Synthesis of kinetically stabilized 1-silanaphthalenes and their properties

Article abstract of DOI:10.1246/bcsj.78.977

The first kinetically stabilized 1-silanaphthalenes bearing a 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl (Tbt) group or a 2,6-bis[bis(trimethylsilyl)methyl]-4-[tris(trimethylsilyl)methyl]phenyl (Bbt) group were synthesized from the corresponding overcrow

Full text of DOI:10.1246/bcsj.78.977

Ó 2005 The Chemical Society of Japan
Bull. Chem. Soc. Jpn., 78, 977–987 (2005)
977
BCSJ Award Article
Synthesis of Kinetically Stabilized 1-Silanaphthalenes
and Their Properties
ꢀ
Akihiro Shinohara, Nobuhiro Takeda, Takahiro Sasamori, and Norihiro Tokitoh
Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011
Received December 7, 2004; E-mail: tokitoh@boc.kuicr.kyoto-u.ac.jp
The first kinetically stabilized 1-silanaphthalenes bearing a 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl (Tbt) group
or a 2,6-bis[bis(trimethylsilyl)methyl]-4-[tris(trimethylsilyl)methyl]phenyl (Bbt) group were synthesized from the corre-
sponding overcrowded bromosilanes by dehydrobromination using LDA (lithium diisopropylamide) in THF at ꢁ40 ꢂC,
respectively. The structures of 1-silanaphthalenes were confirmed by 1H, 13C, and 29Si NMR, UV–vis, Raman, and high-
resolution mass spectroscopic analyses. These results and the NICS calculations indicated high aromaticity of the 1-sila-
naphthalenes. In spite of such high aromaticity, Tbt-substituted 1-silanaphthalene is thermally unstable and undergoes
gradual dimerization in C6D6 solution to give the corresponding ½4 þ 2ꢃ dimer. By contrast, 1-silanaphthalene bearing
ꢂ
a Bbt group on the Si atom was thermally stable even on heating in C6D6 at 120 C. Tbt-substituted 1-silanaphthalene
has high reactivity toward addition reactions at both 1,2- and 1,4-positions, giving the corresponding adducts in the re-
actions with H2O, MeOH, mesitonitrile oxide, benzophenone, and elemental chalcogens. Tbt-substituted 1-silanaphtha-
lene underwent 1,4-addition reaction with CCl4 to give cis- and trans-adducts having a Cl atom on the Si atom and a
CCl3 group at the 4-position.
Heteroaromatic compounds containing a heavier main
group element have attracted much interest from the stand-
points of fundamental and applied chemistry. As for the ele-
ments of the third period, the chemistry of ½4n þ 2ꢃꢀ electron
systems containing a phosphorus atom has been extensively
studied,1 and the compounds are known to show highly aro-
matic characters in their structures, properties, and reactivities.
By contrast, the chemistry of silaaromatic compounds has been
less developed because of the extremely high reactivity and
instability of low-coordinated silicon compounds.2
Although there has been no example for the synthesis of 1-
silanaphthalenes, we have already revealed by the NICS calcu-
lations that the aromaticity of 1- and 2-silanaphthalenes is
comparable to each other and slightly less than that of naphtha-
lene.6a On the other hand, Ashe et al. reported the synthesis of
1-boratanaphthalene and 1-arsanaphthalene, in which they
used 1-bromo-2-(3-bromoallyl)benzene as a key precursor
for 1-heteranaphthalenes.8 These results prompted us to exam-
ine the synthesis of a 1-silanaphthalene using 1-bromo-2-(3-
bromoallyl)benzene as a starting material.
On the other hand, we have reported the synthesis of various
low-coordinated compounds, such as heavy ketones3 and
heavy azo compounds,4 by taking advantage of kinetic stabili-
zation afforded by an effective steric protection group, 2,4,6-
tris[bis(trimethylsilyl)methyl]phenyl (Tbt),5 and revealed their
structures and properties of such compounds. As an extension
of this chemistry to the field of low-coordinated silicon com-
pounds, we have succeeded in the synthesis of kinetically sta-
bilized silaaromatic compounds, e.g., silabenzene, 2-silanaph-
thalene, and 9-silaanthracene, bearing a Tbt group on the cen-
tral Si atom.6 The aromatic character of these species was re-
vealed and confirmed by NMR, UV–vis, and Raman spectral
data, X-ray crystallographic analyses and theoretical calcula-
tions. In spite of having considerable aromatic character, these
compounds were found to undergo ready 1,2- and/or 1,4-addi-
tion reactions due to the high reactivity of the Si–C double
bond.6,7
In a preliminary communication, we have already described
the synthesis of the first 1-silanaphthalene 1a bearing a Tbt
group and found that 1a gradually dimerized at room temper-
ature to afford the corresponding ½4 þ 2ꢃ dimer.9 We now
wish to delineate the synthesis, properties, and reactivities of
kinetically stabilized 1-silanaphthalenes 1a and 1b, the latter
of which bears a sterically bulkier ligand, 2,6-bis[bis(trimeth-
ylsilyl)methyl]-4-[tris(trimethylsilyl)methyl]phenyl
(Chart 1).
(Bbt)10
Results and Discussion
At first, 1,4-dihydro-1-silanaphthalene 2a was synthesized
by the reaction of 1-bromo-2-(3-bromoallyl)benzene with t-bu-
ꢂ
tyllithium in Et2O at ꢁ78 C, followed by the subsequent ad-
dition of TbtSiH3 at room temperature. Bromination of 2a with
NBS (1 molar amount) at room temperature in benzene result-
ed in the formation of the corresponding bromosilane 3a,
Published on the web June 6, 2005; DOI 10.1246/bcsj.78.977

978 Bull. Chem. Soc. Jpn., 78, No. 6 (2005)
BCSJ AWARD ARTICLE
Table 1. Observed and Calculated 29Si, 1H, and 13C NMR
Chemical Shifts of 1-Silanaphthalenes
R
H7
C7
R
Si
H6
H5
Si
H1
H2
C6
C5
C8
C9
C1
C2
Observed
CalculatedaÞ
C4
H4
C3
H3
1a (R ¼ Tbt) 1b (R ¼ Bbt) 1c (R ¼ H) 1d (R ¼ Ph)
1a; R = Tbt
1b; R = Bbt
1c; R = H
Si
91.74
7.10
8.07
90.89
7.00
8.03
75.66
7.38
8.02
95.03
7.00
8.05
H1
H2
H3
H4
H5
H6
H7
C1
C2
C3
C4
C5
C6
C7
C8
C9
1d; R = Ph
SiMe3
SiMe3
7.17
7.73
7.14
7.72
7.25
7.82
7.14
7.80
Me3Si
Me3Si
SiMe3
R'
SiMe3
R' = H; Tbt
R' = SiMe3; Bbt
7.36
7.15
7.34
7.12
7.60
7.24
7.58
7.22
8.22
8.18
8.11
8.38
116.74
137.95
116.89
131.40
128.76
120.58
133.19
131.52
145.33
115.68
137.89
116.71
131.35
128.77
120.61
133.19
131.03
145.36
126.63
142.39
123.49
135.92
132.98
125.03
136.01
140.86
150.22
115.85
142.58
121.17
135.71
132.59
124.71
135.66
135.37
150.64
Chart 1.
R
H
Br
Si
t-BuLi (4 mol. amt.) RSiH3
Et2O, −78 °C
r.t.
Br
2a (R = Tbt)
2b (R = Bbt)
R
Br
Si
R H
Si
a) Calculated by GIAO-B3LYP/6-311G(d)(6-311G(3d) for Si
and 6-311G(d) for C, H)//B3LYP/6-31G(d) level.
NBS (1 mol. amt.)
benzene, r.t.
at 91.7 (1a) and 90.9 (1b) ppm, respectively, which were
assigned to those for the sp2 silicon atoms. The 29Si NMR
chemical shift for 1a (91.2 ppm) in the mixed solvent
(THF:C6D6 = 5:1) was very similar to that in C6D6, suggest-
ing the absence of the coordination of THF as a Lewis base to
the silicon atom of the 1-silanaphthalene ring. Since it is well
known that the coupling constant between adjacent two atoms
can be a good index for the ꢀ-bond order,12 measurement of
2a
2b
3a
3b
Scheme 1.
R
R
Br
Si
Si
LDA (1 mol. amt.)
THF, −40 °C
1
the JSi{C values for the two Si–C bonds in the 1-silanaphtha-
lene rings may give useful information about the properties of
3a
3b
1a (R = Tbt)
1b (R = Bbt)
1
the 1-silanaphthalene rings. Although the JSi{C values in 1a
could not be measured due to the gradual dimerization of 1a
at 10 ꢂC (vide infra), we could observe those in 1b as 90
Scheme 2.
which is a suitable precursor of 1-silanaphthalene 1a
(Scheme 1). Another precursor 3b was prepared by the same
procedure as that for 3a, using BbtSiH3 instead of TbtSiH3.
