An Expedient Procedure for the Synthesis of Benzo[4,5]silolo[2,3-b]thiophenes and Related Systems

Article abstract of DOI:10.1021/acs.organomet.7b00619

The straightforward assembly of various thiophene-fused benzosiloles is accomplished by 2-fold metalation of benzo[b]thiophenes substituted at C3 with ortho-brominated aryl groups followed by electrophilic substitution with dichlorosilanes. The method relies on the innate acidity of the C(sp²)-H bond at C2 of benzo[b]thiophenes and the halogen-metal exchange of the proximal C(sp²)-Br bond. The related indole- and benzofuran-annulated systems are also accessible, but these siloles are chemically less stable. An example of a thiophene-fused benzogermole is included as well.

Full text of DOI:10.1021/acs.organomet.7b00619

Article
pubs.acs.org/Organometallics
An Expedient Procedure for the Synthesis of
Benzo[4,5]silolo[2,3‑b]thiophenes and Related Systems
Susanne Bahr,† Hiroaki Ogasawara,†,‡ Shigehiro Yamaguchi,*,‡,§ and Martin Oestreich*,†
̈
†Institut fur Chemie, Technische Universitat Berlin, Strasse des 17. Juni 115, 10623 Berlin, Germany
̈
̈
‡Department of Chemistry, Graduate School of Science, Nagoya University, Furo, Chikusa, Nagoya 464-8602, Japan
§Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Furo, Chikusa, Nagoya 464-8602, Japan
S
* Supporting Information
ABSTRACT: The straightforward assembly of various thio-
phene-fused benzosiloles is accomplished by 2-fold metalation
of benzo[b]thiophenes substituted at C3 with ortho-bromi-
nated aryl groups followed by electrophilic substitution with
dichlorosilanes. The method relies on the innate acidity of the
C(sp2)−H bond at C2 of benzo[b]thiophenes and the
halogen−metal exchange of the proximal C(sp2)−Br bond.
The related indole- and benzofuran-annulated systems are also
accessible, but these siloles are chemically less stable. An
example of a thiophene-fused benzogermole is included as well.
Scheme 1. 2-Fold Halogen−Metal Exchange as an Entry into
Stoichiometric Silole Synthesis
INTRODUCTION
■
Novel synthetic approaches1 to benzannulated siloles, including
those with annulated heterocycles, continue to attract attention
due to their photophysical properties and potential application
in polymer chemistry.2 Especially thiophene as well as
benzothiophene have been chosen as heterocycles fused to
the silole core, resulting in polycyclic structures that are
referred to as BST (benzo[4,5]silolo[3,2-b]thiophene) 1 or its
regioisomer benzo[4,5]silolo[2,3-b]thiophene 2 (Figure 1).
Figure 1. Regioisomeric benzosilolothiophenes 1 and 2 (R = alkyl,
aryl).
The synthesis of motifs such as 1 and that of related siloles
usually relies on stoichiometric reactions. These trace back to
Gilman’s dibenzosilole synthesis, where 2-fold bromine−
lithium exchange is followed by the reaction with a
dichlorosilane (3 → 4, Scheme 1, top).3,4 Later, Ohshita and
co-workers adopted this procedure for the assembly of systems
such as 8 and 9 with benzothiophene and indole units,
respectively (5 → 8 and 6 → 9, Scheme 1, middle).5 A few
years later, the benzofuran derivative 10 and the corresponding
germole (not shown) were accessed the same way (7 → 10).6
Yields were low though in all cases. Alternative stoichiometric
syntheses of extended, ladder-type systems proceed through
anionic cyclization7 or successive 4-fold metalation/electro-
philic substitution with dichlorosilanes.8 Aside from these
Received: August 12, 2017
© XXXX American Chemical Society
A
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stoichiometric methods, a limited number of catalytic trans-
formations lead to systems similar to 8−10. These methods
range from palladium-9 and rhodium-catalyzed10 processes to
[2 + 2 + 2] cycloaddition11 as well as Ru−S-catalyzed 2-fold
electrophilic C−H silylation.12 The 2-fold bromine−lithium
exchange also works with regioisomeric thiophenes, as
demonstrated by Wang’s synthesis (11 → 12, Scheme 1,
bottom).13
catalyzed cross-coupling of regioisomeric precursors worked
equally well (e.g., 13 → 14, Scheme 2, top); the
benzothiophene could also be replaced by thiophene and
benzofuran rings (not shown).9a A rhodium-catalyzed dehy-
drogenative coupling employing Wilkinson’s catalyst was later
reported (15 → 16, Scheme 2, middle).14 The same
transformation was later accomplished with a platinum catalyst
which led to 16 from 15 with an improved yield of 94% (not
shown).15 A similar scaffold was obtained by a palladium-
catalyzed annulation starting from a prefunctionalized benzo-
thiophene and internal acetylenes (e.g., 17/18 → 19, Scheme 2,
bottom).16 Also, siloloindoles were synthesized with the same
catalyst system starting from C3-arylated indole precursors (not
shown).17
For benzosilolothiophene 2 there is no stoichiometric
protocol available. However, a few catalytic examples do exist
(Scheme 2). The aforementioned intramolecular palladium-
Scheme 2. Reported Catalytic Syntheses of Silolo[2,3-
b]thiophenes
The above catalytic methods mostly require multistep
substrate syntheses, often involving metalated reagents in at
least one step. We thought that we could directly exploit the
innate acidity of the C(sp2)−H bond at C2 of sulfur-, nitrogen-,
and oxygen-containing five-membered heterocycles. Moreover,
we intended to combine this with a halogen−metal exchange in
the ortho position of the aryl ring attached to C3 of that
heterocycle. This would result in a 2-fold metalation, and
addition of a silicon electrophile would deliver the desired
silole.
RESULTS AND DISCUSSION
■
We chose readily available 20 as the model compound (Table
1).18 We indeed observed silole 21 in low yield when 20 was
subsequently treated with stoichiometric amounts of nBuLi and
MePhSi(H)Cl (entry 1); most of the starting material 20 had
remained unconsumed after hydrolysis. The use of tBuLi was
no improvement, and hydrosilanes 22 and 23 were observed
(entry 2), but increasing the reaction temperature to room
temperature for both steps led to good isolated yield (entry 3).
We finally obtained 21 in 85% isolated yield by using
MePhSiCl2 instead of MePhSi(H)Cl as the electrophile
(entry 4). This also facilitated the purification, as the formation
of 22 and 23 is avoided. The molecular structure of 21 was
secured by X-ray diffraction analysis (Figure 2, top left).
a
Table 1. Optimization of the Silole Formation
entry
1
RLi (equiv), T (°C), t (h)
electrophile (equiv), T (°C), t (h)
yield of 21 (%)
b
nBuLi (2.2), −78 → −20, 4
tBuLi (3.0), −78 → −25, 1.5
nBuLi (2.2), room temp, 4
nBuLi (2.2), room temp, 4
MePhSi(H)Cl (1.3), −78 → room temp, 19
MePhSi(H)Cl (1.3), −78 → room temp, 19
MePhSi(H)Cl (1.3), room temp, 4
18
c
2
d
3
4
72
85
MePhSiCl2 (1.3), room temp, 4
a
b
c
All reactions were performed according to GP2 (see the Experimental Section). Incomplete conversion of 20. THF was used as solvent.
