Synthesis of π-Extended Siloles Using Intramolecular Chain Hydrosilylation

Article abstract of DOI:10.1055/s-0036-1590911

Intramolecular chain hydrosilylation afforded benzo- and naphtho-fused siloles in 20-81% yields from the corresponding hydrosilanes in the presence of a small amount of trityl tetrakis(pentafluorophenyl)borate as an initiator. This hydrosilylation can be applied for the synthesis of disiloles such as 1,5-disila-1,5-dihydro- s -indacene and naphthodisiloles.

Full text of DOI:10.1055/s-0036-1590911

SYNTHESIS
0
0
3
9
-
7
8
8
1
1
4
3
7
-
2
1
0
X
© Georg Thieme Verlag Stuttgart · New York
2017, 49, A–G
feature
A
en
H. Arii et al.
Feature
Synthesis
Synthesis of π-Extended Siloles Using Intramolecular Chain Hydro-
silylation
Hidekazu Ariia,b
Kenichi Nakabayashia
Kunio Mochidab
Takayuki Kawashima*c
SiMe3
H
[Ph3C]B(C6F5)4 (1–5 mol%)
Ar
Ar
SiMe3
H
R
benzene, r.t.
Si
Si
R
R
R
a Faculty of Education, University of Miyazaki, 1-1 Gakuen Kibanadai
Nishi, Miyazaki, 889-2192 Miyazaki, Japan
π-extended siloles and disiloles
13 examples
R = Me, i-Pr, Ph
b Department of Chemistry, Gakushuin University, 1-5-1 Mejiro,
Toshima-ku, 171-8588, Tokyo, Japan
yield up to 81%
c Graduate School of Science and Technology, Gunma University,
1-5-1 Tenjin-cho, Kiryu 376-8515 Gunma, Japan
Kawashima.t@gunma-u.ac.jp
This paper is dedicated to Professor Marian Mikolajczyk on the
occasion of his 80th birthday.
Received: 24.08.2017
Accepted after revision: 25.08.2017
Published online: 25.09.2017
Siloles have attracted much attention because of their
optical and electronic properties, which are useful for ma-
terials such as emission components and semiconductors.1
These properties are due to the low-lying LUMO derived
from the orbital interaction between the σ* orbital of the si-
lylene moiety and the π* orbital of butadiene in the silole
framework, which indicates that the siloles have HOMO-
LUMO gaps that are smaller than their carbon analogues.2
An aromatic ring-fused silole can have a decreased gap via
π-conjugation between the silole moiety and the aromatic
ring. Silole derivatives have been synthesized using various
methods, including catalytic and stoichiometric reac-
tions.3,4 Si–C bond formation through C–H activation cata-
lyzed by a transition metal5 is a direct and powerful route
to dibenzosilole and does not require a preliminary prepa-
ration such as functionalization of an aromatic ring
(Scheme 1, a).5b Recently, a Lewis acid catalyst was found to
induce intra- or intermolecular Si–C bond formation ac-
companied by H2 evolution to give benzosiloles Scheme 1,
b).6 The chain reaction promoted by a small amount of an
initiator is also one of the transition-metal-free systems.
The three-coordinated silyl radical and five-coordinated sil-
icate generated by the reactions of the corresponding hy-
drosilane with tert-butyl hydroperoxide (TBHP) and KH, re-
spectively, act as a chain carrier to yield the siloles (Scheme
1, c and d).7,8 The driving force of these reactions seems to
be the formation of unusual coordination numbers 3 and 5
at the silicon atom, which make the species highly reactive.
We have been investigating the reaction, which originates
from the three-coordinated silyl cation with high Lewis
acidity, and reported the syntheses of trisilasumanene as
well as dibenzosiloles via the sila-Friedel–Crafts reaction,
which involves the generation of silyl cations by hydride
abstraction from the corresponding hydrosilanes with a
DOI: 10.1055/s-0036-1590911; Art ID: ss-2017-z0379-fa
Abstract Intramolecular chain hydrosilylation afforded benzo- and
naphtho-fused siloles in 20–81% yields from the corresponding hydro-
silanes in the presence of a small amount of trityl tetrakis(pentafluoro-
phenyl)borate as an initiator. This hydrosilylation can be applied for the
synthesis of disiloles such as 1,5-disila-1,5-dihydro-s-indacene and
naphthodisiloles.
Key words silole, silyl cation, chain hydrosilylation, cyclization, metal-
free
R3
R3
RhCl(PPh3)3 (0.50 mol%)
a)
Si
R1
Si
R2
H
1,4-dioxane, 135 °C
R2
R1
SiMe3
B(C6F5)3 (5 mol%)
2,6-dichloropyridine
R'
Ph
b)
+
Si
CH2Cl2, 60 °C
Ph2SiH2
Ph
R1
R2
R1
R2
TBHP (3.3 equiv)
Bu4NI (1 mol%)
c)
d)
Si
benzene, 90 °C
Si
Ph
H
Ph
Ph
Ph
R2
KH (1.0 equiv)
DME, 0–25 °C
R2
Si
Si
R1
H
R1
R1
R1
Scheme 1 Selected syntheses of benzo- or dibenzosiloles
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–G

B
H. Arii et al.
Feature
Synthesis
triphenylmethyl cation and electrophilic attack on the in-
tramolecular arene moiety followed by deprotonation with
a base (Scheme 2).9
The sila-Friedel–Crafts reaction led us to develop a novel
synthetic route to siloles. We hypothesized that the vinyl
cation generated by the addition of the silyl cation to the
neighboring C≡C bond10 abstracts the hydride from the Si–H
bond of a starting hydrosilane to regenerate the silyl cation,
which may act as a chain carrier to undergo intramolecular
chain hydrosilylation. It was reported as a preliminary
communication that dialkyl[2-(trimethylsilylethynyl)phen-
yl]silanes were converted into the corresponding benzosil-
oles in the presence of
a small amount of trityl
tetrakis(pentafluorophenyl)borate (TTPFPB) as an initiator
Biographical Sketches
Hidekazu Arii received his
Ph.D. in 2003 from Nagoya
Institute of Technology under
the direction of Professor Hideki
Masuda. He moved to Chuo
University as a Research Associ-
ate in 2004 under Professor
Makoto Chikira. In 2006, he
worked as a postdoctoral re-
search fellow at the laboratory of
Professor Hiroyuki Kawaguchi in
Institute for Molecular Science.