1-Silanaphthalenes 1a and 1b were synthesized by the dehy-
drobromination of bromosilanes 3a and 3b using LDA in THF
1
(Si–C1) and 77 Hz (Si–C8). The JSi{C values in 1b are close
11
to those (76–92 Hz) for the silaaromatic compounds previously
synthesized,6 and the bond order of the 1,2-bond is larger than
that of the 1,9-bond in 1b as well as naphthalene (1JC{C ¼ 60:3
and 55.9 Hz, respectively). The results of NMR studies on 1a
and 1b strongly suggest the delocalized 10ꢀ-electron structure
for the 1-silanaphthalene ring system, i.e., the aromatic charac-
ter of 1-silanaphthalene. In order to confirm the conclusion de-
duced from the experimental NMR data, we carried out theo-
retical calculations for the model compounds, 1-silanaphtha-
lene (1c) and 1-phenyl-1-silanaphthalene (1d) (Table 1). It
seems that the results for 1c disagree with the chemical shifts
observed for 1a and 1b. However, it is likely that the calculat-
ed NMR chemical shifts of 1c were influenced by the polar Si–
H bond. The chemical shifts calculated for 1d are in good
agreement with those experimentally observed for 1a and
1b, indicating little perturbation by the bulky Tbt or Bbt group
attached to the 1-silanaphthalene system.13,14
ꢂ
at ꢁ40 C, respectively (Scheme 2). 1-Silanaphthalene 1a is
thermally unstable at room temperature to give the correspond-
ing dimer 4, while 1b is thermally stable (the details of the di-
merization reaction are described below). 1-Silanaphthalenes
1a and 1b are highly moisture-sensitive.
Properties of 1-Silanaphthalenes. The structures of 1-si-
lanaphthalenes 1a and 1b were unambiguously confirmed by
1H, 13C, 29Si NMR, Raman, UV–vis, and high-resolution mass
spectroscopy, although good crystals suitable for X-ray struc-
tural analysis could not be obtained in either case. The 1H and
13C NMR signals of 1a and 1b were assigned by 2D NMR
1
techniques. In the H NMR spectra, characteristic down-field
shifts were observed for the protons at 4-position (from
3.76–3.79 ppm for 2a to 7.17 ppm for 1a and from 3.75–
3.85 ppm for 2b to 7.14 ppm for 1b), and all peaks assignable
to those for the 1-silanaphthalene rings of 1a and 1b in the 1H
and 13C NMR spectra were observed in aromatic regions
(Table 1). The 29Si NMR spectra of 1a and 1b showed signals
The UV–vis spectra of 1a and 1b showed absorption max-
ima red-shifted over 300 nm [ꢁmax 249 (", 7 ꢄ 104), 255
(7 ꢄ 104), 261 (6 ꢄ 104), 304 (2 ꢄ 104), 354 (2 ꢄ 104), 367
(2 ꢄ 104), and 379 (1 ꢄ 104) nm for 1a and ꢁmax 255 (",

A. Shinohara et al.
Bull. Chem. Soc. Jpn., 78, No. 6 (2005)
979
Tbt
Si
[4+2] cycloaddition
R
R = Tbt
Si
Si
Tbt
Abs
4
1a, b
no dimerization
R = Bbt
0
Tbt
Si
250
300
400
Wavelength [nm]
500
Tbt
Si
r.t., 4 months
Fig. 1. UV–vis spectra of 1-silanaphthalenes 1a (blue line)
and 1b (red line).
80 °C
Si
Tbt
Tbt
(a)
(b)
Si
no dimerization
100 °C
Si
Scheme 3.
Fig. 2. Calculated vibration modes with maximum intensi-
ty: (a) 1-silanaphthalene 1c (1328 cmꢁ1) (b) naphthalene
(1360 cmꢁ1).
5 ꢄ 104), 307 (7 ꢄ 103), 356 (1 ꢄ 104), 367 (2 ꢄ 104), and 384
(9 ꢄ 103) nm for 1b] (Fig. 1). Although these maxima are
shifted to a longer wavelength region than those of naphtha-
lene, the spectral patterns observed for 1a and 1b were similar
to those reported for naphthalene [221 (", 1:33 ꢄ 105), 286
(9:3 ꢄ 103), and 312 (2:9 ꢄ 102) nm]15 and Tbt-substituted
2-silanaphthalene [267 (", 2 ꢄ 104), 327 (7 ꢄ 103), and 387
(2 ꢄ 103) nm].6a,b Two prominent bands of 1a and 1b in the
regions around 250 nm and 300–400 nm are assignable to
the 1B band and the overlapped 1La and 1Lb bands, respective-
ly. These results suggest that the 1-silanaphthalene ring system
has an electronic structure similar to those of naphthalene and
2-silanaphthalene.
Fig. 3. Molecular structure of 1-silanaphthalene dimer 4
(50% probability). All hydrogen atoms and solvated
CH2Cl2 molecules are omitted for clarity.
The Raman spectrum of 1a, which is well reproduced in the
calculations of vibrational frequencies for 1-silanaphthalene
1c, showed some characteristic strong lines (Fig. 2). The
Reactivity of 1-Silanaphthalene. Despite the high aroma-
ticity of 1-silanaphthalene 1a, its Si–C double bond (Si–C1)
and 1-silabuta-1,3-diene (Si–C1–C2–C3) moiety are quite re-
active toward various reagents with the modes of 1,2- and/or
1,4-addition reactions.
strongest line of 1a (1340 cmꢁ1) corresponding to the most
intense lines of 1c (1328 cmꢁ1) and 1d (1326 cmꢁ1
)
was
16
assigned to the skeletal vibration within the 1-silanaphthalene
ring plane. It also resembles those assigned to the most intense
line of naphthalene and the Tbt-substituted 2-silanaphtha-
lene,6a,b indicating that 1a has a ring skeleton similar to those
of naphthalene and the Tbt-substituted 2-silanaphthalene.
In our previous report, we proposed that 1-silanaphthalene
has as much aromaticity as naphthalene, judging from the re-
sults of theoretical calculations, i.e., the NICS(1) values and
the energies for aromatic isodesmic isomerizations.6,17–19 The
NICS(1) values for 1-silanaphthalene (1c) were calculated
as large negative values (ꢁ9:1 ppm for the C5Si ring and
ꢁ10:9 ppm for the C6 ring), which were comparable to that
for naphthalene (ꢁ11:5 ppm) [GIAO-B3LYP/6-311G(d) lev-
el]. If one takes into account all the results of spectroscopic
studies and theoretical calculations, one can conclude that 1-
silanaphthalenes 1a and 1b are as highly aromatic as the sila-
aromatic compounds previously reported.6
In contrast to other stable silaaromatic compounds,6 1-sila-
naphthalene 1a was found to undergo gradual dimerization in
solution at room temperature to give the corresponding dimer
4 via a ½4 þ 2ꢃ cycloaddtion reaction (Scheme 3). The structure
of dimer 4 was confirmed based on the 1H, 13C, and 29Si NMR
spectral data, and the stereochemistry in 4 was finally deter-
mined by an X-ray structural analysis (Fig. 3). The dimeriza-
tion reaction of 1a was completed in 1 month at room temper-
ature, while heating of 1a in C6D6 at 100 ꢂC for 12 h afforded
the dimer 4 in 49% yield with complete consumption of 1a.
This conversion of 1a into 4 indicates that dimer 4 is thermo-
dynamically more stable than 1a under these conditions. A
Tbt-substituted silabenzene also gives the corresponding ½4 þ
2ꢃ dimer when its C6D6 solution is left at room temperature for
4 months, and the dimer dissociates into the monomer quanti-

980 Bull. Chem. Soc. Jpn., 78, No. 6 (2005)
BCSJ AWARD ARTICLE
ꢂ
tatively by heating at 80 C for 9 h.11,20 By contrast, thermol-
On the other hand, 1-silanaphthalene 1b bearing a Bbt group
on the Si atom did not dimerize, but kept the monomeric struc-
ture under the same conditions as those for 1a. It should be
noted that thermal stability of 1-silanaphthalene is dramatical-
ly changed by the slight modification of a protection group
from Tbt to Bbt. These results suggested that Bbt group, which
can avoid the dimerization of 1b, is slightly bulkier than Tbt
group. However, both 1-silanaphthalenes, 1a and 1b, have
enough reaction space for small molecules around the reactive
center. Indeed, the reaction of 1b with H2O afforded the cor-
responding 1,2- and 1,4-adducts, as in the case of 1a.
Reactions of 1a with H2O and MeOH afforded the corre-
sponding 1,2- and 1,4-adducts competitively in both cases.
In the reaction with MeOH, the ratio of 6a and 6b was depend-
ent upon the solvent used (Scheme 5, Table 3).21
When 1-silanaphthalene 1a was allowed to react with mesi-
tonitrile oxide and benzophenone, ½2 þ 3ꢃ and ½4 þ 2ꢃ cycload-
dition reactions proceeded to afford the corresponding cyclo-
adducts 7 and 8 in 49% and 60% yields, respectively (Fig. 4).
