Synthesis of Tetrasilatetrathia[8]circulenes through C-I and C-H Silylation

Article abstract of DOI:10.1055/a-1437-9917

We have succeeded in the synthesis of various tetrasilatetrathia[8]circulenes with alkyl and aryl groups on the silicon atoms. We also disclosed the effect of phosphine ligands on palladium-catalyzed silylation of tetraiodotetrathienylene and rhodium-cata

Full text of DOI:10.1055/a-1437-9917

SYNTHESIS
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Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart
2
021, 53, A–F
special topic
A
Bond Activation – in Honor of Prof. Shinji
Synthesis
S. Akahori et al.
Special Topic
Synthesis of Tetrasilatetrathia[8]circulenes through C–I and C–H
Silylation
Shuhei Akahoria
Tetsuaki Fujiharab
Yasushi Tsujib
Hiroshi Shinokuboa
Yoshihiro Miyake*a
a
Department of Molecular and Macromolecular Chemistry,
Graduate School of Engineering, Nagoya University, Furo-cho,
Chikusa-ku, Nagoya 464-8603, Japan
miyake@chembio.nagoya-u.ac.jp
Department of Energy and Hydrocarbon Chemistry, Graduate
b
School of Engineering, Kyoto University, Kyoto 615-8510,
Japan
Published as part of the Special Topic
Bond Activation – in Honor of Prof. Shinji Murai
YDke Muoe ,spahNai Cilrahotmgmiror rioyee nasMpkt4 ioeo6y @nfa4 dkMc- i8heno6eglm0e A3cbu,u iJltoah.prno aar ngn od y Ma - au c. ra oc m. jpolecular Chemistry, Department of Molecular and Macromolecular Chemistry, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-
Received: 05.03.2021
Accepted after revision: 15.03.2021
Published online: 15.03.2021
obtain 1 started with the direct lithiation of tetrathienylene
with lithium diisopropylamide (LDA) followed by the re-
2
DOI: 10.1055/a-1437-9917; Art ID: ss-2021-f0107-st
action with dichlorodimethylsilane. However, this afforded
a complex mixture without the formation of 1. Eventually,
we successfully synthesized tetrasilatetrathia[8]circulenes
Abstract We have succeeded in the synthesis of various tetrasila-
tetrathia[8]circulenes with alkyl and aryl groups on the silicon atoms.
We also disclosed the effect of phosphine ligands on palladium-cata-
lyzed silylation of tetraiodotetrathienylene and rhodium-catalyzed in-
tramolecular silylation of tetrasilyltetrathienylenes. Experimental and
theoretical analysis revealed the effect of the substituents on the silicon
atoms on their electronic property.
1
in two steps from tetraiodotetrathienylene 3 through pal-
ladium-catalyzed C–I silylation with hydrosilane and rhodi-
1
2
um-catalyzed intramolecular C–H silylation. The substitu-
ents (R) on the silicon atoms in 1 are limited to ethyl and
hexyl groups. In this paper, we describe an improved route
for the synthesis of tetrasilatetrathia[8]circulenes 1a–1d
with various alkyl and aryl groups on the silicon atoms. The
effects of phosphine ligands on the palladium-catalyzed si-
lylation of 3 and rhodium-catalyzed intramolecular silyla-
tion of 4 are also evaluated. Furthermore, we have also in-
vestigated the structure and photophysical properties of
tetrasilatetrathia[8]circulenes 1c (R = Ph) and 1d (R = Me).
We examined the palladium-catalyzed silylation of
tetraiodotetrathienylene 3 with hydrosilanes (Table 1). In
entry 1 and 2, treatment of 3 with diethylsilane and dihex-
ylsilane in the presence of Pd(Pt-Bu ) afforded the corre-
Key words circulene, silole, bond activation, silylation, palladium,
rhodium, phosphine ligand
Silicon-containing -conjugated molecules such as si-
loles have attracted considerable attention as novel organic
optoelectronic materials owing to the rigid framework and
1
,2
low-lying LUMO level induced by *–* interaction. The
formation of C–Si bonds is a crucial step in the synthesis of
organosilicon compounds. The synthesis of siloles often
employs nucleophilic substitution reactions of halosilanes
with lithiated arenes and transition-metal-catalyzed C–Si
3
2
sponding tetrasilyltetrathienylenes 4a and 4b in 81% and
77% yield, respectively (Table 1, entries 1 and 2). However,
the reaction of 3 with diphenylsilane under similar condi-
tions did not result in the formation of 4c and provided de-
halogenated product 2 quantitatively (Table 1, entry 3). The
use of Pd(PPh ) and PdCl (PCy ) instead of Pd(Pt-Bu ) was
3
–6
bond formation.
