Regioselective and Stereospecific Dehydrogenative Annulation Utilizing Silylium Ion-Activated Alkenes

Article abstract of DOI:10.1021/acs.joc.6b00793

Treatment of dialkylbenzylsilanes (1) with trityl tetrakis(pentafluorophenyl)borate (TPFPB) afforded the corresponding silylium ions in equilibrium with their intra- or intermolecular π-complexes, which underwent dehydrogenative annulation with various al

Full text of DOI:10.1021/acs.joc.6b00793

Article
pubs.acs.org/joc
Regioselective and Stereospecific Dehydrogenative Annulation
Utilizing Silylium Ion-Activated Alkenes
Hidekazu Arii,*,† Yuto Yano,† Kenichi Nakabayashi,† Syuhei Yamaguchi,‡ Masaki Yamamura,§
Kunio Mochida,*,⊥ and Takayuki Kawashima*,¶
†Faculty of Education, University of Miyazaki, 1-1 Gakuen Kibanadai Nishi, Miyazaki, 889-2192 Miyazaki, Japan
‡Department of Materials Science and Biotechnology, Graduate School of Science and Engineering, Ehime University, 3 Bunkyo-cho,
Matsuyama, 790-8577 Ehime, Japan
§Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, 305-8571 Ibaraki, Japan
⊥Department of Chemistry, Gakushuin University, 1-5-1 Mejiro, Toshima-ku, 171-8588 Tokyo, Japan
¶Graduate School of Science and Technology, Gunma University, 1-5-1 Tenjin-cho, Kiryu, 376-8515 Gunma, Japan
S
* Supporting Information
ABSTRACT: Treatment of dialkylbenzylsilanes (1) with trityl tetrakis-
(pentafluorophenyl)borate (TPFPB) afforded the corresponding silylium
ions in equilibrium with their intra- or intermolecular π-complexes, which
underwent dehydrogenative annulation with various alkenes to form 1,2,3,4-
tetrahydro-2-silanaphthalenes (4) in up to 82% isolated yield. Sterically bulkier
substituents on the silicon atom tended to increase the yield of cyclic products 4. The annulation products retained the
stereochemistry in cases of the reactions using internal alkenes. The use of diisopropyl(1-naphthyl)silane (2) instead of 1 also
resulted in annulation to obtain the 2,3-dihydro-1-sila-1H-phenalene derivatives 6. Electrophilic aromatic substitution at the 8-
position was predominant, despite the two potentially reactive positions on the naphthyl group. The steric hindrance of the
naphthyl group prevented addition of the cis-alkene to the silylium ion, which would considerably decrease yields of the desired
products from 2 compared to those from 1.
INTRODUCTION
■
The silylium ion is a strong Lewis acid and has attracted
attention for organic synthesis due to its reactivity toward
compounds containing multiple bonds.1 The silyl cation center
can coordinate to compounds with electron-rich π bonds, such
as arenes, as well as Lewis bases.2 The electronegativity-induced
polarity of the Siδ+−Hδ− bond promotes the formation of
silylium ions through exergonic hydride abstraction by the trityl
cation.3 The coordination of unsaturated compounds to the
generated silylium ion is expected to produce a corresponding
labile reactive intermediate. The silylium ion has been utilized
not only in stoichiometric systems but also in catalytic systems,
such as [4 + 2] cycloaddition and hydrosilylation of unsaturated
compounds.4−8 Moreover, several Lewis acids (LA) induce
activation of the Si−H bond to form intermediates, such as Si−
(μ-H)−LA, which are functionally equivalent to the silylium
ion. The Lewis acid facilitates heterolytic cleavage of the Si−H
bond, resulting in the formation of a silylium ion complex and
hydride−Lewis acid species. For example, AlCl3 and B(C6F5)3
were found to catalyze the hydrosilylation of olefins, ketones,
and imines.9,10
We developed a sila-Friedel−Crafts reaction, in which the
addition of silylium ion to the aromatic moiety followed by
deprotonation induces Si−C bond formation, and applied the
reaction to synthesize various dibenzosiloles (Figure 1(1)).11
Recently, we reported the dehydrogenative annulation between
dialkylbenzylsilane and alkynes via a silylium ion intermediate
Figure 1. Syntheses of silicon-containing cyclic compounds associated
with silylium ion.
(Figure 1(2)).12 Silacyclic compounds have been reported to
possess medicinal activity,13 which indicates that it is important
to explore a new approach for their synthesis. Herein we
disclose reactions using dialkylbenzylsilanes R2BnSiH (R = Me
(1a), i-Pr (1b), t-Bu (1c)) and diisopropyl(1-naphthyl)silane i-
Pr2NaphSiH (2) as substrates and terminal and internal alkenes
as reactants and describe the scope and limitations of the
reaction as well as its regioselectivity and stereospecificity.
Received: April 25, 2016
© XXXX American Chemical Society
A
DOI: 10.1021/acs.joc.6b00793
J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
RESULTS AND DISCUSSION
Table 2. Dehydrogenative Annulation Using Hydrosilanes
1a−c and Alkenes 3a−g
■
a
A solution of trityl tetrakis(pentafluorophenyl)borate (TPFPB,
1.1 equiv) in benzene was slowly added to a benzene solution
of benzyldimethylsilane (1a), 2,6-di-tert-butyl-4-methylpyridine
(DTBMP, 1.5 equiv), and trimethylvinylsilane (3a, 1.5 equiv),
which was defined as method A (for details, see Experimental
Section), to give 1,2,3,4-tetrahydro-2-silanaphthalene 4aa in
30% isolated yield (Scheme 1 and Table 1, entry 1). For the
alkene
b
entry silane 1
3
R1
R2
R3
yield of 4 (%)
52 (4aa)
1
1a
1a
1a
1a
1a
1b
1b
1b
1b
1b
1b
1c
1c
1c
1c
3a
3b
3c
3d
3e
3a
3c
3d
3e
3f
SiMe3
H
H
H
H
Ph
c
2
−
3
H
H
n-Bu
n-Hex
n-Pr
H
64 (4ac)
4
H
H
67 (4ad)
d
5
n-Pr
SiMe3
H
H
23 (4ae)
Scheme 1. Dehydrogenative Annulation Using Hydrosilanes
1 and Alkenes 3
6
H
17 (4ba)
74 (4bc)
70 (4bd)
54 (4be)
56 (4bf)
61 (4bg)
14 (4ca)
82 (4cc)
80 (4cd)
19 (4ce)
7
H
n-Bu
n-Hex
n-Pr
H
8
H
H
9
n-Pr
n-Pr
H
10
11
12
13
14
15
n-Pr
3g
3a
3c
3d
3e
(CH2)4
H
SiMe3
H
H
H
H
H
H
n-Bu
n-Hex
n-Pr
H
n-Pr
Table 1. Dehydrogenative Annulation Using Hydrosilanes 1a
a
b
c
a
Using method B. Isolated yields based on 1. Not detected.