He moved to Faculty of Science,
Gakushuin University as a Re-
search Associate in 2007 and re-
searched under the direction of
Professor Kunio Mochida. He
moved to University of Miyazaki
as an Associate Professor in
2014. His research interest is
the chemistry of low-coordinat-
ed heavier group 14 elements.
Kenichi Nakabayashi re-
ceived his Ph.D. in 1993 from
Osaka University under the di-
rection of Professor Setsuo
Takamuku. He accepted posi-
tions as a Lecturer, an Associate
Professor, and a Professor at the
University of Miyazaki. He did
research with Professor W.
Schnabel at Hahn Meitner Insti-
tute Berlin from 1990 to 1991.
His research interest involves or-
ganic
photochemistry
and
chemical education.
Kunio Mochida received his
D. Sci. degree in 1976 from
Tohoku University under the su-
pervision of Professor Hideki
Sakurai. After he worked as a re-
search fellow of JSPS (Japan
Society for the Promotion of
Science) in 1976, he moved to
Indiana University as a postdoc-
toral research fellow under the
direction of Professor J. K. Kochi
in 1977. He moved to Faculty of
Science, Gakushuin University as
a Lecturer in 1978, where he
was promoted to Professor in
1986. His research interest is
not only the chemistry of ger-
manium compounds but also
transition-metal chemistry.
Takayuki Kawashima re-
ceived his D. Sci. degree in 1974
from the University of Tokyo un-
der the supervision of Professor
Naoki Inamoto. He was a Re-
Department of Chemistry,
Graduate School of Science, The
University of Tokyo in 1998.
From 1976 to 1978, he did
postdoctoral research with
Professor J. G. Verkade at Iowa
State University and with
Professor W. G. Bentrude at the
University of Utah. In 2010, he
retired from the University of
Tokyo and became Professor
Emeritus at the University of
Tokyo. He was a Visiting Profes-
sor of Gakushuin University
from 2010 to 2013 and he
joined the Graduate School of
search Associate,
a
Lecturer,
Science
and
Technology,
and an Associate Professor of
Department of Chemistry,
Faculty of Science, The Universi-
ty of Tokyo from 1974 to 1998
Gunma University as a Visiting
Professor in 2013. His research
interest is centered on organo-
heteroatom chemistry.
and became
a Professor of
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–G

C
H. Arii et al.
Feature
Synthesis
The substituent of the ethynyl group was limited to the
trimethylsilyl group. Specifically, the aliphatic n-butyl or
bulky tert-butyldimethylsilyl groups prevented the desired
hydrosilylation, in which case the corresponding starting
materials were recovered (Table 1, entries 4 and 5). This im-
plies that the trimethylsilyl group is associated with the
stability of the reaction intermediate, that is, the ethenyl
carbocation is stabilized by additional β-silyl effect of the
trimethylsilyl group, and such double β-silyl effects were
also effective for stable vinyl cations.10 Benzosiloles 2f and
2g bearing a methyl group on the aromatic ring were ob-
tained in yields similar to that of 2c (Table 1, entries 6 and
7). The best yield of 2g seems to be attributable to stabiliza-
tion by the inductive effect of the electron-rich carbon
emerging from hyperconjugation of the 6-methyl group on
the electron deficient carbon of an intermediary ethenyl
carbocation. The methoxy derivative 2h was formed in 34%
yield from 1h upon using 5 mol% TPFPB, although the reac-
tion needed more TTPFPB and a longer time than those re-
quired for reactions using 1a–g (Table 1, entry 8). The sig-
nificantly slower conversion causes intermolecular interac-
tion of the silyl cation with the methoxy group to compete
with its electrophilic addition to the ethynyl moiety. Inter-
estingly, the extension of the reaction time to 2 days resulted
in the formation of regioisomer, 1,1-diisopropyl-7-methoxy-
2-trimethylsilylbenzo[b]silole (2h′) in 20% yield with con-
sumption of 2h (Table 1, entry 9). The rearrangement from
2h to 2h′ is considered to have taken place through the pro-
todesilylation of 2h followed by the sila-Friedel–Crafts reac-
tion at the ortho-position to the methoxy group (see the
Supporting Information, Scheme S1).
This intramolecular chain hydrosilylation was applied to
the synthesis of π-extended benzosiloles. Specifically, the
treatment of 2-diisopropylsilyl-1-trimethylsilylethynyl-
naphthalene (1i) with 2 mol% TTPFPB in benzene afforded
3,3-diisopropyl-2-trimethylsilylnaphtho[2,1-b]silole (2i) in
72% yield (Scheme 3). The regioisomer of 1j was also con-
verted into the corresponding naphthosilole 2j in 76% yield.
On the other hand, 1k, which has a dimethylsilyl group at
the 1-position of 2-trimethylsilylethynylnaphthalene, must
be used because a diisopropylsilyl group cannot be intro-
duced. The reaction using 1k required more time than the
reactions using 1i and 1j to give 2k in 32% yield despite a
less bulky methyl group on the silicon atom. The 1-position
of naphthalene has a kinetic disadvantage for approaching
the other molecules, which causes the slow hydride ab-
straction from the Si–H bond by the trityl cation and an un-
successful introduction of a bulkier diisopropylsilyl group
to the 1-position of 2-trimethylsilylethynylnaphthalene.
However, the reaction that uses 1l with an anthracene
backbone afforded a complex mixture rather than the de-
sired product, probably because the 9- and 10-positions of
1l are very reactive toward electrophiles, which results in
intermolecular reactions with an intermediary silyl cation
at these positions.
[Ph3C]B(C6F5)4
t-Bu
t-Bu
t-Bu
t-Bu
2,6-lutidine
Si
Si
Ph
H
Ph
CH2Cl2, r.t.
Ph
Ph
SiMe3
[Ph3C]B(C6F5)4 (1 mol%)
benzene, r.t.
SiMe3
H
Si
Si
R
R
R
R
Scheme 2 Our previous work on the synthesis of siloles utilizing a silyl
cation
(Scheme 2).11 Herein, we further describe the scope and
limitation of this intramolecular chain hydrosilylation, in-
cluding its application for the synthesis of π-extended disi-
loles.
