Ru3(CO)12-catalyzed dehydrogenative Si–N coupling of indoles with hydrosilanes without additive

Article abstract of DOI:10.1016/j.tet.2018.01.024

An efficient Ru₃(CO)₁₂-catalyzed dehydrogenative Si–N coupling reaction of indoles, pyrrole, and carbazole with hydrosilanes is reported. The reaction does not need any external additive. This catalytic reaction has a wide substrate range, excellent functional group tolerance, and high to excellent reaction efficiency. Gram-scale synthesis demonstrates the practicability of this synthetic method.

Full text of DOI:10.1016/j.tet.2018.01.024

Accepted Manuscript
Ru (CO) -catalyzed dehydrogenative Si-N coupling of indoles with hydrosilanes
3
12
without additive
Wenchao Zhai, Bin Li, Baiquan Wang
PII:
S0040-4020(18)30058-9
10.1016/j.tet.2018.01.024
TET 29239
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 18 November 2017
Revised Date: 9 January 2018
Accepted Date: 15 January 2018
Please cite this article as: Zhai W, Li B, Wang B, Ru (CO) -catalyzed dehydrogenative Si-N coupling
3
12
of indoles with hydrosilanes without additive, Tetrahedron (2018), doi: 10.1016/j.tet.2018.01.024.
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Ru3(CO)12-catalyzed dehydrogenative Si-N
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additive
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Wenchao Zhai, Bin Li, Baiquan Wang

1
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Tetrahedron
journal homepage: www.elsevier.com
Ru3(CO)12-catalyzed dehydrogenative Si−N coupling of indoles with hydrosilanes
without additive
Wenchao Zhai a , Bin Li a, Baiquan Wang a,b,c,
a State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin 300071, People’s Republic of China.
b Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300071, China
c State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, People’s
Republic of China
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
An efficient Ru3(CO)12-catalyzed dehydrogenative Si−N coupling reaction of indoles, pyrrole,
and carbazole with hydrosilanes is reported. The reaction does not need any external additive.
This catalytic reaction has a wide substrate range, excellent functional group tolerance, and high
to excellent reaction efficiency. Gram-scale synthesis demonstrates the practicability of this
synthetic method.
Available online
2009 Elsevier Ltd. All rights reserved
.
Keywords:
Ruthenium carbonyl
Si−N dehydrogenation coupling
Indoles
Hydrosilanes
———
Corresponding author. Tel.: +0-000-000-0000; fax: +0-000-000-0000; e-mail: bqwang@nankai.edu.cn

2
Tetrahedron
ACCEPTED MANUSCRIPT
1. Introduction
With Ru3(CO)12 as the catalyst, the effect of various solvents was
investigated. It showed that dioxane and CH3CN gave 3a in 51 %
and 10% yields, respectively (Table 1, entries 4−5), while the
reaction hardly proceeded in DMF (Table 1, entry 6). Decreasing
the reaction temperature led to lower yield (Table 1, entry 7). It is
worth to note that when the loading of catalyst decreased to 1.5
mol %, 3a was still obtained in 95% yield (Table 1, entry 8).
Adding norbornene as an additive decreased the yield of 3a to
25%. This result implied that the use of a H2 acceptor cannot
improve the reaction efficiency. In the absence of Ru3(CO)12 no
target compound was detected (Table 1, entry 10).