and Alkenes 3a−c
d
Obtained as a cis/trans mixture.
b
alkene
yield (%)
octene (3d) also increased with increasing bulkiness of the
substituent on the silicon atom. This tendency may be
explained based on the Thorpe−Ingold effect.17 However, the
conversion of 1c required a longer reaction time (24 h) and
higher temperature (80 °C) than that of 1a or 1b. In the
reactions using internal alkenes, annulation products were
obtained in low to moderate yields, with retention of the alkene
stereochemistry (entries 9, 10, 11, and 15 in Table 2), except
for the reaction using 1a and 3e, giving a cis/trans mixture of
4ae. The stereochemistry of 4be and 4bf was identified as trans
and cis, respectively, by temperature-dependent NMR spec-
troscopy. The signals due to 4be showed no temperature
dependence, while those due to 4bf showed temperature
dependence, suggesting that 4be has only one stable
conformation, while 4bf has two exchangeable conformations,
which was supported by the DFT calculations (Figure S2,
Supporting Information).
entry
3
R1
R2
R3
4
5
c
1
2
3
3a
3b
3c
SiMe3
H
H
H
H
H
Ph
30 (4aa)
−
c
−
41 (5ab)
H
b
n-Bu
24 (4ac)
c
44 (5ac)
a
Using method A. Isolated yields based on 1a. Not detected.
other alkenes (entries 2 and 3), hydrosilylation products 5 were
obtained as a major product. Similar hydrosilylation of
unsaturated compounds was observed in the reaction of 1a
with 1-hexyne using method A.12 Because the reaction solution
contains a greater amount of 1a than that of the silylium ion
during the dropping of TPFPB, hydride abstraction of the
carbocation formed by coordination of the silylium ion to 3
from the Si−H bond of 1a competed with intramolecular
electrophilic addition to the benzene ring. To prevent this
reaction, the benzene solution of 1a was slowly added to the
solution of TPFBP (1.1 equiv), DTBMP (1.5 eqiv), and alkenes
3a−c (3 equiv), which was defined as method B (for details, see
Experimental Section). Except for the reaction using 3b, giving
a complex mixture, the yields of 4 increased, with a decrease in
the yields of 5 (Table 2, entries 1−3).14 The 1,2,3,4-tetrahydro-
2-silanaphthalene analogues were alternatively synthesized by
AlCl3-catalyzed intramolecular Friedel−Crafts alkylation and
transition metal-catalyzed ring expansion of unsaturated
hydrocarbons.15
Reactions using 2, containing a 1-naphthyl group, and
alkenes 3c−h were carried out using method B to give the
corresponding 2,3-dihydro-1-sila-1H-phenalene derivatives 6 in
40−66% yields (Scheme 2 and Table 3). Although the 2-
Scheme 2. Dehydrogenatice Annulation Using Hydrosilanes
2 and Alkenes 3
For the scope and limitation of 1 and 3 (Table 2), the
sterically bulkier substituents on the silicon atom in 1 improved
the yields of 4; that is, the yields of 4ac, 4bc, and 4cc were 64%,
74%, and 82%, respectively. The hydrosilylation products 5 in
entries 5−15 were isolated in yields less than 3%. The
formation of 4ba or 4ca was accompanied by that of R2BnSiMe
in 31% (R = i-Pr) or 58% (R = t-Bu) yield. Sekiguchi et al.
reported methyl abstraction by a silylium ion from the saturated
silicon atom, giving the more stable silylium ion.16 The
dimethylvinylsilylium ion derived from trimethylvinylsilane
(3a) is more stable than the silylium ions derived from 1b
and 1c due to the conjugation with the double bond, so methyl
abstraction is considered to have occurred to give R2BnSiMe.
The yields of 4 in the reactions using 1-hexene (3c) and 1-
position of the naphthyl group is potentially reactive in
electrophilic aromatic substitution, no five-membered ring
products were detected. Product 6e was obtained as single
crystals suitable for X-ray diffraction analysis. The crystal
structure revealed that the CC moiety of trans-4-octene
bridges the silicon atom and the 8-position on the naphthyl
group to form a six-membered ring and that two n-propyl
groups are oriented in a trans configuration (Figure S3,
Supporting Information). However, the reaction using cis-4-
B
DOI: 10.1021/acs.joc.6b00793
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retention of alkene stereochemistry is an interesting behavior in
the silylium ion-based annulation.
Table 3. Dehydrogenative Annulation Using Hydrosilanes 2
and Alkenes 3c−i
a
alkene
CONCLUSION
■
b
entry
3
R1
R2
R3
yield of 6 (%)
We investigated the dehydrogenative annulation of hydro-
silanes bearing a benzyl or a naphthyl group to terminal,
internal, and cyclic alkenes. The regioselectivity observed in the
annulation for terminal alkenes depends on the stability of the
cationic intermediate. Moreover, the retention of the alkene
stereochemistry of internal alkenes is attributed to the rapid
intramolecular Friedel−Crafts reaction via the resulting
carbocation or [π2s + σ2a] reaction of the benzosilacyclobu-
tenium ion. This procedure provides a useful method for the
synthesis of silicon-containing cyclic compounds under mild
and transition metal-free conditions.