Dehalogenated starting material and hydrosilanes 22 and 23 were obtained as major components, as determined by GLC/GC MS analysis.
d
B
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Scheme 4. Scope II: Preparation of Functionalized
Silolothiophenes and a Related Germole
Figure 2. Molecular structures of siloles 21, 29, 41, and 43.
Scheme 3. Scope I: Variation of the Silicon Electrophile and
Testing of Different Heterocycles
a
Me2GeCl2 was used instead of MePhSiCl2 under otherwise identical
reaction conditions.
and 38 → 39) in the C8 position were tolerated and the siloles
were isolated in high yields. Substrates with a chloro (40 → 41)
and a methoxy substituent (42 → 43) para to the newly formed
C(sp2)−Si bond participated well. For siloles 41 and 43, the
molecular structures were confirmed by X-ray diffraction
analysis (Figure 2, bottom). Furthermore, chlorination at C10
was accepted (44 → 45), and a naphthosilolothiophene
derivative was also successfully synthesized (46 → 47), even
though isolated yields were lower. By the addition of Me2GeCl2
to doubly metalated 20 instead of MePhSiCl2, the correspond-
ing germole was formed quantitatively (20 → 48).19
Among the benzo[4,5]silolo[2,3-b]thiophene derivatives
thus obtained, the UV−vis absorption and fluorescence spectra
of compounds 21, 29, 39, 41, and 43 were measured in
CH2Cl2. Their spectra are shown in Figures 3 and 4, and their
With a high-yielding protocol in hand, we verified its
generality by testing substrates containing indole and
benzofuran units (24 → 25 and 26 → 27, Scheme 3). Both
25 and 27 were indeed formed, but these siloles turned out to
be highly sensitive toward silica gel chromatography. Returning
to benzothiophenes, we were more successful when reacting
the doubly metalated intermediate derived from 20 with
differently substituted dichlorosilanes. The use of Me2SiCl2
resulted in good yield (20 → 28), whereas Ph2SiCl2 led to
lower yield (20 → 29 and molecular structure of 29, Figure 2,
top right). Sterically hindered iPr2SiCl2 reacted to give the
corresponding silole but was obtained along with an unknown
byproduct (20 → 30). Two tert-butyl groups at the silicon atom
were sterically too demanding, and the formation of 31 was not
observed with tBu2Si(H)Cl.
With MePhSiCl2 as the optimal silicon electrophile, we found
that several functionalized precursors were suitable for this
transformation (Scheme 4). Electron-withdrawing (32 → 33
and 34 → 35) as well as electron-donating groups (36 → 37
Figure 3. UV−vis absorption spectra of siloles 21, 29, 39, 41, and 43.
C
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μm, 230−400 mesh, ASTM) by Merck using the indicated solvents.
1H, 13C, 19F, and 29Si NMR spectra were recorded in CDCl3 or C6D6
on Bruker AV 400 and Bruker AV 500 instruments. Chemical shifts are
reported in parts per million (ppm) downfield from tetramethylsilane
and are referenced to the residual solvent resonance as the internal
1
standard (CHCl3: δ 7.26 ppm for H NMR and CDCl3: δ 77.16 ppm
1
for 13C NMR, C6D5H: δ 7.16 ppm for H NMR and C6D6: δ 128.06
ppm for 13C NMR). 19F and 29Si NMR spectra were calibrated
according to the IUPAC recommendation using a unified chemical
shift scale based on the proton resonance of trimethylsilane as a
primary reference. Data are reported as follows: chemical shift,
multiplicity (sbr = broad singlet, s = singlet, d = doublet, t = triplet, q =
quartet, m = multiplet, mc = centrosymmetric multiplet), coupling
constant (Hz), and integration. Infrared (IR) spectra were recorded on
an Agilent Technologies Cary 630 FT-IR spectrometer equipped with
an ATR unit, and the signals are reported in wavenumbers (cm−1).
Melting points (mp) were determined using a Leica Galen III melting
point apparatus (Wagner & Munz) and are not corrected. High-
resolution mass spectrometry (HRMS) was performed by the
Figure 4. Fluorescence spectra of siloles 21, 29, 39, 41, and 43.
data are summarized in Table 2. In the absorption spectra, all
the derivatives have their longest absorption maxima and
Analytical Facility of the Institut fur Chemie, Technische Universitat
̈
̈
Berlin. Data for the single-crystal structure determination were
collected with an Agilent SuperNova diffractometer equipped with a
CCD area Atlas detector and a mirror monochromator by utilizing Cu
Kα radiation (λ = 1.5418 Å). Software packages used: CrysAlis PRO
for data collection, cell refinement, and data reduction,23 SHELXS-97
for structure solution,24 SHELXL-97 for structure refinement,25 and
Mercury 3.1.126 for graphics. UV−vis absorption and fluorescence
spectra were measured with a Shimadzu UV-1800 spectrometer and a
HORIBA FluoroMax-4 spectrometer, respectively, in spectral grade
CH2Cl2. Absolute fluorescence quantum yields were determined with a
Hamamatsu photonics PMA-11 calibrated integrating sphere system.
General Procedure for Suzuki−Miyaura Cross-Coupling
Reactions (GP1). In a Schlenk flask, the boronic acid or boronic
acid ester (1.0−1.1 equiv), the corresponding 2-bromoiodobenzene
(1.0−1.1 equiv), (Ph3P)4Pd (1.0−10 mol %), and K2CO3 (1.5−1.7
equiv) were suspended in a degassed mixture of benzene, EtOH, and
H2O. The reaction mixture was heated to the indicated temperature
for 1−4 days. The reaction was quenched by the addition of H2O. The
phases were separated, the aqueous phase was extracted with tert-butyl
methyl ether (3 ×), and the combined organic phases were dried over
MgSO4. The crude product was purified by flash column
chromatography on silica gel using cyclohexane or cyclohexane/tert-
butyl methyl ether as eluent.
Table 2. Photophysical Data for Benzosilolothiophenes in
CH2Cl2
absorption
fluorescence
a
b
c
compd
λmax (nm)
log ε
λmax (nm)
ΦF
21
29
39
41
43
338
336
386
338
342
3.64
3.56
3.61
3.68
3.61
388
398
460
390
394
0.08
0.09
0.63
0.08
0.09
a
b
The longest absorption maximum wavelength. Excited at the
c
absorption maximum wavelength. Absolute fluorescence quantum
yield determined by a calibrated integrating sphere system.
emission maxima around 340 and 390 nm, respectively, except
for 39 with an electron-donating amino group. It showed a
longer absorption maximum at 386 nm and an intense blue
emission with a maximum at 460 nm as well as a fluorescence
quantum yield of ΦF = 0.63, which is much higher than those of
the other compounds (ΦF < 0.1).