Hetero[8]circulenes are heteroatom-containing macro-
cyclic arenes in which central eight-membered rings are
surrounded by eight fused benzenoids and heteroles.
Hetero[8]circulenes annulated by heteroles such as thio-
phenes, furans, pyrroles, and selenophenes have been suc-
cessfully synthesized. Recently, we have reported the syn-
thesis of tetrasilatetrathia[8]circulenes 1 which consist of
thiophenes and siloles (Scheme 1). Our initial attempts to
7
–14
3
4
2
3
2
3 2
insufficient for this reaction (Table 1, entries 4 and 5).
Yamanoi, Nishihara, and co-workers reported the dehaloge-
nation of aryl iodides occurred in the reaction with bulky
6
b
silanes as substrates. They also proposed that a mono-
©
2021. Thieme. All rights reserved. Synthesis 2021, 53, A–F
Georg Thieme Verlag KG, Rüdigerstraße 14, 70469 Stuttgart, Germany

B
Synthesis
S. Akahori et al.
Special Topic
Li Li
Li Li
S
S
S
S
S
S
S
S
R SiCl2
2
Li
Li
Li
Li
lithiation
Nucleophilic substitution
reaction of halosilanes
2
R2
Si
R2
Si
I
H
S
S
S
S
S
S
S
S
S
S
S
R2SiH2
H
I
SiR2
R2Si
SiR2
I
Intermolecular
C–I silylation
R2Si
Intramolecular
C–H silylation
H
S
H
Si
I
Si
R2
R2
3
4a (R = Et)
1a (R = Et)
4
4
4
b (R = hexyl)
c (R = Ph)
d (R = Me)
1b (R = hexyl)
1c (R = Ph)
1d (R = Me)
Scheme 1 Synthetic strategy of tetrasilatetrathia[8]circulenes 1
phosphine palladium complex serves as a catalytically ac-
tive species in the silylation reaction. The use of a sterically
Table 1 The Effects of Phosphine Ligands on Palladium-Catalyzed
Silylation of 3 with Hydrosilanes
hindered phosphine ligand such as Pt-Bu is critical to pro-
3
mote the formation of the monophosphine palladium spe-
cies. When the combination of allyl(cyclopentadienyl)palla-
dium [Pd(-allyl)Cp] with XPhos was applied to the reac-
tion of 3 with diphenylsilane, silylated product 4c was not
observed with the formation of 2 (Table 1, entry 6). These
results suggest that sterically hindered phosphine ligands
are not useful with bulky silanes. The bowl-shaped phos-
phine (BSP) has already been reported to generate highly
active monophosphine palladium species owing to the suf-
R2
Si
I
R2SiH2 (8.0 equiv)
Pd catalyst
ligand
H
S
S
S
S
S
S
S
S
S
S
S
S
H
SiR2
I
Et3N (8.0 equiv)
R2Si
I
H
THF, rt, 48 h
H
Si
R2
I
3
4a (R = Et)
b (R = hexyl)
c (R = Ph)
2
4
4
ficient empty space around the phosphorus atom and the
bulkiness of peripheral aryl groups.15 Consequently, the use
t-Bu
Me
Me
of BSP provided tetrakis(diphenylsilyl)tetrathienylene 4c in
4
9% yield (Table 1, entry 7).