Much attention has been paid to develop efficient routes for
the functionalization of indoles,1 because the indole ring is one of
the most important skeletons ubiquitously existing in many
natural products and bioactive compounds.2 N-Protected indoles,
in particular, N-silylated indoles are considered as very crucial
synthetic platforms which can be used to build significant indole-
based natural products and pharmaceuticals.3 For example,
Hartwig and co-workers reported that N-silylated indoles
generated in situ can achieve the selective borylation of indoles.4a
Minami and co-workers reported Nickel-catalyzed N-arylation
reaction of N-trimethylsilyl-carbazole with aryl bromides, giving
N-aryl-carbazoles in high yields.4b
Table 1 Optimization of ruthenium-catalyzed dehydrogenative Si−N coupling
of indoles with hydrosilanes.a
The conventional methods to synthesize
N-silylated indoles
generally include preactivation of indoles and subsequent
coupling of the deprotonated indoles with a halosilane (Scheme
1a).3,5 However, this antique method requires a stoichiometric
strong metallic base and a halosilane which in most cases is
sensitive to moisture and hard to handle. The ambient of strong
base is prejudice to some functional groups.6 In light of this, the
direct dehydrogenative coupling of N−H of indoles with
hydrosilanes is an attractive alternative transformation which
generates dihydrogen as the sole by-product. Until now, several
entry
1
catalyst
solvent
toluene
toluene
toluene
CH3CN
dioxane
DMF
yield [%]
97
Ru3(CO)12
[(p-cymene)RuCl2]2
H2Ru(CO)(PPh3)3
Ru3(CO)12
Ru3(CO)12
Ru3(CO)12
Ru3(CO)12
Ru3(CO)12
Ru3(CO)12
No
2
N.R
N.R
10
3
procedures for the dehydrogenative Si
with hydrosilanes have been reported (Scheme 1b). Tsuchimoto
et al.7 reported zinc-catalyzed dehydrogenative
-silylation of
−N coupling of indoles
4
N
5
51
indoles with hydrosilanes with the addition of a catalytic
amount base and a nitrile solvent as the H2 acceptor. Mizuno
et al.8 developed rhodium acetate catalyzed dehydrogenative
6
N.R
83
7b
8c
9d
10
toluene
toluene
toluene
toluene
95
Si
stoichiometric base. Oestreich et al.9 reported a base-free
dehydrogenative Si N coupling of hydrosilanes with indoles as
−N coupling of indoles with hydrosilanes in the presence of
25
−
N.R
well as indolines and anilines with a sulfur-bridged Ru-arene
complex as catalyst. Paradies developed a metal-free B(C6F5)3
aConditions: 1a (0.2 mmol), 2a (0.3 mmol), Ru3(CO)12 (3 mol %), solvent (2
mL), 120 °C, 12 h. Isolated yield.
catalyzed dehydrogenative Si−N coupling of hydrosilanes with
anilines, carbazoles, and indoles.10 Here, we developed a
commercially available Ru3(CO)12 catalyzed base-free
bThe reaction proceeded in 100 °C.
c1.5 mol % of Ru3(CO)12 was used.
d2 equiv of norbornene were added.
dehydrogenative Si−N coupling of indoles with hydrosilanes.
With the optimal reaction conditions in hand, we tested
functional-group compatibilities of indoles and the scope of
different hydrosilane for the reaction. The results showed that
indoles with electron-donating (-Me, -OMe) and electron-
withdrawing groups (-F, -Cl, -Br, -I) all proceeded well, giving
the corresponding products in 80−98% yields (Table 2, 3a−3e,
3i−3s). Especially, indoles with electron-donating groups could
afford the target compounds using half amount of catalyst
loading of optimized conditions in excellent yields over 90 %
(Table 2, condition A). Indoles with electron-withdrawing
groups at C5 also afforded the corresponding N-silylated indoles
in great yields (Table 2, 3j, 3m, 3n, 3p and 3r). These results
could compare well with the previous reports.7,8,9 Indoles with
electron-withdrawing groups (-F, -Cl, -Br) at C4 and C6 are also
eligible in these conditions, affording corresponding target
compounds in excellent yields after proper extension of time
(Table 2, 3i, 3k, 3l, 3o, and 3q). It would be possible to utilize
these functional groups to achieve the further modification of the
indole molecules. It required an increased amount of catalyst (5
mol %) and longer time to get a high yield for indole with C3-Me
(Table 2, 3s). However, indoles with strong electron-withdrawing
groups (_CN, _NO2, -COCH3) and methyl ester group at C2
position did not work in these reaction conditions while indoles
with methyl ester group at C4 or C5 position could only afford
trace of target products along with the decomposition of indole
substrates. 7-Methoxy-1H-indole can be converted to 1-
Scheme 1. Synthetic strategies for N-silylated indoles.
2. Results and discussion
Firstly, we examined different ruthenium catalysts for the
Si−N dehydrogenative coupling reaction of indole (1a) with
Ph2MeSiH (2a) (Table 1). Fortunately, Ru3(CO)12 was found to
show the best catalytic activity, affording 3a in 97% yield when
the reaction was done in toluene at 120 °C with 3 mol % of
catalyst (Table 1, entry 1). [(p-cymene)RuCl2]2 and
H2Ru(CO)(PPh3)3 were totally inactive (Table 1, entries 2−3).

3
(dimethyl(phenyl)silyl)-7-methoxy-1H-indole (3g) in 90% yield,
indicating the steric hindrance at C7 position is tolerable. The site
selectivity of the present method by testing -NH2 or -OH-
substituted indoles was also investigated. The results showed that
the -NH2 or -OH group in different position of indole cannot
couple with hydrosilanes, and only N-silylated indoles were
obtained in 69% to 83% yields (Table 2, 3u-3x). This unique
selectivity may offer potentials in further modification of the
indole molecules in organic synthesis.
moderate to high yields (Table 2, 3h and 3t). Subsequently, we
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investigated the effect of different hydrosilanes as silylating
reagents for the coupling reaction. The results showed that
dimethylphenylsilane and triphenylsilane could also afford the
corresponding N-silylated indoles in moderate to high yields
(Table 2, 3f, 3g, and 3y), whereas triethylsilane did not react even
at higher temperature. It illustrated that an aromatic group at
silicon is essential for the reaction. Triphenylsilane conducted in
a depressed yield likely due to the steric hindrance.