CONCLUSION
General Procedure for the Optimization of the Silole
Synthesis (GP2). In a flame-dried 10 mL Schlenk flask equipped
with a magnetic stir bar, the precursor (73 mg, 0.25 mmol, 1.0 equiv)
was dissolved in Et2O (1 mL). The organolithium reagent (2.2−3.0
equiv) was added at the indicated temperature, and the reaction
mixture was stirred for 1.5−4 h. Chlorohydrosilane or dichlorosilane
(1.3 equiv) was added at the indicated temperature, and the resulting
suspension was stirred for 3−20 h. The reaction was quenched by the
addition of H2O (5 mL). The phases were separated, the aqueous
phase was extracted with tert-butyl methyl ether (3 × 5 mL), and the
combined organic phases were dried over MgSO4. The crude product
was purified by flash column chromatography on silica gel using
cyclohexane or cyclohexane/tert-butyl methyl ether as eluent.
General Procedure for the Synthesis of Siloles and the
Germole (GP3). In a flame-dried 10 mL Schlenk flask equipped with
a magnetic stir bar the corresponding ortho-brominated hetero-
arylphenyl derivative (0.25−0.33 mmol) was dissolved in Et2O (1
mL). nBuLi (2.6 M in hexanes, 2.2 equiv) was added at room
temperature, and the reaction mixture was stirred for 4 h.
Dichlorosilane or dichlorogermane (1.3 equiv) was added, and the
resulting suspension was stirred at room temperature for 18 h. The
reaction was quenched by the addition of H2O (5 mL). The phases
were separated, the aqueous phase was extracted with tert-butyl methyl
ether (3 × 5 mL), and the combined organic phases were dried over
MgSO4. The crude product was purified by flash column
chromatography on silica gel or filtration.
■
In summary, we have developed a short synthesis of
benzosilolothiophenes using easily accessible brominated
precursors. Application to nitrogen- and oxygen-containing
heterocycles as well as germoles was shown to be possible in
principle. Although stoichiometric in the metalating reagent,
the utility of this method lies in the simplicity of the procedure,
allowing for the construction of heteroaryl-fused siloles in one
synthetic operation.
EXPERIMENTAL SECTION
■
General Remarks. All reactions were performed in flame-dried
glassware using conventional Schlenk techniques under a static
pressure nitrogen. Liquids and solutions were transferred with
syringes. Benzene was purified and dried using a MBraun solvent
system. Technical grade solvents (cyclohexane, tert-butyl methyl ether,
EtOH) were distilled prior to use. Et2O and THF were dried and
purified following standard procedures. 1-Methyl-3-(4′,4′,5′,5′-tetra-
methyl-1′,3′,2′-dioxaborolan-2′-yl)indole,20 3-bromo-4-iodo-N,N-di-
methylaniline,21 4-bromo-3-iodoanisole,22 and 1-(2-bromophenyl)-
naphtha[2,1-b]thiophene (46)18 were synthesized according to
reported procedures. All other commercially available reagents were
used as received. Analytical thin-layer chromatography (TLC) was
performed on silica gel SIL G-25 glass plates from Macherey-Nagel.
Flash column chromatography was performed on silica gel 60 (40−63
D
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6-Methyl-6-phenyl-6H-benzo[b]benzo[4,5]silolo[3,2-d]-
thiophene (21). This compound was prepared according to GP3
from 20 (73 mg, 0.25 mmol, 1.0 equiv), nBuLi (2.6 M in hexanes, 0.21
mL, 0.55 mmol, 2.2 equiv), and dichloro(methyl)phenylsilane (53 μL,
0.33 mmol, 1.3 equiv). The crude product was purified by flash
column chromatography on silica gel using cyclohexane as eluent to
afford 21 (70 mg, 85%) as a colorless oil that slowly solidified. Single
crystals of 21 suitable for X-ray diffraction were obtained by slow
vaporization of a CH2Cl2/cyclohexane (approximately 1/1) solution
(see the Supporting Information for further details). Mp: 118 °C
6,6-Diphenyl-6H-benzo[b]benzo[4,5]silolo[3,2-d]thiophene
(29). This compound was prepared according to GP3 from 20 (73 mg,
0.25 mmol, 1.0 equiv), nBuLi (2.6 M in hexanes, 0.21 mL, 0.55 mmol,
2.2 equiv), and dichlorodiphenylsilane (60 μL, 0.33 mmol, 1.3 equiv).
The crude product was purified by flash column chromatography on
silica gel using cyclohexane as eluent to afford 29 (45 mg, 46%) as a
white solid. Single crystals of 29 suitable for X-ray diffraction were
obtained by slow vaporization of a CH2Cl2/cyclohexane (approx-
imately 1/1) solution (see the Supporting Information for further
details). Mp: 163 °C (cyclohexane). Rf = 0.41 (cyclohexane). IR
(ATR): ν
̃
/cm−1 3043 (w), 2920 (w), 2850 (w), 2112 (w), 1583 (w),
(cyclohexane). Rf = 0.56 (cyclohexane). IR (ATR): ν
̃
/cm−1 3035 (w),
1458 (w), 1424 (m), 1348 (w), 1257 (w), 1156 (w), 1106 (m), 1025
(w), 774 (s), 733 (m), 707 (s). HRMS (APCI) for C26H19SSi+ [M +
H]+: calculated 391.0971, found 391.0970. 1H NMR (500 MHz,
CDCl3): δ/ppm 7.29 (mc, 1H), 7.36−7.46 (m, 7H), 7.50 (mc, 1H),
7.52 (mc, 1H), 7.69−7.72 (m, 4H), 7.76 (mc, 1H), 7.96 (d, 3J = 8.1 Hz,
2920 (w), 2889 (w), 2110 (w), 1579 (w), 1547 (w), 1427 (w), 1347
(w), 1249 (w), 1111 (m), 1083 (m), 804 (m), 771 (s), 726 (s), 700
(s). HRMS (APCI) for C21H17SSi+ [M + H]+: calculated 329.0815,
1
found 329.0810. H NMR (500 MHz, CDCl3): δ/ppm 0.83 (s, 3H),
7.26 (mc, 1H), 7.33−7.37 (m, 2H), 7.38−7.42 (m, 2H), 7.50 (mc, 2H),
3
3
1H), 8.18 (d, J = 7.7 Hz, 1H), 8.48 (d, J = 8.3 Hz, 1H). 13C{1H}
NMR (126 MHz, CDCl3): δ/ppm 121.9 (s), 123.2 (s), 123.7 (s),
124.7 (s), 124.8 (s), 126.6 (s), 128.4 (s, 4C), 130.6 (s, 2C), 130.8 (s),
131.5 (s, 2C), 134.2 (s), 135.7 (s, 4C), 135.9 (s), 137.4 (s), 139.0 (s),
146.4 (s), 149.3 (s), 151.0 (s). 29Si{1H} DEPT NMR (99 MHz,
CDCl3, optimized for J = 7 Hz): δ/ppm −14.8. The crystallographic
data are available online in the CCDC database under number CCDC
1567747.
