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DOI: 10.1055/s-2002-32975
Generation of Silylethynolates via C-Si Bond Cleavage of Disilylketenes Induced by t-BuOK [1]
Publikationsverlauf
Publikationsdatum:
25. Juli 2002 (online)
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Abstract
Disilylketenes undergo selective mono-desilylation upon treatment of t-BuOK in the presence of HMPA. The resulting silylethynolates are convertible to other disilylketenes in good yields. The intermediary silylethynolate was analyzed by NMR and IR spectroscopy.
Key words
disilylketene - silylethynolate - potassium t-butoxide - carbon-silicon bond cleavage - HMPA
Presented in part at the 70th Annual Meeting of the Chemical Society of Japan, Tokyo, March 1996, Abstr. 2J392.
- 3
Ito M.Shirakawa E.Takaya H. Synlett 1996, 635 - For reviews on the chemistry of ynolates, see:
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Efimova IV.Kazankova MA.Lutsenko IF. Zh. Obshch. Khim. 1985, 55: 1647 - 7 Recently, Ishikawa and co-workers
reported (Me3Si)3SiLi undergoes nucleophilic
attack onto the silicon center of 1a in THF,
but their attempts to trap the resulting silylethynolate were unsuccesful:
Naka A.Ohshita J.Kunai A.Lee ME.Ishikawa M. J. Organomet. Chem. 1999, 574: 50 -
8a
n-BuLi is known to react with 1a at the ketene sp-carbon in
the absence of HMPA:
Ponomarev SV.rman MB.Lebedev SA.Pechurina SY.Lutsenko IF. Zh. Obsh. Khim. 1971, 41: 127 -
8b Also see:
Woodbury RP.Long NR.Rathke MW. J. Org. Chem. 1978, 43: 376 -
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ylides with 1a or 1b leading
to mono-silylated allenes, see:
Kita Y.Tsuzuki Y.Kitagaki S.Akai S. Chem. Pharm. Bull. 1994, 42: 233 - Analytical data for 2:
-
9a
1,1-Bis(trimethylsilyl)-2-[(1,1-dimethylethyl)dimethylsilyl]oxy-2-phenylethene (2, R = Ph). 1H NMR (CDCl3) δ: -0.31 (s, 9 H), -0.29 (s, 6 H), 0.25 (s, 9 H), 0.86 (s, 9 H), 7.18-7.29 (m, 5 H); 13C NMR (CDCl3) δ: -3.1, 2.1, 2.4, 18.6, 26.3, 109.9, 127.8, 128.0, 129.6, 142.0, 165.9. Anal. Calcd for C20H38OSi3: C, 63.42; H, 10.11. Found: C, 63.31; H, 10.35.
-
9b
1,1-Bis(trimethyl-silyl)-2-[(1,1-dimethylethyl)dimethylsilyl] oxy-1-propene (2, R = Me). This compound was not obtained in pure form and thus only 1H and 13C NMR spectral data were shown.
1H NMR (CDCl3) δ: 0.12 (s, 9 H), 0.14 (s, 9 H), 0.20 (s, 6 H), 0.95 (s, 9 H), 2.03 (s, 3 H); 13C NMR (CDCl3) δ: -2.3, 0.1, 2.7, 2.9, 19.1, 26.5, 107.1, 164.5. - 10 Rathke’s report on the
isolation of 1a by warming a THF solution
of lithio t-butyl bis(trimethylsilyl)acetate
to 25 °C may indicate that the eliminated t-BuOLi
does not undergo C-Si bond cleavage of 1a under
their condition:
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11a
General Procedure for the Preparation of Disilylketenes using t -BuOK: Preparation of [(1,1-dimethylethyl)dimethylsilyl](trimethylsilyl)ketene(1b) from 1a is representative. Disilyllketene 1a (296.5 mg, 1.59 mmol) was dissolved in THF (1.6 mL) and HMPA (0.28 mL, 1.61 mmol). To the resulting yellow solution was added a solution of t-BuOK (180.0 mg, 1.60 mmol) in THF (3.2 mL) at 0 °C. The mixture was stirred for 1 h at the same temperature and quenched by t-BuMeSiOTf (0.37 mL, 1.61 mmol). After stirring the resulting solution for 2 h at room temperature, the reaction mixture was diluted with pentane and washed with water. Then the organic layer was dried by Na2SO4 and filtered through Florisil. Evaporation of the solvent followed by silica-gel chromatography (Wakogel C-200) afforded 1b as a colorless oil (305.4 mg, 84% yield).