1
2
3
4
5
6
3c
3d
3e
3f
H
H
H
H
n-Bu
n-Hex
n-Pr
H
63 (6c)
66 (6d)
43 (6e)
n-Pr
n-Pr
H
c
n-Pr
−
3g
3h
3i
(CH2)4
H
46 (6g)
Et
Et
H
Et
40 (6h)
d
e
7
Et
H
c
5 (6i)
a
b
d
Using method B. Isolated yields based on 2. Not detected. Solvent
is changed from benzene to toluene. Cis/trans = 9/1.
e
octene (3f) did not produce the annulation product, suggesting
that the isopropyl and naphthyl groups prevented access of cis-
4-octene to the silylium ion center. When the less-hindered cis-
3-hexene was used, 6i was obtained in 5% yield by changing the
solvent from benzene to toluene, but a cis/trans (9:1) mixture
was obtained. Although the 2,3-dihydro-1-sila-1H-phenalenes
were previously synthesized by the thermolysis of the
corresponding dichloro(1-naphthyl)vinylsilane,18 our method
has the advantage that alkyl groups can be introduced at 2- and
3-positions under milder conditions.
EXPERIMENTAL SECTION
■
General Procedure. All experiments were carried out using
standard vacuum line and Schlenk techniques in an Ar atmosphere or
drybox. All the reagents were of the highest grade available and were
used without further purification. All solvents used for the syntheses
were distilled according to the general procedure. Benzyldimethylsi-
lane (1a),20 benzyldiisopropylsilane (1b),12 and trityl tetrakis-
(pentafluorophenyl)borate21 were synthesized according to the
previously reported method. Benzyldi-tert-butylsilane (1c) was
prepared by the same method as 1a except for the use of di-tert-
butylchlorosilane as a starting material. Diisopropyl(1-naphthyl)silane
(2) was synthesized by the reaction of 1-naphthyllithium with
chlorodiisopropylsilane in Et2O. The NMR spectral measurements
A mechanism for the dehydrogenative annulation can be
proposed based on the above results (Scheme 3). Electrophilic
were performed on a 400 or 600 MHz spectrometer. The 1H and 13
C
Scheme 3. Plausible Mechanism of the Dehydrogenative
Annulation
chemical shifts are reported relative to the residual protonated solvent
and the solvent, respectively, according to the literature.22 High-
resolution mass spectroscopy was performed on a double-focusing
mass spectrometer with EI mode or on a TOF mass spectrometer with
ESI mode and was calibrated using a suitable standard material.
Elemental analysis was conducted with a correction for acetoanilide.
Gel permeation liquid chromatography (GPLC) was performed using
chloroform as an eluent. All calculations were performed using the
SPARTAN 08 package.23 Calculations were performed with the
B3LYP functional and the basis sets 6-31G*. All structures were
subject to full optimization, and the transition states were checked by
numerical frequency analysis.
X-ray Crystallography. Single crystals of 6e suitable for XRD
analyses were obtained. Each crystal was mounted on a glass fiber, and
the diffraction data were collected on a CCD detector using graphite
monochromated Mo Kα radiation.
All the structures were solved by the combination of the direct
method and Fourier techniques, and all the non-hydrogen atoms were
anisotropically refined by full-matrix least-squares calculations. The
atomic scattering factors and anomalous dispersion terms were
obtained from the International Tables for X-ray Crystallography
IV.24 The refinement of all structures was carried out by full-matrix
least-squares method of SHELXL-97.25
Preparation of Compounds. Method A. To 1a (0.20 mmol), an
alkene (0.30 mmol), and 2,6-di-tert-butyl-4-methylpyridine (DTBMP,
0.30 mmol) in benzene (3 mL) was slowly added a benzene solution
(4 mL) of trityl tetrakis(pentafluorophenyl)borate (TPFPB, 203 mg,
0.22 mmol) at room temperature under Ar atmosphere, and the
resulting solution was stirred for 15 min. The reaction mixture was
quenched with 1 M HCl, and then the organic layer was extracted.
After extraction with hexane, the organic layers were combined and
dried over anhydrous sodium sulfate. After filtration, the filtrate was
concentrated under reduced pressure to remove volatiles, and the
residue was purified by silica gel column (eluent: hexane). Further
purification was carried out by GPLC to obtain each of products.
Method B. To TPFPB (203 mg, 0.22 mmol), an alkene (0.60
mmol), and DTBMP (0.30 mmol) in benzene (4 mL) was slowly
added a benzene solution (2 mL) of a hydrosilane (0.20 mmol) at
addition of the silylium ion to alkenes generates carbocation 7,
leading to an intramolecular Friedel−Crafts reaction (path a).
The regioselectivity of the cyclic products is associated with the
stability of 7, as previously reported in reactions using terminal
alkynes.12 The 3-substituted products 4aa, 4ba, and 4ca and
other 4-substituted products form via carbocations that are
stabilized by the β-effect of the two silyl groups and by the
corresponding secondary carbocations. The intramolecular
electrophilic aromatic substitution is remarkably rapid because
of the retention of alkene stereochemistry and no detection of
benzene- or toluene-derived sila-Friedel−Crafts products.
Alternatively, the benzosilacyclobutenium ion 8 undergoes a
[π2s + σ2a] reaction with the alkene to retain the stereo-
chemistry (path b).19 A partial positive charge appears at the β-
position in the transition state of the [2 + 2] reaction, which
causes the regioselectivity of cyclic products 4 and 6, similarly
to path a. The four-membered ring intermediate 9 generated
from deprotonation of 8 can be ruled out because the reaction
of 9 with alkenes affords 1,2,3,4-tetrahydro-1-silanaphthalene
derivatives via an o-silaquinone methide species in the case of
the reaction using 1 (Scheme S1, Supporting Information). The
C
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room temperature under Ar atmosphere, and the resulting solution
was stirred for 15, 30, and 90 min at room temperature for 1a, 1b, and
2, respectively, and for 24 h at 80 °C for 1c. The following workup was
done according to method A. Other products such as polymeric
materials, disiloxanes, and hydrosilylation products were removed by
GPLC.
14.8, 12.7, 12.0, 9.3, −0.01. HRMS (ESI) m/z: [M]+ calcd for
C18H32Si2, 304.2043; found, 304.2039. i-Pr2BnSiMe: 1H NMR
(CDCl3, 400 MHz): δ 7.20 (t, 2H, J = 7.6 Hz, ArH), 7.08−7.02
(m, 3H, ArH), 2.13 (s, 2H, SiCH2Ar), 1.00−0.87 (m, 14H, i-Pr),
−0.11 (s, 3H, SiMe). 13C NMR (CDCl3, 100 MHz): δ 140.8, 128.3,
128.1, 123.8, 20.8, 18.04, 18.01, 11.6, −8.9. HRMS (ESI) m/z: [M]+
calcd for C14H24Si, 220.1647; found, 220.1650.