With the extensive functional groups adaptability in hand, we
did several gram-scale transformation for indoles with C4, C5,
and C6 bromo/methoxy-substituents to further demonstrate the
practicability of this catalytic reaction, which afforded the
corresponding target products 3 in 90−97% yields (Scheme 2).
The further C–C bond formation reactions have been proved
feasible,7 which demonstrates that N-(SiMePh2)indoles can serve
as useful intermediates for further synthetic transformations.
Table 2 Ru3(CO)12-catalyzed dehydrogenative N-silylation of indoles,
pyrrole, and carbazole with hydrosilanes.a
Scheme 2. Gram-scale preparation of N-silylated indoles.
According to our results and the previous reports,7,8,9,11
a
plausible mechanism for this coupling reaction is described in
Scheme 3. Initially, silyl cation (A) and [Ru]−H intermediate (B)
would be formed by the reaction of Ru3(CO)12 with a
hydrosilane. Subsequently, a nucleophilic attack of the nitrogen
atom of indole to A happened, and followed by deprotonation to
afford the target compound 3. Meanwhile, complex B would
react with H+ to regenerate Ru(0) catalyst by release a H2. It
explained why the aromatic group in the hydrosilanes is
important to the reaction, because the silyl cation with an
aromatic group is more stable and easily to be formed.12
aConditions: 1a (0.2 mmol), 2a (0.3 mmol), toluene (2 mL), isolated yields
Scheme 3 A plausible reaction mechanism for the dehydrogenative N-
silylation of indoles; [Ru0] = Ru3(CO)12.
are given.
b5 mol % of Ru3(CO)12 wad used.
3. Conclusions
Besides indole derivatives, pyrrole and carbazole were also
silylated to afford the corresponding N-silylated products in

4
Tetrahedron
1
In summary, we developed an efficient Ru3(CO)12-
White solid, 95% yield. H NMR (CDCl3, 400 MHz): δ 7.73
(d, J = 7.8 Hz, 1H), 7.61 (d, J = 7.6 Hz, 4H), 7.56 – 7.51 (m, 2H),
7.46 (t, J = 7.5 Hz, 4H), 7.24 – 7.15 (m, 2H), 7.11 – 7.04 (m,
2H), 6.68 (d, J = 3.1 Hz, 1H), 1.13 (s, 3H). 13C NMR (CDCl3,
100 MHz): δ 140.5, 134.8, 133.2, 131.7, 131.4, 130.5, 128.2,
121.4, 120.6, 120.1, 113.8, 105.1, −2.5. The NMR data were in
agreement with reported results.7
ACCEPTED MANUSCRIPT
catalyzed dehydrogenative Si−N coupling of indoles with
hydrosilanes. This catalytic reaction has a broad substrate
range including indole derivatives, pyrrole, and carbazole,
excellent functional group tolerance, and high to excellent
reaction efficiency. Gram-scale preparation of N-silylated
indoles
with
various
bromo/methoxy-substituents
demonstrated the practicability of this synthetic method. A
plausible mechanism involving Ru−H species and silyl cation
is proposed.
