Palladium/Copper Dual Catalysis for the Cross-Coupling of Aryl(trialkyl)silanes with Aryl Bromides

Article abstract of DOI:10.1002/anie.201712081

Whereas aryl(trialkyl)silanes are considered to be ideal organometallic reagents for cross-coupling reactions owing to their stability, low toxicity, solubility, and easy accessibility, they are generally inert under typical cross-coupling conditions. Disclosed herein is a palladium/copper catalytic system that enables the cross-coupling of trimethyl, triethyl, tert-butyldimethyl, and triisopropyl aryl silanes with aryl bromides. This process is applicable to the sequential C?H and C?Si bond arylation of thiophenes and the synthesis of poly(thiophene–fluorene)s.

Full text of DOI:10.1002/anie.201712081

A Journal of the Gesellschaft Deutscher Chemiker
Angewandte
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International Edition
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Accepted Article
Title: Palladium/Copper Dual Catalysis for Cross-coupling of
Aryl(trialkyl)silanes with Aryl Bromides
Authors: Yasunori Minami, Takeshi Komiyama, Yuki Furuya, and
Tamejiro Hiyama
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To be cited as: Angew. Chem. Int. Ed. 10.1002/anie.201712081
Angew. Chem. 10.1002/ange.201712081
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10.1002/anie.201712081
Angewandte Chemie International Edition
COMMUNICATION
Palladium/Copper Dual Catalysis for Cross-coupling of
Aryl(trialkyl)silanes with Aryl Bromides*
Takeshi Komiyama,[a] Yasunori Minami,*[b] Yuki Furuya,[a] and Tamejiro Hiyama*[b]
Abstract: Although aryl(trialkyl)silanes are apparently ideal
Common method
organometalic reagents for the crossꢀcoupling reaction due to
Ar2
cat.
X'
Ar1
X
robustness, low toxicity, solubility, and easy accessibility, they are
generally an inert crossꢀcoupling nucleophile. Disclosed herein is
that a palladium/copper catalytic system achieves the desired crossꢀ
coupling of arylꢀSiMe3, ꢀSiEt3, ꢀSiMe2(tꢀBu), and ꢀSi(iꢀPr)3 with aryl
bromides, allowing application to the sequential C–H and C–Si bond
arylation of thiophenes and the synthesis of poly(thiopheneꢀ
fluorene)s.
X = Br, B(OR')2 or SnR'3
Ar2
CuBr2 cat.
I
Ar1 SiR3
Ar1
Ar2
ref. [9]
(R = alkyl)
Pd/Cu cat.
Ar2
Y
(Y = Br, Cl)
This Work
The cross-coupling reaction is one of the most general tools for access
to biaryl and polyarylenes.[1,2] Among a wide variety of organometallic
nucleophiles, simple organo(trialkyl)silanes have ideal characteristics
in stability, high solubility in various organic solvents, non-toxicity,
easy handling, and high accessibility. Moreover, aryl(triethyl)silanes
are easily prepared by catalytic C–H silylation of aromatic
hydrocarbons.[3] However, aside from a few exception,[4–7] such silanes
are not capable to participate in the cross-coupling. Consequently, they
are often converted into aryl halides, -boronic acids, or stannanes
(Figure 1, upper) before the coupling reaction.[8] Accordingly, these
additional transformations reduce the merit of the silicon reagents.
Direct cross-coupling of aryltrialkylsilanes with iodoarenes is
recently made possible by us using a copper(II) catalyst (Figure 1,
middle).[9] Although this finding is a great step for green chemistry,
harsh conditions and use of iodoarenes has remained yet to be modified
for large-scale synthesis.[10] These issues are also obstacle to operate a
cross-coupling polymerization. To solve them, herein we found that a
Pd/Cu catalytic system accomplished a practical cross-coupling
reaction of aryl(trialkyl)silanes including SiMe3, SiEt3, SiMe2(t-Bu),
and even Si(i-Pr)3 groups with bromoarenes (Figure 1, lower).