2,2-Dimethyl-3-trimethylsilyl-1,2,3,4-tetrahydro-2-silanaphtha-
lene (4aa). 4aa (26.0 mg, 52%) was obtained as a colorless oil from
the reaction using 1a (30.4 mg, 0.202 mmol) and trimethyl(vinyl)-
4-Butyl-2,2-diisopropyl-1,2,3,4-tetrahydro-2-silanaphthalene
(4bc). 4bc (42.6 mg (74%) was obtained as a colorless oil from the
1
1
silane (3a) by method B. H NMR data are consistent with those
reaction using 1b (41.1 mg, 0.199 mmol) and 3c. H NMR data are
reported previously.12
consistent with those reported previously.12
Benzyldimethyl(2-phenylethyl)silane (5ab). 5ab (26.0 mg, 52%))
4-Hexyl-2,2-diisopropyl-1,2,3,4-tetrahydro-2-silanaphthalene
was obtained as a colorless oil from the reaction using 1a (29.6 mg,
(4bd). 4bd (44.4 mg, 70%) was obtained as a colorless oil from the
1
1
0.197 mmol) and styrene (3b) by method A. H NMR (CDCl3, 400
reaction using 1b (41.2 mg, 0.200 mmol) and 3d. H NMR (CDCl3,
MHz): δ 7.30−7.15 (m, 7H, ArH), 7.09 (t, 1H, J = 7.2 Hz, ArH), 7.03
(d, 2H, J = 7.2 Hz, ArH), 2.65−2.55 (m, 2H, CH2CH2Ph), 2.13 (s,
2H, SiCH2Ph), 0.95−0.85 (m, 2H, CH2CH2Ph), 0.024 (s, 6H, SiMe2).
13C NMR (CDCl3, 100 MHz): δ 145.0, 140.2, 128.3, 128.2, 128.1,
127.8, 125.5, 123.9, 29.9, 25.5, 16.9, −3.6. HRMS (ESI) m/z: [M]+
calcd for C17H22Si, 254.1491; found, 254.1476.
400 MHz): δ 7.15−7.05 (m, 4H, ArH), 2.70−2.60 (m, 1H, CH(n-
Hex)), 2.05 (d, 1H, J = 14.8 Hz, SiCH2Ar), 2.00 (d, 1H, J = 14.4 Hz,
SiCH2Ar), 1.95−1.85 (m, 1H, n-Hex), 1.65−1.25 (m, 9H, n-Hex and i-
Pr), 1.06 (dd, 1H, J = 14.4 Hz, J = 4.4 Hz, SiCH2CH), 1.01 (brs, 7H, i-
Pr), 0.91 (t, 3H, J = 7.2 Hz, n-Hex), 0.90−0.80 (m, 7H, i-Pr), 0.36 (dd,
1H, J = 14.8 Hz, J = 10.0 Hz, SiCH2CH). 13C NMR (CDCl3, 100
MHz): δ 144.4, 138.6, 130.0, 125.9, 125.4, 124.6, 39.3, 35.6, 31.9, 29.6,
28.0, 22.7, 18.3, 18.14, 18.10, 17.9, 15.0, 14.1, 12.3, 11.8, 11.7. HRMS
(EI) m/z: [M]+ calcd for C21H36Si, 316.2586; found, 316.2609.
trans-2,2-Diisopropyl-3,4-dipropyl-1,2,3,4-tetrahydro-2-silanaph-
thalene (4be). 4be (34.2 mg, 54%) was obtained as a colorless oil
4-Butyl-2,2-dimethyl-1,2,3,4-tetrahydro-2-silanaphthalene (4ac).
4ac (30.1 mg, 64%) was obtained as a colorless oil from the reaction
1
using 1a (30.4 mg, 0.202 mmol) and 1-hexene (3c) by method B. H
NMR data are consistent with those reported previously.12
Benzyl(hexyl)dimethylsilane (5ac). 5ac (20.5 mg, 44%) was
1
obtained with 4ac (11.0 mg, 24%) as a colorless oil from the reaction
from the reaction using 1b (41.0 mg, 0.199 mmol) and 3e. H NMR
1
of 1a (29.7 mg, 0.198 mmol) with 1-hexene (3c) by method A. H
(CDCl3, 600 MHz): δ 7.08−7.03 (m, 2H, ArH), 7.01−6.96 (m, 2H,
ArH), 2.75 (ddd, 1H, J = 9.0, 6.6, 1.5 Hz, ArCH(n-Pr)), 2.04 (d, 1H, J
= 15 Hz, SiCH2Ar), 1.98 (d, 1H, J = 15 Hz, SiCH2Ar), 1.63−1.45 (m,
3H), 1.41−1.00 (m, 13H), 0.98−0.90 (m, 4H), 0.90 (t, 3H, J = 7.4 Hz,
n-Pr), 0.85 (t, 3H, J = 7.4 Hz, n-Pr), 0.61 (d, 3H, J = 7.3 Hz, i-Pr). 13C
NMR (CDCl3, 150 MHz): δ 143.2, 137.8, 131.0, 130.4, 126.3, 124.4,
48.9, 38.6, 33.9, 25.6, 22.9, 21.6, 19.0, 18.7, 18.4, 18.3, 14.7, 14.2, 14.1,
12.7, 10.9. HRMS (EI) m/z: [M]+ calcd for C21H36Si, 316.2586;
found, 316.2598.
NMR (CDCl3, 400 MHz): δ 7.21 (t, 2H, J = 7.6 Hz, ArH), 7.07 (t,
1H, J = 7.2 Hz, ArH), 7.00 (d, 2H, J = 7.2 Hz, ArH), 2.09 (s, 2H,
SiCH2Ph), 1.40−1.20 (m, 8H, n-Hex), 0.90 (t, 3H, J = 7.2 Hz, n-Hex),
0.55−0.45 (m, 2H, n-Hex), −0.038 (s, 6H, SiMe2). 13C NMR (CDCl3,
100 MHz): δ 140.5, 128.1, 128.0, 123.8, 33.3, 31.6, 25.6, 23.7, 22.6,
14.8, 14.1, −3.6. HRMS (EI) m/z: [M]+ calcd for C15H26Si, 234.1804;
found, 234.1814.
