Diisobutylaluminum hydride promoted cyclization of o -(trimethylsilylethynyl)styrenes to indenes

Article abstract of DOI:10.1021/jo501383v

The reaction of o-(trimethylsilylethynyl)styrenes with diisobutylaluminum hydride (DIBAL-H) provides 2-trimethylsilyl-1H-indenes efficiently. The cyclization mechanism involves regioselective hydroalumination of the alkynyl moiety, geometrical isomerizati

Full text of DOI:10.1021/jo501383v

Article
pubs.acs.org/joc
Diisobutylaluminum Hydride Promoted Cyclization of
o‑(Trimethylsilylethynyl)styrenes to Indenes
Hidenori Kinoshita, Nobuyoshi Hirai, and Katsukiyo Miura*
Department of Applied Chemistry, Graduate School of Science and Engineering, Saitama University, 255 Shimo-ohkubo, Sakura-ku,
Saitama 338-8570, Japan
S
* Supporting Information
ABSTRACT: The reaction of o-(trimethylsilylethynyl)styrenes with diisobutylaluminum hydride (DIBAL-H) provides
2-trimethylsilyl-1H-indenes efficiently. The cyclization mechanism involves regioselective hydroalumination of the alkynyl
moiety, geometrical isomerization of the alkenylaluminums formed, and intramolecular carboalumination. With substrates
bearing a 2-(trimethylsilyl)ethenyl group (R1 = Me3Si, R2 = R3 = H), bis-silylated benzofulvenes are obtained upon treatment of
the reaction mixture with an excess amount of benzaldehyde.
from alkynylsilanes would be utilized for intramolecular carbo-
alumination of C−C multiple bonds leading to carbocycles. To
realize this idea, we attempted the DIBAL-H-promoted cyclization
of o-(trimethylsilylethynyl)styrenes 1 to indenes 2 (Scheme 2).
INTRODUCTION
■
Indenes and benzofulvenes appear frequently as useful
substances, such as biologically active compounds1 and functional
molecular materials.2 Indenes are also precursors to indenyl
anions used as ligands in transition-metal complexes.3 Therefore,
efficient syntheses of indenes4 and benzofulvenes5 have been
studied intensively so far. A main approach to this end is to
develop transition-metal-catalyzed C−C bond-forming reac-
tions. We herein report the aluminum-mediated cyclization of
o-(trimethylsilylethynyl)styrenes to indenes and benzofulvenes.
Alkenylaluminums are valuable for C−C bond formation
as reactive alkenyl donors,6 since they can be easily prepared
from alkynes by hydroalumination with aluminum hydrides
such as DIBAL-H. However, carboalumination of unpolarized
C−C multiple bonds with alkenylaluminums has remained
largely unexplored.7 Recently, we have reported the DIBAL-H-
promoted cyclodimerization of 1-silylalk-3-en-1-ynes to tetra-
substituted benzenes.8 A key step of this transformation is
intermolecular alkyne carboalumination of a substrate with the
α-silylated dienylaluminum intermediate formed from another
substrate molecule by hydroalumination (Scheme 1). With this
study we expected that α-silylated alkenylaluminums prepared
Scheme 2. This Work
RESULTS AND DISCUSSION
■
Indene Synthesis. We commenced the optimization
of the carboalumination-based indene synthesis by using
o-(trimethylsilylethynyl)styrene ((E)-1a) as a probe (Table 1).
Treatment of (E)-1a with 1.5 equiv of DIBAL-H gave the desired
indene 2a in 56% yield along with 35% recovery of (E)-1a
(entry 1). Elongated reaction time improved the yields of 2a
(entries 2 and 3). However, the reaction for 12 h decreased the
yield with a complex mixture of unidentified products (entry 4).
It is likely that the cyclized product prior to an aqueous workup is
not stable and decomposes during the reaction course. Although
the reaction rate decreased at a lower temperature, the combined
yield of 2a and recovered (E)-1a reached 97% due to suppression
of the side reactions (entry 5). The best result was obtained
when the reaction was carried out at 40 °C for 3 h. Under these
conditions, the desired indene 2a was isolated in 97% yield (entry 6).
A decreased amount of DIBAL-H was not effective (entry 7).
Scheme 1. Previous Work
Received: June 20, 2014
Published: August 5, 2014
© 2014 American Chemical Society
8171
dx.doi.org/10.1021/jo501383v | J. Org. Chem. 2014, 79, 8171−8181

The Journal of Organic Chemistry
Article
a
be cyclized to the desired products. These reactions just gave
inseparable product mixtures formed by C−C double/triple
bond reduction and unidentified side reactions.
Table 1. Optimization of Indene Synthesis
Mechanistic Aspects. A plausible mechanism for the pre-
sent cyclization is shown in Scheme 4. First, site-selective and
regioselective hydroalumination of an o-(trimethylsilylethynyl)-
styrene (1) with DIBAL-H forms the α-silylalkenylaluminum
(Z)-4 with a trans configuration between aryl and alumino
groups. The intermediate (Z)-4 is reversibly converted into its
geometrical isomer (E)-4.9 Intramolecular carboalumination of
(E)-4 gives the aluminated indene 5, which undergoes hydrolysis
leading to the corresponding indene 2.
To verify the formation of 5, the reaction mixture obtained
from (E)-1a and DIBAL-H was treated with MeOD (Scheme 5).
As expected, this deuteration provided indene 2a-d, bearing
a deuterio(trimethylsilyl)methyl (CHDSiMe3) group at C1, with
high diastereoselectivity. On the other hand, the cyclization of
(Z)-1a followed by deuteration exclusively formed the
diastereomer of 2a-d: that is, 2a′-d. Judging from the fact that
spontaneous carboalumination proceeds in a syn-addition
mode,10 the cyclization of (E)-1a would give u-2a-d via (E,E)-
4a and u-5a. Similarly l-2a-d would be formed from (Z)-1a via
(Z,E)-4a and l-5a. Therefore, we tentatively assigned 2a-d and
2a′-d to u and l isomers, respectively. Although the relative
configurations of 2a-d and 2a′-d are not clear,11 the stereo-
specificity observed would support the presence of concerted
intramolecular carboalumination as the key step.
We further conducted a deuteration experiment using (E)-1g
to gain a mechanistic insight into the formation of 3 (Scheme 6).
Similar to the case of (E)-1a, the reaction of (E)-1g gave
deuterated indene 2g-d (>99% D) mainly. The byproduct 3-d
was obtained in 14% yield. The 1H and 13C NMR analysis of 3-d
revealed that it was doubly deuterated at the silylated and
benzylic carbons. The benzylic deuteration is indicative of alkene
hydroalumination. The competitive hydroalumination is possi-
bly due to slow cyclization of the corresponding alkenylaluinum
intermediate (E,E)-4g.
Benzofulvene Synthesis. We turned our attention to the
reaction of the aluminated intermediate 5 with carbon electro-
philes for further transformation. When PhCHO (2 equiv) as the
electrophile was introduced into the reaction mixture from
(E)-1a and DIBAL-H, no expected adduct was observed. Instead,
benzofulvene (E)-7a was obtained as a single stereoisomer in
71% yield (Table 3, entry 1). The structure of (E)-7a was clearly
confirmed by X-ray structure analysis (CCDC 992868).12
The effect of the amount of the aldehyde was investigated
(entries 2−4). Use of a large excess (10 equiv) of PhCHO gave
an 89% isolated yield of (E)-7a (entry 3). Shortening the time
for the treatment with PhCHO slightly decreased the yield of
(E)-7a (entries 5 and 6). Use of other carbonyl compounds
(paraformaldehyde and acetone) was not effective in the
formation of (E)-7a.
b
yield (%)
entry
time
temp (°C)
(E)-1a
2a
1
2
3
4
5
6
5 min
10 min
30 min
12 h
50
50
50
50
40
40
40
35
8
56
86
89
61
0
0
30 min
3 h
22
0
75
c
97 (97)
d
7
3 h
0
92
a
(E)-1a (0.50 mmol) and DIBAL-H (1.0 M in hexane, 0.75 mmol)
were used. Determined by H NMR analysis using dibenzyl ether as
an internal standard. Isolated yield. With DIBAL-H (0.60 mmol).
b
1
c
d
With the optimized reaction conditions in hand, we tested
the cyclization of various o-(trimethylsilylethynyl)styrenes 1 to
explore the scope and limitations. The results are shown in Table
2. Styrene (E)-1b, fluorinated on the benzene ring, was smoothly
cyclized to 2b (entry 1). When o-(trimethylsilylethynyl)-
stilbenes (E)-1c−e (R1 = Ph, p-F-C6H4, p-Me-C6H4) were
subjected to the reaction conditions, the corresponding indenes
2c−e were obtained in excellent yields (entries 2−4). Introduc-
tion of these aryl groups as R1 did not affect the transforma-
tion negatively. Stilbene (E)-1f (R1 = p-MeO-C6H4) showed
low reactivity, probably due to deactivation of DIBAL-H by
coordination of the methoxy group. With an increased amount
of DIBAL-H, the desired indene 2f was formed in good yield
(entry 5). Styrene (E)-1g (R1 = n-Hex) also underwent the
cyclization to 2g (entry 6). 1-Octyl-2-[(E)-2-(trimethylsilyl)-
ethenyl]benzene (3), a doubly reduced product, was also formed
in 12% yield. In contrast, the reaction of (E)-1h (R1 = t-Bu) gave
2h in only 11% yield with a complex mixture of byproducts
(entry 7). Presumably the tert-butyl group retards the key
carboalumination step (vide infra) by steric hindrance.
We next examined the effect of alkene geometry on the
cyclization. The cyclization of β-silylated styrene (Z)-1a
proceeded successfully, although it was slightly less efficient
than that of (E)-1a (entry 8). Stilbenes (Z)-1c and (Z)-1i also
have enough reactivity for the indene formation (entries 9 and
10). Unexpectedly the reaction of β-alkylated styrene (Z)-1g
resulted in a trace amount of 2g, unlike that of (E)-1g (entry 11
vs 6). In this case, 3 was obtained as the main product in 41%
yield along with unidentified byproducts. Both the Z geometry
and the electron-donating character of a hexyl group possibly
decelerate the intramolecular carboalumination step (vide infra).
The parent substrate 1j was efficiently converted into 2j under
the standard conditions (entry 12). As predicted from the
sterically demanding alkene terminus, no desired product was
formed from β,β-dimethylstyrene 1k (entry 13). To our surprise
α-methylstyrene 1l was successfully cyclized to 1,1-dimethylindene
2l with the formation of the quaternary carbon (entry 14).
Similarly α,β-disubstituted styrene 1m is usable for the cyclization.
Treatment of 1m with DIBAL-H for 24 h gave spiroindene 2m in
moderate yield (entry 15).
As shown in Scheme 7, the fulvene synthesis from (Z)-1a
resulted in failure. Only a trace amount of (E)-7a could be detected,
and 2a was the main product (47% yield). The cyclization of
(E)-1b followed by treatment with PhCHO gave (E)-7b in 77%
yield. Unfortunately the yield of (E)-7g from (E)-1g was only 23%,
and the corresponding benzofulvene was not detected in the
reaction of (E)-1c. Thus, the benzofulvene synthesis is limited to
(E)-β-silylstyrenes 1.
To extend the utility of the present cyclization, we tried the
synthesis of six-membered carbocycles from homologated
substrates 1n,o (Scheme 3). However, neither of them could
The formation of (E)-7a from (E)-1a can be rationalized
by the dehydroalumination of u-5a with PhCHO via the six-
membered cyclic transition state (TS) A (Scheme 8). This type
8172
dx.doi.org/10.1021/jo501383v | J. Org. Chem. 2014, 79, 8171−8181

The Journal of Organic Chemistry
Article
a
Table 2. Scope and Limitations of Indene Synthesis
a
b
c
All reactions were conducted with 1 (0.50 mmol) and DIBAL-H (1.0 M in hexane, 0.75 mmol) at 40 °C for 3 h. Isolated yield. An E:Z mixture of
d
e
f
1b (E:Z = 94:6) was used. With DIBAL-H (1.25 mmol). Not detected. The reaction was conducted at 40 °C for 24 h.
of carbonyl reduction with alkylaluminums has been revealed.13
In TS A, the silyl group α to the alumino group may assist the
β-hydride elimination by the β-carbocation stabilizing ability
(β-silicon effect), which is a possible reason for the efficient
conversion of (E)-β-silylstyrenes 1 into benzofulvenes (E)-7.
The unsuccessful result with (Z)-1a is probably because TS B in
the dehydroalumination step is destabilized by steric hindrance
between two trimethylsilyl groups.
good to high yields. The application to benzofulvene synthesis
has also been demonstrated. The present study shows the utility
of silicon-directed hydroalumination of alkynes and subsequent
intramolecular carboalumination toward carbocycle synthesis.
Further application of this strategy to other carbocyclizations is
now under investigation.
EXPERIMENTAL SECTION
■
General Experimental Considerations. Unless otherwise noted,
all reactions were carried out under an argon atmosphere. All reagents
were purchased from common suppliers and used as received. Analytical
thin-layer chromatography was performed using 0.25 mm silica gel 60
F254 plates. Chromatography was performed using silica gel 60 N
(spherical, neutral, 63−210 μm). NMR spectra were recorded on a 300,
400, or 500 MHz NMR spectrometer. The chemical shifts are reported
with reference at 7.26 ppm (CHCl3) for the proton and at 77.0 ppm
(centered on the signal of CDCl3) for the carbon. Data for 1H NMR are
CONCLUSION
■
In conclusion, we have succeeded in the efficient synthesis of
silylated indenes by the DIBAL-H-promoted cyclization of
o-(silylethynyl)styrenes. Although the compatibility of this
cyclization with polar functional groups is limited, a variety of
substrates having a different substituent or substitution pattern
can be converted into the corresponding silylated indenes in
8173
dx.doi.org/10.1021/jo501383v | J. Org. Chem. 2014, 79, 8171−8181

The Journal of Organic Chemistry
Article
a
Scheme 3
Table 3. Optimization of Benzofulvene Synthesis
c
yield (%)
(E)-7a
b
entry
amt of PhCHO (equiv)
time (h)
2a
Scheme 4. Plausible Reaction Mechanism
1
2
3
4
5
6
2
5
16
16
16
16
2
71
16
11
5
80
d
10
20
10
10
91 (89)
90
80
84
4
11
9
5
a
The initial cyclization was carried out with (E)-1a (0.5 mmol) and
DIBAL-H (0.75 mmol) in hexane at 40 °C for 3 h. After it was cooled
to room temperature, the reaction mixture was treated with
b
benzaldehyde. The time for the treatment with PhCHO.
c
1
Determined by H NMR analysis using dibenzyl ether as an internal
d
standard. Isolated yield.