4.2.2 4-Methoxy-1-(methyldiphenylsilyl)-1H-indole (3b)
White solid, 97% yield. H NMR (CDCl3, 400 MHz): δ 7.57 –
1
7.50 (m, 4H), 7.50 – 7.44 (m, 2H), 7.42 – 7.37 (m, 4H), 6.98 –
6.88 (m, 2H), 6.78 – 6.69 (m, 2H), 6.53 (d, J = 7.8 Hz, 1H), 3.95
(s, 3H), 1.05 (s, 3H). 13C NMR (CDCl3, 100 MHz): δ 153.2,
142.0, 134.9, 133.3, 130.5, 130.0, 128.2, 122.2, 122.1, 107.3,
102.2, 100.0, 55.2, −2.5. The NMR data were in agreement with
reported results.7
4. Experimental
4.1. General information
All reactions were carried out under argon atmosphere using
standard Schlenk technique. H (400 MHz), 19F (376 MHz), and
1
13C NMR (100 MHz) NMR spectra were recorded on a Bruker
AV400 NMR spectrometer with CDCl3 as solvent. Chemical
4.2.3 5-Methoxy-1-(methyldiphenylsilyl)-1H-indole (3c)
1
White solid, 98% yield. H NMR (CDCl3, 400 MHz): δ 7.64 –
1
shifts of H, 19F, and 13C NMR spectra are reported in parts per
7.56 (m, 4H), 7.55 – 7.49 (m, 2H), 7.48 – 7.40 (m, 4H), 7.17 (d, J
= 2.5 Hz, 1H), 7.09 – 7.01 (m, 2H), 6.73 (dd, J = 8.9, 2.5 Hz,
1H), 6.60 (d, J = 3.1 Hz, 1H), 3.87 (s, 3H), 1.10 (s, 3H). 13C
NMR (CDCl3, 100 MHz): δ 154.3, 135.5, 134.8, 133.3, 132.2,
130.5, 128.2, 114.3, 111.3, 105.0, 102.4, 55.6, −2.5. The NMR
data were in agreement with reported results.7
million (ppm). The residual solvent signals were used as
references and the chemical shifts were converted to the TMS
scale (CDCl3: δH = 7.26 ppm, δC = 77.00 ppm). All coupling
constants (J values) were reported in Hertz (Hz). Multiplicities
were reported as follows: singlet (s), doublet (d), doublet of
doublets (dd), triplet (t), quartet (q), and multiplet (m). Column
chromatography was performed on silica gel 200−300 mesh.
Analytical thin-layer chromatography (TLC) was performed on
pre-coated, glass-backed silica gel plates. Visualization of the
developed chromatogram was performed by UV absorbance (254
nm). High-resolution mass spectrometry (HRMS) was done on a
Varian 7.0 T FTICR-mass spectrometer. Ru3(CO)12 was prepared
from RuCl3.xH2O following a literature procedure.13 Indoles,
pyrrole, carbazole, and silanes are commercially available from
Alfa Aesar China (Tianjin) Chemical Co., Ltd. and used as
received without any further purification.
4.2.4 5-Methyl-1-(methyldiphenylsilyl)-1H-indole (3d)
1
White solid, 92% yield. H NMR (CDCl3, 400 MHz): δ 7.59
(dd, J = 6.5, 1.4 Hz, 4H), 7.56 – 7.48 (m, 3H), 7.48 – 7.40 (m,
4H), 7.06 (d, J = 8.4 Hz, 1H), 7.01 (d, J = 3.1 Hz, 1H), 6.89 (d, J
= 8.4 Hz, 1H), 6.58 (d, J = 2.5 Hz, 1H), 2.47 (s, 3H), 1.10 (s,
3H). 13C NMR (CDCl3, 100 MHz): δ 138.8, 134.8, 133.8, 132.0,
131.5, 130.4, 129.3, 128.2, 123.0, 120.4, 113.4, 104.7, 21.3, −2.5.
The NMR data were in agreement with reported results.7
4.2.5 6-Methyl-1-(methyldiphenylsilyl)-1H-indole (3e)
White solid, 92% yield. Mp: 98−100 oC. 1H NMR (CDCl3, 400
MHz): δ 7.59 – 7.52 (m, 5H), 7.52 – 7.47 (m, 2H), 7.45 – 7.39
(m, 4H), 7.00 – 6.89 (m, 3H), 6.57 (dd, J = 3.2, 0.7 Hz, 1H), 2.31
(s, 3H), 1.08 (s, 3H). 13C NMR (CDCl3, 100 MHz): δ 141.0,
134.9, 133.4, 131.0, 130.9, 130.4, 129.4, 128.2, 121.8, 120.2,
113.8, 104.9, 21.8, −2.4. HRMS (ESI): Calcd for C22H21NSi
[M+H]+ 328.1522, found: 328.1516.
4.2
General
Procedure
N Coupling.
for
Ru3(CO)12-Catalyzed
Dehydrogenative Si
−
Condition A: A mixture of indole (1) (0.2 mmol, 1 equiv),
hydrosilane (2) (0.3 mmol, 1.5 equiv), Ru3(CO)12 (1.9 mg, 0.003
mmol, 1.5 mol %), were weighted in a Schlenk tube equipped
with a stir bar. Dry toluene (2.0 mL) was added and the mixture
was stirred at 120 °C for 12 h under Ar atmosphere. Afterwards,
it was diluted with CH2Cl2 and transferred to a 50 mL round
bottom flask. Silica was added to the flask and solvents were
4.2.6 1-(Dimethyl(phenyl)silyl)-1H-indole (3f)
1
White solid, 85% yield. H NMR (CDCl3, 400 MHz): δ 7.65
(dd, J = 6.9, 1.4 Hz, 1H), 7.58 – 7.52 (m, 2H), 7.46 – 7.36 (m,
3H), 7.29 – 7.26 (m, 1H), 7.16 (d, J = 3.2 Hz, 1H), 7.14 – 7.03
(m, 2H), 6.63 (dd, J = 3.2, 0.7 Hz, 1H), 0.80 (s, 6H). 13C NMR
(CDCl3, 100 MHz): δ 140.2, 135.2, 133.8, 131.6, 130.4, 130.2,
128.2, 121.4, 120.7, 119.9, 113.3, 104.9, −1.3. The NMR data
were in agreement with reported results.7
evaporated
under
reduced
pressure.