3
7.60−7.63 (m, 3H), 7.95 (dm, 3J = 8.1 Hz, 1H), 8.16 (d, J = 7.8 Hz,
1H), 8.47 (d, 3J = 8.1 Hz, 1H). 13C{1H} NMR (126 MHz, CDCl3): δ/
ppm −4.8 (s), 121.6 (s), 123.1 (s), 123.6 (s), 124.6 (s), 124.7 (s),
126.4 (s), 128.3 (s, 2C), 130.4 (s), 130.6 (s), 133.3 (s), 133.5 (s),
134.7 (s, 2C), 135.9 (s), 138.9 (s), 140.4 (s), 146.1 (s), 149.0 (s),
150.5 (s). 29Si{1H} DEPT NMR (99 MHz, CDCl3, optimized for J = 7
Hz): δ/ppm −8.8. The crystallographic data are available online in the
CCDC database under number CCDC 1567746.
8-Chloro-6-methyl-6-phenyl-6H-benzo[b]benzo[4,5]silolo-
[3,2-d]thiophene (33). This compound was prepared according to
GP3 from 32 (81 mg, 0.25 mmol, 1.0 equiv), nBuLi (2.6 M in hexanes,
0.21 mL, 0.55 mmol, 2.2 equiv), and dichloro(methyl)phenylsilane (53
μL, 0.33 mmol, 1.3 equiv). The crude product was purified by flash
column chromatography on silica gel using cyclohexane as eluent to
afford 33 (69 mg, 79%) as a white solid. Mp: 49 °C (CDCl3). Rf = 0.33
5,6-Dimethyl-6-phenyl-5,6-dihydrobenzo[4,5]silolo[2,3-b]-
indole (25). This compound was prepared according to GP3 from 24
(73 mg, 0.25 mmol, 1.0 equiv), nBuLi (2.6 M in hexanes, 0.21 mL,
0.55 mmol, 2.2 equiv), and dichloro(methyl)phenylsilane (53 μL, 0.33
mmol, 1.3 equiv). Toluene (7.2 mg) was added as internal standard to
the crude product, and the yield of 25 was determined to be 38% by
1
integration of baseline-separated signals in the H NMR spectrum.
(cyclohexane). IR (ATR): ν
̃
/cm−1 3084 (w), 2920 (m), 2847 (m),
Attempts to purify 25 by flash column chromatography on silica gel or
aluminum oxide failed. HRMS (APCI) for C22H20NSi+ [M + H]+:
calculated 326.1360, found 326.1360. Selected NMR spectroscopic
data are as follows. 1H NMR (400 MHz, CDCl3): δ/ppm 0.84 (s, 3H),
1580 (w), 1558 (w), 1445 (m), 1426 (m), 1375 (w), 1346 (m), 1249
(m), 1155 (w), 1111 (m), 1080 (m), 918 (w), 885 (w), 812 (s), 786
(m), 742 (s), 692 (s). HRMS (EI) for C21H15ClSSi+ [M]+: calculated
362.0347, found 362.0345. 1H NMR (500 MHz, CDCl3): δ/ppm 0.85
(s, 3H), 7.36−7.39 (m, 2H), 7.40−7.44 (m, 2H), 7.46 (dd, 3J = 8.2 Hz,
4J = 2.2 Hz, 1H), 7.51 (ddd, 3J = 8.2 Hz, 3J = 7.1 Hz, 4J = 1.1 Hz, 1H),
1
3.77 (s, 3H), 7.79 (mc, 1H), 8.02 (mc, 1H). H,29Si HMQC NMR
(500/99 MHz, CDCl3, optimized for J = 7 Hz): δ/ppm 0.84/(−16.2).
6-Methyl-6-phenyl-6H-benzo[4,5]silolo[2,3-b]benzofuran
(27). This compound was prepared according to GP3 from 26 (74 mg,
0.27 mmol, 1.0 equiv), nBuLi (2.6 M in hexanes, 0.23 mL, 0.59 mmol,
2.2 equiv), and dichloro(methyl)phenylsilane (60 μL, 0.37 mmol, 1.3
equiv). Toluene (11.9 mg) was added as internal standard to the crude
product, and the yield of 27 was determined to be 72% by integration
4
3
7.56 (d, J = 2.2 Hz, 1H), 7.59−7.61 (m, 2H), 7.96 (d, J = 8.0 Hz,
1H), 8.06 (d, J = 8.2 Hz, 1H), 8.41 (d, J = 8.1 Hz, 1H). 13C{1H}
NMR (126 MHz, CDCl3): δ/ppm −5.0 (s), 122.4 (s), 122.9 (s), 123.7
(s), 124.8 (s), 124.9 (s), 128.5 (s, 2C), 130.3 (s), 130.7 (s), 132.4 (s),
132.5 (s), 133.3 (s), 134.6 (s, 2C), 135.6 (s), 138.7 (s), 143.2 (s),
144.2 (s), 149.0 (s), 149.6 (s). 29Si{1H} DEPT NMR (99 MHz,
CDCl3, optimized for J = 7 Hz): δ/ppm −8.3.
3
3
1
of baseline-separated signals in the H NMR spectrum. Attempts to
purify 27 by flash column chromatography on silica gel or aluminum
8-Fluoro-6-methyl-6-phenyl-6H-benzo[b]benzo[4,5]silolo-
[3,2-d]thiophene (35). This compound was prepared according to
GP3 from 34 (77 mg, 0.25 mmol, 1.0 equiv), nBuLi (2.6 M in hexanes,
0.21 mL, 0.55 mmol, 2.2 equiv), and dichloro(methyl)phenylsilane (53
μL, 0.33 mmol, 1.3 equiv). The crude product was purified by flash
column chromatography on silica gel using cyclohexane as eluent to
afford 35 (85 mg, 94%) as a colorless oil. Rf = 0.31 (cyclohexane). IR
oxide failed. HRMS (EI) for C21H16OSi+ [M]+: calculated 312.0965,
1
found 312.0956. Selected NMR spectroscopic data are as follows. H
NMR (400 MHz, CDCl3): δ/ppm 0.83 (s, 3H), 7.62 (mc, 2H), 7.76
(ddd, 3J = 7.5 Hz, 4J = 0.8 Hz, 4J = 0.8 Hz, 1H), 7.95−7.97 (mc, 1H).
1H,29Si HMQC NMR (500/99 MHz, CDCl3, optimized for J = 7 Hz):
δ/ppm 0.83/(−18.5).
(ATR): ν
̃
/cm−1 3084 (w), 2959 (w), 2920 (m), 2107 (w), 1591 (m),
6,6-Dimethyl-6H-benzo[b]benzo[4,5]silolo[3,2-d]thiophene
(28). This compound was prepared according to GP3 from 20 (73 mg,
0.25 mmol, 1.0 equiv), nBuLi (2.6 M in hexanes, 0.21 mL, 0.55 mmol,
2.2 equiv), and dichlorodimethylsilane (40 μL, 0.33 mmol, 1.3 equiv).