Dimethyl[2-(trimethylsilylethynyl)phenyl]silane (1a) was
reacted with 1 mol% TTPFPB in benzene to afford the corre-
sponding benzosilole 2a in 34% isolated yield (Table 1, entry
1). The low yield is attributable to the formation of uniden-
tified oligomers by the intermolecular addition of the silyl
cation to the alkyne moiety. The sterically bulkier substitu-
ent on the silicon atom improved the yields of 2b and 2c to
55 and 77%, respectively (entries 2 and 3).
Table 1 Intramolecular Chain Hydrosilylation of Silanes 1 to Benzosil-
oles 2a–h, 2h′
R2
[Ph3C]B(C6F5)4 (1 mol%)
R2
R1
H
benzene, r.t.
Si
R1
2a–h, 2h'
Si
R3
R3
R1
R1
1a–h
Entry Silane 1 R1
R2
R3
Time
(min)
Yield of 2
(%)a
1
1a
1b
1c
1d
1e
1f
Me
Ph
TMS
H
30
34 (2a)b
55 (2b)b
77 (2c)b
–c (2d)b
–c (2e)
2
TMS
TMS
n-Bu
TBDMS
TMS
TMS
TMS
TMS
H
30
30
3
i-Pr
i-Pr
i-Pr
i-Pr
i-Pr
i-Pr
i-Pr
H
4
H
720
720
30
5
H
6
4-Me
5-Me
4-MeO
4-MeO
71 (2f)b
81 (2g)b
34 (2h)e
20 (2h′)f
7
1g
1h
1h
50
8d
9d
720
2880
a Isolated yield based on 1.
b Ref. 11.
c Not obtained.
d TTPFPB used: 5 mol%.
e Ratio of 1h/2h = 1:10 estimated by 1H NMR analysis.
f 2h′ = R1 = i-Pr, R2 = TMS, R3 = 7-OMe.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–G

D
H. Arii et al.
Feature
Synthesis
The postulated mechanism of intramolecular chain hy-
drosilylation is described for benzosiloles as typical exam-
ples in Scheme 4. Trityl cation, as an initiator, abstracts the
hydride from the Si–H bond of 1 to generate the corre-
sponding silyl cation. Subsequently, the intramolecular
electrophilic addition of the silyl cation moiety to the
neighboring C≡C bond produces an alkenyl carbocation,
which is stabilized via the additional β-silyl effect of the
trimethylsilyl group. Finally, the intermolecular hydride ab-
straction of the alkenyl carbocation from another 1 affords
benzosiloles 2 with regeneration of the silyl cation, which
works as a chain carrier.
SiMe3
SiMe3
H
i-Pr
Si
[Ph3C]B(C6F5)4 (2 mol%)
benzene, r.t., 80 min
Si
i-Pr
i-Pr
i-Pr
2i
1i
Me
SiMe3
SiMe3
Me
Si
i-Pr
Si
SiMe3
i-Pr
i-Pr
Si
i-Pr
2k, 32%
(2 mol%, 12 h)
2i, 72%
(2 mol%, 80 min)
2j, 76%
(1 mol%, 30 min)
In summary, we have synthesized various π-extended
siloles, such as benzosiloles, naphthosiloles, 1,5-disila-1,5-
dihydro-s-indacene, and naphthodisiloles, via intramolecu-
lar chain hydrosilylation in low to moderate yields up to
81%. The steric bulkiness on the silyl group affects the yield
of benzosiloles to prevent the undesired alkyne polymer-
ization based on the silyl cation. Although the intramolecu-
lar chain hydrosilylation requires the trimethylsilyl group
on the ethynyl moiety to stabilize the intermediary ethenyl
carbocation via the β-silyl effect, the reaction can be carried
out under mild conditions without any metal. The present
chain hydrosilylation is one of the available methods for the
synthesis of π-extended siloles to reduce waste.
i-Pr
i-Pr
Si
Me3Si
SiMe3
i-Pr
SiMe3
i-Pr
Si
Si
i-Pr
i-Pr
2m, 75%
(2 mol%, 2 h)
2l, mixture
(1 mol%, 30 min)
SiMe3
i-Pr
Si
i-Pr
Si
i-Pr
i-Pr
Me3Si
i-Pr
SiMe3
i-Pr
Si
i-Pr
Me3Si
Si
i-Pr
2o, 45%
(2 mol%, 2 h)
2n, 71%
(2 mol%, 2 h)
All experiments were carried out using standard vacuum line and
Schlenk techniques in an argon atmosphere or dry box. All the re-
agents were of the highest grade available and were used without fur-
ther purification. All solvents used for the synthesis were distilled ac-
cording to the general procedure. [Ph3C]B(C6F5)4,12 1a,13 1b,8 1c,d,f,g,11
and aryl bromides bearing trimethylsilylethynyl group14 were synthe-
sized according to the previously reported methods. The 1H and 13C
NMR spectral measurements were performed on a Varian 400-MR
NMR or a Bruker AV 400M spectrometers. The 29Si NMR spectra were
measured on a JEOL ECA-600 spectrometer using TMS as an external
standard. The 1H and 13C chemical shifts are reported relative to the
residual protonated solvent and the solvent, respectively, according to
the literature.15 High-resolution mass spectra were measured by a
JEOL GCMATE II or JMS-700N operating by electron impact ionization
(EI). Gel permeation liquid chromatography (GPLC) was performed by
a Japan Analytical Industry LC-918 using CHCl3 as an eluent.
Scheme 3 Scope and limitation of π-extended siloles by the chain hy-
drosilylation
Next, double hydrosilylation was examined for synthe-
sizing π-extended disiloles. The reactions using 1m–o were
carried out in the presence of 2 mol% TTPFPB, which has the
same mol% against a silyl group as that used for the single
hydrosilylation. The reactions needed a longer reaction
time (2 h) and gave the desired products 2m–o in 75, 71,
45% yield, respectively. Although the polymerization pro-
ceeded partially, the yields were similar to those of the sin-
gle hydrosilylation products.
R2
R1
Si
R1
R3
Silanes 1e,h–l; General Procedure
2
1
To the corresponding bromo compound (1.3 mmol) in hexane (8 mL)
were added 1.6 M pentane solution of t-BuLi (0.84 mL, 1.4 mmol) and
N,N,N′,N′-tetramethylethylenediamine (0.23 g, 2.0 mmol) at –80 °C,
and the solution was stirred for 20 min at the temperatures below
–70 °C. To the solution was added i-Pr2SiHCl (0.20 g, 1.4 mmol) at –70 °C,
the solution was stirred, and slowly warmed to r.t. The reaction mix-
ture was quenched with 5% aq NH4Cl. The mixture was extracted with
hexane (2 × 20 mL), and the combined organic layers were dried (an-
hyd Na2SO4). The filtrate was concentrated under reduced pressure to
remove volatiles, and the residue was purified by chromatography
over a silica gel column (eluent: hexane). Further purification was
carried out by GPLC to obtain 1e,h–l.