Flash
column
chromatography on silica gel with EtOAc:petroleum ether =
1:100 as eluent afforded the N-silylated indole.
Condition B: A mixture of indole (1) (0.2 mmol, 1equiv),
hydrosilanes (2) (0.3 mmol, 1.5 equiv), Ru3(CO)12 (3.8 mg, 0.006
mmol, 3.0 mol %), were weighted in a Schlenk tube equipped
with a stir bar. Dry toluene (2.0 mL) was added and the mixture
was stirred at 120 °C for 12–24 h under Ar atmosphere.
Afterwards, it was diluted with CH2Cl2 and transferred to a 50
mL round bottom flask. Silica was added to the flask and
solvents were evaporated under reduced pressure. Flash column
chromatography on silica gel with EtOAc:petroleum ether =
1:100 as eluent afforded the N-silylated indole.
4.2.7 1-(Dimethyl(phenyl)silyl)-7-methoxy-1H-indole (3g)
o
1
White solid, 90% yield. Mp: 55−57 C. H NMR (CDCl3, 400
MHz): δ 7.49 (dd, J = 7.6, 1.7 Hz, 2H), 7.42 – 7.31 (m, 3H), 7.25
(d, J = 7.7 Hz, 1H), 7.10 – 7.00 (m, 2H), 6.60 – 6.52 (m, 2H),
3.60 (s, 3H), 0.77 (s, 6H). 13C NMR (CDCl3, 100 MHz): δ 147.4,
137.9, 133.4, 133.2, 131.7, 130.7, 129.3, 127.7, 120.7, 113.3,
104.6, 102.1, 54.1, 0.3. HRMS (ESI): Calcd for C17H19NOSi
[M+H]+ 282.1314, found: 282.1311.
4.2.8 1-(Dimethyl(phenyl)silyl)-1H-pyrrole (3h)
4.2.1 1-(Methyldiphenylsilyl)-1H-indole (3a)

5
1
White solid, 91% yield. H NMR (CDCl3, 400 MHz): δ 7.52 –
(m, 1H), 6.95 – 6.86 (m, 2H), 6.82 – 6.74 (m, 1H), 6.70 (d, J =
ACCEPTED MANUSCRIPT
7.46 (m, 2H), 7.45 – 7.34 (m, 3H), 6.81 (s, 2H), 6.41 – 6.30 (m,
2H), 0.70 (s, 6H). 13C NMR (CDCl3, 100 MHz): δ 135.5, 133.6,
130.2, 128.0, 123.7, 111.0, −1.7. The NMR data were in
agreement with reported results.8
3.2 Hz, 1H), 1.08 (s, 3H). 13C NMR (CDCl3, 100 MHz): δ 157.5,
155.1, 143.2, 143.1, 134.8, 133.9, 132.8, 131.3, 130.7, 128.3,
121.9, 121.8, 120.8, 120.6, 109.9, 105.0, 104.9, 100.9, −2.6. 19F
NMR (CDCl3, 376 MHz): δ −126.64. HRMS (ESI): Calcd for
C21H18FNSi [M+H]+ 332.1271, found: 332.1261.
4.2.9 4-Chloro-1-(methyldiphenylsilyl)-1H-indole (3i)
o
1
White solid, 91% yield. Mp: 75−77 C. H NMR (CDCl3, 400
MHz): δ 7.58 – 7.48 (m, 6H), 7.46 – 7.39 (m, 4H), 7.13 (d, J =
7.5 Hz, 1H), 7.08 – 7.00 (m, 2H), 6.93 (t, J = 7.9 Hz, 1H), 6.74
(d, J = 3.2 Hz, 1H), 1.09 (s, 3H). 13C NMR (CDCl3, 100 MHz): δ
141.2, 134.8, 132.7, 132.0, 130.7, 130.5, 128.3, 125.8, 122.0,
119.9, 112.3, 103.7, −2.6. HRMS (ESI): Calcd for C21H18ClNSi
[M+H]+ 348.0975, found: 348.0969.