In light of examples which employ a copper cocatalyst to promote
palladium-catalyzed cross-coupling using well-designed organosilicon
reagents,[11] we examined the reaction of 1a with 2a employing Pd/Cu
catalysts. After investigating a wide array of reaction conditions, we
found that the reaction gave desired biaryl 3aa in excellent yield with
Pd2(dba)3/tris(2,4,6-trimethoxyphenyl)phosphine (TTMPP) and CuF2
catalysts and CsF in DMI at 100 °C (Table 1, Run 1). When we
replaced the SiEt3 group with other trialkylsilyl groups such as SiMe3,
SiMe2(t-Bu), and Si(i-Pr)3, 3aa was obtained in comparable yields
(Runs 2-4). It is noteworthy that this is the first example of cross-
coupling using a much sterically bulky Si(i-Pr)3 group (Run 4). Control
Figure 1. Crossꢀcoupling Strategy Using Simple Aryl(trialkyl)silanes
experiments showed that the combination of palladium and CuF2 was
crucial for this reaction (Runs 5 and 6). Other ligands such as PPh3,
PCy3, P[2,6-(MeO)2C6H3]3, P(2,4,6-Me3C6H2)3, and (di-tert-
butylphosphino)biphenyl (JohnPhos), or the absence of ligands
exhibited lower or null yields (Runs 7-13). Of note, a comparable yield
was observed at both lower concentration and lower temperature (Runs
11 and 12). CuI and CuBr2 led to lower yields (Runs 14 and 15).
Table 1: Pd/Cuꢀcatalyzed Reaction of 1a with 2a [a]
Pd2(dba)3 (1 mol%)
TTMPP (4 mol%)
CuF2 (10 mol%)
+
SiEt3
OMe
Br
OMe
CsF (1.3 eq)
S
S
DMI, 100 °C, 17 h
1a, 1.1 eq
2a, 1.0 eq
3aa
Run
Variation from the standard conditions
3aa (%)[b]
1
2
3
4
5
none
92[c]
96
94
91
SiMe3 instead of SiEt3
SiMe2(tꢀBu) instead of SiEt3
Si(iꢀPr)3 instead of SiEt3
without CuF2
6
6
7
8
9
without Pd2(dba)3
trace
67
trace
77
14
78
76
13
14
35
PPh3 instead of TTMPP
PCy3 instead of TTMPP
P[2,6ꢀ(MeO)2C6H3]3 instead of TTMPP
P(2,4,6ꢀMe3C6H2)3 instead of TTMPP
JohnPhos instead of TTMPP
JohnPhos instead of TTMPP
without TTMPP
10
11[d]
12[d,e]
13
14
15
CuI instead of CuF2
CuBr2 instead of CuF2
[a] Unless otherwise noted, a mixture of 1a (1.1 eq), 2a (0.3 mmol), Pd2(dba)3
(1 mol%), TTMPP (4 mol%), CuF2 (10 mol%), and CsF (1.3 eq) in DMI (2 M)
was heated at 100 °C for 17 h. The purity of the employed CuF2 is 99.5%.
The purities of the employed CuI and CuBr2 are both 99.999%. [b] NMR
yields. [c] Isolated yield. [d] 30 h. [e] DMI (1 M) at 90 °C.