R2
R2
Ph3C+
– Ph3CH
R2
R1
H
Si+
R1
Si
R1
Si
R3
R3
R3
R1
R1
R1
1
Scheme 4 Plausible reaction mechanism for intramolecular chain hy-
drosilylation of 1
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–G

E
H. Arii et al.
Feature
Synthesis
Diisopropyl[2-(tert-butyldimethylsilylethynyl)phenyl]silane (1e)
HRMS (EI): m/z [M]+ calcd for C17H28Si2: 282.1260; found: 282.1260.
Compound 1e was obtained from 1-bromo-2-tert-butyldimethylsilyl-
ethynylbenzene (0.38 g, 1.3 mmol); yield: 0.26 g (60%); colorless oil.
2-Diisopropylsilyl-3-trimethylsilylethynylanthracene (1l)
1H NMR (CDCl3, 400 MHz): δ = 7.51–7.48 (m, 2 H, ArH), 7.32–7.25 (m,
2 H, ArH), 4.06 (t, 1 H, J = 3.6 Hz, SiH), 1.50–1.41 [m, 2 H, 2 ×
CH(CH3)2], 1.10 [d, J = 7.6 Hz, 6 H, CH(CH3)2], 1.00 (s, 9 H, t-C4H9), 0.99
[d, J = 8.0 Hz, 6 H, CH(CH3)2], 0.18 [s, 6 H, Si(CH3)2].
13C NMR (CDCl3, 100 MHz): δ = 138.0, 136.6, 133.2, 129.3, 128.9,
127.5, 107.4, 94.7, 26.3, 19.3, 19.2, 16.9, 11.3, –4.5.
Compound 1l was obtained from 2-bromo-3-trimethylsilylethynylan-
thracene (70 mg, 0.20 mmol); yield: 25 mg (33%); colorless oil.
1H NMR (CDCl3, 400 MHz): δ = 8.38 (s, 1 H, ArH), 8.33 (s, 1 H, ArH),
8.19 (s, 2 H, ArH), 8.01–7.98 (m, 2 H, ArH), 7.49–7.46 (m, 2 H, ArH),
4.14 (t, J = 4.0 Hz, 1 H, SiH), 1.60–1.51 [m, 2 H, 2 × CH(CH3)2], 1.17 [d,
J = 7.6 Hz, 6 H, CH(CH3)2], 1.05 [d, J = 7.6 Hz, 6 H, CH(CH3)2], 0.30 [s, 9
H, Si(CH3)3].
13C NMR (CDCl3, 100 MHz): δ = 138.6, 133.8, 133.0, 132.50, 132.45,
131.2, 130.3, 128.5, 128.4, 126.6, 126.1, 126.0, 125.9, 123.9, 107.3,
96.6, 19.5, 19.4, 11.6, 0.0.
HRMS (EI): m/z [M]+ calcd for C20H34Si2: 330.2199; found: 330.2199.
Diisopropyl[2-(trimethylsilylethynyl)-4-methoxyphenyl]silane (1h)
Compound 1h was obtained from 1-bromo-4-methoxy-2-trimethyl-
silylethynylbenzene (0.73 g, 2.58 mmol); yield: 0.42 g (51%); colorless
oil.
HRMS (EI): m/z [M]+ calcd for C25H32Si2: 388.2043; found: 388.2044.
Disilanes 1m–o; General Procedure
1H NMR (CDCl3, 400 MHz): δ = 7.38 (d, J = 8.4 Hz, 1 H, ArH), 7.03 (d, J =
2.8 Hz, 1 H, ArH), 6.85 (dd, J = 8.0 Hz, J = 2.8 Hz, 1 H, ArH), 3.98 (t, J =
4.0 Hz, 1 H, SiH), 3.80 (s, 3 H, OCH3), 1.45–1.36 [m, 2 H, 2 × CH(CH3)2],
1.09 [d, J = 7.2 Hz, 6 H, CH(CH3)2], 0.98 [d, J = 7.2 Hz, 6 H, CH(CH3)2],
0.25 [s, 9 H, Si(CH3)3].
13C NMR (CDCl3, 100 MHz): δ = 160.1, 138.1 130.3, 129.2, 117.6, 114.6,
106.6, 96.0, 55.3, 19.3, 11.4, –0.07.
To bis(trimethylsilylethynyl)aryl dibromide (0.66 mmol) in Et2O (12
mL) were added 1.6 M pentane solution of t-BuLi (1.6 mL, 2.6 mmol)
and at –80 °C, and the solution was stirred, and warmed to r.t. gradu-
ally. To the solution was added i-Pr2SiHCl (0.22 g, 1.44 mmol) at –70 °C,
the solution was stirred, and slowly warmed to r.t. The reaction mix-
ture was quenched with 5% aq NH4Cl. The mixture was extracted with
Et2O (2 × 20 mL), and the combined organic layers were dried (anhyd
Na2SO4). The filtrate was concentrated under reduced pressure to re-
move volatiles, and the residue was purified by chromatography over
a silica gel column (eluent: hexane). Further purification was carried
out by GPLC to obtain 1m–o.
HRMS (EI): m/z [M]+ calcd for C18H30OSi2: 318.1835; found: 318.1835.
2-Diisopropylsilyl-1-trimethylsilylethynylnaphthalene (1i)
Compound 1i was obtained from 2-bromo-1-trimethylsilylethynyl-
naphthalene (0.20 g, 0.86 mmol); yield: 0.12 g (54%); colorless oil.
1H NMR (CDCl3, 400 MHz): δ = 8.43 (d, J = 8.4 Hz, 1 H, ArH), 7.82 (d, J =
7.6 Hz, 1 H, ArH), 7.78 (d, J = 8.4 Hz, 1 H, ArH), 7.61–7.49 (m, 3 H,
ArH), 4.20 (t, J = 4.0 Hz, 1 H, SiH), 1.60–1.50 [m, 2 H, 2 × CH(CH3)2],
1.16 [d, J = 7.2 Hz, 6 H, CH(CH3)2], 1.03 [d, J = 7.2 Hz, 6 H, CH(CH3)2],
0.35 [s, 9 H, Si(CH3)3].