4-Hexyl-2,2-dimethyl-1,2,3,4-tetrahydro-2-silanaphthalene
(4ad). 4ad (35.0 mg, 67%) was obtained as a colorless oil from the
reaction using 1a (30.0 mg, 0.200 mmol) and 1-octene (3d) by
method B. 1H NMR (CDCl3, 400 MHz): δ 7.15−7.05 (m, 4H, ArH),
2.80−2.70 (m, 1H, CH(n-Hex)), 2.06 (d, 1H, J = 14.4 Hz, SiCH2Ar),
1.98 (d, 1H, J = 14.8 Hz, SiCH2Ar), 1.90−1.80 (m, 1H, n-Hex), 1.65−
1.50 (m, 1H, n-Hex), 1.50−1.20 (m, 8H, n-Hex), 0.99 (dd, 1H, J =
14.4 Hz, J = 4.8 Hz, SiCH2CH), 0.91 (t, 3H, J = 6.8 Hz, n-Hex), 0.51
(dd, 1H, J = 14.4 Hz, J = 8.8 Hz, SiCH2CH), 0.11 (s, 3H, SiMe2),
0.004 (s, 3H, SiMe2). 13C NMR (CDCl3, 100 MHz): δ 144.3, 138.0,
130.2, 126.3, 125.9, 124.7, 40.0, 35.3, 31.9, 29.5, 28.1, 22.7, 20.8, 18.0,
14.1, −1.2, −1.6. HRMS (EI) m/z: [M]+ calcd for C15H24Si, 232.1647;
found, 232.1621.
cis-2,2-Diisopropyl-3,4-dipropyl-1,2,3,4-tetrahydro-2-silanaph-
thalene (4bf). 4bf (35.7 mg, 56%) was obtained as a colorless oil from
the reaction using 1b (41.2 mg, 0.200 mmol) and 3f. 1H NMR
(CDCl3, 600 MHz): δ 7.08−6.97 (m, 4H, ArH), 2.88 (ddd, 1H, J =
12.0, 3.6, 3.6 Hz, ArCH(n-Pr)), 2.08 (d, 1H, J = 16 Hz, SiCH2Ar),
1.95 (d, 1H, J = 16 Hz, SiCH2Ar), 1.66−1.38 (m, 5H), 1.37−1.28 (m,
1H), 1.22−0.99 (m, 10H), 0.98−0.81(m, 13H). 13C NMR (CDCl3,
150 MHz): δ 144.0, 138.0, 130.8, 128.9, 126.2, 124.3, 46.3, 32.2, 30.4,
25.3, 22.7, 21.6, 19.2, 18.9, 18.3, 18.2, 15.3, 14.3, 14.2, 12.7, 11.6.
HRMS (EI) m/z: [M]+ calcd for C21H36Si, 316.2586; found, 316.2602.
cis-10,10-Diisopropyl-1,2,3,4,4a,9,10,10a-octahydro-10-silaphe-
nanthrene (4bg). 4bg (34.8 mg, 61%) was obtained as a colorless oil
trans-2,2-Dimethyl-3,4-dipropyl-1,2,3,4-tetrahydro-2-silanaph-
thalene (4ae). 4ae (12.1 mg, 23%) was obtained as a colorless oil
from the reaction using 1a (29.7 mg, 0.198 mmol) and trans-4-octene
1
from the reaction using 1b (41.0 mg, 0.200 mmol) and 3g. H NMR
(CDCl3, 400 MHz): δ 7.33−7.27 (m, 1H, ArH), 7.14−7.06 (m, 3H,
ArH), 2.92−2.84 (m, 1H, ArCH), 2.23−2.13 (m, 1H), 2.08 (d, 1H, J =
14.4 Hz), 1.94 (d, 1H, J = 14.8 Hz), 1.95−1.72 (m, 2H), 1.70−1.25
(m, 6H), 1.07−0.86 (m, 12H). 13C NMR (CDCl3, 100 MHz): δ 142.7,
138.7, 130.1, 127.4, 125.8, 124.4, 40.7, 29.6, 27.5, 26.0, 23.9, 23.7, 19.0,
18.7, 18.6, 18.3, 18.2, 15.5, 11.9, 11.3. HRMS (EI) m/z: [M]+ calcd for
C19H30Si, 286.2117; found, 286.2137.
1
(3e) by method B. H NMR (CDCl3, 400 MHz): δ 7.10−6.95 (m,
4H, ArH), 2.80 (ddd, 1H, J = 8.8 Hz, J = 6.0 Hz, J = 2.0 Hz, ArCH(n-
Pr)), 2.10 (d, 1H, J = 15.2 Hz, SiCH2Ar), 1.89 (d, 1H, J = 15.2 Hz,
SiCH2Ar), 1.70−1.40 (m, 3H, n-Pr), 1.35−1.05 (m, 5H, n-Pr), 1.05−
0.95 (m, 1H, SiCH(n-Pr)), 0.86 (t, 3H, J = 7.6 Hz, n-Pr), 0.84 (t, 3H, J
= 7.2 Hz, n-Pr), 0.21 (s, 3H, SiMe2), −0.14 (s, 3H, SiMe2). 13C NMR
(CDCl3, 100 MHz): δ 142.5, 137.0, 130.9, 130.5, 126.2, 124.6, 49.2,
37.4, 34.1, 27.9, 22.5, 21.6, 20.4, 14.2, 14.1, 0.58, −3.9. HRMS (EI) m/
z: [M]+ calcd for C17H28Si, 260.1960; found, 260.1960.