[a]
[b]
T. Komiyama, Y. Furuya
Department of Applied Chemistry, Chuo University
1ꢀ13ꢀ27, Kasuga, Bunkyoꢀku, Tokyo 112ꢀ8551, Japan
Dr. Y. Minami, Prof. Dr. T. Hiyama
The scope of substrates is summarized in Table 2. Initially, we
examined a range of aryltriethylsilanes with 2a. 2-Thienylsilanes
having an aryl group at the 5-position, 1b, 1c and 5-methyl-3,4-
ethylenedioxy-2-silylthiophene 1d, gave products 3ba, 3ca, and 3da in
good yields, respectively. 2-Benzofurylsilane 1e underwent the
reaction to form the product 3ea. 2-Pyridylsilane 1f and 2-
pyradylsilane 1g proved to be effective nucleophiles with PPh2(2-
NMe2C6H4) as a ligand at 120 °C. Perfluorophenyl(triethyl)silane 1h
coupled readily using the 2-dicyclohexylphosphino-2',4',6'-
triisopropylbiphenyl (XPhos) ligand to form 3ha. In addition, 2,6-
Research and Development Initiative, Chuo University
1ꢀ13ꢀ27, Kasuga, Bunkyoꢀku, Tokyo 112ꢀ8551, Japan
Eꢀmail: yminami@kc.chuoꢀu.ac.jp, thiyama@kc.chuoꢀu.ac.jp
This research was supported financially by JST, ACTꢀC (No.
JPMJCR12Z1), and Sumitomo Chemicals. Y.M. also acknowledges
a GrantꢀinꢀAid for Challenging Research (Exploratory) (No.
25870747) from the JSPS. We also thank Prof. Ikeda’s group at
Chuo U. for GPC analysis of copolymer 10.
[*]
Supporting information for this article is given via a link at the end of
the document.
This article is protected by copyright. All rights reserved.

10.1002/anie.201712081
Angewandte Chemie International Edition
COMMUNICATION
Pd2(dba)3 (1 mol%)
difluoro- and 2-fluorophenylsilanes 1i and 1j gave 3ia and 3ja,
respectively, in the presence of PPh2(2-NMe2C6H4) at higher
temperatures. The coupling was also applicable to a variety of aryl
bromides. meta- and ortho-Bromoanisoles 2b and 2c coupled smoothly
with 1a to produce 3ab and 3ac in excellent yields. The reaction
worked with various aryl bromides having other electron-donating and
electron-withdrawing groups at the para-position, giving
corresponding products 3ad-3ai. In the case of electron-deficient
bromoarenes, conditions using JohnPhos ligand at a higher temperature
were required to promote the coupling. Cross-coupling using 1- and 2-
bromonaphthalenes and 9-bromoanthracene gave 3aj, 3ak, and 3al in
excellent yields. Such heteroaryl bromides as 2-bromopyridine (2l)
afforded coupled product 3am. 4-Bromobenzothiadiazole, which plays
important roles in material science,[12] gave coupled product 3an in
good yield.
XPhos (4 mol%)
CuF2 (10 mol%)
+
SiEt3
Cl
2'd, 1.0 eq
(1)
CsF (1.3 eq)
DMI, 100 °C, 17 h
S
S
1a, 1.1 eq
3ad, 78%
2l to give 5b in 89% yield, showing that sterically hindered aryl groups
can be incorporated without significant loss in yield. In addition, 4,7-
bis(triethyl)silyl-5,6-difluorobenzothiadiazole (4b) was found to react
with 2a giving 5c in 61% yield in the presence of PPh2(2-NMe2C6H4)
instead of TTMPP.