THF (70 mL) at −78 °C. After 30 min of stirring, I2 (9.99 g, 39.3 mmol)
was added to the reaction mixture. The mixture was warmed to room
temperature over 4 h and quenched with water. The aqueous mixture
was treated with saturated aqueous Na2S2O3 and extracted with hexane.
The organic layer was dried over Na2SO4 and evaporated. Purification of
the residue by silica gel column chromatography (hexane) gave 1-iodo-
2-[2-(trimethylsilyl)-ethynyl]benzene (S1) as a yellow oil (4.36 g, 14.5
mmol, 93%): 1H NMR (400 MHz, CDCl3) δ 0.29 (s, 9H), 6.99 (td, J =
7.6, 1.6 Hz, 1H), 7.28 (td, J = 7.6, 1.2 Hz, 1H), 7.47 (dd, J = 7.8, 1.6 Hz,
1H), 7.84 (dd, J = 7.8, 1.2 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ
−0.2, 98.8, 101.2, 106.5, 127.7, 129.5, 129.6, 132.7, 138.7.
Scheme 5. Cyclization Followed by Deuteration
1-Iodo-2-[(E)-2-(trimethylsilyl)ethenyl]benzene ((E)-S2). DIBAL-H
(1.0 M in hexane, 21.1 mL, 21.1 mmol) was added to a solution of S1
(3.21 g, 10.7 mmol) in hexane (17 mL) at room temperature. After 48 h
of stirring, the reaction mixture was treated with 40% aqueous Rochelle
salt for 1 h and extracted with hexane. The organic layer was dried over
Na2SO4 and evaporated. Purification of the residue by silica gel column
chromatography (hexane) gave 1-iodo-2-[(E)-2-(trimethylsilyl)-
ethenyl]benzene ((E)-S2) as a yellow oil (2.28 g, 9.18 mmol, 86%):
1H NMR (300 MHz, CDCl3) δ 0.19 (s, 9H), 6.36 (d, J = 18.6 Hz, 1H),
6.93 (td, J = 7.7, 1.5 Hz, 1H), 7.04 (d, J = 18.6 Hz, 1H), 7.31 (tt, J = 7.8,
0.6 Hz, 1H), 7.54 (dd, J = 7.8, 1.8 Hz, 1H), 7.83 (dd, J = 7.8, 1.2 Hz, 1H);
13C NMR (100 MHz, CDCl3) δ −1.3, 99.9, 126.5, 128.3, 129.2, 133.5,
139.4, 141.1, 147.2; IR (neat) 3058, 3007, 2954, 2896, 1597, 1578, 1557,
1456, 1432 1247, 1008, 984, 864, 842, 753 cm−1; HRMS (EI) calcd for
C11H15ISi [M+] 301.9988, found 301.9992.
Scheme 6. Deuteration Experiment with (E)-1g
1-[(E)-2-(Trimethylsilyl)ethenyl]-2-[2-(trimethylsilyl)ethynyl]-
benzene ((E)-1a). A solution of (E)-S2 (1.51 g, 5.00 mmol) in THF
(3 mL) and trimethylsilylacetylene (TMSA; 0.85 mL, 6.00 mmol)
were added to a mixture of PdCl2(PPh3)2 (70.1 mg, 0.10 mmol), CuI
(19.5 mg, 0.10 mmol), Et2NH (6 mL), and THF (3 mL) at room
temperature. After 16 h of stirring, the reaction mixture was quenched
with water and extracted with hexane. The organic layer was dried over
Na2SO4 and evaporated. Purification of the residue by silica gel column
chromatography (hexane) gave (E)-1a (1.26 g, 4.62 mmol, 92%) as a
yellow oil: 1H NMR (500 MHz, CDCl3) δ 0.17 (s, 9H), 0.27 (s, 9H),
6.55 (d, J = 19.5 Hz, 1H), 7.17, (td, J = 7.8, 1.0 Hz, 1H), 7.28 (tt, J = 7.8,
0.5 Hz, 1H), 7.44 (dd, J = 7.8, 1.0 Hz, 1H), 7.44 (d, J = 19.0 Hz, 1H),
7.60 (d, J = 8.0 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ −1.3, 0.02,
99.3, 103.3, 121.8, 124.5, 127.4, 128.6, 131.6, 132.6, 140.0, 141.6; IR
(neat) 3062, 3021, 2956, 2898, 2155, 1950, 1603, 1558, 1470, 1249, 990,
869, 757 cm−1; HRMS (EI) calcd for C16H24Si2 [M+] 272.1417, found
272.1423.
reported as follows: chemical shift, multiplicity (s = singlet, d = doublet,
t = triplet, q = quartet, quint = quintet, m = multiplet), coupling constants
(J, reported as values in hertz (Hz)), and integration. Infrared spectra and
high-resolution mass spectra were obtained for all new compounds. The
high-resolution mass analysis was conducted by a double-focusing
magnetic sector mass spectrometer. Melting points were measured for
solid compounds. X-ray single-crystal analysis of (E)-7a was conducted.
Synthesis of 1-[(E)-2-(Trimethylsilyl)ethenyl]-2-[2-
(trimethylsilyl)ethynyl]benzene ((E)-1a). 1-Iodo-2-[2-
(trimethylsilyl)ethynyl]benzene (S1) [CAS: 137648-47-6].14 n-BuLi
(2.6 M in hexane, 13.9 mL, 36.1 mmol) was added to a solution of
1-bromo-2-[2-(trimethylsilyl)ethynyl]benzene (3.98 g, 15.7 mmol) in
Synthesis of 4-Fluoro-2-iodo-1-[(E)-2-(trimethylsilyl)-
ethenyl]benzene ((E)-1b). 2-Bromo-4-fluoro-1-[2-(trimethylsilyl)-
ethynyl]benzene (S3). TMSA (2.57 mL, 18.2 mmol) was added
to a mixture of PdCl2(PPh3)2 (246 mg, 0.350 mmol), CuI (66.7 mg,
8174
dx.doi.org/10.1021/jo501383v | J. Org. Chem. 2014, 79, 8171−8181

The Journal of Organic Chemistry
Article
Scheme 7. Formation of Benzofulvenes 7
dried over Na2SO4 and evaporated. Purification of the residue by
silica gel column chromatography (hexane) gave 4-fluoro-2-iodo-1-
[2-(trimethylsilyl)ethenyl]benzene (S5) as an EZ mixture (E:Z = 95:5,
2.70 g, 8.43 mmol, 81%) as a colorless oil: 1H NMR (300 MHz, CDCl3)
for E isomer δ 0.18 (s, 9H), 6.28 (d, J = 18.9 Hz, 1H), 6.98 (d, J = 18.9
Hz, 1H), 7.05 (tdd, J = 8.4, 2.7, 0.6 Hz, 1H), 7.49 (dd, J = 8.9, 6.0 Hz,
1H), 7.55 (dd, J = 8.0, 2.7 Hz, 1H), for Z isomer δ −0.05 (s, 9H), 5.89 (d,
J = 14.7 Hz, 1H), 7.12 (d, J = 14.7 Hz, 1H), 7.16−7.61 (m, 3H); 13C
NMR (100 MHz, CDCl3) for E isomer δ −1.3, 98.9 (d, 3JC−F = 8.0 Hz),
Scheme 8. Plausible Mechanism for Benzofulvene Formation
115.6 (d, 2JC−F = 21.0 Hz), 126.0 (d, 2JC−F = 24.0 Hz), 127.1 (d, 3JC−F
=
8.0 Hz), 133.4, 137.5 (d, 4JC−F = 3.0 Hz), 145.9, 161.5 (d, 1JC−F = 251.0
Hz), for Z isomer δ −0.07, 98.2 (d, 3JC−F = 8.0 Hz), 114.7 (d, 2JC−F
=
21.0 Hz), 125.4 (d, 2JC−F = 24.0 Hz), 129.9 (d, 3JC−F = 8.0 Hz), 134.6,
140.5 (d, 4JC−F = 4.0 Hz), 148.7, 161.2 (d, 1JC−F = 250.0 Hz); IR (neat)
2954, 2897, 1591, 1473, 1248, 1227, 863, 841 cm−1; HRMS (EI) calcd
for C11H14FISi [M+] 319.9893, found 319.9897.
4-Fluoro-1-[2-(trimethylsilyl)ethenyl]-2-[2-(trimethylsilyl)ethynyl]-
benzene (1b) (E:Z = 94:6). A solution of S5 (0.91 g, 2.84 mmol) in THF
(3 mL) and TMSA (0.51 mL, 3.60 mmol) were added to a mixture of
PdCl2(PPh3)2 (42.1 mg, 0.06 mmol), CuI (11.4 mg, 0.06 mmol), Et2NH
(6 mL), and THF (3 mL) at 0 °C. After overnight stirring at room
temperature, the reaction mixture was quenched with water and extracted
with hexane. The organic layer was dried over Na2SO4 and evaporated.
Purification of the residue by silica gel column chromatography (hexane)
gave 4-fluoro-1-[2-(trimethylsilyl)ethenyl]-2-[2-(trimethylsilyl)ethynyl]-
benzene (1b; 0.72 g, 2.48 mmol, 87%) as an E:Z mixture (E:Z = 94:6) of a
0.350 mmol), 2-bromo-4-fluoro-1-iodobenzene (5.20 g, 17.3 mmol),
and Et2NH (20 mL) at 0 °C. After 16 h of stirring at room temperature,
the reaction mixture was quenched with water and extracted with hexane.
The organic layer was dried over Na2SO4 and evaporated. Purification of
the residue by silica gel column chromatography (hexane) gave 2-bromo-
4-fluoro-1-[2-(trimethylsilyl)ethynyl]benzene (S3; 3.52 g, 13.0 mmol,
75%) as a colorless oil: 1H NMR (400 MHz, CDCl3) δ 0.27 (s, 9H), 6.97
(td, J = 8.4, 2.4 Hz, 1H), 7.32 (dd, J = 8.2, 2.4 Hz, 1H), 7.47 (dd, J = 8.6,
5.6 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ −0.2, 99.4, 102.0, 114.5 (d,
2JC−F = 21.0 Hz), 119.9 (d, 2JC−F = 24.0 Hz), 121.7 (d, 4JC−F = 4.0 Hz),
1
126.4 (d, 3JC−F = 10.0 Hz), 134.6 (d, 3JC−F = 9.0 Hz), 161.8 (d, 1JC−F
=
yellow oil: H NMR (300 MHz, CDCl3) for E isomer δ 0.17 (s, 9H),
0.27 (s, 9H), 6.46 (d, J = 19.2 Hz, 1H), 6.99 (tdd, J = 8.4, 2.7, 0.6 Hz, 1H),
7.13 (dd, J = 9.0, 2.7 Hz, 1H), 7.37 (d, J = 19.2 Hz, 1H), 7.56 (dd, J = 8.7,
5.7 Hz, 1H), for Z isomer δ 0.02 (s, 9H), 0.25 (s, 9H), 5.90 (d, J = 15.3 Hz,
1H), 6.95−7.60 (m, 4H); 13C NMR (100 MHz, CDCl3) for E isomer δ
−1.3, −0.1, 100.5, 102.0 (d, 4JC−F = 2.0 Hz), 116.2 (d, 2JC−F = 22.0 Hz),
252.0 Hz); IR (neat) 3073, 2960, 2899, 2167, 1595, 1482, 1263, 1252,
1194, 858 cm−1; HRMS (EI) calcd for C11H12BrFSi [M+] 269.9876,
found 269.9877.
4-Fluoro-2-iodo-1-[2-(trimethylsilyl)ethynyl]benzene (S4). n-BuLi
(2.6 M in hexane, 5.23 mL, 13.6 mmol) was added to a solution of S3
(3.07 g, 11.3 mmol) in THF (50 mL) at −78 °C. After 30 min of stirring
at −78 °C, I2 (4.00 g, 15.8 mmol) was added to the mixture at −78 °C.
The resultant mixture was warmed to room temperature over 2 h. After
quenching with water, the aqueous mixture was treated with saturated
aqueous Na2S2O3 and extracted with hexane. The organic layer was
dried over Na2SO4 and evaporated. Purification of the residue by
silica gel column chromatography (hexane) gave 4-fluoro-2-iodo-1-
[2-(trimethylsilyl)ethynyl]benzene (S4; 3.51 g, 11.0 mmol, 97%) as a
colorless oil: 1H NMR (300 MHz, CDCl3) δ 0.28 (s, 9H), 7.01 (td J =
118.7 (d, 2JC−F = 22.0 Hz), 123.3 (d, 3JC−F = 9.0 Hz), 126.3 (d, 3JC−F
=
9.0 Hz), 131.3, 136.5 (d, 4JC−F = 3.0 Hz), 140.5, 161.6 (d, 1JC−F =246.0),
for Z isomer δ −1.6, −0.08, 100.4, 102.4 (d, 4JC−F = 3.0 Hz), 115.1 (d,
2JC−F = 22.0 Hz), 118.6 (d, 2JC−F = 23.0 Hz), 124.0 (d, 3JC−F = 10.0 Hz),
129.7 (d, 3JC−F = 9.0 Hz), 133.9, 138.9 (d, 4JC−F = 3.0 Hz), 144.7, 161.5
(d, 1JC−F =246.0); IR (neat) 3071, 2957, 2898, 2155, 1602, 1473, 1250,
844 cm−1; HRMS (EI) calcd for C16H23FSi2 [M+] 290.1322, found
290.1323.
