Has also been used, in the presence of a catalyst such as p-TsOH, I2, Br2 or TfOH, as a silylating agent for alcohols, phenols and carboxylic acids: Tetrahedron Lett., 21, 835 (1980); J. Org. Chem., 46, 5212 (1981). The advantage over more conventional silylation methods is that the only by-product is the neutral gas propene.
Reactions with electrophiles illustrate the ß-effect (see Appendix 4); e.g. acid chlorides with a Lewis acid give allyl ketones: J. Organomet. Chem., 85, 149 (1975):
More recent studies have shown that TMS cyclopentanes are also formed in these reactions via a competing [3+2] cycloaddition mechanism: Tetrahedron, 49, 9955 (1993). Chemoselective addition to aldehydes can be accomplished in the presence of a ketone, using Scandium(III) trifluoromethanesulfonate hydrate, 40566 as catalyst: Synthesis, 1822 (1998).
In the presence of F-, functions as an allyl anion equivalent, affording homoallylic alcohols from carbonyl compounds: Tetrahedron Lett., 3043 (1978), and adding to a variety of Michael acceptors: Tetrahedron Lett., 25, 3213 (1984); J. Org. Chem., 51, 1745 (1986). For a review of reactivity in the presence of Lewis acids and F-, see: J. Prakt. Chem./ Chem. Ztg., 336, 375 (1994).
Similarly, carbonyl compounds are converted to homoallylic alcohols: J. Organomet. Chem., 69, C15 (1974). In the TiCl4 promoted reaction with enones, behaves as an allyl anion equivalent, giving the product of conjugate addition (Hosomi-Sakurai reaction): J. Am. Chem. Soc., 99, 1673 (1977); 105, 2354 (1983); Org. Synth. Coll., 7, 443 (1990):