These cycloaddition reactions of 1a can be understood as typi-
cal reactions of the previously reported silenes and 1-silabuta-
1,3-diene, respectively.
It is known that Si=C and Si=Si bonds react with elemental
sulfur to afford the corresponding three-membered ring com-
pounds, i.e., sulfurized products having an episulfide skele-
ton.22 Meanwhile, we have synthesized a variety of cyclic poly-
sulfides containing group 14 elements as stable compounds
by taking advantage of a Tbt group,23 and we have recently re-
ported the sulfurization and selenation of germaaromatic com-
pounds kinetically stabilized by a Tbt group, leading to the for-
mation of the corresponding three- or five-membered cyclic
chalcogenides.18,24 Based on these situations, sulfurization of
1a was examined in the hope of forming the corresponding
ꢂ
ysis of 4 at 120 C in the presence of benzophenone gave no
benzophenone adduct of 1a (vide infra), indicating no dissoci-
ation of 4 into 1a by heating at this temperature. A Tbt-substi-
tuted 2-silanaphtalene did not give any dimers on heating in
C6D6 solution at 100 ꢂC.6a,b The difference between 1-sila-
naphthalene 1a and the Tbt-substituted 2-silanaphthalene in
the dimerization can be explained using the results of theoret-
ical calculations [B3LYP/6-31G(d)] on the dimerization ener-
gies (Table 2). Three types of structures (Type A, B, and C) are
expected as dimerization products of silanaphthalenes
(Chart 2), and each type of structure will have two endo-
and exo-isomers and two combinations of (C, Si) and (Si,
C), respectively. In this case, dimer 4 is the type A-endo (C,
Si). One can see from Table 2 that the dimerized reactions
of 1-silanaphthalene are more exothermic (Type A: ꢀH ¼
ꢁ174{119 kJ/mol) than those of 2-silanaphthalene (Type B:
ꢀH ¼ ꢁ28:0{ꢁ11:7 kJ/mol and Type C: ꢀH ¼ ꢁ47:7{38:5
kJ/mol) (Scheme 4). Type B dimers are presumably unstable
due to the unfavorable structures with a weak Si–C double
bond, and Type C dimers are also undesirable products because
they lose the aromaticity of both silabenzene and benzene
moieties.
Table 2. Calculated ꢀH (kJ/mol) of Dimerization Reaction
for Silanaphthalenes [B3LYP/6-31G(d)]
(E, E0)
exo (C, Si) endo (C, Si) exo (Si, C) endo (Si, C)
Type A
Type B
Type C
ꢁ174
ꢁ13:8
ꢁ47:7
ꢁ173
ꢁ11:7
ꢁ46:4
ꢁ120
ꢁ28:0
34.7
ꢁ119
ꢁ27:6
38.5
H
Si
H
H
H
H
E'
E
E'
E'
H
H
Si
H
E
E
x 2
Si
H
Type A-exo
Si
H
Si
H
Type C-exo
Si
H
Type B-exo
∆H = −173 kJ/mol
H
H
H
H
E'
E'
Si
E'
H
H
E
H
H
E
E
Si
x 2
Si
H
Type A-endo
Si
H
Si
H
Type C-endo
Si
H
∆H = −47.7 kJ/mol
Type B-endo
Chart 2.
Scheme 4.
O
N
Tbt OH
Tbt OH
Si
Tbt
Si
+
Si
H2O
Mes
MesCNO
THF, r.t.
Tbt
Si
THF, r.t.
total 54%
5a
5b
7 (49%) Mes = mesityl
Ph Ph
Tbt OMe
Tbt OMe
Si
1a
Si
+
Ph2CO
THF, r.t.
O
MeOH
THF, r.t.
total 80%
Si
Tbt
8 (60%)
6a
6b
Scheme 5.

A. Shinohara et al.
Bull. Chem. Soc. Jpn., 78, No. 6 (2005)
981
Table 3. The Ratio of 1,2-Adduct to 1,4-Adduct in the Re-
action of 1-Silanaphthalene 1a with Methanol
Tbt Cl
Si
Tbt Cl
Si
Tbt
Si
CCl4
hexane, r.t.
dark
+
Ratio
1a
Solvent
1,4-Adduct
1,2-Adduct
Yield (%)
CCl3
Cl3C
H
H
THF
Hexane
3
10
5
9
80
87
cis-10 (35%) trans-10 (35%)
Tbt
Cl
Si
CCl4
CCl3
H
11
Scheme 7.
(a)
Fig. 4. Molecular structure of benzophenone adduct of 1-
silanaphthalene 8 (50% probability). All hydrogen atoms
are omitted for clarity.
(b)
S8
THF, r.t.
inseparable mixture
Tbt
Si
Se Se
Tbt
Si
Se
Se
1a
THF, r.t.
9 (38%)
Scheme 6.
polysulfides fused with the 1-silanaphthalene ring. In contrast
to the case of Tbt-substituted 2-silanaphthalene, which gave
the corresponding five-membered cyclic trisulfide in 20% yield
selectively, the reaction of 1a with elemental sulfur afforded
an inseparable mixture. Although the mass spectrum of the
mixture indicated the formation of three- and five-mem-
bered-ring products, further attempts of separation and charac-
terization of these products were unsuccessful. On the other
hand, the reaction of 1a with elemental selenium afforded
the corresponding five-membered-ring compound 9 in 38%
Fig. 5. Molecular structures of cis-10 (a) and trans-10 (b)
(50% probability). Hydrogen atoms except for the hydro-
gen atom at the 4-position of the 1,4-dihydro-1-silanaph-
thalene ring are omitted for clarity.
metallenes with carbon tetrachloride was theoretically studied
using DFT calculations.27 However, the reactivity of silaaro-
matic compounds toward CCl4 has been unknown so far. Inter-
estingly, 1-silanaphthalene 1a reacted with CCl4 in hexane to
give two types of products, cis-10 and trans-10, each in 35%
yield, as shown in Scheme 7. The regio- and stereochemistries
of the products were confirmed by X-ray crystallographic anal-
ysis (Fig. 5, Table 4). The reaction of 1a with CCl4 using THF
as a solvent instead of hexane resulted in the formation of a
complex mixture. Although the mechanism of non-selective
formation of cis-10 and trans-10 in hexane is not clear at pres-
ent, one can postulate the initial formation of the correspond-
ing reactive radical pairs 11, followed by the radical coupling
reactions giving the products (Scheme 7). In THF, the inter-
mediate 11 might be generated as in the case of hexane, and
it probably reacted with THF to afford a complex mixture.
1
yield (Scheme 6). The structure of 9 was determined by H,
13C, 29Si, and 77Se NMR spectrometry together with elemental
analysis. In the 77Se NMR spectrum, three signals assignable to
those of the triselenasilolane ring were observed at 332.4,
567.1, and 743.3 ppm.
It has already been reported that the reaction of anthracene
with CCl4 under photo-irradiation gives a 9-chloro-10-trichlo-
romethyl adduct of anthracene.25 As for the reactions of low-
coordinated silicon compounds with haloalkanes, Kira et al.
have performed detailed kinetic studies on the reactions of di-
silenes with haloalkanes.26 More recently, the reaction of di-

982 Bull. Chem. Soc. Jpn., 78, No. 6 (2005)
BCSJ AWARD ARTICLE
Table 4. Crystallographic Data for Compounds 4, 8, cis-10, and trans-10b
4 1.5CH2Cl2
8
cis-10
trans-10b
ꢅ
1518.43
Formula
Formula weight
C72H132Si14 1.5CH2Cl2 C49H76OSi7
C37H66Cl4Si7
849.33
C37H66Cl4Si7
849.33
ꢅ
877.73
Crystal size (mm3) 0:30 ꢄ 0:25 ꢄ 0:25
0:10 ꢄ 0:10 ꢄ 0:10 0:40 ꢄ 0:30 ꢄ 0:20 0:20 ꢄ 0:20 ꢄ 0:20
Crystal system
Space group
triclinic
ꢁ
P1 (#2)
triclinic
ꢁ
P1 (#2)
triclinic
ꢁ
P1 (#2)
triclinic
ꢁ
P1 (#2)
ꢂ
a (A)
13.1719(4)
18.4733(3)
20.1882(4)
74.8772(7)
79.6862(8)
78.213(2)
4600.96(18)
2
11.1554(6)
13.6820(8)
17.8237(12)
78.780(2)
79.610(3)
82.755(5)
2613.0(3)
2
9.649(2)
13.051(3)
20.681(5)
91.9360(19)
99.205(3)
111.9395(19)
2372.1(9)
2
9.392(3)
13.041(4)
20.882(7)
80.398(12)
80.142(13)
70.886(8)
2363.9(14)
2
ꢂ
b (A)
ꢂ
c (A)
ꢂ (deg)
ꢃ (deg)
ꢄ (deg)
ꢂ 3
V (A )
Z
Dcalc (g cmꢁ3
Independent
reflections
)
1.096
1.116
1.189
1.193
ꢅ
15217
8617
8350
8306
No. of parameters
R1 (I > 2ꢅðIÞ)
wR2 (all data)
865
532
697
621
0.059
0.177
1.05
0.054
0.116
1.11
0.036
0.105
1.10
0.049
0.124
1.06
Goodness of fit
spectrometer using tetramethylsilane as an external standard.
