Functional group transformations and stereochemistry of silicon-functionalized 7-silabenzonorbornadienes

Article abstract of DOI:10.1246/cl.2005.960

Functional group transformations of 7-silabenzonorbornadiene derivatives have been investigated. The 7-mesityl-7-silanorbornadiene 1 was prepared and converted into the 7-chloro derivative 5. Reductive lithiation of 5 with lithium naphthalenide afforded t

Full text of DOI:10.1246/cl.2005.960

9
60
Chemistry Letters Vol.34, No.7 (2005)
Functional Group Transformations and Stereochemistry
of Silicon-functionalized 7-Silabenzonorbornadienes
ꢀ
Atsushi Kawachi, Masahiro Okimoto, and Yohsuke Yamamoto
Department of Chemistry, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526
(Received March 17, 2005; CL-050360)
Functional group transformations of 7-silabenzonorborna-
yield.3c,4 The X-ray crystallographic analysis of 1 revealed that
the hydrogen at the silicon is syn with respect to the annulated
diene derivatives have been investigated. The 7-mesityl-7-sila-
norbornadiene 1 was prepared and converted into the 7-chloro
derivative 5. Reductive lithiation of 5 with lithium naphthalenide
afforded the silyllithium 6, which reacted with Me3SiCl and
MeI. The reactions of 5 with n-BuLi and PhNHLi gave the 7-
butyl derivative 9 and the 7-amino derivative 10, respectively.
Each stereochemistry during these transformations was deter-
mined by X-ray crystallographic analysis.
4
benzene. The steric bulkiness of the mesityl group in 1 deter-
mines the stereochemistry during the ½4 þ 2ꢁ cycloaddition.
The chlorination of 1 with refluxing carbon tetrachloride in
the presence of palladium dichloride (30 mol %) successfully af-
5
,6
forded 5 in 90% yield (Eq 1). There have been very few exam-
ples of the 7-chloro-7-silanorbornadienes, all of which were pre-
1
c
pared by the ½4 þ 2ꢁ cycloaddition. The stereochemistry of 5
was confirmed to be syn by an X-ray crystallographic analysis.6
This proves that the chlorination reaction proceeds with reten-
tion of its configuration at the silicon. The observed stereochem-
istry is consistent with the trend that reactions of organosilanes
involving the intermediate silyl radicals proceed with the pre-
The 7-silanorbornadienes have been attractive species since
they show unique reactivity attributed to their heavily strained
skeletons.1 Thermolysis or photolysis of the 7-silanorborna-
dienes may produce divalent silylene species with the elimina-
tion of arenes, the former of which undergoes reactions with di-
7
dominant retention of the configuration at the silicon.
Mes
Mes
2
H
Cl
Si
enes, alkynes, hydrosilanes, and alcohols. Thus the 7-silanor-
Si
Ph
Ph
CCl / PdCl2
4
bornadienes are potential precursors of a variety of silicon
compounds, and the introduction of functional groups on the
bridging silicons will increase their synthetic utility. Functional
group transformations of the 7-silanorbornadienes, however,
have been scarcely investigated. We report here the preparations
and stereochemical aspects of silicon-functionalized 7-silaben-
zonorbornadienes, starting from the 2,3-benzo-1,4,5,6-tetra-
phenyl-7-mesityl-7-silanorbornadiene (1).
Ph
Ph
(1)
reflux, 48 h
Ph
Ph
5 90%
Ph
Ph
1
The lithiation of 5 was also successful, giving a nucleophilic
silanorbornadiene species. The exposure of 5 to lithium naphtha-
ꢃ
lenide (4 molar amounts) in THF–benzene at ꢂ78 C for 4 h pro-
8
,9
duced the corresponding silyllithium 6 (Eq 2). Excess amount
of lithium naphthalenide was required to consume 5 completely.