13C NMR (CDCl3, 100 MHz): δ = 137.6, 133.7, 133.4, 132.5, 128.2,
127.6, 127.5, 126.9, 126.8, 126.5, 104.4, 102.5, 19.4, 19.3, 11.5, 0.06.
1,4-Bis(diisopropylsilyl)-2,5-bis(trimethylsilylethynyl)benzene (1m)
Compound 1m was obtained from 1,4-dibromo-2,5-bis(trimethylsilyl-
ethynyl)benzene (0.32 g, 0.66 mmol); yield: 0.16 g (49%); colorless solid;
mp 126.8–128.5 °C.
1H NMR (CDCl3, 400 MHz): δ = 7.59 (s, 2 H, ArH), 3.97 (t, J = 4.0 Hz, 2
H, SiH), 1.48–1.40 [m, 4 H, 4 × CH(CH3)2], 1.10 [d, J = 7.6 Hz, 12 H, 2 ×
CH(CH3)2], 0.98 [d, J = 7.2 Hz, 12 H, 2 × CH(CH3)2], 0.25 [s, 18 H, 2 ×
Si(CH3)3].
HRMS (EI): m/z [M]+ calcd for C21H30Si2: 338.1886; found: 338.1880.
13C NMR (CDCl3, 100 MHz): δ = 140.4, 139.0, 127.8, 106.8, 98.1, 19.4,
19.2, 11.3, –0.09.
2-Diisopropylsilyl-3-trimethylsilylethynylnaphthalene (1j)
Anal. Calcd for C28H50Si4: C, 67.39; H, 10.10. Found: C, 67.20; H, 10.25.
Compound 1j was obtained from 2-bromo-3-trimethylsilylethynyl-
naphthalene (0.26 g, 0.86 mmol); yield: 0.16 g (55%); colorless oil.
1H NMR (CDCl3, 400 MHz): δ = 8.01 (d, J = 7.2 Hz, 2 H, ArH), 7.81–7.74
(m, 2 H, ArH), 7.51–7.46 (m, 2 H, ArH), 4.10 (t, J = 4.4 Hz, 1 H, SiH),
1.57–1.48 [m, 2 H, 2 × CH(CH3)2], 1.14 [d, J = 7.2 Hz, 6 H, CH(CH3)2],
1.01 [d, J = 7.6 Hz, 6 H, CH(CH3)2], 0.28 [s, 9 H, Si(CH3)3].
2,6-Bis(diisopropylsilyl)-1,5-bis(trimethylsilylethynyl)naphtha-
lene (1n)
Compound 1n was obtained from 2,6-dibromo-1,5-bis(trimethylsilyl-
ethynyl)naphthalene (0.21 g, 0.44 mmol); yield: 0.12 g (50%); color-
less solid; mp 163.8–165.2 °C.
13C NMR (CDCl3, 100 MHz): δ = 137.8, 134.7, 133.3, 132.5, 132.3,
128.0, 127.6, 127.1, 126.9, 125.1, 107.1, 96.1, 19.5, 19.4, 11.5, –0.03.
HRMS (EI): m/z [M]+ calcd for C21H30Si2: 338.1886; found: 338.1886.
1H NMR (CDCl3, 400 MHz): δ = 8.37 (d, J = 8.4 Hz, 2 H, ArH), 7.67 (d, J =
8.4 Hz, 2 H, ArH), 4.20 (t, J = 3.6 Hz, 2 H, SiH), 1.58–1.50 [m, 4 H, 4 ×
CH(CH3)2], 1.15 [d, J = 7.6 Hz, 12 H, 2 × CH(CH3)2], 1.02 [d, J = 7.6 Hz, 12
H, 2 × CH(CH3)2], 0.33 [s, 18 H, Si(CH3)3].
13C NMR (CDCl3, 100 MHz): δ = 138.6, 133.6, 133.4, 127.9, 125.7,
104.1, 102.8, 19.30, 19.29, 11.4, 0.03.
1-Dimethylsilyl-2-trimethylsilylethynylnaphthalene (1k)
Compound 1k (0.15 g, 62%) was obtained from 1-bromo-2-trimethyl-
silylethynylnaphthalene (0.26 g, 0.86 mmol) using Me2SiHCl instead
of i-Pr2SiHCl; yield: 0.15 g (62%); colorless oil.
Anal. Calcd for C32H52Si4: C, 70.00; H, 9.55. Found: C, 70.10; H, 9.70.
1H NMR (CDCl3, 400 MHz): δ = 8.44 (d, J = 8.0 Hz, 1 H, ArH), 7.81–7.76
(m, 2 H, ArH), 7.54–7.45 (m, 3 H, ArH), 5.21 (sept, J = 3.6 Hz, 1 H, SiH),
0.58 (d, J = 3.6 Hz, 6 H, 2 × CH3), 0.29 [s, 9 H, Si(CH3)3].
2,6-Bis(diisopropylsilyl)-3,7-bis(trimethylsilylethynyl)naphtha-
lene (1o)
Compound 1o was obtained from 2,6-dibromo-3,7-bis(trimethylsilyl-
ethynyl)naphthalene (0.18 g, 0.38 mmol); yield: 0.12 g (58%); color-
less solid; mp 137.3–138.2 °C.
13C NMR (CDCl3, 100 MHz): δ = 139.2, 137.0, 132.7, 129.9, 129.6,
128.9, 128.22, 128.15, 126.4, 126.3, 107.1, 99.3, –0.08, –2.82.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–G

F
H. Arii et al.
Feature
Synthesis
1H NMR (CDCl3, 400 MHz): δ = 7.98 (s, 2 H, ArH), 7.92 (s, 2 H, ArH),
4.11 (t, J = 4.0 Hz, 2 H, SiH), 1.55–1.47 [m, 4 H, 4 × CH(CH3)2], 1.14 [d,
J = 7.6 Hz, 12 H, 2 × CH(CH3)2], 1.01 [d, J = 7.2 Hz, 12 H, 2 × CH(CH3)2],
0.28 [s, 18 H, Si(CH3)3].
13C NMR (100 MHz, CDCl3): δ = 153.7, 147.4, 143.9, 136.0, 134.9,
129.2, 128.9, 128.7, 126.7, 125.9, 125.8, 123.3, 18.23, 18.17, 11.3, 0.10.
