Synthesis of silole skeletons via metathesis reactions

Article abstract of DOI:10.1055/s-2008-1032096

Silole skeletons are constructed by ring-closing olefin metathesis of silicon-tethered dienes and trienes. A silicon-tethered enyne is also converted to a 2-alkenyl-1-silaindene via ruthenium-catalyzed ring-closing enyne metathesis. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1055/s-2008-1032096

LETTER
561
Synthesis of Silole Skeletons via Metathesis Reactions
S
ynthesis of Sil
a
ole Skeleto
k
ns via
M
eta
t
a
hesis React
n
ions ori Matsuda, Yoshiyuki Yamaguchi, Masahiro Murakami*
Department of Synthetic Chemistry and Biological Chemistry, Kyoto University, Katsura, Kyoto 615-8510, Japan
Fax +81(75)3832752; E-mail: murakami@sbchem.kyoto-u.ac.jp
Received 6 November 2007
Dedicated to the memory of the late Professor Emeritus Makoto Kumada of Kyoto University, who passed away on June 28, 2007
by the use of Ru-II, which afforded 2a quantitatively.
When Mo was used as the catalyst, the RCM occurred at
room temperature, giving 2a in 89% yield. Interestingly,
a different catalyst profile was observed with 3-methoxy-
phenyl derivative 1b: Whereas similar results were ob-
tained with the ruthenium complexes Ru-I and Ru-II, the
more oxophilic molybdenum catalyst Mo failed to pro-
mote the RCM, possibly due to the coordination of the
ether oxygen (entry 2).
Abstract: Silole skeletons are constructed by ring-closing olefin
metathesis of silicon-tethered dienes and trienes. A silicon-tethered
enyne is also converted to a 2-alkenyl-1-silaindene via ruthenium-
catalyzed ring-closing enyne metathesis.
Key words: metathesis, silole, ruthenium, molybdenum, ring clo-
sure
The ring-closing metathesis (RCM) reaction has emerged
as one of the most powerful methods for the construction
of unsaturated carbo- and heterocyclic frameworks.1
Whereas the RCM has been exploited in a number of nat-
ural product syntheses,2 its applicability to the synthesis
of p-conjugated functional materials remains to be ex-
plored. The potential of silole (silacyclopentadiene)
derivatives3 as electron-transporting materials in OLEDs4
prompted us to develop a series of transition-metal-cata-
lyzed reactions constructing silole skeletons.5 Herein, we
report a new synthetic approach to silole derivatives, in
which the silole C2–C3 double bond is created by RCM.6
In addition to the 2-aryl-1-silaindenes 2a and 2b, 2-meth-
yl-1-silaindene 2c was obtained in good yield from iso-
propenyl(2-vinylphenyl)silane 1c (entry 3). The reaction
producing 3-methyl-1-silaindene 2d was rather sluggish
with both Ru-II and Mo (entry 4). In the case of
R = R¢ = H, unsubstituted 1-silaindene 2e was produced
in 89% with Mo, whereas the ruthenium catalyst Ru-II
gave poor results (entry 5).10 The RCM of 1f forming a
tetrasubstituted olefin occurred only with the ruthenium
complex, albeit in low yield (entry 6).
Thus, the RCM approach proved to function well for the
synthesis of 2-substituted 1-silaindenes. Next, other sila-
The RCM reaction of dimethyl(alkenyl)(2-alkenylphen-
yl)silanes 17 with several substitution patterns was exam-
ined (Table 1).8,9 Initially, the three conventional
metathesis catalysts, i.e., the first-generation Grubbs cata-
lyst (Ru-I), the second-generation Grubbs catalyst (Ru-
II), and Schrock catalyst (Mo, Figure 1), were compared
in the reactions of 1a and 1b having a phenyl group and a
3-methoxyphenyl group, respectively, as the substituent
R.