2,2-Di-tert-butyl-3-trimethylsilyl-1,2,3,4-tetrahydro-2-silanaph-
thalene (4ca). 4ca (9.0 mg, 14%) was obtained with t-Bu2BnSiMe
(28.5 mg, 58%) as a colorless oil from the reaction using 1c (46.7 mg,
0.199 mmol) with 3a. 1H NMR (CDCl3, 400 MHz): δ 7.12−6.98 (m,
4H, ArH), 2.07 (s, 2H, SiCH2Ar), 1.90 (dd, 1H, J = 12.8 Hz, J = 3.6
Hz, ArCH2CH), 1.12−1.06 (m, 1H, ArCH2CH), 1.03 (s, 9H, t-Bu),
0.77 (s, 9H, t-Bu), 0.40 (dd, 1H, J = 14.4 Hz, J = 12.8 Hz, SiCH), 0.20
(s, 9H, SiMe3). 13C NMR (CDCl3, 100 MHz): δ 142.5, 141.0, 130.4,
127.8, 125.6, 124.4, 28.6, 28.5, 27.9, 20.1, 19.7, 15.6, 7.5, −1.7. HRMS
(EI) m/z: [M]+ calcd for C20H36Si2, 332.2356; found, 332.2365. t-
2,2-Diisopropyl-3-trimethylsilyl-1,2,3,4-tetrahydro-2-silanaph-
thalene (4ba). 4ba (10.5 mg, 17%) was obtained with i-Pr2BnSiMe
(13.7 mg, 31%) as a colorless oil from the reaction using 1b (41.5 mg,
1
0.201 mmol) and 3a. H NMR (CDCl3, 400 MHz): δ 7.15−7.00 (m,
4H, ArH), 2.71 (dd, 1H, J = 14.0 Hz, J = 3.6 Hz, CHCH2Ar), 2.62 (dd,
1H, J = 13.6 Hz, J = 12.0 Hz, Si2CHCH2Ar), 2.03 (d, 1H, J = 14.8 Hz,
SiCH2Ar), 1.98 (d, 1H, J = 14.8 Hz, SiCH2Ar), 1.20−1.10 (m, 1H, i-
Pr), 1.10−1.05 (m, 6H, i-Pr), 0.95−0.85 (m, 1H, i-Pr), 0.84 (d, 3H, J =
6.4 Hz, i-Pr), 0.79 (d, 3H, J = 6.8 Hz, i-Pr), 0.12 (s, 9H, SiMe3), −0.05
(dd, 1H, J = 12.0 Hz, J = 3.6 Hz, CHCH2Ar). 13C NMR (CDCl3, 100
MHz): δ 142.8, 138.7, 129.6, 127.2, 126.3, 124.5, 32.2, 19.3, 18.8, 18.7,
1
Bu2BnSiMe: H NMR (CDCl3, 400 MHz): δ 7.20 (t, 2H, J = 7.6 Hz,
ArH), 7.10 (d, 2H, J = 8.0 Hz, ArH), 7.06, (t, 1H J = 7.2 Hz, ArH),
2.22 (s, 2H, SiCH2Ar), 0.98 (s, 18H, t-Bu), −0.05 (s, 3H, SiMe). 13C
NMR (CDCl3, 100 MHz): δ 141.5, 128.8, 128.0, 123.8, 28.6, 19.8,
D
DOI: 10.1021/acs.joc.6b00793
J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
19.7, −9.0. HRMS (EI) m/z: [M]+ calcd for C16H28Si, 248.1960;
found, 248.1960.
Pr)), 1.78−1.63 (m, 1H), 1.60−0.95 (m, 18H), 0.92 (t, 3H, J = 7.2 Hz,
n-Pr), 0.87 (d, 3H, J = 7.6 Hz, i-Pr), 0.84 (d, 3H, J = 7.2 Hz, i-Pr), 0.77
(t, 3H, J = 7.2 Hz, n-Pr). 13C NMR (CDCl3, 100 MHz): δ 141.7,
135.9, 133.7, 133.0, 131.4, 129.7, 127.8, 127.2, 124.8, 124.4, 47.6, 41.1,
32.3, 24.3, 22.0, 21.7, 19.1, 19.0, 18.7 (2C), 14.1, 13.9 (2C), 11.9. Anal.
Calcd for 6e (C24H36Si): C, 81.75; H, 10.29. Found: C, 81.59; H,
10.51.
cis-7,7-Diisopropyl-7a,8,9,10,11,11a-hexahydro-7-sila-7H-benzo-
[de]anthracene (6g). 6g (29.5 mg, 46%) was obtained as a colorless
oil from the reaction using 2 (48.4 mg, 0.200 mmol) and 3g. 1H NMR
(CDCl3, 400 MHz): δ 7.87 (dd, 1H, J = 8.4 Hz, J = 1.6 Hz, ArH), 7.72
(d, 1H, J = 8.0 Hz, ArH), 7.66 (dd, 1H, J = 6.4 Hz, J = 1.2 Hz, ArH),
7.52 (d, 1H, J = 7.2 Hz, ArH), 7.46 (dd, 1H, J = 8.4 Hz, J = 6.8 Hz,
ArH), 7.44 (t, 1H, J = 7.6 Hz, ArH), 3.42−3.35 (m, 1H, ArCH), 2.45−
2.31 (m, 1H), 1.97−1.37 (m, 9H), 1.30−1.13 (m, 1H), 1.18 (d, 3H, J
= 7.6 Hz, i-Pr), 1.10 (t, 6H, J = 6.8 Hz, i-Pr), 1.02 (d, 3H, J = 7.2 Hz, i-
Pr). 13C NMR (CDCl3, 100 MHz): δ 140.8, 137.2, 133.8, 133.1, 131.3,
130.1, 127.2, 126.1, 125.2, 124.3, 41.0, 33.1, 27.2, 25.5, 23.9, 23.1, 19.4,
19.1, 18.7, 18.3, 12.9, 11.3. HRMS (ESI) m/z: [M]+ calcd for
C22H30Si, 322.2117; found, 322.2111.
4-Butyl-2,2-di-tert-butyl-1,2,3,4-tetrahydro-2-silanaphthalene
(4cc). 4cc (51.3 mg, 82%) was obtained as a colorless oil from the
1
reaction using 1c (46.2 mg, 0.197 mmol) and 3c. H NMR (CDCl3,
400 MHz): δ 7.16−7.02 (m, 4H, ArH), 2.60−2.50 (m, 1H, CH(n-
Bu)), 2.12−1.93 (d, 3H), 1.65−1.30 (m, 5H), 1.17 (dd, 1H, J = 14.4
Hz, J = 3.6 Hz, SiCH2CH), 1.06 (s, 9H, t-Bu), 0.95 (t, 3H, J = 6.8 Hz,
n-Bu), 0.75 (s, 9H, t-Bu), 0.24 (dd, 1H, J = 14.8 Hz, J = 12.4 Hz,
SiCH2CH). 13C NMR (CDCl3, 100 MHz): δ 144.1, 139.6, 130.0,
125.7, 124.6, 124.3, 38.5, 35.3, 30.1, 28.56, 28.49, 23.1, 20.0, 19.5, 15.1,
14.2, 13.0. HRMS (ESI) m/z: [M]+ calcd for C21H36Si, 316.2586;
found, 316.2565.