29Si DEPT NMR (119 MHz, CDCl3): δ = 24.6, –6.1.
HRMS (EI): m/z [M]+ calcd for C21H30Si2: 338.1886; found: 338.1859.
13C NMR (CDCl3, 100 MHz): δ = 137.2, 136.1, 132.4, 132.0, 126.1,
106.9, 97.0, 19.4, 19.3, 11.5, –0.05.
1,1-Diisopropyl-2-trimethylsilylnaphtho[2,3-b]silole (2j)
Anal. Calcd for C32H52Si4: C, 70.00; H, 9.55. Found: C, 70.06; H, 9.74.
Compound 2j was obtained by the hydrosilylation of 1j (32.8 mg, 96.9
μmol) for 30 min; yield: 24.8 mg (76%); colorless oil.
1H NMR (CDCl3, 400 MHz): δ = 7.97 (s, 1 H, ArH), 7.84–7.78 (m, 2 H,
ArH), 7.78 (s, 1 H, CH=C), 7.66 (s, 1 H, ArH), 7.48–7.41 (m, 2 H, ArH),
1.37 [sept, J = 7.2 Hz, 2 H, 2 × CH(CH3)2], 1.11 [d, J = 7.2 Hz, 6 H,
CH(CH3)2], 0.96 [d, 6 H, J = 7.2 Hz, CH(CH3)2], 0.24 [s, 9 H, Si(CH3)3].
13C NMR (CDCl3, 100 MHz): δ = 158.5, 148.3, 145.3, 135.5, 134.8,
133.3, 133.1, 128.5, 128.3, 126.4, 125.8, 122.2, 18.2, 18.1, 11.6, 0.04.
29Si DEPT NMR (119 MHz, CDCl3): δ = 23.3, –6.2.
HRMS (EI): m/z [M]+ calcd for C21H30Si2: 338.1886; found: 338.1886.
Chain Hydrosilylation; General Procedure
To trityl tetrakis(pentafluorophenyl)borate (TTPFPB, 1.0 mg, 0.10
μmol) in benzene (0.5 mL) was added a benzene solution (1.5 mL) of
the corresponding 1a–l (0.10 mmol) or a benzene solution (0.5 mL) of
the corresponding 1m–o (50.0 μmol) at r.t. under argon atmosphere,
and the resulting solution was stirred at r.t.. After quenching the reac-
tion mixture with 2,6-lutidine (2 μL) and H2O, the mixture was ex-
tracted with hexane (2 × 5 mL). The organic layers were combined
and dried (anhyd Na2SO4), filtered, and the solvent was evaporated
under reduced pressure. Purification was carried out by GPLC to re-
move polymeric materials.
1,1-Dimethyl-2-trimethylsilylnaphtho[1,2-b]silole (2k)
Compound 2k was obtained by the hydrosilylation of 1k (28.3 mg,
100 μmol) with 2 mol% TTPFPB (1.9 mg, 2.0 μmol) for 12 h; yield: 9.0
mg (32%); colorless oil.
1H NMR (400 MHz, CDCl3): δ = 7.84 (d, J = 8.0 Hz, 2 H, ArH), 7.80 (d, J =
8.4 Hz, 1 H, ArH), 7.63 (s, 1 H, CH=C), 7.50–7.40 (m, 3 H, ArH), 0.49 [s,
6 H, Si(CH3)2], 0.22 [s, 9 H, Si(CH3)3].
13C NMR (100 MHz, CDCl3): δ = 155.6, 148.7, 147.0, 139.1, 136.1,
132.9, 130.5, 129.0, 128.5, 126.5, 125.3, 123.3, –0.3, –2.5.
29Si DEPT NMR (119 MHz, CDCl3): δ = 11.8, –6.2.
HRMS (EI): m/z [M]+ calcd for C17H28Si2: 282.1260; found: 282.1261.
1,1-Diisopropyl-5-methoxy-2-trimethylsilylbenzo[b]silole (2h)
Compound 2h was obtained by the hydrosilylation of 1h (30.8 mg,
96.7 μmol) for 12 h with 5 mol% TTPFPB; yield: 10.5 mg (34%); color-
less oil.
1H NMR (CDCl3, 400 MHz): δ = 7.54 (s, 1 H, CH=C), 7.40 (d, J = 7.6 Hz, 1
H, ArH), 6.85 (d, J = 2.4 Hz, 1 H, ArH), 6.75 (dd, J = 7.6, 2.4 Hz, 1 H,
ArH), 3.82 (s, 3 H, OCH3), 1.31–1.22 [m, 2 H, 2 × CH(CH3)2], 1.05 [d, J =
7.2 Hz, 6 H, CH(CH3)2], 0.92 [d, J = 7.6 Hz, 6 H, CH(CH3)2], 0.18 [s, 9 H,
Si(CH3)3].
13C NMR (100 MHz, CDCl3): δ = 161.5, 157.8, 153.2, 145.1, 133.6,
127.9, 112.3, 110.4, 55.2, 18.17, 18.15, 11.40, 11.38, –0.03.
1,1,5,5-Tetraisopropyl-2,6-bis(trimethylsilyl)-1,5-disila-1,5-dihy-
dro-s-indacene (2m)
29Si DEPT NMR (119 MHz, CDCl3): δ = 22.8, –6.5.
HRMS (EI): m/z [M]+ calcd for C18H30OSi2: 318.1835; found: 318.1838.
Compound 2m was obtained by the double hydrosilylation of 1m
(24.7 mg, 49.5 μmol) for 2 h; yield: 18.6 mg (75%); colorless solid; mp
174.5–175.8 °C.
1,1-Diisopropyl-7-methoxy-2-trimethylsilylbenzo[b]silole (2h′)
Compound 2h′ was obtained by the hydrosilylation of 1h (62.6 mg,
0.196 mmol) for 2 days with 5 mol% TTPFPB; yield: 12.3 mg (20%);
colorless oil.
1H NMR (CDCl3, 400 MHz): δ = 7.55 (s, 1 H, CH=C), 7.29 (dd, J = 8.0 Hz,
J = 7.2 Hz, 1 H, ArH), 6.90 (d, J = 7.6 Hz, 1 H, ArH), 6.72 (d, J = 7.6 Hz, 1
H, ArH), 3.79 (s, 3 H, OCH3), 1.38 [sept, J = 7.6 Hz, 2 H, 2 × CH(CH3)2],
1.04 [d, J = 7.6 Hz, 6 H, CH(CH3)2], 0.94 [d, J = 7.2 Hz, 6 H, CH(CH3)2],
0.18 [s, 9 H, Si(CH3)3].