Me
Me
PCy2
Pr
P
iPr
i
Furthermore, we investigated the rhodium-catalyzed
intramolecular dehydrogenative silylation of tetrasilyltetra-
thienylenes 4 (Table 2). Takai, Kuninobu, and co-workers re-
ported the synthesis of silafluorene with Wilkinson catalyst
iPr
t-Bu
3
Xphos
Bowl-shaped phosphine (BSP)
4
a
[
RhCl(PPh ) ]. In this case, however, the desired product
3 3
1
a was obtained in only 16% yield under similar conditions
Pd catalysta
Ligandb
Yield (%)
c
Entry
R
(
[
Table 2, entry 1). The reaction of 4a in the presence of
Rh(cod)Cl] and monodentate phosphine ligands such as
4
2
2
P(C F ) and P(4-CF C H ) yielded a trace amount of 1a (Ta-
6
5
3
3
6
4 3
1
Et
Pd(Pt-Bu
3
3
)
2
2
2
–
81 (4a)
0
0
ble 2, entries 2 and 3). Mitsudo, Suga, and co-workers de-
veloped Rh/bidentate ligand-catalyzed intramolecular de-
2
hexyl
Ph
Pd(Pt-Bu
)
–
77 (4b)
4
d
3
Pd(Pt-Bu3)
–
0
>99
0
hydrogenative silylation leading to benzosilolothiophene.
In contrast to monodentate ligands, the reaction with
Rh(cod)Cl] and bidentate ligands such as dppe (Table 2,
4d
5
Ph
Pd(PPh
PdCl (PCy
–
0
3 4
)
[
2
Ph
2
3
)
2
–
0
>99
entry 4), dppe-F20 (Table 2, entry 5), and dppf (Table 2, en-
try 6) provided the desired product 1a in 50%, 54%, and 60%
yields, respectively. The intramolecular silylation of 4b with
dppf as a ligand furnished the corresponding tetrasilatetra-
thia[8]circulene 1b in 23% yield (Table 2, entry 7). The reac-
tion of 4c under similar conditions afforded 1c in 6% yield.
To improve the yield of 1c, we conducted sila-Friedel–Crafts
reaction of 4c with Ph CB(C F ) and 2,6-lutidine (Scheme
–e
6
Ph
Pd(-allyl)Cp
Pd(-allyl)Cp
XPhos
BSP
0
7
Ph
49 (4c)
0
a
2
2
0 mol% of Pd catalyst was used.
2 mol% of ligand was used.
b
c
Yield determined by 1H NMR analysis using 1,1,2,2-tetrachloroethane as
internal standard.
d
3
2
5% of 3 was recovered.
was detected by H NMR.
e
1
3
6 5 4
©
2021. Thieme. All rights reserved. Synthesis 2021, 53, A–F

C
Synthesis
S. Akahori et al.
Special Topic
Table 2 The Effects of Phosphine Ligands on Rhodium-Catalyzed De-
hydrogenative Intramolecular Silylation of 4a–c
action sequence of palladium-catalyzed silylation, reduc-
tion, and rhodium-catalyzed intramolecular silylation. The
1
H NMR spectrum of 1d in CDCl exhibited one singlet sig-
3
R2
Si
13
R2
Si
nal of methyl groups ( = 0.50). In the C NMR spectrum,
H
S
S
S
S
Rh catalyst
ligand
S
S
S
S
three signals were observed at  = 149.0, 146.1, and –2.0,
suggesting a D4h symmetric structure for 1d.
H
SiR2
R2Si
SiR2
R2Si
H
toluene, 140 °C
24 h
I
Me2(OEt)SiH (8.0 equiv)
H
Si
Si
R2
S
S
S
S
Pd(Pt-Bu3)2 (20 mol%)
Et3N (8.0 equiv)
R2
LiAlH4 (12 equiv)
Et2O, reflux, 24 h
I
4
a (R = Et)
1a (R = Et)
I
4
4
b (R = hexyl)
c (R = Ph)
1b (R = hexyl)
1c (R = Ph)
toluene, rt, 24 h
I
3
Me2
Si
S
PPh2
Fe
S
S
[
RhCl(cod)]2 (15 mol%)
PPh2
P(C6F5)2
Ph2P
(C6F5)2P
dppf (45 mol%)
PPh2
Me2Si
S
SiMe2
toluene, 140 °C, 24 h
dppe
dppe-F20
dppf
Si
1d: 28%
(3 steps from 3)
Me2
Entry
R
Rh catalysta
RhCl(PPh
Ligandb
Yield (%) of 1
Scheme 3 Synthesis of octamethyltetrasilatetrathia[8]circulene 1d
with ethoxydimethylsilane as silicon source
1
2
3
4
5
6
7
Et
3
)
3
–
16 (1a)
trace
Et
[RhCl(cod)]
[RhCl(cod)]
[RhCl(cod)]
[RhCl(cod)]
[RhCl(cod)]
[RhCl(cod)]
[RhCl(cod)]
2
2
2
2
2
2
2
6 5 3
P(C F )
A single crystal of octamethyltetrasilatetrathia[8]circu-
lene 1d was obtained by slow evaporation of a chloroform
solution of 1d. The X-ray diffraction analysis confirmed the
molecular structure of 1d (Figure 1). The mean plane devia-
tion of the circulene core is 0.031 Å. The sum of the inner
angles of the central eight-membered ring is 1079.58°,
which are close to that of a regular octagon (1080°). These
results demonstrate the highly planar structure of 1d,
which is the same as that of the ethyl analogue 1a. The C–C,
C–S, and C–Si bond lengths in 1d were similar to those of 1a
Et
P(4-CF
dppe
3
C
6
H
4
)
3
trace
Et
50 (1a)
54 (1a)
60 (1a)
23 (1b)
6 (1c)
Et
dppe-F20
dppf
Et
hex
Ph
dppf
8
dppf
a
3
9
0 mol% of RhCl(PPh
0 mol% of monodentate ligands and 45 mol% bidentate ligands were
3
)
3
and 15 mol% of [RhCl(cod)]
2
were used.