The silyllithium 6 reacted with methyl iodide and chlorotri-
methylsilane to form the 7-methyl derivative 7 in 45% yield
A parent compound, the 7-hydro derivative 1, was prepared
3
in a manner similar to the reported procedure, as shown in
Scheme 1 [Mes = Mesityl (2,4,6-trimethylphenyl)]. The reac-
tion of 1,4-dilithiotetraphenylbutadiene 2 with trichlorosilane
3
and the 7-trimethylsilyl derivative 8 in 52% yield, respective-
10,11
a
gave the 1H-1-chloro-1-silacyclopentadiene 3. The crude 3
was subsequently treated with mesitylmagnesium bromide to
ly. This is the first example of silicon-lithiated silanorborna-
dienes whereas there have been a few examples of those having a
3
b
12
afford the 1H-1-mesityl-1-silacyclopentadiene 4 in 59% yield.
The ½4 þ 2ꢁ cycloaddition between 4 and benzyne prepared in
transition metal fragment on the silicon atom. The syn stereo-
chemistry of 8 was determined by X-ray crystallographic analy-
1
1,13
situ gave the silanorbornadiene 1 as a diastereoisomer in 78%
sis.
Thus the formation and reaction of 6 undergo the net re-
tention of the configuration at the silicon. This is in good agree-
ment with the known aspects that the reductive lithiation of
chlorosilanes and subsequent reactions with the electrophiles
proceed with the predominant retention of the configuration at
Ph
Ph
Ph
Ph
Ph
Ph
a)
Li
Li
b)
d)
Cl
H
2
Ph
Ph
Si
1
4
the silicon during each step.
Ph
Ph
Mes
Mes
Ph
E
2
3
Li
Si
Si
Ph
Ph
Mes
Ph
a)
b)
Ph
Ph
Ph
Ph
H
5
(2)
Si
c)
Mes
H
Si
Ph
Ph
Ph
Ph
Ph
Ph
Ph
6
7: E = Me
45%
: E = Me3Si 52%
Ph
8
4
59%
1 78%
(
(
a) Lithium naphthalenide (x 4) / THF–benzene / –78 °C, 4 h.
b) MeI or Me3SiCl / –78 °C to room temp.
(
(
(
a) Li / Et O / room temp, 12 h. (b) HSiCl / –196 °C to room temp.
c) MesMgBr / THF / room temp, 12 h.
d) Mg, o-C H FBr / THF / room temp, 48 h.
2
3
The nucleophilic substitution reactions of 5 were also exam-
ined. The treatment of 5 with butyllithium and lithium phenyl-
amide in THF–benzene gave the 7-butyl derivative 9 and the
6
4
Scheme 1.
Copyright Ó 2005 The Chemical Society of Japan

Chemistry Letters Vol.34, No.7 (2005)
961
Group Met. Chem., 17, 8 (1994). f) R. Boukherroub, C. Chatgilialoglu, and
G. Manuel, Organometallics, 15, 1508 (1996).
7
(
-amino derivative 10 in 53% yield and 52% yield, respectively
The X-ray crystallographic analysis of 10 displayed
Eq 3).15,16
its syn stereochemistry,
ꢃ
6
Compound 5: colorless crystals (from CDCl3/hexane), mp 252–253 C
1
1
3,16
indicating the retention of configura-
(decomposed). H NMR (CDCl3, ꢀ) 2.08 (s, 6H), 2.24 (s, 3H), 6.29–6.45
tion at the silicon during the amination reaction. It is noted that
although the nucleophilic displacements of chlorosilanes mainly
undergo inversion at the silicon, the stereochemistry tends to-
wards retention when the silicon is included in a strained ring.7a
(br, 2H), 6.72–6.78 (br, 2H), 6.80–7.04 (m, 8H), 7.09–7.22 (m, 12H),
1
3
7
1
1
.51–7.58 (m, 2H). C NMR (CDCl3, ꢀ) 21.1, 25.6, 61.7, 123.4, 124.4,
25.4, 125.8, 126.3, 127.2, 127.6, 129.0, 130.1, 131.3, 136.0, 137.4,
2
9
40.9, 145.5, 146.8, 147.5. Si NMR (CDCl3, ꢀ) 30.3. MS (EI): m=z 616
þ
þ
(
M þ 2, 21), 614 (M , 45), 432 [(tetraphenylnaphthalene) , 100]. Anal.
Calcd for C43H35ClSi: C, 83.94; H, 5.73%. Found: C, 83.88; H, 5.79%.
