
018, 57, 11030.
9
1
4) Hiyama–Denmark-type coupling reaction of an arylsilane
Entry
Halide
Additive
Yield (%)a
or 10
bearing tBuOMe Si group with 4-iodoanisole under unopti-
mized conditions gave the cross-coupling product in ca. 40%
yield.
2
9
6a
27
Biaryl
1
2
3
9
10
9
none
46
73
26
58
5
4
2
1
(5) (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, 7449. (c) Murata, M.; Ishikura, M.; Nagata, M.;
Watanabe, S.; Masuda, Y. Org. Lett. 2002, 4, 1843. (d) Denmark,
S. E.; Kallemeyn, J. M. Org. Lett. 2003, 5, 3483. (e) Hamze, A.;
Provot, O.; Alami, M.; Brion, J.-D. Org. Lett. 2006, 8, 931.
none
3
48
21
1.5 equiv LiCl
1.5 equiv LiCl
4
10
a
1
Determined by H NMR analysis using mesitylene as an internal standard.
(f) Karshtedt, D.; Bell, A. T.; Tilley, D. T. Organometallics 2006,
©
2020. Thieme. All rights reserved. Synlett 2020, 31, A–E

E
Synlett
K. Fukui et al.
Letter
2
(
2
5, 4471. (g) Iizuka, M.; Kondo, Y. Eur. J. Org. Chem. 2008, 1161.
h) Kurihara, Y.; Yamanoi, Y.; Nishihara, H. Chem. Commun.
013, 49, 11275.
6) (a) Guo, H.; Chen, X.; Zhao, C.; He, W. Chem. Commun. 2015, 51,
and concentrated in vacuo. The residue was purified by column
chromatography on silica gel with an eluent (hexane and hex-
ane/EtOAc = 100:1) to afford 6a (105.6 mg, 0.38 mmol, 75%) as
1
(
colorless oil. H NMR (CDCl , 600 MHz):  = 8.01 (d, J = 8.2 Hz, 2
3
1
2
7410. (b) Liu, X.-W.; Zarate, C.; Martin, R. Angew. Chem. Int. Ed.
019, 58, 2064.
H), 7.67 (d, J = 8.2 Hz, 2 H), 4.38 (q, J = 6.9 Hz, 2 H), 1.39 (t, J = 6.9
13
Hz, 3 H), 1.25 (s, 9 H), 0.39 (s, 6 H). C NMR (CDCl , 151 MHz): 
3
(
7) (a) Matsumoto, H.; Nagashima, S.; Yoshihiro, K.; Nagai, Y.
J. Organomet. Chem. 1975, 85, C1. (b) Azarian, D.; Dua, S. S.;
Eaborn, C.; Walton, D. J. Organomet. Chem. 1976, 117, C55.
= 167.0, 146.8, 133.4, 131.0, 128.6, 73.2, 61.0, 32.2, 14.5, 1.5.
+
HRMS: m/z calcd for C15H25O Si [M + H] : 281.1567; found:
3
281.1569.
(
c) Matsumoto, H.; Yoshihiro, K.; Nagashima, S.; Watanabe, H.;
(10) O’Brien, C. J.; Kantchev, E. A. B.; Valente, C.; Hadai, N.; Chass, G.
A.; Lough, A.; Hopkinson, A. C.; Organ, M. G. Chem. Eur. J. 2006,
12, 4743.
Nagai, Y. J. Organomet. Chem. 1977, 128, 409. (d) Matsumoto, H.;
Shono, K.; Nagai, Y. J. Organomet. Chem. 1981, 208, 145.
(
1
e) Eaborn C., Griffiths R. W., Pidcock A.; J. Organomet. Chem.;
982, 225: 331. (f) Matsumoto, H.; Kasahara, M.; Matsubara, I.;
(11) 1-[4-(tert-Butoxydimethylsilyl)phenyl]ethan-1-one (6b)
Reaction time was 12 h. Column chromatography with an
eluent (hexane to hexane/EtOAc = 30:1) afforded 6b as colorless
Takahashi, M.; Arai, T.; Hasegawa, M.; Nakano, T.; Nagai, Y.
J. Organomet. Chem. 1983, 250, 99. (g) Hatanaka, Y.; Hiyama, T.
Tetrahedron Lett. 1987, 28, 4715. (h) Babin, P.; Bennetau, B.;
Theurig, M.; Dunoguès, J. J. Organomet. Chem. 1993, 446, 135.