1H NMR (CDCl3, 400 MHz): δ = 7.63 (s, 2 H, HC=C), 7.41 (s, 2 H, ArH),
1.30 [sept, J = 7.2 Hz, 4 H, 4 × CH(CH3)2], 1.07 [d, J = 7.2 Hz, 12 H, 2 ×
CH(CH3)2], 0.94 [d, J = 7.2 Hz, 12 H, 2 × CH(CH3)2], 0.18 [s, 18 H,
Si(CH3)3].
13C NMR (CDCl3, 100 MHz): δ = 158.8, 150.0, 142.9, 139.5, 128.5, 18.2,
11.4, 0.02.
9Si DEPT NMR (119 MHz, CDCl3): δ = 23.0, –6.6.
13C NMR (100 MHz, CDCl3): δ = 162.9, 157.6, 153.0, 143.9, 131.7,
Anal. Calcd for C28H50Si4: C, 67.39; H, 10.10. Found: C, 67.21; H, 10.17.
123.6, 117.4, 109.3, 55.1, 18.4, 18.2, 11.3, 0.04.
3,3,8,8-Tetraisopropyl-2,7-bis(trimethylsilyl)naphtho[2,1-b:6,5-
b′]disilole (2n)
29Si DEPT NMR (119 MHz, CDCl3): δ = 28.0, –6.4.
HRMS (EI): m/z [M]+ calcd for C18H30OSi2: 318.1835; found: 318.1866.
Compound 2n was obtained by the double hydrosilylation of 1n (27.3
mg, 49.7 μmol) as a starting material for 2 h; yield: 19.4 mg (71%);
colorless solid; mp 183.5–184.1 °C.
1H NMR (CDCl3, 400 MHz): δ = 8.45 (s, 2 H, HC=C), 8.23 (d, J = 8.0 Hz, 2
H, ArH), 7.70 (d, J = 8.0 Hz, 2 H, ArH), 1.40 [sept, 4 H, 7.2 Hz, 4 ×
CH(CH3)2], 1.10 [d, J = 7.6 Hz, 12 H, 2 × CH(CH3)2], 0.96 [d, J = 7.6 Hz, 12
H, 2 × CH(CH3)2], 0.26 [s, 18 H, Si(CH3)3].
13C NMR (CDCl3, 100 MHz): δ = 154.3, 147.9, 143.9, 135.9, 130.2,
129.0, 121.7, 18.3, 18.2, 11.3, 0.11.
29Si DEPT NMR (119 MHz, CDCl3): δ = 25.0, –6.1.
3,3-Diisopropyl-2-trimethylsilylnaphtho[2,1-b]silole (2i)
Compound 2i was obtained by the hydrosilylation of 1i (32.8 mg, 96.9
μmol) for 80 min; yield: 23.6 mg (72%); colorless oil.
1H NMR (CDCl3, 400 MHz): δ = 8.43 (s, 1 H, CH=C), 8.31 (d, J = 8.4 Hz, 1
H, ArH), 7.85 (d, J = 7.6 Hz, 1 H, ArH), 7.71 (d, J = 7.6 Hz, 1 H, ArH), 7.64
(d, J = 8.0 Hz, 1 H, ArH), 7.53 (ddd, J = 8.4, 6.8, 1.2 Hz, 1 H, ArH), 7.47
(ddd, J = 8.4, 6.8, 1.2 Hz, 1 H, ArH), 1.39 [sept, 7.6 Hz, 2 H, 2 ×
CH(CH3)2], 1.09 [d, J = 7.2 Hz, 6 H, CH(CH3)2], 0.95 [d, J = 7.2 Hz, 6 H,
CH(CH3)2], 0.25 [s, 9 H, Si(CH3)3].
Anal. Calcd for C32H52Si4: C, 70.00; H, 9.55. Found: C, 70.40; H, 9.87.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–G

G
H. Arii et al.
Feature
Synthesis
1,1,6,6-Tetraisopropyl-2,7-bis(trimethylsilyl)naphtho[2,3-b:6,7-
b′]disilole (2o)
(3) (a) Dubac, J.; Laporterie, A.; Manuel, G. Chem. Rev. 1990, 90, 215.
(b) Ilies, L.; Tsuji, H.; Sato, Y.; Nakamura, E. J. Am. Chem. Soc.
2008, 130, 4240. (c) Zhang, F.-B.; Adachi, Y.; Ooyama, Y.;
Ohshita, J. Organometallics 2016, 35, 2327. (d) Kinoshita, H.;
Ueda, A.; Fukumoto, H.; Miura, K. Org. Lett. 2017, 19, 882.
(e) Shintani, R.; Misawa, N.; Tsuda, T.; Iino, R.; Fujii, M.;
Yamashita, K.; Nozaki, K. J. Am. Chem. Soc. 2017, 139, 3861.
(4) (a) Shimizu, M.; Mochida, K.; Hiyama, T. Angew. Chem. Int. Ed.
2008, 47, 9760. (b) Tobisu, M.; Onoe, M.; Kita, Y.; Chatani, N.
J. Am. Chem. Soc. 2009, 131, 7506. (c) Ouyang, K.; Liang, Y.; Xi, Z.
Org. Lett. 2012, 14, 4572. (d) Onoe, M.; Baba, K.; Kim, Y.; Kita, Y.;
Tobisu, M.; Chatani, N. J. Am. Chem. Soc. 2012, 134, 19477.
(5) (a) Matsuda, T.; Kadowaki, S.; Murakami, M. Chem. Commun.
2007, 43, 2627. (b) Ureshino, T.; Yoshida, T.; Kuninobu, Y.; Takai,
K. J. Am. Chem. Soc. 2010, 132, 14324. (c) Matsuda, T.;
Yamaguchi, Y.; Shigeno, M.; Sato, S.; Murakami, M. Chem.
Commun. 2011, 47, 8697. (d) Zhang, Q.-W.; An, K.; He, W.
Angew. Chem. Int. Ed. 2014, 53, 5667. (e) Zhang, Q.-W.; An, K.;
Liu, L.-C.; Guo, S.; Jiang, C.; Guo, H.; He, W. Angew. Chem. Int. Ed.
