New desilylations of phenolic silanes using palladium catalysts and potassium carbonate/ethyl alcohol: Extensions towards asymmetric desymmetrizations

The importance of protecting groups for phenols (particularly TBDMS ethers) in organic synthesis and two new methods for the desilylation of phenolic silanes are discussed. The first method desilylates a variety of phenolic silyl ethers in typically good to excellent yields using 5 mol% PdCl{dollar}sb2{dollar}(CH{dollar}sb3{dollar}CN){dollar}sb2{dollar}, in refluxing wet acetone. The scope and limitations of this method are discussed in detail. The second method desilylates a variety of phenolic silyl ethers in good to excellent yields using 1.1 equivalents of K{dollar}sb2{dollar}CO{dollar}sb3{dollar} in ethanol at 70{dollar}spcirc{dollar}C. Both methods are beneficial since they do not require specialized equipment and are relatively simple, mild and inexpensive procedures. The latter method selectively removes phenolic TBDMS ethers in the presence of alkyl TBDMS ethers.; The asymmetric desymmetrization of meso compounds is a useful strategy in organic chemistry for the preparation of scalemic mixtures. The desymmetrization of meso-silylated diols is discussed using palladium catalysts. Initially, achiral palladium catalysts are used to determine what conditions were necessary to effect a mono-desilylation. A variety of chiral phosphine ligands were then coordinated to the palladium catalyst, but it was found that the desilylation reaction was inhibited completely in the presence of these chiral ligands. A variety of other Lewis acid catalysts are tried with silver triflate showing the most promising results.