4.2.16 5-Fluoro-1-(methyldiphenylsilyl)-1H-indole (3p):
o
1
White solid, 95% yield. Mp: 92−94 C. H NMR (CDCl3, 400
MHz): δ 7.61 – 7.49 (m, 6H), 7.49 – 7.39 (m, 4H), 7.33 – 7.28
(m, 1H), 7.07 (d, J = 3.2 Hz, 1H), 7.03 (dd, J = 8.9, 4.4 Hz, 1H),
6.78 (td, J = 9.1, 2.5 Hz, 1H), 6.60 (d, J = 3.2 Hz, 1H), 1.09 (s,
3H). 13C NMR (CDCl3, 100 MHz): δ 159.2, 156.9, 137.0, 134.8,
133.3, 132.9, 132.2, 132.1, 130.6, 128.3, 114.3, 114.2, 109.8,
109.5, 105.6, 105.3, 105.2, 105.2, −2.5. 19F NMR (CDCl3, 376
MHz): δ −124.25. HRMS (ESI): Calcd for C21H18FNSi [M+H]+
332.1271, found: 332.1265.
4.2.10 5-Chloro-1-(methyldiphenylsilyl)-1H-indole (3j)
White solid, 95% yield. Mp: 99−101 oC. 1H NMR (CDCl3, 400
MHz): δ 7.61 (d, J = 1.9 Hz, 1H), 7.57 – 7.47 (m, 6H), 7.45 –
7.39 (m, 4H), 7.05 – 6.99 (m, 2H), 6.95 (dd, J = 8.8, 2.0 Hz, 1H),
6.56 (d, J = 3.2 Hz, 1H), 1.06 (s, 3H). 13C NMR (CDCl3, 100
MHz): δ 138.9, 134.8, 132.9, 132.8, 130.7, 128.3, 125.9, 121.7,
120.0, 114.6, 104.8, −2.6. HRMS (ESI): Calcd for C21H18ClNSi
[M+H]+ 348.0975, found: 348.0961.
4.2.17 6-Fluoro-1-(methyldiphenylsilyl)-1H-indole (3q)
1
Colorless liquid, 93% yield. H NMR (CDCl3, 400 MHz): δ
7.57 – 7.46 (m, 7H), 7.45 – 7.38 (m, 4H), 6.98 (d, J = 3.2 Hz,
1H), 6.92 – 6.82 (m, 1H), 6.77 (dd, J = 10.5, 1.7 Hz, 1H), 6.58
(d, J = 3.1 Hz, 1H), 1.06 (s, 3H). 13C NMR (CDCl3, 100 MHz): δ
160.4, 158.1, 140.6, 140.5, 134.8, 133.9, 132.7, 131.7, 130.7,
128.3, 121.0, 120.9, 108.9, 108.6, 105.0, 100.3, 100.1, −2.6. 19F
NMR (CDCl3, 376 MHz): δ −120.81. HRMS (ESI): Calcd for
C21H18FNSi [M+H]+ 332.1271, found: 332.1263.
4.2.11 6-Bromo-1-(methyldiphenylsilyl)-1H-indole (3k)
o
1
White solid, 91% yield. Mp: 123−125 C. H NMR (CDCl3,
400 MHz): δ 7.55 – 7.48 (m, 7H), 7.46 – 7.40 (m, 4H), 7.25 –
7.19 (m, 2H), 6.97 (d, J = 3.2 Hz, 1H), 6.58 (d, J = 2.5 Hz, 1H),
1.08 (s, 3H). 13C NMR (CDCl3, 100 MHz): δ 141.4, 134.8, 132.7,
132.2, 130.7, 130.5, 128.3, 123.4, 121.7, 116.5, 115.0, 105.1,
−2.5. HRMS (ESI): Calcd for C21H18BrNSi [M+H]+ 392.0470,
found: 392.0460.