Crystal data for 5 at 173 K (Mac Science DIP2030) (CCDC 270941); see
Supporting Information.
Mes
Mes
R
Cl
Si
Si
Ph
Ph
a) or b)
Ph
Ph
(3)
7
8
a) R. J. P. Corriu, C. Guerin, and J. J. E. Moreau, in ‘‘The Chemistry of
Organic Silicon Compounds,’’ ed. by S. Patai and Z. Rappoport, Wiley,
Chichester (1989), Chap. 4, pp 305–307. b) H. Sakurai, M. Murakami,
and M. Kumada, J. Am. Chem. Soc., 91, 519 (1969).
For reviews of silyllithiums: a) K. Tamao and A. Kawachi, Adv. Organo-
met. Chem., 38, 1 (1995). b) P. D. Lickiss and C. M. Smith, Coord. Chem.
Rev., 145, 75 (1995). c) J. Belzner and U. Dehnert, in ‘‘The Chemistry of
Organic Silicon Compounds,’’ ed. by Z. Rappoport and Y. Apeloig, Wiley,
Chichester (1998), Vol. 2, p 779.
Ph
Ph
Ph
Ph
5
9: R = n-Bu 53%
0: R = PhNH 52%
1
(
a) n-BuLi (x 2) / 0 °C, 3 h. (b) PhNHLi (x 1.2) / room temp, 2 h.
In summary, the Si–H functionality in 1 was converted into
the Si–Cl functionality (5) and then the Si–Si (8) and Si–N (10)
functionalities. These transformations proceed with predominant
retention of configuration at the bridging silicons due to the rigid
skeletons. The nucleophilic and electrophilic silanorbornadienes
prepared here will serve as versatile silicon reagents.
9
The 29Si resonance of 6 could not be confirmed even at low temperatures
perhaps due to the low concentration of the solution of 6 prepared under
the present conditions.
10 Compound 7: colorless crystals (from CHCl /hexane/CH CN), mp 234–
3
3
ꢃ
1
235 C (decomposed). H NMR (CDCl3, ꢀ) 0.20 (s, 3H), 2.05 (s, 6H),
2
.24 (s, 3H), 6.25–6.50 (br, 2H), 6.68–7.25 (m, 22H), 7.50–7.70 (m, 2H).
C NMR (CDCl3, ꢀ) 0.5, 21.1, 25.1, 61.6, 122.8, 123.9, 125.2, 125.8,
27.0, 127.5, 128.6, 128.7, 129.9, 130.4, 131.1, 137.7, 138.2, 139.5,
1
3
This work was supported by a Grants-in-Aid for Scientific
Research (No. 14703027) from the Ministry of Education,
Culture, Sports, Science and Technology, Japan. The measure-
ment of the high resolution mass spectra of 7, 8, and 9 was made
using a JEOL SX102A at the Natural Science Center for Basic
Research and Development (N-BARD), Hiroshima University.
We also thank Prof. Katsuya Inoue, Hiroshima University, for
allowing us to use the Bruker SMART-APEX for the X-ray crys-
tallographic analysis of 8 and 10.
1
2
9
þ
145.1, 147.8, 148.2. Si NMR (CDCl , ꢀ) 51.9. MS (EI): m=z 594 (M ,
3
þ
þ
37), 579 (M ꢂ Me, 5), 432 [(tetraphenylnaphthalene) , 100]. HRMS
EI): m=z found 594.2742; calcd for C44H38Si: 594.2743.
1 Compound 8: colorless crystals (from CDCl3/hexane), mp 243–244 C
(
ꢃ
1
1
(
decomposed). H NMR (CDCl3, ꢀ) ꢂ0:30 (s, 9H), 2.07 (s, 6H), 2.23 (s,
13
3H), 6.17–6.28 (m, 2H), 6.66–7.22 (m, 22H), 7.68–7.75 (m, 2H). C NMR
(CDCl3, ꢀ) 1.4, 21.1, 25.0, 63.1, 123.1, 123.8, 125.3, 125.6, 126.8, 127.0,
1
1
5
28.3, 129.5, 129.6, 130.5, 132.1, 138.1, 138.5, 138.9, 144.6, 148.2,
2
9
þ
49.9. Si NMR (CDCl3, ꢀ) ꢂ15:9, 56.2. MS (EI): m=z 652 (M , 19),
þ
þ
79 (M ꢂ SiMe3, 29), 432 [(tetraphenylnaphthalene) , 43], 205
þ
(MesSiMe2Si , 100). HRMS (EI): m=z found 652.2982; calcd for
References and Notes
1
C46H44Si2, 652.2982. Crystal data for 8 at 298 K (Bruker SMART-APEX)
(CCDC 270942); see Supporting Information.