b
used.
12
(
Figure S8).
2
2
).16 Tetrasilatetrathia[8]circulene 1c was synthesized in
1% yield through palladium-catalyzed silylation and the
sila-Friedel–Crafts reaction.
We have also attempted to synthesize 1d (Scheme 3). In
the synthesis of 1d, ethoxydimethylsilane was used as the
silicon source because dimethylsilane is difficult to handle
at room temperature. Tetraiodotetrathienylene 3 was trans-
formed into 1d in a three-step yield of 28% through the re-
Ph2
Figure 1 Crystal structure of 1d. (a) Top view and (b) side view. Ther-
mal ellipsoids are drawn at the 50% probability level. All hydrogen at-
oms are omitted for clarity.
Ph2SiH2 (8.0 equiv)
Pd(π-allyl)Cp (20 mol%)
BSP (22 mol%)
I
Si
H
S
S
S
S
S
S
S
S
H
I
Et3N (8.0 equiv)
SiPh2
I
2
Ph Si
toluene, rt, 48 h
H
The electronic absorption spectra and emission spectra
I
3
H
Si
Ph2
Ph2
Si
S
of 1c and 1d in CH Cl are shown in Figure 2. These com-
2 2
S
S
4c
Ph3CB(C6F5)4 (4.8 equiv)
,6-lutidine (4.8 equiv)
pounds displayed intense bands around 270 nm and weak
bands at up to 400 nm. Phenyl derivative 1c showed slightly
red-shifted absorption bands in comparison to 1d. The
time-dependent density functional theory (TD-DFT) calcu-
lations were performed at the B3LYP/6-31G+(d,p) level of
theory. The simulated absorption spectra were consistent
with the experimental spectra (Figure S9, S10). The values
2
Ph2Si
SiPh2
CH2Cl2, rt, 6 h
S
Si
1c: 21%
(2 steps from 3)
Ph2
Scheme 2 Synthesis of octaphenyltetrasilatetrathia[8]circulene 1c
through fourfold sila-Friedel–Crafts reaction
©
2021. Thieme. All rights reserved. Synthesis 2021, 53, A–F

D
Synthesis
S. Akahori et al.
Special Topic
of the oscillator strength for the S –S transition of 1c and
0
1
1
d are zero at 399.71 nm and 379.72 nm, respectively, of
which the major contributions are the HOMO–LUMO tran-
sition. Tetrasilatetrathia[8]circulenes 1c and 1d exhibited
blue emission around 400 nm. Both of the fluorescence
quantum yields of 1c and 1d were about 0.01. These low
emission quantum yields should be ascribed to forbidden
11
S –S transition.
0
1
Figure 2 UV-vis absorption (solid line) and emission (dotted line) spec-
tra of 1c (blue) and 1d (red) in CH Cl ( = 270 nm)
2
2
ex
To gain further insight into the electronic effect by the
substituents on silicon atoms, we performed DFT calcula-
tions of 1c and 1d at the B3LYP/6-31G(d) level. Molecular
orbital (MO) diagrams of 1c and 1d are shown in Figure 3.