4.2.18 5-Iodo-1-(methyldiphenylsilyl)-1H-indole (3r)
1
White solid, 80% yield. H NMR (CDCl3, 400 MHz): δ 7.98
(d, J = 1.6 Hz, 1H), 7.56 – 7.46 (m, 6H), 7.45 – 7.38 (m, 4H),
7.26 – 7.23 (m, 1H), 6.97 (d, J = 3.2 Hz, 1H), 6.87 (d, J = 8.7 Hz,
1H), 6.57 – 6.50 (m, 1H), 1.05 (s, 3H). 13C NMR (CDCl3, 100
MHz): δ 139.7, 134.8, 134.3, 132.7, 132.3, 130.7, 129.8, 129.5,
128.3, 115.7, 104.4, 84.0, −2.6. The NMR data were in
agreement with reported results.7
4.2.12 4-Bromo-1-(methyldiphenylsilyl)-1H-indole (3l)
o
1
White solid, 90% yield. Mp: 120−122 C. H NMR (CDCl3,
400 MHz): δ 7.53 – 7.45 (m, 6H), 7.42 – 7.37 (m, 4H), 7.24 (d, J
= 1.9 Hz, 1H), 7.03 (dd, J = 5.8, 2.5 Hz, 2H), 6.84 (t, J = 7.9 Hz,
1H), 6.65 (d, J = 3.2 Hz, 1H), 1.05 (s, 3H). 13C NMR (CDCl3,
100 MHz): δ 140.7, 134.8, 132.7, 132.4, 132.0, 130.7, 128.3,
123.0, 122.4, 114.4, 112.9, 105.4, −2.5. HRMS (ESI): Calcd for
C21H18BrNSi [M+H]+ 392.0470, found: 392.0459.
4.2.19 3-Methyl-1-(methyldiphenylsilyl)-1H-indole (3s)
White solid, 88% yield. Mp: 98−100 oC. 1H NMR (CDCl3, 400
MHz): δ 7.66 – 7.56 (m, 5H), 7.54 – 7.48 (m, 2H), 7.47 – 7.38
(m, 4H), 7.20 – 7.10 (m, 2H), 7.08 – 7.02 (m, 1H), 6.80 (s, 1H),
2.33 (s, 3H), 1.09 (s, 3H). 13C NMR (CDCl3, 100 MHz): δ 140.9,
134.8, 133.6, 132.2, 130.4, 128.5, 128.2, 121.4, 119.5, 118.8,
114.0, 113.7, 9.6, −2.4. HRMS (ESI): Calcd for C22H21NSi
[M+H]+ 328.1522, found: 328.1516.
4.2.13
1-(Methyldiphenylsilyl)-5-(4,4,5,5-tetramethyl-1,3,2-
dioxaborolan-2-yl)-1H-indole (3m)
1
White solid, 85% yield. H NMR (CDCl3, 400 MHz): δ 8.18
(s, 1H), 7.56 – 7.50 (m, 4H), 7.47 (t, J = 7.4 Hz, 3H), 7.39 (t, J =
7.5 Hz, 4H), 7.11 (d, J = 8.3 Hz, 1H), 6.98 (d, J = 3.2 Hz, 1H),
6.62 (d, J = 3.2 Hz, 1H), 1.34 (s, 12H), 1.06 (s, 3H). 13C NMR
(CDCl3, 100 MHz): δ 142.7, 134.8, 133.1, 131.4, 130.5, 128.4,
128.2, 127.5, 113.3, 105.5, 83.3, 24.8, −2.5. The NMR data were
in agreement with reported results.7
4.2.20 9-(Methyldiphenylsilyl)-9H-carbazole (3t)
White solid, 65% yield. H NMR (CDCl3, 400 MHz): δ 8.18 –
1
8.11 (m, 2H), 7.71 – 7.64 (m, 4H), 7.59 – 7.53 (m, 2H), 7.50 –
7.44 (m, 4H), 7.29 – 7.24 (m, 2H), 7.23 – 7.16 (m, 2H), 7.03 (d, J
= 8.3 Hz, 2H), 1.24 (s, 3H). 13C NMR (CDCl3, 100 MHz): δ
144.4, 134.9, 134.2, 133.9, 130.5, 128.4, 127.7, 126.4, 125.2,
119.7, 114.1, −1.3. The NMR data were in agreement with
reported results.7
4.2.14 5-Bromo-1-(methyldiphenylsilyl)-1H-indole (3n)
1
White solid, 95% yield. H NMR (CDCl3, 400 MHz): δ 7.77
(d, J = 1.9 Hz, 1H), 7.55 – 7.47 (m, 6H), 7.45 – 7.38 (m, 4H),
7.09 (dd, J = 8.7, 2.0 Hz, 1H), 7.01 (d, J = 3.2 Hz, 1H), 6.96 (d, J
= 8.7 Hz, 1H), 6.55 (d, J = 3.2 Hz, 1H), 1.06 (s, 3H). 13C NMR
(CDCl3, 100 MHz): δ 139.2, 134.8, 133.5, 132.7, 130.7, 128.3,
124.3, 123.2, 115.1, 113.5, 104.7, −2.6. The NMR data were in
agreement with reported results.7
4.2.21 1-(Methyldiphenylsilyl)-1H-indol-4-amine (3u)
Colorless liquid, 69% yield. H NMR (CDCl3, 400 MHz):
1
δ
7.62 – 7.52 (m, 4H), 7.52 – 7.45 (m, 2H), 7.45 – 7.38 (m, 4H),
6.91 (d, J = 3.3 Hz, 1H), 6.89 – 6.83 (m, 1H), 6.65 (d, J = 8.3