Pd2(dba)3 (1 mol%)
TTMPP (4 mol%)
CuF2 (10 mol%)
O
O
O
O
+
2a
CsF (2.5 eq)
2.1 eq
S
Et3Si
SiEt3
S
DMI, 100 °C, 22 h
MeO
OMe
4a (1.0 eq)
5a, 90%
Other double arylation products
Table 2: Scope of Substrates [a]
S
O
O
N
N
Pd2(dba)3 (1 mol%)
TTMPP (4 mol%)
MeO
OMe
CuF2 (10 mol%)
+
S
Ar1 SiEt3
1, 1.1 eq
Br
Ar2
Ar1
Ar2
CsF (1.3 eq)
F
F
DMI, 100 °C, 17 h
5c, 61%
{PPh2(2ꢀNMe2C6H4), 4 d}
2
3
5b, 89%
Scope of Aryl(triethyl)silanes
O
O
Scheme 1. Double Coupling Using Disilylarenes
Ph
S
S
OMe F
OMe
S
OMe
OMe
As mentioned above, trialkylsilyl groups are stable under various
conditions. This fundamental feature makes the sequential
functionalization of monosilyl substrates possible. Thus, we examined
a combination of catalytic C–H arylation and the present coupling
3ba, 91%
3ca, 92%
3da, 87%
N
OMe
OMe
OMe
N
O
N
3ea, 69%
3fa, 90%b,c
3ga, 77%b,c
(Scheme 2). As
a result, Pd-catalyzed C–H arylation of 2-
F
F
F
F
F
triethylsilylthiophene 6 with p-bromobenzotrifluoride (2h) gave a
monoarylated silylthiophene 7 without loss of the TES group.[14]
Subsequently, 7 coupled with 2a under the Pd/Cu-conditions and
produced unsymmetrical diarylthiophene 8 in excellent yield.
F
OMe
OMe
F
F
3ha, 53%b,d
3ia, 54%b,c,e
3ja, 52%c,f
Scope of Aryl Bromides
C–H
arylation
Crossꢀ
coupling
O
O
MeO
OMe
O
O
O
O
R
S
a
b
SiEt3
S
S
S
S
SiEt3
F3C
OMe
S
F3C
3ab, 96%
3ac, 91%
R = Me, 3ad, 85%
NMe2, 3ae, 97%
NPh2, 3af, 94%
F, 3ag, 93%b,g
6
7, 82%
8, 95%
Reagents and conditions: (a) 6 (1.0 eq), 2h (1.1 eq), Pd(OAc)2 (5 mol%), dppb
(5 mol%), Cs2CO3 (1.2 eq), toluene, 110 °C, 24 h; (b) 7 (1,1 eq), 2a (1.0 eq),
Pd2(dba)3 (1 mol%), TTMPP (4 mol%), CuF2 (10 mol%), CsF, (1.3 eq), DMI,
100 °C, 17 h.
CF3, 3ah, 89%b,g
CN, 3ai, 84%b,g
S
S
3aj, 92%
3ak, 92%b
S
N
N
Scheme 2. Sequential Arylation via C–H/C–Si Activation
S
S
N
S
3am, 62%b,g
3al, 90%
3an, 74%
The present cross-coupling was applicable to the synthesis of
polyarylenes.[15] Indeed, 4a and 2,7-dibromo-9,9-dioctyl-fluorene (9)
underwent cross-coupling polymerization to produce a copolymer 10,
poly(ethylenedioxythiophene-fluorene),[16] with Mn = 13045 and PDI =
2.24 in 22% yield after reprecipitation [Eq. (2)].[17]
[a] Unless otherwise noted, a mixture of 1 (1.1 eq), 2 (0.3 mmol), Pd2(dba)3 (1
mol%), TTMPP (4 mol%), CuF2 (10 mol%), and CsF (1.3 eq) in DMI (0.15 mL)
was heated at 100 °C for 17 h. All described yields are isolated ones. The
purity of the employed CuF2 is 99.5%. [b] 120 °C. [c] PPh2(2ꢀNMe2C6H4) was
used instead of TTMPP. [d] XPhos was used instead of TTMPP and heated
at 120 °C. [e] 3 d. [f] 140 °C for 24 h. [g] JohnPhos was used instead of
TTMPP.
