Synthesis of Silyl Dienol Ethers via Peterson Olefination of Siloxyallylpotassium Species.

We report a general method for synthesizing a diverse array of silyl dienol ethers via the Peterson olefination of aldehydes and benzophenone using 3-silyl-substituted siloxyallylpotassium species. The reaction proceeds smoothly at -78 °C and tolerates a wide range of functional groups on the aldehyde substrate (OMe, NMe2, F, Cl, Br, CN, CO2tBu, CF3, and epoxide). Under our conditions, organolithium bases are ineffective, underscoring the critical role of potassium carbanions. The resulting silyl dienol ethers are readily converted to β,γ-unsaturated ketones. This two-step sequence thus constitutes a formal β-olefination of ketones.