Synthesis of 1-[(E)-2-(Phenyl)ethenyl]-2-[2-(trimethylsilyl)-
ethynyl]benzene ((E)-1c). 1-Iodo-2-[(E)-2-(phenyl)ethenyl]benzene
(S6) [CAS: 5025-41-2].15 Sodium bis(trimethylsilyl)amide (1.9 M in
THF, 4.2 mL, 8.0 mmol) was added dropwise to a solution of diethyl
benzylphosphonate (1.83 g, 8.02 mmol) in THF (2 mL) at 0 °C. After
10 min of stirring, a solution of 2-iodobenzaldehyde (1.86 g, 8.02 mmol)
in THF (5 mL) was added to the mixture. After 12 h of stirring at
room temperature, the reaction mixture was quenched with water and
extracted with Et2O. The organic layer was dried over Na2SO4 and
evaporated. Purification of the residue by silica gel column chromato-
graphy (hexane/AcOEt 5/1) gave 1-iodo-2-[(E)-2-phenylethenyl]-
8.4, 2.7 Hz, 1H), 7.43 (dd, J = 8.7, 5.7 Hz, 1H), 7.56 (dd, J = 8.1, 2.7 Hz,
3
1H); 13C NMR (100 MHz, CDCl3) δ −0.2, 98.5, 101.1 (d, JC−F
=
8.0 Hz), 105.5, 115.3 (d, 2JC−F = 21.0 Hz), 125.9 (d, JC−F = 24.0 Hz),
126.1 (d, 4JC−F = 4.0 Hz), 133.6 (d, 3JC−F = 8.0 Hz), 161.3 (d, 1JC−F = 254.0
Hz); IR(neat) 3067, 2959, 2898, 2164, 1589, 1474, 1251, 1194, 845 cm−1;
HRMS (EI) calcd for C11H12FISi [M+] 317.9737, found 317.9732.
4-Fluoro-2-iodo-1-[2-(trimethylsilyl)ethenyl]benzene (S5) (E:Z =
95:5). DIBAL-H (1.0 M in hexane, 20.8 mL, 20.8 mmol) was added to
a solution of S4 (3.29 g, 10.4 mmol) in hexane (16.6 mL) at room
temperature. After 72 h, the mixture was treated with 40% aqueous
Rochelle salt at 0 °C and stirred at room temperature for 2 h. Then
the aqueous mixture was extracted with hexane. The organic layer was
2
1
benzene (S6) as a colorless oil (1.83 g, 5.98 mmol, 75%): H NMR
(300 MHz, CDCl3) δ 6.69 (td, J = 7.5,1.8 Hz, 1H), 6.97 (d, J = 16.2 Hz,
8175
dx.doi.org/10.1021/jo501383v | J. Org. Chem. 2014, 79, 8171−8181

The Journal of Organic Chemistry
Article
1H), 7.24−7.42 (m, 5H), 7.53−7.58 (m, 2H), 7.63 (dd, J = 7.8, 1.5 Hz,
1H), 7.88 (dd, J = 8.1 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 100.4,
126.3, 126.8, 128.0, 128.4, 128.7, 128.9, 131.6, 132.4, 136.9, 139.6, 140.3.
1-[(E)-2-(Phenyl)ethenyl]-2-[2-(trimethylsilyl)ethynyl]benzene
((E)-1c). The Sonogashira coupling of S6 (1.69 g, 5.52 mmol) and
TMSA (0.93 mL, 6.60 mmol) by the method for the synthesis of (E)-1a
gave (E)-1c (1.43 g, 5.18 mmol, 94%) as a white solid: mp 55.5−
57.5 °C; 1H NMR (400 MHz, CDCl3) δ 0.31 (s, 9H), 7.18 (d, J = 16.4
Hz, 1H), 7.19 (td, J = 7.6, 1.2 Hz, 1H), 7.27−7.34 (m, 2H), 7.35−7.40
(m, 2H), 7.49 (dd, J = 7.8, 1.2 Hz, 1H), 7.52−7.56 (m, 2H), 7.68 (d, J =
16.4 Hz, 1H), 7.68 (d, J = 8.0 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ
0.03, 99.6, 103.6, 122.0, 124.5, 126.7, 126.8, 127.1, 127.8, 128.7, 130.1,
132.8, 137.4, 139.1; IR (Nujol) 3080, 3022, 2151, 1494, 1447, 1250, 965,
868 cm−1; HRMS (EI) calcd for C19H20Si [M+] 276.1334, found
276.1325.
(hexane/AcOEt = 5/1) gave (E)-1f (0.51 g, 1.66 mmol, 55%) as a white
solid: mp 62.0−64.5 °C. 1H NMR (300 MHz, CDCl3) δ 0.30 (s, 9H), 3.84
(s, 3H), 6.91 (d, J = 8.7 Hz, 2H), 7.13 (d, J = 16.2 Hz, 1H), 7.16 (td, J = 7.5,
1.2 Hz, 1H), 7.30 (td, J = 7.7, 0.9 Hz, 1H), 7.45−7.49 (m, 1H), 7.48 (d, J =
8.7 Hz, 2H), 7.54 (d, J = 16.2 Hz, 1H), 7.65 (d, J = 7.8 Hz, 1H); 13C NMR
(125 MHz, CDCl3) δ 0.05, 55.3, 99.4, 103.7, 114.2, 121.7, 124.2, 124.6,
126.7, 127.9, 128.7, 129.7, 130.2, 132.8, 139.4, 159.5; IR (Nujol) 3035,
2145, 1604, 1512, 1445, 1251, 1033, 972, 842 cm−1; HRMS (EI) calcd for
C20H22OSi [M+] 306.1440, found 306.1444.
Synthesis of 1-[(E)-Oct-1-enyl]-2-[2-(trimethylsilyl)ethynyl]-
benzene ((E)-1g). 1-Bromo-2-[(E)-oct-1-enyl]benzene (S8). A
solution of (E)-1-iodooct-1-ene (3.81 g, 16.0 mmol) in THF (8 mL)
was added to a solution of Pd(PPh3)4 (0.46 g, 0.40 mmol) in THF
(17 mL) at room temperature. After 30 min of stirring, a solution
of 2-bromophenylboronic acid (1.61 g, 8.00 mmol) in THF (8 mL) and
aqueous NaOH (1 M, 16.8 mL, 16.8 mmol) were added to the mixture.
The resultant mixture was heated under reflux for 12 h and then cooled
to room temperature. The reaction mixture was diluted with water
(10 mL) and Et2O (20 mL) and extracted with Et2O. The organic layer
was dried over Na2SO4 and evaporated. Purification of the residue by
silica gel column chromatography (hexane) gave 1-bromo-2-[(E)-oct-1-
Synthesis of 1-[(E)-2-(4-Fluorophenyl)ethenyl]-2-[2-
(trimethylsilyl)ethynyl]benzene ((E)-1d). Sodium bis-
(trimethylsilyl)amide (1.9 M in THF, 2.6 mL, 5.0 mmol) was added
to a solution of diethyl (4-fluorobenzyl)phosphonate (1.48 g, 6.01 mmol)
in THF (15 mL) at 0 °C. After 10 min of stirring, a solution of
2-(trimethylsilylethynyl)benzaldehyde (1.02 g, 5.04 mmol) in THF
(8 mL) was added to the mixture. After 16 h of stirring, the reaction
mixture was quenched with aqueous NH4Cl and extracted with Et2O. The
organic layer was dried over Na2SO4 and evaporated. Purification of the
residue by silica gel column chromatography (hexane/AcOEt 40/1) gave
(E)-1d as a needle crystal (0.72 g, 2.45 mmol, 49%): mp 52.5−54.0 °C;
1H NMR (300 MHz, CDCl3) δ 0.30 (s, 9H), 7.07 (t, J = 8.7 Hz, 2H), 7.14
(d, J = 16.8 Hz, 1H), 7.19 (td, J = 7.7, 1.2 Hz, 1H), 7.32 (tdd, J = 7.8, 1.4,
0.3 Hz, 1H), 7.46−7.54 (m, 3H), 7.58 (d, J = 16.5 Hz, 1H), 7.65 (dt, J =
8.1, 0.6 Hz, 1H); 13C NMR (125 MHz, CDCl3) δ 0.03, 99.7, 103.5, 115.7
1
enyl]benzene (S8; 1.59 g, 5.95 mmol, 74%) as a pale yellow oil: H
NMR (500 MHz, CDCl3) δ 0.90 (t, J = 7.0 Hz, 3H), 1.26−1.40 (m, 6H),
1.49 (quint, J = 7.5 Hz, 2H), 2.51 (qd, J = 7.5, 1.0 Hz, 2H), 6.17 (dt, J =
16.0, 7.0 Hz, 1H), 6.70 (d, J = 16.0, 1H), 7.05 (td, J = 8.0, 1.5 Hz, 1H),
7.24 (t, J = 7.3 Hz, 1H), 7.49 (dd, J = 7.8, 1.5 Hz, 1H), 7.52 (dd, J = 8.0,
1.5 Hz, 1H); 13C NMR (125 MHz, CDCl3) δ 0.01, 14.1, 22.6, 28.9, 29.2,
31.7, 33.1, 123.1, 126.8, 127.3, 128.0, 128.6, 132.8, 134.3, 137.7; IR
(neat) 3061, 2955, 2925, 2854, 1466, 1435, 1249, 1022, 963 cm−1;
HRMS (EI) calcd for C14H19Br [M+] 266.0670, found 266.0676.
1-Iodo-2-[(E)-oct-1-enyl]benzene (S9). This compound was pre-
pared from S8 (1.22 g, 4.57 mmol) by the method for the synthesis of S4
from S3. 1-Iodo-2-[(E)-oct-1-enyl]benzene (S9; 1.17 g, 3.72 mmol,
81%) was obtained as a pale yellow oil. 1H NMR (400 MHz, CDCl3) δ
0.90 (t, J = 6.8 Hz, 3H), 1.27−1.42 (m, 6H), 1.44−1.54 (m, 2H), 2.25
(qd, J = 7.0, 1.2 Hz, 2H), 6.09 (dt, J = 15.6, 7.2 Hz, 1H), 6.55 (d, J = 15.6
HZ, 1H), 6.89 (td J = 7.6, 1.6 Hz, 1H), 7.25−7.30 (m, 1H), 7.44 (dd, J =
7.6, 1.6 Hz, 1H), 7.81 (dd, J = 8.0, 1.2 Hz, 1H); 13C NMR (100 MHz,
CDCl3) δ 14.1, 22.6, 28.8, 29.1, 31.7, 32.9, 99.4, 126.3, 128.19, 128.24,
133.5, 134.4, 139.3, 141.0; IR (neat) 3059, 3026, 2955, 2925, 2854,
1461, 1431, 1010, 960, 745 cm−1; HRMS (EI) calcd for C14H19I [M+]
314.0531, found 314.0544.
1-[(E)-Oct-1-enyl]-2-[2-(trimethylsilyl)ethynyl]benzene ((E)-1g).
The Sonogashira coupling of S9 (961 mg, 3.06 mmol) with TMSA
(0.52 mL, 3.67 mmol) by the method for the synthesis of (E)-1a gave
(E)-1g (715 mg, 2.51 mmol, 82%) as a yellow oil: 1H NMR (300 MHz,
CDCl3) δ 0.27 (s, 9H), 0.90 (t, J = 6.6 Hz, 3H), 1.26−1.42 (m, 6H),
1.45−1.55 (m, 2H), 2.25 (qd, J = 6.9, 1.5 Hz, 2H), 6.32 (dt, J = 15.6, 6.9
Hz, 1H), 6.86 (d, J = 15.6 Hz, 1H), 7.11 (td, J = 7.5, 1.2 Hz, 1H), 7.24
(td, J = 7.8, 1.2 Hz, 1H), 7.42 (dd, J = 7.6, 1.2 Hz, 1H), 7.49 (dd, J = 7.5,
0.6 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 0.01, 14.1, 22.6, 28.9, 29.1,
31.8, 33.2, 98.8, 103.9, 121.0, 124.5, 126.3, 127.7, 128.6, 132.7, 133.2,
139.9; IR (neat) 3087, 3060, 3025, 2957, 2926, 2855, 2154, 1474, 1446,
1250, 966, 867, 842 cm−1; HRMS (EI) calcd for C19H28Si [M+]
284.1960, found 284.1958.
(d, 3JC−F = 22.5 Hz), 122.0, 124.5, 126.6, 127.1, 128.1, 128.5 (d, 2JC−F
96.3 Hz), 128.7, 132.9, 133.6 (d, 4JC−F = 5.0 Hz), 138.9, 162.5 (d, 1JC−F
=
=
246.3 Hz); IR (Nujol) 3033, 2154, 1598, 1508, 1233, 969 cm−1; HRMS
(EI) calcd for C19H19FSi [M+] 294.1240, found 294.1242.
Synthesis of 1-[(E)-2-(4-Methylphenyl)ethenyl]-2-[2-
(trimethylsilyl)ethynyl]benzene ((E)-1e). 1-Iodo-2-[(E)-2-(4-
methylphenyl)ethenyl]benzene (S7). This compound was prepared
from2-iodobenzaldehyde(1.86 g, 8.02mmol) and diethyl 4-methylbenzyl
phosphonate (1.94 g, 8.01 mmol) by the method for the synthesis of S6.
Stilbene S7 (2.39 g, 7.46 mmol, 93%) was obtained as a colorless oil:
1H NMR (500 MHz, CDCl3) δ 2.37 (s, 3H), 6.92−6.97 (m, 1H), 6.94 (d,
J = 16.5 Hz, 1H), 7.19 (d, J = 8.0 Hz, 2H), 7.24−7.29 (m, 1H), 7.34 (t,
J = 8.0 Hz, 1H), 7.45 (d, J = 8.0 Hz, 2H), 7.61 (dd, J = 7.5, 1.5 Hz, 1H),
7.87 (dd, J = 8.0, 1.0 Hz, 1H); 13C NMR (125 MHz, CDCl3) δ 21.3, 100.4,
126.1, 126.7, 128.3, 128.7, 129.4, 131.4, 131.5, 134.1, 138.0, 139.5, 140.4;
IR (neat) 3048, 3023, 2918, 2859, 1629, 1579, 1512, 1460, 1432, 1216,
1009, 959, 802, 746 cm−1; HRMS (EI) calcd for C15H13I [M+] 320.0062,
found 320.0054.