Table 1 Comparison of Metathesis Catalysts for the RCM of Sila-
dienes 1a-fa
R´
R´
catalyst (5 mol%)
R
toluene
Si
Si
Me2
Me2
R
2
1
Entry Siladiene
2
Yield (%)b
MesN NMes
PCy3
NAr
Mo
Cl
Cl
Cl
Cl
1
R
R¢
H
Ru-I Ru-II Mo
Ru
Ru
CMe2Ph
RO
RO
Ph
Ph
PCy3
PCy3
1
2
3
4
5
6
1a
1b
1c
1d
1e
1f
Ph
2a
2b
2c
2d
2e
2f
(17)
(15)
Quant. 89
Grubbs 1st
(Ru-I)
Grubbs 2nd
(Ru-II)
Schrock
(Mo)
3-MeOC6H4
H
96
91
0c
d
PCy3 = tricyclohexylphosphine; Mes = 2,4,6-
trimethylphenyl;
Ar = 2,6-diisopropylphenyl; R = CMe(CF3)2
Me
H
H
-
82
(26)e
(89)
0c
d
Me
H
-
(16)
(14)
(14)
Figure 1 Metathesis catalysts
d
H
-
d
Me
Me
-
The RCM of 1a in toluene took place at 80 °C in the pres-
ence of Ru-I, giving 2-phenyl-1-silaindene 2a in 17%
a Conditions using Ru-I: 80 °C, 20–38 h. Conditions using Ru-II:
yield (entry 1). The efficiency was significantly improved 80 °C, 2–24 h. Conditions using Mo: r.t., 2–20 h.
b Isolated yields by preparative TLC. Yields in parentheses refer to
NMR yields.
SYNLETT 2008, No. 4, pp 0561–0564
Advanced online publication: 12.02.2008
DOI: 10.1055/s-2008-1032096; Art ID: U10707ST
© Georg Thieme Verlag Stuttgart · New York
x
x.
x
x.
2
0
0
8
c Conditions: 80 °C, 2–5 h.
d Not examined.
e Conditions: 50 °C, 4 h.

562
T. Matsuda et al.
LETTER
dienes 1 having various bridging groups (X) and substitu-
ents (R) were subjected to the RCM reaction using Ru-II
as the catalyst of choice, and the results are summarized
in Table 2. 1-Silaindenes 2g and 2h, having 4-fluorophe-
nyl and 2-naphthyl groups at the 2-position, were obtained
in excellent yields from the corresponding siladienes 1g
and 1h, respectively (entries 1 and 2). Diethylsilylene and
methylphenylsilylene tethers were tolerated, but required
higher catalyst loading to attain good yields (entries 3 and
4). Germadiene 1k of analogous structure also underwent
a RCM reaction to afford 2-germaindene 2k in high yield
(entry 5). The regioisomers of methylenedioxy-substitut-
ed substrates exhibited significantly different reactivity
(entries 6 and 7): Whereas 4,5-methylenedioxy derivative
1l reacted in excellent yield, the same functionality at the
3,4-positions markedly retarded the reaction.
Ru-II (5 mol%)
toluene, 80 °C
Ph
Si
Me2
Si
Ph
Ph
Pr
Me2
3a
4a 66% (NMR)
Ru-II (5 mol%)
toluene, 80 °C
Ph
Si
Si
Me2
Me2
4b 98% (isolated)
3b
Scheme 1
Ru-II (5 mol%)
toluene
80 °C, 20 h
Si
Me2
5
Table 2 Synthesis of 1-Silaindenes 2 by RCM of 1 Using Ru-IIa
Pr
+
Ru-II (5 mol%)
R
Si
Pr
Si
Me2
toluene, 80 °C
X
Me2
X
R
6 34%
7 34%
1
2
Scheme 2 Enyne RCM
Entry 1
X
R
2
Yield
(%)b
which a dimethylsilylene tether connects o-styryl and
pent-1-ynyl groups resulted in ring closure but in both exo
and endo modes13 to afford a 1:1 mixture of 1-silaindene
6 and 1,2-dihydro-1-silanaphthalene 7 (Scheme 2).14
1
2
3
4
5
1g
SiMe2
4-FC6H4
2g
99
1h SiMe2
2-Naphthyl 2h
98, 81c
72d
1i
1j
SiEt2
Ph
2i
The photophysical properties of selected products are list-
ed in Table 3. For silaindenes, fluorescence maxima at
387–418 nm were observed upon irradiation at 250 nm in
hexane. Considerably high fluorescence quantum effi-
ciency (FF) was observed for 2-naphthylsilaindene 2h.
