[62762-20-3]  · C11H16SSi  · 1-Phenylthio-1-trimethylsilylethylene  · (MW 208.43)

(a reagent for C2 homologation and a Michael acceptor)

Physical Data: colorless liquid; bp 130-134 °C/15 mmHg;1 IR,1,2 1H NMR,1 and MS data1 are available.

Solubility: very sol most organic solvents.

Preparative Methods: by lithiation of Phenyl Vinyl Sulfide with Lithium Diisopropylamide, followed by silylation,1,2 or the base-induced elimination of 2-chloro-1-trimethylsilyl-1-phenylthioethane,2 or the lithiation of ethyl phenyl sulfoxide with LDA followed by silylation,3 or the Pd-catalyzed coupling reactions of trimethylstannyl phenyl sulfide with 1-bromo-1-trimethylsilylethylene.4

Handling, Storage, and Precautions: use in a fume hood.

Addition of Organolithiums.

Organolithiums undergo smooth additions to 1-phenylthio-1-trimethylsilylethylene at low temperature. The resulting adduct anions are stabilized by two anion-stabilizing substituents, phenylthio and trimethylsilyl. They can be quenched with a variety of electrophiles. Sulfines are formed by treatment with Sulfur Dioxide (eq 1),5 phenyl 1-silylalkyl sulfides by hydrolytic quenching with NH4Cl,1 alkanals by oxidation with m-Chloroperbenzoic Acid and subsequent rearrangement reaction (eq 2),6,7 phenyl silylalkyl sulfides by alkylation with a variety of alkylating agents,8 and vinyl sulfides by condensation with aldehydes.8

Cyclopentenone Synthesis.

When activated with Lewis acid catalysts or silver ion, 1-phenylthio-1-trimethylsilylethylene reacts with a,b-unsaturated acid chlorides at a low temperature in CH2Cl2.2,9 The cation intermediates undergo a silicon-directed Nazarov cyclization to give 3-phenylthio-substituted cyclopentenone derivatives (eq 3). The phenylthio moiety at the b-position of cyclopentenones can be effectively utilized for the introduction of an alkyl substituent by addition/elimination.


Although the adduct anions formed by addition of organolithiums to 1-phenylthio-1-trimethylsilylethylene have high stability at low temperature, at higher temperatures (0 °C) in THF the anions may react with another molecule of 1-phenylthio-1-trimethylsilylethylene. The final anions undergo intramolecular alkylation under the reaction conditions to give cyclopropane derivatives in high yields (eq 4).10 Employment of sulfur-stabilized anions as donor molecules is even more effective (eq 5).11

Cyclohexanone Annulation.

The benzyllithium intermediates formed by metalation of o-toluamide derivatives with LDA at -78 °C react with 1-trimethylsilyl-1-phenylthioethylene. The resulting adduct anions undergo intramolecular cyclization on to the adjacent amide moiety to provide a convenient route for cyclohexanone annulation (eq 6).12

Analogous Reagents.

1-Phenylsulfinyl-1-trimethylsilylethylene (1)2 and 1-phenylsulfonyl-1-trimethylsilylethylene (2) are used as synthetic analogs of 1-phenylthio-1-trimethylsilylethylene. The sulfoxide (1) is an electron-deficient alkene so it is a highly reactive dienophile in Diels-Alder reactions. The cycloadduct with Cyclopentadiene undergoes the sila-Pummerer rearrangement to a thioacetal, which is then hydrolyzed to the ketone (eq 7).6 By this sequence, (1) becomes a useful synthetic equivalent of ketene. The sulfone (2) works as an excellent acceptor molecule for the Michael addition reactions using the aryllithium donors generated by the directed lithiation of o-chloroarenes. The adducts then undergo intramolecular cyclizations by the aid of metal amides to offer an excellent entry to benzocyclobutene derivatives.13

1. Ager, D. J. JCS(P1) 1983, 1131.
2. Cooke, F.; Moerck, R.; Schwindeman, J.; Magnus, P. JOC 1980, 45, 1046.
3. Miller, R. D.; Hässig, R. TL 1984, 25, 5351.
4. Carpita, A.; Rossi, R.; Scamuzzi, B. TL 1989, 30, 2699.
5. Van der Leij, M.; Zwanenburg, B. TL 1978, 3383.
6. Williams, R. V.; Lin, X. CC 1989, 1872.
7. Ager, D. J. TL 1981, 22, 587.
8. Ager, D. J. JCS(P1) 1986, 183.
9. Magnus, P.; Quagliato, D. JOC 1985, 50, 1621.
10. Kanemasa, S.; Kobayashi, H.; Tanaka, J.; Tsuge, O. BCJ 1988, 61, 3957.
11. Cohen, T.; Sherbine, J. P.; Mendelson, S. A.; Myers, M. TL 1985, 26, 2965.
12. Date, M.; Watanabe, M.; Furukawa, S. CPB 1990, 38, 902.
13. Iwao, M. JOC 1990, 55, 3622.

Shuji Kanemasa

Kyushu University, Kasuga, Japan

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