(E)-1-Phenylsulfonyl-2-trimethylsilylethylene1

[64489-06-1]  · C11H16O2SSi  · (E)-1-Phenylsulfonyl-2-trimethylsilylethylene  · (MW 240.43)

(dienophile equivalent to a variety of alkynes in Diels-Alder cycloadditions;2 used to prepare a-substituted allylsilanes3)

Physical Data: mp 59-60 °C (petroleum ether).4

Solubility: sol common organic solvents.

Form Supplied in: colorless solid; not commercially available.

Preparative Methods: prepared by hydrogenation of the corresponding readily available acetylene in 48% yield (this method is also amenable to the synthesis of the deutero derivative)2 or by phenylsulfonyl chloride addition to trimethylsilylethylene (78%) followed by Triethylamine-mediated dehydrochlorination (97%);2 selenosulfonation, followed by Hydrogen Peroxide oxidation, can also be used (84%);5 an alternative method of preparation involves dehydrochlorination of 1-phenylsulfonyl-1-chloro-2-trimethylsilylethane (PhSO2CHClCH2SiMe3) with 1,8-Diazabicyclo[5.4.0]undec-7-ene (quantitative);4 can also be prepared by treating the lithium salt of the anion of methylthiomethyl phenyl sulfone (PhSO2CH2SMe) with (Iodomethyl)trimethylsilane to give PhSO2CH(SMe)CH2SiMe3, followed by oxidation to the sulfoxide and elimination of methanesulfenic acid (60%).3b

Handling, Storage, and Precautions: potential alkylating agent; use in a fume hood.

Cycloadditions.

The dienophilic properties of (E)-phenylsulfonyl-2-trimethylsilylethylene allow the preparation of adducts with reactive dienes such as Cyclopentadiene and anthracene.2 The adducts are smoothly converted to alkenes upon treatment with fluoride ion, establishing the equivalence of the title reagent to Acetylene. Alkylation of the a-sulfonyl carbanion can precede the elimination such that synthetic equivalents to HC&tbond;CH, HC&tbond;CD, and RC&tbond;CH are available. The use of this reagent is highlighted by the synthesis of several functionalized dibenzobarrelenes (eq 1).2 The equivalency to DC&tbond;CD and RC&tbond;CD is illustrated by the preparation of deuterated derivatives.

The somewhat low reactivity of (E)-phenylsulfonyl-2-trimethylsilylethylene in Diels-Alder reactions is probably due to steric hindrance exerted by both substituents and by the poor activation imparted by the silyl group. This drawback is partially offset by the effective elimination to the alkene performed under very mild conditions with fluoride ion. The low dienophilic reactivity of the title reagent is evident in the reaction with isodicyclopentadiene, for which it was demonstrated that only the isomer arising from the [1,5]-hydrogen sigmatropic shift was captured by dienophiles of low reactivity. Highly reactive dienophiles react with the symmetric structure, which is obviously a less reactive diene (eq 2).6

Addition Reactions.

The utility of (E)-phenylsulfonyl-2-trimethylsilylethylene in the synthesis of a-substituted allylsilanes3 is exemplified in eq 3 for g-hydroxyvinylsilanes,3a and in eq 4 in the preparation of isoprenoid structures.3b In these reactions the reagent functions as a Michael acceptor, but a-lithiation may compete with less nucleophilic bases such as butyllithium.3b

The availability of analogous reagents bearing different atoms in the place of silicon, such as tin,3 boron,7a and chlorine7b as well as the alkynic homologs, is notable.8 Finally, the sulfide related to the title reagent merits mention.9


1. Block, E.; Aslam, M. T 1988, 44, 281.
2. (a) Paquette, L. A.; Williams, R. V. TL 1981, 22, 4643. (b) Carr, R. V. C.; Williams, R. V.; Paquette, L. A. JOC 1983, 48, 4976. (c) Paquette, L. A.; Bay, E. JACS 1984, 106, 6693.
3. (a) Ochiai, M.; Ukita, T.; Fujita, E. TL 1983, 24, 4025. (b) Ochiai, M.; Kenzo, S.; Fujita, E.; Tada, S. CPB 1983, 31, 3346. (c) Ochiai, M.; Kenzo, S.; Fujita, E. CPB 1984, 32, 3686.
4. Hsiao, C.-N.; Shechter, H. JOC 1988, 53, 2688.
5. (a) Paquette, L. A.; Crouse, G. D. JOC 1983, 48, 141. (b) Lin, H.-S.; Coghlan, M. J.; Paquette, L. A. OS 1988, 67, 157.
6. Paquette, L. A.; Williams, R. V.; Carr, R. V. C.; Charumilind, P.; Blount, J. F. JOC 1982, 47, 4566.
7. (a) Martinez-Fresneda, P.; Vaultier, M. TL 1989, 30, 2929. (b) Montanari, F. G 1956, 86, 406.
8. (a) Williams, R. V.; Sung, C.-L. A. CC 1987, 590. (b) Padwa, A.; Wannamaker, M. W. CC 1987, 1742. (c) Djeghaba, Z.; Jousseaume, B.; Ratier, M.; Duboudin, J.-G. JOM 1986, 304, 115.
9. Magnus, P.; Quagliato, D. JOC 1985, 50, 1621.

Ottorino De Lucchi

Università di Venezia, Italy

Giovanna Delogu

Istituto CNR, IATCAPA, Sassari, Italy



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