Silole 4b had longer absorption and fluorescence maxima
with a larger Stokes shift in comparison to the silaindenes.
SiMePh Ph
2j
2k
92d
1k GeMe2 Ph
92
O
4
O
Ph
6
7
1l
96
O
(2l)
O
Si
Me2
O
5
Si
Me2
Ph
Table 3 Photophysical Properties of Products
O
O
Product
UV/visa
Fluorescenceb
3
O
1m
(16)e
4
Ph
labs
log e
4.92
4.81
4.89
4.91
lem
FF
Si
Me2
Si
2a
2h
2l
333
340
354
389
387
396
418
474
0.83
0.96
0.75
0.33
Me2
Ph
(2m)
a Unless otherwise noted, siladiene 1 was reacted in the presence of
5 mol% Ru-II in toluene at 80 °C for 2-10 h.
b Isolated yields. Yields in parentheses refer to NMR yields.
c Results with 5 mol% Mo in toluene at r.t. for 4 h.
d Additional catalyst (5 mol%) was added after 2 h.
e Conditions: 110 °C, 25 h.
4b
a Measured in CHCl3.
b Meaured in hexane. Determined with reference to quinine sulfate in
0.1 N H2SO4 and anthracene in EtOH (excited at 250 nm).
The RCM occurred as well when the o-phenylene tether
of 1 was replaced by a cis-1,2-vinylene tether, as exempli-
fied in Scheme 1. 2,3,5-Trisubstituted siloles 4a and 4b
were obtained from the corresponding silatrienes 3
(Scheme 1).11
A ring-closing enyne metathesis reaction12 provides an al-
ternative viable synthetic route to silicon-containing cy-
clic skeletons. The Ru-II-catalyzed reaction of enyne 5 in
In summary, the reaction described herein provides a
unique method to prepare fused and densely substituted
silole compounds, some of which, like 4a and 4b, are dif-
ficult to synthesize using current synthetic methods.15
This route would therefore be of significant utility in the
fields of organic photonics and electronics.
Synlett 2008, No. 4, 561–564 © Thieme Stuttgart · New York

LETTER
Synthesis of Silole Skeletons via Metathesis Reactions
563
264.1334; found: 264.1335.
Acknowledgment
Isopropenyldimethyl(2-vinylphenyl)silane (1c)
1H NMR (300 MHz, CDCl3): d = 0.40 (s, 6 H), 1.80 (t,
This work was supported by a Grant-in-Aid for Scientific Research
for Young Scientist (B) (No. 19750074) from the Ministry of Edu-
cation, Culture, Sports, Science and Technology, Japan and the
Ogasawara Foundation for the Promotion of Science and Enginee-
ring.
J = 1.4 Hz, 3 H), 5.22 (dd, J = 10.8, 1.2 Hz, 1 H), 5.36 (q,
J = 0.9 Hz, 1 H), 5.64 (dd, J = 17.3, 1.2 Hz, 1 H), 5.69 (sext,
J = 1.7 Hz, 1 H), 7.04 (dd, J = 17.3, 10.8 Hz, 1 H), 7.25 (dt,
J = 1.3, 7.3 Hz, 1 H), 7.37 (dt, J = 1.5, 7.5 Hz, 1 H), 7.50 (dd,
J = 7.4, 1.4 Hz, 1 H), 7.56 (d, J = 7.5 Hz, 1 H). 13C NMR (75
MHz, CDCl3): d = –2.1, 22.6, 114.7, 125.0, 126.5, 126.9,
129.5, 135.0, 135.7, 138.0, 144.1, 146.6. HRMS (EI): m/z
[M]+ calcd for C13H18Si: 202.1178; found: 202.1173.
