Lewis Acid-Activated Reactions of Silyl Ketenes for the Preparation of α-Silyl Carbonyl Compounds

Silyl-substituted ketenes are attractive molecular building blocks due to their stability and ease of storage, as opposed to unstable alkyl and aryl ketenes. To better understand the reactivity of silyl ketenes and, in turn, their use in the preparation of highly functionalized small molecules, the reaction of silyl ketenes with different nucleophiles was studied. The addition of alcohol, amine, or thiol nucleophiles to the central carbon of silyl ketene, followed by proton transfer afforded alpha-silyl ester, amide, or thio-ester, respectively. Catalytic amounts of Lewis acid greatly increase the rate of the reaction, and the impact of nucleophile, Lewis acid, and silyl substituent are evaluated. The small molecules produced from these reactions give insight into the use of silyl ketenes as building blocks for complex molecular structures.