O
O
Pd2(dba)3 (1 mol%)
TTMPP (4 mol%)
CuF2 (10 mol%)
The present Pd/Cu(II) dual catalysis is shown to be applicable to a
less reactive aryl chloride. The reaction of 1a with p-chlorotoluene
(2’d) using XPhos ligand to give 3ad in 78% yield [Eq. (1)].[13]
With the success of the mono-coupling in hand, double-coupling
was examined using 2,5-disilyl-3,4-ethylenedioxythiophene 4a and 2a
under the standard conditions, providing double arylation product 5a in
90% yield (Scheme 1). Similarly, 4a coupled with 9-bromoanthracene
Et3Si
SiEt3
O
O
S
Oct
Oct
4a (1.00 eq)
+
(2)
CsF (2.5 eq)
DMI (1 M), 100 °C, 7 d
S
Oct Oct
n
Br
Br
10
22%, n = 25, PDI = 2.24
n = 13045, Mw = 29191
9 (1.00 eq)
M
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10.1002/anie.201712081
Angewandte Chemie International Edition
COMMUNICATION
[5]
[6]
a) K. Funaki, H. Kawai, T. Sato, S. Oi, Chem. Lett. 2011, 40, 1050; b) K.
Funaki, T. Sato, S. Oi, Org. Lett. 2012, 14, 6186.
To obtain information on the C–Si bond activation, we treated
disilyl thiophene 11 having SiEt3 and Si(i-Pr)3 groups with a
stoichiometric amount of CsF, and observed silicon scrambling to form
4a and 12 (Table 3). Use of CuF2 (10 mol%) instead of CsF did not
induce the silicon scrambling at all. These results may mean that
arylsilanes react first with CsF to proceed an aryl exchange via
aryl(trialkyl)fluorosilicates.[18] This exchange may be attributed to aryl-
bridged silicate dimer,[19] wherein an interaction between silicates and
silanes takes place in a manner similar to that observed with tri-
/tetracoordinate system,[20] and/or arylcesium reversibly. On the other
hand, addition of CuF2 or CuF2/TTMPP to the mixture of 11 and CsF
did not affect the yields of 4a and 12.[21] Of note, in cases using CuF2,
homo-coupled products, bithiophenes, were not observed at all,
suggesting that formation of Ar-CuI complexes may be excluded.[22]
Although the behavior of CuF2 is unclear yet,[23] it may be asumed to
assist transmetalation between silicates and a palladium complex via
reversible formation of Ar-CuX2 or Ar-CuX.[24]
a) L. T. Ball, G. C. LloydꢀJones, C. A. Russell, Science 2012, 337,
1644; b) L. T. Ball, G. C. LloydꢀJones, C. A. Russell, J. Am. Chem. Soc.
2014, 136, 254; c) T. J. A. Corrie, L. T. Ball, C. A. Russell, G. C. Lloydꢀ
Jones, J. Am. Chem. Soc. 2017, 139, 245.
[7]
[8]
K. Kawasumi, K. Mochida, T. Kajino, Y. Segawa, K. Itami, Org. Lett.
2012, 14, 418.
For examples of direct exchange to boryl groups, see: a) L.ꢀZ. Gong,
Q.ꢀS. Hu, L. Pu, J. Org. Chem. 2001, 66, 2358; b) I. Yamaguchi, K.
Sato, M. Okuno, J. Phys. Org. Chem. 2014, 27, 622; For examples of
the exchange via multiꢀsteps, see: c) M. Weidelener, S. Powar, H. Kast,
Z. Yu, P. P. Boix, C. Li, K. Müllen, T. Geiger, S. Kuster, F. Nüesch, U.
Bach, A. Mishra, P. Bäuerle, Chem. Asian J. 2014, 9, 3251; d) F. M.
Jradi, D. O’Neil, X. Kang, J. Wong, P. Szymanski, T. C. Parker, H. L.
Anderson, M. A. ElꢀSayed, S. R. Marder, Chem. Mater. 2015, 27, 6305;
e) K. Kawashima, T. Fukuhara, Y. Suda, Y. Suzuki, T. Koganezawa, H.
Yoshida, H. Ohkita, I. Osaka, K. Takimiya, J. Am. Chem. Soc. 2016,
138, 10265; f) M. A. Uddin, Y. Kim, R. Younts, W. Lee, B. Gautam, J.