Dimethyl(1-phenylvinyl)(2-vinylphenyl)germane (1k)
1H NMR (300 MHz, CDCl3): d = 0.57 (s, 6 H), 5.22 (dd,
J = 10.5, 1.5 Hz, 1 H), 5.55 (d, J = 2.1 Hz, 1 H), 5.63 (dd,
J = 17.4, 1.2 Hz, 1 H), 6.03 (d, J = 2.1 Hz, 1 H), 6.98 (dd,
J = 17.4, 11.1 Hz, 1 H), 7.15–7.28 (m, 6 H), 7.32–7.38 (m, 1
H), 7.49–7.53 (m, 1 H), 7.56–7.60 (m, 1 H). 13C NMR (75
MHz, CDCl3): d = –1.1, 115.0, 125.1, 126.0, 126.6
[overlapping], 127.1, 128.2, 129.1, 134.3, 137.8, 139.0,
143.2, 143.5, 152.2. HRMS (EI): m/z [M]+ calcd for
C18H20Ge: 310.0777; found: 310.0786.
References and Notes
(1) (a) Armstrong, S. K. J. Chem. Soc., Perkin Trans. 1 1998,
371. (b) Grubbs, R. H.; Chang, S. Tetrahedron 1998, 54,
4413. (c) Fürstner, A. Angew. Chem. Int. Ed. 2000, 39,
3012. (d) Schrock, R. R.; Hoveyda, A. H. Angew. Chem. Int.
Ed. 2003, 42, 4592. (e) Handbook of Metathesis; Grubbs, R.
H., Ed.; Wiley-VCH: Weinheim, 2003. (f) Deiters, A.;
Martin, S. F. Chem. Rev. 2004, 104, 2199. (g)McReynolds,
M. D.; Dougherty, J. M.; Hanson, P. R. Chem. Rev. 2004,
104, 2239.
(2) (a) Schuster, M.; Blechert, S. Angew. Chem., Int. Ed. Engl.
1997, 36, 2036. (b) Fürstner, A. Angew. Chem. Int. Ed.
2000, 39, 3012. (c) Felpin, F.-X.; Lebreton, J. Eur. J. Org.
Chem. 2003, 3693. (d) Nicolaou, K. C.; Bulger, P. G.;
Sarlah, D. Angew. Chem. Int. Ed. 2005, 44, 4490.
(3) For reviews, see: (a) Yamaguchi, S.; Tamao, K. J. Chem.
Soc., Dalton Trans. 1998, 3693. (b) Hissler, M.; Dyer, P.
W.; Réau, R. Coord. Chem. Rev. 2003, 244, 1.
(4) For recent reviews, see: (a) Hughes, G.; Bryce, M. R. J.
Mater. Chem. 2005, 15, 94. (b) Kulkarni, A. P.; Tonzola, C.
J.; Babel, A.; Jenekhe, S. A. Chem. Mater. 2004, 16, 4556.
(c) Shirota, Y.; Kageyama, H. Chem. Rev. 2007, 107, 953.
(5) (a) Matsuda, T.; Kadowaki, S.; Goya, T.; Murakami, M.
Org. Lett. 2007, 9, 133. (b) Matsuda, T.; Kadowaki, S.;
Murakami, M. Chem. Commun. 2007, 2627.
(6) For synthesis of other heteroles by RCM, see: (a) Fujimura,
O.; Fu, G. C.; Grubbs, R. H. J. Org. Chem. 1994, 59, 4029.
(b) Arisawa, M.; Terada, Y.; Nakagawa, M.; Nishida, A.
Angew. Chem. Int. Ed. 2002, 41, 4732. (c) van Otterlo, W.
A. L.; Morgans, G. L.; Madeley, L. G.; Kuzvidza, S.;
Moleele, S. S.; Thornton, N.; de Koning, C. B. Tetrahedron
2005, 61, 7746. For RCM forming aromatic compounds,
see: (d) Iuliano, A.; Piccioli, P.; Fabbri, D. Org. Lett. 2004,
6, 3711. (e) Bonifacio, M. C.; Robertson, C. R.; Jung, J.-Y.;
King, B. T. J. Org. Chem. 2005, 70, 8522. For a review,
see: (f) Donohoe, T. J.; Orr, A. J.; Bingham, M. Angew.