High-resolution mass spectral data were obtained on a JEOL
JMS-700 spectrometer. Wet column chromatography (WCC)
was performed on Nacalai Tesque Silica Gel 60. Preparative gel
permeation liquid chromatography (GPLC) was performed on an
LC-908, LC-918, or LC-908-C60 (Japan Analytical Industry
Co., Ltd.) equipped with JAIGEL 1H and 2H columns (for LC-
908 and LC-918) or JAIGEL 1H-40 and 2H-40 columns (for
LC-908-C60) (eluent: chloroform or toluene). Preparative thin-
layer chromatography (PTLC) was performed with Merck Kiesel-
gel 60 PF254. Electronic spectra were recorded on a JASCO
Ubest V-570. Raman spectra were measured at room temperature
on a Raman spectrometer consisting of a Spex 1877 Triplemate
and an EG & G PARC 1421 intensified photodiode array detector.
An NEC GLG 108 He–Ne laser (632.8 nm) was used for Raman
excitation. All melting points were determined on a Yanaco micro
melting point apparatus and are uncorrected. Elemental analyses
were carried out at the Microanalytical Laboratory of the Institute
for Chemical Research, Kyoto University. 1-Bromo-2-(3-bromo-
allyl)benzene,8 {2,4,6-tris[bis(trimethylsilyl)methyl]phenyl}silane
(TbtSiH3),28 and {2,6-bis[bis(trimethylsilyl)methyl]-4-[tris(tri-
methylsilyl)methyl]phenyl}silane (BbtSiH3)11 were prepared ac-
cording to the reported procedure.
Conclusion
We succeeded in the synthesis of 1-silanaphthalenes 1a and
1b, the first examples of a stable 1-silanaphthalene. Detailed
analyses of the spectral data (1H, 13C, 29Si NMR, UV–vis,
and Raman spectra) and theoretical calculations revealed that
1-silanaphthalenes 1a and 1b have a delocalized 10ꢀ-electron
ring system and high aromaticity. Although 1-silanaphthalene
1a bearing a Tbt group was thermally unstable to give the cor-
responding ½4 þ 2ꢃ dimer 4, 1b bearing a Bbt group, which is
slightly bulkier than the Tbt group, was stable in solution even
at 100 ꢂC. In spite of its aromaticity, 1-silanaphthalene 1a
readily reacted with some reagents to give the corresponding
adducts at the 1,2- and 1,4-positions of the 1-silanaphthalene
ring. In addition, the reaction of 1a with CCl4 afforded the cor-
responding 1,4-adducts, cis-10 and trans-10. The geometries
of cis-10 and trans-10 were confirmed by X-ray crystallo-
graphic analysis to show that a Cl atom was introduced onto
the Si atom and a CCl3 group was on the 4-position in both
compounds. We propose that this reaction proceeded via a
radical mechanisim, i.e., the initial formation of a radical pair
intermediate and the subsequent radical coupling reaction.
Further experiments and theoretical calculations to confirm
the reaction mechanism of silaaromatic compounds with CCl4
are currently in progress.
Theoretical Calculations. The geometries of related refer-
ence molecules 1c and 1d were optimized by using the Gaussian
98 program14 at the B3LYP/6-31G(d) level of density functional
theory. The GIAO-B3LYP and NICS17 calculations were carried
out with the 6-311G(3d) basis set for Si and the 6-311G(d) basis
set for C and H.
Experimental
General Procedure. All experiments were performed under
an argon atmosphere unless otherwise noted. All solvents were
dried by standard methods and were freshly distilled prior to
use. The 1H NMR (400 or 300 MHz) and 13C NMR (100 or 75
MHz) spectra were measured in CDCl3 or C6D6 with a JEOL
AL-400 or AL-300 spectrometer using CHCl3 (7.25 ppm) or
C6D5H (7.15 ppm) as an internal standard for 1H NMR spectrom-
etry, and using CDCl3 (77.0 ppm) or C6D6 (128.0 ppm) as the
standard for 13C NMR spectrometry. The 29Si NMR (59 MHz)
spectra were measured in CDCl3 or C6D6 with a JEOL AL-300
Preparation of 1-{2,4,6-Tris[bis(trimethylsilyl)methyl]phen-
yl}-1,4-dihydro-1-silanaphthalene (2a). To a solution of 1-bro-
mo-2-(3-bromoallyl)benzene (0.991 g, 3.62 mmol) in ether (10
mL) was added 2.32 mol/L pꢂentane solution of t-butyllithium
(6.24 mL, 14.5 mmol) at ꢁ78 C. After the solution was stirred
ꢂ
at ꢁ78 C for 1.5 h and at room temperature for 1 h, a solution
of {2,4,6-tris[bis(trimethylsilyl)methyl]phenyl}silane (357 mg,
0.613 mmol) in ether (4 mL) was added at room temperature. Af-
ter further stirring for 1 h, the reaction mixture was quenched with

A. Shinohara et al.
Bull. Chem. Soc. Jpn., 78, No. 6 (2005)
983
1
an aqueous solution of NH4Cl and extracted with ether. The or-
ganic layer was dried over Na2SO4, filtered, and then evaporated.
The crude product was purified by FCC (hexane) and GPLC
(CHCl3) to give 1,4-dihydro-1-silanaphthalene, 2a (152 mg,
43%). 2a: colorless powder. mp. 168–171 ꢂC. 1H NMR (300
MHz, rt, CDCl3) ꢆ ꢁ0:19 (s, 9H), ꢁ0:16 (s, 9H), 0.04 (s, 18H),
0.06 (s, 18H), 1.32 (s, 1H), 2.30 (br s, 1H), 2.33 (br s, 1H),
3.76–3.79 (m, 2H), 5.58–5.60 (m, 1H), 6.14 (ddd, CHSi, 3J ¼
14 Hz, 4J ¼ 2 Hz, 4J ¼ 2 Hz, 1H), 6.29 (br s, 1H), 6.38 (br s,
1H), 6.94 (ddd, SiCHCH, 3J ¼ 14 Hz, 3J ¼ 4 Hz, 3J ¼ 4 Hz,
1H), 7.11–7.19 (m, 2H), 7.26–7.32 (m, 1H), 7.44 (dd, 3J ¼ 8
Hz, 4J ¼ 2 Hz, 1H). 13C NMR (75 MHz, rt, CDCl3) ꢆ 0.52 (q),
0.72 (q), 0.76 (q), 0.98 (q), 1.27 (q), 28.17 (d), 28.48 (d), 30.53
(d), 36.08 (t), 121.93 (d), 123.72 (s), 124.95 (d), 125.56 (d),
126.91 (d), 128.99 (d), 129.17 (d), 131.33 (s), 136.09 (d),
144.25 (s), 144.97 (s), 146.07 (d), 152.69 (s), 152.87 (s).
29Si NMR (59 MHz, rt, CDCl3) ꢆ ꢁ54:4, 1.8, 1.9. Anal. Calcd
for C36H68Si7: C, 61.99; H, 9.83%. Found: C, 61.93; H, 10.06%.
Preparation of 1-{2,6-Bis[bis(trimethylsilyl)methyl]-4-[tris-
(trimethylsilyl)methyl]phenyl}-1,4-dihydro-1-silanaphthalene
(2b). Compound 2b was synthesized from 1-bromo-2-(3-bromo-
allyl)benzene (750 mg, 2.74 mmol) and {2,6-bis[bis(trimethyl-
silyl)methyl]-4-[tris(trimethylsilyl)methyl]phenyl}silane (1.79 g,
2.74 mmol) in 26% yield (552 mg) by the same procedure as that
used for 2a. 2b: colorless powder. mp. 223–225 ꢂC. 1H NMR (300
MHz, rt, CDCl3) ꢆ ꢁ0:16 (s, 18H), 0.09 (s, 18H), 0.25 (s, 27H),
2.48 (s, 2H), 3.75–3.85 (m, 2H), 5.62–5.64 (m, 1H), 6.17 (ddd,
CHSi, 3J ¼ 14 Hz, 4J ¼ 2 Hz, 4J ¼ 2 Hz, 1H), 6.71 (s, 2H),
6.95 (ddd, SiCHCH, 3J ¼ 14 Hz, 3J ¼ 4 Hz, 3J ¼ 4 Hz, 1H),
7.12–7.20 (m, 2H), 7.28–7.33 (m, 1H), 7.44 (dd, 3J ¼ 8 Hz, 4J ¼
2 Hz, 1H). 13C NMR (75 MHz, rt, CDCl3) ꢆ 1.21 (q), 1.74 (q),
5.43 (q), 22.11 (s), 29.41 (d), 36.14 (t), 124.85 (d), 125.60 (d),
126.41 (s), 126.64 (d), 129.10 (d), 129.34 (d), 131.05 (s),
136.04 (d), 144.15 (s), 146.08 (d), 146.75 (s), 152.69 (s).