The crude product was purified by flash column chromatography on
silica gel using cyclohexane as eluent to afford 28 (56 mg, 84%) as a
1476 (m), 1458 (m), 1426 (m), 1381 (m), 1340 (m), 1251 (m), 1201
(m), 1161 (w), 1134 (m), 1110 (m), 1080 (s), 1057 (m), 968 (m),
853 (s), 791 (s), 725 (s), 693 (s). HRMS (APCI) for C21H16FSSi+ [M
1
+ H]+: calculated 347.0721, found 347.0718. H NMR (400 MHz,
CDCl3): δ/ppm 0.82 (s, 3H), 6.95 (mc, 1H), 7.33−7.44 (m, 4H),
7.49−7.60 (m, 4H), 7.81−7.84 (m, 1H), 7.95 (dmc, 3J = 8.2 Hz, 1H),
8.39 (d, 3J = 8.4 Hz, 1H). 13C{1H} NMR (126 MHz, CDCl3): δ/ppm
colorless viscous oil. Rf = 0.54 (cyclohexane). IR (ATR): ν
̃
/cm−1 3049
(w), 2952 (w), 2849 (w), 1587 (m), 1458 (m), 1345 (m), 1246 (m),
1080 (m), 1044 (w), 918 (w), 839 (m), 774 (s), 747 (m), 723 (m),
723 (s), 671 (m). HRMS (APCI) for C16H15SSi+ [M + H]+ calculated
267.0658, found 267.0659. 1H NMR (500 MHz, CDCl3): δ/ppm 0.52
(s, 6H), 7.26 (mc, 1H), 7.38 (ddd, 3J = 8.1 Hz, 3J = 7.0 Hz, 4J = 1.1 Hz,
2
2
−4.9 (s), 109.7 (d, JC,F = 22.9 Hz), 112.7 (d, JC,F = 20.8 Hz), 122.8
(s), 123.7 (s), 124.8 (s), 125.0 (s), 128.4 (s, 2C), 130.5 (s), 132.9 (s),
134.6 (d, 3JC,F = 7.9 Hz), 134.6 (s, 2C), 135.4 (d, 4JC,F = 3.5 Hz), 135.6
(s), 140.8 (s), 148.3 (d, 3JC,F = 8.4 Hz), 148.9 (s), 149.0 (d, 4JC,F = 2.9
Hz), 165.2 (d, 1JC,F = 246 Hz). 19F{1H} NMR (471 MHz, CDCl3): δ/
ppm −110.2. 29Si{1H} DEPT NMR (99 MHz, CDCl3, optimized for J
= 7 Hz): δ/ppm −9.1.
3
1H), 7.46−7.50 (m, 2H), 7.61 (mc, 1H), 7.95 (mc, 1H), 8.12 (d, J =
3
7.8 Hz, 1H), 8.44 (d, J = 8.2 Hz, 1H). 13C{1H} NMR (126 MHz,
CDCl3): δ/ppm −2.9 (s, 2C), 121.4 (s), 123.0 (s), 123.6 (s), 124.4
(s), 124.7 (s), 126.1 (s), 130.3 (s), 132.8 (s), 135.9 (s), 140.4 (s),
141.7 (s), 145.7 (s), 148.7 (s), 149.5 (s). 29Si{1H} DEPT NMR (99
MHz, CDCl3, optimized for J = 7 Hz): δ/ppm −2.2.
6,8-Dimethyl-6-phenyl-6H-benzo[b]benzo[4,5]silolo[3,2-d]-
thiophene (37). This compound was prepared according to GP3
from 36 (76 mg, 0.25 mmol, 1.0 equiv), nBuLi (2.6 M in hexanes, 0.21
E
DOI: 10.1021/acs.organomet.7b00619
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
mL, 0.55 mmol, 2.2 equiv), and dichloro(methyl)phenylsilane (53 μL,
0.33 mmol, 1.3 equiv). The crude product was purified by flash
column chromatography on silica gel using cyclohexane as eluent to
afford 37 (76 mg, 89%) as a colorless oil that slowly solidified. Mp: 44
cyclohexane/CH2Cl2 (approximately 10/1) solution (see the Support-
ing Information for further details). Mp: 112 °C (cyclohexane). Rf =
0.24 (cyclohexane). IR (ATR): ν
̃
/cm−1 3052 (w), 2924 (m), 2093
(w), 1594 (m), 1562 (m), 1476 (m), 1460 (m), 1426 (m), 1382 (m),
1338 (m), 1298 (m), 1258 (m), 1215 (m), 1143 (m), 1110 (m), 1062
(s), 931 (w), 840 (m), 789 (s), 773 (m), 725 (s), 697 (s). HRMS
(APCI) for C22H18OSSi+ [M]+: calculated 358.0842, found 358.0843.
1H NMR (500 MHz, CDCl3): δ/ppm 0.81 (s, 3H), 3.93 (s, 3H), 6.79
(dd, 3J = 7.9 Hz, 4J = 2.2 Hz, 1H), 7.32−7.41 (m, 4H), 7.49 (ddd, 3J =
°C (cyclohexane). Rf = 0.38 (cyclohexane). IR (ATR): ν
̃
/cm−1 3084
(w), 2997 (w), 2920 (m), 2847 (m), 1458 (m), 1427 (m), 1405 (m),
1348 (m), 1248 (m), 1155 (w), 1111 (m), 1081 (m), 862 (m), 791
(s), 774 (m), 725 (s), 694 (s). HRMS (APCI) for C22H19SSi+ [M +
H]+: calculated 343.0971, found 343.0968. 1H NMR (500 MHz,
CDCl3): δ/ppm 0.84 (s, 3H), 2.40 (s, 3H), 7.32 (mc, 1H), 7.36−7.45
3
4
3
8.1 Hz, J = 7.1 Hz, J = 1.1 Hz, 1H), 7.53 (d, J = 7.8 Hz, 1H), 7.59
(mc, 2H), 7.73−7.74 (m, 1H), 7.94 (d, 3J = 8.1 Hz, 1H), 8.44 (d, 3J =
8.1 Hz, 1H). 13C{1H} NMR (126 MHz, CDCl3): δ/ppm −4.6 (s),
55.5 (s), 109.8 (s), 110.1 (s), 123.0 (s), 123.6 (s), 124.5 (s), 124.8 (s),
128.3 (s, 2C), 130.3 (s), 130.9 (s), 133.7 (s), 134.4 (s), 134.6 (s, 2C),
135.8 (s), 140.5 (s), 147.8 (s), 148.9 (s), 149.7 (s), 162.1 (s). 29Si{1H}
DEPT NMR (99 MHz, CDCl3, optimized for J = 7 Hz): δ/ppm −9.4.
The crystallographic data are available online in the CCDC database
under number CCDC 1567749.