Chem. Int. Ed. 2006, 45, 2664.
(8) For intermolecular cross-metathesis between vinylsilanes
and styrenes, see: (a) Pietraszuk, C.; Marciniec, B.; Fischer,
H. Organometallics 2000, 19, 913. (b) Pietraszuk, C.;
Fischer, H.; Rogalski, S.; Marciniec, B. J. Organomet.
Chem. 2005, 690, 5912. (c) Marciniec, B. Acc. Chem. Res.
2007, 40, 943.
(9) General Procedure for Ring-Closing Metathesis
1,1-Dimethyl-2-phenyl-1-silaindene (2a)14
To Schrock catalyst (11.5 mg, 0.015 mmol) was added a
solution of 1a (76.45 mg, 0.289 mmol) in toluene (5 mL),
and the mixture was stirred at r.t. for 2 h. The reaction
mixture was taken up with hexane and passed through a pad
of Florisil®. Removal of volatile materials afforded 2a (61.4
mg, 0.257 mmol, 89%): 1H NMR (300 MHz, CDCl3):
d = 0.48 (s, 6 H), 7.20–7.40 (m, 6 H), 7.49–7.56 (m, 4 H).
13C NMR (75 MHz, CDCl3): d = –3.1, 124.3, 126.4, 126.6,
127.0, 128.7, 130.0, 131.7, 138.2, 139.0, 141.1, 145.3,
148.8. 29Si NMR (79 MHz, CDCl3): d = –15.9. HRMS (EI):
m/z [M]+ calcd for C16H16Si: 236.1021; found: 236.1019.
2-(3-Methoxyphenyl)-1,1-dimethyl-1-silaindene (2b)
To Grubbs second-generation catalyst (8.7 mg, 0.010 mmol)
was added a solution of 1b (58.62 mg, 0.199 mmol) in
toluene (2 mL), and the mixture was stirred at 80 °C for 2 h.
The reaction mixture was taken up with hexane and passed
through a pad of Florisil® (hexane–EtOAc = 10:1). After
removal of volatile materials, the residue was subjected to
preparative thin-layer chromatography to give 2b (50.66 mg,
0.190 mmol, 96%): 1H NMR (300 MHz, CDCl3): d = 0.49 (s,
6 H), 3.87 (s, 3 H), 6.79–6.85 (m, 1 H), 7.04–7.11 (m, 2 H),
7.19–7.39 (m, 4 H), 7.53–7.57 (m, 2 H). 13C NMR (75 MHz,
CDCl3): d = –3.1, 55.2, 111.9, 112.4, 119.3, 124.3, 126.7,
129.6, 130.0, 131.7, 138.3, 140.5, 141.5, 145.2, 148.7,
159.8. HRMS (EI): m/z [M]+ calcd for C17H18OSi: 266.1127;
found: 266.1121.
(7) Preparation of Siladienes 1
Dimethyl(1-phenylvinyl)(2-vinylphenyl)silane (1a)
To a solution of chlorodimethyl(2-vinylphenyl)silane (2.0 g,
10.2 mmol) in THF (10 mL) was added a solution of (1-
phenylvinyl)magnesium bromide in THF, which was
prepared from a-bromostyrene (5.0 g, 27.3 mmol) and Mg
(0.68 g, 28 mmol) in THF (20 mL) at r.t. for 3 h, at 0 °C.
After the mixture was stirred at r.t. for 10 h, the volatile
materials were removed under reduced pressure. The residue
was quenched by sat. NH4Cl aq solution, and extracted with
hexane. The extract was dried over MgSO4 and
1,1,2-Trimethyl-1-silaindene (2c)
1H NMR (300 MHz, CDCl3): d = 0.28 (s, 6 H), 2.02 (d,
J = 1.5 Hz, 3 H), 6.86 (q, J = 1.5 Hz, 1 H), 7.10–7.15 (m, 2
H), 7.24–7.30 (m, 1 H), 7.46 (d, J = 6.9 Hz, 1 H). 13C NMR
(75 MHz, CDCl3): d = –4.6, 17.4, 122.8, 125.6, 129.7, 131.6,
138.1, 142.7, 144.6, 149.5. HRMS (EI): m/z [M]+ calcd for
C11H14Si: 174.0865; found: 174.0864.