-
11b
We were unable to detect the formation of any
O-silylated product (silyl silylethynyl ether) under these conditions. See ref. [13c] . -
11c
The use of carbon electrophiles (MeI, Me2SO4, Me3OBF4, or PhCHO) instead of R3SiX resulted in the formation of intractable mixtures under similar conditions.
- Analytical data for new disilylketenes (silicon-attached quarternary carbon was not observed in 13C NMR spectra):
-
12a
(Dimethylphenylsilyl)(trimethylsilyl)ketene(1d). 1H NMR (CDCl3) δ: 0.14 (s, 9 H), 0.52 (s, 6 H), 7.40-7.43 (m, 3 H), 7.59-7.63 (m, 2 H); 13C NMR (CDCl3) δ: -0.2, 1.2, 127.8, 129.4, 133.6, 138.3, 166.9; IR(neat) 2084 cm-1 (CCO); MS (70 eV) m/z 248 (M+); bp 62-70 °C (0.05 mmHg). Anal. Calcd for C13H20OSi2: C, 62.84; H, 8.11. Found: C, 63.10; H, 8.28.
-
12b
Bis(triphenylsilyl)ketene(1k). 1H NMR (CDCl3) δ: 7.21-7.49 (m, 30 H); 13C NMR (CDCl3) δ: 127.7, 127.8, 129.7, 129.8, 133.7, 135.2, 135.4, 135.9, 166.2; IR(nujol) 2080 cm-1 (CCO); MS (70 eV) m/z 558 (M+); mp 165-166 °C. Anal. Calcd for C38H30OSi2: C, 81.67; H, 5.41. Found: C, 81.40; H, 5.32.
-
13a
Ponomarev SV.Zolotareva AS.Ezhov RN.Kuznetsov YV.Petrosyan VS. Russ. Chem. Bull. 2001, 50: 1093 -
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Ponomarev SV.Zolotareva AS.Leont’ev AS.Kuznetsov YV.Petrosyan VS. Russ. Chem. Bull. 2001, 50: 1088 -
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Groh BL.Magrum GR.Barton TJ. J. Am. Chem. Soc. 1987, 109: 7568 -
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Buncel E.Edlund TKVU. J. Organomet. Chem. 1992, 437: 85 -
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Bassindale AR.Glynn SJ.Taylor PG. In The Chemistry of Organic Silicon Compounds Part 1, Vol. 2:Rappoport Z.Apeloig Y. John Wiley & Sons; Chichester: 1998. Chap. 7. -
15a Examples
for a related alkali metal alkoxide-induced C-Si bond cleavage
reaction:
Sakurai H.Nishiwaki K.Kira M. Tetrahedron Lett. 1973, 42: 4193 ; see also ref. 13d -
15b
We suppose that HMPA may coordinate onto the smaller silicon center of the disilylketene to form a penta-coordinate silicate, and facilitate the alkoxide-induced Si-C bond cleavage.
References
Presented in part at the 70th Annual Meeting of the Chemical Society of Japan, Tokyo, March 1996, Abstr. 2J392.
2Deceased Oct. 4, 1995. Address all correspondence to Dr. Masato Ito, Department of Applied Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8552, Japan; E-mail: mito@o.cc.titech.ac.jp.