12 a) A. Marinetti-Mignani and R. West, Organometallics, 6, 141 (1987). b) C.
Paek, J. Ko, Y. Kong, C.-H. Kim, and M.-E. Lee, Bull. Korean Chem. Soc.,
15, 460 (1994).
a) H. Gilman, S. G. Cottis, and W. H. Atwell, J. Am. Chem. Soc., 86, 1596
1964). b) H. Gilman, S. G. Cottis, and W. H. Atwell, J. Am. Chem. Soc.,
(
8
4
6, 5584 (1964). c) B. Mayer and W. P. Neumann, Tetrahedron Lett., 21,
887 (1980). d) T. J. Barton, W. F. Goure, J. L. Witiak, and W. D. Wulff,
J. Organomet. Chem., 225, 87 (1982). e) H. Sakurai, H. Sakaba, and Y.
Nakadaira, J. Am. Chem. Soc., 104, 6156 (1982). f) H. Sakurai, Y.
Nakadaira, and H. Sakaba, Organometallics, 2, 1484 (1983). g) H. Appler,
L. W. Gross, B. Mayer, and W. P. Neumann, J. Organomet. Chem., 291, 9
13 Although the yields of the products were not high, the other diastereoisom-
1
ers could not be observed by the H NMR analysis.
14 Studies on configurational stability of sillyllithiums: a) L. H. Sommer and
R. Mason, J. Am. Chem. Soc., 87, 1619 (1965). b) E. Colomer and R. J. P.
Corriu, J. Chem. Soc., Chem. Commun., 1976, 176. c) E. Colomer and
R. J. P. Corriu, J. Organomet. Chem., 133, 159 (1977). d) J. B. Lambert
and M. Urdaneta-P e´ rez, J. Am. Chem. Soc., 100, 157 (1978). e) M. Omote,
T. Tokita, Y. Shimizu, I. Imae, E. Shirakawa, and Y. Kawakami, J. Orga-
nomet. Chem., 611, 20 (2000). f) A. Kawachi, H. Maeda, and K. Tamao,
Organometallics, 21, 1319 (2002).
(
4
1985). h) A. Sekiguchi, S. S. Zigler, and R. West, J. Am. Chem. Soc., 108,
241 (1986). i) M. Kako, M. Mori, K. Hatakenaka, S. Kakuma, Y.
Nakadaira, M. Yasui, and F. Iwasaki, Tetrahedron, 53, 1265 (1997).
P. P. Gasper and R. West, in ‘‘The Chemistry of Organic Silicon Com-
pounds,’’ ed. by Z. Rappoport and Y. Apeloig, Wiley, Chichester (1998),
Vol. 2, pp 2463–2568.
2
3
15 Compound 9: white solid, mp 223–224 C (decomposed). 1H NMR
(CDCl3, ꢀ) 0.60 (t, 3H, J ¼7 Hz), 0.71 (t, 2H, J ¼ 7 Hz), 0.87 (sext, 2H,
J ¼ 7 Hz), 0.97 (quint, 2H, J ¼ 7 Hz), 2.01 (s, 6H), 2.23 (s, 3H), 6.23–
ꢃ
a) W.-C. Joo, J.-H. Hong, S.-B. Choi, H.-E. Son, and C.-H. Kim, J. Orga-
nomet. Chem., 391, 27 (1990). b) Y. Pan, J.-H. Hong, S.-B. Choi, and
P. Boudjouk, Organometallics, 16, 1445 (1997). c) J. Schuppan, B.
Herrschaft, and T. M u¨ ller, Organometallics, 20, 4584 (2001).