concentrated. The residue was purified by column
chromatography on silica gel(hexane). Further purification
by gel-permeation chromatography (GPC) gave 1a (500 mg,
19%): 1H NMR (300 MHz, CDCl3): d = 0.45 (s, 6 H), 5.22
(dd, J = 11.0, 1.3 Hz, 1 H), 5.61 (dd, J = 17.4, 1.3 Hz, 1 H),
5.69 (d, J = 2.9 Hz, 1 H), 6.01 (d, J = 2.9, 1 H), 7.07–7.29
(m, 7 H), 7.35–7.41 (m, 1 H), 7.54–7.59 (m, 2 H). 13C NMR
(75 MHz, CDCl3): d = –1.0, 114.9, 125.2, 126.4, 126.8,
126.9, 128.1, 129.0, 129,6, 135.1, 136.0, 138.0, 134.9,
144.0, 151.5. HRMS (EI): m/z [M]+ calcd for C18H20Si:
1,1,3-Trimethyl-1-silaindene (2d)
1H NMR (300 MHz, CDCl3): d = 0.29 (s, 6 H), 2.22 (s, 3 H),
5.92 (s, 1 H), 7.21–7.27 (m, 1 H), 7.30–7.40 (m, 2 H), 7.51–
7.55 (m, 1 H). 13C NMR (75 MHz, CDCl3): d = –4.0, 19.6,
121.2, 126.5, 127.8, 129.4, 131.2, 139.8, 149.9, 156.2. 29Si
Synlett 2008, No. 4, 561–564 © Thieme Stuttgart · New York

564
T. Matsuda et al.
LETTER
NMR (79 MHz, CDCl3): d = –19.4. HRMS (EI): m/z [M]+
calcd for C11H14Si: 174.0865; found 174.0864.
1H NMR (300 MHz, CDCl3): d = 0.37 (s, 6 H), 2.14 (quin,
J = 7.2 Hz, 2 H), 2.48–2.59 (m, 4 H), 7.12–7.43 (m, 6 H). 13
C
1,1-Diethyl-2-phenyl-1-silaindene (2i)
NMR (75 MHz, CDCl3): d = –3.7, 27.0, 32.7, 32.8, 125.9,
126.4, 128.6, 134.9, 139.5, 142.9, 147.5, 161.4. HRMS–
FAB: m/z [M]+ calcd for C15H18Si: 226.1178; found:
226.1187.
1H NMR (300 MHz, CDCl3): d = 0.85–1.15 (m, 10 H), 7.18–
7.58 (m, 10 H). 13C NMR (75 MHz, CDCl3): d = 4.3, 7.5,
124.2, 126.39, 126.45, 126.9, 128.6, 129.9, 132.3, 136.3,
139.5, 142.4, 143.7, 149.7. 29Si NMR (79 MHz, CDCl3):
d = –8.7. HRMS (EI): m/z [M]+ calcd for C18H20Si:
264.1334; found 264.1332.
2-Phenyl-4,5-dihydronaphtho[1,2-b]silole (4b)
1H NMR (300 MHz, CDCl3): d = 0.55 (s, 6 H), 2.59 (t,
J = 8.4 Hz, 2 H), 2.92 (t, J = 8.1 Hz, 2 H), 7.08–7.50 (m, 10
H). 13C NMR (75 MHz, CDCl3): d = –2.7, 26.3, 28.4, 125.7,
126.1, 126.2, 126.6, 126.8, 127.86 128.7, 134.2, 134.6,
135.9, 138.7, 140.9, 144.7, 152.2. 29Si NMR (79 MHz,
CDCl3): d = –16.2. HRMS (EI): m/z [M]+ calcd for C20H20Si:
288.1334; found: 288.1330.