The *–* interactions between silicons and the tetra-
thienylene skeleton in LUMO of both 1c and 1d were ob-
served. Although the HOMO level of phenyl derivative 1c
was comparable to that of methyl derivative 1d, the LUMO
level of 1c was stabilized compared to that of 1d. The lower
LUMO of 1c is probably ascribed to the inductive effect of
phenyl groups and the extended *–* interaction over the
phenyl rings on the silicon atoms.17
In summary, we have succeeded in the synthesis of vari-
ous tetrasilatetrathia[8]circulenes with alkyl and aryl
groups on the silicon atoms. The effects of the phosphine li-
gand on the palladium-catalyzed silylation of tetraiodo-
tetrathienylene and rhodium-catalyzed intramolecular si-
lylation of tetrasilyltetrathienylene were also examined. Ex-
perimental and theoretical analysis revealed the structure
and electronic property of tetrasilatetrathia[8]circulene.
Figure 3 MO diagrams of 1c and 1d calculated at the B3LYP/6-31G(d)
level
columns (40 mm × 600 mm × 2 mm) with CHCl as eluent. Solvents
3
were dried by the general methods and degassed before use. Unless
otherwise noted, materials obtained from commercial suppliers were
used without further purification. Allyl(cyclopentadienyl)palladium
[
Pd(-allyl)Cp],18 and tris(4,4′′-di-tert-butyl-2,2′′,6,6′′-tetramethyl-m-
15b
terphenyl-5′′-yl)phosphine (BSP)
were prepared according to the
literature procedures. Synthesis of tetraiodotetrathienylene 3, tetrasi-
lyltetrathienylenes 4a, 4b and tetrasilatetrathia[8]circulenes 1a, 1b
has been reported.12
Octaphenyltetrasilatetrathia[8]circulene 1c
In a 20-mL Schlenk flask were placed 3 (41.6 mg, 0.050 mmol), Pd(-
allyl)Cp (5.11 mg, 0.010 mmol), and BSP (13.5 mg, 0.011 mmol) under
argon. THF (1 mL) was added and the mixture was stirred for 15 min.
Then, Et N (0.28 mL, 0.40 mmol) and Ph SiH (0.26 mL, 0.40 mmol)
were added and the resulting mixture was stirred at rt for 48 h. The
mixture was concentrated in vacuo, the residue was purified by short
column chromatography (silica gel, hexane), the resulting crude was
1H NMR (500 MHz) and 13C NMR (126 MHz) spectra were recorded on
a Bruker AVANCE III HD spectrometer, and chemical shifts were re-
3
2
2
ported relative to CDCl3 ( = 7.26) and acetone-d6 ( = 2.05) for 1
H
NMR and CDCl3 ( = 77.16) and acetone-d6 ( = 29.84) for 13C NMR.
UV/vis absorption spectra were recorded on a JASCO V670 spectrom-
eter. Mass spectra were recorded on a Bruker micrOTOF using positive
mode with APCI-TOF methods and Bruker autoflex maX using posi-
tive mode with MALDI-TOF methods. Gel permeation chromatogra-
phy (GPC) was performed using a JAI model LC-928 recycling prepar-
ative HPLC equipped with either JAIGEL-2H-40 and JAIGEL-2.5H-40
purified by GPC (CHCl ), and the solvent removed to afford 4c (23.3
3
mg) as a white solid. In a 20-mL Schlenk flask, 4c (23.3 mg) was
placed under argon and CH Cl2 (1 mL) and 2,6-lutidine (12 L, 0.11
2
mmol) were added. Then a solution of Ph CB(C F ) (97 mg, 0.11
3
6 5 3
mmol) in CH Cl2 (1 mL) was added and the resulting mixture was
2
©
2021. Thieme. All rights reserved. Synthesis 2021, 53, A–F

E
Synthesis
S. Akahori et al.
Special Topic
stirred at rt for 6 h. The mixture was concentrated in vacuo and the
residue was washed with hexane to furnish 1c (10.9 mg, 0.010 mmol,
Supporting Information
Supporting information for this article is available online at
https://doi.org/10.1055/a-1437-9917. Su
21% yield from 3) as a white solid.
p
p
orti
n
g Inform atio
n
Su
p
p
orting Inform atio
n
Tetrasilyltetrathienylene 4c
1
H NMR (CDCl , 500 MHz):  = 7.49–7.42 (m, 16 H), 7.39–7.34 (m, 16
3
References
H), 7.30–7.28 (m, 8 H), 7.17 (s, 4 H), 5.40 (s, 4 H).