29Si NMR (59 MHz, rt, CDCl3) ꢆ ꢁ53:90, 0.70, 1.53, 1.61. Anal.
Calcd for C39H76Si8: C, 60.86; H, 9.95%. Found: C, 60.74; H,
10.05%.
(dec). H NMR (300 MHz, rt, CDCl3) ꢆ ꢁ0:06 (s, 18H), 0.09 (s,
18H), 0.28 (s, 27H), 2.77 (s, 2H), 3.46–3.61 (m, 2H), 6.54 (d, 3J ¼
3
3
13 Hz, 1H), 6.69 (s, 2H), 6.99 (dd, J ¼ 13 Hz, J ¼ 4 Hz, 1H)
7.15 (d, 3J ¼ 7 Hz, 1H), 7.26–7.37 (m, 2H), 8.02 (dd, 3J ¼ 7
Hz, 4J ¼ 2 Hz, 1H). 13C NMR (75 MHz, rt, CDCl3) ꢆ 1.64 (q),
1.94 (q), 5.55 (q), 22.39 (s), 29.14 (d), 36.32 (t), 125.93 (s),
126.72 (d), 127.57 (d), 128.53 (d), 129.34 (d), 131.18 (d),
136.83 (s), 138.15 (d), 144.99 (s), 146.38 (d), 148.16 (s), 152.88
(s). 29Si NMR (59 MHz, rt, CDCl3) ꢆ ꢁ22:88, 1.15, 2.08, 2.23.
Anal. Calcd for C39H75Si8Br: C, 55.20; H, 8.91%. Found: C,
55.15; H, 8.89%.
Synthesis of 1-{2,4,6-Tris[bis(trimethylsilyl)methyl]phenyl}-
1-silanaphthalene (1a). In a glovebox filled with argon, 3a (40.2
mg, 0.0519 mmol) was dissolved in THF (2 mL). To this solution
was added lithium diisopropylamide (a 2.0 mol/L solution in hep-
tane/THF/ethylbenzene, 0.026 mL, 0.052 mmol, Aldrich Chemi-
ꢂ
cals Co.) at ꢁ40 C. After the removal of solvents under reduced
pressure, cold hexane was added to the residue and the resulting
suspension was filtered through CeliteÒ. Evaporation of the filtrate
afforꢂded 1a (34.8 mg, 97%). 1a: pale yellow crystals. mp. 127–
1
ꢂ
132 C (dec). H NMR (400 MHz, 10 C, C6D6) ꢆ 0.04 (s, 9H),
0.08 (s, 9H), 0.15 (s, 18H), 0.18 (s, 18H), 1.55 (s, 1H), 2.49 (br
s, 1H), 2.57 (br s, 1H), 6.64 (br s, 1H), 6.77 (br s, 1H), 7.10 (d,
3J ¼ 12 Hz, 1H), 7.15 (ddd, 3J ¼ 8 Hz, 3J ¼ 7 Hz, 4J ¼ 1 Hz,
3
3
3
1H), 7.17 (d, J ¼ 9 Hz, 1H), 7.36 (ddd, J ¼ 8 Hz, J ¼ 7 Hz,
4J ¼ 2 Hz, 1H), 7.73 (dd, J ¼ 8 Hz, J ¼ 1 Hz, 1H), 8.07 (dd,
3J ¼ 12 Hz, 3J ¼ 9 Hz, 1H), 8.22 (dd, 3J ¼ 8 Hz, 4J ¼ 2 Hz,
1H). 13C NMR (100 MHz, 10 ꢂC, C6D6) ꢆ 0.94 (q), 1.20 (q),
1.26 (q), 1.54 (q), 31.68 (d), 36.52 (d), 36.95 (d), 116.74 (d),
116.89 (d), 120.58 (d), 121.77 (d), 123.64 (s), 126.29 (d),
128.76 (d), 131.40 (d), 131.52 (s), 133.19 (d), 137.95 (d),
145.33 (s), 148.16 (s), 153.05 (s), 153.16 (s). 29Si NMR (59
MHz, 10 ꢂC, C6D6) ꢆ 2.2, 2.5, 2.6, 3.3, 91.7. UV–vis (hexane)
ꢁmax 244 (" ¼ 6 ꢄ 104), 249 (7 ꢄ 104), 255 (7 ꢄ 104), 261
(6 ꢄ 104), 304 (2 ꢄ 104), 354 (2 ꢄ 104), 367 (2 ꢄ 104), and 379
(1 ꢄ 104) nm. Anal. Calcd for C36H66Si7: C, 62.17; H, 9.56%.
Found: C, 60.41; H, 9.31% [analyzed as a hydrolysis product of
1a (calcd for C36H68OSi7: C, 60.60; H, 9.61%.) due to its high
sensitivity to moisture]. High resolution FAB-MS m=z calcd for
C36H66Si7 ([M]þ): 694.3549, found: 694.3556 ([M]þ).
3
4
Preparation of 1-Bromo-1-{2,4,6-tris[bis(trimethylsilyl)-
methyl]phenyl}-1,4-dihydro-1-silanaphthalene (3a). A solu-
tion of 2a (47.2 mg, 0.0678 mmol) and NBS (12.1 mg, 0.0678
mmol) in benzene (3 mL) was stirred in the air. After 12 h, the
solvent was evaporated. Separation of the mixture by GPC
(CHCl3) afforded bromosilane 3a (49.2 mg, 94%). 3a: colorless
powder. mp. 208–210 ꢂC. 1H NMR (300 MHz, rt, CDCl3) ꢆ
ꢁ0:17 (s, 9H), 0.14 (s, 9H), 0.03 (s, 9H), 0.04 (s, 18H), 0.06 (s,
9H), 1.30 (s, 1H), 2.50 (br s, 1H), 2.56 (br s, 1H), 3.49–3.64
Synthesis of 1-{2,6-Bis[bis(trimethylsilyl)methyl]-4-[tris-
(trimethylsilyl)methyl]phenyl}-1-silanaphthalene (1b). 1-Sila-
naphthalene 1b was synthesized from 3b (26.9 mg, 0.0318 mmol)
by the same procedure as that used for 1a. 1b (24.3 mg, 99%):
pale yellow crystals. mp. 177–178 ꢂC (dec). 1H NMR (400
MHz, C6D6) ꢆ 0.07 (s, 18H), 0.15 (s, 18H), 0.37 (s, 27H), 2.73
3
4
3
3
(m, 2H), 6.26 (br s, 1H), 6.49 (dd, J ¼ 14 Hz, J ¼ 2 Hz, 1H),
6.79 (br s, 1H), 6.98 (ddd, 3J ¼ 14 Hz, 3J ¼ 5 Hz, 3J ¼ 4 Hz,
1H), 7.14–7.17 (m, 1H), 7.28–7.39 (m, 2H), 8.02 (dd, 3J ¼ 7
Hz, 4J ¼ 2 Hz, 1H). 13C NMR (75 MHz, rt, CDCl3) ꢆ 0.76 (q),
0.80 (q), 1.06 (q), 1.25 (q), 1.40 (q), 28.22 (d), 28.64 (d), 30.65
(d), 36.28 (t), 122.59 (d), 122.90 (s), 126.58 (d), 127.68 (d),
128.57 (d), 129.39 (d), 130.59 (d), 136.44 (s), 137.99 (d),
144.50 (s), 146.16 (s), 146.19 (d), 152.78 (s), 153.29 (s).
29Si NMR (59 MHz, rt, CDCl3) ꢆ ꢁ23:4, ꢁ0:7, 2.6, 2.8. Anal.
Calcd for C36H67Si7Br: C, 55.69; H, 8.70%. Found: C, 55.67;
H, 8.74%.
(s, 2H), 7.00 (d, J ¼ 12 Hz, 1H), 7.07 (s, 2H), 7.12 (ddd, J ¼
3 4 3
8 Hz, J ¼ 7 Hz, J ¼ 1 Hz, 1H), 7.14 (d, J ¼ 9 Hz, 1H), 7.34
(ddd, 3J ¼ 8 Hz, 3J ¼ 7 Hz, 4J ¼ 2 Hz, 1H), 7.72 (dd, 3J ¼ 8
Hz, 4J ¼ 1 Hz, 1H), 8.03 (dd, 3J ¼ 12 Hz, 3J ¼ 9 Hz, 1H),
8.18 (dd, 3J ¼ 8 Hz, 4J ¼ 2 Hz, 1H). 13C NMR (100 MHz, C6D6)
ꢆ 1.35 (q), 1.52 (q), 5.45 (q), 23.19 (s), 38.56 (d), 115.68 (d),
116.71 (d), 120.61 (d), 126.31 (d), 126.77 (s), 128.77 (d),
131.03 (s), 131.35 (d), 133.19 (d), 137.89 (d), 145.36 (s),
149.77 (s), 152.87 (s). 29Si NMR (60 MHz, C6D6) ꢆ 1.14, 1.57,
2.93, 90.89. UV–vis (hexane) ꢁmax 255 (" ¼ 5 ꢄ 104), 307
(7 ꢄ 103), 356 (1 ꢄ 104), 367 (2 ꢄ 104), and 384 (9 ꢄ 103) nm.