1,1-Dimethyl-2-phenyl-1-germaindene (2k)
1H NMR (300 MHz, CDCl3): d = 0.67 (s, 6 H), 7.20–7.41
(m, 6 H), 7.47–7.58 (m, 4 H). 13C NMR (75 MHz, CDCl3):
d = –2.2, 125.0, 126.6, 126.8, 127.1, 128.7, 129.3, 131.8,
137.8, 139.3, 140.5, 147.6, 148.0. HRMS (EI): m/z [M]+
calcd for C16H16Ge: 282.0464; found: 282.0469.
(12) (a) Poulsen, C. S.; Madsen, R. Synthesis 2003, 1. (b) Diver,
S. T.; Giessert, A. J. Chem. Rev. 2004, 104, 1317. (c) Mori,
M. J. Mol. Catal. A: Chem. 2004, 213, 73. (d) Van de
Weghe, P.; Bissert, P.; Blanchard, N.; Eustache, J. J.
Organomet. Chem. 2006, 691, 5078. (e) Villar, H.; Frings,
M.; Bolm, C. Chem. Soc. Rev. 2007, 36, 55.
(13) For the examples of enyne RCM forming both exo and endo
products, see: (a) Kitamura, T.; Sato, Y.; Mori, M. Adv.
Synth. Catal. 2002, 344, 678. (b) Hansen, E. C.; Lee, D. J.
Am. Chem. Soc. 2003, 125, 9582.
(10) The inferior results of the reaction of 1d and 1e with Ru-II
may be attributed to b-silyl elimination from a
ruthenacyclobutane intermediate, which formes a
nonalkylidene ruthenium complex that no longer exhibits
any RCM activity. See: (a) Pietraszuk, C.; Fischer, H.
Chem. Commun. 2000, 2463. (b) Pietraszuk, C.; Fischer, H.;
Rogalski, S.; Marciniec, B. J. Organomet. Chem. 2005, 690,
5912.
(11) Dimethyl(1-phenylvinyl)(2-vinylcyclopent-1-enyl)silane
(3a)
(14) 1,1-Dimethyl-2-(pent-1-en-2-yl)-1-silaindene (6) and 1,1-
Dimethyl-2-methylene-3-propyl-1,2-dihydro-1-
silanaphthalene (7)
A solution of (2-vinylcyclopent-1-enyl)lithium in THF,
which was prepared from 1-bromo-2-vinylcyclopent-1-ene
(0.69 g, 3.99 mmol) and n-BuLi in hexane (1.55 M, 2.8 mL,
4.34 mmol) in THF (10 mL) at –78 °C for 1 h, was added to
a solution of chlorodimethyl(1-phenylvinyl)silane (0.697 g,
3.54 mmol) in THF (10 mL) at 0 °C. After the mixture was
stirred at r.t. for 10 h, the volatile materials were removed
under reduced pressure. The residue was quenched by sat.
NH4Cl aq solution, and extracted with hexane. The extract
was dried over MgSO4 and concentrated. The residue was
purified by column chromatography on silica gel (hexane) to
afford 3a (0.32 mg, 32%): 1H NMR (300 MHz, CDCl3):
d = 0.29 (s, 6 H), 1.82 (quin, J = 7.5 Hz, 2 H), 2.47–2.60 (m,
4 H), 5.09 (d, J = 10.7 Hz, 1 H), 5.13 (d, J = 17.1 Hz, 1 H),
5.65 (d, J = 3.0 Hz, 1 H), 5.92 (d, J = 3.0 Hz, 1 H), 6.80 (dd,
J = 17.1, 10.7 Hz, 1 H), 7.15–7.30 (m, 5 H). 13C NMR (75
MHz, CDCl3): d = –1.2, 23.6, 34.6, 39.3, 115.3, 126.6,
127.0. 128.2. 128.3, 134.3, 140.9, 144.5, 151.9, 152,7.
HRMS–FAB: m/z calcd for C17H22Si [M+] 254.1491; found:
254.1476.
The title compounds (45.63 mg, 67%, 6/7 = 50:50) were
obtained from enyne RCM of 5 (67.8 mg) using Ru-II. The
isomers were separated by HPLC.