1
3
(1) (a) Yamaguchi, S.; Tamao, K. Bull. Chem. Soc. Jpn. 1996, 69, 2327.
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3
1
33.13, 133.06, 131.0, 130.9, 130.8, 129.0, 128.9.
3
693. (c) Yamaguchi, S.; Tamao, K. Chem. Lett. 2005, 34, 2.
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(
1
Octaphenyltetrasilatetrathia[8]circulene 1c
1
H NMR (CDCl , 500 MHz):  = 7.71 (d, J = 7.0 Hz, 16 H), 7.45 (t, J = 7.5
3
(
(
Hz, 8 H), 7.39 (t, J = 7.5 Hz, 16 H).
The 13C NMR spectrum of 1c was not measured because 1c was not
soluble enough to show detectable signals.
13662. (b) Xu, C.; Wakamiya, A.; Yamaguchi, S. J. Am. Chem. Soc.
2
005, 127, 1638. (c) Mouri, K.; Wakamiya, A.; Yamada, H.;
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+
HRMS (MALDI): m/z [M + H] calcd for C64H41Si S : 1049.1163; found:
4
4
1049.1177.
1
38, 3635.
3) For C–Si formation using organometallic reagents, see:
Octamethyltetrasilatetrathia[8]circulene 1d
(
(
a) Gilman, H.; Gorsich, R. D. J. Am. Chem. Soc. 1955, 77, 6380.
b) Liu, Y.; Stringfellow, T. C.; Ballweg, D.; Guzei, I. A.; West, R.
In a 20 mL Schlenk flask were placed 3 (83.2 mg, 0.10 mmol) and
Pd(Pt-Bu3)2 (10 mg, 0.020 mmol) under argon. Toluene (2 mL) was
added and the solution was stirred for 15 min. Then, Et N (0.11 mL,
J. Am. Chem. Soc. 2002, 124, 49. (c) Ohshita, J.; Nodono, M.; Kai,
H.; Watanabe, T.; Kunai, A.; Komaguchi, K.; Shiotani, M.; Adachi,
A.; Okita, K.; Harima, Y.; Yamashita, K.; Ishikawa, M. Organome-
tallics 1999, 18, 1453. (d) Li, L.; Xiang, J.; Xu, C. Org. Lett. 2007, 9,
3
0
.80 mmol) and Me (EtO)SiH (0.10 mL, 0.80 mmol) were added and
2
the resulting mixture was stirred at rt for 24 h. The mixture was con-
centrated in vacuo and the resulting crude product was purified by
4877. (e) Shimizu, M.; Tatsumi, H.; Mochida, K.; Oda, K.;
GPC (CHCl ) to afford a white solid (52.6 mg). In a 20-mL Schlenk
3
Hiyama, T. Chem. Asian J. 2008, 3, 1238.
flask, the white solid was placed under argon, Et O (7 mL) and LiAlH4
2
(
4) For C–Si formation by C–H bond activation, see: (a) Ureshino, T.;
(
33 mg, 0.85 mmol) were added, and the resulting mixture was re-
Yoshida, T.; Kuninobu, Y.; Takai, K. J. Am. Chem. Soc. 2010, 132,
fluxed at 40 °C for 24 h. After cooling to rt, the mixture was quenched
with aq NH Cl and extracted with Et O (3 × 10 mL). The combined or-
14324. (b) Shibata, T.; Shizuno, T.; Sasaki, T. Chem. Commun.