Choi, C. Wang, K. Gundogdu, B. J. Kim, H. Y. Woo, Macromolecules
2016, 49, 6374.
[9]
a) T. Komiyama, Y. Minami, T. Hiyama, Angew. Chem. Int. Ed. 2016,
55, 15787; b) T. Komiyama, Y. Minami, T. Hiyama, Synlett 2017, 28,
1873.
Table 3: Reactivity of C–Si Bond
O
O
O
O
O
O
additive
+
[10] Attempted CuBr2ꢀcatalyzed reaction of 2ꢀtriethylsilylbenzothiophene
(1a) with pꢀbromoanisole (2a) afforded the targeted product (3aa) in
modest yield, suggesting the reactivity was far from the practical use.
See the Supporting Information.
DMI
100 °C, 20 h
Et3Si
Si(iꢀPr)3
Et3Si
SiEt3 (iꢀPr)3Si
Si(iꢀPr)3
S
S
4a
S
12
11
additive
recovered 11 (%)
4a (%) 12 (%)
[11] For Pd/Cuꢀcatalyzed crossꢀcoupling reaction of organosilicon reagents,
see: a) M. Suginome, H. Kinugasa, Y. Ito, Tetrahedron Lett. 1994, 35,
8635; b) Y. Nakao, H. Imanaka, A. K. Sahoo, A. Yada, T. Hiyama, J.
Am. Chem. Soc. 2005, 127, 6952; c) Y. Nakao, A. K. Sahoo, A. Yada, J.
Chen, T. Hiyama, Sci. Technol. Adv. Mater. 2006, 7, 536; d) Y. Nakao,
H. Imanaka, J. Chen, A. Yada, T. Hiyama, J. Organomet. Chem. 2007,
692, 585; e) Y. Nakao, S. Ebata, J. Chen, H. Imanaka, T. Hiyama,
Chem. Lett. 2007, 36, 606; f) Y. Nakao, J. Chen, M. Tanada, T. Hiyama,
J. Am. Chem. Soc. 2007, 129, 11694; g) J. Chen, M. Tanaka, A. K.
Sahoo, M. Takeda, A. Yada, Y. Nakao, T. Hiyama, Bull. Chem. Soc.
Jpn. 2010, 83, 554; h) K. Shimizu, Y. Minami, Y. Nakao, K. Ohya, H.
Ikehira, T. Hiyama, Chem. Lett. 2013, 42, 45; i) A. Ohgi, K. Semba, T.
Hiyama, Y. Nakao, Chem. Lett. 2016, 45, 973.
CsF (1.3 eq)
CuF2 (10 mol%)
CuF2 (10 mol%), CsF (1.3 eq)
CuF2 / TTMPP (10 mol%), CsF (1.3 eq)
37
>99
34
18
<1
18
15
19
<1
14
15
29
In conclusion, we have demonstrated that the Pd/Cu dual
catalysis undergoes the cross-coupling of aryl(trialkyl)silanes with
bromoarenes under mild conditions. A wide variety of silyl groups
such as SiMe3, SiEt3, SiMe2(t-Bu), and Si(i-Pr)3 are found to be
applicable to the dual catalytic system as well as various aryl groups
in both coupling partners. The stability of trialkylsilyl groups permits
sequential C–H arylation/present cross-coupling using
a
[12] For recent examples, see: a) C. Orofino, C. Foucher, F. Farrell, N. J.
Findlay, B. Breig, A. L. Kanibolotsky, B. Guilhabert, F. Vilela, N.
Laurand, M. D. Dawson, P. J. Skabara, J. Polym. Sci. Part A: Polym.
Chem. 2017, 55, 734; b) B. Walker, D. Han, M. Moon, S. Y. Park, K.ꢀH.
Kim, J. Y. Kim, C. Yang, ACS Appl. Mater. Interfaces 2017, 9, 7091.