1-[(E)-2-(4-Methylphenyl)ethenyl]-2-[2-(trimethylsilyl)ethynyl]-
benzene ((E)-1e). The Sonogashira coupling of S7 (1.28 g, 4.00 mmol)
with TMSA (0.68 mL, 4.80 mmol) by the method for the synthesis of
(E)-1a gave (E)-1e (0.97 g, 3.35 mmol, 84%) as a white solid: mp 54.0−
55.0 °C; 1H NMR (500 MHz, CDCl3) δ 0.31 (s, 9H), 2.37 (s, 3H), 7.16
(d, J = 16.5 Hz, 1H), 7.15−7.20 (m, 1H), 7.19 (d, J = 8.0 Hz, 2H), 7.31
(td, J = 7.5, 1.0 Hz, 1H), 7.44 (d, J = 8.0 Hz, 2H), 7.47 (dd, J = 7.8, 1.0
Hz, 1H), 7.63 (d, J = 16.5 Hz, 1H), 7.67 (d, J = 8.0 Hz, 1H); 13C NMR
(125 MHz, CDCl3) δ 0.05, 21.3, 99.5, 103.6, 121.9, 124.4, 125.8, 126.6,
126.9, 128.7, 129.4, 130.1, 132.8, 134.7, 137.8, 139.3; IR (Nujol) 3060,
3018, 2954, 2154, 1514, 1248, 967, 841 cm−1; HRMS (EI) calcd for
C20H22Si [M+] 290.1491, found 290.1488.
Synthesis of 1-[(E)-3,3-Dimethylbut-1-enyl]-2-[2-
(trimethylsilyl)ethynyl]benzene ((E)-1h). 2-Bromo-1-[(E)-3,3-di-
methylbut-1-enyl]benzene (S10). This compound was prepared from
2-bromophenylboronic acid (2.01 g, 10.0 mmol) and (E)-1-iodo-3,3-
dimethylbut-1-ene (4.20 g, 20.0 mmol) by the method for the synthesis
of S8. 2-Bromo-1-[(E)-3,3-dimethylbut-1-enyl]benzene (S10; 1.70 g,
7.11 mmol, 71%) was obtained as a colorless oil: 1H NMR (300 MHz,
CDCl3) δ 1.15 (s, 9H), 6.18 (d, J = 15.9 Hz, 1H), 6.65 (d. J = 15.9 Hz,
1H), 7.05 (td, J = 7.8, 1.5 Hz, 1H), 7.24 (td, J = 7.7, 1.2 Hz, 1H), 7.47−
7.54 (m, 2H); 13C NMR (125 MHz, CDCl3) δ 29.5, 33.7, 123.5, 123.9,
126.8, 127.3, 128.0, 132.8, 137.8, 144.8; IR (neat) 3056, 2959, 2865,
1465, 1438 1024, 968 cm−1; HRMS (EI) calcd for C12H15Br [M+]
238.0357, found 238.0366.
Synthesis of 1-[(E)-2-(4-Methoxylphenyl)ethenyl]-2-[2-
(trimethylsilyl)ethynyl]benzene ((E)-1f). Sodium bis-
(trimethylsilyl)amide (1.9 M in THF, 1.9 mL, 3.6 mmol) was added
to a solution of diethyl (4-methoxybenzyl)phosphonate (0.93 g,
3.60 mmol) in THF (9 mL) at 0 °C. After 10 min of stirring, a solution
of 2-(trimethylsilylethynyl)benzaldehyde (0.61 g, 3.02 mmol) in THF
(5 mL) was added to the mixture. After overnight stirring at room tem-
perature, the reaction mixture was quenched with aqueous NH4Cl and
extracted with AcOEt. The organic layer was dried over Na2SO4 and
evaporated. Purification of the residue by silica gel column chromatography
1-[(E)-3,3-Dimethylbut-1-enyl]-2-iodobenzene (S11). This com-
pound was prepared from S10 (1.70 g, 7.11 mmol) by the method
8176
dx.doi.org/10.1021/jo501383v | J. Org. Chem. 2014, 79, 8171−8181

The Journal of Organic Chemistry
Article
for the synthesis of S4 from S3. 1-[(E)-3,3-Dimethylbut-1-enyl]-2-
iodobenzene (S11; 1.81 g, 6.33 mmol, 89%) was obtained as a yellow oil:
1H NMR (500 MHz, CDCl3) δ 1.15 (s, 9H), 6.10 (d, J = 16.0 Hz, 1H),
6.49 (d, J = 16.0 Hz, 1H), 6.89 (td, J = 7.5, 1.5 Hz, 1H), 7.28 (td, J = 7.0,
0.5 Hz, 1H), 7.44 (dd, J = 8.0, 1.5 Hz, 1H), 7.81 (dd, J = 7.8, 1.5 Hz, 1H);
13C NMR (125 MHz, CDCl3) δ 29.5, 33.7, 99.9, 126.3, 128.2, 128.2,
129.0, 139.3, 141.1, 144.9; IR (neat) 3058, 2958, 2903, 2865, 1461,
1433, 1362, 1011, 966 cm−1; HRMS (EI) calcd for C12H15I [M+]
286.0218, found 286.0223.
1-[(E)-3,3-Dimethylbut-1-enyl]-2-[2-(trimethylsilyl)ethynyl]-
benzene ((E)-1h). The Sonogashira coupling of S11 (1.67 g, 5.84 mmol)
with TMSA (0.99 mL, 7.01 mmol) by the method of the synthesis of
(E)-1a gave (E)-1h (1.30 g, 5.07 mmol, 87%) as a yellow oil: 1H NMR
(500 MHz, CDCl3) δ 0.27 (s, 9H), 1.14 (s, 9H), 6.32 (d, J = 16.5 Hz,
1H), 6.85 (d, J = 16.5 Hz, 1H), 7.12 (td, J = 7.5, 1.5 Hz, 1H), 7.25 (td, J =
7.3, 1.0 Hz, 1H), 7.42 (dd, J = 7.8, 1.0 Hz, 1H), 7.51 (d, J = 7.5 Hz, 1H);
13C NMR (125 MHz, CDCl3) δ 0.05, 29.5, 33.7, 98.8, 103.8, 121.3,
solution of 2-iodobenzaldehyde (4.22 g, 18.2 mmol) in THF (50 mL)
was added to the mixture at −78 °C. The mixture was warmed to room
temperature overnight and quenched with water. The aqueous mixture
was extracted with hexane/AcOEt (1/1). The organic layer was dried
over Na2SO4 and evaporated. The residue was checked with 1H NMR.
The formation of 1-[(Z)-2-(bromophenyl)ethenyl]-2-iodobenzene
was confirmed. Therefore, this compound was used in the next step
without further purification. The Sonogashira coupling of 1-[(Z)-2-
(bromophenyl)ethenyl]-2-iodobenzene with TMSA (2.57 mL, 18.2
mmol) by the method for the synthesis of (E)-1a gave (Z)-1i (5.12 g,
14.4 mmol, 79% yield over two steps) as a yellow oil: 1H NMR
(400 MHz, CDCl3) δ 0.28 (s, 9H), 6.74 (d, J = 12.0 Hz, 1H), 6.97−7.02
(m, 3H), 7.03−7.07 (m, 2H), 7.07−7.14 (m, 2H), 7.46 (d, J = 7.6 Hz,
1H), 7.57−7.61 (m, 1H); 13C NMR (100 MHz, CDCl3) δ 0.04, 99.4,
103.5, 122.9, 124.0, 126.9, 127.0, 127.9, 128.7, 128.9, 130.0, 130.4, 131.0,
132.6, 132.6, 137.6, 138.8; IR (neat) 3061, 3022, 2959, 2898, 2155,
1463, 1434, 1250, 1025, 868, 758 cm−1; HRMS (EI) calcd for
C19H19BrSi [M+] 354.0439, found 354.0444.
123.0, 124.4, 126.3, 128.6, 132.5, 140.0, 143.5; IR (neat) 3087, 3060,
3025, 2959, 2902, 2866, 2154, 1644, 1472, 1250, 971, 872, 843 cm−1;
HRMS (EI) calcd for C17H24Si [M+] 256.1647, found 256.1652.
Synthesis of 1-[(Z)-2-(Trimethylsilyl)ethenyl]-2-[2-
(trimethylsilyl)ethynyl]benzene ((Z)-1a). DIBAL-H (1.0 M in
hexane, 15.5 mL, 15.5 mmol) was added to a solution of 1-iodo-2-
(trimethylsilylethynyl)benzene (2.10 g, 7.00 mmol) in Et2O (21 mL) at
room temperature. The reaction was monitored with TLC and GC-MS.
After 305 h of stirring, the reaction mixture was quenched with 40%
aqueous Rochelle salt and extracted with hexane. The organic layer was
dried over Na2SO4 and evaporated. The residue was checked with
1H NMR. The formation of 1-iodo-2-[(Z)-2-(trimethylsilyl)ethenyl]-
benzene was confirmed. Therefore, this compound was used in the next
step without further purification. The Sonogashira coupling of 1-iodo-2-
((Z)-trimethylsilylethenyl)benzene with TMSA (0.99 mL, 7.00 mmol)
by the method for the synthesis of (E)-1a gave 1-[(Z)-2-(trimethylsilyl)-
ethenyl]-2-[2-(trimethylsilyl)ethynyl]benzene ((Z)-1a) (0.54 g, 1.98 mmol,
28% yield over 2 steps) as a yellow oil: 1H NMR (500 MHz, CDCl3) δ
0.02 (s, 9H), 0.25 (s, 9H), 5.91 (d, J = 15.0, 1H), 7.20 (td, J = 7.5, 1.5 Hz,
1H), 7.25 (td, J = 7.3, 1.5 Hz, 1H), 7.30 (dd, J = 8.0, 1.5 Hz, 1H), 7.44
(dd, J = 7.5, 1.0 Hz, 1H), 7.53 (d, J = 15.0 Hz, 1H); 13C NMR (125 MHz,
CDCl3) δ 0.04, 0.11, 99.1, 103.7, 122.3, 127.2, 127.8, 128.1, 132.2,
133.7, 142.6, 145.2; IR (neat) 3061, 2958, 2898, 2157, 1592, 1472, 1249,
869, 841 cm−1; HRMS (EI) calcd for C16H24Si2 [M+] 272.1417, found
272.1421.
Synthesis of 1-(Oct-1-enyl)-2-[(Z)-2-(trimethylsilyl)ethynyl]-
benzene ((Z)-1g). 1-Bromo-2-(oct-1-ynyl)benzene (S12) [CAS:
121221-93-0].16 The Sonogashira coupling of 1-bromo-2-iodobenzene
(5.11 g, 18.1 mmol) with 1-octyne (2.94 mL, 19.9 mmol) by the reported
method16 gave 1-bromo-2-(oct-1-ynyl)benzene (S12; 4.33 g, 16.3 mmol,
90%) as a colorless oil: 1H NMR (500 MHz, CDCl3) δ 0.91 (t, J = 7.0 Hz,
3H), 1.30−1.37 (m, 4H), 1.47−1.53 (m, 2H), 1.60−1.67 (m, 2H), 2.46
(t, J = 7.0 Hz, 2H), 7.11 (td, J = 8.0, 1.5 Hz, 1H), 7.22 (td, J = 7.5, 1.0 Hz,
1H), 7.42 (dd, J = 7.8, 1.5 Hz, 1H), 7.55 (dd, J = 8.0, 1.0 Hz, 1H); 13C
NMR (125 MHz, CDCl3) δ 14.1, 19.6, 22.6, 28.5, 28.5, 31.3, 79.4, 95.6,
125.4, 126.1, 126.8, 128.6, 132.2, 133.3.
1-Bromo-2-[(Z)-oct-1-enyl]benzene (S13). DIBAL-H (1.0 M in
hexane, 17.6 mL, 17.6 mol) was added to S12 (4.25 g, 16.0 mmol) at
room temperature. The mixture was stirred at 50 °C for 22 h. The
resultant mixture was treated with 40% aqueous Rochelle salt at 0 °C
and extracted with hexane. The organic layer was dried over Na2SO4
and evaporated. Purification of the residue by silica gel column
chromatography (hexane) gave 1-bromo-2-[(Z)-oct-1-enyl]benzene
(S13; 1.97 g, 7.37 mmol, 46%) as a colorless oil: 1H NMR (500 MHz,
CDCl3) δ 0.86 (t, J = 6.5 Hz, 3H), 1.18−1.32 (m, 6H), 1.41 (quint, J =
7.5 Hz, 2H), 2.17 (qd, J = 7.5, 1.5 Hz, 2H), 5.77 (td, J = 11.5, 7.5 Hz,
1H), 6.44 (d, J = 11.5 Hz, 1H), 7.07−7.12 (m, 1H), 7.24−7.29 (m, 2H),
7.57 (d, 7.5 Hz, 1H); 13C NMR (125 MHz, CDCl3) δ 14.0, 22.6, 28.3,
28.9, 29.6, 31.6, 124.0, 126.7, 128.1, 128.3, 130.6, 132.5, 134.1, 137.7;
IR (neat) 3065, 3015, 2955, 2925, 2855, 1467, 1432, 1026, 762 cm−1;
HRMS (EI) calcd for C14H19Br [M+] 266.0670, found 266.0665.