3
3
4
(m, 4H), 7.46 (sbr, 1H), 7.51 (ddd, J = 8.1 Hz, J = 7.1 Hz, J = 1.1
Hz, 1H), 7.64 (mc, 2H), 7.96 (d, 3J = 8.1 Hz, 1H), 8.06 (d, 3J = 7.9 Hz,
1H), 8.48 (d, 3J = 8.2 Hz, 1H). 13C{1H} NMR (126 MHz, CDCl3): δ/
ppm −4.8 (s), 21.3 (s), 121.3 (s), 123.1 (s), 123.6 (s), 124.5 (s), 124.6
(s), 128.3 (s, 2C), 130.3 (s), 131.0 (s), 133.5 (s), 134.4 (s), 134.7 (s,
2C), 135.9 (s), 135.9 (s), 137.8 (s), 140.6 (s), 143.4 (s), 149.0 (s),
150.6 (s). 29Si{1H} DEPT NMR (99 MHz, CDCl3, optimized for J = 7
Hz): δ/ppm −8.8.
N,N,6-Trimethyl-6-phenyl-6H-benzo[b]benzo[4,5]silolo[3,2-
d]thiophen-8-amine (39). This compound was prepared according
to GP3 from 38 (83 mg, 0.25 mmol, 1.0 equiv), nBuLi (2.6 M in
hexanes, 0.21 mL, 0.55 mmol, 2.2 equiv), and dichloro(methyl)-
phenylsilane (53 μL, 0.33 mmol, 1.3 equiv). The crude product was
purified by flash column chromatography on silica gel using
cyclohexane/tert-butyl methyl ether (50/1) as eluent to afford 39
(85 mg, 92%) as a yellow oil. Rf = 0.30 (cyclohexane/tert-butyl methyl
10-Chloro-6-methyl-6-phenyl-6H-benzo[b]benzo[4,5]silolo-
[3,2-d]thiophene (45). This compound was prepared according to
GP3 from 44 (81 mg, 0.25 mmol, 1.0 equiv), nBuLi (2.6 M in hexanes,
0.21 mL, 0.55 mmol, 2.2 equiv), and dichloro(methyl)phenylsilane (53
μL, 0.33 mmol, 1.3 equiv). The crude product was purified by flash
column chromatography on silica gel using cyclohexane as eluent to
afford 45 (44 mg, 48%) as a colorless oil. Rf = 0.45 (cyclohexane). IR
(ATR): ν
̃
/cm−1 3049 (w), 2921 (w), 2847 (w), 1573 (w), 1544 (w),
ether = 50/1). IR (ATR): ν
̃
/cm−1 3089 (w), 3879 (w), 2806 (w),
1453 (m), 1427 (m), 1402 (w), 1376 (w), 1328 (w), 1249 (m), 1086
(m), 1023 (w), 917 (w), 791 (m), 762 (s), 723 (s), 694 (s). HRMS
(APCI) for C21H16ClSSi+ [M + H]+: calculated 363.0425, found
363.0426. 1H NMR (500 MHz, C6D6): δ/ppm 0.48 (s, 3H), 6.74 (dd,
3J = 7.4 Hz, 3J = 7.4 Hz, 1H), 7.02−7.12 (m, 5H), 7.26−7.31 (m, 2H),
1598 (m), 1525 (m), 1491 (m), 1423 (m), 1361 (m), 1256 (w), 1222
(m), 1172 (w), 1062 (m), 1024 (m), 953 (m), 830 (m), 807 (m), 787
(s), 758 (s), 733 (s), 667 (m). HRMS (APCI) for C23H21NSSi+ [M]+:
calculated 371.1158, found 371.1157. 1H NMR (500 MHz, C6D6): δ/
ppm 0.70 (s, 3H), 2.51 (s, 6H), 6.68 (dd, 3J = 8.6 Hz, 4J = 2.7 Hz, 1H),
7.05 (d, 4J = 2.7 Hz, 1H), 7.08−7.14 (m, 4H), 7.29 (mc, 1H), 7.63 (mc,
2H), 7.68 (d, 3J = 8.1 Hz, 1H), 8.09 (d, 3J = 8.4 Hz, 1H), 8.45 (d, 3J =
8.2 Hz, 1H) 13C{1H} NMR (126 MHz, C6D6): δ/ppm −4.8 (s), 40.3
(s, 2C), 113.6 (s), 118.5 (s), 122.6 (s), 123.5 (s), 123.8 (s), 124.5 (s),
124.6 (s), 128.5 (s, 2C), 130.3 (s), 134.3 (s), 134.7 (s), 135.0 (s, 2C),
135.5 (s), 136.4 (s), 142.3 (s), 149.6 (s), 149.7 (s), 151.9 (s). 29Si{1H}
DEPT NMR (99 MHz, C6D6, optimized for J = 7 Hz): δ/ppm −8.5.
9-Chloro-6-methyl-6-phenyl-6H-benzo[b]benzo[4,5]silolo-
[3,2-d]thiophene (41). This compound was prepared according to
GP3 from 40 (81 mg, 0.25 mmol, 1.0 equiv), nBuLi (2.6 M in hexanes,
0.21 mL, 0.55 mmol, 2.2 equiv), and dichloro(methyl)phenylsilane (53
μL, 0.33 mmol, 1.3 equiv). The crude product was purified by flash
column chromatography on silica gel using cyclohexane as eluent to
afford 41 (75 mg, 83%) as a white solid. Single crystals of 41 suitable
for X-ray diffraction were obtained by slow vaporization of a CDCl3
solution (see the Supporting Information for further details). Mp: 45
3
3
7.40 (mc, 2H), 7.58 (d, J = 8.1 Hz, 1H), 9.12 (d, J = 8.5 Hz, 1H).
13C{1H} NMR (126 MHz, C6D6): δ/ppm −5.2 (s), 123.3 (s), 123.9
(s), 124.8 (s), 127.6 (s), 128.0 (s), 128.3 (s, 2C), 128.6 (s), 130.7 (s),
131.6 (s), 132.8 (s), 133.7 (s), 134.8 (s, 2C), 136.1 (s), 142.1 (s),
144.5 (s), 145.1 (s), 149.8 (s), 151.6 (s). 29Si{1H} DEPT NMR (99
MHz, C6D6, optimized for J = 7 Hz): δ/ppm −8.0.