4
2
2
015, 51, 7802. (c) Murai, M.; Okada, R.; Nishiyama, A.; Takai, K.
ganic layers were dried (Na SO ) and then concentrated in vacuo. The
2
4
Org. Lett. 2016, 18, 4380. (d) Mitsudo, K.; Tanaka, S.; Isobuchi,
R.; Inada, T.; Mandai, H.; Korenaga, T.; Wakamiya, A.; Murata,
Y.; Suga, S. Org. Lett. 2017, 19, 2564. (e) Murai, M.; Okada, R.;
Asako, S.; Takai, K. Chem. Eur. J. 2017, 23, 10861. (f) Zhou, D.;
Gao, Y.; Liu, B.; Tan, Q.; Xu, B. Org. Lett. 2017, 19, 4628.
residue was purified by short column chromatography (silica gel,
hexane) to yield 4d (32.8 mg) as a crude product. In a 20-mL Schlenk
flask were placed [RhCl(cod)] (4.3 mg, 8.7 mol) and dppf (15 mg, 26
2
mol) under argon. Toluene (2 mL) was added and the mixture was
stirred for 15 min. Then, a solution of 4d (32.8 mg) in toluene (4 mL)
was added and the resulting solution was heated at 140 °C for 24 h.
After cooling to rt, the organic solvent was removed under reduced
pressure. The residue was purified by column chromatography (silica
(
5) For C–Si formation by C–Si bond activation, see: (a) Liang, Y.;
Zhang, S.; Xi, Z. J. Am. Chem. Soc. 2011, 133, 9204. (b) Onoe, M.;
Baba, K.; Kim, Y.; Kita, Y.; Tobisu, M.; Chatani, N. J. Am. Chem.
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J. Synth. Org. Chem. Jpn. 2018, 76, 1185.
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Taira, T.; Sato, J.; Nakamura, I.; Nishihara, H. Org. Lett. 2007, 9,
4543. (b) Lesbani, A.; Kondo, H.; Yabusaki, Y.; Nakai, M.;
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gel, hexane) and recrystallized (CHCl /MeOH) to yield 1d (15.4 mg,
3
27.8 mol, 28% yield from 3) as a white solid.
(
1
H NMR (CDCl , 500 MHz):  = 0.50 (s, 24 H).
3
1
3
C NMR (CDCl , 126 MHz):  = 149.0, 146.1, –2.0.
3
HRMS (APCI): m/z [M + H]+ calcd for C24H25S Si : 552.9911; found:
4
4
(
c) Yabusaki, Y.; Ohshima, N.; Kondo, H.; Kusamoto, T.;
552.9929.
Yamanoi, Y.; Nishihara, H. Chem. Eur. J. 2010, 16, 5581.
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2
2
016, 27, 498. (b) Miyake, Y.; Shinokubo, H. Chem. Commun.
020, 56, 15605.
Conflict of Interest
(
8) (a) Nielsen, C. B.; Brock-Nannestad, T.; Reenberg, T. K.;
Hammershøj, P.; Christensen, J. B.; Stouwdam, J. W.; Pittelkow,
M. Chem. Eur. J. 2010, 16, 13030. (b) Brock-Nannestad, T.;
Nielsen, C. B.; Schau-Magnussen, M.; Hammershøj, P.;
Reenberg, T. K.; Petersen, A. B.; Trpcevski, D.; Pittelkow, M. Eur.
J. Org. Chem. 2011, 6320. (c) Nielsen, C. B.; Brock-Nannestad, T.;
Hammershøj, P.; Reenberg, T. K.; Schau-Magnussen, M.;
Trpcevski, D.; Hensel, T.; Salcedo, R.; Baryshnikov, G. V.; Minaev,
B. F.; Pittelkow, M. Chem. Eur. J. 2013, 19, 3898. (d) Hensel, T.;
Trpcevski, D.; Lind, C.; Grosjean, R.; Hammershøj, P.; Nielsen, C.
B.; Brock-Nannestad, T.; Nielsen, B. E.; Schau-Magnussen, M.;
The authors declare no conflict of interest.
Funding Information
This work was supported by a Grant-in-Aid for Scientific Research in
the Innovative Area ‘Soft Crystals (No. 2903)’ (JSPS KAKENHI grant
JP20H04668) and ‘Precisely Designed Catalysts with Customized Scaf-
folding (No. 2702)’ (JSPS KAKENHI grant 16H01013) from MEXT, Ja-
pan. S. A. expresses his gratitude for a JSPS Research Fellowship for
Young Scientists (JP18J22906).JS
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©
2021. Thieme. All rights reserved. Synthesis 2021, 53, A–F

F
Synthesis
S. Akahori et al.
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©
2021. Thieme. All rights reserved. Synthesis 2021, 53, A–F