2016, 55, 6319.
Compound 2o was obtained by the double hydrosilylation of 1o (27.1
mg, 49.4 μmol) for 2 h; yield: 12.1 mg (45%); colorless solid; mp
220.7–221.7 °C.
1H NMR (CDCl3, 400 MHz): δ = 7.91 (s, 2 H, ArH), 7.75 (s, 2 H, HC=C),
7.62 (s, 2H, ArH), 1.35 [sept, J = 7.6 Hz, 4 H, 4 × CH(CH3)2], 1.10 [d, J =
7.2 Hz, 12 H, 2 × CH(CH3)2], 0.95 [d, J = 7.6 Hz, 12 H, 2 × CH(CH3)2],
0.23 [s, 18 H, Si(CH3)3].
13C NMR (CDCl3, 100 MHz): δ = 158.5, 148.5, 144.8, 136.0, 134.3,
133.7, 122.7, 18.2, 18.1, 11.6, 0.06.
29Si DEPT NMR (119 MHz, CDCl3): δ = 23.2, –6.3.
Anal. Calcd for C32H52.5O0.25Si4: C, 69.43; H, 9.56. Found: C, 69.58; H,
9.68.
Funding Information
This work was financially supported by a Grant-in-Aid for Scientific
Research (No. 26410035, T.K.) from the Ministry of Education,
(6) Curless, L. D.; Ingleson, M. J. Organometallics 2014, 33, 7241.
(7) Leifert, D.; Studer, A. Org. Lett. 2015, 17, 386.
(8) Ilies, L.; Tsuji, H.; Nakamura, E. Org. Lett. 2009, 11, 3966.
(9) (a) Furukawa, S.; Kobayashi, J.; Kawashima, T. J. Am. Chem. Soc.
2009, 131, 14192. (b) Furukawa, S.; Kobayashi, J.; Kawashima, T.
Dalton Trans. 2010, 39, 9329.
Culture, Sports, Science and Technology, Japan.
M
n
isitry
of
E
d
u
c
oaitn
,
C
utler
,
S
p
orts,
Secince
a
n
d
Tech
n
o
lg
y
,
a
Jp
a
n;
Gra
n
-ti-A
d
i
o
f
r
Secnifit
Reseacrh
2(
6
4
1
0
0
3
5)
Acknowledgment
(10) Although the synthesis of stable β,β′-disilyl-substituted vinyl
cations by similar intramolecular addition reactions and the X-
ray crystal structure of one of them were reported, there is no
report on the hydride abstraction by these species from the
starting hydrosilanes, see: (a) Müller, T.; Meyer, R.; Lennartz,
D.; Siehl, H.-U. Angew. Chem. Int. Ed. 2000, 39, 3074. (b) Müller,
T.; Juhasz, M.; Reed, C. A. Angew. Chem. Int. Ed. 2004, 43, 1543.
(11) (a) Arii, H.; Nakabayashi, K.; Mochida, K.; Kawashima, T. Molecules
2016, 21, 999. (b) For an intermolecular version giving silacyclic
compounds, see: Arii, H.; Kurihara, T.; Kunio, M.; Kawashima, T.
Chem. Commun. 2014, 50, 6649.
This work was performed under the Cooperative Research Program of
‘Network Joint Research Center for Materials and Devices’ (H.A.). We
acknowledge the Center for Collaborative Research and Community
Cooperation (University of Miyazaki) for 1H and 13C NMR spectrosco-
py. We thank Prof. Masafumi Unno (Graduate School of Science and
Technology, Gunma University) for measurement of 29Si NMR spectra.
We thank Dr. Nobuaki Tsuda (Center for Industry, University and
Government Cooperation, Nagasaki University) for measurement of
high-resolution mass spectroscopy and Ms. Yachiyo Taniyama (Nagoya
Institute of Technology) for measurement of elemental analysis.
(12) Ihara, E.; Young, V. G. Jr.; Jordan, R. F. J. Am. Chem. Soc. 1998, 120,
8277.
Supporting Information
(13) Sudo, T.; Asao, N.; Yamamoto, Y. J. Org. Chem. 2000, 65, 8919.
(14) (a) Matsuda, T.; Kato, K.; Goya, T.; Shimada, S.; Murakami, M.
Chem. Eur. J. 2016, 22, 1941. (b) Jančařík, A.; Rybáček, J.; Cocq,
K.; Chocholoušova, J. V.; Vacek, J.; Pohl, R.; Bednárová, L.;
Fiedler, P.; Císařová, I.; Stará, I. G.; Starý, I. Angew. Chem. Int. Ed.
2013, 52, 9970. (c) Shinamura, S.; Osaka, I.; Miyazaki, E.; Nakao,
A.; Yamagishi, M.; Takeya, J.; Takimiya, K. J. Am. Chem. Soc. 2011,
133, 5024. (d) Škalamera, D.; Mlinarič-Majerski, K.; Martin-
Kleiner, I.; Kralj, M.; Wan, P.; Basarič, N. J. Org. Chem. 2014, 79,
4390. (e) Takimiya, K.; Konda, Y.; Ebata, H.; Niihara, N.; Otsubo,
T. J. Org. Chem. 2005, 70, 10569.
Supporting information for this article is available online at
https://doi.org/10.1055/s-0036-1590911.
S
u
p
p
ortioInfgrmoaitn
S
u
p
p
ortiInfogrmoaitn
References
(1) (a) Yamaguchi, S.; Tamao, K. J. Chem. Soc., Dalton Trans. 1998,
3693. (b) Wong, W. W. H.; Holms, A. B. Adv. Polym. Sci. 2008,
212, 85. (c) Chen, J.; Cao, Y. Acc. Chem. Res. 2009, 42, 1709.
(d) Facchetti, A. Chem. Mater. 2011, 23, 733. (e) Yu, J.; Rong, Y.;
Kuo, C.-T.; Zhou, X.-H.; Chiu, D. T. Anal. Chem. 2017, 89, 42.
(2) Yamaguchi, S.; Tamao, K. Bull. Chem. Soc. Jpn. 1996, 69, 2327.
(15) Fulmer, G. R.; Miller, A. J. M.; Sherden, N. H.; Gottlieb, H. E.;
Nudelman, A.; Stoltz, B. M.; Bercaw, J. E.; Goldberg, K. I.
Organometallics 2010, 29, 2176.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–G