Anal. Calcd for C39H74Si8: C, 61.02; H, 9.72%. Found: C,
59.65; H, 9.81% [analyzed as a hydrolysis product of 1b (calcd
for C39H76OSi8: C, 59.62; H, 9.75%) due to its high sensitivity
to moisture]. High resolution FAB-MS m=z calcd for C39H74Si8
([M]þ): 766.3945, found: 766.3947 ([M]þ).
Preparation of 1-Bromo-1-{2,6-bis[bis(trimethylsilyl)meth-
yl]-4-[tris(trimethylsilyl)methyl]phenyl}-1,4-dihydro-1-sila-
naphthalene (3b).
(135.3 mg, 0.160 mmol) by the same procedure as that used for
Compound 3b was synthesized from 2b
3a. 3b (136.4 mg, 91%): colorless powder. mp. 220–222 ꢂC

984 Bull. Chem. Soc. Jpn., 78, No. 6 (2005)
BCSJ AWARD ARTICLE
Dimerization of 1a. In a glovebox filled with argon, 1a (32.4
mg, 0.0466 mmol) was dissolved in C6D6 (0.6 mL). The solution
was degassed and sealed in a 5 ꢇ NMR tube. After heating at 100
ꢂC for 12 h, the tube was opened. The solvent was evaporated and
hexane was added to the residue. Filtration of the reaction mixture
through CeliteÒ, followed by separation with GPLC (CHCl3) and
PTLC (hexane), afforded 4 (15.9 mg, 49%). 4: colorless powder.
mp. 144–148 ꢂC. 1H NMR (300 MHz, rt, CDCl3) ꢆ ꢁ0:25 (s, 9H),
ꢁ0:22 (s, 9H), ꢁ0:18 (s, 18H), 0.04 (s, 27H), 0.08 (s, 9H), 0.09 (s,
18H), 0.18 (s, 9H), 0.21 (s, 9H), 1.26 (d, 3J ¼ 10 Hz, 1H), 1.28 (s,
1H), 1.35 (s, 1H), 2.10–2.16 (m, 4H), 4.02 (d, 3J ¼ 7 Hz, 1H),
5.89 (d, 3J ¼ 11 Hz, 1H), 6.10 (d, 3J ¼ 8 Hz, 1H), 6.26–6.48
(m, 6H), 6.57–6.59 (m, 1H), 6.77–6.79 (m, 1H), 6.81–6.84 (m,
2H), 6.95–6.98 (m, 1H), 7.57–7.64 (m, 1H). 13C NMR (75 MHz,
rt, CDCl3) ꢆ 0.81 (q), 0.91 (q), 0.98 (q), 0.99 (q), 1.14 (q), 1.27
(q), 1.37 (q), 1.49 (q), 1.69 (q), 1.75 (q), 2.06 (q), 2.12 (q),
15.36 (d), 27.11 (d), 27.21 (d), 28.48 (d ꢄ 2), 30.30 (d), 30.46
(d), 42.28 (d), 122.89 (d), 122.93 (d), 123.18 (d), 123.23 (s),
125.82 (d), 125.85 (d), 127.60 (d), 127.84 (d), 127.86 (d),
127.95 (d), 128.32 (s), 128.59 (d), 128.66 (d), 129.53 (d),
131.21 (d), 133.40 (d), 133.81 (d), 134.81 (s), 135.40 (s),
140.57 (s), 143.87 (s), 144.46 (s), 144.88 (s), 148.91 (d), 152.39
(s), 152.54 (s), 152.83 (s), 152.99 (s). 29Si NMR (59 MHz, rt,
CDCl3) ꢆ ꢁ33:2, ꢁ24:6, 1.67, 1.71, 1.9, 1.98, 2.04, 2.1, 2.2,
2.3, 2.7. Anal. Calcd for C72H132Si14: C, 62.17; H, 9.56%. Found:
C, 61.85; H, 9.53%.
30.39 (d), 122.25 (d), 125.39 (s), 127.03 (d), 127.35 (d), 127.68
(d), 128.59 (d), 130.32 (d), 130.61 (d), 134.39 (d), 135.67 (s),
142.15 (s), 144.86 (s), 152.21 (s), 152.50 (s). 29Si NMR (59
MHz, rt, CDCl3) ꢆ ꢁ11:66, 1.65, 1.78, 1.84, 1.94. Anal. Calcd
for C36H68OSi7: C, 60.60; H, 9.61%. Found: C, 60.31; H, 9.75%.
Reaction of 1a with Methanol. To a solution of 1a (26.7 mg,
0.0384 mmol) in THF (2 mL), was added MeOH (0.5 mL) at room
temperature, and the solution was stirred for 30 min. After the
solvent was removed, the mixture was subjected to GPLC and
PTLC (hexane) to afford a mixture of 1-methoxy-1-{2,4,6-tris-
[bis(trimethylsilyl)methyl]phenyl}-1,4-dihydro-1-silanaphthalene
(6a) and 1-methoxy-1-{2,4,6-tris[bis(trimethylsilyl)methyl]phen-
yl}-1,2-dihydro-1-silanaphthalene (6b) (22.3 mg, total 80%),
and the ratio of 6a and 6b was 3:5 as judged by 1H NMR. The
mixture was separated into 3 portion by careful purification with
PTLC (hexane): pure 6b (the top; 6.3 mg), a mixture of 6a and
6b (the middle; 12.6 mg), and pure 6a (the bottom; 3.4 mg). 6a:
colorless powder. mp. 172–174 ꢂC. 1H NMR (300 MHz, rt,
CDCl3) ꢆ ꢁ0:17 (s, 18H), ꢁ0:01 (s, 9H), 0.01 (s, 9H), 0.03 (s,
18H), 1.28 (s, 1H), 2.61 (s, 1H), 2.62 (s, 1H), 3.09 (s, 3H),
3.62–3.81 (m, 2H), 6.14 (ddd, 3J ¼ 15 Hz, 4J ¼ 3 Hz, 4J ¼ 1
Hz, 1H), 6.23 (br s, 1H), 6.34 (br s, 1H), 7.00 (ddd, 3J ¼ 15
Hz, 3J ¼ 5 Hz, 3J ¼ 3 Hz, 1H), 7.16–7.21 (m, 2H), 7.30 (ddd,
3J ¼ 8 Hz, 3J ¼ 8 Hz, 4J ¼ 1:5 Hz, 1H), 7.53 (dd, 3J ¼ 8 Hz,
4J ¼ 3 Hz, 1H). 13C NMR (75 MHz, rt, CDCl3) ꢆ 0.67 (q), 0.74
(q), 0.77 (q), 0.90 (q), 0.99 (q), 1.27 (q), 26.76 (d), 26.96 (d),
30.32 (d), 36.14 (t), 49.56 (q), 122.38 (d), 123.49 (s), 125.74
(d), 127.48 (d), 127.72 (d), 128.66 (d), 129.10 (d), 133.93 (s),
135.04 (d), 144.66 (s), 144.84 (s), 146.75 (d), 152.89 (s), 153.20
(s). 29Si NMR (59 MHz, rt, CDCl3) ꢆ ꢁ24:62, 1.51, 1.55, 1.71,
1.78. Anal. Calcd for C37H70OSi7: C, 61.08; H, 9.70%. Found:
C, 60.84; H, 9.73%. 6b: colorless powder. mp. 192–194 ꢂC.