Hz, 1H), 6.56 (d, J = 3.3 Hz, 1H), 6.44 (d, J = 7.5 Hz, 1H),
3.95 (s, 2H), 1.07 (s, 3H). 13C NMR (CDCl3, 100 MHz):
δ
141.6, 138.9, 134.8, 133.2, 130.4, 129.8, 128.2, 122.5, 120.9,
105.5, 104.9, 101.3, -2.6. HRMS (ESI): Calcd for C21H20N2Si
[M+H]+ 328.1396, found: 329.1472
4.2.15 4-Fluoro-1-(methyldiphenylsilyl)-1H-indole (3o)
White solid, 91% yield. Mp: 76−78 C. H NMR (CDCl3, 400
MHz): δ 7.57 – 7.47 (m, 6H), 7.46 – 7.39 (m, 4H), 6.98 – 6.95
o
1

6
Tetrahedron
4.2.22 1-(Methyldiphenylsilyl)-1H-indol-5-amine (3v)
The authors wish to thank the National Natural Science
ACCEPTED MANUSCRIPT
o
1
White solid, 83% yield. Mp: 113−115 C H NMR (CDCl3,
Foundation of China (Nos. 21372122, 21672108, and 21421062)
and the Natural Science Foundation of Tianjin (16JCZDJC31700)
for financial support.
400 MHz): δ 7.57 – 7.51 (m, 4H), 7.50 – 7.45 (m, 2H), 7.43 –
7.36 (m, 4H), 6.97 (d, J = 2.1 Hz, 1H), 6.95 – 6.89 (m, 2H),
6.48 (dd, J = 8.6, 2.2 Hz, 1H), 6.45 (d, J = 3.1 Hz, 1H), 3.49
(s, 2H), 1.04 (s, 3H). 13C NMR (CDCl3, 100 MHz): δ 139.5,
135.2, 134.8, 133.4, 132.6, 132.0, 130.4, 128.2, 114.2, 112.1,
105.7, 104.3, -2.5. HRMS (ESI): Calcd for C21H20N2Si [M+H]+
328.1396, found: 329.1473
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4.2.23 1-(Methyldiphenylsilyl)-1H-indol-4-ol (3w)
.
1
Colorless liquid, 70% yield. H NMR (CDCl3, 400 MHz):
δ
8.09 (s, 1H), 7.74 (d, J = 6.4 Hz, 4H), 7.49 – 7.37 (m, 6H),
7.12 – 7.07 (m, 1H), 7.02 (d, J = 8.1 Hz, 1H), 6.98 – 6.90 (m,
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NMR (CDCl3, 100 MHz): δ 148.4, 137.7, 136.0, 134.3, 129.9,
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4.2.24 1-(Methyldiphenylsilyl)-1H-indol-6-ol (3x)
Colorless liquid, 80% yield. H NMR (CDCl3, 400 MHz):
1
δ
7.88 (s, 1H), 7.70 (dd, J = 7.8, 1.6 Hz, 4H), 7.46 – 7.37 (m,
7H), 7.10 – 7.01 (m, 1H), 6.83 (d, J = 1.9 Hz, 1H), 6.74 (dd, J
= 8.5, 2.1 Hz, 1H), 6.48 – 6.42 (m, 1H), 0.76 (s, 3H). 13C
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4.2.25 1-(Triphenylsilyl)-1H-indole (3y)
1
White solid, 65% yield. H NMR (CDCl3, 400 MHz): δ 7.71
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mmol, 1.5 equiv), Ru3(CO)12 (57 mg, 0.09 mmol, 1.5 mol %),
were weighted in a Schlenk tube equipped with a stir bar. Dry
toluene (20 mL) was added and the mixture was stirred at 120 °C
for 12 h under Ar atmosphere. Afterwards, it was diluted with
CH2Cl2 and transferred to a 100 mL round bottom flask. Silica
was added to the flask and solvents were evaporated under
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were weighted in a Schlenk tube equipped with a stir bar. Dry
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for 12 h under Ar atmosphere. Afterwards, it was diluted with
CH2Cl2 and transferred to a 100 mL round bottom flask. Silica
was added to the flask and solvents were evaporated under
reduced pressure. Flash column chromatography on silica gel
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Acknowledgements