8-Methyl-8-phenyl-8H-benzo[4,5]silolo[3,2-b]naphtho[1,2-
d]thiophene (47). This compound was prepared according to GP3
from 46 (85 mg, 0.25 mmol, 1.0 equiv), nBuLi (2.6 M in hexanes, 0.21
mL, 0.55 mmol, 2.2 equiv), and dichloro(methyl)phenylsilane (53 μL,
0.33 mmol, 1.3 equiv). The crude product was purified by flash
column chromatography on silica gel using cyclohexane as eluent to
afford 47 (29 mg, 31%) as a colorless oil that slowly solidified. Mp:
42−44 °C (CDCl3). Rf = 0.43 (cyclohexane). IR (ATR): ν
̃
/cm−1 3046
(w), 2997 (w), 2955 (w), 2850 (w), 2083 (w), 1582 (m), 1543 (w),
1505 (w), 1427 (m), 1385 (w), 1299 (m), 1247 (m), 1151 (w), 1111
(m), 1091 (m), 1051 (m), 914 (w), 795 (m), 760 (m), 726 (s), 693
(s). HRMS (APCI) for C25H19SSi+ [M + H]+: calculated 379.0971,
°C (CDCl3). Rf = 0.57 (cyclohexane). IR (ATR): ν
̃
/cm−1 3048 (w),
1
2960 (w), 2921 (w), 2847 (w), 1575 (m), 1458 (m), 1426 (m), 1374
(w), 1249 (m), 1170 (w), 1100 (m), 1082 (m), 1010 (m), 939 (w),
859 (w), 811 (s), 789 (m), 724 (s), 693 (s). HRMS (APCI) for
C21H16ClSSi+ [M + H]+: calculated 363.0425, found 363.0422. 1H
NMR (500 MHz, C6D6): δ/ppm 0.53 (s, 3H), 7.05−7.11 (m, 5H),
7.12−7.16 (m, 2H), 7.47 (mc, 2H), 7.57 (d, 3J = 8.0 Hz, 1H), 8.12 (d,
3J = 8.2 Hz, 1H), 8.17 (sbr, 1H). 13C{1H} NMR (126 MHz, CDCl3):
found 379.0970. H NMR (500 MHz, CDCl3): δ/ppm 0.86 (s, 3H),
3
4
7.26 (mc, 1H), 7.36 (mc3, 2H), 7.42 (tt, J = 7.4 Hz, J = 1.6 Hz, 1H),
3
4
7.47 (ddd, J = 7.6 Hz, J = 7.6 Hz, J = 1.3 Hz, 1H), 7.55−7.60 (m,
3
3
2H), 7.63−7.66 (m, 3H), 7.76 (d, J = 8.4 Hz, 1H), 7.86 (d, J = 8.5
Hz, 1H), 7.97−7.99 (m, 1H), 8.33 (d, 3J = 7.8 Hz, 1H), 8.97 (mc, 1H).
13C{1H} NMR (126 MHz, CDCl3): δ/ppm −4.6 (s), 121.4 (s), 123.9
(s), 124.9 (s), 125.5 (s), 126.3 (s), 126.3 (s), 126.4 (s), 128.4 (s, 2C),
128.7 (s), 129.7 (s), 130.0 (s), 130.4 (s), 132.1 (s), 132.4 (s), 133.6
(s), 133.7 (s), 134.7 (s, 2C), 139.6 (s), 140.8 (s), 147.0 (s), 147.8 (s),
153.2 (s). 29Si{1H} DEPT NMR (99 MHz, CDCl3, optimized for J = 7
Hz): δ/ppm −9.6.
δ/ppm −5.0 (s), 122.0 (s), 122.9 (s), 123.7 (s), 124.8 (s), 125.0 (s),
126.1 (s), 128.4 (s, 2C), 130.6 (s), 132.6 (s), 134.2 (s), 134.6 (s, 2C),
135.5 (s), 137.0 (s), 138.5 (s), 140.4 (s), 147.7 (s), 148.9 (s), 149.1
(s). 29Si{1H} DEPT NMR (99 MHz, C6D6, optimized for J = 7 Hz):
δ/ppm −8.9. The crystallographic data are available online in the
CCDC database under number CCDC 1567748.
9-Methoxy-6-methyl-6-phenyl-6H-benzo[b]benzo[4,5]silolo-
[3,2-d]thiophene (43). This compound was prepared according to
GP3 from 42 (80 mg, 0.25 mmol, 1.0 equiv), nBuLi (2.6 M in hexanes,
0.21 mL, 0.55 mmol, 2.2 equiv), and dichloro(methyl)phenylsilane (53
μL, 0.33 mmol, 1.3 equiv). The crude product was purified by flash
column chromatography on silica gel using cyclohexane as eluent to
afford 43 (79 mg, 88%) as a white solid. Single crystals of 43 suitable
for X-ray diffraction were obtained by slow vaporization of a
6,6-Dimethyl-6H-benzo[b]benzo[4,5]germolo[3,2-d]-
thiophene (48). This compound was prepared according to GP3
from 20 (73 mg, 0.25 mmol, 1.0 equiv), nBuLi (2.6 M in hexanes, 0.21
mL, 0.55 mmol, 2.2 equiv), and dichlorodimethylgermane (37 μL, 0.33
mmol, 1.3 equiv). The crude product was purified by filtration over
Celite covered with a small plug of silica gel and using cyclohexane as
eluent to afford 48 (80 mg, >99%) as a clear liquid. Rf = 0.38
̃
(cyclohexane). IR (ATR): ν/cm−1 3050 (w), 2903 (w), 2105 (w),
1580 (m), 1457 (m), 1395 (w), 1341 (m), 1236 (w), 1155 (w), 1072
(m), 1029 (m), 935 (w), 915 (w), 837 (m), 801 (m), 767 (s), 724 (s).
F
DOI: 10.1021/acs.organomet.7b00619
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
HRMS (EI) for C16H14GeS+ [M]+: calculated 312.0023, found
(4) Traditional syntheses of siloles without benzannulation also rely
1
312.0026. H NMR (500 MHz, CDCl3): δ/ppm 0.70 (s, 6H), 7.27
on dilithium salts: Braye, E. H.; Hubel, W.; Caplier, I. J. Am. Chem. Soc.
̈
(ddd, 3J = 7.3 Hz, 3J = 7.3 Hz, 4J = 0.9 Hz, 1H), 7.36 (ddd, 3J = 8.1 Hz,
1961, 83, 4406−4413.
4
3
3J = 7.0 Hz, J = 1.1 Hz, 1H), 7.45−7.49 (m, 2H), 7.60 (dd, J = 7.0
(5) Ohshita, J.; Lee, K.-H.; Kimura, K.; Kunai, A. Organometallics
2004, 23, 5622−5625.
4
3
3
Hz, J = 1.2 Hz, 1H), 7.94 (d, J = 8.0 Hz, 1H), 8.19 (d, J = 7.8 Hz,
1H), 8.46 (d, 3J = 8.3 Hz, 1H). 13C{1H} NMR (126 MHz, CDCl3): δ/
ppm −2.1 (s, 2C), 122.0 (s), 122.7 (s), 123.4 (s), 123.9 (s), 124.6 (s),
126.1 (s), 129.6 (s), 132.8 (s), 136.1 (s), 142.8 (s), 144.1 (s), 144.7
(s), 146.8 (s), 148.3 (s). The analytical data are in accordance with
those reported.19
(6) Zhang, F.-B.; Adachi, Y.; Ooyama, Y.; Ohshita, J. Organometallics
2016, 35, 2327−2332.
(7) Mouri, K.; Wakamiya, A.; Yamada, H.; Kajiwara, T.; Yamaguchi,
S. Org. Lett. 2007, 9, 93−96.
(8) (a) Ashraf, R. S.; Chen, Z.; Leem, D. S.; Bronstein, H.; Zhang,
W.; Schroeder, B.; Geerts, Y.; Smith, J.; Watkins, S.; Anthopoulos, T.