1H NMR (300 MHz, rt, CDCl3) ꢆ ꢁ0:16 (s, 18H), ꢁ0:01 (s,
9H), 0.02 (s, 9H), 0.028 (s, 9H), 0.030 (s, 9H), 1.28 (s, 1H),
1.84–1.86 (m, 2H), 2.38 (s, 1H), 2.41 (s, 1H), 3.21 (s, 3H),
6.03–6.10 (m, 1H), 6.23 (br s, 1H), 6.34 (br s, 1H), 6.42 (dd, 3J ¼
11 Hz, 4J ¼ 2 Hz, 1H), 7.10 (dd, 3J ¼ 7 Hz, 4J ¼ 2 Hz, 1H), 7.17
Reaction of 1a with H2O. To a THF solution (2 mL) of 1a
(30.0 mg, 0.0432 mmol) was added H2O (0.5 mL) at room tem-
perature, and the solution was stirred for 1.5 h. After the solvent
was removed, the reaction mixture was subjected to GPLC and
PTLC (hexane:THF = 10:1) to afford a mixture of 1-{2,4,6-tris-
[bis(trimethylsilyl)methyl]phenyl}-1,4-dihydro-1-silanaphthalene-
1-ol (5a) and 1-{2,4,6-tris[bis(trimethylsilyl)methyl]phenyl}-1,2-
dihydro-1-silanaphthalene-1-ol (5b) (21.6 mg, total 54%). The ra-
tio of 5a and 5b was 5:6, as judged by 1H NMR. Careful purifica-
tion by PTLC (hexane:THF = 10:1) resulted in the separation into
3 portions: pure 5a (the top; 5.4 mg), a mixture of 5a and 5b (the
middle; 13.4 mg), and pure 5b (the bottom; 2.8 mg). 5a: colorless
powder. mp. 181–183 ꢂC. 1H NMR (300 MHz, rt, CDCl3) ꢆ ꢁ0:14
(s, 18H), 0.00 (s, 18H), 0.037 (s, 9H), 0.041 (s, 9H), 1.30 (s, 1H),
1.83 (s, Si–OH, 1H), 2.51 (br s, 1H), 2.54 (br s, 1H), 3.62–3.78 (m,
3
3
3
(ddd, J ¼ 9 Hz, J ¼ 7 Hz, 4J ¼ 1 Hz, 1H), 7.33 (ddd, J ¼ 9
Hz, 3J ¼ 8 Hz, 4J ¼ 2 Hz, 1H), 7.50 (dd, 3J ¼ 8 Hz, 4J ¼ 1
Hz, 1H). 13C NMR (75 MHz, rt, CDCl3) ꢆ 0.75 (q), 0.76 (q),
0.96 (q), 1.09 (q), 1.33 (q), 14.67 (t), 26.91 (d), 27.19 (d), 30.33
(d), 49.89 (q), 122.29 (d), 124.90 (s), 126.75 (d), 127.34 (d),
128.00 (d), 128.74 (d), 130.17 (d), 130.80 (d), 132.23 (s),
134.93 (d), 143.00 (s), 144.73 (s), 152.49 (s), 152.78 (s).
29Si NMR (59 MHz, rt, CDCl3) ꢆ ꢁ9:62, 1.61, 1.73, 1.94. Anal.
Calcd for C37H70OSi7: C, 61.08; H, 9.70%. Found: C, 60.90; H,
9.71%.
3
4
4
2H), 6.26 (br s, 1H), 6.29 (ddd, J ¼ 15 Hz, J ¼ 2 Hz, J ¼ 2
Hz, 1H), 6.36 (br s, 1H), 6.92 (ddd, 3J ¼ 15 Hz, 3J ¼ 5 Hz, 3J ¼
4 Hz, 1H), 7.21 (m, 2H), 7.31 (ddd, 3J ¼ 8 Hz, 3J ¼ 8 Hz, 4J ¼ 2
Hz, 1H), 7.63 (dd, 3J ¼ 7 Hz, 4J ¼ 2 Hz, 1H). 13C NMR (75
MHz, rt, CDCl3) ꢆ 0.75 (q), 0.76 (q), 0.90 (q), 1.05 (q), 1.25
(q), 27.11 (d), 27.38 (d), 30.39 (d), 36.12 (t), 122.35 (d), 124.05
(s), 125.99 (d), 127.51 (d), 128.76 (d), 129.25 (d), 129.94 (d),
135.00 (d), 137.04 (s), 144.02 (s), 144.81 (s), 145.33 (d), 152.71
(s), 152.98 (s). 29Si NMR (59 MHz, rt, CDCl3) ꢆ ꢁ27:88, 0.60,
0.64, 0.72, 0.83. Anal. Calcd for C36H68OSi7: C, 60.60; H,
9.61%. Found: C, 60.40; H, 9.62%. 5b: colorless powder. mp.
199–200 ꢂC. 1H NMR (300 MHz, rt, CDCl3) ꢆ ꢁ0:13 (s, 18H),
ꢁ0:007 (s, 9H), 0.010 (s, 9H), 0.04 (s, 9H), 0.05 (s, 9H), 1.30
Reaction of 1a with Mesitonitrile Oxide. In a glovebox filled
with argon, 1a (42.7 mg, 0.0614 mmol) and mesitonitrile oxide
(30.3 mg, 0.188 mmol) were dissolved in THF (2 mL). After stir-
ring for a few minutes, the solvent was evaporated and hexane was
added to the residue. Filtration of the mixture through CeliteÒ, fol-
lowed by separation with GPLC (CHCl3) and PTLC (CHCl3/hex-
ane = 1/1), afforded 7 (23.5 mg, 45%ꢂ). 7: colorless powder. mp.
2
ꢂ
1
(s, 1H), 1.77–1.85 (m, 1H), 1.88 (s, Si–OH, 1H), 2.02 (ddd, J ¼
206–209 C. H NMR (300 MHz, 50 C, CDCl3) ꢆ ꢁ0:17 (br s,
18H), 0.05 (s, 9H), 0.06 (s, 9H), 0.14 (s, 9H), 0.16 (s, 9H), 1.39
(s, 1H), 1.99 (s, 3H), 2.20 (s, 3H), 2.22 (br s, 1H), 2.27 (s, 4H),
19 Hz, 3J ¼ 7 Hz, 4J ¼ 1 Hz, 1H), 2.30 (s, 2H), 6.01–6.08
3
(m, 1H), 6.25 (br s, 1H), 6.36 (br s, 1H), 6.42 (dd, J ¼ 11 Hz,
4J ¼ 1 Hz, 1H), 7.09 (dd, 3J ¼ 8 Hz, 4J ¼ 2 Hz, 1H), 7.19
3.45 (d, J ¼ 8 Hz, 1H), 5.85 (dd, J ¼ 11 Hz, J ¼ 8 Hz, 1H),
6.40 (br s, 1H), 6.49 (br s, 1H), 6.51 (d, 3J ¼ 11 Hz, 1H), 6.84
(br s, 2H), 7.13–7.39 (m, 3H), 7.69 (d, 3J ¼ 7 Hz, 1H). 13C NMR
(75 MHz, rt, CDCl3) ꢆ 0.20 (q), 0.52 (q), 0.63 (q), 0.78 (q), 1.55
(q), 1.86 (q), 19.89 (q), 20.07 (q), 21.06 (q), 28.89 (d), 29.34 (d),
3
3
3
3
4
3
(ddd, J ¼ 8 Hz, 3J ¼ 8 Hz, J ¼ 1 Hz, 1H), 7.34 (ddd, J ¼ 8
3
4
3
4
Hz, J ¼ 8 Hz, J ¼ 2 Hz, 1H), 7.59 (dd, J ¼ 8 Hz, J ¼ 1 Hz,
1H). 13C NMR (75 MHz, rt, CDCl3) ꢆ 0.76 (q), 0.77 (q), 0.81
(q), 0.90 (q), 1.14 (q), 1.27 (q), 18.53 (t), 27.34 (d), 27.66 (d),

A. Shinohara et al.
Bull. Chem. Soc. Jpn., 78, No. 6 (2005)
985
30.78 (d), 36.89 (d), 121.92 (d), 122.72 (d), 123.61 (s), 126.78 (d),
127.70 (d), 128.40 (d), 128.60 (d), 129.37 (s), 129.70 (d), 130.24
(s), 131.04 (d), 133.53 (d), 135.35 (d), 135.46 (s), 137.64 (s),
138.19 (s), 140.29 (s), 146.44 (s), 152.50 (s), 152.73 (s), 164.86
(s). 29Si NMR (59 MHz, rt, CDCl3) ꢆ 1.88, 1.96, 2.06, 2.31,
6.38. Anal. Calcd for C49H76OSi7: C, 64.49; H, 9.06%. Found:
C, 64.15; H, 9.22%.
ꢆ 0.71 (q), 0.86 (q), 0.95 (q), 1.15 (q), 1.23 (q), 28.82 (d), 29.12
(d), 30.85 (d), 62.77 (d), 100.00 (s), 122.01 (s), 122.62 (d),
126.86 (d), 127.14 (d), 127.58 (d), 128.57 (d), 135.12 (d),
137.26 (d), 139.91 (s), 142.62 (s), 146.92 (s), 147.00 (d), 153.52
(s), 153.83 (s). 29Si NMR (59 MHz, rt, CDCl3) ꢆ ꢁ16:3, 2.0,
2.1, 2.3. Anal. Calcd for C37H66Cl4Si7: C, 52.32; H, 7.83%.
Found: C, 52.04; H, 7.74%.