[13] More examples of chlorides will be the future target of our study.
[14] C.ꢀY. Liu, H. Zhao, H. Yu, Org. Lett. 2011, 13, 4068.
monosilylthiophene, leading to a unsymmetrical diarylthiophene.
Moreover, the present cross-coupling is applicable to the polyarylene
synthesis. We are now focusing on extension of the arylsilanes,
especially those containing electron-rich and -neutral aryl groups and
elucidation of the reaction mechanism.
[15] For selected reviews on the crossꢀcoupling polymerization, see: a) J.
Sakamoto, M. Rehahn, G. Wegner, A. D. Schlüter, Macromol. Rapid
Commun. 2009, 30, 653; b) B. Carsten, F. He, H. J. Son, T. Xu, L. Yu,
Chem. Rev. 2011, 111, 1493; c) T. Yokozawa, Y. Nanashima, Y. Ohta,
ACS Macro Lett. 2012, 1, 862; d) M. J. Robb, S.ꢀY. Ku, C. J. Hawker,
Adv. Mater. 2013, 25, 5686; e) Z. J. Bryan, A. J. McNeil,
Macromolecules 2013, 46, 8395.
Keywords: arene • copper • crossꢀcoupling • palladium • silanes
[1]
a) F. Diederich, P. J. Stang, Metal-Catalyzed Cross-Coupling Reactions,
WileyꢀVCH, Weinheim, 1998; b) A. de Meijere, F. Diederich, Metal-
Catalyzed Cross-Coupling Reactions, WileyꢀVCH, Weinheim, 2004,
2nd ed.
[2]
For reviews on the siliconꢀbased crossꢀcoupling reactions, see: a) Y.
Nakao, T. Hiyama, Chem. Soc. Rev. 2011, 40, 4893; b) H. F. Sore, W.
R. J. D. Galloway, D. R. Spring, Chem. Soc. Rev. 2012, 41, 1845; c) S.
E. Denmark, A. Ambrosi, Org. Process Res. Dev. 2015, 19, 982; d) F.
Foubelo, C. Najera, M. Yus, Chem. Rec. 2016, 16, 2521; e) T.
Komiyama, Y. Minami, T. Hiyama, ACS Catal. 2017, 7, 631.
For recent reviews, see: a) C. Cheng, J. F. Hartwig, Chem. Rev. 2015,
115, 8946; b) S. Bähr, M. Oestreich, Angew. Chem. Int. Ed. 2017, 56,
52.
[16] a) P.ꢀH. Aubert, M. Knipper, L. Groenendaal, L. Lutsen, J. Manca, D.
Vanderzande, Macromolecules 2004, 37, 4087; b) S. Narayanan, A.
Abbas, S. P. Raghunathan, K. Sreekumar, C. S. Kartha, R. Joseph,
RSC Adv. 2015, 5, 8657.
[17] Attempted polymerization using 2 mol% of palladium catalyst did not
proceed sufficiently in 24 h and even 4d, showing this polymerization is
slow. Also, the resulting crude product turned out viscous solution.
Thus, we optimized the conditions as shown in Eq. (2) and performed
the polymerization for a longer time.
[3]
[4]
Cross coupling reaction using 2ꢀpyridylꢀSiMe3, 2ꢀbenzofuryl–SiMe3, and
8ꢀSiMe2(tꢀBu)ꢀ1ꢀnaphthols is reported. See: a) P. Pierrat, P. Gros, Y.
Fort, Org. Lett. 2005, 7, 697; b) S. Napier, S. M. Marcuccio, H. Tye, M.
Whittaker, Tetrahedron Lett. 2008, 49, 6314; c) S. Matsuda, M.
Takahashi, D. Monguchi, A. Mori, Synlett 2009, 1941; d) S. Akai, T.