1-Iodo-2-[(Z)-oct-1-enyl]benzene (S14). This compound was
prepared from S13 (1.57 g, 5.88 mmol) by using the same method to
synthesize S4 from S3. 1-Iodo-2-[(Z)-oct-1-enyl]benzene (S14; 1.51 g,
4.81 mmol, 82%) was obtained as a colorless oil: 1H NMR (400 MHz,
CDCl3) δ 0.86 (t, J = 6.8 Hz, 3H), 1.17−1.33 (m, 6H), 1.37−1.45 (m,
2H), 2.17 (qd, J = 7.2 1.6 Hz, 2H), 5.77 (dt, J = 11.2, 7.6 Hz, 1H), 6.44
(d, J = 11.2 Hz, 1H), 7.08−7.12 (m, 1H), 7.24−7.29 (m, 2H), 7.57 (d,
J = 7.6 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 14.1, 22.6, 28.3, 28.9,
29.6, 31.7, 124.0, 126.7, 128.1, 128.3, 130.6, 132.5, 134.1, 137.7; IR
(neat) 3065, 3014, 2955, 2925, 2854, 1467, 1432, 1026, 762 cm−1;
HRMS (EI) calcd for C14H19I [M+] 314.0531, found 314.0533.
1-[(Z)-Oct-1-enyl]-2-[2-(trimethylsilyl)ethynyl]benzene ((Z)-1g).
The Sonogashira coupling of S14 (1.10 g, 3.50 mmol) with TMSA
(0.59 mL, 4.20 mmol) by the method for the synthesis of (E)-1a gave
(Z)-1g (912 mg, 3.21 mmol, 91%) as a yellow oil: 1H NMR (500 MHz,
CDCl3) δ 0.25 (s, 9H), 0.87 (t, J = 6.5 Hz, 3H), 1.20−1.34 (m, 6H), 1.44
(quint, J = 7.5 Hz, 2H), 2.25 (qd, J = 7.3, 1.5 Hz, 2H), 5.75 (td, J = 11.5,
7.0 Hz, 1H), 6.65 (d, J = 11.5 Hz, 1H), 7.16 (td, J = 7.5 Hz, 1H), 7.27 (td,
J = 7.3, 1.0 Hz, 1H), 7.31 (d, J = 7.5 Hz, 1H), 7.47 (dd, J = 7.5, 1.0 Hz,
1H); 13C NMR (125 MHz, CDCl3) δ 0.03, 14.1, 22.6, 28.7, 28.9, 29.8,
31.7, 98.7, 104.0, 122.5, 126.2, 127.2, 127.9, 128.6, 132.5, 134.0, 140.0;
IR (neat) 3060, 3013, 2957, 2925, 2855, 2156, 1474, 1445, 1250, 868,
842, 759 cm−1; HRMS (EI) calcd for C19H28Si [M+] 284.1960, found
284.1968.
Synthesis of 1-[(Z)-2-Phenylethenyl]-2-[2-(trimethylsilyl)-
ethynyl]benzene ((Z)-1c). n-BuLi (2.6 M in hexane, 0.412 mL, 1.07
mmol) was added to a solution of 1-bromo-2-[(Z)-2-phenylethenyl]-
benzene (0.25 g, 0.97 mmol) in THF (5 mL) at −78 °C. After 30 min
of stirring at −78 °C, I2 (0.27 g, 1.07 mmol) was added to the mixture.
The resultant mixture was warmed to room temperature over 2 h and
quenched with water. The aqueous mixture was treated with saturated
aqueous Na2S2O3 and extracted with hexane. The organic layer was
1
dried over Na2SO4 and evaporated. The residue was checked with H
NMR. The formation of 1-iodo-2-[(Z)-(phenyl)ethenyl]benzene was
confirmed. Therefore, this compound was used in the next step without
further purification. The Sonogashira coupling of 1-iodo-2-[(Z)-
(phenyl)ethenyl]benzene with TMSA (0.141 mL, 1.00 mmol) by the
method for the synthesis of (E)-1a gave 1-[(Z)-2-phenylethenyl]-2-[2-
(trimethylsilyl)ethynyl]benzene (0.17 g, 0.61 mmol, 63% yield over two
steps) as a colorless oil: 1H NMR (400 MHz, CDCl3) δ 0.25 (s, 9H),
6.67 (d, J = 12.4 Hz, 1H), 6.82 (d, J = 12.4 Hz, 1H), 7.07 (td, J = 7.4, 0.8
Hz, 1H), 7.14 (td, J = 7.6, 1.2 Hz, 1H), 7.16−7.23 (m, 6H), 7.48 (dd, J =
7.6, 0.8 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 0.01, 99.1, 103.7,
122.7, 126.9, 127.1, 128.0, 128.1, 128.7, 128.9, 129.0, 131.1, 132.6, 137.0,
129.8; IR (neat) 3081, 3059, 3023, 2959, 2898, 2155, 1474, 1445, 1250,
869, 843, 759 cm−1; HRMS (EI) calcd for C19H20Si [M+] 276.1334,
found 276.1345.
Synthesis of 1-[(Z)-2-(2-Bromophenyl)ethenyl]-2-[2-
(trimethylsilyl)ethynyl]benzene ((Z)-1i). Sodium bis-
(trimethylsilyl)amide (1.9 M in THF, 9.58 mL, 18.2 mmol) was
added to a solution of (2-bromobenzyl)triphenylphosphonium bromide
(11.2 g, 21.8 mmol) in THF (90 mL) at 0 °C. After 30 min of stirring, a
Synthesis of 1-Ethenyl-2-[2-(trimethylsilyl)ethynyl]benzene
(1j). The Sonogashira coupling of 2-bromostyrene (1.84 g, 10.0 mmol)
8177
dx.doi.org/10.1021/jo501383v | J. Org. Chem. 2014, 79, 8171−8181

The Journal of Organic Chemistry
Article
with TMSA (2.8 mL, 20.0 mmol) by the method for the synthesis of
(E)-1a gave 1j (0.82 g, 4.09 mmol, 41%) as a yellow oil: 1H NMR (300
MHz, CDCl3) δ 0.27 (s, 9H), 5.36 (dd, J = 11.1, 1.2 Hz, 1H), 5.83 (dd,
J = 17.7, 1.2 Hz, 1H), 7.19 (td, J = 7.5, 1.5 Hz, 1H), 7.21 (dd, J = 17.7,
11.1 Hz, 1H), 7.29 (td, J = 7.8, 1.5 Hz, 1H), 7.46 (dd, J = 7.7, 1.5 Hz,
1H), 7.57 (dt, J = 7.8, 0.8 Hz, 1H); 13C NMR (75 MHz, CDCl3) δ
−0.01, 99.1, 103.3, 115.5, 121.8, 124.5, 127.3, 128.6, 132.8, 134.8, 139.3;
IR (neat) 3087, 3062, 3016, 2959, 2898, 2155, 1474, 1250, 868, 843
cm−1; HRMS (EI) calcd for C13H16Si [M+] 200.1021, found 200.1012.
Synthesis of 1-(2-Methylprop-1-enyl)-2-[2-(trimethylsilyl)-
ethynyl]benzene (1k). n-BuLi (2.6 M in hexane, 1.73 mL, 4.5 mmol)
was added to a solution of isopropyltriphenylphosphonium iodide
(1.95 g, 4.50 mmol) in THF (10 mL) at 0 °C. After 30 min of stirring,
a solution of 2-(trimethylsilylethynyl)benzaldehyde (0.91 g, 4.50 mmol)
in THF (5 mL) was added to the mixture at 0 °C. The resultant mixture
was stirred at room temperature overnight, quenched with water, and
extracted with hexane. The organic layer was dried over Na2SO4 and
evaporated. Purification of the residue by silica gel column chromatog-
raphy (hexane) gave 1-(2-methylprop-1-enyl)-2-[2-(trimethylsilyl)-
ethynyl]benzene (1k; 776 mg, 3.40 mmol, 76%) as a colorless oil:
1H NMR (500 MHz, CDCl3) δ 0.25 (s, 9H), 1.81 (d, J = 1.0 Hz, 3H),
1.93 (d, J = 1.0 Hz, 3H), 6.48 (t, J = 1.0 Hz, 1H), 7.10−7.14 (m, 1H),
7.21−7.30 (m, 2H), 7.45 (d, J = 7.5 Hz, 1H); 13C NMR (100 MHz,
CDCl3) δ 0.03, 19.6, 26.6, 98.3, 104.4, 122.4, 123.9, 125.7, 128.0, 128.9,
132.2, 136.5, 141.1; IR (neat) 3087, 3060, 3021, 2961, 2931, 2909, 2155,
1474, 1444, 1249, 874, 843, 758 cm−1; HRMS (EI) calcd for C15H20Si
[M+] 228.1334, found 228.1328.
Synthesis of 1-(1-Methylethenyl)-2-[2-(trimethylsilyl)-
ethynyl]benzene (1l). 1-Bromo-2-(1-methylethenyl)benzene
(S15). n-BuLi (2.6 M in hexane, 3.85 mL, 10 mmol) was added to a
solution of methyltriphenylphosphonium bromide (3.58 g, 10.0 mmol)
in Et2O (50 mL) at 0 °C. After 1 h, 2-bromoacetophenone (1.99 g,
10.0 mmol) was added to the mixture at 0 °C. The resultant mixture
was stirred at room temperature overnight, quenched with water,
and extracted with hexane. The organic layer was dried over Na2SO4
and evaporated. Purification of the residue by silica gel column
chromatography (hexane) gave 1-bromo-2-(1-methylethenyl)benzene
(S15; 0.84 g, 4.42 mmol, 44%) as a colorless oil: 1H NMR (300 MHz,
CDCl3) δ 2.10 (dd, J = 1.5, 0.9 Hz, 3H), 4.93−4.95 (m, 1H), 5.21−5.24
(m, 1H), 7.11 (td, J = 7.5, 2.1 Hz, 1H), 7.19 (dd, J = 7.7, 2.1 Hz, 1H),
7.27 (td, J = 7.5, 1.2 Hz, 1H), 7.55 (dd, J = 8.0, 1.2 Hz, 1H); 13C NMR
(75 MHz, CDCl3) δ 23.5, 116.0, 121.5, 127.2, 128.3, 130.0, 132.7, 144.8,
145.8; IR (neat) 3082, 3053, 2971, 2914, 1641, 1469, 1433, 1025,
903, 759 cm−1; HRMS (EI) calcd for C9H9Br [M+] 195.9888, found
195.9884.
7.2 mL, 19.0 mmol) was added to a solution of 1,2-dibromobenzene
(2.37 mL, 20.0 mmol) in THF (60 mL)/Et2O (60 mL) at −110 °C over
45 min. After 1 h of stirring at this temperature, cyclohexanone (2.0 mL,
19.0 mmol) was added to the mixture at −110 °C. The mixture was
stirred at −110 °C for another 1 h and then at room temperature for 12 h.
The reaction mixture was quenched with saturated aqueous NH4Cl and
extracted with Et2O. The organic layer was dried over Na2SO4 and
evaporated. Purification of the residue by silica gel column chromatog-
raphy (hexane/AcOEt 5/1) gave 1-(2-bromophenyl)cyclohexanol (S17;
3.58 g, 14.0 mmol, 70%) as a white solid: mp 45.0−46.0 °C; 1H NMR
(400 MHz, CDCl3) δ 1.26−1.34 (m, 1H), 1.64−1.88 (m, 5H), 1.97−
2.02 (m, 2H), 2.14−2.22 (m, 2H), 2.66 (s, 1H), 7.06−7.11 (m, 1H),
7.27−7.32 (m, 1H), 7.58 (dd, J = 7.8, 1.6 Hz, 1H), 7.64 (dd, J = 8.0,
2.0 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 21.9, 25.3, 35.7, 74.2, 120.8,
127.49, 127.52, 128.4, 135.3, 146.1; IR (neat) 3568, 3433, 3059, 2928,
1701, 1561, 1425, 969, 754 cm−1; HRMS (EI+) calcd for C12H15BrO
[M+] 254.0306, found 254.0308.
1-Bromo-2-(cyclohexenyl)benzene (S18). This compound was
synthesized by the reported method.18 p-TsOH·H2O (126 mg, 1.40 mmol,
10 mol %) was added to a solution of S17 (3.58 g 14.0 mmol) in toluene
under air. The mixture was heated under reflux for 1 h, cooled to room
temperature, and evaporated. Purification of the residue by silica gel
column chromatography (hexane) gave 1-bromo-2-(cyclohexenyl)-
benzene (S18; 2.95 g, 12.5 mmol, 89%) as a colorless liquid: 1H NMR
(400 MHz, CDCl3) δ 1.66−1.73 (m, 2H), 1.74−1.81 (m, 2H), 2.15−
2.21 (m, 2H), 2.25−2.31 (m, 2H), 5.61−5.64 (m, 1H), 7.08 (td, J = 7.4,
2.0 Hz, 1H), 7.15 (dd, J = 7.6, 1.6 Hz, 1H), 7.24 (td, J = 7.6, 1.2 Hz, 1H),
7.53 (dd, J = 8.0, 1.2 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 22.0, 22.8,
25.3, 29.3, 122.6, 127.0, 127.1, 127.9, 130.1, 132.6, 139.2, 145.5; IR (neat)
3050, 2929, 2856, 2834, 1587, 1559, 1466, 1433, 1022, 749 cm−1; HRMS
(EI+) calcd for C12H13Br [M+] 236.0201, found 236.0198.
1-Cyclohexenyl-2-iodobenzene (S19). This compound was prepared
from S18 (2.95 g, 12.5 mmol) by using the same method to synthesize S4
from S3. 1-Cyclohexenyl-2-iodobenzene (; 3.20 g, 11.3 mmol, 90%) was
obtained as a colorless liquid: 1H NMR (400 MHz, CDCl3) δ 1.66−1.72
(m, 2H), 1.76−1.81 (m, 2H), 2.15−2.25 (m, 4H), 5.55−5.58 (m, 1H),
6.91 (td, J = 7.8, 2.0 Hz, 1H), 7.13 (dd, J = 7.6, 1.6 Hz, 1H), 7.28 (td, J =
7.6, 1.2 Hz, 1H), 7.82 (dd, J = 8.0, 1.2 Hz, 1H); 13C NMR (100 MHz,
CDCl3) δ 21.9, 22.9, 25.2, 29.7, 98.7, 127.2, 127.9, 128.0, 128.8, 139.0,
142.0, 149.3; IR (neat) 3046, 2996, 2928, 2855, 2832, 1580, 1554, 1461,
1428, 1014, 751 cm−1; HRMS (EI+) calcd for C12H13I [M+] 284.0062,
found 284.0050.
