Oxidant-Controlled Stereoselectivity in the Pd-Catalyzed Allylic Oxidation of cis-Vinylsilanes

The allylic oxidation of cis-vinylsilanes is reported. The reaction requires a low catalyst loading of Pd(OAc)(2) without the need for an external ligand. Interestingly, trans-vinylsilanes are unreactive, whereas allylic oxidations of cis-vinylsilanes proceed in good yields giving a single diastereo- and regioisomer of the branched allylic acetate trans-vinylsilane when benzoquinone is employed. The use of PhI(OAc)(2) as oxidant in place of benzoquinone provides the branched, cis-vinylsilane as the major product. Additionally, the first intramolecular allylic C-H etherifications of cis-vinylsilanes to give oxygen heterocycles are also described.