Ikawa, S. Takayanagi, Y. Morikawa, S. Mohri, M. Tsubakiyama, M. Egi,
Y. Wada, Y. Kita, Angew. Chem. Int. Ed. 2008, 47, 7673.
[18] To check the generation of arylsilicates, we treated 1a with CsF in
DMFꢀd7. As a result, benzothiophene by hydrodesilylation was only
observed with 1a. During this NMR study, no signal in 19F NMR was
detected.
[19] The formation of the bridged dimer may be attributed to the high Lewis
acidity of pentaꢀcoordinated silicates. It therefore seems reasonable to
assume that relatively electronꢀwithdrawing aryl groups locate in the
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bridge site. See: a) Y. L. Frolov, S. G. Shevchenko, M. G. Voronkov, J.
Organomet. Chem. 1985, 292, 159; b) C. Chult, R. J. P. Corriu, C.
Reye, J. C. Young, Chem. Rev. 1993, 93, 1371.
[20] a) A. Schäfer, M. Reiβmann, A. Schäfer, W. Saak, D. Haase, T. Müller,
Angew. Chem. Int. Ed. 2011, 50, 12636; b) A. Schäfer, M. Reiβmann, S.
Jung, A. Schäfer, W. Saak, E. Brendler, T. Müller, Organometallics
2013, 32, 4713; c) A. Feigl, I. Chiorescu, K. Deller, S. U. H. Heidsieck,
M. R. Buchner, V. Karttunen, A. Bockholt, A. Genest, N. Rösch, B.
Rieger, Chem. Eur. J. 2013, 19, 12526; d) K. Müther, P. Hrobárik, V.
Hrobáriková, M. Kaupp, M. Oestreich, Chem. Eur. J. 2013, 19, 16579;
e) R. Labbow, F. Reiβ, A. Schulz, A. Villinger, Organometallics 2014,
33, 3223.
[21] Use of CuBr2 (10 mol%) and CsF (1.3 eq) also reached the same result
as the use of CuF2 and CsF.
[22] J. delPozo, J. A. Casares, P. Espinet, Chem. Eur. J. 2016, 22, 4274.
[23] By NMR analysis, CuF2 did not appear to oxidize a Pd(0) complex to
Pd(II) (See the Supporting Information.). For the oxidation of
palladium(0) by Cu(II), see: a) F. Proutiere, M. Aufiero, F. Schoenebeck,
J. Am. Chem. Soc. 2012, 134, 606; b) M. Aufiero, F. Proutiere, F.
Schoenebeck, Angew. Chem. Int. Ed. 2012, 51, 7226; c) M. Aufiero, T.
Scattolin, F. Proutiére, F. Schoenebeck, Organometallics 2015, 34,
5191.
[24] J.ꢀi. Yoshida, K. Tamao, T. Kakui, A. Kurita, M. Murata, K. Yamada, M.
Kumada, Organometallics 1982, 1, 369.
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Entry for the Table of Contents (Please choose one layout)
Layout 2:
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O
O
Takeshi Komiyama, Yasunori Minami,*
Yuki Furuya, and Tamejiro Hiyama*
Br
S
Applicable to
O
O
Pd/Cu cat.
—
—
—
Use of Si(iꢀPr)3 group
Use of a chloroarene
CꢀH/CꢀSi sequential
coupling with ArꢀBr
or
+
or
Oct Oct
Page No. – Page No.
Et3Si
SiEt3
S
O
O
Oct
Oct
Br
Palladium/Copper Dual Catalysis for
Cross-coupling of Aryl(trialkyl)silanes
with Aryl Bromides
Br
S
n
Under palladium/copper catalysis, aryl(trialkyl)silanes are demonstrated to undergo
practical crossꢀcoupling with haloarenes, giving biaryls and teraryls. Various
trialkylsilyl groups including stable and bulky triisopropylsilyl are applicable to this
reaction. This high reactivity permits the crossꢀcoupling polymerization as well as
sequential C–H arylation/the present Pd/Cuꢀcatalyzed crossꢀcoupling is achieved.
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