1-Cyclohexenyl-2-[2-(trimethylsilyl)ethynyl]benzene (1m). The
Sonogashira coupling of S19 (2.84 g, 10.0 mmol) with TMSA
(1.70 mL, 12.0 mmol) by the method for the synthesis of (E)-1a gave
1m (1.57 g, 6.17 mmol, 62%) as a colorless liquid: 1H NMR (400 MHz,
CDCl3) δ 0.24 (s, 9H), 1.64−1.73 (m, 2H), 1.73−1.81 (m, 2H), 2.18−
2.22 (m, 2H), 2.39−2.44 (m, 2H), 5.80−5.83 (m, 1H), 7.12−7.17 (m,
2H), 7.25 (td, J = 7.6, 1.2 Hz, 1H), 7.45 (dd, J = 8.0 Hz, 1.6 Hz, 1H); 13C
NMR (100 MHz, CDCl3) δ −0.02, 22.1, 23.1, 25.5, 28.9, 96.9, 104.9,
120.9, 126.1, 127.1, 127.9, 128.4, 132.9, 138.0, 147.6; IR (neat) 3059,
3022, 2930, 2857, 2834, 2156, 1474, 1439, 1249, 867, 843, 757 cm−1;
HRMS (EI+) calcd for C17H22Si [M+] 254.1491, found 254.1501.
Synthesis of 1-[(E)-2-(Trimethylsilyl)ethenyl]-2-[3-
(trimethylsilyl)prop-2-ynyl]benzene (1n). 1-Bromo-2-[(E)-
(trimethylsilyl)ethenyl]benzene was prepared from 1-bromo-2-
(trimethylsilylethynyl)benzene (7.48 g, 29.5 mmol) by the same
method for the synthesis of S2 from S1. The residue obtained after
the reaction was checked with 1H NMR. The formation of 1-bromo-2-
[(E)-(trimethylsilyl)ethenyl]benzene was confirmed. Therefore, this
compound was used in the next step without further purification.
A solution of 1-bromo-2-[(E)-(trimethylsilyl)ethenyl]benzene in THF
(30 mL) was added to Mg turnings (729 mg, 30.0 mmol) over 1 h. After
2 h of stirring, the reaction mixture was transferred into a solution
of 3-bromo-1-(trimethylsilyl)prop-1-yne (4.28 g, 22.4 mmol) in THF
(20 mL) via cannula. The mixture was heated under reflux for 12 h.
The reaction mixture was cooled to room temperature, quenched
with aqueous NH4Cl, and extracted with hexane. The organic layer was
dried over Na2SO4 and evaporated. Purification of the residue by silica
gel column chromatography (hexane) gave 1n (3.89 g, 13.6 mmol, 46%
1-Iodo-2-(1-methylethenyl)benzene (S16). This compound was
prepared from S15 (665 mg, 3.37 mmol) by using the same method
to synthesize S4 from S3. 1-Iodo-2-(1-methylethenyl)benzene (S16;
1
693 mg, 2.84 mmol, 84%) was obtained as a colorless oil: H NMR
(400 MHz, CDCl3) δ 2.07 (s, 3H), 4.89 (d, J = 0.4 Hz, 1H), 5.22 (t, J =
1.6 Hz, 1H), 6.94 (td, J = 7.6, 1.6 Hz, 1H), 7.17 (dd, J = 7.6, 1.6 Hz, 1H),
7.30 (td, J = 7.4, 1.2 Hz, 1H), 7.83 (dd, J = 8.0, 1.2 Hz, 1H); 13C NMR
(100 MHz, CDCl3) δ 23.9, 96.9, 116.0, 128.0, 128.4, 128.5, 139.2, 148.4,
148.8; IR (neat) 3080, 3049, 2967, 2912, 2851, 1641, 1467, 1428, 1011,
903, 759 cm−1; HRMS (EI) calcd for C9H9I [M+] 243.9749, found
243.9745.
1-(1-Methylethenyl)-2-[2-(trimethylsilyl)ethynyl]benzene (1l). The
Sonogashira coupling of S16 (578 mg, 2.37 mmol) with TMSA
(0.40 mL, 2.84 mmol) by the method for the synthesis of (E)-1a gave 1l
1
(419 mg, 1.95 mmol, 82%) as a colorless oil: H NMR (500 MHz,
CDCl3) δ 0.23 (s, 9H), 2.18 (dd, J = 1.5, 1.0 Hz, 3H), 5.13 (dd, J = 1.5,
1.0 Hz, 1H), 5.20−5.21 (m, 1H), 7.18 (td, J = 7.5, 1.5 Hz, 1H), 7.21 (dd,
J = 7.0, 1.5 Hz, 1H), 7.26 (td, J = 7.5, 1.5 Hz, 1H), 7.47 (dt, J = 7.8, 0.5
Hz, 1H); 13C NMR (125 MHz, CDCl3) δ −0.2, 23.1, 97.8, 104.7, 115.7,
120.6, 126.6, 127.8, 128.4, 133.1, 144.8, 146.5; IR (neat) 3084, 3060,
3022, 2960, 2917, 2899, 2157, 1636, 1479, 1438, 1250, 867, 843 cm−1;
HRMS (EI) calcd for C14H18Si [M+] 214.1178, found 214.1177.
Synthesis of 1-Cyclohexenyl-2-[2-(trimethylsilyl)ethynyl]-
benzene (1m). 1-(2-Bromophenyl)cyclohexanol (S17). This com-
pound was synthesized by the reported method.17 n-BuLi (2.6 M in hexane,
8178
dx.doi.org/10.1021/jo501383v | J. Org. Chem. 2014, 79, 8171−8181

The Journal of Organic Chemistry
Article
yield over two steps) as a colorless liquid: 1H NMR (500 MHz, CDCl3)
δ 0.17 (s, 18H), 3.68 (s, 2H), 6.40 (d, J = 18.5 Hz, 1H), 7.17 (d, J = 18.5
Hz, 1H), 7.22−7.26 (m, 2H), 7.39−7.42 (m, 1H), 7.51−7.53 (m, 1H);
13C NMR (125 MHz, CDCl3) δ −1.2, 0.1, 24.4, 87.1, 104.0, 125.7, 127.1,
128.0, 128.8, 132.5, 133.3, 137.4, 140.6; IR (neat) 3066, 3019, 2956,
2898, 2176, 1604, 1475, 1249, 1018, 986, 843 cm−1; HRMS (EI) calcd
for C17H26Si2 [M+] 286.1573, found 286.1574.
(s, 9H), 2.32 (dd, J = 14.0, 10.5 Hz, 1H), 3.54 (dd, J = 14.0, 4.5 Hz, 1H),
3.83 (ddd, J = 10.8, 4.5, 1.8 Hz, 1H), 6.59 (d, J = 7.5 Hz, 1H), 6.94−7.02
(m, 3H), 7.07 (dd, J = 1.8, 0.6 Hz, 1H), 7.10−7.14 (m, 2H), 7.20 (td, J =
7.5, 0.6 Hz, 1H), 7.32 (dt, J = 7.5, 0.9 Hz, 1H); 13C NMR (75 MHz,
2
CDCl3) δ −0.4, 36.9, 55.2, 114.0 (d, JC−F = 21.1 Hz), 120.9, 123.9,
124.5, 126.6, 130.6 (d, 3JC−F = 7.5 Hz), 136.0 (d, 4JC−F = 3.0 Hz), 140.9,
144.7, 149.6, 153.0, 161.5 (d, 1JC−F = 243.8 Hz); IR (neat) 3065, 3038,
2929, 2853, 1601, 1510, 1456, 1249, 1225, 1052, 838 cm−1; HRMS
(EI+) calcd for C19H21FSi [M+] 296.1397, found 296.1411.
Synthesis of (E)-1-Cinnamyl-2-[2-(trimethylsilyl)ethynyl]-
benzene (1o). A solution of 1-bromo-2-(trimethylsilylethenyl)-
benzene (2.04 g, 8.00 mmol) in THF (8 mL) was slowly added to
Mg turnings (219 mg, 9.00 mmol) in THF (1 mL) at room temperature
over 1 h. The resultant mixture was heated under reflux for 2 h and
cooled to room temperature. The reaction mixture was transferred into a
solution of (E)-(3-bromoprop-1-enyl)benzene (0.90 mL, 6.10 mmol) in
THF (8 mL) via syringe. The mixture was heated under reflux for 12 h.
The reaction mixture was cooled to room temperature, quenched
with aqueous NH4Cl, and extracted with hexane/AcOEt (30/1). The
organic layer was dried over Na2SO4 and evaporated. Purification of the
residue by silica gel column chromatography (hexane/AcOEt 30/1)
gave (E)-1-cinnamyl-2-[2-(trimethylsilyl)ethynyl]benzene (1o; 719 mg,
2.48 mmol, 41%) as a yellow oil: 1H NMR (500 MHz, CDCl3) δ 0.27
(s, 9H), 3.72 (dd, J = 7.0, 1.0 Hz, 1H), 6.37 (dt, J = 15.5, 7.0 Hz, 1H), 6.49
(d, J = 15.5 Hz, 1H), 7.15−7.21 (m, 2H), 7.25−7.30 (m, 4H), 7.35−7.36
(m, 2H), 7.47 (d, J = 7.5 Hz, 1H); 13C NMR (125 MHz, CDCl3) δ 0.03,
37.9, 98.5, 103.8, 122.6, 126.0, 126.1, 127.0, 128.3, 128.4, 128.8, 131.2,
132.5, 137.5, 142.5; IR (neat) 3082, 3060, 3027, 2959, 2898, 2155, 1480,
1447, 1250, 844 cm−1; HRMS (EI) calcd for C20H22Si [M+] 290.1491,
found 290.1505.
1-(4-Methylbenzyl)-2-trimethylsilyl-1H-indene (2e). White solid
(136 mg, 0.466 mmol, 93%): mp 40.0−43.0 °C; 1H NMR (500 MHz,
CDCl3) δ 0.29 (s, 9H), 2.24 (dd, J = 13.5, 11.0 Hz, 1H), 2.36 (s, 3H),
3.54 (dd, J = 13.8, 4.5 Hz, 1H), 3.86 (ddd, J = 11.3, 4.5, 1.5 Hz, 1H), 6.60
(d, J = 7.5 Hz, 1H), 6.94 (td, J = 7.5, 1.5 Hz, 1H), 7.07 (d, J = 1.5 Hz,
1H), 7.08−7.13 (m, 4H), 7.18 (d, J = 7.5 Hz, 1H), 7.32 (d, J = 7.5 Hz,
1H); 13C NMR (125 MHz, CDCl3) δ −0.6, 21.1, 37.3, 55.4, 120.7,
124.1, 124.4, 126.5, 128.9, 129.1, 135.6, 137.4, 140.6, 144.7, 150.0,
153.4; IR (Nujol) 3021, 1249, 1053, 837 cm−1; HRMS (EI) calcd for
C20H24Si [M+] 292.1647, found 292.1654.
1-(4-Methoxybenzyl)-2-trimethylsilyl-1H-indene (2f). White solid
(120 mg, 0.389 mmol, 78%): mp 59.5−61.5 °C; 1H NMR (500 MHz,
CDCl3) δ 0.29 (s, 9H), 2.24 (dd, J = 14.0, 11.0 Hz, 1H), 3.52 (dd, J =
14.0, 4.5 Hz, 1H), 3.83 (s, 3H), 3.81−3.87 (m, 1H), 6.60 (d, J = 7.5 Hz,
1H) 6.85 (d, J = 8.5 Hz, 2H), 6.95 (td, J = 7.5, 1.0 Hz, 1H), 7.06 (d, J =
1.0 Hz, 1H), 7.11 (d, J = 8.5 Hz, 2H), 7.19 (t, J = 7.5 Hz, 1H), 7.32 (d, J =
7.5 Hz, 1H); 13C NMR (125 MHz, CDCl3) δ −0.4, 36.9, 55.2, 55.6,
113.6, 120.8, 124.1, 124.4, 126.5, 130.2, 132.6, 140.6, 144.7, 150.0, 153.4,
158.1; IR (Nujol) 3056, 3033, 1512, 1248, 834 cm−1; HRMS (EI+) calcd
for C20H24OSi [M+] 308.1596, found 308.1588.
1-Heptyl-2-trimethylsilyl-1H-indene (2g). Colorless oil (116 mg,
0.405 mmol, 81%): 1H NMR (400 MHz, CDCl3) δ 0.23 (s, 9H), 0.84 (t,
J = 6.8 Hz, 3H), 0.86−0.91 (m, 1H), 0.98−1.09 (m, 1H), 1.17−1.27 (m,
8H), 1.75−1.84 (m, 1H), 2.04−2.14 (m, 1H), 3.65 (t, J = 4.4 Hz, 1H),
7.04 (d, J = 1.6 Hz, 1H), 7.17 (td, J = 7.2, 1.2 Hz, 1H), 7.23 (t, J = 7.2 Hz,
1H), 7.34 (t, J = 7.6 Hz, 1H), 7.41 (t, J = 7.2 Hz, 1H); 13C NMR
(100 MHz, CDCl3) δ −0.6, 14.0, 22.6, 24.4, 29.1, 30.0, 30.9, 31.8, 54.1,
120.7, 122.7, 124.7, 126.3, 140.6, 145.1, 150.6, 153.4; IR (neat) 3064,
3020, 2955, 2927, 2855, 1534, 1459, 1248, 1034, 836 cm−1; HRMS
(EI+) calcd for C19H30Si [M+] 286.2117, found 286.2118.
General Procedure for Indene Synthesis. DIBAL-H (1.0 M in
hexane, 0.75 mL, 0.75 mmol) was added to 1 (0.50 mmol) in a 10 mL
two-necked flask at room temperature. The mixture was stirred at 40 °C
for 3 h and then cooled to room temperature. The reaction mixture
was treated with 40% aqueous Rochelle salt (3 mL) for 30 min and
extracted with hexane. The organic layer was dried over Na2SO4 and
evaporated. The residue was purified with silica gel column chromato-
graphy (hexane).
