Facile synthesis of silyl allenol ethers and β-silyl enones through reductive silylation of benzoylacetylenes

Reductive silylation of benzoylacetylenes by magnesium metal in the presence of chlorotrimethylsilane in N,N-dimethylformamide (DMF) gave silyl allenol ethers or β-silyl enones. Isolation of silyl allenol ethers was found to require a careful treatment and only hydrolyzed β-silyl enones were formed in some cases. Diverse multisubstituted allenol silyl ethers and β-silyl enones with good functional group tolerance were selectively synthesized in 38–86% and 23–88% yields under mild reaction conditions.