1
3
6.41 (br, 2H), 6.68–7.22 (m, 22H), 7.54–7.66 (m, 2H). C NMR (CDCl3,
ꢀ) 13.5, 16.4, 21.1, 24.7, 26.4, 26.6, 62.0, 122.8, 123.9, 125.1, 125.7,
126.9, 127.3, 128.1, 128.5, 129.7, 130.4, 131.4, 137.9, 138.4, 139.2,
ꢃ
4
Compound 1: colorless crystals (from CDCl3/hexane), mp 223–224 C
(
decomposed). 1H NMR (CDCl3, ꢀ) 2.19 (s, 6H), 2.23 (s, 3H), 5.01 (s,
2
9
þ
1
8
2
1
3
H), 6.72 (s, 2H), 6.89–7.00 (m, 8H), 7.04–7.09 (m, 4H), 7.10–7.14 (m,
H), 7.16–7.20 (m, 2H), 7.58–7.65 (m, 2H). 13C NMR (CDCl3, ꢀ) 21.3,
4.6, 59.9, 122.5, 124.0, 125.3, 126.0, 126.3, 127.1, 127.6, 128.5, 129.9,
145.1, 148.3, 148.4. Si NMR (CDCl3, ꢀ) 55.2. MS (EI): m=z 636 (M ,
þ
þ
71), 579 (M ꢂ Bu, 31), 432 [(tetraphenylnaphthalene) , 100]. HRMS
(EI): m=z found 636.3211; calcd for C47H44Si, 636.3212.
16 Compound 10: colorless crystals (from CDCl3/hexane), mp 192–193 C
29
ꢃ
30.6, 137.5, 137.8, 140.6, 145.6, 147.1, 148.0. Si NMR (CDCl3, ꢀ)
2.9 (d, 1JSi{H ¼ 206 Hz). MS (EI): m=z 580 (M , 48), 432 [(tetra-
þ
(decomposed). H NMR (C6D6, ꢀ) 2.01 (s, 3H), 2.20 (s, 6H), 4.20 (br,
1H), 6.30–6.40 (m, 2H), 6.52–6.90 (m, 13H), 6.92–7.13 (m, 10H), 7.45–
7.56 (m, 4H), 7.70–7.79 (m, 2H). C NMR (C6D6, ꢀ) 21.2, 24.9, 61.6,
118.7, 119.8, 124.3, 125.1, 125.6, 126.5, 127.6, 127.8, 128.1, 128.3
129.0, 129.5, 131.3, 138.6, 139.3, 140.7, 145.1, 146.6, 147.1, 149.3.
1
þ
phenylnaphthalene) , 100]. Anal. Calcd for C43H36Si: C, 88.92; H,
1
3
6.25%. Found: C, 88.79; H, 6.62%. Crystal data for 1 at 173 K (Mac
Science DIP2030) (CCDC 270940); see Supporting Information.
5
a) Y. Nagai, H. Matsumoto, T. Yagihara, and K. Morishita, Kogyo Kagaku
Zasshi, 71, 1112 (1968). b) D. Seyferth, C. C. Prud’homme, and W. L.
Wang, J. Organomet. Chem., 277, 203 (1984). c) J. Y. Corey, C. S. John,
M. C. Ohmsted, and L. S. Chang, J. Organomet. Chem., 304, 93 (1986).
d) Y. Igarashi, Y. Kabe, T. Hagiwara, and W. Ando, Tetrahedron, 48, 89
2
9
þ
þ
Si NMR (C6D6, ꢀ) 21.6. MS (EI): m=z 672 (MH , 5), 671 (M , 8), 432
þ
[(tetraphenylnaphthalene) , 100]. Anal. Calcd for C49H41NSi: C, 87.59;
H, 6.15; N, 2.08%. Found: C, 87.22; H, 6.11; N, 2.48%. Crystal data
for 10 at 298 K (Bruker SMART-APEX) (CCDC 270943); see Supporting
Information.
(1992). e) R. Boukherroub, V. Dejean, G. Manuel, and W. P. Weber, Main
Published on the web (Advance View) June 4, 2005; DOI 10.1246/cl.2005.960