1-(Trimethylsilyl)methyl-2-trimethylsilyl-1H-indene (2a). The re-
action of 1a (136 mg, 0.500 mmol) with DIBAL-H (1.0 M in hexane,
0.75 mL, 0.75 mmol) by the general procedure gave 2a (133 mg, 0.485
1
mmol, 97%) as a colorless oil: H NMR (300 MHz, CDCl3) δ −0.25
1-Octyl-2-[(E)-2-(trimethylsilyl)ethenyl]benzene (3). Colorless oil
1
(s, 9H), 0.26 (s, 9H), 1.24 (dd, J = 15.0, 6.0 Hz, 1H), 1.47 (dd, J = 15.0,
5.7 Hz, 1H), 3.80 (td, J = 6.0, 1.8 Hz, 1H), 7.03 (d, J = 1.8 Hz, 1H),
7.16 (td, J = 7.5, 1.2 Hz, 1H), 7.24 (td, J = 7.2, 0.6 Hz, 1H), 7.35 (dd, J =
7.2, 1.2 Hz, 1H), 7.42 (d, J = 7.2 Hz, 1H); 13C NMR (75 MHz, CDCl3) δ
−0.24, 0.3, 17.7, 50.8, 120.7, 123.6, 124.5, 126.3, 140.1, 144.6, 151.8,
155.4; IR (neat) 3065, 2953, 2898, 1531, 1459, 1410, 1248, 836 cm−1;
HRMS (EI) calcd for C16H26Si2 [M+] 274.1573, found 274.1576.
5-Fluoro-1-(trimethylsilyl)methyl-2-trimethylsilyl-1H-indene (2b).
Yellow oil (138 mg, 0.472 mmol, 94%): 1H NMR (500 MHz, CDCl3) δ
−0.26 (s, 9H), 0.25 (s, 9H), 1.23 (dd, J = 15.0, 6.0 Hz, 1H), 1.43 (dd, J =
15.0, 6.0 Hz, 1H), 3.76 (tt, J = 6.0, 1.0 Hz, 1H), 6.85 (ddd, J = 9.0, 8.3,
2.5 Hz, 1H), 6.96 (d, J = 2.0 Hz, 1H), 7.00 (dd, J = 9.0, 2.5 Hz, 1H),
7.30 (dd, J = 8.5, 5.5 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ −0.3, 0.3,
17.8, 50.3, 107.5 (d, 2JC−F = 22.0 Hz), 111.1 (d, 2JC−F = 23.8 Hz), 124.1
(d, 3JC−F = 8.8 Hz), 139.3 (d, 4JC−F = 3.8 Hz), 146.3 (d, 3JC−F = 7.5 Hz),
147.2 (d, 4JC−F = 1.3 Hz), 158.3, 162.3 (d, 1JC−F = 240.0 Hz); IR (neat)
3069, 3033, 2953, 2898, 1610, 1599, 1535, 1465, 1248, 838 cm−1;
HRMS (EI) calcd for C16H25FSi2 [M+] 292.1479, found 292.1479.
1-Benzyl-2-trimethylsilyl-1H-indene (2c). Colorless oil (128 mg,
0.460 mmol, 92%): 1H NMR (400 MHz, CDCl3) δ 0.30 (s, 9H), 2.29
(dd, J = 13.8, 11.2 Hz, 1H), 3.59 (dd, J = 13.8, 4.0 Hz, 1H), 3.89 (ddd, J =
10.8, 4.0, 1.6 Hz, 1H), 6.56 (d, J = 7.6 Hz, 1H), 6.94 (td, J = 7.6, 1.2 Hz,
1H), 7.08 (dd, J = 1.6, 0.4 Hz, 1H), 7.17−7.33 (m, 7H); 13C NMR
(100 MHz, CDCl3) δ −0.4, 37.8, 55.3, 120.8, 124.0, 124.5, 126.3, 126.5,
128.2, 129.3, 140.6, 140.7, 144.7, 149.9, 153.4; IR (neat) 3061, 3026,
2953, 2917, 2852, 1603, 1537, 1496, 1454, 1247, 1057, 1052, 1019, 889,
857, 835, 754, 732, 697 cm−1; HRMS (EI+) calcd for C19H22Si [M+]
278.1491, found 278.1494.
(17 mg, 0.058 mmol, 12%): H NMR (400 MHz, CDCl3) δ 0.16 (s,
9H), 0.87 (t, J = 10.8 Hz, 3H), 1.23−1.40 (m, 10H), 1.53−1.60 (m, 2H),
2.69 (t, J = 8.0 Hz, 1H), 6.37 (d, J = 19.2 Hz, 1H), 7.10−7.20 (m, 4H),
7.50−7.55 (m, 1H); 13C NMR (100 MHz, CDCl3) δ −1.2, 14.1, 22.7,
29.3, 29.5, 29.6, 31.3, 31.9, 33.4, 125.5, 126.1, 127.7, 129.6, 131.1, 137.2,
140.2, 141.3; IR (neat) 3064, 3014, 2955, 2926, 2854, 1477, 1467, 1247,
987, 865, 839 cm−1; HRMS (EI) calcd for C19H32Si [M+] 288.2273,
found 288.2274.
1-(2,2-Dimethylpropyl)-2-trimethylsilyl-1H-indene (2h). Colorless
oil (14 mg, 0.054 mmol, 11%): 1H NMR (500 MHz, CDCl3) δ 0.26 (s,
9H), 1.05 (s, 9H), 1.55 (dd, J = 14.5, 6.0 Hz, 1H), 2.06 (dd, J = 14.8, 2.5
Hz, 1H), 3.60−3.63 (m, 1H), 7.01 (d, J = 2.0 Hz, 1H), 7.15 (td, J = 7.5,
1.5 Hz, 1H), 7.22 (t, J = 7.0 Hz, 1H), 7.32 (d, J = 7.5 Hz, 1H), 7.54 (d, J =
7.5 Hz, 1H); 13C NMR (125 MHz, CDCl3) δ −0.1, 30.8, 31.6, 42.8, 51.6,
120.7, 123.8, 124.8, 126.1, 140.4, 144.4, 152.9, 155.2; IR (neat) 3063,
3023, 2952, 2904, 2867, 1535, 1476, 1463, 1364, 1248, 1029, 835 cm−1;
HRMS (EI) calcd for C17H26Si [M+] 258.1804, found 258.1809.
1-(2-Bromobenzyl)-2-trimethylsilyl-1H-indene (2i). Colorless oil
1
(161 mg, 0.451 mmol, 90%): H NMR (500 MHz, CDCl3) δ 0.32 (s,
9H), 2.25 (dd, J = 13.5, 12.0 Hz, 1H), 3.71 (dd, J = 14.0, 5.0 Hz, 1H),
4.13 (dd, J = 11.5, 4.5 Hz, 1H), 6.33 (d, J = 7.5 Hz, 1H), 6.91 (td, J = 7.5,
1.0 Hz, 1H), 6.97 (dd, J = 8.0, 2.0 Hz, 1H), 7.11 (d, J = 2.0 Hz, 1H),
7.14−7.23 (m, 3H), 7.35 (d, J = 7.5 Hz, 1H), 7.63 (dd, J = 8.0, 1.5 Hz,
1H); 13C NMR (125 MHz, CDCl3) δ −0.4, 38.8, 52.8, 120.9, 124.2,
124.5, 124.8, 126.5, 127.0, 128.2, 132.6, 132.9, 139.7, 140.8, 144.7,
149.1, 153.6; IR (neat) 3062, 3021, 2954, 2895, 1567, 1537, 1468, 1442,
1248, 1047, 1025, 855 cm−1; HRMS (EI+) calcd for C19H21BrSi [M+]
356.0596, found 356.0599.
1-(4-Fluorobenzyl)-2-trimethylsilyl-1H-indene (2d). Yellow oil
1-Methyl-2-trimethylsilyl-1H-indene (2j). Colorless oil (86 mg,
1
(141 mg, 0.476 mmol, 95%): H NMR (300 MHz, CDCl3) δ 0.29
0.425 mmol, 85%): 1H NMR (300 MHz, CDCl3) δ 0.24 (s, 9H), 1.36
8179
dx.doi.org/10.1021/jo501383v | J. Org. Chem. 2014, 79, 8171−8181

The Journal of Organic Chemistry
Article
(d, J = 7.5 Hz, 3H), 3.56 (qd, J = 7.5, 1.5 Hz, 1H), 7.03 (d, J = 1.5 Hz,
1H), 7.16−7.27 (m, 2H), 7.33−7.36 (m, 1H), 7.41 (d, J = 6.9 Hz, 1H);
13C NMR (75 MHz, CDCl3) δ −0.7, 16.9, 49.1, 120.7, 122.5, 124.9,
126.4, 139.6, 144.2, 152.3, 155.2; IR (neat) 3065, 3018, 2957, 2928,
2896, 2871, 1534, 1459, 1247, 836 cm−1; HRMS (EI+) calcd for
C13H18Si [M+] 202.1178, found 202.1189.
1,1-Dimethyl-2-trimethylsilyl-1H-indene (2l). Colorless oil (103 mg,
0.476 mmol, 95%): 1H NMR (400 MHz, CDCl3) δ 0.25 (s, 9H), 1.35
(s, 6H), 6.93 (s, 1H), 7.16−7.27 (m, 2H), 7.28−7.31 (m, 2H); 13C NMR
(100 MHz, CDCl3) δ 0.02, 25.5, 54.6, 120.9, 125.3, 126.3, 138.6, 142.5,
157.1, 159.9; IR (neat) 3063, 3018, 2956, 2924, 2898, 2864, 1530, 1467,
1449, 1248, 1000, 837 cm−1; HRMS (EI+) calcd for C14H20Si [M+]
216.1334, found 216.1342.
General Procedure for Benzofulvene Synthesis. DIBAL-H
(1.0 M in hexane, 0.75 mL, 0.75 mmol) was added to 1 (0.50 mmol)
in a 10 mL two-necked flask at room temperature. The mixture was
heated at 40 °C for 3 h and then cooled to room temperature.
Benzaldehyde (0.51 mL, 5 mmol) was added to the resultant mixture.
After 16 h of stirring at room temperature, the reaction mixture was
treated with 40% aqueous Rochelle salt (3 mL) for 30 min and extracted
with hexane. The organic layer was dried over Na2SO4 and evaporated.
The residue was purified with silica gel column chromatography
(hexane).
(E)-1-(Trimethylsilylmethylene)-2-trimethylsilyl-1H-indene ((E)-
7a). The reaction of 1a (136 mg, 0.500 mmol) with DIBAL-H (1.0 M
in hexane, 0.75 mL, 0.75 mmol) and benzaldehyde (0.51 mL, 5.0 mmol)
by the general procedure gave (E)-7a (121 mg, 0.445 mmol, 89% yield)
as a yellow crystal: mp 39.5−40.0 °C; 1H NMR (300 MHz, CDCl3) δ
0.28 (s, 9H), 0.36 (s, 9H), 6.51 (d, J = 0.6 Hz, 1H), 7.08 (s, 1H), 7.13−
7.24 (m, 3H), 7.66 (dd, J = 7.5, 0.9 Hz, 1H); 13C NMR (75 MHz,
CDCl3) δ −0.1, 0.0, 120.6, 123.1, 125.1, 127.9, 137.0, 138.4, 142.4,
145.0, 145.1, 158.7; IR (Nujol) 3063, 3020, 2954, 2898, 1581, 1518,
1453, 1250, 1091, 857 cm−1; HRMS (EI+) calcd for C16H24Si2 [M+]
272.1417, found 272.1428.
2′-Trimethylsilylspiro[cyclohexane-1,1′-indene] (2m). White solid
1
(77 mg, 0.300 mmol, 60%): mp 61.0−62.0 °C; H NMR (400 MHz,
CDCl3) δ 0.28 (s, 9H), 1.24−1.30 (m, 2H), 1.35−1.48 (m, 1H), 1.72−
1.79 (m, 2H), 1.91−2.08 (m, 5H), 6.94 (s, 1H), 7.14 (td, J = 7.4, 1.6 Hz,
1H), 7.25 (td, J = 7.4, 0.8 Hz, 1H), 7.31 (d, J = 7.2 Hz, 1H), 7.79 (d, J =
7.6 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 0.6, 22.7, 25.6, 32.8, 58.8,
121.1, 124.3, 124.8, 126.4, 139.1, 143.9, 155.3, 160.8; IR (Nujol) 3086,
3059, 3034, 1938, 1540, 1448, 1247, 838 cm−1; HRMS (EI) calcd for
C17H24Si [M+] 256.1647, found 256.1645.
(E)-5-Fluoro-1-(trimethylsilylmethylene)-2-trimethylsilyl-1H-in-
1
dene ((E)-7f). Yellow oil (112 mg, 0.386 mmol, 77%): H NMR (400
(1RS,1′SR)-1-[1-Deuterio(trimethylsilyl)methyl]-2-trimethylsilyl-
1H-indene (2a-d; u-2a-d). The reaction of 1a (136 mg, 0.500 mmol)
with DIBAL-H (1.0 M in hexane, 0.75 mL) was performed at 40 °C for
3 h. The reaction mixture was cooled to room temperature and then
treated with MeOD (1 mL) for 3 h. The reaction mixture was quenched
with 40% aqueous Rochelle salt (3 mL), stirred for 30 min, and extracted
with hexane. The organic layer was dried over Na2SO4 and evaporated.
Purification of the residue by silica gel column chromatography (hexane)
MHz, CDCl3) δ 0.28 (s, 9H), 0.35 (s, 9H), 6.49 (s, 1H), 6.84 (td, J = 8.8,
2.4 Hz, 1H), 6.90 (dd, J = 8.8, 2.4 Hz, 1H), 7.01 (s, 1H), 7.57 (dd, J = 8.4,
4.8 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ −0.14, −0.06, 107.7 (d,
2JC−F = 22.0 Hz), 111.4 (d, 2JC−F = 23.0 Hz), 123.9 (d, 3JC−F = 10.0 Hz),
4
4
134.2 (d, JC−F = 1.0 Hz), 137.1, 141.1 (d, JC−F = 2.0 Hz), 147.2 (d,
3JC−F = 8.0 Hz), 147.5, 157.5, 163.1 (d, JC−F = 244.0 Hz); IR (neat)
1
3069, 2955, 2898, 1598, 1520, 1459, 1251, 1133, 1092, 848 cm−1;
HRMS (EI) calcd for C16H23FSi2 [M+] 290.1322, found 290.1311.
