Highly Stereoselective Oxazaborolidinium Ion Catalyzed Synthesis of (Z)-Silyl Enol Ethers from Alkyl Aryl Ketones and Trimethylsilyldiazomethane.

Highly stereoselective (Z)-silyl enol ethers were prepared from alkyl aryl ketones and trimethylsilyldiazomethane (TMSD) using an oxazaborolidinium ion catalyst. In addition, ring-expanded silyl enol ethers were successfully constructed from cyclic ketones. Their synthetic utilities were shown by sequential Mukaiyama aldol and [2 + 2]-cycloaddition reactions.