2,2-Di-tert-butyl-4-hexyl-1,2,3,4-tetrahydro-2-silanaphthalene
(4cd). 4cd (54.3 mg, 80%) was obtained as a colorless oil from the
1
reaction using 1c (45.9 mg, 0.196 mmol) and 3d. H NMR (CDCl3,
400 MHz): δ 7.16−7.03 (m, 4H, ArH), 2.60−2.50 (m, 1H, CH(n-
Hex)), 2.12−1.94 (d, 3H), 1.66−1.55 (m, 1H), 1.44−1.28 (m, 5H),
1.16 (dd, 1H, J = 14.4 Hz, J = 3.6 Hz, SiCH2CH), 1.06 (s, 9H, t-Bu),
0.94−0.86 (m, 3H, n-Hex), 0.75 (s, 9H, t-Bu), 0.23 (dd, 1H, J = 14.4
Hz, J = 12.0 Hz, SiCH2CH). 13C NMR (CDCl3, 100 MHz): δ 144.1,
139.6, 130.0, 125.7, 124.6, 124.3, 38.5, 35.6, 31.9, 29.7, 28.56, 28.50,
27.9, 22.7, 20.0, 19.5, 15.1, 14.1, 13.0. HRMS (ESI) m/z: [M]+ calcd
for C23H40Si, 344.2899; found, 344.2883.
trans-2,3-Diethyl-1,1-diisopropyl-2,3-dihydro-1-sila-1H-phena-
lene (6h). 6h (25.7 mg, 40%) was obtained as a white solid from the
1
reaction using 2 (48.2 mg, 0.199 mmol) and 3h. Mp: 70−71 °C. H
NMR (CDCl3, 400 MHz): δ 7.85 (dd, 1H, J = 8.0 Hz, J = 1.2 Hz,
ArH), 7.70 (dd, 1H, J = 8.0 Hz, J = 1.2 Hz, ArH), 7.68 (dd, 1H, J = 6.8
Hz, J = 1.6 Hz, ArH), 7.46 (dd, 1H, J = 8.0 Hz, J = 6.8 Hz, ArH), 7.35
(dd, 1H, J = 8.0 Hz, J = 6.8 Hz, ArH), 7.25 (dd, 1H, J = 6.4 Hz, J = 1.2
Hz, ArH), 3.15 (ddd, 1H, J = 9.2 Hz, J = 5.2 Hz, J = 2.8 Hz,
ArCH(Et)), 1.75−1.50 (m, 3H), 1.48−1.36 (m, 2H), 1.35−1.22 (m,
8H), 1.10 (t, 3H, J = 6.8 Hz, Et), 0.86 (d, 3H, J = 7.2 Hz, i-Pr), 0.85
(d, 3H, J = 7.2 Hz, i-Pr), 0.69 (t, 3H, J = 7.2 Hz, Et). 13C NMR
(CDCl3, 100 MHz): δ 141.1, 135.9, 133.7, 133.1, 131.4, 129.7, 128.1,
127.3, 124.7, 124.4, 49.3, 31.5, 27.3, 22.9, 19.1, 19.0, 18.7 (2C), 14.2,
13.9, 13.4, 11.9. Anal. Calcd for 6h (C22H32Si): C, 81.41; H, 9.94.
Found: C, 81.32; H, 10.10.
trans-2,2-Di-tert-butyl-3,4-dipropyl-1,2,3,4-tetrahydro-2-sila-
naphthalene (4ce). 4ce (13.3 mg, 19%) was obtained as a colorless oil
1
from the reaction using 1c (46.8 mg, 0.200 mmol) and 3e. H NMR
(CDCl3, 400 MHz): δ 7.10−6.94 (m, 4H, ArH), 2.65 (ddd, 1H, J =
9.6, 6.4, 2.0 Hz, ArCH(n-Pr)), 2.12 (d, 1H, J = 14.4 Hz, SiCH2Ar),
2.05 (d, 1H, J = 14.4 Hz, SiCH2Ar), 1.74−1.16 (m, 7H), 1.14−1.06
(m, 2H), 1.06 (s, 9H, t-Bu), 0.96 (t, 3H, J = 6.8 Hz, n-Pr), 0.85 (t, 3H,
J = 7.2 Hz, n-Pr), 0.71 (s, 9H, t-Bu). 13C NMR (CDCl3, 100 MHz): δ
143.5, 138.2, 130.4, 129.8, 126.3, 124.4, 49.3, 39.8, 35.0, 29.7, 29.0,
27.5, 23.8, 21.6, 20.6, 19.6, 15.8, 14.4, 14.2. HRMS (ESI) m/z: [M]+
calcd for C23H40Si, 344.2899; found, 344.2879.
3-Butyl-1,1-diisopropyl-2,3-dihydro-1-sila-1H-phenalene (6c). 6c
(40.5 mg, 63%) was obtained as a white solid from the reaction using 2
(48.3 mg, 0.199 mmol) and 3c. Mp: 69−70 °C. 1H NMR (CDCl3, 400
MHz): δ 7.86 (dd, 1H, J = 8.4 Hz, J = 1.6 Hz, ArH), 7.71 (dd, 1H, J =
6.8 Hz, J = 1.6 Hz, ArH), 7.69 (dd, 1H, J = 5.2 Hz, J = 1.2 Hz, ArH),
7.46 (dd, 1H, J = 8.0 Hz, J = 6.4 Hz, ArH), 7.39 (t, 1H, J = 8.0 Hz,
ArH), 7.33 (d, 1H, J = 6.8 Hz, ArH), 3.35−3.25 (m, 1H, ArCH(n-
Bu)), 1.80−1.60 (m, 2H), 1.50−1.10 (m, 11H), 1.09 (d, 3H, J = 7.6
Hz, i-Pr), 1.03 (d, 3H, J = 7.2 Hz, i-Pr), 0.89 (t, 3H, J = 7.2 Hz, n-Bu),
0.87 (d, 3H, J = 7.6 Hz, i-Pr). 13C NMR (CDCl3, 100 MHz): δ 143.2,
136.7, 133.8, 132.8, 132.0, 129.9, 127.2, 125.3, 124.9, 124.3, 40.8, 38.4,
30.2, 22.8, 18.8, 18.6, 18.4, 18.3, 14.1, 13.0, 12.4, 10.3. Anal. calcd for
6c·0.2H2O (C22H32.4O0.2Si): C, 80.52; H, 9.95. found: C, 80.56; H,
10.01.