(E)-1-Heptylidene-2-trimethylsilyl-1H-indene ((E)-7g). Pale yellow
solid (33.0 mg, 0.116 mmol, 23%): mp 42.0−47.0 °C; 1H NMR
(400 MHz, CDCl3) δ 0.29 (s, 9H), 0.91 (t, J = 7.2 Hz, 3H), 1.31−1.39
(m, 4H), 1.42−1.50 (m, 2H), 1.65 (quint, J = 7.6 Hz, 2H), 2.81 (q, J =
7.6 Hz, 2H), 6.43 (t, J = 7.6 Hz, 1H), 6.99 (s, 1H), 7.18 (td, J = 7.2, 1.6
Hz, 1H), 7.23 (td, J = 7.2, 1.2 Hz, 1H), 7.26−7.31 (m, 1H), 7.73 (d, J =
7.6 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 0.02, 14.0, 22.6, 29.2, 29.6,
30.0, 31.7, 120.7, 124.0, 125.2, 127.2, 137.9, 139.2, 139.6, 143.7, 144.1,
144.7; IR (Nujol) 3065, 1627, 1510, 1247, 839 cm−1; HRMS (EI) calcd
for C19H28Si [M+] 284.1960, found 284.1955.
1
gave 2a-d (123 mg, 0.445 mmol, 89%) as a colorless oil: H NMR
(500 MHz, CDCl3) δ −0.26 (s, 9H), 0.25 (s, 9H), 1.18−1.22 (m, 1H),
3.78 (d, J = 4.5 Hz, 1H), 7.02 (dd, J = 2.0, 0.5 Hz, 1H), 7.15 (td, J = 7.5,
1.0 Hz, 1H), 7.23 (t, J = 7.0 Hz, 1H), 7.33 (d, J = 7.5 Hz, 1H), 7.41 (d, J =
7.5 Hz, 1H); 13C NMR (125 MHz, CDCl3) δ −0.5, −0.3, 17.3 (t, J =
17.5 Hz), 50.7, 120.7, 123.5, 124.5, 126.3, 140.1, 144.6, 151.8, 155.4; IR
(neat) 3065, 3022, 2953, 2895, 2136, 1937, 1532, 1459, 1407, 1249,
1051, 838 cm−1; HRMS (EI) calcd for C16H25DSi [M+] 275.1636, found
275.1621.
(1RS,1′RS)-1-[1-Deuterio(trimethylsilyl)methyl]-2-trimethylsilyl-
1H-indene (2a′-d; l-2a-d). Colorless oil (107 mg, 0.388 mmol,
1
78%): H NMR (400 MHz, CDCl3) δ −0.24 (s, 9H), 0.27 (s, 9H),
1.46 (d, J = 5.6 Hz, 1H), 3.81 (d, J = 5.6 Hz, 1H), 7.04 (d, J = 1.6 Hz,
1H), 7.17 (td, J = 7.6, 1.2 Hz, 1H), 7.25 (t, J = 7.2 Hz, 1H), 7.35 (d, J =
7.2 Hz, 1H), 7.43 (d, J = 7.2 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ
−0.3, 0.3, 17.3 (t, J = 18.0 Hz), 50.7, 120.7, 123.5, 124.5, 126.3, 140.1,
144.6, 151.8, 155.4; IR (neat) 3065, 3021, 2953, 2897, 2868, 2147, 1937,
1531, 1459, 1406, 1248, 1020, 1011, 837 cm−1; HRMS (EI) calcd for
C16H25DSi [M+] 275.1636, found 275.1639.
ASSOCIATED CONTENT
* Supporting Information
■
S
Figures, tables, and a CIF file giving NMR spectral data for all
new substrates and isolated products and crystallographic data
for (E)-7a. This material is available free of charge via the
Internet at http://pubs.acs.org.
1-(1-Deuterioheptyl)-2-trimethylsilyl-1H-indene (2g-d). Colorless
oil (113 mg, 0.393 mmol, 79%): 1H NMR (400 MHz, CDCl3) δ 0.24 (s,
9H), 0.84 (t, J = 7.2 Hz, 3H), 0.85−0.91 (m, 1H), 0.99−1.07 (m, 1H),
1.15−1.28 (m, 8H), 1.74−1.81 (m, 1H), 3.65 (dd, J = 5.8, 1.2 Hz, 1H),
7.05 (dd, J = 1.8, 0.8 Hz, 1H), 7.17 (td, J = 7.2, 1.2 Hz, 1H), 7.24 (td, J =
7.4, 0.8 Hz, 1H), 7.34 (d, J = 7.6 Hz, 1H), 7.41 (d, J = 7.2 Hz, 1H);
13C NMR (100 MHz, CDCl3) δ −0.64, 14.0, 22.6, 24.3, 29.1, 30.0, 30.5
(d, J = 19.0 Hz), 31.8, 54.0, 120.7, 122.8, 124.7, 126.2, 140.6, 145.1,
150.7, 153.4; IR (neat) 3064, 3023, 2955, 2925, 2853, 2150, 1534, 1460,
1247, 1055, 836 cm−1; HRMS (EI) calcd for C19H29DSi [M+] 287.2180,
found 287.2183.
AUTHOR INFORMATION
Corresponding Author
*E-mail for K.M.: kmiura@apc.saitama-u.ac.jp.
Notes
■
The authors declare no competing financial interest.
REFERENCES
■
(1) (a) Majetich, G.; Shimkus, J. M. J. Nat. Prod. 2010, 73, 284.
(b) Solomak, T.; Stacko, P.; Veetil, A. T.; Pospisil, T.; Klan, P. J. Org.
Chem. 2010, 75, 7300. (c) Lee, B. H.; Choi, Y. L.; Shin, S.; Heo, J.-N. J.
Org. Chem. 2011, 76, 6611.
(2) Yang, J.; Lakshmikantham, M. V.; Cava, M. P.; Lorcy, D.; Bethelot,
J. R. J. Org. Chem. 2000, 65, 6739.
1-(1-Deuteriooctyl)-2-[(E)-2-deuterio-2-(trimethylsilyl)ethenyl]-
1
benzene (3g-d). Colorless oil (21 mg, 0.0723 mmol, 14%): H NMR
(400 MHz, CDCl3) δ 0.17 (s, 9H), 0.89 (t, J = 6.8 Hz, 3H), 1.23−1.40
(m, 10H), 1.53−1.59 (m, 2H), 2.67 (t, J = 8.0 Hz, 1H), 7.10−7.14 (m,
1H), 7.15−7.20 (m, 3H), 7.50−7.55 (m, 1H); 13C NMR (100 MHz,
CDCl3) δ −1.2, 14.1, 22.7, 29.3, 29.5, 29.6, 31.2, 31.9, 33.0 (t, J =
19.0 Hz), 125.5, 126.1, 127.7, 129.6, 130.7 (t, J = 20.0 Hz), 137.2, 140.2,
141.3; IR (neat) 3062, 3014, 2955, 2925, 2854, 1475, 1467, 1247, 992,
839 cm−1; HRMS (EI) calcd for C19H30D2Si [M+] 290.2399, found
290.2396.
(3) (a) Moller, A. C.; Heyn, R. H.; Blom, R.; Swang, O.; Gorbitz, C. H.;
̈
̈
Kopf, J. Dalton Trans. 2004, 1578. (b) Chirik, P. J. Organometallics 2010,
29, 1500. (c) Gloeckner, A.; Bauer, H.; Maekawa, M.; Bannenberg, T.;
Daniliuc, C. G.; Jones, P. G.; Sun, Y.; Sitzmann, H.; Tamm, M.; Walter,
M. D. Dalton Trans. 2012, 41, 6614.
8180
dx.doi.org/10.1021/jo501383v | J. Org. Chem. 2014, 79, 8171−8181

The Journal of Organic Chemistry
Article
(4) For recent examples of indene syntheses, see: (a) Wang, S.; Zhu, Y.;
Wang, Y.; Lu, P. Org. Lett. 2009, 11, 2615. (b) Tobisu, M.; Nakai, H.;
Chatani, N. J. Org. Chem. 2009, 74, 5471. (c) Reddy, B. V. S.; Reddy, B.
B.; Rao, K. V. R.; Yadav, J. S. Tetrahedron Lett. 2010, 51, 5697. (d) Xu, T.;
Yang, Q.; Li, D.; Dong, J.; Yu, Z.; Li, Y. Chem. Eur. J. 2010, 16, 9264.
(e) Tran, D. N.; Cramer, N. Angew. Chem., Int. Ed. 2010, 49, 8181.
(f) Tran, D. N.; Cramer, N. Angew. Chem., Int. Ed. 2011, 50, 11098.
(g) Zhou, F.; Han, X.; Lu, X. J. Org. Chem. 2011, 76, 1491. (h) Sato, T.;
Onuma, T.; Nakamura, I.; Terada, M. Org. Lett. 2011, 13, 4992. (i) Nun,
P.; Gaillard, S.; Poater, A.; Cavallo, L.; Nolan, S. P. Org. Biomol. Chem.
2011, 9, 101. (j) Usanov, D. L.; Yamamoto, H. Org. Lett. 2012, 14, 414.
́
(k) McGonigal, P. R.; de Leon, C.; Wang, Y.; Homs, A.; Solorio-
Alvarado, C. R.; Echavarren, A. M. Angew. Chem., Int. Ed. 2012, 51,
13093. (l) Zhao, J.; Clark, D. A. Org. Lett. 2012, 14, 1668. (m) Eom, D.;
Park, S.; Park, Y.; Ryu, T.; Lee, P. H. Org. Lett. 2012, 14, 5392.
(n) Dethe, D. H.; Murhade, G. Org. Lett. 2013, 15, 429. (o) Mondal, S.;
Mohamed, R. K.; Manoharan, M.; Phan, H.; Alabugin, I. V. Org. Lett.
2013, 15, 5650. (p) Becker, P.; Priebbenow, D. L.; Pirwerdjan, R.; Bolm,
C. Angew. Chem., Int. Ed. 2014, 53, 269.
(5) For recent examples of benzofulvene syntheses, see: (a) Ye, S.;
Gao, K.; Zhao, H.; Wang, X.; Wu, J. Chem. Commun. 2009, 5406.
(b) Bryan, C. S.; Lautens, M. Org. Lett. 2010, 12, 2754. (c) Tsuchikama,
K.; Kasagawa, M.; Endo, K.; Shibata, T. Synlett 2010, 97. (d) Ye, S.;
Yang, X.; Wu, J. Chem. Commun. 2010, 46, 2950. (e) Kim, K. H.; Kim, S.
H.; Park, B. R.; Kim, J. N. Tetrahedron Lett. 2010, 51, 3368.
(6) (a) Akiyama, K.; Gao, F.; Hoveyda, A. H. Angew. Chem., Int. Ed.
2010, 49, 419. (b) Gao, F.; McGrath, K. P.; Lee, Y.; Hoveyda, A. H. J.
Am. Chem. Soc. 2011, 133, 14315. (c) May, T. J.; Dabrowski, J. A.;
Hoveyda, A. H. J. Am. Chem. Soc. 2011, 133, 736. (d) Cottet, P.; Muller,
̈
D.; Alexakis, A. Org. Lett. 2013, 15, 828. (e) Takimoto, M.; Hou, Z.
Chem. Eur. J. 2013, 19, 11439. (f) McGrath, K. P.; Hoveyda, A. H. Angew.
Chem., Int. Ed. 2014, 53, 1910.
(7) Eisch, J. J.; Kaska, W. C. J. Am. Chem. Soc. 1966, 88, 2213.
(8) Kinoshita, H.; Ishikawa, T.; Miura, K. Org. Lett. 2011, 13, 6192.
(9) (a) Eisch, J. J.; Foxton, M. W. J. Org. Chem. 1971, 36, 3520.
(b) Eisch, J. J.; Rhee, S.-G. J. Am. Chem. Soc. 1975, 97, 4673 and
reference 6a..
(10) Eisch, J. J. In Comprehensive Organometallic Chemistry II;
Housecroft, C. E., Ed.; Pergamon: Oxford, U.K., 1995; Vol. 1, p 464.
(11) The relative configurations of 2a-d and 2a′-d could not be
determined on the basis of the coupling constants between vicinal
protons on the stereogenic centers because the J values are so close.
However, the formation of benzofulvene (E)-7a from (E)-1a suggests
the presence of u-5a as an intermediate (Scheme 8), which provides a
good reason for our assignment.
(12) See the Supporting Information for details.
(13) Ashby, E.; Yu, S. H. J. Org. Chem. 1970, 35, 1034.
(14) Karpov, G. V.; Popik, V. V. J. Am. Chem. Soc. 2007, 129, 3792.
(15) Roman, D. S.; Takahashi, Y.; Charette, A. B. Org. Lett. 2011, 13,
3242.
(16) Kashiki, T.; Shinamura, S.; Kohara, M.; Miyazaki, E.; Takimiya,
K.; Ikeda, M.; Kuwahara, H. Org. Lett. 2009, 11, 2473.
(17) Rauniyar, V.; Zhai, H.; Hall, D. G. J. Am. Chem. Soc. 2008, 130,
8481.
(18) Shinozuka, T.; Shimada, K.; Matsui, S.; Yamane, T.; Ama, M.;
Fukuda, T.; Taki, M.; Takeda, Y.; Otsuka, E.; Yamato, M.; Mochizuki, S.;
Ohhota, K.; Naito, S. Bioorg. Med. Chem. 2006, 14, 6789.
8181
dx.doi.org/10.1021/jo501383v | J. Org. Chem. 2014, 79, 8171−8181