When dimethyl(phenyl)silanol is subjected to on electron-deficient olefin in the presence of a stoichiometric amount of Pd(OAc)2, substitution of the CH bond of the olefin by a phenyl group on the silanol occurs in 52–86% yields. The reactions of several aryl- and alkenylsilanols with several olefins are also found to proceed in the system of 10 mol% of Pd(OAc)2, Cu(OAc)2 (3 mol), LiOAc (2 mol) to
Palladium-catalyzed cross-coupling of aryl- or alkenylsilanols, silanediols, and silanetriols with a variety of iodoarenes by the catalysis of palladium(0) and in the presence of silver(I) oxide furnished the coupling products in good to excellent yields. The reactions of silanediols or silanetriols under similar conditions proceeded much faster than those of silanols to afford the corresponding coupling
Alkenylsilanols are prepared by the reaction of hexamethyltrisiloxane (D3) with alkenyllithiums or alternatively by the reaction of cyclic siloxanes substituted by an alkenyl group with organolithiums and transformed to the corresponding cyclopropylsilanols using diiodomethane and diethylzinc. Lithium alkenylsilanolates, primary products of the preparation, also undergo cyclopropanation. As in the case of allylic alcohols, the silanol functionality is found to enhance the rate of cyclopropanation compared with that of alkenyltrialkylsilane or alkoxydialkylsilane. The obtained cyclopropylsilanols are further converted into the corresponding cyclopropanols by the Tamao oxidation.
[GRAPHICS]The reactions of aryl- and alkenylsilanols with organic halides are found to proceed in a catalyst system of 5 mol % of Pd(PPh3)(4) and Ag2O (1 equiv) to give the corresponding coupling products in up to 84% yield.
Novel Carbon-Carbon Bond Formation through Mizoroki-Heck Type Reaction of Silanols and Organotin Compounds
The reaction of dimethyl(phenyl)silanol with butyl acrylate in the presence of a stoichiometric amount of Pd(OAc)2 or by a combined use of 0.1 molar amount of Pd(OAc)2 and Cu(OAc)2/LiOAc (molar ratio 3/2) gave butyl cinnamate in 76% or 57% yield, respectively. The similar reaction with tributyl(phenyl)tin also proceeded in 77% yield. The organotin compound was shown to react faster than the silanol