ꢂ
1
Reaction of 1a with Benzophenone. In a glovebox filled with
argon, 1a (39.5 mg, 0.0570 mmol) and benzophenone (33.0 mg,
0.182 mmol) were dissolved in THF (2 mL). After stirring for
12 h, the solvent was evaporated and hexane was added to the res-
idue. Filtration of the mixture through CeliteÒ, followed by sepa-
ration with GPLC (toluene) and PTLC (CHCl3/hexane = 1/10),
afforded 8 (30.0 mg, 60%). 8: colorless powder. mp. 209–210
ꢂC. 1H NMR (300 MHz, rt, CDCl3) ꢆ 0.04 (br s, 36H), 0.11 (s,
9H), 0.12 (s, 9H), 1.43 (s, 1H), 2.61 (br s, 1H), 2.96 (br s, 1H),
4.87 (dd, 3J ¼ 7 Hz, 4J ¼ 1 Hz, 1H), 6.44 (br s, 1H), 6.53 (br
s, 1H), 6.58 (dd, 3J ¼ 13 Hz, 4J ¼ 1 Hz, 1H), 6.83–7.35 (m,
13H), 7.63–7.66 (m, 2H). 13C NMR (75 MHz, rt, CDCl3) ꢆ 0.81
(q), 0.98 (q), 1.20 (q), 1.32 (q), 1.78 (q), 27.45 (d), 27.90 (d),
30.80 (d), 53.14 (d), 84.40 (s), 118.3 (s), 122.69 (d), 124.62 (d),
125.82 (d), 126.21 (d), 126.25 (d), 127.17 (d), 127.19 (d),
127.43 (d), 127.62 (d), 127.90 (d), 128.12 (d), 131.39 (d),
136.20 (d), 138.75 (s), 145.80 (s), 146.16 (s), 146.25 (s), 146.69
(s), 148.98 (d), 153.38 (s), 153.57 (s). 29Si NMR (59 MHz, rt,
CDCl3) ꢆ ꢁ23:6, 2.0, 2.1, 2.39, 2.44, 2.5. Anal. Calcd for
C53H78OSi7: C, 67.05; H, 8.73%. Found: C, 66.83; H, 9.00%.
Reaction of 1a with Elemental Selenium. To a solution of 1a
(54.7 mg, 0.0787 mmol) in THF (2 mL) was added elemental se-
lenium (51.8 mg, 0.648 mmol) at room temperature. The solution
was stirred for 48 h. After the solvent was removed in vacuo, pu-
rification of the residue by GPLC (toluene) and FCC (hexane) af-
forded 9b-{2,4,6-tris[bis(trimethylsilyl)methyl]phenyl}-3a,9b-di-
hydro-1,2,3-triselena-9b-silacyclopenta[ꢂ]naphthalene (9) (28.0
mg, 38%) as orange brown powder. 9: mp. 153–155 ꢂC. 1H NMR
(300 MHz, rt, C6D6) ꢆ 0.14 (s, 9H), 0.15 (s, 18H), 0.16 (s, 9H),
0.20 (s, 18H), 1.46 (s, 1H), 2.57 (s, 1H), 2.59 (s, 1H), 4.67 (d, 3J ¼
6 Hz, 1 H), 6.21–6.34 (m, 2H), 6.57 (br s, 1H), 6.66 (br s, 1H),
6.79 (dd, 3J ¼ 7 Hz, 4J ¼ 4 Hz, 1H), 7.00–7.03 (m, 2H), 8.03
(dd, 3J ¼ 5 Hz, 4J ¼ 3 Hz, 1H). 13C NMR (75 MHz, rt, C6D6)
ꢆ 0.99 (q), 1.39 (q), 1.46 (q), 1.74 (q), 1.87 (q), 29.93 (d), 30.22
(d), 31.20 (d), 37.23 (d), 122.61 (s), 123.45 (d), 128.53 (d),
128.66 (d), 128.71 (d), 130.12 (d), 130.59 (d), 131.67 (d),
135.17 (s), 137.96 (d), 141.60 (s), 146.57 (s), 153.94 (s), 154.32
(s). 29Si NMR (59 MHz, rt, C6D6) ꢆ 2.13, 2.52, 3.00, 21.56.
77Se NMR (57 MHz, rt, C6D6) ꢆ 332.4, 567.1, 743.3. Anal. Calcd
for C36H66Se3Si7: C, 46.37; H, 7.13%. Found: C, 46.37; H, 7.20%.
Reaction of 1a with CCl4. To a 2 mL of hexane solution of
1a (37.6 mg, 0.0542 mmol) was added CCl4 (0.1 mL). The solu-
tion was stirred for 12 h in the dark. The solvent was evaporated
and filtration of the mixture through CeliteÒ, followed by separa-
tion with GPLC (CHCl3) and PTLC (hexane), afforded cis-
and trans-1-chloro-1-{2,4,6-tris[bis(trimethylsilyl)methyl]phen-
yl}-4-trichloromethyl-1,4-dihydro-1-silanaphthalene, cis-10 (16.2
mg, 35%) and trans-10 (15.9 mg, 35%).
trans-10: colorless powder. mp. 225–226 C. H NMR (300
MHz, rt, CDCl3) ꢆ ꢁ0:14 (s, 9H), ꢁ0:02 (s, 9H), 0.03 (s, 9H),
0.04 (s, 9H), 0.14 (s, 9H), 0.16 (s, 9H), 1.31 (s, 1H), 2.58 (s,
3
1H), 2.63 (s, 1H), 4.65 (d, J ¼ 7 Hz, 1H), 6.12 (br s, 1H), 6.35
3
3
3
(br s, 1H), 6.83 (d, J ¼ 14 Hz, 1H), 7.15 (dd, J ¼ 14 Hz, J ¼
7 Hz, 1H), 7.38–7.53 (m, 3H), 8.17 (dd, J ¼ 8 Hz, 4J ¼ 2 Hz,
3
1H). 13C NMR (75 MHz, rt, CDCl3) ꢆ 0.87 (q), 1.00 (q), 1.16
(q), 1.63 (q), 1.88 (q), 28.06 (d), 28.65 (d), 30.52 (d), 63.06 (d),
102.04 (s), 122.87 (d), 124.10 (s), 127.67 (d), 128.62 (d),
128.93 (d), 133.40 (d), 138.06 (d), 138.83 (d), 139.37 (s),
140.87 (s), 143.44 (d), 145.95 (s), 152.09 (s), 152.72 (s).
29Si NMR (59 MHz, rt, CDCl3) ꢆ ꢁ22:4, 2.0, 2.3. Anal. Calcd
for C37H66Cl4Si7: C, 52.32; H, 7.83%. Found: C, 51.92; H, 7.83%.
X-ray Structural Determination. Crystallographic data for
[4 1.5CH2Cl2], 8, cis-10, and trans-10 are collected in Table 4.
ꢅ
Single crystals were grown at room temperature by the slow evap-
oration of the corresponding saturated solution in CH2Cl2/
CH3CN for [4 1.5CH2Cl2], and CHCl3/CH3CN for 8, cis-10,
ꢅ
and trans-10, respectively. The intensity data were collected on
a Rigaku/MSC Mercury CCD diffractometer with graphite-mono-
ꢂ
chromated Mo Kꢂ radiation (ꢁ ¼ 7:1071 A) to 2ꢈmax ¼ 50 at 93
K. The structures were solved by direct methods (SHELXS-97)
and refined by full-matrix least-squares procedures on F2 for all
reflections (SHELX-97).29 The structures of the disordered
CH2Cl2 molecules in [4 1.5CH2Cl2] were restrained using the
ꢅ
SADI and ISOR instructions. All non-hydrogen atoms were re-
fined anisotropically. All hydrogen atoms in [4 1.5CH2Cl2] and
ꢅ
8 were placed using AFIX instructions. All hydrogen atoms in
cis-10 were refined isotropically. Some hydrogen atoms of
trans-10 were refined isotropically, while the other hydrogen
atoms were placed using AFIX instructions. Crystallographic data
have been deposited at the Cambridge Crystallographic Data Cen-
tre (Nos. CCDC 257052 for [4 1.5CH2Cl2], CCDC 257053 for 8,
ꢅ
CCDC 257054 for cis-10, and CCDC 257055 for trans-10). Cop-
ies of the data can be obtained free of charge via http//www.ccdc.
cam.ac.uk/conts/retrieving.html (or from the Cambridge Crystal-
lographic Data Centre, 12, Union Road, Cambridge, CB2 1EZ,
UK; Fax: +44 1223 336033; e-mail: deposit@ccdc.cam.ac.uk).
This work was partially supported by Grants-in-Aid for
COE Research on Elements Science (No. 12CE2005), Scien-
tific Research on Priority Areas (No. 14078213), Scientific Re-
search A (No. 1424064), and the 21st Century COE Program
on Kyoto University Alliance for Chemistry (No. 14212101)
from the Ministry of Education, Culture, Sports, Science
and Technology, Japan. We thank Central Glass Co., Ltd.,
for the generous gift of tetrafluorosilane. We are grateful to
Professor Yukio Furukawa, Waseda University, for the mea-
surement of FT-Raman spectra.
cis-10: colorless powder. mp. 222–224 ꢂC. 1H NMR (300
MHz, rt, CDCl3) ꢆ ꢁ0:08 (s, 9H), ꢁ0:05 (s, 9H), 0.05 (s, 36H),
1.33 (s, 1H), 2.38 (br s, 1H), 2.43 (br s, 1H), 4.52 (dd, 3J ¼ 4
Hz, 4J ¼ 2 Hz, 1H), 6.28 (br s, 1H), 6.40 (br s, 1H), 6.58 (dd, 3J ¼
13 Hz, 4J ¼ 2 Hz, 1H), 7.21 (dd, 3J ¼ 13 Hz, 3J ¼ 4 Hz, 1H),
7.37–7.41 (m, 2H), 7.92 (dd, 3J ¼ 5 Hz, 4J ¼ 4 Hz, 1H), 8.04
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