1
oil (85.9 mg, 0.34 mmol, 69%) from 4b (77.3 mg, 0.50 mmol). H
NMR (CDCl , 600 MHz):  = 7.92 (d, J = 8.2 Hz, 2 H), 7.70 (d, J =
3
8.2 Hz, 2 H), 2.61 (s, 3 H), 1.26 (s, 9 H), 0.39 (s, 6 H). 13C NMR
(
i) Shirakawa, E.; Kurahashi, T.; Yoshida, H.; Hiyama, T. Chem.
Commun. 2000, 1895. (j) Gooßen, L. J.; Ferwanah, A.-R. S. Synlett
000, 1801. (k) McNeill, E.; Barder, T. E.; Buchwald, S. L. Org.
(CDCl , 151 MHz):  = 198.6, 147.3, 137.5, 133.7, 127.3, 73.2,
3
+
32.2, 26.8, 1.5. HRMS: m/z calcd for C14H23O Si [M + H] :
2
2
251.1462; found: 251.1461.
Lett. 2007, 9, 3785. (l) Minami, Y.; Shimizu, K.; Tsuruoka, C.;
Komiyama, T.; Hiyama, T. Chem. Lett. 2014, 43, 201.
(12) 4-(tert-Butoxydimethylsilyl)benzonitrile (6c)
Reaction time was 12 h. Column chromatography with an
eluent (hexane to hexane/EtOAc = 100:1) afforded 6c as color-
(m) Yamamoto, Y.; Matsubara, H.; Murakami, K.; Yorimitsu, H.;
Osuka, A. Chem. Asian J. 2015, 10, 219.
less oil (89.6 mg, 0.38 mmol, 77%) from 4c (68.8 mg, 0.50
1
(
(
8) Kantchev, E. A. B.; Ying, J. Y. Organometallics 2009, 28, 289.
9) Ethyl 4-(tert-butoxydimethylsilyl)benzoate (6a) – Typical
Procedure
mmol). H NMR (CDCl , 600 MHz):  = 7.68 (d, J = 8.2 Hz, 2 H),
3
7.62 (d, J = 8.2 Hz, 2 H), 1.26 (s, 9 H), 0.39 (s, 6 H). 13C NMR
(CDCl , 151 MHz):  = 147.4, 133.9, 131.1, 119.3, 112.7, 73.4,
3
+
An oven-dried 30 mL Schlenk tube was charged with LiOBz
32.2, 1.5. HRMS: m/z calcd for C13H20NOSi [M + H] : 234.1309;
(96.0 mg, 0.75 mmol), SingaCycle-A3 (10.0 mg, 0.015 mmol),
found: 134.1304.
and DMA (1.5 mL) under nitrogen atmosphere. Ethyl 4-chloro-
benzoate (4a, 92.3 mg, 0.50 mmol), 1,2-di-tert-butoxy-1,1,2,2-
(13) X-ray crystallographic analysis revealed the bulky adamanty-
loxy groups are antiperiplanar across the Si–Si bond. See the
Supporting Information for details.
tetramethydisilane (5, 235 L, 0.75 mmol), and H O stock solu-
2
tion (0.17 M in DMA, 0.15 mL, 25 mol) were sequentially
added to the mixture. DMA (1.35 mL) was added to wash the
inner side of the tube. The reaction mixture was stirred at 100
(14) Maji, A.; Guin, S.; Feng, S.; Dahiya, A.; Singh, V.; Liu, P.; Maiti, D.
Angew. Chem. Int. Ed. 2017, 56, 14903.
(15) We could not deny the possibility that disilane 5 reacts with
Pd(II) benzoate through a concerted six-membered transition
°
C for 12 h and quenched with sat. aq NaHCO3 (10 mL). The
mixture was poured into a separatory funnel with EtOAc (20
mL) and partitioned. The organic phase was collected and
state to give silyl benzoate 15 and an Ar–Pd(II)–SiMe (OtBu)
species, which would then generate arylsilane 6 via reductive
2
washed with sat. aq NaHCO3 (10 mL), sat. aq NH Cl (10 mL),
elimination.
4
brine (10 mL), dried over anhydrous Na SO (ca. 5 g), filtered,
2
4
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2020. Thieme. All rights reserved. Synlett 2020, 31, A–E