cis-2,3-Diethyl-1,1-diisopropyl-2,3-dihydro-1-sila-1H-phenalene
(6i). 6i (3.4 mg, 5%) was obtained as a colorless oil from the reaction
1
using 2 (47.8 mg, 0.197 mmol) and 3i. H NMR (CDCl3, 400 MHz,
253 K): δ 7.86 (d, 1H, J = 8.0 Hz, ArH), 7.71 (d, 1H, J = 8.0 Hz,
ArH), 7.68 (d, 1H, J = 6.8 Hz, ArH), 7.44 (dd, 1H, J = 8.4 Hz, J = 6.8
Hz, ArH), 7.35 (dd, 1H, J = 8.0 Hz, J = 6.8 Hz, ArH), 7.27−7.22 (m,
1H, ArH), 3.04 (td, 1H, J = 12.0 Hz, J = 2.8 Hz, ArCH(Et)), 1.95−
1.70 (m, 3H), 1.55−1.45 (m, 1H), 1.53−1.42 (m, 1H), 1.28 (t, 6H, J =
6.0 Hz, i-Pr), 1.25−1.12 (m, 2H), 1.09 (t, 3H, J = 7.2 Hz, Et), 0.81 (d,
3H, J = 7.6 Hz, i-Pr), 0.69 (d, 3H, J = 7.2 Hz, i-Pr), 0.55 (t, 3H, J = 7.2
Hz, Et). 13C NMR (CDCl3, 100 MHz, 253 K): δ 142.5, 135.6, 133.7,
132.9, 132.2, 129.7, 127.22, 127.16, 124.4, 124.1, 48.1, 27.8, 25.5, 21.6,
19.7, 19.6, 18.6, 18.5, 13.9, 13.6, 13.0, 12.5. HRMS (ESI) m/z: [M]+
calcd for C22H32Si, 324.2273; found, 324.2269.
3-Hexyl-1,1-diisopropyl-2,3-dihydro-1-sila-1H-phenalene (6d). 6d
(46.3 mg, 66%) was obtained as a colorless oil from the reaction using
2 (48.3 mg, 0.199 mmol) and 3d. H NMR (CDCl3, 400 MHz): δ
ASSOCIATED CONTENT
■
1
S
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.joc.6b00793.
7.86 (dd, 1H, J = 8.0 Hz, J = 1.2 Hz, ArH), 7.70 (dd, 1H, J = 6.4 Hz, J
= 1.6 Hz, ArH), 7.68 (dd, 1H, J = 5.2 Hz, J = 1.2 Hz, ArH), 7.46 (dd,
1H, J = 8.4 Hz, J = 6.8 Hz, ArH), 7.38 (t, 1H, J = 8.0 Hz, ArH), 7.32
(d, 1H, J = 7.2 Hz, ArH), 3.35−3.25 (m, 1H, ArCH(n-Hex)), 1.80−
1.60 (m, 2H), 1.50−1.10 (m, 15H), 1.09 (d, 3H, J = 7.6 Hz, i-Pr), 1.02
(d, 3H, J = 7.2 Hz, i-Pr), 0.92−0.83 (m, 6H). 13C NMR (CDCl3, 100
MHz): δ 143.2, 136.7, 133.8, 132.8, 132.0, 129.9, 127.2, 125.3, 124.9,
124.3, 40.8, 38.7, 31.9, 29.4, 27.9, 22.7, 18.8, 18.7, 18.4, 18.3, 14.1,
13.0, 12.4, 10.3. HRMS (ESI) m/z: [M]+ calcd for C24H36Si, 352.2586;
found, 352.2576.
trans-1,1-Diisopropyl-2,3-dipropyl-2,3-dihydro-1-sila-1H-phena-
lene (6e). 6e (30.3 mg, 43%) was obtained as a colorless crystal from
the reaction using 2 (48.4 mg, 0.200 mmol) and 3e. Mp: 54−55 °C.
1H NMR (CDCl3, 400 MHz): δ 7.85 (dd, 1H, J = 8.0 Hz, J = 1.2 Hz,
ArH), 7.69 (dd, 1H, J = 8.0 Hz, J = 1.2 Hz, ArH), 7.67 (dd, 1H, J = 6.8
Hz, J = 1.6 Hz, ArH), 7.46 (dd, 1H, J = 8.0 Hz, J = 6.8 Hz, ArH), 7.34
(dd, 1H, J = 8.0 Hz, J = 6.8 Hz, ArH), 7.23 (dd, 1H, J = 7.2 Hz, J = 1.2
Hz, ArH), 3.23 (ddd, 1H, J = 8.8 Hz, J = 6.4 Hz, J = 2.8 Hz, ArCH(n-
The selected NMR spectra of 4−6 and crystallographic
data of 6e (PDF)
CIF data for 6e (CIF)
AUTHOR INFORMATION
■
Corresponding Authors
*E-mail: hidekazu.arii@cc.miyazaki-u.ac.jp.
*E-mail: kunio.mochida@gakushuin.ac.jp.
*E-mail: kawashima.t@gunma-u.ac.jp.
Notes
The authors declare no competing financial interest.
E
DOI: 10.1021/acs.joc.6b00793
J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
Gandon, V.; Malacria, M.; Aubert, C. Organometallics 2007, 26, 819−
830.
ACKNOWLEDGMENTS
■
This work was financially supported by a Grant-in-Aid for
Scientific Research (no. 26410035, T.K.) from the Ministry of
Education, Culture, Sports, Science and Technology, Japan. We
thank Center for Collaborative Research and Community
Cooperation (University of Miyazaki) for NMR spectroscopy
and elemental analysis.
(16) (a) Sekiguchi, A.; Matsuno, T.; Ichinohe, M. J. Am. Chem. Soc.
2000, 122, 11250−11251. (b) Inoue, S.; Ichinohe, M.; Yamaguchi, T.;
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Biomol. Chem. 2015, 13, 9619−9628.
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ez, E.; Bo, C.; Brown, J. M. Org.
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DOI: 10.1021/acs.joc.6b00793
J. Org. Chem. XXXX, XXX, XXX−XXX