Compound 6: 1H NMR (300 MHz, CDCl3): d = 0.31 (s, 6 H),
0.97 (t, J = 7.5 Hz, 3 H), 1.59 (sext, J = 7.5 Hz, 2 H), 2.43 (t,
J = 7.8 Hz, 2 H), 5.61 (d, J = 1.5 Hz, 1 H), 6.03 (d, J = 1.5
Hz, 1 H), 6.29 (s, 1 H), 7.10–7.20 (m, 2 H), 7.25–7.31 (m, 1
H), 7.48 (d, J = 0.6 Hz, 1 H). 13C NMR (75 MHz, CDCl3):
d = –1.3, 14.1, 22.4, 35.9, 124.7, 126.0, 128.9, 129.2, 129.6,
133.3, 133.8, 140.2, 141.9, 145.0. HRMS (EI): m/z [M]+
calcd for C15H20Si: 228.1334; found: 228.1335.
Compound 7: 1H NMR (300 MHz, CDCl3): d = 0.43 (s, 6 H),
1.00 (t, J = 7.5 Hz, 3 H), 1.61 (sext, J = 7.5 Hz, 2 H), 2.40 (t,
J = 7.8 Hz, 2 H), 5.08 (d, J = 6.6 Hz, 2 H), 7.16–7.35 (m, 4
H), 7.52–7.54 (m, 1 H). 13C NMR (75 MHz, CDCl3): d =
–2.9, 14.0, 21.6, 35.9, 115.0, 124.2, 126.5, 129.9, 131.6,
138.3, 140.5, 146.8, 147.3, 149.0. HRMS (EI): m/z [M]+
calcd for C15H20Si: 228.1334; found: 228.1333.
Dimethyl(1-phenylvinyl)(2-vinyl-3,4-dihydronaph-
thalen-1-yl)silane (3b)
(15) For the known synthetic methods of silole, silaindene
derivatives, see: (a) Dubac, J.; Laporterie, A.; Manuel, G.
Chem. Rev. 1990, 90, 215. (b) Märkl, G.; Berr, K.-P.
Tetrahedron Lett. 1992, 33, 1601. (c) Tamao, K.;
Yamaguchi, S.; Shiro, M. J. Am. Chem. Soc. 1994, 116,
11715. (d) Fagan, P. J.; Nugent, W. A.; Calabrese, J. C. J.
Am. Chem. Soc. 1994, 116, 1880. (e) Sudo, T.; Asao, N.;
Yamamoto, Y. J. Org. Chem. 2000, 65, 8919. (f) Wang, Z.;
Fang, H.; Xi, Z. Tetrahedron Lett. 2005, 46, 499.
(g) Yamaguchi, S.; Xu, C.; Yamada, H.; Wakamiya, A. J.
Organomet. Chem. 2005, 690, 5365. (h) Hudrlik, P. F.; Dai,
D.; Hudrlik, A. M. J. Organomet. Chem. 2006, 691, 1257.
1H NMR (300 MHz, CDCl3): d = 0.45 (s, 6 H), 2.31–2.38
(m, 2 H), 2.58–2.65 (m, 2 H), 5.16 (d, J = 10.8 Hz, 1 H), 5.44
(d, J = 17.1 Hz, 1 H), 5.78 (d, J = 2.7 Hz, 1 H), 5.97 (d,
J = 2.7 Hz, 1 H), 6.96 (dd, J = 17.1, 11.1 Hz, 1 H), 7.09–7.26
(m, 9 H). 13C NMR (75 MHz, CDCl3): d = 2.0, 24.4, 28.5,
114.3, 125.6, 125.9, 126.4, 126.7, 126.8, 127.5, 128.0,
128.1, 135.7, 136.7, 138.1, 138.7, 143.9, 150.6, 153.3.
HRMS (EI): m/z [M]+ calcd for C22H24Si: 316.1647; found:
316.1650.
1,1-Dimethyl-2-phenyl-1,4,5,6-tetrahydrocyclo-
penta[b]silole (4a)
Synlett 2008, No. 4, 561–564 © Thieme Stuttgart · New York

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