D.; Sirringhaus, H.; de Mello, J. C.; Heeney, M.; McCulloch, I. Chem.
Mater. 2011, 23, 768−770. (b) Wang, J.-Y.; Hau, S. K.; Yip, H.-L.;
Davies, J. A.; Chen, K.-S.; Zhang, Y.; Sun, Y.; Jen, A. K.-Y. Chem.
Mater. 2011, 23, 765−767.
ASSOCIATED CONTENT
* Supporting Information
■
S
The Supporting Information is available free of charge on the
ACS Publications Web site. (PDF) Crystallographic data (CIF)
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.7b00619.
(9) (a) Shimizu, M.; Mochida, K.; Hiyama, T. Angew. Chem., Int. Ed.
2008, 47, 9760−9764. (b) Mochida, K.; Shimizu, M.; Hiyama, T. J.
Am. Chem. Soc. 2009, 131, 8350−8351. (c) Shimizu, M.; Mochida, K.;
Hiyama, T. J. Phys. Chem. C 2011, 115, 11265−11274.
(10) For cascade cyclizations, see: (a) Zhang, Q.-W.; An, K.; He, W.
Angew. Chem., Int. Ed. 2014, 53, 5667−5671. For dehydrogenative
cyclizations concomitant with Si−H/C−H bond cleavage, see:
Mitsudo, K.; Tanaka, S.; Isobuchi, R.; Inada, T.; Mandai, H.;
Korenaga, T.; Wakamiya, A.; Murata, Y.; Suga, S. Org. Lett. 2017,
19, 2564−2567.
(11) Shintani, R.; Takagi, C.; Ito, T.; Naito, M.; Nozaki, K. Angew.
Chem., Int. Ed. 2015, 54, 1616−1620.
(12) For 2-fold electrophilic C−H silylation with dihydrosilanes, see:
Omann, L.; Oestreich, M. Organometallics 2017, 36, 767−776.
(13) Zhao, C.; Xu, L.; Shi, J.; Li, C.; Wang, Z.; Wang, H. Int. J. Org.
Chem. 2011, 1, 162−166.
(14) Ureshino, T.; Yoshida, T.; Kuninobu, Y.; Takai, K. J. Am. Chem.
Soc. 2010, 132, 14324−14326.
(15) Murata, M.; Takizawa, M.; Sasaki, H.; Kohari, Y.; Sakagami, H.;
Namikoshi, T.; Watanabe, S. Chem. Lett. 2016, 45, 857−859.
(16) Liang, Y.; Geng, W.; Wei, J.; Xi, Z. Angew. Chem., Int. Ed. 2012,
51, 1934−1937.
(17) (a) Liang, Y.; Zhang, S.; Xi, Z. J. Am. Chem. Soc. 2011, 133,
9204−9207. (b) Hao, W.; Geng, W.; Zhang, W.-X.; Xi, Z. Chem. - Eur.
J. 2014, 20, 2605−2612.
(18) A similar approach was applied to the synthesis of bidentate
phosphine ligands with a (hetero)aryl scaffold: Benincori, T.; Gladiali,
Experimental details and characterization data, NMR
spectra for all compounds, and crystallographic data of
siloles 21, 29, 41, and 43 (PDF)
Accession Codes
CCDC 1567746−1567749 contain the supplementary crystal-
lographic data for this paper. These data can be obtained free of
charge via www.ccdc.cam.ac.uk/data_request/cif, or by email-
ing data_request@ccdc.cam.ac.uk, or by contacting The
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
AUTHOR INFORMATION
Corresponding Authors
*E-mail for S.Y.: yamaguchi@chem.nagoya-u.ac.jp.
*E-mail for M.O.: martin.oestreich@tu-berlin.de.
■
ORCID
Susanne Bahr: 0000-0001-5113-7646
̈
Hiroaki Ogasawara: 0000-0001-8462-562X
Shigehiro Yamaguchi: 0000-0003-0072-8969
Martin Oestreich: 0000-0002-1487-9218
̀
S.; Rizzo, S.; Sannicolo, F. J. Org. Chem. 2001, 66, 5940−5942.
(19) Takai and co-workers described the catalytic synthesis of 48
employing Wilkinson’s catalyst: Murai, M.; Matsumoto, K.; Okada, R.;
Takai, K. Org. Lett. 2014, 16, 6492−6495.
Notes
The authors declare no competing financial interest.
(20) Stahl, T.; Muther, K.; Ohki, Y.; Tatsumi, K.; Oestreich, M. J. Am.
̈
Chem. Soc. 2013, 135, 10978−10981.
ACKNOWLEDGMENTS
■
(21) Shintani, R.; Misawa, N.; Takano, R.; Nozaki, K. Chem. - Eur. J.
2017, 23, 2660−2665.
S.B. thanks the Studienstiftung des deutschen Volkes for a
predoctoral fellowship (2015−2018). Support through the
JSPS Core-to-Core Program (Advanced Research Networks) is
gratefully acknowledged. M.O. is indebted to the Einstein
Foundation (Berlin) for an endowed professorship. We thank
Dr. Elisabeth Irran (TU Berlin) for the X-ray analyses.
(22) Jensen, T.; Pedersen, H.; Bang-Andersen, B.; Madsen, R.;
Jørgensen, M. Angew. Chem., Int. Ed. 2008, 47, 888−890.
(23) Agilent CrysAlis PRO; Agilent Technologies, Yarnton, U.K.,
2012.
(24) Sheldrick, G. M. Acta Crystallogr., Sect. A: Found. Crystallogr.
1990, 46, 467−473.
(25) Sheldrick, G. M. Acta Crystallogr., Sect. A: Found. Crystallogr.
2008, 64, 112−122.
REFERENCES
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(1) For an overview of synthetic methods to access siloles, see:
Kobayashi, J.; Kawashima, T. In Science of Synthesis Knowledge Updates
2014/1; Oestreich, M., Ed.; Thieme: Stuttgart, Germany, 2014; pp
351−369.
(26) Cambridge Crystallographic Data Centre: http://www.ccdc.
cam.ac.uk/Solutions/CSDSystem/Pages/Mercury.aspx.
(2) For reviews on electronic properties of siloles, see: (a) Yamaguchi,
S.; Tamao, K. Chem. Lett. 2005, 34, 2−7. (b) Yamaguchi, S.; Tamao,
K. J. Chem. Soc., Dalton Trans. 1998, 22, 3693−3702. For the
properties of silole-containing polymers, see: (c) Chen, J.; Cao, Y. Acc.
Chem. Res. 2009, 42, 1709−1718. (d) Chen, J.; Cao, Y. Macromol.
Rapid Commun. 2007, 28, 1714−1742.
(3) Gilman, H.; Gorsich, R. D. J. Am. Chem. Soc. 1955, 77, 6380−
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DOI: 10.1021/acs.organomet.7b00619
Organometallics XXXX, XXX, XXX−XXX